1,336 research outputs found
Are low-producing plants sequestering carbon at a geater rate than high-producing plants? : a test within the genus Chionochloa : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Ecology at Massey University, Palmerston North, New Zealand
Plant life and primary production play an important role in the global carbon (C) cycle through
the fixing of atmospheric C into the terrestrial biosphere. However, the sequestration of C into
the soil not only depends on the rate of plant productivity, but also on the rate of litter
decomposition. The triangular relationship between climate, litter quality, and litter
decomposition suggests that whilst low-producing plants fix C at a slower rate than highproducing
plants, they may release C at an even slower rate, due to the production of a
recalcitrant litter.
Here, the relationships between environment, productivity, litter quality and
decomposition are investigated to determine their relative influences on C sequestration for taxa
in the genus Chionochloa. Annual productivity was measured in situ for 23 taxa located across
New Zealand, whilst litter and soil were collected for analyses and two ex-situ decomposition
experiments; litter incubation on a common alpine soil, and litter incubation on each taxon's
home-site soil.
Plant growth rate was found to be positively correlated with both litter nitrogen and
litter fibre content. Litter decomposition on the common soil was instead negatively correlated
with lignin content, which showed a strong correlation with phylogeny, as opposed to
environment or growth rate. When incubated on home-site soils, litter quality had no influence
on decomposition, which was instead positively correlated with the rate of soil C
decomposition, and negatively correlated with both soil organic matter and soil water content.
On the common soil there were weak correlations between productivity and
decomposition; however the proportional increase in productivity was greater than the
corresponding increase in decomposition, resulting in high-producing plants sequestering C at a
greater rate than low-producing plants. However, there was no correlation between productivity
and decomposition on the home-site soil, with soil water content being a better predictor of C
sequestration rate than productivity.
Despite the range of variation in morphology, ecophysiology, productivity and habitat
displayed within the Chionochloa genus, taxa all produced litter of a very similar quality.
Breakdown of that litter is then most strongly influenced by the environment in which
decomposition occurs, as opposed to the quality of the litter. Any subsequent differences in
rates of C sequestration are therefore most influenced by the environment decomposition occurs
in, with wet and cool environments likely to result in increased rates of C sequestration,
independent of the rate of productivity
House Market in Chinese Cities: Dynamic Modeling, In-Sampling Fitting and Out-of-Sample Forecasting
This paper attempts to contribute in several ways. Theoretically, it proposes simple models of house price dynamics and construction dynamics, all based on forward-looking agents’ maximization problems, which may carry independent interests. Simplified version of the model implications are estimated with the data from four major cities in China. Both price and construction dynamics exhibit strong persistence in al cities. Significant heterogeneity across cities is found. Our models out-perform widely used alternatives in in-sample-fitting for all cities, although similar success only limited to highly developed cities in out-of-sample forecasting. Policy implications and future research directions are also discussed.pre-sale, production constraint, collateral constraint, cross-city heterogeneity, fundamental versus policy
First report of Metarhizium anisopliae IP 46 pathogenicity in adult Anopheles gambiae s.s. and An. arabiensis (Diptera; Culicidae).
The entomopathogenic fungus Metarhizium anisopliae isolate IP 46, originating from a soil sample collected in 2001 in the Cerrado of Central Brazil, was tested for its ability to reduce the survival of adult male and female Anopheles gambiae s.s. and An. arabiensis mosquitoes. A 6-h exposure to the fungus coated on test paper at a concentration of 3.3 x 106 conidia cm-2 reduced the daily survival of both mosquito species (HR = 3.14, p < 0.001), with higher risk of dying in An. gambiae s.s relative to An. arabiensis (HR = 1.38, p < 0.001). Fungal sporulation was observed in >95% of mosquito cadavers in the treatment groups. The results indicate that M. anisopliae IP 46 has the potential to be a bio-control agent for African malaria vector species, and is a suitable candidate for further research and development
Arterial pathology in canine mucopolysaccharidosis-I and response to therapy.
Mucopolysaccharidosis-I (MPS-I) is an inherited deficiency of α-L-iduronidase (IdU) that causes lysosomal accumulation of glycosaminoglycans (GAG) in a variety of parenchymal cell types and connective tissues. The fundamental link between genetic mutation and tissue GAG accumulation is clear, but relatively little attention has been given to the morphology or pathogenesis of associated lesions, particularly those affecting the vascular system. The terminal parietal branches of the abdominal aorta were examined from a colony of dogs homozygous (MPS-I affected) or heterozygous (unaffected carrier) for an IdU mutation that eliminated all enzyme activity, and in affected animals treated with human recombinant IdU. High-resolution computed tomography showed that vascular wall thickenings occurred in affected animals near branch points, and associated with low endothelial shear stress. Histologically these asymmetric 'plaques' entailed extensive intimal thickening with disruption of the internal elastic lamina, occluding more than 50% of the vascular lumen in some cases. Immunohistochemistry was used to show that areas of sclerosis contained foamy (GAG laden) macrophages, fibroblasts and smooth muscle cells, with loss of overlying endothelial basement membrane and claudin-5 expression. Lesions contained scattered cells expressing nuclear factor-κβ (p65), increased fibronectin and transforming growth factor β-1 signaling (with nuclear Smad3 accumulation) in comparison to unaffected vessels. Intimal lesion development and morphology was improved by intravenous recombinant enzyme treatment, particularly with immune tolerance to this exogenous protein. The progressive sclerotic vasculopathy of MPS-I shares some morphological and molecular similarities to atherosclerosis, including formation in areas of low shear stress near branch points, and can be reduced or inhibited by intravenous administration of recombinant IdU
Immune-Mediated Inflammation May Contribute to the Pathogenesis of Cardiovascular Disease in Mucopolysaccharidosis Type I.
BackgroundCardiovascular disease, a progressive manifestation of α-L-iduronidase deficiency or mucopolysaccharidosis type I, continues in patients both untreated and treated with hematopoietic stem cell transplantation or intravenous enzyme replacement. Few studies have examined the effects of α-L-iduronidase deficiency and subsequent glycosaminoglycan storage upon arterial gene expression to understand the pathogenesis of cardiovascular disease.MethodsGene expression in carotid artery, ascending, and descending aortas from four non-tolerized, non-enzyme treated 19 month-old mucopolysaccharidosis type I dogs was compared with expression in corresponding vascular segments from three normal, age-matched dogs. Data were analyzed using R and whole genome network correlation analysis, a bias-free method of categorizing expression level and significance into discrete modules. Genes were further categorized based on module-trait relationships. Expression of clusterin, a protein implicated in other etiologies of cardiovascular disease, was assessed in canine and murine mucopolysaccharidosis type I aortas via Western blot and in situ immunohistochemistry.ResultsGene families with more than two-fold, significant increased expression involved lysosomal function, proteasome function, and immune regulation. Significantly downregulated genes were related to cellular adhesion, cytoskeletal elements, and calcium regulation. Clusterin gene overexpression (9-fold) and protein overexpression (1.3 to 1.62-fold) was confirmed and located specifically in arterial plaques of mucopolysaccharidosis-affected dogs and mice.ConclusionsOverexpression of lysosomal and proteasomal-related genes are expected responses to cellular stress induced by lysosomal storage in mucopolysaccharidosis type I. Upregulation of immunity-related genes implicates the potential involvement of glycosaminoglycan-induced inflammation in the pathogenesis of mucopolysaccharidosis-related arterial disease, for which clusterin represents a potential biomarker
House Market in Chinese Cities: Dynamic Modeling, In0 Sample Fitting and Out-of- Sample Forecasting
This paper attempts to contribute in several ways. Theoretically, it proposes simple models of house price dynamics and construction dynamics, all based on the maximization problems of forward-looking agents, which may carry independent interests. Simplified versions of the model implications are estimated with the data from four major cities in China. Both price and construction dynamics exhibit strong persistence in all cities. Significant heterogeneity across cities is found. Our models out-perform widely used alternatives in in-sample-fitting for all cities, although similar success is only limited to highly developed cities in out-of-sample forecasting. Policy implications and future research directions are also discussed.
A New Low Reynolds Number Facility for Active Flow Control Applications
Recent interest in gaining understanding of the dynamics and behavior of the leading-edge vortex structure observed in biological flight systems has prompted the construction of a new low Reynolds number facility. This facility, a recirculating oil tunnel, gives several distinct advantages over similar facilities, utilizing water or air as the working fluid, for this kind of study. Additionally, as understanding is gained, active flow control strategies leading to the stabilization of the leading-edge vortex structure will be investigated, and this facility is specially equipped to enable this study. The tunnel has been designed and installed at the California Institute of Technology Graduate Aeronautical Laboratories. Design features of the facility will be discussed, along with some preliminary measurements conducted on a NACA 0012 wing
Securing tropical forest carbon: the contribution of protected areas to REDD
Forest loss and degradation in the tropics contribute 6-17% of all greenhouse gas emissions. Protected areas cover 217.2 million ha (19.6%) of the world's humid tropical forests and contain c. 70.3 petagrams of carbon (Pg C) in biomass and soil to 1 m depth. Between 2000 and 2005, we estimate that 1.75 million ha of forest were lost from protected areas in humid tropical forests, causing the emission of 0.25-0.33 Pg C. Protected areas lost about half as much carbon as the same area of unprotected forest. We estimate that the reduction of these carbon emissions from ongoing deforestation in protected sites in humid tropical forests could be valued at USD 6,200-7,400 million depending on the land use after clearance. This is >1.5 times the estimated spending on protected area management in these regions. Improving management of protected areas to retain forest cover better may be an important, although certainly not sufficient, component of an overall strategy for reducing emissions from deforestation and forest degradation (REDD
Characterization of meta-Cresol Purple for spectrophotometric pH measurements in saline and hypersaline media at sub-zero temperatures
Accurate pH measurements in polar waters and sea ice brines require pH indicator dyes characterized at near-zero and below-zero temperatures and high salinities. We present experimentally determined physical and chemical characteristics of purified meta-Cresol Purple (mCP) pH indicator dye suitable for pH measurements in seawater and conservative seawater-derived brines at salinities (S) between 35 and 100 and temperatures (T) between their freezing point and 298.15 K (25 °C). Within this temperature and salinity range, using purified mCP and a novel thermostated spectrophotometric device, the pH on the total scale (pHT) can be calculated from direct measurements of the absorbance ratio R of the dye in natural samples as
pHT=−log(kT2e2)+log(R−e11−Re3e2)
Based on the mCP characterization in these extended conditions, the temperature and salinity dependence of the molar absorptivity ratios and − log(kT2e2)
of purified mCP is described by the following functions: e1 = −0.004363 + 3.598 × 10−5T, e3/e2 = −0.016224 + 2.42851 × 10−4T + 5.05663 × 10−5(S − 35), and − log(kT2e2) = −319.8369 + 0.688159 S −0.00018374 S2 + (10508.724 − 32.9599 S + 0.059082S2) T−1 + (55.54253 − 0.101639 S) ln T −0.08112151T. This work takes the characterisation of mCP beyond the currently available ranges of 278.15 K ≤ T ≤ 308.15 K and 20 ≤ S ≤ 40 in natural seawater, thereby allowing high quality pHT measurements in polar systems
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