Survival and growth of Pseudomonas aeruginosa in natural mineral water: a 5-year study

A 5-year study was carried out on the growth curve of two strains of P. aeruginosa inoculated at a density of 10(2) cfu/ml into samples of natural mineral water with different levels of dissolved solids (TDS at 180 degrees C: 72.5 and 382 mg/l) and low organic content (TOC: 0.17 and 0.35 mg/l). The resulting growth curves were similar for both strains, with only slight differences depending on the different amounts of dissolved solids in the water. After 4-5 days counts were increased by 3 log units. This level was maintained until 70-100 days from inoculation, after which a slow decrease began, culminating in the death of one of the strains after 5 years. No difference in recovery was observed between the method using direct inoculation on Cetrimide Agar and the resuscitation technique (preincubation in Tryptone Soya Agar followed by inoculation on Cetrimide Agar) in the exponential phase of the growth curve. During the stationary and death phases, however, the enrichment technique gave statistically slightly higher counts than the selective technique, indicating the presence of damaged P. aeruginosa cells. The use of a resuscitation step when using Cetrimide Agar to assess bottled water quality is recommended.     

Design and performance of the HESSI cryostat

The High Energy Solar Spectroscopic Imager (HESSI) spacecraft, to be launched in July 2000, will be used to observe the Sun with the finest angular and energy resolutions ever achieved from a few keV to hundreds of keV. The spacecraft will use an array of nine germanium (Ge) detectors, each 7.1 cm in diameter and 8.5 cm long, operating at 75 K. The detectors are mounted in a cryostat on a common coldplate, and cooled by a small Stirling-cycle cryocooler. This paper describes the design of the cryostat, special accommodations for the Ge detectors, interfaces with the cryocooler, and thermal performance of the engineering test unit.     

Immunochemical detection of ovalbumin in dairy-based foods

Commercially available antibodies were used for the detection and quantitation of ovalbumin in ice cream and cheese. Electrophoretic separation of protein components, followed by blotting and immunochemical recognition of ovalbumin allowed the detection of the addition of 50 g kg^-1 egg white to processed cheese and allowed detection of egg in ice cream. For quantitative purposes a competitive ELISA method was set up. Calibration curves for ovalbumin in various products were obtained. A marked matrix effect was evident in ice cream, cheese and yoghurt. Different types of cheese gave nearly identical matrix effects. Analytical application of the method should therefore be possible, at least within a given class of products. A study on the influence of thermal treatments on the ELISA response showed that melting of cheese at various temperatures modifies only slightly the ELISA response for ovalbumin.     

Performance Parameters of ATM Networks with Bursts of Errors

In this paper we present the calculation of the error performance of a point-to-point ATM connection transported on an STS-3c SONET (SDH STM-1) interface. The ATM layer performance parameters calculated are Cell Loss Ratio (CLR), Cell Error Ratio (CER), and Severely Errored Cell Block Ratio (SECBR). Statistics of consecutive errored and lost cells are also calculated for each run of the simulation. The physical layer performance parameters such as Bit Error Ratio (BER), Errored Second Ratio (ESR), and Severely Errored Second Ratio (SESR) are compared with corresponding objective values in G.826. The bursty nature of errors in physical communication channels is described by the Hidden Markov Model (HMM) which is obtained from the experimental data. The importance of using this model is demonstrated by the simulation results. The ATM performance for channels with independent errors differs significantly from the ATM performance for channels with bursts of errors and equal bit error ratios.     

Minimax Strategies for Matched-Filter Detection

The best signal and worst jamming are derived for a detection system which uses a matched-filter receiver. The penalty for deviation from the best signal is determined.     

Measurement and modeling of an ultra-wide bandwidth indoor channel

This paper describes the results of frequency-domain channel sounding in residential environments. It consists of detailed characterization of complex frequency responses of ultra-wideband (UWB) signals having a nominal center frequency of 5 GHz. A path loss model as well as a second-order autoregressive model is proposed for frequency response generation of the UWB indoor channel. Probability distributions of the model parameters for different locations are presented. Also, time-domain results such as root mean square delay spread and percent of captured power are presented.     

The intensity of auditory warning tones in the automobile environment: detection and preference evaluations

A variety of auditory warning tones was evaluated to determine generally appropriate intensity levels for presentation in the automobile environment. Twenty-four subjects listened to tones presented at several intensity levels under three background noise conditions recorded in actual vehicles: relatively quiet (35 mile/h (56 km/h), smooth road), relatively loud (55 mile/h (89 km/h), rough road), and radio (35 mile/h (56 km/h), smooth road, and radio broadcast). Data were gathered on the minimum intensity level (in decibels (dB) above the masked threshold (MT) required to achieve a consistent criterion detection rate, as well as the preferred tone intensity level (in dB above the MT) in each background noise condition. The preferred levels were louder than those required to achieve the detection criterion in both the relatively loud and quiet background noise conditions; thus, the preferred levels are the recommended levels under those conditions. This was not the case in the radio condition; therefore, it is recommended that future research efforts evaluate the effects of automatically muting the radio/stereo system when important auditory warning tones are being presented.     

MAP symbol decoding in channels with error bursts

We analyze the forward-backward algorithm for the maximum a posteriori (MAP) decoding of information transmitted over channels with memory and propose a suboptimal forward-only algorithm. We assume that both the information source and channel are described using hidden Markov models (HMMs). The algorithm lends itself to parallel implementation and pipelining. We apply the algorithm to MAP decoding of symbols which were trellis-code modulated and transmitted over channels with error bursts     

Throughput analysis of the go-back-N protocol in fading radiochannels

We derive a formula for calculating the throughput efficiency of the go-back-N (GBN) protocol when error sources in the forward and backward channels are modeled by a hidden Markov model. The result is presented in the matrix form which makes it applicable to models with any number of states. We consider also the relationship between bit-level and block-level models and obtain the probability distribution of the time that a message spends in the system