The occurrence and toxicity of herbicides in reef building corals

Herbicide residues including 2,4-D and 2,4,5-T have been detected in the tissues of corals subject to massive mortality in the Gulf of Chiriquí, Panamá. Tolerance tests conducted using Pocillopora damicornis demonstrated a toxic effect of a commercial herbicide (incorporating 2,4-D) on this coral.     

Mars: Subsurface properties from observed longitudinal variation of the 3.5-mm brightness temperature

Measurements at 3.5 mm of the disk-average brightness temperature of Mars during the 1978 opposition can be represented by

$\text{T}{}_{\mathrm{B}}\text{(Mars, 3 5 mm, Jan/Feb 1978)}\text{=}\textcolor{red}{}$

(The errors cited are from the internal scatter; the estimated absolute calibration uncertainty is 3%.) This longitudinal variation must be taken into account if Mars is to be used as a calibration source at millimeter wavelengths. The total range of the 3.5-mm variation is three to four times larger than both the 2.8-cm and 20-μm variations. This unexpected result can possibly be explained by subsurface scattering from rocks ?1.5-cm radius.     

Seismic Precursors to Space Shuttle Shock Fronts

—?Seismic precursors to space shuttle re-entry shock fronts are detected at TXAR in Southwest Texas when the ground track of the orbiter vehicle passes within ～150–200?km of the observatory. These precursors have been termed “shuttle-quakes” because their seismograms superficially mimic the seismograms of small earthquakes from shallow sources. Analysis of the “shuttle-quake” seismograms, however, reveals one important difference. Unlike ordinary earthquakes, the propagation azimuths and horizontal phase velocities of the individual phases of the “shuttle-quakes” are functionally related. From a theoretical model developed to account for the origin of these precursors it is found that the seismic phases of “shuttle-quakes” are “bow” waves. A “bow” wave originates at the advancing tip of the shock front trace (i.e., intersection of the re-entry shock front with the surface of the earth) when the ground speed of the orbiter vehicle exceeds the horizontal phase velocity of a particular seismic phase. “Bow” waves are shown to differ in two important respects from the ordinary seismic phases. They vanish ahead of the advancing tip of the shock front trace and their propagation azimuths and horizontal phase velocities are functionally related. The ground speed of the orbiter vehicle exceeds the horizontal phase velocities of crustal seismic phase over much of the re-entry flight profile. As a result, P,S, and R _g “bow” waves will be seen as precursors to the re-entry shock front at stations located within a few hundred km of its ground track.     

Post-glacial diatom and geochemical records of ecological status and water level changes of Lake Vorota,Western Beringia

Journal of Paleolimnology - In this study, radiocarbon-dated geochemical and diatom records from Lake Vorota located within the informal meteorological ‘pole of cold’ of the northern...     

Spectroscopic and photometric observations of symbiotic nova PU Vul during 2009–2016

A new set of low-resolution spectral and UBVJHKL-photometric observations of the symbiotic nova PU Vul is presented. The binary has been evolving after its symbiotic nova outburst in 1977 and now it is in the nebular stage. It is found that the third orbital cycle(after 1977) was characterized by great changes in associated light curves. Now, PU Vul exhibits a sine-wave shape in all the light curves(with an amplitude in the U band of about 0.7 mag), which is typical for symbiotic stars in the quiescent state. Brightness variability due to pulsations of the cool component is now clearly visible in the VRI light curves. The amplitude of the pulsations increases from 0.5 mag in the V band to 0.8 mag in the I band. These two types of variability, as well as a very slow change in the physical parameters of the hot component due to evolution after the outburst of 1977, influence the spectral energy distribution(SED)of the system. The variability of emission lines is highly complex. Only hydrogen line fluxes vary with orbital phase. An important feature of the third orbital cycle is the first emergence of the OVI, 6828  Raman scattering line. We determine the temperature of the hot component by means of the Zanstra method applied to the He II, 4686  line. Our estimate is about 150 000 K for the spectrum obtained near orbital maximum in 2014. The VO spectral index derived near pulsation minimum corresponds to M6 spectral class for the cool component of PU Vul.     

Special Issue: IAMG 2019

Mathematical Geosciences -     

Broadband submillimeter measurements of the full Moon center brightness temperature and application to a lunar eclipse

We report on observations of the full Moon brightness temperature covering the frequency range of 300-950 GHz, and also on observations of the lunar eclipse of July 16, 2000, though only covering the frequency range of 165-365 GHz due to poor atmospheric transmission at higher frequencies. All observations were performed from the summit of Mauna Kea (HI) using a Fourier Transform Spectrometer mounted on the Caltech Submillimeter Observatory and supplemented by measurements of the atmospheric opacity using a 183 GHz Water Vapor Monitor. The telescope was pointed to the center of the lunar disk (with a footprint of ∼45-15 km on the Moon at 300 through 900 GHz). In order to obtain the correct values of the Moon brightness temperatures at all frequencies we carefully corrected for the atmospheric absorption, which varies across the submillimeter domain. This correction is fully described. The measured pre-eclipse brightness temperature is around 337 K in the 165-365 GHz range. This temperature slightly increases with frequency to reach ∼353 K at 950 GHz, according to previous broader band data. The magnitude of the temperature drop observed during the eclipse at 265 GHz (central frequency of the band covered) was about ∼70 K, in very good agreement with previous millimeter-wave measurements of other lunar eclipses. We detected, in addition, a clear frequency trend in the temperature drop that has been compared to a thermal and microwave emission model of the lunar regolith, with the result of a good match of the relative flux drop at different frequencies between model and measurements.