Broadband Metallic Carbon Nanotube Saturable Absorber for Ultrashort Pulse Generation in the 1500–2100 nm Spectral Range

Herein, we report on the possibility of ultrashort laser pulse generation in the broadband spectral range using a saturable absorber based on free-standing metallic carbon nanotube thin film. Erbium, thulium, and holmium-doped all-fiber lasers were mode-locked with a single saturable absorber containing a 300 nm thick material layer. Subpicosecond pulses were generated at 1559, 1938, and 2082 nm. Our work validates the broadband operation of metallic carbon nanotube-based saturable absorbers and highlights the suitable performance of nanomatematerial for ultrafast photonic applications.

SN 2014ab: an aspherical Type IIn supernova with low polarization

ABSTRACT We present photometry, spectra, and spectropolarimetry of supernova (SN) 2014ab, obtained through ∼200 d after peak brightness. SN 2014ab was a luminous Type IIn SN (MV < −19.14 mag) discovered after peak brightness near the nucleus of its host galaxy, VV 306c. Pre-discovery upper limits constrain the time of explosion to within 200 d prior to discovery. While SN 2014ab declined by ∼1 mag over the course of our observations, the observed spectrum remained remarkably unchanged. Spectra exhibit an asymmetric emission-line profile with a consistently stronger blueshifted component, suggesting the presence of dust or a lack of symmetry between the far side and near side of the SN. The Pa β emission line shows a profile very similar to that of H α, implying that this stronger blueshifted component is caused either through obscuration by large dust grains, occultation by optically thick material, or a lack of symmetry between the far side and near side of the interaction region. Despite these asymmetric line profiles, our spectropolarimetric data show that SN 2014ab has little detected polarization after accounting for the interstellar polarization. We are likely seeing emission from a photosphere that has only small deviation from circular symmetry in the plane normal to our line of sight, but with either large-grain dust or significant asymmetry in the density of circumstellar material or SN ejecta along our line of sight. We suggest that SN 2014ab and SN 2010jl (as well as other SNe IIn) may be events with similar geometry viewed from different directions.

Probing the circumnuclear absorbing medium of the buried AGN in NGC 1068 through NuSTAR observations

ABSTRACT We present the results of the latest NuSTAR monitoring campaign of the Compton-thick Seyfert 2 galaxy NGC 1068, composed of four ∼50 ks observations performed between 2017 July and 2018 February to search for flux and spectral variability on time-scales from 1 to 6 months. We detect one unveiling and one eclipsing event with time-scales less than 27 and 91 d, respectively, ascribed to Compton-thick material with NH = (1.8 ± 0.8) × 1024 and ≥ (2.4 ± 0.5) × 1024 cm−2 moving across our line of sight. This gas is likely located in the innermost part of the torus or even further inward, thus providing further evidence of the clumpy structure of the circumnuclear matter in this source. Taking advantage of simultaneous Swift–XRT observations, we also detected a new flaring ULX, at a distance d ∼ 30 arcsec (i.e. ∼2 kpc) from the nuclear region of NGC 1068, with a peak X-ray intrinsic luminosity of (3.0 ± 0.4) × 1040 erg s−1 in the 2–10 keV band.

Influence of Microstructural Variation in Thick Section Steels on the Characterisation of Fracture Toughness Using Sub-Size Specimens

The challenges of performing full-thickness fracture toughness tests on steel plates of 100mm thickness and greater means that the use of sub-size specimens is desirable. In this work, 100mm thick parent plate of S690 high strength steel was characterised using SENB fracture toughness specimens with thickness of 12mm, 25mm, 50mm and 100mm. Sub-size specimens were extracted at two different locations through the plate thickness; mid-wall and quarter wall. Sufficient specimens were tested to apply the Master Curve method in ASTM E1921 to predict the behaviour of 100mm thick material from each set of sub-size specimens. The through-thickness microstructural variation in these heavy-wall steel plates meant that significantly different predictions of full-thickness fracture toughness were obtained from the two sampling locations. However, when sampled from the mid-wall location, sub-size specimens down to 25mm thick were able to conservatively predict full-thickness fracture toughness using Master Curve methods.

Investigating the origin of the Fe emission lines of the Seyfert 1 galaxy Mrk 205

ABSTRACT We have investigated the nature and origin of the Fe K emission lines in Mrk 205 using observations with Suzaku and XMM–Newton, aiming to resolve the ambiguity between a broad emission line and multiple unresolved lines of higher ionization. We detect the presence of a narrow Fe K α emission line along with a broad-band Compton reflection hump at energies $E\gt 10\rm \, \, {\rm keV}$. These are consistent with reflected emission of hard X-ray photons off a Compton-thick material of $N_{\rm H}\ge 2.15\times 10^{24}\rm \, \, {\rm cm^{-2}}$. In addition we detect a partially covering ionized absorption with ionization parameter $\log (\xi /\rm \, erg\, cm\, s^{-1})=1.9_{-0.5}^{+0.1}$, column density $N_{\rm H}=(5.6_{-1.9}^{+2.0})\times 10^{22}\rm \, \, {\rm cm^{-2}}$, and a covering factor of $0.22_{-0.06}^{+0.09}$. We detect the presence of emission arising out of ionized disc reflection contributing in the soft and hard X-rays consistently in all the observations. We however, could not definitely ascertain the presence of a relativistically broadened Fe line in the X-ray spectra. Using relativistic reflection models, we found that the data are unable to statistically distinguish between the scenarios when the supermassive black hole is non-rotating and when it is maximally spinning. Using the disc reflection model we also find that the accretion disc of the active galactic nucleus may be truncated at a distance 6RG < R < 12RG, which may suggest why there may not be any broad Fe line. The Eddington rate of the source is low (λEdd = 0.03), which points to an inefficient accretion, possibly due to a truncated disc.

Forces and moments delivered by the PET-G aligner to a maxillary central incisor for palatal tipping and intrusion

ABSTRACT Objective: To evaluate the effect of material thickness and width of the gingival edge on the forces and moments delivered by aligners prepared from Duran foil (PET-G) to a maxillary incisor during tipping and intrusion. Materials and Methods: Aligners prepared from PET-G of three material thicknesses (0.5, 0.625, and 0.75 mm) and three widths of gingival edges (0–1, 3–4, and 6–7 mm) were investigated during incisor palatal tipping and intrusion of 0.5 mm each. Forces and moments were measured with a six-component measuring device. The influence of aligner thickness and aligner extend on the force and moment development were tested for statistical significance (P < .05). Results: The Fx and Fz forces produced during palatal tipping and intrusion by the 0.75-mm aligner material was significantly higher than those produced by the 0.5-mm-thick material (P = .005 and P = .047, respectively). There was no statistical difference between aligner thickness of 0.5 and 0.625 mm and between 0.625 and 0.75 mm. The same behavior was observed for the palatal moment (My). The Fx and Fz forces produced during palatal tipping and intrusion by the aligner with an extension of 0–1 mm edge was significantly lower than that of the aligner with a larger extension (3–4 mm edge: P = .003; 6–7 mm: P = .001). However, there was no statistical difference between aligners with a 3–4-mm and a 6-mm edge. The same behavior was observed for the palatal moment (My). Conclusions: The forces and moments exerted by the PET-G aligner on teeth vary, depending on the material thickness, width of the aligner edge, and direction of tooth movement.

Decreasing Waste of Laser Cutting by Metal Fume Capturing With Water

Decommissioning of aged nuclear reactors is planned, and cutting technologies for thick structure are necessary to reduce storage space of radioactive wastes. Though thermal cutting technology is suitable for cutting thick materials, radioactive fume is one of the problems due to increase the environmental dose. A water jet-guided laser cutting technology is one of the solutions for cutting irradiated materials, because radioactive fume is confined in the water and doze level won’t be increased. However, this technology was developed for precision machining like dicing and slotting of silicon wafers, cutting thick materials by using this process is very diffcult. In this study, cutting technology for thick material with a water jet-guided laser was discussed. Phenomenon during cutting thick stainless steel was observed by using high speed camera and optimum conditions for both water jet and laser cutting were derived. Finally, 50mm thick stainless steel plate was successfully cut by using this technology.