The non-thermal spectra of many extragalactic jets and active galactic nuclei have a power law form over many orders of magnitudes. This kind of spectrum is assumed to be the result of shock acceleration of relativistic elcctrons at these sources.
As observed by Rieke et al. (1982) some of the A.G.N's, especially the BL Lac type, have an abrupt cutoff at IR-V frequencies. In some cases the intensity of the non-thermal radiation decreases by
more than two orders of magnitude over a frequency band of less than one order of magnitude.
Simon P. Anderson and Maxim Engers., Popsáno podle obálky, Pod názvem: Center for Economic Research and Graduate Education. Faculty of Social Sciences. Charles University, and Obsahuje bibliografii
Methylphenidate is commonly used for the treatment of attention deficit hyperactivity disorder. The cardiovascular safety of methylphenidate has been a subject of debate with some studies indicating that methylphenidate increases the likelihood of experiencing a myocardial infarction. However, it is unknown whether methylphenidate worsens the extent of injury during an ischemic insult. The purpose of this study was to determine whether short term exposure to methylphenidate increases the extent of myocardial injury during an ischemic insult. Male and female rats received methylphenidate (5 mg/kg/day) or saline for 10 days by oral gavage. Hearts were subjected to 20 min of ischemia and 2 h of reperfusion on a Langendorff isolated heart apparatus on day 11. Cardiac contractile function was monitored via an intraventricular balloon and myocardial injury was assessed by triphenyltetrazolium chloride staining. Methylphenidate significantly increased locomotor activity in male and female rats, confirming absorption of this psychostimulant into the central nervous system. Male hearts had significantly larger infarcts than female hearts, but methylphenidate had no impact on infarct size or postischemic recovery of contractile function in hearts of either sex. These data indicate that methylphenidate does not increase the extent of injury induced by an ischemic insult., Sarah L. Seeley, Manoranjan S. D’Souza, Thorne S. Stoops, Boyd R. Rorabaugh., and Obsahuje bibliografii
We show that prediction of travel time on a 28-km long highway section based on on-line travel time measurements with video is practicable by a data mining method. We introduce a new prediction model, a result of the GUHA style data mining analysis and tlie Total Fuzzy Similarity method. Comparing the results with the existing Traficon model, oiir model improves the travel time class prediction. The results obtained by our method are comparable to the MLP neural network model, too.
Ants are the most abundant group of soil arthropods in olive groves where they are involved in various trophic relationships of great importance for crops. The system of soil management is one agricultural practice that has a great effect on ants, so the objective of this study was to compare ant populations in organic olive orchards with a ground cover of natural vegetation and others where this natural vegetation is mechanically removed at the beginning of June. Ants were sampled using pitfall traps at 14, 30, 70 and 90 days after the removal of the ground vegetation. Overall, ant biodiversity did not change. However, changes were observed in the abundance of ant species, in particular, in those species that build shallow nests in the soil, both between the rows of trees and under the canopy of olive trees. In contrast, deep nesting species, such as Messor barbarus, were not affected. The response also differed between the various genera: the abundance of Cataglyphis increased, due to there being more of the species C. rosenhaueri, while there was a significant fall in Aphaenogaster, due to the decline in abundance of A. senilis. Thirty days after the removal of vegetation, the response of most of the genera was clearly noticeable, due to the increased activity of workers, and in some cases there were still differences after 90 days. and Mercedes Campos, Luisa Fernández, Francisca Ruano, Belén Cotes, Manuel Cárdenas, Juan Castro.
The aim of the present study was to investigate the effects of Angiotensin II (Ang II) and Arginin-Vasopressin (AVP) on contractility of non-pregnant uterus in diabetic Wistar rats and to explore whether one-week administration of Melatonin (MLT) or Ghrelin (GHR) will change the response of diabetic uterine muscle to AngII and AVP. Uterine horns, prepared by the method of isolated tissues were investigated as w ell as glycemic profile, blood pressure and body weight. The research of smooth muscle contractions was made by a new method of analysis, characterizing in detail the various phases of the myometrial activity. Differences in the development of the peptide-mediated smooth muscle contractions depending on the phase of the estrous cycle were observed. Experimental diabetes had a pronounced negative effect on force and time-parameters of AngII and AVP-stimulated uterine contractions. Administration of GHR or MLT had a beneficial effect on the glycemic status of diabetic rats and partially improved the response of uterine preparations to the peptides. The application of MLT increased both force and time-parameters of Ang II- and AVP-stimulated uterine contractions while treatment with GHR increased power characteristics and shortened contraction and relaxation of the smooth muscle process., T. Georgiev, A. Tolekova, R. Kalfin, P. Hadzhibozheva., and Obsahuje bibliografii
Temporary malnutrition during juvenile development often negatively influences the life-history decisions of adults. Hence, individuals should avoid this effect by compensatory feeding on the limited resource when the food situation improves. In a feeding experiment, bush-crickets (Pholidoptera griseoaptera) responded to nine days depression of animal food supply by increasing their feeding activities on insect carcasses when a full-nutritional diet was available. As a short-term reaction, treated individuals of both sexes took 3.4 times more food from carcasses (0.084 g / 9 h) than control individuals. The increased carcass intake levelled off at 0.025 g / 9 h after an interval of nine hours, indicating that bush-crickets can rapidly compensate for an experimentally increased demand for animal diet. The general daily carcass intake of male and female bush-crickets was 0.07 g fresh weight, corresponding to 16.4% of the bush-cricket's body mass. Carcass intake and body mass development was correlated over the complete period (7 d), but no correlation was found for the time of short-term reaction. We conclude that animal diet is essential for the growth of dark bush-crickets. They were able to compensate for short depressions in animal food supply by increasing feeding frequencies and feeding rates of the limited resource. Hence, bush-crickets can cope with short periods of limited animal food supply, e.g. periods of rainfall, which regularly occur in their natural habitat.
Despite the impact of parasitoids on insect populations being extensively studied, indirect parasitoid-mediated effects remain rarely documented in natural communities. We examined the influence of shared parasitoids on the interactions between two functionally monophagous moths, Nonagria typhae and Archanara sparganii. The moths showed a considerable variation in terms of relative abundance and the degree of phenological synchrony between the species. On average, parasitism levels caused by shared parasitoids did not differ between the two host species. Relative parasitism levels of the two hosts, however, varied considerably among different samples. Percentage parasitism of the scarcer species, A. sparganii, thus could not be fully explained by that of the dominant species, N. typhae. The results indicated that A. sparganii may benefit from the presence of N. typhae. In particular, both low relative density as well as high phenological synchrony with N. typhae reduced parasitism levels in A. sparganii. The case thus indicates the presence of parasitoid-mediated indirect effects between the coexisting herbivores. The patterns of host use observed in this study are consistent with the scenario of frequency-dependent host use caused by changes in parasitoid behavior. Such a host use by parasitoids is suggested to promote numerical stability and coexistence of the moth species in the system studied.