A new spatiotemporal regularization approach for reconstruction of cardiac transmembrane potential patterns

The single-beat reconstruction of electrical cardiac sources from body-surface electrocardiogram data might become an important issue for clinical application. The feasibility and field of application of noninvasive imaging methods strongly depend on development of stable algorithms for solving the underlying ill-posed inverse problems. We propose a novel spatiotemporal regularization approach for the reconstruction of surface transmembrane potential (TMP) patterns. Regularization is achieved by imposing linearly formulated constraints on the solution in the spatial as well as in the temporal domain. In the spatial domain an operator similar to the surface Laplacian, weighted by a regularization parameter, is used. In the temporal domain monotonic nondecreasing behavior of the potential is presumed. This is formulated as side condition without the need of any regularization parameter. Compared to presuming template functions, the weaker temporal constraint widens the field of application because it enables the reconstruction of TMP patterns with ischemic and infarcted regions. Following the line of Tikhonov regularization, but considering all time points simultaneously, we obtain a linearly constrained sparse large-scale convex optimization problem solved by a fast interior point optimizer. We demonstrate the performance with simulations by comparing reconstructed TMP patterns with the underlying reference patterns.     

A comparison of noninvasive reconstruction of epicardial versus transmembrane potentials in consideration of the null space

We compare two source formulations for the electrocardiographic forward problem in consideration of their implications for regularizing the ill-posed inverse problem. The established epicardial potential source model is compared with a bidomain-theory-based transmembrane potential source formulation. The epicardial source approach is extended to the whole heart surface including the endocardial surfaces. We introduce the concept of the numerical null and signal space to draw attention to the problems associated with the nonuniqueness of the inverse solution and show that reconstruction of null-space components is an important issue for physiologically meaningful inverse solutions. Both formulations were tested with simulated data generated with an anisotropic heart model and with clinically measured data of two patients. A linear and a recently proposed quasi-linear inverse algorithm were applied for reconstructions of the epicardial and transmembrane potential, respectively. A direct comparison of both formulations was performed in terms of computed activation times. We found the transmembrane potential-based formulation is a more promising source formulation as stronger regularization by incorporation of biophysical a priori information is permitted.     

Design and imaging performance of achromatic diffractive-refractive x-ray and gamma-ray Fresnel lenses

Achromatic combinations of a diffractive phase Fresnel lens and a refractive correcting element have been proposed for x-ray and gamma-ray astronomy and for microlithography, but considerations of absorption often dictate that the refractive component be given a stepped profile, resulting in a double Fresnel lens. The imaging performance of corrected Fresnel lenses, with and without stepping, is investigated, and the trade-off between resolution and useful bandwidth in different circumstances is discussed. Provided that the focal ratio is large, correction lenses made from low atomic number materials can be used with x rays in the range of approximately 10-100 keV without stepping. The use of stepping extends the possibility of correction to higher-aperture systems, to energies as low as a few kilo electron volts, and to gamma rays of mega electron volt energy.     

A measure of teachers' observations of student behavior.

Describes the construction of the Rochester School Competency Schedule, a 26-item inventory derived by factor analysis to measure the ways in which teachers categorize students' behavior. 4 factors are involved, reflecting cognitive competence, social compliance, motivational orientation, and social competence. Test-retest reliability over 4 wks on a sample of 12 teachers was obtained using the final instrument; reliability coefficients for the 4 factors respectively were .80, .79, .71, and .75, with a coefficient for the total score of .85. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversal shift preferences in process and reactive schizophrenic, brain-damaged, and control group patients.

Compared process and reactive schizophrenic, brain-damaged, and normal control groups (n = 34 each) in frequency of reversal shifts in discrimination learning using the optional-shift paradigm. The main hypothesis that reactive schizophrenics, like normal adults, would show a stronger preference for reversal shifts than would process Ss was supported. Results show that significantly more reactive (68%) than process (44%) Ss made reversal shifts. Significantly more brain-damaged and reactive schizophrenic Ss showed reversal shift preferences when color was learned initially rather than form, while such initial concept preferences were not found in the process schizophrenic or normal control Ss. Previous findings in discrimination learning with pathological groups are discussed in the context of these findings. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laboratory-scale mirrors for submillimeter wavelengths

A machining procedure based on an elementary concept has been applied successfully to produce metal mirrors suitable for submillimeter wavelengths. Ninety-degree off-axis paraboloidal or ellipsoidal mirror sections may be cut from brass or aluminum by means of a series of predetermined increments on a conventional laboratory lathe. Paraboloidal mirrors with low f-numbers (f/2) made by this technique have been used with good results as part of the collecting optics of a submillimeter-wave heterodyne radiometer.     

Temporal lobe epilepsy and schizophrenia: Comparison of reaction time deficits.

Current theory suggests that temporal–limbic dysfunction is responsible for schizophrenic symtomatology. Such theory dovetails with many reports of a higher frequency of schizophreniform psychoses in temporal lobe epilepsy (TLE) than is found with other forms of seizure activity. To explore the possibility of a common neurological substrate for the 2 disorders, a variable foreperiod reaction-time task, on which early crossover has been found to be characteristic of many schizophrenics, was administered to 11 schizophrenics, 12 TLE patients, 9 generalized seizure patients, and 10 normal controls. Results show that only TLE and schizophrenic Ss showed an early crossover of regular and irregular preparatory interval gradients. Discussion focuses on the status of crossover as a marker variable, and relevant animal and human lesion literature is reviewed. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Review of the U.S. Department of Energy's Inertial Fusion Energy Program

This is the final report of a panel set up by the U.S. Department of Energy (DOE) Fusion Energy Sciences Advisory Committee (FESAC) in response to a charge letter from Dr. Ray Orbach (Appendix A). In that letter, Dr. Orbach asked FESAC for an assessment of the present status of inertial fusion energy (IFE) research carried out in contributing programs. These programs include the heavy ion (HI) beam, the high average power laser (HAPL), and Z-Pinch drivers and associated technologies, including fast ignition (FI). This report, presented to FESAC on March 29, 2004, and subsequently approved by them (Appendix B), presents FESAC's response to that charge.