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Phase-plane-derived distortion modeling of a fast and accurate digitizing sampler

Continued efforts to model the distortion behavior of custom-designed digitizing samplers for accurate measurement of dynamic signals are reported. This work is part of ongoing efforts at the National Institute of Standards and Technology (NIST) to advance the state of the art in waveform sampling metrology. In this paper, an analytic error model for a sampler having a -3-dB 6-GHz bandwidth is described. The model is derived from examination of the sampler's error behavior in the phase plane. The model takes as inputs the per-sample estimates of signal amplitude, first derivative, and second derivative, where the derivatives are with respect to time. The model's analytic form consists of polynomials in these terms, which are chosen from consideration of the voltage dependence of the digitizer input capacitance and the previously studied error behavior in a predecessor digitizer. At 1 GHz, an improvement in total harmonic distortion from -32 to -46 dB is obtained when model-generated sample corrections are applied to the waveform. The effect of timebase distortion in the sampling system is also accounted for and corrected. The inclusion of second-derivative dependence in the model is shown to improve the model's fit to the measured data by providing fine temporal adjustment of the fitted waveform.     

Episodic remembering in a population-based sample of nonagenarians: Does major depression exacerbate the memory deficits seen in Alzheimer's disease?

Population-based samples of normal old adults and people with major depression (MD), Alzheimer's disease (AD), and coexisting MD and AD (MD + AD) between 90 and 100 years of age were assessed in face recognition, word recall, and object recall. Results indicated a consistent pattern across tasks: no differences between the normal old and the MD participants or between the AD and MD + AD participants in any task, a clear performance decrement in the AD and MD + AD participants in all task variables reflecting long-term episodic memory, and no group differences in those variables reflecting short-term memory. These data suggest that depression in very old age may not exacerbate the episodic memory deficit that accompanies AD. Further, differences between normal old and MD participants in episodic memory tasks appear to be negligible among the oldest old. The general lack of effects of MD may be due to the fact that those symptoms of this disease that are most likely to affect memory functioning (e.g., loss of energy, concentration difficulties) are common in AD as well as in nondepressed people in the 10th decade of life. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Decomposition of Wustite in the System Ca-Fe-O

The influence of cooling rate upon the decomposition of wustite in the system Ca-Fe-O has been studied. By SEM and EDS measurements the eutectic-like decomposition product is shown to be a mixture of wustite, Ca₂Fe₂O₅, and Fe formed by a eutectoid decomposition of wustite. The CaO-FeO section in the Ca-Fe-O system is shown not to be eutectic, as previously suggested. The phase diagram suggested by Abbatista is regarded as the correct alternative.     

Multiphase diffusion simulations in 1D using the DICTRA homogenization model

A model for multiphase simulations in 1D previously reported in [H. Larsson, A. Engström, Acta Mater. 54 (2006) 2431] has been further developed and incorporated in the DICTRA software. The model is based on the assumption of local equilibrium and locally averaged kinetic properties, which computationally transforms the problem into a single-phase diffusion process. The applicability of the model is discussed and example simulations are presented.     

Pediatric elbow fractures: MRI evaluation

Standard anatomy textbooks describe the mandibular canal as having a consistent, standard path. The fact that variations in its path exist in a significant percentage of the population is of extreme importance for the surgeon who is performing procedures in close proximity to the mandibular canal. A rare, radiographically detectable variation of the standard anatomy of the mandibular canal is reported.