We study weakly disordered quantum wires whose width is large compared to the Fermi wavelength. It is conjectured that such wires display universal metallic behavior as long as their length is shorter than the localization length (which increases with the width). The random matrix theory that accounts for this behavior—the DMPK theory—rests on assumptions that are in general not satisfied by realistic microscopic models. Starting from the Anderson model on a strip, we show that a twofold scaling limit nevertheless allows to recover rigorously the fundaments of DMPK theory, thus opening a way to settle some conjectures on universal metallic behavior.

We study weakly disordered quantum wires whose width is large compared to the Fermi wavelength. It is conjectured that such wires diplay universal metallic behaviour as long as their length is shorter than the localization length (which increases with the width). The random matrix theory that accounts for this behaviour - the DMPK theory- rests on assumptions that are in general not satisfied by realistic microscopic models. Starting from the Anderson model on a strip, we show that a twofold scaling limit nevertheless allows to recover rigorously the fundaments of DMPK theory, thus opening a way to settle some conjectures on universal metallic behaviour.

First-pass left ventriculograms were obtained using digital subtraction angiography in 24 patients after intravenous injection of 30 to 40 ml of iodinated contrast material. An image processing computer was used to enhance the iodine signal in the image relative to the background soft tissue by digitizing each new frame of the fluoroscopic exposure and subtracting from it a stored "mask" image. Digital left ventriculograms were obtained in the 30-degree right anterior oblique (RAO) position using high fluoroscopic exposure levels [8 mA and 70 to 90 kVp] and compared to 30-degree RAO cineangiograms obtained at cardiac catheterization. Standard cineanglograms were performed in 33 patients at cardiac catheterization but six (18%) were excluded because of runs of ventricular tachycardia initiated by the standard intraventricular injection of 40 ml of contrast media. Digital subtraction angiography was attempted in the 33 patients and left ventriculograms of clinically useful quality were obtained in 30 (91%). There were close correlations between end-diastolic volumes (r = 0.82), end-systolic volums (r = 0.93), and ejection fractions (r = 0.96). Multiple premature ventricular contractions occurred in a total of 10 of 33 (30%) patients during standard intraventricular cineangiography but did not occur in any patients during the intravenous first-pass technique. Wall motion abnormalities were visualized as well by digital angiography as by the standard method. Digital angiography appears to be an important new addition to diagnostic cardiology because it provides a less invasive outpatient method for obtaining contrast left ventriculograms which have much greater spatial resolution than radionuclide cineangiograms. © 1982.

In an attempt to improve visualization of the position of the guidewire and dilatation balloon during coronary angioplasty, a method was developed called digital coronary roadmapping. With this method a digitally acquired coronary angiogram is interlaced with the live fluoroscopic image of the guidewire and balloon catheter. The digital coronary angiogram is superimposed at the same magnification and radiologic projection as the live fluoroscopic image onto the video monitor above the catheterization table. The digital roadmap image thus provides immediate feedback to the angiographer to assist in directing the guidewire into the appropriate coronary artery branch and to help in placement of the balloon so that it straddles the site of stenosis.