Search results for "RESONANCE"
showing 10 items of 6625 documents
Decomposition Process of Carboxylate MOF HKUST-1 Unveiled at the Atomic Scale Level
2016
HKUST-1 is a metal-organic framework (MOF) which plays a significant role both in applicative and basic fields of research, thanks to its outstanding properties of adsorption and catalysis but also because it is a reference material for the study of many general properties of MOFs. Its metallic group comprises a pair of Cu2+ ions chelated by four carboxylate bridges, forming a structure known as paddle-wheel unit, which is the heart of the material. However, previous studies have well established that the paddle-wheel is incline to hydrolysis. In fact, the prolonged exposure of the material to moisture promotes the hydrolysis of Cu-O bonds in the paddle-wheels, so breaking the crystalline n…
Methyl Radical in Clathrate Silica Voids. The Peculiar Physisorption Features of the Guest-Host Molecular Dynamics Interaction.
2016
EPR line shape simulations of CH3/SiO2 clathrates and comparison to CH3/N2O and CH3/SiO2 experiments reveal the motional conditions of the CH3 radical up to the unusual regime of its stability, the high-temperature diffusional regime, at 300 K. In the low-temperature region, the CH3 in clathrates is found to rotate around the in-plane axes even at as low temperatures as 3.8 K. However, nonrotating methyls performing only libration about the C2-axes as well as around the C3-axis are also found, proving the existence of special sites in the clathrate voids that begin to accumulate a significant fraction of methyl radicals at temperatures below approximately 7 K. A distinctive feature in the s…
Plasma response to amplitude modulation of the microwave power on a 14 GHz electron cyclotron resonance ion source
2018
This paper reports the effects of sinusoidal microwave power Amplitude Modulation (AM) on the performance of Electron Cyclotron Resonance (ECR) ion sources. The study was conducted on the 14 GHz ECR ion source ECR2 at the University of Jyväskylä. The klystron output was intentionally altered by a variable frequency sinusoidal amplitude modulation. The average microwave power 350 W was modulated between 530 W and 180 W from 0.011-25 kHz. The integrated x-ray energy, the mass analyzed beam current and the forward and reflected microwave power were measured. The energy integrated x-ray signal responded strongly with low frequency modulation and was no longer observable at approximately 2.2 kHz…
Differentiation among dairy products by combination of fast field cycling NMR relaxometry data and chemometrics
2021
A set of commercial milk and Sicilian cheeses was analysed by a combination of fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry and chemometrics. The NMR dispersion (NMRD) curves were successfully analysed with a mathematical model applied on Parmigiano-Reggiano (PR) cheese. Regression parameters were led back to the molecular components of cheeses (water trapped in casein micelles, proteins and fats) and milk samples (water belonging to hydration shells around dispersed colloidal particles of different sizes and bulk water). The application of chemometric analysis on relaxometric data enabled differentiating milk from cheeses and revealing differences within the two sa…
A magnetic look into the protecting layer of Au25 clusters
2016
The field of molecular metal clusters protected by organothiolates is experiencing a very rapid growth. So far, however, a clear understanding of the fine interactions between the cluster core and the capping monolayer has remained elusive, despite the importance of the latter in interfacing the former to the surrounding medium. Here, we describe a very sensitive methodology that enables comprehensive assessment of these interactions. Pulse electron nuclear double resonance (ENDOR) was employed to study the interaction of the unpaired electron with the protons of the alkanethiolate ligands in four structurally related paramagnetic Au25(SR)0 18 clusters (R ¼ ethyl, propyl, butyl, 2-methylpro…
Complete 1H, 13C{1H}, and 31P NMR Spectral Parameters of Some Pyrophosphates
2017
The 1H, 13C{1H}, and 31P NMR spectral parameters of some pyrophosphates were determined in CDCl3. The most complicated 1H spectrum can be solved fully only as (A3MN)R6XX′R6′(MNA3)′, where R6 (= ―N(CH3)2) is coupled only to phosphorus (X). Second-order coupling between phosphorus was found and solved with iterative analysis. A signal shape of one of the carbon resonance cannot be explained only with couplings. Explanation for exceptional shape was searched from molecular modeling results. peerReviewed
Structures and energetic properties of 4-halobenzamides
2018
The amide bond represents one of the most fundamental functional groups in chemistry. The properties of amides are defined by amidic resonance (nN→π*C=O conjugation), which enforces planarity of the six atoms comprising the amide bond. Despite the importance of 4-halo-substituted benzamides in organic synthesis, molecular interactions and medicinal chemistry, the effect of 4-halo-substitution on the properties of the amide bond in N,N-disubstituted benzamides has not been studied. Herein, we report the crystal structures and energetic properties of a full series of 4-halobenzamides. The structures of four 4-halobenzamides (halo = iodo, bromo, chloro and fluoro) in the N-morpholinyl series h…
(p,2)-equations resonant at any variational eigenvalue
2018
We consider nonlinear elliptic Dirichlet problems driven by the sum of a p-Laplacian and a Laplacian (a (p,2) -equation). The reaction term at ±∞ is resonant with respect to any variational eigenvalue of the p-Laplacian. We prove two multiplicity theorems for such equations.
Hoffa’s fat pad thickness: a measurement method with sagittal MRI sequences
2021
Abstract Background Hoffa’s fat pad is a structure located within the fibrous joint capsule of the knee joint, but outside the synovial cavity. It plays an important biomechanical and metabolic role in knee joint, reducing the impact of forces generated by loading and producing cytokines. Changes in its size can induce modifications in the knee homeostasis. However, a great variability exists regarding its measurements. This work aims to evaluate the reliability of a measurement method of Hoffa’s fat pad dimensions through MRI. Methods 3T sagittal IW 2D TSE fat-suppressed MRI sequences, taken from the OAI (Osteoarthritis initiative) database, of 191 male and female patients, aged between 40…
Treatment of Knee Osteoarthritis with Bone Marrow-Derived Mononuclear Cell Injection: 12-Month Follow-up.
2018
Objectives To evaluate the main symptoms of knee osteoarthritis (OA) and tissue structure changes after a single dose bone marrow–derived mononuclear cell (BM MNC) intra articular injection. Case series study. Patients with knee OA Kellgren Lawrence (K-L) grade II and III received 1 injection of BM MNC. The clinical results were analyzed with the Knee injury and Osteoarthritis Outcome Score (KOOS) and Knee Society Score (KSS) before, 3, 6, and 12 months after injection. Radiological evaluation was performed with a calibrated x-ray and the magnetic resonance (MR) imaging before and 6 to 7 months postinjection. Results A total of 34 knees were treated with BM MNC injections. Mean (±SD) age of…