Predictive coupled-cluster isomer orderings for some Sin{}_nCm{}_m (m,n≤12m, n\le 12) clusters; A pragmatic comparison between DFT and complete basis limit coupled-cluster benchmarks

The accurate determination of the preferred ${\rm Si}_{12}{\rm C}_{12}$ isomer is important to guide experimental efforts directed towards synthesizing SiC nano-wires and related polymer structures which are anticipated to be highly efficient exciton materials for opto-electronic devices. In order to definitively identify preferred isomeric structures for silicon carbon nano-clusters, highly accurate geometries, energies and harmonic zero point energies have been computed using coupled-cluster theory with systematic extrapolation to the complete basis limit for set of silicon carbon clusters ranging in size from SiC$_3$ to ${\rm Si}_{12}{\rm C}_{12}$. It is found that post-MBPT(2) correlation energy plays a significant role in obtaining converged relative isomer energies, suggesting that predictions using low rung density functional methods will not have adequate accuracy. Utilizing the best composite coupled-cluster energy that is still computationally feasible, entailing a 3-4 SCF and CCSD extrapolation with triple-$\zeta$ (T) correlation, the {\it closo} ${\rm Si}_{12}{\rm C}_{12}$ isomer is identified to be the preferred isomer in support of previous calculations [J. Chem. Phys. 2015, 142, 034303]. Additionally we have investigated more pragmatic approaches to obtaining accurate silicon carbide isomer energies, including the use of frozen natural orbital coupled-cluster theory and several rungs of standard and double-hybrid density functional theory. Frozen natural orbitals as a way to compute post MBPT(2) correlation energy is found to be an excellent balance between efficiency and accuracy

Valence and Charge-transfer Optical Properties for Some Si\u3csub\u3en\u3c/sub\u3eC\u3csub\u3em\u3c/sub\u3e (m, n ≤ 12) Clusters: Comparing TD-DFT, Complete-basis-limit EOMCC, and Benchmarks from Spectroscopy

Accurate optical characterization of the closo-Si12C12 molecule is important to guide experimental efforts toward the synthesis of nano-wires, cyclic nano-arrays, and related array structures, which are anticipated to be robust and efficient exciton materials for opto-electronic devices. Working toward calibrated methods for the description of closo-Si12C12 oligomers, various electronic structure approaches are evaluated for their ability to reproduce measured optical transitions of the SiC2, Si2Cn (n = 1–3), and Si3Cn (n = 1, 2) clusters reported earlier by Steglich and Maier [Astrophys. J. 801, 119 (2015)]. Complete-basis-limit equation-of-motion coupled-cluster (EOMCC) results are presented and a comparison is made between perturbative and renormalized non-iterative triples corrections. The effect of adding a renormalized correction for quadruples is also tested. Benchmark test sets derived from both measurement and high-level EOMCC calculations are then used to evaluate the performance of a variety of density functionals within the time-dependent density functional theory (TD-DFT) framework. The best-performing functionals are subsequently applied to predict valence TD-DFT excitation energies for the lowest-energy isomers of SinC and Sin−1C7−n (n = 4–6). TD-DFT approaches are then applied to the SinCn (n = 4–12) clusters and unique spectroscopic signatures of closo-Si12C12 are discussed. Finally, various long-range corrected density functionals, including those from the CAM-QTP family, are applied to a charge-transfer excitation in a cyclic (Si4C4)4 oligomer. Approaches for gauging the extent of charge-transfer character are also tested and EOMCC results are used to benchmark functionals and make recommendations

Oral mucosal changes in iron deficiency anemia in a Sri Lankan female population

The oral mucosal changes in iron deficiency anemia were studied in a selected hospital population. A high incidence of oral lesions was present in the anemic group as compared to age- and sex-matched controls. Atrophic changes of the tongue were quite characteristic clinically, and a significant reduction in the mean epithelial thickness of the buccal mucosa was determined histologically

Conservative management of oral submucous fibrosis

Objective: To assess the effectiveness of intralesional injection of methylprednisolone and habit control in the management of oral submucous fibrosis.\ud \ud Patients and Methods: The study included 43 patients who attended the Department of Oral Medicine and Periodontology, University of Peradeniya, Peradeniya, Sri Lanka, from January 2001 to December 2003. The patients were divided into 3 groups according to maximum mouth opening of ≥20 mm (group A), maximum mouth opening from 11 to 19 mm (group B), and maximum mouth opening of ≤10 mm (group C). Bilateral submucosal injection of methylprednisolone 20 mg/0.5 mL was given to predetermined areas of the buccal mucosa once a month for 5 consecutive months. Maximum unaided mouth opening was measured using the same measuring device after each injection. All patients were informed about the causal relationship of their betel chewing habit to oral submucous fibrosis and the risks if they continued to chew betel. They were instructed to stop betel chewing, smoking, and drinking alcohol.\ud \ud Results: After 6 months of follow-up, 37 patients (86.0%) showed significant improvement (z = −5.283; p < 0.05) in mouth opening. Thirty three of 38 patients (86.8%) in group A showed improvement at 6 months' follow-up (z = −5.003; p < 0.05). Although 3 of 4 patients in group B experienced an improvement after 6 months, the difference was not statistically significant.\ud \ud Conclusion: The results strongly suggest that intralesional injection of methylprednisolone to the buccal mucosa for treatment of oral submucous fibrosis significantly improves mouth opening

Management of trigeminal neuralgia — retrospective analysis of 61 patients from Sri Lanka

Objectives: To identify the clinical features of idiopathic trigeminal neuralgia in hospital patients in Sri Lanka and to assess the treatment outcomes. Patients and Methods: Clinical records of 61 patients who attended the Oral Medicine Clinic at the Dental Hospital in Peradeniya, Sri Lanka, during a 4-year period from July 1998 to July 2002 were analysed. All patients were diagnosed on the basis of clinical findings and conservatively managed with medical treatment. Follow up averaged 20.2 months. Results: Trigeminal neuralgia was more common in women (57%) than in men (43%), with a peak incidence during the fifth and sixth decades of life, and with the right side of the face involved with a greater frequency than the left side (p = 0.003). Involvement of the mandibular branch was more frequent than the maxillary branch (p = 0.015). Of the 50 patients who were initially treated with carbamazepine alone, 62% had considerable pain control within 1 month. Sixty four percent of the remaining 11 patients treated with various combinations of carbamazepine and other drugs (phenytoin sodium, sodium valproate, and amitriptyline) had a considerable degree of pain control within 1 month. However, in the long-term, carbamazepine alone was effective only for 18 patients (29.5%). Conclusions: Medical treatment was effective for controlling pain from trigeminal neuralgia. Carbamazepine alone was effective only in the initial stages of the disease, a combination of carbamazepine with other drugs proved to be effective in achieving successful pain control in the long term

The Sinhala version of the Pain Catastrophizing Scale: validation and establishment of the factor structure in pain patients and healthy adults

Objective: This study was conducted to translate the Pain Catastrophizing Scale into and adapt it to the Sinhala language and to examine its psychometric properties and factor structure in pain patients and healthy adults in Sri Lanka.\ud \ud Setting and Design: A cross-sectional study was conducted, recruiting pain patients from multiple clinics and healthy adults from the community as convenience samples.\ud \ud Methods: Cross-cultural adaptation of the Pain Catastrophizing Scale for Sinhala speakers was carried out using recommended methods. The adaptation's psychometric properties and factor structure were tested in 149 pain patients and 172 healthy adults. Temporal stability was tested in a sample of 104 young adults. Pain intensity of patients was assessed using a visual analog scale, and personality traits of all participants were assessed with the Eysenck Personality Questionnaire.\ud \ud Results: Factor analysis revealed that the three-factor structure of the original version of the Pain Catastrophizing Scale was the best fit to the data from participant samples. Cronbach's alpha values of the three components and total scores for patients and healthy adults ranged from 0.72 to 0.87. Pain catastrophizing exhibited moderate positive correlations with neuroticism in patients and healthy adults and with pain intensities in patients. A high intraclass correlation coefficient of agreement (0.81) revealed an acceptable temporal stability in young adults.\ud \ud Conclusions: The results suggest that the Sinhala version of the Pain Catastrophizing Scale retains the original three-factor structure. It is a stable, valid and sufficiently reliable tool to assess pain catastrophizing in Sinhala-speaking individuals in Sri Lanka