False Signatures Research Articles

Voorlopige catalogus van de schilderijen van Pieter Veen

AbstractPieter Veen's name is virtually unmentioned in art-historical sources. Moreover, many of his paintings, some of them bearing false signatures, were sold under other names, which may partly account for his obscurity. Veen lived and worked in Rotterdam, where he was a dean of Saint Luke's guild in 1716, 1720, 1731 and 1736. Eighteenth-century auction catalogues list him as a pupil of Adriaen van der Werff, whose influence can certainly be seen in his work. Not, however, in his earliest extant painting, and the only one to be dated: a portrait of Geertruy van der Hey, a burgomaster's wife, done in 1686. In type, the portrait is closer to the work of Jan Verkolje, who was active in Delft. From a written source we know that Veen painted a portrait of Adriaen Boon in 1684. This justifies the cautious conclusion that he began his career as a portraitist. By far the greater part of his output consisted however of history paintings, most of them religious works. He also painted a few mythological pictures and especially allegories. An occasional link can be established with work by Adriaen van der Werff; Veen's Fall, for instance, is partly based on the latter's Adam and Eve after the Fall. Veen's style is less rigidly classicistic, though. His paintings have a narrative character. In that respect his work has more in common with the notions of classicism as expressed in Gerard Hoet's bible illustrations and Arnold Houbraken's paintings. Veen tends towards the decorative: graceful attitudes, elongated bodies and little parallel folds in garments are characteristic of his style. An eclectic painter, he was influenced by the art of both his own period and the past. Abraham Receiving the Three Angels, Susanna and the Elders and Apollo and Daphne, for instance, appear to derive from sixteenth-century exemplars. The Holy Family with Anna and Angels is actually a direct copy of a composition by Hans van Aken. The landscape in Shepherd Playing a Flute displays the influence of French classicists such as Poussin and Millet, many of whose works Veen could have seen in Rotterdam. Pieter Veen possessed only a modest talent, and there arc hardly any signs of a development in his work. Nonetheless, this forgotten Rotterdam painter deserves a place among the minor masters of the period.

Exponential relationships among multiple hydrogen isotope effects as probes of hydrogen tunneling

For hydrogen transfer reactions with moderate degrees of tunneling, the semiclassical relationship of deuterium, tritium to protium, tritium isotope effects is predicted to break down, such that ( k D k T ) 3.26 < k H k T . By contrast, kinetically complex reactions produce ( k D k T ) 3.26 > k H k T . We now show that these limiting cases may not pertain under the conditions of (i) measured secondary kinetic isotope effects which fall below their equilibrium limits and (ii) extensive hydrogen tunneling. Although condition (i) could lead to a false signature of tunneling, ambiguities of interpretation can be avoided by the simultaneous measurement of exponential relationships for primary and secondary isotope effects. With the exception of reactions where the H-transfer process is known to be fully rate determining, condition (ii) may lead to an underestimate of quantum effects as judged by exponential relationships.

Precipitation Retrieval over Land and Ocean with the SSM/I: Identification and Characteristics of the Scattering Signal

The subject of this study is the identification of precipitation in warm and cold land and ocean environments from the Defense Meteorological Satellite Program's (DMSP) Special Sensor Micmwave/Imager (SSM/I). The high sensitivity of the SSM/I 85.5 GHz channels to volume scattering by precipitation, especially ice above the freezing level, is the basis for this identification. This ice scattering process causes SSM/I 85.5 GHz brightness temperatures to occasionally fall below 100 K. It is demonstrated that the polarization diversity available at 85.5 GHz from the SSM/I allows discrimination between low brightness temperatures due to surface water bodies versus those due to precipitation. An 85.5 GHz polarization corrected temperature (PCT) is formulated to isolate the precipitation effect. A PCT threshold of 255 K is suggested for the delineation of precipitation. This threshold is shown to be lower than what would generally be expected from nonprecipitating cloud water alone, yet high enough to sense relatively light precipitation rates. Based upon aircraft radiometric measurements compared with radar derived rain rates, as well as model calculations, the corresponding average rain rate threshold is approximately 1–3 mm h−1. The majority of precipitation that falls on the earth exceeds this rate. Because the 85.5 GHz measurements of oceanic storms are often dominated by scattering due to precipitation above the freezing level, while the 19.35 GHz radiances are dominated by emission due to rain below the freezing level, there is independent information about the gross vertical structure of oceanic precipitation systems from the SSM/I. Apparent differences between storms in formative, mature, and dissipating stages are inferred from the diagnosed amounts of ice versus raindrops, and supported by time lapse GOES imagery. Deviations from the average relationship between 19.35 GHz warming and 85.5 GHz cooling are suggested for use as a diagnostic tool to evaluate lower level rain/upper level ice relative abundances. As an example of this capability, overrunning precipitation shows a horizontal offset between the advancing ice layer and the trailing rain area, consistent with idealized conceptual models of warm frontal precipitation. Part II of this study will address global screening for the precipitation scattering signal, its statistical characteristics, and the false rain signatures frequently caused by snow cover and cold land.

Some mathematical aspects of mapping DNA cosmids

A number of experimental and mathematical problems must be solved before high resolution physical maps of mammalian chromosomes can be reliably determined. Such a map might consist of an ordered set of nonsequenced, overlapping DNA fragments 20,000-40,000 bases long, produced by digestion of a chromosome, using two restriction enzymes. Map construction requires assigning a signature to each fragment that differentiates it unambiguously from every other fragment, and then devising a computationally efficient algorithm that will provide a unique ordering of the fragments. In the first part of this paper we present a polynomial time algorithm that yields a unique map, and is largely independent of the method for assigning signatures. In the next section we analyze the distribution of lengths of restriction digest fragments and discuss the implications for the algorithm, including the expected number of map gaps. Finally, we discuss a specific method for assigning signatures proposed by Hans Lehrach, based on which of a panel of probes binds to a given fragment. In particular we examine the effects of fragment length heterogeneity on the theoretical optimum length and number of probes, and the extent to which false signatures might be obtained by nonspecific binding. We conclude that the Lehrach strategy is effective provided the number of probes is greater than or equal to 150, but that each fragment will need testing with at most 25 probes.

Hieronymus van der Mij als historie- en genreschilder

Hieronymus van der Mij als historie- en genreschilder

Carpaccio's Meditation on the Passion

The Metropolitan Museum of Art in New York2 is fortunate in the possession of a Carpaccio which, for all its small size, is one of the finest extant paintings by this master. Since Claude Phillips exposed the false signature, ANDREAS MANTINEA, and assigned the picture to Carpaccio3 his attribution has remained unquestioned. He bestowed upon the painting the title it now bears, one which could hardly have been better chosen, as it sums up in simple and appropriate words the subject and the quiet depth of the picture.