Cross-shelf exchange in the northwestern Black Sea

The transports of water, heat, and salt between the northwestern shelf and deep interior of the Black Sea are investigated using a high-resolution three-dimensional primitive equation model. From April to August 2005, both onshore and offshore cross-shelf break transports in the top 20 m were 0.24 Sv on average, which is equivalent to the replacement of 60% of the volume of surface shelf waters (0–20 m) per month. Two main exchange mechanisms are studied: Ekman transport, and transport by mesoscale eddies and associated meanders of the Rim Current. The Ekman drift causes nearly uniform onshore or offshore flow over a large section of the shelf break, but it is confined to the upper layers. In contrast, eddies and meanders penetrate deep down to the bottom, but they are restricted laterally. During the strong wind events of 15–22 April and 1–4 July, some 0.66 × 1012 and 0.44 × 1012 m3 of water were removed from the northwestern shelf, respectively. In comparison, the single long-lived Sevastopol Eddy generated a much larger offshore transfer of 2.84 × 1012 m3 over the period 23 April to 30 June, which is equivalent to 102% of the volume of northwestern shelf waters. Over the study period, salt exchanges increased the average density of the shelf waters by 0.67 kg m−3 and reduced the density contrast between the shelf and deep sea, while lateral heat exchanges reduced the density of the shelf waters by 0.16 kg m−3 and sharpened the shelf break front

Synthesis of Four-Link Basic Kinematic Chains [BKC] with Spherical Pairs for Spatial Mechanisms

A solution to the problem of synthesizing an initial three-dimensional kinematic chain with spherical and rotary kinematic pairs is presented. It is shown that this chain can be used as a structural module for structural-kinematic synthesis of three-dimensional four-link motion generating lever mechanisms by the preset positions of the in-and output links. DOI: 10.5901/mjss.2014.v5n23p262

Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3

We report on the optical properties of undoped single crystal LaMnO_3, the parent compound of the colossal magneto-resistive manganites. Near-Normal incidence reflectance measurements are reported in the frequency range of 20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity, s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance data. The far-infrared spectrum of s_1(w) displays the infrared active optical phonons. We observe a shift of several of the phonon to high frequencies as the temperature is lowered through the Neel temperature of the sample (T_N = 137 K). The high-frequency s_1(w) is characterized by the onset of absorption near 1.5 eV. This energy has been identified as the threshold for optical transitions across the Jahn-Teller split e_g levels. The spectral weight of this feature increases in the low-temperature state. This implies a transfer of spectral weight from the UV to the visible associated with the paramagnetic to antiferromagnetic state. We discuss the results in terms of the double exchange processes that affect the optical processes in this magnetic material.Comment: 7 pages, 5 figure

Chalk-Ex—fate of CaCO3 particles in the mixed layer : evolution of patch optical properties

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): C07020, doi:10.1029/2008JC004902.The fate of particles in the mixed layer is of great relevance to the global carbon cycle as well as to the propagation of light in the sea. We conducted four manipulative field experiments called “Chalk-Ex” in which known quantities of uniform, calcium carbonate particles were injected into the surface mixed layer. Since the production term for these patches was known to high precision, the experimental design allowed us to focus on terms associated with particle loss. The mass of chalk in the patches was evaluated using the well-calibrated light-scattering properties of the chalk plus measurements from a variety of optical measurements and platforms. Patches were surveyed with a temporal resolution of hours over spatial scales of tens of kilometers. Our results demonstrated exponential loss of the chalk particles with time from the patches. There was little evidence for rapid sinking of the chalk. Instead, horizontal eddy diffusion appeared to be the major factor affecting the dispersion of the chalk to concentrations below the limits of detection. There was unequivocal evidence of subduction of the chalk along isopycnals and subsequent formation of thin layers. Shear dispersion is the most likely mechanism to explain these results. Calculations of horizontal eddy diffusivity were consistent with other mixed layer patch experiments. Our results provide insight into the importance of physics in the formation of subsurface particle maxima in the sea, as well as the importance of rapid coccolith production and critical patch size for maintenance of natural coccolithophore blooms in nature.We would like to thank the Office of Naval Research/Optical and Biological Oceanography Program for their support of Chalk-Ex with awards N000140110042 (WMB) and N00014-01-1-0141 (AJP). Additional funding for this work came from ONR (N00014-05-1- 0111) and NASA (NNG04Gl11G, NNX08AC27G, NNG04HZ25C) to W.M.B

In situ fluorescence measurements of dissolved organic matter: a review

YesThere is a need for an inexpensive, reliable and fast monitoring tool to detect contaminants in a short time, for quick mitigation of pollution sources and site remediation, and for characterization of natural dissolved organic matter (DOM). Fluorescence spectroscopy has proven to be an excellent technique in quantifying aquatic DOM, from autochthonous, allochthonous or anthropogenic sources. This paper reviews the advances in in situ fluorescence measurements of DOM and pollutants in various water environments. Studies have demonstrated, using high temporal-frequency DOM fluorescence data, that marine autochthonous production of DOM is highly complex and that the allochthonous input of DOM from freshwater to marine water can be predicted. Furthermore, river measurement studies found a delayed fluorescence response of DOM following precipitation compared to turbidity and discharge, with various lags, depending on season, site and input of dissolved organic carbon (DOC) concentration. In addition, research has shown that blue light fluorescence (λemission = 430–500 nm) can be a good proxy for DOC, in environments with terrestrial inputs, and ultraviolet fluorescence (λemission = UVA–320–400 nm) for biochemical oxygen demand, and also E. coli in environments with sanitation issues. The correction of raw fluorescence data improves the relationship between fluorescence intensity and these parameters. This review also presents the specific steps and parameters that must be considered before and during in situ fluorescence measurement session for a harmonized qualitative and quantitative protocol. Finally, the strengths and weaknesses of the research on in situ fluorescence are identified.Authors, E.M. Carstea and C.L. Popa, acknowledge the support of the Ministry of Research and Innovation, CNCS-UEFISCDI, project number PN-III-P1-1.1-TE-2016-0646, within PNCDI III, project number 18N/2019, under the Core Program OPTRONICA VI, project number 19PFE/17.10.2018 and project number 152/2016, SMIS 108109

Spectral indexation of pixels of MODIS sea surface images for detecting inconstancy of phytopigment composition in water

This paper presents the first results of a new way of using MODIS (Moderate Resolution Imaging Spectroradiometer) sensor data to visualize phytopigment inconstancy in the near-surface layer of water basins. Other sensors of this class alike, the MODIS spectral resolution is too low to reproduce the minimums of reflectance Rrs caused by phytopigments in water. However, MODIS is remarkable for the presence of a channel at 469 nm combined with channels at 412, 443, 488, 531, 547, and 555 nm. This makes it possible to distinguish the spectral limits of preferential light absorption by chlorophyll a (412—469 nm) and by accessory pigments (469—555 nm). These capabilities were realized thanks to spectral pixel indexation (SPI) of MODIS images of the sea surface. The SPI boils down to the fact that a user determines the presence of pigment minima in spectra of every image pixel, finds the sum of the wavelengths of these minima as a WRM code and assigns it to the image pixel as one of its attributes. WRM code = 100 is assigned to pixels free of the minima. Such indexation makes it possible to examine the inconstancy of phytopigments on the background of aquatic environment variability. Application of SPI approach to MODIS images of the Gulf of Mexico and the Baltic Sea made it possible to reveal new patterns of phytopigment dynamics during HABs events

MODELLING OF MODES OF A THREE-PHASE CHAIN WITH CROSS-SECTION ASYMMETRY

In article process of modelling of modes of electric chains in program LabVIEW environment is shown. The modelling purpose is working out of the computer program (device) as for an illustration of electric processes in a three-phase chain at various asymmetrical modes in educational process of internal and correspondence (remote) formation, and for defi nition of parametres of these modes in the practical purposes (calculation К.З)

Influence of the wind field on the radiance of a marine shallow: evidence from the Caspian Sea

The influence of the near-water wind field on the radiance of a marine shallowwas studied on the basis of daily SeaWiFS ocean colour scanner data andQuickScat scatterometer wind data collected from 1999 to 2004 in the southernCaspian Sea, where the deep basin borders a vast shallow west of the shore ofmeridional extent. It was found that radiance distributions, clustered bywind rhumbs, exhibited different long-term mean patterns for winds of opposingdirections: within the shallow's boundaries, the radiances were about twice ashigh for winds having an offshore component with reference to the onshore windconditions. The zonal profile of radiance across the shallow resembleda closed loop whose upper and lower branches corresponded to the offshore and onshore winds respectively. Theloop was the most pronounced at sites with 10-15 m of water for any wavelengthof light, including the red region. On the basis of specific features of the studyarea, we attributed this pattern to sunlight backscattered from bottom sedimentsresuspended by bottom compensation currents induced by the offshorewinds