RHEOLOGICAL TECHNIQUES TO EVALUATE THE SHELF-STABILITY OF STARCH-THICKENED,STRAINED APRICOTS2

The rheological behavior of strained apricots thickened with modified tapioca starch was investigated using mixer viscometry techniques. Initially, the sample showed irreversible thixotropy which was quantified by evaluating time-dependent torque decay. Mechanically degraded samples had time-independent properties and were evaluated as power-law fluids. Rheological techniques developed were successfully used to evaluate the textural shelf-life of strained apricots thickened with different types of modified tapioca starch.     

PROBABILISTIC PUSHDOWN AUTOMATA

The properties of Probabilistic Pushdown Automata (PPA) are examined. First PPA is defined, various basic properties of it are derived, and several more restrictive types are considered. Then, the families of random languages acceptable and generable by various types of PPA, as well as the families of languages acceptable and generable by various types of PPA with cut-point, are studied. The relationships among these families are also examined, and many interesting results are obtained. Among them, it is shown that the family of languages generable by PPA having uniform output length is the homomorphic closure of the family of languages acceptable by PPA.     

Effect of Calcium Salts on Susceptibility to Browning of Avocado Fruit

Fuerte avocados were dipped in 0.18M solutions of calcium chloride (CaCl₂·6H₂O) or calcium phosphate (CaHPO₄) or calcium arsenate [Cas(AsO₄)₂] or calcium nitrate [Ca(NO₃)₂·4H₂O] to determine whether these treatments had any effect on the browning components in avocados. It was found that calcium treatments suppressed both respiration and polyphenol oxidation and also reduced the content of total phenolics, leuco-anthocyanins, and flavonols. Of those calcium treatments used, calcium arsenate gave the best results.     

SENSORY QUALITY OF GALA APPLES AS INFLUENCED BY CONTROLLED AND REGULAR ATMOSPHERE STORAGE

The sensory quality of Gala apples stored for up to 4 months in delayed controlled atmosphere (CA), regular atmosphere (RA), and a combination of sequential CA and RA storage (CR) was evaluated. Sensory analysis included difference and acceptance testing. Firmness, soluble solids and titratable acidity contents, and volatile flavor profiles were measured analytically. Acceptability decreased with storage time. Apples stored in RA were more acceptable than apples stored in CA or CR; the differences between storage treatment were not significant after 4 months of storage. Firmness decreased with storage time, but was not affected by storage treatment. Soluble solids and titratable acidity contents were not affected by storage treatment or time. Storage treatment, storage time, and lot had a significant effect on the volatile flavor profiles. CA storage and extended storage contributed to decreases in the content of volatile flavor compounds.     

Hypercube-based architecture for high speed communication systems

An implementation is presented of digital demultiplexing and demodulation algorithms for an advanced satellite communication system on a hypercube. The mapping on a hypercube provides the high speed necessary for processing hundreds of single channel per carrier/frequency division multiple access (SCPC/FDMA) voice/data channels. Data demultiplexing and demodulation are parts of the recovery of the transmitted digital data in a MODEM. A demultiplexer comprises a filter bank followed by the computation of FFT. A demodulator primarily consists of circuits to recovery carrier signal, clock frequency and data. The computation of FFT on a hypercube is well established (Hwang and Briggs 1984). Therefore, this paper analyses the filter bank and carrier and data recovery algorithms to find an efficient mapping in a multiprocessor environment connected in a hypercubic configuration. A few models to implement these algorithms on a hypercube are provided. Comparison of the speed-up achieved on a hypercube vrsus that on a sequential computer is provided for the three models.     

Loss of Amino Acids and Water Soluble Vitamins During Potato Processing

Processing potatoes to potato flakes almost totally eradicated ascorbic acid, but better than 50% of the original amount of riboflavin and niacin was retained. Thiamin content of potato flakes can vary from 0-65% of its amount in the raw potato depending on the amount of sulfite added during processing. If sulfite addition is controlled, a 100g portion of rehydrated potato flakes can supply about 1/6 of the Recommended Dietary Allowance of thiamin. Some losses of arginine, aspartic acid, glutamic acid, and gamma aminobutyric acid occurred during hot water blanching, and a significant loss of methionine occurred during drum drying. However, amino acids can be considered quite stable during potato flake production.     

Interdiffusion of Calcium in Soda-Lime-Silica Glass at 880° to 1308°C

The interdiffusion of calcium in soda-lime-silica glass under the action of a concentration gradient was studied. Pairs of glass blocks differing by 2.9 mole % in CaO content were fused together to form diffusion couples and were held at 880° to 1308°C. The couples were allowed to cool to room temperature and the diffusion which had taken place was measured by optical interferometry and by an electron microprobe. The diffusion coefficients varied from 4.4 × 10⁻¹⁰cm²/sec at 880°C to 8.0 × 10⁻⁸ cm²/sec at 1308°C. The activation energy was 42,000 cal/mole. It is concluded that oxygen diffuses simultaneously with the calcium, maintaining the electrical neutrality of the glass.     

Diffusion of Oxygen in Vitreous Silica

The diffusivity of the oxygen ion in vitreous silica has been directly determined by exchange measurements employing the stable isotope ¹⁸O and mass spectrometer analysis. It was found that over the temperature range 925° to 1225°C the results can be represented by the equation D = 1.51 × 10⁻² exp (-71,200/ RT ) cm² sec⁻¹. These results are compared with other measurements of oxygen diffusion in silicate glasses. It is proposed that the controlling diffusion step in silicate glasses and nonstoichiometric silica is the rupture of a single oxygen bond to silicon and that the diffusion mechanism is interstitial motion through voids in the lattice. An analysis of theoretical expressions for the pre-exponential term D _O shows that present theories are unable to predict D _O for oxygen diffusion in glasses. It is also shown that the mechanism for electrical conduction in vitreous silica or in electrolytically purified quartz is not migration of oxygen ions.     

A low-current Al-gate C-MOS crystal oscillator

The subthreshold properties of MOS transistors have been used advantageously to implement a crystal oscillator that operates at the sub-microampere current levels, using low-voltage metal-gate C-MOS technology. Composed of a reference current generator, a voltage-amplitude regulator, a Pierce oscillator, and an a.c. amplifier, the circuit can be put into a shutdown mode for power conservation.