bluuebunny/crossref_metadata_2025 huggingface dataset:
Rational Design of Drugs That Induce Human Immunodeficiency Virus Replication
Authors: Hamer Dean H. , Bocklandt Sven , McHugh Louise , Chun Tae-Wook , Blumberg Peter M. , Sigano Dina M. , Marquez Victor E.
Published: September 2003

Drugs that induce human immunodeficiency virus type 1 (HIV-1) replication could be used in combination with highly active antiretroviral therapy (HAART) to reduce the size of the latent reservoir that is in part responsible for viral persistence. Protein kinase C (PKC) is a logical target for such drugs because it activates HIV-1 transcription through multiple mechanisms. Here we show that HIV-1 gene expression can be induced by potent synthetic analogues of the lipid second messenger diacylglycerol (DAG) synthesized on a five-member ring platform that reduces the entropy of binding relative to that of the more flexible DAG template. By varying the alkyl side chains of these synthetic DAG lactones, it was possible to maximize their potency and ability to render latently infected T cells sensitive to killing by an anti-HIV-1 immunotoxin while minimizing the side effects of CD4 and CXCR4 downregulation and tumor necrosis factor alpha upregulation. The two lead compounds, LMC03 and LMC07, regulated a series of PKC-sensitive genes involved in T-cell activation and induced viral gene expression in peripheral blood mononuclear cells from HIV-1-infected individuals. These studies demonstrate the potential for the rational design of agents that, in conjunction with HAART and HIV-specific toxins, can be used to decrease or eliminate the pool of latently infected reservoirs by forcing viral expression.
Proteasome Activator PA28γ-Dependent Nuclear Retention and Degradation of Hepatitis C Virus Core Protein
Authors: Moriishi Kohji , Okabayashi Tamaki , Nakai Kousuke , Moriya Kyoji , Koike Kazuhiko , Murata Shigeo , Chiba Tomoki , Tanaka Keiji , Suzuki Ryosuke , Suzuki Tetsuro , Miyamura Tatsuo , Matsuura Yoshiharu
Published: September 2003

Hepatitis C virus (HCV) core protein plays an important role in the formation of the viral nucleocapsid and a regulatory protein involved in hepatocarcinogenesis. In this study, we have identified proteasome activator PA28γ (11S regulator γ) as an HCV core binding protein by using yeast two-hybrid system. This interaction was demonstrated not only in cell culture but also in the livers of HCV core transgenic mice. These findings are extended to human HCV infection by the observation of this interaction in liver specimens from a patient with chronic HCV infection. Neither the interaction of HCV core protein with other PA28 subtypes nor that of PA28γ with otherFlaviviruscore proteins was detected. Deletion of the PA28γ-binding region from the HCV core protein or knockout of the PA28γ gene led to the export of the HCV core protein from the nucleus to the cytoplasm. Overexpression of PA28γ enhanced the proteolysis of the HCV core protein. Thus, the nuclear retention and stability of the HCV core protein is regulated via a PA28γ-dependent pathway through which HCV pathogenesis may be exerted.
Tissue-Specific Replicating Capacity of a Chimeric Poliovirus That Carries the Internal Ribosome Entry Site of Hepatitis C Virus in a New Mouse Model Transgenic for the Human Poliovirus Receptor
Authors: Yanagiya Akiko , Ohka Seii , Hashida Noriyasu , Okamura Masahito , Taya Choji , Kamoshita Nobuhiko , Iwasaki Kuniko , Sasaki Yukari , Yonekawa Hiromichi , Nomoto Akio
Published: September 2003

Nucleotides (nt) 108 to 742 of an infectious cDNA clone of poliovirus (PV) Mahoney strain, including the corresponding region of the internal ribosome entry site (IRES), was replaced by nt 28 to 710 of hepatitis C virus (HCV) cDNA corresponding to the whole HCV IRES. A chimeric PV (2A-369) was generated by transfecting mammalian cells with an RNA transcribed in vitro from the cDNA. To examine replicating capacity of virus 2A-369 in the brain and liver of a mouse model for poliomyelitis, a new mouse model (MPVRTg25-61) that is transgenic for human PV receptor (hPVR; CD155) was generated in order to obtain a higher expression level of hPVR in the liver than those of hPVRTg mouse lines generated by us so far. The transgene used was constructed by combining a putative regulatory region of the mouse PVR homolog and the whole structural region of the hPVR gene. Virus 2A-369 replicated well in the liver of MPVRTg25-61 but not in the brain, whereas control Mahoney virus replicated well both in the liver and in the brain. The data suggest that the HCV IRES works more efficiently in the liver than in the brain and that PV IRES works well both in the liver and in the brain. The results support the notion that tissue-specific activity of IRES may be reflected in tissue tropism of a virus whose specific translation initiation is driven by IRES, that is, an IRES-dependent virus tropism.
Access of Antibody Molecules to the Conserved Coreceptor Binding Site on Glycoprotein gp120 Is Sterically Restricted on Primary Human Immunodeficiency Virus Type 1
Authors: Labrijn Aran F. , Poignard Pascal , Raja Aarti , Zwick Michael B. , Delgado Karla , Franti Michael , Binley James , Vivona Veronique , Grundner Christoph , Huang Chih-Chin , Venturi Miro , Petropoulos Christos J. , Wrin Terri , Dimitrov Dimiter S. , Robinson James , Kwong Peter D. , Wyatt Richard T. , Sodroski Joseph , Burton Dennis R.
Published: September 2003

Anti-human immunodeficiency virus type 1 (HIV-1) antibodies whose binding to gp120 is enhanced by CD4 binding (CD4i antibodies) are generally considered nonneutralizing for primary HIV-1 isolates. However, a novel CD4i-specific Fab fragment, X5, has recently been found to neutralize a wide range of primary isolates. To investigate the precise nature of the extraordinary neutralizing ability of Fab X5, we evaluated the abilities of different forms (immunoglobulin G [IgG], Fab, and single-chain Fv) of X5 and other CD4i monoclonal antibodies to neutralize a range of primary HIV-1 isolates. Our results show that, for a number of isolates, the size of the neutralizing agent is inversely correlated with its ability to neutralize. Thus, the poor ability of CD4i-specific antibodies to neutralize primary isolates is due, at least in part, to steric factors that limit antibody access to the gp120 epitopes. Studies of temperature-regulated neutralization or fusion-arrested intermediates suggest that the steric effects are important in limiting the binding of IgG to the viral envelope glycoproteins after HIV-1 has engaged CD4 on the target cell membrane. The results identify hurdles in using CD4i epitopes as targets for antibody-mediated neutralization in vaccine design but also indicate that the CD4i regions could be efficiently targeted by small molecule entry inhibitors.
Exploitation of Nucleic Acid Packaging Signals To Generate a Novel Influenza Virus-Based Vector Stably Expressing Two Foreign Genes
Authors: Watanabe Tokiko , Watanabe Shinji , Noda Takeshi , Fujii Yutaka , Kawaoka Yoshihiro
Published: September 2003

At the final step in viral replication, the viral genome must be incorporated into progeny virions, yet the genomic regions required for this process are largely unknown in RNA viruses, including influenza virus. Recently, it was reported that both ends of the neuraminidase (NA) coding region are critically important for incorporation of this vRNA segment into influenza virions (Y. Fujii, H. Goto, T. Watanabe, T. Yoshida, and Y. Kawaoka, Proc. Natl. Acad. Sci. USA
100:
2002-2007, 2003). To determine the signals in the hemagglutinin (HA) vRNA required for its virion incorporation, we made a series of deletion constructs of this segment. Subsequent analysis showed that 9 nucleotides at the 3′ end of the coding region and 80 nucleotides at the 5′ end are sufficient for efficient virion incorporation of the HA vRNA. The utility of this information for stable expression of foreign genes in influenza viruses was assessed by generating a virus whose HA and NA vRNA coding regions were replaced with those of vesicular stomatitis virus glycoprotein (VSVG) and green fluorescent protein (GFP), respectively, while retaining virion incorporation signals for these segments. Despite the lack of HA and NA proteins, the resultant virus, which possessed only VSVG on the virion surface, was viable and produced GFP-expressing plaques in cells even after repeated passages, demonstrating that two foreign genes can be incorporated and maintained stably in influenza A virus. These findings could serve as a model for the construction of influenza A viruses designed to express and/or deliver foreign genes.
Relationship among Location of T-Antigen-Induced DNA Distortion, Auxiliary Sequences, and DNA Replication Efficiency
Authors: Okuley Susan , Call Mindy , Mitchell Tara , Hu Bugen , Woodworth Mary E.
Published: September 2003

T-antigen-induced DNA distortion was studied in a series of simian virus 40 (SV40) plasmid constructs whose relative replication efficiency ranges from 0.2 to 36. Bending was detected in the wild-type SV40 regulatory region consisting of three copies of the GC-rich 21-bp repeat but not in constructs with only one or two copies of the 21-bp repeat. In a construct with enhanced replication efficiency, bending occurred in a 69-bp cellular sequence located upstream of a single copy of the 21-bp repeat. Bending occurred both upstream of
ori
and in the three 21-bp repeats located downstream of
ori
in a construct with reduced replication efficiency. In a construct with no 21-bp repeats, DNA distortion occurred downstream of
ori
. The results indicate that SV40 DNA replication is enhanced when the structure of the regulatory region allows the DNA to form a bent structure upstream of the initial movement of the replication fork.
Dynamics of Subgenomic Hepatitis C Virus Replicon RNA Levels in Huh-7 Cells after Exposure to Nucleoside Antimetabolites
Authors: Stuyver Lieven J. , McBrayer Tamara R. , Tharnish Phillip M. , Hassan Abdalla E. A. , Chu Chung K. , Pankiewicz Krzysztof W. , Watanabe Kyochi A. , Schinazi Raymond F. , Otto Michael J.
Published: September 2003

Treatment with antimetabolites results in chemically induced low nucleoside triphosphate pools and cell cycle arrest in exponentially growing cells. Since steady-state levels of hepatitis C virus (HCV) replicon RNA were shown to be dependent on exponential growth of Huh-7 cells, the effects of antimetabolites for several nucleoside biosynthesis pathways on cell growth and HCV RNA levels were investigated. A specific anti-HCV replicon effect was defined as (i) minimal interference with the exponential cell growth, (ii) minimal reduction in cellular host RNA levels, and (iii) reduction of the HCV RNA copy number per cell compared to that of the untreated control. While most antimetabolites caused a cytostatic effect on cell growth, only inhibitors of the de novo pyrimidine ribonucleoside biosynthesis mimicked observations seen in confluent replicon cells, i.e., cytostasis combined with a sharp decrease in replicon copy number per cell. These results suggest that high levels of CTP and UTP are critical parameters for maintaining the steady-state level replication of HCV replicon in Huh-7 cells.
A simulation model for designing groundfish trawl surveys
Authors: Schnute J T , Haigh R
Published: September 2003

This paper describes a convenient simulation model, based on the compound binomial-gamma distribution, to assist the planning and design of groundfish trawl surveys. The analysis uses swept-area density measurements from stratified tows to give a simple nonparametric biomass estimate. A parametric simulation model requires only three input parameters for each stratum, which can be estimated initially from past surveys or commercial fishery data. Analytical results provide intuitive algorithms for estimating variances, investigating tow allocation strategies, and exploring potential survey results. Simulations make it possible to compare the estimated biomass with its true value and to assess coverage properties of confidence intervals obtained from bootstraps. Bias correction and acceleration both improve the results, but small samples taken from populations with highly variable densities tend to produce underestimates of available biomass. The simulation framework allows easy adaptation to address broader issues, such as the design of a multispecies survey.
Calculation of untrawlable areas within the boundaries of a bottom trawl survey
Authors: Zimmermann Mark
Published: September 2003

A geographic information system (GIS) analysis of 5039 bottom trawl events from U.S. west coast bottom trawl surveys (19771998) estimated that the survey area was about 77% trawlable but five of the 30 strata were less than 50% trawlable. Untrawlable areas, by definition, cannot be surveyed with the bottom trawl; however, there has never been a means of identifying and excluding these areas from relative abundance estimates, which are calculated only from hauls completed in the trawlable portions of each stratum. Unknown amounts of untrawlable habitat are a problem for relative abundance estimation in many bottom trawl surveys. This manuscript describes one method of using the bottom trawling events of a survey, such as ripped-up hauls and abandoned stations, to calculate the amount of area that is untrawlable. A comparison of catch rates between undamaged tows and a limited number of damaged tows, which are normally discarded as faulty samples, showed that Sebastes catch rates were generally higher in damaged tows. Thus untrawlable areas may have substantial importance on relative abundance estimates of Sebastes, the original target species group for this survey.
Productive capacity of an artificial stream in the Canadian Arctic: assessing the effectiveness of fish habitat compensation
Authors: Jones Nicholas E , Tonn William M , Scrimgeour Garry J , Katopodis Chris
Published: September 2003

Few fish habitat compensation projects are assessed with respect to the principle of "no net loss" of productive capacity. Using reference streams as standards against which gains and losses of functions (e.g., production of fish) could be quantified, we examined the effectiveness of a 3.4-km artificial stream in the Northwest Territories, Canada. The artificial stream restored watershed connectivity, allowing fish migration and provided spawning and nursery habitat, particularly for Arctic grayling (Thymallus arcticus). However, the average mass of young-of-the-year (YOY) grayling at the end of summer was lower (57%) in the artificial stream than in natural streams. This difference in growth, in concert with estimates of grayling density, meant that the standing crop produced in the artificial stream averaged 37% of that found in natural streams. A bioenergetics model indicated that cooler water temperatures in the artificial stream had limited influence on growth. Instead, low amounts of autochthonous and allochthonous organic matter and poor physical habitat in the artificial stream appeared to limit the productivity of benthic invertebrates and fish. Our explicit analysis of productive capacity will allow future compensation measures to focus on deficiencies in the artificial stream and on the improvement of its productive capacity as fish habitat.
Relationships between organic matter composition and methyl mercury content of offshore and carbon-rich littoral sediments in an oligotrophic lake
Authors: Kainz Martin , Lucotte Marc , Parrish Christopher C
Published: September 2003

Relationships between organic matter (OM) compounds and methyl mercury concentrations ([MeHg]) have been examined in littoral and offshore sediments of Lake Lusignan (Québec). The highest [MeHg] were generally found at the sedimentwater interface with exceptionally high concentrations at littoral sites (5.8 ± 1.3 ng·g dry weight1), which were four times more elevated than at offshore sites (1.6 ± 0.77 ng·g dry weight1). Source-specific fatty acid (FA) biomarkers identified that littoral sediments contained more than twice as much terrestrial and bacterial OM compounds than offshore sediments, whereas the amount of labile algal OM was three times higher at littoral sites. Results indicate that [MeHg] were higher in the presence of labile OM substrates, and the amount of terrestrial OM compounds could not predict [MeHg]. Correlations between [MeHg] and FA of Desulfovibrio desulfuricans (a sulfate-reducing bacterium producing MeHg) could significantly account for 36% of [MeHg] at offshore sites; however, no significant relationships were found at littoral sites. This study illustrates that the microbial dynamics involved in producing and degrading MeHg in lacustrine sediments are complex and cannot be predicted solely by the quantification of FA biomarkers in D. desulfuricans or by biomarkers in the OM itself.
Contractor financial evaluation model (CFEM)
Authors: Pilateris Peter , McCabe Brenda
Published: September 2003

Very little is known about the financial well-being of contractors, in part because they are generally privately held companies. The goals of this work were to develop a model based on data envelopment analysis to assess contractor performance and to use the model to provide a set of financial benchmarks for the industry. As the efficiency score of contractors decreased, the following trends were evident: decreasing current ratio, increasing accounts receivable and payable times, increasing debt to equity, increasing fixed assets to equity, increasing gross profits to sales, increasing administrative expenses to net worth, decreasing net income to sales, and decreasing net income to equity.Key words: DEA, benchmark, efficiency, peer group, DMU, building contractor, heavy civil contractor, specialty contractor, distinct cultural environment, frontier.
Fracture toughness of polymer-modified asphalt concrete at low temperatures
Authors: Kim Kwang W , Kweon Seung Jun , Doh Young S , Park Tae-Soon
Published: September 2003

The fracture toughness of asphalt concrete increases at low temperature and then decreases at temperatures below a certain level. Some polymers are known to have the property of improving the temperature susceptibility of asphalt binder at low temperatures. Therefore, this study evaluated the fracture toughness (KIC) of some polymer-modified asphalt concretes. Low-density polyethylene (LDPE), styrenebutadienestyrene (SBS), and a mixed polymer of LDPE and SBS were used in this study. The fracture toughness KIC of normal asphalt concrete was compared with that of polymer-modified asphalt (PMA) concrete, and the effectiveness of polymer modification against falling values of KIC was evaluated at low temperatures. The results showed that PMA concretes, in general, showed better KIC than normal asphalt concretes, and the temperature at which the highest KIC was obtained was lower than that in the case of normal asphalt concrete. Therefore, the PMA concretes evaluated in this study had better fracture resistance than normal asphalt at low temperatures.Key words: asphalt concrete, polymer-modified asphalt, PMA, fracture toughness, differential thermal contraction, low-temperature damage.
Results of a pilot study to examine the effective integration of apprentices into the industrial construction sector
Authors: Fayek Aminah Robinson , Shaheen Ahmed , Oduba Ayo
Published: September 2003

The industrial construction sector in Alberta has recently undergone a period of rapid growth, resulting in a shortage of skilled workers in almost all of the major industrial sector trades. To meet these shortages, a need has arisen to increase the utilization of apprentices on industrial construction projects. In an effort to address this issue, the Construction Owners Association of Alberta has established a goal of developing an industry Best Practice on how to improve the on-the-job portion of apprenticeship training and identify means by which the industry can more effectively use apprentices. The challenge is to increase their usage in a cost-effective manner that also provides apprentices with adequate training opportunities. Before this can be done, the impacts and benefits to the various parties involved in industrial construction must be quantified and assessed. This paper describes the findings of a pilot study that was conducted on a major industrial project to help in quantifying the impact of the use of apprentices in the industrial construction sector and to identify methods of effectively increasing their use while simultaneously enhancing their on-the-job learning experience. The main conclusion of this paper is that apprentices can be effectively incorporated in industrial construction, and they can be both productive and cost-effective, provided they are given adequate instruction and supervision. The lessons learned from the study are discussed to provide insight into conducting future studies. Recommendations for an industry Best Practice on the effective utilization of apprentices are presented.Key words: apprentice, electrician, industrial construction, journeyman, labour force, pipefitter, productivity, training, work sampling.
Data acquisition and analysis for highway construction using geographic information systems
Authors: Moselhi Osama , Hassanein Ahmed
Published: September 2003

Earthmoving operations represent a sizeable percentage of highway construction costs. Accurate estimation of cut and fill quantities, as well as haul distances, are thus essential for developing realistic schedules and reliable cost estimates for highway construction projects. This paper presents a model designed to aid highway construction personnel in optimizing earthmoving operations by developing realistic mass haul diagrams. The model automates data acquisition and accounts for the presence of different soil strata and natural and (or) man-made obstructions affecting earthmoving plans. Geographic information systems (GIS) are employed to generate three-dimensional digital terrain models of the topography and soil profiles. The model is supported by a relational database for soil data and has been implemented in a prototype software developed in ArcView® environment. It provides a user-friendly interface to facilitate data entry and efficient reporting capabilities. The model has flexible input and output formats designed to facilitate data sharing with a number of commercially available software systems. A numerical example is presented to demonstrate the features of the developed model.Key words: data acquisition, geographic information systems, quantity estimating, earthwork optimization.
Strengthening of concrete columns with carbon fibre reinforced polymer wrap
Authors: Shrive P L , Azarnejad A , Tadros G , McWhinnie C , Shrive N G
Published: September 2003

Reinforced and prestressed concrete columns with one or two layers of carbon fibre reinforced polymer (CFRP) wrap were tested to failure in axial compression. When the results were compared with the maximum load predictions of two proposed design methods, the predictions consistently underestimated actual loads. The design methods are thus conservative. A simple analysis for circular columns reveals that the confining effect of the wrap is not engaged until the concrete actually starts failing and dilating. A finite element model of a chamfered square column confirms this analysis, as do strain readings from the tests. It is shown that strength gains are not linearly related to wrap thickness. The failure mechanism suggests that design should not be based on the ultimate strength or strain of the wrap and that strength gains can be expected to reduce with increasing brittleness of the concrete and with increasing eccentricity.Key words: concrete columns, FRP wrap, reinforced, strengthening.
Functional distress modelling in Portland cement concrete pavements
Authors: de Solminihac Hernán , Bustos Marcelo G , Altamira Aníbal L , Covarrubias Juan Pablo
Published: September 2003

Concrete is widely used as a construction material in pavements by public and private agencies that administer highway networks because of its high durability and capacity to resist large traffic loads and very rigorous climates. Nevertheless, these agencies have to estimate the evolution of pavement performance to plan and optimize the application of adequate maintenance activities, allowing the pavement to be maintained at an optimum service level throughout its lifetime. Predictive distress models of the incremental type, that is, models capable of predicting annual increments of different distress indicators in the pavement, could be very useful tools in the implementation of maintenance plans, with minimal need for previous data, especially with regard to information on cumulative traffic loads. This paper offers incremental models for distress prediction in jointed plain concrete pavements, related to joint problems such as faulting and spalling, which clearly affect the pavement ride quality. The equations obtained allow for not only the calculation of distress predictions in analyzing road maintenance policies, but also the adjustment of the original designs of these pavements, to minimize the occurrence and magnitude of distress problems.Key words: concrete pavements, distress models, pavement performance, pavement management systems.
Probabilistic model of combined wind and ice loads on overhead power line conductors
Authors: Savadjiev Konstantin , Farzaneh Masoud
Published: September 2003

There is evidence that extreme ice loads combined with moderately high winds may cause catastrophic damage to overhead power lines and prolonged periods of electrical power outage. In this paper, a probabilistic model for combined wind and ice loads was developed for establishing realistic and conservative criteria for design and normalization. The proposed model combines icing of extreme thickness with a moderate wind speed, Vice, reduced by a reduction factor, kr, with respect to the extreme wind speed, Vmax. The evaluation of kr, which is the main purpose of this paper, is done by means of statistical analysis of samples taken from the same initial distribution of hourly wind speeds, Vh. The size of samples corresponds to the average annual icing persistency period, Tipp, observed in the climatic conditions of Quebec. This period, which was established in an earlier study by the authors using statistical analysis of data from the Hydro-Québec passive ice meter (PIM) network, is evaluated to be on average 144 h/year. It was found that kr ranges from 0.4 to 0.7, mainly as a function of the coefficient of variation (COV) of the initial distribution of wind speeds and the return period prescribed for extreme climatic loads.Key words: combined wind and ice loads, probabilistic model, overhead transmission lines.
A novel method for determining effective length factors for solid round steel leg members of guyed lattice towers with cross-bracing
Authors: Ding Yongcong , Ghrib Faouzi , Bhattacharjee Sudip , Madugula Murty K.S
Published: September 2003

A novel method is presented for determining the effective length factors (K factors) for solid round steel leg (vertical) members in all-welded guyed communication towers with cross-bracing. Deflections due to an arbitrary load were used to determine the restraining moments and rotational stiffness of the legs. Using the closed-form solution for buckling of a column with rotational restraint at both ends, K factors were computed. From the study it is found that the K factors varied from 0.61 to 1.00, depending on the relative sizes of the leg and bracing members. An expression for estimating the effective length factors for solid round steel leg members of all-welded guyed lattice towers with cross-bracing is developed.Key words: cross-bracing, effective length factor (K factor), finite element analysis, guyed lattice tower, solid round steel leg member, welded tower.
A practical guide for determining appropriate chemical dosages for direct filtration
Authors: Tchio Maurice , Koudjonou Boniface , Desjardins Raymond , Prévost Michèle , Barbeau Benoit
Published: September 2003

The tests conducted in this study have made it possible to propose a rapid and simple laboratory method for determining the appropriate dosages of chemicals according to filtering materials effective sizes (ES), for direct filtration applications, and for adjusting the dosages according to raw water quality changes. Application of the proposed procedure requires but simple laboratory equipment: an Ives' filterability index measuring device, a filtration system operating under a constant vacuum, and 0.45 and 8 µm membrane filters. The use of 0.45 µm membrane filtration allows one to determine the best dosages for fine material with an effective size of 0.4 mm, whereas Ives' filterability index and 8 µm membrane filtration help determine the best dosage applicable to the 1.2 mm ES. The results obtained showed that for other effective sizes in the 0.41.2 mm range, the best dosages of alum and polymer can be estimated by linear interpolation. This laboratory procedure is a useful tool for quickly determining the best chemical dosages versus filtering media ES for a given water quality. It should be applied to raw waters with unknown characteristics prior to carrying out a more accurate full-scale validation, if necessary.Key words: direct filtration, coagulation, flocculation, alum, effective size, Ives' filterability index.
The effect of long-term wastewater cross-connection on the biofilm of a simulated water distribution system
Authors: Gibbs Shawn G , Meckes Mark C , Scarpino Pasquale V
Published: September 2003

The drinking water distribution system simulator (DSS) from the U.S. EPA was used to assess the effect of long-term wastewater cross-connection on the biofilm of a simulated water distribution system. Initial experimentation determined that at 0.3% wastewater to system volume per day for 90 d injected 0.1% every 8 h into the DSS; study organisms were consistently present in the discharge water sample with only slight aesthetic problems (increased turbidity). During the cross-connection, incoming tap water and wastewater, and system discharge water were monitored to ensure that the source of study organisms was only the wastewater cross-connection and that study organisms were present in the water column of the DSS. Following elimination of the cross-connection, samples showed that study organisms were removed from the water column within 24 h, which was the hydraulic retention time of the system. Increased numbers of heterotrophic organisms were detected in the system discharge following cross-connection. Increased heterotrophs were recovered for the system biofilm, and study organisms, except culturable heterotrophs, were not recovered beyond 24 h. Results indicate that the existing biofilm grew during the cross-connection, and may have inhibited growth of specific study organisms introduced via the cross-connection. Key words: biofilm, wastewater, drinking water, microorganisms, cross-connection.
Acid deposition in the eastern United States and neural network predictions for the future
Authors: Grubert J P
Published: September 2003

Back-propagation type neural networks were trained on total sulphur dioxide emissions from power plants and measured field data on precipitation chemistry. These trained networks were then able to predict seasonal changes in sulphate, hydrogen, nitrate, and ammonium ion concentrations caused by projected decreases in sulphur dioxide emissions from power plants in the eastern United States. Results showed that by 2010 the proposed reductions in sulphur dioxide emissions by the U.S. electric power utilities would just be sufficient to reduce acid rain conditions to the levels where human health problems are avoided. However, pollution from acid rain would still be impacting considerable regions of the north-eastern United States and south-eastern Canada causing other environmental damage such as loss of fish in acidic lakes. Key words: acid rain, desulphurization, modelling, neural networks, pollution.
Étude du colmatage des membranes en ultrafiltration et en coagulationultrafiltration d'eau de surface
Authors: Bouchard C , Sérodes J , Rahni M , Ellis D , Laflamme E , Rodriguez M
Published: September 2003

Ultrafiltration (UF) and coagulationultrafiltration (CUF) of raw water from the Des Roches Lake were performed and compared in terms of natural organic matter (NOM) removal and in terms of membrane permeability variation. The study was carried out at a laboratory scale with a membrane having a nominal pore size of 0.035 μμm. The removal of NOM by UF was significant (10% to more than 50% for UV absorbance at 254 nm and 0% to more than 30% for TOC) but was also very dependent on operating conditions. Membrane fouling occurred rapidly and was strongly accelerated as the permeate flux increased. Fouling also induced a decrease of NOM removal. Coagulation before UF brought a strong increase of NOM removal (TOC removal higher than 60% and reduction of UV absorbance at 254 nm higher than 80%). It also largely reduced membrane permeability loss even for permeation flux higher than 150 L·h1·m2. In the absence of coagulation, and operating with full recirculation of the concentrate, there was a reduction of the SUVA ratio (UV254/TOC) and iron concentration in the feed water. This indicates a preferential deposit of humic substances onto the membranes and shows that iron either plays a role in membrane fouling or could be an indicator of the presence of fouling substances. Key words: ultrafiltration, coagulation, surface water, fouling, organic matter.
Measurements of the size, rise velocity, and specific interfacial area of bubbles in an impinging-jet bubble column
Authors: El-Din Mohamed Gamal , Smith Daniel W
Published: September 2003

A 2-D laser particle dynamics analyzer was used to simultaneously measure the bubble size, bubble rise velocity, bubble size distribution, and gas-phase turbulence intensities in an impinging-jet bubble column that utilized two venturi injectors to create turbulent gasliquid jets in the ambient fluid. These measurements were conducted in clean deionized water and in a Kraft pulp mill effluent that was ozonated using a wide range of utilized ozone doses. The intersecting of the gasliquid jets caused an increase in the turbulence produced in the ambient fluid and as a result, the count mean bubble diameter (dB) and the Sauter mean bubble diameter (dS) were smaller than those obtained in conventional bubble columns. This has led to a significant increase in the specific gas bubble interfacial area (a) compared to that in conventional bubble columns. The count mean bubble and Sauter mean bubble diameters were found to be dependent on the superficial gas and liquid velocities (uG and uL, respectively). The count and Sauter mean bubble diameters were smaller in the raw Kraft pulp mill effluent compared to those in the deionized water. This has led to a significant increase in the specific gas bubble interfacial area and gas hold-up (εεG) compared to those in the deionized water. As the raw Kraft pulp mill effluent was ozonated and the amount of utilized ozone increased, the count mean and Sauter mean bubble diameters increased. The bubble size distributions exhibited different trends depending on the type of the test liquid and on the operating conditions in terms of uG and uL. Generally, those distributions could be well described using normal, gamma, or log-normal density functions. Key words: laser, phase, Doppler, impinging-jet, bubble column, bubble, size, gas hold-up, interfacial area.
Comparison of association theory and Freundlich isotherm for describing granular activated carbon adsorption of secondary sewage effluent
Authors: Chaudhary D S , Vigneswaran S , Ngo H H , Kim S H , Moon H
Published: September 2003

Adsorption equilibria and kinetics are important to evaluate the effectiveness of an adsorption system. In this study, the adsorption behavior of organics in secondary effluent from a sewage treatment plant was investigated, using granular activated carbon (GAC) as an adsorbent. This paper provides details on the adsorption experiments conducted in a sewage treatment plant, and emphasizes the suitability of the association theory for describing adsorption characteristics of secondary sewage. The association theory was found to describe the overall adsorption equilibrium of the sewage system more precisely (with 0.33% error) than the more commonly-used Freundlich isotherm (with 9.9% error). The linear driving force approximation (LDFA) model and the fixed bed dynamics were used to predict the batch kinetics and the fixed bed adsorption experimental results respectively. The prediction was only slightly better when the isotherm parameters estimated from the association theory were used. Average errors in predicting batch and fixed bed experimental results were 0.25 and 0.55% with the association theory, and 0.34 and 0.75% with the Freundlich isotherm, respectively. Key words: adsorption, association theory, granular activated carbon, total organic carbon, wastewater.
Seasonal Variations in the bacterial population in an activated sludge system
Authors: Saleem Muhammad , Bukhari Alaadin A , Al-Malack Mohammed H
Published: September 2003

Diminishing groundwater sources and a growing need of municipal water in arid countries like Saudi Arabia underline the need for an increase in the reuse of treated wastewater. Treatment of wastewater must be reliable and must be subject to monitoring to ensure the public health, safety, and environmental protection. A one-year study was conducted at the Al-Khobar wastewater treatment plant to investigate the effect of seasonal variations of temperature and flow rate on the fate of indicator microorganisms. The raw sewage, secondary effluent, and chlorinated effluent were analyzed for the detection and enumeration of four standard microorganismic indicators: standard plate count, total coliform, fecal coliform, and Clostridium perfringens on a weekly basis. It was found that the microbial populations present in the wastewater are very much sensitive to the wastewater temperature and, to some extent, on the wastewater flowrate. The t-test analysis performed on mean population densities of the indicator microorganisms studied shows higher microbial populations during summer than in winter. The insight gained from this study may be applied to other similar treatment plants operating in this region.Key words: Clostridium perfringens, indicator microorganism, wastewater reuse, seasonal variations, wastewater treatment.
Groundwater treatment for high temperature heat recovery
Authors: Adsett J , Thottan J , Akhand N
Published: September 2003

Aquifer thermal energy storage (ATES) systems have been utilized to conserve high temperature waste heat from industrial processes. In the heat recovery phase, whenever groundwater with a high level of hardness is heated to temperatures in the range of 50°C or higher, heat exchanger surfaces are susceptible to scale buildup with subsequent clogging of the heat exchanger. In this study, the performance of CO2 treatment as a means of preventing CaCO3 scaling in heat exchangers was evaluated. The rate of CO2 gas injected into the water was controlled by a proportional control valve to maintain a CaCO3 saturation index of zero. The CO2 treatment method showed a beneficial effect in controlling scaling on the brass heat exchanger tubes.Key words: aquifer thermal energy storage, CO2 treatment, CaCO3 scaling.
Simulation of the migration of dissolved contaminants through a subaqueous capping layer: model development and application for As migration
Authors: Dueri Sibylle , Therrien René , Locat Jacques
Published: September 2003

TRANSCAP-1D is a numerical model that simulates the vertical migration of dissolved contaminants through a subaqueous capping layer. The model was developed for the prediction of the long-term effectiveness of a sediment cap. It considers advection, diffusion, chemical reactions, and the effect of the burrowing activity of the benthic fauna. The sediment is represented as a dual porosity medium composed of sediment pores and biologically formed tubes. The numerical model was calibrated with the concentration profiles of dissolved arsenic measured in the sediments at two sampling stations in the Saguenay Fjord, in Québec, Canada, where a major flood event caused the natural capping of contaminated sediments. Thereafter several numerical simulations with variable bio-irrigation depth and variable thickness of the capping layer were performed to test the effect of the uncertainty and variability of the input values on the model response. These simulations indicate that the depth of bio-irrigation in the sediment and the release from mineral dissolution are major factors controlling the distribution of dissolved contaminants in the sediment column. Key words: Saguenay Fjord, migration, numerical model, capping layer, sediment, bio-irrigation, heavy metals, arsenic.
Formation of chlorine dioxide under laundry bleaching conditions
Authors: Carr Mary , Carlson Kenneth , Gregory Dean
Published: September 2003

Chlorite ion is a by-product of chlorine dioxide and is typically present at concentrations ranging from 0.3 to 1.0 mg/L in the finished water of systems using this oxidant in the treatment process. When combined with free chlorine, these two reactive ions have been shown to react to form chlorine dioxide. Chlorine dioxide concentrations formed in tap water (either in the distribution system or during domestic use of tap water, such as laundry bleaching) can off-gas in a home and react with volatile organic compounds associated with new carpets and furniture fabrics, resulting in cat-urine type odors and customer complaints. The objective of this study was to determine if chlorine dioxide is formed when the high concentrations of hypochlorite ion that are used in laundry bleaching operations are contacted with residual chlorite ion that is present in tap water of systems using chlorine dioxide at the treatment plant. If chlorine dioxide is forming under these circumstances, it could be a cause of seemingly random odor complaints periodically received by water utilities using chlorine dioxide. The formation of chlorine dioxide was found to be negligible under simulated laundry bleaching conditions. The key factor in chlorine dioxide formation was found to be pH. When chlorine is added as a base (e.g., sodium hypochlorite), the resulting pH is high enough to suppress chlorine dioxide formation.Key words: chlorine dioxide, chlorite ion, hypochlorite ion, re-formation, odors.
A bench-scale evaluation of different treatment options to produce bio-stable drinking water
Authors: Laurent Patrick , Barbeau Benoît , Prévost Michèle , Servais Pierre
Published: September 2003

Owing to increasingly stringent water quality regulations and concerns about emerging pathogens, many drinking water utilities are having to modify their treatment lines. Bench-scale evaluation can be a useful means for carrying out a preliminary assessment of treatment modifications under consideration. An example of such an evaluation, performed as an initial screening of treatment options for a big North American utility, is presented here. Four sampling campaigns aimed at investigating at a bench-scale the impact of different treatments (coagulation-flocculation-settling, moderate ozonation, and filtration; high dosage ozonation; chlorination followed by dechlorination) on water quality were performed in this study. Testing involved measurement of water quality parameters (turbidity, dissolved organic carbon, ultraviolet absorbance, specific ultraviolet absorbance) with special attention paid to parameters driving regrowth potential (biodegradable dissolved organic carbon (BDOC) and bacterial abundances). Main results show that ozonation always increases BDOC levels. "Full treatment" (coagulation-flocculation-settling, moderate ozonation, filtration) would not change the regrowth potential of the raw water drastically. A high dosage ozonation ("high O3" scenario) could result in a substantial seasonal increase in BDOC concentrations. It would be logical to follow up this conclusion with a consideration of whether or not the higher bacterial regrowth that would take place in the distribution system, and due to these increases in BDOC concentration, could be controlled by maintaining oxidant residuals during distribution. Key words: drinking water, bench-scale, biological stability, water treatment, biodegradable dissolved organic carbon.
Treatability studies of black liquor by upflow anaerobic sludge blanket reactor
Authors: Bhoi Zainab Mohd Peer , Mehrotra Indu , Shrivastava A K
Published: September 2003

Treatment of recalcitrant organics through cometabolism is well precedented in the literature. The present work deals with the feasibility studies of anerobically treating black liquor (BL) along with the readily degradable synthetic wastewater (SWW) in a bench-scale upflow anaerobic sludge blanket reactor (UASBR). Treatment has been carried out in four phases of operation. In the first phase, 100% of SWW prepared from molasses was used. In the other phases of operation, 10%, 20%, and 30% of the SWW chemical oxygen demand (COD) was replaced by BL COD successively. In each of the operation phases, the composition of the feed was not changed until COD reduction and gas production were stabilized. The entire operation took 509 d. The results indicate that (i) the COD removal efficiency exhibited a decreasing trend with increase in the percentage of BL and (ii) apparently, UASB cannot be used as a treatment option for SWW containing more than 20% BL.Key words: black liquor, upflow anaerobic sludge blanket reactor (UASBR), synthetic wastewater, loading rate, anaerobic wastewater treatment.
Adaptation in the respiratory control system
Authors: Duffin James , Mahamed Safraaz
Published: September 2003

Exposure to hypoxia, whether for short or prolonged periods or for repeated episodes, produces alterations in the ventilatory responses. This review presents evidence that these adaptations are likely to be mediated by adaptations in the respiratory chemoreflexes, particularly the peripheral chemoreflex, and proposes models of respiratory control explaining the observed changes in ventilation. After a brief introduction to the respiratory control system, a graphical model is developed that illustrates the operation of the system in the steady state, which will be used later. Next, the adaptations in ventilatory responses to hypoxia that have been observed are described, and methods of measuring the alterations in the chemoreflexes that might account for them are discussed. Finally, experimental data supporting the view that changes in the activity of the peripheral chemoreflex can account for the ventilatory adaptations to hypoxia are presented and incorporated into models of chemoreflex behaviour during exposures to hypoxia of various durations.Key words: respiration, chemoreflexes, hypoxia, adaptation, models.
Plasma osmolality and the strong ion difference predict respiratory adaptations in pregnant and nonpregnant women
Authors: Heenan A P , Wolfe L A
Published: September 2003

This study tested the hypothesis that plasma osmolality and the strong ion difference ([SID]) predict PaCO2 during rest and during exercise in physically active pregnant (n = 22; gestational age 37.0 ± 0.2 weeks) and nonpregnant (n = 17) women. Nonpregnant subjects were in varying stages of the menstrual cycle. Arterialized blood gases, hydrogen ion concentration, plasma osmolality, [SID], and circulating levels of progesterone were measured at rest and during upright cycling at work rates corresponding to 70 and 110% of the ventilatory threshold. Pooled data from the two groups at rest revealed significant correlations (P < 0.05) between PaCO2 with plasma osmolality, [SID], and progesterone. Progesterone was also significantly correlated with [SID] and osmolality. Also, changes in PaCO2 with exercise correlated significantly with changes in [SID]. The results support the hypothesis that plasma osmolality and [SID] are important factors in the modulation of respiratory sensitivity in healthy women. Also, the effects of progesterone on PaCO2 may be expressed, at least in part, through progesterone-induced changes in [SID] and osmolality.Key words: pregnancy, strong ion difference, osmolality, respiratory control.