bluuebunny/crossref_metadata_2025 huggingface dataset:
De Novo Initiation of RNA Synthesis by the Arterivirus RNA-Dependent RNA Polymerase
Authors: Beerens Nancy , Selisko Barbara , Ricagno Stefano , Imbert Isabelle , van der Zanden Linda , Snijder Eric J. , Canard Bruno
Published: May 2007

All plus-strand RNA viruses encode an RNA-dependent RNA polymerase (RdRp) that functions as the catalytic subunit of the viral replication/transcription complex, directing viral RNA synthesis in concert with other viral proteins and, sometimes, host proteins. RNA synthesis essentially can be initiated by two different mechanisms, de novo initiation and primer-dependent initiation. Most viral RdRps have been identified solely on the basis of comparative sequence analysis, and for many viruses the mechanism of initiation is unknown. In this study, using the family prototype equine arteritis virus (EAV), we address the mechanism of initiation of RNA synthesis in arteriviruses. The RdRp domains of the members of the arterivirus family, which are part of replicase subunit nsp9, were compared to coronavirus RdRps that belong to the same order of
Nidovirales
, as well as to other RdRps with known initiation mechanisms and three-dimensional structures. We report here the first successful expression and purification of an arterivirus RdRp that is catalytically active in the absence of other viral or cellular proteins. The EAV nsp9/RdRp initiates RNA synthesis by a de novo mechanism on homopolymeric templates in a template-specific manner. In addition, the requirements for initiation of RNA synthesis from the 3′ end of the viral genome were studied in vivo using a reverse genetics approach. These studies suggest that the 3′-terminal nucleotides of the EAV genome play a critical role in viral RNA synthesis.
Hepatitis C Virus p7 and NS2 Proteins Are Essential for Production of Infectious Virus
Authors: Jones Christopher T. , Murray Catherine L. , Eastman Dawnnica K. , Tassello Jodie , Rice Charles M.
Published: May 2007

Hepatitis C virus (HCV) infection is a global health concern affecting an estimated 3% of the world's population. Recently, cell culture systems have been established, allowing recapitulation of the complete virus life cycle for the first time. Since the HCV proteins p7 and NS2 are not predicted to be major components of the virion, nor are they required for RNA replication, we investigated whether they might have other roles in the viral life cycle. Here we utilize the recently described infectious J6/JFH chimera to establish that the p7 and NS2 proteins are essential for HCV infectivity. Furthermore, unprocessed forms of p7 and NS2 were not required for this activity. Mutation of two conserved basic residues, previously shown to be important for the ion channel activity of p7 in vitro, drastically impaired infectious virus production. The protease domain of NS2 was required for infectivity, whereas its catalytic active site was dispensable. We conclude that p7 and NS2 function at an early stage of virion morphogenesis, prior to the assembly of infectious virus.
Mamu-B*08-Positive Macaques Control Simian Immunodeficiency Virus Replication
Authors: Loffredo John T. , Maxwell Jess , Qi Ying , Glidden Chrystal E. , Borchardt Gretta J. , Soma Taeko , Bean Alex T. , Beal Dominic R. , Wilson Nancy A. , Rehrauer William M. , Lifson Jeffrey D. , Carrington Mary , Watkins David I.
Published: May 2007

Certain major histocompatibility complex (MHC) class I alleles are associated with the control of human immunodeficiency virus and simian immunodeficiency virus (SIV) replication. We have designed sequence-specific primers for detection of the rhesus macaque MHC class I alleleMamu-B*08by PCR and screened a cohort of SIV-infected macaques for this allele. Analysis of 196 SIVmac239-infected Indian rhesus macaques revealed thatMamu-B*08was significantly overrepresented in elite controllers; 38% of elite controllers wereMamu-B*08positive compared to 3% of progressors (P= 0.00001).Mamu-B*08was also associated with a 7.34-fold decrease in chronic phase viremia (P= 0.002).Mamu-B*08-positive macaques may, therefore, provide a good model to understand the correlates of MHC class I allele-associated immune protection and viral containment in human elite controllers.
Characterization of Fusion Determinants Points to the Involvement of Three Discrete Regions of Both E1 and E2 Glycoproteins in the Membrane Fusion Process of Hepatitis C Virus
Authors: Lavillette Dimitri , Pécheur Eve-Isabelle , Donot Peggy , Fresquet Judith , Molle Jennifer , Corbau Romuald , Dreux Marlène , Penin François , Cosset François-Loïc
Published: May 2007

Infection of eukaryotic cells by enveloped viruses requires the merging of viral and cellular membranes. Highly specific viral surface glycoproteins, named fusion proteins, catalyze this reaction by overcoming inherent energy barriers. Hepatitis C virus (HCV) is an enveloped virus that belongs to the genus
Hepacivirus
of the family
Flaviviridae
. Little is known about the molecular events that mediate cell entry and membrane fusion for HCV, although significant progress has been made due to recent developments in infection assays. Here, using infectious HCV pseudoparticles (HCVpp), we investigated the molecular basis of HCV membrane fusion. By searching for classical features of fusion peptides through the alignment of sequences from various HCV genotypes, we identified six regions of HCV E1 and E2 glycoproteins that present such characteristics. We introduced conserved and nonconserved amino acid substitutions in these regions and analyzed the phenotype of HCVpp generated with mutant E1E2 glycoproteins. This was achieved by (i) quantifying the infectivity of the pseudoparticles, (ii) studying the incorporation of E1E2 and their capacity to mediate receptor binding, and (iii) determining their fusion capacity in cell-cell and liposome/HCVpp fusion assays. We propose that at least three of these regions (i.e., at positions 270 to 284, 416 to 430, and 600 to 620) play a role in the membrane fusion process. These regions may contribute to the merging of viral and cellular membranes either by interacting directly with lipid membranes or by assisting the fusion process through their involvement in the conformational changes of the E1E2 complex at low pH.
New STS molecular markers for assessment of genetic diversity and DNA fingerprinting in hop (Humulus lupulus L.)
Authors: Patzak Josef , Vrba Lukáš , Matoušek Jaroslav
Published: May 2007

Molecular markers have been increasingly used in genetic studies of crop species for their applicability in breeding programs. In this work, we report on the development of new sequence-tagged site (STS) markers based on sequence information from several identified hop (Humulus lupulus L.) genes. We demonstrate the usefulness of these STS markers and compare them to SSRs for identifying hop genotypes and estimating genetic diversity in a collection of 68 hop cultivars from around the world. We found 3 individual gene variants (A, B, C) of the chs_H1 gene in this collection. The most frequent gene variant, B (AJ304877), was not detected in Mt. Hood, Glacier, and Horizon (US) cultivars. Gene variant A came from an American germplasm through wild hops. We found length polymorphism in intron 1 of the chs2 gene, and 4 different amplified markers were detected in PCRs. The chs3 gene was found in only one third of the cultivars. None of the variants of the studied CHS genes were found in Humulus japonicus . We detected 5 major gene variants of DNA-binding protein in the collection of H. lupulus cultivars and 2 others in H. japonicus. We also found 3 individual gene variants of an endochitinase gene. The distribution of gene variants did not correlate with any resistance. We proved that developed STS markers can be successfully used for the analysis of genetic diversity and can substitute and supplement SSR markers in hop.
Genetic variation in the chloroplast genome suggests multiple domestication of cultivated Asian rice (Oryza sativa L.)
Authors: Kawakami Shin-ichi , Ebana Kaworu , Nishikawa Tomotaro , Sato Yo-ichiro , Vaughan Duncan A. , Kadowaki Koh-ichi
Published: May 2007

Two hundred and seventy-five accessions of cultivated Asian rice and 44 accessions of AA genome Oryza species were classified into 8 chloroplast (cp) genome types (A–H) based on insertion–deletion events at 3 regions (8K, 57K, and 76K) of the cp genome. The ancestral cp genome type was determined according to the frequency of occurrence in Oryza species and the likely evolution of the variable 57K region of the cp genome. When 2 nucleotide substitutions (AA or TT) were taken into account, these 8 cp types were subdivided into 11 cp types. Most indica cultivars had 1 of 3 cp genome types that were also identified in the wild relatives of rice, O. nivara and O. rufipogon , suggesting that the 3 indica cp types had evolved from distinct gene pools of the O. rufipogon – O. nivara complex. The majority of japonica cultivars had 1 of 3 different cp genome types. One of these 3 was identified in O. rufipogon, suggesting that at least 1 japonica type is derived from O. rufipogon with the same cp genome type. These results provide evidence to support a polyphyletic origin of cultivated Asian rice from at least 4 principal lineages in the O. rufipogon – O. nivara complex.
A high-resolution, intraspecific linkage map of pepper (Capsicum annuum L.) and selection of reduced recombinant inbred line subsets for fast mapping
Authors: Barchi Lorenzo , Bonnet Julien , Boudet Christine , Signoret Patrick , Nagy István , Lanteri Sergio , Palloix Alain , Lefebvre Véronique
Published: May 2007

A high-resolution, intraspecific linkage map of pepper ( Capsicum annuum L.) was constructed from a population of 297 recombinant inbred lines. The parents were the large-fruited inbred cultivar ‘Yolo Wonder’ and the hot pepper line ‘Criollo de Morelos 334’, which is heavily used as a source of resistance to a number of diseases. A set of 587 markers (507 amplified fragment length polymorphisms, 40 simple sequence repeats, 19 restriction fragment length polymorphisms, 17 sequence-specific amplified polymorphisms, and 4 sequence tagged sites) were used to generate the map; of these, 489 were assembled into 49 linkage groups (LGs), including 14 LGs with 10 to 60 markers per LG and 35 with 2 to 9 markers per LG. The framework map covered 1857 cM with an average intermarker distance of 5.71 cM. Twenty-three LGs, composed of 69% of the markers and covering 1553 cM, were assigned to 1 of the 12 haploid pepper chromosomes, leaving 26 LGs (304 cM) unassigned. The chromosome framework map built with 250 markers led to a high level of mapping confidence and an average intermarker distance of 6.54 cM. By applying MapPop software, it was possible to select smaller subsets of 141 or 93 most informative individuals with a view to reducing the time and cost of further mapping and phenotyping. To define the smallest number of individuals sufficient for assigning any new marker to a chromosome, subsets from 12 to 45 individuals and a set of 13 markers distributed over all 12 chromosomes were screened. In most cases, the markers were correctly assigned to their expected chromosome, but the accuracy of the map position decreased as the number of individuals was reduced.
Unisexual salamanders (genus Ambystoma) present a new reproductive mode for eukaryotes
Authors: Bogart James P. , Bi Ke , Fu Jinzong , Noble Daniel W.A. , Niedzwiecki John
Published: May 2007

To persist, unisexual and asexual eukaryotes must have reproductive modes that circumvent normal bisexual reproduction. Parthenogenesis, gynogenesis, and hybridogenesis are the modes that have generally been ascribed to various unisexuals. Unisexual Ambystoma are abundant around the Great Lakes region of North America, and have variously been described as having all 3 reproductive modes. Diploid and polyploid unisexuals have nuclear genomes that combine the haploid genomes of 2 to 4 distinct sexual species, but the mtDNA is unlike any of those 4 species and is similar to another species, Ambystoma barbouri . To obtain better resolution of the reproductive mode used by unisexual Ambystoma and to explore the relationship of A. barbouri to the unisexuals, we sequenced the mitochondrial control and highly variable intergenic spacer region of 48 ambystomatids, which included 28 unisexuals, representatives of the 4 sexual species and A. barbouri. The unisexuals have similar sequences over most of their range, and form a close sister group to A. barbouri, with an estimated time of divergence of 2.4–3.9 million years ago. Individuals from the Lake Erie Islands (Kelleys, Pelee, North Bass) have a haplotype that demonstrates an isolation event. We examined highly variable microsatellite loci, and found that the genetic makeup of the unisexuals is highly variable and that unisexual individuals share microsatellite alleles with sexual individuals within populations. Although many progeny from the same female had the same genotype for 5 microsatellite DNA loci, there was no indication that any particular genome is consistently inherited in a clonal fashion in a population. The reproductive mode used by unisexual Ambystoma appears to be unique; we suggest kleptogenesis as a new unisexual reproductive mode that is used by these salamanders.
Strength of Class 3 steel W sections in weak axis bending
Authors: Ashkinadze Konstantin
Published: May 2007

This technical note considers weak axis moment capacity of wide-flange steel members of different section classes. In CSA S16-01 Limit states design of steel structures, there is a disconnect in moment capacity of laterally supported members between Classes 2 and 3: when the section crosses the Class 2 boundary, its calculated capacity drops in the ratio of the elastic to plastic section modulus. This effect is relatively minor for strong axis bending but is rather significant for weak axis bending. A rational theory is presented that explains the phenomena on the transition of the two Classes and proves that the noted gap in the design capacity does not exist. An improved design formula is proposed to mitigate this problem.Key words: bending, class, flange, local buckling, steel beams, strong axis, weak axis.
Large-scale distributed watershed modelling for reservoir operations in cold boreal regions
Authors: St. Laurent M E , Valeo C
Published: May 2007

The macroscale deterministic hydrologic model, SLURP, was modified and tested on two large watersheds in northern Manitoba, the Taylor River watershed (899 km2) and the upper Burntwood River watershed (6959 km2). Calibration and validation of the model on both watersheds between 1985 and 2000 identified a number of model deficiencies and recommendations for improvement. Date-dependent snowmelt rates were replaced with a single constant snowmelt rate, helping to decrease the parameterization of the model. A snowpack temperature deficit model was also incorporated to simulate the effects of snow ripening. These two modifications provided the modelling flexibility needed to control the timing of initial snowmelt and the rate of snowmelt. Annual spring freshet lasts roughly 2 weeks in this region; however, improved model performance was observed well beyond the spring freshet period. These modifications also provided a better representation of the physical processes that delay snowmelt once the air temperature exceeds 0 °C.Key words: frozen ground, boreal forest, hydrological modelling, snow ripening, snowmelt.
Hydraulic effects of ice breakup on bridges
Authors: Beltaos Spyros , Miller Lindon , Burrell Brian C , Sullivan David
Published: May 2007

The passage of river ice during the breakup event can have several effects on bridge structures. Design for ice passage at bridges has largely been empirical, such as the determination of superstructure clearance requirements based on historical stage data. As hydrologic and river ice processes in rivers are modified by climatic change, the use of empirical methods based on past observations and measurements could become less reliable. To advance beyond empiricism, it is necessary to develop rational design criteria based on a thorough understanding of the factors governing the interaction between bridges and ice. This concern applies especially during the breakup event when river flows, velocities, and hydrodynamic forces are usually higher and moving ice is thicker and stronger than during freeze-up. This paper provides guidance on the design of bridges to minimize ice impacts on the structure during the breakup period.Key words: breakup, bridges, design, forces, ice jam, impact, river ice, scour, waves.
Treatment kinetics of aircraft deicing fluid in an anaerobic baffled reactor
Authors: Kennedy Kevin , Barriault Micha
Published: May 2007

A four compartment anaerobic baffled reactor (ABR) operated with and without recycle treated aircraft deicing wastewater. Without recycle a minimum hydraulic retention time (HRT) of 27 h (organic loading rate, OLR, of 6.2 g·L–1·d–1) with a chemical oxygen demand (COD) removal efficiency of 89% and a Uoverall of 0.25 g·g–1·d–1 was achieved. With recycle the minimum HRT was 17 h (OLR of 9.9 g·L–1·d–1) with 93% COD removal efficiency, achieved at a Uoverall of 0.32 g·g–1·d–1. Anaerobic baffled reactor compartments served to naturally separate acidogenic and methanogenic activities longitudinally through the reactor, with acidogenic activity highest in compartment 1. A first order compartment model for substrate removal could not describe ABR performance. The rate coefficients (k1–k4) or kavg were inconsistent and no predictive correlation of k values with substrate concentration, HRT or OLR could be achieved in describing the naturally attenuated two-phase phenomenon.Key words: anaerobic, baffled reactor, deicing fluid, ethylene glycol, treatment.
Determination of first order rate constants for wetlands treating livestock wastewater in cold climates
Authors: Jamieson Rob , Gordon Robert , Wheeler Natalie , Smith Erin , Stratton Glenn , Madani Ali
Published: May 2007

Four years of performance data from a free-water surface constructed wetland receiving dairy wastewater in Nova Scotia was used to compute first order reaction rate constants (Ka) for several parameters including BOD5, TP, TKN, NH4+-N, FC, and TSS. Flow rates at the inlet and outlet of the 5 m wide × 20 m long wetland were continuously measured to assess how external hydrologic influences affected the water budget of the wetland and the system treatment performance. The Ka values were calculated using inlet and outlet concentrations and an assumption of plug flow hydraulics. Adjusted rate constants (Kac) were also computed, in which the effects of dilution and concentration on pollutant concentrations were considered. Precipitation, runoff, and evapotranspiration had a large influence on the wetland water budget. Values of Ka were higher than Kac for all wastewater parameters, illustrating the effects of dilution on outlet pollutant concentrations and the importance of accurately characterizing wetland hydrology when determining or using rate constants. The Kac values did not appear to be influenced by temperature or solar radiation, but were positively correlated with the hydraulic loading rate for most parameters. Rate constants were lower than those reported in the literature for livestock wastewater treatment wetlands operating in warmer climates. This could be due to differences in climate, but could also be attributed to the relatively high strength wastewater and low hydraulic loading rate (0.1 m month–1) used in this study. Key words: treatment wetlands, cold climate, agricultural wastewater, design, rate constants.
An innovative process for the treatment of high loaded surface waters for small communities
Authors: Niquette Patrick , Hausler Robert , Lahaye Pierre , Lacasse Maurice
Published: May 2007

Treatment trials have been realized with a new compact process in order to meet the drinking water regulation newly implemented in the province of Quebec. This process is especially designed for the supply of small communities. It combines complementary treatments operated by a centralized computer: ozonation, membrane filtration, and biological filtration, thus reducing operation to basic tasks. The process functioned very well for the period under review, in spite of extreme conditions met: cold water and constant fluctuation of the raw water quality. The process considerably lowers the contents of organic compounds (TOC, DOC, and color), the turbidity, the chlorine demand, and the concentrations of trihalomethane precursors present in the raw water. For this specific application, the backwash wastewaters may be mixed and discharged directly into a river nearby. Key words: drinking water, small communities, ozonation, membrane filtration, biological activated carbon, turbidity, trihalomethane precursors, TOC.
Erosion characteristics and resuspension of sub-aqueous mine tailings
Authors: Mian M Haneef , Yanful Ernest K
Published: May 2007

The use of shallow water covers for containing sulfide bearing mine tailings in non-arid climates has gained importance over the years due largely to their effectiveness as oxygen barriers. In spite of the numerous documented benefits of these covers, some fundamental questions on the application of the technology still remain; a major one being the contribution of the nature of the tailings particles to the overall performance of the cover. Many of the existing tailings ponds have been designed assuming cohesionless sediment behavior. Total suspended solids and sediment trap measurements at some existing water cover sites, designed using the cohesionless sediment approach, have indicated significant resuspension at these sites. The present study provides information on the cohesive nature of sulfide mine tailings particles using particle size and mineralogical data and results of laboratory erosion experiments. The results show that the erosion patterns for tailings particles are similar to those reported for cohesive natural sediments. A power law erosion equation is proposed for calculating erosion rates and estimating the optimal water cover depth for flooded mine tailings.Key words: sulfide mine wastes, subaqueous disposal, erosion character, cohesive sediments, erosion shear stress relationship.
Impact of UV and secondary disinfection on microbial control in a model distribution system
Authors: Dykstra Trevor S , O'Leary Kevin C , Chauret Christian , Andrews Robert C , Gagnon Graham A
Published: May 2007

This study evaluates the synergistic effects of ultraviolet (UV) and secondary disinfectants on water quality in a model distribution system. Chemical disinfectants evaluated for residual disinfection include chlorine dioxide, monochloramine, and free chlorine. Results suggest that there may be synergistic effects between UV and the chemical disinfectants for controlling microbiological re-growth in drinking water distribution systems. UV disinfection appeared to increase the vulnerability of bacteria located in suspension or within biofilms to chemical disinfection, although only at low disinfectant residual concentrations of 0.25, 0.50, and 1.0 mg/L for chlorine dioxide, free chlorine, and monochloramines, respectively. At high disinfectant residual concentrations of 0.50, 1.0, and 2.0 mg/L for chlorine dioxide, free chlorine, and monochloramines, respectively, results indicated that chemical disinfection alone would be adequate for microbial control. In the reactors receiving UV pre-treatment, both chlorine dioxide and free chlorine disinfection were far more effective in reducing the growth of suspended heterotrophic bacteria than without UV pre-treatment. Similar biofilm and suspended bacterial levels were observed without subsequent chemical disinfection regardless of the presence or absence of UV treatment. Overall, these findings imply that UV treatment prior to chemical disinfection enhances microbial control in distribution systems. These results indicate the use of UV pre-treatment can be effective at reducing the disinfectant concentration necessary for microbial control, therefore reducing the potential for the formation of disinfectant by-product in the system.Key words: drinking water, UV pre-treatment, chlorine dioxide, chlorine, monochloramines, disinfection.
Methane oxidation in landfill cover soil; the combined effects of moisture content, nutrient addition, and cover thickness
Authors: Albanna Muna , Fernandes Leta , Warith Mostafa
Published: May 2007

Oxidation of methane by methanotrophs in the landfill cover soil provides a source reduction for methane. Full factorial 23 experimental design using heterogeneous batch reactors was conducted to investigate statistically the individual and combined effects of soil moisture content, nutrient addition, and cover thickness on the CH4 oxidation process, during the migration through a landfill cover soil. Adding fertilizer as nutrient source to the 200 mm layer thickness of the landfill cover soil that contained 30% moisture content increased the CH4 oxidation efficiency from 38% to 81%. While, adding nutrients to the soil with less moisture content (15%) affected negatively the bacterial performance of methane oxidation, possibly as a result of toxicity or microbial water stress. Kinetic constants were reported and statistical design model was developed to describe the expected methane oxidation efficiencies under different levels of moisture content and nutrient addition that occur in a typical landfill cover soil.Key words: methane oxidation, landfill cover soil, moisture content, nutrients, soil thickness.
Prediction of oxygen content of nappe, transition, and skimming flow regimes in stepped-channel chutes
Authors: Baylar Ahmet , Bagatur Tamer , Emiroglu M Emin
Published: May 2007

In a stepped-channel chute, the chute face is provided with a series of steps, from near the crest to the toe. Like many other high-speed flow configurations in hydraulic engineering, stepped-channel chute flows are characterized by the large amount of self-entrained air. Air entrainment on stepped-channel chutes is also recognized for its contribution to the oxygen transfer. The flow conditions in stepped-channel chutes have been classified into nappe flows, transition flows, and skimming flows. In this study, the aeration efficiency of stepped-channel chutes was investigated, and in particular, the effect of varying flow regimes. The results indicated that the nappe flow regime led to the larger aeration efficiency than the other flow regimes. Moreover, the mass transfer equations were developed to predict the aeration efficiency of the stepped-channel chutes in terms of dissolved oxygen. There is good agreement between the measured aeration efficiency values and the values computed from the predictive equations.Key words: aeration efficiency, oxygen transfer, stepped-channel chute, skimming flow, transition flow, nappe flow.
A comparative study between thermophilic and mesophilic membrane aerated biofilm reactors
Authors: Liao B Q , Liss S N
Published: May 2007

The concept of thermophilic membrane aerated biofilm reactor (MABR) was investigated for the first time and examined for its potential to treat a high strength synthetic wastewater. Biofilms at 55 °C were successfully grown on gas permeable silicone hollow fiber membranes. At a feed chemical oxygen demand (COD) of 1200 mg/L and a reaction time of 1 d, COD removal efficiency (90%) of the thermophilic MABR (55 °C) was much higher than that (67%) of the mesophilic MABR operated at 18–28 °C. Biofilms in the thermophilic reactor were less thick, more hydrophobic, and less negatively charged. This study indicated that MABRs operated at thermophilic temperatures could be an effective means for controlling biofilm thickness and for the treatment of warm high strength organic waste.Key words: membrane aerated biofilm reactor, thermophilic biofilm, mesophilic biofilm, biofilm characterization, COD removal.
Mercury-free sources of VUV/UV radiation: application of modern excimer lamps (excilamps) for water and air treatment
Authors: Oppenländer Thomas
Published: May 2007

This paper reviews recent experimental results concerning the use of modern excilamps (excimer lamps) in photoscience and photochemical technology. The special characteristics of these sources of incoherent vacuum-UV (VUV)/UV radiation are presented and their applications in water and air remediation are discussed. Special attention is paid to the VUV (172 nm)-initiated oxidation and mineralization of organic water and air contaminants. For example, the VUV-initiated production of carbon dioxide and carbon monoxide during 172 nm irradiation of several saturated volatile organic substrates in the gas phase (e. g. methanol, ethanol, 2-propanol, 1,4-dioxane, cyclohexane, and n-hexane) was quantitatively verified by gas chromatography. Depending on the nature of the gaseous substrate and on the flow rate through the excimer-flow-through photoreactor different CO2/CO ratios were obtained. Key words: excimer lamps, excilamps, 172 nm irradiation, VUV oxidation, photo-mineralization, UV disinfection, excilamp flow-through photoreactor, plug-flow photoreactor, gas-phase photo-oxidation.
TiO2/UV: Single stage drinking water treatment for NOM removal?
Authors: Murray Christine A , Goslan Emma H , Parsons Simon A
Published: May 2007

Problems arise at water treatment works due to the reaction of natural organic matter with chlorine to produce disinfection by-products (DBP). Trihalomethanes (THMs) are the main DBP regulated in various countries. The UK THM standard is 100 μg L–1 while in the USA it is 80 μg L–1. At certain times of the year the efficiency of conventional treatment processes is compromised due to seasonal increases in the concentration of natural organic matter (NOM). During these periods water treatment works generally increase the coagulant dose but this subsequently increases the volume of potable sludge generated. Advanced oxidation processes have the potential to remove NOM and thereby reduce the DBP formation. Here the adsorption of NOM onto pelletised titanium dioxide (TiO2) and the oxidation of the surface of the pellets by UV light have been shown to reduce the dissolved organic carbon (DOC) concentration of source water by 70%. Key words: photocatalysis, titanium dioxide, natural organic matter (NOM), trihalomethanes, sludge reduction.
Volume change of the ocular lens during accommodation
Authors: Gerometta R. , Zamudio A. C. , Escobar D. P. , Candia O. A.
Published: May 2007

During accommodation, mammalian lenses change shape from a rounder configuration (near focusing) to a flatter one (distance focusing). Thus the lens must have the capacity to change its volume, capsular surface area, or both. Because lens topology is similar to a torus, we developed an approach that allows volume determination from the lens cross-sectional area (CSA). The CSA was obtained from photographs taken perpendicularly to the lenticular anterior-posterior (A-P) axis and computed with software. We calculated the volume of isolated bovine lenses in conditions simulating accommodation by forcing shape changes with a custom-built stretching device in which the ciliary body-zonulae-lens complex (CB-Z-L) was placed. Two measurements were taken (CSA and center of mass) to calculate volume. Mechanically stretching the CB-Z-L increased the equatorial length and decreased the A-P length, CSA, and lens volume. The control parameters were restored when the lenses were stretched and relaxed in an aqueous physiological solution, but not when submerged in oil, a condition with which fluid leaves the lens and does not reenter. This suggests that changes in lens CSA previously observed in humans could have resulted from fluid movement out of the lens. Thus accommodation may involve changes not only in capsular surface but also in volume. Furthermore, we calculated theoretical volume changes during accommodation in models of human lenses using published structural parameters. In conclusion, we suggest that impediments to fluid flow between the aquaporin-rich lens fibers and the lens surface could contribute to the aging-related loss of accommodative power.
Atherogenic scavenger receptor modulation in the tubulointerstitium in response to chronic renal injury
Authors: Okamura Daryl M. , López-Guisa Jesús M. , Koelsch Katie , Collins Sarah , Eddy Allison A.
Published: May 2007

Oxidized low-density lipoproteins (oxLDL) and their scavenger receptor (SR) binding partners play a central role in atherosclerosis and by analogy may play a role in chronic kidney disease pathogenesis. The present study was designed to investigate in C57BL/6 mice the effects of hypercholesterolemia on renal injury severity and oxLDL generation after unilateral ureteral obstruction (UUO). The expression profiles of CD36, SR class AI/II (SR-A), lectin-like receptor for oxidized low-density lipoprotein-1 (Lox-1), and SR that binds phosphatidylserine and oxLDL (SR-PSOX/CXCL16) were examined. Four experimental groups were studied: sham and UUO male mice on either a high-fat Western diet or a control diet. Significantly more oxLDL accumulated in the tubulointerstitium of hypercholesterolemic mice compared with normocholesterolemic mice after 14 days of UUO ( P < 0.01). Total kidney collagen was significantly higher in the obstructed kidneys of hypercholesterolemic mice compared with normocholesterolemic mice on day 14 ( P < 0.01). After 14 days of obstruction, the number of interstitial F4/80+ macrophages and NF-κB activation increased in hypercholesterolemic mice compared with normocholesterolemic mice ( P < 0.01). In normal kidneys, CD36, SR-A, Lox-1, and CXCL16 were primarily localized to renal tubular epithelia. After ureteral obstruction, CD36 increased at day 7; SR-A and Lox-1 progressively decreased in a time-dependent manner; and CXCL16 increased significantly with the onset of obstruction ( P < 0.01). Strong tubular expression suggests that in addition to inflammatory interstitial cells, renal tubular scavenger receptors may help to orchestrate the inflammatory and fibrogenic pathways that are activated by oxLDL.
Genetic deletion of AT1areceptors attenuates intracellular accumulation of ANG II in the kidney of AT1areceptor-deficient mice
Authors: Li Xiao C. , Navar L. Gabriel , Shao Yuan , Zhuo Jia L.
Published: May 2007

We and others have previously shown that high levels of ANG II are accumulated in the rat kidney via a type 1 (AT1) receptor-mediated mechanism, but it is not known which AT1receptor is involved in this process in rodents. We tested the hypothesis that AT1areceptor-deficient mice (Agtr1a−/−) are unable to accumulate ANG II intracellularly in the kidney because of the absence of AT1areceptor-mediated endocytosis. Adult male wild-type (Agtr1a+/+), heterozygous (Agtr1a+/−), and Agtr1a−/− were treated with vehicle, ANG II (40 ng/min ip via osmotic minipump), or ANG II plus the AT1antagonist losartan (10 mg·kg−1·day−1po) for 2 wk. In wild-type mice, ANG II induced hypertension (168 ± 4 vs. 113 ± 3 mmHg, P < 0.001), increased kidney-to-body weight ratio ( P < 0.01), caused pressure natriuresis ( P < 0.05), and elevated plasma and whole kidney ANG II levels ( P < 0.001). Concurrent administration of ANG II with losartan attenuated these responses to ANG II. In contrast, Agtr1a−/− mice had lower basal systolic pressures ( P < 0.001), smaller kidneys with much fewer AT1breceptors ( P < 0.001), higher basal 24-h urinary sodium excretion ( P < 0.01), as well as basal plasma and whole kidney ANG II levels ( P < 0.01). However, intracellular ANG II levels in the kidney were lower in Agtr1a−/− mice. In Agtr1a−/− mice, ANG II slightly increased systolic pressure ( P < 0.05) but had no effect on the kidney weight, urinary sodium excretion, and whole kidney ANG II levels. Losartan restored systolic pressure to basal levels and decreased whole kidney ANG II levels by ∼20% ( P < 0.05). These results demonstrate a predominant role of AT1areceptors in blood pressure regulation and in the renal responses to long-term ANG II administration, that AT1breceptors may play a limited role in blood pressure control and mediating intrarenal ANG II accumulation in the absence of AT1areceptors.
Neuromuscular Abnormalities Associated With Spasticity of Upper Extremity Muscles in Hemiparetic Stroke
Authors: Mirbagheri M. M. , Settle K. , Harvey R. , Rymer W. Z.
Published: May 2007

Our objective was to assess the mechanical changes associated with spasticity in elbow muscles of chronic hemiparetic stroke survivors and to compare these changes with those recorded in the ankle muscles of a similar cohort. We first characterized elbow dynamic stiffness by applying pseudorandom binary positional perturbations to the joints at different initial angles, over the entire range of motion, with subjects relaxed. We separated this stiffness into intrinsic and reflex components using a novel parallel cascade system identification technique. In addition, for controls, we studied the nonparetic limbs of stroke survivors and limbs of age-matched healthy subjects as primary and secondary controls. We found that both reflex and intrinsic stiffnesses were significantly larger in the stroke than in the nonparetic elbow muscles, and the differences increased as the elbow was extended. Reflex stiffness increased monotonically with the elbow angle in both paretic and nonparetic sides. In contrast, the modulation of intrinsic stiffness with elbow position was different in nonparetic limbs; intrinsic stiffness decreased sharply from full- to mid-flexion in both sides, then it increased continuously with the elbow extension in the paretic side. It remained invariant in the nonparetic side. Surprisingly, reflex stiffness was larger in the nonparetic than in the normal control arm, yet intrinsic stiffness was smaller in the nonparetic arm. Finally, we compare the angular dependence of paretic elbow and ankle muscles and show that the modulation of reflex stiffness with position was strikingly different.
Physiological Properties of Mouse Skin Sensory Neurons Recorded Intracellularly In Vivo: Temperature Effects on Somal Membrane Properties
Authors: Boada M. Danilo , Woodbury C. Jeffery
Published: May 2007

Recent combined analyses of the structural, functional, and molecular attributes of individual skin sensory neurons using semi-intact in vitro preparations from mice have provided a wealth of novel insights into nociceptor biology. How these findings translate to more natural conditions nevertheless remains unresolved. Toward this end, intracellular recordings were obtained from 362 physiologically identified dorsal root ganglion (DRG) neurons in a new in vivo mouse preparation developed for combined structure/function analyses of individual skin sensory neurons. Recordings were conducted at thoracic levels in adult decorticate mice for comparison with in vitro findings from the same trunk region. In all, 270 neurons were recorded at DRG temperatures tightly regulated at normal core values to establish a baseline and 137 skin sensory neurons were included in detailed analyses of somal properties for comparisons with similar data obtained under reduced temperatures mirroring in vitro conditions. Recovery of Neurobiotin-labeled central projections was crucial for verifying perceived afferent identity of certain neurons. Further, profound temperature dependency was seen across diverse physiological properties. Indeed, the broad, inflected somal spikes normally viewed as diagnostic of myelinated nociceptors were found to be a product of reduced temperatures and were not present at normal core values. Moreover, greater complexity was observed peripherally in the mechanical and thermal sensitivity profile of nociceptive and nonnociceptive populations than that seen under in vitro conditions. This novel in vivo preparation therefore holds considerable promise for future analyses of nociceptor function and plasticity in normal and transgenic models of pain mechanisms.
Differential Expression of Intrinsic Membrane Currents in Defined Cell Types of the Anterolateral Bed Nucleus of the Stria Terminalis
Authors: Hammack Sayamwong E. , Mania Irakli , Rainnie Donald G.
Published: May 2007

The anterolateral group of the bed nucleus of the stria terminalis (BNSTALG) plays a critical role in a diverse array of behaviors, although little is known of the physiological properties of neurons in this region. Using whole cell patch-clamp recordings from rat BNSTALG slices in vitro, we describe three distinct physiological cell types. Type I neurons were characterized by the presence of a depolarizing sag in response to hyperpolarizing current injection that resembled activation of the hyperpolarization-activated cation current Ih and a regular firing pattern in response to depolarizing current injection. Type II neurons exhibited the same depolarizing sag in response to hyperpolarizing current injection, but burst-fired in response to depolarizing current injection, which was indicative of the activation of the low-threshold calcium current IT. Type III neurons did not exhibit a depolarizing sag in response to hyperpolarizing current injection, but instead exhibited a fast time-independent rectification that became more pronounced with increased amplitude of hyperpolarizing current injection, and was indicative of activation of the inwardly rectifying potassium current IK(IR). Type III neurons also exhibited a regular firing pattern in response to depolarizing current. Using voltage-clamp analysis we further characterized the primary active currents that shaped the physiological properties of these distinct cell types, including Ih, IT, IK(IR), the voltage-dependent potassium current IA, and the persistent sodium current INaP. The functional relevance of each cell type is discussed in relation to prior anatomical studies, as well as how these currents may interact to modulate neuronal activity within the BNSTALG.
Neuronal Firing Rates and Patterns in the Globus Pallidus Internus of Patients With Cervical Dystonia Differ From Those With Parkinson's Disease
Authors: Tang Joyce K. H. , Moro Elena , Mahant Neil , Hutchison William D. , Lang Anthony E. , Lozano Andres M. , Dostrovsky Jonathan O.
Published: May 2007

Cervical dystonia (CD) is a movement disorder that involves involuntary turning and twisting of the neck caused by abnormal muscle contraction. Deep brain stimulation (DBS) in the globus pallidus internus (GPi) is used to treat both CD and the motor symptoms of Parkinson's disease (PD). It has been suggested that the differing motor symptoms in CD and PD may arise from a decreased GPi output in CD and elevation of output in PD. To test this hypothesis, extracellular recordings of GPi neuronal activity were obtained during stereotactic surgery for the implantation of DBS electrodes in seven idiopathic CD and 14 PD patients. The mean GPi neuronal firing rate recorded from CD patients was lower than that in PD patients ( P < 0.001; means ± SE: 71.4 ± 2.2 and 91.7 ± 3.0 Hz, respectively). Furthermore, GPi neurons fired in a more irregular pattern consisting of more frequent and longer pauses in CD compared with PD patients. When comparisons were done based on locations of recordings, these differences in firing rates and patterns were limited to the ventral portion of the GPi. In contrast, no difference in firing rate or pattern was observed in the globus pallidus externus between the two groups. These findings suggest that alterations in both firing rate and firing pattern may underlie the differing motor symptoms associated with these two movement disorders.
Preparation and Characterization of Poly (1, 3-propylene glycol-hexanedioic acid)-functionalized Carbon Nanotubes
Authors: Meng Qing-Jie , Zhang Xing-Xiang , Wang Xue-Chen
Published: May 2007

An in situ process was used to prepare poly (1, 3-propylene glycol-hexanedioic acid)-functionalized carbon nanotubes using carboxylate-functionalized multi-walled carbon nanotubes, 1, 3-propylene glycol and hexanedioic acid as reactants. The functionalized carbon nanotubes were characterized using transmission electronic microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results indicated that the carboxylate-functionalized carbon nanotubes chemically reacted and were linked with the polyester chains. The extent of polycondensation reaction could be controlled by the concentration of the carboxylate-functionalized carbon nanotubes in the reactant mixture. The carboxylate-functionalized carbon nanotubes were surrounded by a polyester matrix with a maximum thickness of approximately 3 nm.
Synthesis and Characterization of Some Acrylate Copolymers and their Evaluation as Aqueous Developable Photoresists
Authors: El-Demerdash Abdel-Ghaffar , Abdel-Alim Wagih , Ahmed Sayed
Published: May 2007

In the recent past, it has been found that the use of onium salts as acid-generating species has improved the performance of photoresists, particularly for microelectronic applications. However, little research has been dedicated to the use of these photo-initiators in aqueous-developable resists. This work describes the synthesis and characterization of some water-soluble polymers and investigates the feasibility of employing one of the onium salts in the formulation of a resist polymer for use in aqueous conditions. The ability of this onium salt to photo-initiate the cationic polymerization of epoxies residues was exploited using water-soluble copolymers, containing glycidyl methacrylate (GMA). The comonomers included methacrylic acid. Various copolymers were prepared by radical copolymerization typically in methyl ethyl ketone. It was found that the copolymer containing 85 mol.% of GMA unit in feed was soluble in aqueous base and crosslinked in the presence of photogenerated acid caused by acid-initiated ring opening polymerization of the pendant epoxide groups. A good pattern with reasonable resolution was attained by exposure to a UV lamp with λ = 365 nm light followed by a post exposure bake at 80° C for 1 min.
Finite Element Analysis of Multi-axis Strain Sensitivities of Bragg Gratings in PM Fibers
Authors: Prabhugoud Mohanraj , Peters Kara
Published: May 2007

This article presents a numerical analysis of the sensitivity of fiber Bragg grating (FBG) sensors written into polarization maintaining fibers to transverse and thermal loading. These sensors are typically applied for the measurement of multiple strain components for the monitoring of civil structures. The finite element analysis includes both the optical and mechanical variations in the optical fiber. Five fiber types typically used in FBG sensors (elliptical core, D-fiber, elliptical core SAP, Bow-Tie, and Panda) are compared. It is shown that when only the fiber geometry is considered while the material parameters are approximately the same, the D-fiber demonstrates the highest sensitivity to transverse loading. In addition, it is shown that reducing the fiber cladding diameter significantly improves the sensitivities of the FBG sensor to transverse loads. All fiber types exhibit approximately the same sensitivity to thermal loading.
Practical Implementation of Optical Fiber Sensors in Civil Structural Health Monitoring
Authors: Ansari Farhad
Published: May 2007

Implementation of successful civil structural health monitoring strategies requires selection and placement of sensors suitable for measurement of key parameters that influence the performance and health of the structural system. Optical fiber sensors have been successfully implemented in aeronautics, mechanical systems, and medical applications. Civil structures pose further challenges in monitoring mainly due to their large dimensions, diversity as well as heterogeneity of materials involved, and hostile construction environment. This article provides a summary of basic principles pertaining to practical health monitoring of civil engineering structures with optical fiber sensors. The issues discussed include basic sensor principles, strain transfer mechanism, sensor packaging, sensor placement in construction environment, and reliability and survivability of the sensors.