Waldemar H. Lehn

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Carotenemia and extensive caries of primary teeth were the consequence of excessive consumption of carrot products in nursing bottles in children of ages 1 to 5. The carbohydrate content of six juices available to the consumers was analysed to be 6.9 to 14.3 g sugar/100 ml. We examined 142 children whose completely destroyed maxillary anterior teeth had to(More)
The temperature inversions that produce superior mirages are capable of supporting gravity (buoyancy) waves of very low frequency and long wavelength. This paper describes the optics of single mode gravity waves that propagate in a four-layer atmosphere. Images calculated by ray tracing show that (1) relatively short waves add a fine structure to the basic(More)
A mirage is seen when atmospheric refraction distorts or displaces an image. We describe a mirage simulator that uses digital imaging equipment to generate mirage images from normal photographs. The simulation program relocates horizonal image lines into positions that they appear to occupy, according to rays traced from observer to object. Image-brightness(More)
Infrared observations of seaborne thermal sources are subject to the effects of atmospheric refraction. For low elevation angles at long ranges, out to the limit of visibility, the inevitable atmospheric temperature gradients frequently produce mirages. I present an analysis of a 22-min sequence of images recorded on 18 February 1994 at the U.S. Naval(More)
A survey of reported sightings of lake monster phenomena suggests that many of them may be attributable to atmospheric image distortion. The existence of the necessary conditions (surface temperature inversion and hence strong atmospheric refraction) can be inferred from most of the reports. Under such conditions familiar objects can easily take on(More)
The first recordings of the Novaya Zemlya (NZ) effect were made during Willem Barents' third Arctic expedition. Ray-tracing analyses of the three key observations, on 24-27 January 1597, show that all the reported details can be explained by adopting one common and realistic type of temperature inversion. In particular, the Moon-Jupiter conjunction could(More)
The Norse discovery of Greenland is associated with the sighting of low barren islands called Gunnbjörn's Skerries, which have never been satisfactorily identified. Here the historical references that connect the skerries to Greenland are reviewed. A mirage of the Greenland coast, arising specifically from optical ducting under a sharp temperature(More)
The arctic mirage is a phenomenon that is common in higher latitudes. It occurs under conditions of pronounced temperature inversion, which impart to the air a refractive capability that may equal or exceed the curvature of the earth. Manifestations of the arctic mirage, though largely forgotten in modern times, are described in the earliest accounts of(More)
Systematics of the Novaya Zemlya (NZ) effect are discussed in the context of sunsets. We distinguish full mirages, exhibiting oscillatory light paths and their onsets, the subcritical mirages. Ray-tracing examples and sequences of solar images are shown. We discuss two historical observations by Fridtjof Nansen and by Vivian Fuchs, and we report a recent(More)