Search results for "Crown"
showing 10 items of 324 documents
Influence of negative allosteric cooperativity in cation transport.
1992
Abstract The bis-macrocyclic ether5 seems to have a negative allosteric cooperativity and is able to transport double the amount of Na+ and K+ cations as monocyclic systems. This compound could be used as a simple model of the plasma membrane Na+−K+ ATPase which actively pumps Na+ out and K+ into the cell, respectively.
Ruthenium(II) meso-tetra-(benzo-15-crown-5)-porphyrinates: synthesis and spectroscopic investigation
2007
The synthesis of novel ruthenium(II) meso-tetra-(benzo-15-crown-5)-porphyrinates, meso-[( B 15 C 5)4 Por ] Ru ( CO )( MeOH ) (1) and meso-[( B 15 C 5)4 Por ] Ru ( L )2 (2)-(4) (meso-[( B 15 C 5)4 Por ]2-= 5,10,15,20-tetrakis-(benzo-15-crown-5)-porphyrinato-dianion; L = pyridine (py), pyrazine (pyz), 4,4′-bipyridyl (4,4′-bpy)), where CO and MeOH , or two N -donor ligands are axially coordinated to the central metal, are reported. The metalation of the free ligand performed by the reaction of Ru 3( CO )12 with meso-[( B 15 C 5)4 Por ] H 2 in 1,2,4-trichlorobenzene (TCB, bp = 215°C), gives (1) in a high yield. The synthesis of (2)-(4) involves the decarbonylation of (1) with trimethylamine N …
Soft and hard tissue alterations around implants placed in an alveolar ridge with a sloped configuration.
2012
Aim: The aim of this study was to evaluate soft and hard tissue alterations around implants placed in healed, sloped ridge sites. Materials and methods: In this prospective multi-center study, 65 patients between 20 and 74 years of age and with a need for a single tooth replacement were included. All patients presented with a recipient implant site demonstrating a lingual‐buccal bone height discrepancy of 2.0‐5.0 mm and with a neighboring tooth on its mesial aspect. Implant placement (OsseoSpeed Profile implants; Astra Tech AB, M! olndal, Sweden) was performed using a non-submerged installation procedure. The implants were placed in such a way that the sloped part of the device was located …
In-vitro fatigue and fracture performance of three different ferrulized implant connections used in fixed prosthesis
2021
Background/purpose: The aim of the present in vitro study was to evaluate fatigue resistance of dental fixtures in three different types of fixture/abutment finishing line. Materials and methods: Transmucosal dental implants, with or without ferrulized neck, underwent fatigue tests (static and dynamic load) using the following standard protocol: UNI EN ISO 14801:2016. Two types of loading devices (screw- or cement-retained restoration) were also tested, and fatigue cycle tests were run to failure. Data of static and dynamic load tests were analyzed by proper statistical methods. Results: Following standard protocol for fatigue testing, the ILC type (Implant Level with ferrulized neck and ce…
SYNTHESIS OF SELENIUM-CONTAINING CROWN ETHERS AND RELATED COMPOUNDS
1991
Abstract The synthesis of the first examples of selenium-containing crown ethers from the benzene diselenolate anion and dichalcogenated ethers is reported. The reaction is highly dependent on the experimental conditions, particularly the concentration. 1H NMR and mass spectrometry were used to confirm the structures of the new compounds.
Clinical Behavior of Short Dental Implants: Systematic Review and Meta-Analysis
2020
Short implants are an increasingly common alternative to other surgical techniques in areas where bone availability is reduced. Despite the advantages they offer, a variety of biological repercussions have been described in the literature that can even lead to the loss of these. The aim of this systematic review and meta-analysis was to analyze the impact of the use of short implants on their survival and on peri-implant bone loss, evaluating the influence that length, diameter, and crown-to-implant ratio (C/I) have on these parameters. This systematic review was based on guidelines proposed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). An electronic se…
The First Examples of a Crown Ether Intramolecularly Encapsulating Mono- and Diorganotin Dications: Synthesis and Structures of [PhSnCH2([16]crown-5)…
2010
The reaction of silver perchlorate with [PhI 2 SnCH 2 ([16]crown-5)] (1) and [I 3 SnCH 2 ([16]crown-5)] (2) gave the organotin(IV)-substituted crown ether complexes [PhSnCH 2 ([16]crown-5)][ClO 4 ] 2 (3) and [HOSnCH 2 ([16]crown-5)][Y] 2 (4: Y= ClO 4 , 5: Y=CF3 S 03 ) , respectively. All compounds have been isolated as air-stable materials and characterised by 1 H, 13 C, 119 Sn and 119 Sn MAS (5) NMR spectroscopy, ESIMS spectrometry, elemental analysis and by single-crystal X-ray diffraction analysis. The molecular structures of 3-5 show that the tin(IV) cation fits perfectly into the crown ether cavity and is coordinated by the five oxygen atoms of the ring to give a pentagonal bipyramidal…
Redox-active crown ethers derived from biphenyl. Electrochemical and spectroscopic study of binding processes with alkali, alkali-earth and mercury s…
1998
Abstract Three new electroactive ligands, 3a, 3b and 3c, that contain the biphenyl frameworks in their structure were prepared. These new ligands presented three interesting characteristics: 1) they exhibited a reversible oxidation, 2) the oxidation induced a conformational change in the crown moiety and 3) they had two different coordination centers, the crown ether and the dimethylamino groups. Electrochemical and spectroscopic studies using alkali, alkali-earth and mercury salts were carried out.
Unveiling the nature of supramolecular crown ether–C60 interactions
2015
A series of exTTF-(crown ether)2 receptors, designed to host C60, has been prepared. The size of the crown ether and the nature of the heteroatoms have been systematically changed to fine tune the association constants, which were determined by a number of complementary spectroscopic techniques. Electrochemical measurements and transient absorption spectroscopy assisted in corroborating charge transfer in the ground state and in the excited state, leading to the formation of radical ion pairs featuring lifetimes in the range from 12 to 21 ps. To rationalize the nature of the exTTF-(crown ether)2$C60 stabilizing interactions, theoretical calculations have been carried out, suggesting a syner…
Immediate and flapless implant insertion and provisionalization using autogenous bone grafts in the esthetic zone: 5-year results.
2017
Objectives As the 2-year results for immediately inserted and provisionalized implants have been reported, it remained an open issue, whether the initially high success rates and the esthetic outcome remain stable for longer observation periods. Therefore, this prospective study examines the 5-year hard and soft tissue changes at implants placed in the anterior maxilla. Material and methods Meanwhile, 37 microthreaded implants were placed in 21 patients into extraction sockets with and without facial bone deficiencies by a flapless approach. Facial gaps and bony defects were grafted with autogenous bone chips. The implants were immediately provisionalized. The primary outcome parameters wer…