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R. M. Donati M. E. Johnson C. A. Stancer LW. R. Stromberg 《Cellular and molecular life sciences : CMLS》1968,24(5):451-452
Zusammenfassung Verabreichung vond-, wie auch vonl-Triiodothyrosin erzeugt eine ähnliche Vermehrung der Erythropoiesis in nephroektomierten Ratten, wie bei der Messung der Radioeiseninkorporation durch Erythrozyten (18 h nach Injektion von radioaktivem Eisencitrat). Es ergab sich weiter, dassd- undl-Thyrosin, im Unterschied zu Erythropoieten, die reticulozytose Eisenassimilation in vitro vermehrte. Danach scheinen verschiedene Mechanismen bei der Stimulation der Erythropoiesis durch Erythropoieten und Triiodothyronin im Spiele zu sein. 相似文献
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Klironomos JN Allen MF Rillig MC Piotrowski J Makvandi-Nejad S Wolfe BE Powell JR 《Nature》2005,433(7026):621-624
Attempts to understand the ecological effect of increasing atmospheric CO2 concentration, [CO2], usually involve exposing today's ecosystems to expected future [CO2] levels. However, a major assumption of these approaches has not been tested--that exposing ecosystems to a single-step increase in [CO2] will yield similar responses to those of a gradual increase over several decades. We tested this assumption on a mycorrhizal fungal community over a period of six years. [CO2] was either increased abruptly, as is typical of most [CO2] experiments, or more gradually over 21 generations. The two approaches resulted in different structural and functional community responses to increased [CO2]. Some fungi were sensitive to the carbon pulse of the abrupt [CO2] treatment. This resulted in an immediate decline in fungal species richness and a significant change in mycorrhizal functioning. The magnitude of changes in fungal diversity and functioning in response to gradually increasing [CO2] was smaller, and not significantly different to those with ambient [CO2]. Our results suggest that studies may overestimate some community responses to increasing [CO2] because biota may be sensitive to ecosystem changes that occur as a result of abrupt increases. 相似文献
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K. Murawski E. Gomółka M. Kopytko K. Grodecki K. Michalczewski Ł. Kubiszyn W. Gawron P. Martyniuk A. Rogalski J. Piotrowski 《自然科学进展(英文版)》2019,29(4):472-476
InAsSb ternary alloys can be considered as an alternative to HgCdTe for mid-wavelength, as well as long-wavelength infrared applications. Its energy bandgap exhibits nonlinearity versus Sb composition, and hence the correct determination of its value is necessary for the effective design and simulation of optoelectronic devices. The commonly used expression on the InAsSb energy bandgap provided by Wieder and Clawson overestimated energy bandgap values at high temperatures. In this paper, we present two modified empirical relationships which are based on the experimental data obtained in our laboratory and published literature. Both are correct for a wide range of Sb molar composition and temperatures.The nonlinearity of the energy gap is described with the adequate bowing parameter. The data collected in our experiment, for samples grown on lattice mismatched GaAs substrates, fits well with a bowing factor of C = 0.72 eV. The minimum bandgap energy that can be reached at room temperature is about 73 meV for a Sb mole fraction, x = 0.63. In comparison, the bandgap at low temperatures collected in the literature for samples grown on lattice-matched GaSb substrates is smaller than the measured values in our experiment and fits well with a parabola with C = 0.9 eV. 相似文献
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Boekema EJ Hifney A Yakushevska AE Piotrowski M Keegstra W Berry S Michel KP Pistorius EK Kruip J 《Nature》2001,412(6848):745-748
Cyanobacteria are abundant throughout most of the world's water bodies and contribute significantly to global primary productivity through oxygenic photosynthesis. This reaction is catalysed by two membrane-bound protein complexes, photosystem I (PSI) and photosystem II (PSII), which both contain chlorophyll-binding subunits functioning as an internal antenna. In addition, phycobilisomes act as peripheral antenna systems, but no additional light-harvesting systems have been found under normal growth conditions. Iron deficiency, which is often the limiting factor for cyanobacterial growth in aquatic ecosystems, leads to the induction of additional proteins such as IsiA (ref. 3). Although IsiA has been implicated in chlorophyll storage, energy absorption and protection against excessive light, its precise molecular function and association to other proteins is unknown. Here we report the purification of a specific PSI-IsiA supercomplex, which is abundant under conditions of iron limitation. Electron microscopy shows that this supercomplex consists of trimeric PSI surrounded by a closed ring of 18 IsiA proteins binding around 180 chlorophyll molecules. We provide a structural characterization of an additional chlorophyll-containing, membrane-integral antenna in a cyanobacterial photosystem. 相似文献
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Racusin JL Karpov SV Sokolowski M Granot J Wu XF Pal'shin V Covino S van der Horst AJ Oates SR Schady P Smith RJ Cummings J Starling RL Piotrowski LW Zhang B Evans PA Holland ST Malek K Page MT Vetere L Margutti R Guidorzi C Kamble AP Curran PA Beardmore A Kouveliotou C Mankiewicz L Melandri A O'Brien PT Page KL Piran T Tanvir NR Wrochna G Aptekar RL Barthelmy S Bartolini C Beskin GM Bondar S Bremer M Campana S Castro-Tirado A Cucchiara A Cwiok M D'Avanzo P D'Elia V Valle MD de Ugarte Postigo A 《Nature》2008,455(7210):183-188
Long-duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of massive stars. Previous early optical observations of even the most exceptional GRBs (990123 and 030329) lacked both the temporal resolution to probe the optical flash in detail and the accuracy needed to trace the transition from the prompt emission within the outflow to external shocks caused by interaction with the progenitor environment. Here we report observations of the extraordinarily bright prompt optical and gamma-ray emission of GRB 080319B that provide diagnostics within seconds of its formation, followed by broadband observations of the afterglow decay that continued for weeks. We show that the prompt emission stems from a single physical region, implying an extremely relativistic outflow that propagates within the narrow inner core of a two-component jet. 相似文献
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A. J. Zelazowski J. K. Piotrowski 《Cellular and molecular life sciences : CMLS》1977,33(12):1624-1625
Summary The level of metallothionein-like proteins was determined in different tissues of 6 animal species. The highest concentrations were found in pig and rat tissues. The organs richest in metallothionein-like proteins included: kidneys (101–305 g/g), intestine (127–257 g/g) and liver (54–496 g/g).Studies performed under the Polish-American agreement 05-009-2 with National Institute for Occupational Safety and Health, PHS, USA. 相似文献
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