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11.
Toon Verstraelen Bartłomiej M. Szyja David Lesthaeghe Reinout Declerck Veronique Van Speybroeck Michel Waroquier Antonius P. J. Jansen Alexander Aerts Lana R. A. Follens Johan A. Martens Christine E. A. Kirschhock Rutger A. van Santen 《Topics in Catalysis》2009,52(9):1261-1271
Zeolite synthesis is driven by structure-directing agents, such as tetrapropyl ammonium ions (TPA+) for Silicalite-1 and ZSM-5. However, the guiding role of these organic templates in the complex assembly to highly ordered
frameworks remains unclear, limiting the prospects for advanced material synthesis. In this work, both static ab initio and
dynamic classical modeling techniques are employed to provide insight into the interactions between TPA+ and Silicalite-1 precursors. We find that as soon as the typical straight 10-ring channel of Silicalite-1 or ZSM-5 is formed
from smaller oligomers, the TPA+ template is partially squeezed out of the resulting cavity. Partial retention of the template in the cavity is, however,
indispensable to prevent collapse of the channel and subsequent hydrolysis.
相似文献
Rutger A. van Santen (Corresponding author)Email: |
12.
Veronique Demers-Mathieu Ciera DaPra Gabrielle Mathijssen David A. Sela Kirsi M. Jrvinen Antti Seppo Shawn Fels Elena Medo 《International journal of molecular sciences》2021,22(4)
Background: Preexisting immunity to SARS-CoV-2 could be related to cross-reactive antibodies to common human-coronaviruses (HCoVs). This study aimed to evaluate whether human milk antibodies against to S1 and S2 subunits SARS-CoV-2 are cross-reactive to S1 and S2 subunits HCoV-OC43 and HCoV-229E in mothers with a confirmed COVID-19 PCR test, in mothers with previous viral symptoms during COVID-19 pandemic, and in unexposed mothers; Methods: The levels of secretory IgA (SIgA)/IgA, secretory IgM (SIgM)/IgM, and IgG specific to S1 and S2 SARS-CoV-2, and reactive to S1 + S2 HCoV-OC43, and HCoV-229E were measured in milk from 7 mothers with a confirmed COVID-19 PCR test, 20 mothers with viral symptoms, and unexposed mothers (6 Ctl1-2018 and 16 Ctl2-2018) using ELISA; Results: The S2 SARS-CoV-2 IgG levels were higher in the COVID-19 PCR (p = 0.014) and viral symptom (p = 0.040) groups than in the Ctl1-2018 group. We detected a higher number of positive correlations between the antigens and secretory antibodies in the COVID-19 PCR group than in the viral symptom and Ctl-2018 groups. S1 + S2 HCoV-OC43-reactive IgG was higher in the COVID-19 group than in the control group (p = 0.002) but did not differ for the other antibodies; Conclusions: Mothers with a confirmed COVID-19 PCR and mothers with previous viral symptoms had preexisting human milk antibodies against S2 subunit SARS-CoV-2. Human milk IgG were more specific to S2 subunit SARS-CoV-2 than other antibodies, whereas SIgA and SIgM were polyreactive and cross-reactive to S1 or S2 subunit SARS-CoV-2. 相似文献
13.
A. B. Yur’ev N. A. Kozyrev L. V. Korneva N. I. Bedarev O. V. Gileva 《Steel in Translation》2009,39(11):1033-1034
Repeated tempering of bulk-quenched rail reduces the residual stress without significant change in the mechanical properties
and hardness of the metal. Double tempering with optimal cold straightening is suitable for the manufacture of rail that is
resistant to corrosion-fatigue cracks. 相似文献
14.
A. B. Yur’ev I. V. Aleksandrov N. A. Kozyrev L. V. Korneva O. P. Atkonova 《Steel in Translation》2009,39(8):714-715
Means of extending rail life are considered: optimizing the chemical composition of the steel; eliminating nonmetallic inclusions
by vacuum treatment; reduction and modification of the steel; and optimization of heat treatment to attain the required required
linearity, hardness, and mechanical properties. 相似文献
15.
In vivo characterisation of a novel bioresorbable poly(lactide-co-glycolide) tubular foam scaffold for tissue engineering applications 总被引:2,自引:0,他引:2
Day RM Boccaccini AR Maquet V Shurey S Forbes A Gabe SM Jérôme R 《Journal of materials science. Materials in medicine》2004,15(6):729-734
Polylactide-co-glycolide (PLGA) foams of tubular shape were assessed for their use as soft-tissue engineering scaffolds in vitro and in vivo. Porous membranes were fabricated by a thermally induced phase separation process of PLGA solutions in dimethylcarbonate. The parameters investigated were the PLGA concentration and the casting volume of solution. Membranes produced from 5 wt/v % polymer solutions and a 6 ml casting volume of polymer solution were selected for fabricating tubes of 3 mm diameter, 20 mm length and a nominal wall thickness of 1.5 mm. Scanning electron microscopy revealed that the structure of the tubular foams consisted of radially oriented and highly interconnected pores with a large size distribution (50-300 microm). Selected tubes were implanted subcutaneously into adult male Lewis rats. Although the lumen of the tubes collapsed within one week of implantation, histological examination of the implanted scaffolds revealed that the foam tubes were well tolerated. Cellular infiltration into the foams, consisting mainly of fibrovascular tissue, was evident after two weeks and complete within eight weeks of implantation. The polymer was still evident in the scaffolds after eight weeks of implantation. The results from this study demonstrate that the PLGA tubular foams may be useful as soft-tissue engineering scaffolds with modification holding promise for the regeneration of tissues requiring a tubular shape scaffold such as intestine. 相似文献
16.
Replacing the ({beta}{alpha})-unit 8 of E.coli TIM with its chicken homologue leads to a stable and active hybrid enzyme 总被引:2,自引:0,他引:2
Mainfroid Veronique; Goraj Karine; Rentier-Delrue Francoise; Houbrechts Annick; Noble Martin E.M.; Borchert Torben V.; Wierenga Rik K.; Martial Joseph A. 《Protein engineering, design & selection : PEDS》1993,6(8):893-900
In order to investigate how structural modifications interferewith protein stability, we modified a (ß)-unit inE.coli triosephosphate isomerase (TIM), a typical (ß)-barrelprotein, assuming that the pseudosymmetrical ß-barrelcan be divided into eight successive loop/ß-strand/loop/-helixmotifs. We replaced the eighth (ß)-unit of E.coliTIM with the corresponding chicken (ß)-unit. The substitution,involving the replacement of 10 of the 23 residues of this (ß)-unit, was evaluated first by modelling, then experimentally.Modelling by bomology suggests how the amino add replacementsmight be accommodated in the hybrid E.coli/chicken TIM (ETCM8CHI).Both natural and hybrid recombinant TIMs, overproduced in E.coli,were purified to homogeneity and characterized as to their stabilityand kinetics. Our kinetic studies show that the modificationperformed here leads to an active enzyme. The stability studiesindicate that the stability of ETIM8CHI is comparable to thatof the wild type TIM. 相似文献
17.
Pierre Blaise Veronique Tropini Marie Farines Robert L. Wolff 《Journal of the American Oil Chemists' Society》1997,74(2):165-168
The positional distribution of various Δ5-acids in the seed triacylglycerols from several conifer species has been established
after partial chemical degradation with Grignard reagent. The species studied were representative of four conifer families
and were specially selected for their particularly high Δ5-acid contents. These species were Taxus baccata (Taxaceae; 5,9-18:2 acid, 11.9%), Larix decidua (Pinaceae; 5,9,12-18:3 acid, 28.5%), Sciadopytis verticillata (Taxodiaceae; 5,11,14-20:3 acid, 16.7%), and Juniperus communis (Cupressaceae; 5,11,14,17-20:4 acid, 19.8%). Calculations from the fatty acid compositions of triacylglycerols and of the
mixture of 1,2- and 2,3-diacylglycerols generated by the Grignard reagent indicated that, for the four species, there was
a considerable enrichment of Δ5-acids (generally more than ten times) in the 1,3-positions as compared to the 2-position,
where Δ5-acids represented always less than 2% of total fatty acids esterified to triacylglycerols. This distribution was
practically independent from the species (four families studied), the chainlength (18 or 20 carbon atoms), and the number
of ethylenic bonds (two to four) in the Δ5-acids. Similar distributions were established for triacylglycerols from the seeds
of three pine species that are available on a ton-scale: Pinus pinea, P. koraiensis, and P. pinaster. These observations confirm and extend previous studies conducted with other conifer species by similar techniques or by
13C-nuclear magnetic resonance spectroscopy. Consequently, the almost exclusive location of Δ5-acids in the external positions
of triacylglycerols is now well established and appears to be a general feature of conifer seed oils. 相似文献
18.
A. B. Yur’ev I. V. Aleksandrov N. A. Kozyrev D. S. Lemeshevskii A. B. Tverskoi 《Steel in Translation》2010,40(6):562-564
Operating conditions are developed for the electrosmelting of rail steel and regular steel with 100% solid metal batch. Overall, the furnace performance is comparable to that with 50% hot metal. The new approach permits savings of around 170 rub/t of steel. 相似文献
19.
B. P. Yur’ev 《Steel in Translation》2010,40(4):330-333
20.
A. B. Yur’ev N. Kh. Mukhatdinov N. A. Kozyrev L. V. Korneva A. L. Nikulina 《Steel in Translation》2010,40(2):181-183
Metallurgical methods of improving the reliability of the weld seam in bulk-quenched electrosteel rail are considered: optimization of the chemical composition in terms of the basic elements and total impurity content; improvement in plastic properties of the rail by reducing the hardness; and removal of nonmetallic inclusions from the steel. Instability is seen in the weldability of the rails and also in the composition, with the same set of mechanical properties. The need for improvement in welding technology is shown; without the elimination of existing problems, the weldability of electrosteel rail cannot be guaranteed. 相似文献