Fixed-point DSP implementation of nonlinear H(infinity) controller for large gap electromagnetic suspension system

Electromagnetic suspension systems are inherently nonlinear and often face hardware limitation when digitally controlled. The main contributions of this paper are: the design of a nonlinear H(infinity) controller. including dynamic weighting functions, applied to a large gap electromagnetic suspension system and the presentation of a procedure to implement this controller on a fixed-point DSP, through a methodology able to translate a floating-point algorithm into a fixed-point algorithm by using l(infinity) norm minimization due to conversion error. Experimental results are also presented, in which the performance of the nonlinear controller is evaluated specifically in the initial suspension phase. (C) 2009 Elsevier Ltd. All rights reserved.

Postural control during kneeling

Postural control was studied when the subject was kneeling with erect trunk in a quiet posture and compared to that obtained during quiet standing. The analysis was based on the center of pressure motion in the sagittal plane (CPx), both in the time and in the frequency domains. One could assume that postural control during kneeling would be poorer than in standing because it is a less natural posture. This could cause a higher CPx variability. The power spectral density (PSD) of the CPx obtained from the experimental data in the kneeling position (KN) showed a significant decrease at frequencies below 0.3 Hz compared to upright (UP) (P < 0.01), which indicates less sway in KN. Conversely, there was an increase in fast postural oscillations (above 0.7 Hz) during KN compared to UP (P < 0.05). The root mean square (RMS) of the CPx was higher for UP (P < 0.01) while the mean velocity (MV) was higher during KN (P < 0.05). Lack of vision had a significant effect on the PSD and the parameters estimated from the CPx in both positions. We also sought to verify whether the changes in the PSD of the CPx found between the UP and KN positions were exclusively due to biomechanical factors (e.g., lowered center of gravity), or also reflected changes in the neural processes involved in the control of balance. To reach this goal, besides the experimental approach, a simple feedback model (a PID neural system, with added neural noise and controlling an inverted pendulum) was used to simulate postural sway in both conditions (in KN the pendulum was shortened, the mass and the moment of inertia were decreased). A parameter optimization method was used to fit the CPx power spectrum given by the model to that obtained experimentally. The results indicated that the changed anthropometric parameters in KN would indeed cause a large decrease in the power spectrum at low frequencies. However, the model fitting also showed that there were considerable changes also in the neural subsystem when the subject went from standing to kneeling. There was a lowering of the proportional and derivative gains and an increase in the neural noise power. Additional increases in the neural noise power were found also when the subject closed his eyes.

Chaotic Synchronization in Discrete-Time Systems Connected by Bandlimited Channels

Due to the broadband characteristic of chaotic signals, many of the methods that have been proposed for synchronizing chaotic systems do not usually present a satisfactory performance when applied to bandlimited communication channels. Here, the effects of bandwidth limitations imposed by the channel on the synchronous solution of a discrete-time chaotic master-slave network are investigated. The discrete-time system considered in this study is the Henon map. It is analytically shown that synchronism can be achieved in such a network by introducing a digital filter in the feedback loop responsible for generating the chaotic signal that will be sent to the slave node. Numerical simulations relating the filter parameters, such as its order and cut-off frequency, to the maximum Lyapunov exponent of the master node, which determines if the transmitted signal is chaotic or not, are also presented. These results can be useful for practical communication schemes based on chaos.

Linear minimum mean square filter for discrete-time linear systems with Markov jumps and multiplicative noises

In this paper we obtain the linear minimum mean square estimator (LMMSE) for discrete-time linear systems subject to state and measurement multiplicative noises and Markov jumps on the parameters. It is assumed that the Markov chain is not available. By using geometric arguments we obtain a Kalman type filter conveniently implementable in a recurrence form. The stationary case is also studied and a proof for the convergence of the error covariance matrix of the LMMSE to a stationary value under the assumption of mean square stability of the system and ergodicity of the associated Markov chain is obtained. It is shown that there exists a unique positive semi-definite solution for the stationary Riccati-like filter equation and, moreover, this solution is the limit of the error covariance matrix of the LMMSE. The advantage of this scheme is that it is very easy to implement and all calculations can be performed offline. (c) 2011 Elsevier Ltd. All rights reserved.

On state representations of time-varying nonlinear systems

This work considers a nonlinear time-varying system described by a state representation, with input u and state x. A given set of functions v, which is not necessarily the original input u of the system, is the (new) input candidate. The main result provides necessary and sufficient conditions for the existence of a local classical state space representation with input v. These conditions rely on integrability tests that are based on a derived flag. As a byproduct, one obtains a sufficient condition of differential flatness of nonlinear systems. (C) 2009 Elsevier Ltd. All rights reserved.

Contribution of peripheral vanilloid receptor to the nociception induced by injection of spermine in mice

Polyamines (putrescine, spermidine and spermine) are important endogenous regulators of ion channels, such as vanilloid (TRPV1), glutamatergic (NMDA or AMPA/kainate) and acid-sensitive (ASIC) receptors. In the present study, we have investigated the possible nociceptive effect induced by polyamines and the mechanisms involved in this nociception in vivo. The subcutaneous (s.c.) injection of capsaicin (as positive control), spermine, spermidine or putrescine produced nociception with ED(50) of 0.16 (0.07-0.39) nmol/paw, 0.4 (0.2-0.7) mu mol/paw, 0.3 (0.1-0.9) mu mol/paw and 3.2 (0.9-11.5) mu mol/paw, respectively. The antagonists of NMDA (MK801, 1 nmol/paw), AMPA/kainate (DNQX, 1 nmol/paw) or ASIC receptors (amiloride, 100 nmol/paw) failed to reduce the spermine-trigged nociception. However, the TRPV1 antagonists capsazepine or SB366791 (1 nmol/paw) reduced spermine-induced nociception, with inhibition of 81 +/- 10 and 68 +/- 9%, respectively. The previous desensitization with resiniferatoxin (RTX) largely reduced the spermine-induced nociception and TRPV1 expression in the sciatic nerve, with reductions of 82 +/- 9% and 67 +/- 11%, respectively. Furthermore, the combination of spermine (100 nmol/paw) and RTX (0.005 fmol/paw), in doses which alone were not capable of inducing nociception, produced nociceptive behaviors. Moreover, different concentrations of spermine (3-300 mu M) enhanced the specific binding of [(3)H](center dot)-RTX to TRPV1 receptor. Altogether, polyamines produce spontaneous nociceptive effect through the stimulation of TRPV1, but not of ionotropic glutamate or ASIC receptors. (C) 2011 Elsevier Inc. All rights reserved.

Sudden onset of log-periodicity and superdiffusion in non-Markovian random walks with amnestically induced persistence: exact results

Random walks can undergo transitions from normal diffusion to anomalous diffusion as some relevant parameter varies, for instance the L,vy index in L,vy flights. Here we derive the Fokker-Planck equation for a two-parameter family of non-Markovian random walks with amnestically induced persistence. We investigate two distinct transitions: one order parameter quantifies log-periodicity and discrete scale invariance in the first moment of the propagator, whereas the second order parameter, known as the Hurst exponent, describes the growth of the second moment. We report numerical and analytical results for six critical exponents, which together completely characterize the properties of the transitions. We find that the critical exponents related to the diffusion-superdiffusion transition are identical in the positive feedback and negative feedback branches of the critical line, even though the former leads to classical superdiffusion whereas the latter gives rise to log-periodic superdiffusion.

Effect of estradiol benzoate microinjection into the median raphe nucleus on contextual conditioning

Estrogen deficiency has been associated with stress, anxiety and depression. Estrogen receptors have been identified in the median raphe nucleus (MRN). This structure is the main source of serotonergic projections to the hippocampus, a forebrain area implicated in the regulation of defensive responses and in the resistance to chronic stress. There is reported evidence indicating that estrogen modulates 5-HT(1A) receptor function. In the MRN, somatodendritic 5-HT(1A) receptors control the activity of serotonergic neurones by negative feedback. The present study has evaluated the effect of intra-MRN injection of estradiol benzoate (EB, 600 or 1200 ng/0.2 mu l) on the performance of ovariectormized rats submitted to contextual conditioning. Additionally, the same treatment was given after intra-MRN injection of Way 100635 (100 ng/0.2 mu l). a 5-HT(1A) receptor antagonist. Both doses of EB decreased freezing and increased rearing, indicating an anxiolytic effect. Pretreatment with Way 100635 antagonized the anxiolytic effect of estradiol. On the basis of these results, it may be suggested that estrogens modulate anxiety by acting on 5-HT(1A) receptors localized in the MRN. (C) 2009 Elsevier B.V. All rights reserved.

Mutations of the thyroglobulin gene and its relevance to thyroid disorders

Purpose of review To perform an update review on thyroglobulin gene mutations associated with congenital hypothyroidism, thyroid cancer, and autoimmunity. Recent findings Forty-two thyroglobulin mutations have been identified in dyshormonogenetic congenital hypothyroidism. Clinical and laboratory criteria defining defective thyroglobulin synthesis are mostly related to thyroglobulin mutations, generally caused by intracellular thyroglobulin transport defects to the colloid rather than defects in thyroid hormones synthesis. Some mutated thyroglobulin may escape the rigorous chaperone control and reach the colloid, allowing a wide phenotypic spectrum that includes euthyroidism in an adequate iodine environment. In some patients, continuous levothyroxine treatment does not reduce elevated serum thyroid-stimulating hormone (TSH) levels that may lead to goiter development. Prenatally, inactive mutant thyroglobulin will not be able to synthesize thyroid hormones and may increase pituitary thyrotroph threshold for thyroid hormone feedback. Congenital goiter is a risk factor for thyroid cancer and some thyroglobulin variants may confer susceptibility to thyroid autoimmunity. Summary Advances in the understanding of thyroglobulin genetic defects and its severity should allow researchers to perform adequate molecular diagnosis, genetic counseling, and intrauterine treatment to prevent subtle deficits in central nervous system development. This knowledge should improve the understanding of physiological functions of the thyroid and influence of nutritional iodine.

Stuttering treatment control using P300 event-related potentials

Positron emission tomography studies during speech have indicated a failure to show the normal activation of auditory cortical areas in stuttering individuals. In the present study, P300 event-related potentials were used to investigate possible effects of behavioral treatment on the pattern of signal amplitude and latency between waves. In order to compare variations in P300 measurements, a control group paired by age and gender to the group of stutterers, was included in the study. Findings suggest that the group of stutterers presented a significant decrease in stuttering severity after the fluency treatment program. Regarding P300 measurements, stutterers and their controls presented results within normal limits in all testing situations and no significant statistical variations between pre and post treatment testing. When comparing individual results between the testing situations, stutterers presented a higher average decrease in wave latency for the right ear following treatment. The results are discussed in light of previous P300 event-related potentials and functional imaging studies with stuttering adults. Educational objectives: The reader will learn about and be able to describe the: (1) use of P300 event-related potentials in the study of stuttering; (2) differences between stuttering and non-stuttering adults; and (3) effects of behavioral fluency treatment on cerebral activity in stuttering speakers. (C) 2011 Elsevier Inc. All rights reserved.

Neuropeptide Y in Rat Spiral Ganglion Neurons and Inner Hair Cells of Organ of Corti and Effects of a Nontraumatic Acoustic Stimulation

Neuropeptide Y (NPY) is an important neuromodulator found in central and peripheral neurons. NPY was investigated in the peripheral auditory pathway of conventional housed rats and after nontraumatic sound stimulation in order to localize the molecule and also to describe its response to sound stimulus. Rats from the stimulation experiment were housed in monitored sound-proofed rooms. Stimulated animals received sound stimuli (pure tone bursts of 8 kHz, 50 ms duration presented at a rate of 2 per second) at an intensity of 80 dB sound pressure level for 1 hr per day during 7 days. After euthanizing, rat cochleae were processed for one-color immunohistochemistry. The NPY immunoreactivity was detected in inner hair cells (IHC) and also in pillar and Deiters` cells of organ of Corti, and in the spiral ganglion putative type I (1,009 m3) and type II (225 m3) neurons. Outer hair cells (OHC) showed light immunoreaction product. Quantitative microdensitometry showed strong and moderate immunoreactions in IHC and spiral ganglion neurons, respectively, without differences among cochlear turns. One week of acoustic stimulation was not able to induce changes in the NPY immunoreactivity intensity in the IHC of cochlea. However, stimulated rats showed an overall increase in the number of putative type I and type II NPY immunoreactive spiral ganglion neurons with strong, moderate, and weak immunolabeling. Localization and responses of NPY to acoustic stimulus suggest an involvement of the neuropeptide in the neuromodulation of afferent transmission in the rat peripheral auditory pathway.

Increased EMG response following electromyographic biofeedback treatment of rectus femoris muscle after spinal cord injury

Objective To study increases in electromyographic (EMG) response from the right and left rectus femoris muscles of individuals with long-term cervical spinal cord injuries after EMG biofeedback treatment. Design Repeated measure trials compared EMG responses before and after biofeedback treatment in patients with spinal cord injuries. Main outcome measures The Neuroeducator was used to analyse and provide feedback of the EMG signal and to measure EMG response. Setting Department of Traumatic Orthopaedics, School of Medicine, University of Sao Paulo, Brazil. Participants Twenty subjects (three men and 17 women), between 21 and 49 years of age, with incomplete spinal cord injury at level C6 or higher (range C2 to C6). Of these subjects, 10 received their spinal cord injuries from motor vehicle accidents, one from a gunshot, five from diving, three from falls and one from spinal disc herniation. Results Significant differences were found in the EMG response of the right rectus femoris muscle between pre-initial (T1), post-initial (T2) and additional (T3) biofeedback treatment with the subjects in a sitting position [mean (standard deviation) T1: 26 mu V (29); T2: 67 mu V (50); T3: 77 mu V (62)]. The mean differences and 95% confidence intervals for these comparisons were as follows: T1 to T2, -40.7 (-53.1 to -29.4); T2 to T3, -9.6 (-26.1 to 2.3). Similar differences were found for the left leg in a sitting position and for both legs in the sit-to-stand condition. Conclusions The EMG responses obtained in this study showed that treatment involving EMG biofeedback significantly increased voluntary EMG responses from right and left rectus femoris muscles in individuals with spinal cord injuries. (C) 2010 Chartered Society of Physiotherapy. Published by Elsevier Ltd. All rights reserved.

Participatory ergonomics: Understanding the contributions of reflection groups in a hospital food service

Aim: To identify how the methodology of Reflection Groups (RG) can contribute to approach social-psychological problems, so often observed as obstacles in PE efforts. The objective was also to verify the contributions from RG to the implementation of ergonomics recommendations, which were a starting point and organized group discussions. Method: A concrete case was used as an illustration, and studied in depth: RG with administration and production workers` representatives from the Department of Nutrition and Dietetics of a cardiologic hospital in Sao Paulo, Brazil. RG are temporary thinking groups, taking place outside the workplace and having delegative and consultive participation. They make use of Operative Groups, an adapted form of tripartite group, activity as an instrumental resource, group dynamic techniques and videotaping. In 2007, 31 meetings took place during paid working hours with 7 groups of different composition, ranging from 1.5 h to 3 h. Results: Additionally to the positive effects in communication and psychosocial environment, RG could also contribute to changes in interpersonal relationships, cooperation, personal and work behaviours. By dealing with aspects which could hinder the explicit task: fears, conflicts, and stereotyped beliefs and behaviours; resistance to change could be broken and group members could learn. RG allowed input about new risks; continuous information and feedback about ongoing ergonomics interventions so that immediate corrective action could be taken. The main form of participation was in administrative, organizational, and psychosocial problems which required a better clarification and identification of their real causes, commitment, and elaboration of strategies and negotiation of different stakeholders in their solution. Conclusion: RG takes advantage of homogeneous and heterogeneous groups, in face to face communication. The interactions in the groups are task-oriented (explicit task) but attaining groups` goals depends on a relational interaction (implicit task). Relevance to industry: Reflection groups can bring important contributions to ergonomics and industry because they favour the discussion, disclosure of problems and incorporation of solutions, enabling interventions in working organization, psychosocial environment and relationships in a collective and participatory approach, promoting health and social integration. (C) 2010 Elsevier B.V. All rights reserved.

The medial forebrain bundle mediates cardiovascular responses to electrical stimulation of the medial prefrontal cortex

The medial prefrontal cortex (MPFC) is involved in cardiovascular control. MPFC electrical stimulation has been reported to cause depressor and bradycardic responses in anesthetized rats. Although the pathway involved is yet unknown, there is evidence indicating the existence of a relay in the lateral hypothalamus (LH). The medial forebrain bundle (MFB) that courses in the lateral portion of the LH carries the vast majority of telencephalic afferent as well efferent projections, including those from the MPFC. To evaluate if the hypotensive pathway originating in the MPFC courses the MFB, we studied the effect of coronal or sagittal knife cuts through the LH and other brain areas on the cardiovascular responses to MPFC electrical stimulation. Knife cuts were performed using blades I to 6 mm wide. Results indicate that the neural pathway descending from the MFB decussates early in the vicinity of MPFC, crossing the midline within the corpus callosurn and yielding two descending pathways that travel rostro-caudally in the lateral portion of the LH, within the MFB. The decussation was confirmed by histological analysis of brain sections processed after the injection of biotinilated dextran amine in the site of the stimulation in the MPFC. Because knife cuts through the LH ipsilateral had minimal effects on the cardiovascular responses and knife cuts performed contralateral to the stimulated MPFC had no effect on the response to MPFC stimulation, data indicate that the contralateral limb of the pathway may be only activated as an alternative pathway when the ipsilateral pathway is blocked. (c) 2009 Elsevier B.V. All rights reserved.

The peripheral pro-nociceptive state induced by repetitive inflammatory stimuli involves continuous activation of protein kinase A and protein kinase C epsilon and its Na(v)1.8 sodium channel functional regulation in the primary sensory neuron

In the present study, the participation of the Na(v)1.8 sodium channel was investigated in the development of the peripheral pro-nociceptive state induced by daily intraplantar injections of PGE(2) in rats and its regulation in vivo by protein kinase A (PKA) and protein kinase C epsilon (PKC epsilon) as well. In the prostaglandin E(2) (PGE(2))-induced persistent hypernociception, the Na(v)1.8 mRNA in the dorsal root ganglia (DRG) was up-regulated. The local treatment with dipyrone abolished this persistent hypernociception but did not alter the Na(v)1.8 mRNA level in the DRG. Daily intrathecal administrations of antisense Na(v)1.8 decreased the Na(v)1.8 mRNA in the DRG and reduced ongoing persistent hypernociception. once the persistent hypernociception had been abolished by dipyrone, but not by Na(v)1.8 antisense treatment, a small dose of PGE(2) restored the hypernociceptive plateau. These data show that, after a period of recurring inflammatory stimuli, an intense and prolonged nociceptive response is elicited by a minimum inflammatory stimulus and that this pro-nociceptive state depends on Na(v)1.8 mRNA up-regulation in the DRG. in addition, during the persistent hypernociceptive state, the PKA and PKC epsilon expression and activity in the DRG are up-regulated and the administration of the PKA and PKC epsilon inhibitors reduce the hypernociception as well as the Na(v)1.8 mRNA level. In the present study, we demonstrated that the functional regulation of the Na(v)1.8 mRNA by PKA and PKC epsilon in the primary sensory neuron is important for the development of the peripheral pro-nociceptive state induced by repetitive inflammatory stimuli and for the maintenance of the behavioral persistent hypernociception. (C) 2008 Elsevier Inc. All rights reserved.