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The vibration discomfort to the human body in semi-supine posture is currently evaluated as per ISO 2631-1, although it is recommended for sitting, standing and recumbent posture. The present study investigated the frequency-dependence of subjective responses of semi-supine humans to vertical vibration (0.5–1.5 m s−2 r.m.s.) across the frequency range 2.0–16.0 Hz. The subjects (14 males) judged the discomfort caused due to sinusoidal vibration using a modified absolute magnitude estimation method. The significant variation of rate of growth of discomfort across the frequency spectra caused the shape of equivalent comfort contour to vary with the vibration magnitude. The equivalent comfort contours illustrated significant discomfort between 8.0 and 10.0 Hz. Moreover, for frequencies above 10.0 Hz, substantial vibration acceleration was required to cause discomfort of the same intensity, implying that the frequency dependence of semi-supine posture is distinct from other postures. The frequency weighting obtained for semi-supine posture suggested that the discomfort estimation based on ISO 2631-1 was relatively accurate though conservative. Practitioner Summary: The discomfort caused by vertical vibration to the human in semi-supine posture was quite different from other postures. The present study provided the frequency-dependence of vibration discomfort for humans in semi-supine posture. Further, it investigated the suitability of frequency weightings defined in ISO 2631-1 for the acceleration measurements. Abbreviations: ISO: International Organization for Standardization; BS: British Standard; NASA: National Aeronautics and Space Administration; BMI: body mass index; AME: absolute magnitude estimation [ABSTRACT FROM AUTHOR]

The dynamic behaviour of cylindrical roller bearings is presented, in both balanced and unbalanced conditions as a function of speed. The stiffness and damping non-linearities at the contact points (due to Hertzian contact force between rollers and races), radial internal clearance and unbalanced rotor force make the bearing system non-linear. Presently, the differential equations representing the dynamics of the cylindrical roller bearings have been obtained using Lagrange's equation and solved numerically using modified Newmark-β method. The results of the analyses of various motion behaviours are presented as time–displacement responses, orbit plots, phase portraits, Poincaré maps and Fast Fourier Transform plots. The obtained responses revealed the sensitive behaviour of the system from periodic to quasi-periodic and chaotic with speed variations for both balanced and unbalanced rotor conditions. Also, intermittent chaotic behaviour has been observed. A pattern of the interaction between rotational and variable compliance vibration is observed with speed variations. The frequency pattern analysis (with different techniques used like phase/orbit plots and Poincaré plots) for healthy cylindrical bearing and different rotor conditions under different applied non-linearity consideration is a new attempt to analyse dynamic behaviour of the bearing. This analysis is helpful for online monitoring of fault-free cylindrical roller bearings and for studying the impact of speed on system's dynamical behaviour. [ABSTRACT FROM AUTHOR]

The low frequency vibration transmitted to the body can affect the comfort, performance, and health of humans. In this paper, the effect of variations in posture and vibration magnitude on the head motion in three translational axes (fore-and-aft, lateral and vertical) has been studied with a vertical seat vibration. Thirty healthy male subjects were exposed to random vibration with three vibration magnitudes of 0.4, 0.8, and 1.2 m/s2 rms over the frequency range of 1-20 Hz. The results are analysed in terms of seat-to-head-transmissibility (STHT) for the head motions in two seated postures (backrest and leaning forward on table). The measurement of the head motion was made with an apparatus (bite-bar) specifically developed for this purpose. The measured responses to a single axis seat vibration have also shown notable cross-axis responses in both vertical and fore-and-aft axes for both postures. The crossaxis fore-aft and vertical STHT responses showed single peak near 5 Hz in both postures. An increasing intensity of vibration yields a non-linear softening effect in the muscle tension, particularly in the presence of back support, however, the body stiffens under a greater upper body motion in the forward leaning posture. The combined effect of the unsupported back and hands support was observed to be more pronounced around the resonance peak in the forward lean posture. [ABSTRACT FROM AUTHOR]

Vehicle developers and design engineers require understanding of human response to vibration for optimising the seat in order to meet the objective of passenger ride comfort. This paper attempts to develop an artificial neural networks (ANN) based model to measure biodynamic response seat to head transmissibility (STHT), incorporating factors like vibration frequency, vibration magnitude and posture for seated subjects exposed to random whole body vibration (WBV) in three different directions (vertical, fore-aft, lateral). After training the model is able to predict STHT with high accuracy when compared with the experimental values. Cross-axis coupling, i.e., excitation in one axis producing a response in the other axis, is also validated through ANN modelling in this paper. [ABSTRACT FROM AUTHOR]

The transmission of vibration from the vibrating interface to various organs of the human body may influence their functioning during the vibration exposure. Therefore, an experimental study on a vibration simulator has been performed to find the effects of vibration on reading performance, and also to establish the relationship between seat-to-head transmissibility (STHT) with reading difficulty and reduction in reading performance. Twelve seated male subjects were exposed to sinusoidal vibration with three magnitudes (0.5, 1.0 & 1.5 m/s2 rms) at seven different frequencies (4, 5, 6.3, 10, 16, 20, and 25 Hz) in three independent directions (vertical, fore-and-aft, and lateral). The results show that three output measures - STHT, reduction in reading performance, and perceived difficulty in reading - are significantly affected by the frequency of vibration in each direction. All three measures have shown the peak at 4 or 5 Hz in three independent directions of vibration. Another peak at 25 Hz has also been observed for reduction in performance and perceived reading difficulty in vertical direction vibration. The results also show decrease in resonance frequency of the transmissibility with an increase in vibration magnitude, which represents nonlinear behaviour in biodynamic response by the human body. [ABSTRACT FROM AUTHOR]

There is increasing use of laptop computer in rail vehicles for performing various sedentary activities such as reading and typing. The vibration is a major factor influencing the reading performance during the journey. Therefore, an experimental study was conducted to investigate the extent of interference perceived in reading an e-paper in two seated postures (backrest support and leaning over the table) under random vibration. The study involved 30 healthy male subjects who were excited with vibration acceleration in mono-, dual, and multi-axes in 1-20 Hz at 0.4, 0.8, and 1.2 m/s² amplitudes. The task consisted of reading the given paragraph of an e-paper under various vibration stimuli, and it was evaluated by time taken to complete the task and subjective evaluation of reading difficulty. The subjective evaluation showed that the reading difficulty increased with vibration stimuli for both the subject postures. The subjects perceived higher difficulty and degradation in reading performance for vibration in dual and multi-axes, which was comparable to that for lateral and vertical directions also. The perceived difficulty and impairment in reading performance was greater while reading with the laptop on their lap for vibration in the x-axis, while the effect was just the reverse for other axes. [ABSTRACT FROM AUTHOR]

The article focuses on a study to check the performance of sedentary activities under low frequency random vibration in both mono and dual axes. It informs that 30 males were given geometrical figures under vibration environment to sketch in two subject postures, sketch pad on lap and on table and three performance methods were used to measure the effect of vibration stimuli and posture resulting in an increase in distortion and difficulty in sketching with an increase in vibration magnitude.

Whole-body vibrations in trains are known to affect the performance of sedentary activities such as reading, writing, sketching, working on a computer, etc. The objective of the study was to investigate the extent of disturbance perceived in sketching task by seated subjects in two postures under mono- and multi-axis Gaussian random vibration environment. The study involved 21 healthy male subjects in the age group of 23—32 years. Random vibrations were generated both in mono- and multi-axial directions in the frequency range of 1—10 Hz at 0.5, 1.0, and 1.5 m/s2 rms (root mean square) amplitude. The subjects were required to sketch given geometric figures such as a circle, triangle, rectangle, and square with the help of ball-point pen under given vibration stimuli in two postures (sketch pad on lap and sketch pad on table). The deviation in distortion with respect to the given figure is represented in terms of percentage distortion. The influence of vibrations on the sketching activity was investigated both subjectively and by two specifically designed objective methods, namely, RMS (root mean square methodology) and area methods. The judgements of perceived difficulty to sketch were rated using seven-point semantic judgement scale. The percentage distortion and difficulty in sketching activity increased with an increase in vibration magnitude. Both subjective evaluation and the RMS method revealed that the task was affected more while sketching on the table. The percentage distortion was affected similarly and maximum in all the vibration directions except for the vertical, while sketching difficulty was found to be higher only with longitudinal and multi-axis vibration direction. The subjective evaluation also revealed that there was no effect of the type of entity chosen on the sketching difficulty. [ABSTRACT FROM AUTHOR]

In this paper, a laboratory technique for determination of rolling dynamic stiffness and damping coefficients of small-sized, bias-ply tyres has been discussed. The effect of normal load, inflation pressure and speed on four different tyres has been reported. The results show similar trends to those reported by other investigators. [ABSTRACT FROM AUTHOR]

Discusses copolyamides and soluble aromatic polyamides. Syntheses of polyamides; Characterization of polyamides; Effect of structure on properties of polyamides.

Papaver rhoeas plant is common in many regions worldwide and contributes to the landscape with its red flower. In the present study we first carried out morphological investigation by optical and scanning electron microscopy of the ovules within the ovary. After ovules’ isolation we prepared extracts to test possible cytotoxic activities on HL60 leukemia human cells and investigated the extracts using thin-layer chromatography (TLC) and gas-chromatography/mass spectrometry (GC-MS). P. rhoeas ovules showed an elongated, round shape and the presence of ordered sculptures on the ovule surface. The ovule extracts showed cytotoxic activity on HL60 human cells mainly found in some TLC-isolated spots. Compounds consisting of active spots were identified by GC-MS investigations. Our findings on the P. rhoeas ovule compounds open perspectives for further investigations of TLC-isolated spots on other human cancer cell lines.

The impact of raltegravir-resistant HIV-1 minority variants (MVs) on raltegravir treatment failure is unknown. Illumina sequencing offers greater throughput than 454, but sequence analysis tools for viral sequencing are needed. We evaluated Illumina and 454 for the detection of HIV-1 raltegravir-resistant MVs.A5262 was a single-arm study of raltegravir and darunavir/ritonavir in treatment-naïve patients. Pre-treatment plasma was obtained from 5 participants with raltegravir resistance at the time of virologic failure. A control library was created by pooling integrase clones at predefined proportions. Multiplexed sequencing was performed with Illumina and 454 platforms at comparable costs. Illumina sequence analysis was performed with the novel snp-assess tool and 454 sequencing was analyzed with V-Phaser.Illumina sequencing resulted in significantly higher sequence coverage and a 0.095% limit of detection. Illumina accurately detected all MVs in the control library at ≥0.5% and 7/10 MVs expected at 0.1%. 454 sequencing failed to detect any MVs at 0.1% with 5 false positive calls. For MVs detected in the patient samples by both 454 and Illumina, the correlation in the detected variant frequencies was high (R2 = 0.92, P