Comparison of ribosomal DNA length and restriction site polymorphisms in Gremmeniella and Ascocalyx isolates

The small subunit (SSU) and the internal transcribed spacer (ITS) of nuclear ribosomal DNA genes from 27 specimens of the fungal genera Gremmeniella and Ascocalyx were amplified by PCR. Length polymorphisms were observed in the SSU and allowed the differentiation of four groups among the isolates tested: (i) Ascocalyx abietis; (ii) Gremmeniella isolates from Picea spp.; (iii) Gremmeniella isolates from Abies balsamea; and (iv) Gremmeniella isolates from Abies sacchalinensis, Larix spp., and Pinus spp. The amplified ITS was the same length for all Gremmeniella specimens and was 60 bp longer in A. abietis. Phylogenetic analysis of length polymorphisms and of 24 restriction sites in the SSU and ITS showed that Gremmeniella isolates were more related to each other than to the Ascocalyx isolate. Furthermore, seven groups were evident within the genus Gremmeniella. Our results confirm that Gremmeniella and Ascocalyx should be kept as different taxa and suggest that the taxonomy of the former could be revised to consider isolates from Abies balsamea and from Picea spp. to be two different varieties while incorporating Gremmeniella laricina into G. abietina, as a new variety.     

Spin coating over topography

A model for predicting film thickness profiles around topographical features during spin coating is presented. This model is applicable to features of arbitrary geometry in the two lateral dimensions. This generally permits study of the planarization of real device structures, including both isolated and neighboring features, with any orientation with respect to the wafer center. Predictions from this model agree qualitatively with measured thin-film profiles from interferograms taken during spinning. Phenomena such as pile-up and wakes result from interactions between surface tension and other driving forces in the flow     

Carcinoma of the splenic flexure. Nosological and therapeutic contribution

Twenty-one patients undergoing colectomy for carcinoma of the splenic flexure from November 1996 throughout October 1993 were studied retrospectively. Clinical and prognostic features were compared with those of other colon cancers treated in the same period at the same Institution. No differences in symptoms at onset and stage distribution were found in the two groups. The complex removal of the cancer tissue was achieved with the resection of the major part of the transverse colon, splenic flexure, descending colon and its mesocolon. The splenic flexure cancer did not show a worse prognosis than other colon cancers.     

Computer-aided instruction in wave propagation phenomena

A `virtual laboratory' which uses computer simulation and visualisation techniques is proposed for the training of high school and college students in the study of wave propagation phenomena. Physical laboratory experiments are replaced by numerical experiments based on a mathematical model and its numerical simulation on a computer. Simple experiments that can be performed in a water tank with simple tools are simulated in the `virtual laboratory' using the wave equation as a mathematical model. As an example the interference between the waves generated by two time harmonic point sources is studied and Bragg's law observed. In the `virtual laboratory' students can design their own experiments and observe the results of the numerical simulations via animation techniques     

Problems arising in applications of counterflow difference schemes in engineering calculations of contamination of shallow reservoirs

Results of a numerical investigation of the stability and errors in the solution obtained with the use of counterflow difference schemes applied to modeling of transfer of suspended substances and solutes in a movable aqueous medium are discussed. Recommendations regarding the proper choice of schemes in engineering calculations are presented. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2, pp. 349–352, March–April, 1998.     

Growth inhibitory effect of juvenile hormone analogues on epimastigotes of Trypanosoma cruzi

Several compounds, structurally related to the insect growth regulator Fenoxycarb, exhibited interesting inhibition action to control proliferation of Trypanosoma cruzi, the parasite responsible for Chagas' disease. Some of these drugs were shown to be potent growth inhibitors of this parasite. All of these drugs had previously presented juvenoid activity on several non-related bug species such as Tenebrio molitor, Galleria mellonella, Dysdercus cingulatos, and Pyrrhocoris apterus.     

Pressure-coefficient trends for mixed propellants

Spline fitting has been used in processing measurements on the pressure dependence of the burning rate to obtain additional information on the variation in the pressure coefficient v as affected by grain size and composition, as well as by the nature of the components. Conclusions are drawn on the burning mechanism. The peak on v(p) is due to serial-parallel conversion of APC in the condensed and gas phases and to changes in the relative significance of the chemical stages. There is a minimum at elevated pressures for many propellants, which in some cases is transformed into a plateau or inflection on account of interaction between the fuel and the oxidizing agent in the diffusion-kinetic hydrocarbon flame.Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 2, pp. 68–72, March–April, 1993     

Improving the testability of switched-capacitor filters

A design-for-test methodology for SC filters is presented, based on an architecture using some additional circuitry and providing extra capabilities for both off- and on-line tests. The approach uses a comparison (voting) mechanism to indicate whether or not two copies of a filter element (a biquad, for instance) have a similar response during their actual operation. The design and implementation of a few filter examples are included to assess the potential usefulness of this new approach.