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  • Articles  (207)
  • Chemistry  (171)
  • Cell & Developmental Biology  (36)
  • Analytical Chemistry and Spectroscopy  (23)
  • General Chemistry  (20)
  • 1
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    Spatial mapping of sedimentary contaminants in the Baltimore Harbor/Patapsco river/Back river system (2021)
    University of Maryland Center for Environmental Science. Chesapeake Biological Laboratory | Solomons, MD
    In:  http://aquaticcommons.org/id/eprint/2883 | 130 | 2011-09-29 18:17:42 | 2883 | University of Maryland Center for Environmental Science. Chesapeake Biological Laboratory
    Details
    Publication Date: 2021-06-29
    Description: Primary objective was to map concentrations of target contaminants in the surfacial sediments. Secondary objectives included: characterization of potential sites for sediment capping demonstration projects, further characterization of sediment depositional and accumulation patterns, and estimation of historical contaminant inventories through sediment geochronology. (PDF contains 112 pages)
    Description: Maryland Department of the Environment
    Keywords: Ecology ; Pollution ; Environment ; Chemistry ; Polychlorinated biphenyls ; Polycyclic aromatic hydrocarbons ; organochlorine pesticides ; Mercury ; Methylmercury ; Nitrogen ; Sulfur ; Trace metals ; toxic effects ; Chesapeake Bay ; Baltimore Harbor ; Patapsco river ; Back river ; Maryland ; carbon ; PCB ; Cadmium ; Chromium ; Nickel ; Copper ; Zinc
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
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  • 2
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    PCB desorption kinetics under realistic shear and turbulence [progress report] (2021)
    University of Maryland Center for Environmental Science. Chesapeake Biological Laboratory | Solomons, MD
    In:  http://aquaticcommons.org/id/eprint/19005 | 130 | 2015-12-01 18:48:40 | 19005 | University of Maryland Center for Environmental Science. Chesapeake Biological Laboratory
    Details
    Publication Date: 2021-07-13
    Description: We hypothesize that the impact of PCB desorption from resuspended sediments depends upon the intensity of the resuspension (which scales to bottom stress in the absence of organisms), the rate at which each congener desorbs (which depends on the size and hydrophobicity of the chemical, the relative amount of 'labile' and 'resistant' forms, and the size distribution of the suspended particles), and the residence time of the particles in the water column (which depends on the time-variable water column turbulence regime and the particle settling velocities). In order to accurately quantify the impact of PCB desorption from Hudson River sediments, we are conducting experiments that realistically mimic bottom shear stress and water column turbulence and rapidly measure PCB congener release. The objectives of this study are to measure the kinetics of PCB congener desorption from Hudson River sediments under realistic bottom shear and water column turbulence conditions and to quantify the impact of shear stress and contaminant aging on PCB desorption kinetics.
    Description: Hudson River Foundation
    Description: Ref. No. [UMCES] CBL 004-018
    Keywords: Chemistry ; Environment ; Pollution
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 6
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  • 3
    Electronic Resource
    Electronic Resource
    Base stacking in A fluorescent dinucleoside monophosphate: εApεA (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1361-1372 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical properties of the 1,N6 - etheno derivative of ApA (εApεA) have been studied. Absorbance and CD measurements suggest that (1) neutral salts tend to unstack this molecule and (2) the stacking interaction is weaker than in ApA. εApεA is found to be quenched strongly with respect to the monomer. (εAMP); this quenching is solvent dependent (1M NaCl 〉 5M NaClo4〉40%glycerol) and increases with the ratio of temperature to viscosity (T/η) in each case. Fluorescence lifetime measurements also reveal a temperature- and solvent-dependent decay which is nonlinear on a semilog plot. In the presence of 95% glycerol, this decay return to linearity. These data have been considered from two points of view: (1) two-state pictures which are based on thermodynamic least-squares fit to quatum yield and CD curves, together with two exponential fits to the decay curves and (2) a dynamical model in which relatives fluorophore motion leads to deexcitation via intramolecular collision. A simple model of type (2) gives qualitative agreement with the observed behavior.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170519
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  • 4
    Electronic Resource
    Electronic Resource
    Melanin-concentrating hormone: A structural and conformational study based on synthesis, biological activity, high-field nmr, and molecular modeling techniques (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 609-622 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH -  in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290314
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of Self-Assembly of Amphiphilic Redox-Chromophores on Photoionization Processes (1981)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2036-2047 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A surfact derivative of phenothiazine was synthesized which is capable of micelle formation in aqueous solution. Concomitantly with micellization, strong changes in the photochemical behaviour occur. In particular, monophotonic photoionization is only observed above the critical micelle concentration (CMC.). Cooperative effects associated with self-assembly of this amphiphilic redox chromophore leading to local electrostatic barriers are evoked to explain these effects.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19810640708
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of processing on rheological and molecular characteristics of a low density polyethylene (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 377-382 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The viscoelastic responses of some molten polymers, and particularly of low density polyethylene (LDPE), are known to vary with processing history. Reasons for the variations include the effects of shear history on morphological states of the polymer, or on its molecular weight parameters. A typical low density polyethylene has been used to test the shear-history dependence concept following a variety of processing steps. The polymer was sheared in single-screw and twin-screw extruders, and in a high speed melter / mixer (Gelimat). Samples also were precipitated from very dilute solutions in trichlorobenzene and in p-xylene. GPC analyses showed that, in general, these procedures did not affect the various moments of molecular weight. An exception was the Gelimat-mixed sample, for which mild reductions in Mn and Mw were noted. In contrast, melt viscosity and elasticity readings, the former from low shear evaluations and the latter from extrudate swelling, were affected by the various procedures. A drop in melt viscosity and in elasticity was observed, being most pronounced for precipitated and twin-screw extruded versions of the LDPE. Reductions also were observed in the specimen sheared in the Gelimat instrument. Following conditioning at the test extrusion temperature (170°C), viscous and elastic responses tended to revert to those of the unsheared control sample, the exception again being the sample sheared in the Gelimat melter / mixer. Of the various mechanisms proposed in the literature to account for transient property changes such as those reported, temporary changes in the degree of chain entanglement appear the most satisfactory explanation. Irreversible alterations in viscoelastic properties may be associated with changes in molecular weights due to processing at high shear.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760330702
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  • 7
    Electronic Resource
    Electronic Resource
    Infrared spectroscopic studies on polyethylene, 5Part 4: cf.1.. The measurement of chain branching on powder polyethylene specimens (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 975-987 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The scope and limitations of the potassium bromide disc technique for the infra-red determination of chain branching in small samples of polyethylene in powder form have been assessed. Many of the samples encountered have an average particle size, prior to grinding with potassium bromide, of about 100 μm and very satisfactory results have been obtained, but the presence of larger particles leads to poor quality discs and inferior results. The well established double beam technique proves suitable for removing the interfering methylene absorption and compensation with polymethylene in the form of a film rather than as a pressed disc is preferable. Difficulties were encountered in preparing branching standards in a uniform and fine powder form, to avoid variation of the absorption coefficient of the 1 378 cm-1 methyl band with particle size. Such powders are best obtained by precipitation from solution rather than by low temperature milling. Despite these problems chain branching measurements may be made with a precision of between 5 and 10% and an accuracy of about 15%.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021800414
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  • 8
    Electronic Resource
    Electronic Resource
    Infrared spectroscopic studies on polyethylene, 1. The measurement of low levels of chain branching (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 437-448 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Probleme, die bei Anwendung der Kompensationsmethode auf IR-spektroskopische Bestimmungen von niedrigen Verzweigungsgraden in Polyäthylenen hoher Dichte auftreten, werden systematisch untersucht. Die erzielbare Genauigkeit wird bestimmt und es wird gezeigt, daß, wenn möglich, eine Korrektur für die Methyl-Endgruppen angewendet werden sollte. Diese ist bei einigen Polymertypen leicht möglich, bei anderen hingegen schwieriger. Als Kompensationskeil im Referenzstrahl des Spektrometers verwendet man besser Polymethylen als hochmolekulares Polyäthylen. Die äußerste Empfindlichkeit, die mit der manuellen Kompensationsmethode erreicht werden kann, liegt bei einem Methylzweig pro 2000 C-Atome. Wenn diese Methode jedoch ergänzt wird durch Computer-Kurvendämpfung und Computer Mittelung über zahlreiche Momentspektren (“C.A.T.”), kann noch eine deutliche Verbesserung im Signal-Rausch-Verhältnis erzielt werden. Damit wird es möglich noch Verzweigungsgrade bis herunter zu 0,1 Methylgruppen pro 1000 C-Atome zu messen.
    Notes: The problems encountered in the infrared spectroscopic estimation of the low levels of chain branching present in high density polyethylene, using the compensation method, are discussed systematically. The precision to be expected has been determined and it is shown that, if possible, a correction should be applied for methyl groups present at the chain ends. This is feasible with some types of polymer but more difficult with others. The compensating wedge in the reference beam of the spectrometer should be made of polymethylene rather than a high molecular weight polyethylene. The ultimate sensitivity of the manual compensation method is about one methyl branch per two thousand carbon atoms. However, when this is supplemented by computer smoothing and off-line computation of average transients (C.A.T.), a significant improvement is obtained in the signal to noise ratio, and branching levels down to 0,1 methyl groups per thousand carbon atoms are readily measured.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770212
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  • 9
    Electronic Resource
    Electronic Resource
    Axial and paraxial influences on limb morphogenesis (1991)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 208 (1991), S. 367-379 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous studies by Stephens and McNulty and Strecker and Stephens have demonstrated that foil barriers placed between the mesonephros and lateral plate at stages 12 to 15 inhibited limb development, but foil barriers placed between the neural tube and somites at stages 11 to 12 resulted in limbs with normal skeletal patterns. It was concluded that some influence present in the paraxial region of the embryo at stages 11 to 15 is necessary for normal limb development. The present study was undertaken to localize that influence more precisely. Foil barriers were placed in the lateral edge of the somites or segmental plate of stage 10 to 15 chick embryos. Barriers placed into stage 13 to 15 embryos resulted in chicks with normal limbs, but barriers placed into stage 10 to 11 embryos resulted in chicks with defective limbs. Barriers inserted just lateral to Hensen's node at stages 6 to 8 resulted in embryos with defective or absent wings. We also grafted stage 4 to 9 presumptive limb territories with and without Hensen's node. Explants without Hensen's node formed limb-like structures in 1% of the cases. Explants with Hensen's node formed limb-like structures in 27% of the cases. When barriers were implanted and a node was placed on the lateral side of the barrier, limbs formed in 40% of the cases. These data suggest a medial to lateral progression of some as yet unknown morphogenetic influence necessary for normal limb development and we hypothesized that the influence may initially emanate from Hensen's node.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052080310
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  • 10
    Electronic Resource
    Electronic Resource
    Sensilla on the mouthparts and antennae of the elephant louse, Haematomyzus elephantis piaget (Phthiraptera: Haematomyzidae) (1992)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 214 (1992), S. 333-340 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The labial palpus of the elephant louse Haematomyzus elephantis has six sensilla that represent three different types: trichoid, basiconic, and styloconic. Two rows of basiconic sensilla are situated on the dorsal and ventral surfaces of the rostrum, and each row consists of three sensilla. Male and female antennae have 15-17 trichoid sensilla situated on the scape, pedicel, and three antennal annuli. Both sexes have two sensilla basiconica on the dorsal surface of the pedicel near the junction of the scape and pedicel. Two coeloconic (tuft) sensilla are situated on the antennae of both sexes, one sensillum on each of the last two annuli. There are three plate organs, two on the last annulus and one on the penultimate annulus of the male and female antennae. Sexual dimorphism is exhibited in the male and female antennae, in that the male has about twice as many sensilla basiconica on the apex of the last annulus as does the female. The total number of sensilla basiconica on the apex of the male antennae is at least two times the number that is known to be present in any other species of lice. © 1992 Wiley-Liss, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1052140308
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