196,135 research outputs found
Solid State NMR Spectroscopy: A multiscale "lens" for understanding complex materials
No full textComplexity is an intrinsic feature typical of the most attractive innovative materials in many different research and application fields, as chemistry, optoelectronics, energy, recycling, medicine. Complexity arises from the coexistence of different chemical components, interfaces and phases, as well as from structural disorder and/ or heterogeneity. Complexity often hinders a detailed characterization of advanced materials, which, on the other hand, is crucial for understanding the functional performances and orienting the design and optimization of innovative materials. Solid State NMR spectroscopy (SSNMR) is an extremely powerful technique, which can effectively bridge this gap. Indeed, it can be applied to substantially every kind of soft and hard material and, by exploiting many nuclear probes and properties, it allows structural and dynamic properties to be characterized on very wide spatial (0.1-100 nm) and frequency (Hz-GHz) scales [1]. In this contribution I will show case studies of advanced materials characterized in the ICCOM-CNR/UNIPI joint lab [2], which, with the acquisition within the year of a last generation SSNMR spectrometer, will be the largest Italian laboratory for the study of materials by SSNMR. Hopefully this contribution will further increase the opportunity for the DSCTM community of taking advantage of this technique.
References:
[1] a. M. Geppi, S. Borsacchi, G. Mollica, C. A. Veracini, Appl. Spectr. Rev. 2009, 44, 1; b. M. Geppi, S. Borsacchi, G. Mollica, Encyclopedia of Magnetic Resonance, Wiley 2008.
[2] (a) F. Martini, M. Tonelli, M. Geppi, F. Ridi, S. Borsacchi, L. Calucci, Cem. Concr. Res. 2017, 102, 60; (b) F. Martini, S. Borsacchi, G. Barcaro, M. Caporali, M. Vanni, M. Serrano-Ruiz, M. Geppi, M. Peruzzini, L. Calucci J. Phys. Chem. Lett. 2019, 10, 5122; (c) E. Carignani, S. Borsacchi, P. Blasi, A. Schoubben, M. Geppi Mol. Pharmaceutics 2019, 16, 2569-2578
Defining prerequisites for banking Web site design: the WOW! approach
No full textBeing involved in the development of a high standing Web site without having the necessary amount of money, we came to the idea of creating a set of basic features that Web sites should inevitably have in order to meet customers quality basic expectations. The paper reports on the development of the methodology created to face the research question. The result is an innovative methodology called WoW!-Welcome on the Web!. The theoretical framework traces back to Herberg’s motivation-hygiene theory and to the Kano model. They both propose that products and services should meet a set of basic quality features of customers. These are the “features that provide basic quality, such as preconditions or antecedents for user satisfaction to occur” (Zhang and Von Dran 2002). As the main characteristics of hygienic and basic quality expectations is unconsciousness, we thought to observe the actions performed by users so that we could deduce what are such factors. The developed methodology considers five main user actions when surfing a Web site: direct access; indirect access; home page visualization; surfing; personal data submission. Starting from them indicators and measurement criteria were deduced so that the prerequisites could be observed
Structural and dynamic characterization of elastomeric materials by time domain NMR spectroscopy
No full textIn the last decades, many efforts have been dedicated to the improvement of the mechanical properties of elastomeric composite materials, as they are particularly attractive for several industrial applications. As a matter of fact, these properties are mainly related to the motional constraints of the polymer network, which are due to physical entanglements and chemical cross-linking between polymer chains, and may be influenced by the presence of different additives and reinforcement fillers (carbon black, nanosilica, clays) [1,2]. Usually, the cross-link density is monitored by mechanical measurements (modulus, strain at stress, etc.); however, these methods provide only macroscopic observables, but are not suitable for a description of the topology and dynamics of the polymer network at the molecular scale. Indeed, this knowledge is required to have a more complete view of the factors that correlate with the mechanical properties of elastomers and, consequently, to better address the design of optimized materials. In this context, low field 1H time domain NMR (TD-NMR) can give an important contribution [3].
In this work, we studied different elastomeric materials with application in the tyre industry, by TD-NMR spectroscopy, with the aim of investigating the effect of cross-linking and filler particles on polymer structure and dynamics. 1H Multiple Quantum (MQ) experiments [4] were used to evaluate the residual 1H-1H dipolar couplings, which arise from the fast anisotropic motion of the polymer chains and are thus directly related to the amount of topological constraints within the polymer network. Moreover, 1H relaxation times (T1, T2) [5,6] were measured to probe a wide range of motional frequencies of the polymer chains. In particular, 1H spin-lattice relaxation times (T1) were evaluated by means of Fast Field Cycling [6] experiments at different temperatures, covering Larmor frequencies from 10 kHz to 35 MHz.
References:
[1] R. Scotti, M. D'Arienzo, B. Di Credico, L. Giannini and F. Morazzoni, in Hybrid Org. Interfaces, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2017, pp. 151-198.
[2] G. Kraus Angew. Makromol. Chemie 60, 215-248 (1977).
[3] S. Borsacchi, U. Sudhakaran, L. Calucci, F. Martini, E. Carignani, M. Messori and M. Geppi Polymers (Basel) 10, 822 (2018).
[4] K. Saalwächter Prog. Nucl. Mag. Res. Sp. 51, 1-35 (2007).
[5] A. Maus, C. Hertlein and K. Saalwächter Macromol. Chem. Phys. 207, 1150-1158 (2006).
[6] R. Kimmich, Field-cycling NMR Relaxometry: Instrumentation, Model Theories and Applications, Royal Society of Chemistry, Cambridge, 2018
MONITORING THE EFFECT OF FILLER IN ELASTOMERIC MATERIALS BY TIME DOMAIN NMR SPECTROSCOPY
No full textIn the last decades, many eorts have been dedicated to the improvement of the mechanical properties of elastomeric
composite materials, as they are particularly attractive for several industrial applications. As a matter
of fact, these properties are mainly related to the motional constraints of the polymer network, which are due
to physical entanglements and chemical cross-linking between polymer chains, and may be in
uenced by the
presence of dierent additives and reinforcement llers (carbon black, nanosilica, clays) [1,2]. Usually, the mechanical
properties of the materials are monitored by rheological measurements, which provide only macroscopic
observables; however, also a description of the topology and dynamics of the polymer network at the molecular
scale is needed in order to have a more complete comprehension of the factors that in
uence these properties,
with the nal aim to guide the design of optimized materials. In this context, low eld 1H time domain NMR
(TD-NMR) can give an important contribution [3].
In this work, we studied dierent elastomeric materials with application in the tyre industry, by TD-NMR
spectroscopy, with the aim of investigating the eect of ller particles on polymer structure and dynamics. 1H
Multiple Quantum (MQ) experiments [4] were used to evaluate the residual 1H-1H dipolar couplings, which arise
from the fast anisotropic motion of the polymer chains and are thus directly related to the amount of topological
constraints within the polymer network. Moreover, 1H relaxation times (T1, T2) [5,6] were measured to probe
a wide range of motional frequencies of the polymer chains. In particular, 1H spin-lattice relaxation times
(T1) were evaluated by means of Fast Field Cycling [6] experiments at dierent temperatures, covering Larmor
frequencies from 10 kHz to 35 MHz.
References:
[1] R. Scotti, M. D'Arienzo, B. Di Credico, L. Giannini and F. Morazzoni, in Hybrid Org. Interfaces, Wiley-VCH
Verlag GmbH & Co. KGaA, Weinheim, Germany, 151-198, (2017).
[2] G. Kraus Angew. Makromol. Chemie 60, 215-248, (1977).
[3] S. Borsacchi, U. Sudhakaran, L. Calucci, F. Martini, E. Carignani, M. Messori and M. Geppi Polymers
(Basel) 10, 822, (2018).
[4] K. Saalw?achter Prog. Nucl. Mag. Res. Sp. 51, 1-35, (2007).
[5] A. Maus, C. Hertlein and K. Saalw?achter Macromol. Chem. Phys. 207, 1150-1158k, (2006).
[6] R. Kimmich, Field-cycling NMR Relaxometry: Instrumentation, Model Theories and Applications, Royal
Society of Chemistry, Cambridge, (2018)
STRUCTURAL AND DYNAMIC CHARACTERIZATION OF ELASTOMERIC MATERIALS BY TIME DOMAIN NMR SPECTROSCOPY
No full textIn the last decades, many efforts have been dedicated to the improvement of the mechanical properties of elastomeric composite materials, as they are particularly attractive for several industrial applications. As a matter of fact, these properties are mainly related to the motional constraints of the polymer network, which are due to physical entaglements and chemical cross-linking between polymer chains, and may be influenced by the presence of different additives and reinforcement fillers (carbon black, nanosilica, clays) [1,2]. Usually, the cross-link density is monitored by mechanical measurements (modulus, strain at stress, etc.); however, these methods provide only macroscopic observables, but are not suitable for a description of the topology and dynamics of the polymer network at the molecular scale. Indeed, this knowledge is required to have a more complete view of the factors that correlate with the mechanical properties of elastomers and, consequently, to better address the design of optimized materials. In this context, low field 1H time domain (TD) NMR can give an important contribution [3].
In this work, we have investigated the effect of the formulation (polymer, additives, filler) and the vulcanization conditions on the structural and dynamic properties of different elastomeric materials, with application in the tyre industry, by a combination of TD NMR methods. 1H Multiple Quantum (MQ) esperiments [4] were used to evaluate the residual 1H-1H dipolar couplings, which arise from the fast anisotropic motion of the polymer chains and are thus directly related to the amount of topological contraints within the polymer network. 1H relaxation times (T1, T2) [5,6] were measured to probe a wide range of motional frequencies of the polymer chains. In particular, 1H spin-lattice relaxation times (T1) were evaluated by means of Fast Field Cycling [6] experiments at different temperatures, covering Larmor frequencies from 10 kHz to 35 MHz.
References
[1] R. Scotti, M. D'Arienzo, B. Di Credico, L. Giannini and F. Morazzoni, in Hybrid Org. Interfaces, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2017, pp. 151-198.
[2] G. Kraus Angew. Makromol. Chemie 60, 215-248 (1977).
[3] S. Borsacchi, U. Sudhakaran, L. Calucci, F. Martini, E. Carignani, M. Messori and M. Geppi Polymers (Basel) 10, 822 (2018).
[4] K. Saalwächter Prog. Nucl. Mag. Res. Sp. 51, 1-35 (2007).
[5] A. Maus, C. Hertlein and K. Saalwächter Macromol. Chem. Phys. 207, 1150-1158 (2006).
[6] R. Kimmich, Field-cycling NMR Relaxometry: Instrumentation, Model Theories and Applications, Royal Society of Chemistry, Cambridge, 2018
Energy balance of locomotion with pedal-driven watercraft
No full textIn this study, we examined the mechanics and energetics of locomotion with a paddle-wheel boat and a water bike. Power output (Ẇtot) was measured directly on the water bike by means of an instrumented chain-ring. The simultaneous assessment of oxygen uptake (V̇O2) allowed the computation of the "overall" efficiency of locomotion (ηo = Ẇtot/V̇O2). Mean ηo was 0.27 (s = 0.02), which was unaffected by the speed, and was assumed to be the same for the two boats as both are semi-recumbent bicycles. For the paddle-wheel boat, Ẇtot was then obtained from ηo and measures of V̇O2. The power to overcome (passive) drag was calculated as Ẇd = D · v (where D is the force measured by means of a load cell when towing the boats at given speeds). Propelling efficiency was calculated as ηp = Ẇd/Ẇtot, which was lower with the paddle-wheel boat (mean 0.35, s = 0.01) than with the water bike (mean 0.57, s = 0.01). The observed differences in ηp and Ẇd explain why at the highest speed tested (∼3 m · s-1), the energy required to cover a unit distance with the water bike is similar to that required to move the paddle-wheel boat at 1.3 m · s-1
Study of disorder by solid-state NMR spectroscopy
No full textTheory and applications of solid-state NMR spectroscopy to study disorder phenomena in pharmaceutical material
Analysis of an 11.6 kb region from the right arm of chromosome VII of Saccharomyces cerevisiae between the RAD2 and MES1 genes reveals the presence of three new genes
No full textSequence analysis of an 11 628 bp DNA segment from the right arm of Saccharomyces cerevisiae chromosome VII
revealed the presence of the 5* end of the RAD2 gene, the MES1 gene and six open reading frames (ORFs) each
longer than 300 bp. Four of these ORFs are expressed genes, as indicated by transcript analysis. One of them,
YGR261c, which specifies a putative â-adaptine, corresponds to gene YKS5, which has recently been identified as a
suppressor of loss of casein kinase 1 function. The remaining three ORFs are new genes; of these, YGR260w encodes
a protein showing similarity to the S. cerevisiae allantoate permease and YGR262c specifies a putative protein kinase.
The sequence has been deposited in the EMBL data library under Accession Number Y07777. ? 1997 by John
Wiley & Sons, Ltd
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