Selection of the Optimal Critical Velocity for Sand Transport at Low Concentrations for Near-Horizontal Flow

2012 ◽  
Author(s):  
Byron F. Soepyan ◽  
Selen Cremaschi ◽  
Cem Sarica ◽  
Hariprasad J. Subramani
Keyword(s):  
Critical Velocity ◽  
Horizontal Flow ◽  
Sand Transport ◽  
Low Concentrations ◽  
Selection Of

scholarly journals Gelation or molecular recognition; is the bis-(α,β-dihydroxy ester)s motif an omnigelator?

2010 ◽  
Vol 6 ◽  
pp. 1079-1088 ◽  
Author(s):  
Peter C Griffiths ◽  
David W Knight ◽  
Ian R Morgan ◽  
Amy Ford ◽  
James Brown ◽  
...  
Keyword(s):  
Molecular Recognition ◽  
Neutron Scattering ◽  
Spin Echo ◽  
Inelastic Neutron ◽  
Gelation Mechanism ◽  
Regular Structures ◽  
Low Concentrations ◽  
Wide Range ◽  
History Of ◽  
Selection Of

Understanding the gelation of liquids by low molecular weight solutes at low concentrations gives an insight into many molecular recognition phenomena and also offers a simple route to modifying the physical properties of the liquid. Bis-(α,β-dihydroxy ester)s are shown here to gel thermoreversibly a wide range of solvents, raising interesting questions as to the mechanism of gelation. At gelator concentrations of 5–50 mg ml−1, gels were successfully formed in acetone, ethanol/water mixtures, toluene, cyclohexane and chloroform (the latter, albeit at a higher gelator concentration). A range of neutron techniques – in particular small-angle neutron scattering (SANS) – have been employed to probe the structure of a selection of these gels. The universality of gelation in a range of solvent types suggests the gelation mechanism is a feature of the bis-(α,β-dihydroxy ester) motif, with SANS demonstrating the presence of regular structures in the 30–40 Å range. A correlation between the apparent rodlike character of the structures formed and the polarity of the solvent is evident. Preliminary spin-echo neutron scattering studies (SESANS) indicated the absence of any larger scale structures. Inelastic neutron spectroscopy (INS) studies demonstrated that the solvent is largely unaffected by gelation, but does reveal insights into the thermal history of the samples. Further neutron studies of this kind (particularly SESANS and INS) are warranted, and it is hoped that this work will stimulate others to pursue this line of research.

scholarly journals Genetically Modified Vibrio harveyiStrains as Potential Bioindicators of Mutagenic Pollution of Marine Environments

2000 ◽  
Vol 66 (2) ◽  
pp. 599-605 ◽  
Author(s):  
Agata Czyz˙ ◽  
Jacek Jasiecki ◽  
Adam Bogdan ◽  
Hanna Szpilewska ◽  
Grzegorz We˛grzyn
Keyword(s):  
Marine Bacterium ◽  
Genetically Modified ◽  
Marine Environments ◽  
Simple Method ◽  
Naturally Occurring ◽  
Low Concentrations ◽  
Serovar Typhimurium ◽  
Wild Type Counterpart ◽  
Mutagenic Pollution ◽  
Selection Of

ABSTRACT For biodetection of mutagenic pollution of marine environments, an organism naturally occurring in these habitats should be used. We found that marine bacterium Vibrio harveyi may be an appropriate bioindicator of mutagenic pollution. For positive selection of mutants, we developed a simple method for isolation of V. harveyimutants resistant to neomycin. We constructed genetically modifiedV. harveyi strains that produce significantly more neomycin-resistant mutants upon treatment with low concentrations of mutagens than the wild-type counterpart. The sensitivity of the mutagenicity test with the V. harveyi strains is at least comparable to (if not higher than) that of the commonly used Ames test, which uses Salmonella enterica serovar Typhimurium strains. Therefore, we consider that the V. harveyi strains described in this report could be used as potential bioindicators of mutagenic pollution of marine environments.

scholarly journals Considerações sobre hormônios e sexo / Considerations on hormones and sex

2021 ◽  
Vol 66 (1u) ◽  
pp. 1
Author(s):  
Sônia Maria Rolim Rosa Lima
Keyword(s):  
Sexual Function ◽  
Ovarian Function ◽  
Current Knowledge ◽  
Serum Concentrations ◽  
Local Synthesis ◽  
Low Concentrations ◽  
Potential Impact ◽  
Review Current ◽  
Selection Of

Os esteroides sexuais, em particular os estrogênios e os androgênios, representam papel fundamental, na modulação da função sexual feminina. As mulheres após a menopausa, devido ao declínio da função ovariana, são dependentes da síntese local de estrogênios nos tecidos alvo extragonadais. Mantendo-se o quadro carêncial ocorre progressivo estreitamento da vagina, e o sintoma genital mais comum é a secura por diminuição da transudação e da quantidade de muco cervical. Esses fenômenos explicam os processos encontrados no período do climatério ou qualquer período em que ocorra a carência estrogênica, característicos da falência hormonal: vaginite atrófica, leucorréia, prurido, dor e sangramento ao coito. Com relação aos androgênios, vários estudos investigaram associações entre androgênios e função sexual em mulheres. Muitos, mas não todos, identificam uma relação entre o desejo sexual e as concentrações séricas de androgênios circulantes. A variabilidade nos resultados provavelmente reflete as limitações em aferir com precisão suas baixas concentrações, o impacto potencial de outros esteroides, as diferenças no desenho do estudo, na seleção das participantes e nos parâmetros de função sexual. Neste artigo, revisamos o conhecimento atual sobre o papel dos estrogênios e androgênios e seu uso clínico em mulheres com declínio da função ovariana.Palavras chave: Hormônios sexuais, Esteroides, Androgênios, Pós-Menopausa, Disfunções sexuais fisiológicasABSTRACTSex steroids, in particular estrogens and androgens, play a fundamental role in the modulation of female sexual function. Postmenopausal women, due to the decline in ovarian function, are dependent on the local synthesis of estrogens in extragonadal target tissues. If the deficiency is maintained, progressive narrowing of the vagina occurs, and the most common genital symptom is dryness due to decreased transudation and the amount of cervical mucus. These phenomena explain the processes found during the climacteric period or any period in which estrogen deficiency occurs, which are characteristic of hormonal failure: atrophic vaginitis, leukorrhea, itching, pain and bleeding on intercourse. With regard to androgens, several studies have investigated associations between androgens and sexual function in women. Many, but not all, identify a relationship between sexual desire and serum concentrations of circulating androgens. The variability in the results probably reflects the limitations in accurately measuring the low concentrations of androgens in women, the potential impact of other steroids, the differences in the study design, in the selection of participants and in the parameters of sexual function. In this article, we review current knowledge about the role of estrogens and androgens and their clinical use in women with declining ovarian function.Keywords: Sex hormones, Steroids, Androgens, Postmenopause, Physiological sexual dysfunctions

Traces of Imidacloprid Induce Hormesis as a Stimulatory Conditioned Response of Sweetpotato Whitefly (Hemiptera: Aleyrodidae)

2019 ◽  
Author(s):  
M Rakotondravelo ◽  
D Smitley ◽  
E Calabrese ◽  
M Ladoni
Keyword(s):  
Bemisia Tabaci ◽  
Conditioned Response ◽  
Seed Coating ◽  
Field Soil ◽  
Sweetpotato Whitefly ◽  
Low Concentrations ◽  
Selection Of

Abstract Our purpose is to determine whether extremely low concentrations of imidacloprid (2–8 ppb) typically found in field soil 1–3 yr after a crop is grown using seed with a standard imidacloprid seed-coating could impact the fitness of whiteflies, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae). Results of our experiments indicate that imidacloprid-resistant whitefly larvae feeding on cotton seedlings growing in soil with 8.0 ppb imidacloprid are conditioned so that when the same individuals feed on plants treated with imidacloprid as adults their fitness, measured as fecundity, increases 30–70% compared with individuals that were not primed as larvae. This conditioning hormesis stimulates resistant whiteflies more than susceptible whiteflies, which may contribute to the selection of resistant populations.

Effect of antibiotics on cell proliferation in the Closterium peracerosum-strigosum-littorale complex (Charophyceae, Chlorophyta)

Biologia ◽  
2008 ◽  
Vol 63 (6) ◽  
Author(s):  
Jun Abe ◽  
Kaori Sakayori ◽  
Hiroyuki Sekimoto
Keyword(s):  
Cell Proliferation ◽  
Liquid Medium ◽  
Inhibitory Concentration ◽  
Solid Medium ◽  
Marker Genes ◽  
Hygromycin B ◽  
Selectable Marker Genes ◽  
Kanamycin Sulfate ◽  
Low Concentrations ◽  
Selection Of

AbstractThe effects of several antibiotics on the proliferation of cells of the Closterium peracerosum-strigosum-littorale complex, a unicellular charophycean alga, were examined. When cells were cultured on solid medium containing hygromycin B and phleomycin the proliferation of cells was inhibited at low concentrations of these antibiotics, with a minimum inhibitory concentration of 5.0 and 0.2 µg/mL, respectively. By contrast, kanamycin sulfate was less effective at concentrations up to 50 µg/mL. When cells were incubated in liquid medium containing hygromycin B and phleomycin, cell proliferation was severely inhibited at concentrations of 5.0 and 0.01 µg/mL, respectively. It is concluded that hygromycin B and phleomycin are highly effective for inhibiting the proliferation of C. psl. complex both on solid and in liquid medium and thus are useful for the selection of the cells transformed by selectable marker genes.

scholarly journals Very Low Cefotaxime Concentrations Select for Hypermutable Streptococcus pneumoniae Populations

2002 ◽  
Vol 46 (2) ◽  
pp. 528-530 ◽  
Author(s):  
María-Cristina Negri ◽  
María-Isabel Morosini ◽  
María-Rosario Baquero ◽  
Rosa del Campo ◽  
Jesús Blázquez ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Streptococcus Pneumoniae ◽  
Mixed Culture ◽  
Clinical Setting ◽  
Mutation Frequency ◽  
Multiple Resistance ◽  
Mutant Population ◽  
Low Concentrations ◽  
Resistant Mutants ◽  
Selection Of

ABSTRACT A mixed culture of an hypermutable hexA Streptococcus pneumoniae mutant strain and its hexA + isogenic ancestor was challenged with low cefotaxime concentrations. Despite identical original cefotaxime MICs, the hexA mutant population was significantly selected at very low concentrations, and all of the tested selected variants harbored the Thr550→Ala mutation in pbp2x. Since cefotaxime selects hypermutators, the risk of secondary acquisition of antibiotic resistance is increased; as expected, the cefotaxime-resistant mutants had a mutation frequency 10 times higher in response to to ciprofloxacin. The present study presents a model (not necessarily reflecting the clinical setting) illustrating the risk of selection of mutators in the evolution of multiple resistance.

Pharmacokinetic Model Selection for Target Controlled Infusions of Propofol

1995 ◽  
Vol 82 (6) ◽  
pp. 1328-1345. ◽  
Author(s):  
J. F Coetzee ◽  
MMed (Anes.) MBChB ◽  
J. B. Glen ◽  
L. Boshoff
Keyword(s):  
Pharmacokinetic Model ◽  
Computer Assisted ◽  
Prediction Errors ◽  
Pharmacokinetic Variability ◽  
Clinical Criteria ◽  
Drug Concentrations ◽  
Low Concentrations ◽  
Selection For ◽  
Over Time ◽  
Selection Of

Background Computer-assisted target controlled infusions (TCI) result in prediction errors that are influenced by pharmacokinetic variability among and within patients. It is uncertain whether the selection of a propofol pharmacokinetic parameter set significantly influences drug concentrations and clinical acceptability. Methods Thirty patients received similar propofol TCI regimens after being randomly allocated to one of three parameter sets. Arterial and venous concentrations were measured and prediction errors calculated from pooled and intrasubject data. Results Arterial propofol concentrations in the Dyck group revealed greater bias (mean 43%) than did those in the Marsh (-1%) and Tackley (-3%) groups. The Dyck group also showed greater inaccuracy (mean:47%) than the Marsh (29%) and Tackley (24%) groups. There was little tendency for measured concentrations to vary from targeted values over time (divergence). Variability about an observed mean in individual patients (wobble) was low. Venous propofol concentrations were initially much less than arterial concentrations, but this difference decreased over time. Conclusions Although it may be preferable to administer propofol TCI by using a locally derived parameter set, it is acceptable to use a model from elsewhere. The Marsh and Tackley models produced equally good performance and are appropriate for propofol TCI within the range of 3-6 micrograms/ml. The Dyck model was less accurate at maintaining anesthetic concentrations, possibly because it was derived from low concentrations. Concentrations in blood, the most sensitive indicators of performance, demonstrated differences among the parameter sets. Clinically, TCI worked well, and by clinical criteria, the choice of pharmacokinetic model did not appear to make a difference.

Morphology of changes in intestine and peritoneum walls after sanation of the abdominal cavity with sodium hypochlorite solution in rats with peritonitis

2021 ◽  
Vol 2 ◽  
pp. 55-61
Author(s):  
Alla Kashafeeva ◽  
◽  
Sergey Gaimolenko ◽  
Namzhil Tsybikov
Keyword(s):  
Sodium Hypochlorite ◽  
Abdominal Cavity ◽  
Intestinal Wall ◽  
Sodium Hypochlorite Solution ◽  
Ether Anesthesia ◽  
Hypochlorite Solution ◽  
Secondary Damage ◽  
Low Concentrations ◽  
Sexually Mature ◽  
Selection Of

The aim of the study was to reveal the effect of sodium hypochlorite (HCH) solution at concentrations of 0.022%, 0.045% and 0.09% on the morphology of the intestinal wall and peritoneum during peritonitis in the experiment. Materials and methods. The study was carried out on 72 infertile sexually mature rats of both sexes weighting 190-250 g. The animal under ether anesthesia was performed laparotomy and modeling peritonitis according to the method by M.A. Magomedov. On day 1, all rats were irrigated with sodium hypochlorite solution at different concentrations (5 min). Selection of the material for study (part of the intestine) was carried out on the 1, 3 and 7th day of the experiment. Results. Sodium hypochlorite (0.022% and 0.045%) have not a proper antiseptic effect on microorganisms in secondary peritonitis. The HCH solution (0.09%) produces a sufficient bacterial and detergent effect, but contributes to secondary damage to abdominal tissues. Conclusions. 1. As an antiseptic can be recommended 0.09% solution of sodium hypochlorite with an exposure of 3-5 minutes to prevent the development of peritonitis 2. The use of low concentrations of sodium hypochlorite is possible for the purpose of mechanical cleaning of the abdominal cavity.

Quantification and Reduction of Uncertainties for Solids Transport Velocity Predictions at Low Concentrations in Near-Horizontal Flow

2013 ◽  
Author(s):  
Selen Cremaschi ◽  
Cem Sarica ◽  
Hariprasad Janakiram Subramani ◽  
Frits Byron Soepyan ◽  
Gene Edward Kouba
Keyword(s):  
Horizontal Flow ◽  
Solids Transport ◽  
Low Concentrations ◽  
Transport Velocity

The use of chromium oxide to estimate the faecal output of Merinos

1963 ◽  
Vol 14 (2) ◽  
pp. 239 ◽  
Author(s):  
LJ Lambourne ◽  
TF Reardon
Keyword(s):  
Chromium Oxide ◽  
Grab Sampling ◽  
Low Concentrations ◽  
Wide Range ◽  
Main Series ◽  
Series Of Experiments ◽  
The Mean ◽  
High Concentrations ◽  
Fixed Times ◽  
Selection Of

The pattern of chromium oxide (Cr2O3) excretion was studied in Merino wethers. The sheep were dosed twice daily with Cr2O3 at fixed times. In the main series of experiments, sheep were fed fresh herbage in metabolism pens. An oaten chaff diet was also employed. In all cases a diurnal pattern of Cr2O3 excretion in the faeces was observed. The pattern was not consistent from day to day, nor was there any consistent effect of level of intake or feeding frequency on the excretion pattern. Distributions of Cr2O3 were examined in eight grazing sheep killed ½–4 hr after dosing. In six of the animals high concentrations of the marker were found to be mixed with the reticuloruminal ingesta, while low concentrations were observed in the other stomachs. In the remaining two animals high concentrations were observed in the omasum and abomasum, from which it was inferred that the dose had by-passed the main bulk of the reticulorurninal ingesia. It seems unlikely that any real advantage is to be gained by painstaking selection of particular times for dosing and faeces sampling in different environments; and it is suggested that convenient fixed times — say 6 a.m. and 3 p.m., or 9 a.m. and 5 p.m. — should prove satisfactory in estimating output of faeces of grazing animals under a wide range of conditions. In 40 sheep-periods of 10–14 days, the mean daily output of faeces organic matter by pen-fed wethers was estimated with mean 101% and error ±12% of the true figures, by analysis of a single bulked sample obtained by dosing and grab sampling at about 9 a.m. and 5 p.m. daily. In 40 periods when samples were bulked over 5–7 days the average estimate was 102 ± 14% of the true figure. Comparison under extensive grazing conditions showed that estimates obtained by dosing and sampling only once per day were generally some 15% higher than those obtained by dosing and sampling twice daily.

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