Degradation Results (degradation + result)

Distribution by Scientific Domains


Selected Abstracts


A novel reactor for exploring the effect of water content on biofilter degradation rates

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2003
Milinda A. Ranasinghe
A novel batch recycle reactor was developed to investigate the effect of water content changes on the biological degradation rate of gas phase contaminants in low water content systems, such as biofilters. The reactor tightly controlled the water content of the unsaturated packing material using the principle of a suction cell. Matric potential in the compost was controlled between ,6 and ,36 cm H2O. A soil water retention curve relating matric potential to gravimetric water content was generated for the compost. Periodic dry weight analyses of reactor samples, together with the water retention curve, verified moisture content control. Runs were performed with toluene as the contaminant using unamended compost at a constant temperature of 30°C. Degradation results indicated a linear, biologically limited degradation region, followed by a non-linear region at lower concentrations. Elimination capacities were calculated for the linear region for different matric potentials along both the wetting and drying curves, and both changes in the water content and direction of approach affected the removal rates in the linear region. The elimination capacity ranged from 155 g/m3 hr to 24 g/m3 hr for toluene over the matric potential range investigated. Repeatability studies indicated that moisture content was most likely the parameter that influenced changes in performance. [source]


Compensating for wetland losses in the United States

IBIS, Issue 2004
Joy B. Zedler
Impacts of climate change on US wetlands will add to those of historical impacts due to other causes. In the US, wetland losses and degradation result from drainage for agriculture, filling for urbanization and road construction. States that rely heavily on agriculture (California, Iowa, Illinois, Missouri, Ohio, Indiana) have lost over 80% of their historical area of wetlands, and large cities, such as Los Angeles and New York City, have retained only tiny remnants of wetlands, all of which are highly disturbed. The cumulative effects of historical and future degradation will be difficult to abate. A recent review of mitigation efforts in the US shows a net loss of wetland area and function, even though ,no net loss' is the national policy and compensatory measures are mandatory. US policy does not include mitigation of losses due to climate change. Extrapolating from the regulatory experience, one can expect additional losses in wetland areas and in highly valued functions. Coastal wetlands will be hardest hit due to sea-level rise. As wetlands are increasingly inundated, both quantity and quality will decline. Recognition of historical, current and future losses of wetland invokes the precautionary principal: avoid all deliberate loss of coastal wetland area in order to reduce overall net loss. Failing that, our ability to restore and sustain wetlands must be improved substantially. [source]


An efficient approach to synthesize polysaccharides- graft -poly(p -dioxanone) copolymers as potential drug carriers

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2009
Fang Lu
Abstract Starch and poly(p -dioxanone) (PPDO) are the natural and synthetic biodegradable and biocompatible polymers, respectively. Their copolymers can find extensive applications in biomedical materials. However, it is very difficult to synthesize starch- graft -PPDO copolymers in common organic solvents with very good solubility. In this article, well-defined polysaccharides- graft -poly(p -dioxanone) (SAn -PPDO) copolymers were successfully synthesized via the ring-opening polymerization of p -dioxanone (PDO) with an acetylated starch (SA) initiator and a Sn(Oct)2 catalyst in bulk. The copolymers were characterized via Fourier transform infrared spectroscopy, 1H NMR, gel permeation chromatography, thermogravimetric analysis (TG), differential scanning calorimetry, and wide angle x-ray diffraction. The in vitro degradation results showed that the introduction of SA segments into the backbone chains of the copolymers led to an enhancement of the degradation rate, and the degradation rate of SAn -PPDO increased with the increase of SA wt %. Microspheres with an average volume diameter of 20 ,m, which will have potential applications in controlled release of drugs, were successfully prepared by using these new copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5344,5353, 2009 [source]


A Novel Biphasic Bone Scaffold: ,-Calcium Phosphate and Amorphous Calcium Polyphosphate

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009
Gaoxiang Chen
Calcium polyphosphate (CPP) was added to hydroxyapatite (HA) to develop a novel biphasic calcium phosphate (BCP). The effects of varying CPP dosage on the sintering property, the mechanical strength, and the phase compositions of HA were investigated. Results showed that CPP reacted with HA and produced ,-calcium phosphate (,-TCP) and H2O and that an excessive dosage of CPP (>10 wt%) obtained a novel BCP of ,-TCP/amorphous-CPP, while a lesser dosage of CPP (<10 wt%) obtained a traditional BCP (HA/,-TCP). The porous ,-TCP/amorphous-CPP scaffolds (porosity of 66.7%, pore diameter of 150,450 ,m, and compressive strength of 6.70±1.5 MPa) were fabricated and their in vitro degradation results showed a significant improvement of degradation with the addition of CPP. [source]