Traditionally, administered mass is used to describe doses of conventional chemical substances in toxicity studies. For deriving toxic doses of nanomaterials, mass and chemical composition alone... Show moreTraditionally, administered mass is used to describe doses of conventional chemical substances in toxicity studies. For deriving toxic doses of nanomaterials, mass and chemical composition alone may not adequately describe the dose, because particles with the same chemical composition can have completely different toxic mass doses depending on properties such as particle size. Other dose metrics such as particle number, volume, or surface area have been suggested, but consensus is lacking. The discussion regarding the most adequate dose metric for nanomaterials clearly needs a systematic, unbiased approach to determine the most appropriate dose metric for nanomaterials. In the present study, the authors propose such an approach and apply it to results from in vitro and in vivo experiments with silver and silica nanomaterials. The proposed approach is shown to provide a convenient tool to systematically investigate and interpret dose metrics of nanomaterials. Recommendations for study designs aimed at investigating dose metrics are provided. Show less
Proper understanding of the basic processes and specific properties of engineered nanomaterials (NMs) that modify the fate and effects of NMs is crucial for NM-tailored risk assessment. This in... Show moreProper understanding of the basic processes and specific properties of engineered nanomaterials (NMs) that modify the fate and effects of NMs is crucial for NM-tailored risk assessment. This in turn requires developers of NMs and for regulators to consider the most important parameters governing the properties, behavior and toxicity of NMs. As fate and effect studies are commonly performed in laboratory settings, mimicking to a varying extent realistic exposure conditions, it is important to be able to extrapolate results of fate and effect studies in synthetic media to realistic environmental conditions. This requires detailed understanding of the processes controlling the fate and behavior of NMs in terrestrial and aquatic media, as dependent on the composition of the medium. It is the aim of this contribution to provide background reading to the NM and media specific properties and processes that affect the fate and behavior of NMs in aquatic environments, focusing on the specific properties of NMs that modulate the interactions in the aquatic environment. A general introduction on the dominant fate determining processes of NMs is supplemented by case studies on specific classes of NMs: metal NMs, stable oxides, iron oxides, and carbon nanotubes. Based on the synthesis of the current knowledge base toward essential data and information needs, the review provides a description of the particle specific properties and the water characteristics that need monitoring in order to allow for future quantification and extrapolation of fate and behavior properties of NMs in freshwater compartments of varying composition. Show less
The aim of this thesis is to shed light on whether some capacities that are considered linked to, or characteristic for, language are shared between humans and nonhuman animals, which can help to... Show moreThe aim of this thesis is to shed light on whether some capacities that are considered linked to, or characteristic for, language are shared between humans and nonhuman animals, which can help to understand the basic cognitive abilities from which the evolution of human language may have arisen. The thesis starts with comparing human language with other communication systems. Then Chapter 2 addressed the question: what mechanisms are involved in learning a sequence of vocal items in zebra finches. Chapter 3 addressed whether zebra finches are able to discriminate between, and generalize, affixation patterns. Chapter 4 dealt with a controversial topic that is recently getting a lot of attention: whether animals show the ability to learn __algebraic__ rules that are relevant to syntax learning in humans. Chapter 5 examined the ability of zebra finch to learn nonadjacent dependency that is important for learning the hierarchical structure of languages. Altogether, this thesis provides positive evidence for similarities between humans and songbirds in using transitional information, generalizing surface transformations of human affixation patterns and detecting nonadjacent dependencies. Show less
Context. According to traditional gas-phase chemical models, O$_{2}$ should be abundant in molecular clouds, but until recently, attempts to detect interstellar O$_{2}$ line emission with ground-... Show moreContext. According to traditional gas-phase chemical models, O$_{2}$ should be abundant in molecular clouds, but until recently, attempts to detect interstellar O$_{2}$ line emission with ground- and space-based observatories have failed. Aims: Following the multi-line detections of O$_{2}$ with low abundances in the Orion and {$ρ$} Oph A molecular clouds with Herschel, it is important to investigate other environments, and we here quantify the O$_{2}$ abundance near a solar-mass protostar. Methods: Observations of molecular oxygen, O$_{2}$, at 487 GHz toward a deeply embedded low-mass Class 0 protostar, NGC 1333-IRAS 4A, are presented, using the Heterodyne Instrument for the Far Infrared (HIFI) on the Herschel Space Observatory. Complementary data of the chemically related NO and CO molecules are obtained as well. The high spectral resolution data are analysed using radiative transfer models to infer column densities and abundances, and are tested directly against full gas-grain chemical models. Results: The deep HIFI spectrum fails to show O$_{2}$ at the velocity of the dense protostellar envelope, implying one of the lowest abundance upper limits of O$_{2}$/H$_{2}$ at {le}6 { imes} 10$^{-9}$ (3{$σ$}). The O$_{2}$/CO abundance ratio is less than 0.005. However, a tentative (4.5{$σ$}) detection of O$_{2}$ is seen at the velocity of the surrounding NGC 1333 molecular cloud, shifted by 1 km s$^{-1}$ relative to the protostar. For the protostellar envelope, pure gas-phase models and gas-grain chemical models require a long pre-collapse phase (~{}0.7-1 { imes} 10$^{6}$ years), during which atomic and molecular oxygen are frozen out onto dust grains and fully converted to H$_{2}$O, to avoid overproduction of O$_{2}$ in the dense envelope. The same model also reproduces the limits on the chemically related NO molecule if hydrogenation of NO on the grains to more complex molecules such as NH$_{2}$OH, found in recent laboratory experiments, is included. The tentative detection of O$_{2}$ in the surrounding cloud is consistent with a low-density PDR model with small changes in reaction rates. Conclusions: The low O$_{2}$ abundance in the collapsing envelope around a low-mass protostar suggests that the gas and ice entering protoplanetary disks is very poor in O$_{2}$. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at http://www.aanda.orgReduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/558/A58Show less
We present Herschel-HIFI, SPIRE, and PACS 50-670 {$μ$}m imaging and spectroscopy of six FU Orionis-type objects and candidates (FU Orionis, V1735 Cyg, V1515 Cyg, V1057 Cyg, V1331 Cyg, and HBC 722)... Show moreWe present Herschel-HIFI, SPIRE, and PACS 50-670 {$μ$}m imaging and spectroscopy of six FU Orionis-type objects and candidates (FU Orionis, V1735 Cyg, V1515 Cyg, V1057 Cyg, V1331 Cyg, and HBC 722), ranging in outburst date from 1936 to 2010, from the ''FOOSH'' (FU Orionis Objects Surveyed with Herschel) program, as well as ancillary results from Spitzer Infrared Spectrograph and the Caltech Submillimeter Observatory. In their system properties (L $_{bol}$, T $_{bol}$, and line emission), we find that FUors are in a variety of evolutionary states. Additionally, some FUors have features of both Class I and II sources: warm continuum consistent with Class II sources, but rotational line emission typical of Class I, far higher than Class II sources of similar mass/luminosity. Combining several classification techniques, we find an evolutionary sequence consistent with previous mid-IR indicators. We detect [O I] in every source at luminosities consistent with Class 0/I protostars, much greater than in Class II disks. We detect transitions of $^{13}$CO (J $_{up}$ of 5-8) around two sources (V1735 Cyg and HBC 722) but attribute them to nearby protostars. Of the remaining sources, three (FU Ori, V1515 Cyg, and V1331 Cyg) exhibit only low-lying CO, but one (V1057 Cyg) shows CO up to J = 23 { arr} 22 and evidence for H$_{2}$O and OH emission, at strengths typical of protostars rather than T Tauri stars. Rotational temperatures for ''cool'' CO components range from 20 to 81 K, for ~{} 10$^{50}$ total CO molecules. We detect [C I] and [N II] primarily as diffuse emission. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Show less
