Art Out of Order: Jack Burnham, the 1970 Software Show, and the Aesthetics of Information Systems.

In 1970, curator Jack Burnham debuted the lavish exhibition Software at the Jewish Museum in New York. Conceptual artists displayed information-oriented pieces, while technical experts deployed computers, image-making, and multimedia technology in their works. Burnham's goal was to showcase contemporary techniques of computer-based command and control, allowing viewers to respond in real time to the "programmatic situations" artists presented. While critics dismissed Software as a technical and aesthetic disaster, today it stands as a touchstone for efforts to integrate technology with artmaking. This article takes us back to Software's gallery spaces and Burnham's aim of showcasing the potential of interactivity and "real-time systems." More broadly, it situates Software as a provocation to a public unfamiliar with computer technology yet at the threshold of a new postindustrial era, where the power and performative aspects of computing would predominate.

Amateur scientists, the international geophysical year, and the ambitions of Fred Whipple.

The contribution of amateur scientists to the International Geophysical Year (IGY) was substantial, especially in the arena of spotting artificial satellites. This article examines how Fred L. Whipple and his colleagues recruited satellite spotters for Moonwatch, a program for amateur scientists initiated by the Smithsonian Astrophysical Observatory (SAO) in 1956. At the same time, however, the administrators with responsibility for the IGY program closely monitored and managed--sometimes even contested--amateur participation. IGY programs like Moonwatch provided valuable scientific information and gave amateurs opportunities to contribute actively to the research of professional scientists. Moonwatch, which operated until 1975, eventually became the public face of a vast satellite-tracking network that expanded the SAO's global reach and helped further Whipple's professional goals. Understanding amateurs' interactions with the professional science community enables us better to understand the IGY as a phenomenon that enlisted broad participation and transcended traditional boundaries between professional and amateur scientists.

Use of simultaneous high-resolution endoluminal sonography (HRES) and manometry to characterize high pressure zone of distal esophagus.

The purpose of this investigation was to separate the high pressure zone (HPZ) of the distal esophagus into its two components, the intrinsic lower esophageal sphincter (LES) and the extrinsic crural diaphragm (CD), using simultaneous esophageal manometry and high-resolution endoluminal sonography. Five normal subjects were studied during end inspiration using a dual manometry/ultrasound catheter. The HPZ in the distal esophagus was characterized ultrasonographically as the CD distally and as an overlap of CD and LES proximally. In four of five volunteers, the initial distal rise in pressure at the HPZ corresponded to imaging of CD rather than imaging of the LES. In all subjects, peak pressure corresponded to an overlap of CD and LES. In conclusion, it is possible to divide the HPZ into its two components, the LES and CD using simultaneous high-resolution endoluminal sonography and esophageal manometry. During end inspiration, the CD contributes to the initial distal rise in pressure at the HPZ. Peak pressure of the HPZ corresponds to an overlap of the LES with the CD.

Three-dimensional esophageal varix model quantification of variceal volume by high-resolution endoluminal US.

BACKGROUND: The purpose of this study was to evaluate the accuracy and reproducibility of three-dimensional volume measurements by high-resolution endoluminal ultrasound in an esophageal varix model. METHODS: An esophageal varix model was made by filling three esophageal dilatation catheters with various volumes of water. A 20 MHz ultrasonography transducer was then pulled along the length of the catheters at a constant rate (1.25 mm/sec) while videotaping the procedure. Cross-sectional surface area measurements of each catheter were taken every second and the cross-sectional surface area was multiplied by the length of each catheter, as determined by high-resolution endoluminal ultrasound, to determine the volume in each catheter. Interobserver variability was calculated, and three-dimensional reconstruction was performed. RESULTS: The measured volumes corresponded closely with the actual volumes with an error ranging from 0% to 15.4%. The correlation between actual and measured volumes was r = 0.988. The interobserver variability ranged from r = 0.951 to r = 0.994. Actual esophageal varices were then imaged in a similar fashion to determine the feasibility of this method in patients with esophageal varices. CONCLUSIONS: High-resolution endoluminal ultrasound is an accurate and reproducible method of measuring volumes in an esophageal varix model and can be used in a clinical setting to determine variceal volume. Volume studies are now underway in human subjects.

In vivo comparison of esophageal varices at and above the diaphragmatic high pressure zone using high resolution endoluminal sonography.

Our objective in this study was to use high resolution endoluminal sonography to compare the size of esophageal varices within 5 cm of and at the esophageal high pressure zone. We carried out the study in 36 patients with endoscopically proven esophageal varices. A 20-MHz 6.2F ultrasound catheter was passed through a 34F endoscope and used to image esophageal varices as it was slowly withdrawn through the high pressure zone (the level at which the diaphragm was imaged) and into the body of the esophagus approximately 5 cm above the high pressure zone. All images were captured on videotape and reviewed by one of the investigators. The mean, total, and percent cross-sectional surface areas occupied by varices were calculated and then compared within 5 cm and at the esophageal high pressure zone. Six of 36 (17%) patients had no varices imaged at the high pressure zone but did have varices imaged in the distal esophagus. The mean cross-sectional surface area per varix at the high pressure zone (0.036+/-0.006 cm2) was significantly less (p < or = 0.0001) than the mean cross-sectional area per varix 5 cm above the high pressure zone (0.142+/-0.018 cm2). The average total cross-sectional surface area occupied by varices at the high pressure zone (0.137+/-0.034 cm2) was significantly less (p < 0.0001) than the average cross-sectional surface area occupied by varices 5 cm above the high pressure zone (0.672+/-0.080 cm2). The mean percent esophageal wall cross-sectional surface area occupied by varices at the high pressure zone (16%) was significantly less (p < or = 0.0001) than 5 cm above the high pressure zone (49%). We conclude that the mean, total, and percent cross-sectional surface areas of esophageal varices at the high pressure zone are significantly less than those 5 cm above the high pressure zone.

Benign nonpeptic esophageal strictures. Diagnosis and treatment.

This article studies the causes and treatment of benign nonpeptic esophageal strictures. The authors also discuss various therapeutic techniques for esophageal strictures, including esophageal dilatation with various dilators and balloons. Although the goals of stricture therapy are to relieve dysphagia and prevent stricture reoccurrence, only the first of these goals (effective dilatation with bougienage or balloon dilatation) has been achieved. The prevention of stricture reoccurrence remains to be achieved.

Use of high-resolution endoluminal sonography to measure the radius and wall thickness of esophageal varices.

BACKGROUND: Measurement of variceal wall tension theoretically provides the most accurate method of predicting future variceal bleeding. Using high-resolution endoluminal sonography in 45 patients with known portal hypertension, we measured and correlated the two previously unmeasured variables involved in the calculation of variceal wall tension (radius and wall thickness) by the Laplace equation. METHODS: A 20 MHz 6.2F ultrasound transducer was used to image esophageal varices during standard esophagoscopy. All images were captured on videotape and later reviewed by two blinded investigators. Outer and inner variceal wall circumferences were measured at a cross section of each varix. The radius of each varix and the variceal wall thickness were calculated. The radius of each varix was then correlated with its wall thickness. The interobserver and intraobserver variabilities were measured. RESULTS: The mean variceal radius was .86 +/- .34 cm for the inner radius and 1.48 +/- .41 cm for the outer radius; mean variceal wall thickness was .099 +/- 0.037 cm. Intraobserver and interobserver correlation for the radius was r = .98 and r = .97, respectively. The intraobserver and interobserver correlations for the wall thickness were r = .92 and r = .91, respectively. Variceal radius did not correlate with the wall thickness of the varix. CONCLUSIONS: High-resolution endoluminal sonography provides a method for the accurate measurement of esophageal variceal radius and wall thickness. Variceal radius does not correlate with variceal wall thickness, implying that variceal wall tension cannot be accurately estimated by measurement of variceal size alone. Combining these data with measurements of variceal pressure should allow for the direct determination of wall tension and, subsequently, identification of patients at risk for variceal bleeding.

Partial purification and characterization of an endonuclease from spinach that cleaves ultraviolet light-damaged duplex DNA.

An endonuclease that cleaves ultraviolet light (UV)-damaged, supercoiled plasmid DNA was partially purified from spinach leaves (Spinacia oleracea) by a series of column chromatography steps. Dialysis of the enzyme against EDTA resulted in a greater than 90% loss of activity which could be fully restored following the addition of Zn2+, suggesting that divalent cations are associated with the active enzyme. The spinach endonuclease cleaved duplex, UV-damaged, end-labelled DNA of defined sequence at positions of adenine in the presence of salt (KH2PO4 or NaCl) concentrations of 50 mM or higher. Cleavage of UV-irradiated DNA was dose-dependent and increased steadily within a fluence range of 50-10,000 J/m2. The UV damage requirement and adenine cleavage specificity could be eliminated with lower salt concentrations (0-25 mM), suggesting that the endonuclease recognizes and incises single-stranded DNA. The properties of this enzyme, which we have termed nuclease SP, suggest that it may mediate a role in DNA repair and/or recombination processes in spinach.

Nuclease SP: a novel enzyme from spinach that incises damaged duplex DNA preferentially at sites of adenine.

A novel endonuclease has been isolated from extracts of spinach leaves (Spinacia oleracea). The enzyme has been purified by a series of column chromatography steps and has a molecular size of approximately 43,000 daltons. The spinach endonuclease cleaved double stranded DNA damaged by ultraviolet light or cis-diamminedichloroplatinum (II) primarily at sites of adenine when end-labelled DNA fragments of defined sequence were employed as substrates. The nature of the structural distortion contained in damaged, duplex DNA appears to be an important determinant for endonuclease cleavage. DNA helical distortions produced by UV light-induced (6-4) pyrimidine-pyrimidone photoproducts, but not cyclobutane pyrimidine dimers are recognized by the enzyme. The DNA cleavage products generated by the enzyme contain 3'-hydroxyl and 5'-phosphoryl termini. Single stranded DNA and RNA are hydrolyzed by the spinach endonuclease. This enzyme, which we call nuclease SP, is similar in several respects to other single-strand-specific nucleases such as N. crassa and mung bean nucleases and may function in DNA repair and/or recombination events in spinach cells. Nuclease SP should be a useful tool for the analysis of (6-4) photoproducts occurring in duplex DNA.

Thymine glycol-DNA glycosylase/AP endonuclease of CEM-C1 lymphoblasts: a human analog of Escherichia coli endonuclease III.

A thymine glycol-DNA glycosylase/AP endonuclease has been identified in human CEM-C1 lymphoblasts. The enzyme is active in the absence of divalent cations and has an apparent molecular size of approximately 60,000 daltons. The enzyme releases thymine glycol from osmium tetroxide-damaged DNA via an N-glycosylase activity and is associated with an endonuclease activity that mediates phosphodiester bond cleavage at sites of thymine glycol and apurinic sites. We propose that this enzyme, which we call redoxyendonuclease, is the human analog of a bacterial enzyme, E. coli endonuclease III, that recognizes oxidative DNA damage.