| 1. |
- Kuehne, P, et al.
(författare)
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Polarization Selection Rules for Inter-Landau-Level Transitions in Epitaxial Graphene Revealed by the Infrared Optical Hall Effect
- 2013
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 111:7, s. e077402-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the polarization selection rules of inter-Landau-level transitions using reflection-type optical Hall effect measurements from 600 to 4000 cm-1 on epitaxial graphene grown by thermal decomposition of silicon carbide. We observe symmetric and antisymmetric signatures in our data due to polarization preserving and polarization mixing inter-Landau-level transitions, respectively. From field-dependent measurements, we identify that transitions in coupled graphene monolayers are governed by polarization mixing selection rules, whereas transitions in decoupled graphene monolayers are governed by polarization preserving selection rules. The selection rules may find explanation by different coupling mechanisms of inter-Landau-level transitions with free charge carrier magneto-optic plasma oscillations.
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| 2. |
- Yi, Chuixiang, et al.
(författare)
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Climate control of terrestrial carbon exchange across biomes and continents
- 2010
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid-and high-latitudes, (2) a strong function of dryness at mid-and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45 degrees N). The sensitivity of NEE to mean annual temperature breaks down at similar to 16 degrees C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence.
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| 3. |
- Bhatt, Uma S., et al.
(författare)
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Implications of Arctic Sea Ice Decline for the Earth System
- 2014
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Ingår i: Annual Review of Environment and Resources. - : Annual Reviews. - 1545-2050 .- 1543-5938. ; 39, s. 57-57
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Forskningsöversikt (refereegranskat)abstract
- Arctic sea ice decline has led to an amplification of surface warming and is projected to continue to decline from anthropogenic forcing, although the exact timing of ice-free summers is uncertain owing to large natural variability. Sea ice reductions affect surface heating patterns and the atmospheric pressure distribution, which may alter midlatitude extreme weather patterns. Increased light penetration and nutrient availability during spring from earlier ice breakup enhances primary production in the Arctic Ocean and its adjacent shelf seas. Ice-obligate marine mammals may be losers, whereas seasonally migrant species may be winners from rapid sea ice decline. Tundra greening is occurring across most of the Arctic, driven primarily by warming temperatures, and is displaying complex spatial patterns that are likely tied to other factors. Sea ice changes are affecting greenhouse gas exchanges as well as halogen chemistry in the Arctic. This review highlights the heterogeneous nature of Arctic change, which is vital for researchers to better understand.
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| 4. |
- Davenport, Simon C., et al.
(författare)
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Spin-singlet Gaffnian wave function for fractional quantum Hall systems
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:4, s. 045310-
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Tidskriftsartikel (refereegranskat)abstract
- We characterize in detail a wave function conceivable in fractional quantum Hall systems where a spin or equivalent degree of freedom is present. This wave function combines the properties of two previously proposed quantum Hall wave functions, namely the non-Abelian spin-singlet state and the nonunitary Gaffnian wave function. This is a spin-singlet generalization of the spin-polarized Gaffnian, which we call the "spin-singlet Gaffnian" (SSG). In this paper we present evidence demonstrating that the SSG corresponds to the ground state of a certain local Hamiltonian, which we explicitly construct, and, further, we provide a relatively simple analytic expression for the unique ground-state wave functions, which we define as the zero energy eigenstates of that local Hamiltonian. In addition, we have determined a certain nonunitary, rational conformal field theory which provides an underlying description of the SSG and we thus conclude that the SSG is ungapped in the thermodynamic limit. In order to verify our construction, we implement two recently proposed techniques for the analysis of fractional quantum Hall trial states: The "spin dressed squeezing algorithm," and the "generalized Pauli principle."
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| 5. |
- Gils, C., et al.
(författare)
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Anyonic quantum spin chains : Spin-1 generalizations and topological stability
- 2013
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 87:23, s. 235120-
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Tidskriftsartikel (refereegranskat)abstract
- There are many interesting parallels between systems of interacting non-Abelian anyons and quantum magnetism occurring in ordinary SU(2) quantum magnets. Here we consider theories of so-called SU(2)(k) anyons, well-known deformations of SU(2), in which only the first k + 1 angular momenta of SU(2) occur. In this paper, we discuss in particular anyonic generalizations of ordinary SU(2) spin chains with an emphasis on anyonic spin S = 1 chains. We find that the overall phase diagrams for these anyonic spin-1 chains closely mirror the phase diagram of the ordinary bilinear-biquadratic spin-1 chain including anyonic generalizations of the Haldane phase, the AKLT construction, and supersymmetric quantum critical points. A novel feature of the anyonic spin-1 chains is an additional topological symmetry that protects the gapless phases. Distinctions further arise in the form of an even/odd effect in the deformation parameter k when considering su(2)(k) anyonic theories with k >= 5, as well as for the special case of the su(2)(4) theory for which the spin-1 representation plays a special role. We also address anyonic generalizations of spin-1/2 chains with a focus on the topological protection provided for their gapless ground states. Finally, we put our results into the context of earlier generalizations of SU(2) quantum spin chains, in particular so-called (fused) Temperley-Lieb chains.
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| 6. |
- Niimi, Jun, et al.
(författare)
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Aroma-taste interactions between a model cheese aroma and five basic tastes in solution
- 2014
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Ingår i: Food Quality and Preference. - : Elsevier BV. - 0950-3293 .- 1873-6343. ; 31:1
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Tidskriftsartikel (refereegranskat)abstract
- The flavour perception of cheese results from complex sensory interactions between tastes and aromas. Using a model cheese solution, this study investigated perceived interactions between each of five basic tastes and a cheese aroma mixture containing ten volatile compounds commonly found in cheese. The five tastes - sucrose (sweetness), sodium chloride (NaCl) (saltiness), monosodium glutamate (MSG) (umami), lactic acid (sourness), and caffeine (bitterness) - were individually mixed with cheese aroma in water using a 5 taste level (0.2 log series) by 3 aroma level (0.5 log series) design. Aroma controls with no added taste were also included. This resulted in 18 samples for each single taste-aroma combination. An additional 18 samples were produced using a mixture of all 5 tastes with the 3 aroma levels. A panel of trained assessors (n=10) evaluated cheese flavour intensity and taste intensity using 100 point line scales. Evaluation was carried out in duplicate, with samples grouped by taste type; 1 evaluation session per taste per replicate. Within type, order of presentation was balanced, and taste type order was randomised between replicates. Cheese flavour intensity was enhanced by sucrose and NaCl, while being suppressed by lactic acid. NaCl enhanced cheese flavour intensity the most at high aroma level, while lactic acid suppressed the most at low aroma level. When MSG level was increased, cheese flavour intensity was enhanced at both low and medium aroma levels, but was suppressed at the high aroma level. The greatest enhancement of cheese flavour intensity was found with the mixture of 5 tastes. Aroma significantly enhanced umami and bitterness, but did not enhance sweetness, saltiness, or sourness. This study showed that the perceived interaction between taste and cheese aroma depended on taste type and on the concentration levels of both taste type and aroma. The mixture of tastes was more effective at enhancing cheese flavour intensity than single tastes. This study provides knowledge that will underpin further study of taste-aroma interactions in a model cheese that aims to optimise cheese flavour intensity and character.
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| 7. |
- Niimi, Jun, et al.
(författare)
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Cheddar cheese taste can be reconstructed in solution using basic tastes
- 2014
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Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946 .- 1879-0143. ; 34:1, s. 116-124
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Tidskriftsartikel (refereegranskat)abstract
- The taste of cheese contributes to flavour character directly and by cross-modal interactions with aroma. However, the relative contribution of specific tastes, i.e., sweet, salt, umami, sour, and bitter, is not well understood. Twelve cheeses were profiled by a trained sensory panel and the five tastes shown to significantly differ in intensity. Sucrose, NaCl, monosodium glutamate, lactic acid, and caffeine were mixed in water and adjusted using a 25-1 fractional factorial design (FFD) to reconstruct cheese taste; the optimised construct was compared with a Cheddar cheese to measure similarity for each taste type. The FFD provided knowledge of taste-taste interactions and aided the reconstruction of the taste profile of Cheddar cheese in solution. The reconstructed cheese solution did not significantly differ in overall intensity, saltiness, sourness, umami, and bitterness from the Cheddar cheese based on chi-squared tests. Sweetness was a difficult attribute to adjust due to its relatively low intensity.
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| 8. |
- Niimi, Jun, et al.
(författare)
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Cross-modal interaction between cheese taste and aroma
- 2014
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Ingår i: International Dairy Journal. - : Elsevier Ltd. - 0958-6946 .- 1879-0143. ; 39:2, s. 222-228
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Tidskriftsartikel (refereegranskat)abstract
- The relative contributions of taste and aroma to the perception of cheese flavour intensity were investigated using a simultaneous gustometer olfactometer. Within a mixture of five tastes and a multicomponent aroma that had a mature Cheddar cheese character, the levels of NaCl, monosodium glutamate (MSG), lactic acid, and aroma were varied according to a 24 full factorial design, all with appropriate controls. NaCl, lactic acid, and aroma significantly contributed to cheese flavour intensity while MSG did not. The contribution of NaCl, lactic acid, and aroma revealed their potential to enhance cheese flavour intensity. These variables were able to compensate each other towards cheese flavour intensity. Changing the levels of taste and aroma together influenced the cheese flavour intensity greater than changing the levels of a single taste or aroma only. Variation in tastant concentration had a larger effect on cheese flavour intensity than did aroma.
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| 9. |
- Punta, Marco, et al.
(författare)
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The Pfam protein families database
- 2012
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Ingår i: Nucleic Acids Research. - : Oxford University Press (OUP). - 0305-1048 .- 1362-4962. ; 40:D1, s. D290-D301
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Tidskriftsartikel (refereegranskat)abstract
- Pfam is a widely used database of protein families, currently containing more than 13 000 manually curated protein families as of release 26.0. Pfam is available via servers in the UK (http://pfam.sanger.ac.uk/), the USA (http://pfam.janelia.org/) and Sweden (http://pfam.sbc.su.se/). Here, we report on changes that have occurred since our 2010 NAR paper (release 24.0). Over the last 2 years, we have generated 1840 new families and increased coverage of the UniProt Knowledgebase (UniProtKB) to nearly 80%. Notably, we have taken the step of opening up the annotation of our families to the Wikipedia community, by linking Pfam families to relevant Wikipedia pages and encouraging the Pfam and Wikipedia communities to improve and expand those pages. We continue to improve the Pfam website and add new visualizations, such as the 'sunburst' representation of taxonomic distribution of families. In this work we additionally address two topics that will be of particular interest to the Pfam community. First, we explain the definition and use of family-specific, manually curated gathering thresholds. Second, we discuss some of the features of domains of unknown function (also known as DUFs), which constitute a rapidly growing class of families within Pfam.
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