Background and Purpose-We investigated whether computed tomography (CT) perfusion-derived cerebral blood flow (CBF) and cerebral blood volume (CBV) could be used to differentiate between penumbra and infarcted gray matter in a limited, exploratory sample of acute stroke patients. Methods-Thirty patients underwent a noncontrast CT (NCCT), CT angiography (CTA), and CT perfusion (CTP) scan within 7 hours of stroke onset, NCCT and CTA at 24 hours, and NCCT at 5 to 7 days. Twenty-five patients met the criteria for inclusion and were subsequently divided into 2 groups: those with recanalization at 24 hours (nϭ16) and those without (nϭ9). Penumbra was operationally defined as tissue with an admission CBF Ͻ25 mL ⅐ 100 g Ϫ1 ⅐ min
Soil salinity (high levels of water-soluble salt) and sodicity (high levels of exchangeable sodium), called collectively salt-affected soils, affect approximately 932 million ha of land globally. Saline and sodic landscapes are subjected to modified hydrologic processes which can impact upon soil chemistry, carbon and nutrient cycling, and organic matter decomposition. The soil organic carbon (SOC) pool is the largest terrestrial carbon pool, with the level of SOC an important measure of a soil's health. Because the SOC pool is dependent on inputs from vegetation, the effects of salinity and sodicity on plant health adversely impacts upon SOC stocks in salt-affected areas, generally leading to less SOC. Saline and sodic soils are subjected to a number of opposing processes which affect the soil microbial biomass and microbial activity, changing CO 2 fluxes and the nature and delivery of nutrients to vegetation. Sodic soils compound SOC loss by increasing dispersion of aggregates, which increases SOC mineralisation, and increasing bulk density which restricts access to substrate for mineralisation. Saline conditions can increase the decomposability of soil organic matter but also restrict access to substrates due to flocculation of aggregates as a result of high concentrations of soluble salts. Saline and sodic soils usually contain carbonates, which complicates the carbon (C) dynamics. This paper reviews soil processes that commonly occur in saline and sodic soils, and their effect on C stocks and fluxes to identify the key issues involved in the decomposition of soil organic matter and soil aggregation processes which need to be addressed to fully understand C dynamics in salt-affected soils.
A review has been undertaken into how soil organic matter (SOM) affects a range of soil properties that are important for the productive capacity of soils. The potential effect of varying the amount of SOM in soil on a range of individual soil properties was investigated using a literature search of published information largely from Australia, but also including relevant information from overseas. The soil properties considered included aggregate stability, bulk density, water-holding capacity, soil erodibility, soil colour, soil strength, compaction characteristics, friability, nutrient cycling, cation exchange capacity, soil acidity and buffering capacity, capacity to form ligands and complexes, salinity, and the interaction of SOM with soil biology. Increases in SOM have the capacity to have strong influence only the physical properties of the surface soils, perhaps only the top 10 cm, or the top 20 cm at most. This limits the capacity of SOM to influence soil productivity. Even so, the top 20 cm is a critical zone for the soil. It is where seeds are sown, germinate and emerge. It is where a large proportion of plant materials are added to the soil for decomposition and recycling of nutrients and where rainfall either enters the soil or runs off. Therefore, the potential to improve soil condition in the top 0–20 cm is still critical for plant productivity. The SOM through nutrient cycling such as mineralisation of organic nitrogen to nitrate can have an influence on the soil profile.
Interpreting Soil Test Results is a practical reference enabling soil scientists, environmental scientists, environmental engineers, land holders and others involved in land management to better understand a range of soil test methods and interpret the results of these tests. It also contains a comprehensive description of the soil properties relevant to many environmental and natural land resource issues and investigations. This new edition has an additional chapter on soil organic carbon store estimation and an extension of the chapter on soil contamination. It also includes sampling guidelines for landscape design and a section on trace elements. The book updates and expands sections covering acid sulfate soil, procedures for sampling soils, levels of nutrients present in farm products, soil sodicity, salinity and rainfall erosivity. It includes updated interpretations for phosphorus in soils, soil pH and the cation exchange capacity of soils. Interpreting Soil Test Results is ideal reading for students of soil science and environmental science and environmental engineering; professional soil scientists, environmental scientists, engineers and consultants; and local government agencies and as a reference by solicitors and barristers for land and environment cases.
Purpose:To determine whether admission computed tomography (CT) perfusion-derived permeability-surface area product (PS) maps differ between patients with hemorrhagic acute stroke and those with nonhemorrhagic acute stroke. Materials and Methods:This prospective study was institutional review board approved, and all participants gave written informed consent. Forty-one patients who presented with acute stroke within 3 hours after stroke symptom onset underwent two-phase CT perfusion imaging, which enabled PS measurement. Patients were assigned to groups according to whether they had hemorrhage transformation (HT) at follow-up magnetic resonance (MR) imaging and CT and/or whether they received tissue plasminogen activator (TPA) treatment. Clinical, demographic, and CT perfusion variables were compared between the HT and non-HT patient groups. Associations between PS and HT were tested at univariate and multivariate logistic regression analyses and receiver operating characteristic (ROC) analysis. Results:HT developed in 23 (56%) patients. Patients with HT had higher National Institutes of Health Stroke Scale (NIHSS) scores (P ϭ .005), poorer outcomes (P ϭ .001), and a higher likelihood of having received TPA (P ϭ .005) compared with patients without HT. Baseline blood flow (P ϭ .17) and blood volume (P ϭ .11) defects and extent of flow reduction (P ϭ .27) were comparable between the two groups. The mean PS for the HT group, 0.49 mL ⅐ min Ϫ1 ⅐ (100 g) Ϫ1 , was significantly higher than that for the non-HT group, 0.09 mL ⅐ min Ϫ1 ⅐ (100 g) Ϫ1 (P Ͻ .0001). PS (odds ratio, 3.5; 95% confidence interval [CI]: 1.69, 7.06; P ϭ .0007) and size of hypoattenuating area at nonenhanced admission CT (odds ratio, 0.4; 95% CI: 0.2, 0.7; P ϭ .002) were the only independent variables associated with HT at stepwise multivariate analysis. The mean area under the ROC curve was 0.918 (95% CI: 0.828, 1.00). The PS threshold of 0.23 mL ⅐ min Ϫ1 ⅐ (100 g) Ϫ1 had 77% sensitivity and 94% specificity for detection of HT. Conclusion:Admission PS measurement appears promising for distinguishing patients with acute stroke who are likely from those who are not likely to develop HT.
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