Frequency Dimensions Research Articles

Measurement Properties of the Late Life Disability Index Among Individuals Who Use Power Wheelchairs as Their Primary Means of Mobility

ObjectiveTo examine the reliability, validity, and factor structure of the Late Life Disability Instrument (LLDI) in individuals who use power wheelchairs as their primary means of mobility. DesignA 4-week, test-retest study design. SettingFive Canadian cities. ParticipantsThe validity sample included 115 new and experienced power mobility users, and the reliability sample included 85 experienced users (N=115). These volunteer samples included individuals who were aged ≥50 years and independently used power mobility as their primary means of mobility. InterventionsNot applicable. Main Outcome MeasureThe LLDI measures participation in 2 dimensions of 16 life activities: frequency and perceived limitations. Validity measures included the Wheelchair Skills Test–power version, the Assistive Technology Outcomes Profile for Mobility, the Hospital Anxiety and Depression Scale, the Power Mobility Wheelchair Confidence Measure, and the Life Space Assessment. ResultsFor the reliability sample, raw intraclass correlational coefficients for limitation and frequency dimension scores ranged from .855 (95% confidence interval .781–.905) to .883 (95% confidence interval, .822–.924), respectively. For the validity sample, scores on the LLDI were correlated as hypothesized with scores on validity measures. The factor structure that was identified with the original sample was not replicated among power wheelchair users. For LLDI frequency, exploratory factor analysis indicated that 5 of the original 16 items did not perform similarly among power wheelchair users. For LLDI limitations, a 1-factor, rather than a 2-factor, solution was identified. ConclusionsThe study provides evidence in support of the reliability and validity of the measure but suggests that the original subscale scores may not be applicable to power wheelchair users.

Accelerating diffusion-ordered NMR spectroscopy by joint sparse sampling of diffusion and time dimensions.

Diffusion-ordered multidimensional NMR spectroscopy is a valuable technique for the analysis of complex chemical mixtures. However, this method is very time-consuming because of the costly sampling of a multidimensional signal. Various sparse sampling techniques have been proposed to accelerate such measurements, but they have always been limited to frequency dimensions of NMR spectra. It is now revealed how sparse sampling can be extended to diffusion dimensions.

Accelerating Diffusion‐Ordered NMR Spectroscopy by Joint Sparse Sampling of Diffusion and Time Dimensions

AbstractDiffusion‐ordered multidimensional NMR spectroscopy is a valuable technique for the analysis of complex chemical mixtures. However, this method is very time‐consuming because of the costly sampling of a multidimensional signal. Various sparse sampling techniques have been proposed to accelerate such measurements, but they have always been limited to frequency dimensions of NMR spectra. It is now revealed how sparse sampling can be extended to diffusion dimensions.

What About Spectrum Opportunities in ‘Angle’ Dimension for Dynamic Spectrum Access in Cognitive Radio Network context? A new Paradigm in Spectrum Sensing

The cognitive radio technology is the new paradigm to fulfill ever increasing need of bandwidth ultimately the radio spectrum by accommodating the radio spectrum dynamically to secondary users/unlicensed users without causing the interference. In cognitive radio, the spectrum opportunities have been checked for Space, Time and frequency dimensions but `Angle' dimension has not been explored till now. In this paper we have investigated accuracy of various `Angle-of-Arrival (AoA)' estimation algorithms: ESPRIT, MUSIC, Bartlett, and Capon for opportunistic secondary users' network under AWGN and time varying fading channels. The improvement in performance of these algorithms has been observed as array elements, signal-to-noise ratio and samples increases. An `adaptive thresholding' technique has been proposed to improve the performance of AoA algorithms. Thus by estimating an `Angle-of- Arrival' of licensed users, the unlicensed users can be accommodated in the same geographical area into the same channel in the same frequency band at the same time by directing unlicensed users' beam in different direction than the direction of licensed users. Thereby improving spectrum utilization.

Localised two-dimensional correlated spectroscopy based on Hadamard encoding technique

A new pulse sequence based on Hadamard encoding technique, dubbed as Hadamard encoded localised correlation spectroscopy (HLCOSY) was devised to speed up the acquisition of localised two-dimensional (2D) nuclear magnetic resonance (NMR) correlation spectroscopy (LCOSY). Direct frequency-domain (F2) excitation with an array of different radiofrequencies has been used to speed up 2D NMR experiments by a large factor. Multiplex excitation in the indirect frequency (F1) dimension is restricted to the signal-bearing regions and is encoded according to a Hadamard matrix of order N, where N is a relatively small number. The detected signals are decoded by reference to the same Hadamard matrix. An HLCOSY spectrum of a two-compartment phantom was obtained with a total acquisition time of 32 s, with its volume localisation confirmed. The success in achieving 2D LCOSY spectrum of pig marrow within 40 s shows the feasibility of HLCOSY for the detection of biological tissues. It may provide a promising way for in vivo and in vitro NMRs.

Disentangling the frequency and intensity dimensions of nuisance odour, and implications for jurisdictional odour impact criteria

Many jurisdictions compare model predicted odour concentration statistics against regulatory exposure limits or criteria in order to assess the risk of proposed developments resulting in nuisance odour impacts. However dose–response studies designed to calibrate such criteria have returned widely divergent findings, particularly regarding the degree of influence that the frequency and intensity of odour impact events have on adverse community response (annoyance). In the absence of clear guidance from empirical data, jurisdictions have adopted a wide range of odour impact criteria and harmonisation has proven difficult to progress. This lack of harmonisation constitutes a significant gap in best-practice standards for odour impact assessment methodology and creates a substantial risk of poor assessment outcomes.In this paper a conceptual framework is developed which facilitates close investigation of the relationship between annoyance levels, the frequency and intensity dimensions of nuisance odour and exposure criteria. Within this framework the efficacy of single-percentile odour criteria to limit nuisance odour impacts is examined for several models of annoyance. Significant short-comings in single-percentile criteria are identified in those models in which both the frequency and intensity of impact events are assumed to influence annoyance on time-scales such as a year. The merits and limitations of an alternative multi-percentile criterion framework approach are examined. Models of annoyance developed within the framework suggest an improved concept of odour criteria that may lead to better assessment outcomes, assist with the reconciliation of some seemingly disparate dose–response study findings and aid harmonisation of jurisdictional exposure limits.

E-Service Quality in Higher Education and Frequency of Use of the Service

Universities have been at the forefront of online service provision. Regular evaluations and appraisals of its e-services provided to students are regularly improvised to keep pace with the rapid changes of learning technology and competitiveness of its services provided. There is a dread of research works investigating e-service quality supporting learning, research and communication and how it is related to student’s frequency of use from various sources of e-service provided to students. Data were collected from 210 students through questionnaire surveys through a structured random sampling method and analyzed statistically. The dimensions for frequency of use of e-service are from learning and research, administration, coordination, evaluation and contents storage sources. This research work has developed a single dimension comprising six elements to measure the quality of e-service in higher education namely in areas of learning, research and communication support. These elements are: 1) e-service is always available, 2) overall it is very convenience to use, 3) the user interface has a well organized appearance, 4) makes it easy to find what is needed, 5) the e-service has met needs and experience, and 6) e-service assures schedule flexibility. This study has also provided empirical evidence that there are relationships between the level and frequency in the use of e-service quality supporting learning, research and communication.

Influence of some key factors on material damping of steel beams

Material damping affects the dynamic behaviors of engineering structures considerably, but up to till now little research is maintained on influence factors of material damping. Based on the damping-stress function of steel, the material damping of steel beams is obtained by calculating the stress distribution of the beams with an analytical method. Some key influence factors of the material damping, such as boundary condition, amplitude and frequency of excitation, load position as well as the cross-sectional dimension of a steel beam are analyzed respectively. The calculated results show that even in elastic scope, material damping does not remain constant but varies with these influence factors. Although boundary condition affects material damping to some extent, such influence can be neglected when the maximum stress amplitude of the beam is less than the fatigue limit of steel. Exciting frequency, load position and cross-section dimension have great effects on the material damping of the beam which maintain the similar changing trend under different boundary conditions respectively.

Transient 2D-IR spectroscopy of inorganic excited states.

Time-resolved infrared spectroscopy has been proven to be a powerful tool for investigating the structure, dynamics and reactivity of electronically-excited states of inorganic molecules. As applications drive the production of ever more complex molecules however, experimental tools that can deliver more detailed spectroscopic information, or separate multiple contributions to complex signals will become increasingly valuable. In this Perspective, the extension of ultrafast infrared spectroscopy of inorganic excited states to a second frequency dimension using transient 2D-IR spectroscopy (T-2D-IR) methods is discussed. Following a brief discussion of the experimental methodologies, examples will be given of applications of T-2D-IR ranging from studies of the spectroscopy, structure and dynamics of photochemical intermediates to new tools for correlating vibrational modes in ground and excited electronic states and the investigation of excited state solvation dynamics. Future directions for these experiments are also discussed.

Area Per Lipid of Membranes from Natural Abundance Solid-State 13C NMR Spectroscopy

The properties of liquid-crystalline membranes vary according to the molecular composition of the lipid bilayer [1]. Structural investigations of lipid membranes using NMR spectroscopy generally require isotopic labeling of the lipids, thereby precluding investigations of complex lipid systems. Combining natural-abundance solid-state 13C magic-angle-spinning (MAS) NMR with a statistical mean torque (MT) model [2] enabled us to obtain the average area per lipid and volumetric bilayer thickness DB for lipid bilayers. The 2D separated local field (SLF) NMR experiment DROSS gives isotropic chemical shifts in the F2 frequency dimension and site-specific dipolar Pake doublets in the F1 dimension [1]. By analyzing the Pake patterns we extracted 13C-1H residual dipolar couplings (RDCs) and calculated segmental |SCH| order parameters. The |SCH| order parameters carry the structural information that aid calculation of and DB using the MT model. Experiments were conducted with DMPC, POPC, and EYSM lipids as single component (liquid-disordered, ld) lipid bilayers as well as with cholesterol. EYSM is more ordered in the ld phase and hence experiences less structural perturbation upon adding cholesterol to form the liquid-ordered (lo) phase relative to POPC. We infer that the cholesterol stiffening effect on lipid bilayers is limited by the maximum volumetric hydrocarbon thickness [2]. Knowledge of structural parameters like and DB is important for molecular dynamics (MD) simulations and provides information about the balance of forces in membrane lipid bilayers [3]. Our studies demonstrate the applicability of solid-state 13C NMR spectroscopy to site-specific structural investigations of complex lipids, where isotope labeling may be prohibitive, allowing structural studies of biologically relevant membrane systems. [1] A. Leftin et al.(2013) JMB425 2973-2987. [2] H. I. Petrache et al.(2000) BJ.79 3172-3192. [3] A. Leftin et al.(2011) BBA1808 818-839.

Joint DOD and DOA Estimation for High Speed Target Using Bistatic MIMO Radar

In bistatic multiple-input multiple-output (MIMO) radar, range migration and invalidly synthesized virtual array resulting from the serious mismatch of matched filter make it difficult to estimate direction of departure (DOD) and direction of arrival (DOA) of high speed target using the traditional superresolution algorithms. In this study, a method for joint DOD and DOA estimation of high speed target using bistatic MIMO radar is proposed. After multiplying the received signals with the conjugate of the delayed versions of the transmitted signals, Fourier transform (FT) of the multiplied signals over both fast time and slow time is employed. Then, the target components of radar return corresponding to the different transmitted waveforms can be perfectly separated at the receivers by extracting the target frequency-domain data along slow-time frequency dimension when the delay between the transmitted signals and their subsequent returns is timed. By splicing the separated target components distributed along several range cells, the virtual array can be formed, and then DOD and DOA of high speed target can be estimated using the superresolution algorithm with the range migration and the mismatch of matched filter properly removed. Simulation results have proved the validity of the proposed algorithm.

L -infinity norm design of linear-phase robust broadband beamformers using constrained optimization

A new method for the design of linear-phase robust far-field broadband beamformers using constrained optimization is proposed. In the method, the maximum passband ripple and minimum stopband attenuation are ensured to be within prescribed levels, while at the same time maintaining a good linear-phase characteristic at a prescribed group delay in the passband. Since the beamformer is intended primarily for small-sized microphone arrays where the microphone spacing is small relative to the wavelength at low frequencies, the beamformer can become highly sensitive to spatial white noise and array imperfections if a direct minimization of the error is performed. Therefore, to limit the sensitivity of the beamformer the optimization is carried out by constraining a sensitivity parameter, namely, the white noise gain (WNG) to be above prescribed levels across the frequency band. Two novel design variants have been developed. The first variant is formulated as a convex optimization problem where the maximum error in the passband is minimized, while the second variant is formulated as an iterative optimization problem and has the advantage of significantly improving the linear-phase characteristics of the beamformer under any prescribed group delay or linear-array configuration. In the second variant, the passband group-delay deviation is minimized while ensuring that the maximum passband ripple and stopband attenuation are within prescribed levels. To reduce the computational effort in carrying out the optimization, a nonuniform variable sampling approach over the frequency and angular dimensions is used to compute the required parameters. Experiment results show that beamformers designed using the proposed methods have much smaller passband group-delay deviation for similar passband ripple and stopband attenuation than a modified version of an existing method.

Classification of Musical Timbre Using Bayesian Networks

In this article, we explore the use of Bayesian networks for identifying the timbre of musical instruments. Peak spectral amplitude in ten frequency windows is extracted for each of 20 time windows to be used as features. Over a large data set of 24,000 audio examples covering the full musical range of 24 different common orchestral instruments, four different Bayesian network structures, including naive Bayes, are examined and compared with two support vector machines and a k-nearest neighbor classifier. Classification accuracy is examined by instrument, instrument family, and data set size. Bayesian networks with conditional dependencies in the time and frequency dimensions achieved 98 percent accuracy in the instrument classification task and 97 percent accuracy in the instrument family identification task. These results demonstrate a significant improvement over the previous approaches in the literature on this data set. Additionally, we tested our Bayesian approach on the widely used Iowa musical instrument data set, with similar results.

Resolution and measurement of heteronuclear dipolar couplings of a noncrystalline protein immobilized in a biological supramolecular assembly by proton-detected MAS solid-state NMR spectroscopy

Two-dimensional 15N chemical shift/1H chemical shift and three-dimensional 1H–15N dipolar coupling/15N chemical shift/1H chemical shift MAS solid-state NMR correlation spectra of the filamentous bacteriophage Pf1 major coat protein show single-site resolution in noncrystalline, intact-phage preparations. The high sensitivity and resolution result from 1H detection at 600MHz under 50kHz magic angle spinning using ∼0.5mg of perdeuterated and uniformly 15N-labeled protein in which the exchangeable amide sites are partially or completely back-exchanged (reprotonated). Notably, the heteronuclear 1H–15N dipolar coupling frequency dimension is shown to select among 15N resonances, which will be useful in structural studies of larger proteins where the resonances exhibit a high degree of overlap in multidimensional chemical shift correlation spectra.

The CSAI-2: An Examination of the Instrument's Factorial Validity and Reliability of the Intensity, Direction and Frequency Dimensions with Brazilian Athletes

The Competitive State Anxiety Inventory (CSAI-2) has been a widely used instrument for the assessment of anxiety in sport but within limited cultural contexts. Conceptual issues as well as concerns about the psychometric properties of the measure have resulted in questions surrounding its use. The purposes of the present study were (a) to examine the factorial validity and reliability of the CSAI-2, including the intensity, direction, and frequency dimensions with a Brazilian sample; (b) to investigate the inter-scale correlations among the three measured dimensions and between the original and the reduced scales; and (c) to examine the properties of the CSAI-2 within a novel cultural context. A sample of 334 athletes (245 male, 89 female) completed the CSAI-2 questionnaire 1hr prior to competition. Confirmatory factor analyses were conducted that contrasted the proposed model with competing models. These results provided support for a reduced measurement model (CSAI-2R; 16 items) that was comprised of three factors (cognitive anxiety, somatic anxiety and self-confidence). The pattern of inter-scale associations revealed correlated, but not identical, factors. Correlations between the original and the reduced scales were high. In conclusion, these results provide evidence that the CSAI-2R (16 items) has good psychometric properties for all response dimensions within a Brazilian cultural context and is a valid competitive state anxiety and self-confidence measure when used immediately prior to competition.

Vigorexia e níveis de dependência de exercício em frequentadores de academias e fisiculturistas

INTRODUÇÃO: Atualmente, a aparência é sinônimo de sucesso, saúde e determinação. De modo que a sociedade moderna oprima os indivíduos a seguir padrões estereotipados de beleza. E como herança dessa sociedade capitalista e egoísta surgem os transtornos psíquicos da aparência e as dependências psíquicas a eles associadas. OBJETIVOS: i) comparar os níveis de vigorexia e de dependência ao exercício entre frequentadores de academias e fisiculturistas; ii) relacionar as variáveis de prática de exercício físico (tempo de prática, frequência semanal e duração por sessão) com as dimensões de frequência de vigorexia e de dependência ao exercício; e, iii) comparar os níveis de vigorexia segundo grupos de dependência ao exercício (dependentes ou em risco, não dependente sintomático e não dependente assintomático). MÉTODOS: A amostra foi constituída por 151 frequentadores de academia (27,66 ± 6,54 anos e 27,56 ± 5,03 de IMC) e 25 fisiculturistas (30,80 ± 5,54 anos e 26,72 ± 4,24 de IMC), todos do sexo masculino. Os participantes responderam à Escala de Dependência ao Exercício e ao Inventário de Dismorfia Muscular. A análise estatística envolveu procedimentos de análise descritiva, normalidade univariada, comparativa e correlacional. RESULTADOS: Os principais resultados evidenciaram: i) não existir diferenças entre frequentadores de academias e fisiculturistas quanto aos níveis de vigorexia e de dependência ao exercício; ii) que a duração da sessão de treino se correlaciona positivamente com a maioria das dimensões da dependência ao exercício; e, iii) que o grupo classificado como dependente ou em risco revela níveis médios superiores de vigorexia. CONCLUSÃO: Por fim, constatou-se que tanto nos fisiculturistas como nos frequentadores de academias, quanto maior o nível de vigorexia, maior o nível de dependência ao exercício, sendo essa correlação maior em fisiculturistas.

Impact of Transaction Attributes on Transaction Costs in Project Alliances: Disaggregated Analysis

Previous alliancing research has seldom addressed the implication of transaction costs and the impact of transaction attributes on transaction costs in project alliancing. Using multiple regression analysis on a sample of Australian alliances, this study tests the differential impact of uncertainty, frequency, and various dimensions of contracting parties' asset specificity on three individual transaction cost elements (set-up, monitoring, and enforcement costs). The results indicate that the impact of transaction attributes on transaction costs varies. Uncertainty has a positive impact on all three transaction cost elements. Frequency and some dimensions of contracting parties' asset specificity are positively associated with set-up costs and monitoring costs, which, however, does not apply to enforcement costs. The findings provide empirical evidence in support of the transaction cost economics' prediction regarding the influence of transaction attributes on transaction costs in the Australian construction industry, and thereby add another perspective to the knowledge base in the construction management discipline. The measurement methods of transaction attributes and transaction costs presented have valuable implications for future research.

The progression of severe behavior disorder in young children with intellectual and developmental disabilities

Behavior disorders, such as self-injurious, stereotypic, and aggressive behavior are common among individuals with intellectual or developmental disabilities. While we have learned much about those behaviors over the past few decades, longitudinal research that looks at developmental trajectory has been rare. This study was designed to examine the trajectory of these three forms of severe behavior disorders over a one year time period. The behaviors were measured on two dimensions: frequency of occurrence and severity. Participants were 160 infants and toddlers at risk for developmental delays in Lima, Peru. Using structural equation modeling, we found that the frequency of self-injury and stereotypic behavior and the severity of aggressive behavior remained stable over the 12-month period. Uni-directional structural models fit the data best for self-injurious and aggressive behavior (with frequency being a leading indicator of future severity of self-injury and severity being a leading indicator of future frequency for aggression). For stereotypic behavior, a cross-lagged autoregressive model fit the data best, with both dimensions of frequency and severity involved as leading indicators of each other. These models did not vary significantly across diagnostic groups, suggesting that toddlers exhibiting behavior disorders may be assisted with interventions that target the specific frequencies or severities of behaviors, regardless of diagnostic category.

Stress and symptoms of depression among medical students at the University of Copenhagen

This article aims to assess the levels of stress and symptoms of depression among Danish medical students, as well as explore the effect of social support on psychological distress. The results are based on numbers from the follow-up study 'From Student to Graduate' (j.nr 2006-41-6876). Two dimensions of stress, frequency and perception, were measured on a scale from 0-6. Odds ratios and significance of associations between the various exposure variables and the outcome measure, symptoms of depression, were calculated using multiple logistic regression and Wald tests. 30.5% of the students reported depressive symptoms. Stress frequency measured a mean of 2.26 (SD = 1.35). The mean for stress perception was 2.85 (SD = 1.30). Women reported higher levels of stress and depression compared to male medical students, but the differences were not significant (p > 0.05). Only the dimensions of stress and coping alone were significantly associated with reporting symptoms of depression (p < 0.001). Students coping alone had a two times higher odds ratio for reporting depressive symptoms. Nearly one third of the participants reported feeling depressed. Stress levels were moderate, but significantly associated with symptoms of depression. The interaction between the stress dimensions and the outcome measure illustrates the importance of stress appraisal. Coping alone with psychological problems was significantly associated with symptoms of depression.

Frequency and recency context for the management and retrieval of personal information on mobile devices

As users store increasingly larger amounts of personal information on their mobiles, the task of retrieving such items (e.g., contacts) becomes more difficult. We show that users can be categorized by their communication patterns and that each category benefits differently from supporting contact management applications. By examining mobile user call logs, we show that it is possible to aid retrieval tasks using relatively simple heuristics and algorithms that describe usage context, using solely the dimensions of contact use frequency and recency. We compare and discuss the results of the proposed method applied on two different mobile datasets: a large dataset from NOKIA and a smaller dataset collected by ourselves.