616 research outputs found
Identifying The Start of Conflict: Conflict Recognition, Operational Realities and Accountability in the Post-9/11 World
On December 19, 2008, the Convening Authority for the United States Military Commissions at Guantanamo Bay referred charges against Abd al-Rahim Hussein Muhammed Abdu Al-Nashiri for his role in the October 2000 bombing of the U.S.S. Cole. The charge sheet alleged that al-Nashiri committed several actsâincluding murder in violation of the law of war, perfidy, destruction of propertyââin the context of and associated with armed conflictâ on or about October 12, 2000 in connection with the bombing. At the time of the attack, the statement that the United States was engaged in an armed conflict would have been a surprise to many. The Cole bombing was routinely called a âterrorist attackâ and the U.S. response involved numerous parallel investigations into, inter alia: identifying and finding those responsible for the attack; reviewing the actions of the commanding officer and crew of the U.S.S. Cole; and examining the vulnerabilities of U.S. forces abroad. And yet, in the aftermath of the 9/11 attacks and the U.S. military response to those attacks, manyâ including the U.S. government before the military commissionsâargued that the Cole bombing was âone of the opening salvos of the terrorist war on Americansâ3 and therefore part of the U.S. conflict with al-Qaeda. A look at these differing approaches to characterizing the U.S.S. Cole bombing and where it falls along the timeline of U.S. counterterrorism operations and contemporary armed conflicts highlights a significant uncertainty in our current understanding of the U.S. conflict with al-Qaeda: the question of when the conflict started. Most Americans would not have answered âyesâ if asked whether the United States was at war in 2000â but the rhetorical concept of a âwar on terrorâ has created a different perspective for some who now view pre-9/11 terrorist attacks, including the Cole bombing and the 1998 Embassy bombings in Kenya and Tanzania, as part of a coherent conflict. Similarly, our perspective on 9/11 itself, looking back thirteen years hence, is not necessarily the same as it was on the day of the attacks regarding whether America is at war. Many people doubtlessly felt that America was at war upon hearing of and seeing the attacks, but not in the manner or degree that Americans feel, or have been told, that we are in the years since that day. Uncertainty reigns over when this conflict actually started: did it begin on 9/11? When the United States launched its response in October 2001? With the bombing of the U.S.S. Cole? The 1998 Embassy bombings? With Osama bin Ladenâs 1996 declaration of war? Earlier than that? A complicated web of operational authority, prosecutorial decisions, and legal analysis has left this question unanswered and significantly murkier than might be expected
On the optical properties of carbon nanotubes--Part I. A general formula for the dynamical optical conductivity
This paper is the first one of a series of two articles in which we revisit
the optical properties of single-walled carbon nanotubes (SWNT). Produced by
rolling up a graphene sheet, SWNT owe their intriguing properties to their
cylindrical quasi-one-dimensional (quasi-1D) structure (the ratio length/radius
is experimentally of order of 10^3). We model SWNT by circular cylinders of
small diameters on the surface of which the conduction electron gas is confined
by the electric field generated by the fixed carbon ions. The pair-interaction
potential considered is the 3D Coulomb potential restricted to the cylinder. To
reflect the quasi-1D structure, we introduce a 1D effective many-body
Hamiltonian which is the starting-point of our analysis. To investigate the
optical properties, we consider a perturbation by a uniform time-dependent
electric field modeling an incident light beam along the longitudinal
direction. By using Kubo's method, we derive within the linear response theory
an asymptotic expansion in the low-temperature regime for the dynamical optical
conductivity at fixed density of particles. The leading term only involves the
eigenvalues and associated eigenfunctions of the (unperturbed) 1D effective
many-body Hamiltonian, and allows us to account for the sharp peaks observed in
the optical absorption spectrum of SWNT.Comment: Comments: 24 pages. Revised version. Accepted for publication in
J.M.
Developing a Model Framework for Predicting Effects of Woody Expansion and Fire on Ecosystem Carbon and Nitrogen in a Pinyon-Juniper Woodland
Sagebrush-steppe ecosystems are one of the most threatened ecosystems in North America due to woodland expansion, wildfire, and exotic annual grass invasion. Some scientists and policy makers have suggested that woodland expansion will lead to increased carbon (C) storage on the landscape. To assess this potential we used data collected from a Joint Fire Sciences Program demonstration area to develop a Microsoft Excelâą based biomass, carbon, and nitrogen (N) spreadsheet model. The model uses input for tree cover, soil chemistry, soil physical properties, and vegetation chemistry to estimate biomass, carbon, and nitrogen accumulation on the landscape with woodland expansion. The model also estimates C and N losses associated with prescribed burning. On our study plots we estimate in treeless sagebrush-steppe ecosystems, biomass accounts for 4.5 Mg haâ1 C and 0.3 Mg haâ1 N this is \u3c10% of total estimated ecosystem C and N to a soil depth of 53 cm, but as tree cover increases to near closed canopy conditions aboveground biomass may account for 62 Mg haâ1 C and 0.6 Mg haâ1 N which is nearly 53% of total estimated ecosystem C and 13% of total estimated ecosystem N to a soil depth of 53 cm. Prescribed burning removes aboveground biomass, C and N, but may increase soil C at areal tree cover below 26%. The model serves as a tool by which we are able to assess our understanding of the system and identify knowledge gaps which exist for this ecosystem. We believe that further work is necessary to quantify herbaceous biomass, root biomass, woody debris decomposition, and soil C and N with woodland expansion and prescribed fire. It will also be necessary to appropriately scale these estimates from the plot to the landscape
Influence of Prescribed Fire on Ecosystem Biomass, Carbon, and Nitrogen in a Pinyon Juniper Woodland
Increases in pinyon and juniper woodland cover associated with land-use history are suggested to provide offsets for carbon emissions in arid regions. However, the largest pools of carbon in arid landscapes are typically found in soils, and aboveground biomass cannot be considered long-term storage in fire-prone ecosystems. Also, the objectives of carbon storage may conflict with management for other ecosystem services and fuels reduction. Before appropriate decisions can be made it is necessary to understand the interactions between woodland expansion, management treatments, and carbon retention. We quantified effects of prescribed fire as a fuels reduction and ecosystem maintenance treatment on fuel loads, ecosystem carbon, and nitrogen in a pinyonâjuniper woodland in the central Great Basin. We found that plots containing 30% tree cover averaged nearly 40â000 kgâ·âhaâ1 in total aboveground biomass, 80â000 kgâ·âhaâ1 in ecosystem carbon (C), and 5â000 kgâ·âhaâ1 in ecosystem nitrogen (N). Only 25% of ecosystem C and 5% of ecosystem N resided in aboveground biomass pools. Prescribed burning resulted in a 65% reduction in aboveground biomass, a 68% reduction in aboveground C, and a 78% reduction in aboveground N. No statistically significant change in soil or total ecosystem C or N occurred. Prescribed fire was effective at reducing fuels on the landscape and resulted in losses of C and N from aboveground biomass. However, the immediate and long-term effects of burning on soil and total ecosystem C and N is still unclear
Hypochromic red cells as a prognostic indicator of survival among patients with systemic sclerosis screened for pulmonary hypertension
BACKGROUND: Patients with systemic sclerosis (SSc) are frequently affected by iron deficiency, particularly those with pulmonary hypertension (PH). The first data indicate the prognostic importance of hypochromic red cells (% HRC) > 2% among patients with PH. Hence, the objective of our study was to investigate the prognostic value of % HRC in SSc patients screened for PH.
METHODS: In this retrospective, single-center cohort study, SSc patients with a screening for PH were enrolled. Clinical characteristics and laboratory and pulmonary functional parameters associated with the prognosis of SSc were analyzed using uni- and multivariable analysis.
RESULTS: From 280 SSc patients screened, 171 could be included in the analysis having available data of iron metabolism (81% female, 60 ± 13 years of age, 77% limited cutaneous SSc, 65 manifest PH, and 73 pulmonary fibrosis). The patients were followed for 2.4 ± 1.8 (median 2.4) years. HRC > 2% at baseline was significantly associated with worse survival in the uni- (p = 0.018) and multivariable (p = 0.031) analysis independent from the presence of PH or pulmonary parenchymal manifestations. The combination of HRC > 2% and low diffusion capacity for carbon monoxide (DLCO) †65% predicted was significantly associated with survival (p < 0.0001).
CONCLUSION: This is the first study reporting that HRC > 2% is an independent prognostic predictor of mortality and can possibly be used as a biomarker among SSc patients. The combination of HRC > 2% and DLCO †65% predicted could serve in the risk stratification of SSc patients. Larger studies are required to confirm these findings
Woodland Expansion\u27s Influence on Belowground Carbon and Nitrogen in the Great Basin U.S.
Vegetation changes associated with climate shifts and anthropogenic disturbance can have major impacts on biogeochemical cycling and soils. Much of the Great Basin, U.S. is currently dominated by sagebrush (Artemisia tridentate (Rydb.) Boivin) ecosystems. Sagebrush ecosystems are increasingly influenced by pinyon (Pinus monophylla Torr. & FrĂ©m and Pinus edulis Engelm.) and juniper (Juniperus osteosperma Torr. and Juniperus occidentalis Hook.) expansion. Some scientists and policy makers believe that increasing woodland cover in the intermountain western U.S. offers the possibility of increased organic carbon (OC) storage on the landscape; however, little is currently known about the distribution of OC on these landscapes, or the role that nitrogen (N) plays in OC retention. We quantified the relationship between tree cover, belowground OC, and total below ground N in expansion woodlands at 13 sites in Utah, Oregon, Idaho, California, and Nevada, USA. One hundred and twenty nine soil cores were taken using a mechanically driven diamond tipped core drill to a depth of 90 cm. Soil, coarse fragments, and coarse roots were analyzed for OC and total N. Woodland expansion influenced the vertical distribution of root OC by increasing 15â30 cm root OC by 2.6 Mg haâ1 and root N by 0.04 Mg haâ1. Root OC and N increased through the entire profile by 3.8 and 0.06 Mg haâ1 respectively. Woodland expansion influenced the vertical distribution of soil OC by increasing surface soil (0â15 cm) OC by 2.2 Mg haâ1. Woodland expansion also caused a 1.3 Mg haâ1 decrease in coarse fragment associated OC from 75â90 cm. Our data suggests that woodland expansion into sagebrush ecosystems has limited potential to store additional belowground OC, and must be weighed against the risk of increased wildfire and exotic grass invasion
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