A new instrument for targeting falls prevention interventions was accurate and clinically applicable in a hospital setting

Background and Objective: To describe the diagnostic accuracy and practical application of the Peter James Centre Falls Risk Assessment Tool (PJC-FRAT), a multidisciplinary falls risk screening and intervention deployment instrument. Methods: In phase 1, the accuracy of the PJC-FRAT was prospectively compared to a gold standard (the STRATIFY) on a cohort of subacute hospital patients (n = 122). In phase 2, the PJC-FRAT was temporally reassessed using a subsequent cohort (n = 316), with results compared to those of phase 1. Primary outcomes were falls (events), fallers (patients who fell), and hospital completion rates of the PJC-FRAT. Results: In phase 1, PJC-FRAT accuracy of identifying falters showed sensitivity of 73% (bootstrap 95% confidence interval CI = 55, 90) and specificity of 75% (95% CI = 66, 83), compared with the STRATIFY (cutoff >= 2/5) sensitivity of 77% (95% CI = 59, 92) and specificity of 51% (95% CI = 41, 61). This difference was not significant. In phase 2, accuracy of nursing staff using the PJC-FRAT was lower. PJC-FRAT completion rates varied among disciplines over both phases: nurses and physiotherapists, >= 90%; occupational therapists, >= 82%; and medical officers, >= 57%. Conclusion: The PJC-FRAT was practical and relatively accurate as a predictor of falls and a deployment instrument for falls prevention interventions, although continued staff education may be necessary to maintain its accuracy. (c) 2006 Elsevier Inc. All rights reserved.

Bandwidth requirements for shallow, high-resolution seismic reflection

The optimum bandwidth for shallow, high-resolution seismic reflection differs from that required for conventional petroleum reflection. An understanding of this issue is essential for correct choice of acquisition instrumentation. Numerical modelling of simple Bowen Basin coal structures illustrates that, for high-resolution imaging, it is important to accurately record all frequencies up to the limit imposed by earth scattering. On the contrary, the seismic image is much less dependent on frequencies at the lower end of the spectrum. These quantitative observations support the use of specialised high-frequency geophones for high-resolution seismic imaging. Synthetic seismic inversion trials demonstrate that, irrespective of the bandwidth of the seismic data, additional low-frequency impedance control is essential for accurate inversion. Inversion provides no compelling argument for the use of conventional petroleum geophones in the high-resolution arena.

Distortion product otoacoustic emissions in school children: Effects to gender, ear asymmetry and handedness

Accurate interpretation of distortion product otoacoustic emission (DPOAE) data cannot be made without realizing the effects of non-pathological factors on DPOAEs. The present study aimed to examine the effects of ear asymmetry, gender and handedness on DPOAEs obtained from school children. One thousand and three children (528 boys and 475 girls) with a mean age of 6.2 years (SD = 0.4, range = 5.2 7.9 years) were tested in a quiet room at their schools using the GSI-60 DPOAE system. The stimuli consisted of two pure tones of different frequencies f1 and f2 presented at 65 and 55dB SPL respectively. A DP-gram was obtained for each ear with f2 varying from 1.1 to 6.0 kHz and the ratio of f2/f1 being kept at 1.21. The signal-to-noise ratios (SNR) (DPOAE amplitude minus the mean noise floor) at the tested frequencies 1.1, 1.5, 1.9, 2.4, 3.0, 3.8, 4.8, and 6.0 kHz were measured. The results revealed a small, but significant difference in SNR between ears, with right ears showing a higher mean SNR than left ears at 1.9, 3.0, 3.8 and 6.0 kHz. At these frequencies, the difference in mean SNR between ears was less than 1 dB. A significant gender effect was also found, with girls exhibiting a higher SNR than boys at 3.8, 4.8 and 6.0 kHz. The difference in mean SNR, as a result of the gender effect, was about 1 to 2 dB at these frequencies. The results from the present study indicated no significant difference in mean SNR between left-handed and right-handed children for all tested frequencies. In conclusion, these non-pathological characteristics of DPOAEs should be considered in the interpretation of DPOAE results for school children.

Nanofabricated media with negative permeability at visible frequencies

A great deal of attention has recently been focused on a new class of smart materials-so-called left-handed media-that exhibit highly unusual electromagnetic properties and promise new device applications. Left-handed materials require negative permeability ν, an extreme condition that has so far been achieved only for frequencies in the microwave to terahertz range. Extension of the approach described in ref. 7 to achieve the necessary high-frequency magnetic response in visible optics presents a formidable challenge, as no material-natural or artificial-is known to exhibit any magnetism at these frequencies. Here we report a nanofabricated medium consisting of electromagnetically coupled pairs of gold dots with geometry carefully designed at a 10-nm level. The medium exhibits a strong magnetic response at visible-light frequencies, including a band with negative ν. The magnetism arises owing to the excitation of an antisymmetric plasmon resonance. The high-frequency permeability qualitatively reveals itself via optical impedance matching. Our results demonstrate the feasibility of engineering magnetism at visible frequencies and pave the way towards magnetic and left-handed components for visible optics. © 2005 Nature Publishing Group.

Low spatial frequencies are suppressively masked across spatial scale, orientation, field position, and eye of origin

Masking is said to occur when a mask stimulus interferes with the visibility of a target (test) stimulus. One widely held view of this process supposes interactions between mask and test mechanisms (cross-channel masking), and explicit models (e.g., J. M. Foley, 1994) have proposed that the interactions are inhibitory. Unlike a within-channel model, where masking involves the combination of mask and test stimulus within a single mechanism, this cross-channel inhibitory model predicts that the mask should attenuate the perceived contrast of a test stimulus. Another possibility is that masking is due to an increase in noise, in which case, perception of contrast should be unaffected once the signal exceeds detection threshold. We use circular patches and annuli of sine-wave grating in contrast detection and contrast matching experiments to test these hypotheses and investigate interactions across spatial frequency, orientation, field position, and eye of origin. In both types of experiments we found substantial effects of masking that can occur over a factor of 3 in spatial frequency, 45° in orientation, across different field positions and between different eyes. We found the effects to be greatest at the lowest test spatial frequency we used (0.46 c/deg), and when the mask and test differed in all four dimensions simultaneously. This is surprising in light of previous work where it was concluded that suppression from the surround was strictly monocular (C. Chubb, G. Sperling, & J. A. Solomon, 1989). The results confirm that above detection threshold, cross-channel masking involves contrast suppression and not (purely) mask-induced noise. We conclude that cross-channel masking can be a powerful phenomenon, particularly at low test spatial frequencies and when mask and test are presented to different eyes. © 2004 ARVO.

Data analysis methods in optometry Part 3: the analysis of frequencies and proportions

In some studies, the data are not measurements but comprise counts or frequencies of particular events. In such cases, an investigator may be interested in whether one specific event happens more frequently than another or whether an event occurs with a frequency predicted by a scientific model.