Assessing reproducibility of data obtained with instruments based on continuous measurements

Data obtained with any research tool must be reproducible, a concept referred to as reliability. Three techniques are often used to evaluate reliability of tools using continuous data in aging research: intraclass correlation coefficients (ICC), Pearson correlations, and paired t tests. These are often construed as equivalent when applied to reliability. This is not correct, and may lead researchers to select instruments based on statistics that may not reflect actual reliability. The purpose of this paper is to compare the reliability estimates produced by these three techniques and determine the preferable technique. A hypothetical dataset was produced to evaluate the reliability estimates obtained with ICC, Pearson correlations, and paired t tests in three different situations. For each situation two sets of 20 observations were created to simulate an intrarater or inter-rater paradigm, based on 20 participants with two observations per participant. Situations were designed to demonstrate good agreement, systematic bias, or substantial random measurement error. In the situation demonstrating good agreement, all three techniques supported the conclusion that the data were reliable. In the situation demonstrating systematic bias, the ICC and t test suggested the data were not reliable, whereas the Pearson correlation suggested high reliability despite the systematic discrepancy. In the situation representing substantial random measurement error where low reliability was expected, the ICC and Pearson coefficient accurately illustrated this. The t test suggested the data were reliable. The ICC is the preferred technique to measure reliability. Although there are some limitations associated with the use of this technique, they can be overcome.

Measuring the psychosocial characteristics of family caregivers of palliative care patients:psychometric properties of nine self-report instruments

Researchers and clinicians have experienced substantial difficulties locating measures that are suitable for use within palliative care settings. This article details the psychometric properties of nine instruments designed to assess the following psychosocial characteristics of family caregivers: competence, mastery, self-efficacy, burden, optimism, preparedness, social support, rewards, and mutuality. Results are based on the responses of 106 primary family caregivers caring for relatives dying of cancer. Principal components extraction with varimax rotation was used to explore the underlying structure of each measure. Following the exclusion of complex variables, suggested components for most measures comprised relatively homogenous items, which were good to excellent measures of each component. Some components comprised only two items; however, Cronbach's alphas typically indicated moderate to high levels of internal consistency. Overall, the results of this study suggest that most of the measures analyzed, excepting the mastery and mutuality scales, can be recommended to examine the family caregiver experience and test supportive interventions.

Choosing appropriate patient-reported outcomes instrument for glaucoma research: a systematic review of vision instruments

PURPOSE: To identify vision Patient-Reported Outcomes instruments relevant to glaucoma and assess their content validity.

METHODS: MEDLINE, MEDLINE in Process, EMBASE and SCOPUS (to January 2009) were systematically searched. Observational studies or randomised controlled trials, published in English, reporting use of vision instruments in glaucoma studies involving adults were included. In addition, reference lists were scanned to identify additional studies describing development and/or validation to ascertain the final version of the instruments. Instruments' content was then mapped onto a theoretical framework, the World Health Organization International Classification of Functioning, Disability and Health. Two reviewers independently evaluated studies for inclusion and quality assessed instrument content.

RESULTS: Thirty-three instruments were identified. Instruments were categorised into thirteen vision status, two vision disability, one vision satisfaction, five glaucoma status, one glaucoma medication related to health status, five glaucoma medication side effects and six glaucoma medication satisfaction measures according to each instruments' content. The National Eye Institute Visual Function Questionnaire-25, Impact of Vision Impairment and Treatment Satisfaction Survey-Intraocular Pressure had the highest number of positive ratings in the content validity assessment.

CONCLUSION: This study provides a descriptive catalogue of vision-specific PRO instruments, to inform the choice of an appropriate measure of patient-reported outcomes in a glaucoma context.

Dialogic Instruments: Virtuosity (Re)Located in Improvised Performance

This paper introduces a series of new musical instruments that have been designed to
address questions relating to performative virtuosity in the area of ensemble-based
improvisation. The intentionally exploited inconsistent nature of these instruments
raises questions around traditional notions of instrument mastery and opens up
possible methods of recon?guring the performer-instrument relationship.

Physical and numerical constraints in source modeling for finite difference simulation of room acoustics

In finite difference time domain simulation of room acoustics, source functions are subject to various constraints. These depend on the way sources are injected into the grid and on the chosen parameters of the numerical scheme being used. This paper addresses the issue of selecting and designing sources for finite difference simulation, by first reviewing associated aims and constraints, and evaluating existing source models against these criteria. The process of exciting a model is generalized by introducing a system of three cascaded filters, respectively, characterizing the driving pulse, the source mechanics, and the injection of the resulting source function into the grid. It is shown that hard, soft, and transparent sources can be seen as special cases within this unified approach. Starting from the mechanics of a small pulsating sphere, a parametric source model is formulated by specifying suitable filters. This physically constrained source model is numerically consistent, does not scatter incoming waves, and is free from zero- and low-frequency artifacts. Simulation results are employed for comparison with existing source formulations in terms of meeting the spectral and temporal requirements on the outward propagating wave.

Auditory gist: Recognition of very short sounds from timbre cues

Sounds such as the voice or musical instruments can be recognized on the basis of timbre alone. Here, sound recognition was investigated with severely reduced timbre cues. Short snippets of naturally recorded sounds were extracted from a large corpus. Listeners were asked to report a target category (e.g., sung voices) among other sounds (e.g., musical instruments). All sound categories covered the same pitch range, so the task had to be solved on timbre cues alone. The minimum duration for which performance was above chance was found to be short, on the order of a few milliseconds, with the best performance for voice targets. Performance was independent of pitch and was maintained when stimuli contained less than a full waveform cycle. Recognition was not generally better when the sound snippets were time-aligned with the sound onset compared to when they were extracted with a random starting time. Finally, performance did not depend on feedback or training, suggesting that the cues used by listeners in the artificial gating task were similar to those relevant for longer, more familiar sounds. The results show that timbre cues for sound recognition are available at a variety of time scales, including very short ones.

An investigation of the changes in the natural frequency of a Pile affected by Scour

Scour around bridge foundations is one of the leading causes of bridge failure. Up until recently, the monitoring of this phenomenon was primarily based around using underwater instrumentation to monitor the progression of scour holes as they develop around foundation systems. Vibration-based damage detection techniques have been used to detect damage in bridge beams. The application of these vibration based methods to the detection of scour has come to the fore in research in recent years. This paper examines the effect that scour has on the frequency response of a driven pile foundation system, similar to those used to support road and rail bridges. The effect of scour on the vibration characteristics of the pile is examined using laboratory and field testing. It is clear that there is a very clear reduction in the natural frequency of the pile as the severity of scour increases. It is shown that by combining state-of-the-art geotechnical techniques with relatively simple finite element modelling approaches, it is possible to accurately predict the natural frequency of the pile for a given scour depth. Therefore, the paper proposes a method that would allow the estimation of scour depth for a given observed pile frequency.

Assessing the needs of informal caregivers to cancer survivors: a review of the instruments

Objective: Cancer may impact negatively on an informal caregiver's health long after treatment has ended. This review identifies the self-report measures currently in use to measure caregivers need for support and determines their scientific soundness and clinical utility.

Method: A systematic electronic database search of Medline, CINAHL, PsychINFO, BNI ProQuest was conducted. The psychometric properties and clinical utility of needs assessment tools for caregivers of cancer survivors (excluding advanced disease) were extracted and summarised.

Results: Seven cancer survivor caregiver needs assessment tools were identified. Data on instrument development was well reported, although variability was noted in their structure and content. The majority demonstrated some degree of reliability and validity; only two were evaluated for test–retest reliability (CaSPUN and SPUNS) with only the SPUNS showing a high degree of reliability over time. The Health Care Needs Survey (HCNS), Needs Assessment of Family Caregivers-Cancer (NAFC-C) and Cancer Caregiving Tasks Consequences and Needs Questionnaire (CaTCoN) have been validated at various stages of the cancer continuum. Minimal data was available on responsiveness.

Conclusion: All assessment tools identified require further psychometric analysis. For research purposes, the use of the SPUNS (with its acceptable test–retest reliability) appears most appropriate; although its length may be of concern for clinical use; therefore, the shorter SCNS-P&C is likely to be more suitable for use clinically. At present, the NAFC-C demonstrates a great potential in both the research and clinical environments; however, it requires further psychometric testing before it can be fully recommended. Further analysis is necessary on ideal response formats and the meaning of a total needs score.

Sound Synthesis for Contact-Driven Musical Instruments via Discretisation of Hamilton's Equations

Physical modelling of musical instruments involves studying nonlinear interactions between parts of the instrument. These can pose several difficulties concerning the accuracy and stability of numerical algorithms. In particular, when the underlying forces are non-analytic functions of the phase-space variables, a stability proof can only be obtained in limited cases. An approach has been recently presented by the authors, leading to unconditionally stable simulations for lumped collision models. In that study, discretisation of Hamilton’s equations instead of the usual Newton’s equation of motion yields a numerical scheme that can be proven to be energy conserving. In this paper, the above approach is extended to collisions of distributed objects. Namely, the interaction of an ideal string with a flat barrier is considered. The problem is formulated within the Hamiltonian framework and subsequently discretised. The resulting nonlinearmatrix equation can be shown to possess a unique solution, that enables the update of the algorithm. Energy conservation and thus numerical stability follows in a way similar to the lumped collision model. The existence of an analytic description of this interaction allows the validation of the model’s accuracy. The proposed methodology can be used in sound synthesis applications involving musical instruments where collisions occur either in a confined (e.g. hammer-string interaction, mallet impact) or in a distributed region (e.g. string-bridge or reed-mouthpiece interaction).

Investigation of tanpura string vibrations using a two-dimensional time-domain model incorporating coupling and bridge friction

Tanpura string vibrations have been investigated previously using numerical models based on energy conserving schemes derived from a Hamiltonian description in one-dimensional form. Such time-domain models have the property that, for the lossless case, the numerical Hamiltonian (representing total energy of the system) can be proven to be constant from one time step
to the next, irrespective of any of the system parameters; in practice the Hamiltonian can be shown to be conserved within machine precision. Models of this kind can reproduce a jvari effect, which results from the bridge-string interaction. However the one-dimensional formulation has recently been shown to fail to replicate the jvaris strong dependence on the thread placement. As a first step towards simulations which accurately emulate this sensitivity to the thread placement, a twodimensional model is proposed, incorporating coupling of controllable level between the two string polarisations at the string termination opposite from the barrier. In addition, a friction force acting when the string slides across the bridge in horizontal direction is introduced, thus effecting a further damping mechanism. In this preliminary study, the string is terminated at the position of the thread. As in the one-dimensional model, an implicit scheme has to be used to solve the system, employing Newton's method to calculate the updated positions and momentums of each string segment. The two-dimensional model is proven to be energy conserving when the loss parameters are set to zero, irrespective of the coupling constant. Both frequency-dependent and independent losses are then added to the string, so that the model can be compared to analogous instruments. The influence of coupling and the bridge friction are investigated.