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81.
da Silva Mello L. Pontes M.S. Couto de Miranda E. Gonzalez Castellanos P.V. 《Electronics letters》2009,45(10):491-492
Measured data of multipath fading from 20 microwave line-of-sight links, operating in the 4 and 6 GHz frequency bands, were analysed to provide statistics of fade durations as a function of the attenuation threshold. From these results, an empirical method for predicting outage intensity due to multipath propagation was derived, which shows good agreement with the measurements. 相似文献
82.
83.
A Feria-Velasco S Castillo-Medina L Verdugo-Díaz E Castellanos S Orozco-Suárez C Sánchez-Gómez R Drucker-Colín 《Canadian Metallurgical Quarterly》1998,53(5):569-582
The application of nerve growth factor (NGF) to primary adrenal medulla chromaffin cell cultures induces phenotypic changes characterized mainly by the presence of neurites. A similar effect has been seen when these cells are stimulated by extremely low frequency magnetic fields (ELFMF). In this study, newborn rat chromaffin cells were cultured and subjected to NGF or ELFMF in order to compare their histological and ultrastructural characteristics. Cells cultured in the presence of NGF developed cytoplasmic projections and their distal ends showed growth cones as well as filopodia. With scanning and transmission electron microscopy, an increased submembranous electron density was observed in the nuclei of cells as well as irregular, wavy neuritic projections with a moderate number of varicosities, as well as the prevalence of intermediate filaments among the cytoskeleton components. Cells stimulated with ELFMF presented straighter neuritic extensions with a greater number of varicosities. With the transmission electron microscope, numerous neurotubules were observed, both in the cell soma and in their neuritic extensions. In both groups, growth cones were clearly identified by their ultrastructural characteristics. The differences seen in the cytoskeleton of cells stimulated with NGF or ELFMF suggest differential stimulation mechanisms possibly determining the biochemical, electrophysiological, and morphological characteristics in both types of cell cultures. 相似文献
84.
85.
R Galard MA Poca R Catalán M Tintoré JM Castellanos J Sahuquillo 《Canadian Metallurgical Quarterly》1997,41(7):804-809
Cholecystokinin (CCK) levels were measured in cerebrospinal fluid (CSF) of patients with adult chronic hydrocephalus syndrome (ACHS) (n = 16) and compared with levels from a control group (n = 11). The CSF concentration of CCK in the ACHS group (0.79 +/- 0.53 fmol/mL) was significantly reduced (p = .002) with respect to the controls (1.55 +/- 0.54 fmol/mL). As CCK-8, the most prevalent from of CCK in the central nervous system, has been demonstrated to play a significant role in several physiological and behavioral actions, the reduced octapeptide values found in ACHS could be involved in the disturbances associated with this disorder. Continuous monitoring of intracranial pressure (ICP) demonstrated different ICP profiles in ACHS. We found that all patients with abnormal ICP records except one showed CCK values under the detection limit. Three of the 4 patients with normal ICP had CCK levels within the normal range. These preliminary studies could evidence that ICP alterations are responsible for part of the loss of brain neuropeptide levels in ACHS. 相似文献
86.
LK Jacobsen DW Hommer WL Hong FX Castellanos JA Frazier JN Giedd JL Rapoport 《Canadian Metallurgical Quarterly》1996,40(12):1222-1229
Several lines of evidence have implicated central dopaminergic pathways in the modulation of blink rate. In the present study, blink rate during smooth pursuit was examined in 17 children with childhood-onset schizophrenia, on and off of clozapine, and compared to that of age-matched normal children and unmedicated children with attention-deficit hyperactivity disorder (ADHD). As has been observed in adolescent and adult schizophrenics, blink rate was significantly higher in schizophrenic children relative to normal and ADHD controls. Within the schizophrenic group, blink rate did not significantly change with the introduction of clozapine and was not related to clinical variables. Blink rate was positively correlated with deterioration in smooth pursuit in normal subjects. 相似文献
87.
A suitable correlation can be made to represent the simulated distillation of heavy oils starting from thennoaravimetric measurements. This method is applicable to hydrocarbons having an initial boiling point equal or greater than 200°C.
The simulated thermogravimetric distillation fit was obtained from experiments with the standard compounds obtained from ASTM D-2887-83 (Boiling range distribution of petroleum fractions by gas chromatography). This method is simple, fast and without problems when applied to heavy feedstocks
The data were used in the determination of average boiling temperatures of products from thermal cracking and thermal hydrocracking. It was also possible to quantify coke yields
Average relative molecular masses of products from the above processes correlated well with the average boiling point temperatures. It indicates that, with respect to the hydrocarbon types, thermal cracking is not selective in comparison with thermal hydrocracking
The equation applied to find the average boiling temperature is following: T = (1/al) (Ttg-a2). T is the boiling temperature, al and a2 are the correction factors, Ttg is the thermogravimetric temperature. 相似文献
The simulated thermogravimetric distillation fit was obtained from experiments with the standard compounds obtained from ASTM D-2887-83 (Boiling range distribution of petroleum fractions by gas chromatography). This method is simple, fast and without problems when applied to heavy feedstocks
The data were used in the determination of average boiling temperatures of products from thermal cracking and thermal hydrocracking. It was also possible to quantify coke yields
Average relative molecular masses of products from the above processes correlated well with the average boiling point temperatures. It indicates that, with respect to the hydrocarbon types, thermal cracking is not selective in comparison with thermal hydrocracking
The equation applied to find the average boiling temperature is following: T = (1/al) (Ttg-a2). T is the boiling temperature, al and a2 are the correction factors, Ttg is the thermogravimetric temperature. 相似文献
88.
Dr. Ing. Esteban Castellanos Dr. Rafael Diaz Prof. Dr. Hans Neumann 《Petroleum Science and Technology》2013,31(4):543-565
Abstract The purpose of this work is to research the characteristics of the production of coke in thermal and hydrothermal cracking from residual oils and their deasphalted oils Using ethyl acetate, because it allows the elimination of both resins and asphaltenes (colloidal matter) from the parent oil in only one step. This improves the deasphalted oil as coke precursors and basic nitrogen compounds present in the resin fraction are practically eliminated. A 104 ml batch autoclave reactor with a cooling system was used for the thermal and hydrothermal cracking experiments. This reactor can withstand temperatures of up to 500°C, pressures of 500 bar and a rocking velocity of 1 Hz. The influence of the temperature was investigated at 400, 425 and 450°C and at 0, 20, 40, 80, 相似文献
89.
90.
Kline Rex B.; Snyder Joseph; Guilmette Sylvie; Castellanos Maria 《Canadian Metallurgical Quarterly》1992,4(4):426
Scatter analysis of IQ profiles has a long and controversial history. The study was conducted to determine whether the validity of scatter information is any greater for 2 new IQ batteries, the Kaufman Assessment Battery for Children (K-ABC) and the Fourth Edition Stanford-Binet Intelligence Scale (SB4), than for the Wechsler Intelligence Scale for Children—Revised (WISC—R). Within a sample of referred children, numerical indexes were computed of profile elevation, shape, and variability for all IQ tests. Using hierarchical multiple regression with achievement scores as dependent variables, shape information was found that had marginal incremental validity over elevation as a predictor for the WISC—R, even less for the SB4, and virtually none for the K-ABC. Implications of these results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献