A common problem in clinical MRI is anatomic misalignment of imaging slices across successive examinations. This unnecessarily complicates the radiologic assessment of anatomic change over time on serial MRI studies. To address this problem, spherical navigator echoes, which can detect rigid body motion in all six degrees of freedom, were used to guide spatial location and orientation adjustmen...

We have used FORS1 at the ESO VLT to search for light echoes in imaging polarimetry from four historical supernovæ in the face-on nearby spiral galaxy M83 (NGC 5236). No echoes were detected around our targets (SN 1923A, SN 1945B, SN 1950B and SN 1957D). This implies that the interstellar medium in their environs is rather tenuous (a few particles per cm), possibly as a result of previous super...

Correlations are employed in modern physics to explain microscopic and macroscopic phenomena, like the fractional quantum Hall effect and the Mott insulator state in high temperature superconductors and ultracold atoms. Simultaneously probed neurons in the intact brain reveal correlations between their activity, an important measure to study information processing in the brain that also influen...

Spin echoes have been known since 1950. Although their formal description by use of the Bloch equations is straightforward, it does not lead to an intuitive understanding of their behavior except for the special cases of 180" or 90" pulses, especially when many pulses are applied before the magnetization has returned into thermal equilibrium. The extended-phasegraph algorithm, which takes into ...

The hyperbolic frequency-modulated (HFM) waveform has an inherent Doppler-invariant property. It is more conducive than the conventional linear frequency-modulated (LFM) waveform to high speed moving target imaging. In order to apply the HFM waveform to existing inverse synthetic aperture radar (ISAR) imaging systems, a new pulse compression algorithm is proposed. First, the received HFM echoes...

The basic equipment for reflection seismic prospecting is a source for impulsive sound waves, a geophone (something like a microphone), and a multichannel waveform display system. A survey line is defined along the earth’s surface. It could be the path for a ship, in which case the receiver is called a hydrophone. About every 25 meters the source is activated, and the echoes are recorded nearby...

Echoes from small reflectors buried in heavy clutter are weak and difficult to distinguish from the medium backscatter. Detection and imaging with sensor arrays in such media requires filtering out the unwanted backscatter and enhancing the echoes from the reflectors that we wish to locate. We consider a filtering and detection approach based on the singular value decomposition of the local cos...

Object recognition, essential to many animals, often occurs underwater and in poor visibility conditions for bottlenose dolphins. Bottlenose dolphins can use sound through their ability to echolocate in order to recognize objects. Echoic object recognition is an unusual faculty that offers rich research opportunities and is the focus of this article. This review begins with a brief overview of ...

The paper analyzes the structure of optimal trajectories in the one-sector vintage capital model that optimizes the endogenous lifetime of age-structured capital under technological change. A new repetition pattern (anticipation echoes) is demonstrated in both optimal investment and optimal capital lifetime in the case of finite-horizon optimization. The anticipation echoes are caused by expect...