Atom-Chip Fountain Gravimeter Abend, S; Gebbe, M; Gersemann, M ...
Physical review letters,
11/2016, Letnik:
117, Številka:
20
Journal Article
Recenzirano
We demonstrate a quantum gravimeter by combining the advantages of an atom chip for the generation, delta-kick collimation, and coherent manipulation of freely falling Bose-Einstein condensates ...(BECs) with an innovative launch mechanism based on Bloch oscillations and double Bragg diffraction. Our high-contrast BEC interferometer realizes tens of milliseconds of free fall in a volume as little as a one centimeter cube and paves the way for measurements with sub-μGal accuracies in miniaturized, robust devices.
We realize beam splitters and mirrors for atom waves by employing a sequence of light pulses rather than individual ones. In this way we can tailor atom interferometers with improved sensitivity and ...accuracy. We demonstrate our method of composite pulses by creating a symmetric matter-wave interferometer which combines the advantages of conventional Bragg- and Raman-type concepts. This feature leads to an interferometer with a high immunity to technical noise allowing us to devise a large-area Sagnac gyroscope yielding a phase shift of 6.5 rad due to the Earth's rotation. With this device we achieve a rotation rate precision of 120 nrad s(-1) Hz(-1/2) and determine the Earth's rotation rate with a relative uncertainty of 1.2%.
Rare earth elements (REEs) are naturally distributed in the environment, and are increasingly being used in agriculture and high technology materials worldwide, thereby increasing anthropogenic ...contamination and environmental risks. There exists scarce and contradictory toxicity information about REEs; hence, more studies are required, especially on their mixtures. Thus, this study aimed to assess the toxicities of La3+, Nd3+, Sm3+, and the combinations of these elements (binary 1:1 and ternary 1:1:1), to organisms from different trophic levels: producers (the microalgae Chlorella vulgaris and Raphidocelis subcapitata), primary consumers (the microcrustaceans Daphnia similis and Artemia salina), and decomposers (the fungi Penicillium simplicissimum and Aspergillus japonicus). Ecotoxicological bioassays were performed, and toxic concentrations were determined. Thereafter, toxicities of single and mixture REEs were classified as slightly to highly toxic according to their toxic units. Finally, a concentration addition (CA) model was used to estimate how REEs interact upon combining. Nd3+ was the most toxic element for all organisms, especially D. similis (48 h LC50 9.41 mg.L−1), and was therefore classified as highly toxic. Sm3+ promoted cell agglomeration in Chlorella vulgaris and was the most toxic of the tested elements for this organism (72 h IC50 25.78 mg.L−1). The CA model revealed synergistic responses for most of the combinations, principally Nd3+ + Sm3+, which was the most toxic combination for the tested organisms. Both fungi were the most resistant organisms, and A. japonicus produced exudate and sclerotia, which help in the detoxification of chemicals. Owing not only to the fact that fungi displayed a higher resistance to REEs, but also due to the absence of regulations for REEs released from the agricultural or industrial sector, and the lack of methods to treat effluents or to dispose of technological items containing REEs, these organisms should be considered as a model for the biosorption or bioremediation of REEs. Finally, the toxic effects of REEs, particularly Nd3+, on the biota and human health should be the focus of future studies due to their increased use in technology.
•The first study that evaluated the toxicities of La3+, Nd3+, and Sm3+ in mixtures.•Nd3+ was the most toxic element (five of six organisms).•Chlorella vulgaris was more sensitive to Sm3+.•Synergism was observed in the three of four REEs mixtures for the Algae.•Nd3+ + Sm3+mixture presented synergistic effects to four organisms.
Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates ...are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.
Vitamin B12 is an essential micronutrient that functions in two metabolic pathways: the canonical propionate breakdown pathway and the methionine/S-adenosylmethionine (Met/SAM) cycle. In
low vitamin ...B12, or genetic perturbation of the canonical propionate breakdown pathway results in propionate accumulation and the transcriptional activation of a propionate shunt pathway. This propionate-dependent mechanism requires
and is referred to as 'B12-mechanism-I'. Here, we report that vitamin B12 represses the expression of Met/SAM cycle genes by a propionate-independent mechanism we refer to as 'B12-mechanism-II'. This mechanism is activated by perturbations in the Met/SAM cycle, genetically or due to low dietary vitamin B12. B12-mechanism-II requires
to activate Met/SAM cycle gene expression, the vitamin B12 transporter,
, and adjust influx and efflux of the cycle by activating
and repressing
, respectively. Taken together, Met/SAM cycle activity is sensed and transcriptionally adjusted to be in a tight metabolic regime.
In humans, mutations in D-2-hydroxyglutarate (D-2HG) dehydrogenase (D2HGDH) result in D-2HG accumulation, delayed development, seizures, and ataxia. While the mechanisms of 2HG-associated diseases ...have been studied extensively, the endogenous metabolism of D-2HG remains unclear in any organism. Here, we find that, in Caenorhabditis elegans, D-2HG is produced in the propionate shunt, which is transcriptionally activated when flux through the canonical, vitamin B12-dependent propionate breakdown pathway is perturbed. Loss of the D2HGDH ortholog, dhgd-1, results in embryonic lethality, mitochondrial defects, and the up-regulation of ketone body metabolism genes. Viability can be rescued by RNAi of hphd-1, which encodes the enzyme that produces D-2HG or by supplementing either vitamin B12 or the ketone bodies 3-hydroxybutyrate (3HB) and acetoacetate (AA). Altogether, our findings support a model in which C. elegans relies on ketone bodies for energy when vitamin B12 levels are low and in which a loss of dhgd-1 causes lethality by limiting ketone body production.
We employ light-induced double Bragg diffraction of delta-kick collimated Bose-Einstein condensates to create three symmetric Mach-Zehnder interferometers. They rely on (i) first-order, (ii) two ...successive first-order, and (iii) second-order processes which demonstrate the scalability of the corresponding momentum transfer. With respect to devices based on conventional Bragg scattering, these symmetric interferometers double the scale factor and feature a better suppression of noise and systematic uncertainties intrinsic to the diffraction process. Moreover, we utilize these interferometers as tiltmeters for monitoring their inclination with respect to gravity.
Breeding birds in North America's eastern and boreal forests have experienced significant population declines in recent decades due largely to habitat loss. The North American Great Lakes coastal ...zone provides critical stopover and breeding habitat for millions of migratory and resident birds with diverse life history traits. Extensive human land use in this region has resulted in significant forest loss. To understand how functional and taxonomic diversity of breeding bird communities have been affected by agriculture and urbanization in this region, we calculated measures of functional diversity, Shannon's diversity index, and species richness along a gradient of human land use intensity. We analyzed bird survey data collected at 2982 locations within 1 km of the shoreline where upland forest was the dominant habitat. We used hierarchical partitioning to determine the extent to which spatial confounding factors (i.e., broad climatic and biogeographic gradients across the five Great Lakes) accounted for observed differences in diversity measures, and then used fourth-corner analysis to describe the relationship between species, functional traits, and land cover types. Although spatial confounding factors accounted for some variation, functional evenness, species richness, and Shannon's diversity index declined significantly with increasing human land use. Species negatively associated with increasing human land use were those that eat primarily invertebrates by foraging on foliage or bark (75%) and species categorized as long-distance migrants (58%), which suggests increased vulnerability of forest-dependent species to habitat modification and reductions in habitat availability. Functional evenness declined with increasing human land use, while other measures of functional diversity (functional dispersion and Rao's quadratic entropy) remained relatively constant. Understanding the disconnect between functional and taxonomic diversity of bird assemblages and quantifying the degree of resilience of functional community properties is critical for predicting long-term effects of both habitat loss and ecological restoration on biodiversity and ecosystem function.
Species often exhibit regionally specific habitat associations, so habitat association models developed in one region might not be accurate or even appropriate for other regions. Three programs to ...survey wetland‐breeding birds covering (respectively) Great Lakes coastal wetlands, inland Great Lakes wetlands, and the Prairie Pothole Region offer an opportunity to test whether regionally specific models of habitat use by wetland‐obligate breeding birds are transferrable across regions. We first developed independent, regional population density models for four species of wetland‐obligate birds: Pied‐billed Grebe (Podilymbus podiceps), Virginia Rail (Rallus limicola), Sora (Porzana carolina), and American Bittern (Botaurus lentiginosus). We then used adjusted pseudo‐R2 values to compare the amount of variation explained by each model when applied to data collected in each of the three regions. Although certain habitat characteristics, such as emergent vegetation and wetland area, were consistently important across regions, models for each species differed by region—both in variables selected for inclusion and often in the directionality of relationships for common variables—indicating that habitat associations for these species are regionally specific. When we applied a model developed in one region to data collected in another region, we found that explanatory power was reduced in most (71%) models. Therefore, we suggest that ecological analyses should emphasize regionally specific habitat association models whenever possible. Nonetheless, models created from inland Great Lakes wetland data had higher median explanatory power when applied to other regions, and the amount of explanatory power lost by other transferred models was relatively small. Thus, while regionally specific habitat association models are preferable, in the absence of reliable regional data, habitat association models developed in one region may be applied to another region, but the results need to be cautiously interpreted. Additionally, we found that median explanatory power was higher when local‐scale habitat characteristics were included in the models, indicating that regionally specific models should ideally be based on a combination of local‐ and landscape‐scale habitat characteristics. Conservation practitioners can leverage such regionally specific models and associated monitoring data to help prioritize areas for management activities that contribute to regional conservation efforts.
Vitamin B12 functions as a cofactor for methionine synthase to produce the anabolic methyl donor S-adenosylmethionine (SAM) and for methylmalonyl-CoA mutase to catabolize the short-chain fatty acid ...propionate. In the nematode Caenorhabditis elegans, maternally supplied vitamin B12 is required for the development of offspring. However, the mechanism for exporting vitamin B12 from the mother to the offspring is not yet known. Here, we use RNAi of more than 200 transporters with a vitamin B12-sensor transgene to identify the ABC transporter MRP-5 as a candidate vitamin B12 exporter. We show that the injection of vitamin B12 into the gonad of mrp-5 deficient mothers rescues embryonic lethality in the offspring. Altogether, our findings identify a maternal mechanism for the transit of an essential vitamin to support the development of the next generation.
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•ABC transporter MRP-5 transports vitamin B12 from mother to offspring in C. elegans•mrp-5 mutant embryonic lethality is rescued by vitamin B12 injection into gonad•RNAi of mrp-5 reduces S-adenosylmethionine and methionine content in F1 embryos
How dietary vitamin B12 is transported from the mother to developing offspring is unknown. Na et al. demonstrate that the ABC transporter MRP-5 (multidrug resistance protein 5) transports vitamin B12 from the intestine of C. elegans mothers to the offspring to promote embryonic viability and development
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