Simple feed-forward wide-range frequency offset estimator for optical coherent receivers.

We propose and experimentally demonstrate a hardware-efficient, feed-forward, wide-range frequency offset estimator for DSP-based optical coherent receivers. Using a simple relationship of signal spectrum, this estimator is capable to estimate offsets in a range compliant with OIF requirements. Obtained results show that this estimator has a high tolerance to spectrum asymmetry caused by electrical and optical signal filtering, even when using return-to-zero pulse shaping.

A study of injected dose for brain mapping on the ECAT HR+: activation maps for a parametric verbal working memory task.

The success of the 15O-water PET technique to localize statistically significant changes in regional cerebral blood flow is dependent on factors such as the activity level injected and the magnitude of the flow change. Undetectable changes may occur if insufficient activity is injected leading to high levels of statistical noise or the task performed results in only small changes in blood flow. To explore the relationship between injected activity and statistical significance, we performed a series of studies with the ECAT EXACT HR+, a high resolution PET tomograph.

An examination of regional cerebral blood flow during object naming tasks.

The purpose of this study was to examine regional cerebral blood flow using positron emission tomography (PET) during the performance of tasks related to visual confrontation naming. Ten healthy, young participants were scanned twice in each of 5 conditions; blood flow was measured using standard PET [15O]-water technology. Two major findings have replicated previous studies.

Regional cerebral blood flow during word and nonword reading.

The purpose of this study was to examine changes in regional cerebral blood flow (rCBF) using positron emission tomography (PET) during overt word and nonword reading tasks to determine structures involved in semantic processing. Ten young, healthy, right-handed subjects were scanned 12 times, twice in each of six specific conditions. Blood flow was measured by 15O-water using standard PET imaging technology.

Functional connectivity in auditory-verbal short-term memory in Alzheimer's disease.

Alzheimer's disease (AD) patients show normal patterns of regional cerebral blood flow during performance of subspan verbal memory tasks, but appear to allocate new brain regions when performing supraspan recall tasks. To understand the relationships among these interconnected brain regions, their functional connectivity was considered using principal components analysis (PCA). AD patients and controls were scanned in four conditions: visual fixation only and visual fixation with one-word recall, three-word recall, and eight-word recall.