Following the relaxation dynamics of photoexcited aniline in the 273-266 nm region using time-resolved photoelectron imaging

Scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES) have been used to investigate the growth morphology of ultra-thin Pb films on the Ni3Al(111) face at room temperature. A previous study [K. Miśków and A. Krupski Appl Surf Sci 273, 2013, 554] using low-energy electron diffraction (LEED) and real time Auger intensity recording has demonstrated that an initial two-dimensional growth of the first Pb monolayer thick ‘wetting layer’ takes place. With further deposition and for T = 300 K, flat three atomic-layer-high islands are grown. Above 350 K, the Stranski–Krastanov growth mode was observed. In the current study, the analysis of STM measurements indicate and confirm that for coverage θ = 1.0 ML two-dimensional growth of the first Pb monolayer took place. Above θ > 1.0 ML, a three-dimensional growth of the Pb islands was observed with a strongly preferred atomic-scale ‘magic height (N),’ hexagonal shape and flat-tops. At coverage θ = 3.5 ML, only islands containing N = 3, 5, 7 and 11 atomic layers of Pb are observed. At the higher coverage θ = 5.5 ML, three types of regular hexagonal islands with side lengths of 25, 30 and 45 nm are observed. Furthermore, three different island adsorption configurations rotated by 10° ± 1° and 30° ± 6° with respect to each other were observed. After an annealing at T = 400 K of 5.5 ML of lead deposited at RT on the Ni3Al(111) the morphology of the surface changes. Post-anneal, islands of Pb are observed above the ‘wetting layer’ with an estimated average size and diameter of 768 ± 291 nm2 and 38.17 ± 6.56 nm and constant uniform height of two atomic layers (N = 2)

Diagnosing magnetars with transient cooling

Transient X-ray emission, with an approximate t^{-0.7} decay, was observed from SGR 1900+14 over 40 days following the the giant flare of 27 Aug 1998. We calculate in detail the diffusion of heat to the surface of a neutron star through an intense 10^{14}-10^{15} G magnetic field, following the release of magnetic energy in its outer layers. We show that the power law index, the fraction of burst energy in the afterglow, and the return to persistent emission can all be understood if the star is composed of normal baryonic material.Comment: 9 pages, 1 eps figur

Analysis of Flexural Strength and Contact Pressure After Simulated Chairside Adjustment of Pressed Lithium Disilicate Glass-Ceramic

Statement of problem Research evaluating load-to-failure of pressed lithium disilicate glass-ceramic (LDGC) with a clinically validated test after adjustment and repair procedures is scarce. Purpose The purpose of this in vitro study was to investigate the effect of the simulated chairside adjustment of the intaglio surface of monolithic pressed LDGC and procedures intended to repair damage. Material and methods A total of 423 IPS e.max Press (Ivoclar Vivadent AG) disks (15 mm diameter, 1 mm height) were used in the study. The material was tested by using an equibiaxial loading arrangement (n≥30/group) and a contact pressure test (n≥20/group). Specimens were assigned to 1 of 14 groups. One-half was assigned to the equibiaxial load test and the other half underwent contact pressure testing. Testing was performed in 2 parts, before glazing and after glazing. Before-glazing specimens were devested and entered in the test protocol, while after-glazing specimens were devested and glazed before entering the test protocol. Equibiaxial flexure test specimens were placed on a ring-on-ring apparatus and loaded until failure. Contact pressure specimens were cemented to epoxy resin blocks with a resin cement and loaded with a 50-mm diameter hemisphere until failure. Tests were performed on a universal testing machine with a crosshead speed of 0.5 mm/min. Weibull statistics and likelihood ratio contour plots determined intergroup differences (95% confidence bounds). Results Before glazing, the equibiaxial flexural strength test and the Weibull and likelihood ratio contour plots demonstrated a significantly higher failure strength for 1EC (188 MPa) than that of the damaged and/or repaired groups. Glazing following diamond-adjustment (1EGG) was the most beneficial post-damage procedure (176 MPa). Regarding the contact pressure test, the Weibull and likelihood ratio contour plots revealed no significant difference between the 1PC (98 MPa) and 1PGG (98 MPa) groups. Diamond-adjustment, without glazing (1EG and 1PG), resulted in the next-to-lowest equibiaxial flexure strength and the lowest contact pressure. After glazing, the strength of all the groups, when subjected to glazing following devesting, increased in comparison with corresponding groups in the before-glazing part of the study. Conclusions A glazing treatment improved the mechanical properties of diamond-adjusted IPS e.max Press disks when evaluated by equibiaxial flexure and contact pressure tests. Clinical Implications When adjustments are made on the intaglio surface of a pressed lithium disilicate glass-ceramic, a subsequent glazing treatment is recommended to improve strength