Differential analyzer

The Field of Numerical Analysis.—As used here, numerical analysis will be taken to represent the art and science of digital computation. The art is learned mainly by experience hence, this chapter will be concerned with explicit techniques and the mathematical principles that justify them. Digital computation is to be contrasted with analog computation, which is the use of slide rules, differential analyzers, model basins, and other devices in which such physical magnitudes as lengths, voltages, etc., represent the quantities under consideration. 

The so-called differential analyzer developed ca 1930 by Vannevar Bush, is an analog computer used especially for the rapid solution of problems by differential calculus. Its improved version was used during WWII for solving ballistic problems (Ref 1, pp 60-61 ... 

The very concept of a stored program computer had its roots in the work done during World War II on a computing machine called the ENIAC. At the start of World War II, the military felt a need for more and better trajectory tables for artillery. To prepare the tables, the Ballistic Research Laboratory of the U.S. Army Ordnance Department utilized a pair of mechanical differential analyzers. But by 1943 the produaion of ballistic tables was so far behind schedule that the Ordnance Department began to look for another means of preparing the tables. The answer came in April 1943, when a delegation from... 

The early differential analyzers were very interesting. Vannevar Bush s first model was completely electrical, using a house-type watt-hour meter for... 

Fig. 1. The differential analyzer, built in 1935 at the Moore School of Electrical Engineering, University of Pennsylvania. A similar machine was constructed for the Ballistics Research Laboratory at Aberdeen Proving Grounds for the U.S. Army. These differential analyzers were constructed by the Civil Works Administration as part of President Roosevelt s emergency relief program. The work w as directed by Professors Vannevar Bush, S. H. Caldwell, L. S. Frost, and Irven Travis.

Hartree did not have access to computers, of course, but he constructed the so-called differential analyzer with the help of a Meccano kit. He managed to calculate accurate AOs already in 1928. 

Douglas Rayner Hartree (left) and Arthur Porter (right) viewing the Meccano differential analyzer in 1935. 

Owens, L. 1986. Vannevar Bush and the differential analyzer the text and context of an early computer. Technology and Culture 27 63-95. 

It has also been realized that histone modification patterns and levels are an important aspect when studying diseased gene expression states. For instance, it has recently been shown that certain aberrant posttranslational histone modifications are associated with the pathogenesis of the autoimmune disease systemic lupus erythematosus (SLE) [381]. In this study, MS combined with stable isotope labeling was used to differentially analyze histone modifications in splenocytes from a mouse model of SLE. Compared to the control, the disease model showed a global site-specific hypermethylation, except for H3K4, and hypoacetylation in histone H3 and H4. 

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