J Comput Chem
Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602, USA.
Published: May 2013
Many properties of transition-metal complexes depend on the steric bulk of bound ligands, usually quantified by the Tolman (θ) and solid (Θ) cone angles, which have proven utility but suffer from various limitations and coarse approximations. Here, we present an improved, mathematically rigorous method to determine an exact cone angle (θ°) by solving for the most acute right circular cone that contains the entire ligand. The procedure is applicable to any ligand, planar or nonplanar, monodentate or polydentate, bound to any metal center in any environment, and it is ideal for analyzing structures from quantum chemical computations as well as X-ray crystallography experiments. Exact cone angles were evaluated for a wide array of phosphine and amine ligands bound to palladium, nickel, or platinum by optimizing structures using B3LYP/6-31G* density functional theory with effective core potentials for the transition metals. The mean absolute deviations of the standard θ and Θ parameters from the exact cone angles were 15-25°, mostly caused by distortions from the assumed idealized structures.
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http://dx.doi.org/10.1002/jcc.23217 | DOI Listing |
J Prosthet Dent
January 2025
Professor, Department of Dentistry, Federal University of Santa Catarina (UFSC), Florianopolis, SC, Brazil.
Statement Of Problem: Digital surgical guides improve precision by detailing the direction, position, and angle of implants, which reduces surgery time and complications. A bibliometric analysis of guided surgery in implant dentistry is lacking.
Purpose: The aim of this metrics-based analysis was to analyze the trends and key characteristics of articles related to guided surgery in implant dentistry.
Cureus
December 2024
Department of Orthodontics, Kothiwal Dental College and Research Centre, Moradabad, IND.
Introduction The role of the condylar position in the correct functioning of the stomatognathic system has been the center of the study. Using cone-beam computed tomography (CBCT), this study looked at the three-dimensional (3D) position of the condylar bone in patients from Class I, Class II, Division 1, and Division 2. Materials and methods This cross-sectional, retrospective study was conducted using 102 CBCT records, with 34 records allocated to each category of malocclusion classification, such as dentoskeletal Class I, skeletal Class II, and dental Class II, Division 1 and 2.
View Article and Find Full Text PDFPhys Chem Chem Phys
January 2025
School of Mechanical & Vehicle Engineering, Linyi University, Linyi, Shandong 276000, China.
Molecular dynamics simulations demonstrate that regular conical helices of poly(-phenylene) (PPP) chains can be constructed inside the confined space of single-walled carbon nanocones (CNCs). The translocation displacement of the PPP chain combined with the change of the system total potential energy including each energy component and structural parameters of the formed conical helix is discussed to deeply explore the microstructure evolution, driving forces and dynamic mechanisms. In addition, the influence of chain length, cone angle, temperature, chain number, linked position of benzene rings and the form of Lennard-Jones potential on the helical encapsulation is further studied.
View Article and Find Full Text PDFJ Stomatol Oral Maxillofac Surg
January 2025
Department of Orthodontics, Hubei-MOST KLOS & KLOBM, School & Hospital of Stomatology, Wuhan University, Wuhan, China.. Electronic address:
Objectives: This study aims to assess the alterations in condylar positioning in adult skeletal Class I patients with unilateral posterior crossbite after microimplant-assisted rapid palatal expansion (MARPE) treatment.
Methods: This retrospective study involving 30 participants (10 males, 20 females) average age 22.9 ± 4.
Objectives: To examine tooth root length and root volume in cone beam computed tomography (CBCT) images in patients with skeletal Class II and III anomalies who have undergone single-jaw (SJ) and double-jaw (DJ) orthognathic surgery, and to compare the changes between jaws with and without osteotomy.
Materials And Methods: This study was conducted on the archive records of a total of 60 adults: 36 women and 24 men with an average age of 21.1 ± 3.
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