Synthesis of four-bar mechanisms by Freudenstein–Chebyshev

A new dimensional synthesis method is described in the paper. The position function of the four-bar mechanism is presented by the Freudenstein’s equation and it is minimized by the Chebyshev’s best approximation theory. The target function is used as an exactly satisfied equation and the Freudenstein’s equation is considered as a Chebyshev’s polynomial. In some cases the method provides possibilities to find simple solutions of the synthesis tasks. These solutions are known as the best Chebyshev’s approach of the weighted target function. This approach is near the best one for the original target function. A numerical example given here explains the essence of the method.     

Perfectionism: conceptual and clinical aspects

OBJECTIVE: Study of the concept of perfectionism and its phenomenology, etiology, and treatment. METHODS: Review of the literature, phenomenological, and-clinical analyses. RESULTS: The International Classification of Diseases introduced the notion of perfectionism into psychiatric discourse in 1977. In DSM-III, DSM-III-R, and DSM-IV, perfectionism is a diagnostic criterion of obsessive-compulsive disorder, but has never been defined in the psychiatric literature. We differentiate normal perfectionism and pathological perfectionism, which is of some psychiatric interest: normal perfectionism is manifested according to the aptness of the target and its sociocultural value, and is therefore selective and flexible, whereas pathological perfectionism is the compulsive pursuit of a performance level not required by the circumstances and idiosyncratic in nature. Its symptomatology may resemble that of obsessive-compulsive disorder, but is actually quite different: whereas obsessive-compulsive symptoms are absurd and the product of ego-dystonic compulsion, pathological perfectionism is experienced as a personal obligation, and retain an identifiable cultural objective. CONCLUSIONS: The phenomenology of the normal and abnormal manifestations of perfectionism is well defined. While pathological perfectionism and obsessive-compulsive disorder are similar and may even share a common etiology, they should be considered 2 distinct clinical entities. The therapeutic approaches to pathological perfectionism remain empirical.     

Induction of cachexia in mice by a product isolated from the urine of cachectic cancer patients

Urine from cancer patients with weight loss showed the presence of an antigen of M(r) 24,000 detected with a monoclonal antibody formed by fusion of splenocytes from mice with cancer cachexia. The antigen was not present in the urine of normal subjects, patients with weight loss from conditions other than cancer or from cancer patients who were weight stable or with low weight loss (1 kg month(-1)). The antigen was present in the urine from subjects with carcinomas of the pancreas, breast, lung and ovary. The antigen was purified from urine using a combination of affinity chromatography with the mouse monoclonal antibody and reversed-phase high-performance liquid chromotography (HPLC). This procedure gave a 200,000-fold purification of the protein over that in the original urine extract and the material isolated was homogeneous, as determined by silver staining of gels. The N-terminal amino acid sequence showed no homology with any of the recognized cytokines. Administration of this material to mice caused a significant (P<0.005) reduction in body weight when compared with a control group receiving material purified in the same way from the urine of a normal subject. Weight loss occurred without a reduction in food and water intake and was prevented by prior administration of the mouse monoclonal antibody. Body composition analysis showed a decrease in both fat and non-fat carcass mass without a change in water content. The effects on body composition were reversed in mice treated with the monoclonal antibody. There was a decrease in protein synthesis and an increase in degradation in skeletal muscle. Protein degradation was associated with an increased prostaglandin E2 (PGE2) release. Both protein degradation and PGE2 release were significantly reduced in mice pretreated with the monoclonal antibody. These results show that the material of M(r) 24,000 present in the urine of cachectic cancer patients is capable of producing a syndrome of cachexia in mice.     

A mathematical model for foreign body reactions in 2D

The foreign body reactions are commonly referred to the network of immune and inflammatory reactions of human or animals to foreign objects placed in tissues. They are basic biological processes, and are also highly relevant to bioengineering applications in implants, as fibrotic tissue formations surrounding medical implants have been found to substantially reduce the effectiveness of devices. Despite of intensive research on determining the mechanisms governing such complex responses, few mechanistic mathematical models have been developed to study such foreign body reactions. This study focuses on a kinetics-based predictive tool in order to analyze outcomes of multiple interactive complex reactions of various cells/proteins and biochemical processes and to understand transient behavior during the entire period (up to several months). A computational model in two spatial dimensions is constructed to investigate the time dynamics as well as spatial variation of foreign body reaction kinetics. The simulation results have been consistent with experimental data and the model can facilitate quantitative insights for study of foreign body reaction process in general.     

Distribution of physics literature

Percentage distributions of physics papers in 36 countries over ten subfields are compared. Factor and cluster analyses are applied to data from 1978Physics Abstracts. Countries load highly on seven factors. Their meaning is estimated by factor scores. Clusters of countries with similar publishing patterns are presented in a tree diagram.     

Bend sensing with long-period fiber gratings in capillaries embedded in structures

Bend responses of an LPG inscribed with a CO₂ laser in a conventional single-mode fiber are investigated in an arrangement, where the LPG is inserted into a thin silica capillary bonded to a steel strip. The curvature of the strip, laid on two supports and bent with a micrometer driver in the middle between the supports, decreases linearly with distance from the center of bending to the supports. Experiments are done for a very large range of bend deflections with the LPG in three positions shifted with respect to the center of bending, and two distinct opposite rotational orientations with respect to the plane of bending. Responses obtained for the above positions and orientations are greatly different and some of them show features which have not been reported for LPGs bent with a constant curvature and smaller deflections. They are, particularly, maxima and minima of the central wavelength's shift along with reversals of its direction, or the reappearance of a previously vanished attenuation band with increasing magnitude of bending. Also, it is found that the responses depend not only on the average curvature of the bent LPG, but also on the particular dependence of the curvature along the LPG's length. Some of the results obtained cannot be satisfactorily explained at the present level of knowledge, and a more thorough theoretical analysis is needed.     

Stochastic optimal control and estimation methods adapted to the noise characteristics of the sensorimotor system

Optimality principles of biological movement are conceptually appealing and straightforward to formulate. Testing them empirically, however, requires the solution to stochastic optimal control and estimation problems for reasonably realistic models of the motor task and the sensorimotor periphery. Recent studies have highlighted the importance of incorporating biologically plausible noise into such models. Here we extend the linear-quadratic-gaussian framework--currently the only framework where such problems can be solved efficiently--to include control-dependent, state-dependent, and internal noise. Under this extended noise model, we derive a coordinate-descent algorithm guaranteed to converge to a feedback control law and a nonadaptive linear estimator optimal with respect to each other. Numerical simulations indicate that convergence is exponential, local minima do not exist, and the restriction to nonadaptive linear estimators has negligible effects in the control problems of interest. The application of the algorithm is illustrated in the context of reaching movements. A Matlab implementation is available at www.cogsci.ucsd.edu/~todorov.     

Direct measurements of the self-capacitance of induction coils

Conclusions A resonance method which provides greater precision than other known methods for evaluating the self-capacitance C_c of induction coils has been described. It is possible to measure at frequencies considerably lower than the natural resonant frequency of the measured coil and in evaluating C_c to eliminate completely the error due to inaccurate setting of the frequency, and reduce to an insignificant value the error due to inaccurate estimation of the supplementary capacitance.The proposed circuit can be implemented by means of normal components, such as variable capacitors and diodes, and can be assembled in the form of an attachment either built-in or separate from inductance meters.     

A new look at the robust control of discrete-time Markov jump linear systems

In this paper, we make a foray in the role played by a set of four operators on the study of robust H₂ and mixed H₂/H_∞ control problems for discrete-time Markov jump linear systems. These operators appear in the study of mean square stability for this class of systems. By means of new linear matrix inequality (LMI) characterisations of controllers, which include slack variables that, to some extent, separate the robustness and performance objectives, we introduce four alternative approaches to the design of controllers which are robustly stabilising and at the same time provide a guaranteed level of H₂ performance. Since each operator provides a different degree of conservatism, the results are unified in the form of an iterative LMI technique for designing robust H₂ controllers, whose convergence is attained in a finite number of steps. The method yields a new way of computing mixed H₂/H_∞ controllers, whose conservatism decreases with iteration. Two numerical examples illustrate the applicability of the proposed results for the control of a small unmanned aerial vehicle, and for an underactuated robotic arm.