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Akono, Henri. "Managerial equity incentives and anti-dilutive convertible debt decisions." Review of Accounting and Finance 17, no. 3 (August 13, 2018): 341–58. http://dx.doi.org/10.1108/raf-12-2016-0201.
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PurposeThis paper aims to examine whether high equity incentives motivate executives to avoid issuing convertible debt and/or to design convertible debt issues as anti-dilutive to earnings-per-share (EPS).Design/methodology/approachTests are conducted using the Heckman two-step probit model to control for potential self-selection bias between firms that issue straight debt and those that issue convertible debt. Further, analyses are conducted separately and jointly for the Chief Executive Officer (CEO) and the Chief Financial Officer (CFO) to assess the differential impact of CEOs’ and CFOs’ equity incentives on convertible debt issuance and design decisions.FindingsFirms are more likely to design convertible debt issues as anti-dilutive to EPS when CFOs have high levels of equity incentives, but only when the firm stock price is sensitive to diluted EPS. High CEOs’ equity incentives have limited impact of convertible debt issuance and design decisions.Research limitations/implicationsThe main limitation of this study is the generalizability of the findings and implications of this study due to the smaller sample size of convertible debt issues.Originality/valuePrior research has shown that bonus incentives influence CEOs with disincentive for EPS dilution and motivate them to make anti-dilutive financing decisions. Further, there is evidence that high equity incentives motivate CEOs to manage earnings to boost short-term prices. This study extends prior literature by showing that high equity incentives provide executives with disincentive for EPS dilution and motivate CFOs to design convertible debt issues as anti-dilutive to EPS possibly to avoid reduced stock prices. Further, this study shows that CFOs have greater influence over convertible debt design choices than CEOs do.
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Tsanis, I. K., C. Valeo, and Y. Diao. "Comparison of near-field mixing zone models for multiport diffusers in the Great Lakes." Canadian Journal of Civil Engineering 21, no. 1 (February 1, 1994): 141–55. http://dx.doi.org/10.1139/l94-013.
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This paper presents a review of near-field mixing zone models and compares their performance with common outfall diffuser examples in the Great Lakes. The results of initial dilutions for three types of multiport diffusers, based on the Ontario Ministry of Environment (MOE) guidelines and recommendations, are compared with those calculated by using the U.S. Environmental Protection Agency (EPA) models. These models include five integral-type models (UPLUME, UOUTPLM, UDKHDEN, UMERGE, and ULINE) and a "length scale" type expert system (CORMIX2). Results based on the first four EPA integral models give higher initial dilutions when compared to results based on CORMIX2 and the MOE guidelines, ULINE gives unrealistically low dilutions. Excluding UPLUME, the initial dilutions given by the other EPA models increase with increasing ambient current. Alternating diffusers generally give lower initial dilutions than the staged and unidirectional diffusers, while unidirectional diffusers produce the highest of the three. Results from the computation tests based on the mixing models can aid in more reasonable and economical diffuser designs that still meet the requirement of initial dilution criteria. While all the models selected for this study have limitations, CORMIX2 is preferred for most Great Lakes applications. It can be applied to all four types of multiport diffusers and can handle different types of ambient stratification, bottom and shore attachment, wake effects and dead zones, plume trapping and far-field behaviour. CORMIX2 predictions compare well with laboratory data and very limited field data. Given the complexity of the problem, more field studies should be performed for further validation of the models. Key words: mixing zone, multiport diffusers, initial dilution.
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Ilyas, Sheroze, Tehmina Munir, Rabia Sadaf, and Mehreen Gilani. "COMPARATIVE IN- VITRO EVALUATION OF VANCOMYCIN MINIMUM INHIBITORY CONCENTRATIONBY AGAR DILUTION AND E-STRIP IN METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS." PAFMJ 71, no. 1 (February 24, 2021): 150–54. http://dx.doi.org/10.51253/pafmj.v71i1.3529.
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Objective: To compare the in-vitro efficacy by determining Minimum Inhibitory Concentration of Vancomycinusing the reference Agar Dilution to the E-Strip in Methicillin Resistant Staphylococcus aureus isolates.
Study Design: Validation study.
Place and Duration of Study: The department of Microbiology Army Medical College/National University ofMedical Sciences in collaboration with Pak Emirates Military Hospital Rawalpindi, from Dec 2016 to Dec 2017.
Methodology: Non-duplicate 84 isolates of Methicillin resistant Staphylococcus aureus from various clinical specimens were included in the study. All these isolates were screened for susceptibility to glycopeptide by E-strips method (Bio mérieux) as well as Agar Dilution method, using vancomycin concentrations of 0.25, 0.50, 1.00, 2.00, 4.00 and 8.00µgm/ml respectively in two fold serial dilutions.
Results: There was an overall agreement on 83 samples by both the methods i.e. 83 were Vancomycin SensitiveStaphylococcus aureus by both methods while one isolate with intermediate resistance to Vancomycin was onlydetected by Agar Dilution. The sensitivity of the E–strips compared to Agar Dilution was found to be 100%. Thepositive predictive value was 98.8% with a diagnostic accuracy of 98.8%. Specificity and negative predictive valuecould not be ascertained for E-strips because of the limitation of the method to detect the Vancomycin Intermediate Staphylococcus aureus isolates.
Conclusion: E-strip can be a convenient alternative to the gold standard Agar Dilution but its inability to identifyVISA challenges its reliability in determining the Vancomycin resistance in MRSA isolates.
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Romero-Steiner, Sandra, Patricia F. Holder, Patricia Gomez de Leon, Willie Spear, Thomas W. Hennessy, and George M. Carlone. "Avidity Determinations for Haemophilus influenzae Type b Anti-Polyribosylribitol Phosphate Antibodies." Clinical Diagnostic Laboratory Immunology 12, no. 9 (September 2005): 1029–35. http://dx.doi.org/10.1128/cdli.12.9.1029-1035.2005.
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ABSTRACT Determination of antibody avidity measurements can be difficult in human serum depending on the population evaluated. We evaluated three approaches for the determination of antibody avidity for immunoglobulin G (IgG). These approaches were (i) elution of bound antibody with increasing concentrations of a chaotropic agent using a single serum dilution, (ii) binding interference of multiple serum dilutions by a single concentration of a chaotrope, and (iii) elution of multiple serum dilutions by a single concentration of a chaotrope. Parameters that affect the determination of avidity measurements and their limitations were evaluated with pre- and post-Haemophilus influenzae type b conjugate vaccination sera (n = 89). We determined that elution of low-avidity antibodies present in multiple dilutions of the serum sample by a single concentration of a chaotrope (0.15 M sodium thiocyanate [NaSCN]) was optimal for the determination of avidity measurements throughout a wide range of IgG concentrations (0.94 to 304.6 μg/ml). The percent reduction in concentration as determined by the elution assay with 0.15 M NaSCN correlated highly (r = 0.84) with weighted averages obtained by an elution assay with multiple solutions of NaSCN. The correlation (r = 0.57) between elution and binding interference, when a single concentration of a chaotrope was used, was lower than the correlation between the two elution methods (r = 0.84). We found that the serum dilution, the heterogeneity of the antibody population, and the concentration of the chaotrope were the primary variables affecting avidity determinations. In this study, we present multiple analysis methods depending on the methodology used. We also present the factors that affect the analysis of avidity determinations given the polyclonal nature of human sera. This experimental approach should benefit the evaluation of similar antibodies induced by other bacterial polysaccharide vaccines.
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Barnard, Malcolm A., Justin D. Chaffin, Haley E. Plaas, Gregory L. Boyer, Bofan Wei, Steven W. Wilhelm, Karen L. Rossignol, et al. "Roles of Nutrient Limitation on Western Lake Erie CyanoHAB Toxin Production." Toxins 13, no. 1 (January 9, 2021): 47. http://dx.doi.org/10.3390/toxins13010047.
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Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under 40% dilution, and the Sandusky Bay bloom produced anatoxin under N limitation in both dilution treatments. The results demonstrate the importance of nutrient limitation effects on microcystin and anatoxin production. To properly combat cyanotoxin and cyanobacterial biomass production in WLE, both N and P reduction efforts should be implemented in its watershed.
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Barnard, Malcolm A., Justin D. Chaffin, Haley E. Plaas, Gregory L. Boyer, Bofan Wei, Steven W. Wilhelm, Karen L. Rossignol, et al. "Roles of Nutrient Limitation on Western Lake Erie CyanoHAB Toxin Production." Toxins 13, no. 1 (January 9, 2021): 47. http://dx.doi.org/10.3390/toxins13010047.
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Cyanobacterial harmful algal bloom (CyanoHAB) proliferation is a global problem impacting ecosystem and human health. Western Lake Erie (WLE) typically endures two highly toxic CyanoHABs during summer: a Microcystis spp. bloom in Maumee Bay that extends throughout the western basin, and a Planktothrix spp. bloom in Sandusky Bay. Recently, the USA and Canada agreed to a 40% phosphorus (P) load reduction to lessen the severity of the WLE blooms. To investigate phosphorus and nitrogen (N) limitation of biomass and toxin production in WLE CyanoHABs, we conducted in situ nutrient addition and 40% dilution microcosm bioassays in June and August 2019. During the June Sandusky Bay bloom, biomass production as well as hepatotoxic microcystin and neurotoxic anatoxin production were N and P co-limited with microcystin production becoming nutrient deplete under 40% dilution. During August, the Maumee Bay bloom produced microcystin under nutrient repletion with slight induced P limitation under 40% dilution, and the Sandusky Bay bloom produced anatoxin under N limitation in both dilution treatments. The results demonstrate the importance of nutrient limitation effects on microcystin and anatoxin production. To properly combat cyanotoxin and cyanobacterial biomass production in WLE, both N and P reduction efforts should be implemented in its watershed.
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Paerl, Hans W., and N. Dean Bowles. "Dilution bioassays: Their application to assessments of nutrient limitation in." Hydrobiologia 146, no. 3 (March 1987): 265–73. http://dx.doi.org/10.1007/bf00016348.
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Şeker, Sinem, Celal Güven, Handan Akçakaya, Nurten Bahtiyar, Fahri Akbaş, and İlhan Onaran. "Evidence that Extreme Dilutions of Paclitaxel and Docetaxel Alter Gene Expression of In Vitro Breast Cancer Cells." Homeopathy 107, no. 01 (January 23, 2018): 032–39. http://dx.doi.org/10.1055/s-0037-1618585.
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Background Gene expression analysis of cells treated with extreme dilutions or micro amounts of drugs has been used to provide useful suggestions about biological responses. However, most of the previous studies were performed on medicines being prepared from a variety of herbal and metal sources. This study investigated the effects of ultramolecular dilution of the taxane anti-cancer drugs, which are not commonly used in homeopathic medicines, on mRNA expression profiles of five key genes (p53, p21, COX-2, TUBB2A and TUBB3) in the breast cancer cell line MCF-7. Method MCF-7 cells were exposed to paclitaxel (Taxol) or docetaxel (Taxotere) preparations (6X, 5C and 15C dilutions prepared from pharmacological concentration of 25 nmol/L) for 72 hours. The cell culture groups were evaluated with the trypan blue dye exclusion method for the proliferation/cytotoxicity rates, immuno-staining β-tubulin for microtubule organization, and reverse transcription polymerase chain reaction for gene expression levels.Fold-change in gene expression was determined by the ΔΔCt method. Results The administration of diluted preparations had little or no cytotoxic effect on MCF-7 cells, but altered the expression of genes analyzed with a complex effect. According to the ΔΔCt method with a five-fold expression difference (p < 0.05) as a cut-off level, ultra-high dilutions of paclitaxel and docetaxel showed differential effects on the studied genes with a concentration-independent activity. Furthermore, the dilutions disrupted the microtubule structure of MCF-7 cells, suggesting that they retain their biological activity. Conclusion Despite some limitations, our findings demonstrate that gene expression alterations also occur with ultra-high dilutions of taxane drugs.
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Ramette, Alban. "Quantitative Community Fingerprinting Methods for Estimating the Abundance of Operational Taxonomic Units in Natural Microbial Communities." Applied and Environmental Microbiology 75, no. 8 (February 6, 2009): 2495–505. http://dx.doi.org/10.1128/aem.02409-08.
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ABSTRACT Molecular fingerprinting techniques offer great promise for analyzing changes in microbial community structure, especially when dealing with large number of samples. However, a serious limitation has been the lack of quantification offered by such techniques since the relative abundances of the identified operational taxonomic units (OTUs) in the original samples are not measured. A quantitative fingerprinting approach designated “qfingerprinting” is proposed here. This method involves serial dilutions of the sample of interest and further systematic fingerprinting of all dilution series. Using the ultimate dilutions for which OTU are still PCR amplifiable and taking into account peak size inaccuracy and peak reproducibility, the relative abundance of each OTU is then simultaneously determined over a scale spanning several orders of magnitude. The approach was illustrated by using a quantitative version of automated ribosomal intergenic spacer analysis (ARISA), here called qARISA. After validating the concept with a synthetic mixture of known DNA targets, qfingerprinting was applied to well-studied marine sediment samples to examine specific changes in OTU abundance associated with sediment depth. The new strategy represents a major advance for the detailed quantitative description of specific OTUs within complex communities. Further ecological applications of the new strategy are also proposed.
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NG, A. M. L., J. E. SMITH, and A. F. McINTOSH. "Infiuence of Dilution Rate on Enzyme Synthesis in Aspergillus niger in Continuous Culture." Microbiology 81, no. 2 (February 1, 2000): 425–34. http://dx.doi.org/10.1099/00221287-81-2-425.
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Summary: Aspergillus niger was grown in continuous culture under steady-state conditions in citrate-limiting or glucose-limiting medium. The specific activities of hexokinase, phosphofructokinase, pyruvate kinase, fructose diphosphatase, 6-phosphogluconate dehydrogenase and, to a limited extent, citrate synthase under citrate limitation remained at a relatively constant steady-state level irrespective of the dilution rate (0.01 to 0.5 h-1). Increase in dilution rate led to an increase in the specific activities of aconitase, NAD(P) isocitrate dehydrogenase, malate dehydrogenase, and glucose-6-phosphate dehydrogenase in both citrate and glucose limiting culture, and to an increase in citrate synthase, hexokinase, phosphofructokinase, pyruvate kinase, and 6-phosphogluconate dehydrogenase only in glucose limitation. A decrease in specific activity with increasing dilution rate occurred with isocitrate lyase in both citrate and glucose limitation and for fructose diphosphatase only in glucose limitation. The specific activity of malate synthetase showed a peak activity in the middle range of dilution rates.
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Cid, Jesús López-Herce, Marta Rupérez, César Sánchez, and Angel Carrillo. "Limitations of extravascular lung water assessment by dilution methods in children." Critical Care Medicine 35, no. 8 (August 2007): 2001–2. http://dx.doi.org/10.1097/01.ccm.0000277248.70144.5f.
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Michard, Frédéric. "Limitations of extravascular lung water assessment by dilution methods in children." Critical Care Medicine 35, no. 8 (August 2007): 2002. http://dx.doi.org/10.1097/01.ccm.0000277249.96080.e4.
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Naughton, J. R., and M. W. Matsen. "Limitations of the Dilution Approximation for Concentrated Block Copolymer/Solvent Mixtures." Macromolecules 35, no. 14 (July 2002): 5688–96. http://dx.doi.org/10.1021/ma0122066.
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Basu, Abhirup, Akkihebbal Krishnamurthy Suresh, Shantaram Govind Kane, and Jayesh Ramesh Bellare. "A review of machines and devices to potentize homeopathic medicines." Homeopathy 106, no. 04 (November 2017): 240–49. http://dx.doi.org/10.1016/j.homp.2017.09.002.
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Background: Potentization, consisting of serial dilution and succussion, is a key step in the manufacture of homeopathic medicines. Originally prescribed as a manual process, several attempts at mechanization have been published, patented and even commercialised in order to remove the human element and introduce reproducibility without drudgery. Various machines have been used over the years to prepare homeopathic medicines. Although these machines follow the same principles, i.e. energetically mixing the medicines and diluting them significantly, their mode of operation is different from each other. Methods: This review paper surveys the main methods of preparation of homeopathic medicines. The main machines discussed are: Boericke's potentizer, Tyler Kent's instrument, John Alphonse's machine and the fluxion potentizer, which were used in the past, as well as more recent potentizers like arm-and-weight instruments, the K-Tronic potentizer and Quinn's machine. We review the construction and operating principle of each of these machines, along with their advantages and limitations. A scheme for relative performance assessment of these machines is proposed based on the parameters mechanical efficiency, physico-chemical efficiency, turbulence generation, energy dissipation, and accuracy of dilution. Results: Quinn's machine and the arm-and-weight potentizer perform well for generating turbulence due to high impaction forces, while John Alphonse's machine is much more accurate in diluting the homeopathic medicines at every step. Conclusions: Both the commercial potentizers, Quinn's machine and the K-Tronic potentizer, are completely automated and therefore reduce the manual labour and variation in succussive forces during each step, which may produce uniformity in physico-chemical changes within the resulting homeopathic medicines.
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Carrick, Hunter J., Claire L. Schelske, Frederick J. Aldridge, and Michael F. Coveney. "Assessment of Phytoplankton Nutrient Limitation in Productive Waters: Application of Dilution Bioassays." Canadian Journal of Fisheries and Aquatic Sciences 50, no. 10 (October 1, 1993): 2208–21. http://dx.doi.org/10.1139/f93-247.
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Excessive nutrient loads to aquatic systems can complicate otherwise predictable relationships between nutrient concentrations and phytoplankton biomass. We conducted six bioassays on surface phytoplankton assemblages collected from productive Lake Apopka, Florida, to measure the effect of nutrient reduction on phytoplankton growth and nutritional state. Lake water was mixed with one of three diluents to create a gradient of ambient nutrient concentrations; nitrogen (N) and phosphorus (P) limitation at each level of dilution was evaluated in a 2 × 2 factorial design. While the addition of N clearly increased the growth of phytoplankton in undiluted Lake Apopka water, the phytoplankton became more P limited with the reduction of particles (30–60% dilution). Regression of algal yields onto total P concentrations from our bottle experiments indicated that an 8 μg∙L−1 change in P leads to only a 1 μg∙L−1 change in chlorophyll yield, probably due to the high concentration of P in the lake. Because dilution influences factors in addition to ambient nutrient concentrations, results obtained with the technique must be carefully evaluated. Despite this, reduction of particles to improve water quality may, in concept, be a reasonable management scheme in lakes where a large fraction of the nutrients is particulate.
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Morrin, Maureen, and Jacob Jacoby. "Trademark Dilution: Empirical Measures for an Elusive Concept." Journal of Public Policy & Marketing 19, no. 2 (September 2000): 265–76. http://dx.doi.org/10.1509/jppm.19.2.265.17137.
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Consumer researchers have conceptualized brand name dilution in terms of the potentially damaging effects that a company's own brand extensions can have on beliefs and attitudes toward parent brands. A different form of dilution, trademark dilution, can also occur through the unauthorized use of a mark (e.g., brand, logo) by an entity other than its owner. With passage of the Federal Trademark Dilution Act of 1995, an increasing number of trademark dilution cases are being litigated. A recurring issue in these cases has been how to measure trademark dilution. The authors review the concept of trademark dilution and explore how recognition and recall-based methods can be used for empirically assessing trademark dilution. The authors also investigate the impact of brand familiarity and product category similarity on the extent of trademark dilution and discuss implications, limitations, and areas for further research.
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Bougma, Moussa, Thomas K. LeGrand, and Jean-François Kobiané. "Fertility Limitation and Child Schooling in Ouagadougou: Selective Fertility or Resource Dilution?" Studies in Family Planning 46, no. 2 (June 2015): 177–99. http://dx.doi.org/10.1111/j.1728-4465.2015.00023.x.
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Mounaïm-Rousselle, Christine, Pierre Bréquigny, Clément Dumand, and Sébastien Houillé. "Operating Limits for Ammonia Fuel Spark-Ignition Engine." Energies 14, no. 14 (July 9, 2021): 4141. http://dx.doi.org/10.3390/en14144141.
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The objective of this paper is to provide new data about the possibility of using ammonia as a carbon-free fuel in a spark-ignition engine. A current GDI PSA engine (Compression Ratio 10.5:1) was chosen in order to update the results available in the literature mainly obtained in the CFR engine. Particular attention was paid to determine the lowest possible load limit when the engine is supplied with pure ammonia or a small amount of H2, depending on engine speed, in order to highlight the limitation during cold start conditions. It can be concluded that this engine can run stably in most of these operating conditions with less than 10% H2 (of the total fuel volume) added to NH3. Measurements of exhaust pollutants, and in particular NOx, have made it possible to evaluate the possibility of diluting the intake gases and its limitation during combustion with pure H2 under slightly supercharged conditions. In conclusion, the 10% dilution limit allows a reduction of up to 40% in NOx while guaranteeing stable operation.
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Deutsch, Varda, Michal Cipok, Sigi Kay, Yvette Levy, Shoshana Bar On, Ilya Kirgner, Elizabeth Naparstek, and Aaron Tomer. "Heparin-Induced Thrombocytopenia: A Rapid, Reliable and Practical, Functional Flow-Cytometric Assay." Blood 122, no. 21 (November 15, 2013): 1130. http://dx.doi.org/10.1182/blood.v122.21.1130.1130.
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Abstract Background Heparin-induced thrombocytopenia (HIT) is a serious complication of heparin treatment, associated with morbidity and mortality. HIT is characterized by thrombocytopenia and thrombotic complications secondary to the formation of antibodies (Abs) against heparin-platelet-factor 4 (PF4) complexes. The pathologic mechanism involves the binding of the heparin-immune-complex to the platelet-Fc-receptor, resulting in platelet activation, aggregation, and rapid elimination. The diagnosis of HIT requires laboratory confirmation. Common laboratory testing is based on immune detection of antibodies directed against the PF4/heparin complex (ID-H/PF4-PaGIA or ELISA). However, these assays suffer from methodological limitations, especially low specificity, as compared to the platelet functional assays. The “gold standard” functional test for detecting of platelet-activating antibodies is the radioactive [14C] serotonin-release assay (14C-SRA) (Sheridan D, et al, Blood. 1986;67:27-30, Kelton JG, et al.,Blood.1988;72:925-30). However, the assay includes the use of a radiolabeled biological probe and requires considerable expertise to obtain reliable results. Consequently, its use is limited to research laboratories. Aim To overcome the methodological limitations associated with current assays, we modified a functional flow-cytometry assay (FCA), which exhibits high sensitivity and specificity (Tomer, A. Br J Haematol, 1997;98: 648-656 , Tomer, A., et al, Am J Hematol, 1999;61: 53-61). This assay, similar in concept to the 14C-SRA, determines the capacity of the patient's serum to activate platelets in the presence of heparin, using a fluorescent probe. Methods Consecutive samples from 254 patients clinically suspected for HIT were tested. The FCA assay was compared with the standard ID-H/PF4-PaGIA antigenic assay (DiaMed, Switzerland) with two dilutions to assess specificity (Nellen, V., et al.,Haematologica, 2012;97: 89-97). Results Of the total 254 samples tested, 48 (19%) were positive by PaGIA, compared to 13 (5.1%) positive by the functional FCA (Table 1). The number of PaGIA positive samples was reduced to 24 (9.4%) by 1:16 dilution, and to 14 (5.5%) by 1:32 dilution. All FCA positive samples were positive at all PaGIA dilutions (relative sensitivity 93%). Thirty PaGIA negative samples were all negative by the FCA (relative specificity 100%). Conclusion The results suggest that the functional FCA is a practical, sensitive, and highly specific test for the reliable diagnosis of HIT. Disclosures: No relevant conflicts of interest to declare.
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Li, F. Y., P. D. Jamieson, P. R. Johnstone, and A. J. Pearson. "Mechanisms of nitrogen limitation affecting maize growth: a comparison of different modelling hypotheses." Crop and Pasture Science 60, no. 8 (2009): 738. http://dx.doi.org/10.1071/cp08412.
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Two hypothetical mechanisms exist for quantifying crop nitrogen (N) demand and N-deficit effects on crop growth. The Critical N mechanism uses a critical N concentration, while the Leaf N mechanism distinguishes active N in leaves from the N elsewhere in shoots. These two mechanisms were implemented in parallel in a maize model (Amaize) to evaluate their adequacy in predicting crop growth and development. In the Leaf N mechanism, two approaches for quantifying N-deficit effects, by reducing green leaf area (GAI) or diluting specific leaf nitrogen (SLN), were also examined. The model-predicted plant biomass, grain yield, and N uptake were compared with measurements from 47 maize crops grown on 16 sites receiving different N fertiliser treatments. The results showed that model-predicted plant biomass, grain yield and N uptake were insensitive to the approaches used for quantifying N-deficit effects in the Leaf N mechanism. The model-predicted plant biomass, grain yield and N uptake using either N approach were significantly related to measurements (P < 0.01) but had considerable deviations (r2 = 0.66–0.69 for biomass, 0.50–0.54 for grain yield: 0.17–0.33 for N uptake). The linear fits of the predicted against measured values showed no significant difference (P > 0.1) among the three N approaches, with the Leaf N mechanism predicting smaller deviation than the Critical N mechanism. However, the Critical N mechanism was better in simulating plant growth dynamics in early plant growth stages. The Leaf N mechanism distinguished functional from structural N pools in plants, having a sound physiological base. The simulation using the Leaf N mechanism with both SLN dilution and GAI reduction for quantifying N-deficit effects was the best in predicting crop growth and yield.
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Zhao, Xingdong, and Jia’an Niu. "Method of Predicting Ore Dilution Based on a Neural Network and Its Application." Sustainability 12, no. 4 (February 19, 2020): 1550. http://dx.doi.org/10.3390/su12041550.
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A back-propagation neural network prediction model with three layers and six neurons in the hidden layer is established to overcome the limitation of the equivalent linear overbreak slough (ELOS) empirical graph method in estimating unplanned ore dilution. The modified stability number, hydraulic radius, average deviation of the borehole, and powder factor are taken as input variables and the ELOS of quantified unplanned ore dilution as the output variable. The training and testing of the model are performed using 120 sets of data. The average fitting degree r2 of the prediction model is 0.9761, the average mean square error is 0.0001, and the relative error of the prediction is approximately 6.2%. A method of calculating the unplanned ore dilution is proposed and applied to a test stope of the Sandaoqiao lead–zinc mine. The calculated unplanned ore dilution is 0.717 m, and the relative error (i.e., the difference between calculation and measurement of 0.70 m) is 2.4%, which is better than the relative errors for the empirical graph method and numerical simulation (giving dilution values of 0.8 and 0.55 m, respectively). The back-propagation neural network prediction model is confirmed to predict the unplanned ore dilution in real applications.
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Raiber-Moreau, Eun-Ang, James Hadfield, Darren Hodgson, and Marilou Wijdicks. "Assessment of 5-methylcytosine and 5-hydroxymethylcytosine technologies in contrived ctDNA-like samples." Journal of Clinical Oncology 38, no. 15_suppl (May 20, 2020): e15585-e15585. http://dx.doi.org/10.1200/jco.2020.38.15_suppl.e15585.
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e15585 Background: Epigenomic changes to DNA are early driving events in tumorigenesis and are specific markers of the tumour and its microenvironment. Cell-free DNA that is released from the tumour microenvironment can potentially be used for the detection of tumour-specific epigenomic changes for cancer liquid biopsy testing. In this study, we assessed the robustness of 5-methylcytosine and 5-hydroxymethylcytosine technologies in contrived ctDNA-like samples from NSCLC. Additionally, we assessed the limit of detection of the tumour fraction within the tested dilution range looking at a subset of differential epigenomic marks. Methods: 4 NSCLC tumour and buffy coat DNA samples were commercially obtained and processed to generate contrived tumour DNA dilution mimicking circulating tumour DNA at varying tumour fractions. Samples were sent in triplicate to multiple epigenomic assay providers for analysis. The robustness i.e. reproducibility and limit-of-detection within the tested range was determined. Results: Technical replicates all passed method-specific quality controls and were highly reproducible. Cancer specific differentially-methylated or hydroxymethylated regions were determined for each individual tumour sample as a “sample-specific cancer signature”; when applied to the tumour dilution samples, these signatures were capable of distinguishing all tumour dilutions down to 0.05% from normal background DNA. Detection of differential methylation and hydroxymethylation regions was reproducible across technical replicates for all four NCSLC samples at > 0.05%. Generation of pooled methylation “signatures” derived from commercially available healthy plasma and cancer tissue datasets could still detect cancer DNA in these four NCSLC samples at > 0.1% tumour fraction. Conclusions: Our pilot study showed that all assessed technologies generated reproducible, robust data and could detect ctDNA at even clinically relevant levels for early stage cancer. One limitation of this study was the small number of “n” and the use of sonicated contrived sample that may induce artificial bias and reduce sensitivity highlighting a requirement for the development of reference material in the community. The ability to detect cancer-specific epigenomic changes from liquid biopsy with high sensitivity offers new promising avenues for early detection of cancer, which can increase the chances of successful treatment.
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Nolf, Sondra L., David Philip Arthur Craig, and Charles I. Abramson. "Serial Dilutions: A New Area of Research for Animal Behavior." Psychological Reports 111, no. 2 (October 2012): 473–92. http://dx.doi.org/10.2466/11.49.pr0.111.5.473-492.
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This paper attempts to stimulate the psychological investigation of homeopathy and serially agitated dilutions. The history of homeopathy and serial dilutions is provided in a literature review of selected research areas. Two original illustrative experiments are also presented and discussed. The first examined the effect of serially agitated dilutions of Sevin® on the mortality rate of honey bees ( Apis mellifera). In a second experiment, the effect of serially agitated dilutions of sucrose on proboscis extension in honey bees was assessed. No differences were found between serially agitated dilutions of pesticides and sucrose compared with dilutions alone. Implications, limitations, and proposed further work are discussed.
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Anwar, H., J. L. Strap, and J. W. Costerton. "Growth characteristics and expression of iron-regulated outer-membrane proteins of chemostat-grown biofilm cells of Pseudomonas aeruginosa." Canadian Journal of Microbiology 37, no. 10 (October 1, 1991): 737–43. http://dx.doi.org/10.1139/m91-127.
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An in vitro chemostat system was used to study the growth and the expression of iron-regulated outer-membrane proteins (IROMPs) by biofilm cells of Pseudomonas aeruginosa cultivated under conditions of iron limitation. The population of the planktonic cells decreased when the dilution rate was increased. At a dilution rate of 0.05 h−1 the populations of planktonic cells of both mucoid and nonmucoid P. aeruginosa were 3 × 109 cells/mL. This value dropped to 5 × 106 cells/mL when the dilution rate was increased to 1.0 h−1. The reverse was observed for the biofilm cells. The number of biofilm cells colonising the silicone tubing increased when the dilution rate was increased. The number of biofilm cells of the mucoid strain at steady state was 2 × 108 cells/cm (length) when the dilution rate was fixed at 0.05 h−1. The figure increased to 8 × 109 cells/cm when the dilution rate was increased to 1.0 h−1. The population of biofilm cells of the nonmucoid strain was 9 × 107 cells/cm (length) when the dilution rate was 0.05 h−1. It increased to 2 × 109 cells/cm when the dilution rate was set at 1.0 h−1. The expression of IROMPs was induced in the biofilm cells of both mucoid and nonmucoid strains when the dilution rates were 0.05 and 0.2 h−1. IROMPs were reduced but still detectable at the dilution rate of 0.5 h−1. However, the expression of IROMPs was repressed when the dilution rate was increased to 1.0 h−1. The data suggest that the biofilm cells of P. aeruginosa switch on the expression of IROMPs to assist iron acquisition when the dilution rate used for the chemostat run is below 0.5 h−1. The high affinity iron uptake system is not required by the biofilm cells when the dilution rate is increased because the trace amount of iron present in the chemostat is sufficient for the growth of adherent biofilm cells. Key words: Pseudomonas aeruginosa, chemostat, iron, outer-membrane proteins, biofilm.
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Cliff, John B., Peter J. Bottomley, Roy Haggerty, and David D. Myrold. "Modeling the Effects of Diffusion Limitations on Nitrogen-15 Isotope Dilution Experiments with Soil Aggregates." Soil Science Society of America Journal 66, no. 6 (November 2002): 1868–77. http://dx.doi.org/10.2136/sssaj2002.1868.
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Cliff, John B., Peter J. Bottomley, Roy Haggerty, and David D. Myrold. "Modeling the Effects of Diffusion Limitations on Nitrogen-15 Isotope Dilution Experiments with Soil Aggregates." Soil Science Society of America Journal 67, no. 2 (2003): 677. http://dx.doi.org/10.2136/sssaj2003.0677.
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Cliff, John B., Peter J. Bottomley, Roy Haggerty, and David D. Myrold. "Modeling the Effects of Diffusion Limitations on Nitrogen-15 Isotope Dilution Experiments with Soil Aggregates." Soil Science Society of America Journal 67, no. 2 (March 2003): 677. http://dx.doi.org/10.2136/sssaj2003.6770.
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Mollee, Peter, Jill Tate, Goce Dimeski, and Devinder Gill. "Falsely Low Serum Free Light Chain Concentration in Patients with Monoclonal Light Chain Diseases." Blood 106, no. 11 (November 16, 2005): 5077. http://dx.doi.org/10.1182/blood.v106.11.5077.5077.
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Abstract Introduction: Measurement of serum free light chains (FLC) is useful in the diagnosis and monitoring of nonsecretory myeloma, AL amyloidosis (AL) and light-chain myeloma (LCMM). Long-term monitoring of monoclonal FLC disease requires reproducible assay performance. We assessed the FLC assay performance in regard to falsely low FLC values. Methods: We assessed: FLC immunoreactivity and, FLC assay recovery on sample dilution. FLC concentration was measured in serial serum samples collected from patients with AL and LCMM, using a kit assay (The Binding Site Ltd., Birmingham, UK) with the IMMAGETM (Beckman Coulter, Brea, CA) and Hitachi Modular P (Roche Diagnostics) analysers. Monoclonal paraprotein was detected by serum and/or urine protein electrophoresis (Sebia, Issy-les-Moulineaux, France) and immunofixation. Results: FLC immunoreactivity. Of 23 patients with LCMM, one patient had discordant Bence Jones protein (BJP) and FLC results. The patient was a 70-year-old male with kappa LCMM where changes in the level of KBJP correlated with the KFLC concentration and the serum kappa to lambda (K/L) FLC ratio in samples measured between 2002 and mid 2004. Thereafter the FLC ratio remained within the reference range despite increasing urine KBJP. Subsequent investigations revealed that the patient’s monoclonal KFLC had failed to react with three different lot numbers of kit reagent. A fourth reagent lot, however, gave elevated KFLC concentration and K/L ratio consistent with disease relapse. A partial response to the patient’s monoclonal KFLC was observed for the same samples using the Modular assay (i.e., KFLC concentration was approximately 50% or less of the IMMAGE value). FLC recovery. In four patients with AL or LCMM the monoclonal FLC was underestimated when using the manufacturer’s recommended 1:10 on-line dilution and gave higher recoveries at 1:20 to 1:110 sample dilution. Values for the monoclonal FLC differed by up to 100% and recovery on dilution did not parallel the standard curve response. Conclusions: We report the first case of non-reaction of a monoclonal kappa FLC in a patient with LCMM. Urinary BJP monitoring remains necessary in patients with LCMM. Dilutional non-linearity of FLC suggests that the immunoreactive response of some monoclonal FLC does not parallel that of polyclonal calibration materials. This may result in falsely low FLC results. While the FLC assay represents a major advance for these diseases, clinicians should be aware of the assay’s limitations.
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Corrêa, Lygia Fátima da Mata, Frederico José Vieira Passos, Marlene Isabel Vargas Viloria, Olindo Assis Martins Filho, Andréa Teixeira de Carvalho, and Flávia Maria Lopes Passos. "Signals of aging associated with lower growth rates in Kluyveromyces lactis cultures under nitrogen limitation." Canadian Journal of Microbiology 60, no. 9 (September 2014): 605–12. http://dx.doi.org/10.1139/cjm-2014-0236.
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The effects of aging on the specific growth rate of Kluyveromyces lactis cultures, as a function of (NH4)2SO4 concentration, were evaluated. The growth kinetic parameters maximum specific growth rate and saturation constant for (NH4)2SO4 were calculated to be 0.44 h−1 and 0.15 mmol·L−1, respectively. Batch cultures were allowed to age for 16 days without influence of cell density or starvation. The specific growth rates of these cultures were determined each day and decreased as the population aged at different nitrogen concentrations. Aging signals (N-acetylglucosamine content of the cell wall, cell dimensions, and apoptosis markers) were measured. Apoptosis markers were detected after 5 days at limiting (NH4)2SO4 concentrations (0.57, 3.80, and 7.60 mmol·L−1) but only after 8 days at a nonlimiting (NH4)2SO4 concentration (38.0 mmol·L−1). Similarly, continuous cultures of K. lactis performed under nitrogen limitation and, at lower dilution rates, accumulated cells exhibiting aging signals. The results demonstrate that aging affects growth rate and raise the question of whether nitrogen limitation accelerates aging. Because aging is correlated with growth rate, and each dilution rate of the continuous cultures tends to select and accumulate cells with a respective age, cultures growing at lower growth rates can be useful to investigate yeast physiological responses, including aging.
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Abakumova, D. D., Z. A. Temerdashev, and P. G. Abakumov. "Capabilities and limitations of tin direct determination using the spectrometry methods with inductively coupled plasma in Azov and Black sea waters." Аналитика и контроль 25, no. 2 (2021): 84–97. http://dx.doi.org/10.15826/analitika.2021.25.2.007.
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The current study discussed the capabilities and limitations of tin direct determination in the waters of the Black and Azov Seas using the ICP-MS and ICP-AES methods without the separation and concentration of the analyte. The conditions for the analysis of waters, the influence of dilution and matrix components on the results of the analysis were established. As the salinity of the seawater increased, the slope of the calibration curve decreased, regardless of the detection method used. The leveling of the matrix effect of seawater on the analytical signal of tin was achieved by diluting the sample up to 100 times. A significant decrease in the analytical signal of tin was observed on the samples of seawater characterized by the high salinity. These methods allowed determining tin at the concentrations ranging from 0.33 μg/dm3 (ICP-MS), 0.37 μg/dm3 (ICP-AES) to 5 μg/dm3 in natural (fresh) water or seawater with low salinity level according to the calibration curve of the deionized water. For ICP-MS and ICP-AES determination of tin in seawater with the salinity level above 6‰ and tin concentration of more than 5 μg/dm3, it was required to use the calibration dependence constructed on the model seawater considering the salinity of the object. The studies have shown that the content of tin in the Kuban River is 0.13 μg/dm3. In the Sea of Azov, the concentration of tin in the water, depending on the sampling site, was less than 0.33 μg/dm3 (Taman) and 1.8 μg/dm3 (Temryuk, commercial port). In the Black Sea, the concentration of tin in the seawater samples from Novorossiysk city was higher and ranged from 0.55 μg/dm3 (embankment) to 1.5 μg/dm3 (seaport) and 2.1 μg/dm3 (grain terminal).
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Servia, Alberto. "Using modeling to select catalyst dilution methods for mass transfer intensification in lab gas–liquid fixed-bed reactors." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 75 (2020): 74. http://dx.doi.org/10.2516/ogst/2020071.
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Heterogeneous catalyst testing methodology at the lab scale must provide intrinsic kinetics data for reactor design purposes as well as the intrinsic activity ranking during catalyst screening in the field of refining and petrochemistry. The significant downscaling of the past century coupled with the increasingly active catalytic formulations may introduce considerable momentum, mass and heat effects in experiments at small scale. Catalyst dilution has emerged as one versatile and robust way to reduce the impact of momentum and heat effects on heterogeneous catalyst testing. This paper presents a methodology based on global phenomena and catalyst dilution modeling to assess and optimize reactor loading techniques for specific problems. More particularly, the aim is to provide catalysts developers and kinetics experts with concrete guidelines for intensifying gas-liquid mass transfer in lab gas–liquid fixed-bed reactors through catalyst dilution. The methodology is applied to the kinetics determination of the oil residue Hydrodemetallation (HDM) and to the screening of catalysts for benzene hydrogenation. Layered dilution, consisting on the split of the catalyst in two beds separated by an intermediate bed containing an inert material of the same size as the catalyst, poorly improves gas–liquid mass transfer. Uniform dilution, based on the direct mixture of catalyst and inert material of the same size, significantly enhances gas–liquid mass transfer as the reactant local consumption per reactor unit volume is strongly reduced. Combinations of both abovementioned dilution techniques can be used with fast and/or high stoichiometric factor chemical systems operated at conversions higher than 70%. A new criterion is proposed to calculate the minimum dilution factor to guarantee negligible gas–liquid mass transfer limitations as a function of conversion, external mass transfer and global pseudo second-order kinetics.
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Kayser, Anke, Jan Weber, Volker Hecht, and Ursula Rinas. "Metabolic flux analysis of Escherichia coli in glucose-limited continuous culture. I. Growth-rate-dependent metabolic efficiency at steady state." Microbiology 151, no. 3 (March 1, 2005): 693–706. http://dx.doi.org/10.1099/mic.0.27481-0.
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The Escherichia coli K-12 strain TG1 was grown at 28 °C in aerobic glucose-limited continuous cultures at dilution rates ranging from 0·044 to 0·415 h−1. The rates of biomass formation, the specific rates of glucose, ammonium and oxygen uptake and the specific carbon dioxide evolution rate increased linearly with the dilution rate up to 0·3 h−1. At dilution rates between 0·3 h−1 and 0·4 h−1, a strong deviation from the linear increase to lower specific oxygen uptake and carbon dioxide evolution rates occurred. The biomass formation rate and the specific glucose and ammonium uptake rates did not deviate that strongly from the linear increase up to dilution rates of 0·4 h−1. An increasing percentage of glucose carbon flow towards biomass determined by a reactor mass balance and a decreasing specific ATP production rate concomitant with a decreasing adenylate energy charge indicated higher energetic efficiency of carbon substrate utilization at higher dilution rates. Estimation of metabolic fluxes by a stoichiometric model revealed an increasing activity of the pentose phosphate pathway and a decreasing tricarboxylic acid cycle activity with increasing dilution rates, indicative of the increased NADPH and precursor demand for anabolic purposes at the expense of ATP formation through catabolic activities. Thus, increasing growth rates first result in a more energy-efficient use of the carbon substrate for biomass production, i.e. a lower portion of the carbon substrate is channelled into the respiratory, energy-generating pathway. At dilution rates above 0·4 h−1, close to the wash-out point, respiration rates dropped sharply and accumulation of glucose and acetic acid was observed. Energy generation through acetate formation yields less ATP compared with complete oxidation of the sugar carbon substrate, but is the result of maximized energy generation under conditions of restrictions in the tricarboxylic acid cycle or in respiratory NADH turnover. Thus, the data strongly support the conclusion that, in aerobic glucose-limited continuous cultures of E. coli TG1, two different carbon limitations occur: at low dilution rates, cell growth is limited by cell-carbon supply and, at high dilution rates, by energy-carbon supply.
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Ahmad, Nadeem, and Raouf E. Baddour. "Minimum return dilution method to regulate discharge of brine from desalination plants." Canadian Journal of Civil Engineering 41, no. 5 (May 2014): 389–95. http://dx.doi.org/10.1139/cjce-2012-0528.
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The mixing zone approach in regulating the discharge of brine and other toxic dense discharges has many limitations when applied in environmentally sensitive areas. A well-defined minimum return dilution is advocated in this study as an alternative method to regulate the disposal of brine and other toxic dense discharges. This study examined experimentally the development and dilution of turbulent vertical dense jets (or fountains) at small Froude numbers. The study complements an earlier larger Froude number investigation. The mean and fluctuating temperature fields were measured with fast responding thermocouples, and an emphasis was given to the minimum return dilution, which occurred just outside the edge of the discharge pipe. The study has revealed that at small Froude numbers (Fr < 5) the normalized minimum dilution, μmin/Fr, decreased linearly with the Froude number and it became constant only at larger Froude numbers (Fr > 7). Simple design equations for the calculations of minimum return dilution and maximum excess temperature and salinity at the level of the source are provided for small and large Froude number regimes. This study also recognized the advantage of using a vertical discharge configuration (inclination θ = 90o with horizontal) as opposed to an inclined configuration (0o ≤ θ < 90o) when discharging brine into water environments. The inclined discharge configuration has the potential of producing higher concentrations of brine and temperature near the source when ambient currents are in a direction opposite to the discharge.
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Benoni, Hanna, and Yehoshua Tsal. "Controlling for dilution while manipulating load: Perceptual and sensory limitations are just two aspects of task difficulty." Psychonomic Bulletin & Review 19, no. 4 (March 31, 2012): 631–38. http://dx.doi.org/10.3758/s13423-012-0244-8.
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Higgs, Richard E., Jon P. Butler, Bomie Han, and Michael D. Knierman. "Quantitative Proteomics via High Resolution MS Quantification: Capabilities and Limitations." International Journal of Proteomics 2013 (April 23, 2013): 1–10. http://dx.doi.org/10.1155/2013/674282.
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Recent improvements in the mass accuracy and resolution of mass spectrometers have led to renewed interest in label-free quantification using data from the primary mass spectrum (MS1) acquired from data-dependent proteomics experiments. The capacity for higher specificity quantification of peptides from samples enriched for proteins of biological interest offers distinct advantages for hypothesis generating experiments relative to immunoassay detection methods or prespecified peptide ions measured by multiple reaction monitoring (MRM) approaches. Here we describe an evaluation of different methods to post-process peptide level quantification information to support protein level inference. We characterize the methods by examining their ability to recover a known dilution of a standard protein in background matrices of varying complexity. Additionally, the MS1 quantification results are compared to a standard, targeted, MRM approach on the same samples under equivalent instrument conditions. We show the existence of multiple peptides with MS1 quantification sensitivity similar to the best MRM peptides for each of the background matrices studied. Based on these results we provide recommendations on preferred approaches to leveraging quantitative measurements of multiple peptides to improve protein level inference.
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Govoreanu, R., H. Saveyn, P. Van der Meeren, I. Nopens, and P. A. Vanrolleghem. "A methodological approach for direct quantification of the activated sludge floc size distribution by using different techniques." Water Science and Technology 60, no. 7 (October 1, 2009): 1857–67. http://dx.doi.org/10.2166/wst.2009.535.
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The activated sludge floc size distribution (FSD) is investigated by using different measurement techniques in order to gain insight in FSD assessment as well as to detect the strengths and limitations of each technique. A second objective was to determine the experimental conditions that allow a representative and accurate measurement of activated sludge floc size distributions. Laser diffraction, Time Of Transition (TOT) and Dynamic Image Analysis (DIA) devices were connected in series. The sample dilution liquid, the dilution factor and hydraulic flow conditions avoiding flocculation proved to be important. All methods had certain advantages and limitations. The MastersizerS has a broader dynamic size range and provides accurate results at high concentrations. However, it suffers from an imprecise evaluation of small size flocs and is susceptible to particle shape effects. TOT suffers less from size overestimation for non-spherical particles. However, care should be taken with the settings of the transparency check. Being primarily a counting technique, DIA suffers from a limited size detection range but is an excellent technique for process visualization. All evaluated techniques turned out to be reliable methods to quantify the floc size distribution. Selection of a certain method depends on the purpose of the measurement.
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Hallewell, J., T. Alexander, T. Reuter, and K. Stanford. "Limitations of Immunomagnetic Separation for Detection of the Top Seven Serogroups of Shiga Toxin–Producing Escherichia coli." Journal of Food Protection 80, no. 4 (March 9, 2017): 598–603. http://dx.doi.org/10.4315/0362-028x.jfp-16-427.
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ABSTRACT Shiga toxin–producing Escherichia coli (STEC) strains are foodborne pathogens that negatively impact human health and compromise food safety. Serogroup O157 is the most frequently isolated and studied STEC serogroup, but six others (O26, O45, O103, O111, O121, and O145) have also been identified as significant sources of human disease and collectively have been referred to as the “top six” pathogenic serogroups. Because detection methods for non-O157 serogroups are not yet refined, the objective of this study was to compare the effectiveness of immunomagnetic separation (IMS) for recovery of serogroup O157 isolates with that for each of the top six E. coli serogroups in pure and mixed cultures of STEC at 103 to 107 CFU/mL. After serogroup-specific IMS, DNA was extracted from cultured isolates to analyze the specificity of each IMS assay using conventional and quantitative PCR. In pure cultures, DNA copy number obtained after IMS was lower for O111 and O157 (P < 0.01) than for other serogroups. Based on quantitative PCR (qPCR) analyses, specificity was reduced for all IMS assays when STEC isolates were mixed at 7 log CFU/mL, although the O157 IMS assays recovered only O157 over a wider range of concentrations than did assays for non-O157 serogroups. At the lowest dilution tested, conventional PCR was specific for all serogroups except O121 and O145. For these two serogroups, no dilution tested recovered only O121 or O145 when evaluated with conventional PCR. Refinements to IMS assays, development of selective media, and determination of optimal enrichment times to reduce background microflora or competition among serogroups would be especially beneficial for recovery of O111, O121, and O145 serogroups to improve STEC detection and isolation.
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Dinh, Trieu-Vuong, and Jo-Chun Kim. "Moisture Removal Techniques for a Continuous Emission Monitoring System: A Review." Atmosphere 12, no. 1 (January 1, 2021): 61. http://dx.doi.org/10.3390/atmos12010061.
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A continuous emission monitoring system (CEMS) is a well-known tool used to analyze the concentrations of air pollutants from stationary sources. In a CEMS, the presence of a high moisture level in a sample causes a loss of analytes due to artifact formation or absorption. This issue brings about a bias in the measurement data. Thus, moisture removal is an important pretreatment step. Condensation and permeation methods have been widely employed to remove moisture from the CEMS for gaseous compounds. In terms of particulate matter, dilution methods have been applied to reduce the moisture level in the gas stream. Therefore, condensation, permeation, and dilution methods are critically reviewed in this work. The removal efficiencies and recovery rates of analytes are discussed, as well as the advantages and disadvantages of each technique. Furthermore, the suitable applications of each technique are determined. Condensation methods have not been well documented so far, while permeation and dilution methods have been continuously studied. Many types of permeation materials have been developed. The limitations of each method have been overcome over the years. However, the most reliable technique has not yet been discovered.
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Stanchi, Nestor Oscar, and Laura Josefina Balague. "Lyme Disease: antibodies against Borrelia burgdorferi in farm workers in Argentina." Revista de Saúde Pública 27, no. 4 (August 1993): 305–7. http://dx.doi.org/10.1590/s0034-89101993000400011.
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Lyme Disease is a tick-borne (specially by Ixodes ticks) immune-mediated inflammatory disorder caused by a newly recognize spirochete, Borrelia burgdorferi. Indirect fluorescent antibody (IF) staining methods and enzyme-linked immunosorbent assay are frequently relied upon to confirm Lyme borreliosis infections. Although serologic testing for antibodies has limitations, it is still the only practical means of confirming B. burgdorferi infections. Because we have no previous report of Lyme disease in human inhabitants in Argentina, a study was designed as a seroepidemiologic investigation of the immune response to B. burgdorferi in farm workers of Argentina with arthritis symptoms. Three out of 28 sera were positive (#1,5 and 9). Serum # 1 was positive for Immunoglobulin G at dilution 1:320, serum # 5 and # 9 both to dilution 1:160; while for Immunoglobulin M all (#1, 5 and 9) were positive at low dilution (1:40) using IF. The results showed that antibodies against B. burgdorferi are present in an Argentinian population. Thus caution should be exercised in the clinical interpretation of arthritis until the presence of B. burgdorferi be confirmed by culture in specific media.
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Phillips, Melissa M., and Lane C. Sander. "Microwave-Assisted Extraction and Quantitative LC/ID-MS Measurement of Total Choline and Free Carnitine in Food Standard Reference Materials." Journal of AOAC INTERNATIONAL 95, no. 5 (September 1, 2012): 1479–86. http://dx.doi.org/10.5740/jaoacint.12-137.
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Abstract The Stakeholder Panel on Infant Formula and Adult Nutritionals of AOAC INTERNATIONAL has declared both choline and carnitine to be priority nutrients in infant formulas, and ongoing efforts exist to develop or improve Official Methods of AnalysisSM for these nutrients. As a result, matrix-based certified reference materials are needed with assigned values for these compounds. In this work, traditional acid and enzymatic hydrolysis procedures were compared to microwave-assisted acid hydrolysis, and conditions optimized to provide complete sample hydrolysis and recovery of total choline from four food standard reference materials (SRMs): whole milk powder, whole egg powder, infant formula, and soy flour. The extracts were analyzed using LC on a mixed-mode column (simultaneous RP and ion exchange) with isotope dilution-MS detection to achieve simultaneous quantification of total choline and free carnitine. Total choline has been determined in these four food matrixes with excellent precision (0.65 to 2.60%) and accuracy, as confirmed by use of SRM 1849 Infant/Adult Nutritional Formula as a control material. Free carnitine has been determined in two of these food matrixes with excellent precision (0.69 to 2.19%) and accuracy, as confirmed by use of SRM 1849 Infant/Adult Nutritional Formula as a control material. Limitations in simultaneous determination of total choline and free carnitine resulted from extreme differences in concentration of the two components in egg powder and soy flour (at least three orders of magnitude). Samples required dilution to prevent poor LC peak shape, which caused decreased precision in the determination of low concentrations of free carnitine. Despite this limitation, the described method yields results comparable to current AOAC Official Method 999.14 Choline in Infant Formula, with a decrease of more than 2 h in sample preparation time.
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Browner, KH. "Rapid biological assay and limitations in macrophyte ecotoxicology: A review." Marine and Freshwater Research 37, no. 2 (1986): 297. http://dx.doi.org/10.1071/mf9860297.
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Rapid biological assays may be attractive for monitoring toxicity in effluents and trade wastes where mixtures of toxins may have complex additive or antagonistic effects but they are of very little use in assessing the effect of toxins on aquatic macrophytes in flowing water because the importance of the pattern of concentration and period of exposure is often neglected. In particular, there is an alarming scarcity of data for gauging the effect of toxins on submerged aquatic macrophytes. Their response to many photosynthetic inhibitors is complicated at low times of exposure by their resilience; and at low concentrations by the protective and competitive effects of epiphytes. The availance (concentration time product, or integral of concentration with respect to time) is a useful and convenient measure of toxic effect, but only for pulses of moderate concentration and duration. It is of very limited use for assessing the effects of toxins on macrophytes in river systems, where the pattern of exposure is often extreme. The pattern is determined by processes of dispersion and dilution, together with rates of dissipation and inactivation of the toxin. Therefore all these factors should be examined in any toxicity-testing program. In addition, since extremely low concentrations of some inhibitors are deleterious for macrophytes, background contamination from diffuse sources must also be considered.
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Heller, H., K. Granitza, and B. Eixmann. "Respiratory physiology teaching: determination of residual volume by applying the indicator-dilution technique." Advances in Physiology Education 274, no. 6 (June 1998): S53. http://dx.doi.org/10.1152/advances.1998.274.6.s53.
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Apart from the current teaching of spirometric methods in laboratory courses on respiratory physiology, we have included an experiment in which medical students determine their own residual volume by applying the indicator-dilution technique. For hygienic reasons we used a bag-in-the-box system to dilute helium within alveolar space by performing the single-breath method. Although each participant independently underwent only one single-breath maneuver, we gained a reliable relationship between residual volume and subjects' height and body weight in 68 female (r = 0.6, P < 0.0001) and 99 male (r = 0.42, P < 0.0001) students. From this successful outcome and with the opportunity to discuss the limitations of the single-breath method as well, we inferred that this experiment affords a transparent and instructive approach to interpreting the determination of lung volumes on the basis of the indicator-dilution technique.
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Kimmance, SA, WH Wilson, and SD Archer. "Modified dilution technique to estimate viral versus grazing mortality of phytoplankton: limitations associated with method sensitivity in natural waters." Aquatic Microbial Ecology 49 (November 29, 2007): 207–22. http://dx.doi.org/10.3354/ame01136.
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Dang, T. C., M. Fujii, A. L. Rose, M. Bligh, and T. D. Waite. "Characteristics of the Freshwater Cyanobacterium Microcystis aeruginosa Grown in Iron-Limited Continuous Culture." Applied and Environmental Microbiology 78, no. 5 (December 30, 2011): 1574–83. http://dx.doi.org/10.1128/aem.06908-11.
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ABSTRACTA continuous culturing system (chemostat) made of metal-free materials was successfully developed and used to maintain Fe-limited cultures ofMicrocystis aeruginosaPCC7806 at nanomolar iron (Fe) concentrations (20 to 50 nM total Fe). EDTA was used to maintain Fe in solution, with bioavailable Fe controlled by absorption of light by the ferric EDTA complex and resultant reduction of Fe(III) to Fe(II). A kinetic model describing Fe transformations and biological uptake was applied to determine the biologically available form of Fe (i.e., unchelated ferrous iron) that is produced by photoreductive dissociation of the ferric EDTA complex. Prediction by chemostat theory modified to account for the light-mediated formation of bioavailable Fe rather than total Fe was in good agreement with growth characteristics ofM. aeruginosaunder Fe limitation. The cellular Fe quota increased with increasing dilution rates in a manner consistent with the Droop theory. Short-term Fe uptake assays using cells maintained at steady state indicated thatM. aeruginosacells vary their maximum Fe uptake rate (ρmax) depending on the degree of Fe stress. The rate of Fe uptake was lower for cells grown under conditions of lower Fe availability (i.e., lower dilution rate), suggesting that cells in the continuous cultures adjusted to Fe limitation by decreasing ρmaxwhile maintaining a constant affinity for Fe.
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Durner, Roland, Bernard Witholt, and Thomas Egli. "Accumulation of Poly[(R)-3-Hydroxyalkanoates] in Pseudomonas oleovorans during Growth with Octanoate in Continuous Culture at Different Dilution Rates." Applied and Environmental Microbiology 66, no. 8 (August 1, 2000): 3408–14. http://dx.doi.org/10.1128/aem.66.8.3408-3414.2000.
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ABSTRACT Pseudomonas oleovorans ATCC 29347 was grown in chemostat culture at different dilution rates with mineral media varying in their ratios of octanoate to ammonia (C0/N0 ratio). At all dilution rates tested, three distinct growth regimes were observed: (i) carbon limitation with NH4 + in excess at low C0/N0 ratios, (ii) purely nitrogen-limited growth conditions at high C0/N0 ratios with residual octanoate in the culture supernatant, and (iii) an intermediate zone of dual-nutrient-limited growth conditions where both the concentration of octanoate and that of ammonia were very low. The dual-nutrient-limited growth zone shifted to higher C0/N0 ratios with decreasing dilution rates, and the extension of the dual-nutrient-limited growth zone was inversely proportional to the growth rate. The cells accumulated the storage compound medium-chain-length poly[(R)-3-hydroxyalkanoate] (mcl-PHA) during dual (C and N)-nutrient-limited and N-limited growth conditions. Within the dual-nutrient-limited growth zone, the cellular mcl-PHA contents increased when the C0/N0 ratio in the feed was increased, whereas the cellular mcl-PHA level was independent from the feed C0/N0 ratio during N-limited growth. The monomeric composition of the accumulated mcl-PHA was independent of both the dilution rate and the feed C0/N0 ratio and consisted of 12 mol% 3-hydroxyhexanoic acid and 88 mol% 3-hydroxyoctanoic acid. Accumulation of mcl-PHA led to an increase in the cellular C/N ratio and to changes in elemental growth yields for nitrogen and carbon.
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VENTURINI, M. E., D. BLANCO, and R. ORIA. "In Vitro Antifungal Activity of Several Antimicrobial Compounds against Penicillium expansum." Journal of Food Protection 65, no. 5 (May 1, 2002): 834–39. http://dx.doi.org/10.4315/0362-028x-65.5.834.
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Fungicides used in the prevention and control of mold rots in stored apples are subjected to legal, social, and biological limitations. The aim of this study was to find an alternative to postharvest fungicides currently used in the prevention and control of blue mold rot caused by Penicillium expansum in apples. For this purpose, the antimicrobial activity and MIC of several substances against P. expansum were evaluated in vitro using different end point methods: agar diffusion assay, volatility method, and agar dilution and broth dilution MIC assays. Most of the substances tested are common food ingredients and have a recognized antimicrobial activity. Essential oils, such as thymol, eugenol, citral and cineole, vanillin, sodium hypochlorite, acetic acid, potassium sorbate, and hydrogen peroxide, were the substances evaluated. Thymol and citral were the essential oil components that showed the greatest inhibitory effects. The effectiveness of 5 and 10% hydrogen peroxide in growth inhibition of P. expansum in the agar diffusion assay was total, and its MIC as determined by the agar and broth dilution assays was less than 0.025%. These results indicate that the application of small quantities of hydrogen peroxide to the apple skin might be an alternative to fungicides in the elimination of P. expansum.
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Gorrini, Federico Alberto, Jesús Miguel Zamudio Lara, Silvina Inés Biagiola, José Luis Figueroa, Héctor Hernández Escoto, Anne-Lise Hantson, and Alain Vande Wouwer. "Experimental Study of Substrate Limitation and Light Acclimation in Cultures of the Microalgae Scenedesmus obliquus—Parameter Identification and Model Predictive Control." Processes 8, no. 12 (November 27, 2020): 1551. http://dx.doi.org/10.3390/pr8121551.
Full textAbstract:
In this study, the parameters of a dynamic model of cultures of the microalgae Scenedesmus obliquus are estimated from datasets collected in batch photobioreactors operated with various initial conditions and light illumination conditions. Measurements of biomass, nitrogen quota, bulk substrate concentration, as well as chlorophyll concentration are achieved, which allow the determination of parameters with satisfactory confidence intervals and model cross-validation against independent data. The dynamic model is then used as a predictor in a nonlinear model predictive control strategy where the dilution rate and the incident light intensity are simultaneously manipulated in order to optimize the cumulated algal biomass production.
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Squires, Margaret M., and Lance F. W. Lesack. "Water transparency and nutrients as controls on phytoplankton along a flood-frequency gradient among lakes of the Mackenzie Delta, western Canadian Arctic." Canadian Journal of Fisheries and Aquatic Sciences 59, no. 8 (August 1, 2002): 1339–49. http://dx.doi.org/10.1139/f02-085.
Full textAbstract:
Relatively low phytoplankton production among lakes of the Mackenzie Delta has been attributed to light limitation in frequently flooded lakes and to nutrient limitation among infrequently flooded lakes; productivity peaks have been attributed to optimal lightnutrient conditions at intermediate flood frequency. We found that the distribution and abundance of phytoplankton among a large number of lakes was explained by optimal lightnutrient conditions but not by nutrient or light limitation. For a subset of lakes, seasonal dynamics of biomass were consistent with light limitation and optimal lightnutrient conditions but not nutrient limitation; photosynthetic rates were consistent with optimal lightnutrient conditions and nutrient limitation but not light limitation. Results of dilutiondeletion experiments across a lightnutrient gradient indicated transition from light limitation to optimal lightnutrient conditions to nutrient limitation. Surprisingly, adding river water to lake water did not increase photosynthetic rates; this result and experimental incubations in situ during river inflow and lake outflow suggested that continuous supply of river water may be necessary to increase phytoplankton growth rates. Among infrequently flooded lakes, phytoplankton response to nutrient additions showed that phosphorus (P) limitation was no more likely than nitrogen (N) limitation, co-limitation, or no limitation by N or P.
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Cua, W. O., V. Bower, C. Tice, and F. P. Chinard. "Pulmonary vascular extraction and distribution of antipyrine with alveolar flooding." American Journal of Physiology-Heart and Circulatory Physiology 269, no. 5 (November 1, 1995): H1811—H1819. http://dx.doi.org/10.1152/ajpheart.1995.269.5.h1811.
Full textAbstract:
Transport characteristics of antipyrine (AP), 22Na+, and tritiated water (THO) were assessed in dog lungs by multiple indicator-dilution experiments in vivo with anesthesia and in isolated perfused preparations before and after alveolar flooding. In controls, outflow patterns of AP and THO were nearly identical. In flooding, AP and THO patterns separated. THO upslopes decreased and mean (t) and modal (tmax) transit times increased as flooding increased; AP initial upslopes remained relatively unchanged but t increased, whereas tmax decreased. Patterns of 22Na+ were unchanged. The results indicate 22Na+ limitation at the endothelium, AP limitation only at the epithelium, and no THO limitation. A mathematical model is based on axial and orthogonal distribution of AP and THO. With alveolar flooding, diffusional distance may be a limiting factor in this distribution.
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Effros, Richard M., Prapaporn Pornsuriyasak, Janos Porszasz, and Richard Casaburi. "Indicator dilution measurements of extravascular lung water: basic assumptions and observations." American Journal of Physiology-Lung Cellular and Molecular Physiology 294, no. 6 (June 2008): L1023—L1031. http://dx.doi.org/10.1152/ajplung.00533.2007.
Full textAbstract:
Since they were introduced more than five decades ago, a variety of single-pass indicator, thermal, and osmotic dilution approaches have been developed for detecting and measuring excess fluid in the lungs. This brief review discusses why studies of the extravascular lung water (EVLW) continue to intrigue physiologists and clinicians and the likelihood that they will become sufficiently reliable for more widespread use. Emphasis is placed on the basic assumptions that underlie these measurements and limitations imposed by the nature of the data that are collected. A distinction is made between approaches that are based on compartmental models of solute and water exchange and those that represent extensions of more conventional washout procedures, which have been utilized extensively for measurements of gas volumes in the lungs. Although the compartmental approach has been used to simplify indicator dilution studies by eliminating the need for a vascular indicator, it is based on assumptions that may not be realistic. Early recirculation inevitably limits the period in which observations can be made and impairs detection of those portions of the lungs with decreased perfusion. These general principles are also used to develop a new method of analyzing osmotic transient studies. A short account is given of EVLW observations that have been made in animals and humans. Both the sensitivity and specificity of EVLW measurements in humans are uncertain, and the normal clinical range of EVLW remains in doubt.