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The single roots sigmoid model of population dynamics is proposed as a mechanism for enzyme kinetics. Within this paradigm enzyme co‐operativity is analyzed, deriving an alternate formulation for the Hill coefficient and the binding polynomials.

The possibilities that a general autonomous and deterministic dynamical system offers as a model for a single species population is explored in detail. As an application of the algorithm derived from this study, the model is successfully adapted to several concrete situations.

The classical models for volumelry of the heart's left ventricle are based upon the simplifying assumption that this chamber is an ellipsoid. This simplification is needed in order to manually process radiographic images of the left ventricle. Computer processing of these images allows a much more realistic approach by associating with the left ventricle a topologically deformed ellipsoid, which approximately is its actual shape. This is the model proposed and analysed in this paper; from this model an algorithm is derived for accurately calculating left ventricle volumetry. This algorithm is simple enough to be implemented on most microcomputers provided with an analog‐to‐digital converter, like joystick, or a magic pen or digitizer. By this procedure the assessing of hemodynamical parameters can be performed in a few minutes with a great improvement in accuracy as compared with classical methods.

Analyses the possibility of allowing non‐linear synaptic processing in Artificial Neural Networks (ANN) both theoretically and practically. The simple computer simulations described strongly suggest that this is a viable alternative, and preferable to ANN with just linear synapses, because of the savings in hardware (fewer components are needed) and software (reduction in training time) when dealing with similar problems. Derives some considerations regarding a possible relationship between the parallel processor proposed and living nerve cells.

The mathematical model and computer algorithm reported in a previous issue of this journal have been tested on 21 normal heart moulds by comparing the true volume value, measured by Archimedes' principle, with the predicted theoretical volume.

Proposes a modified Hill model for the oxyhaemoglobin dissociation curve. The model fits normal oxyhaemoglobin dissociation experimental data quite accurately, and can easily be adapted to experimental data of subjects suffering haemoglobinopathies when available. Discusses the Adair equation, as well as correcting factors for varying temperature and pH.

The area of artificial neural networks, which dates back to the early twentieth century, could only offer positive contributions to technology after the back‐propagation algorithm was proposed in 1986. In this note an alternative algorithm to the gradient descent used in back‐propagation is proposed. This algorithm is based on the discrete central difference. This procedure, as opposed to the back‐propagation algorithm, offers the possibility of true parallel computation.

The purpose of this paper is to provide a study of inertial propulsion.

In this paper, the theory of inertial propulsion under dry friction and under viscous friction is developed.

As inertia propelled devices do not have any external moving parts; the propelling mechanism is completely enclosed inside the device. For inertial propulsion under dry friction, the equations of movement are explicitly derived and provided in closed form, so that such a device can be designed with its parameters computed exactly. For inertial propulsion under viscous friction, on the other hand, there is no closed form for the equations of movement, its dynamics are provided so that a device can be designed using a computer algebra system, as illustrated in the paper.

The paper demonstrates that an inertia propelled device under dry friction moves in the opposite direction than the same device under viscous friction.

Presents an optimal strategy for managing crocodile farms. The strategy is illustrated with the case study of Caiman Crocodilus Yacare of the farm Coocrijapan. However, the strategy can be easily transferred to other farms, once sufficient data on their own crocodile stock is gathered. The main advantage of the ideas developed is that they deal with just one parameter: the break‐even point of the process. The underlying assumption of having a single parameter is that there is no seasonal change in prices; that is, the unitary price of food (say, per kilogram) and the unitary price of crocodile hide (say, per square centimetre) remain approximately constant in some currency. This may or may not be true in the local currency of the country that hosts the farm. With this assumption, dimensionless quantities for profit and return are found.

This paper focusses on how the educated and less-educated middle class react differently to income increases, against an intertwined literature backdrop of Engel's law, quality of life, aspirational and conspicuous consumption. The paper seeks to answer two main questions: Is there evidence of the middle class, particularly the educated, trying to emulate the upper class by shifting towards aspirational consumption? Is there any distinct expenditure behaviour amongst the middle class?

Combining the Malaysian 2016 Household Expenditure Survey (HES) and the 2016 Consumer Price Indices datasets, quantile estimations are applied on the merged dataset of 14,326 households.

There is evidence of the educated middle class emulating the upper class in terms of food share, home furnishing and starchy produce expenditure behaviour. The less-educated middle class exhibits a predilection for home furnishing expenditures when income increases, whilst the educated shows signs of dissociating themselves from such material acquisitions. The paper concludes that the middle class is collectively an aspirational class, but with diverging paths towards upward social mobility between the educated and less-educated households.

Aspirational consumption of the middle class has not been given detailed empirical treatment at the household micro-level in the literature, especially for upper-middle income countries like Malaysia. The paper starts off by detecting an anomaly in the Engel's food share coefficients, where the middle class sees unexpected larger declines in food share than those of the upper class. This is the paper's departure point from the literature.