Abstract: A cryptographic communications system and method. The system includes a communications channel coupled to at least one terminal having an encoding device and to at least one terminal having a decoding device. A message-to-be-transferred is enciphered to ciphertext at the encoding terminal by first encoding the message as a number M in a predetermined set, and then raising that number to a first predetermined power (associated with the intended receiver) and finally computing the remainder, or residue, C, when the exponentiated number is divided by the product of two predetermined prime numbers (associated with the intended receiver). The residue C is the ciphertext.
Type:
Grant
Filed:
December 14, 1977
Date of Patent:
September 20, 1983
Assignee:
Massachusetts Institute of Technology
Inventors:
Ronald L. Rivest, Adi Shamir, Leonard M. Adleman
Abstract: Disclosed is a wind power generating apparatus for producing megawatt levels of power. The apparatus comprises at least one endless flexible cable supported on the peripheries of two spaced apart wheels. Airfoils are attached to the cable and disposed for generating aerodynamic forces which cause the cable and supporting wheels to turn allowing for the generation of power.
Abstract: Isopenicillin derivatives having antimicrobial properties and a general formula of: ##STR1## where R, R.sub.1, and R.sub.2 are hydrogen, methyl, ethyl, propyl, isopropyl, or halogenated methyl, ethyl, propyl or isopropyl radicals and R.sub.3 is ##STR2## are produced in a cell-free system using an extract from Cephalosporium acremonium. The starting materials for the synthesis consist of tripeptides composed of unsubstituted or .beta.-substituted D-valine, unsubstituted or substituted L cysteine, and L- .alpha.-aminoadipic acid or its analogues. Certain enzymes in the cell-free extract are inactivated so that conversion does not proceed past the isopenicillin stage.
Type:
Grant
Filed:
May 17, 1979
Date of Patent:
February 3, 1981
Assignee:
Massachusetts Institute of Technology
Inventors:
Arnold L. Demain, Toshio Konomi, Jack E. Baldwin
Abstract: An improved metal dual insulator semiconductor capacitor memory is disclosed. The memory contains a plurality of capacitor cells, each cell comprising a semiconductor substrate layer and a high conductivity layer sandwiching two insulator layers. The substrate is doped to provide avalanche breakdown in a surface depletion layer at a voltage comparable to the write voltage in the accumulation direction. The invention also provides a method of reading stored information without disturbing adjacent cells. A small variable voltage is applied across a "flat-band" portion of the hysteresis loop describing the voltage-capacitance relationship for the capacitor memory. A change or the absence of a change in the current through the capacitor indicates the state of the capacitor cell. Methods to fabricate the memory are also disclosed.
Abstract: A thermal engine with entrapped working medium is a device with a principle element in the form of a continuous yieldable belt whose tension and length are responsive to temperature due to the property of the working medium entrapped by the belt. This yieldable belt is then wrapped in sequence over several rollers which are coupled together rigidly by suitable mechanical means to give differential speeds among the rollers. Driven in this manner the yieldable belt will undergo cyclic change in tension and stretch while passing over the rollers in sequence. When heat is applied and removed in proper phasing with the cyclic variation of the mechanical properties exhibited by the belt and the entrapped working medium, the device will act as an engine with adequate power output at the shaft coupled to one of the rollers.
Abstract: This invention provides a composite composition comprising a metallic matrix having a concentration of third phase solid particles homogeneously dispersed throughout the metallic matrix. The metallic matrix can be liquid, solid or partially solid and can have (a) a dendritic structure or (b) up to 65 weight percent of a structure comprising degenerate dendritic or nodular primary discrete solid particles suspended in a secondary phase having a lower melting point than the primary particles which secondary phase can be solid or liquid. The third phase particles can be metallic, non-metallic or a combination metallic-nonmetallic compositions and have a surface composition which is not wet by the metallic matrix when the matrix is a liquid.
Abstract: A metal composition characterized by degenerate dendritic or nodular primary discrete solid particles suspended in a secondary phase having a lower melting point than the primary particles and which secondary phase can be solid or liquid. The method involves raising the temperature of a metal alloy to a value at which the alloy is largely or completely in the molten state. The melt then is subjected to vigorous agitation and the temperature is reduced to increase the portion of the mixture in solid degenerate dendrite or nodular form up to about sixty-five percent, but usually up to about fifty percent, while continuing the agitation. At this juncture the temperature of the liquid-solid composition can be reduced to cause solidification thereof or it can be cast. The solidified composition can be stored and later it can be brought again to the liquid-solid mixture state and then recast.
Type:
Grant
Filed:
July 17, 1973
Date of Patent:
April 6, 1976
Assignee:
Massachusetts Institute of Technology
Inventors:
Merton C. Flemings, Robert Mehrabian, David B. Spencer