In a group of 34 athletes and 11 untrained volunteers the plasma testosterone response to human chorionic gonadotropin (hCG) stimulation was evaluated. The hCG stimulation tests were performed by ...injecting 3000 IU of hCG i.m. on three consecutive days with plasma testosterone determinations before the first injection and 24 h after the last, i.e. third hCG injection. The basal testosterone levels were similar in both trained and untrained individuals. Plasma testosterone levels in response to repeated hCG stimulation were found to be significantly higher in the group of trained subjects.
Saponites are nanosized layered aluminosilicates from the smectite group of clay minerals, which can be further functionalized to prepare low-cost materials for water purification. Mechanochemical ...activation of saponite was achieved by high-energy grinding in a planetary ball mill. X-ray diffraction, infrared spectroscopy, scanning electron microscopy, thermal analysis, and the determination of cation-exchange capacity and specific surface area were used to characterize parent and functionalized solids. Prepared adsorbents were used for Cu2+ and Ni2+ removal from aqueous solutions. Compared to the untreated sample, activated saponites had significantly increased capacity to take away metal cations. The equilibrium data showed the maximum of Cu2+ and Ni2+ uptake of 295 and 129mg/g, respectively. In comparison with the pristine material, the measured values increased by 764% and 170% for Cu2+ and Ni2+ respectively. The formation of reactive Mg(OH)2 as the saponite decomposition product was also discussed.
Display omitted
•Mechanochemically activated smectites were prepared by high-energy grinding of saponite.•After activation, the amount of removed Cu2+ and Ni2+ from water solutions significantly increased.•The removed metal ions form insoluble hydroxides on the surface of ground saponite.•The cations after removal are fixed and unavailable for further ion exchange.
Eight carefully selected organoclays from monoalkyl- to tetraalkylammonium type were prepared from a sodium-saturated <
2
μm fraction of Jelšový Potok bentonite (Slovakia). Four samples contained 1–4 ...octylammonium chains, from monooctylammonium (1C8) to tetraoctylammonium (4C8). Two cations had chains with 16 carbons each, hexadecylammonium (1C16) and dihexadecyldimethylammonium (2C16). Two cations contained a benzene ring, either without reactive bonds (benzyltrimethylammonium, C10) or with a double bond in 4-vinylbenzyl-trimethylammonium (C12). The
d
001
values depended on the size and structure of the organocation. The height of the interlayer space in the 1C8–4C8-Mt series increased from 0.45 to 1.68
nm. 2C8 cation opened the interlayer space more than 1C16; 2C16 was more effective than 4C8. Expansion of only 0.55
nm was obtained with C10 and C12. Mass losses between 150 and 800
°C in N
2 flow were 13–38% for 1C8–4C8-Mt and 40% for 2C16-Mt. Infrared (IR) spectra were similar for 1C8–4C8-Mt but different for the samples with 16
C and 32
C atoms due to altered ratios of CH
3 and CH
2 groups. Downward shift of the CH
2 stretching bands with increasing size of the alkylammonium cation suggest that alkyl chains adopt more ordered structure. The suitability of the prepared materials to be used as fillers for polymer nanocomposites was assessed according to rheological measurements of dispersions in solvents taking solubility parameters as primary factors for comparison of particular solvent and polymer.
► Alkyl- and aryl- ammonium surfactants intercalated in montmorillonite. ► Interlayer distances depend on the size and structure of organocations. ► Rheological data for compatibility of organoclays with polymeric matrix.
Synthetic gel and glass of illitic composition, natural kaolinite, and mixed-layer illitesmectite were used as starting materials for hydrothermal synthesis of ammonium illite. Ammonium illite was ...prepared from synthetic gel by hydrothermal treatment at 300°C. The onset of crystallization began within 3 h, and well-crystallized ammonium illite appeared at 24 h. Increasing reaction time (up to four weeks) led to many illite layers per crystal. In the presence of equivalent proportions of potassium and ammonium, the gel was transformed to illite with equimolar contents of K and NH4. In contrast, synthesis using glass under the same conditions resulted in a mixture of mixed-layer ammonium illite-smectite with large expandability and discrete illite. Hydrothermal treatments of the fine fractions of natural kaolinite and illite-smectite produced ammonium illite from kaolinite but the illite-smectite remained unchanged.
Synthetic gel and glass of illitic composition, natural kaolinite, and mixed-layer illitesmectite were used as starting materials for hydrothermal synthesis of ammonium illite. Ammonium illite was ...prepared from synthetic gel by hydrothermal treatment at 300 °C. The onset of crystallization began within 3 h, and well-crystallized ammonium illite appeared at 24 h. Increasing reaction time (up to four weeks) led to many illite layers per crystal. In the presence of equivalent proportions of potassium and ammonium, the gel was transformed to illite with equimolar contents of K and NH
. In contrast, synthesis using glass under the same conditions resulted in a mixture of mixed-layer ammonium illite-smectite with large expandability and discrete illite. Hydrothermal treatments of the fine fractions of natural kaolinite and illite-smectite produced ammonium illite from kaolinite but the illite-smectite remained unchanged.
