Surface Review and Letters最新文献

The configurations, electronic, and magnetic properties of the H₂DBP-M clusters have been investigated via density functional theory. The results reveal that the TM atoms for the H₂DBP-M ($\mathrm{\text{M}}=\mathrm{\text{Sc}}$, Y, Zr, Nb, Lu, and Hf) clusters deviate from the center planes of the clusters. The H₂DBP-M ($\mathrm{\text{M}}=\mathrm{\text{Sc}}$, Y, and Lu) clusters display the largest dipole magnitudes. Based on the binding energy per atom and HOMO-LUMO gap, the H₂DBP-Ni and H₂DBP-Lu clusters are the most favorable for synthesis. The charge transfer amounts of the TM ($\mathrm{\text{TM}}=\mathrm{\text{Sc}}$, Zn, Y, Cd, Hf, and Hg) atoms for the H₂DBP-M clusters are larger. The TM-d orbitals of the H₂DBP-M ($\mathrm{\text{M}}=\mathrm{\text{Ti}}\sim$Co and Cu) clusters contribute significantly to the Fermi levels. The spin densities of the TM atoms for the H₂DBP-M clusters reduce to 0 except for that ($V=2.459|\mathrm{\text{e}}|$) of the H₂DBP-V clusters.

A large part of the cost of steel production in the world is related to the consumption of graphite electrodes. Electrode is the only material that maintains its electrical conductivity at high temperatures, and hence it is used as a conductor of electric current in EAF furnaces. Considering the high costs of graphite electrodes, any action that leads to reducing the consumption of graphite electrode can lead to increasing the productivity of steelmaking operations. In this study and as its novelty, the electrophoretic method was used to generate a ceramic coating for the protection of graphite electrodes. Electrophoretic deposition (EPD) is a two-step process in which charged particles suspended in a suspension move towards the oppositely charged electrode under the influence of an electric field which combine as a dense film on the surface. In the EPD technique, the particle size limit is not very important if a stable suspension is formed and micro and nano-sized particles can be used in this method. The numerical simulation of the thermal contour on the graphite electrode was done in ABAQUS software. Moreover, the surface morphology of graphite samples has been investigated via scanning electron microscopy (SEM). The created coating was a combination of Al₂O₃ and SiO₂, which was placed on the surface of test samples by EPD treatment. The obtained results have the properties of resistance to thermal shock and show the increase in the life of coated graphite samples at different temperatures and times.

Objective: The primary objective of this study was to compare the magnitude of incisor intrusion and retraction between two different treatment protocols and the secondary objective was to evaluate overall treatment effects.

Materials and methods: Thirty-four patients with proclined upper anterior teeth, increased overbite, and incisal show were randomly assigned to two treatment groups (G1 and G2). Upper first premolar extractions were performed in all cases. In G1, space closure was performed with conventional straight-wire friction mechanics with NiTi (nickel titanium) coil springs placed on 0.019″ × 0.025″ stainless steel wires in a 0.022 slot system with an additional intrusive force via a midline mini-implant. In G2, NiTi coil springs were placed from buccal mini-implants placed onto 0.016″ × 0.022″ SS wires in a 0.022 slot system bilaterally. Lateral cephalograms and study models taken at the beginning and at the end of 6 months of treatment were assessed.

Results: Both groups showed a statistically significant mild maxillary incisor intrusion, reduction in overjet, overbite, incisal show and a reduction in lower anterior facial height. There was a mild intrusion of the maxillary first permanent molar in G2 (not significant). Mesial movement of the maxillary first permanent molar was noted in G1 but distal movement occurred in G2. Constriction of the entire maxillary arch was noted in G1, whereas constriction was seen in the molar region only in G2. Root resorption was noticed in both groups.

Conclusion: Both groups produced comparable results. Except for molar control, all the results obtained were comparable between the two mechanics. Application of an intrusive force in the midline may be beneficial in patients treated with conventional straight-wire mechanics to treat increased overbite when anchorage requirement is not high.

During the machining of aluminum alloys, the adhesion of chips to the tool affects the performance characteristics. Today, different cooling systems are used to eliminate these negativities. In this study, the effects of end milling using HSS and carbide cutting tools of 6061-T6 aluminum alloy on surface roughness, chip thickness ratio and tool wear were examined using different cooling techniques (dry, minimum quantity lubrication (MQL) and nanocutting fluid). Different cutting speeds (180, 200, 220 m/min) and different feed rates (0.05, 0.06, 0.07 mm/rev) were used in the experiments. According to experimental findings, tool wear and surface roughness decreased at low cutting speed and feed rate by using nanocutting fluid with carbide cutting tools. It has been observed that the chip thickness ratio increases with high cutting speeds using nanocutting fluid and decreases with dry machining and high feed rates. The best milling performance of the aluminum alloy was achieved in experiments using carbide cutting tools and nanocutting fluid.

Background: Frontal sinus is one of the most difficult sinuses to approach endoscopically because of its anatomical location. Challenges and difference in opinions still exist in terms of its surgical management. Endoscopic approach to frontal sinus commonly involves either trans-axillary or intact bulla technique. Trans-axillary technique gives a direct access to the frontal sinus even with a 0° endoscope whereas Intact bulla technique warrants the use of 70° scope. Despite both the techniques now existing for quite some time; literature is still controversial regarding the superiority of one technique over the other.

Methods and materials: A randomised prospective study of 40 patients of frontal sinusitis. Patients were randomly allocated into two groups. In approaching frontal sinus, groupA patients underwent trans-axillary technique and group B patients underwent intact bulla technique. Both the groups were statistically compared in terms of time taken for surgery, post operative results and improvement in symptom score.

Results: The pre-operative endoscopic Lund -Kennedy score in group A was 7.1 ± 1.57 while in group B was 6.95 ± 1.1. The mean post -operative endoscopic Lund Kennedy score in group A was 1.25 ± 0.93. and in group B was 1.05 ± 0.89. The mean pre& SNOT-22 score in group A was 79.85 ± 19.1 and in group B was 80.55 ± 16.94. The mean postoperative SNOT-22 Score in Group A was 4.450 ± 2.136 and group B was 2.579 ± 1. 714.The average time taken in group A to reach frontal sinus was 21.1 ± 5.44 min while in group B it was15.9 ± 3.6 min. At 12 weeks follow up recurrence was seen in 4/20 cases in group A and 3/20 Cases in group B. Ostial Stenosis was seen in 3/20 cases in group A and 2/20 cases in group B. Nasal adhesions were seen in 7/20 cases in group A and 1/20 cases in group B. Middle turbinate lateralization was seen in 8/20 cases in group A and 1/19 cases in group B. Lamina Papyracea injury was seen in 1 case in group B but in 3 cases of group A.

Conclusion: Both the techniques were highly efficacious in improving post-operative endoscopic as well as symptom scores. However, some post operative complications like middle turbinate lateralization were more with trans-axillary technique as compared to intact bulla technique.