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Copyright of Boletín de la Sociedad Geológica Mexicana is the property of Sociedad Geologica Mexicana and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Current ethical debates on the use of artificial intelligence (AI) in healthcare treat AI as a product of technology in three ways. First, by assessing risks and potential benefits of currently developed AI-enabled productswith ethical checklists; second, by proposing ex ante lists of ethical values seen as relevant for the design and development of assistive technology, and third, by promoting AI technology to use moral reasoning as part of the automation process. The dominance of these three perspectives in the discourse is demonstrated by a brief summary of the literature. Subsequently, we propose a fourth approach to AI, namely, as a methodological tool to assist ethical reflection. We provide a concept of an AI-simulation informed by three separate elements: 1) stochastic human behavior models based on behavioral data for simulating realistic settings, 2) qualitative empirical data on value statements regarding internal policy, and 3) visualization components that aid in understanding the impact of changes in these variables. The potential of this approach is to inform an interdisciplinary field about anticipated ethical challenges or ethical trade-offs in concrete settings and, hence, to spark a re-evaluation of design and implementation plans. This may be particularly useful for applications that deal with extremely complex values and behavior or with limitations on the communication resources of affected persons (e.g., persons with dementia care or for care of persons with cognitive impairment). Simulation does not replace ethical reflection but does allow for detailed, context-sensitive analysis during the design process and prior to implementation. Finally, we discuss the inherently quantitative methods of analysis afforded by stochastic simulations as well as the potential for ethical discussions and how simulations with AI can improve traditional forms of thought experiments and future-oriented technology assessment. [ABSTRACT FROM AUTHOR]

Continuous-time integrators are a central component in ΔΣ modulators, in analog computers, and general analog signal processing. If several integrators are interconnected, scaling plays an important role: In analog computers, scaling is performed with respect to the machine unit (MU). In ΔΣ modulators, scaling is performed in such a way that at maximum input signal the allowable dynamic range of no integrator is exceeded. In both cases the scaling is a compromise limiting the dynamic range. For analog computers, it was proposed early on to extend the dynamic range by hybrid integrators. Here, an analog range overflow is processed digitally and the analog integrator is reduced to its permissible operating range within the machine unit interval. While in earlier proposals for hybrid integrators only the subsequent integrator stage processes the overflow and works with reduced analog values, our hybrid integrator can process the overflow directly, with the analog reset process being continuous-time. In the case of highly dynamical input signals and transients, analog overload handling is further improved by a prediction of the overload that includes the currently applied input signal in the calculation. For example, with continuous-time ΔΣ modulators, overload of the analog integrator can be reliably avoided. [ABSTRACT FROM AUTHOR]

Locomotion results from an interplay between biomechanical constraints of the muscles attached to the skeleton and the neuronal circuits controlling and coordinating muscle activities. Quadrupeds exhibit a wide range of locomotor gaits. Given our advances in the genetic identification of spinal and supraspinal circuits important to locomotion in the mouse, it is now important to get a better understanding of the full repertoire of gaits in the freely walking mouse. To assess this range, young adult C57BL/6J mice were trained to walk and run on a treadmill at different locomotor speeds. Instead of using the classical paradigm defining gaits according to their footfall pattern, we combined the inter-limb coupling and the duty cycle of the stance phase, thus identifying several types of gaits: lateral walk, trot, out-of-phase walk, rotary gallop, transverse gallop, hop, half-bound, and full-bound. Out-of-phase walk, trot, and full-bound were robust and appeared to function as attractor gaits (i.e., a state to which the network flows and stabilizes) at low, intermediate, and high speeds respectively. In contrast, lateral walk, hop, transverse gallop, rotary gallop, and half-bound were more transient and therefore considered transitional gaits (i.e., a labile state of the network from which it flows to the attractor state). Surprisingly, lateral walk was less frequently observed. Using graph analysis, we demonstrated that transitions between gaits were predictable, not random. In summary, the wild-type mouse exhibits a wider repertoire of locomotor gaits than expected. Future locomotor studies should benefit from this paradigm in assessing transgenic mice or wild-type mice with neurotraumatic injury or neurodegenerative disease affecting gait. [ABSTRACT FROM AUTHOR]

This paper applies some traditional management science tools to the study of Switzerland—a small country characterized by the openness of its politico-economic system to the outside world. Despite its apparent vulnerability to external influences, Switzerland has been able to maintain a remarkable degree of stability throughout the political and economic difficulties of the 1970's and 1980's, in order to help understand the main elements of this ability to absorb major international fluctuations as well as provide decision-makers with ways to analyze them and to investigate the impact of other possible developments, a simulation model of Switzerland has been constructed. This model (SIMSWISS) is based on a representation of the most important sectors of the Swiss politico-economic system, with special emphasis on their connections to the outside. SIMSWISS is constructed via a combination of dynamic simulation and optimization techniques which allow its user to check its accuracy as a representation of reality and to engage in the analysis of possible scenarios and alternative policies. An energy crisis scenario is used to illustrate how the model works and how it can be used to understand the functioning of the Swiss politico-economic system. We hope that this model will serve as the basis for a broader use of management science techniques in the study of other politico-economic systems. [ABSTRACT FROM AUTHOR]

A descriptive comparative study was done to validate the use of the treadmill as an experimental device to investigate the electromyographic (EMG) signal during human locomotion. Eight subjects walked on a walkway and on a treadmill and EMG recordings of several consecutive strides were made during each procedure. These recordings were made from the soleus, rectus femoris, biceps femoris, vastus medialis and tibialis anterior muscles. By using the correlation coefficient and the value of the slope of the regression line resulting from correlating the linear envelopes (digitized at 50 Hz) of EMG activity from the two walk modes, it was shown that similar profiles of EMG activity exist between the walkway and treadmill. This was so for most muscles investigated with one exception, the biceps femoris. Furthermore, there was a tendency for the treadmill data to indicate slightly larger EMG amplitudes, but lower variation, than did the walkway data. However, in view of the overall similarity of the profiles obtained from both conditions, it is concluded that the treadmill is a valid laboratory instrument to study gait. [ABSTRACT FROM PUBLISHER]

Presents a study which describes the application of parallel processing techniques that exploit the irregularly-structured functional parallelism present within a test-bed aerospace system. Overview of a United States Space Shuttle Main Rocket Engine (SSME) simulation; Discussion of the application of deterministic model optimization techniques that facilitate real time execution.

Observed circadian rhythms of nitrate reductase (NR) (EC 1.6.6.1) activity in leaves of barley (Hordeum vulgare L. cv. Herta) under continuous light conditions are described by a simple kinetic model. The oscillatory mechanism has been decomposed into the negative and positive feedback loops which are necessary according to present theories of chemical oscillating systems. Our results indicate that the decrease of NR activity in darkness can be considered as a reversible unimolecular conversion of the active form of NR into an inactive form, forming a negative stabilizing feedback loop. The light‐induced increase of NR activity is related to a positive destabilizing feedback loop. In our treatment this process is represented as an autocatalytical reaction. [ABSTRACT FROM AUTHOR]

A general procedure is presented for the synthesis of active circuits with one-input/ one-output transfer characteristics arbitrarily fixed. The Fortran program that implements this procedure is outlined. The process starts by fitting the curve to be simulated to a piecewise-linear approximation using the least-squares method. Then, the circuit whose transfer characteristic is the piecewise-approximation is calculated. This circuit has two operational amplifiers, working as inverting amplifiers. The program uses as input data only the definition of the function by N points and automatically obtains the breakpoints, the parameters of the straight lines and the mean error of the piecewise-linear approximation, and the parameters of the circuit that synthesizes the function. [ABSTRACT FROM AUTHOR]

An electronic feature-extraction system is presented that simplifies the measurement of five parameters of the action potential. These parameters are: (a) the peak amplitude of the action potential, (b) the maximum slope, (c) the threshold as measured at the inflection on the rising phase of the action potential, (d) the time interval between the inflection and the peak of the action potential, and (e) the time constant of the 'exponentially' rising foot of the action potential. Using this equipment, the foot of the action potential was found in the squid giant axon to be close to a pure exponential only at temperatures less than 15° C. [ABSTRACT FROM AUTHOR]