Quasi Stationary Spiral Structure is the natural Interpretation for grand deqlgn spiral galaxies. The best theoretical tool to descrlbe QSSS morphologles is the study of spiral modes. Modal studies are characterlzed by two distinct stages. At the dynamical level, one wishes to compute spiral modes efflcently on a variety of equilibrium models and to master the relation between the properties of the basic states and the propertles of the relevant spiral modes. At the astrophysical level, realistic basic states are identified by dlscussing the processes of evolutlon and
self-regulatlon; in partlcular, we Identify some basic states conslstent wlth QSSS grand designs and others where more flocculent spiral structure is expected to occur. For thls second stage It is cruclal to have a proper interpretation of the results obtained from one-component models In vlew of the multiple component astrophysical systems to be described (which include stars, Population 1 objects, and cold gas). Followlng this outllne, under the guidance of a slmple analytlc (asymptotic) theory, a very large set of galaxy models has been studled numerically. Thls is essentlally a three dimensional survey wlthln a flexlble class of models, where one parameter measures the amount of partlclpatlng disk mass, a second parameter determlnes the
hotness of the disk and the third is a scale length which combines propertles of the slze of the nuclear bulge and the dlstrlbutlon of the cold gas component. All the essentlal morphologlcal types found in the Hubble diagram have been reproduced; in partlcular, parameter reglmes are identified for SA and SB galaxies and speclfically for SBO, SB-r and SB-s objects. Dlstinction is made between systems where gas is expected to play an actlve or a passlve role.
In this work we investigate some oscillatory properties of solutions of non-linear differential systems with retarded arguments. We consider the system of the form \[ y^{\prime }_i(t)-p_i(t)y_{i+1}(t)=0, \quad i=1,2,\dots , n-2, y^{\prime }_{n-1}(t)-p_{n-1}(t)|y_n(h_n(t))|^\alpha \mathop {\mathrm sgn}[y_n(h_n(t))]=0, y^{\prime }_n(t) \mathop {\mathrm sgn}[y_1(h_1(t))]+p_n(t)|y_1(h_1(t))|^\beta \, \le 0, \] where $ n\ge 3 $ is odd, $ \alpha >0$, $ \beta >0$.
The common bean (Phaseolus vulgaris L.) is sensitive to high temperature, while an ecologically contrasting species (Phaseolus acutifolius A. Gray) is cultivated successfully in hot environments. In this study, the two bean species were respectively acclimated to a control temperature of 25 °C and a moderately elevated temperature of 35 °C in order to compare the thermotolerance capabilities of their photosynthetic light reactions. Growth at 35 °C appeared to have no obvious adverse effect on the photosynthetic activities of the two beans, but changed their thermotolerance. After a short period of heat shock (40 °C for up to 4 h), the photosynthetic activities of 25 °C-grown P. vulgaris declined more severely than those of P. acutifolius grown at 25 °C, implying that the basal thermotolerance of P. vulgaris is inferior to that of P. acutifolius. But after acclimating to 35 °C, the thermotolerances of the two species were both greatly enhanced to about the same level, clearly demonstrating the induction of acquired thermotolerance in their chloroplasts, and P. vulgaris could be as good as P. acutifolius. Temperature acclimation also changed plants' resistance to photoinhibition in a manner similar to those toward heat stress. In addition, acquisition of tolerance to heat and strong irradiance would reduce the dependency of the two beans on xanthophyll pigments to dissipate heat, and also seemed irrelevant to the agents with antioxidant activities such as SOD. and C. M. Tsai, B. D. Hsu.
Mabuya vitatta (Olivier) (Scincidae) and Agama stellio (L.) (Agamidae) were infected with Hemolivia mariae Smallridge et Paperna, 1997 by ingestion of tick viscera from Amblyomma limbatum Neumann, fed as nymphs on naturally infected Australian sleepy lizards, Tiliqua rugosa Gray. The unnatural infection apparently interfered with the developmental schedule of the parasites. Transmission electron microscopic images of merogonic stages were obtained, as well as images of early developing gametocytes. Tissue and intraerythrocytic meronts were bound by a hardened wall. Intraerythrocytic gametocytes were lodged in a parasitophorous vacuole, which was filled with granular material, and were bound by a two-membrane wall. Small and large osmiophilic bodies were located in a sub-pellicular position. With differentiation, the wall membranes tightened with the parasitophorous vacuole wall, and the osmiophilic bodies disappeared. The outer parasite membrane consolidated into a thick encasing with distinct sutures. Late infection in A. stellio comprised gametocytes only.
Accurate measurement of shallow flows is important for hydraulics, hydrology and water resources management. The objective of this paper is to discuss a technique for shallow flow and overland flow velocity estimation that uses infrared thermography. Laboratory flumes and different bare, vegetated and paved field surfaces were used to test the technique. Results show that shallow flow surface velocities estimated using thermal tracers and infrared technology are similar to estimates obtained using the Acoustic Doppler Velocimeter; similar results were also obtained for overland flow velocity estimates using thermography, here comparing with the dye tracer technique. The thermographic approach revealed some potential as a flow visualization technique, and leaves space for future studies and research.