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221.
222.
Entrepreneurship and the process of firms' entry, survival and growth 总被引:12,自引:0,他引:12
223.
The GPI-anchored mannoprotein Ccw12p is a crucial structural component of the cell wall of Saccharomyces cerevisiae. Compared to wild-type, the mutant ccw12 Delta grows more slowly, is highly sensitive to Calcofluor white and contains 2.5 times more cell wall chitin. In this study, electron microscopy of ccw12 Delta cell walls revealed that, with respect to wild-type, the inner glucan layer is thicker with irregular depositions of wall material, whereas the outer mannan layer is less condensed. Biochemical analyses of cell wall glucan suggest that in the absence of Ccw12p, GPI-anchored cell wall proteins are transferred preferentially to chitin and random deposition of cell wall material reinforces the inner glucan-chitin layer, thereby enhancing the overall stability of the cell wall. To further elucidate the role of Ccw12p, structure-function analysis was performed. We demonstrate that Ccw12p is highly N-glycosylated. However, loss of N-glycans does not affect Ccw12p functionality. In contrast, deletion of the repeated amino acid motive TTEAPKNGTSTAAP in the C-terminal part of the protein affects Ccw12p function. 相似文献
224.
Di Lascio Luigi Fischetti Enrico Gisolfi Antonio 《User Modeling and User-Adapted Interaction》1999,9(4):285-320
This paper presents a stereotype-based user model for adaptive hypermedia systems. We use a suitable algebraic fuzzy structure which can adequately reflect some features of the user in the model, and apply this model to adapt the navigation and the content of hypermedia nodes to the user's needs. The model includes temporal representations of the user and approximates every real user by a set of stereotypes, from which the one realizing the best approximation can always be extracted. The set of stereotypes is the support set of the structure and the operations defined therein may be supplied with adequate semantics which allow for the selection of the stereotype. 相似文献
225.
Yasuhiro Shimizu Elisabetta Di Bartolomeo Enrico Traversa Gualtiero Gusmano Takeo Hyodo Kenji Wada Makoto Egashira 《Sensors and actuators. B, Chemical》1999,60(2-3):118-124
NO2 sensing properties of SnO2-based varistor-type sensors have been investigated in the temperature range of 400-650°C and in the NO2 concentration range of 15–30 ppm. Pure SnO2 exhibited a weak nonlinear I–V characteristic in air, but clear nonlinearity in NO2 at 450°C. The breakdown voltage of SnO2 shifted to a high electric field upon exposure to NO2 and the magnitude of the shift was well correlated with NO2 concentration. Thus, SnO2 exhibited some sensitivity to NO2 as a varistor-type sensor. When SnO2 particles coated with a SiO2 thin film were used as a raw material for fabricating a varistor, the breakdown voltage in air was approximately the double that of pure SnO2 and the sensitivity to 15 ppm NO2 was enhanced slightly. However, the sensitivity to 30 ppm NO2 decreased. The Cr2O3-loading on SnO2 also led to an increase in the breakdown voltage in air, but the Cr2O3 addition was not effective for promoting the NO2 sensitivity under the present experimental conditions. 相似文献
226.
The unsteady-state kinetics of the selective catalytic reduction (SCR) of NO with NH3 is studied over V2O5–WO3/TiO2 model catalysts by means of the transient response method. NH3 strongly adsorbs onto the catalyst surface whereas NO does not adsorb appreciably. A dynamic mathematical model based on a Temkin-type desorption process for NH3 and a SCR reaction rate with a complex dependence on the ammonia surface coverage is well suited to represent the data. 相似文献
227.
Amedeo Biasi Valerio Marino Giuditta Dal Cortivo Paolo Enrico Maltese Antonio Mattia Modarelli Matteo Bertelli Leonardo Colombo Daniele DellOrco 《International journal of molecular sciences》2021,22(19)
Guanylate cyclase-activating protein 1 (GCAP1), encoded by the GUCA1A gene, is a neuronal calcium sensor protein involved in shaping the photoresponse kinetics in cones and rods. GCAP1 accelerates or slows the cGMP synthesis operated by retinal guanylate cyclase (GC) based on the light-dependent levels of intracellular Ca2+, thereby ensuring a timely regulation of the phototransduction cascade. We found a novel variant of GUCA1A in a patient affected by autosomal dominant cone dystrophy (adCOD), leading to the Asn104His (N104H) amino acid substitution at the protein level. While biochemical analysis of the recombinant protein showed impaired Ca2+ sensitivity of the variant, structural properties investigated by circular dichroism and limited proteolysis excluded major structural rearrangements induced by the mutation. Analytical gel filtration profiles and dynamic light scattering were compatible with a dimeric protein both in the presence of Mg2+ alone and Mg2+ and Ca2+. Enzymatic assays showed that N104H-GCAP1 strongly interacts with the GC, with an affinity that doubles that of the WT. The doubled IC50 value of the novel variant (520 nM for N104H vs. 260 nM for the WT) is compatible with a constitutive activity of GC at physiological levels of Ca2+. The structural region at the interface with the GC may acquire enhanced flexibility under high Ca2+ conditions, as suggested by 2 μs molecular dynamics simulations. The altered interaction with GC would cause hyper-activity of the enzyme at both low and high Ca2+ levels, which would ultimately lead to toxic accumulation of cGMP and Ca2+ in the photoreceptor outer segment, thus triggering cell death. 相似文献
228.
Maurizio Servili Maura Baldioli Roberto Selvaggini Enrico Miniati Alceo Macchioni Gianfrancesco Montedoro 《Journal of the American Oil Chemists' Society》1999,76(7):873-882
Phenolic compounds are the most important antioxidants of virgin olive oil. This paper reports on the application of solid
phase extraction (SPE) in the separation of phenolic compounds from olive fruit, olive oil, and by-products of the mechanical
extraction of the oil and the complete spectroscopic characterization by nuclear magnetic resonance of demethyloleuropein
and verbascoside extracted from olive fruit. SPE led to a higher recovery of phenolic compounds from olives than did liquid/liquid
extraction. SPE also was used to separate phenolic compounds from pomaces and vegetation waters. Phenylacid and phenyl-alcohol
concentrations in extracts obtained from SPE and liquid/liquid extraction were not significantly different (P<0.05). The recovery of the dialdehydic form of elenolic acid linked to 3,4-(dihydroxyphenyl)ethanol and an isomer of oleuropein
aglycon, however, was low. 相似文献
229.
Sulfonated poly(oxa-p-phenylene-3,3-phthalido-p-phenylene-oxa-p-phenylene-oxy-phenylene) (PEEK-WC) with various degrees of substitution was obtained by reaction of polyetheretherketone with neat chlorosulfuric acid. Highly sulfonated PEEK-WC was freely soluble in cold water. By working under suitable reaction conditions, no degradation of the polymeric chain was detected. The modified PEEK-WC was able to form asymmetric membranes. The expected chlorosulfonated derivatives were never achieved. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 477–482, 1998 相似文献
230.
Massimo Benerecetti Enrico Giunchiglia Luciano Serafini Adolfo Villafiorita 《国际智能系统杂志》1999,14(10):1021-1040
The goal of this paper is to present a logical framework for the formalization of agents' mutual beliefs in a Multi Agent system. The approach is based on a combination of extensional specifications of beliefs and context-based (finite) presentation of the specifications by employing a particular class of Multi Context systems. The extensional specification provides a set-theoretic characterization of beliefs in terms of sets closed under certain conditions. Its finite presentation is provided by using as constructors inference rules inside a Multi Context system. The resulting framework allows for capturing many relevant cases of real (not omniscient) agents, which are very common in Multi Agent scenarios embedded in real world environments. In order to substantiate this claim, two Multi Agent scenarios are formally specified in detail in the specification framework. ©1999 John Wiley & Sons, Inc. 相似文献