排序方式: 共有34条查询结果,搜索用时 15 毫秒
1.
The a.c. conductivity of the proteins lysozyme and subtilisin, both in their active and inactive or inhibited forms were determined theoretically. For this, quantum mechanical calculations and a random walk theory were used. The conclusions are that these enzymatic proteins can easily transport electrons which is most probably important in their role as catalysators of biochemical reactions. The electron transport is sensitive to three-dimensional changes of the active sites of these enzymes which have more flexibility than the whole molecule. Therefore, the flexibility of the active sites of enzyme catalysts is not only important for the conformational fitting with the reactants, but also strongly influences the transport in biochemical reactions. 相似文献
2.
R Pratesi L Gandolfi H Friedman L Farage CA de Castro C Catassi 《Canadian Metallurgical Quarterly》1998,33(8):817-821
BACKGROUND: Our objective was to determine the possible presence of IgA antibodies directed against human central nervous system (CNS) structures in sera from coeliac disease (CD) patients. METHODS: Serum samples were collected from 4 patients with active CD on a gluten-containing diet, 11 biopsy-proven CD patients on a gluten-free diet (GFD), and 52 non-coeliac gastrointestinal controls. In all patients IgA antigliadin antibody (AGA) titres were determined with enzyme-linked immunoassay (ELISA), and IgA antiendomysium antibodies (EMA) with indirect immunofluorescence on human umbilical cord. Cryostat sections of human brain occipital cortex were incubated with the patients' sera and subsequently labelled with anti-human IgA fluorescein conjugate. RESULTS: All sera from patients with active CD on a gluten-containing diet yielded positive results in both the IgG-AGA and EMA test and in indirect immunofluorescence on brain tissue, disclosing a strong fluorescence over blood-vessels structures. All sera from CD patients on a GFD and from non-coeliac gastrointestinal controls gave a negative result on both the EMA test and the immunofluorescence reaction on human brain. CONCLUSIONS: Sera from patients with active CD contain IgA antibodies that react with human brain vessel structures, giving intense fluorescence. These antibodies are not present in sera from coeliac patients on a GFD or non-coeliac controls. This finding might be involved in the abnormal nervous system manifestations frequently described in association with coeliac disease. 相似文献
3.
Bucci S Pratesi G Viti ML Pantani M Bochicchio F Venoso G 《Radiation protection dosimetry》2011,145(2-3):202-205
Extensive radon surveys have been carried out in many countries only in dwellings, whereas surveys in workplaces are rather sparse and generally restricted to specific workplaces/activities, e.g. schools, spas and caves. Moreover, radon-prone areas are generally defined on the basis of radon surveys in dwellings, while radon regulations use this concept to introduce specific requirements in workplaces in such areas. This approach does not take into account that work activities and workplace characteristics can significantly affect radon concentration. Therefore, an extensive survey on radon in different workplaces have been carried out in a large region of Italy (Tuscany), in order to evaluate radon distribution in workplaces over the whole territory and to identify activities and workplace characteristics affecting radon concentration. The results of this extensive survey are compared with the results of the survey carried out in dwellings in the same period. The workplaces monitored were randomly selected among the main work activities in the region, including both public and industrial buildings. The survey monitored over 3500 rooms in more than 1200 buildings for two consecutive periods of ~6 months. Radon concentration was measured by means of passive nuclear track detectors. 相似文献
4.
Alessandro Re Alessandro Lo Giudice Debora AngeliciSilvia Calusi Lorenzo GiuntiniMirko Massi Giovanni Pratesi 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(20):2373-2377
In this paper we report about the micro-PIXE characterisation of lapis lazuli, for a provenance study of this semi-precious stone, used for glyptic as early as 7000 years ago. The final aim is to find markers permitting to identify the origin of the raw material coming from three quarries in regions of historical importance: Afghanistan, Pamir Mountains and Siberia. This may help to reconstruct trade routes, especially for ancient objects for which written testimonies are scanty or absent at all.Due to the heterogeneity of lapis lazuli we concentrate our attention on single phases instead of the whole stone; in particular we focused on two of the main phases: lazurite, responsible for the blue colour, and diopside, the most frequent accessory mineral. This study was preceded and completed by means of microanalysis with Scanning Electron Microscopy (SEM-EDX) and Cold-Cathodoluminescence (cold-CL) analysis.Despite the limited number of analysed samples, results are sufficient to exclude/suggest a few features as provenance markers, partly confirming what has been previously published in literature. 相似文献
5.
An approach to performance evaluation of cellular mobile networksis proposed, which includes the behavior of handover algorithmsin the computation of outage probability.In a general system scenario, with a central cluster and interferingbase stations, the average outage probability is computed along a trip of themobile terminal that involves crossing the boundary between adjacent cells.The effects of correlated co-channel interferersare accounted for in the computationof outage probability, as well as in the dynamics of a relative signalstrengthhandover algorithm.Numerical results are provided and discussed as obtained over a wide rangeof values of system parameters, namely cluster size and channel parameters.Trade-off curves are shown in terms of outage probability and cross-overpoint versus the average number of handovers, and possible design criteriaare outlined.It is also seen that the local outage analysis (without handover triggering)can be referred to as a lower performance bound in cases of practicalinterest. 相似文献
6.
7.
Giarita Ferraro Alessandro Pratesi Damiano Cirri Paola Imbimbo Daria Maria Monti Luigi Messori Antonello Merlino 《International journal of molecular sciences》2021,22(4)
Arsenoplatin-1 (AP-1), the prototype of a novel class of metallodrugs containing a PtAs(OH)2 core, was encapsulated within the apoferritin (AFt) nanocage. UV-Vis absorption spectroscopy and inductively coupled plasma-atomic emission spectroscopy measurements confirmed metallodrug encapsulation and allowed us to determine the average amount of AP-1 trapped inside the cage. The X-ray structure of AP-1-encapsulated AFt was solved at 1.50 Å. Diffraction data revealed that an AP-1 fragment coordinates the side chain of a His residue. The biological activity of AP-1-loaded AFt was comparatively tested on a few representative cancer and non-cancer cell lines. Even though the presence of the cage reduces the overall cytotoxicity of AP-1, it improves its selectivity towards cancer cells. 相似文献
8.
The effective use of spatial information, that is, the geographic locations of population units, in a regression model-based
approach to small area estimation is an important practical issue. One approach for incorporating such spatial information
in a small area regression model is via Geographically Weighted Regression (GWR). In GWR, the relationship between the outcome
variable and the covariates is characterised by local rather than global parameters, where local is defined spatially. In
this paper, we investigate GWR-based small area estimation under the M-quantile modelling approach. In particular, we specify
an M-quantile GWR model that is a local model for the M-quantiles of the conditional distribution of the outcome variable
given the covariates. This model is then used to define a bias-robust predictor of the small area characteristic of interest
that also accounts for spatial association in the data. An important spin-off from applying the M-quantile GWR small area
model is that it can potentially offer more efficient synthetic estimation for out of sample areas. We demonstrate the usefulness
of this framework through both model-based as well as design-based simulations, with the latter based on a realistic survey
data set. The paper concludes with an illustrative application that focuses on estimation of average levels of Acid Neutralising
Capacity for lakes in the Northeast of the USA. 相似文献
9.
Leon Cohen Fernando Soto C. Pratesi L. Faccetti 《Journal of surfactants and detergents》2006,9(1):47-50
In this work several batch sulfoxidation reactions of different fatty acid methyl esters, having chain lengths of C12 to C18,
in the presence of SO2, O2, and ultraviolet light of 253 nm have been carried out. The average reaction conversion for each methyl ester has been calculated
and the selectivity determined by liquid chromatography. The results indicate that conversion increases dramatically with
the increase of carbon chain length, whereas selectivity to monosulfonate seems to increase slightly as the chain length increases. 相似文献
10.
Tortoli P Pratesi M Michelassi V 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(3):716-726
When contrast agents are injected in a fluid, it is implicitly assumed that they move at the same velocity as the fluid itself. However, a series of in vitro tests performed by using air-filled microbubbles suspended in distilled water, have shown that the Doppler spectrum generated in this case may be notably different from that obtained from non-resonating scatterers. In this paper, we show, through a simple simulation model, that the actual movement of microbubbles may be predicted as the result of the complex balance between two forces: the ultrasound radiation force, which tends to move the particles along the sound beam direction, and the fluid drag force, which tends to move the particles along the fluid stream. The contrast agents turn out to be displaced only during the passage of the ultrasound burst; during the remaining time, they are maintained at the fluid velocity by the drag force. Based on the total particle displacement estimated between consecutive pulses, a series of Doppler spectra corresponding to different intensity levels was computed. This series was shown to be in excellent agreement with the experimental spectra obtained in vitro using Levovist(R) (Schering AG, Berlin, Germany) particles suspended in distilled water flowing at a steady rate. 相似文献