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141.
This paper describes risk factors for dental caries identified among 491 2-year-olds in the city of Ume?, Sweden. The study was performed as a risk screening for dental caries according to a method developed for use by dental assistants. The sugar consumption was high, 80% of the 2-year-olds had sweets once a week or more and 25% had sweet beverages once a day or more frequently. In addition, 14% of the children had a meal at night and most common were formula, bovine milk or breastmilk. The majority of the parents brushed the child's teeth at least daily using fluoride toothpaste. Among the children 6% had a chronic somatic disorder and 6% had an intolerance towards specific foods, milk being the most common. The high level of sugar consumption indicates that improved dental health education focusing on the importance of limiting sugar consumption is needed among parents with young children.  相似文献   
142.
Raman and infrared active vibrons and phonons in the solid molecular hydrogen at megabar pressures have been studied by the first–principles band theoretical calculations assuming the hcp lattice of the centers of the molecules. The frequencies of the out–of–phase stretching motion of the two molecules in the unit cell are higher than those of the in–phase stretching motion. Pressure dependence of the frequency of a phonon–like mode, which lies in 1300 cm –1 ~ 1900 cm –1 at pressures 70 GPa ~ 200 GPa, is in good agreement with the recent experiments. Our results suggest that the lattice of the solid hydrogen remains hcp beyond the phase transition at 150 GPa.  相似文献   
143.
144.
The molecular mechanisms of head development are a central question in vertebrate and invertebrate developmental biology. The anteriorly expressed homeobox gene otd in Drosophila and its homolog Otx in mouse are required for the early development of the most anterior part of the body, suggesting that a fundamental genetic program of cephalic development might be conserved between vertebrates and invertebrates. We have examined this hypothesis by introducing the human Otx genes into flies. By inducing expression of the human Otx homologs with a heat shock promoter, we found that both Otx1 and Otx2 functionally complement the cephalic defects of a fly otd mutant through specific activation and inactivation of downstream genes. Combined with previous morphological studies, these results are consistent with the view that a common molecular ground plan of cephalization was invented before the diversification of the protostome and the deuterostome in the course of metazoan evolution.  相似文献   
145.
Individual glomeruli in the mammalian main olfactory bulb represent a single or at most a few types of odorant receptors. Thus the physical arrangement of glomeruli at the surface of the olfactory bulb can be viewed as a sensory map representing approximately 1,000 types of odorant receptors. This review summarizes the recent advance of the knowledge regarding the spatial organization of the sensory map in the main olfactory bulb. Recent studies show that individual olfactory bulbs contain dual sensory maps, one in the lateral hemisphere and the other in the medial hemisphere of the bulb. The tracings of selective subsets of olfactory axons to their target glomeruli in the olfactory bulb show that glomeruli are parceled into large zones or bands. The spatial arrangement of these zones and bands are stereotypical and conserved across individual mice. Optical imaging studies show that glomeruli in the most rostrodosal zone, zone I, are further parceled into smaller functional domains, and suggest that odorant receptors having a common or similar molecular feature receptive site are grouped together and represented by glomeruli within the functional domain. The possible relation between the functional domain organization and the subjectively perceived odor quality (olfactory submodality) is reviewed.  相似文献   
146.
147.
The adsorption of N2 on a copper ion-exchanged ZSM-5 sample (CuZSM-5) prepared by ion exchange using an aqueous solution of copper propionate, Cu(C2H5COO)2, was examined at room temperature by measuring the FT-IR spectra, adsorption isotherms and heat of adsorption. This sample was found to be extremely efficient in terms of N2 adsorption with regard to both the amount and the energy (i.e., heat) of adsorption, compared with samples prepared by a conventional ion-exchange method using an aqueous solution involving Cu2+ and simple counter ions, Cl or NO3. To clarify the specificity of the newly-prepared sample, the ion-exchange of ZSM-5 with Cu2+ was carried out by employing aqueous solutions involving Cu2+ and various types of counter ions [propionate (C2H5COO), acetate (CH3COO), formate (HCOO), chloride (Cl) and nitrate (NO3) ions]. When the ion exchange was performed by using a Cu(C2H5COO)2 or Cu(CH3COO)2 solution, the Cu2+ species with propionate or acetate ligand (in the monomer state) were ion-exchanged in ZSM-5, as confirmed by the DR, EPR and FT-IR spectra for CuZSM-5. In contrast, Cu2+ species were present in the form of aquo-complexes in samples prepared with other solutions. This distinct difference can be ascribed to the difference in the pKa values of the counter ions; carboxylate ions, with a high pKa value, are inclined to form a complex with Cu2+. Using this newly applied Cu(C2H5COO)2 solution, the present ion-exchange method has the potential to develop new effective materials that possess the specific adsorption and catalytic properties of CuZSM-5.  相似文献   
148.
Synthesis of 6-phosphatidyl-L-ascorbic acid by phospholipase D   总被引:1,自引:0,他引:1  
Phospholipase D (EC 3.1.4.4) ofStreptomyces species was found to catalyze transphosphatidylation to L-ascorbic acid from phosphatidylcholine (PC) in a biphasic reaction system. The product was identified as 1,2-diacyl-sn-glycero-3-phospho-6′-L-ascorbic acid (PA-AsA) by mass spectrometry and nuclear magnetic resonance spectroscopy. The optimal pH of transphosphatidylation was 4.5 and the rate of PA-AsA formation increased as concentrations of L-ascorbic acid increased. The conversion of PC to PA-AsA was greater than 80%. PA-AsA was found to be more resistant to hydrolysis by phospholipase D than was PC.  相似文献   
149.
Soybean oil deodorizer distillate (SODD) contains steryl esters in addition to tocopherols and sterols. Tocopherols and sterols have been industrially purified from SODD but no purification process for steryl esters has been developed. SODD was efficiently separated to low b.p. substances (including tocopherols and sterols) and high b.p. substances (including 11.2 wt% DAG, 32.1 wt% TAG, and 45.4 wt% steryl esters) by molecular distillation. The high b.p. fraction is referred to as soybean oil deodorizer distillate steryl ester concentrate (SODDSEC). We attempted to purify steryl esters after a lipase-catalyzed hydrolysis of acylglycerols in SODDSEC. Screening of industrially available lipases indicated that Candida rugosa lipase was most effective. Based on the study of several factors affecting hydrolysis, the reaction conditions were determined as follows: ratio of SODDSEC/water, 1∶1 (w/w); lipase amount, 15 U/g reaction mixture; temperature, 30°C. When SODDSEC was agitated for 24 h under these conditions, acylglycerols were almost completely hydrolyzed and the content of steryl esters did not change. However, study with a mixture of steryl oleate/trilinolein (1∶1, w/w) indicated that about 20% of constituent FA in steryl esters were exchanged with constituent FA in acylglycerols. Steryl esters in the oil layer obtained by the SODDSEC treatment with lipase were successfully purified by molecular distillation (purity, 97.3%; recovery, 87.7%).  相似文献   
150.
An attempt was made to produce structured lipids containing essential fatty acid by acidolysis with 1,3-positional specificRhizopus delemar lipase. The lipase was immobilized on a ceramic carrier by coprecipitation with acetone and then was activated by shaking for 2 d at 30°C in a mixture of 5 g safflower or linseed oil, 10 g caprylic acid, 0.3 g water and 0.6 g of the immobilized enzyme. The activated enzyme was transferred into the same amount of oil/caprylic acid mixture without water, and the mixture was shaken under the same conditions as for the activation. By this reaction, 45–50 mol% of the fatty acids in oils were exchanged for caprylic acid, and the immobilized enzyme could be reused 45 and 55 times for safflower and linseed oils, respectively, without any significant loss of activity. The triglycerides were extracted withn-hexane after the acidolysis and then were allowed to react again with caprylic acid under the same conditions as mentioned above. When acidolysis was repeated three times with safflower oil as a starting material, the only products obtained were 1,3-capryloyl-2-linoleoylglycerol and 1,3-capryloyl-2-oleoyl-glycerol, with a ratio of 86∶14 (w/w). Equally, the products from linseed oil were 1,3-capryloyl-2-α-linolenoyl-glycerol, 1,3-caprylol-2-linoleoyl-glycerol, and 1,3-capryloyl-2-oleoly-glycerol (60∶22∶18, w/w/w). All fatty acids at the 1,3-positions in the original oils were exchanged for caprylic acid by the repeated acidolyses, and the positional specificity ofRhizopus lipase was also confirmed to be strict.  相似文献   
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