WorldWideScience

Sample records for cell contact dependency

  1. Trichomonas vaginalis Contact-Dependent Cytolysis of Epithelial Cells

    Science.gov (United States)

    Lustig, Gila; Ryan, Christopher M.; Secor, W. Evan

    2013-01-01

    Trichomonas vaginalis is an extracellular protozoan parasite that binds to the epithelium of the human urogenital tract during infection. In this study, we examined the propensities of 26 T. vaginalis strains to bind to and lyse prostate (BPH-1) and ectocervical (Ect1) epithelium and to lyse red blood cells (RBCs). We found that only three of the strains had a statistically significant preference for either BPH-1 (MSA1103) or Ect1 (LA1 and MSA1123). Overall, we observed that levels of adherence are highly variable among strains, with a 12-fold range of adherence on Ect1 cells and a 45-fold range on BPH-1 cells. Cytolysis levels displayed even greater variability, from no detectable cytolysis to 80% or 90% cytolysis of Ect1 and BPH-1, respectively. Levels of adherence and cytolysis correlate for weakly adherent/cytolytic strains, and a threshold of attachment was found to be necessary to trigger cytolysis; however, this threshold can be reached without inducing cytolysis. Furthermore, cytolysis was completely blocked when we prevented attachment of the parasites to host cells while allowing soluble factors complete access. We demonstrate that hemolysis was a rare trait, with only 4 of the 26 strains capable of lysing >20% RBCs with a 1:30 parasite/RBC ratio. Hemolysis also did not correlate with adherence to or cytolysis of either male (BPH-1)- or female (Ect1)-derived epithelial cell lines. Our results reveal that despite a broad range of pathogenic properties among different T. vaginalis strains, all strains show strict contact-dependent cytolysis. PMID:23429535

  2. Ouabain modulates cell contacts as well as functions that depend on cell adhesion.

    Science.gov (United States)

    Larre, Isabel; Contreras, Ruben G; Cereijido, Marcelino

    2011-01-01

    Ouabain, a toxic of vegetal origin used for centuries to treat heart failure, has recently been demonstrated to have an endogenous counterpart, most probably ouabain itself, which behaves as a hormone. Therefore, the challenge now is to discover the physiological role of hormone ouabain. We have recently shown that it modulates cell contacts such as gap junctions, which communicate neighboring cells, as well as tight junctions (TJs), which are one of the two differentiated features of epithelial cells, the other being apical/basolateral polarity. The importance of cell contacts can be hardly overestimated, since the most complex object in the universe, the brain, assembles itself depending on what cells contacts what other(s) how, when, and how is the molecular composition and special arrangement of the contacts involved. In the present chapter, we detail the protocols used to demonstrate the effect of ouabain on the molecular structure and functional properties of one of those cell-cell contacts: the TJ.

  3. Cell-Cell Contact Area Affects Notch Signaling and Notch-Dependent Patterning.

    Science.gov (United States)

    Shaya, Oren; Binshtok, Udi; Hersch, Micha; Rivkin, Dmitri; Weinreb, Sheila; Amir-Zilberstein, Liat; Khamaisi, Bassma; Oppenheim, Olya; Desai, Ravi A; Goodyear, Richard J; Richardson, Guy P; Chen, Christopher S; Sprinzak, David

    2017-03-13

    During development, cells undergo dramatic changes in their morphology. By affecting contact geometry, these morphological changes could influence cellular communication. However, it has remained unclear whether and how signaling depends on contact geometry. This question is particularly relevant for Notch signaling, which coordinates neighboring cell fates through direct cell-cell signaling. Using micropatterning with a receptor trans-endocytosis assay, we show that signaling between pairs of cells correlates with their contact area. This relationship extends across contact diameters ranging from micrometers to tens of micrometers. Mathematical modeling predicts that dependence of signaling on contact area can bias cellular differentiation in Notch-mediated lateral inhibition processes, such that smaller cells are more likely to differentiate into signal-producing cells. Consistent with this prediction, analysis of developing chick inner ear revealed that ligand-producing hair cell precursors have smaller apical footprints than non-hair cells. Together, these results highlight the influence of cell morphology on fate determination processes. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. A role for adhesion molecules in contact-dependent T help for B cells

    DEFF Research Database (Denmark)

    Owens, T

    1991-01-01

    The role of cell contact in T-dependent B cell activation was examined. Small resting B cells from C57BL/6 mice were cultured with CBA-derived, non-alloreactive cloned T helper cells in anti-T cell receptor V beta 8-coated microwells. This induced polyclonal B cell activation to enter cell cycle...... that continued cell contact involving adhesion/accessory molecules induces B cells to proliferate and to respond to T cell lymphokines. A signaling role for cell interaction molecules on B cells is proposed, similar to the role of these and analogous molecules on T cells....

  5. Strong adhesion by regulatory T cells induces dendritic cell cytoskeletal polarization and contact-dependent lethargy.

    Science.gov (United States)

    Chen, Jiahuan; Ganguly, Anutosh; Mucsi, Ashley D; Meng, Junchen; Yan, Jiacong; Detampel, Pascal; Munro, Fay; Zhang, Zongde; Wu, Mei; Hari, Aswin; Stenner, Melanie D; Zheng, Wencheng; Kubes, Paul; Xia, Tie; Amrein, Matthias W; Qi, Hai; Shi, Yan

    2017-02-01

    Dendritic cells are targeted by regulatory T (T reg) cells, in a manner that operates as an indirect mode of T cell suppression. In this study, using a combination of single-cell force spectroscopy and structured illumination microscopy, we analyze individual T reg cell-DC interaction events and show that T reg cells exhibit strong intrinsic adhesiveness to DCs. This increased DC adhesion reduces the ability of contacted DCs to engage other antigen-specific cells. We show that this unusually strong LFA-1-dependent adhesiveness of T reg cells is caused in part by their low calpain activities, which normally release integrin-cytoskeleton linkage, and thereby reduce adhesion. Super resolution imaging reveals that such T reg cell adhesion causes sequestration of Fascin-1, an actin-bundling protein essential for immunological synapse formation, and skews Fascin-1-dependent actin polarization in DCs toward the T reg cell adhesion zone. Although it is reversible upon T reg cell disengagement, this sequestration of essential cytoskeletal components causes a lethargic state of DCs, leading to reduced T cell priming. Our results reveal a dynamic cytoskeletal component underlying T reg cell-mediated DC suppression in a contact-dependent manner. © 2017 Chen et al.

  6. Cell-contact-dependent activation of CD4+ T cells by adhesion molecules on synovial fibroblasts.

    Science.gov (United States)

    Mori, Masato; Hashimoto, Motomu; Matsuo, Takashi; Fujii, Takao; Furu, Moritoshi; Ito, Hiromu; Yoshitomi, Hiroyuki; Hirose, Jun; Ito, Yoshinaga; Akizuki, Shuji; Nakashima, Ran; Imura, Yoshitaka; Yukawa, Naoichiro; Yoshifuji, Hajime; Ohmura, Koichiro; Mimori, Tsuneyo

    2017-05-01

    To determine how cell-cell contact with synovial fibroblasts (SF) influence on the proliferation and cytokine production of CD4 +  T cells. Naïve CD4 +  T cells were cultured with SF from rheumatoid arthritis patients, stimulated by anti-CD3/28 antibody, and CD4 +  T cell proliferation and IFN-γ/IL-17 production were analyzed. To study the role of adhesion molecules, cell contact was blocked by transwell plate or anti-intracellular adhesion molecule-1 (ICAM-1)/vascular cell adhesion molecule-1(VCAM-1) antibody. To study the direct role of adhesion molecules for CD4 +  T cells, CD161 +  or CD161 - naïve CD4 +  T cells were stimulated on plastic plates coated by recombinant ICAM-1 or VCAM-1, and the source of IFN-γ/IL-17 were analyzed. SF enhanced naïve CD4 +  T cell proliferation and IFN-γ/IL-17 production in cell-contact and in part ICAM-1-/VCAM-1-dependent manner. Plate-coated ICAM-1 and VCAM-1 enhanced naïve CD4 +  T cell proliferation and IFN-γ production, while VCAM-1 efficiently promoting IL-17 production. CD161 +  naïve T cells upregulating LFA-1 and VLA-4 were the major source of IFN-γ/IL-17 upon interaction with ICAM-1/VCAM-1. CD4 +  T cells rapidly expand and secrete IFN-γ/IL-17 upon cell-contact with SF via adhesion molecules. Interfering with ICAM-1-/VCAM-1 may be beneficial for inhibiting RA synovitis.

  7. IL-1β-Dependent Activation of Dendritic Epidermal T Cells in Contact Hypersensitivity

    DEFF Research Database (Denmark)

    Nielsen, Morten M; Lovato, Paola; Macleod, Amanda S

    2014-01-01

    Substances that penetrate the skin surface can act as allergens and induce a T cell-mediated inflammatory skin disease called contact hypersensitivity (CHS). IL-17 is a key cytokine in CHS and was originally thought to be produced solely by CD4(+) T cells. However, it is now known that several cell...

  8. Microtubule and Cell Contact Dependency of ER-bound PTP1B Localization in Growth Cones

    Science.gov (United States)

    Fuentes, Federico

    2009-01-01

    PTP1B is an ER-bound protein tyrosine phosphatase implied in the regulation of cell adhesion. Here we investigated mechanisms involved in the positioning and dynamics of PTP1B in axonal growth cones and evaluated the role of this enzyme in axons. In growth cones, PTP1B consistently localizes in the central domain, and occasionally at the peripheral region and filopodia. Live imaging of GFP-PTP1B reveals dynamic excursions of fingerlike processes within the peripheral region and filopodia. PTP1B and GFP-PTP1B colocalize with ER markers and coalign with microtubules at the peripheral region and redistribute to the base of the growth cone after treatment with nocodazole, a condition that is reversible. Growth cone contact with cellular targets is accompanied by invasion of PTP1B and stable microtubules in the peripheral region aligned with the contact axis. Functional impairment of PTP1B causes retardation of axon elongation, as well as reduction of growth cone filopodia lifetime and Src activity. Our results highlight the role of microtubules and cell contacts in the positioning of ER-bound PTP1B to the peripheral region of growth cones, which may be required for the positive role of PTP1B in axon elongation, filopodia stabilization, and Src activity. PMID:19158394

  9. HAb18G/CD147 cell-cell contacts confer resistance of a HEK293 subpopulation to anoikis in an E-cadherin-dependent manner

    Directory of Open Access Journals (Sweden)

    Zhu Ping

    2010-04-01

    Full Text Available Abstract Background Acquisition of resistance to "anoikis" facilitates the survival of cells under independent matrix-deficient conditions, such as cells in tumor progression and the production of suspension culture cells for biomedical engineering. There is evidence suggesting that CD147, an adhesion molecule associated with survival of cells in tumor metastasis and cell-cell contacts, plays an important role in resistance to anoikis. However, information regarding the functions of CD147 in mediating cell-cell contacts and anoikis-resistance remains limited and even self-contradictory. Results An anoikis-resistant clone (HEK293ar, derived from anoikis-sensitive parental Human Embryonic Kidney 293 cells, survived anoikis by the formation of cell-cell contacts. The expression of HAb18G/CD147 (a member of the CD147 family was upregulated and the protein was located at cell-cell junctions. Upregulation of HAb18G/CD147 in suspended HEK293ar cells suppressed anoikis by mediating the formation of cell-cell adhesions. Anoikis resistance in HEK293ar cells also required E-cadherin-mediated cell-cell contacts. Knock-down of HAb18G/CD147 and E-cadherin inhibited cell-cell contacts formation and increased anoikis sensitivity respectively. When HAb18G/CD147 was downregulated, E-cadherin expression in HEK293ar cells was significantly suppressed; however, knockdown of E-cadherin by E-cadherin siRNA or blocking of E-cadherin binding activity with a specific antibody and EDTA had no significant effect on HAb18G/CD147 expression. Finally, pretreatment with LY294002, a phosphoinositide 3-kinase (PI3K/AKT inhibitor, disrupted cell-cell contacts and decreased cell number, but this was not the case in cells treated with the extracellular signal-regulated kinase (ERK inhibitor PD98059. Conclusions Our results provide new evidence that HAb18G/CD147-mediated cell-cell contact confers anoikis resistance in an E-cadherin-dependent manner; and cell-cell contact mediated

  10. Dendritic cells' death induced by contact sensitizers is controlled by Nrf2 and depends on glutathione levels

    Energy Technology Data Exchange (ETDEWEB)

    El Ali, Zeina [UMR996 - Inflammation, Chemokines and Immunopathology-, INSERM, Univ Paris-Sud, Université Paris-Saclay, 92296 Châtenay-Malabry (France); Deloménie, Claudine [IFR141 IPSIT, Univ Paris-Sud, Université Paris-Saclay, Châtenay-Malabry (France); Botton, Jérémie [INSERM, UMR1153 Epidemiology and Biostatistics Sorbonne Paris Cité Center (CRESS), Team (France); Pallardy, Marc [UMR996 - Inflammation, Chemokines and Immunopathology-, INSERM, Univ Paris-Sud, Université Paris-Saclay, 92296 Châtenay-Malabry (France); Kerdine-Römer, Saadia, E-mail: saadia.kerdine-romer@u-psud.fr [UMR996 - Inflammation, Chemokines and Immunopathology-, INSERM, Univ Paris-Sud, Université Paris-Saclay, 92296 Châtenay-Malabry (France)

    2017-05-01

    Dendritic cells (DC) are known to play a major role during contact allergy induced by contact sensitizers (CS). Our previous studies showed that Nrf2 was induced in DC and controlled allergic skin inflammation in mice in response to chemicals. In this work, we raised the question of the role of Nrf2 in response to a stress provoked by chemical sensitizers in DC. We used two well-described chemical sensitizers, dinitrochlorobenzene (DNCB) and cinnamaldehyde (CinA), known to have different chemical reactivity and mechanism of action. First, we performed a RT-qPCR array showing that CinA was a higher inducer of immune and detoxification genes compared to DNCB. Interestingly, in the absence of Nrf2, gene expression was dramatically affected in response to DNCB but was slightly affected in response to CinA. These observations prompted us to study DC's cell death in response to both chemicals. DNCB and CinA increased apoptotic cells and decreased living cells in the absence of Nrf2. The characterization of DC apoptosis induced by both CS involved the mitochondrial-dependent caspase pathway and was regulated via Nrf2 in response to both chemicals. Oxidative stress induced by DNCB, and leading to cell death, was regulated by Nrf2. Unlike CinA, DNCB treatment provoked a significant reduction of intracellular GSH levels and up-regulated bcl-2 gene expression, under the control of Nrf2. This work underlies that chemical reactivity may control Nrf2-dependent gene expression leading to different cytoprotective mechanisms in DC. - Highlights: • Nrf2 controls cell death induced by contact sensitizers in dendritic cells. • DNCB reduced GSH levels and up-regulated bcl-2 gene expression unlike CinA. • Chemical reactivity controls Nrf2-dependent genes having protective effect in DC.

  11. The cytokine-dependent MUTZ-3 cell line as an in vitro model for the screening of contact sensitizers

    International Nuclear Information System (INIS)

    Azam, Philippe; Peiffer, Jean-Luc; Chamousset, Delphine; Tissier, Marie-Helene; Bonnet, Pierre-Antoine; Vian, Laurence; Fabre, Isabelle; Ourlin, Jean-Claude

    2006-01-01

    Langerhans cells (LC) are key mediators of contact allergenicity in the skin. However, no in vitro methods exist which are based on the activation process of LC to predict the sensitization potential of chemicals. In this study, we have evaluated the performances of MUTZ-3, a cytokine-dependent human monocytic cell line, in its response to sensitizers. First, we compared undifferentiated MUTZ-3 cells with several standard human cells such as THP-1, KG-1, HL-60, K-562, and U-937 in their response to the strong sensitizer DNCB and the irritant SDS by monitoring the expression levels of HLA-DR, CD54, and CD86 by flow cytometry. Only MUTZ-3 and THP-1 cells show a strong and specific response to sensitizer, while other cell lines showed very variable responses. Then, we tested MUTZ-3 cells against a wider panel of sensitizers and irritants on a broader spectrum of cell surface markers (HLA-DR, CD40, CD54, CD80, CD86, B7-H1, B7-H2, B7-DC). Of these markers, CD86 proved to be the most reliable since it detected all sensitizers, including benzocaine, a classical false negative in local lymph node assay (LLNA) but not irritants. We confirmed the MUTZ-3 response to DNCB by real-time PCR analysis. Taken together, our data suggest that undifferentiated MUTZ-3 cells may represent a valuable in vitro model for the screening of potential sensitizers

  12. Regulatory function of a novel population of mouse autoantigen-specific Foxp3 regulatory T cells depends on IFN-gamma, NO, and contact with target cells.

    Directory of Open Access Journals (Sweden)

    Cyndi Chen

    Full Text Available BACKGROUND: Both naturally arising Foxp3(+ and antigen-induced Foxp3(- regulatory T cells (Treg play a critical role in regulating immune responses, as well as in preventing autoimmune diseases and graft rejection. It is known that antigen-specific Treg are more potent than polyclonal Treg in suppressing pathogenic immune responses that cause autoimmunity and inflammation. However, difficulty in identifying and isolating a sufficient number of antigen-specific Treg has limited their use in research to elucidate the mechanisms underlying their regulatory function and their potential role in therapy. METHODOLOGY/PRINCIPAL FINDINGS: Using a novel class II MHC tetramer, we have isolated a population of CD4(+ Foxp3(- T cells specific for the autoantigen glutamic acid decarboxylase p286-300 peptide (NR286 T cells from diabetes-resistant non-obese resistant (NOR mice. These Foxp3(- NR286 T cells functioned as Treg that were able to suppress target T cell proliferation in vitro and inhibit type 1 diabetes in animals. Unexpected results from mechanistic studies in vitro showed that their regulatory function was dependent on not only IFN-gamma and nitric oxide, but also on cell contact with target cells. In addition, separating NR286 Treg from target T cells in transwell assays abolished both production of NO and suppression of target T cells, regardless of whether IFN-gamma was produced in cell cultures. Therefore, production of NO, not IFN-gamma, was cell contact dependent, suggesting that NO may function downstream of IFN-gamma in mediating regulatory function of NR286 Treg. CONCLUSIONS/SIGNIFICANCE: These studies identified a unique population of autoantigen-specific Foxp3(- Treg that can exert their regulatory function dependent on not only IFN-gamma and NO but also cell contact with target cells.

  13. NKG2D-Dependent Activation of Dendritic Epidermal T cells in Contact Hypersensitivity

    DEFF Research Database (Denmark)

    Nielsen, Morten Milek; Dyring-Andersen, Beatrice; Schmidt, Jonas Damgård

    2015-01-01

    activated and produce IL-17 in an IL-1β-dependent manner during CHS. Various receptors on DETC, including NKG2D, are involved in DETC responses against tumors and during wound healing. The ligands for NKG2D (NKG2DL) are stress-induced proteins such as Mult-1, H60, Rae-1 in mice and MICA, MICB and ULBP...... in humans. Here, we show that allergens up-regulate expression of the NKG2DL Mult-1, H60 and Rae-1 in cultured mouse KC and of MICA in primary human KC. We demonstrate that Mult-1 is expressed in mouse skin exposed to allergen. Furthermore, we find that the vast majority of DETC in murine epidermis and skin...

  14. A tissue adaptation model based on strain-dependent collagen degradation and contact-guided cell traction.

    Science.gov (United States)

    Heck, T A M; Wilson, W; Foolen, J; Cilingir, A C; Ito, K; van Donkelaar, C C

    2015-03-18

    Soft biological tissues adapt their collagen network to the mechanical environment. Collagen remodeling and cell traction are both involved in this process. The present study presents a collagen adaptation model which includes strain-dependent collagen degradation and contact-guided cell traction. Cell traction is determined by the prevailing collagen structure and is assumed to strive for tensional homeostasis. In addition, collagen is assumed to mechanically fail if it is over-strained. Care is taken to use principally measurable and physiologically meaningful relationships. This model is implemented in a fibril-reinforced biphasic finite element model for soft hydrated tissues. The versatility and limitations of the model are demonstrated by corroborating the predicted transient and equilibrium collagen adaptation under distinct mechanical constraints against experimental observations from the literature. These experiments include overloading of pericardium explants until failure, static uniaxial and biaxial loading of cell-seeded gels in vitro and shortening of periosteum explants. In addition, remodeling under hypothetical conditions is explored to demonstrate how collagen might adapt to small differences in constraints. Typical aspects of all essentially different experimental conditions are captured quantitatively or qualitatively. Differences between predictions and experiments as well as new insights that emerge from the present simulations are discussed. This model is anticipated to evolve into a mechanistic description of collagen adaptation, which may assist in developing load-regimes for functional tissue engineered constructs, or may be employed to improve our understanding of the mechanisms behind physiological and pathological collagen remodeling. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. Dengue Virus-Infected Dendritic Cells, but Not Monocytes, Activate Natural Killer Cells through a Contact-Dependent Mechanism Involving Adhesion Molecules.

    Science.gov (United States)

    Costa, Vivian Vasconcelos; Ye, Weijian; Chen, Qingfeng; Teixeira, Mauro Martins; Preiser, Peter; Ooi, Eng Eong; Chen, Jianzhu

    2017-08-01

    Natural killer (NK) cells play a protective role against dengue virus (DENV) infection, but the cellular and molecular mechanisms are not fully understood. Using an optimized humanized mouse model, we show that human NK cells, through the secretion of gamma interferon (IFN-γ), are critical in the early defense against DENV infection. Depletion of NK cells or neutralization of IFN-γ leads to increased viremia and more severe thrombocytopenia and liver damage in humanized mice. In vitro studies using autologous human NK cells show that DENV-infected monocyte-derived dendritic cells (MDDCs), but not monocytes, activate NK cells in a contact-dependent manner, resulting in upregulation of CD69 and CD25 and secretion of IFN-γ. Blocking adhesion molecules (LFA-1, DNAM-1, CD2, and 2β4) on NK cells abolishes NK cell activation, IFN-γ secretion, and the control of DENV replication. NK cells activated by infected MDDCs also inhibit DENV infection in monocytes. These findings show the essential role of human NK cells in protection against acute DENV infection in vivo , identify adhesion molecules and dendritic cells required for NK cell activation, and delineate the sequence of events for NK cell activation and protection against DENV infection. IMPORTANCE Dengue is a mosquito-transmitted viral disease with a range of symptoms, from mild fever to life-threatening dengue hemorrhagic fever. The diverse disease manifestation is thought to result from a complex interplay between viral and host factors. Using mice engrafted with a human immune system, we show that human NK cells inhibit virus infection through secretion of the cytokine gamma interferon and reduce disease pathogenesis, including depletion of platelets and liver damage. During a natural infection, DENV initially infects dendritic cells in the skin. We find that NK cells interact with infected dendritic cells through physical contact mediated by adhesion molecules and become activated before they can control

  16. Geometry-Dependent Electrostatics near Contact Lines

    International Nuclear Information System (INIS)

    Chou, Tom

    2001-01-01

    Long-ranged electrostatic interactions in electrolytes modify contact angles on charged substrates in a scale and geometry-dependent manner. For angles measured at scales smaller than the typical Debye screening length, the wetting geometry near the contact line must be explicitly considered. Using variational and asymptotic methods, we derive new transcendental equations for the contact angle as functions of the electrostatic potential only at the three phase contact line. Analytic expressions are found in certain limits and compared with predictions for contact angles measured with lower resolution. An estimate for electrostatic contributions to line tension is also given

  17. Bone marrow-derived mesenchymal stem cells propagate immunosuppressive/anti-inflammatory macrophages in cell-to-cell contact-independent and -dependent manners under hypoxic culture.

    Science.gov (United States)

    Takizawa, Naoki; Okubo, Naoto; Kamo, Masaharu; Chosa, Naoyuki; Mikami, Toshinari; Suzuki, Keita; Yokota, Seiji; Ibi, Miho; Ohtsuka, Masato; Taira, Masayuki; Yaegashi, Takashi; Ishisaki, Akira; Kyakumoto, Seiko

    2017-09-15

    Immunosuppressive/anti-inflammatory macrophage (Mφ), M2-Mφ that expressed the typical M2-Mφs marker, CD206, and anti-inflammatory cytokine, interleukin (IL)-10, is beneficial and expected tool for the cytotherapy against inflammatory diseases. Here, we demonstrated that bone marrow-derived lineage-positive (Lin+) blood cells proliferated and differentiated into M2-Mφs by cooperation with the bone marrow-derived mesenchymal stem cells (MSCs) under hypoxic condition: MSCs not only promoted proliferation of undifferentiated M2-Mφs, pre-M2-Mφs, in the Lin+ fraction via a proliferative effect of the MSCs-secreted macrophage colony-stimulating factor, but also promoted M2-Mφ polarization of the pre-M2-Mφs through cell-to-cell contact with the pre-M2-Mφs. Intriguingly, an inhibitor for intercellular adhesion molecule (ICAM)-1 receptor/lymphocyte function-associated antigen (LFA)-1, Rwj50271, partially suppressed expression of CD206 in the Lin+ blood cells but an inhibitor for VCAM-1 receptor/VLA-4, BIO5192, did not, suggesting that the cell-to-cell adhesion through LFA-1 on pre-M2-Mφs and ICAM-1 on MSCs was supposed to promoted the M2-Mφ polarization. Thus, the co-culture system consisting of bone marrow-derived Lin+ blood cells and MSCs under hypoxic condition was a beneficial supplier of a number of M2-Mφs, which could be clinically applicable to inflammatory diseases. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. Contact-dependent cytopathogenic mechanisms of Trichomonas vaginalis

    Energy Technology Data Exchange (ETDEWEB)

    Krieger, J.N.; Ravdin, J.I.; Rein, M.F.

    1985-12-01

    The cytopathogenic mechanisms of Trichomonas vaginalis have been debated since the 1940s. We examined the following three proposed pathogenic mechanisms: contact-dependent extracellular killing, cytophagocytosis, and extracellular cytotoxins. Serial observations of Chinese hamster ovary (CHO) cell monolayers exposed to trichomonads revealed that (i) trichomonads form clumps, (ii) the clumps adhere to cells in culture, and (iii) monolayer destruction occurs only in areas of contact with T. vaginalis. Kinetic analysis of target cell killing by trichomonads revealed that the probability of CHO cell death was related to the probability of contact with T. vaginalis, supporting the observation by microscopy that trichomonads kill cells only by direct contact. Simultaneous studies of /sup 111/indium oxine label release from CHO cells and trypan blue dye exclusion demonstrated that T. vaginalis kills target cells without phagocytosis. Filtrates of trichomonad cultures or from media in which trichomonads were killing CHO cells had no effect on CHO cell monolayers, indicating that trichomonads do not kill cells by a cell-free or secreted cytotoxin. The microfilament inhibitor cytochalasin D (10 micrograms/ml) inhibited trichomonad killing of CHO cell monolayers by 80% (P less than 0.0001). In contrast, the microtubule inhibitor vinblastine (10(-6) M) caused only 17% inhibition of trichomonad destruction of CHO cell monolayers (P less than 0.020), whereas colchicine (10(-6) M) had no effect. T. vaginalis kills target cells by direct contact without phagocytosis. This event requires intact trichomonad microfilament function; microtubule function appears not to be essential.

  19. Contact-dependent cytopathogenic mechanisms of Trichomonas vaginalis

    International Nuclear Information System (INIS)

    Krieger, J.N.; Ravdin, J.I.; Rein, M.F.

    1985-01-01

    The cytopathogenic mechanisms of Trichomonas vaginalis have been debated since the 1940s. We examined the following three proposed pathogenic mechanisms: contact-dependent extracellular killing, cytophagocytosis, and extracellular cytotoxins. Serial observations of Chinese hamster ovary (CHO) cell monolayers exposed to trichomonads revealed that (i) trichomonads form clumps, (ii) the clumps adhere to cells in culture, and (iii) monolayer destruction occurs only in areas of contact with T. vaginalis. Kinetic analysis of target cell killing by trichomonads revealed that the probability of CHO cell death was related to the probability of contact with T. vaginalis, supporting the observation by microscopy that trichomonads kill cells only by direct contact. Simultaneous studies of 111 indium oxine label release from CHO cells and trypan blue dye exclusion demonstrated that T. vaginalis kills target cells without phagocytosis. Filtrates of trichomonad cultures or from media in which trichomonads were killing CHO cells had no effect on CHO cell monolayers, indicating that trichomonads do not kill cells by a cell-free or secreted cytotoxin. The microfilament inhibitor cytochalasin D (10 micrograms/ml) inhibited trichomonad killing of CHO cell monolayers by 80% (P less than 0.0001). In contrast, the microtubule inhibitor vinblastine (10(-6) M) caused only 17% inhibition of trichomonad destruction of CHO cell monolayers (P less than 0.020), whereas colchicine (10(-6) M) had no effect. T. vaginalis kills target cells by direct contact without phagocytosis. This event requires intact trichomonad microfilament function; microtubule function appears not to be essential

  20. Solar cell with back side contacts

    Science.gov (United States)

    Nielson, Gregory N; Okandan, Murat; Cruz-Campa, Jose Luis; Resnick, Paul J; Wanlass, Mark Woodbury; Clews, Peggy J

    2013-12-24

    A III-V solar cell is described herein that includes all back side contacts. Additionally, the positive and negative electrical contacts contact compoud semiconductor layers of the solar cell other than the absorbing layer of the solar cell. That is, the positive and negative electrical contacts contact passivating layers of the solar cell.

  1. Measuring The Contact Resistances Of Photovoltaic Cells

    Science.gov (United States)

    Burger, D. R.

    1985-01-01

    Simple method devised to measure contact resistances of photovoltaic solar cells. Method uses readily available equipment and applicable at any time during life of cell. Enables evaluation of cell contact resistance, contact-end resistance, contact resistivity, sheet resistivity, and sheet resistivity under contact.

  2. Suppression of IL-10 production by activated B cells via a cell contact-dependent cyclooxygenase-2 pathway upregulated in IFN-γ-treated mesenchymal stem cells

    Czech Academy of Sciences Publication Activity Database

    Heřmánková, Barbora; Zajícová, Alena; Javorková, Eliška; Chudíčková, Milada; Trošan, Peter; Hájková, Michaela; Krulová, Magdaléna; Holáň, Vladimír

    2016-01-01

    Roč. 221, č. 2 (2016), s. 129-136 ISSN 0171-2985 R&D Projects: GA MŠk(CZ) LO1309; GA ČR(CZ) GA14-12580S; GA MZd NT14102; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:68378041 Keywords : B cells * Cyclooxygenase-2 * IL-10 production * Mesenchymal stem cells * Cyclooxygenase-2 * Immunosuppression Subject RIV: FF - HEENT, Dentistry Impact factor: 2.720, year: 2016

  3. Hybrid emitter all back contact solar cell

    Science.gov (United States)

    Loscutoff, Paul; Rim, Seung

    2016-04-12

    An all back contact solar cell has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. The other emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The solar cell includes contact holes that allow metal contacts to connect to corresponding emitters.

  4. Bias dependent specic contact resistance of phase change material to metal contacts

    NARCIS (Netherlands)

    Roy, Deepu; in 't Zandt, Micha; Wolters, Robertus A.M.

    2010-01-01

    Knowledge of contact resistance of phase change materials (PCM) to metal electrodes is important for scaling, device modeling and optimization of phase change random access memory (PCRAM) cells. In this article, we report the systematic determination of the speci_c contact resistance (_c) with

  5. Transparent contacts for stacked compound photovoltaic cells

    Science.gov (United States)

    Tauke-Pedretti, Anna; Cederberg, Jeffrey; Nielson, Gregory N.; Okandan, Murat; Cruz-Campa, Jose Luis

    2016-11-29

    A microsystems-enabled multi-junction photovoltaic (MEM-PV) cell includes a first photovoltaic cell having a first junction, the first photovoltaic cell including a first semiconductor material employed to form the first junction, the first semiconductor material having a first bandgap. The MEM-PV cell also includes a second photovoltaic cell comprising a second junction. The second photovoltaic cell comprises a second semiconductor material employed to form the second junction, the second semiconductor material having a second bandgap that is less than the first bandgap, the second photovoltaic cell further comprising a first contact layer disposed between the first junction of the first photovoltaic cell and the second junction of the second photovoltaic cell, the first contact layer composed of a third semiconductor material having a third bandgap, the third bandgap being greater than or equal to the first bandgap.

  6. Biofuel cells based on direct enzyme-electrode contacts using PQQ-dependent glucose dehydrogenase/bilirubin oxidase and modified carbon nanotube materials.

    Science.gov (United States)

    Scherbahn, V; Putze, M T; Dietzel, B; Heinlein, T; Schneider, J J; Lisdat, F

    2014-11-15

    Two types of carbon nanotube electrodes (1) buckypaper (BP) and (2) vertically aligned carbon nanotubes (vaCNT) have been used for elaboration of glucose/O2 enzymatic fuel cells exploiting direct electron transfer. For the anode pyrroloquinoline quinone dependent glucose dehydrogenase ((PQQ)GDH) has been immobilized on [poly(3-aminobenzoic acid-co-2-methoxyaniline-5-sulfonic acid), PABMSA]-modified electrodes. For the cathode bilirubin oxidase (BOD) has been immobilized on PQQ-modified electrodes. PABMSA and PQQ act as promoter for enzyme bioelectrocatalysis. The voltammetric characterization of each electrode shows current densities in the range of 0.7-1.3 mA/cm(2). The BP-based fuel cell exhibits maximal power density of about 107 µW/cm(2) (at 490 mV). The vaCNT-based fuel cell achieves a maximal power density of 122 µW/cm(2) (at 540 mV). Even after three days and several runs of load a power density over 110 µW/cm(2) is retained with the second system (10mM glucose). Due to a better power exhibition and an enhanced stability of the vaCNT-based fuel cells they have been studied in human serum samples and a maximal power density of 41 µW/cm(2) (390 mV) can be achieved. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Temperature dependence of contact resistance at metal/MWNT interface

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Eui; Moon, Kyoung-Seok; Sohn, Yoonchul, E-mail: yoonchul.son@samsung.com [Materials Research Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon 443-803 (Korea, Republic of)

    2016-07-11

    Although contact resistance of carbon nanotube (CNT) is one of the most important factors for practical application of electronic devices, a study regarding temperature dependence on contact resistance of CNTs with metal electrodes has not been found. Here, we report an investigation of contact resistance at multiwalled nanotube (MWNT)/Ag interface as a function of temperature, using MWNT/polydimethylsiloxane (PDMS) composite. Electrical resistance of MWNT/PDMS composite revealed negative temperature coefficient (NTC). Excluding the contact resistance with Ag electrode, the NTC effect became less pronounced, showing lower intrinsic resistivity with the activation energy of 0.019 eV. Activation energy of the contact resistance of MWNT/Ag interface was determined to be 0.04 eV, two times larger than that of MWNT-MWNT network. The increase in the thermal fluctuation assisted electron tunneling is attributed to conductivity enhancement at both MWNT/MWNT and MWNT/Ag interfaces with increasing temperature.

  8. Dynamic contact with Signorini's condition and slip rate dependent friction

    Directory of Open Access Journals (Sweden)

    Kenneth Kuttler

    2004-06-01

    Full Text Available Existence of a weak solution for the problem of dynamic frictional contact between a viscoelastic body and a rigid foundation is established. Contact is modelled with the Signorini condition. Friction is described by a slip rate dependent friction coefficient and a nonlocal and regularized contact stress. The existence in the case of a friction coefficient that is a graph, which describes the jump from static to dynamic friction, is established, too. The proofs employ the theory of set-valued pseudomonotone operators applied to approximate problems and a priori estimates.

  9. Universal entrainment mechanism controls contact times with motile cells

    Science.gov (United States)

    Mathijssen, Arnold J. T. M.; Jeanneret, Raphaël; Polin, Marco

    2018-03-01

    Contact between particles and motile cells underpins a wide variety of biological processes, from nutrient capture and ligand binding to grazing, viral infection, and cell-cell communication. The window of opportunity for these interactions depends on the basic mechanism determining contact time, which is currently unknown. By combining experiments on three different species—Chlamydomonas reinhardtii, Tetraselmis subcordiforms, and Oxyrrhis marina—with simulations and analytical modeling, we show that the fundamental physical process regulating proximity to a swimming microorganism is hydrodynamic particle entrainment. The resulting distribution of contact times is derived within the framework of Taylor dispersion as a competition between advection by the cell surface and microparticle diffusion, and predicts the existence of an optimal tracer size that is also observed experimentally. Spatial organization of flagella, swimming speed, and swimmer and tracer size influence entrainment features and provide tradeoffs that may be tuned to optimize the estimated probabilities for microbial interactions like predation and infection.

  10. A Germanium Back Contact Type Thermophotovoltaic Cell

    International Nuclear Information System (INIS)

    Nagashima, Tomonori; Okumura, Kenichi; Yamaguchi, Masafumi

    2007-01-01

    A Ge back contact type photovoltaic cell has been proposed to reduce resistance loss for high current densities in thermophotovoltaic systems. The back contact structure requires less surface recombination velocities than conventional structures with front grid contacts. A SiO2/SiNx double anti-reflection coating including a high refractive index SiNx layer was studied. The SiNx layer has an enough passivation effect to obtain high efficiency. The quantum efficiency of the Ge cell was around 0.8 in the 800-1600 nm wavelength range. The conversion efficiency for infrared lights was estimated at 18% for a blackbody surface and 25% for a selective emitter by using the quantum efficiency and a simulation analysis

  11. Contact enhancement of locomotion in spreading cell colonies

    Science.gov (United States)

    D'Alessandro, Joseph; Solon, Alexandre P.; Hayakawa, Yoshinori; Anjard, Christophe; Detcheverry, François; Rieu, Jean-Paul; Rivière, Charlotte

    2017-10-01

    The dispersal of cells from an initially constrained location is a crucial aspect of many physiological phenomena, ranging from morphogenesis to tumour spreading. In such processes, cell-cell interactions may deeply alter the motion of single cells, and in turn the collective dynamics. While contact phenomena like contact inhibition of locomotion are known to come into play at high densities, here we focus on the little explored case of non-cohesive cells at moderate densities. We fully characterize the spreading of micropatterned colonies of Dictyostelium discoideum cells from the complete set of individual trajectories. From data analysis and simulation of an elementary model, we demonstrate that contact interactions act to speed up the early population spreading by promoting individual cells to a state of higher persistence, which constitutes an as-yet unreported contact enhancement of locomotion. Our findings also suggest that the current modelling paradigm of memoryless active particles may need to be extended to account for the history-dependent internal state of motile cells.

  12. Follow-the-leader cell migration requires biased cell-cell contact and local microenvironmental signals

    Science.gov (United States)

    Wynn, Michelle L.; Rupp, Paul; Trainor, Paul A.; Schnell, Santiago; Kulesa, Paul M.

    2013-06-01

    Directed cell migration often involves at least two types of cell motility that include multicellular streaming and chain migration. However, what is unclear is how cell contact dynamics and the distinct microenvironments through which cells travel influence the selection of one migratory mode or the other. The embryonic and highly invasive neural crest (NC) are an excellent model system to study this question since NC cells have been observed in vivo to display both of these types of cell motility. Here, we present data from tissue transplantation experiments in chick and in silico modeling that test our hypothesis that cell contact dynamics with each other and the microenvironment promote and sustain either multicellular stream or chain migration. We show that when premigratory cranial NC cells (at the pre-otic level) are transplanted into a more caudal region in the head (at the post-otic level), cells alter their characteristic stream behavior and migrate in chains. Similarly, post-otic NC cells migrate in streams after transplantation into the pre-otic hindbrain, suggesting that local microenvironmental signals dictate the mode of NC cell migration. Simulations of an agent-based model (ABM) that integrates the NC cell behavioral data predict that chain migration critically depends on the interplay of biased cell-cell contact and local microenvironment signals. Together, this integrated modeling and experimental approach suggests new experiments and offers a powerful tool to examine mechanisms that underlie complex cell migration patterns.

  13. Simulation Results: Optimization of Contact Ratio for Interdigitated Back-Contact Solar Cells

    Directory of Open Access Journals (Sweden)

    Vinay Budhraja

    2017-01-01

    Full Text Available In the fabrication of interdigitated back contact (IBC solar cells, it is very important to choose the right size of contact to achieve the maximum efficiency. Line contacts and point contacts are the two possibilities, which are being chosen for IBC structure. It is expected that the point contacts would give better results because of the reduced recombination rate. In this work, we are simulating the effect of contact size on the performance of IBC solar cells. Simulations were done in three dimension using Quokka, which numerically solves the charge carrier transport. Our simulation results show that around 10% of contact ratio is able to achieve optimum cell efficiency.

  14. Engineering amount of cell-cell contact demonstrates biphasic proliferative regulation through RhoA and the actin cytoskeleton

    International Nuclear Information System (INIS)

    Gray, Darren S.; Liu, Wendy F.; Shen, Colette J.; Bhadriraju, Kiran; Nelson, Celeste M.; Chen, Christopher S.

    2008-01-01

    Endothelial cell-cell contact via VE-cadherin plays an important role in regulating numerous cell functions, including proliferation. However, using different experimental approaches to manipulate cell-cell contact, investigators have observed both inhibition and stimulation of proliferation depending on the adhesive context. In this study, we used micropatterned wells combined with active positioning of cells by dielectrophoresis in order to investigate whether the number of contacting neighbors affected the proliferative response. Varying cell-cell contact resulted in a biphasic effect on proliferation; one contacting neighbor increased proliferation, while two or more neighboring cells partially inhibited this increase. We also observed that cell-cell contact increased the formation of actin stress fibers, and that expression of dominant negative RhoA (RhoN19) blocked the contact-mediated increase in stress fibers and proliferation. Furthermore, examination of heterotypic pairs of untreated cells in contact with RhoN19-expressing cells revealed that intracellular, but not intercellular, tension is required for the contact-mediated stimulation of proliferation. Moreover, engagement of VE-cadherin with cadherin-coated beads was sufficient to stimulate proliferation in the absence of actual cell-cell contact. In all, these results demonstrate that cell-cell contact signals through VE-cadherin, RhoA, and intracellular tension in the actin cytoskeleton to regulate proliferation

  15. Alloyed Aluminum Contacts for Silicon Solar Cells

    International Nuclear Information System (INIS)

    Tin Tin Aye

    2010-12-01

    Aluminium is usually deposited and alloyed at the back of p-p silicon solar cell for making a good ohmic contact and establishing a back electric field which avoids carrier recombination of the back surface. It was the deposition of aluminum on multicrystalline silicon (mc-Si) substrate at various annealing temperature. Physical and elemental analysis was carried out by using scanning electron microscopy (SEM) and X-rays diffraction (XRD). The electrical (I-V) characteristic of the photovoltaic cell was also measured.

  16. Mathematical Modeling of Contact Resistance in Silicon Photovoltaic Cells

    KAUST Repository

    Black, J. P.

    2013-10-22

    In screen-printed silicon-crystalline solar cells, the contact resistance of a thin interfacial glass layer between the silicon and the silver electrode plays a limiting role for electron transport. We analyze a simple model for electron transport across this layer, based on the driftdiffusion equations. We utilize the size of the current/Debye length to conduct asymptotic techniques to simplify the model; we solve the model numerically to find that the effective contact resistance may be a monotonic increasing, monotonic decreasing, or nonmonotonic function of the electron flux, depending on the values of the physical parameters. © 2013 Society for Industrial and Applied Mathematics.

  17. Ink-Jet Printer Forms Solar-Cell Contacts

    Science.gov (United States)

    Alexander, Paul, Jr.; Vest, R. W.; Binford, Don A.; Tweedell, Eric P.

    1988-01-01

    Contacts formed in controllable patterns with metal-based inks. System forms upper metal contact patterns on silicon photovoltaic cells. Uses metallo-organic ink, decomposes when heated, leaving behind metallic, electrically conductive residue in printed area.

  18. Follow-the-leader cell migration requires biased cell–cell contact and local microenvironmental signals

    International Nuclear Information System (INIS)

    Wynn, Michelle L; Rupp, Paul; Trainor, Paul A; Kulesa, Paul M; Schnell, Santiago

    2013-01-01

    Directed cell migration often involves at least two types of cell motility that include multicellular streaming and chain migration. However, what is unclear is how cell contact dynamics and the distinct microenvironments through which cells travel influence the selection of one migratory mode or the other. The embryonic and highly invasive neural crest (NC) are an excellent model system to study this question since NC cells have been observed in vivo to display both of these types of cell motility. Here, we present data from tissue transplantation experiments in chick and in silico modeling that test our hypothesis that cell contact dynamics with each other and the microenvironment promote and sustain either multicellular stream or chain migration. We show that when premigratory cranial NC cells (at the pre-otic level) are transplanted into a more caudal region in the head (at the post-otic level), cells alter their characteristic stream behavior and migrate in chains. Similarly, post-otic NC cells migrate in streams after transplantation into the pre-otic hindbrain, suggesting that local microenvironmental signals dictate the mode of NC cell migration. Simulations of an agent-based model (ABM) that integrates the NC cell behavioral data predict that chain migration critically depends on the interplay of biased cell–cell contact and local microenvironment signals. Together, this integrated modeling and experimental approach suggests new experiments and offers a powerful tool to examine mechanisms that underlie complex cell migration patterns. (paper)

  19. Estimation of contact resistance in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lianhong; Liu, Ying; Song, Haimin; Wang, Shuxin [School of Mechanical Engineering, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China); Zhou, Yuanyuan; Hu, S. Jack [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2006-11-22

    The contact resistance between the bipolar plate (BPP) and the gas diffusion layer (GDL) is an important factor contributing to the power loss in proton exchange membrane (PEM) fuel cells. At present there is still not a well-developed method to estimate such contact resistance. This paper proposes two effective methods for estimating the contact resistance between the BPP and the GDL based on an experimental contact resistance-pressure constitutive relation. The constitutive relation was obtained by experimentally measuring the contact resistance between the GDL and a flat plate of the same material and processing conditions as the BPP under stated contact pressure. In the first method, which was a simplified prediction, the contact area and contact pressure between the BPP and the GDL were analyzed with a simple geometrical relation and the contact resistance was obtained by the contact resistance-pressure constitutive relation. In the second method, the contact area and contact pressure between the BPP and GDL were analyzed using FEM and the contact resistance was computed for each contact element according to the constitutive relation. The total contact resistance was then calculated by considering all contact elements in parallel. The influence of load distribution on contact resistance was also investigated. Good agreement was demonstrated between experimental results and predictions by both methods. The simplified prediction method provides an efficient approach to estimating the contact resistance in PEM fuel cells. The proposed methods for estimating the contact resistance can be useful in modeling and optimizing the assembly process to improve the performance of PEM fuel cells. (author)

  20. Synaptic Contacts Enhance Cell-to-Cell Tau Pathology Propagation

    Directory of Open Access Journals (Sweden)

    Sara Calafate

    2015-05-01

    Full Text Available Accumulation of insoluble Tau protein aggregates and stereotypical propagation of Tau pathology through the brain are common hallmarks of tauopathies, including Alzheimer’s disease (AD. Propagation of Tau pathology appears to occur along connected neurons, but whether synaptic contacts between neurons are facilitating propagation has not been demonstrated. Using quantitative in vitro models, we demonstrate that, in parallel to non-synaptic mechanisms, synapses, but not merely the close distance between the cells, enhance the propagation of Tau pathology between acceptor hippocampal neurons and Tau donor cells. Similarly, in an artificial neuronal network using microfluidic devices, synapses and synaptic activity are promoting neuronal Tau pathology propagation in parallel to the non-synaptic mechanisms. Our work indicates that the physical presence of synaptic contacts between neurons facilitate Tau pathology propagation. These findings can have implications for synaptic repair therapies, which may turn out to have adverse effects by promoting propagation of Tau pathology.

  1. Corneal cell adhesion to contact lens hydrogel materials enhanced via tear film protein deposition.

    Directory of Open Access Journals (Sweden)

    Claire M Elkins

    Full Text Available Tear film protein deposition on contact lens hydrogels has been well characterized from the perspective of bacterial adhesion and viability. However, the effect of protein deposition on lens interactions with the corneal epithelium remains largely unexplored. The current study employs a live cell rheometer to quantify human corneal epithelial cell adhesion to soft contact lenses fouled with the tear film protein lysozyme. PureVision balafilcon A and AirOptix lotrafilcon B lenses were soaked for five days in either phosphate buffered saline (PBS, borate buffered saline (BBS, or Sensitive Eyes Plus Saline Solution (Sensitive Eyes, either pure or in the presence of lysozyme. Treated contact lenses were then contacted to a live monolayer of corneal epithelial cells for two hours, after which the contact lens was sheared laterally. The apparent cell monolayer relaxation modulus was then used to quantify the extent of cell adhesion to the contact lens surface. For both lens types, lysozyme increased corneal cell adhesion to the contact lens, with the apparent cell monolayer relaxation modulus increasing up to an order of magnitude in the presence of protein. The magnitude of this increase depended on the identity of the soaking solution: lenses soaked in borate-buffered solutions (BBS, Sensitive Eyes exhibited a much greater increase in cell attachment upon protein addition than those soaked in PBS. Significantly, all measurements were conducted while subjecting the cells to moderate surface pressures and shear rates, similar to those experienced by corneal cells in vivo.

  2. Transparent back contacts for P3HT:PCBM bulk heterojunction solar cells

    International Nuclear Information System (INIS)

    Sendova-Vassileva, M; Dikov, H; Popkirov, G; Lazarova, E; Vitanov, P; Gancheva, V; Grancharov, G; Tsocheva, D; Mokreva, P

    2014-01-01

    A new combination of layers functioning as a transparent contact is proposed and tested in real solar cells. The contacts consist of TiO 2 layers and thin metal layers (Ag, Cu) and are deposited by magnetron sputtering. The optical transmission and electrical conductivity of the transparent contact layers (TCL) are measured. The TCLs are applied as back contacts in bulk heterojunction polymer solar cells deposited on ITO covered glass and consisting of the following layers: ITO/PEDOT:PSS/P3HT:PCBM/back contact. The organic layers are deposited by spin-coating. For comparison, the same bulk heterojunction polymer solar cells are prepared with a sputtered Ag back contact. The first results show a dependence of the current-voltage parameters of the studied solar cells on the thickness of the different component layers of the transparent back contacts. There is a balance that has to be observed between the electrical characteristics of the contacts and their optical transparency. Future plans involve their inclusion as intermediate contacts in tandem organic solar cells.

  3. Synaptic Contacts Enhance Cell-to-Cell Tau Pathology Propagation.

    Science.gov (United States)

    Calafate, Sara; Buist, Arjan; Miskiewicz, Katarzyna; Vijayan, Vinoy; Daneels, Guy; de Strooper, Bart; de Wit, Joris; Verstreken, Patrik; Moechars, Diederik

    2015-05-26

    Accumulation of insoluble Tau protein aggregates and stereotypical propagation of Tau pathology through the brain are common hallmarks of tauopathies, including Alzheimer's disease (AD). Propagation of Tau pathology appears to occur along connected neurons, but whether synaptic contacts between neurons are facilitating propagation has not been demonstrated. Using quantitative in vitro models, we demonstrate that, in parallel to non-synaptic mechanisms, synapses, but not merely the close distance between the cells, enhance the propagation of Tau pathology between acceptor hippocampal neurons and Tau donor cells. Similarly, in an artificial neuronal network using microfluidic devices, synapses and synaptic activity are promoting neuronal Tau pathology propagation in parallel to the non-synaptic mechanisms. Our work indicates that the physical presence of synaptic contacts between neurons facilitate Tau pathology propagation. These findings can have implications for synaptic repair therapies, which may turn out to have adverse effects by promoting propagation of Tau pathology. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  4. Anomalous Temperature Dependence in Metal-Black Phosphorus Contact.

    Science.gov (United States)

    Li, Xuefei; Grassi, Roberto; Li, Sichao; Li, Tiaoyang; Xiong, Xiong; Low, Tony; Wu, Yanqing

    2018-01-10

    Metal-semiconductor contact has been the performance limiting problem for electronic devices and also dictates the scaling potential for future generation devices based on novel channel materials. Two-dimensional semiconductors beyond graphene, particularly few layer black phosphorus, have attracted much attention due to their exceptional electronic properties such as anisotropy and high mobility. However, due to its ultrathin body nature, few layer black phosphorus-metal contact behaves differently than conventional Schottky barrier (SB) junctions, and the mechanisms of its carrier transport across such a barrier remain elusive. In this work, we examine the transport characteristic of metal-black phosphorus contact under varying temperature. We elucidated the origin of apparent negative SB heights extracted from classical thermionic emission model and also the phenomenon of metal-insulator transition observed in the current-temperature transistor characteristic. In essence, we found that the SB height can be modulated by the back-gate voltage, which beyond a certain critical point becomes so low that the injected carrier can no longer be described by the conventional thermionic emission theory. The transition from transport dominated by a Maxwell-Boltzmann distribution for the high energy tail states, to that of a Fermi distribution by low energy Fermi sea electrons, is the physical origin of the observed metal-insulator transition. We identified two distinctive tunneling limited transport regimes in the contact: vertical and longitudinal tunneling.

  5. Primary cilia utilize glycoprotein-dependent adhesion mechanisms to stabilize long-lasting cilia-cilia contacts

    Directory of Open Access Journals (Sweden)

    Ott Carolyn

    2012-04-01

    Full Text Available Abstract Background The central tenet of cilia function is sensing and transmitting information. The capacity to directly contact extracellular surfaces would empower primary cilia to probe the environment for information about the nature and location of nearby surfaces. It has been well established that flagella and other motile cilia perform diverse cellular functions through adhesion. We hypothesized that mammalian primary cilia also interact with the extracellular environment through direct physical contact. Methods We identified cilia in rod photoreceptors and cholangiocytes in fixed mouse tissues and examined the structures that these cilia contact in vivo. We then utilized an MDCK cell culture model to characterize the nature of the contacts we observed. Results In retina and liver tissue, we observed that cilia from nearby cells touch one another. Using MDCK cells, we found compelling evidence that these contacts are stable adhesions that form bridges between two cells, or networks between many cells. We examined the nature and duration of the cilia-cilia contacts and discovered primary cilia movements that facilitate cilia-cilia encounters. Stable adhesions form as the area of contact expands from a single point to a stretch of tightly bound, adjacent cilia membranes. The cilia-cilia contacts persisted for hours and were resistant to several harsh treatments such as proteases and DTT. Unlike many other cell adhesion mechanisms, calcium was not required for the formation or maintenance of cilia adhesion. However, swainsonine, which blocks maturation of N-linked glycoproteins, reduced contact formation. We propose that cellular control of adhesion maintenance is active because cilia adhesion did not prevent cell division; rather, contacts dissolved during mitosis as cilia were resorbed. Conclusions The demonstration that mammalian primary cilia formed prolonged, direct, physical contacts supports a novel paradigm: that mammalian primary

  6. Alterations in Helicobacter pylori triggered by contact with gastric epithelial cells

    Directory of Open Access Journals (Sweden)

    Elizabeth M. Johnson

    2012-02-01

    Full Text Available Helicobacter pylori lives within the mucus layer of the human stomach, in close proximity to gastric epithelial cells. While a great deal is known about the effects of H. pylori on human cells and the specific bacterial products that mediate these effects, relatively little work has been done to investigate alterations in H. pylori that may be triggered by bacterial contact with human cells. In this review, we discuss the spectrum of changes in bacterial physiology and morphology that occur when H. pylori is in contact with gastric epithelial cells. Several studies have reported that cell contact causes alterations in H. pylori gene transcription. In addition, H. pylori contact with gastric epithelial cells promotes the formation of pilus-like structures at the bacteria-host cell interface. The formation of these structures requires multiple genes in the cag pathogenicity island, and these structures are proposed to have an important role in the type IV secretion system-dependent process through which CagA enters host cells. Finally, H. pylori contact with epithelial cells can promote bacterial replication and the formation of microcolonies, phenomena that are facilitated by the acquisition of iron and other nutrients from infected cells. In summary, the gastric epithelial cell surface represents an important niche for H. pylori, and upon entry into this niche, the bacteria alter their behavior in a manner that optimizes bacterial proliferation and persistent colonization of the host.

  7. Distinct migration and contact dynamics of resting and IL-2-activated human natural killer cells

    Directory of Open Access Journals (Sweden)

    Per Erik Olofsson

    2014-03-01

    Full Text Available Natural killer (NK cells serve as one of the first lines of defense against viral infections and transformed cells. NK cell cytotoxicity is not dependent on antigen presentation by target cells, but is dependent on integration of activating and inhibitory signals triggered by receptor–ligand interactions formed at a tight intercellular contact between the NK and target cell, i.e. the immune synapse. We have studied the single-cell migration behavior and target-cell contact dynamics of resting and IL-2-activated human peripheral blood NK cells. Small populations of NK cells and target cells were confined in microwells and imaged by fluorescence microscopy for >8 h. Only the IL-2-activated population of NK cells showed efficient cytotoxicity against the human embryonic kidney (HEK 293T target cells. We found that although the average migration speeds were comparable, activated NK cells showed significantly more dynamic migration behavior, with more frequent transitions between periods of low and high motility. Resting NK cells formed fewer and weaker contacts with target cells, which manifested as shorter conjugation times and in many cases a complete lack of post-conjugation attachment to target cells. Activated NK cells were approximately twice as big as the resting cells, displayed a more migratory phenotype, and were more likely to employ motile scanning of the target cell surface during conjugation. Taken together, our experiments quantify, at the single-cell level, how activation by IL-2 leads to altered NK cell cytotoxicity, migration behavior and contact dynamics.

  8. Contact behavior modelling and its size effect on proton exchange membrane fuel cell

    Science.gov (United States)

    Qiu, Diankai; Peng, Linfa; Yi, Peiyun; Lai, Xinmin; Janßen, Holger; Lehnert, Werner

    2017-10-01

    Contact behavior between the gas diffusion layer (GDL) and bipolar plate (BPP) is of significant importance for proton exchange membrane fuel cells. Most current studies on contact behavior utilize experiments and finite element modelling and focus on fuel cells with graphite BPPs, which lead to high costs and huge computational requirements. The objective of this work is to build a more effective analytical method for contact behavior in fuel cells and investigate the size effect resulting from configuration alteration of channel and rib (channel/rib). Firstly, a mathematical description of channel/rib geometry is outlined in accordance with the fabrication of metallic BPP. Based on the interface deformation characteristic and Winkler surface model, contact pressure between BPP and GDL is then calculated to predict contact resistance and GDL porosity as evaluative parameters of contact behavior. Then, experiments on BPP fabrication and contact resistance measurement are conducted to validate the model. The measured results demonstrate an obvious dependence on channel/rib size. Feasibility of the model used in graphite fuel cells is also discussed. Finally, size factor is proposed for evaluating the rule of size effect. Significant increase occurs in contact resistance and porosity for higher size factor, in which channel/rib width decrease.

  9. MARCKS-related protein regulates cytoskeletal organization at cell-cell and cell-substrate contacts in epithelial cells.

    Science.gov (United States)

    Van Itallie, Christina M; Tietgens, Amber Jean; Aponte, Angel; Gucek, Marjan; Cartagena-Rivera, Alexander X; Chadwick, Richard S; Anderson, James M

    2018-02-02

    Treatment of epithelial cells with interferon-γ and TNF-α (IFN/TNF) results in increased paracellular permeability. To identify relevant proteins mediating barrier disruption, we performed proximity-dependent biotinylation (BioID) of occludin and found that tagging of MARCKS-related protein (MRP; also known as MARCKSL1) increased ∼20-fold following IFN/TNF administration. GFP-MRP was focused at the lateral cell membrane and its overexpression potentiated the physiological response of the tight junction barrier to cytokines. However, deletion of MRP did not abrogate the cytokine responses, suggesting that MRP is not required in the occludin-dependent IFN/TNF response. Instead, our results reveal a key role for MRP in epithelial cells in control of multiple actin-based structures, likely by regulation of integrin signaling. Changes in focal adhesion organization and basal actin stress fibers in MRP-knockout (KO) cells were reminiscent of those seen in FAK-KO cells. In addition, we found alterations in cell-cell interactions in MRP-KO cells associated with increased junctional tension, suggesting that MRP may play a role in focal adhesion-adherens junction cross talk. Together, our results are consistent with a key role for MRP in cytoskeletal organization of cell contacts in epithelial cells. © 2018. Published by The Company of Biologists Ltd.

  10. Contact resistance at ceramic interfaces and its dependence on mechanical load

    DEFF Research Database (Denmark)

    Koch, Søren; Hendriksen, P.V.

    2004-01-01

    Low contact resistance between individual components is important for solid oxide fuel cell stacks if high performance is to be achieved. Several mechanisms may result in high contact resistance, e.g., current constriction due to low area of contact and formation of resistive phases between...... the components. In this study, the importance of current constriction due to limited area of contact at an interface is investigated by comparing the characteristics of contacts between LSM pellets with different surface finish. The load behaviour of the contact resistance has been investigated and a power law...... of the contact resistance was calculated using a simple model describing the variation of the contact area with load based on the measured surface roughness. Good agreement between the calculations and the experimentally observed resistances was found. (C) 2004 Elsevier B.V. All rights reserved....

  11. Laminated photovoltaic modules using back-contact solar cells

    Science.gov (United States)

    Gee, James M.; Garrett, Stephen E.; Morgan, William P.; Worobey, Walter

    1999-09-14

    Photovoltaic modules which comprise back-contact solar cells, such as back-contact crystalline silicon solar cells, positioned atop electrically conductive circuit elements affixed to a planar support so that a circuit capable of generating electric power is created. The modules are encapsulated using encapsulant materials such as EVA which are commonly used in photovoltaic module manufacture. The module designs allow multiple cells to be electrically connected in a single encapsulation step rather than by sequential soldering which characterizes the currently used commercial practices.

  12. Device physics underlying silicon heterojunction and passivating-contact solar cells: A topical review

    KAUST Repository

    Chavali, Raghu V. K.

    2018-01-15

    The device physics of commercially dominant diffused-junction silicon solar cells is well understood, allowing sophisticated optimization of this class of devices. Recently, so-called passivating-contact solar cell technologies have become prominent, with Kaneka setting the world\\'s silicon solar cell efficiency record of 26.63% using silicon heterojunction contacts in an interdigitated configuration. Although passivating-contact solar cells are remarkably efficient, their underlying device physics is not yet completely understood, not in the least because they are constructed from diverse materials that may introduce electronic barriers in the current flow. To bridge this gap in understanding, we explore the device physics of passivating contact silicon heterojunction (SHJ) solar cells. Here, we identify the key properties of heterojunctions that affect cell efficiency, analyze the dependence of key heterojunction properties on carrier transport under light and dark conditions, provide a self-consistent multiprobe approach to extract heterojunction parameters using several characterization techniques (including dark J-V, light J-V, C-V, admittance spectroscopy, and Suns-Voc), propose design guidelines to address bottlenecks in energy production in SHJ cells, and develop a process-to-module modeling framework to establish the module\\'s performance limits. We expect that our proposed guidelines resulting from this multiscale and self-consistent framework will improve the performance of future SHJ cells as well as other passivating contact-based solar cells.

  13. The Mast Cell, Contact, and Coagulation System Connection in Anaphylaxis

    Directory of Open Access Journals (Sweden)

    Mar Guilarte

    2017-07-01

    Full Text Available Anaphylaxis is the most severe form of allergic reaction, resulting from the effect of mediators and chemotactic substances released by activated cells. Mast cells and basophils are considered key players in IgE-mediated human anaphylaxis. Beyond IgE-mediated activation of mast cells/basophils, further mechanisms are involved in the occurrence of anaphylaxis. New insights into the potential relevance of pathways other than mast cell and basophil degranulation have been unraveled, such as the activation of the contact and the coagulation systems. Mast cell heparin released upon activation provides negatively charged surfaces for factor XII (FXII binding and auto-activation. Activated FXII, the initiating serine protease in both the contact and the intrinsic coagulation system, activates factor XI and prekallikrein, respectively. FXII-mediated bradykinin (BK formation has been proven in the human plasma of anaphylactic patients as well as in experimental models of anaphylaxis. Moreover, the severity of anaphylaxis is correlated with the increase in plasma heparin, BK formation and the intensity of contact system activation. FXII also activates plasminogen in the fibrinolysis system. Mast cell tryptase has been shown to participate in fibrinolysis through plasmin activation and by facilitating the degradation of fibrinogen. Some usual clinical manifestations in anaphylaxis, such as angioedema or hypotension, or other less common, such as metrorrhagia, may be explained by the direct effect of the activation of the coagulation and contact system driven by mast cell mediators.

  14. Behavior of bone cells in contact with magnesium implant material.

    Science.gov (United States)

    Burmester, Anna; Willumeit-Römer, Regine; Feyerabend, Frank

    2017-01-01

    Magnesium-based implants exhibit several advantages, such as biodegradability and possible osteoinductive properties. Whether the degradation may induce cell type-specific changes in metabolism still remains unclear. To examine the osteoinductivity mechanisms, the reaction of bone-derived cells (MG63, U2OS, SaoS2, and primary human osteoblasts (OB)) to magnesium (Mg) was determined. Mg-based extracts were used to mimic more realistic Mg degradation conditions. Moreover, the influence of cells having direct contact with the degrading Mg metal was investigated. In exposure to extracts and in direct contact, the cells decreased pH and osmolality due to metabolic activity. Proliferating cells showed no significant reaction to extracts, whereas differentiating cells were negatively influenced. In contrast to extract exposure, where cell size increased, in direct contact to magnesium, cell size was stable or even decreased. The amount of focal adhesions decreased over time on all materials. Genes involved in bone formation were significantly upregulated, especially for primary human osteoblasts. Some osteoinductive indicators were observed for OB: (i) an increased cell count after extract addition indicated a higher proliferation potential; (ii) increased cell sizes after extract supplementation in combination with augmented adhesion behavior of these cells suggest an early switch to differentiation; and (iii) bone-inducing gene expression patterns were determined for all analyzed conditions. The results from the cell lines were inhomogeneous and showed no specific stimulus of Mg. The comparison of the different cell types showed that primary cells of the investigated tissue should be used as an in vitro model if Mg is analyzed. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 165-179, 2017. © 2015 Wiley Periodicals, Inc.

  15. Pneumococcal Competence Coordination Relies on a Cell-Contact Sensing Mechanism.

    Directory of Open Access Journals (Sweden)

    Marc Prudhomme

    2016-06-01

    Full Text Available Bacteria have evolved various inducible genetic programs to face many types of stress that challenge their growth and survival. Competence is one such program. It enables genetic transformation, a major horizontal gene transfer process. Competence development in liquid cultures of Streptococcus pneumoniae is synchronized within the whole cell population. This collective behavior is known to depend on an exported signaling Competence Stimulating Peptide (CSP, whose action generates a positive feedback loop. However, it is unclear how this CSP-dependent population switch is coordinated. By monitoring spontaneous competence development in real time during growth of four distinct pneumococcal lineages, we have found that competence shift in the population relies on a self-activated cell fraction that arises via a growth time-dependent mechanism. We demonstrate that CSP remains bound to cells during this event, and conclude that the rate of competence development corresponds to the propagation of competence by contact between activated and quiescent cells. We validated this two-step cell-contact sensing mechanism by measuring competence development during co-cultivation of strains with altered capacity to produce or respond to CSP. Finally, we found that the membrane protein ComD retains the CSP, limiting its free diffusion in the medium. We propose that competence initiator cells originate stochastically in response to stress, to form a distinct subpopulation that then transmits the CSP by cell-cell contact.

  16. Rough surface electrical contact resistance considering scale dependent properties and quantum effects

    International Nuclear Information System (INIS)

    Jackson, Robert L.; Crandall, Erika R.; Bozack, Michael J.

    2015-01-01

    The objective of this work is to evaluate the effect of scale dependent mechanical and electrical properties on electrical contact resistance (ECR) between rough surfaces. This work attempts to build on existing ECR models that neglect potentially important quantum- and size-dependent contact and electrical conduction mechanisms present due to the asperity sizes on typical surfaces. The electrical conductance at small scales can quantize or show a stepping trend as the contact area is varied in the range of the free electron Fermi wavelength squared. This work then evaluates if these effects remain important for the interface between rough surfaces, which may include many small scale contacts of varying sizes. The results suggest that these effects may be significant in some cases, while insignificant for others. It depends on the load and the multiscale structure of the surface roughness

  17. Spin-dependent tunneling transport into CrO2 nanorod devices with nonmagnetic contacts.

    Science.gov (United States)

    Song, Yipu; Schmitt, Andrew L; Jin, Song

    2008-08-01

    Single-crystal nanorods of half-metallic chromium dioxide (CrO2) were synthesized and structurally characterized. Spin-dependent electrical transport was investigated in individual CrO2 nanorod devices contacted with nonmagnetic metallic electrodes. Negative magnetoresistance (MR) was observed at low temperatures due to the spin-dependent direct tunneling through the contact barrier and the high spin polarization in the half-metallic nanorods. The magnitude of this negative magnetoresistance decreases with increasing bias voltage and temperature due to spin-independent inelastic hopping through the barrier, and a small positive magnetoresistance was found at room temperature. It is believed that the contact barrier and the surface state of the nanorods have great influence on the spin-dependent transport limiting the magnitude of MR effect in this first attempt at spin filter devices of CrO2 nanorods with nonmagnetic contacts.

  18. Thermometry in dielectrophoresis chips for contact-free cell handling

    International Nuclear Information System (INIS)

    Jaeger, M S; Mueller, T; Schnelle, T

    2007-01-01

    Cell biology applications, protocols in immunology and stem cell research, require that individual cells are handled under strict control of their contacts to other cells or synthetic surfaces. Dielectrophoresis (DEP) in microfluidic chips is an established technique to investigate, group, wash, cultivate and sort cells contact-free under physiological conditions: microelectrode octode cages, versatile dielectrophoretic elements energized with radio frequency electric fields, stably trap single cells or cellular aggregates. For medical applications and cell cultivation, possible side effects of the dielectrophoretic manipulation, such as membrane polarization and Joule heating, have to be quantified. Therefore, we characterized the electric field-induced warming in dielectrophoretic cages using ohmic resistance measurements, fluorometry, liquid crystal beads, infra-red thermography and bubble size thermometry. We compare the results of these techniques with respect to the influences of voltage, electric conductivity of buffer, frequency, cage size and electrode surface. We conclude that in the culture medium thermal effects may be neglected if low voltages and an electric field-reducing phase pattern are used. Our experimental results provide explicit values for estimating the thermal effect on dielectrophoretically caged cells and show that Joule heating is best minimized by optimizing the cage geometry and reducing the buffer conductivity. The results may additionally serve to evaluate and improve theoretical predictions on field-induced effects. Based on present-day chip processing possibilities, DEP is well suited for the manipulation of cells

  19. Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

    KAUST Repository

    Tomasi, Andrea; Paviet-Salomon, Bertrand; Jeangros, Quentin; Haschke, Jan; Christmann, Gabriel; Barraud, Loris; Descoeudres, Antoine; Seif, Johannes Peter; Nicolay, Sylvain; Despeisse, Matthieu; De Wolf, Stefaan; Ballif, Christophe

    2017-01-01

    For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record efficiency for crystalline-silicon single-junction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm2 tunnel-interdigitated back-contact solar cell with a certified conversion efficiency >22.5%.

  20. Simple processing of back-contacted silicon heterojunction solar cells using selective-area crystalline growth

    KAUST Repository

    Tomasi, Andrea

    2017-04-24

    For crystalline-silicon solar cells, voltages close to the theoretical limit are nowadays readily achievable when using passivating contacts. Conversely, maximal current generation requires the integration of the electron and hole contacts at the back of the solar cell to liberate its front from any shadowing loss. Recently, the world-record efficiency for crystalline-silicon single-junction solar cells was achieved by merging these two approaches in a single device; however, the complexity of fabricating this class of devices raises concerns about their commercial potential. Here we show a contacting method that substantially simplifies the architecture and fabrication of back-contacted silicon solar cells. We exploit the surface-dependent growth of silicon thin films, deposited by plasma processes, to eliminate the patterning of one of the doped carrier-collecting layers. Then, using only one alignment step for electrode definition, we fabricate a proof-of-concept 9-cm2 tunnel-interdigitated back-contact solar cell with a certified conversion efficiency >22.5%.

  1. Sliding contact loading enhances the tensile properties of mesenchymal stem cell-seeded hydrogels

    Directory of Open Access Journals (Sweden)

    AH Huang

    2012-07-01

    Full Text Available The primary goal of cartilage tissue engineering is to recapitulate the functional properties and structural features of native articular cartilage. While there has been some success in generating near-native compressive properties, the tensile properties of cell-seeded constructs remain poor, and key features of cartilage, including inhomogeneity and anisotropy, are generally absent in these engineered constructs. Therefore, in an attempt to instill these hallmark properties of cartilage in engineered cell-seeded constructs, we designed and characterized a novel sliding contact bioreactor to recapitulate the mechanical stimuli arising from physiologic joint loading (two contacting cartilage layers. Finite element modeling of this bioreactor system showed that tensile strains were direction-dependent, while both tensile strains and fluid motion were depth-dependent and highest in the region closest to the contact surface. Short-term sliding contact of mesenchymal stem cell (MSC-seeded agarose improved chondrogenic gene expression in a manner dependent on both the axial strain applied and transforming growth factor-β supplementation. Using the optimized loading parameters derived from these short-term studies, long-term sliding contact was applied to MSC-seeded agarose constructs for 21 d. After 21 d, sliding contact significantly improved the tensile properties of MSC-seeded constructs and elicited alterations in type II collagen and proteoglycan accumulation as a function of depth; staining for these matrix molecules showed intense localization in the surface regions. These findings point to the potential of sliding contact to produce engineered cartilage constructs that begin to recapitulate the complex mechanical features of the native tissue.

  2. APC senses cell-cell contacts and moves to the nucleus upon their disruption.

    Science.gov (United States)

    Brocardo, M G; Bianchini, M; Radrizzani, M; Reyes, G B; Dugour, A V; Taminelli, G L; Gonzalez Solveyra, C; Santa-Coloma, T A

    2001-06-22

    The adenomatous polyposis coli (APC) tumor suppressor protein is involved in the Wnt/wingless pathway, modulating beta-catenin activity. We report the development of a highly specific, chemically synthesized oligobody (oligonucleotide-based synthetic antibody), directed against the N-terminal region of APC. Using this reagent, we found that within 16 h of disrupting HT-29 cell-cell contacts by harvesting cells with trypsin/EDTA treatment and replating, APC was translocated from the cytoplasm to the nucleus. Five days after plating the cells, when the cells had returned to their normal confluent phenotype and cell-cell contacts were reestablished, APC returned to the cytoplasm. These results suggest that APC functions as part of a "sensor" system, and responds to the loss of cell-cell contacts by moving to the nucleus, and returning to the cytoplasm when the contacts are fully restored. Copyright 2001 Academic Press.

  3. Fuel cell electrode interconnect contact material encapsulation and method

    Science.gov (United States)

    Derose, Anthony J.; Haltiner, Jr., Karl J.; Gudyka, Russell A.; Bonadies, Joseph V.; Silvis, Thomas W.

    2016-05-31

    A fuel cell stack includes a plurality of fuel cell cassettes each including a fuel cell with an anode and a cathode. Each fuel cell cassette also includes an electrode interconnect adjacent to the anode or the cathode for providing electrical communication between an adjacent fuel cell cassette and the anode or the cathode. The interconnect includes a plurality of electrode interconnect protrusions defining a flow passage along the anode or the cathode for communicating oxidant or fuel to the anode or the cathode. An electrically conductive material is disposed between at least one of the electrode interconnect protrusions and the anode or the cathode in order to provide a stable electrical contact between the electrode interconnect and the anode or cathode. An encapsulating arrangement segregates the electrically conductive material from the flow passage thereby, preventing volatilization of the electrically conductive material in use of the fuel cell stack.

  4. Modeling of InGaN/Si tandem cells: comparison between 2-contacts/4-contacts

    Directory of Open Access Journals (Sweden)

    El-Huni Walid

    2017-01-01

    Full Text Available Due to its electrical and optical interesting properties, InGaN alloy is being intensively studied to be combined with silicon in order to achieve low-cost high-efficiency solar cell. However, a relatively thick monophasic layer of InGaN is difficult to grow due to the relaxation issue in material. This issue can be avoided by semibulk structure. In this work, we present an InGaN/Si double-junction solar cell modeled using Silvaco-ATLAS TCAD software. We have taken into account polarization effect in III-N materials. We have shown that 50% of indium is needed to ensure the current matching between the top cell and the bottom cell in 2-terminal configuration. Such high indium composition is technologically challenging to grow. Thus, we have modeled a 4-terminals solar cell with relatively low indium composition (In = 25% where current matching is not needed. With technologically feasible structural parameters, we have shown that an efficiency near to 30% can be achieved with InGaN/Si 4-contact tandem cell.

  5. Modeling of InGaN/Si tandem cells: comparison between 2-contacts/4-contacts

    Science.gov (United States)

    El-Huni, Walid; Migan, Anne; Alamarguy, David; Djebbour, Zakaria

    2017-03-01

    Due to its electrical and optical interesting properties, InGaN alloy is being intensively studied to be combined with silicon in order to achieve low-cost high-efficiency solar cell. However, a relatively thick monophasic layer of InGaN is difficult to grow due to the relaxation issue in material. This issue can be avoided by semibulk structure. In this work, we present an InGaN/Si double-junction solar cell modeled using Silvaco-ATLAS TCAD software. We have taken into account polarization effect in III-N materials. We have shown that 50% of indium is needed to ensure the current matching between the top cell and the bottom cell in 2-terminal configuration. Such high indium composition is technologically challenging to grow. Thus, we have modeled a 4-terminals solar cell with relatively low indium composition (In = 25%) where current matching is not needed. With technologically feasible structural parameters, we have shown that an efficiency near to 30% can be achieved with InGaN/Si 4-contact tandem cell.

  6. Temperature Dependence and Magnetic Field Dependence of Quantum Point Contacts in Si-Inversion Layers

    NARCIS (Netherlands)

    Wang, S.L.; Son, P.C. van; Wees, B.J. van; Klapwijk, T.M.

    1992-01-01

    The conductance of ballistic point contacts in high-mobility Si-inversion layers has been studied at several temperatures between 75 and 600 mK both without and in a magnetic field (up to 12T). When the width of constriction is varied in zero magnetic field, step-like features at multiples of 4e2/h

  7. History-Dependent Problems with Applications to Contact Models for Elastic Beams

    International Nuclear Information System (INIS)

    Bartosz, Krzysztof; Kalita, Piotr; Migórski, Stanisław; Ochal, Anna; Sofonea, Mircea

    2016-01-01

    We prove an existence and uniqueness result for a class of subdifferential inclusions which involve a history-dependent operator. Then we specialize this result in the study of a class of history-dependent hemivariational inequalities. Problems of such kind arise in a large number of mathematical models which describe quasistatic processes of contact. To provide an example we consider an elastic beam in contact with a reactive obstacle. The contact is modeled with a new and nonstandard condition which involves both the subdifferential of a nonconvex and nonsmooth function and a Volterra-type integral term. We derive a variational formulation of the problem which is in the form of a history-dependent hemivariational inequality for the displacement field. Then, we use our abstract result to prove its unique weak solvability. Finally, we consider a numerical approximation of the model, solve effectively the approximate problems and provide numerical simulations

  8. History-Dependent Problems with Applications to Contact Models for Elastic Beams

    Energy Technology Data Exchange (ETDEWEB)

    Bartosz, Krzysztof; Kalita, Piotr; Migórski, Stanisław; Ochal, Anna, E-mail: ochal@ii.uj.edu.pl [Jagiellonian University, Faculty of Mathematics and Computer Science (Poland); Sofonea, Mircea [Université de Perpignan Via Domitia, Laboratoire de Mathématiques et Physique (France)

    2016-02-15

    We prove an existence and uniqueness result for a class of subdifferential inclusions which involve a history-dependent operator. Then we specialize this result in the study of a class of history-dependent hemivariational inequalities. Problems of such kind arise in a large number of mathematical models which describe quasistatic processes of contact. To provide an example we consider an elastic beam in contact with a reactive obstacle. The contact is modeled with a new and nonstandard condition which involves both the subdifferential of a nonconvex and nonsmooth function and a Volterra-type integral term. We derive a variational formulation of the problem which is in the form of a history-dependent hemivariational inequality for the displacement field. Then, we use our abstract result to prove its unique weak solvability. Finally, we consider a numerical approximation of the model, solve effectively the approximate problems and provide numerical simulations.

  9. Back contact buffer layer for thin-film solar cells

    Science.gov (United States)

    Compaan, Alvin D.; Plotnikov, Victor V.

    2014-09-09

    A photovoltaic cell structure is disclosed that includes a buffer/passivation layer at a CdTe/Back contact interface. The buffer/passivation layer is formed from the same material that forms the n-type semiconductor active layer. In one embodiment, the buffer layer and the n-type semiconductor active layer are formed from cadmium sulfide (CdS). A method of forming a photovoltaic cell includes the step of forming the semiconductor active layers and the buffer/passivation layer within the same deposition chamber and using the same material source.

  10. Direct contact with endoderm-like cells efficiently induces cardiac progenitors from mouse and human pluripotent stem cells.

    Directory of Open Access Journals (Sweden)

    Hideki Uosaki

    Full Text Available RATIONALE: Pluripotent stem cell-derived cardiac progenitor cells (CPCs have emerged as a powerful tool to study cardiogenesis in vitro and a potential cell source for cardiac regenerative medicine. However, available methods to induce CPCs are not efficient or require high-cost cytokines with extensive optimization due to cell line variations. OBJECTIVE: Based on our in-vivo observation that early endodermal cells maintain contact with nascent pre-cardiac mesoderm, we hypothesized that direct physical contact with endoderm promotes induction of CPCs from pluripotent cells. METHOD AND RESULT: To test the hypothesis, we cocultured mouse embryonic stem (ES cells with the endodermal cell line End2 by co-aggregation or End2-conditioned medium. Co-aggregation resulted in strong induction of Flk1(+ PDGFRa(+ CPCs in a dose-dependent manner, but the conditioned medium did not, indicating that direct contact is necessary for this process. To determine if direct contact with End2 cells also promotes the induction of committed cardiac progenitors, we utilized several mouse ES and induced pluripotent (iPS cell lines expressing fluorescent proteins under regulation of the CPC lineage markers Nkx2.5 or Isl1. In agreement with earlier data, co-aggregation with End2 cells potently induces both Nkx2.5(+ and Isl1(+ CPCs, leading to a sheet of beating cardiomyocytes. Furthermore, co-aggregation with End2 cells greatly promotes the induction of KDR(+ PDGFRa(+ CPCs from human ES cells. CONCLUSIONS: Our co-aggregation method provides an efficient, simple and cost-effective way to induce CPCs from mouse and human pluripotent cells.

  11. Time-dependent contact behavior between diamond and a CNT turf

    International Nuclear Information System (INIS)

    Qiu, A; Bahr, D F; Fowler, S P; Jiao, J; Kiener, D

    2011-01-01

    The elastic and adhesive properties of nominally vertically aligned carbon nanotube (CNT) turfs have been measured using nanoindentation. The perceived stiffness of a CNT turf is dependent on the unloading rate, which decreases at slower unloading rates. Depth-controlled nanoindentation was used to examine adhesion effects. Adhesive loads between the turf and the probe tip increased as the time the tip is in contact with the turf increased. As these effects could be from either more tubes coming into contact with the tip due to relaxation and motion of CNTs relative to one another or each tube in contact increasing its adhesive behavior and sub-contact stiffness due to tube-tube interactions within the turf, electrical resistance measurements during nanoindentation were carried out. When the tip is held at a fixed nominal depth, the current remains constant while the contact load decreases, suggesting the number of tubes in contact with the tip stays constant with time while the relaxation mechanisms in the turf occur at positions lower than the contact surface. These observations, in conjunction with in situ TEM compression test of CNT arrays, are used to describe the relative effects the various length and time scales may have on the perceived properties measured during experiments, including elastic modulus and adhesion for gecko-like dry adhesives.

  12. Time-dependent contact behavior between diamond and a CNT turf

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, A; Bahr, D F [School of Mechanical and Materials Engineering, Washington State University, 99164-2920 WA (United States); Fowler, S P; Jiao, J [Department of Physics, Portland State University, Portland, 97207-0751 OR (United States); Kiener, D, E-mail: anqi_qiu@wsu.edu, E-mail: dbahr@wsu.edu [Department of Materials Physics, University of Leoben, A-8700 Leoben (Austria)

    2011-07-22

    The elastic and adhesive properties of nominally vertically aligned carbon nanotube (CNT) turfs have been measured using nanoindentation. The perceived stiffness of a CNT turf is dependent on the unloading rate, which decreases at slower unloading rates. Depth-controlled nanoindentation was used to examine adhesion effects. Adhesive loads between the turf and the probe tip increased as the time the tip is in contact with the turf increased. As these effects could be from either more tubes coming into contact with the tip due to relaxation and motion of CNTs relative to one another or each tube in contact increasing its adhesive behavior and sub-contact stiffness due to tube-tube interactions within the turf, electrical resistance measurements during nanoindentation were carried out. When the tip is held at a fixed nominal depth, the current remains constant while the contact load decreases, suggesting the number of tubes in contact with the tip stays constant with time while the relaxation mechanisms in the turf occur at positions lower than the contact surface. These observations, in conjunction with in situ TEM compression test of CNT arrays, are used to describe the relative effects the various length and time scales may have on the perceived properties measured during experiments, including elastic modulus and adhesion for gecko-like dry adhesives.

  13. Molar volume and adsorption isotherm dependence of capillary forces in nanoasperity contacts.

    Science.gov (United States)

    Asay, David B; Kim, Seong H

    2007-11-20

    The magnitude of the capillary force at any given temperature and adsorbate partial pressure depends primarily on four factors: the surface tension of the adsorbate, its liquid molar volume, its isothermal behavior, and the contact geometry. At large contacting radii, the adsorbate surface tension and the contact geometry are dominating. This is the case of surface force apparatus measurements and atomic force microscopy (AFM) experiments with micrometer-size spheres. However, as the size of contacting asperities decreases to the nanoscale as in AFM experiments with sharp tips, the molar volume and isotherm of the adsorbate become very important to capillary formation as well as capillary adhesion. This effect is experimentally and theoretically explored with simple alcohol molecules (ethanol, 1-butanol, and 1-pentanol) which have comparable surface tensions but differing liquid molar volumes. Adsorption isotherms for these alcohols on silicon oxide are also reported.

  14. How nonuniform contact profiles of T cell receptors modulate thymic selection outcomes

    Science.gov (United States)

    Chen, Hanrong; Chakraborty, Arup K.; Kardar, Mehran

    2018-03-01

    T cell receptors (TCRs) bind foreign or self-peptides attached to major histocompatibility complex (MHC) molecules, and the strength of this interaction determines T cell activation. Optimizing the ability of T cells to recognize a diversity of foreign peptides yet be tolerant of self-peptides is crucial for the adaptive immune system to properly function. This is achieved by selection of T cells in the thymus, where immature T cells expressing unique, stochastically generated TCRs interact with a large number of self-peptide-MHC; if a TCR does not bind strongly enough to any self-peptide-MHC, or too strongly with at least one self-peptide-MHC, the T cell dies. Past theoretical work cast thymic selection as an extreme value problem and characterized the statistical enrichment or depletion of amino acids in the postselection TCR repertoire, showing how T cells are selected to be able to specifically recognize peptides derived from diverse pathogens yet have limited self-reactivity. Here, we investigate how the diversity of the postselection TCR repertoire is modified when TCRs make nonuniform contacts with peptide-MHC. Specifically, we were motivated by recent experiments showing that amino acids at certain positions of a TCR sequence have large effects on thymic selection outcomes, and crystal structure data that reveal a nonuniform contact profile between a TCR and its peptide-MHC ligand. Using a representative TCR contact profile as an illustration, we show via simulations that the statistical enrichment or depletion of amino acids now varies by position according to the contact profile, and, importantly, it depends on the implementation of nonuniform contacts during thymic selection. We explain these nontrivial results analytically. Our study has implications for understanding the selection forces that shape the functionality of the postselection TCR repertoire.

  15. From interatomic interaction potentials via Einstein field equation techniques to time dependent contact mechanics

    International Nuclear Information System (INIS)

    Schwarzer, N

    2014-01-01

    In order to understand the principle differences between rheological or simple stress tests like the uniaxial tensile test to contact mechanical tests and the differences between quasistatic contact experiments and oscillatory ones, this study resorts to effective first principles. This study will show how relatively simple models simulating bond interactions in solids using effective potentials like Lennard-Jones and Morse can be used to investigate the effect of time dependent stress-induced softening or stiffening of these solids. The usefulness of the current study is in the possibility of deriving relatively simple dependences of the bulk-modulus B on time, shear and pressure P with time t. In cases where it is possible to describe, or at least partially describe a material by Lennard-Jones potential approaches, the above- mentioned dependences are even completely free of microscopic material parameters. Instead of bond energies and length, only specific integral parameters like Young’s modulus and Poisson’s ratio are required. However, in the case of time dependent (viscose) material behavior the parameters are not constants anymore. They themselves depend on time and the actual stress field, especially the shear field. A body completely consisting of so called standard linear solid interacting particles will then phenomenologically show a completely different and usually much more complicated mechanical behavior. The influence of the time dependent pressure-shear-induced Young’s modulus change is discussed with respect to mechanical contact experiments and their analysis in the case of viscose materials. (papers)

  16. The role of adhesion energy in controlling cell?cell contacts

    OpenAIRE

    Ma?tre, Jean-L?on; Heisenberg, Carl-Philipp

    2011-01-01

    Recent advances in microscopy techniques and biophysical measurements have provided novel insight into the molecular, cellular and biophysical basis of cell adhesion. However, comparably little is known about a core element of cell?cell adhesion?the energy of adhesion at the cell?cell contact. In this review, we discuss approaches to understand the nature and regulation of adhesion energy, and propose strategies to determine adhesion energy between cells in vitro and in vivo.

  17. Back-contacted back-junction silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Mangersnes, Krister

    2010-10-15

    Conventional silicon solar cells have a front-side contacted emitter. Back-contacted back-junction (BC-BJ) silicon solar cells, on the other hand, have both the complete metallization and the active diffused regions of both polarities on the backside. World-record efficiencies have already been demonstrated for this type of cell design in production, both on cell and module level. However, the production of these cells is both complex and costly, and a further cost reduction in fabrication is needed to make electricity from BC-BJ silicon solar cells cost-competitive with electricity on the grid ('grid-parity'). During the work with this thesis, we have investigated several important issues regarding BC-BJ silicon solar cells. The aim has been to reduce production cost and complexity while at the same time maintaining, or increasing, the already high conversion efficiencies demonstrated elsewhere. This has been pursued through experimental work as well as through numerical simulations and modeling. Six papers are appended to this thesis, two of which are still under review in scientific journals. In addition, two patents have been filed based on the work presented herein. Experimentally, we have focused on investigating and optimizing single, central processing steps. A laser has been the key processing tool during most of the work. We have used the same laser both to structure the backside of the cell and to make holes in a double-layer of passivating amorphous silicon and silicon oxide, where the holes were opened with the aim of making local contact to the underlying silicon. The processes developed have the possibility of using a relatively cheap and industrially proven laser and obtain results better than most state-of-the-art laser technologies. During the work with the laser, we also developed a thermodynamic model that was able to predict the outcome from laser interaction with amorphous and crystalline silicon. Alongside the experimental work, we

  18. Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.

    Science.gov (United States)

    Chen, Cong; Zhang, Ning; Li, Weizhong; Song, Yongchen

    2015-12-15

    Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.

  19. Time Dependent Frictional Changes in Ice due to Contact Area Changes

    Science.gov (United States)

    Sevostianov, V.; Lipovsky, B. P.; Rubinstein, S.; Dillavou, S.

    2017-12-01

    Sliding processes along the ice-bed interface of Earth's great ice sheets are the largest contributor to our uncertainty in future sea level rise. Laboratory experiments that have probed sliding processes have ubiquitously shown that ice-rock interfaces strengthen while in stationary contact (Schulson and Fortt, 2013; Zoet et al., 2013; McCarthy et al., 2017). This so-called frictional ageing effect may have profound consequences for ice sheet dynamics because it introduces the possibility of basal strength hysteresis. Furthermore this effect is quite strong in ice-rock interfaces (more than an order of magnitude more pronounced than in rock-rock sliding) and can double in frictional strength in a matter of minutes, much faster than most frictional aging (Dieterich, 1972; Baumberger and Caroli, 2006). Despite this importance, the underling physics of frictional ageing of ice remain poorly understood. Here we conduct laboratory experiments to image the microscopic points of contact along an ice-glass interface. We optically measure changes in the real area of contact over time using measurements of this reflected optical light intensity. We show that contact area increases with time of stationary contact. This result suggests that thermally enhanced creep of microscopic icy contacts is responsible for the much larger frictional ageing observed in ice-rock versus rock-rock interfaces. Furthermore, this supports a more physically detailed description of the thermal dependence of basal sliding than that used in the current generation of large scale ice sheet models.

  20. Nonlinear dynamics of contact interaction of a size-dependent plate supported by a size-dependent beam

    Science.gov (United States)

    Awrejcewicz, J.; Krysko, V. A.; Yakovleva, T. V.; Pavlov, S. P.; Krysko, V. A.

    2018-05-01

    A mathematical model of complex vibrations exhibited by contact dynamics of size-dependent beam-plate constructions was derived by taking the account of constraints between these structural members. The governing equations were yielded by variational principles based on the moment theory of elasticity. The centre of the investigated plate was supported by a beam. The plate and the beam satisfied the Kirchhoff/Euler-Bernoulli hypotheses. The derived partial differential equations (PDEs) were reduced to the Cauchy problems by the Faedo-Galerkin method in higher approximations, whereas the Cauchy problem was solved using a few Runge-Kutta methods. Reliability of results was validated by comparing the solutions obtained by qualitatively different methods. Complex vibrations were investigated with the help of methods of nonlinear dynamics such as vibration signals, phase portraits, Fourier power spectra, wavelet analysis, and estimation of the largest Lyapunov exponents based on the Rosenstein, Kantz, and Wolf methods. The effect of size-dependent parameters of the beam and plate on their contact interaction was investigated. It was detected and illustrated that the first contact between the size-dependent structural members implies chaotic vibrations. In addition, problems of chaotic synchronization between a nanoplate and a nanobeam were addressed.

  1. Extended synaptotagmins are Ca2+-dependent lipid transfer proteins at membrane contact sites.

    Science.gov (United States)

    Yu, Haijia; Liu, Yinghui; Gulbranson, Daniel R; Paine, Alex; Rathore, Shailendra S; Shen, Jingshi

    2016-04-19

    Organelles are in constant communication with each other through exchange of proteins (mediated by trafficking vesicles) and lipids [mediated by both trafficking vesicles and lipid transfer proteins (LTPs)]. It has long been known that vesicle trafficking can be tightly regulated by the second messenger Ca(2+), allowing membrane protein transport to be adjusted according to physiological demands. However, it remains unclear whether LTP-mediated lipid transport can also be regulated by Ca(2+) In this work, we show that extended synaptotagmins (E-Syts), poorly understood membrane proteins at endoplasmic reticulum-plasma membrane contact sites, are Ca(2+)-dependent LTPs. Using both recombinant and endogenous mammalian proteins, we discovered that E-Syts transfer glycerophospholipids between membrane bilayers in the presence of Ca(2+) E-Syts use their lipid-accommodating synaptotagmin-like mitochondrial lipid binding protein (SMP) domains to transfer lipids. However, the SMP domains themselves cannot transport lipids unless the two membranes are tightly tethered by Ca(2+)-bound C2 domains. Strikingly, the Ca(2+)-regulated lipid transfer activity of E-Syts was fully recapitulated when the SMP domain was fused to the cytosolic domain of synaptotagmin-1, the Ca(2+)sensor in synaptic vesicle fusion, indicating that a common mechanism of membrane tethering governs the Ca(2+)regulation of lipid transfer and vesicle fusion. Finally, we showed that microsomal vesicles isolated from mammalian cells contained robust Ca(2+)-dependent lipid transfer activities, which were mediated by E-Syts. These findings established E-Syts as a novel class of LTPs and showed that LTP-mediated lipid trafficking, like vesicular transport, can be subject to tight Ca(2+)regulation.

  2. The aryl hydrocarbon receptor-dependent disruption of contact inhibition in rat liver WB-F344 epithelial cells is linked with induction of survivin, but not with inhibition of apoptosis

    Czech Academy of Sciences Publication Activity Database

    Svobodová, Jana; Kabátková, Markéta; Šmerdová, Lenka; Brenerová, P.; Dvořák, Z.; Machala, M.; Vondráček, Jan

    2015-01-01

    Roč. 333, JUL 2015 (2015), s. 37-44 ISSN 0300-483X R&D Projects: GA ČR(CZ) GA13-07711S Institutional support: RVO:68081707 Keywords : TUMOR PROMOTION * AH RECEPTOR * STEM-CELLS Subject RIV: BO - Biophysics Impact factor: 3.817, year: 2015

  3. Temperature-dependent imaging of living cells by AFM

    International Nuclear Information System (INIS)

    Espenel, Cedric; Giocondi, Marie-Cecile; Seantier, Bastien; Dosset, Patrice; Milhiet, Pierre-Emmanuel; Le Grimellec, Christian

    2008-01-01

    Characterization of lateral organization of plasma membranes is a prerequisite to the understanding of membrane structure-function relationships in living cells. Lipid-lipid and lipid-protein interactions are responsible for the existence of various membrane microdomains involved in cell signalization and in numerous pathologies. Developing approaches for characterizing microdomains associate identification tools like recognition imaging with high-resolution topographical imaging. Membrane properties are markedly dependent on temperature. However, mesoscopic scale topographical information of cell surface in a temperature range covering most of cell biology experimentation is still lacking. In this work we have examined the possibility of imaging the temperature-dependent behavior of eukaryotic cells by atomic force microscopy (AFM). Our results establish that the surface of living CV1 kidney cells can be imaged by AFM, between 5 and 37 deg. C, both in contact and tapping modes. These first temperature-dependent data show that large cell structures appeared essentially stable at a microscopic scale. On the other hand, as shown by contact mode AFM, the surface was highly dynamic at a mesoscopic scale, with marked changes in apparent topography, friction, and deflection signals. When keeping the scanning conditions constant, a progressive loss in the image contrast was however observed, using tapping mode, on decreasing the temperature

  4. In vitro reestablishment of cell-cell contacts in adult rat cardiomyocytes. Functional role of transmembrane components in the formation of new intercalated disk-like cell contacts.

    Science.gov (United States)

    Eppenberger, H M; Zuppinger, C

    1999-01-01

    Primary adult rat cardiomyocytes (ARC)in culture are shown to be a model system for cardiac cell hypertrophy in vitro. ARC undergo a process of morphological transformation and grow only by increase in cell size, however, without loss of the cardiac phenotype. The isolated cells spread and establish new cell-cell contacts, eventually forming a two-dimensional heart tissue-like synchronously beating cell sheet. The reformation of specific cell contacts (intercalated disks) is shown also between ventricular and atrial cardiomyocytes by using antibodies against the gap junction protein connexin-43 and after microinjection into ARC of N-cadherin cDNA fused to reporter green fluorescent protein (GFP) cDNA. The expressed fusion protein allowed the study of live cell cultures and of the dynamics of the adherens junction protein N-cadherin during the formation of new cell-cell contacts. The possible use of the formed ARC cell-sheet cells under microgravity conditions as a test system for the reformation of the cytoskeleton of heart muscle cells is proposed.

  5. Conductance of single-atom platinum contacts: Voltage dependence of the conductance histogram

    DEFF Research Database (Denmark)

    Nielsen, S.K.; Noat, Y.; Brandbyge, Mads

    2003-01-01

    The conductance of a single-atom contact is sensitive to the coupling of this contact atom to the atoms in the leads. Notably for the transition metals this gives rise to a considerable spread in the observed conductance values. The mean conductance value and spread can be obtained from the first...... peak in conductance histograms recorded from a large set of contact-breaking cycles. In contrast to the monovalent metals, this mean value for Pt depends strongly on the applied voltage bias and other experimental conditions and values ranging from about 1 G(0) to 2.5 G(0) (G(0)=2e(2)/h) have been...... reported. We find that at low bias the first peak in the conductance histogram is centered around 1.5 G(0). However, as the bias increases past 300 mV the peak shifts to 1.8 G(0). Here we show that this bias dependence is due to a geometric effect where monatomic chains are replaced by single-atom contacts...

  6. Kalker's algorithm Fastsim solves tangential contact problems with slip-dependent friction and friction anisotropy

    Science.gov (United States)

    Piotrowski, J.

    2010-07-01

    This paper presents two extensions of Kalker's algorithm Fastsim of the simplified theory of rolling contact. The first extension is for solving tangential contact problems with the coefficient of friction depending on slip velocity. Two friction laws have been considered: with and without recuperation of the static friction. According to the tribological hypothesis for metallic bodies shear failure, the friction law without recuperation of static friction is more suitable for wheel and rail than the other one. Sample results present local quantities inside the contact area (division to slip and adhesion, traction) as well as global ones (creep forces as functions of creepages and rolling velocity). For the coefficient of friction diminishing with slip, the creep forces decay after reaching the maximum and they depend on the rolling velocity. The second extension is for solving tangential contact problems with friction anisotropy characterised by a convex set of the permissible tangential tractions. The effect of the anisotropy has been shown on examples of rolling without spin and in the presence of pure spin for the elliptical set. The friction anisotropy influences tangential tractions and creep forces. Sample results present local and global quantities. Both extensions have been described with the same language of formulation and they may be merged into one, joint algorithm.

  7. Role of Firing Temperature, Sheet Resistance, and Contact Area in Contact Formation on Screen-Printed Metal Contact of Silicon Solar Cell

    Science.gov (United States)

    Ahmad, Samir Mahmmod; Leong, Cheow Siu; Sopian, K.; Zaidi, Saleem H.

    2018-03-01

    Formation of an Ohmic contact requires a suitable firing temperature, appropriate doping profile, and contact dimensions within resolution limits of the screen-printing process. In this study, the role of the peak firing temperature in standard rapid thermal annealing (RTA) six-zone conveyor belt furnace (CBF) and two inexpensive alternate RTA systems [a custom-designed, three-zone, 5″-diameter quartz tube furnace (QTF) and a tabletop, 3″-diameter rapid thermal processing (RTP)] has been investigated. In addition, the role of sheet resistance and contact area in achieving low-resistance ohmic contacts has been examined. Electrical measurements of ohmic contacts between silver paste/ n +-emitter layer with varying sheet resistances and aluminum paste/ p-doped wafer were carried out in transmission line method configuration. Experimental measurements of the contact resistivity ( ρ c) exhibited the lowest values for CBF at 0.14 mΩ cm2 for Ag and 100 mΩ cm2 for Al at a peak firing temperature of 870°C. For the QTF configuration, lowest measured contact resistivities were 3.1 mΩ cm2 for Ag and 74.1 mΩ cm2 for Al at a peak firing temperature of 925°C. Finally, for the RTP configuration, lowest measured contact resistivities were 1.2 mΩ cm2 for Ag and 68.5 mΩ cm2 for Al at a peak firing temperature of 780°C. The measured contact resistivity exhibits strong linear dependence on sheet resistance. The contact resistivity for Ag decreases with contact area, while for Al the opposite behavior is observed.

  8. Solar cell contact pull strength as a function of pull-test temperature

    Science.gov (United States)

    Yasui, R. K.; Berman, P. A.

    1972-01-01

    Four types of solar cell contacts were given pull-strength tests at temperatures between -173 and +165 C. Contacts tested were: (1) solder-coated titanium-silver contacts on n-p cells, (2) palladium-containing titanium-silver contacts on n-p cells, (3) titanium-silver contacts on 0.2-mm-thick n-p cells, and (4) solder-coated electroless-nickel-plated contacts on p-n cells. Maximum pull strength was demonstrated at temperatures significantly below the air mass zero cell equilibrium temperature of +60 C. At the lowest temperatures, the chief failure mechanism was silicon fracture along crystallographic planes; at the highest temperatures, it was loss of solder strength. In the intermediate temperatures, many failure mechanisms operated. Pull-strength tests give a good indication of the suitability of solar cell contact systems for space use. Procedures used to maximize the validity of the results are described.

  9. [Exercise contacts in the treatment of substance dependence and mental disorders].

    Science.gov (United States)

    Skrede, Atle; Munkvold, Harald; Watne, Øyvind; Martinsen, Egil W

    2006-08-10

    Physical exercise is useful for individuals with mental disorders with additional substance dependency or abuse. Many exercise actively while in institution, but a major challenge is to continue after discharge. Many patients are isolated and lonely and find it hard to motivate themselves to exercise on their own. In Sogn og Fjordane county, Norway, the problem was dealt with through a training program of exercise contacts. These are social support persons who were thus assigned a new function. By way of a 40-hour course that covered physical activity, psychological problems, and substance abuse and dependency, lay people were trained to help people in their home environment. By the end of 2005, almost 300 exercise contacts, living in 25 of the 26 municipalities in the county, had passed the course exam. Their expertise is highly demanded and more courses have been requested. The course evaluations have been quite positive. In particular, the practical instructions about how to exercise, in combination with updated theory on substance abuse/dependence and mental disorders, were highly appreciated. Clients were helped to continue with regular physical activity and they have appreciated the improved physical and mental health that was associated with regular exercise. Moreover, the exercise contacts help clients break social isolation and have given them access to the common social arenas.

  10. Industrially feasible, dopant-free, carrier-selective contacts for high-efficiency silicon solar cells

    KAUST Repository

    Yang, Xinbo; Weber, Klaus; Hameiri, Ziv; De Wolf, Stefaan

    2017-01-01

    quality and cell processing, a remarkable efficiency of 22.1% has been achieved using an n-type silicon solar cell featuring a full-area TiO contact. Next, we demonstrate the compatibility of TiO contacts with an industrial contact-firing process, its low

  11. Back contact to film silicon on metal for photovoltaic cells

    Science.gov (United States)

    Branz, Howard M.; Teplin, Charles; Stradins, Pauls

    2013-06-18

    A crystal oriented metal back contact for solar cells is disclosed herein. In one embodiment, a photovoltaic device and methods for making the photovoltaic device are disclosed. The photovoltaic device includes a metal substrate with a crystalline orientation and a heteroepitaxial crystal silicon layer having the same crystal orientation of the metal substrate. A heteroepitaxial buffer layer having the crystal orientation of the metal substrate is positioned between the substrate and the crystal silicon layer to reduce diffusion of metal from the metal foil into the crystal silicon layer and provide chemical compatibility with the heteroepitaxial crystal silicon layer. Additionally, the buffer layer includes one or more electrically conductive pathways to electrically couple the crystal silicon layer and the metal substrate.

  12. Characterization of Time-Dependent Contact Angles for Oleic Acid Mixed Sands with Different Particle Size Fractions

    DEFF Research Database (Denmark)

    Wijewardana, Y. N. S.; Kawamoto, Ken; Komatsu, Toshiko

    2014-01-01

    ) mixed sands representing four different particle size fractions ranging from 0.105 to 0.84 mm. Initial soil-water contact angle (αi), and the time dependence of contact angle were measured by the sessile drop method. Results showed that the αi value for fine and middle sand fractions increased rapidly...... in contact angle (α), well captured the time dependence of α....

  13. Adherens junction distribution mechanisms during cell-cell contact elongation in Drosophila.

    Directory of Open Access Journals (Sweden)

    Gabrielle Goldenberg

    Full Text Available During Drosophila gastrulation, amnioserosa (AS cells flatten and spread as an epithelial sheet. We used AS morphogenesis as a model to investigate how adherens junctions (AJs distribute along elongating cell-cell contacts in vivo. As the contacts elongated, total AJ protein levels increased along their length. However, genetically blocking this AJ addition indicated that it was not essential for maintaining AJ continuity. Implicating other remodeling mechanisms, AJ photobleaching revealed non-directional lateral mobility of AJs along the elongating contacts, as well as local AJ removal from the membranes. Actin stabilization with jasplakinolide reduced AJ redistribution, and live imaging of myosin II along elongating contacts revealed fragmented, expanding and contracting actomyosin networks, suggesting a mechanism for lateral AJ mobility. Actin stabilization also increased total AJ levels, suggesting an inhibition of AJ removal. Implicating AJ removal by endocytosis, clathrin endocytic machinery accumulated at AJs. However, dynamin disruption had no apparent effect on AJs, suggesting the involvement of redundant or dynamin-independent mechanisms. Overall, we propose that new synthesis, lateral diffusion, and endocytosis play overlapping roles to populate elongating cell-cell contacts with evenly distributed AJs in this in vivo system.

  14. PHYSICAL CONTACT BETWEEN HUMAN VASCULAR ENDOTHELIAL AND SMOOTH MUSCLE CELLS MODULATES CYTOSOLIC AND NUCLEAR CALCIUM HOMEOSTASIS.

    Science.gov (United States)

    Hassan, Ghada S; Jacques, Danielle; D'Orleans-Juste, Pedro; Magder, Sheldon; Bkaily, Ghassan

    2018-05-14

    The interaction between vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs) plays an important role in the modulation of vascular tone. There is however no information on whether direct physical communication regulates the intracellular calcium levels of human VECs (hVECs) and/or hVSMCs . Thus, the objective of the study is to verify whether co-culture of hVECs and hVSMCs modulates cytosolic ([Ca2+]c) and nuclear calcium ([Ca2+]n) levels via physical contact and/or factors released by both cell types. Quantitative 3D confocal microscopy for [Ca2+]c and [Ca2+]n measurement was performed in cultured hVECs or hVSMCs or in co-culture of hVECs-hVSMCs. Our results show that: 1) physical contact between hVECs-hVECs or hVSMCs-hVSMCs does not affect [Ca2+]c and [Ca2+]n in these two cell types; 2) physical contact between hVECs and hVSMCs induces a significant increase only of [Ca2+]n of hVECs without affecting the level of [Ca2+]c and [Ca2+]n of hVSMCs; and 3) preconditioned culture medium of hVECs or hVSMCs does not affect [Ca2+]c and [Ca2+]n of both types of cells. We concluded that physical contact between hVECs and hVSMCs only modulates [Ca2+]n in hVECs. The increase of [Ca2+]n in hVECs may modulate nuclear functions that are calcium dependent.

  15. Short-lived, transitory cell-cell interactions foster migration-dependent aggregation.

    Directory of Open Access Journals (Sweden)

    Melissa D Pope

    Full Text Available During embryonic development, motile cells aggregate into cohesive groups, which give rise to tissues and organs. The role of cell migration in regulating aggregation is unclear. The current paradigm for aggregation is based on an equilibrium model of differential cell adhesivity to neighboring cells versus the underlying substratum. In many biological contexts, however, dynamics is critical. Here, we provide evidence that multicellular aggregation dynamics involves both local adhesive interactions and transport by cell migration. Using time-lapse video microscopy, we quantified the duration of cell-cell contacts among migrating cells that collided and adhered to another cell. This lifetime of cell-cell interactions exhibited a monotonic decreasing dependence on substratum adhesivity. Parallel quantitative measurements of cell migration speed revealed that across the tested range of adhesive substrata, the mean time needed for cells to migrate and encounter another cell was greater than the mean adhesion lifetime, suggesting that aggregation dynamics may depend on cell motility instead of the local differential adhesivity of cells. Consistent with this hypothesis, aggregate size exhibited a biphasic dependence on substratum adhesivity, matching the trend we observed for cell migration speed. Our findings suggest a new role for cell motility, alongside differential adhesion, in regulating developmental aggregation events and motivate new design principles for tuning aggregation dynamics in tissue engineering applications.

  16. Proteomics analysis of dendritic cell activation by contact allergens reveals possible biomarkers regulated by Nrf2

    Energy Technology Data Exchange (ETDEWEB)

    Mussotter, Franz, E-mail: franz.mussotter@bfr.bund.de [German Federal Institute for Risk Assessment (BfR), Department of Chemical and Product Safety, Berlin (Germany); Tomm, Janina Melanie [Helmholtz Centre for Environmental Research (UFZ), Department of Molecular Systems Biology, Leipzig (Germany); El Ali, Zeina; Pallardy, Marc; Kerdine-Römer, Saadia [INSERM UMR 996, Univ Paris-Sud, Université Paris-Saclay, Chátenay-Malabry (France); Götz, Mario [German Federal Institute for Risk Assessment (BfR), Department of Chemical and Product Safety, Berlin (Germany); Bergen, Martin von [Helmholtz Centre for Environmental Research (UFZ), Department of Molecular Systems Biology, Leipzig (Germany); University of Leipzig, Institute of Biochemistry, Leipzig (Germany); Aalborg University, Department of Chemistry and Bioscience, Aalborg (Denmark); Haase, Andrea; Luch, Andreas [German Federal Institute for Risk Assessment (BfR), Department of Chemical and Product Safety, Berlin (Germany)

    2016-12-15

    Allergic contact dermatitis is a widespread disease with high clinical relevance affecting approximately 20% of the general population. Typically, contact allergens are low molecular weight electrophilic compounds which can activate the Keap1/Nrf2 pathway. We performed a proteomics study to reveal possible biomarkers for dendritic cell (DC) activation by contact allergens and to further elucidate the role of Keap1/Nrf2 signaling in this process. We used bone marrow derived dendritic cells (BMDCs) of wild-type (nrf2{sup +/+}) and Nrf2 knockout (nrf2{sup −/−}) mice and studied their response against the model contact sensitizers 2,4-dinitrochlorobenzene (DNCB), cinnamaldehyde (CA) and nickel(II) sulfate by 2-dimensional polyacrylamide gel electrophoresis (2D-PAGE) in combination with electrospray ionization tandem mass spectrometry (ESI-MS/MS). Sodium dodecyl sulfate (SDS, 100 μM) served as irritant control. While treatment with nickel(II) sulfate and SDS had only little effects, CA and DNCB led to significant changes in protein expression. We found 18 and 30 protein spots up-regulated in wild-type cells treated with 50 and 100 μM CA, respectively. For 5 and 10 μM DNCB, 32 and 37 spots were up-regulated, respectively. Almost all of these proteins were not differentially expressed in nrf2{sup −/−} BMDCs, indicating an Nrf2-dependent regulation. Among them proteins were detected which are involved in oxidative stress and heat shock responses, as well as in signal transduction or basic cellular pathways. The applied approach allowed us to differentiate between Nrf2-dependent and Nrf2-independent cellular biomarkers differentially regulated upon allergen-induced DC activation. The data presented might contribute to the further development of suitable in vitro testing methods for chemical-mediated sensitization. - Highlights: • Contact allergens induce proteins involved in DC maturation Nrf2-dependently. • Induction of these proteins points to a functional

  17. Process and structures for fabrication of solar cells with laser ablation steps to form contact holes

    Science.gov (United States)

    Harley, Gabriel; Smith, David D; Dennis, Tim; Waldhauer, Ann; Kim, Taeseok; Cousins, Peter John

    2013-11-19

    Contact holes of solar cells are formed by laser ablation to accomodate various solar cell designs. Use of a laser to form the contact holes is facilitated by replacing films formed on the diffusion regions with a film that has substantially uniform thickness. Contact holes may be formed to deep diffusion regions to increase the laser ablation process margins. The laser configuration may be tailored to form contact holes through dielectric films of varying thickness.

  18. Contact area affects frequency-dependent responses to vibration in the peripheral vascular and sensorineural systems.

    Science.gov (United States)

    Krajnak, Kristine; Miller, G R; Waugh, Stacey

    2018-01-01

    Repetitive exposure to hand-transmitted vibration is associated with development of peripheral vascular and sensorineural dysfunctions. These disorders and symptoms associated with it are referred to as hand-arm vibration syndrome (HAVS). Although the symptoms of the disorder have been well characterized, the etiology and contribution of various exposure factors to development of the dysfunctions are not well understood. Previous studies performed using a rat-tail model of vibration demonstrated that vascular and peripheral nervous system adverse effects of vibration are frequency-dependent, with vibration frequencies at or near the resonant frequency producing the most severe injury. However, in these investigations, the amplitude of the exposed tissue was greater than amplitude typically noted in human fingers. To determine how contact with vibrating source and amplitude of the biodynamic response of the tissue affects the risk of injury occurring, this study compared the influence of frequency using different levels of restraint to assess how maintaining contact of the tail with vibrating source affects the transmission of vibration. Data demonstrated that for the most part, increasing the contact of the tail with the platform by restraining it with additional straps resulted in an enhancement in transmission of vibration signal and elevation in factors associated with vascular and peripheral nerve injury. In addition, there were also frequency-dependent effects, with exposure at 250 Hz generating greater effects than vibration at 62.5 Hz. These observations are consistent with studies in humans demonstrating that greater contact and exposure to frequencies near the resonant frequency pose the highest risk for generating peripheral vascular and sensorineural dysfunction.

  19. Reducing the substrate dependent scanner leveling effect in low-k1 contact printing

    Science.gov (United States)

    Chang, C. S.; Tseng, C. F.; Huang, C. H.; Yang, Elvis; Yang, T. H.; Chen, K. C.

    2015-03-01

    As the scaling down of design rule for high-density memory device, the small depth of focus (DoF) budget may be deteriorated by focus leveling errors, which arises in unpredicted reflectivity from multilayer structures on the topographic wafer. The leveling sensors of ASML scanner use near infrared (NIR) range wavelength which can penetrate through most of films using in semiconductor fabrication such as photo-resist, bottom anti reflective coating (BARC) and dielectric materials. Consequently, the reflected light from underlying substructures would disturb leveling sensors from accurate leveling. The different pattern densities and layout characteristics between array and periphery of a memory chip are expected to result in different leveling signals. Furthermore, the process dependent variations between wafer central and edge areas are also considered to yield different leveling performances during wafer exposure. In this study, lower blind contact immunity was observed for peripheral contacts comparing to the array contacts especially around wafer edge region. In order to overcome this problem, a series of investigations have been carried out. The wafer edge leveling optimization through circuit dependent focus edge clearance (CDFEC) option doesn't get improvement. Air gauge improved process leveling (AGILE) function of ASML immersion scanner doesn't show improved result either. The ILD uniformity improvement and step height treatments around wafer edge such as edge exclusion of film deposition and bevel etching are also ineffective to mitigate the blind contact problem of peripheral patterns. Altering the etch hard-mask stack is finally found to be an effective approach to alleviate the issue. For instance, through either containing high temperature deposition advanced patterning film (APF) in the hard-mask or inserting higher opaque film such as amorphous Si in between the hard-mask stack.

  20. Inactive end cell assembly for fuel cells for improved electrolyte management and electrical contact

    Science.gov (United States)

    Yuh, Chao-Yi [New Milford, CT; Farooque, Mohammad [Danbury, CT; Johnsen, Richard [New Fairfield, CT

    2007-04-10

    An assembly for storing electrolyte in a carbonate fuel cell is provided. The combination of a soft, compliant and resilient cathode current collector and an inactive anode part including a foam anode in each assembly mitigates electrical contact loss during operation of the fuel cell stack. In addition, an electrode reservoir in the positive end assembly and an electrode sink in the negative end assembly are provided, by which ribbed and flat cathode members inhibit electrolyte migration in the fuel cell stack.

  1. Contact- and Protein Transfer-Dependent Stimulation of Assembly of the Gliding Motility Machinery in Myxococcus xanthus.

    Directory of Open Access Journals (Sweden)

    Beata Jakobczak

    2015-07-01

    Full Text Available Bacteria engage in contact-dependent activities to coordinate cellular activities that aid their survival. Cells of Myxococcus xanthus move over surfaces by means of type IV pili and gliding motility. Upon direct contact, cells physically exchange outer membrane (OM lipoproteins, and this transfer can rescue motility in mutants lacking lipoproteins required for motility. The mechanism of gliding motility and its stimulation by transferred OM lipoproteins remain poorly characterized. We investigated the function of CglC, GltB, GltA and GltC, all of which are required for gliding. We demonstrate that CglC is an OM lipoprotein, GltB and GltA are integral OM β-barrel proteins, and GltC is a soluble periplasmic protein. GltB and GltA are mutually stabilizing, and both are required to stabilize GltC, whereas CglC accumulate independently of GltB, GltA and GltC. Consistently, purified GltB, GltA and GltC proteins interact in all pair-wise combinations. Using active fluorescently-tagged fusion proteins, we demonstrate that GltB, GltA and GltC are integral components of the gliding motility complex. Incorporation of GltB and GltA into this complex depends on CglC and GltC as well as on the cytoplasmic AglZ protein and the inner membrane protein AglQ, both of which are components of the gliding motility complex. Conversely, incorporation of AglZ and AglQ into the gliding motility complex depends on CglC, GltB, GltA and GltC. Remarkably, physical transfer of the OM lipoprotein CglC to a ΔcglC recipient stimulates assembly of the gliding motility complex in the recipient likely by facilitating the OM integration of GltB and GltA. These data provide evidence that the gliding motility complex in M. xanthus includes OM proteins and suggest that this complex extends from the cytoplasm across the cell envelope to the OM. These data add assembly of gliding motility complexes in M. xanthus to the growing list of contact-dependent activities in bacteria.

  2. Shape Optimization in Contact Problems with Coulomb Friction and a Solution-Dependent Friction Coefficient

    Czech Academy of Sciences Publication Activity Database

    Beremlijski, P.; Outrata, Jiří; Haslinger, Jaroslav; Pathó, R.

    2014-01-01

    Roč. 52, č. 5 (2014), s. 3371-3400 ISSN 0363-0129 R&D Projects: GA ČR(CZ) GAP201/12/0671 Grant - others:GA MŠK(CZ) CZ.1.05/1.1.00/02.0070; GA MŠK(CZ) CZ.1.07/2.3.00/20.0070 Institutional support: RVO:67985556 ; RVO:68145535 Keywords : shape optimization * contact problems * Coulomb friction * solution-dependent coefficient of friction * mathematical programs with equilibrium constraints Subject RIV: BA - General Mathematics Impact factor: 1.463, year: 2014 http://library.utia.cas.cz/separaty/2014/MTR/outrata-0434234.pdf

  3. Polycomb-dependent regulatory contacts between distant Hox loci in Drosophila

    DEFF Research Database (Denmark)

    Bantignies, Frédéric; Roure, Virginie; Comet, Itys

    2011-01-01

    In Drosophila melanogaster, Hox genes are organized in an anterior and a posterior cluster, called Antennapedia complex and bithorax complex, located on the same chromosome arm and separated by 10 Mb of DNA. Both clusters are repressed by Polycomb group (PcG) proteins. Here, we show that genes...... of the two Hox complexes can interact within nuclear PcG bodies in tissues where they are corepressed. This colocalization increases during development and depends on PcG proteins. Hox gene contacts are conserved in the distantly related Drosophila virilis species and they are part of a large gene...

  4. Strong temperature dependence of extraordinary magnetoresistance correlated to mobility in a two-contact device

    KAUST Repository

    Sun, Jian

    2012-02-21

    A two-contact extraordinary magnetoresistance (EMR) device has been fabricated and characterized at various temperatures under magnetic fields applied in different directions. Large performance variations across the temperature range have been found, which are due to the strong dependence of the EMR effect on the mobility. The device shows the highest sensitivity of 562ω/T at 75 K with the field applied perpendicularly. Due to the overlap between the semiconductor and the metal shunt, the device is also sensitive to planar fields but with a lower sensitivity of about 20 to 25% of the one to perpendicular fields. © 2012 The Japan Society of Applied Physics.

  5. Mesenchymal Stem Cells Induce Epithelial to Mesenchymal Transition in Colon Cancer Cells through Direct Cell-to-Cell Contact

    Directory of Open Access Journals (Sweden)

    Hidehiko Takigawa

    2017-05-01

    Full Text Available We previously reported that in an orthotopic nude mouse model of human colon cancer, bone marrow–derived mesenchymal stem cells (MSCs migrated to the tumor stroma and promoted tumor growth and metastasis. Here, we evaluated the proliferation and migration ability of cancer cells cocultured with MSCs to elucidate the mechanism of interaction between cancer cells and MSCs. Proliferation and migration of cancer cells increased following direct coculture with MSCs but not following indirect coculture. Thus, we hypothesized that direct contact between cancer cells and MSCs was important. We performed a microarray analysis of gene expression in KM12SM colon cancer cells directly cocultured with MSCs. Expression of epithelial-mesenchymal transition (EMT–related genes such as fibronectin (FN, SPARC, and galectin 1 was increased by direct coculture with MSCs. We also confirmed the upregulation of these genes with real-time polymerase chain reaction. Gene expression was not elevated in cancer cells indirectly cocultured with MSCs. Among the EMT-related genes upregulated by direct coculture with MSCs, we examined the immune localization of FN, a well-known EMT marker. In coculture assay in chamber slides, expression of FN was seen only at the edges of cancer clusters where cancer cells directly contacted MSCs. FN expression in cancer cells increased at the tumor periphery and invasive edge in orthotopic nude mouse tumors and human colon cancer tissues. These results suggest that MSCs induce EMT in colon cancer cells via direct cell-to-cell contact and may play an important role in colon cancer metastasis.

  6. Constructal Optimization of Top Contact Metallization of a Photovoltaic Solar Cell

    OpenAIRE

    Bhakta, Aditya; Bandyopadhyay, Santanu

    2010-01-01

    A top contact metallization of a photovoltaic solar cell collects the current generated by incident solar radiation. Several power-loss mechanisms are associated with the current flow through the front contact grid. The design of the top metal contact grid is one of the most important areas of efficient photovoltaic solar cell design. In this paper, an approach based on the constructal theory is proposed to design the grid pattern in a photovoltaic solar cell, minimizing total resistive losse...

  7. Non-motor outcomes of subthalamic stimulation in Parkinson's disease depend on location of active contacts.

    Science.gov (United States)

    Dafsari, Haidar Salimi; Petry-Schmelzer, Jan Niklas; Ray-Chaudhuri, K; Ashkan, Keyoumars; Weis, Luca; Dembek, Till A; Samuel, Michael; Rizos, Alexandra; Silverdale, Monty; Barbe, Michael T; Fink, Gereon R; Evans, Julian; Martinez-Martin, Pablo; Antonini, Angelo; Visser-Vandewalle, Veerle; Timmermann, Lars

    2018-03-16

    Subthalamic nucleus (STN) deep brain stimulation (DBS) improves quality of life (QoL), motor, and non-motor symptoms (NMS) in Parkinson's disease (PD). Few studies have investigated the influence of the location of neurostimulation on NMS. To investigate the impact of active contact location on NMS in STN-DBS in PD. In this prospective, open-label, multicenter study including 50 PD patients undergoing bilateral STN-DBS, we collected NMSScale (NMSS), NMSQuestionnaire (NMSQ), Hospital Anxiety and Depression Scale (anxiety/depression, HADS-A/-D), PDQuestionnaire-8 (PDQ-8), Scales for Outcomes in PD-motor examination, motor complications, activities of daily living (ADL), and levodopa equivalent daily dose (LEDD) preoperatively and at 6 months follow-up. Changes were analyzed with Wilcoxon signed-rank/t-test and Bonferroni-correction for multiple comparisons. Although the STN was targeted visually, we employed an atlas-based approach to explore the relationship between active contact locations and DBS outcomes. Based on fused MRI/CT-images, we identified Cartesian coordinates of active contacts with patient-specific Mai-atlas standardization. We computed linear mixed-effects models with x-/y-/z-coordinates as independent, hemispheres as within-subject, and test change scores as dependent variables. NMSS, NMSQ, PDQ-8, motor examination, complications, and LEDD significantly improved at follow-up. Linear mixed-effect models showed that NMS and QoL improvement significantly depended on more medial (HADS-D, NMSS), anterior (HADS-D, NMSQ, PDQ-8), and ventral (HADS-A/-D, NMSS, PDQ-8) neurostimulation. ADL improved more in posterior, LEDD in lateral neurostimulation locations. No relationship was observed for motor examination and complications scores. Our study provides evidence that more anterior, medial, and ventral STN-DBS is significantly related to more beneficial non-motor outcomes. Copyright © 2018. Published by Elsevier Inc.

  8. A Low Resistance Calcium/Reduced Titania Passivated Contact for High Efficiency Crystalline Silicon Solar Cells

    KAUST Repository

    Allen, Thomas G.

    2017-02-04

    Recent advances in the efficiency of crystalline silicon (c-Si) solar cells have come through the implementation of passivated contacts that simultaneously reduce recombination and resistive losses within the contact structure. In this contribution, low resistivity passivated contacts are demonstrated based on reduced titania (TiOx) contacted with the low work function metal, calcium (Ca). By using Ca as the overlying metal in the contact structure we are able to achieve a reduction in the contact resistivity of TiOx passivated contacts of up to two orders of magnitude compared to previously reported data on Al/TiOx contacts, allowing for the application of the Ca/TiOx contact to n-type c-Si solar cells with partial rear contacts. Implementing this contact structure on the cell level results in a power conversion efficiency of 21.8% where the Ca/TiOx contact comprises only ≈6% of the rear surface of the solar cell, an increase of 1.5% absolute compared to a similar device fabricated without the TiOx interlayer.

  9. IBC c-Si solar cells based on ion-implanted poly-silicon passivating contacts

    NARCIS (Netherlands)

    Yang, G.; Ingenito, A.; Isabella, O.; Zeman, M.

    2016-01-01

    Ion-implanted poly-crystalline silicon (poly-Si), in combination with a tunnel oxide layer, is investigated as a carrier-selective passivating contact in c-Si solar cells based on an interdigitated back contact (IBC) architecture. The optimized poly-Si passivating contacts enable low interface

  10. A Low Resistance Calcium/Reduced Titania Passivated Contact for High Efficiency Crystalline Silicon Solar Cells

    KAUST Repository

    Allen, Thomas G.; Bullock, James; Jeangros, Quentin; Samundsett, Christian; Wan, Yimao; Cui, Jie; Hessler-Wyser, Aï cha; De Wolf, Stefaan; Javey, Ali; Cuevas, Andres

    2017-01-01

    Recent advances in the efficiency of crystalline silicon (c-Si) solar cells have come through the implementation of passivated contacts that simultaneously reduce recombination and resistive losses within the contact structure. In this contribution, low resistivity passivated contacts are demonstrated based on reduced titania (TiOx) contacted with the low work function metal, calcium (Ca). By using Ca as the overlying metal in the contact structure we are able to achieve a reduction in the contact resistivity of TiOx passivated contacts of up to two orders of magnitude compared to previously reported data on Al/TiOx contacts, allowing for the application of the Ca/TiOx contact to n-type c-Si solar cells with partial rear contacts. Implementing this contact structure on the cell level results in a power conversion efficiency of 21.8% where the Ca/TiOx contact comprises only ≈6% of the rear surface of the solar cell, an increase of 1.5% absolute compared to a similar device fabricated without the TiOx interlayer.

  11. Enhancing cell proliferation by non-contact nanosecond PEF treatment of cell culture vials

    NARCIS (Netherlands)

    Bree, van J.W.M.; Geysen, J.J.G.; Pemen, A.J.M.

    2012-01-01

    The applicability of nanosecond pulsed electric fields (nsPEF) has been focused on killing of cells by means of direct contact between the nsPEF electrodes and tissue or liquid, such as in melanoma destruction [1] and sterilization of fluids. Here we present a novel, tabletop device that induces

  12. Pentazocine dependence among sickle cell disease patients ...

    African Journals Online (AJOL)

    Introduction: Sickle cell disease is a chronic disease. Severe bone pain is commonly the hallmark of clinical features. This commonly necessitates the use of analgesics especially Opioids which unfortunately have a high potential to produce dependence. The complications of dependence in patients on any psychoactive ...

  13. The cell biology of T-dependent B cell activation

    DEFF Research Database (Denmark)

    Owens, T; Zeine, R

    1989-01-01

    The requirement that CD4+ helper T cells recognize antigen in association with class II Major Histocompatibility Complex (MHC) encoded molecules constrains T cells to activation through intercellular interaction. The cell biology of the interactions between CD4+ T cells and antigen-presenting cells...... includes multipoint intermolecular interactions that probably involve aggregation of both polymorphic and monomorphic T cell surface molecules. Such aggregations have been shown in vitro to markedly enhance and, in some cases, induce T cell activation. The production of T-derived lymphokines that have been...... implicated in B cell activation is dependent on the T cell receptor for antigen and its associated CD3 signalling complex. T-dependent help for B cell activation is therefore similarly MHC-restricted and involves T-B intercellular interaction. Recent reports that describe antigen-independent B cell...

  14. Aluminum–Titanium Alloy Back Contact Reducing Production Cost of Silicon Thin-Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Hsin-Yu Wu

    2016-11-01

    Full Text Available In this study, metal films are fabricated by using an in-line reactive direct current magnetron sputtering system. The aluminum–titanium (AlTi back contacts are prepared by changing the pressure from 10 mTorr to 25 mTorr. The optical, electrical and structural properties of the metal back contacts are investigated. The solar cells with the AlTi had lower contact resistance than those with the silver (Ag back contact, resulting in a higher fill factor. The AlTi contact can achieve a solar cell conversion efficiency as high as that obtained from the Ag contact. These findings encourage the potential adoption of AlTi films as an alternative back contact to silver for silicon thin-film solar cells.

  15. c-Myc-Dependent Cell Competition in Human Cancer Cells.

    Science.gov (United States)

    Patel, Manish S; Shah, Heta S; Shrivastava, Neeta

    2017-07-01

    Cell Competition is an interaction between cells for existence in heterogeneous cell populations of multicellular organisms. This phenomenon is involved in initiation and progression of cancer where heterogeneous cell populations compete directly or indirectly for the survival of the fittest based on differential gene expression. In Drosophila, cells having lower dMyc expression are eliminated by cell competition through apoptosis when present in the milieu of cells having higher dMyc expression. Thus, we designed a study to develop c-Myc (human homolog) dependent in vitro cell competition model of human cancer cells. Cells with higher c-Myc were transfected with c-myc shRNA to prepare cells with lower c-Myc and then co-cultured with the same type of cells having a higher c-Myc in equal ratio. Cells with lower c-Myc showed a significant decrease in numbers when compared with higher c-Myc cells, suggesting "loser" and "winner" status of cells, respectively. During microscopy, engulfment of loser cells by winner cells was observed with higher expression of JNK in loser cells. Furthermore, elimination of loser cells was prevented significantly, when co-cultured cells were treated with the JNK (apoptosis) inhibitor. Above results indicate elimination of loser cells in the presence of winner cells by c-Myc-dependent mechanisms of cell competition in human cancer cells. This could be an important mechanism in human tumors where normal cells are eliminated by c-Myc-overexpressed tumor cells. J. Cell. Biochem. 118: 1782-1791, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  16. Short-circuit current improvement in thin cells with a gridded back contact

    Science.gov (United States)

    Giuliano, M.; Wohlgemuth, J.

    1980-01-01

    The use of gridded back contact on thin silicon solar cells 50 micrometers was investigated. An unexpected increase in short circuit current of almost 10 percent was experienced for 2 cm x 2 cm cells. Control cells with the standard continuous contact metallization were fabricated at the same time as the gridded back cells with all processes identical up to the formation of the back contact. The gridded back contact pattern was delineated by evaporation of Ti-Pd over a photo-resist mask applied to the back of the wafer; the Ti-Pd film on the controls was applied in the standard fashion in a continuous layer over the back of the cell. The Ti-Pd contacts were similarly applied to the front of the wafer, and the grid pattern on both sides of the cell was electroplated with 8-10 micrometers of silver.

  17. Crystalline silicon solar cell with front and rear polysilicon passivated contacts as bottom cell for hybrid tandems

    NARCIS (Netherlands)

    Luxembourg, S.L.; Zhang, D.; Wu, Y.; Najafi, M.; Zardetto, V.; Verhees, W.; Burgers, A.R.; Veenstra, S.; Geerligs, L.J.

    2017-01-01

    In this paper we analyze and model perovskite/c-Si tandem cells with front and rear polySi passivated contacts on the bottom cell. A high-efficiency tandem approach will benefit from the high Voc potential of a c-Si bottom cell with front and rear polySi passivated contacts while the combination

  18. Influence of the transition region between p- and n-type polycrystalline silicon passivating contacts on the performance of interdigitated back contact silicon solar cells

    Science.gov (United States)

    Reichel, Christian; Müller, Ralph; Feldmann, Frank; Richter, Armin; Hermle, Martin; Glunz, Stefan W.

    2017-11-01

    Passivating contacts based on thin tunneling oxides (SiOx) and n- and p-type semi-crystalline or polycrystalline silicon (poly-Si) enable high passivation quality and low contact resistivity, but the integration of these p+/n emitter and n+/n back surface field junctions into interdigitated back contact silicon solar cells poses a challenge due to high recombination at the transition region from p-type to n-type poly-Si. Here, the transition region was created in different configurations—(a) p+ and n+ poly-Si regions are in direct contact with each other ("pn-junction"), using a local overcompensation (counterdoping) as a self-aligning process, (b) undoped (intrinsic) poly-Si remains between the p+ and n+ poly-Si regions ("pin-junction"), and (c) etched trenches separate the p+ and n+ poly-Si regions ("trench")—in order to investigate the recombination characteristics and the reverse breakdown behavior of these solar cells. Illumination- and injection-dependent quasi-steady state photoluminescence (suns-PL) and open-circuit voltage (suns-Voc) measurements revealed that non-ideal recombination in the space charge regions with high local ideality factors as well as recombination in shunted regions strongly limited the performance of solar cells without a trench. In contrast, solar cells with a trench allowed for open-circuit voltage (Voc) of 720 mV, fill factor of 79.6%, short-circuit current (Jsc) of 41.3 mA/cm2, and a conversion efficiencies (η) of 23.7%, showing that a lowly conducting and highly passivating intermediate layer between the p+ and n+ poly-Si regions is mandatory. Independent of the configuration, no hysteresis was observed upon multiple stresses in reverse direction, indicating a controlled and homogeneously distributed breakdown, but with different breakdown characteristics.

  19. Device physics underlying silicon heterojunction and passivating-contact solar cells: A topical review

    KAUST Repository

    Chavali, Raghu V. K.; De Wolf, Stefaan; Alam, Muhammad A.

    2018-01-01

    The device physics of commercially dominant diffused-junction silicon solar cells is well understood, allowing sophisticated optimization of this class of devices. Recently, so-called passivating-contact solar cell technologies have become prominent

  20. CDI Systems Are Stably Maintained by a Cell-Contact Mediated Surveillance Mechanism.

    Directory of Open Access Journals (Sweden)

    Zachary C Ruhe

    2016-06-01

    Full Text Available Contact-dependent growth inhibition (CDI systems are widespread amongst Gram-negative bacteria where they play important roles in inter-cellular competition and biofilm formation. CDI+ bacteria use cell-surface CdiA proteins to bind neighboring bacteria and deliver C-terminal toxin domains. CDI+ cells also express CdiI immunity proteins that specifically neutralize toxins delivered from adjacent siblings. Genomic analyses indicate that cdi loci are commonly found on plasmids and genomic islands, suggesting that these Type 5 secretion systems are spread through horizontal gene transfer. Here, we examine whether CDI toxin and immunity activities serve to stabilize mobile genetic elements using a minimal F plasmid that fails to partition properly during cell division. This F plasmid is lost from Escherichia coli populations within 50 cell generations, but is maintained in ~60% of the cells after 100 generations when the plasmid carries the cdi gene cluster from E. coli strain EC93. By contrast, the ccdAB "plasmid addiction" module normally found on F exerts only a modest stabilizing effect. cdi-dependent plasmid stabilization requires the BamA receptor for CdiA, suggesting that plasmid-free daughter cells are inhibited by siblings that retain the CDI+ plasmid. In support of this model, the CDI+ F plasmid is lost rapidly from cells that carry an additional cdiI immunity gene on a separate plasmid. These results indicate that plasmid stabilization occurs through elimination of non-immune cells arising in the population via plasmid loss. Thus, genetic stabilization reflects a strong selection for immunity to CDI. After long-term passage for more than 300 generations, CDI+ plasmids acquire mutations that increase copy number and result in 100% carriage in the population. Together, these results show that CDI stabilizes genetic elements through a toxin-mediated surveillance mechanism in which cells that lose the CDI system are detected and eliminated by

  1. Temperature dependent diffusion and epitaxial behavior of oxidized Au/Ni/p-GaN ohmic contact

    International Nuclear Information System (INIS)

    Hu, C.Y.; Qin, Z.X.; Feng, Z.X.; Chen, Z.Z.; Ding, Z.B.; Yang, Z.J.; Yu, T.J.; Hu, X.D.; Yao, S.D.; Zhang, G.Y.

    2006-01-01

    The temperature dependent diffusion and epitaxial behavior of oxidized Au/Ni/p-GaN ohmic contact were studied with Rutherford backscattering spectroscopy/channeling (RBS/C) and synchrotron X-ray diffraction (XRD). It is found that the Au diffuses to the surface of p-GaN to form an epitaxial structure on p-GaN after annealing at 450 deg. C. At the same time, the O diffuses to the metal-semiconductor interface and forms NiO. Both of them are suggested to be responsible for the sharp decrease in the specific contact resistance (ρ c ) at 450 deg. C. At 500 deg. C, the epitaxial structure of Au develops further and the O also diffuses deeper into the interface. As a result, the ρ c reaches the lowest value at this temperature. However, when annealing temperature reaches 600 deg. C, part or all of the interfacial NiO is detached from the p-GaN and diffuses out, which cause the ρ c to increase greatly

  2. Contact resistance of ceramic interfaces between materials used for solid oxide fuel cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Koch, S.

    2002-01-01

    The contact resistance can be divided into two main contributions. The small area of contact between ceramic components results in resistance due to current constriction. Resistive phases or potential barriers at the interface result in an interface contribution to the contact resistance, which may be smaller or larger than the constriction resistance. The contact resistance between pairs of three different materials were analysed (strontium doped lanthanum manganite, yttria stabilised zirconia and strontium and nickel doped lanthanum cobaltite), and the effects of temperature, atmosphere, polarisation and mechanical load on the contact resistance were investigated. The investigations revealed that the mechanical load of a ceramic contact has a high influence on the contact resistance, and generally power law dependence between the contact resistance and the mechanical load was found. The influence of the mechanical load on the contact resistance was ascribed to an area effect. The contact resistance of the investigated materials was dominated by current constriction at high temperatures. The measured contact resistance was comparable to the resistance calculated on basis of the contact areas found by optical and electron microscopy. At low temperatures, the interface contribution to the contact resistance was dominating. The cobaltite interface could be described by one potential barrier at the contact interface, whereas the manganite interfaces required several consecutive potential barriers to model the observed behaviour. The current-voltage behaviour of the YSZ contact interfaces was only weakly non-linear, and could be described by 22{+-}1 barriers in series. Contact interfaces with sinterable contact layers were also investigated, and the measured contact resistance for these interfaces were more than 10 times less than for the other interfaces. (au)

  3. Advances in cell culture: anchorage dependence

    Science.gov (United States)

    Merten, Otto-Wilhelm

    2015-01-01

    Anchorage-dependent cells are of great interest for various biotechnological applications. (i) They represent a formidable production means of viruses for vaccination purposes at very large scales (in 1000–6000 l reactors) using microcarriers, and in the last decade many more novel viral vaccines have been developed using this production technology. (ii) With the advent of stem cells and their use/potential use in clinics for cell therapy and regenerative medicine purposes, the development of novel culture devices and technologies for adherent cells has accelerated greatly with a view to the large-scale expansion of these cells. Presently, the really scalable systems—microcarrier/microcarrier-clump cultures using stirred-tank reactors—for the expansion of stem cells are still in their infancy. Only laboratory scale reactors of maximally 2.5 l working volume have been evaluated because thorough knowledge and basic understanding of critical issues with respect to cell expansion while retaining pluripotency and differentiation potential, and the impact of the culture environment on stem cell fate, etc., are still lacking and require further studies. This article gives an overview on critical issues common to all cell culture systems for adherent cells as well as specifics for different types of stem cells in view of small- and large-scale cell expansion and production processes. PMID:25533097

  4. Development of MoOx thin films as back contact buffer for CdTe solar cells in substrate configuration

    International Nuclear Information System (INIS)

    Gretener, C.; Perrenoud, J.; Kranz, L.; Baechler, C.; Yoon, S.; Romanyuk, Y.E.; Buecheler, S.; Tiwari, A.N.

    2013-01-01

    Molybdenum oxide compounds exhibit unique electrical and optical properties depending on oxygen vacancy concentration and composition and therefore, have recently attracted a lot of attention as a hole transport layer in various devices. In this work CdTe solar cells in substrate configuration were grown with evaporated MoO x back contact buffer layers and efficiencies of up to 10% could be achieved without using Cu in the back contact processing. The buffer layer – at the CdTe/back contact interface – in the finished cell was found to consist of MoO 2 phase instead of the expected MoO 3 phase as observed in as-deposited or annealed MoO x layers without CdTe deposition. In order to obtain MoO x buffer layers with desired stoichiometry, MoO x thin films were deposited by radio-frequency sputtering under different growth conditions. The chemical phase, composition, microstructure and optical properties of such layers were studied for their possible use in CdTe solar cells. - Highlights: ► MoO x is used as a back contact buffer in CdTe solar cells in substrate configuration. ► Efficiency of 10.0% was achieved without the addition of Cu. ► The back contact buffer in the finished device consists only of MoO 2 . ► Phases and microstructure of MoO x can be controlled by sputtering conditions

  5. Ion implantation into amorphous Si layers to form carrier-selective contacts for Si solar cells

    International Nuclear Information System (INIS)

    Feldmann, Frank; Mueller, Ralph; Reichel, Christian; Hermle, Martin

    2014-01-01

    This paper reports our findings on the boron and phosphorus doping of very thin amorphous silicon layers by low energy ion implantation. These doped layers are implemented into a so-called tunnel oxide passivated contact structure for Si solar cells. They act as carrier-selective contacts and, thereby, lead to a significant reduction of the cell's recombination current. In this paper we address the influence of ion energy and ion dose in conjunction with the obligatory high-temperature anneal needed for the realization of the passivation quality of the carrier-selective contacts. The good results on the phosphorus-doped (implied V oc = 725 mV) and boron-doped passivated contacts (iV oc = 694 mV) open a promising route to a simplified interdigitated back contact (IBC) solar cell featuring passivated contacts. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. A mechanical-electrical finite element method model for predicting contact resistance between bipolar plate and gas diffusion layer in PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Xinmin; Liu, Dong' an; Peng, Linfa [State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Ni, Jun [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2008-07-15

    Contact resistance between the bipolar plate (BPP) and the gas diffusion layer (GDL) plays a significant role on the power loss in a proton exchange membrane (PEM) fuel cell. There are two types of contact behavior at the interface of the BPP and GDL, which are the mechanical one and the electrical one. Furthermore, the electrical contact behavior is dependent on the mechanical one. Thus, prediction of the contact resistance is a coupled mechanical-electrical problem. The current FEM models for contact resistance estimation can only simulate the mechanical contact behavior and moreover they are based on the assumption that the contact surface is equipotential, which is not the case in a real BPP/GDL assembly due to the round corner and margin of the BPP. In this study, a mechanical-electrical FEM model was developed to predict the contact resistance between the BPP and GDL based on the experimental interfacial contact resistivity. At first, the interfacial contact resistivity was obtained by experimentally measuring the contact resistance between the GDL and a flat graphite plate of the same material and processing conditions as the BPP. Then, with the interfacial contact resistivity, the mechanical and electrical contact behaviors were defined and the potential distribution of the BPP/GDL assembly was analyzed using the mechanical-electrical FEM model. At last, the contact resistance was calculated according to the potential drop and the current of the contact surface. The numerical results were validated by comparing with those of the model reported previously. The influence of the round corner of the BPP on the contact resistance was also studied and it is found that there exists an optimal round corner that can minimize the contact resistance. This model is beneficial in understanding the mechanical and electrical contact behaviors between the BPP and GDL, and can be used to predict the contact resistance in a new BPP/GDL assembly. (author)

  7. Magnetic field and contact resistance dependence of non-local charge imbalance

    International Nuclear Information System (INIS)

    Kleine, A; Baumgartner, A; Trbovic, J; Schoenenberger, C; Golubev, D S; Zaikin, A D

    2010-01-01

    Crossed Andreev reflection (CAR) in metallic nanostructures, a possible basis for solid-state electron entangler devices, is usually investigated by detecting non-local voltages in multi-terminal superconductor/normal metal devices. This task is difficult because other subgap processes may mask the effects of CAR. One of these processes is the generation of charge imbalance (CI) and the diffusion of non-equilibrium quasi-particles in the superconductor. Here we demonstrate a characteristic dependence of non-local CI on a magnetic field applied parallel to the superconducting wire, which can be understood by a generalization of the standard description of CI to non-local experiments. These results can be used to distinguish CAR and CI and to extract CI relaxation times in superconducting nanostructures. In addition, we investigate the dependence of non-local CI on the resistance of the injector and detector contacts and demonstrate a quantitative agreement with a recent theory using only material and junction characteristics extracted from separate direct measurements.

  8. Mathematical Modeling of Contact Resistance in Silicon Photovoltaic Cells

    KAUST Repository

    Black, J. P.; Breward, C. J. W.; Howell, P. D.; Young, R. J. S.

    2013-01-01

    across this layer, based on the driftdiffusion equations. We utilize the size of the current/Debye length to conduct asymptotic techniques to simplify the model; we solve the model numerically to find that the effective contact resistance may be a

  9. Industrially feasible, dopant-free, carrier-selective contacts for high-efficiency silicon solar cells

    KAUST Repository

    Yang, Xinbo

    2017-05-31

    Dopant-free, carrier-selective contacts (CSCs) on high efficiency silicon solar cells combine ease of deposition with potential optical benefits. Electron-selective titanium dioxide (TiO) contacts, one of the most promising dopant-free CSC technologies, have been successfully implemented into silicon solar cells with an efficiency over 21%. Here, we report further progress of TiO contacts for silicon solar cells and present an assessment of their industrial feasibility. With improved TiO contact quality and cell processing, a remarkable efficiency of 22.1% has been achieved using an n-type silicon solar cell featuring a full-area TiO contact. Next, we demonstrate the compatibility of TiO contacts with an industrial contact-firing process, its low performance sensitivity to the wafer resistivity, its applicability to ultrathin substrates as well as its long-term stability. Our findings underscore the great appeal of TiO contacts for industrial implementation with their combination of high efficiency with robust fabrication at low cost.

  10. Radiosensitivity of four human tumor xenografts. Influence of hypoxia and cell-cell contact

    International Nuclear Information System (INIS)

    Guichard, M.; Dertinger, H.; Malaise, E.P.

    1983-01-01

    Contact effect (CE) and hypoxia have been studied in human tumor cell lines transplanted in athymic nude mice. Four cell lines - one melanoma (Bell) and three colorectal adenocarcinomas (HT29, HRT18, and HCT8) - were studied. Cell survival was determined with an in vivo in vitro colony-forming assay. Survival curves were obtained under three different conditions: (1) tumor cells irradiated in air-breathing mice, (2) tumor cells irradiated in animals asphyxiated for 10 min, and (3) tumor cells plated and irradiated either immediately or 5 hr later. For all cell lines, radiosensitivity appeared to be lower when cells were irradiated in vivo than when they were irradiated in vitro. Only in the case of the HCT8 tumor did the relative in vivo radioresistance seem to be linked to hypoxia; in the other cell lines, hypoxia alone could not account for the lower in vivo radiosensitivity. Our results suggest that a CE plays an important role in the response of human xenografts to irradiation

  11. Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations

    OpenAIRE

    Haagh, Martinus Everardus Johannes; Sîretanu, Igor; Duits, Michel; Mugele, Friedrich Gunther

    2017-01-01

    The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and ...

  12. Analysis of contact stiffness in ultrasound atomic force microscopy: three-dimensional time-dependent ultrasound modeling

    International Nuclear Information System (INIS)

    Piras, Daniele; Sadeghian, Hamed

    2017-01-01

    Ultrasound atomic force microscopy (US-AFM) has been used for subsurface imaging of nanostructures. The contact stiffness variations have been suggested as the origin of the image contrast. Therefore, to analyze the image contrast, the local changes in the contact stiffness due to the presence of subsurface features should be calculated. So far, only static simulations have been conducted to analyze the local changes in the contact stiffness and, consequently, the contrast in US-AFM. Such a static approach does not fully represent the real US-AFM experiment, where an ultrasound wave is launched either into the sample or at the tip, which modulates the contact stiffness. This is a time-dependent nonlinear dynamic problem rather than a static and stationary one. This paper presents dynamic 3D ultrasound analysis of contact stiffness in US-AFM (in contrast to static analysis) to realistically predict the changes in contact stiffness and thus the changes in the subsurface image contrast. The modulation frequency also influences the contact stiffness variations and, thus, the image contrast. The three-dimensional time-dependent ultrasound analysis will greatly aid in the contrast optimization of subsurface nano imaging with US-AFM. (paper)

  13. Intercellular contact: its influence on the Dsub(q) of mammalian cell survival curves

    International Nuclear Information System (INIS)

    Durand, R.E.; Sutherland, R.M.

    1975-01-01

    Cell survival in tissues exposed to a given dose of ionizing radiation is usually greater than that of similar cells grown individually in vitro, despite the fact that the radiosensitivities (D 0 ) are virtually identical under the two conditions. An analogous increase in cell survival is observed when Chinese hamster V79-171 cells are grown in suspension culture and irradiated as multicell spheroids. Unfortunately, the information gained from the survival curves so obtained is limited by the inhomogeneity of the cell population with respect to both degree of contact and cell cycle position. The latter can be studied using synchronized small spheroids. The ratio of Dsub(q) of spheroid cells to Dsub(q) of single cells increased as the cells progressed through the cell cycle, from a minimum of 1.3 for G 1 phase cells to a maximum of 2.2 for late S-phase cells. The enhanced survival, or 'contact effect', developed slowly as the spheroids grew, after an initial latent period of about one generation cycle of the cells. A second effect of intercellular contact on mammalian cell survival has also been observed. When cells are assayed under conditions in which intercellular contact is maintained, the net cellular survival is increased further. This effect is different from the usual repair of potentially lethal damage, in that it occurs much more slowly and results in modification of the survival-curve shoulder. Not all cell types tested have shown enhanced survival when grown as spheroids. Several MNNG-induced mutants of the Chinese hamster V79-171 line have been isolated and sublines which do and do not show the contact effect are now available. These may permit study of the mechanism(s) of contact effects. (author)

  14. Electrochemical deposition of buried contacts in high-efficiency crystalline silicon photovoltaic cells

    DEFF Research Database (Denmark)

    Jensen, Jens Arne Dahl; Møller, Per; Bruton, Tim

    2003-01-01

    This article reports on a newly developed method for electrochemical deposition of buried Cu contacts in Si-based photovoltaic ~PV! cells. Contact grooves, 20 mm wide by 40 mm deep, were laser-cut into Si PV cells, hereafter applied with a thin electroless NiP base and subsequently filled with Cu...... by electrochemical deposition at a rate of up to 10 mm per min. With the newly developed process, void-free, superconformal Cu-filling of the laser-cut grooves was observed by scanning electron microscopy and focused ion beam techniques. The Cu microstructure in grooves showed both bottom and sidewall texture......, with a grain-size decreasing from the center to the edges of the buried Cu contacts and a pronounced lateral growth outside the laser-cut grooves. The measured specific contact resistances of the buried contacts was better than the production standard. Overall performance of the new PV cells was equal...

  15. Electroplated contacts and porous silicon for silicon based solar cells applications

    Energy Technology Data Exchange (ETDEWEB)

    Kholostov, Konstantin, E-mail: kholostov@diet.uniroma1.it [Department of information engineering, electronics and telecommunications, University of Rome “La Sapienza”, Via Eudossiana 18, 00184 Rome (Italy); Serenelli, Luca; Izzi, Massimo; Tucci, Mario [Enea Casaccia Research Centre Rome, via Anguillarese 301, 00123 Rome (Italy); Balucani, Marco [Department of information engineering, electronics and telecommunications, University of Rome “La Sapienza”, Via Eudossiana 18, 00184 Rome (Italy); Rise Technology S.r.l., Lungomare Paolo Toscanelli 170, 00121 Rome (Italy)

    2015-04-15

    Highlights: • Uniformity of the Ni–Si interface is crucial for performance of Cu–Ni contacts on Si. • Uniformly filled PS is the key to obtain the best performance of Cu–Ni contacts on Si. • Optimization of anodization and electroplating allows complete filling of PS layer. • Highly adhesive and low contact resistance Cu–Ni contacts are obtained on Si. - Abstract: In this paper, a two-layer metallization for silicon based solar cells is presented. The metallization consists of thin nickel barrier and thick copper conductive layers, both obtained by electrodeposition technique suitable for phosphorus-doped 70–90 Ω/sq solar cell emitter formed on p-type silicon substrate. To ensure the adhesion between metal contact and emitter a very thin layer of mesoporous silicon is introduced on the emitter surface before metal deposition. This approach allows metal anchoring inside pores and improves silicon–nickel interface uniformity. Optimization of metal contact parameters is achieved varying the anodization and electrodeposition conditions. Characterization of contacts between metal and emitter is carried out by scanning electron microscopy, specific contact resistance and current–voltage measurements. Mechanical strength of nickel–copper contacts is evaluated by the peel test. Adhesion strength of more than 4.5 N/mm and contact resistance of 350 μΩ cm{sup 2} on 80 Ω/sq emitter are achieved.

  16. Mast Cells Limit the Exacerbation of Chronic Allergic Contact Dermatitis in Response to Repeated Allergen Exposure.

    Science.gov (United States)

    Gimenez-Rivera, Vladimir-Andrey; Siebenhaar, Frank; Zimmermann, Carolin; Siiskonen, Hanna; Metz, Martin; Maurer, Marcus

    2016-12-01

    Allergic contact dermatitis is a chronic T cell-driven inflammatory skin disease that is caused by repeated exposure to contact allergens. Based on murine studies of acute contact hypersensitivity, mast cells (MCs) are believed to play a role in its pathogenesis. The role of MCs in chronic allergic contact dermatitis has not been investigated, in part because of the lack of murine models for chronic contact hypersensitivity. We developed and used a chronic contact hypersensitivity model in wild-type and MC-deficient mice and assessed skin inflammatory responses to identify and characterize the role of MCs in chronic allergic contact dermatitis. Ear swelling chronic contact hypersensitivity responses increased markedly, up to 4-fold, in MC-deficient Kit W-sh/W-sh (Sash) and MCPT5-Cre + iDTR + mice compared with wild-type mice. Local engraftment with MCs protected Sash mice from exacerbated ear swelling after repeated oxazolone challenge. Chronic contact hypersensitivity skin of Sash mice exhibited elevated levels of IFN-γ, IL-17α, and IL-23, as well as increased accumulation of Ag-specific IFN-γ-producing CD8 + tissue-resident memory T (T RM ) cells. The CD8 + T cell mitogen IL-15, which was increased in oxazolone-challenged skin of Sash mice during the accumulation of cutaneous T RM cells, was efficiently degraded by MCs in vitro. MCs protect from the exacerbated allergic skin inflammation induced by repeated allergen challenge, at least in part, via effects on CD8 + T RM cells. MCs may notably influence the course of chronic allergic contact dermatitis. A better understanding of their role and the underlying mechanisms may lead to better approaches for the treatment of this common, disabling, and costly condition. Copyright © 2016 by The American Association of Immunologists, Inc.

  17. Collective cell streams in epithelial monolayers depend on cell adhesion

    International Nuclear Information System (INIS)

    Czirók, András; Varga, Katalin; Méhes, Előd; Szabó, András

    2013-01-01

    We report spontaneously emerging, randomly oriented, collective streaming behavior within a monolayer culture of a human keratinocyte cell line, and explore the effect of modulating cell adhesions by perturbing the function of calcium-dependent cell adhesion molecules. We demonstrate that decreasing cell adhesion induces narrower and more anisotropic cell streams, reminiscent of decreasing the Taylor scale of turbulent liquids. To explain our empirical findings, we propose a cell-based model that represents the dual nature of cell–cell adhesions. Spring-like connections provide mechanical stability, while a cellular Potts model formalism represents surface-tension driven attachment. By changing the relevance and persistence of mechanical links between cells, we are able to explain the experimentally observed changes in emergent flow patterns. (paper)

  18. Multi-Material Front Contact for 19% Thin Film Solar Cells

    NARCIS (Netherlands)

    Deelen, J. van; Tezsevin, Y.; Barink, M.

    2016-01-01

    The trade-off between transmittance and conductivity of the front contact material poses abottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing

  19. Pressure effects on interfacial surface contacts and performance of organic solar cells

    NARCIS (Netherlands)

    Agyei-Tuffour, B.; Doumon, Nutifafa Y.; Rwenyagila, E. R.; Asare, J.; Oyewole, O. K.; Shen, Z.; Petoukhoff, C. E.; Zebaze Kana, M. G.; Ocarroll, D. M.; Soboyejo, W. O.

    2017-01-01

    This paper explores the effects of pressure on the interfacial surface contacts and the performance of organic solar cells. A combination of experimental techniques and analytical/computational models is used to study the evolving surface contacts profiles that occur when compliant, semi-rigid and

  20. Trap and corral: a two-step approach for constructing and constraining dynamic cell contact events in differentiating progenitor cell populations

    International Nuclear Information System (INIS)

    Chen, S; Patel, N; Schaffer, D; Maharbiz, M M

    2011-01-01

    Cells are constantly subjected to a host of external signals which can influence their state, phenotype and behavior. Mammalian cells are dependent on signals from surrounding cells to maintain viability, proliferate and coordinate their actions. During developmental and regenerative processes, these lateral signals between cells provide instructive cues informing stem cells how, when and where to differentiate. Moreover, differentiating cells often experience cell–cell contact events interspersed with bouts of motility, process extension and multi-cell agglomeration (Gage 2000 Science 287 1433–8) processes which are not easily recapitulated in existing cell capture devices. Here, we present a two-step process involving microwells to trap cells with high efficiency followed by the alignment of a PDMS mesh around the cells to corral them after the trapping. The microwells trap single cells and paired cells with up to 90% and 80% efficiencies, respectively. After seeding, the PDMS mesh is aligned with the seeded wells to create a 150 µm × 150 µm corral around each trap, allowing cells to interact in a larger arena. The corralling must be done in liquid after seeding because the seeding requires high cell densities to achieve near-full occupancy in the wells. Low-density seeding of the PDMS corrals alone can result in two cells being trapped in each well, but in those conditions, the two cells often engage in very little contact or none at all (and seeding obeys a non-desirable Poisson distribution). Interestingly, trapping cells in proximity and then corralling them elicits much higher contact times than simply seeding into corrals

  1. Disruption of contact inhibition in rat liver epithelial cells by various types of AhR ligands

    Energy Technology Data Exchange (ETDEWEB)

    Vondracek, J.; Chramostova, K.; Kozubik, A. [Institute of Biophysics, Brno (Czech Republic); Krcmar, P.; Machala, M. [Veterinary Research Institute, Brno (Czech Republic)

    2004-09-15

    The maintenance of a balance between cell gain and cell loss is essential for proper liver function. The exact role of aryl hydrocarbon receptor (AhR) in regulating cell proliferation and apoptosis of liver cells remains unclear, since ligand-dependent activation of AhR has been shown to induce cell cycle arrest, proliferation, differentiation or apoptosis, depending on the cellular model used. AhR can directly interact with retinoblastoma protein in hepatic cells, forming protein complexes that can efficiently block cell cycle progression by inducing G1 arrest, or to induce the expression of inhibitors of cyclin-dependent kinases, such as p271. On the other hand, it has been suggested that AhR could play a stimulatory role in cell proliferation, either directly or by mediating a release from contact inhibition. It is now generally accepted that progenitor cells exist in the liver, are activated in various liver diseases and can form a potential target cell population for both tumor initiating and tumor promoting chemicals4. 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD) has been found to release rat liver epithelial cells from contact inhibition by upregulating cyclin A expression and cyclin A/cdk2 activity. Our previous studies have shown that a number of AhR ligands5,6 can stimulate proliferation of confluent of rat liver epithelial ''stem-like'' WB-F344 cells. Such mechanism could play a role in liver tumor promotion. In the present study, we used flavonoid compounds that have been reported to act either as pure agonists, such as beta-naphthoflavone (BNF), or as partial/complete antagonists of AhR - alpha-naphthoflavone (ANF) and 3'-methoxy-4'-nitroflavone (3'M4'NF), in order to investigate effects of AhR agonists/antagonists on confluent rat liver epithelial cells. The present study aimed to investigate the effects of model flavonoids on the release of rat liver epithelial cells from contact inhibition, and on inducibility of

  2. Immune suppression with supraoptimal doses of antigen in contact sensitivity. I. Demonstration of suppressor cells and their sensitivity to cyclophosphamide.

    Science.gov (United States)

    Sy, M S; Miller, S D; Claman, H N

    1977-07-01

    Immunologic suppression was induced in a mouse model of contact sensitization to DNFB by using supraoptimal doses of antigen. In these studies, in vivo measurement of ear swelling as an indication of immunologic responsiveness correlated well with measurement of in vitro antigen-induced cell proliferation. This unresponsiveness was specific, since supraoptimal doses of DNFB did not interfere with the development of contact sensitivity to another contactant, oxazolone. The decrease in responsiveness is a form of active suppression, as lymphoid cells from supraoptimally sensitized donors transferred suppression to normal recipients. Furthermore, pretreatment with cyclophosphamide (Cy) reversed the suppression seen in supraoptimally sensitized animals but had no effect on the optimal sensitization regimen. These results indicate that supraoptimal doses of contactants can activate suppressor cells and that precursors of these cells are sensitive to Cy. Such suppressors regenerate within 7 to 14 days after Cy treatment. The ability of Cy pretreatment to affect supraoptimal sensitization without affecting optimal sensitization confirms other reports indicating that the observed results of Cy treatment depend critically upon the dose of antigen used.

  3. Selective deposition contact patterning using atomic layer deposition for the fabrication of crystalline silicon solar cells

    International Nuclear Information System (INIS)

    Cho, Young Joon; Shin, Woong-Chul; Chang, Hyo Sik

    2014-01-01

    Selective deposition contact (SDC) patterning was applied to fabricate the rear side passivation of crystalline silicon (Si) solar cells. By this method, using screen printing for contact patterning and atomic layer deposition for the passivation of Si solar cells with Al 2 O 3 , we produced local contacts without photolithography or any laser-based processes. Passivated emitter and rear-contact solar cells passivated with ozone-based Al 2 O 3 showed, for the SDC process, an up-to-0.7% absolute conversion-efficiency improvement. The results of this experiment indicate that the proposed method is feasible for conversion-efficiency improvement of industrial crystalline Si solar cells. - Highlights: • We propose a local contact formation process. • Local contact forms a screen print and an atomic layer deposited-Al 2 O 3 film. • Ozone-based Al 2 O 3 thin film was selectively deposited onto patterned silicon. • Selective deposition contact patterning method can increase cell-efficiency by 0.7%

  4. Tantalum Nitride Electron-Selective Contact for Crystalline Silicon Solar Cells

    KAUST Repository

    Yang, Xinbo; Aydin, Erkan; Xu, Hang; Kang, Jingxuan; Hedhili, Mohamed N.; Liu, Wenzhu; Wan, Yimao; Peng, Jun; Samundsett, Christian; Cuevas, Andres; De Wolf, Stefaan

    2018-01-01

    novel electron‐selective, passivating contact for c‐Si solar cells is presented. Tantalum nitride (TaN x ) thin films deposited by atomic layer deposition are demonstrated to provide excellent electron‐transporting and hole‐blocking properties

  5. Determination of the nano-scaled contact area of staphylococcal cells.

    Science.gov (United States)

    Spengler, Christian; Thewes, Nicolas; Jung, Philipp; Bischoff, Markus; Jacobs, Karin

    2017-07-20

    Bacterial adhesion is a crucial step during the development of infections as well as the formation of biofilms. Hence, fundamental research of bacterial adhesion mechanisms is of utmost importance. So far, less is known about the size of the contact area between bacterial cells and a surface. This gap will be filled by this study using a single-cell force spectroscopy-based method to investigate the contact area between a single bacterial cell of Staphylococcus aureus and a solid substrate. The technique relies on the strong influence of the hydrophobic interaction on bacterial adhesion: by incrementally crossing a very sharp hydrophobic/hydrophilic interface while performing force-distance curves with a single bacterial probe, the bacterial contact area can be determined. Assuming circular contact areas, their radii - determined in our experiments - are in the range from tens of nanometers to a few hundred nanometers. The contact area can be slightly enlarged by a larger load force, yet does not resemble a Hertzian contact, rather, the enlargement is a property of the individual bacterial cell. Additionally, Staphylococcus carnosus has been probed, which is less adherent than S. aureus, yet both bacteria exhibit a similar contact area size. This corroborates the notion that the adhesive strength of bacteria is not a matter of contact area, but rather a matter of which and how many molecules of the bacterial species' cell wall form the contact. Moreover, our method of determining the contact area can be applied to other microorganisms and the results might also be useful for studies using nanoparticles covered with soft, macromolecular coatings.

  6. CD3-positive B cells: a storage-dependent phenomenon.

    Directory of Open Access Journals (Sweden)

    Angela Nagel

    Full Text Available The majority of clinical studies requires extensive management of human specimen including e.g. overnight shipping of blood samples in order to convey the samples in a central laboratory or to simultaneously analyze large numbers of patients. Storage of blood samples for periods of time before in vitro/ex vivo testing is known to influence the antigen expression on the surface of lymphocytes. In this context, the present results show for the first time that the T cell antigen CD3 can be substantially detected on the surface of human B cells after ex vivo storage and that the degree of this phenomenon critically depends on temperature and duration after blood withdrawal. The appearance of CD3 on the B cell surface seems to be a result of contact-dependent antigen exchange between T and B lymphocytes and is not attributed to endogenous production by B cells. Since cellular subsets are often classified by phenotypic analyses, our results indicate that ex vivo cellular classification in peripheral blood might result in misleading interpretations. Therefore, in order to obtain results reflecting the in vivo situation, it is suggested to minimize times of ex vivo blood storage after isolation of PBMC. Moreover, to enable reproducibility of results between different research groups and multicenter studies, we would emphasize the necessity to specify and standardize the storage conditions, which might be the basis of particular findings.

  7. T cell lymphomatoid contact dermatitis: a challenging case and review of the literature.

    Science.gov (United States)

    Knackstedt, Thomas J; Zug, Kathryn A

    2015-02-01

    Lymphomatoid contact dermatitis is a pseudolymphoma with clinical and histological features of allergic contact dermatitis and cutaneous T cell lymphoma. Incorrect diagnosis may lead to unnecessary testing, unnecessary treatment, or patient harm. The objective of this study is to present a case to demonstrate the diagnostic challenge and overlap between allergic contact dermatitis and cutaneous T cell lymphoma in a patient with lymphomatoid contact dermatitis caused by methylchoroisothiazolinone/methylisothiazolinone and paraben mix, and to review the existing literature in order to summarize the demographics, clinical features, allergens and treatments reported for lymphomatoid contact dermatitis. A search of major scientific databases was conducted for English-language articles reporting cases of lymphomatoid contact dermatitis or additional synonymous search headings. Nineteen articles with a total of 23 patients were analysed. Lymphomatoid contact dermatitis was more common in men, with an average age of 58.5 years. Fourteen unique allergens were identified and confirmed by patch testing. However, no single test or study was diagnostic of lymphomatoid contact dermatitis. Allergen avoidance was the most useful management tool, but selected patients required topical or systemic immunosuppression. In conclusion, without specific diagnostic features, evaluation for lymphomatoid contact dermatitis should include a thorough history and examination, patch testing, and biopsy with immunohistochemistry and clonality studies. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  8. Mast cell synapses and exosomes: membrane contacts for information exchange.

    NARCIS (Netherlands)

    Carroll-Portillo, A.; Surviladze, Z.; Cambi, A.; Lidke, D.S.; Wilson, B.S.

    2012-01-01

    In addition to their central role in allergy, mast cells are involved in a wide variety of cellular interactions during homeostasis and disease. In this review, we discuss the ability of mast cells to extend their mechanisms for intercellular communication beyond the release of soluble mediators.

  9. Improved contact metallization for high efficiency EFG polycrystalline silicon solar cells

    International Nuclear Information System (INIS)

    Dube, C.E.; Gonsiorawski, R.C.

    1990-01-01

    Improvements in the performance of polycrystalline silicon solar cells based on a novel, laser patterned contact process are described. Small lots of cells having an average conversion efficiency of 14 + %, with several cells approaching 15%, are reported for cells of 45 cm 2 area. The high efficiency contact design is based on YAG laser patterning of the silicon nitride anti-reflection coating. The Cu metallization is done using light-induced plating, with the cell providing the driving voltage for the plating process. The Cu electrodeposits into the laser defined windows in the AR coating for reduced contact area, following which the Cu bridges on top of the Ar coating to form a continuous finger pattern. The higher cell conversion efficiency is attributed to reduced shadow loss, higher junction quality, and reduced metal-semiconductor interfacial area

  10. a-Si:H/c-Si heterojunction front- and back contacts for silicon solar cells with p-type base

    Energy Technology Data Exchange (ETDEWEB)

    Rostan, Philipp Johannes

    2010-07-01

    internal quantum efficiency shows that both types of back contacts lead to effective diffusion lengths in excess of 600 {mu}m. An extended fill factor analysis shows that fill factor limitations for the full-area a-Si:H/c-Si contacts result from non-ideal diode behavior, ascribed to the injection dependence of the heterojunction interface recombination velocity. Analysis of the external quantum efficiency under back side illumination with different bias light intensities delivers the effective surface recombination S{sub eff}({phi}) in dependance of the illumination intensity {phi}. The front contact (emitter) uses a sequence of intrinsic and phosphorous doped amorphous silicon layers together with a ZnO:Al or a SnO{sub 2}:In layer and an Al front contact grid. The emitter is prepared at a maximum temperature of 220 C. Measurements of the minority carrier lifetime on symmetric i/n-a-Si:H coated wafers judge the emitter passivation quality. The best solar cells that use a thermal oxide back side passivation with Al-point contacts and flat a-Si:H emitters have open circuit voltages up to 683 mV and efficiencies up to 17.4 %. The efficiency of such devices is limited by a low short circuit current due to the flat front side. Using the same back contact structure with random pyramid textured wafer front sides and a-Si:H emitters yields open circuit voltages up to 660 mV and efficiencies up to 18.5 %, so far limited by a relatively low fill factor FF {<=} 74.3 %. Analysis of the external quantum efficiency underlines the excellent surface passivation properties of the amorphous emitter. Combining both, amorphous front- and back contacts yields p-type heterojunction solar cells completely fabricated at temperatures below 220 C. The best devices reach an open circuit voltage V{sub oc} = 678 mV and an efficiency {eta} = 18.1 % with random textured wafers, limited by low fill factors FF {approx} 75 %. Besides the cell fabrication and characterization, this thesis reveals that the

  11. Oxygen-dependent sensitization of irradiated cells

    International Nuclear Information System (INIS)

    Ewing, D.; Powers, E.L.

    1979-01-01

    Attention is focused primarily on O 2 effects in three biological systems, all tested in suspension: bacterial spores, vegetative bacterial cells, and mammalian cells. Information from these systems shows that O 2 has more than one process through which it can act. Studies with bacterial spore suspensions provide clear evidence that multiple components to oxygen-dependent radiation sensitization exist. Studies with mammalian cell suspensions also show that at least two oxygen-dependent sensitization processes can be distinguished. Similar studies with vegetative bacteria in suspension have not resolved oxic sensitization into components. The roles of water-derived radicals in radiation sensitivity and, specifically, in sensitization by O 2 were examined. OH radicals are clearly implicated in damage in all three biological test systems. However, the specific roles proposed for OH radicals are different in these organisms. In bacterial spores, OH radical removal in itself does not protect in anoxia or in high concentrations of O 2 . OH radical removal over a limited intermediate range of O 2 concentrations will, however, protect. OH radical scavenging probably results in the formation of the actual protector. In bacteria, the supposition is that OH radical removal will protect both in anoxia and in the presence of O 2 . OH radicals probably react with a cellular target molecule and leave a radicalsite; this is the site which can then react with O 2 to cause damage; DNA is the likely cellular target. In mammalian cells, a reaction scheme, similar to that proposed for bacteria, has been suggested for O 2 -dependent sensitization

  12. Immunosuppressive Effect of Litsea cubeba L. Essential Oil on Dendritic Cell and Contact Hypersensitivity Responses

    Directory of Open Access Journals (Sweden)

    Hsin-Chun Chen

    2016-08-01

    Full Text Available Litsea cubeba L., also named as Makauy, is a traditional herb and has been used as cooking condiment or tea brewing to treat diseases for aborigines. The present study was undertaken to explore the chemical compositions of the fruit essential oil of L. cubeba (LCEO and the immunomodulatory effect of LCEO on dendritic cells and mice. The LCEO was analyzed using gas chromatography (GC and gas chromatography/mass spectrometry (GC/MS with direct injection (DI/GC or headspace-solid phase microextraction (HS-SPME/GC. In total, 56 components were identified, of which 48 were detected by DI/GC and 49 were detected by HS-SPME/GC. The principal compounds were citral (neral and geranial. An immunosuppressive activity of LCEO was investigated with bone marrow-derived dendritic cells (DCs which have a critical role to trigger the adaptive immunity. Additionally, the inhibitory effect of LCEO on immune response was elucidated by performing the contact hypersensitivity (CHS responses in mice. Our results clearly showed that LCEO decreases the production of TNF-α and cytokine IL-12 in a dose-dependent manner in lipopolysaccharide (LPS-stimulated DCs. CHS response and the infiltrative T cells were inhibited in the tested ears of the mice co-treated with LCEO. We demonstrate, for the first time, that the LCEO mainly containing citral exhibits an immunosuppressive effect on DCs and mice, indicating that LCEO can potentially be applied in the treatment of CHS, inflammatory diseases, and autoimmune diseases.

  13. Fabrication of contacts for silicon solar cells including printing burn through layers

    Science.gov (United States)

    Ginley, David S; Kaydanova, Tatiana; Miedaner, Alexander; Curtis, Calvin J; Van Hest, Marinus Franciscus Antonius Maria

    2014-06-24

    A method for fabricating a contact (240) for a solar cell (200). The method includes providing a solar cell substrate (210) with a surface that is covered or includes an antireflective coating (220). For example, the substrate (210) may be positioned adjacent or proximate to an outlet of an inkjet printer (712) or other deposition device. The method continues with forming a burn through layer (230) on the coating (220) by depositing a metal oxide precursor (e.g., using an inkjet or other non-contact printing method to print or apply a volume of liquid or solution containing the precursor). The method includes forming a contact layer (240) comprising silver over or on the burn through layer (230), and then annealing is performed to electrically connect the contact layer (240) to the surface of the solar cell substrate (210) through a portion of the burn through layer (230) and the coating (220).

  14. Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems : the Critical Role of Divalent Cations

    NARCIS (Netherlands)

    Haagh, Martinus Everardus Johannes; Sîretanu, Igor; Duits, Michel; Mugele, Friedrich Gunther

    2017-01-01

    The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting

  15. Correlation of Cell Surface Biomarker Expression Levels with Adhesion Contact Angle Measured by Lateral Microscopy.

    Science.gov (United States)

    Walz, Jenna A; Mace, Charles R

    2018-06-05

    Immunophenotyping is typically achieved using flow cytometry, but any influence a biomarker may have on adhesion or surface recognition cannot be determined concurrently. In this manuscript, we demonstrate the utility of lateral microscopy for correlating cell surface biomarker expression levels with quantitative descriptions of cell morphology. With our imaging system, we observed single cells from two T cell lines and two B cell lines adhere to antibody-coated substrates and quantified this adhesion using contact angle measurements. We found that SUP-T1 and CEM CD4+ cells, both of which express similar levels of CD4, experienced average changes in contact angle that were not statistically different from one another on surfaces coated in anti-CD4. However, MAVER-1 and BJAB K20 cells, both of which express different levels of CD20, underwent average changes in contact angle that were significantly different from one another on surfaces coated in anti-CD20. Our results indicate that changes in cell contact angles on antibody-coated substrates reflect the expression levels of corresponding antigens on the surfaces of cells as determined by flow cytometry. Our lateral microscopy approach offers a more reproducible and quantitative alternative to evaluate adhesion compared to commonly used wash assays and can be extended to many additional immunophenotyping applications to identify cells of interest within heterogeneous populations.

  16. Simulation, elaboration and analysis of inter-digitated back contacts photovoltaic cells

    International Nuclear Information System (INIS)

    Nichiporuk, O.

    2005-05-01

    Solar energy is the most promising and powerful energy source among renewable energies. Photovoltaic electricity is obtained by direct transformation of the sunlight into electricity by means of photovoltaic cells. The objective of this work is to develop photovoltaic cells with back inter-digitated contacts. In the first chapter, we recall the principle of operation and the fundamental parameters of a photovoltaic cell. In a second part, we explain specificities of the inter-digitated back-contact solar cells, as well as the advantages and the disadvantages of such cells. In the second chapter we study the operation of inter-digitated back-contacts solar cells by two dimensional numerical simulation in order to optimize the geometry and doping profiles of the cell. The third chapter relates to the techniques and the methods of characterization of photovoltaic devices and components. In the fourth chapter, we describe the elaboration of inter-digitated back-contact cells. Three technological processes are presented in order to develop a simple technology for cells realization. In particular, we develop the auto-aligned technological process, which enables to elaborate the cells by using only one lithography step. In the last chapter we examine various approaches to reduce the surface recombination: SiO 2 , silicon nitride deposited by UVCVD, hydrogen annealing, etc.. (author)

  17. Simulation, elaboration and analysis of inter-digitated back-contacts photovoltaic cells

    International Nuclear Information System (INIS)

    Nichiporuk, O.

    2005-05-01

    Solar energy is the most promising and powerful energy source among renewable energies. Photovoltaic electricity is obtained by direct transformation of the sunlight into electricity by means of photovoltaic cells. The objective of this work is to develop photovoltaic cells with back inter-digitated contacts. In the first chapter, we recall the principle of operation and the fundamental parameters of a photovoltaic cell. In a second part, we explain specificities of the inter-digitated back-contact solar cells, as well as the advantages and the disadvantages of such cells. In the second chapter we study the operation of inter-digitated back-contacts solar cells by two dimensional numerical simulation in order to optimize the geometry and doping profiles of the cell. The third chapter relates to the techniques and the methods of characterization of photovoltaic devices and components. In the fourth chapter, we describe the elaboration of inter-digitated back-contact cells. Three technological processes are presented in order to develop a simple technology for cells realization. In particular, we develop the auto-aligned technological process, which enables to elaborate the cells by using only one lithography step. In the last chapter we examine various approaches to reduce the surface recombination: SiO 2 , silicon nitride deposited by UVCVD, hydrogen annealing, etc... (author)

  18. Label free imaging of cell-substrate contacts by holographic total internal reflection microscopy.

    Science.gov (United States)

    Mandracchia, Biagio; Gennari, Oriella; Marchesano, Valentina; Paturzo, Melania; Ferraro, Pietro

    2017-09-01

    The study of cell adhesion contacts is pivotal to understand cell mechanics and interaction at substrates or chemical and physical stimuli. We designed and built a HoloTIR microscope for label-free quantitative phase imaging of total internal reflection. Here we show for the first time that HoloTIR is a good choice for label-free study of focal contacts and of cell/substrate interaction as its sensitivity is enhanced in comparison with standard TIR microscopy. Finally, the simplicity of implementation and relative low cost, due to the requirement of less optical components, make HoloTIR a reasonable alternative, or even an addition, to TIRF microscopy for mapping cell/substratum topography. As a proof of concept, we studied the formation of focal contacts of fibroblasts on three substrates with different levels of affinity for cell adhesion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Tunnel oxide passivated contacts formed by ion implantation for applications in silicon solar cells

    International Nuclear Information System (INIS)

    Reichel, Christian; Feldmann, Frank; Müller, Ralph; Hermle, Martin; Glunz, Stefan W.; Reedy, Robert C.; Lee, Benjamin G.; Young, David L.; Stradins, Paul

    2015-01-01

    Passivated contacts (poly-Si/SiO x /c-Si) doped by shallow ion implantation are an appealing technology for high efficiency silicon solar cells, especially for interdigitated back contact (IBC) solar cells where a masked ion implantation facilitates their fabrication. This paper presents a study on tunnel oxide passivated contacts formed by low-energy ion implantation into amorphous silicon (a-Si) layers and examines the influence of the ion species (P, B, or BF 2 ), the ion implantation dose (5 × 10 14  cm −2 to 1 × 10 16  cm −2 ), and the subsequent high-temperature anneal (800 °C or 900 °C) on the passivation quality and junction characteristics using double-sided contacted silicon solar cells. Excellent passivation quality is achieved for n-type passivated contacts by P implantations into either intrinsic (undoped) or in-situ B-doped a-Si layers with implied open-circuit voltages (iV oc ) of 725 and 720 mV, respectively. For p-type passivated contacts, BF 2 implantations into intrinsic a-Si yield well passivated contacts and allow for iV oc of 690 mV, whereas implanted B gives poor passivation with iV oc of only 640 mV. While solar cells featuring in-situ B-doped selective hole contacts and selective electron contacts with P implanted into intrinsic a-Si layers achieved V oc of 690 mV and fill factor (FF) of 79.1%, selective hole contacts realized by BF 2 implantation into intrinsic a-Si suffer from drastically reduced FF which is caused by a non-Ohmic Schottky contact. Finally, implanting P into in-situ B-doped a-Si layers for the purpose of overcompensation (counterdoping) allowed for solar cells with V oc of 680 mV and FF of 80.4%, providing a simplified and promising fabrication process for IBC solar cells featuring passivated contacts

  20. Robust Load Cell Cell for Discrete Contact Force Measurements of Sampling Systems and/or Instruments, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Bear Engineering proposes to develop a simple, robust, extreme environment compatible, mechanical load cell to enable the control of contact forces for placement of...

  1. An analytical model and parametric study of electrical contact resistance in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhiliang; Wang, Shuxin; Zhang, Lianhong [School of Mechanical Engineering, Tianjin University, Tianjin 300072 (China); Hu, S. Jack [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2009-04-15

    This paper presents an analytical model of the electrical contact resistance between the carbon paper gas diffusion layers (GDLs) and the graphite bipolar plates (BPPs) in a proton exchange membrane (PEM) fuel cell. The model is developed based on the classical statistical contact theory for a PEM fuel cell, using the same probability distributions of the GDL structure and BPP surface profile as previously described in Wu et al. [Z. Wu, Y. Zhou, G. Lin, S. Wang, S.J. Hu, J. Power Sources 182 (2008) 265-269] and Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Results show that estimates of the contact resistance compare favorably with experimental data by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783]. Factors affecting the contact behavior are systematically studied using the analytical model, including the material properties of the two contact bodies and factors arising from the manufacturing processes. The transverse Young's modulus of chopped carbon fibers in the GDL and the surface profile of the BPP are found to be significant to the contact resistance. The factor study also sheds light on the manufacturing requirements of carbon fiber GDLs for a better contact performance in PEM fuel cells. (author)

  2. Rac1 acts in conjunction with Nedd4 and dishevelled-1 to promote maturation of cell-cell contacts

    NARCIS (Netherlands)

    M. Nethe (Micha); B.J. de Kreuk (Bart-Jan); D.V.F. Tauriello (Daniele); E.C. Anthony (Eloise); B. Snoek (Barbara); T. Stumpel (Thomas); M. Salinas; K. Maurice (Karelle); D. Geerts (Dirk); A.M. Deelder (André); P. Hensbergen (Paul); P.L. Hordijk (Peter )

    2012-01-01

    textabstractThe Rho-GTPase Rac1 promotes actin polymerization and membrane protrusion that mediate initial contact and subsequent maturation of cell-cell junctions. Here we report that Rac1 associates with the ubiquitin-protein ligase neural precursor cell expressed developmentally down-regulated 4

  3. Multi-Material Front Contact for 19% Thin Film Solar Cells

    Directory of Open Access Journals (Sweden)

    Joop van Deelen

    2016-02-01

    Full Text Available The trade-off between transmittance and conductivity of the front contact material poses a bottleneck for thin film solar panels. Normally, the front contact material is a metal oxide and the optimal cell configuration and panel efficiency were determined for various band gap materials, representing Cu(In,GaSe2 (CIGS, CdTe and high band gap perovskites. Supplementing the metal oxide with a metallic copper grid improves the performance of the front contact and aims to increase the efficiency. Various front contact designs with and without a metallic finger grid were calculated with a variation of the transparent conductive oxide (TCO sheet resistance, scribing area, cell length, and finger dimensions. In addition, the contact resistance and illumination power were also assessed and the optimal thin film solar panel design was determined. Adding a metallic finger grid on a TCO gives a higher solar cell efficiency and this also enables longer cell lengths. However, contact resistance between the metal and the TCO material can reduce the efficiency benefit somewhat.

  4. Early local differentiation of the cell wall matrix defines the contact sites in lobed mesophyll cells of Zea mays.

    Science.gov (United States)

    Giannoutsou, E; Sotiriou, P; Apostolakos, P; Galatis, B

    2013-10-01

    The morphogenesis of lobed mesophyll cells (MCs) is highly controlled and coupled with intercellular space formation. Cortical microtubule rings define the number and the position of MC isthmi. This work investigated early events of MC morphogenesis, especially the mechanism defining the position of contacts between MCs. The distributions of plasmodesmata, the hemicelluloses callose and (1 → 3,1 → 4)-β-d-glucans (MLGs) and the pectin epitopes recognized by the 2F4, JIM5, JIM7 and LM6 antibodies were studied in the cell walls of Zea mays MCs. Matrix cell wall polysaccharides were immunolocalized in hand-made sections and in sections of material embedded in LR White resin. Callose was also localized using aniline blue in hand-made sections. Plasmodesmata distribution was examined by transmission electron microscopy. Before reorganization of the dispersed cortical microtubules into microtubule rings, particular bands of the longitudinal MC walls, where the MC contacts will form, locally differentiate by selective (1) deposition of callose and the pectin epitopes recognized by the 2F4, LM6, JIM5 and JIM7 antibodies, (2) degradation of MLGs and (3) formation of secondary plasmodesmata clusterings. This cell wall matrix differentiation persists in cell contacts of mature MCs. Simultaneously, the wall bands between those of future cell contacts differentiate with (1) deposition of local cell wall thickenings including cellulose microfibrils, (2) preferential presence of MLGs, (3) absence of callose and (4) transient presence of the pectins identified by the JIM5 and JIM7 antibodies. The wall areas between cell contacts expand determinately to form the cell isthmi and the cell lobes. The morphogenesis of lobed MCs is characterized by the early patterned differentiation of two distinct cell wall subdomains, defining the sites of the future MC contacts and of the future MC isthmi respectively. This patterned cell wall differentiation precedes cortical microtubule

  5. Transmission Electron Microscopy Studies of Electron-Selective Titanium Oxide Contacts in Silicon Solar Cells

    KAUST Repository

    Ali, Haider; Yang, Xinbo; Weber, Klaus; Schoenfeld, Winston V.; Davis, Kristopher O.

    2017-01-01

    In this study, the cross-section of electron-selective titanium oxide (TiO2) contacts for n-type crystalline silicon solar cells were investigated by transmission electron microscopy. It was revealed that the excellent cell efficiency of 21

  6. Temperature and coupling dependence of the universal contact intensity for an ultracold Fermi gas

    International Nuclear Information System (INIS)

    Palestini, F.; Perali, A.; Pieri, P.; Strinati, G. C.

    2010-01-01

    Physical properties of an ultracold Fermi gas in the temperature-coupling phase diagram can be characterized by the contact intensity C, which enters the pair-correlation function at short distances and describes how the two-body problem merges into its surrounding. We show that the local order established by pairing fluctuations about the critical temperature T c of the superfluid transition considerably enhances the contact C in a temperature range where pseudogap phenomena are maximal. Our ab initio results for C in a trap compare well with recently available experimental data over a wide coupling range. An analysis is also provided for the effects of trap averaging on C.

  7. Light trapping with plasmonic back contacts in thin-film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paetzold, Ulrich Wilhelm

    2013-02-08

    Trapping light in silicon solar cells is essential as it allows an increase in the absorption of incident sunlight in optically thin silicon absorber layers. This way, the costs of the solar cells can be reduced by lowering the material consumption and decreasing the physical constraints on the material quality. In this work, plasmonic light trapping with Ag back contacts in thin-film silicon solar cells is studied. Solar cell prototypes with plasmonic back contacts are presented along with optical simulations of these devices and general design considerations of plasmonic back contacts. Based on three-dimensional electromagnetic simulations, the conceptual design of plasmonic nanostructures on Ag back contacts in thin-film silicon solar cells is studied in this work. Optimizations of the nanostructures regarding their ability to scatter incident light at low optical losses into large angles in the silicon absorber layers of the thin-film silicon solar cells are presented. Geometrical parameters as well as the embedding dielectric layer stack of the nanostructures on Ag layers are varied. Periodic as well as isolated hemispherical Ag nanostructures of dimensions above 200 nm are found to scatter incident light at high efficiencies and low optical losses. Hence, these nanostructures are of interest for light trapping in solar cells. In contrast, small Ag nanostructures of dimension below 100 nm are found to induce optical losses. At the surface of randomly textured Ag back contacts small Ag nanostructures exist which induce optical losses. In this work, the relevance of these localized plasmon induced optical losses as well as optical losses caused by propagating plasmons are investigated with regard to the reflectance of the textured back contacts. In state-of-the-art solar cells, the plasmon-induced optical losses are shifted out of the relevant wavelength range by incorporating a ZnO:Al interlayer of low refractive index at the back contact. The additional but

  8. Mesenchymal stem cells induce mature dendritic cells into a novel Jagged-2-dependent regulatory dendritic cell population.

    Science.gov (United States)

    Zhang, Bin; Liu, Rui; Shi, Dan; Liu, Xingxia; Chen, Yuan; Dou, Xiaowei; Zhu, Xishan; Lu, Chunhua; Liang, Wei; Liao, Lianming; Zenke, Martin; Zhao, Robert C H

    2009-01-01

    Mesenchymal stem cells (MSCs), in addition to their multilineage differentiation, exert immunomodulatory effects on immune cells, even dendritic cells (DCs). However, whether they influence the destiny of full mature DCs (maDCs) remains controversial. Here we report that MSCs vigorously promote proliferation of maDCs, significantly reduce their expression of Ia, CD11c, CD80, CD86, and CD40 while increasing CD11b expression. Interestingly, though these phenotypes clearly suggest their skew to immature status, bacterial lipopolysaccharide (LPS) stimulation could not reverse this trend. Moreover, high endocytosic capacity, low immunogenicity, and strong immunoregulatory function of MSC-treated maDCs (MSC-DCs) were also observed. Furthermore we found that MSCs, partly via cell-cell contact, drive maDCs to differentiate into a novel Jagged-2-dependent regulatory DC population and escape their apoptotic fate. These results further support the role of MSCs in preventing rejection in organ transplantation and treatment of autoimmune disease.

  9. Tantalum Nitride Electron-Selective Contact for Crystalline Silicon Solar Cells

    KAUST Repository

    Yang, Xinbo

    2018-04-19

    Minimizing carrier recombination at contact regions by using carrier‐selective contact materials, instead of heavily doping the silicon, has attracted considerable attention for high‐efficiency, low‐cost crystalline silicon (c‐Si) solar cells. A novel electron‐selective, passivating contact for c‐Si solar cells is presented. Tantalum nitride (TaN x ) thin films deposited by atomic layer deposition are demonstrated to provide excellent electron‐transporting and hole‐blocking properties to the silicon surface, due to their small conduction band offset and large valence band offset. Thin TaNx interlayers provide moderate passivation of the silicon surfaces while simultaneously allowing a low contact resistivity to n‐type silicon. A power conversion efficiency (PCE) of over 20% is demonstrated with c‐Si solar cells featuring a simple full‐area electron‐selective TaNx contact, which significantly improves the fill factor and the open circuit voltage (Voc) and hence provides the higher PCE. The work opens up the possibility of using metal nitrides, instead of metal oxides, as carrier‐selective contacts or electron transport layers for photovoltaic devices.

  10. Evaluation of a Surrogate Contact Model in Force-Dependent Kinematic Simulations of Total Knee Replacement

    NARCIS (Netherlands)

    Marra, M.A.; Andersen, M.S.; Damsgaard, M.; Koopman, B.; Janssen, D.W.; Verdonschot, N.J.

    2017-01-01

    Knowing the forces in the human body is of great clinical interest and musculoskeletal (MS) models are the most commonly used tool to estimate them in vivo. Unfortunately, the process of computing muscle, joint contact, and ligament forces simultaneously is computationally highly demanding. The goal

  11. Evaluation of a surrogate contact model in force-dependent kinematic simulations of total knee replacement

    NARCIS (Netherlands)

    Marra, Marco Antonio; Andersen, Michael S.; Damsgaard, Michael; Koopman, Bart F.J.M.; Janssen, Dennis; Verdonschot, Nico

    2017-01-01

    Knowing the forces in the human body is of great clinical interest and musculoskeletal (MS) models are the most commonly used tool to estimate them in vivo. Unfortunately, the process of computing muscle, joint contact, and ligament forces simultaneously is computationally highly demanding. The goal

  12. Hole-Collection Mechanism in Passivating Metal-Oxide Contacts on Si Solar Cells: Insights From Numerical Simulations

    KAUST Repository

    Vijayan, Ramachandran Ammapet; Essig, Stephanie; De Wolf, Stefaan; Ramanathan, Bairava Ganesh; Loper, Philipp; Ballif, Christophe; Varadharajaperumal, Muthubalan

    2018-01-01

    Silicon heterojunction solar cells enable high conversion efficiencies, thanks to their passivating contacts which consist of layered stacks of intrinsic and doped amorphous silicon. However, such contacts may reduce the photo current, when present

  13. Stiffness of sphere–plate contacts at MHz frequencies: dependence on normal load, oscillation amplitude, and ambient medium

    Directory of Open Access Journals (Sweden)

    Jana Vlachová

    2015-03-01

    Full Text Available The stiffness of micron-sized sphere–plate contacts was studied by employing high frequency, tangential excitation of variable amplitude (0–20 nm. The contacts were established between glass spheres and the surface of a quartz crystal microbalance (QCM, where the resonator surface had been coated with either sputtered SiO2 or a spin-cast layer of poly(methyl methacrylate (PMMA. The results from experiments undertaken in the dry state and in water are compared. Building on the shifts in the resonance frequency and resonance bandwidth, the instrument determines the real and the imaginary part of the contact stiffness, where the imaginary part quantifies dissipative processes. The method is closely analogous to related procedures in AFM-based metrology. The real part of the contact stiffness as a function of normal load can be fitted with the Johnson–Kendall–Roberts (JKR model. The contact stiffness was found to increase in the presence of liquid water. This finding is tentatively explained by the rocking motion of the spheres, which couples to a squeeze flow of the water close to the contact. The loss tangent of the contact stiffness is on the order of 0.1, where the energy losses are associated with interfacial processes. At high amplitudes partial slip was found to occur. The apparent contact stiffness at large amplitude depends linearly on the amplitude, as predicted by the Cattaneo–Mindlin model. This finding is remarkable insofar, as the Cattaneo–Mindlin model assumes Coulomb friction inside the sliding region. Coulomb friction is typically viewed as a macroscopic concept, related to surface roughness. An alternative model (formulated by Savkoor, which assumes a constant frictional stress in the sliding zone independent of the normal pressure, is inconsistent with the experimental data. The apparent friction coefficients slightly increase with normal force, which can be explained by nanoroughness. In other words, contact splitting

  14. Novel Contact Materials for Improved Performance CdTe Solar Cells Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Rockett, Angus [Colorado School of Mines, Golden, CO (United States); Marsillac, Sylvain [Old Dominion Univ., Norfolk, VA (United States); Collins, Robert [Univesity of Toledo

    2018-04-15

    This program has explored a number of novel materials for contacts to CdTe solar cells in order to reduce the back contact Schottky barrier to zero and produce an ohmic contact. The project tested a wide range of potential contact materials including TiN, ZrN, CuInSe2:N, a-Si:H and alloys with C, and FeS2. Improved contacts were achieved with FeS2. As part of understanding the operation of the devices and controlling the deposition processes, a number of other important results were obtained. In the process of this project and following its conclusion it led to research that resulted in seven journal articles, nine conference publications, 13 talks presented at conferences, and training of eight graduate students. The seven journal articles were published in 2015, 2016, and 2017 and have been cited, as of March 2018, 52 times (one cited 19 times and two cited 11 times). We demonstrated high levels of doping of CIS with N but electrical activity of the resulting N was not high and the results were difficult to reproduce. Furthermore, even with high doping the contacts were not good. Annealing did not improve the contacts. A-Si:H was found to produce acceptable but unstable contacts, degrading even over a day or two, apparently due to H incorporation into the CdTe. Alloying with C did not improve the contacts or stability. The transition metal nitrides produced Schottky type contacts for all materials tested. While these contacts were found to be unsatisfactory, we investigated FeS2 and found this material to be effective and comparable to the best contacts currently available. The contacts were found to be chemically stable under heat treatment and preferable to Cu doped contacts. Thus, we demonstrated an improved contact material in the course of this project. In addition, we developed new ways of controlling the deposition of CdTe and other materials, demonstrated the nature of defects in CdTe, and studied the distribution of conductivity and carrier type in Cd

  15. Physical-mechanical image of the cell surface on the base of AFM data in contact mode

    Science.gov (United States)

    Starodubtseva, M. N.; Starodubtsev, I. E.; Yegorenkov, N. I.; Kuzhel, N. S.; Konstantinova, E. E.; Chizhik, S. A.

    2017-10-01

    Physical and mechanical properties of the cell surface are well-known markers of a cell state. The complex of the parameters characterizing the cell surface properties, such as the elastic modulus (E), the parameters of adhesive (Fa), and friction (Ff) forces can be measured using atomic force microscope (AFM) in a contact mode and form namely the physical-mechanical image of the cell surface that is a fundamental element of the cell mechanical phenotype. The paper aims at forming the physical-mechanical images of the surface of two types of glutaraldehyde-fixed cancerous cells (human epithelial cells of larynx carcinoma, HEp-2c cells, and breast adenocarcinoma, MCF-7 cells) based on the data obtained by AFM in air and revealing the basic difference between them. The average values of friction, elastic and adhesive forces, and the roughness of lateral force maps, as well as dependence of the fractal dimension of lateral force maps on Z-scale factor have been studied. We have revealed that the response of microscale areas of the HEp-2c cell surface having numerous microvilli to external mechanical forces is less expressed and more homogeneous in comparison with the response of MCF-7 cell surface.

  16. Shape-dependent regulation of proliferation in normal and malignant human cells and its alteration by interferon

    International Nuclear Information System (INIS)

    Kulesh, D.A.; Greene, J.J.

    1986-01-01

    The relationship between cell morphology, proliferation, and contact inhibition was studied in normal and malignant human cells which varied in their sensitivity to contact inhibition. Their ability to proliferate was examined under conditions where the cells were constrained into different shapes by plating onto plastic surfaces coated with poly(2-hydroxyethyl methacrylate). Poly(2-hydroxyethyl methacrylate) can precisely vary the shape of cells without toxicity. Cell proliferation was quantitated by cell counts and labeling indices were determined by autoradiography. The normal JHU-1 foreskin fibroblasts and IMR-90 lung fibroblasts exhibited contact-inhibited growth with a saturation density of 2.9 X 10(5) and 2.0 X 10(5) cells/cm2, respectively. These cells also exhibited stringent dependency on cell shape with a mitotic index of less than 3% at poly(2-hydroxyethyl methacrylate) concentrations at which the cells were rounded versus a labeling index of 75-90% when the cells were flat. The malignant bladder carcinoma line RT-4 exhibited partial contact-inhibited growth. Its dependency on cell shape was less stringent than that of normal cells with a mitotic index of 37-40% when rounded and 79% when flat. The malignant fibrosarcoma line, HT1080, was not contact inhibited and was entirely shape independent with a mitotic index of 70-90% regardless of cell shape. Treatment of HT1080 cells with low concentration of human fibroblast interferon (less than 40 units/ml) restored shape-dependent proliferation while having little effect on normal cells. Subantiproliferative doses of interferon were also shown to restore contact-inhibited proliferation control to malignant cells previously lacking it

  17. Sulfur passivation and contact methods for GaAs nanowire solar cells

    International Nuclear Information System (INIS)

    Tajik, N; Peng, Z; Kuyanov, P; LaPierre, R R

    2011-01-01

    The effect of sulfur passivation on core-shell p-n junction GaAs nanowire (NW) solar cells has been investigated. Devices of two types were investigated, consisting of indium tin oxide contact dots or opaque Au finger electrodes. Lateral carrier transport from the NWs to the contact fingers was achieved via a p-doped GaAs surface conduction layer. NWs between the opaque contact fingers had sidewall surfaces exposed for passivation by sulfur. The relative cell efficiency increased by 19% upon passivation. The contribution of the thin film grown between the NWs to the total cell efficiency was estimated by removing the NWs using a sonication procedure. Mechanisms of carrier transport and photovoltaic effects are discussed on the basis of spatially resolved laser scanning measurements.

  18. Involvement of IRF4 dependent dendritic cells in T cell dependent colitis

    DEFF Research Database (Denmark)

    Pool, Lieneke; Rivollier, Aymeric Marie Christian; Agace, William Winston

    in genetically susceptible individuals and pathogenic CD4+ T cells, which accumulate in the inflamed mucosa, are believed to be key drivers of the disease. While dendritic cells (DCs) are important in the priming of intestinal adaptive immunity and tolerance their role in the initiation and perpetuation...... of chronic intestinal inflammation remains unclear. In the current study we used the CD45RBhi T cell transfer model of colitis to determine the role of IRF4 dependent DCs in intestinal inflammation. In this model naïve CD4+ T cells when transferred into RAG-/- mice, proliferate and expand in response...... to bacterial derived luminal antigen, localize to the intestinal mucosa and induce colitis. Adoptive transfer of naïve T cells into CD11cCre.IRF4fl/fl.RAG-1-/- mice resulted in reduced monocyte recruitment to the intestine and mesenteric lymph nodes (MLN) compared to Cre- controls. Inflammatory cytokines...

  19. Design guideline for Si/organic hybrid solar cell with interdigitated back contact structure

    Science.gov (United States)

    Bimo Prakoso, Ari; Rusli; Li, Zeyu; Lu, Chenjin; Jiang, Changyun

    2018-03-01

    We study the design of Si/organic hybrid (SOH) solar cells with interdigitated back contact (IBC) structure. SOH solar cells formed between n-Si and poly(3,4-ethylenedioxythiophene): polystyrenesulphonate (PEDOT:PSS) is a promising concept that combines the excellent electronic properties of Si with the solution-based processing advantage of an organic polymer. The IBC cell structure is employed to minimize parasitic absorption losses in the organic polymer, eliminate grid shadowing losses, and allow excellent passivation of the front Si surface in one step over a large area. The influence of Si thickness, doping concentration and contact geometry are simulated in this study to optimize the performance of the SOH-IBC solar cell. We found that a high power conversion efficiency of >20% can be achieved for optimized SOH-IBC cell based on a thin c-Si substrate of 40 μm thickness.

  20. Control of back surface reflectance from aluminum alloyed contacts on silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Cudzinovic, M.; Sopori, B. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    A process for forming highly reflective aluminum back contacts with low contact resistance to silicon solar cells is described. By controlling the process conditions, it is possible to vary the silicon/aluminum interface from a specular to a diffuse reflector while maintaining a high interface reflectance. The specular interface is found to be a uniform silicon/aluminum alloy layer a few angstroms thick that has epitaxially regrown on the silicon. The diffuse interface consists of randomly distributed (111) pyramids produced by crystallographic out-diffusion of the bulk silicon. The light trapping ability of the diffuse contact is found to be close to the theoretical limit. Both types of contacts are found to have specific contact resistivities of 10{sup {minus}5} {Omega}-cm{sup 2}. The process for forming the contacts involves illuminating the devices with tungsten halogen lamps. The process is rapid (under 100 s) and low temperature (peak temperature < 580{degrees}C), making it favorable for commercial solar cell fabrication.

  1. Regulation of promyogenic signal transduction by cell-cell contact and adhesion

    International Nuclear Information System (INIS)

    Krauss, Robert S.

    2010-01-01

    Skeletal myoblast differentiation involves acquisition of the muscle-specific transcriptional program and morphological changes, including fusion into multinucleated myofibers. Differentiation is regulated by extracellular signaling cues, including cell-cell contact and adhesion. Cadherin and Ig adhesion receptors have been implicated in distinct but overlapping stages of myogenesis. N-cadherin signals through the Ig receptor Cdo to activate p38 MAP kinase, while the Ig receptor neogenin signals to activate FAK; both processes promote muscle-specific gene expression and myoblast fusion. M-cadherin activates Rac1 to enhance fusion. Specific Ig receptors (Kirre and Sns) are essential for myoblast fusion in Drosophila, also signaling through Rac, and vertebrate orthologs of Kirre and Sns have partially conserved function. Mice lacking specific cytoplasmic signaling factors activated by multiple receptors (e.g., Rac1) have strong muscle phenotypes in vivo. In contrast, mice lacking individual adhesion receptors that lie upstream of these factors have modest phenotypes. Redundancy among receptors may account for this. Many of the mammalian Ig receptors and cadherins associate with each other, and multivalent interactions within these complexes may require removal of multiple components to reveal dramatic defects in vivo. Nevertheless, it is possible that the murine adhesion receptors rate-limiting in vivo have not yet been identified or fully assessed.

  2. Regulation of promyogenic signal transduction by cell-cell contact and adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Krauss, Robert S., E-mail: Robert.Krauss@mssm.edu [Department of Developmental and Regenerative Biology, Mount Sinai School of Medicine, New York, NY 10029 (United States)

    2010-11-01

    Skeletal myoblast differentiation involves acquisition of the muscle-specific transcriptional program and morphological changes, including fusion into multinucleated myofibers. Differentiation is regulated by extracellular signaling cues, including cell-cell contact and adhesion. Cadherin and Ig adhesion receptors have been implicated in distinct but overlapping stages of myogenesis. N-cadherin signals through the Ig receptor Cdo to activate p38 MAP kinase, while the Ig receptor neogenin signals to activate FAK; both processes promote muscle-specific gene expression and myoblast fusion. M-cadherin activates Rac1 to enhance fusion. Specific Ig receptors (Kirre and Sns) are essential for myoblast fusion in Drosophila, also signaling through Rac, and vertebrate orthologs of Kirre and Sns have partially conserved function. Mice lacking specific cytoplasmic signaling factors activated by multiple receptors (e.g., Rac1) have strong muscle phenotypes in vivo. In contrast, mice lacking individual adhesion receptors that lie upstream of these factors have modest phenotypes. Redundancy among receptors may account for this. Many of the mammalian Ig receptors and cadherins associate with each other, and multivalent interactions within these complexes may require removal of multiple components to reveal dramatic defects in vivo. Nevertheless, it is possible that the murine adhesion receptors rate-limiting in vivo have not yet been identified or fully assessed.

  3. Genome-Derived Cytosolic DNA Mediates Type I Interferon-Dependent Rejection of B Cell Lymphoma Cells

    Directory of Open Access Journals (Sweden)

    Yu J. Shen

    2015-04-01

    Full Text Available The DNA damage response (DDR induces the expression of type I interferons (IFNs, but the underlying mechanisms are poorly understood. Here, we show the presence of cytosolic DNA in different mouse and human tumor cells. Treatment of cells with genotoxic agents increased the levels of cytosolic DNA in a DDR-dependent manner. Cloning of cytosolic DNA molecules from mouse lymphoma cells suggests that cytosolic DNA is derived from unique genomic loci and has the potential to form non-B DNA structures, including R-loops. Overexpression of Rnaseh1, which resolves R-loops, reduced the levels of cytosolic DNA, type I Ifn transcripts, and type I IFN-dependent rejection of lymphoma cells. Live-cell imaging showed a dynamic contact of cytosolic DNA with mitochondria, an important organelle for innate immune recognition of cytosolic nucleotides. In summary, we found that cytosolic DNA is present in many tumor cells and contributes to the immunogenicity of tumor cells.

  4. Shape optimization in 2D contact problems with given friction and a solution-dependent coefficient of friction

    Czech Academy of Sciences Publication Activity Database

    Haslinger, J.; Outrata, Jiří; Pathó, R.

    2012-01-01

    Roč. 20, č. 1 (2012), s. 31-59 ISSN 1877-0533 R&D Projects: GA AV ČR IAA100750802 Institutional research plan: CEZ:AV0Z10750506 Institutional support: RVO:67985556 Keywords : shape optimization * Signorini problem * model with given frinction * solution-dependent coefficient of friction * mathematical probrams with equilibrium constraints Subject RIV: BA - General Mathematics Impact factor: 1.036, year: 2012 http://library.utia.cas.cz/separaty/2012/MTR/outrata-shape optimization in 2d contact problems with given friction and a solution-dependent coefficient of friction .pdf

  5. Do the contact angle and line tension of surface-attached droplets depend on the radius of curvature?

    Science.gov (United States)

    Das, Subir K; Egorov, Sergei A; Virnau, Peter; Winter, David; Binder, Kurt

    2018-06-27

    Results from Monte Carlo simulations of wall-attached droplets in the three-dimensional Ising lattice gas model and in a symmetric binary Lennard-Jones fluid, confined by antisymmetric walls, are analyzed, with the aim to estimate the dependence of the contact angle [Formula: see text] on the droplet radius [Formula: see text] of curvature. Sphere-cap shape of the wall-attached droplets is assumed throughout. An approach, based purely on 'thermodynamic' observables, e.g. chemical potential, excess density due to the droplet, etc, is used, to avoid ambiguities in the decision which particles belong (or do not belong, respectively) to the droplet. It is found that the results are compatible with a variation [Formula: see text], [Formula: see text] being the contact angle in the thermodynamic limit ([Formula: see text]). The possibility to use such results to estimate the excess free energy related to the contact line of the droplet, namely the line tension, at the wall, is discussed. Various problems that hamper this approach and were not fully recognized in previous attempts to extract the line tension are identified. It is also found that the dependence of wall tensions on the difference of chemical potential of the droplet from that at the bulk coexistence provides effectively a change of the contact angle of similar magnitude. The simulation approach yields precise estimates for the excess density due to wall-attached droplets and the corresponding free energy excess, relative to a system without a droplet at the same chemical potential. It is shown that this information suffices to estimate nucleation barriers, not affected by ambiguities on droplet shape, contact angle and line tension.

  6. Modeling and characterization of double resonant tunneling diodes for application as energy selective contacts in hot carrier solar cells

    Science.gov (United States)

    Jehl, Zacharie; Suchet, Daniel; Julian, Anatole; Bernard, Cyril; Miyashita, Naoya; Gibelli, Francois; Okada, Yoshitaka; Guillemolles, Jean-Francois

    2017-02-01

    Double resonant tunneling barriers are considered for an application as energy selective contacts in hot carrier solar cells. Experimental symmetric and asymmetric double resonant tunneling barriers are realized by molecular beam epitaxy and characterized by temperature dependent current-voltage measurements. The negative differential resistance signal is enhanced for asymmetric heterostructures, and remains unchanged between low- and room-temperatures. Within Tsu-Esaki description of the tunnel current, this observation can be explained by the voltage dependence of the tunnel transmission amplitude, which presents a resonance under finite bias for asymmetric structures. This effect is notably discussed with respect to series resistance. Different parameters related to the electronic transmission of the structure and the influence of these parameters on the current voltage characteristic are investigated, bringing insights on critical processes to optimize in double resonant tunneling barriers applied to hot carrier solar cells.

  7. The formation mechanism for printed silver-contacts for silicon solar cells.

    Science.gov (United States)

    Fields, Jeremy D; Ahmad, Md Imteyaz; Pool, Vanessa L; Yu, Jiafan; Van Campen, Douglas G; Parilla, Philip A; Toney, Michael F; van Hest, Maikel F A M

    2016-04-01

    Screen-printing provides an economically attractive means for making Ag electrical contacts to Si solar cells, but the use of Ag substantiates a significant manufacturing cost, and the glass frit used in the paste to enable contact formation contains Pb. To achieve optimal electrical performance and to develop pastes with alternative, abundant and non-toxic materials, a better understanding the contact formation process during firing is required. Here, we use in situ X-ray diffraction during firing to reveal the reaction sequence. The findings suggest that between 500 and 650 °C PbO in the frit etches the SiNx antireflective-coating on the solar cell, exposing the Si surface. Then, above 650 °C, Ag(+) dissolves into the molten glass frit - key for enabling deposition of metallic Ag on the emitter surface and precipitation of Ag nanocrystals within the glass. Ultimately, this work clarifies contact formation mechanisms and suggests approaches for development of inexpensive, nontoxic solar cell contacting pastes.

  8. Salinity-Dependent Contact Angle Alteration in Oil/Brine/Silicate Systems: the Critical Role of Divalent Cations.

    Science.gov (United States)

    Haagh, M E J; Siretanu, I; Duits, M H G; Mugele, F

    2017-04-11

    The effectiveness of water flooding oil recovery depends to an important extent on the competitive wetting of oil and water on the solid rock matrix. Here, we use macroscopic contact angle goniometry in highly idealized model systems to evaluate how brine salinity affects the balance of wetting forces and to infer the microscopic origin of the resultant contact angle alteration. We focus, in particular, on two competing mechanisms debated in the literature, namely, double-layer expansion and divalent cation bridging. Our experiments involve aqueous droplets with a variable content of chloride salts of Na + , K + , Ca 2+ , and Mg 2+ , wetting surfaces of muscovite and amorphous silica, and an environment of ambient decane containing small amounts of fatty acids to represent polar oil components. By diluting the salt content in various manners, we demonstrate that the water contact angle on muscovite, not on silica, decreases by up to 25° as the divalent cation concentration is reduced from typical concentrations in seawater to zero. Decreasing the ionic strength at a constant divalent ion concentration, however, has a negligible effect on the contact angle. We discuss the consequences for the interpretation of core flooding experiments and the identification of a microscopic mechanism of low salinity water flooding, an increasingly popular, inexpensive, and environment-friendly technique for enhanced oil recovery.

  9. Analysis of a Dynamic Viscoelastic Contact Problem with Normal Compliance, Normal Damped Response, and Nonmonotone Slip Rate Dependent Friction

    Directory of Open Access Journals (Sweden)

    Mikaël Barboteu

    2016-01-01

    Full Text Available We consider a mathematical model which describes the dynamic evolution of a viscoelastic body in frictional contact with an obstacle. The contact is modelled with a combination of a normal compliance and a normal damped response law associated with a slip rate-dependent version of Coulomb’s law of dry friction. We derive a variational formulation and an existence and uniqueness result of the weak solution of the problem is presented. Next, we introduce a fully discrete approximation of the variational problem based on a finite element method and on an implicit time integration scheme. We study this fully discrete approximation schemes and bound the errors of the approximate solutions. Under regularity assumptions imposed on the exact solution, optimal order error estimates are derived for the fully discrete solution. Finally, after recalling the solution of the frictional contact problem, some numerical simulations are provided in order to illustrate both the behavior of the solution related to the frictional contact conditions and the theoretical error estimate result.

  10. Excitable waves at the margin of the contact area between a cell and a substrate

    International Nuclear Information System (INIS)

    Ali, O; Albigès-Rizo, C; Block, M R; Fourcade, B

    2009-01-01

    In this paper, we study a new physical mechanism to generate an activator field which signals the extreme margin of the contact area between an adherent cell and the substrate. This mechanism is based on the coupling between the adhesive bridges connecting the substrate to the cytoskeleton and a cytosolic activator. Once activated by adhesion on the adhesive bridges, this activator is free to diffuse on the membrane. We propose that this activator is part of the mecano-transduction pathway which links adhesion to actin polymerization and, thus, to cellular motility. The consequences of our model are as follows: (a) the activator is localized at the rim of the contact area, (b) the adhesion is reinforced at the margin of the contact area between the cell and the substrate, (c) excitable waves of the activator can propagate along the adhesion rim

  11. Dependence of compressive strength of green compacts on pressure, density and contact area of powder particles

    International Nuclear Information System (INIS)

    Salam, A.; Akram, M.; Shahid, K.A.; Javed, M.; Zaidi, S.M.

    1994-08-01

    The relationship between green compressive strength and compacting pressure as well as green density has been investigated for uniaxially pressed aluminium powder compacts in the range 0 - 520 MPa. Two linear relationships occurred between compacting pressure and green compressive strength which corresponded to powder compaction stages II and III respectively, increase in strength being large during stage II and quite small in stage III with increasing pressure. On the basis of both, the experimental results and a previous model on cold compaction of powder particles, relationships between green compressive strength and green density and interparticle contact area of the compacts has been established. (author) 9 figs

  12. Micropatterning of poly(4-hydroxystyrene) by ion beam contact lithography for the control of cell adhesion

    International Nuclear Information System (INIS)

    Hwang, In Tae; Jung, Chan Hee; Choi, Jae Hak; Nho, Young Chang; Lee, Byoung Min; Hong, Sung Kwon

    2009-01-01

    In this study, we report on a simple method of micropatterning of cells by using ion beam contact lithography. Thin poly(4-hydroxystyrene) (Phds) films spin-coated on a silicon wafer were irradiated through a pattern mask in a contact mode with proton ions and then developed to generate the patterns of the Phds. Well-defined 50 μm line (pitch 150 μm) patterns were obtained without using any additives. The remaining thickness after development was increased with an increasing fluence up to 3 x 10 14 ions cm -2 after which it leveled off. The in-vitro cell culture test revealed that the cells were preferentially adhered to and proliferated only on the space regions between the Phds line patterns. Inhibition of cell adhesion on the Phds patterns could be due to antifouling property of the irradiated PHS

  13. Intracellular contacts - effect of survival curve of mammal cells on the Dq value

    International Nuclear Information System (INIS)

    Durand, R.E.; Sutherland, R.M.

    1980-01-01

    Survival increase is observed in cells of the Chinese hamster of the V79-171 line which grow in the composition of multicell spheroids as compared with the survival after irradiation in a single state. The ratio of the Dsub(q) cell value in the composition of spheroids to Dsub(q) of separately growing cells increases as the mitotic cycle proceeds from the minimum value of 1.3 for cells in the Gi phase to the maximum value of 2.2 for cells in a late S-phase. The increase of survival during growth in the composition of spheroids is not characteristic for all cell types. Only a part of cultured MNNG-mutants of cells of the V79-171 Chinese hamster reveal radiomodifying effect of cell contact acting [ru

  14. Microbial counts of food contact surfaces at schools depending on a feeding scheme

    Directory of Open Access Journals (Sweden)

    Nthabiseng Nhlapo

    2014-11-01

    Full Text Available The prominence of disease transmission between individuals in confined environments is a concern, particularly in the educational environment. With respect to school feeding schemes, food contact surfaces have been shown to be potential vehicles of foodborne pathogens. The aim of this study was to assess the cleanliness of the surfaces that come into contact with food that is provided to children through the National School Nutrition Programme in central South Africa. In each school under study, microbiological samples were collected from the preparation surface and the dominant hand and apron of the food handler. The samples were analysed for total viable counts, coliforms, Escherichia coli, Staphylococcus aureus and yeasts and moulds. The criteria specified in the British Columbia Guide for Environmental Health Officers were used to evaluate the results. Total viable counts were high for all surfaces, with the majority of colonies being too numerous to count (over 100 colonies per plate. Counts of organisms were relatively low, with 20% of the surfaces producing unsatisfactory enumeration of S. aureus and E. coli and 30% unsatisfactory for coliforms. Yeast and mould produced 50% and 60% unsatisfactory counts from preparation surfaces and aprons, respectively. Statistically significant differences could not be established amongst microbial counts of the surfaces, which suggests cross-contamination may have occurred. Contamination may be attributed to foodstuffs and animals in the vicinity of the preparation area rather than to the food handlers, because hands had the lowest counts of enumerated organisms amongst the analysed surfaces.

  15. Resonant characteristics and sensitivity dependency on the contact surface in QCM-micropillar-based system of coupled resonator sensors

    International Nuclear Information System (INIS)

    Kashan, M A M; Kalavally, V; Ramakrishnan, N; Lee, H W

    2016-01-01

    We report the characteristics and sensitivity dependence over the contact surface in coupled resonating sensors (CRSs) made of high aspect ratio resonant micropillars attached to a quartz crystal microbalance (QCM). Through experiments and simulation, we observed that when the pillars of resonant heights were placed in maximum displacement regions the resonance frequency of the QCM increased following the coupled resonance characteristics, as the pillar offered elastic loading to the QCM surface. However, the same pillars when placed in relatively lower displacement regions, in spite of their resonant dimension, offered inertial loading and resulted in a decrease in QCM resonance frequency, as the displacement amplitude was insufficient to couple the vibrations from the QCM to the pillars. Accordingly, we discovered that the coupled resonance characteristics not only depend on the resonant structure dimensions but also on the contact regions in the acoustic device. Further analysis revealed that acoustic pressure at the contact surface also influences the resonance frequency characteristics and sensitivity of the CRS. To demonstrate the significance of the present finding for sensing applications, humidity sensing is considered as the example measurand. When a sensing medium made of resonant SU-8 pillars was placed in a maximum displacement region on a QCM surface, the sensitivity increased by 14 times in comparison to a resonant sensing medium placed in a lower displacement region of a QCM surface. (paper)

  16. Fabrication and characterization of contact layers in amorphous silicon solar cells

    International Nuclear Information System (INIS)

    Kolter, M.

    1993-04-01

    The production and characterisation of amorphous and microcrystalline n-doped layers (a-Si:H(n) and c-Si:H(n)) for thin film solar cells is described together contact investigations. The layers were produced in a plasma CVD. The electric conductivity was measured

  17. Conflicting selective forces affect T cell receptor contacts in an immunodominant human immunodeficiency virus epitope

    DEFF Research Database (Denmark)

    Iversen, Astrid K N; Stewart-Jones, Guillaume; Learn, Gerald H

    2006-01-01

    two principal, diametrically opposed evolutionary pathways that exclusively affect T cell-receptor contact residues. One pathway was characterized by acquisition of CTL escape mutations and the other by selection for wild-type amino acids. The pattern of CTL responses to epitope variants shaped which...

  18. Tuning back contact property via artificial interface dipoles in Si/organic hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dan [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Department of Physics and Institute of Solid-state electronics physical, Ningbo University, Ningbo 315211 (China); Sheng, Jiang, E-mail: shengjiang@nimte.ac.cn; Wu, Sudong; Zhu, Juye; Chen, Shaojie; Gao, Pingqi; Ye, Jichun, E-mail: jichun.ye@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2016-07-25

    Back contact property plays a key role in the charge collection efficiency of c-Si/poly(3,4-ethylthiophene):poly(styrenesulfonate) hybrid solar cells (Si-HSCs), as an alternative for the high-efficiency and low-cost photovoltaic devices. In this letter, we utilize the water soluble poly (ethylene oxide) (PEO) to modify the Al/Si interface to be an Ohmic contact via interface dipole tuning, decreasing the work function of the Al film. This Ohmic contact improves the electron collection efficiency of the rear electrode, increasing the short circuit current density (J{sub sc}). Furthermore, the interface dipoles make the band bending downward to increase the total barrier height of built-in electric field of the solar cell, enhancing the open circuit voltage (V{sub oc}). The PEO solar cell exhibits an excellent performance, 12.29% power conversion efficiency, a 25.28% increase from the reference solar cell without a PEO interlayer. The simple and water soluble method as a promising alternative is used to develop the interfacial contact quality of the rear electrode for the high photovoltaic performance of Si-HSCs.

  19. Transmission Electron Microscopy Studies of Electron-Selective Titanium Oxide Contacts in Silicon Solar Cells

    KAUST Repository

    Ali, Haider

    2017-08-15

    In this study, the cross-section of electron-selective titanium oxide (TiO2) contacts for n-type crystalline silicon solar cells were investigated by transmission electron microscopy. It was revealed that the excellent cell efficiency of 21.6% obtained on n-type cells, featuring SiO2/TiO2/Al rear contacts and after forming gas annealing (FGA) at 350°C, is due to strong surface passivation of SiO2/TiO2 stack as well as low contact resistivity at the Si/SiO2/TiO2 heterojunction. This can be attributed to the transformation of amorphous TiO2 to a conducting TiO2-x phase. Conversely, the low efficiency (9.8%) obtained on cells featuring an a-Si:H/TiO2/Al rear contact is due to severe degradation of passivation of the a-Si:H upon FGA.

  20. The Biocompatibility and Bioactivity of Biodentine in Contact with Cementoblast Cells

    Science.gov (United States)

    2016-07-18

    and counting by inverted reflected light microscopy and software analysis . Error bars are SEM. The straight line shows a linear regression analysis...Biodentine® in Contact with Cementoblast Cells ABSTRACT Introduction : Biodentine® is a dental material used for perforation repairs, root-end fillings...pH and calcium ion levels, suggesting surface topology could have a negative effect on cells. INTRODUCTION An ideal endodontic

  1. Inhibition of Staphylococcus aureus invasion into bovine mammary epithelial cells by contact with live Lactobacillus casei.

    Science.gov (United States)

    Bouchard, Damien S; Rault, Lucie; Berkova, Nadia; Le Loir, Yves; Even, Sergine

    2013-02-01

    Staphylococcus aureus is a major pathogen that is responsible for mastitis in dairy herds. S. aureus mastitis is difficult to treat and prone to recurrence despite antibiotic treatment. The ability of S. aureus to invade bovine mammary epithelial cells (bMEC) is evoked to explain this chronicity. One sustainable alternative to treat or prevent mastitis is the use of lactic acid bacteria (LAB) as mammary probiotics. In this study, we tested the ability of Lactobacillus casei strains to prevent invasion of bMEC by two S. aureus bovine strains, RF122 and Newbould305, which reproducibly induce acute and moderate mastitis, respectively. L. casei strains affected adhesion and/or internalization of S. aureus in a strain-dependent manner. Interestingly, L. casei CIRM-BIA 667 reduced S. aureus Newbould305 and RF122 internalization by 60 to 80%, and this inhibition was confirmed for two other L. casei strains, including one isolated from bovine teat canal. The protective effect occurred without affecting bMEC morphology and viability. Once internalized, the fate of S. aureus was not affected by L. casei. It should be noted that L. casei was internalized at a low rate but survived in bMEC cells with a better efficiency than that of S. aureus RF122. Inhibition of S. aureus adhesion was maintained with heat-killed L. casei, whereas contact between live L. casei and S. aureus or bMEC was required to prevent S. aureus internalization. This first study of the antagonism of LAB toward S. aureus in a mammary context opens avenues for the development of novel control strategies against this major pathogen.

  2. Inhibition of Staphylococcus aureus Invasion into Bovine Mammary Epithelial Cells by Contact with Live Lactobacillus casei

    Science.gov (United States)

    Bouchard, Damien S.; Rault, Lucie; Berkova, Nadia; Le Loir, Yves

    2013-01-01

    Staphylococcus aureus is a major pathogen that is responsible for mastitis in dairy herds. S. aureus mastitis is difficult to treat and prone to recurrence despite antibiotic treatment. The ability of S. aureus to invade bovine mammary epithelial cells (bMEC) is evoked to explain this chronicity. One sustainable alternative to treat or prevent mastitis is the use of lactic acid bacteria (LAB) as mammary probiotics. In this study, we tested the ability of Lactobacillus casei strains to prevent invasion of bMEC by two S. aureus bovine strains, RF122 and Newbould305, which reproducibly induce acute and moderate mastitis, respectively. L. casei strains affected adhesion and/or internalization of S. aureus in a strain-dependent manner. Interestingly, L. casei CIRM-BIA 667 reduced S. aureus Newbould305 and RF122 internalization by 60 to 80%, and this inhibition was confirmed for two other L. casei strains, including one isolated from bovine teat canal. The protective effect occurred without affecting bMEC morphology and viability. Once internalized, the fate of S. aureus was not affected by L. casei. It should be noted that L. casei was internalized at a low rate but survived in bMEC cells with a better efficiency than that of S. aureus RF122. Inhibition of S. aureus adhesion was maintained with heat-killed L. casei, whereas contact between live L. casei and S. aureus or bMEC was required to prevent S. aureus internalization. This first study of the antagonism of LAB toward S. aureus in a mammary context opens avenues for the development of novel control strategies against this major pathogen. PMID:23183972

  3. Gap junctions at the dendritic cell-T cell interface are key elements for antigen-dependent T cell activation.

    Science.gov (United States)

    Elgueta, Raul; Tobar, Jaime A; Shoji, Kenji F; De Calisto, Jaime; Kalergis, Alexis M; Bono, Maria R; Rosemblatt, Mario; Sáez, Juan C

    2009-07-01

    The acquired immune response begins with Ag presentation by dendritic cells (DCs) to naive T cells in a heterocellular cell-cell contact-dependent process. Although both DCs and T cells are known to express connexin43, a gap junction protein subunit, the role of connexin43 on the initiation of T cell responses remains to be elucidated. In the present work, we report the formation of gap junctions between DCs and T cells and their role on T cell activation during Ag presentation by DCs. In cocultures of DCs and T cells, Lucifer yellow microinjected into DCs is transferred to adjacent transgenic CD4(+) T cells, only if the specific antigenic peptide was present at least during the first 24 h of cocultures. This dye transfer was sensitive to gap junction blockers, such as oleamide, and small peptides containing the extracellular loop sequences of conexin. Furthermore, in this system, gap junction blockers drastically reduced T cell activation as reflected by lower proliferation, CD69 expression, and IL-2 secretion. This lower T cell activation produced by gap junction blockers was not due to a lower expression of CD80, CD86, CD40, and MHC-II on DCs. Furthermore, gap junction blocker did not affect polyclonal activation of T cell induced with anti-CD3 plus anti-CD28 Abs in the absence of DCs. These results strongly suggest that functional gap junctions assemble at the interface between DCs and T cells during Ag presentation and that they play an essential role in T cell activation.

  4. Immobilization method of yeast cells for intermittent contact mode imaging using the atomic force microscope

    International Nuclear Information System (INIS)

    De, Tathagata; Chettoor, Antony M.; Agarwal, Pranav; Salapaka, Murti V.; Nettikadan, Saju

    2010-01-01

    The atomic force microscope (AFM) is widely used for studying the surface morphology and growth of live cells. There are relatively fewer reports on the AFM imaging of yeast cells (Kasas and Ikai, 1995), (Gad and Ikai, 1995). Yeasts have thick and mechanically strong cell walls and are therefore difficult to attach to a solid substrate. In this report, a new immobilization technique for the height mode imaging of living yeast cells in solid media using AFM is presented. The proposed technique allows the cell surface to be almost completely exposed to the environment and studied using AFM. Apart from the new immobilization protocol, for the first time, height mode imaging of live yeast cell surface in intermittent contact mode is presented in this report. Stable and reproducible imaging over a 10-h time span is observed. A significant improvement in operational stability will facilitate the investigation of growth patterns and surface patterns of yeast cells.

  5. Direct contact between dendritic cells and bronchial epithelial cells inhibits T cell recall responses towards mite and pollen allergen extracts in vitro

    DEFF Research Database (Denmark)

    Papazian, Dick; Wagtmann, Valery R; Hansen, Soren

    2015-01-01

    (DCs), we have investigated recall T cell responses in allergic patients sensitized to house dust mite, grass, and birch pollen. Conclusions: Using allergen extract-loaded DCs to stimulate autologous allergen-specific T cell lines, we show that AEC-imprinted DCs inhibit T cell proliferation...... production of both Th1 and Th2 cytokines upon re-challenge. The inhibitory effects of AECs' contact with DCs were absent when allergen extract-loaded DCs had only been exposed to AECs supernatants, but present after direct contact with AECs. We conclude that direct contact between DCs and AECs inhibits T...

  6. Transport and contact-free investigation of REBCO thin film temperature dependent pinning landscapes

    Science.gov (United States)

    Sinclair, John; Jaroszynski, Jan; Hu, Xinbo; Santos, Michael

    2013-03-01

    Studies of the pinning mechanisms and landscapes of REBa2Cu3Ox (RE=rare earth elements) thin films have been a topic of study in recent years due to, among other reasons, their ability to introduce nonsuperconducting phases and defects. Here we will focus on REBCO thin films with BaZrO3 nanocolumns and other isotropic defects. The evolution of the dominant pinning mechanisms seems to change as a function of temperature even to the point that samples with similar critical current density properties at high temperatures can have distinctly different properties at low temperatures. Earlier work focused on the angular selectivity of the current density profile, though other properties (such as alpha values) can evolve as well. Characteristic results accentuating this evolution of current density properties will be presented. Challenges exist in evaluating these low temperature properties in high magnetic fields, therefore both transport and contact-free results were be presented to compliment the work. Support for this work is provided by the NHMFL via NSF DRM 0654118.

  7. Influence of hole transport material/metal contact interface on perovskite solar cells

    Science.gov (United States)

    Lei, Lei; Zhang, Shude; Yang, Songwang; Li, Xiaomin; Yu, Yu; Wei, Qingzhu; Ni, Zhichun; Li, Ming

    2018-06-01

    Interfaces have a significant impact on the performance of perovskite solar cells. This work investigated the influence of hole transport material/metal contact interface on photovoltaic behaviours of perovskite solar devices. Different hole material/metal contact interfaces were obtained by depositing the metal under different conditions. High incident kinetic energy metal particles were proved to penetrate and embed into the hole transport material. These isolated metal particles in hole transport materials capture holes and increase the apparent carrier transport resistance of the hole transport layer. Sample temperature was found to be of great significance in metal deposition. Since metal vapour has a high temperature, the deposition process accumulated a large amount of heat. The heat evaporated the additives in the hole transport layer and decreased the hole conductivity. On the other hand, high temperature may cause iodization of the metal contact.

  8. Surface Tension Flows inside Surfactant-Added Poly(dimethylsiloxane Microstructures with Velocity-Dependent Contact Angles

    Directory of Open Access Journals (Sweden)

    Jyh Jian Chen

    2014-03-01

    Full Text Available Filling of liquid samples is realized in a microfluidic device with applications including analytical systems, biomedical devices, and systems for fundamental research. The filling of a disk-shaped polydimethylsiloxane (PDMS microchamber by liquid is analyzed with reference to microstructures with inlets and outlets. The microstructures are fabricated using a PDMS molding process with an SU-8 mold. During the filling, the motion of the gas-liquid interface is determined by the competition among inertia, adhesion, and surface tension. A single ramp model with velocity-dependent contact angles is implemented for the accurate calculation of surface tension forces in a three-dimensional volume-of-fluid based model. The effects of the parameters of this functional form are investigated. The influences of non-dimensional parameters, such as the Reynolds number and the Weber number, both determined by the inlet velocity, on the flow characteristics are also examined. An oxygen-plasma-treated PDMS substrate is utilized, and the microstructure is modified to be hydrophilic. Flow experiments are conducted into both hydrophilic and hydrophobic PDMS microstructures. Under a hydrophobic wall condition, numerical simulations with imposed boundary conditions of static and dynamic contact angles can successfully predict the moving of the meniscus compared with experimental measurements. However, for a hydrophilic wall, accurate agreement between numerical and experimental results is obvious as the dynamic contact angles were implemented.

  9. Myotube formation is affected by adipogenic lineage cells in a cell-to-cell contact-independent manner

    International Nuclear Information System (INIS)

    Takegahara, Yuki; Yamanouchi, Keitaro; Nakamura, Katsuyuki; Nakano, Shin-ichi; Nishihara, Masugi

    2014-01-01

    Intramuscular adipose tissue (IMAT) formation is observed in some pathological conditions such as Duchenne muscular dystrophy (DMD) and sarcopenia. Several studies have suggested that IMAT formation is not only negatively correlated with skeletal muscle mass but also causes decreased muscle contraction in sarcopenia. In the present study, we examined w hether adipocytes affect myogenesis. For this purpose, skeletal muscle progenitor cells were transfected with siRNA of PPARγ (siPPARγ) in an attempt to inhibit adipogenesis. Myosin heavy chain (MHC)-positive myotube formation was promoted in cells transfected with siPPARγ compared to that of cells transfected with control siRNA. To determine whether direct cell-to-cell contact between adipocytes and myoblasts is a prerequisite for adipocytes to affect myogenesis, skeletal muscle progenitor cells were cocultured with pre- or mature adipocytes in a Transwell coculture system. MHC-positive myotube formation was inhibited when skeletal muscle progenitor cells were cocultured with mature adipocytes, but was promoted when they were cocultured with preadipocytes. Similar effects were observed when pre- or mature adipocyte-conditioned medium was used. These results indicate that preadipocytes play an important role in maintaining skeletal muscle mass by promoting myogenesis; once differentiated, the resulting mature adipocytes negatively affect myogenesis, leading to the muscle deterioration observed in skeletal muscle pathologies. - Highlights: • We examined the effects of pre- and mature adipocytes on myogenesis in vitro. • Preadipocytes and mature adipocytes affect myoblast fusion. • Preadipocytes play an important role in maintaining skeletal muscle mass. • Mature adipocytes lead to muscle deterioration observed in skeletal muscle pathologies

  10. Myotube formation is affected by adipogenic lineage cells in a cell-to-cell contact-independent manner

    Energy Technology Data Exchange (ETDEWEB)

    Takegahara, Yuki; Yamanouchi, Keitaro, E-mail: akeita@mail.ecc.u-tokyo.ac.jp; Nakamura, Katsuyuki; Nakano, Shin-ichi; Nishihara, Masugi

    2014-05-15

    Intramuscular adipose tissue (IMAT) formation is observed in some pathological conditions such as Duchenne muscular dystrophy (DMD) and sarcopenia. Several studies have suggested that IMAT formation is not only negatively correlated with skeletal muscle mass but also causes decreased muscle contraction in sarcopenia. In the present study, we examined w hether adipocytes affect myogenesis. For this purpose, skeletal muscle progenitor cells were transfected with siRNA of PPARγ (siPPARγ) in an attempt to inhibit adipogenesis. Myosin heavy chain (MHC)-positive myotube formation was promoted in cells transfected with siPPARγ compared to that of cells transfected with control siRNA. To determine whether direct cell-to-cell contact between adipocytes and myoblasts is a prerequisite for adipocytes to affect myogenesis, skeletal muscle progenitor cells were cocultured with pre- or mature adipocytes in a Transwell coculture system. MHC-positive myotube formation was inhibited when skeletal muscle progenitor cells were cocultured with mature adipocytes, but was promoted when they were cocultured with preadipocytes. Similar effects were observed when pre- or mature adipocyte-conditioned medium was used. These results indicate that preadipocytes play an important role in maintaining skeletal muscle mass by promoting myogenesis; once differentiated, the resulting mature adipocytes negatively affect myogenesis, leading to the muscle deterioration observed in skeletal muscle pathologies. - Highlights: • We examined the effects of pre- and mature adipocytes on myogenesis in vitro. • Preadipocytes and mature adipocytes affect myoblast fusion. • Preadipocytes play an important role in maintaining skeletal muscle mass. • Mature adipocytes lead to muscle deterioration observed in skeletal muscle pathologies.

  11. Smooth dependence on data of solutions and contact regions for a Signorini problem

    Czech Academy of Sciences Publication Activity Database

    Eisner, Jan; Kučera, Milan; Recke, L.

    2010-01-01

    Roč. 72, 3-4 (2010), s. 1358-1378 ISSN 0362-546X R&D Projects: GA AV ČR IAA100190506 Institutional research plan: CEZ:AV0Z10190503 Keywords : smooth dependence on date * Signorini problem * variational inequality Subject RIV: BA - General Mathematics Impact factor: 1.279, year: 2010 http://www.sciencedirect.com/science/article/pii/S0362546X09009808

  12. Behaviour of moderately differentiated osteoblast-like cells cultured in contact with bioactive glasses

    Directory of Open Access Journals (Sweden)

    Hattar S.

    2002-12-01

    Full Text Available Bioactive glasses have been shown to stimulate osteogenesis both in vivo and in vitro. However, the molecular mechanisms underlying this process are still poorly understood. In this study, we have investigated the behaviour of osteoblast-like cells (MG63, cultured in the presence of bioglass particles. Three types of granules were used: 45S5registered bioactive glass, 45S5registered granules preincubated in tris buffer and 60S non-reactive glass, used as control. Phase contrast microscopy permitted step-by-step visualization of cell cultures in contact with the particles. Ultrastructural observations of undecalcified sections revealed direct contacts of the cells and an electron-dense layer located at the periphery of the material. Protein synthesis was evaluated biochemically and showed a gradual increase throughout the culture time in the three types of cultures. Alkaline phosphatase was detected in situ, in clusters of packed cells either in contact with the material or in the background cell layer. Semi-quantitative RT-PCR analysis of the main osteoblastic markers showed that gene expression was maintained in all three cultures. The fact that osteocalcin was not detected, supports the fact that the MG63 cell line is composed of less differentiated osteogenic cells rather than mature osteoblasts. We also demonstrated for the first time in this cell line, the expression of Msx-2, Dlx-3 and Dlx-7 homeogenes, known to regulate in vivo foetal skeletogenesis as well as adult skeletal regeneration. However, no significant differences could be recognised in the expression pattern of bone markers between the three types of cultures. Yet these preliminary results indicate that bioactive glasses provided a suitable environment for the growth and proliferation of osteoblasts in vitro, since no drastic changes in phenotype expression of pre-osteoblasts was noted.

  13. The influence of surface chemistry and topography on the contact guidance of MG63 osteoblast cells.

    Science.gov (United States)

    Ismail, F S Magdon; Rohanizadeh, R; Atwa, S; Mason, R S; Ruys, A J; Martin, P J; Bendavid, A

    2007-05-01

    The purpose of the present study was to determine in vitro the effects of different surface topographies and chemistries of commercially pure titanium (cpTi) and diamond-like carbon (DLC) surfaces on osteoblast growth and attachment. Microgrooves (widths of 2, 4, 8 and 10 microm and a depth of 1.5-2 microm) were patterned onto silicon (Si) substrates using microlithography and reactive ion etching. The Si substrates were subsequently vapor coated with either cpTi or DLC coatings. All surfaces were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Using the MG63 Osteoblast-Like cell line, we determined cell viability, adhesion, and morphology on different substrates over a 3 day culture period. The results showed cpTi surfaces to be significantly more hydrophilic than DLC for groove sizes larger than 2 microm. Cell contact guidance was observed for all grooved samples in comparison to the unpatterned controls. The cell viability tests indicated a significantly greater cell number for 8 and 10 microm grooves on cpTi surfaces compared to other groove sizes. The cell adhesion study showed that the smaller groove sizes, as well as the unpatterned control groups, displayed better cell adhesion to the substrate.

  14. Front buried metallic contacts and thin porous silicon combination for efficient polycrystalline silicon solar cells

    International Nuclear Information System (INIS)

    Ben Rabha, M.; Boujmil, M.F.; Meddeb, N.; Saadoun, M.; Bessais, B.

    2006-01-01

    We investigate the impacts of achieving buried grid metallic contacts (BGMC), with and without application of a front porous silicon (PS) layer, on the photovoltaic properties of polycrystalline silicon (pc-Si) solar cells. A grooving method based on Chemical Vapor Etching (CVE) was used to perform buried grid contacts on the emitter of pc-Si solar cells. After realizing the n + /p junction using a phosphorus diffusion source, BGMCs were realized using the screen printing technique. We found that the buried metallic contacts improve the short circuit current from 16 mA/cm 2 (for reference cell without buried contacts) to about 19 mA/cm 2 . After application of a front PS layer on the n + emitter, we observe an enhancement of the short circuit current from 19 to 24 mA/cm 2 with a decrease of the reflectivity by about 40% of its initial value. The dark I-V characteristics of the pc-Si cells with PS-based emitter show an important reduction of the reverse current together with an improvement of the rectifying behaviour. Spectral response measurements performed at a wavelength range of 400-1100 nm showed a significant increase in the quantum efficiency, particularly at shorter wavelength (400-650 nm). These results indicate that the BGMCs improve the carrier collection and that the PS layer acts as an antireflective coating that reduces reflection losses and passivates the front surface. This low cost and simple technology based on the CVE technique could enable preparing efficient polycrystalline silicon solar cells

  15. Low temperature deposition of bifacial CIGS solar cells on Al-doped Zinc Oxide back contacts

    Energy Technology Data Exchange (ETDEWEB)

    Cavallari, Nicholas, E-mail: nicholas.cavallari@imem.cnr.it [IMEM-CNR, Parco Area delle Scienze 37/a, 43124 Parma (Italy); Department of Mathematical, Physical and Computer Sciences, University of Parma, Parco Area delle Scienze 7/a, 43124 Parma (Italy); Pattini, Francesco; Rampino, Stefano; Annoni, Filippo [IMEM-CNR, Parco Area delle Scienze 37/a, 43124 Parma (Italy); Barozzi, Mario [FBK—CMM—Micro Nano Facility, Via Sommarive 18, 38123 Trento (Italy); Bronzoni, Matteo; Gilioli, Edmondo; Gombia, Enos [IMEM-CNR, Parco Area delle Scienze 37/a, 43124 Parma (Italy); Maragliano, Carlo [Solar Bankers LLC, Phoenix, AZ (United States); Mazzer, Massimo [IMEM-CNR, Parco Area delle Scienze 37/a, 43124 Parma (Italy); Pepponi, Giancarlo [FBK—CMM—Micro Nano Facility, Via Sommarive 18, 38123 Trento (Italy); Spaggiari, Giulia; Fornari, Roberto [IMEM-CNR, Parco Area delle Scienze 37/a, 43124 Parma (Italy); Department of Mathematical, Physical and Computer Sciences, University of Parma, Parco Area delle Scienze 7/a, 43124 Parma (Italy)

    2017-08-01

    Highlights: • AZO and CIGS were deposited by Low-Temperature Pulsed Electron Deposition (LT-PED). • CIGS/AZO contacts with ohmic behavior and resistance of 1.07 Ω cm{sup 2} were fabricated. • LT-PED deposition of AZO and CIGS prevents formation of Ga{sub 2}O{sub 3} interlayer. • CIGS-based bifacial solar cells with AZO back contact were realized. • Front PV efficiency of 9.3% and equivalent bifacial efficiency of 11.6% were achieved. - Abstract: We report on the fabrication and characterization of Cu(In,Ga)Se{sub 2} (CIGS)-based thin film bifacial solar cells using Al-doped ZnO (AZO) as cost-effective and non-toxic transparent back contact. We show that, by depositing both CIGS and AZO by Low Temperature Pulsed Electron Deposition at a maximum temperature of 250 °C, a good ohmic contact is formed between the two layers and good quality solar cells can be fabricated as a result. Photovoltaic efficiencies as high as 9.3% (front illumination), 5.1% (backside illumination) and 11.6% (bifacial illumination) have been obtained so far. These values are remarkably higher than those previously reported in the literature. We demonstrate that this improvement is ascribed to the low-temperature deposition process that avoids the formation of Ga{sub 2}O{sub 3} at the CIGS/AZO interface and favours the formation of a low-resistivity contact in agreement with device simulations.

  16. Contact assembly of cell-laden hollow microtubes through automated micromanipulator tip locating

    International Nuclear Information System (INIS)

    Wang, Huaping; Shi, Qing; Guo, Yanan; Li, Yanan; Sun, Tao; Huang, Qiang; Fukuda, Toshio

    2017-01-01

    This paper presents an automated contact assembly method to fabricate a cell-laden microtube based on accurate locating of the micromanipulator tip. Essential for delivering nutrients in thick engineered tissues, a vessel-mimetic microtube can be precisely assembled through microrobotic contact biomanipulation. The biomanipulation is a technique to spatially order and immobilize cellular targets with high precision. However, due to image occlusion during contact, it is challenging to locate the micromanipulator tip for fully automated assembly. To achieve pixel-wise tracking and locating of the tip in contact, a particle filter algorithm integrated with a determined level set model is employed here. The model ensures precise convergence of the micromanipulator’s contour during occlusion. With the converged active contour, the algorithm is able to pixel-wisely separate the micromanipulator from the low-contrast background and precisely locate the tip with error around 1 pixel (2 µ m at 4  ×  magnification). As a result, the cell-laden microtube is automatically assembled at six layers/min, which is effective enough to fabricate vessel-mimetic constructs for vascularization in tissue engineering. (paper)

  17. Investigation of ITO layers for application as transparent contacts in flexible photovoltaic cell structures

    Science.gov (United States)

    Znajdek, Katarzyna; Sibiński, Maciej

    2013-07-01

    In this paper authors present the mechanical, optical and electrical parameters of Indium Tin Oxide (ITO) Transparent Conductive Layers (TCL) deposited on flexible substrate. Layers' properties are analyzed and verified. Investigated Transparent Conductive Oxide (TCO) was deposited, using magnetron sputtering method. Flexible polymer PET (polyethylene terephthalate) foil was used as a substrate, in order to photovoltaic (PV) cell's emitter contact application of investigated material. ITO-coated PET foils have been dynamically bent on numerous cylinders of various diameters according to the standard requirements. Resistance changes for each measured sample were measured and recorded during bending cycle. Thermal durability, as well as temperature influence on resistance and optical transmission are verified. Presented results were conducted to verify practical suitability and to evaluate possible applications of Indium Tin Oxide as a front contact in flexible photovoltaic cell structures.

  18. Series Resistance Analysis of Passivated Emitter Rear Contact Cells Patterned Using Inkjet Printing

    Directory of Open Access Journals (Sweden)

    Martha A. T. Lenio

    2012-01-01

    Full Text Available For higher-efficiency solar cell structures, such as the Passivated Emitter Rear Contact (PERC cells, to be fabricated in a manufacturing environment, potentially low-cost techniques such as inkjet printing and metal plating are desirable. A common problem that is experienced when fabricating PERC cells is low fill factors due to high series resistance. This paper identifies and attempts to quantify sources of series resistance in inkjet-patterned PERC cells that employ electroless or light-induced nickel-plating techniques followed by copper light-induced plating. Photoluminescence imaging is used to determine locations of series resistance losses in these inkjet-patterned and plated PERC cells.

  19. Role of metal/silicon semiconductor contact engineering for enhanced output current in micro-sized microbial fuel cells

    KAUST Repository

    Mink, Justine E.

    2013-11-25

    We show that contact engineering plays an important role to extract the maximum performance from energy harvesters like microbial fuel cells (MFCs). We experimented with Schottky and Ohmic methods of fabricating contact areas on silicon in an MFC contact material study. We utilized the industry standard contact material, aluminum, as well as a metal, whose silicide has recently been recognized for its improved performance in smallest scale integration requirements, cobalt. Our study shows that improvements in contact engineering are not only important for device engineering but also for microsystems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. BMP signaling regulates satellite cell-dependent postnatal muscle growth.

    Science.gov (United States)

    Stantzou, Amalia; Schirwis, Elija; Swist, Sandra; Alonso-Martin, Sonia; Polydorou, Ioanna; Zarrouki, Faouzi; Mouisel, Etienne; Beley, Cyriaque; Julien, Anaïs; Le Grand, Fabien; Garcia, Luis; Colnot, Céline; Birchmeier, Carmen; Braun, Thomas; Schuelke, Markus; Relaix, Frédéric; Amthor, Helge

    2017-08-01

    Postnatal growth of skeletal muscle largely depends on the expansion and differentiation of resident stem cells, the so-called satellite cells. Here, we demonstrate that postnatal satellite cells express components of the bone morphogenetic protein (BMP) signaling machinery. Overexpression of noggin in postnatal mice (to antagonize BMP ligands), satellite cell-specific knockout of Alk3 (the gene encoding the BMP transmembrane receptor) or overexpression of inhibitory SMAD6 decreased satellite cell proliferation and accretion during myofiber growth, and ultimately retarded muscle growth. Moreover, reduced BMP signaling diminished the adult satellite cell pool. Abrogation of BMP signaling in satellite cell-derived primary myoblasts strongly diminished cell proliferation and upregulated the expression of cell cycle inhibitors p21 and p57 In conclusion, these results show that BMP signaling defines postnatal muscle development by regulating satellite cell-dependent myofiber growth and the generation of the adult muscle stem cell pool. © 2017. Published by The Company of Biologists Ltd.

  1. Design and application of ion-implanted polySi passivating contacts for interdigitated back contact c-Si solar cells

    International Nuclear Information System (INIS)

    Yang, Guangtao; Ingenito, Andrea; Hameren, Nienke van; Isabella, Olindo; Zeman, Miro

    2016-01-01

    Ion-implanted passivating contacts based on poly-crystalline silicon (polySi) are enabled by tunneling oxide, optimized, and used to fabricate interdigitated back contact (IBC) solar cells. Both n-type (phosphorous doped) and p-type (boron doped) passivating contacts are fabricated by ion-implantation of intrinsic polySi layers deposited via low-pressure chemical vapor deposition and subsequently annealed. The impact of doping profile on the passivation quality of the polySi doped contacts is studied for both polarities. It was found that an excellent surface passivation could be obtained by confining as much as possible the implanted-and-activated dopants within the polySi layers. The doping profile in the polySi was controlled by modifying the polySi thickness, the energy and dose of ion-implantation, and the temperature and time of annealing. An implied open-circuit voltage of 721 mV for n-type and 692 mV for p-type passivating contacts was achieved. Besides the high passivating quality, the developed passivating contacts exhibit reasonable high conductivity (R sh n-type  = 95 Ω/□ and R sh p-type  = 120 Ω/□). An efficiency of 19.2% (V oc  = 673 mV, J sc  = 38.0 mA/cm 2 , FF = 75.2%, and pseudo-FF = 83.2%) was achieved on a front-textured IBC solar cell with polySi passivating contacts as both back surface field and emitter. By improving the front-side passivation, a V OC of 696 mV was also measured

  2. Low-cost multicrystalline back-contact silicon solar cells with screen printed metallization

    International Nuclear Information System (INIS)

    Neu, W.; Kress, A.; Jooss, W.; Fath, P.; Bucher, E.

    2002-01-01

    Adaptation to market requirements is a permanent challenge in industrial solar-cell production. Both increase of cell efficiency as well as lowering costs is demanded. Back-contacted solar cells offer multiple advantages in terms of reducing module assembling costs and enhanced cell efficiency. The investigated emitter-wrap-through (EWT) design [1] has a collecting emitter on front and rear side. These emitter areas are electrically connected by small holes. Due to the double-sided collecting junction, this cell design is favourable for materials with a low-minority charge carrier diffusion length leading to a higher short circuit current density. Until now most investigations on EWT solar cells were performed on Cz or even FZ silicon. This was justified as long as different processing techniques had to be developed and compared. But as an industrially applicable process sequence has recently been developed [2], the advantages of the EWT concept compared to conventionally processed cells have to be shown on multicrystalline material. In the following, a manufacturing process of EWT solar cells is presented which is especially adapted to the requirements of multicrystalline silicon. Effective surface texturization was reached by mechanical V-texturization and bulk passivation by a hydrogen plasma treatment. The efficiency of the best solar cells within this process reached 14.2% which is the highest efficiency reported so far for mc-Si 10x10 cm 2 EWT solar cells [3]. (author)

  3. Heterotypic contact reveals a COX-2-mediated suppression of osteoblast differentiation by endothelial cells: A negative modulatory role for prostanoids in VEGF-mediated cell: cell communication?

    International Nuclear Information System (INIS)

    Clarkin, Claire E.; Garonna, Elena; Pitsillides, Andrew A.; Wheeler-Jones, Caroline P.D.

    2008-01-01

    In bone, angiogenesis must be initiated appropriately, but limited once remodelling or repair is complete. Our recent findings have supported a role for prostaglandins (PG), known modulators of osteoblast (OB) and endothelial cell (EC) behaviour, in facilitating VEGF-mediated paracrine communication from OBs to 'remotely located' ECs, but the mechanism(s) regulating OB:EC crosstalk when these cells are closely opposed are undefined. In this study we have examined: (i) the effects of exogenous PGE 2 on VEGF-driven events in ECs, and (ii) the role of endogenous COX-2-derived prostanoids in mediating communication between intimately opposed OBs and ECs in direct contact. Exposure of ECs to PGE 2 increased ERK1/2 phosphorylation, COX-2 induction, 6-keto-PGF 1α release and EC proliferation. In contrast, PGE 2 attenuated VEGF 165 -induced VEGFR2/Flk1 phosphorylation, ERK1/2 activation and proliferation of ECs, suggesting that exogenous PGE 2 restricts the actions of VEGF. However, the COX-2-selective inhibitor, NS398, also attenuated VEGF-induced proliferation, implying a distinct role for endogenous COX-2 activity in regulating EC behaviour. To examine the effect of OB:EC proximity and the role of COX-2 products further, we used a confrontational co-culture model. These studies showed that COX-2 blockade with NS398 enhanced EC-dependent increases in OB differentiation, that this effect was reversed by exogenous PGH 2 (immediate COX-2 product), and that exogenous VEGF did not influence EC-dependent OB differentiation under these conditions. Our findings indicate that locally produced prostanoids may serve distinct roles depending on OB:EC proximity and negatively modulate VEGF-mediated changes in EC behaviour when these cells are closely opposed to control angiogenesis during bone (re)modelling

  4. Indentation versus Rolling: Dependence of Adhesion on Contact Geometry for Biomimetic Structures.

    Science.gov (United States)

    Moyle, Nichole; He, Zhenping; Wu, Haibin; Hui, Chung-Yuen; Jagota, Anand

    2018-04-03

    Numerous biomimetic structures made from elastomeric materials have been developed to produce enhancement in properties such as adhesion, static friction, and sliding friction. As a property, one expects adhesion to be represented by an energy per unit area that is usually sensitive to the combination of shear and normal stresses at the crack front but is otherwise dependent only on the two elastic materials that meet at the interface. More specifically, one would expect that adhesion measured by indentation (a popular and convenient technique) could be used to predict adhesion hysteresis in the more practically important rolling geometry. Previously, a structure with a film-terminated fibrillar geometry exhibited dramatic enhancement of adhesion by a crack-trapping mechanism during indentation with a rigid sphere. Roughly isotropic structures such as the fibrillar geometry show a strong correlation between adhesion enhancement in indentation versus adhesion hysteresis in rolling. However, anisotropic structures, such as a film-terminated ridge-channel geometry, surprisingly show a dramatic divergence between adhesion measured by indentation versus rolling. We study this experimentally and theoretically, first comparing the adhesion of the anisotropic ridge-channel structure to the roughly isotropic fibrillar structure during indentation with a rigid sphere, where only the isotropic structure shows adhesion enhancement. Second, we examine in more detail the anomalous anisotropic film-terminated ridge-channel structure during indentation with a rigid sphere versus rolling to show why these structures show a dramatic adhesion enhancement for the rolling case and no adhesion enhancement for indentation.

  5. Effect of electroless nickel on the series resistance of high-efficiency inkjet printed passivated emitter rear contacted solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Lenio, Martha A.T. [REC Technology US, Inc., 1159 Triton Dr., Foster City, CA 94301 (United States); Lennon, A.J.; Ho-Baillie, A.; Wenham, S.R. [ARC Photovoltaics Centre of Excellence, University of NSW, Sydney, NSW 2052 (Australia)

    2010-12-15

    Many existing and emerging solar cell technologies rely on plated metal to form the front surface contacts, and aluminium to form the rear contact. Interactions between the metal plating solutions and the aluminium rear can have a significant impact on cell performance. This paper describes non-uniform nickel deposition on the sintered aluminium rear surface of passivated emitter and rear contacted (PERC) cells patterned using an inkjet printing technique. Rather than being plated homogeneously over the entire rear surface as is observed on an alloyed aluminium rear, the nickel is plated only in the vicinity of the point openings in the rear surface silicon dioxide dielectric layer. Furthermore, this non-uniform nickel deposition was shown to increase the contact resistance of the rear point contacts by an order of magnitude, resulting in higher series resistance values for these fabricated PERC cells. (author)

  6. Numerical investigation of flow field configuration and contact resistance for PEM fuel cell performance

    Energy Technology Data Exchange (ETDEWEB)

    Akbari, Mohammad Hadi; Rismanchi, Behzad [Department of Mechanical Engineering, Shiraz University, Shiraz 71348-51154 (Iran)

    2008-08-15

    A steady-state three-dimensional non-isothermal computational fluid dynamics (CFD) model of a proton exchange membrane fuel cell is presented. Conservation of mass, momentum, species, energy, and charge, as well as electrochemical kinetics are considered. In this model, the effect of interfacial contact resistance is also included. The numerical solution is based on a finite-volume method. In this study the effects of flow channel dimensions on the cell performance are investigated. Simulation results indicate that increasing the channel width will improve the limiting current density. However, it is observed that an optimum shoulder size of the flow channels exists for which the cell performance is the highest. Polarization curves are obtained for different operating conditions which, in general, compare favorably with the corresponding experimental data. Such a CFD model can be used as a tool in the development and optimization of PEM fuel cells. (author)

  7. Large area, low cost space solar cells with optional wraparound contacts

    Science.gov (United States)

    Michaels, D.; Mendoza, N.; Williams, R.

    1981-01-01

    Design parameters for two large area, low cost solar cells are presented, and electron irradiation testing, thermal alpha testing, and cell processing are discussed. The devices are a 2 ohm-cm base resistivity silicon cell with an evaporated aluminum reflector produced in a dielectric wraparound cell, and a 10 ohm-cm silicon cell with the BSF/BSR combination and a conventional contact system. Both cells are 5.9 x 5.9 cm and require 200 micron thick silicon material due to mission weight constraints. Normalized values for open circuit voltage, short circuit current, and maximum power calculations derived from electron radiation testing are given. In addition, thermal alpha testing values of absorptivity and emittance are included. A pilot cell processing run produced cells averaging 14.4% efficiencies at AMO 28 C. Manufacturing for such cells will be on a mechanized process line, and the area of coverslide application technology must be considered in order to achieve cost effective production.

  8. Temperature dependence of organic solar cell parameters

    Energy Technology Data Exchange (ETDEWEB)

    Richter, Matthias; Mueller, Klaus; Philip, Shine; Paloumpa, Ioanna; Henkel, Karsten; Schmeisser, Dieter [Brandenburgische Technische Universitaet Cottbus (Germany). Angewandte Physik - Sensorik

    2009-07-01

    The influence of an annealing step on the parameters of bulk heterojunction organic solar cells is investigated. In order to fabricate the solar cells we use glass coated with ITO (indium-tin oxide) as a substrate on which the active layer consisting of P3HT and PCBM is spincoated. Al-electrodes are evaporated on top of the active layer. We use PEDOT:PSS as buffer layer. Each sample is annealed at different temperatures for a short time. Between every temperature step the I-V characteristic of the cell is measured. The following parameters are derived afterwards: FF, I{sub sc} (density), V{sub oc}. Also the efficiency is estimated. The results show a maximum cell efficiency for drying at 100 C for 20sec. A further important step for preparation is the drying procedure of the PEDOT:PSS layer. Here an improvement of about 50% in cell efficiency is measured after drying at 50 C for 5 days under inert gas atmosphere.

  9. The role of creep in the time-dependent resistance of Ohmic gold contacts in radio frequency microelectromechanical system devices

    Science.gov (United States)

    Rezvanian, O.; Brown, C.; Zikry, M. A.; Kingon, A. I.; Krim, J.; Irving, D. L.; Brenner, D. W.

    2008-07-01

    It is shown that measured and calculated time-dependent electrical resistances of closed gold Ohmic switches in radio frequency microelectromechanical system (rf-MEMS) devices are well described by a power law that can be derived from a single asperity creep model. The analysis reveals that the exponent and prefactor in the power law arise, respectively, from the coefficient relating creep rate to applied stress and the initial surface roughness. The analysis also shows that resistance plateaus are not, in fact, limiting resistances but rather result from the small coefficient in the power law. The model predicts that it will take a longer time for the contact resistance to attain a power law relation with each successive closing of the switch due to asperity blunting. Analysis of the first few seconds of the measured resistance for three successive openings and closings of one of the MEMS devices supports this prediction. This work thus provides guidance toward the rational design of Ohmic contacts with enhanced reliabilities by better defining variables that can be controlled through material selection, interface processing, and switch operation.

  10. Simple fabrication of back contact heterojunction solar cells by plasma ion implantation

    Science.gov (United States)

    Koyama, Koichi; Yamaguchi, Noboru; Hironiwa, Daisuke; Suzuki, Hideo; Ohdaira, Keisuke; Matsumura, Hideki

    2017-08-01

    A back-contact amorphous-silicon (a-Si)/crystalline silicon (c-Si) heterojunction is one of the most promising structures for high-efficiency solar cells. However, the patterning of back-contact electrodes causes the increase in fabrication cost. Thus, to simplify the fabrication of back-contact cells, we attempted to form p-a-Si/i-a-Si/c-Si and n-a-Si/i-a-Si/c-Si regions by the conversion of a patterned area of p-a-Si/i-a-Si/c-Si to n-a-Si/i-a-Si/c-Si by plasma ion implantation. It is revealed that the conversion of the conduction type can be realized by the plasma ion implantation of phosphorus (P) atoms into p-a-Si/i-a-Si/c-Si regions, and also that the quality of passivation can be kept sufficiently high, the same as that before ion implantation, when the samples are annealed at around 250 °C and also when the energy and dose of ion implantation are appropriately chosen for fitting to a-Si layer thickness and bulk c-Si carrier density.

  11. Assessment of the U937 cell line for the detection of contact allergens

    International Nuclear Information System (INIS)

    Python, Francois; Goebel, Carsten; Aeby, Pierre

    2007-01-01

    The human myeloid cell line U937 was evaluated as an in vitro test system to identify contact sensitizers in order to develop alternatives to animal tests for the cosmetic industry. Specific culture conditions (i.e., presence of interleukin-4, IL-4) were applied to obtain a dendritic cell-like phenotype. In the described test protocol, these cells were exposed to test chemicals and then analyzed by flow cytometry for CD86 expression and by quantitative real-time reverse transcriptase-polymerase chain reaction for IL-1β and IL-8 gene expressions. Eight sensitizers, three non-sensitizers and five oxidative hair dye precursors were examined after 24-, 48- and 72-h exposure times. Test item-specific modulations of the chosen activation markers (CD86, IL-1β and IL-8) suggest that this U937 activation test could discriminate test items classified as contact sensitizers or non-sensitizers in the local lymph node assay in mice (LLNA). More specifically, a test item can be considered as a potential sensitizer when it significantly induced the upregulation of the expression of at least two markers. Using this approach, we could correctly evaluate the dendritic cell (DC) activation potential for 15 out of 16 tested chemicals. We conclude that the U937 activation test may represent an useful tool in a future in vitro test battery for predicting sensitizing properties of chemicals

  12. Flow cytometric analysis of regulatory T cells during hyposensitization of acquired allergic contact dermatitis.

    Science.gov (United States)

    Fraser, Kathleen; Abbas, Mariam; Hull, Peter R

    2014-01-01

    We previously demonstrated that repeated intradermal steroid injections administered at weekly intervals into positive patch-test sites induce hyposensitization and desensitization. To examine changes in CD4CD25CD127lo/ regulatory T cells during the attenuation of the patch-test response. Ten patients with known allergic contact dermatitis were patch tested weekly for 10 weeks. The patch-test site was injected intradermally with 2 mg triamcinolone. At weeks 1 and 7, a biopsy was performed on the patch-test site in 6 patients, and flow cytometry was performed assessing CD4CD25CD127lo/ regulatory T cells. Secondary outcomes were clinical score, reaction size, erythema, and temperature. Statistical analysis included regression, correlation, and repeated-measures analysis of variance. The percentage of CD4CD25CD127lo/ regulatory T cells, measured by flow cytometry, increased from week 1 to week 7 by an average of 19.2%. The average grade of patch-test reaction decreased from +++ (vesicular reaction) to ++ (palpable erythema). The mean drop in temperature following treatment was 0.28°C per week. The mean area decreased 8.6 mm/wk over 10 weeks. Intradermal steroid injections of weekly patch-test reactions resulted in hyposensitization of the allergic contact dermatitis reaction. CD4CD25CD127lo/ regulatory T cells showed a tendency to increase; however, further studies are needed to determine if this is significant.

  13. Acrylic acid surface-modified contact lens for the culture of limbal stem cells.

    Science.gov (United States)

    Zhang, Hong; Brown, Karl David; Lowe, Sue Peng; Liu, Guei-Sheung; Steele, David; Abberton, Keren; Daniell, Mark

    2014-06-01

    Surface treatment to a biomaterial surface has been shown to modify and help cell growth. Our aim was to determine the best surface-modified system for the treatment of limbal stem cell deficiency (LSCD), which would facilitate expansion of autologous limbal epithelial cells, while maintaining cultivated epithelial cells in a less differentiated state. Commercially available contact lenses (CLs) were variously surface modified by plasma polymerization with ratios of acrylic acid to octadiene tested at 100% acrylic acid, 50:50% acrylic acid:octadiene, and 100% octadiene to produce high-, mid-, and no-acid. X-ray photoelectron spectroscopy was used to analyze the chemical composition of the plasma polymer deposited layer. Limbal explants cultured on high acid-modified CLs outgrew more cells. Immunofluorescence and RT2-PCR array results indicated that a higher acrylic acid content can also help maintain progenitor cells during ex vivo expansion of epithelial cells. This study provides the first evidence for the ability of high acid-modified CLs to preserve the stemness and to be used as substrates for the culture of limbal cells in the treatment of LSCD.

  14. Involvement of YAP, TAZ and HSP90 in contact guidance and intercellular junction formation in corneal epithelial cells.

    Directory of Open Access Journals (Sweden)

    Vijay Krishna Raghunathan

    Full Text Available The extracellular environment possesses a rich milieu of biophysical and biochemical signaling cues that are simultaneously integrated by cells and influence cellular phenotype. Yes-associated protein (YAP and transcriptional co-activator with PDZ-binding motif (WWTR1; TAZ, two important signaling molecules of the Hippo pathway, have been recently implicated as nuclear relays of cytoskeletal changes mediated by substratum rigidity and topography. These proteins intersect with other important intracellular signaling pathways (e.g. Wnt and TGFβ. In the cornea, epithelial cells adhere to the stroma through a 3-dimensional topography-rich basement membrane, with features in the nano-submicron size-scale that are capable of profoundly modulating a wide range of fundamental cell behaviors. The influences of substratum-topography, YAP/TAZ knockdown, and HSP90 inhibition on cell morphology, YAP/TAZ localization, and the expression of TGFβ2 and CTGF, were investigated. The results demonstrate (a that knockdown of TAZ enhances contact guidance in a YAP dependent manner, (b that CTGF is predominantly regulated by YAP and not TAZ, and (c that TGFβ2 is regulated by both YAP and TAZ in these cells. Additionally, inhibition of HSP90 resulted in nuclear localization and subsequent transcriptional-activation of YAP, formation of cell-cell junctions and co-localization of E-cadherin and β-catenin at adherens junctions. Results presented in this study reflect the complexities underlying the molecular relationships between the cytoskeleton, growth factors, heat shock proteins, and co-activators of transcription that impact mechanotransduction. The data reveal the importance of YAP/TAZ on the cell behaviors, and gene and protein expression.

  15. Atomic-layer deposited Nb2O5 as transparent passivating electron contact for c-Si solar cells

    NARCIS (Netherlands)

    Macco, Bart; Black, Lachlan E.; Melskens, Jimmy; van de Loo, Bas W.H.; Berghuis, Willem Jan H.; Verheijen, Marcel A.; Kessels, Wilhelmus M.M.

    2018-01-01

    Passivating contacts based on metal oxides have proven to enable high energy conversion efficiencies for crystalline silicon (c-Si) solar cells at low processing complexity. In this work, the potential of atomic-layer deposited (ALD) Nb2O5 as novel electron-selective passivating contact is explored

  16. CIGS cells with metallized front contact: Longer cells and higher efficiency

    NARCIS (Netherlands)

    Deelen, J. van; Frijters, C.

    2017-01-01

    We have investigated the benefit of a patterned metallization on top of a transparent conductive oxide in CIGS thin-film solar panels. It was found that cells with a grid have a higher efficiency compared to cells with only a TCO. This was observed for all cell lengths used. Furthermore, metallic

  17. Data for chromosome contacts and matched transcription profiles at three cell cycle phases in the fission yeast

    Directory of Open Access Journals (Sweden)

    Ralph S. Grand

    2015-06-01

    Full Text Available The data described in this article pertains to Grand et al. (2014, “Chromosome conformation maps in fission yeast reveal cell cycle dependent sub nuclear structure” [1]. Temperature sensitive Schizosaccharomyces pombe cell division cycle (cdc mutants, which are induced by a shift in temperature to 36 °C, were chosen for the analysis of genome structure in the G1 phase, G2 phase and mitotic anaphase of the cell cycle. Chromatin and total RNA were isolated from the same cell culture following synchronization. Two biological replicates were analyzed for each condition. The global, three-dimensional organization of the chromosomes was captured at high resolution using Genome Conformation Capture (GCC. GCC libraries and RNA samples were sequenced using an Illumina Hi-Seq 2000 platform (Beijing Genomics Institute (China. DNA sequences were processed using the Topography suite v1.19 [2] to obtain chromosome contact frequency matrices. RNA sequences were processed using the Cufflinks pipeline [3] to measure gene transcript levels and how these varied between the conditions. All sequence data, processed GCC and transcriptome files are available under the Gene Expression Omnibus (GEO accession number GSE52287 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE52287.

  18. Optical Evaluation of the Rear Contacts of Crystalline Silicon Solar Cells by Coupled Electromagnetic and Statistical Ray-Optics Modeling

    KAUST Repository

    Dabirian, Ali; Morales-Masis, Monica; Haug, Franz-Josef; De Wolf, Stefaan; Ballif, Christophe

    2017-01-01

    High-efficiency crystalline silicon (c-Si) solar cells increasingly feature sophisticated electron and hole contacts aimed at minimizing electronic losses. At the rear of photovoltaic devices, such contacts—usually consisting of stacks of functional

  19. A new technique for direct traceability of contact thermometry Co-C eutectic cells to the ITS-90

    Energy Technology Data Exchange (ETDEWEB)

    Failleau, G.; Deuzé, T.; Bourson, F.; Briaudeau, S.; Sadli, M. [Laboratoire Commun de Métrologie LNE-Cnam, 61 rue du Landy 93210 La Plaine Saint Denis (France)

    2013-09-11

    The eutectic Co-C melting point is a promising system to serve as a thermometric fixed-point in the temperature range above 1084.62 °C (copper freezing point). During the last decade, LNE-Cnam has developed and characterized some fixed-point devices, based on eutectic Co-C alloy, for applications to contact and radiation thermometry. Above 962 °C, the ITS-90 is realized by radiation thermometry by the extrapolation from a Ag, Au or Cu fixed point using the Planck law for radiation. So the only way for assigning a temperature in the scale to a Co-C cell (∼1324 °C) is by radiation thermometry. An indirect method is commonly used to assign a temperature to a high-temperature fixed point (HTFP) cell designed for contact thermometry is to fill a pyrometric cell with the same mixture as the contact thermometry cell. In this case, the temperature assigned to the pyrometric cell is attributed to the contact cell. This paper describes a direct method allowing the determination of the melting temperature realized by a 'contact thermometry' Co-C cell by comparison to a 'radiation thermometry' Co-C cell whose melting temperature was assigned in accordance to the scale by extrapolation from the Cu point. In addition, the same Co-C cell is studied with a standard Pt/Pd thermocouple.

  20. Influences of Contact Pressure on the Performances of Polymer Electrolyte Fuel Cells

    Directory of Open Access Journals (Sweden)

    Prakash C. Ghosh

    2013-01-01

    Full Text Available Fuel cells face major challenges in sustaining the laboratory-scale performance during the scale up. The contact resistance mainly arises from the dimensional mismatch between gasket and gas diffusion layer during scale up, which may cause diminution in performance. In the present work, experiment as well as modelling is carried out for different combinations of clamping force and gasket thickness. The polarisation behaviours of PEFCs configured under different clamping torques and gasket thicknesses are analysed. The combination of 0.3 mm gasket and 0.3 mm GDL under 3 Nm and 5 Nm clamping forces offers 480 mΩ cm2 and 148 mΩ cm2 contact resistances, respectively. The configurations under 3 Nm and 5 Nm clamping torques with 0.2 mm thick gasket offer contact resistances as low as 23 mΩ cm2 and 11 mΩ cm2, respectively. The polarisation behaviour obtained from the experiment of such configurations is found to be in good agreement with the modelling results.

  1. Wet-Chemical Preparation of Silicon Tunnel Oxides for Transparent Passivated Contacts in Crystalline Silicon Solar Cells.

    Science.gov (United States)

    Köhler, Malte; Pomaska, Manuel; Lentz, Florian; Finger, Friedhelm; Rau, Uwe; Ding, Kaining

    2018-05-02

    Transparent passivated contacts (TPCs) using a wide band gap microcrystalline silicon carbide (μc-SiC:H(n)), silicon tunnel oxide (SiO 2 ) stack are an alternative to amorphous silicon-based contacts for the front side of silicon heterojunction solar cells. In a systematic study of the μc-SiC:H(n)/SiO 2 /c-Si contact, we investigated selected wet-chemical oxidation methods for the formation of ultrathin SiO 2 , in order to passivate the silicon surface while ensuring a low contact resistivity. By tuning the SiO 2 properties, implied open-circuit voltages of 714 mV and contact resistivities of 32 mΩ cm 2 were achieved using μc-SiC:H(n)/SiO 2 /c-Si as transparent passivated contacts.

  2. Exercise-Dependent Regulation of NK Cells in Cancer Protection

    DEFF Research Database (Denmark)

    Idorn, Manja; Hojman, Pernille

    2016-01-01

    Natural killer (NK) cells are the most responsive immune cells to exercise, displaying an acute mobilization to the circulation during physical exertion. Recently, exercise-dependent mobilization of NK cells was found to play a central role in exercise-mediated protection against cancer. Here, we...... a mechanistic explanation for the protective effect of exercise on cancer, and we propose that exercise represents a potential strategy as adjuvant therapy in cancer, by improving NK cell recruitment and infiltration in solid tumors....... review the link between exercise and NK cell function, focusing on circulating exercise factors and additional effects, including vascularization, hypoxia, and body temperature in mediating the effects on NK cell functionality. Exercise-dependent mobilization and activation of NK cells provides...

  3. A micro-scale model for predicting contact resistance between bipolar plate and gas diffusion layer in PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Y.; Lin, G.; Shih, A.J.; Hu, S.J. [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2007-01-01

    Contact resistance between the bipolar plate (BPP) and the gas diffusion layer (GDL) in a proton exchange membrane (PEM) fuel cell constitutes a significant portion of the overall fuel cell electrical resistance under the normal operation conditions. Most current methods for contact resistance estimation are experimental and there is a lack of well developed theoretical methods. A micro-scale numerical model is developed to predict the electrical contact resistance between BPP and GDL by simulating the BPP surface topology and GDL structure and numerically determining the status for each contact spot. The total resistance and pressure are obtained by considering all contact spots as resistances in parallel and summing the results together. This model shows good agreements with experimental results. Influences of BPP surface roughness parameters on contact resistance are also studied. This model is beneficial in understanding the contact behavior between BPP and GDL and can be integrated with other fuel cell simulations to predict the overall performance of PEM fuel cells. (author)

  4. PGE2 maintains self-renewal of human adult stem cells via EP2-mediated autocrine signaling and its production is regulated by cell-to-cell contact.

    Science.gov (United States)

    Lee, Byung-Chul; Kim, Hyung-Sik; Shin, Tae-Hoon; Kang, Insung; Lee, Jin Young; Kim, Jae-Jun; Kang, Hyun Kyoung; Seo, Yoojin; Lee, Seunghee; Yu, Kyung-Rok; Choi, Soon Won; Kang, Kyung-Sun

    2016-05-27

    Mesenchymal stem cells (MSCs) possess unique immunomodulatory abilities. Many studies have elucidated the clinical efficacy and underlying mechanisms of MSCs in immune disorders. Although immunoregulatory factors, such as Prostaglandin E2 (PGE2), and their mechanisms of action on immune cells have been revealed, their effects on MSCs and regulation of their production by the culture environment are less clear. Therefore, we investigated the autocrine effect of PGE2 on human adult stem cells from cord blood or adipose tissue, and the regulation of its production by cell-to-cell contact, followed by the determination of its immunomodulatory properties. MSCs were treated with specific inhibitors to suppress PGE2 secretion, and proliferation was assessed. PGE2 exerted an autocrine regulatory function in MSCs by triggering E-Prostanoid (EP) 2 receptor. Inhibiting PGE2 production led to growth arrest, whereas addition of MSC-derived PGE2 restored proliferation. The level of PGE2 production from an equivalent number of MSCs was down-regulated via gap junctional intercellular communication. This cell contact-mediated decrease in PGE2 secretion down-regulated the suppressive effect of MSCs on immune cells. In conclusion, PGE2 produced by MSCs contributes to maintenance of self-renewal capacity through EP2 in an autocrine manner, and PGE2 secretion is down-regulated by cell-to-cell contact, attenuating its immunomodulatory potency.

  5. Non-chemical and non-contact cell-to-cell communication: a short review

    Czech Academy of Sciences Publication Activity Database

    Scholkmann, F.; Fels, D.; Cifra, Michal

    2013-01-01

    Roč. 5, č. 6 (2013), s. 586-593 ISSN 1943-8141 R&D Projects: GA ČR GA13-29294S Institutional support: RVO:67985882 Keywords : Cell-to-cell communication * physical signaling Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.226, year: 2013

  6. Simulation of thermal stresses in anode-supported solid oxide fuel cell stacks. Part II: Loss of gas-tightness, electrical contact and thermal buckling

    Science.gov (United States)

    Nakajo, Arata; Wuillemin, Zacharie; Van herle, Jan; Favrat, Daniel

    Structural stability issues in planar solid oxide fuel cells arise from the mismatch between the coefficients of thermal expansion of the components. The stress state at operating temperature is the superposition of several contributions, which differ depending on the component. First, the cells accumulate residual stresses due to the sintering phase during the manufacturing process. Further, the load applied during assembly of the stack to ensure electric contact and flatten the cells prevents a completely stress-free expansion of each component during the heat-up. Finally, thermal gradients cause additional stresses in operation. The temperature profile generated by a thermo-electrochemical model implemented in an equation-oriented process modelling tool (gPROMS) was imported into finite-element software (ABAQUS) to calculate the distribution of stress and contact pressure on all components of a standard solid oxide fuel cell repeat unit. The different layers of the cell in exception of the cathode, i.e. anode, electrolyte and compensating layer were considered in the analysis to account for the cell curvature. Both steady-state and dynamic simulations were performed, with an emphasis on the cycling of the electrical load. The study includes two different types of cell, operation under both thermal partial oxidation and internal steam-methane reforming and two different initial thicknesses of the air and fuel compressive sealing gaskets. The results generated by the models are presented in two papers: Part I focuses on cell cracking. In the present paper, Part II, the occurrences of loss of gas-tightness in the compressive gaskets and/or electrical contact in the gas diffusion layer were identified. In addition, the dependence on temperature of both coefficients of thermal expansion and Young's modulus of the metallic interconnect (MIC) were implemented in the finite-element model to compute the plastic deformation, while the possibilities of thermal buckling

  7. Printed Nano Cu and NiSi Contacts and Metallization for Solar Cell Modules

    Energy Technology Data Exchange (ETDEWEB)

    Carmody, Michael John [Intrinsiq Materials Inc., Rochester, NY (United States)

    2017-10-11

    There has long been a desire to replace the front-side silver contacts in silicon solar cells. There are two driving forces to do this. First, silver is an expensive precious metal. Secondly, the process to use silver requires that it be formulated into screen print pastes that need a lead-containing glass frit, and the use of lead is forbidden in many parts of the world. Because of the difficulty in replacing these pastes and the attendant processes, lead exemptions have granted to solar cells. Copper has been the replacement metal of choice because it is significantly cheaper than silver and is very close to silver in electrical conductivity. Using processes which do not use lead, obviates it as an environmental contaminant. However, copper cannot be in contact with the silicon of the cell since it migrates through the silicon and causes defects which severely damage the efficiency of the cell. Hence, a conductive barrier must be placed between the copper and silicon and nickel, and especially nickel silicide, have been shown to be materials of choice. However, nickel must be sputtered and annealed to create the nickel silicide barrier, and copper has either been sputtered or plated. All of these processes require expensive, specialized equipment and plating uses environmentally unfriendly chemicals. Therefore, Intrinsiq proposed using printed nano nickel silicide ink (which we had previously invented) and printed nano copper ink to create these electrodes and barriers. We found that nano copper ink could be readily printed and sintered under a reducing atmosphere to give highly conductive grids. We further showed that nano nickel silicide ink could be readily jetted into grids on top of the silicon cell. It could then be annealed to create a barrier. However, it was found that the combination of printed NiSi and printed Cu did not give contact resistivity good enough to produce efficient cells. Only plated copper on top of the printed NiSi gave useful contact

  8. Amorphous silicon passivation for 23.3% laser processed back contact solar cells

    Science.gov (United States)

    Carstens, Kai; Dahlinger, Morris; Hoffmann, Erik; Zapf-Gottwick, Renate; Werner, Jürgen H.

    2017-08-01

    This paper presents amorphous silicon deposited at temperatures below 200 °C, leading to an excellent passivation layer for boron doped emitter and phosphorus doped back surface field areas in interdigitated back contact solar cells. A higher deposition temperature degrades the passivation of the boron emitter by an increased hydrogen effusion due to lower silicon hydrogen bond energy, proved by hydrogen effusion measurements. The high boron surface doping in crystalline silicon causes a band bending in the amorphous silicon. Under these conditions, at the interface, the intentionally undoped amorphous silicon becomes p-type conducting, with the consequence of an increased dangling bond defect density. For bulk amorphous silicon this effect is described by the defect pool model. We demonstrate, that the defect pool model is also applicable to the interface between amorphous and crystalline silicon. Our simulation shows the shift of the Fermi energy towards the valence band edge to be more pronounced for high temperature deposited amorphous silicon having a small bandgap. Application of optimized amorphous silicon as passivation layer for the boron doped emitter and phosphorus doped back surface field on the rear side of laser processed back contact solar cells, fabricated using four laser processing steps, yields an efficiency of 23.3%.

  9. Tunnel Oxides Formed by Field-Induced Anodisation for Passivated Contacts of Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Jingnan Tong

    2018-02-01

    Full Text Available Tunnel silicon oxides form a critical component for passivated contacts for silicon solar cells. They need to be sufficiently thin to allow carriers to tunnel through and to be uniform both in thickness and stoichiometry across the silicon wafer surface, to ensure uniform and low recombination velocities if high conversion efficiencies are to be achieved. This paper reports on the formation of ultra-thin silicon oxide layers by field-induced anodisation (FIA, a process that ensures uniform oxide thickness by passing the anodisation current perpendicularly through the wafer to the silicon surface that is anodised. Spectroscopical analyses show that the FIA oxides contain a lower fraction of Si-rich sub-oxides compared to wet-chemical oxides, resulting in lower recombination velocities at the silicon and oxide interface. This property along with its low temperature formation highlights the potential for FIA to be used to form low-cost tunnel oxide layers for passivated contacts of silicon solar cells.

  10. Lack of TAK1 in dendritic cells inhibits the contact hypersensitivity response induced by trichloroethylene in local lymph node assay.

    Science.gov (United States)

    Yao, Pan; Hongqian, Chu; Qinghe, Meng; Lanqin, Shang; Jianjun, Jiang; Xiaohua, Yang; Xuetao, Wei; Weidong, Hao

    2016-09-15

    Trichloroethylene (TCE) is a ubiquitous environmental contaminant. Occupational TCE exposure has been associated with severe, generalized contact hypersensitivity (CHS) skin disorder. The development of CHS depends on innate and adaptive immune functions. Transforming growth factor-β activated kinase-1 (TAK1) controls the survival of dendritic cells (DCs) that affect the immune system homeostasis. We aimed to investigate the role of TAK1 activity in DC on TCE-induced CHS response. Control mice and DC-specific TAK1 deletion mice were treated with 80% (v/v) TCE using local lymph node assay (LLNA) to establish a TCE-induced CHS model. The draining lymph nodes (DLNs) were excised and the lymphocytes were measure for proliferation by BrdU-ELISA, T-cell phenotype analysis by flow cytometry and signaling pathway activation by western blot. The ears were harvested for histopathological analysis. Control mice in the 80% TCE group displayed an inflammatory response in the ears, increased lymphocyte proliferation, elevated regulatory T-cell and activated T-cell percentages, and more IFN-γ producing CD8(+) T cells in DLNs. In contrast to control mice, DC-specific TAK1 deletion mice in the 80% TCE group showed an abolished CHS response and this was associated with defective T-cell expansion, activation and IFN-γ production. This effect may occur through Jnk and NF-κB signaling pathways. Overall, this study demonstrates a pivotal role of TAK1 in DCs in controlling TCE-induced CHS response and suggests that targeting TAK1 function in DCs may be a viable approach to preventing and treating TCE-related occupational health hazards. Copyright © 2016 Elsevier Inc. All rights reserved.

  11. Cyclin-dependent kinases regulate apoptosis of intestinal epithelial cells

    Science.gov (United States)

    Bhattacharya, Sujoy; Ray, Ramesh M.; Johnson, Leonard R.

    2014-01-01

    Homeostasis of the gastrointestinal epithelium is dependent upon a balance between cell proliferation and apoptosis. Cyclin-dependent kinases (Cdks) are well known for their role in cell proliferation. Previous studies from our group have shown that polyamine-depletion of intestinal epithelial cells (IEC-6) decreases cyclin-dependent kinase 2 (Cdk2) activity, increases p53 and p21Cip1 protein levels, induces G1 arrest, and protects cells from camptothecin (CPT)-induced apoptosis. Although emerging evidence suggests that members of the Cdk family are involved in the regulation of apoptosis, their roles directing apoptosis of IEC-6 cells are not known. In this study, we report that inhibition of Cdk1, 2, and 9 (with the broad range Cdk inhibitor, AZD5438) in proliferating IEC-6 cells triggered DNA damage, activated p53 signaling, inhibited proliferation, and induced apoptosis. By contrast, inhibition of Cdk2 (with NU6140) increased p53 protein and activity, inhibited proliferation, but had no effect on apoptosis. Notably, AZD5438 sensitized, whereas, NU6140 rescued proliferating IEC-6 cells from CPT-induced apoptosis. However, in colon carcinoma (Caco2) cells with mutant p53, treatment with either AZD5438 or NU6140 blocked proliferation, albeit more robustly with AZD5438. Both Cdk inhibitors induced apoptosis in Caco2 cells in a p53-independent manner. In serum starved quiescent IEC-6 cells, both AZD5438 and NU6140 decreased TNF- /CPT-induced activation of p53 and, consequently, rescued cells from apoptosis, indicating that sustained Cdk activity is required for apoptosis of quiescent cells. Furthermore, AZD5438 partially reversed the protective effect of polyamine depletion whereas NU6140 had no effect. Together, these results demonstrate that Cdks possess opposing roles in the control of apoptosis in quiescent and proliferating cells. In addition, Cdk inhibitors uncouple proliferation from apoptosis in a p53-dependent manner. PMID:24242917

  12. Interaction between x-irradiated plateau-phase bone marrow stromal cell lines and co-cultivated factor-dependent cell lines leading to leukemogenesis in vitro

    International Nuclear Information System (INIS)

    Naparstek, E.; Anklesaria, P.; FitzGerald, T.J.; Sakakeeny, M.A.; Greenberger, J.S.

    1987-01-01

    Plateau-phase mouse clonal bone marrow stromal cell lines D2XRII and C3H cl 11 produce decreasing levels of M-CSF (CSF-1), a specific macrophage progenitor cell humoral regulator, following X-irradiation in vitro. The decrease did not go below 40% of control levels, even after irradiation doses of 50,000 rad (500 Gy). In contrast, a distinct humoral regulator stimulating growth of GM-CSF/IL-3 factor-dependent (FD) hematopoietic progenitor cell lines was detected following radiation to doses above 2000 rad. This humoral factor was not detectable in conditioned medium from irradiated cells, weakly detected using factor-dependent target cell populations in agar overlay, and was prominently detected by liquid co-cultivation of factor-dependent cells with irradiated stromal cell cultures. Subclonal lines of FD cells, derived after co-cultivation revealed karyotypic abnormalities and induced myeloblastic tumors in syngeneic mice. Five-eight weeks co-cultivation was required for induction of factor independence and malignancy and was associated with dense cell to cell contact between FD cells and stromal cells demonstrated by light and electron microscopy. Increases in hematopoietic to stromal cell surface area, total number of adherent cells per flask, total non-adherent cell colonies per flask, and cumulative non-adherent cell production were observed after irradiation. The present data may prove very relevant to an understanding of the cell to cell interactions during X-irradiation-induced leukemia

  13. Al-Si alloy point contact formation and rear surface passivation for silicon solar cells using double layer porous silicon

    International Nuclear Information System (INIS)

    Moumni, Besma; Ben Jaballah, Abdelkader; Bessais, Brahim

    2012-01-01

    Lowering the rear surface recombination velocities by a dielectric layer has fascinating advantages compared with the standard fully covered Al back-contact silicon solar cells. In this work the passivation effect by double layer porous silicon (PS) (wide band gap) and the formation of Al-Si alloy in narrow p-type Si point contact areas for rear passivated solar cells are analysed. As revealed by Fourier transform infrared spectroscopy, we found that a thin passivating aluminum oxide (Al 2 O 3 ) layer is formed. Scanning electron microscopy analysis performed in cross sections shows that with bilayer PS, liquid Al penetrates into the openings, alloying with the Si substrate at depth and decreasing the contact resistivity. At the solar cell level, the reduction in the contact area and resistivity leads to a minimization of the fill factor losses.

  14. Analytical Model for Voltage-Dependent Photo and Dark Currents in Bulk Heterojunction Organic Solar Cells

    Directory of Open Access Journals (Sweden)

    Mesbahus Saleheen

    2016-05-01

    Full Text Available A physics-based explicit mathematical model for the external voltage-dependent forward dark current in bulk heterojunction (BHJ organic solar cells is developed by considering Shockley-Read-Hall (SRH recombination and solving the continuity equations for both electrons and holes. An analytical model for the external voltage-dependent photocurrent in BHJ organic solar cells is also proposed by incorporating exponential photon absorption, dissociation efficiency of bound electron-hole pairs (EHPs, carrier trapping, and carrier drift and diffusion in the photon absorption layer. Modified Braun’s model is used to compute the electric field-dependent dissociation efficiency of the bound EHPs. The overall net current is calculated considering the actual solar spectrum. The mathematical models are verified by comparing the model calculations with various published experimental results. We analyze the effects of the contact properties, blend compositions, charge carrier transport properties (carrier mobility and lifetime, and cell design on the current-voltage characteristics. The power conversion efficiency of BHJ organic solar cells mostly depends on electron transport properties of the acceptor layer. The results of this paper indicate that improvement of charge carrier transport (both mobility and lifetime and dissociation of bound EHPs in organic blend are critically important to increase the power conversion efficiency of the BHJ solar cells.

  15. Increased cell proliferation in spleen and lymph nodes peripheral to contact allergen application site

    International Nuclear Information System (INIS)

    Chipinda, Itai; Anderson, Stacey E.; Butterworth, Leon F.; Beezhold, Donald; Siegel, Paul D.

    2009-01-01

    The local lymph node assay (LLNA) is widely used to identify chemicals that are contact sensitizers. The assay involves dosing mice with the chemical on both ears and pooling the superficial parotid lymph nodes for assessment of lymphocyte proliferation as a marker of sensitization. The present study explored potential reduction in animal usage by dosing one ear with the allergen and the other with vehicle-only. The respective draining lymph nodes were processed separately for tritiated thymidine ( 3 H-TdR) incorporation. Cell proliferation in proper axillary and renal nodes, as well as in the spleen was also assessed. Cross-contamination of the chemicals from the dosed ears to other parts of the body via preening was prevented by dosing restrained animals and washing off the residual chemical with saline after 4 h. Dosing the left ear with 0.02% oxazolone (OX) on unrestrained animals resulted in marked cell proliferation in its draining lymph node (stimulation index, SI = 12.8) and in the lymph node draining the contra-lateral vehicle-dosed ear (SI = 6), as well as the proper axillary lymph nodes (SI = 3.3). Increased 3 H-TdR incorporation was not observed in the renal lymph nodes (SI = 1.1). Similar stimulation of cells was observed in the lymph node draining the ear contra-lateral to the 30% hexylcinnamaldehyde (HCA)-dosed ear. Increased proliferative activity was observed in contra-lateral draining lymph nodes of restrained mice demonstrating that these results cannot be attributed to cross-contamination of adjacent skin. A significant increase in proliferation of splenocytes was also observed. It is concluded that dermal application of a contact allergen, as exemplified by OX and HCA, may induce cell proliferation in the neighboring lymph nodes and spleen indicative of hapten and/or haptenated proteins diffusing through the skin to peripheral nodes and the blood to produce systemic sensitization. It is also possible that lymphatic capillaries may communicate

  16. Direct Cell-Cell Contact between Mesenchymal Stem Cells and Endothelial Progenitor Cells Induces a Pericyte-Like Phenotype In Vitro

    Directory of Open Access Journals (Sweden)

    Markus Loibl

    2014-01-01

    Full Text Available Tissue engineering techniques for the regeneration of large bone defects require sufficient vascularisation of the applied constructs to ensure a sufficient supply of oxygen and nutrients. In our previous work, prevascularised 3D scaffolds have been successfully established by coculture of bone marrow derived stem cells (MSCs and endothelial progenitor cells (EPCs. We identified stabilising pericytes (PCs as part of newly formed capillary-like structures. In the present study, we report preliminary data on the interactions between MSCs and EPCs, leading to the differentiation of pericyte-like cells. MSCs and EPCs were seeded in transwell cultures, direct cocultures, and single cultures. Cells were cultured for 10 days in IMDM 10% FCS or IMDM 5% FCS 5% platelet lysate medium. Gene expression of PC markers, CD146, NG2, αSMA, and PDGFR-β, was analysed using RT-PCR at days 0, 3, 7, and 10. The upregulation of CD146, NG2, and αSMA in MSCs in direct coculture with EPCs advocates the MSCs’ differentiation towards a pericyte-like phenotype in vitro. These results suggest that pericyte-like cells derive from MSCs and that cell-cell contact with EPCs is an important factor for this differentiation process. These findings emphasise the concept of coculture strategies to promote angiogenesis for cell-based tissue engineered bone grafts.

  17. A simulation study on the electrical structure of interdigitated back-contact silicon solar cells

    Science.gov (United States)

    Kang, Min Gu; Song, Hee-eun; Kim, Soo Min; Kim, Donghwan

    2015-05-01

    In this paper, a simulation for interdigitated back-contact (IBC) silicon solar cells was performed by using Silvaco TCAD ATLAS to investigate the cell's electrical properties. The impacts of various parameters, including the depth of the front surface field(FSF), the FSF peak doping concentration, the depths of the emitter and the back surface field(BSF), the peak doping concentrations of the emitter and BSF, the base doping, and the bulk lifetime on the output characteristics like the light current-voltage curves and the internal quantum efficiency of the IBC solar cell, were investigated. The light absorption was determined by adjusting the antireflection coating and the Al thickness. The FSF must be thin and have a low doping concentration for high-efficiency IBC cells. If the conversion efficiency is to be improved, a thick emitter and a high doping concentration are needed. Because of the low resistivity of the Si substrate, the series resistance was reduced, but recombination was increased. With a high-resistivity Si substrate, the opposite trends were observed. By counter-balancing the series resistance and the recombination, we determined by simulation that the optimized resistivity for the IBC cells was 1 Ω·cm. Because all metal electrodes in the IBC cells are located on the back side, a higher minority carrier lifetime showed a higher efficiency. After the various parameters had been optimized, texturing and surface recombination were added into the simulation. The simulated IBC cells showed a short-circuit current density of 42.89 mA/cm2, an open-circuit voltage of 714.8 mV, a fill factor of 84.04%, and a conversion efficiency of 25.77%.

  18. MGL2 Dermal dendritic cells are sufficient to initiate contact hypersensitivity in vivo.

    Directory of Open Access Journals (Sweden)

    Yosuke Kumamoto

    Full Text Available Dendritic cells (DCs are the most potent antigen-presenting cells in the mammalian immune system. In the skin, epidermal Langerhans cells (LCs and dermal dendritic cells (DDCs survey for invasive pathogens and present antigens to T cells after migration to the cutaneous lymph nodes (LNs. So far, functional and phenotypic differences between these two DC subsets remain unclear due to lack of markers to identify DDCs.In the present report, we demonstrated that macrophage galactose-type C-type lectin (MGL 2 was exclusively expressed in the DDC subset in the skin-to-LN immune system. In the skin, MGL2 was expressed on the majority (about 88% of MHCII(+CD11c(+ cells in the dermis. In the cutaneous LN, MGL2 expression was restricted to B220(-CD8alpha(loCD11b(+CD11c(+MHCII(hi tissue-derived DC. MGL2(+DDC migrated from the dermis into the draining LNs within 24 h after skin sensitization with FITC. Distinct from LCs, MGL2(+DDCs localized near the high endothelial venules in the outer T cell cortex. In FITC-induced contact hypersensitivity (CHS, adoptive transfer of FITC(+MGL2(+DDCs, but not FITC(+MGL2(-DCs into naive mice resulted in the induction of FITC-specific ear swelling, indicating that DDCs played a key role in initiation of immune responses in the skin.These results demonstrated the availability of MGL2 as a novel marker for DDCs and suggested the contribution of MGL2(+ DDCs for initiating CHS.

  19. The challenge of screen printed Ag metallization on nano-scale poly-silicon passivated contacts for silicon solar cells

    Science.gov (United States)

    Jiang, Lin; Song, Lixin; Yan, Li; Becht, Gregory; Zhang, Yi; Hoerteis, Matthias

    2017-08-01

    Passivated contacts can be used to reduce metal-induced recombination for higher energy conversion efficiency for silicon solar cells, and are obtained increasing attentions by PV industries in recent years. The reported thicknesses of passivated contact layers are mostly within tens of nanometer range, and the corresponding metallization methods are realized mainly by plating/evaporation technology. This high cost metallization cannot compete with the screen printing technology, and may affect its market potential comparing with the presently dominant solar cell technology. Very few works have been reported on screen printing metallization on passivated contact solar cells. Hence, there is a rising demand to realize screen printing metallization technology on this topic. In this work, we investigate applying screen printing metallization pastes on poly-silicon passivated contacts. The critical challenge for us is to build low contact resistance that can be competitive to standard technology while restricting the paste penetrations within the thin nano-scale passivated contact layers. The contact resistivity of 1.1mohm-cm2 and the open circuit voltages > 660mV are achieved, and the most appropriate thickness range is estimated to be around 80 150nm.

  20. Optical Evaluation of the Rear Contacts of Crystalline Silicon Solar Cells by Coupled Electromagnetic and Statistical Ray-Optics Modeling

    KAUST Repository

    Dabirian, Ali

    2017-02-15

    High-efficiency crystalline silicon (c-Si) solar cells increasingly feature sophisticated electron and hole contacts aimed at minimizing electronic losses. At the rear of photovoltaic devices, such contacts—usually consisting of stacks of functional layers—offer opportunities to enhance the infrared response of the solar cells. Here, we propose an accurate and simple modeling procedure to evaluate the infrared performance of rear contacts in c-Si solar cells. Our method combines full-wave electromagnetic modeling of the rear contact with a statistical ray optics model to obtain the fraction of optical energy dissipated from the rear contact relative to that absorbed by the Si wafer. Using this technique, we study the impact of the refractive index, extinction coefficient, and thickness of the rear-passivating layer and establish basic design rules. In addition, we evaluate novel optical structures, including stratified thin films, nanoparticle composites, and conductive nanowires embedded in a low-index dielectric matrix, for integration into advanced rear contacts in c-Si photovoltaic devices. From an optical perspective, nanowire structures preserving low contact resistance appear to be the most effective approach to mitigating dissipation losses from the rear contact.

  1. Contact size scaling of a W-contact phase-change memory cell based on numerical simulation

    International Nuclear Information System (INIS)

    Wei Yiqun; Lin Xinnan; Jia Yuchao; Cui Xiaole; Zhang Xing; Song Zhitang

    2012-01-01

    In the design of phase-change memory (PCM), it is important to perform numerical simulations to predict the performances of different device structures. This work presents a numerical simulation using a coupled system including Poisson's equation, the current continuity equation, the thermal conductivity equation, and phase-change dynamics to simulate the thermal and electric characteristics of phase-change memory. This method discriminates the common numerical simulation of PCM cells, from which it applies Possion's equation and current continuity equations instead of the Laplace equation to depict the electric characteristics of PCM cells, which is more adoptable for the semiconductor characteristics of phase-change materials. The results show that the simulation agrees with the measurement, and the scalability of PCM is predicted.

  2. Inter-chromosomal Contact Properties in Live-Cell Imaging and in Hi-C.

    Science.gov (United States)

    Maass, Philipp G; Barutcu, A Rasim; Weiner, Catherine L; Rinn, John L

    2018-03-15

    Imaging (fluorescence in situ hybridization [FISH]) and genome-wide chromosome conformation capture (Hi-C) are two major approaches to the study of higher-order genome organization in the nucleus. Intra-chromosomal and inter-chromosomal interactions (referred to as non-homologous chromosomal contacts [NHCCs]) have been observed by several FISH-based studies, but locus-specific NHCCs have not been detected by Hi-C. Due to crosslinking, neither of these approaches assesses spatiotemporal properties. Toward resolving the discrepancies between imaging and Hi-C, we sought to understand the spatiotemporal properties of NHCCs in living cells by CRISPR/Cas9 live-cell imaging (CLING). In mammalian cells, we find that NHCCs are stable and occur as frequently as intra-chromosomal interactions, but NHCCs occur at farther spatial distance that could explain their lack of detection in Hi-C. By revealing the spatiotemporal properties in living cells, our study provides fundamental insights into the biology of NHCCs. Copyright © 2018 Elsevier Inc. All rights reserved.

  3. Efficient and stable solution-processed planar perovskite solar cells via contact passivation

    KAUST Repository

    Tan, Hairen; Jain, Ankit; Voznyy, Oleksandr; Lan, Xinzheng; Garcí a de Arquer, F. Pelayo; Fan, James Z.; Quintero-Bermudez, Rafael; Yuan, Mingjian; Zhang, Bo; Zhao, Yicheng; Fan, Fengjia; Li, Peicheng; Quan, Li Na; Zhao, Yongbiao; Lu, Zheng-Hong; Yang, Zhenyu; Hoogland, Sjoerd; Sargent, Edward H.

    2017-01-01

    Planar perovskite solar cells (PSCs) made entirely via solution processing at low temperatures (<150°C) offer promise for simple manufacturing, compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO2 colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temperature planar solar cells. We fabricated solar cells with certified efficiencies of 20.1 and 19.5% for active areas of 0.049 and 1.1 square centimeters, respectively, achieved via low-temperature solution processing. Solar cells with efficiency greater than 20% retained 90% (97% after dark recovery) of their initial performance after 500 hours of continuous room-temperature operation at their maximum power point under 1-sun illumination (where 1 sun is defined as the standard illumination at AM1.5, or 1 kilowatt/square meter).

  4. Efficient and stable solution-processed planar perovskite solar cells via contact passivation

    KAUST Repository

    Tan, Hairen

    2017-02-03

    Planar perovskite solar cells (PSCs) made entirely via solution processing at low temperatures (<150°C) offer promise for simple manufacturing, compatibility with flexible substrates, and perovskite-based tandem devices. However, these PSCs require an electron-selective layer that performs well with similar processing. We report a contact-passivation strategy using chlorine-capped TiO2 colloidal nanocrystal film that mitigates interfacial recombination and improves interface binding in low-temperature planar solar cells. We fabricated solar cells with certified efficiencies of 20.1 and 19.5% for active areas of 0.049 and 1.1 square centimeters, respectively, achieved via low-temperature solution processing. Solar cells with efficiency greater than 20% retained 90% (97% after dark recovery) of their initial performance after 500 hours of continuous room-temperature operation at their maximum power point under 1-sun illumination (where 1 sun is defined as the standard illumination at AM1.5, or 1 kilowatt/square meter).

  5. Control of density-dependent, cell state-specific signal transduction by the cell adhesion molecule CEACAM1, and its influence on cell cycle regulation

    International Nuclear Information System (INIS)

    Scheffrahn, Inka; Singer, Bernhard B.; Sigmundsson, Kristmundur; Lucka, Lothar; Oebrink, Bjoern

    2005-01-01

    Growth factor receptors, extracellular matrix receptors, and cell-cell adhesion molecules co-operate in regulating the activities of intracellular signaling pathways. Here, we demonstrate that the cell adhesion molecule CEACAM1 co-regulates growth-factor-induced DNA synthesis in NBT-II epithelial cells in a cell-density-dependent manner. CEACAM1 exerted its effects by regulating the activity of the Erk 1/2 MAP kinase pathway and the expression levels of the cyclin-dependent kinase inhibitor p27 Kip1 . Interestingly, both inhibitory and stimulatory effects were observed. Confluent cells continuously exposed to fetal calf serum showed little Erk activity and DNA synthesis compared with sparse cells. Under these conditions, anti-CEACAM1 antibodies strongly stimulated Erk activation, decreased p27 expression, and induced DNA synthesis. In serum-starved confluent cells, re-addition of 10% fetal calf serum activated the Erk pathway, decreased p27 expression, and stimulated DNA synthesis to the same levels as in sparse cells. Under these conditions anti-CEACAM1 antibodies de-activated Erk, restored the level of p27, and inhibited DNA synthesis. These data indicate that CEACAM1 mediates contact inhibition of proliferation in cells that are constantly exposed to growth factors, but co-activates growth-factor-induced proliferation in cells that have been starved for growth factors; exposure to extracellular CEACAM1 ligands reverts these responses

  6. ER-mitochondria contacts control surface glycan expression and sensitivity to killer lymphocytes in glioma stem-like cells.

    Science.gov (United States)

    Bassoy, Esen Yonca; Kasahara, Atsuko; Chiusolo, Valentina; Jacquemin, Guillaume; Boydell, Emma; Zamorano, Sebastian; Riccadonna, Cristina; Pellegatta, Serena; Hulo, Nicolas; Dutoit, Valérie; Derouazi, Madiha; Dietrich, Pierre Yves; Walker, Paul R; Martinvalet, Denis

    2017-06-01

    Glioblastoma is a highly heterogeneous aggressive primary brain tumor, with the glioma stem-like cells (GSC) being more sensitive to cytotoxic lymphocyte-mediated killing than glioma differentiated cells (GDC). However, the mechanism behind this higher sensitivity is unclear. Here, we found that the mitochondrial morphology of GSCs modulates the ER-mitochondria contacts that regulate the surface expression of sialylated glycans and their recognition by cytotoxic T lymphocytes and natural killer cells. GSCs displayed diminished ER-mitochondria contacts compared to GDCs. Forced ER-mitochondria contacts in GSCs increased their cell surface expression of sialylated glycans and reduced their susceptibility to cytotoxic lymphocytes. Therefore, mitochondrial morphology and dynamism dictate the ER-mitochondria contacts in order to regulate the surface expression of certain glycans and thus play a role in GSC recognition and elimination by immune effector cells. Targeting the mitochondrial morphology, dynamism, and contacts with the ER could be an innovative strategy to deplete the cancer stem cell compartment to successfully treat glioblastoma. © 2017 The Authors.

  7. Characteristics of molybdenum bilayer back contacts for Cu(In,Ga)Se{sub 2} solar cells on Ti foils

    Energy Technology Data Exchange (ETDEWEB)

    Roger, Charles, E-mail: charles.rgr@gmail.com [CEA, LITEN, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France); Noël, Sébastien; Sicardy, Olivier; Faucherand, Pascal; Grenet, Louis; Karst, Nicolas; Fournier, Hélène; Roux, Frédéric [CEA, LITEN, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France); Ducroquet, Frédérique [IMEP-LAHC, Minatec, Grenoble-INP, CNRS UMR 5130, 38016 Grenoble (France); Brioude, Arnaud [Laboratoire des Multimatériaux et Interfaces, UMR 5615, Villeurbanne (France); Perraud, Simon [CEA, LITEN, 17 Rue des Martyrs, 38054 Grenoble Cedex 9 (France)

    2013-12-02

    Molybdenum back contact properties are critical for Cu(In,Ga)Se{sub 2} (CIGS) solar cell performance on metallic substrates. In this work, we investigated the properties of sputter-deposited Mo bilayer back contacts on Ti foils. The morphology, electrical resistivity, optical reflectance and residual mechanical stress of the bottom Mo layer were modified by varying the working pressure during its deposition. Working pressures ranging from 0.27 Pa to 4.00 Pa were used. The top Mo layer was deposited using constant conditions at a pressure of 0.13 Pa. It was demonstrated that unlike a Mo monolayer, the use of a Mo bilayer allows controlling the mechanical stress at the Mo/CIGS interface without degrading the optical reflectance and the electrical resistance of the back contact. It was also found that the morphology of the bottom Mo layer affects the growth of the top Mo layer, resulting in a modified back contact surface morphology. This induces changes in the crystalline orientation of the CIGS layer. The resulting solar cell characteristics strongly vary as a function of the bottom Mo layer deposition pressure. A bottom Mo layer growth at 2.93 Pa allows improving the solar cell conversion efficiency by 1.5 times compared to a bottom Mo layer deposited at 0.27 Pa. Using the improved Mo bilayer back contact, a maximum solar cell efficiency of 10.0% was obtained without sodium addition nor anti-reflection coating. - Highlights: • Mo bilayer back contacts for Cu(In,Ga)Se{sub 2} solar cells were grown on Ti substrates. • The sputtering pressure of the bottom Mo layer was varied between 0.27 Pa and 4 Pa. • The top Mo layer controls the optical and electrical properties of the back contact. • The structure of the bottom Mo layer influences the morphology of the top Mo layer. • The back contact affects the CIGS texture, device series resistance and efficiency.

  8. Characteristics of molybdenum bilayer back contacts for Cu(In,Ga)Se2 solar cells on Ti foils

    International Nuclear Information System (INIS)

    Roger, Charles; Noël, Sébastien; Sicardy, Olivier; Faucherand, Pascal; Grenet, Louis; Karst, Nicolas; Fournier, Hélène; Roux, Frédéric; Ducroquet, Frédérique; Brioude, Arnaud; Perraud, Simon

    2013-01-01

    Molybdenum back contact properties are critical for Cu(In,Ga)Se 2 (CIGS) solar cell performance on metallic substrates. In this work, we investigated the properties of sputter-deposited Mo bilayer back contacts on Ti foils. The morphology, electrical resistivity, optical reflectance and residual mechanical stress of the bottom Mo layer were modified by varying the working pressure during its deposition. Working pressures ranging from 0.27 Pa to 4.00 Pa were used. The top Mo layer was deposited using constant conditions at a pressure of 0.13 Pa. It was demonstrated that unlike a Mo monolayer, the use of a Mo bilayer allows controlling the mechanical stress at the Mo/CIGS interface without degrading the optical reflectance and the electrical resistance of the back contact. It was also found that the morphology of the bottom Mo layer affects the growth of the top Mo layer, resulting in a modified back contact surface morphology. This induces changes in the crystalline orientation of the CIGS layer. The resulting solar cell characteristics strongly vary as a function of the bottom Mo layer deposition pressure. A bottom Mo layer growth at 2.93 Pa allows improving the solar cell conversion efficiency by 1.5 times compared to a bottom Mo layer deposited at 0.27 Pa. Using the improved Mo bilayer back contact, a maximum solar cell efficiency of 10.0% was obtained without sodium addition nor anti-reflection coating. - Highlights: • Mo bilayer back contacts for Cu(In,Ga)Se 2 solar cells were grown on Ti substrates. • The sputtering pressure of the bottom Mo layer was varied between 0.27 Pa and 4 Pa. • The top Mo layer controls the optical and electrical properties of the back contact. • The structure of the bottom Mo layer influences the morphology of the top Mo layer. • The back contact affects the CIGS texture, device series resistance and efficiency

  9. IRF8 Transcription-Factor-Dependent Classical Dendritic Cells Are Essential for Intestinal T Cell Homeostasis

    DEFF Research Database (Denmark)

    Luda, Katarzyna M.; Joeris, Thorsten; Persson, Emma K.

    2016-01-01

    The role of dendritic cells (DCs) in intestinal immune homeostasis remains incompletely defined. Here we show that mice lacking IRF8 transcription-factor-dependent DCs had reduced numbers of T cells in the small intestine (SI), but not large intestine (LI), including an almost complete absence...... dependent DCs in the maintenance of intestinal T cell homeostasis....

  10. Development of MoO{sub x} thin films as back contact buffer for CdTe solar cells in substrate configuration

    Energy Technology Data Exchange (ETDEWEB)

    Gretener, C., E-mail: christina.gretener@empa.ch [Laboratory for Thin Films and Photovoltaics, Empa — Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, 8600 Dübendorf (Switzerland); Perrenoud, J.; Kranz, L.; Baechler, C. [Laboratory for Thin Films and Photovoltaics, Empa — Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, 8600 Dübendorf (Switzerland); Yoon, S. [Laboratory for Solid State Chemistry and Catalysis, Empa — Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, 8600 Dübendorf (Switzerland); Romanyuk, Y.E.; Buecheler, S.; Tiwari, A.N. [Laboratory for Thin Films and Photovoltaics, Empa — Swiss Federal Laboratories for Materials Science and Technology, Überlandstr. 129, 8600 Dübendorf (Switzerland)

    2013-05-01

    Molybdenum oxide compounds exhibit unique electrical and optical properties depending on oxygen vacancy concentration and composition and therefore, have recently attracted a lot of attention as a hole transport layer in various devices. In this work CdTe solar cells in substrate configuration were grown with evaporated MoO{sub x} back contact buffer layers and efficiencies of up to 10% could be achieved without using Cu in the back contact processing. The buffer layer – at the CdTe/back contact interface – in the finished cell was found to consist of MoO{sub 2} phase instead of the expected MoO{sub 3} phase as observed in as-deposited or annealed MoO{sub x} layers without CdTe deposition. In order to obtain MoO{sub x} buffer layers with desired stoichiometry, MoO{sub x} thin films were deposited by radio-frequency sputtering under different growth conditions. The chemical phase, composition, microstructure and optical properties of such layers were studied for their possible use in CdTe solar cells. - Highlights: ► MoO{sub x} is used as a back contact buffer in CdTe solar cells in substrate configuration. ► Efficiency of 10.0% was achieved without the addition of Cu. ► The back contact buffer in the finished device consists only of MoO{sub 2}. ► Phases and microstructure of MoO{sub x} can be controlled by sputtering conditions.

  11. III-V/Si Tandem Cells Utilizing Interdigitated Back Contact Si Cells and Varying Terminal Configurations: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Schnabel, Manuel; Klein, Talysa R.; Jain, Nikhil; Essig, Stephanie; Schulte-Huxel, Henning; Warren, Emily; van Hest, Maikel F. A. M.; Geisz, John; Stradins, Paul; Tamboli, Adele; Rienacker, Michael; Merkle, Agnes; Schmidt, Jan; Brendel, Rolf; Peibst, Robby

    2017-07-11

    Solar cells made from bulk crystalline silicon (c-Si) dominate the market, but laboratory efficiencies have stagnated because the current record efficiency of 26.3% is already very close to the theoretical limit of 29.4% for a single-junction c-Si cell. In order to substantially boost the efficiency of Si solar cells we have been developing stacked III-V/Si tandem cells, recently attaining efficiencies above 32% in four-terminal configuration. In this contribution, we use state-of-the-art III-V cells coupled with equivalent circuit simulations to compare four-terminal (4T) to three- and two-terminal (3T, 2T) operation. Equivalent circuit simulations are used to show that tandem cells can be operated just as efficiently using three terminals as with four terminals. However, care must be taken not to overestimate 3T efficiency, as the two circuits used to extract current interact, and a method is described to accurately determine this efficiency. Experimentally, a 4T GaInP/Si tandem cell utilizing an interdigitated back contact cell is shown, exhibiting a 4T efficiency of 31.5% and a 2T efficiency of 28.1%. In 3T configuration, it is used to verify the finding from simulation that 3T efficiency is overestimated when interactions between the two circuits are neglected. Considering these, a 3T efficiency approaching the 4T efficiency is found, showing that 3T operation is efficient, and an outlook on fully integrated high-efficiency 3T and 2T tandem cells is given.

  12. Rac1 recruits the adapter protein CMS/CD2AP to cell-cell contacts

    NARCIS (Netherlands)

    van Duijn, Trynette J.; Anthony, Eloise C.; Hensbergen, Paul J.; Deelder, André M.; Hordijk, Peter L.

    2010-01-01

    Rac1 is a member of the Rho family of small GTPases, which regulate cell adhesion and migration through their control of the actin cytoskeleton. Rho-GTPases are structurally very similar, with the exception of a hypervariable domain in the C terminus. Using peptide-based pulldown assays in

  13. Rethinking cell-cycle-dependent gene expression in Schizosaccharomyces pombe.

    Science.gov (United States)

    Cooper, Stephen

    2017-11-01

    Three studies of gene expression during the division cycle of Schizosaccharomyces pombe led to the proposal that a large number of genes are expressed at particular times during the S. pombe cell cycle. Yet only a small fraction of genes proposed to be expressed in a cell-cycle-dependent manner are reproducible in all three published studies. In addition to reproducibility problems, questions about expression amplitudes, cell-cycle timing of expression, synchronization artifacts, and the problem with methods for synchronizing cells must be considered. These problems and complications prompt the idea that caution should be used before accepting the conclusion that there are a large number of genes expressed in a cell-cycle-dependent manner in S. pombe.

  14. T-cell recognition of Mycobacterium tuberculosis culture filtrate fractions in tuberculosis patients and their household contacts

    DEFF Research Database (Denmark)

    Demissie, A; Ravn, P; Olobo, J

    1999-01-01

    We examined the immune responses of patients with active pulmonary tuberculosis (TB) and their healthy household contacts to short-term culture filtrate (ST-CF) of Mycobacterium tuberculosis or molecular mass fractions derived from it. Our goal was to identify fractions strongly recognized...... to the antigens between the two groups was also found. In general, while all fractions stimulated immune responses, the highest activity was seen with the low-molecular-mass fractions, which include well-defined TB antigens such as ESAT-6. Leukocytes from contacts of TB patients with severe disease produced...... higher levels of antigen-specific IFN-gamma than those from contacts of patients with minimal disease. Both groups of contacts exhibited higher cell-mediated responses than the patients themselves. The enhanced immune response of healthy contacts, especially those of patients with severe disease...

  15. Optimization of solar cell contacts by system cost-per-watt minimization

    Science.gov (United States)

    Redfield, D.

    1977-01-01

    New, and considerably altered, optimum dimensions for solar-cell metallization patterns are found using the recently developed procedure whose optimization criterion is the minimum cost-per-watt effect on the entire photovoltaic system. It is also found that the optimum shadow fraction by the fine grid is independent of metal cost and resistivity as well as cell size. The optimum thickness of the fine grid metal depends on all these factors, and in familiar cases it should be appreciably greater than that found by less complete analyses. The optimum bus bar thickness is much greater than those generally used. The cost-per-watt penalty due to the need for increased amounts of metal per unit area on larger cells is determined quantitatively and thereby provides a criterion for the minimum benefits that must be obtained in other process steps to make larger cells cost effective.

  16. Contact Resistance of Ceramic Interfaces Between Materials Used for Solid Oxide Fuel Cell Applications

    DEFF Research Database (Denmark)

    Koch, Søren

    The contact resistance can be divided into two main contributions. The small area of contact between ceramic components results in resistance due to current constriction. Resistive phases or potential barriers at the interface result in an interface contribution to the contact resistance, which may....... The influence of the mechanical load on the contact resistance was ascribed to an area effect. The contact resistance of the investigated materials was dominated by current constric-tion at high temperatures. The measured contact resistance was comparable to the resis-tance calculated on basis of the contact...... areas found by optical and electron microscopy. At low temperatures, the interface contribution to the contact resistance was dominating. The cobaltite interface could be described by one potential barrier at the contact interface, whereas the manganite interfaces required several consecutive potential...

  17. Short-stack modeling of degradation in solid oxide fuel cells. Part I. Contact degradation

    Energy Technology Data Exchange (ETDEWEB)

    Gazzarri, J.I. [Department of Mechanical Engineering, University of British Columbia, 2054-6250 Applied Science Lane, Vancouver, BC V6T 1Z4 (Canada); Kesler, O. [Department of Mechanical and Industrial Engineering, University of Toronto, 5 King' s College Road, Toronto, ON M5S 3G8 (Canada)

    2008-01-21

    As the first part of a two paper series, we present a two-dimensional impedance model of a working solid oxide fuel cell (SOFC) to study the effect of contact degradation on the impedance spectrum for the purpose of non-invasive diagnosis. The two dimensional modeled geometry includes the ribbed interconnect, and is adequate to represent co- and counter-flow configurations. Simulated degradation modes include: cathode delamination, interconnect oxidation, and interconnect-cathode detachment. The simulations show differences in the way each degradation mode impacts the impedance spectrum shape, suggesting that identification is possible. In Part II, we present a sensitivity analysis of the results to input parameter variability that reveals strengths and limitations of the method, as well as describing possible interactions between input parameters and concurrent degradation modes. (author)

  18. Short-stack modeling of degradation in solid oxide fuel cells. Part I. Contact degradation

    Science.gov (United States)

    Gazzarri, J. I.; Kesler, O.

    As the first part of a two paper series, we present a two-dimensional impedance model of a working solid oxide fuel cell (SOFC) to study the effect of contact degradation on the impedance spectrum for the purpose of non-invasive diagnosis. The two dimensional modeled geometry includes the ribbed interconnect, and is adequate to represent co- and counter-flow configurations. Simulated degradation modes include: cathode delamination, interconnect oxidation, and interconnect-cathode detachment. The simulations show differences in the way each degradation mode impacts the impedance spectrum shape, suggesting that identification is possible. In Part II, we present a sensitivity analysis of the results to input parameter variability that reveals strengths and limitations of the method, as well as describing possible interactions between input parameters and concurrent degradation modes.

  19. Influence of the mechanical properties of sputtered Mo solar cell back contacts on laser scribing

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, Christof; Schuele, Manuel; Quaschning, Volker; Stegemann, Bert; Fink, Frank [University of Applied Sciences (HTW) Berlin, Wilhelminenhofstr. 75A, 12459 Berlin (Germany); Endert, Heinrich [Newport Spectra-Physics GmbH, Ruhlsdorfer Strasse 95, 14532 Stahnsdorf (Germany); Bonse, Joern [BAM Bundesanstalt fuer Materialforschung und -pruefung, Berlin (Germany); Rau, Bjoern; Schlatmann, Rutger [PVcomB - Competence Centre Thin-Film and Nanotechnology for Photovoltaics Berlin, Schwarzschildstr. 3, 12489 Berlin (Germany)

    2012-07-01

    In thin-film photovoltaics complete laser structuring of the solar modules is aimed to perform appropriate monolithic serial interconnection. We have studied the laser ablation behavior of sputtered molybdenum back contacts for chalcopyrite solar cells. The properties of these Mo layer are sensitive to the sputter conditions. The process pressure influences the mechanical layer properties and, thus, contributes directly to the quality of the laser scribes. Precise, reliable and reproducible laser scribing requires the proper adaptation of the laser parameters to the material properties. In our study it was achieved by comprehensive analysis of the laser matter interaction and by detailed determination of the ablation thresholds as a function of the Mo layer thickness and ductility for different laser wavelengths and pulse durations, accompanied by thermal modeling.

  20. Transparent conducting oxide contacts and textured metal back reflectors for thin film silicon solar cells

    Science.gov (United States)

    Franken, R. H.-J.

    2006-09-01

    With the growing population and the increasing environmental problems of the 'common' fossil and nuclear energy production, the need for clean and sustainable energy sources is evident. Solar energy conversion, such as in photovoltaic (PV) systems, can play a major role in the urgently needed energy transition in electricity production. At the present time PV module production is dominated by the crystalline wafer technology. Thin film silicon technology is an alternative solar energy technology that operates at lower efficiencies, however, it has several significant advantages, such as the possibility of deposition on cheap (flexible) substrates and the much smaller silicon material consumption. Because of the small thickness of the solar cells, light trapping schemes are needed in order to obtain enough light absorption and current generation. This thesis describes the research on thin film silicon solar cells with the focus on the optimization of the transparent conducting oxide (TCO) layers and textured metal Ag substrate layers for the use as enhanced light scattering back reflectors in n-i-p type of solar cells. First we analyzed ZnO:Al (TCO) layers deposited in an radio frequent (rf) magnetron deposition system equipped with a 7 inch target. We have focused on the improvement of the electrical properties without sacrificing the optical properties by increasing the mobility and decreasing the grain boundary density. Furthermore, we described some of the effects on light trapping of ZnO:Al enhanced back reflectors. The described effects are able to explain the observed experimental data. Furthermore, we present a relation between the surface morphology of the Ag back contact and the current enhancement in microcrystalline (muc-Si:H) solar cells. We show the importance of the lateral feature sizes of the Ag surface on the light scattering and introduce a method to characterize the quality of the back reflector by combining the vertical and lateral feature sizes

  1. Efficient Regular Perovskite Solar Cells Based on Pristine [70]Fullerene as Electron-Selective Contact.

    Science.gov (United States)

    Collavini, Silvia; Kosta, Ivet; Völker, Sebastian F; Cabanero, German; Grande, Hans J; Tena-Zaera, Ramón; Delgado, Juan Luis

    2016-06-08

    [70]Fullerene is presented as an efficient alternative electron-selective contact (ESC) for regular-architecture perovskite solar cells (PSCs). A smart and simple, well-described solution processing protocol for the preparation of [70]- and [60]fullerene-based solar cells, namely the fullerene saturation approach (FSA), allowed us to obtain similar power conversion efficiencies for both fullerene materials (i.e., 10.4 and 11.4 % for [70]- and [60]fullerene-based devices, respectively). Importantly, despite the low electron mobility and significant visible-light absorption of [70]fullerene, the presented protocol allows the employment of [70]fullerene as an efficient ESC. The [70]fullerene film thickness and its solubility in the perovskite processing solutions are crucial parameters, which can be controlled by the use of this simple solution processing protocol. The damage to the [70]fullerene film through dissolution during the perovskite deposition is avoided through the saturation of the perovskite processing solution with [70]fullerene. Additionally, this fullerene-saturation strategy improves the performance of the perovskite film significantly and enhances the power conversion efficiency of solar cells based on different ESCs (i.e., [60]fullerene, [70]fullerene, and TiO2 ). Therefore, this universal solution processing protocol widens the opportunities for the further development of PSCs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Degradation of some ceria electrolytes under hydrogen contact nearby anode in solid oxide fuel cells (SOFCs

    Directory of Open Access Journals (Sweden)

    Malta Luiz Fernando Brum

    2004-01-01

    Full Text Available This work is concerned with thermodynamic analysis of the stability of some ceria electrolytes under contact with hydrogen gas nearby anode in fuel cells. It was considered the following types of ceria-electrolytes: pure ceria, strontium-doped ceria, calcium-doped ceria and calcium-bismuth-doped ceria. The equilibrium Log (pH2O/pH2 vs. T diagrams were constructed for x = 0.1 and 0.01, where x is the fraction of initial ceria converted to Ce2O3 (proportional to the ratio between activities of Ce3+ and Ce4+ in the ceria electrolyte, which is proportional to the fraction of electronic conduction in the electrolyte at a given temperature. The predictions of the diagrams are as follows: (a Ce1.9Ca0.1Bi0.8O5.1 and Ce0.9Sr0.1O1.9 are less stable than pure ceria for the whole temperature range (from 0 to 1000 °C; (b Ce0.9Ca0.1O1.9 is more stable than pure ceria below about 650 °C for x = 0.1 and below about 400 °C for x = 0.01; (c at each temperature in the considered range the pressure ratio pH2O(g/pH2(g has to be higher than thermodynamically predicted in order to keep CeO2 stable in the electrolyte contacting hydrogen gas. Thermodynamic predictions are entirely capable of explaining experimental data published on the subject (irreversible cell degradation in the case of SrO-doped ceria; weight loss from doped-ceria electrolyte above 700 °C; oxygen gas release during sintering of ceria.

  3. Crafting semiconductor organic-inorganic nanocomposites via placing conjugated polymers in intimate contact with nanocrystals for hybrid solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Lei; Lin, Zhiqun [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA (United States)

    2012-08-22

    Semiconductor organic-inorganic hybrid solar cells incorporating conjugated polymers (CPs) and nanocrystals (NCs) offer the potential to deliver efficient energy conversion with low-cost fabrication. The CP-based photovoltaic devices are complimented by an extensive set of advantageous characteristics from CPs and NCs, such as lightweight, flexibility, and solution-processability of CPs, combined with high electron mobility and size-dependent optical properties of NCs. Recent research has witnessed rapid advances in an emerging field of directly tethering CPs on the NC surface to yield an intimately contacted CP-NC nanocomposite possessing a well-defined interface that markedly promotes the dispersion of NCs within the CP matrix, facilitates the photoinduced charge transfer between these two semiconductor components, and provides an effective platform for studying the interfacial charge separation and transport. In this Review, we aim to highlight the recent developments in CP-NC nanocomposite materials, critically examine the viable preparative strategies geared to craft intimate CP-NC nanocomposites and their photovoltaic performance in hybrid solar cells, and finally provide an outlook for future directions of this extraordinarily rich field. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. A Herbivore Tag-and-Trace System Reveals Contact- and Density-Dependent Repellence of a Root Toxin.

    Science.gov (United States)

    Bont, Zoe; Arce, Carla; Huber, Meret; Huang, Wei; Mestrot, Adrien; Sturrock, Craig J; Erb, Matthias

    2017-03-01

    Foraging behavior of root feeding organisms strongly affects plant-environment-interactions and ecosystem processes. However, the impact of plant chemistry on root herbivore movement in the soil is poorly understood. Here, we apply a simple technique to trace the movement of soil-dwelling insects in their habitats without disturbing or restricting their interactions with host plants. We tagged the root feeding larvae of Melolontha melolontha with a copper ring and repeatedly located their position in relation to their preferred host plant, Taraxacum officinale, using a commercial metal detector. This method was validated and used to study the influence of the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G) on the foraging of M. melolontha. TA-G is stored in the latex of T. officinale and protects the roots from herbivory. Using behavioral arenas with TA-G deficient and control plants, we tested the impact of physical root access and plant distance on the effect of TA-G on M. melolontha. The larvae preferred TA-G deficient plants to control plants, but only when physical root contact was possible and the plants were separated by 5 cm. Melolontha melolontha showed no preference for TA-G deficient plants when the plants were grown 15 cm apart, which may indicate a trade-off between the cost of movement and the benefit of consuming less toxic food. We demonstrate that M. melolontha integrates host plant quality and distance into its foraging patterns and suggest that plant chemistry affects root herbivore behavior in a plant-density dependent manner.

  5. Light-dependent governance of cell shape dimensions in cyanobacteria

    Directory of Open Access Journals (Sweden)

    Beronda L Montgomery

    2015-05-01

    Full Text Available The regulation of cellular dimension is important for the function and survival of cells. Cellular dimensions, such as size and shape, are regulated throughout the life cycle of bacteria and can be adapted in response to environmental changes to fine-tune cellular fitness. Cell size and shape are generally coordinated with cell growth and division. Cytoskeletal regulation of cell shape and cell wall biosynthesis and/or deposition occurs in a range of organisms. Photosynthetic organisms, such as cyanobacteria, particularly exhibit light-dependent regulation of morphogenes and generation of reactive oxygen species and other signals that can impact cellular dimensions. Environmental signals initiate adjustments of cellular dimensions, which may be vitally important for optimizing resource acquisition and utilization or for coupling the cellular dimensions with the regulation of subcellular organization to maintain optimal metabolism. Although the involvement of cytoskeletal components in the regulation of cell shape is widely accepted, the signaling factors that regulate cytoskeletal and other distinct components involved in cell shape control, particularly in response to changes in external light cues, remain to be fully elucidated. In this review, factors impacting the inter-coordination of growth and division, the relationship between the regulation of cellular dimensions and central carbon metabolism, and consideration of the effects of specific environment signals, primarily light, on cell dimensions in cyanobacteria will be discussed. Current knowledge about the molecular bases of the light-dependent regulation of cellular dimensions and cell shape in cyanobacteria will be highlighted.

  6. Direct physical contact between intercalated cells in the distal convoluted tubule and the afferent arteriole in mouse kidneys.

    Directory of Open Access Journals (Sweden)

    Hao Ren

    Full Text Available Recent physiological studies in the kidney proposed the existence of a secondary feedback mechanism termed 'crosstalk' localized after the macula densa. This newly discovered crosstalk contact between the nephron tubule and its own afferent arteriole may potentially revolutionize our understanding of renal vascular resistance and electrolyte regulation. However, the nature of such a crosstalk mechanism is still debated due to a lack of direct and comprehensive morphological evidence. Its exact location along the nephron, its prevalence among the different types of nephrons, and the type of cells involved are yet unknown. To address these issues, computer assisted 3-dimensional nephron tracing was applied in combination with direct immunohistochemistry on plastic sections and electron microscopy. 'Random' contacts in the cortex were identified by the tracing and excluded. We investigated a total of 168 nephrons from all cortical regions. The results demonstrated that the crosstalk contact existed, and that it was only present in certain nephrons (90% of the short-looped and 75% of the long-looped nephrons. The crosstalk contacts always occurred at a specific position--the last 10% of the distal convoluted tubule. Importantly, we demonstrated, for the first time, that the cells found in the tubule wall at the contact site were always type nonA-nonB intercalated cells. In conclusion, the present work confirmed the existence of a post macula densa physical crosstalk contact.

  7. Direct physical contact between intercalated cells in the distal convoluted tubule and the afferent arteriole in mouse kidneys.

    Science.gov (United States)

    Ren, Hao; Liu, Ning-Yu; Andreasen, Arne; Thomsen, Jesper S; Cao, Liu; Christensen, Erik I; Zhai, Xiao-Yue

    2013-01-01

    Recent physiological studies in the kidney proposed the existence of a secondary feedback mechanism termed 'crosstalk' localized after the macula densa. This newly discovered crosstalk contact between the nephron tubule and its own afferent arteriole may potentially revolutionize our understanding of renal vascular resistance and electrolyte regulation. However, the nature of such a crosstalk mechanism is still debated due to a lack of direct and comprehensive morphological evidence. Its exact location along the nephron, its prevalence among the different types of nephrons, and the type of cells involved are yet unknown. To address these issues, computer assisted 3-dimensional nephron tracing was applied in combination with direct immunohistochemistry on plastic sections and electron microscopy. 'Random' contacts in the cortex were identified by the tracing and excluded. We investigated a total of 168 nephrons from all cortical regions. The results demonstrated that the crosstalk contact existed, and that it was only present in certain nephrons (90% of the short-looped and 75% of the long-looped nephrons). The crosstalk contacts always occurred at a specific position--the last 10% of the distal convoluted tubule. Importantly, we demonstrated, for the first time, that the cells found in the tubule wall at the contact site were always type nonA-nonB intercalated cells. In conclusion, the present work confirmed the existence of a post macula densa physical crosstalk contact.

  8. Plasmonic back contacts with non-ordered Ag nanostructures for light trapping in thin-film silicon solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paetzold, Ulrich W., E-mail: u.paetzold@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Meier, Matthias, E-mail: ma.meier@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Moulin, Etienne, E-mail: e.moulin@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Smirnov, Vladimir, E-mail: v.smirnov@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Pieters, Bart E., E-mail: b.pieters@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Rau, Uwe, E-mail: u.rau@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany); Carius, Reinhard, E-mail: r.carius@fz-juelich.de [IEK5-Photovoltaik, Forschungszentrum Juelich, D-52425 Juelich (Germany)

    2013-05-15

    In this work, we investigate the light trapping of thin-film silicon solar cells which apply plasmonic Ag back contacts with non-ordered Ag nanostructures. The preparation, characterization and three-dimensional electromagnetic simulations of these back contacts with various distributions of non-ordered Ag nanostructures are presented. The measured reflectance spectra of the Ag back contacts with non-ordered nanostructures in air are well reproduced in reflectance spectra derived from the three-dimensional electromagnetic simulations of isolated nanostructures on Ag back contacts. The light–matter interaction of these nanostructures is given by localized surface plasmons and, thus, the measured diffuse reflectance of the back contacts is attributed to plasmon-induced light scattering. A significant plasmonic light-trapping effect in n-i-p substrate-type μc-Si:H thin-film solar cell prototypes which apply a Ag back contact with non-ordered nanostructures is identified when compared with flat reference solar cells.

  9. Plasmonic back contacts with non-ordered Ag nanostructures for light trapping in thin-film silicon solar cells

    International Nuclear Information System (INIS)

    Paetzold, Ulrich W.; Meier, Matthias; Moulin, Etienne; Smirnov, Vladimir; Pieters, Bart E.; Rau, Uwe; Carius, Reinhard

    2013-01-01

    In this work, we investigate the light trapping of thin-film silicon solar cells which apply plasmonic Ag back contacts with non-ordered Ag nanostructures. The preparation, characterization and three-dimensional electromagnetic simulations of these back contacts with various distributions of non-ordered Ag nanostructures are presented. The measured reflectance spectra of the Ag back contacts with non-ordered nanostructures in air are well reproduced in reflectance spectra derived from the three-dimensional electromagnetic simulations of isolated nanostructures on Ag back contacts. The light–matter interaction of these nanostructures is given by localized surface plasmons and, thus, the measured diffuse reflectance of the back contacts is attributed to plasmon-induced light scattering. A significant plasmonic light-trapping effect in n-i-p substrate-type μc-Si:H thin-film solar cell prototypes which apply a Ag back contact with non-ordered nanostructures is identified when compared with flat reference solar cells

  10. Lack of TAK1 in dendritic cells inhibits the contact hypersensitivity response induced by trichloroethylene in local lymph node assay

    Energy Technology Data Exchange (ETDEWEB)

    Yao, Pan; Hongqian, Chu; Qinghe, Meng; Lanqin, Shang; Jianjun, Jiang; Xiaohua, Yang; Xuetao, Wei; Weidong, Hao, E-mail: whao@bjmu.edu.cn

    2016-09-15

    Trichloroethylene (TCE) is a ubiquitous environmental contaminant. Occupational TCE exposure has been associated with severe, generalized contact hypersensitivity (CHS) skin disorder. The development of CHS depends on innate and adaptive immune functions. Transforming growth factor-β activated kinase-1 (TAK1) controls the survival of dendritic cells (DCs) that affect the immune system homeostasis. We aimed to investigate the role of TAK1 activity in DC on TCE-induced CHS response. Control mice and DC-specific TAK1 deletion mice were treated with 80% (v/v) TCE using local lymph node assay (LLNA) to establish a TCE-induced CHS model. The draining lymph nodes (DLNs) were excised and the lymphocytes were measure for proliferation by BrdU-ELISA, T-cell phenotype analysis by flow cytometry and signaling pathway activation by western blot. The ears were harvested for histopathological analysis. Control mice in the 80% TCE group displayed an inflammatory response in the ears, increased lymphocyte proliferation, elevated regulatory T-cell and activated T-cell percentages, and more IFN-γ producing CD8{sup +} T cells in DLNs. In contrast to control mice, DC-specific TAK1 deletion mice in the 80% TCE group showed an abolished CHS response and this was associated with defective T-cell expansion, activation and IFN-γ production. This effect may occur through Jnk and NF-κB signaling pathways. Overall, this study demonstrates a pivotal role of TAK1 in DCs in controlling TCE-induced CHS response and suggests that targeting TAK1 function in DCs may be a viable approach to preventing and treating TCE-related occupational health hazards. - Highlights: • Lack of TAK1 in DC caused an abolished TCE-induced CHS response. • TAK1 in DCs was essential to maintain the homeostasis of T cells in TCE-induced CHS. • Intact TAK1 in DCs was critical to promote T-cell priming in TCE-induced CHS. • DC-specific TAK1 deficiency abolished the TCE-mediated phosphorylation of Jnk.

  11. Lack of TAK1 in dendritic cells inhibits the contact hypersensitivity response induced by trichloroethylene in local lymph node assay

    International Nuclear Information System (INIS)

    Yao, Pan; Hongqian, Chu; Qinghe, Meng; Lanqin, Shang; Jianjun, Jiang; Xiaohua, Yang; Xuetao, Wei; Weidong, Hao

    2016-01-01

    Trichloroethylene (TCE) is a ubiquitous environmental contaminant. Occupational TCE exposure has been associated with severe, generalized contact hypersensitivity (CHS) skin disorder. The development of CHS depends on innate and adaptive immune functions. Transforming growth factor-β activated kinase-1 (TAK1) controls the survival of dendritic cells (DCs) that affect the immune system homeostasis. We aimed to investigate the role of TAK1 activity in DC on TCE-induced CHS response. Control mice and DC-specific TAK1 deletion mice were treated with 80% (v/v) TCE using local lymph node assay (LLNA) to establish a TCE-induced CHS model. The draining lymph nodes (DLNs) were excised and the lymphocytes were measure for proliferation by BrdU-ELISA, T-cell phenotype analysis by flow cytometry and signaling pathway activation by western blot. The ears were harvested for histopathological analysis. Control mice in the 80% TCE group displayed an inflammatory response in the ears, increased lymphocyte proliferation, elevated regulatory T-cell and activated T-cell percentages, and more IFN-γ producing CD8 + T cells in DLNs. In contrast to control mice, DC-specific TAK1 deletion mice in the 80% TCE group showed an abolished CHS response and this was associated with defective T-cell expansion, activation and IFN-γ production. This effect may occur through Jnk and NF-κB signaling pathways. Overall, this study demonstrates a pivotal role of TAK1 in DCs in controlling TCE-induced CHS response and suggests that targeting TAK1 function in DCs may be a viable approach to preventing and treating TCE-related occupational health hazards. - Highlights: • Lack of TAK1 in DC caused an abolished TCE-induced CHS response. • TAK1 in DCs was essential to maintain the homeostasis of T cells in TCE-induced CHS. • Intact TAK1 in DCs was critical to promote T-cell priming in TCE-induced CHS. • DC-specific TAK1 deficiency abolished the TCE-mediated phosphorylation of Jnk.

  12. In vivo localization of cloned IL-2-dependent T cells

    International Nuclear Information System (INIS)

    Carroll, A.M.; Palladino, M.A.; Oettgen, H.; De Sousa, M.

    1983-01-01

    The quantitative organ distribution and tissue microenvironment positioning of radioisotopically labeled cloned T cells were characterized. Intravenous (iv) injection of 51chromium ( 51 Cr)-labeled, long-term cultured cloned T-helper cells and cells from several cloned cytolytic T-lymphocyte lines (CTLL) resulted in poor localization of these cells in recipient lymphoid tissues, similar to results reported for activated lymphoblastoid cells. Simultaneous administration of interleukin 2 (IL-2) with labeled cells resulted in enhanced recovery from recipient spleen. By the intraperitoneal (ip) injection route, overall percentage recovery of injected radioactivity was lower than by the iv route, but significant localization to lymph nodes occurred. Examination of autoradiographs of tissue sections from recipients of [ 3 H]adenosine-labeled cells showed most label associated with intact, isolated cells in the liver, lungs, spleen, and small intestine. By 24 hr after iv injection, labeled cells in spleen sections were distributed to both nonlymphoid and T- and B-lymphoid areas. These findings suggest that poor localization of these cells to recipient lymphoid tissue is due both to intrinsic characteristics of cultured lymphocytes and to the possible reduced viability of IL-2-dependent cells in vivo

  13. Contact-mediated and humoral communication between vascular endothelial and smooth muscle cells in vitro

    International Nuclear Information System (INIS)

    Davies, P.F.

    1986-01-01

    Vascular endothelial cells (EC) and smooth muscle cells (SMC) co-exist in close apposition to each other in all blood vessels except capillaries. Investigations of the metabolic interactions that may occur between these cells are essential to an understanding of vascular homeostasis and the pathogenesis of atherosclerosis. The authors have developed two in vitro models of co-temporal vascular cell communication. The first facilitates reversible microcarrier-mediated gap junctional communication between EC and SMC monolayers. When either EC or SMC were prelabelled with 3 H-uridine, intracellular nucleotide rapidly transferred across the region of heterocellular attachment to the complementary cell population. Cytoplasmic continuity between EC and SMC allowed metabolic cooperation via ions and small molecules (<1.5 KD). Thus, vascular reactivity, particularly in the microcirculation where myoendothelial gap junctions have been observed, may involve cytoplasmic second messengers transported from EC to SMC. In the second model, humoral communication was established between separated cultures of EC and SMC which shared the same culture medium. Endothelial-specific stimulation of SMC growth and lipoprotein metabolism via soluble factors was demonstrated. Two mechanisms of stimulation of SMC lipoprotein metabolism were identified; one endothelial derived mitogen-dependent, the other mitogen-independent which was mediated via low molecular weight endothelial cell products

  14. Tunnel oxide passivated rear contact for large area n-type front junction silicon solar cells providing excellent carrier selectivity

    Directory of Open Access Journals (Sweden)

    Yuguo Tao

    2016-01-01

    Full Text Available Carrier-selective contact with low minority carrier recombination and efficient majority carrier transport is mandatory to eliminate metal-induced recombination for higher energy conversion efficiency for silicon (Si solar cells. In the present study, the carrier-selective contact consists of an ultra-thin tunnel oxide and a phosphorus-doped polycrystalline Si (poly-Si thin film formed by plasma enhanced chemical vapor deposition (PECVD and subsequent thermal crystallization. It is shown that the poly-Si film properties (doping level, crystallization and dopant activation anneal temperature are crucial for achieving excellent contact passivation quality. It is also demonstrated quantitatively that the tunnel oxide plays a critical role in this tunnel oxide passivated contact (TOPCON scheme to realize desired carrier selectivity. Presence of tunnel oxide increases the implied Voc (iVoc by ~ 125 mV. The iVoc value as high as 728 mV is achieved on symmetric structure with TOPCON on both sides. Large area (239 cm2 n-type Czochralski (Cz Si solar cells are fabricated with homogeneous implanted boron emitter and screen-printed contact on the front and TOPCON on the back, achieving 21.2% cell efficiency. Detailed analysis shows that the performance of these cells is mainly limited by boron emitter recombination on the front side.

  15. Burnup dependence of coolant void reactivity for ACR-1000 cell

    International Nuclear Information System (INIS)

    Le Tellier, R.; Marleau, G.; Hebert, A.; Roubstov, D.; Altiparmakov, D.; Irish, D.

    2008-01-01

    The Advanced Candu Reactor (ACR-1000) is light water cooled, fueled with enriched uranium and has a smaller lattice pitch than the Candu-6. As a result, the neutronic behavior of the ACR-1000 cell is expected to be somewhat different from that of the Candu-6 leading to a negative coolant void reactivity (CVR). Here we evaluate the CVR for the ACR-1000 cell using the lattice code DRAGON and compare our results with those obtained using the code WIMS-AECL. The differences observed between these two codes for the burnup dependence of the CVR is mainly explained in terms of the specific cell leakage model used by both codes. (authors)

  16. Temperature dependence of photovoltaic cells, modules, and systems

    Energy Technology Data Exchange (ETDEWEB)

    Emery, K.; Burdick, J.; Caiyem, Y. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1996-05-01

    Photovoltaic (PV) cells and modules are often rated in terms of a set of standard reporting conditions defined by a temperature, spectral irradiance, and total irradiance. Because PV devices operates over a wide range of temperatures and irradiances, the temperature and irradiance related behavior must be known. This paper surveys the temperature dependence of crystalline and thin-film, state-of-the-art, research-size cells, modules, and systems measured by a variety of methods. The various error sources and measurement methods that contribute to cause differences in the temperature coefficient for a given cell or module measured with various methods are discussed.

  17. Context-dependent incremental timing cells in the primate hippocampus.

    Science.gov (United States)

    Sakon, John J; Naya, Yuji; Wirth, Sylvia; Suzuki, Wendy A

    2014-12-23

    We examined timing-related signals in primate hippocampal cells as animals performed an object-place (OP) associative learning task. We found hippocampal cells with firing rates that incrementally increased or decreased across the memory delay interval of the task, which we refer to as incremental timing cells (ITCs). Three distinct categories of ITCs were identified. Agnostic ITCs did not distinguish between different trial types. The remaining two categories of cells signaled time and trial context together: One category of cells tracked time depending on the behavioral action required for a correct response (i.e., early vs. late release), whereas the other category of cells tracked time only for those trials cued with a specific OP combination. The context-sensitive ITCs were observed more often during sessions where behavioral learning was observed and exhibited reduced incremental firing on incorrect trials. Thus, single primate hippocampal cells signal information about trial timing, which can be linked with trial type/context in a learning-dependent manner.

  18. The Cell Adhesion Molecule Necl-4/CADM4 Serves as a Novel Regulator for Contact Inhibition of Cell Movement and Proliferation.

    Directory of Open Access Journals (Sweden)

    Shota Yamana

    Full Text Available Contact inhibition of cell movement and proliferation is critical for proper organogenesis and tissue remodeling. We show here a novel regulatory mechanism for this contact inhibition using cultured vascular endothelial cells. When the cells were confluently cultured, Necl-4 was up-regulated and localized at cell-cell contact sites where it cis-interacted with the vascular endothelial growth factor (VEGF receptor. This interaction inhibited the tyrosine-phosphorylation of the VEGF receptor through protein-tyrosine phosphatase, non-receptor type 13 (PTPN13, eventually reducing cell movement and proliferation. When the cells were sparsely cultured, Necl-4 was down-regulated but accumulated at leading edges where it inhibited the activation of Rho-associated protein kinase through PTPN13, eventually facilitating the VEGF-induced activation of Rac1 and enhancing cell movement. Necl-4 further facilitated the activation of extracellular signal-regulated kinase 1/2, eventually enhancing cell proliferation. Thus, Necl-4 serves as a novel regulator for contact inhibition of cell movement and proliferation cooperatively with the VEGF receptor and PTPN13.

  19. Intercellular transfer of P-glycoprotein from the drug resistant human bladder cancer cell line BIU-87 does not require cell-to-cell contact.

    Science.gov (United States)

    Zhou, Hui-liang; Zheng, Yong-jun; Cheng, Xiao-zhi; Lv, Yi-song; Gao, Rui; Mao, Hou-ping; Chen, Qin

    2013-09-01

    The efflux activity of transmembrane P-glycoprotein prevents various therapeutic drugs from reaching lethal concentrations in cancer cells, resulting in multidrug resistance. We investigated whether drug resistant bladder cancer cells could transfer functional P-glycoprotein to sensitive parental cells. Drug sensitive BIU-87 bladder cancer cells were co-cultured for 48 hours with BIU-87/ADM, a doxorubicin resistant derivative of the same cell line, in a Transwell® system that prevented cell-to-cell contact. The presence of P-glycoprotein in recipient cell membranes was established using fluorescein isothiocyanate, laser scanning confocal microscopy and Western blot. P-glycoprotein mRNA levels were compared between cell types. Rhodamine 123 efflux assay was done to confirm that P-glycoprotein was biologically active. The amount of P-glycoprotein protein in BIU-87 cells co-cultured with BIU-87/ADM was significantly higher than in BIU-87 cells (0.44 vs 0.25) and BIU-87/H33342 cells (0.44 vs 0.26, each p transfer. P-glycoprotein mRNA expression was significantly higher in BIU-87/ADM cells than in co-cultured BIU-87 cells (1.28 vs 0.30), BIU-87/H33342 (0.28) and BIU-87 cells (0.25, each p <0.001), ruling out a genetic mechanism. After 30 minutes of efflux, rhodamine 123 fluorescence intensity was significantly lower in BIU-87/ADM cells (5.55 vs 51.45, p = 0.004) and co-cultured BIU-87 cells than in BIU-87 cells (14.22 vs 51.45, p <0.001), indicating that P-glycoprotein was functional. Bladder cancer cells can acquire functional P-glycoprotein through a nongenetic mechanism that does not require direct cell contact. This mechanism is consistent with a microparticle mediated process. Copyright © 2013 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

  20. Staying Tight: Plasmodesmal Membrane Contact Sites and the Control of Cell-to-Cell Connectivity in Plants.

    Science.gov (United States)

    Tilsner, Jens; Nicolas, William; Rosado, Abel; Bayer, Emmanuelle M

    2016-04-29

    Multicellularity differs in plants and animals in that the cytoplasm, plasma membrane, and endomembrane of plants are connected between cells through plasmodesmal pores. Plasmodesmata (PDs) are essential for plant life and serve as conduits for the transport of proteins, small RNAs, hormones, and metabolites during developmental and defense signaling. They are also the only pathways available for viruses to spread within plant hosts. The membrane organization of PDs is unique, characterized by the close apposition of the endoplasmic reticulum and the plasma membrane and spoke-like filamentous structures linking the two membranes, which define PDs as membrane contact sites (MCSs). This specialized membrane arrangement is likely critical for PD function. Here, we review how PDs govern developmental and defensive signaling in plants, compare them with other types of MCSs, and discuss in detail the potential functional significance of the MCS nature of PDs.

  1. Perovskite/silicon-based heterojunction tandem solar cells with 14.8% conversion efficiency via adopting ultrathin Au contact

    Science.gov (United States)

    Fan, Lin; Wang, Fengyou; Liang, Junhui; Yao, Xin; Fang, Jia; Zhang, Dekun; Wei, Changchun; Zhao, Ying; Zhang, Xiaodan

    2017-01-01

    A rising candidate for upgrading the performance of an established narrow-bandgap solar technology without adding much cost is to construct the tandem solar cells from a crystalline silicon bottom cell and a high open-circuit voltage top cell. Here, we present a four-terminal tandem solar cell architecture consisting of a self-filtered planar architecture perovskite top cell and a silicon heterojunction bottom cell. A transparent ultrathin gold electrode has been used in perovskite solar cells to achieve a semi-transparent device. The transparent ultrathin gold contact could provide a better electrical conductivity and optical reflectance-scattering to maintain the performance of the top cell compared with the traditional metal oxide contact. The four-terminal tandem solar cell yields an efficiency of 14.8%, with contributions of the top (8.98%) and the bottom cell (5.82%), respectively. We also point out that in terms of optical losses, the intermediate contact of self-filtered tandem architecture is the uppermost problem, which has been addressed in this communication, and the results show that reducing the parasitic light absorption and improving the long wavelength range transmittance without scarifying the electrical properties of the intermediate hole contact layer are the key issues towards further improving the efficiency of this architecture device. Project supported by the International Cooperation Projects of the Ministry of Science and Technology (No. 2014DFE60170), the National Natural Science Foundation of China (Nos. 61474065, 61674084), the Tianjin Research Key Program of Application Foundation and Advanced Technology (No. 15JCZDJC31300), the Key Project in the Science & Technology Pillar Program of Jiangsu Province (No. BE2014147-3), and the 111 Project (No. B16027).

  2. Cell adhesion-mediated radioresistance (CAM-RR). Extracellular matrix-dependent improvement of cell survival in human tumor and normal cells in vitro

    International Nuclear Information System (INIS)

    Cordes, N.; Meineke, V.

    2003-01-01

    Background: Cell-extracellular matrix (ECM) contact is thought to have great impact on cellular mechanisms resulting in increased cell survival upon exposure to ionizing radiation. Several human tumor cell lines and normal human fibroblastic cell strains of different origin, all of them expressing the wide-spread and important integrin subunit β1, were irradiated, and clonogenic cell survival, β1-integrin cell surface expression, and adhesive functionality were investigated. Material and Methods: Human tumor cell lines A172 (glioblastoma), PATU8902 (pancreas carcinoma), SKMES1 (lung carcinoma), A549 (lung carcinoma), and IPC298 (melanoma) as well as normal human skin (HSF1) and lung fibroblasts (CCD32) and human keratinocytes (HaCaT) were irradiated with 0-8 Gy. Besides colony formation assays, β1-integrin cell surface expression by flow cytometry and adhesive functionality by adhesion assays were analyzed. Results: All cell lines showed improved clonogenic survival after irradiation in the presence of fibronectin as compared to plastic. Irradiated cells exhibited a significant, dose-dependent increase in β1-integrin cell surface expression following irradiation. As a parameter of the adhesive functionality of the β1-integrin, a radiation-dependent elevation of cell adhesion to fibronectin in comparison with adhesion to plastic was demonstrated. Conclusion: The in vitro cellular radiosensitivity is highly influenced by fibronectin according to the phenomenon of cell adhesion-mediated radioresistance. Additionally, our emerging data question the results of former and current in vitro cytotoxicity studies performed in the absence of an ECM. These findings might also be important for the understanding of malignant transformation, anchorage-independent cell growth, optimization of radiotherapeutic regimes and the prevention of normal tissue side effects on the basis of experimental radiobiological data. (orig.)

  3. A Comparative Study of the Expression of Cytotoxic Proteins in Allergic Contact Dermatitis and Psoriasis : Spongiotic Skin Lesions in Allergic Contact Dermatitis Are Highly Infiltrated by T Cells Expressing Perforin and Granzyme B

    OpenAIRE

    Yawalkar, Nikhil; Hunger, Robert E.; Buri, Caroline; Schmid, Simone; Egli, Fabienne; Brand, Christoph U.; Mueller, Christoph; Pichler, Werner J.; Braathen, Lasse R.

    2001-01-01

    Recent reports indicate that cytotoxic T cells are critically involved in contact hypersensitivity reactions in animals. In this study we sought to investigate the in vivo expression of cytotoxic granule proteins in the elicitation phase of allergic contact dermatitis in humans. Skin biopsy specimens were obtained from patients with allergic contact dermatitis (n = 8) and psoriasis (n = 6) and from controls with normal skin (n = 6). Expression of perforin and granzyme B was investigated by in...

  4. Mobilization of HIV Spread by Diaphanous 2 Dependent Filopodia in Infected Dendritic Cells

    Science.gov (United States)

    Aggarwal, Anupriya; Iemma, Tina L.; Shih, Ivy; Newsome, Timothy P.; McAllery, Samantha; Cunningham, Anthony L.; Turville, Stuart G.

    2012-01-01

    Paramount to the success of persistent viral infection is the ability of viruses to navigate hostile environments en route to future targets. In response to such obstacles, many viruses have developed the ability of establishing actin rich-membrane bridges to aid in future infections. Herein through dynamic imaging of HIV infected dendritic cells, we have observed how viral high-jacking of the actin/membrane network facilitates one of the most efficient forms of HIV spread. Within infected DC, viral egress is coupled to viral filopodia formation, with more than 90% of filopodia bearing immature HIV on their tips at extensions of 10 to 20 µm. Live imaging showed HIV filopodia routinely pivoting at their base, and projecting HIV virions at µm.sec−1 along repetitive arc trajectories. HIV filopodial dynamics lead to up to 800 DC to CD4 T cell contacts per hour, with selection of T cells culminating in multiple filopodia tethering and converging to envelope the CD4 T-cell membrane with budding HIV particles. Long viral filopodial formation was dependent on the formin diaphanous 2 (Diaph2), and not a dominant Arp2/3 filopodial pathway often associated with pathogenic actin polymerization. Manipulation of HIV Nef reduced HIV transfer 25-fold by reducing viral filopodia frequency, supporting the potency of DC HIV transfer was dependent on viral filopodia abundance. Thus our observations show HIV corrupts DC to CD4 T cell interactions by physically embedding at the leading edge contacts of long DC filopodial networks. PMID:22685410

  5. Mobilization of HIV spread by diaphanous 2 dependent filopodia in infected dendritic cells.

    Directory of Open Access Journals (Sweden)

    Anupriya Aggarwal

    Full Text Available Paramount to the success of persistent viral infection is the ability of viruses to navigate hostile environments en route to future targets. In response to such obstacles, many viruses have developed the ability of establishing actin rich-membrane bridges to aid in future infections. Herein through dynamic imaging of HIV infected dendritic cells, we have observed how viral high-jacking of the actin/membrane network facilitates one of the most efficient forms of HIV spread. Within infected DC, viral egress is coupled to viral filopodia formation, with more than 90% of filopodia bearing immature HIV on their tips at extensions of 10 to 20 µm. Live imaging showed HIV filopodia routinely pivoting at their base, and projecting HIV virions at µm.sec⁻¹ along repetitive arc trajectories. HIV filopodial dynamics lead to up to 800 DC to CD4 T cell contacts per hour, with selection of T cells culminating in multiple filopodia tethering and converging to envelope the CD4 T-cell membrane with budding HIV particles. Long viral filopodial formation was dependent on the formin diaphanous 2 (Diaph2, and not a dominant Arp2/3 filopodial pathway often associated with pathogenic actin polymerization. Manipulation of HIV Nef reduced HIV transfer 25-fold by reducing viral filopodia frequency, supporting the potency of DC HIV transfer was dependent on viral filopodia abundance. Thus our observations show HIV corrupts DC to CD4 T cell interactions by physically embedding at the leading edge contacts of long DC filopodial networks.

  6. Influence of the contacting scheme in simulations of radial silicon nanorod solar cells

    International Nuclear Information System (INIS)

    Voigt, Felix; Stelzner, Thomas; Christiansen, Silke H.

    2012-01-01

    Silicon nanorod solar cells were simulated using the Silvaco Technical Computer Aided Design (TCAD) software suite. For reasons of speed optimization the simulations were performed in cylinder coordinates taking advantage of the model's symmetry. Symmetric doping was assumed with a dopant density of 10 18 cm −3 in the p-type core and in the n-type shell, and the location of the pn-junction was chosen such that the space charge region was located adjacent to the shell surface. Two contact configurations were explored. In configuration A the cathode contact was wrapped around the semiconductor nanorod, while in configuration B the cathode was assumed just on top of the nanorod. In both cases the anode was located at the bottom of the rod. Cell efficiency was optimized with regard to rod radius and rod length. Optimization was performed in a three-step procedure consisting in radius optimization, length optimization and again radius optimization. A maximum in efficiency with respect to rod length L was visible in configuration A, leading to an optimum value of L = 48 μm. This maximum is explained by the combination of an increase of short-circuit current density J sc and a decrease of open-circuit voltage U oc with L. In configuration B, J sc also increases with L, but U oc stays rather constant and the maximum in efficiency only appears at very large values of L ≈ 12 mm. We restricted the rod length to L ≤ 100 μm for further optimization, in order to stay in an experimentally feasible range. During the optimization of rod radius R in configuration A the open circuit voltage increased continuously, while short circuit current density stayed rather constant. This leads to an increase in efficiency with R, which only stops at very large radii, where R starts to be comparable with L. In configuration B efficiency is almost independent of R, provided that the radius is large enough to comprise a well-formed space charge region, here only a shallow maximum can be

  7. Influence of the contacting scheme in simulations of radial silicon nanorod solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Voigt, Felix, E-mail: felix.voigt@uni-oldenburg.de [Institute of Photonic Technology, Jena (Germany); Institute of Physics, University of Oldenburg (Germany); Stelzner, Thomas [Institute of Photonic Technology, Jena (Germany); Christiansen, Silke H. [Institute of Photonic Technology, Jena (Germany); Max Planck Institute for the Science of Light, Erlangen (Germany)

    2012-10-01

    Silicon nanorod solar cells were simulated using the Silvaco Technical Computer Aided Design (TCAD) software suite. For reasons of speed optimization the simulations were performed in cylinder coordinates taking advantage of the model's symmetry. Symmetric doping was assumed with a dopant density of 10{sup 18} cm{sup -3} in the p-type core and in the n-type shell, and the location of the pn-junction was chosen such that the space charge region was located adjacent to the shell surface. Two contact configurations were explored. In configuration A the cathode contact was wrapped around the semiconductor nanorod, while in configuration B the cathode was assumed just on top of the nanorod. In both cases the anode was located at the bottom of the rod. Cell efficiency was optimized with regard to rod radius and rod length. Optimization was performed in a three-step procedure consisting in radius optimization, length optimization and again radius optimization. A maximum in efficiency with respect to rod length L was visible in configuration A, leading to an optimum value of L = 48 {mu}m. This maximum is explained by the combination of an increase of short-circuit current density J{sub sc} and a decrease of open-circuit voltage U{sub oc} with L. In configuration B, J{sub sc} also increases with L, but U{sub oc} stays rather constant and the maximum in efficiency only appears at very large values of L Almost-Equal-To 12 mm. We restricted the rod length to L {<=} 100 {mu}m for further optimization, in order to stay in an experimentally feasible range. During the optimization of rod radius R in configuration A the open circuit voltage increased continuously, while short circuit current density stayed rather constant. This leads to an increase in efficiency with R, which only stops at very large radii, where R starts to be comparable with L. In configuration B efficiency is almost independent of R, provided that the radius is large enough to comprise a well-formed space

  8. AM fungal exudates activate MAP kinases in plant cells in dependence from cytosolic Ca(2+) increase.

    Science.gov (United States)

    Francia, Doriana; Chiltz, Annick; Lo Schiavo, Fiorella; Pugin, Alain; Bonfante, Paola; Cardinale, Francesca

    2011-09-01

    The molecular dialogue occurring prior to direct contact between the fungal and plant partners of arbuscular-mycorrhizal (AM) symbioses begins with the release of fungal elicitors, so far only partially identified chemically, which can activate specific signaling pathways in the host plant. We show here that the activation of MAPK is also induced by exudates of germinating spores of Gigaspora margarita in cultured cells of the non-leguminous species tobacco (Nicotiana tabacum), as well as in those of the model legume Lotus japonicus. MAPK activity peaked about 15 min after the exposure of the host cells to the fungal exudates (FE). FE were also responsible for a rapid and transient increase in free cytosolic Ca(2+) in Nicotiana plumbaginifolia and tobacco cells, and pre-treatment with a Ca(2+)-channel blocker (La(3+)) showed that in these cells, MAPK activation was dependent on the cytosolic Ca(2+) increase. A partial dependence of MAPK activity on the common Sym pathway could be demonstrated for a cell line of L. japonicus defective for LjSym4 and hence unable to establish an AM symbiosis. Our results show that MAPK activation is triggered by an FE-induced cytosolic Ca(2+) transient, and that a Sym genetic determinant acts to modulate the intensity and duration of this activity. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  9. CD1d knockout mice exhibit aggravated contact hypersensitivity responses due to reduced interleukin-10 production predominantly by regulatory B cells

    DEFF Research Database (Denmark)

    Fjelbye, Jonas; Antvorskov, Julie C; Buschard, Karsten

    2015-01-01

    .05) and peritoneal cavity (80.8% decrease; P challenge, which suggests an important regulatory and protective role of CD1d-dependent NKT cells in CHS in our model, at least in part via regulation of IL-10 producing B(regs) ....... knockout (CD1d KO) and wild-type (Wt) mice after contact allergen exposure. For induction of CHS, C57BL/6 CD1d KO mice (n = 6) and C57BL/6 Wt mice (n = 6) were sensitised with 1% (w/v) dinitrochlorobenzene (DNCB) or vehicle for three consecutive days and subsequently challenged with a single dose of 0...

  10. Localized cyclic AMP-dependent protein kinase activity is required for myogenic cell fusion

    International Nuclear Information System (INIS)

    Mukai, Atsushi; Hashimoto, Naohiro

    2008-01-01

    Multinucleated myotubes are formed by fusion of mononucleated myogenic progenitor cells (myoblasts) during terminal skeletal muscle differentiation. In addition, myoblasts fuse with myotubes, but terminally differentiated myotubes have not been shown to fuse with each other. We show here that an adenylate cyclase activator, forskolin, and other reagents that elevate intracellular cyclic AMP (cAMP) levels induced cell fusion between small bipolar myotubes in vitro. Then an extra-large myotube, designated a 'myosheet,' was produced by both primary and established mouse myogenic cells. Myotube-to-myotube fusion always occurred between the leading edge of lamellipodia at the polar end of one myotube and the lateral plasma membrane of the other. Forskolin enhanced the formation of lamellipodia where cAMP-dependent protein kinase (PKA) was accumulated. Blocking enzymatic activity or anchoring of PKA suppressed forskolin-enhanced lamellipodium formation and prevented fusion of multinucleated myotubes. Localized PKA activity was also required for fusion of mononucleated myoblasts. The present results suggest that localized PKA plays a pivotal role in the early steps of myogenic cell fusion, such as cell-to-cell contact/recognition through lamellipodium formation. Furthermore, the localized cAMP-PKA pathway might be involved in the specification of the fusion-competent areas of the plasma membrane in lamellipodia of myogenic cells

  11. Clonogenic growth of human breast cancer cells co-cultured in direct contact with serum-activated fibroblasts

    International Nuclear Information System (INIS)

    Samoszuk, Michael; Tan, Jenny; Chorn, Guillaume

    2005-01-01

    Accumulating evidence suggests that fibroblasts play a pivotal role in promoting the growth of breast cancer cells. The objective of the present study was to characterize and validate an in vitro model of the interaction between small numbers of human breast cancer cells and human fibroblasts. We measured the clonogenic growth of small numbers of human breast cancer cells co-cultured in direct contact with serum-activated, normal human fibroblasts. Using DNA microarrays, we also characterized the gene expression profile of the serum-activated fibroblasts. In order to validate the in vivo relevance of our experiments, we then analyzed clinical samples of metastatic breast cancer for the presence of myofibroblasts expressing α-smooth muscle actin. Clonogenic growth of human breast cancer cells obtained directly from in situ and invasive tumors was dramatically and consistently enhanced when the tumor cells were co-cultured in direct contact with serum-activated fibroblasts. This effect was abolished when the cells were co-cultured in transwells separated by permeable inserts. The fibroblasts in our experimental model exhibited a gene expression signature characteristic of 'serum response' (i.e. myofibroblasts). Immunostaining of human samples of metastatic breast cancer tissue confirmed that myofibroblasts are in direct contact with breast cancer cells. Serum-activated fibroblasts promote the clonogenic growth of human breast cancer cells in vitro through a mechanism that involves direct physical contact between the cells. This model shares many important molecular and phenotypic similarities with the fibroblasts that are naturally found in breast cancers

  12. Impact of built-in fields and contact configuration on the characteristics of ultra-thin GaAs solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Aeberhard, Urs, E-mail: u.aeberhard@fz-juelich.de [IEK-5 Photovoltaik, Forschungszentrum Jülich, D-52425 Jülich (Germany)

    2016-07-18

    We discuss the effects of built-in fields and contact configuration on the photovoltaic characteristics of ultra-thin GaAs solar cells. The investigation is based on advanced quantum-kinetic simulations reaching beyond the standard semi-classical bulk picture concerning the consideration of charge carrier states and dynamics in complex potential profiles. The thickness dependence of dark and photocurrent in the ultra-scaled regime is related to the corresponding variation of both, the built-in electric fields and associated modification of the density of states, and the optical intensity in the films. Losses in open-circuit voltage and short-circuit current due to the leakage of electronically and optically injected carriers at minority carrier contacts are investigated for different contact configurations including electron and hole blocking barrier layers. The microscopic picture of leakage currents is connected to the effect of finite surface recombination velocities in the semi-classical description, and the impact of these non-classical contact regions on carrier generation and extraction is analyzed.

  13. Ultraviolet laser ablation of fluorine-doped tin oxide thin films for dye-sensitized back-contact solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Huan [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, 430074 (China); Fu, Dongchuan [ARC Centre of Excellence for Electromaterials Science, Department of Materials Engineering and School of Chemistry, Monash University, Clayton Victoria, 3800 (Australia); Jiang, Ming [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, 430074 (China); Duan, Jun, E-mail: duans@hust.edu.cn [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, 430074 (China); Zhang, Fei; Zeng, Xiaoyan [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, Hubei, 430074 (China); Bach, Udo [ARC Centre of Excellence for Electromaterials Science, Department of Materials Engineering and School of Chemistry, Monash University, Clayton Victoria, 3800 (Australia)

    2013-03-01

    In this study, laser ablation of a fluorine-doped tin oxide (FTO) thin film on a glass substrate was conducted using a 355 nm Nd:YVO{sub 4} ultraviolet (UV) laser to obtain a 4 × 4 mm microstructure. The microstructure contains a symmetric set of interdigitated FTO finger electrodes of a monolithic back-contact dye-sensitized solar cell (BC-DSC) on a common substrate. The effects of UV laser ablation parameters (such as laser fluence, repetition frequency, and scanning speed) on the size precision and quality of the microstructure were investigated using a 4 × 4 orthogonal design and an assistant experimental design. The incident photon-to-electron conversion efficiency and the current–voltage characteristics of the BC-DSC base of the interdigitated FTO finger electrodes were also determined. The experimental results show that an FTO film microstructure with high precision and good quality can be produced on a glass substrate via laser ablation with high scanning speed, high repetition frequency, and appropriate laser fluence. - Highlights: ► The ablation width and depth generally depend on the laser fluence. ► The scanning speed and the repetition frequency must match each other. ► Slight ablation of the glass substrate can completely remove F-doped tin oxide.

  14. A multiwell platform for studying stiffness-dependent cell biology.

    Science.gov (United States)

    Mih, Justin D; Sharif, Asma S; Liu, Fei; Marinkovic, Aleksandar; Symer, Matthew M; Tschumperlin, Daniel J

    2011-01-01

    Adherent cells are typically cultured on rigid substrates that are orders of magnitude stiffer than their tissue of origin. Here, we describe a method to rapidly fabricate 96 and 384 well platforms for routine screening of cells in tissue-relevant stiffness contexts. Briefly, polyacrylamide (PA) hydrogels are cast in glass-bottom plates, functionalized with collagen, and sterilized for cell culture. The Young's modulus of each substrate can be specified from 0.3 to 55 kPa, with collagen surface density held constant over the stiffness range. Using automated fluorescence microscopy, we captured the morphological variations of 7 cell types cultured across a physiological range of stiffness within a 384 well plate. We performed assays of cell number, proliferation, and apoptosis in 96 wells and resolved distinct profiles of cell growth as a function of stiffness among primary and immortalized cell lines. We found that the stiffness-dependent growth of normal human lung fibroblasts is largely invariant with collagen density, and that differences in their accumulation are amplified by increasing serum concentration. Further, we performed a screen of 18 bioactive small molecules and identified compounds with enhanced or reduced effects on soft versus rigid substrates, including blebbistatin, which abolished the suppression of lung fibroblast growth at 1 kPa. The ability to deploy PA gels in multiwell plates for high throughput analysis of cells in tissue-relevant environments opens new opportunities for the discovery of cellular responses that operate in specific stiffness regimes.

  15. A multiwell platform for studying stiffness-dependent cell biology.

    Directory of Open Access Journals (Sweden)

    Justin D Mih

    Full Text Available Adherent cells are typically cultured on rigid substrates that are orders of magnitude stiffer than their tissue of origin. Here, we describe a method to rapidly fabricate 96 and 384 well platforms for routine screening of cells in tissue-relevant stiffness contexts. Briefly, polyacrylamide (PA hydrogels are cast in glass-bottom plates, functionalized with collagen, and sterilized for cell culture. The Young's modulus of each substrate can be specified from 0.3 to 55 kPa, with collagen surface density held constant over the stiffness range. Using automated fluorescence microscopy, we captured the morphological variations of 7 cell types cultured across a physiological range of stiffness within a 384 well plate. We performed assays of cell number, proliferation, and apoptosis in 96 wells and resolved distinct profiles of cell growth as a function of stiffness among primary and immortalized cell lines. We found that the stiffness-dependent growth of normal human lung fibroblasts is largely invariant with collagen density, and that differences in their accumulation are amplified by increasing serum concentration. Further, we performed a screen of 18 bioactive small molecules and identified compounds with enhanced or reduced effects on soft versus rigid substrates, including blebbistatin, which abolished the suppression of lung fibroblast growth at 1 kPa. The ability to deploy PA gels in multiwell plates for high throughput analysis of cells in tissue-relevant environments opens new opportunities for the discovery of cellular responses that operate in specific stiffness regimes.

  16. Stochastic cellular automata model of neurosphere growth: Roles of proliferative potential, contact inhibition, cell death, and phagocytosis.

    Science.gov (United States)

    Sipahi, Rifat; Zupanc, Günther K H

    2018-05-14

    Neural stem and progenitor cells isolated from the central nervous system form, under specific culture conditions, clonal cell clusters known as neurospheres. The neurosphere assay has proven to be a powerful in vitro system to study the behavior of such cells and the development of their progeny. However, the theory of neurosphere growth has remained poorly understood. To overcome this limitation, we have, in the present paper, developed a cellular automata model, with which we examined the effects of proliferative potential, contact inhibition, cell death, and clearance of dead cells on growth rate, final size, and composition of neurospheres. Simulations based on this model indicated that the proliferative potential of the founder cell and its progenitors has a major influence on neurosphere size. On the other hand, contact inhibition of proliferation limits the final size, and reduces the growth rate, of neurospheres. The effect of this inhibition is particularly dramatic when a stem cell becomes encapsulated by differentiated or other non-proliferating cells, thereby suppressing any further mitotic division - despite the existing proliferative potential of the stem cell. Conversely, clearance of dead cells through phagocytosis is predicted to accelerate growth by reducing contact inhibition. A surprising prediction derived from our model is that cell death, while resulting in a decrease in growth rate and final size of neurospheres, increases the degree of differentiation of neurosphere cells. It is likely that the cellular automata model developed as part of the present investigation is applicable to the study of tissue growth in a wide range of systems. Copyright © 2018 Elsevier Ltd. All rights reserved.

  17. Electron-selective contacts via ultra-thin organic interface dipoles for silicon organic heterojunction solar cells

    Science.gov (United States)

    Reichel, Christian; Würfel, Uli; Winkler, Kristina; Schleiermacher, Hans-Frieder; Kohlstädt, Markus; Unmüssig, Moritz; Messmer, Christoph A.; Hermle, Martin; Glunz, Stefan W.

    2018-01-01

    In the last years, novel materials for the formation of electron-selective contacts on n-type crystalline silicon (c-Si) heterojunction solar cells were explored as an interfacial layer between the metal electrode and the c-Si wafer. Besides inorganic materials like transition metal oxides or alkali metal fluorides, also interfacial layers based on organic molecules with a permanent dipole moment are promising candidates to improve the contact properties. Here, the dipole effect plays an essential role in the modification of the interface and effective work function of the contact. The amino acids L-histidine, L-tryptophan, L-phenylalanine, glycine, and sarcosine, the nucleobase adenine, and the heterocycle 4-hydroxypyridine were investigated as dipole materials for an electron-selective contact on the back of p- and n-type c-Si with a metal electrode based on aluminum (Al). Furthermore, the effect of an added fluorosurfactant on the resulting contact properties was examined. The performance of n-type c-Si solar cells with a boron diffusion on the front was significantly increased when L-histidine and/or the fluorosurfactant was applied as a full-area back surface field. This improvement was attributed to the modification of the interface and the effective work function of the contact by the dipole material which was corroborated by numerical device simulations. For these solar cells, conversion efficiencies of 17.5% were obtained with open-circuit voltages (Voc) of 625 mV and fill factors of 76.3%, showing the potential of organic interface dipoles for silicon organic heterojunction solar cells due to their simple formation by solution processing and their low thermal budget requirements.

  18. Temperature dependence of annealing on the contact resistance of MoS2 with graphene electrodes observed

    Science.gov (United States)

    Lu, Qin; Fang, Cizhe; Liu, Yan; Shao, Yao; Han, Genquan; Zhang, Jincheng; Hao, Yue

    2018-04-01

    Two-dimensional (2D) materials are promising candidates for atomically thin nanoelectronics. Among them, MoS2 has attracted considerable attention in the nanoscience and nanotechnology community owing to its unique characteristics including high electron mobility and intrinsic band gap. In this study, we experimentally explored the contact resistances of MoS2 films based on much layered graphene films as electrodes using the circular transmission line model (CTLM). The variation in the chemical composition of the material is thoroughly analyzed by Raman and X-ray photoelectric spectroscopy (XPS) measurements. Experimental results demonstrate that annealing followed by oxygen plasma treatment can effectively improve the contact resistance. Furthermore, the current-voltage curves measured after different annealing temperatures indicate good linear characteristics, which means a marked improvement in electrical property. Calculations show that a relatively low contact resistance of ˜4.177 kΩ (ignoring its size) without back gate voltage in a single-layer graphene/MoS2 structure at an optimal annealing temperature of 500 °C is achieved. This work about the effect of annealing temperature on contact resistance can also be employed for other 2D materials, which lays a foundation for further development of novel 2D material devices.

  19. Extracellular adenosine controls NKT-cell-dependent hepatitis induction.

    Science.gov (United States)

    Subramanian, Meenakshi; Kini, Radhika; Madasu, Manasa; Ohta, Akiko; Nowak, Michael; Exley, Mark; Sitkovsky, Michail; Ohta, Akio

    2014-04-01

    Extracellular adenosine regulates inflammatory responses via the A2A adenosine receptor (A2AR). A2AR deficiency results in much exaggerated acute hepatitis, indicating nonredundancy of adenosine-A2AR pathway in inhibiting immune activation. To identify a critical target of immunoregulatory effect of extracellular adenosine, we focused on NKT cells, which play an indispensable role in hepatitis. An A2AR agonist abolished NKT-cell-dependent induction of acute hepatitis by concanavalin A (Con A) or α-galactosylceramide in mice, corresponding to downregulation of activation markers and cytokines in NKT cells and of NK-cell co-activation. These results show that A2AR signaling can downregulate NKT-cell activation and suppress NKT-cell-triggered inflammatory responses. Next, we hypothesized that NKT cells might be under physiological control of the adenosine-A2AR pathway. Indeed, both Con A and α-galactosylceramide induced more severe hepatitis in A2AR-deficient mice than in WT controls. Transfer of A2AR-deficient NKT cells into A2AR-expressing recipients resulted in exaggeration of Con A-induced liver damage, suggesting that NKT-cell activation is controlled by endogenous adenosine via A2AR, and this physiological regulatory mechanism of NKT cells is critical in the control of tissue-damaging inflammation. The current study suggests the possibility to manipulate NKT-cell activity in inflammatory disorders through intervention to the adenosine-A2AR pathway. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Sex-Dependent Gene Expression in Human Pluripotent Stem Cells

    Directory of Open Access Journals (Sweden)

    Daniel Ronen

    2014-08-01

    Full Text Available Males and females have a variety of sexually dimorphic traits, most of which result from hormonal differences. However, differences between male and female embryos initiate very early in development, before hormonal influence begins, suggesting the presence of genetically driven sexual dimorphisms. By comparing the gene expression profiles of male and X-inactivated female human pluripotent stem cells, we detected Y-chromosome-driven effects. We discovered that the sex-determining gene SRY is expressed in human male pluripotent stem cells and is induced by reprogramming. In addition, we detected more than 200 differentially expressed autosomal genes in male and female embryonic stem cells. Some of these genes are involved in steroid metabolism pathways and lead to sex-dependent differentiation in response to the estrogen precursor estrone. Thus, we propose that the presence of the Y chromosome and specifically SRY may drive sex-specific differences in the growth and differentiation of pluripotent stem cells.

  1. Blistering in ALD Al2O3 passivation layers as rear contacting for local Al BSF Si solar cells

    NARCIS (Netherlands)

    Vermang, B.; Goverde, J.C.; Uruena, A.; Lorenz, A.; Cornagliotti, E.; Rothschild, A.; John, J.; Poortmans, J.; Mertens, R.

    2012-01-01

    Random Al back surface field (BSF) p-type Si solar cells are presented, where a stack of Al2O3 and SiNx is used as rear surface passivation layer containing blisters. It is shown that no additional contact opening step is needed, since during co-firing local Al BSFs are induced at the location of

  2. ITO-free inverted polymer/fullerene solar cells: Interface effects and comparison of different semi-transparent front contacts

    NARCIS (Netherlands)

    Wilken, Sebastian; Hoffmann, Thomas; von Hauff, Elizabeth; Borchert, Holger; Parisi, Juergen

    Polymer/fullerene solar cells with an inverted layer sequence and free from indium tin oxide (ITO) are presented in this study. We concentrate on critical interface effects in inverted devices and compare different semi-transparent front contacts, such as ultra-thin Au films and Au grid structures.

  3. Charge-carrier selective electrodes for organic bulk heterojunction solar cell by contact-printed siloxane oligomers

    International Nuclear Information System (INIS)

    Hwang, Hyun-Sik; Khang, Dahl-Young

    2015-01-01

    ‘Smart’ (or selective) electrode for charge carriers, both electrons and holes, in organic bulk-heterojunction (BHJ) solar cells using insertion layers made of hydrophobically-recovered and contact-printed siloxane oligomers between electrodes and active material has been demonstrated. The siloxane oligomer insertion layer has been formed at a given interface simply by conformally-contacting a cured slab of polydimethylsiloxane stamp for less than 100 s. All the devices, either siloxane oligomer printed at one interface only or printed at both interfaces, showed efficiency enhancement when compared to non-printed ones. The possible mechanism that is responsible for the observed efficiency enhancement has been discussed based on the point of optimum symmetry and photocurrent analysis. Besides its simplicity and large-area applicability, the demonstrated contact-printing technique does not involve any vacuum or wet processing steps and thus can be very useful for the roll-based, continuous production scheme for organic BHJ solar cells. - Highlights: • Carrier-selective insertion layer in organic bulk heterojunction solar cells • Simple contact-printing of siloxane oligomers improves cell efficiency. • Printed siloxane layer reduces carrier recombination at electrode surfaces. • Siloxane insertion layer works equally well at both electrode surfaces. • Patterned PDMS stamp shortens the printing time within 100 s

  4. Optical Design of Textured Thin-Film CIGS Solar Cells with Nearly-Invisible Nanowire Assisted Front Contacts

    NARCIS (Netherlands)

    Deelen, J. van; Omar, A.; Barink, M.

    2017-01-01

    The conductivity of transparent front contacts can be improved by patterned metallic nanowires, albeit at the cost of optical loss. The associated optical penalty can be strongly reduced by texturization of the cell stack. Remarkably, the nanowires themselves are not textured and not covered in our

  5. Al and Cu Implantation into Silicon Substrate for Ohmic Contact in Solar Cell Fabrication

    International Nuclear Information System (INIS)

    Sri Sulamdari; Sudjatmoko; Wirjoadi; Yunanto; Bambang Siswanto

    2002-01-01

    Research on the implantation of Al and Cu ions into silicon substrate for ohmic contact in solar cell fabrication has been carried using ion accelerator machine. Al and Cu ions are from 98% Al and 99.9% Cu powder ionized in ion source system. provided in ion implantor machine. Before implantation process, (0.5 x 1) cm 2 N type and P type silicon were washed in water and then etched in Cp-4A solution. After that, P type silicon were implanted with Al ions and N type silicon were implanted with Cu ions with the ions dose from 10 13 ion/cm 2 - 10 16 ion/cm 2 and energy 20 keV - 80 keV. Implanted samples were then annealed at temperature 400 o C - 850 o C. Implanted and annealed samples were characterized their resistivities using four point probe FPP-5000. It was found that at full electrically active conditions the ρ s for N type was 1.30 x 10 8 Ω/sq, this was achieved at ion dose 10 13 ion/cm 2 and annealing temperature 500 o C. While for P type, the ρ s was 1.13 x 10 2 Ω/sq, this was achieved at ion dose 10 13 ion/cm 2 and energy 40 keV, and annealing temperature 500 o C. (author)

  6. Resonant tunneling diodes as energy-selective contacts used in hot-carrier solar cells

    International Nuclear Information System (INIS)

    Takeda, Yasuhiko; Sugimoto, Noriaki; Ichiki, Akihisa; Kusano, Yuya; Motohiro, Tomoyoshi

    2015-01-01

    Among the four features unique to hot-carrier solar cells (HC-SCs): (i) carrier thermalization time and (ii) carrier equilibration time in the absorber, (iii) energy-selection width and (iv) conductance of the energy-selective contacts (ESCs), requisites of (i)-(iii) for high conversion efficiency have been clarified. We have tackled the remaining issues related to (iv) in the present study. The detailed balance model of HC-SC operation has been improved to involve a finite value of the ESC conductance to find the required values, which in turn has been revealed to be feasible using resonant tunneling diodes (RTDs) consisting of semiconductor quantum dots (QDs) and quantum wells (QWs) by means of a formulation to calculate the conductance of the QD- and QW-RTDs derived using the rigorous solutions of the effective-mass Hamiltonians. Thus, all of the four requisites unique to HC-SCs to achieve high conversion efficiency have been elucidated, and the two requisites related to the ESCs can be fulfilled using the QD- and QW-RTDs

  7. Resonant tunneling diodes as energy-selective contacts used in hot-carrier solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Yasuhiko, E-mail: takeda@mosk.tytlabs.co.jp; Sugimoto, Noriaki [Toyota Central Research and Development Laboratories, Inc., 41-1, Yokomichi, Nagakute, Aichi 480-1192 (Japan); Ichiki, Akihisa [Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Kusano, Yuya [Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Toyota Motor Corp., 1200 Mishuku, Susono, Shizuoka 410-1193 (Japan); Motohiro, Tomoyoshi [Toyota Central Research and Development Laboratories, Inc., 41-1, Yokomichi, Nagakute, Aichi 480-1192 (Japan); Green Mobility Collaborative Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan)

    2015-09-28

    Among the four features unique to hot-carrier solar cells (HC-SCs): (i) carrier thermalization time and (ii) carrier equilibration time in the absorber, (iii) energy-selection width and (iv) conductance of the energy-selective contacts (ESCs), requisites of (i)-(iii) for high conversion efficiency have been clarified. We have tackled the remaining issues related to (iv) in the present study. The detailed balance model of HC-SC operation has been improved to involve a finite value of the ESC conductance to find the required values, which in turn has been revealed to be feasible using resonant tunneling diodes (RTDs) consisting of semiconductor quantum dots (QDs) and quantum wells (QWs) by means of a formulation to calculate the conductance of the QD- and QW-RTDs derived using the rigorous solutions of the effective-mass Hamiltonians. Thus, all of the four requisites unique to HC-SCs to achieve high conversion efficiency have been elucidated, and the two requisites related to the ESCs can be fulfilled using the QD- and QW-RTDs.

  8. The optimization of molybdenum back contact films for Cu(In,Ga)Se{sub 2} solar cells by the cathodic arc ion plating method

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Yong Ki, E-mail: choyk@kitech.re.kr [Heat Treatment and Surface Engineering R and D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Kim, Gang Sam; Song, Young Sik; Lim, Tae Hong [Heat Treatment and Surface Engineering R and D Group, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Jung, Donggeun [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of)

    2013-12-02

    Molybdenum back contact films for Cu(In,Ga)Se{sub 2} (CIGS) solar cells have been deposited using DC magnetron sputtering methods. The electronic pathway properties of the molybdenum film have been highly dependent on the working gas pressure in magnetron sputtering, which should be carefully controlled to obtain high conductivity and adhesion. A coating method, cathodic arc ion plating, was used for molybdenum back contact electrode fabrication. The aim of this work was to find a metallization method for CIGS solar cells, which has less sensitivity on the working pressure. The resistivity, grain size, growth structures, stress, and efficiency of the films in CIGS solar cells were investigated. The results reveal that the growth structures of the molybdenum films mainly affect the conductivity. The lowest electrical resistivity of the ion-plated molybdenum films was 6.9 μΩ-cm at a pressure of 0.7 Pa. The electrical resistivity variation showed a gently increasing slope with linearity under a working gas pressure of 13.3 Pa. However, a high value of the residual stress of over 1.3 GPa was measured. In order to reduce stress, titanium film was selected as the buffer layer material, and the back contact films were optimized by double-layer coating of two kinds of hetero-materials with arc ion plating. CIGS solar cells prepared molybdenum films to measure the efficiency and to examine the effects of the back contact electrode. The resistivity, grain size, and surface morphology of molybdenum films were measured by four-point probe, X-ray diffraction, and a scanning electron microscope. The residual stress of the films was calculated from differences in bending curvatures measured using a laser beam. - Highlights: • Molybdenum back contact films for Cu(In,Ga)Se{sub 2} solar cells were prepared by the cathodic arc ion plating. • The lowest electrical resistivity of molybdenum film was 6.9 μΩ-cm. • Titanium buffer layer reduced the compressive residual stress

  9. Cell-geometry-dependent changes in plasma membrane order direct stem cell signalling and fate

    Science.gov (United States)

    von Erlach, Thomas C.; Bertazzo, Sergio; Wozniak, Michele A.; Horejs, Christine-Maria; Maynard, Stephanie A.; Attwood, Simon; Robinson, Benjamin K.; Autefage, Hélène; Kallepitis, Charalambos; del Río Hernández, Armando; Chen, Christopher S.; Goldoni, Silvia; Stevens, Molly M.

    2018-03-01

    Cell size and shape affect cellular processes such as cell survival, growth and differentiation1-4, thus establishing cell geometry as a fundamental regulator of cell physiology. The contributions of the cytoskeleton, specifically actomyosin tension, to these effects have been described, but the exact biophysical mechanisms that translate changes in cell geometry to changes in cell behaviour remain mostly unresolved. Using a variety of innovative materials techniques, we demonstrate that the nanostructure and lipid assembly within the cell plasma membrane are regulated by cell geometry in a ligand-independent manner. These biophysical changes trigger signalling events involving the serine/threonine kinase Akt/protein kinase B (PKB) that direct cell-geometry-dependent mesenchymal stem cell differentiation. Our study defines a central regulatory role by plasma membrane ordered lipid raft microdomains in modulating stem cell differentiation with potential translational applications.

  10. Possible Immune Regulation of Natural Killer T Cells in a Murine Model of Metal Ion-Induced Allergic Contact Dermatitis

    Directory of Open Access Journals (Sweden)

    Kenichi Kumagai

    2016-01-01

    Full Text Available Metal often causes delayed-type hypersensitivity reactions, which are possibly mediated by accumulating T cells in the inflamed skin, called irritant or allergic contact dermatitis. However, accumulating T cells during development of a metal allergy are poorly characterized because a suitable animal model is unavailable. We have previously established novel murine models of metal allergy and found accumulation of both metal-specific T cells and natural killer (NK T cells in the inflamed skin. In our novel models of metal allergy, skin hypersensitivity responses were induced through repeated sensitizations by administration of metal chloride and lipopolysaccharide into the mouse groin followed by metal chloride challenge in the footpad. These models enabled us to investigate the precise mechanisms of the immune responses of metal allergy in the inflamed skin. In this review, we summarize the immune responses in several murine models of metal allergy and describe which antigen-specific responses occur in the inflamed skin during allergic contact dermatitis in terms of the T cell receptor. In addition, we consider the immune regulation of accumulated NK T cells in metal ion–induced allergic contact dermatitis.

  11. Cell cycle-dependent Rho GTPase activity dynamically regulates cancer cell motility and invasion in vivo.

    Science.gov (United States)

    Kagawa, Yoshinori; Matsumoto, Shinji; Kamioka, Yuji; Mimori, Koshi; Naito, Yoko; Ishii, Taeko; Okuzaki, Daisuke; Nishida, Naohiro; Maeda, Sakae; Naito, Atsushi; Kikuta, Junichi; Nishikawa, Keizo; Nishimura, Junichi; Haraguchi, Naotsugu; Takemasa, Ichiro; Mizushima, Tsunekazu; Ikeda, Masataka; Yamamoto, Hirofumi; Sekimoto, Mitsugu; Ishii, Hideshi; Doki, Yuichiro; Matsuda, Michiyuki; Kikuchi, Akira; Mori, Masaki; Ishii, Masaru

    2013-01-01

    The mechanism behind the spatiotemporal control of cancer cell dynamics and its possible association with cell proliferation has not been well established. By exploiting the intravital imaging technique, we found that cancer cell motility and invasive properties were closely associated with the cell cycle. In vivo inoculation of human colon cancer cells bearing fluorescence ubiquitination-based cell cycle indicator (Fucci) demonstrated an unexpected phenomenon: S/G2/M cells were more motile and invasive than G1 cells. Microarray analyses showed that Arhgap11a, an uncharacterized Rho GTPase-activating protein (RhoGAP), was expressed in a cell-cycle-dependent fashion. Expression of ARHGAP11A in cancer cells suppressed RhoA-dependent mechanisms, such as stress fiber formation and focal adhesion, which made the cells more prone to migrate. We also demonstrated that RhoA suppression by ARHGAP11A induced augmentation of relative Rac1 activity, leading to an increase in the invasive properties. RNAi-based inhibition of Arhgap11a reduced the invasion and in vivo expansion of cancers. Additionally, analysis of human specimens showed the significant up-regulation of Arhgap11a in colon cancers, which was correlated with clinical invasion status. The present study suggests that ARHGAP11A, a cell cycle-dependent RhoGAP, is a critical regulator of cancer cell mobility and is thus a promising therapeutic target in invasive cancers.

  12. Cell cycle-dependent Rho GTPase activity dynamically regulates cancer cell motility and invasion in vivo.

    Directory of Open Access Journals (Sweden)

    Yoshinori Kagawa

    Full Text Available The mechanism behind the spatiotemporal control of cancer cell dynamics and its possible association with cell proliferation has not been well established. By exploiting the intravital imaging technique, we found that cancer cell motility and invasive properties were closely associated with the cell cycle. In vivo inoculation of human colon cancer cells bearing fluorescence ubiquitination-based cell cycle indicator (Fucci demonstrated an unexpected phenomenon: S/G2/M cells were more motile and invasive than G1 cells. Microarray analyses showed that Arhgap11a, an uncharacterized Rho GTPase-activating protein (RhoGAP, was expressed in a cell-cycle-dependent fashion. Expression of ARHGAP11A in cancer cells suppressed RhoA-dependent mechanisms, such as stress fiber formation and focal adhesion, which made the cells more prone to migrate. We also demonstrated that RhoA suppression by ARHGAP11A induced augmentation of relative Rac1 activity, leading to an increase in the invasive properties. RNAi-based inhibition of Arhgap11a reduced the invasion and in vivo expansion of cancers. Additionally, analysis of human specimens showed the significant up-regulation of Arhgap11a in colon cancers, which was correlated with clinical invasion status. The present study suggests that ARHGAP11A, a cell cycle-dependent RhoGAP, is a critical regulator of cancer cell mobility and is thus a promising therapeutic target in invasive cancers.

  13. Silicon-Rich Silicon Carbide Hole-Selective Rear Contacts for Crystalline-Silicon-Based Solar Cells.

    Science.gov (United States)

    Nogay, Gizem; Stuckelberger, Josua; Wyss, Philippe; Jeangros, Quentin; Allebé, Christophe; Niquille, Xavier; Debrot, Fabien; Despeisse, Matthieu; Haug, Franz-Josef; Löper, Philipp; Ballif, Christophe

    2016-12-28

    The use of passivating contacts compatible with typical homojunction thermal processes is one of the most promising approaches to realizing high-efficiency silicon solar cells. In this work, we investigate an alternative rear-passivating contact targeting facile implementation to industrial p-type solar cells. The contact structure consists of a chemically grown thin silicon oxide layer, which is capped with a boron-doped silicon-rich silicon carbide [SiC x (p)] layer and then annealed at 800-900 °C. Transmission electron microscopy reveals that the thin chemical oxide layer disappears upon thermal annealing up to 900 °C, leading to degraded surface passivation. We interpret this in terms of a chemical reaction between carbon atoms in the SiC x (p) layer and the adjacent chemical oxide layer. To prevent this reaction, an intrinsic silicon interlayer was introduced between the chemical oxide and the SiC x (p) layer. We show that this intrinsic silicon interlayer is beneficial for surface passivation. Optimized passivation is obtained with a 10-nm-thick intrinsic silicon interlayer, yielding an emitter saturation current density of 17 fA cm -2 on p-type wafers, which translates into an implied open-circuit voltage of 708 mV. The potential of the developed contact at the rear side is further investigated by realizing a proof-of-concept hybrid solar cell, featuring a heterojunction front-side contact made of intrinsic amorphous silicon and phosphorus-doped amorphous silicon. Even though the presented cells are limited by front-side reflection and front-side parasitic absorption, the obtained cell with a V oc of 694.7 mV, a FF of 79.1%, and an efficiency of 20.44% demonstrates the potential of the p + /p-wafer full-side-passivated rear-side scheme shown here.

  14. SGLT1-mediated transport in Caco-2 cells is highly dependent on cell bank origin

    DEFF Research Database (Denmark)

    Steffansen, B; Pedersen, Maria; Laghmoch, A M

    2017-01-01

    The Caco-2 cell line is a well-established in vitro model for studying transport phenomena for prediction of intestinal nutrient and drug absorption. However, for substances depending on transporters such predictions are complicated due to variable transporter expression and limited knowledge about...... transporter function during multiple cell passaging and cell thawings. In the case of SGLT1, a key transporter of oral absorption of D-glucose, one reason for compromised prediction could be inadequate expression of SGLT1 in Caco-2 cells and thereby limited sensitivity in the determination of SGLT1-mediated...... permeability (PSGLT1). Here, the objective was to characterize and compare SGLT1-mediated uptake in Caco-2 cells obtained from different cell banks. SGLT1-mediated uptake of the standard SGLT1 substrate, α-MDG, in Caco-2 cells was shown to be highly dependent on cell bank origin. The most robust and reliable...

  15. Bleb Expansion in Migrating Cells Depends on Supply of Membrane from Cell Surface Invaginations.

    Science.gov (United States)

    Goudarzi, Mohammad; Tarbashevich, Katsiaryna; Mildner, Karina; Begemann, Isabell; Garcia, Jamie; Paksa, Azadeh; Reichman-Fried, Michal; Mahabaleshwar, Harsha; Blaser, Heiko; Hartwig, Johannes; Zeuschner, Dagmar; Galic, Milos; Bagnat, Michel; Betz, Timo; Raz, Erez

    2017-12-04

    Cell migration is essential for morphogenesis, organ formation, and homeostasis, with relevance for clinical conditions. The migration of primordial germ cells (PGCs) is a useful model for studying this process in the context of the developing embryo. Zebrafish PGC migration depends on the formation of cellular protrusions in form of blebs, a type of protrusion found in various cell types. Here we report on the mechanisms allowing the inflation of the membrane during bleb formation. We show that the rapid expansion of the protrusion depends on membrane invaginations that are localized preferentially at the cell front. The formation of these invaginations requires the function of Cdc42, and their unfolding allows bleb inflation and dynamic cell-shape changes performed by migrating cells. Inhibiting the formation and release of the invaginations strongly interfered with bleb formation, cell motility, and the ability of the cells to reach their target. Copyright © 2017 Elsevier Inc. All rights reserved.

  16. Myosin heavy chain-like localizes at cell contact sites during Drosophila myoblast fusion and interacts in vitro with Rolling pebbles 7

    Energy Technology Data Exchange (ETDEWEB)

    Bonn, Bettina R.; Rudolf, Anja; Hornbruch-Freitag, Christina; Daum, Gabor; Kuckwa, Jessica; Kastl, Lena; Buttgereit, Detlev [Developmental Biology, Department of Biology, Philipps-Universität Marburg, Karl-von-Frisch-Strasse 8, 35037 Marburg (Germany); Renkawitz-Pohl, Renate, E-mail: renkawit@biologie.uni-marburg.de [Developmental Biology, Department of Biology, Philipps-Universität Marburg, Karl-von-Frisch-Strasse 8, 35037 Marburg (Germany)

    2013-02-15

    Besides representing the sarcomeric thick filaments, myosins are involved in many cellular transport and motility processes. Myosin heavy chains are grouped into 18 classes. Here we show that in Drosophila, the unconventional group XVIII myosin heavy chain-like (Mhcl) is transcribed in the mesoderm of embryos, most prominently in founder cells (FCs). An ectopically expressed GFP-tagged Mhcl localizes in the growing muscle at cell–cell contacts towards the attached fusion competent myoblast (FCM). We further show that Mhcl interacts in vitro with the essential fusion protein Rolling pebbles 7 (Rols7), which is part of a protein complex established at cell contact sites (Fusion-restricted Myogenic-Adhesive Structure or FuRMAS). Here, branched F-actin is likely needed to widen the fusion pore and to integrate the myoblast into the growing muscle. We show that the localization of Mhcl is dependent on the presence of Rols7, and we postulate that Mhcl acts at the FuRMAS as an actin motor protein. We further show that Mhcl deficient embryos develop a wild-type musculature. We thus propose that Mhcl functions redundantly to other myosin heavy chains in myoblasts. Lastly, we found that the protein is detectable adjacent to the sarcomeric Z-discs, suggesting an additional function in mature muscles. - Highlights: ► The class XVIII myosin encoding gene Mhcl is transcribed in the mesoderm. ► Mhcl localization at contact sites of fusing myoblasts depends on Rols7. ► Mhcl interacts in vitro with Rols7 which is essential for myogenesis. ► Functional redundancy with other myosins is likely as mutants show no muscle defects. ► Mhcl localizes adjacent to Z-discs of sarcomeres and might support muscle integrity.

  17. Myosin heavy chain-like localizes at cell contact sites during Drosophila myoblast fusion and interacts in vitro with Rolling pebbles 7

    International Nuclear Information System (INIS)

    Bonn, Bettina R.; Rudolf, Anja; Hornbruch-Freitag, Christina; Daum, Gabor; Kuckwa, Jessica; Kastl, Lena; Buttgereit, Detlev; Renkawitz-Pohl, Renate

    2013-01-01

    Besides representing the sarcomeric thick filaments, myosins are involved in many cellular transport and motility processes. Myosin heavy chains are grouped into 18 classes. Here we show that in Drosophila, the unconventional group XVIII myosin heavy chain-like (Mhcl) is transcribed in the mesoderm of embryos, most prominently in founder cells (FCs). An ectopically expressed GFP-tagged Mhcl localizes in the growing muscle at cell–cell contacts towards the attached fusion competent myoblast (FCM). We further show that Mhcl interacts in vitro with the essential fusion protein Rolling pebbles 7 (Rols7), which is part of a protein complex established at cell contact sites (Fusion-restricted Myogenic-Adhesive Structure or FuRMAS). Here, branched F-actin is likely needed to widen the fusion pore and to integrate the myoblast into the growing muscle. We show that the localization of Mhcl is dependent on the presence of Rols7, and we postulate that Mhcl acts at the FuRMAS as an actin motor protein. We further show that Mhcl deficient embryos develop a wild-type musculature. We thus propose that Mhcl functions redundantly to other myosin heavy chains in myoblasts. Lastly, we found that the protein is detectable adjacent to the sarcomeric Z-discs, suggesting an additional function in mature muscles. - Highlights: ► The class XVIII myosin encoding gene Mhcl is transcribed in the mesoderm. ► Mhcl localization at contact sites of fusing myoblasts depends on Rols7. ► Mhcl interacts in vitro with Rols7 which is essential for myogenesis. ► Functional redundancy with other myosins is likely as mutants show no muscle defects. ► Mhcl localizes adjacent to Z-discs of sarcomeres and might support muscle integrity

  18. Performance and Metastability of CdTe Solar Cells with a Te Back-Contact Buffer Layer

    Science.gov (United States)

    Moore, Andrew

    Thin-film CdTe photovoltaics are quickly maturing into a viable clean-energy solution through demonstration of competitive costs and performance stability with existing energy sources. Over the last half decade, CdTe solar technology has achieved major gains in performance; however, there are still aspects that can be improved to progress toward their theoretical maximum efficiency. Perhaps equally valuable as high photovoltaic efficiency and a low levelized cost of energy, is device reliability. Understanding the root causes for changes in performance is essential for accomplishing long-term stability. One area for potential performance enhancement is the back contact of the CdTe device. This research incorporated a thin-film Te-buffer layer into the contact structure, between the CdTe and contact metal. The device performance and characteristics of many different back contact configurations were rigorously studied. CdTe solar cells fabricated with the Te-buffer contact showed short-circuit current densities and open-circuit voltages that were on par with the traditional back-contacts used at CSU. However, the Te-buffer contact typically produced 2% larger fill-factors on average, leading to greater conversation efficiency. Furthermore, using the Te buffer allowed for incorporation of 50% less Cu, which is used for p-type doping but is also known to decrease lifetime and stability. This resulted in an additional 3% fill-factor gain with no change in other parameters compared to the standard-Cu treated device. In order to better understand the physical mechanisms of the Te-buffer contact, electrical and material properties of the Te layer were extracted and used to construct a simple energy band diagram. The Te layer was found to be highly p-type (>1018 cm-3) and possess a positive valence-band offset of 0.35-0.40 eV with CdTe. An existing simulation model incorporating the Te-layer properties was implemented and validated by comparing simulated results of Cd

  19. The influence of the spin-dependent phases of tunneling electrons on the conductance of a point ferromagnet/isolator/d-wave superconductor contact.

    Science.gov (United States)

    Vodopyanov, B P

    2010-05-12

    The influence of the spin-dependent phase shifts (SDPSs) associated with the electronic reflection and transmission amplitudes acquired by electrons upon scattering at the potential barrier on the Andreev reflection probability of electron and hole excitations for a ferromagnet/isolator/d-wave superconductor (FIS) contact and on the charge conductance of the FIS contact is studied. Various superconductor orientations are considered. It has been found that for strong ferromagnets and ultrathin interface potential for the {110} oriented d-wave superconductor the presence of the SDPS can lead to the appearance of finite-voltage peaks in the charge conductance of the F/I/d-wave superconductor contact. On the contrary, for the {100} orientation of the d-wave superconductor the presence of the SDPS can lead to restoration of the zero-voltage peak and suppression of finite-voltage peaks. The spin-dependent amplitudes of the Andreev reflection probability and energy levels of the spin-dependent Andreev bound states are found.

  20. Minimizing cell size dependence in micromagnetics simulations with thermal noise

    Energy Technology Data Exchange (ETDEWEB)

    MartInez, E [Departamento de Ingenieria Electromecanica, Universidad de Burgos, Plaza Misael Banuelos, s/n, E-09001, Burgos (Spain); Lopez-DIaz, L [Departamento de Fisica Aplicada. Universidad Salamanca. Plaza de la Merced s/n. Salamanca E-37008 (Spain); Torres, L [Departamento de Fisica Aplicada. Universidad Salamanca. Plaza de la Merced s/n. Salamanca E-37008 (Spain); GarcIa-Cervera, C J [Department of Mathematics. University of California, Santa Barbara, CA 93106 (United States)

    2007-02-21

    Langevin dynamics treats finite temperature effects in a micromagnetics framework by adding a thermal fluctuation field to the effective field. Several works have addressed the dependence of numerical results on the cell size used to split the ferromagnetic samples on the nanoscale regime. In this paper, some former problems dealing with the dependence on the spatial discretization at finite temperature have been revised. We have focused our attention on the stability of the numerical schemes used to integrate the Langevin equation. In particular, a detailed analysis of results was carried out as a function of the time step. It was confirmed that the mentioned dependence can be minimized if an unconditional stable integration method is used to numerically solve the Langevin equation.

  1. Minimizing cell size dependence in micromagnetics simulations with thermal noise

    International Nuclear Information System (INIS)

    MartInez, E; Lopez-DIaz, L; Torres, L; GarcIa-Cervera, C J

    2007-01-01

    Langevin dynamics treats finite temperature effects in a micromagnetics framework by adding a thermal fluctuation field to the effective field. Several works have addressed the dependence of numerical results on the cell size used to split the ferromagnetic samples on the nanoscale regime. In this paper, some former problems dealing with the dependence on the spatial discretization at finite temperature have been revised. We have focused our attention on the stability of the numerical schemes used to integrate the Langevin equation. In particular, a detailed analysis of results was carried out as a function of the time step. It was confirmed that the mentioned dependence can be minimized if an unconditional stable integration method is used to numerically solve the Langevin equation

  2. Melanin dependent survival of Apergillus fumigatus conidia in lung epithelial cells.

    Science.gov (United States)

    Amin, Shayista; Thywissen, Andreas; Heinekamp, Thorsten; Saluz, Hans Peter; Brakhage, Axel A

    2014-07-01

    Aspergillus fumigatus is the most important air-borne pathogenic fungus of humans. Upon inhalation of conidia, the fungus makes close contact with lung epithelial cells, which only possess low phagocytic activity. These cells are in particular interesting to address the question whether there is some form of persistence of conidia of A. fumigatus in the human host. Therefore, by also using uracil-auxotrophic mutant strains, we were able to investigate the interaction of A549 lung epithelial cells and A. fumigatus conidia in detail for long periods. Interestingly, unlike professional phagocytes, our study showed that the presence of conidial dihydroxynaphthalene (DHN) melanin enhanced the uptake of A. fumigatus conidia by epithelial cells when compared with non-pigmented pksP mutant conidia. Furthermore, conidia of A. fumigatus were able to survive within epithelial cells. This was due to the presence of DHN melanin in the cell wall of conidia, because melanised wild-type conidia showed a higher survival rate inside epithelial cells and led to inhibition of acidification of phagolysosomes. Both effects were not observed for white (non-melanised) conidia of the pksP mutant strain. Moreover, in contrast to pksP mutant conidia, melanised wild-type conidia were able to inhibit the extrinsic apoptotic pathway in A549 lung epithelial cells even for longer periods. The anti-apoptotic effect was not restricted to conidia, because both conidia-derived melanin ghosts (cell-free DHN melanin) and a different type of melanin, dihydroxyphenylalanine (DOPA) melanin, acted anti-apoptotically. Taken together, these data indicate the possibility of melanin-dependent persistence of conidia in lung epithelial cells. Copyright © 2014 Elsevier GmbH. All rights reserved.

  3. Cell-cycle-dependent repair of heavy-ion damage

    International Nuclear Information System (INIS)

    Blakely, E.A.; Chang, P.Y.; Lommel, L.; Tobias, C.A.

    1985-01-01

    Synchronized human T-1 cells have been used to investigate the G1-phase age dependence of repair of potentially lethal damage (PLDR). The cells were irradiated with single doses of either 225 kVp X rays or Bragg-peak 425 MeV/μ neon ions at ages between 1.5 and 6.0 hrs after mitotic selection, and then either trypsinized and plated immediately, or held at 37 0 C for 6 hrs in PBS, or PBS containing 60μM of the DNA-polymerase-inhibitor 1-β-D-arabinofurano-syladenine (β-araA) before trypsinization and plating. Delayed plating showed significant PLDR at all ages irradiated with X rays, with the increase of survival varying between 2- to 8-fold. At equivalent survival levels, there was a reduced capacity for PLDT at each cell age irradiated with neon ions. In early G1 after neon-ion exposures, delayed plating actually enhanced cell killing; whereas, in late G1 the survival increased about 2-fold. β-araA almost completely eliminated the PLDR after X rays, reducing the survival to that measured with immediate plating. β-araA slightly enhanced neon-ion cell killing at all cell ages

  4. Changes in homologous and heterologous gap junction contacts during maturation-inducing hormone-dependent meiotic resumption in ovarian follicles of Atlantic croaker

    Science.gov (United States)

    Bolamba, D.; Patino, R.; Yoshizaki, G.; Thomas, P.

    2003-01-01

    Homologous (granulosa cell-granulosa cell) gap junction (GJ) contacts increase in ovarian follicles of Atlantic croaker (Micropogonias undulatus) during the early (first) stage of maturation, but their profile during the second stage [i.e., during maturation-inducing hormone (MIH)-mediated meiotic resumption] is unknown. The profile of homologous GJ contacts during the second stage of maturation in croaker follicles was examined in this study and compared to that of heterologous (granulosa cell-oocyte) GJ, for which changes have been previously documented. Follicles were incubated with human chorionic gonadotropin to induce maturational competence (first stage), and then with MIH to induce meiotic resumption. The follicles were collected for examination immediately before and after different durations of MIH exposure until the oocyte had reached the stage of germinal vesicle breakdown (GVBD; index of meiotic resumption). Ultrathin sections were observed by transmission electron microscopy, and homologous and heterologous GJ contacts were quantified along a 100-??m segment of granulosa cell-zona radiata complex per follicle (three follicles/time/fish, n=3 fish). Relatively high numbers of both types of GJ were observed before and after the first few hours of MIH exposure (up to the stage of oil droplet coalescence). GJ numbers declined during partial yolk globule coalescence (at or near GVBD) and were just under 50% of starting values after the completion of GVBD (P<0.05). These results confirm earlier observations that GVBD temporally correlates with declining heterologous GJ contacts, and for the first time in teleosts show that there is a parallel decline in homologous GJ. The significance of the changes in homologous and heterologous GJ is uncertain and deserves further study. ?? 2003 Elsevier Science (USA). All rights reserved.

  5. Transparent front contact optimization in dye sensitized solar cells: use of cadmium stannate and titanium oxide by sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Braga, A., E-mail: antonio.braga@iit.it [CNR-IDASC SENSOR Lab and Department of Chemistry and Physics, Brescia University, Via Valotti 9, 25131 Brescia (Italy); Baratto, C. [CNR-IDASC SENSOR Lab and Department of Chemistry and Physics, Brescia University, Via Valotti 9, 25131 Brescia (Italy); Bontempi, E. [INSTM and Chemistry for Technologies Laboratory, University of Brescia, Via Branze 28, 25133 Brescia (Italy); Colombi, P. [Centro Coating C.S.M.T. Gestione S.c.a.r.l., Via Branze, 45 25123 Brescia (Italy); Sberveglieri, G. [CNR-IDASC SENSOR Lab and Department of Chemistry and Physics, Brescia University, Via Valotti 9, 25131 Brescia (Italy)

    2014-03-31

    A reliable transparent front contact of cadmium stannate (CTO) and titanium oxide (TiO{sub 2}) entirely deposited by magnetron sputtering has been studied and applied to build standard dye-sensitized solar cell. CTO gives very high average optical transmittance (T{sub avg} ≥ 90%) along with competitive sheet resistance (R{sub sheet} ≤ 15 Ω/sq), while a very thin layer of TiO{sub 2} (thickness < 5 nm) acts as buffer layer to prevent charge recombination. The matched materials allow achievement of good performances of the cells, in terms of short circuit current and power conversion efficiency. UV-visible spectrophotometry, glancing incident X-rays diffraction and X-rays reflectivity techniques were used to characterize thin films before cell realization; sealed solar cells were tested under simulated solar irradiance at 1 Sun to determine functional properties. - Highlights: • Double layer cadmium stannate–TiO{sub 2} transparent front contact by sputtering. • Very thin TiO{sub 2} buffer layer for charge recombination prevention. • Application of novel transparent contact in standard dye sensitized solar cells.

  6. Application Of Artificial Neural Networks In Modeling Of Manufactured Front Metallization Contact Resistance For Silicon Solar Cells

    Directory of Open Access Journals (Sweden)

    Musztyfaga-Staszuk M.

    2015-09-01

    Full Text Available This paper presents the application of artificial neural networks for prediction contact resistance of front metallization for silicon solar cells. The influence of the obtained front electrode features on electrical properties of solar cells was estimated. The front electrode of photovoltaic cells was deposited using screen printing (SP method and next to manufactured by two methods: convectional (1. co-fired in an infrared belt furnace and unconventional (2. Selective Laser Sintering. Resistance of front electrodes solar cells was investigated using Transmission Line Model (TLM. Artificial neural networks were obtained with the use of Statistica Neural Network by Statsoft. Created artificial neural networks makes possible the easy modelling of contact resistance of manufactured front metallization and allows the better selection of production parameters. The following technological recommendations for the screen printing connected with co-firing and selective laser sintering technology such as optimal paste composition, morphology of the silicon substrate, co-firing temperature and the power and scanning speed of the laser beam to manufacture the front electrode of silicon solar cells were experimentally selected in order to obtain uniformly melted structure well adhered to substrate, of a small front electrode substrate joint resistance value. The prediction possibility of contact resistance of manufactured front metallization is valuable for manufacturers and constructors. It allows preserving the customers’ quality requirements and bringing also measurable financial advantages.

  7. Transparent front contact optimization in dye sensitized solar cells: use of cadmium stannate and titanium oxide by sputtering

    International Nuclear Information System (INIS)

    Braga, A.; Baratto, C.; Bontempi, E.; Colombi, P.; Sberveglieri, G.

    2014-01-01

    A reliable transparent front contact of cadmium stannate (CTO) and titanium oxide (TiO 2 ) entirely deposited by magnetron sputtering has been studied and applied to build standard dye-sensitized solar cell. CTO gives very high average optical transmittance (T avg ≥ 90%) along with competitive sheet resistance (R sheet ≤ 15 Ω/sq), while a very thin layer of TiO 2 (thickness < 5 nm) acts as buffer layer to prevent charge recombination. The matched materials allow achievement of good performances of the cells, in terms of short circuit current and power conversion efficiency. UV-visible spectrophotometry, glancing incident X-rays diffraction and X-rays reflectivity techniques were used to characterize thin films before cell realization; sealed solar cells were tested under simulated solar irradiance at 1 Sun to determine functional properties. - Highlights: • Double layer cadmium stannate–TiO 2 transparent front contact by sputtering. • Very thin TiO 2 buffer layer for charge recombination prevention. • Application of novel transparent contact in standard dye sensitized solar cells

  8. The dependence of fibroblast radiosensitivity on cell pH

    International Nuclear Information System (INIS)

    Veksler, A.M.; Kublik, L.N.; Degtyareva, O.V.; Ehjdus, L.Kh.

    1983-01-01

    The problem of the change of radiosensitivity of Chinese hamster fibroblasts, irradiated under aerobic and hypoxic conditions in the course of intracellular pH (pHsub(intr.)) change by means of a phosphate buffer has been studied. It has been found that pHsub(intr.) reduction considerably increases the radiosensitivity, the effect being more pronounced on hypoxic cells which is essential for radiotherapy of tumors. The survival rate of cell irradiated under hypoxia conditions does not depend on season while cell resistance in case of irradiation in open air in spring and autumn is different. The effect discovery in case of pHsub(intr.) reduction upon irradiation shows up the influence of the studied factor on repair processes

  9. Cell-substrate interaction with cell-membrane-stress dependent adhesion.

    Science.gov (United States)

    Jiang, H; Yang, B

    2012-01-10

    Cell-substrate interaction is examined in a two-dimensional mechanics model. The cell and substrate are treated as a shell and an elastic solid, respectively. Their interaction through adhesion is treated using nonlinear springs. Compared to previous cell mechanics models, the present model introduces a cohesive force law that is dependent not only on cell-substrate distance but also on internal cell-membrane stress. It is postulated that a living cell would establish focal adhesion sites with density dependent on the cell-membrane stress. The formulated mechanics problem is numerically solved using coupled finite elements and boundary elements for the cell and the substrate, respectively. The nodes in the adhesion zone from either side are linked by the cohesive springs. The specific cases of a cell adhering to a homogeneous substrate and a heterogeneous bimaterial substrate are examined. The analyses show that the substrate stiffness affects the adhesion behavior significantly and regulates the direction of cell adhesion, in good agreement with the experimental results in the literature. By introducing a reactive parameter (i.e., cell-membrane stress) linking biological responses of a living cell to a mechanical environment, the present model offers a unified mechanistic vehicle for characterization and prediction of living cell responses to various kinds of mechanical stimuli including local extracellular matrix and neighboring cells. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. IRF8 dependent classical dendritic cells are essential for intestinal T cell homeostasis

    DEFF Research Database (Denmark)

    Luda, K.; Joeris, Thorsten; Persson, E. K.

    2016-01-01

    The role of dendritic cells (DCs) in intestinal immune homeostasis remains incompletely defined. Here we show that mice lacking IRF8 dependent DCs have reduced numbers of T cells in the small intestine (SI), but not large intestine (LI), including an almost complete absence of SI CD8ab+ andCD4+CD8......aa+ T cells; the latter requiring b8 integrin expression by migratory IRF8 dependent CD103+CD11b- DCs. SI homing receptor induction was impaired during T cell priming in mesenteric lymph nodes (MLN), which correlated with a reduction in aldehyde dehydrogenase activity by SI derived MLN DCs......, and inefficient T cell localization to the SI. Finally, mice with a DC deletion in IRF8 lacked intestinal T helper 1 (Th1) cells, and failed to support Th1 cell differentiation in MLN and mount Th1 responses to Trichuris muris infection. Collectively these results highlight multiple non-redundant roles for IRF8...

  11. The quest for targets executing MYC-dependent cell transformation

    Directory of Open Access Journals (Sweden)

    Markus eHartl

    2016-06-01

    Full Text Available MYC represents a transcription factor with oncogenic potential converting multiple cellular signals into a broad transcriptional response, thereby controlling the expression of numerous protein-coding and non-coding RNAs important for cell proliferation, metabolism, differentiation, and apoptosis. Constitutive activation of MYC leads to neoplastic cell transformation, and deregulated MYC alleles are frequently observed in many human cancer cell types. Multiple approaches have been performed to isolate genes differentially expressed in cells containing aberrantly activated MYC proteins leading to the identification of thousands of putative targets. Functional analyses of genes differentially expressed in MYC-transformed cells had revealed that so far more than forty upregulated or downregulated MYC targets are actively involved in cell transformation or tumorigenesis. However, for determination which of the known, or yet unidentified targets are responsible for processing the oncogenic MYC program, further systematic and selective approaches are required. The search for critical targets in MYC-dependent tumor cells is exacerbated by the fact that during tumor development, cancer cells progressively evolve in a multistep process thereby acquiring their characteristic features in an additive manner. Functional expression cloning, combinatorial gene expression and appropriate in vivo tests could represent adequate tools for dissecting the complex scenario of MYC-specified cell transformation. In this context, the central goal is to identify a minimal set of targets that suffices to phenocopy oncogenic MYC. Recently developed genomic editing tools could be employed to confirm the requirement of crucial transformation-associated targets.Knowledge about essential MYC regulated genes is beneficial to expedite the development of specific inhibitors to interfere with growth and viability of human tumor cells in which MYC is aberrantly activated

  12. Enhancement of cell-cell contact by a nonmitogenic lectin increases blastogenic response and IL-2 release by mitogen-stimulated mouse thymocytes.

    Science.gov (United States)

    Favero, J; Marti, J; Dornand, J; Bonnafous, J C; Mani, J C

    1986-03-01

    We have examined the influence of peanut agglutinin (PNA), a lectin which agglutinates but does not stimulate mouse thymocytes, on the responsiveness of these cells to concanavalin A (Con A) or galactose oxidase stimulation. Binding low amounts of PNA on unseparated mouse thymocytes pretreated with neuraminidase highly enhances the mitogenic response and the level of interleukin 2 release in the culture medium upon Con A stimulation. We have shown that PNA present on the cell surface acts as a crosslinking agent which favors intercellular binding between accessory cells (macrophages) and thymocytes, leading through this enhanced cooperation by cell-cell contact to an enhanced blastogenic response.

  13. Angular-dependent light scattering from cancer cells in different phases of the cell cycle.

    Science.gov (United States)

    Lin, Xiaogang; Wan, Nan; Weng, Lingdong; Zhou, Yong

    2017-10-10

    Cancer cells in different phases of the cell cycle result in significant differences in light scattering properties. In order to harvest cancer cells in particular phases of the cell cycle, we cultured cancer cells through the process of synchronization. Flow cytometric analysis was applied to check the results of cell synchronization and prepare for light scattering measurements. Angular-dependent light scattering measurements of cancer cells arrested in the G1, S, and G2 phases have been performed. Based on integral calculations for scattering intensities from 5° to 10° and from 110° to 150°, conclusions have been reached. Clearly, the sizes of the cancer cells in different phases of the cell cycle dominated the forward scatter. Accompanying the increase of cell size with the progression of the cell cycle, the forward scattering intensity also increased. Meanwhile, the DNA content of cancer cells in every phase of the cell cycle is responsible for light scattering at large scatter angles. The higher the DNA content of cancer cells was, the greater the positive effect on the high-scattering intensity. As expected, understanding the relationships between the light scattering from cancer cells and cell cycles will aid in the development of cancer diagnoses. Also, it may assist in the guidance of antineoplastic drugs clinically.

  14. Influence of Electrode Design and Contacting Layers on Performance of Electrolyte Supported SOFC/SOEC Single Cells

    Directory of Open Access Journals (Sweden)

    Mihails Kusnezoff

    2016-11-01

    Full Text Available The solid oxide cell is a basis for highly efficient and reversible electrochemical energy conversion. A single cell based on a planar electrolyte substrate as support (ESC is often utilized for SOFC/SOEC stack manufacturing and fulfills necessary requirements for application in small, medium and large scale fuel cell and electrolysis systems. Thickness of the electrolyte substrate, and its ionic conductivity limits the power density of the ESC. To improve the performance of this cell type in SOFC/SOEC mode, alternative fuel electrodes, on the basis of Ni/CGO as well as electrolytes with reduced thickness, have been applied. Furthermore, different interlayers on the air side have been tested to avoid the electrode delamination and to reduce the cell degradation in electrolysis mode. Finally, the influence of the contacting layer on cell performance, especially for cells with an ultrathin electrolyte and thin electrode layers, has been investigated. It has been found that Ni/CGO outperform traditional Ni/8YSZ electrodes and the introduction of a ScSZ interlayer substantially reduces the degradation rate of ESC in electrolysis mode. Furthermore, it was demonstrated that, for thin electrodes, the application of contacting layers with good conductivity and adhesion to current collectors improves performance significantly.

  15. Influence of Electrode Design and Contacting Layers on Performance of Electrolyte Supported SOFC/SOEC Single Cells.

    Science.gov (United States)

    Kusnezoff, Mihails; Trofimenko, Nikolai; Müller, Martin; Michaelis, Alexander

    2016-11-08

    The solid oxide cell is a basis for highly efficient and reversible electrochemical energy conversion. A single cell based on a planar electrolyte substrate as support (ESC) is often utilized for SOFC/SOEC stack manufacturing and fulfills necessary requirements for application in small, medium and large scale fuel cell and electrolysis systems. Thickness of the electrolyte substrate, and its ionic conductivity limits the power density of the ESC. To improve the performance of this cell type in SOFC/SOEC mode, alternative fuel electrodes, on the basis of Ni/CGO as well as electrolytes with reduced thickness, have been applied. Furthermore, different interlayers on the air side have been tested to avoid the electrode delamination and to reduce the cell degradation in electrolysis mode. Finally, the influence of the contacting layer on cell performance, especially for cells with an ultrathin electrolyte and thin electrode layers, has been investigated. It has been found that Ni/CGO outperform traditional Ni/8YSZ electrodes and the introduction of a ScSZ interlayer substantially reduces the degradation rate of ESC in electrolysis mode. Furthermore, it was demonstrated that, for thin electrodes, the application of contacting layers with good conductivity and adhesion to current collectors improves performance significantly.

  16. Bulk and contact resistances of gas diffusion layers in proton exchange membrane fuel cells

    Science.gov (United States)

    Ye, Donghao; Gauthier, Eric; Benziger, Jay B.; Pan, Mu

    2014-06-01

    A multi-electrode probe is employed to distinguish the bulk and contact resistances of the catalyst layer (CL) and the gas diffusion layer (GDL) with the bipolar plate (BPP). Resistances are compared for Vulcan carbon catalyst layers (CL), carbon paper and carbon cloth GDL materials, and GDLs with microporous layers (MPL). The Vulcan carbon catalyst layer bulk resistance is 100 times greater than the bulk resistance of carbon paper GDL (Toray TG-H-120). Carbon cloth (CCWP) has bulk and contact resistances twice those of carbon paper. Compression of the GDL decreases the GDL contact resistance, but has little effect on the bulk resistance. Treatment of the GDL with polytetrafluoroethylene (PTFE) increases the contact resistance, but has little effect on the bulk resistance. A microporous layer (MPL) added to the GDL decreases the contact resistance, but has little effect on the bulk resistance. An equivalent circuit model shows that for channels less than 1 mm wide the contact resistance is the major source of electronic resistance and is about 10% of the total ohmic resistance associated with the membrane electrode assembly.

  17. An Isotope Study of Hydrogenation of poly-Si/SiOx Passivated Contacts for Si Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Schnabel, Manuel; Nemeth, William; van de Loo, Bas, W.H.; Macco, Bart; Kessels, Wilhelmus, M.M.; Stradins, Paul; Young, David, L.

    2017-06-26

    For many years, the record Si solar cell efficiency stood at 25.0%. Only recently have several companies and institutes managed to produce more efficient cells, using passivated contacts of made doped poly-Si or a-Si:H and a passivating intrinsic interlayer in all cases. Common to these designs is the need to passivate the layer stack with hydrogen. In this contribution, we perform a systematic study of passivated contact passivation by hydrogen, using poly-Si/SiOx passivated contacts on n-Cz-Si, and ALD Al2O3 followed by a forming gas anneal (FGA) as the hydrogen source. We study p-type and n-type passivated contacts with implied Voc exceeding 690 and 720 mV, respectively, and perform either the ALD step or the FGA with deuterium instead of hydrogen in order to separate the two processes via SIMS. By examining the deuterium concentration at the SiOx in both types of samples, we demonstrate that the FGA supplies negligible hydrogen species to the SiOx, regardless of whether the FGA is hydrogenated or deuterated. Instead, it supplies the thermal energy needed for hydrogen species in the Al2O3 to diffuse there. Furthermore, the concentration of hydrogen species at the SiOx can saturate while implied Voc continues to increase, showing that the energy from the FGA is also required for hydrogen species already at the SiOx to find recombination-active defects to passivate.

  18. Cell cycle dependent changes in the plasma membrane organization of mammalian cells.

    Science.gov (United States)

    Denz, Manuela; Chiantia, Salvatore; Herrmann, Andreas; Mueller, Peter; Korte, Thomas; Schwarzer, Roland

    2017-03-01

    Lipid membranes are major structural elements of all eukaryotic and prokaryotic organisms. Although many aspects of their biology have been studied extensively, their dynamics and lateral heterogeneity are still not fully understood. Recently, we observed a cell-to-cell variability in the plasma membrane organization of CHO-K1 cells (Schwarzer et al., 2014). We surmised that cell cycle dependent changes of the individual cells from our unsynchronized cell population account for this phenomenon. In the present study, this hypothesis was tested. To this aim, CHO-K1 cells were arrested in different cell cycle phases by chemical treatments, and the order of their plasma membranes was determined by various fluorescent lipid analogues using fluorescence lifetime imaging microscopy. Our experiments exhibit significant differences in the membrane order of cells arrested in the G2/M or S phase compared to control cells. Our single-cell analysis also enabled the specific selection of mitotic cells, which displayed a significant increase of the membrane order compared to the control. In addition, the lipid raft marker GPImYFP was used to study the lateral organization of cell cycle arrested cells as well as mitotic cells and freely cycling samples. Again, significant differences were found between control and arrested cells and even more pronounced between control and mitotic cells. Our data demonstrate a direct correlation between cell cycle progression and plasma membrane organization, underlining that cell-to-cell heterogeneities of membrane properties have to be taken into account in cellular studies especially at the single-cell level. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. In Vitro Model for Predicting the Protective Effect of Ultraviolet-Blocking Contact Lens in Human Corneal Epithelial Cells.

    Science.gov (United States)

    Abengózar-Vela, Antonio; Arroyo, Cristina; Reinoso, Roberto; Enríquez-de-Salamanca, Amalia; Corell, Alfredo; González-García, María Jesús

    2015-01-01

    To develop an in vitro method to determine the protective effect of UV-blocking contact lenses (CLs) in human corneal epithelial (HCE) cells exposed to UV-B radiation. SV-40-transformed HCE cells were covered with non-UV-blocking CL, UV-blocking CL or not covered, and exposed to UV-B radiation. As control, HCE cells were covered with both types of CLs or not covered, but not exposed to UV-B radiation. Cell viability at 24, 48 and 72 h, after UV-B exposure and removing CLs, was determined by alamarBlue(®) assay. Percentage of live, dead and apoptotic cells was also assessed by flow cytometry after 24 h of UV-B exposure. Intracellular reactive oxygen species (ROS) production after 1 h of exposure was assessed using the dye H(2)DCF-DA. Cell viability significantly decreased, apoptotic cells and intracellular ROS production significantly increased when UVB-exposed cells were covered with non-UV-blocking CL or not covered compared to non-irradiated cells. When cells were covered with UV-blocking CL, cell viability significantly increased and apoptotic cells and intracellular ROS production did not increase compared to exposed cells. UV-B radiation induces cell death by apoptosis, increases ROS production and decreases viable cells. UV-blocking CL is able to avoid these effects increasing cell viability and protecting HCE cells from apoptosis and ROS production induced by UV-B radiation. This in vitro model is an alternative to in vivo methods to determine the protective effect of UV-blocking ophthalmic biomaterials because it is a quicker, cheaper and reliable model that avoids the use of animals.

  20. 2D simulation and performance evaluation of bifacial rear local contact c-Si solar cells under variable illumination conditions

    KAUST Repository

    Katsaounis, Theodoros

    2017-09-18

    A customized 2D computational tool has been developed to simulate bifacial rear local contact PERC type PV structures based on the numerical solution of the transport equations through the finite element method. Simulations were performed under various device material parameters and back contact geometry configurations in order to optimize bifacial solar cell performance under different simulated illumination conditions. Bifacial device maximum power output was also compared with the monofacial equivalent one and the industrial standard Al-BSF structure. The performance of the bifacial structure during highly diffused irradiance conditions commonly observed in the Middle East region due to high concentrations of airborne dust particles was also investigated. Simulation results demonstrated that such conditions are highly favorable for the bifacial device because of the significantly increased diffuse component of the solar radiation which enters the back cell surface.

  1. 2D simulation and performance evaluation of bifacial rear local contact c-Si solar cells under variable illumination conditions

    KAUST Repository

    Katsaounis, Theodoros; Kotsovos, Konstantinos; Gereige, Issam; Al-Saggaf, Ahmed; Tzavaras, Athanasios

    2017-01-01

    A customized 2D computational tool has been developed to simulate bifacial rear local contact PERC type PV structures based on the numerical solution of the transport equations through the finite element method. Simulations were performed under various device material parameters and back contact geometry configurations in order to optimize bifacial solar cell performance under different simulated illumination conditions. Bifacial device maximum power output was also compared with the monofacial equivalent one and the industrial standard Al-BSF structure. The performance of the bifacial structure during highly diffused irradiance conditions commonly observed in the Middle East region due to high concentrations of airborne dust particles was also investigated. Simulation results demonstrated that such conditions are highly favorable for the bifacial device because of the significantly increased diffuse component of the solar radiation which enters the back cell surface.

  2. IRF8 Transcription-Factor-Dependent Classical Dendritic Cells Are Essential for Intestinal T Cell Homeostasis.

    Science.gov (United States)

    Luda, Katarzyna M; Joeris, Thorsten; Persson, Emma K; Rivollier, Aymeric; Demiri, Mimoza; Sitnik, Katarzyna M; Pool, Lieneke; Holm, Jacob B; Melo-Gonzalez, Felipe; Richter, Lisa; Lambrecht, Bart N; Kristiansen, Karsten; Travis, Mark A; Svensson-Frej, Marcus; Kotarsky, Knut; Agace, William W

    2016-04-19

    The role of dendritic cells (DCs) in intestinal immune homeostasis remains incompletely defined. Here we show that mice lacking IRF8 transcription-factor-dependent DCs had reduced numbers of T cells in the small intestine (SI), but not large intestine (LI), including an almost complete absence of SI CD8αβ(+) and CD4(+)CD8αα(+) T cells; the latter requiring β8 integrin expression by migratory IRF8 dependent CD103(+)CD11b(-) DCs. SI homing receptor induction was impaired during T cell priming in mesenteric lymph nodes (MLN), which correlated with a reduction in aldehyde dehydrogenase activity by SI-derived MLN DCs, and inefficient T cell localization to the SI. These mice also lacked intestinal T helper 1 (Th1) cells, and failed to support Th1 cell differentiation in MLN and mount Th1 cell responses to Trichuris muris infection. Collectively these results highlight multiple non-redundant roles for IRF8 dependent DCs in the maintenance of intestinal T cell homeostasis. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Abnormal mitosis triggers p53-dependent cell cycle arrest in human tetraploid cells.

    Science.gov (United States)

    Kuffer, Christian; Kuznetsova, Anastasia Yurievna; Storchová, Zuzana

    2013-08-01

    Erroneously arising tetraploid mammalian cells are chromosomally instable and may facilitate cell transformation. An increasing body of evidence shows that the propagation of mammalian tetraploid cells is limited by a p53-dependent arrest. The trigger of this arrest has not been identified so far. Here we show by live cell imaging of tetraploid cells generated by an induced cytokinesis failure that most tetraploids arrest and die in a p53-dependent manner after the first tetraploid mitosis. Furthermore, we found that the main trigger is a mitotic defect, in particular, chromosome missegregation during bipolar mitosis or spindle multipolarity. Both a transient multipolar spindle followed by efficient clustering in anaphase as well as a multipolar spindle followed by multipolar mitosis inhibited subsequent proliferation to a similar degree. We found that the tetraploid cells did not accumulate double-strand breaks that could cause the cell cycle arrest after tetraploid mitosis. In contrast, tetraploid cells showed increased levels of oxidative DNA damage coinciding with the p53 activation. To further elucidate the pathways involved in the proliferation control of tetraploid cells, we knocked down specific kinases that had been previously linked to the cell cycle arrest and p53 phosphorylation. Our results suggest that the checkpoint kinase ATM phosphorylates p53 in tetraploid cells after abnormal mitosis and thus contributes to proliferation control of human aberrantly arising tetraploids.

  4. Plasma polymer-coated contact lenses for the culture and transfer of corneal epithelial cells in the treatment of limbal stem cell deficiency.

    Science.gov (United States)

    Brown, Karl David; Low, Suet; Mariappan, Indumathi; Abberton, Keren Maree; Short, Robert; Zhang, Hong; Maddileti, Savitri; Sangwan, Virender; Steele, David; Daniell, Mark

    2014-02-01

    Extensive damage to the limbal region of the cornea leads to a severe form of corneal blindness termed as limbal stem cell deficiency (LSCD). Whereas most cases of corneal opacity can be treated with full thickness corneal transplants, LSCD requires stem cell transplantation for successful ocular surface reconstruction. Current treatments for LSCD using limbal stem cell transplantation involve the use of murine NIH 3T3 cells and human amniotic membranes as culture substrates, which pose the threat of transmission of animal-derived pathogens and donor tissue-derived cryptic infections. In this study, we aimed to produce surface modified therapeutic contact lenses for the culture and delivery of corneal epithelial cells for the treatment of LSCD. This approach avoids the possibility of suture-related complications and is completely synthetic. We used plasma polymerization to deposit acid functional groups onto the lenses at various concentrations. Each surface was tested for its suitability to promote corneal epithelial cell adhesion, proliferation, retention of stem cells, and differentiation and found that acid-based chemistries promoted better cell adhesion and proliferation. We also found that the lenses coated with a higher percentage of acid functional groups resulted in a higher number of cells transferred onto the corneal wound bed in rabbit models of LSCD. Immunohistochemistry of the recipient cornea confirmed the presence of autologous, transplanted 5-bromo-2'-deoxyuridine (BrdU)-labeled cells. Hematoxylin staining has also revealed the presence of a stratified epithelium at 26 days post-transplantation. This study provides the first evidence for in vivo transfer and survival of cells transplanted from a contact lens to the wounded corneal surface. It also proposes the possibility of using plasma polymer-coated contact lenses with high acid functional groups as substrates for the culture and transfer of limbal cells in the treatment of LSCD.

  5. Volume-dependent K+ transport in rabbit red blood cells comparison with oxygenated human SS cells

    Energy Technology Data Exchange (ETDEWEB)

    Al-Rohil, N.; Jennings, M.L.

    1989-07-01

    In this study the volume-dependent or N-ethylmaleimide (NEM)-stimulated, ouabain-insensitive K+ influx and efflux were measured with the tracer 86Rb+ in rabbit red blood cells. The purpose of the work was to examine the rabbit as a potential model for cell volume regulation in human SS red blood cells and also to investigate the relationship between the NEM-reactive sulfhydryl group(s) and the signal by which cell swelling activates the transport. Ouabain-resistant K+ efflux and influx increase nearly threefold in cells swollen hypotonically by 15%. Pretreatment with 2 mM NEM stimulates efflux 5-fold and influx 10-fold (each measured in an isotonic medium). The ouabain-resistant K+ efflux was dependent on the major anion in the medium. The anion dependence of K+ efflux in swollen or NEM-stimulated cells was as follows: Br- greater than Cl- much greater than NO3- = acetate. The magnitudes of both the swelling- and the NEM-stimulated fluxes are much higher in young cells (density separated but excluding reticulocytes) than in older cells. Swelling- or NEM-stimulated K+ efflux in rabbit red blood cells was inhibited 50% by 1 mM furosemide, and the inhibitory potency of furosemide was enhanced by extracellular K+, as is known to be true for human AA and low-K+ sheep red blood cells. The swelling-stimulated flux in both rabbit and human SS cells has a pH optimum at approximately 7.4. We conclude that rabbit red blood cells are a good model for swelling-stimulated K+ transport in human SS cells.

  6. Characterization of laser doped silicon and overcoming adhesion challenges of solar cells with nickel-copper plated contacts

    Energy Technology Data Exchange (ETDEWEB)

    Geisler, Christian

    2015-07-01

    The combination of localized laser patterning and metal plating allows to replace conventional silver screen printing with nickel-copper plating to form inexpensive front contacts for crystalline silicon solar cells. In this work, a focus is put on effects that could cause inhomogeneous metal deposition and low metal contact adhesion. A descriptive model of the silicon nitride ablation mechanism is derived from SEM imaging and a precise recombination analysis using QSSPC measurements. Surface sensitive XPS measurements are conducted to prove the existence of a parasitic surface layer, identified as SiO{sub x}N{sub y}. The dense SiO{sub x}N{sub y} layer is an effective diffusion barrier, hindering the formation of a nickel silicide interlayer. After removal of the SiO{sub x}N{sub y} layer, cells show severe degradation caused by metal-induced shunting. These shunts are imaged using reverse biased electroluminescence imaging. A shunting mechanism is proposed and experimentally verified. New laser process sequences are devised and proven to produce cells with adhering Ni-Cu contacts. Conclusively the developed processes are assessed based on their industrial feasibility as well as on their efficiency potential.

  7. Studies on ADCC (antibody-dependent cell-mediated cytotoxicity) using sheep red blood cells as target cells, 2

    International Nuclear Information System (INIS)

    Ichikawa, Yukinobu; Takaya, Masatoshi; Arimori, Shigeru

    1979-01-01

    A non-specific cytotoxic mediator from effector cells (human peripheral blood leukocytes) was investigated in the ADCC (antibody-dependent cell-mediated cytotoxicity) system using antibody-coated sheep red blood cells (SRBC) as target cells. 51 Cr-labelled homologous (sheep) or heterologous (human) red blood cells were used as adjacent cells. Either crude lymphocyte fraction, phagocyte depleted fraction or granulocyte rich fraction separated from human peripheral leukocytes showed moderate cytotoxic effect on homologous adjacent cells, however no cytotoxic activity on heterologous adjacent cells was demonstrated in any leukocyte fraction. This suggests that the cytotoxic effects on homologous adjacent cells were resulted from the translocation of antibody molecules to adjacent cells from antibody-coated target cells. We concluded that the cytotoxic mechanism in this ADCC system was not mediated by non-specific soluble factors released from either human peripheral lymphocytes, monocytes or granulocytes. (author)

  8. Differential Effects of Peptidoglycan Recognition Proteins on Experimental Atopic and Contact Dermatitis Mediated by Treg and Th17 Cells

    Science.gov (United States)

    Park, Shin Yong; Gupta, Dipika; Kim, Chang H.; Dziarski, Roman

    2011-01-01

    Skin protects the body from the environment and is an important component of the innate and adaptive immune systems. Atopic dermatitis and contact dermatitis are among the most frequent inflammatory skin diseases and are both determined by multigenic predisposition, environmental factors, and aberrant immune response. Peptidoglycan Recognition Proteins (Pglyrps) are expressed in the skin and we report here that they modulate sensitivity to experimentally-induced atopic dermatitis and contact dermatitis. Pglyrp3 −/− and Pglyrp4 −/− mice (but not Pglyrp2 −/− mice) develop more severe oxazolone-induced atopic dermatitis than wild type (WT) mice. The common mechanism underlying this increased sensitivity of Pglyrp3 −/− and Pglyrp4 −/− mice to atopic dermatitis is reduced recruitment of Treg cells to the skin and enhanced production and activation Th17 cells in Pglyrp3 −/− and Pglyrp4 −/− mice, which results in more severe inflammation and keratinocyte proliferation. This mechanism is supported by decreased inflammation in Pglyrp3 −/− mice following in vivo induction of Treg cells by vitamin D or after neutralization of IL-17. By contrast, Pglyrp1 −/− mice develop less severe oxazolone-induced atopic dermatitis and also oxazolone-induced contact dermatitis than WT mice. Thus, Pglyrp3 and Pglyrp4 limit over-activation of Th17 cells by promoting accumulation of Treg cells at the site of chronic inflammation, which protects the skin from exaggerated inflammatory response to cell activators and allergens, whereas Pglyrp1 has an opposite pro-inflammatory effect in the skin. PMID:21949809

  9. Nanosecond laser scribing of CIGS thin film solar cell based on ITO bottom contact

    Science.gov (United States)

    Kuk, Seungkuk; Wang, Zhen; Fu, Shi; Zhang, Tao; Yu, Yi Yin; Choi, JaeMyung; Jeong, Jeung-hyun; Hwang, David J.

    2018-03-01

    Cu(In,Ga)Se2 (CIGS) thin films, a promising photovoltaic architecture, have mainly relied on Molybdenum for the bottom contact. However, the opaque nature of Molybdenum (Mo) poses limitations in module level fabrication by laser scribing as a preferred method for interconnect. We examined the P1, P2, and P3 laser scribing processes on CIGS photovoltaic architecture on the indium tin oxide (ITO) bottom contact with a cost-effective nanosecond pulsed laser of 532 nm wavelength. Laser illuminated from the substrate side, enabled by the transparent bottom contact, facilitated selective laser energy deposition onto relevant interfaces towards high-quality scribing. Parametric tuning procedures are described in conjunction with experimental and numerical investigation of relevant mechanisms, and preliminary mini-module fabrication results are also presented.

  10. Field, temperature, and angle dependent critical current density Jc(H,T,θ) in coated conductors obtained via contact-free methods

    International Nuclear Information System (INIS)

    Thompson, J R; Christen, D K; Zhang Yifei; Zuev, Y L; Cantoni, C; Sinclair, J W; Chen Yimin; Selvamanickam, V

    2010-01-01

    Applications of coated conductors based on high- T c superconductors often require detailed knowledge of their critical current density J c as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods for obtaining the angularly dependent J c using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.

  11. Field, temperature, and angle dependent critical current density Jc(H,T, ) in coated conductors obtained via contact-free methods

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, James R [ORNL; Sinclair IV, John W [ORNL; Christen, David K [ORNL; Zhang, Yifei [ORNL; Zuev, Yuri L [ORNL; Cantoni, Claudia [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2010-01-01

    Applications of coated conductors based on high-Tc superconductors often require detailed knowledge of their critical current density Jc as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods to obtain the angularly dependent Jc using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.

  12. Field, temperature, and angle dependent critical current density J{sub c}(H,T,{theta}) in coated conductors obtained via contact-free methods

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, J R; Christen, D K; Zhang Yifei; Zuev, Y L; Cantoni, C [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6092 (United States); Sinclair, J W [Department of Physics, University of Tennessee, Knoxville, TN 37996-1200 (United States); Chen Yimin; Selvamanickam, V [SuperPower, Incorporated, 450 Duane Avenue, Schenectady, NY 12304 (United States)

    2010-01-15

    Applications of coated conductors based on high- T{sub c} superconductors often require detailed knowledge of their critical current density J{sub c} as a function of magnetic field orientation as well as field strength and temperature. This work demonstrates experimental methods for obtaining the angularly dependent J{sub c} using contact-free magnetic measurements, and qualifies those methods using several well defined conditions. The studies complement traditional transport techniques and are readily extended to conditions of field and temperature where the current density is very large and transport methods become difficult. Results on representative materials are presented.

  13. Initial stage sintering of polymer particles – Experiments and modelling of size-, temperature- and time-dependent contacts

    Directory of Open Access Journals (Sweden)

    Fuchs Regina

    2017-01-01

    Full Text Available The early-stage sintering of thin layers of micron-sized polystyrene (PS particles, at sintering temperatures near and above the glass transition temperature Tg (~ 100°C, is studied utilizing 3D tomography, nanoindentation and confocal microscopy. Our experimental results confirm the existence of a critical particle radius (rcrit ~ 1 μm below which surface forces need to be considered as additional driving force, on top of the usual surfacetension driven viscous flow sintering mechanism. Both sintering kinetics and mechanical properties of particles smaller than rcrit are dominated by contact deformation due to surface forces, so that sintering of larger particles is generally characterized by viscous flow. Consequently, smaller particles require shorter sintering. These experimental observations are supported by discrete particle simulations that are based on analytical models: for small particles, if only viscous sintering is considered, the model under-predicts the neck radius during early stage sintering, which confirms the need for an additional driving mechanism like elastic-plastic repulsion and surface forces that are both added to the DEM model.

  14. Fire-through Ag contact formation for crystalline Si solar cells using single-step inkjet printing.

    Science.gov (United States)

    Kim, Hyun-Gang; Cho, Sung-Bin; Chung, Bo-Mook; Huh, Joo-Youl; Yoon, Sam S

    2012-04-01

    Inkjet-printed Ag metallization is a promising method of forming front-side contacts on Si solar cells due to its non-contact printing nature and fine grid resolution. However, conventional Ag inks are unable to punch through the SiN(x) anti-reflection coating (ARC) layer on emitter Si surfaces. In this study, a novel formulation of Ag ink is examined for the formation of fire-through contacts on a SiN(x)-coated Si substrate using the single-step printing of Ag ink, followed by rapid thermal annealing at 800 degrees C. In order to formulate Ag inks with fire-through contact formation capabilities, a liquid etching agent was first formulated by dissolving metal nitrates in an organic solvent and then mixing the resulting solution with a commercial Ag nanoparticle ink at various volume ratios. During the firing process, the dissolved metal nitrates decomposed into metal oxides and acted in a similar manner to the glass frit contained in Ag pastes for screen-printed Ag metallization. The newly formulated ink with a 1 wt% loading ratio of metal oxides to Ag formed finely distributed Ag crystallites on the Si substrate after firing at 800 degrees C for 1 min.

  15. Raft-dependent endocytic movement and intracellular cluster formation during T cell activation triggered by concanavalin A.

    Science.gov (United States)

    Yabuuchi, Satomi; Endo, Satoshi; Baek, KeangOk; Hoshino, Kunihide; Tsujino, Yoshio; Vestergaard, Mun'delanji C; Takagi, Masahiro

    2017-12-01

    Certain food ingredients can stimulate the human immune system. A lectin, concanavalin A (ConA), from Canavalia ensiformis (jack bean) is one of the most well-known food-derived immunostimulants and mediates activation of cell-mediated immunity through T cell proliferation. Generally, T cell activation is known to be triggered by the interaction between T cells and antigen-presenting cells (APCs) via a juxtacrine (contact-dependent) signaling pathway. The mechanism has been well characterized and is referred to as formation of the immunological synapse (IS). We were interested in the mechanism behind the T cell activation by food-derived ConA which might be different from that of T cell activation by APCs. The purpose of this study was to characterize T cell activation by ConA with regard to (i) movement of raft domain, (ii) endocytic vesicular transport, (iii) the cytoskeleton (actin and microtubules), and (iv) cholesterol composition. We found that raft-dependent endocytic movement was important for T cell activation by ConA and this movement was dependent on actin, microtubules, and cholesterol. The T cell signaling mechanism triggered by ConA can be defined as endocrine signaling which is distinct from the activation process triggered by interaction between T cells and APCs by juxtacrine signaling. Therefore, we hypothesized that T cell activation by ConA includes both two-dimensional superficial raft movement on the membrane surface along actin filaments and three-dimensional endocytic movement toward the inside of the cell along microtubules. These findings are important for developing new methods for immune stimulation and cancer therapy based on the function of ConA. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  16. Passivating electron contact based on highly crystalline nanostructured silicon oxide layers for silicon solar cells

    Czech Academy of Sciences Publication Activity Database

    Stuckelberger, J.; Nogay, G.; Wyss, P.; Jeangros, Q.; Allebe, Ch.; Debrot, F.; Niquille, X.; Ledinský, Martin; Fejfar, Antonín; Despeisse, M.; Haug, F.J.; Löper, P.; Ballif, C.

    2016-01-01

    Roč. 158, Dec (2016), s. 2-10 ISSN 0927-0248 R&D Projects: GA MŠk LM2015087 Institutional support: RVO:68378271 Keywords : surface passivation * passivating contact * nanostructure * silicon oxide * nanocrystalline * microcrystalline * poly-silicon * crystallization * Raman * transmission line measurement Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.784, year: 2016

  17. Contact Resistance of Tantalum Coatings in Fuel Cells and Electrolyzers using Acidic Electrolytes at Elevated Temperatures

    DEFF Research Database (Denmark)

    Jensen, Annemette Hindhede; Christensen, Erik; Barner, Jens H. Von

    2014-01-01

    stainless steel were found to be far below the US Department of Energy target value of 10mcm2. The good contact resistance of tantalum was demonstrated by simulating high temperature polymer electrolyte membrane electrolysis conditions by anodization performed in 85% phosphoric acid at 130◦C, followed...

  18. A plasmacytoid dendritic cell (CD123+/CD11c-) based assay system to predict contact allergenicity of chemicals

    Science.gov (United States)

    Ayehunie, Seyoum; Snell, Maureen; Child, Matthew; Klausner, Mitchell

    2009-01-01

    A predictive allergenicity test system for assessing the contact allergenicity of chemicals is needed by the cosmetic and pharmaceutical industry to monitor product safety in the marketplace. Development of such non-animal alternative assay systems for skin sensitization and hazard identification has been pursued by policy makers and regulatory agencies. We investigated whether phenotypic and functional changes to a subset of dendritic cells (DC), plasmacytoid DC (pDC), could be used to identify contact allergens. To achieve this goal, normal human DC were generated from CD34+ progenitor cells and cryopreserved. Frozen DC were thawed and the pDC fraction (CD123+/CD11c-) was harvested using FACS sorting. The pDC were cultured, expanded, and exposed to chemical allergens (N=26) or non-allergens (N=22). Concentrations of each chemical that resulted in >50% viability was determined using FACS analysis of propidium iodide stained cells using pDC from 2-5 donors. Expression of the surface marker, CD86, which has been implicated in dendritic cell maturation, was used as a marker of allergenicity. CD86 expression increased (≥ 1.5 fold) for 25 of 26 allergens (sensitivity = 96%) but did not increase for 19 of 22 non-allergens (specificity = 86%). In a direct comparison to historical data for the regulatory approved, mouse local lymph node assay (LLNA) for 23 allergens and 22 non-allergens, the pDC method had sensitivity and specificity of 96% and 86%, respectively, while the sensitivity and specificity of the LLNA assay was 83% and 82%, respectively. In conclusion, CD86 expression in pDC appears to be a sensitive and specific indicator to identify contact allergenicity. Such an assay method utilizing normal human cells will be useful for high throughput screening of chemicals for allergenicity. PMID:19665512

  19. A plasmacytoid dendritic cell (CD123+/CD11c-) based assay system to predict contact allergenicity of chemicals

    International Nuclear Information System (INIS)

    Ayehunie, Seyoum; Snell, Maureen; Child, Matthew; Klausner, Mitchell

    2009-01-01

    A predictive allergenicity test system for assessing the contact allergenicity of chemicals is needed by the cosmetic and pharmaceutical industry to monitor product safety in the marketplace. Development of such non-animal alternative assay systems for skin sensitization and hazard identification has been pursued by policy makers and regulatory agencies. We investigated whether phenotypic and functional changes to a subset of dendritic cells (DC), plasmacytoid DC (pDC), could be used to identify contact allergens. To achieve this goal, normal human DC were generated from CD34+ progenitor cells and cryopreserved. Frozen DC were thawed and the pDC fraction (CD123+/CD11c-) was harvested using FACS sorting. The pDC were cultured, expanded, and exposed to chemical allergens (N = 26) or non-allergens (N = 22). Concentrations of each chemical that resulted in >50% viability was determined using FACS analysis of propidium iodide stained cells using pDC from 2 to 5 donors. Expression of the surface marker, CD86, which has been implicated in dendritic cell maturation, was used as a marker of allergenicity. CD86 expression increased (≥1.5-fold) for 25 of 26 allergens (sensitivity = 96%) but did not increase for 19 of 22 non-allergens (specificity = 86%). In a direct comparison to historical data for the regulatory approved, mouse local lymph node assay (LLNA) for 23 allergens and 22 non-allergens, the pDC method had sensitivity and specificity of 96% and 86%, respectively, while the sensitivity and specificity of the LLNA assay was 83% and 82%, respectively. In conclusion, CD86 expression in pDC appears to be a sensitive and specific indicator to identify contact allergenicity. Such an assay method utilizing normal human cells will be useful for high throughput screening of chemicals for allergenicity.

  20. Electron tomography of the contact between T cells and SIV/HIV-1: implications for viral entry.

    Directory of Open Access Journals (Sweden)

    Rachid Sougrat

    2007-05-01

    Full Text Available The envelope glycoproteins of primate lentiviruses, including human and simian immunodeficiency viruses (HIV and SIV, are heterodimers of a transmembrane glycoprotein (usually gp41, and a surface glycoprotein (gp120, which binds CD4 on target cells to initiate viral entry. We have used electron tomography to determine the three-dimensional architectures of purified SIV virions in isolation and in contact with CD4+ target cells. The trimeric viral envelope glycoprotein surface spikes are heterogeneous in appearance and typically approximately 120 A long and approximately 120 A wide at the distal end. Docking of SIV or HIV-1 on the T cell surface occurs via a neck-shaped contact region that is approximately 400 A wide and consistently consists of a closely spaced cluster of five to seven rod-shaped features, each approximately 100 A long and approximately 100 A wide. This distinctive structure is not observed when viruses are incubated with T lymphocytes in the presence of anti-CD4 antibodies, the CCR5 antagonist TAK779, or the peptide entry inhibitor SIVmac251 C34. For virions bound to cells, few trimers were observed away from this cluster at the virion-cell interface, even in cases where virus preparations showing as many as 70 envelope glycoprotein trimers per virus particle were used. This contact zone, which we term the "entry claw", provides a spatial context to understand the molecular mechanisms of viral entry. Determination of the molecular composition and structure of the entry claw may facilitate the identification of improved drugs for the inhibition of HIV-1 entry.

  1. Viscosity, surface tension, density and contact angle of selected PbI2, PbCl2 and methylammonium lead halide perovskite solutions used in perovskite solar cells

    Directory of Open Access Journals (Sweden)

    Mohammad-Reza Ahmadian-Yazdi

    2018-02-01

    Full Text Available Perovskite solar cells (PSCs are currently under vigorous research and development, owing to their compelling power conversion efficiencies. PSCs are solution-processed and, therefore, are fabricated using casting and printing methods, such as spin, spray and blade coating. The coating characteristics significantly depend on the physical and rheological properties of the solutions. Thus, due to the scarcity of such properties, in this work, we report the surface tension, viscosity, density, and contact angle of selected methylammonium lead halide perovskite solutions, in order to gain insight into the behavior of the perovskite solutions and the range of such physical properties. The contact angles were measured on PEDOT:PSS and compact TiO2 (c-TiO2 substrates, commonly used as the underneath layers of the perovskite film. In total, 12 solutions of CH3NH3PbI3 and CH3NH3PbI3-xClx dissolved in common solvents, as well as solutions of PbI2, PbCl2, and CH3NH3I were tested. Among the results, it is shown that the tested perovskite solutions are Newtonian, the apparent contact angles on the mesoporous TiO2 (m-TiO2 are close to zero, on the PEDOT:PSS are around 10°, and on the c-TiO2 are around 30°. Also, contact angle hysteresis is observed in the case of the c-TiO2 substrates. Representative impact dynamics and spreading of perovskite solution droplets are also studied, to demonstrate the importance of the solution properties and process parameters on the coating process.

  2. Viscosity, surface tension, density and contact angle of selected PbI2, PbCl2 and methylammonium lead halide perovskite solutions used in perovskite solar cells

    Science.gov (United States)

    Ahmadian-Yazdi, Mohammad-Reza; Rahimzadeh, Amin; Chouqi, Zineb; Miao, Yihe; Eslamian, Morteza

    2018-02-01

    Perovskite solar cells (PSCs) are currently under vigorous research and development, owing to their compelling power conversion efficiencies. PSCs are solution-processed and, therefore, are fabricated using casting and printing methods, such as spin, spray and blade coating. The coating characteristics significantly depend on the physical and rheological properties of the solutions. Thus, due to the scarcity of such properties, in this work, we report the surface tension, viscosity, density, and contact angle of selected methylammonium lead halide perovskite solutions, in order to gain insight into the behavior of the perovskite solutions and the range of such physical properties. The contact angles were measured on PEDOT:PSS and compact TiO2 (c-TiO2) substrates, commonly used as the underneath layers of the perovskite film. In total, 12 solutions of CH3NH3PbI3 and CH3NH3PbI3-xClx dissolved in common solvents, as well as solutions of PbI2, PbCl2, and CH3NH3I were tested. Among the results, it is shown that the tested perovskite solutions are Newtonian, the apparent contact angles on the mesoporous TiO2 (m-TiO2) are close to zero, on the PEDOT:PSS are around 10°, and on the c-TiO2 are around 30°. Also, contact angle hysteresis is observed in the case of the c-TiO2 substrates. Representative impact dynamics and spreading of perovskite solution droplets are also studied, to demonstrate the importance of the solution properties and process parameters on the coating process.

  3. Unusual postero-inferior condylar movements that depend on the position of occlusal contact during fictive mastication in rabbits.

    Science.gov (United States)

    Morita, Takumi; Hiraba, Katsunari; Matsunaga, Tomoko; Ito, Yu; Maruo, Hisanobu; Kurita, Kenichi

    2015-03-01

    The mandible can be modelled as a triangular plate supported at two joints and the point of occlusion. The mandible is stable if the vector of the jaw-closing muscle forces lies within the triangle of support. If this vector lies outside of the triangle of support, one of the three contact points will tend to separate as the mandible rotates around a line connecting the other two points. Here, we examined whether postero-inferior condylar movements (Pi-Cm) due to mandibular rotation may occur during fictive mastication in anaesthetized rabbits. EMG activities of the masseter (MS) and lateral pterygoid (LP) muscles and movements of the condyle and incisal points were recorded. Condylar movements in the sagittal plane were recorded using a high speed CCD camera. Pi-Cm were observed on the working side during occlusal phase in half of the rabbits (altered-movement group), if the biting point was restricted at the posterior most tooth (M3) on the working side using a metal biting plate. Pi-Cm appeared in the period between the estimated maximum force of the MS and the LP during late occlusal phase. The MS EMG ratio between the working and balancing sides in the altered-movement group was significantly less than that in the unaltered-movement group. Since the space lying between the condyle and the articular eminence expanded during the Pi-Cm, it is likely that the posterior band of the articular disc tended to slip anteriorly. The clinical significance of the Pi-Cm is discussed concerning the anterior dislocation of the disc in patients with TMJ disorder. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Contact mechanics: contact area and interfacial separation from small contact to full contact

    International Nuclear Information System (INIS)

    Yang, C; Persson, B N J

    2008-01-01

    We present a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. The numerical calculations mainly focus on the contact area and the interfacial separation from small contact (low load) to full contact (high load). For a small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For a high load the contact area approaches the nominal contact area (i.e. complete contact), and the interfacial separation approaches zero. The numerical results have been compared with analytical theory and experimental results. They are in good agreement with each other. The present findings may be very important for soft solids, e.g. rubber, or for very smooth surfaces, where complete contact can be reached at moderately high loads without plastic deformation of the solids

  5. Cell-cycle-dependent regulation of cell motility and determination of the role of Rac1

    DEFF Research Database (Denmark)

    Walmod, Peter S.; Hartmann-Petersen, Rasmus; Prag, S.

    2004-01-01

    comparable to those of control cells in G1. In contrast, transfection with dominant-negative Rac1 reduced cell speed and resulted in cellular displacements, which were identical in G1 and G2. These observations indicate that migration of cultured cells is regulated in a cell-cycle-dependent manner...... for calculation of three key parameters describing cell motility: speed, persistence time and rate of diffusion. All investigated cell lines demonstrated a lower cell displacement in the G2 phase than in the G1/S phases. This was caused by a decrease in speed and/or persistence time. The decrease in motility...... was accompanied by changes in morphology reflecting the larger volume of cells in G2 than in G1. Furthermore, L-cells and HeLa-cells appeared to be less adherent in the G2 phase. Transfection of L-cells with constitutively active Rac1 led to a general increase in the speed and rate of diffusion in G2 to levels...

  6. A Study and Review of Effects of Botulinum Toxins on Mast Cell Dependent and Independent Pruritus.

    Science.gov (United States)

    Ramachandran, Roshni; Marino, Marc J; Paul, Snighdha; Wang, Zhenping; Mascarenhas, Nicholas L; Pellett, Sabine; Johnson, Eric A; DiNardo, Anna; Yaksh, Tony L

    2018-03-23

    Pruriceptive itch originates following activation of peripheral sensory nerve terminals when pruritogens come in contact with the skin. The ability of botulinum neurotoxins (BoNTs) to attenuate transmitter release from afferent terminals provides a rationale for studying its effect on pruritus. This study investigated the effects of BoNT/A1 and BoNT/B1 on mast cell dependent (Compound 48/80:48/80) and independent (Chloroquine:CQ) scratching. C57Bl/6 male mice received intradermal injection of 1.5 U of BoNT/A1, BoNT/B1 or saline 2, 7, 14 and 21 days prior to ipsilateral 48/80 or CQ at the nape of the neck. Ipsilateral hind paw scratching was determined using an automated recording device. The effect of BoNTs on 48/80 mediated mast cell degranulation was analyzed in human and murine mast cells and the presence of SNAREs was determined using qPCR, immunostaining and Western blot. Pre-treatment with BoNT/A1 and BoNT/B1 reduced 48/80 and CQ induced scratching behavior starting on day 2 with reversal by day 21. Both serotypes inhibited 48/80 induced mast cell degranulation. qPCR and immunostaining detected SNAP-25 mRNA and protein, respectively, in mast cells, however, Western blots did not. This study demonstrates the long-lasting anti-pruritic effects of two BoNT serotypes, in a murine pruritus model using two different mechanistically driven pruritogens. These data also indicate that BoNTs may have a direct effect upon mast cell degranulation.

  7. Investigation on the variation of channel resistance and contact resistance of SiZnSnO semiconductor depending on Si contents using transmission line method

    Science.gov (United States)

    Lee, Byeong Hyeon; Han, Sangmin; Lee, Sang Yeol

    2018-01-01

    Amorphous silicon-zinc-tin-oxide (a-SZTO) thin film transistors (TFTs) have been fabricated depending on the silicon ratio in channel layers. The a-SZTO TFT exhibited high electrical properties, such as high mobility of 23 cm2 V-1 s-1, subthreshold swing of 0.74 V/decade and ION/OFF of 2.8 × 108, despite of the addition of Si suppressor. The physical mechanism on the change of the sheet resistance and the contact resistance in a-SZTO TFT has been investigated and proposed closely related with the Si ratio. Both resistances were increased as increasing Si ratio, which clearly indicated that the role of Si is a carrier suppressor directly leading to the increase of channel and contact resistances. To explain the role of Si as a carrier suppressor, the conduction band offset mechanism has been also proposed depending on the change of carrier concentration in channel layer and at the interface between electrode and channel layer. 2007.01-2011.12 Senior Researcher at korea institute of science and technology (KOREA). 2008.01-2011.12 Professor at University of Science and Technology (KOREA). 1995.01-2007.12 Professor at Yonsei University (KOREA). 2002.01-2003.12 Inviting Researcher at Los Alamos National Lab (USA). 1993.01-1995.12 Senior Researcher at Electronics and Telecommunications Research Institute (KOREA). 1992.01-1993.01 Research Associate at State University of New York at Buffalo (USA).

  8. SRT1720 induces lysosomal-dependent cell death of breast cancer cells.

    Science.gov (United States)

    Lahusen, Tyler J; Deng, Chu-Xia

    2015-01-01

    SRT1720 is an activator of SIRT1, a NAD(+)-dependent protein and histone deacetylase that plays an important role in numerous biologic processes. Several studies have illustrated that SRT1720 treatment could improve metabolic conditions in mouse models and in a study in cancer SRT1720 caused increased apoptosis of myeloma cells. However, the effect of SRT1720 on cancer may be complex, as some recent studies have demonstrated that SRT1720 may not directly activate SIRT1 and another study showed that SRT1720 treatment could promote lung metastasis. To further investigate the role of SRT1720 in breast cancer, we treated SIRT1 knockdown and control breast cancer cell lines with SRT1720 both in vitro and in vivo. We showed that SRT1720 more effectively decreased the viability of basal-type MDA-MB-231 and BT20 cells as compared with luminal-type MCF-7 breast cancer cells or nontumorigenic MCF-10A cells. We demonstrated that SRT1720 induced lysosomal membrane permeabilization and necrosis, which could be blocked by lysosomal inhibitors. In contrast, SRT1720-induced cell death occurred in vitro irrespective of SIRT1 status, whereas in nude mice, SRT1720 exhibited a more profound effect in inhibiting the growth of allograft tumors of SIRT1 proficient cells as compared with tumors of SIRT1-deficient cells. Thus, SRT1720 causes lysosomal-dependent necrosis and may be used as a therapeutic agent for breast cancer treatment. ©2014 American Association for Cancer Research.

  9. An improved model for predicting electrical contact resistance between bipolar plate and gas diffusion layer in proton exchange membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zhiliang; Wang, Shuxin [School of Mechanical Engineering, Tianjin University, Tianjin 300072 (China); Zhou, Yuanyuan; Lin, Guosong; Hu, S. Jack [Department of Mechanical Engineering, The University of Michigan, Ann Arbor, MI 48109-2125 (United States)

    2008-07-15

    Electrical contact resistance between bipolar plates (BPPs) and gas diffusion layers (GDLs) in PEM fuel cells has attracted much attention since it is one significant part of the total contact resistance which plays an important role in fuel cell performance. This paper extends a previous model by Zhou et al. [Y. Zhou, G. Lin, A.J. Shih, S.J. Hu, J. Power Sources 163 (2007) 777-783] on the prediction of electrical contact resistance within PEM fuel cells. The original microscale numerical model was based on the Hertz solution for individual elastic contacts, assuming that contact bodies, GDL carbon fibers and BPP asperities are isotropic elastic half-spaces. The new model features a more practical contact by taking into account the bending behavior of carbon fibers as well as their anisotropic properties. The microscale single contact process is solved numerically using the finite element method (FEM). The relationship between the contact pressure and the electrical resistance at the GDL/BPP interface is derived by multiple regression models. Comparisons of the original model by Zhou et al. and the new model with experimental data show that the original model slightly overestimates the electrical contact resistance, whereas a better agreement with experimental data is observed using the new model. (author)

  10. Involvement of up-regulated Necl-5/Tage4/PVR/CD155 in the loss of contact inhibition in transformed NIH3T3 cells

    International Nuclear Information System (INIS)

    Minami, Yukiko; Ikeda, Wataru; Kajita, Mihoko; Fujito, Tsutomu; Monden, Morito; Takai, Yoshimi

    2007-01-01

    Normal cells show contact inhibition of cell movement and proliferation, but this is lost following transformation. We found that Necl-5, originally identified as a poliovirus receptor and up-regulated in many cancer cells, enhances growth factor-induced cell movement and proliferation. We showed that when cells contact other cells, Necl-5 interacts in trans with nectin-3 and is removed by endocytosis from the cell surface, resulting in a reduction of cell movement and proliferation. We show here that up-regulation of the gene encoding Necl-5 by the oncogene V12-Ki-Ras causes enhanced cell movement and proliferation. Upon cell-cell contact, de novo synthesis of Necl-5 exceeds the rate of Necl-5 endocytosis, eventually resulting in a net increase in the amount of Necl-5 at the cell surface. In addition, expression of the gene encoding nectin-3 is markedly reduced in transformed cells. Thus, up-regulation of Necl-5 following transformation contributes to the loss of contact inhibition in transformed cells

  11. High throughput parallel backside contacting and periodic texturing for high-efficiency solar cells

    Science.gov (United States)

    Daniel, Claus; Blue, Craig A.; Ott, Ronald D.

    2014-08-19

    Disclosed are configurations of long-range ordered features of solar cell materials, and methods for forming same. Some features include electrical access openings through a backing layer to a photovoltaic material in the solar cell. Some features include textured features disposed adjacent a surface of a solar cell material. Typically the long-range ordered features are formed by ablating the solar cell material with a laser interference pattern from at least two laser beams.

  12. Regulatory T cells and type 2 innate lymphoid cell-dependent asthma.

    Science.gov (United States)

    Aron, J L; Akbari, O

    2017-08-01

    Group 2 innate lymphoid cells (ILC2s) are a recently identified group of cells with the potent capability to produce Th2-type cytokines such as interleukin (IL)-5 and IL-13. Several studies suggest that ILC2s play an important role in the development of allergic diseases and asthma. Activation of pulmonary ILC2s in murine models lacking T and B cells induces eosinophilia and airway hyper-reactivity (AHR), which are cardinal features of asthma. More importantly, numerous recent studies have highlighted the role of ILC2s in asthma persistence and exacerbation among human subjects, and thus, regulation of pulmonary ILC2s is a major area of investigation aimed at curbing allergic lung inflammation and exacerbation. Emerging evidence reveals that a group of regulatory T cells, induced Tregs (iTregs), effectively suppress the production of ILC2-driven, pro-inflammatory cytokines IL-5 and IL-13. The inhibitory effects of iTregs are blocked by preventing direct cellular contact or by inhibiting the ICOS-ICOS-ligand (ICOSL) pathway, suggesting that both direct contact and ICOS-ICOSL interaction are important in the regulation of ILC2 function. Also, cytokines such as IL-10 and TGF-β1 significantly reduce cytokine secretion by ILC2s. Altogether, these new findings uncover iTregs as potent regulators of ILC2 activation and implicate their utility as a therapeutic approach for the treatment of ILC2-mediated allergic asthma and respiratory disease. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Dependence of cell adhesion on extracellular matrix materials formed on pore bridge boundaries by nanopore opening and closing geometry.

    Science.gov (United States)

    Kim, Sueon; Han, Dong Yeol; Chen, Zhenzhong; Lee, Won Gu

    2018-04-30

    In this study, we report experimental results for characterization of the growth and formation of pore bridge materials that modified the adhesion structures of cells cultured on nanomembranes with opening and closing geometry. To perform the proof-of-concept experiments, we fabricated two types of anodized alumina oxide substrates with single-sided opening (i.e., one side open, but closed at the other side) and double-sided opening (i.e., both sides open). In our experiment, we compared the densities of pores formed and of bridge materials which differently act as connective proteins depending on the size of pores. The results show that the pore opening geometry can be used to promote the net contact force between pores, resulting in the growth and formation of pore bridge materials before and after cell culture. The results also imply that the bridge materials can be used to attract the structural protrusion of filopodia that can promote the adhesion of cell-to-cell and cell-to-pore bridge. It is observed that the shape and size of cellular structures of filopodia depend on the presence of pore bridge materials. Overall, this observation brought us a significant clue that cells cultured on nanopore substrates would change the adhesion property depending on not only the formation of nanopores formed on the surface of topological substrates, but also that of pore bridge materials by its morphological growth.

  14. Investigation of a Spinel-forming Cu-Mn Foam as an Oxygen Electrode Contact Material in a Solid Oxide Cell Single Repeating Unit

    DEFF Research Database (Denmark)

    Zielke, Philipp; Wulff, Anders Christian; Sun, Xiufu

    2017-01-01

    A critical issue in state-of-the-art solid oxide cell stacks is the contacting of the oxygen electrode. The commonly used ceramic contact layers are applied in a green state and cannot be sintered properly, due to compliance limitations arising from other stack components like sealing glasses...

  15. Enhancement of photovoltaic properties of multicrystalline silicon solar cells by combination of buried metallic contacts and thin porous silicon

    Energy Technology Data Exchange (ETDEWEB)

    Ben Rabha, M.; Bessais, B. [Laboratoire de Photovoltaique, Centre de Recherches et des Technologies de l' Energie, Technopole de Borj-Cedria, BP 95, 2050 Hammam-Lif (Tunisia)

    2010-03-15

    Photovoltaic properties of buried metallic contacts (BMCs) with and without application of a front porous silicon (PS) layer on multicrystalline silicon (mc-Si) solar cells were investigated. A Chemical Vapor Etching (CVE) method was used to perform front PS layer and BMCs of mc-Si solar cells. Good electrical performance for the mc-Si solar cells was observed after combination of BMCs and thin PS films. As a result the current-voltage (I-V) characteristics and the internal quantum efficiency (IQE) were improved, and the effective minority carrier diffusion length (Ln) increases from 75 to 110 {mu}m after BMCs achievement. The reflectivity was reduced to 8% in the 450-950 nm wavelength range. This simple and low cost technology induces a 12% conversion efficiency (surface area = 3.2 cm{sup 2}). The obtained results indicate that the BMCs improve charge carrier collection while the PS layer passivates the front surface. (author)

  16. An 8.68% efficiency chemically-doped-free graphene-silicon solar cell using silver nanowires network buried contacts.

    Science.gov (United States)

    Yang, Lifei; Yu, Xuegong; Hu, Weidan; Wu, Xiaolei; Zhao, Yan; Yang, Deren

    2015-02-25

    Graphene-silicon (Gr-Si) heterojunction solar cells have been recognized as one of the most low-cost candidates in photovoltaics due to its simple fabrication process. However, the high sheet resistance of chemical vapor deposited (CVD) Gr films is still the most important limiting factor for the improvement of the power conversion efficiency of Gr-Si solar cells, especially in the case of large device-active area. In this work, we have fabricated a novel transparent conductive film by hybriding a monolayer Gr film with silver nanowires (AgNWs) network soldered by the graphene oxide (GO) flakes. This Gr-AgNWs hybrid film exhibits low sheet resistance and larger direct-current to optical conductivity ratio, quite suitable for solar cell fabrication. An efficiency of 8.68% has been achieved for the Gr-AgNWs-Si solar cell, in which the AgNWs network acts as buried contacts. Meanwhile, the Gr-AgNWs-Si solar cells have much better stability than the chemically doped Gr-Si solar cells. These results show a new route for the fabrication of high efficient and stable Gr-Si solar cells.

  17. Molybdenum thin film deposited by in-line DC magnetron sputtering as a back contact for Cu(In,Ga)Se{sub 2} solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Li Zhaohui; Cho, Eou-Sik [Department of Electronics Engineering, Kyungwon University, San 65, Bokjung-dong, Soojung-gu, Seongnam city, Kyunggi-do, 461-701 (Korea, Republic of); Kwon, Sang Jik, E-mail: sjkwon@kyungwon.ac.kr [Department of Electronics Engineering, Kyungwon University, San 65, Bokjung-dong, Soojung-gu, Seongnam city, Kyunggi-do, 461-701 (Korea, Republic of)

    2011-09-01

    In this paper, we reported the effect of the power and the working pressure on the molybdenum (Mo) films deposited using an in-line direct current (DC) magnetron sputtering system. The electrical and the structural properties of Mo film were improved by increasing DC power from 1 to 3 kW. On the other side, the resistivity of the Mo films became higher with the increasing working pressure. However, the adhesion property was improved when the working pressure was higher. In this work, in order to obtain an optimal Mo film as a back metal contact of Cu(In,Ga)Se{sub 2} (CIGS) solar cells, a bilayer Mo film was formed through the different film structures depending on the working pressure. The first layer was formed at a high pressure of 12 mTorr for a better adhesion and the second layer was formed at a low pressure of 3 mTorr for a lower resistivity.

  18. Language Contact.

    Science.gov (United States)

    Nelde, Peter Hans

    1995-01-01

    Examines the phenomenon of language contact and recent trends in linguistic contact research, which focuses on language use, language users, and language spheres. Also discusses the role of linguistic and cultural conflicts in language contact situations. (13 references) (MDM)

  19. Opposite cytokine synthesis by fibroblasts in contact co-culture with osteosarcoma cells compared with transwell co-cultures.

    Science.gov (United States)

    David, Manu S; Kelly, Elizabeth; Zoellner, Hans

    2013-04-01

    We recently reported exchange of membrane and cytoplasm during contact co-culture between human Gingival Fibroblasts (h-GF) and SAOS-2 osteosarcoma cells, a process we termed 'cellular sipping' to reflect the manner in which cells become morphologically diverse through uptake of material from the opposing cell type, independent of genetic change. Cellular sipping is increased by Tumor Necrosis Factor-α (TNF-α), and we here show for the first time altered cytokine synthesis in contact co-culture supporting cellular sipping compared with co-culture where h-GF and SAOS-2 were separated in transwells. SAOS-2 had often undetectably low cytokine levels, while Interleukin-6 (IL-6), Granulocyte Colony Stimulating Factor (G-CSF) and Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) were secreted primarily by TNF-α stimulated h-GF and basic Fibroblast Growth Factor (FGF) was prominent in h-GF lysates (p cultures permitting cellular sipping had lower IL-6, G-CSF and GM-CSF levels, as well as higher lysate FGF levels compared with TNF-α treated h-GF alone (p cultures in transwells, with increased IL-6, G-CSF and GM-CSF levels (p cultures where cellular sipping occurs, potentially contributing to tumor inflammatory responses. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.

  20. Hole-Collection Mechanism in Passivating Metal-Oxide Contacts on Si Solar Cells: Insights From Numerical Simulations

    KAUST Repository

    Vijayan, Ramachandran Ammapet

    2018-02-14

    Silicon heterojunction solar cells enable high conversion efficiencies, thanks to their passivating contacts which consist of layered stacks of intrinsic and doped amorphous silicon. However, such contacts may reduce the photo current, when present on the illuminated side of the cell. This motivates the search for wider bandgap contacting materials, such as metal oxides. In this paper, we elucidate the precise impact of the material parameters of MoO$_{x}$ on device characteristics, based on numerical simulations. The simulation results allow us to propose design principles for hole-collecting induced junctions. We find that if MoO$_{x}$ has a sufficiently high electron affinity ($\\\\ge\\\\! \\\\text{{5.7 eV}}$), direct band-to-band tunneling is the dominant transport mechanism; whereas if it has a lower electron affinity ($ <\\\\! \\\\text{{5.7 eV}}$), trap-assisted tunneling dominates, which might introduce additional series resistance. At even lower electron affinity, S-shaped J–V curves may appear for these solar cells, which are found to be due to an insufficient trap state density in the MoO$_{x}$ film in contrast to the expectation of better performance at low trap density. These traps may assist carrier transport when present near the conduction band edge of the MoO$_{x}$ film. Our simulations predict that performance optimization for the MoO$_{x}$ film has to target either 1) a high electron affinity and a moderate doping density film or, 2) if the electron affinity is lower than the optimum value, a high defect density not exceeding the doping density inside the film.

  1. Crosslinked Remote-Doped Hole-Extracting Contacts Enhance Stability under Accelerated Lifetime Testing in Perovskite Solar Cells.

    Science.gov (United States)

    Xu, Jixian; Voznyy, Oleksandr; Comin, Riccardo; Gong, Xiwen; Walters, Grant; Liu, Min; Kanjanaboos, Pongsakorn; Lan, Xinzheng; Sargent, Edward H

    2016-04-13

    A crosslinked hole-extracting electrical contact is reported, which simultaneously improves the stability and lowers the hysteresis of perovskite solar cells. Polymerizable monomers and crosslinking processes are developed to obviate in situ degradation of the under lying perovskite. The crosslinked material is band-aligned with perovskite. The required free carrier density is induced by a high-work-function metal oxide layer atop the device, following a remote-doping strategy. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Inhibition of Breast Cancer Progression by Blocking Heterocellular Contact Between Epithelial Cells and Fibroblasts

    Science.gov (United States)

    2013-04-01

    tumor cells and fibroblasts in co-cultures.14 More recently, cell– polymer suspensions microinjected in collagen gels have been used to form 3D cell...Spaink, B. van de Water and E. H. J. Danen, Automated microinjection of cell- polymer suspensions in 3D ECM scaffolds for high-through- put quantitative...operation The microfluidic devices were fabricated using multilayered SU-8 molds and PDMS- based soft-lithography. In brief, three layers of SU8 -100

  3. Intermittent contact of fluidized anode particles containing exoelectrogenic biofilms for continuous power generation in microbial fuel cells

    KAUST Repository

    Liu, Jia

    2014-09-01

    Current generation in a microbial fuel cell can be limited by the amount of anode surface area available for biofilm formation, and slow substrate degradation kinetics. Increasing the anode surface area can increase the amount of biofilm, but performance will improve only if the anode material is located near the cathode to minimize solution internal resistance. Here we demonstrate that biofilms do not have to be in constant contact with the anode to produce current in an MFC. Granular activated carbon particles enriched with exoelectrogenic biofilm are fluidized (by stirring) in the anode chamber of the MFC, resulting in only intermittent contact between the particles and the anode current collector. The maximum power density generated is 951 ± 10 mW m-2, compared to 813 ± 2 mW m-2 for the control without stirring (packed bed), and 525 ± 1 mW m-2 in the absence of GAC particles and without stirring. GAC-biofilm particles demonstrate capacitor-like behavior, but achieve nearly constant discharge conditions due to the large number of particles that contact the current collector. These results provide proof of concept for the development of flowable electrode reactors, where anode biofilms can be electrically charged in a separate storage tank and then rapidly discharged in compact anode chambers. © 2014 Elsevier B.V. All rights reserved.

  4. Intermittent contact of fluidized anode particles containing exoelectrogenic biofilms for continuous power generation in microbial fuel cells

    KAUST Repository

    Liu, Jia; Zhang, Fang; He, Weihua; Zhang, Xiaoyuan; Feng, Yujie; Logan, Bruce E.

    2014-01-01

    Current generation in a microbial fuel cell can be limited by the amount of anode surface area available for biofilm formation, and slow substrate degradation kinetics. Increasing the anode surface area can increase the amount of biofilm, but performance will improve only if the anode material is located near the cathode to minimize solution internal resistance. Here we demonstrate that biofilms do not have to be in constant contact with the anode to produce current in an MFC. Granular activated carbon particles enriched with exoelectrogenic biofilm are fluidized (by stirring) in the anode chamber of the MFC, resulting in only intermittent contact between the particles and the anode current collector. The maximum power density generated is 951 ± 10 mW m-2, compared to 813 ± 2 mW m-2 for the control without stirring (packed bed), and 525 ± 1 mW m-2 in the absence of GAC particles and without stirring. GAC-biofilm particles demonstrate capacitor-like behavior, but achieve nearly constant discharge conditions due to the large number of particles that contact the current collector. These results provide proof of concept for the development of flowable electrode reactors, where anode biofilms can be electrically charged in a separate storage tank and then rapidly discharged in compact anode chambers. © 2014 Elsevier B.V. All rights reserved.

  5. The heparin-binding domain of HB-EGF mediates localization to sites of cell-cell contact and prevents HB-EGF proteolytic release

    Energy Technology Data Exchange (ETDEWEB)

    Prince, Robin N.; Schreiter, Eric R.; Zou, Peng; Wiley, H. S.; Ting, Alice Y.; Lee, Richard T.; Lauffenburger, Douglas A.

    2010-07-01

    Heparin-binding EGF-like growth factor (HB-EGF) is a ligand for EGF receptor (EGFR) and possesses the ability to signal in juxtacrine, autocrine and/or paracrine mode, with these alternatives being governed by the degree of proteolytic release of the ligand. Although the spatial range of diffusion of released HB-EGF is restricted by binding heparan-sulfate proteoglycans (HSPGs) in the extracellular matrix and/or cellular glycocalyx, ascertaining mechanisms governing non-released HB-EGF localization is also important for understanding its effects. We have employed a new method for independently tracking the localization of the extracellular EGFlike domain of HB-EGF and the cytoplasmic C-terminus. A striking observation was the absence of the HB-EGF transmembrane proform from the leading edge of COS-7 cells in a wound-closure assay; instead, this protein localized in regions of cell-cell contact. A battery of detailed experiments found that this localization derives from a trans interaction between extracellular HSPGs and the HBEGF heparin-binding domain, and that disruption of this interaction leads to increased release of soluble ligand and a switch in cell phenotype from juxtacrine-induced growth inhibition to autocrine-induced proliferation. Our results indicate that extracellular HSPGs serve to sequester the transmembrane pro-form of HB-EGF at the point of cell-cell contact, and that this plays a role in governing the balance between juxtacrine versus autocrine and paracrine signaling.

  6. Myosin-Va-dependent cell-to-cell transfer of RNA from Schwann cells to axons.

    Directory of Open Access Journals (Sweden)

    José R Sotelo

    Full Text Available To better understand the role of protein synthesis in axons, we have identified the source of a portion of axonal RNA. We show that proximal segments of transected sciatic nerves accumulate newly-synthesized RNA in axons. This RNA is synthesized in Schwann cells because the RNA was labeled in the complete absence of neuronal cell bodies both in vitro and in vivo. We also demonstrate that the transfer is prevented by disruption of actin and that it fails to occur in the absence of myosin-Va. Our results demonstrate cell-to-cell transfer of RNA and identify part of the mechanism required for transfer. The induction of cell-to-cell RNA transfer by injury suggests that interventions following injury or degeneration, particularly gene therapy, may be accomplished by applying them to nearby glial cells (or implanted stem cells at the site of injury to promote regeneration.

  7. Myosin-Va-dependent cell-to-cell transfer of RNA from Schwann cells to axons.

    Science.gov (United States)

    Sotelo, José R; Canclini, Lucía; Kun, Alejandra; Sotelo-Silveira, José R; Xu, Lei; Wallrabe, Horst; Calliari, Aldo; Rosso, Gonzalo; Cal, Karina; Mercer, John A

    2013-01-01

    To better understand the role of protein synthesis in axons, we have identified the source of a portion of axonal RNA. We show that proximal segments of transected sciatic nerves accumulate newly-synthesized RNA in axons. This RNA is synthesized in Schwann cells because the RNA was labeled in the complete absence of neuronal cell bodies both in vitro and in vivo. We also demonstrate that the transfer is prevented by disruption of actin and that it fails to occur in the absence of myosin-Va. Our results demonstrate cell-to-cell transfer of RNA and identify part of the mechanism required for transfer. The induction of cell-to-cell RNA transfer by injury suggests that interventions following injury or degeneration, particularly gene therapy, may be accomplished by applying them to nearby glial cells (or implanted stem cells) at the site of injury to promote regeneration.

  8. Establishment of cell lines from adult T-cell leukemia cells dependent on negatively charged polymers.

    Science.gov (United States)

    Kagami, Yoshitoyo; Uchiyama, Susumu; Kato, Harumi; Okada, Yasutaka; Seto, Masao; Kinoshita, Tomohiro

    2017-07-05

    Growing adult T-cell leukemia/lymphoma (ATLL) cells in vitro is difficult. Here, we examined the effects of static electricity in the culture medium on the proliferation of ATLL cells. Six out of 10 ATLL cells did not proliferate in vitro and thus had to be cultured in a medium containing negatively charged polymers. In the presence of poly-γ-glutamic acid (PGA) or chondroitin sulfate (CDR), cell lines (HKOX3-PGA, HKOX3-CDR) were established from the same single ATLL case using interleukin (IL)-2, IL-4, and feeder cells expressing OX40L (OX40L + HK). Dextran sulfate inhibited growth in both HKOX3 cell lines. Both PGA and OX40L + HK were indispensable for HKOX3-PGA growth, but HKOX3-CDR could proliferate in the presence of CDR or OX40L + HK alone. Thus, the specific action of each negatively charged polymer promoted the growth of specific ATLL cells in vitro.

  9. Experimental study on direct-contact liquid film cooling simulated dense-array solar cells in high concentrating photovoltaic system

    International Nuclear Information System (INIS)

    Wang, Yiping; Shi, Xusheng; Huang, Qunwu; Cui, Yong; Kang, Xue

    2017-01-01

    Highlights: • Direct-contact liquid film cooling dense-array solar cells was first proposed. • Average temperature was controlled well below 80 °C. • The maximum temperature difference was less than 10 °C. • The heat transfer coefficient reached up to 11.91 kW/(m"2·K) under 589X. - Abstract: This paper presented a new method of cooling dense-array solar cells in high concentrating photovoltaic system by direct-contact liquid film, and water was used as working fluid. An electric heating plate was designed to simulate the dense-array solar cells in high concentrating photovoltaic system. The input power of electric heating plate simulated the concentration ratios. By heat transfer experiments, the effect of water temperatures and flow rates on heat transfer performance was investigated. The results indicated that: the average temperature of simulated solar cells was controlled well below 80 °C under water temperature of 30 °C and flow rate of 300 L/h when concentration ratio ranged between 300X and 600X. The maximum temperature difference among temperature measurement points was less than 10 °C, which showed the temperature distribution was well uniform. The heat transfer coefficient reached up to 11.91 kW/(m"2·K) under concentration ratio of 589X. To improve heat transfer performance and obtain low average temperature of dense-array solar cells, lower water temperature and suitable water flow rate are preferred.

  10. Interdigitated Back-Surface-Contact Solar Cell Modeling Using Silvaco Atlas

    Science.gov (United States)

    2015-06-01

    and Gallium Arsenide, and triple -junction cells with Indium Gallium Phosphide, Gallium Arsenide, and Germanium. Work was also done by Fotis [4] on...output power at various points on the IV curve, from [15]. ............................18 Figure 15. IV curve with the MPP. The orange area is...53 Figure 35. Simulation results of cell power output at maximum power point for varying bulk thicknesses

  11. Inducible ablation of mouse Langerhans cells diminishes but fails to abrogate contact hypersensitivity

    NARCIS (Netherlands)

    Bennett, Clare L.; van Rijn, Erwin; Jung, Steffen; Inaba, Kayo; Steinman, Ralph M.; Kapsenberg, Martien L.; Clausen, Björn E.

    2005-01-01

    Langerhans cells (LC) form a unique subset of dendritic cells ( DC) in the epidermis but so far their in vivo functions in skin immunity and tolerance could not be determined, in particular in relation to dermal DC ( dDC). Here, we exploit a novel diphtheria toxin (DT) receptor (DTR)/ DT- based

  12. Glycosynapses: microdomains controlling carbohydrate-dependent cell adhesion and signaling

    Directory of Open Access Journals (Sweden)

    Senitiroh Hakomori

    2004-09-01

    Full Text Available The concept of microdomains in plasma membranes was developed over two decades, following observation of polarity of membrane based on clustering of specific membrane components. Microdomains involved in carbohydrate-dependent cell adhesion with concurrent signal transduction that affect cellular phenotype are termed "glycosynapse". Three types of glycosynapse have been distinguished: "type 1" having glycosphingolipid associated with signal transducers (small G-proteins, cSrc, Src family kinases and proteolipids; "type 2" having O-linked mucin-type glycoprotein associated with Src family kinases; and "type 3" having N-linked integrin receptor complexed with tetraspanin and ganglioside. Different cell types are characterized by presence of specific types of glycosynapse or their combinations, whose adhesion induces signal transduction to either facilitate or inhibit signaling. E.g., signaling through type 3 glycosynapse inhibits cell motility and differentiation. Glycosynapses are distinct from classically-known microdomains termed "caveolae", "caveolar membrane", or more recently "lipid raft", which are not involved in carbohydrate-dependent cell adhesion. Type 1 and type 3 glycosynapses are resistant to cholesterol-binding reagents, whereas structure and function of "caveolar membrane" or "lipid raft" are disrupted by these reagents. Various data indicate a functional role of glycosynapses during differentiation, development, and oncogenic transformation.O conceito de microdomínios em membrana plasmática foi desenvolvido há mais de duas décadas, após a observação da polaridade da membrana baseada no agrupamento de componentes específicos da membrana. Microdomínios envolvidos na adesão celular dependente de carboidrato, com transdução de sinal que afeta o fenótipo celular são denominados ''glicosinapses''. Três tipos de glicosinapse foram observados: ''tipo 1'' que possue glicoesfingolipídio associado com transdutores de sinal

  13. HTSC-Josephson step contacts

    International Nuclear Information System (INIS)

    Herrmann, K.

    1994-03-01

    In this work the properties of josephson step contacts are investigated. After a short introduction into Josephson step contacts the structure, properties and the Josphson contacts of YBa 2 Cu 3 O 7-x high-T c superconductors is presented. The fabrication of HTSC step contacts and the microstructure is discussed. The electric properties of these contacts are measured together with the Josephson emission and the magnetic field dependence. The temperature dependence of the stationary transport properties is given. (WL)

  14. Interface studies on the tunneling contact of a MOCVD-prepared tandem solar cell; Grenzflaechenuntersuchungen am Tunnelkontakt einer MOCVD-praeparierten Tandemsolarzelle

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, U.

    2007-07-10

    In this thesis a tandem solar cell with a novel tunneling contact was developed. For the development of the monolithic preparation especailly critical hetero-interfaces were studied in the region of the tunneling contact with surface-sensitive measuring method. The tandem solar cell consisted of single solar cells with absorber layers of In{sub 0.53}Ga{sub 0.47}As (E{sub g}=0.73 eV) and In{sub 0.78}Ga{sub 0.22}As{sub 0.491}P{sub 0.51} (E{sub g}=1.03 eV), the serial switching of which was pursued with a tunneling contact (ESAKI diode, which consisted of a very thin n-doped InGaAs and a p-doped GaAsSb layer. The III-V semiconductor layers were prepared by metalorganic gas phase epitaxy (MOCVD) monocrystallinely on an InP(100) substrate lattice-matchedly. Especially the influence of the preparation of InGaAs surfaces on the sharpness of the InGaAs/GaAsSb interface was in-situ studied by reflection-anisotropy spectroscopy and after a contamination-free transfer into the ultrahigh vacuum with photoelectron spectroscopy and with low-energetic electron diffraction (LEED). Thereby for the first time three different reconstructions of the MOCVD-prepared InGaAs surfaces could be observed, which were dependent on the heating temperature under pure hydrogen. The arsenic-rich InGaAs surface was observed for temperatures less than 300 C and showed in the LEED picture a (4 x 3) reconstruction. In the temperature range from 300 C until about 500 C a (2 x 4) reconstruction was observed, above 500 C the InGaAs surface 94 x 2)/c(8 x 2) was reconstructed. Subsequently the study of the growth of thin GaAsSb layers on these three InGaAs surface reconstructions followed. XPS measurements showed that the Sb/As ratio in GaAsSb at the growth on the As-rich (4 x 3) reconstructed surface in the first monolayers was too low. The preparation of the GaAsSb on the two other InGaAs surfaces yielded however in both cases a distinctly higher Sb/As ratio. Finally tandem solar cells with differently

  15. Proliferation and differentiation of stem cells in contact with eluate from fibrin-rich plasma membrane

    Directory of Open Access Journals (Sweden)

    Fernanda Gimenez de Souza

    Full Text Available ABSTRACT Objective: To evaluate the ability of the eluate from fibrin-rich plasma (FRP membrane to induce proliferation and differentiation of isolated human adipose-derived stem cells (ASCs into chondrocytes. Method: FRP membranes were obtained by centrifugation of peripheral blood from two healthy donors, cut, and maintained in culture plate wells for 48 h to prepare the fibrin eluate. The SCATh were isolated from adipose tissue by collagenase digestion solution, and expanded in vitro. Cells were expanded and treated with DMEM-F12 culture, a commercial media for chondrogenic differentiation, and eluate from FRP membrane for three days, and labeled with BrdU for quantitative assessment of cell proliferation using the High-Content Operetta® imaging system. For the chondrogenic differentiation assay, the SCATh were grown in micromass for 21 days and stained with toluidine blue and aggrecan for qualitative evaluation by light microscopy. The statistical analysis was performed using ANOVA and Tukey's test. Results: There was a greater proliferation of cells treated with the eluate from FRP membrane compared to the other two treatments, where the ANOVA test showed significance (p < 0.001. The differentiation into chondrocytes was visualized by the presence of mucopolysaccharide in the matrix of the cells marked in blue toluidine and aggrecan. Conclusions: Treatment with eluate from FRP membrane stimulated cell proliferation and induced differentiation of the stem cells into chondrocytes, suggesting a potential application of FRP membranes in hyaline cartilage regeneration therapies.

  16. Control of Listeria innocua Biofilms on Food Contact Surfaces with Slightly Acidic Electrolyzed Water and the Risk of Biofilm Cells Transfer to Duck Meat.

    Science.gov (United States)

    Jeon, Hye Ri; Kwon, Mi Jin; Yoon, Ki Sun

    2018-04-01

    Biofilm formation on food contact surfaces is a potential hazard leading to cross-contamination during food processing. We investigated Listeria innocua biofilm formation on various food contact surfaces and compared the washing effect of slightly acidic electrolyzed water (SAEW) at 30, 50, 70, and 120 ppm with that of 200 ppm of sodium hypochlorite (NaClO) on biofilm cells. The risk of L. innocua biofilm transfer and growth on food at retail markets was also investigated. The viability of biofilms that formed on food contact surfaces and then transferred cells to duck meat was confirmed by fluorescence microscopy. L. innocua biofilm formation was greatest on rubber, followed by polypropylene, glass, and stainless steel. Regardless of sanitizer type, washing removed biofilms from polypropylene and stainless steel better than from rubber and glass. Among the various SAEW concentrations, washing with 70 ppm of SAEW for 5 min significantly reduced L. innocua biofilms on food contact surfaces during food processing. Efficiency of transfer of L. innocua biofilm cells was the highest on polypropylene and lowest on stainless steel. The transferred biofilm cells grew to the maximum population density, and the lag time of transferred biofilm cells was longer than that of planktonic cells. The biofilm cells that transferred to duck meat coexisted with live, injured, and dead cells, which indicates that effective washing is essential to remove biofilm on food contact surfaces during food processing to reduce the risk of foodborne disease outbreaks.

  17. The Frequency Spectral Properties of Electrode-Skin Contact Impedance on Human Head and Its Frequency-Dependent Effects on Frequency-Difference EIT in Stroke Detection from 10Hz to 1MHz.

    Directory of Open Access Journals (Sweden)

    Lin Yang

    Full Text Available Frequency-difference electrical impedance tomography (fdEIT reconstructs frequency-dependent changes of a complex impedance distribution. It has a potential application in acute stroke detection because there are significant differences in impedance spectra between stroke lesions and normal brain tissues. However, fdEIT suffers from the influences of electrode-skin contact impedance since contact impedance varies greatly with frequency. When using fdEIT to detect stroke, it is critical to know the degree of measurement errors or image artifacts caused by contact impedance. To our knowledge, no study has systematically investigated the frequency spectral properties of electrode-skin contact impedance on human head and its frequency-dependent effects on fdEIT used in stroke detection within a wide frequency band (10 Hz-1 MHz. In this study, we first measured and analyzed the frequency spectral properties of electrode-skin contact impedance on 47 human subjects' heads within 10 Hz-1 MHz. Then, we quantified the frequency-dependent effects of contact impedance on fdEIT in stroke detection in terms of the current distribution beneath the electrodes and the contact impedance imbalance between two measuring electrodes. The results showed that the contact impedance at high frequencies (>100 kHz significantly changed the current distribution beneath the electrode, leading to nonnegligible errors in boundary voltages and artifacts in reconstructed images. The contact impedance imbalance at low frequencies (<1 kHz also caused significant measurement errors. We conclude that the contact impedance has critical frequency-dependent influences on fdEIT and further studies on reducing such influences are necessary to improve the application of fdEIT in stroke detection.

  18. The Frequency Spectral Properties of Electrode-Skin Contact Impedance on Human Head and Its Frequency-Dependent Effects on Frequency-Difference EIT in Stroke Detection from 10Hz to 1MHz.

    Science.gov (United States)

    Yang, Lin; Dai, Meng; Xu, Canhua; Zhang, Ge; Li, Weichen; Fu, Feng; Shi, Xuetao; Dong, Xiuzhen

    2017-01-01

    Frequency-difference electrical impedance tomography (fdEIT) reconstructs frequency-dependent changes of a complex impedance distribution. It has a potential application in acute stroke detection because there are significant differences in impedance spectra between stroke lesions and normal brain tissues. However, fdEIT suffers from the influences of electrode-skin contact impedance since contact impedance varies greatly with frequency. When using fdEIT to detect stroke, it is critical to know the degree of measurement errors or image artifacts caused by contact impedance. To our knowledge, no study has systematically investigated the frequency spectral properties of electrode-skin contact impedance on human head and its frequency-dependent effects on fdEIT used in stroke detection within a wide frequency band (10 Hz-1 MHz). In this study, we first measured and analyzed the frequency spectral properties of electrode-skin contact impedance on 47 human subjects' heads within 10 Hz-1 MHz. Then, we quantified the frequency-dependent effects of contact impedance on fdEIT in stroke detection in terms of the current distribution beneath the electrodes and the contact impedance imbalance between two measuring electrodes. The results showed that the contact impedance at high frequencies (>100 kHz) significantly changed the current distribution beneath the electrode, leading to nonnegligible errors in boundary voltages and artifacts in reconstructed images. The contact impedance imbalance at low frequencies (<1 kHz) also caused significant measurement errors. We conclude that the contact impedance has critical frequency-dependent influences on fdEIT and further studies on reducing such influences are necessary to improve the application of fdEIT in stroke detection.

  19. Manifestation of π-contacts in magnetic field dependence of I-V characteristics for proximity-type 2D Josephson junction array

    International Nuclear Information System (INIS)

    Rivera, V.A.G.; Sergeenkov, S.; Marega, E.; Araujo-Moreira, F.M.

    2009-01-01

    Results on the temperature and magnetic field dependence of current-voltage characteristics (CVC) are presented for SNS-type 2D ordered array of Nb-Cu 0.95 Al 0.05 -Nb junctions. The critical current I C (T,H) and the power exponent a(T,H)=1+Φ 0 I C (T,H)/2k B T of the nonlinear CVC law V=R[I-I C (T,H)] a(T,H) are found to have a maximum at non-zero value of applied magnetic field H p =225 Oe, which is attributed to manifestation of π-type Josephson contacts in our sample.

  20. A small molecular pH-dependent fluorescent probe for cancer cell imaging in living cell.

    Science.gov (United States)

    Ma, Junbao; Li, Wenqi; Li, Juanjuan; Shi, Rongguang; Yin, Gui; Wang, Ruiyong

    2018-05-15

    A novel pH-dependent two-photon fluorescent molecular probe ABMP has been prepared based on the fluorophore of 2, 4, 6-trisubstituted pyridine. The probe has an absorption wavelength at 354 nm and corresponding emission wavelength at 475 nm with the working pH range from 2.20 to 7.00, especially owning a good liner response from pH = 2.40 to pH = 4.00. ABMP also has excellent reversibility, photostability and selectivity which promotes its ability in analytical application. The probe can be excited with a two-photon fluorescence microscopy and the fluorescence cell imaging indicated that the probe can distinguish Hela cancer cells out of normal cells with a two-photon fluorescence microscopy which suggested its potential application in tumor cell detection. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Bulk Heterojunction Organic Solar Cell Area-Dependent Parameter Fluctuation

    Directory of Open Access Journals (Sweden)

    A. J. Trindade

    2017-01-01

    Full Text Available Organic solar cell efficiency is known to be active area dependent and is usually a problem in the upscale factor for market applications. In this work, a detailed study of organic photovoltaic devices with active layer based on poly(3-hexylthiophene (P3HT and 1-(3-methoxycarbonyl-propyl-1-phenyl-(6,6C61 (PCBM is made, evaluating the effect of the change on the active area from 10−2 to 4 cm4. The device structure was kept simple in order to allow the understanding of the physical effects involved. Device figures of merit were extracted from the equivalent circuit using a genetic-based algorithm, and their relationship with the active area was compared. It is observed that the efficiency drops significantly with the active area increase (as the fill factor while the parallel and series resistance, adjusted to the active area, seems to be relatively constant and increases linearly, respectively. The short circuit current and the generated photocurrent also drop significantly with the active area increase. The open circuit voltage does not show major changes. These results are discussed considering the main influences for the observed efficiency data. Particularly, as the basic circuit model seems to fail to explain the macroscopic results, the behavior can be related with the enlargement of defect interaction.

  2. Intraspecies Variability Affects Heterotypic Biofilms of Porphyromonas gingivalis and Prevotella intermedia: Evidences of Strain-Dependence Biofilm Modulation by Physical Contact and by Released Soluble Factors.

    Directory of Open Access Journals (Sweden)

    Graziela Murta Barbosa

    Full Text Available It is well known that strain and virulence diversity exist within the population structure of Porphyromonas gingivalis. In the present study we investigate intra- and inter-species variability in biofilm formation of Porphyromonas gingivalis and partners Prevotella intermedia and Prevotella nigrescens. All strains tested showed similar hydrophobicity, except for P. gingivalis W83 which has roughly half of the hydrophobicity of P. gingivalis ATCC33277. An intraspecies variability in coaggregation of P. gingivalis with P. intermedia was also found. The association P. gingivalis W83/P. intermedia 17 produced the thickest biofilm and strain 17 was prevalent. In a two-compartment system P. gingivalis W83 stimulates an increase in biomass of strain 17 and the latter did not stimulate the growth of P. gingivalis W83. In addition, P. gingivalis W83 also stimulates the growth of P. intermedia ATCC25611 although strain W83 was prevalent in the association with P. intermedia ATCC25611. P. gingivalis ATCC33277 was prevalent in both associations with P. intermedia and both strains of P. intermedia stimulate the growth of P. gingivalis ATCC33277. FISH images also showed variability in biofilm structure. Thus, the outcome of the association P. gingivalis/P. intermedia seems to be strain-dependent, and both soluble factors and physical contact are relevant. The association P. gingivalis-P. nigrescens ATCC33563 produced larger biomass than each monotypic biofilm, and P. gingivalis was favored in consortia, while no differences were found in the two-compartment system. Therefore, in consortia P. gingivalis-P. nigrescens physical contact seems to favor P. gingivalis growth. The intraspecies variability found in our study suggests strain-dependence in ability of microorganisms to recognize molecules in other bacteria which may further elucidate the dysbiosis event during periodontitis development giving additional explanation for periodontal bacteria, such as P

  3. Intraspecies Variability Affects Heterotypic Biofilms of Porphyromonas gingivalis and Prevotella intermedia: Evidences of Strain-Dependence Biofilm Modulation by Physical Contact and by Released Soluble Factors.

    Science.gov (United States)

    Barbosa, Graziela Murta; Colombo, Andrea Vieira; Rodrigues, Paulo Henrique; Simionato, Maria Regina Lorenzetti

    2015-01-01

    It is well known that strain and virulence diversity exist within the population structure of Porphyromonas gingivalis. In the present study we investigate intra- and inter-species variability in biofilm formation of Porphyromonas gingivalis and partners Prevotella intermedia and Prevotella nigrescens. All strains tested showed similar hydrophobicity, except for P. gingivalis W83 which has roughly half of the hydrophobicity of P. gingivalis ATCC33277. An intraspecies variability in coaggregation of P. gingivalis with P. intermedia was also found. The association P. gingivalis W83/P. intermedia 17 produced the thickest biofilm and strain 17 was prevalent. In a two-compartment system P. gingivalis W83 stimulates an increase in biomass of strain 17 and the latter did not stimulate the growth of P. gingivalis W83. In addition, P. gingivalis W83 also stimulates the growth of P. intermedia ATCC25611 although strain W83 was prevalent in the association with P. intermedia ATCC25611. P. gingivalis ATCC33277 was prevalent in both associations with P. intermedia and both strains of P. intermedia stimulate the growth of P. gingivalis ATCC33277. FISH images also showed variability in biofilm structure. Thus, the outcome of the association P. gingivalis/P. intermedia seems to be strain-dependent, and both soluble factors and physical contact are relevant. The association P. gingivalis-P. nigrescens ATCC33563 produced larger biomass than each monotypic biofilm, and P. gingivalis was favored in consortia, while no differences were found in the two-compartment system. Therefore, in consortia P. gingivalis-P. nigrescens physical contact seems to favor P. gingivalis growth. The intraspecies variability found in our study suggests strain-dependence in ability of microorganisms to recognize molecules in other bacteria which may further elucidate the dysbiosis event during periodontitis development giving additional explanation for periodontal bacteria, such as P. gingivalis and P

  4. Antigenic protein synthesis of Campylobacter jejuni in contact with chicken cells

    DEFF Research Database (Denmark)

    Vegge, Christina Skovgaard; Bang, Dang D.; Li, Yiping

    the synthesis of antigenic C. jejuni proteins upon cultivation with chicken cells. Two strains of C. jejuni (the human isolate NCTC11168 and the chicken isolate DVI-SC11) were incubated with primary intestinal chicken cells and subsequently used to raise antisera in rabbits. Negative controls were carried out...... to the environment of the avian gastrointestinal tract. Consequently, the most important reservoir for C. jejuni is the gut of chickens, which are colonized efficiently without causing disease in the birds. Upon co-cultivation with mammalian cells, C. jejuni secrete specific Cia proteins, which are required...... for internalization into host cells. However, the pathogenic lifestyle of C. jejuni in the human intestine is different from the commensal colonization of the chicken gut, and it was therefore hypothesized that different proteins are secreted during chicken colonization. This hypothesis was tested by analyzing...

  5. The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells.

    Directory of Open Access Journals (Sweden)

    Nezha Ahmad Agha

    Full Text Available Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity.

  6. The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells.

    Science.gov (United States)

    Ahmad Agha, Nezha; Willumeit-Römer, Regine; Laipple, Daniel; Luthringer, Bérengère; Feyerabend, Frank

    2016-01-01

    Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys) is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells) are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity.

  7. Tumor endothelial marker 5 expression in endothelial cells during capillary morphogenesis is induced by the small GTPase Rac and mediates contact inhibition of cell proliferation

    Energy Technology Data Exchange (ETDEWEB)

    Vallon, Mario, E-mail: m.vallon@arcor.de [Nuklearmedizinische Klinik und Poliklinik, Technische Universitaet Muenchen, Ismaninger Strasse 22, 81675 Munich (Germany); Rohde, Franziska; Janssen, Klaus-Peter [Chirurgische Klinik und Poliklinik, Technische Universitaet Muenchen, Munich (Germany); Essler, Markus [Nuklearmedizinische Klinik und Poliklinik, Technische Universitaet Muenchen, Ismaninger Strasse 22, 81675 Munich (Germany)

    2010-02-01

    Tumor endothelial marker (TEM) 5 is an adhesion G-protein-coupled receptor upregulated in endothelial cells during tumor and physiologic angiogenesis. So far, the mechanisms leading to upregulation of TEM5 and its function during angiogenesis have not been identified. Here, we report that TEM5 expression in endothelial cells is induced during capillary-like network formation on Matrigel, during capillary morphogenesis in a three-dimensional collagen I matrix, and upon confluence on a two-dimensional matrix. TEM5 expression was not induced by a variety of soluble angiogenic factors, including VEGF and bFGF, in subconfluent endothelial cells. TEM5 upregulation was blocked by toxin B from Clostridium difficile, an inhibitor of the small GTPases Rho, Rac, and Cdc42. The Rho inhibitor C3 transferase from Clostridium botulinum did not affect TEM5 expression, whereas the Rac inhibitor NSC23766 suppressed TEM5 upregulation. An excess of the soluble TEM5 extracellular domain or an inhibitory monoclonal TEM5 antibody blocked contact inhibition of endothelial cell proliferation resulting in multilayered islands within the endothelial monolayer and increased vessel density during capillary formation. Based on our results we conclude that TEM5 expression during capillary morphogenesis is induced by the small GTPase Rac and mediates contact inhibition of proliferation in endothelial cells.

  8. Enhanced Contacts for Inverted Metamorphic Multi-Junction Solar Cells Using Carbon Nanotube Metal Matrix Composites

    Science.gov (United States)

    2018-01-18

    substrates through a shadow mask. The native oxide was removed by HCl (hydrochloric acid) immersion immediately before the deposition process...34Pushing Inverted Metamorphic Multijunction Solar Cells Toward Higher Efficiency at Realistic Operating Conditions," IEEE Journal of Photovoltaics, vol. 3...Multijunction Solar Cells," IEEE Journal of Photovoltaics, vol. 2, pp. 377-381, Jul 2012. [7] F. Newman, et al., "PROGRESS IN ADAPTING INVERTED

  9. CONTACT RESISTANCE MODELING

    Directory of Open Access Journals (Sweden)

    S. V. LOSKUTOV

    2018-05-01

    Full Text Available Purpose. To determine the contribution of the real contact spots distribution in the total conductivity of the conductors contact. Methodology. The electrical contact resistance research was carried out on models. The experimental part of this work was done on paper with a graphite layer with membranes (the first type and conductive liquids with discrete partitions (the second type. Findings. It is shown that the contact electrical resistance is mainly determined by the real area of metal contact. The experimental dependence of the electrical resistance of the second type model on the distance between the electrodes and the potential distribution along the sample surface for the first type model were obtained. The theoretical model based on the principle of electric field superposition was considered. The dependences obtained experimentally and calculated by using the theoretical model are in good agreement. Originality. The regularity of the electrical contact resistance formation on a large number of membranes was researched for the first time. A new model of discrete electrical contact based on the liquid as the conducting environment with nuclear membrane partitions was developed. The conclusions of the additivity of contact and bulk electrical resistance were done. Practical value. Based on these researches, a new experimental method of kinetic macroidentation that as a parameter of the metal surface layer deformation uses the real contact area was developed. This method allows to determine the value of average contact stresses, yield point, change of the stress on the depth of deformation depending on the surface treatment.

  10. Mitochondrial Sirt3 supports cell proliferation by regulating glutamine-dependent oxidation in renal cell carcinoma

    International Nuclear Information System (INIS)

    Choi, Jieun; Koh, Eunjin; Lee, Yu Shin; Lee, Hyun-Woo; Kang, Hyeok Gu; Yoon, Young Eun; Han, Woong Kyu; Choi, Kyung Hwa; Kim, Kyung-Sup

    2016-01-01

    Clear cell renal carcinoma (RCC), the most common malignancy arising in the adult kidney, exhibits increased aerobic glycolysis and low mitochondrial respiration due to von Hippel-Lindau gene defects and constitutive hypoxia-inducible factor-α expression. Sirt3 is a major mitochondrial deacetylase that mediates various types of energy metabolism. However, the role of Sirt3 as a tumor suppressor or oncogene in cancer depends on cell types. We show increased Sirt3 expression in the mitochondrial fraction of human RCC tissues. Sirt3 depletion by lentiviral short-hairpin RNA, as well as the stable expression of the inactive mutant of Sirt3, inhibited cell proliferation and tumor growth in xenograft nude mice, respectively. Furthermore, mitochondrial pyruvate, which was used for oxidation in RCC, might be derived from glutamine, but not from glucose and cytosolic pyruvate, due to depletion of mitochondrial pyruvate carrier and the relatively high expression of malic enzyme 2. Depletion of Sirt3 suppressed glutamate dehydrogenase activity, leading to impaired mitochondrial oxygen consumption. Our findings suggest that Sirt3 plays a tumor-progressive role in human RCC by regulating glutamine-derived mitochondrial respiration, particularly in cells where mitochondrial usage of cytosolic pyruvate is severely compromised. -- Highlights: •Sirt3 is required for the maintenance of RCC cell proliferation. •Mitochondrial usage of cytosolic pyruvate is severely compromised in RCC. •Sirt3 supports glutamine-dependent oxidation in RCC.

  11. Mitochondrial Sirt3 supports cell proliferation by regulating glutamine-dependent oxidation in renal cell carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jieun; Koh, Eunjin; Lee, Yu Shin; Lee, Hyun-Woo; Kang, Hyeok Gu [Department of Biochemistry and Molecular Biology, Brain Korea 21 PLUS Project for Medical Sciences, Institute of Genetic Science, Integrated Genomic Research Center for Metabolic Regulation, Yonsei University College of Medicine, Seoul 120-752 (Korea, Republic of); Yoon, Young Eun; Han, Woong Kyu [Department of Urology, Urological Science Institute, Yonsei University College of Medicine, Seoul 120-752 (Korea, Republic of); Choi, Kyung Hwa [Department of Urology, CHA Bundang Medical Center, CHA University, Seongnam 463-712 (Korea, Republic of); Kim, Kyung-Sup, E-mail: KYUNGSUP59@yuhs.ac [Department of Biochemistry and Molecular Biology, Brain Korea 21 PLUS Project for Medical Sciences, Institute of Genetic Science, Integrated Genomic Research Center for Metabolic Regulation, Yonsei University College of Medicine, Seoul 120-752 (Korea, Republic of)

    2016-06-03

    Clear cell renal carcinoma (RCC), the most common malignancy arising in the adult kidney, exhibits increased aerobic glycolysis and low mitochondrial respiration due to von Hippel-Lindau gene defects and constitutive hypoxia-inducible factor-α expression. Sirt3 is a major mitochondrial deacetylase that mediates various types of energy metabolism. However, the role of Sirt3 as a tumor suppressor or oncogene in cancer depends on cell types. We show increased Sirt3 expression in the mitochondrial fraction of human RCC tissues. Sirt3 depletion by lentiviral short-hairpin RNA, as well as the stable expression of the inactive mutant of Sirt3, inhibited cell proliferation and tumor growth in xenograft nude mice, respectively. Furthermore, mitochondrial pyruvate, which was used for oxidation in RCC, might be derived from glutamine, but not from glucose and cytosolic pyruvate, due to depletion of mitochondrial pyruvate carrier and the relatively high expression of malic enzyme 2. Depletion of Sirt3 suppressed glutamate dehydrogenase activity, leading to impaired mitochondrial oxygen consumption. Our findings suggest that Sirt3 plays a tumor-progressive role in human RCC by regulating glutamine-derived mitochondrial respiration, particularly in cells where mitochondrial usage of cytosolic pyruvate is severely compromised. -- Highlights: •Sirt3 is required for the maintenance of RCC cell proliferation. •Mitochondrial usage of cytosolic pyruvate is severely compromised in RCC. •Sirt3 supports glutamine-dependent oxidation in RCC.

  12. A cellular Potts model for the MMP-dependent and -independent cancer cell migration in matrix microtracks of different dimensions

    Science.gov (United States)

    Scianna, Marco; Preziosi, Luigi

    2014-03-01

    Cell migration is fundamental in a wide variety of physiological and pathological phenomena, among other in cancer invasion and development. In particular, the migratory/invasive capability of single metastatic cells is fundamental in determining the malignancy of a solid tumor. Specific cell migration phenotypes result for instance from the reciprocal interplay between the biophysical and biochemical properties of both the malignant cells themselves and of the surrounding environment. In particular, the extracellular matrices (ECMs) forming connective tissues can provide both loosely organized zones and densely packed barriers, which may impact cell invasion mode and efficiency. The critical processes involved in cell movement within confined spaces are (i) the proteolytic activity of matrix metalloproteinases (MMPs) and (ii) the deformation of the entire cell body, and in particular of the nucleus. We here present an extended cellular Potts model (CPM) to simulate a bio-engineered matrix system, which tests the active motile behavior of a single cancer cell into narrow channels of different widths. As distinct features of our approach, the cell is modeled as a compartmentalized discrete element, differentiated in the nucleus and in the cytosolic region, while a directional shape-dependent movement is explicitly driven by the evolution of its polarity vector. As outcomes, we find that, in a large track, the tumor cell is not able to maintain a directional movement. On the contrary, a structure of subcellular width behaves as a contact guidance sustaining cell persistent locomotion. In particular, a MMP-deprived cell is able to repolarize and follow the micropattern geometry, while a full MMP activity leads to a secondary track expansion by degrading the matrix structure. Finally, we confirm that cell movement within a subnuclear structure can be achieved either by pericellular proteolysis or by a significant deformation of cell nucleus.

  13. Capture of cell culture-derived influenza virus by lectins: strain independent, but host cell dependent.

    Science.gov (United States)

    Opitz, Lars; Zimmermann, Anke; Lehmann, Sylvia; Genzel, Yvonne; Lübben, Holger; Reichl, Udo; Wolff, Michael W

    2008-12-01

    Strategies to control influenza outbreaks are focused mainly on prophylactic vaccination. Human influenza vaccines are trivalent blends of different virus subtypes. Therefore and due to frequent antigenic drifts, strain independent manufacturing processes are required for vaccine production. This study verifies the strain independency of a capture method based on Euonymus europaeus lectin-affinity chromatography (EEL-AC) for downstream processing of influenza viruses under various culture conditions propagated in MDCK cells. A comprehensive lectin binding screening was conducted for two influenza virus types from the season 2007/2008 (A/Wisconsin/67/2005, B/Malaysia/2506/2004) including a comparison of virus-lectin interaction by surface plasmon resonance technology. EEL-AC resulted in a reproducible high product recovery rate and a high degree of contaminant removal in the case of both MDCK cell-derived influenza virus types demonstrating clearly the general applicability of EEL-AC. In addition, host cell dependency of EEL-AC was studied with two industrial relevant cell lines: Vero and MDCK cells. However, the choice of the host cell lines is known to lead to different product glycosylation profiles. Hence, altered lectin specificities have been observed between the two cell lines, requiring process adaptations between different influenza vaccine production systems.

  14. Cell cycle age dependence for radiation-induced G2 arrest: evidence for time-dependent repair

    International Nuclear Information System (INIS)

    Rowley, R.

    1985-01-01

    Exponentially growing eucaryotic cells, irradiated in interphase, are delayed in progression to mitosis chiefly by arrest in G 2 . The sensitivity of Chinese hamster ovary cells to G 2 arrest induction by X rays increases through the cell cycle, up to the X-ray transition point (TP) in G 2 . This age response can be explained by cell cycle age-dependent changes in susceptibility of the target(s) for G 2 arrest and/or by changes in capability for postirradiation recovery from G 2 arrest damage. Discrimination between sensitivity changes and repair phenomena is possible only if the level of G 2 arrest-causing damage sustained by a cell at the time of irradiation and the level ultimately expressed as arrest can be determined. The ability of caffeine to ameliorate radiation-induced G 2 arrest, while inhibiting repair of G 2 arrest-causing damage makes such an analysis possible. In the presence of caffeine, progression of irradiated cells was relatively unperturbed, but on caffeine removal, G 2 arrest was expressed. The duration of G 2 arrest was independent of the length of the prior caffeine exposure. This finding indicates that the target for G 2 arrest induction is present throughout the cell cycle and that the level of G 2 arrest damage incurred is initially constant for all cell cycle phases. The data are consistent with the existence of a time-dependent recovery mechanism to explain the age dependence for radiation induction of G 2 arrest

  15. Scribble is required for normal epithelial cell–cell contacts and lumen morphogenesis in the mammalian lung

    Science.gov (United States)

    Yates, Laura L.; Schnatwinkel, Carsten; Hazelwood, Lee; Chessum, Lauren; Paudyal, Anju; Hilton, Helen; Romero, M. Rosario; Wilde, Jonathan; Bogani, Debora; Sanderson, Jeremy; Formstone, Caroline; Murdoch, Jennifer N.; Niswander, Lee A.; Greenfield, Andy; Dean, Charlotte H.

    2013-01-01

    During lung development, proper epithelial cell arrangements are critical for the formation of an arborized network of tubes. Each tube requires a lumen, the diameter of which must be tightly regulated to enable optimal lung function. Lung branching and lumen morphogenesis require close epithelial cell–cell contacts that are maintained as a result of adherens junctions, tight junctions and by intact apical–basal (A/B) polarity. However, the molecular mechanisms that maintain epithelial cohesion and lumen diameter in the mammalian lung are unknown. Here we show that Scribble, a protein implicated in planar cell polarity (PCP) signalling, is necessary for normal lung morphogenesis. Lungs of the Scrib mouse mutant Circletail (Crc) are abnormally shaped with fewer airways, and these airways often lack a visible, ‘open’ lumen. Mechanistically we show that Scrib genetically interacts with the core PCP gene Vangl2 in the developing lung and that the distribution of PCP pathway proteins and Rho mediated cytoskeletal modification is perturbed in ScribCrc/Crc lungs. However A/B polarity, which is disrupted in Drosophila Scrib mutants, is largely unaffected. Notably, we find that Scrib mediates functions not attributed to other PCP proteins in the lung. Specifically, Scrib localises to both adherens and tight junctions of lung epithelia and knockdown of Scrib in lung explants and organotypic cultures leads to reduced cohesion of lung epithelial cells. Live imaging of Scrib knockdown lungs shows that Scrib does not affect bud bifurcation, as previously shown for the PCP protein Celsr1, but is required to maintain epithelial cohesion. To understand the mechanism leading to reduced cell–cell association, we show that Scrib associates with β-catenin in embryonic lung and the sub-cellular distribution of adherens and tight junction proteins is perturbed in mutant lung epithelia. Our data reveal that Scrib is required for normal lung epithelial organisation and lumen

  16. Microglia Induce Neurotoxic IL-17+ γδ T Cells Dependent on TLR2, TLR4, and TLR9 Activation.

    Directory of Open Access Journals (Sweden)

    Katja Derkow

    Full Text Available Interleukin-17 (IL-17 acts as a key regulator in central nervous system (CNS inflammation. γδ T cells are an important innate source of IL-17. Both IL-17+ γδ T cells and microglia, the major resident immune cells of the brain, are involved in various CNS disorders such as multiple sclerosis and stroke. Also, activation of Toll-like receptor (TLR signaling pathways contributes to CNS damage. However, the mechanisms underlying the regulation and interaction of these cellular and molecular components remain unclear.In this study, we investigated the crosstalk between γδ T cells and microglia activated by TLRs in the context of neuronal damage. To this end, co-cultures of IL-17+ γδ T cells, neurons, and microglia were analyzed by immunocytochemistry, flow cytometry, ELISA and multiplex immunoassays.We report here that IL-17+ γδ T cells but not naïve γδ T cells induce a dose- and time-dependent decrease of neuronal viability in vitro. While direct stimulation of γδ T cells with various TLR ligands did not result in up-regulation of CD69, CD25, or in IL-17 secretion, supernatants of microglia stimulated by ligands specific for TLR2, TLR4, TLR7, or TLR9 induced activation of γδ T cells through IL-1β and IL-23, as indicated by up-regulation of CD69 and CD25 and by secretion of vast amounts of IL-17. This effect was dependent on the TLR adaptor myeloid differentiation primary response gene 88 (MyD88 expressed by both γδ T cells and microglia, but did not require the expression of TLRs by γδ T cells. Similarly to cytokine-primed IL-17+ γδ T cells, IL-17+ γδ T cells induced by supernatants derived from TLR-activated microglia also caused neurotoxicity in vitro. While these neurotoxic effects required stimulation of TLR2, TLR4, or TLR9 in microglia, neuronal injury mediated by bone marrow-derived macrophages did not require TLR signaling. Neurotoxicity mediated by IL-17+ γδ T cells required a direct cell-cell contact between T

  17. Distribution of electrode elements near contacts and junction layers in amorphous silicon solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Imura, T; Hiraki, A; Okamoto, H

    1982-01-01

    Auger electron spectroscopy with the ion sputter-etching technique and secondary ion mass spectroscopy have been utilized to investigate the depth distribution of Sn and In electrode elements in amorphous silicon layers of the photovoltaic device. The comparison of the depth profiles with the cell performances has indicated that the presence of the reduced state of In in both the p and i-layers affects the solar cell performance, but that of Sn does not. It was also shown that layered structure of In-Sn oxide (ITO)/SnO2 effectively prevents the diffusion of In and achieves high cell performances, having the thickness of the SnO2 layer about 200 A. 8 references.

  18. Imiquimod activates p53-dependent apoptosis in a human basal cell carcinoma cell line.

    Science.gov (United States)

    Huang, Shi-Wei; Chang, Shu-Hao; Mu, Szu-Wei; Jiang, Hsin-Yi; Wang, Sin-Ting; Kao, Jun-Kai; Huang, Jau-Ling; Wu, Chun-Ying; Chen, Yi-Ju; Shieh, Jeng-Jer

    2016-03-01

    The tumor suppressor p53 controls DNA repair, cell cycle, apoptosis, autophagy and numerous other cellular processes. Imiquimod (IMQ), a synthetic toll-like receptor (TLR) 7 ligand for the treatment of superficial basal cell carcinoma (BCC), eliminates cancer cells by activating cell-mediated immunity and directly inducing apoptosis and autophagy in cancer cells. To evaluate the role of p53 in IMQ-induced cell death in skin cancer cells. The expression, phosphorylation and subcellular localization of p53 were detected by real-time PCR, luciferase reporter assay, cycloheximide chase analysis, immunoblotting and immunocytochemistry. Using BCC/KMC1 cell line as a model, the upstream signaling of p53 activation was dissected by over-expression of TLR7/8, the addition of ROS scavenger, ATM/ATR inhibitors and pan-caspase inhibitor. The role of p53 in IMQ-induced apoptosis and autophagy was assessed by genetically silencing p53 and evaluated by a DNA content assay, immunoblotting, LC3 puncta detection and acridine orange staining. IMQ induced p53 mRNA expression and protein accumulation, increased Ser15 phosphorylation, promoted nuclear translocation and up-regulated its target genes in skin cancer cells in a TLR7/8-independent manner. In BCC/KMC1 cells, the induction of p53 by IMQ was achieved through increased ROS production to stimulate the ATM/ATR-Chk1/Chk2 axis but was not mediated by inducing DNA damage. The pharmacological inhibition of ATM/ATR significantly suppressed IMQ-induced p53 activation and apoptosis. Silencing of p53 significantly decreased the IMQ-induced caspase cascade activation and apoptosis but enhanced autophagy. Mutant p53 skin cancer cell lines were more resistant to IMQ-induced apoptosis than wildtype p53 skin cancer cell lines. IMQ induced ROS production to stimulate ATM/ATR pathways and contributed to p53-dependent apoptosis in a skin basal cell carcinoma cell line BCC/KMC1. Copyright © 2015 Japanese Society for Investigative Dermatology

  19. From nano to micro: topographical scale and its impact on cell adhesion, morphology and contact guidance

    International Nuclear Information System (INIS)

    Nguyen, Anh Tuan; Sathe, Sharvari R; Yim, Evelyn K F

    2016-01-01

    Topography, among other physical factors such as substrate stiffness and extracellular forces, is known to have a great influence on cell behaviours. Optimization of topographical features, in particular topographical dimensions ranging from nanoscale to microscale, is the key strategy to obtain the best cellular performance for various applications in tissue engineering and regenerative medicine. In this review, we provide a comprehensive survey on the significance of sizes of topography and their impacts on cell adhesion, morphology and alignment, and neurite guidance. Also recent works mimicking the hierarchical structure of natural extracellular matrix by combining both nanoscale and microscale topographies are highlighted. (topical review)

  20. Trench process and structure for backside contact solar cells with polysilicon doped regions

    Science.gov (United States)

    De Ceuster, Denis; Cousins, Peter John; Smith, David D.

    2010-12-14

    A solar cell includes polysilicon P-type and N-type doped regions on a backside of a substrate, such as a silicon wafer. An interrupted trench structure separates the P-type doped region from the N-type doped region in some locations but allows the P-type doped region and the N-type doped region to touch in other locations. Each of the P-type and N-type doped regions may be formed over a thin dielectric layer. Among other advantages, the resulting solar cell structure allows for increased efficiency while having a relatively low reverse breakdown voltage.

  1. EGFR-dependent signalling reduced and p38 dependent apoptosis required by Gallic acid in Malignant Mesothelioma cells.

    Science.gov (United States)

    Demiroglu-Zergeroglu, Asuman; Candemir, Gulsife; Turhanlar, Ebru; Sagir, Fatma; Ayvali, Nurettin

    2016-12-01

    The unrestrained EGFR signalling contributes to malignant phenotype in a number of cancers including Malignant Mesotheliomas. Present study was designed to evaluate EGFR-dependent anti-proliferative and apoptotic effects of Gallic acid in transformed Mesothelial (MeT-5A) and Malignant Mesothelioma (SPC212) cells. Gallic acid reduced the viability of Malignant Mesothelioma cells in a concentration and time-dependent manner. However, viability of mesothelial cells reduced only at high concentration and longer time periods. Gallic acid restrained the activation of EGFR, ERK1/2 and AKT proteins and down regulated expression of Cyclin D and Bcl-2 genes, but upregulated the expression of p21 gene in EGF-induced SPC212 cells. GA-induced transitory G1 arrest and triggered mitochondrial and death receptor mediated apoptosis, which requires p38MAPK activation. The data provided here indicate that GA is able to inhibit EGFR dependent proliferation and survival signals and induces p38 pathway dependent apoptosis in Malignant Mesothelioma cells. On the basis of these experimental findings it is worthwhile to investigate further the biological activity of Gallic acid on other Mesothelioma cell lines harbouring aberrant EGFR signals. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  2. Efficiency loss prevention in monolithically integrated thin film solar cells by improved front contact

    NARCIS (Netherlands)

    Deelen, J. van; Barink, M.; Klerk, L.; Voorthuijzen, P.; Hovestad, A.

    2015-01-01

    Modeling indicates a potential efficiency boost of 17% if thin-film solar panels are featured with a metallic grid. Variations of transparent conductive oxide sheet resistance, cell length, and grid dimensions are discussed. These parameters were optimized simultaneously to obtain the best result.

  3. Metabolic cleavage of cell-penetrating peptides in contact with epithelial models

    DEFF Research Database (Denmark)

    Tréhin, Rachel; Nielsen, Hanne Mørck; Jahnke, Heinz-Georg

    2004-01-01

    We assessed the metabolic degradation kinetics and cleavage patterns of some selected CPP (cell-penetrating peptides) after incubation with confluent epithelial models. Synthesis of N-terminal CF [5(6)-carboxyfluorescein]-labelled CPP, namely hCT (human calcitonin)-derived sequences, Tat(47-57) a...

  4. Dendritic cell migration assay: a potential prediction model for identification of contact allergens.

    Science.gov (United States)

    Gibbs, Susan; Spiekstra, Sander; Corsini, Emanuela; McLeod, Julie; Reinders, Judith

    2013-04-01

    This manuscript describes methodology and a prediction model for the MUTZ-LC migration assay. The assay represents the physiological change in Langerhans cell (LC) behavior after exposure to a sensitizing chemical, resulting in LC migration from the epidermis to the dermis. MUTZ-LC are derived from the commercially available MUTZ-3 cell line. Upon exposure to a sensitizer MUTZ-LC migrate preferentially towards CXCL12 whereas upon exposure to a non-sensitizer MUTZ-LC migrate towards CCL5. A CXCL12/CCL5 ratio >1.10 in 2/3 independent experiments is indicative of a sensitizer, whereas a CXCL12/CCL5 ratio ≤1.10 is indicative of a non-sensitizer. At non cytotoxic chemical concentrations 9 sensitizers (2,4-dinitrochlorobenzene, paraphenylendiamine, cinnamaldehyde, isoeugenol, nickel-sulfate, tetramethylthiuram disulfide, eugenol, cinnamic-alcohol, ammonium-hexachloroplatinate) were distinguished from 4 non sensitizers (sodium lauryl sulfate, salicylic acid, phenol, octanoic acid). Critical points in assay performance are (i) MUTZ-3 passage number after thawing (p6-p40); (ii) cell viability (>80%); (iii) standard curve to optimize correlation of fluorescence with cell number; and (iv) optimization of the concentration of rhCXCL12 and rhCCL5 in transwell. The protocol has been tested in three European laboratories and results suggest that it may provide working conditions for performing the DC migration assay which is aimed at distinguishing sensitizers from non sensitizers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Interstitial cell migration: integrin-dependent and alternative adhesion mechanisms.

    NARCIS (Netherlands)

    Schmidt, S.; Friedl, P.H.A.

    2010-01-01

    Adhesion and migration are integrated cell functions that build, maintain and remodel the multicellular organism. In migrating cells, integrins are the main transmembrane receptors that provide dynamic interactions between extracellular ligands and actin cytoskeleton and signalling machineries. In

  6. Backup pathways of NHEJ in cells of higher eukaryotes: Cell cycle dependence

    International Nuclear Information System (INIS)

    Iliakis, George

    2009-01-01

    DNA double-strand breaks (DSBs) induced by ionizing radiation (IR) in cells of higher eukaryotes are predominantly repaired by a pathway of non-homologous end joining (NHEJ) utilizing Ku, DNA-PKcs, DNA ligase IV, XRCC4 and XLF/Cernunnos (D-NHEJ) as central components. Work carried out in our laboratory and elsewhere shows that when this pathway is chemically or genetically compromised, cells do not shunt DSBs to homologous recombination repair (HRR) but instead use another form of NHEJ operating as a backup (B-NHEJ). Here I review our efforts to characterize this repair pathway and discuss its dependence on the cell cycle as well as on the growth conditions. I present evidence that B-NHEJ utilizes ligase III, PARP-1 and histone H1. When B-NHEJ is examined throughout the cell cycle, significantly higher activity is observed in G2 phase that cannot be attributed to HRR. Furthermore, the activity of B-NHEJ is compromised when cells enter the plateau phase of growth. Together, these observations uncover a repair pathway with unexpected biochemical constitution and interesting cell cycle and growth factor regulation. They generate a framework for investigating the mechanistic basis of HRR contribution to DSB repair.

  7. Special regulatory T-cell review: T-cell dependent suppression revisited.

    Science.gov (United States)

    Basten, Antony; Fazekas de St Groth, Barbara

    2008-01-01

    The concept of T-cell dependent regulation of immune responses has been a central tenet of immunological thinking since the delineation of the two cell system in the 1960s. Indeed T-cell dependent suppression was discovered before MHC restriction. When reviewing the data from the original wave of suppression, it is intriguing to reflect not just on the decline and fall of suppressor T cells in the 1980s, but on their equally dramatic return to respectability over the past decade. Hopefully their resurgence will be supported by solid mechanistic data that will underpin their central place in our current and future understanding of the immune system. Cannon to right of them, Cannon to left of them, Cannon in front of them Volley'd and thunder'd Storm'd at with shot and shell, Boldly they rode and well, Into the jaws of Death, Into the mouth of Hell, Rode the six hundred (suppressionists). (Adapted from The Charge of the Light Brigade, Alfred, Lord Tennyson)

  8. Chelerythrine induced cell death through ROS-dependent ER stress in human prostate cancer cells

    Directory of Open Access Journals (Sweden)

    Wu S

    2018-05-01

    Full Text Available Songjiang Wu, Yanying Yang, Feiping Li, Lifu Huang, Zihua Han, Guanfu Wang, Hongyuan Yu, Haiping Li Department of Urology, Enze Hospital of Taizhou Enze Medical Center (Group, Taizhou, China Introduction: Prostate cancer is the most common noncutaneous cancer and the second leading cause of cancer-related mortality worldwide and the third in USA in 2017. Chelerythrine (CHE, a naturalbenzo[c]phenanthridine alkaloid, formerly identified as a protein kinase C inhibitor, has also shown anticancer effect through a number of mechanisms. Herein, effect and mechanism of the CHE-induced apoptosis via reactive oxygen species (ROS-mediated endoplasmic reticulum (ER stress in prostate cancer cells were studied for the first time. Methods: In our present study, we investigated whether CHE induced cell viability decrease, colony formation inhibition, and apoptosis in a dose-dependent manner in PC-3 cells. In addition, we showed that CHE increases intracellular ROS and leads to ROS-dependent ER stress and cell apoptosis. Results: Pre-treatment with N-acetyl cysteine, an ROS scavenger, totally reversed the CHE-induced cancer cell apoptosis as well as ER stress activation, suggesting that the ROS generation was responsible for the anticancer effects of CHE. Conclusion: Taken together, our findings support one of the anticancer mechanisms by which CHE increased ROS accumulation in prostate cancer cells, thereby leading to ER stress and caused intrinsic apoptotic signaling. The study reveals that CHE could be a potential candidate for application in the treatment of prostate cancer. Keywords: chelerythrine, reactive oxygen species, endoplasmic reticulum stress, apoptosis, prostate cancer

  9. Substrate-dependent cell elasticity measured by optical tweezers indentation

    Science.gov (United States)

    Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

    2016-01-01

    In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

  10. Low temperature surface passivation of crystalline silicon and its application to interdigitated back contact silicon heterojunction (ibc-shj) solar cell

    Science.gov (United States)

    Shu, Zhan

    With the absence of shading loss together with improved quality of surface passivation introduced by low temperature processed amorphous silicon crystalline silicon (a-Si:H/c-Si) heterojunction, the interdigitated back contact silicon heterojunction (IBC-SHJ) solar cell exhibits a potential for higher conversion efficiency and lower cost than a traditional front contact diffused junction solar cell. In such solar cells, the front surface passivation is of great importance to achieve both high open-circuit voltage (Voc) and short-circuit current (Jsc). Therefore, the motivation of this work is to develop a low temperature processed structure for the front surface passivation of IBC-SHJ solar cells, which must have an excellent and stable passivation quality as well as a good anti-reflection property. Four different thin film materials/structures were studied and evaluated for this purpose, namely: amorphous silicon nitride (a-SiNx:H), thick amorphous silicon film (a-Si:H), amorphous silicon/silicon nitride/silicon carbide (a-Si:H/a-SiN x:H/a-SiC:H) stack structure with an ultra-thin a-Si:H layer, and zinc sulfide (ZnS). It was demonstrated that the a-Si:H/a-SiNx:H/a-SiC:H stack surpasses other candidates due to both of its excellent surface passivation quality (SRVSi surface is found to be resulted from (i) field effect passivation due to the positive fixed charge (Q fix~1x1011 cm-2 with 5 nm a-Si:H layer) in a-SiNx:H as measured from capacitance-voltage technique, and (ii) reduced defect state density (mid-gap Dit~4x1010 cm-2eV-1) at a-Si:H/c-Si interface provided by a 5 nm thick a-Si:H layer, as characterized by conductance-frequency measurements. Paralleled with the experimental studies, a computer program was developed in this work based on the extended Shockley-Read-Hall (SRH) model of surface recombination. With the help of this program, the experimental injection level dependent SRV curves of the stack passivated c-Si samples were successfully reproduced and

  11. Peroxide accumulation and cell death in filamentous fungi induced by contact with a contestant.

    Science.gov (United States)

    Silar, Philippe

    2005-02-01

    Podospora anserina and Coprinopsis cinerea (syn. Coprinus cinereus) are endowed with a defence system able to differentiate self vs. non-self and involving the generation of peroxide. Indeed, they produce peroxide when confronted with a filamentous fungus, only in non-self confrontations. Both species are not able to recognize yeasts and show a differential response to bacteria. The accumulation of peroxides in the ascomycete Podospora anserina requires an NADPH oxidase and a MAP kinase cascade, previously shown to be involved in fruit body formation, cell differentiation and cell degeneration. Confrontation is accompanied by the death of the contestant hyphae only in specific combinations of species. As in animals and plants, data suggest that peroxide is likely involved in signalling rather than playing a direct toxic role. Fungi display more complex behaviours than generally acknowledged, i.e. they are able to recognize potential contestants and built up defence reactions involving evolutionary conserved enzymes.

  12. Towards hybrid heterojunction silicon solar cells with organic charge carrier selective contacts

    OpenAIRE

    Jäckle, Sara Lisa

    2017-01-01

    Photovoltaic is an essential part of the needed global transition towards renewable energies. Even though many materials have good absorption and energy conversion properties, the market is dominated by technologies based on crystalline silicon. Silicon has the advantage of being neither toxic nor rare on earth and it is very well investigated due to its extensive use in microelectronics. The best power conversion efficiencies of silicon solar cells and modules are achieved by sophisticated d...

  13. The Use of Solar Cells with a Bifacial Contact Grid under the Conditions of Kazakhstan

    Science.gov (United States)

    Tokmoldin, N. S.; Chuchvaga, N. A.; Verbitskii, V. N.; Titov, A. S.; Zholdybayev, K. S.; Terukov, E. I.; Tokmoldin, S. Zh.

    2017-12-01

    The paper reports on the results of simulations of output characteristics of silicon solar cells based on the amorphous silicon-crystalline silicon heterojunction. In addition, the prospect of utilizing high-efficiency bifacial silicon solar modules for various orientational configurations is evaluated. The evaluations are based on the geographical location of the city of Astana (Kazakhstan) located at 51.2° N and 71.4° E at an altitude of 354 m above the sea level

  14. Inhibition of Staphylococcus aureus Invasion into Bovine Mammary Epithelial Cells by Contact with Live Lactobacillus casei

    OpenAIRE

    Bouchard, Damien S.; Rault, Lucie; Berkova, Nadia; Le Loir, Yves; Even, Sergine

    2013-01-01

    Staphylococcus aureus is a major pathogen that is responsible for mastitis in dairy herds. S. aureus mastitis is difficult to treat and prone to recurrence despite antibiotic treatment. The ability of S. aureus to invade bovine mammary epithelial cells (bMEC) is evoked to explain this chronicity. One sustainable alternative to treat or prevent mastitis is the use of lactic acid bacteria (LAB) as mammary probiotics. In this study, we tested the ability of Lactobacillus casei strains to prevent...

  15. Silicon heterojunction solar cell with passivated hole selective MoOx contact

    Science.gov (United States)

    Battaglia, Corsin; de Nicolás, Silvia Martín; De Wolf, Stefaan; Yin, Xingtian; Zheng, Maxwell; Ballif, Christophe; Javey, Ali

    2014-03-01

    We explore substoichiometric molybdenum trioxide (MoOx, x MoOx, we observe a substantial gain in photocurrent of 1.9 mA/cm2 in the ultraviolet and visible part of the solar spectrum, when compared to a p-type amorphous silicon emitter of a traditional silicon heterojunction cell. Our results emphasize the strong potential for oxides as carrier selective heterojunction partners to inorganic semiconductors.

  16. Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

    OpenAIRE

    Yang, C.; Persson, B. N. J.

    2007-01-01

    We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the i...

  17. Controlled lecithin release from a hierarchical architecture on blood-contacting surface to reduce hemolysis of stored red blood cells.

    Science.gov (United States)

    Shi, Qiang; Fan, Qunfu; Ye, Wei; Hou, Jianwen; Wong, Shing-Chung; Xu, Xiaodong; Yin, Jinghua

    2014-06-25

    Hemolysis of red blood cells (RBCs) caused by implant devices in vivo and nonpolyvinyl chloride containers for RBC preservation in vitro has recently gained much attention. To develop blood-contacting biomaterials with long-term antihemolysis capability, we present a facile method to construct a hydrophilic, 3D hierarchical architecture on the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS) with poly(ethylene oxide) (PEO)/lecithin nano/microfibers. The strategy is based on electrospinning of PEO/lecithin fibers onto the surface of poly [poly(ethylene glycol) methyl ether methacrylate] [P(PEGMEMA)]-modified SEBS, which renders SEBS suitable for RBC storage in vitro. We demonstrate that the constructed 3D architecture is composed of hydrophilic micro- and nanofibers, which transforms to hydrogel networks immediately in blood; the controlled release of lecithin is achieved by gradual dissolution of PEO/lecithin hydrogels, and the interaction of lecithin with RBCs maintains the membrane flexibility and normal RBC shape. Thus, the blood-contacting surface reduces both mechanical and oxidative damage to RBC membranes, resulting in low hemolysis of preserved RBCs. This work not only paves new way to fabricate high hemocompatible biomaterials for RBC storage in vitro, but provides basic principles to design and develop antihemolysis biomaterials for implantation in vivo.

  18. Chronic low-dose UVA irradiation induces local suppression of contact hypersensitivity, Langerhans cell depletion and suppressor cell activation in C3H/HeJ mice

    International Nuclear Information System (INIS)

    Bestak, Rosa; Halliday, G.M.

    1996-01-01

    It has previously been demonstrated that chronic low-dose solar-simulated UV radiation could induce both local and systemic immunosuppression as well as tolerance to a topically applied hapten. In this study, we have used a chronic low-dose UV-irradiation protocol to investigate the effects of UVA on the skin immune system of C3H/HeJ mice. Irradiation with UVA+B significantly suppressed the local and systemic primary contact hypersensitivity (CHS) response to the hapten 2,4,6-trinitrochlorobenzene. Furthermore, UVA+B reduced Langerhans cell (LC) and dendritic epidermal T cell (DETC) densities in chronically UV-irradiated mice. Ultraviolet A irradiation induced local, but not systemic, immunosuppression and reduced LC (32%) but not DETC from the epidermis compared to the shaved control animals. Treatment of mice with both UVA+B and UVA radiation also induced an impaired secondary CHS response, and this tolerance was transferable with spleen cells. (Author)

  19. Clonal progression during the T cell-dependent B cell antibody response depends on the immunoglobulin DH gene segment repertoire.

    Directory of Open Access Journals (Sweden)

    Ahmad eTrad

    2014-08-01

    Full Text Available The diversity of the third complementarity determining region of the Ig H chain is constrained by natural selection of immunoglobulin diversity (DH sequence. To test the functional significance of this constraint in the context of thymus-dependent (TD immune responses, we immunized BALB/c mice with WT or altered DH sequence with 2-phenyloxazolone-coupled chicken serum albumin (phOx-CSA. We chose this antigen because studies of the humoral immune response to the hapten phOx were instrumental in the development of the current theoretical framework on which our understanding of the forces driving TD responses is based. To allow direct comparison, we used the classic approach of generating monoclonal Ab (mAb from various stages of the immune response to phOx to assess the effect of changing the sequence of the DH on clonal expansion, class switching and affinity maturation, which are hallmarks of TD responses. Compared to WT, TD-induced humoral IgM as well as IgG antibody production in the D-altered D-DFS and D-iD strains were significantly reduced. An increased prevalence of IgM producing hybridomas from late primary, secondary, and tertiary memory responses suggested either impaired class switch recombination (CSR or impaired clonal expansion of class switched B cells with phOx reactivity. Neither of the D-altered strains demonstrated the restriction in the VH/VL repertoire, the elimination of VH1 family-encoded antibodies, the focusing of the distribution of CDR-H3 lengths, or the selection for the normally dominant Ox1 clonotype which all are hallmarks of the anti-phOx response in WT mice. These changes in clonal selection and expansion as well as class switch recombination indicate that the genetic constitution of the DH locus, which has been selected by evolution, can strongly influence the functional outcome of a TD humoral response.

  20. MicroRNA expression profile and functional analysis reveal their roles in contact inhibition and its disruption switch of rat vascular smooth muscle cells.

    Science.gov (United States)

    Sun, Ye-Ying; Qin, Shan-Shan; Cheng, Yun-Hui; Wang, Chao-Yun; Liu, Xiao-Jun; Liu, Ying; Zhang, Xiu-Li; Zhang, Wendy; Zhan, Jia-Xin; Shao, Shuai; Bian, Wei-Hua; Luo, Bi-Hui; Lu, Dong-Feng; Yang, Jian; Wang, Chun-Hua; Zhang, Chun-Xiang

    2018-05-01

    Contact inhibition and its disruption of vascular smooth muscle cells (VSMCs) are important cellular events in vascular diseases. But the underlying molecular mechanisms are unclear. In this study we investigated the roles of microRNAs (miRNAs) in the contact inhibition and its disruption of VSMCs and the molecular mechanisms involved. Rat VSMCs were seeded at 30% or 90% confluence. MiRNA expression profiles in contact-inhibited confluent VSMCs (90% confluence) and non-contact-inhibited low-density VSMCs (30% confluence) were determined. We found that multiple miRNAs were differentially expressed between the two groups. Among them, miR-145 was significantly increased in contact-inhibited VSMCs. Serum could disrupt the contact inhibition as shown by the elicited proliferation of confluent VSMCs. The contact inhibition disruption accompanied with a down-regulation of miR-145. Serum-induced contact inhibition disruption of VSMCs was blocked by overexpression of miR-145. Moreover, downregulation of miR-145 was sufficient to disrupt the contact inhibition of VSMCs. The downregulation of miR-145 in serum-induced contact inhibition disruption was related to the activation PI3-kinase/Akt pathway, which was blocked by the PI3-kinase inhibitor LY294002. KLF5, a target gene of miR-145, was identified to be involved in miR-145-mediated effect on VSMC contact inhibition disruption, as it could be inhibited by knockdown of KLF5. In summary, our results show that multiple miRNAs are differentially expressed in contact-inhibited VSMCs and in non-contact-inhibited VSMCs. Among them, miR-145 is a critical gene in contact inhibition and its disruption of VSMCs. PI3-kinase/Akt/miR-145/KLF5 is a critical signaling pathway in serum-induced contact inhibition disruption. Targeting of miRNAs related to the contact inhibition of VSMCs may represent a novel therapeutic approach for vascular diseases.

  1. Arctigenin inhibits osteoclast differentiation and function by suppressing both calcineurin-dependent and osteoblastic cell-dependent NFATc1 pathways.

    Science.gov (United States)

    Yamashita, Teruhito; Uehara, Shunsuke; Udagawa, Nobuyuki; Li, Feng; Kadota, Shigetoshi; Esumi, Hiroyasu; Kobayashi, Yasuhiro; Takahashi, Naoyuki

    2014-01-01

    Arctigenin, a lignan-derived compound, is a constituent of the seeds of Arctium lappa. Arctigenin was previously shown to inhibit osteoclastogenesis; however, this inhibitory mechanism has yet to be elucidated. Here, we showed that arctigenin inhibited the action of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), a key transcription factor for osteoclastogenesis. NFATc1 in osteoclast precursors was activated through two distinct pathways: the calcineurin-dependent and osteoblastic cell-dependent pathways. Among the several lignan-derived compounds examined, arctigenin most strongly inhibited receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast-like cell formation in mouse bone marrow macrophage (BMM) cultures, in which the calcineurin-dependent NFATc1 pathway was activated. Arctigenin suppressed neither the activation of nuclear factor κB and mitogen-activated protein kinases nor the up-regulation of c-Fos expression in BMMs treated with RANKL. However, arctigenin suppressed RANKL-induced NFATc1 expression. Interestingly, the treatment of osteoclast-like cells with arctigenin converted NFATc1 into a lower molecular weight species, which was translocated into the nucleus even in the absence of RANKL. Nevertheless, arctigenin as well as cyclosporin A (CsA), a calcineurin inhibitor, suppressed the NFAT-luciferase reporter activity induced by ionomycin and phorbol 12-myristate 13-acetate in BMMs. Chromatin immunoprecipitation analysis confirmed that arctigenin inhibited the recruitment of NFATc1 to the promoter region of the NFATc1 target gene. Arctigenin, but not CsA suppressed osteoclast-like cell formation in co-cultures of osteoblastic cells and bone marrow cells, in which the osteoblastic cell-dependent NFATc1 pathway was activated. The forced expression of constitutively active NFATc1 rescued osteoclastogenesis in BMM cultures treated with CsA, but not that treated with arctigenin. Arctigenin also suppressed the pit

  2. Arctigenin inhibits osteoclast differentiation and function by suppressing both calcineurin-dependent and osteoblastic cell-dependent NFATc1 pathways.

    Directory of Open Access Journals (Sweden)

    Teruhito Yamashita

    Full Text Available Arctigenin, a lignan-derived compound, is a constituent of the seeds of Arctium lappa. Arctigenin was previously shown to inhibit osteoclastogenesis; however, this inhibitory mechanism has yet to be elucidated. Here, we showed that arctigenin inhibited the action of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1, a key transcription factor for osteoclastogenesis. NFATc1 in osteoclast precursors was activated through two distinct pathways: the calcineurin-dependent and osteoblastic cell-dependent pathways. Among the several lignan-derived compounds examined, arctigenin most strongly inhibited receptor activator of nuclear factor κB ligand (RANKL-induced osteoclast-like cell formation in mouse bone marrow macrophage (BMM cultures, in which the calcineurin-dependent NFATc1 pathway was activated. Arctigenin suppressed neither the activation of nuclear factor κB and mitogen-activated protein kinases nor the up-regulation of c-Fos expression in BMMs treated with RANKL. However, arctigenin suppressed RANKL-induced NFATc1 expression. Interestingly, the treatment of osteoclast-like cells with arctigenin converted NFATc1 into a lower molecular weight species, which was translocated into the nucleus even in the absence of RANKL. Nevertheless, arctigenin as well as cyclosporin A (CsA, a calcineurin inhibitor, suppressed the NFAT-luciferase reporter activity induced by ionomycin and phorbol 12-myristate 13-acetate in BMMs. Chromatin immunoprecipitation analysis confirmed that arctigenin inhibited the recruitment of NFATc1 to the promoter region of the NFATc1 target gene. Arctigenin, but not CsA suppressed osteoclast-like cell formation in co-cultures of osteoblastic cells and bone marrow cells, in which the osteoblastic cell-dependent NFATc1 pathway was activated. The forced expression of constitutively active NFATc1 rescued osteoclastogenesis in BMM cultures treated with CsA, but not that treated with arctigenin. Arctigenin also suppressed the

  3. Arctigenin Inhibits Osteoclast Differentiation and Function by Suppressing Both Calcineurin-Dependent and Osteoblastic Cell-Dependent NFATc1 Pathways

    Science.gov (United States)

    Yamashita, Teruhito; Uehara, Shunsuke; Udagawa, Nobuyuki; Li, Feng; Kadota, Shigetoshi; Esumi, Hiroyasu; Kobayashi, Yasuhiro; Takahashi, Naoyuki

    2014-01-01

    Arctigenin, a lignan-derived compound, is a constituent of the seeds of Arctium lappa. Arctigenin was previously shown to inhibit osteoclastogenesis; however, this inhibitory mechanism has yet to be elucidated. Here, we showed that arctigenin inhibited the action of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), a key transcription factor for osteoclastogenesis. NFATc1 in osteoclast precursors was activated through two distinct pathways: the calcineurin-dependent and osteoblastic cell-dependent pathways. Among the several lignan-derived compounds examined, arctigenin most strongly inhibited receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast-like cell formation in mouse bone marrow macrophage (BMM) cultures, in which the calcineurin-dependent NFATc1 pathway was activated. Arctigenin suppressed neither the activation of nuclear factor κB an