366 research outputs found
Estimates of fire emissions from an active deforestation region in the southern Amazon based on satellite data and biogeochemical modelling
Tropical deforestation contributes to the build-up of atmospheric carbon dioxide in the atmosphere. Within the deforestation process, fire is frequently used to eliminate biomass in preparation for agricultural use. Quantifying these deforestation-induced fire emissions represents a challenge, and current estimates are only available at coarse spatial resolution with large uncertainty. Here we developed a biogeochemical model using remote sensing observations of plant productivity, fire activity, and deforestation rates to estimate emissions for the Brazilian state of Mato Grosso during 2001–2005. Our model of DEforestation CArbon Fluxes (DECAF) runs at 250-m spatial resolution with a monthly time step to capture spatial and temporal heterogeneity in fire dynamics in our study area within the ''arc of deforestation'', the southern and eastern fringe of the Amazon tropical forest where agricultural expansion is most concentrated. Fire emissions estimates from our modelling framework were on average 90 Tg C year<sup>&minus;1</sup>, mostly stemming from fires associated with deforestation (74%) with smaller contributions from fires from conversions of Cerrado or pastures to cropland (19%) and pasture fires (7%). In terms of carbon dynamics, about 80% of the aboveground living biomass and litter was combusted when forests were converted to pasture, and 89% when converted to cropland because of the highly mechanized nature of the deforestation process in Mato Grosso. The trajectory of land use change from forest to other land uses often takes more than one year, and part of the biomass that was not burned in the dry season following deforestation burned in consecutive years. This led to a partial decoupling of annual deforestation rates and fire emissions, and lowered interannual variability in fire emissions. Interannual variability in the region was somewhat dampened as well because annual emissions from fires following deforestation and from maintenance fires did not covary, although the effect was small due to the minor contribution of maintenance fires. Our results demonstrate how the DECAF model can be used to model deforestation fire emissions at relatively high spatial and temporal resolutions. Detailed model output is suitable for policy applications concerned with annual emissions estimates distributed among post-clearing land uses and science applications in combination with atmospheric emissions modelling to provide constrained global deforestation fire emissions estimates. DECAF currently estimates emissions from fire; future efforts can incorporate other aspects of net carbon emissions from deforestation including soil respiration and regrowth
Global fire emissions and the contribution of deforestation, savanna, forest, agricultural, and peat fires (1997-2009)
New burned area datasets and top-down constraints from atmospheric
concentration measurements of pyrogenic gases have decreased the large
uncertainty in fire emissions estimates. However, significant gaps remain in
our understanding of the contribution of deforestation, savanna, forest,
agricultural waste, and peat fires to total global fire emissions. Here we
used a revised version of the Carnegie-Ames-Stanford-Approach (CASA)
biogeochemical model and improved satellite-derived estimates of area
burned, fire activity, and plant productivity to calculate fire emissions
for the 1997–2009 period on a 0.5° spatial resolution with a monthly
time step. For November 2000 onwards, estimates were based on burned area,
active fire detections, and plant productivity from the MODerate resolution
Imaging Spectroradiometer (MODIS) sensor. For the partitioning we focused on
the MODIS era. We used maps of burned area derived from the Tropical Rainfall
Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS) and Along-Track
Scanning Radiometer (ATSR) active fire data prior to MODIS (1997–2000) and
estimates of plant productivity derived from Advanced Very High Resolution
Radiometer (AVHRR) observations during the same period. Average global fire
carbon emissions according to this version 3 of the Global Fire Emissions
Database (GFED3) were 2.0 Pg C year<sup>−1</sup> with significant interannual
variability during 1997–2001 (2.8 Pg C year<sup>−1</sup> in 1998 and
1.6 Pg C year<sup>−1</sup> in 2001). Globally, emissions during 2002–2007 were relatively
constant (around 2.1 Pg C year<sup>−1</sup>) before declining in 2008
(1.7 Pg C year<sup>−1</sup>) and 2009 (1.5 Pg C year<sup>−1</sup>) partly due to lower deforestation
fire emissions in South America and tropical Asia. On a regional basis,
emissions were highly variable during 2002–2007 (e.g., boreal Asia, South
America, and Indonesia), but these regional differences canceled out at a
global level. During the MODIS era (2001–2009), most carbon emissions were
from fires in grasslands and savannas (44%) with smaller contributions
from tropical deforestation and degradation fires (20%), woodland fires
(mostly confined to the tropics, 16%), forest fires (mostly in the
extratropics, 15%), agricultural waste burning (3%), and tropical peat
fires (3%). The contribution from agricultural waste fires was likely a
lower bound because our approach for measuring burned area could not detect
all of these relatively small fires. Total carbon emissions were on average
13% lower than in our previous (GFED2) work. For reduced trace gases such
as CO and CH<sub>4</sub>, deforestation, degradation, and peat fires were more
important contributors because of higher emissions of reduced trace gases
per unit carbon combusted compared to savanna fires. Carbon emissions from
tropical deforestation, degradation, and peatland fires were on average 0.5 Pg C year<sup>−1</sup>.
The carbon emissions from these fires may not be balanced
by regrowth following fire. Our results provide the first global assessment
of the contribution of different sources to total global fire emissions for
the past decade, and supply the community with an improved 13-year fire
emissions time series
Severity of cardiomyopathy associated with adenine nucleotide translocator-1 deficiency correlates with mtDNA haplogroup
Mutations of both nuclear and mitochondrial DNA (mtDNA)-encoded mitochondrial proteins can cause cardiomyopathy associated with mitochondrial dysfunction. Hence, the cardiac phenotype of nuclear DNA mitochondrial mutations might be modulated by mtDNA variation. We studied a 13-generation Mennonite pedigree with autosomal recessive myopathy and cardiomyopathy due to an SLC25A4 frameshift null mutation (c.523delC, p.Q175RfsX38), which codes for the heart-muscle isoform of the adenine nucleotide translocator-1. Ten homozygous null (adenine nucleotide translocator-1(-/-)) patients monitored over a median of 6 years had a phenotype of progressive myocardial thickening, hyperalaninemia, lactic acidosis, exercise intolerance, and persistent adrenergic activation. Electrocardiography and echocardiography with velocity vector imaging revealed abnormal contractile mechanics, myocardial repolarization abnormalities, and impaired left ventricular relaxation. End-stage heart disease was characterized by massive, symmetric, concentric cardiac hypertrophy; widespread cardiomyocyte degeneration; overabundant and structurally abnormal mitochondria; extensive subendocardial interstitial fibrosis; and marked hypertrophy of arteriolar smooth muscle. Substantial variability in the progression and severity of heart disease segregated with maternal lineage, and sequencing of mtDNA from five maternal lineages revealed two major European haplogroups, U and H. Patients with the haplogroup U mtDNAs had more rapid and severe cardiomyopathy than those with haplogroup H
Hyperfine structure of the ground state muonic He-3 atom
On the basis of the perturbation theory in the fine structure constant
and the ratio of the electron to muon masses we calculate one-loop
vacuum polarization and electron vertex corrections and the nuclear structure
corrections to the hyperfine splitting of the ground state of muonic helium
atom . We obtain total result for the ground state hyperfine
splitting MHz which improves the previous
calculation of Lakdawala and Mohr due to the account of new corrections of
orders and . The remaining difference between our
theoretical result and experimental value of the hyperfine splitting lies in
the range of theoretical and experimental errors and requires the subsequent
investigation of higher order corrections.Comment: Talk on poster section of XXIV spectroscopy congress, 28 February-5
March 2010, Moscow-Troitsk, Russia, 21 pages, LaTeX, 8 figure
Thinner bark increases sensitivity of wetter Amazonian tropical forests to fire
Understory fires represent an accelerating threat to Amazonian tropical forests and can, during drought, affect larger areas than deforestation itself. These fires kill trees at rates varying from < 10 to c. 90% depending on fire intensity, forest disturbance history and tree functional traits. Here, we examine variation in bark thickness across the Amazon. Bark can protect trees from fires, but it is often assumed to be consistently thin across tropical forests. Here, we show that investment in bark varies, with thicker bark in dry forests and thinner in wetter forests. We also show that thinner bark translated into higher fire‐driven tree mortality in wetter forests, with between 0.67 and 5.86 gigatonnes CO2 lost in Amazon understory fires between 2001 and 2010. Trait‐enabled global vegetation models that explicitly include variation in bark thickness are likely to improve the predictions of fire effects on carbon cycling in tropical forests
Interferometric Bell-state preparation using femtosecond-pulse-pumped Spontaneous Parametric Down-Conversion
We present theoretical and experimental study of preparing maximally
entangled two-photon polarization states, or Bell states, using femtosecond
pulse pumped spontaneous parametric down-conversion (SPDC). First, we show how
the inherent distinguishability in femtosecond pulse pumped type-II SPDC can be
removed by using an interferometric technique without spectral and amplitude
post-selection. We then analyze the recently introduced Bell state preparation
scheme using type-I SPDC. Theoretically, both methods offer the same results,
however, type-I SPDC provides experimentally superior methods of preparing Bell
states in femtosecond pulse pumped SPDC. Such a pulsed source of highly
entangled photon pairs is useful in quantum communications, quantum
cryptography, quantum teleportation, etc.Comment: 11 pages, two-column format, to appear in PR
Academic requirements for Certificate of Completion of Training in surgical training: Consensus recommendations from the Association of Surgeons in Training/National Research Collaborative Consensus Group.
BACKGROUND: Surgical trainees are expected to demonstrate academic achievement in order to obtain their certificate of completion of training (CCT). These standards are set by the Joint Committee on Surgical Training (JCST) and specialty advisory committees (SAC). The standards are not equivalent across all surgical specialties and recognise different achievements as evidence. They do not recognise changes in models of research and focus on outcomes rather than process. The Association of Surgeons in Training (ASiT) and National Research Collaborative (NRC) set out to develop progressive, consistent and flexible evidence set for academic requirements at CCT. METHODS: A modified-Delphi approach was used. An expert group consisting of representatives from the ASiT and the NRC undertook iterative review of a document proposing changes to requirements. This was circulated amongst wider stakeholders. After ten iterations, an open meeting was held to discuss these proposals. Voting on statements was performed using a 5-point Likert Scale. Each statement was voted on twice, with ≥80% of votes in agreement meaning the statement was approved. The results of this vote were used to propose core and optional academic requirements for CCT. RESULTS: Online discussion concluded after ten rounds. At the consensus meeting, statements were voted on by 25 delegates from across surgical specialties and training-grades. The group strongly favoured acquisition of 'Good Clinical Practice' training and research methodology training as CCT requirements. The group agreed that higher degrees, publications in any author position (including collaborative authorship), recruiting patients to a study or multicentre audit and presentation at a national or international meeting could be used as evidence for the purpose of CCT. The group agreed on two essential 'core' requirements (GCP and methodology training) and two of a menu of four 'additional' requirements (publication with any authorship position, presentation, recruitment of patients to a multicentre study and completion of a higher degree), which should be completed in order to attain CCT. CONCLUSION: This approach has engaged stakeholders to produce a progressive set of academic requirements for CCT, which are applicable across surgical specialties. Flexibility in requirements whilst retaining a high standard of evidence is desirable
Physics of Solar Prominences: I - Spectral Diagnostics and Non-LTE Modelling
This review paper outlines background information and covers recent advances
made via the analysis of spectra and images of prominence plasma and the
increased sophistication of non-LTE (ie when there is a departure from Local
Thermodynamic Equilibrium) radiative transfer models. We first describe the
spectral inversion techniques that have been used to infer the plasma
parameters important for the general properties of the prominence plasma in
both its cool core and the hotter prominence-corona transition region. We also
review studies devoted to the observation of bulk motions of the prominence
plasma and to the determination of prominence mass. However, a simple inversion
of spectroscopic data usually fails when the lines become optically thick at
certain wavelengths. Therefore, complex non-LTE models become necessary. We
thus present the basics of non-LTE radiative transfer theory and the associated
multi-level radiative transfer problems. The main results of one- and
two-dimensional models of the prominences and their fine-structures are
presented. We then discuss the energy balance in various prominence models.
Finally, we outline the outstanding observational and theoretical questions,
and the directions for future progress in our understanding of solar
prominences.Comment: 96 pages, 37 figures, Space Science Reviews. Some figures may have a
better resolution in the published version. New version reflects minor
changes brought after proof editin
- …