The SF36 as an outcome measure of services for end stage renal failure

OBJECTIVE: —To evaluate the use of the short form 36 (SF36) as a measure of health related quality of life of patients with end stage renal failure, document the results, and investigate factors, including mode of treatment, which may influence it. DESIGN: Cross sectional survey of patients with end stage renal failure, with the standard United Kingdom version of the SF36 supplemented by specific questions for end stage renal failure. SETTING: A teaching hospital renal unit. Subjects and methods—660 patients treated at the Sheffield Kidney Institute by haemodialysis, peritoneal dialysis, and transplantation. Internal consistency, percentage of maximal or minimal responses, SF36 scores, effect sizes, correlations between independent predictor variables and individual dimension scores of the SF36. Multiple regression analysis of the SF36 scores for the physical functioning, vitality, and mental health dimensions against treatment, age, risk (comorbidity) score, and other independent variables. RESULTS: A high response rate was achieved. Internal consistency was good. There were no floor or ceiling effects other than for the two “role” dimensions. Overall health related quality of life was poor compared with the general population. Having a functioning transplant was a significant predictor of higher score in the three dimensions (physical functioning, vitality, and mental health) for which multiple regression models were constructed. Age, sex, comorbidity, duration of treatment, level of social and emotional support, household numbers, and hospital dialysis were also (variably) significant predictors. CONCLUSIONS: The SF36 is a practical and consistent questionnaire in this context, and there is evidence to support its construct validity. Overall the health related quality of life of these patients is poor, although transplantation is associated with higher scores independently of the effect of age and comorbidity. Age, comorbidity, and sex are also predictive of the scores attained in the three dimensions studied. Further studies are required to ascertain whether altering those predictor variables which are under the influence of professional carers is associated with changes in health related quality of life, and thus confirm the value of this outcome as a measure of quality of care

Focused Rayleigh wave EMAT for characterisation of surface-breaking defects

Developments towards higher resolution and the ability to detect small defects are bringing a step-change in non-destructive testing. This paper presents a new method for increasing resolution, using a focused electromagnetic acoustic transducer (EMAT) optimised to generate Rayleigh waves at 2 MHz. This high frequency allows detection of mm-depth defects, and the focusing allows sizing of much shorter defects than is possible when using standard EMATs. The focusing behaviour and the aperture angle effect are analysed using laser vibrometry and finite element modelling, showing that a reduced aperture shifts the focal point from the designed value and increases the focal depth. The dual-EMAT has excellent signal to noise ratio (up to 30 dB) and has been used in single shot mode to image a variety of surface-breaking defects, including detecting and positioning a pair of real defects in an aluminium billet sample, and a machined defect of 2 mm length, 0.2 mm width, and 1.5 mm depth, giving an upper limit on the defect length of 2.1 plus or minus 0.5 mm. The results can be used to design an EMAT with optimised focal behaviour for defect detection

Enhanced Surface Defect Detection Using Focused Electromagnetic Acoustic Transducers (EMATs)

Electromagnetic Acoustic Transducers (EMATs) are non-contact ultrasound transducers which function primarily via Lorentz force induction. Their non-contact nature allows for fast scanning, inspection of challenging surfaces, and performance in harsh environments. To meet industry demand, non-destructive evaluation (NDE) techniques need increasingly high resolution for the detection of smaller defects. For surface acoustic wave inspection of surface-breaking defects, using a higher frequency wave gives better depth resolution. However, the EMAT coil width has to decrease to increase the frequency, leading to a trade off with the signal strength. The use of geometric focusing is showing promise for increasing ultrasound strength and defect imaging precision, overcoming some of the issues associated with the use of higher frequency surface acoustic waves. Understanding and optimising transducer design is essential to obtain optimal signal strength, high frequency operation, and the ability to operate at stand-off from the sample. In this work multiple focused and unfocused EMAT coil configurations are presented. Focusing is seen to give significantly enhanced resolution for defects, with accurate detection of thin cracks, 0.2 wide, 2 mm length, 1.5 mm depth. The relationship between coil design and stand-off is investigated. Multiple phased coils are proposed to increase signal strength without lowering the frequency

The effect of EMAT coil geometry on the Rayleigh wave frequency behaviour

Understanding of optimal signal generation and frequency content for electromagnetic acoustic transducers (EMATs) is key to improving their design and signal to noise ratio. Linear and meander coil designs are fairly well understood, but other designs such as racetrack or focused coils have recently been proposed. Multiple transmission racetrack coil EMATs, with focused and unfocused designs, were constructed. The optimum driving frequency for maximum detected signal was found to range between 1.1 and 1.4 MHz on aluminium for a 1.5 mm width coil. A simple analytical model based on the instantaneous velocity of a wave predicts a maximum signal at 1.44 MHz. Modelling the detection coil as a spatial square wave agrees with this, and predicts a general relation of fP = 0.761v / L between the optimum frequency fP , the wave velocity v, and the coil width L. A time domain model of the detection coil predicts a 1.4 to 1.5 MHz peak for continuous wave excitation, with a frequency that decreases as the length of the wavepacket is decreased, consistent with the experimental data. Linear coil modelling using the same technique is shown to be consistent with previous work, with improving detection at lower wave frequencies, and signal minima at every integer multiple of the wavelength. Finite Element Analysis (FEA) is used to model the effects of the spatial width of the racetrack generation coil and focused geometry, and no significant difference is found between the focused and the unfocused EMAT response. This highlights the importance of designing the EMAT coil for the correct lift-off and desired frequency of operation

Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

Electromagnetic Acoustic Transducers (EMATs) are a useful ultrasonic tool for non-destructive evaluation in harsh environments due to their non-contact capabilities, and their ability to operate through certain coatings. This work presents a new Rayleigh wave EMAT transducer design, employing geometric focusing to improve the signal strength and detection precision of surface breaking defects. The design is robust and versatile, and can be used at frequencies centered around 1 MHz. Two coils are used in transmission mode, which allows the usage of frequency-based measurement of the defect depth. Using a 2 MHz driving signal, a focused beam spot with a width of 1.3±0.25 mm and a focal depth of 3.7±0.25 mm is measured, allowing for defect length measurements with an accuracy of±0.4 mm and detection of defects as small as 0.5 mm depth and 1 mm length. A set of four coils held under one magnet is used to find defects at orientations offset from normal to the ultrasound beam propagation direction. This EMAT has a range which allows detection of defects which propagate at angles from 16° to 170° relative to the propagation direction over the range of 0–180°, and the setup has the potential to be able to detect defects propagating at all angles relative to the wave propagation direction if two coils are alternately employed as generation coils

Improving the Dirac Operator in Lattice QCD

Recently various new concepts for the construction of Dirac operators in lattice Quantum Chromodynamics (QCD) have been introduced. These operators satisfy the so-called Ginsparg-Wilson condition (GWC), thus obeying the Atiyah-Singer index theorem and violating chiral symmetry only in a modest and local form. Here we present studies in 4-d for SU(3) gauge configurations with non-trivial topological content. We study the flow of eigenvalues and we compare the numerical stability and efficiency of a recently suggested chirally improved operator with that of others in this respect.Comment: Contrib. to Conf. on Comp. Physics, Sept. 2001 (Aachen); 4 pages, 4 figures, (LaTeX style files cpauth.cls, elsart.cls

Low-Lying Nucleons from Chirally Improved Fermions

We report on our preliminary results on the low-lying excited nucleon spectra which we obtain through a variational basis formed with three different interpolators.Comment: Contributed to Lattice 2003(spectrum), Tsukub

The condensate for two dynamical chirally improved quarks in QCD

We compare the eigenvalue spectra of the Dirac operator from a simulation with two mass degenerate dynamical chirally improved fermions with Random Matrix Theory. Comparisons with distribution of k-th eigenvalues (k=1,2) in fixed topological sectors (nu=0,1) are carried out using the Kolmogorov-Smirnov test. The eigenvalue distributions are well described by the RMT predictions. The match allows us to read off the quark condensate in the chiral limit directly. Correcting for finite size and renormalization we obtain a mean value of -(276 (11)(16) MeV)**3 in the MS-bar scheme.Comment: 8 pages, 2 figures, Final version. To be publishe

The zeros of the QCD partition function

We establish a relationship between the zeros of the partition function in the complex mass plane and the spectral properties of the Dirac operator in QCD. This relation is derived within the context of chiral Random Matrix Theory and applies to QCD when chiral symmetry is spontaneously broken. Further, we introduce and examine the concept of normal modes in chiral spectra. Using this formalism we study the consequences of a finite Thouless energy for the zeros of the partition function. This leads to the demonstration that certain features of the QCD partition function are universal.Comment: 13 page