Reconsideration of Second Harmonic Generation from neat Air/Water Interface: Broken of Kleinman Symmetry from Dipolar Contribution

It has been generally accepted that there are significant quadrupolar and bulk contributions to the second harmonic generation (SHG) reflected from the neat air/water interface, as well as common liquid interfaces. Because there has been no general methodology to determine the quadrupolar and bulk contributions to the SHG signal from a liquid interface, this conclusion was reached based on the following two experimental phenomena. Namely, the broken of the macroscopic Kleinman symmetry, and the significant temperature dependence of the SHG signal from the neat air/water interface. However, because sum frequency generation vibrational spectroscopy (SFG-VS) measurement of the neat air/water interface observed no apparent temperature dependence, the temperature dependence in the SHG measurement has been reexamined and proven to be an experimental artifact. Here we present a complete microscopic analysis of the susceptibility tensors of the air/water interface, and show that dipolar contribution alone can be used to address the issue of broken of the macroscopic Kleinman symmetry at the neat air/water interface. Using this analysis, the orientation of the water molecules at the interface can be obtained, and it is consistent with the measurement from SFG-VS. Therefore, the key rationales to conclude significantly quadrupolar and bulk contributions to the SHG signal of the neat air/water interface can no longer be considered as valid as before. This new understanding of the air/water interface can shed light on our understanding of the nonlinear optical responses from other molecular interfaces as well

Delayed diagnosis of Townes‑Brocks syndrome with multicystic kidneys and renal failure caused by a novel SALL1 nonsense mutation: A case report

Townes‑Brocks syndrome (TBS) is a rare autosomal dominant congenital anomaly syndrome characterized by the triad of anorectal, hand and external ear malformations. Kidney involvement is less common and may progress to end‑stage renal failure (ESRF) early in life. The present study reports the case of a male patient presenting with multiple bilateral cortical kidney cysts at the age of 4 years, at which time the kidneys were of normal size and function. A clinical diagnosis of autosomal recessive polycystic kidney disease was made initially as the patient's parents are clinically healthy. However, the consideration of extra‑renal involvements (imperforate anus at birth, preaxial polydactyly and dysplastic right ear) following the progression of the patient to ESRF at the age of 16 years, led to the diagnosis of TBS. This prompted sequencing of the SALL1 gene, which identified a novel heterozygous nonsense mutation in the mutational ‘hotspot’ of exon 2 (c.874C>T, p.Q292X), and this mutation was not detected in healthy controls. The current case highlights that TBS may present with normal sized, cystic kidneys in childhood, while recognition of extra‑renal features of cystic kidney diseases, such as TBS, and genetic testing may facilitate the correct diagnosis and transmission mode. Reaching a correct diagnosis of as TBS is important since this condition has a 50% rate of transmission to offspring and can progress to ESRF early in life

LBT/LUCIFER Observations of the z~2 Lensed Galaxy J0900+2234

We present rest-frame optical images and spectra of the gravitationally lensed, star-forming galaxy J0900+2234 (z=2.03). The observations were performed with the newly commissioned LUCIFER1 near-infrared instrument mounted on the Large Binocular Telescope (LBT). We fit lens models to the rest-frame optical images and find the galaxy has an intrinsic effective radius of 7.4 kpc with a lens magnification factor of about 5 for the A and B components. We also discovered a new arc belonging to another lensed high-z source galaxy, which makes this lens system a potential double Einstein ring system. Using the high S/N rest-frame optical spectra covering H+K band, we detected Hbeta, OIII, Halpha, NII and SII emission lines. Detailed physical properties of this high-z galaxy were derived. The extinction towards the ionized HII regions (E_g(B-V)) is computed from the flux ratio of Halpha and Hbeta and appears to be much higher than that towards stellar continuum (E_s(B-V)), derived from the optical and NIR broad band photometry fitting. The metallicity was estimated using N2 and O3N2 indices. It is in the range of 1/5-1/3 solar abundance, which is much lower than the typical z~2 star-forming galaxies. From the flux ratio of SII 6717 and 6732, we found that the electron number density of the HII regions in the high-z galaxy were >1000 cm^-3, consistent with other z~2 galaxies but much higher than that in local HII regions. The star-formation rate was estimated via the Halpha luminosity, after correction for the lens magnification, to be about 365\pm69 Msun/yr. Combining the FWHM of Halpha emission lines and the half-light radius, we found the dynamical mass of the lensed galaxy is 5.8\pm0.9x10^10 Msun. The gas mass is 5.1\pm1.1x10^10~Msun from the H\alpha flux surface density by using global Kennicutt-Schmidt Law, indicating a very high gas fraction of 0.79\pm0.19 in J0900+2234.Comment: 11 pages, 6 figures accepted by ApJ, revised based on referee repor

Topological phase diagram and saddle point singularity in a tunable topological crystalline insulator

We report the evolution of the surface electronic structure and surface material properties of a topological crystalline insulator (TCI) Pb1-xSnxSe as a function of various material parameters including composition x, temperature T and crystal structure. Our spectroscopic data demonstrate the electronic groundstate condition for the saddle point singularity, the tunability of surface chemical potential, and the surface states' response to circularly polarized light. Our results show that each material parameter can tune the system between trivial and topological phase in a distinct way unlike as seen in Bi2Se3 and related compounds, leading to a rich and unique topological phase diagram. Our systematic studies of the TCI Pb1-xSnxSe are valuable materials guide to realize new topological phenomena.Comment: 10 pages, 7 figures. Expanded version of arXiv:1403.156

Understanding AGN-Host Connection in Partially Obscured Active Galactic Nuclei. Part I: The Nature of AGN+HII Composites

The goal of our serial papers is to examine the evolutionary connection between AGN and star formation in its host galaxy in the partially obscured AGNs (i.e., Seyfert 1.8 and 1.9 galaxies). Taking advantage of these galaxies, the properties of both components can be studied together by direct measurements. In this paper, we focus on the broad-line composite galaxies (composite AGNs) which are located between the theoretical and empirical separation lines in the [NII]/Ha vs. [OIII]/Hb diagram. These galaxies are searched for from the composite galaxies provided by the SDSS DR4 MPA/JHU catalogs. After re-analyze the spectra, we perform a fine classification for the 85 composite AGNs in terms of the BPT diagrams. All the objects located below the three theoretical separation lines are associated with a young stellar population (<1Gyrs), while either a young or old stellar population is identified in the individual multiply-classified object. The multiply-classified objects with a very old stellar population are located in the LINER region in the [OI]/Ha vs. [OIII]/Hb diagram. We then consider the connection between AGN and star formation to derive the key results. The Eddington ratio inferred from the broad Ha emission, the age of the stellar population of AGN's host as assessed by D_n(4000), and the line ratio [OI]/Ha are found to be related with each other. These relations strongly support the evolutionary scenario in which AGNs evolve from high L/L_Edd state with soft spectrum to low L/L_Edd state with hard spectrum as young stellar population ages and fades. The significant correlation between the line ratio [OI]/Ha and D_n(4000) leads us to suggest that the line ratio could be used to trace the age of stellar population in type I AGNs.Comment: 39 pages, 11 figures, 1 table, accepted by Ap

LBT and Spitzer Spectroscopy of Star-Forming Galaxies at 1 < z < 3: Extinction and Star Formation Rate Indicators

We present spectroscopic observations in the rest-frame optical and near- to mid-infrared wavelengths of four gravitationally lensed infrared (IR) luminous star-forming galaxies at redshift 1 < z < 3 from the LUCIFER instrument on the Large Binocular Telescope and the Infrared Spectrograph on Spitzer. The sample was selected to represent pure, actively star-forming systems, absent of active galactic nuclei. The large lensing magnifications result in high signal-to-noise spectra that can probe faint IR recombination lines, including Pa-alpha and Br-alpha at high redshifts. The sample was augmented by three lensed galaxies with similar suites of unpublished data and observations from the literature, resulting in the final sample of seven galaxies. We use the IR recombination lines in conjunction with H-alpha observations to probe the extinction, Av, of these systems, as well as testing star formation rate (SFR) indicators against the SFR measured by fitting spectral energy distributions to far-IR photometry. Our galaxies occupy a range of Av from ~0 to 5.9 mag, larger than previously known for a similar range of IR luminosities at these redshifts. Thus, estimates of SFR even at z ~ 2 must take careful count of extinction in the most IR luminous galaxies. We also measure extinction by comparing SFR estimates from optical emission lines with those from far-IR measurements. The comparison of results from these two independent methods indicates a large variety of dust distribution scenarios at 1 < z < 3. Without correcting for dust extinction, the H-alpha SFR indicator underestimates the SFR; the size of the necessary correction depends on the IR luminosity and dust distribution scenario. Individual SFR estimates based on the 6.2 micron PAH emission line luminosity do not show a systematic discrepancy with extinction, although a considerable, ~0.2 dex scatter is observed.Comment: Accepted for publication in The Astrophysical Journal; 14 pages, 8 figure

The Discovery of a Gravitationally Lensed Quasar at z = 6.51

Strong gravitational lensing provides a powerful probe of the physical properties of quasars and their host galaxies. A high fraction of the most luminous high-redshift quasars was predicted to be lensed due to magnification bias. However, no multiple imaged quasar was found at z>5 in previous surveys. We report the discovery of J043947.08+163415.7, a strongly lensed quasar at z=6.51, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z>5. High-resolution HST imaging reveals a multiple imaged system with a maximum image separation theta ~ 0.2", best explained by a model of three quasar images lensed by a low luminosity galaxy at z~0.7, with a magnification factor of ~50. The existence of this source suggests that a significant population of strongly lensed, high redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy.Comment: 8 pages, 4 figures, submitted to ApJ

Energy Platform for Directed Charge Transfer in the Cascade Z-Scheme Heterojunction: CO2 Photoreduction without a Cocatalyst

A universal strategy is developed to construct a cascade Z-scheme system, in which an effective energy platform is a core to direct charge transfer and separation, blocking the unexpected type-II charge transfer pathway. The dimension-matched (001)TiO 2 -g-C 3 N 4 /BiVO 4 nanosheet heterojunction (T-CN/BVNS) is the first such model. The optimized cascade Z-scheme exhibits ~19-fold photoactivity improvement for CO 2 reduction to CO in the absence of cocatalysts and costly sacrificial agents under visible-light irradiation, compared with BVNS, which is also superior to other reported Z-scheme systems even with noble metals as mediators. The experimental results and DFT calculations based on Van der Waals structural models on the ultrafast timescale reveal the introduced T as the platform could not only prolong the lifetimes of spatially separated electrons and holes but also did not compromise their reduction and oxidation potentials