bluuebunny/crossref_metadata_2025_split huggingface dataset:
Toxic effect of serial perfluorosulfonic and perfluorocarboxylic acids on the membrane system of a freshwater alga measured by flow cytometry
Authors: Liu Wei , Chen Shuo , Quan Xie , Jin Yi-He 
Published: June 2008

AbstractFlow cytometric measurements were used to investigate the toxic effect of perfluorobutanoic sulfonate (PFBS), perfluorooctane sulfonate (PFOS), perfluorohexanoic acid (PFHxA), perfluorooctanoic acid (PFOA), perfluorododecanoic acid (PFDoA), and perfluorotetradecanoic acid (PFTeA) on some membrane systems of the freshwater alga species Scenedesmus obliquus. Among the test compounds, PFOS, PFDoA, and PFTeA inhibited algal growth rate in a concentration-dependent manner while PFBS, PFHxA, and PFOA did not inhibit algal growth within the test concentration ranges. An enhancement of the mitochondrial membrane potential (MMP) and cell membrane permeability in S. obliquus was observed caused by exposure to PFOS, PFOA, PFDoA, and PFTeA. Both carbon chain length and acid group influenced the toxicity of PFAAs, where the toxicity increased with increasing carbon chain length for the compounds belonging to the same class. The observed effective concentrations lie in the micromole range and the test compounds disrupted membrane properties at concentrations below those associated with algal growth inhibition. Flow cytometry is proved to be a useful technique for toxicity testing with microalgae and provide additional information regarding the mode of action of PFAAs to algal species.
A review of independent action compared to concentration addition as reference models for mixtures of compounds with different molecular target sites
Authors: Cedergreen Nina , Christensen Anne M , Kamper Anja , Kudsk Per , Mathiassen Solvejg K , Streibig Jens C , Sørensen Helle 
Published: June 2008

Abstract
From a theoretical point of view, it has often been argued that the model of independent action (IA) is the most correct reference model to use for predicting the joint effect of mixtures of chemicals with different molecular target sites. The theory of IA, however, relies on a number of assumptions that are rarely fulfilled in practice. It has even been argued that, theoretically, the concentration addition (CA) model could be just as correct. In the present study, we tested the accuracy of both IA and CA in describing binary dose-response surfaces of chemicals with different molecular targets using statistical software. We compared the two models to determine which best describes data for 158 data sets. The data sets represented 98 different mixtures of, primarily, pesticides and pharmaceuticals tested on one or several of seven test systems containing one of the following: Vibrio fischeri, activated sludge microorganisms, Daphnia magna, Pseudokirchneriella subcapitata, Lemna minor, Tripleurospermum inodorum, or Stellaria media. The analyses showed that approximately 20% of the mixtures were adequately predicted only by IA, 10% were adequately predicted only by CA, and both models could predict the outcome of another 20% of the experiment. Half of the experiments could not be correctly described with either of the two models. When quantifying the maximal difference between modeled synergy or antagonism and the reference model predictions at a 50% effect concentration, neither of the models proved significantly better than the other. Thus, neither model can be selected over the other on the basis of accuracy alone.
Examining the single and interactive effects of three insecticides on amphibian metamorphosis
Authors: Boone Michelle D 
Published: June 2008

Abstract
Although aquatic communities frequently are exposed to a number of pesticides, the effects of chemical mixtures are not well understood. In two separate studies, I examined how insecticide mixtures influenced the likelihood of unpredictable, nonadditive effects on American toad (Bufo americanus) and green frog (Rana clamitans) tadpoles reared in outdoor aquatic communities. I exposed tadpoles to single or multiple insecticides at approximately half the reported median lethal concentrations using insecticides that were either acetylcholinesterase inhibitors (carbaryl or malathion) or a sodium-channel disruptor (permethrin). I found that combinations of insecticides with the same mode of action were more likely to have nonadditive effects on amphibian metamorphosis compared with those having different modes of action. Additionally, in one study, a commercial formulation of permethrin led to near-complete elimination of American toads, suggesting that this formulation could have adverse effects on aquatic communities. Many community studies exploring the ecological effects of expected environmental concentrations of pesticides have suggested that indirect effects in the food web, rather than direct effects on individual physiology, have the largest effect on amphibians. The present study indicates that direct effects of pesticides may become particularly important when insecticides with the same mode of action are present in the environment.
Hormesis: Why it is important to toxicology and toxicologists
Authors: Calabrese Edward J 
Published: June 2008

AbstractThis article provides a comprehensive review of hormesis, a dose-response concept that is characterized by a low-dose stimulation and a high-dose inhibition. The article traces the historical foundations of hormesis, its quantitative features and mechanistic foundations, and its risk assessment implications. The article indicates that the hormetic dose response is the most fundamental dose response, significantly outcompeting other leading dose-response models in large-scale, head-to-head evaluations. The hormetic dose response is highly generalizable, being independent of biological model, endpoint measured, chemical class, and interindividual variability. Hormesis also provides a framework for the study and assessment of chemical mixtures, incorporating the concept of additivity and synergism. Because the hormetic biphasic dose response represents a general pattern of biological responsiveness, it is expected that it will become progressively more significant within toxicological evaluation and risk assessment practices as well as have numerous biomedical applications.
The influences of ambient and body calcium on cadmium and zinc accumulation in Daphnia magna
Authors: Tan Qiao-Guo , Wang Wen-Xiong 
Published: June 2008

Abstract
The dissolved uptake rate constant (ku), dietary assimilation efficiency (AE), and efflux rate constant (ke) of cadmium (Cd) and zinc (Zn) were quantified in a freshwater zooplankton Daphnia magna cultured at different ambient calcium (Ca) concentrations. The animals were first acclimated to different ambient Ca levels for 7 d from birth before the biokinetic measurements at corresponding Ca levels. With increasing ambient Ca level from 0.5 to 200 mg/L, the body Ca content increased from 0.91% (as tissue dry wt) to 3.75%. The ku for Cd decreased by nine times; for Zn it decreased by 2.6 times; and the AE decreased from 62 to 19% and from 46 to 24% for Cd and Zn, respectively. In contrast, Ca levels did not affect significantly the efflux rates of Cd and Zn. The effects of ambient and body Ca levels were separated by measuring the biokinetic parameters in both low- (0.5 mg/L) and high- (50 mg/L) Ca environments using the daphnids containing different body Ca levels. Ambient and body Ca levels had synergistic inhibitory effects on the AEs of Cd and Zn; however, the protective effects against dissolved uptake of Cd and Zn were explained fully by the effects of ambient Ca. The body Ca either had no significant effect (for Cd) or stimulative effects (for Zn). Multiphase biokinetic modeling using the measured parameters gave reasonable predictions of the body burdens of Cd and Zn in different Ca environments. Our results better explain the role of ambient and body Ca in the accumulation of Cd and Zn in D. magna.
Effective Open Hole Horizontal Completion System for Multistage Fracturing and Stimulation
Authors: Seale R. , Athans J. 
Published: June 2008

Abstract
This paper describes an efficient multistage horizontal openhole (OH) completion technique as an alternative to conventional openhole or cemented and perforated lateral completions. The application focuses on OH completions in the Edwards Lime of South Texas. Horizontal wells have been drilled extensively in this deep high temperature gas field. This paper will detail the new horizontal completion system run as part of the production liner, which does not require cementing and provides mechanical diversion at specified intervals, so fracturing and stimulations can be pumped effectively to their targeted zone. Details of the engineering design and testing will be specified, with extensive elaboration on the applications and case histories were these systems have been successfully deployed. The case histories will detail the operational efficiencies of the system in conjunction with the enhanced production realized.
Hydrajet Perforating and Proppant Plug Diversion in Multi-Interval Horizontal Well Fracture Stimulation: Case Histories
Authors: East Loyd E. , Bailey Michael , McDaniel B. W. 
Published: June 2008

Abstract
This case history paper presents fracture stimulation using coiled tubing (CT) hydrajetting, followed by (1) annular-path pumping of the fracturing treatment and (2) use of high-concentration proppant slugs to create proppant plugs for diversion. The process of hydrajet perforating and annular-path pumping (HPAP) has been used effectively for vertical well completions and is especially applicable for multi-interval completions. Further, use of this process for multi-interval fracturing of horizontal well completions has been performed successfully in several North America reservoirs, and in Texas at depths below 15,700 ft true vertical depth (TVD) and measured depths (MD) of more than 16,700 ft.
Cased and cemented horizontal completions present several challenges for the HPAP method, including (1) unique CT calculations and operating procedures, and (2) proppant plug-setting procedures. This multi-stage completion process can also be applied in other methods of horizontal completions that incorporate a solid liner.
Several case histories are examined to (1) highlight lessons learned in performance of this method on horizontal well completions, and (2) demonstrate efficiencies gained as compared to following conventional practices.
Improved Single-Trip Multistage Completion Systems for Unconventional Gas Formations
Authors: Durst Doug G. , Travis Harris , Contreras Jesus D. , Watson Don R. 
Published: June 2008

Abstract
Cost-effective development of unconventional gas resources depends upon strategic application of advancing technologies. By employing efficient fracturing techniques with an appropriate multi-stage fracturing completion, operators can achieve higher initial gas rates, increased recovery rates and reduced completion costs. The completion process employs a single-trip multi-stage isolation completion system which is driving the cost-effective exploitation of difficult reservoirs. Operational issues, case studies and system improvements, such as the means to isolate water producing zones, will be covered.
Key factors to be reviewed include reserve estimates, selection of number of fractures, production behavior analysis, production forecast analysis, risk analysis, fracture design, and economic evaluation.
Installation strategy issues will be addressed regarding equipment and operations such as quantity and spacing of packers and sleeves as well as the fracturing process. These strategies are critical relative to achieving mechanical, volumetric and economic success which is established by the efficiency of each fracture and total gas production rate when compared to initial evaluations.
The one-trip multi-stage isolation fracturing completion process reduces rig time and cost for hydraulic fracturing services, accelerates production and improves reservoir drainage. When coupled with effective fracturing strategies and best practice procedures, the system provides improved production from unconventional gas formations.
Observations From Tight Gas Reservoir Stimulations in the Rocky Mountain Region
Authors: Borchardt Erik , Cavens Jessica , Wieland Craig , Pluemer Brian , Graham Don , Erwemi Abdunnaser , Kazantsev Aleksey , Calvez Joel Le 
Published: June 2008

Abstract
Introduction
Unconventional tight gas reservoirs are made economical through effective stimulation techniques. Hydraulic fracture mapping combined with an in-depth knowledge of reservoir geology and geomechanics can give a better understanding to the effectiveness of reservoir stimulation. Massive hydraulic fractures from two wells in the Rocky Mountain region were mapped in real time with a 3-D stimulation viewer software package. One well employed techniques standard to the area –while some experimental fracture techniques were tested on the other. A general east-west orientation of planar fracture geometry was found with a maximum fracture event length of 800 feet. The planer fracturing scheme is consistent with low amounts of acoustic anisotropy recorded. Increasing treating and bottom hole pressures with time observed in this study indicate fracture length growth for each stage. 11 and 12 stages were chosen for the two well completion program based on data from an open hole logging and geomechanics.
Some experimental fracturing techniques were tested including longer pump times, larger sand volumes, high viscosity fracture fluids, re-fracturing for re-orientation, using temporary, degradable fiber plugs between stages, and plugging of stages with ball sealers. Perforation entry by stage was effective and some stages could possibly be eliminated to save cost. There is not a direct correlation between pump time, sand volume, and stage height. Ball sealers were not an optimum method for closing off a stage for fracturing, but there is evidence that degradable fiber plugs could be a cost saving option between stages. This paper outlines in more detail the observations from hydraulic fracture mapping in this area.
Regional Background
This area of study includes 3000 vertical feet of fluvial and marine sands located in the Rocky Mountain region of the United States. (Figure 1) The formation contains natural fractures, laterally restricted lenticular sandstones, and tight brittle sands. The main natural gas reservoir interval is from 5000 to 8500 feet. The productive sands have an average porosity of about 7% and permeability is in the micro-Darcy range. The first well was drilled in this region of the Rocky Mountains in 1955. In the late 1990's the discovery of increased production by fracturing lenticular sands has made this a profitable area. Due to the nature of these tight sands – wells can be located in closer proximity without lowering the production rates of neighboring wells. Wells are currently drilled on 10 acre density. Much of the area uses directional drilling from pad wells to reduce surface damage.
The main wastewater treatment plant of Vienna: favourable operation conditions as a consequence of well designed tender procedures
Authors: Partaj T. , Papp M. , Weiss J. 
Published: June 2008

In the planning phase of the extension of the Main Treatment Plant of Vienna, special effort and emphasis were put on the conception of the tender procedure. The project tender was divided into several tender units in order to achieve optimum quality standards by specialised workmanship. Important parameters for operation conditions, especially energy consumption and maintenance costs, were considered and valuated according to the tender guidelines. Suppliers were required to prove the guaranteed quality standards of the tender documents by means of preliminary installation units and extensive performance check procedures. Only after fulfilment of all requirements were suppliers allowed to apply the design of the preliminary installation works to the entire installation. If necessary, extensive optimization works were carried out. Thus favourable operation conditions were achieved and, in particular, a highly efficient aeration system was implemented.
Process parameters were optimized by means of a follow-up project during the regular operation phase, taking into consideration the results of the performance check procedures. Further optimization of energy consumption was thereby achieved.
A cost comparison of traditional drainage and SUDS in Scotland
Authors: Duffy A. , Jefferies C. , Waddell G. , Shanks G. , Blackwood D. , Watkins A. 
Published: June 2008

The Dunfermline Eastern Expansion (DEX) is a 350 ha mixed development which commenced in 1996. Downstream water quality and flooding issues necessitated a holistic approach to drainage planning and the site has become a European showcase for the application of Sustainable Urban Drainage Systems (SUDS). However, there is minimal data available regarding the real costs of operating and maintaining SUDS to ensure they continue to perform as per their design function. This remains one of the primary barriers to the uptake and adoption of SUDS. This paper reports on what is understood to be the only study in the UK where actual costs of constructing and maintaining SUDS have been compared to an equivalent traditional drainage solution. To compare SUDS costs with traditional drainage, capital and maintenance costs of underground storage chambers of analogous storage volumes were estimated. A whole life costing methodology was then applied to data gathered. The main objective was to produce a reliable and robust cost comparison between SUDS and traditional drainage.
The cost analysis is supportive of SUDS and indicates that well designed and maintained SUDS are more cost effective to construct, and cost less to maintain than traditional drainage solutions which are unable to meet the environmental requirements of current legislation.
In situ measurements of shear stresses of a flushing wave in a circular sewer using ultrasound
Authors: Staufer P. , Pinnekamp J. 
Published: June 2008

Deposits build up in sewer networks during both spells of dry weather and in connection with storm water events. In order to reduce the negative effects of deposit on the environment, different cleaning technologies and strategies are applied to remove the deposits. Jet cleaning represents the most widely used method to clean sewers. Another alternative cleaning procedure is flushing. On account of new developments in measurement and control panels, the flushing method is becoming more important. Therefore, in the last few years a number of new flushing devices have been constructed for application in basins, main sewers and initial reaches. Today, automatic flushing gates are able to accomplish cleaning procedures under economical and ecological conditions.
The properties of flushing waves for cleaning sewers have been determined by several mathematical-numerical studies. These various investigations use altering numerical schemes, are based on different sets of physical equations and take one- or more dimensional aspects into account. Considering that bottom shear stress is the key value to evaluate the beginning of motion of any deposit, one may use this value that has to be determined by measurements. This paper deals with shear stresses caused by flushing waves which have been measured by an ultrasonic device that can determine the velocity in different depths of flow. Thus, it is possible, within certain limits, to calculate bottom shear stresses based on the log-wall law. Further discussion will deal with the requirements of measurements, its uncertainty and aspects in respect to the application of simulation of flushing waves.
Risk-profile and outcome of small papillary and follicular thyroid carcinomas (≤1 cm)
Authors: Hutzenlaub V. , Fischer R.-J. , Schober O. , Riemann B. , Rahbar K. 
Published: June 2008

Summary
Aim: According to the procedure guidelines of the German Society of Nuclear Medicine no radioiodine ablation is necessary in patients with papillary microcarcinomas in case of limited surgical resection. Few data are available with respect to the optimal management of patients with small follicular thyroid carcinomas. It was the aim to compare risk-profile and outcome of patients with small papillary (PTC) and follicular thyroid carcinomas (FTC) ≤1 cm. Patients, methods: 1594 patients with thyroid cancer were attended at our department between 1995 and 2006. For the subgroup of 383 patients with small PTC and FTC ≤1 cm a comparative correlation of multifocality, extrathyroidal growth, lymph node spread, distant metastasis, local recurrence and survival was performed. Patients were monitored for a mean follow-up time of six years. Results: A total of 361 patients had PTC and 22 FTC ≤1 cm. At presentation the mean age of the 306 women and 77 men was 49 ± 13 years. An ablative radioiodine therapy was performed in 77% and 100% of patients with small PTC and FTC, respectively. Multifocality (14% vs. 9%), extrathyroidal growth (10% vs. 5%), lymph node spread (14% vs. 5%), local recurrence (0.5% vs. 0%) and progressive disease (1% vs. 0%) were more common in patients with small PTC than FTC, whereas the corresponding values for distant metastasis were 2% vs. 5%, respectively; however, these figures did not reach statistical significance. Eight patients with papillary microcarcinomas died because of nonthyroidal diseases. Conclusion: Our data show no statistically significant differences in the risk-profile and outcome of patients with small PTC and FTC ≤1 cm. Therefore, the decision for or against radioiodine ablation in patients with small differentiated thyroid carcinomas should be discussed individually.
Thyroid sonomorphology, thyroid peroxidase antibodies and thyroid function
Authors: Balzer K. , Diener J. , Wegscheider K. , Vaupel R. , Grünwald F. , Döbert N. 
Published: June 2008

Summary
Aim: Employees of Sanofi-Aventis Deutschland GmbH underwent thyroid screening in 2006 to assess new data about the prevalence of irregular sonomorphological pattern, elevated thyroid peroxidase antibodies (TPO AB) and thyroid function in an unselected adult German population. Participants, methods: The examination included 700 unselected employees. Blood samples were analyzed for serum TSH and TPO AB, and ultrasound of the thyroid was performed. Results: In 40.7% of the participants (n = 285) an irregular sonomorphological pattern was detected: goiter in 13.7%, nodules in 35.6%, nodular goiter in 8.6% and a hypoechogenic pattern of the thyroid gland in 20.4%. Serum TSH was increased in 3.9% and decreased in 0.6%. Elevated TPO AB values were observed in 13%. Only 1.4% (n= 10) showed elevated TPO AB combined with a TSH increase. Sonomorphological abnormalities were associated with increased TPO AB in 7.1%. Elevated TPO AB was observed significantly more often in combination with sonomorphological pathology (54.9%) than without (45.1%) (p = 0.003). Conclusions: Sonomorphological disorders are still very common in Germany and our results are comparable with previous screening examinations. Elevated TPO AB correlated significantly with the sonomorphological pattern of nodules and goiter. This may reflect an improved iodine supply or a hypertrophic stage of autoimmune thyroiditis in some cases.