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Laboratory Study (laboratory + study)
Selected AbstractsEffect of Auxiliary Grooves on Molar Crown Preparations Lacking Resistance Form: A Laboratory StudyJOURNAL OF PROSTHODONTICS, Issue 2 2008DClinDent, GradDipClinDent, Po-Ching Lu BDSc(Hons) Abstract Purpose: To investigate the effect of auxiliary grooves on resistance to dislodgment of crowns on compromised molar preparations lacking resistance form. Materials and Methods: Thirty human molar teeth were randomly assigned to three groups of ten, and prepared to a height-to-width ratio of 0.3 with a total convergence of 50°, and 1-mm shoulder margin. Base metal alloy copings were constructed with a 45° loading platform and cemented with zinc phosphate cement under a 50 N load. Initially, resistance testing was conducted using a Universal Testing Machine (Instron) at 1 mm/min for all 30 specimens. Following crown dislodgment, Group 1 copings were recemented and retested, Group 2 had one axial groove added, and Group 3 had two axial grooves added. New copings for Groups 2 and 3 were made, cemented, and again tested for resistance. Standardized radiographs were taken prior to initial cementation and scanned into digital images. The percentage of area occupied by the pulpal chamber above the acrylic mounting (PS), and the closest distance to pulp from the preparation surface (CD) were measured. Results: Recementation or the addition of one groove did not affect the dislodgment values (p > 0.05), but addition of two grooves caused a highly significant increase in resistance (p < 0.001). Regression analysis showed an inverse relationship between initial resistance values and pulpal space area. Lower resistance values were observed when the pulpal space area was large (p= 0.004). Conclusions: Crowns can be recemented without affecting resistance to dislodgment. Two grooves should be incorporated into compromised molar crown preparations to increase resistance form. Teeth with large pulps and therefore less coronal dentine have poorer resistance form, and therefore would benefit from placement of auxiliary grooves. [source] Laboratory Study of the Intracapsular Development and Juvenile Growth of the Banded Murex, Hexaplex trunculusJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2010Youssef Lahbib Spawning, intracapsular development, and juvenile growth of Hexaplex trunculus were investigated in the laboratory. Each female deposited nightly an average of 138.83 ± 58.70 yellowish egg capsules per spawn. Each capsule contained 358.57 ± 102.45 eggs with an average diameter of 207.23 ± 18.18 µm. Observations on the intracapsular development showed that H. trunculus is a spiralian unequal-cleaving gastropod, with polar lobes being extruded at early segmentation. Embryos develop within the egg capsule through the provision of nurse eggs as an extraembryonic source of nutrition. Hatching occurred after 52 d of incubation. However, the hatchlings were not completely metamorphosed because velum was still present. At this moment, the average of shell length was 1.04 ± 0.13 mm (n = 107). The average number of hatchlings per capsule was 14.73 ± 4.40 including 3.4% malformed individuals. During the first 5 mo of life, juveniles rapidly grew in shell length (growth rate = 3.56 mm/mo). However, in the remaining period (26 mo), growth rhythm decreased considerably (growth rate = 0.64 mm/mo). The weight growth rhythm was irregular with alternation between fast and slow increases observed over the rearing experiment. This kind of data could be useful for assessing the potential of this species for future molluscan aquaculture programs. [source] Secondary Apoptosis of Spiral Ganglion Cells Induced by Aminoglycoside: Fas,Fas Ligand Signaling Pathway,THE LARYNGOSCOPE, Issue 9 2008Woo Yong Bae MD Abstract Objectives/Hypothesis: Hair cell loss results in the secondary loss of spiral ganglion neurons (SGNs), over a period of several weeks. The death of the SGNs themselves results from apoptosis. Previous studies have shown that several molecules are involved in the apoptosis of SGNs that occurred secondary to hair cell loss. However, the precise mechanism of apoptosis of the SGNs remains unclear. The aim of this study was to ascertain the secondary apoptosis of spiral ganglion cells induced by aminoglycoside and to investigate the role of the Fas,FasL signaling pathway using guinea pigs as an experimental animal model. Study Design: Laboratory study using experimental animals. Methods: Guinea pigs weighing 250 to 300 g (n = 21) from 3 to 4 weeks of age were used. Gentamicin (60 ,L) was injected through a cochleostomy site on their left side. At 1 (n = 7), 2 (n = 7), and 3 (n = 7) weeks after gentamicin treatment, their cochleas were obtained from their temporal bone. Hematoxylin and eosin and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling staining were performed to observe apoptosis. To investigate the involvement of the Fas,FasL signaling pathway in the secondary apoptosis of SGNs, we performed reverse transcription-polymerase chain reaction (RT-PCR), western blotting, and immunohistochemistry. Results: A progressive loss of spiral ganglion cells with increasing time after gentamicin treatment was observed on light microscopic examination. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling staining demonstrated induction of apoptotic cell death in SGNs after gentamicin treatment. Expression of FasL increased over time after gentamicin treatment as determined by RT-PCR and western blotting. On immunohistochemical staining, we observed the localization of FasL in the SGNs. The proapoptotic molecules Bax and Bad were increased, but levels of the antiapoptotic molecule Bcl-2 were decreased at increasing survival times after gentamicin treatment on RT-PCR. The gentamicin-treated group displayed initial activation of caspase-8 and increased the cleavage of caspase-3, caspase-8, and PARP protein in a time-dependent manner. Conclusions: The secondary apoptosis of SGNs could be a result of the apoptotic Fas,FasL signaling pathway. Blocking the Fas,FasL signaling pathway could be considered as a method for preventing secondary degeneration of SGNs, and further studies are needed to confirm this. [source] Cadaveric and Engineering Analysis of the Septal L-Strut,THE LARYNGOSCOPE, Issue 11 2007Ted Mau MD Abstract Objectives: To identify patterns of failure of the L-strut, to identify elements of the nasal framework that support the L-strut, and to investigate the effect of altering L-strut design on its stability. Study Design: Laboratory study with human cadaveric heads and computational modeling. Methods: Directional forces were applied to cadaveric L-struts and patterns of failure with incremental force were noted. Computational modeling using the finite element method (FEM) was employed to determine quantitatively the effect of various modifications on the stability of the L-strut. Results: The L-strut was found to respond to frontal force initially by buckling. This buckling was reversible until the force exceeded a certain threshold when the L-strut broke at the bony-cartilaginous junction. The threshold force varied depending on the length of the overlap with the bony vault. Intact mucoperichondrium provided significant stability. Modeling with FEM showed that the preservation of a triangular piece of cartilage at the dorsal anchor of a narrowed L-strut can offset some of the loss in mechanical stability. Conclusions: Intrinsic elasticity of the septal cartilage, the mucoperichondrial flap, and overlap with the bony vault all contribute to the stability of the L-strut, which is enhanced by preserving a small segment of cartilage at the bony-cartilaginous junction of the dorsal L-strut. [source] Candidate's Thesis: Direct Evidence of Bacterial Biofilms in Otitis Media,THE LARYNGOSCOPE, Issue 12 2001J. Christopher Post MD Abstract Objectives/Hypothesis Bacteriologic studies of otitis media with effusion (OME) using highly sensitive techniques of molecular biology such as the polymerase chain reaction have demonstrated that traditional culturing methods are inadequate to detect many viable bacteria present in OME. The presence of pathogens attached to the middle-ear mucosa as a bacterial biofilm, rather than as free-floating organisms in a middle-ear effusion, has previously been suggested to explain these observations. The suggestion has been speculative, however, because no visual evidence of such biofilms on middle-ear mucosa has heretofore been collected. The hypotheses motivating the current study were: 1) biofilms of nontypable Hemophilus influenzae will form on the middle-ear mucosa of chinchillas in an experimental model of OME, 2) these biofilms will exhibit changes in density or structure over time, and 3) biofilms are also present on tympanostomy tubes in children with refractory post-tympanostomy otorrhea. The objective of this study was to collect visual evidence of the formation of bacterial biofilms in these situations. Study Design Laboratory study of bacteriology in an animal model and on medical devices removed from pediatric patients. Methods Experimental otitis media was induced in chinchillas by transbullar injection of nontypable H. influenzae. Animals were killed in a time series and the surface of the middle-ear mucosa was examined by scanning electron microscopy (SEM) for the presence of bacterial biofilms. Adult and fetal chinchilla uninfected controls were similarly examined for comparison. In addition, tympanostomy tubes that had been placed in children's ears to treat OME and removed after onset of refractory otorrhea or other problems were examined by SEM and by confocal scanning laser microscopy for bacterial biofilms, and compared with unused control tubes. Results Bacterial biofilms were visually detected by SEM on the middle-ear mucosa of multiple chinchillas in which H. influenzae otitis media had been induced. Qualitative evaluation indicated that the density and thickness of the biofilm might increase until at least 96 hours after injection. The appearance of the middle-ear mucosa of experimental animals contrasted with that of uninjected control animals. Robust bacterial biofilms were also visually detected on tympanostomy tubes removed from children's ears for clinical reasons, in contrast with unused control tubes. Conclusions Bacterial biofilms form on the middle-ear mucosa of chinchillas in experimentally induced H. influenzae otitis media and can form on tympanostomy tubes placed in children's ears. Such biofilms can be directly observed by microscopy. These results reinforce the hypothesis that the bacterial aggregates called biofilms, resistant to treatment by antibiotics and to detection by standard culture techniques, may play a major etiologic role in OME and in one of its frequent complications, post-tympanostomy otorrhea. [source] Evaluation of tooth-fragment reattachment: a clinical and laboratory studyDENTAL TRAUMATOLOGY, Issue 4 2010Yucel Yilmaz Materials and Methods:, The clinical study was conducted on 43 fractured incisors: 22 uncomplicated crown fractures (Group A) and 21 complicated crown fractures (Group B). The 43 incisal fragments: 23 were kept dry for 47 h and 20 were kept wet for 24 h by the patients before they were reattached. The fragments were kept in 0.9% saline solution for 30 min before reattachment. The fragments in Group A were reattached using a dentin bonding agent, a flowable and a hybrid resin composite, whereas the fragments in Group B were reattached to the tooth remnant after a pulpotomy was performed. The laboratory study was conducted on 56 extracted incisors. Teeth were divided equally into four groups: Group I , Uncomplicated crown fracture + wet medium; Group II , Uncomplicated crown fracture + dry medium; Group III , Complicated crown fracture + wet medium, and Group IV , Complicated crown fracture + dry medium. The fragments were then reattached in a manner that was similar to that used in the clinical study. The restored teeth were then re-fractured. All data were analyzed statistically. Results: In the clinical study, the restored teeth were followed up for 2 years. Neither the type of trauma nor the storage medium had any significant effect on the survival, color, and bond strength of the restored teeth when assessed in the clinical and laboratory study. The color disharmony that was encountered initially in restored teeth resolved significantly on its own accord within 12 months after reattachment of the fragment. Conclusion: Fragment reattachment can be used to treat fractured teeth successfully in children and adolescents. [source] Close range digital photogrammetric analysis of experimental drainage basin evolutionEARTH SURFACE PROCESSES AND LANDFORMS, Issue 3 2003J. Brasington Abstract Despite the difficulties of establishing formal hydraulic and geometric similarity, small-scale models of drainage basins have often been used to investigate the evolution and dynamics of larger-scale landforms. Historically, this analysis has been restricted to planform basin characteristics and only in the last decade has the topographic similarity of experimental landscapes been explored through explicitly three-dimensional parameters such as the distributions of cumulative drainage area, area,slope and catchment elevation. The current emphasis on three-dimensional morphometry reflects a growing awareness of the descriptive paucity of planform data and the need for more robust analysis of spatial scaling relationships. This paradigm shift has been significantly facilitated by technological developments in topographic survey and digital elevation modelling (DEM) which now present the opportunity to acquire and analyse high-resolution, distributed elevation data. Few studies have, however, attempted to use topographic modelling to provide information on the changing pattern and rate of sediment transport though an evolving landscape directly by using multitemporal DEM differencing techniques. This paper reports a laboratory study in which digital photogrammetry was employed to derive high-resolution DEMs of a simulated landscape in declining equilibrium at 15 minute frequency through a 240 minute simulation. Detailed evaluation of the DEMs revealed a vertical precision of 1·2 mm and threshold level of change detection between surfaces of ±3 mm at the 95 per cent confidence level. This quality assurance set the limits for determining the volumetric change between surfaces, which was used to recover the sediment budget through the experiment and to examine local - and basin-scale rates of sediment transport. A comparison of directly observed and morphometric estimates of sediment yield at the basin outlet was used to quantify the closure of the sediment budget over the simulation, and revealed an encouragingly small 6·2 per cent error. The application of this dynamic morphological approach has the potential to offer new insights into the controls on landform development, as demonstrated here by an analysis of the changing pattern of the basin sediment delivery ratio during network growth. Copyright © 2003 John Wiley & Sons, Ltd. [source] Validation of daily increment formation and the effects of different temperatures and feeding regimes on short-term otolith growth in Australian smelt Retropinna semoniECOLOGY OF FRESHWATER FISH, Issue 2 2008Z. Tonkin Abstract,,, To aid otolith interpretation of wild fish, we conducted a laboratory study using metalarval Australian smelt (Retropinna semoni) collected from the Murray River, to examine daily increment deposition and the effects of different temperatures and feeding regimes on otolith growth. Daily increment deposition was confirmed by comparing the number of increments from an oxytetracycline mark with the known number of days from marking. After holding fish at two temperature levels and three feeding rates, both food density and temperature were found to have a significant effect on otolith growth, with food density having the greatest influence. Overall trends in final lengths and condition of fish were well represented by recent otolith growth. The results of the experiment have implications for estimating growth histories and its relationship to various environmental conditions. [source] Recollective experience in alcohol dependence: a laboratory studyADDICTION, Issue 12 2008Patrizia Thoma ABSTRACT Aims Alcohol dependence has been linked to dysfunction of fronto-temporo-striatal circuits which mediate memory and executive function. The present study aimed to explore the specificity of recognition memory changes in alcohol dependence. Design, setting and participants Twenty hospitalized alcohol-dependent detoxified patients and 20 healthy control subjects completed a verbal list discrimination task. Measurements Hits and false alarm rates were analysed. Additionally, both the dual process signal detection model (DPSD) and the process dissociation procedure (PDP) were used to derive estimates of the contribution of recollection and familiarity processes to the recognition memory performance in patients and controls. Findings Alcohol-dependent patients showed intact hit rates, but increased false alarm rates and an impaired ability to remember the learning context. Both the DPSD model and PDP estimates yielded significantly reduced recollection estimates in the alcohol-dependent compared to control subjects. Whether or not familiarity was impaired, depended upon the sensitivity of the estimation procedure. Conclusion Taken together, the result pattern suggests a significant impairment in recollection and mild familiarity changes in recently detoxified, predominantly male, alcohol-dependent subjects. [source] Structural diversity of bacterial communities in a heavy metal mineralized granite outcropENVIRONMENTAL MICROBIOLOGY, Issue 3 2006Deirdre Gleeson Summary This laboratory study of a variably mineralized and hydrothermally altered granite outcrop investigated the influences of rock-surface chemistry and heavy metal content on resident bacterial populations. Results indicated that elevated heavy metal concentrations had a profound impact on bacterial community structure, with strong relationships found between certain ribotypes and particular chemical/heavy metal elements. Automated ribosomal intergenic sequence analysis (ARISA) was used to assess the nature and extent of bacterial diversity, and this was combined with chemical analysis and multivariate statistics to identify the main geochemical factors influencing bacterial community structure. A randomization test revealed significant changes in bacterial structure between samples, while canonical correspondence analysis (CCA) related each individual ARISA profile to linear combinations of the chemical variables (mineralogy, major element and heavy metal concentrations) revealing the geochemical factors that correlated with changes in the ARISA data. anova was performed to further explore interactions between individual ribotypes and chemical/heavy metal composition, and revealed that a high proportion of ribotypes correlated significantly with heavy metals. [source] Chromate reduction in wastewater at different pH levels using thin iron wires,A laboratory studyENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 3 2005Li-Yang Chang Abstract The effectiveness of using thin zero-valent iron (Fe0) wires in the treatment of wastewater generated from a metal cleaning facility and with a pH in the range of 2 to 10 was examined. It was found that (1) when the sample containing low levels of total chromium (,14 mg/L) was mixed with iron wires at a pH of 3 to 8, 50 to 90% of the total chromium could be reduced in 4 h; (2) the initial reduction efficiency was pH-dependent: the lower the pH, the higher the reduction rate; (3) variations of solution pH, redox electrical potential, and electrical conductivity (EC) in samples were also pH-dependent; (4) the adsorption/reduction efficiency was limited by the diffusion of Cr(VI) from wastewater to the iron surface when the test duration was long; (5) when the initial pH = 3, iron corrosion and redox reaction dominated the reduction process; however, with pH = 8 or 10, corrosion, surface passivation, or metal precipitation could compete with reduction; (6) the used iron wires were still effective in chromium removal in new samples at pH = 3; and (7) some desorption of adsorbed chromium was observed in acidic samples when the test duration was long. Scanning electron microscope images and energy-dispersive X-ray spectra collected from iron samples also indicate that the efficiency of chromium adsorption/reduction is pH-dependent. Our results suggest that using zero-valent iron to polish acidic wastewater containing low contents of chromium and other heavy metals is feasible. © 2005 American Institute of Chemical Engineers Environ Prog, 2005 [source] Alteration of normal cellular profiles in the scleractinian coral (Pocillopora damicornis) following laboratory exposure to fuel oilENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2006Luc Rougée Abstract Petroleum contamination from oil spills is a continuing threat to our ocean's fragile ecosystems. Herein, we explored the effects of the water-soluble fraction of crude oil on a stony coral, Pocillopora damicornis (Linneaeus 1758). We developed methods for exposing corals to various concentrations of crude oil and for assessing the potential molecular responses of the corals. Corals were exposed to water-accommodated fraction solutions, and appropriate cellular biomarkers were quantified. When compared to the "healthy" control specimens, exposed corals exhibited shifts in biomarker concentrations that were indicative of a shift from homeostasis. Significant changes were seen in cytochrome P450 1-class, cytochrome P450 2-class, glutathione- S -transferase-pi, and cnidarian multixenobiotic resistance protein-1 biomarkers, which are involved the cellular response to, and manipulation and excretion of, toxic compounds, including polycyclic aromatic hydrocarbons. A shift in biomarkers necessary for porphyrin production (e.g., protoporphyrinogen oxidase IX and ferrochelatase) and porphyrin destruction (e.g., heme oxygenase-1 and invertebrate neuroglobin homologue) illustrates only one of the cellular protective mechanisms. The response to oxidative stress was evaluated through measurements of copper/zinc superoxide dismutase-1 and DNA glycosylase MutY homologue-1 concentrations. Likewise, changes in heat shock protein 70 and small heat shock proteins indicated an adjustment in the cellular production of proteins. Finally, the results of this laboratory study were nearly identical to what we observed previously among corals of a different species, Porites lobata, exposed to an oil spill in the field after the grounding of the Merchant Vessel Kyowa Violet. [source] Dissipation kinetics and mobility of chlortetracycline, tylosin, and monensin in an agricultural soil in Northumberland County, Ontario, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2006Jules C. Carlson Abstract A robust high-throughput method was refined to extract three growth-promoting antibiotics, tylosin (TYL), chlortetracycline (CTC), and monensin (MON), from soil. Analysis was performed by electrospray liquid chromatography tandem mass spectrometry. Soil dissipation rate studies were performed in a farm field soil for antibiotics applied with and without manure. Tylosin, CTC, and MON followed first-order dissipation kinetics with half-lives of 4.5, 24, and 3.3 d, respectively, with the addition of manure and 6.1, 21, and 3.8 d, respectively, without manure. Manure application significantly increased TYL dissipation rate, perhaps because of the introduced microbial flora, but had no significant effect on CTC or MON. Monensin dissipation half-life was found to be much shorter in the field study than in a controlled laboratory study, perhaps because of differences in microbial communities. The antimicrobials were not highly mobile. Chlortetracycline was the only antibiotic detected at 25 to 35 cm depth and only up to 2% of the initial concentration in a sandy loam soil. These antibiotics are therefore expected to degrade primarily in agricultural soils before moving to greater depths or to groundwater in significant concentrations in most agricultural systems. [source] CLINICAL STUDY: Proof-of-concept human laboratory study for protracted abstinence in alcohol dependence: effects of gabapentinADDICTION BIOLOGY, Issue 1 2009Barbara J. Mason ABSTRACT There is a need for safe medications that can effectively support recovery by treating symptoms of protracted abstinence that may precipitate relapse in alcoholics, e.g. craving and disturbances in sleep and mood. This proof-of-concept study reports on the effectiveness of gabapentin 1200 mg for attenuating these symptoms in a non-treatment-seeking sample of cue-reactive, alcohol-dependent individuals. Subjects were 33 paid volunteers with current Diagnostic and Statistical Manual of Mental Disorders-IV alcohol dependence and a strength of craving rating 1 SD or greater for alcohol than water cues. Subjects were randomly assigned to gabapentin or placebo for 1 week and then participated in a within-subjects trial where each was exposed to standardized sets of pleasant, neutral and unpleasant visual stimuli followed by alcohol or water cues. Gabapentin was associated with significantly greater reductions than placebo on several measures of subjective craving for alcohol as well as for affectively evoked craving. Gabapentin was also associated with significant improvement on several measures of sleep quality. Side effects were minimal, and gabapentin effects were not found to resemble any major classes of abused drugs. Results suggest that gabapentin may be effective for treating the protracted abstinence phase in alcohol dependence and that a randomized clinical trial would be an appropriate next step. The study also suggests the value of cue-reactivity studies as proof-of-concept screens for potential antirelapse drugs. [source] Effects of drying regime on microbial colonization and shredder preference in seasonal woodland wetlandsFRESHWATER BIOLOGY, Issue 3 2008MARTYN D. INKLEY Summary 1. Energy budgets of wetlands in temperate deciduous forests are dominated by terrestrially derived leaf litter that decays under different drying conditions depending on autumn precipitation. We compared decay rates and microbial colonization of maple leaves under different inundation schedules in a field experiment, and then conducted a laboratory study on shredder preference. In the field, litter bags either remained submerged (permanent), were moved to a dried part of the basin once and then returned (semi-permanent), or were alternated between wet and dry conditions for 8 weeks (temporary). 2. There was no difference in decay rates among treatments, but leaves incubated under permanent and semi-permanent conditions had higher fungal and bacterial biomass, and lower C : N ratios than those incubated under alternating drying and wetting conditions. 3. To determine the effects of these differences in litter nutritional quality on shredder preference, we conducted a laboratory preference test with larvae of leaf-shredding caddisflies that inhabit the wetland. Caddisflies spent twice as much time foraging on permanent and semi-permanent litter than on litter incubated under temporary conditions. 4. There is considerable variation among previous studies in how basin drying affects litter breakdown in wetlands, and no previous information on shredder preference. We found that frequent drying in a shallow wetland reduces the nutritional quality of leaf litter (lower microbial biomass and nitrogen content), and therefore preference by invertebrate shredders. These results suggest that inter-annual shifts in drying regime should alter detritus processing rates, and hence the mobilization of the energy and nutrients in leaf litter to the wetland food web. [source] Pushing the edge: extended activity as an alternative to risky body temperatures in a herbivorous teiid lizard (Cnemidophorus murinus: Squamata)FUNCTIONAL ECOLOGY, Issue 1 2005L. J. VITT Summary 1A combination field and laboratory study tested the hypothesis that a herbivorous lizard, Cnemidophorus murinus, extends activity at high body temperatures to digest plant material. 2Body temperatures (Tb) of active lizards averaged 37·2 °C and were no higher than those of insect-eating Cnemidophorus. 3Near constant Tb was maintained by behavioural means even though habitat temperatures varied greatly. 4Field-based behavioural data show that C. murinus extend activity by shifting among microhabitats to increase duration of time available at high Tb for digestion. 5Laboratory studies revealed large variation in selected temperatures (Tsel), but the overall average was 35·9 °C, which is lower than field Tb. 6By carefully selecting microhabitats and extending activity, C. murinus maintains constant high body temperatures to digest plant material without risking potentially lethal overheating. [source] A laboratory study of seismic velocity and attenuation anisotropy in near-surface sedimentary rocksGEOPHYSICAL PROSPECTING, Issue 5 2007Angus I. Best ABSTRACT The laboratory ultrasonic pulse-echo method was used to collect accurate P- and S-wave velocity (±0.3%) and attenuation (±10%) data at differential pressures of 5,50 MPa on water-saturated core samples of sandstone, limestone and siltstone that were cut parallel and perpendicular to the vertical borehole axis. The results, when expressed in terms of the P- and S-wave velocity and attenuation anisotropy parameters for weakly transversely isotropic media (,, ,, ,Q, ,Q) show complex variations with pressure and lithology. In general, attenuation anisotropy is stronger and more sensitive to pressure changes than velocity anisotropy, regardless of lithology. Anisotropy is greatest (over 20% for velocity, over 70% for attenuation) in rocks with visible clay/organic matter laminations in hand specimens. Pressure sensitivities are attributed to the opening of microcracks with decreasing pressure. Changes in magnitude of velocity and attenuation anisotropy with effective pressure show similar trends, although they can show different signs (positive or negative values of ,, ,Q, ,, ,Q). We conclude that attenuation anisotropy in particular could prove useful to seismic monitoring of reservoir pressure changes if frequency-dependent effects can be quantified and modelled. [source] Gravel-Corrected Kd ValuesGROUND WATER, Issue 6 2000Daniel I. Kaplan Standard measurements of solute sorption to sediments are typically made on the <2 mm sediment fraction. This fraction is used by researchers to standardize the method and to ease experimental protocol so that large labware is not required to accommodate the gravel fraction (>2 mm particles). Since sorption is a phenomenon directly related to surface area, sorption measurements based on the <2 mm fraction would be expected to overestimate actual whole-sediment values for sediments containing gravel. This inaccuracy is a problem for ground water contaminant transport modelers who use laboratory-derived sorption values, typically expressed as a distribution coefficients (Kd), to calculate the retardation factor (Rf), a parameter that accounts for solute-sediment chemical interactions. The objectives of this laboratory study were to quantify the effect of gravel on strontium Kd and Rf values and to develop an empirical method to calculate gravel-corrected Kdgc values for the study site (Hanford Site in Richland, Washington). Three gravel corrections, Kd values, were evaluated: a correction based on the assumption that the gravel simply diluted the Kd<2mm and had no sorption capacity (Kdgc,g=0), a correction based on the assumption that the Kd of the intact sediment (Kdtot was a composite of the Kd<2mm and the Kd>2mm (Kdgc,g = x), and a correction based on surface area (Kdgc,surf). On average, Kd<2mm tended to overestimate Kdtot by 28% to 47%; Kdgc,g = x overestimated Kdtot by only 3% to 5%; and Kdgc,g = 0 and Kdgc,surf underestimated Kdtot by 10% to 39%. Kdgc,g = x provided the best estimate of actual values (Kdtot); however, Kdgc,g = 0 was appreciably easier to acquire. Although other contaminants will likely have different gravel-correction values, these results have important implications regarding the traditional approach to modeling contaminant transport which uses Kd<2mm values. Such calculations may overestimate the tendency of gravel-containing sediments to retard contaminant migration. [source] Multichannel surface electromyography in ergonomics: Potentialities and limitsHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 4 2010Marco Gazzoni Abstract The prevention of work-related musculoskeletal disorders is one of the main goals in ergonomics. Among others, surface electromyography (sEMG) is an important tool for the evaluation of risks related to work activity. Three main issues have been approached in ergonomics via sEMG: 1) the analysis of muscle activation, 2) the analysis of exerted forces and torques, and 3) the analysis of muscle fatigue. Many studies have been carried out in static conditions. In ergonomics, however, it is more relevant to study muscle activity and fatigue during real tasks that are, in general, dynamic. From isometric to dynamic contractions, the complexity of the interpretation of sEMG signals increases considerably. Changes in sEMG signals are related to the continuous modifications in force output, muscle fiber length, and relative position of surface electrodes and sources. To increase the reliability of the information extracted from sEMG, multichannel detection systems have been applied, showing the possibility of overcoming some limits of the standard technique. Some illustrative laboratory and field studies are reported in this work to illustrate the potentialities and the open problems in the use of multichannel sEMG in ergonomics. Case 1 is a laboratory study investigating the myoelectric manifestations of fatigue in the biceps brachii (BB) during dynamic elbow flexion/extension. Case 2 is a laboratory study investigating the myoelectric manifestations of fatigue during a repetitive lifting task. Case 3 is a field study, carried out in an automotive plant, investigating muscle activation during the welding of a car door. Many factors play a leading role in the correct interpretation of information provided by sEMG. Even though multichannel sEMG provides information able to improve the estimation of force and/or fatigue during working tasks, many problems related to the signal acquisition and interpretation are still open. Further improvements are necessary to develop multichannel sEMG into an effective tool supporting other methodologies for the evaluation of work-related risks. © 2010 Wiley Periodicals, Inc. [source] A safety and tolerability laboratory study of the combination of aripiprazole and topiramate in volunteers who drink alcoholHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 6 2009George A. Kenna Abstract Objective There are no reports examining the safety of taking both topiramate and aripiprazole together with alcohol. The ultimate aim for this research is to determine whether this combination is safe and is superior to either drug taken alone in reducing alcohol use in alcohol dependent patients. Method This was an open-label trial. Thirteen heavy drinking participants not seeking treatment for alcoholism were randomized. Participants were titrated up to 300,mg of topiramate and 30,mg of aripiprazole a day over 35 days. Participants reported adverse events (AEs) daily alcohol use and participated in an alcohol challenge session (ACS). Results The eight participants who completed the study achieved the maximum doses of drugs. The AEs of the drugs would suggest that the AEs profile is broader but not additive. Alcohol use from the 28 days before screening to the seven days before the ACS was reduced (p,=,0.08). Conclusion There was no evidence that AEs of aripiprazole and topiramate are additive and can, therefore, be administered safely together with a modest amount of alcohol. There was also a trend for a reduction of alcohol use by participants. This finding has implications for further investigation of this combination of drugs for alcohol dependence. Copyright © 2009 John Wiley & Sons, Ltd. [source] The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysisINTERNATIONAL ENDODONTIC JOURNAL, Issue 5 2005C. S. Teixeira Abstract Aim, To verify, under the scanning electron microscope (SEM), the influence of irrigation time with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl) on intracanal smear layer removal. Methodology, Twenty-one extracted human permanent teeth with single straight root canals were included. The root canals of the teeth were instrumented and, at the end of preparation, were irrigated with 3 mL of 15% EDTA, followed by 3 mL of 1% NaOCl for 1 min (group 1), for 3 min (group 2), and for 5 min (group 3). The canals of teeth in group 4 (control) did not receive the final irrigation. The teeth were sectioned longitudinally and prepared for an SEM. The dentinal wall of cervical, middle and apical thirds was graded according to the amount of debris and smear layer remaining on the walls. The results were analysed using the Kruskal,Wallis and Conover,Inman tests. Results, In all the canals of experimental groups irrigation with EDTA and NaOCl completely removed the smear layer from the cervical and middle thirds. In the apical third, the dentine surface were partially covered, particularly in the teeth of group 1, where there was significantly more smear layer when compared with the other thirds in the same group (P < 0.007). However, the Kruskal,Wallis test showed overall that there were no significant differences between groups 1, 2 and 3 (P > 0.05). Conclusion, In this limited laboratory study, canal irrigation with EDTA and NaOCl for 1, 3 and 5 min were equally effective in removing the smear layer from the canal walls of straight roots. [source] Accuracy of the Justy II Apex locator in determining working length in simulated horizontal and vertical fracturesINTERNATIONAL ENDODONTIC JOURNAL, Issue 3 2004M. Azabal Abstract Aim, To study the effectiveness of an electronic apex locator (EAL; Justy II; Yoshida Dentcraft, Tokyo, Japan) in locating simulated horizontal and vertical fractures in single roots. Methodology, An EAL was used to measure the distance within the canal of horizontal (n = 31) and vertical (n = 31) fractures, created with a disk in single-rooted teeth. Accuracy of the EAL was evaluated by comparing the measurements with those made using a size 10 file. Data were analysed with the non-parametric Passing and Bablok method. Results, For simulated horizontal fractures, the EAL measured exactly the same length as a size 10 file, without constant or proportional errors. In vertical simulated fractures, the EAL measured (on average) with a constant error of 7.5 mm shorter than the size 10 file; the difference had a wide confidence interval (,72.3 to 2.6 mm). Conclusions, In this laboratory study, the Justy II EAL was able to determine accurately the position of simulated horizontal fractures, but was unreliable when measuring simulated vertical fractures. [source] Evaluation of root-end cavity preparation using ultrasonic retrotipsINTERNATIONAL ENDODONTIC JOURNAL, Issue 9 2003H. Ishikawa Abstract Aim, To evaluate and compare the efficiency of root-end preparations using ultrasonic retrotips coated with diamond and zirconium nitride. Methodology, Eighty-five extracted single-rooted teeth were root filled, and then resected 3 mm from their apices. Root-end cavities were prepared with KiS (zirconium nitride-coated retrotip), CT-5 (stainless steel tip) or diamond-coated (DC) ultrasonic retrotips, and 10 teeth served as controls. Thirty teeth were used for evaluation of the time required to prepare the root-end cavity, the number of microcracks produced on the resected surface and the number of dentinal tubule openings on the root-canal wall using scanning electron microscope (SEM) images. A further 55 teeth were used for evaluation of dye penetration following filling of the root-end cavities with Super EBA. The degree of dye penetration in millimetres was measured under the microscope after 7 days of immersion in India ink. Statistical analyses were performed using the one-way anova and Scheffe's F -test as the post hoc test. Results, There was no significant difference in the number of microcracks and dentinal tubule openings present in the root apices prepared by the three retrotips. The time required for root-end cavity preparation using the DC retrotip was significantly less than that using the other groups (P < 0.01). Positive controls showed dye penetration throughout the length of the root-end cavity, and negative controls showed no dye penetration. There was no significant difference between the three experimental groups in dye penetration. Conclusions, In this laboratory study, the time required to prepare root-end cavities using KiS retrotips was the same as that using CT-5 retrotips, and longer than that using DC retrotips. There was no significant difference in the number of microcracks or dye penetration between the three kinds of retrotips. [source] Increasing distribution and damage to palms by the Neotropical whitefly, Aleurotrachelus atratus (Hemiptera: Aleyrodidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 6 2010N. Borowiec Abstract In recent years, the coconut whitefly, Aleurotrachelus atratus Hempel, has been recorded from various islands in the southwestern Indian Ocean. Field surveys in La Réunion, the Seychelles, the Comoros and glasshouses in Paris have allowed us to record this whitefly on 56 palm species, some of which are endemic and/or threatened species. Most of trees showed low infestation levels, except for the coconut palm that is its main host plant. Such a wide host range has facilitated the rapid geographical dissemination of this whitefly. A field study was conducted in 2006 in La Réunion, to gain a better understanding of the bioecology of A. atratus in a tropical insular ecosystem. The whitefly was found throughout the island, from sea level to 800-m altitude. Five parasitoid species (Hymenoptera: Aphelinidae) were found associated with the populations of this pest, with Eretmocerus cocois Delvare being the dominant one. A laboratory study showed that the pre-imaginal development of A. atratus is around 48 days at 25,27°C, which is relatively long compared to other whitefly species. With a sex ratio of one male per 1022 females collected in La Réunion, it appears that the whitefly reproduces by thelytoky. It represents a threat to ornamental and agricultural palms as well as to natural palm ecosystems in the absence of effective parasitoids. [source] Functional response of Picromerus bidens: effects of host plantJOURNAL OF APPLIED ENTOMOLOGY, Issue 3 2007K. Mahdian Abstract:, The influence of three solanaceous plants (tomato, sweet pepper and eggplant) on the functional response of the predatory bug Picromerus bidens to densities of fourth-instar larvae of the beet armyworm Spodoptera exigua was assessed. Logistic regression indicated a type II functional response on all host plants. Over all prey densities, P. bidens killed significantly fewer fourth instars of S. exigua on tomato than on sweet pepper or eggplant (1.96 ± 0.17 vs. 4.37 ± 0.19 and 3.90 ± 0.15 larvae per predator per 24 h respectively). A higher theoretical maximum predation rate was estimated on sweet pepper (11.1 prey larvae per day) and eggplant (7.4) than on tomato (5.4). The mean number of prey killed per day by P. bidens females ranged from 0.78 at a density of one prey on tomato to 8.45 at a density of 24 prey on sweet pepper. The data indicated that the estimates of handling time (Th) and attack rate (a) were highly affected by host plant. Based on asymptotic 95% confidence intervals, a lower attack coefficient was found on tomato (0.02 h,1) than on sweet pepper or eggplant (0.07 and 0.11 h,1 respectively). On the other hand, handling times were significantly longer on tomato (4.42 h) and eggplant (3.23 h) than on sweet pepper (2.15 h). This laboratory study suggests that plant characteristics influence the ability of P. bidens to respond to changes in prey density. [source] Using Attributions to Understand the Effects of Explanations on Applicant Reactions: Are Reactions Consistent With the Covariation Principle?,JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 2 2005Robert E. Ployhart Research has shown that explanations for selection decisions may influence a variety of applicant perceptions and behavior, but an understanding of how and why this occurs remains largely unknown. This study attempts to understand the effects of explanations by adopting Kelley's (1967, 1972) covariation model of the attribution process. Specifically, explanations that vary on consensus, distinctiveness, and consistency covariation information should produce predictable effects on applicant perceptions and attributions. Results from 2 studies, the first a laboratory study and the second a field study with actual applicants, support the utility of the covariation model for understanding the influence of explanations for selection decisions on locus attributions, fairness, self-perceptions, and organizational attractiveness. These results suggest that the covariation model may be a useful means to construe the explanation-attribution-perception relationship, and thus provide a number of theoretical and practical implications. [source] Repressive Coping and Blood Measures of Disease Risk: Lipids and Endocrine and Immunological Responses to a Laboratory Stressor,JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 8 2000Steven D. Barger Relations between repressive coping and a variety of health-related variahles including insulin, lipids, catecholamines, and cellular immune components, were investigated in a laboratory study of acute stress among a sample of healthy male college students (N - 83). Compared to nonrepressors, at baseline, repressors had fewer numbers of circulating CD4 (T-helper) cells, greater numbers of natural killer (NK) cells. lower high-density lipoprotein (HDL), a higher total/HDL cholesterol ratio, and higher fasting insulin levels. In response to an acute laboratory stressor (Stroop Color Word Conflict Test). repressors demonstrated an attenuated increase in the number of circulating NK cells compared to nonrepressors. Confounds such as physical activity, age, and smoking were unrelated to the dependent measures. [source] I felt low and my purse feels light: depleting mood regulation attempts affect risk decision makingJOURNAL OF BEHAVIORAL DECISION MAKING, Issue 2 2009Sabrina D. Bruyneel Abstract We propose that negative affect can induce people to engage in risky decisions. We test two alternative hypotheses as to how this effect may emerge. The mood repair hypothesis states that risky choices in risk decision making serve as a means to repair one's negative affect. The depletion hypothesis, in contrast, states that risky choices in risk decision making are the mere consequence of a state of depletion resulting from engagement in active mood regulation attempts. The results of a first laboratory study establish a link between risky choices in risk decision making and negative affect. Subsequent experiments provide evidence that depletion due to active mood regulation attempts, rather than mood repair, is the underlying process for this link. Copyright © 2008 John Wiley & Sons, Ltd. [source] Attraction of slimy sculpins to chemical cues of brook charr eggsJOURNAL OF FISH BIOLOGY, Issue 3 2002R. S. Mirza In a laboratory study to examine the responses of slimy sculpin Cottus cognatus to chemical cues of brook charr Salvelinus fontinalis eggs, water that held freshly laid eggs (<20 min old), water-hardened eggs (i.e. eggs >4 h old) or injured eggs was collected and used in a series of two-choice tests. Slimy sculpin were exposed to paired stimuli of (1) hard egg water v. control water, (2) fresh egg water v. control water, (3) hard egg water v. injured egg water or (4) hard egg water v. fresh egg water. Sculpin spent considerably more time on the side of the tank with hard egg water and fresh egg water v. control water and injured egg water v. hard egg water. Sculpin did not show a preference for hard egg water v. fresh egg water. In a field study, brook charr were attracted to chemical cues from brook charr eggs, suggesting that brook charr eggs produce sufficient odour to attract some species under natural conditions. [source] Naltrexone Selectively Elevates GABAergic Neuroactive Steroid Levels in Heavy Drinkers With the ASP40 Allele of the OPRM1 Gene: A Pilot InvestigationALCOHOLISM, Issue 8 2010Lara A. Ray Background:, Preclinical studies have implicated GABAergic neurosteroids in behavioral responses to alcohol. Naltrexone is thought to blunt the reinforcing effects of alcohol, and a few studies have found that the effects of naltrexone are moderated by the Asn40Asp polymorphisms of the OPRM1 gene. The present study seeks to integrate these lines of research by testing (i) the moderating role of the functional Asn40Asp polymorphism of the OPRM1 gene on naltrexone-induced alternations in GABAergic neurosteroid levels, namely (3,,5,)-3-hydroxypregnan-20-one (allopregnanolone, ALLO); and (ii) the combined effects of naltrexone or genotype with alcohol administration on neurosteroid levels in a sample of at-risk drinkers. Methods:, Participants were 32 (9 females) nontreatment-seeking heavy drinkers who completed a placebo-controlled laboratory study of naltrexone (50 mg/d for 3 days) and provided complete sets of serum samples for ALLO assays before and after alcohol administration under both naltrexone and placebo conditions. Results:, Naltrexone treatment raised ALLO levels among carriers of the Asp40 allele, but not homozygotes for the Asn40 allele. The Asn40Asp polymorphism did not moderate effects of naltrexone on cortisol levels. Ethanol infusion modestly reduced ALLO levels in all subjects, independent of genotype or naltrexone exposure. Conclusions:, Naltrexone increased ALLO levels among individuals with the Asn40Asp allele suggesting a potential neurosteroid contribution to the neuropharmacological effects of naltrexone among Asp40 carriers. [source] | ||||||||||||||||||||||||||||