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Special issue devoted to the life and works of Gustavo Adolfo Becquer. (DS)

Special issue devoted to life and works of Gustavo Adolfo Becquer. (DS)

The thermomagnetic force is observed as a magnetic field induced change in the thermal force exerted on an object suspended in a heat‐conducting rarefied polyatomic gas. A recently developed extremely sensitive stress measuring technique and higher magnetic fields have permitted the experimental investigation of the thermomagnetic force to saturation levels in the gases N2, CO, and NH3 at 300°K. We have studied the force effects for three well‐defined temperature fields produced by isothermal boundaries with different geometry. The increased accuracy of the experimental results has permitted the fit of the data to a typical saturation curve. From this curve saturation values and the position on the H/p axis at which the effect reaches half‐magnitude (H/p)1/2 values have been determined for the various gases under different conditions of temperature field and pressure. A comparison is made with the Senftleben–Beenakker thermal conductivity effects.

El artículo da cuenta de la complejidad de desarrollar estudios integrales en ciudades históricas permanentemente habitadas, a través de los resultados de una reciente excavación de la confluencia de dos cloacas romanas y su contextualización con otros hallazgos de similares características en Toledo. La gran cantidad de restos arqueológicos de Toletum descubiertos en los últimos años contrasta con la escasez de trabajos publicados, lo que sigue condicionando la imagen académica establecida desde hace décadas para la ciudad antigua. Aunque aún queda un largo camino por recorrer, los últimos hallazgos han permitido matizar aspectos sobre su diseño urbano y evolución desde la II Edad del Hierro hasta el final de la época romana. The recent discovery and excavation of two Roman sewers junction in one of the main Toledo arteries has highlighted the need to reflect on the academic image of Roman Toledo developed in the last few decades. Due to the lack of published works, any attempt to develop theories about its urban plan is rather daring. Nevertheless, the latest findings have allowed for the explanation of part of its layout and evolution from the Second Iron Age to the Roman period. Consequently, these two sewers from two different periods and with different orientation give information about the road and water networks they belong to, as well as illustrating the complexity of this type of studies in permanently inhabited cities, and pointing out the long way still ahead for their complete understanding.

A description is given of an extremely sensitive stress gauge system designed for studying rarefied gas transport in magnetic fields. A novel approach employing a vertical quartz cantilever with an associated optical electronic readout is used to detect changes in the Maxwell stress on a thin aluminum disk in the magnetic‐thermal field. Forces acting on the detecting disk as small as 10−5 dyn can be resolved.

During a 2-year period, 70 species of leafhoppers were collected on sticky-board traps placed in and around several X-diseased peach and sour cherry orchards in southwest Michigan. Of those species known to be X-disease vectors, Paraphlepsius irroratus (Say) and Scaphytopius acutus (Say) were most abundant, whereas Colladonus clitellarius (Say). Norvellina seminuda (Say), and Fieberiella florii (Stal) were found only in low numbers. Many more P. irroratus were trapped in cherry orchards than in peach orchards, whereas S. acutus was slightly more common in peach orchards. Both species appear to have 2 generations/year. The importance of 7 additional species as possible vectors is discussed.

The proton NMR spectra of epimeric mixtures of menthone (1), carvomenthone (2), carquejone (3), 2,5-dimethyl-1,4-cyclohexanedione (4) and piqueridione (5) were studied using the chemical shift reagent Eu(DPM)3. The results allow quantifications of the epimers and some conformational assignments to be made.