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Sampling Time (sampling + time)
Selected AbstractsPerennial grassland dynamics on fertile plains: Is coexistence mediated by disturbance?AUSTRAL ECOLOGY, Issue 2 2008TOM LEWIS Abstract The response of grasslands to disturbance varies with the nature of the disturbance and the productivity of the landscape. In highly productive grasslands, competitive exclusion often results in decreased species richness and grazing may allow more species to coexist. Once widespread, grasslands dominated by Dichanthium sericeum (Queensland bluegrass) and Astrebla spp. (Mitchell grass) occur on fertile plains but have been reduced in extent by cultivation. We tested the effects of exclusion of livestock grazing on these grasslands by comparing the floristic composition of sites in a nature reserve with an adjacent stock reserve. In addition, sites that had been cultivated within the nature reserve were compared with those where grazing but no cultivation had occurred. To partition the effects of temporal variation from spatial variation we sampled sites in three different years (1998, 2002 and 2004). Some 194 taxa were recorded at the nature reserve and surrounding stock routes. Sampling time, the occurrence of past cultivation and livestock grazing all influenced species composition. Species richness varied greatly between sampling periods relating to highly variable rainfall and water availability on heavy clay soils. Native species richness was significantly lower at previously cultivated sites (13,22 years after cultivation), but was not significantly influenced by grazing exclusion. After 8 years it appears that reintroducing disturbance in the form of livestock grazing is not necessary to maintain plant species richness in the reserve. The highly variable climate (e.g. droughts) probably plays an important role in the coexistence of species by negating competitive exclusion and allowing interstitial species to persist. [source] Species abundance distributions over timeECOLOGY LETTERS, Issue 5 2007Anne E. Magurran Abstract It has been known for 50 years that the time period over which data are collected affects the shape of empirical species abundance distributions. However, despite a recent resurgence of interest in characterizing and explaining these patterns the temporal component of species abundance distributions has been largely ignored. I argue that it is essential to take account of time, and not only because sampling duration can have a profound influence on the perceived shape of the distribution. Partitions of species abundance distributions based on temporal occurrence in the record will facilitate tests of both biological and neutral models and may lead to a better understanding of rarity. These temporal partitions also have interesting, but as yet barely explored, parallels with spatial ones such as the core-satellite division. Moreover, changes in abundance distributions across all three of Preston's temporal scales (sampling time, ecological time and evolutionary time) present rich opportunities for ecological research. [source] Genetic damage detected in CD-1 mouse pups exposed perinatally to 3,-azido-3,-deoxythymidine and dideoxyinosine via maternal dosing, nursing, and direct gavageENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2004Jack B. Bishop Abstract Human immunodeficiency virus (HIV)-infected pregnant women are administered nucleoside-analogue antiretrovirals to reduce maternal-infant viral transmission. The current protocol recommends treating newborns for 6 additional weeks postpartum. The treatment is effective, but the risk of drug-induced chromosomal damage in neonates remains undefined. We used a mouse model to investigate this concern. In a multigeneration reproductive toxicity study, female CD-1 mice received 3,-azido-3,-deoxythymidine (AZT) and dideoxyinosine (ddI) (50/250, 75/375, 150/750 mg/kg/day AZT/ddI) by gavage twice daily in equal fractions beginning prior to mating and continuing throughout gestation and lactation. Direct pup dosing (same regimen) began on postnatal day (PND) 4. Peripheral blood erythrocytes of male pups were screened for micronuclei, markers of chromosomal damage, on PNDs 1, 4, 8, and 21. Extraordinary increases in micronucleated cells were noted in pups for each treatment group at each sampling time; treated dams exhibited smaller yet significant increases in micronucleated erythrocytes. The frequencies of micronucleated cells in untreated pups were higher than in the untreated dams, and all pups had markedly elevated levels of circulating reticulocytes compared to dams. These observations suggest that fetal and neonatal mouse hematopoietic precursor cells have heightened sensitivity to genotoxic agents, perhaps due to rapid cell proliferation during the perinatal period of development. The amount of genetic damage observed in treated pups raises concern for the potential of similar damage in humans. Investigations of chromosomal integrity in exposed newborns and children are recommended. Environ. Mol. Mutagen. 43:3,9, 2004. © 2004 Wiley-Liss, Inc. [source] Toxicokinetics of waterborne bisphenol a in landlocked salmon (Salmo salar m. Sebago) eggs at various temperaturesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2001Jani O. Honkanen Abstract Eye-pigmented eggs of landlocked salmon were exposed to waterbone [14C]-labeled bisphenol A at four temperatures (2, 6, 8, and 12°C). Both in accumulation and depuration experiments, the eggs were exposed to a bisphenol A concentration of 1 ,g/L for 196 h. In the depuration experiment, the exposed eggs were placed into clean water for 96 h. At each sampling time, the eggs were dissected into three parts (eggshell, embryo, and yolk sac), and all of these parts were weighed and analyzed separately in a liquid scintillation counter. The results show that waterborne bisphenol A accumulates in developing salmon eggs. Accumulation of bisphenol A showed a clear trend both in whole eggs and in dissected parts: the higher the temperature, the higher the uptake rate constant and the concentration of bisphenol A. Steady state was reached only in the embryos at the lowest temperature; in other cases, accumulation was linear. Depuration was significant only in the embryos at 2 and 6°C. As the accumulation and the depuration results show, the elimination of bisphenol A was evidently more significant at lower temperatures. [source] Hierarchical patterns of invertebrate assemblage structure in stony upland streams change with time and flow permanenceFRESHWATER BIOLOGY, Issue 6 2005B. J. ROBSON Summary 1. Studies in several parts of the world have examined variation in univariate descriptors of macroinvertebrate assemblage structure in perennially flowing stony streams across hierarchies of spatial scale using nested analyses of variance. However, few have investigated whether this spatial variation changes with time or whether these results are representative of habitats other than riffles or of other stream types, such as intermittently flowing streams. 2. We describe patterns in taxon richness and abundance from two sets of samples from stony streams in the Otway Range and the Grampians Range, Victoria, Australia, collected using hierarchical designs. Sampling of riffles was repeated in the Otways, to determine whether spatial patterns were consistent among times. In the Grampians, spatial patterns were compared between intermittent and perennially flowing streams (stream type) by sampling pools. 3. In the Otways streams, most variation in the dependent variables occurred between sample units. Patterns of variation among the other scales (streams, segments, riffles, groups of stones) were not consistent between sampling times, suggesting that they may have little ecological significance. 4. In the Grampians streams, variation in macroinvertebrate taxon richness and abundance differed significantly between replicate streams within each stream type but not between stream types or pools. The largest source of variation in taxon richness was stream type. Little variation occurred among sample units. 5. The pattern of most variation occurring among sample units is robust both to differences in the method of sampling and different dependent variables among studies and increasingly appears to be a property of riffles in stony, perennial upland streams. High variation among sample units (residual variation) limits the explanatory power of linear models and therefore, where samples are from a single sampling time, small but significant components of variation are unlikely to represent features of assemblage structure that will be stable over time. [source] Will northern fish populations be in hot water because of climate change?GLOBAL CHANGE BIOLOGY, Issue 10 2007SAPNA SHARMA Abstract Predicted increases in water temperature in response to climate change will have large implications for aquatic ecosystems, such as altering thermal habitat and potential range expansion of fish species. Warmwater fish species, such as smallmouth bass, Micropterus dolomieu, may have access to additional favourable thermal habitat under increased surface-water temperatures, thereby shifting the northern limit of the distribution of the species further north in Canada and potentially negatively impacting native fish communities. We assembled a database of summer surface-water temperatures for over 13 000 lakes across Canada. The database consists of lakes with a variety of physical, chemical and biological properties. We used general linear models to develop a nation-wide maximum lake surface-water temperature model. The model was extended to predict surface-water temperatures suitable to smallmouth bass and under climate-change scenarios. Air temperature, latitude, longitude and sampling time were good predictors of present-day maximum surface-water temperature. We predicted lake surface-water temperatures for July 2100 using three climate-change scenarios. Water temperatures were predicted to increase by as much as 18 °C by 2100, with the greatest increase in northern Canada. Lakes with maximum surface-water temperatures suitable for smallmouth bass populations were spatially identified. Under several climate-change scenarios, we were able to identify lakes that will contain suitable thermal habitat and, therefore, are vulnerable to invasion by smallmouth bass in 2100. This included lakes in the Arctic that were predicted to have suitable thermal habitat by 2100. [source] Adaptive transfer function-based control of nonlinear process.INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 10 2007Case study: Control of temperature in industrial methane tank Abstract The state model-based transfer function models are applied for adaptation of linear controller and disturbance compensator in a feedback/feed-forward control system of nonlinear process. An advantage of the presented adaptation method is the avoidance of artificial disturbances or iterative identification procedures for on-line estimation of process dynamic parameters. The adaptation is based on linearization of the process model at each sampling time about the current state point, independent of the process being at steady-state or transient conditions. The linear time-varying dynamics model is updated on-line using measured values of process variables and reduced to the first-order plus time delay transfer function models in order to directly apply well-developed controller tuning rules. Computational aspects of the adaptation method are discussed and computation algorithms are presented. The adaptive feedback/feed-forward control system was applied for controlling temperature in industrial methane tank, dynamic parameters of which vary in a wide range due to variations of methane-tank process load and external conditions. The heat balance-based process state model is developed and validated using observation data of real plant. Computer simulation of the proposed control system performance under extreme operating conditions demonstrates fast adaptation of controller parameters, robust behaviour and significant improvement in the controllers' performance compared to that of fixed-gain controllers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Output feedback stabilization of constrained systems with nonlinear predictive controlINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 3-4 2003Rolf Findeisen Abstract We present an output feedback stabilization scheme for uniformly completely observable nonlinear MIMO systems combining nonlinear model predictive control (NMPC) and high-gain observers. The control signal is recalculated at discrete sampling instants by an NMPC controller using a system model for the predictions. The state information necessary for the prediction is provided by a continuous time high-gain observer. The resulting ,optimal' control signal is open-loop implemented until the next sampling instant. With the proposed scheme semi-global practical stability is achieved. That is, for initial conditions in any compact set contained in the region of attraction of the NMPC state feedback controller, the system states will enter any small set containing the origin, if the high-gain observers is sufficiently fast and the sampling time is small enough. In principle the proposed approach can be used for a variety of state feedback NMPC schemes. Copyright © 2003 John Wiley & Sons, Ltd. [source] Bacteriological and chemical changes occurring in Bunker-stored silage covered with biodegradable coatingJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2007P. Denoncourt Abstract Aims:, To evaluate the efficacy of a biodegradable silage coating for the ability to protect timothy (Phleum pratensa) type silage against spoilage and its quality under natural conditions. Methods and Results:, Triplicate mini-silos of silage were prepared for three treatments (1: uncoated; 2: coated with biodegradable coating and 3: sealed with plastic), two types of storage (unprotected or protected from rain) and 10 sampling times (0, 7, 14, 21, 28, 35, 42, 56, 63 and 70 days postensiling). Triplicate mini-silos were opened at each sampling time for microbiological (total aerobic bacteria, lactic acid bacteria, moulds and yeasts) and biochemical analyses [pH, dry matter (DM), water-soluble sugars (WSC), lactic (LA), acetic, propionic and butyric acids content]. The study showed that at day 70, counts of moulds and yeasts in silages protected against rain and coated with biodegradable coating were 5·98 log CFU g,1 when compared with 5·92 and 3·62 log CFU g,1 in samples from plastic-sealed silage and uncoated silage, respectively. The pH was low and stable pH (4·34) when compared with uncoated (7·17) and plastic sealed (8·34) silages (P 0·05). A DM, WSC and LA content of 421·7, 13·4 and 20·9 g kg,1 was, respectively, observed. For silage stored outdoors, a level of moulds and yeasts of 3·77 log CFU g,1 of silage was also observed in silages coated with biodegradable coating after 28 days of storage. A stable pH showing a mean value of 4 was also observed. The pH, DM, WSC and LA content were, respectively, 4·18, 341·1, 13·34 and 31·8 g kg,1 in these samples. After 70 days of storage, the level of moulds and yeasts on silage sealed with biodegradable coating was 7·73 log CFU g,1. A DM, WSC and LA content of 291·9, 5·56 and 10·0 g kg,1 was, respectively, observed. Conclusions:, When compared with uncoated silage, the application of biodegradable coating can preserve the quality of silage for up to a month when exposed to rain and up to 70 days when protected from rain. Significance and Impact of the Study:, Results emphasize the possibility of the use of a biodegradable coating as an alternative to plastic film for sealing horizontal bunker silos. [source] Carotenoid coloration in great black-backed gull Larus marinus reflects individual qualityJOURNAL OF AVIAN BIOLOGY, Issue 1 2006Kai O. Kristiansen Carotenoids are a large group of biochemicals, with similar properties, synthesised by bacteria, fungi, algae and plants. Vertebrates obtain these biologically active pigments through the diet, and they are a disproportionately common component of animal colour signals and play important roles in immune functions and as antioxidants. Carotenoids are believed to be a limited resource and because of the trade-off between allocation of carotenoids to signals and to other functions, carotenoid based signals are often thought to be handicap signals. The purpose of this study was to investigate the signalling potential of carotenoid-based tissue coloration in the great black-backed gull Larus marinus. The intensity of carotenoid-based coloration in bill, gape and eye-ring coloration was investigated in relation to body condition, reproductive parameters, levels of immune activity, and sexual dimorphism. In males there was a positive relationship between colour intensity and body condition, but in females no such relationship was found. However, females with high colour intensity had larger eggs and clutches. Additionally, females with high red scores tended to have high density of circulating lymphocytes. There was no sexual dimorphism in coloration and there was a negative relationship between colour intensity and sampling time, which indicates that this coloration is most intensely expressed early in the breeding season. The results in this study suggest that carotenoid-based coloration in great black-backed gull are partly condition dependent and reveal information about individual quality in both males an females. Hence, it might have evolved as an important signal for assessing the quality of potential mates. [source] How to obtain statistically converged MM/GBSA resultsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2010Samuel Genheden Abstract The molecular mechanics/generalized Born surface area (MM/GBSA) method has been investigated with the aim of achieving a statistical precision of 1 kJ/mol for the results. We studied the binding of seven biotin analogues to avidin, taking advantage of the fact that the protein is a tetramer with four independent binding sites, which should give the same estimated binding affinities. We show that it is not enough to use a single long simulation (10 ns), because the standard error of such a calculation underestimates the difference between the four binding sites. Instead, it is better to run several independent simulations and average the results. With such an approach, we obtain the same results for the four binding sites, and any desired precision can be obtained by running a proper number of simulations. We discuss how the simulations should be performed to optimize the use of computer time. The correlation time between the MM/GBSA energies is ,5 ps and an equilibration time of 100 ps is needed. For MM/GBSA, we recommend a sampling time of 20,200 ps for each separate simulation, depending on the protein. With 200 ps production time, 5,50 separate simulations are required to reach a statistical precision of 1 kJ/mol (800,8000 energy calculations or 1.5,15 ns total simulation time per ligand) for the seven avidin ligands. This is an order of magnitude more than what is normally used, but such a number of simulations is needed to obtain statistically valid results for the MM/GBSA method. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010 [source] Physiological responses in Nile tilapia exposed to different photoperiod regimesJOURNAL OF FISH BIOLOGY, Issue 3 2004A. K. Biswas After conditioning Nile tilapia Oreochromis niloticus for 2 weeks, the photoperiod regime of 12 tanks of fish was changed to a 6L : 6D photoperiod while 12 further tanks were retained on the conditioning photoperiod regime (12L : 12D). Blood samples were collected 3 days (first sampling) and 3 months (second sampling) after changing the photoperiod regime. Blood was collected at 6 h intervals from both photoperiod regimes (1000, 1600, 2200 and 0400 hours). At the first sampling time, fish in the 6L : 6D had significantly higher cortisol both in the light and dark phases than levels in fish in the 12L : 12D photoperiod. At the second sampling time, the levels were significantly higher only in the light phase. The levels of cortisol, glucose and Cl, in fish exposed to the 6L : 6D photoperiod, however, were far lower than those of acute stress-induced levels observed in fish exposed to a stress experiment. Furthermore, there were no significant differences in overall values of all the variables between the photoperiod regimes at the second sampling time. This indicated that the fish exposed to the 6L : 6D photoperiod were not chronically stressed. Significantly higher blood lymphocyte counts were observed in fish exposed to the 6L : 6D compared to those of the 12L : 12D photoperiod during the light phase at the second sampling time. Other variables (glucose, Cl,, haematocrit and neutrophil) did not show a significant difference between the treatments at either sampling time. These results demonstrated that the artificial photoperiod regime did not cause a significant acute or chronic stress response in Nile tilapia. [source] Quality Changes of Highbush Blueberries Fruit Stored in CA with Different CO2 LevelsJOURNAL OF FOOD SCIENCE, Issue 4 2009Carolina Duarte ABSTRACT:, Quality changes of blueberries (Vacccinium corymbosum L. cv Brigitta) were evaluated during CA storage (0 °C) with different concentrations of CO2 (5%, 10%, and 15%) combined with 5% O2, respectively. Atmospheric air (20.9% O2+ 0.03% CO2) was used as control. From samples taken at 0, 24, and 48 d of storage, unmarketable fruits and weight loss were recorded as well as color (h), firmness (g), soluble solid content (%), titratable acidity (% citric acid), ratio, and the monomeric anthocyanin content (ppm). At each sampling time, additional units were kept for 3 d at 10 °C to simulate retail holding conditions. Irrespective of gas concentration, 0.9% of the initial fresh weight was lost after 48 d at 0 °C. CA fruit had better quality than control at the 24 d sampling but due to the high number of unmarketable fruits, this advantage was not observed at 48 d at 0 °C. After 24 d of storage, fruits for CA treatments were more firm and had better color, with higher anthocyanin and acidity levels. Soluble solid content showed no significant differences throughout the cold storage period. Residual effect of CA storage was observed at the retail holding condition yielding better firmness, acidity, and ratio. However, the CO2 level tested increased the number of unmarketable fruit in long-term storage (48 d). Response of "Brigitta" blueberries to the different CO2 levels studied was moderate and could be related to the high storage potential of this cultivar. [source] Isocitrate dehydrogenase as a marker of centrilobular hepatic necrosis in the experimental model of rats,JOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 3 2001Young-Hwa Chung Abstract Background and Aims: Serum alanine aminotransferase (ALT) and aspartate aminotransferase may not detect centrilobular hepatic necrosis (CLN) of a mild degree because these enzymes are known to be located predominantly in the periportal area. The aim of this study was to evaluate the usefulness of plasma isocitrate dehydrogenase (ICDH), which is located predominantly in the centrilobular zone, as a marker of CLN. Methods: In 56 adult male rats, centrilobular (n = 21) and periportal hepatic necrosis (PPN; n = 21) were induced experimentally by the intraperitoneal injection of bromobenzene and allylalcohol, respectively. Seven rats were used as solvent controls in both groups. Isocitrate dehydrogenase and ALT activities were measured in the plasma of rats with mild to moderate hepatic necrosis (17 CLN and 19 PPN). Isocitrate dehydrogenase and ALT were compared according to the sampling time (12, 24 and 48 h) and the location of hepatic necrosis. Ratios of ICDH/ALT were also calculated and compared between CLN and PPN groups at any time points. Results: Plasma ICDH activities were higher in rats with CLN than in those with PPN. In contrast, plasma ALT levels were higher in rats with PPN than in those with CLN at 12 h and were similar in both groups after 12 h. The ICDH/ALT ratios were much higher in rats with CLN compared to those with PPN (P < 0.001). The ratios were above 1.0 in 13 of 17 rats (77%) with CLN in contrast to none of the 19 rats with PPN. Conclusions: Our data suggested that the plasma ICDH/ALT ratio might be useful to differentiate between mild to moderate degrees of CLN from PPN, at least in the experimental model of rats. [source] Sequential and iterative architectures for distributed model predictive control of nonlinear process systemsAICHE JOURNAL, Issue 8 2010Jinfeng Liu Abstract In this work, we focus on distributed model predictive control of large scale nonlinear process systems in which several distinct sets of manipulated inputs are used to regulate the process. For each set of manipulated inputs, a different model predictive controller is used to compute the control actions, which is able to communicate with the rest of the controllers in making its decisions. Under the assumption that feedback of the state of the process is available to all the distributed controllers at each sampling time and a model of the plant is available, we propose two different distributed model predictive control architectures. In the first architecture, the distributed controllers use a one-directional communication strategy, are evaluated in sequence and each controller is evaluated only once at each sampling time; in the second architecture, the distributed controllers utilize a bi-directional communication strategy, are evaluated in parallel and iterate to improve closed-loop performance. In the design of the distributed model predictive controllers, Lyapunov-based model predictive control techniques are used. To ensure the stability of the closed-loop system, each model predictive controller in both architectures incorporates a stability constraint which is based on a suitable Lyapunov-based controller. We prove that the proposed distributed model predictive control architectures enforce practical stability in the closed-loop system and optimal performance. The theoretical results are illustrated through a catalytic alkylation of benzene process example. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Intensification of liquid,liquid two-phase mass transfer by gas agitation in a microchannelAICHE JOURNAL, Issue 8 2009Yuanhai Su Abstract In this experiment, the inert gas is used to agitate two immiscible fluids in microchannels. The mass transfer performances with or without gas agitation are investigated. 30% TBP (in kerosene)-acetic acid-water is chosen as testing system, and nitrogen as agitating gas. The superficial velocities of the immiscible liquid,liquid two phases and gas phase are varied in the range from 0.02 to 1.2 m/s, and 0 to 3.0 m/s, respectively. In microchannels, with enough gas agitating intensity, high dispersion between two immiscible liquid phases can be obtained. The overall volumetric mean mass transfer coefficients are two-folds higher than those without gas agitating, which are in the range of 3.8,30.6 s,1. Some parameters which impact on the mass transfer process, such as the mixture superficial velocity of the immiscible liquid,liquid two phases, the gas superficial velocity, the microchannel structure, the gas inlet locations and the sampling time are experimentally investigated. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Distributed model predictive control of nonlinear process systemsAICHE JOURNAL, Issue 5 2009Jinfeng Liu Abstract This work focuses on a class of nonlinear control problems that arise when new control systems which may use networked sensors and/or actuators are added to already operating control loops to improve closed-loop performance. In this case, it is desirable to design the pre-existing control system and the new control system in a way such that they coordinate their actions. To address this control problem, a distributed model predictive control method is introduced where both the pre-existing control system and the new control system are designed via Lyapunov-based model predictive control. Working with general nonlinear models of chemical processes and assuming that there exists a Lyapunov-based controller that stabilizes the nominal closed-loop system using only the pre-existing control loops, two separate Lyapunov-based model predictive controllers are designed that coordinate their actions in an efficient fashion. Specifically, the proposed distributed model predictive control design preserves the stability properties of the Lyapunov-based controller, improves the closed-loop performance, and allows handling input constraints. In addition, the proposed distributed control design requires reduced communication between the two distributed controllers since it requires that these controllers communicate only once at each sampling time and is computationally more efficient compared to the corresponding centralized model predictive control design. The theoretical results are illustrated using a chemical process example. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] EFFECTS OF SAMPLING CONDITIONS ON TEMPORAL PERCEPTION OF BITTERNESS IN YERBA MATE (ILEX PARAGUARIENSIS) INFUSIONSJOURNAL OF SENSORY STUDIES, Issue 3 2004AMALIA CALVIÑO ABSTRACT Time-intensity (TI) methodology and a trained panel were used to characterize the perceived bitterness of Yerba mate (YM) Ilex paraguariensis infusions. Two sampling procedures (sip and spit; sip and swallow) and two conditions for residence time in mouth (free or fixed duration of 5 s until spit or swallow) were evaluated. At a fixed duration the maximum bitterness as well as the time to reach it showed a significant YM concentration dependence. No change on bitterness was observed by swallowing or spitting YM infusions except a larger rate of decay of the response (vr) at spit condition. Dynamic bitterness at free sampling time showed that the decision period to spit or swallow the YM infusion approximately duplicated the fixed one of 5 s. [source] Potential of solid phase microextraction and gas chromatography for quarantine-required detection of wood packaging in shipping containersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2007Nicole A. More Abstract Solid phase microextraction (SPME) coupled with gas chromatography (GC) was used to detect terpene hydrocarbons inside shipping containers entering New Zealand. The utility of this system for the rapid detection of undeclared wood packaging for quarantine purposes was demonstrated. A portable dynamic air-sampling device was built to house a SPME fibre and allow the air from shipping containers to be sampled. The effects of sample flow rate and sampling time were investigated and sampling conditions of 100 mL/min for 30 s were chosen to keep sampling within the linear range. A CV of less than 15% (n = 12) was obtained for all the compounds analysed under these conditions. To obtain an estimate for the limit of detection (LOD) for the terpene hydrocarbons of interest, small quantities of lime oil were placed in an empty shipping container and the air inside was analysed. LOD (S/N = 3) was estimated to be in the order of 50,100 ng/L of air using GC with flame ionisation detection (GC-FID). Finally, the device was tested in fully laden containers and was shown to be effective for trapping terpene hydrocarbons indicative of wood packaging. [source] The effect of digesta sampling time and dietary protein source on ileal nitrogen digestibility for the growing rat,JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2002Christine A Butts Abstract The effect of time that digesta were collected on the quantity and representativeness of ileal digesta and on the determination of apparent and true ileal nitrogen (N) digestibility for growing rats was investigated. Semi-synthetic diets containing chromic oxide as an indigestible marker were given to 200,g live weight rats for 8 days as a single daily meal. The experimental treatments comprised six diets (lactalbumin, soy protein isolate, wheat gluten, fish, protein-free (PF), enzymically hydrolysed casein (EHC)) and four ileal digesta sampling times (3, 4, 5 and 6,h after the start of feeding). On the eighth day the rats were fed and slaughtered according to treatment, and digesta were sampled from the terminal ileum. Endogenous ileal nitrogen excretion was determined using both the protein-free and peptide alimentation methods. There was a significant (P,,=,0.027) effect of experimental diet averaged across sampling times for chromium recovery (CrRec). The CrRec was higher for the rats fed the PF diet than for the other diets. Responses to sampling time varied significantly (P,<,0.05) among diets for ileal digesta weight (IDW), nitrogen/chromium (N/Cr) ratio, ileal digesta weight relative to dry matter intake (IDW/DMI), CrRec, N flow, apparent N digestibility and true N digestibility (determined using the protein-free method). The optimal digesta sampling times for each of the diets were 3,h for PF, EHC, lactalbumin and fish and 4,h for soy protein isolate and wheat gluten. Consequently, 3 or 4,h after the start of feeding is recommended as the optimum ileal digesta sampling time for most purified protein sources when fed to the growing rat as a single daily meal. © 2002 Society of Chemical Industry [source] ANTICOAGULANT EFFECTS OF LOW MOLECULAR WEIGHT HEPARIN IN HEALTHY CATSJOURNAL OF VETERINARY EMERGENCY AND CRITICAL CARE, Issue S1 2004AJ Alwood Objectives: 1) Validate a chromogenic assay to measure Factor Xa inhibitory activity (anti-Xa activity) in normal feline plasma and following administration of low molecular weight heparins and unfractionated heparin. 2) Compare the effects of two commercially available low molecular weight heparins (LMWH), unfractionated heparin (UFH), and placebo on TEG, anti-Xa activity, PT/aPTT, PCV/TS and platelet count in healthy cats. Methods: Our study consisted of two phases: 1) the evaluation of a commercially available chromogenic anti-Xa assay (Rotachrom Heparin, Diagnostic Stago) for use in cats, and 2) the evaluation of hemostatic effects of LMWH in healthy cats. Phase 1: The anti-Xa assay was validated for use in cats using feline plasma and serial dilutions of the plasma spiked with UFH, enoxaparin, and dalteparin. Phase 2: Five healthy cats were included in a randomized Latin Squares model crossover-design to compare the effects of UFH and LMWH in cats. The cats then received one of the following subcutaneously: 1) 250 IU/kg UFH QID, 2) 100 IU/kg dalteparin BID, 3) 1 mg/kg enoxaparin BID, 4) 0.25 mL/kg 0.9% saline (placebo) QID. A minimum of a two-week washout period separated each treatment period. Each drug was administered for 5 days. Blood samples were obtained to measure anti-Xa, TEG, PT/aPTT, platelet count, and PCV/TS on Days 1, 3, 5, and 6 of each treatment cycle. Samples were collected at time 0 on each sample day for all parameters and on select days at hours 4, 8, and 12 for anti-Xa and TEG. Results: Preliminary results using the validated anti-Xa assay (from the first part of this study) demonstrate that LMWH treatment results in peak anti-Xa activity at the 4-hour sampling time that returned toward baseline by 8 hours (in 5/6 cats treated with LMWH thus far). Similar anticoagulant effects were noted in the TEG parameters of cats receiving LMWH (i.e., peak effects were noted at 4 hours). Analysis of current data by linear regression identifies a relationship between anti-Xa measurements and TEG parameters for cats treated with all heparin therapies (p<0.001). A similar relationship exists between anti-Xa and aPTT. Conclusions: Preliminary results suggest an anticoagulant effect of LMWH in cats that may not be uniform across individuals. Anti-Xa activity or TEG may provide useful tools for monitoring LMWH. [source] Pharmacokinetics of gamithromycin in cattle with comparison of plasma and lung tissue concentrations and plasma antibacterial activityJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 3 2010R. A. HUANG Huang, R. A., Letendre, L. T., Banav, N., Fischer, J., Somerville, B. Pharmacokinetics of gamithromycin in cattle with comparison of plasma and lung tissue concentrations and plasma antibacterial activity. J. vet. Pharmacol. Therap.33, 227,237. The pharmacokinetics (PK) and dose proportionality of gamithromycin (ZACTRAN®), a novel azalide, after a single intravenous (i.v.) dose of 3 mg/kg or subcutaneous (s.c.) injection at 3, 6 and 9 mg/kg body weight were studied in 13 male castrate and 13 female Angus cattle. Following i.v. administration, the mean area under the curve extrapolated to infinity (AUCinf) was 4.28 ± 0.536 ,g·h/mL, and mean elimination half-life (t1/2) was 44.9 ± 4.67 h, with a large volume of distribution (Vss) of 24.9 ± 2.99 L/kg and a high clearance rate (Clobs) of 712 ± 95.7 mL/h/kg. For cattle treated with s.c. injection of 3, 6 or 9 mg/kg, mean AUCinf values were 4.55 ± 0.690, 9.42 ± 1.11 and 12.2 ± 1.13 ,g·h/mL, respectively, and the mean elimination half-lives (t1/2) were 51.2 ± 6.10, 50.8 ± 3.80 and 58.5 ± 5.50 h. Gamithromycin was well absorbed and fully bioavailable (97.6,112%) after s.c. administration. No statistically significant (, = 0.05) gender differences in the AUCInf or elimination half-life values were observed. Dose proportionality was established based on AUCInf over the range of 0.5 to 1.5 times of the recommended dosage of 6 mg/kg of body weight. Further investigations were conducted to assess plasma PK, lung/plasma concentration ratios and plasma antibacterial activity using 36 cattle. The average maximum gamithromycin concentration measured in whole lung homogenate was 18 500 ng/g at first sampling time of 1 day (,24 h) after treatment. The ratios of lung to plasma concentration were 265, 410, 329 and 247 at 1, 5, 10 and 15 days postdose. The lung AUCinf was 194 times higher than the corresponding plasma AUCinf. The apparent elimination half-life for gamithromycin in lung was 90.4 h (,4 days). Antibacterial activity was observed with plasma collected at 6 h postdose with a corresponding average gamithromycin plasma concentration of 261 ng/mL. In vitro plasma protein binding in bovine plasma was determined to be 26.0 ± 0.60% bound over a range of 0.1,3.0 ,g/mL of gamithromycin. The dose proportionality of AUC, high bioavailability, rapid and extensive distribution to lung tissue and low level of plasma protein binding are beneficial PK parameters for an antimicrobial drug used for the treatment and prevention of bovine respiratory disease. [source] Genetic characterization of spoilage pseudomonads isolated from retail-displayed beefLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2008M. Aslam Abstract Aim:, This study genetically characterized Pseudomonas isolated from beef using the random amplification of polymorphic DNA (RAPD) method and correlate predominant genotypes with spoilage changes. Methods and Results:, Pseudomonads were recovered from beef loins and steaks on days 0, 2, 4, 6, 8 and 10. A total of 309 pseudomonads were grouped into 50 RAPD types (>85% similarity). One major RAPD type contained 45% of the isolates comprising 71%, 45%, 31%, 35%, 50% and 37% of isolates from days 0, 2, 4, 6, 8 and 10, respectively, from steaks and 48% of the isolates recovered from beef loins. Nineteen RAPD types consisted of isolates that were shared between more than two sampling times, whereas the remaining 31 types were unique to one particular time. Conclusions:, A genetically diverse Pseudomonas population was present on the loins and steaks at each sampling time. Although pseudomonads associated with beef loins were transferred to the steaks prepared from it, a genetically diverse Pseudomonas population emerged during the retail display. Significance and Impact of the Study:, Information about the heterogeneous nature of Pseudomonas recovered from meat would help understanding the spoilage owing to predominant strains. The meat industry can use the knowledge to develop control strategies for prevalent spoilage strains. [source] Porphyrinuria in childhood autistic disorder is not associated with urinary creatinine deficiencyPEDIATRICS INTERNATIONAL, Issue 4 2008Robert Nataf Abstract Background: Urinary metabolite measurements are often normalized to levels of the ubiquitous metabolite creatinine (CRT) to take account of variations in fluid export. Following CRT normalization, excesses of porphyrins and isoprostanes have been reported in the urines of children with neurodevelopmental disorders. It was suggested (Whiteley et al., 2006, Pediatr. Int. 2006; 48: 292,297) that urinary CRT levels may be depressed in children with autism spectrum disorders. This prompted re-evaluation of CRT levels in such children. Methods: First matinal urinary CRT levels were compared between subjects in different diagnostic categories including autistic disorder, pervasive developmental disorder not otherwise specified (PDD-NOS) and hyperactivity, before and after correction for age and gender. A larger reference group, consisting of subjects with unrelated disorders and Asperger disorder, with no reported porphyrin excess, was also compared to the group with autistic disorder, both for CRT and for porphyrin (coproporphyrin, COPRO) excess. Results: No significant difference in CRT was observed between any of the categories analyzed, also when corrected for age and gender. In contrast, urinary COPRO levels were significantly higher in autistic disorder versus reference groups, either when expressed as absolute values (independent of CRT levels) or when normalized to CRT. Conclusions: These data do not support a systematic reduction in urinary CRT levels in subjects with autism spectrum disorders including autistic disorder and PDD-NOS. Urinary COPRO excess in autistic disorder was not associated with or consequent upon urinary CRT deficiency. Differences between affected and control subjects in age and sampling time, as reported by Whiteley et al., may underlie the apparent CRT reduction. [source] Nonparametric confidence intervals for Tmax in sequence-stratified crossover studiesPHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 1 2008Susan A. Willavize Abstract Tmax is the time associated with the maximum serum or plasma drug concentration achieved following a dose. While Tmax is continuous in theory, it is usually discrete in practice because it is equated to a nominal sampling time in the noncompartmental pharmacokinetics approach. For a 2-treatment crossover design, a Hodges,Lehmann method exists for a confidence interval on treatment differences. For appropriately designed crossover studies with more than two treatments, a new median-scaling method is proposed to obtain estimates and confidence intervals for treatment effects. A simulation study was done comparing this new method with two previously described rank-based nonparametric methods, a stratified ranks method and a signed ranks method due to Ohrvik. The Normal theory, a nonparametric confidence interval approach without adjustment for periods, and a nonparametric bootstrap method were also compared. Results show that less dense sampling and period effects cause increases in confidence interval length. The Normal theory method can be liberal (i.e. less than nominal coverage) if there is a true treatment effect. The nonparametric methods tend to be conservative with regard to coverage probability and among them the median-scaling method is least conservative and has shortest confidence intervals. The stratified ranks method was the most conservative and had very long confidence intervals. The bootstrap method was generally less conservative than the median-scaling method, but it tended to have longer confidence intervals. Overall, the median-scaling method had the best combination of coverage and confidence interval length. All methods performed adequately with respect to bias. Copyright © 2007 John Wiley & Sons, Ltd. [source] A selection tool for freezing tolerance in common wheat using the fast chlorophyll a fluorescence transientPLANT BREEDING, Issue 3 2009M. Rapacz Abstract The analysis of fast chlorophyll fluorescence induction kinetics in dark-adapted leaves (JIP-test) is proposed as a rapid method for evaluating freezing tolerance in wheat. Wheat leaves were detached from the plants of 40 cultivars grown in an open-field in Smolice, during December and March of winters 2004/2005 and 2005/2006, transferred to laboratory in Krakow and frozen in ,15°C. Next, measurements of chlorophyll fluorescence were taken. The correlation coefficients between the JIP-test parameters with freezing tolerance data obtained in multiple field-laboratory studies, varied between 0.58 and 0.70 depending on sampling time and parameter measured. The chlorophyll fluorescence parameter, which can always be used for the screening of freezing tolerance in the method described here, is the performance index (PI), which characterizes the overall energy flow efficiency in photosystem II (PSII). The results indicate, that the technique proposed here can be useful for freezing tolerance screening in plant breeding programmes. However, this method seems to be a more reliable tool in the selection of freezing tolerant germplasm, than for discarding freezing susceptible materials. [source] Effects of 5,-uridylic acid feeding on postprandial plasma concentrations of metabolites and metabolic hormones in pre-weaning goatsANIMAL SCIENCE JOURNAL, Issue 5 2009Yoshihisa OHTANI ABSTRACT 5,-Uridylic acid (UMP), which is present at high concentrations in cow's colostrum, has been shown to cause a reduction in increased plasma levels of insulin and glucose after ingestion of milk replacer in pre-weaning calves. However, the precise mechanisms of UMP action have not been investigated, and its action has not been investigated in other pre-weaning ruminants. In order to demonstrate whether UMP causes changes in postprandial metabolic and hormonal parameters in pre-weaning goats, 11 Saanen kids were given milk replacer (twice a day) without (n = 5) or with (n = 6) UMP (1 g for each meal, 2 g/day for each head) for 14 days. Analysis of blood samples taken in the morning of day 14 demonstrated that the feeding of milk replacer with UMP abolished the significant changes in postprandial plasma glucose, NEFA, GH and insulin concentrations induced by feeding of milk replacer alone, and demonstrated a tendency to increase IGF-I levels. However, there was no significant difference between the two groups at any sampling time. We conclude that UMP feeding with milk replacer showed a tendency to blunt the postprandial changes in levels of some plasma metabolites and hormones that are induced by replacer alone in pre-weaning goats. [source] Changes in skin colour and cortisol response of Australian snapper Pagrus auratus (Bloch & Schneider, 1801) to different background coloursAQUACULTURE RESEARCH, Issue 5 2009Ben J Doolan Abstract A two-factor experiment was carried out to investigate the change in skin colour and plasma cortisol response of cultured Australian snapper Pagrus auratus to a change in background colour. Snapper (mean weight=437 g) were held in black or white tanks and fed diets containing 39 mg unesterified astaxanthin kg,1 for 49 days before being transferred from white tanks to black cages (WB) or black tanks to white cages (BW). Skin colour values [L* (lightness), a* (redness) and b* (yellowness)] of all snapper were measured at stocking (t=0 days) and from cages of fish randomly assigned to each sampling time at 0.25, 0.5, 1, 2, 3, 5 and 7 days. Plasma cortisol was measured in anaesthetized snapper following colour measurements at 0, 1 and 7 days. Fish from additional black-to-black (BB) and white-to-white (WW) control treatments were also sampled for colour and cortisol at those times. Rapid changes occurred in skin lightness (L* values) after altering background colour with maximum change in L* values for BW and WB treatments occurring within 1 day. Skin redness (a*) of BW snapper continued to steadily decrease over the 7 days (a*=7.93 × e,0.051 × time). Plasma cortisol concentrations were highest at stocking when fish were held at greater densities and were not affected by cage colour. The results of this study suggest that transferring dark coloured snapper to white cages for 1 day is sufficient to affect the greatest benefit in terms of producing light coloured fish while minimizing the reduction in favourable red skin colouration. [source] Microbial and nutrient pollution in the coastal bathing waters of Dar es SalaamAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2009Thomas J. Lyimo Abstract 1.The objective of the present study was to assess the microbial and nutrient quality of coastal beach waters used for bathing in the city of Dar es Salaam, Tanzania. Concentrations of traditional and alternative microbial indicators of faecal pollution and nutrients were assessed over a 1 year period (August 2005 to August 2006) using standard methods and the results were compared with the WHO water quality guidelines. 2.Faecal indicator bacteria values varied in a consistent fashion and correlated significantly with eachother, reflecting the presumed human faecal pollution. 3.The maximum counts (MPN per 100,mL) were observed on the site close to the city centre (Ocean Road) throughout the sampling period where values ranged from 1700 to>240 000 total coliform (TC), 200 to 92000 faecal coliform (FC) and 11 to 4900 enterococci (ENT). Other sites showed less predictable results with a range of values from 0,920, 0,540 and 0,46 for TC, FC and ENT, respectively. Furthermore, the faecal indicator bacteria concentration varied significantly with sampling time (P<0.05) and between sampling points (P<0.05). 4.Similarly, nutrients were significantly higher (P<0.05) at Ocean Road where concentration (µmolL,1) ranges were 0.2,54 (NO3), 0.0,20 (NO2) and 0.3,45 (PO4). 5.The levels of faecal indicator bacteria and nutrients were higher during the rainy seasons than the dry seasons, showing the inclusion of rain run-off as a source of contamination. The faecal indicator bacteria correlated positively with nutrients in both 1 year and daily data sets (P<0.01). Positive relationships were also observed among faecal indicators. This strongly suggests that an important role is played by sewage contamination in the extent of microbial pollution at the studied urbanized coastal beaches. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effects of operating conditions on particle size in sonocrystallizationASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010Hussein Oubani Abstract This work presents systematic investigations on sonocrystallization to elucidate the effects of key variables on sonocrystallization product properties. A novel continuous flow sonocrystallization apparatus was used to prepare NaCl microparticles from a NaCl,ethanol,water antisolvent system. By implementing a full factorial experimental design, we investigated the effects of ultrasonic power (75,225 W), antisolvent feed rate (0.5,6.5 l/h), system flow rate (2.8,4.1 l/min) and sonication time (5,30 min) on product crystal size. Data from these experiments were regressed to develop an empirical model that was found to be in agreement with experiments. The model identified the interaction between sonication power and system flow to be rather significant. Model simulations found that particle size decreases when antisolvent feed rate or ultrasonic power increases. This was found to be in contrast to increasing the system flow which resulted in larger particle sizes. The regression model was subsequently used to determine optimal operating conditions that minimize mean size, as smaller sizes are commonly required for pharmaceuticals such as for inhalation particles. These optimal values were found to be as follows: antisolvent flow rate = 6.5 l/h, power ultrasound = 225 W, system flow = 2.8 l/min and sampling time = 15 min. The optimal mean size predicted at these conditions was 28.6 ± 5.7 µm which is very close to the observed value of 27.6 µm. A high-speed camera was used to visualize the ultrasonic irradiation in the sonoreactor and was crucial in explaining the significant interactive effect of sonication power and system flow on crystal size. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. 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