Magnetic-free Extended Kalman Filter for upper limb kinematic assessment in Yoga.

Human motion analysis is gaining increased importance in several fields, from movement assessment in rehabilitation to recreational applications such as virtual coaching. Among all the technologies involved in motion capture, Magneto-Inertial Measurements Units (MIMUs) is one of the most promising due to their small dimensions and low costs. Nevertheless, their usage is strongly limited by different error sources, among which magnetic disturbances, which are particularly problematic in indoor environments. Inertial Measurement Units (IMUs) could, thus, be considered as alternative solution. Indeed, relying exclusively on accelerometers and gyroscopes, they are insensitive to magnetic disturbances. Even if the literature has started to propose few algorithms that do not take into account magnetometer input, their application is limited to robotics and aviation. The aim of the present work is to introduce a magnetic-free quaternion based Extended Kalman filter for upper limb kinematic assessment in human motion (i.e., yoga). The algorithm was tested on five expert yoga trainers during the execution of the sun salutation sequence. Joint angle estimations were compared with the ones obtained from an optoelectronic reference system by evaluating the Mean Absolute Errors (MAEs) and Pearson's correlation coefficients. The achieved worst-case was 6.17°, while the best one was 2.65° for MAEs mean values. The accuracy of the algorithm was further confirmed by the high values of the Pearson's correlation coefficients (lowest mean value of 0.86).Clinical Relevance- The proposed work validated a magnetic free algorithm for kinematic reconstruction with inertial units. It could be used as a wearable solution to track human movements in indoor environments being insensitive to magnetic disturbances, and thus could be potentially used also for rehabilitation purposes.

Perception of Time-Discrete Haptic Feedback on the Waist is Invariant With Gait Events.

The effectiveness of haptic feedback devices highly depends on the perception of tactile stimuli, which differs across body parts and can be affected by movement. In this study, a novel wearable sensory feedback apparatus made of a pair of pressure-sensitive insoles and a belt equipped with vibrotactile units is presented; the device provides time-discrete vibrations around the waist, synchronized with biomechanically-relevant gait events during walking. Experiments with fifteen healthy volunteers were carried out to investigate users' tactile perception on the waist. Stimuli of different intensities were provided at twelve locations, each time synchronously with one pre-defined gait event (i.e. heel strike, flat foot or toe off), following a pseudo-random stimulation sequence. Reaction time, detection rate and localization accuracy were analyzed as functions of the stimulation level and site and the effect of gait events on perception was investigated. Results revealed that above-threshold stimuli (i.e. vibrations characterized by acceleration amplitudes of 1.92g and 2.13g and frequencies of 100 Hz and 150 Hz, respectively) can be effectively perceived in all the sites and successfully localized when the intertactor spacing is set to 10 cm. Moreover, it was found that perception of time-discrete vibrations was not affected by phase-related gating mechanisms, suggesting that the waist could be considered as a preferred body region for delivering haptic feedback during walking.

Movement analysis in early infancy: Towards a motion biomarker of age.

BACKGROUND: Early motor development is characterized by progressive changes in general movements paralleled by a gradual organization of the four limbs' repertoire towards the midline, as shown by computerised movement analysis. AIMS: Our aim was to test the performance of quantitative computerised kinematic indexes as predictors of post-term age in an independent cohort of typically developing subjects at fidgety age, tested cross-sectionally. SUBJECTS: We selected twelve low risk term infants, who were video recorded between 9 and 20 weeks (fidgety age) during one spontaneous movements session. STUDY DESIGN: We correlated post-term age with I)indexes of coordination including interlimb correlation of velocity and position, II)indexes of distance, including interlimb and limb-to- ground, both expressed as linear distance and as probability of midline limbs position III)indexes of global movement quality by calculating Hjorth's activity, mobility and complexity parameters. All indexes were calculated for both upper and lower limbs. RESULTS: Significant positive correlations were found between post-term age and indexes of distance, and probability of occurrence of upper-limb antigravity patterns, and with both indexes of global movement quality. By combining linear and non-linear parameters related to the upper limb kinematics, we determined individual post-term age with a mean error of <1 week (5.2 days). No correlations were found between age and indexes of coordination. CONCLUSIONS: Quantitative computerised analysis of upper-limb movements is a promising predictor of post-term age in typically developing subjects at fidgety age.

Accuracy of the Orientation Estimate Obtained Using Four Sensor Fusion Filters Applied to Recordings of Magneto-Inertial Sensors Moving at Three Rotation Rates.

Magneto-Inertial technology is a well-established alternative to optical motion capture for human motion analysis applications since it allows prolonged monitoring in free-living conditions. Magneto and Inertial Measurement Units (MIMUs) integrate a triaxial accelerometer, a triaxial gyroscope and a triaxial magnetometer in a single and lightweight device. The orientation of the body to which a MIMU is attached can be obtained by combining its sensor readings within a sensor fusion framework. Despite several sensor fusion implementations have been proposed, no well-established conclusion about the accuracy level achievable with MIMUs has been reached yet. The aim of this preliminary study was to perform a direct comparison among four popular sensor fusion algorithms applied to the recordings of MIMUs rotating at three different rotation rates, with the orientation provided by a stereophotogrammetric system used as a reference. A procedure for suboptimal determination of the parameter filter values was also proposed. The findings highlighted that all filters exhibited reasonable accuracy (rms errors <; 6.4°). Moreover, in accordance with previous studies, every algorithm's accuracy worsened as the rotation rate increased. At the highest rotation rate, the algorithm from Sabatini (2011) showed the best performance with errors smaller than 4.1° rms.

Pre-impact detection algorithm to identify lack of balance due to tripping-like perturbations.

This study investigates the performance of an updated version of our pre-impact detection algorithm while parsing out hip kinematics in order to identify unexpected tripping-like perturbations during walking. This approach grounds on the hypothesis that due to unexpected gait disturbances, the cyclic features of hip kinematics are suddenly altered thus promptly highlighting that the balance is challenged. To achieve our goal, hip angles of eight healthy young subjects were recorded while they were managing unexpected tripping trials delivered during the steady locomotion. Results showed that the updated version of our pre-impact detection algorithm allows for identifying a lack of balance due to tripping-like perturbations, after a suitable tuning of the algorithm parameters. The best performance is represented by a mean detection time ranging within 0.8-0.9 s with a low percentage of false alarms (i.e., lower than 10%). Accordingly, we can conclude that the proposed strategy is able to detect lack of balance due to different kinds of gait disturbances (e.g., slippages, tripping) and that it could be easily implemented in lower limb orthoses/prostheses since it only relies on joint angles.

Evaluation of time-frequency features as detectors of lack of balance due to tripping-like perturbations.

Unbalancing events during gait can end up in falls and, thus, injury. Detecting events that could bring to fall and consequently activating fall prevention systems before the impact may help to mitigate related injuries. However, there is uncertainty about signals and methods that could offer the best performance. In this paper we investigated a novel trip detection method based on time-frequency features to evaluate the performances of these features as trip detectors. Hip angles of eight healthy young subjects were recorded while performing unexpected tripping trials delivered during steady locomotion. Then the Short-Time Fourier Transform (STFT) of the hip angle was estimated. Median frequency, power, centroidal frequency as well as frequency dispersion were computed for each time sliced power spectrum. These features were used as input for a trip detection algorithm. We assessed detection time (Tdetect), specificity (Spec) and sensitivity (Sens) for each feature. Performances obtained with median frequencies over time(Tdetect 0.91 ± 0.47 s; Sens 0.96) were better than those obtained using the hip angle signal in time domain (Tdetect 1.19 ± 0.27 s; Sens 0.83). Other features did not show significant results. Thus, median frequency over time expected to achieve effective real-time event detection systems, with the aim of a future on-board application concerning detection and prevention measures.

A novel functional calibration method for real-time elbow joint angles estimation with magnetic-inertial sensors.

Magnetic-inertial measurement units (MIMUs) are often used to measure the joint angles between two body segments. To obtain anatomically meaningful joint angles, each MIMU must be computationally aligned (i.e., calibrated) with the anatomical rotation axes. In this paper, a novel four-step functional calibration method is presented for the elbow joint, which relies on a two-degrees-of-freedom elbow model. In each step, subjects are asked to perform a simple task involving either one-dimensional motions around some anatomical axes or a static posture. The proposed method was implemented on a fully portable wearable system, which, after calibration, was capable of estimating the elbow joint angles in real time. Fifteen subjects participated in a multi-session experiment that was designed to assess accuracy, repeatability and robustness of the proposed method. When compared against an optical motion capture system (OMCS), the proposed wearable system showed an accuracy of about 4° along each degree of freedom. The proposed calibration method was tested against different MIMU mountings, multiple repetitions and non-strict observance of the calibration protocol and proved to be robust against these factors. Compared to previous works, the proposed method does not require the wearer to maintain specific arm postures while performing the calibration motions, and therefore it is more robust and better suited for real-world applications.

Helminth parasites of fish and shellfish from the Santa Gilla Lagoon in southern Sardinia, Italy.

An extensive survey of helminth parasites in fish and shellfish species from Santa Gilla, a brackish water lagoon in southern Sardinia (western Mediterranean), resulted in the identification of 69 helminth parasite taxa and/or species from 13 fish species (n= 515) and seven bivalve species (n= 2322) examined between September 2001 and July 2011. The list summarizes information on the helminth parasites harboured by fish and molluscs contained in the available literature. Digenea species (37), both adults and larvae, dominated the parasite fauna, whereas Cestoda were the least represented class (three species). Monogenea, Nematoda and Acanthocephala were present with 17, 6 and 6 species, respectively, which were mainly adults. The most widespread parasite species was the generalist Contracaecum rudolphii A (Nematoda). Other species, such as the Haploporidae and Ascocotyle (Phagicola) spp. 1 and 2 (Digenea), showed a high family specificity in Mugilidae. Importantly, the study recorded the occurrence of potential zoonotic agents, such as Heterophyes heterophyes, Ascocotyle (Phagicola) spp. and C. rudolphii A, the latter two reaching the highest indices of infection in the highly marketed fish grey mullet and sea bass, respectively. The highest parasite richness was detected in Dicentrarchus labrax, which harboured 17 helminth species, whereas the lowest value was observed in Atherina boyeri, infected by only three species. The list includes the first geographical record in Italian coastal waters of Robinia aurata and Stictodora sawakinensis, and 30 reports of new host-parasite complexes, including the larval stages of Ascocotyle (Ascocotyle) sp. and Southwellina hispida in D. labrax.

Prophylactic arterial catheterization in the management of high risk patients for obstetric haemorrhage.

OBJECTIVES: Post-partum haemorrhage still remains one of the major causes of maternal morbidity and mortality. In case of abnormal placentation it is possible to carry out preventive and therapeutic actions. To maintain fertility in reproductive-aged women and to avoid a more radical surgery, embolization has been introduced in patients at high risk for haemorrhage. To describe a new option in the management of patients with abnormal placentation by an elective, preventive arterial catheterization and selective embolization of pelvic arteries. PATIENTS AND METHODS: A retrospective study including thirty six patients with abnormal placental invasion. All patients were prepared in the angiographic room and preventive arterial catheterization was performed before elective caesarean delivery. Materials for interventional angiography were transferred to the operating room. During surgery, selective embolization of pelvic arteries was realized in case of uncontrolled bleeding. RESULTS: Thirty-six elective arterial catheterizations were performed: 4 cases (11.1%) required embolization, haemorrhage was stopped in 2 patients. Hysterectomy was performed in two cases (5.5%). No death was reported. Two humeral thrombosis (5.5%) were registered. CONCLUSIONS: Prophylactic arterial catheterization appears to be safe. The main advantage is the reduction of the interval between the onset of bleeding and the embolization. This new option of management may contribute to reduce the risk of hysterectomy and maternal death.

Are we giving patients enough information on how to use topical treatments? Analysis of 767 prescriptions in psoriasis.

BACKGROUND: Unclear instructions probably contribute to the suboptimal efficacy and adherence to topical agents in psoriasis. OBJECTIVES: To analyse the quality of prescriptions for topical therapy in psoriasis and to determine factors associated with high-quality prescription writing. METHODS: We made a systematic analysis of 767 topical prescriptions written by dermatologists and general practitioners (GPs). The following parameters were recorded: writing mode (electronic vs. hand written), indication of formulation, frequency of administration, duration of treatment, indication of areas to be treated, and indication of amount of product to be used. We considered prescriptions of high quality to be those including at least four of the five prospectively defined quality parameters. RESULTS: Only 35·7% of prescriptions fulfilled the definition of a high-quality prescription. Quality of prescription writing was significantly influenced by two factors: electronic writing [odds ratio (OR) 3·04, 95% confidence interval (CI) 2·2-4·21; P < 10(-4) ] and specialty of the prescriber, dermatologists writing higher quality prescriptions compared with GPs (OR 1·61, 95% CI 1·54-2·14; P < 10(-4) ). CONCLUSIONS: Almost two-thirds of topical prescriptions are not adequately written and do not include the required information to help patients manage their topical treatment in psoriasis correctly. The quality of topical prescriptions could be improved by making the use of electronic prescriptions widespread and by the development of aids for easy evaluation of the right amount of topical treatment to be applied according to body surface area involved.

Quaternion-based strap-down integration method for applications of inertial sensing to gait analysis.

The proposed strap-down integration method exploits the cyclical nature of human gait: during the gait swing phase, the quaternion-based attitude representation is integrated using a gyroscope from initial conditions that are determined during stance by an accelerometer. Positioning requires double time integration of the gravity-compensated accelerometer signals during swing. An interpolation technique applied to attitude quaternions was developed to improve the accuracy of orientation and positioning estimates by accounting for the effect of sensor bias and scale factor drifts. A simulation environment was developed for the analysis and testing of the proposed algorithm on a synthetic movement trajectory. The aim was to define the true attitude and positioning used in the computation of estimation errors. By thermal modelling, the changes of bias and scale factor of the inertial sensors, calibrated at a single reference temperature, were analysed over a range of +/- 10 degrees C, for measurement noise standard deviations up to sigma(g) = 2.5 degrees s(-1) (gyroscope) and sigma(a) = 0.05 m s(-2) (accelerometer). The compensation technique reduced the maximum root mean square errors (RMSEs) to: RMSE(theta) = 14.6 degrees (orientation) and RMSE(d) = 17.7cm (positioning) for an integration interval of one gait cycle (an improvement of 3 degrees and 7 cm); RMSE(theta) = 14.8 degrees and RMSE(d) = 30.0 cm for an integration interval of two gait cycles (an improvement of 11 degrees and 262 cm).

Automated and manual luminescent assay of antioxidant capacity: analytical features by comparison.

The analytical performances of a manual and a partially automated chemiluminescent (CL) assay, of total antioxidant capacity (TAC) were assessed. In both cases the light emitting reaction involved luminol, horseradish peroxidase and hydrogen peroxyde, but the emission kinetics and the parameters taken into account to calculate TAC values were completely different. The major characteristics expressing the quality of the two analytical methods, i.e. inaccuracy, repeteability and reproducibility, sensitivity, time required for the analysis and detection limit, were estimated by using standard solutions of Trolox. The reliability of the automated method, in comparison with the more validated manual one, was demonstrated testing food samples such as honey, wine and dietary supplements and performing a statistical analysis of the results. The comparison of the two series of data by t-test resulted in p values in the range 0.1-0.01. The time required for the analysis of each sample was reduced to one third using the automated method.

Artificial neural network model of the mapping between electromyographic activation and trajectory patterns in free-arm movements.

Artificial neural networks (ANNs) have been used to identify the relationship between electromyographic (EMG) activity and arm kinematics during the execution of motor tasks. Although considerable work has been devoted to showing that ANNs perform this mapping, there has been little work to explore any relationship with physiological properties of the neuromuscular systems. A back-propagation through time (BPTT) ANN was used to map the EMG of five selected muscles (pectoralis major (PM), anterior deltoid (AD), posterior deltoid (PD), biceps brachii (BB) and triceps brachii (TB)) on arm kinematics in seven normal subjects performing three-dimensional unrestrained grasping movements. To investigate the physiological validity of the BPTT-ANN, inputs were artificially altered, and the predicted outputs were analysed. Results show that the BPTT-ANN performed the mapping correctly (root mean square (RMS) error between target and predicted outputs averaged across subject test sets was 0.092 +/- 0.015). Moreover, it provided insights into the roles of muscles in performing the movement (average indexes measuring the output alteration with respect to the target were 0.070 +/- 0.027, 0.356 +/- 0.172, 0.568 +/- 0.413, 0.510 +/- 0.268, 0.681 +/- 0.430 for PM, AD, PD, BB, TB, respectively, in the movement forward phase, and 0.077 +/- 0.015, 0.179 +/- 0.147, 0.291 +/- 0.247, 0.671 +/- 0.054, 0.232 +/- 0.097 in the return phase).

Real-time Kalman filter applied to biomechanical data for state estimation and numerical differentiation.

This study focused on the application of real-time Kalman filters to biomechanical data and, in particular, the simulation environment used to compare the performance of modified and standard two-state Kalman filters when estimating displacement and velocity from noisy displacement data. The modification proposed in this paper was the numerical tachometer, augmented by a median smoother. The numerical tachometer integrated the derivative estimates from finite differences of noisy sampled data into the Kalman filter structure; the median smoother acted before differentiation, to protect from grossly erroneous measurements. The numerical tachometer allowed better fits to the simulated data than can be achieved without it: the root mean square errors decreased by 10% in the displacement domain and by 54% in the velocity domain, for sampling frequencies and signal contamination levels that were typical in human movement sciences. The sensitivity to errors in the modelling of the signal and noise characteristics was less than in the standard filter implementation. The use of the median smoother improved the robustness of the filtering algorithm against additive white Gaussian measurement noise and allowed the cancellation of isolated noise spikes.

[Epidemiology of unintentional drowning in children younger than 5 years in Italy]. / Epidemiologia dell'annegamento accidentale in Italia nei bambini di età inferiore a 5 anni.

The objective of the study was to describe the epidemiology of unintentional drowning in Italy in the period 1983-1997, in the age-group 0-4 years. We used mortality data from the Italian National Statistical Institute (ISTAT), and calculated the potential years of life lost (PYLL), for the single age-group and for all the children aged 0-4 years, following the CDC method (age limit 65 years). Only in 1983 the rate of mortality due to accidental drowning in the age-group 0-4 years was over 1.00 per 100,000 inhabitants (1.27). In the male sex the rate was over 1/100,000 in 1983 (1.93), 1984 (1.18) and 1989 (1.03). In the females the higher rate reached was 0.66/100,000 (1984). Considering both genders, the lower rate was reached in 1997 (0.33/100,000), and it was 0.42 for males (1992) and 0.07 for females (1988). Considering all ages, statistically significant differences in the mean death rates were found by sex (0.8/100,000 for males and 0.31/100,000 for females; t = 4.504; p < 0.0001). Considering the single age-groups, statistically significant differences in the mean death rates were found by sex only for 2, 3 and 4 years (respectively, p = 0.005; p = 0.001 e p < 0.0001). Considering all children, we estimated a PYLL of 15,750 years (PYLL for males representing 72.2%). The mean death rate for unintentional drowning in the age-group 0-4 years in Italy is lower than the mean vaues in other countries, but there is a clear need to lower this kind of death, that accounted for almost 16,000 PYLL in the period 1983-1997.

Expression of the neurokinin 1 receptor in the rabbit retina.

Substance P is the preferred ligand for the neurokinin 1 (NK1) receptor. In vertebrate retinas, substance P is expressed by amacrine, interplexiform and ganglion cells. Substance P influences the activity of amacrine and ganglion cells and it is reported to evoke dopamine release. We investigated NK1 receptor expression in the rabbit retina using affinity-purified NK1 receptor antibodies. NK1 receptors were expressed by two distinct populations of retinal neurons. One is a population of ON-type bipolar cells characterized by axonal arborizations that ramified in the inner plexiform layer near the ganglion cell layer. Double-label studies showed that NK1 receptor-expressing bipolar cells were distinct from rod bipolar cells and from other immunocytochemically identified types of cone bipolar cells. Their density was about 2250 cells/mm2 in the visual streak and 1115 cells/mm2 in ventral mid-periphery. They were distributed in a non-random pattern. In the outer plexiform layer, the dendrites of these bipolar cells converged into heavily immunostained clusters having a punctate appearance. The density of these clusters in mid-peripheral ventral regions (about 13000 clusters/mm2) was similar to the reported cone density [Famiglietti and Sharpe (1995) Vis. Neurosci. 12, 1151-1175], suggesting these dendrites contact all cone photoreceptors. The second NK1 receptor expressing cell population corresponds to the tyrosine hydroxylase-containing amacrine cell population. NK1 receptor immunostaining was localized to the cell body and processes, but not to the processes that form the 'rings' that are known to encircle somata of AII amacrine cells. These findings show that NK1 receptor immunoreactivity is localized to a population of ON-type cone bipolar cells and to dopaminergic amacrine cells, suggesting that substance P acting on NK1 receptors influences multiple retinal circuits in the rabbit retina.

Determination of organophosphorus pesticides in honeybees after solid-phase microextraction.

A method based on solid-phase microextraction (SPME) followed by gas chromatography with nitrogen-phosphorus detection was developed for the purpose of determining 18 organophosphorus pesticide residues in honeybee samples (Apis mellifera). The extraction capacities of polyacrylate and poly(dimethylsiloxane) fibers were compared. The main factors affecting the SPME process, such as the absorption time profile, salt, and temperature, were optimized. The method involved honeybee sample homogenization, elution with an acetone:water solution (1:1) and dilution in water prior to fiber extraction. Moreover, the matrix effect on the extraction was evaluated. In samples spiked at the 0.2 mg kg(-1) level, the coefficient variation was between 1 and 13% and the detection limits were below 10 microg kg(-1). The SPME procedure was found to be quicker and more cost-effective than the solvent extraction method commonly used. The method was applied successfully to environmental screening. Parathion methyl was detected and confirmed in the real samples analyzed.

Multiresidual method for the gas chromatographic analysis of pesticides in honeybees cleaned by gel permeation chromatography.

The analysis of several organophosphorus and carbamate pesticide residues in the bodies of honeybees using gas chromatography (GC) and gel permeation chromatography (GPC) clean-up is described. Freeze-dried or lyophilized insect samples were blended with diatomaceous earth (Extrelut) then underwent elution with methylene chloride. This extraction method has shown good recovery on various spike standard levels. Samples are cleaned up by GPC with a Bio Beads SX 3 column and a cyclohexane-ethylacetate (1:1) eluant. Organophosphorus and carbamate compounds are quantified using capillary gas chromatography. Good linearity ranges were observed for all compounds. The extraction process was rapid and results were good, despite the complexity of the matrix on which it was applied. It allowed a reduction both in cost and the consumption of solvents, thereby safeguarding the health of the analyst and the environment. Environmental monitoring using bees was confirmed to be a valid procedure.