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Sample records for cenocepacia j2315 sessile

  1. Orderly Replication and Segregation of the Four Replicons of Burkholderia cenocepacia J2315.

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    Wen-Li Du

    2016-07-01

    Full Text Available Bacterial genomes typically consist of a single chromosome and, optionally, one or more plasmids. But whole-genome sequencing reveals about ten per-cent of them to be multipartite, with additional replicons which by size and indispensability are considered secondary chromosomes. This raises the questions of how their replication and partition is managed without compromising genome stability and of how such genomes arose. Vibrio cholerae, with a 1 Mb replicon in addition to its 3 Mb chromosome, is the only species for which maintenance of a multipartite genome has been investigated. In this study we have explored the more complex genome of Burkholderia cenocepacia (strain J2315. It comprises an extra replicon (c2 of 3.21 Mb, comparable in size to the3.87Mb main chromosome (c1, another extra replicon(c3 of 0.87 Mb and a plasmid of 0.09 Mb. The replication origin of c1 is typically chromosomal and those of c2 and c3 are plasmid-like; all are replicated bidirectionally. Fluorescence microscopy of tagged origins indicates that all initiate replication at mid-cell and segregate towards the cell quarter positions sequentially, c1-c2-p1/c3. c2 segregation is as well-phased with the cell cycle as c1, implying that this plasmid-like origin has become subject to regulation not typical of plasmids; in contrast, c3 segregates more randomly through the cycle. Disruption of individual Par systems by deletion of parAB or by addition of parS sites showed each Par system to govern the positioning of its own replicon only. Inactivation of c1, c2 and c3 Par systems not only reduced growth rate, generated anucleate cells and compromised viability but influenced processes beyond replicon partition, notably regulation of replication, chromosome condensation and cell size determination. In particular, the absence of the c1 ParA protein altered replication of all three chromosomes, suggesting that the partition system of the main chromosome is a major participant in the

  2. Candidate Essential Genes in Burkholderia cenocepacia J2315 Identified by Genome-Wide TraDIS

    KAUST Repository

    Wong, Yee-Chin

    2016-08-22

    Burkholderia cenocepacia infection often leads to fatal cepacia syndrome in cystic fibrosis patients. However, antibiotic therapy rarely results in complete eradication of the pathogen due to its intrinsic resistance to many clinically available antibiotics. Recent attention has turned to the identification of essential genes as the proteins encoded by these genes may serve as potential targets for development of novel antimicrobials. In this study, we utilized TraDIS (Transposon Directed Insertion-site Sequencing) as a genome-wide screening tool to facilitate the identification of B. cenocepacia genes essential for its growth and viability. A transposon mutant pool consisting of approximately 500,000 mutants was successfully constructed, with more than 400,000 unique transposon insertion sites identified by computational analysis of TraDIS datasets. The saturated library allowed for the identification of 383 genes that were predicted to be essential in B. cenocepacia. We extended the application of TraDIS to identify conditionally essential genes required for in vitro growth and revealed an additional repertoire of 439 genes to be crucial for B. cenocepacia growth under nutrient-depleted conditions. The library of B. cenocepacia mutants can subsequently be subjected to various biologically related conditions to facilitate the discovery of genes involved in niche adaptation as well as pathogenicity and virulence.

  3. The genome of Burkholderia cenocepacia J2315, an epidemic pathogen of cystic fibrosis patients

    DEFF Research Database (Denmark)

    Holden, Matthew T G; Seth-Smith, Helena M B; Crossman, Lisa C;

    2009-01-01

    Bacterial infections of the lungs of cystic fibrosis (CF) patients cause major complications in the treatment of this common genetic disease. Burkholderia cenocepacia infection is particularly problematic since this organism has high levels of antibiotic resistance, making it difficult to eradica...

  4. Phenotypic and genotypic characterisation of Burkholderia cenocepacia J2315 mutants affected in homoserine lactone and diffusible signal factor-based quorum sensing systems suggests interplay between both types of systems.

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    Claudia Udine

    Full Text Available Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS circuits. These QS systems either use N-acyl homoserine lactones (AHL or cis-2-dodecenoic acid ("Burkholderia diffusible signal factor", BDSF as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870, CciI (BCAM0239a and the BDSF synthase (BCAM0581 were inactivated, and also constructed double (ΔcepIΔBCAM0581, ΔcciIΔBCAM0581 and ΔcepIΔcciI mutants and a triple (ΔcepIΔcciIΔBCAM0581 mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The ΔBCAM0581 mutant and the ΔcepIΔBCAM0581 and ΔcciIΔBCAM0581 double mutants produced significantly less AHL compared to the WT strain and the ΔcepI and ΔcciI single mutant, respectively. The expression of cepI and cciI in ΔBCAM0581, was approximately 3-fold and 7-fold (p<0.05 lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the ΔBCAM0581 mutant could (at least partially be restored by addition of BDSF. Our data suggest that, in B. cenocepacia J2315, AHL and BDSF-based QS systems co-regulate the same set of genes, regulate different sets of genes that are involved in the same phenotypes and/or that the BDSF system controls the AHL-based QS system. As the expression of the gene encoding the C6-HSL synthase CciI (and to a

  5. Differential roles of RND efflux pumps in antimicrobial drug resistance of sessile and planktonic Burkholderia cenocepacia cells.

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    Buroni, Silvia; Matthijs, Nele; Spadaro, Francesca; Van Acker, Heleen; Scoffone, Viola C; Pasca, Maria Rosalia; Riccardi, Giovanna; Coenye, Tom

    2014-12-01

    Burkholderia cenocepacia is notorious for causing respiratory tract infections in people with cystic fibrosis. Infections with this organism are particularly difficult to treat due to its high level of intrinsic resistance to most antibiotics. Multidrug resistance in B. cenocepacia can be ascribed to different mechanisms, including the activity of efflux pumps and biofilm formation. In the present study, the effects of deletion of the 16 operons encoding resistance-nodulation-cell division (RND)-type efflux pumps in B. cenocepacia strain J2315 were investigated by determining the MICs of various antibiotics and by investigating the antibiofilm effect of these antibiotics. Finally, the expression levels of selected RND genes in treated and untreated cultures were investigated using reverse transcriptase quantitative PCR (RT-qPCR). Our data indicate that the RND-3 and RND-4 efflux pumps are important for resistance to various antimicrobial drugs (including tobramycin and ciprofloxacin) in planktonic B. cenocepacia J2315 populations, while the RND-3, RND-8, and RND-9 efflux systems protect biofilm-grown cells against tobramycin. The RND-8 and RND-9 efflux pumps are not involved in ciprofloxacin resistance. Results from the RT-qPCR experiments on the wild-type strain B. cenocepacia J2315 suggest that there is little regulation at the level of mRNA expression for these efflux pumps under the conditions tested.

  6. Assessment of three Resistance-Nodulation-Cell Division drug efflux transporters of Burkholderia cenocepacia in intrinsic antibiotic resistance

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    Venturi Vittorio

    2009-09-01

    Full Text Available Abstract Background Burkholderia cenocepacia are opportunistic Gram-negative bacteria that can cause chronic pulmonary infections in patients with cystic fibrosis. These bacteria demonstrate a high-level of intrinsic antibiotic resistance to most clinically useful antibiotics complicating treatment. We previously identified 14 genes encoding putative Resistance-Nodulation-Cell Division (RND efflux pumps in the genome of B. cenocepacia J2315, but the contribution of these pumps to the intrinsic drug resistance of this bacterium remains unclear. Results To investigate the contribution of efflux pumps to intrinsic drug resistance of B. cenocepacia J2315, we deleted 3 operons encoding the putative RND transporters RND-1, RND-3, and RND-4 containing the genes BCAS0591-BCAS0593, BCAL1674-BCAL1676, and BCAL2822-BCAL2820. Each deletion included the genes encoding the RND transporter itself and those encoding predicted periplasmic proteins and outer membrane pores. In addition, the deletion of rnd-3 also included BCAL1672, encoding a putative TetR regulator. The B. cenocepacia rnd-3 and rnd-4 mutants demonstrated increased sensitivity to inhibitory compounds, suggesting an involvement of these proteins in drug resistance. Moreover, the rnd-3 and rnd-4 mutants demonstrated reduced accumulation of N-acyl homoserine lactones in the growth medium. In contrast, deletion of the rnd-1 operon had no detectable phenotypes under the conditions assayed. Conclusion Two of the three inactivated RND efflux pumps in B. cenocepacia J2315 contribute to the high level of intrinsic resistance of this strain to some antibiotics and other inhibitory compounds. Furthermore, these efflux systems also mediate accumulation in the growth medium of quorum sensing molecules that have been shown to contribute to infection. A systematic study of RND efflux systems in B. cenocepacia is required to provide a full picture of intrinsic antibiotic resistance in this opportunistic

  7. Investigation of the multifaceted iron acquisition strategies of Burkholderia cenocepacia.

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    Tyrrell, J; Whelan, N; Wright, C; Sá-Correia, I; McClean, S; Thomas, M; Callaghan, Máire

    2015-04-01

    Burkholderia cenocepacia is a bacterial pathogen which causes severe respiratory infections in cystic fibrosis (CF). These studies were aimed at gaining an insight into the iron acquisition strategies of B. cenocepacia. In iron restricted conditions, genes associated with the synthesis and utilisation of ornibactin (pvdA, orbA, orb F) were significantly upregulated compared to the expression of pyochelin associated genes (pchD, fptA). In the absence of alternative iron sources, B. cenocepacia J2315 and 715j utilised ferritin and haemin, but not transferrin or lactoferrin for growth. Significantly, mutants unable to produce ornibactin, (715j-orbI) or ornibactin and pyochelin, (715j-pobA), utilised haemin and ferritin more efficiently than the wild-type. Moreover, both mutants were also able to utilise lactoferrin for growth (P ≤ 0.01) and additionally 715j-pobA utilised transferrin (P ≤ 0.01), potentially facilitating adaptation to the host environment. Furthermore, B. cenocepacia increased ornibactin gene expression in response to pyoverdine from Pseudomonas aeruginosa (P ≤ 0.01), demonstrating the capacity to compete for iron in co-colonised niches. Pyoverdine also significantly diminished the growth of B. cenocepacia (P < 0.001) which was related to its iron chelating activity. In a study of three B. cenocepacia sequential clonal isolates obtained from a CF patient over a 3.5 year period, ornibactin upregulation in response to pyoverdine was less pronounced in the last isolate compared to the earlier isolates, as was growth in the presence of haemin and ferritin, indicating alternative iron acquisition mechanism(s) may dominate as chronic infection progresses. These data demonstrate the multifaceted iron acquisition strategies of B. cenocepacia and their capacity to be differentially activated in the presence of P. aeruginosa and during chronic infection.

  8. Efflux pump genes of the resistance-nodulation-division family in Burkholderia cenocepacia genome

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    Manina Giulia

    2006-07-01

    Full Text Available Abstract Background Burkholderia cenocepacia is recognized as opportunistic pathogen that can cause lung infections in cystic fibrosis patients. A hallmark of B. cenocepacia infections is the inability to eradicate the organism because of multiple intrinsic antibiotic resistance. As Resistance-Nodulation-Division (RND efflux systems are responsible for much of the intrinsic multidrug resistance in Gram-negative bacteria, this study aims to identify RND genes in the B. cenocepacia genome and start to investigate their involvement into antimicrobial resistance. Results Genome analysis and homology searches revealed 14 open reading frames encoding putative drug efflux pumps belonging to RND family in B. cenocepacia J2315 strain. By reverse transcription (RT-PCR analysis, it was found that orf3, orf9, orf11, and orf13 were expressed at detectable levels, while orf10 appeared to be weakly expressed in B. cenocepacia. Futhermore, orf3 was strongly induced by chloramphenicol. The orf2 conferred resistance to fluoroquinolones, tetraphenylphosphonium, streptomycin, and ethidium bromide when cloned and expressed in Escherichia coli KAM3, a strain lacking the multidrug efflux pump AcrAB. The orf2-overexpressing E. coli also accumulate low concentrations of ethidium bromide, which was restored to wild type level in the presence of CCCP, an energy uncoupler altering the energy of the drug efflux pump. Conclusion The 14 RND pumps gene we have identified in the genome of B. cenocepacia suggest that active efflux could be a major mechanism underlying antimicrobial resistance in this microorganism. We have characterized the ORF2 pump, one of these 14 potential RND efflux systems. Its overexpression in E. coli conferred resistance to several antibiotics and to ethidium bromide but it remains to be determined if this pump play a significant role in the antimicrobial intrinsic resistance of B. cenocepacia. The characterization of antibiotic efflux pumps in B

  9. Development of a multiple-locus variable-number tandem-repeat typing scheme for genetic fingerprinting of Burkholderia cenocepacia and application to nationwide epidemiological analysis.

    Science.gov (United States)

    Segonds, Christine; Thouverez, Michelle; Barthe, Antoine; Bossuet-Greif, Nadège; Tisseyre, Lenka; Plésiat, Patrick; Vergnaud, Gilles; Chabanon, Gérard; Pourcel, Christine

    2015-02-01

    Organisms of the Burkholderia cepacia complex are especially important pathogens in cystic fibrosis (CF), with a propensity for patient-to-patient spread and long-term respiratory colonization. B. cenocepacia and Burkholderia multivorans account for the majority of infections in CF, and major epidemic clones have been recognized throughout the world. The aim of the present study was to develop and evaluate a multilocus variable-number tandem-repeat (VNTR) analysis (MLVA) scheme for B. cenocepacia. Potential VNTR loci were identified upon analysis of the annotated genome sequences of B. cenocepacia strains AU1054, J2315, and MCO-3, and 10 of them were selected on the basis of polymorphisms and size. A collection of 100 B. cenocepacia strains, including epidemiologically related and unrelated strains, as well as representatives of the major epidemic lineages, was used to evaluate typeability, epidemiological concordance, and the discriminatory power of MLVA-10 compared with those of pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Longitudinal stability was assessed by testing 39 successive isolates from 14 patients. Typeability ranged from 0.91 to 1, except for that of one marker, which was not amplified in 53% of the B. cenocepacia IIIA strains. The MLVA types were shown to be stable in chronically colonized patients and within outbreak-related strains, with excellent epidemiological concordance. Epidemic and/or globally distributed lineages (epidemic Edinburgh-Toronto electrophoretic type 12 [ET-12], sequence type 32 [ST-32], ST-122, ST-234, and ST-241) were successfully identified. Conversely, the discriminatory power of MLVA was lower than that of PFGE or MLST, although PFGE variations within the epidemic lineages sometimes masked their genetic relatedness. In conclusion, MLVA represents a promising cost-effective first-line tool in B. cenocepacia surveillance.

  10. Sessile drops in microgravity

    CERN Document Server

    Sparavigna, Amelia Carolina

    2013-01-01

    Interfaces with a liquid are governing several phenomena. For instance, these interfaces are giving the shape of sessile droplets and rule the spread of liquids on surfaces. Here we analyze the shape of sessile axisymmetric drops and how it is depending on the gravity, obtaining results in agreement with experimental observations under conditions of microgravity.

  11. NCBI nr-aa BLAST: CBRC-PVAM-01-0284 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-PVAM-01-0284 ref|YP_002233319.1| putative lipoprotein [Burkholderia cenocepaci...a J2315] emb|CAR54555.1| putative lipoprotein [Burkholderia cenocepacia J2315] YP_002233319.1 8e-96 64% ...

  12. Sessile nanofluid droplet drying.

    Science.gov (United States)

    Zhong, Xin; Crivoi, Alexandru; Duan, Fei

    2015-03-01

    Nanofluid droplet evaporation has gained much audience nowadays due to its wide applications in painting, coating, surface patterning, particle deposition, etc. This paper reviews the drying progress and deposition formation from the evaporative sessile droplets with the suspended insoluble solutes, especially nanoparticles. The main content covers the evaporation fundamental, the particle self-assembly, and deposition patterns in sessile nanofluid droplet. Both experimental and theoretical studies are presented. The effects of the type, concentration and size of nanoparticles on the spreading and evaporative dynamics are elucidated at first, serving the basis for the understanding of particle motion and deposition process which are introduced afterward. Stressing on particle assembly and production of desirable residue patterns, we express abundant experimental interventions, various types of deposits, and the effects on nanoparticle deposition. The review ends with the introduction of theoretical investigations, including the Navier-Stokes equations in terms of solutions, the Diffusion Limited Aggregation approach, the Kinetic Monte Carlo method, and the Dynamical Density Functional Theory. Nanoparticles have shown great influences in spreading, evaporation rate, evaporation regime, fluid flow and pattern formation of sessile droplets. Under different experimental conditions, various deposition patterns can be formed. The existing theoretical approaches are able to predict fluid dynamics, particle motion and deposition patterns in the particular cases. On the basis of further understanding of the effects of fluid dynamics and particle motion, the desirable patterns can be obtained with appropriate experimental regulations.

  13. Drag on Sessile Drops

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    Milne, Andrew J. B.; Fleck, Brian; Nobes, David; Sen, Debjyoti; Amirfazli, Alidad; University of Alberta Mechanical Engineering Collaboration

    2013-11-01

    We present the first ever direct measurements of the coefficient of drag on sessile drops at Reynolds numbers from the creeping flow regime up to the point of incipient motion, made using a newly developed floating element differential drag sensor. Surfaces of different wettabilities (PMMA, Teflon, and a superhydrophobic surface (SHS)), wet by water, hexadecane, and various silicone oils, are used to study the effects of drop shape, and fluid properties on drag. The relation between drag coefficient and Reynolds number (scaled by drop height) varies slightly with liquid-solid system and drop volume with results suggesting the drop experiences increased drag compared to similar shaped solid bodies due to drop oscillation influencing the otherwise laminar flow. Drops adopting more spherical shapes are seen to experience the greatest force at any given airspeed. This indicates that the relative exposed areas of drops is an important consideration in terms of force, with implications for the shedding of drops in applications such as airfoil icing and fuel cell flooding. The measurement technique used in this work can be adapted to measure drag force on other deformable, lightly adhered objects such as dust, sand, snow, vesicles, foams, and biofilms. The authours acknowledge NSERC, Alberta Innovates Technology Futures, and the Killam Trusts.

  14. Draft Genome Sequence of Burkholderia cenocepacia Strain 869T2, a Plant-Beneficial Endophytic Bacterium.

    Science.gov (United States)

    Ho, Ying-Ning; Huang, Chieh-Chen

    2015-11-12

    An endophytic bacterium, Burkholderia cenocepacia 869T2, isolated from vetiver grass, has shown its abilities for both in planta biocontrol and plant growth promotion. Its draft genome sequence was determined to provide insights into those metabolic pathways involved in plant-beneficial activity. This is the first genome report for endophytic B. cenocepacia.

  15. Burkholderia cenocepacia zinc metalloproteases influence resistance to antimicrobial peptides.

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    Kooi, Cora; Sokol, Pamela A

    2009-09-01

    Burkholderia cenocepacia secretes two zinc-dependent metalloproteases, designated ZmpA and ZmpB. Previously, ZmpA and ZmpB have been shown to cleave several proteins important in host defence. In this study, the ability of ZmpA and ZmpB to digest and inactivate antimicrobial peptides involved in innate immunity was examined. ZmpB but not ZmpA cleaved beta-defensin-1. ZmpA but not ZmpB cleaved the cathelicidin LL-37. Both enzymes cleaved elafin and secretory leukocyte inhibitor, which are antimicrobial peptides as well as neutrophil elastase inhibitors. Both ZmpA and ZmpB cleaved protamine, a fish antimicrobial peptide, and a zmpA zmpB mutant was more sensitive to protamine killing than the parental strain. ZmpA or ZmpB cleavage of elafin inactivated its anti-protease activity. The effect of ZmpA and ZmpB on the neutrophil proteases elastase and cathepsin G was also examined but neither enzyme was active against these host proteases. These studies suggest that ZmpA and ZmpB may influence the resistance of B. cenocepacia to host antimicrobial peptides as well as alter the host protease/anti-protease balance in chronic respiratory infections.

  16. New identities for sessile drops

    CERN Document Server

    Hajirahimi, Maryam; Fatollahi, Amir H

    2014-01-01

    A new set of mathematical identities is presented for axi-symmetric sessile drops on flat and curved substrates. The geometrical parameters, including the apex curvature and height, and the contact radius, are related by the identities. The validity of the identities are checked by various numerical solutions both for flat and curved substrates.

  17. Hydrodynamics of evaporating sessile drops

    CERN Document Server

    Barash, L Yu

    2010-01-01

    Several dynamical stages of the Marangoni convection of an evaporating sessile drop are obtained. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop and the diffusion of vapor in air. The stages are characterized by different number of vortices in the drop and the spatial location of vortices. During the early stage the array of vortices arises near a surface of the drop and induces a non-monotonic spatial distribution of the temperature over the drop surface. The number of near-surface vortices in the drop is controlled by the Marangoni cell size, which is calculated similar to that given by Pearson for flat fluid layers. The number of vortices quickly decreases with time, resulting in three bulk vortices in the intermediate stage. The vortex structure finally evolves into the single convection vortex in the drop, existing during about 1/2 of the evaporation time.

  18. Draft Genome Sequence of Burkholderia cenocepacia Strain CEIB S5-2, a Methyl Parathion- and p-Nitrophenol-Degrading Bacterium, Isolated from Agricultural Soils in Morelos, Mexico.

    Science.gov (United States)

    Martínez-Ocampo, Fernando; Fernández López, Maikel Gilberto; Lozano-Aguirre Beltrán, Luis Fernando; Popoca-Ursino, Elida Carolina; Ortiz-Hernández, M Laura; Sánchez-Salinas, Enrique; Ramos Quintana, Fernando; Villalobos-López, Miguel A; Dantán-González, Edgar

    2016-04-28

    Burkholderia cenocepacia is an opportunistic pathogen that belongs to Burkholderia cepacia complex (BCC). Burkholderia cenocepacia strain CEIB S5-2 was isolated from agricultural soils in Morelos, Mexico, and previously has shown its abilities for bioremediation. In this study, we report the draft genome sequence of Burkholderia cenocepacia strain CEIB S5-2.

  19. Excited Sessile Drops Perform Harmonically

    CERN Document Server

    Chang, Chun-Ti; Steen, Paul H

    2013-01-01

    In our fluid dynamics video, we demonstrate our method of visualizing and identifying various mode shapes of mechanically oscillated sessile drops. By placing metal mesh under an oscillating drop and projecting light from below, the drop's shape is visualized by the visually deformed mesh pattern seen in the top view. The observed modes are subsequently identified by their number of layers and sectors. An alternative identification associates them with spherical harmonics, as demonstrated in the tutorial. Clips of various observed modes are presented, followed by a 10-second quiz of mode identification.

  20. Burkholderia cenocepacia Strain CEIB S5-1, a Rhizosphere-Inhabiting Bacterium with Potential in Bioremediation

    OpenAIRE

    Martínez-Ocampo, Fernando; Lozano-Aguirre Beltrán, Luis Fernando; Hernández-Mendoza, Armando; Rojas-Espinoza, Luis Enrique; Popoca-Ursino, Elida Carolina; Ortiz-Hernández, María Laura; Sánchez-Salinas, Enrique; Ramos Quintana, Fernando; Dantán-González, Edgar

    2015-01-01

    Burkholderia cenocepacia is considered an opportunistic pathogen from humans and may cause disease in plants. A bioprospection from a plaguicide-contaminated agricultural field in Mexico identified several methyl parathion-degrading bacteria. Here, we report the draft genome sequence of B. cenocepacia strain CEIB S5-1, which gave us clues into ecological biodiversity.

  1. Burkholderia cenocepacia Strain CEIB S5-1, a Rhizosphere-Inhabiting Bacterium with Potential in Bioremediation.

    Science.gov (United States)

    Martínez-Ocampo, Fernando; Lozano-Aguirre Beltrán, Luis Fernando; Hernández-Mendoza, Armando; Rojas-Espinoza, Luis Enrique; Popoca-Ursino, Elida Carolina; Ortiz-Hernández, María Laura; Sánchez-Salinas, Enrique; Ramos Quintana, Fernando; Dantán-González, Edgar

    2015-03-05

    Burkholderia cenocepacia is considered an opportunistic pathogen from humans and may cause disease in plants. A bioprospection from a plaguicide-contaminated agricultural field in Mexico identified several methyl parathion-degrading bacteria. Here, we report the draft genome sequence of B. cenocepacia strain CEIB S5-1, which gave us clues into ecological biodiversity.

  2. Clinafloxacin for Treatment of Burkholderia cenocepacia Infection in a Cystic Fibrosis Patient.

    Science.gov (United States)

    Balwan, Akshu; Nicolau, David P; Wungwattana, Minkey; Zuckerman, Jonathan B; Waters, Valerie

    2016-01-01

    Respiratory infection with Burkholderia cenocepacia is associated with accelerated decline in lung function and increased mortality in cystic fibrosis (CF) patients (A. M. Jones, M. E. Dodd, J. R. W. Govan, V. Barcus, C. J. Doherty, J. Morris, and A. K. Webb, Thorax 59:948-951, 2004, http://dx.doi.org/10.1136/thx.2003.017210). B. cenocepacia often possesses innate resistance to multiple antimicrobial classes, making eradication uncommon in established infection (P. B. Davis, Am J Respir Crit Care Med 173:475-482, 2006, http://dx.doi.org/10.1164/rccm.200505-840OE). We report the use of clinafloxacin in a CF patient with advanced B. cenocepacia infection, present pharmacokinetic (PK) data, and discuss the potential therapeutic role of clinafloxacin in patients with this condition.

  3. Identification of Burkholderia cenocepacia strain H111 virulence factors using nonmammalian infection hosts

    DEFF Research Database (Denmark)

    Schwager, Stephan; Agnoli, Kirsty; Köthe, Manuela;

    2013-01-01

    Burkholderia cenocepacia H111, a strain isolated from a cystic fibrosis patient, has been shown to effectively kill the nematode Caenorhabditis elegans. We used the C. elegans model of infection to screen a mini-Tn5 mutant library of B. cenocepacia H111 for attenuated virulence....... Of the approximately 5,500 B. cenocepacia H111 random mini-Tn5 insertion mutants that were screened, 22 showed attenuated virulence in C. elegans. Except for the quorum-sensing regulator cepR, none of the mutated genes coded for the biosynthesis of classical virulence factors such as extracellular proteases...... or siderophores. Instead, the mutants contained insertions in metabolic and regulatory genes. Mutants attenuated in virulence in the C. elegans infection model were also tested in the Drosophila melanogaster pricking model, and those also attenuated in this model were further tested in Galleria mellonella. Six...

  4. Evaluation of combination therapy for Burkholderia cenocepacia lung infection in different in vitro and in vivo models

    Science.gov (United States)

    Brackman, Gilles; Crabbé, Aurélie; Rigole, Petra; Vercruysse, Jurgen; Verstraete, Glenn; Cappoen, Davie; Vervaet, Chris; Cos, Paul

    2017-01-01

    Burkholderia cenocepacia is an opportunistic pathogen responsible for life-threatening infections in cystic fibrosis patients. B. cenocepacia is extremely resistant towards antibiotics and therapy is complicated by its ability to form biofilms. We investigated the efficacy of an alternative antimicrobial strategy for B. cenocepacia lung infections using in vitro and in vivo models. A screening of the NIH Clinical Collection 1&2 was performed against B. cenocepacia biofilms formed in 96-well microtiter plates in the presence of tobramycin to identify repurposing candidates with potentiator activity. The efficacy of selected hits was evaluated in a three-dimensional (3D) organotypic human lung epithelial cell culture model. The in vivo effect was evaluated in the invertebrate Galleria mellonella and in a murine B. cenocepacia lung infection model. The screening resulted in 60 hits that potentiated the activity of tobramycin against B. cenocepacia biofilms, including four imidazoles of which econazole and miconazole were selected for further investigation. However, a potentiator effect was not observed in the 3D organotypic human lung epithelial cell culture model. Combination treatment was also not able to increase survival of infected G. mellonella. Also in mice, there was no added value for the combination treatment. Although potentiators of tobramycin with activity against biofilms of B. cenocepacia were identified in a repurposing screen, the in vitro activity could not be confirmed nor in a more sophisticated in vitro model, neither in vivo. This stresses the importance of validating hits resulting from in vitro studies in physiologically relevant model systems. PMID:28248999

  5. Correlation for Sessile Drop Evaporation

    Science.gov (United States)

    Kelly-Zion, Peter; Pursell, Christopher; Wassom, Gregory; Mandelkorn, Brenton; Nkinthorn, Chris

    2016-11-01

    To better understand how the evaporation of sessile drops and small puddles is controlled by the vapor phase transport mechanisms of mass diffusion and buoyancy-induced convection, the evaporation rates of eight liquids evaporating under a broad range of ambient conditions were correlated with physical and geometrical properties. Examination of the correlation provides valuable insight into how the roles of diffusive and convective transport change with physical and geometrical parameters. The correlation predicts measured evaporation rates to within a root-mean-square error of 7.3%. The correlation is composed of two terms, a term which provides the rate of evaporation under diffusion-only conditions, and a term which provides the influence of convection. This second term suggests the manner in which the processes of diffusion and convection are coupled. Both processes are dependent on the distribution of the vapor, through the molar concentration gradient for diffusion and through the mass density gradient for convection. The term representing the influence of convection is approximately inversely proportional to the square root of diffusivity, indicating the tendency of diffusive transport to reduce convection by making the vapor distribution more uniform. Financial support was provided by the ACS Petroleum Research Fund.

  6. Numerical simulations of vibrating sessile drop

    Science.gov (United States)

    Kahouadji, Lyes; Chergui, Jalel; Juric, Damir; Shin, Seungwon; Craster, Richard; Matar, Omar

    2016-11-01

    A vibrated drop constitutes a very rich physical system, blending both interfacial and volume phenomena. A remarkable experimental study was performed by M. Costalonga highlighting sessile drop motion subject to horizontal, vertical and oblique vibration. Several intriguing phenomena are observed such as drop walking and rapid droplet ejection. We perform three-dimensional direct numerical simulations of vibrating sessile drops where the phenomena described above are computed using the massively parallel multiphase code BLUE. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).

  7. Cyanide toxicity to Burkholderia cenocepacia is modulated by polymicrobial communities and environmental factors

    Directory of Open Access Journals (Sweden)

    Steve P. Bernier

    2016-05-01

    Full Text Available Microbes within polymicrobial communities can establish positive and negative interactions that have the potential to influence the overall behaviour of the community. Pseudomonas aeruginosa and species of the Burkholderia cepacia complex (Bcc can co-exist in the lower airways, however several studies have shown that P. aeruginosa can effectively kill the Bcc in vitro, for which hydrogen cyanide was recently proposed to play a critical role. Here we show that modification of the environment (i.e. culture medium, long-term genetic adaptation of P. aeruginosa to the cystic fibrosis (CF lung, or the addition of another bacterial species to the community can alter the sensitivity of Burkholderia cenocepacia to P. aeruginosa toxins. We specifically demonstrate that undefined rich media leads to higher susceptibility of B. cenocepacia to P. aeruginosa toxins like cyanide as compared to a synthetic medium (SCFM, that mimics the CF lung nutritional content. Overall, our study shows that the polymicrobial environment can have profound effects on negative interactions mediated by P. aeruginosa against B. cenocepacia. In fact, evolved P. aeruginosa or the presence of other species such as Staphylococcus aureus can directly abolish the direct competition mediated by cyanide and consequently maintaining a higher level of species diversity within the community.

  8. Discovery of new diketopiperazines inhibiting Burkholderia cenocepacia quorum sensing in vitro and in vivo

    Science.gov (United States)

    Scoffone, Viola C.; Chiarelli, Laurent R.; Makarov, Vadim; Brackman, Gilles; Israyilova, Aygun; Azzalin, Alberto; Forneris, Federico; Riabova, Olga; Savina, Svetlana; Coenye, Tom; Riccardi, Giovanna; Buroni, Silvia

    2016-01-01

    Burkholderia cenocepacia, an opportunistic respiratory pathogen particularly relevant for cystic fibrosis patients, is difficult to eradicate due to its high level of resistance to most clinically relevant antimicrobials. Consequently, the discovery of new antimicrobials as well as molecules capable of inhibiting its virulence is mandatory. In this regard quorum sensing (QS) represents a good target for anti-virulence therapies, as it has been linked to biofilm formation and is important for the production of several virulence factors, including proteases and siderophores. Here, we report the discovery of new diketopiperazine inhibitors of the B. cenocepacia acyl homoserine lactone synthase CepI, and report their anti-virulence properties. Out of ten different compounds assayed against recombinant CepI, four were effective inhibitors, with IC50 values in the micromolar range. The best compounds interfered with protease and siderophore production, as well as with biofilm formation, and showed good in vivo activity in a Caenorhabditis elegans infection model. These molecules were also tested in human cells and showed very low toxicity. Therefore, they could be considered for in vivo combined treatments with established or novel antimicrobials, to improve the current therapeutic strategies against B. cenocepacia. PMID:27580679

  9. Remote control of moving sessile droplets

    CERN Document Server

    Noblin, Xavier; Celestini, Franck

    2010-01-01

    We recently put in evidence (\\cite{noblin2}) that combined vertical and horizontal vibrations can induced a controlled motion of a sessile supported drop. In this video we generalize this finding and demonstrate that a remote 2d controlled motion is possible. This video was submitted as part of the Gallery of Fluid Motion 2010 which is showcase of fluid dynamics videos.

  10. Reciprocal regulation by the CepIR and CciIR quorum sensing systems in Burkholderia cenocepacia

    Directory of Open Access Journals (Sweden)

    Malott Rebecca J

    2009-09-01

    Full Text Available Abstract Background Burkholderia cenocepacia belongs to a group of closely related organisms called the B. cepacia complex (Bcc which are important opportunistic human pathogens. B. cenocepacia utilizes a mechanism of cell-cell communication called quorum sensing to control gene expression including genes involved in virulence. The B. cenocepacia quorum sensing network includes the CepIR and CciIR regulatory systems. Results Global gene expression profiles during growth in stationary phase were generated using microarrays of B. cenocepacia cepR, cciR and cepRcciIR mutants. This is the first time CciR was shown to be a global regulator of quorum sensing gene expression. CepR was primarily responsible for positive regulation of gene expression while CciR generally exerted negative gene regulation. Many of the genes that were regulated by both quorum sensing systems were reciprocally regulated by CepR and CciR. Microarray analysis of the cepRcciIR mutant suggested that CepR is positioned upstream of CciR in the quorum sensing hierarchy in B. cenocepacia. A comparison of CepIR-regulated genes identified in previous studies and in the current study showed a substantial amount of overlap validating the microarray approach. Several novel quorum sensing-controlled genes were confirmed using qRT-PCR or promoter::lux fusions. CepR and CciR inversely regulated flagellar-associated genes, the nematocidal protein AidA and a large gene cluster on Chromosome 3. CepR and CciR also regulated genes required for iron transport, synthesis of extracellular enzymes and surface appendages, resistance to oxidative stress, and phage-related genes. Conclusion For the first time, the influence of CciIR on global gene regulation in B. cenocepacia has been elucidated. Novel genes under the control of the CepIR and CciIR quorum sensing systems in B. cenocepacia have been identified. The two quorum sensing systems exert reciprocal regulation of many genes likely enabling fine

  11. Phenylalanine induces Burkholderia cenocepacia phenylacetic acid catabolism through degradation to phenylacetyl-CoA in synthetic cystic fibrosis sputum medium.

    Science.gov (United States)

    Yudistira, Harry; McClarty, Leigh; Bloodworth, Ruhi A M; Hammond, Sydney A; Butcher, Haley; Mark, Brian L; Cardona, Silvia T

    2011-09-01

    Synthetic cystic fibrosis sputum medium (SCFM) is rich in amino acids and supports robust growth of Burkholderia cenocepacia, a member of the Burkholderia cepacia complex (Bcc). Previous work demonstrated that B. cenocepacia phenylacetic acid (PA) catabolic genes are up-regulated during growth in SCFM and are required for full virulence in a Caenorhabditis elegans host model. In this work, we investigated the role of phenylalanine, one of the aromatic amino acids present in SCFM, as an inducer of the PA catabolic pathway. Phenylalanine degradation intermediates were used as sole carbon sources for growth and gene reporter experiments. In addition to phenylalanine and PA, phenylethylamine, phenylpyruvate, and 2-phenylacetamide were usable as sole carbon sources by wild type B. cenocepacia K56-2, but not by a PA catabolism-defective mutant. EMSA analysis showed that the binding of PaaR, the negative regulator protein of B. cenocepacia PA catabolism, to PA regulatory DNA could only be relieved by phenylacetyl-Coenzyme A (PA-CoA), but not by any of the putative phenylalanine degradation intermediates. Taken together, our results show that in B. cenocepacia, phenylalanine is catabolized to PA and induces PA catabolism through PA activation to PA-CoA. Thus, PaaR shares the same inducer with PaaX, the regulator of PA catabolism in Escherichia coli, despite belonging to a different protein family.

  12. Sessile droplet evaporation on superheated superhydrophobic surfaces

    CERN Document Server

    Hays, Robb C; Maynes, Daniel; Webb, Brent W

    2013-01-01

    This fluid dynamics video depicts the evaporation of sessile water droplets placed on heated superhydrophobic (SH) surfaces of varying cavity fraction, F_c, and surface temperature, T_s, above the saturation temperature, T_sat. Images were captured at 10,000 FPS and are played back at 30 FPS in this video. Teflon-coated silicon surfaces of F_c = 0, 0.5, 0.8, and 0.95 were used for these experiments. T_s ranging from 110{\\deg}C to 210{\\deg}C were studied. The video clips show how the boiling behavior of sessile droplets is altered with changes in surface microstructure. Quantitative results from heat transfer rate experiments conducted by the authors are briefly discussed near the end of the video.

  13. Footprint Geometry and Sessile Drop Resonance

    Science.gov (United States)

    Chang, Chun-Ti; Daniel, Susan; Steen, Paul H.

    2016-11-01

    How does a sessile drop resonate if its footprint is square (square drop)? In this talk, we discuss the two distinct families of observed modes in our experiments. One family (spherical modes) is identified with the natural modes of capillary spherical caps, and the other (grid modes) with Faraday waves on a square bath (square Faraday waves). A square drop exhibits grid or spherical modes depending on its volume, and the two families of modes arise depending on how wavenumber selection of footprint geometry and capillarity compete. For square drops, a dominant effect of footprint constraint leads to grid modes which are constrained response; otherwise the drops exhibit spherical modes, the characteristic of sessile drops on flat plates. Chun-Ti Chang takes his new position at National Taiwan University on Aug. 15th, 2016. Until then, Chun-Ti Chang is affiliated with Technical University Dortmund, Germany.

  14. Sessile Drop Evaporation and Leidenfrost Phenomenon

    OpenAIRE

    A. K. Mozumder; M. R. Ullah; Hossain, A.; Islam, M A

    2010-01-01

    Problem statement: Quenching and cooling are important process in manufacturing industry for controlling the mechanical properties of materials, where evaporation is a vital mode of heat transfer. Approach: This study experimentally investigated the evaporation of sessile drop for four different heated surfaces of Aluminum, Brass, Copper and Mild steel with a combination of four different liquids as Methanol, Ethanol, Water and NaCl solution. The time of evaporation for the droplet on the hot...

  15. Sessile drop deformations under an impinging jet

    Science.gov (United States)

    Feng, James Q.

    2015-08-01

    The problem of steady axisymmetric deformations of a liquid sessile drop on a flat solid surface under an impinging gas jet is of interest for understanding the fundamental behavior of free surface flows as well as for establishing the theoretical basis in process design for the Aerosol direct-write technology. It is studied here numerically using a Galerkin finite-element method, by computing solutions of Navier-Stokes equations. For effective material deposition in Aerosol printing, the desired value of Reynolds number for the laminar gas jet is found to be greater than ~500. The sessile drop can be severely deformed by an impinging gas jet when the capillary number is approaching a critical value beyond which no steady axisymmetric free surface deformation can exist. Solution branches in a parameter space show turning points at the critical values of capillary number, which typically indicate the onset of free surface shape instability. By tracking solution branches around turning points with an arc-length continuation algorithm, critical values of capillary number can be accurately determined. Near turning points, all the free surface profiles in various parameter settings take a common shape with a dimple at the center and bulge near the contact line. An empirical formula for the critical capillary number for sessile drops with contact angle is derived for typical ranges of jet Reynolds number and relative drop sizes especially pertinent to Aerosol printing.

  16. FUNGAL ASSOCIATION WITH SESSILE MARINE INVERTEBRATES

    Directory of Open Access Journals (Sweden)

    Oded eYarden

    2014-05-01

    Full Text Available The presence and association of fungi with sessile marine animals such as coral and sponges has been well established, yet information on the extent of diversity of the associated fungi is still in its infancy. Culture- as well as metagenomic- and transcriptomic-based analyses have shown that fungal presence in association with these animals can be dynamic and can include core residents as well as shifts in fungal communities. Evidence for detrimental and beneficial interactions between fungi and their marine hosts is accumulating and current challenges include the elucidation of the chemical and cellular crosstalk between fungi and their associates within the holobionts. The ecological function of fungi in association with sessile marine animals is complex and is founded on a combination of factors such as fungal origin, host health, environmental conditions and the presence of other resident or invasive microorganisms in the host. Based on evidence from the much more studied terrestrial systems, the evaluation of marine animal-fungal symbioses under varying environmental conditions may well prove to be critical in predicting ecosystem response to global change, including effects on the health of sessile marine animals.

  17. Strains of Burkholderia cenocepacia genomovar IIIA possessing the cblA gene that are distinct from ET12.

    Science.gov (United States)

    Turton, Jane F; O'Brien, Emily; Megson, Brian; Kaufmann, Mary E; Pitt, Tyrone L

    2009-05-01

    Three strains of Burkholderia cenocepacia genomovar IIIA that were polymerase chain reaction positive for cblA, bcrA, and the epidemic strain marker, but were distinct from representatives of ET12 by pulsed-field gel electrophoresis, are described. One of these strains was shown to express cable pili by electron microscopy.

  18. Kinetic characterization of an oxidative, cooperative HMG-CoA reductase from Burkholderia cenocepacia.

    Science.gov (United States)

    Schwarz, Benjamin H; Driver, Joseph; Peacock, Riley B; Dembinski, Holly E; Corson, Melissa H; Gordon, Samuel S; Watson, Jeffrey M

    2014-02-01

    3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) is a key enzyme in endogenous cholesterol biosynthesis in mammals and isoprenoid biosynthesis via the mevalonate pathway in other eukaryotes, archaea and some eubacteria. In most organisms that express this enzyme, it catalyzes the NAD(P)H-dependent reduction of HMG-CoA to mevalonate. We have cloned and characterized the 6x-His-tagged HMGR from the opportunistic lung pathogen Burkholderia cenocepacia. Kinetic characterization shows that the enzyme prefers NAD(H) over NADP(H) as a cofactor, suggesting an oxidative physiological role for the enzyme. This hypothesis is supported by the fact that the Burkholderia cenocepacia genome lacks the genes for the downstream enzymes of the mevalonate pathway. The enzyme exhibits positive cooperativity toward the substrates of the reductive reaction, but the oxidative reaction exhibits unusual double-saturation kinetics, distinctive among characterized HMG-CoA reductases. The unusual kinetics may arise from the presence of multiple active oligomeric states, each with different Vmax values.

  19. Biofilms produced by Burkholderia cenocepacia: influence of media and solid supports on composition of matrix exopolysaccharides.

    Science.gov (United States)

    Pellizzoni, Elena; Ravalico, Fabio; Scaini, Denis; Delneri, Ambra; Rizzo, Roberto; Cescutti, Paola

    2016-02-01

    Bacteria usually grow forming biofilms, which are communities of cells embedded in a self-produced dynamic polymeric matrix, characterized by a complex three-dimensional structure. The matrix holds cells together and above a surface, and eventually releases them, resulting in colonization of other surfaces. Although exopolysaccharides (EPOLs) are important components of the matrix, determination of their structure is usually performed on samples produced in non-biofilm conditions, or indirectly through genetic studies. Among the Burkholderia cepacia complex species, Burkholderia cenocepacia is an important pathogen in cystic fibrosis (CF) patients and is generally more aggressive than other species. In the present investigation, B. cenocepacia strain BTS2, a CF isolate, was grown in biofilm mode on glass slides and cellulose membranes, using five growth media, one of which mimics the nutritional content of CF sputum. The structure of the matrix EPOLs was determined by 1H-NMR spectroscopy, while visualization of the biofilms on glass slides was obtained by means of confocal laser microscopy, phase-contrast microscopy and atomic force microscopy. The results confirmed that the type of EPOLs biosynthesized depends both on the medium used and on the type of support, and showed that mucoid conditions do not always lead to significant biofilm production, while bacteria in a non-mucoid state can still form biofilm containing EPOLs.

  20. Mass Remaining During Evaporation of Sessile Drop

    Science.gov (United States)

    2008-09-01

    to> \\fyj Greek Symbols P Contact angle of sessile drop . n Droplet shape factor = h/d 6 Non-dimensional time = t/i V Air kinematic viscosity...factor n, = h / d (where h = maximum height of the drop ), which can also be directly related to the contact angle (P) of the drop , that is r| = (l-cos(P...three drop size (initial mass or volume) conditions with all other conditions the same. These runs have a constant contact angle , (3 = 16.5° ± 1.5

  1. Survival dynamics of cystic fibrosis-related Gram-negative bacterial pathogens (Pseudomonas aeruginosa and Burkholderia cenocepacia) in Dead Sea and Atlantic Ocean waters.

    Science.gov (United States)

    Shteinberg, Michal; Kis-Papo, Tamar; Millar, Beverley C; Rendall, Jacqueline C; Downey, Damian G; Elborn, J Stuart; Moore, John E

    2015-09-01

    Clinical cystic fibrosis (CF) Pseudomonas aeruginosa (n=6) and Burkholderia cenocepacia (n=4) were inoculated in marine brines from the Dead Sea and the Atlantic Ocean and their survival was monitored over a 1 month duration. In Dead Sea samples, all P. aeruginosa and B. cenocepacia isolates were non-detectable by culture following 24 h incubation, including the non-selective enrichment samples. In the Atlantic Ocean brine, over a 1 month period, mean P. aeruginosa counts decreased by only 0.25 log10 units and mean B. cenocepacia counts decreased by approximately 4 log10 units (10,000 cfu/ml). This study demonstrated that Dead Sea brine exerted a lethal effect within 24 h on planktonic P. aeruginosa and B. cenocepacia. Thus, the Dead Sea effectively purges these organisms from its environment on a daily basis.

  2. The CRP/FNR family protein Bcam1349 is a c-di-GMP effector that regulates biofilm formation in the respiratory pathogen Burkholderia cenocepacia

    DEFF Research Database (Denmark)

    Fazli, Mustafa; O'Connell, Aileen; Nilsson, Martin

    2011-01-01

    to control a wide range of functions in bacteria, but little is known about these regulatory mechanisms in B. cenocepacia. Here we investigated the role that c-di-GMP plays in the regulation of biofilm formation and virulence in B. cenocepacia. Elevated intracellular levels of c-di-GMP promoted wrinkly...... colony, pellicle and biofilm formation in B. cenocepacia. A screen for transposon mutants unable to respond to elevated levels of c-di-GMP led to the identification of the mutant bcam1349 that did not display increased biofilm and pellicle formation with excessive c-di-GMP levels, and displayed a biofilm...... larvae infection model. Taken together, these findings suggest that the Bcam1349 protein is a transcriptional regulator that binds c-di-GMP and regulates biofilm formation and virulence in B. cenocepacia in response to the level of c-di-GMP....

  3. Electric field induced deformation of sessile drops

    Science.gov (United States)

    Corson, Lindsey; Tsakonas, Costas; Duffy, Brian; Mottram, Nigel; Brown, Carl; Wilson, Stephen

    2014-11-01

    The ability to control the shape of a drop with the application of an electric field has been exploited for many technological applications including measuring surface tension, producing an optical display device, and optimising the optical properties of microlenses. In this work we consider, both theoretically and experimentally, the deformation of pinned sessile drops with contact angles close to either 0° or 90° resting on the lower substrate inside a parallel plate capacitor due to an A.C. electric field. Using both asymptotic and numerical approaches we obtain predictive equations for the static and dynamic drop shape deformations as functions of the key experimental parameters (drop size, capacitor plate separation, electric field magnitude and contact angle). The asymptotic results agree well with the experimental results for a range of liquids. We gratefully acknowledge the financial support of EPSRC via research Grants EP/J009865 and EP/J009873.

  4. Sessile Drop Evaporation and Leidenfrost Phenomenon

    Directory of Open Access Journals (Sweden)

    A. K. Mozumder

    2010-01-01

    Full Text Available Problem statement: Quenching and cooling are important process in manufacturing industry for controlling the mechanical properties of materials, where evaporation is a vital mode of heat transfer. Approach: This study experimentally investigated the evaporation of sessile drop for four different heated surfaces of Aluminum, Brass, Copper and Mild steel with a combination of four different liquids as Methanol, Ethanol, Water and NaCl solution. The time of evaporation for the droplet on the hot metallic surface was measured and compared with a proposed correlation as well. With the time temperature plot of these experimental data, the Leidenfrost phenomena had been elucidated. In the pool boiling curve for liquid, just after the transition boiling region and before the film boiling region, the heat transfer approaches its minimum value. The corresponding temperature of this minimum value was termed as the Leidenfrost temperature and the phenomenon is known as Leidenfrost phenomena. According to the experimental data, the Leidenfrost temperature was within a range of 150-200°C for all the experimental conditions. Results: This revealed that Leidenfrost temperature was independent of thermo-physical properties of solid and liquid. Sessile drop evaporation time was the maximum for water, then decreases gradually for Nacl solution, methanol and was the minimum for ethanol for a particular solid material. On the other hand, this time was the highest for copper and the lowest for mild steel for a specific liquid. Conclusion: The experimental data for the evaporation time fairly agree with the proposed correlation within a certain range. The collected time and temperature data may be used as a good data bank for the researchers.

  5. Comparative analysis of two phenotypically-similar but genomically-distinct Burkholderia cenocepacia-specific bacteriophages

    Directory of Open Access Journals (Sweden)

    Lynch Karlene H

    2012-06-01

    Full Text Available Abstract Background Genomic analysis of bacteriophages infecting the Burkholderia cepacia complex (BCC is an important preliminary step in the development of a phage therapy protocol for these opportunistic pathogens. The objective of this study was to characterize KL1 (vB_BceS_KL1 and AH2 (vB_BceS_AH2, two novel Burkholderia cenocepacia-specific siphoviruses isolated from environmental samples. Results KL1 and AH2 exhibit several unique phenotypic similarities: they infect the same B. cenocepacia strains, they require prolonged incubation at 30°C for the formation of plaques at low titres, and they do not form plaques at similar titres following incubation at 37°C. However, despite these similarities, we have determined using whole-genome pyrosequencing that these phages show minimal relatedness to one another. The KL1 genome is 42,832 base pairs (bp in length and is most closely related to Pseudomonas phage 73 (PA73. In contrast, the AH2 genome is 58,065 bp in length and is most closely related to Burkholderia phage BcepNazgul. Using both BLASTP and HHpred analysis, we have identified and analyzed the putative virion morphogenesis, lysis, DNA binding, and MazG proteins of these two phages. Notably, MazG homologs identified in cyanophages have been predicted to facilitate infection of stationary phase cells and may contribute to the unique plaque phenotype of KL1 and AH2. Conclusions The nearly indistinguishable phenotypes but distinct genomes of KL1 and AH2 provide further evidence of both vast diversity and convergent evolution in the BCC-specific phage population.

  6. Burkholderia cenocepacia Differential Gene Expression during Host–Pathogen Interactions and Adaptation to the Host Environment

    Science.gov (United States)

    O’Grady, Eoin P.; Sokol, Pamela A.

    2011-01-01

    Members of the Burkholderia cepacia complex (Bcc) are important in medical, biotechnological, and agricultural disciplines. These bacteria naturally occur in soil and water environments and have adapted to survive in association with plants and animals including humans. All Bcc species are opportunistic pathogens including Burkholderia cenocepacia that causes infections in cystic fibrosis and chronic granulomatous disease patients. The adaptation of B. cenocepacia to the host environment was assessed in a rat chronic respiratory infection model and compared to that of high cell-density in vitro grown cultures using transcriptomics. The distribution of genes differentially expressed on chromosomes 1, 2, and 3 was relatively proportional to the size of each genomic element, whereas the proportion of plasmid-encoded genes differentially expressed was much higher relative to its size and most genes were induced in vivo. The majority of genes encoding known virulence factors, components of types II and III secretion systems and chromosome 2-encoded type IV secretion system were similarly expressed between in vitro and in vivo environments. Lower expression in vivo was detected for genes encoding N-acyl-homoserine lactone synthase CepI, orphan LuxR homolog CepR2, zinc metalloproteases ZmpA and ZmpB, LysR-type transcriptional regulator ShvR, nematocidal protein AidA, and genes associated with flagellar motility, Flp type pilus formation, and type VI secretion. Plasmid-encoded type IV secretion genes were markedly induced in vivo. Additional genes induced in vivo included genes predicted to be involved in osmotic stress adaptation or intracellular survival, metal ion, and nutrient transport, as well as those encoding outer membrane proteins. Genes identified in this study are potentially important for virulence during host–pathogen interactions and may be associated with survival and adaptation to the host environment during chronic lung infections. PMID:22919581

  7. Records of Australian Fouling Organisms: Sessile Barnacles (Crustacea, Cirripedia),

    Science.gov (United States)

    1981-04-01

    Dr. W.A. Newman) Laboratorio de Ensayo de Materiales e Investigaciones Tecnologicas (LEMIT), Argentina. (Attention: Dr. V. Rascio) Dept. of Zoology...AD-A105 265 MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA) FIG B/1 RECORDS OF AUSTRALIAN FOULING ORGANISMS: SESSILE BARNACLES (CRU--ETC(U) APR 81 J A...SCIENCE AND TECHNOLOGY ORGANISATION MATERIALS RESEARCH LABORATORIES MELBOURNE, VICTORIA REPORT . MRL-R-809 RECORDS OF AUSTRALIAN FOULING ORGANISMS: SESSILE

  8. Hydrodynamics and evaporation of a sessile drop of capillary size

    CERN Document Server

    Barash, L Yu

    2010-01-01

    Fluid dynamics video of an evaporating sessile drop of capillary size is presented. The corresponding simulation represents the description taking into account jointly time dependent hydrodynamics, vapor diffusion and thermal conduction in an evaporating sessile drop. The fluid convection in the drop is driven by Marangoni forces associated with the temperature dependence of the surface tension. For the first time the evolution of the vortex structure in the drop during an evaporation process is obtained.

  9. Hydrodynamics and evaporation of a sessile drop of capillary size

    OpenAIRE

    Barash, L. Yu.

    2010-01-01

    Fluid dynamics video of an evaporating sessile drop of capillary size is presented. The corresponding simulation represents the description taking into account jointly time dependent hydrodynamics, vapor diffusion and thermal conduction in an evaporating sessile drop. The fluid convection in the drop is driven by Marangoni forces associated with the temperature dependence of the surface tension. For the first time the evolution of the vortex structure in the drop during an evaporation process...

  10. PARTICLE DEPOSITION ON SUPERHYDROPHOBIC SURFACES BY SESSILE DROPLET EVAPORATION

    OpenAIRE

    Dicuangco, Mercy G.

    2014-01-01

    Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hyd...

  11. A Pipeline for Screening Small Molecules with Growth Inhibitory Activity against Burkholderia cenocepacia.

    Directory of Open Access Journals (Sweden)

    Carrie Selin

    Full Text Available Infections with the bacteria Burkholderia cepacia complex (Bcc are very difficult to eradicate in cystic fibrosis patients due the intrinsic resistance of Bcc to most available antibiotics and the emergence of multiple antibiotic resistant strains during antibiotic treatment. In this work, we used a whole-cell based assay to screen a diverse collection of small molecules for growth inhibitors of a relevant strain of Bcc, B. cenocepacia K56-2. The primary screen used bacterial growth in 96-well plate format and identified 206 primary actives among 30,259 compounds. From 100 compounds with no previous record of antibacterial activity secondary screening and data mining selected a total of Bce bioactives that were further analyzed. An experimental pipeline, evaluating in vitro antibacterial and antibiofilm activity, toxicity and in vivo antibacterial activity using C. elegans was used for prioritizing compounds with better chances to be further investigated as potential Bcc antibacterial drugs. This high throughput screen, along with the in vitro and in vivo analysis highlights the utility of this experimental method to quickly identify bioactives as a starting point of antibacterial drug discovery.

  12. Interactions of Burkholderia cenocepacia and other Burkholderia cepacia complex bacteria with epithelial and phagocytic cells.

    Science.gov (United States)

    Saldías, M Soledad; Valvano, Miguel A

    2009-09-01

    Burkholderia cenocepacia is a member of the B. cepacia complex (Bcc), a group of opportunistic bacteria that infect the airways of patients with cystic fibrosis (CF) and are extraordinarily resistant to almost all clinically useful antibiotics. Infections in CF patients with Bcc bacteria generally lead to a more rapid decline in lung function, and in some cases to the 'cepacia syndrome', a virtually deadly exacerbation of the lung infection with systemic manifestations. These characteristics of Bcc bacteria contribute to higher morbidity and mortality in infected CF patients. In the last 10 years considerable progress has been made in understanding the interactions between Bcc bacteria and mammalian host cells. Bcc isolates can survive either intracellularly within eukaryotic cells or extracellularly in host tissues. They survive within phagocytes and respiratory epithelial cells, and they have the ability to breach the respiratory epithelium layer. Survival and persistence of Bcc bacteria within host cells and tissues are believed to play a key role in pulmonary infection and to contribute to the persistent inflammation observed in patients with CF. This review summarizes recent findings concerning the interaction between Bcc bacteria and epithelial and phagocytic cells.

  13. The exopolysaccharide gene cluster Bcam1330-Bcam1341 is involved in Burkholderia cenocepacia biofilm formation, and its expression is regulated by c-di-GMP and Bcam1349

    DEFF Research Database (Denmark)

    Fazli, Mustafa; McCarthy, Yvonne; Givskov, Michael

    2013-01-01

    In Burkholderia cenocepacia, the second messenger cyclic diguanosine monophosphate (c-di-GMP) has previously been shown to positively regulate biofilm formation and the expression of cellulose and type-I fimbriae genes through binding to the transcriptional regulator Bcam1349. Here, we provide...... evidence that cellulose and type-I fimbriae are not involved in B. cenocepacia biofilm formation in flow chambers, and we identify a novel Bcam1349/c-di-GMP-regulated exopolysaccharide gene cluster which is essential for B. cenocepacia biofilm formation. Overproduction of Bcam1349 in trans promotes wrinkly...... matrix exopolysaccharide and to be essential for flow-chamber biofilm formation. We demonstrate that Bcam1349 binds to the promoter region of genes in the Bcam1330-Bcam1341 cluster and that this binding is enhanced by the presence of c-di-GMP. Furthermore, we demonstrate that overproduction of both c...

  14. Genetic relationships among Italian and Mexican maize-rhizosphere Burkholderia cepacia complex (BCC populations belonging to Burkholderia cenocepacia IIIB and BCC6 group

    Directory of Open Access Journals (Sweden)

    Bevivino Annamaria

    2011-10-01

    Full Text Available Abstract Background A close association between maize roots and Burkholderia cepacia complex (BCC bacteria has been observed in different locations globally. In this study we investigated by MultiLocus Restriction Typing (MLRT the genetic diversity and relationships among Burkholderia cenocepacia IIIB and BCC6 populations associated with roots of maize plants cultivated in geographically distant countries (Italy and Mexico, in order to provide new insights into their population structure, evolution and ecology. Results The 31 B. cenocepacia IIIB and 65 BCC6 isolates gave rise to 29 and 39 different restriction types (RTs, respectively. Two pairs of isolates of B. cenocepacia IIIB and BCC6, recovered from both Italian and Mexican maize rhizospheres, were found to share the same RT. The eBURST (Based Upon Related Sequence Types analysis of MLRT data grouped all the B. cenocepacia IIIB isolates into four clonal complexes, with the RT-4-complex including the 42% of them, while the majority of the BCC6 isolates (94% were grouped into the RT-104-complex. These two main clonal complexes included RTs shared by both Italian and Mexican maize rhizospheres and a clear relationship between grouping and maize variety was also found. Grouping established by eBURST correlated well with the assessment using unweighted-pair group method with arithmetic mean (UPGMA. The standardized index of association values obtained in both B. cenocepacia IIIB and BCC6 suggests an epidemic population structure in which occasional clones emerge and spread. Conclusions Taken together our data demonstrate a wide dispersal of certain B. cenocepacia IIIB and BCC6 isolates in Mexican and Italian maize rhizospheres. Despite the clear relationship found between the geographic origin of isolates and grouping, identical RTs and closely related isolates were observed in geographically distant regions. Ecological factors and selective pressure may preferably promote some genotypes within

  15. Surface tension of molten tin investigated with sessile drop method

    Institute of Scientific and Technical Information of China (English)

    LI Jing; YUAN Zhang-fu; FAN Jian-feng; KE Jia-jun

    2005-01-01

    The surface tension of molten tin was determined by a set of self-developed digital equipment with sessile drop method at oxygen partial pressure of 1.0 × 10-6 MPa under different temperatures, and the dependence of surface tension of molten tin on temperature was also discussed. The emphasis was placed on the comparison of surface tension of the same molten tin sample measured by using different equipments with sessile drop method. Results of the comparison indicate that the measurement results with sessile drop method under the approximate experimental conditions are coincident, and the self-developed digital equipment for surface tension measurement has higher stability and accuracy. The relationships of surface tension of molten tin and its temperature coefficient with temperature and oxygen partial pressure were also elucidated from the thermodynamic equilibrium analysis.

  16. The Vibration of an Inviscid Incompressible Sessile Drop

    Science.gov (United States)

    Smith, Marc

    2009-11-01

    The fundamental frequencies and normal modes of vibration of a sessile drop supported on a horizontal planar surface are found using an integrated analytical and numerical technique. Spherical coordinates are used to describe the interface shape, but the potential flow field inside the drop is computed numerically using the finite element method. The numerical velocity potentials at the interface for both the fluid inside the drop and outside are fitted using a Legendre series. When these series are combined in the interfacial normal-stress balance the result is a linear eigenvalue problem that is solved numerically. Results will be presented for sessile drops with different contact angles without gravity and compared to experimental data. This technique can also be extended to sessile drops with gravity, in which the drop shape is flattened, and to substrate geometries that are not planar, such as a drop in a shallow cavity or hole.

  17. Putrescine reduces antibiotic-induced oxidative stress as a mechanism of modulation of antibiotic resistance in Burkholderia cenocepacia.

    Science.gov (United States)

    El-Halfawy, Omar M; Valvano, Miguel A

    2014-07-01

    Communication of antibiotic resistance among bacteria via small molecules is implicated in transient reduction of bacterial susceptibility to antibiotics, which could lead to therapeutic failures aggravating the problem of antibiotic resistance. Released putrescine from the extremely antibiotic-resistant bacterium Burkholderia cenocepacia protects less-resistant cells from different species against the antimicrobial peptide polymyxin B (PmB). Exposure of B. cenocepacia to sublethal concentrations of PmB and other bactericidal antibiotics induces reactive oxygen species (ROS) production and expression of the oxidative stress response regulator OxyR. We evaluated whether putrescine alleviates antibiotic-induced oxidative stress. The accumulation of intracellular ROS, such as superoxide ion and hydrogen peroxide, was assessed fluorometrically with dichlorofluorescein diacetate, while the expression of OxyR and putrescine synthesis enzymes was determined in luciferase assays using chromosomal promoter-lux reporter system fusions. We evaluated wild-type and isogenic deletion mutant strains with defects in putrescine biosynthesis after exposure to sublethal concentrations of PmB and other bactericidal antibiotics. Exogenous putrescine protected against oxidative stress induced by PmB and other antibiotics, whereas reduced putrescine synthesis resulted in increased ROS generation and a parallel increased sensitivity to PmB. Of the 3 B. cenocepacia putrescine-synthesizing enzymes, PmB induced only BCAL2641, an ornithine decarboxylase. This study reveals BCAL2641 as a critical component of the putrescine-mediated communication of antibiotic resistance and as a plausible target for designing inhibitors that would block the communication of such resistance among different bacteria, ultimately reducing the window of therapeutic failure in treating bacterial infections.

  18. Burkholderia cenocepacia type VI secretion system mediates escape of type II secreted proteins into the cytoplasm of infected macrophages.

    Directory of Open Access Journals (Sweden)

    Roberto Rosales-Reyes

    Full Text Available Burkholderia cenocepacia is an opportunistic pathogen that survives intracellularly in macrophages and causes serious respiratory infections in patients with cystic fibrosis. We have previously shown that bacterial survival occurs in bacteria-containing membrane vacuoles (BcCVs resembling arrested autophagosomes. Intracellular bacteria stimulate IL-1β secretion in a caspase-1-dependent manner and induce dramatic changes to the actin cytoskeleton and the assembly of the NADPH oxidase complex onto the BcCV membrane. A Type 6 secretion system (T6SS is required for these phenotypes but surprisingly it is not required for the maturation arrest of the BcCV. Here, we show that macrophages infected with B. cenocepacia employ the NLRP3 inflammasome to induce IL-1β secretion and pyroptosis. Moreover, IL-1β secretion by B. cenocepacia-infected macrophages is suppressed in deletion mutants unable to produce functional Type VI, Type IV, and Type 2 secretion systems (SS. We provide evidence that the T6SS mediates the disruption of the BcCV membrane, which allows the escape of proteins secreted by the T2SS into the macrophage cytoplasm. This was demonstrated by the activity of fusion derivatives of the T2SS-secreted metalloproteases ZmpA and ZmpB with adenylcyclase. Supporting this notion, ZmpA and ZmpB are required for efficient IL-1β secretion in a T6SS dependent manner. ZmpA and ZmpB are also required for the maturation arrest of the BcCVs and bacterial intra-macrophage survival in a T6SS-independent fashion. Our results uncover a novel mechanism for inflammasome activation that involves cooperation between two bacterial secretory pathways, and an unanticipated role for T2SS-secreted proteins in intracellular bacterial survival.

  19. Oscillations of a sessile droplet in open air

    Energy Technology Data Exchange (ETDEWEB)

    Korenchenko, A. E., E-mail: korenchenko@physics.susu.ac.ru [Optics and Spectroscopy Department, National Research South Ural State University, 76 Lenin Avenue, 454080 Chelyabinsk (Russian Federation); Beskachko, V. P. [General and Theoretical Physics Department, National Research South Ural State University, 76 Lenin Avenue, 454080 Chelyabinsk (Russian Federation)

    2013-11-15

    The open system consisting of a sessile drop, a neutral gas, and a substrate is analyzed by numerical methods. The mode with constant contact angle is considered. The model takes into account evaporation from drop surface, free and forced convection in gas, buoyancy, and Marangoni effect in the liquid phase. It was established that every considered mechanical and thermodynamical disturbance of the system leads to the drop surface oscillations, and thus a drop in an open air oscillates almost inevitably. The displacement of the liquid-gas interface due to oscillations is analyzed in terms of its impact on the accuracy of measurement of the surface tension by sessile drop method.

  20. Oscillations of a sessile droplet in open air

    Science.gov (United States)

    Korenchenko, A. E.; Beskachko, V. P.

    2013-11-01

    The open system consisting of a sessile drop, a neutral gas, and a substrate is analyzed by numerical methods. The mode with constant contact angle is considered. The model takes into account evaporation from drop surface, free and forced convection in gas, buoyancy, and Marangoni effect in the liquid phase. It was established that every considered mechanical and thermodynamical disturbance of the system leads to the drop surface oscillations, and thus a drop in an open air oscillates almost inevitably. The displacement of the liquid-gas interface due to oscillations is analyzed in terms of its impact on the accuracy of measurement of the surface tension by sessile drop method.

  1. Sessile Animals on an Artificial Fish Reef with Pine Tree

    OpenAIRE

    吉永, 圭輔; ヨシナガ, ケイスケ; YOSHINAGA, Keisuke

    1999-01-01

    This study was carried out to reveal the sessile animals attached to a pine tree reef. The artificial reef was placed off the coast of Ibusuki City in Kagoshima Bay on 21 December 1995. A piece of pine log was recovered from this reef on 30 October 1998, and animal community attached to the pine log was examined. Abundant ship-worms, Teredo navalis japonica, burrowed their ways from the cut end to the core. Sessile animals clung to the bark. There were also observed many other animals within ...

  2. The temperate Burkholderia phage AP3 of the Peduovirinae shows efficient antimicrobial activity against B. cenocepacia of the IIIA lineage.

    Science.gov (United States)

    Roszniowski, Bartosz; Latka, Agnieszka; Maciejewska, Barbara; Vandenheuvel, Dieter; Olszak, Tomasz; Briers, Yves; Holt, Giles S; Valvano, Miguel A; Lavigne, Rob; Smith, Darren L; Drulis-Kawa, Zuzanna

    2017-02-01

    Burkholderia phage AP3 (vB_BceM_AP3) is a temperate virus of the Myoviridae and the Peduovirinae subfamily (P2likevirus genus). This phage specifically infects multidrug-resistant clinical Burkholderia cenocepacia lineage IIIA strains commonly isolated from cystic fibrosis patients. AP3 exhibits high pairwise nucleotide identity (61.7 %) to Burkholderia phage KS5, specific to the same B. cenocepacia host, and has 46.7-49.5 % identity to phages infecting other species of Burkholderia. The lysis cassette of these related phages has a similar organization (putative antiholin, putative holin, endolysin, and spanins) and shows 29-98 % homology between specific lysis genes, in contrast to Enterobacteria phage P2, the hallmark phage of this genus. The AP3 and KS5 lysis genes have conserved locations and high amino acid sequence similarity. The AP3 bacteriophage particles remain infective up to 5 h at pH 4-10 and are stable at 60 °C for 30 min, but are sensitive to chloroform, with no remaining infective particles after 24 h of treatment. AP3 lysogeny can occur by stable genomic integration and by pseudo-lysogeny. The lysogenic bacterial mutants did not exhibit any significant changes in virulence compared to wild-type host strain when tested in the Galleria mellonella moth wax model. Moreover, AP3 treatment of larvae infected with B. cenocepacia revealed a significant increase (P < 0.0001) in larvae survival in comparison to AP3-untreated infected larvae. AP3 showed robust lytic activity, as evidenced by its broad host range, the absence of increased virulence in lysogenic isolates, the lack of bacterial gene disruption conditioned by bacterial tRNA downstream integration site, and the absence of detected toxin sequences. These data suggest that the AP3 phage is a promising potent agent against bacteria belonging to the most common B. cenocepacia IIIA lineage strains.

  3. Segregation in desiccated sessile drops of biological fluids.

    Science.gov (United States)

    Tarasevich, Yu Yu; Pravoslavnova, D M

    2007-04-01

    It is shown here that concurrence between advection and diffusion in a drying sessile drop of a biological fluid can produce spatial redistribution of albumen and salt. The result gives an explanation for the patterns observed in the dried drops of the biological fluids.

  4. Simple Model of Shape Evolution of Desiccated Colloidal Sessile Drop

    OpenAIRE

    Tarasevich, Yu. Yu.; Vodolazskaya, I. V.; Isakova, O. P.

    2011-01-01

    We propose simple model of colloidal sessile drop desiccation. The model describes correctly both evolution of the phase boundary between sol and gel inside such a drop and the final shape of the dried film (deposit). The model is based on mass conservation and natural assumption that deposit (gel phase) prevents flows and evaporation.

  5. Evaporation of Sessile Droplets of Liquid on Solid Substrates

    Science.gov (United States)

    Semenov, S.; Starov, V. M.; Velarde, M. G.; Rubio, R. G.

    Evaporation of sessile droplets of liquid on solid substrates is considered here. Different parameters and processes influencing the evaporation rate are discussed. Cases of complete wetting and partial wetting with contact angle hysteresis are described mathematically. The influence of Kelvin's and kinetic effects and subsequent deviation from diffusion-limited evaporation is shown by means of computer simulations.

  6. Burkholderia cenocepacia K56-2 trimeric autotransporter adhesin BcaA binds TNFR1 and contributes to induce airway inflammation.

    Science.gov (United States)

    Mil-Homens, Dalila; Pinto, Sandra N; Matos, Rute G; Arraiano, Cecília; Fialho, Arsenio M

    2017-04-01

    Chronic lung disease caused by persistent bacterial infections is a major cause of morbidity and mortality in patients with cystic fibrosis (CF). CF pathogens acquire antibiotic resistance, overcome host defenses, and impose uncontrolled inflammation that ultimately may cause permanent damage of lungs' airways. Among the multiple CF-associated pathogens, Burkholderia cenocepacia and other Burkholderia cepacia complex bacteria have become prominent contributors of disease progression. Here, we demonstrate that BcaA, a trimeric autotransporter adhesin (TAA) from the epidemic strain B. cenocepacia K56-2, is a tumor necrosis factor receptor 1-interacting protein able to regulate components of the tumor necrosis factor signaling pathway and ultimately leading to a significant production of the proinflammatory cytokine IL-8. Notably, this study is the first to demonstrate that a protein belonging to the TAA family is involved in the induction of the inflammatory response during B. cenocepacia infections, contributing to the success of the pathogen. Moreover, our results reinforce the relevance of the TAA BcaA as a multifunctional protein with a major role in B. cenocepacia virulence.

  7. Dynamic electrowetting of sessile drops on soft surfaces

    CERN Document Server

    Dey, Ranabir; DasGupta, Sunando; Chakraborty, Suman

    2014-01-01

    Electrically-mediated dynamic wetting behaviour of sessile liquid drops on dielectric films is governed by the combined interplay of the wetting line friction and the internal viscous dissipation. We show here that such classical description of the electrospreading phenomenon, as prevalent in the contemporary literature, fails to address the electro-capillarity induced dynamic wetting of sessile drops on soft dielectrics. We first delineate the temporal variations of the macroscopic dynamic contact angle, and the contact radius, during electrowetting on rheologically tunable soft surfaces, at different applied electric potentials; subsequently, we prove through a scaling analysis, and an energy conservation approach, that the dielectric elasticity dependent, microscale elastocapillary deformation of the soft substrate, near the three-phase contact line, plays the integral role in dictating the macroscopic electrowetting behaviour. Interestingly, under such electro-elastocapillary phenomenon on soft dielectric...

  8. Stability of thin liquid films and sessile droplets under confinement.

    Science.gov (United States)

    Dörfler, Fabian; Rauscher, Markus; Dietrich, S

    2013-07-01

    The stability of nonvolatile thin liquid films and of sessile droplets is strongly affected by finite size effects. We analyze their stability within the framework of density functional theory using the sharp kink approximation, i.e., on the basis of an effective interface Hamiltonian. We show that finite size effects suppress spinodal dewetting of films because it is driven by a long-wavelength instability. Therefore nonvolatile films are stable if the substrate area is too small. Similarly, nonvolatile droplets connected to a wetting film become unstable if the substrate area is too large. This instability of a nonvolatile sessile droplet turns out to be equivalent to the instability of a volatile drop which can attain chemical equilibrium with its vapor.

  9. Sessile drops and condensation on chemically patterned micropillars

    Science.gov (United States)

    Shardt, Orest; Waghmare, Prashant; Orejon, Daniel; Gunda, Naga; Takata, Yasuyuki; Mitra, Sushanta

    2014-11-01

    We examine the state of sessile drops on silicon micropillars with patterned wettability as well as condensation of water onto such surfaces. These patterned micropillar arrays were created by treatment with a perfluoroalkylsilane to create a hydrophobic surface and subsequent patterning with sodium hydroxide solution to create hydrophilic regions. The surfaces were characterized by measuring the contact angles and observing the states of sessile drops, and the results are compared with those of uniformly hydrophobic and hydrophilic pillars. The nature of condensation onto patterned pillars has been examined with environmental scanning electron microscopy (ESEM). The results show the initial dropwise condensation on the different types of pillars and the transition to a film. Surfaces that combine texturing with chemical patterning could be useful for enhanced control of condensation and droplet motion.

  10. Experimental Investigation of Pendant and Sessile Drops in Microgravity

    Science.gov (United States)

    Zhu, Zhi-Qiang; Brutin, David; Liu, Qiu-Sheng; Wang, Yang; Mourembles, Alexandre; Xie, Jing-Chang; Tadrist, Lounes

    2010-09-01

    The experiments regarding the contact angle behavior of pendant and sessile evaporating drops were carried out in microgravity environment. All the experiments were performed in the Drop Tower of Beijing, which could supply about 3.6 s of microgravity (free-fall) time. In the experiments, firstly, drops were injected to create before microgravity. The wettability at different surfaces, contact angles dependance on the surface temperature, contact angle variety in sessile and pendant drops were measured. Different influence of the surface temperature on the contact angle of the drops were found for different substrates. To verify the feasibility of drops creation in microgravity and obtain effective techniques for the forthcoming satellite experiments, we tried to inject liquid to create bigger drop as soon as the drop entering microgravity condition. The contact angle behaviors during injection in microgravity were also obtained.

  11. On the coalescence of sessile drops with miscible liquids.

    Science.gov (United States)

    Borcia, R; Bestehorn, M

    2011-08-01

    Sessile drops sitting on highly wettable solid substrates fuse in qualitatively different ways after contact, depending on the surface tension gradients between the mixing droplets. In early time evolution the drop coalescence can be fast or delayed (intermittent). In long time evolution a secondary drop formation can occur. We study numerically droplet dynamics during coalescence in two and three spatial dimensions, within a phase field approach. We discuss criteria to distinguish different coalescence regimes. A comparison with recent experiments will be done.

  12. Hildebrand solubility parameters measurement via sessile drops evaporation

    Science.gov (United States)

    Fang, Xiaohua; Li, Bingquan; Sokolov, Jonathan C.; Rafailovich, Miriam H.; Gewaily, Dina

    2005-08-01

    A method for the measurement of Hildebrand solubility parameter has been developed. This method was based on the measurement of the sessile drop contact angle and contact base width during its evaporation. Experimental results showed that this method is accurate and insensitive to the measurement conditions. The major advantages of this method are that it is time efficient and requires a small amount of liquid (microliter) for the measurement.

  13. Analytical solution for inviscid flow inside an evaporating sessile drop

    OpenAIRE

    Masoud, Hassan; Felske, James D.

    2008-01-01

    Inviscid flow within an evaporating sessile drop is analyzed. The field equation, E^2(Psi)=0, is solved for the stream function. The exact analytical solution is obtained for arbitrary contact angle and distribution of evaporative flux along the free boundary. Specific results and computations are presented for evaporation corresponding to both uniform flux and purely diffusive gas phase transport into an infinite ambient. Wetting and non-wetting contact angles are considered with flow patter...

  14. The evaporation behavior of sessile droplets from aqueous saline solutions.

    Science.gov (United States)

    Soulié, Virginie; Karpitschka, Stefan; Lequien, Florence; Prené, Philippe; Zemb, Thomas; Moehwald, Helmuth; Riegler, Hans

    2015-09-14

    Quantitative experiments on the evaporation from sessile droplets of aqueous saline (NaCl) solutions show a strong dependence on salt concentration and droplet shape. The experiments were performed with seven decades of initial NaCl concentrations, with various droplet sizes and with different contact angles. The evaporation rate is significantly lower for high salt concentrations and small contact angles than what is expected from the well-accepted diffusion-controlled evaporation scenario for sessile droplets, even if the change of the vapor pressure due to the salt is taken into account. Particle tracking velocimetry reveals that this modification of the evaporation behavior is caused by marangoni flows that are induced by surface tension gradients originating from the local evaporative peripheral salt enrichment. In addition it is found that already very low salt concentrations lead to a pinning of the three phase contact line. Whereas droplets with concentration ≥10(-6) M NaCl are pinned as soon as evaporation starts, droplets with lower salt concentration do evaporate in a constant contact angle mode. Aside from new, fundamental insights the findings are also relevant for a better understanding of the widespread phenomenon of corrosion initiated by sessile droplets.

  15. Lotka-Volterra competition models for sessile organisms.

    Science.gov (United States)

    Spencer, Matthew; Tanner, Jason E

    2008-04-01

    Markov models are widely used to describe the dynamics of communities of sessile organisms, because they are easily fitted to field data and provide a rich set of analytical tools. In typical ecological applications, at any point in time, each point in space is in one of a finite set of states (e.g., species, empty space). The models aim to describe the probabilities of transitions between states. In most Markov models for communities, these transition probabilities are assumed to be independent of state abundances. This assumption is often suspected to be false and is rarely justified explicitly. Here, we start with simple assumptions about the interactions among sessile organisms and derive a model in which transition probabilities depend on the abundance of destination states. This model is formulated in continuous time and is equivalent to a Lotka-Volterra competition model. We fit this model and a variety of alternatives in which transition probabilities do not depend on state abundances to a long-term coral reef data set. The Lotka-Volterra model describes the data much better than all models we consider other than a saturated model (a model with a separate parameter for each transition at each time interval, which by definition fits the data perfectly). Our approach provides a basis for further development of stochastic models of sessile communities, and many of the methods we use are relevant to other types of community. We discuss possible extensions to spatially explicit models.

  16. Substrate constraint modifies the Rayleigh spectrum of vibrating sessile drops.

    Science.gov (United States)

    Chang, Chun-Ti; Bostwick, Joshua B; Steen, Paul H; Daniel, Susan

    2013-08-01

    In this work, we study the resonance behavior of mechanically oscillated, sessile water drops. By mechanically oscillating sessile drops vertically and within prescribed ranges of frequencies and amplitudes, a rich collection of resonance modes are observed and their dynamics subsequently investigated. We first present our method of identifying each mode uniquely, through association with spherical harmonics and according to their geometric patterns. Next, we compare our measured resonance frequencies of drops to theoretical predictions using both the classical theory of Lord Rayleigh and Lamb for free, oscillating drops, and a prediction by Bostwick and Steen that explicitly considers the effect of the solid substrate on drop dynamics. Finally, we report observations and analysis of drop mode mixing, or the simultaneous coexistence of multiple mode shapes within the resonating sessile drop driven by one sinusoidal signal of a single frequency. The dynamic response of a deformable liquid drop constrained by the substrate it is in contact with is of interest in a number of applications, such as drop atomization and ink jet printing, switchable electronically controlled capillary adhesion, optical microlens devices, as well as digital microfluidic applications where control of droplet motion is induced by means of a harmonically driven substrate.

  17. Stability of a compound sessile drop at the axisymmetric configuration.

    Science.gov (United States)

    Zhang, Ying; Chatain, Dominique; Anna, Shelley L; Garoff, Stephen

    2016-01-15

    The equilibrium configuration of compound sessile drops has been calculated previously in the absence of gravity. Using the Laplace equations, we establish seven dimensionless parameters describing the axisymmetric configuration in the presence of gravity. The equilibrium axisymmetric configuration can be either stable or unstable depending on the fluid properties. A stability criterion is established by calculating forces on a perturbed Laplacian shape. In the zero Bond number limit, the stability criterion depends on the density ratio, two ratios of interfacial tensions, the volume ratio of the two drops, and the contact angle. We use Surface Evolver to examine the stability of compound sessile drops at small and large Bond numbers and compare with the zero Bond number approximation. Experimentally, we realize a stable axisymmetric compound sessile drop in air, where the buoyancy force exerted by the air is negligible. Finally, using a pair of fluids in which the density ratio can be tuned nearly independently of the interfacial tensions, the stability transition is verified for the axisymmetric configuration. Even though the perturbations are different for the theory, simulations and experiments, both simulations and experiments agree closely with the zero Bond number approximation, exhibiting a small discrepancy at large Bond number.

  18. Sessile multidroplets and salt droplets under high tangential electric fields

    Science.gov (United States)

    Xie, Guoxin; He, Feng; Liu, Xiang; Si, Lina; Guo, Dan

    2016-01-01

    Understanding the interaction behaviors between sessile droplets under imposed high voltages is very important in many practical situations, e.g., microfluidic devices and the degradation/aging problems of outdoor high-power applications. In the present work, the droplet coalescence, the discharge activity and the surface thermal distribution response between sessile multidroplets and chloride salt droplets under high tangential electric fields have been investigated with infrared thermography, high-speed photography and pulse current measurement. Obvious polarity effects on the discharge path direction and the temperature change in the droplets in the initial stage after discharge initiation were observed due to the anodic dissolution of metal ions from the electrode. In the case of sessile aligned multidroplets, the discharge path direction could affect the location of initial droplet coalescence. The smaller unmerged droplet would be drained into the merged large droplet as a result from the pressure difference inside the droplets rather than the asymmetric temperature change due to discharge. The discharge inception voltages and the temperature variations for two salt droplets closely correlated with the ionization degree of the salt, as well as the interfacial electrochemical reactions near the electrodes. Mechanisms of these observed phenomena were discussed. PMID:27121926

  19. Substrate constraint modifies the Rayleigh spectrum of vibrating sessile drops

    Science.gov (United States)

    Chang, Chun-Ti; Bostwick, Joshua B.; Steen, Paul H.; Daniel, Susan

    2013-08-01

    In this work, we study the resonance behavior of mechanically oscillated, sessile water drops. By mechanically oscillating sessile drops vertically and within prescribed ranges of frequencies and amplitudes, a rich collection of resonance modes are observed and their dynamics subsequently investigated. We first present our method of identifying each mode uniquely, through association with spherical harmonics and according to their geometric patterns. Next, we compare our measured resonance frequencies of drops to theoretical predictions using both the classical theory of Lord Rayleigh and Lamb for free, oscillating drops, and a prediction by Bostwick and Steen that explicitly considers the effect of the solid substrate on drop dynamics. Finally, we report observations and analysis of drop mode mixing, or the simultaneous coexistence of multiple mode shapes within the resonating sessile drop driven by one sinusoidal signal of a single frequency. The dynamic response of a deformable liquid drop constrained by the substrate it is in contact with is of interest in a number of applications, such as drop atomization and ink jet printing, switchable electronically controlled capillary adhesion, optical microlens devices, as well as digital microfluidic applications where control of droplet motion is induced by means of a harmonically driven substrate.

  20. High-resolution structure of the M14-type cytosolic carboxypeptidase from Burkholderia cenocepacia refined exploiting PDB-REDO strategies

    Energy Technology Data Exchange (ETDEWEB)

    Rimsa, Vadim; Eadsforth, Thomas C. [University of Dundee, Dundee DD1 5EH, Scotland (United Kingdom); Joosten, Robbie P. [Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands); Hunter, William N., E-mail: w.n.hunter@dundee.ac.uk [University of Dundee, Dundee DD1 5EH, Scotland (United Kingdom)

    2014-02-01

    The structure of a bacterial M14-family carboxypeptidase determined exploiting microfocus synchrotron radiation and highly automated refinement protocols reveals its potential to act as a polyglutamylase. A potential cytosolic metallocarboxypeptidase from Burkholderia cenocepacia has been crystallized and a synchrotron-radiation microfocus beamline allowed the acquisition of diffraction data to 1.9 Å resolution. The asymmetric unit comprises a tetramer containing over 1500 amino acids, and the high-throughput automated protocols embedded in PDB-REDO were coupled with model–map inspections in refinement. This approach has highlighted the value of such protocols for efficient analyses. The subunit is constructed from two domains. The N-terminal domain has previously only been observed in cytosolic carboxypeptidase (CCP) proteins. The C-terminal domain, which carries the Zn{sup 2+}-containing active site, serves to classify this protein as a member of the M14D subfamily of carboxypeptidases. Although eukaryotic CCPs possess deglutamylase activity and are implicated in processing modified tubulin, the function and substrates of the bacterial family members remain unknown. The B. cenocepacia protein did not display deglutamylase activity towards a furylacryloyl glutamate derivative, a potential substrate. Residues previously shown to coordinate the divalent cation and that contribute to peptide-bond cleavage in related enzymes such as bovine carboxypeptidase are conserved. The location of a conserved basic patch in the active site adjacent to the catalytic Zn{sup 2+}, where an acetate ion is identified, suggests recognition of the carboxy-terminus in a similar fashion to other carboxypeptidases. However, there are significant differences that indicate the recognition of substrates with different properties. Of note is the presence of a lysine in the S1′ recognition subsite that suggests specificity towards an acidic substrate.

  1. Burkholderia cenocepacia BC2L-C is a super lectin with dual specificity and proinflammatory activity.

    Directory of Open Access Journals (Sweden)

    Ondřej Sulák

    2011-09-01

    Full Text Available Lectins and adhesins are involved in bacterial adhesion to host tissues and mucus during early steps of infection. We report the characterization of BC2L-C, a soluble lectin from the opportunistic pathogen Burkholderia cenocepacia, which has two distinct domains with unique specificities and biological activities. The N-terminal domain is a novel TNF-α-like fucose-binding lectin, while the C-terminal part is similar to a superfamily of calcium-dependent bacterial lectins. The C-terminal domain displays specificity for mannose and l-glycero-d-manno-heptose. BC2L-C is therefore a superlectin that binds independently to mannose/heptose glycoconjugates and fucosylated human histo-blood group epitopes. The apo form of the C-terminal domain crystallized as a dimer, and calcium and mannose could be docked in the binding site. The whole lectin is hexameric and the overall structure, determined by electron microscopy and small angle X-ray scattering, reveals a flexible arrangement of three mannose/heptose-specific dimers flanked by two fucose-specific TNF-α-like trimers. We propose that BC2L-C binds to the bacterial surface in a mannose/heptose-dependent manner via the C-terminal domain. The TNF-α-like domain triggers IL-8 production in cultured airway epithelial cells in a carbohydrate-independent manner, and is therefore proposed to play a role in the dysregulated proinflammatory response observed in B. cenocepacia lung infections. The unique architecture of this newly recognized superlectin correlates with multiple functions including bacterial cell cross-linking, adhesion to human epithelia, and stimulation of inflammation.

  2. Assessment of the relative error in sessile drop method automation task

    OpenAIRE

    Levitskaya T.О.

    2015-01-01

    Assessment of the relative error in the sessile drop method automation. Further development of the sessile drop method is directly related to the development of new techniques and specially developed algorithms enabling automatic computer calculation of surface properties. The sessile drop method mathematical apparatus improvement, drop circuit equation transformation to a form suitable for working, the drop surface calculation method automation, analysis of relative errors in the calculation...

  3. Large-scale facilitation of a sessile community by an invasive habitat-forming snail

    DEFF Research Database (Denmark)

    Thyrring, Jakob; Thomsen, Mads Solgaard; Wernberg, Thomas

    2013-01-01

    Abstract We provide an example of extensive facilitation of a sessile community throughout an invaded estuary by the invasive snail Batillaria australis. We show that B. australis greatly increases a limiting resource (attachment space) to a community of sessile organisms and estimate that a large...... part of the invaded estuary now contain ca. 50 times more sessile individuals associated with the invader than all native snails combined. We argue that native snails are unlikely to have been dramatically reduced by the invader, and we therefore suggest that the shell-attached sessile community...

  4. Nasal immunization with Burkholderia multivorans outer membrane proteins and the mucosal adjuvant adamantylamide dipeptide confers efficient protection against experimental lung infections with B. multivorans and B. cenocepacia.

    Science.gov (United States)

    Bertot, Gustavo M; Restelli, Marcela A; Galanternik, Laura; Aranibar Urey, Rene C; Valvano, Miguel A; Grinstein, Saúl

    2007-06-01

    Chronic lung infection by opportunistic pathogens, such as Pseudomonas aeruginosa and members of the Burkholderia cepacia complex, is a major cause of morbidity and mortality in patients with cystic fibrosis. Outer membrane proteins (OMPs) of gram-negative bacteria are promising vaccine antigen candidates. In this study, we evaluated the immunogenicity, protection, and cross-protection conferred by intranasal vaccination of mice with OMPs from B. multivorans plus the mucosal adjuvant adamantylamide dipeptide (AdDP). Robust mucosal and systemic immune responses were stimulated by vaccination of naive animals with OMPs from B. multivorans and B. cenocepacia plus AdDP. Using a mouse model of chronic pulmonary infection, we observed enhanced clearance of B. multivorans from the lungs of vaccinated animals, which correlated with OMP-specific secretory immunoglobulin A responses. Furthermore, OMP-immunized mice showed rapid resolution of the pulmonary infection with virtually no lung pathology after bacterial challenge with B. multivorans. In addition, we demonstrated that administration of B. multivorans OMP vaccine conferred protection against B. cenocepacia challenge in this mouse infection model, suggesting that OMPs provide cross-protection against the B. cepacia complex. Therefore, we concluded that mucosal immunity to B. multivorans elicited by intranasal vaccination with OMPs plus AdDP could prevent early steps of colonization and infection with B. multivorans and also ameliorate lung tissue damage, while eliciting cross-protection against B. cenocepacia. These results support the notion that therapies leading to increased mucosal immunity in the airways may help patients with cystic fibrosis.

  5. Low power sessile droplet actuation via modulated surface acoustic waves

    CERN Document Server

    Baudoin, Michael; Matar, Olivier Bou; Herth, Etienne

    2012-01-01

    Low power actuation of sessile droplets is of primary interest for portable or hybrid lab-on-a-chip and harmless manipulation of biofluids. In this paper, we show that the acoustic power required to move or deform droplets via surface acoustic waves can be substantially reduced through the forcing of the drops inertio-capillary modes of vibrations. Indeed, harmonic, superharmonic and subharmonic (parametric) excitation of these modes are observed when the high frequency acoustic signal (19.5 MHz) is modulated around Rayleigh-Lamb inertio-capillary frequencies. This resonant behavior results in larger oscillations and quicker motion of the drops than in the non-modulated case.

  6. Sessile serrated adenomas:Demographic,endoscopic and pathological characteristics

    Institute of Scientific and Technical Information of China (English)

    Suryakanth; R; Gurudu; Russell; I; Heigh; Giovanni; De; Petris; Evelyn; G; Heigh; Jonathan; A; Leighton; Shabana; F; Pasha; Isaac; B; Malagon; Ananya; Das

    2010-01-01

    AIM:To study the demographic and endoscopic characteristics of patients with sessile serrated adenoma(SSA) in a single center.METHODS:Patients with SSA were identified by review of the pathology database of Mayo Clinic Arizona from 2005 to 2007.A retrospective chart review was performed to extract data on demographics,polyp characteristics,presence of synchronous adenomatous polyps or cancer,polypectomy methods,and related complications.RESULTS:One hundred and seventy-one(2.9%) of all patients undergoing co...

  7. Vibration spectroscopy of a sessile drop and its contact line.

    Science.gov (United States)

    Mettu, S; Chaudhury, M K

    2012-10-02

    Resonance frequencies of small sessile liquid drops (1-20 μL) were estimated from the power spectra of their height fluctuations after subjecting them to white noise vibration. Various resonance modes could be identified with this method as a function of the mass of the drop. Studies with water drops on such supports as polystyrene (θ ≈ 80°) and a superhydrophobic surface of microfibrillar silicone rubber (θ ≈ 162°) demonstrated that the resonant frequency decreases with the contact angle, θ. This trend is in remarkable agreement with the current models of the resonant vibration of sessile drops. A novel aspect of this study is the analysis of the modes of a slipping contact line that indicated that its higher frequency modes are more severely damped than its lower ones. Another case is with the glycerol-water solutions, where the resonance frequency decreases with the concentration of glycerol purely due to the capillary effects. The interface fluctuation, on the other hand, is strongly correlated with the kinematic viscosity of the liquid. Thus, these experiments provide a means to measure the surface tension and the viscosity of very small droplets.

  8. Contact angle of sessile drops in Lennard-Jones systems.

    Science.gov (United States)

    Becker, Stefan; Urbassek, Herbert M; Horsch, Martin; Hasse, Hans

    2014-11-18

    Molecular dynamics simulations are used for studying the contact angle of nanoscale sessile drops on a planar solid wall in a system interacting via the truncated and shifted Lennard-Jones potential. The entire range between total wetting and dewetting is investigated by varying the solid-fluid dispersive interaction energy. The temperature is varied between the triple point and the critical temperature. A correlation is obtained for the contact angle in dependence of the temperature and the dispersive interaction energy. Size effects are studied by varying the number of fluid particles at otherwise constant conditions, using up to 150,000 particles. For particle numbers below 10,000, a decrease of the contact angle is found. This is attributed to a dependence of the solid-liquid surface tension on the droplet size. A convergence to a constant contact angle is observed for larger system sizes. The influence of the wall model is studied by varying the density of the wall. The effective solid-fluid dispersive interaction energy at a contact angle of θ = 90° is found to be independent of temperature and to decrease linearly with the solid density. A correlation is developed that describes the contact angle as a function of the dispersive interaction, the temperature, and the solid density. The density profile of the sessile drop and the surrounding vapor phase is described by a correlation combining a sigmoidal function and an oscillation term.

  9. Wetting of sessile water drop under an external electrical field

    Science.gov (United States)

    Vancauwenberghe, Valerie; di Marco, Paolo; Brutin, David; Amu Collaboration; Unipi Collaboration

    2013-11-01

    The enhancement of heat and mass transfer using a static electric field is an interesting process for industrial applications, due to its low energy consumption and potentially high level of evaporation rate enhancement. However, to date, this phenomenon is still not understood in the context of the evaporation of sessile drops. We previously synthesized the state of the art concerning the effect of an electric field on sessile drops with a focus on the change of contact angle and shape and the influence of the evaporation rate [1]. We present here the preliminary results of an new experiment set-up. The novelty of the set-up is the drop injection from the bottom that allows to generate safety the droplet under the electrostatic field. The evaporation at room temperature of water drops having three different volumes has been investigated under an electric field up to 10.5 kV/cm. The time evolutions of the contact angles, volumes and diameters have been analysed. As reported in the literature, the drop elongate along the direction of the electric field. Despite the hysteresis effect of the contact angle, the receding contact angle increases with the strength of the electric field. This is clearly observable for the small drops for which the gravity effect can be neglected.

  10. Perturbation solution of the shape of a nonaxisymmetric sessile drop.

    Science.gov (United States)

    Prabhala, Bharadwaj; Panchagnula, Mahesh; Subramanian, Venkat R; Vedantam, Srikanth

    2010-07-06

    We develop an approximate analytical solution for the shape of a nonaxisymmetric sessile drop using regular perturbation methods and ignoring gravity. We assume that the pinned, contorted triple-line shape is known and is a small perturbation of the circular footprint of a spherical cap. We obtain an analytical solution using regular perturbation methods that we validate by comparing to the numerical solution of the Young-Laplace equation obtained using publicly available Surface Evolver software. In this process, we also show that the pressure inside the perturbed drop is unchanged and relate this to the curvature of the drop using the Young-Laplace equation. The rms error between the perturbation and Evolver solutions is calculated for a range of contact angles and amplitudes of triple-line perturbations. We show that the perturbation solution matches the numerical results well for a wide range of contact angles. In addition, we calculate the extent to which the drop surface is affected by triple-line contortions. We discuss the applicability of this solution to the possibility of real time hybrid experimental/computational characterization of the 3D sessile drop shapes, including obtaining local contact angle information.

  11. Contact angle dependence of the resonant properties of sessile drops

    Science.gov (United States)

    Sharp, James

    2012-02-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre sessile drops of glycerol/water mixtures with glycerol compositions ranging from 0% to 75%. A photodiode was used to detect time dependent variations in the intensity of laser light reflected from the droplets. The intensity variations were Fourier transformed to obtain information about the resonant properties of the drops (frequency and width of the resonance). These experiments were performed on a range of different substrates where the contact angle formed by the droplets varied between 38±2^o and 160±4^o. The measured resonant frequency values were found to be in agreement with a recently developed theory of vibrations which considers standing wave states along the profile length of the droplet. The widths of the resonances were also compared with theories which predict the influence of substrate effects, surface contamination effects and bulk viscous effects on the damping of capillary waves at the free surface of the droplets. These experiments indicate that the dominant source of damping in sessile liquid droplet is due to bulk viscous effects but that for small contact angles damping due to the droplet/substrate interaction becomes more important.

  12. Dynamics of a Disturbed Sessile Drop Measured by Atomic Force Microscopy (AFM)

    NARCIS (Netherlands)

    McGuiggan, Patricia M.; Grave, Daniel A.; Wallace, Jay S.; Cheng, Shengfeng; Prosperetti, Andrea; Robbins, Mark O.

    2011-01-01

    A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r 20–30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liq

  13. Dynamics of sessile drops. Part 3. Theory of forced oscillations

    CERN Document Server

    Bostwick, Joshua B

    2016-01-01

    A partially-wetting sessile drop is driven by a sinusoidal pressure field that produces capillary waves on the liquid/gas interface. The analysis presented in Part 1 of this series (Bostwick & Steen 2014) is extended by computing response diagrams and phase shifts for the viscous droplet, whose three phase contact-line moves with contact-angle that is a smooth function of the contact line speed. Viscous dissipation is incorporated through the viscous potential flow approximation and the critical Ohnesorge number bounding regions beyond which a given mode becomes over-damped is computed. Davis dissipation originating from the contact-line speed condition leads to damped oscillations for drops with finite contact-line mobility, even for inviscid fluids. The critical mobility and associated driving frequency to generate the largest Davis dissipation is computed. Lastly, regions of modal coexistence where two modes can be simultaneously excited by a single forcing frequency are identified. Predictions compare...

  14. Evaporation of Ethanol-Water Binary Mixture Sessile Liquid Marbles.

    Science.gov (United States)

    Ooi, Chin Hong; Bormashenko, Edward; Nguyen, Anh V; Evans, Geoffrey M; Dao, Dzung V; Nguyen, Nam-Trung

    2016-06-21

    Liquid marble is a liquid droplet coated with particles. Recently, the evaporation process of a sessile liquid marble using geometric measurements has attracted great attention from the research community. However, the lack of gravimetric measurement limits further insights into the physical changes of a liquid marble during the evaporation process. Moreover, the evaporation process of a marble containing a liquid binary mixture has not been reported before. The present paper investigates the effective density and the effective surface tension of an evaporating liquid marble that contains aqueous ethanol at relatively low concentrations. The effective density of an evaporating liquid marble is determined from the concurrent measurement of instantaneous mass and volume. Density measurements combined with surface profile fitting provide the effective surface tension of the marble. We found that the density and surface tension of an evaporating marble are significantly affected by the particle coating.

  15. Fractal pattern formation in metallic ink sessile droplets

    Science.gov (United States)

    Hadj-Achour, Miloud; Brutin, David

    2014-11-01

    We report a fingering instability that occurs during the spreading and evaporation of a nanosuspension droplet. The patterns has a fractal structure similar to those reported by N. Shahidzadeh-Bonn et al. (2008) for salt crystallisation, during evaporation of saturated Na2SO4 on a hydrophilic surface. The fingering instability has been widely studied for both Newtonian and non-Newtonian fluids. However, we describe for the first time that a fingering instability is observed for the spreading of a nanosuspension sessile droplet. We demonstrate that in certain cases, the contact line evolves through different spreading regimes according to J. De Coninck et al. (2001) with an enhancement in the evaporation rate due the formation of the fractal patterns.

  16. As-placed contact angles for sessile drops.

    Science.gov (United States)

    Tadmor, Rafael; Yadav, Preeti S

    2008-01-01

    As-placed contact angle is the contact angle a drop adapts as a result of its placement on a surface. As expected, the as-placed contact angle, thetaAP, of a sessile drop on a horizontal surface decreases with the drop size due to the increase in hydrostatic pressure. We present a theoretical prediction for thetaAP which shows that it is a unique function of the advancing contact angle, thetaA, drop size, and material properties (surface tensions and densities). We test our prediction with published and new data. The theory agrees with the experiments. From the relation of the as-placed contact angle to drop size the thermodynamic equilibrium contact angle is also calculated.

  17. Analytical solution for inviscid flow inside an evaporating sessile drop.

    Science.gov (United States)

    Masoud, Hassan; Felske, James D

    2009-01-01

    Inviscid flow within an evaporating sessile drop is analyzed. The field equation E;{2}psi=0 is solved for the stream function. The exact analytical solution is obtained for arbitrary contact angle and distribution of evaporative flux along the free boundary. Specific results and computations are presented for evaporation corresponding to both uniform flux and purely diffusive gas phase transport into an infinite ambient. Wetting and nonwetting contact angles are considered, with flow patterns in each case being illustrated. The limiting behaviors of small contact angle and droplets of hemispherical shape are treated. All of the above categories are considered for the cases of droplets whose contact lines are either pinned or free to move during evaporation.

  18. Sessile droplet de-pinning: new life for gravimetric data.

    Science.gov (United States)

    Chan, Kwaichow B; Pierce, Scott M

    2007-02-01

    Using three different types of surfaces as exemplars, we report a gravimetric method as a viable tool for studying the de-pinning process. Namely, the de-pin time, tau(d) (the time required for a horizontal sessile droplet to de-pin at the triple phase line on a given substrate), is estimated without using a time consuming and expensive video imaging system. This is made possible by deciphering the non-linear portion of mass vs time data of an evaporating sessile droplet. Typical gravimetric glass-substrate evaporative mass loss vs time data has two regimes: a long, linear regime followed by a short, non-linear regime. Traditionally, researchers extract only the evaporation rate of a droplet from the linear regime but discard (by truncating the data) or ignore (thus deriving no information from) the non-linear regime. The origin of the linear to non-linear transition, found almost universally in gravimetric data, persists unremarked upon. By constructing three very different types of surfaces and comparing gravimetric data with video imaging data taken simultaneously, we report the transition is correlated to the onset of the de-pinning event in each case. This realization enables us to measure the de-pin time, tau(d), with gravimetric data only; i.e., without the video system, gathering more information from gravimetric data than previously considered. The method has application in estimating the de-pin time of a droplet deposited on a substrate that yields poor top-view contrast for videography, such as a water droplets on silicon wafers or glass substrates. Finally, gravimetric data is more accurate for evaporation modeling when substrate/droplet interaction areas are not circular.

  19. Coalescence and noncoalescence of sessile drops: impact of surface forces.

    Science.gov (United States)

    Karpitschka, Stefan; Hanske, Christoph; Fery, Andreas; Riegler, Hans

    2014-06-17

    Due to capillarity, sessile droplets of identical liquids will instantaneously fuse when they come in contact at their three-phase lines. However, with drops of different, completely miscible liquids, instantaneous coalescence can be suppressed. Instead, the drops remain in a state of noncoalescence for some time, with the two drop bodies connected only by a thin neck. The reason for this noncoalescence is the surface tension difference, Δγ, between the liquids. If Δγ is sufficiently large, then it induces a sufficiently strong Marangoni flow, which keeps the main drop bodies temporarily separated. Studies with spreading drops have revealed that the boundary between instantaneous coalescence and noncoalescence is sharp (Karpitschka, S.; Riegler, H. J. Fluid. Mech. 2014, 743, R1). The boundary is a function of two parameters only: Δγ and Θ(a), the arithmetic mean of the contact angles in the moment of drop-drop contact. It appears plausible that surface forces (the disjoining pressure) could also influence the coalescence behavior. However, in experiments with spreading drops, surface forces always promote coalescence and their influence might be obscured. Therefore, we present here coalescence experiments with partially wetting liquids and compare the results to the spreading case. We adjust different equilibrium contact angles (i.e., different surface forces) with different substrate surface coatings. As for spreading drops, we observe a sharp boundary between regimes of coalescence and noncoalescence. The boundary follows the same power law relation for both partially and completely wetting cases. Therefore, we conclude that surface forces have no significant, explicit influence on the coalescence behavior of sessile drops from different miscible liquids.

  20. Particle deposition on superhydrophobic surfaces by sessile droplet evaporation

    Science.gov (United States)

    Dicuangco, Mercy Grace

    Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is to explore the morphology of particles deposited on superhydrophobic surfaces by the evaporation of sessile water droplets containing suspended latex spheres. Droplet evaporation experiments are performed on non-wetting, textured surfaces with varying geometric parameters. The temporal evolution of the droplet contact radius and contact angle throughout the evaporation process are tracked by visualizing the transient droplet shape and wetting behavior. The droplets are observed to exhibit a combination of the following modes of evaporation: the constant contact radius mode, the constant contact angle mode, and the mixed mode in which the contact angle and the contact radius change simultaneously. After complete dry-out, the remaining particulate deposits are qualitatively and quantitatively characterized to describe their spatial distribution. In the first part of the study, the test surfaces are maintained at different temperatures. Experiments are conducted at ambient conditions and at elevated substrate temperatures of approximately 40°C, 50°C, and 60°C. The results show that droplet evaporation on superhydrophobic surfaces, driven by either mass diffusion at ambient conditions or by substrate heating, suppresses

  1. Large-scale facilitation of a sessile community by an invasive habitat-forming snail

    Science.gov (United States)

    Thyrring, Jakob; Thomsen, Mads Solgaard; Wernberg, Thomas

    2013-12-01

    We provide an example of extensive facilitation of a sessile community throughout an invaded estuary by the invasive snail Batillaria australis. We show that B. australis greatly increases a limiting resource (attachment space) to a community of sessile organisms and estimate that a large part of the invaded estuary now contain ca. 50 times more sessile individuals associated with the invader than all native snails combined. We argue that native snails are unlikely to have been dramatically reduced by the invader, and we therefore suggest that the shell-attached sessile community, as a functional group, has benefitted significantly from this invasion. These results expand the current understanding of how invaded marine systems respond to habitat-forming invaders.

  2. Evaporation and fluid dynamics of a sessile drop of capillary size

    OpenAIRE

    Barash, L. Yu.; Bigioni, T. P.; Vinokur, V.M.; Shchur, L. N.

    2008-01-01

    Theoretical description and numerical simulation of an evaporating sessile drop are developed. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop and the diffusion of vapor in air. A shape of the rotationally symmetric drop is determined within the quasistationary approximation. Nonstationary effects in the diffusion of the vapor are also taken into account. Simulation results agree well with the data of evaporation rat...

  3. Induction of immune response to the 17 kDa OMPA Burkholderia cenocepacia polypeptide and protection against pulmonary infection in mice after nasal vaccination with an OMP nanoemulsion-based vaccine.

    Science.gov (United States)

    Makidon, P E; Knowlton, J; Groom, J V; Blanco, L P; LiPuma, J J; Bielinska, A U; Baker, J R

    2010-05-01

    Burkholderia cepacia complex (Bcc) are opportunistic bacteria associated with life-threatening illness in persons with cystic fibrosis. Once Bcc colonization is established, these antimicrobial-resistant and biofilm-forming bacteria are difficult to eradicate and are associated with increased rates of morbidity and mortality. At present, no vaccines are available to prevent the Bcc infection. There is currently a paucity of published information regarding the development of vaccines designed to prevent Burkholderia colonization. This work expands on the recent studies published by Bertot et al. [Infect Immun 75(6):2740-2752, 2007], where successful protective immune responses were generated in mice using a B. multivorans OMP-based vaccine. Here, we evaluate an experimental mucosal vaccine against Bcc using a novel mucosal adjuvant (nanoemulsion) and a novel B. cenocepacia-based OMP antigen. The OMP antigen derived from B. cenocepacia was mixed with either nanoemulsion or with PBS and delivered intranasally to CD-1 mice. Serum analysis showed robust IgG and mucosal secretory IgA immune responses in vaccinated versus control mice. The antibodies had cross-neutralizing activity against both B. cenocepacia and B. multivorans species. We found that immunized mice were protected against pulmonary colonization with B. cenocepacia. We have also identified that a 17 kDa OmpA-like protein highly conserved between Burkholderia and Ralstonia species as a new immunodominant epitope in mucosal immunization.

  4. The ornibactin biosynthesis and transport genes of Burkholderia cenocepacia are regulated by an extracytoplasmic function sigma factor which is a part of the Fur regulon.

    Science.gov (United States)

    Agnoli, Kirsty; Lowe, Carolyn A; Farmer, Kate L; Husnain, Seyyed I; Thomas, Mark S

    2006-05-01

    Burkholderia cenocepacia mutants that fail to produce the siderophore ornibactin were obtained following mutagenesis with mini-Tn5Tp. These mutants were shown to be growth restricted under conditions of iron depletion. In eight of the mutants, the transposon had integrated into one of two genes, orbI and orbJ, encoding nonribosomal peptide synthetases. In the other mutant, the transposon had inserted into an open reading frame, orbS, located upstream from orbI. The polypeptide product of orbS exhibits a high degree of similarity to the Pseudomonas aeruginosa extracytoplasmic function (ECF) sigma factor PvdS but possesses an N-terminal extension of approximately 29 amino acids that is not present in PvdS. Three predicted OrbS-dependent promoters were identified within the ornibactin gene cluster, based on their similarity to PvdS-dependent promoters. The iron-regulated activity of these promoters was shown to require OrbS. Transcription of the orbS gene was found to be under the control of an iron-regulated sigma(70)-dependent promoter. This promoter, but not the OrbS-dependent promoters, was shown to be a target for repression by the global regulator Fur. Our results demonstrate that production of ornibactin by B. cenocepacia in response to iron starvation requires transcription of an operon that is dependent on the Fur-regulated ECF sigma factor gene orbS. A mechanism is also proposed for the biosynthesis of ornibactin.

  5. Characterization of biofluids prepared by sessile drop formation.

    Science.gov (United States)

    Esmonde-White, Karen A; Esmonde-White, Francis W L; Morris, Michael D; Roessler, Blake J

    2014-06-07

    Sessile drop formation, also called drop deposition, has been studied as a potential medical diagnostic, but the effects of complex biofluid rheology on the final deposition pattern are not well understood. We studied two model biofluids, blood plasma and synovial fluid, when deposited onto slightly hydrophilic substrates forming a contact angle of 50-90°. Drops were imaged during the evaporation process and geometric properties of the drop, such as contact angle and drop height, were calculated from the images. The resulting dried biofluid drops were then examined using light microscopy and Raman spectroscopy to assess morphological and chemical composition of the dried drop. The effect of substrate contact angle (surface wetting) and fluid concentration was examined. We found that when biofluids are deposited onto slightly hydrophilic surfaces, with a contact angle of 50-90°, a ring-shaped deposit was formed. Analysis of the drying drop's geometric properties indicates that biofluid dynamics follow the piling model of drop formation, as proposed by Deegan et al. The final deposition pattern varied with substrate surface and concentration, as shown by light microscopy photos of dried drops. The chemical composition of the outer ring was minimally affected by substrate surface, but the spatial heterogeneity of protein distribution within the ring varied with concentration. These results indicate that biofluid drop deposition produces ring-shaped deposits which can be examined by multiple analytical techniques.

  6. Measurement of dynamic surface tension by mechanically vibrated sessile droplets

    Science.gov (United States)

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.

  7. Evaporation of sessile droplets on smooth and structured substrates

    Science.gov (United States)

    Colinet, Pierre; Flandroy, Marie; Dehaeck, Sam; Rednikov, Alexey; Sobac, Benjamin; Tsoumpas, Yannis

    2015-11-01

    Evaporation of sessile droplets remains a topic of active research nowadays, not only due to its widespread occurrence both in nature and technology, but also because it raises a number of interesting fundamental questions. Among these, the influence of the substrate topography is far from being understood. In this presentation, we focus on the difference between droplet evaporation dynamics on a smooth substrate and on substrates with controlled geometrical heterogeneities (square or hexagonal arrays of cylindrical pillars). While the wetting dynamics of droplets on such structured substrates has already been studied (in particular it is known that the droplet shape typically tends to adopt the symmetry of the pattern it lies upon), the influence the structure has on the evaporation dynamics (including the influence of pinning) has not yet received much attention. From interferometric measurements of droplet shapes, we highlight in particular that the evaporation from structured substrates is generally faster than on smooth substrates, and that the scaling exponents characterizing the evolution of radius versus time are also different. Pinning is also shown to be favored above a certain surface fraction of pillars, both for hexagonal and square arrays. Financial support of FRS-FNRS, ESA-BELSPO PRODEX, ULB, and BELSPO IAP 7/38 is gratefully acknowledged.

  8. Ultrasonic estimation of the contact angle of a sessile droplet

    Energy Technology Data Exchange (ETDEWEB)

    Quintero, R.; Simonetti, F. [Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, OH 45221 (United States)

    2014-02-18

    Radiation of energy by large amplitude leaky Rayleigh waves is regarded as one of the key physical mechanisms regulating the actuation and manipulation of droplets in surface acoustic wave (SAW) microfluidic devices. The interaction between a SAW and a droplet is highly complex and is presently the subject of extensive research. This paper investigates the existence of an additional interaction mechanism based on the propagation of quasi-Stoneley waves inside sessile droplets deposited on a solid substrate. In contrast with the leaky Rayleigh wave, the energy of the Stoneley wave is confined within a thin fluid layer in contact with the substrate. The hypothesis is confirmed by three-dimensional finite element simulations and ultrasonic scattering experiments measuring the reflection of Rayleigh waves from droplets of different diameters. Moreover, real-time monitoring of the droplet evaporation process reveals a clear correlation between the droplet contact angle and the spectral information of the reflected Rayleigh signal, thus paving the way for ultrasonic measurements of surface tension.

  9. Understanding (sessile/constrained) bubble and drop oscillations.

    Science.gov (United States)

    Milne, A J B; Defez, B; Cabrerizo-Vílchez, M; Amirfazli, A

    2014-01-01

    The diffuse literature on drop oscillation is reviewed, with an emphasis on capillary wave oscillations of constrained drops. Based on the review, a unifying conceptual framework is presented for drop and bubble oscillations, which considers free and constrained drops/bubbles, oscillation of the surface or the bulk (i.e. center of mass) of the drop/bubble, as well as different types of restoring forces (surface tension, gravity, electromagnetic, etc). Experimental results (both from literature and from a new set of experiments studying sessile drops in cross flowing air) are used to test mathematical models from literature, using a novel whole profile analysis technique for the new experiments. The cause of oscillation (cross flowing air, vibrated surface, etc.) is seen not to affect oscillation frequency. In terms of models, simplified models are seen to poorly predict oscillation frequencies. The most advanced literature models are found to be relatively accurate at predicting frequency. However it is seen that no existing models are reliably accurate across a wide range of contact angles, indicating the need for advanced models/empirical relations especially for drops undergoing the lowest frequency mode of oscillation (the order 1 degree 1 non-axisymmetric 'bending' mode that corresponds to a lateral 'rocking' motion of the drop).

  10. How long does it take for sessile droplets to evaporate?

    Science.gov (United States)

    Wilson, Stephen; Stauber, Jutta; Duffy, Brian; Sefiane, Khellil

    2014-11-01

    The evaporation of sessile droplets plays a crucial part in many practical applications, and in many of these applications it is important to be able to understand and/or control the lifetimes of droplets. The lifetime of an evaporating droplet depends on the manner in which it evaporates. There are various qualitatively different modes of droplet evaporation, of which the most extreme are the constant radius mode (in which the contact line is always pinned) and the constant angle mode (in which the contact angle θ always takes its initial value θ =θ0), and probably the most commonly occurring is the stick-slide mode (in which the drop initially evaporates in a constant radius phase until θ reaches a critical transition angle θ*, and thereafter evaporates in a constant angle phase with θ =θ*). In this talk we describe a theoretical model for the stick-slide mode and discuss the relationship between θ0 and θ* and its implications. Theoretical predictions for the lifetimes of droplets are compared with previously published experimental results. Further details of the theoretical model are given in the recent paper by Stauber, Wilson, Duffy and Sefiane [J. Fluid Mech. 744, R2 (2014)]. Currently a Leverhulme Trust Research Fellow supported by Award RF-2013-355.

  11. Face Coat Materials Through Sessile Drop and Investment Casting Methods

    Science.gov (United States)

    Cheng, Xu; Yuan, Chen; Blackburn, Stuart; Withey, Paul A.

    2014-06-01

    Investment casting is uniquely suited to the manufacture of Ti alloys for the production of near net-shape components, reducing material waste, and machining costs. Because of the high reactivity of titanium and its based alloy, the molds which are used in the investment casting process require high chemical inertness, which results in them being very costly and non-recyclable. In order to reduce the cost of these molds, traditionally using yttria as the face coat, two alternative molds are developed in this study with face coat materials of Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2. The slurry properties and chemical inertness of the face coats were evaluated for viscosity, thermal expansion, friability, and phase development. The chemical inertness of these two molds were determined using both the sessile drop test and investment casting to identify the levels of interaction with a Ti-45Al-2Mn-2Nb-0.2B alloy. The results illustrated that the molds using Y2O3-Al2O3 and Y2O3-Al2O3-ZrO2 as the face coats both showed excellent sintering properties and chemical inertness when compared to the yttria face coat. They can consequently be used as two alternative face coats for the investment casting of TiAl alloys.

  12. Sessile alveolar macrophages communicate with alveolar epithelium to modulate immunity

    Science.gov (United States)

    Westphalen, Kristin; Gusarova, Galina A.; Islam, Mohammad N.; Subramanian, Manikandan; Cohen, Taylor S.; Prince, Alice S.; Bhattacharya, Jahar

    2014-02-01

    The tissue-resident macrophages of barrier organs constitute the first line of defence against pathogens at the systemic interface with the ambient environment. In the lung, resident alveolar macrophages (AMs) provide a sentinel function against inhaled pathogens. Bacterial constituents ligate Toll-like receptors (TLRs) on AMs, causing AMs to secrete proinflammatory cytokines that activate alveolar epithelial receptors, leading to recruitment of neutrophils that engulf pathogens. Because the AM-induced response could itself cause tissue injury, it is unclear how AMs modulate the response to prevent injury. Here, using real-time alveolar imaging in situ, we show that a subset of AMs attached to the alveolar wall form connexin 43 (Cx43)-containing gap junction channels with the epithelium. During lipopolysaccharide-induced inflammation, the AMs remained sessile and attached to the alveoli, and they established intercommunication through synchronized Ca2+ waves, using the epithelium as the conducting pathway. The intercommunication was immunosuppressive, involving Ca2+-dependent activation of Akt, because AM-specific knockout of Cx43 enhanced alveolar neutrophil recruitment and secretion of proinflammatory cytokines in the bronchoalveolar lavage. A picture emerges of a novel immunomodulatory process in which a subset of alveolus-attached AMs intercommunicates immunosuppressive signals to reduce endotoxin-induced lung inflammation.

  13. Ring formation from a drying sessile colloidal droplet

    Directory of Open Access Journals (Sweden)

    Wenbin Zhang

    2013-10-01

    Full Text Available Ring formation from drying sessile colloidal droplets (∼1.0 mm in size containing microparticles of silicon or polystyrene was investigated with video microscopy. Results show that ring formation begins at the pinned contact line with the growth of an annular nucleus in a line by line way, which recedes inward albeit only slightly, followed by stacking of particles when the flow velocity becomes sufficiently large. The central height of the droplet decreases linearly with evaporation time, which implies that in the early stage, the number of particles arriving at contact line increases with time in a power law N∝t3/(1 + λ, where the parameter λ, according to Deegan's evaporation model, is related to the contact angle via λ=π−2θc2π−2θc. Experimental values of λ agree well with model calculation for small contact angles, but are relatively smaller in the case of large contact angles. ‘Amorphization’ mechanism for the deposit at different stages of evaporation is discussed. Marangoni flow in a droplet on heated substrate introduces a desorption path for particles along the liquid surface, which can partially resolve the ring. Residual particles floating on the liquid surface may leave behind a homogeneous monolayer coating inside the dried spot. A “jump” in the droplet surface area at later stage of evaporation seems inevitably to cause a depletion zone of particles next to the ring. These results may be helpful for the development of strategies towards suppression of coffee ring effect and/or obtaining homogeneous coatings from drying colloidal suspension.

  14. Effect of essential oils prepared from Thai culinary herbs on sessile Candida albicans cultures.

    Science.gov (United States)

    Hovijitra, Ray S; Choonharuangdej, Suwan; Srithavaj, Theerathavaj

    2016-01-01

    Although medicinal herbs with fungicidal effects have been ubiquitously employed in traditional medicine, such effects of culinary herbs and spices still have to be elucidated. Therefore, it is noteworthy to determine the antifungal efficacy of some edible herbs used in Thai cuisine against sessile Candida albicans cultures, and to inquire if they can be further utilized as naturally-derived antifungals. Fourteen essential oils extracted from Thai culinary herbs and spices were tested for their antifungal activity against C. albicans using the agar disk diffusion method followed by broth micro-dilution method for the determination of minimum inhibitory concentration (MIC) and minimum fungicidal concentration. The oils with potent antifungal effects against planktonic fungi were then assessed for their effect against sessile fungus (adherent organisms and established biofilm culture). MIC of the oils against sessile C. albicans was evaluated by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide reduction assay. All selected culinary herbs and spices, except galangal, garlic, and turmeric, exhibited inhibitory effects on planktonic yeast cells. Cinnamon bark and sweet basil leaf essential oils exhibited potent fungicidal effect on planktonic and sessile fungus. Sessile MICs were 8-16 times higher than planktonic MICs. Consequently, both cinnamon bark and sweet basil leaf herbal oils seem to be highly effective anti-Candida choices. (J Oral Sci 58, 365-371, 2016).

  15. Simple Hydrostatic Model of Contact Angle Hysteresis of a Sessile Drop on Rough Surface

    Institute of Scientific and Technical Information of China (English)

    毛在砂; 杨超; 陈家镛

    2005-01-01

    The phenomenon of hysteresis of contact angle is an important topic subject to a long time of argument.A simple hydrostatic model of sessile drops under the gravity in combination with an ideal surface roughness model is used to interpret the process of drop volume increase or decrease of a planar sessile drop and to shed light on the contact angle hysteresis and its relationship with the solid surface roughness. With this model, the advancing and receding contact angles are conceptually explained in terms of equilibrium contact angle and surface roughness only,without invoking the thermodynamic multiplicity. The model is found to be qualitatively consistent to experimental observations on contact angle hysteresis and it suggests a possible way to approach the hysteresis of three-dimensional sessile drops.

  16. Phytosociological studies of the forests with sessile oak and Norway spruce from South-Eastern Transylvania

    Directory of Open Access Journals (Sweden)

    Adrian Indreica

    2011-02-01

    Full Text Available The forests with sessile oak (Quercus petraea and Norway spruce (Picea abies from south-eastern Transylvania represent a peculiar type of phytocenoses, rather unusual for the present-day vegetation of Romania’s territory. Aim of the study is to provide a detailed description of the vegetation and to identify the phytosociological and typological units to which it could belong. Beside this, stand structure and regeneration status of the main tree species are illustrated. The studied area is located around Carpathian intermountain depressions Braşov and Ciuc, where vegetation had a peculiar history and today sessile oak forests on high altitude exists, interfering with spruce forests. The hypothesis of the process naturalness is supported by vegetation history in the area, climate, stand structure and peculiarities of herb layer composition (the mixture of relic of both mountain-boreal origin and south-European origin, like Vaccinium vitis-idaea, Pyrola rotundifolia and respectively Potentilla micrantha, Lathyrus venetus respectively. Sintaxonomically, studied phytocenoses with sessile oak and spruce belong mainly to acidophilus oak forests (Luzulo luzuloidis-Quercetum petraeae, but some of them resemble oak-hornbeam forests (Carici pilosae-Carpinetum, indicating a more recent change in stand structure and suggesting that not the soil, but the climate is the driving force of succession. Regeneration of sessile oak is at least satisfactory, but the expansion of spruce in such stands could seriously restrict the survival of sessile oak. A new typological unit will be appropriate,for a better management of sessile oak forests with spruce admixture.

  17. Recruitment Variability of Coral Reef Sessile Communities of the Far North Great Barrier Reef.

    Science.gov (United States)

    Luter, Heidi M; Duckworth, Alan R; Wolff, Carsten W; Evans-Illidge, Elizabeth; Whalan, Steve

    2016-01-01

    One of the key components in assessing marine sessile organism demography is determining recruitment patterns to benthic habitats. An analysis of serially deployed recruitment tiles across depth (6 and 12 m), seasons (summer and winter) and space (meters to kilometres) was used to quantify recruitment assemblage structure (abundance and percent cover) of corals, sponges, ascidians, algae and other sessile organisms from the northern sector of the Great Barrier Reef (GBR). Polychaetes were most abundant on recruitment titles, reaching almost 50% of total recruitment, yet covered reefs.

  18. Numerical simulations of evaporative instabilities in sessile drops of ethanol on heated substrates

    Science.gov (United States)

    Semenov, Sergey; Carle, Florian; Medale, Marc; Brutin, David

    2015-11-01

    The work is focussed on numerical simulations of thermo-convective instabilities in evaporating pinned sessile droplets of ethanol on heated substrates. Computed evaporation rate of a droplet is validated against parabolic flight experiments and semi-empirical theory presented here. To the best authors' knowledge, this is the first study which combines theoretical, experimental and computational approaches in convective evaporation of sessile droplets. The influence of gravity level on evaporation rate and contributions of different mechanisms of vapor transport (diffusion, Stefan flow, natural convection) are shown. The qualitative difference (in terms of developing thermo-convective instabilities) between steady-state and unsteady numerical approaches is demonstrated.

  19. Particle and substrate charge effects on colloidal self-assembly in a sessile drop.

    Science.gov (United States)

    Yan, Qingfeng; Gao, Li; Sharma, Vyom; Chiang, Yet-Ming; Wong, C C

    2008-10-21

    By direct video monitoring of dynamic colloidal self-assembly during solvent evaporation in a sessile drop, we investigated the effect of surface charge on the ordering of colloidal spheres. The in situ observations revealed that the interaction between charged colloidal spheres and substrates affects the mobility of colloidal spheres during convective self-assembly, playing an important role in the colloidal crystal growth process. Both ordered and disordered growth was observed depending on different chemical conditions mediated by surface charge and surfactant additions to the sessile drop system. These different self-assembly behaviors were explained by the Coulombic and hydrophobic interactions between surface-charged colloidal spheres and substrates.

  20. Evaporation dynamics and Marangoni number estimation for sessile picoliter liquid drop of binary mixture solution

    Directory of Open Access Journals (Sweden)

    Lebedev-Stepanov Peter

    2016-01-01

    Full Text Available We propose the evaporation model of picoliter sessile drop of binary solvent mixture (with infinitely soluble in each other components based on Hu and Larson solution for single solvent sessile drop and Raoult law for saturated vapor density of components of binary mixture in wide range of undimensional molar binary concentration of the components. Concentration Marangoni number estimation for such a system is also considered for prediction of liquid flows structure for further applications in dissipative particle dynamics in binary mixture evaporating drop.

  1. On the derivation of Young's equation for sessile drops: nonequilibrium effects due to evaporation.

    Science.gov (United States)

    Butt, Hans-Jürgen; Golovko, Dmytro S; Bonaccurso, Elmar

    2007-05-17

    Sessile liquid drops have a higher vapor pressure than planar liquid surfaces, as quantified by Kelvin's equation. In classical derivations of Young's equation, this fact is often not taken into account. For an open system, a sessile liquid drop is never in thermodynamic equilibrium and will eventually evaporate. Practically, for macroscopic drops the time of evaporation is so long that nonequilibrium effects are negligible. For microscopic drops evaporation cannot be neglected. When a liquid is confined to a closed system, real equilibrium can be established. Experiments on the evaporation of water drops confirm the calculations.

  2. Amplifying and attenuating the coffee-ring effect in drying sessile nanofluid droplets

    Science.gov (United States)

    Crivoi, A.; Duan, Fei

    2013-04-01

    Experiments and simulations to promote or attenuate the “coffee-ring effect” for pinned sessile nanofluid droplets are presented. The addition of surfactant inside a water suspension of aluminum oxide nanoparticles results in coffee-ring formation after the pinned sessile droplets are fully dried on a substrate, while droplets of the same suspension without the surfactant produce a fine uniform coverage. A mathematical model based on diffusion-limited cluster-cluster aggregation has been developed to explain the observed difference in the experiments. The simulations show that the particle sticking probability is a crucial factor on the morphology of finally dried structures.

  3. Evaluating surface energy components of asphalt binders using Wilhelmy Plate and Sessile Drop Techniques

    OpenAIRE

    Bahramian, Anohe

    2012-01-01

    In this Study, the surface energy was investigated for six penetration grade 70/100 bitumen binders. Wilhelmy Plate and the Sessile Drop were used to determine the contact angles. The purpose of this study was to compare the Wilhelmy Plate method with the Sessile Drop method, and to compare the significance of Owens-Wendt model with the significance of Acid Base model by correlating surface energy components. Better R2 –values were found for surface energy components by using the Owens-Wendt ...

  4. Odorous house ants (Tapinoma sessile) as back-seat drivers of localized ant decline in urban habitats.

    Science.gov (United States)

    Salyer, Adam; Bennett, Gary W; Buczkowski, Grzegorz A

    2014-01-01

    Invasive species and habitat disturbance threaten biodiversity worldwide by modifying ecosystem performance and displacing native organisms. Similar homogenization impacts manifest locally when urbanization forces native species to relocate or reinvade perpetually altered habitat. This study investigated correlations between ant richness and abundance in response to urbanization and the nearby presence of invasive ant species, odorous house ants (Tapinoma sessile), within its native region. Surveying localized ant composition within natural, semi-natural, and urban habitat supported efforts to determine whether T. sessile appear to be primary (drivers) threats as instigators or secondary (passengers) threats as inheritors of indigenous ant decline. Sampling 180 sites, evenly split between all habitats with and without T. sessile present, yielded 45 total species. Although urbanization and T. sessile presence factors were significantly linked to ant decline, their interaction correlated to the greatest reduction of total ant richness (74%) and abundance (81%). Total richness appeared to decrease from 27 species to 18 when natural habitat is urbanized and from 18 species to 7 with T. sessile present in urban plots. Odorous house ant presence minimally influenced ant communities within natural and semi-natural habitat, highlighting the importance of habitat alteration and T. sessile presence interactions. Results suggest urbanization releases T. sessile from unknown constraints by decreasing ant richness and competition. Within urban environment, T. sessile are pre-adapted to quickly exploit new resources and grow to supercolony strength wherein T. sessile drive adjacent biodiversity loss. Odorous house ants act as passengers and drivers of ecological change throughout different phases of urban 'invasion'. This progression through surviving habitat alteration, exploiting new resources, thriving, and further reducing interspecific competition supports a "back

  5. Bubble formation during the collision of a sessile drop with a meniscus

    NARCIS (Netherlands)

    Keij, D.L.; Winkels, K.G.; Castelijns, H.; Riepen, M.; Snoeijer, J.H.

    2013-01-01

    The impact of a sessile droplet with a moving meniscus, as encountered in processes such as dip-coating, generically leads to the entrapment of small air bubbles. Here we experimentally study this process of bubble formation by looking through the liquid using high-speed imaging. Our central finding

  6. Impact of manufactured TiO2 nanoparticles on planktonic and sessile bacterial communities.

    Science.gov (United States)

    Jomini, Stéphane; Clivot, Hugues; Bauda, Pascale; Pagnout, Christophe

    2015-07-01

    In the present study, we conducted a 2 week microcosm experiment with a natural freshwater bacterial community to assess the effects of titanium dioxide nanoparticles (TiO2-NPs) at various concentrations (0, 1, 10 and 100 mg/L) on planktonic and sessile bacteria under dark conditions. Results showed an increase of planktonic bacterial abundance at the highest TiO2-NP concentration, concomitant with a decrease from that of sessile bacteria. Bacterial assemblages were most affected by the 100 mg/L TiO2-NP exposure and overall diversity was found to be lower for planktonic bacteria and higher for sessile bacteria at this concentration. In both compartments, a 100 mg/L TiO2-NPs exposure induced a decrease in the ratio between the Betaproteobacteria and Bacteroidetes. For planktonic communities, a decrease of Comamonadaceae was observed concomitant with an increase of Oxalobacteraceae and Cytophagaceae (especially Emticicia). For sessile communities, results showed a strong decrease of Betaproteobacteria and particularly of Comamonadaceae.

  7. Comparison of the lateral retention forces on sessile and pendant water drops on a solid surface

    OpenAIRE

    de la Madrid, Rafael; Whitehead, Taylor; Irwin, George

    2015-01-01

    We present a simple experiment that demonstrates how a water drop hanging from a Plexiglas surface (pendant drop) experiences a lateral retention force that is comparable to, and in some cases larger than, the lateral retention force on a drop resting on top of the surface (sessile drop). The experiment also affords a simple demonstration of the Coriolis effect in two dimensions.

  8. Evaporation of pure liquid sessile and spherical suspended drops: a review.

    Science.gov (United States)

    Erbil, H Yildirim

    2012-01-15

    A sessile drop is an isolated drop which has been deposited on a solid substrate where the wetted area is limited by a contact line and characterized by contact angle, contact radius and drop height. Diffusion-controlled evaporation of a sessile drop in an ambient gas is an important topic of interest because it plays a crucial role in many scientific applications such as controlling the deposition of particles on solid surfaces, in ink-jet printing, spraying of pesticides, micro/nano material fabrication, thin film coatings, biochemical assays, drop wise cooling, deposition of DNA/RNA micro-arrays, and manufacture of novel optical and electronic materials in the last decades. This paper presents a review of the published articles for a period of approximately 120 years related to the evaporation of both sessile drops and nearly spherical droplets suspended from thin fibers. After presenting a brief history of the subject, we discuss the basic theory comprising evaporation of micrometer and millimeter sized spherical drops, self cooling on the drop surface and evaporation rate of sessile drops on solids. The effects of drop cooling, resultant lateral evaporative flux and Marangoni flows on evaporation rate are also discussed. This review also has some special topics such as drop evaporation on superhydrophobic surfaces, determination of the receding contact angle from drop evaporation, substrate thermal conductivity effect on drop evaporation and the rate evaporation of water in liquid marbles.

  9. Velocity field measurements in an evaporating sessile droplet by means of micro-PIV technique

    Directory of Open Access Journals (Sweden)

    Yagodnitsyna Anna

    2016-01-01

    Full Text Available Velocity fields are measured in evaporating sessile droplets on two substrates with different contact angles and contact angle hysteresis using micro resolution particle image velocimetry technique. Different flow patterns are observed in different stages of droplet evaporation: a flow with vortices and a radial flow. Flow structure is found to be similar for droplets on different substrates.

  10. Speciation, diversification, and coexistence of sessile species that compete for space

    DEFF Research Database (Denmark)

    Mitarai, Namiko; Heinsalu, Els; Sneppen, Kim

    2014-01-01

    characterized by many types of ecological interactions. A general problem is to understand conditions that support a dynamically maintained coexistence of many species in an ecosystem over a long time span. In the present paper we propose a lattice model of multiple competing and evolving sessile species. When...

  11. Comparison of the lateral retention forces on sessile and pendant water drops on a solid surface

    Science.gov (United States)

    de la Madrid, Rafael; Whitehead, Taylor; Irwin, George M.

    2015-06-01

    We present a simple experiment that demonstrates how a water drop hanging from a Plexiglas surface (pendant drop) experiences a lateral retention force that is comparable to, and in some cases larger than, the lateral retention force on a drop resting on top of the surface (sessile drop). The experiment also affords a simple demonstration of the Coriolis effect in two dimensions.

  12. Multimodality imaging in the diagnosis of deep vein thrombosis and popliteal pseudoaneurysm complicating a sessile osteochondroma

    Energy Technology Data Exchange (ETDEWEB)

    Christensen, Jared D.; Monu, Johnny U.V. [University of Rochester School of Medicine and Dentistry, Department of Imaging Sciences, 601 Elmwood Ave., Box 648, Rochester, NY (United States)

    2008-08-15

    Synergistic use of ultrasonography, radiography, multidetector CT (MDCT) and MRI enabled a prompt and accurate diagnosis of a nonocclusive popliteal vein thrombus (deep venous thrombosis, DVT) and a pseudoaneurysm complicating a sessile osteochondroma in an 11-year-old boy who presented in the emergency department with sudden-onset nontraumatic pain in the posterior aspect of the knee. (orig.)

  13. The Role of Tree Mortality in Vitality Assessment of Sessile Oak Forests

    Directory of Open Access Journals (Sweden)

    Imre Berki

    2016-12-01

    Full Text Available Background and Purpose: The drought-induced vitality loss of sessile oak (Quercus petraea (Matt. Liebl. has been continuously observed in Hungary for more than three decades. The decrease in stand density as a consequence of drought-induced mortality has not been taken into consideration in most of the monitoring methods. Materials and Methods: Forest stands without any forest intervention during the last 30 years were selected. Quadrats were designated for the analysis in 18 sessile oak stands along a climatic transect in which foliage transparency and stand density were measured. Drought stress was defined by the water balance approach. By combining the foliage transparency and the relative stand density, a new cumulative assessment method of stand level vitality was introduced to get a more realistic picture about the effects of long-term drought (lasting for several decades on the sessile oak forests in South-East Europe. Results: The calculated health status (100% - vital; 0% - dead of the sessile oak stands was between 70-90% in the moist South-West Hungary and below 50% close to its xeric limit. The individual tree-based vitality assessment method gave considerably higher values on 17 out of 18 sites. Conclusions: Forest monitoring should also consider stand level-based tree mortality in oak forests while assessing health condition especially close to its xeric limit. The proposed new method provides a more realistic picture about the effects of climate change on sessile oak stands particularly for forest managers interested in changing in the wood stock of forests.

  14. How Natural Evaporation Temporally Self-Tunes an Oscillating Sessile Droplet To Resonate at Different Modes.

    Science.gov (United States)

    Sanyal, Apratim; Basu, Saptarshi

    2016-05-17

    We report the dynamics and underlying physics of evaporation driven transitions and autotuning of oscillation modes in sessile droplets subject to substrate perturbations. We have shown that evaporation controls temporal transition of the oscillation mode with a spatially downward shift of nodes (surface locations with zero displacement) toward the three-phase contact line. We have explained the physical mechanism using two parameters: the first quantifies evaporation driven tuning for resonance detection, and the second parameter characterizes mode lifetime which is found to be governed by evaporation dynamics. It is desirable to achieve autotuning of the oscillation modes in sessile droplets that essentially self-evolves in a spatiotemporal manner with continued evaporation. The insights suggest control of mode resonances is possible, which in turn will allow precision manipulations at droplet scale crucial for many applications such as surface patterning and others.

  15. Incarceration of a sessile uterine fibroid in an umbilical hernia during pregnancy.

    Science.gov (United States)

    Seims, A D; Lube, M W

    2009-06-01

    On rare occasions, uterine fibroids complicate pregnancy. More commonly, fibroids exert a mass effect that either prevents implantation of an egg or becomes problematic as a fetus grows. Less frequently, pregnancies are affected by fibroid herniation through a fascial defect. Several publications describing herniation of pedunculated fibroids exist, two of which were in umbilical hernia sacs. There is, to our knowledge, only one publication describing the presence of a sessile uterine fibroid in an umbilical hernia. This case report adds to the literature by describing a 34-year-old primigravid woman with an umbilical hernia that contained a sessile uterine fibroid and provides parameters that can be used in the initial evaluation of a pregnant woman with an abdominal wall hernia.

  16. Dynamics of a disturbed sessile drop measured by atomic force microscopy (AFM).

    Science.gov (United States)

    McGuiggan, Patricia M; Grave, Daniel A; Wallace, Jay S; Cheng, Shengfeng; Prosperetti, Andrea; Robbins, Mark O

    2011-10-04

    A new method for studying the dynamics of a sessile drop by atomic force microscopy (AFM) is demonstrated. A hydrophobic microsphere (radius, r ∼ 20-30 μm) is brought into contact with a small sessile water drop resting on a polytetrafluoroethylene (PTFE) surface. When the microsphere touches the liquid surface, the meniscus rises onto it because of capillary forces. Although the microsphere volume is 6 orders of magnitude smaller than the drop, it excites the normal resonance modes of the liquid interface. The sphere is pinned at the interface, whose small (drop volumes between 5 and 200 μL. The results for the two lowest normal modes are quantitatively consistent with continuum calculations for the natural frequency of hemispherical drops with no adjustable parameters. The method may enable sensitive measurements of volume, surface tension, and viscosity of small drops.

  17. Evaporation kinetics of sessile droplets of aqueous suspensions of inorganic nanoparticles.

    Science.gov (United States)

    Trybala, Anna; Okoye, Adaora; Semenov, Sergey; Agogo, Hezekiah; Rubio, Ramón G; Ortega, Francisco; Starov, Víctor M

    2013-08-01

    Evaporation kinetics of sessile droplets of aqueous suspension of inorganic nanoparticles on solid substrates of various wettabilities is investigated from both experimental and theoretical points of view. Experimental results on evaporation of various kinds of inorganic nanosuspensions on solid surfaces of different hydrophobicities/hydrophilicities are compared with our theoretical predictions of diffusion limited evaporation of sessile droplets in the presence of contact angle hysteresis. The theory describes two main stages of evaporation process: (I) evaporation with a constant radius of the droplet base when the contact angle decreases from static advancing contact angle down to static receding contact angle and (II) evaporation with constant contact angle equal to the static receding contact angle when the radius of the droplet base decreases. Theoretically predicted universal dependences for both evaporation stages are compared with experimental data, and a very good agreement is found.

  18. Comparison of sessile drop and captive bubble methods on rough homogeneous surfaces: a numerical study.

    Science.gov (United States)

    Montes Ruiz-Cabello, F J; Rodríguez-Valverde, M A; Marmur, A; Cabrerizo-Vílchez, M A

    2011-08-02

    Quasi-static experiments using sessile drops and captive bubbles are the most employed methods for measuring advancing and receding contact angles on real surfaces. These observable contact angles are the most easily accessible and reproducible. However, some properties of practical surfaces induce certain phenomena that cause a built-in uncertainty in the estimation of advancing and receding contact angles. These phenomena are well known in surface thermodynamics as stick-slip phenomena. Following the work of Marmur (Marmur, A. Colloids Surf., A 1998, 136, 209-215), where the stick-slip effects were studied with regard to sessile drops and captive bubbles on heterogeneous surfaces, we developed a novel extension of this study by adding the effects of roughness to both methods for contact angle measurement. We found that the symmetry between the surface roughness problem and the chemical heterogeneity problem breaks down for drops and bubbles subjected to stick-slip effects.

  19. An analytical solution for determination of small contact angles from sessile drops of arbitrary size.

    Science.gov (United States)

    Allen, Jeffrey S

    2003-05-15

    An analytical solution to the capillary equation of Young and Laplace is derived that allows determination of the static contact angle based on the volume of a sessile drop and the wetted area of the substrate. This solution does not require numerical integration to determine the drop profile and accounts for surface deformation due to gravitational effects. Calculation of the static contact angle by this method is remarkably simple and accurate when the contact angle is less than 30 degrees. A natural scaling arises in the solution, which provides indication of when a drop is small enough so as to neglect gravitational influences on the surface shape which, for small contact angles, is generally less than 1 microl. The technique described has the simplicity of the spherical cap approximation but remains accurate for any size of sessile drop.

  20. Time-resolved interference unveils nanoscale surface dynamics in evaporating sessile droplet

    Science.gov (United States)

    Verma, Gopal; Singh, Kamal P.

    2014-06-01

    We report a simple optical technique to measure time-resolved nanoscale surface profile of an evaporating sessile fluid droplet. By analyzing the high contrast Newton-ring like dynamical fringes formed by interfering Fresnel reflections, we demonstrated λ/100 ≈ 5 nm sensitivity in surface height (at 0.01-160 nm/s rate) of an evaporating water drop. The remarkably high sensitivity allowed us to precisely measure its transient surface dynamics during contact-line slips, weak perturbations on the evaporation due to external magnetic field and partial confinement of the drop. Further, we measured evaporation dynamics of a sessile water drop on soft deformable surface to demonstrate wide applicability of this technique.

  1. Habitat segregation of sessile marine organisms; Kaiyo fuchaku seibutsu no sumiwake

    Energy Technology Data Exchange (ETDEWEB)

    Isoai, A. [Asahi Glass Co. Ltd., Tokyo (Japan); Kawahara, H.; Shizuri, Y.

    1996-08-01

    In order to develop the safe control agent of sessile marine organisms, the mechanism of habitat segregation of them has been investigated. Among various marine organisms, around 120 species of Porifera and Coelenterata accompanied with less the other sessile organisms were collected, to examine the adhesion prevention activity of their extracts against barnacles and Mytilus edulis. As a result, this activity was found out for 33% of Porifera and 27% of Coelenterata specimens. This means these organisms contain the adhesion prevention substances, and it is considered these chemical substances are practically used for the habitat segregation. Isolation structures of the chemical substances used for the habitat segregation were determined from these organisms. It was made clear that two acceptor genes successfully cloned from Balanus amphitrate are new G-protein coupling type acceptors having similar homology to the adrenaline and serotonin acceptors. 15 refs., 3 figs.

  2. The AHL- and BDSF-dependent quorum sensing systems control specific and overlapping sets of genes in Burkholderia cenocepacia H111.

    Directory of Open Access Journals (Sweden)

    Nadine Schmid

    Full Text Available Quorum sensing in Burkholderia cenocepacia H111 involves two signalling systems that depend on different signal molecules, namely N-acyl homoserine lactones (AHLs and the diffusible signal factor cis-2-dodecenoic acid (BDSF. Previous studies have shown that AHLs and BDSF control similar phenotypic traits, including biofilm formation, proteolytic activity and pathogenicity. In this study we mapped the BDSF stimulon by RNA-Seq and shotgun proteomics analysis. We demonstrate that a set of the identified BDSF-regulated genes or proteins are also controlled by AHLs, suggesting that the two regulons partially overlap. The detailed analysis of two mutually regulated operons, one encoding three lectins and the other one encoding the large surface protein BapA and its type I secretion machinery, revealed that both AHLs and BDSF are required for full expression, suggesting that the two signalling systems operate in parallel. In accordance with this, we show that both AHLs and BDSF are required for biofilm formation and protease production.

  3. Resolving an ostensible inconsistency in calculating the evaporation rate of sessile drops.

    Science.gov (United States)

    Chini, S F; Amirfazli, A

    2016-06-04

    This paper resolves an ostensible inconsistency in the literature in calculating the evaporation rate for sessile drops in a quiescent environment. The earlier models in the literature have shown that adapting the evaporation flux model for a suspended spherical drop to calculate the evaporation rate of a sessile drop needs a correction factor; the correction factor was shown to be a function of the drop contact angle, i.e. f(θ). However, there seemed to be a problem as none of the earlier models explicitly or implicitly mentioned the evaporation flux variations along the surface of a sessile drop. The more recent evaporation models include this variation using an electrostatic analogy, i.e. the Laplace equation (steady-state continuity) in a domain with a known boundary condition value, or known as the Dirichlet problem for Laplace's equation. The challenge is that the calculated evaporation rates using the earlier models seemed to differ from that of the recent models (note both types of models were validated in the literature by experiments). We have reinvestigated the recent models and found that the mathematical simplifications in solving the Dirichlet problem in toroidal coordinates have created the inconsistency. We also proposed a closed form approximation for f(θ) which is valid in a wide range, i.e. 8°≤θ≤131°. Using the proposed model in this study, theoretically, it was shown that the evaporation rate in the CWA (constant wetted area) mode is faster than the evaporation rate in the CCA (constant contact angle) mode for a sessile drop.

  4. Density Measurement of Liquid Ni-Ta Alloys by a Modified Sessile Drop Method

    Institute of Scientific and Technical Information of China (English)

    FANG Liang; XIAO Feng; TAO Zainan; Kusuhiro Mukai

    2005-01-01

    The density of liquid Ni-Ta alloys was measured by using a modified sessile drop method. It is found that the density of the liquid Ni-Ta alloys decreases with the increasing temperature, but increases with the increase of tantalum concentration in the alloys. The molar volume of liquid Ni-Ta binary alloys increases with the increase of temperature and tantalum concentration.

  5. Mechanics of transport phenomena in multi-component sessile drops with solidification

    Science.gov (United States)

    Su, Yeong-Jen; Yang, Wen-Jei; Liu, Jiaching

    1990-01-01

    The mechanics of transport phenomena in multicomponent sessile drops with internal solidification is determined on the basis of an experimental study. A shadowgraph-schlieren system and a microscope-video system are used for the study. It is suggested that present data can be used to enhance the solid or crystal quality in a reduced-gravity environment where both thermo- and diffuso-capillary effects of solidification and crystal growth are dominant.

  6. Graphite/copper alloy interfacial energies determined using the sessile drop method

    Science.gov (United States)

    Devincent, Sandra M.; Ellis, David L.; Michal, Gary M.

    1991-01-01

    Graphite surfaces are not wet by pure copper. This lack of wetting is responsible for a debonding phenomenon that was found in continuous graphite fiber/copper matrix composites materials subjected to elevated temperatures. By suitably alloying copper, its capability to wet graphite surfaces can be enhanced. In situ measurements of graphite/copper alloy wetting angles were made using the sessile drop method. Interfacial energy values were calculated based upon these measurements.

  7. Constrained sessile drop as a new configuration to measure low surface tension in lung surfactant systems.

    Science.gov (United States)

    Yu, Laura M Y; Lu, James J; Chan, Yawen W; Ng, Amy; Zhang, Ling; Hoorfar, Mina; Policova, Zdenka; Grundke, Karina; Neumann, A Wilhelm

    2004-08-01

    Existing methodology for surface tension measurements based on drop shapes suffers from the shortcoming that it is not capable to function at very low surface tension if the liquid dispersion is opaque, such as therapeutic lung surfactants at clinically relevant concentrations. The novel configuration proposed here removes the two big restrictions, i.e., the film leakage problem that is encountered with such methods as the pulsating bubble surfactometer as well as the pendant drop arrangement, and the problem of the opaqueness of the liquid, as in the original captive bubble arrangement. A sharp knife edge is the key design feature in the constrained sessile drop that avoids film leakage at low surface tension. The use of the constrained sessile drop configuration in conjunction with axisymmetric drop shape analysis to measure surface tension allows complete automation of the setup. Dynamic studies with lung surfactant can be performed readily by changing the volume of a sessile drop, and thus the surface area, by means of a motor-driven syringe. To illustrate the validity of using this configuration, experiments were performed using an exogenous lung surfactant preparation, bovine lipid extract surfactant (BLES) at 5.0 mg/ml. A comparison of results obtained for BLES at low concentration between the constrained sessile drop and captive bubble arrangement shows excellent agreement between the two approaches. When the surface area of the BLES film (0.5 mg/ml) was compressed by about the same amount in both systems, the minimum surface tensions attained were identical within the 95% confidence limits.

  8. Dependence of fluid flows in an evaporating sessile droplet on the characteristics of the substrate

    OpenAIRE

    2014-01-01

    Temperature distributions and the corresponding vortex structures in an evaporating sessile droplet are obtained by performing detailed numerical calculations. A Marangoni convection induced by thermal conduction processes in the drop and the substrate is demonstrated to be able to result not only in a single vortex, but also in two or three vortices, depending on the ratio of substrate to fluid thermal conductivities, on the substrate thickness and the contact angle. The "phase diagrams" con...

  9. Particle Separation inside a Sessile Droplet with Variable Contact Angle Using Surface Acoustic Waves.

    Science.gov (United States)

    Destgeer, Ghulam; Jung, Jin Ho; Park, Jinsoo; Ahmed, Husnain; Sung, Hyung Jin

    2017-01-03

    A sessile droplet of water carrying polystyrene microparticles of different diameters was uniformly exposed to high frequency surface acoustic waves (SAWs) produced by an interdigitated transducer (IDT). We investigated the concentration behavior of the microparticles as the SAWs generated a strong acoustic streaming flow (ASF) inside the water droplet and exerted a direct acoustic radiation force (ARF) on the suspended particles, the magnitude of which depended upon the particle diameter. As a result of the ARF, the microparticles were concentrated according to their diameters at different positions inside the sessile droplet placed in the path of the SAW, right in front of the IDT. The microparticle concentration behavior changed as the sessile droplet contact angle with the substrate was varied by adding surfactant to the water or by gradually evaporating the water. The positions at which the smaller and larger microparticles were concentrated remained distinguishable, even at very different experimental conditions. The long-term exposure of the droplets to the SAWs was accompanied by the gradual evaporation of the carrier fluid, which dynamically changed the droplet contact angle as well as the concentration of particles. Complete evaporation of the fluid left behind several concentrated yet separated clusters of particles on the substrate surface. The effect of the droplet contact angle on particles' concentration behavior and consequent separation of particles has been uniquely studied in this SAW-based report.

  10. Comparison of the relaxation of sessile drops driven by harmonic and stochastic mechanical excitations.

    Science.gov (United States)

    Ruiz-Cabello, F J Montes; Rodríguez-Valverde, M A; Cabrerizo-Vílchez, M A

    2011-07-19

    Currently, there is no conclusive evidence regarding the global equilibrium condition of vibrated drops. However, it is well-known that vibration of sessile drops effectively reduces the contact angle hysteresis. In this work, applying a recent methodology for evaluating the most-stable contact angle, we examined the impact of the type of excitation signal (random signal versus periodical signal) on the values of the most-stable contact angle for polymer surfaces. Using harmonic signals, the oscillation frequency affected the postvibration contact angle. Instead, the white noise signal enabled sessile drops to relax regardless of their initial configuration. In spite of that, the values of most-stable contact angle obtained with different signals mostly agreed. We concluded that not only the amount of relaxation can be important for relaxing a sessile drop but also the rate of relaxation. Together with receding contact angle, most-stable contact angle, measured with the proposed methodology, was able to capture the thermodynamic changes of "wetted" polymer surfaces.

  11. Evaporation and fluid dynamics of a sessile drop of capillary size.

    Science.gov (United States)

    Barash, L Yu; Bigioni, T P; Vinokur, V M; Shchur, L N

    2009-04-01

    Theoretical description and numerical simulation of an evaporating sessile drop are developed. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop, and the diffusion of vapor in air. A shape of the rotationally symmetric drop is determined within the quasistationary approximation. Nonstationary effects in the diffusion of the vapor are also taken into account. Simulation results agree well with the data of evaporation rate measurements for the toluene drop. Marangoni forces associated with the temperature dependence of the surface tension generate fluid convection in the sessile drop. Our results demonstrate several dynamical stages of the convection characterized by different number of vortices in the drop. During the early stage the array of vortices arises near a surface of the drop and induces a nonmonotonic spatial distribution of the temperature over the drop surface. The initial number of near-surface vortices in the drop is controlled by the Marangoni cell size which is similar to that given by Pearson for flat fluid layers. This number quickly decreases with time resulting in three bulk vortices in the intermediate stage. The vortices finally transform into the single convection vortex in the drop existing during about 1/2 of the evaporation time.

  12. Surfactant-Enhanced Spreading of Sessile Water Drops on Polypropylene Surfaces.

    Science.gov (United States)

    Wang, Xiang; Venzmer, Joachim; Bonaccurso, Elmar

    2016-08-23

    Spreading of water drops resting in equilibrium on polypropylene surfaces was initiated by dispensing surfactant-laden droplets on their apex. Upon contact of the two drops two processes were kicked-off: surfactant from the droplets spread along the water/air interface of the sessile drops and a train of capillary waves propagated along the sessile drops. The contact line of the sessile drops remained initially pinned and started spreading only when surfactant reached it while the capillary waves did not have an apparent effect on initiating drop spreading. However, surfactant influenced the propagation velocity of the capillary waves. Though the spreading dynamics of such nonhomogeneously mixed surfactant/water drops on polypropylene surfaces was initially different from that of homogeneously mixed drops, the later spreading dynamics was similar and was dominated by viscosity and surface tension in both cases. These results can help in discriminating the path of action of surfactants in bulk and at the water/air interface, which is also relevant for understanding phenomena such as superspreading.

  13. Direct and accurate measurement of size dependent wetting behaviors for sessile water droplets

    Science.gov (United States)

    Park, Jimin; Han, Hyung-Seop; Kim, Yu-Chan; Ahn, Jae-Pyeong; Ok, Myoung-Ryul; Lee, Kyung Eun; Lee, Jee-Wook; Cha, Pil-Ryung; Seok, Hyun-Kwang; Jeon, Hojeong

    2015-12-01

    The size-dependent wettability of sessile water droplets is an important matter in wetting science. Although extensive studies have explored this problem, it has been difficult to obtain empirical data for microscale sessile droplets at a wide range of diameters because of the flaws resulting from evaporation and insufficient imaging resolution. Herein, we present the size-dependent quantitative change of wettability by directly visualizing the three phase interfaces of droplets using a cryogenic-focused ion beam milling and SEM-imaging technique. With the fundamental understanding of the formation pathway, evaporation, freezing, and contact angle hysteresis for sessile droplets, microdroplets with diameters spanning more than three orders of magnitude on various metal substrates were examined. Wetting nature can gradually change from hydrophobic at the hundreds-of-microns scale to super-hydrophobic at the sub-μm scale, and a nonlinear relationship between the cosine of the contact angle and contact line curvature in microscale water droplets was demonstrated. We also showed that the wettability could be further tuned in a size-dependent manner by introducing regular heterogeneities to the substrate.

  14. Marangoni Effect on the Shape of Freely Receding Evaporating Sessile Droplets of Perfectly Wetting Liquids

    Science.gov (United States)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2014-11-01

    Freely receding evaporating sessile droplets of perfectly wetting liquids (HFE-7100, 7200 and 7500), with small finite contact angles induced by evaporation, are studied with a Mach-Zehnder interferometer. Surprisingly, the experimentally obtained profiles turn out to deviate from the classical macroscopic static shape of a sessile droplet (as determined by gravity and capillarity), often used when modeling evaporating droplets. These deviations can be seen in two ways. Namely, either the droplet appears to be inflated as compared to the classical static shape assuming the same contact angle and contact radius, or the apparent contact angle appears lower than the classical static one assuming the same volume and contact radius. In reality, the experimental profiles exhibit a local decrease of the slope near the contact line, which we attribute to the Marangoni effect in an evaporating sessile droplet. In this case, the radially inward (along the liquid-air interface) direction of the flow delivers more liquid to the center of the droplet making it appear inflated. When the Marangoni effect is weak, as in the case of the poorly volatile HFE-7500, no significant influence is noticed on the drop shape. The experimental results are compared with the predictions of a lubrication-type theoretical model that incorporates the evaporation-induced Marangoni flow. Financial support of FP7 Marie Curie MULTIFLOW Network (PITN-GA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

  15. A robust algorithm for the simultaneous parameter estimation of interfacial tension and contact angle from sessile drop profiles.

    Science.gov (United States)

    Dingle, Nicole M; Harris, Michael T

    2005-06-15

    The pendant and sessile drop profile analysis using the finite element method (PSDA-FEM) is an algorithm which allows simultaneous determination of the interfacial tension (gamma) and contact angle (theta(c)) from sessile drop profiles. The PSDA-FEM algorithm solves the nonlinear second-order spherical coordinate form of the Young-Laplace equation. Thus, the boundary conditions at the drop apex and contact position of the drop with the substrate are required to solve for the drop profile coordinates. The boundary condition at the position where the drop contacts the substrate may be specified as a fixed contact line or fixed contact angle. This paper will focus on the fixed contact angle boundary condition for sessile drops on a substrate and how this boundary condition is used in the PSDA-FEM curve-fitting algorithm. The PSDA-FEM algorithm has been tested using simulated drop shapes with and without the addition of random error to the drop profile coordinates. The random error is varied to simulate the effect of camera resolution on the estimates of gamma and theta(c) values obtained from the curve-fitting algorithm. The error in the experimental values for gamma from sessile drops of water on acrylic and Mazola corn oil on acrylic falls within the predicted range of errors obtained for gamma values from simulated sessile drop profiles with randomized errors that are comparable in magnitude to the resolution of the experimental setup.

  16. New Method Developed to Measure Contact Angles of a Sessile Drop

    Science.gov (United States)

    Chao, David F.; Zhang, Nengli

    2002-01-01

    The spreading of an evaporating liquid on a solid surface occurs in many practical processes and is of importance in a number of practical situations such as painting, textile dyeing, coating, gluing, and thermal engineering. Typical processes involving heat transfer where the contact angle plays an important role are film cooling, boiling, and the heat transfer through heat pipes. The biological phenomenon of cell spreading also is analogous to a drop spreading (ref. 1). In the study of spreading, the dynamic contact angle describes the interfacial properties on solid substrates and, therefore, has been studied by physicists and fluid mechanics investigators. The dynamic contact angle of a spreading nonvolatile liquid drop provides a simple tool in the study of the free-boundary problem, but the study of the spreading of a volatile liquid drop is of more practical interest because the evaporation of common liquids is inevitable in practical processes. The most common method to measure the contact angle, the contact radius, and the height of a sessile drop on a solid surface is to view the drop from its edge through an optical microscope. However, this method gives only local information in the view direction. Zhang and Yang (ref. 2) developed a laser shadowgraphy method to investigate the evaporation of sessile drop on a glass plate. As described here, Zhang and Chao (refs. 3 and 4) improved the method and suggested a new optical arrangement to measure the dynamic contact angle and the instant evaporation rate of a sessile drop with much higher accuracy (less than 1 percent). With this method, any fluid motion in the evaporating drop can be visualized through shadowgraphy without using a tracer, which often affects the field under investigation.

  17. Evaporation of an intensively heated sessile droplet into the open atmosphere

    Directory of Open Access Journals (Sweden)

    Semenov Andrey

    2016-01-01

    Full Text Available Evaporation of a heated sessile water drop was studied experimentally at a temperature difference between the substrate and surrounding atmosphere from 30 to 60°C. The studies were performed on the substrates with micro- and nanocoatings with different wettability. The features of evaporation were studied for the pinned, partially pinned and depinned contact line (solid-liquid-gas interface. It is found that during the evaporation process the specific evaporation rate (mass loss per unit of the drop surface area increases, particularly at the last stage of the drop lifetime.

  18. Study on evaporation characteristics of a sessile drop of sulfur mustard on glass.

    Science.gov (United States)

    Jung, Hyunsook; Myung, Sung Min; Park, Myung Kyu; Lee, Hae Wan; Ryu, Sam Gon

    2012-05-01

    The evaporation characteristics (evaporation rates and process) of a sessile drop of sulfur mustard on glass has been studied using a laboratory-sized wind tunnel, gas chromatograph mass spectrometry, and drop shape analysis. It showed that the evaporation rates of the droplet increased with temperature and air flow. The effect of temperature on the rates was more pronounced at lower air flow. Air flow was less effective at lower temperature. The contact angle of the droplet was initially observed as θ = 19.5° ± 0.7 and decreased linearly with time until it switched to a constant mode.

  19. Poloidal flow and toroidal particle ring formation in a sessile drop driven by megahertz order vibration.

    Science.gov (United States)

    Rezk, Amgad R; Yeo, Leslie Y; Friend, James R

    2014-09-23

    Poloidal flow is curiously formed in a microliter sessile water drop over 157-225 MHz because of acoustic streaming from three-dimensional standing Lamb waves in a lithium niobate substrate. The flow possesses radial symmetry with downwelling at the center and upwelling around the periphery of the drop. Outside this frequency range, the attenuation occurs over a length scale incompatible with the drop size and the poloidal flow vanishes. Remarkably, shear-induced migration was found to drive toroidal particle ring formation with diameters inversely proportional to the frequency of the acoustic irradiation.

  20. Simple analytical model of capillary flow in an evaporating sessile drop.

    Science.gov (United States)

    Tarasevich, Yuri Yu

    2005-02-01

    An analytical expression of hydrodynamic potential inside an evaporating sessile drop with pinned contact line is found. The problem is considered for a hemispherical drop (with the contact angle of 90 degrees ) at the very early stages of the evaporation process when the shape of the drop is still a hemisphere and the evaporation field is uniform. The capillary flow carries a fluid from the drop apex to the contact line. Comparison with the published calculations performed using lubrication approximation (very thin drop) suggests that qualitative picture of the capillary flow is insensitive to the ratio of initial drop height to the drop radius.

  1. Dynamic Chemically Driven Dewetting, Spreading, and Self-Running of Sessile Droplets on Crystalline Silicon.

    Science.gov (United States)

    Arscott, Steve

    2016-12-06

    A chemically driven dewetting effect is demonstrated using sessile droplets of dilute hydrofluoric acid on chemically oxidized silicon wafers. The dewetting occurs as the thin oxide is slowly etched by the droplet and replaced by a hydrogen-terminated surface; the result of this is a gradual increase in the contact angle of the droplet with time. The time-varying work of adhesion is calculated from the time-varying contact angle; this corresponds to the changing chemical nature of the surface during dewetting and can be modeled by the well-known logistic (sigmoid) function often used for the modeling of restricted growth, in this case, the transition from an oxidized surface to a hydrogen-terminated silicon surface. The observation of the time-varying contact angle allows one to both measure the etch rate of the silicon oxide and estimate the hydrogenation rate as a function of HF concentration and wafer type. In addition to this, at a certain HF concentration, a self-running droplet effect is observed. In contrast, on hydrogen-terminated silicon wafers, a chemically induced spreading effect is observed using sessile droplets of nitric acid. The droplet spreading can also be modeled using a logistical function, where the restricted growth is the transition from hydrogen-terminated to a chemically induced oxidized silicon surface. The chemically driven dewetting and spreading observed here add to the methods available to study dynamic wetting (e.g., the moving three-phase contact line) of sessile droplets on surfaces. By slowing down chemical kinetics of the wetting, one is able to record the changing profile of the sessile droplet with time and gather information concerning the time-varying surface chemistry. The data also indicates a chemical interface hysteresis (CIH) that is compared to contact angle hysteresis (CAH). The approach can also be used to study the chemical etching and deposition behavior of thin films using liquids by monitoring the macroscopic

  2. Investigation of wetting behavior of coal-chars with liquid iron by sessile drop method.

    OpenAIRE

    Veena Sahajwalla; Fiona McCarthy; Rita Khanna

    2008-01-01

    Using the sessile drop approach, the wettability of four non-graphitic coal-chars with electrolytic iron and Fe-2 % C-0.01 % S alloy has been determined at 1550°C, in a horizontal tube resistance furnace with an argon atmosphere. The ash concentration in chars ranged between 9.04 to 12.61 wt %, with alumina and silica as predominant ash components. The contact angles of these chars with liquid Fe-2 % C-0.01 % S alloy showed lesser variations with time as compared to corresponding angles with ...

  3. Novel Sessile Drop Software for Quantitative Estimation of Slag Foaming in Carbon/Slag Interactions

    Science.gov (United States)

    Khanna, Rita; Rahman, Mahfuzur; Leow, Richard; Sahajwalla, Veena

    2007-08-01

    Novel video-processing software has been developed for the sessile drop technique for a rapid and quantitative estimation of slag foaming. The data processing was carried out in two stages: the first stage involved the initial transformation of digital video/audio signals into a format compatible with computing software, and the second stage involved the computation of slag droplet volume and area of contact in a chosen video frame. Experimental results are presented on slag foaming from synthetic graphite/slag system at 1550 °C. This technique can be used for determining the extent and stability of foam as a function of time.

  4. Optimization of the RNeasy Mini Kit to obtain high-quality total RNA from sessile cells of Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    C. O. Beltrame

    2015-12-01

    Full Text Available Biofilm formed by Staphylococcus aureus is considered an important virulence trait in the pathogenesis of infections associated with implantable medical devices. Gene expression analyses are important strategies for determining the mechanisms involved in production and regulation of biofilm. Obtaining intact RNA preparations is the first and most critical step for these studies. In this article, we describe an optimized protocol for obtaining total RNA from sessile cells of S. aureus using the RNeasy Mini Kit. This method essentially consists of a few steps, as follows: 1 addition of acetone-ethanol to sessile cells, 2 lysis with lysostaphin at 37°C/10 min, 3 vigorous mixing, 4 three cycles of freezing and thawing, and 5 purification of the lysate in the RNeasy column. This simple pre-kit procedure yields high-quality total RNA from planktonic and sessile cells of S. aureus.

  5. Dynamics of sessile and pendant drop excited by surface acoustic waves: gravity effects and correlation between oscillatory and translational motions

    CERN Document Server

    Bussonière, Adrien; Brunet, Philippe; Matar, Olivier Bou

    2016-01-01

    When sessile droplets are excited by ultrasonic traveling surface acoustic waves (SAWs), they undergo complex dynamics with both oscillations and translational motion. While the nature of the Rayleigh-Lamb quadrupolar drop oscillations has been identified, their origin and their influence on the drop mobility remains unexplained. Indeed the physics behind this peculiar dynamics is complex with nonlinearities involved both at the excitation level (acoustic streaming and radiation pressure) and in the droplet response (nonlinear oscillations and contact line dynamics). In this paper, we investigate the dynamics of sessile and pendant drops excited by SAWs. For pendant drops, so-far unreported dynamics are observed close to the drop detachment threshold with the suppression of the translational motion. Away from this threshold, the comparison between pendant and sessile drop dynamics allows us to identify the role played by gravity or more generally by an initial or dynamically induced stretching of the drop. In...

  6. Recruitment Variability of Coral Reef Sessile Communities of the Far North Great Barrier Reef.

    Directory of Open Access Journals (Sweden)

    Heidi M Luter

    Full Text Available One of the key components in assessing marine sessile organism demography is determining recruitment patterns to benthic habitats. An analysis of serially deployed recruitment tiles across depth (6 and 12 m, seasons (summer and winter and space (meters to kilometres was used to quantify recruitment assemblage structure (abundance and percent cover of corals, sponges, ascidians, algae and other sessile organisms from the northern sector of the Great Barrier Reef (GBR. Polychaetes were most abundant on recruitment titles, reaching almost 50% of total recruitment, yet covered <5% of each tile. In contrast, mean abundances of sponges, ascidians, algae, and bryozoans combined was generally less than 20% of total recruitment, with percentage cover ranging between 15-30% per tile. Coral recruitment was very low, with <1 recruit per tile identified. A hierarchal analysis of variation over a range of spatial and temporal scales showed significant spatio-temporal variation in recruitment patterns, but the highest variability occurred at the lowest spatial scale examined (1 m-among tiles. Temporal variability in recruitment of both numbers of taxa and percentage cover was also evident across both summer and winter. Recruitment across depth varied for some taxonomic groups like algae, sponges and ascidians, with greatest differences in summer. This study presents some of the first data on benthic recruitment within the northern GBR and provides a greater understanding of population ecology for coral reefs.

  7. Confinement-induced alterations in the evaporation dynamics of sessile droplets.

    Science.gov (United States)

    Bansal, Lalit; Chakraborty, Suman; Basu, Saptarshi

    2017-02-07

    Evaporation of sessile droplets has been a topic of extensive research. However, the effect of confinement on the underlying dynamics has not been well explored. Here, we report the evaporation dynamics of a sessile droplet in a confined fluidic environment. Our findings reveal that an increase in the channel length delays the completion of the evaporation process and leads to unique spatio-temporal evaporation flux and internal flow. The evaporation modes (constant contact angle and constant contact radius) during the droplet lifetime however exhibit global similarity when normalized by appropriate length and timescales. These results are explained in light of an increase in vapor concentration inside the channel due to greater accumulation of water vapor on account of increased channel length. We have formulated a theoretical framework which introduces two key parameters namely an enhanced concentration of the vapor field in the vicinity of the confined droplet and a corresponding accumulation lengthscale over which the accumulated vapor relaxes to the ambient concentration. Using these two parameters and modified diffusion based evaporation we are able to show that confined droplets exhibit a universal behavior in terms of the temporal evolution of each evaporation mode irrespective of the channel length. These results may turn out to be of profound importance in a wide variety of applications, ranging from surface patterning to microfluidic technology.

  8. Expressions for the evaporation of sessile liquid droplets incorporating the evaporative cooling effect.

    Science.gov (United States)

    Wang, Yilin; Ma, Liran; Xu, Xuefeng; Luo, Jianbin

    2016-12-15

    The evaporation along the surface of pinned, sessile droplets is investigated numerically by using the combined field approach. In the present model, the evaporative cooling at the droplet surface which leads to a reduction in the evaporation is taken into account. Simple, yet accurate analytical expressions for the local evaporation flux and for the total evaporation rate of sessile droplets are obtained. The theoretical analyses indicate that the reduction in the evaporation becomes more pronounced as the evaporative cooling number Ec increases. The results also reveal that the variation of total evaporation rate with contact angle will change its trend as the intensity of the evaporative cooling changes. For small values of Ec, the total evaporation rate increases with the contact angle, the same as predicted by Deegan et al. and by Hu and Larson in their isothermal models in which the evaporative cooling is neglected. Contrarily, when the evaporative cooling effect is strong enough, the total evaporation rate will decrease as the contact angle increases. The present theory is corroborated experimentally, and found in good agreement with the expressions proposed by Hu and Larson in the limiting isothermal case.

  9. Nonlinear oscillations of a sessile drop on a hydrophobic surface induced by ac electrowetting.

    Science.gov (United States)

    Lee, Joohee; Park, Jun Kwon; Hong, Jiwoo; Lee, Sang Joon; Kang, Kwan Hyoung; Hwang, Hyung Ju

    2014-09-01

    We examine the nature of ac electrowetting (EW)-driven axisymmetric oscillations of a sessile water drop on a dielectric substrate. In ac EW, small-amplitude oscillations of a drop differ from the Rayleigh linear modes of freely oscillating drops. In this paper, we demonstrate that changes in the time-averaged contact angle of the sessile drop attributed to the presence of an electric field and a solid substrate mainly caused this discrepancy. We combine the domain perturbation method with the Lindsted-Poincaré method to derive an asymptotic formula for resonant frequency. Theoretical analysis shows that the resonant frequency is a function of the time-averaged contact angle. Each mode of the resonance frequency is a linear function of ɛ(1), which is the magnitude of the cosine of the time-averaged contact angle. The most dominant mode in this study, that is, the fundamental mode n=2, decreases linearly with ɛ(1). The results of the theoretical model are compared with those of both the experiments and numerical simulations. The average resonant frequency deviation between the perturbation solutions and numerical simulations is 4.3%, whereas that between the perturbation solutions and the experiments is 1.8%.

  10. Fluid dynamics and deposit patterns in evaporating sessile drop containing microparticles: substrate heating and wettability effects

    Science.gov (United States)

    Patil, Nagesh D.; Bhardwaj, Rajneesh; Sharma, Atul

    2016-11-01

    The evaporation of sessile water drops containing colloidal microparticles is investigated on non-heated and heated hydrophilic and hydrophobic substrates. Time-varying drop shapes and temperatures of liquid-gas interface are recorded using high-speed and infrared camera, respectively. In heated case, infrared-thermography shows larger temperature gradient across the liquid-gas interface and recorded motion of the particles confirm Marangoni flow from the contact line to apex inside the drop. On non-heated hydrophilic substrates, a ring-like pattern forms, as reported extensively in the literature; while on heated hydrophilic substrates, a thin ring with an inner-deposit forms. On non-heated hydrophobic substrates, the contact line depins to form inner-deposit without ring; while on heated hydrophobic substrates, the contact line pins to form inner-deposit with thin ring. This pinning transition occurs due to the particles self-pinning in a stagnation region developed by the Marangoni flow near the contact line. This work gives fundamental insights on the thermal and wettability effects on internal fluid dynamics of the evaporating sessile drop and associated deposit shape, with applications in ink-jet printing and biosensors. PhD Scholar.

  11. Work of Adhesion of a Sessile Drop to a Clean Surface.

    Science.gov (United States)

    Schroder

    1999-05-15

    According to the Young-Dupré equation, as interpreted by Bangham and Razouk, the work of adhesion of a sessile drop to a smooth solid surface is given by WS(V)L = gammaL (1 + cos θ), where θ is the equilibrium contact angle measured at equilibrium of the system with the saturated vapor of the liquid, and WS(V)L is the work of adhesion of that drop to the solid surface which is in equilibrium with that vapor and may contain an adlayer of the vapor. For calculation of WSL, the work of adhesion of a sessile drop to a clean solid surface, the equation WSL = gammaL (1 + cos θ) + Pie is generally used (although Bangham and Razouk never proposed it). Pie is the negative of the free energy of formation of the adlayer, sometimes called the spreading pressure. In the present work it is shown that the latter equation cannot be accurate. Copyright 1999 Academic Press.

  12. Using the sessile drop geometry to measure fluid and elastic block copolymer interfaces.

    Science.gov (United States)

    Rozairo, Damith P; Croll, Andrew B

    2015-02-03

    There is considerable interest in the fabrication and mechanics of soft spheres and capsules because of their use in a large number of applications ranging from targeted drug delivery to cosmetically active agents. Many systems, such as lipid and block copolymer vesicles, are already finding considerable industrial use where the performance of soft spheres depends intimately on their mechanics. New advanced features such as fast cargo delivery can be realized only if they fit into the existing mechanical niche of the system in question. Here we present a model system to demonstrate how a capsule structure can be fundamentally changed while maintaining its overall mechanical response as well as a simple, universal method to measure the resulting capsule material properties. Specifically, we use confocal microscopy to adapt the sessile drop geometry to a measurement of the static properties of an ensemble of polystyrene-b-poly(ethylene oxide) (PS-PEO)-stabilized oil droplets. We then synthesize a polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-PAA-PS) elastic-shell-coated emulsion drop that shows an identical deformation to the fluidlike PS-PEO droplets. Both systems, in sessile geometry, can be related to their basic material properties through appropriate modeling. We find that the elastic shell is dominated by its surface tension, easily enabling it to match the static response of a purely fluid drop.

  13. Effect of wettability on sessile drop freezing: when superhydrophobicity stimulates an extreme freezing delay.

    Science.gov (United States)

    Boinovich, Ludmila; Emelyanenko, Alexandre M; Korolev, Vadim V; Pashinin, Andrei S

    2014-02-18

    An increasing number of studies directed at supercooling water droplets on surfaces with different wettabilities have appeared in recent years. This activity has been stimulated by the recognition that water supercooling phenomena can be effectively used to develop methods for protecting outdoor equipment and infrastructure elements against icing and snow accretion. In this article, we discuss the nucleation kinetics of supercooled sessile water droplets on hydrophilic, hydrophobic, and superhydrophobic surfaces under isothermal conditions at temperatures of -8, -10, and -15 °C and a saturated water vapor atmosphere. The statistics of nucleation events for the ensembles of freezing sessile droplets is completed by the detailed analysis of the contact angle temperature dependence and freezing of individual droplets in a saturated vapor atmosphere. We have demonstrated that the most essential freezing delay is characteristic of the superhydrophobic coating on aluminum, with the texture resistant to contact with ice and water. This delay can reach many hours at T = -8 °C and a few minutes at -23 °C. The observed behavior is analyzed on the basis of different nucleation mechanisms. The dissimilarity in the total nucleation rate, detected for two superhydrophobic substrates having the same apparent contact angle of the water drop but different resistivities of surface texture to the contact with water/ice, is associated with the contribution of heterogeneous nucleation on external centers located at the water droplet/air interface.

  14. Effect of Marangoni Flows on the Shape of Thin Sessile Droplets Evaporating into Air

    Science.gov (United States)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2015-11-01

    With the help of Mach-Zehnder interferometry, we study the (largely) axisymmetric shapes of freely receding evaporating sessile droplets of various HFE liquids. The droplets evaporate into ambient air and, although the liquids are perfectly wetting, possess small finite contact angles reckoned to be evaporation-induced. The experimentally determined droplet profiles are shown here to deviate, under some conditions, from the classical macroscopic static profile of a sessile droplet, as this is determined by gravity and capillarity. These deviations are attributed to a Marangoni flow, due to evaporation-induced thermal gradients along the liquid-air interface, and are mostly observed in conditions of high evaporation. Unlike the classical static shapes, the distorted experimental profiles exhibit an inflection point at the contact line area. When a poorly volatile liquid is considered, however, the temperature differences and the Marangoni stresses are weak, and the measurements are found to be in a good agreement with the classical static shape. Overall, the experimental findings are quantitatively confirmed by the predictions of a lubrication model accounting for the impact of the Marangoni effect on the droplet shape. Financial support of FP7 Marie Curie MULTIFLOW Network (PITNGA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

  15. In vitro activity of Aloe vera inner gel against microorganisms grown in planktonic and sessile phases.

    Science.gov (United States)

    Cataldi, V; Di Bartolomeo, S; Di Campli, E; Nostro, A; Cellini, L; Di Giulio, M

    2015-12-01

    The failure of traditional antimicrobial treatments is becoming a worldwide problem. The use of Aloe vera is of particular interest for its role as curative agent and its efficacy in complementary therapies for a variety of illnesses. This study evaluated the antimicrobial activity of A. vera inner gel against a panel of microorganisms, Gram-positive and -negative bacteria, and Candida albicans. In addition to A. vera inner gel being used in the treatment of peptic ulcers, in dermatological treatments, and wound healing, it was also tested on the sessile phase of clinical Helicobacter pylori strains (including multi-drug-resistant strains) and on planktonic and sessile phase of Staphylococcus aureus/Pseudomonas aeruginosa clinical isolates from venous leg ulcers.A. vera inner gel expresses its prevalent activity against Gram-negative bacteria and C. albicans in respect to Gram-positive bacteria. The results of the A. vera antibiofilm activity showed a decrease of the produced biomass in a concentration-dependent-way, in each analyzed microorganism. The data obtained show that A. vera inner gel has both an antimicrobial and antibiofilm activity suggesting its potential use for the treatment of microbial infections, in particular for H. pylori gastric infection, especially in case of multi-drug-resistance, as well as for an effective wound dressing.

  16. Nonlinear oscillations of a sessile drop on a hydrophobic surface induced by ac electrowetting

    Science.gov (United States)

    Lee, Joohee; Park, Jun Kwon; Hong, Jiwoo; Lee, Sang Joon; Kang, Kwan Hyoung; Hwang, Hyung Ju

    2014-09-01

    We examine the nature of ac electrowetting (EW)-driven axisymmetric oscillations of a sessile water drop on a dielectric substrate. In ac EW, small-amplitude oscillations of a drop differ from the Rayleigh linear modes of freely oscillating drops. In this paper, we demonstrate that changes in the time-averaged contact angle of the sessile drop attributed to the presence of an electric field and a solid substrate mainly caused this discrepancy. We combine the domain perturbation method with the Lindsted-Poincaré method to derive an asymptotic formula for resonant frequency. Theoretical analysis shows that the resonant frequency is a function of the time-averaged contact angle. Each mode of the resonance frequency is a linear function of ɛ1, which is the magnitude of the cosine of the time-averaged contact angle. The most dominant mode in this study, that is, the fundamental mode n =2, decreases linearly with ɛ1. The results of the theoretical model are compared with those of both the experiments and numerical simulations. The average resonant frequency deviation between the perturbation solutions and numerical simulations is 4.3%, whereas that between the perturbation solutions and the experiments is 1.8%.

  17. Tensiometric Characterization of Superhydrophobic Surfaces As Compared to the Sessile and Bouncing Drop Methods.

    Science.gov (United States)

    Hisler, Valentin; Jendoubi, Hiba; Hairaye, Camille; Vonna, Laurent; Le Houérou, Vincent; Mermet, Frédéric; Nardin, Michel; Haidara, Hamidou

    2016-08-09

    We have considered in this work the Wilhelmy plate tensiometer to characterize the wetting properties of two model surface textures: (i) a series of three superhydrophobic micropillared surfaces and (ii) a series of two highly water-repellent surfaces microtextured with a femtosecond laser. The wetting forces obtained on these surfaces with the Wilhelmy plate technique were compared to the contact angles of water droplets measured with the sessile drop technique and to the bouncing behavior of water droplets recorded at a high frame rate. We showed that it is possible with this technique to directly measure triple-line anchoring forces that are not accessible with the commonly used sessile drop technique. In addition, we have demonstrated on the basis of the bouncing drop experiments wetting transitions induced by the specific test conditions associated with the Wilhelmy plate tensiometer for the two series of textured surfaces. Finally, the tensiometer technique is proposed as an alternative test for characterizing the wetting properties of highly liquid-repellent surface, especially under immersion conditions.

  18. Assessing the accuracy of contact angle measurements for sessile drops on liquid-repellent surfaces.

    Science.gov (United States)

    Srinivasan, Siddarth; McKinley, Gareth H; Cohen, Robert E

    2011-11-15

    Gravity-induced sagging can amplify variations in goniometric measurements of the contact angles of sessile drops on super-liquid-repellent surfaces. The very large value of the effective contact angle leads to increased optical noise in the drop profile near the solid-liquid free surface and the progressive failure of simple geometric approximations. We demonstrate a systematic approach to determining the effective contact angle of drops on super-repellent surfaces. We use a perturbation solution of the Bashforth-Adams equation to estimate the contact angles of sessile drops of water, ethylene glycol, and diiodomethane on an omniphobic surface using direct measurements of the maximum drop width and height. The results and analysis can be represented in terms of a dimensionless Bond number that depends on the maximum drop width and the capillary length of the liquid to quantify the extent of gravity-induced sagging. Finally, we illustrate the inherent sensitivity of goniometric contact angle measurement techniques to drop dimensions as the apparent contact angle approaches 180°.

  19. Risk of colorectal cancer in patients with sessile serrated adenomas/polyps is the same magnitude or even higher than in patients with conventinal adenomas

    DEFF Research Database (Denmark)

    Erichsen, Rune; Baron, John A; Snover, Dale;

    2014-01-01

    Risk of colorectal cancer in patients with sessile serrated adenomas/polyps is the same magnitude or even higher than in patients with conventinal adenomas......Risk of colorectal cancer in patients with sessile serrated adenomas/polyps is the same magnitude or even higher than in patients with conventinal adenomas...

  20. Blown Away: The Shedding and Oscillation of Sessile Drops by Cross Flowing Air

    Science.gov (United States)

    Milne, Andrew James Barnabas

    For drops sessile on a solid surface, cross flowing air can drive drop oscillation or shedding, based on the balance and interaction of aerodynamic drag force (based on drop size/shape and air speed) and adhesion/capillary forces (based on surface tension and drop size/shape). Better understanding of the above has applications to, e.g., fuel cell flooding, airfoil icing, and visibility in rain. To understand the basic physics, experiments studying individual sessile drops in a low speed wind tunnel were performed in this thesis. Analysis of high speed video gave time resolved profiles and airspeed for shedding. Testing 0.5 mul to 100 mul drops of water and hexadecane on poly(methyl methacrylate) PMMA, Teflon, and a superhydrophobic surface (SHS) yielded a master curve describing critical airspeed for shedding for water drops on all surface tested. This curve predicts behavior for new surfaces, and explains experimental results published previously. It also indicates that the higher contact angle leads to easier shedding due to decreased adhesion and increased drag. Developing a novel floating element differential drag sensor gave the first measurements of the microNewton drag force experienced by drops. Forces magnitude is comparable to gravitational shedding from a tilted plate and to simplified models for drop adhesion, with deviations that suggest effects due to the air flow. Fluid properties are seen to have little effect on drag versus airspeed, and decreased adhesion is seen to be more important than increased drag for easing shedding. The relation between drag coefficient and Reynolds number increases slightly with liquid-solid contact angle, and with drop volume. Results suggest that the drop experiences increased drag compared to similarly shaped solid bodies due to drop oscillations aeroelasticly coupling into the otherwise laminar flow. The bulk and surface oscillations of sessile drops in cross flow was also studied, using a full profile analysis

  1. Comparison of the carbon stock in forest soil of sessile oak and beech forests

    Science.gov (United States)

    Horváth, Adrienn; Bene, Zsolt; Bidló, András

    2016-04-01

    Forest ecosystems are the most important carbon sinks. The forest soils play an important role in the global carbon cycle, because the global climate change or the increase of atmospheric CO2 level. We do not have enough data about the carbon stock of soils and its change due to human activities, which have similar value to carbon content of biomass. In our investigation we measured the carbon stock of soil in 10 stands of Quercus petraea and Fagus sylvatica. We took a 1.1 m soil column with soil borer and divided to 11 samples each column. The course organic and root residues were moved. After evaluation, we compared our results with other studies and the carbon stock of forests to each other. Naturally, the amount of SOC was the highest in the topsoil layers. However, we found significant difference between forest stands which stayed on the same homogenous bedrock, but very close to each other (e.g. distance was 1 or 2 km). We detected that different forest utilizations and tree species have an effect on the forest carbon as the litter as well (amount, composition). In summary, we found larger amount (99.1 C t/ha on average) of SOC in soil of stands, where sessile oak were the main stand-forming tree species. The amount of carbon was the least in turkey oak-sessile oak stands (85.4 C t/ha on average). We found the highest SOC (118.3 C t/ha) in the most mixed stand (silver lime-beech-red oak). In the future, it will be very important: How does climate change affect the spread of tree species or on carbon storage? Beech is more sensitive, but even sessile oak. These species are expected to replace with turkey oak, which is less sensitive to drought. Thus, it is possible in the future that we can expect to decrease of forest soil carbon stock capacity, which was confirmed by our experiment. Keywords: carbon sequestration, mitigation, Fagus sylvatica, Quercus petraea, litter Acknowledgements: Research is supported by the "Agroclimate.2" (VKSZ_12-1-2013-0034) EU

  2. Dendrochronological research in an artificially established sessile oak stand in the area of Fruška Gora

    Directory of Open Access Journals (Sweden)

    Stajić Branko

    2014-01-01

    Full Text Available This paper presents the first regional research of the chronologies of sessile oak trees and definition of the local (master chronology of sessile oak in the area of Fruška Gora. In addition, the aim of this study is to determine the strength of the common signal in the growth of sessile oak and its dendroclimatological potential under the given conditions. The quality of the local series of radial increment (chronology and the strength of the common and climatic signals were evaluated using the following parameters: average mean sensitivity, expressed population signal, signal-to-noise ratio and the variance explained by eigenvectors in the procedure of analysis of the principal components. The results have shown that the obtained master chronologies are of satisfactory quality and reliability, and that they contain a sufficient general common ”signal”, which is a characteristic of all analyzed trees that can be processed in all dendroclimatological analyses. It was concluded that, under the investigated site conditions, sessile oak showed low to medium sensitivity of reaction to the modifications of environmental conditions in the past 90 years. [Projekat Ministarstva nauke Republike Srbije: Šumski zasadi u funkciji povećanja pošumljenosti Srbije

  3. Qualities of sessile serrated adenoma/polyp/lesion and its borderline variant in the context of synchronous colorectal carcinoma

    DEFF Research Database (Denmark)

    Mohammadi, Mahin; Kristensen, Michael Holmsgaard; Nielsen, Hans Jørgen

    2012-01-01

    Although much data have accumulated on sessile serrated adenoma/polyp/lesion (SSA/P/L) in general, its characteristics in specified contexts are less well elucidated. This lack of knowledge is even more conspicuous concerning its borderline counterpart, referred to as BSSA/P/L. The previous histo...

  4. Dynamics of sessile and pendant drops excited by surface acoustic waves: Gravity effects and correlation between oscillatory and translational motions

    Science.gov (United States)

    Bussonnière, A.; Baudoin, M.; Brunet, P.; Matar, O. Bou

    2016-05-01

    When sessile droplets are excited by ultrasonic traveling surface acoustic waves (SAWs), they undergo complex dynamics with both oscillations and translational motion. While the nature of the Rayleigh-Lamb quadrupolar drop oscillations has been identified, their origin and their influence on the drop mobility remains unexplained. Indeed, the physics behind this peculiar dynamics is complex with nonlinearities involved both at the excitation level (acoustic streaming and radiation pressure) and in the droplet response (nonlinear oscillations and contact line dynamics). In this paper, we investigate the dynamics of sessile and pendant drops excited by SAWs. For pendant drops, so-far unreported dynamics are observed close to the drop detachment threshold with the suppression of the translational motion. Away from this threshold, the comparison between pendant and sessile drop dynamics allows us to identify the role played by gravity or, more generally, by an initial or dynamically induced stretching of the drop. In turn, we elucidate the origin of the resonance frequency shift, as well as the origin of the strong correlation between oscillatory and translational motion. We show that for sessile drops, the velocity is mainly determined by the amplitude of oscillation and that the saturation observed is due to the nonlinear dependence of the drop response frequency on the dynamically induced stretching.

  5. A New Approach to Measure Contact Angle and Evaporation Rate with Flow Visualization in a Sessile Drop

    Science.gov (United States)

    Zhang, Nengli; Chao, David F.

    1999-01-01

    The contact angle and the spreading process of sessile droplet are very crucial in many technological processes, such as painting and coating, material processing, film-cooling applications, lubrication, and boiling. Additionally, as it is well known that the surface free energy of polymers cannot be directly, measured for their elastic and viscous restraints. The measurements of liquid contact angle on the polymer surfaces become extremely important to evaluate the surface free energy of polymers through indirect methods linked with the contact angle data. Due to the occurrence of liquid evaporation is inevitable, the effects of evaporation on the contact angle and the spreading become very important for more complete understanding of these processes. It is of interest to note that evaporation can induce Marangoni-Benard convection in sessile drops. However, the impacts of the inside convection on the wetting and spreading processes are not clear. The experimental methods used by previous investigators cannot simultaneously measure the spreading process and visualize the convection inside. Based on the laser shadowgraphic system used by the present author, a very simple optical procedure has been developed to measure the contact angle, the spreading speed, the evaporation rate, and to visualize inside convection of a sessile drop simultaneously. Two CCD cameras were used to synchronously record the real-time diameter of the sessile drop, which is essential for determination of both spreading speed and evaporation rate, and the shadowgraphic image magnified by the sessile drop acting as a thin plano-convex lens. From the shadowgraph, the inside convection of the drop can be observed if any and the image outer diameter, which linked to the drop profile, can be measured. Simple equations have been derived to calculate the drop profile, including the instantaneous contact angle, height, and volume of the sessile drop, as well as the evaporation rate. The influence of

  6. Novel mobbing strategies of a fish population against a sessile annelid predator.

    Science.gov (United States)

    Lachat, Jose; Haag-Wackernagel, Daniel

    2016-09-12

    When searching for food, foraging fishes expose themselves to hidden predators. The strategies that maximize the survival of foraging fishes are not well understood. Here, we describe a novel type of mobbing behaviour displayed by foraging Scolopsis affinis. The fish direct sharp water jets towards the hidden sessile annelid predator Eunice aphroditois (Bobbit worm). We recognized two different behavioural roles for mobbers (i.e., initiator and subsequent participants). The first individual to exhibit behaviour indicating the discovery of the Bobbit directed, absolutely and per time unit, more water jets than the subsequent individuals that joined the mobbing. We found evidence that the mobbing impacted the behaviour of the Bobbit, e.g., by inducing retraction. S. affinis individuals either mob alone or form mobbing groups. We speculate that this behaviour may provide social benefits for its conspecifics by securing foraging territories for S. affinis. Our results reveal a sophisticated and complex behavioural strategy to protect against a hidden predator.

  7. Insight into the Evaporation Dynamics of a Pair of Sessile Droplets on a Hydrophobic Substrate.

    Science.gov (United States)

    Shaikeea, Angkur Jyoti Dipanka; Basu, Saptarshi

    2016-02-09

    In this work, we have demonstrated three unique regimes in the evaporation lifecycle of a pair of sessile droplets placed in variable proximity on a hydrophobic substrate. For small separation distance, the droplets undergo asymmetric spatiotemporal evaporation leading to contact angle hysteresis and suppressed vaporization. The reduced evaporation has been attributed quantitatively to the existence of a constrained vapor-rich dome between the two droplets. However, a dynamic decrease in the droplet radius due to solvent removal marks a return to symmetry in terms of evaporation and contact angle. We have described the variation in evaporation flux using a universal correction factor. We have also demonstrated the existence of a critical separation distance beyond which the droplets in the droplet pair do not affect each other. The results are crucial to a plethora of applications ranging from surface patterning to lab-on-a-chip devices.

  8. Density of Liquid Ni-Mo Alloys Measured by a Modified Sessile Drop Method

    Institute of Scientific and Technical Information of China (English)

    Liang FANG; Zushu LI; ZaiNan TAO; Feng XIAO

    2004-01-01

    The density of liquid binary Ni-Mo alloys with molybdenum concentration from 0 to 20% (mass fraction) was measured by a modified sessile drop method. It has been found that the density of the liquid Ni-Mo alloys decreases with increasing temperature, but increases with the increase of molybdenum concentration in the alloys. The molar volume of liquid Ni-Mo binary alloys increases with the increase of temperature and molybdenum concentration. The partial molar volume of molybdenum in Ni-Mo binary alloy has been approximately calculated as [13.18 - 2.65 × 10-3T + (-47.94 + 3.10 × 10-2T) × 10-2XMo] × 10-6m3·mol-1. The molar volume of Ni-Mo alloy determined in the present work shows a negative deviation from the ideal linear mixing molar volume.

  9. Surface modes of a sessile water drop: an optical tweezer based study.

    Science.gov (United States)

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  10. Local Heat Transfer to an Evaporating Sessile Droplet in an Electric Field

    Science.gov (United States)

    Gibbons, M. J.; Howe, C. M.; Di Marco, P.; Robinson, A. J.

    2016-09-01

    Local heat transfer of an evaporating sessile droplet under a static electric field is an underdeveloped topic. In this research an 80 μl water droplet is placed in the centre of a 25 μm thick stainless steel substrate. A static electric field is applied by an electrode positioned 10 mm above the substrate. A high speed thermal imaging camera is placed below the substrate to capture the thermal footprint of the evaporating droplet. Four electric fields were characterised; 0, 5, 10 and 11 kV/cm. As the electric field is increased the contact angle was observed to decrease. The local heat flux profile, peak and radial location of this peek were observed to be independent of the applied electric field for all test points for this working fluid and surface combination.

  11. Precision stacking of nanoparticle laden sessile droplets to control solute deposit morphology

    Science.gov (United States)

    Kabi, Prasenjit; Basu, Saptarshi; Sanyal, Apratim; Chaudhuri, Swetaprovo

    2015-02-01

    Stacking pure solvent droplets on a solid substrate is apparently impossible in the absence of an external force as the second droplet will invariably spill over the first leading to a large wetted area. However, the unique feature that emerges during the drying of a nanoparticle laden droplet is the progressively enlarging thin solid film along the evaporating sessile droplet liquid periphery. This solid interface: the edge of which we shall refer to as the agglomeration front comprises of a thin layer of nanoparticle assembly and can support a carefully dispensed second droplet thereby allowing droplet stacking. It will be shown that the growth of this agglomeration front can also be effectively controlled by the dispensing time difference and the nanoparticle concentration in the two droplets. So far, we are commonly aware of material stacking in solid phase. This letter demonstrates stacking in the liquid phase and control over the thin solid interface growth.

  12. Effect of Heat Treatment upon Dimensional Stability and Static Bending Strength of Sessile Oak Wood

    Directory of Open Access Journals (Sweden)

    Alin OLARESCU

    2011-06-01

    Full Text Available The paper presents the results of an experimentalstudy performed with sessile oak wood (Quercuspetrea L.. After drying and conditioning at 12%MC,the test pieces were heat-treated at three differenthigh temperatures (120, 130 and 140°C for 1h, 2hand 3h. After the treatment and cooling, standardsamples for physical and mechanical tests were cut,in order to determine comparatively the density, thedimensional stability, the static bending strength andMOE of the differently treated samples.Based on the obtained results, the optimumtreatment schedule was established, namely the onewhich enables improved dimensional stability withoutaffecting significantly the wood strength. Theseresults can be applied at the manufacturing of solidwood panels with improved dimensional stabilityusing heat-treated wood lamellas.

  13. Sharp Transition between Coalescence and Noncoalescence of Sessile Drops: Interplay between Marangoni Flow and Local Topography

    CERN Document Server

    Karpitschka, Stefan

    2013-01-01

    The first detailed experimental data on the impact of the contact angle on the coalescence behavior of sessile drops from different but completely miscible liquids are presented. For the wide range of investigated surface tensions $\\gamma_1$ and $\\gamma_2$, and liquid viscosities $\\eta$, the arithmetic mean of the contact angles, $\\ThetaAdjAv$, and the surface tension difference $\\Dg$ are identified as main system control parameters. They govern the transition between the regimes of immediate coalescence and noncoalescence. The theoretical analysis reveals a specific Marangoni number $\\M=3\\Dg/(2\\gAv\\ThetaAdjAv^2)$ as the unique key parameter. It universally characterizes the coalescence behavior regarding both, the physicochemical liquid properties and the contact region topography. Experiments and simulations yield a threshold Marangoni number $\\Mcrit$ for the rather sharp transition between the coalescence regimes. The simulations reveal a slight dependence of $\\Mcrit$ on the molecular diffusivity. The expe...

  14. Electrowetting-on-dielectric (EWOD) of sessile liquid drops on rheologically tuned soft surfaces

    CERN Document Server

    Dey, Ranabir; Chakraborty, Suman

    2013-01-01

    The Young-Lippmann equation does not address the influence of mechanical properties of the dielectric layer, like elasticity, on the electrowetting behaviour of sessile liquid drops, within the classical electrowetting-on-dielectric (EWOD) framework. Here, we show for the first time, the alterations in the electrowetting response of conductive liquid drops over rheologically tuned soft surfaces. The influence of decreasing dielectric elasticity on the electrowetting behaviour is experimentally demonstrated by delineating the variations in apparent contact angle, and contact radius, over a complete electrowetting cycle, for substrates with varying elasticity. The significant effects of surface softness, on the electrowetting phenomenon, are explained by taking in purview the liquid-substrate interfacial interactions, as dictated by surface elasticity.

  15. Dependence of fluid flows in an evaporating sessile droplet on the characteristics of the substrate

    Science.gov (United States)

    Barash, Lev

    2015-11-01

    Temperature distributions and the corresponding vortex structures in an evaporating sessile droplet are obtained by performing detailed numerical calculations. A Marangoni convection induced by thermal conduction in the drop and the substrate is demonstrated to be able to result not only in a single vortex, but also in two or three vortices, depending on the ratio of substrate to fluid thermal conductivities, on the substrate thickness and the contact angle. The ``phase diagrams'' containing information on the number, orientation and spatial location of the vortices for quasistationary fluid flows are presented and analysed. The results obtained demonstrate that the fluid flow structure in evaporating droplets can be influenced in a controlled manner by selecting substrates with appropriate properties.

  16. Surface modes of a sessile water drop: An optical tweezer based study

    Science.gov (United States)

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S.

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  17. Method for estimating interfacial tensions and contact angles from sessile and pendant drop shapes

    Energy Technology Data Exchange (ETDEWEB)

    Huh, C.; Reed, R.L.

    1983-02-01

    Optimal estimation techniques were developed for measurement of interfacial tensions and contact angles for multiphase microemulsion systems of the following types: (1) lower-phase microemulsion in equilibrium with excess oil, (2) upper-phase microemulsion in equilbrium with excess brine, and (3) middle-phase microemulsion in equilibrium with excess brine and excess oil. The surfactant was the monoethanol amine salt of dodecyl o-xylene sulfonate mixed with a cosolvent of t-amyl alcohol in the ratio 63/67 by vol. The oil was a mixture of 90% paraffinic oil (Isopar M) and 10% heavy aromatic naphtha (by volume), and the brine was various concentrations of NaCl in distilled water. The method is applied to sessile drops, bubbles, and pendant configurations. 21 referernces.

  18. Evaporation of sessile drops containing colloidal rods: coffee-ring and order-disorder transition.

    Science.gov (United States)

    Dugyala, Venkateshwar Rao; Basavaraj, Madivala G

    2015-03-05

    Liquid drops containing insoluble solutes when dried on solid substrates leave distinct ring-like deposits at the periphery or along the three-phase contact line-a phenomena popularly known as the coffee-ring or the coffee stain effect. The formation of such rings as well as their suppression is shown to have applications in particle separation and disease diagnostics. We present an experimental study of the evaporation of sessile drops containing silica rods to elucidate the structural arrangement of particles in the ring, an effect of the addition of surfactant and salt. To this end, the evaporation of aqueous sessile drops containing model rod-like silica particles of aspect ratio ranging from ∼4 to 15 on a glass slide is studied. We first show that when the conditions such as (1) solvent evaporation, (2) nonzero contact angle, (3) contact line pinning, (4) no surface tension gradient driven flow, and (5) repulsive particle-particle/particle-substrate interactions, that are necessary for the formation of the coffee-ring are met, the suspension drops containing silica rods upon evaporation leave a ring-like deposit. A closer examination of the ring deposits reveals that several layers of silica rods close to the edge of the drop are ordered such that the major axis of the rods are oriented parallel to the contact line. After the first few layers of ordered arrangement of particles, a random arrangement of particles in the drop interior is observed indicating an order-disorder transition in the ring. We monitor the evolution of the ring width and particle velocity during evaporation to elucidate the mechanism of the order-disorder transition. Moreover, when the evaporation rate is lowered, the ordering of silica rods is observed to extend over large areas. We demonstrate that the nature of the deposit can be tuned by the addition of a small quantity of surfactant or salt.

  19. Evaporation of Sessile Droplets on Slippery Liquid-Infused Porous Surfaces (SLIPS).

    Science.gov (United States)

    Guan, Jian H; Wells, Gary G; Xu, Ben; McHale, Glen; Wood, David; Martin, James; Stuart-Cole, Simone

    2015-11-03

    Over the past decade, the most common approach to creating liquid shedding surfaces has been to amplify the effects of nonwetting surface chemistry, using micro/nanotexturing to create superhydrophobic and superoleophobic surfaces. Recently, an alternative approach using impregnation of micro/nanotextured surfaces with immiscible lubricating liquids to create slippery liquid-infused porous surfaces (SLIPS) has been developed. These types of surfaces open up new opportunities to study the mechanism of evaporation of sessile droplets in zero contact angle hysteresis situations where the contact line is completely mobile. In this study, we fabricated surfaces consisting of square pillars (10-90 μm) of SU-8 photoresist arranged in square lattice patterns with the center-to-center separation between pillars of 100 μm, on which a hydrophobic coating was deposited and the textures impregnated by a lubricating silicone oil. These surfaces showed generally low sliding angles of 1° or less for small droplets of water. Droplet profiles were more complicated than on nonimpregnated surfaces and displayed a spherical cap shape modified by a wetting ridge close to the contact line due to balancing the interfacial forces at the line of contact between the droplet, the lubricant liquid and air (represented by a Neumann triangle). The wetting ridge leads to the concept of a wetting "skirt" of lubricant around the base of the droplet. For the SLIP surfaces, we found that the evaporation of small sessile droplets (∼2 mm in diameter) followed an ideal constant contact angle mode where the apparent contact angle was defined from the intersection of the substrate profile with the droplet spherical cap profile. A theoretical model based on diffusion controlled evaporation was able to predict a linear dependence in time for the square of the apparent contact radius. The experimental data was in excellent quantitative agreement with the theory and enabled estimates of the diffusion

  20. Caustics and Caustic-Diffraction in Laser Shadowgraphy of a Sessile Drop and Identification of Profile Near Contact Line

    Science.gov (United States)

    Zhang, Neng-Li; Chao, David F.

    2003-01-01

    This paper presents an optical method based on the caustics and caustic-difraction in laser shadowgaphy of a sessile drop to identify and estimate the drop profile near the contact line. A parallel laser beam passes through a liquid sessile drop placed on a transparent substrate to produce a shadowgraphic image of the drop on the screen far from the substrate. Along the inflection line of the drop the Gaussian curvature of the wavefront deformed by the drop vanishes, and therefore the inflection line gives caustics in the far field of the wave, which can be seen on the screen. The neighboring light rays at both sides of the inflection line interfere with each other to form interference fringes at the inner side of the caustics. According to the pattern of the caustics, the drop-profile shape can be identified and estimated.

  1. Application of time-dependent sessile drop contact angles on compacts to characterise the surface energetics of sulfathiazole crystals.

    Science.gov (United States)

    Muster, Tim H; Prestidge, Clive A

    2002-03-02

    The time-dependent wetting of sulfathiazole compacts with sessile water drops was evaluated using video microscopy. The influence of sulfathiazole crystalline form, particle size, pre-saturation with water, humidity and compaction pressure on the droplet spreading kinetics and contact angles are reported. The rate and extent of droplet spreading decreased for compact surfaces of high microscopic roughness; this was determined by atomic force microscopy (AFM). Pre-saturation of powder compacts with water (pre-saturated with sulfathiazole) enhanced droplet spreading and enabled pseudo-equilibrium contact angles to be determined for up to 10 min. Sessile-drop contact angles on both sulfathiazole powder compacts and single crystals are compared with particle contact angles determined by liquid penetration. This study has led to an improved understanding of the influence of physical heterogeneities and the face-specific surface chemistry of individual crystals on the wetting characteristics of pharmaceutical compacts.

  2. Experimental and numerical study of spread and sorption of VX sessile droplets into medium grain-size sand.

    Science.gov (United States)

    D'Onofrio, Terrence G; Navaz, Homayun K; Markicevic, Bojan; Mantooth, Brent A; Sumpter, Kenneth B

    2010-03-02

    The experimental measurement and modeling of liquid chemical agent spread and sorption on a porous substrate are described. Experimental results with the nerve agent O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX) demonstrate that the wetted imprint volume increases, even after the sessile drop volume is exhausted. This indicates the wetted imprint is only partially saturated, and a multiphase flow problem formulation is needed to predict the VX fate in porous substrates. Three characteristics and their changes in time: (i) sessile volume remaining, (ii) wetted imprint area on the sand surface where the droplet is deposited, and (iii) VX penetration depth into sand, are computed numerically and compared to experimentally measured values. A very good qualitative and quantitative agreement was found between the numerical and experimental results. These numerical and experimental methods can be used to determine the spread and sorption of hazardous materials into a variety of substrates.

  3. Sperm motility parameters and spermatozoa morphometric characterization in marine species: a study of swimmer and sessile species.

    Science.gov (United States)

    Gallego, V; Pérez, L; Asturiano, J F; Yoshida, M

    2014-09-15

    The biodiversity of marine ecosystems is diverse and a high number of species coexist side by side. However, despite the fact that most of these species share a common fertilization strategy, a high variability in terms of the size, shape, and motion of spermatozoa can be found. In this study, we have analyzed both the sperm motion parameters and the spermatozoa morphometric features of two swimmer (pufferfish and European eel) and two sessile (sea urchin and ascidian) marine species. The most important differences in the sperm motion parameters were registered in the swimming period. Sessile species sperm displayed notably higher values than swimmer species sperm. In addition, the sperm motilities and velocities of the swimmer species decreased sharply once the sperm was activated, whereas the sessile species were able to maintain their initial values for a long time. These results are linked directly to the species-specific lifestyles. Although sessile organisms, which show limited or no movement, need sperm with a capacity to swim for long distances to find the oocytes, swimmer organisms can move toward the female and release gametes near it, and therefore the spermatozoa does not need to swim for such a long time. At the same time, sperm morphology is related to sperm motion parameters, and in this study an in-depth morphometric analysis of ascidian, sea urchin, and pufferfish spermatozoa, using computer-assisted sperm analysis software, has been carried out for the first time. A huge variability in shapes, sizes, and structures of the studied species was found using electron microscopy.

  4. Endoscopic mucosal resection of flat and sessile colorectal adenomas: Our experience with long-term follow-ups

    Directory of Open Access Journals (Sweden)

    Grgov Saša

    2014-01-01

    Full Text Available Bacground/Aim. Endoscopic mucosal resection (EMR or mucosectomy is a removing method of flat or sessile lesions, laterally spreading tumors and carcinoma of the colon or the rectum limited to mucosa or the surface part of the submucosa. The aim of the study was to estimate the efficacy and safety of EMR in removing flat and sessile colorectal adenomas. Methods. This prospective study involved 140 patients during the period of 8 years. A total of 187 colorectal adenomas were removed using the EMR method “inject and cut with snare”. Results. The approximate size of mucosectomised adenomas was 13.6 mm (from 8 mm to 60 mm. There was a total of 48 (25.7% flat adenomas and 139 (74.3% sessile adenomas, (p < 0.01. Using “en bloc” and “piecemeal” resection, 173 (92.5% and 14 (7.5% of colorectal adenomas were removed, respectively. In all the cases, a complete removal of colorectal adenomas was achieved. Two (1.4% patients had adenoma removal with intramucosal carcinoma each. In the average follow-up period of 21.2 ± 17.8 months, 2 (1.4% patients had adenoma relapse after EMR. Considering complications, there was bleeding in 1 (0.7% patient with a big rectum adenoma removed with EMR. Furthermore, one (0.7% patient had a postcoagulation syndrome after cecal adenoma was removed by EMR. Conclusion. EMR is an efficient, safe and minimally invasive technique of removing flat and sessile adenomas in the colon and the rectum, with a very low percentage of adenoma recurrence over a long period of monitoring.

  5. Low-Bond Axisymmetric Drop Shape Analysis for Surface Tension and Contact Angle Measurements of Sessile Drops

    OpenAIRE

    Stalder, A.F.; Melchior, T.; Müller, M.; Sage, D; T. Blu; Unser, M

    2010-01-01

    A new method based on the Young-Laplace equation for measuring contact angles and surface tensions is presented. In this approach, a first-order perturbation technique helps to analytically solve the Young-Laplace equation according to photographic images of axisymmetric sessile drops. When appropriate, the calculated drop contour is extended by mirror symmetry so that reflection of the drop into substrate allows the detection of position of the contact points. To keep a wide range of applica...

  6. Sessile macro-epibiotic community of solitary ascidians, ecosystem engineers in soft substrates of Potter Cove, Antarctica

    Directory of Open Access Journals (Sweden)

    Clara Rimondino

    2015-01-01

    Full Text Available The muddy bottoms of inner Potter Cove, King George Island (Isla 25 de Mayo, South Shetlands, Antarctica, show a high density and richness of macrobenthic species, particularly ascidians. In other areas, ascidians have been reported to play the role of ecosystem engineers, as they support a significant number of epibionts, increasing benthic diversity. In this study, a total of 21 sessile macro-epibiotic taxa present on the ascidian species Corella antarctica Sluiter, 1905, Cnemidocarpa verrucosa (Lesson, 1830 and Molgula pedunculata Herdman, 1881 were identified, with Bryozoa being the most diverse. There were differences between the three ascidian species in terms of richness, percent cover and diversity of sessile macro-epibionts. The morphological characteristics of the tunic surface, the available area for colonization (and its relation with the age of the basibiont individuals and the pH of the ascidian tunic seem to explain the observed differences. Recent environmental changes in the study area (increase of suspended particulate matter caused by glaciers retreat have been related to observed shifts in the benthic community structure, negatively affecting the abundance and distribution of the studied ascidian species. Considering the diversity of sessile macro-epibionts found on these species, the impact of environmental shifts may be greater than that estimated so far.

  7. Sharp Interface Level Set Method based Study for Evaporation of a Sessile Droplet on Hydrophilic and Hydrophobic Substrates

    Science.gov (United States)

    Shaikh, Javed; Sharma, Atul; Bhardwaj, Rajneesh

    2016-11-01

    The evaporation of a sessile droplet is important in many applications like hot-spot cooling, surface patterning etc. An understanding of the droplet dynamics in terms of evaporation rate, evaporative cooling and substrate wettability is important for designing the droplet based devices. Extensive theoretical and experimental research has been conducted on evaporating droplets in recent years; however, the effect of surrounding vapors on the evaporation dynamics of a sessile droplet is not found in the literature. In this work, an in-house sharp-interface level set code based on the Ghost Fluid Method (GFM) is used. Energy, species, and momentum equations are coupled for studying the sessile droplet evaporation phenomenon on hydrophilic and hydrophobic substrates. Different modes of droplet evaporation i.e. constant contact radius (CCR), constant contact angle (CCA) are observed for the two types of substrates. The coupling of energy and species equations is used for capturing the evaporating cooling induced dip in the droplet surface temperature. The effect of surrounding vapors like fluorocarbon vapors, on the evaporative cooling, is presented for water droplet on the hydrophilic and hydrophobic substrates. Research Scholar.

  8. Single port VATS resection of a sessile solitary fibrous tumour of the visceral pleura. A case report.

    Science.gov (United States)

    Mazzella, Antonio; Izzo, Alessandro; Amore, Dario; Cennamo, Antonio; Cerqua, Francesco Saverio; Perrotta, Fabio

    2015-09-24

    Il tumore fibroso solitario della pleura viscerale è una neoplasia rara che deriva dalle cellule mesenchimali adiacenti al tessuto mesoteliali di pleura. La resezione chirurgica è il trattamento di scelta nelle sia nelle lesione benigne che maligne. La recidiva locale può essere il risultato di una chirurgia incompleta o conservatrice, di una mancanza di identificazione dei lembi del tumore durante l’operazione o di crescita di una neoplasia sincrona indipendente da quello rimossa. La resezione chirurgica è anche gravata da qualche difficoltà come la dimensione del tumore, il rapporto con le strutture anatomiche viciniori e la identificazione del peduncolo vascolare. Riportiamo un caso di un uomo di 72 anni con un tumore fibroso solitario sessile della pleura viscerale. Il paziente è stato trattato mediante videotoracoscopia con approccio uniportale. Questo caso, rappresenta una resezione in VATS uniportale di un SFTP sessile con ampia base di impianto. In letteratura, solo due casi di SFTP sono stati trattati mediante approccio uniportale. In tutti i due casi, il tumore era piccolo (4x3 cm nel primo, nel secondo 33 x 22mm) e peduncolato. Nel nostro caso, si parla di un STFP di dimensioni maggiore, sessile e con larga base di impianto. I vantaggi dell’approccio uniportale rispetto alla tradizionale VATS triportale sono la riduzione del dolore post-operatorio, la minore durata di utilizzo dei tubi di drenaggio, la ridotta degenza ospedaliera ed un miglior risultato estetico.

  9. In vitro water wettability of silicone hydrogel contact lenses determined using the sessile drop and captive bubble techniques.

    Science.gov (United States)

    Maldonado-Codina, Carole; Morgan, Philip B

    2007-11-01

    This study investigated the water contact angles of five commercially available silicone hydrogel contact lenses (Acuvue Advance, Acuvue Oasys, Focus Night & Day, O2 Optix, and PureVision) using sessile drop and captive bubble techniques. The only lens type that showed a significant difference in water contact angle when measured by sessile drop direct from the blister compared with after 48 h of soaking/washing in saline was the Acuvue Advance lens (from 66 degrees to 96 degrees, respectively) (p=0.0002), presumably because of surface active agents within the blister solution. The water contact angle data split the lenses into two distinct groups (psessile drop measures and relatively low captive bubble values (thereby displaying significant hysteresis) whereas the Focus Night & Day and O2 Optix lenses showed relatively low sessile drop measures and relatively high captive bubble values (with little hysteresis). Contact angle analysis of hydrogel lens surfaces is highly methodologically dependent and may be able to predict the clinical performance of contact lenses in vivo.

  10. Influence of culture media on biofilm formation by Candida species and response of sessile cells to antifungals and oxidative stress.

    Science.gov (United States)

    Serrano-Fujarte, Isela; López-Romero, Everardo; Reyna-López, Georgina Elena; Martínez-Gámez, Ma Alejandrina; Vega-González, Arturo; Cuéllar-Cruz, Mayra

    2015-01-01

    The aims of the study were to evaluate the influence of culture media on biofilm formation by C. albicans, C. glabrata, C. krusei, and C. parapsilosis and to investigate the responses of sessile cells to antifungals and reactive oxygen species (ROS) as compared to planktonic cells. For biofilm formation, the Candida species were grown at different periods of time in YP or YNB media supplemented or not with 0.2 or 2% glucose. Sessile and planktonic cells were exposed to increasing concentrations of antifungals, H2O2, menadione or silver nanoparticles (AgNPs). Biofilms were observed by scanning electron microscopy (SEM) and quantified by the XTT assay. C. albicans formed biofilms preferentially in YPD containing 2% glucose (YPD/2%), C. glabrata in glucose-free YNB or supplemented with 0.2% glucose (YNB/0.2%), while C. krusei and C. parapsilosis preferred YP, YPD/0.2%, and YPD/2%. Interestingly, only C. albicans produced an exopolymeric matrix. This is the first report dealing with the in vitro effect of the culture medium and glucose on the formation of biofilms in four Candida species as well as the resistance of sessile cells to antifungals, AgNPs, and ROS. Our results suggest that candidiasis in vivo is a multifactorial and complex process where the nutritional conditions, the human immune system, and the adaptability of the pathogen should be considered altogether to provide an effective treatment of the patient.

  11. Lamb Wave-Based Acoustic Radiation Force-Driven Particle Ring Formation Inside a Sessile Droplet.

    Science.gov (United States)

    Destgeer, Ghulam; Ha, Byunghang; Park, Jinsoo; Sung, Hyung Jin

    2016-04-05

    We demonstrate an acoustofluidic device using Lamb waves (LWs) to manipulate polystyrene (PS) microparticles suspended in a sessile droplet of water. The LW-based acoustofluidic platform used in this study is advantageous in that the device is actuated over a range of frequencies without changing the device structure or electrode pattern. In addition, the device is simple to operate and cheap to fabricate. The LWs, produced on a piezoelectric substrate, attenuate inside the fluid and create acoustic streaming flow (ASF) in the form of a poloidal flow with toroidal vortices. The PS particles experience direct acoustic radiation force (ARF) in addition to being influenced by the ASF, which drive the concentration of particles to form a ring. This phenomenon was previously attributed to the ASF alone, but the present experimental results confirm that the ARF plays an important role in forming the particle ring, which would not be possible in the presence of only the ASF. We used a range of actuation frequencies (45-280 MHz), PS particle diameters (1-10 μm), and droplet volumes (5, 7.5, and 10 μL) to experimentally demonstrate this phenomenon.

  12. Revegetation of a uranium mine dump by using fertilizer treated sessile oaks.

    Science.gov (United States)

    Lange, Christian A; Böcker, Lutz; Katzur, Joachim

    2011-01-01

    The rehabilitation of contaminated sites and the establishment of suitable trees for revegetation purposes is often problematic due to the mostly suboptimal nutrient supply and the poor humus reservoir. For these reasons hydrogels (Stockosorb) and novel humus substitutes (NOVIHUM), serving as long lasting fertilizer (LLF), were recently tested successfully. At the beginning of this multiyear study, those LLFs were administered to the root zone of young sessile oaks (Quercus petraea (Mattuschka) Liebl.), growing in test trials on a uranium mine dump in Schlema (Germany). To quantify the effect of LLFs on plant vitality, chlorophyll a fluorescence measurements and JIP test analyses were used. The results revealed up to 49% higher average photosynthetic vitality (PI(ABS)) of the LLF treated plants compared to controls. Particularly in the first test year, the efficiency of photosynthetic electron transport was strongly increased. This stimulation of photosynthetic activity was supported by direct measurements showing up to 129% increased diameter growth of the treated plants after a four year experimental period. Furthermore an increase of the maximum water holding capacity of the dump soil was attained by using LLFs. Overall, the findings reported here represent a feasible, ecologically justifiable reforestation method with a low environmental hazard potential.

  13. Understanding thermal Marangoni flow in water sessile evaporating drops via 3D-PTV

    Science.gov (United States)

    Rossi, Massimiliano; Marin, Alvaro; Kaehler, Christian J.

    2016-11-01

    Understanding the flow inside sessile evaporating drops is of great interest both from a fundamental and technological point of view. Despite strong research efforts in the recent years, a complete picture on the phenomena involved in this process and a way to control them is still far to be reached. This is due to a lack of reliable experimental data on the internal flow but more dramatically on the interfacial flow. A relevant open debate concerns the role played by the Marangoni flow induced by thermal gradients. We recently show how 3D particle tracking techniques are suitable to measure the internal flow of drops and to derive quantities such as surface shear and surface tension differences. Such experiments also indicated an increase of the thermal Marangoni flow as the droplet becomes thinner, in disagreement with current theoretical models and simulations. A possible reason for that could be a discrepancy of the imposed boundary conditions in the simulations and the experimental ones. This work follows up these observations with fully 3D time-resolved measurements of the flow inside drops evaporating on a quartz substrate, which temperature is controlled using a feedback temperature control and a microscope incubator system. Supported by DFG, Grant No. KA 1808/22.

  14. Think laterally: horizontal gene transfer from symbiotic microbes may extend the phenotype of marine sessile hosts

    Directory of Open Access Journals (Sweden)

    Sandie M Degnan

    2014-11-01

    Full Text Available Since the origin of the animal kingdom, marine animals have lived in association with viruses, prokaryotes and unicellular eukaryotes, often as symbionts. This long and continuous interaction has provided ample opportunity not only for the evolution of intimate interactions such as sharing of metabolic pathways, but also for horizontal gene transfer (HGT of non-metazoan genes into metazoan genomes. The number of demonstrated cases of inter-kingdom HGT is currently small, such that it is not yet widely appreciated as a significant player in animal evolution. Sessile marine invertebrates that vertically inherit bacterial symbionts, that have no dedicated germ line, or that bud or excise pluripotent somatic cells during their life history may be particularly receptive to HGT from their symbionts. Closer scrutiny of the growing number of genomes being accrued for these animals may thus reveal HGT as a regular source of novel variation that can function to extend the host phenotype metabolically, morphologically or even behaviourally. Taxonomic identification of symbionts will help to address the intriguing question of whether past HGT events may constrain contemporary symbioses.

  15. Triple-line behavior and wettability controlled by nanocoated substrates: influence on sessile drop evaporation.

    Science.gov (United States)

    Sobac, B; Brutin, D

    2011-12-20

    In this article, we investigate the influence of the surface properties of substrates on the evaporation process. Using various nanocoatings, it is possible to modify the surface properties of substrates, such as the roughness and the surface energy, while maintaining constant thermal properties. Experiments are conducted under atmospheric conditions with five fluids (methanol, ethanol, propanol, toluene and water) and four coatings (PFC, PTFE, SiOC, and SiO(x)). The various combinations of these fluids and coatings allow for a wide range of drop evaporation properties to be studied: the dynamics of the triple line, the volatility of fluids, and a large range of wettabilities (from 17 to 135°). The experimental data are in very good quantitative agreement with existing models of quasi-steady, diffusion-driven evaporation. The experimental results show that the dynamics of the evaporative rate are proportional to the dynamics of the wetting radius. Thus, the models succeed in describing the evaporative dynamics throughout the evaporation process regardless of the behavior of the triple line. Moreover, the use of various liquids reveals the validity of the models regardless of their volatility. The results also confirm the recent finding of a universal relation for the time evolution of the drop mass, independent of the drop size and initial contact angle. Finally, this study highlights the separate and coupled roles of the triple line and the wettability on the sessile drop evaporation process. Data reveal that the more wet and pinned a drop, the shorter the evaporation time.

  16. Heat Flux at the Surface of Metal Foil Heater under Evaporating Sessile Droplets

    Directory of Open Access Journals (Sweden)

    Igor Marchuk

    2015-01-01

    Full Text Available Evaporating water drops on a horizontal heated substrate were investigated experimentally. The heater was made of a constantan foil with the thickness of 25 μm and size of 42 × 35 mm2. The temperature of the bottom foil surface was measured by the infrared (IR camera. To determine the heat flux density during evaporation of liquid near the contact line, the Cauchy problem for the heat equation was solved using the temperature data. The maximum heat flux density is obtained in the contact line region and exceeds the average heat flux density from the entire foil surface by the factor of 5–7. The average heat flux density in the region wetted by the drop exceeds the average heat flux density from the entire foil surface by the factor of 3–5. This fact is explained by the heat influx from the foil periphery to the drop due to the relatively high heat conductivity coefficient of the foil material and high evaporation rate in the contact line region. Heat flux density profiles for pairs of sessile droplets are also investigated.

  17. Free energy of colloidal particles at the surface of sessile drops.

    Science.gov (United States)

    Guzowski, J; Tasinkevych, M; Dietrich, S

    2010-11-01

    The influence of finite system size on the free energy of a spherical particle floating at the surface of a sessile droplet is studied both analytically and numerically. In the special case that the contact angle at the substrate equals π/2 , a capillary analogue of the method of images is applied in order to calculate small deformations of the droplet shape if an external force is applied to the particle. The type of boundary conditions for the droplet shape at the substrate determines the sign of the capillary monopole associated with the image particle. Therefore, the free energy of the particle, which is proportional to the interaction energy of the original particle with its image, can be of either sign, too. The analytic solutions, given by the Green's function of the capillary equation, are constructed such that the condition of the forces acting on the droplet being balanced and of the volume constraint are fulfilled. Besides the known phenomena of attraction of a particle to a free contact line and repulsion from a pinned one, we observe a local free-energy minimum for the particle being located at the drop apex or at an intermediate angle, respectively. This peculiarity can be traced back to a non-monotonic behavior of the Green's function, which reflects the interplay between the deformations of the droplet shape and the volume constraint.

  18. Density of liquid NiCoAlCr quarternary alloys measured by modified sessile drop method

    Institute of Scientific and Technical Information of China (English)

    FANG Liang; ZHANG Shu-fang; XIAO Feng; YANG Ling-chuan; DONG Jian-xin; CAO Chun-lan; TAO Zai-nan; K. MUKAI

    2006-01-01

    The densities of liquid NiCoAlCr quaternary alloys with a fixed molar ratio of Ni to Co to Al (x(Ni)-x(Co)-x(Al)≈73-12-15) which is close to the average value of the commercial Ni-based superalloys TMS75, INCO713, CM247LC and CMSX-4, and the mass fraction of chromium changes from 0 to 9% were measured by a modified sessile drop method. It is found that with increasing temperature and chromium concentration in the alloys, the densities of the liquid NiCoAlCr quaternary alloys decrease, whereas the molar volume of the liquid NiCoAlCr quaternary alloys increases. And the liquid densities of NiCoAlCr quaternary alloys calculated from the partial molar volumes of nickel, cobalt, aluminum and chromium in the corresponding Ni-bases binary alloys are in good agreement with the experimental ones, i.e. within the error tolerance range the densities of the liquid Ni-based multi-component alloys can be predicted from the partial volumes of elements in Ni-based binary alloys in liquid state. The molar volume of liquid NiCoAlCr binary alloy shows a negative deviation from the ideal linear mixing and the deviation changes small with the increase of chromium concentration at the same temperature.

  19. Stretching and squeezing of sessile dielectric drops by the optical radiation pressure.

    Science.gov (United States)

    Chraïbi, Hamza; Lasseux, Didier; Arquis, Eric; Wunenburger, Régis; Delville, Jean-Pierre

    2008-06-01

    We study numerically the deformation of sessile dielectric drops immersed in a second fluid when submitted to the optical radiation pressure of a continuous Gaussian laser wave. Both drop stretching and drop squeezing are investigated at steady state where capillary effects balance the optical radiation pressure. A boundary integral method is implemented to solve the axisymmetric Stokes flow in the two fluids. In the stretching case, we find that the drop shape goes from prolate to near-conical for increasing optical radiation pressure whatever the drop to beam radius ratio and the refractive index contrast between the two fluids. The semiangle of the cone at equilibrium decreases with the drop to beam radius ratio and is weakly influenced by the index contrast. Above a threshold value of the radiation pressure, these "optical cones" become unstable and a disruption is observed. Conversely, when optically squeezed, the drop shifts from an oblate to a concave shape leading to the formation of a stable "optical torus." These findings extend the electrohydrodynamics approach of drop deformation to the much less investigated "optical domain" and reveal the openings offered by laser waves to actively manipulate droplets at the micrometer scale.

  20. Dislodging a sessile drop by a high-Reynolds-number shear flow at subfreezing temperatures.

    Science.gov (United States)

    Roisman, Ilia V; Criscione, Antonio; Tropea, Cameron; Mandal, Deepak Kumar; Amirfazli, Alidad

    2015-08-01

    The drop, exposed to an air flow parallel to the substrate, starts to dislodge when the air velocity reaches some threshold value, which depends on the substrate wetting properties and drop volume. In this study the critical air velocity is measured for different drop volumes, on substrates of various wettabilities. The substrate initial temperatures varied between the normal room temperature (24.5∘C) and subfreezing temperatures (-5∘C and -1∘C). The physics of the drop did not change at the subfreezing temperatures of the substrates, which clearly indicates that the drop does not freeze and remains liquid for a relatively long time. During this time solidification is not initiated, neither by the air flow nor by mechanical disturbances. An approximate theoretical model is proposed that allows estimation of the aerodynamic forces acting on the sessile drop. The model is valid for the case when the drop height is of the same order as the thickness of the viscous boundary in the airflow, but the inertial effects are still dominant. Such a situation, relevant to many practical applications, was never modeled before. The theoretical predictions for the critical velocity of drop dislodging agree well with the experimental data for both room temperature and lower temperatures of the substrates.

  1. Evaporation dynamics of non-spherical sessile drops of pure fluids and binary mixtures

    Science.gov (United States)

    Saenz, Pedro J.; Matar, Omar K.; Sefiane, Khellil; Valluri, Prashant; Kim, Jungho

    2015-11-01

    The dynamics of pure axisymmetric volatile sessile droplets have been meticulously examined over the last four decades but remain poorly understood. Studies focusing on more realistic non-spherical configurations are virtually non-existent. The dynamics of the latter are examined in this investigation by means of experiments and numerical simulations. We show that the lifetime and bulk flow characteristics of these drops depend on their size and shape. The irregular geometries lead to the emergence preferential convection currents in the liquid as well as differential local evaporation rates noticeable along the contact line. Similarly, we inspect the thermocapillary stability of the flow, which results as the liquid volatility increases, and find that this is also affected by the non-uniform wettability along the triple line. The Marangoni-driven instabilities grow in an intricate spatio-temporal fashion leading to the emergence of different flow regimes. Finally, we also provide new insights into the evaporation process of binary-mixture drops. Memphis Multiphase (EPSRC EP/K003976/1) & ThermaPOWER (EU IRSES-PIRSES GA-2011-294905).

  2. Bubble formation during the collision of a sessile drop with a meniscus

    CERN Document Server

    Keij, Diederik L; Castelijns, Hein; Riepen, Michel; Snoeijer, Jacco H

    2013-01-01

    The impact of a sessile droplet with a moving meniscus, as encountered in processes such as dip-coating, generically leads to the entrapment of small air bubbles. Here we experimentally study this process of bubble formation by looking through the liquid using high-speed imaging. Our central finding is that the size of the entrapped bubble crucially depends on the location where coalescence between the drop and the moving meniscus is initiated: (i) at a finite height above the substrate, or (ii) exactly at the contact line. In the first case, we typically find bubble sizes of the order of a few microns, independent of the size and speed of the impacting drop. By contrast, the bubbles that are formed when coalescence starts at the contact line become increasingly large, as the size or the velocity of the impacting drop is increased. We show how these observations can be explained from a balance between the lubrication pressure in the air layer and the capillary pressure of the drop.

  3. Measuring the Nonuniform Evaporation Dynamics of Sprayed Sessile Microdroplets with Quantitative Phase Imaging.

    Science.gov (United States)

    Edwards, Chris; Arbabi, Amir; Bhaduri, Basanta; Wang, Xiaozhen; Ganti, Raman; Yunker, Peter J; Yodh, Arjun G; Popescu, Gabriel; Goddard, Lynford L

    2015-10-13

    We demonstrate real-time quantitative phase imaging as a new optical approach for measuring the evaporation dynamics of sessile microdroplets. Quantitative phase images of various droplets were captured during evaporation. The images enabled us to generate time-resolved three-dimensional topographic profiles of droplet shape with nanometer accuracy and, without any assumptions about droplet geometry, to directly measure important physical parameters that characterize surface wetting processes. Specifically, the time-dependent variation of the droplet height, volume, contact radius, contact angle distribution along the droplet's perimeter, and mass flux density for two different surface preparations are reported. The studies clearly demonstrate three phases of evaporation reported previously: pinned, depinned, and drying modes; the studies also reveal instances of partial pinning. Finally, the apparatus is employed to investigate the cooperative evaporation of the sprayed droplets. We observe and explain the neighbor-induced reduction in evaporation rate, that is, as compared to predictions for isolated droplets. In the future, the new experimental methods should stimulate the exploration of colloidal particle dynamics on the gas-liquid-solid interface.

  4. Evaluation of the Inertness of Investment Casting Molds Using Both Sessile Drop and Centrifugal Casting Methods

    Science.gov (United States)

    Cheng, Xu; Yuan, Chen; Green, Nick; Withey, Paul

    2013-02-01

    The investment casting process is an economic production method for engineering components in TiAl-based alloys and offers the benefits of a near net-shaped component with a good surface finish. An investigation was undertaken to develop three new face coat systems based on yttria, but with better sintering properties. These face coat systems were mainly based on an yttria-alumina-zirconia system (Y2O3-0.5 wt pct Al2O3-0.5 wt pct ZrO2), an yttria-fluoride system (Y2O3-0.15 wt pct YF3), and an yttria-boride system (Y2O3-0.15 wt pct B2O3). After sintering, the chemical inertness of the face coat was first tested and analyzed using a sessile drop test through the metal wetting behavioral change for each face coat surface. Then, the interactions between the shell and metal were studied by centrifugal investment casting TiAl bars. Although the sintering aids in yttria can decrease the chemical inertness of the face coat, the thickness of the interaction layer in the casting was less than 10 μm; therefore, these face coats still can be possible face coat materials for investment casting TiAl alloys.

  5. Quantifying stick-slip contact line motion of evaporating sessile droplets

    Science.gov (United States)

    Wood, Clay; Pye, Justin; Burton, Justin

    Sessile droplet evaporation often involves an apparent stick-slip motion of pinning and de-pinning of the drop's edge. The small forces and complex hydrodynamics at the contact line make this phenomena difficult to quantify, although easily observable. We have characterized the stick-slip motion on gold and glass surfaces with the use of a quartz crystal microbalance (QCM). We observe changes in both the resonant frequency and dissipation during droplet evaporation. Depositing a droplet onto this oscillating surface greatly decreases the frequency while the dissipation increases. Evaporation occurs in two stages; when the droplet's contact line is pinned to the surface, its contact angle decreases. Then, at a critical angle, the contact line is pulled over pinning points and continues to evaporate with a receding contact area. These stick-slip events appear in our data as a sharp increase in frequency, followed by a sharp decrease; simultaneously, the dissipation displays a single sharp peak. QCMs pre-cleaned in an oxygen plasma environment exhibited a significantly reduced occurrence and magnitude of these features. We interpret these features and quantify the forces involved in the stick-slip motion using a dynamic model of the QCM with additional surface forces at the contact line.

  6. Investigation of wetting behavior of coal-chars with liquid iron by sessile drop method.

    Directory of Open Access Journals (Sweden)

    Veena Sahajwalla

    2008-06-01

    Full Text Available Using the sessile drop approach, the wettability of four non-graphitic coal-chars with electrolytic iron and Fe-2 % C-0.01 % S alloy has been determined at 1550°C, in a horizontal tube resistance furnace with an argon atmosphere. The ash concentration in chars ranged between 9.04 to 12.61 wt %, with alumina and silica as predominant ash components. The contact angles of these chars with liquid Fe-2 % C-0.01 % S alloy showed lesser variations with time as compared to corresponding angles with electrolytic iron. While the initial contact angles ranged between 106° and 137°, the contact angles for all coal-chars were quite similar after 60 minutes of contact (105 - 110°. While no well defined correlations could be observed between the initial char structure (Lc values and ash concentration / composition and contact angles in the initial stages of contact, the contact angles over extended periods were significantly affected by the presence of reaction products and impurity deposits in the interfacial region. With coal-chars generally showing a non-wetting behavior with liquid iron, these results are discussed in terms of the transfer of carbon and sulphur by mass transport across the interface, the formation of an enriched interfacial layer containing calcium, sulphur and alumina, reduction of reducible oxides such as silica and iron oxides, and possible transfer of these elements into the liquid iron.

  7. When sessile drops are no longer small: transitions from spherical to fully flattened.

    Science.gov (United States)

    Extrand, C W; Moon, Sung In

    2010-07-20

    We measured the dimensions and contact angles of sessile drops using three liquids on a variety of polymer and silicon surfaces. Drops ranged in size from a few microliters to several milliliters. With increasing liquid volume, heights of the drops initially rose steeply and then gradually tapered to a constant value. The heights of small, undistorted drops as well as the heights of the largest drops were accurately predicted by well-established models. A recently derived expression for meniscus height was used to estimate the heights of intermediate-size drops. While it was not exact, this expression produced reasonable approximations without having to resort to iterative numerical methods. We also identified transition points where gravity began to distort drop shape and ultimately limited drop height. Relatively simple closed analytical expressions for estimating these transition points were also derived. Predicted values of the height and volume at the onset of distortion agreed fairly well with the measured ones. Contact angles carefully measured by the tangent method were independent of drop size.

  8. Microscale fibre alignment by a three-dimensional sessile drop on a wettable pad

    Science.gov (United States)

    Reznik, S. N.; Salalha, W.; Yarin, A. L.; Zussman, E.

    Fluidic assembly provides solutions for assembling particles with sizes from nano- metres to centimetres. Fluidic techniques based on patterned shapes of monolayers and capillary forces are widely used to assemble microfabrication devices. Usually, for self-assembly, the precondition is that the components must be mobile in a fluidic environment. In the present work, a shape-directed fluidic self-assembly of rod-like microstructures, such as an optical fibre on a wettable pad is demonstrated experimentally with submicrometre positioning precision. A model of the process is proposed, which accounts for the following two stages of the orientation of a fibre submerged in a sessile drop: (i) the drop melting and spreading over a wettable pad; (ii) fibre reorientation related to the surface-tension-driven shrinkage of the drop surface area. At the end of stage (ii), the fibre is oriented along the pad. The experi- mental results for the optical-fibre assembly by a solder joint have been compared to the modelling results, and a reasonable agreement has been found. The major outcome of the experiments and modelling is that surface tension forces on the fibre piercing a drop align the fibre rather than the flow owing to the spreading of the drop over the horizontal pad, i.e. stage (ii) mostly contributes to the alignment.

  9. Sessile drops imbibition over nano porous substrates : application for art painting restoration

    Science.gov (United States)

    Léang, Marguerite; Pauchard, Ludovic; Lee, Lay-Theng; Ott, Frédéric; Giorgiutti-Dauphiné, Frédérique

    2016-11-01

    Art painting restoration aims to restore and preserve the integrity of a painting. Most of the techniques consist of depositing solvents on the surface of the painting to dissolve the varnish layer. However the sublayers can be damaged by the penetration of the solvent, possibly resulting in swelling or cracking processes. Due to the physical and chemical complexity of the pictorial layer, we propose to study solvent penetration in model nano porous media obtained by controlled drying of aqueous dispersions of silica nanoparticles. We present the dynamics of imbibition of sessile solvent drops on porous media with different pore sizes. Three different regimes in the evolution of the drop size with time are identified. Our experimental set-up provides a precise direct quantification of the different flows outside and through the porous media. Different experimental techniques are used to characterize the porous media : neutron imaging to determine the permeability and microindentation testing to estimate the mechanical properties of the media after the imbibition process. Supported by PALM LabEx Grant.

  10. Fracture toughness from atomistic simulations: Brittleness induced by emission of sessile dislocations

    Energy Technology Data Exchange (ETDEWEB)

    Farkas, D. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering

    1998-08-04

    Using atomistic simulations of crack response for intermetallic materials the author shows that when the emitted dislocations are sessile and stay in the immediate vicinity of the crack tip the emitted dislocations can actually lead to brittle failure. She present the results of an atomistic simulation study of the simultaneous dislocation emission and crack propagation process in this class of materials. She used a molecular statics technique with embedded atom (EAM) potentials developed for NiAl. The crystal structure of NiAl is the CsCl type (B2) with a lattice parameter of 0.287 nm, which is reproduced by the potential together with the cohesive energy and elastic constants. The compound stays ordered up to the melting point, indicating a strong tendency towards chemical ordering with a relatively high energy of the antiphase boundary (APB). As a result of this relatively large energy the dislocations of 1/2<111> type Burgers vectors imply a high energy and the deformation process occurs via the larger <100> type dislocations.

  11. Effect of low Reynolds number flow on the quorum sensing behavior of sessile bacteria

    Science.gov (United States)

    Ingremeau, Francois; Minyoung, Kevin Kim; Bassler, Bonnie; Stone, Howard; Mechanical; Aerospace Engineering, Complex fluids Group Team; Molecular Biology Lab Team

    2014-11-01

    Sessile and planktonic bacteria can be sensitive to the bacteria cell density around them through a chemical mediated communication called quorum sensing. When the quorum sensing molecules reach a certain value, the metabolism of the bacteria changes. Quorum sensing is usually studied in static conditions or in well mixed environments. However, bacteria biofilms can form in porous media or in the circulatory system of an infected body: quorum sensing in such flowing environment at low Reynolds number is not well studied. Using microfluidic devices, we observe how the flow of a pure media affects quorum sensing of bacteria attached to the wall. The biofilm formation is quantified by measuring the optical density in brightfield microscopy and the quorum sensing gene expression is observed through the fluorescence of a green fluorescent protein, which is a reporter for one of the quorum sensing genes. We measured without flow the amount of Staphylococcus aureus biofilm when the quorum sensing gene expression starts. In contrast, when the media is flowing in the microchannel, the quorum sensing expression is delayed. This effect can be understood and modelled by considering the diffusion of the quorum sensing molecules in the biofilm and their convection by the flowing media.

  12. Springtime Leaf Development of Mature Sessile Oak Trees as Based on Multi-Seasonal Monitoring Data

    Directory of Open Access Journals (Sweden)

    NYITRAI, Balázs

    2012-01-01

    Full Text Available Based on a four year leaf growth data-set we modelled the thermal time-dependent leafontogeny in upper and lower canopy layers of mature sessile oak trees, in a Quercetum petraeae-cerrisforest stand (NE Hungary. Our regression models revealed no considerable differences between thetiming of leaf unfolding and leaf expansion of different canopy layers. On the other hand seasonalcourse in leaf mass-to-area ratio (LMA indicated that sun leaves needed considerably longer thermaltime to fully develop their anatomical structures compared to shade leaves. LMA of sun leaves washigher during the whole leaf maturation process suggesting that ‘sun’ and ‘shade’ characteristicsdevelop in very early stage of leaf ontogeny. Functioning of photosynthetic apparatus (Fv/Fo in shadeleaves have built up faster and performed better in all developmental stages which could be attributedto two main factors: 1 very early determination of leaf traits as a function of light environment and 2evolving shading effect of upper canopy layer eliminates photoinhibition in lower leaves.

  13. Production potential of the soil and the basic elements of productivity of the most widely spred sessil types in the u. N.P. „Đerdap”

    Directory of Open Access Journals (Sweden)

    Knežević Milan

    2010-01-01

    Full Text Available This paper is on the results of the soil and its production potential in the types of forests of sessile oaks (Quercus petraea in the area of the National Park „Đerdap” in the community units of Zlatica, Đerdap, Štrbačko korito, Desna reka and Kožica. There are the most widely spread types of the sprout forests of the sessile oaks in the research area, deep deluvium, luvisoil, eutric cambsoils, and a great number of subtypes of acid brown soil. Considering the fact that the production potential of the defined types of soil depends on the depth, skeleton and other physical characteristics which determine acception, keeping and moving of water and this means that the production value of the studied soils is in the direct correlation with physical-geographical conditions of the environment. Taking into account that solum is well developed and the low contents of skeleton, all the studied soil in the most widely spread types of sessile oaks in the area of N.P. „Đerdap”, are very productive natural habitats. The exception is acid brown soil, which characteristics vary as well as their production potential. Apart from a good production potential of the studied soils within this paper, sessile forests in the researched areas irrationally use production potential of the habitat. In the research area in the last 20 years, the processes of devitalizing and the appearance of decaying of sessile oaks are expressed. In the sessile forests of Serbia, there are forests of the production and protection character, and the structure of the sessile forests at global level is characterized by not normal state with domination of middle aged and in great extent mature withering ingredients, what is the main cause of insufficiently used good potential of the soil.

  14. Source of temperature and pressure pulsations during sessile droplet evaporation into multicomponent atmospheres.

    Science.gov (United States)

    Persad, Aaron H; Sefiane, Khellil; Ward, Charles A

    2013-10-29

    During sessile droplet evaporation, studies with IR thermography and shadowgraphs have indicated temperature pulsations. We confirm those observations with microthermocouples, but microthermocouples also indicate temperature pulsations in the atmosphere of the droplet. The pressure in this atmosphere pulsated as well and was correlated with the temperature pulsations in the droplet. Also, we find that if a droplet evaporates into its own vapor, there are no temperature or pressure pulsations. The pulsations occur only if the droplet evaporates into an atmosphere with a component having a heat of solution with the droplet when it adsorbs-absorbs. None of the currently proposed mechanisms for the temperature pulsations provide an explanation for the coupling between the temperature pulsations in the droplet and the vapor-phase pressure pulsations, and for the absence of the pulsations when the system is single-component. As a mechanism for the pulsations, we propose that when a droplet is exposed to an atmosphere containing a component that has a heat of solution with the droplet, energy will be released from adsorption-absorption. This energy will cause pulsations in the evaporation flux, and these pulsations could cause the observed temperature and pressure pulsations. We examine this mechanism by showing that, if the measured temperature pulsations in a water droplet exposed to a methanol atmosphere are used as the input to a theory of evaporation kinetics (statistical rate theory), the pressure pulsations of the water vapor in the methanol atmosphere are predicted and agree with those measured with a quadrupole mass analyzer. When the inputs and outputs are reversed in the theory, we find that the temperature pulsations in the droplet are correctly predicted from the measured water vapor pulsations in the atmosphere.

  15. Loss of expression and promoter methylation of SLIT2 are associated with sessile serrated adenoma formation.

    Science.gov (United States)

    Beggs, Andrew D; Jones, Angela; Shepherd, Neil; Arnaout, Abed; Finlayson, Caroline; Abulafi, A Muti; Morton, Dion G; Matthews, Glenn M; Hodgson, Shirley V; Tomlinson, Ian P M

    2013-05-01

    Serrated adenomas form a distinct subtype of colorectal pre-malignant lesions that may progress to malignancy along a different molecular pathway than the conventional adenoma-carcinoma pathway. Previous studies have hypothesised that BRAF mutation and promoter hypermethylation plays a role, but the evidence for this is not robust. We aimed to carry out a whole-genome loss of heterozygosity analysis, followed by targeted promoter methylation and expression analysis to identify potential pathways in serrated adenomas. An initial panel of 9 sessile serrated adenomas (SSA) and one TSA were analysed using Illumina Goldengate HumanLinkage panel arrays to ascertain regions of loss of heterozygosity. This was verified via molecular inversion probe analysis and microsatellite analysis of a further 32 samples. Methylation analysis of genes of interest was carried out using methylation specific PCR (verified by pyrosequencing) and immunohistochemistry used to correlate loss of expression of genes of interest. All experiments used adenoma samples and normal tissue samples as control. SSA samples were found on whole-genome analysis to have consistent loss of heterozygosity at 4p15.1-4p15.31, which was not found in the sole TSA, adenomas, or normal tissues. Genes of interest in this region were PDCH7 and SLIT2, and combined MSP/IHC analysis of these genes revealed significant loss of SLIT2 expression associated with promoter methylation of SLIT2. Loss of expression of SLIT2 by promoter hypermethylation and loss of heterozygosity events is significantly associated with serrated adenoma development, and SLIT2 may represent a epimutated tumour suppressor gene according to the Knudson "two hit" hypothesis.

  16. Different harvest intensity and soil CO2 efflux in sessile oak coppice forests

    Directory of Open Access Journals (Sweden)

    Darenova E

    2016-08-01

    Full Text Available Soil CO2 efflux accounts for about 45-80% of total ecosystem respiration and is therefore an important part of the ecosystem carbon cycle. Soil CO2 efflux has been poorly studied in forests managed in the ancient coppicing manner. In our study, soil CO2 efflux, temperature, and moisture were measured in sessile oak stands with different harvesting intensity (control: 0% intensity; V1: 75%; V2: 80 %; V3: 85%; and V4: 100% during the fifth and sixth years after harvesting. Soil CO2 efflux was in the range 2-8 µmol CO2 m-2 s-1 and indicated an increasing pattern with increasing harvesting intensity. The slope of that pattern became less steep from the fifth to the sixth year after harvesting, thus indicating gradual recovery of soil carbon dynamics in the coppiced stand toward the equilibrium state existing before harvesting. Temperature sensitivity of soil CO2 efflux ranged between 2.1 and 2.8, with the lowest values measured in the control stand. Soil CO2 efflux in the control stand was more sensitive to changes in soil moisture than was that on harvested plots. By our calculations, 6.2 tC ha-1 was released from the control stand and 6.2-6.8 tC ha-1 from the harvested stands during the sixth year after harvesting. If mean temperature were to rise by 1 °C, the amount of soil carbon released would increase by 7.7% in the control stand and, depending on harvesting intensity, by 9.0-10.8% in the harvested stands.

  17. Volume evolution of small sessile droplets evaporating in stick-slip mode

    Science.gov (United States)

    Hu, Dinghua; Wu, Huiying

    2016-04-01

    This work is aimed at developing a simple and efficient predictive model and revealing the volume evolution behavior of small sessile droplets evaporating in stick-slip (SS) mode, covering a wide range of initial (θ0) and receding (θrec) contact angles (0 ∘contact angle and contact radius of droplets evaporating in SS mode are first developed, and are then validated with the experimental data in the literature. With the proposed expressions, the volume evolutions of evaporating droplets with different θ0 and θrec are predicted and analyzed. The results show that on a hydrophilic surface (θ0≤90 ∘ ), the volume evolution of droplets in SS mode always occurs in a way between the constant contact radius (CCR) and constant contact angle (CCA) modes (i.e., two extreme modes); however, on a hydrophobic surface (θ0>90 ∘ ), as θrec increases from 0 to θ0, the volume evolution of droplets in SS mode first departs from the CCR mode, then approaches the SS mode with θrec=90 ∘ , and finally returns to the CCA mode. More interestingly, the initially identical droplets evaporating on hydrophobic surfaces with different receding contact angles (θrec=90∘±Δ θ ) can even have approximately the same volume evolution behavior. It is also found that the widely accepted 2/3 law is applicable only for volume evolution of droplets in SS mode with large initial contact angle or small contact angle hysteresis, with the predicted deviation less than 1.5% for θ0≥150∘ or θ0≥50∘ when θ0-θrec≤15∘ . Finally, a physical interpretation for the volume evolution behaviors of droplets in SS mode is proposed.

  18. Volume evolution of small sessile droplets evaporating in stick-slip mode.

    Science.gov (United States)

    Hu, Dinghua; Wu, Huiying

    2016-04-01

    This work is aimed at developing a simple and efficient predictive model and revealing the volume evolution behavior of small sessile droplets evaporating in stick-slip (SS) mode, covering a wide range of initial (θ_{0}) and receding (θ_{rec}) contact angles (0^{∘}mode are first developed, and are then validated with the experimental data in the literature. With the proposed expressions, the volume evolutions of evaporating droplets with different θ_{0} and θ_{rec} are predicted and analyzed. The results show that on a hydrophilic surface (θ_{0}≤90^{∘}), the volume evolution of droplets in SS mode always occurs in a way between the constant contact radius (CCR) and constant contact angle (CCA) modes (i.e., two extreme modes); however, on a hydrophobic surface (θ_{0}>90^{∘}), as θ_{rec} increases from 0 to θ_{0}, the volume evolution of droplets in SS mode first departs from the CCR mode, then approaches the SS mode with θ_{rec}=90^{∘}, and finally returns to the CCA mode. More interestingly, the initially identical droplets evaporating on hydrophobic surfaces with different receding contact angles (θ_{rec}=90^{∘}±Δθ) can even have approximately the same volume evolution behavior. It is also found that the widely accepted 2/3 law is applicable only for volume evolution of droplets in SS mode with large initial contact angle or small contact angle hysteresis, with the predicted deviation less than 1.5% for θ_{0}≥150^{∘} or θ_{0}≥50^{∘} when θ_{0}-θ_{rec}≤15^{∘}. Finally, a physical interpretation for the volume evolution behaviors of droplets in SS mode is proposed.

  19. Assessing the effectiveness of marine reserves on unsustainably harvested long-lived sessile invertebrates.

    Science.gov (United States)

    Linares, Cristina; Garrabou, Joaquim; Hereu, Bernat; Diaz, David; Marschal, Christian; Sala, Enric; Zabala, Mikel

    2012-02-01

    Although the rapid recovery of fishes after establishment of a marine reserve is well known, much less is known about the response of long-lived, sessile, benthic organisms to establishment of such reserves. Since antiquity, Mediterranean red coral (Corallium rubrum) has been harvested intensively for use in jewelry, and its distribution is currently smaller than its historical size throughout the Mediterranean Sea. To assess whether establishment of marine reserves is associated with a change in the size and number of red coral colonies that historically were not harvested sustainably, we analyzed temporal changes in mean colony diameter and density from 1992 to 2005 within red coral populations at different study sites in the Medes Islands Marine Reserve (established in 1992) and in adjacent unprotected areas. Moreover, we compared colony size in the Medes Islands Marine Reserve, where recreational diving is allowed and poaching has been observed after reserve establishment, with colony size in three other marine protected areas (Banyuls, Carry-le-Rouet, and Scandola) with the enforced prohibition of fishing and diving. At the end of the study, the size of red coral colonies at all sampling sites in the Medes Islands was significantly smaller than predicted by growth models and smaller than those in marine protected areas without fishing and diving. The annual number of recreational dives and the percent change in the basal diameter of red coral colonies were negatively correlated, which suggests that abrasion by divers may increase the mortality rates of the largest red coral colonies within this reserve . Our study is the first quantitative assessment of a poaching event, which was detected during our monitoring in 2002, inside the marine reserve. Poaching was associated with a loss of approximately 60% of the biomass of red coral colonies.

  20. Strategy of seedlings to overcome their sessile nature: auxin in the mobility control

    Directory of Open Access Journals (Sweden)

    Petra eZadnikova

    2015-04-01

    Full Text Available Plants are sessile organisms that are permanently restricted to their site of germination. Tocompensate for their lack of mobility, plants evolved unique mechanisms enabling them torapidly react to ever changing environmental conditions and flexibly adapt their postembryonicdevelopmental program. A prominent demonstration of this developmental plasticity is theirability to bend organs in order to reach the position most optimal for growth and utilization oflight, nutrients, and other resources. Shortly after germination, dicotyledonous seedlings form abended structure, the so-called apical hook, to protect the delicate shoot meristem andcotyledons from damage when penetrating through the soil. Upon perception of a lightstimulus, the apical hook rapidly opens and the photomorphogenic developmental program isactivated. After germination, plant organs are able to align their growth with the light sourceand adopt the most favorable orientation through bending, in a process named phototropism.On the other hand, when roots and shoots are diverted from their upright orientation, theyimmediately detect a change in the gravity vector and bend to maintain a vertical growthdirection.Noteworthy, despite the diversity of external stimuli perceived by different plantorgans, all plant tropic movements share a common mechanistic basis: differential cell growth.In our review, we will discuss the molecular principles underlying various tropic responses withthe focus on mechanisms mediating the perception of external signals, transduction cascadesand downstream responses that regulate differential cell growth and consequently, organbending. In particular, we highlight common and specific features of regulatory pathways incontrol of the bending of organs and a role for the plant hormone auxin as a key regulatorycomponent.

  1. Loss of expression and promoter methylation of SLIT2 are associated with sessile serrated adenoma formation.

    Directory of Open Access Journals (Sweden)

    Andrew D Beggs

    2013-05-01

    Full Text Available Serrated adenomas form a distinct subtype of colorectal pre-malignant lesions that may progress to malignancy along a different molecular pathway than the conventional adenoma-carcinoma pathway. Previous studies have hypothesised that BRAF mutation and promoter hypermethylation plays a role, but the evidence for this is not robust. We aimed to carry out a whole-genome loss of heterozygosity analysis, followed by targeted promoter methylation and expression analysis to identify potential pathways in serrated adenomas. An initial panel of 9 sessile serrated adenomas (SSA and one TSA were analysed using Illumina Goldengate HumanLinkage panel arrays to ascertain regions of loss of heterozygosity. This was verified via molecular inversion probe analysis and microsatellite analysis of a further 32 samples. Methylation analysis of genes of interest was carried out using methylation specific PCR (verified by pyrosequencing and immunohistochemistry used to correlate loss of expression of genes of interest. All experiments used adenoma samples and normal tissue samples as control. SSA samples were found on whole-genome analysis to have consistent loss of heterozygosity at 4p15.1-4p15.31, which was not found in the sole TSA, adenomas, or normal tissues. Genes of interest in this region were PDCH7 and SLIT2, and combined MSP/IHC analysis of these genes revealed significant loss of SLIT2 expression associated with promoter methylation of SLIT2. Loss of expression of SLIT2 by promoter hypermethylation and loss of heterozygosity events is significantly associated with serrated adenoma development, and SLIT2 may represent a epimutated tumour suppressor gene according to the Knudson "two hit" hypothesis.

  2. Line tension and morphology of a sessile droplet on a spherical substrate

    Science.gov (United States)

    Iwamatsu, Masao

    2016-05-01

    The effects of line tension on the morphology of a sessile droplet placed on top of a convex spherical substrate are studied. The morphology of the droplet is determined from the global minimum of the Helmholtz free energy. The contact angle between the droplet and the spherical substrate is expressed by the generalized Young's formula. When the line tension is positive and large, the contact angle jumps discontinuously to 180∘, the circular contact line shrinks towards the top of the substrate, and the droplet detaches from the substrate, forming a spherical droplet if the substrate is hydrophobic (i.e., the Young's contact angle is large). This finding is consistent with that predicted by Widom [J. Phys. Chem. 99, 2803 (1995), 10.1021/j100009a041]; the line tension induces a drying transition on a flat substrate. On the other hand, the contact angle jumps to 0∘, the circular contact line shrinks towards the bottom of the substrate, and the droplet spreads over the substrate to form a wrapped spherical droplet if the substrate is hydrophilic (i.e., the Young's contact angle is small). Therefore, not only the drying transition of a cap-shaped to a detached spherical droplet but also the wetting transition of a cap-shaped to a wrapped spherical droplet could occur on a spherical substrate as the surface area of the substrate is finite. When the line tension is negative and its magnitude increases, the contact line asymptotically approaches the equator from either above or below. The droplet with a contact line that coincides with the equator is an isolated, singular solution of the first variational problem. In this instance, the contact line is pinned and cannot move as far as the line tension is smaller than the critical magnitude, where the wetting transition occurs.

  3. Towards universal buckling dynamics in nanocolloidal sessile droplets: the effect of hydrophilic to superhydrophobic substrates and evaporation modes.

    Science.gov (United States)

    Basu, Saptarshi; Bansal, Lalit; Miglani, Ankur

    2016-06-14

    The evaporation of a nanocolloidal sessile droplet exhibits preferential particle assembly, nanoporous shell formation and buckling to form cavities with unique morphological features. Here, we have established many universal trends that explain the buckling dynamics under one umbrella irrespective of hydrophobicity, evaporation mode and particle loading. We provide a regime map explaining the droplet morphology and buckling characteristics for droplet evaporation on various substrates. Specifically, we find that the final droplet volume and the radius of curvature at the buckling onset are universal functions of particle concentration. Furthermore, we establish that post-buckling cavity growth is evaporation driven regardless of the substrate.

  4. Dynamic response of a thin sessile drop of conductive liquid to an abruptly applied or removed electric field

    Science.gov (United States)

    Corson, L. T.; Mottram, N. J.; Duffy, B. R.; Wilson, S. K.; Tsakonas, C.; Brown, C. V.

    2016-10-01

    We consider, both theoretically and experimentally, a thin sessile drop of conductive liquid that rests on the lower plate of a parallel-plate capacitor. We derive analytical expressions for both the initial deformation and the relaxation dynamics of the drop as the electric field is either abruptly applied or abruptly removed, as functions of the geometrical, electrical, and material parameters, and investigate the ranges of validity of these expressions by comparison with full numerical simulations. These expressions provide a reasonable description of the experimentally measured dynamic response of a drop of conductive ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate.

  5. Imaging internal flows in a drying sessile polymer dispersion drop using Spectral Radar Optical Coherence Tomography (SR-OCT).

    Science.gov (United States)

    Manukyan, Selin; Sauer, Hans M; Roisman, Ilia V; Baldwin, Kyle A; Fairhurst, David J; Liang, Haida; Venzmer, Joachim; Tropea, Cameron

    2013-04-01

    In this work, we present the visualization of the internal flows in a drying sessile polymer dispersion drop on hydrophilic and hydrophobic surfaces with Spectral Radar Optical Coherence Tomography (SR-OCT). We have found that surface features such as the initial contact angle and pinning of the contact line, play a crucial role on the flow direction and final shape of the dried drop. Moreover, imaging through selection of vertical slices using optical coherence tomography offers a feasible alternative compared to imaging through selection of narrow horizontal slices using confocal microscopy for turbid, barely transparent fluids.

  6. Axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD): a film balance technique for high collapse pressures.

    Science.gov (United States)

    Saad, Sameh M I; Policova, Zdenka; Acosta, Edgar J; Neumann, A Wilhelm

    2008-10-07

    Collapse pressure of insoluble monolayers is a property determined from surface pressure/area isotherms. Such isotherms are commonly measured by a Langmuir film balance or a drop shape technique using a pendant drop constellation (ADSA-PD). Here, a different embodiment of a drop shape analysis, called axisymmetric drop shape analysis-constrained sessile drop (ADSA-CSD) is used as a film balance. It is shown that ADSA-CSD has certain advantages over conventional methods. The ability to measure very low surface tension values (e.g., drop setup, and leak-proof design make the constrained sessile drop constellation a better choice than the pendant drop constellation in many situations. Results of compression isotherms are obtained on three different monolayers: octadecanol, dipalmitoyl-phosphatidyl-choline (DPPC), and dipalmitoyl-phosphatidyl-glycerol (DPPG). The collapse pressures are found to be reproducible and in agreement with previous methods. For example, the collapse pressure of DPPC is found to be 70.2 mJ/m2. Such values are not achievable with a pendant drop. The collapse pressure of octadecanol is found to be 61.3 mJ/m2, while that of DPPG is 59.0 mJ/m2. The physical reasons for these differences are discussed. The results also show a distinctive difference between the onset of collapse and the ultimate collapse pressure (ultimate strength) of these films. ADSA-CSD allows detailed study of this collapse region.

  7. Investigation of the contact angles between various molten metals and substrates of niobium and zirconium. Final report. [Sessile drop technique

    Energy Technology Data Exchange (ETDEWEB)

    Munir, Z.A.

    1977-08-01

    The sessile drop technique was utilized for the determination of the contact angles between droplets of liquid tin, indium, and gallium; and substrates of niobium and zirconium. Contact angles, theta, were measured for various substrate surface roughness and over the temperature range 30 to 650/sup 0/C. Values of theta for all of these systems were found to be greater than 90/sup 0/ i.e., constituting a case of nonwetting between the liquid metals and the substrates. Three characteristic regions of the temperature dependence of contact angles were observed. A steady-state region in which the contact angle is relatively independent of temperature was preceded and followed by regions in which theta decreased rapidly with increasing temperature. For the steady-state or second region, contact angles were found to be independent of time whereas in the third region contact angles showed a decreasing trend with time at constant temperature. In accordance with theoretical predictions for theta greater than 90/sup 0/, increasing roughness of the substrate caused a corresponding increase in theta. Electron microprobe analyses showed that only the Ga--Zr system exhibited evidence of diffusion at the interface. Photographs of the sessile drop of this system over a period of time indicated that the drop had spread over a greater area thus supporting the possibility of a surface diffusion mass-transport process.

  8. Simultaneous monitoring of protein adsorption at the solid-liquid interface from sessile solution droplets by ellipsometry and axisymmetric drop shape analysis by profile

    NARCIS (Netherlands)

    Wormeester, H; Busscher, HK

    1999-01-01

    In this paper two in situ techniques are combined to simultaneously examine protein adsorption at the solid-liquid interface from sessile solution droplets. With axisymmetric drop shape analysis by profile (ADSA-P) the change in solid-liquid interfacial tension is determined, while ellipsometry is e

  9. Approximate expressions that describe the profiles of sessile and pendent drops for the cases of small Bond numbers and strong wetting

    Science.gov (United States)

    Galaktionov, E. V.; Galaktionova, N. E.; Tropp, E. A.

    2016-12-01

    Variational formulations of the problems of sessile and pendent drops are given taking into account the force of gravity in the axially symmetric case. Approximate expressions that describe the surface profiles of these drops by the asymptotic method for small Bond numbers have been obtained by the linearization method in the case of strong wetting.

  10. Simultaneous monitoring of protein adsorption at the solid–liquid interface from sessile solution droplets by ellipsometry and axisymmetric drop shape analysis by profile

    NARCIS (Netherlands)

    Noordmans, Jaap; Wormeester, Herbert; Busscher, Henk J.

    1999-01-01

    In this paper two in situ techniques are combined to simultaneously examine protein adsorption at the solid–liquid interface from sessile solution droplets. With axisymmetric drop shape analysis by profile (ADSA-P) the change in solid–liquid interfacial tension is determined, while ellipsometry is e

  11. Axisymmetric Drop Shape Analysis: Computational Methods for the Measurement of Interfacial Properties from the Shape and Dimensions of Pendant and Sessile Drops.

    Science.gov (United States)

    Río; Neumann

    1997-12-15

    State-of-the-art axisymmetric drop shape analysis (ADSA) techniques for the computation of interfacial tensions and contact angles by fitting the Laplace equation of capillarity to the shape and dimensions of pendant and sessile drops are presented. More accurate, efficient, and reliable versions of the technique for the measurement of contact angles from the volume and diameter of sessile drops [axisymmetric drop shape analysis-diameter (ADSA-D)] and for interfacial tension measurements from a series of arbitrary profile coordinates of sessile and pendant drops [axisymmetric drop shape analysis-profile (ADSA-P)] have been developed. Advanced numerical methods have been used to improve the numerical stability and global convergence, for more accurate results and a wider range of applicability of the methods. A new technique called axisymmetric drop shape analysis-height and diameter (ADSA-HD) has been developed to estimate interfacial tensions from the height and diameter of sessile and pendant drops. Numerical simulations using numerically generated drop profiles were used to evaluate the accuracy and applicability of the methods. Copyright 1997 Academic Press.

  12. Sessile animals` distribution and their water quality purification function in Tokyo inner bay; Tokyoto naiwan ni okeru fuchaku dobutsu no bunpu to suishitsu joka kino

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, K.; Tsuchiya, T. [Tokyo Metropolitan Research Inst. for Environmental Protection, Tokyo (Japan); Inamori, Y. [National Inst. for Environmental Studies, Tsukuba (Japan); Okutomi, S. [Saitama University, Saitama (Japan). Faculty of Engineering; Nishimura, O.; Sudo, R. [Tohoku University, Sendai (Japan)

    1998-01-10

    With sea banks in the Tokyo Inner Bay as the object, discussions were given on identification of actual living conditions for sessile animals and purification function of their dominant species. In the investigation, submerged visual observations and identification on existing quantities were performed in July, September and November, 1995 and February 1996. The following matters were made clear as a result of the investigation: the number of species ranges from 43 to 46 and is stabilized throughout a year; a phenomenon is repeated that the number of individuals decreases in summer and winter, and increases in spring and fall as breeding seasons as a result of the addition of larva; the existing quantity is accounted for 90% or more by four dominant species of M. e. galloprovincialis, L. f. kikuchii, C. gigas and Balanus spp in that order; sessile animals weighing 9,110 tons are living annually in average in the sea banks extending over a distance of 192 km; amount of COD purification based on the annual average deposition quantity is calculated 19 tons as a daily average, which corresponds to 23% of the total COD quantity flowing in from the Tokyo urban area; and on the other hand, COD, N and P produced by sessile animals become new loads to environment over the life of these sessile animals. 26 refs., 6 figs., 2 tabs.

  13. Concepts and tools for exploiting sessile bio-filters as early warning elements: introductory applications for marine ecosystem preservation

    Directory of Open Access Journals (Sweden)

    M Scalici

    2015-11-01

    Full Text Available Current evidence suggests that integrating diverse warning systems at different biological levels may not only increase the probability of detecting threats but also mitigate their impact. Here, we propose the use of both molecular and morphological descriptors at different biological levels in sessile bivalves (a suitable biological model in monitoring programs to collect information on the ecosystem health of coastal marine habitats. In this context, studies may be implemented on biomarkers to exploit some population features, with the aim to propose an actual monitoring program that predictively would provide possible scenarios on the species fitness and ecosystem changes. Thus, the use of quality biotic elements may provide an objective environmental monitoring method and facilitate the development of sanitary, economic, and social strategies related to sustainable exploitation.

  14. Effects of Substrate Heating and Wettability on Evaporation Dynamics and Deposition Patterns for a Sessile Water Droplet Containing Colloidal Particles

    CERN Document Server

    Patil, Nagesh D; Bhardwaj, Rajneesh; Sharma, Atul

    2016-01-01

    Effects of substrate temperature, substrate wettability and particles concentration are experimentally investigated for evaporation of a sessile water droplet containing colloidal particles. Time-varying droplet shapes and temperature of the liquid-gas interface are measured using high-speed visualization and infrared thermography, respectively. The motion of the particles inside the evaporating droplet is qualitatively visualized by an optical microscope and profile of final particle deposit is measured by an optical profilometer. On a non-heated hydrophilic substrate, a ring-like deposit forms after the evaporation, as reported extensively in the literature; while on a heated hydrophilic substrate, a thinner ring with an inner deposit is reported in the present work. The latter is attributed to Marangoni convection and recorded motion of the particles as well as measured temperature gradient across the liquid-gas interface confirms this hypothesis. The thinning of the ring scales with the substrate temperat...

  15. Approximate analytical descriptions of the stationary single-vortex Marangoni convection inside an evaporating sessile droplet of capillary size

    CERN Document Server

    Barash, L Yu

    2013-01-01

    Three versions of an approximate analytical description of the stationary single vortex Marangoni convection in an axially symmetrical sessile drop of capillary size are studied for arbitrary contact angle and compared with the results of numerical simulations. The first approach is heuristic extension of the well-known lubrication approximation. Two other descriptions are developed here and named n\\tau- and rz-description. They are free from most of restrictive assumptions of the lubrication approach. For droplets with large contact angles they result in better accuracy compared to the heuristic extension of the lubrication approach, which still gives reasonable results within the accuracy 10-30 per cent. For droplets with small contact angles all three analytical descriptions well agree with the numerical data.

  16. 静滴法测表面张力中各参数的确定%Parameters in Surface Tension Measured by Sessile Drop Method

    Institute of Scientific and Technical Information of China (English)

    陈安涛; 张胜全; 王胜

    2013-01-01

    Combining digital photography with AutoCAD and Proe,the parameters in surface tension measured by sessile drop method was determined.The results show that the method for calculating the surface tension has high accuracy,which can provide computer aid for adopting sessile drop method measuring high temperature metal surface tension.%应用致码撮影与电脑软件AutoCAD和Proe相结合的方法,确定静滴法计算表面张力公式中的各参数值.结果表明,该方法计算的表面张力具有较高精度,为静滴法测量高温金属表面张力提供电脑辅助.

  17. Soil pro pert ies in sessile oak fore sts (Quercetum montanum typicum Čer. et Jov. 1953 in the are a of Fruška Gora

    Directory of Open Access Journals (Sweden)

    Knežević Milan

    2011-01-01

    Full Text Available The soils formed on sandstones in sessile oak forests (Quercetum montanum typicum Čer. et Jov. 1953 were researched in the area of Fruška Gora. On permanent sample plots established in management units “Čortanovačka Forest-Hopovo-Velika Remeta“ and “Beočin-Manastir-Katanske Livade-Osovlje“, in the are of NP “Fruška Gora“, aiming at the monitoring of the effect of light regime on the development of sessile oak progeny in the given environmental conditions, based on the morphogenetic characteristics of the soil and analytic values of the soil properties, and based on the soil classification by Škorić et al. (1985, the following two soil types were defined: acid brown soil (dystric cambisol, and illimerised soil (luvisol. Acid brown soil belongs to the form of medium deep soils, and illimerised soil is classified as deep soil.

  18. Genomic sequence and activity of KS10, a transposable phage of the Burkholderia cepacia complex

    Directory of Open Access Journals (Sweden)

    Shrivastava Savita

    2008-12-01

    Full Text Available Abstract Background The Burkholderia cepacia complex (BCC is a versatile group of Gram negative organisms that can be found throughout the environment in sources such as soil, water, and plants. While BCC bacteria can be involved in beneficial interactions with plants, they are also considered opportunistic pathogens, specifically in patients with cystic fibrosis and chronic granulomatous disease. These organisms also exhibit resistance to many antibiotics, making conventional treatment often unsuccessful. KS10 was isolated as a prophage of B. cenocepacia K56-2, a clinically relevant strain of the BCC. Our objective was to sequence the genome of this phage and also determine if this prophage encoded any virulence determinants. Results KS10 is a 37,635 base pairs (bp transposable phage of the opportunistic pathogen Burkholderia cenocepacia. Genome sequence analysis and annotation of this phage reveals that KS10 shows the closest sequence homology to Mu and BcepMu. KS10 was found to be a prophage in three different strains of B. cenocepacia, including strains K56-2, J2315, and C5424, and seven tested clinical isolates of B. cenocepacia, but no other BCC species. A survey of 23 strains and 20 clinical isolates of the BCC revealed that KS10 is able to form plaques on lawns of B. ambifaria LMG 19467, B. cenocepacia PC184, and B. stabilis LMG 18870. Conclusion KS10 is a novel phage with a genomic organization that differs from most phages in that its capsid genes are not aligned into one module but rather separated by approximately 11 kb, giving evidence of one or more prior genetic rearrangements. There were no potential virulence factors identified in KS10, though many hypothetical proteins were identified with no known function.

  19. Effects of fertilization on the vascular ground vegetation of European beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Lieb.) stands

    OpenAIRE

    Misson, Laurent; Gaëtan Du Bus De Warnaffe,; Jonard, Mathieu

    2001-01-01

    International audience; The objective of this study was to assess the effects of base cation (Ca, Mg, K) and phosphorous (P) fertilization on the vascular ground vegetation in mature European beech and sessile oak stands located on acid brown soils. Two types of treatment were applied next to control plots (dolomite lime, dolomite lime + natural phosphate + potassium sulphate). Specific richness, total cover (% ), equitability coefficient as well as the Ecological Group of the ground vegetati...

  20. The use of coal fly ash in concrete for marine artificial reefs in the southeastern Mediterranean: compressive strength, sessile biota, and chemical composition

    Energy Technology Data Exchange (ETDEWEB)

    Kress, N.; Tom, M.; Spanier, E. [National Institute of Oceanography, Haifa (Israel)

    2002-07-01

    To examine the possible use of coal fly ash (CFA) in concrete for artificial reefs, blocks containing 0%, 40%, 60% and 80% CFA as a substitute for sand were deployed in the Mediterranean at 18.5-m depth off the coast of Israel during a period of 33 months. Changes in compressive strength, composition, and coverage of sessile biota species, as well as in trace element concentration of the block surface and in sessile biota from four taxonomic groups, were determined as a function of time at sea and block type. Compressive strength clearly increased with time in all types to values well above the minimal strength considered necessary for stability of the blocks at sea. Moreover, the 40% and 60% CFA blocks were 1.5 times stronger than the 0% and 80% ones. Main sessile taxa recorded were filamentous green algae, bryozoa, barnacles, serpulid polychaeta, hydrozoa, and bivalves. Number of species settled and biotic coverage varied among block side and seasonally, but did not differ significantly between block types. The initial heavy metal composition (Hg, Cd, Pb, Cu, Zn, Cr, Mn, Fe, Al) of the block material was directly proportional to the CFA percentage. At the end of the study, Pb had decreased in all types, Cd in the 60% CFA block, and Fe and Al in the 40% and 60% blocks, while Mn had increased in the blocks with 0% and 80% CFA. After 21 months at sea, the only detectable change was a decrease in Pb concentration in all types, indicating that changes may be due to long-term processes. Trace metal levels (Hg, Cd, Zn, Mn, Cu, Fe, and Al) were measured in the sessile biota (hydrozoa, polychaeta, and bivalvia). In most cases, no dependence was found between metal levels and time at sea or CFA content of the blocks. In the hydroid, metal concentration even decreased over time.

  1. Contact angle of copper-bearing shales using the sessile drop and captive bubble methods in the presence of selected frothers

    OpenAIRE

    Danuta Szyszka; Wojciech Szczepański

    2016-01-01

    This paper describes the measurement of contact angle of copper-bearing shales. The values of advancing and receding contact angles were determined using the sessile drop and captive bubble methods in the presence of aqueous solutions of acetal and pyridine and distilled water. Both methods demonstrated that the tested substances had only minor impact on the surface hydrophobicity of copper-bearing shales expressed by contact angle. The tests carried out proved that neither acetal nor pyridin...

  2. Sessile Organisms on PVC Panels in the Waters around a Coral Reef of Ishigaki Island, Yaeyama Islands, Japan, Immediately after the Catastrophic Coral Bleaching in 1998

    OpenAIRE

    Nandakumar, Kanavillil; Takada, Yoshitake; Shibuno, Takuro

    1999-01-01

    Sessile organisms on PVC panels suspended inside and outside coral reef at Ishigaki Island, Yaeyama Islands, Japan, was monitored for 20 days just after the wide-spread incident of coral bleaching in September, 1998. The settlement of a total of 16 species of algae and invertebrates was recorded. Generally, Enteromorpha sp. (Chlorophyceae) dominated the panels. The percentage area cover, number of species, biomass and algal growth were significantly greater in waters outside the reef.

  3. The influence of gravity on the distribution of the deposit formed onto a substrate by sessile, hanging, and sandwiched hanging drop evaporation.

    Science.gov (United States)

    Sandu, Ion; Fleaca, Claudiu Teodor

    2011-06-15

    The focus of the present article is the study of the influence of gravity on the particle deposition profiles on a solid substrate during the evaporation of sessile, hanging and sandwiched hanging drops of colloidal particle suspensions. For concentrations of nanoparticles in the colloidal solutions in the range 0.0001-1 wt.%, highly diluted suspensions will preferentially form rings while concentrated suspensions will preferentially form spots in both sessile and hanging drop evaporation. For intermediary concentrations, the particle deposition profiles will depend on the nanoparticle aggregation dynamics in the suspension during the evaporation process, gravity and on the detailed evaporation geometry. The evaporation of a drop of toluene/carbon nanoparticle suspension hanging from a pendant water drop will leave on the substrate a circular spot with no visible external ring. By contrast, a clear external ring is formed on the substrate by the sessile evaporation of a similar drop of suspension sandwiched between a water drop and the substrate. From the application viewpoint, these processes can be used to create preferential electrical conductive carbon networks and contacts for arrays of self-assembled nanostructures fabricated on solid substrates as well as on flexible polymeric substrates.

  4. Promoter complexity and tissue-specific expression of stress response components in Mytilus galloprovincialis, a sessile marine invertebrate species.

    Directory of Open Access Journals (Sweden)

    Chrysa Pantzartzi

    Full Text Available The mechanisms of stress tolerance in sessile animals, such as molluscs, can offer fundamental insights into the adaptation of organisms for a wide range of environmental challenges. One of the best studied processes at the molecular level relevant to stress tolerance is the heat shock response in the genus Mytilus. We focus on the upstream region of Mytilus galloprovincialis Hsp90 genes and their structural and functional associations, using comparative genomics and network inference. Sequence comparison of this region provides novel evidence that the transcription of Hsp90 is regulated via a dense region of transcription factor binding sites, also containing a region with similarity to the Gamera family of LINE-like repetitive sequences and a genus-specific element of unknown function. Furthermore, we infer a set of gene networks from tissue-specific expression data, and specifically extract an Hsp class-associated network, with 174 genes and 2,226 associations, exhibiting a complex pattern of expression across multiple tissue types. Our results (i suggest that the heat shock response in the genus Mytilus is regulated by an unexpectedly complex upstream region, and (ii provide new directions for the use of the heat shock process as a biosensor system for environmental monitoring.

  5. On the motion of a sessile drop on an incline: Effect of non-monotonic thermocapillary stresses

    Science.gov (United States)

    Mamalis, Dimitrios; Koutsos, Vasileios; Sefiane, Khellil

    2016-12-01

    We studied the short-time contact-line dynamics of a self-rewetting sessile droplet sliding "freely" on a silicone oil layer, on an inclined, uniformly heated substrate under non-isothermal conditions (liquid-solid). The effect of thermocapillarity and the contribution of surface tension gradients (Marangoni effect) to the droplet motion was investigated. The temperature of the substrate in conjunction with the non-monotonic surface tension/temperature dependence of the deformed self-rewetting droplet was found to significantly affect the early-stage inertial-capillary spreading regime. Infrared (IR) thermography images were also acquired to investigate the generation of thermal patterns at the liquid surface due to the strong surface-tension gradients. Our results demonstrate that the presence of strong surface tension driven flows at the liquid interface combined with droplet deformation (contact-angle hysteresis) gives rise to complex droplet dynamics. The interplay between thermocapillary stresses and body forces results in enhanced spreading rates, temporal non-monotonic dependence of the contact-line speed, as well as the droplet motion overcoming gravity in some instances.

  6. Surface tension and its temperature coefficient of molten tin determined with the sessile drop method at different oxygen partial pressures.

    Science.gov (United States)

    Yuan, Zhang Fu; Mukai, Kusuhiro; Takagi, Katsuhiko; Ohtaka, Masahiko; Huang, Wen Lai; Liu, Qiu Sheng

    2002-10-15

    The surface tension of molten tin has been determined by the sessile drop method at temperatures ranging from 523 to 1033 K and in the oxygen partial pressure (P(O(2))) range from 2.85 x 10(-19) to 8.56 x 10(-6) MPa, and its dependence on temperature and oxygen partial pressure has been analyzed. At P(O(2))=2.85 x 10(-19) and 1.06 x 10(-15) MPa, the surface tension decreases linearly with the increase of temperature and its temperature coefficients are -0.151 and -0.094 mN m(-1) K(-1), respectively. However, at high P(O(2)) (3.17 x 10(-10), 8.56 x 10(-6) MPa), the surface tension increases with the temperature near the melting point (505 K) and decreases above 723 K. The surface tension decrease with increasing P(O(2)) is much larger near the melting point than at temperatures above 823 K. The contact angle between the molten tin and the alumina substrate is 158-173 degrees, and the wettability is poor.

  7. Determination of surface heterogeneity of D-mannitol by sessile drop contact angle and finite concentration inverse gas chromatography.

    Science.gov (United States)

    Ho, Raimundo; Hinder, Steven J; Watts, John F; Dilworth, Sarah E; Williams, Daryl R; Heng, Jerry Y Y

    2010-03-15

    The sensitivity of two techniques in tracking changes in surface energetics was investigated for a crystalline excipient, D-mannitol. Macroscopic crystals of D-mannitol were grown from saturated water solution by slow cooling, and sessile drop contact angle was employed to measure the anisotropic surface energy. The facet-specific surface energy was consistent with localised hydroxyl group concentrations determined by X-ray photoelectron spectroscopy (XPS), and was also in excellent agreement with the surface energy distribution of the powder form of mannitol measured via a new methodology using inverse gas chromatography (IGC) at finite concentrations. The gamma(SV)(d) was found to vary between 39.5 mJ/m(2) and 44.1 mJ/m(2) for contact angle and between 40 mJ/m(2) and 49 mJ/m(2) for IGC measurements. We report here, a high level of surface heterogeneity on the native mannitol crystal surfaces. When the surfaces of both D-mannitol samples (powder and large single crystals) were modified by dichlorodimethylsilane to induce surface hydrophobicity, both IGC and contact angle revealed a homogeneous surface due to functionalisation of mannitol crystal surface with methyl groups resulting in gamma(SV)(d) of approximately 34 mJ/m(2). It was shown that both IGC and contact angle techniques are able to detect surface chemical variations and detailed surface energetic distribution.

  8. Effect of Surface Roughness on Contact Angle Measurement of Nanofluid on Surface of Stainless Steel 304 by Sessile Drop Method

    Science.gov (United States)

    Prajitno, D. H.; Maulana, A.; Syarif, D. G.

    2016-08-01

    Contact angles play an important role in the mass and heat transfer. Stainless steel 304 has been used for nuclear power plan structure material until now. An experiment to measure contact angle of demineralized aqua and nanofluid containing nano particle of zirconia on metal surface of stainless steel 304 with sessile drop method was conducted. The measurement to measure the static contact angle and drop of nano fluid containing nano particle zirconia on stainless steel with different surface roughness was carried out. It was observed that stainless steel 304 was good hydrophylic properties with decreasing surface roughness of stainless steel during drop of aqua demineralized and nano fluid respectively. As a result the contact angle of demineralized aqua is decreased from 97.39 to 78.42 and contact angle of nano fluid from 94.3 to 67.50, respectively with decreasing surface roughness of stainless stee 304. Wettability of nanofluid on surface stainless steel 304 is better than aqua demineralized.

  9. Political systems affect mobile and sessile species diversity--a legacy from the post-WWII period.

    Science.gov (United States)

    Cousins, Sara A O; Kaligarič, Mitja; Bakan, Branko; Lindborg, Regina

    2014-01-01

    Political ideologies, policies and economy affect land use which in turn may affect biodiversity patterns and future conservation targets. However, few studies have investigated biodiversity in landscapes with similar physical properties but governed by different political systems. Here we investigate land use and biodiversity patterns, and number and composition of birds and plants, in the borderland of Austria, Slovenia and Hungary. It is a physically uniform landscape but managed differently during the last 70 years as a consequence of the political "map" of Europe after World War I and II. We used a historical map from 1910 and satellite data to delineate land use within three 10-kilometre transects starting from the point where the three countries meet. There was a clear difference between countries detectable in current biodiversity patterns, which relates to land use history. Mobile species richness was associated with current land use whereas diversity of sessile species was more associated with past land use. Heterogeneous landscapes were positively and forest cover was negatively correlated to bird species richness. Our results provide insights into why landscape history is important to understand present and future biodiversity patterns, which is crucial for designing policies and conservation strategies across the world.

  10. Political systems affect mobile and sessile species diversity--a legacy from the post-WWII period.

    Directory of Open Access Journals (Sweden)

    Sara A O Cousins

    Full Text Available Political ideologies, policies and economy affect land use which in turn may affect biodiversity patterns and future conservation targets. However, few studies have investigated biodiversity in landscapes with similar physical properties but governed by different political systems. Here we investigate land use and biodiversity patterns, and number and composition of birds and plants, in the borderland of Austria, Slovenia and Hungary. It is a physically uniform landscape but managed differently during the last 70 years as a consequence of the political "map" of Europe after World War I and II. We used a historical map from 1910 and satellite data to delineate land use within three 10-kilometre transects starting from the point where the three countries meet. There was a clear difference between countries detectable in current biodiversity patterns, which relates to land use history. Mobile species richness was associated with current land use whereas diversity of sessile species was more associated with past land use. Heterogeneous landscapes were positively and forest cover was negatively correlated to bird species richness. Our results provide insights into why landscape history is important to understand present and future biodiversity patterns, which is crucial for designing policies and conservation strategies across the world.

  11. Stick-Jump (SJ) Evaporation of Strongly Pinned Nanoliter Volume Sessile Water Droplets on Quick Drying, Micropatterned Surfaces.

    Science.gov (United States)

    Debuisson, Damien; Merlen, Alain; Senez, Vincent; Arscott, Steve

    2016-03-22

    We present an experimental study of stick-jump (SJ) evaporation of strongly pinned nanoliter volume sessile water droplets drying on micropatterned surfaces. The evaporation is studied on surfaces composed of photolithographically micropatterned negative photoresist (SU-8). The micropatterning of the SU-8 enables circular, smooth, trough-like features to be formed which causes a very strong pinning of the three phase (liquid-vapor-solid) contact line of an evaporating droplet. This is ideal for studying SJ evaporation as it contains sequential constant contact radius (CCR) evaporation phases during droplet evaporation. The evaporation was studied in nonconfined conditions, and forced convection was not used. Micropatterned concentric circles were defined having an initial radius of 1000 μm decreasing by a spacing ranging from 500 to 50 μm. The droplet evaporates, successively pinning and depinning from circle to circle. For each pinning radius, the droplet contact angle and volume are observed to decrease quasi-linearly with time. The experimental average evaporation rates were found to decrease with decreasing pining radii. In contrast, the experimental average evaporation flux is found to increase with decreasing droplet radii. The data also demonstrate the influence of the initial contact angle on evaporation rate and flux. The data indicate that the total evaporation time of a droplet depends on the specific micropattern spacing and that the total evaporation time on micropatterned surfaces is always less than on flat, homogeneous surfaces. Although the surface patterning is observed to have little effect on the average droplet flux-indicating that the underlying evaporation physics is not significantly changed by the patterning-the total evaporation time is considerably modified by patterning, up to a factor or almost 2 compared to evaporation on a flat, homogeneous surface. The closely spaced concentric circle pinning maintains a large droplet radius and

  12. Carbon pools and temporal dynamics along a rotation period in sessile oak dominated high forest and coppice with standards stands

    Science.gov (United States)

    Bruckman, V. J.; Yan, S.; Hochbichler, E.; Glatzel, G.

    2012-04-01

    Carbon pools in two Quercus petraea (sessile oak) dominated chronosequences under different forest management (high forest and coppice with standards) were investigated. The objective was to study temporal carbon dynamics, in particular carbon sequestration in the soil and woody biomass production, in common forest management systems in eastern Austria along with stand development. The chronosequence approach was used to substitute time-for-space to enable coverage of a full rotation period in each system. Carbon content was determined in the following compartments: aboveground biomass, litter, soil to a depth of 50 cm, living root biomass and decomposing residues in the mineral soil horizons. Biomass carbon pools, except fine roots and residues, were estimated using species-specific allometric functions. Total carbon pools were on average 143 Mg ha-1 in the high forest stand (HF) and 213 Mg ha-1 in the coppice with standards stand (CS). The mean share of the total organic carbon pool (TOC) which is soil organic carbon (SOC) differs only marginally between HF (43.4%) and CS (42.1%), indicating the dominance of site factors, particularly climate, in controlling this ratio. While there was no significant change in O-layer and SOC stores over stand development, we found clear relationships between living biomass (aboveground and belowground) pools and C:N ratio in topsoil horizons with stand age. SOC pools seem to be very stable and an impact of silvicultural interventions was not detected with the applied method. Rapid decomposition and mineralization of litter, indicated by low O-horizon pools with wide C:N ratios of residual woody debris at the end of the vegetation period, suggests high rates of turnover in this fraction. CS, in contrast to HF benefits from rapid resprouting after coppicing and hence seems less vulnerable to conditions of low rainfall and drying topsoil. Keywords: carbon dynamics; soil carbon; chronosequence; Quercus petraea; coppice; high forest

  13. Impacts of residual insecticide barriers on perimeter-invading ants, with particular reference to the odorous house ant, Tapinoma sessile.

    Science.gov (United States)

    Scharf, Michael E; Ratliff, Catina R; Bennett, Gary W

    2004-04-01

    Three liquid insecticide formulations were evaluated as barrier treatments against perimeter-invading ants at a multifamily housing complex in West Lafayette, IN. Several ant species were present at the study site, including (in order of abundance) pavement ant, Tetramorium caespitum (L.); honey ant, Prenolepis imparis (Say); odorous house ant, Tapinoma sessile (Say); thief ant, Solenopsis molesta (Say); acrobat ant, Crematogaster ashmeadi (Mayr); crazy ant, Paratrechina longicornis (Latrielle), field ants, Formica spp.; and carpenter ant Camponotus pennsylvanicus (DeGeer). Studies began in May 2001 and concluded 8 wk later in July. Individual replicate treatments were placed 0.61 in (2 feet) up and 0.92 m (3 feet) out from the ends of 46.1 by 10.1-m (151 by 33-foot) apartment buildings. Ant sampling was performed with 10 placements of moist cat food for 1 h within treatment zones, followed by capture and removal of recruited ants for later counting. All treatments led to substantial reductions in ant numbers relative to untreated controls. The most effective treatment was fipronil, where 2% of before-treatment ant numbers were present at 8 wk after treatment. Both imidacloprid and cyfluthrin barrier treatments had efficacy comparative with fipronil, but to 4 and 2 wk, respectively. Odorous house ants were not sampled before treatment. Comparisons of ant species composition between treatments and controls revealed an increase in odorous house ant frequencies at 1-8 wk after treatment in treated locations only. These results demonstrate efficacy for both nonrepellent and repellent liquid insecticides as perimeter treatments for pest ants. In addition, our findings with odorous house ant highlight an apparent invasive-like characteristic of this species that may contribute to its dramatic increase in structural infestation rates in many areas of the United States.

  14. Noncoalescence of sessile drops from different but miscible liquids: hydrodynamic analysis of the twin drop contour as a self-stabilizing traveling wave.

    Science.gov (United States)

    Karpitschka, Stefan; Riegler, Hans

    2012-08-10

    Capillarity always favors drop fusion. Nevertheless, sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate noncoalescence is observed. Two separate drop bodies, connected by a thin liquid neck, move over the substrate. Supported by new experimental data, a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave, i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings.

  15. Non-coalescence of sessile drops from different but miscible liquids: Hydrodynamic analysis of the twin drop contour as self stabilizing, traveling wave

    CERN Document Server

    Karpitschka, Stefan

    2015-01-01

    Capillarity always favors drop fusion. Nevertheless sessile drops from different but completely miscible liquids often do not fuse instantaneously upon contact. Rather, intermediate non-coalescence is observed. Two separate drop bodies, connected by a thin liquid neck move over the substrate. Supported by new experimental data a thin film hydrodynamic analysis of this state is presented. Presumably advective and diffusive volume fluxes in the neck region establish a localized and temporarily stable surface tension gradient. This induces a local surface (Marangoni) flow that stabilizes a traveling wave i.e., the observed moving twin drop configuration. The theoretical predictions are in excellent agreement with the experimental findings.

  16. Contact angle of copper-bearing shales using the sessile drop and captive bubble methods in the presence of selected frothers

    Directory of Open Access Journals (Sweden)

    Danuta Szyszka

    2016-01-01

    Full Text Available This paper describes the measurement of contact angle of copper-bearing shales. The values of advancing and receding contact angles were determined using the sessile drop and captive bubble methods in the presence of aqueous solutions of acetal and pyridine and distilled water. Both methods demonstrated that the tested substances had only minor impact on the surface hydrophobicity of copper-bearing shales expressed by contact angle. The tests carried out proved that neither acetal nor pyridine may be classified to the collecting reagents because none of them improves hydrophobicity of copper-bearing shales. These reagents are only flotation frothers.

  17. Age-related variation in carbon allocation at tree and stand scales in beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl.) using a chronosequence approach.

    Science.gov (United States)

    Genet, H; Bréda, N; Dufrêne, E

    2010-02-01

    Two types of physiological mechanisms can contribute to growth decline with age: (i) the mechanisms leading to the reduction of carbon assimilation (input) and (ii) those leading to modification of the resource economy. Surprisingly, the processes relating to carbon allocation have been little investigated as compared to research on the processes governing carbon assimilation. The objective of this paper was thus to test the hypothesis that growth decrease related to age is accompanied by changes in carbon allocation to the benefit of storage and reproductive functions in two contrasting broad-leaved species: beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl.). Age-related changes in carbon allocation were studied using a chronosequence approach. Chronosequences, each consisting of several even-aged stands ranging from 14 to 175 years old for beech and from 30 to 134 years old for sessile oak, were divided into five or six age classes. In this study, carbon allocations to growth, storage and reproduction were defined as the relative amount of carbon invested in biomass increment, carbohydrate increment and seed production, respectively. Tree-ring width and allometric relationships were used to assess biomass increment at the tree and stand scales. Below-ground biomass was assessed using a specific allometric relationship between root:shoot ratio and age, established from the literature review. Seasonal variations of carbohydrate concentrations were used to assess carbon allocation to storage. Reproduction effort was quantified for beech stands by collecting seed and cupule production. Age-related flagging of biomass productivity was assessed at the tree and stand scales, and carbohydrate quantities in trees increased with age for both species. Seed and cupule production increased with stand age in beech from 56 gC m(-)(2) year(-1) at 30 years old to 129 gC m(-2) year(-1) at 138 years old. In beech, carbon allocation to storage and

  18. Frequency of coexistent carcinoma in sessile serrated adenoma/polyps and traditional serrated adenomas removed by endoscopic resection

    Science.gov (United States)

    Saiki, Hirotsugu; Nishida, Tsutomu; Yamamoto, Masashi; Hayashi, Shiro; Shimakoshi, Hiromi; Shimoda, Akiyoshi; Amano, Takahiro; Sakamoto, Aisa; Otake, Yuriko; Sugimoto, Aya; Takahashi, Kei; Mukai, Kaori; Matsubara, Tokuhiro; Nakajima, Sachiko; Fukui, Koji; Inada, Masami; Yamamoto, Katsumi; Tokuda, Ryozo; Adachi, Shiro

    2016-01-01

    Background and study aims: Sessile serrated adenoma/polyps (SSA/Ps) have a different potential than traditional adenomatous polyps for developing into malignant colorectal cancer. However, little is known about the coexistent cancer rate. Here, we evaluate the frequency of carcinoma in serrated polyps removed by endoscopic resection (ER). Patients and methods: This was a retrospective single-center cohort study of consecutive patients with colorectal polyps who underwent ER from March 2003 to October 2014. We determined the frequency of serrated polyps among all resected colorectal polyps and analyzed the clinicopathological findings as well as the frequency and characteristics of coexistent carcinoma in the serrated polyps resected by ER based on pathology reports. Results: A total of 21,048 polyps from 15,326 patients were identified, including 15,984 traditional adenomatous polyps (75.9 %), 621 SSA/Ps (3.0 %), 136 traditional serrated adenomas (TSAs) (0.6 %), 1,121 hyperplastic polyps (5.3 %), and 3,186 polyps of other types (15.1 %). The clinical and endoscopic findings of SSA/Ps revealed a male predominance (68.6 %), with 61.7 % of the polyps located in the proximal colon. Males accounted for 77.2 % of all patients with TSAs, and 77.2 % of these polyps were located in the distal colon. The mean sizes of the SSA/Ps and TSAs were 8.8 and 10.7 mm, respectively. Among the SSA/Ps, 8 (1.3 %) cases had coexistent carcinoma, and 1 (0.7 %) patient with TSA showed coexistent carcinoma. In the patients with SSA/Ps, female sex and a tumor size ≥ 10 mm were predictive factors for coexistent carcinoma. Conclusions: The frequency of SSA/Ps with carcinoma was lower than that for traditional adenoma. Female sex and tumor size ≥ 10 mm were significant predictive factors for coexistent carcinoma. PMID:27092327

  19. 粗糙固体平面上液滴的接触角滞后的简单流体静力学模型%Simple Hydrostatic Model of Contact Angle Hysteresis of a Sessile Drop on Rough Surface

    Institute of Scientific and Technical Information of China (English)

    毛在砂; 杨超; 陈家镛

    2005-01-01

    The phenomenon of hysteresis of contact angle is an important topic subject to a long time of argument.A simple hydrostatic model of sessile drops under the gravity in combination with an ideal surface roughness model is used to interpret the process of drop volume increase or decrease of a planar sessile drop and to shed light on the contact angle hysteresis and its relationship with the solid surface roughness. With this model, the advancing and receding contact angles are conceptually explained in terms of equilibrium contact angle and surface roughness only,without invoking the thermodynamic multiplicity. The model is found to be qualitatively consistent to experimental observations on contact angle hysteresis and it suggests a possible way to approach the hysteresis of three-dimensional sessile drops.

  20. Coalescence of sessile drops

    CERN Document Server

    Nikolayev, Vadim; Pomeau, Yves; Andrieu, Claire

    2016-01-01

    We present an experimental and theoretical description of the kinetics of coalescence of two water drops on a plane solid surface. The case of partial wetting is considered. The drops are in an atmosphere of nitrogen saturated with water where they grow by condensation and eventually touch each other and coalesce. A new convex composite drop is rapidly formed that then exponentially and slowly relaxes to an equilibrium hemispherical cap. The characteristic relaxation time is proportional to the drop radius R * at final equilibrium. This relaxation time appears to be nearly 10 7 times larger than the bulk capillary relaxation time t b = R * $\\eta$/$\\sigma$, where $\\sigma$ is the gas--liquid surface tension and $\\eta$ is the liquid shear viscosity. In order to explain this extremely large relaxation time, we consider a model that involves an Arrhenius kinetic factor resulting from a liquid--vapour phase change in the vicinity of the contact line. The model results in a large relaxation time of order t b exp(L/R...

  1. THE EFFECT OF THE HEAT TREATMENT OF SESSILE OAK WOOD (Quercus petrea L. FROM YOUNG TREES ON THE PROPERTIES OF PANELS WITH TRANSVERSAL GRAIN

    Directory of Open Access Journals (Sweden)

    Noemi MARTON

    2012-06-01

    Full Text Available Sessile oak from young trees represents asecondary resource with potential for superiorapplications in furniture panels providing theirdimensional stability to variations of relative airhumidity is reduced. A possibility to improve thisproperty was examined in this paper, by thermaltreatment of the raw material before manufacturingdecorative furniture panels with transversal grain.Panels with crosscut grain were manufactured fromboth heat treated and untreated wood and theirproperties were compared: dimensional changewith climate, the moisture content at equilibrium, theabsolute density, colour and their MOE and MOR.The results have shown that the thermaltreatment at 130ºC for 2h of sessile oak from youngtrees has improved the dimensional stability and theequilibrium moisture content of the panels and didnot impair their mechanical strength. The colour gotslightly darker and density had an almost negligibledecrease by the heat treatment. Attractive bydesign, because of their grain orientation, but in thisway subjected to axial stresses perpendicular to thegrain, the panels could be used in furnitureapplications where the bending stresses are notcritical.

  2. Morphology of four new solitary sessile peritrich ciliates from the Yellow Sea, China, with description of an unidentified species of Paravorticella (Ciliophora, Peritrichia).

    Science.gov (United States)

    Sun, Ping; Al-Farraj, Saleh A; Warren, Alan; Ma, Honggang

    2017-02-01

    Sessile peritrichs are a large assemblage of ciliates that have a wide distribution in soil, freshwater and marine waters. Here, we document four new and one unidentified species of solitary sessile peritrichs from aquaculture ponds and coastal waters of the northern Yellow Sea, China. Based on their living morphology, infraciliature and silverline system, four of the five forms were identified as new members belonging to one of three genera, Vorticella, Pseudovorticella and Scyphidia, representing two families, Vorticellidae and Scyphidiidae. The other isolate was found to be an unidentified species of the poorly known genus Paravorticella. Vorticella chiangi sp. nov. is characterized by its inverted bell-shaped zooid, short row 3 in infundibular polykinety 3 and marine habitat. Pseudovorticella liangae sp. nov. posseses a thin, broad peristomial lip and a granular pellicle. Pseudovorticella haiboensis sp. nov. is differentiated from its congeners by having an elongated zooid that is covered by a layer of thin pellicular vesicles, and two rows of kineties in infundibular polykinety 3. Scyphidia perezuzae sp. nov. and Paravorticella sp. are stalkless ectoparasites or ectocommensals of aquatic animals. The former has a short, plump body, a narrow peristomial lip and a conspicuous, flattened, disc-shaped scopula for adhesion. Paravorticella sp. has an extremely elongated clavate body, a broad peristomial lip, and a narrow scopula.

  3. Trimeric autotransporter adhesins in members of the Burkholderia cepacia complex: a multifunctional family of proteins implicated in virulence

    Directory of Open Access Journals (Sweden)

    Arsénio Mendes Fialho

    2011-12-01

    Full Text Available Trimeric autotransporter adhesins (TAAs are multimeric surface proteins, involved in various biological traits of pathogenic Gram-negative bacteria including adherence, biofilm formation, invasion, survival within eukaryotic cells, serum resistance and cytotoxicity. TAAs have a modular architecture composed by a conserved membrane-anchored C-terminal domain and a variable number of stalk and head domains. In this study, a bioinformatic approach has been used to analyze the distribution and architecture of TAAs among Burkholderia cepacia complex (Bcc genomes. Fifteen genomes were probed revealing a total of 74 encoding sequences. Compared with other bacterial species, the Bcc genomes contain a disproportionately large number of TAAs (two genes to up to 8 genes, such as in B.cenocepacia. Phylogenetic analysis showed that the TAAs grouped into at least eight distinct clusters. TAAs with serine-rich repeats are clearly well separated from others, thereby representing a different evolutionary lineage. Comparative gene mapping across Bcc genomes reveals that TAA genes are inserted within conserved synteny blocks. We further focused our analysis on the epidemic strain B. cenocepacia J2315 in which 7 TAAs were annotated. Among these, 3 TAA-encoding genes (BCAM019, BCAM0223 and BCAM0224 are organized into a cluster and are candidates for multifunctional virulence factors. Here we review the current insights into the functional role of BCAM0224 as a model locus.

  4. Influence of viscosity on acoustic streaming in sessile droplets: an experimental and a numerical study with a Streaming Source Spatial Filtering (SSSF) method

    CERN Document Server

    Riaud, Antoine; Matar, Oliver Bou; Thomas, Jean-Louis; Brunet, Philippe

    2016-01-01

    When an acoustic wave travels in a lossy medium such as a liquid, it progressively transfers its pseudo-momentum to the fluid, which results in a steady acoustic streaming. Remarkably, the phenomenon involves a balance between sound attenuation and shear, such that viscosity vanishes in the final expression of the velocity field. For this reason, the effect of viscosity has long been ignored in acoustic streaming experiments. Here, we show experimentally that the viscosity plays a major role in cavities such as the streaming induced by surface acoustic waves in sessile droplets. We develop a numerical model based on the spatial filtering of the streaming source term to compute the induced flow motion with dramatically reduced computational requirements. We evidence that acoustic fields in droplets are a superposition of a chaotic field and a few powerful caustics. It appears that the caustics drive the flow, which allows a qualitative prediction of the flow structure. Finally, we reduce the problem to two dim...

  5. Evaporative deposition patterns of bacteria from a sessile drop: effect of changes in surface wettability due to exposure to a laboratory atmosphere.

    Science.gov (United States)

    Baughman, Kyle F; Maier, Raina M; Norris, Theresa A; Beam, Brooke M; Mudalige, Anoma; Pemberton, Jeanne E; Curry, Joan E

    2010-05-18

    Evaporative deposition from a sessile drop is a simple and appealing way to deposit materials on a surface. In this work, we deposit living, motile colloidal particles (bacteria) on mica from drops of aqueous solution. We show for the first time that it is possible to produce a continuous variation in the deposition pattern from ring deposits to cellular pattern deposits by incremental changes in surface wettability which we achieve by timed exposure of the mica surface to the atmosphere. We show that it is possible to change the contact angle of the drop from less than 5 degrees to near 20 degrees by choice of atmospheric exposure time. This controls the extent of drop spreading, which in turn determines the architecture of the deposition pattern.

  6. Citrate-capped silver nanoparticles showing good bactericidal effect against both planktonic and sessile bacteria and a low cytotoxicity to osteoblastic cells.

    Science.gov (United States)

    Flores, Constanza Y; Miñán, Alejandro G; Grillo, Claudia A; Salvarezza, Roberto C; Vericat, Carolina; Schilardi, Patricia L

    2013-04-24

    A common problem with implants is that bacteria can form biofilms on their surfaces, which can lead to infection and, eventually, to implant rejection. An interesting strategy to inhibit bacterial colonization is the immobilization of silver (Ag) species on the surface of the devices. The aim of this paper is to investigate the action of citrate-capped silver nanoparticles (AgNPs) on clinically relevant Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria in two different situations: (i) dispersed AgNPs (to assess the effect of AgNPs against planktonic bacteria) and (ii) adsorbed AgNPs on titanium (Ti) substrates, a material widely used for implants (to test their effect against sessile bacteria). In both cases, the number of surviving cells was quantified. The small amount of Ag on the surface of Ti has an antimicrobial effect similar to that of pure Ag surfaces. We have also investigated the capability of AgNPs to kill planktonic bacteria and their cytotoxic effect on UMR-106 osteoblastic cells. The minimum bactericidal concentration found for both strains is much lower than the AgNP concentration that leads to cytotoxicity to osteoblasts. Planktonic P. aeruginosa show a higher susceptibility to Ag than S. aureus, which can be caused by the different wall structures, while for sessile bacteria, similar results are obtained for both strains. This can be explained by the presence of extracellular polymeric substances in the early stages of P. aeruginosa biofilm formation. Our findings can be important to improving the performance of Ti-based implants because a good bactericidal action is obtained with very small quantities of Ag, which are not detrimental to the cells involved in the osseointegration process.

  7. The effect of bacteriocin-producing Lactobacillus plantarum strains on the intracellular pH of sessile and planktonic Listeria monocytogenes single cells.

    Science.gov (United States)

    Nielsen, Dennis S; Cho, Gyu-Sung; Hanak, Alexander; Huch, Melanie; Franz, Charles M A P; Arneborg, Nils

    2010-07-31

    A wide range of lactic acid bacteria (LAB) produce bacteriocins mainly active against other closely related LAB, but some bacteriocins are also active against the food-borne pathogen Listeria monocytogenes. With the aim of increasing food safety it has thus been considered to utilise bacteriocins and/or bacteriocin-producing LAB as "natural" food preservatives in foods such as cheese, meat and ready-to-eat products. Some strains of Lactobacillus plantarum produce bacteriocins termed plantaricins. Using a single-cell based approach, the effect on the intracellular pH as a measure of the physiological state of sessile and planktonic L. monocytogenes (strains EGDe and N53-1) during co-culturing with plantaricin-producing L. plantarum (strains BFE 5092 and PCS 20) was investigated using fluorescence ratio imaging microscopy (FRIM). Mono-cultures of L. monocytogenes were used as control. Expression levels of plantaricin-encoding genes by sessile and planktonic L. plantarum were determined using qRT-PCR. L.plantarum BFE 5092 possesses the genes for plantaricin EF, JK and N, while L. plantarum PCS 20 contains the genes for plantaricin EF, although determination of the nucleotide sequence of the PCS 20 plantaricin E gene showed that this peptide is probably non-functional. When cultured as mono-culture, both L. monocytogenes strains maintained pH(i) at a constant level around 7.2-7.6 throughout the experiment, independently of the matrix. On a solid surface, L. plantarum BFE 5092 strongly affected pH(i) of L. monocytogenes N53-1 with only 20% of the cells being able to maintain pH(i) in the physiological optimal range with pH>7 and 52% of the cells with pH(i) approximately pH(ex,) showing that the cells had no proton gradient towards the environment. The effect on L. monocytogenes EGDe was less pronounced, but still notable. L.plantarum PCS 20 left both strains of L. monocytogenes virtually unaffected when co-cultured on a solid surface. In liquid, both L. plantarum

  8. DETERMINATION OF THE SURFACE FREE ENERGY OF ASPHALT BINDERS BY SESSILE DROP METHOD%躺滴法表征沥青的表面自由能

    Institute of Scientific and Technical Information of China (English)

    魏建明; 张玉贞; YOUTCHEFF JOHN S

    2009-01-01

    The surface free energy is an important parameter that can be used to estimate the cohesion work (cohesive strength) of asphalt binders and the adhesion work between the asphalt binder and aggregates. In addition, the surface free energy characteristics of water may be mathematically combined with the surface free energy values of the asphalt binder and the aggregates to assess the moisture susceptibility of asphalt mixture, which is composed of graded aggregates, asphalt, and air voids. The sessile drop method was employed in this study to measure the static contact angle between several strategic highway research program (SHRP) asphalt binders and probe liquids. From these measurements, the surface free energies of the asphalt binder were estimated by the Owens-Wendt method. The surface free energy results of the sessile method for the different asphalt binders were similar to the results measured by contact angle method, giving credence to the applicability of this method for evaluating different types of asphalt binders. The cohesion work of asphalt binders, which is described by surface free energy, was in agreement with that obtained from pull-off tensile strength.%表面自由能足用来确定沥青材料自身的黏聚功(黏聚强度)以及沥青与石料之间的黏附功的重要参数.此外,沥青混合料(包括沥青、石料和空气)的水敏感性也可使用沥青与石料的表面自由能参数进行评价.笔者采用躺滴法测定了几种战略公路研究计划(SHRP)沥青与液体的静态接触角,采用Owens-Wendt法确定了沥青的表面自由能.结果表明,躺滴法得到的沥青表面自由能与由接触角得到的数值比较接近,说明可以应用躺滴法来测定沥青的表面自由能.由沥青的表面自由能表征的沥青黏聚能结果与Pull-off强度试验结果相吻合.

  9. Effects of Northern red oak (Quercus rubra L. and sessile oak (Quercus petraea (Mattusch. Liebl. on the forest soil chemical properties

    Directory of Open Access Journals (Sweden)

    Miltner Stanislav

    2016-09-01

    Full Text Available Northern red oak (Quercus rubra L. is one of the most important introduced tree species in the Czech Republic, occupying about 6,000 ha with ca. 900,000 m3 of the standing volume. The presented study aims to evaluate its soil forming effects on natural oak sites. Soil chemistry of the upper soil layers (F+H, Ah, B horizons was studied in three pairs of stands of both species. In each stand, four bulk samples were taken separately for particular horizons, each consisting of 5 soil-borer cores. The soil characteristics analysed were: pH (active and potential, soil adsorption complex characteristics (content of bases, exchangeable cation capacity, base saturation, exchangeable acidity (exchangeable Al and H, total carbon and nitrogen content, and plant available nutrients content (P, K, Ca, Mg. Total macronutrient content (P, K, Ca, Mg was analysed only in holorganic horizons. Results confirmed acidification effects of red oak on the upper forest soil layers such as decreased pH, base content, base saturation, all nutrient contents in total as well as plant-available form and increased soil exchangeable acidity (exchangeable Al in comparison to the sessile oak stands, especially in holorganic horizons and in the uppermost mineral layer (Ah horizon. Northern red oak can be considered as a slightly site-soil degrading species in the studied sites and environmental conditions in comparison to native oak species.

  10. Humus characteristics and seasonal changes of soil arthropod communities in a natural sessile oak (Quercus petraea L.) stand and adjacent Austrian pine (Pinus nigra Arnold) plantation.

    Science.gov (United States)

    Cakir, Meric; Makineci, Ender

    2013-11-01

    In order to assess the effects of conversion of natural stands into plantations, soil invertebrate micro- and macroarthropod communities were evaluated for their abundance and richness in a sessile oak (SO; Quercus petraea L.) stand and adjacent Austrian pine (AP; Pinus nigra Arnold) plantation. Sites were sampled four times a year in 3-month intervals from May 2009 to February 2010. Humus characteristics such as total mass; carbon, lignin, and cellulose contents; and C/N ratio were significantly different between SO and AP. Statistically significant differences were detected on soil pH, carbon and nitrogen contents, and electrical conductivity between the two sites. The number of microarthropods was higher in AP than in the SO site. The annual mean abundance values of microarthropods in a square meter were 67,763 in AP and 50,542 in SO, and the annual mean abundance values of macroarthropods were 921 m(-2) in AP and 427 m(-2) in SO. Among the soil microarthropods, Acari and Collembola were the dominant groups. Shannon's diversity index was more affected by evenness than species number despite the species diversity (H') of soil arthropods being generally higher in the SO stand. The abundance of microarthropods showed clear seasonal trends depending upon the humidity of the soil.

  11. C-di-GMP Regulates Motile to Sessile Transition by Modulating MshA Pili Biogenesis and Near-Surface Motility Behavior in Vibrio cholerae.

    Science.gov (United States)

    Jones, Christopher J; Utada, Andrew; Davis, Kimberly R; Thongsomboon, Wiriya; Zamorano Sanchez, David; Banakar, Vinita; Cegelski, Lynette; Wong, Gerard C L; Yildiz, Fitnat H

    2015-10-01

    In many bacteria, including Vibrio cholerae, cyclic dimeric guanosine monophosphate (c-di-GMP) controls the motile to biofilm life style switch. Yet, little is known about how this occurs. In this study, we report that changes in c-di-GMP concentration impact the biosynthesis of the MshA pili, resulting in altered motility and biofilm phenotypes in V. cholerae. Previously, we reported that cdgJ encodes a c-di-GMP phosphodiesterase and a ΔcdgJ mutant has reduced motility and enhanced biofilm formation. Here we show that loss of the genes required for the mannose-sensitive hemagglutinin (MshA) pilus biogenesis restores motility in the ΔcdgJ mutant. Mutations of the predicted ATPase proteins mshE or pilT, responsible for polymerizing and depolymerizing MshA pili, impair near surface motility behavior and initial surface attachment dynamics. A ΔcdgJ mutant has enhanced surface attachment, while the ΔcdgJmshA mutant phenocopies the high motility and low attachment phenotypes observed in a ΔmshA strain. Elevated concentrations of c-di-GMP enhance surface MshA pilus production. MshE, but not PilT binds c-di-GMP directly, establishing a mechanism for c-di-GMP signaling input in MshA pilus production. Collectively, our results suggest that the dynamic nature of the MshA pilus established by the assembly and disassembly of pilin subunits is essential for transition from the motile to sessile lifestyle and that c-di-GMP affects MshA pilus assembly and function through direct interactions with the MshE ATPase.

  12. Investigation of wetting characteristics of liquid iron on dense MgAION-based ceramics by X-ray sessile drop technique

    Science.gov (United States)

    Zhang, Z. T.; Matsushita, T.; Seetharaman, S.; Li, W. C.

    2006-06-01

    The wetting characteristics of liquid iron on dense MgAION-based composite ceramics were investigated using X-ray sessile drop technique. The contact angles were measured on substrates of different composites as functions of temperature and varying partial pressures of oxygen. The results with pure argon gas showed that contact angles kept almost constant in the temperature range 1823 to 1873 K. The contact angle was found to show a slight increase with increasing boron nitride (BN) content in MgAION-BN composites. These are attributed to the higher contact angle between BN substrate and liquid iron drop compared with that obtained for MgAION substrate. When the CO-CO2-Ar gas mixtures were introduced into the system, the contact angle showed an initial quick decrease followed by a slow decrease and then a period of nearly constant contact angle at a given temperature corresponding to the steady-state condition. Even in this case, BN seemed to cause an increase in the equilibrium contact angle. The equilibrium contact angle was found to decrease with increasing temperature. XRD results indicated that the substrate was oxidized and the oxidation products combined with FeO formed by the oxidation of the iron drop to from FeAl2O4 and Mg1-xFex) These were likely to form a ternary FeO-Al2O3-MgO slag or a quaternary slag by combining with B2O3. An interesting observation is that the iron drop moved away from the original site, probably due to the Marangoni effect.

  13. Contact Angle Hysteresis for Sessile Water Nanodroplets Using Molecular Dynamics Simulation%固着纳米水滴接触角滞后的分子动力学模拟

    Institute of Scientific and Technical Information of China (English)

    王宝和; 王甜; 夏良志

    2015-01-01

    Using molecular dynamics simulation ,contact angle hysteresis for sessile water nanodroplets is studied.Simulation results show whether the surfaces are smooth or nanotextured rough , contact angle hysteresis increases with the solid surface potential energy increasing .Under the same solid surface po-tential energy , contact angle hysteresis of sessile water nanodroplets on nanotextured rough surfaces is bigger than on smooth , and the square column matrix form surface has a stronger contact angel hysteresis than the fencing form surface .%采用分子动力学模拟技术,研究了固着纳米水滴的接触角滞后。模拟结果表明,无论是光滑壁面还是纳米粗糙壁面,随着壁面作用势能的增大,纳米水滴的接触角滞后增大。在壁面作用势能相同的条件下,纳米水滴在纳米粗糙壁面上的接触角滞后要大于光滑壁面,方柱矩阵形比栏栅形纳米粗糙壁面的接触角滞后更大。

  14. The Influence of ZrO2 Concentration in an Yttria-Based Face Coat for Investment Casting a Ti-45Al-2Mn-2Nb-0.2TiB Alloy Using a Sessile Drop Method

    Science.gov (United States)

    Cheng, Xu; Yuan, Chen; Blackburn, Stuart; Withey, Paul A.

    2015-03-01

    Investment casting is widely used to cast near-net shape components, reducing material waste and process cost. Due to the high reactivity of titanium and its alloys, in order to reduce the interaction between the mold and molten titanium, very costly materials are used in the mold face coat. In order to reduce the material cost while maintaining the chemical inertness of the face coat, ZrO2 was added into an yttria-based face coat in different concentrations in this study. The face coat properties of the different systems were analyzed using dilatometry and XRD. The chemical inertness of the different face coat systems were tested using a sessile drop test using a Ti-45Al-2Mn-2Nb-0.2TiB alloy, and the interactions between the face coat and the alloy were analyzed by the interfacial microstructures, contact angle, and hardness changes. The results showed that small amounts of ZrO2 can be added into yttria without changing the chemical inertness of the face coat. High amounts of ZrO2 in the face coat can interact with TiAl alloy to form different interaction products. Meanwhile, both Y2O3 and ZrO2 filler materials were observed to dissolve in molten TiAl during the sessile drop test.

  15. Density and Molar Volume of Molten Ni-Based Commercial Alloys Measured by Modified Sessile Drop Method%用改良静滴法测量液态Ni基合金的密度和摩尔体积

    Institute of Scientific and Technical Information of China (English)

    肖锋; 杨仁辉; 刘兰霄; 赵红凯; 方亮; 张弛

    2009-01-01

    The densities of four kinds of molten Ni-based commercial alloys were measured with a modified sessile drop method, and calculated using the calculating software. It is found that the densities of the molten Ni-based commercial alloys decrease and their molar volume increase with increasing of temperature. Compared with the ideal mixing, the molar volumes of the molten Ni-based commercial alloys show negative deviations. It can be attributed to an accommodation between various atoms in the alloys.%采用改良静滴法测量并通过软件的计算得到了4种商用镍基合金的密度.结果表明,随着温度的升高,4种液态镍基合金的密度逐渐减小,摩尔体积逐渐增大.与理想混合状态相比,液体镍基合金的摩尔体积出现负偏差.从而可以推测在合金中各种原子之间发生了调整.

  16. Architecture of Burkholderia cepacia complex σ70 gene family: evidence of alternative primary and clade-specific factors, and genomic instability

    Directory of Open Access Journals (Sweden)

    Menard Aymeric

    2007-09-01

    Full Text Available Abstract Background The Burkholderia cepacia complex (Bcc groups bacterial species with beneficial properties that can improve crop yields or remediate polluted sites but can also lead to dramatic human clinical outcomes among cystic fibrosis (CF or immuno-compromised individuals. Genome-wide regulatory processes of gene expression could explain parts of this bacterial duality. Transcriptional σ70 factors are components of these processes. They allow the reversible binding of the DNA-dependent RNA polymerase to form the holoenzyme that will lead to mRNA synthesis from a DNA promoter region. Bcc genome-wide analyses were performed to investigate the major evolutionary trends taking place in the σ70 family of these bacteria. Results Twenty σ70 paralogous genes were detected in the Burkholderia cenocepacia strain J2315 (Bcen-J2315 genome, of which 14 were of the ECF (extracytoplasmic function group. Non-ECF paralogs were related to primary (rpoD, alternative primary, stationary phase (rpoS, flagellin biosynthesis (fliA, and heat shock (rpoH factors. The number of σ70 genetic determinants among this genome was of 2,86 per Mb. This number is lower than the one of Pseudomonas aeruginosa, a species found in similar habitats including CF lungs. These two bacterial groups showed strikingly different σ70 family architectures, with only three ECF paralogs in common (fecI-like, pvdS and algU. Bcen-J2315 σ70 paralogs showed clade-specific distributions. Some paralogs appeared limited to the ET12 epidemic clone (ecfA2, particular Bcc species (sigI, the Burkholderia genus (ecfJ, ecfF, and sigJ, certain proteobacterial groups (ecfA1, ecfC, ecfD, ecfE, ecfG, ecfL, ecfM and rpoS, or were broadly distributed in the eubacteria (ecfI, ecfK, ecfH, ecfB, and rpoD-, rpoH-, fliA-like genes. Genomic instability of this gene family was driven by chromosomal inversion (ecfA2, recent duplication events (ecfA and RpoD, localized (ecfG and large scale deletions (sig

  17. Density of Liquid Binary Ni-W Alloys Measured by Modified Sessile Drop Method%用改良静滴法测量液态Ni-W二元合金的密度

    Institute of Scientific and Technical Information of China (English)

    方亮; 肖锋; 陶再南

    2004-01-01

    In order ot provide a scientific base for studying the shrinkage, transport phenomena and macrosegregation during the solidification of an alloy, the density of liquid binary Ni-W alloys with tungsten concentration from 0 to 15 mass% was measured by a modified sessile drop method. It has been found that the density of the liquid Ni-W alloys decreases with increasing temperature, but increases with the increase of tungsten concentration in the alloys. The molar volume of liquid Ni-W binary alloys increases with the increase of temperature and tungsten concentration. The partial molar volume of tungsten in Ni-W binary alloy has been evaluated approximately as (10.80-1.35× 10-3T) × 10-6 m3·mol-1.%为了给研究合金在凝固过程中发生收缩、迁移现象和偏析提供科学依据,我们用改良静滴法对钨浓度为0到15%的液态Ni-W二元合金的密度进行了测量.结果表明:Ni-W二元合金的液态密度随温度的增加而减少,但随合金中钨浓度的增加而增加;液态Ni-W二元合金的摩尔体积随温度和合金中钨浓度的增加而增加.金属钨在Ni-W二元合金中的偏摩尔体积约为(10.80-1.35×10-3T)×10-6m3·mol-1.

  18. Evaporation of sessile microdrops studied with microcantilevers

    OpenAIRE

    Golovko, D.

    2008-01-01

    The aim of this work is to investigate the evaporation dynamics of water microdrops deposited on atomic force microscope cantilevers, which were employed as sensitive stress, mass and temperature sensors with high time resolution. The technique has some advantages with respect to video-microscope imaging and ultra-precision weighting with electronic microbalances or quartz crystal microbalances, since it allows to measure more drop parameters simultaneously for smaller drop sizes. On hydropho...

  19. Nonlinear Resonance of Mechanically Excited Sessile Drops

    Science.gov (United States)

    Chang, Chun-Ti; Daniel, Susan; Steen, Paul

    2013-11-01

    The spectrum of frequencies and mode shapes for an inviscid drop on a planar substrate have recently been documented. For vertical excitation, zonal modes respond to the driving frequency harmonically and non-zonal modes subharmonically, consistent with the prior literature. In this study, we report observations from the regime of nonlinear response. Here, zonals can respond non-harmonically, both sub- and super-harmonic responses are reported. The principal challenge to generating and observing superharmonic resonances of higher zonal modes is a mode-mixing behavior. However, using a simple visual simulation based on the ray-tracing technique, the individual contributions to the mixed resonance behavior can be extracted. In summary, results from experiment and theory show that the zonal modes, which respond harmonically and can mix with non-zonal modes without interfering with one another in the linear regime, tend to respond sub- or superharmonically and compete with non-zonal modes in the nonlinear regime.

  20. Evaluación de la reproducibilidad del diagnóstico microscópico del adenoma serrado de sésil de colon Assessing the reproducibility of the microscopic diagnosis of sessile serrated adenoma of the colon

    Directory of Open Access Journals (Sweden)

    M. Bustamante-Balén

    2009-04-01

    Full Text Available Introducción: el adenoma serrado sésil (ASS es una lesión descrita recientemente y que puede estar relacionada con el desarrollo de hasta un 15% de los cánceres colorrectales (CCR. Objetivo: determinar la eficacia de los criterios morfológicos para el diagnóstico del ASS evaluando el grado de acuerdo entre patólogos. Material y métodos: se estudió la concordancia entre dos patólogos para el diagnóstico de las lesiones serradas de colon en 195 lesiones (187 pólipos hiperplásicos y 7 adenomas serrados. De cada lesión se recogió el tamaño, la localización, la morfología y la forma de obtención de la muestra. Los dos patólogos eran desconocedores del diagnóstico inicial, las características macroscópicas y la localización de las lesiones. Los posibles diagnósticos fueron: ASS, adenoma serrado tradicional (AST, pólipo hiperplásico (PH, pólipo serrado, adenoma tubular o formas mixtas. Las dudas diagnósticas debían describirse. La concordancia entre los dos observadores se evaluó mediante el índice kappa (κ. También se evaluó la influencia de las variables recogidas de las lesiones en el grado de acuerdo en el diagnóstico. Resultados: el acuerdo global para el diagnóstico histológico fue pobre (κ = 0,14. También lo fue el acuerdo para el diagnóstico de ASS (κ = 0,23. La concordancia para el diagnóstico de ASS mejoró con el tamaño > 5 mm (κ = 0,64 y para la localización proximal (κ = 0,43. Conclusión: en un contexto clínico real, los criterios morfológicos existentes para la identificación del ASS pueden ser de difícil aplicación.Introduction: sessile serrated adenoma (SSA is a recently described lesion that may be related to the development of up to 15% of colorectal cancers (CRCs. Objective: to determine the accuracy of morphological criteria for the diagnosis of SSA by assessing concordance between pathologists. Material and methods: concordance between two pathologists in the diagnosis of

  1. Use of a Burkholderia cenocepacia ABTS Oxidizer in a Microbial Fuel Cell

    Science.gov (United States)

    Microbial fuel cells (MFCs) often use biological processes to generate electrons from organic material contained in the anode chamber and abiotic processes employing atmospheric oxygen as the oxidant in the cathode chamber. This study investigated the accumulation of an oxidant in bacterial cultures...

  2. Role of natural convection in the dissolution of sessile droplets

    CERN Document Server

    Dietrich, Erik; Visser, Claas Willem; Hofhuis, Kevin; Kooij, E Stefan; Zandvliet, Harold J W; Lohse, Detlef

    2016-01-01

    The dissolution process of small (initial (equivalent) radius $R_0 Ra_t$, where $Ra_t = 12$ is the transition Ra-number as extracted from the data. For $Ra < Ra_t$ and smaller, convective transport is progressively overtaken by diffusion and the above scaling relations break down.

  3. Growth control of sessile microbubbles in PDMS devices

    CERN Document Server

    Volk, Andreas; Kähler, Christian J; Hilgenfeldt, Sascha; Marin, Alvaro

    2015-01-01

    In a microfluidic environment, the presence of bubbles is often detrimental to the functionality of the device, leading to clogging or cavitation, but microbubbles can also be an indispensable asset in other applications such as microstreaming. In either case, it is crucial to understand and control the growth or shrinkage of these bodies of air, in particular in common soft-lithography devices based on polydimethylsiloxane (PDMS), which is highly permeable to gases. In this work, we study the gas transport into and out of a bubble positioned in a microfluidic device, taking into account the direct gas exchange through PDMS as well as the transport of gas through the liquid in the device. Hydrostatic pressure regulation allows for the quantitative control of growth, shrinkage, or the attainment of a stable equilibrium bubble size. We find that the vapor pressure of the liquid plays an important role for the balance of gas transport, accounting for variability in experimental conditions and suggesting addition...

  4. Worm-like instability of a vibrated sessile drop

    CERN Document Server

    Hemmerle, Arnaud; Bergeron, Vance; Charitat, Thierry; Farago, Jean

    2016-01-01

    We study the effects of vertical sinusoidal vibrations on a liquid droplet with a low surface tension (ethanol) deposited on a solid substrate. In a precise range of amplitudes and frequencies, the drop exhibits a dramatic worm-like shape instability with a strong symmetry breaking, comparable to the one observed by Pucci et al. (Phys. Rev. Lett., 106 (2011) 024503) on a vibrated floating lens. However, the geometry of our system is much simpler since it does not involve the oscillation and deformation of a liquid-liquid-air contact line. We show that the Faraday waves appearing on the surface of the droplet control its shape and we draw a systematic phase diagram of the instability. A simple theoretical model allows us to derive a relation between the elongation of the droplet and the amplitude of the Faraday wave, in good agreement with measurements of both quantities.

  5. Evaporation of Sessile Droplets Laden with Particles and Insoluble Surfactants.

    Science.gov (United States)

    Karapetsas, George; Chandra Sahu, Kirti; Matar, Omar K

    2016-07-12

    We consider the flow dynamics of a thin evaporating droplet in the presence of an insoluble surfactant and noninteracting particles in the bulk. On the basis of lubrication theory, we derive a set of evolution equations for the film height, the interfacial surfactant, and bulk particle concentrations, taking into account the dependence of liquid viscosity on the local particle concentration. An important ingredient of our model is that it takes into account the fact that the surfactant adsorbed at the interface hinders evaporation. We perform a parametric study to investigate how the presence of surfactants affects the evaporation process as well as the flow dynamics with and without the presence of particles in the bulk. Our numerical calculations show that the droplet lifetime is affected significantly by the balance between the ability of the surfactant to enhance spreading, suppressing the effect of thermal Marangoni stresses-induced motion, and to hinder the evaporation flux through the reduction of the effective interfacial area of evaporation, which tend to accelerate and decelerate the evaporation process, respectively. For particle-laden droplets and in the case of dilute solutions, the droplet lifetime is found to be weakly dependent on the initial particle concentration. We also show that the particle deposition patterns are influenced strongly by the direct effect of the surfactant on the evaporative flux; in certain cases, the "coffee-stain" effect is enhanced significantly. A discussion of the delicate interplay between the effects of capillary pressure and solutal and thermal Marangoni stresses, which drive the liquid flow inside of the evaporating droplet giving rise to the observed results, is provided herein.

  6. Flow transition within an evaporating binary mixture sessile drop.

    Science.gov (United States)

    Christy, John R E; Hamamoto, Yoshinori; Sefiane, Khellil

    2011-05-20

    The flow field along the base of an evaporating ethanol-water droplet and its evolution time was measured by particle image velocimetry. Three stages are revealed, a first stage dominated by multiple vortices, a second transition stage characterized by a remarkable spike in outward flow not previously identified, and a third stage dominated by outward flow identical to that found for pure water. Stage I is thought to be driven by surface tension gradients arising from local concentration variation. The spike in outward flow is explained in terms of a transition corresponding to almost total depletion of ethanol. An exponential decay in vorticity during the transition stage is explained in terms of ethanol diffusion from the bulk to the interface. We speculate on the existence of a zero-concentration wave propagating from the apex to the contact line corresponding to the final total depletion of ethanol.

  7. Modeling evaporation of sessile drops with moving contact lines.

    Science.gov (United States)

    Murisic, N; Kondic, L

    2008-12-01

    We consider evaporation of pure liquid drops on a thermally conductive substrate. Two commonly used evaporative models are considered: one that concentrates on the liquid phase in determining the evaporative flux and the other one that centers on the gas-vapor phase. A single governing equation for the evolution of drop thickness, including both models, is developed. We show how the derived governing equation can be used to predict which evaporation model is appropriate for different considered experimental conditions.

  8. Structural and evaporative evolutions in desiccating sessile drops of blood.

    Science.gov (United States)

    Sobac, B; Brutin, D

    2011-07-01

    We report an experimental investigation of the drying of a deposited drop of whole blood. Flow motion, adhesion, gelation, and fracturation all occur during the evaporation of this complex matter, leading to a final typical pattern. Two distinct regimes of evaporation are highlighted: the first is driven by convection, diffusion, and gelation in a liquid phase, whereas the second, with a much slower rate of evaporation, is characterized by the mass transport of the liquid left over in the gellified biocomponent matter. A diffusion model of the drying process allows a prediction of the transition between these two regimes of evaporation. Moreover, the formation of cracks and other events occurring during the drying are examined and shown to be driven by critical solid mass concentrations.

  9. Sessile Nanodroplets on Elliptical Patches of Enhanced Lyophilicity

    Science.gov (United States)

    2017-01-01

    We theoretically investigate the shape of a nanodroplet on a lyophilic elliptical patch in lyophobic surroundings on a flat substrate. To compute the droplet equilibrium shape, we minimize its interfacial free energy using both Surface Evolver and Monte Carlo calculations, finding good agreement between the two methods. We observe different droplet shapes, which are controlled by the droplet volume and the aspect ratio of the ellipse. In particular, we study the behavior of the nanodroplet contact angle along the three-phase contact line, explaining the different droplet shapes. Although the nanodroplet contact angle is constant and fixed by Young’s law inside and outside the elliptical patch, its value varies along the rim of the elliptical patch. We find that because of the pinning of the nanodroplet contact line at the rim of the elliptical patch, which has a nonconstant curvature, there is a regime of aspect ratios of the elliptical patch in which the nanodroplet starts expanding to the lyophobic part of the substrate, although there is still a finite area of the lyophilic patch free to be wetted. PMID:28248114

  10. Quasi-static relaxation of arbitrarily shaped sessile drops

    CERN Document Server

    Iliev, S; Nikolayev, Vadim

    2016-01-01

    We study a spontaneous relaxation dynamics of arbitrarily shaped liquid drops on solid surfaces in the partial wetting regime. It is assumed that the energy dissipated near the contact line is much larger than that in the bulk of the fluid. We have shown rigorously in the case of quasi-static relaxation using the standard mechanical description of dissipative system dynamics that the introduction of a dissipation term proportional to the contact line length leads to the well known local relation between the contact line velocity and the dynamic contact angle at every point of an arbitrary contact line shape. A numerical code is developed for 3D drops to study the dependence of the relaxation dynamics on the initial drop shape. The available asymptotic solutions are tested against the obtained numerical data. We show how the relaxation at a given point of the contact line is influenced by the dynamics of the whole drop which is a manifestation of the non-local

  11. Forces Acting on Sessile Droplet on Inclined Surfaces

    OpenAIRE

    Annapragada, S. Ravi; Murthy, Jayathi Y.; Garimella, Suresh V.

    2009-01-01

    Although many analytical, experimental and numerical studies have focused on droplet motion, the mechanics of the droplet while still in its static state, and just before motion starts, are not well understood. A study of static droplets would shed light on the threshold voltage (or critical inclination) for initiating electrically (or gravitationally) induced droplet motion. Before the droplet starts to move, the droplet shape changes such that the forces acting at the triple contact line ba...

  12. Numerical investigation of phase relationships in an oscillating sessile drop

    Science.gov (United States)

    Korenchenko, A. E.; Malkova, J. P.

    2015-10-01

    Forced linear oscillations of a viscous drop placed on a horizontal surface vibrating in perpendicular direction are investigated. The problem is solved for two cases: (1) constant contact angle, and (2) pinned contact line. Phase-frequency and amplitude-frequency characteristics of oscillations of the drop apex are found for the first axisymmetrical mode of oscillations. The independence of the difference of oscillation phases of the drop apex and the substrate on fluid density, viscosity, surface tension, and drop size as well as on presence or absence of the gravity force was demonstrated.

  13. Partial coalescence of sessile drops with different liquids

    Science.gov (United States)

    Borcia, Rodica; Bestehorn, Michael

    2014-11-01

    We examine numerically the interaction between two deformable drops consisting of two perfectly miscible liquids sitting on a solid substrate under a given contact angle. Driven by solutal Marangoni forces, several distinct coalescence regimes are achieved after the droplets collision. Phase diagrams for different control parameters are emphasized, which give predictions about drop behavior along the solid substrates, control of various interfacial effects, manipulations of tiny droplets in micro- and nano-fluidic devices without power supply, design of droplets or cleaning surfaces. This work was partially supported by Deutsche Forschungsgemeinschaft (DFG) under the project ``Dynamics of interfaces between drops with miscible liquids''.

  14. Growth control of sessile microbubbles in PDMS devices.

    Science.gov (United States)

    Volk, Andreas; Rossi, Massimiliano; Kähler, Christian J; Hilgenfeldt, Sascha; Marin, Alvaro

    2015-12-21

    In a microfluidic environment, the presence of bubbles is often detrimental to the functionality of the device, leading to clogging or cavitation, but microbubbles can also be an indispensable asset in other applications such as microstreaming. In either case, it is crucial to understand and control the growth or shrinkage of these bodies of air, in particular in common soft-lithography devices based on polydimethylsiloxane (PDMS), which is highly permeable to gases. In this work, we study the gas transport into and out of a bubble positioned in a microfluidic device, taking into account the direct gas exchange through PDMS as well as the transport of gas through the liquid in the device. Hydrostatic pressure regulation allows for the quantitative control of growth, shrinkage, or the attainment of a stable equilibrium bubble size. We find that the vapor pressure of the liquid plays an important role for the balance of gas transport, accounting for variability in experimental conditions and suggesting additional means of bubble size control in applications.

  15. The transition between sessile and motile bacterial lifestyles

    NARCIS (Netherlands)

    Tsompanidou, Eleni

    2012-01-01

    Nader inzicht in effectiviteit Staphylococcus aureus Eleni Tsompanidou verrichtte onderzoek naar de mechanismen die de verspreiding van de Staphylococcus aureus verklaren. Ze ontdekte dat alleen stammen van S. aureus met een actief agr-regulatiesysteem zich goed kunnen verspreiden over oppervlakken.

  16. MANGROVE-EXPORTED NUTRIENT INCORPORATION BY SESSILE CORAL REEF INVERTEBRATES

    Science.gov (United States)

    Coastal mangrove forests were historically considered as a source of organic matter (OM) for adjacent marine systems due to high net primary production; yet recent research suggesting little uptake through the food web because of low nutritional quality, challenges the concept of...

  17. Study on characterization of extracellular polymers in MBR-sessile worm reactor system by using three-dimensional excitation and emission matrix fluorescence spectroscopy%MBR+蠕虫床耦合系统内胞外聚合物三维荧光特性

    Institute of Scientific and Technical Information of China (English)

    延崇建; 韩雪; 李伶艳; 任正元; 崔崇威

    2012-01-01

    采用三维荧光技术研究了MBR+蠕虫床耦合系统内蠕虫作用对MBR内胞外聚合物(EPSS及EPSB)特性的影响.MBR -A、MBR -B和SSBWR内EPSS的EEM光谱中均主要有四个特征峰,SS-BWR的作用未破坏MBR -B内EPSS中酪氨酸类蛋白质的结构,使色氨酸类蛋白质的峰发生了较大程度的红移,两类芳香性蛋白质、类腐殖酸以及类富里酸物质含量均有大量增加.耦合系统内EPSB的EEM光谱均主要有两个特征峰,分别为酪氨酸和色氨酸类蛋白质,EPSB主要由蛋白质类物质构成.经SSBWR作用后EPSB中两类蛋白质含量减少明显,并且色氨酸类蛋白质的特征峰产生了5~10nm的蓝移.MBR -B的污泥混合液经SSBWR作用后,其I(B)/I(A)值有了一定程度的降低,蠕虫的捕食作用使污泥混合液中易生物降解的有机质减少,降低了污泥混合液的可生化性.%Fluorescence excitation emission matrix spectroscopy(EEMS)was used to study the impact of worms on the extracellular polymers( EPSS and EPSB) in MBR - sessile worm reactor system. There were four peaks in MBR - A,MBR - B and SSBWR. SSBWR did not destroy the tyrosine s structure of EPSS in MBR - B, however, lead to a large read shift of tryptophan. Those two kinds of protein, fulvic acid-like and humic acid-like increased greatly in quantity. Two peaks were found in the EEM of EPSB in the combined system, which was tyrosine and tryptophan. So, EPSB was consisted of substances like protein. SSBWR lead to a significant decrease in the quantity of those two kinds of protein, in addition, result in a 5 ~ 10 nm blue shift in the peak of tryptophan. After sludge mixed liquor in MBR - B was predated by worms in SSBWR, I(B)/I(A) decreased at a certain degree. The amount of organic matter which was easily degraded in sludge mixed liquor and the biodegraded ability droped, due to the predation of worms.

  18. A sensor kinase recognizing the cell-cell signal BDSF (cis-2-dodecenoic acid) regulates virulence in Burkholderia cenocepacia

    DEFF Research Database (Denmark)

    McCarthy, Y.; Yang, Liang; Twomey, K.B.;

    2010-01-01

    the input domain of RpfC was active in BDSF signal perception when expressed in X. campestris. Mutation of BCAM0227 gave rise to reduced cytotoxicity to Chinese hamster ovary cells and reduced virulence to Wax moth larvae and in the agar-bead mouse model of pulmonary infection. The findings identify BCAM...

  19. Biofilm-grown Burkholderia cepacia complex cells survive antibiotic treatment by avoiding production of reactive oxygen species.

    Directory of Open Access Journals (Sweden)

    Heleen Van Acker

    Full Text Available The presence of persister cells has been proposed as a factor in biofilm resilience. In the present study we investigated whether persister cells are present in Burkholderia cepacia complex (Bcc biofilms, what the molecular basis of antimicrobial tolerance in Bcc persisters is, and how persisters can be eradicated from Bcc biofilms. After treatment of Bcc biofilms with high concentrations of various antibiotics often a small subpopulation survived. To investigate the molecular mechanism of tolerance in this subpopulation, Burkholderia cenocepacia biofilms were treated with 1024 µg/ml of tobramycin. Using ROS-specific staining and flow cytometry, we showed that tobramycin increased ROS production in treated sessile cells. However, approximately 0.1% of all sessile cells survived the treatment. A transcriptome analysis showed that several genes from the tricarboxylic acid cycle and genes involved in the electron transport chain were downregulated. In contrast, genes from the glyoxylate shunt were upregulated. These data indicate that protection against ROS is important for the survival of persisters. To confirm this, we determined the number of persisters in biofilms formed by catalase mutants. The persister fraction in ΔkatA and ΔkatB biofilms was significantly reduced, confirming the role of ROS detoxification in persister survival. Pretreatment of B. cenocepacia biofilms with itaconate, an inhibitor of isocitrate lyase (ICL, the first enzyme in the glyoxylate shunt, reduced the persister fraction approx. 10-fold when the biofilms were subsequently treated with tobramycin. In conclusion, most Bcc biofilms contain a significant fraction of persisters that survive treatment with high doses of tobramycin. The surviving persister cells downregulate the TCA cycle to avoid production of ROS and at the same time activate an alternative pathway, the glyoxylate shunt. This pathway may present a novel target for combination therapy.

  20. NCBI nr-aa BLAST: CBRC-CREM-01-1310 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CREM-01-1310 ref|YP_624641.1| acyltransferase 3 [Burkholderia cenocepacia AU 1...054] ref|YP_837010.1| acyltransferase 3 [Burkholderia cenocepacia HI2424] ref|ZP_01565190.1| acyltransferase 3 [Burkholder...ia cenocepacia MC0-3] gb|ABF79668.1| acyltransferase 3 [Burkholderia cenocepacia AU 1054] gb|A...BK10117.1| acyltransferase 3 [Burkholderia cenocepacia HI2424] gb|EAV56867.1| acyltransferase 3 [Burkholderia cenocepacia MC0-3] YP_624641.1 1e-65 56% ...

  1. Plastic responses of a sessile prey to multiple predators: a field and experimental study.

    Directory of Open Access Journals (Sweden)

    Philipp Emanuel Hirsch

    Full Text Available Theory predicts that prey facing a combination of predators with different feeding modes have two options: to express a response against the feeding mode of the most dangerous predator, or to express an intermediate response. Intermediate phenotypes protect equally well against several feeding modes, rather than providing specific protection against a single predator. Anti-predator traits that protect against a common feeding mode displayed by all predators should be expressed regardless of predator combination, as there is no need for trade-offs.We studied phenotypic anti-predator responses of zebra mussels to predation threat from a handling-time-limited (crayfish and a gape-size-limited (roach predator. Both predators dislodge mussels from the substrate but diverge in their further feeding modes. Mussels increased expression of a non-specific defense trait (attachment strength against all combinations of predators relative to a control. In response to roach alone, mussels showed a tendency to develop a weaker and more elongated shell. In response to crayfish, mussels developed a harder and rounder shell. When exposed to either a combination of predators or no predator, mussels developed an intermediate phenotype. Mussel growth rate was positively correlated with an elongated weaker shell and negatively correlated with a round strong shell, indicating a trade-off between anti-predator responses. Field observations of prey phenotypes revealed the presence of both anti-predator phenotypes and the trade-off with growth, but intra-specific population density and bottom substrate had a greater influence than predator density.Our results show that two different predators can exert both functionally equivalent and inverse selection pressures on a single prey. Our field study suggests that abiotic factors and prey population density should be considered when attempting to explain phenotypic diversity in the wild.

  2. Antimicrobial design of titanium surface that kill sessile bacteria but support stem cells adhesion

    Science.gov (United States)

    Zhu, Chen; Bao, Ni-Rong; Chen, Shuo; Zhao, Jian-Ning

    2016-12-01

    Implant-related bacterial infection is one of the most severe postoperative complications in orthopedic or dental surgery. In this context, from the perspective of surface modification, increasing efforts have been made to enhance the antibacterial capability of titanium surface. In this work, a hierarchical hybrid surface architecture was firstly constructed on titanium surface by two-step strategy of acid etching and H2O2 aging. Then silver nanoparticles were firmly immobilized on the hierarchical surface by ion implantation, showing no detectable release of silver ions from surface. The designed titanium surface showed good bioactivity. More importantly, this elaborately designed titanium surface can effectively inactivate the adherent S. aureus on surface by virtue of a contact-killing mode. Meanwhile, the designed titanium surface can significantly facilitate the initial adhesion and spreading behaviors of bone marrow mesenchymal stem cells (MSCs) on titanium. The results suggested that, the elaborately designed titanium surface might own a cell-favoring ability that can help mammalian cells win the initial adhesion race against bacteria. We hope the present study can provide a new insight for the better understanding and designing of antimicrobial titanium surface, and pave the way to satisfying clinical requirements.

  3. Low dynamics, high longevity and persistence of sessile structural species dwelling on Mediterranean coralligenous outcrops.

    Directory of Open Access Journals (Sweden)

    Núria Teixidó

    Full Text Available There is still limited understanding of the processes underlying benthic species dynamics in marine coastal habitats, which are of disproportionate importance in terms of productivity and biodiversity. The life-history traits of long-lived benthic species in these habitats are particularly poorly documented. In this study, we assessed decadal patterns of population dynamics for ten sponge and anthozoan species that play key structural roles in coralligenous outcrops (∼25 m depth in two areas of the NW Mediterranean Sea. This study was based on examination of a unique long-term photographic series, which allowed analysis of population dynamics over extensive spatial and time spans for the very first time. Specifically, 671 individuals were censused annually over periods of 25-, 15-, and 5-years. This long-term study quantitatively revealed a common life-history pattern among the ten studied species, despite the fact they present different growth forms. Low mortality rates (3.4% yr(-1 for all species combined and infrequent recruitment events (mean value of 3.1±0.5 SE recruits yr(-1 provided only a very small fraction of the new colonies required to maintain population sizes. Overall, annual mortality and recruitment rates did not differ significantly among years; however, some species displayed important mortality events and recruitment pulses, indicating variability among species. Based on the growth rates of these 10 species, we projected their longevity and, obtained a mean estimated age of 25-200 years. Finally, the low to moderate turnover rates (mean value 0.80% yr(-1 observed among the coralligenous species were in agreement with their low dynamics and persistence. These results offer solid baseline data and reveal that these habitats are among the most vulnerable to the current increases of anthropogenic disturbances.

  4. Fate of sessile droplet chemical agents in environmental substrates in the presence of physiochemical processes

    Science.gov (United States)

    Navaz, H. K.; Dang, A. L.; Atkinson, T.; Zand, A.; Nowakowski, A.; Kamensky, K.

    2014-05-01

    A general-purpose multi-phase and multi-component computer model capable of solving the complex problems encountered in the agent substrate interaction is developed. The model solves the transient and time-accurate mass and momentum governing equations in a three dimensional space. The provisions for considering all the inter-phase activities (solidification, evaporation, condensation, etc.) are included in the model. The chemical reactions among all phases are allowed and the products of the existing chemical reactions in all three phases are possible. The impact of chemical reaction products on the transport properties in porous media such as porosity, capillary pressure, and permeability is considered. Numerous validations for simulants, agents, and pesticides with laboratory and open air data are presented. Results for chemical reactions in the presence of pre-existing water in porous materials such as moisture, or separated agent and water droplets on porous substrates are presented. The model will greatly enhance the capabilities in predicting the level of threat after any chemical such as Toxic Industrial Chemicals (TICs) and Toxic Industrial Materials (TIMs) release on environmental substrates. The model's generality makes it suitable for both defense and pharmaceutical applications.

  5. Structure build-up and evolution in the drying of sessile blood droplets

    Science.gov (United States)

    Craster, Richard; Uppal, Aran; Matar, Omar

    2016-11-01

    Experimental observations have recorded blood undergoing a sol-gel transition during the evaporation process. Consequently, the rheology becomes non-uniform throughout the droplet and exhibits transitional complex phenomena that we must capture if we wish to accurately model the evaporative/cracking process. We propose a model where thixotropy is introduced to capture the evolving rheology as evaporation occurs. Thixotropy is often used to describe fluids which exhibit a decrease in viscosity due to flow and subsequent slow recovery of viscosity after the cessation of the flow. We introduce an additional parameter to describe the internal structure of the fluid at each point and consider a droplet in the limit of the lubrication approximation. We present a discussion of our results that demonstrates the dependence of structure build-up, which accompanies the spatio-temporal evolution of the drop, on system parameters. EPSRC UK Centre for Doctoral Training.

  6. Evaporation of sessile droplets affected by graphite nanoparticles and binary base fluids.

    Science.gov (United States)

    Zhong, Xin; Duan, Fei

    2014-11-26

    The effects of ethanol component and nanoparticle concentration on evaporation dynamics of graphite-water nanofluid droplets have been studied experimentally. The results show that the formed deposition patterns vary greatly with an increase in ethanol concentration from 0 to 50 vol %. Nanoparticles have been observed to be carried to the droplet surface and form a large piece of aggregate. The volume evaporation rate on average increases as the ethanol concentration increases from 0 to 50 vol % in the binary mixture nanofluid droplets. The evaporation rate at the initial stage is more rapid than that at the late stage to dry, revealing a deviation from a linear fitting line, standing for a constant evaporation rate. The deviation is more intense with a higher ethanol concentration. The ethanol-induced smaller liquid-vapor surface tension leads to higher wettability of the nanofluid droplets. The graphite nanoparticles in ethanol-water droplets reinforce the pinning effect in the drying process, and the droplets with more ethanol demonstrate the depinning behavior only at the late stage. The addition of graphite nanoparticles in water enhances a droplet baseline spreading at the beginning of evaporation, a pinning effect during evaporation, and the evaporation rate. However, with a relatively high nanoparticle concentration, the enhancement is attenuated.

  7. Crystal deposition patterns from evaporating sessile drops on superhydrophobic and liquid impregnated surfaces

    Science.gov (United States)

    McBride, Samantha; Dash, Susmita; Varanasi, Kripa; Varanasi Group Team

    2016-11-01

    Accelerated corrosion and scale buildup near oceans is partially due to deposition of salty sea mist onto ships, cars, and building structures. Many corrosion preventative measures are expensive, time intensive, and/or have negative impacts on the environment. One solution is the use of specific surfaces that are engineered for scale resistance. In this work, we show that we can delay crystallization and reduce scale adhesion on specifically engineered liquid impregnated surfaces (LIS). The low contact angle hysteresis of the LIS results in a sliding contact line of the saline droplet during evaporation, and the elevated energy barrier of the smooth liquid interface delays crystallization. Experiments conducted on surfaces with different wettability also demonstrate the corresponding influence in controlling salt crystal polymorphism.

  8. Structural transitions in a ring stain created at the contact line of evaporating nanosuspension sessile drops

    Science.gov (United States)

    Askounis, Alexandros; Sefiane, Khellil; Koutsos, Vasileios; Shanahan, Martin E. R.

    2013-01-01

    Monodisperse nanosuspension droplets, placed on a flat surface, evaporated following the stick-slip motion of the three-phase contact line. Unexpectedly, a disordered region formed at the exterior edge of a closely packed nanocolloidal crystalline structure during the “stick” period. In order to assess the role of particle velocity on particle structuring, we did experiments in a reduced pressure environment which allowed the enhancement of particle velocity. These experiments revealed the promotion of hexagonal packing at the very edge of the crystallite with increasing velocity. Quantification of particle velocity and comparison with measured deposit shape for each case allowed us to provide a tentative description of the underlying mechanisms that govern particle deposition of nanoparticles at the triple line of an evaporating droplet. Behavior is governed by an interplay between the fluid, and hence particle, flow velocity (main ordering parameter) and wedge constraints, and consequently disjoining pressure (main disordering parameter). Furthermore, the formation of a second disordered particle region at the interior edge of the deposit (towards bulk fluid) was found and attributed to the rapid motion of the triple line during the “slip” regime. Additionally, the magnitude of the pinning forces acting on the triple line of the same drops was calculated. These findings provide further insight into the mechanisms of the phenomenon and could facilitate its exploitation in various nanotechnological applications.

  9. Sessile serrated lesion and its borderline variant - Variables with impact on recorded data

    DEFF Research Database (Denmark)

    Mohammadi, Mahin; Garbyal, Rajendra S; Kristensen, Michael H.

    2011-01-01

    has its relation to SPs with subtle aberrant features, falling short of definite SSL-histology, been sufficiently addressed. The aim of this study was to highlight variables that may influence recorded data on SSL and to further discuss the appropriate place of SPs that possess histological attributes...

  10. How algae influence sessile marine organisms: The tube worms case of study

    Science.gov (United States)

    Casoli, Edoardo; Bonifazi, Andrea; Ardizzone, Giandomenico; Gravina, Maria Flavia

    2016-09-01

    Tube worms and phytobenthic assemblages in three infralittoral and shallow circalittoral Mediterranean benthic communities developed between 5 and 35 m depth at Punta del Lazzaretto (Giglio Island, Central Thyrrenian sea) were investigated. Despite being three algae-dominated habitats, these displayed different covering both in terms of algal layers and algal morphologies, reflecting different structural organizations. Twenty-eight serpulid taxa have been reported, increasing both diversity and density values from most photophilic to most sciaphilous habitats. Multivariate analyses showed how algal thalli and tube worm assemblages were strongly correlated; substrata are influenced both physically and biologically, providing different conditions for tube worm settlement.

  11. Effect of sessile drop volume on the wetting anisotropy observed on grooved surfaces.

    Science.gov (United States)

    Yang, Jing; Rose, Felicity R A J; Gadegaard, Nikolaj; Alexander, Morgan R

    2009-03-03

    This study reports experimental measurements of the water contact angle (WCA) measured on surfaces with grooves of different widths using drop volumes ranging from 400 pL to 4.5 microL. These measurements were carried out on both relatively hydrophobic and hydrophilic surface chemistry formed using a conformal plasma polymer coating of topographically embossed poly(methyl methacrylate) (PMMA). Anisotropic wetting of the grooved surfaces was found to be more marked for larger drops on both the hydrophilic and hydrophobic surfaces. Above a certain drop base diameter to groove width ratio, topography had no effect on the measured WCA; this ratio was found to be dependent on the water drop volume. The WCA measured from the direction perpendicular to the grooves using submicroliter water drops is found to be a good indicator of the WCA on the flat surface with equivalent wettabilities. To the best of our knowledge, this is the first study on the phenomenon of anisotropic wetting using picoliter water drops.

  12. Evaporation of sessile water/ethanol drops in a controlled environment.

    Science.gov (United States)

    Liu, Chuanjun; Bonaccurso, Elmar; Butt, Hans-Jürgen

    2008-12-21

    The evaporation of water/ethanol drops with different mixing ratios was investigated at controlled vapor pressure of water (relative humidity) and ethanol in the background gas. Therefore, a drop of about 1 microL was deposited on a hydrophobized silicon substrate at room temperature in a closed cell. With a microscope camera we monitored the contact angle, the volume and the contact radius of the drops as function of time. Pure water drops evaporated in constant contact angle mode. The evaporation rate of water decreased with increasing humidity. In mixed drops ethanol did not evaporate completely at first, but a fraction still remained in the drop until the end of evaporation. Depending on ethanol concentration in the drop and on relative humidity in the background gas, water vapor condensed at the beginning of the evaporation of mixed drops. Also, at a high vapor pressure of ethanol, ethanol condensed at the beginning of the evaporation. The presence of ethanol vapor accelerated the total evaporation time of water drops.

  13. Discussion on a mechanical equilibrium condition of a sessile drop on a smooth solid surface.

    Science.gov (United States)

    Yonemoto, Yukihiro; Kunugi, Tomoaki

    2009-04-14

    Young's equation describes an interfacial equilibrium condition of a liquid droplet on a smooth solid surface. This relation is derived by Thomas Young in 1805. It has been discussed until today after his work. In general, Young's equation is discussed from the viewpoint of thermodynamics and derived by minimizing the total free energy of the system with intensive parameters in the total free energy kept constant, i.e., the variation in the total free energy is zero. In the derivation, the virtual work variations in the horizontal and vertical directions of the droplet on the smooth solid are considered independently. However, the virtual work variation at the droplet surface depends on the variation of the horizontal and vertical directions, which are related to an incline of the droplet surface. This point has been overlooked in past studies. In this study, by considering this directional dependency, we derive the modified Young's equation based on the thermodynamics. Finally, we evaluate the modified Young's equation by comparing the analytical solution of the relationship between a contact angle and the contact line radii of the droplet with some experimental data. Moreover, we investigated the line tension itself.

  14. Comparative sessile drop and dip pen nanolithography investigation for various hydrophilic ink/surface systems.

    Science.gov (United States)

    Yadav, Pradeep K; Lemoine, Patrick

    2012-01-01

    We present a dip pen nanolithography study of various hydrophilic ink/surface systems with application in the field of biosensors and novel nano-materials. The inking process was investigated by studying a number of inks, such as Deoxyribonucleic acid (DNA), Bovine serum albumin (BSA), Streptavidin, 16-mercaptohexadecanoic acid (MHA) and a 20 nm nanosphere (NS) polystyrene solution onto a range of substrates, namely glass, silicon, gold and tetrahedral amorphous carbon (taC). In the majority of cases, this resulted in patterns with sub-100 nm line widths and dot diameters. Importantly, contact angle measurements in the microl range showed a decrease of contact angle with drop volume, interpreted as a line tension effect. The significance of this to the nanoscale wetting behaviour is discussed. The effect of dwell time and writing speed indicates that the inking process is not solely defined by surface diffusion but also influenced by the ink dissolution rate from the tip.

  15. Captive bubble and sessile drop surface characterization of a submerged aquatic plant, Hydrilla verticillata

    Science.gov (United States)

    The surface energy parameters of the invasive aquatic weed, Hydrilla verticillata, were determined using contact angle measurements using two different methods. The abaxial and adaxial surfaces of the leaves and stem were characterized for the weed while submerged in water using captive air and octa...

  16. Dynamics and universal scaling law in geometrically-controlled sessile drop evaporation.

    Science.gov (United States)

    Sáenz, P J; Wray, A W; Che, Z; Matar, O K; Valluri, P; Kim, J; Sefiane, K

    2017-03-15

    The evaporation of a liquid drop on a solid substrate is a remarkably common phenomenon. Yet, the complexity of the underlying mechanisms has constrained previous studies to spherically symmetric configurations. Here we investigate well-defined, non-spherical evaporating drops of pure liquids and binary mixtures. We deduce a universal scaling law for the evaporation rate valid for any shape and demonstrate that more curved regions lead to preferential localized depositions in particle-laden drops. Furthermore, geometry induces well-defined flow structures within the drop that change according to the driving mechanism. In the case of binary mixtures, geometry dictates the spatial segregation of the more volatile component as it is depleted. Our results suggest that the drop geometry can be exploited to prescribe the particle deposition and evaporative dynamics of pure drops and the mixing characteristics of multicomponent drops, which may be of interest to a wide range of industrial and scientific applications.

  17. A Mesoscopic Self-assembled Ring of a Femtomole Fluorescein Sessile Droplet on Glass Slide Support

    Institute of Scientific and Technical Information of China (English)

    Cheng Zhi HUANG; Ying LIU; Yuan Fang LI

    2004-01-01

    Since the solvent evaporation of a droplet on a hydrophobically pretreated glass slide, femtomole amount of fluorescent materials is carried by the evaporation and results in outward capillary flow to the perimeter of the droplet spot where the solute deposits, and forms a fluorescent ring like deposit (RLD) with submicrometer-scale structures.

  18. Controlling the Growth Modes of Femtoliter Sessile Droplets Nucleating on Chemically Patterned Surfaces

    Science.gov (United States)

    Zhang, Xuehua; Bao, Lei; Werbiuk, Zenon; Lohse, Detlef

    2016-11-01

    Femtoliter droplet arrays on immersed substrates are essential elements in a broad range of advanced droplet-based technologies, such as light manipulation, sensing, and high throughput diagnosis. Solvent exchange is a bottom-up approach for producing those droplets from a pulse of oil oversaturation when a good solvent of the droplet liquid is displaced by a poor solvent. The position and arrangement of the droplets are regulated by chemical micropatterns on the substrate. Here we show experimentally and theoretically that the growth modes of droplets confined in planar micropatterns on the surface can be manipulated through the laminar flow of the solvent exchange. The control parameters are the area size of the micropatterns and the flow rate, and the observables are the contact angle and the final droplet volume. For a given pattern size, the Peclet number of the flow determines whether the growing droplets switch from an initial constant contact angle mode to a subsequent constant contact radius mode. Good agreement is achieved between the experimental results and our theoretical model that describes the dependence of the final droplet size on Pe.

  19. Detection of introduced sessile species on the near shore continental shelf in southern Brazil

    Directory of Open Access Journals (Sweden)

    Janaína de Araújo Bumbeer

    2012-04-01

    Full Text Available Invasion by marine species, often considered a grave threat to marine ecosystems, occurs throughout the world as a consequence of many anthropogenic activities. In coastal Paraná, many factors including shipping, aquaculture and the use of artificial substrates provide suitable environments for the establishment and rapid spread of introduced marine species. To better understand this process, the encrusting community was studied on polyethylene plates (n = 120, 10 x 10 cm that were placed seasonally at fixed locations on the inner continental shelf to detect non-native species. Of the 62 taxa found, 40 were identified to species, 14 of which were native, 9 introduced and 17 cryptogenic. We found a new introduction while most introduced species were previously reported at a nearby estuary with an international port. Possible complementary explanations for these detections are 1 estuaries influence ecological processes on the inner continental shelf, 2 the study area is near the route of cargo and other ships entering the port, 3 other local vectors, such as hulls of fishing and recreational boats, and artificial reefs link the estuary to the offshore areas. Thus, not only are estuaries invaded by exotic species, but also non-indigenous marine species may be present in the open sea where they are likely to colonize artificial substrates.

  20. Measuring the resonant vibration of a sessile droplet using MEMS based cantilevers

    Science.gov (United States)

    Nguyen, Thanh-Vinh; Matsumoto, Kiyoshi; Shimoyama, Isao

    2015-11-01

    We directly measure the normal force distribution on the contact area during the 1st mode resonant vibration of a droplet using an array of MEMS based cantilever. The measurement result shows that the normal force change is the largest at the periphery of the contact area. The ratio between the amplitude of the normal force change at the periphery of the contact area over that at the center of the contact area was approximately 20 times, in the case of 1.8 μL water droplet whose equilibrium contact angle is 140 degrees. We also demonstrate a method to estimate viscosity based on the measurement of the droplet vibration using MEMS cantilevers. The proposed method is able to estimate viscosity using less than 3 μL sample and has a simple operating principle. We believe that this method is suitable for point-of-care testing and characterization of chemical and biological solutions.

  1. Low-order models of the motion of sessile droplets on highly hydrophobic surfaces

    Science.gov (United States)

    Wray, Alex; Kahouadji, Lyes; Matar, Omar; Davis, Stephen

    2016-11-01

    We consider the behaviour of a droplet deposited onto a hydroophobic substrate. This and associated problems have received attention due to their significance in a wide array of experimental and industrial contexts, such as the post-rupture wetting problem is of importance to coating flow applications. Such systems have typically defied low-order analysis due to the multi-valued nature of the interface, but we demonstrate how to resolve this issue in this instance. We begin by analysing the static case. We find that the system is governed by the Young-Laplace equation with the equilbrium shape depending on the Bond number, the contact angle and the volume of the droplet. We solve the system numerically, and use these results to validate a variety of low-order models. We then solve the dynamic problem using both direct numerical simulations and a low-order model based on conservation of energy. EPSRC UK platform Grant MACIPh (EP/L020564/1) and programme Grant MEMPHIS (EP/K003976/1).

  2. Phagocytosis and hydrophobicity: a method of calculating contact angles based on the diameter of sessile drops.

    Science.gov (United States)

    Dahlgren, C; Sunqvist, T

    1981-01-01

    The correlation between the contact angle and degree of phagocytosis of different yeast particles has been investigated. To facilitate the estimation of the contact angle, we have tested the hypothesis that the shape of a small liquid drop put on a flat surface is that of a truncated sphere. By making this approximation it is possible to calculate the contact angle, i.e. the tangent to the drop in the 3-phase liquid/solid/air meeting point, by measuring the drop diameter. Known volumes of saline were put on different surfaces and the diameters of the drops were measured from above. Calculation of the contact angle with drops of different volumes, and comparison between expected and measured height of 10 microl drops, indicated that the assumption that the shape of a drop is that of a truncated sphere is valid. Monolayers of leukocytes was shown to give rise to a contact angle of 17.9 degrees. Particles with a lower contact angle than the phagocytic cells resisted phagocytosis, but opsonization of the particles with normal human serum rendered them susceptible to phagocytosis, conferring a higher contact angle than that of the phagocytic cells.

  3. Relative humidity influence on the spreading dynamics of sessile drops of blood

    Science.gov (United States)

    Brutin, David; Bouzeid, Wassim

    2014-11-01

    We studied the effect of relative humidity on the initial stages of spreading dynamics for drops of whole human blood. A range of relative humidities from 8% to 90% was studied. Drops of the same volume were gently deposited on ultra-clean microscope glass substrates. We show that the drop spreading is driven by two distinct regimes. The first is characterized by fast dynamics and competition between viscous forces and capillary forces, whereas the second regime is characterized by competition between viscous dissipation and evaporation and exhibits slower dynamics. At early stages of spreading, the power law r(t) ~ tn (n = 0.65) was observed regardless of the humidity. At later stages of spreading, the exponent of the power law r(t) ~ tn (n = 0.19) was found to be higher than that of Tanner's law because of the effect of humidity and Marangoni stresses. Spreading time and spreading dynamics were found to be related to relative humidity. This is explained by the adhesion of red blood cells to the substrate that is similar to the mechanism observed for nanofluid droplets. The mean velocity of the triple line followed the same behavior as Tanner's model, where the final wetting radius and the apparent contact angle are functions of relative humidity.

  4. Local analysis of the contact region of an evaporating sessile drop

    Science.gov (United States)

    Morris, S. J. S.

    2014-11-01

    In experiments by Guéna et al. (2007), a drop of perfectly wetting pure liquid evaporates from a non-heated substrate at a rate controlled by vapour diffusion. The drop spreads until reaching a radius a determined by initial drop volume; the apparent contact line then reverses direction. The apparent contact angle measured at reversal was found experimentally to vary as a - 1 / 6 for a drops θ decreases more strongly. Local analysis (Morris, J. Fluid Mech. 739, 308 (2014)) predicts that θ ~a - 1 / 6 ; for the smaller drops obeying the 1/6th rule, predicted values agree with experiment to within 10-30%. Though the behaviour of drops smaller than the capillary length thus appears to be understood, that of larger drops is not.

  5. Elastomeric PDMS Planoconvex Lenses Fabricated by a Confined Sessile Drop Technique.

    Science.gov (United States)

    Ekgasit, S; Kaewmanee, N; Jangtawee, P; Thammacharoen, C; Donphoongpri, M

    2016-08-10

    The ubiquity of high quality smartphones at affordable prices not only accelerated the social penetration in the global population but also promoted nontraditional usage of smartphones as point-of-care medical diagnostic devices, sensors, and portable digital microscopes. This paper reveals a simple, rapid, cost-effective, and template-free technique for mass-scale production of an elastomeric PDMS (ePDMS) planoconvex lens capable of converting a smartphone into a portable digital microscope. By taking advantage of the resistance to spreading of liquid by a sharp edge, highly stable spherical cap of viscous liquid PDMS (lPDMS) on a smooth PMMA circular disk was fabricated. The axisymmetric spreading of lPDMS under the gravitational force and interfacial tension force enable the formation of spherical cap with a certain radius of curvature. A thermal treatment at 80 °C for 30 min cured the spherical cap lPDMS into a bubble-free ePDMS planoconvex lens. Lenses with focal lengths of 55.2-3.4 mm could be reproducibly fabricated by adjusting the volume of dispensed lPDMSs and diameter of PMMA disks. High-resolution panoramic microscope images without a distortion of small cylindrical object could be constructed on-the-fly using the imbedded smartphone app. Applications of the smartphone digital microscope equipped with an ePDMS planoconvex lens for imaging of micro printings, gun shot residues, cylindrical objects, and bullet toolmarks were explored.

  6. The sessile drop method for immunohistochemical processing of unmounted sections of nervous tissue.

    Science.gov (United States)

    Nadelhaft, I

    1984-12-01

    A novel method for the immunohistochemical processing of free-floating tissue sections is described. Sections are immersed within drops of solution arranged on a hydrophobic surface. The procedure consists of sequentially suctioning away one fluid drop and replacing it by another, while the section remains in place. The technique permits easy testing of different antiserum dilutions, comparisons among different immunohistochemical protocols, and comparison of different antisera on serial tissue sections. Comparison is made to processing mounted sections.

  7. Effect of substrate conductivity on the evaporation of small sessile droplets

    Science.gov (United States)

    Bazargan, Vahid; Stoeber, Boris

    2016-09-01

    Here we show the effect of the thermal conductivity of the substrate on the evaporation process of small droplets. We deposited small droplets on the order of 100 - 500 μ m in diameter on four different substrates with different thermal conductivities and surface properties, and we measured the evaporation time. Also, a numerical model that describes this process was developed to include thermal effects inside the droplet and heat transfer from the substrate. Our model considers the entire time of evaporation including the pinned and depinned stages. This model uses a new approach for the contact line behavior. It uses experimental results to define the movement of the contact line as a function of the contact angle.

  8. Larval anatomy of the pterobranch Cephalodiscus gracilis supports secondarily derived sessility concordant with molecular phylogenies

    Science.gov (United States)

    Stach, Thomas

    2013-12-01

    Pterobranchs have been interpreted as "missing links" combining primitive invertebrate features with advanced vertebrate-like characteristics. The first detailed morphological description of an ontogenetic stage of a pterobranch, based on digital 3D-reconstruction at electron microscopic resolution, reveals a triploblastic animal with monociliated epithelia, an extensive coelomic cavity, a through gut with an asymmetrically developed gill slit but no signs of planktonic specializations, such as ciliated bands. Therefore, this crawling larva supports the hypothesis proposed in previous molecular phylogenetic studies that pterobranchs could be derived within enteropneusts rather than being "missing links".

  9. NCBI nr-aa BLAST: CBRC-BTAU-01-3033 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-BTAU-01-3033 ref|ZP_00977438.1| COG2207: AraC-type DNA-binding domain-containing proteins [Burkholder...ia cenocepacia PC184] ref|YP_623398.1| transcriptional regulator, AraC family [Burkholder...ia cenocepacia AU 1054] ref|YP_838462.1| transcriptional regulator, AraC family [Burkholderia cenocepaci...a HI2424] gb|ABF78425.1| transcriptional regulator, AraC family [Burkholderia cen...ocepacia AU 1054] gb|ABK11569.1| transcriptional regulator, AraC family [Burkholderia cenocepacia HI2424] gb

  10. NCBI nr-aa BLAST: CBRC-AGAM-04-0109 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-AGAM-04-0109 ref|ZP_01563785.1| NADH:flavin oxidoreductase/NADH oxidase [Burkholderia... cenocepacia MC0-3] gb|EAV58290.1| NADH:flavin oxidoreductase/NADH oxidase [Burkholderia cenocepacia ...MC0-3] gb|EAY65940.1| NADH:flavin oxidoreductase/NADH oxidase [Burkholderia cenocepacia PC184] ZP_01563785.1 4.6 26% ...

  11. Hysteresis of Contact Angle of Sessile Droplets on Smooth Homogeneous Solid Substrates via Disjoining/Conjoining Pressure.

    Science.gov (United States)

    Kuchin, I; Starov, V

    2015-05-19

    A theory of contact angle hysteresis of liquid droplets on smooth, homogeneous solid substrates is developed in terms of the shape of the disjoining/conjoining pressure isotherm and quasi-equilibrium phenomena. It is shown that all contact angles, θ, in the range θr contact angle θ ≠ θe, correspond to the state of slow "microscopic" advancing or receding motion of the liquid if θe contact angle reaches the critical values θa or θr, correspondingly. The values of the static receding, θr, and static advancing, θa, contact angles in cylindrical capillaries were calculated earlier, based on the shape of disjoining/conjoining pressure isotherm. It is shown now that (i) both advancing and receding contact angles of a droplet on a on smooth, homogeneous solid substrate can be calculated based on shape of disjoining/conjoining pressure isotherm, and (ii) both advancing and receding contact angles depend on the drop volume and are not unique characteristics of the liquid-solid system. The latter is different from advancing/receding contact angles in thin capillaries. It is shown also that the receding contact angle is much closer to the equilibrium contact angle than the advancing contact angle. The latter conclusion is unexpected and is in a contradiction with the commonly accepted view that the advancing contact angle can be taken as the first approximation for the equilibrium contact angle. The dependency of hysteresis contact angles on the drop volume has a direct experimental confirmation.

  12. 3D computation of an incipient motion of a sessile drop on a rigid surface with contact angle hysteresis

    Science.gov (United States)

    Linder, Nicklas; Criscione, Antonio; Roisman, Ilia V.; Marschall, Holger; Tropea, Cameron

    2015-12-01

    Contact line phenomena govern a large number of multiphase flows. A reliable description of the contact line dynamics is therefore essential for prediction of such flows. Well-known difficulties of computation of the wetting phenomena include the mesh dependence of the results caused by flow singularity near the contact line and accurate estimation of its propagating velocity. The present study deals with the computational problem arising from the discontinuity in the dependence of the dynamic contact angle on the propagation velocity, associated with the contact angle hysteresis. The numerical simulations are performed using the volume of fluid method. The boundary conditions in the neighborhood of the contact line are switched depending on the value of the computed current local contact angle between a propagating contact line and a pinning condition. The method is applied to the simulation of the deformation and incipient motion of a shedding drop. The model is validated by comparison of the numerical predictions with experimental data.

  13. Size-selective sliding of sessile drops on a slightly inclined plane using low-frequency AC electrowetting.

    Science.gov (United States)

    Hong, Jiwoo; Lee, Seung Jun; Koo, Bonchull C; Suh, Yong Kweon; Kang, Kwan Hyoung

    2012-04-17

    When placed on an inclined solid plane, drops often stick to the solid surface due to pinning forces caused by contact angle hysteresis. When the drop size or the plane's incline angle is small, the drop is difficult to slide due to a decrease in gravitational force. Here we demonstrate that small drops (0.4-9 μL) on a slightly inclined plane (~12°, Teflon and parylene-C surface) can be mobilized through patterned electrodes by applying low-frequency ac electrowetting under 400 Hz (110-180 V(rms)), which has a mechanism different from that of the high-frequency ac method that induces sliding by reducing contact angle hysteresis. We attribute the sliding motion of our method to a combination of contact angle hysteresis and interfacial oscillation driven by ac electrowetting instead of the minimization of contact angle hysteresis at a high frequency. We investigated the effects of ac frequency on the sliding motion and terminal sliding of drops; the terminal sliding velocity is greatest at resonance frequency. Varying the electrowetting number (0.21-0.56) at a fixed frequency (40 Hz) for 5 μL drops, we found an empirical relationship between the electrowetting number and the terminal sliding velocity. Using the relationship between the drop size and ac frequency, we can selectively slide drops of a specific size or merge two drops along an inclined plane. This simple method will help with constructing microfluidic platforms with sorting, merging, transporting, and mixing of drops without a programmable control of electrical signals. Also, this method has a potential in heat transfer applications because heat removal capacity can be enhanced significantly through drop oscillation.

  14. Parametric instability of a liquid metal sessile drop under the action of low-frequency alternating magnetic fields

    Institute of Scientific and Technical Information of China (English)

    LEI Zuo-sheng; GUO Jia-hong; REN Zhong-ming

    2013-01-01

    A 2-D mathematical model is developed in order to simulate a parametric electromagnetic instability oscillation process of a liquid metal droplet under the action of low frequency magnetic field.The Arbitrary Lagrangian-Eulerian (ALE) method and weak form constraint boundary condition are introduced in this model for implementation of the surface tension and electromagnetic force on liquid droplet free surface.The results of the numerical calculations indicate the appearance of various regimes of oscillation.It is found that according to the magnetic field frequency various types of oscillation modes may be found.The oscillation is originated from an instability phenomenon.The stability diagram of liquid metal droplet in the parameter space of magnetic frequency and magnetic flux density is determined numerically.The diagram is very similar to that found in the so-called parametric instability.

  15. Observations of internal flow inside an evaporating nanofluid sessile droplet in the presence of an entrapped air bubble

    Science.gov (United States)

    Shin, Dong Hwan; Allen, Jeffrey S.; Lee, Seong Hyuk; Choi, Chang Kyoung

    2016-09-01

    Using a unique, near-field microscopy technique, fringe patterns and nanoparticle motions are visualized immediately following a nanofluid droplet deposition on a glass substrate in which an air bubble is entrapped. The nanofluid consists of DI-water, 0.10% Aluminum Oxide nanoparticles with an average diameter of 50 nm, and 0.0005% yellow-green polystyrene fluorescent particles of 1 μm diameter. High-speed, fluorescent-mode confocal imaging enables investigation of depth-wise sectioned particle movements in the nanofluid droplet inside which a bubble is entrapped. The static contact angle is increased when a bubble is applied. In the presence of the bubble in the droplet, the observed flow toward the center of the droplet is opposite to the flow observed in a droplet without the bubble. When the bubble is present, the evaporation process is retarded. Also, random motion is observed in the contact line region instead of the typical evaporation-driven flow toward the droplet edge. Once the bubble bursts, however, the total evaporation time decreases due to the change in the contact line characteristics. Moreover, the area of fringe patterns beneath the bubble increases with time. Discussed herein is a unique internal flow that has not been observed in nanofluid droplet evaporation.

  16. Thermocapillary-driven motion of a sessile drop: effect of non-monotonic dependence of surface tension on temperature.

    Science.gov (United States)

    Karapetsas, George; Sahu, Kirti Chandra; Sefiane, Khellil; Matar, Omar K

    2014-04-22

    We study the thermocapillary-driven spreading of a droplet on a nonuniformly heated substrate for fluids associated with a non-monotonic dependence of the surface tension on temperature. We use lubrication theory to derive an evolution equation for the interface that accounts for capillarity and thermocapillarity. The contact line singularity is relieved by using a slip model and a Cox-Voinov relation; the latter features equilibrium contact angles that vary depending on the substrate wettability, which, in turn, is linked to the local temperature. We simulate the spreading of droplets of fluids whose surface tension-temperature curves exhibit a turning point. For cases wherein these turning points correspond to minima, and when these minima are located within the droplet, then thermocapillary stresses drive rapid spreading away from the minima. This gives rise to a significant acceleration of the spreading whose characteristics resemble those associated with the "superspreading" of droplets on hydrophobic substrates. No such behavior is observed for cases in which the turning point corresponds to a surface tension maximum.

  17. The effect of temperature and gas Reynolds number on evaporation of a sessile liquid drop in mini-channel

    Directory of Open Access Journals (Sweden)

    Orlik Evgeniy

    2016-01-01

    Full Text Available Experimental setup has been designed and manufactured to study the evaporation processes of liquid drop under blowing gas in mini-channel. The height of channel can be varied from 3 to 20 mm. Substrates are removable and its surface temperature is kept to constant value. The shadow method is main measurement technique. Series of experiments with 100 μl water drop on polished stainless still substrate are carried out in channel with 9 mm height. Dependences of evaporating rate for different range of temperatures and gas Reynolds numbers are obtained.

  18. The effect of temperature and gas Reynolds number on evaporation of a sessile liquid drop in mini-channel

    OpenAIRE

    Orlik Evgeniy; Bykovskaya Elena; Bai Bo-Feng

    2016-01-01

    Experimental setup has been designed and manufactured to study the evaporation processes of liquid drop under blowing gas in mini-channel. The height of channel can be varied from 3 to 20 mm. Substrates are removable and its surface temperature is kept to constant value. The shadow method is main measurement technique. Series of experiments with 100 μl water drop on polished stainless still substrate are carried out in channel with 9 mm height. Dependences of evaporating rate for different ra...

  19. Evaporation of Binary Sessile Drops: Infrared and Acoustic Methods To Track Alcohol Concentration at the Interface and on the Surface.

    Science.gov (United States)

    Chen, Pin; Toubal, Malika; Carlier, Julien; Harmand, Souad; Nongaillard, Bertrand; Bigerelle, Maxence

    2016-09-27

    Evaporation of droplets of three pure liquids (water, 1-butanol, and ethanol) and four binary solutions (5 wt % 1-butanol-water-based solution and 5, 25, and 50 wt % ethanol-water-based solutions) deposited on hydrophobic silicon was investigated. A drop shape analyzer was used to measure the contact angle, diameter, and volume of the droplets. An infrared camera was used for infrared thermal mapping of the droplet's surface. An acoustic high-frequency echography technique was, for the first time, applied to track the alcohol concentration in a binary-solution droplet. Evaporation of pure alcohol droplets was executed at different values of relative humidity (RH), among which the behavior of pure ethanol evaporation was notably influenced by the ambient humidity as a result of high hygrometry. Evaporation of droplets of water and binary solutions was performed at a temperature of 22 °C and a mean humidity of approximately 50%. The exhaustion times of alcohol in the droplets estimated by the acoustic method and the visual method were similar for the water-1-butanol mixture; however, the time estimated by the acoustic method was longer when compared with that estimated by the visual method for the water-ethanol mixture due to the residual ethanol at the bottom of the droplet.

  20. Sessile serrated polyps of the colorectum are rare in patients with Lynch syndrome and in familial colorectal cancer families

    DEFF Research Database (Denmark)

    Andersen, S H; Lykke, E; Folker, M B;

    2008-01-01

    (FCF) is addressed. Polyps coded as hyperplastic polyps (HP) from subjects with Lynch syndrome and FCF enrolled in the HNPCC-register at the Hvidovre University Hospital as well as adenomas from this population were retrieved and reviewed for features of SSP. Ninety-eight polyps coded as HP and 41...

  1. Dynamics of development and dispersal in sessile microbial communities: examples from Pseudomonas aeruginosa and Pseudomonas putida model biofilms

    DEFF Research Database (Denmark)

    Klausen, M.; Gjermansen, Morten; Kreft, J.-U.;

    2006-01-01

    Surface-associated microbial communities in many cases display dynamic developmental patterns. Model biofilms formed by Pseudomonas aeruginosa and Pseudomonas putida in laboratory flow-chamber setups represent examples of such behaviour. Dependent on the experimental conditions the bacteria...... organisms do not possess comprehensive genetic programs for biofilm development. Instead the bacteria appear to have evolved a number of different mechanisms to optimize surface colonization, of which they express a subset in response to the prevailing environmental conditions. These mechanisms include...

  2. NCBI nr-aa BLAST: CBRC-AGAM-03-0072 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-AGAM-03-0072 ref|ZP_01560354.1| hypothetical protein Bcenmc03DRAFT_5869 [Burkholderia... cenocepacia MC0-3] gb|EAV62210.1| hypothetical protein Bcenmc03DRAFT_5869 [Burkholderia cenocepacia MC0-3] ZP_01560354.1 0.002 26% ...

  3. NCBI nr-aa BLAST: CBRC-PHAM-01-1691 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-PHAM-01-1691 ref|YP_001773964.1| hypothetical protein Bcenmc03_6354 [Burkholderia... cenocepacia MC0-3] gb|ACA95469.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] YP_001773964.1 2e-67 45% ...

  4. NCBI nr-aa BLAST: CBRC-FCAT-01-1259 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-FCAT-01-1259 ref|ZP_01559985.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV61841.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01559985.1 1e-19 42% ...

  5. NCBI nr-aa BLAST: CBRC-RNOR-09-0007 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-RNOR-09-0007 ref|YP_621794.1| hypothetical protein Bcen_1918 [Burkholderia cen...ocepacia AU 1054] gb|ABF76821.1| conserved hypothetical protein [Burkholderia cenocepacia AU 1054] YP_621794.1 1e-53 70% ...

  6. NCBI nr-aa BLAST: CBRC-BTAU-01-1684 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-BTAU-01-1684 ref|YP_838849.1| Haemagluttinin domain protein [Burkholderia ceno...cepacia HI2424] gb|ABK11956.1| Haemagluttinin domain protein [Burkholderia cenocepacia HI2424] YP_838849.1 0.001 27% ...

  7. NCBI nr-aa BLAST: CBRC-AGAM-03-0017 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-AGAM-03-0017 ref|ZP_01561792.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV60539.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01561792.1 0.004 27% ...

  8. NCBI nr-aa BLAST: CBRC-CREM-01-1290 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CREM-01-1290 ref|ZP_01562587.1| uracil-xanthine permease [Burkholderia cenocep...acia MC0-3] gb|EAV59325.1| uracil-xanthine permease [Burkholderia cenocepacia MC0-3] ZP_01562587.1 2e-94 68% ...

  9. NCBI nr-aa BLAST: CBRC-AGAM-03-0072 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-AGAM-03-0072 ref|ZP_01567096.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV54827.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01567096.1 3e-05 26% ...

  10. NCBI nr-aa BLAST: CBRC-FCAT-01-0154 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-FCAT-01-0154 ref|ZP_01567157.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV54750.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01567157.1 0.030 31% ...

  11. NCBI nr-aa BLAST: CBRC-XTRO-01-0143 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0143 ref|ZP_01560289.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV62145.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01560289.1 0.001 27% ...

  12. NCBI nr-aa BLAST: CBRC-PMAR-01-0763 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-PMAR-01-0763 ref|YP_623013.1| Haemagluttinin motif protein [Burkholderia cenoc...epacia AU 1054] gb|ABF78040.1| Haemagluttinin motif protein [Burkholderia cenocepacia AU 1054] YP_623013.1 3e-71 28% ...

  13. NCBI nr-aa BLAST: CBRC-XTRO-01-2343 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-2343 ref|YP_626365.1| Outer membrane autotransporter barrel [Burkholderia... cenocepacia AU 1054] gb|ABF81392.1| Outer membrane autotransporter barrel [Burkholderia cenocepacia AU 1054] YP_626365.1 6e-04 29% ...

  14. NCBI nr-aa BLAST: CBRC-PMAR-01-0718 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-PMAR-01-0718 ref|YP_838849.1| Haemagluttinin domain protein [Burkholderia ceno...cepacia HI2424] gb|ABK11956.1| Haemagluttinin domain protein [Burkholderia cenocepacia HI2424] YP_838849.1 4e-85 26% ...

  15. NCBI nr-aa BLAST: CBRC-CBRE-01-0787 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CBRE-01-0787 ref|YP_840388.1| PE-PGRS family protein [Burkholderia cenocepacia... HI2424] gb|ABK13495.1| PE-PGRS family protein [Burkholderia cenocepacia HI2424] YP_840388.1 7e-04 28% ...

  16. NCBI nr-aa BLAST: CBRC-CJAC-01-0283 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CJAC-01-0283 ref|YP_840388.1| PE-PGRS family protein [Burkholderia cenocepacia... HI2424] gb|ABK13495.1| PE-PGRS family protein [Burkholderia cenocepacia HI2424] YP_840388.1 2e-09 26% ...

  17. NCBI nr-aa BLAST: CBRC-XTRO-01-0143 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0143 ref|ZP_01564992.1| hypothetical protein Bcenmc03DRAFT_7449 [Burkholder...ia cenocepacia MC0-3] gb|EAV57107.1| hypothetical protein Bcenmc03DRAFT_7449 [Burkholderia cenocepacia MC0-3] ZP_01564992.1 0.002 23% ...

  18. NCBI nr-aa BLAST: CBRC-CJAC-01-1085 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CJAC-01-1085 ref|ZP_01559985.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV61841.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01559985.1 2e-58 63% ...

  19. NCBI nr-aa BLAST: CBRC-PVAM-01-0739 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-PVAM-01-0739 ref|YP_626364.1| PE-PGRS family protein [Burkholderia cenocepacia... AU 1054] gb|ABF81391.1| PE-PGRS family protein [Burkholderia cenocepacia AU 1054] YP_626364.1 5e-10 26% ...

  20. NCBI nr-aa BLAST: CBRC-FRUB-02-0738 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-FRUB-02-0738 ref|ZP_01567160.1| Haemagluttinin motif [Burkholderia cenocepacia... MC0-3] gb|EAV54748.1| Haemagluttinin motif [Burkholderia cenocepacia MC0-3] ZP_01567160.1 4e-24 29% ...

  1. NCBI nr-aa BLAST: CBRC-DMEL-08-0031 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-DMEL-08-0031 ref|YP_838849.1| Haemagluttinin domain protein [Burkholderia ceno...cepacia HI2424] gb|ABK11956.1| Haemagluttinin domain protein [Burkholderia cenocepacia HI2424] YP_838849.1 3e-09 31% ...

  2. NCBI nr-aa BLAST: CBRC-CREM-01-1362 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CREM-01-1362 ref|ZP_01564035.1| 200 kDa antigen p200, putative [Burkholderia c...enocepacia MC0-3] gb|EAV58079.1| 200 kDa antigen p200, putative [Burkholderia cenocepacia MC0-3] ZP_01564035.1 7e-36 33% ...

  3. NCBI nr-aa BLAST: CBRC-DSIM-01-0065 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-DSIM-01-0065 ref|ZP_01559985.1| conserved hypothetical protein [Burkholderia c...enocepacia MC0-3] gb|EAV61841.1| conserved hypothetical protein [Burkholderia cenocepacia MC0-3] ZP_01559985.1 8e-50 46% ...

  4. NCBI nr-aa BLAST: CBRC-RNOR-23-0023 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-RNOR-23-0023 ref|YP_840446.1| YadA C-terminal domain protein [Burkholderia cen...ocepacia HI2424] gb|ABK13553.1| YadA C-terminal domain protein [Burkholderia cenocepacia HI2424] YP_840446.1 1.0 31% ...

  5. NCBI nr-aa BLAST: CBRC-PMAR-01-0179 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-PMAR-01-0179 ref|ZP_01560690.1| hypothetical protein Bcenmc03DRAFT_2689 [Burkh...olderia cenocepacia MC0-3] gb|EAV61335.1| hypothetical protein Bcenmc03DRAFT_2689 [Burkholderia cenocepacia MC0-3] ZP_01560690.1 3e-07 28% ...

  6. NCBI nr-aa BLAST: CBRC-BTAU-01-2512 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-BTAU-01-2512 ref|ZP_01560879.1| hypothetical protein Bcenmc03DRAFT_2878 [Burkh...olderia cenocepacia MC0-3] gb|EAV61524.1| hypothetical protein Bcenmc03DRAFT_2878 [Burkholderia cenocepacia MC0-3] ZP_01560879.1 0.005 27% ...

  7. NCBI nr-aa BLAST: CBRC-XTRO-01-2967 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-2967 ref|ZP_01566576.1| hypothetical protein Bcenmc03DRAFT_1196 [Burkh...olderia cenocepacia MC0-3] gb|EAV55453.1| hypothetical protein Bcenmc03DRAFT_1196 [Burkholderia cenocepacia MC0-3] ZP_01566576.1 4e-25 22% ...

  8. NCBI nr-aa BLAST: CBRC-FCAT-01-0851 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-FCAT-01-0851 ref|ZP_01560690.1| hypothetical protein Bcenmc03DRAFT_2689 [Burkh...olderia cenocepacia MC0-3] gb|EAV61335.1| hypothetical protein Bcenmc03DRAFT_2689 [Burkholderia cenocepacia MC0-3] ZP_01560690.1 0.039 33% ...

  9. NCBI nr-aa BLAST: CBRC-AGAM-03-0017 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-AGAM-03-0017 ref|ZP_01562088.1| hypothetical protein Bcenmc03DRAFT_2302 [Burkh...olderia cenocepacia MC0-3] gb|EAV60091.1| hypothetical protein Bcenmc03DRAFT_2302 [Burkholderia cenocepacia MC0-3] ZP_01562088.1 4e-04 26% ...

  10. NCBI nr-aa BLAST: CBRC-AGAM-01-0052 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-AGAM-01-0052 ref|ZP_01564777.1| hypothetical protein Bcenmc03DRAFT_4887 [Burkh...olderia cenocepacia MC0-3] gb|EAV57364.1| hypothetical protein Bcenmc03DRAFT_4887 [Burkholderia cenocepacia MC0-3] ZP_01564777.1 5e-05 28% ...

  11. NCBI nr-aa BLAST: CBRC-FCAT-01-0154 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-FCAT-01-0154 ref|ZP_01560690.1| hypothetical protein Bcenmc03DRAFT_2689 [Burkh...olderia cenocepacia MC0-3] gb|EAV61335.1| hypothetical protein Bcenmc03DRAFT_2689 [Burkholderia cenocepacia MC0-3] ZP_01560690.1 0.039 33% ...

  12. NCBI nr-aa BLAST: CBRC-OCUN-01-1280 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-OCUN-01-1280 ref|ZP_01566981.1| hypothetical protein Bcenmc03DRAFT_7238 [Burkh...olderia cenocepacia MC0-3] gb|EAV54955.1| hypothetical protein Bcenmc03DRAFT_7238 [Burkholderia cenocepacia MC0-3] ZP_01566981.1 1.1 38% ...

  13. NCBI nr-aa BLAST: CBRC-XTRO-01-3129 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-3129 ref|ZP_01566576.1| hypothetical protein Bcenmc03DRAFT_1196 [Burkh...olderia cenocepacia MC0-3] gb|EAV55453.1| hypothetical protein Bcenmc03DRAFT_1196 [Burkholderia cenocepacia MC0-3] ZP_01566576.1 2e-37 47% ...

  14. NCBI nr-aa BLAST: CBRC-XTRO-01-0105 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0105 ref|ZP_01566576.1| hypothetical protein Bcenmc03DRAFT_1196 [Burkh...olderia cenocepacia MC0-3] gb|EAV55453.1| hypothetical protein Bcenmc03DRAFT_1196 [Burkholderia cenocepacia MC0-3] ZP_01566576.1 4e-12 21% ...

  15. NCBI nr-aa BLAST: CBRC-CJAC-01-0227 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-CJAC-01-0227 ref|ZP_01566546.1| Collagen triple helix repeat [Burkholderia cen...ocepacia MC0-3] gb|EAV55423.1| Collagen triple helix repeat [Burkholderia cenocepacia MC0-3] ZP_01566546.1 2e-18 52% ...

  16. NCBI nr-aa BLAST: CBRC-GACU-01-0025 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-GACU-01-0025 ref|ZP_01566546.1| Collagen triple helix repeat [Burkholderia cen...ocepacia MC0-3] gb|EAV55423.1| Collagen triple helix repeat [Burkholderia cenocepacia MC0-3] ZP_01566546.1 8e-15 33% ...

  17. Comparing the chlorine disinfection of detached biofilm clusters with those of sessile biofilms and planktonic cells in single- and dual-species cultures.

    Science.gov (United States)

    Behnke, Sabrina; Parker, Albert E; Woodall, Dawn; Camper, Anne K

    2011-10-01

    Although the detachment of cells from biofilms is of fundamental importance to the dissemination of organisms in both public health and clinical settings, the disinfection efficacies of commonly used biocides on detached biofilm particles have not been investigated. Therefore, the question arises whether cells in detached aggregates can be killed with disinfectant concentrations sufficient to inactivate planktonic cells. Burkholderia cepacia and Pseudomonas aeruginosa were grown in standardized laboratory reactors as single species and in coculture. Cluster size distributions in chemostats and biofilm reactor effluent were measured. Chlorine susceptibility was assessed for planktonic cultures, attached biofilm, and particles and cells detached from the biofilm. Disinfection tolerance generally increased with a higher percentage of larger cell clusters in the chemostat and detached biofilm. Samples with a lower percentage of large clusters were more easily disinfected. Thus, disinfection tolerance depended on the cluster size distribution rather than sample type for chemostat and detached biofilm. Intact biofilms were more tolerant to chlorine independent of species. Homogenization of samples led to significantly increased susceptibility in all biofilm samples as well as detached clusters for single-species B. cepacia, B. cepacia in coculture, and P. aeruginosa in coculture. The disinfection efficacy was also dependent on species composition; coculture was advantageous to the survival of both species when grown as a biofilm or as clusters detached from biofilm but, surprisingly, resulted in a lower disinfection tolerance when they were grown as a mixed planktonic culture.

  18. Ultrastructure of the ciliated cells of the free-swimming larva, and sessile stages, of the marine sponge Haliclona indistincta (Demospongiae: Haplosclerida).

    Science.gov (United States)

    Stephens, Kelly M; Ereskovsky, Alexander; Lalor, Pierce; McCormack, Grace P

    2013-11-01

    We provide a detailed, comparative study of the ciliated cells of the marine haplosclerid sponge Haliclona indistincta, in order to make data available for future phylogenetic comparisons at the ultrastructural level. Our study focuses on the description and analysis of the larval epithelial cells, and choanocytes of the metamorphosed juvenile sponge. The ultrastructure of the two cell types is sufficiently different to prevent our ability to conclusively determine the origin of the choanocytes from the larval ciliated cells. However, ciliated, epithelial cells were observed in a migratory position within the inner cell mass of the larval stages. Some cilia were observed within the cell's cytoplasm, which is indicative of the ciliated epithelial cell undergoing transdifferentiation into a choanocyte; while traces of other ciliated epithelial cells were contained within phagosomes, suggesting they are phagocytosed. We compared our data with other species described in the literature. However, any phylogenetic inference must wait until further detailed comparisons can be made with species whose phylogenetic position has been determined by other means, such as phylogenomics, in order to more closely link genomic, and morphological information.

  19. Conserving biodiversity in a human-dominated world: degradation of marine sessile communities within a protected area with conflicting human uses.

    Directory of Open Access Journals (Sweden)

    Valeriano Parravicini

    Full Text Available Conservation research aims at understanding whether present protection schemes are adequate for the maintenance of ecosystems structure and function across time. We evaluated long-term variation in rocky reef communities by comparing sites surveyed in 1993 and again in 2008. This research took place in Tigullio Gulf, an emblematic case study where various conservation measures, including a marine protected area, have been implemented to manage multiple human uses. Contrary to our prediction that protection should have favored ecosystem stability, we found that communities subjected to conservation measures (especially within the marine protected area exhibited the greatest variation toward architectural complexity loss. Between 1993 and 2008, chronic anthropogenic pressures (especially organic load that had already altered unprotected sites in 1993 expanded their influence into protected areas. This expansion of human pressure likely explains our observed changes in the benthic communities. Our results suggest that adaptive ecosystem-based management (EBM, that is management taking into account human interactions, informed by continuous monitoring, is needed in order to attempt reversing the current trend towards less architecturally complex communities. Protected areas are not sufficient to stop ecosystem alteration by pressures coming from outside. Monitoring, and consequent management actions, should therefore extend to cover the relevant scales of those pressures.

  20. Identification of adaptation-specific differences in mRNA expression of sessile and pedunculate oak based on osmotic-stress-induced genes.

    Science.gov (United States)

    Porth, Ilga; Koch, Margit; Berenyi, Maria; Burg, Agnes; Burg, Kornel

    2005-10-01

    Quercus petraea (Matt.) Liebl. and Q. robur L. hybridize frequently and occupy similar, though distinct, ecological niches. So far, genetic discrimination between these species at the molecular level has been based mainly on neutral markers. Because such markers often exhibit low species differentiation because of high genetic compatibility and exchange between Q. robur and Q. petraea at these loci, we used adaptation-related expressed genes as markers. Accordingly, we identified osmotic-stress-induced genes in a Q. petraea cell line grown under moderate osmotic stress conditions. Two subtraction libraries were established from callus cells cultured under hyperosmotic stress for 1 or 48 h. Thirty-three differentially expressed sequence tags (ESTs) (from 70 originally isolated) were classified according to their putative functions. At least five of these gene products may contribute to osmotic-stress tolerance in oak: betaine aldehyde dehydrogenase, two trans-acting transcription factors (one abscsic acid (ABA)-responsive, the other ABA-independent), a glutathione-S- transferase and a heat-shock cognate protein. Seven genes were selected based on their putative function and their expression monitored in vivo. Leaf tissue from Q. petraea and Q. robur plantlets grown hydroponically under hyperosmotic conditions was harvested after 0, 1, 6, 24 or 72 h and analyzed by real-time polymerase chain reaction (PCR). We found indications of osmotic stress adaptation in Q. petraea based on up-regulation of genes related to protective functions, whereas down-regulation of these genes was evident in Q. robur. Thus, genetic markers related to adaptive traits may be useful for differentiating Q. petraea and Q. robur genotypes.

  1. In vitro activity of the new water-dispersible Fe{sub 3}O{sub 4}@usnic acid nanostructure against planktonic and sessile bacterial cells

    Energy Technology Data Exchange (ETDEWEB)

    Grumezescu, Alexandru Mihai, E-mail: grumezescu@yahoo.com [Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Department of Science and Engineering of Oxidic Materials and Nanomaterials (Romania); Cotar, Ani Ioana [Faculty of Biology, University of Bucharest, Department of Microbiology Immunology (Romania); Andronescu, Ecaterina; Ficai, Anton; Ghitulica, Cristina Daniela; Grumezescu, Valentina; Vasile, Bogdan Stefan [Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, Department of Science and Engineering of Oxidic Materials and Nanomaterials (Romania); Chifiriuc, Mariana Carmen [Faculty of Biology, University of Bucharest, Department of Microbiology Immunology (Romania)

    2013-07-15

    A new water-dispersible nanostructure based on magnetite (Fe{sub 3}O{sub 4}) and usnic acid (UA) was prepared in a well-shaped spherical form by a precipitation method. Nanoparticles were well individualized and homogeneous in size. The presence of Fe{sub 3}O{sub 4}@UA was confirmed by transmission electron microscopy, Fourier transform-infrared spectroscopy, and X-ray diffraction. The UA was entrapped in the magnetic nanoparticles during preparation and the amount of entrapped UA was estimated by thermogravimetric analysis. Fabricated nanostructures were tested on planktonic cells growth (minimal inhibitory concentration assay) and biofilm development on Gram-positive Staphylococcusaureus (S.aureus),Enterococcus faecalis (E.faecalis) and Gram-negative Escherichia coli (E.coli),Pseudomonasaeruginosa (P.aeruginosa) reference strains. Concerning the influence of Fe{sub 3}O{sub 4}@UA on the planktonic bacterial cells, the functionalized magnetic nanoparticles exhibited a significantly improved antimicrobial activity against E.faecalis and E.coli, as compared with the Fe{sub 3}O{sub 4} control. The UA incorporated into the magnetic nanoparticles exhibited a very significant inhibitory effect on the biofilm formed by the S.aureus and E.faecalis, on a wide range of concentrations, while in case of the Gram-negative microbial strains, the UA-loaded nanoparticles inhibited the E.coli biofilm development, only at high concentrations, while for P.aeruginosa biofilms, no inhibitory effect was observed. The obtained results demonstrate that the new water-dispersible Fe{sub 3}O{sub 4}@UA nanosystem, combining the advantages of the intrinsic antimicrobial features of the UA with the higher surface to volume ratio provided by the magnetic nanocarrier dispersible in water, exhibits efficient antimicrobial activity against planktonic and adherent cells, especially on Gram-positive strains.

  2. In vitro activity of the new water-dispersible Fe3O4@usnic acid nanostructure against planktonic and sessile bacterial cells

    Science.gov (United States)

    Grumezescu, Alexandru Mihai; Cotar, Ani Ioana; Andronescu, Ecaterina; Ficai, Anton; Ghitulica, Cristina Daniela; Grumezescu, Valentina; Vasile, Bogdan Stefan; Chifiriuc, Mariana Carmen

    2013-07-01

    A new water-dispersible nanostructure based on magnetite (Fe3O4) and usnic acid (UA) was prepared in a well-shaped spherical form by a precipitation method. Nanoparticles were well individualized and homogeneous in size. The presence of Fe3O4@UA was confirmed by transmission electron microscopy, Fourier transform-infrared spectroscopy, and X-ray diffraction. The UA was entrapped in the magnetic nanoparticles during preparation and the amount of entrapped UA was estimated by thermogravimetric analysis. Fabricated nanostructures were tested on planktonic cells growth (minimal inhibitory concentration assay) and biofilm development on Gram-positive Staphylococcus aureus ( S. aureus), Enterococcus faecalis ( E. faecalis) and Gram-negative Escherichia coli ( E. coli), Pseudomonas aeruginosa (P. aeruginosa) reference strains. Concerning the influence of Fe3O4@UA on the planktonic bacterial cells, the functionalized magnetic nanoparticles exhibited a significantly improved antimicrobial activity against E. faecalis and E. coli, as compared with the Fe3O4 control. The UA incorporated into the magnetic nanoparticles exhibited a very significant inhibitory effect on the biofilm formed by the S. aureus and E. faecalis, on a wide range of concentrations, while in case of the Gram-negative microbial strains, the UA-loaded nanoparticles inhibited the E. coli biofilm development, only at high concentrations, while for P. aeruginosa biofilms, no inhibitory effect was observed. The obtained results demonstrate that the new water-dispersible Fe3O4@UA nanosystem, combining the advantages of the intrinsic antimicrobial features of the UA with the higher surface to volume ratio provided by the magnetic nanocarrier dispersible in water, exhibits efficient antimicrobial activity against planktonic and adherent cells, especially on Gram-positive strains.

  3. Quantifying genetic variations and phenotypic plasticity of leaf phenology and growth for two temperate Fagaceae species (sessile oak and european beech)

    Science.gov (United States)

    Delzon, Sylvain; Vitasse, Yann; Alberto, Florian; Bresson, Caroline; Kremer, Antoine

    2010-05-01

    Under current climate change, research on inherent adaptive capacities of organisms is crucial to assess future evolutionary changes of natural populations. Genetic diversity and phenotypic plasticity constitute adaptative capacities that could allow populations to respond to new environmental conditions. The aim of the present study was (i) to determine whether there are genetic variations among populations from altitudinal gradients using a lowland common garden experiment and (ii) to assess the magnitude of phenotypic plasticity using a reciprocal transplant experiment (5 elevations from 100 to 1600 m asl.) for leaf phenology (flushing and senescence) and growth of two fagaceae species (Fagus sylvatica and Quercus petraea). We found significant differences in phenology among provenances for most species, and evidenced that these among-population differences in phenology were related to annual temperature of the provenance sites for both species. It's noteworthy that, along the same climatic gradient, the species exhibited opposite genetic clines: beech populations from high elevation flushed earlier than those of low elevation, whereas we observed an opposite trend for oak. Finally, we highlighted that both phenology timing and growth rate were highly consistent year to year. The results demonstrated that in spite of the proximity of the populations in their natural area, altitude led to genetic differentiations in their phenology and growth. Moreover, a high phenological plasticity was found for both species. We evidenced that reaction norms of flushing timing to temperature followed linear clinal trends for both species with an average shift of 5.7 days per degree increase. Timing of leaf senescence exhibited hyperbolic trends for beech and no or slight trends for oak. Furthermore, within species, there was no difference in magnitude of phenological plasticity among populations neither for flushing, nor for senescence. Consequently, for both species, the growing season length increased to reach maximum values for annual temperature ranging from 10°C to 13°C according to the population. These adaptive capacities (genetic differentiations and high magnitude of plasticity) could allow populations to respond immediately to temperature variations in term of leaf phenology and then to cope with current climate change. Finally, we also highlight that current populations tend to occupy suboptimal environments, i.e, populations inhabit climates colder that their optimum.

  4. The effect of bacteriocin-producing Lactobacillus plantarum strains on the intracellular pH of sessile and planktonic Listeria monocytongenes single cells

    DEFF Research Database (Denmark)

    Nielsen, Dennis Sandris; Cho, Gyu-Sung; Hanak, Alexander

    2010-01-01

    A wide range of lactic acid bacteria (LAB) produce bacteriocins mainly active against other closely related LAB, but some bacteriocins are also active against the food-borne pathogen Listeria monocytogenes. With the aim of increasing food safety it has thus been considered to utilise bacteriocins...... unaffected after 5 h of co-culturing and after 8 h 50% of the cells still maintained pHi = 7. Higher concentrations of lactic acid were produced in liquid compared to a solid surface, and the different response of EGDe and N53-1 to the activities of the two L. plantarum strains probably reflect higher...... and/or bacteriocin-producing LAB as “natural” food preservatives in foods such as cheese, meat and ready-to-eat products. Some strains of Lactobacillus plantarum produce bacteriocins termed plantaricins. Using a single-cell based approach, the effect on the intracellular pH as a measure...

  5. INTERFACIAL TENSION MEASUREMENT BY SESSILE DROP METHOD COMBINING IMAGE ANALYSIS%躺滴法结合图像处理测量界面张力的方法

    Institute of Scientific and Technical Information of China (English)

    尚朝辉; 张贵才; 蒋平; 裴海华; 葛际江

    2008-01-01

    采用躺滴法结合图像处理来测量界面张力较大体系的界面张力.为了提取图像中的有效信息,需要对获得的图像进行预处理.图像预处理包括图像的裁剪,以获得图像的核心部分;绘制出裁剪后图像的灰度直方图得到该幅图像的阈值;利用阈值法将图像二值化.对二值图像进行边缘榆测得到其边界,再采用二次多项式拟合边界曲线,于是可以通过Bashforth-Adams方程计算得到该体系的界面张力.通过实验验证了该方法的计算结果具有较高的精度.

  6. A sessile drop setup for the time-resolved synchrotron study of solid-liquid interactions: Application to intermetallic formation in 55%Al-Zn alloys

    Energy Technology Data Exchange (ETDEWEB)

    Bernier, N., E-mail: n.bernier@yahoo.fr; De Bruyn, D.; De Craene, M.; Scheers, J.; Claessens, S. [OCAS N.V., ArcelorMittal Global R and D Gent, Pres. J.F. Kennedylaan 3, 9060 Zelzate (Belgium); Vaughan, G. B. M.; Vitoux, H.; Gleyzolle, H.; Gorges, B. [European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex (France)

    2014-04-28

    We introduce a dedicated setup for measuring by synchrotron diffraction in-situ crystallographic and chemical information at the solid–liquid interface. This setup mostly consists of a double-heating furnace composed of a resistive heating for the solid surface and an inductive heating to produce a liquid droplet. The available high energy and high flux beams allow the rapid reaction kinetics to be investigated with very good time resolution down to 1 ms. An application of this setup is illustrated for the growth mechanisms of intermetallic phases during the hot-dipping of steel in a 55%Al-Zn bath. Results show that the three η-Al{sub 5}Fe{sub 2}, θ-Al{sub 13}Fe{sub 4}, and α-Al{sub 8}Fe{sub 2}Si phases grow at different times and rates during the dipping process, whereas the face-centered cubic AlFe{sub 3} phase is not formed.

  7. Environmental scanning electron microscopy study of the fine structure of the triple line and cassie-wenzel wetting transition for sessile drops deposited on rough polymer substrates.

    Science.gov (United States)

    Bormashenko, Edward; Bormashenko, Yelena; Stein, Tamir; Whyman, Gene; Pogreb, Roman; Barkay, Zahava

    2007-04-10

    The wetting of rough honeycomb micrometrically scaled polymer substrates was studied. A very strong dependence of the apparent contact angle on the drop volume has been established experimentally. The environmental scanning electron microscopy study of the fine structure of the triple line is reported first. The triple line is not smooth and prefers grasping the polymer matrix over air holes. The precursor rim surrounding the drop has been observed. The revealed dependence of the apparent contact angle on the drop volume is explained by the transition between the pure Cassie and combined Wenzel-Cassie wetting regimes, which is induced by capillarity penetration of water into the holes of relief.

  8. Patterns of mast fruiting of common beech, sessile and common oak, Norway spruce and Scots pine in Central and Northern Europe

    DEFF Research Database (Denmark)

    Nussbaumer, Anita; Waldner, Peter; Etzold, Sophia

    2016-01-01

    and Scots pine in Central and Northern Europe over the last two to three decades. We analysed data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and additional Danish, German, Flemish and Swiss datasets.Within-plot synchrony...

  9. Mixed culture biofilms of Salmonella Typhimurium and cultivable indigenous microorganisms on lettuce show enhanced resistance of their sessile cells to cold oxygen plasma.

    Science.gov (United States)

    Jahid, Iqbal Kabir; Han, Noori; Zhang, Cheng-Yi; Ha, Sang-Do

    2015-04-01

    Control of foodborne pathogens in fresh produce is crucial for food safety, and numerous Salmonella Typhimurium (ST) outbreaks have been reported already. The present study was done to assess effectiveness of cold oxygen plasma (COP) against biofilms of ST mixed with cultivable indigenous microorganisms (CIM). ST and CIM were grown at 15 °C as monocultures and mixed cultures for planktonic state, biofilm on stainless steel, and lettuce leaves. Thereafter, the samples were treated with COP and surviving populations were counted using plate counting methods. Biofilms and stomatal colonization were examined using field emission scanning electron microscopy (FESEM) and food quality was assessed after treatment. Mixed cultures of ST and CIM showed an antagonistic interaction on lettuce but not on SS or in planktonic state. Mixed cultures showed significantly (p biofilms on lettuce but not on SS or planktonic state. Shift from smooth to rugose colony type was found for planktonic and for biofilms on SS but not on lettuce for ST. Mixed culture biofilms colonized stomata on the inside as demonstrated by FESEM. Although, lettuce quality was not affected by COP, this technology has to be optimized for further development of the successful inactivation of complex multispecies biofilm structures presented by real food environment.

  10. Using Sessile Drop Technique to Investigate Wettability of Nickel Based Ceramic Alloy%用座滴法考察金瓷润湿性的研究

    Institute of Scientific and Technical Information of China (English)

    麻健丰; 张大风; 刘传通; 李洪庆

    2003-01-01

    目的:介绍一种考察金瓷润湿性能的方法,通过对其接触角的测定,为金瓷润湿性的定量分析提供新的测量方法.方法:采用座滴法把置有瓷粉柱的合金板加热到1 100 ℃,维持30 min,拍照测定其接触角.结果:瓷粉在合金板上呈现一定的接触角,并能通过测量,计算出具体角度,能定量地反映合金与烤瓷的润湿性能.结论:座滴法首次应用于口腔临床修复金瓷润湿性能的定量分析测试.本实验揭示座滴法不失为一种准确、直接考察金瓷润湿性能的理想方法.

  11. Abundance and diversity patterns of the sessile macrobenthic community associated with environmental gradients in Vitória Harbor, southeastern Brazil

    Directory of Open Access Journals (Sweden)

    Ilana Rosental Zalmon

    2011-10-01

    Full Text Available Harbor terminals and urban sewage effluents affect the composition and distribution of epibenthic organisms. In this study, we hypothesized that the benthic community structure at the Vitoria Harbor changes spatially in a ~3 km scale, and that these changes are associated with environmental gradients resulting from point-source sewage and differences in the physical and chemical parameters of the water along the harbor access channel. Four sites, internal (PI, intermediate-internal (PMI, intermediate-external (PME and external (PE, varying from 0.5 to 4.0 km off the harbor, were sampled on five quadrats at six sampling dates (N = 30 per site. The epibenthic community on the shallow sublitoral rocky shore was sampled fortnightly from December 2005 to February 2006 by point-intersection method. A total of 27 taxa were registered with higher richness and diversity values at the external sites. The similarity analysis indicated two distinct systems, with the internal sites PI and PMI apart from the external PME and PE, which showed 97% of dissimilarity. While the internal sites presented some estuarine characteristics and a high coverage (> 60% of hydrozoans and bryozoans with silt/clay, the external ones showed coastal water influence and higher amounts of sedimentary material substrate (> 50%. This pattern reflects the estuarine gradient and the suspended sedimentary material at the internal sites, which is carried out to the external parts of the channel. The data showed two distinct benthic communities and support the hypothesis that the community structure varies along the harbor access channel in a gradient from the inner to the outer portion of the estuary.

  12. Detecting Technology for the Outline of Sessile Drop Based on the Computer Vision%基于计算机视觉的透明液滴外形的检测技术

    Institute of Scientific and Technical Information of China (English)

    张德奎; 马军山

    2007-01-01

    在微流体变焦透镜的研究中,准确检测电解小液滴外形随外加电压的变化情况对寻找材料和衡量微流体透镜性能起到了重要作用.同时,待测液滴的形状参数也是描述液体与特定材料之间亲和力和液滴物理特性的重要参数之一.根据最小二乘法原理,设计了基于图像采集与处理的液滴外形检测系统.搭建实验平台,通过摄像物镜和CCD采集处于一定容器中的液滴外形轮廓图像数据,再经过图像滤波、边缘增强、二值化等图像处理技术,最后以数学模型形式描述液滴轮廓边缘曲线,并对边缘曲线数据进行曲线拟合计算液滴与容器边缘的接触角度.

  13. Surface Tension and Density of Molten Borosilicate Glass Measured by Sessile Drop Method%低膨胀硼硅酸盐玻璃熔体密度和表面张力测量

    Institute of Scientific and Technical Information of China (English)

    李建强; 张晓瑞; 陆平

    2009-01-01

    采用静滴法测量并对比典型低膨胀硼硅酸盐玻璃和普通钠钙硅玻璃的熔体密度和表面张力.结果表明,硼硅酸盐玻璃的密度要低于钠钙硅玻璃,二者均随温度升高而线性降低.硼硅酸盐玻璃的热膨胀系数要低于普通钠钙硅玻璃.在1000~1200 ℃的温度区间内,钠钙硅玻璃的表面张力低于硼硅酸盐玻璃,均随温度升高而线性增加,表面张力温度系数分别为0.11867和0.27867.

  14. 液饼高度法研究固体表面的润湿性质%Study of wetting on solid surfaces by measuring height of large sessile drop

    Institute of Scientific and Technical Information of China (English)

    赵振国

    2001-01-01

    介绍了液饼高度法测定铺展系数的基本原理.测定了一些液体在石蜡和明胶薄膜上的铺展系数.结果表明,由铺展系数计算出的接触角与实测值相等.表面活性剂可改进润湿性质.

  15. Atividade antimicrobiana de óleos essenciais em bactérias patogênicas de origem alimentar Antimicrobial activity of essential oils against sessile and planktonic pathogens of food source

    Directory of Open Access Journals (Sweden)

    C. Valeriano

    2012-01-01

    Full Text Available Objetivou-se identificar e quantificar os constituintes e avaliar a atividade antimicrobiana dos óleos essenciais de Mentha piperita, Cymbopogon citratus, Ocimum basilicum e Origanum majorana contra cepas de Escherichia coli enteropatogênica, Salmonella enterica Enteritidis, Listeria monocytogenes e Enterobacter sakazaki. A obtenção dos óleos essenciais foi realizada a partir de folhas secas, empregando-se a técnica de hidrodestilação e utilizando-se a aparelho de Clevenger modificado. A atividade antibacteriana dos óleos essenciais foi determinada pelo método de difusão em ágar. Observou-se que os óleos essenciais inibiram o crescimento bacteriano, mas a efetividade foi variada. Entre os óleos essenciais testados, M. piperita apresentou maior atividade antibacteriana para E. coli, (8.106 UA mL-1 quando comparada as demais bactérias, atividade moderada para Salmonella enterica Enteritidis e Enterobacter sakazakii (1.706 e 3.200 UA mL-1 respectivamente e baixa atividade para Listeria monocytogenes (106,67 UA mL-1. Já óleo essencial de Cymbopogon citratus apresentou maior atividade antimicrobiana frente a E. coli (9.386 UA mL-1 e atividade moderada frente a Enterobacter sakazakii, Salmonella enterica Enteritidis e Listeria monocytogenes (2.773 UA mL-1 para ambas. Ocimum basilicum apresentou maior atividade antibacteriana frente E. coli e Enterobacter sakazakii (6.826 e 8.106 UA mL-1 respectivamente, moderada atividade frente a Salmonella enterica Enteritidis (1.600 UA mL-1 e não apresentou atividade frente a Listeria monocytogenes.Origanum majorana também foi testado neste estudo e apresentou maior atividade antimicrobiana frente E. coli (5.973 UA mL-1, atividade moderada para Salmonella enterica Enteritidis e Enterobacter sakazakii (1.706 e 2.346 UA mL-1 , respectivamente e não apresentou atividade para Listeria monocytogenes.ABSTRACT The objective of this work was to identify and quantify the constituents, and to evaluate the antimicrobial activity of the essential oils from Mentha piperita, Cymbopogon citratus, Ocimum basilicum and Origanum majorana, against enteropathogenic Escherichia coli, Salmonella enterica Enteritidis, Listeria monocytogenes and Enterobacter sakazakii. The essential oils were obtained from dried leaves by using the hydrodistillation technique and the modified Clevenger apparatus, and their bacterial activity was determined by using the agar diffusion technique. The essential oils inhibited bacterial growth, but their effectiveness was varied. Among the essential oils tested, that from M. piperita showed a greater antimicrobial activity against E. coli (8.106 UA mL-1, moderate activity for S. enterica Enteritidis and E. sakazakii (1.706 e 3.200 UA mL-1 respectively and low activity for L. monocytogenes (106,67 UA mL-1. However, the essential oil from C. citratus presented a greater antimicrobial activity against E. coli (9.386 UA mL-1 and a moderate activity against E. sakazakii, S. enterica Enteritidis and L. monocytogenes (2.773 UA mL-1 for both. The essential oil from O. basilicum showed a greater antimicrobial activity against E. coli and E. sakazakii (6.826 e 8.106 UA mL-1 respectively,moderate activity against S. enterica Enteritidis (1.600 UA mL-1, and was inactive against L, monocytogenes. Origanum majorana, which was also tested in our work, showed a greater antibacterial activity against E. coli, (5.973 UA mL-1 moderate activity against S. enterica Enteritidis and E. sakazakii (1.706 e 2.346 UA mL-1 , respectively, and was inactive against L. monocytogenes.

  16. Measurement of Contact Angle of Water on Silicone Polymer Surface by Height of Large Drop Sessile Method%用液饼高度法测定水在硅聚合物表面的接触角

    Institute of Scientific and Technical Information of China (English)

    陈建梅; 朱方; 顾浩

    2011-01-01

    用半永久性离型剂(SP离型剂)涂复模具可以连续使用几十次到近百次.这项技术上的进步给铸造工艺带来巨大的经济效益和社会效益.目前用于树脂模具的SP离型剂中的成膜剂很多采用反应性硅聚合物.市场上的SP离型剂的配方属于生产商的技术秘密,即使在专利中也难于找到硅聚合物SP离型剂的详细配方.同时文献上鲜有关于硅聚合物表面能的报道.为研究硅聚合物SP离型剂提供基础数据,用液饼高度法测定了水在四种配方的SP离型剂硫化后生成的硅聚合物表面上的接触角.结果表明:水在这四种SP离型剂硫化后生成的硅聚合物表面上的接触角的差别≤1.1°,说明具有相似的化学结构是硅聚合物表面能的决定性因素;而组成SP离型剂中的硅聚合物的平均相对分子质量,交联剂、催化剂和稳定剂的品种和用量等仅对硅聚合物表面能产生次要的影响.

  17. Chemical communication of antibiotic resistance by a highly resistant subpopulation of bacterial cells.

    Directory of Open Access Journals (Sweden)

    Omar M El-Halfawy

    Full Text Available The overall antibiotic resistance of a bacterial population results from the combination of a wide range of susceptibilities displayed by subsets of bacterial cells. Bacterial heteroresistance to antibiotics has been documented for several opportunistic Gram-negative bacteria, but the mechanism of heteroresistance is unclear. We use Burkholderia cenocepacia as a model opportunistic bacterium to investigate the implications of heterogeneity in the response to the antimicrobial peptide polymyxin B (PmB and also other bactericidal antibiotics. Here, we report that B. cenocepacia is heteroresistant to PmB. Population analysis profiling also identified B. cenocepacia subpopulations arising from a seemingly homogenous culture that are resistant to higher levels of polymyxin B than the rest of the cells in the culture, and can protect the more sensitive cells from killing, as well as sensitive bacteria from other species, such as Pseudomonas aeruginosa and Escherichia coli. Communication of resistance depended on upregulation of putrescine synthesis and YceI, a widely conserved low-molecular weight secreted protein. Deletion of genes for the synthesis of putrescine and YceI abrogate protection, while pharmacologic inhibition of putrescine synthesis reduced resistance to polymyxin B. Polyamines and YceI were also required for heteroresistance of B. cenocepacia to various bactericidal antibiotics. We propose that putrescine and YceI resemble "danger" infochemicals whose increased production by a bacterial subpopulation, becoming more resistant to bactericidal antibiotics, communicates higher level of resistance to more sensitive members of the population of the same or different species.

  18. Laplacian drop shapes and effect of random perturbations on accuracy of surface tension measurement for different drop constellations.

    Science.gov (United States)

    Saad, Sameh M I; Neumann, A Wilhelm

    2015-08-01

    Theoretical drop shapes are calculated for three drop constellations: pendant drops, constrained sessile drops, and unconstrained sessile drops. Based on total Gaussian curvature, shape parameter and critical shape parameter are discussed as a function of different drop sizes and surface tensions. The shape parameter is linked to physical parameters for every drop constellation. The as yet unavailable detailed dimensional analysis for the unconstrained sessile drop is presented. Results show that the unconstrained sessile drop shape depends on a dimensionless volume term and the contact angle. Random perturbations are introduced and the accuracy of surface tension measurement is assessed for precise and perturbed profiles of the three drop constellations. It is concluded that pendant drops are the best method for accurate surface tension measurement, followed by constrained sessile drops. The unconstrained sessile drops come last because they tend to be more spherical at low and moderate contact angles. Of course, unconstrained sessile drops are the only option if contact angles are to be measured.

  19. Оцінка відносної похибки в задачі автоматизації методу лежачої краплі

    OpenAIRE

    Levitskaya, T. О.

    2015-01-01

    Assessment of the relative error in the sessile drop method automation. Further development of the sessile drop method is directly related to the development of new techniques and specially developed algorithms enabling automatic computer calculation of surface properties. The sessile drop method mathematical apparatus improvement, drop circuit equation transformation to a form suitable for working, the drop surface calculation method automation, analysis of relative errors in the calculation...

  20. Cave Rings

    Science.gov (United States)

    2010-10-13

    hypothesis, that cave rings are formed in the same manner as coffee rings[3], that is, due to the enhanced deposition at the edges of sessile drops ...ring’ is the deposit formed when a sessile drop of a solution containing dissolved particles, such as coffee or salt, dries. This was investigated by...who expanded on Deegan et al.[3] to find an exact form for the evaporation flux over a sessile drop . It turns out that solving 179 for the flux is

  1. Wetting Properties of EMIIm & its Relevance to Electrospray Design

    Science.gov (United States)

    2012-03-12

    contact angle measurements taken us- ing the goniometer- sessile drop technique. We also examine the surface tension of...de gr ee s) Sessile Drop Base Diameter (cm) Advancing Receding Contact Angles (EMIIm - Silica)[Ambient TemperaturePressure] Fig. 11...C on ta ct A ng le ( de gr ee s) Sessile Drop Base Diameter (cm) Advancing Receding Contact Angles (EMIIm - PTFE)[Ambient

  2. Relationship Between Water Wettability and Ice Adhesion (Preprint)

    Science.gov (United States)

    2010-10-21

    angle of tilt required to induce sliding of sessile liquid drops does not correlate with any one contact angle ...considering shear and tensile phenomena.61, 62 Drop sliding is inherently a shearing process; the minimum angle of tilt (α) at which a sessile droplet...syringe into or out of sessile droplets ( drop volume ~5 μL). Ice Adhesion Measurements. While goniometers are widely used to measure liquid contact

  3. EMIIM Wetting Properties & Their Effect on Electrospray Thruster Design

    Science.gov (United States)

    2012-03-01

    contact angle measure- ments using the sessile drop technique are generally accepted as having an uncertainty of... Sessile Drop Base Diameter (cm) Advancing Receding Contact Angles (EMIIm - PTFE)[Ambient TemperaturePressure] Figure 45: Advancing and receding...on Contact Angle ,” Vol. 71, 1979. [35] Allen, J. S., “An analytical solution for determination of small contact angles from sessile drops of arbitrary size,” Vol.

  4. EMIIM Wetting Properties of & Their Effect on Electrospray Thruster Design

    Science.gov (United States)

    2012-03-21

    characterized using contact angle measurements taken using goniometer- sessile drop technique. We also ex- amine the surface tension of the liquid for comparison...Figure 26. This variation was problematic as contact angle measure- ments using the sessile drop technique are generally accepted as having an... Sessile Drop Base Diameter (cm) Advancing Receding Contact Angles (EMIIm - PTFE)[Ambient TemperaturePressure] Figure 45: Advancing and

  5. Aerosol phage therapy efficacy in Burkholderia cepacia complex respiratory infections.

    Science.gov (United States)

    Semler, Diana D; Goudie, Amanda D; Finlay, Warren H; Dennis, Jonathan J

    2014-07-01

    Phage therapy has been suggested as a potential treatment for highly antibiotic-resistant bacteria, such as the species of the Burkholderia cepacia complex (BCC). To address this hypothesis, experimental B. cenocepacia respiratory infections were established in mice using a nebulizer and a nose-only inhalation device. Following infection, the mice were treated with one of five B. cenocepacia-specific phages delivered as either an aerosol or intraperitoneal injection. The bacterial and phage titers within the lungs were assayed 2 days after treatment, and mice that received the aerosolized phage therapy demonstrated significant decreases in bacterial loads. Differences in phage activity were observed in vivo. Mice that received phage treatment by intraperitoneal injection did not demonstrate significantly reduced bacterial loads, although phage particles were isolated from their lung tissue. Based on these data, aerosol phage therapy appears to be an effective method for treating highly antibiotic-resistant bacterial respiratory infections, including those caused by BCC bacteria.

  6. Identification and onion pathogenicity of Burkholderia cepacia complex isolates from the onion rhizosphere and onion field soil.

    Science.gov (United States)

    Jacobs, Janette L; Fasi, Anthony C; Ramette, Alban; Smith, James J; Hammerschmidt, Raymond; Sundin, George W

    2008-05-01

    Burkholderia cepacia complex strains are genetically related but phenotypically diverse organisms that are important opportunistic pathogens in patients with cystic fibrosis (CF,) as well as pathogens of onion and banana, colonizers of the rhizospheres of many plant species, and common inhabitants of bulk soil. Genotypic identification and pathogenicity characterization were performed on B. cepacia complex isolates from the rhizosphere of onion and organic soils in Michigan. A total of 3,798 putative B. cepacia complex isolates were recovered on Pseudomonas cepacia azelaic acid tryptamine and trypan blue tetracycline semiselective media during the 2004 growing season from six commercial onion fields located in two counties in Michigan. Putative B. cepacia complex isolates were identified by hybridization to a 16S rRNA gene probe, followed by duplex PCR using primers targeted to the 16S rRNA gene and recA sequences and restriction fragment length polymorphism analysis of the recA sequence. A total of 1,290 isolates, 980 rhizosphere and 310 soil isolates, were assigned to the species B. cepacia (160), B. cenocepacia (480), B. ambifaria (623), and B. pyrrocinia (27). The majority of isolates identified as B. cepacia (85%), B. cenocepacia (90%), and B. ambifaria (76%) were pathogenic in a detached onion bulb scale assay and caused symptoms of water soaking, maceration, and/or necrosis. A phylogenetic analysis of recA sequences from representative B. cepacia complex type and panel strains, along with isolates collected in this study, revealed that the B. cenocepacia isolates associated with onion grouped within the III-B lineage and that some strains were closely related to strain AU1054, which was isolated from a CF patient. This study revealed that multiple B. cepacia complex species colonize the onion rhizosphere and have the potential to cause sour skin rot disease of onion. In addition, the onion rhizosphere is a natural habitat and a potential environmental source

  7. Genetic Diversity of Burkholderia contaminans Isolates from Cystic Fibrosis Patients in Argentina

    OpenAIRE

    Martina, Pablo F.; Bettiol, Marisa; Vescina, Cecilia; Montanaro, Patricia; Mannino, Maria Constanza; Prieto, Claudia Inés; Vay, Carlos Alberto; Naumann, Dieter; Schmitt, Juergen; Yantorno, Osvaldo Miguel; Lagares, Antonio; Bosch, María Alejandra

    2013-01-01

    A total of 120 Burkholderia cepacia complex isolates collected during 2004?2010 from 66 patients in two cystic fibrosis reference centers in Argentina were analyzed. Burkholderia contaminans was the species most frequently recovered (57.6%), followed by Burkholderia cenocepacia (15%), a species distribution not reported so far. The recA-PCR-based techniques applied to the B. contaminans isolates revealed that 85% of the population carried the recA-ST-71 allele. Our results showed the utili...

  8. Role of lipase in Burkholderia cepacia complex (Bcc) invasion of lung epithelial cells.

    Science.gov (United States)

    Mullen, T; Markey, K; Murphy, P; McClean, S; Callaghan, M

    2007-12-01

    The Burkholderia cepacia complex (Bcc) is a group of ten closely related species associated with life-threatening infection in cystic fibrosis (CF). These bacteria are highly antibiotic resistant, with some strains transmissible, and in a subgroup of patients, they can cause a rapid and fatal necrotising pneumonia. The Bcc organisms produce a range of exoproducts with virulence potential, including exopolysaccharide, proteases and lipases. Many members of the Bcc are also capable of epithelial cell invasion, although the mechanism(s) involved are poorly understood. This study investigates a role for Bcc lipase in epithelial cell invasion by Bcc strains. Lipase activity was measured in eight species of the Bcc. Strains that produced high levels of lipase were predominantly from the B. multivorans and B. cenocepacia species. Pre-treatment of two epithelial cell lines with Bcc lipase significantly increased invasion by two B. multivorans strains and one B. cenocepacia strain and did not affect either plasma membrane or tight junction integrity. Inhibition of Bcc lipase production by the lipase inhibitor Orlistat significantly decreased invasion by both B. multivorans and B. cenocepacia strains in a concentration-dependent manner. This study demonstrates the extent of lipase production across the Bcc and establishes a potential role for lipase in Bcc epithelial cell invasion.

  9. Polyphasic characterisation of Burkholderia cepacia complex species isolated from children with cystic fibrosis

    Science.gov (United States)

    Vicenzi, Fernando José; Pillonetto, Marcelo; de Souza, Helena Aguilar Peres Homem de Mello; Palmeiro, Jussara Kasuko; Riedi, Carlos Antônio; Rosario-Filho, Nelson Augusto; Dalla-Costa, Libera Maria

    2016-01-01

    Cystic fibrosis (CF) patients with Burkholderia cepacia complex (Bcc) pulmonary infections have high morbidity and mortality. The aim of this study was to compare different methods for identification of Bcc species isolated from paediatric CF patients. Oropharyngeal swabs from children with CF were used to obtain isolates of Bcc samples to evaluate six different tests for strain identification. Conventional (CPT) and automatised (APT) phenotypic tests, polymerase chain reaction (PCR)-recA, restriction fragment length polymorphism-recA, recAsequencing, and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) were applied. Bacterial isolates were also tested for antimicrobial susceptibility. PCR-recA analysis showed that 36 out of the 54 isolates were Bcc. Kappa index data indicated almost perfect agreement between CPT and APT, CPT and PCR-recA, and APT and PCR-recA to identify Bcc, and MALDI-TOF and recAsequencing to identify Bcc species. The recAsequencing data and the MALDI-TOF data agreed in 97.2% of the isolates. Based on recA sequencing, the most common species identified were Burkholderia cenocepacia IIIA (33.4%),Burkholderia vietnamiensis (30.6%), B. cenocepaciaIIIB (27.8%), Burkholderia multivorans (5.5%), and B. cepacia (2.7%). MALDI-TOF proved to be a useful tool for identification of Bcc species obtained from CF patients, although it was not able to identify B. cenocepacia subtypes. PMID:26814642

  10. Nasal Immunization with Burkholderia multivorans Outer Membrane Proteins and the Mucosal Adjuvant Adamantylamide Dipeptide Confers Efficient Protection against Experimental Lung Infections with B. multivorans and B. cenocepacia▿

    Science.gov (United States)

    Bertot, Gustavo M.; Restelli, Marcela A.; Galanternik, Laura; Aranibar Urey, Rene C.; Valvano, Miguel A.; Grinstein, Saúl

    2007-01-01

    Chronic lung infection by opportunistic pathogens, such as Pseudomonas aeruginosa and members of the Burkholderia cepacia complex, is a major cause of morbidity and mortality in patients with cystic fibrosis. Outer membrane proteins (OMPs) of gram-negative bacteria are promising vaccine antigen candidates. In this study, we evaluated the immunogenicity, protection, and cross-protection conferred by intranasal vaccination of mice with OMPs from B. multivorans plus the mucosal adjuvant adamantylamide dipeptide (AdDP). Robust mucosal and systemic immune responses were stimulated by vaccination of naive animals with OMPs from B. multivorans and B. cenocepacia plus AdDP. Using a mouse model of chronic pulmonary infection, we observed enhanced clearance of B. multivorans from the lungs of vaccinated animals, which correlated with OMP-specific secretory immunoglobulin A responses. Furthermore, OMP-immunized mice showed rapid resolution of the pulmonary infection with virtually no lung pathology after bacterial challenge with B. multivorans. In addition, we demonstrated that administration of B. multivorans OMP vaccine conferred protection against B. cenocepacia challenge in this mouse infection model, suggesting that OMPs provide cross-protection against the B. cepacia complex. Therefore, we concluded that mucosal immunity to B. multivorans elicited by intranasal vaccination with OMPs plus AdDP could prevent early steps of colonization and infection with B. multivorans and also ameliorate lung tissue damage, while eliciting cross-protection against B. cenocepacia. These results support the notion that therapies leading to increased mucosal immunity in the airways may help patients with cystic fibrosis. PMID:17296759

  11. Application of Computer Graphic Processing Technology in Measurement of Surface Tension of Liquid Metal with Sessile Drop Method%电脑图形处理在静滴法测量液态金属表面张力中的应用

    Institute of Scientific and Technical Information of China (English)

    钱国统; 彭孜; 宋雪明; 张强; 王旭波

    2011-01-01

    介绍了一种电脑图形处理技术在静滴法测量液态金属表面张力中的应用,及详细操作过程.该方法应用数码摄影、Windows和AutoCAD软件相结合的电脑图形处理技术,测得其他方法无法精确测量的多个参数值,为静滴法测量液态金属表面张力提供一种新的辅助测量技术手段.

  12. 旨在观察熔融镍与固态多晶Al2O3润湿性的改良静滴方法评价%Evaluation of Modified Sessile Drop Method for Observing the Wettability of Molten Nickel with Solid Polycrystalline Alumina

    Institute of Scientific and Technical Information of China (English)

    肖锋; 野城清

    2004-01-01

    对传统的静滴法进行改良,通过观察熔融Ni与固态多晶Al2O3间的润湿行为并测定接触角,计算了新方法的测定误差,评价了2种材料间的润湿性.熔融Ni与固态多晶Al2O3间的润湿行为为反应润湿,初始接触角为115°,随着时间的延长,接触角有下降趋势.

  13. STUDIES OF WETTING CHARACTERISTICS OF LIQUID Fe - Cr ALLOYS ON OXIDE SUBSTRATES BY SESSILE DROP TECHNIQUE%利用固滴技术对氧化基片上液态Fe - Cr合金润湿性的研究

    Institute of Scientific and Technical Information of China (English)

    J. Lee; M. Shin; J. H.Park; S. Seetharaman; 石莹

    2011-01-01

    本文的目的是研究三种不同的氧化基片(氧化铝、氧化镁及白云石)的润湿特性,以检验Fe - Cr合金在这些基片上的粘附功.利用固滴技术在H2气氛中1823 K下,对氧化基片上液滴(Fe - Cr合金)的接触角进行了研究.随着Cr浓度的增加在氧化铝和白云石基片上的接触角会稍微减小,但不会像在氧化镬基片上变化那么大.在测试基片中,氧化铝基片接触角最大,白云石基片接触角最小.因此,白云石的粘附功最大,这与实际工艺中观察到的结果相符.

  14. Chenopodiaceae

    NARCIS (Netherlands)

    Backer, C.A.

    1948-01-01

    Annual or perennial herbs or shrubs, often fleshy, glabrous, papillate or hairy. Leaves opposite or alternate, exstipulate, sometimes seemingly wanting, stalked or sessile, entire, dentate-serrate-lobed or irregularly gashed. Flowers solitary, 2—3-nate or glomerate, usually sessile, either axillary

  15. Perturbation induced changes in substrate use by the blue mussel, Mytilus edulis, in sedimentary systems

    NARCIS (Netherlands)

    Kangeri, A.K.; Jansen, J.M.; Barkman, B.R.; Donker, J.J.A.; Joppe, D.J.; Dankers, N.M.J.A.

    2014-01-01

    For sessile benthic marine organisms adhesion to a stable substrate is important for survival. Sedimentary systems, however, generally lack stable surfaces. How sessile species like the mussel, Mytilus edulis, are able to achieve stability in unstable sediments is not fully understood. An intertidal

  16. Pertubation induced changes in substrate use by the blue mussel, Mytilus edulis, in sedimentary systems

    NARCIS (Netherlands)

    wa Kangeri, A.K.; Jansen, J.M.; Barkman, B.R.; Donker, J. J. A.; Joppe, D.J.; Dankers, N.M.J.A.

    2014-01-01

    For sessile benthic marine organisms adhesion to a stable substrate is important for survival. Sedimentary systems, however, generally lack stable surfaces. How sessile species like the mussel, Mytilus edulis, are able to achieve stability in unstable sediments is not fully understood. An intertidal

  17. Basellaceae

    NARCIS (Netherlands)

    Stoffers, A.L.

    1980-01-01

    Perennial, glabrous, herbaceous vines with slender or stout and fleshy stems, often with a rhizome or tuberous roots. Leaves alternate, entire, often fleshy, sessile or petiolate. Stipules wanting. Inflorescence consisting of spikes, panicles or clusters, the flowers sessile or short-pedicellate. Br

  18. Evaporation into Couette Flow

    Science.gov (United States)

    2008-01-01

    v Yi Statistical analysis dependent variable Greek Symbols 13 Contact angle of sessile drop a Concentration thickness A Evaporated vapor penetration...31 5 FIGURES 1. Configuration of Three Sessile Drops ............................................. 10 2. Sketch of...Droplet Geometry ............................................................. 11 3. Shape Factor as a Function of Contact Angle

  19. Pseudomonas aeruginosa displays an altered phenotype in vitro when grown in the presence of mannitol.

    Science.gov (United States)

    Moore, J E; Rendall, J C; Downey, D G

    2015-01-01

    D-mannitol has been approved in dry powder formulation as an effective antimucolytic agent in patients with cystic fibrosis. What is not known is the effect of adding a metabolisable sugar on the biology of chronic bacterial pathogens in the CF lung. Therefore, a series of simple in vitro experiments were performed to examine the effect of adding D-mannitol on the phenotype of the CF respiratory pathogens Pseudomonas aeruginosa and Burkholderia cenocepacia. Clinical isolates (n = 86) consisting of P. aeruginosa (n = 51), B. cenocepacia (n = 26), P. putida (n = 4), Stenotrophomonas maltophila (n = 3) and Pseudomonas spp. (n = 2) were examined by supplementing basal nutrient agar with varying concentrations of D-mannitol (0-20% [w/v]) and subsequently examining for any change in microbial phenotype. The effect of supplementation with mannitol was four-fold, namely i) To increase the proliferation and increase in cell density of all CF organisms examined, with an optimal concentration of 2-4% (w/v) D-mannitol. No such increase in cell proliferation was observed when mannitol was substituted with sodium chloride. ii) Enhanced pigment production was observed in 2/51 (3.9%) of the P. aeruginosa isolates examined, in one of the P. putida isolates, and in 3/26 (11.5%) of the B. cenocepacia isolates examined. iii). When examined at 4.0% (w/v) supplementation with mannitol, 11/51 (21.6%) P. aeruginosa isolates and 3/26 (11.5%) B. cenocepacia isolates were seen to exhibit the altered adhesion phenotype. iv). With respect to the altered mucoid phenotype, 5/51 (9.8%) P. aeruginosa produced this phenotype when grown at 4% mannitol. Mucoid production was greatest at 4%, was poor at 10% and absent at 20% (w/v) mannitol. The altered mucoid phenotype was not observed in the B. cenocepacia isolates or any of the other clinical taxa examined. Due consideration therefore needs to be given, where there is altered physiology within the small airways, leading to a potentially altered

  20. Interface Lattice Engineering of Si Composite Wafers for Large-Format HgCdTe Infrared Focal Plane Arrays

    Science.gov (United States)

    2012-08-07

    sessile dislocation. Examples of such sessile dislocation coalescence are the Lomer lock a 2 [011̄] + a 2 [101] → a 2 [110], (2.22) or a Lomer-Cottrell...Hg droplets condensing on to the layer. This will leave concentric circular marks where the Hg drop forms and evaporates away as seen in figure 5.2(d...sake, also assume that bα+ bβ = bsessile, where the result is a sessile dislocation. Finally, stipulate that when is near a side wall, α dislocations

  1. Droplet evaporation with complexity of evaporation modes

    Science.gov (United States)

    Hwang, In Gyu; Kim, Jin Young; Weon, Byung Mook

    2017-01-01

    Evaporation of a sessile droplet often exhibits a mixed evaporation mode, where the contact radius and the contact angle simultaneously vary with time. For sessile water droplets containing polymers with different initial polymer concentrations, we experimentally study their evaporation dynamics by measuring mass and volume changes. We show how diffusion-limited evaporation governs droplet evaporation, regardless of the complexity of evaporation behavior, and how the evaporation rate depends on the polymer concentration. Finally, we suggest a unified expression for a diffusion-limited evaporation rate for a sessile droplet with complexity in evaporation dynamics.

  2. The use of nanoscale visible light-responsive photocatalyst TiO2-Pt for the elimination of soil-borne pathogens.

    Directory of Open Access Journals (Sweden)

    Ya-Lei Chen

    Full Text Available Exposure to the soil-borne pathogens Burkholderia pseudomallei and Burkholderia cenocepacia can lead to severe infections and even mortality. These pathogens exhibit a high resistance to antibiotic treatments. In addition, no licensed vaccine is currently available. A nanoscale platinum-containing titania photocatalyst (TiO(2-Pt has been shown to have a superior visible light-responsive photocatalytic ability to degrade chemical contaminants like nitrogen oxides. The antibacterial activity of the catalyst and its potential use in soil pathogen control were evaluated. Using the plating method, we found that TiO(2-Pt exerts superior antibacterial performance against Escherichia coli compared to other commercially available and laboratory prepared ultraviolet/visible light-responsive titania photocatalysts. TiO(2-Pt-mediated photocatalysis also affectively eliminates the soil-borne bacteria B. pseudomallei and B. cenocepacia. An air pouch infection mouse model further revealed that TiO(2-Pt-mediated photocatalysis could reduce the pathogenicity of both strains of bacteria. Unexpectedly, water containing up to 10% w/v dissolved soil particles did not reduce the antibacterial potency of TiO(2-Pt, suggesting that the TiO(2-Pt photocatalyst is suitable for use in soil-contaminated environments. The TiO(2-Pt photocatalyst exerted superior antibacterial activity against a broad spectrum of human pathogens, including B. pseudomallei and B. cenocepacia. Soil particles (<10% w/v did not significantly reduce the antibacterial activity of TiO(2-Pt in water. These findings suggest that the TiO(2-Pt photocatalyst may have potential applications in the development of bactericides for soil-borne pathogens.

  3. Garlic revisited: antimicrobial activity of allicin-containing garlic extracts against Burkholderia cepacia complex.

    Directory of Open Access Journals (Sweden)

    Daynea Wallock-Richards

    Full Text Available The antimicrobial activities of garlic and other plant alliums are primarily based on allicin, a thiosulphinate present in crushed garlic bulbs. We set out to determine if pure allicin and aqueous garlic extracts (AGE exhibit antimicrobial properties against the Burkholderia cepacia complex (Bcc, the major bacterial phytopathogen for alliums and an intrinsically multiresistant and life-threatening human pathogen. We prepared an AGE from commercial garlic bulbs and used HPLC to quantify the amount of allicin therein using an aqueous allicin standard (AAS. Initially we determined the minimum inhibitory concentrations (MICs of the AGE against 38 Bcc isolates; these MICs ranged from 0.5 to 3% (v/v. The antimicrobial activity of pure allicin (AAS was confirmed by MIC and minimum bactericidal concentration (MBC assays against a smaller panel of five Bcc isolates; these included three representative strains of the most clinically important species, B. cenocepacia. Time kill assays, in the presence of ten times MIC, showed that the bactericidal activity of AGE and AAS against B. cenocepacia C6433 correlated with the concentration of allicin. We also used protein mass spectrometry analysis to begin to investigate the possible molecular mechanisms of allicin with a recombinant form of a thiol-dependent peroxiredoxin (BCP, Prx from B. cenocepacia. This revealed that AAS and AGE modifies an essential BCP catalytic cysteine residue and suggests a role for allicin as a general electrophilic reagent that targets protein thiols. To our knowledge, we report the first evidence that allicin and allicin-containing garlic extracts possess inhibitory and bactericidal activities against the Bcc. Present therapeutic options against these life-threatening pathogens are limited; thus, allicin-containing compounds merit investigation as adjuncts to existing antibiotics.

  4. Garlic revisited: antimicrobial activity of allicin-containing garlic extracts against Burkholderia cepacia complex.

    Science.gov (United States)

    Wallock-Richards, Daynea; Doherty, Catherine J; Doherty, Lynsey; Clarke, David J; Place, Marc; Govan, John R W; Campopiano, Dominic J

    2014-01-01

    The antimicrobial activities of garlic and other plant alliums are primarily based on allicin, a thiosulphinate present in crushed garlic bulbs. We set out to determine if pure allicin and aqueous garlic extracts (AGE) exhibit antimicrobial properties against the Burkholderia cepacia complex (Bcc), the major bacterial phytopathogen for alliums and an intrinsically multiresistant and life-threatening human pathogen. We prepared an AGE from commercial garlic bulbs and used HPLC to quantify the amount of allicin therein using an aqueous allicin standard (AAS). Initially we determined the minimum inhibitory concentrations (MICs) of the AGE against 38 Bcc isolates; these MICs ranged from 0.5 to 3% (v/v). The antimicrobial activity of pure allicin (AAS) was confirmed by MIC and minimum bactericidal concentration (MBC) assays against a smaller panel of five Bcc isolates; these included three representative strains of the most clinically important species, B. cenocepacia. Time kill assays, in the presence of ten times MIC, showed that the bactericidal activity of AGE and AAS against B. cenocepacia C6433 correlated with the concentration of allicin. We also used protein mass spectrometry analysis to begin to investigate the possible molecular mechanisms of allicin with a recombinant form of a thiol-dependent peroxiredoxin (BCP, Prx) from B. cenocepacia. This revealed that AAS and AGE modifies an essential BCP catalytic cysteine residue and suggests a role for allicin as a general electrophilic reagent that targets protein thiols. To our knowledge, we report the first evidence that allicin and allicin-containing garlic extracts possess inhibitory and bactericidal activities against the Bcc. Present therapeutic options against these life-threatening pathogens are limited; thus, allicin-containing compounds merit investigation as adjuncts to existing antibiotics.

  5. Marine benthos - A future perspective

    Digital Repository Service at National Institute of Oceanography (India)

    Govindan, K.

    Benthic organisms are reported from different kinds of substrate like hard bottom, soft bottom, coarse bottom and also from organic matter and other macrodebris. Benthos are in general, sessile and slow moving in nature. 75% of benthic animals live...

  6. Reference: 444 [Arabidopsis Phenome Database[Archive

    Lifescience Database Archive (English)

    Full Text Available ng et al. 2006 Oct. Plant J. 48(1):73-84. Plants, as sessile organisms, employ multiple mechanisms to adapt ... the overall tolerance of the plant to elevated temperatures. To identify the various mechanisms of thermoto

  7. Pentaphylacaceae

    NARCIS (Netherlands)

    Steenis, van C.G.G.J.

    1955-01-01

    Evergreen, subglabrous shrubs or trees. Twigs lengthwise grooved and ridged. Buds perular. Leaves simple, entire, penninerved, spirally arranged; midrib and petiole sulcate. Stipules absent. Flowers bisexual, actinomorphic, rather small, in ± sessile, bracteate, axillary pseudo-spikes or -racemes wh

  8. A new angle on microscopic suspension feeders near boundaries.

    Science.gov (United States)

    Pepper, Rachel E; Roper, Marcus; Ryu, Sangjin; Matsumoto, Nobuyoshi; Nagai, Moeto; Stone, Howard A

    2013-10-15

    Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces they live upon, whereas we observe that sessile suspension feeders often feed at an angle to these boundaries. Using experiments and calculations, we show that living suspension feeders (Vorticella) likely actively regulate the angle that they feed relative to a substratum. We then use theory and simulations to show that angled feeding increases nutrient and particle uptake by reducing the reprocessing of depleted water. This work resolves an open question of how a key class of suspension-feeding organisms escapes physical limitations associated with their sessile lifestyle.

  9. Fish Structural Habitat Surveys from Grays Reef National Marine Sanctuary Research Open Management Zones

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — In situ visual surveys were conducted to generate size estimates and species composition of fish community habitat measurements (ledge height, macroalgal ht, sessile...

  10. Lattice Boltzmann Models for Multicomponent Fluids

    Science.gov (United States)

    2007-11-02

    between multiphase fluids. Two specific physical problems investigated: the shape of a sessile drop on a horizontal surface subjected to a gravitational field, and the effect of surface tension on contact angle .

  11. Punicaceae

    NARCIS (Netherlands)

    Backer, C.A.

    1948-01-01

    Shrubs or small trees, usually spiny. Leaves opposite, alternate or fascicled, exstipulate, simple, entire, penninerved, small. Flowers terminal and subterminal, sessile or nearly so, rather large, ♀, actinomorphic. Calyx thickly coriaceous, coloured, gamophyllous; tube campanulate-urceolate, adnate

  12. Benthic communities associated with ferromanganese nodules from the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Pavithran, S.; Goltekar, R.

    for grazers, shelter for burrowers and sessile organisms as well as protection for mobile fauna. It is concluded that benthic organisms like nematodes, polychaetes and foraminiferas may have strong influence on nodule formation and growth....

  13. Producción de un polímero tipo polihidroxialcanoato (PHA) empleando residuos de la producción de biodiesel

    OpenAIRE

    Becerra Jiménez, Mónica Liliana

    2013-01-01

    El aumento en la producción de biodiesel ha generado un exceso de glicerol y otros residuos disponibles para el desarrollo de la industria biotecnológica; estos constituyen materias primas útiles para la producción de polihidroxialcanoatos (PHAs). En este trabajo se evaluó el crecimiento de seis cepas acumuladoras de PHAs sobre glicerol USP y tres residuos provenientes de diferentes plantas de producción de biodiesel, lo cuál permitió concluir que Burkholderia cenocepacia 2G-57 es la que mejo...

  14. Jamming bacterial communications: new strategies to combat bacterial infections and the development of biofilms

    DEFF Research Database (Denmark)

    Givskov, Michael Christian; Hentzer, Morten

    2006-01-01

    with surfaces and we as scientists must therefore turn our attention to this sessile mode of growth (33). It appears that the ability to form surface-associated, structured and cooperative consortia (referred to as biofilms) is one of the most remarkable and ubiquitous characteristics of bacteria (12......). In this sessile life form, bacteria can cause various problems in industrial settings, ranging from corrosion and biofouling to food contamination....

  15. A New Angle on Microscopic Suspension Feeders near Boundaries

    OpenAIRE

    Pepper, Rachel E.; Roper, Marcus; Ryu, Sangjin; Matsumoto, Nobuyoshi; Nagai, Moeto; Stone, Howard A.

    2013-01-01

    Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces...

  16. Surface-Modified Nanofibrous Biomaterial Bridge for the Enhancement and Control of Neurite Outgrowth

    Science.gov (United States)

    2010-12-22

    wettability of the surface was determined using a sessile drop contact angle system First Ten Ångstroms with an RS170 camera. The contact angles were...coupling reaction 5 mg/ml, 1:1. c Attachment of protein through reaction with amine groups. FIG. 3. Color onlne a Sessile - drop water contact...Thus, scaffolds with fibers in the nanometer regime could be advantageous . Electrospinning is a technique that produces fibers with diameters in the

  17. Evaluation of 5-cm Agent Fate Wind Tunnel Velocity Profiles

    Science.gov (United States)

    2007-09-01

    y/v Greek Symbols P3 Contact angle of sessile drop 3 Momentum thickness . Boundary layer thickness 6* Displacement thickness KC von Karman universal...proposed 6. Although the drop is expected to be smooth with a gentle slope ( contact angle of about 20’) the height is significant and its effects should...a simple two-dimensional problem of evaporation into a laminar Couette flow was investigated 6. This represents the sessile drop condition present

  18. Small-Item Vapor Test Method, FY11 Release

    Science.gov (United States)

    2012-07-01

    exposed. sessile drop : A liquid droplet that is firmly attached to a surface. If the droplet significantly spreads across the surface, it is better...following information regarding the observations. o Written description of applied drops as they appeared for each sample (e.g., sessile , spread). o... techniques for this method. The airflow and air volume are key variables required to assess risk. Residual agent: Because full-item extraction

  19. Advanced Ceramic Composites for Improved Thermal Management in Molten Aluminum Applications

    Science.gov (United States)

    2009-02-01

    interaction of the TCON material with the molten aluminum [18]. Sessile Drop Testing. Static and dynamic sessile drop methods were employed for...conventional processing techniques and from readily-available precursor and inert additive materials; 2) Carrying out the displacement reaction by fully...small quantity of aluminum alloy melted by induction heating in a reducing atmosphere and dropped onto the refractory substrate. Results showed non

  20. Disinfection of Burkholderia cepacia complex from non-touch taps in a neonatal nursery.

    Science.gov (United States)

    Kotsanas, Despina; Brett, Judith; Kidd, Tim J; Stuart, Rhonda L; Korman, Tony M

    2008-01-01

    Burkholderia cepacia complex (Bcc) comprises nine closely related species or genomovars. It is an important causative agent of opportunistic infections and waterborne nosocomial infections. B. cepacia (formerly genomovar I) was identified from the blood culture of a baby in our neonatal unit (NU) in March 2005. B. cepacia was isolated four times from clinical specimens since the introduction of non-touch taps in the NU from 2000 to 2005 and only once from 1994 to 2000. Environmental samples were collected from the NU, including tap water from non-touch taps. Clinical and environmental isolates of Bcc were characterized using molecular identification and strain typing. A literature review was undertaken to delineate a method for eradication of Bcc. Several variations for hot water eradication of the organism from the taps were attempted. Genotyping and molecular analysis revealed that tap water isolates were B. cenocepacia which was a different species from the B. cepacia isolated from blood cultures of the neonate. However, B. cenocepacia has been known to cause nosocomial outbreaks and it was eventually eradicated from the NU by using repeated thermal shock (hot water at 65 degrees C for 10 min), changing taps and decolonizing sinks with hypochlorite. Molecular typing is useful in assisting the investigation of Bcc nosocomial infections.

  1. Character displacement and the evolution of niche complementarity in a model biofilm community.

    Science.gov (United States)

    Ellis, Crystal N; Traverse, Charles C; Mayo-Smith, Leslie; Buskirk, Sean W; Cooper, Vaughn S

    2015-02-01

    Colonization of vacant environments may catalyze adaptive diversification and be followed by competition within the nascent community. How these interactions ultimately stabilize and affect productivity are central problems in evolutionary ecology. Diversity can emerge by character displacement, in which selection favors phenotypes that exploit an alternative resource and reduce competition, or by facilitation, in which organisms change the environment and enable different genotypes or species to become established. We previously developed a model of long-term experimental evolution in which bacteria attach to a plastic bead, form a biofilm, and disperse to a new bead. Here, we focus on the evolution of coexisting mutants within a population of Burkholderia cenocepacia and how their interactions affected productivity. Adaptive mutants initially competed for space, but later competition declined, consistent with character displacement and the predicted effects of the evolved mutations. The community reached a stable equilibrium as each ecotype evolved to inhabit distinct, complementary regions of the biofilm. Interactions among ecotypes ultimately became facilitative and enhanced mixed productivity. Observing the succession of genotypes within niches illuminated changing selective forces within the community, including a fundamental role for genotypes producing small colony variants that underpin chronic infections caused by B. cenocepacia.

  2. Susceptibility of Caenorhabditis elegans to Burkholderia infection depends on prior diet and secreted bacterial attractants.

    Directory of Open Access Journals (Sweden)

    Vaughn S Cooper

    Full Text Available The nematode Caenorhabditis elegans may be killed by certain pathogenic bacteria and thus is a model organism for studying interactions between bacteria and animal hosts. However, growing nematodes on prey bacteria may influence their susceptibility to potential pathogens. A method of axenic nematode culture was developed to isolate and quantify interactions between C. elegans and potentially pathogenic strains of the Burkholderia cepacia complex. Studying these dynamics in liquid solution rather than on agar surfaces minimized nematode avoidance behavior and resolved more differences among isolates. Most isolates of B. cenocepacia, B. ambifaria and B. cepacia caused 60-80% mortality of nematodes after 7 days, whereas isolates of B. multivorans caused less mortality (<25% and supported nematode reproduction. However, some B. cenocepacia isolates recovered from chronic infections were much less virulent (5-28% mortality. As predicted, prior diet altered the outcome of interactions between nematodes and bacteria. When given the choice between Burkholderia and E. coli as prey on agar, axenically raised nematodes initially preferred most lethal Burkholderia isolates to E. coli as a food source, but this was not the case for nematodes fed E. coli, which avoided toxic Burkholderia. This food preference was associated with the cell-free supernatant and thus secreted compounds likely mediated bacterial-nematode interactions. This model, which isolates interactions between bacteria and nematodes from the effects of prior feeding, demonstrates that bacteria can influence nematode behavior and their susceptibility to pathogens.

  3. Bacteria of the Burkholderia cepacia complex are cyanogenic under biofilm and colonial growth conditions

    Directory of Open Access Journals (Sweden)

    Hoshino Saiko

    2008-06-01

    Full Text Available Abstract Background The Burkholderia cepacia complex (Bcc is a collection of nine genotypically distinct but phenotypically similar species. They show wide ecological diversity and include species that are used for promoting plant growth and bio-control as well species that are opportunistic pathogens of vulnerable patients. Over recent years the Bcc have emerged as problematic pathogens of the CF lung. Pseudomonas aeruginosa is another important CF pathogen. It is able to synthesise hydrogen cyanide (HCN, a potent inhibitor of cellular respiration. We have recently shown that HCN production by P. aeruginosa may have a role in CF pathogenesis. This paper describes an investigation of the ability of bacteria of the Bcc to make HCN. Results The genome of Burkholderia cenocepacia has 3 putative HCN synthase encoding (hcnABC gene clusters. B. cenocepacia and all 9 species of the Bcc complex tested were able to make cyanide at comparable levels to P. aeruginosa, but only when grown surface attached as colonies or during biofilm growth on glass beads. In contrast to P. aeruginosa and other cyanogenic bacteria, cyanide was not detected during planktonic growth of Bcc strains. Conclusion All species in the Bcc are cyanogenic when grown as surface attached colonies or as biofilms.

  4. Modelling distribution of marine benthos from hydroacoustics and underwater video

    Science.gov (United States)

    Holmes, K. W.; Van Niel, K. P.; Radford, B.; Kendrick, G. A.; Grove, S. L.

    2008-08-01

    Broad-scale mapping of marine benthos is required for marine resource management and conservation. This study combines textural derivatives based on bathymetry from multibeam hydroacoustics with underwater video observations to model and map sessile biota between 10- and 60-m water depth over 35 km 2 in Point Addis Marine National Park (MNP), Vic., Australia. Classification tree models and maps were developed for macroalgae (all types, mixed red algae, Ecklonia, and rhodoliths) and sessile invertebrates (all types, sponges, and ascidians). Model accuracy was tested on 25% of the video observation dataset reserved from modelling. Models fit well for most macroalgae categories (correct classification rates of 67-84%), but are not as good for sessile invertebrate classes (correct classification rates of 57-62%). The poor fit of the sessile invertebrate models may be the combined result of grouping organisms with different environmental requirements and the effect of false absences recorded during video interpretation due to poor image quality. Probability maps, binary single-class maps, and multi-class maps supply spatially explicit, detailed information on the distribution of sessile benthic biota within the MNP and provide information at a landscape-scale for ecological investigations and marine management.

  5. Shear distortion and failure of capillary bridges. Wetting information beyond contact angle analysis.

    Science.gov (United States)

    Wang, Liming; McCarthy, Thomas J

    2013-06-25

    Water capillary bridges are prepared that span hydrophilic pinning features on parallel opposing smooth, flat, and hydrophobic surfaces. These bridges are distorted by shearing the parallel plates at a low rate. The capillary bridges lengthen and distort to balance Laplace pressure (equilibrate mean curvature) as the features are separated and eventually rupture at a distance that is a function of the liquid volume, the advancing and receding contact angles of the surfaces, the separation between the parallel surfaces, and in particular, the shape and orientation of the hydrophilic pinning features. Two modes of capillary bridge failure are observed: (1) tensile, in which the capillary bridge breaks to form sessile drops on both the upper and lower surfaces, and (2) sessile, in which sessile capillary bridge rupture occurs on one surface to form a puddle (contact-line-distorted sessile drop) on the feature and a retained capillary bridge spanning the hydrophobic surface and the hydrophilic feature on the opposing surface. The shape and orientation of the features control the mode of capillary bridge failure as well as the distribution of water between the two separate sessile drops or the retained capillary bridge and the puddle.

  6. Long-term assessment of the oil spill at Bahia Las Minas, Panama. Synthesis report. Volume 2. Technical report. Part 2

    Energy Technology Data Exchange (ETDEWEB)

    Keller, B.D.; Jackson, J.B.C.

    1993-11-01

    The submerged prop roots of mangroves on the outer fringe of mangrove forests support diverse assemblages of sessile invertebrates and algae, and act as nursery areas for various mobile animals, including commercially valuable fishes and invertebrates. The study examined effects of a major oil spill on both the physical structure of the mangrove fringe and the assemblages of attached epibiota on submerged prop roots over a 5-yr period. Initial oiling was heavy in all three habitats. Prior to the spill and in unoiled habitats postspill, the most common species or groups of epibiota in each habitat were (1) foliose algae and sessile invertebrates on the open coast, (2) the oyster Crassostrea virginica in channels, and (3) the false mussel Mytilopsis sallei in drainage streams. On the open coast, foliose algae and sessile invertebrates were coated with oil and died.

  7. High temperature solder alloys for underhood applications. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Drewien, C.A.; Yost, F.G.; Sackinger, S. [Sandia National Labs., Albuquerque, NM (United States); Kern, J.; Weiser, M.W. [Univ. of New Mexico (United States). Dept. of Mechanical Engineering

    1995-02-01

    Under a cooperative research and development agreement with General Motors Corporation, lead-free solder systems including the flux, metallization, and solder are being developed for high temperature, underhood applications. Six tin-rich solders, five silver-rich metallizations, and four fluxes were screened using an experimental matrix whereby every combination was used to make sessile drops via hot plate or Heller oven processing. The contact angle, sessile drop appearance, and in some instances the microstructure was evaluated to determine combinations that would yield contact angles of less than 30{degrees}, well-formed sessile drops, and fine, uniform microstructures. Four solders, one metallization, and one flux were selected and will be used for further aging and mechanical property studies.

  8. Reinterpretation of histology of proximal colon polyps called hyperplastic in 2001

    Institute of Scientific and Technical Information of China (English)

    Omer Khalid; Sofyan Radaideh; Oscar W Cummings; Michael J O'Brien; John R Goldblum; Douglas K Rex

    2009-01-01

    AIM: To evaluate how proximal colon polyps interpreted as hyperplastic polyps in 2001 would be interpreted by expert pathologists in 2007. METHODS: Forty consecutive proximal colon polyps ≥ 5 mm in size, removed in 2001, and originally interpreted as hyperplastic polyps by general pathologists at Indiana University, were reviewed in 2007 by 3 GI pathologists. RESULTS: The gastrointestinal (GI) pathologists interpreted 85%, 43% and 30% of the polyps as sessile serrated polyps (sessile serrated adenomas). The overall Kappa was 0.16. When diagnoses were compared in pairs, Kappa values were 0.38 and 0.25 (fair agreement) and 0.14 (slight agreement). CONCLUSION: Many polyps interpreted as hyperplastic in 2001 were considered sessile serrated lesions by GI pathologists in 2007, but there is substantial inter-observer variation amongst GI pathologists.

  9. Experimental Measurements of Spreading of Volatile Liquid Droplets

    Science.gov (United States)

    Zhang, Neng-Li; Chao, David F.

    2001-01-01

    Based on the laser shadowgraphic system used by the first author of the present paper, a simple optical system, which combined the laser shadowgraphy and the direct magnified-photography, has been developed to measure the contact angle, the spreading speed, and the evaporation rate. Additionally, the system can also visualize thermocapillary convection inside of a sessile drop simultaneously. The experimental results show that evaporation/condensation and thermocapillary convection in the sessile drop induced by the evaporation strongly affects the wetting and spreading of the drop. Condensation always promotes the wetting and spreading of the drop. Evaporation may increase or decrease the contact angle of the evaporating sessile drops, depending on the evaporation rate. The thermocapillary convection in the drop induced by the evaporation enhances the effects of evaporation to suppress the spreading.

  10. [Determination of critical surface tension--a comparison of 2 methods].

    Science.gov (United States)

    Lippold, B C; Ohm, A

    1988-03-01

    Two methods for the determination of the critical surface tension (gamma c) of pharmaceutical powders are compared: the so called "sinking-technique", which works by measuring the complete sinking of powders in liquids of varying surface tension and the determination of the critical surface tension by measuring the contact angle in dependence on the surface tension of wetting solvent/water-mixtures by means of the sessile drop-technique. The simple sinking-technique gives gamma c-values which only show a moderate degree of agreement with those determined by the sessile drop-technique. Thus the values determined by the sinking-technique are usually 1-3 mN/m higher than those determined by the sessile drop-technique.

  11. Global gene expression in Escherichia coli biofilms

    DEFF Research Database (Denmark)

    Schembri, Mark; Kjærgaard, K.; Klemm, Per

    2003-01-01

    in expression have no current defined function. These genes, as well as those induced by stresses relevant to biofilm growth such as oxygen and nutrient limitation, may be important factors that trigger enhanced resistance mechanisms of sessile communities to antibiotics and hydrodynamic shear forces.......It is now apparent that microorganisms undergo significant changes during the transition from planktonic to biofilm growth. These changes result in phenotypic adaptations that allow the formation of highly organized and structured sessile communities, which possess enhanced resistance...... to antimicrobial treatments and host immune defence responses. Escherichia coli has been used as a model organism to study the mechanisms of growth within adhered communities. In this study, we use DNA microarray technology to examine the global gene expression profile of E. coli during sessile growth compared...

  12. Measurement errors related to contact angle analysis of hydrogel and silicone hydrogel contact lenses.

    Science.gov (United States)

    Read, Michael L; Morgan, Philip B; Maldonado-Codina, Carole

    2009-11-01

    This work sought to undertake a comprehensive investigation of the measurement errors associated with contact angle assessment of curved hydrogel contact lens surfaces. The contact angle coefficient of repeatability (COR) associated with three measurement conditions (image analysis COR, intralens COR, and interlens COR) was determined by measuring the contact angles (using both sessile drop and captive bubble methods) for three silicone hydrogel lenses (senofilcon A, balafilcon A, lotrafilcon A) and one conventional hydrogel lens (etafilcon A). Image analysis COR values were about 2 degrees , whereas intralens COR values (95% confidence intervals) ranged from 4.0 degrees (3.3 degrees , 4.7 degrees ) (lotrafilcon A, captive bubble) to 10.2 degrees (8.4 degrees , 12.1 degrees ) (senofilcon A, sessile drop). Interlens COR values ranged from 4.5 degrees (3.7 degrees , 5.2 degrees ) (lotrafilcon A, captive bubble) to 16.5 degrees (13.6 degrees , 19.4 degrees ) (senofilcon A, sessile drop). Measurement error associated with image analysis was shown to be small as an absolute measure, although proportionally more significant for lenses with low contact angle. Sessile drop contact angles were typically less repeatable than captive bubble contact angles. For sessile drop measures, repeatability was poorer with the silicone hydrogel lenses when compared with the conventional hydrogel lens; this phenomenon was not observed for the captive bubble method, suggesting that methodological factors related to the sessile drop technique (such as surface dehydration and blotting) may play a role in the increased variability of contact angle measurements observed with silicone hydrogel contact lenses.

  13. Evaporation of liquid microdroplets levitated above a solid surface heated below the saturation temperature

    Science.gov (United States)

    Kirichenko, D. P.; Zaitsev, D. V.; Kabov, O. A.

    2016-10-01

    This paper presents a study of the interaction of liquid microdroplets falling on a solid surface whose temperature is varied from 75 °C to 155 °C. It has been shown for the first time that droplet levitation above a solid surface is possible at a temperature below the saturation temperature. It has been found that for levitated droplets, the specific evaporation rate is constant in time, but for sessile droplets, it increases sharply. The evaporation rate for sessile droplet was found an order of magnitude higher than that for levitated droplets.

  14. Pendant bubble method for an accurate characterization of superhydrophobic surfaces.

    Science.gov (United States)

    Ling, William Yeong Liang; Ng, Tuck Wah; Neild, Adrian

    2011-12-06

    The commonly used sessile drop method for measuring contact angles and surface tension suffers from errors on superhydrophobic surfaces. This occurs from unavoidable experimental error in determining the vertical location of the liquid-solid-vapor interface due to a camera's finite pixel resolution, thereby necessitating the development and application of subpixel algorithms. We demonstrate here the advantage of a pendant bubble in decreasing the resulting error prior to the application of additional algorithms. For sessile drops to attain an equivalent accuracy, the pixel count would have to be increased by 2 orders of magnitude.

  15. Wetting properties of AFM probes by means of contact angle measurement

    Science.gov (United States)

    Tao, Zhenhua; Bhushan, Bharat

    2006-09-01

    An atomic force microscopy (AFM) based technique was developed to measure the wetting properties of probe tips. By advancing and receding the AFM tip across the water surface, the meniscus force between the tip and the liquid was measured at the tip-water separation. The water contact angle was determined from the meniscus force. The obtained contact angle results were compared with that by the sessile drop method. It was found that the AFM based technique provided higher contact angle values than the sessile drop method. The mechanisms responsible for the difference are discussed.

  16. Wetting of soap bubbles on hydrophilic, hydrophobic and superhydrophobic surfaces

    CERN Document Server

    Arscott, Steve

    2013-01-01

    Wetting of sessile bubbles on solid and liquid surfaces has been studied. A model is presented for the contact angle of a sessile bubble based on a modified Young equation - the experimental results agree with the model. A hydrophilic surface results in a bubble contact angle of 90 deg whereas on a superhydrophobic surface one observes 134 deg. For hydrophilic surfaces, the bubble angle diminishes with bubble radius - whereas on a superhydrophobic surface, the bubble angle increases. The size of the Plateau borders governs the bubble contact angle - depending on the wetting of the surface.

  17. Persistence in a single species CSTR model with suspended flocs and wall attached biofilms.

    Science.gov (United States)

    Mašić, Alma; Eberl, Hermann J

    2012-04-01

    We consider a mathematical model for a bacterial population in a continuously stirred tank reactor (CSTR) with wall attachment. This is a modification of the Freter model, in which we model the sessile bacteria as a microbial biofilm. Our analysis indicates that the results of the algebraically simpler original Freter model largely carry over. In a computational simulation study, we find that the vast majority of bacteria in the reactor will eventually be sessile. However, we also find that suspended biomass is relatively more efficient in removing substrate from the reactor than biofilm bacteria.

  18. Dicty_cDB: Contig-U13423-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available AAC00-1, co... 37 1.1 CP000615_1134( CP000615 |pid:none) Burkholderia vietnamiensis G4 ...36 2.5 CP000447_2805( CP000447 |pid:none) Shewanella frigidimarina NCIMB ... 36 2.5 AM445006_1( AM445006 |pid:none) Vitis vin...none) Burkholderia cenocepacia MC0-3 c... 36 2.5 AL939108_142( AL939108 |pid:none) Streptomyces coelicolor A3(2) co...... 46 3.2 1 >( BJ432551 ) Dictyostelium discoideum cDNA clone:ddv19d02, 3' end, single read. Length = 747 Sco...se [ubiquinone] 1 alpha s... 712 0.0 AC115607_16( AC115607 |pid:none) Dictyostelium discoid

  19. Quantification of Pseudomonas aeruginosa in multispecies biofilms using PMA-qPCR

    Directory of Open Access Journals (Sweden)

    Sarah Tavernier

    2015-02-01

    Full Text Available Multispecies biofilms are an important healthcare problem and may lead to persistent infections. These infections are difficult to treat, as cells in a biofilm are highly resistant to antimicrobial agents. While increasingly being recognized as important, the properties of multispecies biofilms remain poorly studied. In order to do so, the quantification of the individual species is needed. The current cultivation-based approaches can lead to an underestimation of the actual cell number and are time-consuming. In the present study we set up a culture-independent approach based on propidium monoazide qPCR (PMA-qPCR to quantify Pseudomonas aeruginosa in a multispecies biofilm. As a proof of concept, we explored the influence of the combined presence of Staphylococcus aureus, Streptococcus anginosus and Burkholderia cenocepacia on the antimicrobial susceptibility of P. aeruginosa using this PMA-qPCR approach.

  20. Investigating Burkholderia cepacia complex populations recovered from Italian maize rhizosphere by multilocus sequence typing.

    Science.gov (United States)

    Dalmastri, Claudia; Baldwin, Adam; Tabacchioni, Silvia; Bevivino, Annamaria; Mahenthiralingam, Eshwar; Chiarini, Luigi; Dowson, Christopher

    2007-07-01

    The Burkholderia cepacia complex (BCC) comprises at least nine closely related species of abundant environmental microorganisms. Some of these species are highly spread in the rhizosphere of several crop plants, particularly of maize; additionally, as opportunistic pathogens, strains of the BCC are capable of colonizing humans. We have developed and validated a multilocus sequence typing (MLST) scheme for the BCC. Although widely applied to understand the epidemiology of bacterial pathogens, MLST has seen limited application to the population analysis of species residing in the natural environment; we describe its novel application to BCC populations within maize rhizospheres. 115 BCC isolates were recovered from the roots of different maize cultivars from three different Italian regions over a 9-year period (1994-2002). A total of 44 sequence types (STs) were found of which 41 were novel when compared with existing MLST data which encompassed a global database of 1000 clinical and environmental strains representing nearly 400 STs. In this study of rhizosphere isolates approximately 2.5 isolates per ST was found, comparable to that found for the whole BCC population. Multilocus sequence typing also resolved inaccuracies associated with previous identification of the maize isolates based on recA gene restriction fragment length polymorphims and species-specific polymerase chain reaction. The 115 maize isolates comprised the following BCC species groups, B. ambifaria (39%), BCC6 (29%), BCC5 (10%), B. pyrrocinia (8%), B. cenocepacia IIIB (7%) and B. cepacia (6%), with BCC5 and BCC6 potentially constituting novel species groups within the complex. Closely related clonal complexes of strains were identified within B. cepacia, B. cenocepacia IIIB, BCC5 and BCC6, with one of the BCC5 clonal complexes being distributed across all three sampling sites. Overall, our analysis demonstrates that the maize rhizosphere harbours a massive diversity of novel BCC STs, so that their

  1. Burkholderia cepacia complex Phage-Antibiotic Synergy (PAS): antibiotics stimulate lytic phage activity.

    Science.gov (United States)

    Kamal, Fatima; Dennis, Jonathan J

    2015-02-01

    The Burkholderia cepacia complex (Bcc) is a group of at least 18 species of Gram-negative opportunistic pathogens that can cause chronic lung infection in cystic fibrosis (CF) patients. Bcc organisms possess high levels of innate antimicrobial resistance, and alternative therapeutic strategies are urgently needed. One proposed alternative treatment is phage therapy, the therapeutic application of bacterial viruses (or bacteriophages). Recently, some phages have been observed to form larger plaques in the presence of sublethal concentrations of certain antibiotics; this effect has been termed phage-antibiotic synergy (PAS). Those reports suggest that some antibiotics stimulate increased production of phages under certain conditions. The aim of this study is to examine PAS in phages that infect Burkholderia cenocepacia strains C6433 and K56-2. Bcc phages KS12 and KS14 were tested for PAS, using 6 antibiotics representing 4 different drug classes. Of the antibiotics tested, the most pronounced effects were observed for meropenem, ciprofloxacin, and tetracycline. When grown with subinhibitory concentrations of these three antibiotics, cells developed a chain-like arrangement, an elongated morphology, and a clustered arrangement, respectively. When treated with progressively higher antibiotic concentrations, both the sizes of plaques and phage titers increased, up to a maximum. B. cenocepacia K56-2-infected Galleria mellonella larvae treated with phage KS12 and low-dose meropenem demonstrated increased survival over controls treated with KS12 or antibiotic alone. These results suggest that antibiotics can be combined with phages to stimulate increased phage production and/or activity and thus improve the efficacy of bacterial killing.

  2. The third replicon of members of the Burkholderia cepacia Complex, plasmid pC3, plays a role in stress tolerance.

    Science.gov (United States)

    Agnoli, Kirsty; Frauenknecht, Carmen; Freitag, Roman; Schwager, Stephan; Jenul, Christian; Vergunst, Annette; Carlier, Aurelien; Eberl, Leo

    2014-02-01

    The metabolically versatile Burkholderia cepacia complex (Bcc) occupies a variety of niches, including the plant rhizosphere and the cystic fibrosis lung (where it is often fatal to the patient). Bcc members have multipartite genomes, of which the third replicon, pC3 (previously chromosome 3), has been shown to be a nonessential megaplasmid which confers virulence and both antifungal and proteolytic activity on several strains. In this study, pC3 curing was extended to cover strains of 16 of the 17 members of the Bcc, and the phenotypes conferred by pC3 were determined. B. cenocepacia strains H111, MCO-3, and HI2424 were previously cured of pC3; however, this had not proved possible in the epidemic strain K56-2. Here, we investigated the mechanism of this unexpected stability and found that efficient toxin-antitoxin systems are responsible for maintaining pC3 of strain K56-2. Identification of these systems allowed neutralization of the toxins and the subsequent deletion of K56-2pC3. The cured strain was found to exhibit reduced antifungal activity and was attenuated in both the zebrafish and the Caenorhabditis elegans model of infection. We used a PCR screening method to examine the prevalence of pC3 within 110 Bcc isolates and found that this replicon was absent in only four cases, suggesting evolutionary fixation. It is shown that plasmid pC3 increases the resistance of B. cenocepacia H111 to various stresses (oxidative, osmotic, high-temperature, and chlorhexidine-induced stresses), explaining the prevalence of this replicon within the Bcc.

  3. Pore-forming pyocin S5 utilizes the FptA ferripyochelin receptor to kill Pseudomonas aeruginosa.

    Science.gov (United States)

    Elfarash, Ameer; Dingemans, Jozef; Ye, Lumeng; Hassan, Ahmed Amir; Craggs, Michael; Reimmann, Cornelia; Thomas, Mark S; Cornelis, Pierre

    2014-02-01

    Pyocins are toxic proteins produced by some strains of Pseudomonas aeruginosa that are lethal for related strains of the same species. Some soluble pyocins (S2, S3 and S4) were previously shown to use the pyoverdine siderophore receptors to enter the cell. The P. aeruginosa PAO1 pore-forming pyocin S5 encoding gene (PAO985) was cloned into the expression vector pET15b, and the affinity-purified protein product tested for its killing activity against different P. aeruginosa strains. The results, however, did not show any correlation with a specific ferripyoverdine receptor. To further identify the S5 receptor, transposon mutants were generated. Pooled mutants were exposed to pyocin S5 and the resistant colonies growing in the killing zone were selected. The majority of S5-resistant mutants had an insertion in the fptA gene encoding the receptor for the siderophore pyochelin. Complementation of an fptA transposon mutant with the P. aeruginosa fptA gene in trans restored the sensitivity to S5. In order to define the receptor-binding domain of pyocin S5, two hybrid pyocins were constructed containing different regions from pyocin S5 fused to the C-terminal translocation and DNase killing domains of pyocin S2. Only the protein containing amino acid residues 151 to 300 from S5 showed toxicity, indicating that the pyocin S5 receptor-binding domain is not at the N-terminus of the protein as in other S-type pyocins. Pyocin S5 was, however, unable to kill Burkholderia cenocepacia strains producing a ferripyochelin FptA receptor, nor was the B. cenocepacia fptA gene able to restore the sensitivity of the resistant fptA mutant P. aeruginosa strain.

  4. Severe disseminated phaeohyphomycosis in an immunocompetent patient caused by Veronaea botryosa

    NARCIS (Netherlands)

    Bonifaz, A.; Davoudi, M.M.; de Hoog, G.S.; Padilla-Desgarennes, C.; Vazquez-Gonzalez, D.; Navarrete, G.; Meis, J.F.G.M.; Badali, H.

    2013-01-01

    We present a severe case of disseminated phaeohyphomycosis due to Veronaea botryosa. A 32-year-old female, native from Cuautla, Morelos, Mexico, presented a chronic dermatosis which started 10 years earlier with multiple exophytic, multilobulated, soft, and pedunculated or sessile neoformations of d

  5. The Intelligent Behavior of Plants

    NARCIS (Netherlands)

    van Loon, Leendert C

    2016-01-01

    Plants are as adept as animals and humans in reacting effectively to their ever-changing environment. Of necessity, their sessile nature requires specific adaptations, but their cells possess a network-type communication system with emerging properties at the level of the organ or entire plant. The

  6. The evolution of plant chemical defence - new roles for hydroxynitrile glucosides in Lotus japonicus

    DEFF Research Database (Denmark)

    Knudsen, Camilla

    Plants are sessile organisms well-known to produce a vast array of chemical compounds of which many are used in chemical defence against herbivores and pathogens. The biosynthesis of these plant chemical defence compounds poses a considerable risk of self-toxicity for the plant itself. Several ty...

  7. Evaluation of stability for monolayer injection molding tools coating

    DEFF Research Database (Denmark)

    Cech, Jiri; Taboryski, Rafael J.

    2012-01-01

    We tested and characterized molecular coating of Aluminium and Nickel prototype molds and mold inserts for polymer replication via injection molding (IM). X-Ray photoelectron spectroscopy (XPS) data, sessile drop contact angles with multiple fluids, surface energy and roughness data have been...... and especially suitable for rapid prototyping and mold geometry testing....

  8. Endoluminal compression clip : full-thickness resection of the mesenteric bowel wall in a porcine model

    NARCIS (Netherlands)

    Kopelman, Yael; Siersema, Peter D.; Nir, Yael; Szold, Amir; Bapaye, Amol; Segol, Ori; Willenz, Ehud P.; Lelcuk, Shlomo; Geller, Alexander; Kopelman, Doron

    2009-01-01

    Background: Performing a full-thickness intestinal wall resection Of a sessile polyp located on the mesenteric side with a compression clip may lead to compression of mesenteric vessels. The application of such a clip may therefore cause a compromised blood supply in the particular bowel segment, le

  9. RNF43 germline and somatic mutation in serrated neoplasia pathway and its association with BRAF mutation

    NARCIS (Netherlands)

    Yan, Helen H N; Lai, Jeffrey C W; Ho, Siu Lun; Leung, Wai Keung; Law, Wai Lun; Lee, Janet F Y; Chan, Anthony K W; Tsui, Wai Yin; Chan, Annie S Y; Lee, Bernard C H; Yue, Sarah S K; Man, Alice H Y; Clevers, Hans; Yuen, Siu Tsan; Leung, Suet Yi

    2016-01-01

    OBJECTIVE: Serrated polyps (hyperplastic polyps, sessile or traditional serrated adenomas), which can arise in a sporadic or polyposis setting, predispose to colorectal cancer (CRC), especially those with microsatellite instability (MSI) due to MLH1 promoter methylation (MLH1(me+)). We investigate g

  10. Drop shape analysis for determination of dynamic contact angles by double sided elliptical fitting method

    DEFF Research Database (Denmark)

    Andersen, Nis Korsgaard; Taboryski, Rafael J.

    2017-01-01

    Contact angle measurements are a fast and simple way to measure surface properties and is therefore widely used to measure surface energy and quantify wetting of a solid surface by a liquid substance. In common praxis contact angle measurements are done with sessile drops on a horizontal surface ...

  11. Effect of Oxygen Limitation and Starvation on the Benzalkonium Chloride Susceptibility of Escherichia coli

    DEFF Research Database (Denmark)

    Bjergbæk, L.A.; Haagensen, Janus Anders Juul; Molin, Søren

    2008-01-01

    Aims: To investigate the effect of oxygen limitation, glucose-starvation and temperature on the susceptibility of Escherichia coli towards the quaternary ammonium biocide benzalkonium chloride (BAC). Methods and Results: The effect of BAC on planktonic and sessile cells were investigated using...

  12. Ambient temperature‐directed flowering time regulation

    NARCIS (Netherlands)

    Verhage, Dina Sara Leonie

    2017-01-01

    As a consequence of a sessile lifestyle, plants are constantly facing a fluctuating environment. In order to both profit maximally and protect themselves from these environmental cues, plants evolved ways to sense and respond to signals. Ambient temperature is one of the cues for which plants have a

  13. Planktonic replication is essential for biofilm formation by Legionella pneumophila in a complex medium under static and dynamic flow conditions

    DEFF Research Database (Denmark)

    Mampel, J.; Spirig, T.; Weber, S.S.

    2006-01-01

    formed biofilms in the inverse system if the medium was exchanged twice a day. However, after addition of Acanthamoeba castellanii, the bacteria proliferated and adhered to surfaces. Sessile (surface-attached) and planktonic (free-swimming) L. pneumophila expressed beta-galactosidase activity to similar...

  14. Unraveling transcriptional and translational control in plant energy homeostasis : a bioinformatic approach

    NARCIS (Netherlands)

    Peviani, A.

    2016-01-01

    Due to their sessile nature, plants require a tight regulation of energy homeostasis in order to survive and reproduce in changing environmental conditions. Regulation of gene expression is controlled at several levels, from transcription to translation and beyond. Sugars themselves can act directly

  15. Current-driven Flow across a Stationary Jellyfish

    CERN Document Server

    Hamlet, Christina; Fan, Roger; Dollinger, Makani; Harenber, Steve

    2011-01-01

    We present several dye visualization and numerical simulation fluid dynamics videos of a sessile jellyfish subjected to channel flow. The low resolution video and the high resolution video display the vortex patterns in different channel flows. This description accompanies the video submission V038 to the 2011 APS DFD Gallery of Fluid Motion.

  16. Soil-water repellency characteristic curves for soil profiles with organic carbon gradients

    DEFF Research Database (Denmark)

    Wijewardana, Nadeeka Senani; Müller, Karin; Møldrup, Per;

    2016-01-01

    Highlights •Water repellency at different soil organic carbon (SOC) contents was measured. •Repellency was restricted to the top 20 cm of the soil profiles. •The sessile drop method is highly sensitive at high SOC contents. •We proposed six repellency parameters for repellent soils. •Functions...

  17. A Fish Larvae and Egg Exposure System (FLEES) for Evaluating the Effects of Suspended Sediments on Aquatic Life

    Science.gov (United States)

    2012-08-01

    replication. For larger or sessile organisms, exposure often occurs in the open aquarium. Screens are placed over the suction and inflow ports of...of bucket dredging plumes on walleye spawning habitat in Maumee Bay, Ohio. Proceedings of the 18th World Dredging Congress (WODCON XVIII), Lake

  18. Batidaceae

    NARCIS (Netherlands)

    Royen, van P.

    1955-01-01

    Dioecious or monoecious small shrubs with thick woody roots. Leaves simple, opposite, sessile, fleshy, with a distinctly saccate, colourless base. Stipules minute. Flowers unisexual, either solitary and terminal or axillary, or in small axillary spikes. ♂ Flowers subtended by bracts, enclosed in a m

  19. Sucrose controlled translation mediated by a sequence conserved peptide in Arabidopsis thaliana

    NARCIS (Netherlands)

    Lastdrager, Jeroen

    2015-01-01

    The sessile nature of plants demands adaptation to a variety of external stimuli. Sugars have well established roles in steering growth and developmental processes, and sugar levels are a good proxy for the energy status in plants. Molecular sugar signaling networks perceive the availability of suga

  20. How to make sticky surfaces slippery: Contact angle hysteresis in electrowetting with alternating voltage

    NARCIS (Netherlands)

    Li, F.; Mugele, Frieder

    2008-01-01

    Contact angle hysteresis caused by random pinning forces is a major obstacle in moving small quantities of liquid on solid surfaces. Here, we demonstrate that the contact angle hysteresis for sessile drops in electrowetting almost disappears with increasing alternating voltage, whereas for direct vo