Nonlinear elastic multi-path reciprocal method for damage localisation in composite materials.

Nonlinear ultrasonic techniques rely on the measurement of nonlinear elastic effects caused by the interaction of ultrasonic waves with the material damage, and have shown high sensitivity to detect micro-cracks and defects in the early stages. This paper presents a nonlinear ultrasonic technique, here named nonlinear elastic multi-path reciprocal method, for the identification and localisation of micro-damage in composite laminates. In the proposed methodology, a sparse array of surface bonded ultrasonic transducers is used to measure the second harmonic elastic response associated with the material flaw. A reciprocal relationship of nonlinear elastic parameters evaluated from multiple transmitter-receiver pairs is then applied to locate the micro-damage. Experimental results on a damaged composite panel revealed that an accurate damage localisation was obtained using the normalised second order nonlinear parameter with a high signal-to-noise-ratio (∼11.2dB), whilst the use of bicoherence coefficient provided high localisation accuracy with a lower signal-to-noise-ratio (∼1.8dB). The maximum error between the calculated and the real damage location was nearly 13mm. Unlike traditional linear ultrasonic techniques, the proposed nonlinear elastic multi-path reciprocal method allows detecting material damage on composite materials without a priori knowledge of the ultrasonic wave velocity nor a baseline with the undamaged component.

Disability seen from within.

An old physician describes with a ad auto-hironic humor the changes by ageing, with all the insight that the medical profession can give on the process of progressive disability.

Functional resources to increase gait speed in people with stroke: strategies adopted compared to healthy controls.

Thirty-nine adult individuals with stroke in the stable phase were asked to walk at their preferred speed and then as fast as possible. A set of gait indexes were computed, including spatial temporal parameters, ankle and hip mechanical work, and timing of ankle push-off onset, for comparison with normal velocity-dependent profiles. Algorithms were used to classify the resulting gait patterns when the patients walked at their preferred speed and fast and to identify the patients' strategies to maximise speed. Patients' strategies were characterised by a variation in the parameters, which were reduced, equal or increased, in relation to normal patterns. At both speeds, stroke individuals tended to walk at higher cadence and with shorter stride length. At the preferred speed the investigated parameters for all patients were mostly within the normal profile (71.8-94.9%). The exception was the finding of positive work at the ankle where 64% of the stroke individuals showed reduced work production. At fast speed (increments to 36%BH/s) fewer patients presented values within the normal profile for all the parameters (17.9-74.4%), with the exception of negative work at the ankle and hip. The parameter variations showed a more consistently abnormal picture. The results indicate that, in order to increase gait speed, patients with hemiparesis have different functional resources on which to draw, and these vary from individual to individual. Thus, gait analysis at different gait speed should be adopted to develop individualised programs that will improve quality of life for the patients.

Electromyographic activity to keep a lower limb in a raised position in healthy subjects and subjects with multiple sclerosis.

UNLABELLED: The objective of this work was to assess the activation of the stabilization muscles used to keep one lower limb raised from a supine position, in healthy subjects and in subjects with multiple sclerosis (MS) in two different conditions. The test required subjects to keep the right lower limb at 45 degrees from the supine position on a horizontal bed plane, with the knee extended. The position was reached in two ways: by raising the right limb (A), and by resting the left lower limb on the bed after both limbs had been raised (B). During the test, pelvis and hip kinematics and the surface electromyographic (sEMG) activity were acquired. Fourteen healthy subjects and 14 subjects with multiple sclerosis were included in the study. RESULTS: showed that in the A condition, healthy subjects had a greater activation of the biceps femoris than the abdominal muscles, while in the B condition the difference between the two muscles decreased. In the MS group there was no difference in muscular activation for the two conditions. The data show that in the MS subjects there is an alteration of the stabilization muscles with regard the quality of the activation. Starting from these data new exercises of motor rehabilitation in subjects with multiple sclerosis could be recommended.

Biomechanics of lower limb raising from the supine position.

AIM: This study analyses the kinematics of the lower limb raising movement from the supine position and the electromyography activity of the muscles involved. METHODS: Twenty healthy right hand subjects performed the right lower limb raising from the supine position, starting from the clinical bed plane and up to a 70 degrees inclination of the thigh over the horizontal plane, while the knee was kept flexed at 120 degrees by a soft splint. The same exercise was executed with no resistance and with 2 kg and 8 kg respectively applied to the ankle. The kinematics was recorded utilising an optoelectronic system, whereas the electromyography activity was recorded by a surface electromyography (EMG) applied to the following muscles: right rectus femoris, left biceps femoris, rectus abominalis from both sides and dorsal major from both sides. RESULTS: In all the cases the pelvis performed a backwards rotation retroversion. The highest increase of EMG activation was recorded on the right rectus femoris as well as on the left biceps femoris; the increase was lower in the right rectus abdominis and in the right dorsal major, whereas it was minimum in the left rectus abdominis and in the left dorsal major. A great variability in the activation times was reported in the various muscles of the different subjects, regardless of the trials. The only muscle anticipating the right rectus femoris activation was the left biceps femoris. CONCLUSIONS: The research has shown how the simple movement under study is more complex than what is usually described by the text books, both in regard to the kinematics and to muscles' actions. Even the individual variability in utilising the agonist and stabilisation muscles can be of relevance for a more rational utilisation of the physical exercise in motor re-education.

[The epidemiology of musculoskeletal changes due to biomechanical overload of the spine in the manual lifting of patients]. / Epidemiologia delle alterazioni muscolo-scheletriche da sovraccarico biomeccanico del rachide nella movimentazione manuale di pazienti.

The painful lumbosacral symptoms associated with manual lifting by nursing staff constitutes an increasingly important problem in Occupational Health. This category of workers is in fact particularly exposed to risk situations involving the lumbar region of the spine, due especially to the extreme variability of work on the shift, the nature of what is lifted and not always sufficient knowledge and proper performance of the movements. On the basis of a review of a series of studies made on this topic, it was possible to assess the incidence and prevalence of low back pain in selected populations and identify the postural risk to which nursing staff are exposed at work, stressing also the importance of a correct knowledge of manual lifting techniques, frequency and mode of performing them, and the psychological aspects (perception of the intensity of tasks and osteoarticular strain). It was also observed that the data on painful lumbosacral symptoms were underestimated due to the type of epidemiological investigations carried out (mostly cross-sectional) and that comparison of the data proposed was often difficult due to the different criteria of evaluation used to classify the painful symptoms and also to the various epidemiological parameters used (incidence, cumulative incidence, prevalence).

Muscular effort and musculo-skeletal disorders in piano students: electromyographic, clinical and preventive aspects.

An investigation was made on the relationship between music practice and musculo-skeletal disorders among piano students, with the main aim of developing health education programmes that would improve the performance and health of the students. The investigation covered three areas: (a) Analysis of study organization and main musculo-skeletal complaints achieved by a questionnaire distributed to all piano students at the Milan Conservatory. (b) Vocational electromyographic analysis of the effort exerted by the various muscle groups of the trunk, of the shoulder and shoulder blade girdle, and of the arm during performance of a standard set of piano exercises, an unseen passage and a passage of maximum difficulty. This analysis was made on a sample of six subjects. (c) A series of preventive measures was developed on the basis of a critical assessment of the results (38% of the students practised for excessively long periods without breaks; 62% had from 1 to 5 complaints, the most affected sites being the spine and the trapezius muscles). These consisted largely of a health education programme aimed at helping the students to suitably organize practice and rest periods and in instructing them in appropriate exercises for relaxation and stretching of overused muscle groups and strengthening the supporting muscle groups. Changes in lifestyle were also suggested.

Clinical and functional examination of the spine in working communities: occurrence of alterations in the male control group.

The paper reports the results obtained by applying a clinical method for the study of spinal disease as described elsewhere' in a control group of 200 male subjects, stratified for age, who had not been exposed to classically accepted occupational risk indicators for spinal disorders. For each age class the following data are supplied: frequency of cervical thoracic and lumbar disease; frequency of scoliosis and dissymmetry of lower limbs; mean values and range of mobility parameters for the various spinal regions. The possible application are discussed.

New procedure for evaluation of normal and abnormal gait.

In this paper a new procedure is presented that permits a quantitative clinical evaluation of an important aspect of human locomotion. It involves a spatio-temporal representation of the evolution of the group reaction vector (sagittal plane) for a single hind limb during the stance phase of a step. This representation is provided directly on line by use of a computer. Some preliminary results are presented for normal subjects and for patients with a variety of motor disorders.