963 research outputs found
The effect of signal acquisition and processing choices on ApEn values: Towards a âgold standardâ for distinguishing effort levels from isometric force records
Approximate Entropy (ApEn) is frequently used to identify changes in the complexity of isometric force records with ageing and disease. Different signal acquisition and processing parameters have been used, making comparison or confirmation of results difficult. This study determined the effect of sampling and parameter choices by examining changes in ApEn values across a range of submaximal isometric contractions of the First Dorsal Interosseus. Reducing the sample rate by decimation changed both the value and pattern of ApEn values dramatically. The pattern of ApEn values across the range of effort levels was not sensitive to the filter cut-off frequency, or the criterion used to extract the section of data for analysis. The complexity increased with increasing effort levels using a fixed ârâ value (which accounts for measurement noise) but decreased with increasing effort level when ârâ was set to 0.1 of the standard deviation of force. It is recommended isometric force records are sampled at frequencies >200 Hz, template length (âmâ) is set to 2, and 'r' set to measurement system noise or 0.1 SD depending on physiological process to be distinguished. It is demonstrated that changes in ApEn across effort levels are related to changes in force gradation strategy
A comparative study on approximate entropy measure and poincaré plot indexes of minimum foot clearance variability in the elderly during walking
Background: Trip-related falls which is a major problem in the elderly population, might be linked to declines in the balance control function due to ageing. Minimum foot clearance (MFC) which provides a more sensitive measure of the motor function of the locomotor system, has been identified as a potential gait parameter associated with trip-related falls in older population. This paper proposes nonlinear indexes (approximate entropy (ApEn) and Poincaré plot indexes) of MFC variability and investigates the relationship of MFC with derived indexes of elderly gait patterns. The main aim is to find MFC variability indexes that well correlate with balance impairments.
Methods:
MFC data during treadmill walking for 14 healthy elderly and 10 elderly participants with balance problems and a history of falls (falls risk) were analysed using a PEAK-2D motion analysis system. ApEn and Poincaré plot indexes of all MFC data sets were calculated and compared.
Results:
Significant relationships of mean MFC with Poincaré plot indexes (SD1, SD2) and ApEn (r = 0.70, p < 0.05; r = 0.86, p < 0.01; r = 0.74, p < 0.05) were found in the falls-risk elderly group. On the other hand, such relationships were absent in the healthy elderly group. In contrast, the ApEn values of MFC data series were significantly (p < 0.05) correlated with Poincaré plot indexes of MFC in the healthy elderly group, whereas correlations were absent in the falls-risk group. The ApEn values in the falls-risk group (mean ApEn = 0.18 ± 0.03) was significantly (p < 0.05) higher than that in the healthy group (mean ApEn = 0.13 ± 0.13). The higher ApEn values in the falls-risk group might indicate increased irregularities and randomness in their gait patterns and an indication of loss of gait control mechanism. ApEn values of randomly shuffled MFC data of falls risk subjects did not show any significant relationship with mean MFC.
Conclusion:
Results have implication for quantifying gait dynamics in normal and pathological conditions, thus could be useful for the early diagnosis of at-risk gait. Further research should provide important information on whether falls prevention intervention can improve the gait performance of falls risk elderly by monitoring the change in MFC variability indexes
The Galactic Magnetic Field's Effect in Star-Forming Region
We investigate the effect of the Milky Way's magnetic field in star forming
regions using archived 350 micron polarization data on 52 Galactic star
formation regions from the Hertz polarimeter module. The polarization angles
and percentages for individual telescope beams were combined in order to
produce a large-scale average for each source and for complexes of sources. In
more than 80% of the sources, we find a meaningful mean magnetic field
direction, implying the existence of an ordered magnetic field component at the
scale of these sources. The average polarization angles were analyzed with
respect to the Galactic coordinates in order to test for correlations between
polarization percentage, polarization angle, intensity, and Galactic location.
No correlation was found, which suggests that the magnetic field in dense
molecular clouds is decoupled from the large-scale Galactic magnetic field.
Finally, we show that the magnetic field directions in the complexes are
consistent with a random distribution on the sky
Why I tense up when you watch me: inferior parietal cortex mediates an audienceâs influence on motor performance
The presence of an evaluative audience can alter skilled motor performance through changes in force output. To investigate how this is mediated within the brain, we emulated real-time social monitoring of participantsâ performance of a fine grip task during functional magnetic resonance neuroimaging. We observed an increase in force output during social evaluation that was accompanied by focal reductions in activity within bilateral inferior parietal cortex. Moreover, deactivation of the left inferior parietal cortex predicted both inter- and intra-individual differences in socially-induced change in grip force. Social evaluation also enhanced activation within the posterior superior temporal sulcus, which conveys visual information about othersâ actions to the inferior parietal cortex. Interestingly, functional connectivity between these two regions was attenuated by social evaluation. Our data suggest that social evaluation can vary force output through the altered engagement of inferior parietal cortex; a region implicated in sensorimotor integration necessary for object manipulation, and a component of the action-observation network which integrates and facilitates performance of observed actions. Social-evaluative situations may induce high-level representational incoherence between oneâs own intentioned action and the perceived intention of others which, by uncoupling the dynamics of sensorimotor facilitation, could ultimately perturbe motor output
Experiences with Airborne and Ground-Based Polarimetry
Polarimetry in the far-infrared and submillimeter has been valuable in
tracing magnetic fields in bright Galactic Clouds. We discuss the techniques we
have developed and trends we have found in polarization vs column density, and
vs wavelength. The polarization spectrum has proven to be more interesting than
had been anticipated. It is potentially valuable in explaining grain alignment
and in characterizing dust species. One can expect the infrared cirrus to be a
much simpler environment than the molecular clouds that have heretofore been
explored at multiple wavelengths. Although cirrus observations must deal with
low signals and wide extent, it is becoming possible to measure accurately the
spectral energy distribution from mid-infrared to microwave frequencies and it
should soon become feasible to determine the polarization spectrum over the
same range.Comment: 12 pages, 6 figures, To be published in the proceedings of ``The
Cosmic Microwave Background and its Polarization'', New Astronomy Reviews
(eds. S. Hanany and K. A.Olive
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Maternal gaze to the infant face: effects of infant age and facial configuration during mother-infant engagement in the first nine weeks
Background
Adult gaze plays an important role in early infant development, and infants are highly sensitive to its presence and direction. Little is known, however, about how adults look at infants while interacting with them. Using eye-tracking technology, this study investigated maternal gaze during naturalistic interactions, and how it was influenced by infant age, focusing on the transition from the first to the second month when social expressiveness emerges, and by infant facial configuration, focusing on the effect of cleft lip.
Methods
Thirty infants (10 with a cleft lip), and their mothers, were seen at 1, 3, 5, 7, and 9 weeks. Mothers were asked to interact with their infants while wearing eye-tracking glasses. Fixation duration and count were calculated for general (infant face, body, and surrounding environment), and infant facial (eyes, mouth, other) areas.
Results
At all ages, mothers gazed almost exclusively towards their infantâs face, but this was reduced in the presence of a cleft lip. Within the infantâs face, the eyes attracted the greatest attention, for all mothers, at all ages. From the first to the second month, all mothers increased their visual attention towards their infantâs mouth. Regardless of infant age, the presence of a cleft lip was associated with decreased maternal gaze to the infantâs mouth.
Conclusions
This study provides novel findings concerning maternal gaze to infant faces during naturalistic interactions. Maternal gaze changes with infant age, in line with established shifts in social development, and according to infant facial configuration. Decreased gaze to the mouth area associated with infant cleft lip might affect maternal responsiveness, and suggests new dimensions to target in supporting these mothers
A comparative study on approximate entropy measure and poincaré plot indexes of minimum foot clearance variability in the elderly during walking
Background: Trip-related falls which is a major problem in the elderly population, might be linked to declines in the balance control function due to ageing. Minimum foot clearance (MFC) which provides a more sensitive measure of the motor function of the locomotor system, has been identified as a potential gait parameter associated with trip-related falls in older population. This paper proposes nonlinear indexes (approximate entropy (ApEn) and Poincaré plot indexes) of MFC variability and investigates the relationship of MFC with derived indexes of elderly gait patterns. The main aim is to find MFC variability indexes that well correlate with balance impairments.
Methods:
MFC data during treadmill walking for 14 healthy elderly and 10 elderly participants with balance problems and a history of falls (falls risk) were analysed using a PEAK-2D motion analysis system. ApEn and Poincaré plot indexes of all MFC data sets were calculated and compared.
Results:
Significant relationships of mean MFC with Poincaré plot indexes (SD1, SD2) and ApEn (r = 0.70, p < 0.05; r = 0.86, p < 0.01; r = 0.74, p < 0.05) were found in the falls-risk elderly group. On the other hand, such relationships were absent in the healthy elderly group. In contrast, the ApEn values of MFC data series were significantly (p < 0.05) correlated with Poincaré plot indexes of MFC in the healthy elderly group, whereas correlations were absent in the falls-risk group. The ApEn values in the falls-risk group (mean ApEn = 0.18 ± 0.03) was significantly (p < 0.05) higher than that in the healthy group (mean ApEn = 0.13 ± 0.13). The higher ApEn values in the falls-risk group might indicate increased irregularities and randomness in their gait patterns and an indication of loss of gait control mechanism. ApEn values of randomly shuffled MFC data of falls risk subjects did not show any significant relationship with mean MFC.
Conclusion:
Results have implication for quantifying gait dynamics in normal and pathological conditions, thus could be useful for the early diagnosis of at-risk gait. Further research should provide important information on whether falls prevention intervention can improve the gait performance of falls risk elderly by monitoring the change in MFC variability indexes
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The effects of maternal mirroring on the development of infant social expressiveness: the case of infant cleft lip
Parent-infant social interactions start early in development, with infants showing active communicative expressions by just two months. A key question is how this social capacity develops. Maternal mirroring of infant expressions is considered an important, intuitive, parenting response, but evidence is sparse in the first two months concerning the conditions under which mirroring occurs and its developmental sequelae, including in clinical samples where the infantâs social expressiveness may be affected. We investigated these questions by comparing the development of mother-infant interactions between a sample where the infant had cleft lip and a normal, unaffected, comparison sample. We videotaped dyads in their homes five times from one to ten weeks and used a microanalytic coding scheme for maternal and infant behaviours, including infant social expressions, and maternal mirroring and marking responses. We also recorded maternal gaze to the infant, using eye-tracking glasses. Although infants with cleft lip did show communicative behaviours, the rate of their development was slower than in comparison infants. This group difference was mediated by a lower rate of mirroring of infant expressions by mothers of infants with cleft lip; this effect was, in turn, partly accounted for by reduced gaze to the infantâs mouth, although the clarity of infant social expressions (indexed by cleft severity) and maternal self-blame regarding the cleft were also influential. Results indicate the robustness of parent-infant interactions but also their sensitivity to specific variations in interactantsâ appearance and behaviour. Parental mirroring appears critical in infant social development, likely supported by the mirror neuron system and underlying clinical and, possibly, cultural differences in infant behaviour. These findings suggest new avenues for clinical intervention
The cell envelope subtilisin-like proteinase is a virulence determinant for Streptococcus suis
<p>Abstract</p> <p>Background</p> <p><it>Streptococcus suis </it>is a major swine pathogen and zoonotic agent that mainly causes septicemia, meningitis, and endocarditis. It has recently been suggested that proteinases produced by <it>S. suis </it>(serotype 2) are potential virulence determinants. In the present study, we screened a <it>S. suis </it>mutant library created by the insertion of Tn<it>917 </it>transposon in order to isolate a mutant deficient in a cell surface proteinase. We characterized the gene and assessed the proteinase for its potential as a virulence factor.</p> <p>Results</p> <p>Two mutants (G6G and M3G) possessing a single Tn<it>917 </it>insertion were isolated. The affected gene coded for a protein (SSU0757) that shared a high degree of identity with <it>Streptococccus thermophilus </it>PrtS (95.9%) and, to a lesser extent, with <it>Streptococcus agalactiae </it>CspA (49.5%), which are cell surface serine proteinases. The SSU0757 protein had a calculated molecular mass of 169.6 kDa and contained the catalytic triad characteristic of subtilisin family proteinases: motif I (Asp<sub>200</sub>), motif II (His<sub>239</sub>), and motif III (Ser<sub>568</sub>). SSU0757 also had the Gram-positive cell wall anchoring motif (Leu-Pro-X-Thr-Gly) at the carboxy-terminus, which was followed by a hydrophobic domain. All the <it>S. suis </it>isolates tested, which belonged to different serotypes, possessed the gene encoding the SSU0757 protein. The two mutants devoid of subtilisin-like proteinase activity had longer generation times and were more susceptible to killing by whole blood than the wild-type parent strain P1/7. The virulence of the G6G and M3G mutants was compared to the wild-type strain in the CD1 mouse model. Significant differences in mortality rates were noted between the P1/7 group and the M3G and G6G groups (<it>p </it>< 0.001).</p> <p>Conclusion</p> <p>In summary, we identified a gene coding for a cell surface subtilisin-like serine proteinase that is widely distributed in <it>S. suis</it>. Evidences were brought for the involvement of this proteinase in <it>S. suis </it>virulence.</p
Polarisation Observations of VY Canis Majoris Water Vapour 5{32}-4{41} 620.701 GHz Maser Emission with HIFI
CONTEXT: Water vapour maser emission from evolved oxygen-rich stars remains
poorly understood. Additional observations, including polarisation studies and
simultaneous observation of different maser transitions may ultimately lead to
greater insight. AIMS: We have aimed to elucidate the nature and structure of
the VY CMa water vapour masers in part by observationally testing a theoretical
prediction of the relative strengths of the 620.701 GHz and the 22.235 GHz
maser components of ortho water vapour. METHODS: In its high-resolution mode
(HRS) the Herschel Heterodyne Instrument for the Infrared (HIFI) offers a
frequency resolution of 0.125 MHz, corresponding to a line-of-sight velocity of
0.06 km/s, which we employed to obtain the strength and linear polarisation of
maser spikes in the spectrum of VY CMa at 620.701 GHz. Simultaneous ground
based observations of the 22.235 GHz maser with the Max-Planck-Institut f\"ur
Radioastronomie 100-meter telescope at Effelsberg, provided a ratio of 620.701
GHz to 22.235 GHz emission. RESULTS:We report the first astronomical detection
to date of water vapour maser emission at 620.701 GHz. In VY CMa both the
620.701 and the 22.235 GHz polarisation are weak. At 620.701 GHz the maser
peaks are superposed on what appears to be a broad emission component, jointly
ejected asymmetrically from the star. We observed the 620.701 GHz emission at
two epochs 21 days apart, both to measure the potential direction of linearly
polarised maser components and to obtain a measure of the longevity of these
components. Although we do not detect significant polarisation levels in the
core of the line, they rise up to approximately 6% in its wings
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