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Biomedical subjects

J Hrbek

Publications and source records attributed to J Hrbek.

At least 19 recordsLinked to original sources
PubMed2005

Reaction of SO2 with AuCeO2(111): importance of O vacancies in the activation of gold.

Synchrotron-based high-resolution photoemission was used to study the adsorption and chemistry of SO(2) on AuCeO(2)(111) and AuO(x)CeO(2) surfaces. The heat of adsorption of the molecule on Au nanoparticles supported on stoichiometric CeO(2)(111) was 4-7 kcalmol larger than on Au(111). However, there was negligible dissociation of SO(2) on the AuCeO(2)(111) surfaces. The full decomposition of SO(2) was observed only after introducing O vacancies in the ceria support. AuO(x)CeO(2) surfaces were found to be much less chemically active than AuCeO(2)(111) or AuCeO(2-x)(111) surfaces. The active sites in {Au + AuO(x)}ceria catalysts should involve pure gold nanoparticles in contact with O vacancies.

Journal Article↗
PubMed2001

Chemistry of NO2 on oxide surfaces: formation of NO3 on TiO2(110) and NO2<-->O vacancy interactions.

Synchrotron-based high-resolution photoemission, X-ray absorption near-edge spectroscopy, and first-principles density functional (DF) slab calculations were used to study the interaction of NO(2) with a TiO(2)(110) single crystal and powders of titania. The main product of the adsorption of NO(2) on TiO(2)(110) is surface nitrate with a small amount of chemisorbed NO(2). A similar result is obtained after the reaction of NO(2) with polycrystalline powders of TiO(2) or other oxide powders. This trend, however, does not imply that the metal centers of the oxides are unreactive toward NO(2). An unexpected mechanism is seen for the formation of NO(3). Photoemission data and DF calculations indicate that the surface nitrate forms through the disproportionation of NO(2) on Ti sites (2NO(2,ads) --> NO(3,ads) + NO(gas)) rather than direct adsorption of NO(2) on O centers of titania. Complex interactions take place between NO(2) and O vacancies of TiO(2)(110). Electronic states associated with O vacancies play a predominant role in the bonding and surface chemistry of NO(2). The adsorbed NO(2), on its part, affects the thermochemical stability of O vacancies, facilitating their migration from the bulk to the surface of titania. The behavior of the NO(2)/titania system illustrates the importance of surface and subsurface defects when using an oxide for trapping or destroying NO(x)() species in the prevention of environmental pollution (DeNOx operations).

Environmental Pollutants↗
PubMed1989

On acute effects of some drugs on the higher nervous activity in man. Ethanol (0.5 g/kg) and its interaction with diazepam (5 mg) and meclophenoxate (100 mg). Part LVIII.

1. Acute effects of ethanol (0.5 g/kg of body weight) and its interactions with diazepam (5 mg) and meclophenoxate (100 mg) and placebo on the higher nervous activity were tested on a group of 16 healthy and unfatigued volunteers-university students (8 females, 8 males, aged 21 years). The experimental subjects were given the following combinations of the studied drugs: (a) Ethanol plus meclophenoxate, (b) Ethanol plus placebo, (c) Ethanol plus diazepam, (d) Placebo solution plus placebo. The method of artificial conditioned speech connections was made use of. Three statistically balanced trials were always carried out: before, and one and two hours after the administration of the tested drug combinations during the early and late forenoon hours. The investigation-sets consisted of two optic, two complex tactile, and two acoustic associations. The criteria for the evaluation of the results were the number of repetitions necessary for mastering the given task, then the number of correct responses and the frequencies of responses in the first eight repetitions of the sets when the active knowledge of the persons under investigation was tested. 2. One hour after the application, there appeared a statistically significant impairment in NNR and NCR, both after ethanol alone and ethanol in combinations with diazepam and meclophenoxate. The frequency of responses was impaired only after the combination of ethanol plus diazepam. 3. Two hours after the administration, the combinations of ethanol plus diazepam and ethanol plus meclophenoxate impaired significantly the number of necessary repetitions. NCR impairment was observed only after application of ethanol with diazepam. Ethanol administered separately did not impair the followed up characteristics of learning. 4. The most marked effect appeared during the formation of artificial conditioned speech connections with acoustic stimuli.

Adult↗
PubMed1989

Acute effects of ethanol (0.5 mg/kg) and its interaction with diazepam (5 mg) and meclophenoxate (100 mg) on the blood pressure, the body temperature and the heart rate in man.

1. In the course of an experiment in which acute effects of perorally applied ethanol alone (0.5 g/kg of body weight) or in combination with diazepam (5 mg) and meclophenoxate (100 mg) on verbal learning were studied, the values of the blood pressure, the body temperature and the heart rate of experimental subject were simultaneously registered with the help of polyphysiograph Physiomat. 2. The method of artificial conditioned speech connections was adopted. The experimental subjects were 16 healthy and unfatigued volunteers - university students (8 females, 8 males, age 21 years). The investigation-sets consisted of two optic, two complex tactile, and two acoustic associations. Three trials were always carried out: before, and one and two hours after the administration of the studied drugs. 3. The values of the blood pressure, the body temperature and the heart rate were not significantly influenced by the applied substances. Only two hours after application of ethanol in combination with diazepam, a marked decrease of systolic and diastolic blood pressure was registered in comparison with the values observed after application of placebo.

Adult↗
PubMed1989

Effects of single administration of scopolamine, physostigmine and their combination on biogenic amine levels in rat brain.

There were studied the changes of norepinephrine and dopamine levels in the brain cortex, the brain stem and hypothalamus of rats after the application of scopolamine, physostigmine and their combination. The application of scopolamine (0.5 mg/kg) or physostigmine (1.0 mg/kg) increased the levels of NE and in many cases statistically significantly. The simultaneous application of both drugs was manifested by less marked or neglectable changes of NE and DA levels in comparison with the control group.

Animals↗