Assemblage Composition and Vertical Distributions of Deep-Sea Anglerfishes (Suborder: Ceratioidei) of the Northern Gulf of Mexico

The bathypelagic zone, despite being the largest cumulative ecosystem on the planet, represents the largest data gap in biological oceanography. In a deep environment with no solar light and pressures so high that survival is impossible for most marine organisms, some species have been able to adapt and overcome these challenges to radiate into diverse and successful taxa. Among the most notable of these successful taxa are the deep-sea anglerfishes (Lophiiformes: Ceratioidei). Ceratioid anglerfishes possess unique adaptations such as a symbiotic bioluminescent lure (females) and extreme dwarfism (males) that make them a particularly interesting group to study. Despite this research attractiveness, low sample sizes in ichthyological questions preclude detailed characterizations of fundamental assemblage properties, such as faunal composition, sex ratios, and vertical distributions in specific water bodies; i.e., most of what we know is compiled from sparse data across all oceans. Ceratioids were collected in the Gulf of Mexico (GoM) as a part of an extensive pelagic survey following the Deepwater Horizon oil spill. Using high-speed rope trawls and a multiple opening and closing net system, ceratioids were collected day and night throughout the northern GoM. The faunal composition of females, males, and larvae were analyzed separately by life stage/sex and by family to gain insight into assemblage structure and vertical distribution. A total of 1726 ceratioids were collected, representing all 11 families in the suborder. The assemblage was dominated numerically by females of the family Ceratiidae, in particular the species Cryptopsaras couesii. Males and larval numbers were dominated by the family Linophrynidae. The type of net used affected the taxon and size of specimens captured. Four patterns of vertical distributions were identified: 1) primarily epipelagic distribution with a rapid descent to great depth; 2) primarily mesopelagic residence; 3) a wide, “spanner” vertical distribution independent of solar cycle; and, 4) a primarily bathypelagic distribution. Larvae, particularly Linophrynidae larvae, best typified Pattern 1, the family Ceratiidae typified Pattern 2, the linophrynid species Haplophryne mollis typified Pattern 3, and males of many taxa typified Pattern 4. Vertical distribution patterns were not strictly related to taxon, sex, or life stage; for example, females within the same family (e.g., Linophrynidae) often displayed different patterns. This study demonstrates that ceratioid anglerfishes are not only among the most successful fish taxa of the bathypelagic zone, they also occupy one of the largest depth ranges among all taxa

From Solar to Stellar Brightness Variations: The Effect of Metallicity

Context. Comparison studies of Sun-like stars with the Sun suggest an anomalously low photometric variability of the Sun compared to Sun-like stars with similar magnetic activity. Comprehensive understanding of stellar variability is needed, to find a physical reasoning for this observation. Aims. We investigate the effect of metallicity and effective temperature on the photometric brightness change of Sun-like stars seen at different inclinations. The considered range of fundamental stellar parameters is sufficiently small so the stars, investigated here, still count as Sun-like or even as solar twins. Methods. To model the brightness change of stars with solar magnetic activity, we extend a well established model of solar brightness variations, SATIRE (which stands for Spectral And Total Irradiance Reconstruction), which is based on solar spectra, to stars with different fundamental parameters. For that we calculate stellar spectra for different metallicities and effective temperature using the radiative transfer code ATLAS9. Results. We show that even a small change (e.g. within the observational error range) of metallicity or effective temperature significantly affects the photometric brightness change compared to the Sun. We find that for Sun-like stars, the amplitude of the brightness variations obtained for Str\"omgren (b + y)/2 reaches a local minimum for fundamental stellar parameters close to the solar metallicity and effective temperature. Moreover, our results show that the effect of inclination decreases for metallicity values greater than the solar metallicity. Overall, we find that an exact determination of fundamental stellar parameters is crucially important for understanding stellar brightness changes.Comment: 12 pages, 12 figures, accepted in A&

Corrosion Study of AA2024-T3 by Scanning Kelvin Probe Force Microscopy and In Situ Atomic Force Microscopy Scratching

The localized corrosion of AA2024-T3, and the behavior of intermetallic particles in particular, were studied using different capabilities of the atomic force microscope (AFM). The role of intermetallic particles in determining the locations and rates of localized corrosion was determined using scanning Kelvin probe force microscopy in air after exposure to chloride solutions. Al-Cu-Mg particles, which have a noble Volta potential in air because of an altered surface film, are actively dissolved in chloride solution after a certain induction time. Al-Cu-(Fe, Mn) particles are heterogeneous in nature and exhibit nonuniform dissolution in chloride solution as well as trenching of the matrix around the particles. Light scratching of the surface by rastering with the AFM tip in contact mode in chloride solution results in accelerated dissolution of both pure Al and alloy 2024-T3. The abrasion associated with contact AFM in situ resulted in the immediate dissolution of the Al-Cu-Mg particles because of a destabilization of the surface film.This work was supported by the Air Force Office of Scientific Research under contact no. F49620-96-1-0479, Major H. De Long, Administrator. P. S. was partially supported by the Swiss National Foundation of Research

The role of the Fraunhofer lines in solar brightness variability

The solar brightness varies on timescales from minutes to decades. A clear identification of the physical processes behind such variations is needed for developing and improving physics-based models of solar brightness variability and reconstructing solar brightness in the past. This is, in turn, important for better understanding the solar-terrestrial and solar-stellar connections. We estimate the relative contributions of the continuum, molecular, and atomic lines to the solar brightness variations on different timescales. Our approach is based on the assumption that variability of the solar brightness on timescales greater than a day is driven by the evolution of the solar surface magnetic field. We calculated the solar brightness variations employing the solar disc area coverage of magnetic features deduced from the MDI/SOHO observations. The brightness contrasts of magnetic features relative to the quiet Sun were calculated with a non-LTE radiative transfer code as functions of disc position and wavelength. By consecutive elimination of molecular and atomic lines from the radiative transfer calculations, we assessed the role of these lines in producing solar brightness variability. We show that the variations in Fraunhofer lines define the amplitude of the solar brightness variability on timescales greater than a day and even the phase of the total solar irradiance variability over the 11-year cycle. We also demonstrate that molecular lines make substantial contribution to solar brightness variability on the 11-year activity cycle and centennial timescales. In particular, our model indicates that roughly a quarter of the total solar irradiance variability over the 11-year cycle originates in molecular lines. The maximum of the absolute spectral brightness variability on timescales greater than a day is associated with the CN violet system between 380 and 390 nm.Comment: 9 pages, 4 figures, accepted for publication in Astronomy&Astrophysic

A New Approach for the Study of Chemical Mechanical Polishing

The process of chemical mechanical polishing (CMP) can be studied using in situ atomic force microscopy (AFM) by intentionally using a high tip/sample interaction force. The nominal removal rate ofAl during AFM scratching is studied under a range of conditions including varying tip/sample force, solution pH, and electrode potential. This approach should be useful for CMP process development and furthering the fundamental understanding of CMP mechanisms