A method is provided for controlling thrombogenicity of a vascular graft prosthesis by controlling the surface charge of at least the intimal surface of the prosthesis by reaction with a compound selected from the group consisting of albumin, glyoxals, ethoxyformic anhydride, formic acid, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and the like. The surface charge is then stabilized by treatment with glutaraldehyde, dialdehyde starch, formalin or the like.

An arrangement for generating characters of relatively elongated vertical dimension and having a descender portion in a system wherein the character information is stored in read-only memory of substantially equal size for each of the characters to be generated, the upper portion of the elongated characters being stored in a primary read-only memory with all of the remaining characters and the descender portion of each elongated character being stored in a supplemental read-only memory. In displaying such an elongated character, the upper portion thereof is output from the primary read-only memory and the descender portion is output immediately thereafter from the supplemental read-only memory to form the character in composite form.

A video display terminal is disclosed for use in displaying images of data characters on a display screen. Multibit coded data words are supplied by a data source, such as a memory, to a character generator circuit which controls the display of data characters on the face of a video display screen. Character codes are used to address a dot pattern memory which stores dot patterns to provide an image of the required data character to be displayed. The dot patterns may be stored on one size matrix in the dot pattern memory, such as in a 9.times.9 cell, and displayed on a larger dot matrix, such as 9.times.16, on the display screen. Subscripts or descending characters may be stored in the dot pattern memory and vertically repositioned when displayed on the screen. Means are also provided for adjusting the vertical positioning of a line of characters.

A text-processing system for presenting input data on a display device such as a cathode ray tube (CRT) and/or a data receiving unit from which the data may be selectively retrieved and presented in a predetermined format. The system comprises memory addressing and interpreting means which functions substantially independently for CRT beam controlling means, thus enabling parallel operation of these functions. The system further comprises slewing means for controlling beam movement directly between any selected points on the CRT face. Provision is made for italicizing and/or altering the size of selected ones of the displayed characters.

An image processing system is described in which an image is converted into a plurality of image elements or cells which are arranged in a predetermined pattern. These cells are then simultaneously rearranged into a second predetermined pattern to provide a transformed representation of the original image. In this transformed state, the positions of all of the cells may be simultaneously shifted in a manner which produces modifications of the original image, such as scaling or rotating. The highly parallel manner in which the present system manipulates the image cells allows the desired image modifications to be effected more simply and rapidly than has been previously possible. In a preferred embodiment of the invention these image cell manipulations are performed in a three dimensional shift register of novel design. A number of alternative embodiments of the invention are set forth which are of particular value in pattern recognition systems and in graphic display systems in which the ability to modify or animate images is desired.