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  • Articles  (26)
  • Springer  (14)
  • Mineralogical Society of Great Britain and Ireland  (5)
  • National Academy of Sciences  (5)
  • Mineralogical Society of America  (2)
  • Public Library of Science (PLoS)
  • Geosciences  (14)
  • Medicine  (10)
  • Natural Sciences in General  (7)
  • Technology  (1)
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  • Articles  (26)
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  • 1
    Electronic Resource
    Electronic Resource
    Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate? (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 577-585 
    Details
    ISSN: 1437-3262
    Keywords: Manganese nodules ; Thorium dating ; Uranium isotopes ; Peru basin ; TIMS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got values of 0.06–0.59 ppb (230Th), 0.43–1.40 ppm (232Th), 0.09–0.49 ppb (234U) and 1.66–8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02369012
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative studies of enzyme-substrate compartmentation, functional coupling and metabolic channelling in muscle cells (1998)
    Springer
    Molecular and cellular biochemistry 184 (1998), S. 291-307 
    Details
    ISSN: 1573-4919
    Keywords: creatine kinase ; mitochondria ; respiration ; contraction ; regulation ; thermodynamics ; compartmentation ; functional coupling ; metabolic channelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Some historical aspects of development of the concepts of functional coupling, metabolic channelling, compartmentation and energy transfer networks are reviewed. Different quantitative approaches, including kinetic and mathematical modeling of energy metabolism, intracellular energy transfer and metabolic regulation of energy production and fluxes in the cells in vivo are analyzed. As an example of the system with metabolic channelling, thermodynamic aspects of the functioning the mitochondrial creatine kinase functionally coupled to the oxidative phosphorylation are considered. The internal thermodynamics of the mitochondrial creatine kinase reaction is similar to that for other isoenzymes of creatine kinase, and the oxidative phosphorylation process specifically influences steps of association and dissociation of MgATP with the enzyme due to channelling of ATP from adenine nucleotide translocase. A new paradigm of muscle bioenergetics - the paradigm of energy transfer and feedback signaling networks based on analysis of compartmentation phenomena and structural and functional interactions in the cell is described. Analysis of the results of mathematical modeling of the compartmentalized energy transfer leads to conclusion that both calcium and ADP, which concentration changes synchronously in contraction cycle, may simultaneously activate oxidative phosphorylation in the muscle cells in vivo. The importance of the phosphocreatine circuit among other pathways of intracellular energy transfer network is discussed on the basis of the recent data published in the literature, with some experimental demonstration. The results of studies of perfused rat hearts with completely inhibited creatine kinase show significantly decreased work capacity and respectively, energy fluxes, in these hearts in spite of significant activation of adenylate kinase system (Dzeja et al. this volume). These results, combined with those of mathematical analysis of the energy metabolism of hearts of transgenic mice with switched off creatine kinase isoenzymes confirm the importance of phosphocreatine pathway for energy transfer for cell function and energetics in mature heart and many other types of cells, as one of major parts of intracellular energy transfer network and metabolic regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006828106322
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  • 3
    Electronic Resource
    Electronic Resource
    Zur Theorie der Widerstandsänderung in starken Magnetfeldern (1930)
    Springer
    Naturwissenschaften 18 (1930), S. 751-752 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01493343
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  • 4
    Electronic Resource
    Electronic Resource
    The half-cycle sinusoid as an alternative defibrillating waveform in low-energy applications (1977)
    Springer
    Annals of biomedical engineering 5 (1977), S. 157-163 
    Details
    ISSN: 1573-9686
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The standard Lown-type capacitor discharge waveform was compared with a single half-cycle 60-Hz sinusoid for effectiveness of defibrillation. Both shock types were used in attempts to defibrillate a series of dogs over a range of intensities from that below the minimum required for defibrillation to values well above those which consistently were successful. An on-line computer was used to monitor energy, peak current, and peak voltage of each shock. The results were plotted as percent success vs each parameter and comparisons were made at the 80% level. The half-cycle sinusoid required 18% more energy but 20% less peak current and 15% less peak voltage for 80% probability of success at these intensity levels. These results indicate that the half-cycle 60-Hz sinusoid is a reasonable alternative as a defibrillating waveform for low-energy applications (open chest surgery, some pediatric cases, and small animal applications) where its advantages of waveform unaffected by load impedance, and simplicity of circuit, may be realized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02364016
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  • 5
    Electronic Resource
    Electronic Resource
    Thorium and uranium isotopes in a manganese nodule from the Peru basin determined by alpha spectrometry and thermal ionization mass spectrometry (TIMS): Are manganese supply and growth related to climate? (1996)
    Springer
    Geologische Rundschau 85 (1996), S. 577-585 
    Details
    ISSN: 0016-7835
    Keywords: Key words Manganese nodules ; Thorium dating ; Uranium isotopes ; Peru basin ; TIMS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution 230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got values of 0.06–0.59 ppb (230Th), 0.43-1.40 ppm (232Th), 0.09–0.49 ppb (234U) and 1.66–8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the 230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant 230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005310050098
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  • 6
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    Isoprene photochemistry over the Amazon rainforest (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-05-16
    Description: Isoprene photooxidation is a major driver of atmospheric chemistry over forested regions. Isoprene reacts with hydroxyl radicals (OH) and molecular oxygen to produce isoprene peroxy radicals (ISOPOO). These radicals can react with hydroperoxyl radicals (HO2) to dominantly produce hydroxyhydroperoxides (ISOPOOH). They can also react with nitric oxide (NO) to largely produce methyl vinyl ketone (MVK) and methacrolein (MACR). Unimolecular isomerization and bimolecular reactions with organic peroxy radicals are also possible. There is uncertainty about the relative importance of each of these pathways in the atmosphere and possible changes because of anthropogenic pollution. Herein, measurements of ISOPOOH and MVK + MACR concentrations are reported over the central region of the Amazon basin during the wet season. The research site, downwind of an urban region, intercepted both background and polluted air masses during the GoAmazon2014/5 Experiment. Under background conditions, the confidence interval for the ratio of the ISOPOOH concentration to that of MVK + MACR spanned 0.4–0.6. This result implies a ratio of the reaction rate of ISOPOO with HO2 to that with NO of approximately unity. A value of unity is significantly smaller than simulated at present by global chemical transport models for this important, nominally low-NO, forested region of Earth. Under polluted conditions, when the concentrations of reactive nitrogen compounds were high (〉1 ppb), ISOPOOH concentrations dropped below the instrumental detection limit (
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 7
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    Stratospheric solar geoengineering without ozone loss (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-12-12
    Description: Injecting sulfate aerosol into the stratosphere, the most frequently analyzed proposal for solar geoengineering, may reduce some climate risks, but it would also entail new risks, including ozone loss and heating of the lower tropical stratosphere, which, in turn, would increase water vapor concentration causing additional ozone loss and surface warming. We propose a method for stratospheric aerosol climate modification that uses a solid aerosol composed of alkaline metal salts that will convert hydrogen halides and nitric and sulfuric acids into stable salts to enable stratospheric geoengineering while reducing or reversing ozone depletion. Rather than minimizing reactive effects by reducing surface area using high refractive index materials, this method tailors the chemical reactivity. Specifically, we calculate that injection of calcite (CaCO3) aerosol particles might reduce net radiative forcing while simultaneously increasing column ozone toward its preanthropogenic baseline. A radiative forcing of −1 W⋅m−2, for example, might be achieved with a simultaneous 3.8% increase in column ozone using 2.1 Tg⋅y−1 of 275-nm radius calcite aerosol. Moreover, the radiative heating of the lower stratosphere would be roughly 10-fold less than if that same radiative forcing had been produced using sulfate aerosol. Although solar geoengineering cannot substitute for emissions cuts, it may supplement them by reducing some of the risks of climate change. Further research on this and similar methods could lead to reductions in risks and improved efficacy of solar geoengineering methods.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 8
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    Expression of the type 2 receptor for cysteinyl leukotrienes (CysLT2R) by human mast cells: Functional distinction from CysLT1R (2003)
    National Academy of Sciences
    Details
    Publication Date: 2003-09-17
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    LOX mutation causes aortic aneurysm and dissection [Genetics] (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-08-03
    Description: Thoracic aortic aneurysms and dissections (TAAD) represent a substantial cause of morbidity and mortality worldwide. Many individuals presenting with an inherited form of TAAD do not have causal mutations in the set of genes known to underlie disease. Using whole-genome sequencing in two first cousins with TAAD, we identified a...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Manganoquadratite, AgMnAsS3, a new manganese-bearing sulfosalt from the Uchucchacua polymetallic deposit, Lima Department, Peru: Description and crystal structure (2012)
    Mineralogical Society of America
    Details
    Publication Date: 2012-07-01
    Description: Manganoquadratite, ideally AgMnAsS3, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as dark gray, anhedral to subhedral grains up 0.5 mm across, closely associated with alabandite, Mn-rich calcite, Mn-rich sphalerite, proustite, pyrite, pyrrhotite, tennantite, argentotennantite, stannite, and other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S. Manganoquadratite is opaque with a metallic luster and possesses a reddish-brown streak. It is brittle, the Vickers microhardness (VHN10) is 81 kg/mm2 (range 75–96) (corresponding Mohs hardness of 2–2½). The calculated density is 4.680 g/cm3 (on the basis of the empirical formula). In plane-polarized reflected light, manganoquadratite is moderately bireflectant and very weakly pleochroic from dark gray to a blue gray. Internal reflections are absent. Between crossed polars, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 29.5, 31.8 (471.1 nm), 28.1, 30.5 (548.3 nm), 27.3, 29.3 (586.6 nm), and 26.0, 28.2 (652.3 nm), respectively.Manganoquadratite is tetragonal, space group P4322, with unit-cell parameters: a = 5.4496(5), c = 32.949(1) Å, V = 978.5(1) Å3, c:a = 6.046, Z = 8. The structure, refined to R1 = 0.0863 for 907 reflections with Fo 〉 4σ(Fo), consists of a stacking along [001] of alabandite-like Mn2S2 layers connected to each to other by a couple of AgAsS2 sheets where As3+ forms typical AsS3 groups, whereas Ag+ cations are fivefold coordinated. The six strongest lines in the observed X-ray powder-diffraction pattern [d in Å (I/I0) (hkl)] are: 3.14 (60) (116), 2.739 (50) (0 0 12), 2.710 (100) (200), 1.927(70) (2 0 12 + 220), 1.645 (25) (3 0 16), and 1.573 (20) (22 12).Electron microprobe analyses gave the chemical formula (on the basis of six atoms) (Ag0.95Cu0.05)∑=1.00 (Mn0.96Pb0.04)∑=1.00(As0.87Sb0.14)∑=1.01S2.99, leading to the simplified formula AgMnAsS3.The name was chosen to indicate the close analogy of the formula and unit-cell dimensions with quadratite, Ag(Cd,Pb)(As,Sb)S3. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA 2011-008.
    Print ISSN: 0003-004X
    Electronic ISSN: 1945-3027
    Topics: Geosciences
    Published by Mineralogical Society of America
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