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Sample records for model membrane disruption

  1. Plasma membrane disruption: repair, prevention, adaptation

    Science.gov (United States)

    McNeil, Paul L.; Steinhardt, Richard A.

    2003-01-01

    Many metazoan cells inhabit mechanically stressful environments and, consequently, their plasma membranes are frequently disrupted. Survival requires that the cell rapidly repair or reseal the disruption. Rapid resealing is an active and complex structural modification that employs endomembrane as its primary building block, and cytoskeletal and membrane fusion proteins as its catalysts. Endomembrane is delivered to the damaged plasma membrane through exocytosis, a ubiquitous Ca2+-triggered response to disruption. Tissue and cell level architecture prevent disruptions from occurring, either by shielding cells from damaging levels of force, or, when this is not possible, by promoting safe force transmission through the plasma membrane via protein-based cables and linkages. Prevention of disruption also can be a dynamic cell or tissue level adaptation triggered when a damaging level of mechanical stress is imposed. Disease results from failure of either the preventive or resealing mechanisms.

  2. Cationic peptide exposure enhances pulsed-electric-field-mediated membrane disruption.

    Science.gov (United States)

    Kennedy, Stephen M; Aiken, Erik J; Beres, Kaytlyn A; Hahn, Adam R; Kamin, Samantha J; Hagness, Susan C; Booske, John H; Murphy, William L

    2014-01-01

    The use of pulsed electric fields (PEFs) to irreversibly electroporate cells is a promising approach for destroying undesirable cells. This approach may gain enhanced applicability if the intensity of the PEF required to electrically disrupt cell membranes can be reduced via exposure to a molecular deliverable. This will be particularly impactful if that reduced PEF minimally influences cells that are not exposed to the deliverable. We hypothesized that the introduction of charged molecules to the cell surfaces would create regions of enhanced transmembrane electric potential in the vicinity of each charged molecule, thereby lowering the PEF intensity required to disrupt the plasma membranes. This study will therefore examine if exposure to cationic peptides can enhance a PEF's ability to disrupt plasma membranes. We exposed leukemia cells to 40 μs PEFs in media containing varying concentrations of a cationic peptide, polyarginine. We observed the internalization of a membrane integrity indicator, propidium iodide (PI), in real time. Based on an individual cell's PI fluorescence versus time signature, we were able to determine the relative degree of membrane disruption. When using 1-2 kV/cm, exposure to >50 μg/ml of polyarginine resulted in immediate and high levels of PI uptake, indicating severe membrane disruption, whereas in the absence of peptide, cells predominantly exhibited signatures indicative of no membrane disruption. Additionally, PI entered cells through the anode-facing membrane when exposed to cationic peptide, which was theoretically expected. Exposure to cationic peptides reduced the PEF intensity required to induce rapid and irreversible membrane disruption. Critically, peptide exposure reduced the PEF intensities required to elicit irreversible membrane disruption at normally sub-electroporation intensities. We believe that these cationic peptides, when coupled with current advancements in cell targeting techniques will be useful tools in

  3. Cell membrane disruption stimulates cAMP and Ca2+ signaling to potentiate cell membrane resealing in neighboring cells

    Directory of Open Access Journals (Sweden)

    Tatsuru Togo

    2017-12-01

    Full Text Available Disruption of cellular plasma membranes is a common event in many animal tissues, and the membranes are usually rapidly resealed. Moreover, repeated membrane disruptions within a single cell reseal faster than the initial wound in a protein kinase A (PKA- and protein kinase C (PKC-dependent manner. In addition to wounded cells, recent studies have demonstrated that wounding of Madin-Darby canine kidney (MDCK cells potentiates membrane resealing in neighboring cells in the short-term by purinergic signaling, and in the long-term by nitric oxide/protein kinase G signaling. In the present study, real-time imaging showed that cell membrane disruption stimulated cAMP synthesis and Ca2+ mobilization from intracellular stores by purinergic signaling in neighboring MDCK cells. Furthermore, inhibition of PKA and PKC suppressed the ATP-mediated short-term potentiation of membrane resealing in neighboring cells. These results suggest that cell membrane disruption stimulates PKA and PKC via purinergic signaling to potentiate cell membrane resealing in neighboring MDCK cells.

  4. Atmospheric-pressure guided streamers for liposomal membrane disruption

    International Nuclear Information System (INIS)

    Svarnas, P.; Aleiferis, Sp.; Matrali, S. H.; Gazeli, K.; Clément, F.; Antimisiaris, S. G.

    2012-01-01

    The potential to use liposomes (LIPs) as a cellular model in order to study interactions of cold atmospheric-pressure plasma with cells is herein investigated. Cold atmospheric-pressure plasma is formed by a dielectric-barrier discharge reactor. Large multilamellar vesicle liposomes, consisted of phosphatidylcholine and cholesterol, are prepared by the thin film hydration technique, to encapsulate a small hydrophilic dye, i.e., calcein. The plasma-induced release of calcein from liposomes is then used as a measure of liposome membrane integrity and, consequently, interaction between the cold atmospheric plasma and lipid bilayers. Physical mechanisms leading to membrane disruption are suggested, based on the plasma characterization including gas temperature calculation.

  5. Two-Step Mechanism of Membrane Disruption by Aβ through Membrane Fragmentation and Pore Formation

    Science.gov (United States)

    Sciacca, Michele F.M.; Kotler, Samuel A.; Brender, Jeffrey R.; Chen, Jennifer; Lee, Dong-kuk; Ramamoorthy, Ayyalusamy

    2012-01-01

    Disruption of cell membranes by Aβ is believed to be one of the key components of Aβ toxicity. However, the mechanism by which this occurs is not fully understood. Here, we demonstrate that membrane disruption by Aβ occurs by a two-step process, with the initial formation of ion-selective pores followed by nonspecific fragmentation of the lipid membrane during amyloid fiber formation. Immediately after the addition of freshly dissolved Aβ1–40, defects form on the membrane that share many of the properties of Aβ channels originally reported from single-channel electrical recording, such as cation selectivity and the ability to be blockaded by zinc. By contrast, subsequent amyloid fiber formation on the surface of the membrane fragments the membrane in a way that is not cation selective and cannot be stopped by zinc ions. Moreover, we observed that the presence of ganglioside enhances both the initial pore formation and the fiber-dependent membrane fragmentation process. Whereas pore formation by freshly dissolved Aβ1–40 is weakly observed in the absence of gangliosides, fiber-dependent membrane fragmentation can only be observed in their presence. These results provide insights into the toxicity of Aβ and may aid in the design of specific compounds to alleviate the neurodegeneration of Alzheimer’s disease. PMID:22947931

  6. Liposomal membrane disruption by means of miniaturized dielectric-barrier discharge in air: liposome characterization

    Science.gov (United States)

    Svarnas, P.; Asimakoulas, L.; Katsafadou, M.; Pachis, K.; Kostazos, N.; Antimisiaris, S. G.

    2017-08-01

    The increasing interest of the plasma community in the application of atmospheric-pressure cold plasmas to bio-specimen treatment has led to the creation of the emerging field of plasma biomedicine. Accordingly, plasma setups based on dielectric-barrier discharges have already been widely tested for the inactivation of various cells. Most of these systems refer to the plasma jet concept where noble gases penetrate atmospheric air and are subjected to the influence of high electric fields, thus forming guided streamers. Following the original works of our group where liposomal membranes were proposed as models for studying the interaction between plasma jets and cells, we present herein a study on liposomal membrane disruption by means of miniaturized dielectric-barrier discharge running in atmospheric air. Liposomal membranes of various lipid compositions, lamellarities, and sizes are treated at different times. It is shown that the dielectric-barrier discharge of low mean power leads to efficient liposomal membrane disruption. The latter is achieved in a controllable manner and depends on liposome properties. Additionally, it is clearly demonstrated that liposomal membrane disruption takes place even after plasma extinction, i.e. during post-treatment, resembling thus an ‘apoptosis’ effect, which is well known today mainly for cell membranes. Thus, the adoption of the present concept would be beneficial for tailoring studies on plasma-treated cell-mimics. Finally, the liposome treatment is discussed with respect to possible physicochemical mechanisms and potential discharge modification due to the various compositions of the liquid electrode.

  7. Applying fluorescence correlation spectroscopy to investigate peptide-induced membrane disruption

    DEFF Research Database (Denmark)

    Kristensen, Kasper; Henriksen, Jonas Rosager; Andresen, Thomas Lars

    2017-01-01

    to quantify leakage of fluorescent molecules of different sizes from large unilamellar lipid vesicles, thereby providing a tool for estimating the size of peptide-induced membrane disruptions. If fluorescently labeled lipids are incorporated into the membranes of the vesicles, FCS can also be used to obtain...

  8. SV40 late protein VP4 forms toroidal pores to disrupt membranes for viral release.

    Science.gov (United States)

    Raghava, Smita; Giorda, Kristina M; Romano, Fabian B; Heuck, Alejandro P; Hebert, Daniel N

    2013-06-04

    Nonenveloped viruses are generally released from the cell by the timely lysis of host cell membranes. SV40 has been used as a model virus for the study of the lytic nonenveloped virus life cycle. The expression of SV40 VP4 at later times during infection is concomitant with cell lysis. To investigate the role of VP4 in viral release and its mechanism of action, VP4 was expressed and purified from bacteria as a fusion protein for use in membrane disruption assays. Purified VP4 perforated membranes as demonstrated by the release of fluorescent markers encapsulated within large unilamellar vesicles or liposomes. Dynamic light scattering results revealed that VP4 treatment did not cause membrane lysis or change the size of the liposomes. Liposomes encapsulated with 4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-3-indacene-labeled streptavidin were used to show that VP4 formed stable pores in membranes. These VP4 pores had an inner diameter of 1-5 nm. Asymmetrical liposomes containing pyrene-labeled lipids in the outer monolayer were employed to monitor transbilayer lipid diffusion. Consistent with VP4 forming toroidal pore structures in membranes, VP4 induced transbilayer lipid diffusion or lipid flip-flop. Altogether, these studies support a central role for VP4 acting as a viroporin in the disruption of cellular membranes to trigger SV40 viral release by forming toroidal pores that unite the outer and inner leaflets of membrane bilayers.

  9. Helicobacter pylori Disrupts Host Cell Membranes, Initiating a Repair Response and Cell Proliferation

    Directory of Open Access Journals (Sweden)

    Hsueh-Fen Juan

    2012-08-01

    Full Text Available Helicobacter pylori (H. pylori, the human stomach pathogen, lives on the inner surface of the stomach and causes chronic gastritis, peptic ulcer, and gastric cancer. Plasma membrane repair response is a matter of life and death for human cells against physical and biological damage. We here test the hypothesis that H. pylori also causes plasma membrane disruption injury, and that not only a membrane repair response but also a cell proliferation response are thereby activated. Vacuolating cytotoxin A (VacA and cytotoxin-associated gene A (CagA have been considered to be major H. pylori virulence factors. Gastric cancer cells were infected with H. pylori wild type (vacA+/cagA+, single mutant (ΔvacA or ΔcagA or double mutant (ΔvacA/ΔcagA strains and plasma membrane disruption events and consequent activation of membrane repair components monitored. H. pylori disrupts the host cell plasma membrane, allowing localized dye and extracellular Ca2+ influx. Ca2+-triggered members of the annexin family, A1 and A4, translocate, in response to injury, to the plasma membrane, and cell surface expression of an exocytotic maker of repair, LAMP-2, increases. Additional forms of plasma membrane disruption, unrelated to H. pylori exposure, also promote host cell proliferation. We propose that H. pylori activation of a plasma membrane repair is pro-proliferative. This study might therefore provide new insight into potential mechanisms of H. pylori-induced gastric carcinogenesis.

  10. Interaction of Defensins with Model Cell Membranes

    Science.gov (United States)

    Sanders, Lori K.; Schmidt, Nathan W.; Yang, Lihua; Mishra, Abhijit; Gordon, Vernita D.; Selsted, Michael E.; Wong, Gerard C. L.

    2009-03-01

    Antimicrobial peptides (AMPs) comprise a key component of innate immunity for a wide range of multicellular organisms. For many AMPs, activity comes from their ability to selectively disrupt and lyse bacterial cell membranes. There are a number of proposed models for this action, but the detailed molecular mechanism of selective membrane permeation remains unclear. Theta defensins are circularized peptides with a high degree of selectivity. We investigate the interaction of model bacterial and eukaryotic cell membranes with theta defensins RTD-1, BTD-7, and compare them to protegrin PG-1, a prototypical AMP, using synchrotron small angle x-ray scattering (SAXS). The relationship between membrane composition and peptide induced changes in membrane curvature and topology is examined. By comparing the membrane phase behavior induced by these different peptides we will discuss the importance of amino acid composition and placement on membrane rearrangement.

  11. Membrane Raft Organization Is More Sensitive to Disruption by (n-3) PUFA Than Nonraft Organization in EL4 and B Cells123

    OpenAIRE

    Rockett, Benjamin Drew; Franklin, Andrew; Harris, Mitchel; Teague, Heather; Rockett, Alexis; Shaikh, Saame Raza

    2011-01-01

    Model membrane and cellular detergent extraction studies show (n-3) PUFA predominately incorporate into nonrafts; thus, we hypothesized (n-3) PUFA could disrupt nonraft organization. The first objective of this study was to determine whether (n-3) PUFA disrupted nonrafts of EL4 cells, an extension of our previous work in which we discovered an (n-3) PUFA diminished raft clustering. EPA or DHA treatment of EL4 cells increased plasma membrane accumulation of the nonraft probe 1,1′-dilinoleyl-3,...

  12. A Peptidomimetic Antibiotic Targets Outer Membrane Proteins and Disrupts Selectively the Outer Membrane in Escherichia coli.

    Science.gov (United States)

    Urfer, Matthias; Bogdanovic, Jasmina; Lo Monte, Fabio; Moehle, Kerstin; Zerbe, Katja; Omasits, Ulrich; Ahrens, Christian H; Pessi, Gabriella; Eberl, Leo; Robinson, John A

    2016-01-22

    Increasing antibacterial resistance presents a major challenge in antibiotic discovery. One attractive target in Gram-negative bacteria is the unique asymmetric outer membrane (OM), which acts as a permeability barrier that protects the cell from external stresses, such as the presence of antibiotics. We describe a novel β-hairpin macrocyclic peptide JB-95 with potent antimicrobial activity against Escherichia coli. This peptide exhibits no cellular lytic activity, but electron microscopy and fluorescence studies reveal an ability to selectively disrupt the OM but not the inner membrane of E. coli. The selective targeting of the OM probably occurs through interactions of JB-95 with selected β-barrel OM proteins, including BamA and LptD as shown by photolabeling experiments. Membrane proteomic studies reveal rapid depletion of many β-barrel OM proteins from JB-95-treated E. coli, consistent with induction of a membrane stress response and/or direct inhibition of the Bam folding machine. The results suggest that lethal disruption of the OM by JB-95 occurs through a novel mechanism of action at key interaction sites within clusters of β-barrel proteins in the OM. These findings open new avenues for developing antibiotics that specifically target β-barrel proteins and the integrity of the Gram-negative OM. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  13. Membrane Incorporation, Channel Formation, and Disruption of Calcium Homeostasis by Alzheimer's β-Amyloid Protein

    Directory of Open Access Journals (Sweden)

    Masahiro Kawahara

    2011-01-01

    Full Text Available Oligomerization, conformational changes, and the consequent neurodegeneration of Alzheimer's β-amyloid protein (AβP play crucial roles in the pathogenesis of Alzheimer's disease (AD. Mounting evidence suggests that oligomeric AβPs cause the disruption of calcium homeostasis, eventually leading to neuronal death. We have demonstrated that oligomeric AβPs directly incorporate into neuronal membranes, form cation-sensitive ion channels (“amyloid channels”, and cause the disruption of calcium homeostasis via the amyloid channels. Other disease-related amyloidogenic proteins, such as prion protein in prion diseases or α-synuclein in dementia with Lewy bodies, exhibit similarities in the incorporation into membranes and the formation of calcium-permeable channels. Here, based on our experimental results and those of numerous other studies, we review the current understanding of the direct binding of AβP into membrane surfaces and the formation of calcium-permeable channels. The implication of composition of membrane lipids and the possible development of new drugs by influencing membrane properties and attenuating amyloid channels for the treatment and prevention of AD is also discussed.

  14. Nanosecond pulsed electric field (nsPEF) enhance cytotoxicity of cisplatin to hepatocellular cells by microdomain disruption on plasma membrane.

    Science.gov (United States)

    Yin, Shengyong; Chen, Xinhua; Xie, Haiyang; Zhou, Lin; Guo, Danjing; Xu, Yuning; Wu, Liming; Zheng, Shusen

    2016-08-15

    Previous studies showed nanosecond pulsed electric field (nsPEF) can ablate solid tumors including hepatocellular carcinoma (HCC) but its effect on cell membrane is not fully understood. We hypothesized nsPEF disrupt the microdomains on outer-cellular membrane with direct mechanical force and as a result the plasma membrane permeability increases to facilitate the small molecule intake. Three HCC cells were pulsed one pulse per minute, an interval longer than nanopore resealing time. The cationized ferritin was used to mark up the electronegative microdomains, propidium iodide (PI) for membrane permeabilization, energy dispersive X-ray spectroscopy (EDS) for the negative cell surface charge and cisplatin for inner-cellular cytotoxicity. We demonstrated that the ferritin marked-microdomain and negative cell surface charge were disrupted by nsPEF caused-mechanical force. The cell uptake of propidium and cytotoxicity of DNA-targeted cisplatin increased with a dose effect. Cisplatin gains its maximum inner-cellular cytotoxicity when combining with nsPEF stimulation. We conclude that nsPEF disrupt the microdomains on the outer cellular membrane directly and increase the membrane permeabilization for PI and cisplatin. The microdomain disruption and membrane infiltration changes are caused by the mechanical force from the changes of negative cell surface charge. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Nanosecond pulsed electric field (nsPEF) enhance cytotoxicity of cisplatin to hepatocellular cells by microdomain disruption on plasma membrane

    International Nuclear Information System (INIS)

    Yin, Shengyong; Chen, Xinhua; Xie, Haiyang; Zhou, Lin; Guo, Danjing; Xu, Yuning; Wu, Liming; Zheng, Shusen

    2016-01-01

    Previous studies showed nanosecond pulsed electric field (nsPEF) can ablate solid tumors including hepatocellular carcinoma (HCC) but its effect on cell membrane is not fully understood. We hypothesized nsPEF disrupt the microdomains on outer-cellular membrane with direct mechanical force and as a result the plasma membrane permeability increases to facilitate the small molecule intake. Three HCC cells were pulsed one pulse per minute, an interval longer than nanopore resealing time. The cationized ferritin was used to mark up the electronegative microdomains, propidium iodide (PI) for membrane permeabilization, energy dispersive X-ray spectroscopy (EDS) for the negative cell surface charge and cisplatin for inner-cellular cytotoxicity. We demonstrated that the ferritin marked-microdomain and negative cell surface charge were disrupted by nsPEF caused-mechanical force. The cell uptake of propidium and cytotoxicity of DNA-targeted cisplatin increased with a dose effect. Cisplatin gains its maximum inner-cellular cytotoxicity when combining with nsPEF stimulation. We conclude that nsPEF disrupt the microdomains on the outer cellular membrane directly and increase the membrane permeabilization for PI and cisplatin. The microdomain disruption and membrane infiltration changes are caused by the mechanical force from the changes of negative cell surface charge.

  16. Nanosecond pulsed electric field (nsPEF) enhance cytotoxicity of cisplatin to hepatocellular cells by microdomain disruption on plasma membrane

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Shengyong; Chen, Xinhua; Xie, Haiyang; Zhou, Lin [Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, 310003 Hangzhou (China); Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health and Key Laboratory of Organ Transplantation of Zhejiang Province, The Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital, Zhejiang University, Hangzhou 310003 (China); Guo, Danjing; Xu, Yuning [Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health and Key Laboratory of Organ Transplantation of Zhejiang Province, The Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital, Zhejiang University, Hangzhou 310003 (China); Wu, Liming, E-mail: wlm@zju.edu.cn [Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, 310003 Hangzhou (China); Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health and Key Laboratory of Organ Transplantation of Zhejiang Province, The Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital, Zhejiang University, Hangzhou 310003 (China); Zheng, Shusen, E-mail: shusenzheng@zju.edu.cn [Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, Zhejiang University, 310003 Hangzhou (China); Key Laboratory of Combined Multi-organ Transplantation, Ministry of Public Health and Key Laboratory of Organ Transplantation of Zhejiang Province, The Department of Hepatobiliary and Pancreatic Surgery, The First Affiliated Hospital, Zhejiang University, Hangzhou 310003 (China)

    2016-08-15

    Previous studies showed nanosecond pulsed electric field (nsPEF) can ablate solid tumors including hepatocellular carcinoma (HCC) but its effect on cell membrane is not fully understood. We hypothesized nsPEF disrupt the microdomains on outer-cellular membrane with direct mechanical force and as a result the plasma membrane permeability increases to facilitate the small molecule intake. Three HCC cells were pulsed one pulse per minute, an interval longer than nanopore resealing time. The cationized ferritin was used to mark up the electronegative microdomains, propidium iodide (PI) for membrane permeabilization, energy dispersive X-ray spectroscopy (EDS) for the negative cell surface charge and cisplatin for inner-cellular cytotoxicity. We demonstrated that the ferritin marked-microdomain and negative cell surface charge were disrupted by nsPEF caused-mechanical force. The cell uptake of propidium and cytotoxicity of DNA-targeted cisplatin increased with a dose effect. Cisplatin gains its maximum inner-cellular cytotoxicity when combining with nsPEF stimulation. We conclude that nsPEF disrupt the microdomains on the outer cellular membrane directly and increase the membrane permeabilization for PI and cisplatin. The microdomain disruption and membrane infiltration changes are caused by the mechanical force from the changes of negative cell surface charge.

  17. Membrane raft organization is more sensitive to disruption by (n-3) PUFA than nonraft organization in EL4 and B cells.

    Science.gov (United States)

    Rockett, Benjamin Drew; Franklin, Andrew; Harris, Mitchel; Teague, Heather; Rockett, Alexis; Shaikh, Saame Raza

    2011-06-01

    Model membrane and cellular detergent extraction studies show (n-3) PUFA predominately incorporate into nonrafts; thus, we hypothesized (n-3) PUFA could disrupt nonraft organization. The first objective of this study was to determine whether (n-3) PUFA disrupted nonrafts of EL4 cells, an extension of our previous work in which we discovered an (n-3) PUFA diminished raft clustering. EPA or DHA treatment of EL4 cells increased plasma membrane accumulation of the nonraft probe 1,1'-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate by ~50-70% relative to a BSA control. Förster resonance energy transfer imaging showed EPA and DHA also disrupted EL4 nanometer scale nonraft organization by increasing the distance between nonraft molecules by ~25% compared with BSA. However, changes in nonrafts were due to an increase in cell size; under conditions where EPA or DHA did not increase cell size, nonraft organization was unaffected. We next translated findings on EL4 cells by testing if (n-3) PUFA administered to mice disrupted nonrafts and rafts. Imaging of B cells isolated from mice fed low- or high-fat (HF) (n-3) PUFA diets showed no change in nonraft organization compared with a control diet (CD). However, confocal microscopy revealed the HF (n-3) PUFA diet disrupted lipid raft clustering and size by ~40% relative to CD. Taken together, our data from 2 different model systems suggest (n-3) PUFA have limited effects on nonrafts. The ex vivo data, which confirm previous studies with EL4 cells, provide evidence that (n-3) PUFA consumed through the diet disrupt B cell lipid raft clustering.

  18. N-3 fatty acids and membrane microdomains: from model membranes to lymphocyte function.

    Science.gov (United States)

    Shaikh, Saame Raza; Teague, Heather

    2012-12-01

    This article summarizes the author's research on fish oil derived n-3 fatty acids, plasma membrane organization and B cell function. We first cover basic model membrane studies that investigated how docosahexaenoic acid (DHA) targeted the organization of sphingolipid-cholesterol enriched lipid microdomains. A key finding here was that DHA had a relatively poor affinity for cholesterol. This work led to a model that predicted DHA acyl chains in cells would manipulate lipid-protein microdomain organization and thereby function. We then review how the predictions of the model were tested with B cells in vitro followed by experiments using mice fed fish oil. These studies reveal a highly complex picture on how n-3 fatty acids target lipid-protein organization and B cell function. Key findings are as follows: (1) n-3 fatty acids target not just the plasma membrane but also endomembrane organization; (2) DHA, but not eicosapentaenoic acid (EPA), disrupts microdomain spatial distribution (i.e. clustering), (3) DHA alters protein lateral organization and (4) changes in membrane organization are accompanied by functional effects on both innate and adaptive B cell function. Altogether, the research over the past 10 years has led to an evolution of the original model on how DHA reorganizes membrane microdomains. The work raises the intriguing possibility of testing the model at the human level to target health and disease. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Membrane Raft Organization Is More Sensitive to Disruption by (n-3) PUFA Than Nonraft Organization in EL4 and B Cells123

    Science.gov (United States)

    Rockett, Benjamin Drew; Franklin, Andrew; Harris, Mitchel; Teague, Heather; Rockett, Alexis; Shaikh, Saame Raza

    2011-01-01

    Model membrane and cellular detergent extraction studies show (n-3) PUFA predominately incorporate into nonrafts; thus, we hypothesized (n-3) PUFA could disrupt nonraft organization. The first objective of this study was to determine whether (n-3) PUFA disrupted nonrafts of EL4 cells, an extension of our previous work in which we discovered an (n-3) PUFA diminished raft clustering. EPA or DHA treatment of EL4 cells increased plasma membrane accumulation of the nonraft probe 1,1′-dilinoleyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate by ~50–70% relative to a BSA control. Förster resonance energy transfer imaging showed EPA and DHA also disrupted EL4 nanometer scale nonraft organization by increasing the distance between nonraft molecules by ~25% compared with BSA. However, changes in nonrafts were due to an increase in cell size; under conditions where EPA or DHA did not increase cell size, nonraft organization was unaffected. We next translated findings on EL4 cells by testing if (n-3) PUFA administered to mice disrupted nonrafts and rafts. Imaging of B cells isolated from mice fed low- or high-fat (HF) (n-3) PUFA diets showed no change in nonraft organization compared with a control diet (CD). However, confocal microscopy revealed the HF (n-3) PUFA diet disrupted lipid raft clustering and size by ~40% relative to CD. Taken together, our data from 2 different model systems suggest (n-3) PUFA have limited effects on nonrafts. The ex vivo data, which confirm previous studies with EL4 cells, provide evidence that (n-3) PUFA consumed through the diet disrupt B cell lipid raft clustering. PMID:21525263

  20. Mechanical algal disruption for efficient biodiesel extraction

    Science.gov (United States)

    Krehbiel, Joel David

    Biodiesel from algae provides several benefits over current biodiesel feedstocks, but the energy requirements of processing algae into a useable fuel are currently so high as to be prohibitive. One route to improving this is via disruption of the cells prior to lipid extraction, which can significantly increase energy recovery. Unfortunately, several obvious disruption techniques require more energy than can be gained. This dissertation examines the use of microbubbles to improve mechanical disruption of algal cells using experimental, theoretical, and computational methods. New laboratory experiments show that effective ultrasonic disruption of algae is achieved by adding microbubbles to an algal solution. The configuration studied flows the solution through a tube and insonifies a small section with a high-pressure ultrasound wave. Previous biomedical research has shown effective cell membrane damage on animal cells with similar methods, but the present research is the first to extend such study to algal cells. Results indicate that disruption increases with peak negative pressure between 1.90 and 3.07 MPa and with microbubble concentration up to 12.5 x 107 bubbles/ml. Energy estimates of this process suggest that it requires only one-fourth the currently most-efficient laboratory-scale disruption process. Estimates of the radius near each bubble that causes disruption (i.e. the disruption radius) suggest that it increases with peak negative pressure and is near 9--20 microm for all cases tested. It is anticipated that these procedures can be designed for better efficiency and efficacy, which will be facilitated by identifying the root mechanisms of the bubble-induced disruption. We therefore examine whether bubble expansion alone creates sufficient cell deformation for cell rupture. The spherically-symmetric Marmottant model for bubble dynamics allows estimation of the flow regime under experimental conditions. Bubble expansion is modeled as a point source of

  1. Plasma disruption modeling and simulation

    International Nuclear Information System (INIS)

    Hassanein, A.

    1994-01-01

    Disruptions in tokamak reactors are considered a limiting factor to successful operation and reliable design. The behavior of plasma-facing components during a disruption is critical to the overall integrity of the reactor. Erosion of plasma facing-material (PFM) surfaces due to thermal energy dump during the disruption can severely limit the lifetime of these components and thus diminish the economic feasibility of the reactor. A comprehensive understanding of the interplay of various physical processes during a disruption is essential for determining component lifetime and potentially improving the performance of such components. There are three principal stages in modeling the behavior of PFM during a disruption. Initially, the incident plasma particles will deposit their energy directly on the PFM surface, heating it to a very high temperature where ablation occurs. Models for plasma-material interactions have been developed and used to predict material thermal evolution during the disruption. Within a few microseconds after the start of the disruption, enough material is vaporized to intercept most of the incoming plasma particles. Models for plasma-vapor interactions are necessary to predict vapor cloud expansion and hydrodynamics. Continuous heating of the vapor cloud above the material surface by the incident plasma particles will excite, ionize, and cause vapor atoms to emit thermal radiation. Accurate models for radiation transport in the vapor are essential for calculating the net radiated flux to the material surface which determines the final erosion thickness and consequently component lifetime. A comprehensive model that takes into account various stages of plasma-material interaction has been developed and used to predict erosion rates during reactor disruption, as well during induced disruption in laboratory experiments

  2. The disruption management model.

    Science.gov (United States)

    McAlister, James

    2011-10-01

    Within all organisations, business continuity disruptions present a set of dilemmas that managers may not have dealt with before in their normal daily duties. The disruption management model provides a simple but effective management tool to enable crisis management teams to stay focused on recovery in the midst of a business continuity incident. The model has four chronological primary headlines, which steer the team through a quick-time crisis decision-making process. The procedure facilitates timely, systematic, rationalised and justified decisions, which can withstand post-event scrutiny. The disruption management model has been thoroughly tested within an emergency services environment and is proven to significantly support clear and concise decision making in a business continuity context.

  3. From Digital Disruption to Business Model Scalability

    DEFF Research Database (Denmark)

    Nielsen, Christian; Lund, Morten; Thomsen, Peter Poulsen

    2017-01-01

    This article discusses the terms disruption, digital disruption, business models and business model scalability. It illustrates how managers should be using these terms for the benefit of their business by developing business models capable of achieving exponentially increasing returns to scale...... will seldom lead to business model scalability capable of competing with digital disruption(s)....... as a response to digital disruption. A series of case studies illustrate that besides frequent existing messages in the business literature relating to the importance of creating agile businesses, both in growing and declining economies, as well as hard to copy value propositions or value propositions that take...

  4. Lipid-mediated interactions tune the association of glycophorin A helix and its disruptive mutants in membranes

    NARCIS (Netherlands)

    Sengupta, Durba; Marrink, Siewert J.

    2010-01-01

    The specific and non-specific driving forces of helix association within membranes are still poorly understood. Here, we use coarse-grain molecular dynamics simulations to study the association behavior of glycophorin A and two disruptive mutants, T87F and a triple mutant of the GxxxG motif

  5. Steam Explosion and Vibrating Membrane Filtration to Improve the Processing Cost of Microalgae Cell Disruption and Fractionation

    Directory of Open Access Journals (Sweden)

    Esther Lorente

    2018-03-01

    Full Text Available The aim of this study is to explore an innovative downstream route for microalgae processing to reduce cost production. Experiments have been carried out on cell disruption and fractionation stages to recover lipids, sugars, and proteins. Steam explosion and dynamic membrane filtration were used as unit operations. The species tested were Nannochloropsis gaditana, Chlorella sorokiniana, and Dunaliella tertiolecta with different cell wall characteristics. Acid-catalysed steam explosion permitted cell disruption, as well as the hydrolysis of carbohydrates and partial hydrolysis of proteins. This permitted a better access to non-polar solvents for lipid extraction. Dynamic filtration was used to moderate the impact of fouling. Filtration enabled two streams: A permeate containing water and monosaccharides and a low-volume retentate containing the lipids and proteins. The necessary volume of solvent to extract the lipids is thus much lower. An estimation of operational costs of both steam explosion and membrane filtration was performed. The results show that the steam explosion operation cost varies between 0.005 $/kg and 0.014 $/kg of microalgae dry sample, depending on the cost of fuel. Membrane filtration cost in fractionation was estimated at 0.12 $/kg of microalgae dry sample.

  6. Liposome Disruption Assay to Examine Lytic Properties of Biomolecules.

    Science.gov (United States)

    Jimah, John R; Schlesinger, Paul H; Tolia, Niraj H

    2017-08-05

    Proteins may have three dimensional structural or amino acid features that suggest a role in targeting and disrupting lipids within cell membranes. It is often necessary to experimentally investigate if these proteins and biomolecules are able to disrupt membranes in order to conclusively characterize the function of these biomolecules. Here, we describe an in vitro assay to evaluate the membrane lytic properties of proteins and biomolecules. Large unilamellar vesicles (liposomes) containing carboxyfluorescein at fluorescence-quenching concentrations are treated with the biomolecule of interest. A resulting increase in fluorescence due to leakage of the dye from liposomes and subsequent dilution in the buffer demonstrates that the biomolecule is sufficient for disrupting liposomes and membranes. Additionally, since liposome disruption may occur via pore-formation or via general solubilization of lipids similar to detergents, we provide a method to distinguish between these two mechanisms. Pore-formation can be identified and evaluated by examining the blockade of carboxyfluorescein release with dextran molecules that fit the pore. The methods described here were used to determine that the malaria vaccine candidate CelTOS and proapoptotic Bax disrupt liposomes by pore formation (Saito et al. , 2000; Jimah et al. , 2016). Since membrane lipid binding by a biomolecule precedes membrane disruption, we recommend the companion protocol: Jimah et al. , 2017.

  7. Disruption modeling in support of ITER

    International Nuclear Information System (INIS)

    Bandyopadhyay, I.

    2015-01-01

    Plasma current disruptions and Vertical Displacement Events (VDEs) are one of the major concerns in any tokamak as they lead to large electromagnetic forces to tokamak first wall components and vacuum vessel. Their occurrence also means disruption to steady state operations of tokamaks. Thus future fusion reactors like ITER must ensure that disruptions and VDEs are minimized. However, since there is still finite probability of their occurrence, one must be able to characterize disruptions and VDEs and able to predict, for example, the plasma current quench time and halo current amplitude, which mainly determine the magnitude of the electromagnetic forces. There is a concerted effort globally to understand and predict plasma and halo current evolution during disruption in tokamaks through MHD simulations. Even though Disruption and VDEs are often 3D MHD perturbations in nature, presently they are mostly simulated using 2D axisymmetric MHD codes like the Tokamak Simulation Code (TSC) and DINA. These codes are also extensively benchmarked against experimental data in present day tokamaks to improve these models and their ability to predict these events in ITER. More detailed 3D models like M3D are only recently being developed, but they are yet to be benchmarked against experiments, as also they are massively computationally exhaustive

  8. Interpreting Disruption Prediction Models to Improve Plasma Control

    Science.gov (United States)

    Parsons, Matthew

    2017-10-01

    In order for the tokamak to be a feasible design for a fusion reactor, it is necessary to minimize damage to the machine caused by plasma disruptions. Accurately predicting disruptions is a critical capability for triggering any mitigative actions, and a modest amount of attention has been given to efforts that employ machine learning techniques to make these predictions. By monitoring diagnostic signals during a discharge, such predictive models look for signs that the plasma is about to disrupt. Typically these predictive models are interpreted simply to give a `yes' or `no' response as to whether a disruption is approaching. However, it is possible to extract further information from these models to indicate which input signals are more strongly correlated with the plasma approaching a disruption. If highly accurate predictive models can be developed, this information could be used in plasma control schemes to make better decisions about disruption avoidance. This work was supported by a Grant from the 2016-2017 Fulbright U.S. Student Program, administered by the Franco-American Fulbright Commission in France.

  9. Interplay of electrostatics and lipid packing determines the binding of charged polymer coated nanoparticles to model membranes.

    Science.gov (United States)

    Biswas, Nupur; Bhattacharya, Rupak; Saha, Arindam; Jana, Nikhil R; Basu, Jaydeep K

    2015-10-07

    Understanding of nanoparticle-membrane interactions is useful for various applications of nanoparticles like drug delivery and imaging. Here we report on the studies of interaction between hydrophilic charged polymer coated semiconductor quantum dot nanoparticles with model lipid membranes. Atomic force microscopy and X-ray reflectivity measurements suggest that cationic nanoparticles bind and penetrate bilayers of zwitterionic lipids. Penetration and binding depend on the extent of lipid packing and result in the disruption of the lipid bilayer accompanied by enhanced lipid diffusion. On the other hand, anionic nanoparticles show minimal membrane binding although, curiously, their interaction leads to reduction in lipid diffusivity. It is suggested that the enhanced binding of cationic QDs at higher lipid packing can be understood in terms of the effective surface potential of the bilayers which is tunable through membrane lipid packing. Our results bring forth the subtle interplay of membrane lipid packing and electrostatics which determine nanoparticle binding and penetration of model membranes with further implications for real cell membranes.

  10. BUSINESS MODEL PATTERNS FOR DISRUPTIVE TECHNOLOGIES

    OpenAIRE

    BENJAMIN AMSHOFF; CHRISTIAN DÜLME; JULIAN ECHTERFELD; JÜRGEN GAUSEMEIER

    2015-01-01

    Companies nowadays face a myriad of business opportunities as a direct consequence of manifold disruptive technology developments. As a basic characteristic, disruptive technologies lead to a severe shift in value-creation networks giving rise to new market segments. One of the key challenges is to anticipate the business logics within these nascent and formerly unknown markets. Business model patterns promise to tackle this challenge. They can be interpreted as proven business model elements...

  11. Disrupting assembly of the inner membrane complex blocks Plasmodium falciparum sexual stage development.

    Directory of Open Access Journals (Sweden)

    Molly Parkyn Schneider

    2017-10-01

    Full Text Available Transmission of malaria parasites relies on the formation of a specialized blood form called the gametocyte. Gametocytes of the human pathogen, Plasmodium falciparum, adopt a crescent shape. Their dramatic morphogenesis is driven by the assembly of a network of microtubules and an underpinning inner membrane complex (IMC. Using super-resolution optical and electron microscopies we define the ultrastructure of the IMC at different stages of gametocyte development. We characterize two new proteins of the gametocyte IMC, called PhIL1 and PIP1. Genetic disruption of PhIL1 or PIP1 ablates elongation and prevents formation of transmission-ready mature gametocytes. The maturation defect is accompanied by failure to form an enveloping IMC and a marked swelling of the digestive vacuole, suggesting PhIL1 and PIP1 are required for correct membrane trafficking. Using immunoprecipitation and mass spectrometry we reveal that PhIL1 interacts with known and new components of the gametocyte IMC.

  12. Modeling of interactions between nanoparticles and cell membranes

    Science.gov (United States)

    Ban, Young-Min

    Rapid development of nanotechnology and ability to manufacture materials and devices with nanometer feature size leads to exciting innovations in many areas including the medical and electronic fields. However, the possible health and environmental impacts of manufactured nanomaterials are not fully known. Recent experimental reports suggest that some of the manufactured nanomaterials, such as fullerenes and carbon nanotubes, are highly toxic even in small concentrations. The goal of the current work is to understand the mechanisms responsible for the toxicity of nanomaterials. In the current study coarse-grained molecular dynamics simulations are employed to investigate the interactions between NPs and cellular membranes at a molecular level. One of the possible toxicity mechanisms of the nanomaterials is membrane disruption. Possibility of membrane disruption exposed to the manufactured nanomaterials are examined by considering chemical reactions and non-reactive physical interactions as chemical as well as physical mechanisms. Mechanisms of transport of carbon-based nanoparticles (fullerene and its derivative) across a phospholipid bilayer are investigated. The free energy profile is obtained using constrained simulations. It is shown that the considered nanoparticles are hydrophobic and therefore they tend to reside in the interior of the lipid bilayer. In addition, the dynamics of the membrane fluctuations is significantly affected by the nanoparticles at the bilayer-water interface. The hydrophobic interaction between the particles and membrane core induces the strong coupling between the nanoparticle motion and membrane deformation. It is observed that the considered nanoparticles affect several physical properties of the membrane. The nanoparticles embedded into the membrane interior lead to the membrane softening, which becomes more significant with increase in CNT length and concentration. The lateral pressure profile and membrane energy in the membrane

  13. Modeling of the axon membrane skeleton structure and implications for its mechanical properties.

    Directory of Open Access Journals (Sweden)

    Yihao Zhang

    2017-02-01

    Full Text Available Super-resolution microscopy recently revealed that, unlike the soma and dendrites, the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under tension. Currently, the structure-function relationship of the axonal structure is unclear. Here, we used atomic force microscopy (AFM to show that the stiffness of the axon plasma membrane is significantly higher than the stiffnesses of dendrites and somata. To examine whether the structure of the axon plasma membrane determines its overall stiffness, we introduced a coarse-grain molecular dynamics model of the axon membrane skeleton that reproduces the structure identified by super-resolution microscopy. Our proposed computational model accurately simulates the median value of the Young's modulus of the axon plasma membrane determined by atomic force microscopy. It also predicts that because the spectrin filaments are under entropic tension, the thermal random motion of the voltage-gated sodium channels (Nav, which are bound to ankyrin particles, a critical axonal protein, is reduced compared to the thermal motion when spectrin filaments are held at equilibrium. Lastly, our model predicts that because spectrin filaments are under tension, any axonal injuries that lacerate spectrin filaments will likely lead to a permanent disruption of the membrane skeleton due to the inability of spectrin filaments to spontaneously form their initial under-tension configuration.

  14. Modeling of the axon membrane skeleton structure and implications for its mechanical properties.

    Science.gov (United States)

    Zhang, Yihao; Abiraman, Krithika; Li, He; Pierce, David M; Tzingounis, Anastasios V; Lykotrafitis, George

    2017-02-01

    Super-resolution microscopy recently revealed that, unlike the soma and dendrites, the axon membrane skeleton is structured as a series of actin rings connected by spectrin filaments that are held under tension. Currently, the structure-function relationship of the axonal structure is unclear. Here, we used atomic force microscopy (AFM) to show that the stiffness of the axon plasma membrane is significantly higher than the stiffnesses of dendrites and somata. To examine whether the structure of the axon plasma membrane determines its overall stiffness, we introduced a coarse-grain molecular dynamics model of the axon membrane skeleton that reproduces the structure identified by super-resolution microscopy. Our proposed computational model accurately simulates the median value of the Young's modulus of the axon plasma membrane determined by atomic force microscopy. It also predicts that because the spectrin filaments are under entropic tension, the thermal random motion of the voltage-gated sodium channels (Nav), which are bound to ankyrin particles, a critical axonal protein, is reduced compared to the thermal motion when spectrin filaments are held at equilibrium. Lastly, our model predicts that because spectrin filaments are under tension, any axonal injuries that lacerate spectrin filaments will likely lead to a permanent disruption of the membrane skeleton due to the inability of spectrin filaments to spontaneously form their initial under-tension configuration.

  15. Zinc oxide nanoparticles decrease the expression and activity of plasma membrane calcium ATPase, disrupt the intracellular calcium homeostasis in rat retinal ganglion cells.

    Science.gov (United States)

    Guo, Dadong; Bi, Hongsheng; Wang, Daoguang; Wu, Qiuxin

    2013-08-01

    Zinc oxide nanoparticle is one of the most important materials with diverse applications. However, it has been reported that zinc oxide nanoparticles are toxic to organisms, and that oxidative stress is often hypothesized to be an important factor in cytotoxicity mediated by zinc oxide nanoparticles. Nevertheless, the mechanism of toxicity of zinc oxide nanoparticles has not been completely understood. In this study, we investigated the cytotoxic effect of zinc oxide nanoparticles and the possible molecular mechanism involved in calcium homeostasis mediated by plasma membrane calcium ATPase in rat retinal ganglion cells. Real-time cell electronic sensing assay showed that zinc oxide nanoparticles could exert cytotoxic effect on rat retinal ganglion cells in a concentration-dependent manner; flow cytometric analysis indicated that zinc oxide nanoparticles could lead to cell damage by inducing the overproduction of reactive oxygen species. Furthermore, zinc oxide nanoparticles could also apparently decrease the expression level and their activity of plasma membrane calcium ATPase, which finally disrupt the intracellular calcium homeostasis and result in cell death. Taken together, zinc oxide nanoparticles could apparently decrease the plasma membrane calcium ATPase expression, inhibit their activity, cause the elevated intracellular calcium ion level and disrupt the intracellular calcium homeostasis. Further, the disrupted calcium homeostasis will trigger mitochondrial dysfunction, generate excessive reactive oxygen species, and finally initiate cell death. Thus, the disrupted calcium homeostasis is involved in the zinc oxide nanoparticle-induced rat retinal ganglion cell death. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Quantifying pulsed electric field-induced membrane nanoporation in single cells.

    Science.gov (United States)

    Moen, Erick K; Ibey, Bennett L; Beier, Hope T; Armani, Andrea M

    2016-11-01

    Plasma membrane disruption can trigger a host of cellular activities. One commonly observed type of disruption is pore formation. Molecular dynamic (MD) simulations of simplified lipid membrane structures predict that controllably disrupting the membrane via nano-scale poration may be possible with nanosecond pulsed electric fields (nsPEF). Until recently, researchers hoping to verify this hypothesis experimentally have been limited to measuring the relatively slow process of fluorescent markers diffusing across the membrane, which is indirect evidence of nanoporation that could be channel-mediated. Leveraging recent advances in nonlinear optical microscopy, we elucidate the role of pulse parameters in nsPEF-induced membrane permeabilization in live cells. Unlike previous techniques, it is able to directly observe loss of membrane order at the onset of the pulse. We also develop a complementary theoretical model that relates increasing membrane permeabilization to membrane pore density. Due to the significantly improved spatial and temporal resolution possible with our imaging method, we are able to directly compare our experimental and theoretical results. Their agreement provides substantial evidence that nanoporation does occur and that its development is dictated by the electric field distribution. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Toxins in botanical dietary supplements: blue cohosh components disrupt cellular respiration and mitochondrial membrane potential.

    Science.gov (United States)

    Datta, Sandipan; Mahdi, Fakhri; Ali, Zulfiqar; Jekabsons, Mika B; Khan, Ikhlas A; Nagle, Dale G; Zhou, Yu-Dong

    2014-01-24

    Certain botanical dietary supplements have been associated with idiosyncratic organ-specific toxicity. Similar toxicological events, caused by drug-induced mitochondrial dysfunction, have forced the withdrawal or U.S. FDA "black box" warnings of major pharmaceuticals. To assess the potential mitochondrial liability of botanical dietary supplements, extracts from 352 authenticated plant samples used in traditional Chinese, Ayurvedic, and Western herbal medicine were evaluated for the ability to disrupt cellular respiration. Blue cohosh (Caulophyllum thalictroides) methanol extract exhibited mitochondriotoxic activity. Used by some U.S. midwives to help induce labor, blue cohosh has been associated with perinatal stroke, acute myocardial infarction, congestive heart failure, multiple organ injury, and neonatal shock. The potential link between mitochondrial disruption and idiosyncratic herbal intoxication prompted further examination. The C. thalictroides methanol extract and three saponins, cauloside A (1), saponin PE (2), and cauloside C (3), exhibited concentration- and time-dependent mitochondriotoxic activities. Upon treatment, cell respiration rate rapidly increased and then dramatically decreased within minutes. Mechanistic studies revealed that C. thalictroides constituents impair mitochondrial function by disrupting membrane integrity. These studies provide a potential etiological link between this mitochondria-sensitive form of cytotoxicity and idiosyncratic organ damage.

  18. Toxins in Botanical Dietary Supplements: Blue Cohosh Components Disrupt Cellular Respiration and Mitochondrial Membrane Potential

    Science.gov (United States)

    Datta, Sandipan; Mahdi, Fakhri; Ali, Zulfiqar; Jekabsons, Mika B.; Khan, Ikhlas A.; Nagle, Dale G.; Zhou, Yu-Dong

    2014-01-01

    Certain botanical dietary supplements have been associated with idiosyncratic organ-specific toxicity. Similar toxicological events, caused by drug-induced mitochondrial dysfunction, have forced the withdrawal or U.S. FDA “Black Box” warnings of major pharmaceuticals. To assess the potential mitochondrial liability of botanical dietary supplements, extracts from 352 authenticated plant samples used in traditional Chinese, Ayurvedic, and Western herbal medicine were evaluated for the ability to disrupt cellular respiration. Blue cohosh (Caulophyllum thalictroides) methanol extract exhibited mitochondriotoxic activity. Used by some U.S. midwives to help induce labor, blue cohosh has been associated with perinatal stroke, acute myocardial infarction, congestive heart failure, multiple organ injury, and neonatal shock. The potential link between mitochondrial disruption and idiosyncratic herbal intoxication prompted further examination. The C. thalictroides methanol extract and three saponins, cauloside A (1), saponin PE (2), and cauloside C (3) exhibited concentration- and time-dependent mitochondriotoxic activities. Upon treatment, cell respiration rate rapidly increased and then dramatically decreased within minutes. Mechanistic studies revealed that C. thalictroides constituents impair mitochondrial function by disrupting membrane integrity. These studies provide a potential etiological link between this mitochondria-sensitive form of cytotoxicity and idiosyncratic organ damage. PMID:24328138

  19. Model cell membranes

    DEFF Research Database (Denmark)

    Günther-Pomorski, Thomas; Nylander, Tommy; Cardenas Gomez, Marite

    2014-01-01

    The high complexity of biological membranes has motivated the development and application of a wide range of model membrane systems to study biochemical and biophysical aspects of membranes in situ under well defined conditions. The aim is to provide fundamental understanding of processes control...

  20. Mathematical modelling of membrane separation

    DEFF Research Database (Denmark)

    Vinther, Frank

    This thesis concerns mathematical modelling of membrane separation. The thesis consists of introductory theory on membrane separation, equations of motion, and properties of dextran, which will be the solute species throughout the thesis. Furthermore, the thesis consist of three separate mathemat......This thesis concerns mathematical modelling of membrane separation. The thesis consists of introductory theory on membrane separation, equations of motion, and properties of dextran, which will be the solute species throughout the thesis. Furthermore, the thesis consist of three separate...... mathematical models, each with a different approach to membrane separation. The first model is a statistical model investigating the interplay between solute shape and the probability of entering the membrane. More specific the transition of solute particles from being spherical to becoming more elongated...

  1. A model for disruption generated runaway electrons

    International Nuclear Information System (INIS)

    Russo, A.J.; Campbell, R.B.

    1993-01-01

    One of the possible consequences of disruptions in tokamaks is the generation of runaway electrons which can impact plasma facing components and cause damage, owing to high local energy deposition. This problem becomes more serious as the machine size and plasma current increase. Since large size and high currents are characteristics of proposed future machines, control of runaway generation is an important design consideration. A lumped circuit model for disruption runaway electron generation indicates that impurity concentration and type, as well as plasma motion, can strongly influence runaway behaviour. A comparison of disruption data from several runs on JET and DIII-D with model results demonstrate the effects of impurities, and plasma motion, on runaway number density and energy. The model is also applied to the calculation of runaway currents for ITER. (author). 16 refs, 13 figs

  2. Disruption model

    International Nuclear Information System (INIS)

    Murray, J.G.; Bronner, G.

    1982-07-01

    Calculations of disruption time and energy dissipation have been obtained by simulating the plasma as an electrical conducting loop that varies in resistivity, current density, major radius. The calculations provide results which are in good agreement with experimental observations. It is believed that this approach allows engineering designs for disruptions to be completed in large tokamaks such as INTOR or FED

  3. A novel chimeric cell-penetrating peptide with membrane-disruptive properties for efficient endosomal escape.

    Science.gov (United States)

    Salomone, Fabrizio; Cardarelli, Francesco; Di Luca, Mariagrazia; Boccardi, Claudia; Nifosì, Riccardo; Bardi, Giuseppe; Di Bari, Lorenzo; Serresi, Michela; Beltram, Fabio

    2012-11-10

    Efficient endocytosis into a wide range of target cells and low toxicity make the arginine-rich Tat peptide (Tat(11): YGRKKRRQRRR, residues 47-57 of HIV-1 Tat protein) an excellent transporter for delivery purposes. Unfortunately, molecules taken up by endocytosis undergo endosomal entrapment and possible metabolic degradation. Escape from the endosome is therefore actively researched. In this context, antimicrobial peptides (AMPs) provide viable templates for the design of new membrane-disruptive motifs. In particular the Cecropin-A and Melittin hybrids (CMs) are among the smallest and most effective peptides with membrane-perturbing abilities. Here we present a novel chimeric peptide in which the Tat(11) motif is fused to the CM(18) hybrid (KWKLFKKIGAVLKVLTTG, residues 1-7 of Cecropin-A and 2-12 of Melittin). When administered to cells, CM(18)-Tat(11) combines the two desired functionalities: efficient uptake and destabilization of endocytotic-vesicle membranes. We show that this chimeric peptide effectively increases cargo-molecule cytoplasm availability and allows the subsequent intracellular localization of diverse membrane-impermeable molecules (i.e. Tat(11)-EGFP fusion protein, calcein, dextrans, and plasmidic DNA) with no detectable cytotoxicity. The present results open the way to the rational engineering of "modular" cell-penetrating peptides (CPPs) that combine (i) efficient translocation from the extracellular milieu into vesicles and (ii) efficient release of molecules from vesicles into the cytoplasm. Copyright © 2012 Elsevier B.V. All rights reserved.

  4. Membrane Disordering is not Sufficient for Membrane Permeabilization by Islet Amyloidogenic Polypeptide: Studies of IAPP(20-29) Fragments

    Science.gov (United States)

    Brender, Jeffrey R.; Heyl, Deborah L.; Samisetti, Shyamprasad; Kotler, Samuel A.; Osborne, Joshua M.; Pesaru, Ranadheer R.; Ramamoorthy, Ayyalusamy

    2013-01-01

    A key factor in the development of type II diabetes is the loss of insulin-producing beta-cells. Human islet amyloid polypeptide protein (human-IAPP) is believed to play a crucial role in this process by forming small aggregates that exhibit toxicity by disrupting the cell membrane. The actual mechanism of membrane disruption is complex and appears to involve an early component before fiber formation and later component associated with fiber formation on the membrane. By comparing the peptide-lipid interactions derived from solid-state NMR experiments of two IAPP fragments that bind the membrane and cause membrane disordering to IAPP derived peptides known to cause significant early membrane permeabilization, we show here that membrane disordering is not likely to be sufficient by itself to cause the early membrane permeabilization observed by IAPP, and may play a lesser role in IAPP membrane disruption than expected. PMID:23493863

  5. Structure and physical properties of bio membranes and model membranes

    International Nuclear Information System (INIS)

    Tibor Hianik

    2006-01-01

    Bio membranes belong to the most important structures of the cell and the cell organelles. They play not only structural role of the barrier separating the external and internal part of the membrane but contain also various functional molecules, like receptors, ionic channels, carriers and enzymes. The cell membrane also preserves non-equilibrium state in a cell which is crucial for maintaining its excitability and other signaling functions. The growing interest to the bio membranes is also due to their unique physical properties. From physical point of view the bio membranes, that are composed of lipid bilayer into which are incorporated integral proteins and on their surface are anchored peripheral proteins and polysaccharides, represent liquid s crystal of smectic type. The bio membranes are characterized by anisotropy of structural and physical properties. The complex structure of bio membranes makes the study of their physical properties rather difficult. Therefore several model systems that mimic the structure of bio membranes were developed. Among them the lipid monolayers at an air-water interphase, bilayer lipid membranes, supported bilayer lipid membranes and liposomes are most known. This work is focused on the introduction into the physical word of the bio membranes and their models. After introduction to the membrane structure and the history of its establishment, the physical properties of the bio membranes and their models are stepwise presented. The most focus is on the properties of lipid monolayers, bilayer lipid membranes, supported bilayer lipid membranes and liposomes that were most detailed studied. This lecture has tutorial character that may be useful for undergraduate and graduate students in the area of biophysics, biochemistry, molecular biology and bioengineering, however it contains also original work of the author and his co-worker and PhD students, that may be useful also for specialists working in the field of bio membranes and model

  6. Molecular Interactions at Membranes

    DEFF Research Database (Denmark)

    Jagalski, Vivien

    . Today, we know more than ever before about the properties of biological membranes. Advanced biophysical techniques and sophisticated membrane models allow us to answer specific questions about the structure of the components within membranes and their interactions. However, many detailed structural...... the surface-immobilization of LeuT by exchanging the detergent with natural phosphatidylcholine (PC) lipids. Various surface sensitive techniques, including neutron reflectometry (NR), are employed and finally enabled us to confirm the gross structure of LeuT in a lipid environment as predicted by molecular...... dynamic simulations. In a second study, the co-localization of three toxic plant-derived diterpene resin acids (RAs) within DPPC membranes was investigated. These compounds are reported to disrupt the membrane and increase its fluidity. The RAs used in this study vary in their toxicity while...

  7. Membrane fouling mechanism of biofilm-membrane bioreactor (BF-MBR): Pore blocking model and membrane cleaning.

    Science.gov (United States)

    Zheng, Yi; Zhang, Wenxiang; Tang, Bing; Ding, Jie; Zheng, Yi; Zhang, Zhien

    2018-02-01

    Biofilm membrane bioreactor (BF-MBR) is considered as an important wastewater treatment technology that incorporates advantages of both biofilm and MBR process, as well as can alleviate membrane fouling, with respect to the conventional activated sludge MBR. But, to be efficient, it necessitates the establishment of proper methods for the assessment of membrane fouling. Four Hermia membrane blocking models were adopted to quantify and evaluate the membrane fouling of BF-MBR. The experiments were conducted with various operational conditions, including membrane types, agitation speeds and transmembrane pressure (TMP). Good agreement between cake formation model and experimental data was found, confirming the validity of the Hermia models for assessing the membrane fouling of BF-MBR and that cake layer deposits on membrane. Moreover, the influences of membrane types, agitation speeds and transmembrane pressure on the Hermia pore blocking coefficient of cake layer were investigated. In addition, the permeability recovery after membrane cleaning at various operational conditions was studied. This work confirms that, unlike conventional activated sludge MBR, BF-MBR possesses a low degree of membrane fouling and a higher membrane permeability recovery after cleaning. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Drug-model membrane interactions

    International Nuclear Information System (INIS)

    Deniz, Usha K.

    1994-01-01

    In the present day world, drugs play a very important role in medicine and it is necessary to understand their mode of action at the molecular level, in order to optimise their use. Studies of drug-biomembrane interactions are essential for gaining such as understanding. However, it would be prohibitively difficult to carry out such studies, since biomembranes are highly complex systems. Hence, model membranes (made up of these lipids which are important components of biomembranes) of varying degrees of complexity are used to investigate drug-membrane interactions. Bio- as well as model-membranes undergo a chain melting transition when heated, the chains being in a disordered state above the transition point, T CM . This transition is of physiological importance since biomembranes select their components such that T CM is less than the ambient temperature but not very much so, so that membrane flexibility is ensured and porosity, avoided. The influence of drugs on the transition gives valuable clues about various parameters such as the location of the drug in the membrane. Deep insights into drug-membrane interactions are obtained by observing the effect of drugs on membrane structure and the mobilities of the various groups in lipids, near T CM . Investigation of such changes have been carried out with several drugs, using techniques such as DSC, XRD and NMR. The results indicate that the drug-membrane interaction not only depends on the nature of drug and lipids but also on the form of the model membrane - stacked bilayer or vesicles. The light that these results shed on the nature of drug-membrane interactions is discussed. (author). 13 refs., 13 figs., 1 tab

  9. Multivariate statistical models for disruption prediction at ASDEX Upgrade

    International Nuclear Information System (INIS)

    Aledda, R.; Cannas, B.; Fanni, A.; Sias, G.; Pautasso, G.

    2013-01-01

    In this paper, a disruption prediction system for ASDEX Upgrade has been proposed that does not require disruption terminated experiments to be implemented. The system consists of a data-based model, which is built using only few input signals coming from successfully terminated pulses. A fault detection and isolation approach has been used, where the prediction is based on the analysis of the residuals of an auto regressive exogenous input model. The prediction performance of the proposed system is encouraging when it is applied to the same set of campaigns used to implement the model. However, the false alarms significantly increase when we tested the system on discharges coming from experimental campaigns temporally far from those used to train the model. This is due to the well know aging effect inherent in the data-based models. The main advantage of the proposed method, with respect to other data-based approaches in literature, is that it does not need data on experiments terminated with a disruption, as it uses a normal operating conditions model. This is a big advantage in the prospective of a prediction system for ITER, where a limited number of disruptions can be allowed

  10. Metabolic effects of bariatric surgery in mouse models of circadian disruption.

    Science.gov (United States)

    Arble, D M; Sandoval, D A; Turek, F W; Woods, S C; Seeley, R J

    2015-08-01

    Mounting evidence supports a link between circadian disruption and metabolic disease. Humans with circadian disruption (for example, night-shift workers) have an increased risk of obesity and cardiometabolic diseases compared with the non-disrupted population. However, it is unclear whether the obesity and obesity-related disorders associated with circadian disruption respond to therapeutic treatments as well as individuals with other types of obesity. Here, we test the effectiveness of the commonly used bariatric surgical procedure, Vertical Sleeve Gastrectomy (VSG), in mouse models of genetic and environmental circadian disruption. VSG led to a reduction in body weight and fat mass in both Clock(Δ19) mutant and constant-light mouse models (Pdisruption. Interestingly, the decrease in body weight occurred without altering diurnal feeding or activity patterns (P>0.05). Within circadian-disrupted models, VSG also led to improved glucose tolerance and lipid handling (Pdisruption, and that the potent effects of bariatric surgery are orthogonal to circadian biology. However, as the effects of bariatric surgery are independent of circadian disruption, VSG cannot be considered a cure for circadian disruption. These data have important implications for circadian-disrupted obese patients. Moreover, these results reveal new information about the metabolic pathways governing the effects of bariatric surgery as well as of circadian disruption.

  11. Comprehensive model for disruption erosion in a reactor environment

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, I.

    1995-01-01

    A comprehensive disruption erosion model which takes into account the interplay of major physical processes during plasma-material interaction has been developed. The model integrates with sufficient detail and in a self-consistent way, material thermal evolution response, plasma-vapor interaction physics, vapor hydrodynamics and radiation transport in order to realistically simulate the effects of a plasma disruption on plasma-facing components. Candidate materials such as beryllium and carbon have been analyzed. The dependence of the net erosion rate on disruption physics and various parameters was analyzed and is discussed. ((orig.))

  12. Cytoskeletal Components Define Protein Location to Membrane Microdomains*

    Science.gov (United States)

    Szymanski, Witold G.; Zauber, Henrik; Erban, Alexander; Gorka, Michal; Wu, Xu Na; Schulze, Waltraud X.

    2015-01-01

    The plasma membrane is an important compartment that undergoes dynamic changes in composition upon external or internal stimuli. The dynamic subcompartmentation of proteins in ordered low-density (DRM) and disordered high-density (DSM) membrane phases is hypothesized to require interactions with cytoskeletal components. Here, we systematically analyzed the effects of actin or tubulin disruption on the distribution of proteins between membrane density phases. We used a proteomic screen to identify candidate proteins with altered submembrane location, followed by biochemical or cell biological characterization in Arabidopsis thaliana. We found that several proteins, such as plasma membrane ATPases, receptor kinases, or remorins resulted in a differential distribution between membrane density phases upon cytoskeletal disruption. Moreover, in most cases, contrasting effects were observed: Disruption of actin filaments largely led to a redistribution of proteins from DRM to DSM membrane fractions while disruption of tubulins resulted in general depletion of proteins from the membranes. We conclude that actin filaments are necessary for dynamic movement of proteins between different membrane phases and that microtubules are not necessarily important for formation of microdomains as such, but rather they may control the protein amount present in the membrane phases. PMID:26091700

  13. Analytic modeling of axisymmetric disruption halo currents

    International Nuclear Information System (INIS)

    Humphreys, D.A.; Kellman, A.G.

    1999-01-01

    Currents which can flow in plasma facing components during disruptions pose a challenge to the design of next generation tokamaks. Induced toroidal eddy currents and both induced and conducted poloidal ''halo'' currents can produce design-limiting electromagnetic loads. While induction of toroidal and poloidal currents in passive structures is a well-understood phenomenon, the driving terms and scalings for poloidal currents flowing on open field lines during disruptions are less well established. A model of halo current evolution is presented in which the current is induced in the halo by decay of the plasma current and change in enclosed toroidal flux while being convected into the halo from the core by plasma motion. Fundamental physical processes and scalings are described in a simplified analytic version of the model. The peak axisymmetric halo current is found to depend on halo and core plasma characteristics during the current quench, including machine and plasma dimensions, resistivities, safety factor, and vertical stability growth rate. Two extreme regimes in poloidal halo current amplitude are identified depending on the minimum halo safety factor reached during the disruption. A 'type I' disruption is characterized by a minimum safety factor that remains relatively high (typically 2 - 3, comparable to the predisruption safety factor), and a relatively low poloidal halo current. A 'type II' disruption is characterized by a minimum safety factor comparable to unity and a relatively high poloidal halo current. Model predictions for these two regimes are found to agree well with halo current measurements from vertical displacement event disruptions in DIII-D [T. S. Taylor, K. H. Burrell, D. R. Baker, G. L. Jackson, R. J. La Haye, M. A. Mahdavi, R. Prater, T. C. Simonen, and A. D. Turnbull, open-quotes Results from the DIII-D Scientific Research Program,close quotes in Proceedings of the 17th IAEA Fusion Energy Conference, Yokohama, 1998, to be published in

  14. A Production Model for Deteriorating Inventory Items with Production Disruptions

    OpenAIRE

    Yong He; Ju He

    2010-01-01

    Disruption management has recently become an active area of research. In this study, an extension is made to consider the fact that some products may deteriorate during storage. A production-inventory model for deteriorating items with production disruptions is developed. Then the optimal production and inventory plans are provided, so that the manufacturer can reduce the loss caused by disruptions. Finally, a numerical example is used to illustrate the model.

  15. Disruption of River Networks in Nature and Models

    Science.gov (United States)

    Perron, J. T.; Black, B. A.; Stokes, M.; McCoy, S. W.; Goldberg, S. L.

    2017-12-01

    Many natural systems display especially informative behavior as they respond to perturbations. Landscapes are no exception. For example, longitudinal elevation profiles of rivers responding to changes in uplift rate can reveal differences among erosional mechanisms that are obscured while the profiles are in equilibrium. The responses of erosional river networks to perturbations, including disruption of their network structure by diversion, truncation, resurfacing, or river capture, may be equally revealing. In this presentation, we draw attention to features of disrupted erosional river networks that a general model of landscape evolution should be able to reproduce, including the consequences of different styles of planetary tectonics and the response to heterogeneous bedrock structure and deformation. A comparison of global drainage directions with long-wavelength topography on Earth, Mars, and Saturn's moon Titan reveals the extent to which persistent and relatively rapid crustal deformation has disrupted river networks on Earth. Motivated by this example and others, we ask whether current models of river network evolution adequately capture the disruption of river networks by tectonic, lithologic, or climatic perturbations. In some cases the answer appears to be no, and we suggest some processes that models may be missing.

  16. Contribution of the Tyr-1 in Plantaricin149a to Disrupt Phospholipid Model Membranes

    Directory of Open Access Journals (Sweden)

    Georgina Tonarelli

    2013-06-01

    Full Text Available Plantaricin149a (Pln149a is a cationic antimicrobial peptide, which was suggested to cause membrane destabilization via the carpet mechanism. The mode of action proposed to this antimicrobial peptide describes the induction of an amphipathic α-helix from Ala7 to Lys20, while the N-terminus residues remain in a coil conformation after binding. To better investigate this assumption, the purpose of this study was to determine the contributions of the Tyr1 in Pln149a in the binding to model membranes to promote its destabilization. The Tyr to Ser substitution increased the dissociation constant (KD of the antimicrobial peptide from the liposomes (approximately three-fold higher, and decreased the enthalpy of binding to anionic vesicles from −17.2 kcal/mol to −10.2 kcal/mol. The peptide adsorption/incorporation into the negatively charged lipid vesicles was less effective with the Tyr1 substitution and peptide Pln149a perturbed the liposome integrity more than the analog, Pln149S. Taken together, the peptide-lipid interactions that govern the Pln149a antimicrobial activity are found not only in the amphipathic helix, but also in the N-terminus residues, which take part in enthalpic contributions due to the allocation at a lipid-aqueous interface.

  17. Disruption of Mitochondria-Associated Endoplasmic Reticulum Membrane (MAM) Integrity Contributes to Muscle Insulin Resistance in Mice and Humans.

    Science.gov (United States)

    Tubbs, Emily; Chanon, Stéphanie; Robert, Maud; Bendridi, Nadia; Bidaux, Gabriel; Chauvin, Marie-Agnès; Ji-Cao, Jingwei; Durand, Christine; Gauvrit-Ramette, Daphné; Vidal, Hubert; Lefai, Etienne; Rieusset, Jennifer

    2018-04-01

    Modifications of the interactions between endoplasmic reticulum (ER) and mitochondria, defined as mitochondria-associated membranes (MAMs), were recently shown to be involved in the control of hepatic insulin action and glucose homeostasis, but with conflicting results. Whereas skeletal muscle is the primary site of insulin-mediated glucose uptake and the main target for alterations in insulin-resistant states, the relevance of MAM integrity in muscle insulin resistance is unknown. Deciphering the importance of MAMs on muscle insulin signaling could help to clarify this controversy. Here, we show in skeletal muscle of different mice models of obesity and type 2 diabetes (T2D) a marked disruption of ER-mitochondria interactions as an early event preceding mitochondrial dysfunction and insulin resistance. Furthermore, in human myotubes, palmitate-induced insulin resistance is associated with a reduction of structural and functional ER-mitochondria interactions. Importantly, experimental increase of ER-mitochondria contacts in human myotubes prevents palmitate-induced alterations of insulin signaling and action, whereas disruption of MAM integrity alters the action of the hormone. Lastly, we found an association between altered insulin signaling and ER-mitochondria interactions in human myotubes from obese subjects with or without T2D compared with healthy lean subjects. Collectively, our data reveal a new role of MAM integrity in insulin action of skeletal muscle and highlight MAM disruption as an essential subcellular alteration associated with muscle insulin resistance in mice and humans. Therefore, reduced ER-mitochondria coupling could be a common alteration of several insulin-sensitive tissues playing a key role in altered glucose homeostasis in the context of obesity and T2D. © 2018 by the American Diabetes Association.

  18. The Non-structural Protein of Crimean-Congo Hemorrhagic Fever Virus Disrupts the Mitochondrial Membrane Potential and Induces Apoptosis*

    Science.gov (United States)

    Barnwal, Bhaskar; Karlberg, Helen; Mirazimi, Ali; Tan, Yee-Joo

    2016-01-01

    Viruses have developed distinct strategies to overcome the host defense system. Regulation of apoptosis in response to viral infection is important for virus survival and dissemination. Like other viruses, Crimean-Congo hemorrhagic fever virus (CCHFV) is known to regulate apoptosis. This study, for the first time, suggests that the non-structural protein NSs of CCHFV, a member of the genus Nairovirus, induces apoptosis. In this report, we demonstrated the expression of CCHFV NSs, which contains 150 amino acid residues, in CCHFV-infected cells. CCHFV NSs undergoes active degradation during infection. We further demonstrated that ectopic expression of CCHFV NSs induces apoptosis, as reflected by caspase-3/7 activity and cleaved poly(ADP-ribose) polymerase, in different cell lines that support CCHFV replication. Using specific inhibitors, we showed that CCHFV NSs induces apoptosis via both intrinsic and extrinsic pathways. The minimal active region of the CCHFV NSs protein was determined to be 93–140 amino acid residues. Using alanine scanning, we demonstrated that Leu-127 and Leu-135 are the key residues for NSs-induced apoptosis. Interestingly, CCHFV NSs co-localizes in mitochondria and also disrupts the mitochondrial membrane potential. We also demonstrated that Leu-127 and Leu-135 are important residues for disruption of the mitochondrial membrane potential by NSs. Therefore, these results indicate that the C terminus of CCHFV NSs triggers mitochondrial membrane permeabilization, leading to activation of caspases, which, ultimately, leads to apoptosis. Given that multiple factors contribute to apoptosis during CCHFV infection, further studies are needed to define the involvement of CCHFV NSs in regulating apoptosis in infected cells. PMID:26574543

  19. Disruptive innovation in health care delivery: a framework for business-model innovation.

    Science.gov (United States)

    Hwang, Jason; Christensen, Clayton M

    2008-01-01

    Disruptive innovation has brought affordability and convenience to customers in a variety of industries. However, health care remains expensive and inaccessible to many because of the lack of business-model innovation. This paper explains the theory of disruptive innovation and describes how disruptive technologies must be matched with innovative business models. The authors present a framework for categorizing and developing business models in health care, followed by a discussion of some of the reasons why disruptive innovation in health care delivery has been slow.

  20. Modeling SOL evolution during disruptions

    International Nuclear Information System (INIS)

    Rognlien, T.D.; Cohen, R.H.; Crotinger, J.A.

    1996-01-01

    We present the status of our models and transport simulations of the 2-D evolution of the scrape-off layer (SOL) during tokamak disruptions. This evolution is important for several reasons: It determines how the power from the core plasma is distributed on material surfaces, how impurities from those surfaces or from gas injection migrate back to the core region, and what are the properties of the SOL for carrying halo currents. We simulate this plasma in a time-dependent fashion using the SOL transport code UEDGE. This code models the SOL plasma using fluid equations of plasma density, parallel momentum (along the magnetic field), electron energy, ion energy, and neutral gas density. A multispecies model is used to follow the density of different charge-states of impurities. The parallel transport is classical but with kinetic modifications; these are presently treated by flux limits, but we have initiated more sophisticated models giving the correct long-mean-free path limit. The cross-field transport is anomalous, and one of the results of this work is to determine reasonable values to characterize disruptions. Our primary focus is on the initial thermal quench phase when most of the core energy is lost, but the total current is maintained. The impact of edge currents on the MHD equilibrium will be discussed

  1. Modeling plasma/material interactions during a tokamak disruption

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, I.

    1994-10-01

    Disruptions in tokamak reactors are still of serious concern and present a potential obstacle for successful operation and reliable design. Erosion of plasma-facing materials due to thermal energy dump during a disruption can severely limit the lifetime of these components, therefore diminishing the economic feasibility of the reactor. A comprehensive disruption erosion model which takes into account the interplay of major physical processes during plasma-material interaction has been developed. The initial burst of energy delivered to facing-material surfaces from direct impact of plasma particles causes sudden ablation of these materials. As a result, a vapor cloud is formed in front of the incident plasma particles. Shortly thereafter, the plasma particles are stopped in the vapor cloud, heating and ionizing it. The energy transmitted to the material surfaces is then dominated by photon radiation. It is the dynamics and the evolution of this vapor cloud that finally determines the net erosion rate and, consequently, the component lifetime. The model integrates with sufficient detail and in a self-consistent way, material thermal evolution response, plasma-vapor interaction physics, vapor hydrodynamics, and radiation transport in order to realistically simulate the effects of a plasma disruption on plasma-facing components. Candidate materials such as beryllium and carbon have been analyzed. The dependence of the net erosion rate on disruption physics and various parameters was analyzed and is discussed

  2. Recent Insights in Islet Amyloid Polypeptide-Induced Membrane Disruption and Its Role in β-Cell Death in Type 2 Diabetes Mellitus

    Directory of Open Access Journals (Sweden)

    Lucie Khemtémourian

    2008-01-01

    Full Text Available The presence of fibrillar protein deposits (amyloid of human islet amyloid polypeptide (hIAPP in the pancreatic islets of Langerhans is thought to be related to death of the insulin-producing islet β-cells in type 2 diabetes mellitus (DM2. The mechanism of hIAPP-induced β-cell death is not understood. However, there is growing evidence that hIAPP-induced disruption of β-cell membranes is the cause of hIAPP cytotoxicity. Amyloid cytotoxicity by membrane damage has not only been suggested for hIAPP, but also for peptides and proteins related to other misfolding diseases, like Alzheimer’s disease, Parkinson’s disease, and prion diseases. Here we review the interaction of hIAPP with membranes, and discuss recent progress in the field, with a focus on hIAPP structure and on the proposed mechanisms of hIAPP-induced membrane damage in relation to β-cell death in DM2.

  3. Giant plasma membrane vesicles: models for understanding membrane organization.

    Science.gov (United States)

    Levental, Kandice R; Levental, Ilya

    2015-01-01

    The organization of eukaryotic membranes into functional domains continues to fascinate and puzzle cell biologists and biophysicists. The lipid raft hypothesis proposes that collective lipid interactions compartmentalize the membrane into coexisting liquid domains that are central to membrane physiology. This hypothesis has proven controversial because such structures cannot be directly visualized in live cells by light microscopy. The recent observations of liquid-liquid phase separation in biological membranes are an important validation of the raft hypothesis and enable application of the experimental toolbox of membrane physics to a biologically complex phase-separated membrane. This review addresses the role of giant plasma membrane vesicles (GPMVs) in refining the raft hypothesis and expands on the application of GPMVs as an experimental model to answer some of key outstanding problems in membrane biology. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. Membrane Disruption Mechanism of a Prion Peptide (106-126) Investigated by Atomic Force Microscopy, Raman and Electron Paramagnetic Resonance Spectroscopy.

    Science.gov (United States)

    Pan, Jianjun; Sahoo, Prasana K; Dalzini, Annalisa; Hayati, Zahra; Aryal, Chinta M; Teng, Peng; Cai, Jianfeng; Rodriguez Gutierrez, Humberto; Song, Likai

    2017-05-18

    A fragment of the human prion protein spanning residues 106-126 (PrP106-126) recapitulates many essential properties of the disease-causing protein such as amyloidogenicity and cytotoxicity. PrP106-126 has an amphipathic characteristic that resembles many antimicrobial peptides (AMPs). Therefore, the toxic effect of PrP106-126 could arise from a direct association of monomeric peptides with the membrane matrix. Several experimental approaches are employed to scrutinize the impacts of monomeric PrP106-126 on model lipid membranes. Porous defects in planar bilayers are observed by using solution atomic force microscopy. Adding cholesterol does not impede defect formation. A force spectroscopy experiment shows that PrP106-126 reduces Young's modulus of planar lipid bilayers. We use Raman microspectroscopy to study the effect of PrP106-126 on lipid atomic vibrational dynamics. For phosphatidylcholine lipids, PrP106-126 disorders the intrachain conformation, while the interchain interaction is not altered; for phosphatidylethanolamine lipids, PrP106-126 increases the interchain interaction, while the intrachain conformational order remains similar. We explain the observed differences by considering different modes of peptide insertion. Finally, electron paramagnetic resonance spectroscopy shows that PrP106-126 progressively decreases the orientational order of lipid acyl chains in magnetically aligned bicelles. Together, our experimental data support the proposition that monomeric PrP106-126 can disrupt lipid membranes by using similar mechanisms found in AMPs.

  5. Pulse radiolysis studies of model membranes

    International Nuclear Information System (INIS)

    Heijman, M.G.J.

    1984-01-01

    In this thesis the influence of the structure of membranes on the processes in cell membranes were examined. Different models of the membranes were evaluated. Pulse radiolysis was used as the technique to examine the membranes. (R.B.)

  6. Membrane Compartmentalization Reducing the Mobility of Lipids and Proteins within a Model Plasma Membrane.

    Science.gov (United States)

    Koldsø, Heidi; Reddy, Tyler; Fowler, Philip W; Duncan, Anna L; Sansom, Mark S P

    2016-09-01

    The cytoskeleton underlying cell membranes may influence the dynamic organization of proteins and lipids within the bilayer by immobilizing certain transmembrane (TM) proteins and forming corrals within the membrane. Here, we present coarse-grained resolution simulations of a biologically realistic membrane model of asymmetrically organized lipids and TM proteins. We determine the effects of a model of cytoskeletal immobilization of selected membrane proteins using long time scale coarse-grained molecular dynamics simulations. By introducing compartments with varying degrees of restraints within the membrane models, we are able to reveal how compartmentalization caused by cytoskeletal immobilization leads to reduced and anomalous diffusional mobility of both proteins and lipids. This in turn results in a reduced rate of protein dimerization within the membrane and of hopping of membrane proteins between compartments. These simulations provide a molecular realization of hierarchical models often invoked to explain single-molecule imaging studies of membrane proteins.

  7. A general model for membrane-based separation processes

    DEFF Research Database (Denmark)

    Soni, Vipasha; Abildskov, Jens; Jonsson, Gunnar Eigil

    2009-01-01

    behaviour will play an important role. In this paper, modelling of membrane-based processes for separation of gas and liquid mixtures are considered. Two general models, one for membrane-based liquid separation processes (with phase change) and another for membrane-based gas separation are presented....... The separation processes covered are: membrane-based gas separation processes, pervaporation and various types of membrane distillation processes. The specific model for each type of membrane-based process is generated from the two general models by applying the specific system descriptions and the corresponding...

  8. A statistical model describing combined irreversible electroporation and electroporation-induced blood-brain barrier disruption.

    Science.gov (United States)

    Sharabi, Shirley; Kos, Bor; Last, David; Guez, David; Daniels, Dianne; Harnof, Sagi; Mardor, Yael; Miklavcic, Damijan

    2016-03-01

    Electroporation-based therapies such as electrochemotherapy (ECT) and irreversible electroporation (IRE) are emerging as promising tools for treatment of tumors. When applied to the brain, electroporation can also induce transient blood-brain-barrier (BBB) disruption in volumes extending beyond IRE, thus enabling efficient drug penetration. The main objective of this study was to develop a statistical model predicting cell death and BBB disruption induced by electroporation. This model can be used for individual treatment planning. Cell death and BBB disruption models were developed based on the Peleg-Fermi model in combination with numerical models of the electric field. The model calculates the electric field thresholds for cell kill and BBB disruption and describes the dependence on the number of treatment pulses. The model was validated using in vivo experimental data consisting of rats brains MRIs post electroporation treatments. Linear regression analysis confirmed that the model described the IRE and BBB disruption volumes as a function of treatment pulses number (r(2) = 0.79; p disruption, the ratio increased with the number of pulses. BBB disruption radii were on average 67% ± 11% larger than IRE volumes. The statistical model can be used to describe the dependence of treatment-effects on the number of pulses independent of the experimental setup.

  9. Towards a Disruptive Digital Platform Model

    DEFF Research Database (Denmark)

    Kazan, Erol

    that digital platforms leverage on three strategic design elements (i.e., business, architecture, and technology design) to create supportive conditions for facilitating disruption. To shed light on disruptive digital platforms, I opted for payment platforms as my empirical context and unit of analysis......Digital platforms are layered modular information technology architectures that support disruption. Digital platforms are particularly disruptive, as they facilitate the quick release of digital innovations that may replace established innovations. Yet, despite their support for disruption, we have...... not fully understood how such digital platforms can be strategically designed and configured to facilitate disruption. To that end, this thesis endeavors to unravel disruptive digital platforms from the supply perspective that are grounded on strategic digital platform design elements. I suggest...

  10. Evolution and development of model membranes for physicochemical and functional studies of the membrane lateral heterogeneity.

    Science.gov (United States)

    Morigaki, Kenichi; Tanimoto, Yasushi

    2018-03-14

    One of the main questions in the membrane biology is the functional roles of membrane heterogeneity and molecular localization. Although segregation and local enrichment of protein/lipid components (rafts) have been extensively studied, the presence and functions of such membrane domains still remain elusive. Along with biochemical, cell observation, and simulation studies, model membranes are emerging as an important tool for understanding the biological membrane, providing quantitative information on the physicochemical properties of membrane proteins and lipids. Segregation of fluid lipid bilayer into liquid-ordered (Lo) and liquid-disordered (Ld) phases has been studied as a simplified model of raft in model membranes, including giant unilamellar vesicles (GUVs), giant plasma membrane vesicles (GPMVs), and supported lipid bilayers (SLB). Partition coefficients of membrane proteins between Lo and Ld phases were measured to gauze their affinities to lipid rafts (raftophilicity). One important development in model membrane is patterned SLB based on the microfabrication technology. Patterned Lo/Ld phases have been applied to study the partition and function of membrane-bound molecules. Quantitative information of individual molecular species attained by model membranes is critical for elucidating the molecular functions in the complex web of molecular interactions. The present review gives a short account of the model membranes developed for studying the lateral heterogeneity, especially focusing on patterned model membranes on solid substrates. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. STARD4 knockdown in HepG2 cells disrupts cholesterol trafficking associated with the plasma membrane, ER, and ERC

    DEFF Research Database (Denmark)

    Garbarino, J.; Pan, M. H.; Chin, H. F.

    2012-01-01

    small hairpin RNA knockdown technology to reduce STARD4 expression in HepG2 cells. In a cholesterol-poor environment, we found that a reduction in STARD4 expression leads to retention of cholesterol at the plasma membrane, reduction of endoplasmic reticulum-associated cholesterol, and decreased ACAT...... synthesized cholesteryl esters. Furthermore, D4 KD cells exhibited a reduced rate of sterol transport to the endocytic recycling compartment after cholesterol repletion. Although these cells displayed normal endocytic trafficking in cholesterol-poor and replete conditions, cell surface low density lipoprotein...... membrane and the endocytic recycling compartment to the endoplasmic reticulum and perhaps other intracellular compartments as well. -Garbarino, J., M. Pan, H.F. Chin, F.W. Lund, F.R. Maxfield, and J.L. Breslow. STARD4 knockdown in HepG2 cells disrupts cholesterol trafficking associated with the plasma...

  12. Simulation Model of Membrane Gas Separator Using Aspen Custom Modeler

    Energy Technology Data Exchange (ETDEWEB)

    Song, Dong-keun [Korea Institute of Machinery and Materials, Daejeon (Korea, Republic of); Shin, Gahui; Yun, Jinwon; Yu, Sangseok [Chungnam Nat’l Univ., Daejeon (Korea, Republic of)

    2016-12-15

    Membranes are used to separate pure gas from gas mixtures. In this study, three different types of mass transport through a membrane were developed in order to investigate the gas separation capabilities of a membrane. The three different models typically used are a lumped model, a multi-cell model, and a discretization model. Despite the multi-cell model producing similar results to a discretization model, the discretization model was selected for this investigation, due to the cell number dependence of a multi-cell model. The mass transport model was then used to investigate the effects of pressure difference, flow rate, total exposed area, and permeability. The results showed that the pressure difference increased with the stage cut, but the selectivity was a trade-off for the increasing pressure difference. Additionally, even though permeability is an important parameter, the selectivity and stage cut of the membrane converged as permeability increased.

  13. Modeling methodology for supply chain synthesis and disruption analysis

    Science.gov (United States)

    Wu, Teresa; Blackhurst, Jennifer

    2004-11-01

    The concept of an integrated or synthesized supply chain is a strategy for managing today's globalized and customer driven supply chains in order to better meet customer demands. Synthesizing individual entities into an integrated supply chain can be a challenging task due to a variety of factors including conflicting objectives, mismatched incentives and constraints of the individual entities. Furthermore, understanding the effects of disruptions occurring at any point in the system is difficult when working toward synthesizing supply chain operations. Therefore, the goal of this research is to present a modeling methodology to manage the synthesis of a supply chain by linking hierarchical levels of the system and to model and analyze disruptions in the integrated supply chain. The contribution of this research is threefold: (1) supply chain systems can be modeled hierarchically (2) the performance of synthesized supply chain system can be evaluated quantitatively (3) reachability analysis is used to evaluate the system performance and verify whether a specific state is reachable, allowing the user to understand the extent of effects of a disruption.

  14. BAX channel activity mediates lysosomal disruption linked to Parkinson disease.

    Science.gov (United States)

    Bové, Jordi; Martínez-Vicente, Marta; Dehay, Benjamin; Perier, Celine; Recasens, Ariadna; Bombrun, Agnes; Antonsson, Bruno; Vila, Miquel

    2014-05-01

    Lysosomal disruption is increasingly regarded as a major pathogenic event in Parkinson disease (PD). A reduced number of intraneuronal lysosomes, decreased levels of lysosomal-associated proteins and accumulation of undegraded autophagosomes (AP) are observed in PD-derived samples, including fibroblasts, induced pluripotent stem cell-derived dopaminergic neurons, and post-mortem brain tissue. Mechanistic studies in toxic and genetic rodent PD models attribute PD-related lysosomal breakdown to abnormal lysosomal membrane permeabilization (LMP). However, the molecular mechanisms underlying PD-linked LMP and subsequent lysosomal defects remain virtually unknown, thereby precluding their potential therapeutic targeting. Here we show that the pro-apoptotic protein BAX (BCL2-associated X protein), which permeabilizes mitochondrial membranes in PD models and is activated in PD patients, translocates and internalizes into lysosomal membranes early following treatment with the parkinsonian neurotoxin MPTP, both in vitro and in vivo, within a time-frame correlating with LMP, lysosomal disruption, and autophagosome accumulation and preceding mitochondrial permeabilization and dopaminergic neurodegeneration. Supporting a direct permeabilizing effect of BAX on lysosomal membranes, recombinant BAX is able to induce LMP in purified mouse brain lysosomes and the latter can be prevented by pharmacological blockade of BAX channel activity. Furthermore, pharmacological BAX channel inhibition is able to prevent LMP, restore lysosomal levels, reverse AP accumulation, and attenuate mitochondrial permeabilization and overall nigrostriatal degeneration caused by MPTP, both in vitro and in vivo. Overall, our results reveal that PD-linked lysosomal impairment relies on BAX-induced LMP, and point to small molecules able to block BAX channel activity as potentially beneficial to attenuate both lysosomal defects and neurodegeneration occurring in PD.

  15. Modeling and Analysis of Wrinkled Membranes: An Overview

    Science.gov (United States)

    Yang, B.; Ding, H.; Lou, M.; Fang, H.; Broduer, Steve (Technical Monitor)

    2001-01-01

    Thin-film membranes are basic elements of a variety of space inflatable/deployable structures. Wrinkling degrades the performance and reliability of these membrane structures, and hence has been a topic of continued interest. Wrinkling analysis of membranes for general geometry and arbitrary boundary conditions is quite challenging. The objective of this presentation is two-fold. Firstly, the existing models of wrinkled membranes and related numerical solution methods are reviewed. The important issues to be discussed are the capability of a membrane model to characterize taut, wrinkled and slack states of membranes in a consistent and physically reasonable manner; the ability of a wrinkling analysis method to predict the formation and growth of wrinkled regions, and to determine out-of-plane deformation and wrinkled waves; the convergence of a numerical solution method for wrinkling analysis; and the compatibility of a wrinkling analysis with general-purpose finite element codes. According to this review, several opening issues in modeling and analysis of wrinkled membranes that are to be addressed in future research are summarized, The second objective of this presentation is to discuss a newly developed membrane model of two viable parameters (2-VP model) and associated parametric finite element method (PFEM) for wrinkling analysis are introduced. The innovations and advantages of the proposed membrane model and PFEM-based wrinkling analysis are: (1) Via a unified stress-strain relation; the 2-VP model treat the taut, wrinkled, and slack states of membranes consistently; (2) The PFEM-based wrinkling analysis has guaranteed convergence; (3) The 2-VP model along with PFEM is capable of predicting membrane out-of-plane deformations; and (4) The PFEM can be integrated into any existing finite element code. Preliminary numerical examples are also included in this presentation to demonstrate the 2-VP model and PFEM-based wrinkling analysis approach.

  16. Stability of transmembrane amyloid β-peptide and membrane integrity tested by molecular modeling of site-specific Aβ42 mutations.

    Directory of Open Access Journals (Sweden)

    Chetan Poojari

    Full Text Available Interactions of the amyloid β-protein (Aβ with neuronal cell membranes, leading to the disruption of membrane integrity, are considered to play a key role in the development of Alzheimer's disease. Natural mutations in Aβ42, such as the Arctic mutation (E22G have been shown to increase Aβ42 aggregation and neurotoxicity, leading to the early-onset of Alzheimer's disease. A correlation between the propensity of Aβ42 to form protofibrils and its effect on neuronal dysfunction and degeneration has been established. Using rational mutagenesis of the Aβ42 peptide it was further revealed that the aggregation of different Aβ42 mutants in lipid membranes results in a variety of polymorphic aggregates in a mutation dependent manner. The mutant peptides also have a variable ability to disrupt bilayer integrity. To further test the connection between Aβ42 mutation and peptide-membrane interactions, we perform molecular dynamics simulations of membrane-inserted Aβ42 variants (wild-type and E22G, D23G, E22G/D23G, K16M/K28M and K16M/E22G/D23G/K28M mutants as β-sheet monomers and tetramers. The effects of charged residues on transmembrane Aβ42 stability and membrane integrity are analyzed at atomistic level. We observe an increased stability for the E22G Aβ42 peptide and a decreased stability for D23G compared to wild-type Aβ42, while D23G has the largest membrane-disruptive effect. These results support the experimental observation that the altered toxicity arising from mutations in Aβ is not only a result of the altered aggregation propensity, but also originates from modified Aβ interactions with neuronal membranes.

  17. Modelling of proteins in membranes

    DEFF Research Database (Denmark)

    Sperotto, Maria Maddalena; May, S.; Baumgaertner, A.

    2006-01-01

    This review describes some recent theories and simulations of mesoscopic and microscopic models of lipid membranes with embedded or attached proteins. We summarize results supporting our understanding of phenomena for which the activities of proteins in membranes are expected to be significantly ...

  18. Modeling electrically active viscoelastic membranes.

    Directory of Open Access Journals (Sweden)

    Sitikantha Roy

    Full Text Available The membrane protein prestin is native to the cochlear outer hair cell that is crucial to the ear's amplification and frequency selectivity throughout the whole acoustic frequency range. The outer hair cell exhibits interrelated dimensional changes, force generation, and electric charge transfer. Cells transfected with prestin acquire unique active properties similar to those in the native cell that have also been useful in understanding the process. Here we propose a model describing the major electromechanical features of such active membranes. The model derived from thermodynamic principles is in the form of integral relationships between the history of voltage and membrane resultants as independent variables and the charge density and strains as dependent variables. The proposed model is applied to the analysis of an active force produced by the outer hair cell in response to a harmonic electric field. Our analysis reveals the mechanism of the outer hair cell active (isometric force having an almost constant amplitude and phase up to 80 kHz. We found that the frequency-invariance of the force is a result of interplay between the electrical filtering associated with prestin and power law viscoelasticity of the surrounding membrane. Paradoxically, the membrane viscoelasticity boosts the force balancing the electrical filtering effect. We also consider various modes of electromechanical coupling in membrane with prestin associated with mechanical perturbations in the cell. We consider pressure or strains applied step-wise or at a constant rate and compute the time course of the resulting electric charge. The results obtained here are important for the analysis of electromechanical properties of membranes, cells, and biological materials as well as for a better understanding of the mechanism of hearing and the role of the protein prestin in this mechanism.

  19. Role of the membrane skeleton in preventing the shedding of procoagulant-rich microvesicles from the platelet plasma membrane

    OpenAIRE

    1990-01-01

    The platelet plasma membrane is lined by a membrane skeleton that appears to contain short actin filaments cross-linked by actin-binding protein. Actin-binding protein is in turn associated with specific plasma membrane glycoproteins. The aim of this study was to determine whether the membrane skeleton regulates properties of the plasma membrane. Platelets were incubated with agents that disrupted the association of the membrane skeleton with membrane glycoproteins. The consequences of this c...

  20. On modeling of beryllium molten depths in simulated plasma disruptions

    International Nuclear Information System (INIS)

    Tsotridis, G.; Rother, H.

    1996-01-01

    Plasma-facing components in tokamak-type fusion reactors are subjected to intense heat loads during plasma disruptions. The influence of high heat fluxes on the depth of heat-affected zones of pure beryllium metal and beryllium containing very low levels of surface active impurities is studied by using a two-dimensional transient computer model that solves the equations of motion and energy. Results are presented for a range of energy densities and disruption times. Under certain conditions, impurities, through their effect on surface tension, create convective flows and hence influence the flow intensities and the resulting depths of the beryllium molten layers during plasma disruptions. The calculated depths of the molten layers are also compared with other mathematical models that are based on the assumption that heat is transported through the material by conduction only. 32 refs., 6 figs., 1 tab

  1. An in vitro model of the glomerular capillary wall using electrospun collagen nanofibres in a bioartificial composite basement membrane.

    Directory of Open Access Journals (Sweden)

    Sadie C Slater

    Full Text Available The filtering unit of the kidney, the glomerulus, contains capillaries whose walls function as a biological sieve, the glomerular filtration barrier. This comprises layers of two specialised cells, glomerular endothelial cells (GEnC and podocytes, separated by a basement membrane. Glomerular filtration barrier function, and dysfunction in disease, remains incompletely understood, partly due to difficulties in studying the relevant cell types in vitro. We have addressed this by generation of unique conditionally immortalised human GEnC and podocytes. However, because the glomerular filtration barrier functions as a whole, it is necessary to develop three dimensional co-culture models to maximise the benefit of the availability of these cells. Here we have developed the first two tri-layer models of the glomerular capillary wall. The first is based on tissue culture inserts and provides evidence of cell-cell interaction via soluble mediators. In the second model the synthetic support of the tissue culture insert is replaced with a novel composite bioartificial membrane. This consists of a nanofibre membrane containing collagen I, electrospun directly onto a micro-photoelectroformed fine nickel supporting mesh. GEnC and podocytes grew in monolayers on either side of the insert support or the novel membrane to form a tri-layer model recapitulating the human glomerular capillary in vitro. These models will advance the study of both the physiology of normal glomerular filtration and of its disruption in glomerular disease.

  2. A physical model of Mirnov oscillations and plasma disruptions

    International Nuclear Information System (INIS)

    Cross, R.C.

    1983-07-01

    A physical model is proposed which accounts for the general behaviour of Mirnov oscillations and plasma disruptions in tokamak devices. The model also accounts for the stability of those devices which operate with edge safety factors less than 1.5. The model is based on the propagation of localized torsional Alfven and ion acoustic wavepackets. These packets remain phase coherent for considerable distances and are guided along helical field lines in toroidal plasmas, leading to the formation of standing waves on those field lines which close on themselves after one or more toroidal revolutions. Standing waves are driven resonantly on the rational surfaces by fluctuations in the poloidal field, causing localized heating and hence filamentation of the plasma current. This model indicates that Mirnov oscillations are produced by standing acoustic waves, while plasma disruptions occur as a result of the formation of MHD unstable current filaments

  3. Business Model as an Inducer of Disruptive Innovations: The Case of Gol Airlines

    Directory of Open Access Journals (Sweden)

    Sirlei de Almeida Pereira

    2015-10-01

    Full Text Available This study was undertaken to investigate the premises that the success of disruptive innovation is related to the business model adopted by organizations. An analysis of five business models from the literature review - Bovet and Martha (2000, Applegate (2001, Chesbrough and Rosenbloom (2002, Osterwalder and Pigneur (2010, and Rodrigues, Maccari and Lenzi (2012 – was conducted based on the case of the Brazilian Gol Airlines who is recognized as a success business that promoted a disruptive innovation. The results suggest that the assertive choice of the business model can leverage innovation processes, and two of the models listed are adherence to the case studied. Keywords: Disruptive Innovation; Business Model; Innovation Elements; Strategy; Gol Airlines.

  4. Simple membrane-based model of the Min oscillator

    International Nuclear Information System (INIS)

    Petrášek, Zdeněk; Schwille, Petra

    2015-01-01

    Min proteins in E. coli bacteria organize into a dynamic pattern oscillating between the two cell poles. This process identifies the middle of the cell and enables symmetric cell division. In an experimental model system consisting of a flat membrane with effectively infinite supply of proteins and energy source, the Min proteins assemble into travelling waves. Here we propose a simple one-dimensional model of the Min dynamics that, unlike the existing models, reproduces the sharp decrease of Min concentration when the majority of protein detaches from the membrane, and even the narrow MinE maximum immediately preceding the detachment. The proposed model thus provides a possible mechanism for the formation of the MinE ring known from cells. The model is restricted to one dimension, with protein interactions described by chemical kinetics allowing at most bimolecular reactions, and explicitly considering only three, membrane-bound, species. The bulk solution above the membrane is approximated as being well-mixed, with constant concentrations of all species. Unlike other models, our proposal does not require autocatalytic binding of MinD to the membrane. Instead, it is assumed that two MinE molecules are necessary to induce the dissociation of the MinD dimer and its subsequent detachment from the membrane. We investigate which reaction schemes lead to unstable homogeneous steady states and limit cycle oscillations, and how diffusion affects their stability. The suggested model qualitatively describes the shape of the Min waves observed on flat membranes, and agrees with the experimental dependence of the wave period on the MinE concentration. These results highlight the importance of MinE presence on the membrane without being bound to MinD, and of the reactions of Min proteins on the membrane. (paper)

  5. Business model innovation vs. business model inertia: The role of disruptive technologies

    OpenAIRE

    Vorbach, Stefan; Wipfler, Harald; Schimpf, Sven

    2017-01-01

    This contribution addresses the impact of disruptive technologies on business model innovation. While such technologies have the potential to significantly alter the way in which businesses operate, business model inertia hinders companies from adopting the new technological possibilities. Little research has focused on the difficulties incumbents face when innovating their business models. By reviewing current literature on business model innovation, this paper summarizes challenges companie...

  6. A System Shock Approach to Modelling Clandestine Network Disruption

    National Research Council Canada - National Science Library

    Dipper, Tamlan

    2004-01-01

    .... This model took as its focus the disruption of successful terrorist operations. In doing so it drew upon operational art, group behavioural studies, and psychological research into problem solving...

  7. Mesoscopic models of biological membranes

    DEFF Research Database (Denmark)

    Venturoli, M.; Sperotto, Maria Maddalena; Kranenburg, M.

    2006-01-01

    Phospholipids are the main components of biological membranes and dissolved in water these molecules self-assemble into closed structures, of which bilayers are the most relevant from a biological point of view. Lipid bilayers are often used, both in experimental and by theoretical investigations...... to coarse grain a biological membrane. The conclusion of this comparison is that there can be many valid different strategies, but that the results obtained by the various mesoscopic models are surprisingly consistent. A second objective of this review is to illustrate how mesoscopic models can be used...

  8. Computational model of surface ablation from tokamak disruptions

    International Nuclear Information System (INIS)

    Ehst, D.; Hassanein, A.

    1993-10-01

    Energy transfer to material surfaces is dominated by photon radiation through low temperature plasma vapors if tokamak disruptions are due to low kinetic energy particles ( < 100 eV). Simple models of radiation transport are derived and incorporated into a fast-running computer routine to model this process. The results of simulations are in fair agreement with plasma gun erosion tests on several metal targets

  9. Antibacterial Activity and Membrane-Disruptive Mechanism of 3-p-trans-Coumaroyl-2-hydroxyquinic Acid, a Novel Phenolic Compound from Pine Needles of Cedrus deodara, against Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    Yanping Wu

    2016-08-01

    Full Text Available Recently, we reported that a novel phenolic compound isolated from Cedrus deodara, 3-p-trans-coumaroyl-2-hydroxyquinic acid (CHQA, exhibits a potent antioxidant activity. The present study aimed to evaluate the antibacterial activity of CHQA against eleven food-borne pathogens and to elucidate its mechanism of action against Staphylococcus aureus. The results from minimum inhibitory concentration (MIC determinations showed that CHQA exhibited moderate inhibitory effects on all of the tested pathogens with MIC values ranging from 2.5–10 mg/mL. Membrane potential measurements and flow cytometric analysis demonstrated that CHQA damaged the cytoplasmic membrane of S. aureus, causing a significant membrane hyperpolarization with a loss of membrane integrity. Moreover, CHQA induced an increase in membrane fluidity and conformational changes in membrane protein of S. aureus, suggesting that CHQA probably acts on the cell membrane by interactions with membrane lipid and protein. Transmission electron microscopic observations further confirmed that CHQA disrupted the cell membrane of S. aureus and caused severe morphological changes, which even led to leakage of intracellular constituents. These findings indicated that CHQA could have the potential to serve as a natural antibacterial agent to control and prevent the growth of pathogens in food and in food-processing environments.

  10. Picornavirus RNA is protected from cleavage by ribonuclease during virion uncoating and transfer across cellular and model membranes.

    Science.gov (United States)

    Groppelli, Elisabetta; Levy, Hazel C; Sun, Eileen; Strauss, Mike; Nicol, Clare; Gold, Sarah; Zhuang, Xiaowei; Tuthill, Tobias J; Hogle, James M; Rowlands, David J

    2017-02-01

    Picornaviruses are non-enveloped RNA viruses that enter cells via receptor-mediated endocytosis. Because they lack an envelope, picornaviruses face the challenge of delivering their RNA genomes across the membrane of the endocytic vesicle into the cytoplasm to initiate infection. Currently, the mechanism of genome release and translocation across membranes remains poorly understood. Within the enterovirus genus, poliovirus, rhinovirus 2, and rhinovirus 16 have been proposed to release their genomes across intact endosomal membranes through virally induced pores, whereas one study has proposed that rhinovirus 14 releases its RNA following disruption of endosomal membranes. For the more distantly related aphthovirus genus (e.g. foot-and-mouth disease viruses and equine rhinitis A virus) acidification of endosomes results in the disassembly of the virion into pentamers and in the release of the viral RNA into the lumen of the endosome, but no details have been elucidated as how the RNA crosses the vesicle membrane. However, more recent studies suggest aphthovirus RNA is released from intact particles and the dissociation to pentamers may be a late event. In this study we have investigated the RNase A sensitivity of genome translocation of poliovirus using a receptor-decorated-liposome model and the sensitivity of infection of poliovirus and equine-rhinitis A virus to co-internalized RNase A. We show that poliovirus genome translocation is insensitive to RNase A and results in little or no release into the medium in the liposome model. We also show that infectivity is not reduced by co-internalized RNase A for poliovirus and equine rhinitis A virus. Additionally, we show that all poliovirus genomes that are internalized into cells, not just those resulting in infection, are protected from RNase A. These results support a finely coordinated, directional model of viral RNA delivery that involves viral proteins and cellular membranes.

  11. Picornavirus RNA is protected from cleavage by ribonuclease during virion uncoating and transfer across cellular and model membranes.

    Directory of Open Access Journals (Sweden)

    Elisabetta Groppelli

    2017-02-01

    Full Text Available Picornaviruses are non-enveloped RNA viruses that enter cells via receptor-mediated endocytosis. Because they lack an envelope, picornaviruses face the challenge of delivering their RNA genomes across the membrane of the endocytic vesicle into the cytoplasm to initiate infection. Currently, the mechanism of genome release and translocation across membranes remains poorly understood. Within the enterovirus genus, poliovirus, rhinovirus 2, and rhinovirus 16 have been proposed to release their genomes across intact endosomal membranes through virally induced pores, whereas one study has proposed that rhinovirus 14 releases its RNA following disruption of endosomal membranes. For the more distantly related aphthovirus genus (e.g. foot-and-mouth disease viruses and equine rhinitis A virus acidification of endosomes results in the disassembly of the virion into pentamers and in the release of the viral RNA into the lumen of the endosome, but no details have been elucidated as how the RNA crosses the vesicle membrane. However, more recent studies suggest aphthovirus RNA is released from intact particles and the dissociation to pentamers may be a late event. In this study we have investigated the RNase A sensitivity of genome translocation of poliovirus using a receptor-decorated-liposome model and the sensitivity of infection of poliovirus and equine-rhinitis A virus to co-internalized RNase A. We show that poliovirus genome translocation is insensitive to RNase A and results in little or no release into the medium in the liposome model. We also show that infectivity is not reduced by co-internalized RNase A for poliovirus and equine rhinitis A virus. Additionally, we show that all poliovirus genomes that are internalized into cells, not just those resulting in infection, are protected from RNase A. These results support a finely coordinated, directional model of viral RNA delivery that involves viral proteins and cellular membranes.

  12. Transferable coarse-grained model for perfluorosulfonic acid polymer membranes

    Science.gov (United States)

    Kuo, An-Tsung; Okazaki, Susumu; Shinoda, Wataru

    2017-09-01

    Perfluorosulfonic acid (PFSA) polymer membranes are widely used as proton exchange membranes. Because the structure of the aqueous domain within the PFSA membrane is expected to directly influence proton conductance, many coarse-grained (CG) simulation studies have been performed to investigate the membrane morphology; these studies mostly used phenomenological models, such as dissipative particle dynamics. However, a chemically accurate CG model is required to investigate the morphology in realistic membranes and to provide a concrete molecular design. Here, we attempt to construct a predictive CG model for the structure and morphology of PFSA membranes that is compatible with the Sinoda-DeVane-Klein (SDK) CG water model [Shinoda et al., Mol. Simul. 33, 27 (2007)]. First, we extended the parameter set for the SDK CG force field to examine a hydrated PFSA membrane based on thermodynamic and structural data from experiments and all-atom (AA) molecular dynamics (MD) simulations. However, a noticeable degradation of the morphology motivated us to improve the structural properties by using the iterative Boltzmann inversion (IBI) approach. Thus, we explored a possible combination of the SDK and IBI approaches to describe the nonbonded interaction. The hybrid SDK/IBI model improved the structural issues of SDK, showing a better agreement with AA-MD in the radial distribution functions. The hybrid SDK/IBI model was determined to reasonably reproduce both the thermodynamic and structural properties of the PFSA membrane for all examined water contents. In addition, the model demonstrated good transferability and has considerable potential for application to realistic long-chained PFSA membranes.

  13. Challenges in Commercializing Biomimetic Membranes.

    Science.gov (United States)

    Perry, Mark; Madsen, Steen Ulrik; Jørgensen, Tine; Braekevelt, Sylvie; Lauritzen, Karsten; Hélix-Nielsen, Claus

    2015-11-05

    The discovery of selective water channel proteins-aquaporins-has prompted growing interest in using these proteins, as the building blocks for designing new types of membranes. However, as with any other new and potentially disruptive technology, barriers for successful market entry exist. One category includes customer-related barriers, which can be influenced to some extent. Another category includes market-technical-related barriers, which can be very difficult to overcome by an organization/company aiming at successfully introducing their innovation on the market-in particular if both the organization and the technology are at early stages. Often, one faces barriers from both these categories at the same time, which makes it necessary to gain insight of the particular market when introducing a new innovative product. In this review we present the basic concepts and discuss some of these barriers and challenges associated with introducing biomimetic aquaporin membranes. These include technical issues in membrane production and product testing. Then we discuss possible business models for introducing new technologies in general, followed by a presentation of beach-head market segments relevant for biomimetic aquaporin membranes.

  14. Biophysical studies of cholesterol in unsaturated phospholipid model membranes

    Science.gov (United States)

    Williams, Justin Adam

    PUFAs can incorporate into lipid rafts, which are domains enriched in SM and chol in the plasma membrane, and potentially disrupt the activity of signaling proteins that reside therein. DHA, furthermore, may be the more potent component of fish oil. PUFA-chol interactions were also examined through affinity measurements. A novel method utilizing electron paramagnetic resonance (EPR) was developed, to monitor the partitioning of a spin-labeled analog of chol, 3beta-doxyl-5alpha-cholestane (chlstn), between large unilamellar vesicles (LUVs) and methyl-beta-cyclodextrin (mbetaCD). The EPR spectra for chlstn in the two environments are distinguishable due to the substantial differences in tumbling rates, allowing the population distribution ratio to be determined by spectral simulation. Advantages of this approach include speed of implementation and avoidance of potential artifacts associated with physical separation of LUV and mbetaCD. Additionally, in a check of the method, the relative partition coefficients between lipids measured for the spin label analog agree with values obtained for chol by isothermal titration calorimetry (ITC). Results from LUV with different composition confirmed a hierarchy of decreased sterol affinity for phospholipids with increasing acyl chain unsaturation, PDPC possessing half the affinity of the corresponding monounsaturated phospholipid. Taken together, the results of these studies on model membranes demonstrate the potential for PUFA-driven alteration of the architecture of biomembranes, a mechanism through which human health may be impacted.

  15. Management of posterior urethral disruption injuries.

    Science.gov (United States)

    Myers, Jeremy B; McAninch, Jack W

    2009-03-01

    Posterior urethral disruption is a traumatic injury to the male urethra, which most often results from pelvic fracture. After trauma, the distraction defect between the two ends of the urethra often scars and becomes fibrotic, blocking the urethra and bladder emptying. Increasing evidence suggests that many posterior urethral disruptions occur at the junction between the membranous urethra and the bulbar urethra, which is distal to the rhabdosphincter. In the acute setting, when a posterior urethral disruption is suspected, retrograde urethrography should be performed. Posterior urethral disruptions can be managed acutely by realignment of the urethra over a urethral catheter or by placement of a suprapubic catheter for bladder drainage only. Once fibrosis has stabilized, the patient can undergo posterior urethroplasty. In most cases, this procedure can be performed via a perineal approach in a single-stage surgery. The results of this single-stage perineal urethroplasty are excellent, and a patent urethra can be re-established in the majority of men who undergo surgery.

  16. Skin barrier disruption by acetone: observations in a hairless mouse skin model

    NARCIS (Netherlands)

    Rissmann, R.; Oudshoorn, M.H.M.; Hennink, W.E.; Ponec, M.; Bouwstra, J.A.

    2009-01-01

    To disrupt the barrier function of the skin, different in vivo methods have been established, e.g., by acetone wiping or tape-stripping. In this study, the acetone-induced barrier disruption of hairless mice was investigated in order to establish a reliable model to study beneficial, long-term

  17. Effect of narcotics on membrane-bound mitochondrial processes in fish

    DEFF Research Database (Denmark)

    Vergauwen, Lucia; Nørgaard Schmidt, Stine; Michiels, Ellen

    and endoplasmic reticulum membrane are known to closely interact with the cell membrane, we hypothesize that narcotics can be further partitioned into these organelle membranes where they can disrupt essential membrane-bound processes. The electron transport chain (ETC) is an example of a crucial mitochondrial...

  18. Disruption management in the airline industry-Concepts, models and methods

    DEFF Research Database (Denmark)

    Clausen, Jens; Larsen, Allan; Larsen, Jesper

    2010-01-01

    This paper provides a thorough review of the current state-of-the-art within airline disruption management of resources, including aircraft, crew, passenger and integrated recovery. An overview of model formulations of the aircraft and crew scheduling problems is presented in order to emphasize...... similarities between solution approaches applied to the planning and recovery problems. A brief overview of research within schedule robustness in airline scheduling is included in the review, since this proactive measure is a natural complement to disruption management....

  19. Empirical membrane lifetime model for heavy duty fuel cell systems

    Science.gov (United States)

    Macauley, Natalia; Watson, Mark; Lauritzen, Michael; Knights, Shanna; Wang, G. Gary; Kjeang, Erik

    2016-12-01

    Heavy duty fuel cells used in transportation system applications such as transit buses expose the fuel cell membranes to conditions that can lead to lifetime-limiting membrane failure via combined chemical and mechanical degradation. Highly durable membranes and reliable predictive models are therefore needed in order to achieve the ultimate heavy duty fuel cell lifetime target of 25,000 h. In the present work, an empirical membrane lifetime model was developed based on laboratory data from a suite of accelerated membrane durability tests. The model considers the effects of cell voltage, temperature, oxygen concentration, humidity cycling, humidity level, and platinum in the membrane using inverse power law and exponential relationships within the framework of a general log-linear Weibull life-stress statistical distribution. The obtained model is capable of extrapolating the membrane lifetime from accelerated test conditions to use level conditions during field operation. Based on typical conditions for the Whistler, British Columbia fuel cell transit bus fleet, the model predicts a stack lifetime of 17,500 h and a membrane leak initiation time of 9200 h. Validation performed with the aid of a field operated stack confirmed the initial goal of the model to predict membrane lifetime within 20% of the actual operating time.

  20. Simulations of simple linoleic acid-containing lipid membranes and models for the soybean plasma membranes.

    Science.gov (United States)

    Zhuang, Xiaohong; Ou, Anna; Klauda, Jeffery B

    2017-06-07

    The all-atom CHARMM36 lipid force field (C36FF) has been tested with saturated, monounsaturated, and polyunsaturated lipids; however, it has not been validated against the 18:2 linoleoyl lipids with an unsaturated sn-1 chain. The linoleoyl lipids are common in plants and the main component of the soybean membrane. The lipid composition of soybean plasma membranes has been thoroughly characterized with experimental studies. However, there is comparatively less work done with computational modeling. Our molecular dynamics (MD) simulation results show that the pure linoleoyl lipids, 1-stearoyl-2-linoleoyl-sn-glycero-3-phosphocholine (18:0/18:2) and 1,2-dilinoleoyl-sn-glycero-3-phosphocholine (di-18:2), agree very well with the experiments, which demonstrates the accuracy of the C36FF for the computational study of soybean membranes. Based on the experimental composition, the soybean hypocotyl and root plasma membrane models are developed with each containing seven or eight types of linoleoyl phospholipids and two types of sterols (sitosterol and stigmasterol). MD simulations are performed to characterize soybean membranes, and the hydrogen bonds and clustering results demonstrate that the lipids prefer to interact with the lipids of the same/similar tail unsaturation. All the results suggest that these two soybean membrane models can be used as a basis for further research in soybean and higher plant membranes involving membrane-associated proteins.

  1. Cytotoxic effects induced by interferon-ω gene lipofection through ROS generation and mitochondrial membrane potential disruption in feline mammary carcinoma cells.

    Science.gov (United States)

    Villaverde, Marcela Solange; Targovnik, Alexandra Marisa; Miranda, María Victoria; Finocchiaro, Liliana María Elena; Glikin, Gerardo Claudio

    2016-08-01

    Progress in comparative oncology promises advances in clinical cancer treatments for both companion animals and humans. In this context, feline mammary carcinoma (FMC) cells have been proposed as a suitable model to study human breast cancer. Based on our previous data about the advantages of using type I interferon gene therapy over the respective recombinant DNA derived protein, the present work explored the effects of feline interferon-ω gene (fIFNω) transfer on FMC cells. Three different cell variants derived from a single spontaneous highly aggressive FMC tumor were successfully established and characterized. Lipofection of the fIFNω gene displayed a significant cytotoxic effect on the three cell variants. The extent of the response was proportional to ROS generation, mitochondrial membrane potential disruption and calcium uptake. Moreover, a lower sensitivity to the treatment correlated with a higher malignant phenotype. Our results suggest that fIFNω lipofection could offer an alternative approach in veterinary oncology with equal or superior outcome and with less adverse effects than recombinant fIFNω therapy. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. A Recovery Model for Production Scheduling: Combination of Disruption Management and Internet of Things

    Directory of Open Access Journals (Sweden)

    Yang Jiang

    2016-01-01

    Full Text Available It is difficult to generate the new schedule effectively for minimizing the negative impact when an unanticipated disruption occurs after a subset of tasks has been finished in production scheduling. In such cases, continuing with the original schedule may not be optimal or feasible. Based on disruption management and Internet of things (IoT, this study designs a real-time status analyzer to identify the disruption and propose a recovery model to deal with the disruption. The computational result proves that our algorithm is competitive with the existing heuristics. Furthermore, due to the tradeoff between all participators (mainly including customers, managers of production enterprise, and workers involved in production scheduling, our model is more effective than the total rescheduling and right-shift rescheduling.

  3. Otolithic membrane damage in patients with endolymphatic hydrops and drop attacks.

    Science.gov (United States)

    Calzada, Audrey P; Lopez, Ivan A; Ishiyama, Gail; Ishiyama, Akira

    2012-12-01

    1. Evaluate the otolithic membrane in patients with endolymphatic hydrops (EH) and vestibular drop attacks (VDA) undergoing ablative labyrinthectomy. 2. Correlate intraoperative findings to archival temporal bone specimens of patients with EH. Retrospective case review. Tertiary referral center. SPECIMEN SOURCE: 1. Patients undergoing labyrinthectomy for incapacitating Ménière's disease (MD), delayed EH, VDA, or acoustic neuroma (AN) between 2004 and 2011. 2. Archival temporal bone specimens of patients with MD. Ablative labyrinthectomy. Examination of the utricular otolithic membrane. The otolithic membrane of the utricle was evaluated intraoperatively in 28 patients undergoing labyrinthectomy. Seven (25%) had a history of VDA, 6 (21%) had delayed EH, 9 (32%) had MD, and 6 (21%) had AN. All patients with VDA showed evidence of a disrupted utricular otolithic membrane, whereas only 50% and 56% of patients with delayed EH and MD, respectively, demonstrated otolithic membrane disruption (p = 0.051). None of the patients with AN showed otolithic membrane disruption (p = 0.004). The mean thickness of the otolithic membrane in 5 archival temporal bone MD specimens was 11.45 micrometers versus 38 micrometers in normal specimens (p = 0.001). The otolithic membrane is consistently damaged in patients with VDA. In addition, there is a significantly higher incidence of otolithic membrane injury in patients with MD and delayed EH compared with patients without hydrops, suggesting that the underlying pathophysiology in VDA results from injury to the otolithic membrane of the saccule and utricle, resulting in free-floating otoliths and atrophy.

  4. Performance modeling of direct contact membrane distillation (DCMD) seawater desalination process using a commercial composite membrane

    KAUST Repository

    Lee, Junggil

    2015-01-10

    This paper presents the development of a rigorous theoretical model to predict the transmembrane flux of a flat sheet hydrophobic composite membrane, comprising both an active layer of polytetrafluoroethylene and a scrim-backing support layer of polypropylene, in the direct contact membrane distillation (DCMD) process. An integrated model includes the mass, momentum, species and energy balances for both retentate and permeate flows, coupled with the mass transfer of water vapor through the composite membrane and the heat transfer across the membrane and through the boundary layers adjacent to the membrane surfaces. Experimental results and model predictions for permeate flux and performance ratio are compared and shown to be in good agreement. The permeate flux through the composite layer can be ignored in the consideration of mass transfer pathways at the composite membrane. The effect of the surface porosity and the thickness of active and support layers on the process performance of composite membrane has also been studied. Among these parameters, surface porosity is identified to be the main factor significantly influencing the permeate flux and performance ratio, while the relative influence of the surface porosity on the performance ratio is less than that on flux.

  5. Two-dimensional stochastic modeling of membrane fouling

    NARCIS (Netherlands)

    Wessling, Matthias

    2001-01-01

    The phenomenon of fouling of microfiltration membranes by much smaller particles such as proteins is described by a new developed simulation algorithm based on diffusion limited aggregation simulation techniques. The model specifies the membrane morphology explicitly and allows to (a) characterize

  6. Challenges in Commercializing Biomimetic Membranes

    Directory of Open Access Journals (Sweden)

    Mark Perry

    2015-11-01

    Full Text Available The discovery of selective water channel proteins—aquaporins—has prompted growing interest in using these proteins, as the building blocks for designing new types of membranes. However, as with any other new and potentially disruptive technology, barriers for successful market entry exist. One category includes customer-related barriers, which can be influenced to some extent. Another category includes market-technical-related barriers, which can be very difficult to overcome by an organization/company aiming at successfully introducing their innovation on the market—in particular if both the organization and the technology are at early stages. Often, one faces barriers from both these categories at the same time, which makes it necessary to gain insight of the particular market when introducing a new innovative product. In this review we present the basic concepts and discuss some of these barriers and challenges associated with introducing biomimetic aquaporin membranes. These include technical issues in membrane production and product testing. Then we discuss possible business models for introducing new technologies in general, followed by a presentation of beach-head market segments relevant for biomimetic aquaporin membranes.

  7. Cationic nanoparticles induce nanoscale disruption in living cell plasma membranes.

    Science.gov (United States)

    Chen, Jiumei; Hessler, Jessica A; Putchakayala, Krishna; Panama, Brian K; Khan, Damian P; Hong, Seungpyo; Mullen, Douglas G; Dimaggio, Stassi C; Som, Abhigyan; Tew, Gregory N; Lopatin, Anatoli N; Baker, James R; Holl, Mark M Banaszak; Orr, Bradford G

    2009-08-13

    It has long been recognized that cationic nanoparticles induce cell membrane permeability. Recently, it has been found that cationic nanoparticles induce the formation and/or growth of nanoscale holes in supported lipid bilayers. In this paper, we show that noncytotoxic concentrations of cationic nanoparticles induce 30-2000 pA currents in 293A (human embryonic kidney) and KB (human epidermoid carcinoma) cells, consistent with a nanoscale defect such as a single hole or group of holes in the cell membrane ranging from 1 to 350 nm(2) in total area. Other forms of nanoscale defects, including the nanoparticle porating agents adsorbing onto or intercalating into the lipid bilayer, are also consistent; although the size of the defect must increase to account for any reduction in ion conduction, as compared to a water channel. An individual defect forming event takes 1-100 ms, while membrane resealing may occur over tens of seconds. Patch-clamp data provide direct evidence for the formation of nanoscale defects in living cell membranes. The cationic polymer data are compared and contrasted with patch-clamp data obtained for an amphiphilic phenylene ethynylene antimicrobial oligomer (AMO-3), a small molecule that is proposed to make well-defined 3.4 nm holes in lipid bilayers. Here, we observe data that are consistent with AMO-3 making approximately 3 nm holes in living cell membranes.

  8. Polyether sulfone membrane modeling and construction for the ...

    African Journals Online (AJOL)

    Polyether sulfone membrane modeling and construction for the removal of nitrate from water using ion interference sulfate and iron nano-particle. ... The aim of this study was constructed the polyether sulfone membrane and modelling it, and for checking impact pressure, the amount of iron nanoparticles and sulfate iron ...

  9. Interaction of elaiophylin with model bilayer membrane

    Science.gov (United States)

    Genova, J.; Dencheva-Zarkova, M.

    2017-01-01

    Elaiophylin is a new macrodiolide antibiotic, which is produced by the Streptomyces strains [1]. It displays biological activities against Gram-positive bacteria and fungi. The mode of action of this antibiotic has been attributed to an alteration of the membrane permeability. When this antibiotic is inserted into the bilayer membranes destabilization of the membrane and formation of ion-penetrable channels is observed. The macrodiolide antibiotic forms stable cation selective ion channels in synthetic lipid bilayer membranes. The aim of this work was to study the interactions of Elaiophylin with model bilayer membranes and to get information on the mechanical properties of lipid bilayers in presence of this antibiotic. Patch-clamp technique [2] were used in the study

  10. Performance modeling of direct contact membrane distillation (DCMD) seawater desalination process using a commercial composite membrane

    KAUST Repository

    Lee, Junggil; Kim, Youngdeuk; Kim, Wooseung; Francis, Lijo; Amy, Gary L.; Ghaffour, NorEddine

    2015-01-01

    membrane and the heat transfer across the membrane and through the boundary layers adjacent to the membrane surfaces. Experimental results and model predictions for permeate flux and performance ratio are compared and shown to be in good agreement

  11. An Integrated Framework Advancing Membrane Protein Modeling and Design.

    Directory of Open Access Journals (Sweden)

    Rebecca F Alford

    2015-09-01

    Full Text Available Membrane proteins are critical functional molecules in the human body, constituting more than 30% of open reading frames in the human genome. Unfortunately, a myriad of difficulties in overexpression and reconstitution into membrane mimetics severely limit our ability to determine their structures. Computational tools are therefore instrumental to membrane protein structure prediction, consequently increasing our understanding of membrane protein function and their role in disease. Here, we describe a general framework facilitating membrane protein modeling and design that combines the scientific principles for membrane protein modeling with the flexible software architecture of Rosetta3. This new framework, called RosettaMP, provides a general membrane representation that interfaces with scoring, conformational sampling, and mutation routines that can be easily combined to create new protocols. To demonstrate the capabilities of this implementation, we developed four proof-of-concept applications for (1 prediction of free energy changes upon mutation; (2 high-resolution structural refinement; (3 protein-protein docking; and (4 assembly of symmetric protein complexes, all in the membrane environment. Preliminary data show that these algorithms can produce meaningful scores and structures. The data also suggest needed improvements to both sampling routines and score functions. Importantly, the applications collectively demonstrate the potential of combining the flexible nature of RosettaMP with the power of Rosetta algorithms to facilitate membrane protein modeling and design.

  12. Challenges in the modeling of tidal disruption events lightcurves

    Directory of Open Access Journals (Sweden)

    Lodato G.

    2012-12-01

    Full Text Available In this contribution, I review the recent developments on the modeling of the lightcurve of tidal disruption events. Our understanding has evolved significantly from the earlier seminal results that imply a simple power-law decay of the bolometric light curve as t−5/3. We now know that the details of the rise to the peak of the lightcurve is determined mainly by the internal structure of the disrupted star. We also have improved models for the disc thermal emission, showing that in this case the decline of the luminosity with time should be much flatter than the standard t−5/3 law, especially in optical and UV wavelengths, while the X-ray lightcurve is generally best suited to track the bolometric one. Finally, we are just starting to explore the interesting general relativistic effects that might arise for such events, for which the tidal radius lies very close to the black hole event horizon.

  13. Model of SNARE-mediated membrane adhesion kinetics.

    Directory of Open Access Journals (Sweden)

    Jason M Warner

    Full Text Available SNARE proteins are conserved components of the core fusion machinery driving diverse membrane adhesion and fusion processes in the cell. In many cases micron-sized membranes adhere over large areas before fusion. Reconstituted in vitro assays have helped isolate SNARE mechanisms in small membrane adhesion-fusion and are emerging as powerful tools to study large membrane systems by use of giant unilamellar vesicles (GUVs. Here we model SNARE-mediated adhesion kinetics in SNARE-reconstituted GUV-GUV or GUV-supported bilayer experiments. Adhesion involves many SNAREs whose complexation pulls apposing membranes into contact. The contact region is a tightly bound rapidly expanding patch whose growth velocity v(patch increases with SNARE density Gamma(snare. We find three patch expansion regimes: slow, intermediate, fast. Typical experiments belong to the fast regime where v(patch ~ (Gamma(snare(2/3 depends on SNARE diffusivities and complexation binding constant. The model predicts growth velocities ~10 - 300 microm/s. The patch may provide a close contact region where SNAREs can trigger fusion. Extending the model to a simple description of fusion, a broad distribution of fusion times is predicted. Increasing SNARE density accelerates fusion by boosting the patch growth velocity, thereby providing more complexes to participate in fusion. This quantifies the notion of SNAREs as dual adhesion-fusion agents.

  14. How Can Blockchain Technology Disrupt the Existing Business Models?

    OpenAIRE

    Witold Nowiński; Miklós Kozma

    2017-01-01

    Objective: The main purpose of the paper is to show that blockchain technology may disrupt the existing business models and to explore how this may occur. Research Design & Methods: This is a theory development paper which relies on a literature review and desk re-search. The discussion of the reviewed sources leads to the formulation of three re-search propositions. Findings: The paper provides a short overview of key literature on business models and business model innovation, indic...

  15. Modeling and optimization of membrane lifetime in dead-end ultra filtration

    NARCIS (Netherlands)

    Zondervan, E.; Roffel, B.

    2008-01-01

    In this paper, a membrane lifetime model is developed and experimentally validated. The lifetime model is based on the Weibull probability density function. The lifetime model can be used to determine an unambiguous characteristic membrane lifetime. Experimental results showed that membrane lifetime

  16. Modeling of Multicomponent Mixture Separation Processes Using Hollow fiber Membrane

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sin-Ah; Kim, Jin-Kuk; Lee, Young Moo; Yeo, Yeong-Koo [Hanyang University, Seoul (Korea, Republic of)

    2015-02-15

    So far, most of research activities on modeling of membrane separation processes have been focused on binary feed mixture. But, in actual separation operations, binary feed is hard to find and most separation processes involve multicomponent feed mixture. In this work models for membrane separation processes treating multicomponent feed mixture are developed. Various model types are investigated and validity of proposed models are analysed based on experimental data obtained using hollowfiber membranes. The proposed separation models show quick convergence and exhibit good tracking performance.

  17. Interaction of Mastoparan with Model Membranes

    Science.gov (United States)

    Haloot, Justin

    2010-10-01

    The use of antimicrobial agents began during the 20th century to reduce the effects of infectious diseases. Since the 1990s, antimicrobial resistance has become an ever-increasing global problem. Our laboratory recently found that small antimicrobial peptides (AMPs) have potent antimicrobial activity against a wide range of Gram-negative and Gram-positive organisms including antibiotic resistant organisms. These AMPs are potential therapeutic agents against the growing problem of antimicrobial resistance. AMPs are small peptides produced by plants, insects and animals. Several hypotheses concede that these peptides cause some type of structural perturbations and increased membrane permeability in bacteria however, how AMPs kill bacteria remains unclear. The goal of this study was to design an assay that would allow us to evaluate and monitor the pore forming ability of an AMP, Mastoparan, on model membrane structures called liposomes. Development of this model will facilitate the study of how mastoparan and related AMPs interact with the bacterial membrane.

  18. Informed Principal Model and Contract in Supply Chain with Demand Disruption Asymmetric Information

    Directory of Open Access Journals (Sweden)

    Huan Zhang

    2016-01-01

    Full Text Available Because of the frequency and disastrous influence, the supply chain disruption has caused extensive concern both in the industry and in the academia. In a supply chain with one manufacturer and one retailer, the demand of the retailer is uncertain and meanwhile may suffer disruption with a probability. Taking the demand disruption probability as the retailer’s asymmetric information, an informed principal model with the retailer as the principal is explored to make the contract. The retailer can show its information to the manufacturer through the contract. It is found out that the high-risk retailer intends to pretend to be the low-risk one. So the separating contract is given through the low-information-intensity allocation, in which the order quantity and the transferring payment for the low-risk retailer distort upwards, but those of high-risk retailer do not distort. In order to reduce the signaling cost which the low-risk retailer pays, the interim efficient model is introduced, which ends up with the order quantity and transferring payment distorting upwards again but less than before. In the numerical examples, with two different mutation probabilities, the informed principal contracts show the application of the informed principal model in the supply chain with demand disruption.

  19. Modeling bubble dynamics and radical kinetics in ultrasound induced microalgal cell disruption.

    Science.gov (United States)

    Wang, Meng; Yuan, Wenqiao

    2016-01-01

    Microalgal cell disruption induced by acoustic cavitation was simulated through solving the bubble dynamics in an acoustical field and their radial kinetics (chemical kinetics of radical species) occurring in the bubble during its oscillation, as well as calculating the bubble wall pressure at the collapse point. Modeling results indicated that increasing ultrasonic intensity led to a substantial increase in the number of bubbles formed during acoustic cavitation, however, the pressure generated when the bubbles collapsed decreased. Therefore, cumulative collapse pressure (CCP) of bubbles was used to quantify acoustic disruption of a freshwater alga, Scenedesmus dimorphus, and a marine alga, Nannochloropsis oculata and compare with experimental results. The strong correlations between CCP and the intracellular lipid fluorescence density, chlorophyll-a fluorescence density, and cell particle/debris concentration were found, which suggests that the developed models could accurately predict acoustic cell disruption, and can be utilized in the scale up and optimization of the process. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Mathematical model of a PEMFC using a PBI membrane

    International Nuclear Information System (INIS)

    Cheddie, Denver; Munroe, Norman

    2006-01-01

    Proton exchange membrane fuel cells (PEMFC) operating with Nafion[reg] membranes have encountered numerous problems associated with water management and CO poisoning because of their low temperature of operation. Alternative high temperature membranes have been investigated, one such membrane being polybenzimidazole (PBI). This paper presents a one dimensional mathematical model, which predicts the polarization performance of a PEMFC using a PBI membrane. Peak power densities in the same order as Nafion[reg] are predicted. Results indicate that the greatest scope for improving PBI PEMFC performance is increasing the membrane conductivity and improving the catalyst performance as it interfaces with the PBI membrane

  1. Dynamic molecular confinement in the plasma membrane by microdomains and the cytoskeleton meshwork.

    Science.gov (United States)

    Lenne, Pierre-François; Wawrezinieck, Laure; Conchonaud, Fabien; Wurtz, Olivier; Boned, Annie; Guo, Xiao-Jun; Rigneault, Hervé; He, Hai-Tao; Marguet, Didier

    2006-07-26

    It is by now widely recognized that cell membranes show complex patterns of lateral organization. Two mechanisms involving either a lipid-dependent (microdomain model) or cytoskeleton-based (meshwork model) process are thought to be responsible for these plasma membrane organizations. In the present study, fluorescence correlation spectroscopy measurements on various spatial scales were performed in order to directly identify and characterize these two processes in live cells with a high temporal resolution, without any loss of spatial information. Putative raft markers were found to be dynamically compartmented within tens of milliseconds into small microdomains (Ø confinement of the transferrin receptor protein. A free-like diffusion was observed when both the lipid-dependent and cytoskeleton-based organizations were disrupted, which suggests that these are two main compartmentalizing forces at work in the plasma membrane.

  2. Modeling of Hollow-Fiber Membrane System During Ultrafiltration

    International Nuclear Information System (INIS)

    EI-Bialy, S.H.

    2004-01-01

    The present study aims to evaluate the performance of hollow fiber membrane module during ultrafiltration of aqueous solutions. The model is represented by a set of differential equations for permeate and residue pressure drop and volumetric flow rates in the axial direction, beside the principle equations of both solvent and solute fluxes through the membrane, while osmotic pressure was neglected in model equations. The shell and tube module type was considered where feed pass in the shell and permeate in the bore side. Tortousily factor of membrane pores in addition to concentration polarization modulus were taken into account in calculations. The model was solved numerically with the help of suitable program in both co current and countercurrent flow pattern and comparison of results were carried out

  3. Formulation and characterization of poly(propylacrylic acid)/poly(lactic-co-glycolic acid) blend microparticles for pH-dependent membrane disruption and cytosolic delivery.

    Science.gov (United States)

    Fernando, Lawrence P; Lewis, Jamal S; Evans, Brian C; Duvall, Craig L; Keselowsky, Benjamin G

    2018-04-01

    Poly(lactic-co-glycolic acid) (PLGA) is widely used as a vehicle for delivery of pharmaceutically relevant payloads. PLGA is readily fabricated as a nano- or microparticle (MP) matrix to load both hydrophobic and hydrophilic small molecular drugs as well as biomacromolecules such as nucleic acids and proteins. However, targeting such payloads to the cell cytosol is often limited by MP entrapment and degradation within acidic endolysosomes. Poly(propylacrylic acid) (PPAA) is a polyelectrolyte polymer with the membrane disruptive capability triggered at low pH. PPAA has been previously formulated in various carrier configurations to enable cytosolic payload delivery, but requires sophisticated carrier design. Taking advantage of PPAA functionality, we have incorporated PPAA into PLGA MPs as a simple polymer mixture to enhance cytosolic delivery of PLGA-encapsulated payloads. Rhodamine loaded PLGA and PPAA/PLGA blend MPs were prepared by a modified nanoprecipitation method. Incorporation of PPAA into PLGA MPs had little to no effect on the size, shape, or loading efficiency, and evidenced no toxicity in Chinese hamster ovary epithelial cells. Notably, incorporation of PPAA into PLGA MPs enabled pH-dependent membrane disruption in a hemolysis assay, and a three-fold increased endosomal escape and cytosolic delivery in dendritic cells after 2 h of MP uptake. These results demonstrate that a simple PLGA/PPAA polymer blend is readily fabricated into composite MPs, enabling cytosolic delivery of an encapsulated payload. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1022-1033, 2018. © 2017 Wiley Periodicals, Inc.

  4. Confined Mobility of TonB and FepA in Escherichia coli Membranes.

    Directory of Open Access Journals (Sweden)

    Yoriko Lill

    Full Text Available The important process of nutrient uptake in Escherichia coli, in many cases, involves transit of the nutrient through a class of beta-barrel proteins in the outer membrane known as TonB-dependent transporters (TBDTs and requires interaction with the inner membrane protein TonB. Here we have imaged the mobility of the ferric enterobactin transporter FepA and TonB by tracking them in the membranes of live E. coli with single-molecule resolution at time-scales ranging from milliseconds to seconds. We employed simple simulations to model/analyze the lateral diffusion in the membranes of E.coli, to take into account both the highly curved geometry of the cell and artifactual effects expected due to finite exposure time imaging. We find that both molecules perform confined lateral diffusion in their respective membranes in the absence of ligand with FepA confined to a region [Formula: see text] μm in radius in the outer membrane and TonB confined to a region [Formula: see text] μm in radius in the inner membrane. The diffusion coefficient of these molecules on millisecond time-scales was estimated to be [Formula: see text] μm2/s and [Formula: see text] μm2/s for FepA and TonB, respectively, implying that each molecule is free to diffuse within its domain. Disruption of the inner membrane potential, deletion of ExbB/D from the inner membrane, presence of ligand or antibody to FepA and disruption of the MreB cytoskeleton was all found to further restrict the mobility of both molecules. Results are analyzed in terms of changes in confinement size and interactions between the two proteins.

  5. A stochastic inventory management model for a dual sourcing supply chain with disruptions

    Science.gov (United States)

    Iakovou, Eleftherios; Vlachos, Dimitrios; Xanthopoulos, Anastasios

    2010-03-01

    As companies continue to globalise their operations and outsource significant portion of their value chain activities, they often end up relying heavily on order replenishments from distant suppliers. The explosion in long-distance sourcing is exposing supply chains and shareholder value at ever increasing operational and disruption risks. It is well established, both in academia and in real-world business environments, that resource flexibility is an effective method for hedging against supply chain disruption risks. In this contextual framework, we propose a single period stochastic inventory decision-making model that could be employed for capturing the trade-off between inventory policies and disruption risks for an unreliable dual sourcing supply network for both the capacitated and uncapacitated cases. Through the developed model, we obtain some important managerial insights and evaluate the merit of contingency strategies in managing uncertain supply chains.

  6. A theoretical model for gas permeability in a composite membrane

    International Nuclear Information System (INIS)

    Serrano, D. A

    2009-01-01

    We present in this work an analytical expression for permeability in a two-layer composite membrane, which was derived assuming the same hypothesis as those of Adzumi model for permeability in a homogeneous membrane. Whereas in Adzumi model permeability shows a linear dependence on the mean pressure, our model for a composite membrane related permeability to pressure through a rather complex expression, which covers the whole range of flow, from molecular-Knudsen to viscous-Poiseuille regimes. The expression obtained for permeability contained information of membrane structural properties as pore size, porosity and thickness of each layer, as well as gas nature and operational conditions. Our two-layer-model expression turns into Adzumi formula when the structure of the layers approach to each other. [es

  7. Modeling Steroidogenesis Disruption Using High-Throughput ...

    Science.gov (United States)

    Environmental chemicals can elicit endocrine disruption by altering steroid hormone biosynthesis and metabolism (steroidogenesis) causing adverse reproductive and developmental effects. Historically, a lack of assays resulted in few chemicals having been evaluated for effects on steroidogenesis. The steroidogenic pathway is a series of hydroxylation and dehydrogenation steps carried out by CYP450 and hydroxysteroid dehydrogenase enzymes, yet the only enzyme in the pathway for which a high-throughput screening (HTS) assay has been developed is aromatase (CYP19A1), responsible for the aromatization of androgens to estrogens. Recently, the ToxCast HTS program adapted the OECD validated H295R steroidogenesis assay using human adrenocortical carcinoma cells into a high-throughput model to quantitatively assess the concentration-dependent (0.003-100 µM) effects of chemicals on 10 steroid hormones including progestagens, androgens, estrogens and glucocorticoids. These results, in combination with two CYP19A1 inhibition assays, comprise a large dataset amenable to clustering approaches supporting the identification and characterization of putative mechanisms of action (pMOA) for steroidogenesis disruption. In total, 514 chemicals were tested in all CYP19A1 and steroidogenesis assays. 216 chemicals were identified as CYP19A1 inhibitors in at least one CYP19A1 assay. 208 of these chemicals also altered hormone levels in the H295R assay, suggesting 96% sensitivity in the

  8. Membrane-elasticity model of Coatless vesicle budding induced by ESCRT complexes.

    Directory of Open Access Journals (Sweden)

    Bartosz Różycki

    Full Text Available The formation of vesicles is essential for many biological processes, in particular for the trafficking of membrane proteins within cells. The Endosomal Sorting Complex Required for Transport (ESCRT directs membrane budding away from the cytosol. Unlike other vesicle formation pathways, the ESCRT-mediated budding occurs without a protein coat. Here, we propose a minimal model of ESCRT-induced vesicle budding. Our model is based on recent experimental observations from direct fluorescence microscopy imaging that show ESCRT proteins colocalized only in the neck region of membrane buds. The model, cast in the framework of membrane elasticity theory, reproduces the experimentally observed vesicle morphologies with physically meaningful parameters. In this parameter range, the minimum energy configurations of the membrane are coatless buds with ESCRTs localized in the bud neck, consistent with experiment. The minimum energy configurations agree with those seen in the fluorescence images, with respect to both bud shapes and ESCRT protein localization. On the basis of our model, we identify distinct mechanistic pathways for the ESCRT-mediated budding process. The bud size is determined by membrane material parameters, explaining the narrow yet different bud size distributions in vitro and in vivo. Our membrane elasticity model thus sheds light on the energetics and possible mechanisms of ESCRT-induced membrane budding.

  9. Interactions of Model Cell Membranes with Nanoparticles

    Science.gov (United States)

    D'Angelo, S. M.; Camesano, T. A.; Nagarajan, R.

    2011-12-01

    The same properties that give nanoparticles their enhanced function, such as high surface area, small size, and better conductivity, can also alter the cytotoxicity of nanomaterials. Ultimately, many of these nanomaterials will be released into the environment, and can cause cytotoxic effects to environmental bacteria, aquatic organisms, and humans. Previous results from our laboratory suggest that nanoparticles can have a detrimental effect on cells, depending on nanoparticle size. It is our goal to characterize the properties of nanomaterials that can result in membrane destabilization. We tested the effects of nanoparticle size and chemical functionalization on nanoparticle-membrane interactions. Gold nanoparticles at 2, 5,10, and 80 nm were investigated, with a concentration of 1.1x1010 particles/mL. Model cell membranes were constructed of of L-α-phosphatidylcholine (egg PC), which has negatively charged lipid headgroups. A quartz crystal microbalance with dissipation (QCM-D) was used to measure frequency changes at different overtones, which were related to mass changes corresponding to nanoparticle interaction with the model membrane. In QCM-D, a lipid bilayer is constructed on a silicon dioxide crystal. The crystals, oscillate at different harmonic frequencies depending upon changes in mass or energy dissipation. When mass is added to the crystal surface, such as through addition of a lipid vesicle solution, the frequency change decreases. By monitoring the frequency and dissipation, we could verify that a supported lipid bilayer (SLB) formed on the silica surface. After formation of the SLB, the nanoparticles can be added to the system, and the changes in frequency and dissipation are monitored in order to build a mechanistic understanding of nanoparticle-cell membrane interactions. For all of the smaller nanoparticles (2, 5, and 10 nm), nanoparticle addition caused a loss of mass from the lipid bilayer, which appears to be due to the formation of holes

  10. Improvements in disruption prediction at ASDEX Upgrade

    Energy Technology Data Exchange (ETDEWEB)

    Aledda, R., E-mail: raffaele.aledda@diee.unica.it; Cannas, B., E-mail: cannas@diee.unica.it; Fanni, A., E-mail: fanni@diee.unica.it; Pau, A., E-mail: alessandro.pau@diee.unica.it; Sias, G., E-mail: giuliana.sias@diee.unica.it

    2015-10-15

    Highlights: • A disruption prediction system for AUG, based on a logistic model, is designed. • The length of the disruptive phase is set for each disruption in the training set. • The model is tested on dataset different from that used during the training phase. • The generalization capability and the aging of the model have been tested. • The predictor performance is compared with the locked mode detector. - Abstract: In large-scale tokamaks disruptions have the potential to create serious damage to the facility. Hence disruptions must be avoided, but, when a disruption is unavoidable, minimizing its severity is mandatory. A reliable detection of a disruptive event is required to trigger proper mitigation actions. To this purpose machine learning methods have been widely studied to design disruption prediction systems at ASDEX Upgrade. The training phase of the proposed approaches is based on the availability of disrupted and non-disrupted discharges. In literature disruptive configurations were assumed appearing into the last 45 ms of each disruption. Even if the achieved results in terms of correct predictions were good, it has to be highlighted that the choice of such a fixed temporal window might have limited the prediction performance. In fact, it generates confusing information in cases of disruptions with disruptive phase different from 45 ms. The assessment of a specific disruptive phase for each disruptive discharge represents a relevant issue in understanding the disruptive events. In this paper, the Mahalanobis distance is applied to define a specific disruptive phase for each disruption, and a logistic regressor has been trained as disruption predictor. The results show that enhancements on the achieved performance on disruption prediction are possible by defining a specific disruptive phase for each disruption.

  11. Improvements in disruption prediction at ASDEX Upgrade

    International Nuclear Information System (INIS)

    Aledda, R.; Cannas, B.; Fanni, A.; Pau, A.; Sias, G.

    2015-01-01

    Highlights: • A disruption prediction system for AUG, based on a logistic model, is designed. • The length of the disruptive phase is set for each disruption in the training set. • The model is tested on dataset different from that used during the training phase. • The generalization capability and the aging of the model have been tested. • The predictor performance is compared with the locked mode detector. - Abstract: In large-scale tokamaks disruptions have the potential to create serious damage to the facility. Hence disruptions must be avoided, but, when a disruption is unavoidable, minimizing its severity is mandatory. A reliable detection of a disruptive event is required to trigger proper mitigation actions. To this purpose machine learning methods have been widely studied to design disruption prediction systems at ASDEX Upgrade. The training phase of the proposed approaches is based on the availability of disrupted and non-disrupted discharges. In literature disruptive configurations were assumed appearing into the last 45 ms of each disruption. Even if the achieved results in terms of correct predictions were good, it has to be highlighted that the choice of such a fixed temporal window might have limited the prediction performance. In fact, it generates confusing information in cases of disruptions with disruptive phase different from 45 ms. The assessment of a specific disruptive phase for each disruptive discharge represents a relevant issue in understanding the disruptive events. In this paper, the Mahalanobis distance is applied to define a specific disruptive phase for each disruption, and a logistic regressor has been trained as disruption predictor. The results show that enhancements on the achieved performance on disruption prediction are possible by defining a specific disruptive phase for each disruption.

  12. Disruptions in Tokamaks

    International Nuclear Information System (INIS)

    Bondeson, A.

    1987-01-01

    This paper discusses major and minor disruptions in Tokamaks. A number of models and numerical simulations of disruptions based on resistive MHD are reviewed. A discussion is given of how disruptive current profiles are correlated with the experimentally known operational limits in density and current. It is argued that the q a =2 limit is connected with stabilization of the m=2/n=1 tearing mode for a approx.< 2.7 by resistive walls and mode rotation. Experimental and theoretical observations indicate that major disruptions usually occur in at least two phases, first a 'predisruption', or loss of confinement in the region 1 < q < 2, leaving the q approx.= 1 region almost unaffected, followed by a final disruption of the central part, interpreted here as a toroidal n = 1 external kink mode. (author)

  13. Severe blood-brain barrier disruption and surrounding tissue injury.

    Science.gov (United States)

    Chen, Bo; Friedman, Beth; Cheng, Qun; Tsai, Phil; Schim, Erica; Kleinfeld, David; Lyden, Patrick D

    2009-12-01

    Blood-brain barrier opening during ischemia follows a biphasic time course, may be partially reversible, and allows plasma constituents to enter brain and possibly damage cells. In contrast, severe vascular disruption after ischemia is unlikely to be reversible and allows even further extravasation of potentially harmful plasma constituents. We sought to use simple fluorescent tracers to allow wide-scale visualization of severely damaged vessels and determine whether such vascular disruption colocalized with regions of severe parenchymal injury. Severe vascular disruption and ischemic injury was produced in adult Sprague Dawley rats by transient occlusion of the middle cerebral artery for 1, 2, 4, or 8 hours, followed by 30 minutes of reperfusion. Fluorescein isothiocyanate-dextran (2 MDa) was injected intravenously before occlusion. After perfusion-fixation, brain sections were processed for ultrastructure or fluorescence imaging. We identified early evidence of tissue damage with Fluoro-Jade staining of dying cells. With increasing ischemia duration, greater quantities of high molecular weight dextran-fluorescein isothiocyanate invaded and marked ischemic regions in a characteristic pattern, appearing first in the medial striatum, spreading to the lateral striatum, and finally involving cortex; maximal injury was seen in the mid-parietal areas, consistent with the known ischemic zone in this model. The regional distribution of the severe vascular disruption correlated with the distribution of 24-hour 2,3,5-triphenyltetrazolium chloride pallor (r=0.75; P<0.05) and the cell death marker Fluoro-Jade (r=0.86; P<0.05). Ultrastructural examination showed significantly increased areas of swollen astrocytic foot process and swollen mitochondria in regions of high compared to low leakage, and compared to contralateral homologous regions (ANOVA P<0.01). Dextran extravasation into the basement membrane and surrounding tissue increased significantly from 2 to 8 hours of

  14. Modeling of thermal effects on TIBER II divertor during plasma disruptions

    International Nuclear Information System (INIS)

    Bruhn, M.L.; Perkins, L.J.

    1987-01-01

    Mapping the disruption power flow from the mid-plane of the TIBER Engineering Test Reactor to its divertor and calculating the resulting thermal effects are accomplished through the modification and coupling of three presently existing computer codes. The resulting computer code TADDPAK (Thermal Analysis Divertor during Disruption PAcKage) provides three-dimensional graphic presentations of time and positional dependent thermal effects on a poloidal cross section of the double-null-divertor configured reactor. These thermal effects include incident heat flux, surface temperature, vaporization rate, total vaporization, and melting depth. The dependence of these thermal effects on material choice, disruption pulse shape, and the characteristic thickness of the plasma scrape-off layer is determined through parametric analysis with TADDPAK. This computer code is designed to be a convenient, rapid, and user-friendly modeling tool which can be easily adapted to most tokamak double-null-divertor reactor designs

  15. Stochastic lattice model of synaptic membrane protein domains.

    Science.gov (United States)

    Li, Yiwei; Kahraman, Osman; Haselwandter, Christoph A

    2017-05-01

    Neurotransmitter receptor molecules, concentrated in synaptic membrane domains along with scaffolds and other kinds of proteins, are crucial for signal transmission across chemical synapses. In common with other membrane protein domains, synaptic domains are characterized by low protein copy numbers and protein crowding, with rapid stochastic turnover of individual molecules. We study here in detail a stochastic lattice model of the receptor-scaffold reaction-diffusion dynamics at synaptic domains that was found previously to capture, at the mean-field level, the self-assembly, stability, and characteristic size of synaptic domains observed in experiments. We show that our stochastic lattice model yields quantitative agreement with mean-field models of nonlinear diffusion in crowded membranes. Through a combination of analytic and numerical solutions of the master equation governing the reaction dynamics at synaptic domains, together with kinetic Monte Carlo simulations, we find substantial discrepancies between mean-field and stochastic models for the reaction dynamics at synaptic domains. Based on the reaction and diffusion properties of synaptic receptors and scaffolds suggested by previous experiments and mean-field calculations, we show that the stochastic reaction-diffusion dynamics of synaptic receptors and scaffolds provide a simple physical mechanism for collective fluctuations in synaptic domains, the molecular turnover observed at synaptic domains, key features of the observed single-molecule trajectories, and spatial heterogeneity in the effective rates at which receptors and scaffolds are recycled at the cell membrane. Our work sheds light on the physical mechanisms and principles linking the collective properties of membrane protein domains to the stochastic dynamics that rule their molecular components.

  16. Antifungal Activity of (+-2,2’-Epicytoskyrin A and Its Membrane-Disruptive Action

    Directory of Open Access Journals (Sweden)

    Dewi Wulansari

    2016-12-01

    Full Text Available (+-2,2’-Epicytoskyrin A, a bis-anthraquinone isolated from fungal endophyte Diaporthe sp. GNBP-10 associated with Uncaria gambir Roxb., was investigated for its antifungal activity. The broth microdilution method was used to determine the minimum inhibitory concentration (MIC against 22 yeast strains and three filamentous fungi. The MICs of (+-2,2’-epicytoskyrin A ranged from 16 to 128 µg/mL, which exhibited lower activity than the antifungal nystatin. A study of the mechanism of action revealed similar effects of (+-2,2’-epicytoskyrin A and nystatin on Candida tropicalis at their MICs (16 and 8 µg/mL, respectively and 2 times of the MIC. Both compounds caused cytoplasmic material and ion leakages on fungal cell, which were characterized by an increase in absorbance at 260 nm and 280 nm as well as Ca2+ and K+ ion concentrations. The morphology of the fungal cells after (+-2,2’-epicytoskyrin A treatment was observed under a scanning electron microscope. The control cells, which were not treated with either (+-2,2’-epicytoskyrin A or nystatin, showed a smooth surface, while the cells treated with either (+-2,2’-epicytoskyrin A or nystatin shrank and displayed a donut-like shape. More shrinkage was observed in the 2 times MIC concentration and even more in the cells exposed to nystatin. The action of (+-2,2’-epicytoskyrin A was proposed through membrane disruption.

  17. There Is No Simple Model of the Plasma Membrane Organization

    Science.gov (United States)

    Bernardino de la Serna, Jorge; Schütz, Gerhard J.; Eggeling, Christian; Cebecauer, Marek

    2016-01-01

    Ever since technologies enabled the characterization of eukaryotic plasma membranes, heterogeneities in the distributions of its constituents were observed. Over the years this led to the proposal of various models describing the plasma membrane organization such as lipid shells, picket-and-fences, lipid rafts, or protein islands, as addressed in numerous publications and reviews. Instead of emphasizing on one model we in this review give a brief overview over current models and highlight how current experimental work in one or the other way do not support the existence of a single overarching model. Instead, we highlight the vast variety of membrane properties and components, their influences and impacts. We believe that highlighting such controversial discoveries will stimulate unbiased research on plasma membrane organization and functionality, leading to a better understanding of this essential cellular structure. PMID:27747212

  18. Internal disruption in tokamaks

    International Nuclear Information System (INIS)

    Kuvshinov, B.N.; Savrukhin, P.V.

    1990-01-01

    A review of results of experimental and theoretical investigations of internal disruption in tokamaks is given. Specific features of various types of saw-tooth oscillations are described and their classification is performed. Theoretical models of the process of development of internal disruption instability are discussed. Effect of internal disruption on parameters of plasma, confined in tokamak, is considered. Scalings of period and amplitude of saw-tooth oscillations, as well as version radius are presented. Different methods for stabilizing instability of internal disruption are described

  19. Internal disruptions in tokamaks

    International Nuclear Information System (INIS)

    Kuvshinov, B.N.; Savrukhin, P.V.

    1990-01-01

    Experimental and theoretical studies of the phenomenon of internal disruptions in tokamaks are reviewed. A classification scheme is introduced and the features of different types of sawtooth oscillations are described. A theoretical model for the development of the internal disruption instability is discussed. The effect of internal disruptions on the parameters of plasma confined in tokamaks is discussed. Scaling laws for the period and amplitude of sawtooth oscillations, as well as for the inversion radius, are presented. Different methods of stabilizing the internal disruption instability are described

  20. A Membrane Model from Implicit Elasticity Theory

    Science.gov (United States)

    Freed, A. D.; Liao, J.; Einstein, D. R.

    2014-01-01

    A Fungean solid is derived for membranous materials as a body defined by isotropic response functions whose mathematical structure is that of a Hookean solid where the elastic constants are replaced by functions of state derived from an implicit, thermodynamic, internal-energy function. The theory utilizes Biot’s (1939) definitions for stress and strain that, in 1-dimension, are the stress/strain measures adopted by Fung (1967) when he postulated what is now known as Fung’s law. Our Fungean membrane model is parameterized against a biaxial data set acquired from a porcine pleural membrane subjected to three, sequential, proportional, planar extensions. These data support an isotropic/deviatoric split in the stress and strain-rate hypothesized by our theory. These data also demonstrate that the material response is highly non-linear but, otherwise, mechanically isotropic. These data are described reasonably well by our otherwise simple, four-parameter, material model. PMID:24282079

  1. Injectible candidate sealants for fetal membrane repair: Bonding and toxicity in vitro

    Science.gov (United States)

    Bilic, Grozdana; Brubaker, Carrie; Messersmith, Phillip B.; Mallik, Ajit S.; Quinn, Thomas M.; Haller, Claudia; Done, Elisa; Gucciardo, Leonardo; Zeisberger, Steffen M.; Zimmermann, Roland; Deprest, Jan; Zisch, Andreas H.

    2010-01-01

    Objective This study was undertaken to test injectible surgical sealants that are biocompatible with fetal membranes, eventually for closure of iatrogenic membrane defects. Study Design Dermabond, Histoacryl, Tissucol fibrin glue, and three types of in situ forming poly(ethylene glycol)-based polymer hydrogels were tested for acute toxicity upon direct contact with fetal membranes for 24h. For determination of elution toxicity, extracts of sealants were incubated on amnion cell cultures for 72h. Bonding and toxicity was assessed through morphological and/or biochemical analysis. Results Extracts of all adhesives were non-toxic for cultured cells. However, only Tissucol and one type of poly(ethylene glycol)-based hydrogel, mussel-mimetic tissue adhesive, showed efficient, non-disruptive, non-toxic bonding to fetal membranes. Mussel-mimetic tissue adhesive applied over membrane defects created with a 3.5 mm trocar accomplished leak-proof closure that withstood membrane stretch in an in vitro model. Conclusion A synthetic hydrogel-type tissue adhesive emerged as potential sealing modality for iatrogenic membrane defects that merits further evaluation in vivo. PMID:20096254

  2. Modelling inter-supply chain competition with resource limitation and demand disruption

    Science.gov (United States)

    Chen, Zhaobo; Teng, Chunxian; Zhang, Ding; Sun, Jiayi

    2016-05-01

    This paper proposes a comprehensive model for studying supply chain versus supply chain competition with resource limitation and demand disruption. We assume that there are supply chains with heterogeneous supply network structures that compete at multiple demand markets. Each supply chain is comprised of internal and external firms. The internal firms are coordinated in production and distribution and share some common but limited resources within the supply chain, whereas the external firms are independent and do not share the internal resources. The supply chain managers strive to develop optimal strategies in terms of production level and resource allocation in maximising their profit while facing competition at the end market. The Cournot-Nash equilibrium of this inter-supply chain competition is formulated as a variational inequality problem. We further study the case when there is demand disruption in the plan-execution phase. In such a case, the managers need to revise their planned strategy in order to maximise their profit with the new demand under disruption and minimise the cost of change. We present a bi-criteria decision-making model for supply chain managers and develop the optimal conditions in equilibrium, which again can be formulated by another variational inequality problem. Numerical examples are presented for illustrative purpose.

  3. A Network Disruption Modeling Tool

    National Research Council Canada - National Science Library

    Leinart, James

    1998-01-01

    Given that network disruption has been identified as a military objective and C2-attack has been identified as the mechanism to accomplish this objective, a target set must be acquired and priorities...

  4. Membrane properties involved in calcium-stimulated microparticle release from the plasma membranes of S49 lymphoma cells.

    Science.gov (United States)

    Campbell, Lauryl E; Nelson, Jennifer; Gibbons, Elizabeth; Judd, Allan M; Bell, John D

    2014-01-01

    This study answered the question of whether biophysical mechanisms for microparticle shedding discovered in platelets and erythrocytes also apply to nucleated cells: cytoskeletal disruption, potassium efflux, transbilayer phospholipid migration, and membrane disordering. The calcium ionophore, ionomycin, disrupted the actin cytoskeleton of S49 lymphoma cells and produced rapid release of microparticles. This release was significantly inhibited by interventions that impaired calcium-activated potassium current. Microparticle release was also greatly reduced in a lymphocyte cell line deficient in the expression of scramblase, the enzyme responsible for calcium-stimulated dismantling of the normal phospholipid transbilayer asymmetry. Rescue of the scrambling function at high ionophore concentration also resulted in enhanced particle shedding. The effect of membrane physical properties was addressed by varying the experimental temperature (32-42°C). A significant positive trend in the rate of microparticle release as a function of temperature was observed. Fluorescence experiments with trimethylammonium diphenylhexatriene and Patman revealed significant decrease in the level of apparent membrane order along that temperature range. These results demonstrated that biophysical mechanisms involved in microparticle release from platelets and erythrocytes apply also to lymphocytes.

  5. Expansion of thermodynamic model of solute permeation through reverse osmosis membrane

    International Nuclear Information System (INIS)

    Nishimaki, Kenzo; Koyama, Akio

    1994-01-01

    Many studies have been performed on permeation mechanism of solute and solvent in membrane separation process like reverse osmosis or ultrafiltration, and several models of solute/solvent permeation through membrane are proposed. Among these models, Kedem and Katchalsky, based on the theory of thermodynamics of irreversible processes, formulated the one-solute permeation process in their mathematical model, which treats membrane as a black box, not giving consideration to membrane structure and to interaction between membrane material and permeates, viz. solute and solvent. According to this theory, the driving force of solute/solvent permeation through membrane is the difference of their chemical potential between both sides of membrane, and the linear phenomenological equation is applied to describing the relation between driving force and flux of solute/solvent. This equation can be applied to the irreversible process only when the process is almost in equilibrium. This condition is supposed to be satisfied in the solute/solvent permeation process through compact membrane with fine pores like reverse osmosis membrane. When reverse osmosis is applied to treatment process for liquid waste, which usually contains a lot of solutes as contaminants, we can not predict the behavior of contaminants by the above one-solute process model. In the case of multi-solutes permeation process for liquid waste, the number of parameter in thermodynamic model increases rapidly with the number of solute, because of coupling phenomenon among solutes. In this study, we expanded the above thermodynamic model to multi-solute process applying operational calculus to the differential equations which describe the irreversible process of the system, and expressed concisely solute concentration vector as a matrix product. In this way, we predict the behavior of solutes in multi-solutes process, using values of parameters obtained in two-solutes process. (author)

  6. QSAR Models for Reproductive Toxicity and Endocrine Disruption Activity

    Directory of Open Access Journals (Sweden)

    Marjan Vračko

    2010-03-01

    Full Text Available Reproductive toxicity is an important regulatory endpoint, which is required in registration procedures of chemicals used for different purposes (for example pesticides. The in vivo tests are expensive, time consuming and require large numbers of animals, which must be sacrificed. Therefore an effort is ongoing to develop alternative In vitro and in silico methods to evaluate reproductive toxicity. In this review we describe some modeling approaches. In the first example we describe the CAESAR model for prediction of reproductive toxicity; the second example shows a classification model for endocrine disruption potential based on counter propagation artificial neural networks; the third example shows a modeling of relative binding affinity to rat estrogen receptor, and the fourth one shows a receptor dependent modeling experiment.

  7. Fabrication and Molecular Transport Studies of Highly c-Oriented AFI Membranes

    KAUST Repository

    Liu, Yang; Zhang, Bing; Liu, Defei; Sheng, Ping; Lai, Zhiping

    2017-01-01

    -packed and c-oriented monolayer of plate-like seeds that is manually assembled on a porous alumina support. The straight channels in the membrane are not only aligned vertically along the membrane depth, but are also continuous without disruption. The transport

  8. Multi-layer membrane model for mass transport in a direct ethanol fuel cell using an alkaline anion exchange membrane

    Science.gov (United States)

    Bahrami, Hafez; Faghri, Amir

    2012-11-01

    A one-dimensional, isothermal, single-phase model is presented to investigate the mass transport in a direct ethanol fuel cell incorporating an alkaline anion exchange membrane. The electrochemistry is analytically solved and the closed-form solution is provided for two limiting cases assuming Tafel expressions for both oxygen reduction and ethanol oxidation. A multi-layer membrane model is proposed to properly account for the diffusive and electroosmotic transport of ethanol through the membrane. The fundamental differences in fuel crossover for positive and negative electroosmotic drag coefficients are discussed. It is found that ethanol crossover is significantly reduced upon using an alkaline anion exchange membrane instead of a proton exchange membrane, especially at current densities higher than 500 A m

  9. Physical model for membrane protrusions during spreading

    International Nuclear Information System (INIS)

    Chamaraux, F; Ali, O; Fourcade, B; Keller, S; Bruckert, F

    2008-01-01

    During cell spreading onto a substrate, the kinetics of the contact area is an observable quantity. This paper is concerned with a physical approach to modeling this process in the case of ameboid motility where the membrane detaches itself from the underlying cytoskeleton at the leading edge. The physical model we propose is based on previous reports which highlight that membrane tension regulates cell spreading. Using a phenomenological feedback loop to mimic stress-dependent biochemistry, we show that the actin polymerization rate can be coupled to the stress which builds up at the margin of the contact area between the cell and the substrate. In the limit of small variation of membrane tension, we show that the actin polymerization rate can be written in a closed form. Our analysis defines characteristic lengths which depend on elastic properties of the membrane–cytoskeleton complex, such as the membrane–cytoskeleton interaction, and on molecular parameters, the rate of actin polymerization. We discuss our model in the case of axi-symmetric and non-axi-symmetric spreading and we compute the characteristic time scales as a function of fundamental elastic constants such as the strength of membrane–cytoskeleton adherence

  10. Carbon dioxide (hydrogen sulfide) membrane separations and WGS membrane reactor modeling for fuel cells

    Science.gov (United States)

    Huang, Jin

    Acid-gas removal is of great importance in many environmental or energy-related processes. Compared to current commercial technologies, membrane-based CO2 and H2S capture has the advantages of low energy consumption, low weight and space requirement, simplicity of installation/operation, and high process flexibility. However, the large-scale application of the membrane separation technology is limited by the relatively low transport properties. In this study, CO2 (H2S)-selective polymeric membranes with high permeability and high selectivity have been studied based on the facilitated transport mechanism. The membrane showed facilitated effect for both CO2 and H2S. A CO2 permeability of above 2000 Barrers, a CO2/H2 selectivity of greater than 40, and a CO2/N2 selectivity of greater than 200 at 100--150°C were observed. As a result of higher reaction rate and smaller diffusing compound, the H2S permeability and H2S/H2 selectivity were about three times higher than those properties for CO2. The novel CO2-selective membrane has been applied to capture CO 2 from flue gas and natural gas. In the CO2 capture experiments from a gas mixture with N2 and H2, a permeate CO 2 dry concentration of greater than 98% was obtained by using steam as the sweep gas. In CO2/CH4 separation, decent CO 2 transport properties were obtained with a feed pressure up to 500 psia. With the thin-film composite membrane structure, significant increase on the CO2 flux was achieved with the decrease of the selective layer thickness. With the continuous removal of CO2, CO2-selective water-gas-shift (WGS) membrane reactor is a promising approach to enhance CO conversion and increase the purity of H2 at process pressure under relatively low temperature. The simultaneous reaction and transport process in the countercurrent WGS membrane reactor was simulated by using a one-dimensional non-isothermal model. The modeling results show that a CO concentration of less than 10 ppm and a H2 recovery of greater

  11. Novel thermal efficiency-based model for determination of thermal conductivity of membrane distillation membranes

    International Nuclear Information System (INIS)

    Vanneste, Johan; Bush, John A.; Hickenbottom, Kerri L.; Marks, Christopher A.; Jassby, David

    2017-01-01

    Development and selection of membranes for membrane distillation (MD) could be accelerated if all performance-determining characteristics of the membrane could be obtained during MD operation without the need to recur to specialized or cumbersome porosity or thermal conductivity measurement techniques. By redefining the thermal efficiency, the Schofield method could be adapted to describe the flux without prior knowledge of membrane porosity, thickness, or thermal conductivity. A total of 17 commercially available membranes were analyzed in terms of flux and thermal efficiency to assess their suitability for application in MD. The thermal-efficiency based model described the flux with an average %RMSE of 4.5%, which was in the same range as the standard deviation on the measured flux. The redefinition of the thermal efficiency also enabled MD to be used as a novel thermal conductivity measurement device for thin porous hydrophobic films that cannot be measured with the conventional laser flash diffusivity technique.

  12. A Model of Direct Contact Membrane Distillation of Black Currant Juice

    DEFF Research Database (Denmark)

    Jensen, Morten Busch; Christensen, Knud Villy; Andrésen, René

    2011-01-01

    A numerical model to describe a direct contact membrane distillation proces has been developed. Said model is based on the Dusty Gas model and shell mass and energy balances over a tubular membrane module.  "The solution is applicable to laminar, incompressible and continuous flow in shell......-side spacing of tubular-type unit."  Turtuosity and porosity are characteristics of the membrane in use and have been estimated base don eksperimental studies on destillation of pure water. The fitted model shows a good fit to experimental data obtained by destillation of black currant juice....

  13. Membrane Modeling, Simulation and Optimization for Propylene/Propane Separation

    KAUST Repository

    Alshehri, Ali

    2015-06-01

    Energy efficiency is critical for sustainable industrial growth and the reduction of environmental impacts. Energy consumption by the industrial sector accounts for more than half of the total global energy usage and, therefore, greater attention is focused on enhancing this sector’s energy efficiency. It is predicted that by 2020, more than 20% of today’s energy consumption can be avoided in countries that have effectively implemented an action plan towards efficient energy utilization. Breakthroughs in material synthesis of high selective membranes have enabled the technology to be more energy efficient. Hence, high selective membranes are increasingly replacing conventional energy intensive separation processes, such as distillation and adsorption units. Moreover, the technology offers more special features (which are essential for special applications) and its small footprint makes membrane technology suitable for platform operations (e.g., nitrogen enrichment for oil and gas offshore sites). In addition, its low maintenance characteristics allow the technology to be applied to remote operations. For these reasons, amongst other, the membrane technology market is forecast to reach $16 billion by 2017. This thesis is concerned with the engineering aspects of membrane technology and covers modeling, simulation and optimization of membranes as a stand-alone process or as a unit operation within a hybrid system. Incorporating the membrane model into a process modeling software simplifies the simulation and optimization of the different membrane processes and hybrid configurations, since all other unit operations are pre-configured. Various parametric analyses demonstrated that only the membrane selectivity and transmembrane pressure ratio parameters define a membrane’s ability to accomplish a certain separation task. Moreover, it was found that both membrane selectivity and pressure ratio exhibit a minimum value that is only defined by the feed composition

  14. Modeling of hydrodynamics in hollow fiber membrane bioreactor for mammalian cells cultivation

    Directory of Open Access Journals (Sweden)

    N. V. Menshutina

    2016-01-01

    Full Text Available The mathematical modelling in CFD-packages are powerfull instrument for design and calculation of any engineering tasks. CFD-package contains the set of programs that allow to model the different objects behavior based on the mathematical lows. ANSYS Fluent are widely used for modelling of biotechnological and chemical-technological processes. This package is convenient to describe their hydrodynamics. As cell cultivation is one of the actual scientific direction in modern biotechnology ANSYS Fluent was used to create the model of hollow fiber membrane bioreactor. The fibers are hollow cylindrical membrane to be used for cell cultivation. The criterion of process effectiveness for cell growth is full filling of the membrane surface by cells in the bioreactor. While the cell growth the fiber permeability is decreased which effects to feed flow through membrane pores. The specific feature of this process is to ensure such feed flow to deliver the optimal nutrition for the cells on the external membrane surface. The velocity distribution inside the fiber and in all bioreactor as a whole has been calculated based on mass an impulse conservation equations taking into account the mathematical model assumptions. The hydrodynamics analysis in hollow fiber membrane bioreactor is described by the three-dimensional model created in ANSYS Fluent. The specific features of one membrane model are considered and for whole bioreactor too.

  15. Pore-scale modeling and simulation of flow, transport, and adsorptive or osmotic effects in membranes: the influence of membrane microstructure

    KAUST Repository

    Calo, Victor M.

    2015-07-17

    The selection of an appropriate membrane for a particular application is a complex and expensive process. Computational modeling can significantly aid membrane researchers and manufacturers in this process. The membrane morphology is highly influential on its efficiency within several applications, but is often overlooked in simulation. Two such applications which are very important in the provision of clean water are forward osmosis and filtration using functionalized micro/ultra/nano-filtration membranes. Herein, we investigate the effect of the membrane morphology in these two applications. First we present results of the separation process using resolved finger- and sponge-like support layers. Second, we represent the functionalization of a typical microfiltration membrane using absorptive pore walls, and illustrate the effect of different microstructures on the reactive process. Such numerical modeling will aid manufacturers in optimizing operating conditions and designing efficient membranes.

  16. Development of permeate flux model for municipal wastewater treatment using membrane bioreactor

    International Nuclear Information System (INIS)

    Geissler, S.; Zhou, H.; Zytner, R.; Melin, T.

    2002-01-01

    In municipal wastewater treatment, membrane filtration technologies receive great attention because they usually produce the better quality effluent, generate less sludge and require a smaller aeration tank volume. However, one main challenge of using membranes is membrane fouling, which results in a permeate flux decrease or transmembrane pressure increase over the time. Many efforts have been directed to develop the mechanistic permeate flux model to correlate the permeate flux with process parameters. However, their applicability has been largely thwarted due to complicated membrane fouling mechanisms and the interactions of many factors affecting the membrane bioreactor. This paper proposes a semi-empirical permeate flux model for the membrane bioreactor (MBR) process using ZENON immersed hollow fibre membrane modules. The semi-empirical model was proposed by assuming that the permeate flux is equal to transmembrane pressure divided by total resistance. The total resistance is divided into two components: an inside membrane resistance and an outer fouling layer resistance. These membrane resistances are then related to the ageing of membrane used. Good correlation was found between the predicted and measured flux, with the mean absolute deviation being less than 4%. The observations also identified some general rules for operating membrane systems. Ideally, it is advisable that high pressure periods be avoided as this leads to a faster increase of non-reversal membrane resistance. It was also observed that membrane preservatives should be washed out carefully prior to use. (author)

  17. T-tubule disruption promotes calcium alternans in failing ventricular myocytes: mechanistic insights from computational modeling.

    Science.gov (United States)

    Nivala, Michael; Song, Zhen; Weiss, James N; Qu, Zhilin

    2015-02-01

    In heart failure (HF), T-tubule (TT) disruption contributes to dyssynchronous calcium (Ca) release and impaired contraction, but its role in arrhythmogenesis remains unclear. In this study, we investigate the effects of TT disruption and other HF remodeling factors on Ca alternans in ventricular myocytes using computer modeling. A ventricular myocyte model with detailed spatiotemporal Ca cycling modeled by a coupled Ca release unit (CRU) network was used, in which the L-type Ca channels and the ryanodine receptor (RyR) channels were simulated by random Markov transitions. TT disruption, which removes the L-type Ca channels from the associated CRUs, results in "orphaned" RyR clusters and thus provides increased opportunity for spark-induced Ca sparks to occur. This effect combined with other HF remodeling factors promoted alternans by two distinct mechanisms: 1) for normal sarco-endoplasmic reticulum Ca ATPase (SERCA) activity, alternans was caused by both CRU refractoriness and coupling. The increased opportunity for spark-induced sparks by TT disruption combined with the enhanced CRU coupling by Ca elevation in the presence or absence of increased RyR leakiness facilitated spark synchronization on alternate beats to promote Ca alternans; 2) for down-regulated SERCA, alternans was caused by the sarcoplasmic reticulum (SR) Ca load-dependent mechanism, independent of CRU refractoriness. TT disruption and increased RyR leakiness shifted and steepened the SR Ca release-load relationship, which combines with down-regulated SERCA to promote Ca alternans. In conclusion, the mechanisms of Ca alternans for normal and down-regulated SERCA are different, and TT disruption promotes Ca alternans by both mechanisms, which may contribute to alternans at different stages of HF. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Disrupted Cortical Connectivity as an Explanatory Model for Autism Spectrum Disorder

    Directory of Open Access Journals (Sweden)

    Jenniefer Drude Borup

    2014-02-01

    Full Text Available The aim of this article is to explain the theory of Disrupted Cortical Connectivity and discuss whether or not it can integrate the following three theories: Theory of Mind, Executive Functioning, and Weak Central Coherence that dominate the field of autism spectrum disorder research. Due to a lack of existing literature discussing this potential integration, we have consequentially undertaken such an endeavour. In our opinion, integration appears to be possible since this explanatory model can account for difficulties in both social cognition and executive functioning commonly found in autism spectrum disorder. Moreover, the theory of Disrupted Cortical Connectivity could be described as an extension of the theory of Weak Central Coherence.

  19. Sleep Disruption Medical Intervention Forecasting (SDMIF) Module for the Integrated Medical Model

    Science.gov (United States)

    Lewandowski, Beth; Brooker, John; Mallis, Melissa; Hursh, Steve; Caldwell, Lynn; Myers, Jerry

    2011-01-01

    The NASA Integrated Medical Model (IMM) assesses the risk, including likelihood and impact of occurrence, of all credible in-flight medical conditions. Fatigue due to sleep disruption is a condition that could lead to operational errors, potentially resulting in loss of mission or crew. Pharmacological consumables are mitigation strategies used to manage the risks associated with sleep deficits. The likelihood of medical intervention due to sleep disruption was estimated with a well validated sleep model and a Monte Carlo computer simulation in an effort to optimize the quantity of consumables. METHODS: The key components of the model are the mission parameter program, the calculation of sleep intensity and the diagnosis and decision module. The mission parameter program was used to create simulated daily sleep/wake schedules for an ISS increment. The hypothetical schedules included critical events such as dockings and extravehicular activities and included actual sleep time and sleep quality. The schedules were used as inputs to the Sleep, Activity, Fatigue and Task Effectiveness (SAFTE) Model (IBR Inc., Baltimore MD), which calculated sleep intensity. Sleep data from an ISS study was used to relate calculated sleep intensity to the probability of sleep medication use, using a generalized linear model for binomial regression. A human yes/no decision process using a binomial random number was also factored into sleep medication use probability. RESULTS: These probability calculations were repeated 5000 times resulting in an estimate of the most likely amount of sleep aids used during an ISS mission and a 95% confidence interval. CONCLUSIONS: These results were transferred to the parent IMM for further weighting and integration with other medical conditions, to help inform operational decisions. This model is a potential planning tool for ensuring adequate sleep during sleep disrupted periods of a mission.

  20. Effect of Amphotericin B antibiotic on the properties of model lipid membrane

    International Nuclear Information System (INIS)

    Kiryakova, S; Dencheva-Zarkova, M; Genova, J

    2014-01-01

    Model membranes formed from natural and synthetic lipids are an interesting object for scientific investigations due to their similarity to biological cell membrane and their simple structure with controlled composition and properties. Amphotericin B is an important polyene antifungal antibiotic, used for treatment of systemic fungal infections. It is known from the literature that the studied antibiotic has a substantial effect on the transmembrane ionic channel structures. When applied to the lipid membranes it has the tendency to create pores and in this way to affect the structure and the properties of the membrane lipid bilayer. In this work the thermally induced shape fluctuations of giant quasi-spherical liposomes have been used to study the influence of polyene antibiotic amphotericin B on the elastic properties of model lipid membranes. It have been shown experimentally that the presence of 3 mol % of AmB in the lipid membrane reduces the bending elasticity of the lipid membrane for both studied cases: pure SOPC membrane and mixed SOPC-Cholesterol membrane. Interaction of the amphotericin B with bilayer lipid membranes containing channels have been studied in this work. Model membranes were self-assembled using the patch-clamp and tip-dip patch clamp technique. We have found that amphotericin B is an ionophore and reduces the resistance of the lipid bilayer

  1. Optimization of bead milling parameters for the cell disruption of microalgae: process modeling and application to Porphyridium cruentum and Nannochloropsis oculata.

    Science.gov (United States)

    Montalescot, V; Rinaldi, T; Touchard, R; Jubeau, S; Frappart, M; Jaouen, P; Bourseau, P; Marchal, L

    2015-11-01

    A study of cell disruption by bead milling for two microalgae, Nannochloropsis oculata and Porphyridium cruentum, was performed. Strains robustness was quantified by high-pressure disruption assays. The hydrodynamics in the bead mill grinding chamber was studied by Residence Time Distribution modeling. Operating parameters effects were analyzed and modeled in terms of stress intensities and stress number. RTD corresponded to a 2 CSTR in series model. First order kinetics cell disruption was modeled in consequence. Continuous bead milling was efficient for both strains disruption. SI-SN modeling was successfully adapted to microalgae. As predicted by high pressure assays, N. oculata was more resistant than P. cruentum. The critical stress intensity was twice more important for N. oculata than for P. cruentum. SI-SN modeling allows the determination of operating parameters minimizing energy consumption and gives a scalable approach to develop and optimize microalgal disruption by bead milling. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Plasma membrane of a marine T cell lymphoma: surface labelling, membrane isolation, separation of membrane proteins and distribution of surface label amongst these proteins

    International Nuclear Information System (INIS)

    Crumpton, M.J.; Marchalonis, J.J.; Haustein, D.; Atwell, J.L.; Harris, A.W.

    1976-01-01

    Two established techniques for analysis of plasma membranes, namely, lactoperoxidase catalyzed surface radioiodination of intact cells and bulk membrane isolation following disruption of cells by shear forces, were applied in studies of membrane proteins of continuously cultured cells of the monoclonal T lymphoma line WEHI-22. It was found that macromolecular 125 I-iodide incorporated into plasma membrane proteins of intact cells was at least as good a marker for the plasma as was the commonly used enzyme 5'-nucleotidase, T lymphoma plasma membrane proteins were complex when analysed by polyacrylamide gel electrophoresis in sodium dodecylsulphate-containing buffers and more than thirty distinct components were resolved. More than fifteen of the components observed on a mass basis were also labelled with 125 I-iodide. Certain bands, however, exhibited a degree of label disproportionate to their staining properties with Coomassie Blue. This was interpreted in terms of their accessibility to the solvent in the intact cells. (author)

  3. Desipramine induces disorder in cholesterol-rich membranes: implications for viral trafficking

    Science.gov (United States)

    Pakkanen, Kirsi; Salonen, Emppu; Mäkelä, Anna R.; Oker-Blom, Christian; Vattulainen, Ilpo; Vuento, Matti

    2009-12-01

    In this study, the effect of desipramine (DMI) on phospholipid bilayers and parvoviral entry was elucidated. In atomistic molecular dynamics simulations, DMI was found to introduce disorder in cholesterol-rich phospholipid bilayers. This was manifested by a decrease in the deuterium order parameter SCD as well as an increase in the membrane area. Disordering of the membrane suggested DMI to destabilize cholesterol-rich membrane domains (rafts) in cellular conditions. To relate the raft disrupting ability of DMI with novel biological relevance, we studied the intracellular effect of DMI using canine parvovirus (CPV), a virus known to interact with endosomal membranes and sphingomyelin, as an intracellular probe. DMI was found to cause retention of the virus in intracellular vesicular structures leading to the inhibition of viral proliferation. This implies that DMI has a deleterious effect on the viral traffic. As recycling endosomes and the internal vesicles of multivesicular bodies are known to contain raft components, the effect of desipramine beyond the plasma membrane step could be caused by raft disruption leading to impaired endosomal function and possibly have direct influence on the penetration of the virus through an endosomal membrane.

  4. Desipramine induces disorder in cholesterol-rich membranes: implications for viral trafficking

    International Nuclear Information System (INIS)

    Pakkanen, Kirsi; Mäkelä, Anna R; Oker-Blom, Christian; Vuento, Matti; Salonen, Emppu; Vattulainen, Ilpo

    2009-01-01

    In this study, the effect of desipramine (DMI) on phospholipid bilayers and parvoviral entry was elucidated. In atomistic molecular dynamics simulations, DMI was found to introduce disorder in cholesterol-rich phospholipid bilayers. This was manifested by a decrease in the deuterium order parameter S CD as well as an increase in the membrane area. Disordering of the membrane suggested DMI to destabilize cholesterol-rich membrane domains (rafts) in cellular conditions. To relate the raft disrupting ability of DMI with novel biological relevance, we studied the intracellular effect of DMI using canine parvovirus (CPV), a virus known to interact with endosomal membranes and sphingomyelin, as an intracellular probe. DMI was found to cause retention of the virus in intracellular vesicular structures leading to the inhibition of viral proliferation. This implies that DMI has a deleterious effect on the viral traffic. As recycling endosomes and the internal vesicles of multivesicular bodies are known to contain raft components, the effect of desipramine beyond the plasma membrane step could be caused by raft disruption leading to impaired endosomal function and possibly have direct influence on the penetration of the virus through an endosomal membrane

  5. Heat transfer modelling of first walls subject to plasma disruption

    International Nuclear Information System (INIS)

    Fillo, J.A.; Makowitz, H.

    1981-01-01

    A brief description of the plasma disruption problem and potential thermal consequences to the first wall is given. Thermal models reviewed include: a) melting of a solid with melt layer in place; b) melting of a solid with complete removal of melt (ablation); c) melting/vaporization of a solid; and d) vaporization of a solid but no phase change affecting the temperature profile

  6. Modeling hydrogen starvation conditions in proton-exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Ohs, Jan Hendrik; Sauter, Ulrich; Maass, Sebastian [Robert Bosch GmbH, Robert-Bosch-Platz 1, 70839 Gerlingen-Schillerhoehe (Germany); Stolten, Detlef [Forschungszentrum Juelich GmbH, IEF-3: Fuel Cells, 52425 Juelich (Germany)

    2011-01-01

    In this study, a steady state and isothermal 2D-PEM fuel cell model is presented. By simulation of a single cell along the channel and in through-plane direction, its behaviour under hydrogen starvation due to nitrogen dilution is analysed. Under these conditions, carbon corrosion and water electrolysis are observed on the cathode side. This phenomenon, causing severe cell degradation, is known as reverse current decay mechanism in literature. Butler-Volmer equations are used to model the electrochemical reactions. In addition, we account for permeation of gases through the membrane and for the local water content within the membrane. The results show that the membrane potential locally drops in areas starved from hydrogen. This leads to potential gradients >1.2 V between electrode and membrane on the cathode side resulting in significant carbon corrosion and electrolysis reaction rates. The model enables the analysis of sub-stoichiometric states occurring during anode gas recirculation or load transients. (author)

  7. Modeling of a membrane bioreactor for production of biodiesel

    International Nuclear Information System (INIS)

    Solano, Paola Andrea; Moncada, Jorge Andres; Cardona, Carlos Ariel; Ruiz, Orlando Simon

    2008-01-01

    Through the use of an enzymatic catalyst lipase, produced by Candida Antarctica a membrane bioreactor was modeled and simulated to obtain biodiesel from palm oil and ethanol. A conversion of 0.97 was reached for a residence time of 10.64 min. The membrane bioreactor was compared to a CSTR reactor, where a conversion of 0.76 was obtained. It was concluded that the membrane bioreactor is a better way of producing biodiesel than the CSTR

  8. Automatic location of disruption times in JET

    Science.gov (United States)

    Moreno, R.; Vega, J.; Murari, A.

    2014-11-01

    The loss of stability and confinement in tokamak plasmas can induce critical events known as disruptions. Disruptions produce strong electromagnetic forces and thermal loads which can damage fundamental components of the devices. Determining the disruption time is extremely important for various disruption studies: theoretical models, physics-driven models, or disruption predictors. In JET, during the experimental campaigns with the JET-C (Carbon Fiber Composite) wall, a common criterion to determine the disruption time consisted of locating the time of the thermal quench. However, with the metallic ITER-like wall (JET-ILW), this criterion is usually not valid. Several thermal quenches may occur previous to the current quench but the temperature recovers. Therefore, a new criterion has to be defined. A possibility is to use the start of the current quench as disruption time. This work describes the implementation of an automatic data processing method to estimate the disruption time according to this new definition. This automatic determination allows both reducing human efforts to locate the disruption times and standardizing the estimates (with the benefit of being less vulnerable to human errors).

  9. Automatic location of disruption times in JET.

    Science.gov (United States)

    Moreno, R; Vega, J; Murari, A

    2014-11-01

    The loss of stability and confinement in tokamak plasmas can induce critical events known as disruptions. Disruptions produce strong electromagnetic forces and thermal loads which can damage fundamental components of the devices. Determining the disruption time is extremely important for various disruption studies: theoretical models, physics-driven models, or disruption predictors. In JET, during the experimental campaigns with the JET-C (Carbon Fiber Composite) wall, a common criterion to determine the disruption time consisted of locating the time of the thermal quench. However, with the metallic ITER-like wall (JET-ILW), this criterion is usually not valid. Several thermal quenches may occur previous to the current quench but the temperature recovers. Therefore, a new criterion has to be defined. A possibility is to use the start of the current quench as disruption time. This work describes the implementation of an automatic data processing method to estimate the disruption time according to this new definition. This automatic determination allows both reducing human efforts to locate the disruption times and standardizing the estimates (with the benefit of being less vulnerable to human errors).

  10. Neutrophil glycoprotein Mo1 is an integral membrane protein of plasma membranes and specific granules

    International Nuclear Information System (INIS)

    Stevenson, K.B.; Nauseef, W.M.; Clark, R.A.

    1987-01-01

    The glucoprotein Mo1 has previously been demonstrated to be on the cell surface and in the specific granule fraction of neutrophils and to be translocated to the cell surface during degranulation. It is not known, however, whether Mo1 is an integral membrane protein or a soluble, intragranular constituent loosely associated with the specific granule membrane. Purified neutrophils were disrupted by nitrogen cavitation and separated on Percoll density gradients into four fractions enriched for azurophilic granules, specific granules, plasma membrane, and cytosol, respectively. The glycoproteins in these fractions were labeled with 3 H-borohydride reduction, extracted with Triton X-114, and immunoprecipitated with 60.3, an anti-Mo1 monoclonal antibody. Mo1 was detected only in the specific granule and plasma membrane fractions and partitioned exclusively into the detergent-rich fraction consistent with Mo1 being an integral membrane protein. In addition, treatment of specific granule membranes with a high salt, high urea buffer to remove adsorbed or peripheral proteins failed to dissociate Mo1. These data support the hypothesis that Mo1 is an integral membrane protein of plasma and specific granule membranes in human neutrophils

  11. Modeling and Simulation for Fuel Cell Polymer Electrolyte Membrane

    Directory of Open Access Journals (Sweden)

    Takahiro Hayashi

    2013-01-01

    Full Text Available We have established methods to evaluate key properties that are needed to commercialize polyelectrolyte membranes for fuel cell electric vehicles such as water diffusion, gas permeability, and mechanical strength. These methods are based on coarse-graining models. For calculating water diffusion and gas permeability through the membranes, the dissipative particle dynamics–Monte Carlo approach was applied, while mechanical strength of the hydrated membrane was simulated by coarse-grained molecular dynamics. As a result of our systematic search and analysis, we can now grasp the direction necessary to improve water diffusion, gas permeability, and mechanical strength. For water diffusion, a map that reveals the relationship between many kinds of molecular structures and diffusion constants was obtained, in which the direction to enhance the diffusivity by improving membrane structure can be clearly seen. In order to achieve high mechanical strength, the molecular structure should be such that the hydrated membrane contains narrow water channels, but these might decrease the proton conductivity. Therefore, an optimal design of the polymer structure is needed, and the developed models reviewed here make it possible to optimize these molecular structures.

  12. A REMARK ON FORMAL MODELS FOR NONLINEARLY ELASTIC MEMBRANE SHELLS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper gives all the two-dimensional membrane models obtained from formal asymptotic analysis of the three-dimensional geometrically exact nonlinear model of a thin elastic shell made with a Saint Venant-Kirchhoff material. Therefore, the other models can be quoted as flexural nonlinear ones. The author also gives the formal equations solved by the associated stress tensor and points out that only one of those models leads, by linearization, to the “classical” linear limiting membrane model, whose juetification has already been established by a convergence theorem.

  13. Modelling and sequential simulation of multi-tubular metallic membrane and techno-economics of a hydrogen production process employing thin-layer membrane reactor

    KAUST Repository

    Shafiee, Alireza

    2016-09-24

    A theoretical model for multi-tubular palladium-based membrane is proposed in this paper and validated against experimental data for two different sized membrane modules that operate at high temperatures. The model is used in a sequential simulation format to describe and analyse pure hydrogen and hydrogen binary mixture separations, and then extended to simulate an industrial scale membrane unit. This model is used as a sub-routine within an ASPEN Plus model to simulate a membrane reactor in a steam reforming hydrogen production plant. A techno-economic analysis is then conducted using the validated model for a plant producing 300 TPD of hydrogen. The plant utilises a thin (2.5 μm) defect-free and selective layer (Pd75Ag25 alloy) membrane reactor. The economic sensitivity analysis results show usefulness in finding the optimum operating condition that achieves minimum hydrogen production cost at break-even point. A hydrogen production cost of 1.98 $/kg is estimated while the cost of the thin-layer selective membrane is found to constitute 29% of total process capital cost. These results indicate the competiveness of this thin-layer membrane process against conventional methods of hydrogen production. © 2016 Hydrogen Energy Publications LLC

  14. Disrupting Business

    DEFF Research Database (Denmark)

    Cox, Geoff; Bazzichelli, Tatiana

    Disruptive Business explores some of the interconnections between art, activism and the business concept of disruptive innovation. With a backdrop of the crisis of financial capitalism, austerity cuts in the cultural sphere, the idea is to focus on potential art strategies in relation to a broken...... economy. In a perverse way, we ask whether this presents new opportunities for cultural producers to achieve more autonomy over their production process. If it is indeed possible, or desirable, what alternative business models emerge? The book is concerned broadly with business as material for reinvention...

  15. Critical Review of Membrane Bioreactor Models

    DEFF Research Database (Denmark)

    Naessens, W.; Maere, T.; Ratkovich, Nicolas Rios

    2012-01-01

    Membrane bioreactor technology exists for a couple of decades, but has not yet overwhelmed the market due to some serious drawbacks of which operational cost due to fouling is the major contributor. Knowledge buildup and optimisation for such complex systems can heavily benefit from mathematical...... modelling. In this paper, the vast literature on hydrodynamic and integrated modelling in MBR is critically reviewed. Hydrodynamic models are used at different scales and focus mainly on fouling and only little on system design/optimisation. Integrated models also focus on fouling although the ones...

  16. Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It.

    Science.gov (United States)

    Kraft, Mary L

    2016-01-01

    Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with

  17. Computer-aided modeling framework – a generic modeling template for catalytic membrane fixed bed reactors

    DEFF Research Database (Denmark)

    Fedorova, Marina; Sin, Gürkan; Gani, Rafiqul

    2013-01-01

    and users to generate and test models systematically, efficiently and reliably. In this way, development of products and processes can be faster, cheaper and very efficient. In this contribution, as part of the framework a generic modeling template for the systematic derivation of problem specific catalytic...... membrane fixed bed models is developed. The application of the modeling template is highlighted with a case study related to the modeling of a catalytic membrane reactor coupling dehydrogenation of ethylbenzene with hydrogenation of nitrobenzene....

  18. Amyloid protein unfolding and insertion kinetics on neuronal membrane mimics

    Science.gov (United States)

    Qiu, Liming; Buie, Creighton; Vaughn, Mark; Cheng, Kwan

    2010-03-01

    Atomistic details of beta-amyloid (Aβ ) protein unfolding and lipid interaction kinetics mediated by the neuronal membrane surface are important for developing new therapeutic strategies to prevent and cure Alzheimer's disease. Using all-atom MD simulations, we explored the early unfolding and insertion kinetics of 40 and 42 residue long Aβ in binary lipid mixtures with and without cholesterol that mimic the cholesterol-depleted and cholesterol-enriched lipid nanodomains of neurons. The protein conformational transition kinetics was evaluated from the secondary structure profile versus simulation time plot. The extent of membrane disruption was examined by the calculated order parameters of lipid acyl chains and cholesterol fused rings as well as the density profiles of water and lipid headgroups at defined regions across the lipid bilayer from our simulations. Our results revealed that both the cholesterol content and the length of the protein affect the protein-insertion and membrane stability in our model lipid bilayer systems.

  19. Advanced Wastewater Treatment Engineering—Investigating Membrane Fouling in both Rotational and Static Membrane Bioreactor Systems Using Empirical Modelling

    Directory of Open Access Journals (Sweden)

    Parneet Paul

    2016-01-01

    Full Text Available Advanced wastewater treatment using membranes are popular environmental system processes since they allow reuse and recycling. However, fouling is a key limiting factor and so proprietary systems such as Avanti’s RPU-185 Flexidisks membrane bioreactor (MBR use novel rotating membranes to assist in ameliorating it. In earlier research, this rotating process was studied by creating a simulation model based on first principles and traditional fouling mechanisms. In order to directly compare the potential benefits of this rotational system, this follow-up study was carried out using Avanti’s newly developed static (non-rotating Flexidisks MBR system. The results from operating the static pilot unit were simulated and modelled using the rotational fouling model developed earlier however with rotational switching functions turned off and rotational parameters set to a static mode. The study concluded that a rotating MBR system could increase flux throughput when compared against a similar static system. It is thought that although the slowly rotating spindle induces a weak crossflow shear, it is still able to even out cake build up across the membrane surface, thus reducing the likelihood of localised critical flux being exceeded at the micro level and lessening the potential of rapid trans-membrane pressure increases at the macro level.

  20. NH125 kills methicillin-resistant Staphylococcus aureus persisters by lipid bilayer disruption.

    Science.gov (United States)

    Kim, Wooseong; Fricke, Nico; Conery, Annie L; Fuchs, Beth Burgwyn; Rajamuthiah, Rajmohan; Jayamani, Elamparithi; Vlahovska, Petia M; Ausubel, Frederick M; Mylonakis, Eleftherios

    2016-01-01

    NH125, a known WalK inhibitor kills MRSA persisters. However, its precise mode of action is still unknown. The mode of action of NH125 was investigated by comparing its spectrum of antimicrobial activity and its effects on membrane permeability and giant unilamellar vesicles (GUVs) with walrycin B, a WalR inhibitor and benzyldimethylhexadecylammonium chloride (16-BAC), a cationic surfactant. NH125 killed persister cells of a variety of Staphylococcus aureus strains. Similar to 16-BAC, NH125 killed MRSA persisters by inducing rapid membrane permeabilization and caused the rupture of GUVs, whereas walrycin B did not kill MRSA persisters or induce membrane permeabilization and did not affect GUVs. NH125 kills MRSA persisters by interacting with and disrupting membranes in a detergent-like manner.

  1. A layer model of ethanol partitioning into lipid membranes.

    Science.gov (United States)

    Nizza, David T; Gawrisch, Klaus

    2009-06-01

    The effect of membrane composition on ethanol partitioning into lipid bilayers was assessed by headspace gas chromatography. A series of model membranes with different compositions have been investigated. Membranes were exposed to a physiological ethanol concentration of 20 mmol/l. The concentration of membranes was 20 wt% which roughly corresponds to values found in tissue. Partitioning depended on the chemical nature of polar groups at the lipid/water interface. Compared to phosphatidylcholine, lipids with headgroups containing phosphatidylglycerol, phosphatidylserine, and sphingomyelin showed enhanced partitioning while headgroups containing phosphatidylethanolamine resulted in a lower partition coefficient. The molar partition coefficient was independent of a membrane's hydrophobic volume. This observation is in agreement with our previously published NMR results which showed that ethanol resides almost exclusively within the membrane/water interface. At an ethanol concentration of 20 mmol/l in water, ethanol concentrations at the lipid/water interface are in the range from 30-15 mmol/l, corresponding to one ethanol molecule per 100-200 lipids.

  2. Understanding disruptions in tokamaksa)

    Science.gov (United States)

    Zakharov, Leonid E.; Galkin, Sergei A.; Gerasimov, Sergei N.; contributors, JET-EFDA

    2012-05-01

    This paper describes progress achieved since 2007 in understanding disruptions in tokamaks, when the effect of plasma current sharing with the wall was introduced into theory. As a result, the toroidal asymmetry of the plasma current measurements during vertical disruption event (VDE) on the Joint European Torus was explained. A new kind of plasma equilibria and mode coupling was introduced into theory, which can explain the duration of the external kink 1/1 mode during VDE. The paper presents first results of numerical simulations using a free boundary plasma model, relevant to disruptions.

  3. Models of dynamic extraction of lipid tethers from cell membranes

    International Nuclear Information System (INIS)

    Nowak, Sarah A; Chou, Tom

    2010-01-01

    When a ligand that is bound to an integral membrane receptor is pulled, the membrane and the underlying cytoskeleton can deform before either the membrane delaminates from the cytoskeleton or the ligand detaches from the receptor. If the membrane delaminates from the cytoskeleton, it may be further extruded and form a membrane tether. We develop a phenomenological model for this process by assuming that deformations obey Hooke's law up to a critical force at which the cell membrane locally detaches from the cytoskeleton and a membrane tether forms. We compute the probability of tether formation and show that tethers can be extruded only within an intermediate range of force loading rates and pulling velocities. The mean tether length that arises at the moment of ligand detachment is computed as are the force loading rates and pulling velocities that yield the longest tethers

  4. Antimicrobial mechanism of flavonoids against Escherichia coli ATCC 25922 by model membrane study

    International Nuclear Information System (INIS)

    He, Mengying; Wu, Ting; Pan, Siyi; Xu, Xiaoyun

    2014-01-01

    Antimicrobial mechanism of four flavonoids (kaempferol, hesperitin, (+)-catechin hydrate, biochanin A) against Escherichia coli ATCC 25922 was investigated through cell membranes and a liposome model. The release of bacterial protein and images from transmission electron microscopy demonstrated damage to the E. coli ATCC 25922 membrane. A liposome model with dipalmitoylphosphatidylethanolamine (DPPE) (0.6 molar ratio) and dipalmitoylphosphatidylglycerol (DPPG) (0.4 molar ratio), representative of the phospholipid membrane of E. coli ATCC 25922, was used to specify the mode of action of four selected flavonoids through Raman spectroscopy and differential scanning calorimetry. It is suggested that for flavonoids, to be effective antimicrobials, interaction with the polar head-group of the model membrane followed by penetration into the hydrophobic regions must occur. The antimicrobial efficacies of the flavonoids were consistent with liposome interaction activities, kaempferol > hesperitin > (+)-catechin hydrate > biochanin A. This study provides a liposome model capable of mimicking the cell membrane of E. coli ATCC 25922. The findings are important in understanding the antibacterial mechanism on cell membranes.

  5. Antimicrobial mechanism of flavonoids against Escherichia coli ATCC 25922 by model membrane study

    Energy Technology Data Exchange (ETDEWEB)

    He, Mengying; Wu, Ting; Pan, Siyi; Xu, Xiaoyun, E-mail: xiaoyunxu88@gmail.com

    2014-06-01

    Antimicrobial mechanism of four flavonoids (kaempferol, hesperitin, (+)-catechin hydrate, biochanin A) against Escherichia coli ATCC 25922 was investigated through cell membranes and a liposome model. The release of bacterial protein and images from transmission electron microscopy demonstrated damage to the E. coli ATCC 25922 membrane. A liposome model with dipalmitoylphosphatidylethanolamine (DPPE) (0.6 molar ratio) and dipalmitoylphosphatidylglycerol (DPPG) (0.4 molar ratio), representative of the phospholipid membrane of E. coli ATCC 25922, was used to specify the mode of action of four selected flavonoids through Raman spectroscopy and differential scanning calorimetry. It is suggested that for flavonoids, to be effective antimicrobials, interaction with the polar head-group of the model membrane followed by penetration into the hydrophobic regions must occur. The antimicrobial efficacies of the flavonoids were consistent with liposome interaction activities, kaempferol > hesperitin > (+)-catechin hydrate > biochanin A. This study provides a liposome model capable of mimicking the cell membrane of E. coli ATCC 25922. The findings are important in understanding the antibacterial mechanism on cell membranes.

  6. Membrane models and generalized Z2 gauge theories

    International Nuclear Information System (INIS)

    Lowe, M.J.; Wallace, D.J.

    1980-01-01

    We consider models of (d-n)-dimensional membranes fluctuating in a d-dimensional space under the action of surface tension. We investigate the renormalization properties of these models perturbatively and in 1/n expansion. The potential relationships of these models to generalized Z 2 gauge theories are indicated. (orig.)

  7. Ice formation in model biological membranes in the presence of cryoprotectors

    Energy Technology Data Exchange (ETDEWEB)

    Kiselev, M.A. E-mail: kiselev@nf.jinr.ru; Lesieur, P.; Kisselev, A.M.; Ollivon, M

    2000-06-21

    Ice formation in model biological membranes is studied by SAXS and WAXS in the presence of cryoprotectors: dimethyl sulfoxide and glycerol. Three types of phospholipid membranes: DPPC, DMPC, DSPC are chosen for the investigation as well-studied model biological membranes. A special cryostat is used for sample cooling from 14.1 deg. C to -55.4 deg. C. The ice formation is detected only by WAXS in binary phospholipid/water and ternary phospholipid/cryoprotector/water systems in the condition of excess solvent. Ice formation in a binary phospholipid/water system creates an abrupt decrease of the membrane repeat distance by {delta}d, the so-called ice-induced dehydration of intermembrane space. The value of {delta}d decreases as the cryoprotector concentration increases. The formation of ice does not influence the membrane structure ({delta}d=0) for cryoprotector mole fractions higher than 0.05.

  8. There Is No Simple Model of the Plasma Membrane Organization

    Czech Academy of Sciences Publication Activity Database

    de la serna, J. B.; Schütz, G.; Eggeling, Ch.; Cebecauer, Marek

    2016-01-01

    Roč. 4, SEP 2016 (2016), 106 ISSN 2296-634X R&D Projects: GA ČR GA15-06989S Institutional support: RVO:61388955 Keywords : plasma membrane * membrane organization models * heterogeneous distribution Subject RIV: CF - Physical ; Theoretical Chemistry

  9. Mathematical models of membrane fouling in cross-flow micro-filtration

    Directory of Open Access Journals (Sweden)

    Mónica Jimena Ortíz Jerez

    2008-01-01

    Full Text Available The greatest difficulty arising during cross-flow micro-filtration is the formation of a cake layer on the membrane sur-face (also called fouling, thereby affecting system performance. Fouling has been related to permeate flux decay re-sulting from changes in operating variables. Many articles have been published in an attempt to explain this phe-nomenon but it has not yet been fully understood because it depends on specific solution/membrane interactions and differing parameters. This work was aimed at presenting an analytical review of recently published mathematical models to explain fouling. Although the reviewed models can be adjusted to any type of application, a simple “con-centration polarisation” model is advisable in the particular case of tropical fruit juices for describing the insoluble solids being deposited on membrane surface.

  10. Probabilistic analysis of tokamak plasma disruptions

    International Nuclear Information System (INIS)

    Sanzo, D.L.; Apostolakis, G.E.

    1985-01-01

    An approximate analytical solution to the heat conduction equations used in modeling component melting and vaporization resulting from plasma disruptions is presented. This solution is then used to propagate uncertainties in the input data characterizing disruptions, namely, energy density and disruption time, to obtain a probabilistic description of the output variables of interest, material melted and vaporized. (orig.)

  11. Analysis of mass transfer characteristics in a tubular membrane using CFD modeling.

    Science.gov (United States)

    Yang, Jixiang; Vedantam, Sreepriya; Spanjers, Henri; Nopens, Ingmar; van Lier, Jules B

    2012-10-01

    In contrast to the large amount of research into aerobic membrane bioreactors, little work has been reported on anaerobic membrane bioreactors (AMBRs). As to the application of membrane bioreactors, membrane fouling is a key issue. Membrane fouling generally occurs more seriously in AMBRs than in aerobic membrane bioreactors. However, membrane fouling could be managed through the application of suitable shear stress that can be introduced by the application of a two-phase flow. When the two-phase flow is applied in AMBRs, little is known about the mass transfer characteristics, which is of particular importance, in tubular membranes of AMBRs. In our present work, we have employed fluid dynamic modeling to analyze the mass transfer characteristics in the tubular membrane of a side stream AMBR in which, gas-lift two-phase flow was applied. The modeling indicated that the mass transfer capacity at the membrane surface at the noses of gas bubbles was higher than the mass transfer capacity at the tails of the bubbles, which is in contrast to the results when water instead of sludge is applied. At the given mass transfer rate, the filterability of the sludge was found to have a strong influence on the transmembrane pressure at a steady flux. In addition, the model also showed that the shear stress in the internal space of the tubular membrane was mainly around 20 Pa but could be as high as about 40 Pa due to gas bubble movements. Nonetheless, at these shear stresses a stable particle size distribution was found for sludge particles. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Understanding Detergent Effects on Lipid Membranes: A Model Study of Lysolipids

    DEFF Research Database (Denmark)

    Henriksen, Jonas Rosager; Andresen, Thomas Lars; Feldborg, Lise Nørkjær

    2010-01-01

    Lysolipids and fatty acids are the natural products formed by the hydrolysis of phospholipids. Lysolipids and fatty acids form micelles in solution and acts as detergents in the presence of lipid membranes. In this study, we investigate the detergent strength of a homologous series of lyso......-chain mismatch between LPC and POPC determines the magnitude of the membrane mechanical perturbation per LPC molecule in the membrane. Finally, the three-stage model describing detergent membrane interaction has been extended by a parameter D-MCI, which governs the membrane curvature stability in the detergent...

  13. FIG4 regulates lysosome membrane homeostasis independent of phosphatase function.

    Science.gov (United States)

    Bharadwaj, Rajnish; Cunningham, Kathleen M; Zhang, Ke; Lloyd, Thomas E

    2016-02-15

    FIG4 is a phosphoinositide phosphatase that is mutated in several diseases including Charcot-Marie-Tooth Disease 4J (CMT4J) and Yunis-Varon syndrome (YVS). To investigate the mechanism of disease pathogenesis, we generated Drosophila models of FIG4-related diseases. Fig4 null mutant animals are viable but exhibit marked enlargement of the lysosomal compartment in muscle cells and neurons, accompanied by an age-related decline in flight ability. Transgenic animals expressing Drosophila Fig4 missense mutations corresponding to human pathogenic mutations can partially rescue lysosomal expansion phenotypes, consistent with these mutations causing decreased FIG4 function. Interestingly, Fig4 mutations predicted to inactivate FIG4 phosphatase activity rescue lysosome expansion phenotypes, and mutations in the phosphoinositide (3) phosphate kinase Fab1 that performs the reverse enzymatic reaction also causes a lysosome expansion phenotype. Since FIG4 and FAB1 are present together in the same biochemical complex, these data are consistent with a model in which FIG4 serves a phosphatase-independent biosynthetic function that is essential for lysosomal membrane homeostasis. Lysosomal phenotypes are suppressed by genetic inhibition of Rab7 or the HOPS complex, demonstrating that FIG4 functions after endosome-to-lysosome fusion. Furthermore, disruption of the retromer complex, implicated in recycling from the lysosome to Golgi, does not lead to similar phenotypes as Fig4, suggesting that the lysosomal defects are not due to compromised retromer-mediated recycling of endolysosomal membranes. These data show that FIG4 plays a critical noncatalytic function in maintaining lysosomal membrane homeostasis, and that this function is disrupted by mutations that cause CMT4J and YVS. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  14. Investigation of membrane mechanics using spring networks: application to red-blood-cell modelling.

    Science.gov (United States)

    Chen, Mingzhu; Boyle, Fergal J

    2014-10-01

    In recent years a number of red-blood-cell (RBC) models have been proposed using spring networks to represent the RBC membrane. Some results predicted by these models agree well with experimental measurements. However, the suitability of these membrane models has been questioned. The RBC membrane, like a continuum membrane, is mechanically isotropic throughout its surface, but the mechanical properties of a spring network vary on the network surface and change with deformation. In this work spring-network mechanics are investigated in large deformation for the first time via an assessment of the effect of network parameters, i.e. network mesh, spring type and surface constraint. It is found that a spring network is conditionally equivalent to a continuum membrane. In addition, spring networks are employed for RBC modelling to replicate the optical tweezers test. It is found that a spring network is sufficient for modelling the RBC membrane but strain-hardening springs are required. Moreover, the deformation profile of a spring network is presented for the first time via the degree of shear. It is found that spring-network deformation approaches continuous as the mesh density increases. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Designing reliable supply chain network with disruption risk

    Directory of Open Access Journals (Sweden)

    Ali Bozorgi Amiri

    2013-01-01

    Full Text Available Although supply chains disruptions rarely occur, their negative effects are prolonged and severe. In this paper, we propose a reliable capacitated supply chain network design (RSCND model by considering random disruptions in both distribution centers and suppliers. The proposed model determines the optimal location of distribution centers (DC with the highest reliability, the best plan to assign customers to opened DCs and assigns opened DCs to suitable suppliers with lowest transportation cost. In this study, random disruption occurs at the location, capacity of the distribution centers (DCs and suppliers. It is assumed that a disrupted DC and a disrupted supplier may lose a portion of their capacities, and the rest of the disrupted DC's demand can be supplied by other DCs. In addition, we consider shortage in DCs, which can occur in either normal or disruption conditions and DCs, can support each other in such circumstances. Unlike other studies in the extent of literature, we use new approach to model the reliability of DCs; we consider a range of reliability instead of using binary variables. In order to solve the proposed model for real-world instances, a Non-dominated Sorting Genetic Algorithm-II (NSGA-II is applied. Preliminary results of testing the proposed model of this paper on several problems with different sizes provide seem to be promising.

  16. Membrane contactor/separator for an advanced ozone membrane reactor for treatment of recalcitrant organic pollutants in water

    International Nuclear Information System (INIS)

    Chan, Wai Kit; Jouët, Justine; Heng, Samuel; Yeung, King Lun; Schrotter, Jean-Christophe

    2012-01-01

    An advanced ozone membrane reactor that synergistically combines membrane distributor for ozone gas, membrane contactor for pollutant adsorption and reaction, and membrane separator for clean water production is described. The membrane reactor represents an order of magnitude improvement over traditional semibatch reactor design and is capable of complete conversion of recalcitrant endocrine disrupting compounds (EDCs) in water at less than three minutes residence time. Coating the membrane contactor with alumina and hydrotalcite (Mg/Al=3) adsorbs and traps the organics in the reaction zone resulting in 30% increase of total organic carbon (TOC) removal. Large surface area coating that diffuses surface charges from adsorbed polar organic molecules is preferred as it reduces membrane polarization that is detrimental to separation. - Graphical abstract: Advanced ozone membrane reactor synergistically combines membrane distributor for ozone, membrane contactor for sorption and reaction and membrane separator for clean water production to achieve an order of magnitude enhancement in treatment performance compared to traditional ozone reactor. Highlights: ► Novel reactor using membranes for ozone distributor, reaction contactor and water separator. ► Designed to achieve an order of magnitude enhancement over traditional reactor. ► Al 2 O 3 and hydrotalcite coatings capture and trap pollutants giving additional 30% TOC removal. ► High surface area coating prevents polarization and improves membrane separation and life.

  17. Human Lipoproteins at Model Cell Membranes

    DEFF Research Database (Denmark)

    Browning, K L; Lind, T K; Maric, S

    2017-01-01

    High and low density lipoproteins (HDL and LDL) are thought to play vital roles in the onset and development of atherosclerosis; the biggest killer in the western world. Key issues of initial lipoprotein (LP) interactions at cellular membranes need to be addressed including LP deposition and lipid...... exchange. Here we present a protocol for monitoring the in situ kinetics of lipoprotein deposition and lipid exchange/removal at model cellular membranes using the non-invasive, surface sensitive methods of neutron reflection and quartz crystal microbalance with dissipation. For neutron reflection, lipid...... support the notion of HDL acting as the 'good' cholesterol, removing lipid material from lipid-loaded cells, whereas LDL acts as the 'bad' cholesterol, depositing lipid material into the vascular wall....

  18. A membrane model for cytosolic calcium oscillations. A study using Xenopus oocytes.

    OpenAIRE

    Jafri, M S; Vajda, S; Pasik, P; Gillo, B

    1992-01-01

    Cytosolic calcium oscillations occur in a wide variety of cells and are involved in different cellular functions. We describe these calcium oscillations by a mathematical model based on the putative electrophysiological properties of the endoplasmic reticulum (ER) membrane. The salient features of our membrane model are calcium-dependent calcium channels and calcium pumps in the ER membrane, constant entry of calcium into the cytosol, calcium dependent removal from the cytosol, and buffering ...

  19. Fish skin as a model membrane: structure and characteristics.

    Science.gov (United States)

    Konrádsdóttir, Fífa; Loftsson, Thorsteinn; Sigfússon, Sigurdur Dadi

    2009-01-01

    Synthetic and cell-based membranes are frequently used during drug formulation development for the assessment of drug availability. However, most of the currently used membranes do not mimic mucosal membranes well, especially the aqueous mucous layer of the membranes. In this study we evaluated catfish (Anarichas lupus L) skin as a model membrane. Permeation of hydrocortisone, lidocaine hydrochloride, benzocaine, diethylstilbestrol, naproxen, picric acid and sodium nitrate through skin from a freshly caught catfish was determined in Franz diffusion cells. Both lipophilic and hydrophilic molecules permeate through catfish skin via hydrated channels or aqueous pores. No correlation was observed between the octanol/water partition coefficient of the permeating molecules and their permeability coefficient through the skin. Permeation through catfish skin was found to be diffusion controlled. The results suggest that permeation through the fish skin proceeds via a diffusion-controlled process, a process that is similar to drug permeation through the aqueous mucous layer of a mucosal membrane. In addition, the fish skin, with its collagen matrix structure, appears to possess similar properties to the eye sclera.

  20. Influence of estrogenic pesticides on membrane integrity and membrane transfer of monosaccharide into the human red cell

    International Nuclear Information System (INIS)

    Ingermann, R.L.

    1989-01-01

    Some natural and synthetic estrogens inhibit carrier-mediated transport of glucose into human red blood cells and membrane vesicles from the placenta. The inhibitory action of these estrogens on transport appears to be a direct effect at the membrane and does not involve receptor binding and protein synthesis. It is not clear, however, whether such inhibition is a common feature among estrogenic agents. Several chlorinated hydrocarbon pesticides have been shown to possess estrogenic activity. These pesticides could have inhibitory effects on the human sodium-independent glucose transporter. Owing to the apparent importance of this membrane transporter in human tissues, direct interaction of hormones and xenobiotics with the glucose transporter is of fundamental significance. Some pesticides have been shown to alter membrane structure directly and alter the passive permeability of membranes. Whether the estrogenic pesticides influence passive diffusion of sugars across membranes has not been established. Finally, preliminary observations have suggested that some estrogens and pesticides have lytic effects on intact cells. Consequently, this study focuses on the ability of several estrogens and estrogenic pesticides to disrupt the cell membrane, influence the monosaccharide transporter, and alter the rate of monosaccharide permeation through the membrane by simple diffusion

  1. An Amphipathic Helix Directs Cellular Membrane Curvature Sensing and Function of the BAR Domain Protein PICK1.

    Science.gov (United States)

    Herlo, Rasmus; Lund, Viktor K; Lycas, Matthew D; Jansen, Anna M; Khelashvili, George; Andersen, Rita C; Bhatia, Vikram; Pedersen, Thomas S; Albornoz, Pedro B C; Johner, Niklaus; Ammendrup-Johnsen, Ina; Christensen, Nikolaj R; Erlendsson, Simon; Stoklund, Mikkel; Larsen, Jannik B; Weinstein, Harel; Kjærulff, Ole; Stamou, Dimitrios; Gether, Ulrik; Madsen, Kenneth L

    2018-05-15

    BAR domains are dimeric protein modules that sense, induce, and stabilize lipid membrane curvature. Here, we show that membrane curvature sensing (MCS) directs cellular localization and function of the BAR domain protein PICK1. In PICK1, and the homologous proteins ICA69 and arfaptin2, we identify an amphipathic helix N-terminal to the BAR domain that mediates MCS. Mutational disruption of the helix in PICK1 impaired MCS without affecting membrane binding per se. In insulin-producing INS-1E cells, super-resolution microscopy revealed that disruption of the helix selectively compromised PICK1 density on insulin granules of high curvature during their maturation. This was accompanied by reduced hormone storage in the INS-1E cells. In Drosophila, disruption of the helix compromised growth regulation. By demonstrating size-dependent binding on insulin granules, our finding highlights the function of MCS for BAR domain proteins in a biological context distinct from their function, e.g., at the plasma membrane during endocytosis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  2. Dynamic modeling of ultrafiltration membranes for whey separation processes

    NARCIS (Netherlands)

    Saltik, M.B.; Ozkan, L.; Jacobs, M.; van der Padt, A.

    2017-01-01

    In this paper, we present a control relevant rigorous dynamic model for an ultrafiltration membrane unit in a whey separation process. The model consists of a set of differential algebraic equations and is developed for online model based applications such as model based control and process

  3. Modeling the ion transfer and polarization of ion exchange membranes in bioelectrochemical systems.

    Science.gov (United States)

    Harnisch, Falk; Warmbier, Robert; Schneider, Ralf; Schröder, Uwe

    2009-06-01

    An explicit numerical model for the charge balancing ion transfer across monopolar ion exchange membranes under conditions of bioelectrochemical systems is presented. Diffusion and migration equations have been solved according to the Nernst-Planck Equation and the resulting ion concentrations, pH values and the resistance values of the membrane for different conditions were computed. The modeling results underline the principle limitations of the application of ion exchange membranes in biological fuel cells and electrolyzers, caused by the inherent occurrence of a pH-gradient between anode and cathode compartment, and an increased ohmic membrane resistance at decreasing electrolyte concentrations. Finally, the physical and numerical limitations of the model are discussed.

  4. Nuclide separation modeling through reverse osmosis membranes in radioactive liquid waste

    Directory of Open Access Journals (Sweden)

    Byung-Sik Lee

    2015-12-01

    Full Text Available The aim of this work is to investigate the transport mechanism of radioactive nuclides through the reverse osmosis (RO membrane and to estimate its effectiveness for nuclide separation from radioactive liquid waste. An analytical model is developed to simulate the RO separation, and a series of experiments are set up to confirm its estimated separation behavior. The model is based on the extended Nernst–Plank equation, which handles the convective flux, diffusive flux, and electromigration flux under electroneutrality and zero electric current conditions. The distribution coefficient which arises due to ion interactions with the membrane material and the electric potential jump at the membrane interface are included as boundary conditions in solving the equation. A high Peclet approximation is adopted to simplify the calculation, but the effect of concentration polarization is included for a more accurate prediction of separation. Cobalt and cesium are specifically selected for the experiments in order to check the separation mechanism from liquid waste composed of various radioactive nuclides and nonradioactive substances, and the results are compared with the estimated cobalt and cesium rejections of the RO membrane using the model. Experimental and calculated results are shown to be in excellent agreement. The proposed model will be very useful for the prediction of separation behavior of various radioactive nuclides by the RO membrane.

  5. Nuclide separation modeling through reverse osmosis membranes in radioactive liquid waste

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byung Sik [KEPCO Engineering and Construction, Gimcheon (Korea, Republic of)

    2015-12-15

    The aim of this work is to investigate the transport mechanism of radioactive nuclides through the reverse osmosis (RO) membrane and to estimate its effectiveness for nuclide separation from radioactive liquid waste. An analytical model is developed to simulate the RO separation, and a series of experiments are set up to confirm its estimated separation behavior. The model is based on the extended Nernst-Plank equation, which handles the convective flux, diffusive flux, and electromigration flux under electroneutrality and zero electric current conditions. The distribution coefficient which arises due to ion interactions with the membrane material and the electric potential jump at the membrane interface are included as boundary conditions in solving the equation. A high Peclet approximation is adopted to simplify the calculation, but the effect of concentration polarization is included for a more accurate prediction of separation. Cobalt and cesium are specifically selected for the experiments in order to check the separation mechanism from liquid waste composed of various radioactive nuclides and nonradioactive substances, and the results are compared with the estimated cobalt and cesium rejections of the RO membrane using the model. Experimental and calculated results are shown to be in excellent agreement. The proposed model will be very useful for the prediction of separation behavior of various radioactive nuclides by the RO membrane.

  6. Modeling CO2-facilitated transport across a diethanolamine liquid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Lihong Bao; Michael C. Trachtenberg [Carbozyme Inc., Monmouth Junction, NJ (United States)

    2005-12-15

    We compared experimental and model data for the facilitated transport of CO2 from a CO2-air mixture across an aqueous solution of diethanolamine (DEA) via a hollow fiber, contained liquid membrane (HFCLM) permeator. A two-step carbamate formation model was devised to analyze the data instead of the one-step mechanism used by previous investigators. The effects of DEA concentration, liquid membrane thickness and feed CO2 concentration were also studied. With a 20% (wt) DEA liquid membrane and feed of 15% CO2 in CO2-air mixture at atmosphere pressure, the permeance reached 1.51E-8 mol/m{sup 2} s Pa with a CO2/N2 selectivity of 115. Model predictions compared well with the experimental results at CO2 concentrations of industrial importance. Short-term stability of the HFCLM permeator performance was examined. The system was stable during 5-days of testing.

  7. Modeling and simulation of melt-layer erosion during a plasma disruption

    International Nuclear Information System (INIS)

    Hassanein, A.; Belan, V.; Konkashbaev, I.; Nikandrov, L.; Safronov, V.; Zhitlukhin, A.; Litunovsky, V.

    1997-01-01

    Metallic plasma-facing components (PFCs) e.g. beryllium and tungsten, will be subjected to severe melting during plasma instabilities such as disruptions, edge-localized modes and high power excursions. Because of the greater thickness of the resulting melt layers relative to that of the surface vaporization, the potential loss of the developing melt-layer can significantly shorten PFC lifetime, severely contaminate the plasma and potentially prevent successful operation of the tokamak reactor. Mechanisms responsible for melt-layer loss during plasma instabilities are being modeled and evaluated. Of particular importance are hydrodynamic instabilities developed in the liquid layer due to various forces such as those from magnetic fields, plasma impact momentum, vapor recoil and surface tension. Another mechanism found to contribute to melt-layer splashing loss is volume bubble boiling, which can result from overheating of the liquid layer. To benchmark these models, several new experiments were designed and performed in different laboratory devices for this work; the SPLASH codes) are generally in good agreement with the experimental results. The effect of in-reactor disruption conditions, which do not exist in simulation experiments, on melt-layer erosion is discussed. (orig.)

  8. Studies on the biocidal and cell membrane disruption potentials of stem bark extracts of Afzelia africana (Smith

    Directory of Open Access Journals (Sweden)

    DAVID A AKINPELU

    2009-01-01

    Full Text Available We had recently reported antibacterial activity in the crude extract of the stem bark of Afzelia africana (Akinpelu et al., 2008. In this study, we assessed the biocidal and cell membrane disruption potentials of fractions obtained from the crude extract of the plant. The aqueous (AQ and butanol (BL fractions exhibited appreciable antibacterial activities against the test bacteria. The minimum inhibitory concentrations of the AQ and BL fractions ranged between 0.313 and 2.5 mg/ml, while their minimum bactericidal concentrations varied between 0.625 and 5.0 mg/ml. Also, the AQ fraction killed about 95.8% of E. coli cells within 105 min at a concentration of 5 mg/ml, while about 99.1% of Bacillus pumilus cells were killed by this fraction at the same concentration and exposure time. A similar trend was observed for the BL fraction. At a concentration of 5 mg/ml, the butanol fraction leaked 9.8 μg/ml of proteins from E. coli cells within 3 h, while the aqueous fraction leaked 6.5 μg/ml of proteins from the same organisms at the same concentration and exposure time. We propose that the stem bark of Afzelia africana is a potential source of bioactive compounds of importance to the pharmaceutical industry.

  9. Modeling of air-gap membrane distillation process: A theoretical and experimental study

    KAUST Repository

    Alsaadi, Ahmad Salem

    2013-06-03

    A one dimensional (1-D) air gap membrane distillation (AGMD) model for flat sheet type modules has been developed. This model is based on mathematical equations that describe the heat and mass transfer mechanisms of a single-stage AGMD process. It can simulate AGMD modules in both co-current and counter-current flow regimes. The theoretical model was validated using AGMD experimental data obtained under different operating conditions and parameters. The predicted water vapor flux was compared to the flux measured at five different feed water temperatures, two different feed water salinities, three different air gap widths and two MD membranes with different average pore sizes. This comparison showed that the model flux predictions are strongly correlated with the experimental data, with model predictions being within +10% of the experimentally determined values. The model was then used to study and analyze the parameters that have significant effect on scaling-up the AGMD process such as the effect of increasing the membrane length, and feed and coolant flow rates. The model was also used to analyze the maximum thermal efficiency of the AGMD process by tracing changes in water production rate and the heat input to the process along the membrane length. This was used to understand the gain in both process production and thermal efficiency for different membrane surface areas and the resultant increases in process capital and water unit cost. © 2013 Elsevier B.V.

  10. Finsler Geometry Modeling of an Orientation-Asymmetric Surface Model for Membranes

    Science.gov (United States)

    Proutorov, Evgenii; Koibuchi, Hiroshi

    2017-12-01

    In this paper, a triangulated surface model is studied in the context of Finsler geometry (FG) modeling. This FG model is an extended version of a recently reported model for two-component membranes, and it is asymmetric under surface inversion. We show that the definition of the model is independent of how the Finsler length of a bond is defined. This leads us to understand that the canonical (or Euclidean) surface model is obtained from the FG model such that it is uniquely determined as a trivial model from the viewpoint of well definedness.

  11. Polycyclic aromatic hydrocarbons in model bacterial membranes - Langmuir monolayer studies.

    Science.gov (United States)

    Broniatowski, Marcin; Binczycka, Martyna; Wójcik, Aneta; Flasiński, Michał; Wydro, Paweł

    2017-12-01

    High molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) are persistent organic pollutants which due to their limited biodegradability accumulate in soils where their increased presence can lead to the impoverishment of the decomposer organisms. As very hydrophobic PAHs easily penetrate cellular membranes of soil bacteria and can be incorporated therein, changing the membrane fluidity and other functions which in consequence can lead to the death of the organism. The structure and size of PAH molecule can be crucial for its membrane activity; however the correlation between PAH structure and its interaction with phospholipids have not been investigated so far. In our studies we applied phospholipid Langmuir monolayers as model bacterial membranes and investigated how the incorporation of six structurally different PAH molecules change the membrane texture and physical properties. In our studies we registered surface pressure and surface potential isotherms upon the monolayer compression, visualized the monolayer texture with the application of Brewster angle microscopy and searched the ordering of the film-forming molecules with molecular resolution with the application of grazing incidence X-ray diffraction (GIXD) method. It turned out that the phospholipid-PAH interactions are strictly structure dependent. Four and five-ring PAHs of the angular or cluster geometry can be incorporated into the model membranes changing profoundly their textures and fluidity; whereas linear or large cluster PAHs cannot be incorporated and separate from the lipid matrix. The observed phenomena were explained based on structural similarities of the applied PAHs with membrane steroids and hopanoids. Copyright © 2017. Published by Elsevier B.V.

  12. Disruption Management in Passenger Railway Transportation

    DEFF Research Database (Denmark)

    Jespersen-Groth, Julie; Potthoff, Daniel; Clausen, Jens

    This paper deals with disruption management in passenger railway transportation. In the disruption management process, many actors belonging to different organizations play a role. In this paper we therefore describe the process itself and the roles of the different actors. Furthermore, we discuss...... the three main subproblems in railway disruption management: timetable adjustment, and rolling stock and crew re-scheduling. Next to a general description of these problems, we give an overview of the existing literature and we present some details of the specific situations at DSB S-tog and NS....... These are the railway operators in the suburban area of Copenhagen, Denmark, and on the main railway lines in the Netherlands, respectively. Since not much research has been carried out yet on Operations Research models for disruption management in the railway context, models and techniques that have been developed...

  13. Solving Problem of Graph Isomorphism by Membrane-Quantum Hybrid Model

    Directory of Open Access Journals (Sweden)

    Artiom Alhazov

    2015-10-01

    Full Text Available This work presents the application of new parallelization methods based on membrane-quantum hybrid computing to graph isomorphism problem solving. Applied membrane-quantum hybrid computational model was developed by authors. Massive parallelism of unconventional computing is used to implement classic brute force algorithm efficiently. This approach does not suppose any restrictions of considered graphs types. The estimated performance of the model is less then quadratic that makes a very good result for the problem of \\textbf{NP} complexity.

  14. Experimental type II diabetes and related models of impaired glucose metabolism differentially regulate glucose transporters at the proximal tubule brush border membrane.

    Science.gov (United States)

    Chichger, Havovi; Cleasby, Mark E; Srai, Surjit K; Unwin, Robert J; Debnam, Edward S; Marks, Joanne

    2016-06-01

    What is the central question of this study? Although SGLT2 inhibitors represent a promising treatment for patients suffering from diabetic nephropathy, the influence of metabolic disruption on the expression and function of glucose transporters is largely unknown. What is the main finding and its importance? In vivo models of metabolic disruption (Goto-Kakizaki type II diabetic rat and junk-food diet) demonstrate increased expression of SGLT1, SGLT2 and GLUT2 in the proximal tubule brush border. In the type II diabetic model, this is accompanied by increased SGLT- and GLUT-mediated glucose uptake. A fasted model of metabolic disruption (high-fat diet) demonstrated increased GLUT2 expression only. The differential alterations of glucose transporters in response to varying metabolic stress offer insight into the therapeutic value of inhibitors. SGLT2 inhibitors are now in clinical use to reduce hyperglycaemia in type II diabetes. However, renal glucose reabsorption across the brush border membrane (BBM) is not completely understood in diabetes. Increased consumption of a Western diet is strongly linked to type II diabetes. This study aimed to investigate the adaptations that occur in renal glucose transporters in response to experimental models of diet-induced insulin resistance. The study used Goto-Kakizaki type II diabetic rats and normal rats rendered insulin resistant using junk-food or high-fat diets. Levels of protein kinase C-βI (PKC-βI), GLUT2, SGLT1 and SGLT2 were determined by Western blotting of purified renal BBM. GLUT- and SGLT-mediated d-[(3) H]glucose uptake by BBM vesicles was measured in the presence and absence of the SGLT inhibitor phlorizin. GLUT- and SGLT-mediated glucose transport was elevated in type II diabetic rats, accompanied by increased expression of GLUT2, its upstream regulator PKC-βI and SGLT1 protein. Junk-food and high-fat diet feeding also caused higher membrane expression of GLUT2 and its upstream regulator PKC

  15. Network Formation under the Threat of Disruption

    NARCIS (Netherlands)

    Hoyer, B.

    2013-01-01

    The studies in this thesis are focused on the impact the presence of a network disruptor has on network formation models. In particular, we build two theoretical models to study the effect of network disruption on network formation and test the effect network disruption has on equilibrium selection

  16. Stability of model membranes in extreme environments.

    Science.gov (United States)

    Namani, Trishool; Deamer, David W

    2008-08-01

    The first forms of cellular life required a source of amphiphilic compounds capable of assembling into stable boundary structures. Membranes composed of fatty acids have been proposed as model systems of primitive membranes, but their bilayer structure is stable only within a narrow pH range and low ionic strength. They are particularly sensitive to aggregating effects of divalent cations (Mg+2, Ca+2, Fe+2) that would be present in Archaean sea water. Here we report that mixtures of alkyl amines and fatty acids form vesicles at strongly basic and acidic pH ranges which are resistant to the effects of divalent cations up to 0.1 M. Vesicles formed by mixtures of decylamine and decanoic acid (1:1 mole ratio) are relatively permeable to pyranine, a fluorescent anionic dye, but permeability could be reduced by adding 2 mol% of a polycyclic aromatic hydrocarbon such as pyrene. Permeability to the dye was also reduced by increasing the chain length of the amphiphiles. For instance, 1:1 mole ratio mixtures of dodecylamine and dodecanoic acid were able to retain pyranine dye during and following gel filtration. We conclude that primitive cell membranes were likely to be composed of mixtures of amphiphilic and hydrophobic molecules that manifested increased stability over pure fatty acid membranes.

  17. Mathematical modelling of dextran filtration through hollow fibre membranes

    DEFF Research Database (Denmark)

    Vinther, Frank; Pinelo, Manuel; Brøns, Morten

    2014-01-01

    In this paper we present a mathematical model of an ultrafiltration process. The results of the model are produced using standard numerical techniques with Comsol Multiphysics. The model describes the fluid flow and separation in hollow fibre membranes. The flow of solute and solvent within the h...

  18. Disrupted cortical connectivity theory as an explanatory model for autism spectrum disorders

    Science.gov (United States)

    Kana, Rajesh K.; Libero, Lauren E.; Moore, Marie S.

    2011-12-01

    such as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD.

  19. Consensus models to predict endocrine disruption for all ...

    Science.gov (United States)

    Humans are potentially exposed to tens of thousands of man-made chemicals in the environment. It is well known that some environmental chemicals mimic natural hormones and thus have the potential to be endocrine disruptors. Most of these environmental chemicals have never been tested for their ability to disrupt the endocrine system, in particular, their ability to interact with the estrogen receptor. EPA needs tools to prioritize thousands of chemicals, for instance in the Endocrine Disruptor Screening Program (EDSP). Collaborative Estrogen Receptor Activity Prediction Project (CERAPP) was intended to be a demonstration of the use of predictive computational models on HTS data including ToxCast and Tox21 assays to prioritize a large chemical universe of 32464 unique structures for one specific molecular target – the estrogen receptor. CERAPP combined multiple computational models for prediction of estrogen receptor activity, and used the predicted results to build a unique consensus model. Models were developed in collaboration between 17 groups in the U.S. and Europe and applied to predict the common set of chemicals. Structure-based techniques such as docking and several QSAR modeling approaches were employed, mostly using a common training set of 1677 compounds provided by U.S. EPA, to build a total of 42 classification models and 8 regression models for binding, agonist and antagonist activity. All predictions were evaluated on ToxCast data and on an exte

  20. Mass and Heat Transfer Analysis of Membrane Humidifier with a Simple Lumped Mass Model

    International Nuclear Information System (INIS)

    Lee, Young Duk; Bae, Ho June; Ahn, Kook Young; Yu, Sang Seok; Hwang, Joon Young

    2009-01-01

    The performance of proton exchange membrane fuel cell (PEMFC) is seriously changed by the humidification condition which is intrinsic characteristics of the PEMFC. Typically, the humidification of fuel cell is carried out with internal or external humidifier. A membrane humidifier is applied to the external humidification of residential power generation fuel cell due to its convenience and high performance. In this study, a simple static model is constructed to understand the physical phenomena of the membrane humidifier in terms of geometric parameters and operating parameters. The model utilizes the concept of shell and tube heat exchanger but the model is also able to estimate the mass transport through the membrane. Model is constructed with FORTRAN under Matlab/Simulink □ environment to keep consistency with other components model which we already developed. Results shows that the humidity of wet gas and membrane thickness are critical parameters to improve the performance of the humidifier

  1. Multienzyme Immobilized Polymeric Membrane Reactor for the Transformation of a Lignin Model Compound

    Directory of Open Access Journals (Sweden)

    Rupam Sarma

    2018-04-01

    Full Text Available We have developed an integrated, multienzyme functionalized membrane reactor for bioconversion of a lignin model compound involving enzymatic catalysis. The membrane bioreactors were fabricated through the layer-by-layer assembly approach to immobilize three different enzymes (glucose oxidase, peroxidase and laccase into pH-responsive membranes. This novel membrane reactor couples the in situ generation of hydrogen peroxide (by glucose oxidase to oxidative conversion of a lignin model compound, guaiacylglycerol-β-guaiacyl ether (GGE. Preliminary investigation of the efficacy of these functional membranes towards GGE degradation is demonstrated under convective flow mode. Over 90% of the initial feed could be degraded with the multienzyme immobilized membranes at a residence time of approximately 22 s. GGE conversion product analysis revealed the formation of oligomeric oxidation products upon reaction with peroxidase, which may be a potential hazard to membrane bioreactors. These oxidation products could further be degraded by laccase enzymes in the multienzymatic membranes, explaining the potential of multi enzyme membrane reactors. The multienzyme incorporated membrane reactors were active for more than 30 days of storage time at 4 °C. During this time span, repetitive use of the membrane reactor was demonstrated involving 5–6 h of operation time for each cycle. The membrane reactor displayed encouraging performance, losing only 12% of its initial activity after multiple cycles of operation.

  2. A Coarse Grained Model for a Lipid Membrane with Physiological Composition and Leaflet Asymmetry.

    Directory of Open Access Journals (Sweden)

    Satyan Sharma

    Full Text Available The resemblance of lipid membrane models to physiological membranes determines how well molecular dynamics (MD simulations imitate the dynamic behavior of cell membranes and membrane proteins. Physiological lipid membranes are composed of multiple types of phospholipids, and the leaflet compositions are generally asymmetric. Here we describe an approach for self-assembly of a Coarse-Grained (CG membrane model with physiological composition and leaflet asymmetry using the MARTINI force field. An initial set-up of two boxes with different types of lipids according to the leaflet asymmetry of mammalian cell membranes stacked with 0.5 nm overlap, reliably resulted in the self-assembly of bilayer membranes with leaflet asymmetry resembling that of physiological mammalian cell membranes. Self-assembly in the presence of a fragment of the plasma membrane protein syntaxin 1A led to spontaneous specific positioning of phosphatidylionositol(4,5bisphosphate at a positively charged stretch of syntaxin consistent with experimental data. An analogous approach choosing an initial set-up with two concentric shells filled with different lipid types results in successful assembly of a spherical vesicle with asymmetric leaflet composition. Self-assembly of the vesicle in the presence of the synaptic vesicle protein synaptobrevin 2 revealed the correct position of the synaptobrevin transmembrane domain. This is the first CG MD method to form a membrane with physiological lipid composition as well as leaflet asymmetry by self-assembly and will enable unbiased studies of the incorporation and dynamics of membrane proteins in more realistic CG membrane models.

  3. Modelling of a tubular membrane contactor for pre-combustion CO2 capture using ionic liquids: Influence of the membrane configuration, absorbent properties and operation parameters

    Directory of Open Access Journals (Sweden)

    Zhongde Dai

    2016-10-01

    Full Text Available A membrane contactor using ionic liquids (ILs as solvent for pre-combustion capture CO2 at elevated temperature (303–393 K and pressure (20 bar has been studied using mathematic model in the present work. A comprehensive two-dimensional (2D mass-transfer model was developed based on finite element method. The effects of liquid properties, membrane configurations, as well as operation parameters on the CO2 removal efficiency were systematically studied. The simulation results show that CO2 can be effectively removed in this process. In addition, it is found that the liquid phase mass transfer dominated the overall mass transfer. Membranes with high porosity and small thickness could apparently reduce the membrane resistance and thus increase the separation efficiency. On the other hand, the membrane diameter and membrane length have a relatively small influence on separation performance within the operation range. Keywords: CO2 capture, Pre-combustion, Membrane contactor, Ionic liquids, Modelling

  4. Basolateral cholesterol depletion alters Aquaporin-2 post-translational modifications and disrupts apical plasma membrane targeting.

    Science.gov (United States)

    Moeller, Hanne B; Fuglsang, Cecilia Hvitfeldt; Pedersen, Cecilie Nøhr; Fenton, Robert A

    2018-01-01

    Apical plasma membrane accumulation of the water channel Aquaporin-2 (AQP2) in kidney collecting duct principal cells is critical for body water homeostasis. Posttranslational modification (PTM) of AQP2 is important for regulating AQP2 trafficking. The aim of this study was to determine the role of cholesterol in regulation of AQP2 PTM and in apical plasma membrane targeting of AQP2. Cholesterol depletion from the basolateral plasma membrane of a collecting duct cell line (mpkCCD14) using methyl-beta-cyclodextrin (MBCD) increased AQP2 ubiquitylation. Forskolin, cAMP or dDAVP-mediated AQP2 phosphorylation at Ser269 (pS269-AQP2) was prevented by cholesterol depletion from the basolateral membrane. None of these effects on pS269-AQP2 were observed when cholesterol was depleted from the apical side of cells, or when MBCD was applied subsequent to dDAVP stimulation. Basolateral, but not apical, MBCD application prevented cAMP-induced apical plasma membrane accumulation of AQP2. These studies indicate that manipulation of the cholesterol content of the basolateral plasma membrane interferes with AQP2 PTM and subsequently regulated apical plasma membrane targeting of AQP2. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Endocrine-disrupting chemicals: associated disorders and mechanisms of action.

    Science.gov (United States)

    De Coster, Sam; van Larebeke, Nicolas

    2012-01-01

    The incidence and/or prevalence of health problems associated with endocrine-disruption have increased. Many chemicals have endocrine-disrupting properties, including bisphenol A, some organochlorines, polybrominated flame retardants, perfluorinated substances, alkylphenols, phthalates, pesticides, polycyclic aromatic hydrocarbons, alkylphenols, solvents, and some household products including some cleaning products, air fresheners, hair dyes, cosmetics, and sunscreens. Even some metals were shown to have endocrine-disrupting properties. Many observations suggesting that endocrine disruptors do contribute to cancer, diabetes, obesity, the metabolic syndrome, and infertility are listed in this paper. An overview is presented of mechanisms contributing to endocrine disruption. Endocrine disruptors can act through classical nuclear receptors, but also through estrogen-related receptors, membrane-bound estrogen-receptors, and interaction with targets in the cytosol resulting in activation of the Src/Ras/Erk pathway or modulation of nitric oxide. In addition, changes in metabolism of endogenous hormones, cross-talk between genomic and nongenomic pathways, cross talk with estrogen receptors after binding on other receptors, interference with feedback regulation and neuroendocrine cells, changes in DNA methylation or histone modifications, and genomic instability by interference with the spindle figure can play a role. Also it was found that effects of receptor activation can differ in function of the ligand.

  6. Endocrine-Disrupting Chemicals: Associated Disorders and Mechanisms of Action

    Directory of Open Access Journals (Sweden)

    Sam De Coster

    2012-01-01

    Full Text Available The incidence and/or prevalence of health problems associated with endocrine-disruption have increased. Many chemicals have endocrine-disrupting properties, including bisphenol A, some organochlorines, polybrominated flame retardants, perfluorinated substances, alkylphenols, phthalates, pesticides, polycyclic aromatic hydrocarbons, alkylphenols, solvents, and some household products including some cleaning products, air fresheners, hair dyes, cosmetics, and sunscreens. Even some metals were shown to have endocrine-disrupting properties. Many observations suggesting that endocrine disruptors do contribute to cancer, diabetes, obesity, the metabolic syndrome, and infertility are listed in this paper. An overview is presented of mechanisms contributing to endocrine disruption. Endocrine disruptors can act through classical nuclear receptors, but also through estrogen-related receptors, membrane-bound estrogen-receptors, and interaction with targets in the cytosol resulting in activation of the Src/Ras/Erk pathway or modulation of nitric oxide. In addition, changes in metabolism of endogenous hormones, cross-talk between genomic and nongenomic pathways, cross talk with estrogen receptors after binding on other receptors, interference with feedback regulation and neuroendocrine cells, changes in DNA methylation or histone modifications, and genomic instability by interference with the spindle figure can play a role. Also it was found that effects of receptor activation can differ in function of the ligand.

  7. A Rat α-Fetoprotein Binding Activity Prediction Model to Facilitate Assessment of the Endocrine Disruption Potential of Environmental Chemicals.

    Science.gov (United States)

    Hong, Huixiao; Shen, Jie; Ng, Hui Wen; Sakkiah, Sugunadevi; Ye, Hao; Ge, Weigong; Gong, Ping; Xiao, Wenming; Tong, Weida

    2016-03-25

    Endocrine disruptors such as polychlorinated biphenyls (PCBs), diethylstilbestrol (DES) and dichlorodiphenyltrichloroethane (DDT) are agents that interfere with the endocrine system and cause adverse health effects. Huge public health concern about endocrine disruptors has arisen. One of the mechanisms of endocrine disruption is through binding of endocrine disruptors with the hormone receptors in the target cells. Entrance of endocrine disruptors into target cells is the precondition of endocrine disruption. The binding capability of a chemical with proteins in the blood affects its entrance into the target cells and, thus, is very informative for the assessment of potential endocrine disruption of chemicals. α-fetoprotein is one of the major serum proteins that binds to a variety of chemicals such as estrogens. To better facilitate assessment of endocrine disruption of environmental chemicals, we developed a model for α-fetoprotein binding activity prediction using the novel pattern recognition method (Decision Forest) and the molecular descriptors calculated from two-dimensional structures by Mold² software. The predictive capability of the model has been evaluated through internal validation using 125 training chemicals (average balanced accuracy of 69%) and external validations using 22 chemicals (balanced accuracy of 71%). Prediction confidence analysis revealed the model performed much better at high prediction confidence. Our results indicate that the model is useful (when predictions are in high confidence) in endocrine disruption risk assessment of environmental chemicals though improvement by increasing number of training chemicals is needed.

  8. Distribution of macular xanthophylls between domains in a model of photoreceptor outer segment membranes.

    Science.gov (United States)

    Wisniewska, Anna; Subczynski, Witold K

    2006-10-15

    A model of photoreceptor outer segment (POS) membranes has been proposed, consisting of an equimolar ternary mixture of 1-palmitoyl-2-docosahexaenoylphosphatidylcholine/distearoylphosphatidylcholine/cholesterol. It was shown that, as in membranes made from the raft-forming mixture, in the model of POS membranes, two domains are formed: the raft domain (detergent resistant membranes, DRM), and the bulk domain (detergent soluble membranes, DSM). Saturation-recovery EPR discrimination by oxygen transport method also demonstrated the presence of two domains in this model system in situ at a wide range of temperatures (10-55 degrees C), showing additionally that neither lutein nor zeaxanthin at 1 mol% affect the formation of these domains. These membrane domains have been separated using cold Triton X-100 extraction from a model of POS membranes containing 1 mol% of either lutein or zeaxanthin. The results indicated that the macular xanthophylls lutein and zeaxanthin are substantially excluded from DRM and remain concentrated in DSM, a domain enriched in highly unsaturated docosahexaenoyl acid which is abundant in retina membranes. The concentration of xanthophylls in DRM and DSM calculated as the mol ratio of either xanthophyll to total lipid (phospholipid+cholesterol) was 0.0028 and 0.0391, respectively. Thus, xanthophylls are about 14 times more concentrated in DSM than in DRM. No significant difference in the distribution of lutein and zeaxanthin was found. The obtained results suggest that in POS membranes macular xanthophylls should also be concentrated in domains enriched in polyunsaturated chains.

  9. Disruption mitigation studies in DIII-D

    International Nuclear Information System (INIS)

    Taylor, P.L.; Kellman, A.G.; Evans, T.E.

    1999-01-01

    Data on the discharge behavior, thermal loads, halo currents, and runaway electrons have been obtained in disruptions on the DIII-D tokamak. These experiments have also evaluated techniques to mitigate the disruptions while minimizing runaway electron production. Experiments injecting cryogenic impurity killer pellets of neon and argon and massive amounts of helium gas have successfully reduced these disruption effects. The halo current generation, scaling, and mitigation are understood and are in good agreement with predictions of a semianalytic model. Results from killer pellet injection have been used to benchmark theoretical models of the pellet ablation and energy loss. Runaway electrons are often generated by the pellets and new runaway generation mechanisms, modifications of the standard Dreicer process, have been found to explain the runaways. Experiments with the massive helium gas puff have also effectively mitigated disruptions without the formation of runaway electrons that can occur with killer pellets

  10. [Computer modeling the hydrostatic pressure characteristics of the membrane potential for polymeric membrane, separated non-homogeneous electrolyte solutions].

    Science.gov (United States)

    Slezak, Izabella H; Jasik-Slezak, Jolanta; Rogal, Mirosława; Slezak, Andrzej

    2006-01-01

    On the basis of model equation depending the membrane potential deltapsis, on mechanical pressure difference (deltaP), concentration polarization coefficient (zetas), concentration Rayleigh number (RC) and ratio concentration of solutions separated by membrane (Ch/Cl), the characteristics deltapsis = f(deltaP)zetas,RC,Ch/Cl for steady values of zetas, RC and Ch/Cl in single-membrane system were calculated. In this system neutral and isotropic polymeric membrane oriented in horizontal plane, the non-homogeneous binary electrolytic solutions of various concentrations were separated. Nonhomogeneity of solutions is results from creations of the concentration boundary layers on both sides of the membrane. Calculations were made for the case where on a one side of the membrane aqueous solution of NaCl at steady concentration 10(-3) mol x l(-1) (Cl) was placed and on the other aqueous solutions of NaCl at concentrations from 10(-3) mol x l(-1) to 2 x 10(-2) mol x l(-1) (Ch). Their densities were greater than NaCl solution's at 10(-3) mol x l(-1). It was shown that membrane potential depends on hydrodynamic state of a complex concentration boundary layer-membrane-concentration boundary layer, what is controlled by deltaP, Ch/Cl, RC and zetas.

  11. Induced mitochondrial membrane potential for modeling solitonic conduction of electrotonic signals.

    Directory of Open Access Journals (Sweden)

    R R Poznanski

    Full Text Available A cable model that includes polarization-induced capacitive current is derived for modeling the solitonic conduction of electrotonic potentials in neuronal branchlets with microstructure containing endoplasmic membranes. A solution of the nonlinear cable equation modified for fissured intracellular medium with a source term representing charge 'soakage' is used to show how intracellular capacitive effects of bound electrical charges within mitochondrial membranes can influence electrotonic signals expressed as solitary waves. The elastic collision resulting from a head-on collision of two solitary waves results in localized and non-dispersing electrical solitons created by the nonlinearity of the source term. It has been shown that solitons in neurons with mitochondrial membrane and quasi-electrostatic interactions of charges held by the microstructure (i.e., charge 'soakage' have a slower velocity of propagation compared with solitons in neurons with microstructure, but without endoplasmic membranes. When the equilibrium potential is a small deviation from rest, the nonohmic conductance acts as a leaky channel and the solitons are small compared when the equilibrium potential is large and the outer mitochondrial membrane acts as an amplifier, boosting the amplitude of the endogenously generated solitons. These findings demonstrate a functional role of quasi-electrostatic interactions of bound electrical charges held by microstructure for sustaining solitons with robust self-regulation in their amplitude through changes in the mitochondrial membrane equilibrium potential. The implication of our results indicate that a phenomenological description of ionic current can be successfully modeled with displacement current in Maxwell's equations as a conduction process involving quasi-electrostatic interactions without the inclusion of diffusive current. This is the first study in which solitonic conduction of electrotonic potentials are generated by

  12. Sideways wall force produced during tokamak disruptions

    Science.gov (United States)

    Strauss, H.; Paccagnella, R.; Breslau, J.; Sugiyama, L.; Jardin, S.

    2013-07-01

    A critical issue for ITER is to evaluate the forces produced on the surrounding conducting structures during plasma disruptions. We calculate the non-axisymmetric ‘sideways’ wall force Fx, produced in disruptions. Simulations were carried out of disruptions produced by destabilization of n = 1 modes by a vertical displacement event (VDE). The force depends strongly on γτwall, where γ is the mode growth rate and τwall is the wall penetration time, and is largest for γτwall = constant, which depends on initial conditions. Simulations of disruptions caused by a model of massive gas injection were also performed. It was found that the wall force increases approximately offset linearly with the displacement from the magnetic axis produced by a VDE. These results are also obtained with an analytical model. Disruptions are accompanied by toroidal variation of the plasma current Iφ. This is caused by toroidal variation of the halo current, as verified computationally and analytically.

  13. Overvoltage protection for magnetic system during disruption in tokamak

    International Nuclear Information System (INIS)

    Zhang, Ming; Li, Xiaolong; He, Yang; Zhang, Jun; Chen, Zhongyong; Yu, Kexun

    2015-01-01

    Highlights: • We investigate the way to limit the plasma disruption overvoltage by using the MOVs. • An overvoltage model of plasma disruption is introduced. • The overvoltage protection scheme has been verified by disruption experiments. • The overvoltage during plasma disruption can be limited to 330 V. - Abstract: During a plasma disruption the magnetic flux in the tokamak changes rapidly, which in most cases will cause high-voltage surges among the magnetic systems and may bring severe damage to the components if there is no overvoltage protection. This paper investigates the way to limit the plasma disruption overvoltage and absorb the energy with the use of metal oxide varistors (MOVs). An overvoltage model of plasma disruption is introduced which can be used for the simulation of plasma disruption and the analysis of the overvoltage. The effectiveness of the overvoltage protection system is validated with disruption experiments. It shows that by optimizing the varistors voltage, the overvoltage during plasma disruption can be limited to an ideal low value. Now the overvoltage protection system has been deployed in J-TEXT tokamak and serves well for daily experiments.

  14. Analysis and optimization of a proton exchange membrane fuel cell using modeling techniques

    International Nuclear Information System (INIS)

    Torre Valdés, Ing. Raciel de la; García Parra, MSc. Lázaro Roger; González Rodríguez, MSc. Daniel

    2015-01-01

    This paper proposes a three-dimensional, non-isothermal and steady-state model of Proton Exchange Membrane Fuel Cell using Computational Fluid Dynamic techniques, specifically ANSYS FLUENT 14.5. It's considered multicomponent diffusion and two-phasic flow. The model was compared with experimental published data and with another model. The operation parameters: reactants pressure and temperature, gases flow direction, gas diffusion layer and catalyst layer porosity, reactants humidification and oxygen concentration are analyzed. The model allows the fuel cell design optimization taking in consideration the channels dimensions, the channels length and the membrane thickness. Furthermore, fuel cell performance is analyzed working with SPEEK membrane, an alternative electrolyte to Nafion. In order to carry on membrane material study, it's necessary to modify the expression that describes the electrolyte ionic conductivity. It's found that the device performance has got a great sensibility to pressure, temperature, reactant humidification and oxygen concentration variations. (author)

  15. Interaction of multiple biomimetic antimicrobial polymers with model bacterial membranes

    Energy Technology Data Exchange (ETDEWEB)

    Baul, Upayan, E-mail: upayanb@imsc.res.in; Vemparala, Satyavani, E-mail: vani@imsc.res.in [The Institute of Mathematical Sciences, C.I.T. Campus, Taramani, Chennai 600113 (India); Kuroda, Kenichi, E-mail: kkuroda@umich.edu [Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan 48109 (United States)

    2014-08-28

    Using atomistic molecular dynamics simulations, interaction of multiple synthetic random copolymers based on methacrylates on prototypical bacterial membranes is investigated. The simulations show that the cationic polymers form a micellar aggregate in water phase and the aggregate, when interacting with the bacterial membrane, induces clustering of oppositely charged anionic lipid molecules to form clusters and enhances ordering of lipid chains. The model bacterial membrane, consequently, develops lateral inhomogeneity in membrane thickness profile compared to polymer-free system. The individual polymers in the aggregate are released into the bacterial membrane in a phased manner and the simulations suggest that the most probable location of the partitioned polymers is near the 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG) clusters. The partitioned polymers preferentially adopt facially amphiphilic conformations at lipid-water interface, despite lacking intrinsic secondary structures such as α-helix or β-sheet found in naturally occurring antimicrobial peptides.

  16. Enhanced biofouling resistance of polyethersulfone membrane surface modified with capsaicin derivative and itaconic acid

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jian [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100 (China); Gao, Xueli, E-mail: gxl_ouc@126.com [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100 (China); Wang, Qun; Sun, Haijing; Wang, Xiaojuan [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100 (China); Gao, Congjie, E-mail: gaocjie@ouc.edu.cn [Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Ocean University of China, Qingdao 266100 (China); College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100 (China)

    2015-11-30

    Graphical abstract: - Highlights: • PES membrane was modified with a capsaicin derivative. • UV-assisted graft polymerization was carried out on membrane surface. • The capsaicin derivative modified membrane shows better antibiofouling property. - Abstract: The culprit of biofouling is the reproduction of viable microorganisms on the membrane surface. Recently, functionalization of membrane surface with natural antibacterial agents has drawn great attention. This work presents the fabrication of antibiofouling polyethersulfone (PES) ultrafiltration (UF) membranes by UV-assisted photo grafting of capsaicin derivative (N-(4-hydroxy-3-methoxy-benzyl)-acrylamide, HMBA) and itaconic acid (IA) on the surface of PES membrane. Results of FTIR-ATR, water static contact angle (WSCA) and atomic force microscopy (AFM) analysis confirmed the successful grafting of HMBA and IA on the membrane surface. We investigated the antifouling and antibacterial properties of these membranes using BSA and Escherichia coli as the test model, respectively. During a 150-min test, the modified membranes show much lower flux decline (42.7% for PES-g-1H0I, 22.2% for PES-g-1H1I and 7.7% for PES-g-1H5I) when compared with the pristine membrane (flux declined by 77%). The modified membranes exhibit excellent antibacterial activity (nearly 100%) when UV irradiation time was 6 min. The morphological study suggested that the E. coli on the pristine membrane showed a regular and smooth surface while that on the modified membrane was disrupted, which validated the antibacterial activity of the modified membranes.

  17. Enhanced biofouling resistance of polyethersulfone membrane surface modified with capsaicin derivative and itaconic acid

    International Nuclear Information System (INIS)

    Wang, Jian; Gao, Xueli; Wang, Qun; Sun, Haijing; Wang, Xiaojuan; Gao, Congjie

    2015-01-01

    Graphical abstract: - Highlights: • PES membrane was modified with a capsaicin derivative. • UV-assisted graft polymerization was carried out on membrane surface. • The capsaicin derivative modified membrane shows better antibiofouling property. - Abstract: The culprit of biofouling is the reproduction of viable microorganisms on the membrane surface. Recently, functionalization of membrane surface with natural antibacterial agents has drawn great attention. This work presents the fabrication of antibiofouling polyethersulfone (PES) ultrafiltration (UF) membranes by UV-assisted photo grafting of capsaicin derivative (N-(4-hydroxy-3-methoxy-benzyl)-acrylamide, HMBA) and itaconic acid (IA) on the surface of PES membrane. Results of FTIR-ATR, water static contact angle (WSCA) and atomic force microscopy (AFM) analysis confirmed the successful grafting of HMBA and IA on the membrane surface. We investigated the antifouling and antibacterial properties of these membranes using BSA and Escherichia coli as the test model, respectively. During a 150-min test, the modified membranes show much lower flux decline (42.7% for PES-g-1H0I, 22.2% for PES-g-1H1I and 7.7% for PES-g-1H5I) when compared with the pristine membrane (flux declined by 77%). The modified membranes exhibit excellent antibacterial activity (nearly 100%) when UV irradiation time was 6 min. The morphological study suggested that the E. coli on the pristine membrane showed a regular and smooth surface while that on the modified membrane was disrupted, which validated the antibacterial activity of the modified membranes.

  18. Thymocyte plasma membrane of the rainbow trout, Salmo gairdneri: Associated immunoglobulin and heteroantigens

    Science.gov (United States)

    Warr, G.W.; DeLuca, D.; Anderson, D.P.

    1983-01-01

    1. Thymic lymphocytes of the rainbow trout, S. gairdneri were disrupted and a plasma membrane containing fraction isolated by differential and buoyant density centrifugation.2. Radioiodine introduced into the membrane by the lactoperoxidase catalyzed reaction and immunoglobulin (identified by radioimmunoassay with monoclonal antibody) both copurified in the plasma membrane fraction.3. Rabbit antibody raised to the plasma membrane fraction showed a strong reaction with trout lymphocytes in immunofluorescence, was mitogenic for trout lymphocytes, and recognized lymphocyte membrane heteroantigens of molecular weight > 70,000 in the thymus and 45,000–95,000 in the head kidney.

  19. On the study of catalytic membrane reactor for water detritiation: Modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Liger, Karine, E-mail: karine.liger@cea.fr [CEA, DEN, DTN/SMTA/LIPC Cadarache, Saint Paul-lez-Durance F-13108 (France); Mascarade, Jérémy [CEA, DEN, DTN/SMTA/LIPC Cadarache, Saint Paul-lez-Durance F-13108 (France); Joulia, Xavier; Meyer, Xuan-Mi [Université de Toulouse, INPT, UPS, Laboratoire de Génie Chimique, 4, Allée Emile Monso, Toulouse F-31030 (France); CNRS, Laboratoire de Génie Chimique, Toulouse F-31030 (France); Troulay, Michèle; Perrais, Christophe [CEA, DEN, DTN/SMTA/LIPC Cadarache, Saint Paul-lez-Durance F-13108 (France)

    2016-11-01

    Highlights: • Experimental results for the conversion of tritiated water (using deuterium as a simulant of tritium) by means of a catalytic membrane reactor in view of tritium recovery. • Phenomenological 2D model to represent catalytic membrane reactor behavior including the determination of the compositions of gaseous effluents. • Good agreement between the simulation results and experimental measurements performed on the dedicated facility. • Explanation of the unexpected behavior of the catalytic membrane reactor by the modeling results and in particular the gas composition estimation. - Abstract: In the framework of tritium recovery from tritiated water, efficiency of packed bed membrane reactors have been successfully demonstrated. Thanks to protium isotope swamping, tritium bonded water can be recovered under the valuable Q{sub 2} form (Q = H, D or T) by means of isotope exchange reactions occurring on catalyst surface. The use of permselective Pd-based membrane allows withdrawal of reactions products all along the reactor, and thus limits reverse reaction rate to the benefit of the direct one (shift effect). The reactions kinetics, which are still little known or unknown, are generally assumed to be largely greater than the permeation ones so that thermodynamic equilibriums of isotope exchange reactions are generally assumed. This paper proposes a new phenomenological 2D model to represent catalytic membrane reactor behavior with the determination of gas effluents compositions. A good agreement was obtained between the simulation results and experimental measurements performed on a dedicated facility. Furthermore, the gas composition estimation permits to interpret unexpected behavior of the catalytic membrane reactor. In the next future, further sensitivity analysis will be performed to determine the limits of the model and a kinetics study will be conducted to assess the thermodynamic equilibrium of reactions.

  20. On the study of catalytic membrane reactor for water detritiation: Modeling approach

    International Nuclear Information System (INIS)

    Liger, Karine; Mascarade, Jérémy; Joulia, Xavier; Meyer, Xuan-Mi; Troulay, Michèle; Perrais, Christophe

    2016-01-01

    Highlights: • Experimental results for the conversion of tritiated water (using deuterium as a simulant of tritium) by means of a catalytic membrane reactor in view of tritium recovery. • Phenomenological 2D model to represent catalytic membrane reactor behavior including the determination of the compositions of gaseous effluents. • Good agreement between the simulation results and experimental measurements performed on the dedicated facility. • Explanation of the unexpected behavior of the catalytic membrane reactor by the modeling results and in particular the gas composition estimation. - Abstract: In the framework of tritium recovery from tritiated water, efficiency of packed bed membrane reactors have been successfully demonstrated. Thanks to protium isotope swamping, tritium bonded water can be recovered under the valuable Q_2 form (Q = H, D or T) by means of isotope exchange reactions occurring on catalyst surface. The use of permselective Pd-based membrane allows withdrawal of reactions products all along the reactor, and thus limits reverse reaction rate to the benefit of the direct one (shift effect). The reactions kinetics, which are still little known or unknown, are generally assumed to be largely greater than the permeation ones so that thermodynamic equilibriums of isotope exchange reactions are generally assumed. This paper proposes a new phenomenological 2D model to represent catalytic membrane reactor behavior with the determination of gas effluents compositions. A good agreement was obtained between the simulation results and experimental measurements performed on a dedicated facility. Furthermore, the gas composition estimation permits to interpret unexpected behavior of the catalytic membrane reactor. In the next future, further sensitivity analysis will be performed to determine the limits of the model and a kinetics study will be conducted to assess the thermodynamic equilibrium of reactions.

  1. Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability.

    Science.gov (United States)

    Smith, Alyson S; Nowak, Roberta B; Zhou, Sitong; Giannetto, Michael; Gokhin, David S; Papoin, Julien; Ghiran, Ionita C; Blanc, Lionel; Wan, Jiandi; Fowler, Velia M

    2018-05-08

    The biconcave disk shape and deformability of mammalian RBCs rely on the membrane skeleton, a viscoelastic network of short, membrane-associated actin filaments (F-actin) cross-linked by long, flexible spectrin tetramers. Nonmuscle myosin II (NMII) motors exert force on diverse F-actin networks to control cell shapes, but a function for NMII contractility in the 2D spectrin-F-actin network of RBCs has not been tested. Here, we show that RBCs contain membrane skeleton-associated NMIIA puncta, identified as bipolar filaments by superresolution fluorescence microscopy. MgATP disrupts NMIIA association with the membrane skeleton, consistent with NMIIA motor domains binding to membrane skeleton F-actin and contributing to membrane mechanical properties. In addition, the phosphorylation of the RBC NMIIA heavy and light chains in vivo indicates active regulation of NMIIA motor activity and filament assembly, while reduced heavy chain phosphorylation of membrane skeleton-associated NMIIA indicates assembly of stable filaments at the membrane. Treatment of RBCs with blebbistatin, an inhibitor of NMII motor activity, decreases the number of NMIIA filaments associated with the membrane and enhances local, nanoscale membrane oscillations, suggesting decreased membrane tension. Blebbistatin-treated RBCs also exhibit elongated shapes, loss of membrane curvature, and enhanced deformability, indicating a role for NMIIA contractility in promoting membrane stiffness and maintaining RBC biconcave disk cell shape. As structures similar to the RBC membrane skeleton exist in many metazoan cell types, these data demonstrate a general function for NMII in controlling specialized membrane morphology and mechanical properties through contractile interactions with short F-actin in spectrin-F-actin networks.

  2. Disruption of steroidogenesis: Cell models for mechanistic investigations and as screening tools.

    Science.gov (United States)

    Odermatt, Alex; Strajhar, Petra; Engeli, Roger T

    2016-04-01

    In the modern world, humans are exposed during their whole life to a large number of synthetic chemicals. Some of these chemicals have the potential to disrupt endocrine functions and contribute to the development and/or progression of major diseases. Every year approximately 1000 novel chemicals, used in industrial production, agriculture, consumer products or as pharmaceuticals, are reaching the market, often with limited safety assessment regarding potential endocrine activities. Steroids are essential endocrine hormones, and the importance of the steroidogenesis pathway as a target for endocrine disrupting chemicals (EDCs) has been recognized by leading scientists and authorities. Cell lines have a prominent role in the initial stages of toxicity assessment, i.e. for mechanistic investigations and for the medium to high throughput analysis of chemicals for potential steroidogenesis disrupting activities. Nevertheless, the users have to be aware of the limitations of the existing cell models in order to apply them properly, and there is a great demand for improved cell-based testing systems and protocols. This review intends to provide an overview of the available cell lines for studying effects of chemicals on gonadal and adrenal steroidogenesis, their use and limitations, as well as the need for future improvements of cell-based testing systems and protocols. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Action spectrum for photochemical retinal pigment epithelium (RPE) disruption in an in vivo monkey model

    Science.gov (United States)

    Zhang, Jie; Sabarinathan, Ranjani; Bubel, Tracy; Williams, David R.; Hunter, Jennifer J.

    2016-03-01

    Observations of RPE disruption and autofluorescence (AF) photobleaching at light levels below the ANSI photochemical maximum permissible exposure (MPE) (Morgan et al., 2008) indicates a demand to modify future light safety standards to protect the retina from harm. To establish safe light exposures, we measured the visible light action spectrum for RPE disruption in an in vivo monkey model with fluorescence adaptive optics retinal imaging. Using this high resolution imaging modality can provide insight into the consequences of light on a cellular level and allow for longitudinal monitoring of retinal changes. The threshold retinal radiant exposures (RRE) for RPE disruption were determined for 4 wavelengths (460, 488, 544, and 594 nm). The anaesthetized macaque retina was exposed to a uniform 0.5° × 0.5° field of view (FOV). Imaging within a 2° × 2° FOV was performed before, immediately after and at 2 week intervals for 10 weeks. At each wavelength, multiple RREs were tested with 4 repetitions each to determine the threshold for RPE disruption. For qualitative analysis, RPE disruption is defined as any detectable change from the pre exposure condition in the cell mosaic in the exposed region relative to the corresponding mosaic in the immediately surrounding area. We have tested several metrics to evaluate the RPE images obtained before and after exposure. The measured action spectrum for photochemical RPE disruption has a shallower slope than the current ANSI photochemical MPE for the same conditions and suggests that longer wavelength light is more hazardous than other measurements would suggest.

  4. A Finite Element Solution of Lateral Periodic Poisson–Boltzmann Model for Membrane Channel Proteins

    Science.gov (United States)

    Xu, Jingjie; Lu, Benzhuo

    2018-01-01

    Membrane channel proteins control the diffusion of ions across biological membranes. They are closely related to the processes of various organizational mechanisms, such as: cardiac impulse, muscle contraction and hormone secretion. Introducing a membrane region into implicit solvation models extends the ability of the Poisson–Boltzmann (PB) equation to handle membrane proteins. The use of lateral periodic boundary conditions can properly simulate the discrete distribution of membrane proteins on the membrane plane and avoid boundary effects, which are caused by the finite box size in the traditional PB calculations. In this work, we: (1) develop a first finite element solver (FEPB) to solve the PB equation with a two-dimensional periodicity for membrane channel proteins, with different numerical treatments of the singular charges distributions in the channel protein; (2) add the membrane as a dielectric slab in the PB model, and use an improved mesh construction method to automatically identify the membrane channel/pore region even with a tilt angle relative to the z-axis; and (3) add a non-polar solvation energy term to complete the estimation of the total solvation energy of a membrane protein. A mesh resolution of about 0.25 Å (cubic grid space)/0.36 Å (tetrahedron edge length) is found to be most accurate in linear finite element calculation of the PB solvation energy. Computational studies are performed on a few exemplary molecules. The results indicate that all factors, the membrane thickness, the length of periodic box, membrane dielectric constant, pore region dielectric constant, and ionic strength, have individually considerable influence on the solvation energy of a channel protein. This demonstrates the necessity to treat all of those effects in the PB model for membrane protein simulations. PMID:29495644

  5. Electrical Thermal Network for Direct Contact Membrane Distillation Modeling and Analysis

    KAUST Repository

    Karam, Ayman M.

    2015-02-04

    Membrane distillation is an emerging water distillation technology that offers several advantages compared to conventional water desalination processes. Although progress has been made to model and understand the physics of the process, many studies are based on steady-state assumptions or are computationally not appropriate for real time control. This paper presents the derivation of a novel dynamical model, based on analogy between electrical and thermal systems, for direct contact membrane distillation (DCMD). The proposed model captures the dynamics of temperature distribution and distilled water flux. To demonstrate the adequacy of the proposed model, validation with transient and steady-state experimental data is presented.

  6. Cadmium Disrupts Subcellular Organelles, Including Chloroplasts, Resulting in Melatonin Induction in Plants

    Directory of Open Access Journals (Sweden)

    Hyoung-Yool Lee

    2017-10-01

    Full Text Available Cadmium is a well-known elicitor of melatonin synthesis in plants, including rice. However, the mechanisms by which cadmium induces melatonin induction remain elusive. To investigate whether cadmium influences physical integrities in subcellular organelles, we treated tobacco leaves with either CdCl2 or AlCl3 and monitored the structures of subcellular organelles—such as chloroplasts, mitochondria, and the endoplasmic reticulum (ER—using confocal microscopic analysis. Unlike AlCl3 treatment, CdCl2 (0.5 mM treatment significantly disrupted chloroplasts, mitochondria, and ER. In theory, the disruption of chloroplasts enabled chloroplast-expressed serotonin N-acetyltransferase (SNAT to encounter serotonin in the cytoplasm, leading to the synthesis of N-acetylserotonin followed by melatonin synthesis. In fact, the disruption of chloroplasts by cadmium, not by aluminum, gave rise to a huge induction of melatonin in rice leaves, which suggests that cadmium-treated chloroplast disruption plays an important role in inducing melatonin in plants by removing physical barriers, such as chloroplast double membranes, allowing SNAT to gain access to the serotonin substrate enriched in the cytoplasm.

  7. Practice Oriented Algorithmic Disruption Management in Passenger Railways

    NARCIS (Netherlands)

    J.C. Wagenaar (Joris)

    2016-01-01

    markdownabstractHow to deal with a disruption is a question railway companies face on a daily basis. This thesis focusses on the subject how to handle a disruption such that the passenger service is upheld as much as possible. The current mathematical models for disruption management can not yet be

  8. Converting differential-equation models of biological systems to membrane computing.

    Science.gov (United States)

    Muniyandi, Ravie Chandren; Zin, Abdullah Mohd; Sanders, J W

    2013-12-01

    This paper presents a method to convert the deterministic, continuous representation of a biological system by ordinary differential equations into a non-deterministic, discrete membrane computation. The dynamics of the membrane computation is governed by rewrite rules operating at certain rates. That has the advantage of applying accurately to small systems, and to expressing rates of change that are determined locally, by region, but not necessary globally. Such spatial information augments the standard differentiable approach to provide a more realistic model. A biological case study of the ligand-receptor network of protein TGF-β is used to validate the effectiveness of the conversion method. It demonstrates the sense in which the behaviours and properties of the system are better preserved in the membrane computing model, suggesting that the proposed conversion method may prove useful for biological systems in particular. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  9. Electrostatic models of electron-driven proton transfer across a lipid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, Anatoly Yu; Nori, Franco [Advanced Science Institute, RIKEN, Wako-shi, Saitama, 351-0198 (Japan); Mourokh, Lev G [Department of Physics, Queens College, The City University of New York, Flushing, NY 11367 (United States)

    2011-06-15

    We present two models for electron-driven uphill proton transport across lipid membranes, with the electron energy converted to the proton gradient via the electrostatic interaction. In the first model, associated with the cytochrome c oxidase complex in the inner mitochondria membranes, the electrostatic coupling to the site occupied by an electron lowers the energy level of the proton-binding site, making proton transfer possible. In the second model, roughly describing the redox loop in a nitrate respiration of E. coli bacteria, an electron displaces a proton from the negative side of the membrane to a shuttle, which subsequently diffuses across the membrane and unloads the proton to its positive side. We show that both models can be described by the same approach, which can be significantly simplified if the system is separated into several clusters, with strong Coulomb interaction inside each cluster and weak transfer couplings between them. We derive and solve the equations of motion for the electron and proton creation/annihilation operators, taking into account the appropriate Coulomb terms, tunnel couplings, and the interaction with the environment. For the second model, these equations of motion are solved jointly with a Langevin-type equation for the shuttle position. We obtain expressions for the electron and proton currents and determine their dependence on the electron and proton voltage build-ups, on-site charging energies, reorganization energies, temperature, and other system parameters. We show that the quantum yield in our models can be up to 100% and the power-conversion efficiency can reach 35%.

  10. Electrostatic models of electron-driven proton transfer across a lipid membrane

    International Nuclear Information System (INIS)

    Smirnov, Anatoly Yu; Nori, Franco; Mourokh, Lev G

    2011-01-01

    We present two models for electron-driven uphill proton transport across lipid membranes, with the electron energy converted to the proton gradient via the electrostatic interaction. In the first model, associated with the cytochrome c oxidase complex in the inner mitochondria membranes, the electrostatic coupling to the site occupied by an electron lowers the energy level of the proton-binding site, making proton transfer possible. In the second model, roughly describing the redox loop in a nitrate respiration of E. coli bacteria, an electron displaces a proton from the negative side of the membrane to a shuttle, which subsequently diffuses across the membrane and unloads the proton to its positive side. We show that both models can be described by the same approach, which can be significantly simplified if the system is separated into several clusters, with strong Coulomb interaction inside each cluster and weak transfer couplings between them. We derive and solve the equations of motion for the electron and proton creation/annihilation operators, taking into account the appropriate Coulomb terms, tunnel couplings, and the interaction with the environment. For the second model, these equations of motion are solved jointly with a Langevin-type equation for the shuttle position. We obtain expressions for the electron and proton currents and determine their dependence on the electron and proton voltage build-ups, on-site charging energies, reorganization energies, temperature, and other system parameters. We show that the quantum yield in our models can be up to 100% and the power-conversion efficiency can reach 35%.

  11. Decision on risk-averse dual-channel supply chain under demand disruption

    Science.gov (United States)

    Yan, Bo; Jin, Zijie; Liu, Yanping; Yang, Jianbo

    2018-02-01

    We studied dual-channel supply chains using centralized and decentralized decision-making models. We also conducted a comparative analysis of the decisions before and after demand disruption. The study shows that the amount of change in decision-making is a linear function of the amount of demand disruption, and it is independent of the risk-averse coefficient. The optimal sales volume decision of the disturbing supply chain is related to market share and demand disruption in the decentralized decision-making model. The optimal decision is only influenced by demand disruption in the centralized decision-making model. The stability of the sales volume of the two models is related to market share and demand disruption. The optimal system production of the two models shows robustness, but their stable internals are different.

  12. Disruption Physics and Mitigation on DIII-D

    International Nuclear Information System (INIS)

    Whyte, D.G.; Humphreys, D.A.; Kellman, A.G.

    2005-01-01

    The contributions of the DIII-D tokamak toward the understanding and control of disruptions are reviewed. Disruptions are found to be deterministic, and the underlying causes of disruption can therefore be predicted and avoided. With sufficiently rapid detection, possible damage from disruptions can be mitigated using an understanding of disruption phenomenology and plasma physics. Regimes of high β are readily available in DIII-D and provide access to relatively high energy density disruptions, despite DIII-D's moderate magnetic field and size. DIII-D, with all-graphite wall armor and wall conditioning between discharges, has proven highly resilient to the deleterious effects that disruptions can have on plasma operations. Simultaneously, exploitation and adaptation of DIII-D's extensive core and edge plasma diagnostic set have allowed for unique plasma measurements during disruptions. These measurements have tied into the development of several physical models used to understand aspects of disruptions, such as magnetohydrodynamic growth at the disruption onset, radiation energy balance through the thermal quench, and halo currents during the current quench. Based on this fundamental understanding, DIII-D has developed techniques to mitigate the harmful effects of disruptions by radiative dissipation of the plasma energy and extrapolated these techniques for possible use on larger devices like ITER

  13. Exploring the Spatiotemporal Organization of Membrane Proteins in Living Plant Cells.

    Science.gov (United States)

    Wang, Li; Xue, Yiqun; Xing, Jingjing; Song, Kai; Lin, Jinxing

    2018-04-29

    Plasma membrane proteins have important roles in transport and signal transduction. Deciphering the spatiotemporal organization of these proteins provides crucial information for elucidating the links between the behaviors of different molecules. However, monitoring membrane proteins without disrupting their membrane environment remains difficult. Over the past decade, many studies have developed single-molecule techniques, opening avenues for probing the stoichiometry and interactions of membrane proteins in their native environment by providing nanometer-scale spatial information and nanosecond-scale temporal information. In this review, we assess recent progress in the development of labeling and imaging technology for membrane protein analysis. We focus in particular on several single-molecule techniques for quantifying the dynamics and assembly of membrane proteins. Finally, we provide examples of how these new techniques are advancing our understanding of the complex biological functions of membrane proteins.

  14. Aroma Stripping under various Forms of Membrane Distillation Processes: Experiments and modeling

    DEFF Research Database (Denmark)

    Jonsson, Gunnar Eigil

    Concentration of fruit juices by membrane distillation is an interesting process as it can be done at low temperature giving a gentle concentration process with little deterioration of the juices. Since the juices contains many different aroma compounds with a wide range of chemical properties...... such as volatility, activity coefficient and vapor pressure, it is important to know how these aroma compounds will eventually pass through the membrane. Experiments have been made on an aroma model solution and on black currant juice in a lab scale membrane distillation set up which can be operated in various types...... of MD configurations: Vacuum Membrane Distillation , Sweeping Gas Membrane Distillation , Direct Contact Membrane Distillation and Osmotic Membrane Distillation. The influence of feed temperature and feed flow rate on the permeate flux and concentration factor for different types of aroma compounds have...

  15. Current density distribution during disruptions and sawteeth in a simple model of plasma current in a tokamak

    International Nuclear Information System (INIS)

    Stefanovskii, A. M.

    2011-01-01

    The processes that are likely to accompany discharge disruptions and sawteeth in a tokamak are considered in a simple plasma current model. The redistribution of the current density in plasma is supposed to be primarily governed by the onset of the MHD-instability-driven turbulent plasma mixing in a finite region of the current column. For different disruption conditions, the variation in the total plasma current (the appearance of a characteristic spike) is also calculated. It is found that the numerical shape and amplitude of the total current spikes during disruptions approximately coincide with those measured in some tokamak experiments. Under the assumptions adopted in the model, the physical mechanism for the formation of the spikes is determined. The mechanism is attributed to the diffusion of the negative current density at the column edge into the zero-conductivity region. The numerical current density distributions in the plasma during the sawteeth differ from the literature data.

  16. Disrupted cortical connectivity theory as an explanatory model for autism spectrum disorders.

    Science.gov (United States)

    Kana, Rajesh K; Libero, Lauren E; Moore, Marie S

    2011-12-01

    as Theory-of-Mind, cognitive flexibility, and information processing; and 2) how connection abnormalities relate to, and may determine, behavioral symptoms hallmarked by the triad of Impairments in ASD. Furthermore, we will relate the disrupted cortical connectivity model to existing cognitive and neural models of ASD. Published by Elsevier B.V.

  17. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  18. Membrane Vesicles of Group B Streptococcus Disrupt Feto-Maternal Barrier Leading to Preterm Birth.

    Directory of Open Access Journals (Sweden)

    Manalee Vishnu Surve

    2016-09-01

    Full Text Available Infection of the genitourinary tract with Group B Streptococcus (GBS, an opportunistic gram positive pathogen, is associated with premature rupture of amniotic membrane and preterm birth. In this work, we demonstrate that GBS produces membrane vesicles (MVs in a serotype independent manner. These MVs are loaded with virulence factors including extracellular matrix degrading proteases and pore forming toxins. Mice chorio-decidual membranes challenged with MVs ex vivo resulted in extensive collagen degradation leading to loss of stiffness and mechanical weakening. MVs when instilled vaginally are capable of anterograde transport in mouse reproductive tract. Intra-amniotic injections of GBS MVs in mice led to upregulation of pro-inflammatory cytokines and inflammation mimicking features of chorio-amnionitis; it also led to apoptosis in the chorio-decidual tissue. Instillation of MVs in the amniotic sac also resulted in intrauterine fetal death and preterm delivery. Our findings suggest that GBS MVs can independently orchestrate events at the feto-maternal interface causing chorio-amnionitis and membrane damage leading to preterm birth or fetal death.

  19. Membrane Vesicles of Group B Streptococcus Disrupt Feto-Maternal Barrier Leading to Preterm Birth

    Science.gov (United States)

    Sthanam, Lakshmi Kavitha; Srivastava, Rohit; Basu, Bhakti; Dutta, Suryendu; Sen, Shamik; Modi, Deepak

    2016-01-01

    Infection of the genitourinary tract with Group B Streptococcus (GBS), an opportunistic gram positive pathogen, is associated with premature rupture of amniotic membrane and preterm birth. In this work, we demonstrate that GBS produces membrane vesicles (MVs) in a serotype independent manner. These MVs are loaded with virulence factors including extracellular matrix degrading proteases and pore forming toxins. Mice chorio-decidual membranes challenged with MVs ex vivo resulted in extensive collagen degradation leading to loss of stiffness and mechanical weakening. MVs when instilled vaginally are capable of anterograde transport in mouse reproductive tract. Intra-amniotic injections of GBS MVs in mice led to upregulation of pro-inflammatory cytokines and inflammation mimicking features of chorio-amnionitis; it also led to apoptosis in the chorio-decidual tissue. Instillation of MVs in the amniotic sac also resulted in intrauterine fetal death and preterm delivery. Our findings suggest that GBS MVs can independently orchestrate events at the feto-maternal interface causing chorio-amnionitis and membrane damage leading to preterm birth or fetal death. PMID:27583406

  20. Modeling Of Proton Exchange Membrane Fuel Cell Systems

    DEFF Research Database (Denmark)

    Nielsen, Mads Pagh

    The objective of this doctoral thesis was to develop reliable steady-state and transient component models suitable to asses-, develop- and optimize proton exchange membrane (PEM) fuel cell systems. Several components in PEM fuel cell systems were characterized and modeled. The developed component...... cell systems. Consequences of indirectly fueling PEM stacks with hydrocarbons using reforming technology were investigated using a PEM stack model including CO poisoning kinetics and a transient Simulink steam reforming system model. Aspects regarding the optimization of PEM fuel cell systems...

  1. Phenomenology of high density disruptions in the TFTR tokamak

    International Nuclear Information System (INIS)

    Fredrickson, E.D.; McGuire, K.M.; Bell, M.G.

    1993-01-01

    Studies of high density disruptions on TFTR, including a comparison of minor and major disruptions at high density, provide important new information regarding the nature of the disruption mechanism. Further, for the first time, an (m,n)=(1,1) 'cold bubble' precursor to high density disruptions has been experimentally observed in the electron temperature profile. The precursor to major disruptions resembles the 'vacuum bubble' model of disruptions first proposed by B.B. Kadomtsev and O.P. Pogutse (Sov. Phys. - JETP 38 (1974) 283). (author). Letter-to-the-editor. 25 refs, 3 figs

  2. Sleep disruption increases seizure susceptibility: Behavioral and EEG evaluation of an experimental model of sleep apnea.

    Science.gov (United States)

    Hrnčić, Dragan; Grubač, Željko; Rašić-Marković, Aleksandra; Šutulović, Nikola; Šušić, Veselinka; Bjekić-Macut, Jelica; Stanojlović, Olivera

    2016-03-01

    Sleep disruption accompanies sleep apnea as one of its major symptoms. Obstructive sleep apnea is particularly common in patients with refractory epilepsy, but causing factors underlying this are far from being resolved. Therefore, translational studies regarding this issue are important. Our aim was to investigate the effects of sleep disruption on seizure susceptibility of rats using experimental model of lindane-induced refractory seizures. Sleep disruption in male Wistar rats with implanted EEG electrodes was achieved by treadmill method (belt speed set on 0.02 m/s for working and 0.00 m/s for stop mode, respectively). Animals were assigned to experimental conditions lasting 6h: 1) sleep disruption (sleep interrupted, SI; 30s working and 90 s stop mode every 2 min; 180 cycles in total); 2) activity control (AC, 10 min working and 30 min stop mode, 9 cycles in total); 3) treadmill chamber control (TC, only stop mode). Afterwards, the animals were intraperitoneally treated with lindane (L, 4 mg/kg, SI+L, AC+L and TC+L groups) or dimethylsulfoxide (DMSO, SIc, ACc and TCc groups). Convulsive behavior was assessed by seizure incidence, latency time to first seizure, and its severity during 30 min after drug administration. Number and duration of ictal periods were determined in recorded EEGs. Incidence and severity of lindane-induced seizures were significantly increased, latency time significantly decreased in animals undergoing sleep disruption (SI+L group) compared with the animals from TC+L. Seizure latency was also significantly decreased in SI+L compared to AC+L groups. Number of ictal periods were increased and duration of it presented tendency to increase in SI+L comparing to AC+L. No convulsive signs were observed in TCc, ACc and SIc groups, as well as no ictal periods in EEG. These results indicate sleep disruption facilitates induction of epileptic activity in rodent model of lindane-epilepsy enabling translational research of this phenomenon. Copyright

  3. Two-dimensional analytical model of a proton exchange membrane fuel cell

    International Nuclear Information System (INIS)

    Liu, Jia Xing; Guo, Hang; Ye, Fang; Ma, Chong Fang

    2017-01-01

    In this study, a two-dimensional full cell analytical model of a proton exchange membrane fuel cell is developed. The analytical model describes electrochemical reactions on the anode and cathode catalyst layer, reactants diffusion in the gas diffusion layer, and gases flow in the gas channel, etc. The analytical solution is derived according to the basic physical equations. The performance predicted by the model is in good agreement with the experimental data. The results show that the polarization mainly occurs in the cathode side of the proton exchange membrane fuel cell. The anodic overpotential cannot be neglected. The hydrogen and oxygen concentrations decrease along the channel flow direction. The hydrogen and oxygen concentrations in the catalyst layer decrease with the current density. As predicted by the model, concentration polarization mainly occurs in the cathode side. - Highlights: • A 2D full cell analytical model of a proton exchange membrane fuel cell is developed. • The analytical solution is deduced according to the basic equations. • The anode overpotential is not so small that it cannot be neglected. • Species concentration distributions in the fuel cell is obtained and analyzed.

  4. Business Model as an Inducer of Disruptive Innovations: The Case of Gol Airlines

    OpenAIRE

    Pereira, Sirlei de Almeida; Imbrizi, Fabricio Garcia; de Freitas, Alessandra Demite Goncalves; Alvarenga, Marcelo Aparecido

    2015-01-01

    This study was undertaken to investigate the premises that the success of disruptive innovation is related to the business model adopted by organizations. An analysis of five business models from the literature review - Bovet and Martha (2000), Applegate (2001), Chesbrough and Rosenbloom (2002), Osterwalder and Pigneur (2010), and Rodrigues, Maccari and Lenzi (2012) – was conducted based on the case of the Brazilian Gol Airlines who is recognized as a success business that promoted a disrupti...

  5. Isolation of plasma membranes from cultured glioma cells and application to evaluation of membrane sphingomyelin turnover

    International Nuclear Information System (INIS)

    Cook, H.W.; Palmer, F.B.; Byers, D.M.; Spence, M.W.

    1988-01-01

    A rapid and reliable method for the isolation of plasma membranes and microsomes of high purity and yield from cultured glioma cells is described. The procedure involves disruption by N2 cavitation, preliminary separation by centrifugation in Tricine buffer, and final separation on a gradient formed from 40% Percoll at pH 9.3. Enzyme and chemical markers indicated greater than 60% yield with six- to eightfold enrichment for plasma membranes and greater than 25% yield with three- to fourfold enrichment for a microsomal fraction consisting mainly of endoplasmic reticulum. The final fractions were obtained with high reproducibility in less than 1 h from the time of cell harvesting. Application of this procedure to human fibroblasts in culture is assessed. The isolation procedure was applied to investigations of synthesis and turnover of sphingomyelin and phosphatidylcholine in plasma membranes of glioma cells following incubation for 4-24 h with [methyl- 3 H]choline. These studies indicated that radioactivity from phosphatidylcholine synthesized in microsomes from exogenous choline may serve as a precursor of the head-group of sphingomyelin accumulating in the plasma membrane

  6. DSTAR: A comprehensive tokamak resistive disruption model for vacuum vessel components

    International Nuclear Information System (INIS)

    Merrill, B.J.; Jardin, S.C.

    1987-01-01

    A computer code, DSTAR, has recently been developed to quantify the surface erosion and induced forces than can occur during major tokamak plasma disruptions. A disruption analysis has been performed for the TFCX fusion device. The limiters and inboard first wall were assumed to be clad with beryllium. Disruption simulations were performed with and without these structures present, to determine their electromagnetic influence. The results with structure show that the ablated wall material is transported poloidally, as well as radially, in the plasma causing the outermost regions of the plasma to cool. The plasma moves downward and deforms while maintaining contact with the lower limiter. This motion maintains the peak impurity radiant source directly above the exposed surface. For the disruption simulation without the vacuum vessel included, the plasma moves radially along the lower limiter until it contacts the inboard wall, causing ablation of this surface as well. The conclusion is drawn that disruption simulations that do not include both the thermal and electromagnetic response of the vaccum vessel will not result in an accurate prediction. (orig.)

  7. Pursuing minimally disruptive medicine: disruption from illness and health care-related demands is correlated with patient capacity.

    Science.gov (United States)

    Boehmer, Kasey R; Shippee, Nathan D; Beebe, Timothy J; Montori, Victor M

    2016-06-01

    Chronic conditions burden patients with illness and treatments. We know little about the disruption of life by the work of dialysis in relation to the resources patients can mobilize, that is, their capacity, to deal with such demands. We sought to determine the disruption of life by dialysis and its relation to patient capacity to cope. We administered a survey to 137 patients on dialysis at an academic medical center. We captured disruption from illness and treatment, and physical, mental, personal, social, financial, and environmental aspects of patient capacity using validated scales. Covariates included number of prescriptions, hours spent on health care, existence of dependents, age, sex, and income level. On average, patients reported levels of capacity and disruption comparable to published levels. In multivariate regression models, limited physical, financial, and mental capacity were significantly associated with greater disruption. Patients in the top quartile of disruption had lower-than-expected physical, financial, and mental capacity. Our sample generally had capacity comparable to other populations and may be able to meet the demands imposed by treatment. Those with reduced physical, financial, and mental capacity reported higher disruption and represent a vulnerable group that may benefit from innovations in minimally disruptive medicine. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  8. Actin filaments growing against an elastic membrane: Effect of membrane tension

    Science.gov (United States)

    Sadhu, Raj Kumar; Chatterjee, Sakuntala

    2018-03-01

    We study the force generation by a set of parallel actin filaments growing against an elastic membrane. The elastic membrane tries to stay flat and any deformation from this flat state, either caused by thermal fluctuations or due to protrusive polymerization force exerted by the filaments, costs energy. We study two lattice models to describe the membrane dynamics. In one case, the energy cost is assumed to be proportional to the absolute magnitude of the height gradient (gradient model) and in the other case it is proportional to the square of the height gradient (Gaussian model). For the gradient model we find that the membrane velocity is a nonmonotonic function of the elastic constant μ and reaches a peak at μ =μ* . For μ membrane energy keeps increasing with time. For the Gaussian model, the system always reaches a steady state and the membrane velocity decreases monotonically with the elastic constant ν for all nonzero values of ν . Multiple filaments give rise to protrusions at different regions of the membrane and the elasticity of the membrane induces an effective attraction between the two protrusions in the Gaussian model which causes the protrusions to merge and a single wide protrusion is present in the system. In both the models, the relative time scale between the membrane and filament dynamics plays an important role in deciding whether the shape of elasticity-velocity curve is concave or convex. Our numerical simulations agree reasonably well with our analytical calculations.

  9. Transmembrane helices can induce domain formation in crowded model membranes

    NARCIS (Netherlands)

    Domanski, Jan; Marrink, Siewert J.; Schäfer, Lars V.

    We studied compositionally heterogeneous multi-component model membranes comprised of saturated lipids, unsaturated lipids, cholesterol, and a-helical TM protein models using coarse-grained molecular dynamics simulations. Reducing the mismatch between the length of the saturated and unsaturated

  10. Visual in-pile fuel disruption experiments

    International Nuclear Information System (INIS)

    Cano, G.L.; Ostensen, R.W.; Young, M.F.

    1978-01-01

    In a loss-of-flow (LOF) accident in an LMFBR, the mode of disruption of fuel may determine the probability of a subsequent energetic excursion. To investigate these phenomena, in-pile disruption of fission-heated irradiated fuel pellets was recorded by high speed cinematography. Instead of fuel frothing or dust-cloud breakup (as used in the SAS code) massive and very rapid fuel swelling, not predicted by analytical models, occurred. These tests support massive fuel swelling as the initial mode of fuel disruption in a LOF accident. (author)

  11. Relating transport modeling to nanofiltration membrane fabrication: Navigating the permeability-selectivity trade-off in desalination pretreatment

    OpenAIRE

    Labban, Omar; Lienhard, John H

    2018-01-01

    Faced with a pressing need for membranes with a higher permeability and selectivity, the field of membrane technology can benefit from a systematic framework for designing membranes with the necessary physical characteristics. In this work, we present an approach through which transport modeling is employed in fabricating specialized nanofiltration membranes, that experimentally demonstrate enhanced selectivity. Specifically, the Donnan-Steric Pore Model with dielectric exclusion (DSPM-DE) is...

  12. Interaction of abscisic acid with phospholipid membranes

    International Nuclear Information System (INIS)

    Stillwell, W.; Brengle, B.; Hester, P.; Wassall, S.T.

    1989-01-01

    The plant hormone abscisic acid (ABA) is shown, under certain conditions, to greatly enhance the permeability of phospholipid bilayer membranes to the nonelectrolyte erythritol (followed spectrophotometrically by osmotic swelling) and the anion carboxyfluorescein (followed by fluorescence). The hormone is ineffective with single- and mixed-component phosphatidylcholine membranes in the liquid-crystalline or gel states. In contrast, substantial ABA-induced permeability is measured for two-component membranes containing lipids with different polar head groups or containing phosphatidylcholines with different acyl chains at temperatures where gel and liquid-crystalline phases coexist. Despite the large ABA-induced enhancement in bilayer permeability, no evidence for a substantial change at the molecular level was seen in the membranes by magnetic resonance techniques. 13 C NMR spin-lattice relaxation times, T 1 , in sonicated unilamellar vesicles and ESR of spin-labeled fatty acids intercalated into membranes showed negligible effect on acyl chain order and dynamics within the bilayer, while 31 P NMR of sonicated unilamellar vesicles indicated negligible effect on molecular motion and conformation in the head-group region. The authors propose that, instead of causing a general nonspecific perturbation to the membrane, the hormone acts at membrane defects formed due to mismatch in molecular packing where two different head groups or acyl chain states interface. Increased membrane disruption by ABA at these points of membrane instability could then produce an enhancement in permeability

  13. Detergent-resistant membranes in human erythrocytes and their ...

    Indian Academy of Sciences (India)

    Unknown

    SLP, stomatin-like-protein-2; TX-100, Triton X-100. ... via electrostatic interactions that can be disrupted by the simultaneous increase in pH and ionic strength of the solubilization .... dentified components of the DRMs and the membrane ..... Analysis of proteins and cholesterol in 6 ... Band 3, the main integral protein of the.

  14. Role of plasma membrane and of cytomatrix in maintenance of intracellular to extracellular ion gradients in chicken erythrocytes

    International Nuclear Information System (INIS)

    Cameron, I.L.; Hunter, K.E.; Smith, N.K.; Hazlewood, C.F.; Ludany, A.; Kellermayer, M.

    1988-01-01

    Ultrastructural observations in combination with electron probe X-ray microanalysis on detergent (Brij 58) permeabilized (disruption of the plasma membrane) nucleated chicken erythrocytes support the view that a large fraction of cytoplasmic and nuclear K+ is not freely diffusible and that adsorption of K+ on detergent released mobilizable proteins exists within the cell. The data also suggest that the detergent proteins are normally immobilized by a detergent-resistant cytoskeleton so that they are not immediately free to diffuse from the cell for several minutes after detergent disruption of the plasma membrane

  15. Monitoring the Orientational Changes of Alamethicin during Incorporation into Bilayer Lipid Membranes.

    Science.gov (United States)

    Forbrig, Enrico; Staffa, Jana K; Salewski, Johannes; Mroginski, Maria Andrea; Hildebrandt, Peter; Kozuch, Jacek

    2018-02-13

    Antimicrobial peptides (AMPs) are the first line of defense after contact of an infectious invader, for example, bacterium or virus, with a host and an integral part of the innate immune system of humans. Their broad spectrum of biological functions ranges from cell membrane disruption over facilitation of chemotaxis to interaction with membrane-bound or intracellular receptors, thus providing novel strategies to overcome bacterial resistances. Especially, the clarification of the mechanisms and dynamics of AMP incorporation into bacterial membranes is of high interest, and different mechanistic models are still under discussion. In this work, we studied the incorporation of the peptaibol alamethicin (ALM) into tethered bilayer lipid membranes on electrodes in combination with surface-enhanced infrared absorption (SEIRA) spectroscopy. This approach allows monitoring the spontaneous and potential-induced ion channel formation of ALM in situ. The complex incorporation kinetics revealed a multistep mechanism that points to peptide-peptide interactions prior to penetrating the membrane and adopting the transmembrane configuration. On the basis of the anisotropy of the backbone amide I and II infrared absorptions determined by density functional theory calculations, we employed a mathematical model to evaluate ALM reorientations monitored by SEIRA spectroscopy. Accordingly, ALM was found to adopt inclination angles of ca. 69°-78° and 21° in its interfacially adsorbed and transmembrane incorporated states, respectively. These orientations can be stabilized efficiently by the dipolar interaction with lipid head groups or by the application of a potential gradient. The presented potential-controlled mechanistic study suggests an N-terminal integration of ALM into membranes as monomers or parallel oligomers to form ion channels composed of parallel-oriented helices, whereas antiparallel oligomers are barred from intrusion.

  16. Impact of two different saponins on the organization of model lipid membranes.

    Science.gov (United States)

    Korchowiec, Beata; Gorczyca, Marcelina; Wojszko, Kamila; Janikowska, Maria; Henry, Max; Rogalska, Ewa

    2015-10-01

    Saponins, naturally occurring plant compounds are known for their biological and pharmacological activity. This activity is strongly related to the amphiphilic character of saponins that allows them to aggregate in aqueous solution and interact with membrane components. In this work, Langmuir monolayer techniques combined with polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and Brewster angle microscopy were used to study the interaction of selected saponins with lipid model membranes. Two structurally different saponins were used: digitonin and a commercial Merck Saponin. Membranes of different composition, namely, cholesterol, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine or 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) were formed at the air/water and air/saponin solution interfaces. The saponin-lipid interaction was characterized by changes in surface pressure, surface potential, surface morphology and PM-IRRAS signal. Both saponins interact with model membranes and change the physical state of membranes by perturbing the lipid acyl chain orientation. The changes in membrane fluidity were more significant upon the interaction with Merck Saponin. A higher affinity of saponins for cholesterol than phosphatidylglycerols was observed. Moreover, our results indicate that digitonin interacts strongly with cholesterol and solubilize the cholesterol monolayer at higher surface pressures. It was shown, that digitonin easily penetrate to the cholesterol monolayer and forms a hydrogen bond with the hydroxyl groups. These findings might be useful in further understanding of the saponin action at the membrane interface and of the mechanism of membrane lysis. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. A simple ideal magnetohydrodynamical model of vertical disruption events in tokamaks

    International Nuclear Information System (INIS)

    Fitzpatrick, R.

    2009-01-01

    A simple model of axisymmetric vertical disruption events (VDEs) in tokamaks is presented in which the halo current force exerted on the vacuum vessel is calculated directly from linear, marginally stable, ideal-magnetohydrodynamical (MHD) stability analysis. The basic premise of the model is that the halo current force modifies pressure balance at the edge of the plasma, and therefore also modifies ideal-MHD plasma stability. In order to prevent the ideal vertical instability, responsible for the VDE, from growing on the very short Alfven time scale, the halo current force must adjust itself such that the instability is rendered marginally stable. The model predicts halo currents which are similar in magnitude to those observed experimentally. An approximate nonaxisymmetric version of the model is developed in order to calculate the toroidal peaking factor for the halo current force.

  18. Models of plasma membrane organization can be applied to mitochondrial membranes to target human health and disease with polyunsaturated fatty acids.

    Science.gov (United States)

    Raza Shaikh, Saame; Brown, David A

    2013-01-01

    Bioactive n-3 polyunsaturated fatty acids (PUFA), abundant in fish oil, have potential for treating symptoms associated with inflammatory and metabolic disorders; therefore, it is essential to determine their fundamental molecular mechanisms. Recently, several labs have demonstrated the n-3 PUFA docosahexaenoic acid (DHA) exerts anti-inflammatory effects by targeting the molecular organization of plasma membrane microdomains. Here we briefly review the evidence that DHA reorganizes the spatial distribution of microdomains in several model systems. We then emphasize how models on DHA and plasma membrane microdomains can be applied to mitochondrial membranes. We discuss the role of DHA acyl chains in regulating mitochondrial lipid-protein clustering, and how these changes alter several aspects of mitochondrial function. In particular, we summarize effects of DHA on mitochondrial respiration, electron leak, permeability transition, and mitochondrial calcium handling. Finally, we conclude by postulating future experiments that will augment our understanding of DHA-dependent membrane organization in health and disease. Copyright © 2012 Elsevier Ltd. All rights reserved.

  19. Impact of the antimicrobial peptide Novicidin on membrane structure and integrity

    DEFF Research Database (Denmark)

    Nielsen, Søren B; Otzen, Daniel Erik

    2010-01-01

    We have studied the impact of an 18-residue cationic antimicrobial peptide Novicidin (Nc) on the structure and integrity of partially anionic lipid membranes using oriented circular dichroism (OCD), quartz crystal microbalance with dissipation (QCM-D), dual polarization interferometry (DPI......), calcein dye leakage and fluorescence spectroscopy. OCD consistently showed that Nc is bound in an alpha-helical, surface bound state over a range of peptide to lipid (P/L) ratios up to approximately 1:15. Realignment of Nc at higher P/L ratios correlates to loss of membrane integrity as shown by Laurdan...... concentration, probably through formation of transient pores or transient disruption of the membrane integrity, followed by more extensive membrane disintegration at higher P/L ratios....

  20. Three-dimensional dynamic modelling of Polymer-Electrolyte-Membrane-Fuel-Cell-Systems; Dreidimensionale dynamische Modellierung und Berechnung von Polymer-Elektrolyt-Membran-Brennstoffzellen

    Energy Technology Data Exchange (ETDEWEB)

    Vath, Andreas

    2008-12-15

    This thesis deals with dynamic and multi-dimensional modelling of Polymer- Electrolyte-Membrane-Fuel-Cells (PEMFC). The developed models include all the different layers of the fuel cell e.g. flow field, gas diffusion layer, catalyst layer and membrane with their particular physical, chemical and electrical characteristics. The simulation results have been verified by detailed measurements performed at the research centre for hydrogen and solar energy in Ulm (ZSW Ulm). The developed three dimensional model describes the time- and spatial-dependent charge and mass transport in a fuel cell. Additionally, this model allows the analysis of critical operating conditions. For example, the current density distribution for different membranes is shown during insufficient humidification which results in local overstraining and degradation. The model also allows to analyse extreme critical operating conditions, e.g. short time breakdown of the humidification. Furthermore, the model shows the available potential of improvement opportunities in power density and efficiency of PEMFC due to optimisation of the gas diffusion layer, the catalyst and membrane. In the second part of the work the application of PEMFC systems for combined heat and power units is described by one-dimensional models for an electrical power range between 1 kW and 5 kW. This model contains the necessary components, e.g. gas processing, humidification, gas supply, fuel cell stack, heat storage, pumps, auxiliary burner, power inverter und additional aggregates. As a main result, it is possible to distinctly reduce the energy demand and the carbon dioxide exhaust for different load profiles. Today the costs for fuel cell systems are considerably higher than that of the conventional electrical energy supply. (orig.)

  1. Scale-Up Design Analysis and Modelling of Cobalt Oxide Silica Membrane Module for Hydrogen Processing

    Directory of Open Access Journals (Sweden)

    Guozhao Ji

    2013-08-01

    Full Text Available This work shows the application of a validated mathematical model for gas permeation at high temperatures focusing on demonstrated scale-up design for H2 processing. The model considered the driving force variation with spatial coordinates and the mass transfer across the molecular sieve cobalt oxide silica membrane to predict the separation performance. The model was used to study the process of H2 separation at 500 °C in single and multi-tube membrane modules. Parameters of interest included the H2 purity in the permeate stream, H2 recovery and H2 yield as a function of the membrane length, number of tubes in a membrane module, space velocity and H2 feed molar fraction. For a single tubular membrane, increasing the length of a membrane tube led to higher H2 yield and H2 recovery, owing to the increase of the membrane area. However, the H2 purity decreased as H2 fraction was depleted, thus reducing the driving force for H2 permeation. By keeping the membrane length constant in a multi-tube arrangement, the H2 yield and H2 recovery increase was attributed to the higher membrane area, but the H2 purity was again compromised. Increasing the space velocity avoided the reduction of H2 purity and still delivered higher H2 yield and H2 recovery than in a single membrane arrangement. Essentially, if the membrane surface is too large, the driving force becomes lower at the expense of H2 purity. In this case, the membrane module is over designed. Hence, maintaining a driving force is of utmost importance to deliver the functionality of process separation.

  2. Dimer-based model for heptaspanning membrane receptors.

    Science.gov (United States)

    Franco, Rafael; Casadó, Vicent; Mallol, Josefa; Ferré, Sergi; Fuxe, Kjell; Cortés, Antonio; Ciruela, Francisco; Lluis, Carmen; Canela, Enric I

    2005-07-01

    The existence of intramembrane receptor-receptor interactions for heptaspanning membrane receptors is now fully accepted, but a model considering dimers as the basic unit that binds to two ligand molecules is lacking. Here, we propose a two-state-dimer model in which the ligand-induced conformational changes from one component of the dimer are communicated to the other. Our model predicts cooperativity in binding, which is relevant because the other current models fail to address this phenomenon satisfactorily. Our two-state-dimer model also predicts the variety of responses elicited by full or partial agonists, neutral antagonists and inverse agonists. This model can aid our understanding of the operation of heptaspanning receptors and receptor channels, and, potentially, be important for improving the treatment of cardiovascular, neurological and neuropsychyatric diseases.

  3. Smart membranes for monitoring membrane based desalination processes

    KAUST Repository

    Laleg-Kirati, Taous-Meriem

    2017-10-12

    Various examples are related to smart membranes for monitoring membrane based process such as, e.g., membrane distillation processes. In one example, a membrane, includes a porous surface and a plurality of sensors (e.g., temperature, flow and/or impedance sensors) mounted on the porous surface. In another example, a membrane distillation (MD) process includes the membrane. Processing circuitry can be configured to monitor outputs of the plurality of sensors. The monitored outputs can be used to determine membrane degradation, membrane fouling, or to provide an indication of membrane replacement or cleaning. The sensors can also provide temperatures or temperature differentials across the porous surface, which can be used to improve modeling or control the MD process.

  4. Experimental simulation and numerical modeling of vapor shield formation and divertor material erosion for ITER typical plasma disruptions

    International Nuclear Information System (INIS)

    Wuerz, H.; Arkhipov, N.I.; Bakhtin, V.P.; Konkashbaev, I.; Landman, I.; Safronov, V.M.; Toporkov, D.A.; Zhitlukhin, A.M.

    1995-01-01

    The high divertor heat load during a tokamak plasma disruption results in sudden evaporation of a thin layer of divertor plate material, which acts as vapor shield and protects the target from further excessive evaporation. Formation and effectiveness of the vapor shield are theoretically modeled and are experimentally analyzed at the 2MK-200 facility under conditions simulating the thermal quench phase of ITER tokamak plasma disruptions. ((orig.))

  5. The polyene antimycotics nystatin and filipin disrupt the plasma membrane, whereas natamycin inhibits endocytosis in germinating conidia of Penicillium discolor

    NARCIS (Netherlands)

    Leeuwen, van M.R.; Golovina, E.A.; Dijksterhuis, J.

    2009-01-01

    To investigate the differences in membrane permeability and the effect on endocytosis of the polyene antimycotics nystatin, filipin and natamycin on germinating fungal conidia. Methods and Results: The model system was Penicillium discolor, a food spoilage fungus. Filipin resulted in

  6. Market disruption, cascading effects, and economic recovery:a life-cycle hypothesis model.

    Energy Technology Data Exchange (ETDEWEB)

    Sprigg, James A.

    2004-11-01

    This paper builds upon previous work [Sprigg and Ehlen, 2004] by introducing a bond market into a model of production and employment. The previous paper described an economy in which households choose whether to enter the labor and product markets based on wages and prices. Firms experiment with prices and employment levels to maximize their profits. We developed agent-based simulations using Aspen, a powerful economic modeling tool developed at Sandia, to demonstrate that multiple-firm economies converge toward the competitive equilibria typified by lower prices and higher output and employment, but also suffer from market noise stemming from consumer churn. In this paper we introduce a bond market as a mechanism for household savings. We simulate an economy of continuous overlapping generations in which each household grows older in the course of the simulation and continually revises its target level of savings according to a life-cycle hypothesis. Households can seek employment, earn income, purchase goods, and contribute to savings until they reach the mandatory retirement age; upon retirement households must draw from savings in order to purchase goods. This paper demonstrates the simultaneous convergence of product, labor, and savings markets to their calculated equilibria, and simulates how a disruption to a productive sector will create cascading effects in all markets. Subsequent work will use similar models to simulate how disruptions, such as terrorist attacks, would interplay with consumer confidence to affect financial markets and the broader economy.

  7. Devices for overcoming biological barriers: the use of physical forces to disrupt the barriers.

    Science.gov (United States)

    Mitragotri, Samir

    2013-01-01

    Overcoming biological barriers including skin, mucosal membranes, blood brain barrier as well as cell and nuclear membrane constitutes a key hurdle in the field of drug delivery. While these barriers serve the natural protective function in the body, they limit delivery of drugs into the body. A variety of methods have been developed to overcome these barriers including formulations, targeting peptides and device-based technologies. This review focuses on the use of physical methods including acoustic devices, electric devices, high-pressure devices, microneedles and optical devices for disrupting various barriers in the body including skin and other membranes. A summary of the working principles of these devices and their ability to enhance drug delivery is presented. Copyright © 2012. Published by Elsevier B.V.

  8. Investigating Disruption

    DEFF Research Database (Denmark)

    Lundgaard, Stine Schmieg; Rosenstand, Claus Andreas Foss

    This book shares knowledge collected from 2015 and onward within the Consortium for Digital Disruption anchored at Aalborg University (www.dd.aau.dk). Evidenced by this publication, the field of disruptive innovation research has gone through several stages of operationalizing the theory. In recent...... years, researchers are increasingly looking back towards the origins of the theory in attempts to cure it from its most obvious flaws. This is especially true for the use of the theory in making predictions about future disruptions. In order to continue to develop a valuable theory of disruption, we...... find it useful to first review what the theory of disruptive innovation initially was, how it has developed, and where we are now. A cross section of disruptive innovation literature has been reviewed in order to form a general foundation from which we might better understand the changing world...

  9. Disruption of the mitochondria-associated ER membrane (MAM) plays a central role in palmitic acid-induced insulin resistance.

    Science.gov (United States)

    Shinjo, Satoko; Jiang, Shuying; Nameta, Masaaki; Suzuki, Tomohiro; Kanai, Mai; Nomura, Yuta; Goda, Nobuhito

    2017-10-01

    The mitochondria-associated ER membrane (MAM) is a specialized subdomain of ER that physically connects with mitochondria. Although disruption of inter-organellar crosstalk via the MAM impairs cellular homeostasis, its pathological significance in insulin resistance in type 2 diabetes mellitus remains unclear. Here, we reveal the importance of reduced MAM formation in the induction of fatty acid-evoked insulin resistance in hepatocytes. Palmitic acid (PA) repressed insulin-stimulated Akt phosphorylation in HepG2 cells within 12h. Treatment with an inhibitor of the ER stress response failed to restore PA-mediated suppression of Akt activation. Mitochondrial reactive oxygen species (ROS) production did not increase in PA-treated cells. Even short-term exposure (3h) to PA reduced the calcium flux from ER to mitochondria, followed by a significant decrease in MAM contact area, suggesting that PA suppressed the functional interaction between ER and mitochondria. Forced expression of mitofusin-2, a critical component of the MAM, partially restored MAM contact area and ameliorated the PA-elicited suppression of insulin sensitivity with Ser473 phosphorylation of Akt selectively improved. These results suggest that loss of proximity between ER and mitochondria, but not perturbation of homeostasis in the two organelles individually, plays crucial roles in PA-evoked Akt inactivation in hepatic insulin resistance. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Toxins and antimicrobial peptides: interactions with membranes

    Science.gov (United States)

    Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

    2009-08-01

    The innate immunity to pathogenic invasion of organisms in the plant and animal kingdoms relies upon cationic antimicrobial peptides (AMPs) as the first line of defense. In addition to these natural peptide antibiotics, similar cationic peptides, such as the bee venom toxin melittin, act as nonspecific toxins. Molecular details of AMP and peptide toxin action are not known, but the universal function of these peptides to disrupt cell membranes of pathogenic bacteria (AMPs) or a diverse set of eukaryotes and prokaryotes (melittin) is widely accepted. Here, we have utilized spectroscopic techniques to elucidate peptide-membrane interactions of alpha-helical human and mouse AMPs of the cathelicidin family as well as the peptide toxin melittin. The activity of these natural peptides and their engineered analogs was studied on eukaryotic and prokaryotic membrane mimics consisting of resistant pathogens.

  11. Interaction pathways between soft lipid nanodiscs and plasma membranes: A molecular modeling study.

    Science.gov (United States)

    Li, Shixin; Luo, Zhen; Xu, Yan; Ren, Hao; Deng, Li; Zhang, Xianren; Huang, Fang; Yue, Tongtao

    2017-10-01

    Lipid nanodisc, a model membrane platform originally synthesized for study of membrane proteins, has recently been used as the carrier to deliver amphiphilic drugs into target tumor cells. However, the central question of how cells interact with such emerging nanomaterials remains unclear and deserves our research for both improving the delivery efficiency and reducing the side effect. In this work, a binary lipid nanodisc is designed as the minimum model to investigate its interactions with plasma membranes by using the dissipative particle dynamics method. Three typical interaction pathways, including the membrane attachment with lipid domain exchange of nanodiscs, the partial membrane wrapping with nanodisc vesiculation, and the receptor-mediated endocytosis, are discovered. For the first pathway, the boundary normal lipids acting as ligands diffuse along the nanodisc rim to gather at the membrane interface, repelling the central bola lipids to reach a stable membrane attachment. If bola lipids are positioned at the periphery and act as ligands, they diffuse to form a large aggregate being wrapped by the membrane, leaving the normal lipids exposed on the membrane exterior by assembling into a vesicle. Finally, by setting both central normal lipids and boundary bola lipids as ligands, the receptor-mediated endocytosis occurs via both deformation and self-rotation of the nanodiscs. All above pathways for soft lipid nanodiscs are quite different from those for rigid nanoparticles, which may provide useful guidelines for design of soft lipid nanodiscs in widespread biomedical applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Membrane paradigm

    International Nuclear Information System (INIS)

    Price, R.H.; Thorne, K.S.

    1986-01-01

    The membrane paradigm is a modified frozen star approach to modeling black holes, with particles and fields assuming a complex, static, boundary-layer type structure (membrane) near the event horizon. The membrane has no effects on the present or future evolution of particles and fields above itself. The mathematical representation is a combination of a formalism containing terms for the shear and bulk viscosity, surface pressure, momentum, temperature, entropy, etc., of the horizon and the 3+1 formalism. The latter model considers a family of three-dimensional spacelike hypersurfaces in one-dimensional time. The membrane model considers a magnetic field threading the hole and undergoing torque from the hole rotation. The field is cleaned by the horizon and distributed over the horizon so that ohmic dissipation is minimized. The membrane paradigm is invalid inside the horizon, but is useful for theoretically probing the properties of slowly evolving black holes

  13. A co-cultured skin model based on cell support membranes

    International Nuclear Information System (INIS)

    Dai, N.-T.; Yeh, M.-K.; Liu, Demeral David; Adams, E.F.; Chiang, C.-H.; Yen, C.-Y.; Shih, C.-M.; Sytwu, H.-K.; Chen, Tim-Mo; Wang, H.-J.; Williamson, M.R.; Coombes, A.G.A.

    2005-01-01

    Tissue engineering of skin based on collagen: PCL biocomposites using a designed co-culture system is reported. The collagen: PCL biocomposites having collagen: PCL (w/w) ratios of 1:4, 1:8, and 1:20 have been proven to be biocompatible materials to support both adult normal human epidermal Keratinocyte (NHEK) and mouse 3T3 fibroblast growth in cell culture, respectively, by Dai, Coombes, et al. in 2004. Films of collagen: PCL biocomposites were prepared using non-crosslinking method by impregnation of lyophilized collagen mats with PCL/dichloromethane solutions followed by solvent evaporation. To mimic the dermal/epidermal structure of skin, the 1:20 collagen: PCL biocomposites were selected for a feasibility study of a designed co-culture technique that would subsequently be used for preparing fibroblast/biocomposite/keratinocyte skin models. A 55.3% increase in cell number was measured in the designed co-culture system when fibroblasts were seeded on both sides of a biocomposite film compared with cell culture on one surface of the biocomposite in the feasibility study. The co-culture of human keratinocytes and 3T3 fibroblasts on each side of the membrane was therefore studied using the same co-culture system by growing keratinocytes on the top surface of membrane for 3 days and 3T3 fibroblasts underneath the membrane for 6 days. Scanning electron microscopy (SEM) and immunohistochemistry assay revealed good cell attachment and proliferation of both human keratinocytes and 3T3 fibroblasts with these two types of cells isolated well on each side of the membrane. Using a modified co-culture technique, a co-cultured skin model presenting a confluent epidermal sheet on one side of the biocomposite film and fibroblasts populated on the other side of the film was developed successfully in co-culture system for 28 days under investigations by SEM and immunohistochemistry assay. Thus, the design of a co-culture system based on 1:20 (w/w) collagen: PCL biocomposite

  14. Research on Biomimetic Models and Nanomechanical Behaviour of Membranous Wings of Chinese Bee Apis cerana cerana Fabricius

    Directory of Open Access Journals (Sweden)

    Yanru Zhao

    2018-01-01

    Full Text Available The structures combining the veins and membranes of membranous wings of the Chinese bee Apis cerana cerana Fabricius into a whole have excellent load-resisting capacity. The membranous wings of Chinese bees were taken as research objects and the mechanical properties of a biomimetic model of membranous wings as targets. In order to understand and learn from the biosystem and then make technical innovation, the membranous wings of Chinese bees were simulated and analysed with reverse engineering and finite element method. The deformations and stress states of the finite element model of membranous wings were researched under the concentrated force, uniform load, and torque. It was found that the whole model deforms evenly and there are no unusual deformations arising. The displacements and deformations are small and transform uniformly. It was indicated that the veins and membranes combine well into a whole to transmit loads effectively, which illustrates the membranous wings of Chinese bees having excellent integral mechanical behaviour and structure stiffness. The realization of structure models of the membranous wings of Chinese bees and analysis of the relativity of structures and performances or functions will provide an inspiration for designing biomimetic thin-film materials with superior load-bearing capacity.

  15. Control-oriented model of a membrane humidifier for fuel cell applications

    International Nuclear Information System (INIS)

    Solsona, Miguel; Kunusch, Cristian; Ocampo-Martinez, Carlos

    2017-01-01

    Highlights: • A control-oriented model of a Nafion® membrane gas humidifier has been developed. • The control-oriented model has been experimentally validated. • A non-linear control strategy has been used to test its suitability for control purposes. - Abstract: Improving the humidification of polymer electrolyte membrane fuel-cells (PEMFC) is essential to optimize its performance and stability. Therefore, this paper presents an experimentally validated model of a low temperature PEMFC cathode humidifier for control/observation design purposes. A multi-input/multi-output non-linear fourth order model is derived, based on the mass and heat dynamics of circulating air. In order to validate the proposed model and methodology, experimental results are provided. Finally, a non-linear control strategy based on second order sliding mode is designed and analyzed in order to show suitability and usefulness of the approach.

  16. Mechanics of membrane-cytoskeleton attachment in Paramecium

    Science.gov (United States)

    Campillo, C.; Jerber, J.; Fisch, C.; Simoes-Betbeder, M.; Dupuis-Williams, P.; Nassoy, P.; Sykes, C.

    2012-12-01

    In this paper we assess the role of the protein MKS1 (Meckel syndrome type 1) in the cortical membrane mechanics of the ciliated protist Paramecium. This protein is known to be crucial in the process of cilium formation, and we investigate its putative role in membrane-cytoskeleton attachment. Therefore, we compare cells where the gene coding for MKS1 is silenced to wild-type cells. We found that scanning electron microscopy observation of the cell surface reveals a cup-like structure in wild-type cells that is lost in silenced cells. Since this structure is based on the underlying cytoskeleton, one hypothesis to explain this observation is a disruption of membrane attachment to the cytoskeleton in the absence of MKS1 that should affect plasma membrane mechanics. We test this by probing the mechanics of wild-type and silenced cells by micropipette aspiration. Strikingly, we observe that, at the same aspiration pressure, the membrane of silenced cells is easily aspirated by the micropipette whereas that of wild-type cells enters only at a moderate velocity, an effect that suggests a detachment of the membrane from the underlying cytoskeleton in silenced cells. We quantify this detachment by measuring the deformation of the cell cortex and the rate of cell membrane entry in the micropipette. This study offers a new perspective for the characterization of membrane-cytoskeleton attachment in protists and paves the way for a better understanding of the role of membrane-cortex attachment in cilium formation.

  17. An assessment of disruption erosion in ITER environment

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, I.

    1994-01-01

    The behavior of divertor materials during a major disruption in ITER is very important for the successful and reliable operation of the reactor. Erosion of material surfaces due to the thermal energy dump can severely limit the lifetime of the plasma facing components therefore degrading reactor economic feasibility. A comprehensive numerical model recently developed is used in this analysis in which all major physical processes taking place during plasma-material interactions are included. Models to account for material thermal evolution, plasma-vapor interaction physics, and models for hydrodynamic radiation transport in the developed vapor cloud are implemented in a self-consistent manner to realistically assess the disruption damage. The extent of the self-protection from the developed vapor cloud in front of the incoming plasma particles is critically important in determining the overall disruption lifetime. The aim of this study is to estimate the divertor lifetime for a range of reactor conditions. Candidate materials such as beryllium and graphite are both considered in this analysis. The dependence of the divertor disruption lifetime on the characteristics of plasma-vapor interaction zone for incident plasma ions and electrons is analyzed and discussed. The effect of uncertainties in reactor disruption conditions on the overall divertor erosion lifetime is also analyzed

  18. Modeling and Simulation of Membrane-Based Dehumidification and Energy Recovery Process

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhiming [ORNL; Abdelaziz, Omar [ORNL; Qu, Ming [ORNL

    2017-01-01

    This paper introduces a first-order physics-based model that accounts for the fundamental heat and mass transfer between a humid-air vapor stream on feed side to another flow stream on permeate side. The model comprises a few optional submodels for membrane mass transport; and it adopts a segment-by-segment method for discretizing heat and mass transfer governing equations for flow streams on feed and permeate sides. The model is able to simulate both dehumidifiers and energy recovery ventilators in parallel-flow, cross-flow, and counter-flow configurations. The predicted tresults are compared reasonably well with the measurements. The open-source codes are written in C++. The model and open-source codes are expected to become a fundament tool for the analysis of membrane-based dehumidification in the future.

  19. Membrane interactions and antimicrobial effects of layered double hydroxide nanoparticles

    DEFF Research Database (Denmark)

    Malekkhaiat Häffner, S; Nyström, L; Nordström, R

    2017-01-01

    Membrane interactions are critical for the successful use of inorganic nanoparticles as antimicrobial agents and as carriers of, or co-actives with, antimicrobial peptides (AMPs). In order to contribute to an increased understanding of these, we here investigate effects of particle size (42-208 nm...... into size-dependent synergistic effects with the antimicrobial peptide LL-37. Due to strong interactions with anionic lipopolysaccharide and peptidoglycan layers, direct membrane disruption of both Gram-negative and Gram-positive bacteria is suppressed. However, LDH nanoparticles cause size-dependent charge...

  20. Modeling of thermal effects on TIBER II [Tokamak Ignition/Burn Experimental Reactor] divertor during plasma disruption

    International Nuclear Information System (INIS)

    Bruhn, M.L.; Perkins, L.J.

    1987-01-01

    Mapping the disruption power flow from the mid-plane of the TIBER Engineering Test Reactor to its divertor and calculating the resulting thermal effects are accomplished through the modification and coupling of three presently existing computer codes. The resulting computer code TADDPAK (Thermal Analysis Divertor during Disruption PAcKage) provides three-dimensional graphic presentations of time and positional dependent thermal effects on a poloidal cross section of the double-null-divertor configured reactor. These thermal effects include incident heat flux, surface temperature, vaporization rate, total vaporization, and melting depth. The dependence of these thermal effects on material choice, disruption pulse shape, and the characteristic thickness of the plasma scrape-off layer is determined through parametric analysis with TADDPAK. This computer code is designed to be a convenient, rapid, and user-friendly modeling tool which can be easily adapted to most tokamak double-null-divertor reactor designs. 14 refs

  1. Disruption of Pseudomonas putida by high pressure homogenization: a comparison of the predictive capacity of three process models for the efficient release of arginine deiminase.

    Science.gov (United States)

    Patil, Mahesh D; Patel, Gopal; Surywanshi, Balaji; Shaikh, Naeem; Garg, Prabha; Chisti, Yusuf; Banerjee, Uttam Chand

    2016-12-01

    Disruption of Pseudomonas putida KT2440 by high-pressure homogenization in a French press is discussed for the release of arginine deiminase (ADI). The enzyme release response of the disruption process was modelled for the experimental factors of biomass concentration in the broth being disrupted, the homogenization pressure and the number of passes of the cell slurry through the homogenizer. For the same data, the response surface method (RSM), the artificial neural network (ANN) and the support vector machine (SVM) models were compared for their ability to predict the performance parameters of the cell disruption. The ANN model proved to be best for predicting the ADI release. The fractional disruption of the cells was best modelled by the RSM. The fraction of the cells disrupted depended mainly on the operating pressure of the homogenizer. The concentration of the biomass in the slurry was the most influential factor in determining the total protein release. Nearly 27 U/mL of ADI was released within a single pass from slurry with a biomass concentration of 260 g/L at an operating pressure of 510 bar. Using a biomass concentration of 100 g/L, the ADI release by French press was 2.7-fold greater than in a conventional high-speed bead mill. In the French press, the total protein release was 5.8-fold more than in the bead mill. The statistical analysis of the completely unseen data exhibited ANN and SVM modelling as proficient alternatives to RSM for the prediction and generalization of the cell disruption process in French press.

  2. Anode partial flooding modelling of proton exchange membrane fuel cells: Model development and validation

    International Nuclear Information System (INIS)

    Xing, Lei; Du, Shangfeng; Chen, Rui; Mamlouk, Mohamed; Scott, Keith

    2016-01-01

    A two-dimensional along-the-channel CFD (computational fluid dynamic) model, coupled with a two-phase flow model of liquid water and gas transport for a PEM (proton exchange membrane) fuel cell is described. The model considers non-isothermal operation and thus the non-uniform temperature distribution in the cell structure. Water phase-transfer between the vapour, liquid water and dissolved phase is modelled with the combinational transport mechanism through the membrane. Liquid water saturation is simulated inside the electrodes and channels at both the anode and cathode sides. Three types of models are compared for the HOR (hydrogen oxidation reaction) and ORR (oxygen reduction reaction) in catalyst layers, including Butler–Volmer (B–V), liquid water saturation corrected B–V and agglomerate mechanisms. Temperature changes in MEA (membrane electrode assembly) and channels due to electrochemical reaction, ohmic resistance and water phase-transfer are analysed as a function of current density. Nonlinear relations of liquid water saturations with respect to current densities at both the anode and cathode are regressed. At low and high current densities, liquid water saturation at the anode linearly increases as a consequence of the linear increase of liquid water saturation at the cathode. In contrast, exponential relation is found to be more accurate at medium current densities. - Highlights: • A fully coupled 2D, along-the-channel, two-phase flow, non-isothermal, CFD model is developed. • Temperature rise due to electrochemical reactions, ohmic resistance and water phase-transfer is analysed. • Mathematical expressions of liquid water saturation against current density at anode and cathode are regressed. • Relationship between the liquid water saturation at anode and cathode is built.

  3. Manipulation of cell membrane using carbon nanotube scaffold as a photoresponsive stimuli generator.

    Science.gov (United States)

    Sada, Takao; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2014-08-01

    We describe, for the first time, the perforation of the cell membrane in the targeted single cell based on the nanosecond pulsed near-infrared (NIR) laser irradiation of a thin film of carbon nanotubes that act as an effective photon absorber as well as stimuli generator. When the power of NIR laser is over 17.5 μ J/pulse, the cell membrane after irradiation is irreversibly disrupted and results in cell death. In sharp contrast, the perforation of the cell membrane occurs at suitable laser power (∼15 μ J/pulse) without involving cell termination.

  4. Membrane-active mechanism of LFchimera against Burkholderia pseudomallei and Burkholderia thailandensis.

    Science.gov (United States)

    Kanthawong, Sakawrat; Puknun, Aekkalak; Bolscher, Jan G M; Nazmi, Kamran; van Marle, Jan; de Soet, Johannes J; Veerman, Enno C I; Wongratanacheewin, Surasakdi; Taweechaisupapong, Suwimol

    2014-10-01

    LFchimera, a construct combining two antimicrobial domains of bovine lactoferrin, lactoferrampin265-284 and lactoferricin17-30, possesses strong bactericidal activity. As yet, no experimental evidence was presented to evaluate the mechanisms of LFchimera against Burkholderia isolates. In this study we analyzed the killing activity of LFchimera on the category B pathogen Burkholderia pseudomallei in comparison to the lesser virulent Burkholderia thailandensis often used as a model for the highly virulent B. pseudomallei. Killing kinetics showed that B. thailandensis E264 was more susceptible for LFchimera than B. pseudomallei 1026b. Interestingly the bactericidal activity of LFchimera appeared highly pH dependent; B. thailandensis killing was completely abolished at and below pH 6.4. FITC-labeled LFchimera caused a rapid accumulation within 15 min in the cytoplasm of both bacterial species. Moreover, freeze-fracture electron microscopy demonstrated extreme effects on the membrane morphology of both bacterial species within 1 h of incubation, accompanied by altered membrane permeability monitored as leakage of nucleotides. These data indicate that the mechanism of action of LFchimera is similar for both species and encompasses disruption of the plasma membrane and subsequently leakage of intracellular nucleotides leading to cell dead.

  5. [Computer modeling the dependences of the membrane potential for polymeric membrane separated non-homogeneous electrolyte solutions on concentration Rayleigh number].

    Science.gov (United States)

    Slezak, Izabella H; Jasik-Slezak, Jolanta; Bilewicz-Wyrozumska, Teresa; Slezak, Andrzej

    2006-01-01

    On the basis of model equation describing the membrane potential delta psi(s) on concentration Rayleigh number (R(C)), mechanical pressure difference (deltaP), concentration polarization coefficient (zeta s) and ratio concentration of solutions separated by membrane (Ch/Cl), the characteristics delta psi(s) = f(Rc)(delta P, zeta s, Ch/Cl) for steady values of zeta s, R(C) and Ch/Cl in single-membrane system were calculated. In this system neutral and isotropic polymeric membrane oriented in horizontal plane, the non-homogeneous binary electrolytic solutions of various concentrations were separated. Nonhomogeneity of solutions is results from creations of the concentration boundary layers on both sides of the membrane. Calculations were made for the case where on a one side of the membrane aqueous solution of NaCl at steady concentration 10(-3) mol x l(-1) (Cl) was placed and on the other aqueous solutions of NaCl at concentrations from 10(-3) mol x l(-1) to 2 x 10(-2) mol x l(-1) (Ch). Their densities were greater than NaCl solution's at 10(-3) mol x l(-1). It was shown that membrane potential depends on hydrodynamic state of a complex concentration boundary layer-membrane-concentration boundary layer, what is controlled by deltaP, Ch/Cl, Rc and Zeta(s).

  6. SC lipid model membranes designed for studying impact of ceramide species on drug diffusion and permeation--part II: diffusion and permeation of model drugs.

    Science.gov (United States)

    Ochalek, M; Podhaisky, H; Ruettinger, H-H; Wohlrab, J; Neubert, R H H

    2012-10-01

    The barrier function of two quaternary stratum corneum (SC) lipid model membranes, which were previously characterized with regard to the lipid organization, was investigated based on diffusion studies of model drugs with varying lipophilicities. Diffusion experiments of a hydrophilic drug, urea, and more lipophilic drugs than urea (i.e. caffeine, diclofenac sodium) were conducted using Franz-type diffusion cells. The amount of permeated drug was analyzed using either HPLC or CE technique. The subjects of interest in the present study were the investigation of the influence of physicochemical properties of model drugs on their diffusion and permeation through SC lipid model membranes, as well as the study of the impact of the constituents of these artificial systems (particularly ceramide species) on their barrier properties. The diffusion through both SC lipid model membranes and the human SC of the most hydrophilic model drug, urea, was faster than the permeation of the more lipophilic drugs. The slowest rate of permeation through SC lipid systems occurred in the case of caffeine. The composition of SC lipid model membranes has a significant impact on their barrier function. Model drugs diffused and permeated faster through Membrane II (presence of Cer [EOS]). In terms of the barrier properties, Membrane II is much more similar to the human SC than Membrane I. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Digital Disruption

    DEFF Research Database (Denmark)

    Rosenstand, Claus Andreas Foss

    det digitale domæne ud over det niveau, der kendetegner den nuværende debat, så præsenteres der ny viden om digital disruption. Som noget nyt udlægges Clayton Christens teori om disruptiv innovation med et særligt fokus på små organisationers mulighed for eksponentiel vækst. Specielt udfoldes...... forholdet mellem disruption og den stadig accelererende digitale udvikling i konturerne til ny teoridannelse om digital disruption. Bogens undertitel ”faretruende og fascinerende forandringer” peger på, at der er behov for en nuanceret debat om digital disruption i modsætning til den tone, der er slået an i...... videre kalder et ”disruption-råd”. Faktisk er rådet skrevet ind i 2016 regeringsgrundlaget for VLK-regeringen. Disruption af organisationer er ikke et nyt fænomen; men hastigheden, hvormed det sker, er stadig accelererende. Årsagen er den globale mega-trend: Digitalisering. Og derfor er specielt digital...

  8. Titanium Dioxide Nanoparticles Induce Endoplasmic Reticulum Stress-Mediated Autophagic Cell Death via Mitochondria-Associated Endoplasmic Reticulum Membrane Disruption in Normal Lung Cells

    Science.gov (United States)

    Yu, Kyeong-Nam; Chang, Seung-Hee; Park, Soo Jin; Lim, Joohyun; Lee, Jinkyu; Yoon, Tae-Jong; Kim, Jun-Sung; Cho, Myung-Haing

    2015-01-01

    Nanomaterials are used in diverse fields including food, cosmetic, and medical industries. Titanium dioxide nanoparticles (TiO2-NP) are widely used, but their effects on biological systems and mechanism of toxicity have not been elucidated fully. Here, we report the toxicological mechanism of TiO2-NP in cell organelles. Human bronchial epithelial cells (16HBE14o-) were exposed to 50 and 100 μg/mL TiO2-NP for 24 and 48 h. Our results showed that TiO2-NP induced endoplasmic reticulum (ER) stress in the cells and disrupted the mitochondria-associated endoplasmic reticulum membranes (MAMs) and calcium ion balance, thereby increasing autophagy. In contrast, an inhibitor of ER stress, tauroursodeoxycholic acid (TUDCA), mitigated the cellular toxic response, suggesting that TiO2-NP promoted toxicity via ER stress. This novel mechanism of TiO2-NP toxicity in human bronchial epithelial cells suggests that further exhaustive research on the harmful effects of these nanoparticles in relevant organisms is needed for their safe application. PMID:26121477

  9. QSAR models for reproductive toxicity and endocrine disruption in regulatory use – a preliminary investigation

    DEFF Research Database (Denmark)

    Jensen, Gunde Egeskov; Niemelä, Jay Russell; Wedebye, Eva Bay

    2008-01-01

    the new legislation. This article focuses on a screening exercise by use of our own and commercial QSAR models for identification of possible reproductive toxicants. Three QSAR models were used for reproductive toxicity for the endpoints teratogenic risk to humans (based on animal tests, clinical data...... for humans owing to possible developmental toxic effects: Xn (Harmful) and R63 (Possible risk of harm to the unborn child). The chemicals were also screened in three models for endocrine disruption....

  10. Membrane interaction of antimicrobial peptides using E. coli lipid extract as model bacterial cell membranes and SFG spectroscopy.

    Science.gov (United States)

    Soblosky, Lauren; Ramamoorthy, Ayyalusamy; Chen, Zhan

    2015-04-01

    Supported lipid bilayers are used as a convenient model cell membrane system to study biologically important molecule-lipid interactions in situ. However, the lipid bilayer models are often simple and the acquired results with these models may not provide all pertinent information related to a real cell membrane. In this work, we use sum frequency generation (SFG) vibrational spectroscopy to study molecular-level interactions between the antimicrobial peptides (AMPs) MSI-594, ovispirin-1 G18, magainin 2 and a simple 1,2-dipalmitoyl-d62-sn-glycero-3-phosphoglycerol (dDPPG)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) bilayer. We compared such interactions to those between the AMPs and a more complex dDPPG/Escherichia coli (E. coli) polar lipid extract bilayer. We show that to fully understand more complex aspects of peptide-bilayer interaction, such as interaction kinetics, a heterogeneous lipid composition is required, such as the E. coli polar lipid extract. The discrepancy in peptide-bilayer interaction is likely due in part to the difference in bilayer charge between the two systems since highly negative charged lipids can promote more favorable electrostatic interactions between the peptide and lipid bilayer. Results presented in this paper indicate that more complex model bilayers are needed to accurately analyze peptide-cell membrane interactions and demonstrates the importance of using an appropriate lipid composition to study AMP interaction properties. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  11. Cell-penetrating peptides for drug delivery across membrane barriers

    DEFF Research Database (Denmark)

    Foged, Camilla; Nielsen, Hanne Moerck

    2008-01-01

    During the last decade, cell-penetrating peptides have been investigated for their ability to overcome the plasma membrane barrier of mammalian cells for the intracellular or transcellular delivery of cargoes as diverse as low molecular weight drugs, imaging agents, oligonucleotides, peptides......, proteins and colloidal carriers such as liposomes and polymeric nanoparticles. Their ability to cross biological membranes in a non-disruptive way without apparent toxicity is highly desired for increasing drug bioavailability. This review provides an overview of the application of cell......-penetrating peptides as transmembrane drug delivery agents, according to the recent literature, and discusses critical issues and future challenges in relation to fully understanding the fundamental principles of the cell-penetrating peptide-mediated membrane translocation of cargoes and the exploitation...

  12. Mitochondrial membrane studies using impedance spectroscopy with parallel pH monitoring.

    Directory of Open Access Journals (Sweden)

    Divya Padmaraj

    Full Text Available A biological microelectromechanical system (BioMEMS device was designed to study complementary mitochondrial parameters important in mitochondrial dysfunction studies. Mitochondrial dysfunction has been linked to many diseases, including diabetes, obesity, heart failure and aging, as these organelles play a critical role in energy generation, cell signaling and apoptosis. The synthesis of ATP is driven by the electrical potential across the inner mitochondrial membrane and by the pH difference due to proton flux across it. We have developed a tool to study the ionic activity of the mitochondria in parallel with dielectric measurements (impedance spectroscopy to gain a better understanding of the properties of the mitochondrial membrane. This BioMEMS chip includes: 1 electrodes for impedance studies of mitochondria designed as two- and four-probe structures for optimized operation over a wide frequency range and 2 ion-sensitive field effect transistors for proton studies of the electron transport chain and for possible monitoring other ions such as sodium, potassium and calcium. We have used uncouplers to depolarize the mitochondrial membrane and disrupt the ionic balance. Dielectric spectroscopy responded with a corresponding increase in impedance values pointing at changes in mitochondrial membrane potential. An electrical model was used to describe mitochondrial sample's complex impedance frequency dependencies and the contribution of the membrane to overall impedance changes. The results prove that dielectric spectroscopy can be used as a tool for membrane potential studies. It can be concluded that studies of the electrochemical parameters associated with mitochondrial bioenergetics may render significant information on various abnormalities attributable to these organelles.

  13. Vaporized wall material/plasma interaction during plasma disruption

    International Nuclear Information System (INIS)

    Merrill, B.J.; Carroll, M.C.; Jardin, S.C.

    1983-01-01

    The purpose of this paper is to discuss a new plasma disruption model that has been developed for analyzing the consequences to the limiter/first wall structures. This model accounts for: nonequilibrium surface vaporization for the ablating structure, nonequilibrium ionization of and radiation emitted from the ablated material in the plasma, plasma particle and energy transport, and plasma electromagnetic field evolution during the disruption event. Calculations were performed for a 5 ms disruption on a stainless steel flat limiter as part of a D-shaped first wall. These results indicated that the effectiveness of the ablated wall material to shield the exposed structure is greater than predicted by earlier models, and that the rate of redeposition of the ablated wall material ions is very dramatic. Impurity transport along magnetic field lines, global plasma motion, and radiation transport in an optically thick plasma are important factors that require additional modeling. Experimental measurements are needed to verify these models

  14. A new-generation asymmetric multi-bore hollow fiber membrane for sustainable water production via vacuum membrane distillation.

    Science.gov (United States)

    Wang, Peng; Chung, Tai-Shung

    2013-06-18

    Due to the growing demand for potable water, the capacities for wastewater reclamation and saline water desalination have been increasing. More concerns are raised on the poor efficiency of removing certain contaminants by the current water purification technologies. Recent studies demonstrated superior separation performance of the vacuum membrane distillation (VMD) technology for the rejection of trace contaminants such as boron, dye, endocrine-disruptive chemical, and chloro-compound. However, the absence of suitable membranes with excellent wetting resistance and high permeation flux has severely hindered the VMD application as an effective water production process. This work presents a new generation multibore hollow fiber (MBF) membrane with excellent mechanical durability developed for VMD. Its micromorphology was uniquely designed with a tight surface and a fully porous matrix to maximize both high wetting resistance and permeation flux. Credit to the multibore configuration, a 65% improvement was obtained on the antiwetting property. Using a synthetic seawater feed, the new membrane with optimized fabrication condition exhibits a high flux and the salt rejection is consistently greater than 99.99%. In addition, a comparison of 7-bore and 6-bore MBF membranes was performed to investigate the optimum geometry design. The newly designed MBF membrane not only demonstrates its suitability for VMD but also makes VMD come true as an efficient process for water production.

  15. Assembly of the membrane domain of ATP synthase in human mitochondria.

    Science.gov (United States)

    He, Jiuya; Ford, Holly C; Carroll, Joe; Douglas, Corsten; Gonzales, Evvia; Ding, Shujing; Fearnley, Ian M; Walker, John E

    2018-03-20

    The ATP synthase in human mitochondria is a membrane-bound assembly of 29 proteins of 18 kinds. All but two membrane components are encoded in nuclear genes, synthesized on cytoplasmic ribosomes, and imported into the matrix of the organelle, where they are assembled into the complex with ATP6 and ATP8, the products of overlapping genes in mitochondrial DNA. Disruption of individual human genes for the nuclear-encoded subunits in the membrane portion of the enzyme leads to the formation of intermediate vestigial ATPase complexes that provide a description of the pathway of assembly of the membrane domain. The key intermediate complex consists of the F 1 -c 8 complex inhibited by the ATPase inhibitor protein IF 1 and attached to the peripheral stalk, with subunits e, f, and g associated with the membrane domain of the peripheral stalk. This intermediate provides the template for insertion of ATP6 and ATP8, which are synthesized on mitochondrial ribosomes. Their association with the complex is stabilized by addition of the 6.8 proteolipid, and the complex is coupled to ATP synthesis at this point. A structure of the dimeric yeast F o membrane domain is consistent with this model of assembly. The human 6.8 proteolipid (yeast j subunit) locks ATP6 and ATP8 into the membrane assembly, and the monomeric complexes then dimerize via interactions between ATP6 subunits and between 6.8 proteolipids (j subunits). The dimers are linked together back-to-face by DAPIT (diabetes-associated protein in insulin-sensitive tissue; yeast subunit k), forming long oligomers along the edges of the cristae.

  16. Air gap membrane distillation. 2. Model validation and hollow fibre module performance analysis

    NARCIS (Netherlands)

    Guijt, C.M.; Meindersma, G.W.; Reith, T.; de Haan, A.B.

    2005-01-01

    In this paper the experimental results of counter current flow air gap membrane distillation experiments are presented and compared with predictive model calculations. Measurements were carried out with a cylindrical test module containing a single hollow fibre membrane in the centre and a

  17. Membrane tension regulates clathrin-coated pit dynamics

    Science.gov (United States)

    Liu, Allen

    2014-03-01

    Intracellular organization depends on close communication between the extracellular environment and a network of cytoskeleton filaments. The interactions between cytoskeletal filaments and the plasma membrane lead to changes in membrane tension that in turns help regulate biological processes. Endocytosis is thought to be stimulated by low membrane tension and the removal of membrane increases membrane tension. While it is appreciated that the opposing effects of exocytosis and endocytosis have on keeping plasma membrane tension to a set point, it is not clear how membrane tension affects the dynamics of clathrin-coated pits (CCPs), the individual functional units of clathrin-mediated endocytosis. Furthermore, although it was recently shown that actin dynamics counteracts membrane tension during CCP formation, it is not clear what roles plasma membrane tension plays during CCP initiation. Based on the notion that plasma membrane tension is increased when the membrane area increases during cell spreading, we designed micro-patterned surfaces of different sizes to control the cell spreading sizes. Total internal reflection fluorescence microscopy of living cells and high content image analysis were used to quantify the dynamics of CCPs. We found that there is an increased proportion of CCPs with short (<20s) lifetime for cells on larger patterns. Interestingly, cells on larger patterns have higher CCP initiation density, an effect unexpected based on the conventional view of decreasing endocytosis with increasing membrane tension. Furthermore, by analyzing the intensity profiles of CCPs that were longer-lived, we found CCP intensity decreases with increasing cell size, indicating that the CCPs are smaller with increasing membrane tension. Finally, disruption of actin dynamics significantly increased the number of short-lived CCPs, but also decreased CCP initiation rate. Together, our study reveals new mechanistic insights into how plasma membrane tension regulates

  18. Antibacterial activity of alkyl gallates is a combination of direct targeting of FtsZ and permeabilization of bacterial membranes

    NARCIS (Netherlands)

    Krol, Ewa; de Sousa Borges, Anabela; da Silva, Isabel; Polaquini, Carlos; Regasini, Luis; Ferreira, Henrique; Scheffers, Dirk

    2015-01-01

    Alkyl gallates are compounds with reported antibacterial activity. One of the modes of action is binding of the alkyl gallates to the bacterial membrane and interference with membrane integrity. However, alkyl gallates also cause cell elongation and disruption of cell division in the important plant

  19. Extraction of nucleic acids from yeast cells and plant tissues using ethanol as medium for sample preservation and cell disruption.

    Science.gov (United States)

    Linke, Bettina; Schröder, Kersten; Arter, Juliane; Gasperazzo, Tatiana; Woehlecke, Holger; Ehwald, Rudolf

    2010-09-01

    Here we report that dehydrated ethanol is an excellent medium for both in situ preservation of nucleic acids and cell disruption of plant and yeast cells. Cell disruption was strongly facilitated by prior dehydration of the ethanol using dehydrated zeolite. Following removal of ethanol, nucleic acids were extracted from the homogenate pellet using denaturing buffers. The method provided DNA and RNA of high yield and integrity. Whereas cell wall disruption was essential for extraction of DNA and large RNA molecules, smaller molecules such as tRNAs could be selectively extracted from undisrupted, ethanol-treated yeast cells. Our results demonstrate the utility of absolute ethanol for sample fixation, cell membrane and cell wall disruption, as well as preservation of nucleic acids during sample storage.

  20. Model-based fault detection for proton exchange membrane fuel cell ...

    African Journals Online (AJOL)

    In this paper, an intelligent model-based fault detection (FD) is developed for proton exchange membrane fuel cell (PEMFC) dynamic systems using an independent radial basis function (RBF) networks. The novelty is that this RBF networks is used to model the PEMFC dynamic systems and residuals are generated based ...

  1. Finsler Geometry Modeling of Phase Separation in Multi-Component Membranes

    Directory of Open Access Journals (Sweden)

    Satoshi Usui

    2016-08-01

    Full Text Available A Finsler geometric surface model is studied as a coarse-grained model for membranes of three components, such as zwitterionic phospholipid (DOPC, lipid (DPPC and an organic molecule (cholesterol. To understand the phase separation of liquid-ordered (DPPC rich L o and liquid-disordered (DOPC rich L d , we introduce a binary variable σ ( = ± 1 into the triangulated surface model. We numerically determine that two circular and stripe domains appear on the surface. The dependence of the morphological change on the area fraction of L o is consistent with existing experimental results. This provides us with a clear understanding of the origin of the line tension energy, which has been used to understand these morphological changes in three-component membranes. In addition to these two circular and stripe domains, a raft-like domain and budding domain are also observed, and the several corresponding phase diagrams are obtained.

  2. Disruption?

    DEFF Research Database (Denmark)

    2016-01-01

    This is a short video on the theme disruption and entrepreneurship. It takes the form of an interview with John Murray......This is a short video on the theme disruption and entrepreneurship. It takes the form of an interview with John Murray...

  3. A distributed dynamic model of a monolith hydrogen membrane reactor

    International Nuclear Information System (INIS)

    Michelsen, Finn Are; Wilhelmsen, Øivind; Zhao, Lei; Aasen, Knut Ingvar

    2013-01-01

    Highlights: ► We model a rigorous distributed dynamic model for a HMR unit. ► The model includes enough complexity for steady-state and dynamic analysis. ► Simulations show that the model is non-linear within the normal operating range. ► The model is useful for studying and handling disturbances such as inlet changes and membrane leakage. - Abstract: This paper describes a distributed mechanistic dynamic model of a hydrogen membrane reformer unit (HMR) used for methane steam reforming. The model is based on a square channel monolith structure concept, where air flows adjacent to a mix of natural gas and water distributed in a chess pattern of channels. Combustion of hydrogen gives energy to the endothermic steam reforming reactions. The model is used for both steady state and dynamic analyses. It therefore needs to be computationally attractive, but still include enough complexity to study the important steady state and dynamic features of the process. Steady-state analysis of the model gives optimum for the steam to carbon and steam to oxygen ratios, where the conversion of methane is 92% and the hydrogen used as energy for the endothermic reactions is 28% at the nominal optimum. The dynamic analysis shows that non-linear control schemes may be necessary for satisfactory control performance

  4. Molecular dynamics study of lipid bilayers modeling the plasma membranes of mouse hepatocytes and hepatomas.

    Science.gov (United States)

    Andoh, Yoshimichi; Aoki, Noriyuki; Okazaki, Susumu

    2016-02-28

    Molecular dynamics (MD) calculations of lipid bilayers modeling the plasma membranes of normal mouse hepatocytes and hepatomas in water have been performed under physiological isothermal-isobaric conditions (310.15 K and 1 atm). The changes in the membrane properties induced by hepatic canceration were investigated and were compared with previous MD calculations included in our previous study of the changes in membrane properties induced by murine thymic canceration. The calculated model membranes for normal hepatocytes and hepatomas comprised 23 and 24 kinds of lipids, respectively. These included phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, sphingomyelin, lysophospholipids, and cholesterol. We referred to previously published experimental values for the mole fraction of the lipids adopted in the present calculations. The calculated structural and dynamic properties of the membranes such as lateral structure, order parameters, lateral self-diffusion constants, and rotational correlation times all showed that hepatic canceration causes plasma membranes to become more ordered laterally and less fluid. Interestingly, this finding contrasts with the less ordered structure and increased fluidity of plasma membranes induced by thymic canceration observed in our previous MD study.

  5. The problem of fouling in submerged membrane bioreactors - Model validation and experimental evidence

    Science.gov (United States)

    Tsibranska, Irene; Vlaev, Serafim; Tylkowski, Bartosz

    2018-01-01

    Integrating biological treatment with membrane separation has found a broad area of applications and industrial attention. Submerged membrane bioreactors (SMBRs), based on membrane modules immersed in the bioreactor, or side stream ones connected in recycle have been employed in different biotechnological processes for separation of thermally unstable products. Fouling is one of the most important challenges in the integrated SMBRs. A number of works are devoted to fouling analysis and its treatment, especially exploring the opportunity for enhanced fouling control in SMBRs. The main goal of the review is to provide a comprehensive yet concise overview of modeling the fouling in SMBRs in view of the problematics of model validation, either by real system measurements at different scales or by analysis of the obtained theoretical results. The review is focused on the current state of research applying computational fluid dynamics (CFD) modeling techniques.

  6. Coordinating Supply Chain Distribution in the Presence of Production Disruption Risks

    Directory of Open Access Journals (Sweden)

    Xuanguo Xu

    2010-09-01

    Full Text Available With the impacts of unexpected events, production processes of supply chain system may be forced to interrupt in a certain period, which may decrease the supply capacity of manufacturer to its retailers. This paper discusses methods to distribute the limited stock in case the production disruptions occur. To ascertain a reasonable replenish sequence and quantity after the production disruption, a production disruption-oriented supply chain distribution model is offered, which can be used to minimize the negative impact of production disruption to supply chain system. And then a constraint satisfaction optimization method is established to resolve the model. Finally, validity of the model is verified with an actual application in an air-conditioner factory in China.

  7. Abnormal energy deposition on the wall through plasma disruptions

    International Nuclear Information System (INIS)

    Yamazaki, K.; Schmidt, G.L.

    1984-07-01

    The dissipation of plasma kinetic and magnetic energy during sawtooth oscillstions and disruptions in tokamaks is analyzed using Kadomtsev's disruption model and the plasma-circuit equations. New simple scalings of several characteristic times are obtained for sawteeth and for thermal and magnetic energy quenches of disruptions. The abnormal energy deposition on the wall during major or minor disruptions, estimated from this analysis, is compared with bolometric measurements in the PDX tokamak. Especially, magnetic energy dissipation during current termination period is shown to be reduced by the strong coupling of the plasma current with external circuits. These analyses are found to be useful to predict the phenomenological behavior of plasma disruptions in large future tokamaks, and to estimate abnormal heat deposition on the wall during plasma disruptions. (author)

  8. Antimicrobial agent triclosan disrupts mitochondrial structure, revealed by super-resolution microscopy, and inhibits mast cell signaling via calcium modulation.

    Science.gov (United States)

    Weatherly, Lisa M; Nelson, Andrew J; Shim, Juyoung; Riitano, Abigail M; Gerson, Erik D; Hart, Andrew J; de Juan-Sanz, Jaime; Ryan, Timothy A; Sher, Roger; Hess, Samuel T; Gosse, Julie A

    2018-06-15

    The antimicrobial agent triclosan (TCS) is used in products such as toothpaste and surgical soaps and is readily absorbed into oral mucosa and human skin. These and many other tissues contain mast cells, which are involved in numerous physiologies and diseases. Mast cells release chemical mediators through a process termed degranulation, which is inhibited by TCS. Investigation into the underlying mechanisms led to the finding that TCS is a mitochondrial uncoupler at non-cytotoxic, low-micromolar doses in several cell types and live zebrafish. Our aim was to determine the mechanisms underlying TCS disruption of mitochondrial function and of mast cell signaling. We combined super-resolution (fluorescence photoactivation localization) microscopy and multiple fluorescence-based assays to detail triclosan's effects in living mast cells, fibroblasts, and primary human keratinocytes. TCS disrupts mitochondrial nanostructure, causing mitochondria to undergo fission and to form a toroidal, "donut" shape. TCS increases reactive oxygen species production, decreases mitochondrial membrane potential, and disrupts ER and mitochondrial Ca 2+ levels, processes that cause mitochondrial fission. TCS is 60 × more potent than the banned uncoupler 2,4-dinitrophenol. TCS inhibits mast cell degranulation by decreasing mitochondrial membrane potential, disrupting microtubule polymerization, and inhibiting mitochondrial translocation, which reduces Ca 2+ influx into the cell. Our findings provide mechanisms for both triclosan's inhibition of mast cell signaling and its universal disruption of mitochondria. These mechanisms provide partial explanations for triclosan's adverse effects on human reproduction, immunology, and development. This study is the first to utilize super-resolution microscopy in the field of toxicology. Copyright © 2018 Elsevier Inc. All rights reserved.

  9. Interaction of arsenic compounds with model phospholipid membranes

    International Nuclear Information System (INIS)

    Jemiola-Rzeminska, Malgorzata; Rivera, Cecilia; Suwalsky, Mario; Strzalka, Kazimierz

    2007-01-01

    This study is part of a project aimed at examining the influence of arsenic on biological membranes. By the use of differential scanning calorimetry (DSC) we have followed the thermotropic behavior of multilamellar vesicles prepared from dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) upon incorporation of sodium arsenite (AsI), disodium arsenate (AsII), cacodylic acid (AsIII) and disodium methyl arsenate (AsIV). The effectiveness of perturbations exerted by various arsenic compounds on thermotropic phase transition was further analysed in terms of thermodynamic parameters: transition temperature, enthalpy and molar heat capacity, determined for lipid/As systems on the basis of heating and cooling scans. It is found that while it only has a slight influence on the thermotropic properties of DMPC, arsenic is able to significantly modify DMPE model membranes

  10. Ion transport Modeling in a Bipolar Membrane

    International Nuclear Information System (INIS)

    Kim, Jung Soo; Park, Kwang Heon; Kim, Kwang Wook

    2010-01-01

    The COL(Carbonate-based Oxidative Leaching) process is an environmentally-friendly technique for collecting only uranium from spent fuel with oxidation leaching/ precipitation of carbonate solution. The bipolar membrane used for the electrolyte circulation of the salt used in the COL process is a special form of ion exchange membrane which combines CEM(cation exchange membrane) and AEM(anion exchange membrane). After arranging positive ion exchange layer toward negative terminal and positive ion exchange layer toward positive terminal, then supply electricity, water molecules are decomposed into protons and hydroxyl ions by a strong electric field in the transition region inside bipolar membrane.1) In this study, a theoretical approach to increase the efficiency of Na + and NO3 - ion collecting device using bipolar membrane was taken and simulating using the COMSOL program was tried. The details of results are also discussed

  11. Adrenal Chromaffin Cells Exposed to 5-ns Pulses Require Higher Electric Fields to Porate Intracellular Membranes than the Plasma Membrane: An Experimental and Modeling Study.

    Science.gov (United States)

    Zaklit, Josette; Craviso, Gale L; Leblanc, Normand; Yang, Lisha; Vernier, P Thomas; Chatterjee, Indira

    2017-10-01

    Nanosecond-duration electric pulses (NEPs) can permeabilize the endoplasmic reticulum (ER), causing release of Ca 2+ into the cytoplasm. This study used experimentation coupled with numerical modeling to understand the lack of Ca 2+ mobilization from Ca 2+ -storing organelles in catecholamine-secreting adrenal chromaffin cells exposed to 5-ns pulses. Fluorescence imaging determined a threshold electric (E) field of 8 MV/m for mobilizing intracellular Ca 2+ whereas whole-cell recordings of membrane conductance determined a threshold E-field of 3 MV/m for causing plasma membrane permeabilization. In contrast, a 2D numerical model of a chromaffin cell, which was constructed with internal structures representing a nucleus, mitochondrion, ER, and secretory granule, predicted that exposing the cell to the same 5-ns pulse electroporated the plasma and ER membranes at the same E-field amplitude, 3-4 MV/m. Agreement of the numerical simulations with the experimental results was obtained only when the ER interior conductivity was 30-fold lower than that of the cytoplasm and the ER membrane permittivity was twice that of the plasma membrane. A more realistic intracellular geometry for chromaffin cells in which structures representing multiple secretory granules and an ER showed slight differences in the thresholds necessary to porate the membranes of the secretory granules. We conclude that more sophisticated cell models together with knowledge of accurate dielectric properties are needed to understand the effects of NEPs on intracellular membranes in chromaffin cells, information that will be important for elucidating how NEPs porate organelle membranes in other cell types having a similarly complex cytoplasmic ultrastructure.

  12. Aroma Stripping under various Forms of Membrane Distillation Processes: Experiments and modeling

    DEFF Research Database (Denmark)

    Jonsson, Gunnar Eigil

    the large different in permeate flux and concentration factor that was observed for the different MD configurations. This is highly related to the heat and mass transfer resistances in the membrane as well as in the boundary layers adjacent to the membrane surface and how the driving force develops along......Concentration of fruit juices by membrane distillation is an interesting process as it can be done at low temperature giving a gentle concentration process with little deterioration of the juices. Since the juices contains many different aroma compounds with a wide range of chemical properties...... such as volatility, activity coefficient and vapor pressure, it is important to know how these aroma compounds will eventually pass through the membrane. Experiments have been made on an aroma model solution and on black currant juice in a lab scale membrane distillation set up which can be operated in various types...

  13. Neutrons and model membranes

    Science.gov (United States)

    Fragneto, G.

    2012-11-01

    Current research in membrane protein biophysics highlights the emerging role of lipids in shaping membrane protein function. Cells and organisms have developed sophisticated mechanisms for controlling the lipid composition and many diseases are related to the failure of these mechanisms. One of the recent advances in the field is the discovery of the existence of coexisting micro-domains within a single membrane, important for regulating some signaling pathways. Many important properties of these domains remain poorly characterized. The characterization and analysis of bio-interfaces represent a challenge. Performing measurements on these few nanometer thick, soft, visco-elastic and dynamic systems is close to the limits of the available tools and methods. Neutron scattering techniques including small angle scattering, diffraction, reflectometry as well as inelastic methods are rapidly developing for these studies and are attracting an increasing number of biologists and biophysicists at large facilities. This manuscript will review some recent progress in the field and provide perspectives for future developments. It aims at highlighting neutron reflectometry as a versatile method to tackle questions dealing with the understanding and function of biomembranes and their components. The other important scattering methods are only briefly introduced.

  14. Testing the effects of safety climate and disruptive children behavior on school bus drivers performance: A multilevel model.

    Science.gov (United States)

    Zohar, Dov; Lee, Jin

    2016-10-01

    The study was designed to test a multilevel path model whose variables exert opposing effects on school bus drivers' performance. Whereas departmental safety climate was expected to improve driving safety, the opposite was true for in-vehicle disruptive children behavior. The driving safety path in this model consists of increasing risk-taking practices starting with safety shortcuts leading to rule violations and to near-miss events. The study used a sample of 474 school bus drivers in rural areas, driving children to school and school-related activities. Newly developed scales for measuring predictor, mediator and outcome variables were validated with video data taken from inner and outer cameras, which were installed in 29 buses. Results partially supported the model by indicating that group-level safety climate and individual-level children distraction exerted opposite effects on the driving safety path. Furthermore, as hypothesized, children disruption moderated the strength of the safety rule violation-near miss relationship, resulting in greater strength under high disruptiveness. At the same time, the hypothesized interaction between the two predictor variables was not supported. Theoretical and practical implications for studying safety climate in general and distracted driving in particular for professional drivers are discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Mathematical modeling of liquid/liquid hollow fiber membrane contactor accounting for interfacial transport phenomena: Extraction of lanthanides as a surrogate for actinides

    International Nuclear Information System (INIS)

    Rogers, J.D.

    1994-01-01

    This report is divided into two parts. The second part is divided into the following sections: experimental protocol; modeling the hollow fiber extractor using film theory; Graetz model of the hollow fiber membrane process; fundamental diffusive-kinetic model; and diffusive liquid membrane device-a rigorous model. The first part is divided into: membrane and membrane process-a concept; metal extraction; kinetics of metal extraction; modeling the membrane contactor; and interfacial phenomenon-boundary conditions-applied to membrane transport

  16. Analysis of coupled proton and water transport in a PEM fuel cell using the binary friction membrane model

    International Nuclear Information System (INIS)

    Carnes, B.; Djilali, N.

    2006-01-01

    Transport of liquid water within a polymer electrolyte membrane (PEM) is critical to the operation of a PEM fuel cell, due to the strong dependence of the membrane transport coefficients on water content. In addition, enhanced predictive abilities are particularly significant in the context of passive air breathing fuel cell designs where lower water contents will prevail in the membrane. We investigate and analyze the numerical predictions of a recently proposed rational model for transport of protons and water in a PEM, when compared to a widely used empirical model. While the performance is similar for a saturated membrane, for PEMs with low water content, the difference in computed current density and membrane water crossover can be substantial. The effects of coupling partially saturated gas diffusion electrodes (GDLs) with the membrane are studied in both a 1D and 2D context. In addition, a simplified 1D analytical membrane water transport model is validated against the complete 1D model predictions. Our numerical results predict a higher current density and more uniform membrane hydration using a dry cathode instead of a dry anode, and illustrate that the strongest 2D effects are for water vapor transport

  17. Structural models of the membrane anchors of envelope glycoproteins E1 and E2 from pestiviruses

    International Nuclear Information System (INIS)

    Wang, Jimin; Li, Yue; Modis, Yorgo

    2014-01-01

    The membrane anchors of viral envelope proteins play essential roles in cell entry. Recent crystal structures of the ectodomain of envelope protein E2 from a pestivirus suggest that E2 belongs to a novel structural class of membrane fusion machinery. Based on geometric constraints from the E2 structures, we generated atomic models of the E1 and E2 membrane anchors using computational approaches. The E1 anchor contains two amphipathic perimembrane helices and one transmembrane helix; the E2 anchor contains a short helical hairpin stabilized in the membrane by an arginine residue, similar to flaviviruses. A pair of histidine residues in the E2 ectodomain may participate in pH sensing. The proposed atomic models point to Cys987 in E2 as the site of disulfide bond linkage with E1 to form E1–E2 heterodimers. The membrane anchor models provide structural constraints for the disulfide bonding pattern and overall backbone conformation of the E1 ectodomain. - Highlights: • Structures of pestivirus E2 proteins impose constraints on E1, E2 membrane anchors. • Atomic models of the E1 and E2 membrane anchors were generated in silico. • A “snorkeling” arginine completes the short helical hairpin in the E2 membrane anchor. • Roles in pH sensing and E1–E2 disulfide bond formation are proposed for E1 residues. • Implications for E1 ectodomain structure and disulfide bonding pattern are discussed

  18. Structural models of the membrane anchors of envelope glycoproteins E1 and E2 from pestiviruses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jimin, E-mail: jimin.wang@yale.edu; Li, Yue; Modis, Yorgo, E-mail: yorgo.modis@yale.edu

    2014-04-15

    The membrane anchors of viral envelope proteins play essential roles in cell entry. Recent crystal structures of the ectodomain of envelope protein E2 from a pestivirus suggest that E2 belongs to a novel structural class of membrane fusion machinery. Based on geometric constraints from the E2 structures, we generated atomic models of the E1 and E2 membrane anchors using computational approaches. The E1 anchor contains two amphipathic perimembrane helices and one transmembrane helix; the E2 anchor contains a short helical hairpin stabilized in the membrane by an arginine residue, similar to flaviviruses. A pair of histidine residues in the E2 ectodomain may participate in pH sensing. The proposed atomic models point to Cys987 in E2 as the site of disulfide bond linkage with E1 to form E1–E2 heterodimers. The membrane anchor models provide structural constraints for the disulfide bonding pattern and overall backbone conformation of the E1 ectodomain. - Highlights: • Structures of pestivirus E2 proteins impose constraints on E1, E2 membrane anchors. • Atomic models of the E1 and E2 membrane anchors were generated in silico. • A “snorkeling” arginine completes the short helical hairpin in the E2 membrane anchor. • Roles in pH sensing and E1–E2 disulfide bond formation are proposed for E1 residues. • Implications for E1 ectodomain structure and disulfide bonding pattern are discussed.

  19. Computational simulation of water transport in PEM fuel cells using an improved membrane model

    International Nuclear Information System (INIS)

    Cao, J.; Djilali, N.

    2000-01-01

    Computational models and simulation tools can provide valuable insight and guidance for design, performance optimization, and cost reduction of fuel cells. In proton-exchange membrane fuel cells it is particularly important to maintain appropriate water content and temperature in the electrolyte membrane. In this paper we describe a mathematical model for the membrane that takes into account the diffusion of water, the pressure variation, and the electro-osmotic drag in the membrane. Applying conservation laws for water and current and using an empirical relationship between electro-osmotic drag and water content, we obtain a transport equation for water molar concentration and derive a new equation for the electric potential that accounts for variable water content and is more accurate than the conventionally employed Laplace's equation does. The model is coupled with a computational fluid dynamics model for diffusive transport in the electrodes and convective transport in the reactant flow channels. Simulations for a two-dimensional cell are performed over nominal current densities ranging form i=0.1 A/cm≅ to 1.2 A/cm≅. The impact and importance of temperature and pressure non-uniformity, and of two-dimensionality are assessed and discussed. (author)

  20. Technology and plasma-materials interaction processes of tokamak disruptions

    International Nuclear Information System (INIS)

    McGrath, R.T.; Kellman, A.G.

    1992-01-01

    A workshop on the technology and plasma-materials interaction processes of tokamak disruptions was held April 3, 1992 in Monterey, California, as a satellite meeting of the 10th International Conference on Plasma-Surface Interactions. The objective was to bring together researchers working on disruption measurements in operating tokamaks, those performing disruption simulation experiments using pulsed plasma gun, electron beam and laser systems, and computational physicists attempting to model the evolution and plasma-materials interaction processes of tokamak disruptions. This is a brief report on the workshop. 4 refs

  1. Effects of Disruption Risks on Biorefinery Location Design

    Directory of Open Access Journals (Sweden)

    Yun Bai

    2015-02-01

    Full Text Available While ever-growing bio-ethanol production poses considerable challenges to the bioenergy supply chain, the risk of refinery operation disruptions further compromises the efficiency and reliability of the energy supply system. This paper applies discrete and continuous reliable facility location models to the design of reliable bio-ethanol supply chains so that the system can hedge against potential operational disruptions. The discrete model is shown to be suitable for obtaining the exact optimality for small or moderate instances, while the continuous model has superior computational tractability for large-scale applications. The impacts of both site-independent and dependent disruptions (i.e., due to flooding are analyzed in empirical case study for the State of Illinois (one of the main biomass supply states in the U.S.. The reliable solution is compared with a deterministic solution under the same setting. It is found that refinery disruptions, especially those site-dependent ones, affect both optimal refinery deployment and the supply chain cost. Sensitivity analysis is also conducted to show how refinery failure probability and fixed cost (for building biorefineries affect optimal supply chain configuration and the total expected system cost.

  2. CFD modelling of a membrane reactor for hydrogen production from ammonia

    Science.gov (United States)

    Shwe Hla, San; Dolan, Michael D.

    2018-01-01

    Despite the growing use of hydrogen (H2) as a transport fuel, one of the major barriers still remaining is efficient and inexpensive fuel distribution and storage. Current approaches, such as compression, liquefaction or metal hydride formation, incur a significant energy penalty. Ammonia (NH3) has long been considered a prospective H2 medium, exhibiting a higher volumetric H2 density than liquid H2, through liquid-phase storage at mild pressure. Decomposition of NH3 into H2 and N2 can be achieved via use of catalytic reactors and fuel-cell-grade H2 can be produced using metal membranes at H2 distribution sites.In this study, a 3-Dimensional (3D) Computational Fluid Dynamics (CFD) model has been developed to understand the performance of the H2 separation process in gas mixtures derived from an NH3-cracking reaction. The reactor consists of 19 tubular membrane tubes, each 470 mm long, inside a tubular shell with an inner diameter of 130 mm. Standard transport and energy equations governing a 3D, pressure-based, steady-state model were derived from the laws of conservation of mass, momentum and energy. The governing equations were solved using commercial CFD software ANSYS Fluent 18.0. Gas flow and mixing were modelled by the two-equation standard k-epsilon model for closure. Coupled solver was used for pressure-velocity coupling, enabling a pseudo-transient option with pseudo time steps of 0.01 s. To estimate H2 permeation through the metal membrane, a constant H2 permeability of 3.0E-07 mol.m-1 s-1 Pa-0.5 derived from series of experiments tested under a range of industrial conditions, was used. Model simulations were conducted for an adiabatic temperature of 300 °C, a feed-side pressure of 7.8 bara and a permeate side pressure of 0.1 bara. A parametric analysis was carried out to explore the effects of variation in total feed-gas flow and effects of changes in NH3-cracking efficiency on H2 production rates and H2 yields. The model estimated that 4.6-11.6 kg H2

  3. Cyto-Sim: a formal language model and stochastic simulator of membrane-enclosed biochemical processes.

    Science.gov (United States)

    Sedwards, Sean; Mazza, Tommaso

    2007-10-15

    Compartments and membranes are the basis of cell topology and more than 30% of the human genome codes for membrane proteins. While it is possible to represent compartments and membrane proteins in a nominal way with many mathematical formalisms used in systems biology, few, if any, explicitly model the topology of the membranes themselves. Discrete stochastic simulation potentially offers the most accurate representation of cell dynamics. Since the details of every molecular interaction in a pathway are often not known, the relationship between chemical species in not necessarily best described at the lowest level, i.e. by mass action. Simulation is a form of computer-aided analysis, relying on human interpretation to derive meaning. To improve efficiency and gain meaning in an automatic way, it is necessary to have a formalism based on a model which has decidable properties. We present Cyto-Sim, a stochastic simulator of membrane-enclosed hierarchies of biochemical processes, where the membranes comprise an inner, outer and integral layer. The underlying model is based on formal language theory and has been shown to have decidable properties (Cavaliere and Sedwards, 2006), allowing formal analysis in addition to simulation. The simulator provides variable levels of abstraction via arbitrary chemical kinetics which link to ordinary differential equations. In addition to its compact native syntax, Cyto-Sim currently supports models described as Petri nets, can import all versions of SBML and can export SBML and MATLAB m-files. Cyto-Sim is available free, either as an applet or a stand-alone Java program via the web page (http://www.cosbi.eu/Rpty_Soft_CytoSim.php). Other versions can be made available upon request.

  4. Theoretical modeling and experimental validation of transport and separation properties of carbon nanotube electrospun membrane distillation

    KAUST Repository

    Lee, Jung Gil; Lee, Eui-Jong; Jeong, Sanghyun; Guo, Jiaxin; An, Alicia Kyoungjin; Guo, Hong; Kim, Joonha; Leiknes, TorOve; Ghaffour, NorEddine

    2016-01-01

    Developing a high flux and selective membrane is required to make membrane distillation (MD) a more attractive desalination process. Amongst other characteristics membrane hydrophobicity is significantly important to get high vapor transport and low wettability. In this study, a laboratory fabricated carbon nanotubes (CNTs) composite electrospun (E-CNT) membrane was tested and has showed a higher permeate flux compared to poly(vinylidene fluoride-co-hexafluoropropylene) (PH) electrospun membrane (E-PH membrane) in a direct contact MD (DCMD) configuration. Only 1% and 2% of CNTs incorporation resulted in an enhanced permeate flux with lower sensitivity to feed salinity while treating a 35 and 70 g/L NaCl solutions. Experimental results and the mechanisms of E-CNT membrane were validated by a proposed new step-modeling approach. The increased vapor transport in E-CNT membranes could not be elucidated by an enhancement of mass transfer only at a given physico-chemical properties. However, the theoretical modeling approach considering the heat and mass transfers simultaneously enabled to explain successfully the enhanced flux in the DCMD process using E-CNT membranes. This indicates that both mass and heat transfers improved by CNTs are attributed to the enhanced vapor transport in the E-CNT membrane.

  5. Theoretical modeling and experimental validation of transport and separation properties of carbon nanotube electrospun membrane distillation

    KAUST Repository

    Lee, Jung Gil

    2016-12-27

    Developing a high flux and selective membrane is required to make membrane distillation (MD) a more attractive desalination process. Amongst other characteristics membrane hydrophobicity is significantly important to get high vapor transport and low wettability. In this study, a laboratory fabricated carbon nanotubes (CNTs) composite electrospun (E-CNT) membrane was tested and has showed a higher permeate flux compared to poly(vinylidene fluoride-co-hexafluoropropylene) (PH) electrospun membrane (E-PH membrane) in a direct contact MD (DCMD) configuration. Only 1% and 2% of CNTs incorporation resulted in an enhanced permeate flux with lower sensitivity to feed salinity while treating a 35 and 70 g/L NaCl solutions. Experimental results and the mechanisms of E-CNT membrane were validated by a proposed new step-modeling approach. The increased vapor transport in E-CNT membranes could not be elucidated by an enhancement of mass transfer only at a given physico-chemical properties. However, the theoretical modeling approach considering the heat and mass transfers simultaneously enabled to explain successfully the enhanced flux in the DCMD process using E-CNT membranes. This indicates that both mass and heat transfers improved by CNTs are attributed to the enhanced vapor transport in the E-CNT membrane.

  6. Abnormal energy deposition on the wall through plasma disruptions

    International Nuclear Information System (INIS)

    Yamazaki, K.; Schmidt, G.L.

    1984-01-01

    The dissipation of plasma kinetic and magnetic energy during sawtooth oscillations and disruptions in tokamak is analyzed using Kadomtsev's disruption model and the plasma-circuit equations. New simple scalings of several characteristic times are obtained for sawteeth and for thermal and magnetic energy quenches of disruptions. The abnormal energy deposition on the wall during major or minor disruptions, estimated from this analysis, is compared with bolometric measurements in the PDX tokamak. Especially, magnetic energy dissipation during the current termination period is shown to be reduced by the strong coupling of the plasma current with external circuits. These analyses are found to be useful to predict the phenomenological behavior of plasma disruptions in large future tokamaks, and to estimate abnormal heat deposition on the wall during plasma disruptions. (orig.)

  7. Disruptive Innovation in Chinese and Indian Businesses

    DEFF Research Database (Denmark)

    markets, has made these emerging economies fertile ground for developing and applying disruptive innovations. A novel mix of key attributes distinctive from those of established technologies or business models, disruptive innovations are typically inferior, yet affordable and "good-enough" products...... or services, which originate in lower-end market segments, but later move up to compete with those provided by incumbent firms. This book sheds new light on disruptive innovations both from and for the bottom of the pyramid in China and India, from the point of view of local entrepreneurs and international...... firms seeking to operate their businesses there. It covers both the theoretical and practical implications of disruptive innovation using conceptual frameworks alongside detailed case studies, whilst also providing a comparison of conditions and strategic options in India and China. Further, unlike...

  8. All-in-one nanowire-decorated multifunctional membrane for rapid cell lysis and direct DNA isolation.

    KAUST Repository

    So, Hongyun; Lee, Kunwoo; Murthy, Niren; Pisano, Albert P

    2014-01-01

    This paper describes a handheld device that uses an all-in-one membrane for continuous mechanical cell lysis and rapid DNA isolation without the assistance of power sources, lysis reagents, and routine centrifugation. This nanowire-decorated multifunctional membrane was fabricated to isolate DNA by selective adsorption to silica surface immediately after disruption of nucleus membranes by ultrasharp tips of nanowires for a rapid cell lysis, and it can be directly assembled with commercial syringe filter holders. The membrane was fabricated by photoelectrochemical etching to create microchannel arrays followed by hydrothermal synthesis of nanowires and deposition of silica. The proposed membrane successfully purifies high-quality DNA within 5 min, whereas a commercial purification kit needs more than an hour.

  9. All-in-one nanowire-decorated multifunctional membrane for rapid cell lysis and direct DNA isolation.

    KAUST Repository

    So, Hongyun

    2014-11-24

    This paper describes a handheld device that uses an all-in-one membrane for continuous mechanical cell lysis and rapid DNA isolation without the assistance of power sources, lysis reagents, and routine centrifugation. This nanowire-decorated multifunctional membrane was fabricated to isolate DNA by selective adsorption to silica surface immediately after disruption of nucleus membranes by ultrasharp tips of nanowires for a rapid cell lysis, and it can be directly assembled with commercial syringe filter holders. The membrane was fabricated by photoelectrochemical etching to create microchannel arrays followed by hydrothermal synthesis of nanowires and deposition of silica. The proposed membrane successfully purifies high-quality DNA within 5 min, whereas a commercial purification kit needs more than an hour.

  10. Biological nitrogen and phosphorus removal in membrane bioreactors: model development and parameter estimation.

    Science.gov (United States)

    Cosenza, Alida; Mannina, Giorgio; Neumann, Marc B; Viviani, Gaspare; Vanrolleghem, Peter A

    2013-04-01

    Membrane bioreactors (MBR) are being increasingly used for wastewater treatment. Mathematical modeling of MBR systems plays a key role in order to better explain their characteristics. Several MBR models have been presented in the literature focusing on different aspects: biological models, models which include soluble microbial products (SMP), physical models able to describe the membrane fouling and integrated models which couple the SMP models with the physical models. However, only a few integrated models have been developed which take into account the relationships between membrane fouling and biological processes. With respect to biological phosphorus removal in MBR systems, due to the complexity of the process, practical use of the models is still limited. There is a vast knowledge (and consequently vast amount of data) on nutrient removal for conventional-activated sludge systems but only limited information on phosphorus removal for MBRs. Calibration of these complex integrated models still remains the main bottleneck to their employment. The paper presents an integrated mathematical model able to simultaneously describe biological phosphorus removal, SMP formation/degradation and physical processes which also include the removal of organic matter. The model has been calibrated with data collected in a UCT-MBR pilot plant, located at the Palermo wastewater treatment plant, applying a modified version of a recently developed calibration protocol. The calibrated model provides acceptable correspondence with experimental data and can be considered a useful tool for MBR design and operation.

  11. Transport parameters for the modelling of water transport in ionomer membranes for PEM-fuel cells

    International Nuclear Information System (INIS)

    Meier, Frank; Eigenberger, Gerhart

    2004-01-01

    The water transport number (drag coefficient) and the hydraulic permeability were measured for Nafion. The results show a significant increase of both parameters with increasing water content indicating that they are strongly influenced by the membrane microstructure. Based on these experimental studies a new model approach to describe water transport in the H 2 -PEFC membrane is presented. This approach considers water transport by electro-osmosis caused by the proton flux through the membrane and by osmosis caused by a gradient in the chemical potential of water. It is parametrized by the measured data for the water transport number and the hydraulic permeability of Nafion. First simulation results applying this approach to a one-dimensional model of the H 2 -PEFC show good agreement with experimental data. Therefore, the developed model can be used for a new insight into the dominating mechanisms of water transport in the membrane

  12. Disruption from the Inside-Out: Innovation in the Restaurant Industry

    Directory of Open Access Journals (Sweden)

    Makaela Reinke

    2016-01-01

    Full Text Available Eating out looks much like it always has, even amidst today's storms of disruptive and breakthrough models. How is it that while so much of our world changes, the business of eating has essentially stayed the same? Has the restaurant industry been affected by disruptive models at all?

  13. Structural models of the membrane anchors of envelope glycoproteins E1 and E2 from pestiviruses

    Science.gov (United States)

    Wang, Jimin; Li, Yue; Modis, Yorgo

    2014-01-01

    The membrane anchors of viral envelope proteins play essential roles in cell entry. Recent crystal structures of the ectodomain of envelope protein E2 from a pestivirus suggest that E2 belongs to a novel structural class of membrane fusion machinery. Based on geometric constraints from the E2 structures, we generated atomic models of the E1 and E2 membrane anchors using computational approaches. The E1 anchor contains two amphipathic perimembrane helices and one transmembrane helix; the E2 anchor contains a short helical hairpin stabilized in the membrane by an arginine residue, similar to flaviviruses. A pair of histidine residues in the E2 ectodomain may participate in pH sensing. The proposed atomic models point to Cys987 in E2 as the site of disulfide bond linkage with E1 to form E1–E2 heterodimers. The membrane anchor models provide structural constraints for the disulfide bonding pattern and overall backbone conformation of the E1 ectodomain. PMID:24725935

  14. An articulated predictive model for fluid-free artificial basilar membrane as broadband frequency sensor

    Science.gov (United States)

    Ahmed, Riaz; Banerjee, Sourav

    2018-02-01

    In this article, an extremely versatile predictive model for a newly developed Basilar meta-Membrane (BM2) sensors is reported with variable engineering parameters that contribute to it's frequency selection capabilities. The predictive model reported herein is for advancement over existing method by incorporating versatile and nonhomogeneous (e.g. functionally graded) model parameters that could not only exploit the possibilities of creating complex combinations of broadband frequency sensors but also explain the unique unexplained physical phenomenon that prevails in BM2, e.g. tailgating waves. In recent years, few notable attempts were made to fabricate the artificial basilar membrane, mimicking the mechanics of the human cochlea within a very short range of frequencies. To explain the operation of these sensors a few models were proposed. But, we fundamentally argue the "fabrication to explanation" approach and proposed the model driven predictive design process for the design any (BM2) as broadband sensors. Inspired by the physics of basilar membrane, frequency domain predictive model is proposed where both the material and geometrical parameters can be arbitrarily varied. Broadband frequency is applicable in many fields of science, engineering and technology, such as, sensors for chemical, biological and acoustic applications. With the proposed model, which is three times faster than its FEM counterpart, it is possible to alter the attributes of the selected length of the designed sensor using complex combinations of model parameters, based on target frequency applications. Finally, the tailgating wave peaks in the artificial basilar membranes that prevails in the previously reported experimental studies are also explained using the proposed model.

  15. Development of a Comprehensive Fouling Model for a Rotating Membrane Bioreactor System Treating Wastewater

    Directory of Open Access Journals (Sweden)

    Parneet Paul

    2015-01-01

    Full Text Available Membrane bioreactors (MBRs are now main stream wastewater treatment technologies. In recent times, novel pressure driven rotating membrane disc modules have been specially developed that induce high shear on the membrane surface, thereby reducing fouling. Previous research has produced dead-end filtration fouling model which combines all three classical mechanisms that was later used by another researcher as a starting point for a greatly refined model of a cross flow side-stream MBR that incorporated both hydrodynamics and soluble microbial products’ (SMP effects. In this study, a comprehensive fouling model was created based on this earlier work that incorporated all three classical fouling mechanisms for a rotating MBR system. It was tested and validated for best fit using appropriate data sets. The initial model fit appeared good for all simulations, although it still needs to be calibrated using further appropriate data sets.

  16. Kinetic models of controllable pore growth of anodic aluminum oxide membrane

    Science.gov (United States)

    Huang, Yan; Zeng, Hong-yan; Zhao, Ce; Qu, Ye-qing; Zhang, Pin

    2012-06-01

    An anodized Al2O3 (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure ( σ) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time ( r= G· t+ G'), but decreased with increased concentration ( r = - K·ln c- K') through the derived mathematic formula. Also, the values of G, G', K, and K' were derived from our experimental data.

  17. The high density and high βpol disruption mechanism on TFTR

    International Nuclear Information System (INIS)

    Fredrickson, E.D.; Manickam, J.; McGuire, K.M.; Monticello, D.; Nagayama, Y.; Park, W.; Taylor, G.

    1992-01-01

    Studies of disruptions on TFTR have been extended to include high density disruptions as well as the high β pol disruptions. The data strongly suggests that the (m,n)=(1,1) mode plays an important role in both types of disruptions. Further, for the first time, it is unambiguously shown, using a fast electron cyclotron emission (ECE) instrument for the electron temperature profile measurements, that the (m,n)=(1,1) precursor to the high density disruptions has a 'cold bubble' structure. The precursor to the major disruption at high density resembles the 'vacuum bubble' model of disruptions first proposed by Kadomtsev and Pogutse. (author) 2 refs., 2 figs

  18. Analysis of recent fuel-disruption experiments

    International Nuclear Information System (INIS)

    Kramer, J.M.; Kraft, T.E.; DiMelfi, R.J.; Fenske, G.R.; Gruber, E.E.

    1982-01-01

    Recent USDOE-sponsored DEH, FGR, and TREAT F series fuel-disruption experiments are analyzed with existing analytical models. The experiments are interpreted and the results used to evaluate the models. Calculations are presented using the FRAS3 fission-gas-behavior code and the DiMelfi-Deitrich fuel-response model

  19. Key factors regulating the mass delivery of macromolecules to model cell membranes

    DEFF Research Database (Denmark)

    Campbell, Richard A.; Watkins, Erik B.; Jagalski, Vivien

    2014-01-01

    We show that both gravity and electrostatics are key factors regulating interactions between model cell membranes and self-assembled liquid crystalline aggregates of dendrimers and phospholipids. The system is a proxy for the trafficking of reservoirs of therapeutic drugs to cell membranes for slow...... of the aggregates to activate endocytosis pathways on specific cell types is discussed in the context of targeted drug delivery applications....

  20. Membrane-based seawater desalination: Present and future prospects

    KAUST Repository

    Amy, Gary L.

    2016-10-20

    Given increasing regional water scarcity and that almost half of the world\\'s population lives within 100 km of an ocean, seawater represents a virtually infinite water resource. However, its exploitation is presently limited by the significant specific energy consumption (kWh/m) required by conventional desalination technologies, further exasperated by high unit costs ($/m) and environmental impacts including GHG emissions (g CO-eq/m), organism impingement/entrainment through intakes, and brine disposal through outfalls. This paper explores the state-of-the-art in present seawater desalination practice, emphasizing membrane-based technologies, while identifying future opportunities in step improvements to conventional technologies and development of emerging, potentially disruptive, technologies through advances in material science, process engineering, and system integration. In this paper, seawater reverse osmosis (RO) serves as the baseline conventional technology. The discussion extends beyond desalting processes into membrane-based salinity gradient energy production processes, which can provide an energy offset to desalination process energy requirements. The future membrane landscape in membrane-based desalination and salinity gradient energy is projected to include ultrahigh permeability RO membranes, renewable-energy driven desalination, and emerging processes including closed-circuit RO, membrane distillation, forward osmosis, pressure retarded osmosis, and reverse electrodialysis according various niche applications and/or hybrids, operating separately or in conjunction with RO.

  1. Making CVE Work: A Focused Approach Based on Process Disruption

    Directory of Open Access Journals (Sweden)

    J.M. Berger

    2016-05-01

    Full Text Available One of the biggest barriers to designing a comprehensive Countering Violent Extremism (CVE programme is defining its scope. This paper argues for a narrow approach, focusing on disengagement and the disruption of recruitment. The author develops a simplified model of radicalisation and the concurrent terrorist recruitment process, proposing concrete themes for disruptive intervention and messaging. After analysing case studies of disengagement, the author offers recommendations for specific action to accomplish CVE goals by disrupting recruitment processes and deploying targeted messaging within the framework of the correlated models.

  2. Erosion of melt layers developed during a plasma disruption

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, A.; Konkashbaev, I.

    1994-08-01

    Material erosion of plasma-facing components during a tokamak disruption is a serious problem that limits reactor operation and economical reactor lifetime. In particular, metallic low-Z components such as Be will be subjected to severe melting during disruptions and edge localized models (ELMs). Loss of the developed melt layer will critically shorten the lifetime of these components, severely contaminate the plasma, and seriously inhibit successful and reliable operation of the reactor. In this study mechanisms responsible for melt-layer loss during a disruption are modeled and evaluated. Implications of melt-layer loss on the performance of metallic facing components in the reactor environment are discussed

  3. Modeling electrochemical performance in large scale proton exchange membrane fuel cell stacks

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J H [Los Alamos National Lab., NM (United States); Lalk, T R [Texas A and M Univ., College Station, TX (United States). Dept. of Mechanical Engineering; Appleby, A J [Center for Electrochemical Studies and Hydrogen Research, Texas Engineering Experimentation Station, Texas A and M Univ., College Station, TX (United States)

    1998-02-01

    The processes, losses, and electrical characteristics of a Membrane-Electrode Assembly (MEA) of a Proton Exchange Membrane Fuel Cell (PEMFC) are described. In addition, a technique for numerically modeling the electrochemical performance of a MEA, developed specifically to be implemented as part of a numerical model of a complete fuel cell stack, is presented. The technique of calculating electrochemical performance was demonstrated by modeling the MEA of a 350 cm{sup 2}, 125 cell PEMFC and combining it with a dynamic fuel cell stack model developed by the authors. Results from the demonstration that pertain to the MEA sub-model are given and described. These include plots of the temperature, pressure, humidity, and oxygen partial pressure distributions for the middle MEA of the modeled stack as well as the corresponding current produced by that MEA. The demonstration showed that models developed using this technique produce results that are reasonable when compared to established performance expectations and experimental results. (orig.)

  4. Exposure to Engineered Nanomaterial Results in Disruption of Brush Borders in Epithelia Models in vitro

    Science.gov (United States)

    Faust, James J.

    Engineered nanoparticles (NP; 10-9 m) have found use in a variety of consumer goods and medical devices because of the unique changes in material properties that occur when synthesized on the nanoscale. Although many definitions for nanoparticle exist, from the perspective of size, nanoparticle is defined as particles with diameters less than 100 nm in any external dimension. Examples of their use include titanium dioxide added as a pigment in products intended to be ingested by humans, silicon dioxide NPs are used in foods as an anticaking agent, and gold or iron oxide NPs can be used as vectors for drug delivery or contrast agents for specialized medical imaging. Although the intended use of these NPs is often to improve human health, it has come to the attention of investigators that NPs can have unintended or even detrimental effects on the organism. This work describes one such unintended effect of NP exposure from the perspective of exposure via the oral route. First, this Dissertation will explain an event referred to as brush border disruption that occurred after nanoparticles interacted with an in vitro model of the human intestinal epithelium. Second, this Dissertation will identify and characterize several consumer goods that were shown to contain titanium dioxide that are intended to be ingested. Third, this Dissertation shows that sedimentation due to gravity does not artifactually result in disruption of brush borders as a consequence of exposure to food grade titanium dioxide in vitro. Finally, this Dissertation will demonstrate that iron oxide nanoparticles elicited similar effects after exposure to an in vitro brush border expressing model of the human placenta. Together, these data suggest that brush border disruption is not an artifact of the material/cell culture model, but instead represents a bona fide biological response as a result of exposure to nanomaterial.

  5. Modelling the transport of carbonic acid anions through anion-exchange membranes

    International Nuclear Information System (INIS)

    Nikonenko, V.; Lebedev, K.; Manzanares, J.A.; Pourcelly, G.

    2003-01-01

    Electrodiffusion of carbonate and bicarbonate anions through anion-exchange membranes (AEM) is described on the basis of the Nernst-Planck equations taking into account coupled hydrolysis reactions in the external diffusion boundary layers (DBLs) and internal pore solution. The model supposes local electroneutrality as well as chemical and thermodynamic equilibrium. The transport is considered in three layers being an anion exchange membrane and two adjoining diffusion layers. A mechanism of competitive transport of HCO 3 - and CO 3 2- anions through the membrane which takes into account Donnan exclusion of H + ions is proposed. It is predicted that the pH of the depleting solution decreases and that of the concentrating solution increases during electrodialysis (ED). Eventual deviations from local electroneutrality and local chemical equilibrium are discussed

  6. Disruption Management of Rolling Stock in Passenger Railway Transportation

    NARCIS (Netherlands)

    L.K. Nielsen (Lars Kjaer); G. Maróti (Gábor)

    2009-01-01

    textabstractThis paper deals with real-time disruption management of rolling stock in passenger railway transportation. We present a generic framework for modeling disruptions in railway rolling stock schedules. The framework is presented as an online combinatorial decision problem where the

  7. On the avalanche generation of runaway electrons during tokamak disruptions

    International Nuclear Information System (INIS)

    Martín-Solís, J. R.; Loarte, A.; Lehnen, M.

    2015-01-01

    A simple zero dimensional model for a tokamak disruption is developed to evaluate the avalanche multiplication of a runaway primary seed during the current quench phase of a fast disruptive event. Analytical expressions for the plateau runaway current, the energy of the runaway beam, and the runaway energy distribution function are obtained allowing the identification of the parameters dominating the formation of the runaway current during disruptions. The effect of the electromagnetic coupling to the vessel and the penetration of the external magnetic energy during the disruption current quench as well as of the collisional dissipation of the runaway current at high densities are investigated. Current profile shape effects during the formation of the runaway beam are also addressed by means of an upgraded one-dimensional model

  8. Validation of kinetic modeling of progesterone release from polymeric membranes

    Directory of Open Access Journals (Sweden)

    Analia Irma Romero

    2018-01-01

    Full Text Available Mathematical modeling in drug release systems is fundamental in development and optimization of these systems, since it allows to predict drug release rates and to elucidate the physical transport mechanisms involved. In this paper we validate a novel mathematical model that describes progesterone (Prg controlled release from poly-3-hydroxybutyric acid (PHB membranes. A statistical analysis was conducted to compare the fitting of our model with six different models and the Akaike information criterion (AIC was used to find the equation with best-fit. A simple relation between mass and drug released rate was found, which allows predicting the effect of Prg loads on the release behavior. Our proposed model was the one with minimum AIC value, and therefore it was the one that statistically fitted better the experimental data obtained for all the Prg loads tested. Furthermore, the initial release rate was calculated and therefore, the interface mass transfer coefficient estimated and the equilibrium distribution constant of Prg between the PHB and the release medium was also determined. The results lead us to conclude that our proposed model is the one which best fits the experimental data and can be successfully used to describe Prg drug release in PHB membranes.

  9. Simulating Impacts of Disruptions to Liquid Fuels Infrastructure

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Michael [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Resilience and Regulatory Effects; Corbet, Thomas F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Policy and Decision Analytics; Baker, Arnold B. [ABB Consulting, Albuquerque, NM (United States); O' Rourke, Julia M. [Univ. of Texas, Austin, TX (United States). Dept. of Mechanical Engineering

    2015-04-01

    This report presents a methodology for estimating the impacts of events that damage or disrupt liquid fuels infrastructure. The impact of a disruption depends on which components of the infrastructure are damaged, the time required for repairs, and the position of the disrupted components in the fuels supply network. Impacts are estimated for seven stressing events in regions of the United States, which were selected to represent a range of disruption types. For most of these events the analysis is carried out using the National Transportation Fuels Model (NTFM) to simulate the system-level liquid fuels sector response. Results are presented for each event, and a brief cross comparison of event simulation results is provided.

  10. ROCK1-directed basement membrane positioning coordinates epithelial tissue polarity.

    Science.gov (United States)

    Daley, William P; Gervais, Elise M; Centanni, Samuel W; Gulfo, Kathryn M; Nelson, Deirdre A; Larsen, Melinda

    2012-01-01

    The basement membrane is crucial for epithelial tissue organization and function. However, the mechanisms by which basement membrane is restricted to the basal periphery of epithelial tissues and the basement membrane-mediated signals that regulate coordinated tissue organization are not well defined. Here, we report that Rho kinase (ROCK) controls coordinated tissue organization by restricting basement membrane to the epithelial basal periphery in developing mouse submandibular salivary glands, and that ROCK inhibition results in accumulation of ectopic basement membrane throughout the epithelial compartment. ROCK-regulated restriction of PAR-1b (MARK2) localization in the outer basal epithelial cell layer is required for basement membrane positioning at the tissue periphery. PAR-1b is specifically required for basement membrane deposition, as inhibition of PAR-1b kinase activity prevents basement membrane deposition and disrupts overall tissue organization, and suppression of PAR-1b together with ROCK inhibition prevents interior accumulations of basement membrane. Conversely, ectopic overexpression of wild-type PAR-1b results in ectopic interior basement membrane deposition. Significantly, culture of salivary epithelial cells on exogenous basement membrane rescues epithelial organization in the presence of ROCK1 or PAR-1b inhibition, and this basement membrane-mediated rescue requires functional integrin β1 to maintain epithelial cell-cell adhesions. Taken together, these studies indicate that ROCK1/PAR-1b-dependent regulation of basement membrane placement is required for the coordination of tissue polarity and the elaboration of tissue structure in the developing submandibular salivary gland.

  11. Rubber particle proteins, HbREF and HbSRPP, show different interactions with model membranes.

    Science.gov (United States)

    Berthelot, Karine; Lecomte, Sophie; Estevez, Yannick; Zhendre, Vanessa; Henry, Sarah; Thévenot, Julie; Dufourc, Erick J; Alves, Isabel D; Peruch, Frédéric

    2014-01-01

    The biomembrane surrounding rubber particles from the hevea latex is well known for its content of numerous allergen proteins. HbREF (Hevb1) and HbSRPP (Hevb3) are major components, linked on rubber particles, and they have been shown to be involved in rubber synthesis or quality (mass regulation), but their exact function is still to be determined. In this study we highlighted the different modes of interactions of both recombinant proteins with various membrane models (lipid monolayers, liposomes or supported bilayers, and multilamellar vesicles) to mimic the latex particle membrane. We combined various biophysical methods (polarization-modulation-infrared reflection-adsorption spectroscopy (PM-IRRAS)/ellipsometry, attenuated-total reflectance Fourier-transform infrared (ATR-FTIR), solid-state nuclear magnetic resonance (NMR), plasmon waveguide resonance (PWR), fluorescence spectroscopy) to elucidate their interactions. Small rubber particle protein (SRPP) shows less affinity than rubber elongation factor (REF) for the membranes but displays a kind of "covering" effect on the lipid headgroups without disturbing the membrane integrity. Its structure is conserved in the presence of lipids. Contrarily, REF demonstrates higher membrane affinity with changes in its aggregation properties, the amyloid nature of REF, which we previously reported, is not favored in the presence of lipids. REF binds and inserts into membranes. The membrane integrity is highly perturbed, and we suspect that REF is even able to remove lipids from the membrane leading to the formation of mixed micelles. These two homologous proteins show affinity to all membrane models tested but neatly differ in their interacting features. This could imply differential roles on the surface of rubber particles. © 2013.

  12. Calcium and Magnesium Ions Are Membrane-Active against Stationary-Phase Staphylococcus aureus with High Specificity

    Science.gov (United States)

    Xie, Yuntao; Yang, Lihua

    2016-02-01

    Staphylococcus aureus (S. aureus) is notorious for its ability to acquire antibiotic-resistance, and antibiotic-resistant S. aureus has become a wide-spread cause of high mortality rate. Novel antimicrobials capable of eradicating S. aureus cells including antibiotic-resistant ones are thus highly desired. Membrane-active bactericides and species-specific antimicrobials are two promising sources of novel anti-infective agents for fighting against bacterial antibiotic-resistance. We herein show that Ca2+ and Mg2+, two alkaline-earth-metal ions physiologically essential for diverse living organisms, both disrupt model S. aureus membranes and kill stationary-phase S. aureus cells, indicative of membrane-activity. In contrast to S. aureus, Escherichia coli and Bacillus subtilis exhibit unaffected survival after similar treatment with these two cations, indicative of species-specific activity against S. aureus. Moreover, neither Ca2+ nor Mg2+ lyses mouse red blood cells, indicative of hemo-compatibility. This works suggests that Ca2+ and Mg2+ may have implications in targeted eradication of S. aureus pathogen including the antibiotic-resistant ones.

  13. Membrane Protein Mobility and Orientation Preserved in Supported Bilayers Created Directly from Cell Plasma Membrane Blebs.

    Science.gov (United States)

    Richards, Mark J; Hsia, Chih-Yun; Singh, Rohit R; Haider, Huma; Kumpf, Julia; Kawate, Toshimitsu; Daniel, Susan

    2016-03-29

    Membrane protein interactions with lipids are crucial for their native biological behavior, yet traditional characterization methods are often carried out on purified protein in the absence of lipids. We present a simple method to transfer membrane proteins expressed in mammalian cells to an assay-friendly, cushioned, supported lipid bilayer platform using cell blebs as an intermediate. Cell blebs, expressing either GPI-linked yellow fluorescent proteins or neon-green fused transmembrane P2X2 receptors, were induced to rupture on glass surfaces using PEGylated lipid vesicles, which resulted in planar supported membranes with over 50% mobility for multipass transmembrane proteins and over 90% for GPI-linked proteins. Fluorescent proteins were tracked, and their diffusion in supported bilayers characterized, using single molecule tracking and moment scaling spectrum (MSS) analysis. Diffusion was characterized for individual proteins as either free or confined, revealing details of the local lipid membrane heterogeneity surrounding the protein. A particularly useful result of our bilayer formation process is the protein orientation in the supported planar bilayer. For both the GPI-linked and transmembrane proteins used here, an enzymatic assay revealed that protein orientation in the planar bilayer results in the extracellular domains facing toward the bulk, and that the dominant mode of bleb rupture is via the "parachute" mechanism. Mobility, orientation, and preservation of the native lipid environment of the proteins using cell blebs offers advantages over proteoliposome reconstitution or disrupted cell membrane preparations, which necessarily result in significant scrambling of protein orientation and typically immobilized membrane proteins in SLBs. The bleb-based bilayer platform presented here is an important step toward integrating membrane proteomic studies on chip, especially for future studies aimed at understanding fundamental effects of lipid interactions

  14. Sterol-recognition ability and membrane-disrupting activity of Ornithogalum saponin OSW-1 and usual 3-O-glycosyl saponins.

    Science.gov (United States)

    Malabed, Raymond; Hanashima, Shinya; Murata, Michio; Sakurai, Kaori

    2017-12-01

    OSW-1 is a structurally unique steroidal saponin isolated from the bulbs of Ornithogalum saundersiae, and has exhibited highly potent and selective cytotoxicity in tumor cell lines. This study aimed to investigate the molecular mechanism for the membrane-permeabilizing activity of OSW-1 in comparison with those of other saponins by using various spectroscopic approaches. The membrane effects and hemolytic activity of OSW-1 were markedly enhanced in the presence of membrane cholesterol. Binding affinity measurements using fluorescent cholestatrienol and solid-state NMR spectroscopy of a 3-d-cholesterol probe suggested that OSW-1 interacts with membrane cholesterol without forming large aggregates while 3-O-glycosyl saponin, digitonin, forms cholesterol-containing aggregates. The results suggest that OSW-1/cholesterol interaction is likely to cause membrane permeabilization and pore formation without destroying the whole membrane integrity, which could partly be responsible for its highly potent cell toxicity. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. A computational model predicting disruption of blood vessel development.

    Directory of Open Access Journals (Sweden)

    Nicole Kleinstreuer

    2013-04-01

    Full Text Available Vascular development is a complex process regulated by dynamic biological networks that vary in topology and state across different tissues and developmental stages. Signals regulating de novo blood vessel formation (vasculogenesis and remodeling (angiogenesis come from a variety of biological pathways linked to endothelial cell (EC behavior, extracellular matrix (ECM remodeling and the local generation of chemokines and growth factors. Simulating these interactions at a systems level requires sufficient biological detail about the relevant molecular pathways and associated cellular behaviors, and tractable computational models that offset mathematical and biological complexity. Here, we describe a novel multicellular agent-based model of vasculogenesis using the CompuCell3D (http://www.compucell3d.org/ modeling environment supplemented with semi-automatic knowledgebase creation. The model incorporates vascular endothelial growth factor signals, pro- and anti-angiogenic inflammatory chemokine signals, and the plasminogen activating system of enzymes and proteases linked to ECM interactions, to simulate nascent EC organization, growth and remodeling. The model was shown to recapitulate stereotypical capillary plexus formation and structural emergence of non-coded cellular behaviors, such as a heterologous bridging phenomenon linking endothelial tip cells together during formation of polygonal endothelial cords. Molecular targets in the computational model were mapped to signatures of vascular disruption derived from in vitro chemical profiling using the EPA's ToxCast high-throughput screening (HTS dataset. Simulating the HTS data with the cell-agent based model of vascular development predicted adverse effects of a reference anti-angiogenic thalidomide analog, 5HPP-33, on in vitro angiogenesis with respect to both concentration-response and morphological consequences. These findings support the utility of cell agent-based models for simulating a

  16. Highly potent antimicrobial peptides from N-terminal membrane-binding region of E. coli MreB.

    Science.gov (United States)

    Saikia, Karabi; Sravani, Yalavarthi Durga; Ramakrishnan, Vibin; Chaudhary, Nitin

    2017-02-23

    Microbial pathogenesis is a serious health concern. The threat escalates as the existing conventional antimicrobials are losing their efficacy against the evolving pathogens. Peptides hold promise to be developed into next-generation antibiotics. Antimicrobial peptides adopt amphipathic structures that could selectively bind to and disrupt the microbial membranes. Interaction of proteins with membranes is central to all living systems and we reasoned that the membrane-binding domains in microbial proteins could be developed into efficient antimicrobials. This is an interesting approach as self-like sequences could elude the microbial strategies of degrading the antimicrobial peptides, one of the mechanisms of showing resistance to antimicrobials. We selected the 9-residue-long membrane-binding region of E. coli MreB protein. The 9-residue peptide (C-terminal amide) and its N-terminal acetylated analog displayed broad-spectrum activity, killing Gram-negative bacteria, Gram-positive bacteria, and fungi. Extension with a tryptophan residue at the N-terminus drastically improved the activity of the peptides with lethal concentrations ≤10 μM against all the organisms tested. The tryptophan-extended peptides caused complete killing of C. albicans as well as gentamicin and methicillin resistant S. aureus at 5 μM concentration. Lipid-binding studies and electron microscopic analyses of the peptide-treated microbes suggest membrane disruption as the mechanism of killing.

  17. Sensing Phosphatidylserine in Cellular Membranes

    Directory of Open Access Journals (Sweden)

    Jason G. Kay

    2011-01-01

    Full Text Available Phosphatidylserine, a phospholipid with a negatively charged head-group, is an important constituent of eukaryotic cellular membranes. On the plasma membrane, rather than being evenly distributed, phosphatidylserine is found preferentially in the inner leaflet. Disruption of this asymmetry, leading to the appearance of phosphatidylserine on the surface of the cell, is known to play a central role in both apoptosis and blood clotting. Despite its importance, comparatively little is known about phosphatidylserine in cells: its precise subcellular localization, transmembrane topology and intracellular dynamics are poorly characterized. The recent development of new, genetically-encoded probes able to detect phosphatidylserine within live cells, however, is leading to a more in-depth understanding of the biology of this phospholipid. This review aims to give an overview of the current methods for phosphatidylserine detection within cells, and some of the recent realizations derived from their use.

  18. Determination of membrane disruption and genomic DNA binding of cinnamaldehyde to Escherichia coli by use of microbiological and spectroscopic techniques.

    Science.gov (United States)

    He, Tian-Fu; Zhang, Zhi-Hong; Zeng, Xin-An; Wang, Lang-Hong; Brennan, Charles S

    2018-01-01

    This work was aimed to investigate the antibacterial action of cinnamaldehyde (CIN) against Escherichia coli ATCC 8735 (E. coli) based on membrane fatty acid composition analysis, alterations of permeability and cell morphology as well as interaction with genomic DNA. Analysis of membrane fatty acids using gas chromatography-mass spectrometry (GC-MS) revealed that the proportion of unsaturated fatty acids (UFA) and saturated fatty acids (SFA) were the major fatty acids in plasmic membrane, and their levels were significantly changed after exposure of E. coli to CIN at low concentrations. For example, the proportion of UFA decreased from 39.97% to 20.98%, while the relative content of SFA increased from 50.14% to 67.80% as E. coli was grown in increasing concentrations of CIN (from 0 to 0.88mM). Scanning electron microscopy (SEM) showed that the morphology of E. coli cells to be wrinkled, distorted and even lysed after exposure to CIN, which therefore decreased the cell viability. The binding of CIN to genomic DNA was probed using fluorescence, UV-Visible absorption spectra, circular dichroism, molecular modeling and atomic force microscopy (AFM). Results indicated that CIN likely bound to the minor groove of genomic DNA, and changed the secondary structure and morphology of this biomacromolecule. Therefore, CIN can be deem as a kind of natural antimicrobial agents, which influence both cell membrane and genomic DNA. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Disruptions in JET

    International Nuclear Information System (INIS)

    Wesson, J.A.; Gill, R.D.; Hugon, M.

    1989-01-01

    In JET, both high density and low-q operation are limited by disruptions. The density limit disruptions are caused initially by impurity radiation. This causes a contraction of the plasma temperature profile and leads to an MHD unstable configuration. There is evidence of magnetic island formation resulting in minor disruptions. After several minor disruptions, a major disruption with a rapid energy quench occurs. This event takes place in two stages. In the first stage there is a loss of energy from the central region. In the second stage there is a more rapid drop to a very low temperature, apparently due to a dramatic increase in impurity radiation. The final current decay takes place in the resulting cold plasma. During the growth of the MHD instability the initially rotating mode is brought to rest. This mode locking is believed to be due to an electromagnetic interaction with the vacuum vessel and external magnetic field asymmetries. The low-q disruptions are remarkable for the precision with which they occur at q ψ = 2. These disruptions do not have extended precursors or minor disruptions. The instability grows and locks rapidly. The energy quench and current decay are generally similar to those of the density limit. (author). 43 refs, 35 figs, 3 tabs

  20. Probing the interaction of brain fatty acid binding protein (B-FABP with model membranes.

    Directory of Open Access Journals (Sweden)

    Fábio Dyszy

    Full Text Available Brain fatty acid-binding protein (B-FABP interacts with biological membranes and delivers polyunsaturated fatty acids (FAs via a collisional mechanism. The binding of FAs in the protein and the interaction with membranes involve a motif called "portal region", formed by two small α-helices, A1 and A2, connected by a loop. We used a combination of site-directed mutagenesis and electron spin resonance to probe the changes in the protein and in the membrane model induced by their interaction. Spin labeled B-FABP mutants and lipidic spin probes incorporated into a membrane model confirmed that B-FABP interacts with micelles through the portal region and led to structural changes in the protein as well in the micelles. These changes were greater in the presence of LPG when compared to the LPC models. ESR spectra of B-FABP labeled mutants showed the presence of two groups of residues that responded to the presence of micelles in opposite ways. In the presence of lysophospholipids, group I of residues, whose side chains point outwards from the contact region between the helices, had their mobility decreased in an environment of lower polarity when compared to the same residues in solution. The second group, composed by residues with side chains situated at the interface between the α-helices, experienced an increase in mobility in the presence of the model membranes. These modifications in the ESR spectra of B-FABP mutants are compatible with a less ordered structure of the portal region inner residues (group II that is likely to facilitate the delivery of FAs to target membranes. On the other hand, residues in group I and micelle components have their mobilities decreased probably as a result of the formation of a collisional complex. Our results bring new insights for the understanding of the gating and delivery mechanisms of FABPs.

  1. Critical review of membrane bioreactor models--part 2: hydrodynamic and integrated models.

    Science.gov (United States)

    Naessens, W; Maere, T; Ratkovich, N; Vedantam, S; Nopens, I

    2012-10-01

    Membrane bioreactor technology exists for a couple of decades, but has not yet overwhelmed the market due to some serious drawbacks of which operational cost due to fouling is the major contributor. Knowledge buildup and optimisation for such complex systems can heavily benefit from mathematical modelling. In this paper, the vast literature on hydrodynamic and integrated MBR modelling is critically reviewed. Hydrodynamic models are used at different scales and focus mainly on fouling and only little on system design/optimisation. Integrated models also focus on fouling although the ones including costs are leaning towards optimisation. Trends are discussed, knowledge gaps identified and interesting routes for further research suggested. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Pore surface fractal analysis of palladium-alumina ceramic membrane using Frenkel-Halsey-Hill (FHH) model.

    Science.gov (United States)

    Ahmad, A L; Mustafa, N N N

    2006-09-15

    The alumina ceramic membrane has been modified by the addition of palladium in order to improve the H(2) permeability and selectivity. Palladium-alumina ceramic membrane was prepared via a sol-gel method and subjected to thermal treatment in the temperature range 500-1100 degrees C. Fractal analysis from nitrogen adsorption isotherm is used to study the pore surface roughness of palladium-alumina ceramic membrane with different chemical composition (nitric acid, PVA and palladium) and calcinations process in terms of surface fractal dimension, D. Frenkel-Halsey-Hill (FHH) model was used to determine the D value of palladium-alumina membrane. Following FHH model, the D value of palladium-alumina membrane increased as the calcinations temperature increased from 500 to 700 degrees C but decreased after calcined at 900 and 1100 degrees C. With increasing palladium concentration from 0.5 g Pd/100 ml H(2)O to 2 g Pd/100 ml H(2)O, D value of membrane decreased, indicating to the smoother surface. Addition of higher amount of PVA and palladium reduced the surface fractal of the membrane due to the heterogeneous distribution of pores. However, the D value increased when nitric acid concentration was increased from 1 to 15 M. The effect of calcinations temperature, PVA ratio, palladium and acid concentration on membrane surface area, pore size and pore distribution also studied.

  3. Cost Consequences of a Port-Related Supply Chain Disruption

    OpenAIRE

    Hui Shan LOH; Vinh Van THAI

    2015-01-01

    Port functionality is a significant and important aspect of cargo transportation. Previous studies have identified a list of port-related supply chain disruption threats and developed a management model that seeks to address these threats. This paper adds value to these related studies by comparing four consequences of an example of these threats: (1) avoidance of disruption, (2) mitigation of disruption, (3) deviation of transportation plan and (4) delays and deviation of transportation plan...

  4. Periodic disruptions in the MT-1 tokamak

    International Nuclear Information System (INIS)

    Zoletnik, S.

    1988-11-01

    Disruptive instabilities are common phenomena in toroidal devices, especially in tokamaks. Three types can be distinguished: internal, minor and major disruptions. Periodic minor disruptions in the MT-1 tokamak were measured systematically with values of the limiter safety factor between 4 and 10. The density limit as a function of plasma current and horizontal displacement was investigated. Precursor oscillations always appear before the instability with increasing amplitude but can be observed at the density limit with quasi-stationary amplitude. Phase correlation between precursor oscillations were measured with Mirnov coils and x-ray detectors, and they show good agreement with a simple magnetic island model. (R.P.) 11 refs.; 6 figs

  5. (CryoTransmission Electron Microscopy of Phospholipid Model Membranes Interacting with Amphiphilic and Polyphilic Molecules

    Directory of Open Access Journals (Sweden)

    Annette Meister

    2017-10-01

    Full Text Available Lipid membranes can incorporate amphiphilic or polyphilic molecules leading to specific functionalities and to adaptable properties of the lipid bilayer host. The insertion of guest molecules into membranes frequently induces changes in the shape of the lipid matrix that can be visualized by transmission electron microscopy (TEM techniques. Here, we review the use of stained and vitrified specimens in (cryoTEM to characterize the morphology of amphiphilic and polyphilic molecules upon insertion into phospholipid model membranes. Special emphasis is placed on the impact of novel synthetic amphiphilic and polyphilic bolalipids and polymers on membrane integrity and shape stability.

  6. The practical use of resistance modelling to interpret the gas separation properties of hollow fiber membranes

    International Nuclear Information System (INIS)

    Ahmad Fauzi Ismail; Shilton, S.J.

    2000-01-01

    A simple resistance modelling methodology is presented for gas transport through asymmetric polymeric membranes. The methodology allows fine structural properties such as active layer thickness and surface porosity, to be determined from experimental gas permeation data. This paper, which could be regarded as a practical guide, shows that resistance modeling, if accompanied by realistic working assumptions, need not be difficult and can provide a valuable insight into the relationships between the membrane fabrication conditions and performance of gas separation membranes. (Author)

  7. Modeling water flux and salt rejection of mesoporous γ-alumina and microporous organosilica membranes

    NARCIS (Netherlands)

    Farsi, A.; Boffa, V.; Qureshi, H.F.; Nijmeijer, Arian; Winnubst, Aloysius J.A.; Lykkegaard Christensen, M.

    2014-01-01

    The water and ion transport through a mesoporous γ-alumina membrane and a microporous organosilica membrane was simulated using the extended Nernst Planck equation combined with models for Donnan, steric and dielectric interfacial exclusion mechanisms. Due to the surface charge within the pore, the

  8. MHD instabilities leading to disruption in JT-60U reversed shear plasmas

    International Nuclear Information System (INIS)

    Takechi, M.; Fujita, T.; Ishii, Y.; Ozeki, T.; Suzuki, T.; Isayama, A.

    2005-01-01

    High performance reversed shear discharges with strong internal transport barrier (ITB) and flat pressure profile in the plasma core region disrupt frequently even with low beta. We analyzed MHD instabilities leading to low beta disruption with measuring fluctuations and current profile with MSE measurement. We mainly observed two type of disruptions. One is the disruption without precursor at q surf ∼integer. The other is the disruption with n=1 precursor of γ>10 ms. The poloidal mode number of the n=1 mode is equal to outermost integer of q. The n=1 mode exist from peripheral region to ITB layer or peripheral region and ITB and the phase is 180 degree different between them. To explain these characteristics of disruption, we introduce the simple model such as, disruption occurs when the both MHD instabilities at plasma surface and at safety factor being equal to surface mode are unstable. This simple model can explain almost all observed disruption by two process. One is the surface mode triggered disruption, which occurs when q surf change, corresponding q surface at ITB layer change discretely. The other is the internal mode triggered disruption, which occurs when corresponding q surface become unstable gradually. (author)

  9. Production control and supplier selection under demand disruptions

    Directory of Open Access Journals (Sweden)

    Xianzhe Chen

    2010-12-01

    Full Text Available This paper investigates the effects of demand disruptions on production control and supplier selection in a three-echelon supply chain system. The customer demand is modeled as a jump-diffusion process in a continuous-time setting. A two-number production-inventory policy is implemented in the production control model for the manufacturer. The objective is to minimize the long-term average total cost consisting of backlog cost, holding cost, switching cost, and ordering cost. The simulated annealing method is applied to search the optimal critical switching values. Furthermore, an improved analytical hierarchy process (AHP is proposed to select the best supplier, based on quantitative factors such as the optimal long-term total cost obtained through the simulated annealing method under demand disruptions and qualitative factors such as quality and service. Numerical studies are conducted to demonstrate the effects of demand disruptions in the face of various risk scenarios. Managerial insights from simulation results are provided as well. Our approaches can be implemented as the “stress test” for companies in front of various supply chain disruption scenarios.

  10. Digital disruption ?syndromes.

    Science.gov (United States)

    Sullivan, Clair; Staib, Andrew

    2017-05-18

    The digital transformation of hospitals in Australia is occurring rapidly in order to facilitate innovation and improve efficiency. Rapid transformation can cause temporary disruption of hospital workflows and staff as processes are adapted to the new digital workflows. The aim of this paper is to outline various types of digital disruption and some strategies for effective management. A large tertiary university hospital recently underwent a rapid, successful roll-out of an integrated electronic medical record (EMR). We observed this transformation and propose several digital disruption "syndromes" to assist with understanding and management during digital transformation: digital deceleration, digital transparency, digital hypervigilance, data discordance, digital churn and post-digital 'depression'. These 'syndromes' are defined and discussed in detail. Successful management of this temporary digital disruption is important to ensure a successful transition to a digital platform. What is known about this topic? Digital disruption is defined as the changes facilitated by digital technologies that occur at a pace and magnitude that disrupt established ways of value creation, social interactions, doing business and more generally our thinking. Increasing numbers of Australian hospitals are implementing digital solutions to replace traditional paper-based systems for patient care in order to create opportunities for improved care and efficiencies. Such large scale change has the potential to create transient disruption to workflows and staff. Managing this temporary disruption effectively is an important factor in the successful implementation of an EMR. What does this paper add? A large tertiary university hospital recently underwent a successful rapid roll-out of an integrated electronic medical record (EMR) to become Australia's largest digital hospital over a 3-week period. We observed and assisted with the management of several cultural, behavioural and

  11. Light radiation pressure upon a wrinkled membrane – parametrization of an optically orthotropic model

    Science.gov (United States)

    Nerovny, N. A.; Zimin, V. N.

    2018-04-01

    In this paper, the problem of representing the light pressure force upon the surface of a thin wrinkled film is discussed. The common source of wrinkles is the shear deformation of the membrane sample. The optical model of such a membrane is assumed to be optically orthotropic and an analytic equation for infinitesimal light pressure force is written. A linear regression model in the case of wrinkle geometry, where a surface element can have different optical parameters, is constructed and the Bayesian approach is used to calculate the parameters of this model.

  12. Reduced-Order Dynamic Modeling, Fouling Detection, and Optimal Control of Solar-Powered Direct Contact Membrane Distillation

    KAUST Repository

    Karam, Ayman M.

    2016-12-01

    Membrane Distillation (MD) is an emerging sustainable desalination technique. While MD has many advantages and can be powered by solar thermal energy, its main drawback is the low water production rate. However, the MD process has not been fully optimized in terms of its manipulated and controlled variables. This is largely due to the lack of adequate dynamic models to study and simulate the process. In addition, MD is prone to membrane fouling, which is a fault that degrades the performance of the MD process. This work has three contributions to address these challenges. First, we derive a mathematical model of Direct Contact Membrane Distillation (DCMD), which is the building block for the next parts. Then, the proposed model is extended to account for membrane fouling and an observer-based fouling detection method is developed. Finally, various control strategies are implemented to optimize the performance of the DCMD solar-powered process. In part one, a reduced-order dynamic model of DCMD is developed based on lumped capacitance method and electrical analogy to thermal systems. The result is an electrical equivalent thermal network to the DCMD process, which is modeled by a system of nonlinear differential algebraic equations (DAEs). This model predicts the water-vapor flux and the temperature distribution along the module length. Experimental data is collected to validate the steady-state and dynamic responses of the proposed model, with great agreement demonstrated in both. The second part proposes an extension of the model to account for membrane fouling. An adaptive observer for DAE systems is developed and convergence proof is presented. A method for membrane fouling detection is then proposed based on adaptive observers. Simulation results demonstrate the performance of the membrane fouling detection method. Finally, an optimization problem is formulated to maximize the process efficiency of a solar-powered DCMD. The adapted method is known as Extremum

  13. Study of structural stability and damaging effect on membrane for four Aβ42 dimers.

    Directory of Open Access Journals (Sweden)

    Wei Feng

    Full Text Available Increasing evidence shows that Aβ oligomers are key pathogenic molecules in Alzheimer's disease. Among Aβ oligomers, dimer is the smallest aggregate and toxic unit. Therefore, understanding its structural and dynamic properties is quite useful to prevent the formation and toxicity of the Aβ oligomers. In this study, we performed molecular dynamic simulations on four Aβ42 dimers, 2NCb, CNNC, NCNC and NCCN, within the hydrated DPPC membrane. Four Aβ42 dimers differ in the arrangements of two Aβ42 peptides. This study aims to investigate the impact of aggregation pattern of two Aβ peptides on the structural stability of the Aβ42 dimer and its disruption to the biological membrane. The MD results demonstrate that the NCCN, CNNC and NCNC have the larger structural fluctuation at the N-terminus of Aβ42 peptide, where the β-strand structure converts into the coil structure. The loss of the N-terminal β-strand further impairs the aggregate ability of Aβ42 dimer. In addition, inserting Aβ42 dimer into the membrane can considerably decrease the average APL of DPPC membrane. Moreover this decrease effect is largely dependent on the distance to the location of Aβ42 dimer and its secondary structure forms. Based on the results, the 2NCb is considered as a stable dimeric unit for aggregating the larger Aβ42 oligomer, and has a potent ability to disrupt the membrane.

  14. Modeling and Optimization of NLDH/PVDF Ultrafiltration Nanocomposite Membrane Using Artificial Neural Network-Genetic Algorithm Hybrid.

    Science.gov (United States)

    Arefi-Oskoui, Samira; Khataee, Alireza; Vatanpour, Vahid

    2017-07-10

    In this research, MgAl-CO 3 2- nanolayered double hydroxide (NLDH) was synthesized through a facile coprecipitation method, followed by a hydrothermal treatment. The prepared NLDHs were used as a hydrophilic nanofiller for improving the performance of the PVDF-based ultrafiltration membranes. The main objective of this research was to obtain the optimized formula of NLDH/PVDF nanocomposite membrane presenting the best performance using computational techniques as a cost-effective method. For this aim, an artificial neural network (ANN) model was developed for modeling and expressing the relationship between the performance of the nanocomposite membrane (pure water flux, protein flux and flux recovery ratio) and the affecting parameters including the NLDH, PVP 29000 and polymer concentrations. The effects of the mentioned parameters and the interaction between the parameters were investigated using the contour plot predicted with the developed model. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle techniques were applied to characterize the nanocomposite membranes and to interpret the predictions of the ANN model. The developed ANN model was introduced to genetic algorithm (GA) as a bioinspired optimizer to determine the optimum values of input parameters leading to high pure water flux, protein flux, and flux recovery ratio. The optimum values for NLDH, PVP 29000 and the PVDF concentration were determined to be 0.54, 1, and 18 wt %, respectively. The performance of the nanocomposite membrane prepared using the optimum values proposed by GA was investigated experimentally, in which the results were in good agreement with the values predicted by ANN model with error lower than 6%. This good agreement confirmed that the nanocomposite membranes prformance could be successfully modeled and optimized by ANN-GA system.

  15. Development of organic membrane and biosensor. ; Artificial membrane chemical sensor on the model of olfactory cells. Seitaimaku to bio sensor no hatten. ; Kyusaibo wo model to shita jinkomaku kagaku sensor

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, S; Kashiwayanagi, M; Kurihara, K [Hokkaido University, Sapporo (Japan). Faculty of Pharmaceutical Science

    1991-05-05

    The olfactory cell is the most prominent chemical sensor to detect various kinds of external chemical substances with high sensibility. Consequently, on the model of such an organic chemical sensor mechanism, an artificial membrane with functions to detect and distinguish various chemical substances has been developed. In this study, a test using a lipid bimolecular membrane was carried out. As a result, it was found that the lipid bimolecular membrane showed membrane potential changes responding to various odorants. The mambrane with proper lipid composition presented almost the same sensibility to odorants as an olfactory organ. Response characteristic against various odors changed greatly due to the lipid composition and the addition of protein. It was also found that various odors can be discriminated by analyzing response information obtained from a lot of mambranes with different compositions Such ideas can be applied to the odor discrimination of the artificial membrane sensor. 14 refs., 13 figs.

  16. Electrical equivalent thermal network for direct contact membrane distillation modeling and analysis

    KAUST Repository

    Karam, Ayman M.

    2016-09-19

    Membrane distillation (MD) is an emerging water desalination technology that offers several advantages compared to conventional desalination methods. Although progress has been made to model the physics of the process, there are two common limitations of existing models. Firstly, many of the models are based on the steady-state analysis of the process and secondly, some of the models are based on partial differential equations, which when discretized introduce many states which are not accessible in practice. This paper presents the derivation of a novel dynamic model, based on the analogy between electrical and thermal systems, for direct contact membrane distillation (DCMD). An analogous electrical thermal network is constructed and its elements are parameterized such that the response of the network models the DCMD process. The proposed model captures the spatial and temporal responses of the temperature distribution along the flow direction and is able to accurately predict the distilled water flux output. To demonstrate the adequacy of the proposed model, validation with time varying and steady-state experimental data is presented. (C) 2016 Elsevier Ltd. All rights reserved.

  17. Estrogen-induced disruption of intracellular iron metabolism leads to oxidative stress, membrane damage, and cell cycle arrest in MCF-7 cells.

    Science.gov (United States)

    Bajbouj, Khuloud; Shafarin, Jasmin; Abdalla, Maher Y; Ahmad, Iman M; Hamad, Mawieh

    2017-10-01

    It is well established that several forms of cancer associate with significant iron overload. Recent studies have suggested that estrogen (E2) disrupts intracellular iron homeostasis by reducing hepcidin synthesis and maintaining ferroportin integrity. Here, the ability of E2 to alter intracellular iron status and cell growth potential was investigated in MCF-7 cells treated with increasing concentrations of E2. Treated cells were assessed for intracellular iron status, the expression of key proteins involved in iron metabolism, oxidative stress, cell survival, growth, and apoptosis. E2 treatment resulted in a significant reduction in hepcidin expression and a significant increase in hypoxia-inducible factor 1 alpha, ferroportin, transferrin receptor, and ferritin expression; a transient decrease in labile iron pool; and a significant increase in total intracellular iron content mainly at 20 nM/48 h E2 dose. Treated cells also showed increased total glutathione and oxidized glutathione levels, increased superoxide dismutase activity, and increased hemoxygenase 1 expression. Treatment with E2 at 20 nM for 48 h resulted in a significant reduction in cell growth (0.35/1 migration rate) and decreased cell survival (iron metabolism and precipitates adverse effects concerning cell viability, membrane integrity, and growth potential.

  18. Modeling of air-gap membrane distillation process: A theoretical and experimental study

    KAUST Repository

    Alsaadi, Ahmad Salem; Ghaffour, NorEddine; Li, Junde; Gray, Stephen R.; Francis, Lijo; Maab, Husnul; Amy, Gary L.

    2013-01-01

    A one dimensional (1-D) air gap membrane distillation (AGMD) model for flat sheet type modules has been developed. This model is based on mathematical equations that describe the heat and mass transfer mechanisms of a single-stage AGMD process

  19. Membrane plasmalogen composition and cellular cholesterol regulation: a structure activity study

    Directory of Open Access Journals (Sweden)

    Su-Myat Khine K

    2010-06-01

    Full Text Available Abstract Background Disrupted cholesterol regulation leading to increased circulating and membrane cholesterol levels is implicated in many age-related chronic diseases such as cardiovascular disease (CVD, Alzheimer's disease (AD, and cancer. In vitro and ex vivo cellular plasmalogen deficiency models have been shown to exhibit impaired intra- and extra-cellular processing of cholesterol. Furthermore, depleted brain plasmalogens have been implicated in AD and serum plasmalogen deficiencies have been linked to AD, CVD, and cancer. Results Using plasmalogen deficient (NRel-4 and plasmalogen sufficient (HEK293 cells we investigated the effect of species-dependent plasmalogen restoration/augmentation on membrane cholesterol processing. The results of these studies indicate that the esterification of cholesterol is dependent upon the amount of polyunsaturated fatty acid (PUFA-containing ethanolamine plasmalogen (PlsEtn present in the membrane. We further elucidate that the concentration-dependent increase in esterified cholesterol observed with PUFA-PlsEtn was due to a concentration-dependent increase in sterol-O-acyltransferase-1 (SOAT1 levels, an observation not reproduced by 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA reductase inhibition. Conclusion The present study describes a novel mechanism of cholesterol regulation that is consistent with clinical and epidemiological studies of cholesterol, aging and disease. Specifically, the present study describes how selective membrane PUFA-PlsEtn enhancement can be achieved using 1-alkyl-2-PUFA glycerols and through this action reduce levels of total and free cholesterol in cells.

  20. α-Synuclein-induced lysosomal dysfunction occurs through disruptions in protein trafficking in human midbrain synucleinopathy models.

    Science.gov (United States)

    Mazzulli, Joseph R; Zunke, Friederike; Isacson, Ole; Studer, Lorenz; Krainc, Dimitri

    2016-02-16

    Parkinson's disease (PD) is an age-related neurodegenerative disorder characterized by the accumulation of protein aggregates comprised of α-synuclein (α-syn). A major barrier in treatment discovery for PD is the lack of identifiable therapeutic pathways capable of reducing aggregates in human neuronal model systems. Mutations in key components of protein trafficking and cellular degradation machinery represent important risk factors for PD; however, their precise role in disease progression and interaction with α-syn remains unclear. Here, we find that α-syn accumulation reduced lysosomal degradation capacity in human midbrain dopamine models of synucleinopathies through disrupting hydrolase trafficking. Accumulation of α-syn at the cell body resulted in aberrant association with cis-Golgi-tethering factor GM130 and disrupted the endoplasmic reticulum-Golgi localization of rab1a, a key mediator of vesicular transport. Overexpression of rab1a restored Golgi structure, improved hydrolase trafficking and activity, and reduced pathological α-syn in patient neurons. Our work suggests that enhancement of lysosomal hydrolase trafficking may prove beneficial in synucleinopathies and indicates that human midbrain disease models may be useful for identifying critical therapeutic pathways in PD and related disorders.

  1. Aqueous magnesium as an environmental selection pressure in the evolution of phospholipid membranes on early earth

    Science.gov (United States)

    Dalai, Punam; Ustriyana, Putu; Sahai, Nita

    2018-02-01

    Early compartmentalization of simple biomolecules by membrane bilayers was, presumably, a critical step in the emergence of the first cell-like entities, protocells. Their membranes were likely composed of single chain amphiphiles (SCAs), but pure SCA membranes especially those with short-chains are highly unstable towards divalent cations, which are ubiquitous in aqueous environments. The prebiotic synthesis of phospholipids (PLs), even in only trace amounts, may also have been possible. PL membranes are much more stable towards divalent cations. Here, we show the transition of fatty acid membranes to mixed fatty acid-PL and, finally, to PL membranes in the presence of Mg2+, which acts as an environmental selection pressure, and we propose different mechanisms for the observed increased Mg2+-immunity. The "fatal" concentration ([Mg2+]fatal) at which vesicles are disrupted increased dramatically by an order of magnitude from OA to mixed to POPC vesicles. Two mechanisms for the increasing immunity were determined. The negative charge density of the vesicles decreased with increasing POPC content, so more Mg2+ was required for disruption. More interestingly, Mg2+ preferentially bound to and abstracted OA from mixed lipid membranes, resulting in relatively POPC-enriched vesicles compared to the initial ratio. The effect was the most dramatic for the largest initial OA-POPC ratio representing the most primitive protocells. Thus, Mg2+ acted to evolve the mixed membrane composition towards PL enrichment. To the best of our knowledge, this is the first report of selective lipid abstraction from mixed SCA-PL vesicles. These results may hold implications for accommodating prebiotic Mg2+-promoted processes such as non-enzymatic RNA polymerization on early Earth.

  2. Function and failure of the fetal membrane: Modelling the mechanics of the chorion and amnion.

    Directory of Open Access Journals (Sweden)

    Stefaan W Verbruggen

    Full Text Available The fetal membrane surrounds the fetus during pregnancy and is a thin tissue composed of two layers, the chorion and the amnion. While rupture of this membrane normally occurs at term, preterm rupture can result in increased risk of fetal mortality and morbidity, as well as danger of infection in the mother. Although structural changes have been observed in the membrane in such cases, the mechanical behaviour of the human fetal membrane in vivo remains poorly understood and is challenging to investigate experimentally. Therefore, the objective of this study was to develop simplified finite element models to investigate the mechanical behaviour and rupture of the fetal membrane, particularly its constituent layers, under various physiological conditions. It was found that modelling the chorion and amnion as a single layer predicts remarkably different behaviour compared with a more anatomically-accurate bilayer, significantly underestimating stress in the amnion and under-predicting the risk of membrane rupture. Additionally, reductions in chorion-amnion interface lubrication and chorion thickness (reported in cases of preterm rupture both resulted in increased membrane stress. Interestingly, the inclusion of a weak zone in the fetal membrane that has been observed to develop overlying the cervix would likely cause it to fail at term, during labour. Finally, these findings support the theory that the amnion is the dominant structural component of the fetal membrane and is required to maintain its integrity. The results provide a novel insight into the mechanical effect of structural changes in the chorion and amnion, in cases of both normal and preterm rupture.

  3. Pore-scale modeling and simulation of flow, transport, and adsorptive or osmotic effects in membranes: the influence of membrane microstructure

    KAUST Repository

    Calo, Victor M.; Iliev, Oleg; Lakdawala, Z.; Leonard, K. H. L.; Printsypar, Galina

    2015-01-01

    typical microfiltration membrane using absorptive pore walls, and illustrate the effect of different microstructures on the reactive process. Such numerical modeling will aid manufacturers in optimizing operating conditions and designing efficient

  4. Characterization of Type Three Secretion System Translocator Interactions with Phospholipid Membranes.

    Science.gov (United States)

    Adam, Philip R; Barta, Michael L; Dickenson, Nicholas E

    2017-01-01

    In vitro characterization of type III secretion system (T3SS) translocator proteins has proven challenging due to complex purification schemes and their hydrophobic nature that often requires detergents to provide protein solubility and stability. Here, we provide experimental details for several techniques that overcome these hurdles, allowing for the direct characterization of the Shigella translocator protein IpaB with respect to phospholipid membrane interaction. The techniques specifically discussed in this chapter include membrane interaction/liposome flotation, liposome sensitive fluorescence quenching, and protein-mediated liposome disruption assays. These assays have provided valuable insight into the role of IpaB in T3SS-mediated phospholipid membrane interactions by Shigella and should readily extend to other members of this important class of proteins.

  5. Longitudinal association between marital disruption and child BMI and obesity.

    Science.gov (United States)

    Arkes, Jeremy

    2012-08-01

    This research examines whether family disruptions (i.e., divorces and separation) contribute to children's weight problems. The sample consists of 7,299 observations for 2,333 children, aged 5-14, over the 1986-2006 period, from a US representative sample from the Child and Young Adult Survey accompanying the National Longitudinal Survey of Youth (NLSY). The study uses individual-fixed-effects models in a longitudinal framework to compare children's BMI and weight problems before and after a disruption. Furthermore, besides doing a before-after comparison for children, the study also estimates the effects at various periods relative to the disruption in order to examine whether children are affected before the disruption and whether any effects change as time passes from the disruption, as some effects may be temporary or slow to develop. Despite having a larger sample than the previous studies, the results provide no evidence that, on average, children's BMI and BMI percentile scores (measured with continuous outcomes) are affected before the disruption, after the disruption, and as time passes from the disruption, relative to a baseline period a few years before the disruption. However, children experiencing a family disruption do have an increased risk of obesity (having a BMI percentile score of 95 or higher) in the two years leading up to the disruption as well as after the disruption, and as time passes from the disruption.

  6. Comparison of the Modeling Approach between Membrane Bioreactor and Conventional Activated Sludge Processes

    DEFF Research Database (Denmark)

    Jiang, Tao; Sin, Gürkan; Spanjers, Henri

    2009-01-01

    Activated sludge models (ASM) have been developed and largely applied in conventional activated sludge (CAS) systems. The applicability of ASM to model membrane bioreactors (MBR) and the differences in modeling approaches have not been studied in detail. A laboratory-scale MBR was modeled using ASM...

  7. Instabilities and diffusion in a hydrodynamic model of a fluid membrane coupled to a thin active fluid layer.

    Science.gov (United States)

    Sarkar, N; Basu, A

    2012-11-01

    We construct a coarse-grained effective two-dimensional (2d hydrodynamic theory as a theoretical model for a coupled system of a fluid membrane and a thin layer of a polar active fluid in its ordered state that is anchored to the membrane. We show that such a system is prone to generic instabilities through the interplay of nonequilibrium drive, polar order and membrane fluctuation. We use our model equations to calculate diffusion coefficients of an inclusion in the membrane and show that their values depend strongly on the system size, in contrast to their equilibrium values. Our work extends the work of S. Sankararaman and S. Ramaswamy (Phys. Rev. Lett., 102, 118107 (2009)) to a coupled system of a fluid membrane and an ordered active fluid layer. Our model is broadly inspired by and should be useful as a starting point for theoretical descriptions of the coupled dynamics of a cell membrane and a cortical actin layer anchored to it.

  8. In an in-vitro model using human fetal membranes, 17-α hydroxyprogesterone caproate is not an optimal progestogen for inhibition of fetal membrane weakening.

    Science.gov (United States)

    Kumar, Deepak; Moore, Robert M; Mercer, Brian M; Mansour, Joseph M; Mesiano, Sam; Schatz, Frederick; Lockwood, Charles J; Moore, John J

    2017-12-01

    The progestogen 17-α hydroxyprogesterone caproate (17-OHPC) is 1 of only 2 agents recommended for clinical use in the prevention of spontaneous preterm delivery, and studies of its efficacy have been conflicting. We have developed an in-vitro model to study the fetal membrane weakening process that leads to rupture in preterm premature rupture of the fetal membranes (pPROM). Inflammation/infection associated with tumor necrosis factor-α (TNF-α) induction and decidual bleeding/abruption associated thrombin release are leading causes of preterm premature rupture of the fetal membranes. Both agents (TNF-α and thrombin) cause fetal membrane weakening in the model system. Furthermore, granulocyte-macrophage colony-stimulating factor (GM-CSF) is a critical intermediate for both TNF-α and thrombin-induced fetal membrane weakening. In a previous report, we demonstrated that 3 progestogens, progesterone, 17-alpha hydroxyprogesterone (17-OHP), and medroxyprogesterone acetate (MPA), each inhibit both TNF-α- and thrombin-induced fetal membrane weakening at 2 distinct points of the fetal membrane weakening pathway. Each block both the production of and the downstream action of the critical intermediate granulocyte-macrophage colony-stimulating factor. The objective of the study was to characterize the inhibitory effects of 17-OHPC on TNF-α- and thrombin-induced fetal membrane weakening in vitro. Full-thickness human fetal membrane fragments from uncomplicated term repeat cesarean deliveries were mounted in 2.5 cm Transwell inserts and cultured with/without 17-alpha hydroxyprogesterone caproate (10 -9 to 10 -7 M). After 24 hours, medium (supernatant) was removed and replaced with/without the addition of tumor necrosis factor-alpha (20 ng/mL) or thrombin (10 U/mL) or granulocyte-macrophage colony-stimulating factor (200 ng/mL). After 48 hours of culture, medium from the maternal side compartment of the model was assayed for granulocyte-macrophage colony

  9. Identification of frog photoreceptor plasma and disk membrane proteins by radioiodination

    International Nuclear Information System (INIS)

    Witt, P.L.; Bownds, M.D.

    1987-01-01

    Several functions have been identified for the plasma membrane of the rod outer segment, including control of light-dependent changes in sodium conductance and a sodium-calcium exchange mechanism. However, little is known about its constituent proteins. Intact rod outer segments substantially free of contaminants were prepared in the dark and purified on a density gradient of Percoll. Surface proteins were then labeled by lactoperoxidase-catalyzed radioiodination, and intact rod outer segments were reisolated. Membrane proteins were identified by polyacrylamide gel electrophoresis and autoradiography. The surface proteins labeled included rhodopsin, the major membrane protein, and 12 other proteins. To compare the protein composition of plasma membrane with that of the internal disk membrane, purified rod outer segments were lysed by hypotonic disruption or freeze-thawing, and plasma plus disk membranes were radioiodinated. In these membrane preparations, rhodopsin was the major iodinated constituent, with 12 other proteins also labeled. Autoradiographic evidence indicated some differences in protein composition between disk and plasma membranes. A quantitative comparison of the two samples showed that labeling of two proteins, 24 kilodaltons (kDa) and 13 kDa, was enriched in the plasma membrane, while labeling of a 220-kDa protein was enriched in the disk membrane. These plasma membrane proteins may be associated with important functions such as the light-sensitive conductance and the sodium-calcium exchanger

  10. Fuel disruption mechanisms determined in-pile in the ACRR

    International Nuclear Information System (INIS)

    Wright, S.A.; Fischer, E.A.

    1984-09-01

    Over thirty in-pile experiments were performed to investigate fuel disruption behavior for LMFBR loss of flow (LOF) accidents. These experiments reproduced the heating transients for a variety of accidents ranging from slow LOF accidents to rapid LOF-driven-TOP accidents. In all experiments the timing and mode of the fuel disruption were observed with a high speed camera, enabling detailed comparisons with a fuel pin code, SANDPIN. This code transient intra- and inter-granular fission gas behavior to predict the macroscopic fuel behavior, such as fission gas induced swelling and frothing, cracking and breakup of solid fuel, and fuel vapor pressure driven dispersal. This report reviews the different modes of fuel disruption as seen in the experiments and then describes the mechanism responsible for the disruption. An analysis is presented that describes a set of conditions specifying the mode of fuel disruption and the heating conditions required to produce the disruption. The heating conditions are described in terms of heating rate (K/s), temperature gradient, and fuel temperature. A fuel disruption map is presented which plots heating rate as a function of fuel temperature to illustrate the different criteria for disruption. Although this approach to describing fuel disruption oversimplifies the fission gas processes modeled by SANDPIN, it does illustrate the criteria used to determine which fuel disruption mechanism is dominant and on what major fission gas parameters it depends

  11. Modelling and analysis of CVD processes for ceramic membrane preparation

    NARCIS (Netherlands)

    Brinkman, H.W.; Cao, G.Z.; Meijerink, J.; de Vries, Karel Jan; Burggraaf, Anthonie

    1993-01-01

    A mathematical model is presented that describes the modified chemical vapour deposition (CVD) process (which takes place in advance of the electrochemical vapour deposition (EVD) process) to deposit ZrO2 inside porous media for the preparation and modification of ceramic membranes. The isobaric

  12. Nanodisc-solubilized membrane protein library reflects the membrane proteome.

    Science.gov (United States)

    Marty, Michael T; Wilcox, Kyle C; Klein, William L; Sligar, Stephen G

    2013-05-01

    The isolation and identification of unknown membrane proteins offers the prospect of discovering new pharmaceutical targets and identifying key biochemical receptors. However, interactions between membrane protein targets and soluble ligands are difficult to study in vitro due to the insolubility of membrane proteins in non-detergent systems. Nanodiscs, nanoscale discoidal lipid bilayers encircled by a membrane scaffold protein belt, have proven to be an effective platform to solubilize membrane proteins and have been used to study a wide variety of purified membrane proteins. This report details the incorporation of an unbiased population of membrane proteins from Escherichia coli membranes into Nanodiscs. This solubilized membrane protein library (SMPL) forms a soluble in vitro model of the membrane proteome. Since Nanodiscs contain isolated proteins or small complexes, the SMPL is an ideal platform for interactomics studies and pull-down assays of membrane proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the protein population before and after formation of the Nanodisc library indicates that a large percentage of the proteins are incorporated into the library. Proteomic identification of several prominent bands demonstrates the successful incorporation of outer and inner membrane proteins into the Nanodisc library.

  13. Optimal Management of Supply Disruptions when Contracting with Unreliable, Risk-averse, Suppliers

    OpenAIRE

    Parlane, Sarah; Tsai, Ying-Yi

    2017-01-01

    This paper investigates the optimal management of supply disruptions by a manufacturer who uses order inflation and/or investments in process reliability when contracting two risk-averse suppliers. We consider that these investments can be subject to moral hazard. Technically we solve a newsvendor optimization problem using a random capacity model of disruption. In such a model, the order size does not affect the average production but impacts the probability of disruption. When investments a...

  14. Bile acids modulate signaling by functional perturbation of plasma membrane domains.

    Science.gov (United States)

    Zhou, Yong; Maxwell, Kelsey N; Sezgin, Erdinc; Lu, Maryia; Liang, Hong; Hancock, John F; Dial, Elizabeth J; Lichtenberger, Lenard M; Levental, Ilya

    2013-12-13

    Eukaryotic cell membranes are organized into functional lipid and protein domains, the most widely studied being membrane rafts. Although rafts have been associated with numerous plasma membrane functions, the mechanisms by which these domains themselves are regulated remain undefined. Bile acids (BAs), whose primary function is the solubilization of dietary lipids for digestion and absorption, can affect cells by interacting directly with membranes. To investigate whether these interactions affected domain organization in biological membranes, we assayed the effects of BAs on biomimetic synthetic liposomes, isolated plasma membranes, and live cells. At cytotoxic concentrations, BAs dissolved synthetic and cell-derived membranes and disrupted live cell plasma membranes, implicating plasma membrane damage as the mechanism for BA cellular toxicity. At subtoxic concentrations, BAs dramatically stabilized domain separation in Giant Plasma Membrane Vesicles without affecting protein partitioning between coexisting domains. Domain stabilization was the result of BA binding to and disordering the nonraft domain, thus promoting separation by enhancing domain immiscibility. Consistent with the physical changes observed in synthetic and isolated biological membranes, BAs reorganized intact cell membranes, as evaluated by the spatial distribution of membrane-anchored Ras isoforms. Nanoclustering of K-Ras, related to nonraft membrane domains, was enhanced in intact plasma membranes, whereas the organization of H-Ras was unaffected. BA-induced changes in Ras lateral segregation potentiated EGF-induced signaling through MAPK, confirming the ability of BAs to influence cell signal transduction by altering the physical properties of the plasma membrane. These observations suggest general, membrane-mediated mechanisms by which biological amphiphiles can produce their cellular effects.

  15. Membrane order in the plasma membrane and endocytic recycling compartment.

    Science.gov (United States)

    Iaea, David B; Maxfield, Frederick R

    2017-01-01

    The cholesterol content of membranes plays an important role in organizing membranes for signal transduction and protein trafficking as well as in modulating the biophysical properties of membranes. While the properties of model or isolated membranes have been extensively studied, there has been little evaluation of internal membranes in living cells. Here, we use a Nile Red based probe, NR12S, and ratiometric live cell imaging, to analyze the membrane order of the plasma membrane and endocytic recycling compartment. We find that after a brief incubation to allow endocytosis, NR12S is distributed between the plasma membrane and the endocytic recycling compartment. The NR12S reports that the endocytic recycling compartment is more highly ordered than the plasma membrane. We also find that the plasma membrane and the endocytic recycling compartment are differentially affected by altering cellular cholesterol levels. The membrane order of the plasma membrane, but not the endocytic recycling compartment, is altered significantly when cellular cholesterol content is increased or decreased by 20%. These results demonstrate that changes in cellular cholesterol differentially alter membrane order within different organelles.

  16. Study on properties of cation-exchange membranes containing sulfonate groups

    International Nuclear Information System (INIS)

    Zu Jianhua; Wu Minghong; Qiu Shilong; Yao Side; Ye Yin

    2004-01-01

    Strong acid cation-exchange membranes were obtained by irradiation grafting of acrylic acid (AA) and sodium styrene sulfonate (SSS) onto high-density polyethylene (HDPE). Thermal and chemical stability of the cation-exchange membranes was investigated. The effectiveness of sulfonate-containing films was conformed in inducing high resistance to oxidative degradation. Thermal stability of the grafted HDPE was weaker than HDPE as detected by TGA analyzing technique. Char residue by TGA of the grafted HDPE is greater than that of HDPE. It shows that the branch chains including -SO 3 Na and -COOH was grafted onto the backbone of HDPE, and thus give a catalytic impetus to the charing. Crystallinity of the grafted membranes decreased with increasing grafting yield of the membrane samples. It is supposed that the decreased crystallinity is due to collective effects of the inherent crystallinity dilution by the amorphous grafted chains and disruption of spherulitic crystallites of the HDPE component

  17. Flow and fouling in membrane filters: Effects of membrane morphology

    Science.gov (United States)

    Sanaei, Pejman; Cummings, Linda J.

    2015-11-01

    Membrane filters are widely-used in microfiltration applications. Many types of filter membranes are produced commercially, for different filtration applications, but broadly speaking the requirements are to achieve fine control of separation, with low power consumption. The answer to this problem might seem obvious: select the membrane with the largest pore size and void fraction consistent with the separation requirements. However, membrane fouling (an inevitable consequence of successful filtration) is a complicated process, which depends on many parameters other than membrane pore size and void fraction; and which itself greatly affects the filtration process and membrane functionality. In this work we formulate mathematical models that can (i) account for the membrane internal morphology (internal structure, pore size & shape, etc.); (ii) fouling of membranes with specific morphology; and (iii) make some predictions as to what type of membrane morphology might offer optimum filtration performance.

  18. Resveratrol induces membrane and DNA disruption via pro-oxidant activity against Salmonella typhimurium.

    Science.gov (United States)

    Lee, Wonjong; Lee, Dong Gun

    2017-07-22

    Resveratrol is a flavonoid found in various plants including grapes, which has been reported to be active against various pathogenic bacteria. However, antibacterial effects and mechanisms via pro-oxidant property of resveratrol remain unknown and speculative. This research investigated antibacterial mechanism of resveratrol against a food-borne human pathogen Salmonella typhimurium, and confirmed the cell death associated oxidative damage. Resveratrol increased outer membrane permeability and membrane depolarization. It also was observed DNA injury responses such as DNA fragmentation, increasing DNA contents and cell division inhibition. Intracellular ROS accumulation, GSH depletion and significant increased malondialdehyde levels were confirmed, which indicated pro-oxidant activity of resveratrol and oxidative stress. Furthermore, the observed lethal damages were reduced by antioxidant N-acetylcysteine treatment supported the view that resveratrol-induced oxidative stress stimulated S. typhimurium cell death. In conclusion, this study expands understanding on role of pro-oxidant property and insight into previously unrecognized oxygen-dependent anti-Salmonella mechanism on resveratrol. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Synaptotoxicity of Alzheimer beta amyloid can be explained by its membrane perforating property.

    Directory of Open Access Journals (Sweden)

    Fernando J Sepulveda

    Full Text Available The mechanisms that induce Alzheimer's disease (AD are largely unknown thereby deterring the development of disease-modifying therapies. One working hypothesis of AD is that Abeta excess disrupts membranes causing pore formation leading to alterations in ionic homeostasis. However, it is largely unknown if this also occurs in native brain neuronal membranes. Here we show that similar to other pore forming toxins, Abeta induces perforation of neuronal membranes causing an increase in membrane conductance, intracellular calcium and ethidium bromide influx. These data reveal that the target of Abeta is not another membrane protein, but that Abeta itself is the cellular target thereby explaining the failure of current therapies to interfere with the course of AD. We propose that this novel effect of Abeta could be useful for the discovery of anti AD drugs capable of blocking these "Abeta perforates". In addition, we demonstrate that peptides that block Abeta neurotoxicity also slow or prevent the membrane-perforating action of Abeta.

  20. New insights into membrane-active action in plasma membrane of fungal hyphae by the lipopeptide antibiotic bacillomycin L.

    Science.gov (United States)

    Zhang, Bao; Dong, Chunjuan; Shang, Qingmao; Han, Yuzhu; Li, Pinglan

    2013-09-01

    Bacillomycin L, a natural iturinic lipopeptide produced by Bacillus amyloliquefaciens, is characterized by strong antifungal activities against a variety of agronomically important filamentous fungi including Rhizoctonia solani Kühn. Prior to this study, the role of membrane permeabilization in the antimicrobial activity of bacillomycin L against plant pathogenic fungi had not been investigated. To shed light on the mechanism of this antifungal activity, the permeabilization of R. solani hyphae by bacillomycin L was investigated and compared with that by amphotericin B, a polyene antibiotic which is thought to act primarily through membrane disruption. Our results derived from electron microscopy, various fluorescent techniques and gel retardation experiments revealed that the antifungal activity of bacillomycin L may be not solely a consequence of fungal membrane permeabilization, but related to the interaction of it with intracellular targets. Our findings provide more insights into the mode of action of bacillomycin L and other iturins, which could in turn help to develop new or improved antifungal formulations or result in novel strategies to prevent fungal spoilage. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  1. Modeling the improvement of ultrafiltration membrane mass transfer when using biofiltration pretreatment in surface water applications.

    Science.gov (United States)

    Netcher, Andrea C; Duranceau, Steven J

    2016-03-01

    In surface water treatment, ultrafiltration (UF) membranes are widely used because of their ability to supply safe drinking water. Although UF membranes produce high-quality water, their efficiency is limited by fouling. Improving UF filtrate productivity is economically desirable and has been attempted by incorporating sustainable biofiltration processes as pretreatment to UF with varying success. The availability of models that can be applied to describe the effectiveness of biofiltration on membrane mass transfer are lacking. In this work, UF water productivity was empirically modeled as a function of biofilter feed water quality using either a quadratic or Gaussian relationship. UF membrane mass transfer variability was found to be governed by the dimensionless mass ratio between the alkalinity (ALK) and dissolved organic carbon (DOC). UF membrane productivity was optimized when the biofilter feed water ALK to DOC ratio fell between 10 and 14. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Dissipation of magnetic energy during disruptive current termination

    International Nuclear Information System (INIS)

    Yamazaki, K.; Schmidt, G.L.

    1983-09-01

    The magnetic coupling during a disruption between the plasma and the various coil systems on the PDX tokamak has been modeled. Using measured coil currents, the model indicates that dissipation of magnetic energy in the plasma equal to 75 % of the energy stored in the poloidal field of the plasma current does occur and that coupling between the plasma and the coil systems can reduce such dissipation. In the case of PDX ohmic discharges, bolometric measurements of radiation and charge exchange, integrated over a disruption, account for 90 % of the calculated energy dissipation. (author)

  3. The influence of NBD fluorescent probe on model membranes containing POPC and DPPC.

    Science.gov (United States)

    Weng, Chi-Jung; Wu, Ju-Ping; Kuo, Ming-Yen; Hsueh, Ya-Wei

    2016-03-01

    To investigate the effect of fluorescent probe on the properties of membranes, we studied model membranes composed of 1,2- dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1-palmitoyl 2-oleoyl-sn-glycero-3-phosphocholine (POPC) in the presence and absence of fluorescent probe. The morphology of giant unilamellar vesicles (GUVs) has been observed as a function of temperature and composition by fluorescence microscopy using NBD-DOPE or C 6 -NBD-PC as the probe. The phase behavior of model membranes containing no fluorescent probe was investigated by 2 H-NMR spectroscopy. We found that the bright phase observed on GUVs was the fluid phase enriched in POPC and the dark phase was the gel phase enriched in DPPC. NBD-DOPE and C 6 -NBD-PC preferentially participated in the fluid-phase domains when GUVs were in the gel + fluid phase coexistence. Inclusion of both fluorescent probes (1 mol%) lowered the transition temperature of POPC/DPPC membranes. In addition, C 6 -NBD-PC exhibited a stronger effect than NBD-DOPE, which was considered to be associated with the structures of fluorescent molecules.

  4. Influence of membrane phospholipid composition and structural organization on spontaneous lipid transfer between membranes.

    Science.gov (United States)

    Pankov, R; Markovska, T; Antonov, P; Ivanova, L; Momchilova, A

    2006-09-01

    Investigations were carried out on the influence of phospholipid composition of model membranes on the processes of spontaneous lipid transfer between membranes. Acceptor vesicles were prepared from phospholipids extracted from plasma membranes of control and ras-transformed fibroblasts. Acceptor model membranes with manipulated levels of phosphatidylethanolamine (PE), sphingomyelin and phosphatidic acid were also used in the studies. Donor vesicles were prepared of phosphatidylcholine (PC) and contained two fluorescent lipid analogues, NBD-PC and N-Rh-PE, at a self-quenching concentration. Lipid transfer rate was assessed by measuring the increase of fluorescence in acceptor membranes due to transfer of fluorescent lipid analogues from quenched donor to unquenched acceptor vesicles. The results showed that spontaneous NBD-PC transfer increased upon fluidization of acceptor vesicles. In addition, elevation of PE concentration in model membranes was also accompanied by an increase of lipid transfer to all series of acceptor vesicles. The results are discussed with respect to the role of lipid composition and structural order of cellular plasma membranes in the processes of spontaneous lipid exchange between membrane bilayers.

  5. Petri Net-Based Model of Helicobacter pylori Mediated Disruption of Tight Junction Proteins in Stomach Lining during Gastric Carcinoma

    Directory of Open Access Journals (Sweden)

    Anam Naz

    2017-09-01

    Full Text Available Tight junctions help prevent the passage of digestive enzymes and microorganisms through the space between adjacent epithelial cells lining. However, Helicobacter pylori encoded virulence factors negatively regulate these tight junctions and contribute to dysfunction of gastric mucosa. Here, we have predicted the regulation of important tight junction proteins, such as Zonula occludens-1, Claudin-2 and Connexin32 in the presence of pathogenic proteins. Molecular events such as post translational modifications and crosstalk between phosphorylation, O-glycosylation, palmitoylation and methylation are explored which may compromise the integrity of these tight junction proteins. Furthermore, the signaling pathways disrupted by dysregulated kinases, proteins and post-translational modifications are reviewed to design an abstracted computational model showing the situation-dependent dynamic behaviors of these biological processes and entities. A qualitative hybrid Petri Net model is therefore constructed showing the altered host pathways in the presence of virulence factor cytotoxin-associated gene A, leading to the disruption of tight junction proteins. The model is qualitative logic-based, which does not depend on any kinetic parameter and quantitative data and depends on knowledge derived from experiments. The designed model provides insights into the tight junction disruption and disease progression. Model is then verified by the available experimental data, nevertheless formal in vitro experimentation is a promising way to ensure its validation. The major findings propose that H. pylori activated kinases are responsible to trigger specific post translational modifications within tight junction proteins, at specific sites. These modifications may favor alterations in gastric barrier and provide a route to bacterial invasion into host cells.

  6. Loss of elongation factor P disrupts bacterial outer membrane integrity

    DEFF Research Database (Denmark)

    Zou, S Betty; Hersch, Steven J; Roy, Hervé

    2012-01-01

    background ameliorates the detergent, antibiotic, and osmosensitivity phenotypes and restores wild-type permeability to NPN. Our data support a role for EF-P in the translational regulation of a limited number of proteins that, when perturbed, renders the cell susceptible to stress by the adventitious......Elongation factor P (EF-P) is posttranslationally modified at a conserved lysyl residue by the coordinated action of two enzymes, PoxA and YjeK. We have previously established the importance of this modification in Salmonella stress resistance. Here we report that, like poxA and yjeK mutants......, Salmonella strains lacking EF-P display increased susceptibility to hypoosmotic conditions, antibiotics, and detergents and enhanced resistance to the compound S-nitrosoglutathione. The susceptibility phenotypes are largely explained by the enhanced membrane permeability of the efp mutant, which exhibits...

  7. Analysis of direct contact membrane distillation based on a lumped-parameter dynamic predictive model

    KAUST Repository

    Karam, Ayman M.; Alsaadi, Ahmad Salem; Ghaffour, NorEddine; Laleg-Kirati, Taous-Meriem

    2016-01-01

    Membrane distillation (MD) is an emerging technology that has a great potential for sustainable water desalination. In order to pave the way for successful commercialization of MD-based water desalination techniques, adequate and accurate dynamical models of the process are essential. This paper presents the predictive capabilities of a lumped-parameter dynamic model for direct contact membrane distillation (DCMD) and discusses the results under wide range of steady-state and dynamic conditions. Unlike previous studies, the proposed model captures the time response of the spacial temperature distribution along the flow direction. It also directly solves for the local temperatures at the membrane interfaces, which allows to accurately model and calculate local flux values along with other intrinsic variables of great influence on the process, like the temperature polarization coefficient (TPC). The proposed model is based on energy and mass conservation principles and analogy between thermal and electrical systems. Experimental data was collected to validated the steady-state and dynamic responses of the model. The obtained results shows great agreement with the experimental data. The paper discusses the results of several simulations under various conditions to optimize the DCMD process efficiency and analyze its response. This demonstrates some potential applications of the proposed model to carry out scale up and design studies. © 2016

  8. Analysis of direct contact membrane distillation based on a lumped-parameter dynamic predictive model

    KAUST Repository

    Karam, Ayman M.

    2016-10-03

    Membrane distillation (MD) is an emerging technology that has a great potential for sustainable water desalination. In order to pave the way for successful commercialization of MD-based water desalination techniques, adequate and accurate dynamical models of the process are essential. This paper presents the predictive capabilities of a lumped-parameter dynamic model for direct contact membrane distillation (DCMD) and discusses the results under wide range of steady-state and dynamic conditions. Unlike previous studies, the proposed model captures the time response of the spacial temperature distribution along the flow direction. It also directly solves for the local temperatures at the membrane interfaces, which allows to accurately model and calculate local flux values along with other intrinsic variables of great influence on the process, like the temperature polarization coefficient (TPC). The proposed model is based on energy and mass conservation principles and analogy between thermal and electrical systems. Experimental data was collected to validated the steady-state and dynamic responses of the model. The obtained results shows great agreement with the experimental data. The paper discusses the results of several simulations under various conditions to optimize the DCMD process efficiency and analyze its response. This demonstrates some potential applications of the proposed model to carry out scale up and design studies. © 2016

  9. Coxsackievirus protein 2B modifies endoplasmic reticulum membrane and plasma membrane permeability and facilitates virus release.

    Science.gov (United States)

    van Kuppeveld, F J; Hoenderop, J G; Smeets, R L; Willems, P H; Dijkman, H B; Galama, J M; Melchers, W J

    1997-01-01

    Digital-imaging microscopy was performed to study the effect of Coxsackie B3 virus infection on the cytosolic free Ca2+ concentration and the Ca2+ content of the endoplasmic reticulum (ER). During the course of infection a gradual increase in the cytosolic free Ca2+ concentration was observed, due to the influx of extracellular Ca2+. The Ca2+ content of the ER decreased in time with kinetics inversely proportional to those of viral protein synthesis. Individual expression of protein 2B was sufficient to induce the influx of extracellular Ca2+ and to release Ca2+ from ER stores. Analysis of mutant 2B proteins showed that both a cationic amphipathic alpha-helix and a second hydrophobic domain in 2B were required for these activities. Consistent with a presumed ability of protein 2B to increase membrane permeability, viruses carrying a mutant 2B protein exhibited a defect in virus release. We propose that 2B gradually enhances membrane permeability, thereby disrupting the intracellular Ca2+ homeostasis and ultimately causing the membrane lesions that allow release of virus progeny. PMID:9218794

  10. Three-Dimensional Simulation of Ultrasound-Induced Microalgal Cell Disruption.

    Science.gov (United States)

    Wang, M; Yuan, W; Hale, Andy

    2016-03-01

    The three-dimensional distribution (x, y, and z) of ultrasound-induced microalgal cell disruption in a sonochemical reactor was predicted by solving the Helmholtz equation using a three-dimensional acoustic module in the COMSOL Multiphysics software. The simulated local ultrasound pressure at any given location (x, y, and z) was found to correlate with cell disruption of a freshwater alga, Scenedesmus dimorphus, represented by the change of algal cell particle/debris concentration, chlorophyll-a fluorescence density (CAFD), and Nile red stained lipid fluorescence density (LFD), which was also validated by the model reaction of potassium iodide oxidation (the Weissler reaction). Furthermore, the effect of ultrasound power intensity and processing duration on algal cell disruption was examined to address the limitation of the model.

  11. Specific Disruption of Hippocampal Mossy Fiber Synapses in a Mouse Model of Familial Alzheimer's Disease

    Science.gov (United States)

    Wilke, Scott A.; Raam, Tara; Antonios, Joseph K.; Bushong, Eric A.; Koo, Edward H.; Ellisman, Mark H.; Ghosh, Anirvan

    2014-01-01

    The earliest stages of Alzheimer's disease (AD) are characterized by deficits in memory and cognition indicating hippocampal pathology. While it is now recognized that synapse dysfunction precedes the hallmark pathological findings of AD, it is unclear if specific hippocampal synapses are particularly vulnerable. Since the mossy fiber (MF) synapse between dentate gyrus (DG) and CA3 regions underlies critical functions disrupted in AD, we utilized serial block-face electron microscopy (SBEM) to analyze MF microcircuitry in a mouse model of familial Alzheimer's disease (FAD). FAD mutant MF terminal complexes were severely disrupted compared to control – they were smaller, contacted fewer postsynaptic spines and had greater numbers of presynaptic filopodial processes. Multi-headed CA3 dendritic spines in the FAD mutant condition were reduced in complexity and had significantly smaller sites of synaptic contact. Significantly, there was no change in the volume of classical dendritic spines at neighboring inputs to CA3 neurons suggesting input-specific defects in the early course of AD related pathology. These data indicate a specific vulnerability of the DG-CA3 network in AD pathogenesis and demonstrate the utility of SBEM to assess circuit specific alterations in mouse models of human disease. PMID:24454724

  12. Finite element method (FEM) model of the mechanical stress on phospholipid membranes from shock waves produced in nanosecond electric pulses (nsEP)

    Science.gov (United States)

    Barnes, Ronald; Roth, Caleb C.; Shadaram, Mehdi; Beier, Hope; Ibey, Bennett L.

    2015-03-01

    The underlying mechanism(s) responsible for nanoporation of phospholipid membranes by nanosecond pulsed electric fields (nsEP) remains unknown. The passage of a high electric field through a conductive medium creates two primary contributing factors that may induce poration: the electric field interaction at the membrane and the shockwave produced from electrostriction of a polar submersion medium exposed to an electric field. Previous work has focused on the electric field interaction at the cell membrane, through such models as the transport lattice method. Our objective is to model the shock wave cell membrane interaction induced from the density perturbation formed at the rising edge of a high voltage pulse in a polar liquid resulting in a shock wave propagating away from the electrode toward the cell membrane. Utilizing previous data from cell membrane mechanical parameters, and nsEP generated shockwave parameters, an acoustic shock wave model based on the Helmholtz equation for sound pressure was developed and coupled to a cell membrane model with finite-element modeling in COMSOL. The acoustic structure interaction model was developed to illustrate the harmonic membrane displacements and stresses resulting from shockwave and membrane interaction based on Hooke's law. Poration is predicted by utilizing membrane mechanical breakdown parameters including cortical stress limits and hydrostatic pressure gradients.

  13. Vesicle-associated membrane protein 2 mediates trafficking of α5β1 integrin to the plasma membrane

    International Nuclear Information System (INIS)

    Hasan, Nazarul; Hu, Chuan

    2010-01-01

    Integrins are major receptors for cell adhesion to the extracellular matrix (ECM). As transmembrane proteins, the levels of integrins at the plasma membrane or the cell surface are ultimately determined by the balance between two vesicle trafficking events: endocytosis of integrins at the plasma membrane and exocytosis of the vesicles that transport integrins. Here, we report that vesicle-associated membrane protein 2 (VAMP2), a SNARE protein that mediates vesicle fusion with the plasma membrane, is involved in the trafficking of α5β1 integrin. VAMP2 was present on vesicles containing endocytosed β1 integrin. Small interfering RNA (siRNA) silencing of VAMP2 markedly reduced cell surface α5β1 and inhibited cell adhesion and chemotactic migration to fibronectin, the ECM ligand of α5β1, without altering cell surface expression of α2β1 integrin or α3β1 integrin. By contrast, silencing of VAMP8, another SNARE protein, had no effect on cell surface expression of the integrins or cell adhesion to fibronectin. In addition, VAMP2-mediated trafficking is involved in cell adhesion to collagen but not to laminin. Consistent with disruption of integrin functions in cell proliferation and survival, VAMP2 silencing diminished proliferation and triggered apoptosis. Collectively, these data indicate that VAMP2 mediates the trafficking of α5β1 integrin to the plasma membrane and VAMP2-dependent integrin trafficking is critical in cell adhesion, migration and survival.

  14. The fractal dimension of cell membrane correlates with its capacitance: A new fractal single-shell model

    Science.gov (United States)

    Wang, Xujing; Becker, Frederick F.; Gascoyne, Peter R. C.

    2010-01-01

    The scale-invariant property of the cytoplasmic membrane of biological cells is examined by applying the Minkowski–Bouligand method to digitized scanning electron microscopy images of the cell surface. The membrane is found to exhibit fractal behavior, and the derived fractal dimension gives a good description of its morphological complexity. Furthermore, we found that this fractal dimension correlates well with the specific membrane dielectric capacitance derived from the electrorotation measurements. Based on these findings, we propose a new fractal single-shell model to describe the dielectrics of mammalian cells, and compare it with the conventional single-shell model (SSM). We found that while both models fit with experimental data well, the new model is able to eliminate the discrepancy between the measured dielectric property of cells and that predicted by the SSM. PMID:21198103

  15. Polyamide Thin-Film Composite Membranes for Potential Raw Biogas Purification: Experiments and Modelling.

    Czech Academy of Sciences Publication Activity Database

    Šimčík, Miroslav; Růžička, Marek; Kárászová, Magda; Sedláková, Zuzana; Vejražka, Jiří; Veselý, M.; Čapek, P.; Friess, K.; Izák, Pavel

    2016-01-01

    Roč. 167, JUL 14 (2016), s. 163-173 ISSN 1383-5866 R&D Projects: GA ČR GA14-12695S; GA TA ČR TE01020080; GA MŠk(CZ) LD13018; GA MŠk LH14006 Institutional support: RVO:67985858 Keywords : thin film composite membrane * biogas membrane separation * transport modeling Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 3.359, year: 2016

  16. Process modeling of the impedance characteristics of proton exchange membrane fuel cells

    International Nuclear Information System (INIS)

    Rezaei Niya, Seyed Mohammad; Phillips, Ryan K.; Hoorfar, Mina

    2016-01-01

    Highlights: • The impedance of the PEM fuel cell is analytically calculated. • The measured impedances are presented for different operating conditions. • The high frequency arc in the measured Nyquist plot is related to the anode. • The intermediate frequency arc is related to the cathode. • The low frequency arc and high frequency resistance are related to the membrane. - Abstract: A complete process modeling of the impedance characteristics of the proton exchange membrane fuel cells is presented. The impedance of the cell is determined analytically and the resultant equivalent circuit is calculated. The model predictions are then compared against the measured impedances in different current densities, operating temperatures and anode and cathode relative humidities. It is shown that the model predicts the Nyquist plots in all different operating conditions extremely well. Next, the trends observed in the Nyquist plots reported in the literature are compared against the model predictions. The result of this comparison confirms the accuracy of the model. Using the verified model, various arcs in the Nyquist plots are separated and related to the fuel cell physical parameters.

  17. Minimally Disruptive Medicine: A Pragmatically Comprehensive Model for Delivering Care to Patients with Multiple Chronic Conditions

    Directory of Open Access Journals (Sweden)

    Aaron L. Leppin

    2015-01-01

    Full Text Available An increasing proportion of healthcare resources in the United States are directed toward an expanding group of complex and multimorbid patients. Federal stakeholders have called for new models of care to meet the needs of these patients. Minimally Disruptive Medicine (MDM is a theory-based, patient-centered, and context-sensitive approach to care that focuses on achieving patient goals for life and health while imposing the smallest possible treatment burden on patients’ lives. The MDM Care Model is designed to be pragmatically comprehensive, meaning that it aims to address any and all factors that impact the implementation and effectiveness of care for patients with multiple chronic conditions. It comprises core activities that map to an underlying and testable theoretical framework. This encourages refinement and future study. Here, we present the conceptual rationale for and a practical approach to minimally disruptive care for patients with multiple chronic conditions. We introduce some of the specific tools and strategies that can be used to identify the right care for these patients and to put it into practice.

  18. Study of runaway electron generation during major disruptions in JET

    International Nuclear Information System (INIS)

    Plyusnin, V.V.; Riccardo, V.; Jaspers, R.; Alper, B.; Kiptily, V.G.; Mlynar, J.; Popovichev, S.; Luna, E. de La; Andersson, F.

    2006-01-01

    Extensive analysis of disruptions in JET has helped advance the understanding of trends of disruption-generated runaway electrons. Tomographic reconstruction of the soft x-ray emission has made possible a detailed observation of the magnetic flux geometry evolution during disruptions. With the aid of soft and hard x-ray diagnostics runaway electrons have been detected at the very beginning of disruptions. A study of runaway electron parameters has shown that an approximate upper bound for the conversion efficiency of pre-disruptive plasma currents into runaways is about 60% over a wide range of plasma currents in JET. Runaway generation has been simulated with a test particle model in order to verify the results of experimental data analysis and to obtain the background for extrapolation of the existing results onto larger devices such as ITER. It was found that close agreement between the modelling results and experimental data could be achieved if in the calculations the post-disruption plasma electron temperature was assumed equal to 10 eV and if the plasma column geometry evolution is taken into account in calculations. The experimental trends and numerical simulations show that runaway electrons are a critical issue for ITER and, therefore, the development of mitigation methods, which suppress runaway generation, is an essential task

  19. Numerical Model on Sound-Solid Coupling in Human Ear and Study on Sound Pressure of Tympanic Membrane

    Directory of Open Access Journals (Sweden)

    Yao Wen-juan

    2011-01-01

    Full Text Available Establishment of three-dimensional finite-element model of the whole auditory system includes external ear, middle ear, and inner ear. The sound-solid-liquid coupling frequency response analysis of the model was carried out. The correctness of the FE model was verified by comparing the vibration modes of tympanic membrane and stapes footplate with the experimental data. According to calculation results of the model, we make use of the least squares method to fit out the distribution of sound pressure of external auditory canal and obtain the sound pressure function on the tympanic membrane which varies with frequency. Using the sound pressure function, the pressure distribution on the tympanic membrane can be directly derived from the sound pressure at the external auditory canal opening. The sound pressure function can make the boundary conditions of the middle ear structure more accurate in the mechanical research and improve the previous boundary treatment which only applied uniform pressure acting to the tympanic membrane.

  20. An analysis of recent fuel disruption experiments

    International Nuclear Information System (INIS)

    Kramer, J.M.; Kraft, T.E.; Dimelfi, R.J.; Fenske, G.R.; Gruber, E.E.

    1982-01-01

    Recent USDOE-Sponsored DEH, FGR, and TREAT F series fuel disruption experiments are analyzed with existing analytical models. The experiments are interpreted and the results used to evaluate the models. Calculations are presented using the FRAS3 fission gas behavior code and the DiMelfi-Deitrich fuel response model

  1. Probing lipid membrane electrostatics

    Science.gov (United States)

    Yang, Yi

    The electrostatic properties of lipid bilayer membranes play a significant role in many biological processes. Atomic force microscopy (AFM) is highly sensitive to membrane surface potential in electrolyte solutions. With fully characterized probe tips, AFM can perform quantitative electrostatic analysis of lipid membranes. Electrostatic interactions between Silicon nitride probes and supported zwitterionic dioleoylphosphatidylcholine (DOPC) bilayer with a variable fraction of anionic dioleoylphosphatidylserine (DOPS) were measured by AFM. Classical Gouy-Chapman theory was used to model the membrane electrostatics. The nonlinear Poisson-Boltzmann equation was numerically solved with finite element method to provide the potential distribution around the AFM tips. Theoretical tip-sample electrostatic interactions were calculated with the surface integral of both Maxwell and osmotic stress tensors on tip surface. The measured forces were interpreted with theoretical forces and the resulting surface charge densities of the membrane surfaces were in quantitative agreement with the Gouy-Chapman-Stern model of membrane charge regulation. It was demonstrated that the AFM can quantitatively detect membrane surface potential at a separation of several screening lengths, and that the AFM probe only perturbs the membrane surface potential by external field created by the internai membrane dipole moment. The analysis yields a dipole moment of 1.5 Debye per lipid with a dipole potential of +275 mV for supported DOPC membranes. This new ability to quantitatively measure the membrane dipole density in a noninvasive manner will be useful in identifying the biological effects of the dipole potential. Finally, heterogeneous model membranes were studied with fluid electric force microscopy (FEFM). Electrostatic mapping was demonstrated with 50 nm resolution. The capabilities of quantitative electrostatic measurement and lateral charge density mapping make AFM a unique and powerful

  2. A Generic Model for Prediction of Separation Performance of Olefin/Paraffin Mixture by Glassy Polymer Membranes

    Directory of Open Access Journals (Sweden)

    A.A. Ghoreyshi

    2008-02-01

    Full Text Available The separation of olefin/paraffin mixtures is an important process in petrochemical industries, which is traditionally performed by low temperature distillation with a high-energy consumption, or complex extractive distillationand adsorption techniques. Membrane separation process is emerging as an alternative for traditional separation processes with respect to low energy and simple operation. Investigations made by various researchers on polymeric membranes it is found that special glassy polymers render them as suitable materials for olefin/paraffin mixture separation. In this regard, having some knowledge on the possible transport mechanism of these processes would play a significant role in their design and applications. In this study, separation behavior of olefin/paraffin mixtures through glassy polymers was modeled by three different approaches: the so-called dual transport model, the basic adsorption-diffusion theory and the general Maxwell-Stefan formulation. The systems chosen to validate the developed transport models are separation of ethane-ethylene mixture by 6FDA-6FpDA polyimide membrane and propane-propylene mixture by 6FDA-TrMPD polyimide membrane for which the individual sorption and permeation data are available in the literature. Acritical examination of dual transport model shows that this model fails clearly to predict even the proper trend for selectivities. The adjustment of pemeabilities by accounting for the contribution of non-selective bulk flow in the transport model introduced no improvement in the predictability of the model. The modeling results based on the basic adsorption-diffusion theory revealed that in this approach only using mixed permeability data, an acceptable result is attainable which fades out the advantages of predictibility of multicomponent separation performance from pure component data. Finally, the results obtained from the model developed based on Maxwell-Stefan formulation approach show a

  3. Unconditionally energy stable numerical schemes for phase-field vesicle membrane model

    Science.gov (United States)

    Guillén-González, F.; Tierra, G.

    2018-02-01

    Numerical schemes to simulate the deformation of vesicles membranes via minimizing the bending energy have been widely studied in recent times due to its connection with many biological motivated problems. In this work we propose a new unconditionally energy stable numerical scheme for a vesicle membrane model that satisfies exactly the conservation of volume constraint and penalizes the surface area constraint. Moreover, we extend these ideas to present an unconditionally energy stable splitting scheme decoupling the interaction of the vesicle with a surrounding fluid. Finally, the well behavior of the proposed schemes are illustrated through several computational experiments.

  4. MHD stability, operational limits and disruptions

    International Nuclear Information System (INIS)

    1999-01-01

    (vii) 'integrated' modelling of disruptions and fast shutdown and of the ensuing effects. In each instance, the presentation within a given topical area progresses from a summary of present experimental and theoretical understanding to how this understanding projects or extrapolates to an ITER class reactor regime tokamak. Examples of extrapolations to the specific ITER design concept developed during the course of the ITER EDA are given, and assessments of the degree of adequacy of present understanding are also provided. In areas where present understanding is identified to be less than fully adequate, areas in which continuing or new research is needed are identified. (author)

  5. Experimental investigation and modeling of industrial oily wastewater treatment using modified polyethersulfone ultrafiltration hollow fiber membranes

    International Nuclear Information System (INIS)

    Salahi, Abdolhamid; Mohammadi, Toraj; Behbahani, Reza Mosayebi; Hemmati, Mahmood

    2015-01-01

    Hollow fiber membranes were prepared from polyethersulfone/additives/NMP and DMSO system via phase inversion induced by precipitation in non-solvent coagulation bath. The interaction effects of polyethylene-glycol (PEG), propionic-acid (PA), Tween-20, PEG molecular weight and polyvinyl-pyrrolidone (PVP) on morphology and performance of synthesized membranes were investigated. Taguchi method (L 16 orthogonal array) was used initially to plan a minimum number of experiments. 32 membranes were synthesized (with two replications) and their permeation flux and TOC rejection properties to oily wastewater treatment were studied. The obtained results indicated that addition of PA to spinning dope decreases flux while it increases TOC rejection of prepared membranes. Also, the result shows that addition of PVP, Tween-20 and PEG content in spinning dope enhances permeation flux while reducing TOC rejection. The obtained results indicated that the synthesized membranes was effective and suitable for treatment of the oily wastewater to achieve up to 92.6, 98.2, and 98.5% removal of TOC, TSS, and OGC, respectively with a flux of 247.19 L/(m 2 h). Moreover, Hermia's models were used for permeation flux decline prediction. Experimental data and models predictions were compared. The results showed that there is reasonable agreement between experimental data and the cake layer model followed by the intermediate blocking model

  6. Experimental investigation and modeling of industrial oily wastewater treatment using modified polyethersulfone ultrafiltration hollow fiber membranes

    Energy Technology Data Exchange (ETDEWEB)

    Salahi, Abdolhamid; Mohammadi, Toraj [Iran University of Science and Technology (IUST), Tehran (Iran, Islamic Republic of); Behbahani, Reza Mosayebi [Petroleum University of Technology (PUT), Ahwaz (Iran, Islamic Republic of); Hemmati, Mahmood [Research Institute of Petroleum Industry, Tehran (Iran, Islamic Republic of)

    2015-06-15

    Hollow fiber membranes were prepared from polyethersulfone/additives/NMP and DMSO system via phase inversion induced by precipitation in non-solvent coagulation bath. The interaction effects of polyethylene-glycol (PEG), propionic-acid (PA), Tween-20, PEG molecular weight and polyvinyl-pyrrolidone (PVP) on morphology and performance of synthesized membranes were investigated. Taguchi method (L{sub 16} orthogonal array) was used initially to plan a minimum number of experiments. 32 membranes were synthesized (with two replications) and their permeation flux and TOC rejection properties to oily wastewater treatment were studied. The obtained results indicated that addition of PA to spinning dope decreases flux while it increases TOC rejection of prepared membranes. Also, the result shows that addition of PVP, Tween-20 and PEG content in spinning dope enhances permeation flux while reducing TOC rejection. The obtained results indicated that the synthesized membranes was effective and suitable for treatment of the oily wastewater to achieve up to 92.6, 98.2, and 98.5% removal of TOC, TSS, and OGC, respectively with a flux of 247.19 L/(m{sup 2}h). Moreover, Hermia's models were used for permeation flux decline prediction. Experimental data and models predictions were compared. The results showed that there is reasonable agreement between experimental data and the cake layer model followed by the intermediate blocking model.

  7. HAMLET interacts with lipid membranes and perturbs their structure and integrity.

    Science.gov (United States)

    Mossberg, Ann-Kristin; Puchades, Maja; Halskau, Øyvind; Baumann, Anne; Lanekoff, Ingela; Chao, Yinxia; Martinez, Aurora; Svanborg, Catharina; Karlsson, Roger

    2010-02-23

    Cell membrane interactions rely on lipid bilayer constituents and molecules inserted within the membrane, including specific receptors. HAMLET (human alpha-lactalbumin made lethal to tumor cells) is a tumoricidal complex of partially unfolded alpha-lactalbumin (HLA) and oleic acid that is internalized by tumor cells, suggesting that interactions with the phospholipid bilayer and/or specific receptors may be essential for the tumoricidal effect. This study examined whether HAMLET interacts with artificial membranes and alters membrane structure. We show by surface plasmon resonance that HAMLET binds with high affinity to surface adherent, unilamellar vesicles of lipids with varying acyl chain composition and net charge. Fluorescence imaging revealed that HAMLET accumulates in membranes of vesicles and perturbs their structure, resulting in increased membrane fluidity. Furthermore, HAMLET disrupted membrane integrity at neutral pH and physiological conditions, as shown by fluorophore leakage experiments. These effects did not occur with either native HLA or a constitutively unfolded Cys-Ala HLA mutant (rHLA(all-Ala)). HAMLET also bound to plasma membrane vesicles formed from intact tumor cells, with accumulation in certain membrane areas, but the complex was not internalized by these vesicles or by the synthetic membrane vesicles. The results illustrate the difference in membrane affinity between the fatty acid bound and fatty acid free forms of partially unfolded HLA and suggest that HAMLET engages membranes by a mechanism requiring both the protein and the fatty acid. Furthermore, HAMLET binding alters the morphology of the membrane and compromises its integrity, suggesting that membrane perturbation could be an initial step in inducing cell death.

  8. Introducing Membrane Charge and Membrane Potential to T Cell Signaling

    Directory of Open Access Journals (Sweden)

    Yuanqing Ma

    2017-11-01

    Full Text Available While membrane models now include the heterogeneous distribution of lipids, the impact of membrane charges on regulating the association of proteins with the plasma membrane is often overlooked. Charged lipids are asymmetrically distributed between the two leaflets of the plasma membrane, resulting in the inner leaflet being negatively charged and a surface potential that attracts and binds positively charged ions, proteins, and peptide motifs. These interactions not only create a transmembrane potential but they can also facilitate the formation of charged membrane domains. Here, we reference fields outside of immunology in which consequences of membrane charge are better characterized to highlight important mechanisms. We then focus on T cell receptor (TCR signaling, reviewing the evidence that membrane charges and membrane-associated calcium regulate phosphorylation of the TCR–CD3 complex and discuss how the immunological synapse exhibits distinct patterns of membrane charge distribution. We propose that charged lipids, ions in solution, and transient protein interactions form a dynamic equilibrium during T cell activation.

  9. Mechanics and dynamics of triglyceride-phospholipid model membranes

    DEFF Research Database (Denmark)

    Pakkanen, Kirsi I.; Duelund, Lars; Qvortrup, Klaus

    2011-01-01

    We demonstrate here that triolein alters the mechanical properties of phospholipid membranes and induces extraordinary conformational dynamics. Triolein containing membranes exhibit fluctuations up to size range of 100µm and with the help of these are e.g. able to squeeze through narrow passages...... with larger lamellar distances observed in the TOPOPC membranes. These findings suggest repulsion between adjacent membranes. We provide a comprehensive discussion on the possible explanations for the observed mechanics and dynamics in the TOPOPC system and on their potential cellular implications....

  10. Chitosan derivatives targeting lipid bilayers: Synthesis, biological activity and interaction with model membranes.

    Science.gov (United States)

    Martins, Danubia Batista; Nasário, Fábio Domingues; Silva-Gonçalves, Laiz Costa; de Oliveira Tiera, Vera Aparecida; Arcisio-Miranda, Manoel; Tiera, Marcio José; Dos Santos Cabrera, Marcia Perez

    2018-02-01

    The antimicrobial activity of chitosan and derivatives to human and plant pathogens represents a high-valued prospective market. Presently, two low molecular weight derivatives, endowed with hydrophobic and cationic character at different ratios were synthesized and characterized. They exhibit antimicrobial activity and increased performance in relation to the intermediate and starting compounds. However, just the derivative with higher cationic character showed cytotoxicity towards human cervical carcinoma cells. Considering cell membranes as targets, the mode of action was investigated through the interaction with model lipid vesicles mimicking bacterial, tumoral and erythrocyte membranes. Intense lytic activity and binding are demonstrated for both derivatives in anionic bilayers. The less charged compound exhibits slightly improved selectivity towards bacterial model membranes, suggesting that balancing its hydrophobic/hydrophilic character may improve efficiency. Observing the aggregation of vesicles, we hypothesize that the "charge cluster mechanism", ascribed to some antimicrobial peptides, could be applied to these chitosan derivatives. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Mathematical Modeling and Numerical Simulation of CO2 Removal by Using Hollow Fiber Membrane Contactors

    Directory of Open Access Journals (Sweden)

    Mohammad Mesbah

    2017-10-01

    Full Text Available Abstract In this study, a mathematical model is proposed for CO2 separation from N2/CO2 mixtureusing a hollow fiber membrane contactor by various absorbents. The contactor assumed as non-wetted membrane; radial and axial diffusions were also considered in the model development. The governing equations of the model are solved via the finite element method (FEM. To ensure the accuracy of the developed model, the simulation results were validated using the reported experimental data for potassium glycinate (PG, monoethanol amine (MEA, and methyldiethanol amine (MDEA. The results of the proposed model indicated that PG absorbent has the highest removal efficiency of CO2, followed by potassium threonate (PT, MEA, amino-2-methyl-1-propanol (AMP, diethanol amine (DEA, and MDEA in sequence. In addition, the results revealed that the CO2 removal efficiency was favored by absorbent flow rate and liquid temperature, while the gas flow rate has a reverse effect. The simulation results proved that the hollow fiber membrane contactors have a good potential in the area of CO2 capture.

  12. Data supporting the validation of a simulation model for multi-component gas separation in polymeric membranes.

    Science.gov (United States)

    Giordano, Lorena; Roizard, Denis; Bounaceur, Roda; Favre, Eric

    2016-12-01

    The article describes data concerning the separation performances of polymeric hollow-fiber membranes. The data were obtained using a model for simulating gas separation, described in the research article entitled "Interplay of inlet temperature and humidity on energy penalty for CO 2 post-combustion capture: rigorous analysis and simulation of a single stage gas permeation process" (L. Giordano, D. Roizard, R. Bounaceur, E. Favre, 2016) [1]. The data were used to validate the model by comparison with literature results. Considering a membrane system based on feed compression only, data from the model proposed and that from literature were compared with respect to the molar composition of permeate stream, the membrane area and specific energy requirement, varying the feed pressure and the CO 2 separation degree.

  13. Disruptive instabilities in the TBR-1

    International Nuclear Information System (INIS)

    Vannucci, A.

    1987-01-01

    The disruptive instabilities in the TBR-1 tokamak of the Plasma Physics Laboratory of the Institute of Physics-USP were investigated by using surface-barrier detectors and Mirnov magnetic coils, measuring soft X-ray emited by the plasma and poloidal magnetic fluctuations, respectively. Minor and major disruptions, as well sawteeth oscillations, were identified at the TBR-1 discharges, and their main characteristics were studied. Comparing the measured period of the internal disruptions (sawteeth) with the ones expected from scaling laws, good agreements is reached. The measured sawteeth crashes agree with the values expected from the Kadomtsev's model. External helical fields (CHR), corresponding to m/n=2/1 helicity were produced in order to inhibit or criate disruptive instabilities. A strong weakening of the mhd activity, present in the TBR-1 discharges, was clearly detected. The soft X-ray detection system, projected and constructed for this work, was used to obtain the electron temperatures of regions close to the center of the plasma column (T(r=0) ∼ 205 eV and T(r ± 3,8) ∼ 85 eV), using the absorbing foils method. Using the Spitzer formula, Z sub (eff) values were also obtained. (author) [pt

  14. A Unified Model for Tidal Disruption Events

    Science.gov (United States)

    Dai, Lixin; McKinney, Jonathan C.; Roth, Nathaniel; Ramirez-Ruiz, Enrico; Miller, M. Coleman

    2018-06-01

    In the past few years wide-field optical and UV transient surveys and X-ray telescopes have allowed us to identify a few dozen candidate tidal disruption events (TDEs). While in theory the physical processes in TDEs are ubiquitous, a few distinct classes of TDEs have been observed. Some TDEs radiate mainly in NUV/optical, while others produce prominent X-rays. Moreover, relativistic jets have been observed in only a handful of TDEs. This diversity might be related to the details of the super-Eddington accretion and emission physics relevant to TDE disks. In this Letter, we utilize novel three-dimensional general relativistic radiation magnetohydrodynamics simulations to study the super-Eddington compact disk phase expected in TDEs. Consistent with previous studies, geometrically thick disks, wide-angle optically thick fast outflows, and relativistic jets are produced. The outflow density and velocity depend sensitively on the inclination angle, and hence so does the reprocessing of emission produced from the inner disk. We then use Monte Carlo radiative transfer to calculate the reprocessed spectra and find that that the observed ratio of optical to X-ray fluxes increases with increasing inclination angle. This naturally leads to a unified model for different classes of TDEs in which the spectral properties of the TDE depend mainly on the viewing angle of the observer with respect to the orientation of the disk.

  15. Disruption in a Neurodevelopmental Model of Schizophrenia

    Directory of Open Access Journals (Sweden)

    Benjamin Rolland

    2012-01-01

    Full Text Available Oxidative stress has been implicated in neurodevelopmental theories of schizophrenia. Antioxidant Peroxysome Proliferator-Activated Receptors α (PPARα agonist fenofibrate has neuroprotective properties and could reverse early preclinical infringements that could trigger the illness. We have evaluated the neuroprotective interest of fenofibrate in a neurodevelopmental rat model of schizophrenia. The oxidative lesion induced by Kainic Acid (KA injection at postnatal day (PND 7 has previously been reported to disrupt Prepulse Inhibition (PPI at PND56 but not at PND35. In 4 groups of 15 male rats each, KN (KA-PND7 + normal postweaning food, KF (KA-PND7 + fenofibrate 0.2% food, ON (saline-PND7 + normal food, and OF (saline + fenofibrate food, PPI was recorded at PND35 and PND56. Three levels of prepulse were used: 73 dB, 76 dB, and 82 dB for a pulse at 120 dB. Four PPI scores were analyzed: PPI73, PPI76, PPI82, and mean PPI (PPIm. Two-way ANOVAs were used to evaluate the effects of both factors (KA + fenofibrate, and, in case of significant results, intergroup Student’s t-tests were performed. We notably found a significant difference (P<0.05 in PPIm between groups KN and KF at PND56, which supposes that fenofibrate could be worthy of interest for early neuroprotection in schizophrenia.

  16. Surfactant-free purification of membrane protein complexes from bacteria: application to the staphylococcal penicillin-binding protein complex PBP2/PBP2a

    International Nuclear Information System (INIS)

    Paulin, Sarah; Rosado, Helena; Taylor, Peter W; Jamshad, Mohammed; Dafforn, Timothy R; Garcia-Lara, Jorge; Foster, Simon J; Galley, Nicola F; Roper, David I

    2014-01-01

    Surfactant-mediated removal of proteins from biomembranes invariably results in partial or complete loss of function and disassembly of multi-protein complexes. We determined the capacity of styrene-co-maleic acid (SMA) co-polymer to remove components of the cell division machinery from the membrane of drug-resistant staphylococcal cells. SMA-lipid nanoparticles solubilized FtsZ-PBP2-PBP2a complexes from intact cells, demonstrating the close physical proximity of these proteins within the lipid bilayer. Exposure of bacteria to (-)-epicatechin gallate, a polyphenolic agent that abolishes β-lactam resistance in staphylococci, disrupted the association between PBP2 and PBP2a. Thus, SMA purification provides a means to remove native integral membrane protein assemblages with minimal physical disruption and shows promise as a tool for the interrogation of molecular aspects of bacterial membrane protein structure and function. (paper)

  17. Surfactant-free purification of membrane protein complexes from bacteria: application to the staphylococcal penicillin-binding protein complex PBP2/PBP2a

    Science.gov (United States)

    Paulin, Sarah; Jamshad, Mohammed; Dafforn, Timothy R.; Garcia-Lara, Jorge; Foster, Simon J.; Galley, Nicola F.; Roper, David I.; Rosado, Helena; Taylor, Peter W.

    2014-07-01

    Surfactant-mediated removal of proteins from biomembranes invariably results in partial or complete loss of function and disassembly of multi-protein complexes. We determined the capacity of styrene-co-maleic acid (SMA) co-polymer to remove components of the cell division machinery from the membrane of drug-resistant staphylococcal cells. SMA-lipid nanoparticles solubilized FtsZ-PBP2-PBP2a complexes from intact cells, demonstrating the close physical proximity of these proteins within the lipid bilayer. Exposure of bacteria to (-)-epicatechin gallate, a polyphenolic agent that abolishes β-lactam resistance in staphylococci, disrupted the association between PBP2 and PBP2a. Thus, SMA purification provides a means to remove native integral membrane protein assemblages with minimal physical disruption and shows promise as a tool for the interrogation of molecular aspects of bacterial membrane protein structure and function.

  18. Wound Disruption Following Colorectal Operations.

    Science.gov (United States)

    Moghadamyeghaneh, Zhobin; Hanna, Mark H; Carmichael, Joseph C; Mills, Steven; Pigazzi, Alessio; Nguyen, Ninh T; Stamos, Michael J

    2015-12-01

    Postoperative wound disruption is associated with high morbidity and mortality. We sought to identify the risk factors and outcomes of wound disruption following colorectal resection. The American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database was used to examine the clinical data of patients who underwent colorectal resection from 2005 to 2013. Multivariate regression analysis was performed to identify risk factors of wound disruption. We sampled a total of 164,297 patients who underwent colorectal resection. Of these, 2073 (1.3 %) had wound disruption. Patients with wound disruption had significantly higher mortality (5.1 vs. 1.9 %, AOR: 1.46, P = 0.01). The highest risk of wound disruption was seen in patients with wound infection (4.8 vs. 0.9 %, AOR: 4.11, P disruption such as chronic steroid use (AOR: 1.71, P disruption compared to open surgery (AOR: 0.61, P disruption occurs in 1.3 % of colorectal resections, and it correlates with mortality of patients. Wound infection is the strongest predictor of wound disruption. Chronic steroid use, obesity, severe COPD, prolonged operation, non-elective admission, and serum albumin level are strongly associated with wound disruption. Utilization of the laparoscopic approach may decrease the risk of wound disruption when possible.

  19. Summary report for ITER Task - T226B: Evaluation of ITER disruption erosion

    International Nuclear Information System (INIS)

    Hassanein, A.

    1995-02-01

    The behavior of divertor materials during a major disruption in a tokamak reactor is very important to successful and reliable operation of the device. Erosion of material surfaces due to a thermal energy dump can severely limit the lifetimes of plasma-facing components and thus diminish the reactor's economic feasibility. A comprehensive numerical model has been developed and used in this analysis, which includes all major physical processes taking place during plasma/material interactions. Models to account for material thermal evolution, plasma/vapor interaction physics, and models for hydrodynamic radiation transport in the developed vapor cloud above the exposed surface are implemented in a self-consistent manner to realistically assess disruption damage. The extent of self-protection from the developed vapor cloud in front of the incoming plasma particles is critically important in determining the overall disruption lifetime. Models to study detailed effects of the strong magnetic field on the behavior of the vapor cloud and on the net erosion rate have also been developed and analyzed. Candidate materials such as beryllium and carbon are considered in this analysis. The dependence of divertor disruption lifetime on disruption physics and reactor conditions is analyzed and discussed. In addition, material erosion from melting of plasma-facing components during a tokamak disruption is also a serious problem that limits reactor operation and economical reactor lifetime. In particular, metallic low-Z components such as Be will be subjected to severe melting during disruptions and edge localized modes (ELMs). Loss of the developed melt layer will critically shorten the lifetime of these components, severely contaminate the plasma, and seriously inhibit successful and reliable operation of the reactor. In this study mechanisms responsible for melt-layer loss during a disruption are also modeled and evaluated

  20. Critical review of membrane bioreactor models--part 1: biokinetic and filtration models.

    Science.gov (United States)

    Naessens, W; Maere, T; Nopens, I

    2012-10-01

    Membrane bioreactor technology exists for a couple of decades, but has not yet overwhelmed the market due to some serious drawbacks of which operational cost due to fouling is the major contributor. Knowledge buildup and optimisation for such complex systems can significantly benefit from mathematical modelling. In this paper, the vast literature on modelling MBR biokinetics and filtration is critically reviewed. It was found that models cover the wide range of empirical to detailed mechanistic descriptions and have mainly been used for knowledge development and to a lesser extent for system optimisation/control. Moreover, studies are still predominantly performed at lab or pilot scale. Trends are discussed, knowledge gaps identified and interesting routes for further research suggested. Copyright © 2012 Elsevier Ltd. All rights reserved.

  1. The influence of plasma motion on disruption generated runaway electrons

    International Nuclear Information System (INIS)

    Russo, A.J.

    1991-01-01

    One of the possible consequences of disruptions is the generation of runaway electrons which can impact plasma facing components and cause damage due to high local energy deposition. This problem becomes more serious as the machine size and plasma current increases. Since large size and high currents are characteristics of proposed future machines, control of runaway generation is an important design consideration. A lumped circuit model for disruption runaway electron generation indicates that control circuitry on strongly influence runaway behavior. A comparison of disruption data from several shots on JET and D3-D with model results, demonstrate the effects of plasma motion on runaway number density and energy. 6 refs., 12 figs

  2. Ultrathin Ceramic Membranes as Scaffolds for Functional Cell Coculture Models on a Biomimetic Scale

    Science.gov (United States)

    Jud, Corinne; Ahmed, Sher; Müller, Loretta; Kinnear, Calum; Vanhecke, Dimitri; Umehara, Yuki; Frey, Sabine; Liley, Martha; Angeloni, Silvia; Petri-Fink, Alke; Rothen-Rutishauser, Barbara

    2015-01-01

    Abstract Epithelial tissue serves as an interface between biological compartments. Many in vitro epithelial cell models have been developed as an alternative to animal experiments to answer a range of research questions. These in vitro models are grown on permeable two-chamber systems; however, commercially available, polymer-based cell culture inserts are around 10 μm thick. Since the basement membrane found in biological systems is usually less than 1 μm thick, the 10-fold thickness of cell culture inserts is a major limitation in the establishment of realistic models. In this work, an alternative insert, accommodating an ultrathin ceramic membrane with a thickness of only 500 nm (i.e., the Silicon nitride Microporous Permeable Insert [SIMPLI]-well), was produced and used to refine an established human alveolar barrier coculture model by both replacing the conventional inserts with the SIMPLI-well and completing it with endothelial cells. The structural–functional relationship of the model was evaluated, including the translocation of gold nanoparticles across the barrier, revealing a higher translocation if compared to corresponding polyethylene terephthalate (PET) membranes. This study demonstrates the power of the SIMPLI-well system as a scaffold for epithelial tissue cell models on a truly biomimetic scale, allowing construction of more functionally accurate models of human biological barriers. PMID:26713225

  3. [Effect of solution environments on ceramic membrane microfiltration of model system of Chinese medicines].

    Science.gov (United States)

    Zhang, Lianjun; Lu, Jin; Le, Kang; Fu, Tingming; Guo, Liwei

    2010-07-01

    To investigate the effect of differents solution environments on the ceramic membrane microfiltration of model system of Chinese medicines. Taking binary system of soybean protein-berberine as the research object, flux, transmittance of berberine and traping rate of protein as indexes, different solution environment on membrane process were investigated. When the concentration of soybean protein was under 1 g x L(-1), the membrane flux was minimum with the traping of berberine decreased slightly as the concentration increased. When pH was 4, the flux was maximum with the traping rate of protein was 99%, and the transmittance of berberine reached above 60%. The efficiency of membrane separation can be improved by optimizing the solution environment of water-extraction of chinese medicines. The efficiency of membrane separation is the best when adjust the pH to the isoelectric point of proteins for the proteins as the main pollutant in aqueous solution.

  4. Interactions between lipids and proteins are critical for organization of plasma membrane-ordered domains in tobacco BY-2 cells.

    Science.gov (United States)

    Grosjean, Kevin; Der, Christophe; Robert, Franck; Thomas, Dominique; Mongrand, Sébastien; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

    2018-06-27

    The laterally heterogeneous plant plasma membrane (PM) is organized into finely controlled specialized areas that include membrane-ordered domains. Recently, the spatial distribution of such domains within the PM has been identified as playing a key role in cell responses to environmental challenges. To examine membrane order at a local level, BY-2 tobacco suspension cell PMs were labelled with an environment-sensitive probe (di-4-ANEPPDHQ). Four experimental models were compared to identify mechanisms and cell components involved in short-term (1 h) maintenance of the ordered domain organization in steady-state cell PMs: modulation of the cytoskeleton or the cell wall integrity of tobacco BY-2 cells; and formation of giant vesicles using either a lipid mixture of tobacco BY-2 cell PMs or the original lipid and protein combinations of the tobacco BY-2 cell PM. Whilst inhibiting phosphorylation or disrupting either the cytoskeleton or the cell wall had no observable effects, we found that lipids and proteins significantly modified both the abundance and spatial distribution of ordered domains. This indicates the involvement of intrinsic membrane components in the local physical state of the plant PM. Our findings support a major role for the 'lipid raft' model, defined as the sterol-dependent ordered assemblies of specific lipids and proteins in plant PM organization.

  5. Structure and properties of cell membranes. Volume 3: Methodology and properties of membranes

    International Nuclear Information System (INIS)

    Benga, G.

    1985-01-01

    This book covers the topics: Quantum chemical approach to study the mechanisms of proton translocation across membranes through protein molecules; monomolecular films as biomembrane models; planar lipid bilayers in relation to biomembranes; relation of liposomes to cell membranes; reconstitution of membrane transport systems; structure-function relationships in cell membranes as revealed by X-ray techniques; structure-function relationships in cell membranes as revealed by spin labeling ESR; structure and dynamics of cell membranes as revealed by NMR techniques; the effect of dietary lipids on the composition and properties of biological membranes and index

  6. Cost Consequences of a Port-Related Supply Chain Disruption

    Directory of Open Access Journals (Sweden)

    Hui Shan LOH

    2015-09-01

    Full Text Available Port functionality is a significant and important aspect of cargo transportation. Previous studies have identified a list of port-related supply chain disruption threats and developed a management model that seeks to address these threats. This paper adds value to these related studies by comparing four consequences of an example of these threats: (1 avoidance of disruption, (2 mitigation of disruption, (3 deviation of transportation plan and (4 delays and deviation of transportation plan. The impact of these consequences is simulated in a case study using data from a chemical manufacturer based in Singapore. This paper quantitatively measures the impact of a port-related threat on supply chains and thus highlights the importance of port-related supply chain disruption management.

  7. Effect of phospholipid metabolites on model membrane fusion

    Energy Technology Data Exchange (ETDEWEB)

    Shragin, A.S.; Vasilenko, I.A.; Selishcheva, A.A.; Shvets, V.I.

    1985-01-01

    /sup 31/P-NMR spectroscopy and formation of fluorescent complexes between Tb/sup 3 +/ and dipicolinic acid were used to monitor liposome fusion and the effects of phospholipases C and D on the process. Phospholipase C was found highly efficient in initiating liposomal fusion, regardless of the phospholipid composition of the bilayer membranes. However, phospholipase D promoted liposomal fusion only in cases in which the membranes contained high concentrations of phospholipids incapable of forming bilayer membranes, such as phosphatidylethanolamine and cardiolipin. The mechanism of action of both enzymes in promoting liposomal fusion was ascribed to the generation of a metastable state in the membranes as a result of enzymatic formation of lipophilic metabolites 1,2-diacylglycerol and phosphatidic acid. The perturbation, or fluidity, of the liposomal membranes favored fusion on contact. 21 references, 4 figures.

  8. Damage of Escherichia coli membrane by bactericidal agent polyhexamethylene guanidine hydrochloride: micrographic evidences.

    Science.gov (United States)

    Zhou, Z X; Wei, D F; Guan, Y; Zheng, A N; Zhong, J J

    2010-03-01

    The purpose of this study was to provide micrographic evidences for the damaged membrane structure and intracellular structure change of Escherichia coli strain 8099, induced by polyhexamethylene guanidine hydrochloride (PHMG). The bactericidal effect of PHMG on E. coli was investigated based on beta-galactosidase activity assay, fluorescein-5-isothiocyanate confocal laser scanning microscopy, field emission scanning electron microscopy and transmission electron microscopy. The results revealed that a low dose (13 microg ml(-1)) of PHMG slightly damaged the outer membrane structure of the treated bacteria and increased the permeability of the cytoplasmic membrane, while no significant damage was observed to the morphological structure of the cells. A high dose (23 microg ml(-1)) of PHMG collapsed the outer membrane structure, led to the formation of a local membrane pore across the membrane and badly damaged the internal structure of the cells. Subsequently, intracellular components were leaked followed by cell inactivation. Dose-dependent membrane disruption was the main bactericidal mechanism of PHMG. The formation of the local membrane pores was probable after exposure to a high dose (23 microg ml(-1)) of PHMG. Micrographic evidences were provided about the damaged membrane structure and intracellular structure change of E. coli. The presented information helps understand the bactericidal mechanism of PHMG by membrane damage.

  9. An Approach to Modeling Complex Socio-Economic Impacts and Responses to Climate Disruption

    Science.gov (United States)

    Pikas, C. K.; Nix, M.; Ihde, A. G.; Weiss, M.; Simpkins, S.; Fountain, G. H.; Paxton, L. J.

    2011-12-01

    In this paper we describe the application of a proven methodology for modeling the complex social and economic interactions of a system under stress to the issues that are arising and will arise from global climate disruption. There is a long history in the Defense community of using what are known as strategic simulations or "wargames" to model the complex interactions between the environment, people, resources, infrastructure and the economy in a competitive environment. We describe in this paper, work that we have done on understanding how this heritage can be repurposed to help us explore how the complex interplay between climate disruption and our socio/political and economic structures will affect our future. These strategic simulations would be done under the auspices of the GAIA project (http://gaia.jhuapl.edu). While these simulations cannot definitively predict what will happen, they do illuminate non-linear feedbacks between human choices and the environment. These simulations can be focused on the global, regional, or local environment and capture the various actors (governments, agencies, resources, industries, religious/political groups, etc.) that compete to achieve their particular goals. We note that these simulations are not "zero sum" games - there need not be a winner and a loser. They are, however, competitive influence games: they represent the tools that a nation, state, faction or group has at its disposal to influence policy (diplomacy), finances, industry (economy), infrastructure, information, etc to achieve their particular goals. In the simulation, humans play various roles and understand that not everyone shares the same definition of a successful or favorable outcome. Rigorous post-analysis is used to illuminate where decisions were made that enabled or prevented a particular outcome from occurring. In addition, the simulations allow us to investigate how effective "technology injects" can be in achieving a particular, desired end

  10. Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β.

    Science.gov (United States)

    Roundhill, Elizabeth; Turnbull, Doug; Burchill, Susan

    2016-05-01

    Overexpression of plasma membrane multidrug resistance-associated protein 1 (MRP-1) in Ewing's sarcoma (ES) predicts poor outcome. MRP-1 is also expressed in mitochondria, and we have examined the submitochondrial localization of MRP-1 and investigated the mechanism of MRP-1 transport and role of this organelle in the response to doxorubicin. The mitochondrial localization of MRP-1 was examined in ES cell lines by differential centrifugation and membrane solubilization by digitonin. Whether MRP-1 is chaperoned by heat shock proteins (HSPs) was investigated by immunoprecipitation, immunofluorescence microscopy, and HSP knockout using small hairpin RNA and inhibitors (apoptozole, 17-AAG, and NVPAUY). The effect of disrupting mitochondrial MRP-1-dependent efflux activity on the cytotoxic effect of doxorubicin was investigated by counting viable cell number. Mitochondrial MRP-1 is glycosylated and localized to the outer mitochondrial membrane, where it is coexpressed with HSP90. MRP-1 binds to both HSP90 and HSP70, although only inhibition of HSP90β decreases expression of MRP-1 in the mitochondria. Disruption of mitochondrial MRP-1-dependent efflux significantly increases the cytotoxic effect of doxorubicin (combination index, MRP-1 is expressed in the outer mitochondrial membrane and is a client protein of HSP90β, where it may play a role in the doxorubicin-induced resistance of ES.-Roundhill, E., Turnbull, D., Burchill, S. Localization of MRP-1 to the outer mitochondrial membrane by the chaperone protein HSP90β. © FASEB.

  11. Zeolitic Imidazolate Framework-8 Membrane for H2/CO2 Separation: Experimental and Modeling

    Science.gov (United States)

    Lai, L. S.; Yeong, Y. F.; Lau, K. K.; Azmi, M. S.; Chew, T. L.

    2018-03-01

    In this work, ZIF-8 membrane synthesized through solvent evaporation secondary seeded growth was tested for single gas permeation and binary gases separation of H2 and CO2. Subsequently, a modified mathematical modeling combining the effects of membrane and support layers was applied to represent the gas transport properties of ZIF-8 membrane. Results showed that, the membrane has exhibited H2/CO2 ideal selectivity of 5.83 and separation factor of 3.28 at 100 kPa and 303 K. Besides, the experimental results were fitted well with the simulated results by demonstrating means absolute error (MAE) values ranged from 1.13 % to 3.88 % for single gas permeation and 10.81 % to 21.22 % for binary gases separation. Based on the simulated data, most of the H2 and CO2 gas molecules have transported through the molecular pores of membrane layer, which was up to 70 %. Thus, the gas transport of the gases is mainly dominated by adsorption and diffusion across the membrane.

  12. EXPERIMENTAL DESIGN AND RESPONSE SURFACE MODELING OF PI/PES-ZEOLITE 4A MIXED MATRIX MEMBRANE FOR CO2 SEPARATION

    Directory of Open Access Journals (Sweden)

    T. D. KUSWORO

    2015-09-01

    Full Text Available This paper investigates the effect of preparation of polyimide/polyethersulfone (PI/PES blending-zeolite mixed matrix membrane through the manipulation of membrane production variables such as polymer concentration, blending composition and zeolite loading. Combination of central composite design and response surface methodology were applied to determine the main effect and interaction effects of these variables on membrane separation performance. The quadratic models between each response and the independent parameters were developed and the response surface models were tested with analysis of variance (ANOVA. In this study, PI/ (PES–zeolite 4A mixed matrix membranes were casted using dry/wet phase inversion technique. The separation performance of mixed matrix membrane had been tested using pure gases such as CO2 and CH4. The results showed that zeolite loading was the most significant variable that influenced the CO2/CH4 selectivity among three variables and the experimental results were in good agreement with those predicted by the proposed regression models. The gas separation performance of the membrane was relatively higher as compare to polymeric membrane. Therefore, combination of central composite design and response surface methodology can be used to prepare optimal condition for mixed matrix membrane fabrication. The incorporation of 20 wt% zeolite 4A into 25 wt% of PI/PES matrix had resulted in a high separation performance of membrane material.

  13. Robust Optimization of Fourth Party Logistics Network Design under Disruptions

    Directory of Open Access Journals (Sweden)

    Jia Li

    2015-01-01

    Full Text Available The Fourth Party Logistics (4PL network faces disruptions of various sorts under the dynamic and complex environment. In order to explore the robustness of the network, the 4PL network design with consideration of random disruptions is studied. The purpose of the research is to construct a 4PL network that can provide satisfactory service to customers at a lower cost when disruptions strike. Based on the definition of β-robustness, a robust optimization model of 4PL network design under disruptions is established. Based on the NP-hard characteristic of the problem, the artificial fish swarm algorithm (AFSA and the genetic algorithm (GA are developed. The effectiveness of the algorithms is tested and compared by simulation examples. By comparing the optimal solutions of the 4PL network for different robustness level, it is indicated that the robust optimization model can evade the market risks effectively and save the cost in the maximum limit when it is applied to 4PL network design.

  14. [Saccharomyces boulardii modulates dendritic cell properties and intestinal microbiota disruption after antibiotic treatment].

    Science.gov (United States)

    Collignon, A; Sandré, C; Barc, M-C

    2010-09-01

    Saccharomyces boulardii is a non-pathogenic yeast with biotherapeutic properties that has been used successfully to prevent and to treat various infectious and antibiotic-associated diarrheas. The intestinal microbiota is responsible for colonization resistance and immune response to pathogens but can be disrupted by antibiotics and lose its barrier effect. Dendritic cells (DCs) are professional antigen-presenting cells of the immune system with the ability to initiate a primary immune response or immune tolerance. In a human microbiota-associated mouse model, we evaluated the influence of S. boulardii on the composition of the microbiota and on the properties of dendritic cells in normal homeostatic conditions and after antibiotic-induced stress. The DCs were derived from splenic precursors. Membrane antigen expression and phagocytosis of FITC-latex beads by DCs were evaluated by flow cytometry. The molecular analysis of the microbiota was performed with fluorescence in situ hybridization (FISH) combined with flow cytometry or confocal microscopy using group specific 16S rRNA targeted probes. This evaluation was conducted during and after a 7-day oral treatment with amoxicillin-clavulanic acid alone and in combination with the administration of the yeast. The antibiotic treatment increased the phagocytic activity of DCs. Their antigen presenting function (MHC class II antigen and CD 86 costimulatory molecule membrane expression) was up-regulated. This reflects a functional activation of DCs. In the presence of S. boulardii, the modification of membrane antigen expression was down regulated. To correlate these modifications to the microbiota disruption, we analyzed in parallel the composition of the intestinal microbiota. As previously shown, the amoxicillin-clavulanic acid treatment, both alone and with S. boulardii, did not quantitatively alter the total microbiota. In contrast, after one day of the antibiotic treatment the Clostridium coccoides group decreased

  15. Membrane Contact Sites: Complex Zones for Membrane Association and Lipid Exchange

    Science.gov (United States)

    Quon, Evan; Beh, Christopher T.

    2015-01-01

    Lipid transport between membranes within cells involves vesicle and protein carriers, but as agents of nonvesicular lipid transfer, the role of membrane contact sites has received increasing attention. As zones for lipid metabolism and exchange, various membrane contact sites mediate direct associations between different organelles. In particular, membrane contact sites linking the plasma membrane (PM) and the endoplasmic reticulum (ER) represent important regulators of lipid and ion transfer. In yeast, cortical ER is stapled to the PM through membrane-tethering proteins, which establish a direct connection between the membranes. In this review, we consider passive and facilitated models for lipid transfer at PM–ER contact sites. Besides the tethering proteins, we examine the roles of an additional repertoire of lipid and protein regulators that prime and propagate PM–ER membrane association. We conclude that instead of being simple mediators of membrane association, regulatory components of membrane contact sites have complex and multilayered functions. PMID:26949334

  16. Identification of antifungal H+-ATPase inhibitors with effect on the plasma membrane potential

    DEFF Research Database (Denmark)

    Kjellerup, Lasse; Gordon, Sandra; Cohrt, Karen O'Hanlon

    2017-01-01

    to depolarize the membrane and inhibit extracellular acidification in intact fungal cells, concomitant with a significant increase in intracellular ATP levels. Collectively, we suggest these effects may be a common feature for Pma1 inhibitors. Additionally, the work uncovered a dual mechanism for the previously......The plasma membrane H(+)-ATPase (Pma1) is an essential fungal protein and a proposed target for new antifungal medications. A small-molecule library containing ∼191,000 commercially available compounds was screened for inhibition of S. cerevisiae plasma membranes containing Pma1. The overall hit...... identified cationic peptide BM2, revealing fungal membrane disruption in addition to Pma1 inhibition. The methods presented here provide a solid platform for the evaluation of Pma1-specific inhibitors in a drug development setting. The present inhibitors could serve as a starting point for the development...

  17. Vaporization studies of plasma interactive materials in simulated plasma disruption events

    International Nuclear Information System (INIS)

    Stone, C.A. IV; Croessmann, C.D.; Whitley, J.B.

    1988-03-01

    The melting and vaporization that occur when plasma facing materials are subjected to a plasma disruption will severely limit component lifetime and plasma performance. A series of high heat flux experiments was performed on a group of fusion reactor candidate materials to model material erosion which occurs during plasma disruption events. The Electron Beam Test System was used to simulate single disruption and multiple disruption phenomena. Samples of aluminum, nickel, copper, molybdenum, and 304 stainless steel were subjected to a variety of heat loads, ranging from 100 to 400 msec pulses of 8 to 18 kWcm 2 . It was found that the initial surface temperature of a material strongly influences the vaporization process and that multiple disruptions do not scale linearly with respect to single disruption events. 2 refs., 9 figs., 5 tabs

  18. Two-Phase Contiguous Supported Lipid Bilayer Model for Membrane Rafts via Polymer Blotting and Stenciling.

    Science.gov (United States)

    Richards, Mark J; Daniel, Susan

    2017-02-07

    The supported lipid bilayer has been portrayed as a useful model of the cell membrane compatible with many biophysical tools and techniques that demonstrate its appeal in learning about the basic features of the plasma membrane. However, some of its potential has yet to be realized, particularly in the area of bilayer patterning and phase/composition heterogeneity. In this work, we generate contiguous bilayer patterns as a model system that captures the general features of membrane domains and lipid rafts. Micropatterned polymer templates of two types are investigated for generating patterned bilayer formation: polymer blotting and polymer lift-off stenciling. While these approaches have been used previously to create bilayer arrays by corralling bilayers patches with various types of boundaries impenetrable to bilayer diffusion, unique to the methods presented here, there are no physical barriers to diffusion. In this work, interfaces between contiguous lipid phases define the pattern shapes, with continuity between them allowing transfer of membrane-bound biomolecules between the phases. We examine effectors of membrane domain stability including temperature and cholesterol content to investigate domain dynamics. Contiguous patterning of supported bilayers as a model of lipid rafts expands the application of the SLB to an area with current appeal and brings with it a useful toolset for characterization and analysis. These combined tools should be helpful to researchers investigating lipid raft dynamics and function and biomolecule partitioning studies. Additionally, this patterning technique may be useful for applications such as bioseparations that exploit differences in lipid phase partitioning or creation of membranes that bind species like viruses preferentially at lipid phase boundaries, to name a few.

  19. Preliminary Study on the Removal of Steroidal Estrogens Using TiO2-Doped PVDF Ultrafiltration Membranes

    Directory of Open Access Journals (Sweden)

    Mingquan Wang

    2016-04-01

    Full Text Available Steroidal estrogens are a representative type of endocrine-disrupting chemical contaminant that has been detected in surface water. In this paper, modified polyvinylidene fluoride (PVDF membranes were prepared by adding different amounts of polyvinyl pyrrolidone (PVP and nano-TiO2 particles. PVDF-PVP membrane adsorption, UV photolysis and PVDF-PVP-TiO2 membrane photocatalysis performance were investigated by considering the rejection of estrone (E1 and 17β-estradiol (E2 in the cross-flow filtration experiments. The mechanism of photocatalytic degradation on TiO2-doped PVDF membranes was also evaluated. The results from the study indicated that adding PVP and nano-TiO2 appropriately in PVDF membranes could be an effective method for better E1and E2 rejection due to adsorption and photocatalytic degradation.

  20. Protein/lipid coaggregates are formed during α-synuclein-induced disruption of lipid bilayers

    DEFF Research Database (Denmark)

    van Maarschalkerweerd, Andreas; Vetri, Valeria; Langkilde, Annette Eva

    2014-01-01

    Amyloid formation is associated with neurodegenerative diseases such as Parkinson's disease (PD). Significant α-synuclein (αSN) deposition in lipid-rich Lewy bodies is a hallmark of PD. Nonetheless, an unraveling of the connection between neurodegeneration and amyloid fibrils, including the molec......Amyloid formation is associated with neurodegenerative diseases such as Parkinson's disease (PD). Significant α-synuclein (αSN) deposition in lipid-rich Lewy bodies is a hallmark of PD. Nonetheless, an unraveling of the connection between neurodegeneration and amyloid fibrils, including...... the molecular mechanisms behind potential amyloid-mediated toxic effects, is still missing. Interaction between amyloid aggregates and the lipid cell membrane is expected to play a key role in the disease progress. Here, we present experimental data based on hybrid analysis of two-photon-microscopy, solution...... small-angle X-ray scattering and circular dichroism data. Data show in real time changes in liposome morphology and stability upon protein addition and reveal that membrane disruption mediated by amyloidogenic αSN is associated with dehydration of anionic lipid membranes and stimulation of protein...

  1. Solubilization of human erythrocyte membranes by ASB detergents

    Directory of Open Access Journals (Sweden)

    C.C. Domingues

    2008-09-01

    Full Text Available Understanding the membrane solubilization process and finding effective solubilizing agents are crucial challenges in biochemical research. Here we report results on the interaction of the novel linear alkylamido propyl dimethyl amino propanosulfonate detergents, ASB-14 and ASB-16, with human erythrocyte membranes. An estimation of the critical micelle concentration of these zwitterionic detergents (ASB-14 = 100 µM and ASB-16 = 10 µM was obtained using electron paramagnetic resonance. The amount of proteins and cholesterol solubilized from erythrocytes by these detergents was then determined. The hemolytic activities of the ASB detergents were assayed and the detergent/lipid molar ratios for the onset of hemolysis (Re sat and total lysis (Re sol were calculated, allowing the determination of the membrane binding constants (Kb. ASB-14 presented lower membrane affinity (Kb = 7050 M-1 than ASB-16 (Kb = 15610 M-1. The amount of proteins and cholesterol solubilized by both ASB detergents was higher while Re sat values (0.22 and 0.08 detergent/lipid for ASB-14 and ASB-16, respectively were smaller than those observed with the classic detergents CHAPS and Triton X-100. These results reveal that, besides their well-known use as membrane protein solubilizers to enhance the resolution of two dimensional electrophoresis/mass spectrometry, ASB-14 and ASB-16 are strong hemolytic agents. We propose that the physicochemical properties of ASB detergents determine their membrane disruption efficiency and can help to explain the improvement in the solubilization of membrane proteins, as reported in the literature.

  2. Endocrine Disrupting Chemicals (EDCs)

    Science.gov (United States)

    ... Center Pacientes y Cuidadores Hormones and Health The Endocrine System Hormones Endocrine Disrupting Chemicals (EDCs) Steroid and Hormone ... Hormones and Health › Endocrine Disrupting Chemicals (EDCs) The Endocrine System Hormones Endocrine Disrupting Chemicals (EDCs) EDCs Myth vs. ...

  3. User's manual for DSTAR MOD1: A comprehensive tokamak disruption code

    International Nuclear Information System (INIS)

    Merrill, B.J.; Jardin, S.J.

    1986-01-01

    A computer code, DSTAR, has recently been developed to quantify the surface erosion and induced forces that can occur during major tokamak plasma disruptions. The DSTAR code development effort has been accomplished by coupling a recently developed free boundary tokamak plasma transport computational model with other models developed to predict impurity transport and radiation, and the electromagnetic and thermal dynamic response of vacuum vessel components. The combined model, DSTAR, is a unique tool for predicting the consequences of tokamak disruptions. This informal report discusses the sequence of events of a resistive disruption, models developed to predict plasma transport and electromagnetic field evolution, the growth of the stochastic region of the plasma, the transport and nonequilibrium ionization/emitted radiation of the ablated vacuum vessel material, the vacuum vessel thermal and magnetic response, and user input and code output

  4. Conformational study of melectin and antapin antimicrobial peptides in model membrane environments

    Science.gov (United States)

    Kocourková, Lucie; Novotná, Pavlína; Čujová, Sabína; Čeřovský, Václav; Urbanová, Marie; Setnička, Vladimír

    2017-01-01

    Antimicrobial peptides have long been considered as promising compounds against drug-resistant pathogens. In this work, we studied the secondary structure of antimicrobial peptides melectin and antapin using electronic (ECD) and vibrational circular dichroism (VCD) spectroscopies that are sensitive to peptide secondary structures. The results from quantitative ECD spectral evaluation by Dichroweb and CDNN program and from the qualitative evaluation of the VCD spectra were compared. The antimicrobial activity of the selected peptides depends on their ability to adopt an amphipathic α-helical conformation on the surface of the bacterial membrane. Hence, solutions of different zwitterionic and negatively charged liposomes and micelles were used to mimic the eukaryotic and bacterial biological membranes. The results show a significant content of α-helical conformation in the solutions of negatively charged liposomes mimicking the bacterial membrane, thus correlating with the antimicrobial activity of the studied peptides. On the other hand in the solutions of zwitterionic liposomes used as models of the eukaryotic membranes, the fraction of α-helical conformation was lower, which corresponds with their moderate hemolytic activity.

  5. Thyroid Hormone Disruption Effects Lamination of the Neocortex but not the Cerebellum in a Model of Developmental Hypothyroidism and Hypothyroxinemia

    Science.gov (United States)

    Introduction: Research on neurodevelopmental changes resulting from thyroid hormone (TH) disruption has important basic and clinical implications. We previously demonstrated, in a rodent model, that developmental hypothyroidism or hypothyroxinemia can cause ...

  6. Disruptive instabilities in the discharges of the TBR-1 small Tokamak

    International Nuclear Information System (INIS)

    Vannucci, A.; Nascimento, I.C.; Caldas, I.L.

    1989-01-01

    Minor and major disruptions as well as sawteeth oscillations (internal disruptions) were identified in the small Tokamak TBR-1, and their main characteristics were investigated. The coupling of a growing m=2 resistive mode with an m=1 perturbation seems to be the basic process for the development of a major disruption, while the minor disruption could be associated with the growth of a stochastic region of the plasma between the q=2 and q=3 islands. Measured sawteeth periods were compared with those predicted by scaling laws and good agreement was found. The time necessary for the sawteeth crashes also agrees with the values expected from KADOMTSEV's model. However, there are some sawteeth oscillations, corresponding to conditions of higher plasma Z eff , which showed longer crashes and could not be explained by this model. (author)

  7. Mixing characterisation of full-scale membrane bioreactors: CFD modelling with experimental validation.

    Science.gov (United States)

    Brannock, M; Wang, Y; Leslie, G

    2010-05-01

    Membrane Bioreactors (MBRs) have been successfully used in aerobic biological wastewater treatment to solve the perennial problem of effective solids-liquid separation. The optimisation of MBRs requires knowledge of the membrane fouling, biokinetics and mixing. However, research has mainly concentrated on the fouling and biokinetics (Ng and Kim, 2007). Current methods of design for a desired flow regime within MBRs are largely based on assumptions (e.g. complete mixing of tanks) and empirical techniques (e.g. specific mixing energy). However, it is difficult to predict how sludge rheology and vessel design in full-scale installations affects hydrodynamics, hence overall performance. Computational Fluid Dynamics (CFD) provides a method for prediction of how vessel features and mixing energy usage affect the hydrodynamics. In this study, a CFD model was developed which accounts for aeration, sludge rheology and geometry (i.e. bioreactor and membrane module). This MBR CFD model was then applied to two full-scale MBRs and was successfully validated against experimental results. The effect of sludge settling and rheology was found to have a minimal impact on the bulk mixing (i.e. the residence time distribution).

  8. The Relative Ineffectiveness of Criminal Network Disruption

    Science.gov (United States)

    Duijn, Paul A. C.; Kashirin, Victor; Sloot, Peter M. A.

    2014-01-01

    Researchers, policymakers and law enforcement agencies across the globe struggle to find effective strategies to control criminal networks. The effectiveness of disruption strategies is known to depend on both network topology and network resilience. However, as these criminal networks operate in secrecy, data-driven knowledge concerning the effectiveness of different criminal network disruption strategies is very limited. By combining computational modeling and social network analysis with unique criminal network intelligence data from the Dutch Police, we discovered, in contrast to common belief, that criminal networks might even become ‘stronger’, after targeted attacks. On the other hand increased efficiency within criminal networks decreases its internal security, thus offering opportunities for law enforcement agencies to target these networks more deliberately. Our results emphasize the importance of criminal network interventions at an early stage, before the network gets a chance to (re-)organize to maximum resilience. In the end disruption strategies force criminal networks to become more exposed, which causes successful network disruption to become a long-term effort. PMID:24577374

  9. A study of the isobutane dehydrogenation in a porous membrane catalytic reactor: design, use and modelling

    Energy Technology Data Exchange (ETDEWEB)

    Casanave, D

    1996-01-26

    The aim of this study was to set up and model a catalytic fixed-bed membrane reactor for the isobutane dehydrogenation. The catalyst, developed at Catalysis Research Institute (IRC), was a silicalite-supported Pt-based catalyst. Their catalytic performances (activity, selectivity, stability) where found better adapted to the membrane reactor, when compared with commercial Pt or Cr based catalysts. The kinetic study of the reaction has been performed in a differential reactor and led to the determination of a kinetic law, suitable when the catalyst is used near thermodynamic equilibrium. The mass transfer mechanisms were determined in meso-porous and microporous membranes through both permeability and gas mixtures (iC{sub 4}/H{sub 2}/N{sub 2}) separation measurements. For the meso-porous {gamma}-alumina, the mass transfer is ensured by a Knudsen diffusion mechanism which can compete with surface diffusion for condensable gas like isobutane. The resulting permselectivity H{sub 2}/iC4 of this membrane is low ({approx} 4). For the microporous zeolite membrane, molecular sieving occurs due to steric hindrance, leading to higher permselectivity {approx}14. Catalyst/membrane associations were compared in terms of isobutane dehydrogenation performances, for both types of membranes (meso-porous and microporous) and for two different reactor configurations (co-current and counter-current sweep gas flow). The best experimental results were obtained with the zeolite membrane, when sweeping the outer compartment in a co-current flow. The equilibrium displacement observed with the {gamma}-alumina membrane was lower and mainly due to a dilution effect of the reaction mixture by the sweep gas. A mathematical model was developed, which correctly describes all the experimental results obtained with the zeolite membrane, when the co-current mode is used. (Abstract Truncated)

  10. Improved cell disruption of Pichia pastoris utilizing aminopropyl magnesium phyllosilicate (AMP) clay.

    Science.gov (United States)

    Kim, Sun-Il; Wu, Yuanzheng; Kim, Ka-Lyun; Kim, Geun-Joong; Shin, Hyun-Jae

    2013-06-01

    An efficient method for Pichia cell disruption that employs an aminopropyl magnesium phyllosilicate (AMP) clay-assisted glass beads mill is presented. AMP clay is functionalized nanocomposite resembling the talc parent structure Si8Mg6O20(OH)4 that has been proven to permeate the bacterial membrane and cause cell lysis. The recombinant capsid protein of cowpea chlorotic mottle virus (CCMV) expressed in Pichia pastoris GS115 was used as demonstration system for their ability of self-assembly into icosahedral virus-like particles (VLPs). The total protein concentration reached 4.24 mg/ml after 4 min treatment by glass beads mill combined with 0.2 % AMP clay, which was 11.2 % higher compared to glass beads mill only and the time was half shortened. The stability of purified CCMV VLPs illustrated AMP clay had no influence on virus assembly process. Considering the tiny amount added and simple approach of AMP clay, it could be a reliable method for yeast cell disruption.

  11. Brief Report: Examining children’s disruptive behavior in the wake of trauma - A two-piece growth curve model before and after a school shooting

    Science.gov (United States)

    Liao, Yue; Shonkoff, Eleanor T.; Barnett, Elizabeth; Wen, CK Fred; Miller, Kimberly A.; Eddy, J. Mark

    2015-01-01

    School shootings may have serious negative impacts on children years after the event. Previous research suggests that children exposed to traumatic events experience heightened fear, anxiety, and feelings of vulnerability, but little research has examined potential aggressive and disruptive behavioral reactions. Utilizing a longitudinal dataset in which a local school shooting occurred during the course of data collection, this study sought to investigate whether the trajectory of disruptive behaviors was affected by the shooting. A two-piece growth curve model was used to examine the trajectory of disruptive behaviors during the pre-shooting years (i.e., piece one) and post-shooting years (i.e., piece two). Results indicated that the two-piece growth curve model fit the data better than the one-piece model and that the school shooting precipitated a faster decline in aggressive behaviors. This study demonstrated a novel approach to examining effects of an unexpected traumatic event on behavioral trajectories using an existing longitudinal data set. PMID:26298676

  12. Disruptions in the TFTR tokamak

    International Nuclear Information System (INIS)

    Janos, A.; Fredrickson, E.D.; McGuire, K.; Batha, S.H.; Bell, M.G.; Bitter, M.; Budny, R.; Bush, C.E.; Efthimion, P.C.; Hawryluk, R.J.; Hill, K.W.; Hosea, J.; Jobes, F.C.; Johnson, D.W.; Levinton, F.; Mansfield, D.; Meade, D.; Medley, S.S.; Monticello, D.; Mueller, D.; Nagayama, Y.; Owens, D.K.; Park, H.; Park, W.; Post, D.E.; Schivell, J.; Strachan, J.D.; Taylor, G.; Ulrickson, M.; Goeler, S. von; Wilfrid, E.; Wong, K.L.; Yamada, M.; Young, K.M.; Zarnstorff, M.C.; Zweben, S.J.; Drake, J.F.; Kleva, R.G.; Fleischmann, H.H.

    1993-03-01

    For a successful reactor, it will be useful to predict the occurrence of disruptions and to understand disruption effects including how a plasma disrupts onto the wall and how reproducibly it does so. Studies of disruptions on TFTR at both high-β pol and high-density have shown that, in both types, a fast growing m/n=1/1 mode plays an important role. In highdensity disruptions, a newly observed fast m/n = 1/1 mode occurs early in the thermal decay phase. For the first time in TFTR q-profile measurements just prior to disruptions have been made. Experimental studies of heat deposition patterns on the first wall of TFTR due to disruptions have provided information on MHD phenomena prior to or during the disruption, how the energy is released to the wall, and the reproducibility of the heat loads from disruptions. This information is important in the design of future devices such as ITER. Several new processes of runaway electron generation are theoretically suggested and their application to TFTR and ITER is considered, together with a preliminary assessment of x-ray data from runaways generated during disruptions

  13. Mathematical Modeling for the Extraction of Uranium and Molybdenum with Emulsion Liquid Membrane, Including Industrial Application and Cost Evaluation of the Uranium Recovery

    International Nuclear Information System (INIS)

    Kris Tri Basuki

    2008-01-01

    Emulsion liquid membrane systems are double emulsion drops. Two immiscible phases are separated by a third phase which is immiscible with the other two phases. The liquid membrane systems were classified into two types: (1) carrier mediated mass transfer, (2) mass transfer without any reaction involved. Uranium extraction, molybdenum extraction and solvent extraction were used as purposed elements for each type of the membrane systems in the derivation of their mathematical models. Mass transfer in emulsion liquid membrane (ELM) systems has been modeled by several differential and algebraic equations. The models take into account the following : mass transfer of the solute from the bulk external phase to the external phase-membrane interface; an equilibrium reaction between the solute and the carrier to form the solute-carrier complex at the interface; mass transfer by diffusion of the solute-carrier complex in the membrane phase to the membrane-internal phase interface; another equilibrium reaction of the solute-carrier complex to release the solute at the membrane-internal phase interface into the internal phase. Models with or without the consideration of film resistances were developed and compared. The models developed in this study can predict the extraction rate through emulsion liquid membranes theoretically. All parameters required in the models can be determined before an experimental extraction run. Experimental data from literature (uranium extraction) and (molybdenum extraction and solvent extraction) were used to test the models. The agreements between the theoretical predictions and the experimental data were very good. The advantages of emulsion liquid membrane systems over traditional methods were discussed. The models developed in this research can be used directly for the design of emulsion liquid membrane systems. The results of this study represent a very significant step toward the practical applications of the emulsion liquid membrane

  14. Disruption of Spectrin-Like Cytoskeleton in Differentiating Keratinocytes by PKCδ Activation Is Associated with Phosphorylated Adducin

    Science.gov (United States)

    Zhao, Kong-Nan; Masci, Paul P.; Lavin, Martin F.

    2011-01-01

    Spectrin is a central component of the cytoskeletal protein network in a variety of erythroid and non-erythroid cells. In keratinocytes, this protein has been shown to be pericytoplasmic and plasma membrane associated, but its characteristics and function have not been established in these cells. Here we demonstrate that spectrin increases dramatically in amount and is assembled into the cytoskeleton during differentiation in mouse and human keratinocytes. The spectrin-like cytoskeleton was predominantly organized in the granular and cornified layers of the epidermis and disrupted by actin filament inhibitors, but not by anti-mitotic drugs. When the cytoskeleton was disrupted PKCδ was activated by phosphorylation on Thr505. Specific inhibition of PKCδ(Thr505) activation with rottlerin prevented disruption of the spectrin-like cytoskeleton and the associated morphological changes that accompany differentiation. Rottlerin also inhibited specific phosphorylation of the PKCδ substrate adducin, a cytoskeletal protein. Furthermore, knock-down of endogenous adducin affected not only expression of adducin, but also spectrin and PKCδ, and severely disrupted organization of the spectrin-like cytoskeleton and cytoskeletal distribution of both adducin and PKCδ. These results demonstrate that organization of a spectrin-like cytoskeleton is associated with keratinocytes differentiation, and disruption of this cytoskeleton is mediated by either PKCδ(Thr505) phosphorylation associated with phosphorylated adducin or due to reduction of endogenous adducin, which normally connects and stabilizes the spectrin-actin complex. PMID:22163289

  15. Performances of nanofiltration and low pressure reverse osmosis membranes for desalination: characterization and modelling

    Science.gov (United States)

    Boussouga, Y. A.; Lhassani, A.

    2017-03-01

    The nanofiltration and the reverse osmosis processes are the most common techniques for the desalination of water contaminated by an excess of salts. In this present study, we were interested in the characterization of commercial, composite and asymmetric membranes of nanofiltration (NF90, NF270) and low pressure reverse osmosis (BW30LE). The two types of characterization that we opted for our study: (i) characterization of electrical proprieties, in terms of the surface charge of various membranes studied by the measurement of the streaming potential, (ii) hydrodynamic characterization in terms of hydraulic permeability with pure water, mass transfer and phenomenological parameters for each system membrane/salt using hydrodynamic approaches. The irreversible thermodynamics allowed us to model the observed retention Robs of salts (NaCl and Na2SO4) for the different membranes studied, to understand and to predict a good filtration with a membrane. A study was conducted on the type of mass transfer for each system membrane/salt: convection and diffusion. The results showed that all tested membranes are negatively charged for the solutions at neutral pH, this is explained by their material composition. The results also showed competitiveness between the different types of membranes. In view of that the NF remains effective in terms of selective retention with less energy consumption than LPRO.

  16. MOOCs as a disruptive force in online education

    Directory of Open Access Journals (Sweden)

    Dennis Viehland

    Full Text Available MOOCs - massive open online courses - have emerged as the dominant topic in online education in New Zealand and elsewhere. MOOCs have been variously described as a tsunami, a paradigm shift and a disruptive force to both place-based and online tertiary education. This paper offers a comprehensive description of MOOCs and discusses key disruptive aspects of MOOC-based education such as university/student disengagement, low completion rates, peer assessment and business models.

  17. Inflation and Instability of a Polymeric Membrane

    DEFF Research Database (Denmark)

    Hassager, Ole; Kristensen, Susanne Brogaard; Larsen, Johannes Ruben

    1999-01-01

    We consider an axisymmetric polymeric membrane inflated by a uniform pressure difference acting across the membrane. The polymeric material is described by an arbitrary combination of a viscoelastic and a purely viscous component to the stress. Some viscoelastic materials described by a Mooney......-Rivlin model show a monotone increasing pressure during inflation of a spherical membrane. These materials develop a homogeneous membrane thickness in agreement with the Considere-Pearson condition. Molecularly based models such as the neo-Hookean, Doi-Edwards or Tom-Pom model show a pressure maximum when...... inflated. Membranes described by these models develop a local thinning of the membrane which may lead to bursting in finite time. (C) 1999 Elsevier Science B.V. All rights reserved....

  18. Meso-scale Modeling of Block Copolymers Self-Assembly in Casting Solutions for Membrane Manufacture

    KAUST Repository

    Moreno Chaparro, Nicolas

    2016-05-01

    Isoporous membranes manufactured from diblock copolymer are successfully produced at laboratory scale under controlled conditions. Because of the complex phenomena involved, membrane preparation requires trial and error methodologies to find the optimal conditions, leading to a considerable demand of resources. Experimental insights demonstrate that the self-assembly of the block copolymers in solution has an effect on the final membrane structure. Nevertheless, the complete understanding of these multi-scale phenomena is elusive. Herein we use the coarse-grained method Dissipative Particle Dynamics to study the self-assembly of block copolymers that are used for the preparation of the membranes. To simulate representative time and length scales, we introduce a framework for model reduction of polymer chain representations for dissipative particle dynamics, which preserves the properties governing the phase equilibria. We reduce the number of degrees of freedom by accounting for the correlation between beads in fine-grained models via power laws and the consistent scaling of the simulation parameters. The coarse-graining models are consistent with the experimental evidence, showing a morphological transition of the aggregates as the polymer concentration and solvent affinity change. We show that hexagonal packing of the micelles can occur in solution within different windows of polymer concentration depending on the solvent affinity. However, the shape and size dispersion of the micelles determine the characteristic arrangement. We describe the order of crew-cut micelles using a rigid-sphere approximation and propose different phase parameters that characterize the emergence of monodisperse-spherical micelles in solution. Additionally, we investigate the effect of blending asymmetric diblock copolymers (AB/AC) over the properties of the membranes. We observe that the co-assembly mechanism localizes the AC molecules at the interface of A and B domains, and induces

  19. Assembly factors for the membrane arm of human complex I.

    Science.gov (United States)

    Andrews, Byron; Carroll, Joe; Ding, Shujing; Fearnley, Ian M; Walker, John E

    2013-11-19

    Mitochondrial respiratory complex I is a product of both the nuclear and mitochondrial genomes. The integration of seven subunits encoded in mitochondrial DNA into the inner membrane, their association with 14 nuclear-encoded membrane subunits, the construction of the extrinsic arm from 23 additional nuclear-encoded proteins, iron-sulfur clusters, and flavin mononucleotide cofactor require the participation of assembly factors. Some are intrinsic to the complex, whereas others participate transiently. The suppression of the expression of the NDUFA11 subunit of complex I disrupted the assembly of the complex, and subcomplexes with masses of 550 and 815 kDa accumulated. Eight of the known extrinsic assembly factors plus a hydrophobic protein, C3orf1, were associated with the subcomplexes. The characteristics of C3orf1, of another assembly factor, TMEM126B, and of NDUFA11 suggest that they all participate in constructing the membrane arm of complex I.

  20. Circadian Rhythm Disruption Promotes Lung Tumorigenesis.

    Science.gov (United States)

    Papagiannakopoulos, Thales; Bauer, Matthew R; Davidson, Shawn M; Heimann, Megan; Subbaraj, Lakshmipriya; Bhutkar, Arjun; Bartlebaugh, Jordan; Vander Heiden, Matthew G; Jacks, Tyler

    2016-08-09

    Circadian rhythms are 24-hr oscillations that control a variety of biological processes in living systems, including two hallmarks of cancer, cell division and metabolism. Circadian rhythm disruption by shift work is associated with greater risk for cancer development and poor prognosis, suggesting a putative tumor-suppressive role for circadian rhythm homeostasis. Using a genetically engineered mouse model of lung adenocarcinoma, we have characterized the effects of circadian rhythm disruption on lung tumorigenesis. We demonstrate that both physiologic perturbation (jet lag) and genetic mutation of the central circadian clock components decreased survival and promoted lung tumor growth and progression. The core circadian genes Per2 and Bmal1 were shown to have cell-autonomous tumor-suppressive roles in transformation and lung tumor progression. Loss of the central clock components led to increased c-Myc expression, enhanced proliferation, and metabolic dysregulation. Our findings demonstrate that both systemic and somatic disruption of circadian rhythms contribute to cancer progression. Copyright © 2016 Elsevier Inc. All rights reserved.