Calculating quantities of ice for cooling and maintenance of freshly harvested fish at sea.

UNLABELLED: A new generalized model for predicting quantities of ice to cool and maintain freshly harvested fish at sea in insulated boxes is presented. The model addresses the universal need for fisherman to know in advance of going to sea just how much ice will be needed to cool down the expected day's catch to a desired temperature, maintain the catch, and to allow for losses. Illustrative predictions are presented for southern bluefin tuna (SBT) (Thunnus maccoyii) for a range of day's catch from 2000 to 8000 kg in ambient temperature ranging from 15 to 35 °C. The amount of ice needed to cool down SBT from an initial uniform harvest temperature of 28 °C to a maintenance temperature of 5 °C is shown to be the controlling contribution to total ice needed. Predictions highlight that a useful, safe rule-of-thumb is 1 kg of ice will be needed for each 3.5 kg of SBT. Importantly, the model is based on fundamental principles and predictive accuracy is demonstrated to be largely insensitive to a range of assumptions including volume of the void in the insulated boxes and overall coefficient of heat influx from ambient. The model can be used to predict the number of insulated boxes of defined dimension that will be needed to cool and hold the fish, ice and water for a wide range of fish species. It will be of interest to fisherman and boat owners and agents who invest in ice to preserve fish at sea. PRACTICAL APPLICATION: This research addresses the universal need for fisherman to know in advance of going to sea how much ice will be needed on-board boats to cool down an expected day's catch to a desired temperature, maintain the catch and to allow for losses. The model is generalized and can be applied to a wide range of fish species.

Localization and characterization of speech arrest during transcranial magnetic stimulation.

OBJECTIVE: To determine the anatomic and physiologic localization of speech arrest induced by repetitive transcranial magnetic stimulation (rTMS), and to examine the relationship of speech arrest to language function. METHODS: Ten normal, right-handed volunteers were tested in a battery of language tasks during rTMS. Four underwent mapping of speech arrest on a 1 cm grid over the left frontal region. Compound motor action potentials from the right face and hand were mapped onto the same grid. Mean positions for speech arrest and muscle activation were identified in two subjects on 3-dimensional MRI. RESULTS: All subjects had lateralized arrest of spontaneous speech and reading aloud during rTMS over the left posterior-inferior frontal region. Writing, comprehension, repetition, naming, oral praxis, and singing were relatively spared (P < .05). Stimulation on the right during singing abolished melody in two subjects, but minimally affected speech production. The area of speech arrest overlay the caudal portion of the left precentral gyrus, congruous with the region where stimulation produced movement of the right face. CONCLUSIONS: The site of magnetic speech arrest appears to be the facial motor cortex. Its characteristics differ from those of classic aphasias, and include a prominent dissociation among different types of speech output.

Significance of pre-incubation temperature and inoculum concentration on subsequent growth of Listeria monocytogenes at 14 degrees C.

The influence of the bacterial concentration of an inoculum (10(1) or 10(3) cfu ml-1) of two strains of Listeria monocytogenes (Scott A: serotype 4b and V7: serotype 1) and one strain of L. innocua (Lin 11), and the time and temperature at which the inoculum was stored (cold storage: 4 degrees C for 4 weeks, or without cold storage: -20 degrees C before immediate transfer), and the temperature at which cells were pre-incubated (30 degrees C and 14 degrees C) on subsequent growth in Richard's broth at 14 degrees C was investigated. Richard's broth at a pH 5.9 was used to simulate potential growth in soft cheese (camembert type) and an incubation temperature of 14 degrees C was used to simulate storage-temperature ripening of cheese. Enumeration of the number of viable cells was by plate count method, except where viable cell numbers were less that 10(3) cfu ml-1, when the MPN (Most Probable Number) technique was used. With cold storage and an inoculum of 10(3) cfu ml-1 (high bacterial concentration) the pre-incubation temperatures (30 degrees C and 14 degrees C) did not significantly influence the subsequent growth curve: there was no significant lag (less that 21 h) and cell numbers peaked in about 8.5 d. However, with cold storage and an inoculum of 10(1) cfu ml-1 (low bacterial concentration) and a pre-incubation temperature of 30 degrees C a significant shift in the growth curve was observed over that pre-incubated at f14 degrees C, with the appearance of a lag of about 7.7 d. At a pre-incubation temperature of 14 degrees C with the low inoculum concentration, there was a measurable lag of about 1 d. Without cold storage and a pre-incubation temperature of 30 degrees C, there was a lag time of 2.3 d. Storage conditions, pre-incubation temperature and inoculum concentration therefore appear to influence the subsequent growth curve. Importantly, however, the growth curves for cultures from inocula, pre-incubated at either 30 degrees C or 14 degrees C, appeared to involve two distinct values of the exponential growth rate (k): the initial portion of the growth curve described by a low value of k and the subsequent portion by a consistently and significantly greater value. The appearance of two distinct growth phases was reproduced in further data determined for all the studied strains of the microorganism. Further study to explain these unexpected and reproducible findings is being conducted.

Modelling the combined effect of temperature and pH on the rate coefficient for bacterial growth.

An extension of a model of Davey (1989a) has been used to model data of Adams et al. (1991) describing the combined effect of temperature and pH on the rate coefficient for growth of Yersinia enterocolitica in liquid media acidified with four different acidulants: sulphuric, citric, lactic and acetic acids. The model explained between 97.8% and 99.1% of the variance in the results. This very good fit between the predictions and the observed data confirms pH can be incorporated into a model that had previously been applied to the combined effect of temperature and water activity, and to the effect of temperature alone. These findings, taken together with previously reported results, demonstrate the value of the model for predicting the combined effect of two environmental factors on the growth rate. Based on results reported in this paper and previously reported results, a generalised model is proposed for the combined effect of three or more environmental factors, that is amenable to testing.

Cause of death in multiple endocrine neoplasia type 1.

OBJECTIVE: Little data are available on the natural history of untreated multiple endocrine neoplasia type 1 (MEN-1). These data are essential in deciding treatment that may carry significant morbidity. We determined the causes of death in a large MEN-1 kindred with data available over a period of 130 years. Most cases were unrecognized as MEN-1 at the time of patient's death. DESIGN: Retrospective study of recorded medical data from 1861 to 1991. PATIENTS: One hundred fifty-nine deaths occurred, of which 46 were in individuals classified as "highly probable" of having MEN-1. RESULTS: Of 46 deaths in those classified as "highly probable" of having MEN-1, 20 (43.5%) died of a recognized complication of MEN-1 (12 of malignant neoplasms, six of renal calculi, and two of peptic ulcer). If accidental deaths are excluded, 50% of the deaths in patients with MEN-1 were the result of MEN-1, and the mean age of death (50.9 years)was significantly younger than that of other family members. CONCLUSIONS: It is concluded that MEN-1 leads to premature death, and that neoplasia rather than peptic ulcer disease is the main cause of death. Deaths from pituitary tumor or malignant endocrine tumors within the thorax were just as common or more common than deaths from pancreatic malignant neoplasms.

Magnetic brain stimulation and brain size: relevance to animal studies.

Magnetic brain stimulation (MBS) is widely used for the investigation of brain function in man, but there have been only a few reports of its safety in animals. These results were predominantly benign, but the effectiveness of stimulation in animals is unclear. Because the stimulators produced obvious motor effects in humans, or had a comparable peak magnetic field strength, they were assumed to produce comparable electric field intensities and neuronal effects in animal brains. We tested this assumption using 3 stimulus coils of different sizes and design, plus 6 saline-filled spheres that spanned a range of volume from 0.5 to 1800 ml. The induced electric field diminished monotonically with decreasing radius, by factors of 4.7-6.2 at the extremes of size. Comparable results were found using a mathematical model. These results suggest that the efficiency of magnetic stimulation is drastically reduced in smaller brains, and that threshold and safety studies in some animal models may not be valid.

Prediction of magnetically induced electric fields in biological tissue.

There are many potential medical applications in which it is desirable to noninvasively induce electric fields. One such application that serves as the backdrop of this work is that of stimulating neurons in the brain. The magnetic fields necessary must be quite high in magnitude, and fluctuate rapidly in time to induce the internal electric fields necessary for stimulation. Attention is focused on the calculation of the induced electric fields commensurate with rapidly changing magnetic fields in biological tissue. The problem is not a true eddy current problem in that the magnetic fields induced do not influence the source fields. Two techniques are introduced for numerically predicting the fields, each employing a different gauge for the potentials used to represent the electric field. The first method employs a current vector potential (analogous to A in classical magnetic field theory where DEL x A = B) and is best suited to two-dimensional (2-D) models. The second represents the electric field as the sum of a vector plus the gradient of a scalar field; because the vector can be determined quickly using Biot Savart (which for circular coils degenerates to an efficient evaluation employing elliptic integrals), the numerical model is a scalar problem even in the most complicated three dimensional geometry. These two models are solved for the case of a circular current carrying coil near a conducting body with sharp corners.

Localizing the site of magnetic brain stimulation in humans.

Magnetic stimulation of the human brain is performed in clinical and research settings, but the site of activation has not been clearly localized in humans or other species. We used a set of magnetic stimulus coils with different field profiles to isolate movement of single digits at motor threshold and to calculate corresponding electric field strengths at various distances beneath the scalp. Two coils could produce the same electric field intensity at only 1 point. Thus, we could estimate the depth of stimulation by finding the intersection of the electric field plots, which were then superimposed on MRIs of the underlying brain. In each of 3 subjects the field plots intersected at the crown of a gyrus, in the region of the central sulcus, an near the level of the gray-white junction. This position and the electric field orientation support localization to layer VI of cerebral cortex.

Equilibrium temperature in a clump of bacteria heated in fluid.

A theoretical model was developed and used to estimate quantitatively the "worst case", i.e., the longest, time to reach equilibrium temperature in the center of a clump of bacteria heated in fluid. For clumps with 10 to 10(6) cells heated in vapor, such as dry and moist air, and liquid fluids such as purees and juices, predictions show that temperature equilibrium will occur with sterilization temperatures up to 130 degrees C in under 0.02 s. Model development highlighted that the controlling influence on time for heating up the clump is the surface convection thermal resistance and that the internal conduction resistance of the clump mass is negligible by comparison. The time for a clump to reach equilibrium sterilization temperature was therefore decreased with relative turbulence (velocity) of the heating fluid, such as occurs in many process operations. These results confirm widely held suppositions that the heat-up time of bacteria in vapor or liquid is not significant with usual sterilization times.

A predictive model for combined temperature and water activity on microbial growth during the growth phase.

An empirical and generalized model is presented, based on a modified Arrhenius equation, for predicting the combined effect of temperature and water activity on the growth rate of bacteria. When it was applied to seven separate sets of wide ranging published results, spanning some 50 years and including a spore-former and a silage micro-organism, predictions explained between 92.9 and 99.0% of the variation in the results with an overall mean of 96.6%. Advantages over existing models are that it is relatively easy to fit to data using least squares regression and requires only five coefficients. These, together with its simplicity and demonstrated wide application, will facilitate its practical use.

Effect of chilling on the hardness of fat on sides of beef.

The effect of chilling procedure on the resulting hardness (i.e. cutability) of subcutaneous adipose tissue (fat) on sides of beef has been objectively investigated using a sliding pin consistometer (SPC). Instrument readings obtained from a model system of samples of beef dripping (made with subcutaneous adipose tissue and kidney fat but without added bone trim) indicated fat hardness could be significantly (P < 0·05) influenced by chilling procedure. However, for sides from 19 grass-fed animals which were chilled using either a 'hot' or 'cold' extreme treatment which would comply with current Australian Regulations (i.e. 20°C deep butt temperature in 20h) there was no significant difference 20 h post mortem between the hardness of the fat at a temperature of 10°C. It would appear, therefore, that the hardness of the fat on sides of chilled beef cannot be managed through manipulation of the chilling procedure in conventional processing.

Design of an integral computer-based wheelchair controller/linear synchronous motor system.

The purpose of this paper is to illustrate the advantages of designing computer-based motor controllers together with innovative motors, such that maximum controller/motor system benefits are obtained. Specifically, this paper describes how a computer-based controller/drive system for powered wheelchairs has been designed and is being built and tested. This type of integral controller/drive system has been possible to build into a wheelchair only with the advent of the microprocessor-based feedback motor controller. The type of motor chosen for this project was a linear synchronous motor (LSM), which is highly efficient (90%+) and could easily be made an integral part of a wheelchair wheel, providing a "no-moving-parts" drive system. However, an LSM cannot be variable-speed-controlled without knowledge of, and controlled adjustment to, the absolute rotor versus stator position at each point in time. Microprocessor-based feedback motor controllers make precise, efficient control of LSMs possible at a reasonable cost. In addition, this combination of controller and motor provides a very flexible wheelchair control/drive system that may be easily programmed to suit the needs and necessities of the wide variety of over 200,000 persons now using powered wheelchairs.