JOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2004
PAYAP MASNIYOM
The effect of modified atmosphere packaging (80% CO2, 10% O2, 10% N2) on ATPase activity, surface hydrophobicity, sulfhydryl content and degradation of proteins in seabass muscle during storage at 4C was investigated. No changes in Ca2+ -, Mg2+ -, Mg2+ -Ca2+ -ATPase activities of natural actomyosin (NAM) in seabass slices kept under MAP were observed throughout the storage for up to 21 days (P > 0.05). However, a slightly increased Mg2+ -EGTA-ATPase was found. For seabass slices stored under air atmosphere, Ca2+ -ATPase activity decreased, whereas Mg2+ -EGTA-ATPase activity increased (P < 0.05) with a concomitant loss in Ca2+ -sensitivity. Lower decreases in total sulfhydryl content but higher increases in surface hydrophobicity were observed in samples stored under MAP, compared to those kept under air atmosphere. No marked autolytic degradation in samples kept under MAP was observed throughout the storage as monitored by no changes in myosin heavy chain, free ,-amino acid and trichloroacetic acid soluble peptide. Conversely, a considerable degradation was found in samples kept under air atmosphere, especially after 9 days of storage. Therefore, MAP is a promising means to retard the changes in muscle proteins, especially degradation. [source]

EFFECT OF SLAUGHTER METHOD ON DEGRADATION OF INTRAMUSCULAR TYPE V COLLAGEN DURING SHORT-TERM CHILLED STORAGE OF CHUB MACKEREL SCOMBER JAPONICUS

JOURNAL OF FOOD BIOCHEMISTRY, Issue 5 2002
KENJI SATO
ABSTRACT The present paper demonstrates that a nonstntggling slaughter method can delay degradation of type V collagen in meat of chub mackerel Scomber japonicus and softening of the meat during postharvest chilled storage. The fish were slaughtered by piercing a knife into nape (nonstruggling method) or by leaving on ground (struggling method) and then stored in an ice box. Sensory study revealed that the postharvest softening of the meat was moderated at 4 and 8 h by the non-struggling slaughter method in comparison with the struggling method. On the basis of the specific solubilization of type V collagen and reduced tyrosine content in it, a cleavage of the nonhelical regions (telopeptides) of the type V collagen occurred during the chilled storage in the fish slaughtered by the struggling method. The degradation of type V collagen was also slower in the meat of the fish slaughtered by the nonstruggling method, which can be directly linked to the moderation of the postharvest softening. [source]

MINIMIZING COLOR DEGRADATION IN BLUSH WINES,

JOURNAL OF FOOD QUALITY, Issue 5 2003
J. HATFIELD
Cabernet Sauvignon wines produced with sulfur dioxide (SO2) at different levels (0, 30, 60, and 120 mg/L) added at crush and bottling were evaluated during 12 months of storage at 16C. Addition of SO2 at crush did not affect browning (absorbance at 420 nm) but increased red color (absorbance at 520 nm). As SO2 levels at bottling increased, browning and red color decreased. Prefermentation treatments (hyperoxidation, nitrogen sparging, and SO2 addition) and tannic acid addition at bottling in Cabernet Sauvignon, Delaware, and Noble blush wines stored at 16 and 37C were evaluated. Prefermentation treatments did not affect red color. Browning differences were observed in Cabernet Sauvignon but not in Delaware and Noble wines. In blush wines from all cultivars, as tannic acid levels increased, browning and red color increased. The prefermentation treatments can be used to minimize color degradation in the cultivars evaluated. [source]

EFFECT OF LACTIC ACID AND LACTIC ACID BACTERIA TREATMENT ON MYOFIBRILLAR PROTEIN DEGRADATION AND DYNAMIC RHEOLOGY OF BEEF

JOURNAL OF TEXTURE STUDIES, Issue 3 2007
M. SIGNORINI
ABSTRACT Lactic acid has been used as an efficient decontaminant in meats aimed for direct consumption or product fabrication. However, reports on the functionality of proteins extracted from lactic acid-treated meat are scattered. The objective of this work was to study the degradation and gelling ability of myofibrillar protein extracts obtained from beef treated with lactic acid of chemical and microbial origins, stored at 4 and 20C. The gelling ability was considerably reduced by lactic acid treatment as a result of protein denaturation in acid conditions at both storage temperatures. Scanning electron microscopy showed loose structures resulting in low penetration resistance and storage modulus. Treatments with lactic acid or lactic acid bacteria (LAB) had similar effect on tan,, affecting gel rigidity but not elasticity. Penetration in gels obtained from LAB-treated meat was highly correlated with myosin degradation. Lactobacillus carnis -treated meat produced compact gels with high penetration resistance and storage modulus, although the structure became looser with storage time. LAB treatment, although not as efficient as lactic acid as a meat preservative, is a milder process causing less severe changes in meat structure rheology. PRACTICAL APPLICATIONS The potential of lactic fermentation by selected strains is somewhat limited as compared to lactic acid preservation of meat substrates, regarding pH reduction and its consequence on pathogens and spoilage microorganism population reduction. However, lactic acid bacteria (LAB) treatments are milder; therefore, changes in protein structure and rheology are less severe. Lactic acid in its chemical form promotes protein changes, whereas LAB does not. As myofibrillar protein configuration is responsible for most meat functional properties, such as gel and emulsion formation, it is important that protein structure remains unchanged as much as possible. Using nonproteolytic strains, protein degradation can only be altered by endogenous or bacteria-produced enzymes, which can be inhibited by several means. Meat preservation by lactic fermentation with selected strains can be an alternative when keeping meat protein functional properties unaltered. [source]

SOIL EROSION AND DEGRADATION BASED ON SAND PARTICLES TRANSPORT CAUSED BY WIND BLOWING

NATURAL RESOURCE MODELING, Issue 2 2010
MIHAI DUPAC
Abstract In this paper, the effect of sand particles transport caused by wind blowing and its role in the land degradation and desertification process is considered. For the modeling of the 3D landscape, a grayscale height map has been used, the vegetation has been modeled using a Lindenmayer system, and the sand particles have been modeled as a 3D mesh-free particles system. It was assumed that both the sand motion and the wind motion are incompressible continuum systems and their behavior follows the Navier,Stokes equations. To simulate the sand transport, the Navier,Stokes equations are discretized using the moving particle Semi-implicit (MPS) method. Different types of revegetation patterns (windbreakers) have been used to show some effective measures preventing soils from erosion. [source]

REDUCED MATRIX DEGRADATION IN DIABETIC NEPHROPATHY: AMELIORATION WITH ACE INHIBITION

NEPHROLOGY, Issue 3 2000
McLennan Sv
[source]

EVALUATING HISTOLOGICAL METHODS FOR ASSESSING HAIR FIBRE DEGRADATION

ARCHAEOMETRY, Issue 3 2010
A. S. WILSON
The hair shaft has increasing importance in bioarchaeology, since it is now possible to retrieve detailed biomolecular information on recent life history using individual fibres (e.g., on diet, drug use and DNA). Data on hair condition is an important cornerstone to ensuring that reliable information is obtained. The following study defines morphological features of degradative change in human terminal scalp hair using different microscopy techniques. Evidence of degradative change is translated into a ranked histology for assessing hair sample condition. The approach is applied to samples of cut modern scalp hair subjected to degradation under soil burial/simulated grave conditions. [source]

Kinetic analysis of hyaluronidase activity using a bioactive MRI contrast agent

CONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2006
Liora Shiftan
Abstract One of the attractions of molecular imaging using ,smart' bioactive contrast agents is the ability to provide non-invasive data on the spatial and temporal changes in the distribution and expression patterns of specific enzymes. The tools developed for that aim could potentially also be developed for functional imaging of enzyme activity itself, through quantitative analysis of the rapid dynamics of enzymatic conversion of these contrast agents. High molecular weight hyaluronan, the natural substrate of hyaluronidase, is a major antiangiogenic constituent of the extracellular matrix. Degradation by hyaluronidase yields low molecular weight fragments, which are proangiogenic. A novel contrast material, HA-GdDTPA-beads, was designed to provide a substrate analog of hyaluronidase in which relaxivity changes are induced by enzymatic degradation. We show here a first-order kinetic analysis of the time-dependent increase in R2 as a result of hyaluronidase activity. The changes in R2 and the measured relaxivity of intact HA-GdDTPA-beads (r2B) and HA-GdDTPA fragments (r2D) were utilized for derivation of the temporal drop in concentration of GdDTPA in HA-GdDTPA-beads as the consequence of the release of HA-GdDTPA fragments. The rate of dissociation of HA-GdDTPA from the beads showed typical bell-shaped temperature dependence between 7 and 36 °C with peak activity at 25 °C. The tools developed here for quantitative dynamic analysis of hyaluronidase activity by MRI would allow the use of activation of HA-GdDTPA-beads for the determination of the role of hyaluronidase in altering the angiogenic microenvironment of tumor micro metastases. Copyright © 2006 John Wiley & Sons, Ltd. [source]

In Vitro Resistance to Degradation of Hyaluronic Acid Dermal Fillers by Ovine Testicular Hyaluronidase

DERMATOLOGIC SURGERY, Issue 2010
DEREK JONES MD
BACKGROUND Although adverse events are uncommon with hyaluronic acid (HA) fillers, the use of hyaluronidase permits the reversal of treatment complications or overcorrection. OBJECTIVE This study sought to determine an in vitro dose-response relationship between ovine testicular hyaluronidase (OTH) and three HA dermal fillers (24-mg/mL smooth gel, 20-mg/mL particulate gel, and 5.5-mg/mL particulate gel with 0.3% lidocaine). METHODS AND MATERIALS The dose response of each was measured after incubation for 30 minutes in concentrations ranging between 5 and 40 U of OTH. Timed responses for the 24-mg/mL and 20-mg/mL HA fillers were obtained after incubation with 20 U of OTH for 15 to 120 minutes. RESULTS After all dose responses and timed-interval tests, the 24-mg/mL HA smooth gel filler exhibited more resistance against in vitro enzymatic degradation to OTH than the 20- and 5.5-mg/mL HA particulate gels. CONCLUSION This resistance to degradation in vitro may be attributed to the higher HA content of the 24-mg/mL HA smooth gel, the degree of crosslinking, and the cohesive property of the gel filler. This study was funded by a grant from Allergan, Inc., Santa Barbara, CA. Derek Jones, MD, is a consultant, investigator, advisory board member, and speaker for Allergan, Inc. He received no compensation for this study. Drs. Tezel and Borrell are employed by Allergan, Inc., Santa Barbara, CA. Editorial assistance was provided by Health Learning Systems, a part of CommonHealth, Parsippany, NJ. [source]

Degradation in insulin sensitivity with increasing severity of the metabolic syndrome in obese postmenopausal women

DIABETES OBESITY & METABOLISM, Issue 3 2006
A. D. Karelis
Aim:, We investigated the relationship between insulin sensitivity and the graded increase in the number of features of the metabolic syndrome in a cross-sectional sample of obese postmenopausal women. We hypothesized that insulin sensitivity would deteriorate with an increased number of metabolic syndrome phenotypes. Methods:, Insulin sensitivity was measured in 75 obese postmenopausal women (age: 57.3 ± 5.3 years; BMI: 32.8 ± 4.5 kg/m2) by using both the hyperinsulinaemic,euglycaemic clamp and the homeostasis model assessment (HOMA-IR). Features of the metabolic syndrome included visceral fat (>130 cm2), HDL-cholesterol (<1.29 mmol/l), fasting triglycerides (,1.7 mmol/l), blood pressure (,130/,85 mmHg) and fasting glucose (,6.1 mmol/l). Participants were classified into three categories based on the presence of metabolic syndrome phenotypes: 0,1 vs. 2 vs. ,3 features of the metabolic syndrome. Results:, We found that insulin sensitivity decreased in a graded fashion (12.19 ± 3.2 vs. 11.80 ± 2.3 vs. 9.29 ± 2.6 mg/min/FFM) and HOMA-IR increased in a similar manner (2.95 ± 1.1 vs. 3.28 ± 1.3 vs. 4.65 ± 2.2), as the number of features of the metabolic syndrome increased from 0,1 to ,3. When insulin sensitivity was statistically adjusted for visceral fat (as measured by computed tomography) and plasma triglycerides, the differences among groups were abolished. Conclusions:, These findings suggest that a decreased insulin sensitivity is associated with increased features of the metabolic syndrome in obese postmenopausal women and that visceral fat as well as plasma triglyceride accumulation might be potential mediators of this relationship. [source]

Electrochemical Monitoring of Singlet Oxygen Production

ELECTROANALYSIS, Issue 21 2009
Duncan Sharp
Abstract The exploitation of singlet oxygen generating compounds as a means of targeted therapies drives the need to develop methods for assessing the efficacy of such compounds and their capacity for generating the reactive oxygen species. Degradation of diphenylisobenzofuran by singlet oxygen is widely used as a spectroscopic probe but its application can be problematic. An alternative detection strategy exploiting the electrochemical monitoring of the quencher concentration, by square wave voltammetry, has been shown to provide a more sensitive and flexible option that could be used to address the increasing interest in photosensitizing materials. [source]

Dynamics of Benzene and Toluene Degradation in Pseudomonas putida F1 in the Presence of the Alternative Substrate Succinate

ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 4 2007
I. Rüegg
Abstract In batch and continuous culture, the regulation of benzene and toluene degradation by Pseudomonas putida,F1 was investigated in the presence of the alternative carbon and energy source succinate. In batch culture, benzene and toluene were used simultaneously, whereas succinate suppressed benzene consumption under carbon excess conditions resulting in diauxic growth. In carbon-limited continuous culture mixed substrate growth was observed. Since in nature low substrate concentrations and ever changing conditions prevail, this paper focuses on the dynamics of benzene/toluene degradation, biomass synthesis, and the regulation of benzene/toluene-degrading enzymes in cultures growing continuously at a dilution rate of 0.1,h,1, when shifting the supply of the carbon and energy source from succinate to various mixtures of succinate and benzene/toluene, or to benzene only. When the succinate concentration was kept constant (1.25,mM) and the medium was supplemented with benzene (2,mM), growth with benzene began already two hours after the shift. In contrast, replacing succinate with benzene only led to a wash out of biomass for more then ten hours, before biomass production from benzene started. A striking and reproducible transition pattern was observed for all shifts where the succinate concentration was reduced or succinate was omitted. After an initial period of biomass production from benzene, the culture collapsed and a wash-out of biomass was observed. However, this wash-out was not accompanied by an increase in benzene in the cultivation liquid, indicating a benzene uptake without conversion into biomass. Another possibility is that in phases of low biomass concentrations, cells were only able to use the low amounts of benzene/toluene dissolved in the cultivation liquid yielding low biomass concentrations whereas in phases of high biomass concentrations, they were able to rapidly utilize the aromatic solvents so that additional benzene from the gas phase diffused into the cultivation liquid resulting in more biomass production. In most cases, growth resumed again after 10 to 80,h. Currently, the reasons for the decrease in biomass after the first rise are unknown. However, several indications rule out intoxication of the cells by either the solvents benzene or toluene themselves, or by toxic degradation intermediates, or by-products. [source]

Degradation of alkanes by bacteria

ENVIRONMENTAL MICROBIOLOGY, Issue 10 2009
Fernando Rojo
Summary Pollution of soil and water environments by crude oil has been, and is still today, an important problem. Crude oil is a complex mixture of thousands of compounds. Among them, alkanes constitute the major fraction. Alkanes are saturated hydrocarbons of different sizes and structures. Although they are chemically very inert, most of them can be efficiently degraded by several microorganisms. This review summarizes current knowledge on how microorganisms degrade alkanes, focusing on the biochemical pathways used and on how the expression of pathway genes is regulated and integrated within cell physiology. [source]

Benzidine transformation processes in natural sediments

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2006
Joel Harden
Abstract Aromatic amines, such as benzidine and 3,3,-dichlorobenzidine, are chemicals used in the pigment and dye processes. Release of these compounds into the environment is important because of their carcinogenic and toxic nature. In the present study, the sediment and water samples were collected from Lake Macatawa (Holland, MI, USA) and subsequently spiked with benzidine. The grain size distribution of the sediment samples investigated here ranged in composition from sandy to silty-clay sediment types. The sediment,water systems spiked with benzidine were incubated under anaerobic conditions at 4, 15, and 23°C for 211 d. Degradation of benzidine was observed over the time-course analysis of the sediment,water mixtures. Three possible metabolites (aniline, 2-ethyl-1-hexanol, and 1-amino-2-hexene) were observed during this investigation as a result of gas chromatography/mass spectrometry and liquid chromatography/mass spectrometry. No metabolites were observed in autoclaved bottles, suggesting that the transformation of benzidine in the sediment,water mixtures was the result of microbial activity. From sediment,water distribution experiments, benzidine demonstrated higher sorption affinity for the different sediment phases than its degradation product, aniline. Therefore, microbially mediated transformation of benzidine to aniline is expected to yield a greater total concentration of the more mobile compound, aniline, in the water phase and a greater possibility for transport of aniline in the water phase. [source]

Degradation and sorption of selected organophosphate and carbamate insecticides in urban stream sediments

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2004
Svetlana Bondarenko
Abstract Monitorings studies show that urban surface streams in the United States are commonly contaminated with pesticides, and contamination by organophosphates and carbamates is of particular concern because of their aquatic toxicity. The degradation and sorption of four common organophosphate and carbamate insecticides were studied in urban creek sediments from southern California, USA. In sediment, malathion was quickly degraded under either aerobic or anaerobic conditions, with a half-life (t1/2) <3 d. Diazinon and chlorpyrifos were moderately persistent under aerobic conditions (t1/2 = 14,24 d). However, persistence of chlorpyrifos increased significantly under anaerobic conditions, and t1/2 was prolonged to 58 to 223 d. The greatest effect of redox potential was found with carbaryl. Although rapid dissipation occurred under aerobic conditions (t1/2 = 1.8,4.9 d), carbaryl became virtually nondegradable under anaerobic conditions (t1/2 = 125,746 d). The sorption coefficient consistently increased with time for all pesticides, and chlorpyrifos displayed greater sorption potential than the other pesticides. This study indicates that pesticides in sediment may become less available with time because of increased sorption, and pesticide persistence in sediment may vary greatly among compounds and with redox conditions. Under anaerobic conditions, long persistence may occur even for nonpersistent compounds. [source]

Degradation and formation of polycyclic aromatic compounds during bioslurry treatment of an aged gasworks soil

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2003
Staffan Lundstedt
Abstract The goals of this study were to investigate the relative degradation rates of polycyclic aromatic compounds (PACs) in contaminated soil, and to assess whether persistent oxidation products are formed during their degradation. Samples were taken on five occasions during a pilot-scale bioslurry treatment of soil from a former gasworks site. More than 100 PACs were identified in the soil, including unsubstituted polycyclic aromatic hydrocarbons (PAHs), alkylated PAHs (alkyl-PAHs), heterocyclic PACs, and oxygenated PAHs (oxy-PAHs), such as ketones, quinones, and coumarins. During the treatment, the low molecular weight PAHs and heterocyclics were degraded faster than the high molecular weight compounds. The unsubstituted PAHs also appear to have degraded more quickly than the corresponding alkyl-PAHs and nitrogen-containing heterocyclics. No new oxidation products that were not present in the untreated soil were identified after the soil treatment. However, oxy-PAHs that were present in the untreated soil were generally degraded more slowly than the parent compounds, suggesting that they were formed during the treatment or that they are more persistent. Two oxidation products, 1-acenaphthenone and 4-oxapyrene-5-one, were found at significantly higher concentrations at the end of the study. Because oxy-PAHs can be acutely toxic, mutagenic, or carcinogenic, we suggest that this group of compounds should also be monitored during the treatment of PAH-contaminated soil. [source]

Degradation of nonylphenol ethoxylates in estuarine sediment under aerobic and anaerobic conditions

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2003
P. Lee Ferguson
Abstract Nonylphenol ethoxylate (NPEO) surfactants and their metabolites are ubiquitous contaminants of the aquatic environment. Despite considerable interest in the environmental fate of these compounds due to concerns over toxicity and estrogenic activity, the pathways of NPEO degradation in sediments have not previously been reported, in spite of the fact that sediment appears to be an important sink for these compounds in the environment. In the present work, we have examined the rates and pathways of NPEO degradation in batch sediment slurry experiments using radiolabeled NPEO mixtures. Results suggest that NPEOs are more persistent in sediments under anaerobic conditions than in the presence of oxygen. In addition, it was illustrated that NPEO degradation proceeds via separate pathways in oxic and anoxic sediment. Discernible metabolites were identified and an overall mass balance for NPEO degradation in oxic and anoxic sediment was achieved. In contrast with previous studies, no evidence was observed for net production of nonylphenol from NPEOs during aerobic or anaerobic degradation. The observed relative rates at which NPEO ethoxymers disappeared in the sediment slurry experiments were consistent with previous reports for these compounds in sediment and other environmental media, although the absolute rates measured were somewhat faster than those reported for field sediments. [source]

Degradation of chlorpyrifos, fenamiphos, and chlorothalonil alone and in combination and their effects on soil microbial activity

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2002
Brajesh Kumar Singh
Abstract The effects of repeated application and of combinations of pesticides on their degradation rates in soil and on some soil microbial properties were studied. Repeated application of chlorpyrifos did not modify its degradation rate, whereas repeated applications of fenamiphos and chlorothalonil suppressed their own rates of degradation. When applied in combination, the presence of chlorothalonil reduced the degradation rate of both chlorpyrifos and fenamiphos, and the half-life of chlorothalonil was extended in the presence of chlorpyrifos. The dynamics of residues of the major metabolites of the different compounds were also affected by the pesticide combinations and, particularly, by the presence of chlorothalonil. The measured soil microbial parameters (enzyme activities and total microbial biomass) were stable in the pesticide-free control soils throughout the 90-d incubation period, but they were all adversely affected by the presence of chlorothalonil in the soil. The effects from fenamiphos or chlorpyrifos on the soil microbial characteristics were either very small or insignificant. [source]

Anaerobic biodegradation of alkanes by enriched consortia under four different reducing conditions

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2001
Chi Ming So
Abstract Enrichments of alkane-degrading microorganisms were established under sulfate-reducing, denitrifying, iron-reducing, and methanogenic conditions using an estuarine sediment. The sulfate-reducing and denitrifying enrichments mineralized [1- 14C]hexadecane to 14CO2. Degradation was coupled to sulfate reduction and denitrification, as indicated by the ratios of hexadecane degraded to the electron acceptors reduced. Dependence of hexadecane degradation by the sulfate-reducing enrichments on sulfate reduction was also shown. The results indicate the existence of diverse microbial communities capable of alkane degradation in the sediment studied. [source]

Distribution of degradation products of alkylphenol ethoxylates near sewage treatment plants in the lower Great Lakes, North America

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2000
Erin R. Bennett
Abstract Degradation of alkylphenol ethoxylate (APEO) surfactants in the environment leads to the formation of relatively hydrophobic compounds such as nonylphenol (NP), octylphenol (OP), nonylphenol monoethoxylate (NP1EO), and nonylphenol diethoxylate (NP2EO) that have been shown to have estrogenic activity. Previous studies have shown that sewage treatment plants (STPs) are point sources for these compounds in the aquatic environment. We collected sediment samples at several sites in the vicinity of STPs in Hamilton Harbour and in the Detroit River to determine the spatial distribution of the degradation products of APEOs. In addition, we deployed semipermeable membrane devices (SPMDs) and caged freshwater mussels (Elliptio complanata) at these locations to determine the distribution of these compounds in the dissolved phase and their potential to bioaccumulate in aquatic organisms. The NP, OP, NP1EO, and NP2EO were found at ,g/g (dry wt.) concentrations in sediments and accumulated to ng/g (wet wt.) concentrations in caged mussels near the STPs. However, in the Detroit River, the concentrations of these compounds declined to near background levels in the sediments, water column (i.e., SPMDs), and biota at stations about 1 km downstream from STPs. At stations in Hamilton Harbour, concentrations of APEO degradation products also declined markedly in sediments and SPMDs located a few hundred meters from the STP. These data indicate that degradation products of APEOs can be accumulated by biota near STPs. However, the environmental distribution of these compounds is localized to areas close to the point of discharge. [source]

Modeling of Environmental Degradation in Fatigue-Life Prediction of Near-, Titanium Alloy IMI 834 under Complex High-Temperature Loading Conditions,

ADVANCED ENGINEERING MATERIALS, Issue 6 2003
R.G. Teteruk
The crack propagation model successfully applies to life-prediction of near-,-titanium alloy IMI 834 under complex high-temperature fatigue-loading conditions. The predictive capabilities of the model can be attributed to the close correlation of the model with the relevant damage mechanisms (among them environmental degradation under varying conditions) and micro-structural processes. The Figure shows an SEM image of a typical crack-initiation site for a test run at 400,°C. [source]

Origin of Radiation-Induced Degradation in Polymer Solar Cells

ADVANCED FUNCTIONAL MATERIALS, Issue 16 2010
Ankit Kumar
Abstract Polymer solar cells have been shown to degrade under X-rays. Here, in situ polymer photovoltaic performance and recombination lifetimes are measured and it is found that charge accumulation is the primary reason for degradation of solar cells. This is affected by the mixing ratio of donor and acceptor in the bulk heterojunction. Both a quantitative understanding and the physical model of the degradation mechanism are presented. Understanding of the degradation mechanism is extended in polymer donor,acceptor bulk heterojunction systems to propose a material combination for making radiation hard diodes that can find important application in fields ranging from memory arrays to organic X-ray detectors for medical imaging. [source]

Degradation of transcription factor IRF-1 by the ubiquitin,proteasome pathway

FEBS JOURNAL, Issue 6 2000
The C-terminal region governs the protein stability
Interferon regulatory factor-1(IRF-1) is a transcriptional activator of interferon genes and interferon-inducible genes. It has been shown that IRF-1 functions not only as a regulator of the interferon-responsive system but also as a regulator of cell growth and apoptosis. In addition, it is known that IRF-1 is a short-lived protein, but the mechanism that regulates its stability has not yet been clarified. Here, we show that IRF-1 is degraded via the ubiquitin,proteasome pathway. IRF-1 protein degradation in HeLa and NIH3T3 cells was inhibited by treatment with proteasome-specific inhibitors. Overexpression of IRF-1 protein and ubiquitin in COS7 cells revealed specific multiubiquitination of IRF-1. Although the full-length IRF-1 was unstable, IRF-1 mutants with C-terminal truncations larger than 39 amino acids were found to be almost stable, suggesting that the 39-residue C-terminal region controls the stability of IRF-1. Further analysis of the stability of a green fluorescent protein-fusion protein containing the 39-residue C-terminal region of IRF-1 showed that this C-terminal region confers instability on green fluorescent protein, a normally stable protein, suggesting that this region functions as a protein-degradation signal. Taking the results together, it can be concluded that the 39-residue C-terminal region is necessary and sufficient to control the stability of the IRF-1 protein. [source]

Degradation of N -acyl homoserine lactone quorum sensing signal molecules by forest root-associated fungi

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2008
Stephane Uroz
Abstract A collection of mycorrhizal and nonmycorrhizal root-associated fungi coming from forest environments was screened for their ability to degrade N -acyl homoserine lactones (AHL) or to prevent AHL recognition by producing quorum sensing inhibitors (QSI). No production of QS-inhibitors or -activators was detected using the two biosensors Chromobacterium violaceum CV026 and Agrobacterium tumefaciens in the culture supernatant of these fungi. However, the ability to degrade C6- and 3O,C6-HSL was detected for three fungal isolates. Acidification assay revealed that the AHL were degraded by a lactonase activity for two of these isolates. These results demonstrated for the first time that the forest root-associated fungi are capable of degrading the AHL signal molecules. [source]

Temperature and Impurity Concentration Effects on Degradation of Nickel/Yttria-stabilised Zirconia Anode in PH3 -Containing Coal Syngas

FUEL CELLS, Issue 1 2010
M. Zhi
Abstract Degradation of the Ni/yttria-stabilised zirconia (YSZ) anode of the solid oxide fuel cell has been evaluated in the coal syngas containing different PH3 concentrations in the temperature range from 750 to 900,°C. Thermodynamic equilibrium calculations show that PH3 in the coal syngas gas is converted mostly to P2O3 at 750,900,°C. The phosphorous impurity reacts with the Ni-YSZ anode to form phosphates. The P-impurity poisoning leads to the deactivation of the Ni catalyst and to the reduction in the electronic conductivity of the anode. The impurity poisoning effect on the anode is exacerbated by increase in the temperature and/or the PH3 concentration. [source]

Degradation of TCE with Iron: The Role of Competing Chromate and Nitrate Reduction

GROUND WATER, Issue 3 2000
Oliver Schlicker
This study evaluates the potential of using granular iron metal for the abiotic removal of the organic ground water pollutant trichloroethene (TCE) in the presence of the common inorganic co-contaminants chromate and nitrate, respectively. Our long-term column experiments indicate a competitive process between TCE dechlorination and reductive transformation of chromate and nitrate, which is reflected in a significantly delayed onset of TCE dechlorination. Delay times and therefore the ranges of the nonreactive flowpaths increased with increasing experimental duration, resulting in a migration of the contaminants through the iron metal treatment zone. The present investigation also indicates that the calculated migration rates of TCE and the added cocontaminants chromate and nitrate are linearly related to the initial content of the cocontaminants. With an average pore water velocity of 0.6 m/d and a surface area concentration of 0.55 m2/mL in the column, the calculated migration rates varled between 0.10 cm/d and 5.86 cm/d. The particular similarity between the values of TCE migration and the migration of the strong oxidants chromate and nitrate and the long-term steady state of the TCE dechlorination in the absence of the chromate and nitrate indicates that these competitive transformations are the driving force for the gradual passivation of the granular iron due to the buildup of an electrically insulating Fe(III)-oxyhydroxide. Based on these passivation processes, general formulae were developed that allow a simplified approximation of breakthrough times for the contaminants TCE, chromate, and nitrate. [source]

On the Origin of Green Emission in Polyfluorene Polymers: The Roles of Thermal Oxidation Degradation and Crosslinking,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2004
W. Zhao
Abstract The green emission of poly(9,9,,-dioctylfluorenyl-2,7,,-diyl), end-capped by polyhedral oligomeric silsequioxanes, (PFO-POSS) has been investigated by photoluminescence (PL) and photoexcitation (PE), gel permeation chromatography (GPC), and transmission Fourier transform infrared (FTIR) spectroscopy. The green emission is closely correlated with thermal oxidation degradation and crosslinking of the polymer and is enhanced by annealing at elevated temperatures. The green-to-blue emission intensity ratio, used to assess the emission properties of thin (90,nm) films, was 3.70, 4.35, and 1.54 for an air-annealed film, its insoluble residue (crosslinked), and a film cast from its soluble portion, respectively. For thick (5,6,,m) film, the ratios are 13.33, 13.33, and 0.79, respectively. However, FTIR spectroscopy of thick films leads to the conclusion that the carbonyl-to-aromatic ring concentration ratio are 0.018, 0.015, and 0.032, respectively. Focusing on the recast films, the green emission is relatively low while the carbonyl concentration is relatively high. This suggests that the energy traps at crosslinked chains play an important role in green emission. It is likely that the crosslinking enhances the excitation energy migration and energy transfer to the defects by hindering chain segment twisting. [source]

The Influence of , -Tricalcium Phosphate Nanoparticles and Microparticles on the Degradation of Poly(D,L -lactide-co-glycolide)

ADVANCED MATERIALS, Issue 38-39 2009
Zhijie Yang
The in vitro degradation behavior of a series of resorbable, bioactive nano- and microcomposites designed for orthopaedic application is explored. Nanoparticles of , -tricalcium phosphate are significantly more effective than the equivalent microparticles in reducing heterogeneity of the poly(D,L -lactide-co-glycolide) degradation. More uniform degradation, reduced acid release, and less swelling of polymer were observed. [source]

Knowledge-Based Approach towards Hydrolytic Degradation of Polymer-Based Biomaterials

ADVANCED MATERIALS, Issue 32-33 2009
Dieter Hofmann
Abstract The concept of hydrolytically degradable biomaterials was developed to enable the design of temporary implants that substitute or fulfill a certain function as long as required to support (wound) healing processes or to control the release of drugs. Examples are surgical implants, e.g., sutures, or implantable drug depots for treatment of cancer. In both cases degradability can help to avoid a second surgical procedure for explanation. Although degradable surgical sutures are established in the clinical practice for more than 30 years, still more than 40% of surgical sutures applied in clinics today are nondegradable.1 A major limitation of the established degradable suture materials is the fact that their degradation behavior cannot reliably be predicted by applying existing experimental methodologies. Similar concerns also apply to other degradable implants. Therefore, a knowledge-based approach is clearly needed to overcome the described problems and to enable the tailored design of biodegradable polymer materials. In this Progress Report we describe two methods (as examples for tools for this fundamental approach): molecular modeling combining atomistic bulk interface models with quantum chemical studies and experimental investigations of macromolecule degradation in monolayers on Langmuir,Blodgett (LB) troughs. Finally, an outlook on related future research strategies is provided. [source]

Regulation of human neutrophil-mediated cartilage proteoglycan degradation by phosphatidylinositol-3-kinase

IMMUNOLOGY, Issue 1 2001
C. S. T. Hii
Summary The ability of neutrophils to degrade cartilage proteoglycan suggests that the neutrophils that accumulate in the joints of rheumatoid arthritis patients are mediators of tissue damage. The regulatory mechanisms which are relevant to the proteoglycan-degrading activity of neutrophils are poorly understood. Since phosphatidylinositol 3-kinase (PI3-K), protein kinase C (PKC), the extracellular signal-regulated protein kinase (ERK)1/ERK2 and cyclic adenosine monophosphate (cAMP) have been reported to regulate neutrophil respiratory burst and/or degranulation, a role for these signalling molecules in regulating proteoglycan degradation was investigated. Preincubation of human neutrophils with GF109203X (an inhibitor of PKC), PD98059 (an inhibitor of MEK, the upstream regulator of ERK1/ERK2) or with forskolin or dibutyryl cAMP, failed to suppress proteoglycan degradation of opsonized bovine cartilage. In contrast, preincubation of neutrophils with wortmannin or LY294002, specific inhibitors of PI3-K, inhibited proteoglycan degradation. Incubation of neutrophils with cartilage resulted in the activation of PI3-K in neutrophils, consistent with a role for PI3-K in proteoglycan degradation. Activation of PI3-K and proteoglycan degradation was enhanced by tumour necrosis factor-,. Degradation caused by neutrophils from the synovial fluid of rheumatoid arthritis patients was also inhibited by wortmannin. These data demonstrate that the proteoglycan degradative activity of neutrophils required PI3-K but not PKC or the ERK1/ERK2/ERK5 cascades and was insensitive to increases in intracellular cAMP concentrations. [source]