30,896 research outputs found
Contributions of biomass/biofuel burning to organic aerosols and particulate matter in Tanzania, East Africa, based on analyses of ionic species, organic and elemental carbon, levoglucosan and mannosan
Atmospheric aerosol samples of PM<sub>2.5</sub> and PM<sub>10</sub> were collected at a rural site in Tanzania, East Africa, in 2011 during wet and dry seasons and were analysed for carbonaceous components, levoglucosan, mannosan and water-soluble inorganic ions. The contributions of biomass/biofuel burning to the organic carbon (OC) and particulate matter (PM) mass were estimated to be 46–52% and 87–13%, respectively. The mean mass concentrations of PM<sub>2.5</sub> and PM<sub>10</sub> were 28 ± 6 ÎŒg m<sup>â3</sup> and 47 ± 8 ÎŒg m<sup>â3</sup> in wet season, and 39 ± 10 ÎŒg m<sup>â3</sup> and 61 ± 19 ÎŒg m<sup>â3</sup> in dry season, respectively. Total carbon (TC) accounted for 16–19% of the PM<sub>2.5</sub> mass and 13–15% of the PM<sub>10</sub> mass. On average, 86 to 89% of TC in PM<sub>2.5</sub> and 87 to 90% of TC in PM<sub>10</sub> was OC, of which 67–72% and 63% was found to be water-soluble organic carbon (WSOC) in PM<sub>2.5</sub> and PM<sub>10</sub>, respectively. We found that concentrations of levoglucosan and mannosan (specific organic tracers of pyrolysis of cellulose) well correlated with non-sea-salt potassium (nss-K<sup>+</sup>) (<i>r</i><sup>2</sup> = 0.56–0.75), OC (<i>r</i><sup>2</sup> = 0.75–0.96) and WSOC (<i>r</i><sup>2</sup> = 0.52–0.78). The K<sup>+</sup> / OC ratios varied from 0.06 to 0.36 in PM<sub>2.5</sub> and from 0.03 to 0.36 in PM<sub>10</sub> with slightly higher ratios in dry season. Mean percent ratios of levoglucosan and mannosan to OC were found to be 3–4% for PM<sub>2.5</sub> and PM<sub>10</sub> in both seasons. We found lower levoglucosan / K<sup>+</sup> ratios and higher K<sup>+</sup> / EC (elemental carbon) ratios in the biomass-burning aerosols from Tanzania than those reported from other regions. This feature is consistent with the high levels of potassium reported in the soils of Morogoro, Tanzania, suggesting an importance of direct emission of potassium by soil resuspension although K<sup>+</sup> is present mostly in fine particles. It is also likely that biomass burning of vegetation of Tanzania emits high levels of potassium that may be enriched in plant tissues. The present study demonstrates that emissions from mixed biomass- and biofuel-burning activities largely influence the air quality in Tanzania
Decoupling of Layers in the Three-dimensional Abelian Higgs Model
The Abelian Higgs model with anisotropic couplings in 2+1 dimensions is
studied in both the compact and non-compact formulations. Decoupling of the
space-like planes takes place in the extreme anisotropic limit, so charged
particles and gauge fields are presumably localized within these planes. The
behaviour of the model under the influence of an external magnetic field is
examined in the compact case and yields further characterization of the phases.Comment: 23 pages, 12 figures, plain late
L-functions of Symmetric Products of the Kloosterman Sheaf over Z
The classical -variable Kloosterman sums over the finite field
give rise to a lisse -sheaf on , which we call the Kloosterman
sheaf. Let be the
-function of the -fold symmetric product of . We
construct an explicit virtual scheme of finite type over such that the -Euler factor of the zeta function of coincides with
. We also prove
similar results for and .Comment: 16 page
Layered Higgs Phase as a Possible Field Localisation on a Brane
So far it has been found by using lattice techniques that in the anisotropic
five--dimensional Abelian Higgs model, a layered Higgs phase exists in addition
to the expected five--dimensional one. The exploration of the phase diagram has
shown that the two Higgs phases are separated by a phase transition from the
confining phase. This transition is known to be first order. In this paper we
explore the possibility of finding a second order transition point in the
critical line which separates the first order phase transition from the
crossover region. This is shown to be the case only for the four--dimensional
Higgs layered phase whilst the phase transition to the five--dimensional broken
phase remains first order. The layered phase serves as the possible realisation
of four--dimensional spacetime dynamics which is embedded in a
five--dimensional spacetime. These results are due to gauge and scalar field
localisation by confining interactions along the extra fifth direction.Comment: 1+15 pages, 12 figure
Using Moran's I and GIS to study the spatial pattern of forest litter carbon density in a subtropical region of southeastern China
Spatial pattern information of carbon density in forest ecosystem including
forest litter carbon (FLC) plays an important role in evaluating carbon
sequestration potentials. The spatial variation of FLC
density in the typical subtropical forests in southeastern China was
investigated using Moran's I, geostatistics and a geographical information
system (GIS). A total of 839 forest litter samples were collected based on a
12 km (southânorth) Ă 6 km (eastâwest) grid system in Zhejiang
province. Forest litter carbon density values were very variable, ranging
from 10.2 kg ha<sup>â1</sup> to 8841.3 kg ha<sup>â1</sup>, with an average of
1786.7 kg ha<sup>â1</sup>. The aboveground biomass had the strongest positive correlation
with FLC density, followed by forest age and elevation. Global Moran's I
revealed that FLC density had significant positive spatial autocorrelation.
Clear spatial patterns were observed using local Moran's I. A spherical
model was chosen to fit the experimental semivariogram. The moderate
"nugget-to-sill" (0.536) value revealed that both natural and
anthropogenic factors played a key role in spatial heterogeneity of FLC
density. High FLC density values were mainly distributed in northwestern and
western part of Zhejiang province, which were related to adopting long-term
policy of forest conservation in these areas, while Hang-Jia-Hu (HJH) Plain,
Jin-Qu (JQ) Basin and coastal areas had low FLC density due to low forest
coverage and intensive management of economic forests. These spatial
patterns were in line with the spatial-cluster map described by local
Moran's I. Therefore, Moran's I, combined with geostatistics and GIS, could
be used to study spatial patterns of environmental variables related to
forest ecosystem
Properties of implanted and CVD incorporated nitrogen-vacancy centers: preferential charge state and preferential orientation
The combination of the long electron state spin coherence time and the optical coupling of the ground electronic states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate for quantum information processing. To date the best spin and optical properties have been found in centers deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties close to the diamond surface. We report on properties including charge state control and preferential orientation for near surface NVs formed either in CVD growth or through implantation and annealing
Quantum control without access to the controlling interaction
In our model a fixed Hamiltonian acts on the joint Hilbert space of a quantum
system and its controller. We show under which conditions measurements, state
preparations, and unitary implementations on the system can be performed by
quantum operations on the controller only.
It turns out that a measurement of the observable A and an implementation of
the one-parameter group exp(iAr) can be performed by almost the same sequence
of control operations. Furthermore measurement procedures for A+B, for (AB+BA),
and for i[A,B] can be constructed from measurements of A and B. This shows that
the algebraic structure of the set of observables can be explained by the Lie
group structure of the unitary evolutions on the joint Hilbert space of the
measuring device and the measured system.
A spin chain model with nearest neighborhood coupling shows that the border
line between controller and system can be shifted consistently.Comment: 10 pages, Revte
Signatures of personality on dense 3D facial images
It has long been speculated that cues on the human face exist that allow observers to make reliable judgments of others' personality traits. However, direct evidence of association between facial shapes and personality is missing from the current literature. This study assessed the personality attributes of 834 Han Chinese volunteers (405 males and 429 females), utilising the five-factor personality model ('Big Five'), and collected their neutral 3D facial images. Dense anatomical correspondence was established across the 3D facial images in order to allow high-dimensional quantitative analyses of the facial phenotypes. In this paper, we developed a Partial Least Squares (PLS) -based method. We used composite partial least squares component (CPSLC) to test association between the self-tested personality scores and the dense 3D facial image data, then used principal component analysis (PCA) for further validation. Among the five personality factors, agreeableness and conscientiousness in males and extraversion in females were significantly associated with specific facial patterns. The personality-related facial patterns were extracted and their effects were extrapolated on simulated 3D facial models
Coexistence of the topological state and a two-dimensional electron gas on the surface of Bi2Se3
Topological insulators are a recently discovered class of materials with
fascinating properties: While the inside of the solid is insulating,
fundamental symmetry considerations require the surfaces to be metallic. The
metallic surface states show an unconventional spin texture, electron dynamics
and stability. Recently, surfaces with only a single Dirac cone dispersion have
received particular attention. These are predicted to play host to a number of
novel physical phenomena such as Majorana fermions, magnetic monopoles and
unconventional superconductivity. Such effects will mostly occur when the
topological surface state lies in close proximity to a magnetic or electric
field, a (superconducting) metal, or if the material is in a confined geometry.
Here we show that a band bending near to the surface of the topological
insulator BiSe gives rise to the formation of a two-dimensional
electron gas (2DEG). The 2DEG, renowned from semiconductor surfaces and
interfaces where it forms the basis of the integer and fractional quantum Hall
effects, two-dimensional superconductivity, and a plethora of practical
applications, coexists with the topological surface state in BiSe. This
leads to the unique situation where a topological and a non-topological, easily
tunable and potentially superconducting, metallic state are confined to the
same region of space.Comment: 12 pages, 3 figure
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