Biodynamics of the human body under whole-body vibration: Synthesis of the reported data

Identification of most probable ranges of biodynamic responses of the human body exposed to whole-body vibration is essential for developing effective integrated human-machine system design tools, improved vibration mitigation devices and frequency-weighting for exposure assessment. The international standard, ISO-5982 (2001), defines such ranges for very limited conditions, namely for body seated without a back support and exposed to vertical vibration. The reported data on biodynamic responses of the seated and standing human body exposed to whole-body vibration along different directions and the associated experimental conditions are systematically reviewed in an attempt to identify datasets that are likely to represent comparable and practical postural and exposure conditions. Syntheses of datasets, selected on the basis of a set of criterion, are performed to identify the most probable ranges of biodynamic responses of the human body to whole-body vibration. These include the driving-point biodynamic responses of the body seated with and without a back support while exposed to fore-aft, lateral and vertical vibration and those of the standing body to vertical vibration, and seat-to-head vibration transmissibility of the seated body. The proposed ranges are expected to serve as reasonable target functions in various applications involving coupled human-system dynamics in the design process, and potentially for developing better frequency-weightings for exposure assessments

Apparent mass of small children: Experimental measurements

A test facility and protocol were developed for measuring the seated, vertical, whole-body vibration response of small children of less than 18 kg in mass over the frequency range from 1 to 45 Hz. The facility and protocol adhered to the human vibration testing guidelines of BS7085 and to current codes of ethics for research involving children. Additional procedures were also developed which are not currently defined in the guidelines, including the integral involvement of the parents and steps taken to maximize child happiness. Eight children were tested at amplitudes of 0.8 and 1.2 m/s2 using band-limited, Gaussian, white noise acceleration signals defined over the frequency interval from 1 to 50 Hz. Driving point apparent mass modulus and phase curves were determined for all eight children at both test amplitudes. All results presented a single, principal, anti-resonance, and were similar to data reported for primates and for adult humans seated in an automotive posture which provided backrest support. The mean frequency of the apparent mass peak was 6.25 Hz for the small children, as compared to values between 6.5 - 8.5 Hz for small primates and values between 6.5 - 8.6 Hz for adults seated with backrest support. The peak value of the mean, normalized, apparent mass was 1.54 for the children, which compares to values from 1.19 to 1.45 reported in the literature for small primates and 1.28 for adults seated with backrest support. ISO standard 5982, which specifies a mean, normalized, apparent mass modulus peak of 1.50 at a frequency of 4.0 Hz for adults seated without backrest support, provides significant differences

Vibration reduction for vision systems on board unmanned aerial vehicles using a neuro-fuzzy controller

In this paper, an intelligent control approach based on neuro-fuzzy systems performance is presented, with the objective of counteracting the vibrations that affect the low-cost vision platform onboard an unmanned aerial system of rotating nature. A scaled dynamical model of a helicopter is used to simulate vibrations on its fuselage. The impact of these vibrations on the low-cost vision system will be assessed and an intelligent control approach will be derived in order to reduce its detrimental influence. Different trials that consider a neuro-fuzzy approach as a fundamental part of an intelligent semi-active control strategy have been carried out. Satisfactory results have been achieved compared to those obtained by means of vibration reduction passive techniques

DNA Methylation Analysis Reveals Distinct Methylation Signatures in Pediatric Germ Cell Tumors

Background: Aberrant DNA methylation is a prominent feature of many cancers, and may be especially relevant in germ cell tumors (GCTs) due to the extensive epigenetic reprogramming that occurs in the germ line during normal development. Methods: We used the Illumina GoldenGate Cancer Methylation Panel to compare DNA methylation in the three main histologic subtypes of pediatric GCTs (germinoma, teratoma and yolk sac tumor (YST); N = 51) and used recursively partitioned mixture models (RPMM) to test associations between methylation pattern and tumor and demographic characteristics. We identified genes and pathways that were differentially methylated using generalized linear models and Ingenuity Pathway Analysis. We also measured global DNA methylation at LINE1 elements and evaluated methylation at selected imprinted loci using pyrosequencing. Results: Methylation patterns differed by tumor histology, with 18/19 YSTs forming a distinct methylation class. Four pathways showed significant enrichment for YSTs, including a human embryonic stem cell pluripotency pathway. We identified 190 CpG loci with significant methylation differences in mature and immature teratomas (q \u3c 0.05), including a number of CpGs in stem cell and pluripotency-related pathways. Both YST and germinoma showed significantly lower methylation at LINE1 elements compared with normal adjacent tissue while there was no difference between teratoma (mature and immature) and normal tissue. DNA methylation at imprinted loci differed significantly by tumor histology and location. Conclusion: Understanding methylation patterns may identify the developmental stage at which the GCT arose and the at-risk period when environmental exposures could be most harmful. Further, identification of relevant genetic pathways could lead to the development of new targets for therapy

Mechanical impedances distributed at the fingers and palm of the human hand in three orthogonal directions

The objective of this study is to investigate the basic characteristics of the three axis mechanical impedances distributed at the fingers and palm of the hand subjected to vibrations along three orthogonal directions (xh, yh, and zh). Seven subjects participated in the experiment on a novel three-dimensional (3-D) hand–arm vibration test system equipped with a 3-D instrumented handle. The total impedance of the entire hand–arm system was obtained by performing a sum of the distributed impedances. Two major resonances were observed in the impedance data in each direction. For the hand forces (30 N grip and 50 N push) and body postures applied in this study, the first resonance was in the range of 20–40 Hz, and it was primarily observed in the impedance at the palm. The second resonance was generally observed in the impedance at the fingers, while the resonance frequency varied greatly with the subject and vibration direction, ranging from 100 to 200 Hz in the xh direction, 60 to 120 Hz in the yh direction, and 160 to 300 Hz in the zh direction. The impedance at the palm was greater than that at the fingers below a certain frequency in the range of 50–100 Hz, depending on the vibration direction. At higher frequencies, however, the impedance magnitude at the fingers either approached or exceeded that at the palm. The impedance in the zh direction was generally higher than those in the other directions, but it became comparable with that in the xh direction at frequencies above 250 Hz, while the impedance in the yh direction was the lowest. The frequency dependencies of the vibration power absorptions for the entire hand–arm system in the three directions were different, but their basic trends were similar to that of the frequency weighting defined in the current ISO standard. The implications of the results are discussed