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Neoplasms of the maxilla have multiple different origins and histology, and often extend towards the infratemporal fossa, orbit, or skull base. Extensive resection may be required, often leading to poor esthetic and functional results. Usually, these lesions are removed via a transfacial approach. The aim of this study was to compare the outcomes of the transoral versus transfacial approach for maxillary tumors. A single-institution retrospective study was conducted on patients with maxillary-midface tumors, treated between January 2009 and December 2019. The patients were divided into two groups according to the surgical approach, transfacial or transoral, and the following outcomes were assessed: extent of the resection based on Brown's classification; postoperative pathology margin assessment; reconstruction technique; esthetic/functional results. A total of 178 patients were included. A satisfactory resection was obtained in both groups, with the transoral cohort achieving a higher rate of clear oncological margins (positive margins: transoral group 3.7% versus transfacial group 6.8%, P = 0.389) and a significantly higher University of Washington Quality of Life score (mean 72.2 versus 67.8, P < 0.001). Even large and invasive tumors can be treated successfully with the transoral approach, avoiding unesthetic facial scars while still providing complete resection of the tumor. [ABSTRACT FROM AUTHOR]

Opioids are often the mainstay of postoperative pain management, despite strong evidence of their ill effects and potential for long-term addiction. The goal of this study was to quantify opioid use and contrast pain management strategies of multiple international institutions performing fibula free flap reconstruction. A retrospective multicenter cohort study was designed, including five international centers. For inclusion, the patients had to have undergone a primary fibula free flap reconstruction of the mandible. A total of 185 patients were included. The median opioid use across all centers at 72 hours was 133 oral morphine equivalents. The highest utilization was in the USA (P < 0.001), which was approximately six times that of Italy, four times that of Argentina, and twice that of India, despite all centers performing a similar procedure. Based on this study there are clear differences in prescribing practices and ideologies among surgeons from different countries. [ABSTRACT FROM AUTHOR]

The 30-day readmission rate is a highly scrutinized metric of quality surgical care, because readmission is costly and perceived to be avoidable with planning and patient education. Head and neck surgery patients generally have multiple risk factors for readmission, as readmitted patients are generally older, with more co-morbidities, lower socio-economic status, and a history of multiple emergency department visits and readmissions. A retrospective cohort study was implemented to determine the incidence and etiology of 30-day readmission after microvascular head and neck reconstructive surgery, focusing on social risk factors. Data were analyzed by χ2 test, analysis of variance, t -test, and logistic regression, with statistical significance set at P < 0.05. Of 209 patients included in this study, 35 (16.7%) had a 30-day readmission. Increased needs at discharge were associated with increased readmission, while other social risk factors were less significant for a readmission in this study. [ABSTRACT FROM AUTHOR]

Virtual surgical planning (VSP) promises higher accuracy, efficiency, and superior patient outcomes, helping normalize outcomes from surgeons of different experience levels. A systematic review was conducted in agreement with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The objective was to evaluate the accuracy and secondarily efficiency of VSP compared with free-hand surgery, for mandibular reconstruction with free flaps. Six studies met inclusion criteria and had quantitative data suitable for meta-analysis. Intercondylar distance and gonion angle were used to assess accuracy, evaluated by mean change from preoperative VSP and postoperative imaging. The mean weighted difference in VSP intercondylar distance was 2.0 mm, compared with 3.9 mm for free hand (P = 0.101) and mean change in gonion angle for VSP was 3.6°, compared with 7.7° for free hand (P < 0.05). Efficiency assessed by mean ischemia time, was 73.8 min and 109.9 min, for VSP and free hand, respectively (P = 0.203), and by total operative time, which was 391.8 min and 457.6 min in the VSP and free hand, respectively (P = 0.340). VSP is consistently proven to be more accurate and efficient than traditional free-hand surgery; however, a standardized method for accuracy and efficiency measurements is still missing, causing heterogeneity among the scientific reports. [ABSTRACT FROM AUTHOR]

Motivated by solid-state studies on the cleavage force in Si, and the consequent stretching of chemical bonds, we here study bond stretching in the, as yet unsynthesized, free space molecule Si6H6. We address the question as to whether substantial bond stretching (but constrained to uniform scaling on all bonds) can result in a transition from ring current behaviour, characteristic say of benzene at its equilibrium geometry, to localized π-electrons on Si atoms. Some calculations are also recorded on dissociation into 6 SiH radicals. While the main studies have been carried out by unrestricted Hartree–Fock (HF) theory, the influence of electron correlation has been examined using two forms of density functional theory. Planar Si6H6 treated by HF is bound to be unstable, not all vibrational frequencies being real. Some buckling is then allowed, which results in real frequencies and stability. Evidence is then provided that the non-planar structure, as the Si–Si distance is increased, exhibits π-electron localization in the range 1.2–1.5 times the equilibrium distance. [Copyright &y& Elsevier]

Abstract: Motivated by the theoretical study of Saito and Ono (2011) on three crystalline forms of SiO2 under pressure, quantum-chemical calculations on various free-space clusters of and for are reported here. Both neutral and cationic clusters have been examined, for both geometry and equilibrium bond lengths. Coupled clusters and correlation-corrected MP2 calculations are presented. For the cations, we emphasize especially the structural distortions occurring in removing degeneracies. [Copyright &y& Elsevier]

Abstract: Recent experimental work by Strobel et al. [T.A. Strobel, M. Somayazulu, R.J. Hemley, Phys. Rev. Lett. 103 (2009) 065701] on a molecular solid subjected to high pressures has motivated the present study. We first investigate a molecular cluster containing one silane molecule plus two H2 molecules, by ab initio quantum mechanics. Geometrical and electronic structures for the ground state of such a cluster are thereby proposed. The di-cluster is next examined, and the coming together of two H2 molecules is predicted. Finally, the tri-cluster is studied and important aspects of the di-cluster bonding are found to remain largely intact. [Copyright &y& Elsevier]

Abstract: A crystalline form of LiBC is known which has been predicted to be superconducting, with a comparable to that of MgB2. In both compounds, superconductivity is enhanced by the presence of two electronic bands, one of which is close to a dimensional crossover. Here, we take a quantum chemical approach, and investigate the structural and electronic properties of small clusters (). With increasing cluster size, we find that several properties of crystalline LiBC evolve naturally from the corresponding properties of the clusters. In particular, one may recognize the origin of the solid bilayered structure, typical of magnesium diboride, and the character of the electronic σ-band, arising from the overlap of the atomic orbitals in the in-plane BC rings. Two aspects especially emphasized are (a) the HOMO–LUMO gap as function of n and (b) the role of different spin multiplicity. [Copyright &y& Elsevier]

Imaging the effects of an impurity like Zn in high-Tc superconductors [Nature 61 (2000) 746] has rekindled interest in defect problems in the superconducting phase. This has prompted us here to re-examine the early work of March and Murray [Phys. Rev. 120 (1960) 830] on the linear response function in an initially translationally invariant Fermi gas. In particular, we present corresponding results for a superconductor at zero temperature, both in the s- and in the d-wave case, and mention their direct physical relevance in the case when the impurity potential is highly localized. [Copyright &y& Elsevier]

The Hartree-Fock (HF) method, supplemented by low-order Møller-Plesset (MP2) perturbation theory, has been utilized to predict the nuclear geometry, assuming planarity, of a low-lying isomer of the free space cluster BOSi2. The planar structure found at equilibrium geometry is shown to be stable against small amplitude molecular vibrations. Finally, some brief comments are made on the possible relevance of the above free-space cluster geometry to the known B-O defects which limit the improvement of minority carrier lifetime in a form of p-type silicon. [ABSTRACT FROM AUTHOR]