Trends in bulk electron-structural features of early transition-metal carbides

A detailed and systematic density-functional theory (DFT) study of a series of early transition-metal carbides (TMC's) in the NaCl structure is presented. The focus is on the trends in the electronic structure and nature of bonding, which are essential for the understanding of the reactivity of TMC's. The employed approach is based on a thorough complementary analysis of the electron density differences, the density of states (DOS), the band structure, and the real-space wave functions to gain insight into the bonding of this class of materials and get a more detailed picture of it than previously achieved, as the trend study allows for a systematic identification of the bond character along the different bands. Our approach confirms the presence of both the well-known TM--C and TM--TM bonds and, more importantly, it shows the existence and significance of direct C--C bonds in all investigated TMC's, which are frequently neglected but have been recently identified in some cases [Solid State Commun. 121, 411 (2002); Phys. Rev. B 75, 235438 (2007)]. New information on the spatial extent of the bonds, their \textit{k}-space location within the band structure, and their importance for the bulk cohesion is provided. Trends in covalency and ionicity are presented. The resulting electron-structural trends are analyzed and discussed within a two-level model

Nature of Versatile Chemisorption on TiC(111) and TiN(111) Surfaces

Density-functional calculations on the polar TiX(111) (X = C, N) surfaces show (i) for clean surfaces, strong Ti3d-derived surface resonances (SR's) at the Fermi level and X2p-derived SR's deep in the upper valence band and (ii) for adatoms in periods 1-3, pyramidic trends in atomic adsorption energies, peaking at oxygen (9 eV). A concerted-coupling model, where adatom states couple to both kinds of SR's in a concerted way, describes the adsorption. The chemisorption versatility and the general nature of the model indicate ramifications and predictive abilities in, e.g., growth and catalysis.Comment: 5 pages, 4 figures, submitted to Physical Review Letters (2006

Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: A trend study of surface electronic factors

This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMC's) by means of density-functional theory calculations. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, delta-MoC, TaC, and WC and the adsorbates H, B, C, N, O, F, NH, NH2, and NH3. Trends in adsorption strength are explained in terms of surface electronic factors, by correlating the calculated adsorption energy values with the calculated surface electronic structures. The results are rationalized with use of a concerted-coupling model (CCM), which has previously been applied succesfully to the description of adsorption on TiC(111) and TiN(111) surfaces [Solid State Commun. 141, 48 (2007)]. First, the clean TMC(111) surfaces are characterized by calculating surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOS's). Detailed comparisons between surface and bulk DOS's reveal the existence of transition-metal localized SR's (TMSR's) in the pseudogap and of several C-localized SR's (CSR's) in the upper valence band on all considered TMC(111) surfaces. Then, atomic and molecular adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOS's reveals a presence of both adsorbate--TMSR and adsorbate--CSR's interactions, of varying strengths depending on the surface and the adsorbate. These variations are correlated to the variations in adsorption energies. The results are used to generalize the content and applications of the previously proposed CCM to this larger class of substrates and adsorbates. Implications for other classes of materials, for catalysis, and for other surface processes are discussed

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Defense mechanisms and quality of life in military personnel with a burnout syndrome

© 2019, Inst. Sci. inf., Univ. Defence in Belgrade. All rights reserved. Background/Aim. Professional military personnel are exposed to a number of stressors during the war as well as in peacetime conditions that can cause some hidden or manifest disorders, especially anxiety and depression, but also the development of a burnout syndrome. The aim of our investigation was to determine the defense mechanisms and subjective assessment of quality of life and anxiety in professional military personnel of the Serbian Armed Forces with the burnout syndrome. Methods. The cross-sectional study included a total of 55 professional military personnel, from 25 to 55 years of age, without current mental problem. In the investigation, the Maslach Burnout Inventory (MBI), Defense Style Questionnaire (DSQ-40), World Health Organization Abbreviated Instrument for Quality of Life Assessment (WHOQOL-BREF) and Beck Anxiety Inventory were used. The statistical analysis included parametric and nonparametric descriptive statistics. Results. Emotional exhaustion and depersonalization were present in 10.9% of subjects and in 12.7% of subjects respectively, in moderate level, while personal accomplishment was present in 21.8% of subjects of high level. Humor was higher in the subjects with a moderate level of burnout on the personal accomplishment (PA) scale and altruism in the subjects with a low level of burnout on the depersonalization (DP) scale as well as acting-out and rationalization on the PA scale in the subjects with a moderate level of burnout. High level of anxiety was present in 14.5% of subjects. Conclusion. Professional military personnel with lower level of burnout were less anxious, use mature defense mechanisms and have a perception of better quality of life. When burnout is diagnosed, psychological interventions requires training through the adoption of mechanisms for overcoming everyday stress, which may affect the reduction of anxiety and the improvement of the quality of life. Professional assistance, including psychotherapy is required in severe cases

Nature of Chemisorption on Titanium Carbide and Nitride

Extensive density-functional calculations are performed to understand atomic chemisorption on the TiC(111) and TiN(111) surfaces, in particular the calculated pyramid-shaped trends in the adsorption energies for second- and third-period adatoms. Our previously proposed concerted-coupling model for chemisorption on TiC(111) is tested against new results for adsorption on TiN(111) and found to apply on this surface as well, thus reflecting both similarities and differences in electronic structure between the two compounds.Comment: 7 pages, 4 figures, conference proceeding presented at IWSP-2005 (Polanica Zdoj, Poland, 2005), submitted to Surf. Sci. (2005

Rosacea Flare - Up after Photodynamic Therapy (PDT) for Field Cancerization and a Review on Adverse Events with PDT in General

BACKGROUND: Actinic keratoses (AKs) are precancerous epidermal lesions induced by chronic exposure to ultraviolet light. Several topical and surgical treatments are available. For field cancerization, photodynamic therapy (PDT) is a very effective noninvasive treatment with excellent outcome and cosmesis. The management of treatment-associated adverse events, however, is crucial to achieve the treatment aims and to ensure patients adherence to PDT. CASE REPORT: We report on adverse events and their management related to PDT. We conducted literature research on PUBMED (R). Also, we present a case of an uncommon adverse event-PDT-induced rosacea flare-up on scalp and eyes. The patient was treated successfully by submicrobial slow-release doxycycline orally. Conclusions: PDT is an excellent treatment option for multiple AKs such as in bald scalp field cancerization. The management of adverse events during and after PDT is an essential part of a successful treatment plan

Treatment of Psoriasis: Novel Approaches to Topical Delivery

Topical treatment is the cornerstone for the management of mild to moderate psoriasis. Despite efforts in drug development, patient's satisfaction with the available topical treatments is limited. A strategy to improve safety, efficacy and comfort of topical treatment provides the development of new drug delivery and drug carrier systems. This review provides an overview of recent advances in this field with a focus on psoriasis. Laser-assisted drug delivery, foam formulations, nanoparticles, ethosomes, and niomes are considered. Hopefully, these new developments will improve topical drug therapy and patient satisfaction