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| 2. |
- Dahlqvist, Martin, et al.
(författare)
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Complex magnetism in nanolaminated Mn2GaC
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have used first-principles calculations and Heisenberg Monte Carlo simulations to search for the magnetic ground state of Mn2GaC, a recently synthesized magnetic nanolaminate. We have, independent on method, identified a range of low energy collinear as well as non-collinear magnetic configurations, indicating a highly frustrated magnetic material with several nearly degenerate magnetic states. An experimentally obtained magnetization of only 0.29 per Mn atom in Mn2GaC may be explained by canted spins in an antiferromagnetic configuration of ferromagnetically ordered sub-layers with alternating spin orientation, denoted AFM[0001]. Furthermore, low temperature X-ray diffraction show a new basal plane peak appearing upon a magnetic transition, which is consistent with the here predicted change in inter-layer spacing for the AFM[0001] configuration.
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| 3. |
- Freitas, Flavio L. M., 1986-, et al.
(författare)
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Recent political development threaten terrestrial mammal diversity in Brazil
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Recent political developments may weaken the legal protection of native vegetation in Brazil, which holds large areas of high biodiversity value. We assess the extent to which legislation protects terrestrial mammal species in Brazil. To this end, we quantify the natural population of mammal species in each fragment of native vegetation and relating this quantification to relevant legislation. We also assess the urgency of interventions to improve the protection of the mammal species. The results indicate that the legislation concerning private and public lands protects at least 40%, and about one-third, of the habitats where half of the threatened mammal species live, respectively. In scenarios of full compliance with relevant legislation, at least 40% of habitats supporting about one-third of these species are unprotected or undesignated lacking command and control regulations protecting the native vegetation. The implications of these results are discussed in light of recent policy developments in Brazil.
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| 4. |
- Persson, Anders, 1982-, et al.
(författare)
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Low-frequency noise in planar Hall effect bridge sensors
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The low-frequency characteristics of planar Hall effect bridge sensors are investigated as function of the sensor bias current and the applied magnetic field. The noise spectra reveal a Johnson-like spectrum at high frequencies, and a 1/f-like excess noise spectrum at lower frequencies, with a knee frequency of around 400 Hz. The 1/f-like excess noise can be described by the phenomenological Hooge equation with a Hooge parameter of gH=0.016. The detectivity is shown to depend on the total length, width and thickness of the bridge branches. Increasing the total length by a factor of 10 improves the detectivity by a factor of 101/2. Moreover, the detectivity is shown to depend on the amplitude of the applied magnetic field, revealing a magnetic origin to part of the 1/f noise.
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| 5. |
- Persson, Anders, 1982-, et al.
(författare)
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Low-frequency picotesla field detection with planar Hall effect bridge sensors
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The applicability of miniaturized magnetic field sensors are being explored in several fields of magnetic field detection, due to their integratability, low mass, and potentially low cost. In this respect, different thin-film technologies, especially those employing magnetoresistance, show great potential, being compatible with micro- and nanotechnology batch processing. For low-frequency magnetic field detection, sensors based on the planar Hall effect, especially planar Hall effect bridge (PHEB) sensors, show promising performance given their inherent low-field linearity, limited hysteresis and moderate noise figure. In this work, the applicability of such PHEB sensors to different areas is investigated. An analytical model was constructed, to estimate the performance of an arbitrary PHEB in terms of e.g. sensitivity and detectivity. The model incorporates a number of approximations and, to validate the results, modelled data is compared to measurements on actual PHEBs. It is concluded that the model slightly underestimated the detectivity, especially at low frequencies and when demagnetizing effects becomes apparent. The model is also sensitive to fabrication process induced variations of the material parameters of the sensors. Nevertheless, accounting for these discrepancies, the modelled data is typically within 10% from the experimental data and the model can be used to estimate the performance of a particular PHEB design. The model is also used to establish a design process for optimizing a PHEB to a particular set of requirements on the bandwidth, detectivity, compliance voltage and amplified signal-to-noise ratio. By applying this design process, the size, sensitivity, resistance, bias current and power consumption of the PHEB can be calculated. The model shows that PHEBs are applicable to several different science areas including archaeological surveying, satellite attitude determination, scientific space missions, and magnetic bead detection in lab-on-a-chip applications.
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| 6. |
- Persson, Tomas, et al.
(författare)
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Amino acid metabolism in roots and actinorhizal nodules from Alnus glutinosa and Datisca glomerata: γ-aminobutyric acid and β-alanine are important metabolites
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Roots and nodules of the actinorhizal plants Alnus glutinosa and Datisca glomerata, as well as Frankia alni ACN14a grown in minimal and ammonium supplemented media, were analyzed for amino acid profiles. To analyze nitrogen and carbon metabolism, the transcriptome in nodules of the microsymbiont of D. glomerata, Frankia datiscae Dg1, was sequenced and compared with transcriptome data from symbiotic F. alni ACN14a (Alloisio et al. 2011). The amino acid profile of A. glutinosa roots suggests that Citrulline, Asparagine and Glutamine are transported in the xylem. Moreover, the comparatively high concentration of γ-aminobutyric acid in A. glutinosa roots suggest that this compound has a function in plant nitrogen metabolism. γ-aminobutyric acid could, as was suggested for the legume symbiosis, act as a signal factor for the plant nitrogen status to symbiotic Frankia. It could also be imported by the bacteria as a carbon and nitrogen source. Moreover, the expression of the gene for the enzyme catalyzing β-Alanine synthesis was elevated in both Frankia strains in symbiosis. Elevated concentrations of β-Alanine in nodules of D. glomerata and A. glutinosa compared to roots suggest that β-Alanine is produced by the bacteria in large amounts, possibly as a storage compound for Coenzyme A production.
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