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排序方式: 共有148条查询结果,搜索用时 781 毫秒
91.
Pierpaolo Bruscolini Carla Buzano Alessandro Pelizzola Marco Pretti 《Macromolecular Symposia》2002,181(1):261-274
Poly(N-isopropylacrylamide) (PNIPAM) in dilute aqueous solution undergoes a collapse transition from coil to globule on increasing temperature. Such coil-to-globule collapse is usually considered analogous to the cold renaturation of small globular proteins. In this paper we propose a theoretical approach that is able to reproduce, in a semi-quantitative way, the unusual behavior of PNIPAM, and the observed thermodynamic properties. The procedure is based on two main steps: (i) the characterization of single monomer hydration thermodynamics, interpreted by a balance between the removal of monomer-monomer interactions and the addition of water-monomer interactions, and (ii) a simplified analysis of a lattice self-avoiding walk (SAW) model, which allows to account for the configurational entropy in a controlled way, and hence to relate the microscopic interactions to the “macroscopic” behavior of the polymer chain. The results show that the temperature dependence and magnitude of the interaction parameters that best fit experimental data validate a recently proposed qualitative interpretation of the mechanism of collapse transition for PNIPAM. The latter result turns out to be relevant to support the analogy with the cold renaturation of small globular proteins, and to clarify some important aspects of protein thermodynamics. 相似文献
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93.
Dario Pasini Michele Zema Pierpaolo Righetti 《Journal of chemical crystallography》2007,37(8):537-541
The title compound crystallizes in the trigonal space group R-3, with unit-cell parameters: a = 23.261(4), c = 9.537(2) Å; λ(MoKα) = 0.71073 Å, V = 4469(2) Å3, and Z = 6. The structure has been solved by direct methods using X-ray diffraction techniques. The final reliability index for the computed structure is 0.0826 for 929 observed reflections and 121 refined parameters. Crown ether adopts an almost circular shape and macrocycles are piled up in a columnar arrangement forming tubular nanochannels. The channels are filled with guest CDCl3 molecules, characterised by rotational disorder. 相似文献
94.
David Perpetuini Antonio Maria Chiarelli Chiara Filippini Daniela Cardone Pierpaolo Croce Ludovica Rotunno Nelson Anzoletti Michele Zito Filippo Zappasodi Arcangelo Merla 《Entropy (Basel, Switzerland)》2020,22(12)
Alzheimer’s disease (AD) is characterized by working memory (WM) failures that can be assessed at early stages through administering clinical tests. Ecological neuroimaging, such as Electroencephalography (EEG) and functional Near Infrared Spectroscopy (fNIRS), may be employed during these tests to support AD early diagnosis within clinical settings. Multimodal EEG-fNIRS could measure brain activity along with neurovascular coupling (NC) and detect their modifications associated with AD. Data analysis procedures based on signal complexity are suitable to estimate electrical and hemodynamic brain activity or their mutual information (NC) during non-structured experimental paradigms. In this study, sample entropy of whole-head EEG and frontal/prefrontal cortex fNIRS was evaluated to assess brain activity in early AD and healthy controls (HC) during WM tasks (i.e., Rey–Osterrieth complex figure and Raven’s progressive matrices). Moreover, conditional entropy between EEG and fNIRS was evaluated as indicative of NC. The findings demonstrated the capability of complexity analysis of multimodal EEG-fNIRS to detect WM decline in AD. Furthermore, a multivariate data-driven analysis, performed on these entropy metrics and based on the General Linear Model, allowed classifying AD and HC with an AUC up to 0.88. EEG-fNIRS may represent a powerful tool for the clinical evaluation of WM decline in early AD. 相似文献
95.
Pierpaolo Cordone Hari Krishna Namballa Wayne Wesley Harding 《Journal of heterocyclic chemistry》2020,57(10):3709-3713
Heterocycles that bear the novel 5,6,14,14a-tetrahydro-8H-benzo[6,7][1,4]thiazepino[3,4-a]isoquinoline and the 5,6,14,14a-tetrahydro-8H-13l2-benzo[6,7][1,4]diazepino[3,4-a]isoquinoline frameworks were synthesized in a facile manner. These tetrahydroprotoberberine (THPB)-inspired scaffolds demonstrate selective affinity for the σ1R in contrast to the naturally occurring THPB congeners that show D1R and σ2R selectivity. 相似文献
96.
Tiziano Ghisu Francesco Cambuli Pierpaolo Puddu Natalino Mandas Pranay Seshadri Geoffrey T. Parks 《Meccanica》2018,53(14):3437-3456
In recent years, a number of authors have studied entropy generation in Wells turbines. This is potentially a very interesting topic, as it can provide important insights into the irreversibilities of the system, as well as a methodology for identifying, and possibly minimizing, the main sources of loss. Unfortunately, the approach used in these studies contains some crude simplifications that lead to a severe underestimation of entropy generation and, more importantly, to misleading conclusions. This paper contains a re-examination of the mechanisms for entropy generation in fluid flow, with a particular emphasis on RANS equations. An appropriate methodology for estimating entropy generation in isolated airfoils and Wells turbines is presented. Results are verified for different flow conditions, and a comparison with theoretical values is presented. 相似文献
97.
Sanchita Paul Dr. Pierpaolo Morgante Dr. Samantha N. MacMillan Prof. Jochen Autschbach Prof. David C. Lacy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(40):e202201042
This work details the synthesis, characterization, and catalytic activity of reactive low-coordinate organozinc complexes. The complexes activate hydrogen and they appear to be more active in hydrogenation of ketones and imines than their tridentate pincer analogs. This is thought, in part, to be due to the lack of trailing third phosphorus arm present in previous work. DFT computations reveal a sigma-bond metathesis mechanism is comparable to an alternative aromatization/dearomatization metal-ligand cooperative mechanism. 相似文献
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100.
Pierpaolo Ferrante 《应用数学学报(英文版)》2018,34(2):373-385
This paper is aimed at investigating the transient losses in the M/M/1/1 Erlang loss system. We evaluate the explicit form of the probability distribution of the number of losses in the time interval [0, t) and provide two alternative representations: one based on the iterated derivatives of hyperbolic sinus and cosine and the other on the spherical modified Bessel function of the second kind. The mathematical structures of the transient loss rate and of the transient probability of losing all customers are described and several analytical properties are derived. 相似文献