Synthesis of MCM-41 with a phosphonium template

Cetyltrimethyl phosphonium bromide was successfully used as a template in the synthesis of MCM-41. The material was characterized by small-angle X-ray diffraction, transmission electron microscopy, nitrogen adsorption, and 29Si, 13C, and 31P solid-state NMR spectroscopy. These results were compared with those of MCM-41 prepared with the conventional cetyltrimethylammonium bromide surfactant showing that the material is highly ordered. Interestingly, the materials showed a “temporary” hydrothermal stability induced by residual P2O5 produced by the calcination. NMR measurements on the reaction mixture showed that 31P can be used as an excellent probe for in situ investigation of the formation mechanism

Properties of the silica layer during the formation of MCM-41 studied by EPR of a silica-bound spin probe

The properties of the silica layer during the formation of the mesoporous material MCM-41 were investigated by electron paramagnetic resonance (EPR) experiments carried out on a specifically designed, organo(trialkoxy)silane spin probe, SL1SiEt. Minute amounts of the spin probe were co-condensed with the silica source, tetraethyl orthosilicate (TEOS), in the synthesis of MCM-41 with cetyltrimethylammonium bromide (CTAB) under basic conditions. The mobility and location of the spin probe were followed in the CTAB micellar solution before the reaction, in the reaction mixture and in the final ordered material. It was found that the EPR spectra of hydrolyzed SL1SiEt throughout the room temperature part of the reaction are characteristic of a fast tumbling species, indicating that the silica is highly fluid prior to drying. After filtering, a slow motion type spectrum was observed, showing that the spin-label experiences considerable motional hindrance. The liquidlike behavior could be restored upon stirring the material in water. When the reaction is performed with a hydrothermal stage, the spectrum of SL1SiEt in the final product is the same as that of the room temperature synthesized material, but the addition of water did not restore the high mobility, due to a higher degree of silica cross-linking. The location of SL1SiEt throughout the formation process was obtained from electron spin-echo envelope modulation (ESEEM) measurements on MCM-41 prepared with CTAB deuterated either at the N-methyl or the alpha position and in a reaction carried out in D2O. Comparing the deuterium modulation depth, k(2H), induced by CTAB-alpha-d2, CTAB-d9, or D2O in CTAB micellar solutions of a number of reference spin probes with those of SL1SiEt revealed that the hydrolyzed SL1SiEt is located near the polar heads of the surfactant in the absence of base and TEOS. This supports the postulation of charge matching at the interface as a driving force for the formation of the mesostructure. Similar experiments carried out on reaction mixtures containing SL1SiEt showed a decrease of k(2H) from CTAB-alpha-d2 and CTAB-d9 compared to the micellar solution, exhibiting practically no time dependence. This indicates that the spin probe is pulled away from the micelle-water interface into the loosely linked, forming silica network. After drying, the modulation depth induced by CTAB-alpha-d2 and CTAB-d9 increases, showing that, once the water is removed, the silica walls contract around the micelles, pushing the silica-linked spin probe into the organic phase within the mesopores

Electronic Structure of Binuclear Mixed Valence Copper Azacryptates Derived from Integrated Advanced EPR and DFT Calculations

Binuclear, mixed valence copper complexes with a [Cu+1.5, Cu+1.5] redox state and S = 1/2 can be stabilized with rigid azacryptand ligands. In this system the unpaired electron is delocalized equally over the two copper ions, and it is one of the very few synthetic models for the electron mediating CuA site of nitrous oxide reductase and cytochrome c oxidase. The spatial and electronic structures of the copper complex in frozen solution were obtained from the magnetic interactions, namely the g-tensor and the 63,65Cu, 14N, 2H, and 1H hyperfine couplings, in combination with density functional theory (DFT) calculations. The magnetic interactions were determined from continuous wave (CW) electron paramagnetic resonance (EPR), pulsed electron nuclear double resonance (ENDOR), two-dimensional TRIPLE, and hyperfine sublevel correlation spectroscopy (HYSCORE) carried out at W-band or/and X-band frequencies. The DFT calculated g and Cu hyperfine values were in good agreement with the experimental values showing that the structure in solution is indeed close to that of the optimized structure. Then, the DFT calculated hyperfine parameters were used as guidelines and starting points in the simulations of the various experimental ENDOR spectra. A satisfactory agreement with the experimental results was obtained for the 14N hyperfine and quadrupole interactions. For 1H the DFT calculations gave good predictions for the hyperfine tensor orientations and signs, and they were also successful in reproducing trends in the magnitude of the various proton hyperfine couplings. These, in turn, were very useful for ENDOR signals assignments and served as constraints on the simulation parameters

The use of polyethylene glycol to reduce the anti-nutritional effects of tannins Semina: Ciências Agrárias, Londrina, v. 36, n. 3, suplemento 1, p. 2247-2258, 2015 Sunflower cake in diets for lambs: intake, digestibility, nitrogen balance and rumen parame

Abstract The effect of polyethylene glycol (PEG) on intake and digestibility in Sarda goats either fed in metabolic crates or browsing a Mediterranean scrubland, featured by tannin-rich species, was studied. In metabolic cages (Experiment 1) nine dry goats were fed ad libitum with foliage of lentisk (Pistacia lentiscus L.) supplemented with 200 g per day of a concentrate and either 0, 25 or 50 g per day of PEG. In the scrubland (Experiment 2), with lentisk as main species, 20 goats at the end of lactation, were supplemented with hay and concentrate, receiving 0 or 50 g per day of PEG. In both experiments the PEG did not affect the diet intake. The in vivo CP digestibility of the diet raised from 37% without PEG to 71% with 50 g of PEG in Experiment 1 (P<0.05) and from 40 to 53% in Experiment 2 (P<0.01). In the latter experiment the PEG supplemented goats had a higher proportion of lentisk in the diet than the controls (P<0.05). The milk production and the milk urea content increased as a consequence of PEG supplementation. The PEG showed its capacity to neutralize the tannins allowing a better utilisation of tanniferous species.

Polyethylene glycol affects goats' feeding behavior in a tannin-rich environment

High concentrations of condensed tannins in browse impair brush clearing by goats. We studied the effect of polyethylene glycol (PEG, MW 4000), a polymer that binds condensed tannins, on the feeding behavior of Damascus goats (Capra hircas) on a range dominated by tannin-rich lentisk (Pistacia lentiscus L.). This was done with or without a nutritious alternative to browse (alfalfa hay) available at pasture. In phase 1, no hay was provided to goats; in phase 2, hay was distributed daily in the field. In both phases, 6 goats had free access to PEG while at pasture, while 6 goats that grazed separately on another paddock did not. All goats received each night an allowance of concentrate (400 g day-1 of 40% ground corn grain, 40% ground barley, 17% soybean meal and 3% of a mineral-vitamin premix, and contained as fed 16% crude protein (CP) and 2.66 Mcal kg-1 of Metabolizable Energy). The 2 groups of goats alternated daily between paddocks. Goats supplemented with PEG spent more time browsing lentisk than goats in the control group (73 and 41%, respectively, P < 0.0001). Goats in the control group spent more time foraging on dry grasses than their PEG-fed counterparts (28 and 12%, respectively, P < 0.0001). Goats from the PEG group gained body weight at a higher rate than controls. The daily intake of PEG was 450 g, with an intake rate of 1.2 g sec-1. Supplemental alfalfa hay substituted partly for dry grasses in goats' diets, but did not modify the percent of time goats in either treatment spent browsing lentisk. Our data suggest that PEG has the potential to increase intake of tannin-rich species, even where alternative fodder of better nutritional quality is present. However, self-feeding of PEG may not be the best way to provide PEG because goats may ingest more PEG than needed to annul the aversive effects of tannins on food intake.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202

Polyethylene Glycol Affects Goats\u27 Feeding Behavior in a Tannin-Rich Environment

High concentrations of condensed tannins in browse impair brush clearing by goats. We studied the effect of polyethylene glycol (PEG, MW 4000), a polymer that binds condensed tannins, on the feeding behavior of Damascus goats (Capra hircas) on a range dominated by tannin-rich lentisk (Pistacia lentiscus L.). This was done with or without a nutritious alternative to browse (alfalfa hay) available at pasture. In phase 1, no hay was provided to goats; in phase 2, hay was distributed daily in the field. In both phases, 6 goats had free access to PEG while at pasture, while 6 goats that grazed separately on another paddock did not. All goats received each night an allowance of concentrate (400 g day-1 of 40% ground corn grain, 40% ground barley, 17% soybean meal and 3% of a mineral-vitamin premix, and contained as fed 16% crude protein (CP) and 2.66 Mcal kg-1 of Metabolizable Energy). The 2 groups of goats alternated daily between paddocks. Goats supplemented with PEG spent more time browsing lentisk than goats in the control group (73 and 41%, respectively, P \u3c 0.0001). Goats in the control group spent more time foraging on dry grasses than their PEG-fed counterparts (28 and 12%, respectively, P \u3c 0.0001). Goats from the PEG group gained body weight at a higher rate than controls. The daily intake of PEG was 450 g, with an intake rate of 1.2 g sec-1. Supplemental alfalfa hay substituted partly for dry grasses in goats\u27 diets, but did not modify the percent of time goats in either treatment spent browsing lentisk. Our data suggest that PEG has the potential to increase intake of tannin-rich species, even where alternative fodder of better nutritional quality is present. However, self-feeding of PEG may not be the best way to provide PEG because goats may ingest more PEG than needed to annul the aversive effects of tannins on food intake

The ratio between dietary rumen degradable organic matter and crude protein may affect milk yield and composition in dairy sheep

Abstract The current ruminant protein systems aim at synchronizing the provision of rumen degradable organic matter (RDOM) and degradable crude protein (RDCP) but no specific information on their optimal ratio for dairy sheep is available. We studied the effect of the ratio of RDOM to RDCP on milk yield and composition, during a summer lactation, in 34 confined Assaf sheep managed under farm condition. Individual feed intake was assessed by using PEG (MW 4000) as external marker of fecal output, and indigestible INDF as internal marker of digestibility. Four total mixed rations contained two levels of RDCP (108 and 117 g/kg DM) and two levels of RDOM (510 and 570 g/kg DM). This resulted in one diet featuring high (5.3), one diet featuring medium (4.8) ratio, and two diets featuring low (4.5) ratio of RDOM to RDCP. Individual DM intake, digestibility, and the daily yields of milk components were not affected by RDOM, RDCP or RDOM/RDCP. High RDOM/RDCP tended (P &lt; 0.10) to be associated with higher milk yield, and lower (P &lt; 0.05) CP content. The casein/CP ratio and urea-N in milk were lowest when both dietary RDCP and RDOM were low, whereas lactose was highest (P &lt; 0.05) when both RDOM and RDCP concentrations were high. Our data suggest that RDOM and RDCP interact on milk composition in a way that is not fully encompassed by the RDOM/RDCP ratio and that the use of this ratio to formulate diets for pre-determined milk composition is not warranted