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Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations., Graphical abstract Image 1, Highlights • 1-wt% CMCS adjusting could form a 1μm partly demineralized zone with interfibrillar minerals in a clinically viable time. • The stability of dentin collagen and bonding could be enhanced by “selective demineralization” with 1-wt% CMCS in 30 s. • A user-friendly adhesion scheme achieved strong dentin bonding strength and durability with a strengthened interface. • A new bonding scheme can be used to improve the bonding interface stability and foster the longevity of restorations.

The application of pit and fissure sealants is a well-established method to prevent and treat early childhood caries. Resin-based sealants with antibacterial properties provide additional benefits for caries prevention in a cariogenic oral environment. The objective of this study was to evaluate the effect of an antibacterial core-shell AgBr/cationic polymer nanocomposite (AgBr/BHPVP) on the properties of a resin-based pit and fissure sealant. A commercialized pit and fissure sealant without fluoride, Concise (3M, ESPE, USA), was used as the parent material and negative control. Experimental antibacterial sealants were formulated by the addition of AgBr/BHPVP nanoparticles at mass fractions of 0.5, 1.0, and 1.5 wt% to the parent material. A fluoride-releasing sealant, Clinpro (3M, ESPE), was used as the positive control. Bacterial colony-forming unit (CFU) counts, metabolic activity tests, field emission-scanning electron microscopy (FE-SEM), and confocal laser scanning microscopy (CLSM) observations were used to evaluate the antibacterial properties of AgBr/BHPVP-modified sealants against Streptococcus mutans before and after five months of aging. The Vickers microhardness, degree of conversion, and microleakage level of the sealants were also investigated. According to the results of CFU counts and metabolic tests, sealants containing AgBr/BHPVP showed better contact-killing bactericidal activity against S. mutans than the two commercial sealants, irrespective of aging conditions (both P 0.05). The AgBr/BHPVP-modified sealants also showed a significant inhibitory effect on the planktonic S. mutans around the cured sealant surfaces. In addition, the Vickers microhardness, degree of conversion, and microleakage level of the parent material were not damaged by modification with AgBr/BHPVP (P 0.05). AgBr/BHPVP-modified pit and fissure sealant with a dual bactericidal mechanism is a promising option for the prevention of pit and fissure caries.

Electron beam coupled-bunch instabilities can limit and degrade the performance of storage ring based light sources. A longitudinal feedback system has been developed for the Duke storage ring to suppress multi-bunch beam instabilities which prevent stable, high-current operation of the storage ring based free-electron lasers (FELs) and an FEL driven Compton gamma source, the high intensity gamma-ray source (HIGS) at Duke University. In this work, we report the development of a state-of-the-art second generation longitudinal feedback system which employs a field programmable gate array (FPGA) based processor, and a broadband, high shunt-impedance kicker cavity. With two inputs and two outputs, the kicker cavity was designed with a resonant frequency of 937 MHz, a bandwidth of 97 MHz, and a shunt impedance of 1530 Ω . We also developed an S-matrix based technique to fully characterize the performance of the kicker cavity in the cold test. This longitudinal feedback system has been commissioned and optimized to stabilize high-current electron beams with a wide range of electron beam energies (250 MeV to 1.15 GeV) and a number of electron beam bunch modes, including the single-bunch mode and all possible symmetric bunch modes. This feedback system has become a critical instrument to ensure stable, high-flux operation of HIGS to produce nearly monochromatic, highly polarized Compton gamma-ray beams.

Touschek lifetime of an electron beam in a storage ring depends on the beam polarization through the intrabeam scattering effect. Therefore, the electron beam polarization can be determined from the Touschek lifetime measurement. In this paper, we report on a systematic experimental procedure we developed to study the radiative polarization of a stored electron beam. Using this technique, we successfully observed the radiative polarization of an electron beam in the Duke storage ring, and determined the equilibrium degree of polarization and the time constant of the polarization build-up process.

The aim of the current study was to investigate the effects of Yes-associated protein 1 (YAP1) gene expression after birth on the development of muscle and the relationship between YAP1 and myostatin (MSTN) and myogenin (MyoG). Reverse transcription polymerase chain reaction was used to analyze the trends in YAP1, MSTN, and MyoG temporal and spatial expression levels in various skeletal muscles (i.e., longissimus dorsi muscle, soleus muscle, gastrocnemius muscle, and extensor digitorum longus) and across 3 different growth stages (i.e., 2 days old, 2 and 6 months old) of Hu Sheep. The results showed that YAP1 expression was significantly different in the skeletal muscles of sheep; the expression level gradually increased with age; it was highly expressed in the gastrocnemius muscle and minimally expressed in the longissimus dorsi muscle. MSTN, a negative regulator of skeletal muscle development, was minimally expressed in the soleus muscle and might be related to the enlargement of muscle fiber diameter. MyoG, an important factor in regulating skeletal muscle development, was minimally expressed in the longissimus dorsi muscle and extensor digitorum longus, and highly expressed in the gastrocnemius and soleus muscles; it might inhibit the enlargement of muscle fiber diameter after birth. YAP1 expression was significantly (P < 0.05) or extremely significantly (P < 0.01) and positively correlated with MSTN and MyoG at 2 days old, 2 and 6 months old. YAP1 expression was related to muscle fiber development after birth and might be a candidate gene for the regulation of muscle growth.

With the application of a genetically modified yeast, estrogen receptor-activating compounds were detected in the soot and emission gas of a wood-burning household stove. The EC50 value of 17beta-estradiol was divided by the EC50 value of soot, and the obtained relative estrogenic value for raw soot was 2.37E-5, indicating that soot was about 100,000 times less estrogenic than 17beta-estradiol. Chemical analysis revealed that alkyl phenol, benzonic acid, and PAHs represented the major constituents in the most potent fractions of the soot. Along with PAHs, other constituents might also contribute to the estrogenicity of soot. (C) 2002 Elsevier Science (USA).

Emissions of biomass fuel combustion in residential stove from Chinese countryside were analyzed to determine the endocrine disrupters by using recombinant yeast bioassay. The results showed that there were significant steroid modulating activities found in combustion soot of five kinds of biomass fuels, which were wood, crop residue, grass, bush and rice straw. The steroid activities in the different sub-fractions from chromatographic separation were also determined, and the results indicated that polar fraction extracted by methanol and aromatic fraction extracted by benzene had relatively high steroid activities, and aliphatic fraction almost had no activity. The GC/MS results showed that polycyclic aromatic compounds and their derivatives, substituted phenolic compounds and their derivatives, aromatic carbonyl compounds, and higher molecular weight alcohols and ketones may be the main steroid disrupters in these soots.

Surface sediment samples from five different sites were collected in Donghu Lake, Wuhan City, Hubei Province, China during November 2000. Over 180 organic chemicals were detected using GC-MS controlled by a Hewlett Packard Chemstation after soxhlet extraction. Derivatives of benzene, phthalate esters, PAHs, phenols, isophorone as priority pollutants or endocrine disruptors, respectively, were detected. The concentration of organic pollutants were found to be highest at the sampling site located at Southwest Donghu Lake (Shuiguo), caused most probably by the untreated wastewater discharge, average at the southern and lowest at the northern part of the lake.

The aim of the present study was to detect delta-like 1 ho-molog (DLK1) and insulin-like growth factor-I (IGF-I) gene expression in the longissimus dorsi of Hu sheep at different growth stages and study the association between these genes and meat quality. The diameter and density of muscle fibers and tenderness of the longissimus dorsi were measured. Growth stage, but not sex, significantly affected DLK1 and IGF-I expression. DLK1 and IGF-I expression in the sheep longissimus dorsi gradually increased with growth, but also decreased during some periods. These results suggest that different growth stages significantly affect DLK1 and IGF-I gene expression in sheep muscle tissue. The ex-pression of DLK1 and IGF-I genes were positively and significantly (P < 0.01) correlated with muscle fiber diameter and muscle fiber shear stress, and negatively and significantly (P < 0.01) correlated with muscle fiber density. Muscle fiber diameter was positively and significantly (P < 0.01) correlated with muscle fiber shear stress, and negatively and significantly (P < 0.01) correlated with muscle fiber density. In addition, DLK-1 expression was significantly (P < 0.01) and positively correlated with IGF-I expression.

The sediment of Ya-Er Lake had been heavily polluted by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from the former chloralkali industry. The total amounts of PCDD/Fs and I-TEQ decreased along the water flow direction and also decreased from top to bottom layers of sediment cores. Sediment of Pond 1 was dominated by PCDF, especially TCDF. In contrast, in the other four ponds, PCDD dominated in all layers and octachlorinated dibenzo-p-dioxin (OCDD) predominated in all of the homologues. When homologue profiles from sediments and water samples were compared using principal component analysis (PCA), the first two principal components represented 95.2% of the variance in the data. The first component explained 75.9% of the variance and the second one 19.3%. Two clusters were most distinct, presenting a shift in PCDD/Fs composition from PCDF to heptachlorinated dibenzo-p-dioxin (HpCDD) and OCDD in sediments and water from Pond I to Ponds 2-5. The pattern variation between Pond 1 and Ponds 2-5 in Ya-Er Lake was most likely due to the change of process in the chemical plant after the dams between the ponds were built. The results of the present study also showed that log K-oc of PCDD/Fs calculated from data of sediment and water in the field were comparable with theoretical log K-oc. The results also implied that the concentrations of PCDD/Fs in water and sediments could be predicted from each other by log K-oc. (C) 2001 Elsevier Science Ltd. All rights reserved.

The concentrations of polychlorinayed dibenzo-p-dioxins and dibenzofurans (PCDD/F) in surface sediment, soil, human hair, and fish muscle from Ya-Er Lake area, China, were analyzed. The results showed that there were very high concentrations of PCDD/F existing in these samples. The results also indicated that Ya-Er Lake, which received a large amount of waste water from a nearby chloroalkali plant, was heavily polluted by PCDD/F. The present study demonstrated that those congeners, which possess at least three chlorine atoms in the lateral position with a fourth chlorine atom in the neighborhood bond of the third single chlorine atom, such as 1,2,7,8-TCDF and 2,3,6,7-TCDF, were very resistant to biodegradation due to the “neighbor effect” of every two chlorine atoms. The present study suggested that human hair may be a suitable alternative bioindicator for detecting PCDD/F exposure. Keywords: Ya-Er Lake, PCDD/F, Persistence, Neighbor effect, Exposure

Bioaccumulation of PCDD/F in the foodweb was investigated in the Ya-Er Lake area, which was heavily polluted by PCDD/F. The high concentrations of PCDD/F in sediment can be transferred and bioaccumulated by aquatic organisms and humans through various pathways. Benthonic invertebrate animals and aquatic plants with a lot of fibers in the root can accumulate PCDD/F from sediment and water. Snail (Bellamya aeruginosa), shrimp (Macrobranchium sp.) and freshwater mussel (Acuticosta chinensis (Lea)) took up PCDD/F from the water and maintained the emission patterns, whereas fish tended to selectively accumulate 2,3,7,8-substituted isomers. The tissues of fish-eating bird and duck (Anas platyrhynchos) were very highly contaminated by PCDD/F due to ingestion of fish and other aquatic organisms from sediment. The residual concentration in breast milk depended on the original concentration of PCDD/F in the food. A resident in Ya-Er Lake area showed a daily intake of PCDD/ F of about 9.14 pg TEQ/kg body weight/day. This is higher than the tolerable daily intake (TDI) for PCDD/F (1 pg TEQ/kg body weight/day), which was recommended by the World Health Organization (WHO). (C) 2001 Elsevier Science Ltd. All rights reserved.

The sexual ratio of Gobiocypris rarus exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 17 beta -estradiol from embryo to sexually mature revealed feminization and overdevelopment of connective tissue in male fish gonad in 2-30 pg/L TCDD concentration range. Daphnia magna was not sensitive to the high dose of TCDD (0.1-1000 ng/ml), but the reproduction of D. magna treated with TCDD decreased after the 8th day. 7-Ethoxyresorufin-O-deethylase (EROD) activities in newly fertilized eggs of G. rarus exposed to TCDD dosage groups (1000-100,000 pg/L) were significantly induced and increased with TCDD concentrations at the early life stage, while no difference was found between low TCDD dosage groups (

The graphite electrode sludge was sampled from a huge chloralkali plant in central China. The total level of PCDD/F was found as high as 378.85 mu g/kg sludge (dry weight). The patterns of PCDD/F in each homologue indicated the predominance of tetra- to octa-chlorinated PCDFs, Furthermore, the toxic 2,3,7,8-substituted PCDFs constituted over 80% of the total PCDFs in the sludge and the corresponding PCDDs were only at 15 mu g/kg level. The calculated value of the international toxic equivalence (I-TEQ) in sludge was 21.65 mu g/kg sludge (dry weight). This typical "dioxin chloralkali pattern" was apparently identified in the sediments near the effluent outlet of the chloralkali plant.

The retention equations ln k' = A + B/T of 49 polychlorinated dibenzo-p-dioxins (PCDDs) and 4 polybrominated dibenzo-p-dioxins (PBDDs) in gas chromatography (GC) have been investigated to evaluate the properties of regression coefficients A and B. The quantitative relationships between A and B values of PCDDs and those of PBDDs are found. The regression equations derived have correlation coefficients greater than 0.997. The A, B values of any PBDD can be predicted by using the A, B values of the PCDD according to these relationships. Using these predicted A and B values, the retention times of all PBDDs can be predicted at any temperature program. It is very useful to identify the peak position of any PBDD because at present there are only a few standards of PBDDs available. (C) 2000 Elsevier Science Ltd. All rights reserved.

A method has been developed for peak recognition of 136 polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) at different temperature programs. Their retention behaviours are predicted on the basis of an identification database of retention values (A, B) of gas chromatography. By the retention times of C-13 labelled 2,3,7,8-substituted PCDD/F internal standards, the retentions of all PCDDs and PCDFs can be calculated. After comparison with the retentions of practical environmental samples, the predicted values have been proved to be very accurate. (C) 2000 Elsevier Science Ltd. All rights reserved.

A column method was developed to conveniently and reliably determine the soil organic partition coefficients (K-oc) of three insecticides (methiocarb, azinphos-methyl, fenthion), four fungicides (triadimenol, fuberidazole, tebuconazole, pencycuron), and one herbicide (atrazine), in which real soil acted as a stationary phase and the water solution of pesticide as an eluent. The processes of sorption equilibrium were directly shown through a breakthrough curve(BTC). The log K-oc values are 1.69, 1.95, 2.25, 2.55, 2.69, 2.67, 3.10, and 3.33 for atrazine, triadimenol, methiocarb, fuberidazole, azinphos-methyl, tebuconazole, fenthion and pencycuron, respectively.

Polyhalogenated aromatic hydrocarbons (PHAH) such as polychlorinat ed dibenzop-dioxins (PCDD), dibenzofurans (PCDF), and biphenyls (PCB) are persistent environmental pollutants, that bioaccumulate throughout the food chain and may pose a health risk to humans and animals (Safe 1994). The most toxic and most studied PHAH is 2,3,7,8-TCDD. PCDD, PCDF, and PCB elicit a number of common biologic and toxic effects in laboratory animals and mammalian cells in culture. The induction of hepatoma microsomal EROD or the associated cytochrome P450 isoenzymes is one of the most characteristic and sensitive response. The toxic mechanism is mediated through combining with the arylhydrocarbon (Ah) receptor (Poland and Knutson 1982; Safe 1990; Whitlock 1993). Since biota in the environment is exposed to mixtures of these compounds rather than to a single congener, simultaneous or sequential exposure of organism to two or more of these compounds may alter quantitative and qualitative biological responses. Therefore, studies with mixtures could provide more information about the possible interactive effects between these compounds and the fundamental mechanisms behind these interactive effects. The concept of independent action, which is sometimes termed effect multiplication, is based on agents acting on different molecular target sites only. An evaluation of tendency and degree of over or under estimation of mixture toxicity can be done by comparative analysis of dose-additive and independent action. The new approach is the use of doseresponse curves (DRC) for evaluating observed combined effects with respect to additive as well as to independence (Poch 1993; Poch et al. 1995). This model and analysis method occasionally are applied in pharmacologic al studies. In general, the simplest cost and time saving approach is to do a dose-response study with a substance A alone and in the presence of a fixed dose of a “similarly” acting substance B. This method is proved can provide a rather simple procedure for obtaining evidence of magnitude and mechanism of action. The aim of the present study was to evaluate the combined effects of 2,3,7,8

This paper reported the sorption, biodegradation and isomerization of hexachlorocyclohexane (HCH) in laboratory sediment/water system under aerobic and anaerobic conditions, respectively. The effect of organic nutrient addition to the sorption of HCH was also investigated. It indicates that HCH is highly adsorbed on sediments under both conditions. During the tests, the biodegradation and isomerization of HCH were dramatically speeded up after organic nutrient additions, especially in the case of the observation under aerobic condition. It was found, beta-HCH was the most persistent in the environment, that is due to the isomerization of alpha-HCH in a big amount to beta-HCH, besides its chemical stability. (C) 1997 Elsevier Science Ltd.

Sediments and soils collected from the Ya-Er Lake area in China were analysed for the polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyl (PCBs), hexachlorocyclohexane (HCHs) and hexachlorobenzene (HCB). The results indicated the main pollution problems in the Ya-Er Lake area, which was heavily polluted by HCHs and chlorobenzenes, now is dominantly polluted by PCDD/Fs, PCBs and HCB. The occurrence of PCDD/Fs and PCBs with relatively high levels of HpCDDs, OCDD and low chlorinated-substituted PCBs, is attributed to the discharge of waste water and biodegradation. The vertical distributions of HCH-residues are related with the content of organic carbon and particle size. Copyright (C) 1996 Elsevier Science Ltd

Extraction experiments with spiking of C-13(12)-PCDD/Fs were performed with a variety of PCDD/Fs contaminated samples. The extraction recovery of PCDD/Fs was mainly influenced by PCDD/Fs concentration and the sample matrix. Generally, the first soxhlet extraction with toluene has suitable recovery. From the selected samples, only FAMS4 and 5 which are fly ashes with high concentration, the recovery of the first soxhlet extraction with 24 hr. is low, but PCDD/Fs were almost completely removed after 72 hr. Copyright (C) 1996 Elsevier Science Ltd

The leaching of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was measured in soil and standard fly ash column eluted with pure water and linear alkylbenzene sulfonate (LAS)- water. The data obtained were used to evaluate the leachability of PCDD/Fs from waste dump like incineration residual slag and fly ash deposition. The leaching rate was shown to be increased significantly by using LAS water. The leachate contents of PCDD/Fs were above their known water solubility. Concentration of PCDD/Fs in the leachates as well as the relative leaching (calculated on the fly ash content) increased with increasing chlorinating degree and decreasing water solubility. LAS above the critical micelle concentration (CMC) probably enhances PCDD/Fs solubility.

Dynamic equations governing the free vibration of laminated composite beams are developed using Hamilton's principle. The effects of transverse shear and rotary inertia are included in the energy formulation. Analytical solutions are obtained by the method of Lagrange multipliers wherein the free vibration problem is posed as a constrained variational problem, the constraints being imposed through Lagrange multipliers. Natural frequencies and mode shapes of clamped-clamped and clamped-supported composite beams are presented to demonstrate the efficiency of the methodology.

To cure harmful longitudinal coupled-bunch mode beam instabilities during high-current and multi-bunch beam operations at the Duke free electron laser (FEL) and high intensity gamma-ray source (HIgammaS) facilities, we have been developing a new generation digital bunch-by-bunch longitudinal feedback (LFB) system which is based on an Integrated gigasample processor (iGp-64F). In this paper, we describe the new generation digital longitudinal feedback system for the Duke FEL and HIgammaS facilities.

Sensitization in kidney transplantation is associated with more acute rejections, inferior graft survival, and an increase in delayed graft function. This study was designed to evaluate the efficacy and safety of preoperative single bolus antithymocyte globulin (ATG) induction therapy in sensitized renal transplant recipients. Methods Fifty-six cadaveric donor kidney transplant recipients were divided into two groups: Group I (nonsensitized group, n = 30) and group II (sensitized group, PRA>10%, n = 26). ATG was given as a single preoperative bolus induction therapy to group II (ATG IV; 9 mg/kg). The group I patients were treated with mycophenolate mofetil preoperatively as induction therapy. The basic immunosuppressive regimen included tacrolimus (FK-506) or cyclosporine, mycophenolate mofetil, and prednisolone. After hospital discharge, patients were followed on a routine outpatient basis for 12 months. Results Acute rejection episodes (ARE) occurred in 20% (6/30) of group I and 15.38% (4/26) of group II patients (P = NS). Infections occurred in eight patients (26.7%) as 11 episodes (36.7%), averaging 1.4 episodes per infected patient in group 1, and 6 patients (23.1%) for a total of 10 episodes (38.5%), averaging 1.7 episodes per infected patient, in group II (P = NS). Occurrence of side effects and hospital stay were almost comparable in the two groups. No delayed graft function was observed in either group. The 12-month actuarial patient and graft survival were 100% in Group I and II. Conclusion A preoperative single bolus ATG induction therapy was an effective and safe therapeutic measure, yielding an acceptable acute rejection rate in presensitized renal transplant recipients.

A concise quantitative model that incorporates information on both environmental temperature M and molecular structures, for logarithm of octanol-air partition coefficient (K-OA) to base 10 (logK(OA)) of PCDDs, was developed. Partial least squares (PLS) analysis together with 14 quantum chemical descriptors were used to develop the quantitative relationships between structures, environmental temperatures and properties (QRSETP) model. It has been validated that the obtained QRSETP model can be used to predict logK(OA) of other PCDDs. Molecular size, environmental temperature (T), q(+) (the most positive net atomic charge on hydrogen or chlorine atoms in PCDD molecules) and E-LUMO (the energy of the lowest unoccupied molecular orbital) are main factors governing logK(OA) of PCDD/Fs under study. The intermolecular dispersive interactions and thus the size of the molecules play a leading role in governing logK(OA). The more chlorines in PCDD molecules, the greater the logK(OA) values. Increasing E-LUMO values of the molecules leads to decreasing logK(OA) values, implying possible intermolecular interactions between the molecules under study and octanol molecules. Greater q(+) values results in greater intermolecular electrostatic repulsive interactions between PCDD and octanol molecules and smaller logK(OA) values. (C) 2002 Elsevier Science B.V. All rights reserved.

Organic pollutants, especially persistent organic pollutants were examined in the water and surface sediments of Taihu Lake, China. Both 12 water and 12 sediment samples were collected over the lake. C-18 solid-phase extraction technique was applied to extract organic pollutants in collected water samples. Soxhlet extraction procedure was used to extract organic pollutants in sediment samples. The analysis was performed by GC-MS controlled by a Hewlett Packard chemstation. Two hundred and seventy-three kinds of organic chemicals in water were examined, 200 more than that detected in 1985; 188 kinds of chemicals in sediments were detected as well. Among them 21 kinds of chemicals belong to priority pollutants as well as 17 kinds to be the endocrine disruptors. The concentrations of the pollutants were more than 2 times higher than that in 1985. The possible source and relation to anthropogenic activity were discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.

The contamination and distribution of polychlorinated dibeinizo-p-dioxins and dibenzofurans (PCDD/Fs) from two agricultural fields of a heavily polluted lake area in China (Ya-Er Lake) are presented. The vertical distribution pattern of total PCDD/Fs in soil cores reveals that the maximum concentration was in the layer of 20-30 cm. The concentrations in the top layer of soil at the two sites were similar (17.48 ng/kg at Site 1 and 18.10 ng/kg at Site 2), but the maximum concentration of Site 1 (120.8 ng/kg) was two times higher than that of Site 2 (64.39 ng/kg). The maximum concentration of PCDD/Fs in mud cores in rice fields (0-50 cm) at Sites 1 and 2 was in the layer of 0-10 cm. The maximum PCDD/F concentration in the top layer in mud at Site 1 (203.1 ng/kg) was higher than that at Site 2: (143.3 ng/kg). Significant correlations were found between the mind PCDD/Fs and the organic carbon content (R = 0.9743, P< 0,05 at Site 1; R = 0.9821, P< 0.05 at Site 2), the two variables being highly correlated (R = 0.9049, P< 0.05, at Site 1; R = 0.9916, P< 0.05 at Site 2). All correlation coefficients were significant at the 95% level. Concentrations were highly correlated with organic carbon, indicating that sorption to organic carbon was the dominant mechanism. Using principal component analysis, the homologue profiles of soil, mud, and plants (rice and radish) were compared. The PCDD/F patterns in plants were found not to be correlated to those in soil and mud. This suggests that atmospheric deposition may be the main source of PCDD/Fs in rice grain. However, mixed exposure involving uptake mechanisms and atmospheric deposition is considered main the source of PCDD/F pollution in radishes. (C) 2002 Elsevier Science (USA).

The present study monitored fish from sites contaminated for many years, and the data reflected the results of actual, long-term environmental exposure. The sum concentrations and TEQs of PCDD/F in the muscle of common carp (Cyprinus carpio (linnaeus)) and big head (Aristichthys nobilis) from the different site of a heavily polluted lake in China are decreased with decrease of PCDD/F concentration in sediment and water. Concentration in fish can be highly variable, but the concentration is comparable in muscle between different species of fish if the concentrations are normalized by lipid content. PCDD/F accumulate in certain tissues with the highest proportions found in the liver of fish. The concentrations and TEQs in livers were also decreased with concentrations of sediments and water. The concentrations of PCDD/F in muscle are significantly correlated with those in liver. BCFs of 2,3,7,8-substituted PCDD/F calculated directly from water were consistent with that calculated indirectly from sediment. PCDD/F concentrations in sediment are much higher than that in water, therefore the measurement is much easier and the results are more accurate. Estimated BCFs for superhydrophobic chemicals derived from sediment may also serve as acceptable surrogates for "true" bioaccumulation potential. (C) 2001 Elsevier Science Ltd. All rights reserved.

The present study monitored 10-year-old fish and piscivorous birds from sites contaminated for many years. The data reflected the results of actual, long-term environmental exposures. The results demonstrate that different tissues of fish have quite different concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F). The concentration order of PCDD/F within fish is liver congruent with egg congruent with intestine>kidney congruent with heart>gill congruent with bladder>muscle>brain. The concentration order of PCDD/F within piscivorous birds was liver>egg congruent with heart>muscle congruent with stomach>brain. The results obtained also demonstrate that the accumulation patterns of piscivorous birds and fish are quite different. The tissues of fish and piscivorous birds have different capacities for bioaccumulation and biotransformation of PCDD/F; variable proportions of TEQs were also found throughout their bodies. In fish, toxic equivalency quotient (TEQ): PCDD/F ratios in various tissues ranged from 0.01 to 0.07, whereas in birds the ratios ranged from 0.07 to 0.43. If the concentrations are normalized with lipid content, the results vary less. The effect of different lipid properties is obvious in the case of brain tissue, which is richer in phospholipids.

Cytological and biochemical alterations of crucial carp (Carassius auratus) hepatocytes were characterized after exposure to sediments from a lake contaminated with dioxins and other industrial chemicals. Carp were exposed in 20 L water containing 25, 50, or 100 g of contaminated sediment for 2 and 4 weeks. Ultrastructural changes in the liver were characterized by severe enlargement of hepatocytes. Alterations in the cell included formation of condensed and irregular cell nucleus, polynuclei, dispersed heterochromatin, enlargement of the nucleolus, and degeneration of the nucleus. Mitochondrial numbers were reduced and cristae were deformed. Myelin figures and lysosomes were increased, and sometimes cell organelles and cell matrix were totally lost after 4 weeks of exposure. The ultrastructural alterations were correlated with exposure time and sediment concentrations. Hepatosometic index was significantly increased in experimental groups at 2 and 4 weeks as compared with the control group. EROD enzyme activities were strongly induced in liver. A trend from rough endoplasmic reticulum (RER) to SER was observed. Our results suggest that the dioxin-like compounds bound by sediment were bioavailable to C. auratus and cause sublethal effects.

A new Enzyme ImmunoAssay (EIA) for PCDD/F TEQ measurement in extracts of environmental samples was described. The bioassay TEQ which derived from EIA and EROD were compared with each other and with results from chemical analysis. For all environmental samples, the EROD-TEQ is higher than the value from chemical analysis. However, the EIA-TEQ is much more identical with the value from chemical analysis. Our results indicate that the EIA assay is a complementary method to the EROD assay and should be useful as a rapid and sensitive screening tool for environmental samples in many situations.

The effects of aquatic humic acids on the bioconcentration and acute toxicity of fenpropathrin were evaluated using grass carp, Ctenopharyngodon idellus, in laboratory freshwater systems. The results demonstrated that both bioavailability and acute toxicity decreased in the presence of aquatic humic acid 5 and 10 mg/liter. In addition, the extent of influence increased with increasing concentration of aquatic humic acid.

Small transverse oscillation of an endless band supported by wheels couples the response of the free spans of the band to oscillation of the wheels. The coupling arises from the finite curvature of the free spans of the band when its bending stiffness is finite. Significant modeling error can occur if a single span of the band is modeled as a simply supported, axially moving beam. The coupling provides an opportunity to dissipate vibration energy. Experiments and finite element analyses support the coupling discussion presented.

Simple torsion parametric resonance and combination torsion-bending parametric resonance can be excited in an axially moving band by an in-plane periodic edge loading that is normal to the longitudinal axis of the band. The model simulates band saws, belts, magnetic tapes and like systems under edge forces. Sum combination instabilities, in particular, permit the excitation of low frequency resonances by higher frequency edge forces. Simple bending, combination torsion-torsion, combination bending-bending and difference type parametric instabilities are not excited by periodic normal edge forces. The space of band parameters leading to parametric instability shrinks with increasing axial tension and with increasing band velocity.