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61.
Bonalde I Yanoff BD Salamon MB Van Harlingen DJ Chia EM Mao ZQ Maeno Y 《Physical review letters》2000,85(22):4775-4778
We report measurements of the magnetic penetration depth in single crystals of Sr2RuO4 down to 0.04 K using a tunnel-diode based, self-inductive technique. We observe a power law temperature dependence below 0.8 K, with no sign of a second phase transition nor of a crossover predicted for a multiband superconductor. A power law dependence suggests that the gap function has nodes, inconsistent with candidate p-wave states. We argue that nonlocal effects, rather than impurity scattering, can explain the observed T2 dependence instead of the T-linear behavior expected for line nodes. 相似文献
62.
DJ Smith KW Ledingham RP Singhal T McCanny P Graham HS Kilic P Tzallas C Kosmidis AJ Langley PF Taday 《Rapid communications in mass spectrometry : RCM》1999,13(14):1366-1373
With the development of high intensity femtosecond lasers, the ionisation and dissociation dynamics of molecules has become an area of considerable interest. Using the technique of femtosecond laser mass spectrometry (FLMS), the molecules carbon disulphide, pyrimidine, toluene, cyclohexanone and benzaldehyde are studied with pulse widths of 50 fs in the near infrared (IR) wavelength region (790 nm). Results are presented and contrasted for laser beam intensities around 10(15) and 10(16) W cm(-2). For the lower intensities, the mass spectra yield dominant singly charged parent ions. Additionally, the appearance of doubly charged parent ions is evident for carbon disulphide, toluene and benzaldehyde with envelopes of doubly charged satellite species existing in these local regions. Carbon disulphide also reveals a small triply charged component. Such atomic-like features are thought to be a strong fingerprint of FLMS at these intensities. However, upon increasing the laser intensity to approximately 10(16) W cm(-2), parent ion dominance decreases and the appearance of multiply charged atomic species occurs, particularly carbon. This phenomenon has been attributed to Coulomb explosions in which the fast absorption of many photons may produce transient highly ionised parent species which can subsequently blow apart. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
63.
Quantum physics, despite its intrinsically probabilistic nature, lacks a definition of entropy fully accounting for the randomness of a quantum state. For example, von Neumann entropy quantifies only the incomplete specification of a quantum state and does not quantify the probabilistic distribution of its observables; it trivially vanishes for pure quantum states. We propose a quantum entropy that quantifies the randomness of a pure quantum state via a conjugate pair of observables/operators forming the quantum phase space. The entropy is dimensionless, it is a relativistic scalar, it is invariant under canonical transformations and under CPT transformations, and its minimum has been established by the entropic uncertainty principle. We expand the entropy to also include mixed states. We show that the entropy is monotonically increasing during a time evolution of coherent states under a Dirac Hamiltonian. However, in a mathematical scenario, when two fermions come closer to each other, each evolving as a coherent state, the total system’s entropy oscillates due to the increasing spatial entanglement. We hypothesize an entropy law governing physical systems whereby the entropy of a closed system never decreases, implying a time arrow for particle physics. We then explore the possibility that as the oscillations of the entropy must by the law be barred in quantum physics, potential entropy oscillations trigger annihilation and creation of particles. 相似文献
64.
Renato A. da Costa Joo A. P. da Rocha Alan S. Pinheiro Andria do S. S. da Costa Elaine C. M. da Rocha Rai. C. Silva Arlan da S. Gonalves Cleydson B. R. Santos Davi do S. B. Brasil 《Molecules (Basel, Switzerland)》2022,27(13)
Dengue virus (DENV) is a danger to more than 400 million people in the world, and there is no specific treatment. Thus, there is an urgent need to develop an effective method to combat this pathology. NS2B/NS3 protease is an important biological target due it being necessary for viral replication and the fact that it promotes the spread of the infection. Thus, this study aimed to design DENV NS2B/NS3pro allosteric inhibitors from a matrix compound. The search was conducted using the Swiss Similarity tool. The compounds were subjected to molecular docking calculations, molecular dynamics simulations (MD) and free energy calculations. The molecular docking results showed that two compounds, ZINC000001680989 and ZINC000001679427, were promising and performed important hydrogen interactions with the Asn152, Leu149 and Ala164 residues, showing the same interactions obtained in the literature. In the MD, the results indicated that five residues, Lys74, Leu76, Asn152, Leu149 and Ala166, contribute to the stability of the ligand at the allosteric site for all of the simulated systems. Hydrophobic, electrostatic and van der Waals interactions had significant effects on binding affinity. Physicochemical properties, lipophilicity, water solubility, pharmacokinetics, druglikeness and medicinal chemistry were evaluated for four compounds that were more promising, showed negative indices for the potential penetration of the Blood Brain Barrier and expressed high human intestinal absorption, indicating a low risk of central nervous system depression or drowsiness as the the side effects. The compound ZINC000006694490 exhibited an alert with a plausible level of toxicity for the purine base chemical moiety, indicating hepatotoxicity and chromosome damage in vivo in mouse, rat and human organisms. All of the compounds selected in this study showed a synthetic accessibility (SA) score lower than 4, suggesting the ease of new syntheses. The results corroborate with other studies in the literature, and the computational approach used here can contribute to the discovery of new and potent anti-dengue agents. 相似文献
65.
Joice Ceolin Josiéli Demetrio Siqueira Francisco Mainardi Martins Paulo C. Piquini Bernardo A. Iglesias Davi F. Back Gelson Manzoni de Oliveira 《应用有机金属化学》2018,32(4)
This work describes the synthesis of copper(II) complexes, their identification using spectroscopic and electrochemical methods, structural characterization with X‐ray diffraction and density functional theory calculations (DFT), as well as their catalytic activity mimicking that of superoxide dismutase. Structural analysis revealed the formation of complexes with cyclization of ligands L1 and L2 with the formation of a heterocycle, 1,3‐oxazolidine. The DFT calculations confirmed this trend by stabilizing with lower energy. In addition, evaluations of mimetic enzymatic activity of complexes C1, C2, C3 and C4 revealed promising IC50 values compared to other results seen in the literature (IC50 = 0.22, 0.328, 0.55 and 0.92). Also, calf thymus DNA interactive experiments using UV–visible spectroscopy were conducted in the presence of the copper(II) complexes. 相似文献
66.
Ernesto Schulz Lang Gelson Manzoni de Oliveira Davi Fernando Back Sailer Santos dos Santos 《无机化学与普通化学杂志》2004,630(5):730-734
The six‐membered ring Hg3Te3 of [Hg3Cl3(μ‐TePh)3]·2 DMSO {(Ph = C6H5; DMSO = (CH3)2SO} was opened by redissolution with DMSO, reacting with Co[Hg(SCN)4] and affording polymeric . The monoclinic novel compound belong to the space group P21/n and assembles in a bidimensional lattice tetrahedral HgII(SCN)2Te2‐ and octahedral CoII(NCS)4(DMSO)2‐chains linked trough SCN bridges along the crystallographic axis b and diagonally to the ac axes. The structure of [(DMSO)2Co(NCS)4(Hg—TePh)2]n is limited by the DMSO ligands in the axial positions of the Co‐octahedrons. 相似文献
67.
The synthesis of a potential intermediate for the preparation of the very intensive sweetening agent (-)-Monatin is described. The synthesis is based on a highly diastereoselective alkylation reaction of a pyroglutamate derivative with an electrophile obtained from indole. 相似文献
68.
Adding Remnant Magnetization and Anisotropic Exchange to Propeller‐like Single‐Molecule Magnets through Chemical Design 下载免费PDF全文
Kátia Cristina M. Westrup Dr. Marie‐Emmanuelle Boulon Dr. Pasquale Totaro Dr. Giovana G. Nunes Dr. Davi F. Back Dr. Andersson Barison Dr. Martin Jackson Dr. Carley Paulsen Prof. Dante Gatteschi Dr. Lorenzo Sorace Prof. Andrea Cornia Prof. Jaísa F. Soares Prof. Roberta Sessoli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13681-13691
The selective replacement of the central iron(III) ion with vanadium(III) in a tetrairon(III) propeller‐shaped single‐molecule magnet has allowed us to increase the ground spin state from S=5 to S=13/2. As a consequence of the pronounced anisotropy of vanadium(III), the blocking temperature for the magnetization has doubled. Moreover, a significant remnant magnetization, practically absent in the parent homometallic molecule, has been achieved owing to the suppression of zero‐field tunneling of the magnetization for the half‐integer molecular spin. Interestingly, the contribution of vanadium(III) to the magnetic anisotropy barrier occurs through the anisotropic exchange interaction with iron(III) spins and not through single ion anisotropy as in most single‐molecule magnets. 相似文献
69.
Martin N Pierre C Davi M Jazzar R Baudoin O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4480-4484
All C-H bonds are not equal: The intramolecular arylation of unactivated C(sp(3))-H bonds in the presence of a chiral Pd/binepine catalyst allows the synthesis of fused cyclopentanes efficiently and in an diastereo- and enantioselective manner (see scheme). 相似文献
70.
Corrigendum: Diastereo‐ and Enantioselective Intramolecular C(sp3)H Arylation for the Synthesis of Fused Cyclopentanes 下载免费PDF全文