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Sample records for class switch recombination

  1. Ig heavy chain class switch recombination: mechanism and regulation

    OpenAIRE

    Stavnezer, Janet; Schrader, Carol E.

    2014-01-01

    Ig heavy chain class switching occurs rapidly after activation of mature naïve B cells, resulting in a switch from expressing IgM and IgD to expression of IgG, IgE, or IgA; this switch improves the ability of antibodies to remove the pathogen that induces the humoral immune response. Class switching occurs by a deletional recombination between two different switch (S) regions, each of which is associated with a heavy chain constant (CH) region gene. Class switch recombination (CSR) is instiga...

  2. IgH chain class switch recombination: mechanism and regulation.

    Science.gov (United States)

    Stavnezer, Janet; Schrader, Carol E

    2014-12-01

    IgH class switching occurs rapidly after activation of mature naive B cells, resulting in a switch from expression of IgM and IgD to expression of IgG, IgE, or IgA; this switch improves the ability of Abs to remove the pathogen that induces the humoral immune response. Class switching occurs by a deletional recombination between two switch regions, each of which is associated with a H chain constant region gene. Class switch recombination (CSR) is instigated by activation-induced cytidine deaminase, which converts cytosines in switch regions to uracils. The uracils are subsequently removed by two DNA-repair pathways, resulting in mutations, single-strand DNA breaks, and the double-strand breaks required for CSR. We discuss several aspects of CSR, including how CSR is induced, CSR in B cell progenitors, the roles of transcription and chromosomal looping in CSR, and the roles of certain DNA-repair enzymes in CSR. PMID:25411432

  3. Parp3 negatively regulates immunoglobulin class switch recombination.

    Science.gov (United States)

    Robert, Isabelle; Gaudot, Léa; Rogier, Mélanie; Heyer, Vincent; Noll, Aurélia; Dantzer, Françoise; Reina-San-Martin, Bernardo

    2015-05-01

    To generate highly specific and adapted immune responses, B cells diversify their antibody repertoire through mechanisms involving the generation of programmed DNA damage. Somatic hypermutation (SHM) and class switch recombination (CSR) are initiated by the recruitment of activation-induced cytidine deaminase (AID) to immunoglobulin loci and by the subsequent generation of DNA lesions, which are differentially processed to mutations during SHM or to double-stranded DNA break intermediates during CSR. The latter activate the DNA damage response and mobilize multiple DNA repair factors, including Parp1 and Parp2, to promote DNA repair and long-range recombination. We examined the contribution of Parp3 in CSR and SHM. We find that deficiency in Parp3 results in enhanced CSR, while SHM remains unaffected. Mechanistically, this is due to increased occupancy of AID at the donor (Sμ) switch region. We also find evidence of increased levels of DNA damage at switch region junctions and a bias towards alternative end joining in the absence of Parp3. We propose that Parp3 plays a CSR-specific role by controlling AID levels at switch regions during CSR. PMID:26000965

  4. Parp3 negatively regulates immunoglobulin class switch recombination.

    Directory of Open Access Journals (Sweden)

    Isabelle Robert

    2015-05-01

    Full Text Available To generate highly specific and adapted immune responses, B cells diversify their antibody repertoire through mechanisms involving the generation of programmed DNA damage. Somatic hypermutation (SHM and class switch recombination (CSR are initiated by the recruitment of activation-induced cytidine deaminase (AID to immunoglobulin loci and by the subsequent generation of DNA lesions, which are differentially processed to mutations during SHM or to double-stranded DNA break intermediates during CSR. The latter activate the DNA damage response and mobilize multiple DNA repair factors, including Parp1 and Parp2, to promote DNA repair and long-range recombination. We examined the contribution of Parp3 in CSR and SHM. We find that deficiency in Parp3 results in enhanced CSR, while SHM remains unaffected. Mechanistically, this is due to increased occupancy of AID at the donor (Sμ switch region. We also find evidence of increased levels of DNA damage at switch region junctions and a bias towards alternative end joining in the absence of Parp3. We propose that Parp3 plays a CSR-specific role by controlling AID levels at switch regions during CSR.

  5. Non-redundancy of cytidine deaminases in class switch recombination.

    Science.gov (United States)

    Fugmann, Sebastian D; Rush, James S; Schatz, David G

    2004-03-01

    Class switch recombination (CSR), somatic hypermutation, and gene conversion are immunoglobulin diversification mechanisms that are strictly dependent on the activity of the activation-induced cytidine deaminase (AID). The precise role and substrate(s) of AID in these processes remain to be well defined. The closest homologue of AID is APOBEC-1, a bona fide mRNA-editing enzyme, which shares with AID the ability to deaminate cytidines within single-stranded DNA in vitro and in prokaryotic cells. To determine whether APOBEC-1 can therefore substitute for AID in activated B cells, we expressed human AID, a catalytic mutant thereof, and rat APOBEC-1 in AID-deficient murine B cells. Whereas AID rescued CSR, neither the inactive mutant nor APOBEC-1 could complement AID deficiency. This indicates that cytidine deaminase activity is necessary but not sufficient to initiate CSR, and suggests that AID is specifically targeted to its cognate substrate, the immunoglobulin genes or a distinct mRNA, by an as-yet-unknown mechanism. PMID:14991614

  6. Ongoing Immunoglobulin Class Switch DNA Recombination in Lupus B Cells: Analysis of Switch Regulatory Regions

    OpenAIRE

    Liu, Shiquan; Cerutti, Andrea; Casali, Paolo; CROW, MARY K.

    2004-01-01

    Inflammation and tissue damage in systemic lupus erythematosus (SLE) are mediated by class-switched autoantibodies reactive with nucleic acids, nucleic acid-binding proteins, phospholipids and other self-antigens. While some healthy individuals produce IgM antibodies with specificities similar to those of lupus patients, immunoglobulin class switching to mature downstream isotypes appears to be required for the generation of pathogenic autoantibodies. To characterize the cellular and molecula...

  7. Constraints contributed by chromatin looping limit recombination targeting during Ig class switch recombination.

    Science.gov (United States)

    Feldman, Scott; Achour, Ikbel; Wuerffel, Robert; Kumar, Satyendra; Gerasimova, Tatiana; Sen, Ranjan; Kenter, Amy L

    2015-03-01

    Engagement of promoters with distal elements in long-range looping interactions has been implicated in regulation of Ig class switch recombination (CSR). The principles determining the spatial and regulatory relationships among Igh transcriptional elements remain poorly defined. We examined the chromosome conformation of C region (CH) loci that are targeted for CSR in a cytokine-dependent fashion in mature B lymphocytes. Germline transcription (GLT) of the γ1 and ε CH loci is controlled by two transcription factors, IL-4-inducible STAT6 and LPS-activated NF-κB. We showed that although STAT6 deficiency triggered loss of GLT, deletion of NF-κB p50 abolished both GLT and γ1 locus:enhancer looping. Thus, chromatin looping between CH loci and Igh enhancers is independent of GLT production and STAT6, whereas the establishment and maintenance of these chromatin contacts requires NF-κB p50. Comparative analysis of the endogenous γ1 locus and a knock-in heterologous promoter in mice identified the promoter per se as the interactive looping element and showed that transcription elongation is dispensable for promoter/enhancer interactions. Interposition of the LPS-responsive heterologous promoter between the LPS-inducible γ3 and γ2b loci altered GLT expression and essentially abolished direct IgG2b switching while maintaining a sequential μ→γ3→γ2b format. Our study provides evidence that promoter/enhancer looping interactions can introduce negative constraints on distal promoters and affect their ability to engage in germline transcription and determine CSR targeting. PMID:25624452

  8. Enhancement of antibody class-switch recombination by the cumulative activity of four separate elements.

    Science.gov (United States)

    Dunnick, Wesley A; Shi, Jian; Zerbato, Jennifer M; Fontaine, Clinton A; Collins, John T

    2011-11-01

    Class-switch recombination of Ab isotype is mediated by a recombinational DNA deletion event and must be robustly upregulated during Ag-driven differentiation of B cells. The enhancer region 3' of the Cα gene is important for the upregulation of switch recombination. Using a transgene of the entire H chain C region locus, we demonstrate in this study that it is the four 3' enhancer elements themselves (a total of 4.7 kb) that are responsible for the upregulation rather than the 24 kb of DNA in between them. Neither allelic exclusion nor transgenic μ expression is reduced by deletion of the four 3' enhancers. We also test deletions of two or three of the 3' enhancers and show that deletion of more 3' enhancers results in a progressive reduction in both switch recombination and germline transcription of all H chain genes. Nevertheless, we find evidence for special roles for some 3' enhancers; different H chain genes are affected by different 3' enhancer deletions. Thus, we find that the dramatic induction of class-switch recombination during Ag-driven differentiation is the result of an interaction among four separated regulatory elements. PMID:21949022

  9. ALKBH1 is dispensable for abasic site cleavage during base excision repair and class switch recombination.

    Science.gov (United States)

    Müller, Tina A; Yu, Kefei; Hausinger, Robert P; Meek, Katheryn

    2013-01-01

    Potential roles of the abasic site lyase activity associated with AlkB homolog 1 (ALKBH1) were assessed by studies focusing on the two cellular processes that create abasic sites as intermediates: base excision repair and class switch recombination. Alkbh1(-/-) pups (lacking exon 3) were born at a lower than expected frequency from heterozygous parents, suggesting a reduced survival rate and non-Mendelian inheritance, and they exhibited a gender bias in favor of males (70% males and 30% females). To study ALKBH1's potential involvement in DNA repair, fibroblasts were isolated from Alkbh1(-/-) mice, spontaneously immortalized and tested for resistance to DNA damaging agents. Alkbh1(-/-) and isogenic cells expressing hALKBH1 showed no difference in survival to the DNA damaging agents methyl-methionine sulfate or H2O2. This result indicates that ALKBH1 does not play a major role in the base excision repair pathway. To assess ALKBH1's role in class switch recombination, splenic B cells were isolated from Alkbh1(-/-) and Alkbh1(+/+) mice and subjected to switching from IgM to IgG1. No differences were found in IgG1 switching, suggesting that Alkbh1 is not involved in class switch recombination of the immunoglobulin heavy chain during B lymphocyte activation. PMID:23825659

  10. ALKBH1 is dispensable for abasic site cleavage during base excision repair and class switch recombination.

    Directory of Open Access Journals (Sweden)

    Tina A Müller

    Full Text Available Potential roles of the abasic site lyase activity associated with AlkB homolog 1 (ALKBH1 were assessed by studies focusing on the two cellular processes that create abasic sites as intermediates: base excision repair and class switch recombination. Alkbh1(-/- pups (lacking exon 3 were born at a lower than expected frequency from heterozygous parents, suggesting a reduced survival rate and non-Mendelian inheritance, and they exhibited a gender bias in favor of males (70% males and 30% females. To study ALKBH1's potential involvement in DNA repair, fibroblasts were isolated from Alkbh1(-/- mice, spontaneously immortalized and tested for resistance to DNA damaging agents. Alkbh1(-/- and isogenic cells expressing hALKBH1 showed no difference in survival to the DNA damaging agents methyl-methionine sulfate or H2O2. This result indicates that ALKBH1 does not play a major role in the base excision repair pathway. To assess ALKBH1's role in class switch recombination, splenic B cells were isolated from Alkbh1(-/- and Alkbh1(+/+ mice and subjected to switching from IgM to IgG1. No differences were found in IgG1 switching, suggesting that Alkbh1 is not involved in class switch recombination of the immunoglobulin heavy chain during B lymphocyte activation.

  11. p53 Represses Class Switch Recombination to IgG2a through its Antioxidant Function1

    OpenAIRE

    Guikema, Jeroen E. J.; Schrader, Carol E.; Brodsky, Michael H.; Linehan, Erin K.; Richards, Adam; El Falaky, Nahla; Li, Daniel H.; Sluss, Hayla K.; Szomolanyi-Tsuda, Eva; Stavnezer, Janet

    2010-01-01

    Immunoglobulin class switch recombination (CSR) occurs in activated mature B cells, and causes an exchange of the IgM isotype for IgG, IgE or IgA isotypes, which increases the effectiveness of the humoral immune response. DNA double-stranded breaks (DSBs) in recombining switch (S) regions, where CSR occurs, are required for recombination. Activation-induced cytidine deaminase (AID) initiates DSB formation by deamination of cytosines in S regions. This reaction requires reactive oxygen species...

  12. Roles of nonhomologous DNA end joining, V(D)J recombination, and class switch recombination in chromosomal translocations.

    Science.gov (United States)

    Lieber, Michael R; Yu, Kefei; Raghavan, Sathees C

    2006-09-01

    When a single double-strand break arises in the genome, nonhomologous DNA end joining (NHEJ) is a major pathway for its repair. When double-strand breaks arise at two nonhomologous sites in the genome, NHEJ also appears to be a major pathway by which the translocated ends are joined. The mechanism of NHEJ is briefly summarized, and alternative enzymes are also discussed. V(D)J recombination and class switch recombination are specialized processes designed to create double-strand DNA breaks at specific locations in the genomes of lymphoid cells. Sporadic Burkitt's lymphoma and myelomas can arise due to translocation of the c-myc gene into the Ig heavy chain locus during class switch recombination. In other lymphoid neoplasms, the RAG complex can create double-strand breaks that result in a translocation. Such RAG-generated breaks occur at very specific nucleotides that are directly adjacent to sequences that resemble canonical heptamer/nonamer sequences characteristic of normal V(D)J recombination. This occurs in some T cell leukemias and lymphomas. The RAG complex also appears capable of recognizing regions for their altered DNA structure rather than their primary sequence, and this may account for the action by RAGs at some chromosomal translocation sites, such as at the bcl-2 major breakpoint region in the follicular lymphomas that arise in B lymphocytes. PMID:16793349

  13. Interaction between HIV-1 Tat and DNA-PKcs modulates HIV transcription and class switch recombination.

    Science.gov (United States)

    Zhang, Shi-Meng; Zhang, He; Yang, Tian-Yi; Ying, Tian-Yi; Yang, Pei-Xiang; Liu, Xiao-Dan; Tang, Sheng-Jian; Zhou, Ping-Kun

    2014-01-01

    HIV-1 tat targets a variety of host cell proteins to facilitate viral transcription and disrupts host cellular immunity by inducing lymphocyte apoptosis, but whether it influences humoral immunity remains unclear. Previously, our group demonstrated that tat depresses expression of DNA-PKcs, a critical component of the non-homologous end joining pathway (NHEJ) of DNA double-strand breaks repair, immunoglobulin class switch recombination (CSR) and V(D)J recombination, and sensitizes cells to ionizing radiation. In this study, we demonstrated that HIV-1 Tat down-regulates DNA-PKcs expression by directly binding to the core promoter sequence. In addition, Tat interacts with and activates the kinase activity of DNA-PKcs in a dose-dependent and DNA independent manner. Furthermore, Tat inhibits class switch recombination (CSR) at low concentrations (≤ 4 µg/ml) and stimulates CSR at high concentrations (≥ 8 µg/ml). On the other hand, low protein level and high kinase activity of DNA-PKcs promotes HIV-1 transcription, while high protein level and low kinase activity inhibit HIV-1 transcription. Co-immunoprecipitation results revealed that DNA-PKcs forms a large complex comprised of Cyclin T1, CDK9 and Tat via direct interacting with CDK9 and Tat but not Cyclin T1. Taken together, our results provide new clues that Tat regulates host humoral immunity via both transcriptional depression and kinase activation of DNA-PKcs. We also raise the possibility that inhibitors and interventions directed towards DNA-PKcs may inhibit HIV-1 transcription in AIDS patients. PMID:25332688

  14. Cernunnos influences human immunoglobulin class switch recombination and may be associated with B cell lymphomagenesis.

    Science.gov (United States)

    Du, Likun; Peng, Roujun; Björkman, Andrea; Filipe de Miranda, Noel; Rosner, Cornelia; Kotnis, Ashwin; Berglund, Mattias; Liu, Chonghai; Rosenquist, Richard; Enblad, Gunilla; Sundström, Christer; Hojjat-Farsangi, Mohammad; Rabbani, Hodjattallah; Teixeira, Manuel R; Revy, Patrick; Durandy, Anne; Zeng, Yixin; Gennery, Andrew R; de Villartay, Jean-Pierre; Pan-Hammarström, Qiang

    2012-02-13

    Cernunnos is involved in the nonhomologous end-joining (NHEJ) process during DNA double-strand break (DSB) repair. Here, we studied immunoglobulin (Ig) class switch recombination (CSR), a physiological process which relies on proper repair of the DSBs, in B cells from Cernunnos-deficient patients. The pattern of in vivo generated CSR junctions is altered in these cells, with unusually long microhomologies and a lack of direct end-joining. The CSR junctions from Cernunnos-deficient patients largely resemble those from patients lacking DNA ligase IV, Artemis, or ATM, suggesting that these factors are involved in the same end-joining pathway during CSR. By screening 269 mature B cell lymphoma biopsies, we also identified a somatic missense Cernunnos mutation in a diffuse large B cell lymphoma sample. This mutation has a dominant-negative effect on joining of a subset of DNA ends in an in vitro NHEJ assay. Translocations involving both Ig heavy chain loci and clonal-like, dynamic IgA switching activities were observed in this tumor. Collectively, our results suggest a link between defects in the Cernunnos-dependent NHEJ pathway and aberrant CSR or switch translocations during the development of B cell malignancies. PMID:22312109

  15. PP4 is essential for germinal center formation and class switch recombination in mice.

    Directory of Open Access Journals (Sweden)

    Ming-Yu Chen

    Full Text Available PP4 is a serine/threonine phosphatase required for immunoglobulin (Ig VDJ recombination and pro-B/pre-B cell development in mice. To elucidate the role of PP4 in mature B cells, we ablated the catalytic subunit of murine PP4 in vivo utilizing the CD23 promoter and cre-loxP recombination and generated CD23(crePP4(F/F mice. The development of follicular and marginal zone B cells was unaffected in these mutants, but the proliferation of mature PP4-deficient B cells stimulated by in vitro treatment with either anti-IgM antibody (Ab or LPS was partially impaired. Interestingly, the induction of CD80 and CD86 expression on these stimulated B cells was normal. Basal levels of serum Igs of all isotypes were strongly reduced in CD23(crePP4(F/F mice, and their B cells showed a reduced efficiency of class switch recombination (CSR in vitro upon stimulation by LPS or LPS plus IL-4. When CD23(crePP4(F/F mice were challenged with either the T cell-dependent antigen TNP-KLH or the T cell-independent antigen TNP-Ficoll, or by H1N1 virus infection, the mutant animals failed to form germinal centers (GCs in the spleen and the draining mediastinal lymph nodes, and did not efficiently mount antigen-specific humoral responses. In the resting state, PP4-deficient B cells exhibited pre-existing DNA fragmentation. Upon stimulation by DNA-damaging drug etoposide in vitro, mutant B cells showed increased cleavage of caspase 3. In addition, the mutant B cells displayed impaired CD40-mediated MAPK activation, abnormal IgM-mediated NF-κB activation, and reduced S phase entry upon IgM/CD40-stimulation. Taken together, our results establish a novel role for PP4 in CSR, and reveal crucial functions for PP4 in the maintenance of genomic stability, GC formation, and B cell-mediated immune responses.

  16. A Damage-Independent Role for 53BP1 that Impacts Break Order and Igh Architecture during Class Switch Recombination

    Directory of Open Access Journals (Sweden)

    Pedro P. Rocha

    2016-06-01

    Full Text Available During class switch recombination (CSR, B cells replace the Igh Cμ or δ exons with another downstream constant region exon (CH, altering the antibody isotype. CSR occurs through the introduction of AID-mediated double-strand breaks (DSBs in switch regions and subsequent ligation of broken ends. Here, we developed an assay to investigate the dynamics of DSB formation in individual cells. We demonstrate that the upstream switch region Sμ is first targeted during recombination and that the mechanism underlying this control relies on 53BP1. Surprisingly, regulation of break order occurs through residual binding of 53BP1 to chromatin before the introduction of damage and independent of its established role in DNA repair. Using chromosome conformation capture, we show that 53BP1 mediates changes in chromatin architecture that affect break order. Finally, our results explain how changes in Igh architecture in the absence of 53BP1 could promote inversional rearrangements that compromise CSR.

  17. A Damage-Independent Role for 53BP1 that Impacts Break Order and Igh Architecture during Class Switch Recombination.

    Science.gov (United States)

    Rocha, Pedro P; Raviram, Ramya; Fu, Yi; Kim, JungHyun; Luo, Vincent M; Aljoufi, Arafat; Swanzey, Emily; Pasquarella, Alessandra; Balestrini, Alessia; Miraldi, Emily R; Bonneau, Richard; Petrini, John; Schotta, Gunnar; Skok, Jane A

    2016-06-28

    During class switch recombination (CSR), B cells replace the Igh Cμ or δ exons with another downstream constant region exon (CH), altering the antibody isotype. CSR occurs through the introduction of AID-mediated double-strand breaks (DSBs) in switch regions and subsequent ligation of broken ends. Here, we developed an assay to investigate the dynamics of DSB formation in individual cells. We demonstrate that the upstream switch region Sμ is first targeted during recombination and that the mechanism underlying this control relies on 53BP1. Surprisingly, regulation of break order occurs through residual binding of 53BP1 to chromatin before the introduction of damage and independent of its established role in DNA repair. Using chromosome conformation capture, we show that 53BP1 mediates changes in chromatin architecture that affect break order. Finally, our results explain how changes in Igh architecture in the absence of 53BP1 could promote inversional rearrangements that compromise CSR. PMID:27320916

  18. Differential regulation of S-region hypermutation and class-switch recombination by noncanonical functions of uracil DNA glycosylase

    OpenAIRE

    Yousif, Ashraf S.; Stanlie, Andre; Mondal, Samiran; Honjo, Tasuku; Begum, Nasim A.

    2014-01-01

    Uracil DNA glycosylase (UNG) has been known as a critical base excision repair protein required for class switch recombination (CSR) and somatic hypermutation (SHM). On the other hand, its precise function in both CSR and SHM is extremely debatable and elusive. Here, we showed that UNG suppresses S region SHM (s-SHM) by recruiting the faithful DNA repair complex and, in the absence of UNG, the error-prone repair complex that induces s-SHM overrides. Moreover, UNG promotes activation-induced c...

  19. APE1 is dispensable for S-region cleavage but required for its repair in class switch recombination

    OpenAIRE

    Xu, Jianliang; Husain, Afzal; Hu, Wenjun; Honjo, Tasuku; Kobayashi, Maki

    2014-01-01

    Apurinic/apyrimidinic endonuclease 1 (APE1) has been shown to be a critical endonuclease required for class switch recombination (CSR). Here we show that APE1’s endonuclease activity, but not its redox regulation or transcriptional regulation activity, is important for CSR. Conversely, APE1 is dispensable for activation-induced cytidine deaminase (AID)-induced somatic hypermutation (SHM) as well as IgH/c-myc translocation. Moreover, during CSR, APE1 is not required for AID-induced S-region br...

  20. AID expression increased by TNF-α is associated with class switch recombination of Igα gene in cancers.

    Science.gov (United States)

    Duan, Zhi; Zheng, Hui; Liu, Haidan; Li, Ming; Tang, Min; Weng, Xinxian; Yi, Wei; Bode, Ann M; Cao, Ya

    2016-07-01

    Recently, immunoglobulins (Igs) were unexpectedly found to be expressed in epithelial cancers. Immunoglobulin class switching or class switch recombination (CSR) is a natural biological process that alters a B cell's production of antibodies (immunoglobulins) from one class to another. However, the mechanism of CSR of Ig genes in cancer is still unknown. Here, we confirmed by detecting the hallmark of CSR that the Igα gene in cancer underwent CSR. Then we focused on activation-induced cytidine deaminase (AID), a crucial factor for initiating CSR. Further studies using tumor necrosis factor (TNF)-α stimulation and specific inhibitor of NF-κB revealed that TNF-α could increase AID expression through NF-κB signaling. Finally, we demonstrated that AID could co-localize with protein kinase A and bind to the switching (Sα) region of the Igα gene. Overexpression of AID obviously enhanced Igα heavy chain expression and its binding ability to the Sα region. These findings indicated that TNF-α-induced AID expression is involved with CSR in cancer. PMID:25849121

  1. Redundant function of DNA ligase 1 and 3 in alternative end-joining during immunoglobulin class switch recombination.

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    Masani, Shahnaz; Han, Li; Meek, Katheryn; Yu, Kefei

    2016-02-01

    Nonhomologous end-joining (NHEJ) is the major DNA double-strand break (DSB) repair pathway in mammals and resolves the DSBs generated during both V(D)J recombination in developing lymphocytes and class switch recombination (CSR) in antigen-stimulated B cells. In contrast to the absolute requirement for NHEJ to resolve DSBs associated with V(D)J recombination, DSBs associated with CSR can be resolved in NHEJ-deficient cells (albeit at a reduced level) by a poorly defined alternative end-joining (A-EJ) pathway. Deletion of DNA ligase IV (Lig4), a core component of the NHEJ pathway, reduces CSR efficiency in a mouse B-cell line capable of robust cytokine-stimulated CSR in cell culture. Here, we report that CSR levels are not further reduced by deletion of either of the two remaining DNA ligases (Lig1 and nuclear Lig3) in Lig4(-/-) cells. We conclude that in the absence of Lig4, Lig1, and Lig3 function in a redundant manner in resolving switch region DSBs during CSR. PMID:26787901

  2. ATM increases activation-induced cytidine deaminase activity at downstream S regions during class-switch recombination.

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    Khair, Lyne; Guikema, Jeroen E J; Linehan, Erin K; Ucher, Anna J; Leus, Niek G J; Ogilvie, Colin; Lou, Zhenkun; Schrader, Carol E; Stavnezer, Janet

    2014-05-15

    Activation-induced cytidine deaminase (AID) initiates Ab class-switch recombination (CSR) in activated B cells resulting in exchanging the IgH C region and improved Ab effector function. During CSR, AID instigates DNA double-strand break (DSB) formation in switch (S) regions located upstream of C region genes. DSBs are necessary for CSR, but improper regulation of DSBs can lead to chromosomal translocations that can result in B cell lymphoma. The protein kinase ataxia telangiectasia mutated (ATM) is an important proximal regulator of the DNA damage response (DDR), and translocations involving S regions are increased in its absence. ATM phosphorylates H2AX, which recruits other DNA damage response (DDR) proteins, including mediator of DNA damage checkpoint 1 (Mdc1) and p53 binding protein 1 (53BP1), to sites of DNA damage. As these DDR proteins all function to promote repair and recombination of DSBs during CSR, we examined whether mouse splenic B cells deficient in these proteins would show alterations in S region DSBs when undergoing CSR. We find that in atm(-/-) cells Sμ DSBs are increased, whereas DSBs in downstream Sγ regions are decreased. We also find that mutations in the unrearranged Sγ3 segment are reduced in atm(-/-) cells. Our data suggest that ATM increases AID targeting and activity at downstream acceptor S regions during CSR and that in atm(-/-) cells Sμ DSBs accumulate as they lack a recombination partner. PMID:24729610

  3. Opinion: uracil DNA glycosylase (UNG) plays distinct and non-canonical roles in somatic hypermutation and class switch recombination.

    Science.gov (United States)

    Yousif, Ashraf S; Stanlie, Andre; Begum, Nasim A; Honjo, Tasuku

    2014-10-01

    Activation-induced cytidine deaminase (AID) is essential to class switch recombination (CSR) and somatic hypermutation (SHM). Uracil DNA glycosylase (UNG), a member of the base excision repair complex, is required for CSR. The role of UNG in CSR and SHM is extremely controversial. AID deficiency in mice abolishes both CSR and SHM, while UNG-deficient mice have drastically reduced CSR but augmented SHM raising a possibility of differential functions of UNG in CSR and SHM. Interestingly, UNG has been associated with a CSR-specific repair adapter protein Brd4, which interacts with acetyl histone 4, γH2AX and 53BP1 to promote non-homologous end joining during CSR. A non-canonical scaffold function of UNG, but not the catalytic activity, can be attributed to the recruitment of essential repair proteins associated with the error-free repair during SHM, and the end joining during CSR. PMID:24994819

  4. Non-canonical uracil processing in DNA gives rise to double-strand breaks and deletions: relevance to class switch recombination

    OpenAIRE

    Bregenhorn, Stephanie; Kallenberger, Lia; Artola-Borán, Mariela; Peña-Diaz, Javier; Jiricny, Josef

    2016-01-01

    During class switch recombination (CSR), antigen-stimulated B-cells rearrange their immunoglobulin constant heavy chain (CH) loci to generate antibodies with different effector functions. CSR is initiated by activation-induced deaminase (AID), which converts cytosines in switch (S) regions, repetitive sequences flanking the CH loci, to uracils. Although U/G mispairs arising in this way are generally efficiently repaired to C/Gs by uracil DNA glycosylase (UNG)-initiated base excision repair (B...

  5. Mediator facilitates transcriptional activation and dynamic long-range contacts at the IgH locus during class switch recombination.

    Science.gov (United States)

    Thomas-Claudepierre, Anne-Sophie; Robert, Isabelle; Rocha, Pedro P; Raviram, Ramya; Schiavo, Ebe; Heyer, Vincent; Bonneau, Richard; Luo, Vincent M; Reddy, Janardan K; Borggrefe, Tilman; Skok, Jane A; Reina-San-Martin, Bernardo

    2016-03-01

    Immunoglobulin (Ig) class switch recombination (CSR) is initiated by the transcription-coupled recruitment of activation-induced cytidine deaminase (AID) to Ig switch regions (S regions). During CSR, the IgH locus undergoes dynamic three-dimensional structural changes in which promoters, enhancers, and S regions are brought to close proximity. Nevertheless, little is known about the underlying mechanisms. In this study, we show that Med1 and Med12, two subunits of the mediator complex implicated in transcription initiation and long-range enhancer/promoter loop formation, are dynamically recruited to the IgH locus enhancers and the acceptor regions during CSR and that their knockdown in CH12 cells results in impaired CSR. Furthermore, we show that conditional inactivation of Med1 in B cells results in defective CSR and reduced acceptor S region transcription. Finally, we show that in B cells undergoing CSR, the dynamic long-range contacts between the IgH enhancers and the acceptor regions correlate with Med1 and Med12 binding and that they happen at a reduced frequency in Med1-deficient B cells. Our results implicate the mediator complex in the mechanism of CSR and are consistent with a model in which mediator facilitates the long-range contacts between S regions and the IgH locus enhancers during CSR and their transcriptional activation. PMID:26903242

  6. Fanca deficiency reduces A/T transitions in somatic hypermutation and alters class switch recombination junctions in mouse B cells.

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    Nguyen, Thuy Vy; Riou, Lydia; Aoufouchi, Saïd; Rosselli, Filippo

    2014-06-01

    Fanconi anemia is a rare genetic disorder that can lead to bone marrow failure, congenital abnormalities, and increased risk for leukemia and cancer. Cells with loss-of-function mutations in the FANC pathway are characterized by chromosome fragility, altered mutability, and abnormal regulation of the nonhomologous end-joining (NHEJ) pathway. Somatic hypermutation (SHM) and immunoglobulin (Ig) class switch recombination (CSR) enable B cells to produce high-affinity antibodies of various isotypes. Both processes are initiated after the generation of dG:dU mismatches by activation-induced cytidine deaminase. Whereas SHM involves an error-prone repair process that introduces novel point mutations into the Ig gene, the mismatches generated during CSR are processed to create double-stranded breaks (DSBs) in DNA, which are then repaired by the NHEJ pathway. As several lines of evidence suggest a possible role for the FANC pathway in SHM and CSR, we analyzed both processes in B cells derived from Fanca(-/-) mice. Here we show that Fanca is required for the induction of transition mutations at A/T residues during SHM and that despite globally normal CSR function in splenic B cells, Fanca is required during CSR to stabilize duplexes between pairs of short microhomology regions, thereby impeding short-range recombination downstream of DSB formation. PMID:24799500

  7. Regulation of immunoglobulin class-switch recombination: choreography of noncoding transcription, targeted DNA deamination, and long-range DNA repair.

    Science.gov (United States)

    Matthews, Allysia J; Zheng, Simin; DiMenna, Lauren J; Chaudhuri, Jayanta

    2014-01-01

    Upon encountering antigens, mature IgM-positive B lymphocytes undergo class-switch recombination (CSR) wherein exons encoding the default Cμ constant coding gene segment of the immunoglobulin (Ig) heavy-chain (Igh) locus are excised and replaced with a new constant gene segment (referred to as "Ch genes", e.g., Cγ, Cɛ, or Cα). The B cell thereby changes from expressing IgM to one producing IgG, IgE, or IgA, with each antibody isotype having a different effector function during an immune reaction. CSR is a DNA deletional-recombination reaction that proceeds through the generation of DNA double-strand breaks (DSBs) in repetitive switch (S) sequences preceding each Ch gene and is completed by end-joining between donor Sμ and acceptor S regions. CSR is a multistep reaction requiring transcription through S regions, the DNA cytidine deaminase AID, and the participation of several general DNA repair pathways including base excision repair, mismatch repair, and classical nonhomologous end-joining. In this review, we discuss our current understanding of how transcription through S regions generates substrates for AID-mediated deamination and how AID participates not only in the initiation of CSR but also in the conversion of deaminated residues into DSBs. Additionally, we review the multiple processes that regulate AID expression and facilitate its recruitment specifically to the Ig loci, and how deregulation of AID specificity leads to oncogenic translocations. Finally, we summarize recent data on the potential role of AID in the maintenance of the pluripotent stem cell state during epigenetic reprogramming. PMID:24507154

  8. Aberrant recombination and repair during immunoglobulin class switching in BRCA1-deficient human B cells

    DEFF Research Database (Denmark)

    Björkman, Andrea; Qvist, Per; Du, Likun;

    2015-01-01

    machinery. A shift to the use of microhomology-based, alternative end-joining (A-EJ) and increased frequencies of intra-S region deletions as well as insertions of inverted S sequences were observed at the recombination junctions amplified from BRCA1-deficient human B cells. Furthermore, increased use of...... underlying BRCA1’s function in maintaining genome stability and tumor suppression but may also point to a previously unrecognized role of BRCA1 in B-cell lymphomagenesis....

  9. Differential regulation of S-region hypermutation and class-switch recombination by noncanonical functions of uracil DNA glycosylase.

    Science.gov (United States)

    Yousif, Ashraf S; Stanlie, Andre; Mondal, Samiran; Honjo, Tasuku; Begum, Nasim A

    2014-03-18

    Activation-induced cytidine deaminase (AID) is essential to class-switch recombination (CSR) and somatic hypermutation (SHM) in both V region SHM and S region SHM (s-SHM). Uracil DNA glycosylase (UNG), a member of the base excision repair (BER) complex, is required for CSR. Strikingly, however, UNG deficiency causes augmentation of SHM, suggesting involvement of distinct functions of UNG in SHM and CSR. Here, we show that noncanonical scaffold functions of UNG regulate s-SHM negatively and CSR positively. The s-SHM suppressive function of UNG is attributed to the recruitment of faithful BER components at the cleaved DNA locus, with competition against error-prone polymerases. By contrast, the CSR-promoting function of UNG enhances AID-dependent S-S synapse formation by recruiting p53-binding protein 1 and DNA-dependent protein kinase, catalytic subunit. Several loss-of-catalysis mutants of UNG discriminated CSR-promoting activity from s-SHM suppressive activity. Taken together, the noncanonical function of UNG regulates the steps after AID-induced DNA cleavage: error-prone repair suppression in s-SHM and end-joining promotion in CSR. PMID:24591630

  10. Differential regulation of S-region hypermutation and class-switch recombination by noncanonical functions of uracil DNA glycosylase

    Science.gov (United States)

    Yousif, Ashraf S.; Stanlie, Andre; Mondal, Samiran; Honjo, Tasuku; Begum, Nasim A.

    2014-01-01

    Activation-induced cytidine deaminase (AID) is essential to class-switch recombination (CSR) and somatic hypermutation (SHM) in both V region SHM and S region SHM (s-SHM). Uracil DNA glycosylase (UNG), a member of the base excision repair (BER) complex, is required for CSR. Strikingly, however, UNG deficiency causes augmentation of SHM, suggesting involvement of distinct functions of UNG in SHM and CSR. Here, we show that noncanonical scaffold functions of UNG regulate s-SHM negatively and CSR positively. The s-SHM suppressive function of UNG is attributed to the recruitment of faithful BER components at the cleaved DNA locus, with competition against error-prone polymerases. By contrast, the CSR-promoting function of UNG enhances AID-dependent S-S synapse formation by recruiting p53-binding protein 1 and DNA-dependent protein kinase, catalytic subunit. Several loss-of-catalysis mutants of UNG discriminated CSR-promoting activity from s-SHM suppressive activity. Taken together, the noncanonical function of UNG regulates the steps after AID-induced DNA cleavage: error-prone repair suppression in s-SHM and end-joining promotion in CSR. PMID:24591630

  11. T-Independent Activation-Induced Cytidine Deaminase Expression, Class-Switch Recombination, and Antibody Production by Immature/Transitional 1 B Cells1

    OpenAIRE

    Ueda, Yoshihiro; Liao, Dongmei; Yang, Kaiyong; Patel, Anjali; Kelsoe, Garnett

    2007-01-01

    Inflammation elicits a splenic lymphopoiesis of unknown physiologic significance but one that juxtaposes developing B cells and exogenous Ag. We show that immature and transitional 1 (immature/T1) B cells constitutively express activation-induced cytidine deaminase and B lymphocyte-induced maturation protein 1 in amounts that support accelerated plasmacytic differentiation and limited class-switch recombination. In vivo, activation of immature/T1 B cells by TLR ligands or bacterial vaccine ra...

  12. Elucidation of the enigmatic IgD class-switch recombination via germline deletion of the IgH 3′ regulatory region

    OpenAIRE

    Rouaud, Pauline; Saintamand, Alexis; Saad, Faten; Carrion, Claire; Lecardeur, Sandrine; Cogné, Michel; Denizot, Yves

    2014-01-01

    Classical class-switch recombination (cCSR) substitutes the Cμ gene with Cγ, Cε, or Cα, thereby generating IgG, IgE, or IgA classes, respectively. This activation-induced deaminase (AID)–driven process is controlled by the IgH 3′ regulatory region (3′RR). Regulation of rare IgD CSR events has been enigmatic. We show that μδCSR occurs in mouse mesenteric lymph node (MLN) B cells and is AID-dependent. AID attacks differ from those in cCSR because they are not accompanied by extensive somatic hy...

  13. Non-canonical uracil processing in DNA gives rise to double-strand breaks and deletions: relevance to class switch recombination.

    Science.gov (United States)

    Bregenhorn, Stephanie; Kallenberger, Lia; Artola-Borán, Mariela; Peña-Diaz, Javier; Jiricny, Josef

    2016-04-01

    During class switch recombination (CSR), antigen-stimulated B-cells rearrange their immunoglobulin constant heavy chain (CH) loci to generate antibodies with different effector functions. CSR is initiated by activation-induced deaminase (AID), which converts cytosines in switch (S) regions, repetitive sequences flanking the CH loci, to uracils. Although U/G mispairs arising in this way are generally efficiently repaired to C/Gs by uracil DNA glycosylase (UNG)-initiated base excision repair (BER), uracil processing in S-regions of activated B-cells occasionally gives rise to double strand breaks (DSBs), which trigger CSR. Surprisingly, genetic experiments revealed that CSR is dependent not only on AID and UNG, but also on mismatch repair (MMR). To elucidate the role of MMR in CSR, we studied the processing of uracil-containing DNA substrates in extracts of MMR-proficient and -deficient human cells, as well as in a system reconstituted from recombinant BER and MMR proteins. Here, we show that the interplay of these repair systems gives rise to DSBs in vitro and to genomic deletions and mutations in vivo, particularly in an S-region sequence. Our findings further suggest that MMR affects pathway choice in DSB repair. Given its amenability to manipulation, our system represents a powerful tool for the molecular dissection of CSR. PMID:26743004

  14. Microbiota regulate the ability of lung dendritic cells to induce IgA class-switch recombination and generate protective gastrointestinal immune responses.

    Science.gov (United States)

    Ruane, Darren; Chorny, Alejo; Lee, Haekyung; Faith, Jeremiah; Pandey, Gaurav; Shan, Meimei; Simchoni, Noa; Rahman, Adeeb; Garg, Aakash; Weinstein, Erica G; Oropallo, Michael; Gaylord, Michelle; Ungaro, Ryan; Cunningham-Rundles, Charlotte; Alexandropoulos, Konstantina; Mucida, Daniel; Merad, Miriam; Cerutti, Andrea; Mehandru, Saurabh

    2016-01-11

    Protective immunoglobulin A (IgA) responses to oral antigens are usually orchestrated by gut dendritic cells (DCs). Here, we show that lung CD103(+) and CD24(+)CD11b(+) DCs induced IgA class-switch recombination (CSR) by activating B cells through T cell-dependent or -independent pathways. Compared with lung DCs (LDC), lung CD64(+) macrophages had decreased expression of B cell activation genes and induced significantly less IgA production. Microbial stimuli, acting through Toll-like receptors, induced transforming growth factor-β (TGF-β) production by LDCs and exerted a profound influence on LDC-mediated IgA CSR. After intranasal immunization with inactive cholera toxin (CT), LDCs stimulated retinoic acid-dependent up-regulation of α4β7 and CCR9 gut-homing receptors on local IgA-expressing B cells. Migration of these B cells to the gut resulted in IgA-mediated protection against an oral challenge with active CT. However, in germ-free mice, the levels of LDC-induced, CT-specific IgA in the gut are significantly reduced. Herein, we demonstrate an unexpected role of the microbiota in modulating the protective efficacy of intranasal vaccination through their effect on the IgA class-switching function of LDCs. PMID:26712806

  15. Murine germinal center B cells require functional Fms-like tyrosine kinase 3 signaling for IgG1 class-switch recombination.

    Science.gov (United States)

    Svensson, Mattias N D; Andersson, Karin M E; Wasén, Caroline; Erlandsson, Malin C; Nurkkala-Karlsson, Merja; Jonsson, Ing-Marie; Brisslert, Mikael; Bemark, Mats; Bokarewa, Maria I

    2015-12-01

    Switched antibody classes are important for efficient immune responses. Aberrant antibody production to otherwise harmless antigens may result in autoimmunity. The protein kinase fms-like tyrosine kinase 3 receptor (Flt3) has an important role during early B-cell development, but the role of Flt3 in peripheral B cells has not been assessed before. Herein we describe a previously unappreciated role for Flt3 in IgG1 class-switch recombination (CSR) and production. We show that Flt3 is reexpressed on B-cell lymphoma 6(+) germinal center B cells in vivo and following LPS activation of peripheral B cells in vitro. Absence of Flt3 signaling in Flt3 ligand-deficient mice results in impaired IgG1 CSR and accumulation of IgM-secreting plasma cells. On activated B cells, Flt3 is coexpressed and functions in synergy with the common-gamma chain receptor family. B cells from Flt3 ligand-deficient mice have impaired IL-4R signaling, with reduced phosphorylation of signal transducer and activator of transcription (Stat) 6, and demonstrate a failure to initiate CSR to IgG1 with low expression of γ1 germ-line transcripts, resulting in impaired IgG1 production. Thus, functional synergy between Flt3 and IL-4R signaling is critical for Stat-mediated regulation of sterile γ1 germ-line transcripts and CSR to IgG1. PMID:26627255

  16. Staggered AID-dependent DNA double strand breaks are the predominant DNA lesions targeted to S mu in Ig class switch recombination.

    Science.gov (United States)

    Rush, James S; Fugmann, Sebastian D; Schatz, David G

    2004-04-01

    Class switch recombination (CSR) is the process whereby B cells alter the effector properties of their Ig molecules. Whilst much is known about the cellular regulation of this process, many of the molecular details remain elusive. Recent evidence suggests that CSR involves blunt DNA double strand breaks (dsbs), and that formation of these dsbs requires the function of the activation-induced cytidine deaminase (AID). We sought to characterize the structural properties and kinetics of induction of the DNA lesions associated with CSR. Using ligation-mediated PCR, we found that AID-dependent DNA dsbs were specifically induced in the S mu region of murine B cells stimulated to undergo CSR. While blunt dsbs were detected, they were only a minor species, with staggered breaks being more than an order of magnitude more abundant. In addition, these breaks could be detected at equal frequency at upstream and downstream portions of S mu, and were induced prior to expression of newly switched isotypes. Collectively, these results provide direct evidence that staggered, S mu-targeted AID-dependent dsbs are the predominant DNA lesion associated with CSR, with important implications for the mechanisms by which CSR DNA lesions are made and processed. PMID:15039385

  17. Elucidation of the enigmatic IgD class-switch recombination via germline deletion of the IgH 3' regulatory region.

    Science.gov (United States)

    Rouaud, Pauline; Saintamand, Alexis; Saad, Faten; Carrion, Claire; Lecardeur, Sandrine; Cogné, Michel; Denizot, Yves

    2014-05-01

    Classical class-switch recombination (cCSR) substitutes the Cμ gene with Cγ, Cε, or Cα, thereby generating IgG, IgE, or IgA classes, respectively. This activation-induced deaminase (AID)-driven process is controlled by the IgH 3' regulatory region (3'RR). Regulation of rare IgD CSR events has been enigmatic. We show that μδCSR occurs in mouse mesenteric lymph node (MLN) B cells and is AID-dependent. AID attacks differ from those in cCSR because they are not accompanied by extensive somatic hypermutation (SHM) of targeted regions and because repaired junctions exhibit features of the alternative end-joining (A-EJ) pathway. In contrast to cCSR and SHM, μδCSR is 3'RR-independent, as its absence affects neither breakpoint locations in Sμ- and Sδ-like (σ(δ)) nor mutation patterns at Sμ-σ(δ) junctions. Although mutations occur in the immediate proximity of the μδ junctions, SHM is absent distal to the junctions within both Sμ and rearranged VDJ regions. In conclusion, μδCSR is active in MLNs, occurs independently of 3'RR-driven assembly, and is even dramatically increased in 3'RR-deficient mice, further showing that its regulation differs from cCSR. PMID:24752300

  18. Hotspots for Vitamin-Steroid-Thyroid Hormone Response Elements Within Switch Regions of Immunoglobulin Heavy Chain Loci Predict a Direct Influence of Vitamins and Hormones on B Cell Class Switch Recombination.

    Science.gov (United States)

    Hurwitz, Julia L; Penkert, Rhiannon R; Xu, Beisi; Fan, Yiping; Partridge, Janet F; Maul, Robert W; Gearhart, Patricia J

    2016-03-01

    Vitamin A deficiencies are common throughout the world and have a significant negative influence on immune protection against viral infections. Mouse models demonstrate that the production of IgA, a first line of defense against viruses at mucosal sites, is inhibited in the context of vitamin A deficiency. In vitro, the addition of vitamin A to activated B cells can enhance IgA expression, but downregulate IgE. Previous reports have demonstrated that vitamin A modifies cytokine patterns, and in so doing may influence antibody isotype expression by an indirect mechanism. However, we have now discovered hundreds of potential response elements among Sμ, Sɛ, and Sα switch sites within immunoglobulin heavy chain loci. These hotspots appear in both mouse and human loci and include targets for vitamin receptors and related proteins (e.g., estrogen receptors) in the nuclear receptor superfamily. Full response elements with direct repeats are relatively infrequent or absent in Sγ regions although half-sites are present. Based on these results, we pose a hypothesis that nuclear receptors have a direct effect on the immunoglobulin heavy chain class switch recombination event. We propose that vitamin A may alter S site accessibility to activation-induced deaminase and nonhomologous end-joining machinery, thereby influencing the isotype switch, antibody production, and protection against viral infections at mucosal sites. PMID:26741514

  19. Requirement of 8-mercaptoguanosine as a costimulus for IL-4-dependent μ to γ1 class switch recombination in CD38-activated B cells

    International Nuclear Information System (INIS)

    Mature B-2 cells expressing surface IgM and IgD proliferate upon stimulation by CD38, CD40 or lipopolysaccharide (LPS) and differentiate into IgG1-producing plasma cells in the presence of cytokines. The process of class switch recombination (CSR) from IgM to other isotypes is highly regulated by cytokines and activation-induced cytidine deaminase (AID). Blimp-1 and XBP-1 play an essential role in the terminal differentiation of switched B-2 cells to Ig-producing plasma cells. IL-5 induces AID and Blimp-1 expression in CD38- and CD40-activated B-2 cells, leading to μ to γ1 CSR at DNA level and IgG1 production. IL-4, a well-known IgG1-inducing factor, does not induce μ to γ1 CSR in CD38-activated B-2 cells or Blimp-1, while IL-4 induces μ to γ1 CSR, XBP-1 expression, and IgG1 production expression in CD40-activated B-2 cells. Interestingly, the addition of 8-mercaptoguanosine (8-SGuo) with IL-4 to the culture of CD38-activated B cells can induce μ to γ1 CSR, Blimp-1 expression, and IgG1 production. Intriguingly, 8-SGuo by itself induces AID expression in CD38-activated B cells. However, it does not induce μ to γ1 CSR. These results imply that the mode of B-cell activation for extracellular stimulation affects the outcome of cytokine stimulation with respect to the efficiency and direction of CSR, and the requirements of the transcriptional regulator and the generation of antibody-secreting cells. Furthermore, our data suggest the requirement of additional molecules in addition to AID for CSR

  20. The SAGA Deubiquitination Module Promotes DNA Repair and Class Switch Recombination through ATM and DNAPK-Mediated γH2AX Formation.

    Science.gov (United States)

    Ramachandran, Shaliny; Haddad, Dania; Li, Conglei; Le, Michael X; Ling, Alexanda K; So, Clare C; Nepal, Rajeev M; Gommerman, Jennifer L; Yu, Kefei; Ketela, Troy; Moffat, Jason; Martin, Alberto

    2016-05-17

    Class switch recombination (CSR) requires activation-induced deaminase (AID) to instigate double-stranded DNA breaks at the immunoglobulin locus. DNA breaks activate the DNA damage response (DDR) by inducing phosphorylation of histone H2AX followed by non-homologous end joining (NHEJ) repair. We carried out a genome-wide screen to identify CSR factors. We found that Usp22, Eny2, and Atxn7, members of the Spt-Ada-Gcn5-acetyltransferase (SAGA) deubiquitination module, are required for deubiquitination of H2BK120ub following DNA damage, are critical for CSR, and function downstream of AID. The SAGA deubiquitinase activity was required for optimal irradiation-induced γH2AX formation, and failure to remove H2BK120ub inhibits ATM- and DNAPK-induced γH2AX formation. Consistent with this effect, these proteins were found to function upstream of various double-stranded DNA repair pathways. This report demonstrates that deubiquitination of histone H2B impacts the early stages of the DDR and is required for the DNA repair phase of CSR. PMID:27160905

  1. B cell TLR1/2, TLR4, TLR7 and TLR9 interact in induction of class switch DNA recombination: modulation by BCR and CD40, and relevance to T-independent antibody responses

    OpenAIRE

    Pone, Egest J; Lou, Zheng; Lam, Tonika; Greenberg, Milton L.; Wang, Rui; Xu, Zhenming; Casali, Paolo

    2015-01-01

    Ig class switch DNA recombination (CSR) in B cells is crucial to the maturation of antibody responses. It requires IgH germline IH-CH transcription and expression of AID, both of which are induced by engagement of CD40 or dual engagement of a Toll-like receptor (TLR) and B cell receptor (BCR). Here, we have addressed cross-regulation between two different TLRs or between a TLR and CD40 in CSR induction by using a B cell stimulation system involving lipopolysaccharides (LPS). LPS mediated long...

  2. Lineage tracing of human B cells reveals the in vivo landscape of human antibody class switching.

    Science.gov (United States)

    Horns, Felix; Vollmers, Christopher; Croote, Derek; Mackey, Sally F; Swan, Gary E; Dekker, Cornelia L; Davis, Mark M; Quake, Stephen R

    2016-01-01

    Antibody class switching is a feature of the adaptive immune system which enables diversification of the effector properties of antibodies. Even though class switching is essential for mounting a protective response to pathogens, the in vivo patterns and lineage characteristics of antibody class switching have remained uncharacterized in living humans. Here we comprehensively measured the landscape of antibody class switching in human adult twins using antibody repertoire sequencing. The map identifies how antibodies of every class are created and delineates a two-tiered hierarchy of class switch pathways. Using somatic hypermutations as a molecular clock, we discovered that closely related B cells often switch to the same class, but lose coherence as somatic mutations accumulate. Such correlations between closely related cells exist when purified B cells class switch in vitro, suggesting that class switch recombination is directed toward specific isotypes by a cell-autonomous imprinted state. PMID:27481325

  3. B cell TLR1/2, TLR4, TLR7 and TLR9 interact in induction of class switch DNA recombination: modulation by BCR and CD40, and relevance to T-independent antibody responses.

    Science.gov (United States)

    Pone, Egest J; Lou, Zheng; Lam, Tonika; Greenberg, Milton L; Wang, Rui; Xu, Zhenming; Casali, Paolo

    2015-02-01

    Ig class switch DNA recombination (CSR) in B cells is crucial to the maturation of antibody responses. It requires IgH germline IH-CH transcription and expression of AID, both of which are induced by engagement of CD40 or dual engagement of a Toll-like receptor (TLR) and B cell receptor (BCR). Here, we have addressed cross-regulation between two different TLRs or between a TLR and CD40 in CSR induction by using a B cell stimulation system involving lipopolysaccharides (LPS). LPS-mediated long-term primary class-switched antibody responses and memory-like antibody responses in vivo and induced generation of class-switched B cells and plasma cells in vitro. Consistent with the requirement for dual TLR and BCR engagement in CSR induction, LPS, which engages TLR4 through its lipid A moiety, triggered cytosolic Ca2+ flux in B cells through its BCR-engaging polysaccharidic moiety. In the presence of BCR crosslinking, LPS synergized with a TLR1/2 ligand (Pam3CSK4) in CSR induction, but much less efficiently with a TLR7 (R-848) or TLR9 (CpG) ligand. In the absence of BCR crosslinking, R-848 and CpG, which per se induced marginal CSR, virtually abrogated CSR to IgG1, IgG2a, IgG2b, IgG3 and/or IgA, as induced by LPS or CD154 (CD40 ligand) plus IL-4, IFN-γ or TGF-β, and reduced secretion of class-switched Igs, without affecting B cell proliferation or IgM expression. The CSR inhibition by TLR9 was associated with the reduction in AID expression and/or IgH germline IH-S-CH transcription, and required co-stimulation of B cells by CpG with LPS or CD154. Unexpectedly, B cells also failed to undergo CSR or plasma cell differentiation when co-stimulated by LPS and CD154. Overall, by addressing the interaction of TLR1/2, TLR4, TLR7 and TLR9 in the induction of CSR and modulation of TLR-dependent CSR by BCR and CD40, our study suggests the complexity of how different stimuli cross-regulate an important B cell differentiation process and an important role of TLRs in inducing

  4. Combinatorial H3K9acS10ph Histone Modification in IgH Locus S Regions Targets 14-3-3 Adaptors and AID to Specify Antibody Class-Switch DNA Recombination

    Directory of Open Access Journals (Sweden)

    Guideng Li

    2013-11-01

    Full Text Available Class-switch DNA recombination (CSR is central to the antibody response, in that it changes the immunoglobulin heavy chain (IgH constant region, thereby diversifying biological effector functions of antibodies. The activation-induced cytidine deaminase (AID-centered CSR machinery excises and rejoins DNA between an upstream (donor and a downstream (acceptor S region, which precede the respective constant region DNA. AID is stabilized on S regions by 14-3-3 adaptors. These adaptors display a high affinity for 5′-AGCT-3′ repeats, which recur in all S regions. However, how 14-3-3, AID, and the CSR machinery target exclusively the donor and acceptor S regions is poorly understood. Here, we show that histone methyltransferases and acetyltransferases are induced by CD40 or Toll-like receptor signaling and catalyze H3K4me3 and H3K9ac/K14ac histone modifications, which are enriched in S regions but do not specify the S region targets of CSR. By contrast, the combinatorial H3K9acS10ph modification specifically marks the S regions set to recombine and directly recruits 14-3-3 adaptors for AID stabilization there. Inhibition of the enzymatic activity of GCN5 and PCAF histone acetyltransferases reduces H3K9acS10ph in S regions, 14-3-3 and AID stabilization, and CSR. Thus, H3K9acS10ph is a histone code that is “written” specifically in S regions and is “read” by 14-3-3 adaptors to target AID for CSR as an important biological outcome.

  5. Lineage tracing of human B cells reveals the in vivo landscape of human antibody class switching

    Science.gov (United States)

    Horns, Felix; Vollmers, Christopher; Croote, Derek; Mackey, Sally F; Swan, Gary E; Dekker, Cornelia L; Davis, Mark M; Quake, Stephen R

    2016-01-01

    Antibody class switching is a feature of the adaptive immune system which enables diversification of the effector properties of antibodies. Even though class switching is essential for mounting a protective response to pathogens, the in vivo patterns and lineage characteristics of antibody class switching have remained uncharacterized in living humans. Here we comprehensively measured the landscape of antibody class switching in human adult twins using antibody repertoire sequencing. The map identifies how antibodies of every class are created and delineates a two-tiered hierarchy of class switch pathways. Using somatic hypermutations as a molecular clock, we discovered that closely related B cells often switch to the same class, but lose coherence as somatic mutations accumulate. Such correlations between closely related cells exist when purified B cells class switch in vitro, suggesting that class switch recombination is directed toward specific isotypes by a cell-autonomous imprinted state. DOI: http://dx.doi.org/10.7554/eLife.16578.001 PMID:27481325

  6. Genome-wide analysis reveals selective modulation of microRNAs and mRNAs by histone deacetylase inhibitor in B cells induced to undergo class switch DNA recombination and plasma cell differentiation

    Directory of Open Access Journals (Sweden)

    Tian eShen

    2015-12-01

    Full Text Available As we have suggested, epigenetic factors, such as microRNAs (miRNAs, can interact with genetic programs to regulate B cell functions, thereby informing antibody and autoantibody responses. We have shown that histone deacetylase inhibitors (HDI inhibit the differentiation events critical to the maturation of the antibody response: class-switch DNA recombination (CSR, somatic hypermutation (SHM and plasma cell differentiation, by modulating intrinsic B cell mechanisms. HDI repress the expression of AID and Blimp-1, which are critical for CSR/SHM and plasma cell differentiation, respectively, in mouse and human B cells by upregulating selected miRNAs that silenced AICDA/Aicda and PRDM1/Prdm1 mRNAs, as demonstrated by multiple qRT-PCRs (J. Immunol. 193:5933-5950, 2014. To further define the selectivity of HDI-mediated modulation of miRNA and gene expression, we performed genome-wide miRNA-Seq and mRNA-Seq analysis in B cells stimulated by LPS plus IL-4 and treated with HDI or nil. Consistent with what we have shown using qRT-PCR, these HDI-treated B cells displayed reduced expression of Aicda and Prdm1, and increased expression of miR-155, miR-181b and miR-361, which target Aicda, and miR-23b, miR-30a and miR-125b, which target Prdm1. In B cells induced to undergo CSR and plasma cell differentiation, about 23% of over 22,000 mRNAs analyzed were expressed at a significantly high copy number (more than 20 copies/cell. Only 18 (0.36% of these highly expressed mRNAs, including Aicda, Prdm1 and Xbp1, were downregulated by HDI by 50% or more. Further, only 16 (0.30% of the highly expressed mRNAs were upregulated (more than twofold by HDI. The selectivity of HDI-mediated modulation of gene expression was emphasized by unchanged expression of the genes that are involved in regulation, targeting or DNA repair processes of CSR, as well as unchanged expression of the genes encoding epigenetic regulators and factors that are important for cell signaling or

  7. Genome-Wide Analysis Reveals Selective Modulation of microRNAs and mRNAs by Histone Deacetylase Inhibitor in B Cells Induced to Undergo Class-Switch DNA Recombination and Plasma Cell Differentiation.

    Science.gov (United States)

    Shen, Tian; Sanchez, Helia N; Zan, Hong; Casali, Paolo

    2015-01-01

    As we have suggested, epigenetic factors, such as microRNAs (miRNAs), can interact with genetic programs to regulate B cell functions, thereby informing antibody and autoantibody responses. We have shown that histone deacetylase (HDAC) inhibitors (HDI) inhibit the differentiation events critical to the maturation of the antibody response: class-switch DNA recombination (CSR), somatic hypermutation (SHM), and plasma cell differentiation, by modulating intrinsic B cell mechanisms. HDI repress the expression of AID and Blimp-1, which are critical for CSR/SHM and plasma cell differentiation, respectively, in mouse and human B cells by upregulating selected miRNAs that silenced AICDA/Aicda and PRDM1/Prdm1 mRNAs, as demonstrated by multiple qRT-PCRs (J Immunol 193:5933-5950, 2014). To further define the selectivity of HDI-mediated modulation of miRNA and gene expression, we performed genome-wide miRNA-Seq and mRNA-Seq analysis in B cells stimulated by LPS plus IL-4 and treated with HDI or nil. Consistent with what we have shown using qRT-PCR, these HDI-treated B cells displayed reduced expression of Aicda and Prdm1, and increased expression of miR-155, miR-181b, and miR-361, which target Aicda, and miR-23b, miR-30a, and miR-125b, which target Prdm1. In B cells induced to undergo CSR and plasma cell differentiation, about 23% of over 22,000 mRNAs analyzed were expressed at a significantly high copy number (more than 20 copies/cell). Only 18 (0.36%) of these highly expressed mRNAs, including Aicda, Prdm1, and Xbp1, were downregulated by HDI by 50% or more. Further, only 16 (0.30%) of the highly expressed mRNAs were upregulated (more than twofold) by HDI. The selectivity of HDI-mediated modulation of gene expression was emphasized by unchanged expression of the genes that are involved in regulation, targeting, or DNA repair processes of CSR, as well as unchanged expression of the genes encoding epigenetic regulators and factors that are important for cell signaling or

  8. Stabilization of a class of switched nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The stabilization of a class of switched nonlinear systems is investigated in the paper. The systems concerned are of (generalized) switched Byrnes-Isidori canonical form, which has all switched models in (generalized) ByrnesIsidori canonical form. First, a stability result of switched systems is obtained. Then it is used to solve the stabilization problem of the switched nonlinear control systems. In addition, necessary and sufficient conditions are obtained for a switched affine nonlinear system to be feedback equivalent to (generalized) switched Byrnes-Isidori canonical systems are presented.Finally, as an application the stability of switched lorenz systems is investigated.

  9. 中药制剂毛萼乙素对免疫球蛋白类别转换的作用%Effects of Eriocalyxin B on immunoglobulin class switch recombination

    Institute of Scientific and Technical Information of China (English)

    任建婷; 张洪信; 陆顺元; 顾鸣敏; 王铸钢

    2013-01-01

    Objective To investigate the effects of Eriocalyxin B (EriB) on immunoglobulin class switch recombination (CSR).Methods B lymphocytes (1B4.B6) were treated with lipopolysaccharide (LPS) and different doses (0 μmol/L,0.75 μmol/L,1.5 μmol/L and 2.0 μmol/L) of EriB,the proliferation of these cells was analyzed by MTT and flow cytometry,the generation of immunoglobulin,efficiency of CSR and expression of relevant genes which play important roles in CSR were examined by ELISA,RT-PCR and Western blotting respectively,and the regulation of NF-κB transcription via EriB was determined by luciferase assay.Results With the increase of EriB concentration,the proliferation and CSR of B cells were defective.EriB inhibited the activation of NF-κB1 through blocking IκBα phosphorylation and degradation.It also directly repressed the transcription level of NF-κB1.Conclusion EriB could inhibit CSR through repressing the activation of NF-κB signaling pathway.%目的 研究中药制剂毛萼乙素(EriB)对免疫球蛋白类别转换(CSR)的作用.方法 以不同剂量的EriB(0、0.75、1.5和2.0 μmol/L)处理脂多糖(LPS)刺激下的B淋巴细胞系1B4.B6细胞,采用MTT和流式细胞术检测细胞的生长状态,并分别采用ELISA、RT-PCR和Western blotting方法检测免疫球蛋白的产生及其CSR的效率以及CSR相关基因的表达水平,采用报告基因法检测EriB对NF-κB的转录调控作用.结果 随着EriB浓度的升高,B细胞增殖及CSR均出现障碍.进一步实验证实EriB通过抑制IKKα的活性阻断IκB磷酸化,进而抑制NF-κB1活化入核;同时直接抑制NF-κB1的转录从而导致其表达水平降低.结论 EriB可通过NF-κB信号通路抑制CSR的发生.

  10. HIV-1 Diversity After a Class Switch Failure

    OpenAIRE

    Kolber, Michael A.; Buendia, Patricia; Degruttola, Victor; Moore, Richard D.

    2010-01-01

    The purpose of this study is to evaluate whether the choice of a PI- or an efavirenz (EFV)-based HAART initial regimen impacts on the viral diversity after failure from a second, class-switch salvage regimen. Sequential HAART failures after a class switch were identified for which the genotypes showed evidence of signature mutations at each failure. Each second failure was required to be from a viral burden

  11. Extended Class of Pruned Crossbar Switches for Optical Networks

    Directory of Open Access Journals (Sweden)

    Hitoshi Obara

    2013-01-01

    Full Text Available Reducing crosspoints of conventional pruned crossbar switches (PXBSs with N23 crosspoints, where N is the switch size, was investigated from an architectural point of view. PXBSs have been created by removing parts of 2x2 switching elements (or simply cells from crossbar switches (XBSs, while preserving both the switches’ planar structure and wide-sense nonblocking property. In this paper, we consider an extended class of PXBSs that has either a 3D structure or rearrangeably nonblocking capability. Two new families of extended PXBSs are described. The first is wide-sense nonblocking; it has a 3D structure of N(N1 cells. Its form is similar to those of ILLIAC(N, N1 torus networks and is isomorphic to a degree-four chordal ring. Its switch control complexity becomes O(1 like conventional XBSs. The second has nearly 3N2/4 cells in a planar structure; it is rearrangeably nonblocking and its switch control complexity is O(N. Its maximum number of rearrangements remains three, regardless of N for N5. It decreases to two, if a pair of input and output ports is left unused. We point out that the second switch provides a missing link between crossbar switches of N2 cells and triangular switches of N(N1/2 cells and yields different rearrangeably nonblocking switches, with the number of rearrangements ranging from three to N2.

  12. Ultra-Low Voltage Class AB Switched Current Memory Cell

    DEFF Research Database (Denmark)

    Igor, Mucha

    1996-01-01

    This paper presents the theoretical basis for the design of class AB switched current memory cells employing floating-gate MOS transistors, suitable for ultra-low-voltage applications. To support the theoretical assumptions circuits based on these cells were designed using a CMOS process with...

  13. Escherichia coli extract-catalyzed recombination in switch regions of mouse immunoglobulin genes.

    OpenAIRE

    Kataoka, T.; Takeda, S.; Honjo, T

    1983-01-01

    We have shown that Escherichia coli extracts catalyze recombination between mouse immunoglobulin mu and alpha genes inserted separately in lambda phage vectors carrying different genetic markers. Most of the recombination sites in the inserts are located in the switch regions of the heavy chain genes, as previously found in the expressed genes of myeloma cells. The recombination took place at relatively high frequency (10(-4)). The recombinational system in E. coli or lambda phage seems to pr...

  14. Pillar switchings and acyclic embedding in mapping class group

    CERN Document Server

    Jeong, Chan-Seok

    2012-01-01

    The braid group $B_g$ is embedded in the ribbon braid group that is defined to be the mapping class group $\\Gamma_{0,(g),1}$. By gluing two copies of surface $S_{0,g+2}$ along $g+1$ holes, we get surface $S_{g,1}$. A pillar switching is a self-homeomorphism of $S_{g,1}$ which switches two pillars of surfaces by $180{}^\\circ$ horizontal rotation. We analyze the actions of pillar switchings on $\\pi_1 S_{g,1}$ and then give concrete expressions of pillar switchings in terms of standard Dehn twists. The map $\\psi: B_g \\rightarrow \\Gamma_{g,1}$ sending the generators of $B_g$ to pillar switchings on $S_{g,1}$ is defined by extending the embedding $B_g \\hookrightarrow \\Gamma_{0,(g+1),1}$. We show that this map is injective by analyzing the actions of pillar switchings on $\\pi_1 S_{g,1}$. The second part of this paper is to prove that this map induces a trivial homology homomorphism in the stable range. For the proof we use the categorical delooping. We construct a suitable monoidal 2-functor from tile category to s...

  15. Class switch recombination in selective IgA-deficient subjects

    DEFF Research Database (Denmark)

    Jensen, Lone Hummelshøj; Ryder, L P; Nielsen, L K;

    2006-01-01

    Selective IgA deficiency is a common immunodeficiency in Caucasians, but the molecular basis of the disorder remains elusive. To address this issue we examined the molecular events leading to IgA production. Naive IgD positive B cells were purified from four donors with IgA deficiency and four...... control donors, all Caucasians. Stimulation of B cells from IgA-deficient donors with the cytokines transforming growth factor (TGF)-beta, interferon (IFN)-gamma or interleukin (IL)-10 in the presence of anti-CD40 antibodies showed reduced expression of both activation-induced cytidine deaminase (AID) and...... alpha germline transcripts (GLT) compared to controls. It was possible, however, to induce AID and alpha GLT when stimulating the cells with anti-CD40 antibody and TGF-beta in the combination with IL-10. Moreover, in anti-CD40 antibody-stimulated cultures, addition of IL-10 or IL-10 + TGF-beta in...

  16. Class switch recombination in selective IgA-deficient subjects

    DEFF Research Database (Denmark)

    Jensen, Lone Hummelshøj; Ryder, L P; Nielsen, L K;

    2006-01-01

    control donors, all Caucasians. Stimulation of B cells from IgA-deficient donors with the cytokines transforming growth factor (TGF)-beta, interferon (IFN)-gamma or interleukin (IL)-10 in the presence of anti-CD40 antibodies showed reduced expression of both activation-induced cytidine deaminase (AID) and...

  17. The roles of APE1, APE2, DNA polymerase β and mismatch repair in creating S region DNA breaks during antibody class switch

    OpenAIRE

    Schrader, Carol E.; Guikema, Jeroen E.J.; Wu, Xiaoming; Stavnezer, Janet

    2008-01-01

    Immunoglobulin class switch recombination (CSR) occurs by an intrachromosomal deletion requiring generation of double-stranded DNA breaks (DSBs) in immunoglobulin switch region DNA. The initial steps of DSB formation have been elucidated: cytosine deamination by activation-induced cytidine deaminase (AID) and the generation of abasic sites by uracil-DNA glycosylase (UNG). We show that abasic sites are converted into single-strand breaks (SSBs) by apurinic/apyrimidinic endonucleases (APE1 and ...

  18. A PTIP-PA1 subcomplex promotes transcription for IgH class switching independently from the associated MLL3/MLL4 methyltransferase complex

    DEFF Research Database (Denmark)

    Starnes, Linda M; Su, Dan; Pikkupeura, Laura M;

    2016-01-01

    Class switch recombination (CSR) diversifies antibodies for productive immune responses while maintaining stability of the B-cell genome. Transcription at the immunoglobulin heavy chain (Igh) locus targets CSR-associated DNA damage and is promoted by the BRCT domain-containing PTIP (Pax...

  19. Essential role of Id2 in negative regulation of IgE class switching.

    Science.gov (United States)

    Sugai, Manabu; Gonda, Hiroyuki; Kusunoki, Takashi; Katakai, Tomoya; Yokota, Yoshifumi; Shimizu, Akira

    2003-01-01

    Serum concentrations of immunoglobulin E (IgE) in normal circumstances are kept much lower than those of other Ig isotypes to avoid allergic reactions. B cells lacking Id2 have increased E2A activity, which leads to specific enhancement of germline transcription of the immunoglobulin epsilon locus. As a consequence, Id2-deficient B cells undergo class switch recombination (CSR) to IgE at a much higher frequency than wild-type B cells. In contrast, Id2 is induced in wild-type B cells by transforming growth factor-beta1 (TGF-beta1) and suppresses IgE CSR. Our results provide evidence for the inhibitory and selective role of Id2 in IgE CSR in response to TGF-beta1. Id2 might act as molecular safeguard to suppress IgE CSR to prevent serious complications such as allergic hypersensitivity during the normal course of immune responses. PMID:12483209

  20. Two-output Class E Isolated dc-dc Converter at 5 MHz Switching Frequency

    OpenAIRE

    Pavlovic, Zoran; Oliver Ramírez, Jesús Angel; Alou Cervera, Pedro; García Suárez, Oscar; Prieto López, Roberto; Cobos Márquez, José Antonio

    2010-01-01

    This paper presents a two output class-E isolated dcdc converter that regulates the output voltages at fixed switching frequency. The converter is simulated at operating frequency of 5 MHz. The converter output power is 40 W and the output voltages are 15 V and 5 V. All the switches operate at zero voltage switching (ZVS) conditions for the full load range. The circuit configuration is simple with small passive components which reduce the size of the converter. The circuit also has ...

  1. Analysis of IgG4 class switch-related molecules in IgG4-related disease

    OpenAIRE

    Tsuboi, Hiroto; Matsuo, Naomi; Iizuka, Mana; Tsuzuki, Sayaka; Kondo, Yuya; Tanaka, Akihiko; Moriyama, Masafumi; Matsumoto, Isao; Nakamura, Seiji; Sumida, Takayuki

    2012-01-01

    Introduction Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a new disease entity characterized by high serum IgG4 levels, IgG4-positive plasmacytic infiltration, and fibrosis in various organs. The purpose of this study was to determine the mechanism of upregulation of IgG4 class switch recombination in IgG4-RD. Methods We extracted RNA from peripheral blood mononuclear cells (PBMCs) of patients with IgG4-RD (n = 6), Sjögren syndrome (SS) (n = 6), and healthy controls (n = 8), from CD3...

  2. Investigation of switching frequency variations in self-oscillating class D amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael A. E.

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in class D amplifiers is known as self-oscillation. An parameter of key interest in self-oscillating class D amplifiers is the switching fre...... distortion. The switching frequency is tracked through accurate spectrum measurements, and very good compliance with simulation results are observed....

  3. Stabilization for a Class of Switched Nonlinear Systems With Novel Average Dwell Time Switching by T-S Fuzzy Modeling.

    Science.gov (United States)

    Zhao, Xudong; Yin, Yunfei; Niu, Ben; Zheng, Xiaolong

    2016-08-01

    In this paper, the problem of switching stabilization for a class of switched nonlinear systems is studied by using average dwell time (ADT) switching, where the subsystems are possibly all unstable. First, a new concept of ADT is given, which is different from the traditional definition of ADT. Based on the new proposed switching signals, a sufficient condition of stabilization for switched nonlinear systems with unstable subsystems is derived. Then, the T-S fuzzy modeling approach is applied to represent the underlying nonlinear system to make the obtained condition easily verified. A novel multiple quadratic Lyapunov function approach is also proposed, by which some conditions are provided in terms of a set of linear matrix inequalities to guarantee the derived T-S fuzzy system to be asymptotically stable. Finally, a numerical example is given to demonstrate the effectiveness of our developed results. PMID:26316288

  4. Analysis of Iterative Learning Control for a Class of Linear Discrete-Time Switched Systems

    OpenAIRE

    Xuan Yang; Xiaoe Ruan

    2015-01-01

    An iterative learning control scheme is applied to a class of linear discrete-time switched systems with arbitrary switching rules. The application is based on the assumption that the switched system repetitively operates over a finite time interval. By taking advantage of the super vector approach, convergence is discussed when noise is free and robustness is analyzed when the controlled system is disturbed by bounded noise. The analytical results manifest that the iterative learning control...

  5. A Class of Stochastic Hybrid Systems with State-Dependent Switching Noise

    DEFF Research Database (Denmark)

    Leth, John-Josef; Rasmussen, Jakob Gulddahl; Schiøler, Henrik; Wisniewski, Rafal

    In this paper, we develop theoretical results based on a proposed method for modeling switching noise for a class of hybrid systems with piecewise linear partitioned state space, and state-depending switching. We devise a stochastic model of such systems, whose global dynamics is governed by a...

  6. A pink mouse reports the switch from red to green fluorescence upon Cre-mediated recombination

    Directory of Open Access Journals (Sweden)

    Hartwich Heiner

    2012-06-01

    Full Text Available Abstract Background Targeted genetic modification in the mouse becomes increasingly important in biomedical and basic science. This goal is most often achieved by use of the Cre/loxP system and numerous Cre-driver mouse lines are currently generated. Their initial characterization requires reporter mouse lines to study the in vivo spatiotemporal activity of Cre. Findings Here, we report a dual fluorescence reporter mouse line, which switches expression from the red fluorescent protein mCherry to eGFP after Cre-mediated recombination. Both fluorescent proteins are expressed from the ubiquitously active and strong CAGGS promoter. Among the founders, we noticed a pink mouse line, expressing high levels of the red fluorescent protein mCherry throughout the entire body. Presence of mCherry in the living animal as well as in almost all organs was clearly visible without optical equipment. Upon Cre-activity, mCherry expression was switched to eGFP, demonstrating functionality of this reporter mouse line. Conclusions The pink mouse presented here is an attractive novel reporter line for fluorescence-based monitoring of Cre-activity. The high expression of mCherry, which is visible to the naked eye, facilitates breeding and crossing, as no genotyping is required to identify mice carrying the reporter allele. The presence of two fluorescent proteins allows in vivo monitoring of recombined and non-recombined cells. Finally, the pink mouse is an eye-catching animal model to demonstrate the power of transgenic techniques in teaching courses.

  7. Constant Switching Frequency Self-Oscillating Controlled Class-D Amplifiers

    DEFF Research Database (Denmark)

    Nguyen-Duy, Khiem; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    The self-oscillating control approach has been used extensively in class-D amplifiers. It has several advantages such as high bandwidth and high audio performance. However, one of the primary disadvantages in a self-oscillating controlled system is that the switching frequency of the amplifier...... varies with the ratio of the output voltage to the input rail voltage. In other words, the switching frequency varies with the duty cycle of the output. The drop in the frequency results in lower control bandwidth and higher output voltage ripple, which are undesirable. This paper proposes a new self......-oscillating control scheme that maintains a constant switching frequency over the full range of output voltage. The frequency difference is processed by a compensator whose output adjusts the total loop gain of the control system. It has been proven by simulation that a con-stant switching frequency self...

  8. Identity and Language Functions: High School Chinese Immigrant Students' Code-Switching Dilemmas in ESL Classes

    Science.gov (United States)

    Liang, Xiaoping

    2006-01-01

    This study examines classroom code-switching in relation to individual and group identity and to functional use of two languages. It investigates how high school Chinese immigrant students perceive the use of first language (L1) and second language (L2) in class, and how they use these languages during group activities. The interview data…

  9. S-band class-F power amplifier with integrated switched mode power supply

    NARCIS (Netherlands)

    Bent, G. van der; Hek, A.P. de; Geurts, S.; Brouzes, H.; Vliet, F.E. van

    2012-01-01

    An S-band radar transmitter MMIC is reported containing a class-F power amplifier and a switched mode power supply. The integration of the power supply offers the possibility to optimize the power amplifier bias voltage for each individual device in a AESA antenna. This has several advantages such a

  10. Ultra Low Voltage Class AB Switched Current Memory Cells Based on Floating Gate Transistors

    DEFF Research Database (Denmark)

    Mucha, Igor

    1999-01-01

    A proposal for a class AB switched current memory cell, suitable for ultra-low-voltage applications is presented. The proposal employs transistors with floating gates, allowing to build analog building blocks for ultralow supply voltage operation also in CMOS processes with high threshold voltages...

  11. Investigation of switching frequency variations and EMI properties in self-oscillating class D amplifiers

    DEFF Research Database (Denmark)

    Nielsen, Dennis; Knott, Arnold; Pfaffinger, Gerhard; Andersen, Michael A. E.

    2009-01-01

    Class D audio amplifiers have gained significant influence in sound reproduction due to their high efficiency. One of the most commonly used control methods in these amplifiers is self-oscillation. A parameter of key interest in self-oscillating amplifiers is the switching frequency, which is kno...

  12. Constant Switching Frequency Self-Oscillating Controlled Class-D Amplifiers

    OpenAIRE

    Nguyen-Duy, Khiem; Knott, Arnold; Andersen, Michael A. E.

    2014-01-01

    The self-oscillating control approach has been used extensively in class-D amplifiers. It has several advantages such as high bandwidth and high audio performance. However, one of the primary disadvantages in a self-oscillating controlled system is that the switching frequency of the amplifier varies with the ratio of the output voltage to the input rail voltage. In other words, the switching frequency varies with the duty cycle of the output. The drop in the frequency results in lower contro...

  13. Looping out and deletion mechanism for the immunoglobulin heavy-chain class switch

    International Nuclear Information System (INIS)

    In the mouse pre-B-cell line 18-81, cells can switch production in vitro from immunoglobulin μ chain to γ2b chain. The gene encoding the γ2b chain is created by a rearrangement of the μ gene. This rearrangement always takes place within a homolog. In cells with a γ2b gene, most of the time the gene segment encoding the constant region of the μ chain is deleted, but often the rearrangement leads to cells that produce no immunoglobulin, and all DNA sequences are retained. The latter result is due to an inversion. Inversions exclude the unequal sister chromatid exchange model of the heavy-chain class switch. Looping out is an intermediate step in the process of generating an inversion. These finding demonstrate that the switch rearrangement occurs by looping out and deletion

  14. Design of Filter for a Class of Switched Linear Neutral Systems

    Directory of Open Access Journals (Sweden)

    Caiyun Wu

    2013-01-01

    Full Text Available This paper is concerned with the filtering problem for a class of switched linear neutral systems with time-varying delays. The time-varying delays appear not only in the state but also in the state derivatives. Based on the average dwell time approach and the piecewise Lyapunov functional technique, sufficient conditions are proposed for the exponential stability of the filtering error dynamic system. Then, the corresponding solvability condition for a desired filter satisfying a weighted performance is established. All the conditions obtained are delay-dependent. Finally, two numerical examples are given to illustrate the effectiveness of the proposed theory.

  15. Non-fragile hybrid guaranteed cost control for a class of uncertain switched linear systems

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper focuses on the problem of non-fragile hybrid guaranteed cost control for a class of uncertain switched linear systems. The controller gain to be designed is assumed to have additive gain variations. Based on multiple-Lyapunov function technique, the design of non-fragile hybrid guaranteed cost controllers is derived to make the corresponding closed-loop system asymptotically stable for all admissible uncertainties. Furthermore, a convex optimization approach with LMIs constraints is introduced to select the optimal non-fragile guaranteed cost controllers. Finally, a simulation example illustrates the effectiveness of the proposed approach.

  16. Stability and stabilization studies for a class of switched nonlinear systems via vector norms approach.

    Science.gov (United States)

    Sakly, Anis; Kermani, Marwen

    2015-07-01

    This paper is concerned with the problems of stability analysis and stabilization with a state feedback controller through pole placement for a class of both continuous and discrete-time switched nonlinear systems. These systems are modeled by differential or difference equations. Then, a transformation under the arrow form is employed. Note that, the main contribution in this work is twofold: firstly, based on the construction of an appropriated common Lyapunov function, as well the use of the vector norms notion, the recourse to the Kotelyanski lemma, the M-matrix proprieties, the aggregation techniques and the application of the Borne-Gentina criterion, new sufficient stability conditions under arbitrary switching for the autonomous system are deduced. Secondly, this result is extended for designing a state feedback controller by using pole assignment control, which guarantee that the corresponding closed-loop system is globally asymptotically stable under arbitrary switching. The main novelties features of these obtained results are the explicitness and the simplicity in their application. Moreover, they allow us to avoid the search of a common Lyapunov function which is a difficult matter. Finally, as validation to stabilize a shunt DC motor under variable mechanical loads is performed to demonstrate the effectiveness of the proposed results. PMID:25701192

  17. Disodium cromoglycate inhibits S mu-->S epsilon deletional switch recombination and IgE synthesis in human B cells

    OpenAIRE

    1994-01-01

    IgE synthesis requires interleukin 4 (IL-4) and a T-B cell interaction that involves the B cell antigen CD40 and its ligand expressed on activated T cells. IL-4 induces epsilon germline transcription whereas ligation of CD40 results in deletional S mu-->S epsilon switch recombination, expression of mature epsilon transcripts, and IgE synthesis and secretion. We demonstrate that disodium cromoglycate (DSCG), a drug commonly used for the prophylactic treatment of allergic disease, inhibits T ce...

  18. Functional recombinant MHC class II molecules and high-throughput peptide-binding assays

    DEFF Research Database (Denmark)

    Justesen, Sune; Harndahl, Mikkel; Lamberth, Kasper; Nielsen, Lise-Lotte B; Buus, Søren

    2009-01-01

    . coli , extracted into urea, and purified under denaturing and non-reducing conditions using conventional column chromatography. Subsequently, diluting the two chains into a folding reaction with appropriate peptide resulted in efficient peptide-MHC-II complex formation. Several different formats of......BACKGROUND: Molecules of the class II major histocompability complex (MHC-II) specifically bind and present exogenously derived peptide epitopes to CD4+ T helper cells. The extreme polymorphism of the MHC-II hampers the complete analysis of peptide binding. It is also a significant hurdle in the...... generation of MHC-II molecules as reagents to study and manipulate specific T helper cell responses. Methods to generate functional MHC-II molecules recombinantly, and measure their interaction with peptides, would be highly desirable; however, no consensus methodology has yet emerged. RESULTS: We generated...

  19. Immunogenicity of recombinant class 1 protein from Neisseria meningitidis refolded into phospholipid vesicles and detergent.

    Science.gov (United States)

    Niebla, O; Alvarez, A; Martín, A; Rodríguez, A; Delgado, M; Falcón, V; Guillén, G

    2001-05-14

    The possibility of eliciting bactericidal antibodies against a recombinant class 1 protein (P1) from Neisseria meningitidis, joined to the first 45 amino acids of the neisserial LpdA protein (PM82), was examined. P1 was produced in Escherichia coli as intracellular inclusion bodies, from which it was purified and reconstituted by (a) inclusion into phospholipid vesicles and detergent and (b) refolding in 0.1% SDS. When Balb/c mice were immunised, high titres of subtype-specific bactericidal antibodies against P1 were obtained in both cases. These results suggest that in spite of being a denaturing agent, it is possible to use SDS to reconstitute the P1 protein in a conformation that exposes the immunodominat regions. PMID:11348724

  20. Diversity of metalloproteinases in Bothrops neuwiedi snake venom transcripts: evidences for recombination between different classes of SVMPs

    Directory of Open Access Journals (Sweden)

    Valente Richard H

    2011-11-01

    Full Text Available Abstract Background Snake venom metalloproteinases (SVMPs are widely distributed in snake venoms and are versatile toxins, targeting many important elements involved in hemostasis, such as basement membrane proteins, clotting proteins, platelets, endothelial and inflammatory cells. The functional diversity of SVMPs is in part due to the structural organization of different combinations of catalytic, disintegrin, disintegrin-like and cysteine-rich domains, which categorizes SVMPs in 3 classes of precursor molecules (PI, PII and PIII further divided in 11 subclasses, 6 of them belonging to PII group. This heterogeneity is currently correlated to genetic accelerated evolution and post-translational modifications. Results Thirty-one SVMP cDNAs were full length cloned from a single specimen of Bothrops neuwiedi snake, sequenced and grouped in eleven distinct sequences and further analyzed by cladistic analysis. Class P-I and class P-III sequences presented the expected tree topology for fibrinolytic and hemorrhagic SVMPs, respectively. In opposition, three distinct segregations were observed for class P-II sequences. P-IIb showed the typical segregation of class P-II SVMPs. However, P-IIa grouped with class P-I cDNAs presenting a 100% identity in the 365 bp at their 5' ends, suggesting post-transcription events for interclass recombination. In addition, catalytic domain of P-IIx sequences segregated with non-hemorrhagic class P-III SVMPs while their disintegrin domain grouped with other class P-II disintegrin domains suggesting independent evolution of catalytic and disintegrin domains. Complementary regions within cDNA sequences were noted and may participate in recombination either at DNA or RNA levels. Proteins predicted by these cDNAs show the main features of the correspondent classes of SVMP, but P-IIb and P-IIx included two additional cysteines cysteines at the C-termini of the disintegrin domains in positions not yet described. Conclusions In

  1. H∞ Control Based on LMIs for a Class of Time-delay Switched Systems

    Institute of Scientific and Technical Information of China (English)

    Chun-ming LI; Xue-min TIAN

    2010-01-01

    The problem of H∞ stability analysis and control synthesis of switched systems with delayed states under arbitrary switching laws is considered. By means of Lyapunov function and linear matrix inequality tools, sufficient condition of H∞ stability is presented in terms of linear matrix inequalities. Furthermore, the robust H∞ control synthesis via state feedback and output feedback is studied. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method.

  2. Laser triggering of water switches in terrawatt-class pulse power accelerators

    International Nuclear Information System (INIS)

    Focused Beams from high-power lasers have been used to command trigger gas switches in pulse power accelerators for more than two decades. This Laboratory-Directed Research and Development project was aimed at determining whether high power lasers could also command trigger water switches on high-power accelerators. In initial work, we determined that focused light from three harmonics of a small pulsed Nd:YAG laser at 1064 nm, 532 nm, and 355 nm could be used to form breakdown arcs in water, with the lowest breakdown thresholds of 110 J/cm2 or 14 GW/cm2 at 532 nm in the green. In laboratory-scale laser triggering experiments with a 170-kV pulse-charged water switch with a 3-mm anode-cathode gap, we demonstrated that ∼90 mJ of green laser energy could trigger the gap with a 1-σ jitter of less than 2ns, a factor of 10 improvement over the jitter of the switch in its self breaking mode. In the laboratory-scale experiments we developed optical techniques utilizing polarization rotation of a probe laser beam to measure current in switch channels and electric field enhancements near streamer heads. In the final year of the project, we constructed a pulse-power facility to allow us to test laser triggering of water switches from 0.6- MV to 2.0 MV. Triggering experiments on this facility using an axicon lens for focusing the laser and a switch with a 740 kV self-break voltage produced consistent laser triggering with a ± 16-ns 1-σ jitter, a significant improvement over the ± 24-ns jitter in the self-breaking mode

  3. Global tracking for a class of uncertain nonlinear systems with unknown sign-switching control direction by output feedback

    Science.gov (United States)

    Roux Oliveira, Tiago; Jacoud Peixoto, Alessandro; Hsu, Liu

    2015-09-01

    This paper addresses the design of a sliding mode controller for a class of high-order uncertain nonlinear plants with unmatched state-dependent nonlinearities and unknown sign of the high frequency gain, i.e., the control direction is assumed unknown. Differently from most previous studies, the control direction is allowed to switch its sign. We show that it is possible to obtain global exact tracking using only output-feedback by coupling a relay periodic switching function with a norm state observer. One significant advantage of the new scheme is its robustness and improved transient response under arbitrary changes of the control direction which have been theoretically demonstrated for jump variations and successfully tested by simulations. The proposed controller is also evaluated with a DC motor control experiment.

  4. A PTIP-PA1 subcomplex promotes transcription for IgH class switching independently from the associated MLL3/MLL4 methyltransferase complex.

    Science.gov (United States)

    Starnes, Linda M; Su, Dan; Pikkupeura, Laura M; Weinert, Brian T; Santos, Margarida A; Mund, Andreas; Soria, Rebeca; Cho, Young-Wook; Pozdnyakova, Irina; Kubec Højfeldt, Martina; Vala, Andrea; Yang, Wenjing; López-Méndez, Blanca; Lee, Ji-Eun; Peng, Weiqun; Yuan, Joan; Ge, Kai; Montoya, Guillermo; Nussenzweig, André; Choudhary, Chunaram; Daniel, Jeremy A

    2016-01-15

    Class switch recombination (CSR) diversifies antibodies for productive immune responses while maintaining stability of the B-cell genome. Transcription at the immunoglobulin heavy chain (Igh) locus targets CSR-associated DNA damage and is promoted by the BRCT domain-containing PTIP (Pax transactivation domain-interacting protein). Although PTIP is a unique component of the mixed-lineage leukemia 3 (MLL3)/MLL4 chromatin-modifying complex, the mechanisms for how PTIP promotes transcription remain unclear. Here we dissected the minimal structural requirements of PTIP and its different protein complexes using quantitative proteomics in primary lymphocytes. We found that PTIP functions in transcription and CSR separately from its association with the MLL3/MLL4 complex and from its localization to sites of DNA damage. We identified a tandem BRCT domain of PTIP that is sufficient for CSR and identified PA1 as its main functional protein partner. Collectively, we provide genetic and biochemical evidence that a PTIP-PA1 subcomplex functions independently from the MLL3/MLL4 complex to mediate transcription during CSR. These results further our understanding of how multifunctional chromatin-modifying complexes are organized by subcomplexes that harbor unique and distinct activities. PMID:26744420

  5. A PTIP–PA1 subcomplex promotes transcription for IgH class switching independently from the associated MLL3/MLL4 methyltransferase complex

    Science.gov (United States)

    Starnes, Linda M.; Su, Dan; Pikkupeura, Laura M.; Weinert, Brian T.; Santos, Margarida A.; Mund, Andreas; Soria, Rebeca; Cho, Young-Wook; Pozdnyakova, Irina; Kubec Højfeldt, Martina; Vala, Andrea; Yang, Wenjing; López-Méndez, Blanca; Lee, Ji-Eun; Peng, Weiqun; Yuan, Joan; Ge, Kai; Montoya, Guillermo; Nussenzweig, André; Choudhary, Chunaram; Daniel, Jeremy A.

    2016-01-01

    Class switch recombination (CSR) diversifies antibodies for productive immune responses while maintaining stability of the B-cell genome. Transcription at the immunoglobulin heavy chain (Igh) locus targets CSR-associated DNA damage and is promoted by the BRCT domain-containing PTIP (Pax transactivation domain-interacting protein). Although PTIP is a unique component of the mixed-lineage leukemia 3 (MLL3)/MLL4 chromatin-modifying complex, the mechanisms for how PTIP promotes transcription remain unclear. Here we dissected the minimal structural requirements of PTIP and its different protein complexes using quantitative proteomics in primary lymphocytes. We found that PTIP functions in transcription and CSR separately from its association with the MLL3/MLL4 complex and from its localization to sites of DNA damage. We identified a tandem BRCT domain of PTIP that is sufficient for CSR and identified PA1 as its main functional protein partner. Collectively, we provide genetic and biochemical evidence that a PTIP–PA1 subcomplex functions independently from the MLL3/MLL4 complex to mediate transcription during CSR. These results further our understanding of how multifunctional chromatin-modifying complexes are organized by subcomplexes that harbor unique and distinct activities. PMID:26744420

  6. Direct Adaptive Fuzzy Sliding Mode Control with Variable Universe Fuzzy Switching Term for a Class of MIMO Nonlinear Systems

    Directory of Open Access Journals (Sweden)

    Guo Haigang

    2012-01-01

    Full Text Available Combining adaptive fuzzy sliding mode control with fuzzy or variable universe fuzzy switching technique, this study develops two novel direct adaptive schemes for a class of MIMO nonlinear systems with uncertainties and external disturbances. The proposed control schemes consist of fuzzy equivalent control terms, fuzzy switching control terms (in scheme one or variable universe fuzzy switching control terms (in scheme two, and compensation control terms. The compensation control terms are used to relax the assumption on fuzzy approximation error. Based on Lyapunov stability theory, the parameters update laws are adaptively tuned online and the global asymptotic stability of the closed-loop system can be guaranteed. The major contribution of this study is to develop a novel framework for designing direct adaptive fuzzy sliding mode control scheme facing model uncertainties and external disturbances. The derived schemes can effectively solve the chattering problem and the equivalent control calculation in that environment. Simulation results performed on a two-link robotic manipulator demonstrate the feasibility of the proposed control schemes.

  7. A High-Voltage class-D power amplifier with switching frequency regulation for improved high-efficiency output power range

    OpenAIRE

    Ma, Haifeng; Zee, van der, S.E.A.T.M.; Nauta, Bram

    2015-01-01

    This paper describes the power dissipation analysis and the design of an efficiency-improved high-voltage class-D power amplifier. The amplifier adaptively regulates its switching frequency for optimal power efficiency across the full output power range. This is based on detecting the switching output node voltage level at the turn-on transition of the power switches. Implemented in a 0.14 μm SOI BCD process, the amplifier achieves 93% efficiency at 45 W output power, > 80% power efficiency d...

  8. Efficient assembly of recombinant major histocompatibility complex class I molecules with preformed disulfide bonds

    DEFF Research Database (Denmark)

    Ostergaard Pedersen, L; Nissen, Mogens Holst; Hansen, N J;

    2001-01-01

    The expression of major histocompatibility class I (MHC-I) crucially depends upon the binding of appropriate peptides. MHC-I from natural sources are therefore always preoccupied with peptides complicating their purification and analysis. Here, we present an efficient solution to this problem...... suggests that de novo folding of denatured MHC-I molecules proceed efficiently if directed by preformed disulfide bond(s). Importantly, these molecules express serological epitopes and stain specific T cells; and they bind peptides specifically. Several denatured MHC-I heavy chains were analyzed and shown...

  9. Specific features of switch-on processes in high-voltage (18 kV class) optically triggered 4H-SiC thyristors

    Science.gov (United States)

    Mnatsakanov, T. T.; Yurkov, S. N.; Levinshtein, M. E.; Cheng, L.; Palmour, J. W.

    2014-05-01

    A computer simulation has been carried out to analyze and explain the specific features of the switch-on process in super-high-voltage (18 kV class) optically triggered 4H-SiC thyristors. It is shown that the previously experimentally observed two-stage character of the switch-on processes can be understood in a one-dimensional approach. The two-stage turn-on of the 18 kV structures is accounted for by the rather slow current rise in the structure with a very wide (160 µm) blocking base. In full agreement with the experimental results, a simulation in the frame of the same approximations demonstrated that, in the 12 kV class thyristor structures with a blocking base thickness of 90 µm, the current increases monotonically during the switch-on process.

  10. The Molecular Switching Mechanism at the Conserved D(E)RY Motif in Class-A GPCRs.

    Science.gov (United States)

    Sandoval, Angelica; Eichler, Stefanie; Madathil, Sineej; Reeves, Philip J; Fahmy, Karim; Böckmann, Rainer A

    2016-07-12

    The disruption of ionic and H-bond interactions between the cytosolic ends of transmembrane helices TM3 and TM6 of class-A (rhodopsin-like) G protein-coupled receptors (GPCRs) is a hallmark for their activation by chemical or physical stimuli. In the bovine photoreceptor rhodopsin, this is accompanied by proton uptake at Glu(134) in the class-conserved D(E)RY motif. Studies on TM3 model peptides proposed a crucial role of the lipid bilayer in linking protonation to stabilization of an active state-like conformation. However, the molecular details of this linkage could not be resolved and have been addressed in this study by molecular dynamics (MD) simulations on TM3 model peptides in a bilayer of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). We show that protonation of the conserved glutamic acid alters the peptide insertion depth in the membrane, its side-chain rotamer preferences, and stabilizes the C-terminal helical structure. These factors contribute to the rise of the side-chain pKa (> 6) and to reduced polarity around the TM3 C terminus as confirmed by fluorescence spectroscopy. Helix stabilization requires the protonated carboxyl group; unexpectedly, this stabilization could not be evoked with an amide in MD simulations. Additionally, time-resolved Fourier transform infrared (FTIR) spectroscopy of TM3 model peptides revealed a different kinetics for lipid ester carbonyl hydration, suggesting that the carboxyl is linked to more extended H-bond clusters than an amide. Remarkably, this was seen as well in DOPC-reconstituted Glu(134)- and Gln(134)-containing bovine opsin mutants and demonstrates that the D(E)RY motif is a hydrated microdomain. The function of the D(E)RY motif as a proton switch is suggested to be based on the reorganization of the H-bond network at the membrane interface. PMID:27410736

  11. Global Uniform Asymptotic Stability of a Class of Switched Linear Systems with an Infinite Number of Subsystems

    Directory of Open Access Journals (Sweden)

    L. F. Araghi

    2014-01-01

    Full Text Available Stability of switching systems with an infinite number of subsystems is important in some structure of systems, like fuzzy systems, neural networks, and so forth. Because of the relationship between stability of a set of matrices and switching systems, this paper first studies the stability of a set of matrices, then and the results are applied for stability of switching systems. Some new conditions for globally uniformly asymptotically stability (GUAS of discrete-time switched linear systems with an infinite number of subsystems are proposed. The paper considers some examples and simulation results.

  12. Electrostatic switches that mediate the pH-dependent conformational change of “short” recombinant human pseudocathepsin D

    OpenAIRE

    Goldfarb, Nathan E.; Lam MT, Minh T.; Bose, Arjo K.; Patel, Ambar M.; Duckworth, Alexander J.; Ben M Dunn

    2005-01-01

    Human Cathepsin D (hCatD) is an aspartic peptidase with a low pH optimum. X-ray crystal structures have been solved for an active, low pH (pH 5.1) form (CatDlo) [Baldwin ET, Bhat, T.N., Gulnik, S., Hosur, M.V., Sowder, R.C., Cachau, R.E., Collins, J., Silva, A.M. and Erickson J.W. (1993) Proc. Natl. Acad. Sci. 90:6796–6800] and an inactive, high pH (pH 7.5) form (CatDhi) [Lee AY, Gulnik SV, Erickson JW. (1998) Nat Struct Biol 5:866–871]. It has been suggested that ionizable switches involving...

  13. MHC Class II Derived Recombinant T Cell Receptor Ligands Protect DBA/1LacJ Mice from Collagen-Induced Arthritis1

    OpenAIRE

    Huan, Jianya; Kaler, Laurie J.; Mooney, Jeffery L.; Subramanian, Sandhya; Hopke, Corwyn; Vandenbark, Arthur A.; Rosloniec, Edward F.; Burrows, Gregory G.; Offner, Halina

    2008-01-01

    We previously demonstrated the therapeutic effects of MHC class II derived recombinant T cell receptor ligands (RTL), single-chain two domain complexes of the α1 and β1 domains of MHC class II molecules genetically linked with an immunodominant peptide, in experimental autoimmune encephalomyelitis. In the current study, we produced a monomeric murine I-Aq-derived RTL construct covalently linked with bovine collagen type II peptide (bCII257–270) suitable for use in DBA/1LacJ mice that develop ...

  14. Cytokine switch and bystander suppression of autoimmune responses to multiple antigens in experimental autoimmune encephalomyelitis by a single recombinant T-cell receptor ligand.

    Science.gov (United States)

    Sinha, Sushmita; Subramanian, Sandhya; Miller, Lisa; Proctor, Thomas M; Roberts, Chris; Burrows, Gregory G; Vandenbark, Arthur A; Offner, Halina

    2009-03-25

    Recombinant T-cell receptor ligands (RTLs) can reverse clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in an antigen-specific manner, and are currently in clinical trials for treatment of subjects with multiple sclerosis (MS). Antigen specificity of RTL raises the question as to whether this treatment would be successful in MS patients where target antigens are unknown. Using spinal cord homogenate or combinations of two different peptides to induce disease, we found that treatment with single RTL could reverse EAE as long as targeted T-cells were present. Therapy with three different RTLs each caused a significant reduction in IL-17 and increases in IL-10 and IL-13 in peptide-activated splenocytes, reduced proliferation of both cognate and bystander specificities of lymph node cells, and reduced inflammatory lesions and secreted IL-17 and IL-2 from peptide-activated spinal cord cells. These results show that treatment with single RTLs can induce a cytokine switch in cognate T-cells that inhibits both the target and bystander T-cells, providing new evidence for the potential applicability of RTL therapy in MS. PMID:19321778

  15. Expression and characterization of recombinant single-chain salmon class I MHC fused with ß2-microglobulin with biological activity

    NARCIS (Netherlands)

    Zhao, H.; Stet, R.J.M.; Skjodt, K.; Savelkoul, H.F.J.

    2008-01-01

    Heterodimeric class I major histocompatibility complex (MHC) molecules consist of a putative 45-kDa heavy chain and a 12-kDa ß2-microglobulin (ß2m) light chain. The knowledge about MHC genes in Atlantic salmon accumulated during the last decade has allowed us to generate soluble and stable MHC class

  16. Expression and characterization of recombinant single-chain salmon class I MHC fused with beta2-microglobulin with biological activity

    DEFF Research Database (Denmark)

    Zhao, Heng; Stet, René J M; Skjødt, Karsten;

    2008-01-01

    Heterodimeric class I major histocompatibility complex (MHC) molecules consist of a putative 45-kDa heavy chain and a 12-kDa beta2-microglobulin (beta2m) light chain. The knowledge about MHC genes in Atlantic salmon accumulated during the last decade has allowed us to generate soluble and stable ...... molecules by biosensor analysis. This production of sufficient amounts of class I MHC proteins may represent a useful tool to study the peptide-binding specificity of MHC class I molecules, in order to design a peptide vaccine against viral pathogens....... resistance to infectious salmon anaemia virus. The single-chain salmon MHC class I molecule has been designed and generated, in which the carboxyl terminus of beta2m is joined together with a flexible 15 or 20 amino acid peptide linker to the amino terminus of the heavy chain (Sasabeta2mUBA*0301). Monoclonal...

  17. The diabetogenic mouse MHC class II molecule I-A[subscript g7] is endowed with a switch that modulates TCR affinity

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Kenji; Corper, Adam L.; Herro, Rana; Jabri, Bana; Wilson, Ian A.; Teyton, Luc (Scripps); (UC)

    2011-11-16

    Genetic susceptibility to autoimmunity is frequently associated with specific MHC alleles. Diabetogenic MHC class II molecules, such as human HLA-DQ8 and mouse I-A{sub g7}, typically have a small, uncharged amino acid residue at position 57 of their {beta} chain ({beta}57); this results in the absence of a salt bridge between {beta}57 and Arg{alpha}76, which is adjacent to the P9 pocket of the peptide-binding groove. However, the influence of Arg{alpha}76 on the selection of the TCR repertoire remains unknown, particularly when the MHC molecule binds a peptide with a neutral amino acid residue at position P9. Here, we have shown that diabetogenic MHC class II molecules bound to a peptide with a neutral P9 residue primarily selected and expanded cells expressing TCRs bearing a negatively charged residue in the first segment of their complementarity determining region 3{beta}. The crystal structure of one such TCR in complex with I-A{sub g7} bound to a peptide containing a neutral P9 residue revealed that a network of favorable long-range (greater than 4 {angstrom}) electrostatic interactions existed among Arg{alpha}76, the neutral P9 residue, and TCR, which supported the substantially increased TCR/peptide-MHC affinity. This network could be modulated or switched to a lower affinity interaction by the introduction of a negative charge at position P9 of the peptide. Our results support the existence of a switch at residue {beta}57 of the I-Ag7 and HLA-DQ8 class II molecules and potentially link normal thymic TCR selection with abnormal peripheral behavior.

  18. MHC class IIB Exon 2 Polymorphism in the Grey Partridge (Perdix perdix) is shaped by selection, recombination and gene conversion

    Czech Academy of Sciences Publication Activity Database

    Promerová, Marta; Králová, Tereza; Bryjová, Anna; Albrecht, Tomáš; Bryja, Josef

    2013-01-01

    Roč. 8, č. 7 (2013), e69135. E-ISSN 1932-6203 R&D Projects: GA ČR GA206/08/1281 Institutional support: RVO:68081766 Keywords : major histocompatibility complex (MHC) * snipe Gallinago-media * Class-I genes * minimal-essential-MHC Subject RIV: EG - Zoology Impact factor: 3.534, year: 2013

  19. Low risk of inhibitor formation in haemophilia A patients following en masse switch in treatment to a third generation full length plasma and albumin-free recombinant factor VIII product (ADVATE®).

    LENUS (Irish Health Repository)

    Bacon, C L

    2011-05-01

    Previous studies have suggested that development of inhibitors in previously treated patients (PTPs) may be attributable to a switch in factor VIII (FVIII) therapeutic product. Consequently, it is widely recognized that inhibitor development must be assessed in PTPs following the introduction of any new FVIII product. Following a national tender process in 2006, all patients with haemophilia A in Ireland changed their FVIII treatment product en masse to a plasma and albumin-free recombinant full-length FVIII product (ADVATE(®)). In this study, we retrospectively reviewed the case records of Irish PTPs to evaluate risk of inhibitor formation following this treatment switch. One hundred and thirteen patients participated in the study. Most patients (89%) had severe haemophilia. Only one of 96 patients with no inhibitor history developed an inhibitor. Prior to the switch in his recombinant FVIII (rFVIII) treatment of choice, this child had only experienced three exposure days (EDs). Consequently, in total he had only received 6 EDs when his inhibitor was first diagnosed. In keeping with this lack of de novo inhibitor development, we observed no evidence of any recurrent inhibitor formation in any of 16 patients with previously documented inhibitors. Similarly, following a previous en masse switch, we have previously reported that changing from a Chinese hamster ovary cell-produced to a baby hamster kidney cell-produced rFVIII was also associated with a low risk of inhibitor formation in PTPs. Our cumulative findings from these two studies clearly emphasizes that the risk of inhibitor development for PTPs following changes in commercial rFVIII product is low, at least in the Irish population.

  20. Treatment with Recombinant Trichinella spiralis Cathepsin B-like Protein Ameliorates Intestinal Ischemia/Reperfusion Injury in Mice by Promoting a Switch from M1 to M2 Macrophages.

    Science.gov (United States)

    Liu, Wei-Feng; Wen, Shi-Hong; Zhan, Jian-Hua; Li, Yun-Sheng; Shen, Jian-Tong; Yang, Wen-Jing; Zhou, Xing-Wang; Liu, Ke-Xuan

    2015-07-01

    Intestinal ischemia/reperfusion (I/R) injury, in which macrophages play a key role, can cause high morbidity and mortality. The switch from classically (M1) to alternatively (M2) activated macrophages, which is dependent on the activation of STAT6 signaling, has been shown to protect organs from I/R injuries. In the current study, the effects of recombinant Trichinella spiralis cathepsin B-like protein (rTsCPB) on intestinal I/R injury and the potential mechanism related to macrophage phenotypes switch were investigated. In a mouse I/R model undergoing 60-min intestinal ischemia followed by 2-h or 7-d reperfusion, we demonstrated that intestinal I/R caused significant intestinal injury and induced a switch from M2 to M1 macrophages, evidenced by a decrease in levels of M2 markers (arginase-1 and found in inflammatory zone protein), an increase in levels of M1 markers (inducible NO synthase and CCR7), and a decrease in the ratio of M2/M1 macrophages. RTsCPB reversed intestinal I/R-induced M2-M1 transition and promoted M1-M2 phenotype switch evidenced by a significant decrease in M1 markers, an increase in M2 markers, and the ratio of M2/M1 macrophages. Meanwhile, rTsCPB significantly ameliorated intestinal injury and improved intestinal function and survival rate of animals, accompanied by a decrease in neutrophil infiltration and an increase in cell proliferation in the intestine. However, a selective STAT6 inhibitor, AS1517499, reversed the protective effects of rTsCPB by inhibiting M1 to M2 transition. These findings suggest that intestinal I/R injury causes a switch from M2 to M1 macrophages and that rTsCPB ameliorates intestinal injury by promoting STAT6-dependent M1 to M2 transition. PMID:25987744

  1. Biochemical characterization of a recombinant plant class III chitinase from the pitcher of the carnivorous plant Nepenthes alata.

    Science.gov (United States)

    Ishisaki, Kana; Arai, Sachiko; Hamada, Tatsuro; Honda, Yuji

    2012-11-01

    A class III chitinase belonging to the GH18 family from Nepenthes alata (NaCHIT3) was expressed in Escherichia coli. The enzyme exhibited hydrolytic activity toward colloidal chitin, ethylene glycol chitin, and (GlcNAc)(n) (n=5 and 6). The enzyme hydrolyzed the fourth glycosidic linkage from the non-reducing end of (GlcNAc)(6). The anomeric form of the products indicated it was a retaining enzyme. The colloidal chitin hydrolytic reaction displayed high activity between pH 3.9 and 6.9, but the pH optimum of the (GlcNAc)(6) hydrolytic reaction was 3.9 at 37 °C. The optimal temperature for activity was 65 °C in 50 mM sodium acetate buffer (pH 3.9). The pH optima of NaCHIT3 and NaCHIT1 might be related to their roles in chitin degradation in the pitcher fluid. PMID:23026711

  2. MHC class II derived recombinant T cell receptor ligands protect DBA/1LacJ mice from collagen-induced arthritis.

    Science.gov (United States)

    Huan, Jianya; Kaler, Laurie J; Mooney, Jeffery L; Subramanian, Sandhya; Hopke, Corwyn; Vandenbark, Arthur A; Rosloniec, Edward F; Burrows, Gregory G; Offner, Halina

    2008-01-15

    We previously demonstrated the therapeutic effects of MHC class II derived recombinant T cell receptor ligands (RTL), single-chain two domain complexes of the alpha1 and beta1 domains of MHC class II molecules genetically linked with an immunodominant peptide, in experimental autoimmune encephalomyelitis. In the current study, we produced a monomeric murine I-Aq-derived RTL construct covalently linked with bovine collagen type II peptide (bCII257-270) suitable for use in DBA/1LacJ mice that develop collagen-induced arthritis (CIA), an animal model of human rheumatoid arthritis, after immunization with bCII protein in CFA. In this study, we demonstrate that the I-Aq-derived RTLs reduced the incidence of the disease, suppressed the clinical and histological signs of CIA and induced long-term modulation of T cells specific for arthritogenic Ags. Our results showed that the I-Aq/bCII257-270 molecule could systemically reduce proinflammatory IL-17 and IFN-gamma production and significantly increase anti-inflammatory IL-10, IL-13, and FoxP3 gene expression in splenocytes. Moreover, I-Aq/bCII257-270 molecule could also selectively inhibit IL-1beta, IL-6, and IL-23 expression in local joint tissue. This is the first report demonstrating effective prevention of joint inflammation and clinical signs of CIA with an I-Aq-derived RTL, thus supporting the possible clinical use of this approach for treating rheumatoid arthritis in humans. PMID:18178865

  3. Cytokine Switch and Bystander Suppression of Autoimmune Responses to Multiple Antigens in Experimental Autoimmune Encephalomyelitis by a Single Recombinant T-Cell Receptor Ligand

    OpenAIRE

    Sinha, Sushmita; Subramanian, Sandhya; Miller, Lisa; Proctor, Thomas M.; Roberts, Chris; Burrows, Gregory G.; Vandenbark, Arthur A.; Offner, Halina

    2009-01-01

    Recombinant T-cell receptor ligands (RTLs) can reverse clinical and histological signs of experimental autoimmune encephalomyelitis (EAE) in an antigen-specific manner, and are currently in clinical trials for treatment of subjects with multiple sclerosis (MS). Antigen specificity of RTL raises the question as to whether this treatment would be successful in MS patients where target antigens are unknown. Using spinal cord homogenate or combinations of two different peptides to induce disease,...

  4. On stability of switched linear systems with perturbed switching paths

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper addresses the stability issue of switched linear systems with perturbed switching paths. First,by introducing thenotions of child-path and parent-path, we are able to define the distance between two switching paths by means of their switching matrices chains. Next, we present the nice properties of the defined distance. Then, a stability criterion is presented for a class of switched linear systems with perturbed switching paths. Finally, an illustrative example is presented to verify the effectiveness of the approach.

  5. Expression of Recombinant Antibodies

    OpenAIRE

    Frenzel, André; Hust, Michael; Schirrmann, Thomas

    2013-01-01

    Recombinant antibodies are highly specific detection probes in research, diagnostics, and have emerged over the last two decades as the fastest growing class of therapeutic proteins. Antibody generation has been dramatically accelerated by in vitro selection systems, particularly phage display. An increasing variety of recombinant production systems have been developed, ranging from Gram-negative and positive bacteria, yeasts and filamentous fungi, insect cell lines, mammalian cells to transg...

  6. Stability of Markov regenerative switched linear systems

    OpenAIRE

    Ogura, Masaki; Preciado, Victor M.

    2015-01-01

    In this paper, we give a necessary and sufficient condition for mean stability of switched linear systems having a Markov regenerative process as its switching signal. This class of switched linear systems, which we call Markov regenerative switched linear systems, contains Markov jump linear systems and semi-Markov jump linear systems as special cases. We show that a Markov regenerative switched linear system is $m$th mean stable if and only if a particular matrix is Schur stable, under the ...

  7. Effect of gamma radiation on retroviral recombination.

    Science.gov (United States)

    Hu, W S; Temin, H M

    1992-07-01

    To elucidate the mechanism(s) of retroviral recombination, we exposed virions to gamma radiation prior to infecting target cells. By using previously described spleen necrosis virus-based vectors containing multiple markers, recombinant proviruses were studied after a single round of retrovirus replication. The current models of retroviral recombination predict that breaking virion RNA should promote minus-strand recombination (forced copy-choice model), decrease or not affect plus-strand recombination (strand displacement/assimilation model), and shift plus-strand recombination towards the 3' end of the genome. However, we found that while gamma irradiation of virions reduced the amount of recoverable viral RNA, it did not primarily cause breaks. Thus, the frequency of selected recombinants was not significantly altered with greater doses of radiation. In spite of this, the irradiation did decrease the number of recombinants with only one internal template switch. As a result, the average number of additional internal template switches in the recombinant proviruses increased from 0.7 to 1.4 as infectivity decreased to 6%. The unselected internal template switches tended to be 5' of the selected crossover even in the recombinants from irradiated viruses, inconsistent with a plus-strand recombination mechanism. PMID:1602553

  8. Bilingual Teachers’ In-class Code-switching Mechanism from the Perspective of Taxonomy of Educational Objectives%双语教师课堂语码转换机制设计研究

    Institute of Scientific and Technical Information of China (English)

    高昂之

    2016-01-01

    以美国教育心理学家本杰明·布卢姆的教育目标分类学为理论依据,选取理论中学习者的知识过程维度和认知过程维度为参照,以高校《国际贸易实务》双语课为例,对双语教师的课堂语码转换机制进行设计,旨在厘清双语教师课堂教学中汉英双语的使用比重、转换方式和转换情境。%This paper aims to design an in-class code-switching mechanism for bilingual teachers from the theoretical perspective of taxonomy of educational objectives of Benjamin Bloom, American educator and psychologist and in the dimensions of knowledge and cognition. It examines the case of the bilingual course of International Trade Practice to highlight bilingual teachers’ Chinese-English code-switching proportion, switching mode and situation respectively.

  9. Differences in meiotic recombination rates in childhood acute lymphoblastic leukemia at an MHC class II hotspot close to disease associated haplotypes.

    Directory of Open Access Journals (Sweden)

    Pamela Thompson

    Full Text Available Childhood Acute Lymphoblastic Leukemia (ALL is a malignant lymphoid disease of which B-cell precursor- (BCP and T-cell- (T ALL are subtypes. The role of alleles encoded by major histocompatibility loci (MHC have been examined in a number of previous studies and results indicating weak, multi-allele associations between the HLA-DPB1 locus and BCP-ALL suggested a role for immunosusceptibility and possibly infection. Two independent SNP association studies of ALL identified loci approximately 37 kb from one another and flanking a strong meiotic recombination hotspot (DNA3, adjacent to HLA-DOA and centromeric of HLA-DPB1. To determine the relationship between this observation and HLA-DPB1 associations, we constructed high density SNP haplotypes of the 316 kb region from HLA-DMB to COL11A2 in childhood ALL and controls using a UK GWAS data subset and the software PHASE. Of four haplotype blocks identified, predicted haplotypes in Block 1 (centromeric of DNA3 differed significantly between BCP-ALL and controls (P = 0.002 and in Block 4 (including HLA-DPB1 between T-ALL and controls (P = 0.049. Of specific common (>5% haplotypes in Block 1, two were less frequent in BCP-ALL, and in Block 4 a single haplotype was more frequent in T-ALL, compared to controls. Unexpectedly, we also observed apparent differences in ancestral meiotic recombination rates at DNA3, with BCP-ALL showing increased and T-ALL decreased levels compared to controls. In silico analysis using LDsplit sotware indicated that recombination rates at DNA3 are influenced by flanking loci, including SNPs identified in childhood ALL association studies. The observed differences in rates of meiotic recombination at this hotspot, and potentially others, may be a characteristic of childhood leukemia and contribute to disease susceptibility, alternatively they may reflect interactions between ALL-associated haplotypes in this region.

  10. The Smallest Molecular Switch

    OpenAIRE

    Emberly, Eldon G.; Kirczenow, George

    2003-01-01

    Ab-initio total energy calculations reveal benzene-dithiolate (BDT) molecules on a gold surface, contacted by a monoatomic gold STM tip to have two classes of low energy conformations with differing symmetries. Lateral motion of the tip or excitation of the molecule cause it to change from one conformation class to the other and to switch between a strongly and a weakly conducting state. Thus, surprisingly, despite their apparent simplicity these Au/BDT/Au nanowires are shown to be electrical...

  11. Gain of function mutation in tobacco MADS box promoter switch on the expression of flowering class B genes converting sepals to petals.

    Science.gov (United States)

    Mahajan, Monika; Yadav, Sudesh Kumar

    2014-02-01

    One mutant transgenic line displaying homeotic conversion of sepals to petals with other phenotypic aberrations was selected and characterized at molecular level. The increased transcript level of gene encoding anthocyanidin synthase and petal specific class B genes, GLOBOSA and DEFECIENS in sepals of mutant line may be responsible for its homeotic conversion to petaloid organs. While characterizing this mutant line for locus identification, T-DNA was found to be inserted in 3' untranslated region of promoter of class B MADS box gene, GLOBOSA. Here, CaMV 35S promoter of T-DNA might be deriving the expression of class B genes. PMID:24362510

  12. Independent Roles of Switching and Hypermutation in the Development and Persistence of B Lymphocyte Memory.

    Science.gov (United States)

    Gitlin, Alexander D; von Boehmer, Lotta; Gazumyan, Anna; Shulman, Ziv; Oliveira, Thiago Y; Nussenzweig, Michel C

    2016-04-19

    Somatic hypermutation (SHM) and class-switch recombination (CSR) increase the affinity and diversify the effector functions of antibodies during immune responses. Although SHM and CSR are fundamentally different, their independent roles in regulating B cell fate have been difficult to uncouple because a single enzyme, activation-induced cytidine deaminase (encoded by Aicda), initiates both reactions. Here, we used a combination of Aicda and antibody mutant alleles that separate the effects of CSR and SHM on polyclonal immune responses. We found that class-switching to IgG1 biased the fate choice made by B cells, favoring the plasma cell over memory cell fate without significantly affecting clonal expansion in the germinal center (GC). In contrast, SHM reduced the longevity of memory B cells by creating polyreactive specificities that were selected against over time. Our data define the independent contributions of SHM and CSR to the generation and persistence of memory in the antibody system. PMID:26944202

  13. Optimal Guaranteed Cost Control of a Class of Discrete-Time Nonlinear Systems with Markovian Switching and Mode-Dependent Mixed Time Delays

    OpenAIRE

    Yurong Liu; Hamid Reza Karimi; Xiaohui Liu

    2013-01-01

    The guaranteed cost control problem is investigated for a class of nonlinear discrete-time systems with Markovian jumping parameters and mixed time delays. The mixed time delays involved consist of both the mode-dependent discrete delay and the distributed delay with mode-dependent lower bound. The associated cost function is of a quadratic summation form over the infinite horizon. The nonlinear functions are assumed to satisfy sector-bounded conditions. By introducing new Lyapunov-Krasovskii...

  14. Pseudospark switches

    International Nuclear Information System (INIS)

    The pseudospark discharge is bound to a geometrical structure which is particularly well suited for switching high currents and voltages at high power levels. This type of discharge offers the potential for improvement in essentially all areas of switching operation: peak current and current density, current rise, stand-off voltage, reverse current capability, cathode life, and forward drop. The first pseudospark switch was built at CERN at 1981. Since then, the basic switching characteristics of pseudospark chambers have been studied in detail. The main feature of a pseudospark switch is the confinement of the discharge plasma to the device axis. The current transition to the hollow electrodes is spread over a rather large surface area. Another essential feature is the easy and precise triggering of the pseudospark switch from the interior of the hollow electrodes, relatively far from the main discharge gap. Nanosecond delay and jitter values can be achieved with trigger energies of less than 0.1 mJ, although cathode heating is not required. Pseudospark gaps may cover a wide range of high-voltage, high-current, and high-pulse-power switching at repetition rates of many kilohertz. This report reviews the basic researh on pseudospark switches which has been going on at CERN. So far, applications have been developed in the range of thyratron-like medium-power switches at typically 20 to 40 kV and 0.5 to 10 kA. High-current pseudospark switches have been built for a high-power 20 kJ pulse generator which is being used for long-term tests of plasma lenses developed for the future CERN Antiproton Collector (ACOL). The high-current switches have operated for several hundred thousand shots, with 20 to 50 ns jitter at 16 kV charging voltage and more than 100 kA peak current amplitude. (orig.)

  15. CIRCUIT SWITCHING VERSUS PACKET SWITCHING

    OpenAIRE

    Sneps-Sneppe, Manfred

    2015-01-01

    Communication specialists around the world are facing the same problem: shifting from circuit switching (CS) to packet switching (CS). Communication service providers are favoring “All-over-IP” technologies hoping to boost their profits by providing multimedia services. The main stakeholder in this field of the paradigm shift is the industry itself: packet switching hardware manufacturers are going to earn billions of dollars and thus pay engineers and journalists many millions for the promot...

  16. Optical switches and switching methods

    Energy Technology Data Exchange (ETDEWEB)

    Doty, Michael

    2008-03-04

    A device and method for collecting subject responses, particularly during magnetic imaging experiments and testing using a method such as functional MRI. The device comprises a non-metallic input device which is coupled via fiber optic cables to a computer or other data collection device. One or more optical switches transmit the subject's responses. The input device keeps the subject's fingers comfortably aligned with the switches by partially immobilizing the forearm, wrist, and/or hand of the subject. Also a robust nonmetallic switch, particularly for use with the input device and methods for optical switching.

  17. 47 CFR 32.2210 - Central office-switching.

    Science.gov (United States)

    2010-10-01

    ... Central office—switching. This account shall be used by Class B companies to record the original cost of switching assets of the type and character required of Class A companies in Accounts 2211 through 2212. ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Central office-switching. 32.2210 Section...

  18. Non-fragile H∞ Control for a Class of Uncertain Time-Delay Switched Systems%一类不确定时滞切换系统的非脆弱H∞控制

    Institute of Scientific and Technical Information of China (English)

    李春吉; 陈霞

    2012-01-01

    讨论了一类不确定时滞切换系统在特定切换条件下的非脆弱状态反馈的H∞控制问题.主要利用凸组合技术、公共Lyapunov函数及线性矩阵不等式等方法,给出了在不确定时滞切换系统中存在非脆弱状态反馈控制器并且满足H∞性能指标γ的充分条件.最后给出了仿真算例,验证了其结果的有效性.定理的条件是以线性矩阵不等式形式给出的,因此便于工程实现.%The problem of non-fragile state feedback H∞ control for a class of uncertain time-delay switched systems was discussed on the particularly switched condition.Based on the common Lyapunov function,convex combination technique and linear matrix inequality,the sufficient condition for the existence of non-fragile state feedback controller was given,and this condition also met the H∞ performance index.In the end,the simulation example was given to verify the effectiveness of the proposed method.The condition of the theorem in the form of linear matrix inquality was put forward,which is easy to realize in practice.

  19. Magnetic switching

    International Nuclear Information System (INIS)

    Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented. 12 refs., 8 figs., 1 tab

  20. Switched steerable multiple beam antenna system

    Science.gov (United States)

    Iwasaki, Richard S.

    1988-09-01

    A steerable multibeam five element cross-feed cluster antenna system is described. The feed power is divided into five branches. Each branch includes a switching network comprised of a plurality of time delay elements each individually controlled by a respective electromagnetic latching switch. Frequency independent individual two-dimensional beam steering at intermediate (IF) scanning frequencies is thereby provided wherein discrete incremental time delays are introduced by the switching networks into each branch and the signals recombined thereafter to form each beam. The electromagnetic latched switching reduces power consumption and permits higher power switching and reciprocal coincident tranmsit and receive operation. Frequency independence due to incremental time delay switching permits coincident reciprocal operation and steering for transmit-receive signal paths carrying different transmit-receive frequencies. Diagonal quarter wave plates in the waveguides alter polarization from the circular to orthogonal linear to provide transmitter-receiver isolation.

  1. Learner Code-Switching versus English Only

    Science.gov (United States)

    Sampson, Andrew

    2012-01-01

    This article describes a study into the functions of code-switching in EFL classes at a Colombian language school. It was undertaken to decide whether the official "English-only" policy in place in this and other classrooms is pedagogically justified. The results suggest that code-switching may not necessarily be connected to ability level and…

  2. On formalism and stability of switched systems

    DEFF Research Database (Denmark)

    Leth, John-Josef; Wisniewski, Rafal

    2012-01-01

    In this paper, we formulate a uniform mathematical framework for studying switched systems with piecewise linear partitioned state space and state dependent switching. Based on known results from the theory of differential inclusions, we devise a Lyapunov stability theorem suitable for this class...

  3. Switching-mode Audio Power Amplifiers with Direct Energy Conversion

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2005-01-01

    This paper presents a new class of switching-mode audio power amplifiers, which are capable of direct energy conversion from the AC mains to the audio output. They represent an ultimate integration of a switching-mode power supply and a Class D audio power amplifier, where the intermediate DC bus...... component count, volume and cost....

  4. Wide Bandgap Extrinsic Photoconductive Switches

    Science.gov (United States)

    Sullivan, James Stephen

    Wide Bandgap Extrinsic Photoconductive Switches Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6H-SiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators. The successful development of a vanadium compensated, 6H-SiC extrinsic photoconductive switch for use as a closing switch for compact accelerator applications was realized by improvements made to the vanadium, nitrogen and boron impurity densities. The changes made to the impurity densities were based on the physical intuition outlined and simple rate equation models. The final 6H-SiC impurity 'recipe' calls for vanadium, nitrogen and boron densities of 2.5 e17 cm-3, 1.25e17 cm-3 and ≤ 1e16 cm-3, respectively. This recipe was originally developed to maximize the quantum efficiency of the vanadium compensated 6H-SiC, while maintaining a thermally stable semi-insulating material. The rate equation models indicate that, besides increasing the quantum efficiency, the impurity recipe should be expected to also increase the carrier recombination time. Three generations of 6H-SiC materials were tested. The

  5. Lymphocyte-specific compensation for XLF/cernunnos end-joining functions in V(D)J recombination.

    Science.gov (United States)

    Li, Gang; Alt, Frederick W; Cheng, Hwei-Ling; Brush, James W; Goff, Peter H; Murphy, Mike M; Franco, Sonia; Zhang, Yu; Zha, Shan

    2008-09-01

    Mutations in XLF/Cernunnos (XLF) cause lymphocytopenia in humans, and various studies suggest an XLF role in classical nonhomologous end joining (C-NHEJ). We now find that XLF-deficient mouse embryonic fibroblasts are ionizing radiation (IR) sensitive and severely impaired for ability to support V(D)J recombination. Yet mature lymphocyte numbers in XLF-deficient mice are only modestly decreased. Moreover, XLF-deficient pro-B lines, while IR-sensitive, perform V(D)J recombination at nearly wild-type levels. Correspondingly, XLF/p53-double-deficient mice are not markedly prone to the pro-B lymphomas that occur in previously characterized C-NHEJ/p53-deficient mice; however, like other C-NHEJ/p53-deficient mice, they still develop medulloblastomas. Despite nearly normal V(D)J recombination in developing B cells, XLF-deficient mature B cells are moderately defective for immunoglobulin heavy-chain class switch recombination. Together, our results implicate XLF as a C-NHEJ factor but also indicate that developing mouse lymphocytes harbor cell-type-specific factors/pathways that compensate for the absence of XLF function during V(D)J recombination. PMID:18775323

  6. Nanoelectromechanical contact switches

    Science.gov (United States)

    Loh, Owen Y.; Espinosa, Horacio D.

    2012-05-01

    Nanoelectromechanical (NEM) switches are similar to conventional semiconductor switches in that they can be used as relays, transistors, logic devices and sensors. However, the operating principles of NEM switches and semiconductor switches are fundamentally different. These differences give NEM switches an advantage over semiconductor switches in some applications -- for example, NEM switches perform much better in extreme environments -- but semiconductor switches benefit from a much superior manufacturing infrastructure. Here we review the potential of NEM-switch technologies to complement or selectively replace conventional complementary metal-oxide semiconductor technology, and identify the challenges involved in the large-scale manufacture of a representative set of NEM-based devices.

  7. An evaluation of Access Tier local area network switches.

    Energy Technology Data Exchange (ETDEWEB)

    Eldridge, John M.; Olsberg, Ronald R.

    2004-06-01

    This reports tabulates the Test and Evaluation results of the Access Class Switch tests conducted by members of Department 9336. About 15 switches were reviewed for use in the enterprise network as access tier switches as defined in a three tier architecture. The Access Switch Tier has several functions including: aggregate customer desktop ports, preserve and apply QoS tags, provide switched LAN access, provide VLAN assignment, as well as others. The typical switch size is 48 or less user ports. The evaluation team reviewed network switch evaluation reports from the Tolly Group as well as other sources. We then used these reports as a starting point to identify particular switches for evaluation. In general we reviewed the products of dominant equipment manufacturers. Also, based on architectural design requirements, the majority of the switches tested were of relatively small monolithic unit variety.

  8. CO2 laser pulse switching by optically excited semiconductors

    International Nuclear Information System (INIS)

    The construction and the study of a semi-conductor optical switch used for generating short infrared pulses and to analyse the semiconductor characteristics, are presented. The switch response time depends on semiconductor and control laser characteristics. The results obtained using a Ge switch controlled by N2, NdYag and Dye lasers are presented. The response time was 50 ns limited by Ge recombination time. The reflectivity increased from 7% to 59% using N2 laser to control the switch. A simple model for semiconductor optical properties that explain very well the experimental results, is also presented. (author)

  9. Passivity of switched recurrent neural networks with time-varying delays.

    Science.gov (United States)

    Lian, Jie; Wang, Jun

    2015-02-01

    This paper is concerned with the passivity analysis for switched neural networks subject to stochastic disturbances and time-varying delays. First, using the multiple Lyapunov functions method, a state-dependent switching law is designed to present a stochastic passivity condition. Second, a hysteresis switching law involving both the current state and the previous value of the switching signal are presented to avoid chattering resulted from the state-dependent switching. Third, based on the average dwell-time approach, a class of switching signals is determined to guarantee the switched neural network stochastically passive. Finally, three numerical examples are provided to illustrate the characteristics of three proposed switching laws. PMID:25576577

  10. Switched on!

    CERN Multimedia

    2008-01-01

    Like a star arriving on stage, impatiently followed by each member of CERN personnel and by millions of eyes around the world, the first beam of protons has circulated in the LHC. After years in the making and months of increasing anticipation, today the work of hundreds of people has borne fruit. WELL DONE to all! Successfully steered around the 27 kilometres of the world’s most powerful particle accelerator at 10:28 this morning, this first beam of protons circulating in the ring marks a key moment in the transition from over two decades of preparation to a new era of scientific discovery. "It’s a fantastic moment," said the LHC project leader Lyn Evans, "we can now look forward to a new era of understanding about the origins and evolution of the universe". Starting up a major new particle accelerator takes much more than flipping a switch. Thousands of individual elements have to work in harmony, timings have to be synchronize...

  11. ADAPTIVE GENERALIZED PREDICTIVE CONTROL OF SWITCHED SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    WANG Yi-jing; WANG Long

    2005-01-01

    The problem of adaptive generalized predictive control which consists of output prediction errors for a class of switched systems is studied. The switching law is determined by the output predictive errors of a finite number of subsystems. For the single subsystem and multiple subsystems cases, it is proved that the given direct algorithm of generalized predictive control guarantees the global convergence of the system. This algorithm overcomes the inherent drawbacks of the slow convergence and large transient errors for the conventional adaptive control.

  12. Understanding Markov-switching rational expectations models

    OpenAIRE

    Roger E.A. Farmer; Daniel F. Waggoner; Zha, Tao

    2009-01-01

    We develop a set of necessary and sufficient conditions for equilibria to be determinate in a class of forward-looking Markov-switching rational expectations models, and we develop an algorithm to check these conditions in practice. We use three examples, based on the new Keynesian model of monetary policy, to illustrate our technique. Our work connects applied econometric models of Markov switching with forward-looking rational expectations models and allows an applied researcher to construc...

  13. New pulse modulator with low switching frequency

    OpenAIRE

    Golub V. S.

    2014-01-01

    The author presents an integrating pulse modulator (analog signal converter) with the pulse frequency and duration modulation similar to sigma-delta modulation (with low switching frequency), without quantization. The modulator is characterized by the absence of the quantization noise inherent in sigma-delta modulator, and a low switching frequency, unlike the pulse-frequency modulator. The modulator is recommended, in particular, to convert signals at the input of the class D power amplifier.

  14. Some results on quadratic stability of switched systems with interval uncertainty

    OpenAIRE

    Zeheb, Ezra; Mason, Oliver; SOLMAZ, Selim; Shorten, Robert

    2007-01-01

    In this paper we present some results on the quadratic stability of switched systems with uncertain parameters. We show that the quadratic stability of a class of switched uncertain systems may be readily veried using simple algebraic conditions.

  15. Recombinant Technology and Probiotics

    Directory of Open Access Journals (Sweden)

    Icy D’Silva

    2011-09-01

    Full Text Available Recombinant technology has led the way to monumental advances in the development of useful molecules, including the development of safe probiotics. The development of novel approaches using recombinant technology and probiotics that allow accurate targeting of therapeutics to the mucosa is an interesting area of research. The creation and use of recombinant probiotics expressing recombinantovalbumin, recombinant ovalbumin mutants and yet-to-be-designed recombinant hypo/non-allergenic molecules offer the opportunity to further investigate their effects for food, nutrition, environment andhealth. This review highlights advances in native probiotics and recombinant probiotics expressing native and recombinant molecules for food, nutrition, environment and health.

  16. Fluctuation-induced switching and the switching path distribution.

    Science.gov (United States)

    Dykman, Mark

    2009-03-01

    Fluctuation-induced switching is at the root of diverse phenomena currently studied in Josephson junctions, nano-mechanical systems, nano-magnets, and optically trapped atoms. In a fluctuation leading to switching the system must overcome an effective barrier, making switching events rare, for low fluctuation intensity. We will provide an overview of the methods of finding the switching barrier for systems away from thermal equilibrium. Generic features of the barrier, such as scaling with the system parameters, will be discussed. We will also discuss the motion of the system in switching and the ways of controlling it. Two major classes of systems will be considered: dynamical systems, where fluctuations are induced by noise, and birth-death systems. Even though the motion during switching is random, the paths followed in switching form a narrow tube in phase space of the system centered at the most probable path. The paths distribution is generally Gaussian and has specific features, which have been seen in the experiment [1]. Finding the most probable path itself can be reduced to solving a problem of Hamiltonian dynamics of an auxiliary noise-free system. The solution also gives the switching barrier. The barrier can be found explicitly close to parameter values where the number of stable states of the system changes and the dynamics is controlled by a slow variable. The scaling of the barrier height depends on the type of the corresponding bifurcation. We show that, both for birth-death and for Gaussian noise driven systems, the presence of even weak non-Gaussian noise can strongly modify the switching rate. The effect is described in a simple explicit form [2,3]. Weak deviations of the noise statistics from Gaussian can be sensitively detected using balanced dynamical bridge, where this deviation makes the populations of coexisting stable states different from each other; a realization of such a bridge will be discussed. We will also discuss the sharp

  17. Isotype-switched follicular lymphoma displays dissociation between activation-induced cytidine deaminase expression and somatic hypermutation.

    Science.gov (United States)

    Scherer, Florian; Navarrete, Marcelo A; Bertinetti-Lapatki, Cristina; Boehm, Joachim; Schmitt-Graeff, Annette; Veelken, Hendrik

    2016-01-01

    In B-cells, activation-induced cytidine deaminase (AID) is required for somatic hypermutation (SHM) and class switch recombination (CSR) of immunoglobulin genes. AID introduces mutations in immunoglobulin variable regions (IGV) during B-cell receptor affinity maturation, but may also introduce aberrant mutations into non-immunoglobulin genes, most commonly BCL6. Follicular lymphoma (FL) B-cells constitutively express AID and undergo CSR, SHM and aberrant SHM. We have studied AID expression, the presence of SHM mutations, CSR, and aberrant SHM in BCL6 in a cohort of 75 FL patients. Whereas IgM-expressing (non-switched) FL were characterized by an expected positive correlation between AID and IGV and BCL6 mutations, isotype-switched FL showed dissociation between AID expression and aberrant SHM, and inverse correlation between SHM and AID expression. Our results unveil two manifest biological subgroups of FL and indicate that the specific dissociation between AID and SHM after isotype switch may correlate with the clinical outcome of this heterogeneous disease. PMID:25860234

  18. Robust feedback switching control: dynamic programming and viscosity solutions

    OpenAIRE

    Bayraktar, Erhan; Cosso, Andrea; Pham, Huyen

    2014-01-01

    We consider a robust switching control problem. The controller only observes the evolution of the state process, and thus uses feedback (closed-loop) switching strategies, a non standard class of switching controls introduced in this paper. The adverse player (nature) chooses open-loop controls that represent the so-called Knightian uncertainty, i.e., misspecifications of the model. The (half) game switcher versus nature is then formulated as a two-step (robust) optimization problem. We devel...

  19. Cost functions in optical burst-switched networks

    OpenAIRE

    Klusek, Bartlomiej

    2006-01-01

    Optical Burst Switching (OBS) is a new paradigm for an all-optical Internet. It combines the best features of Optical Circuit Switching (OCS) and Optical Packet Switching (OPS) while avoidmg the mam problems associated with those networks .Namely, it offers good granularity, but its hardware requirements are lower than those of OPS. In a backbone network, low loss ratio is of particular importance. Also, to meet varying user requirements, it should support multiple classes of service. In ...

  20. Recombinant DNA in Medicine

    OpenAIRE

    Cederbaum, Stephen D.; Fareed, George C.; Lovett, Michael A.; Shapiro, Larry J.

    1984-01-01

    Studies in bacteria and bacterial viruses have led to methods to manipulate and recombine DNA in unique and reproducible ways and to amplify these recombined molecules millions of times. Once properly identified, the recombinant DNA molecules can be used in various ways useful in medicine and human biology. There are many applications for recombinant DNA technology. Cloned complementary DNA has been used to produce various human proteins in microorganisms. Insulin and growth hormone have been...

  1. Improving baculovirus recombination

    OpenAIRE

    Zhao, Yuguang; Chapman, David A. G.; Jones, Ian M.

    2003-01-01

    Recombinant baculoviruses have established themselves as a favoured technology for the high-level expression of recombinant proteins. The construction of recombinant viruses, however, is a time consuming step that restricts consideration of the technology for high throughput developments. Here we use a targeted gene knockout technology to inactivate an essential viral gene that lies adjacent to the locus used for recombination. Viral DNA prepared from the knockout fails to initiate an infecti...

  2. On the quadratic stability of switched interval systems: Preliminary results

    OpenAIRE

    Zeheb, Ezra; Mason, Oliver; SOLMAZ, Selim; Shorten, Robert

    2005-01-01

    In this paper we present some preliminary results on the quadratic stability of switched systems with uncertain parameters. We show that the quadratic stability of a class of switched uncertain systems may be readily verified using simple algebraic conditions. Examples are presented to demonstrate the efficacy of our techniques.

  3. $l^p$ Gain Bounds for Switched Adaptive Controllers

    OpenAIRE

    French, Mark; Trenn, Stephan

    2005-01-01

    A class of discrete plants controlled by a switching adaptive strategy is considered, and $l^p$ bounds, $1 \\le p \\le \\infty$, are obtained for the closed loop gain relating input and output disturbances to internal signals.

  4. H-infinity control for cascade minimum-phase switched nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    Shengzhi ZHAO; Jun ZHAO

    2005-01-01

    This paper is concerned with the H-infinity control problem for a class of cascade switched nonlinear systems.Each switched system in this class is composed of a zero-input asymptotically stable nonlinear part,which is also a switched system,and a linearizable part which is controllable.Conditions under which the H-infinity control problem is solvable under arbitrary switching law and under some designed switching law are derived respectively.The nonlinear state feedback and switching law are designed.We exploit the structural characteristics of the switched nonlinear systems to construct common Lyapunov functions for arbitrary switching and to find a single Lyapunov function for designed switching law.The proposed methods do not rely on the solutions of Hamilton-Jacobi inequalities.

  5. Understanding household switching behavior in the retail electricity market

    International Nuclear Information System (INIS)

    Deregulation of the Danish retail electricity market nearly a decade ago has produced little consumer switching among suppliers or renegotiation of supplier service contracts. From an energy policy perspective, a certain amount of supplier switching is an important indicator of the success of market deregulation. This argues that poor relationship management and a lack of economic benefits are two critical barriers to consumer switching. Latent class analysis indicates that only 11.4% of consumers are non-switchers, whereas 41.1% can be considered potential switchers and approximately one-half (47.5%) can be considered apathetic consumers. We also discuss the managerial implications for both electricity suppliers and policy makers. - Highlights: • This paper investigates the barriers for electricity supplier switching in Denmark. • Four switching barriers were identified. • Relationship management and economic benefits are critical for consumer switching. • Three consumer segments for electricity supplier switching were identified

  6. Therapeutic Recombinant Monoclonal Antibodies

    Science.gov (United States)

    Bakhtiar, Ray

    2012-01-01

    During the last two decades, the rapid growth of biotechnology-derived techniques has led to a myriad of therapeutic recombinant monoclonal antibodies with significant clinical benefits. Recombinant monoclonal antibodies can be obtained from a number of natural sources such as animal cell cultures using recombinant DNA engineering. In contrast to…

  7. Molecular mechanisms of DNA recombination: testing mitotic and meiotic models

    International Nuclear Information System (INIS)

    A hyperhaploid n + 1 strain of Saccharomyces cerevisiae (LBL1) disomic for chromosome VII was employed to isolate hyper-rec and hypo-rec mutations affecting spontaneous mitotic gene conversion and intergenic recombination. The genotype of LBL1 permits simultaneous and independent identification of rec mutations that enhance or diminish gene conversion and those that enhance or diminish intergenic recombination. Five phenotypic groups of rec mutants were isolated following ultraviolet light mutagenesis. Rec mutations that simultaneously abolish or enhance both classes of recombinational events were detected. These results demonstrate that gene conversion and intergenic recombination are under joint genetic control in mitotic cells. Conversion-specific and intergenic recombination-specific rec mutants were also recovered. Their properties indicate that conversion and intergenic recombination are separable pheonomena dependent upon discrete REC genes. The rec mutants isolated in LBL1 provide a method to test molecular models of mitotic and meiotic recombination

  8. Genetic Recombination as a Chemical Reaction Network

    OpenAIRE

    Müller, Stefan; Hofbauer, Josef

    2015-01-01

    The process of genetic recombination can be seen as a chemical reaction network with mass-action kinetics. We review the known results on existence, uniqueness, and global stability of an equilibrium in every compatibility class and for all rate constants, from both the population genetics and the reaction networks point of view.

  9. Heat Switches for ADRs

    Science.gov (United States)

    DiPirro, M. J.; Shirron, P. J.

    2014-01-01

    Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are detailed in this paper.

  10. Controller Architectures for Switching

    DEFF Research Database (Denmark)

    Niemann, Hans Henrik; Poulsen, Niels Kjølstad

    2009-01-01

    This paper investigate different controller architectures in connection with controller switching. The controller switching is derived by using the Youla-Jabr-Bongiorno-Kucera (YJBK) parameterization. A number of different architectures for the implementation of the YJBK parameterization are...... described and applied in connection with controller switching. An architecture that does not include inversion of the coprime factors is introduced. This architecture will make controller switching particular simple....

  11. Switching mode power supplies

    OpenAIRE

    Beard, David W.

    1980-01-01

    The subject of switching mode power supplies was examined. A comparison between linear regulators and switching mode power supplies was made to show the options available for the various types of convertors. Two switching mode power supplies were constructed and tested. The operating efficiency of both systems was found to be more than eighty percent over the specified input voltage and load current conditions. The switching mode power supply circuits required additional ...

  12. MOSFET as a Switch

    OpenAIRE

    Dhaval Agrawal

    2014-01-01

    s as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as a switch. Also it shows the different problems and some remedy to solve those problems with equations and simulatis as ...

  13. On Input-to-State Stability of Switched Stochastic Nonlinear Systems Under Extended Asynchronous Switching.

    Science.gov (United States)

    Kang, Yu; Zhai, Di-Hua; Liu, Guo-Ping; Zhao, Yun-Bo

    2016-05-01

    An extended asynchronous switching model is investigated for a class of switched stochastic nonlinear retarded systems in the presence of both detection delay and false alarm, where the extended asynchronous switching is described by two independent and exponentially distributed stochastic processes, and further simplified as Markovian. Based on the Razumikhin-type theorem incorporated with average dwell-time approach, the sufficient criteria for global asymptotic stability in probability and stochastic input-to-state stability are given, whose importance and effectiveness are finally verified by numerical examples. PMID:26068932

  14. Q-Switching in a Neodymium Laser

    Science.gov (United States)

    Holgado, Warein; Sola, Inigo J.; Jarque, Enrique Conejero; Jarabo, Sebastian; Roso, Luis

    2012-01-01

    We present a laboratory experiment for advanced undergraduate or graduate laser-related classes to study the performance of a neodymium laser. In the experiment, the student has to build the neodymium laser using an open cavity. After that, the cavity losses are modulated with an optical chopper located inside, so the Q-switching regime is…

  15. Switching from Computer to Microcomputer Architecture Education

    Science.gov (United States)

    Bolanakis, Dimosthenis E.; Kotsis, Konstantinos T.; Laopoulos, Theodore

    2010-01-01

    In the last decades, the technological and scientific evolution of the computing discipline has been widely affecting research in software engineering education, which nowadays advocates more enlightened and liberal ideas. This article reviews cross-disciplinary research on a computer architecture class in consideration of its switching to…

  16. Photoionization and Recombination

    Science.gov (United States)

    Nahar, Sultana N.

    2000-01-01

    Theoretically self-consistent calculations for photoionization and (e + ion) recombination are described. The same eigenfunction expansion for the ion is employed in coupled channel calculations for both processes, thus ensuring consistency between cross sections and rates. The theoretical treatment of (e + ion) recombination subsumes both the non-resonant recombination ("radiative recombination"), and the resonant recombination ("di-electronic recombination") processes in a unified scheme. In addition to the total, unified recombination rates, level-specific recombination rates and photoionization cross sections are obtained for a large number of atomic levels. Both relativistic Breit-Pauli, and non-relativistic LS coupling, calculations are carried out in the close coupling approximation using the R-matrix method. Although the calculations are computationally intensive, they yield nearly all photoionization and recombination parameters needed for astrophysical photoionization models with higher precision than hitherto possible, estimated at about 10-20% from comparison with experimentally available data (including experimentally derived DR rates). Results are electronically available for over 40 atoms and ions. Photoionization and recombination of He-, and Li-like C and Fe are described for X-ray modeling. The unified method yields total and complete (e+ion) recombination rate coefficients, that can not otherwise be obtained theoretically or experimentally.

  17. Hairpin-induced tRNA-mediated (HITME) recombination in HIV-1

    NARCIS (Netherlands)

    P. Konstantinova; P. de Haan; A.T. Das; B. Berkhout

    2006-01-01

    Recombination due to template switching during reverse transcription is a major source of genetic variability in retroviruses. In the present study we forced a recombination event in human immunodeficiency virus type 1 (HIV-1) by electroporation of T cells with DNA from a molecular HIV-1 clone that

  18. Recombineering Homologous Recombination Constructs in Drosophila

    OpenAIRE

    Carreira-Rosario, Arnaldo; Scoggin, Shane; Shalaby, Nevine A.; Williams, Nathan David; Hiesinger, P. Robin; Buszczak, Michael

    2013-01-01

    The continued development of techniques for fast, large-scale manipulation of endogenous gene loci will broaden the use of Drosophila melanogaster as a genetic model organism for human-disease related research. Recent years have seen technical advancements like homologous recombination and recombineering. However, generating unequivocal null mutations or tagging endogenous proteins remains a substantial effort for most genes. Here, we describe and demonstrate techniques for using recombineeri...

  19. Optical packet switched networks

    DEFF Research Database (Denmark)

    Hansen, Peter Bukhave

    1999-01-01

    Optical packet switched networks are investigated with emphasis on the performance of the packet switch blocks. Initially, the network context of the optical packet switched network is described showing that a packet network will provide transparency, flexibility and bridge the granularity gap...... between the electrical switched layer and the WDM transport layer. Analytical models are implemented to determine the signal quality ghrough the switch blocks in terms of power penalty and to assess the traffic performance of different switch block architectures. Further, a computer simulation model...... in interferometric wavelength converters is investigated showing that a 10 Gbit/s 19 4x4 swich blocks can be cascaded at a BER of 10-14. An analytical traffic model enables the calculation of the traffice performance of a WDM packet network. Hereby the importance of WDM and wavelegth conversion in the switch blocks...

  20. Geometry of the Limit Sets of Linear Switched Systems

    CERN Document Server

    Balde, Moussa

    2010-01-01

    The paper is concerned with asymptotic stability properties of linear switched systems. Under the hypothesis that all the subsystems share a non strict quadratic Lyapunov function, we provide a large class of switching signals for which a large class of switched systems are asymptotically stable. For this purpose we define what we call non chaotic inputs, which generalize the different notions of inputs with dwell time. Next we turn our attention to the behaviour for possibly chaotic inputs. To finish we give a sufficient condition for a system composed of a pair of Hurwitz matrices to be asymptotically stable for all inputs.

  1. Variable time-period optical switching: a novel OBS implementation

    Institute of Scientific and Technical Information of China (English)

    Jinsong Zhang(张劲松); Mingcui Cao(曹明翠); Fengguang Luo(罗风光); Tao Chen(陈涛)

    2003-01-01

    In this paper, we proposed a novel optical switching method based on optical burst switching (OBS), we call it variable time-period optical switching (VTPOS). It can both support circuit services and other immerged packet services. It has better usability of bandwidth, shorter offset and latency time than others of unidirectional transport signaling mechanisms for OBS. It supports deflection switching for improve blocking performance without the need of schedule buffer. It introduces a time pointer and phase indicator that made synchronous more precisely and requires less guard time, it also classifies the different services classes with a relative QoS model.

  2. Robust Stability Analysis of Nonlinear Switched Systems with Filippov Solutions

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal;

    2012-01-01

    This paper addresses the stability problem of a class of nonlinear switched systems with partitioned state-space and state-dependent switching. In lieu of the Caratheodory solutions, the general Filippov solutions are considered. This encapsulates solutions with infinite switching in finite time....... Based on the theory of differential inclusions, a Lyapunov stability theorem is brought forward. These results are also extended to autonomous switched systems subject to polytopic uncertainty. Furthermore, the proposed stability theorems are reformulated using the sum of squares decomposition method...

  3. Fission yeast mating-type switching: programmed damage and repair

    DEFF Research Database (Denmark)

    Egel, Richard

    2005-01-01

    Mating-type switching in fission yeast follows similar rules as in budding yeast, but the underlying mechanisms are entirely different. Whilst the initiating double-strand cut in Saccharomyces cerevisiae requires recombinational repair for survival, the initial damage in Schizosaccharomyces pombe...

  4. Fundamental study of recombination and recombineering in Escherichia coli

    OpenAIRE

    Sun, Xiaohang; Huang, Yang

    2008-01-01

    Recombination and recombineering systems have been used in Escherichia coli to recombinant DNA sequences. With endonuclease and DNA lipase the bacterial plasmid and target DNA fragment can bind together and recombinant for a new DNA sequences. Red Proteins have been used in recombineering system to perform the function as the enzymes in recombination system, and faster and easier than the other way of recombinant new DNA sequences in E.coli. In this report we get to know the pr...

  5. Selective and genetic constraints on pneumococcal serotype switching.

    Directory of Open Access Journals (Sweden)

    Nicholas J Croucher

    2015-03-01

    Full Text Available Streptococcus pneumoniae isolates typically express one of over 90 immunologically distinguishable polysaccharide capsules (serotypes, which can be classified into "serogroups" based on cross-reactivity with certain antibodies. Pneumococci can alter their serotype through recombinations affecting the capsule polysaccharide synthesis (cps locus. Twenty such "serotype switching" events were fully characterised using a collection of 616 whole genome sequences from systematic surveys of pneumococcal carriage. Eleven of these were within-serogroup switches, representing a highly significant (p < 0.0001 enrichment based on the observed serotype distribution. Whereas the recombinations resulting in between-serogroup switches all spanned the entire cps locus, some of those that caused within-serogroup switches did not. However, higher rates of within-serogroup switching could not be fully explained by either more frequent, shorter recombinations, nor by genetic linkage to genes involved in β-lactam resistance. This suggested the observed pattern was a consequence of selection for preserving serogroup. Phenotyping of strains constructed to express different serotypes in common genetic backgrounds was used to test whether genotypes were physiologically adapted to particular serogroups. These data were consistent with epistatic interactions between the cps locus and the rest of the genome that were specific to serotype, but not serogroup, meaning they were unlikely to account for the observed distribution of capsule types. Exclusion of these genetic and physiological hypotheses suggested future work should focus on alternative mechanisms, such as host immunity spanning multiple serotypes within the same serogroup, which might explain the observed pattern.

  6. Introduction to Optical Burst Switching

    OpenAIRE

    KERNÁCS János; SZILÁGYI Szabolcs

    2010-01-01

    Optical Burst Switching (OBS) isconsidered a popular switching paradigm for therealization of all-optical networks due to the balance itoffers between the coarse-grained Optical CircuitSwitching (OSC) and fine-grained Optical PacketSwitching (OPS). Given that the data are switched allopticallyat the burst level, Optical Burst Switchingcombines the transparency of Optical CircuitSwitching with the benefits of statistical multiplexingin Optical Packet Switching.

  7. Saturated Switching Systems

    CERN Document Server

    Benzaouia, Abdellah

    2012-01-01

    Saturated Switching Systems treats the problem of actuator saturation, inherent in all dynamical systems by using two approaches: positive invariance in which the controller is designed to work within a region of non-saturating linear behaviour; and saturation technique which allows saturation but guarantees asymptotic stability. The results obtained are extended from the linear systems in which they were first developed to switching systems with uncertainties, 2D switching systems, switching systems with Markovian jumping and switching systems of the Takagi-Sugeno type. The text represents a thoroughly referenced distillation of results obtained in this field during the last decade. The selected tool for analysis and design of stabilizing controllers is based on multiple Lyapunov functions and linear matrix inequalities. All the results are illustrated with numerical examples and figures many of them being modelled using MATLAB®. Saturated Switching Systems will be of interest to academic researchers in con...

  8. A Novel Molecular Switch

    OpenAIRE

    Daber, Robert; Lewis, Mitchell

    2009-01-01

    Transcriptional regulation is a fundamental process for regulating the flux of all metabolic pathways. For the last several decades, the lac operon has served as a valuable model for studying transcription. More recently, the switch that controls the operon has also been successfully adapted to function in mammalian cells. Here we describe how, using directed evolution, we have created a novel switch that recognizes an asymmetric operator sequence. The new switch has a repressor with altered ...

  9. FreeSWITCH Cookbook

    CERN Document Server

    Minessale, Anthony

    2012-01-01

    This is a problem-solution approach to take your FreeSWITCH skills to the next level, where everything is explained in a practical way. If you are a system administrator, hobbyist, or someone who uses FreeSWITCH on a regular basis, this book is for you. Whether you are a FreeSWITCH expert or just getting started, this book will take your skills to the next level.

  10. Atomic Scale Plasmonic Switch

    OpenAIRE

    Emboras, A.; Niegemann, J.; Ma, P; Haffner, C; Pedersen, A.; Luisier, M.; Hafner, C; Schimmel, T.; Leuthold, J.

    2016-01-01

    The atom sets an ultimate scaling limit to Moore’s law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocat...

  11. Switched Networks and Complementarity

    OpenAIRE

    Camlıbel, M.K.; Heemels, W.P.M.H; Schaft, van der, A.J.; Schumacher, J.M.

    2003-01-01

    A modeling framework is proposed for circuits that are subject both to externally induced switches (time events) and to state events. The framework applies to switched networks with linear and piecewise-linear elements, including diodes. We show that the linear complementarity formulation, which already has proved effective for piecewise-linear networks, can be extended in a natural way to also cover switching circuits. To achieve this, we use a generalization of the linear complementarity pr...

  12. Stochastic Switching Circuit Synthesis

    OpenAIRE

    Wilhelm, Daniel; Bruck, Jehoshua

    2009-01-01

    Shannon in his 1938 Masterpsilas Thesis demonstrated that any Boolean function can be realized by a switching relay circuit, leading to the development of deterministic digital logic. Here, we replace each classical switch with a probabilistic switch (pswitch). We present algorithms for synthesizing circuits closed with a desired probability, including an algorithm that generates optimal size circuits for any binary fraction. We also introduce a new duality property for series-parallel stocha...

  13. In vitro analysis of a primary, major histocompatibility complex (MHC)-restricted, cytotoxic T-lymphocyte response to avian leukosis virus (ALV), using target cells expressing MHC class I cDNA inserted into a recombinant ALV vector.

    Science.gov (United States)

    Thacker, E L; Fulton, J E; Hunt, H D

    1995-10-01

    The interaction between the major histocompatibility complex (MHC) and cytotoxic T lymphocytes (CTLs) is an important component of the host's resistance to viral infections and tumor formation. In this study, an avian leukosis virus (ALV) vector system, RCASBP, expressing MHC chicken class I (B-F) cDNA was used to develop target cells expressing the chicken class I glycoproteins complexed with ALV antigens on the cell surface. Peripheral blood from chickens inoculated with ALV was shown to contain antigen-specific, MHC-restricted, CD8+ effector CTLs, using a 51Cr release assay utilizing the RCASBP B-F target cells. The stimulated effector cells were also predominantly alpha beta T-cell receptor-positive (TCR2) T cells. The CTL response varied between two haplotypes of chickens which differed in their response to Rous sarcoma virus (RSV)-induced tumors. Chickens with the B21 haplotype which regress RSV-induced tumors showed maximal cytolytic activity, while chickens with the B13 haplotype which do not regress RSV-induced tumors had minimal to no cytolytic activity. In addition to assessing the CTL response to ALV, the creation of MHC-specific immortal target cell lines will be extremely useful in evaluating CTL responses to other viral disease in chickens. PMID:7666545

  14. Guaranteed cost control with constructing switching law of uncertain discrete-time switched systems

    Institute of Scientific and Technical Information of China (English)

    Zhang Ying; Duan Guangren

    2007-01-01

    A guaranteed cost control problem for a class of linear discrete-time switched systems with normbounded uncertainties is considered in this article. The purpose is to construct a switching rule and design a state feedback control law, such that, the closed-loop system is asymptotically stable and the closed-loop cost function value is not more than a specified upper bound for all admissible uncertainties under the constructed switching rule.A sufficient condition for the existence of guaranteed cost controllers and switching rules is derived based on the Lyapunov theory together with the linear matrix inequality (LMI) approach. Furthermore, a convex optimization problem with LMI constraints is formulated to select the suboptimal guaranteed cost controller. A numerical example demonstrates the validity of the proposed design approach.

  15. Asymmetrical Switch Costs in Children

    Science.gov (United States)

    Ellefson, Michelle R.; Shapiron, Laura R.; Chater, Nick

    2006-01-01

    Switching between tasks produces decreases in performance as compared to repeating the same task. Asymmetrical switch costs occur when switching between two tasks of unequal difficulty. This asymmetry occurs because the cost is greater when switching to the less difficult task than when switching to the more difficult task. Various theories about…

  16. [Switching and combining strategies of antidepressant medications].

    Science.gov (United States)

    Charpeaud, Thomas; Moliere, Fanny; Bubrovszky, Maxime; Haesebaert, Frédéric; Allaïli, Najib; Bation, Rémy; Nieto, Isabel; Richieri, Raphaëlle; Saba, Ghassen; Bellivier, Frank; Bennabi, Djamila; Holtzmann, Jérôme; Camus, Vincent; Courtet, Philippe; Courvoisier, Pierre; d'Amato, Thierry; Doumy, Olivier; Garnier, Marion; Bougerol, Thierry; Lançon, Christophe; Haffen, Emmanuel; Leboyer, Marion; Llorca, Pierre-Michel; Vaiva, Guillaume; El-Hage, Wissam; Aouizerate, Bruno

    2016-03-01

    Switching antidepressant medication may be helpful in depressed patients having no benefit from the initial antidepressant treatment. Before considering switching strategy, the initial antidepressant treatment should produce no therapeutic effect after at least 4 weeks of administration at adequate dosage. Choosing an antidepressant of pharmacologically distinct profile fails to consistently demonstrate a significant superiority in terms of effectiveness over the switching to another antidepressant within the same pharmacological class. Augmenting SSRI/SNRIs with mirtazapine/mianserin has become the most recommended strategy of antidepressant combinations. Augmenting SSRI with tricyclic drugs is now a less recommended strategy of antidepressant combinations given the increased risk for the occurrence of pharmacokinetic drug-drug interactions and adverse effects. PMID:26995511

  17. Multidimensional set switching.

    Science.gov (United States)

    Hahn, Sowon; Andersen, George J; Kramer, Arthur F

    2003-06-01

    The present study examined the organization of preparatory processes that underlie set switching and, more specifically, switch costs. On each trial, subjects performed one of two perceptual judgment tasks, color or shape discrimination. Subjects also responded with one of two different response sets. The task set and/or the response set switched from one to the other after 2-6 repeated trials. Response set, task set, and double set switches were performed in both blocked and randomized conditions. Subjects performed with short (100-msec) and long (800-msec) preparatory intervals. Task and response set switches had an additive effect on reaction times (RTs) in the blocked condition. Such a pattern of results suggests a serial organization of preparatory processes when the nature of switches is predictable. However, task and response set switches had an underadditive effect on RTs in the random condition when subjects performed with a brief cue-to-target interval. This pattern of results suggests overlapping task and response set preparation. These findings are discussed in terms of strategic control of preparatory processes in set switching. PMID:12921431

  18. Single Atom Plasmonic Switch

    CERN Document Server

    Emboras, Alexandros; Ma, Ping; Haffner, Christian; Luisier, Mathieu; Hafner, Christian; Schimmel, Thomas; Leuthold, Juerg

    2015-01-01

    The atom sets an ultimate scaling limit to Moores law in the electronics industry. And while electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling-similar to electronics-is only limited by the atom. More precisely, we introduce an electrically controlled single atom plasmonic switch. The switch allows for fast and reproducible switching by means of the relocation of an individual or at most - a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ration of 10 dB and operation at room temperature with femtojoule (fJ) power consumption for a single switch operation. This demonstration of a CMOS compatible, integrated quantum device allowing to control photons at the single-atom level opens intriguing perspectives for a fully i...

  19. Switch on, switch off: stiction in nanoelectromechanical switches

    KAUST Repository

    Wagner, Till J W

    2013-06-13

    We present a theoretical investigation of stiction in nanoscale electromechanical contact switches. We develop a mathematical model to describe the deflection of a cantilever beam in response to both electrostatic and van der Waals forces. Particular focus is given to the question of whether adhesive van der Waals forces cause the cantilever to remain in the \\'ON\\' state even when the electrostatic forces are removed. In contrast to previous studies, our theory accounts for deflections with large slopes (i.e. geometrically nonlinear). We solve the resulting equations numerically to study how a cantilever beam adheres to a rigid electrode: transitions between \\'free\\', \\'pinned\\' and \\'clamped\\' states are shown to be discontinuous and to exhibit significant hysteresis. Our findings are compared to previous results from linearized models and the implications for nanoelectromechanical cantilever switch design are discussed. © 2013 IOP Publishing Ltd.

  20. Towards single molecule switches.

    Science.gov (United States)

    Zhang, Jia Lin; Zhong, Jian Qiang; Lin, Jia Dan; Hu, Wen Ping; Wu, Kai; Xu, Guo Qin; Wee, Andrew T S; Chen, Wei

    2015-05-21

    The concept of using single molecules as key building blocks for logic gates, diodes and transistors to perform basic functions of digital electronic devices at the molecular scale has been explored over the past decades. However, in addition to mimicking the basic functions of current silicon devices, molecules often possess unique properties that have no parallel in conventional materials and promise new hybrid devices with novel functions that cannot be achieved with equivalent solid-state devices. The most appealing example is the molecular switch. Over the past decade, molecular switches on surfaces have been intensely investigated. A variety of external stimuli such as light, electric field, temperature, tunneling electrons and even chemical stimulus have been used to activate these molecular switches between bistable or even multiple states by manipulating molecular conformations, dipole orientations, spin states, charge states and even chemical bond formation. The switching event can occur either on surfaces or in break junctions. The aim of this review is to highlight recent advances in molecular switches triggered by various external stimuli, as investigated by low-temperature scanning tunneling microscopy (LT-STM) and the break junction technique. We begin by presenting the molecular switches triggered by various external stimuli that do not provide single molecule selectivity, referred to as non-selective switching. Special focus is then given to selective single molecule switching realized using the LT-STM tip on surfaces. Single molecule switches operated by different mechanisms are reviewed and discussed. Finally, molecular switches embedded in self-assembled monolayers (SAMs) and single molecule junctions are addressed. PMID:25757483

  1. A Transformer Class E Amplifier

    Directory of Open Access Journals (Sweden)

    Mikolajewski Miroslaw

    2014-12-01

    Full Text Available In a high-efficiency Class E ZVS resonant amplifier a matching and isolation transformer can replace some or even all inductive components of the amplifier thus simplifying the circuit and reducing its cost. In the paper a theoretical analysis, a design example and its experimental verification for a transformer Class E amplifier are presented. In the experimental amplifier with a transformer as the only inductive component in the circuit high efficiency ηMAX = 0.95 was achieved for supply voltage VI = 36 V, maximum output power POMAX = 100 W and the switching frequency f = 300 kHz. Measured parameters and waveforms showed a good agreement with theoretical predictions. Moreover, the relative bandwidth of the switching frequency was only 19% to obtain output power control from 4.8 W to POMAX with efficiency not less than 0.9 in the regulation range.

  2. Analysis and Synthesis of pHEMT Class-E Amplifiers with Shunt Inductor including ON-State Active-Device Resistance Effects

    OpenAIRE

    Thian, Mury; Fusco, Vincent

    2006-01-01

    In this theoretical paper, the analysis of the effect that ON-state active-device resistance has on the performance of a Class-E tuned power amplifier using a shunt inductor topology is presented. The work is focused on the relatively unexplored area of design facilitation of Class-E tuned amplifiers where intrinsically low-output-capacitance monolithic microwave integrated circuit switching devices such as pseudomorphic high electron mobility transistors are used. In the paper, the switching...

  3. Optical packet switching

    Science.gov (United States)

    Shekel, Eyal; Ruschin, Shlomo; Majer, Daniel; Levy, Jeff; Matmon, Guy; Koenigsberg, Lisa; Vecht, Jacob; Geron, Amir; Harlavan, Rotem; Shfaram, Harel; Arbel, Arnon; McDermott, Tom; Brewer, Tony

    2005-02-01

    We report here a scalable, multichassis, 6.3 terabit core router, which utilizes our proprietary optical switch. The router is commercially available and deployed in several customer sites. Our solution combines optical switching with electronic routing. An internal optical packet switching network interconnects the router"s electronic line cards, where routing and buffering functions take place electronically. The system architecture and performance will be described. The optical switch is based on Optical Phased Array (OPA) technology. It is a 64 x 64, fully non-blocking, optical crossbar switch, capable of switching in a fraction of a nanosecond. The basic principles of operation will be explained. Loss and crosstalk results will be presented, as well as the results of BER measurements of a 160 Gbps transmission through one channel. Basic principles of operation and measured results will be presented for the burst-mode-receivers, arbitration algorithm and synchronization. Finally, we will present some of our current research work on a next-generation optical switch. The technological issues we have solved in our internal optical packet network can have broad applicability to any global optical packet network.

  4. JUNOS Enterprise Switching

    CERN Document Server

    Reynolds, Harry

    2009-01-01

    JUNOS Enterprise Switching is the only detailed technical book on Juniper Networks' new Ethernet-switching EX product platform. With this book, you'll learn all about the hardware and ASIC design prowess of the EX platform, as well as the JUNOS Software that powers it. Not only is this extremely practical book a useful, hands-on manual to the EX platform, it also makes an excellent study guide for certification exams in the JNTCP enterprise tracks. The authors have based JUNOS Enterprise Switching on their own Juniper training practices and programs, as well as the configuration, maintenanc

  5. SPARK GAP SWITCH

    Science.gov (United States)

    Neal, R.B.

    1957-12-17

    An improved triggered spark gap switch is described, capable of precisely controllable firing time while switching very large amounts of power. The invention in general comprises three electrodes adjustably spaced and adapted to have a large potential impressed between the outer electrodes. The central electrode includes two separate elements electrically connected togetaer and spaced apart to define a pair of spark gaps between the end electrodes. Means are provided to cause the gas flow in the switch to pass towards the central electrode, through a passage in each separate element, and out an exit disposed between the two separate central electrode elements in order to withdraw ions from the spark gap.

  6. A Metabolic Switch

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    Our muscles are metabolically flexible, i.e., they are capable of `switching' between two types of oxidation: (1) when fasting, a predominantly lipid oxidation with high rates of fatty acid uptake, and (2) when fed, suppression of lipid oxidation in favour of increased glucose uptake, oxidation and...... storage, in response to insulin. One of the many manifestations of obesity and Type 2 diabetes is an insulin resistance of the skeletal muscles, which suppresses this metabolic switch. This talk describes recent development of a low-dimensional system of ODEs that model the metabolic switch, displaying a...

  7. Switch mode power supply

    International Nuclear Information System (INIS)

    This book concentrates on switch mode power supply. It has four parts, which are introduction of switch mode power supply with DC-DC converter such as Buck converter boost converter, Buck-boost converter and PWM control circuit, explanation for SMPS with DC-DC converter modeling and power mode control, resonance converter like resonance switch, converter, multi resonance converter and series resonance and parallel resonance converters, basic test of SMPS with PWM control circuit, Buck converter, Boost converter, flyback converter, forward converter and IC for control circuit.

  8. Class size versus class composition

    DEFF Research Database (Denmark)

    Jones, Sam

    Raising schooling quality in low-income countries is a pressing challenge. Substantial research has considered the impact of cutting class sizes on skills acquisition. Considerably less attention has been given to the extent to which peer effects, which refer to class composition, also may affect...

  9. Switching Fuzzy Guaranteed Cost Control for Nonlinear Networked Control Systems

    OpenAIRE

    Linqin Cai; Zhuo Yang; Jimin Yu; Zhenhua Zhang

    2014-01-01

    This paper deals with the problem of guaranteed cost control for a class of nonlinear networked control systems (NCSs) with time-varying delay. A guaranteed cost controller design method is proposed to achieve the desired control performance based on the switched T-S fuzzy model. The switching mechanism is introduced to handle the uncertainties of NCSs. Based on Lyapunov functional approach, some sufficient conditions for the existence of state feedback robust guaranteed cost controller are p...

  10. A thiol antioxidant regulates IgE isotype switching by inhibiting activation of nuclear factor-kappaB.

    Science.gov (United States)

    Yanagihara, Y; Basaki, Y; Kajiwara, K; Ikizawa, K

    1997-12-01

    The binding site for nuclear factor-kappaB (NF-kappaB) is present at the promoter region of the germline Cepsilon gene, but there is little information on whether this factor is involved in regulating IgE synthesis by human B cells. Accordingly, we studied the role of NF-kappaB in germline Cepsilon transcription by using two human Burkitt's lymphoma B cell lines, DND39 and DG75. In both cell lines, n-acetyl-L-cysteine (NAC), a potent thiol antioxidant, inhibited the triggering of the nuclear expression of NF-kappaB by IL-4 and by anti-CD40 monoclonal antibody. Although IL-4 activated signal transducers and activators of transcription (STAT) 6 in addition to NF-kappaB, NAC treatment or the transfection of decoy oligodeoxynucleotides for NF-kappaB or STAT6 only partly blocked IL-4-induced germline Cepsilon transcription. However, these two decoy oligodeoxynucleotides together almost completely abrogated IL-4-induced germline Cepsilon transcription. Of note, CD40-mediated enhancement of IL-4-driven germline Cepsilon transcription was markedly decreased by NAC or by a decoy oligodeoxynucleotide for NF-kappaB. The effect of NAC was also examined on deletional switch recombination underlying the isotype switch to IgE. NAC inhibited the generation of Smu/Sepsilon switch fragments in normal human B cells costimulated with IL-4 and anti-CD40 monoclonal antibody. It also abolished IL-4-induced upregulation of CD40 but promoted upregulation of CD23. These results suggest that coordination of NF-kappaB and STAT6 may be required for induction of germline Cepsilon transcription by IL-4, and that CD40-mediated NF-kappaB activation may be important in regulating both enhancement of germline Cepsilon transcription and class switching to IgE. PMID:9440542

  11. Word classes

    DEFF Research Database (Denmark)

    Rijkhoff, Jan

    2007-01-01

    This article provides an overview of recent literature and research on word classes, focusing in particular on typological approaches to word classification. The cross-linguistic classification of word class systems (or parts-of-speech systems) presented in this article is based on statements found...... in grammatical descriptions of some 50 languages, which together constitute a representative sample of the world’s languages (Hengeveld et al. 2004: 529). It appears that there are both quantitative and qualitative differences between word class systems of individual languages. Whereas some languages...... employ a parts-of-speech system that includes the categories Verb, Noun, Adjective and Adverb, other languages may use only a subset of these four lexical categories. Furthermore, quite a few languages have a major word class whose members cannot be classified in terms of the categories Verb – Noun...

  12. A Novel Single-Switch Single-Stage Electronic Ballast

    Institute of Scientific and Technical Information of China (English)

    Lu-Hua Zhu; Xing-Bi Chen; Hong-Sheng Zhong

    2009-01-01

    A single-stage single-switch high- frequency electronic ballast topology is presented. The circuit topology is the integration of a buck power- factor-correction (PFC) converter and a class E resonant inverter with only one active power switch. The buck converter is operated in discontinuous conduction mode and at a fixed switching frequency, and constant duty cycle to achieve high power factor and it can be controlled easily. Detailed analysis of the operation and characteristics of the circuit is provided. Simulation results satisfy present standard require- ments.

  13. Switched linear differential systems

    OpenAIRE

    Mayo Maldonado, Jonathan

    2015-01-01

    In this thesis we study systems with switching dynamics and we propose new mathematical tools to analyse them. We show that the postulation of a global state space structure in current frameworks is restrictive and lead to potential difficulties that limit its use for the analysis of new emerging applications. In order to overcome such shortcomings, we reformulate the foundations in the study of switched systems by developing a trajectory-based approach, where we allow the use of models that ...

  14. Photonics in switching

    CERN Document Server

    Midwinter, John E; Kelley, Paul

    1993-01-01

    Photonics in Switching provides a broad, balanced overview of the use of optics or photonics in switching, from materials and devices to system architecture. The chapters, each written by an expert in the field, survey the key technologies, setting them in context and highlighting their benefits and possible applications. This book is a valuable resource for those working in the communications industry, either at the professional or student level, who do not have extensive background knowledge or the underlying physics of the technology.

  15. uv preilluminated gas switches

    International Nuclear Information System (INIS)

    We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 1012 amps/sec with 1 ns jitter. Twenty such modules will be used on the Nova Inertial Confinement Fusion Laser System for plasma retropulse shutters

  16. uv preilluminated gas switches

    Energy Technology Data Exchange (ETDEWEB)

    Bradley, L.P.; Orham, E.L.; Stowers, I.F.; Braucht, J.R.

    1980-06-03

    We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 10/sup 12/ amps/sec with 1 ns jitter. Twenty such modules will be used on the Nova Inertial Confinement Fusion Laser System for plasma retropulse shutters.

  17. Switching to Photonics

    OpenAIRE

    Hinton, Harvard S.

    1992-01-01

    The use of hardware that exploits the interplay of photons and electrons to switch voice, data, and video is discussed. The two directions being taken by current research-guided-wave and free-space photonics-are examined. Photonic time-slot interchanges are described. Multidivisional fabrics, based on a combination of space-division and time-division multiplexing, are considered, as is the wavelength-division-based photonic packet switch, another kind of multidimensional fabric. The use of se...

  18. Switch Attention to Listen

    OpenAIRE

    Dhamani, Imran; Leung, Johahn; Carlile, Simon; Sharma, Mridula

    2013-01-01

    The aim of this research was to evaluate the ability to switch attention and selectively attend to relevant information in children (10–15 years) with persistent listening difficulties in noisy environments. A wide battery of clinical tests indicated that children with complaints of listening difficulties had otherwise normal hearing sensitivity and auditory processing skills. Here we show that these children are markedly slower to switch their attention compared to their age-matched peers. T...

  19. Ferroelectric switching of elastin

    OpenAIRE

    Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; WANG, YUNJIE; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; SHARMA, PRADEEP; Zhang, Yanhang; Li, Jiangyu

    2014-01-01

    Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present, to our knowledge, the first macroscopic observation of ferroelectric switching in a biological system, and we elucidate the origin and mechanism underpinning ferroelectric switching of elastin. It is discovered that the polarization in elastin is intrinsic at the monomer level, analogous to the unit cell level polarizatio...

  20. Response switching and self-efficacy in Peer Instruction classrooms

    Science.gov (United States)

    Miller, Kelly; Schell, Julie; Ho, Andrew; Lukoff, Brian; Mazur, Eric

    2015-06-01

    Peer Instruction, a well-known student-centered teaching method, engages students during class through structured, frequent questioning and is often facilitated by classroom response systems. The central feature of any Peer Instruction class is a conceptual question designed to help resolve student misconceptions about subject matter. We provide students two opportunities to answer each question—once after a round of individual reflection and then again after a discussion round with a peer. The second round provides students the choice to "switch" their original response to a different answer. The percentage of right answers typically increases after peer discussion: most students who answer incorrectly in the individual round switch to the correct answer after the peer discussion. However, for any given question there are also students who switch their initially right answer to a wrong answer and students who switch their initially wrong answer to a different wrong answer. In this study, we analyze response switching over one semester of an introductory electricity and magnetism course taught using Peer Instruction at Harvard University. Two key features emerge from our analysis: First, response switching correlates with academic self-efficacy. Students with low self-efficacy switch their responses more than students with high self-efficacy. Second, switching also correlates with the difficulty of the question; students switch to incorrect responses more often when the question is difficult. These findings indicate that instructors may need to provide greater support for difficult questions, such as supplying cues during lectures, increasing times for discussions, or ensuring effective pairing (such as having a student with one right answer in the pair). Additionally, the connection between response switching and self-efficacy motivates interventions to increase student self-efficacy at the beginning of the semester by helping students develop early mastery or

  1. Understanding and Supporting Window Switching

    NARCIS (Netherlands)

    Tak, S.

    2011-01-01

    Switching between windows on a computer is a frequent activity, but finding and switching to the target window can be inefficient. This thesis aims to better un-derstand and support window switching. It explores two issues: (1) the lack of knowledge of how people currently interact with and switch b

  2. Optical switching systems using nanostructures

    DEFF Research Database (Denmark)

    Stubkjær, Kristian

    2004-01-01

    High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems.......High capacity multiservice optical networks require compact and efficient switches. The potential benefits of optical switch elements based on nanostructured material are reviewed considering various material systems....

  3. Regulation of Meiotic Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Gregory p. Copenhaver

    2011-11-09

    Meiotic recombination results in the heritable rearrangement of DNA, primarily through reciprocal exchange between homologous chromosome or gene conversion. In plants these events are critical for ensuring proper chromosome segregation, facilitating DNA repair and providing a basis for genetic diversity. Understanding this fundamental biological mechanism will directly facilitate trait mapping, conventional plant breeding, and development of genetic engineering techniques that will help support the responsible production and conversion of renewable resources for fuels, chemicals, and the conservation of energy (1-3). Substantial progress has been made in understanding the basal recombination machinery, much of which is conserved in organisms as diverse as yeast, plants and mammals (4, 5). Significantly less is known about the factors that regulate how often and where that basal machinery acts on higher eukaryotic chromosomes. One important mechanism for regulating the frequency and distribution of meiotic recombination is crossover interference - or the ability of one recombination event to influence nearby events. The MUS81 gene is thought to play an important role in regulating the influence of interference on crossing over. The immediate goals of this project are to use reverse genetics to identify mutants in two putative MUS81 homologs in the model plant Arabidopsis thaliana, characterize those mutants and initiate a novel forward genetic screen for additional regulators of meiotic recombination. The long-term goal of the project is to understand how meiotic recombination is regulated in higher eukaryotes with an emphasis on the molecular basis of crossover interference. The ability to monitor recombination in all four meiotic products (tetrad analysis) has been a powerful tool in the arsenal of yeast geneticists. Previously, the qrt mutant of Arabidopsis, which causes the four pollen products of male meiosis to remain attached, was developed as a facile system

  4. Intravenous to oral antibiotic switch therapy.

    Science.gov (United States)

    Cunha, Burke A.

    2001-05-01

    I.v.-to-p.o. switch therapy has become the mainstay of antibiotic therapy for the majority of patients. I.v.-to-p.o. switch therapy is inappropriate for critically ill patients who require i.v. antibiotic therapy and should not be considered in patients who have the inability to absorb drugs. These exceptions constitute a very small percentage of hospitalized patients for which i.v.-to-p.o. switch therapy is ideal. I.v.-to-p.o. switch therapy is best achieved with antibiotics that have high bioavailability that result in the same blood and tissue concentrations of antibiotic as their intravenous counterpart and have few gastrointestinal side effects. Antibiotics ideal for i.v.-to-p.o. switch programs include chloramphenicol, clindamycin, metronidazole, TMP-SMX, fluconazole, itraconazole, voriconazole, doxycycline, minocycline, levofloxacin, gatifloxacin, moxifloxacin and linezolid. Antibiotics that may be used in i.v.-to-p.o. switch programs that have lower bioavailability but are effective include beta-lactams and macrolides. For antibiotics with no oral formulation, e.g., carbapenems, equivalent coverage must be provided with an oral antibiotic from an unrelated class. Excluding gastrointestinal malabsorptive disorders, disease state is not a determinant of suitability for i.v.-to-p.o. switch programs. I.v.-to-p.o. switch programs should be used in patients with any infectious disease disorder for which there is effective oral therapy and is not limited to certain infectious diseases. Oral absorption of antibiotics is near normal in all but the most critically ill patients. Therefore, even in sick, hospitalized individuals, p.o. therapy is appropriate. I.v-to-p.o. switch therapy has several important advantages including decreasing drug cost (i.v. vs. p.o.), decreasing length of stay permitting earlier discharge and optimal reimbursement and decreasing or eliminating i.v. line phlebitis and sepsis with its cost implications. Clinicians should consider all

  5. Genetic recombination in plant-infecting messenger-sense RNA viruses: overview and research perspectives

    Directory of Open Access Journals (Sweden)

    Jozef Julian Bujarski

    2013-03-01

    Full Text Available RNA recombination is one of the driving forces of genetic variability in (+-strand RNA viruses. Various types of RNA-RNA crossovers were described including crosses between the same or different viral RNAs or between viral and cellular RNAs. Likewise, a variety of molecular mechanisms are known to support RNA recombination, such as replicative events (based on internal or end-to-end replicase switchings along with nonreplicative joining among RNA fragments of viral and/or cellular origin. Such mechanisms as RNA decay or RNA interference are responsible for RNA fragmentation and trans-esterification reactions which are likely accountable for ligation of RNA fragments. Numerous host factors were found to affect the profiles of viral RNA recombinants and significant differences in recombination frequency were observed among various RNA viruses. Comparative analyses of viral sequences allowed for the development of evolutionary models in order to explain adaptive phenotypic changes and co-evolving sites. Many questions remain to be answered by forthcoming RNA recombination research. (i How various factors modulate the ability of viral replicase to switch templates, (ii What is the intracellular location of RNA-RNA template switchings, (iii Mechanisms and factors responsible for non-replicative RNA recombination, (iv Mechanisms of integration of RNA viral sequences with cellular genomic DNA, and (v What is the role of RNA splicing and ribozyme activity. From an evolutionary stand point, it is not known how RNA viruses parasitize new host species via recombination, nor is it obvious what the contribution of RNA recombination is among other RNA modification pathways. We do not understand why the frequency of RNA recombination varies so much among RNA viruses and the status of RNA recombination as a form of sex is not well documented.

  6. Switching Power Universality in Unipolar Resistive Switching Memories

    Science.gov (United States)

    Kim, Jongmin; Jung, Kyooho; Kim, Yongmin; Jo, Yongcheol; Cho, Sangeun; Woo, Hyeonseok; Lee, Seongwoo; Inamdar, A. I.; Hong, Jinpyo; Lee, Jeon-Kook; Kim, Hyungsang; Im, Hyunsik

    2016-04-01

    We investigate the resistive switching power from unipolar resistive switching current-voltage characteristics in various binary metal oxide films sandwiched by different metal electrodes, and find a universal feature (the so-called universality) in the switching power among these devices. To experimentally derive the switching power universality, systematic measurements of the switching voltage and current are performed, and neither of these correlate with one another. As the switching resistance (R) increases, the switching power (P) decreases following a power law P ∝ R‑β, regardless of the device configurations. The observed switching power universality is indicative of the existence of a commonly applicable switching mechanism. The origin of the power universality is discussed based on a metallic filament model and thermo-chemical reaction.

  7. Comparison of Memory Assignment Schemes for Switch Architectures with Shareable Parallel Memory Modules

    Directory of Open Access Journals (Sweden)

    Sanjeev Kumar

    2010-01-01

    Full Text Available Switching Architectures deploying shareable parallel memory modules are quite versatile in their ability to scale to higher capacity while retaining the advantage of sharing its entire memory resource among all input and output ports. The two main classes of such architectures, namely, the Shared Multibuffer-(SMB- based switch and the Sliding-Window-(SW- based packet switch, both deploy parallel memory modules that are physically separate but logically connected. Inspite of their similarity in regards to using shareable parallel memory modules, they differ in switching control and scheduling of packets to parallel memory modules. SMB switch uses centralized control whereas the SW switch uses a decentralized control for switching operations. In this paper, we present a new memory assignment scheme for the Sliding-Window (SW switch for assigning packets to parallel memory modules that maximizes the parallel storage of packets to multiple memory modules. We compare the performance of a sliding-window switch deploying this new memory assignment scheme with that of an SMB switch architecture under conditions of identical traffic type and memory resources deployed. The simulation results show that the new memory assignment scheme for the sliding window switch maximizes parallel storage of packets input in a given switch cycle, and it does not require speed-up of memory modules. Furthermore, it provides a superior performance compared to that of the SMB switch under the constraints of fixed memory-bandwidth and memory resources.

  8. Recombination in ionized gases

    International Nuclear Information System (INIS)

    In this paper it is shown how capture-stabilized methodology (both macroscopic and microscopic) can provide a generic basis for a unified treatment of all of the above recombination mechanisms. A new semiclassical theory of dissociative recombination is also presented in an effort to gain further insight into the physics not included in the first-order treatment and difficult to extract from numerical quantal treatments based on configuration mixing and on multichannel quantum defect theory. A simple analytical expression more accurate than the standard first-order result is obtained for the cross section σ and rate coefficient α. (author)

  9. Immunoglobulin/Myc recombinations in murine Peyer's patch follicles.

    Science.gov (United States)

    Müller, J R; Mushinski, E B; Williams, J A; Hausner, P F

    1997-09-01

    Immunoglobulin heavy chain (Igh)/Myc recombinations are a hallmark of pristane-induced mouse plasmacytomas but are also frequently found in non-tumorous tissues. Here we describe for the first time a PCR-based technique for detecting fusions between Igh mu or Igh alpha and Myc in situ. Igh/Myc recombinations were found in transplanted and primary plasmacytomas. In addition, the gut-associated lymphoid tissues of plasmacytoma-free BALB/c mice were investigated for the presence of Igh/Myc fusions. Igh/Myc rearrangements were detected in Peyer's patch follicles and in the intestinal lamina propria both in normal mice and in mice shortly after pristane treatment. The sequence analysis showed that i) three to five different Igh/Myc hybrid sequences were present in individual follicles, ii) Igh/Myc recombinations can be subjected to additional switch recombinations as shown by related sequences in neighboring cells, and iii) cells harboring these rearrangements migrate into the adjacent lamina propria. The results indicate that Peyer's patches are a hyper-recombinogenic tissue. Myc recombination-positive cells are present in at least 100-fold more frequently than expected if recombinations were random, which suggests that this kind of trans-chromosomal rearrangement may be targeted. PMID:9290947

  10. Atomic Scale Plasmonic Switch.

    Science.gov (United States)

    Emboras, Alexandros; Niegemann, Jens; Ma, Ping; Haffner, Christian; Pedersen, Andreas; Luisier, Mathieu; Hafner, Christian; Schimmel, Thomas; Leuthold, Juerg

    2016-01-13

    The atom sets an ultimate scaling limit to Moore's law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocation of an individual or, at most, a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ratio of 9.2 dB and operation at room temperature up to MHz with femtojoule (fJ) power consumption for a single switch operation. This demonstration of an integrated quantum device allowing to control photons at the atomic level opens intriguing perspectives for a fully integrated and highly scalable chip platform, a platform where optics, electronics, and memory may be controlled at the single-atom level. PMID:26670551

  11. Energy reversible switching from amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-08-01

    We report observation of energy reversible switching from amorphous metal based nanoelectromechanical (NEM) switch. For ultra-low power electronics, NEM switches can be used as a complementary switching element in many nanoelectronic system applications. Its inherent zero power consumption because of mechanical detachment is an attractive feature. However, its operating voltage needs to be in the realm of 1 volt or lower. Appropriate design and lower Young\\'s modulus can contribute achieving lower operating voltage. Therefore, we have developed amorphous metal with low Young\\'s modulus and in this paper reporting the energy reversible switching from a laterally actuated double electrode NEM switch. © 2013 IEEE.

  12. Genetic recombination in plant-infecting messenger-sense RNA viruses: overview and research perspectives

    OpenAIRE

    Bujarski, Jozef J.

    2013-01-01

    RNA recombination is one of the driving forces of genetic variability in (+)-strand RNA viruses. Various types of RNA–RNA crossovers were described including crosses between the same or different viral RNAs or between viral and cellular RNAs. Likewise, a variety of molecular mechanisms are known to support RNA recombination, such as replicative events (based on internal or end-to-end replicase switchings) along with non-replicative joining among RNA fragments of viral and/or cellular origin. ...

  13. An optically controlled semiconductor closing and opening switch

    International Nuclear Information System (INIS)

    A concept and preliminary experiment for an optically controlled bulk semiconductor switch are discussed. A direct semiconductor is doped with a material which generates deep acceptor levels and is counterdoped with donors in shallow levels. An increase in the conductivity - closing of the switch- is obtained through photoionization of electrons from the occupied deep traps into the conduction band. A reduction of the conductivity -opening of the switch- is accomplished through photoionization of holes in the valence band from the deep centers and subsequent direct recombination of electron hole pairs. The features of this type of laser-controlled switch are its high control efficiency, because lasers are only used to drive the switch into and out of the conductive state, not to sustain the conductivity, and the fast opening determined by direct photoluminescence processes. The turn-on and turn-off transients of a GaAs switch, doped with Cu, have been modeled using a set of rate equations. Photoconductance measurements with CdS:Cu have proven the feasibility of this concept

  14. Recombination analysis and structure prediction show correlation between breakpoint clusters and RNA hairpins in the pol gene of human immunodeficiency virus type 1 unique recombinant forms

    DEFF Research Database (Denmark)

    Galli, Andrea; Lai, Alessia; Corvasce, Stefano;

    2008-01-01

    Recombination is recognized as a primary force in human immunodeficiency virus type 1 (HIV-1) evolution, increasing viral diversity through reshuffling of genomic portions. The strand-switching activity of reverse transcriptase is required to complete HIV-1 replication and can occur randomly...

  15. An automatic electronic switch

    International Nuclear Information System (INIS)

    The paper describes an electronic switch which, on the order of a single pulse, successively selects a given number of channels. The switching time for all channels may be the same, or may vary according to channel; one or more positions may be maintained by external control for an indefinite length of time. This circuit is very flexible in programming; it can if necessary act as a counter and as a pulse generator. It is convenient to limit the number of switched channels to ten, but this can be greatly increased by a general extension of the system. Applications of an apparatus for transferring the contents of decimal scalers to a printing machine are described; this machine employs the sequential series method and with a binary-decimal scale converter which operates by summing the weights of the different binary digits. (author)

  16. Optical computer switching network

    Science.gov (United States)

    Clymer, B.; Collins, S. A., Jr.

    1985-01-01

    The design for an optical switching system for minicomputers that uses an optical spatial light modulator such as a Hughes liquid crystal light valve is presented. The switching system is designed to connect 80 minicomputers coupled to the switching system by optical fibers. The system has two major parts: the connection system that connects the data lines by which the computers communicate via a two-dimensional optical matrix array and the control system that controls which computers are connected. The basic system, the matrix-based connecting system, and some of the optical components to be used are described. Finally, the details of the control system are given and illustrated with a discussion of timing.

  17. Recombinant DNA for Teachers.

    Science.gov (United States)

    Duvall, James G., III

    1992-01-01

    A science teacher describes his experience at a workshop to learn to teach the Cold Spring Harbor DNA Science Laboratory Protocols. These protocols lead students through processes for taking E. coli cells and transforming them into a new antibiotic resistant strain. The workshop featured discussions of the role of DNA recombinant technology in…

  18. Recombineering Pseudomonas syringae

    Science.gov (United States)

    Here we report the identification of functions that promote genomic recombination of linear DNA introduced into Pseudomonas cells by electroporation. The genes encoding these functions were identified in Pseudomonas syringae pv. syringae B728a based on similarity to the lambda Red Exo/Beta and RecE...

  19. Photonics in Switching

    OpenAIRE

    Hinton, Harvard S.

    1992-01-01

    One of the keys to the future of telecommunications companies will be their ability to provide new broadband services to both the business community and residential customers. With the new services will come the need for the equivalent of a broadband switching office. Such a system could require the capability of supporting in excess of 10000 users with broadband channel bit rates exceeding 100 Mb/s. This implies a switching fabric the aggregate bit rate of which could be greater than 1 Tb/s....

  20. Laboratory Switching Power Supply

    OpenAIRE

    Slezák, Jakub

    2009-01-01

    This bachelor’s thesis is concerned with design switching power supply based on forward converter with output voltage regulated in the range of 3 to 30V and load current to 1 A. First of all, it discusses the theoretical solution of basic types of converters and switching power supply problems. Followed by a proposal of various parts source, which was first established in the test version on the test board. Then was proposed printed circuit board and complete mechanical solutions. Source is a...

  1. Dynamics of all-optically switched micropillar resonances

    CERN Document Server

    Thyrrestrup, Henri; Ctistis, Georgios; Claudon, Julien; Vos, Willem L

    2014-01-01

    Here we do frequency and time resolved switching of a single GaAs/AlGa micropillar cavity with a pillar diameter of 6 mu using a ultrafast pump-probe setup. The switching is achieved by two-photon excitation of free carriers by an femtosecond pump pulse. We observe a simultaneously frequency shift of the first two transverse micropillar modes and obtain high resolution frequency traces of the two resonances in time. A difference in the the maximum switching magnitude of 12% point is caused by spatial inhomogeneous excitation of carriers in the pillar. The relaxation dynamic of the two resonances show a strongly non-exponential decay. We interpret the non-exponential dynamics in term of a second order decay model for the spontaneous recombination of electron and hole for the free carriers and a slow free carrier trapping time of ~300 ps.

  2. Optimal control of uncertain stochastic systems with Markovian switching and its applications to portfolio decisions

    OpenAIRE

    Weiyin Fei

    2014-01-01

    This paper first describes a class of uncertain stochastic control systems with Markovian switching, and derives an It\\^o-Liu formula for Markov-modulated processes. And we characterize an optimal control law, which satisfies the generalized Hamilton-Jacobi-Bellman (HJB) equation with Markovian switching. Then, by using the generalized HJB equation, we deduce the optimal consumption and portfolio policies under uncertain stochastic financial markets with Markovian switching. Finally, for cons...

  3. Impulsive control for synchronizing delayed discrete complex networks with switching topology

    OpenAIRE

    Li, Chaojie; Gao, David Y; Liu, Chao; Chen, Guo

    2013-01-01

    In this paper, global exponential synchronization of a class of discrete delayed complex networks with switching topology has been investigated by using Lyapunov-Ruzimiki method. The impulsive scheme is designed to work at the time instant of switching occurrence. A time-varying delay-dependent criterion for impulsive synchronization is given to ensure the delayed discrete complex networks switching topology tending to a synchronous state. Furthermore, a numerical simulation is given to illus...

  4. Ligand-responsive RNA switches: viral translation regulators, therapeutic targets, and tunable building blocks for nanotechnology

    OpenAIRE

    Boerneke, Mark A.

    2016-01-01

    Ligand-responsive RNA mechanical switches represent a new class of simple and small switching modules which regulate viral translation initiation by adopting well-defined ligand-free and bound conformational states without undergoing large secondary structure rearrangements, distinguishing them from metabolite-sensing riboswitches. Initially discovered in the internal ribosome entry site (IRES) of hepatitis C virus (HCV), RNA switch motifs have now been discovered in the genomes of diverse o...

  5. Contraction and incremental stability of switched Carath\\'{e}odory systems using multiple norms

    OpenAIRE

    Lu, Wenlian; Di Bernardo, Mario

    2015-01-01

    In this paper, incremental exponential asymptotic stability of a class of switched Carath\\'{e}odory nonlinear systems is studied based on the novel concept of measure of switched matrices via multiple norms and the transaction coefficients between these norms. This model is rather general and includes the case of staircase switching signals as a special case. Sufficient conditions are derived for incremental stability allowing for the system to be incrementally exponentially asymptotically st...

  6. Research on Chinese College English Teachers’ Classroom Code-switching: Beliefs and Attitudes

    OpenAIRE

    Xiaoli Cheng

    2013-01-01

    This article documents the beliefs and attitudes of Chinese college English teachers towards classroom code-switching. The findings suggest that teachers’ code-switching is commonplace in class, although most of them still hold negative attitude toward it. Besides, students’ ability is regarded as the most significant factor affecting teachers’ code-switching, and the first language (L1) is mainly used to teach grammar and abstract words. The conclusion is that, in Chinese E...

  7. Assessment of Recombination in the S-segment Genome of Crimean-Congo Hemorrhagic Fever Virus in Iran

    Directory of Open Access Journals (Sweden)

    Sadegh Chinikar

    2015-10-01

    Full Text Available  Background: Crimean-Congo Hemorrhagic Fever Virus (CCHFV belongs to genus Nairovirus and family Bunyaviridae. The main aim of this study was to investigate the extent of recombination in S-segment genome of CCHFV in Iran.Methods: Samples were isolated from Iranian patients and those available in GenBank, and analyzed by phyloge­netic and bootscan methods.Results: Through comparison of the phylogenetic trees based on full length sequences and partial fragments in the S-segment genome of CCHFV, genetic switch was evident, due to recombination event. Moreover, evidence of multi­ple recombination events was detected in query isolates when bootscan analysis was used by SimPlot software.Conclusion: Switch of different genomic regions between different strains by recombination could contribute to CCHFV diversification and evolution. The occurrence of recombination in CCHFV has a critical impact on epidemi­ological investigations and vaccine design. 

  8. Recombination in the 5' leader of murine leukemia virus is accurate and influenced by sequence identity with a strong bias toward the kissing-loop dimerization region

    DEFF Research Database (Denmark)

    Mikkelsen, J G; Lund, Anders Henrik; Duch, M; Pedersen, F S

    1998-01-01

    Retroviral recombination occurs frequently during reverse transcription of the dimeric RNA genome. By a forced recombination approach based on the transduction of Akv murine leukemia virus vectors harboring a primer binding site knockout mutation and the entire 5' untranslated region, we studied ...... facilitate template switching. We discuss the putative role of the dimerization domain in the overall structure of the reverse-transcribed RNA dimer and note that related mechanisms of template switching may be found in remote RNA viruses....

  9. High-speed switching characteristics of integrated optoelectronic crossbar switch

    Science.gov (United States)

    Gouin, Francois L.; Almeida, Carlos; Callender, Claire L.; Robitaille, Lucie; Noad, Julian P.

    1999-04-01

    Optoelectronic (OE) switching is a promising approach for routing signals in fiber optic networks. Recently, the integration of a 4 X 4 MSM array with optical surface waveguides has been reported. This technique greatly simplifies the packaging of an OE switch. The on-chip polyimide optical waveguides perform the optical signal distribution to a matrix of MSMs which are responsible for the switching operation itself. Photoresponse bandwidths exceeding 4 GHz have been demonstrated. Another important characteristic of a switch is the switching speed since it determines the reconfiguration time. Mechanical and thermal optical waveguide switches offer switching speeds of the order of milliseconds which is sufficient for network traffic management but too slow for packet switching. We report measurements on the switching characteristics of a 4 X 4 optoelectronic switch performed in both the frequency and time domain. In the time domain, the individual crosspoints exhibit a rise time of 3 ns. However, a sizeable overshoot and ringing settles only after 35 ns. This constitutes the reconfiguration time at present. This is confirmed by measurements in the frequency domain of the electrical transmission from control line to output line. The 3-dB switching bandwidth is a few hundred megahertz. The 35 ns reconfiguration time indicates that it is already suitable for packet switching in a 10 Mb/s network. Switching speed measurements on individual MSMs suggests that modifications to the switch circuit could improve the switching time. The switch could also find application as a component in the wavelength conversion circuit of a WDM fiber optic network.

  10. A high performance switching audio amplifier using sliding mode control

    OpenAIRE

    Pillonnet, Gael; Cellier, Rémy; Abouchi, Nacer; Chiollaz, Monique

    2008-01-01

    International audience The switching audio amplifiers are widely used in various portable and consumer electronics due to their high efficiency, but suffers from low audio performances due to inherent nonlinearity. This paper presents an integrated class D audio amplifier with low consumption and high audio performances. It includes a power stage and an efficient control based on sliding mode technique. This monolithic class D amplifier is capable of delivering up to 1W into 8Ω load at les...

  11. Robust stability analysis of switched Hopfield neural networks with time-varying delay under uncertainty

    International Nuclear Information System (INIS)

    With the development of intelligent control, switched systems have been widely studied. Here we try to introduce some ideas of the switched systems into the field of neural networks. In this Letter, a class of switched Hopfield neural networks with time-varying delay is investigated. The parametric uncertainty is considered and assumed to be norm bounded. Firstly, the mathematical model of the switched Hopfield neural networks is established in which a set of Hopfield neural networks are used as the individual subsystems and an arbitrary switching rule is assumed; Secondly, robust stability analysis for such switched Hopfield neural networks is addressed based on the Lyapunov-Krasovskii approach. Some criteria are given to guarantee the switched Hopfield neural networks to be globally exponentially stable for all admissible parametric uncertainties. These conditions are expressed in terms of some strict linear matrix inequalities (LMIs). Finally, a numerical example is provided to illustrate our results

  12. True ferroelectric switching in thin films of trialkylbenzene-1,3,5-tricarboxamide (BTA).

    Science.gov (United States)

    Gorbunov, A V; Putzeys, T; Urbanavičiūtė, I; Janssen, R A J; Wübbenhorst, M; Sijbesma, R P; Kemerink, M

    2016-08-24

    We have investigated the ferroelectric polarization switching properties of trialkylbenzene-1,3,5-tricarboxamide (BTA), which is a model system for a large class of novel organic ferroelectric materials. In the solid state BTAs form a liquid crystalline columnar hexagonal phase that provides long range order that was previously shown to give rise to hysteretic dipolar switching. In this work the nature of the polar switching process is investigated by a combination of dielectric relaxation spectroscopy, depth-resolved pyroelectric response measurements, and classical frequency- and time-dependent electrical switching. We show that BTAs, when brought in a homeotropically aligned hexagonal liquid crystalline phase, are truly ferroelectric. Analysis of the transient switching behavior suggests that the ferroelectric switching is limited by a highly dispersive nucleation process, giving rise to a wide distribution of switching times. PMID:27510767

  13. Triggers of IgE class switching and allergy development

    DEFF Research Database (Denmark)

    Poulsen, Lars K.; Hummelshoj, Lone

    2007-01-01

    The prevalence of immunoglobulin E (IgE)-mediated allergic diseases has been increasing for the last four decades. In this review determinants for an increased IgE synthesis are discussed on both an epidemiological and on an immunological level with special emphasis on the differentiation of the ...... the need for more knowledge on preventable causes of IgE- and allergy development....

  14. Optical Packet Switching Demostrator

    DEFF Research Database (Denmark)

    Mortensen, Brian Bach; Berger, Michael Stübert

    2002-01-01

    In the IST project DAVID (data and voice integration over DWDM) work is carried out defining possible architectures of future optical packet switched networks. The feasibility of the architecture is to be verified in a demonstration set-up. This article describes the demonstrator set-up and the...

  15. Ultrafast gas switching experiments

    International Nuclear Information System (INIS)

    We describe recent experiments which studied the physics of ultrafast gas breakdown under the extreme overvoltages which occur when a high pressure gas switch is pulse charged to hundreds of kV in 1 ns or less. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes Khz at > 100 kV/m E field

  16. Molecular Rotors as Switches

    Directory of Open Access Journals (Sweden)

    Kang L. Wang

    2012-08-01

    Full Text Available The use of a functional molecular unit acting as a state variable provides an attractive alternative for the next generations of nanoscale electronics. It may help overcome the limits of conventional MOSFETd due to their potential scalability, low-cost, low variability, and highly integratable characteristics as well as the capability to exploit bottom-up self-assembly processes. This bottom-up construction and the operation of nanoscale machines/devices, in which the molecular motion can be controlled to perform functions, have been studied for their functionalities. Being triggered by external stimuli such as light, electricity or chemical reagents, these devices have shown various functions including those of diodes, rectifiers, memories, resonant tunnel junctions and single settable molecular switches that can be electronically configured for logic gates. Molecule-specific electronic switching has also been reported for several of these device structures, including nanopores containing oligo(phenylene ethynylene monolayers, and planar junctions incorporating rotaxane and catenane monolayers for the construction and operation of complex molecular machines. A specific electrically driven surface mounted molecular rotor is described in detail in this review. The rotor is comprised of a monolayer of redox-active ligated copper compounds sandwiched between a gold electrode and a highly-doped P+ Si. This electrically driven sandwich-type monolayer molecular rotor device showed an on/off ratio of approximately 104, a read window of about 2.5 V, and a retention time of greater than 104 s. The rotation speed of this type of molecular rotor has been reported to be in the picosecond timescale, which provides a potential of high switching speed applications. Current-voltage spectroscopy (I-V revealed a temperature-dependent negative differential resistance (NDR associated with the device. The analysis of the device

  17. Exponential stability of switched systems with impulsive effect

    Institute of Scientific and Technical Information of China (English)

    Guangdeng ZONG; Yuqiang WU

    2005-01-01

    The exponential stability of a class of switched systems containing stable and unstable subsystems with impulsive effect is analyzed by using the matrix measure concept and the average dwell-time approach.It is shown that if appropriately a large amount of the average dwell-time and the ratio of the total activation time of the subsystems with negative matrix measure to the total activation time of the subsystems with nonnegative matrix measure is chosen,the exponential stability of a desired degree is guaranteed.Using the proposed switching scheme,we studied the robust exponential stability for a class of switched systems with impulsive effect and structure perturbations.Simulations validate the main results.

  18. A Collaborative, Investigative Recombinant DNA Technology Course with Laboratory

    Science.gov (United States)

    Pezzementi, Leo; Johnson, Joy F.

    2002-01-01

    A recombinant DNA technology course was designed to promote contextual, collaborative, inquiry-based learning of science where students learn from one another and have a sense of ownership of their education. The class stressed group presentations and critical reading and discussion of scientific articles. The laboratory consisted of two research…

  19. Stabilization of complex network with hybrid impulsive and switching control

    International Nuclear Information System (INIS)

    This paper studies the asymptotic stability properties of a class of complex dynamical networks under a hybrid impulsive and switching control. By utilizing the concept of impulsive control and the stability results for impulsive systems, some new criteria for global and local stability are established for this model. Some numerical examples and simulations are included to illustrate the effectiveness of the theoretical results

  20. Global Synchronization of Directed Networks with Fast Switching Topologies

    International Nuclear Information System (INIS)

    Global synchronization of a class of directed dynamical networks with switching topologies is investigated. It is found that if there is a directed spanning tree in the fixed time-average of network topology and the time-average is achieved sufficiently fast, then the network will reach global synchronization for sufficiently large coupling strength. (general)

  1. Genes required for initiation and resolution steps of mating-type switching in fission yeast.

    OpenAIRE

    Egel, R; Beach, D H; Klar, A J

    1984-01-01

    The fission yeast Schizosaccharomyces pombe switches mating type by transposition of a copy of DNA derived from either of the two storage cassettes, mat2 -P and mat3 -M, into the expression locus, mat1 . The recombinational event of switching is initiated by a double-stranded DNA break present in approximately 20% of the molecules at mat1 . Fifty-three mutants defective in switching of mating type have been isolated previously, and each has been assigned to 1 of 10 linkage groups. One group c...

  2. A Bivariate Markov Regime Switching GARCH Approach to Estimate Time Varying Minimum Variance Hedge Ratios

    OpenAIRE

    Hsiang-Tai Lee; Jonathan Yoder

    2005-01-01

    This paper develops a new bivariate Markov regime switching BEKK-GARCH (RS-BEKK-GARCH) model. The model is a state-dependent bivariate BEKK- GARCH model, and an extension of Gray’s univariate generalized regime- switching (GRS) model to the bivariate case. To solve the path- dependency problem inherent in the bivariate regime switching BEKK-GARCH model, we propose a recombining method for the covariance term in the conditional variance-covariance matrix. The model is applied to estimate time-...

  3. Language Switching and Language Competition

    Science.gov (United States)

    Macizo, Pedro; Bajo, Teresa; Paolieri, Daniela

    2012-01-01

    This study examined the asymmetrical language switching cost in a word reading task (Experiment 1) and in a categorization task (Experiment 2 and 3). In Experiment 1, Spanish-English bilinguals named words in first language (L1) and second language (L2) in a switching paradigm. They were slower to switch from their weaker L2 to their more dominant…

  4. Job Switching and Wage Growth

    OpenAIRE

    Faberman, R. Jason; Justiniano, Alejandro

    2015-01-01

    This article shows a remarkably strong relationship between job switching and nominal wage growth. We also find a fairly strong relationship between job switching and the cyclical component of inflation. Furthermore, job switching seems to be predictive of both wage growth and inflation.

  5. Engineering thermoacidophilic archaea using linear DNA recombination.

    Science.gov (United States)

    Maezato, Yukari; Dana, Karl; Blum, Paul

    2011-01-01

    Thermoacidophilic archaea comprise one of the major classes of extremophiles. Most belong to the family Sulfolobales within the phylum Crenarchaeota. They are of applied interest as sources of hyperstable enzymes, for biomining of base and precious metals, and for evolutionary studies because of their use of eukaryotic-like subcellular mechanisms. Genetic methods are available for several species particularly Sulfolobus solfataricus. This organism has a considerable number of methods available for the construction of novel cell lines with unique functions. This chapter presents recent developments in the use of homologous recombination and linear DNA for the engineering of site-specific changes in the genome of S. solfataricus. PMID:21815108

  6. Recombinant influenza vaccines.

    Science.gov (United States)

    Sedova, E S; Shcherbinin, D N; Migunov, A I; Smirnov, Iu A; Logunov, D Iu; Shmarov, M M; Tsybalova, L M; Naroditskiĭ, B S; Kiselev, O I; Gintsburg, A L

    2012-10-01

    This review covers the problems encountered in the construction and production of new recombinant influenza vaccines. New approaches to the development of influenza vaccines are investigated; they include reverse genetics methods, production of virus-like particles, and DNA- and viral vector-based vaccines. Such approaches as the delivery of foreign genes by DNA- and viral vector-based vaccines can preserve the native structure of antigens. Adenoviral vectors are a promising gene-delivery platform for a variety of genetic vaccines. Adenoviruses can efficiently penetrate the human organism through mucosal epithelium, thus providing long-term antigen persistence and induction of the innate immune response. This review provides an overview of the practicability of the production of new recombinant influenza cross-protective vaccines on the basis of adenoviral vectors expressing hemagglutinin genes of different influenza strains. PMID:23346377

  7. Active Learning with Monty Hall in a Game Theory Class

    Science.gov (United States)

    Brokaw, Alan J.; Merz, Thomas E.

    2004-01-01

    The authors describe a game that students can play on the first day of a game theory class. The game introduces the 4 essential elements of any game and is designed so that its sequel, also played on the first day of class, has students playing the well-known Monty Hall game, which raises the question: Should you switch doors? By implementing a…

  8. RECOMBINANT INFLUENZA VACCINES

    OpenAIRE

    Sedova, E.; Shcherbinin, D.; Migunov, A.; Smirnov, Iu; Logunov, D.; Shmarov, M.; Tsybalova, L.; Naroditskiĭ, B.; O. Kiselev; Gintsburg, A.

    2012-01-01

    This review covers the problems encountered in the construction and production of new recombinant influenza vaccines. New approaches to the development of influenza vaccines are investigated; they include reverse genetics methods, production of virus-like particles, and DNA- and viral vector-based vaccines. Such approaches as the delivery of foreign genes by DNA- and viral vector-based vaccines can preserve the native structure of antigens. Adenoviral vectors are a promising gene-delivery pla...

  9. Soluble recombinant influenza vaccines.

    OpenAIRE

    Fiers, W; Neirynck, S; Deroo, T; Saelens, X; Jou, W M

    2001-01-01

    Soluble, recombinant forms of influenza A virus haemagglutinin and neuraminidase have been produced in cells of lower eukaryotes, and shown in a mouse model to induce complete protective immunity against a lethal virus challenge. Soluble neuraminidase, produced in a baculovirus system, consisted of tetramers, dimers and monomers. Only the tetramers were enzymatically active. The immunogenicity decreased very considerably in the order tetra > di > mono. Therefore, we fused the head part of the...

  10. Nonradiative recombination in semiconductors

    CERN Document Server

    Abakumov, VN; Yassievich, IN

    1991-01-01

    In recent years, great progress has been made in the understandingof recombination processes controlling the number of excessfree carriers in semiconductors under nonequilibrium conditions. As a result, it is now possible to give a comprehensivetheoretical description of these processes. The authors haveselected a number of experimental results which elucidate theunderlying physical problems and enable a test of theoreticalmodels. The following topics are dealt with: phenomenological theory ofrecombination, theoretical models of shallow and deep localizedstates, cascade model of carrier captu

  11. Class distinction

    Science.gov (United States)

    White, M. Catherine

    Typical 101 courses discourage many students from pursuing higher level science and math courses. Introductory classes in science and math serve largely as a filter, screening out all but the most promising students, and leaving the majority of college graduates—including most prospective teachers—with little understanding of how science works, according to a study conducted for the National Science Foundation. Because few teachers, particularly at the elementary level, experience any collegiate science teaching that stresses skills of inquiry and investigation, they simply never learn to use those methods in their teaching, the report states.

  12. Biochemical switching device: how to turn on (off) the switch.

    Science.gov (United States)

    Okamoto, M; Sakai, T; Hayashi, K

    1989-01-01

    We previously showed with computer simulations that cyclic enzyme systems have the reliability of ON-OFF types of operation (McCulloch-Pitts' neuronic equation) and the applicability for a switching circuit in a biocomputer. The switching time was inevitably determined in accordance with the difference in amount between two inputs of the system. This characteristic is, however, a disadvantage for practical use of a switching device; we need to improve the system in order for the switching time to optionally be changed. We shall present here how to turn on (off) the switch independently of the modes of two inputs. By introducing pulse perturbation, we could optionally set up the switching time of a cyclic enzyme system (biochemical switching device). PMID:2720139

  13. Synchronization Between Two Different Switched Chaotic Systems By Switching Control

    Directory of Open Access Journals (Sweden)

    Du Li Ming

    2016-01-01

    Full Text Available This paper is concerned with the synchronization problem of two different switched chaotic systems, considering the general case that the master-slave switched chaotic systems have uncertainties. Two basic problems are considered: one is projective synchronization of switched chaotic systems under arbitrary switching; the other is projective synchronization of switched chaotic systems by design of switching when synchronization cannot achieved by using any subsystems alone. For the two problems, common Lyapunov function method and multiple Lyapunov function method are used respectively, an adaptive control scheme has been presented, some sufficient synchronization conditions are attainted, and the switching signal is designed. Finally, the numerical simulation is provide to show the effectiveness of our method.

  14. Monopole Charge Domain in High-Gain Gallium Arsenide Photoconductive Switches

    Institute of Scientific and Technical Information of China (English)

    施卫; 陈二柱; 张显斌; 李琦

    2002-01-01

    Considering that semi-insulating gallium arsenide photoconductive switches can be triggered into the high gain mode and no reliable theories can account for the observed transient characteristics, we propose the monopole charge domain model to explain the peculiar switching phenomena occurring in the high gain mode and we discuss the requirements for the lock-on switching. During operation on this mode, the applied field across the switch and the lock-on field are all larger than the Gunn threshold field. Our developed monopole charge domain is based on the transferred-electron effect, but the domain is only composed of large numbers of electrons piled up due to the negative differential mobility. Using the model and taking the physical mechanism of the avalanche impact ionization and recombination radiation into consideration, we interpret the typical phenomena of the lock-on effect, such as the time delay between the beginning of optical illumination and turning-on of the switch, and the conduction mechanism of the sustaining phase. Under different conditions of bias field intensity and incident light energy, the time delay of the switching is calculated. The results show that the physical mechanisms of impact ionization and recombination radiation occurring in the monopole charge domain are responsible for the lock-on switching.

  15. Practical switching power supply design

    CERN Document Server

    Brown, Martin C

    1990-01-01

    Take the ""black magic"" out of switching power supplies with Practical Switching Power Supply Design! This is a comprehensive ""hands-on"" guide to the theory behind, and design of, PWM and resonant switching supplies. You'll find information on switching supply operation and selecting an appropriate topology for your application. There's extensive coverage of buck, boost, flyback, push-pull, half bridge, and full bridge regulator circuits. Special attention is given to semiconductors used in switching supplies. RFI/EMI reduction, grounding, testing, and safety standards are also deta

  16. Two portable recombination enhancers direct donor choice in fission yeast heterochromatin

    DEFF Research Database (Denmark)

    Jakociunas, Tadas; Holm, Lærke Rebekka; Hansen, Janne Verhein; Trusina, Ala; Thon, Genevieve

    2013-01-01

    Mating-type switching in fission yeast results from gene conversions of the active mat1 locus by heterochromatic donors. mat1 is preferentially converted by mat2-P in M cells and by mat3-M in P cells. Here, we report that donor choice is governed by two portable recombination enhancers capable of...

  17. Switched Matrix Accelerator

    International Nuclear Information System (INIS)

    We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm-wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We provide also an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392. GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high-power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium

  18. Python Switch Statement

    Directory of Open Access Journals (Sweden)

    2008-06-01

    Full Text Available The Python programming language does not have a built in switch/case control structure as found in many other high level programming languages. It is thought by some that this is a deficiency in the language, and the control structure should be added. This paper demonstrates that not only is the control structure not needed, but that the methods available in Python are more expressive than built in case statements in other high level languages.

  19. Magnetic Cellular Switches

    OpenAIRE

    Overby, Darryl R.; Alenghat, Francis J.; Montoya-Zavala, Martín; Bei, HuCheng; Oh, Philmo; Karavitis, John; Ingber, Donald E.

    2004-01-01

    This paper focuses on the development of magnetic cellular switches to enable magnetic control of intracellular functions in living mammalian cells, including receptor signal transduction and gene transcription. Our approach takes advantage of the mechanosensitivity of adenosine 3′,5′-monophosphate (cAMP) induction and downstream transcription controlled by the cAMP regulatory element (CRE) to engineer gene constructs that optically report gene expression in living cells. We activate transcri...

  20. Molecular current switch

    Czech Academy of Sciences Publication Activity Database

    Nešpůrek, Stanislav; Sworakowski, J.

    Brno : Faculty of Chemistry, Brno University of Technology, 2002 - (Schauer, F.), s. 89-96 ISBN 80-214-2265-3. [Seminar on Physics and Chemistry of Molecular Systems /7./. Brno (CZ), 13.12.2001] R&D Projects: GA AV ČR IAA1050901; GA ČR GA202/01/0518 Institutional research plan: CEZ:AV0Z4050913 Keywords : current switch * local states * dipolar species Subject RIV: BM - Solid Matter Physics ; Magnetism

  1. MCT/MOSFET Switch

    Science.gov (United States)

    Rippel, Wally E.

    1990-01-01

    Metal-oxide/semiconductor-controlled thyristor (MCT) and metal-oxide/semiconductor field-effect transistor (MOSFET) connected in switching circuit to obtain better performance. Offers high utilization of silicon, low forward voltage drop during "on" period of operating cycle, fast turnon and turnoff, and large turnoff safe operating area. Includes ability to operate at high temperatures, high static blocking voltage, and ease of drive.

  2. Ad 2.0: a novel recombineering platform for high-throughput generation of tailored adenoviruses.

    Science.gov (United States)

    Mück-Häusl, Martin; Solanki, Manish; Zhang, Wenli; Ruzsics, Zsolt; Ehrhardt, Anja

    2015-04-30

    Recombinant adenoviruses containing a double-stranded DNA genome of 26-45 kb were broadly explored in basic virology, for vaccination purposes, for treatment of tumors based on oncolytic virotherapy, or simply as a tool for efficient gene transfer. However, the majority of recombinant adenoviral vectors (AdVs) is based on a small fraction of adenovirus types and their genetic modification. Recombineering techniques provide powerful tools for arbitrary engineering of recombinant DNA. Here, we adopted a seamless recombineering technology for high-throughput and arbitrary genetic engineering of recombinant adenoviral DNA molecules. Our cloning platform which also includes a novel recombination pipeline is based on bacterial artificial chromosomes (BACs). It enables generation of novel recombinant adenoviruses from different sources and switching between commonly used early generation AdVs and the last generation high-capacity AdVs lacking all viral coding sequences making them attractive candidates for clinical use. In combination with a novel recombination pipeline allowing cloning of AdVs containing large and complex transgenes and the possibility to generate arbitrary chimeric capsid-modified adenoviruses, these techniques allow generation of tailored AdVs with distinct features. Our technologies will pave the way toward broader applications of AdVs in molecular medicine including gene therapy and vaccination studies. PMID:25609697

  3. Robust exponential stability of uncertain discrete time impulsive switching systems with state delay

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new class of hybrid impulsive and switching models are introduced and their robust exponential stability and control synthesis are addressed.The proposed switched system is composed of stable subsystems and unstable subsystems,which not only involves state delay and norm-bounded time-varying parameter uncertainties,but also contains the impulsive switching effects between the subsystems.Based on the extension of the system dimension and the concept of average dwell time,a kind of practically useful switching rule is presented which guarantees the desired robust exponential stability.A swished state feedback controller is also given.

  4. Recombinant Collagenlike Proteins

    Science.gov (United States)

    Fertala, Andzej

    2007-01-01

    A group of collagenlike recombinant proteins containing high densities of biologically active sites has been invented. The method used to express these proteins is similar to a method of expressing recombinant procollagens and collagens described in U. S. Patent 5,593,859, "Synthesis of human procollagens and collagens in recombinant DNA systems." Customized collagenous proteins are needed for biomedical applications. In particular, fibrillar collagens are attractive for production of matrices needed for tissue engineering and drug delivery. Prior to this invention, there was no way of producing customized collagenous proteins for these and other applications. Heretofore, collagenous proteins have been produced by use of such biological systems as yeasts, bacteria, and transgenic animals and plants. These products are normal collagens that can also be extracted from such sources as tendons, bones, and hides. These products cannot be made to consist only of biologically active, specific amino acid sequences that may be needed for specific applications. Prior to this invention, it had been established that fibrillar collagens consist of domains that are responsible for such processes as interaction with cells, binding of growth factors, and interaction with a number of structural proteins present in the extracellular matrix. A normal collagen consists of a sequence of domains that can be represented by a corresponding sequence of labels, e.g., D1D2D3D4. A collagenlike protein of the present invention contains regions of collagen II that contain multiples of a single domain (e.g., D1D1D1D1 or D4D4D4D4) chosen for its specific biological activity. By virtue of the multiplicity of the chosen domain, the density of sites having that specific biological activity is greater than it is in a normal collagen. A collagenlike protein according to this invention can thus be made to have properties that are necessary for tissue engineering.

  5. Primordial magnetogenesis before recombination

    CERN Document Server

    Fabre, Ophélia

    2015-01-01

    The origin of large magnetic fields in the Universe remains currently unknown. We investigate here a mechanism before recombination based on known physics. The source of the vorticity is due to the changes in the photon distribution function caused by the fluctuations in the background photons. We show that the magnetic field generated in the MHD limit, due to the Coulomb scattering, is of the order $10^{-49}$ G. We explicitly show that the magnetic fields generated from this process are sustainable and are not erased by resistive diffusion. We compare the results with current observations and discuss the implications.

  6. CRMAGE: CRISPR Optimized MAGE Recombineering

    OpenAIRE

    Carlotta Ronda; Lasse Ebdrup Pedersen; Sommer, Morten O. A.; Alex Toftgaard Nielsen

    2016-01-01

    A bottleneck in metabolic engineering and systems biology approaches is the lack of efficient genome engineering technologies. Here, we combine CRISPR/Cas9 and λ Red recombineering based MAGE technology (CRMAGE) to create a highly efficient and fast method for genome engineering of Escherichia coli. Using CRMAGE, the recombineering efficiency was between 96.5% and 99.7% for gene recoding of three genomic targets, compared to between 0.68% and 5.4% using traditional recombineering. For modulat...

  7. Switching from natalizumab to fingolimod

    Science.gov (United States)

    Radue, Ernst-Wilhelm; Comi, Giancarlo; Montalban, Xavier; Butzkueven, Helmut; Wiendl, Heinz; Giovannoni, Gavin; Hartung, Hans-Peter; Derfuss, Tobias; Naegelin, Yvonne; Sprenger, Till; Mueller-Lenke, Nicole; Griffiths, Sarah; von Rosenstiel, Philipp; Gottschalk, Rebecca; Zhang, Ying; Dahlke, Frank; Tomic, Davorka

    2015-01-01

    Objective: To investigate the effect of different natalizumab washout (WO) periods on recurrence of MRI and clinical disease activity in patients switching from natalizumab to fingolimod. Methods: In this multicenter, double-blind, placebo-controlled trial (TOFINGO), patients with relapsing-remitting multiple sclerosis (RRMS) were randomized 1:1:1 to 8-, 12-, or 16-week WO followed by fingolimod treatment over 32 weeks from last natalizumab infusion (LNI). Brain MRI was performed at baseline and weeks 8, 12, 16, 20, and 24. Results: Of 142 enrolled and randomized patients, 112 (78.9%) completed the study (8 weeks, n = 41/50; 12 weeks, n = 31/42; 16 weeks, n = 40/50). Number (95% confidence interval [CI]) of active (new/newly enlarged T2) lesions from LNI through 8 weeks of fingolimod treatment (primary outcome) was similar in the 8-week (2.1 [1.7–2.6]) and 12-week WO groups (1.7 [1.3–2.2]) and higher in the 16-week WO group (8.2 [7.3–9.1]). During the WO period only, the number (95% CI) of active lesions increased with increasing WO duration (8 weeks, 0.4 [0.2–0.6]; 12 weeks, 2.1 [1.6–2.6]; 16 weeks, 3.6 [3.0–4.2]). Over the 24 weeks from LNI, gadolinium-enhancing T1 lesion counts were lower in the 8-week WO group (14.1 [5.67–22.53]) than in the 12-week (21.3 [1.41–41.19]) or 16-week (18.5 [8.40–28.60]) WO groups. More patients were relapse-free in the 8-week (88%) and 12-week (91%) WO groups than the 16-week WO group (84%). Sixty-eight percent of patients experienced adverse events (mostly mild/moderate), with similar incidence across groups. No unusually severe relapses or opportunistic infections occurred. Conclusions: Initiating fingolimod therapy 8–12 weeks after natalizumab discontinuation is associated with a lower risk of MRI and clinical disease reactivation than initiation after 16-week WO. Classification of evidence: This study provides Class II evidence that for patients with RRMS switching from natalizumab to fingolimod, shorter

  8. STOCHASTIC ADAPTIVE SWITCHING CONTROL BASED ON MULTIPLE MODELS

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yanxia; GUO Lei

    2002-01-01

    It is well known that the transient behaviors of the traditional adaptive control may be very poor in general, and that the adaptive control designed based on switching between multiple models is an intuitively appealing and practically feasible approach to improve the transient performances. In this paper, we shall prove that for a typical class of linear systems disturbed by random noises, the multiple model based least-squares (LS)adaptive switching control is stable and convergent, and has the same convergence rate as that established for the standard least-squares-based self-tunning regulators. Moreover,the mixed case combining adaptive models with fixed models is also considered.

  9. Optimal queue-size scaling in switched networks

    OpenAIRE

    Shah, D; Walton, N. S.; Zhong, Y

    2011-01-01

    We consider a switched (queuing) network in which there are constraints on which queues may be served simultaneously; such networks have been used to effectively model input-queued switches and wireless networks. The scheduling policy for such a network specifies which queues to serve at any point in time, based on the current state or past history of the system. In the main result of this paper, we provide a new class of online scheduling policies that achieve optimal queue-size scaling for ...

  10. Research Progress on Multimode Interference Switches

    Institute of Scientific and Technical Information of China (English)

    GAO Qing; SHENG Zhi-rui; JIANG Xiao-qing; WANG Ming-hua

    2005-01-01

    Optical switches are key components for constructing optical communication networks, so it is necessary to design optical switches and optical switch arrays with high performance and low cost. As one type of optical switches, the multimode interference(MMI) switches have received considerable attention due to their unique merits. The structures and operation principles of various types of MMI switches are introduced,and the recent progresses of MMI switches are also discussed.

  11. Delay-decomposing approach to robust stability for switched interval networks with state-dependent switching.

    Science.gov (United States)

    Li, Ning; Cao, Jinde; Hayat, Tasawar

    2014-08-01

    This paper is concerned with a class of nonlinear uncertain switched networks with discrete time-varying delays . Based on the strictly complete property of the matrices system and the delay-decomposing approach, exploiting a new Lyapunov-Krasovskii functional decomposing the delays in integral terms, the switching rule depending on the state of the network is designed. Moreover, by piecewise delay method, discussing the Lyapunov functional in every different subintervals, some new delay-dependent robust stability criteria are derived in terms of linear matrix inequalities, which lead to much less conservative results than those in the existing references and improve previous results. Finally, an illustrative example is given to demonstrate the validity of the theoretical results. PMID:25009673

  12. The economics of lamp switching

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-09-01

    The effect of switching off fluorescent lamps, in terms of electricity cost, was discussed. Fluorescent lamps are designed to burn for thousands of hours. Initially, it was believed that turning them off was not economical. However, with new fluorescent lamps available today, this no longer holds true. It was shown that as energy costs increase, it is advantageous to switch lamps off in office buildings during lunch, coffee breaks and other non-essential periods. Also, as labour and lamp costs increase it becomes even more economical to turn lamps on only when needed in some areas such as washrooms, stockrooms, etc. Inexpensive photo-electric and time-switch controls are readily available for automatic switching to eliminate the `human error` of forgetting to turn light off when they are not required. Over time, the energy saved would offset the cost of the switch controllers and the reduction in lamp life caused by repeated switching. 4 tabs., 2 figs.

  13. Circuit model of Rimfire switch

    International Nuclear Information System (INIS)

    A cascade gaps circuit model for Rimfire switch has been developed. The circuit model includes all stray capacitances and spark channel on-state conduction characteristics. It can not only describe the behavior of Rimfire switch, but also allow analysis of the time varying voltage and current at each part of the switch, describing the internal characters of the switch. PSpice was used to implement the cascade gaps circuit model and simulate a 700 kV Rimfire switch. The simulation shows that, the voltage of the whole switch will be higher than 700 kV when the laser triggered section has broken down but all cascade gaps keep dielectric, and the voltage of all gaps attenuates with high frequency oscillation. (authors)

  14. Recent developments in switching theory

    CERN Document Server

    Mukhopadhyay, Amar

    2013-01-01

    Electrical Science Series: Recent Developments in Switching Theory covers the progress in the study of the switching theory. The book discusses the simplified proof of Post's theorem on completeness of logic primitives; the role of feedback in combinational switching circuits; and the systematic procedure for the design of Lupanov decoding networks. The text also describes the classical results on counting theorems and their application to the classification of switching functions under different notions of equivalence, including linear and affine equivalences. The development of abstract har

  15. Noise-induced coherent switch

    Institute of Scientific and Technical Information of China (English)

    YUAN ZhanJiang; ZHANG Jiadun; ZHOU TianShou

    2008-01-01

    Taking the famous genetic toggle switch as an example, we numerically investigated the effect of noise on bistability. We found that extrinsic noise resulting from stochastic fluctuations in synthesis and degradation rates and from the environmental fluctuation in gene regulatory processes can induce coherent switch, and that there is an optimal noise intensity such that the noise not only can induce this switch, but also can amplify a weak input signal. In addition, we found that the intrinsic noise introduced through the Poisson τ-leap algorithm cannot induce such a switch.

  16. Noise-induced coherent switch

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Taking the famous genetic toggle switch as an example,we numerically investigated the effect of noise on bistability.We found that extrinsic noise resulting from stochastic fluctuations in synthesis and degradation rates and from the environmental fluctuation in gene regulatory processes can induce coherent switch,and that there is an optimal noise intensity such that the noise not only can induce this switch,but also can amplify a weak input signal.In addition,we found that the intrinsic noise introduced through the Poisson τ-leap algorithm cannot induce such a switch.

  17. Neuromorphic atomic switch networks.

    Directory of Open Access Journals (Sweden)

    Audrius V Avizienis

    Full Text Available Efforts to emulate the formidable information processing capabilities of the brain through neuromorphic engineering have been bolstered by recent progress in the fabrication of nonlinear, nanoscale circuit elements that exhibit synapse-like operational characteristics. However, conventional fabrication techniques are unable to efficiently generate structures with the highly complex interconnectivity found in biological neuronal networks. Here we demonstrate the physical realization of a self-assembled neuromorphic device which implements basic concepts of systems neuroscience through a hardware-based platform comprised of over a billion interconnected atomic-switch inorganic synapses embedded in a complex network of silver nanowires. Observations of network activation and passive harmonic generation demonstrate a collective response to input stimulus in agreement with recent theoretical predictions. Further, emergent behaviors unique to the complex network of atomic switches and akin to brain function are observed, namely spatially distributed memory, recurrent dynamics and the activation of feedforward subnetworks. These devices display the functional characteristics required for implementing unconventional, biologically and neurally inspired computational methodologies in a synthetic experimental system.

  18. Data center coolant switch

    Science.gov (United States)

    Iyengar, Madhusudan K.; Parida, Pritish R.; Schultz, Mark D.

    2015-10-06

    A data center cooling system is operated in a first mode; it has an indoor portion wherein heat is absorbed from components in the data center, and an outdoor heat exchanger portion wherein outside air is used to cool a first heat transfer fluid (e.g., water) present in at least the outdoor heat exchanger portion of the cooling system during the first mode. The first heat transfer fluid is a relatively high performance heat transfer fluid (as compared to the second fluid), and has a first heat transfer fluid freezing point. A determination is made that an appropriate time has been reached to switch from the first mode to a second mode. Based on this determination, the outdoor heat exchanger portion of the data cooling system is switched to a second heat transfer fluid, which is a relatively low performance heat transfer fluid, as compared to the first heat transfer fluid. It has a second heat transfer fluid freezing point lower than the first heat transfer fluid freezing point, and the second heat transfer fluid freezing point is sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point.

  19. Cell biology of mitotic recombination

    DEFF Research Database (Denmark)

    Lisby, Michael; Rothstein, Rodney

    2015-01-01

    Homologous recombination provides high-fidelity DNA repair throughout all domains of life. Live cell fluorescence microscopy offers the opportunity to image individual recombination events in real time providing insight into the in vivo biochemistry of the involved proteins and DNA molecules as w...

  20. Hybrid switch for resonant power converters

    Science.gov (United States)

    Lai, Jih-Sheng; Yu, Wensong

    2014-09-09

    A hybrid switch comprising two semiconductor switches connected in parallel but having different voltage drop characteristics as a function of current facilitates attainment of zero voltage switching and reduces conduction losses to complement reduction of switching losses achieved through zero voltage switching in power converters such as high-current inverters.

  1. LCT protective dump-switch tests

    International Nuclear Information System (INIS)

    Each of the six coils in the Large Coil Task (LCT) has a separate power supply, dump resistor, and switching circuit. Each switching circuit contains five switches, two of which are redundant. The three remaining switches perform separate duties in an emergency dump situation. These three switches were tested to determine their ability to meet the LCT conditions

  2. Estimating treatment effects with treatment switching via semicompeting risks models: an application to a colorectal cancer study

    OpenAIRE

    Zeng, Donglin; Chen, Qingxia; Chen, Ming-Hui; Ibrahim, Joseph G.

    2011-01-01

    Treatment switching is a frequent occurrence in clinical trials, where, during the course of the trial, patients who fail on the control treatment may change to the experimental treatment. Analysing the data without accounting for switching yields highly biased and inefficient estimates of the treatment effect. In this paper, we propose a novel class of semiparametric semicompeting risks transition survival models to accommodate treatment switches. Theoretical properties of the proposed model...

  3. Convertible resistive switching characteristics between memory switching and threshold switching in a single ferritin-based memristor.

    Science.gov (United States)

    Zhang, Chaochao; Shang, Jie; Xue, Wuhong; Tan, Hongwei; Pan, Liang; Yang, Xi; Guo, Shanshan; Hao, Jian; Liu, Gang; Li, Run-Wei

    2016-04-01

    A bio-memristor fabricated with ferritin exhibits novel resistive switching characteristics wherein memory switching and threshold switching are made steadily coexistent and inter-convertible through controlling the magnitude of compliance current presets. PMID:26967024

  4. Design and Simulation of a Soft Switched Dc Boost Converter for Switched Reluctance Motor

    OpenAIRE

    X. F. Joseph; Kumar, S. P.

    2012-01-01

    Problem statement: This study presents the design and simulation of a soft switched boost converter for a switched reluctance motor with a closed loop controller. A soft switching scheme is proposed in the converter with minimum components, which reduces the switching loss and stress across the switch so that the harmonic generation is reduced in the output. The switch used in this converter switched ON at zero current and switched OFF at zero voltage. Approach: Most of the research was done ...

  5. New results on switched linear systems with actuator saturation

    Science.gov (United States)

    Duan, Chang; Wu, Fen

    2016-04-01

    This paper further studies the analysis and control problems of continuous-time switched linear systems subject to actuator saturation. Using the norm-bounded differential inclusion description of the saturated systems and the minimal switching rule, a set of switched output feedback controllers is designed to minimise the disturbance attenuation level defined by the regional ? gain over a class of energy-bounded disturbances. The synthesis conditions are expressed as bilinear matrix inequalities, and can be solved by numerical search coupled with linear matrix inequality optimisation. Compared to the previous method based on polytopic differential inclusion, the proposed approach has good scalability and potentially renders better performance. Numerical examples are provided to verify the effectiveness of the proposed approach.

  6. Partial synchronization in stochastic dynamical networks with switching communication channels

    Science.gov (United States)

    Huang, Chi; Ho, Daniel W. C.; Lu, Jianquan; Kurths, Jürgen

    2012-06-01

    In this paper, the partial synchronization problem of stochastic dynamical networks (SDNs) is investigated. Unlike the existing models, the SDN considered in this paper suffers from a class of communication constraint—only part of nodes' states can be transmitted. Thus, less nodes' states can be used to synchronize the SDN, which makes the analysis of the synchronization problem much harder. A set of channel matrices are introduced to reflect such kind of constraint. Furthermore, due to unpredictable environmental changes, the channel matrices can switch among some communication modes. The switching considered here is governed by a Markov process. To overcome the difficulty, a regrouping method is employed to derive our main results. The obtained conditions guarantee that partial synchronization can be achieved for SDNs under switching communication constraint. Finally, numerical examples are given to illustrate the effectiveness of the theoretical results and how the communication constraint influences synchronization result.

  7. Task Switching: A PDP Model

    Science.gov (United States)

    Gilbert, Sam J.; Shallice, Tim

    2002-01-01

    When subjects switch between a pair of stimulus-response tasks, reaction time is slower on trial N if a different task was performed on trial N--1. We present a parallel distributed processing (PDP) model that simulates this effect when subjects switch between word reading and color naming in response to Stroop stimuli. Reaction time on "switch…

  8. Battery switch for downhole tools

    Science.gov (United States)

    Boling, Brian E.

    2010-02-23

    An electrical circuit for a downhole tool may include a battery, a load electrically connected to the battery, and at least one switch electrically connected in series with the battery and to the load. The at least one switch may be configured to close when a tool temperature exceeds a selected temperature.

  9. Switching Costs in Accounting Services

    OpenAIRE

    Fatih Koç; Nisa Kıymet Şahin

    2015-01-01

    Switching cost is defined as possible costs that customers may encounter when they want to change the firm they buy service, and an important subject in terms of accounting services. Particularly, small business entrepreneurs’ not having knowledge about accounting procedures, and sharing private information with accounting firms make switching costs more important for accounting services. Thus, the aim of this study is...

  10. Topology optimized RF MEMS switches

    DEFF Research Database (Denmark)

    Philippine, M. A.; Zareie, H.; Sigmund, Ole; Rebeiz, G. M.; Kenny, T. W.

    optimization for an RF MEM capacitive switch. Extensive experimental data confirms that the switches perform as designed by the optimizations, and that our simulation models are accurate. A subset of measurements are presented here. Broader results have been submitted in full journal format....

  11. Biomimetic production of silk-like recombinant squid sucker ring teeth proteins.

    Science.gov (United States)

    Ding, Dawei; Guerette, Paul A; Hoon, Shawn; Kong, Kiat Whye; Cornvik, Tobias; Nilsson, Martina; Kumar, Akshita; Lescar, Julien; Miserez, Ali

    2014-09-01

    The sucker ring teeth (SRT) of Humboldt squid exhibit mechanical properties that rival those of robust engineered synthetic polymers. Remarkably, these properties are achieved without a mineral phase or covalent cross-links. Instead, SRT are exclusively made of silk-like proteins called "suckerins", which assemble into nanoconfined β-sheet reinforced supramolecular networks. In this study, three streamlined strategies for full-length recombinant suckerin protein production and purification were developed. Recombinant suckerin exhibited high solubility and colloidal stability in aqueous-based solvents. In addition, the colloidal suspensions exhibited a concentration-dependent conformational switch, from random coil to β-sheet enriched structures. Our results demonstrate that recombinant suckerin can be produced in a facile manner in E. coli and processed from mild aqueous solutions into materials enriched in β-sheets. We suggest that recombinant suckerin-based materials offer potential for a range of biomedical and engineering applications. PMID:25068184

  12. Circuit switched optical networks

    DEFF Research Database (Denmark)

    Kloch, Allan

    2003-01-01

    Some of the most important components required for enabling optical networking are investigated through both experiments and modelling. These all-optical components are the wavelength converter, the regenerator and the space switch. When these devices become "off-the-shelf" products, optical cross......-connects can substitute the electrical nodes that today connect the installed optical fibres. This substitution will enable a massive increase in capacity since the bandwidth of the individual wavelength channels can be increased drastically when the electronic bit processing can be omitted. Furthermore, it is...... expected that the optical solution will offer an economical benefit for hight bit rate networks. This thesis begins with a discussion of the expected impact on communications systems from the rapidly growing IP traffic, which is expected to become the dominant source for traffic. IP traffic has some...

  13. Experiments in magnetic switching

    International Nuclear Information System (INIS)

    Magnetic switching offers an alternative to overcoming the rep-rate and life limitations of the spark gaps in the ETA/ATA induction accelerators. The principle has been applied for many years to radar modulators but at much lower power levels and longer pulse lengths. Comparatively recent developments in magnetic materials together with some optimal circuits have made it possible to go well beyond the state of the art. A magnetic modulator has been built which steps up and compresses a 25 kV, 5 μs pulse into a 250 kV, 50 ns pulse. A second magnetic modulator has been built and installed to replace four Blumleins and spark gaps in order to provide triggers for the complete ETA injector and accelerator. The paper outlines some practical and theoretical considerations affecting the design of the magnetic pulse generator

  14. Simulation method of ATM switch architecture and proposal for the delay priority control in ATM crosspoint switch; ATM kokanki no simulation shuho to crosspoint switch ni okeru chien yusen seigyo no teian

    Energy Technology Data Exchange (ETDEWEB)

    Doi, H. [Central Research Institute of Electric Power Industry, Tokyo (Japan)

    1996-03-01

    A simulation method for switch analysis of ATM (asynchronous transfer mode) switch architecture has been developed. When various electric power information is integrated in the ATM switch architecture, delay priority control method has been proposed, by which the delay time and delay time fluctuation can be guaranteed for important information, such as system protection control information. The simulation method has been developed for analyzing the output buffer type crosspoint switch. The analysis solutions of waiting time of cells at the switch were determined and compared with the simulation results. The both agreed well mutually, and the validity of this method was confirmed. Priority was added to the cells of crosspoint switch, and different buffer was given for each priority, to exchange the important information, selectively. Thus, a switch was proposed, by which the delay time and delay time fluctuation can be restricted. The mean waiting time of the high class cells was suppressed less than 1 cts even at the switch load factor of 0.98, and the fluctuation range of 4 cts was guaranteed. 11 refs., 19 figs.

  15. Amorphous metal based nanoelectromechanical switch

    KAUST Repository

    Mayet, Abdulilah M.

    2013-04-01

    Nanoelectromechanical (NEM) switch is an interesting ultra-low power option which can operate in the harsh environment and can be a complementary element in complex digital circuitry. Although significant advancement is happening in this field, report on ultra-low voltage (pull-in) switch which offers high switching speed and area efficiency is yet to be made. One key challenge to achieve such characteristics is to fabricate nano-scale switches with amorphous metal so the shape and dimensional integrity are maintained to achieve the desired performance. Therefore, we report a tungsten alloy based amorphous metal with fabrication process development of laterally actuated dual gated NEM switches with 100 nm width and 200 nm air-gap to result in <5 volts of actuation voltage (Vpull-in). © 2013 IEEE.

  16. Radio recombination lines from H II regions

    International Nuclear Information System (INIS)

    Radio recombination lines have been observed from forty-six H II regions. The Arecibo 1000-foot radio telescope was used to provide high sensitivity and high angular resolution at 1400 MHz (gain approx. 7.70K/Jy, HPBW = 3:2) and 2372 MHZ (gain approx. 6.30K/Jy, HPBW = 2'). Observations were made at 1400 MHz in the frequency switching mode, and at 2372 MHz in the total power mode. Gaussians were fit to be observed lines to derive velocities, line widths, and line temperatures. From the velocities kinematic distances were derived. For eleven sources H I absorption measurements were also made. The absorption spectra enabled the kinematic distance ambiguity to be resolved for some sources. The absorption spectra themselves were found to have extremely sharp, non-gaussian edges. One explanation for these is a model where the interstellar medium contains many H I cloudlets with T/sub s/less than or equal to 1000K and turbulent velocities less than or equal to 3 km/s. The H I absorption spectrum is then a superposition of many narrow gaussian profiles. It was also found from a comparison of H I absorption velocities with radio recombination line velocities that peculiar motions exist in the interstellar medium with velocities of up to 10 km/s. Using the measured line temperatures and continuum temperatures, estimates were desired of emission measures, electron temperatures, and electron densities, using a non-LTE analysis. Non-LTE effects were important only for the hottest and densest H II regions. The non-LTE calculations were checked through a comparison derivation of electron temperatures using hydrogen beta lines

  17. Delayed recombination and standard rulers

    International Nuclear Information System (INIS)

    Measurements of baryonic acoustic oscillations (BAOs) in galaxy surveys have been recognized as a powerful tool for constraining dark energy. However, this method relies on the knowledge of the size of the acoustic horizon at recombination derived from cosmic microwave background (CMB) anisotropy measurements. This estimate is typically derived assuming a standard recombination scheme; additional radiation sources can delay recombination altering the cosmic ionization history and the cosmological inferences drawn from CMB and BAO data. In this paper we quantify the effect of delayed recombination on the determination of dark energy parameters from future BAO surveys such as the Baryon Oscillation Spectroscopic Survey and the Wide-Field Multi-Object Spectrograph. We find the impact to be small but still not negligible. In particular, if recombination is nonstandard (to a level still allowed by CMB data), but this is ignored, future surveys may incorrectly suggest the presence of a redshift-dependent dark energy component. On the other hand, in the case of delayed recombination, adding to the analysis one extra parameter describing deviations from standard recombination does not significantly degrade the error bars on dark energy parameters and yields unbiased estimates. This is due to the CMB-BAO complementarity.

  18. Class Vectors: Embedding representation of Document Classes

    OpenAIRE

    Sachan, Devendra Singh; Kumar, Shailesh

    2015-01-01

    Distributed representations of words and paragraphs as semantic embeddings in high dimensional data are used across a number of Natural Language Understanding tasks such as retrieval, translation, and classification. In this work, we propose "Class Vectors" - a framework for learning a vector per class in the same embedding space as the word and paragraph embeddings. Similarity between these class vectors and word vectors are used as features to classify a document to a class. In experiment o...

  19. Teachers in Class

    Science.gov (United States)

    Van Galen, Jane

    2008-01-01

    In this article, I argue for a closer read of the daily "class work" of teachers, as posited by Reay, 1998. In developing exploratory class portraits of four teachers who occupy distinctive social positions (two from working-class homes now teaching upper-middle-class children and two from upper-middle-class homes now teaching poor children), I…

  20. Robust Fractional order PI Controller for Switching Systems

    OpenAIRE

    HosseinNia, S. Hassan; Tejado, Ines; Vinagre, Blas M.

    2012-01-01

    This paper is concerned with the robust design for a class of switching systems from a fractional order control (FOC) perspective. In particular, the tuning of the robust fractional order PI (RFPI) controller is proposed based on phase margin and cross over frequency specifications, ensuring the quadratic stability of the system, i.e., the third design specification is given by the stability condition. The quadratic stability is analyzed using a frequency-domain method equivalent to the commo...

  1. Practical stability and instability of regime-switching diffusions

    Institute of Scientific and Technical Information of China (English)

    G.George YIN; Bo ZHANG; Chao ZHU

    2008-01-01

    This work is devoted to practical stability of a class of regime-switching diffusions.First,the notion of practical stability is introduced.Then,sufficient conditions for practical stability and practical instability in probability and in pth mean are provided using a Lyapunov function argument.In addition,easily verifiable conditions on drift and diffusion coefficients are also given.Moreover,examples are supplied for demonstration purposes.

  2. Global Asymptotic Stability of Switched Neural Networks with Delays

    OpenAIRE

    Zhenyu Lu; Kai Li; Yan Li

    2015-01-01

    This paper investigates the global asymptotic stability of a class of switched neural networks with delays. Several new criteria ensuring global asymptotic stability in terms of linear matrix inequalities (LMIs) are obtained via Lyapunov-Krasovskii functional. And here, we adopt the quadratic convex approach, which is different from the linear and reciprocal convex combinations that are extensively used in recent literature. In addition, the proposed results here are very easy to be verified ...

  3. Ultrashort soliton switching based on coherent energy hiding.

    Science.gov (United States)

    Romagnoli, M; Wabnitz, S; Zoccolotti, L

    1991-08-15

    Coherent coupling between light and atoms may be exploited for conceiving a novel class of all-optical signalprocessing devices without a direct counterpart in the continuous-wave regime. We show that the self-switching of ultrashort soliton pulses on resonance with a transition of doping centers in a slab waveguide directional coupler is based on nonlinear group-velocity (instead of the usual phase-velocity) changes. PMID:19776934

  4. EXPONENTIAL ESTIMATES FOR STOCHASTIC DELAY HYBRID SYSTEMS WITH MARKOVIAN SWITCHING

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper deals with the problem of norm bounds for the solutions of stochastic hybrid systems with Markovian switching and time delay. Based on Lyapunov-Krasovskii theory for functional differential equations and the linear matrix inequality (LMI) approach, mean square exponential estimates for the solutions of this class of linear stochastic hybrid systems are derived. Finally, An example is illustrated to show the applicability and effectiveness of our method.

  5. Multistable decision switches for flexible control of epigenetic differentiation.

    Directory of Open Access Journals (Sweden)

    Raúl Guantes

    2008-11-01

    Full Text Available It is now recognized that molecular circuits with positive feedback can induce two different gene expression states (bistability under the very same cellular conditions. Whether, and how, cells make use of the coexistence of a larger number of stable states (multistability is however largely unknown. Here, we first examine how autoregulation, a common attribute of genetic master regulators, facilitates multistability in two-component circuits. A systematic exploration of these modules' parameter space reveals two classes of molecular switches, involving transitions in bistable (progression switches or multistable (decision switches regimes. We demonstrate the potential of decision switches for multifaceted stimulus processing, including strength, duration, and flexible discrimination. These tasks enhance response specificity, help to store short-term memories of recent signaling events, stabilize transient gene expression, and enable stochastic fate commitment. The relevance of these circuits is further supported by biological data, because we find them in numerous developmental scenarios. Indeed, many of the presented information-processing features of decision switches could ultimately demonstrate a more flexible control of epigenetic differentiation.

  6. Delay analysis of networked control systems based on 100 M switched Ethernet.

    Science.gov (United States)

    Li, Ming

    2014-01-01

    For the delay may degrade the performance of networked control systems, networked control systems based on 100 M switched Ethernet are proposed in this paper. According to the working principle of Ethernet switch, the formulas of the upper bound delay of the single-level switched Ethernet and the multiple-level switched Ethernet are deduced by the timing diagram method, and the values of the upper bound delay are also given. The key factors that influence the upper bound delay of switched Ethernet are analyzed; then, the characteristics of the upper bound delay are presented, which show that the delay induced by the single-level 100 M switched Ethernet has little effect on the performance of control systems, while the delay induced by the multiple-level 100 M switched Ethernet may meet the time requirements of all classes of control systems if the numbers of levels and the numbers of nodes connecting to switches are set properly. Finally, the performance of networked control systems is simulated by TrueTime, and the results further show the feasibility and superiority of 100 M switched Ethernet based networked control systems without modification of the network protocols. PMID:25003152

  7. Generation of Recombinant Monoclonal Antibodies from Immunised Mice and Rabbits via Flow Cytometry and Sorting of Antigen-Specific IgG+ Memory B Cells.

    Directory of Open Access Journals (Sweden)

    Dale O Starkie

    Full Text Available Single B cell screening strategies, which avoid both hybridoma fusion and combinatorial display, have emerged as important technologies for efficiently sampling the natural antibody repertoire of immunized animals and humans. Having access to a range of methods to interrogate different B cell subsets provides an attractive option to ensure large and diverse panels of high quality antibody are produced. The generation of multiple antibodies and having the ability to find rare B cell clones producing IgG with unique and desirable characteristics facilitates the identification of fit-for-purpose molecules that can be developed into therapeutic agents or research reagents. Here, we describe a multi-parameter flow cytometry single-cell sorting technique for the generation of antigen-specific recombinant monoclonal antibodies from single IgG+ memory B cells. Both mouse splenocytes and rabbit PBMC from immunised animals were used as a source of B cells. Reagents staining both B cells and other unwanted cell types enabled efficient identification of class-switched IgG+ memory B cells. Concurrent staining with antigen labelled separately with two spectrally-distinct fluorophores enabled antigen-specific B cells to be identified, i.e. those which bind to both antigen conjugates (double-positive. These cells were then typically sorted at one cell per well using FACS directly into a 96-well plate containing reverse transcriptase reaction mix. Following production of cDNA, PCR was performed to amplify cognate heavy and light chain variable region genes and generate transcriptionally-active PCR (TAP fragments. These linear expression cassettes were then used directly in a mammalian cell transfection to generate recombinant antibody for further testing. We were able to successfully generate antigen-specific recombinant antibodies from both the rabbit and mouse IgG+ memory B cell subset within one week. This included the generation of an anti-TNFR2 blocking

  8. The ion beam opening switch

    International Nuclear Information System (INIS)

    Plasma opening switches (POS's) have shown excellent characteristics in pulsed power applications. Proposed POS scaling predicts that the fastest opening time for a given conducted current should occur using a high-velocity low-density plasma as the switch medium. The ion beam opening switch (IBOS) uses a charge-neutral ion beam of 100-300 kV, ≤ 120 A/cm/sup 2/ as the switch ''plasma''. Its velocity of up to 600 cm/μs and density of -- 10/sup 12//cm/sup 3/ make this a very fast low-density plasma compared with typical 10 cm/μs and 10/sup 13//cm/sup 3/ POS plasmas. The IBOS has conducted ≥ 70 kA flowing in a parallel-plate transmission line driven by a 4-Ω pulser. IBOS opening time is load dependent, being ≤4 ns into a 15-nH load and about twice as long into a 4-Ω electron diode load. However, switch impedance is not zero during the entire conduction time, rising to ≥ 3 Ω by the time of peak current. Peak current conducted before opening does not vary linearly with either injected ion current or switch axial length. Instead, the conduction current scales with plasma density in the switch, and is nearly independent of switch area until the area is restricted to a narrow (-- 1 cm) strip. In this experimental geometry, replacing the IBOS with a standard POS gave essentially identical behavior, except first, an order of magnitude less injected flux was required to conduct a given current with the POS than with IBOS, corresponding to similar injected plasma densities for the two types of switches; second, clear evidence of J X B motion of the POS plasma was seen, while none was evident with IBOS

  9. Two Mutually Exclusive Local Chromatin States Drive Efficient V(D)J Recombination.

    Science.gov (United States)

    Bolland, Daniel J; Koohy, Hashem; Wood, Andrew L; Matheson, Louise S; Krueger, Felix; Stubbington, Michael J T; Baizan-Edge, Amanda; Chovanec, Peter; Stubbs, Bryony A; Tabbada, Kristina; Andrews, Simon R; Spivakov, Mikhail; Corcoran, Anne E

    2016-06-14

    Variable (V), diversity (D), and joining (J) (V(D)J) recombination is the first determinant of antigen receptor diversity. Understanding how recombination is regulated requires a comprehensive, unbiased readout of V gene usage. We have developed VDJ sequencing (VDJ-seq), a DNA-based next-generation-sequencing technique that quantitatively profiles recombination products. We reveal a 200-fold range of recombination efficiency among recombining V genes in the primary mouse Igh repertoire. We used machine learning to integrate these data with local chromatin profiles to identify combinatorial patterns of epigenetic features that associate with active VH gene recombination. These features localize downstream of VH genes and are excised by recombination, revealing a class of cis-regulatory element that governs recombination, distinct from expression. We detect two mutually exclusive chromatin signatures at these elements, characterized by CTCF/RAD21 and PAX5/IRF4, which segregate with the evolutionary history of associated VH genes. Thus, local chromatin signatures downstream of VH genes provide an essential layer of regulation that determines recombination efficiency. PMID:27264181

  10. Cell encoding recombinant human erythropoietin

    Energy Technology Data Exchange (ETDEWEB)

    Beck, A.K.; Withy, R.M.; Zabrecky, J.R.; Masiello, N.C.

    1990-09-04

    This patent describes a C127 cell transformed with a recombinant DNA vector. It comprises: a DNA sequence encoding human erythropoietin, the transformed cell being capable of producing N-linked and O-linked glycosylated human erythropoietin.

  11. Three Decades of Recombinant DNA.

    Science.gov (United States)

    Palmer, Jackie

    1985-01-01

    Discusses highlights in the development of genetic engineering, examining techniques with recombinant DNA, legal and ethical issues, GenBank (a national database of nucleic acid sequences), and other topics. (JN)

  12. Stable recombination hotspots in birds.

    Science.gov (United States)

    Singhal, Sonal; Leffler, Ellen M; Sannareddy, Keerthi; Turner, Isaac; Venn, Oliver; Hooper, Daniel M; Strand, Alva I; Li, Qiye; Raney, Brian; Balakrishnan, Christopher N; Griffith, Simon C; McVean, Gil; Przeworski, Molly

    2015-11-20

    The DNA-binding protein PRDM9 has a critical role in specifying meiotic recombination hotspots in mice and apes, but it appears to be absent from other vertebrate species, including birds. To study the evolution and determinants of recombination in species lacking the gene that encodes PRDM9, we inferred fine-scale genetic maps from population resequencing data for two bird species: the zebra finch, Taeniopygia guttata, and the long-tailed finch, Poephila acuticauda. We found that both species have recombination hotspots, which are enriched near functional genomic elements. Unlike in mice and apes, most hotspots are shared between the two species, and their conservation seems to extend over tens of millions of years. These observations suggest that in the absence of PRDM9, recombination targets functional features that both enable access to the genome and constrain its evolution. PMID:26586757

  13. Does Class Size Matter?

    Science.gov (United States)

    Ehrenberg, Ronald G.; Brewer, Dominic J.; Gamoran, Adam; Willms, J. Douglas

    2001-01-01

    Reports on the significance of class size to student learning. Includes an overview of class size in various countries, the importance of teacher adaptability, and the Asian paradox of large classes allied to high test scores. (MM)

  14. Effect of high-energy electrons component on recombination plasma with pulse plasma flow

    International Nuclear Information System (INIS)

    Experiments on a recombination plasma with pulse plasma flow have been performed in the linear divertor simulator TPD-SheetIV. The pulse plasma flow was generated using a switching circuit controlled by the electric potential of the adjacent floating electrode in the plasma source. The duration of the pulse was 0.3 ms at a frequency of 50 Hz. The time dependence of the electron density ne, temperature Te, and energy distribution function fe(E) were measured using a Langmuir probe. The ionization and recombination events are analyzed using the Collisional-Radiative model, taking into account high-energy electrons. (author)

  15. Combinatorics in Recombinational Population Genomics

    Science.gov (United States)

    Parida, Laxmi

    The work that I will discuss is motivated by the need for understanding, and processing, the manifestations of recombination events in chromosome sequences. In this talk, we focus on two related problems. First, we explore the very general problem of reconstructability of pedigree history. How plausible is it to unravel the history of a complete unit (chromosome) of inheritance? The second problem deals with reconstructing the recombinational history of a collection of chromosomes.

  16. Progenitors of Recombining Supernova Remnants

    OpenAIRE

    Moriya, Takashi J.

    2012-01-01

    Usual supernova remnants have either ionizing plasma or plasma in collisional ionization equilibrium, i.e., the ionization temperature is lower than or equal to the electron temperature. However, the existence of recombining supernova remnants, i.e., supernova remnants with the ionization temperature higher than the electron temperature, is recently confirmed. One suggested way to have recombining plasma in a supernova remnant is to have a dense circumstellar medium at the time of the superno...

  17. Do mitochondria recombine in humans?

    OpenAIRE

    Eyre-Walker, A

    2000-01-01

    Until very recently, mitochondria were thought to be clonally inherited through the maternal line in most higher animals. However, three papers published in 2000 claimed population-genetic evidence of recombination in human mitochondrial DNA. Here I review the current state of the debate. I review the evidence for the two main pathways by which recombination might occur: through paternal leakage and via a mitochondrial DNA sequence in the nuclear genome. There is no strong evidence for either...

  18. Recombinant snake venom prothrombin activators

    OpenAIRE

    Lövgren, Ann

    2012-01-01

    Three prothrombin activators; ecarin, which was originally isolated from the venom of the saw-scaled viper Echis carinatus, trocarin from the rough-scaled snake Tropidechis carinatus, and oscutarin from the Taipan snake Oxyuranus scutellatus, were expressed in mammalian cells with the purpose to obtain recombinant prothrombin activators that could be used to convert prothrombin to thrombin. We have previously reported that recombinant ecarin can efficiently generate thrombin without the need ...

  19. Ergodic directional switching in mobile insect groups

    KAUST Repository

    Escudero, Carlos

    2010-07-29

    We obtain a Fokker-Planck equation describing experimental data on the collective motion of locusts. The noise is of internal origin and due to the discrete character and finite number of constituents of the swarm. The stationary probability distribution shows a rich phenomenology including nonmonotonic behavior of several order and disorder transition indicators in noise intensity. This complex behavior arises naturally as a result of the randomness in the system. Its counterintuitive character challenges standard interpretations of noise induced transitions and calls for an extension of this theory in order to capture the behavior of certain classes of biologically motivated models. Our results suggest that the collective switches of the group\\'s direction of motion might be due to a random ergodic effect and, as such, they are inherent to group formation. © 2010 The American Physical Society.

  20. Electrically switched ion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Lilga, M.A. [Pacific Northwest National Lab., Richland, WA (United States); Schwartz, D.T.; Genders, D.

    1997-10-01

    A variety of waste types containing radioactive {sup 137}Cs are found throughout the DOE complex. These waste types include water in reactor cooling basins, radioactive high-level waste (HLW) in underground storage tanks, and groundwater. Safety and regulatory requirements and economics require the removal of radiocesium before these wastes can be permanently disposed of. Electrically Switched Ion Exchange (ESIX) is an approach for radioactive cesium separation that combines IX and electrochemistry to provide a selective, reversible, and economic separation method that also produces little or no secondary waste. In the ESIX process, an electroactive IX film is deposited electrochemically onto a high-surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. For cesium, the electroactive films under investigation are ferrocyanides, which are well known to have high selectivities for cesium in concentrated sodium solutions. When a cathode potential is applied to the film, Fe{sup +3} is reduced to the Fe{sup +2} state, and a cation must be intercalated into the film to maintain charge neutrality (i.e., Cs{sup +} is loaded). Conversely, if an anodic potential is applied, a cation must be released from the film (i.e., Cs{sup +} is unloaded). Therefore, to load the film with cesium, the film is simply reduced; to unload cesium, the film is oxidized.

  1. The magnetoelectrochemical switch.

    Science.gov (United States)

    Popa, Petru Lunca; Kemp, Neil T; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

    2014-07-22

    In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 10(3). The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

  2. Adaptive switching control of discrete time nonlinear systems based on multiple models

    Institute of Scientific and Technical Information of China (English)

    Rui KAN

    2004-01-01

    We use the approach of "optimal" switching to design the adaptive control because the design among multiple models is intuitively more practically feasible than the traditional adaptive control in improving the performances. We prove that for a typical class of nonlinear systems disturbed by random noise, the multiple model adaptive switching control based on WLS(Weighted Least Squares) or projected-LS (Least Squares) is stable and convergent.

  3. Novel zero-voltage switching techniques for pulse-width-modulated converters

    OpenAIRE

    Hua, Guichao

    1991-01-01

    Two new classes of soft switching pulse-width-modulated (PWM) converters, named zero-voltage-switched (ZVS) PWM converters and zero-voltage-transition (ZVT) PWM converters, are proposed. The proposed ZVS-PWM converters combine the merits of conventional PWM and ZVS-QRC techniques. They are capable of regulating the output for a wide load and input voltage range while maintaining constant-frequency operation. By employing a saturable inductor, the load range under which ZVS i...

  4. Performance Analysis of Delay in Optical Packet Switching Using Various Traffic Patterns

    OpenAIRE

    A Kavitha; V.Rajamni; P. Anandhakumar

    2010-01-01

    Quality of Service parameters are improved for development of optical packet switching technology. Delay is an important parameter in optical packet switching networks and it affects the performance of the network. In this paper, a mathematical model is presented to evaluate the delay rate. Delay rates are analyzed for fixed packet length and variable length packet for various traffic patterns viz. Non-uniform, Poisson and ON-OFF traffic models for various service classes using Reservation Bi...

  5. Direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp

    OpenAIRE

    Ljusev, Petar; Andersen, Michael Andreas E.

    2005-01-01

    This paper discusses the advantages and problems when implementing direct energy conversion switching-mode audio power amplifiers. It is shown that the total integration of the power supply and Class D audio power amplifier into one compact direct converter can simplify the design, increase efficiency, reduce the product volume and lower its cost. As an example, the principle of operation and the measurements made on a direct-conversion switching-mode audio power amplifier with active capacit...

  6. Delayed recombination and cosmic parameters

    International Nuclear Information System (INIS)

    Current cosmological constraints from cosmic microwave background anisotropies are typically derived assuming a standard recombination scheme, however additional resonance and ionizing radiation sources can delay recombination, altering the cosmic ionization history and the cosmological inferences drawn from the cosmic microwave background data. We show that for recent observations of the cosmic microwave background anisotropy, from the Wilkinson microwave anisotropy probe satellite mission (WMAP) 5-year survey and from the arcminute cosmology bolometer array receiver experiment, additional resonance radiation is nearly degenerate with variations in the spectral index, ns, and has a marked effect on uncertainties in constraints on the Hubble constant, age of the universe, curvature and the upper bound on the neutrino mass. When a modified recombination scheme is considered, the redshift of recombination is constrained to z*=1078±11, with uncertainties in the measurement weaker by 1 order of magnitude than those obtained under the assumption of standard recombination while constraints on the shift parameter are shifted by 1σ to R=1.734±0.028. From the WMAP5 data we obtain the following constraints on the resonance and ionization sources parameters: εαi<0.058 at 95% c.l.. Although delayed recombination limits the precision of parameter estimation from the WMAP satellite, we demonstrate that this should not be the case for future, smaller angular scales measurements, such as those by the Planck satellite mission.

  7. Exponential Stability of Time-Switched Two-Subsystem Nonlinear Systems with Application to Intermittent Control

    Directory of Open Access Journals (Sweden)

    Huang Tingwen

    2009-01-01

    Full Text Available This paper studies the exponential stability of a class of periodically time-switched nonlinear systems. Three cases of such systems which are composed, respectively, of a pair of unstable subsystems, of both stable and unstable subsystems, and of a pair of stable systems, are considered. For the first case, the proposed result shows that there exists periodically switching rule guaranteeing the exponential stability of the whole system with (sufficient small switching period if there is a Hurwitz linear convex combination of two uncertain linear systems derived from two subsystems by certain linearization. For the second case, we present two general switching criteria by means of multiple and single Lyapunov function, respectively. We also investigate the stability issue of the third case, and the switching criteria of exponential stability are proposed. The present results for the second case are further applied to the periodically intermittent control. Several numerical examples are also given to show the effectiveness of theoretical results.

  8. Guaranteed Cost H∞ Controller Synthesis for Switched Systems Defined on Semi-algebraic Sets

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafael

    2014-01-01

    A methodology to design guaranteed cost H∞ controllers for a class of switched systems with polynomial vector fields is proposed. To this end, we use sum of squares programming techniques. In addition, instead of the customary Carathéodory solutions, the analysis is performed in the framework...... feasibility tests leading to a stabilizing switching controller. Finally, we propose a scheme to synthesize stabilizing switching controllers with a guaranteed cost H∞ disturbance attenuation performance. The applicability of the proposed methods is elucidated thorough simulation analysis....... of Filippov solutions which subsumes solutions with infinite switching in finite time and sliding modes. Firstly, conditions assuring asymptotic stability of Filippov solutions pertained to a switched system defined on semi-algebraic sets are formulated. Accordingly, we derive a set of sum of squares...

  9. SERUM ANTIBODIES TO WHOLE-CELL AND RECOMBINANT ANTIGENS OF BORRELIA BURGDORFERI IN COTTONTAIL RABBITS

    OpenAIRE

    Magnarelli, Louis A.; Norris, Steven J; Fikrig, Erol

    2012-01-01

    Archived serum samples, from 95 eastern cottontail rabbits (Sylvilagus floridanus) captured in New York, New York, USA and Millbrook, New York, USA, during 1985–86, were analyzed in solid-phase enzyme-linked immunosorbent assays (ELISA) for total and class-specific immunoglobulin (Ig) M antibodies to whole-cell or recombinant antigens of Borrelia burgdorferi sensu stricto. Using a polyvalent conjugate, rabbit sera contained antibodies to whole-cell and recombinant antigens (protein [p]35, p37...

  10. Switching Oxide Traps

    Science.gov (United States)

    Oldham, Timothy R.

    2003-01-01

    We consider radiation-induced charge trapping in SiO2 dielectric layers, primarily from the point of view of CMOS devices. However, SiO2 insulators are used in many other ways, and the same defects occur in other contexts. The key studies, which determined the nature of the oxide charge traps, were done primarily on gate oxides in CMOS devices, because that was the main radiation problem in CMOS at one time. There are two major reviews of radiation-induced oxide charge trapping already in the literature, which discuss the subject in far greater detail than is possible here. The first of these was by McLean et al. in 1989, and the second, ten years later, was intended as an update, because of additional, new work that had been reported. Basically, the picture that has emerged is that ionizing radiation creates electron-hole pairs in the oxide, and the electrons have much higher mobility than the holes. Therefore, the electrons are swept out of the oxide very rapidly by any field that is present, leaving behind any holes that escape the initial recombination process. These holes then undergo a polaron hopping transport toward the Si/SiO2 interface (under positive bias). Near the interface, some fraction of them fall into deep, relatively stable, long-lived hole traps. The nature and annealing behavior of these hole traps is the main focus of this paper.

  11. Wide Bandgap Extrinsic Photoconductive Switches

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, James S. [State Univ. of New York (SUNY), Plattsburgh, NY (United States); Univ. of California, Davis, CA (United States)

    2012-01-20

    Photoconductive semiconductor switches (PCSS) have been investigated since the late 1970s. Some devices have been developed that withstand tens of kilovolts and others that switch hundreds of amperes. However, no single device has been developed that can reliably withstand both high voltage and switch high current. Yet, photoconductive switches still hold the promise of reliable high voltage and high current operation with subnanosecond risetimes. Particularly since good quality, bulk, single crystal, wide bandgap semiconductor materials have recently become available. In this chapter we will review the basic operation of PCSS devices, status of PCSS devices and properties of the wide bandgap semiconductors 4H-SiC, 6H-SiC and 2H-GaN.

  12. Industry switching in developing countries

    DEFF Research Database (Denmark)

    Newman, Carol; Rand, John; Tarp, Finn

    2013-01-01

    Firm turnover (i.e., firm entry and exit) is a well-recognized source of sector-level productivity growth. In contrast, the role and importance of firms that switch activities from one sector to another is not well understood. Firm switchers are likely to be unique, differing from both newly esta...... of switching merits attention in the future design of firm surveys across developing countries and in associated analytical studies....... established entrants and exiting firms that are closing down operations. In this study, we develop an empirical model that examines switching behavior using data from Vietnamese manufacturing firms during the 2001–2008 period. The diagnostic shows that switching firms exhibit different characteristics and...

  13. Electron collisions in gas switches

    International Nuclear Information System (INIS)

    Many technologies rely on the conduction/insulation properties of gaseous matter for their successful operation. Many others (e.g., pulsed power technologies) rely on the rapid change (switching or modulation) of the properties of gaseous matter from an insulator to a conductor and vice versa. Studies of electron collision processes in gases aided the development of pulsed power gas switches, and in this paper we shall briefly illustrate the kind of knowledge on electron collision processes which is needed to optimize the performance of such switching devices. To this end, we shall refer to three types of gas switches: spark gap closing, self-sustained diffuse discharge closing, and externally-sustained diffuse discharge opening. 24 refs., 15 figs., 2 tabs

  14. Product choice and product switching

    OpenAIRE

    Andrew B. Bernard; Redding, Stephen; Peter K. Schott

    2003-01-01

    This paper develops a model of endogenous product selection by firms. The theory is motivated by new evidence we present on the importance of product switching by U.S. manufacturers. Two-thirds of continuing firms change their product mix every five years, and product switches involve more than 40% of firm output and almost half of existing products. The theoretical model incorporates heterogeneous firms, heterogeneous products, and ongoing entry and exit. In equilibrium, firm productivity is...

  15. Microwatt Switched Capacitor Circuit Design

    OpenAIRE

    Vittoz, E.

    1982-01-01

    The micropower CMOS implementation of the three basic components of switched capacitor circuits is discussed. Switches must be carefully designed to allow low voltage operation and compensation of clock feed-through by dummy transistors. Matched capacitors can be implemented in single polysilicon technologies primarily designed for digital micropower circuits. Excellent micropower amplifiers are realized by using simple one-stage circuits which take advantage of the special behaviour of MOS t...

  16. Statistical switching kinetics in ferroelectrics

    OpenAIRE

    Lou, X. J.

    2008-01-01

    By assuming a more realistic nucleation and polarization reversal scenario we build a new statistical switching model for ferroelectrics, which is different from either the Kolmogorov-Avrami-Ishibashi (KAI) model or the Nucleation-Limited-Switching (NLS) model. After incorporating a time-dependent depolarization field this model gives a good description about the retardation behavior in polycrystalline thin films at medium or low fields, which can not be described by the traditional KAI model...

  17. Superannuation: Switching and Roulette Wheels

    OpenAIRE

    Michael E. Drew

    2007-01-01

    The introduction of choice has resulted in Australia’s superannuation system providing unprecedented flexibility (through increased investment options and the timing choices) for members to optimise their expected benefits. This paper examines the impact of switching between investment options using a normalised ranked return or “roulette wheel” approach developed by Bauer and Dahlquist (2001) for the Australian setting. The paper tests various switching strategies for both single-sector and ...

  18. The effect of a single recombination event

    DEFF Research Database (Denmark)

    Schierup, Mikkel Heide; Jensen, Thomas Mailund; Wiuf, Carsten

    the effect of a recombination event is the genealogical type of the event and whether SNP variation is present that can reveal the genealogical consequences of the recombination event. Recombination events that only change some branch lengths in the genealogy have a very small, but detectable, effect....... The more lineages left when the recombination event occurs, the larger effect it has, implying that it is mainly young recombination events that we detect when estimating the rate. If the population is growing, though, more lineages are present back in time and relatively more ancient recombination...... shared by these two populations are expected to contribute compared to the effect of private recombination events...

  19. Working Memory Costs of Task Switching

    Science.gov (United States)

    Liefooghe, Baptist; Barrouillet, Pierre; Vandierendonck, Andre; Camos, Valerie

    2008-01-01

    Although many accounts of task switching emphasize the importance of working memory as a substantial source of the switch cost, there is a lack of evidence demonstrating that task switching actually places additional demands on working memory. The present study addressed this issue by implementing task switching in continuous complex span tasks…

  20. Contrasting roles of interallelic recombination at the HLA-A and HLA-B loci

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, A.L.; Hughes, M.K. (Pennsylvania State Univ., University Park (United States)); Watkins, D.I. (Univ. of Wisconsin, Madison (United States))

    1993-03-01

    A statistical study of DNA sequences of alleles at the highly polymorphic class I MHC loci of humans, HLA-A and HLA-B, showed evidence of both large-scale recombination events(involving recombination of exons 1-2 of one allele with exons 3-8 of another) and small scale recombination events (involving apparent exchange of short DNA segments). The latter events occurred disproportionately in the region of the gene encoding the antigen recognition site (ARS) of the class I molecule. Furthermore, they involved the ARS codons which are under the strongest selection favoring allelic diversity at the amino acid level. Thus, the frequency of recombinant alleles appears to have been increased by some form of balancing selection (such as overdominant selection) favoring heterozygosity in the ARS. These analyses also revealed a striking difference between the A and B loci. Recombination events appear to have occurred about twice as frequently at the B locus, and recombinants at the B locus were significantly more likely to affect polymorphic sites in the ARS. At the A locus, there are well-defined allelic lineages that have persisted since prior to the human-chimpanzee divergence; but at the B locus, there is no evidence for such long-lasting allelic lineages. Thus, relatively frequent interallelic recombination has apparently been a feature of the long-term evolution of the B locus but not of the A locus. 45 refs., 4 figs., 5 tabs.

  1. Investigations for designing catalytic recombiners

    International Nuclear Information System (INIS)

    In case of a severe accident in pressurised water reactors (PWR) a high amount of hydrogen up to about 20,000 m3 might be generated and released into the containments. The mixture consisting of hydrogen and oxygen may either burn or detonate, if ignited. In case of detonation the generated shock wave may endanger the components of the plant or the plant itself. Consequently, effective removal of hydrogen is required. The fact that hydrogen and oxygen react exo-thermally on catalytically acting surfaces already at low temperatures generating steam and heat is made use of in catalytic recombiners. They consist of substrates coated with catalyst (mainly platinum or palladium) which are arranged inside a casing. Being passively acting measures, recombiners do not need any additional energy supply. Experimental investigations on catalytic hydrogen recombination are conducted at FZJ (Forschungszentrum Juelich) using three test facilities. The results yield insight in the development potential of contemporary recombiner systems as well as of innovative systems. Detailed investigations on a recombiner section show strong temperature gradients over the surface of a catalytically coated sample. Dependent on the flow velocity, ignition temperature may be reached at the leading edge already at an inlet hydrogen concentration of about 5 vol.-%. The thermal strain of the substrate leads to considerable detachment of catalyst particles probably causing unintended ignition of the flammable mixture. Temperature peaks can be prevented effectively by leaving the first part of the plate uncoated. In order to avoid overheating of the catalyst elements of a recombiner even at high hydrogen concentrations a modular system of porous substrates is proposed. The metallic substrates are coated with platinum at low catalyst densities thus limiting the activity of the single specimen. A modular arrangement of these elements provides high recombination rates over a large hydrogen concentration

  2. Magnetic-fluid-based smart centrifugal switch

    International Nuclear Information System (INIS)

    A new type of centrifugal switch, which we call 'smart centrifugal switch' is designed and developed utilizing the novel properties of magnetic fluid. No mechanical movement is involved in the sensing and switching operations of this centrifugal switch and both these operations are achieved in a smart way. The performance of the switch is studied. This switch has several important advantages over conventional centrifugal switches like smart and non-contact type operation, sparkless and hence explosion proof working and inertia-less simple structure

  3. Transcutaneous RF-Powered Implantable Minipump Driven by a Class-E Transmitter

    OpenAIRE

    Moore, William H.; Holschneider, Daniel P.; Givrad, Tina K.; Maarek, Jean-Michel I.

    2006-01-01

    We describe the design and testing of an inductive coupling system used to power an implantable minipump for applications in ambulating rats. A 2 MHz class-E oscillator driver powered a coil transmitter wound around a 33-cm-diameter rat cage. A receiver coil, a filtered rectifier, and a voltage-sensitive switch powered the implant. The implant DC current at the center of the primary coil (5.1 V) exceeded the level required to activate the solenoid valve in the pump. The variations of the impl...

  4. Homologous Recombination in Negative Sense RNA Viruses

    OpenAIRE

    Michael Worobey; Guan-Zhu Han

    2011-01-01

    Recombination is an important process that influences biological evolution at many different levels. More and more homologous recombination events have been reported among negative sense RNA viruses recently. While sporadic authentic examples indicate that homologous recombination does occur, recombination seems to be generally rare or even absent in most negative sense RNA viruses, and most of the homologous recombination events reported in the literature were likely generated artificially d...

  5. Analysis of the class E amplifier used as electronic ballast with dimming capability for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Ponce, M.; Arau, J. [CENIDET-Electro' , Cuernavaca (Mexico); Alonso, J.M.; Rico-Secades, M. [ATE, Universidad de Oviedo, Campus de Viesques s/n Gijon (Spain)

    2001-07-01

    The analysis and design of a dimmable electronic ballast based on the class E amplifier and fed from solar cells with 12V backup batteries is described. The class E amplifier uses a capacitive impedance inverter as resonant tank and one diode antiparallel with the switch; these elements allow implementation of a dimming feature for the ballast and ignition of the lamp while maintaining zero voltage commutations in the switch. The designed electronic ballast drives a 21W lamp and operates at a switching frequency of 370kHz. Dimming is implemented using an SG3524 in a voltage-controlled oscillator fashion. (Author)

  6. Accelerated homologous recombination and subsequent genome modification in Drosophila.

    Science.gov (United States)

    Baena-Lopez, Luis Alberto; Alexandre, Cyrille; Mitchell, Alice; Pasakarnis, Laurynas; Vincent, Jean-Paul

    2013-12-01

    Gene targeting by 'ends-out' homologous recombination enables the deletion of genomic sequences and concurrent introduction of exogenous DNA with base-pair precision without sequence constraint. In Drosophila, this powerful technique has remained laborious and hence seldom implemented. We describe a targeting vector and protocols that achieve this at high frequency and with very few false positives in Drosophila, either with a two-generation crossing scheme or by direct injection in embryos. The frequency of injection-mediated gene targeting can be further increased with CRISPR-induced double-strand breaks within the region to be deleted, thus making homologous recombination almost as easy as conventional transgenesis. Our targeting vector replaces genomic sequences with a multifunctional fragment comprising an easy-to-select genetic marker, a fluorescent reporter, as well as an attP site, which acts as a landing platform for reintegration vectors. These vectors allow the insertion of a variety of transcription reporters or cDNAs to express tagged or mutant isoforms at endogenous levels. In addition, they pave the way for difficult experiments such as tissue-specific allele switching and functional analysis in post-mitotic or polyploid cells. Therefore, our method retains the advantages of homologous recombination while capitalising on the mutagenic power of CRISPR. PMID:24154526

  7. Comparative Study of Hard Switching and Soft Switching Boost Converter Fed from a PV Source

    Directory of Open Access Journals (Sweden)

    B. Angeline Jerusha, S. Anu Vadhana, A. Arrul Dhana Mathy, R. Ramaprabha

    2013-09-01

    Full Text Available This paper presents a comparative study of hard switching and soft switching boost converter for interfacing photovoltaic (PV systems. This paper mainly focuses on the minimization of switching loss by adopting soft switching technology when compared to hard switching.

  8. Recombining WMAP: Constraints on ionizing and resonance radiation at recombination

    International Nuclear Information System (INIS)

    We place new constraints on sources of ionizing and resonance radiation at the epoch of the recombination process using the recent cosmic microwave background temperature and polarization spectra coming from the Wilkinson Microwave Anisotropy Probe (WMAP). We find that non-standard recombination scenarios are still consistent with the current data. In light of this we study the impact that such models can have on the determination of several cosmological parameters. In particular, the constraints on curvature and baryon density appear to be weakly affected by a modified recombination scheme. However, it may affect the current WMAP constraints on inflationary parameters such as the spectral index ns and its running. Physically motivated models, such as those based on primordial black holes or super heavy dark matter decay, are able to provide a good fit to the current data. Future observations in both temperature and polarization will be needed to more stringently test these models

  9. Experimental Realization of an NMR Quantum Switch

    OpenAIRE

    Tsai, I. M.; Kuo, S. Y.; Huang, S. L.; Lin, Y. C.; Chen, T. T.

    2004-01-01

    In this paper, we report an experimental realization of quantum switch using nuclear spins and magnetic resonant pulses. The nuclear spins of H and C in carbon-13 labelled chloroform are used to carry the information, then nuclear magnetic resonance pulses are applied to perform either bypass or cross function to achieve the switching. Compared with a traditional space or time domain switch, this switching architecture is much more scalable, therefore a high throughput switching device can be...

  10. Principles of broadband switching and networking

    CERN Document Server

    Liew, Soung C

    2010-01-01

    An authoritative introduction to the roles of switching and transmission in broadband integrated services networks Principles of Broadband Switching and Networking explains the design and analysis of switch architectures suitable for broadband integrated services networks, emphasizing packet-switched interconnection networks with distributed routing algorithms. The text examines the mathematical properties of these networks, rather than specific implementation technologies. Although the pedagogical explanations in this book are in the context of switches, many of the fundamenta

  11. Inhibition of tumor angiogenesis by angiostatin: from recombinant protein to gene therapy.

    Science.gov (United States)

    Dell'Eva, Raffaella; Pfeffer, Ulrich; Indraccolo, S; Albini, Adriana; Noonan, Douglas

    2002-01-01

    Tumor growth, local invasion, and metastatic dissemination are dependent on the formation of new microvessels. The process of angiogenesis is regulated by a balance between pro-angiogenic and anti-angiogenic factors, and the shift to an angiogenic phenotype (the "angiogenic switch") is a key event in tumor progression. The use of anti-angiogenic agents to restore this balance represents a promising approach to cancer treatment. Known physiological inhibitors include trombospondin, several interleukins, and the proteolytic break-down products of several proteins. Angiostatin, an internal fragment of plasminogen, is one of the more potent of this latter class of angiogenesis inhibitors. Like endostatin, another anti-angiogenic peptide derived from collagen XVIII, angiostatin can induce tumor vasculature regression, leading to a complete cessation of tumor growth. Inhibitors of angiogenesis target normal endothelial cells, therefore the development of resistance to these drugs is unlikely. The efficacy of angiostatin has been demonstrated in animal models for many different types of solid tumors. Anti-angiogenic cancer therapy with angiostatin requires prolonged administration of the peptide. The production of the functional polypeptides is expensive and technical problems related to physical properties and purity are frequently encountered. Gene transfer represents an alternative method to deliver angiostatin. Gene therapy has the potential to produce the therapeutic agent in high concentrations in a local area for a sustained period, thereby avoiding the problems encountered with long-term administration of recombinant proteins, monoclonal antibodies, or anti-angiogenic drugs. In this review we compare the different gene therapy strategies that have been applied to angiostatin, with special regard to their ability to provide sufficient angiostatin at the target site. PMID:12901356

  12. IL-10 selectively regulates murine Ig isotype switching.

    Science.gov (United States)

    Shparago, N; Zelazowski, P; Jin, L; McIntyre, T M; Stuber, E; Peçanha, L M; Kehry, M R; Mond, J J; Max, E E; Snapper, C M

    1996-05-01

    A role for IL-10 in regulating Ig isotype switching directly at the level of the murine B cell has not been previously reported. In this report we show that IL-10 selectively up-regulated IgM to IgG3 class switching in lipopolysaccharide (LPS)-activated cultures through a direct effect on membrane (m) IgM+IgG3(-)B cells in vitro. IL-10 stimulated a 3- to 4-fold enhancement (from 6-8 to 20-30%) in membrane mIgG3(+) cells and a significant increase in Smu-Sgamma3 DNA rearrangement events as measured by digestion-circularization PCR (DC-PCR) over that observed with LPS alone. IL-10 induction of switching to IgG3 was not accompanied by a corresponding increase in the steady-state levels of germline CHgamma3 RNA. By contrast, IL-10 strongly inhibited the transforming growth factor-beta-mediated generation of mIgA+ cells and Smu-Salpha DNA rearrangement events in LPS-, but not CD40 ligand (CD40L)-activated B cells. This effect was not accompanied by changes in the steady-state levels of germline CHalpha RNA. IL-10 had no effect on IL-4-mediated switching to either IgG1 or IgE in either LPS- or CD40L-activated B cells. Thus, IL-10 can either enhance or suppress switching to particular murine Ig isotypes but it differs from most other murine cytokines in that its effects on switching do not appear to be associated with changes in the corresponding steady-state levels of germline CH RNA. PMID:8671667

  13. Spin-transfer magnetization switching in ordered alloy-based nanopillar devices

    International Nuclear Information System (INIS)

    This paper reviews spin-transfer magnetization switching in ordered alloy-based nanopillar devices. L10-ordered FePt was used for one of the earliest demonstrations of spin-transfer switching in perpendicularly magnetized systems. The behaviour of magnetization switching deviates from the predictions based on a macro-spin model, suggesting incoherent magnetization switching in the system with a large perpendicular magnetic anisotropy. The effect of a 900 spin injector on spin-transfer switching was also examined using L10-ordered FePt. Full-Heusler alloys are in another fascinating material class for spin-transfer switching because of their high-spin polarization of conduction electrons and possible small magnetization damping. A B2-ordered Co2FeAl0.5Si0.5-based device showed a low intrinsic critical current density of 9.3 x 106 A cm-2 for spin-transfer switching as well as a relatively large current-perpendicular-to-plane giant-magnetoresistance (CPP-GMR) up to ∼9%. The specific physical properties of ordered alloys may be useful for fundamental studies and applications in spin-transfer switching.

  14. Inhomogeneous recombinations during cosmic reionization

    CERN Document Server

    Sobacchi, Emanuele

    2014-01-01

    By depleting the ionizing photon budget available to expand cosmic HII regions, recombining systems (or Lyman limit systems) can have a large impact during (and following) cosmic reionization. Unfortunately, directly resolving such structures in large-scale reionization simulations is computationally impractical. Instead, here we implement a sub-grid prescription for tracking inhomogeneous recombinations in the intergalactic medium. Building on previous work parameterizing photo-heating feedback on star-formation, we present large-scale, semi-numeric reionization simulations which self-consistently track the local (sub-grid) evolution of both sources and sinks of ionizing photons. Our simple, single-parameter model naturally results in both an extended reionization and a modest, slowly-evolving emissivity, consistent with observations. Recombinations are instrumental in slowing the growth of large HII regions, and damping the rapid rise of the ionizing background in the late stages of (and following) reioniza...

  15. Recombinant snake venom prothrombin activators.

    Science.gov (United States)

    Lövgren, Ann

    2013-01-01

    Three prothrombin activators; ecarin, which was originally isolated from the venom of the saw-scaled viper Echis carinatus, trocarin from the rough-scaled snake Tropidechis carinatus, and oscutarin from the Taipan snake Oxyuranus scutellatus, were expressed in mammalian cells with the purpose to obtain recombinant prothrombin activators that could be used to convert prothrombin to thrombin. We have previously reported that recombinant ecarin can efficiently generate thrombin without the need for additional cofactors, but does not discriminate non-carboxylated prothrombin from biologically active γ-carboxylated prothrombin. Here we report that recombinant trocarin and oscutarin could not efficiently generate thrombin without additional protein co-factors. We confirm that both trocarin and oscutarin are similar to human coagulation Factor X (FX), explaining the need for additional cofactors. Sequencing of a genomic fragment containing 7 out of the 8 exons coding for oscutarin further confirmed the similarity to human FX. PMID:23111318

  16. Improvement on Switching Characteristics and Switching Losses of IGBT by ZVS—PWM①

    Institute of Scientific and Technical Information of China (English)

    ZHANGChunjiang; GUHerong; 等

    1997-01-01

    The principle of ZVS-PWM inverting circuit is first described by means of inverting welder supply.The contrastive study is made on switching characteristics and switching losses of IGBT between ZVS-PWM and hard-switching.

  17. IGBT: A solid state switch

    International Nuclear Information System (INIS)

    A Copper Vapor Laser Power Supply has been designed using a solid state switch consisting in eighteen Isolated Gate Bipolar Transistors (IGBT), 1,200 volts, 400 Amps, each, in parallel. This paper presents the Isolated Gate Bipolar Transistor (IGBTs) replaced in the Power Electronic components evolution, and describes the IGBT conduction mechanism, presents the parallel association of IGBTs, and studies the application of these components to a Copper Vapor Laser Power Supply. The storage capacitor voltage is 820 Volts, the peak current of the solid state switch is 17,000 Amps. The switch is connected on the primary of a step-up transformer, followed by a magnetic modulator. The reset of the magnetic modulator is provided by part of the laser reflected energy with a patented circuit. The charging circuit is a resonant circuit with a charge controlled by an IGBT switch. When the switch is open, the inductance energy is free-wheeled by an additional winding and does not extend the charging phase of the storage capacitor. The design allows the storage capacitor voltage to be very well regulated. This circuit is also patented. The electric pulse in the laser has 30,000 Volt peak voltage, 2,000 Amp peak current, and is 200 nanoseconds long, for a 200 Watt optical power Copper Vapor Laser

  18. IGBT: a solid state switch

    International Nuclear Information System (INIS)

    A Copper Vapour Laser Power Supply has been designed using a solid state switch consisting in eighteen Isolated Gate Bipolar Transistors (IGBT), -1200 volts, 400 Amps, each-in parallel. This paper presents the Isolated Gate Bipolar Transistor (IGBTs) replaced in the Power Electronic components evolution, and describes the IGBT conduction mechanism, presents the parallel association of IGBTs, and studies the application of these components to a Copper Vapour Laser Power Supply. The storage capacitor voltage is 820 volts, the peak current of the solid state switch is 17.000 Amps. The switch is connected on the primary of a step-up transformer, followed by a magnetic modulator. The reset of the magnetic modulator is provided by part of the laser reflected energy with a patented circuit. The charging circuit is a resonant circuit with a charge controlled by an IGBT switch. When the switch is open, the inductance energy is free-wheeled by an additional winding and does not extend the charging phase of the storage capacitor. The design allows the storage capacitor voltage to be very well regulated. This circuit is also patented. The electric pulse in the laser has 30.000 Volt peak voltage, 2000 Amp peak current, and is 200 nanoseconds long, for a 200 Watt optical power Copper Vapour Laser

  19. Recombinant expression and purification of the tomato defensin TPP3 and its preliminary X-ray crystallographic analysis

    OpenAIRE

    Lay, Fung T.; Veneer, Prem K.; Hulett, Mark D.; Kvansakul, Marc

    2012-01-01

    TPP3 is a class II plant defensin from tomato. Here, the expression, purification, crystallization and preliminary X-ray crystallographic analysis of recombinant TPP3 are reported in order to define its structure and function in relation to other class II plant defensins.

  20. Loosely coupled class families

    DEFF Research Database (Denmark)

    Ernst, Erik

    2001-01-01

    Families of mutually dependent classes that may be accessed polymor- phically provide an advanced tool for separation of concerns, in that it enables client code to use a group of instances of related classes safely without depending on the exact classes involved. However, class families which are...... expressed using virtual classes seem to be very tightly coupled internally. While clients have achieved the freedom to dynamically use one or the other family, it seems that any given family contains a xed set of classes and we will need to create an entire family of its own just in order to replace one of...... the members with another class. This paper shows how to express class families in such a manner that the classes in these families can be used in many dierent combinations, still enabling family polymorphism and ensuring type safety....

  1. Identification of Recombination and Positively Selected Genes in Brucella.

    Science.gov (United States)

    Vishnu, Udayakumar S; Sankarasubramanian, Jagadesan; Sridhar, Jayavel; Gunasekaran, Paramasamy; Rajendhran, Jeyaprakash

    2015-12-01

    Brucella is a facultative intracellular bacterium belongs to the class alpha proteobacteria. It causes zoonotic disease brucellosis to wide range of animals. Brucella species are highly conserved in nucleotide level. Here, we employed a comparative genomics approach to examine the role of homologous recombination and positive selection in the evolution of Brucella. For the analysis, we have selected 19 complete genomes from 8 species of Brucella. Among the 1599 core genome predicted, 24 genes were showing signals of recombination but no significant breakpoint was found. The analysis revealed that recombination events are less frequent and the impact of recombination occurred is negligible on the evolution of Brucella. This leads to the view that Brucella is clonally evolved. On other hand, 56 genes (3.5 % of core genome) were showing signals of positive selection. Results suggest that natural selection plays an important role in the evolution of Brucella. Some of the genes that are responsible for the pathogenesis of Brucella were found positively selected, presumably due to their role in avoidance of the host immune system. PMID:26543263

  2. An integrated circuit/packet switched video conferencing system

    International Nuclear Information System (INIS)

    The HEP Network Resource Center (HEPNRC) at Fermilab and the Collider Detector Facility (CDF) collaboration have evolved a flexible, cost-effective, widely accessible video conferencing system for use by high energy physics collaborations and others wishing to use video conferencing. No current systems seemed to fully meet the needs of high energy physics collaborations. However, two classes of video conferencing technology: circuit-switched and packet-switched, if integrated, might encompass most of HEPS's needs. It was also realized that, even with this integration, some additional functions were needed and some of the existing functions were not always wanted. HEPNRC with the help of members of the CDF collaboration set out to develop such an integrated system using as many existing subsystems and components as possible. This system is called VUPAC (Video conferencing Using Packets and Circuits). This paper begins with brief descriptions of the circuit-switched and packet-switched video conferencing systems. Following this, issues and limitations of these systems are considered. Next the VUPAC system is described. Integration is accomplished primarily by a circuit/packet video conferencing interface. Augmentation is centered in another subsystem called MSB (Multiport MultiSession Bridge). Finally, there is a discussion of the future work needed in the evolution of this system. (author)

  3. Packet switching in 1990's

    Science.gov (United States)

    Rybczynski, A.

    The author assesses wide-area networking end-user needs as they evolve into the 1990s. He then turns to the network operator environment, both public and private, by examining service evolution trends. The author concludes with an assessment of how packet switching services and technologies are evolving to continue to match the identified market requirements, with specific emphasis on Northern Telecom's DPN Data Networking System. Key evolving DPN capabilities include the introduction of the high-end DPN100 30-kb/s switch, a variety of access options including ISDN (integrated services digital network) packet mode services, higher throughput virtual circuits, megabit trunking for improved network throughput and end-user transit delay, and SNA session switching, the latter being an example of adding value to packet networking through communication processing.

  4. Easy axis switching in magnetite

    International Nuclear Information System (INIS)

    The easy magnetic axis switching in magnetite is investigated. Magnetization data confirmed activation character of the process with activation energy of the same order as that of the Verwey transition, suggesting common origin. On the other hand this activation energy rises with pressure (up to 1.2GPa), unlike TV. The axis switching is clearly reflected in field dependence of resistivity and the direct structural data showed that it is simultaneous with the reorganization of structure. Thus, control of the structure can be possible with the application of magnetic field, as in shape memory materials. Finally, NMR showed that all, possibly decoupled entities: lattice distortion and charge and orbital orderings, change simultaneously while the axis switching occurs.

  5. PROMOTION, SWITCHING BARRIERS, AND LOYALTY

    Directory of Open Access Journals (Sweden)

    Gu-Shin Tung

    2011-06-01

    Full Text Available This paper investigates the causal relationships among promotion effects, switching barriers, and loyalty in the department stores. The relationship between switching barriers and loyalty reveals partially the same results as the switching barriers theory of Jones et al. (2000. The reasons arise from “too often” and “too similar” sales promotion programs of competitive department stores in Taiwan, leading the promotion effects to not contribute to the attractiveness of competitors. The promotion effects have a positive and significant influence on loyalty, which is consistent with the prior literature. Promotion effects are also the most important weight to loyalty in our tested model but it reveals a seeming loyalty, because the loyalty depends on the reward of promotion. The negative relationship between promotion effects and attractiveness of alternative supports the promotion effects, which can lower the attractiveness of competitors, but these similar promotion plans are not attributed to interpersonal relationships.

  6. Recombinant mitochondrial genome with standard transmission route from Mediterranean mussel Mytilus galloprovincialis.

    Science.gov (United States)

    Śmietanka, Beata; Filipowicz, Monika; Burzyński, Artur

    2016-01-01

    Several bivalve species, including marine mussels Mytilus are atypical in having two gender-specific and highly divergent mtDNA genomes. This peculiar genetic system allows not only the recombination to occur but also facilitates its detection. Previous reports associated the existence of mosaic recombinant haplotypes with the switch of their transmission route. Here we report nearly complete sequence of a mitochondrial genome isolated from a homoplasmic female individual of Mediterranean Mytilus galloprovincialis. The genome has clear phylogenetic affinity with and organization identical to the M. galloprovincialis female haplotypes, in the coding part. However, the genome is very large, approximately 20,600 bp long, exclusively due to a long and complex control region. It contains an array of repeats, some of which are degenerated. A large part of the control region is derived from the paternal genome. This finding shows that not all haplotypes with recombinant control regions must be paternally inherited in Mytilus. PMID:24724974

  7. Topology optimized RF MEMS switches

    DEFF Research Database (Denmark)

    Philippine, M. A.; Zareie, H.; Sigmund, Ole;

    2013-01-01

    Topology optimization is a rigorous and powerful method that should become a standard MEMS design tool - it can produce unique and non-intuitive designs that meet complex objectives and can dramatically improve the performance and reliability of MEMS devices. We present successful uses of topology...... optimization for an RF MEM capacitive switch. Extensive experimental data confirms that the switches perform as designed by the optimizations, and that our simulation models are accurate. A subset of measurements are presented here. Broader results have been submitted in full journal format....

  8. Statistical switching kinetics in ferroelectrics

    CERN Document Server

    Lou, X J

    2008-01-01

    By assuming a more realistic nucleation and polarization reversal scenario we build a new statistical switching model for ferroelectrics, which is different from either the Kolmogorov-Avrami-Ishibashi (KAI) model or the Nucleation-Limited-Switching (NLS) model. After incorporating a time-dependent depolarization field this model gives a good description about the retardation behavior in polycrystalline thin films at medium or low fields, which can not be described by the traditional KAI model. This model predicts correctly n=1 for polycrystalline thin films at high Eappl or ceramic bulks in the ideal case.

  9. STABILITY OF SWITCHED POLYNOMIAL SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    Zhiqiang LI; Yupeng QIAO; Hongsheng QI; Daizhan CHENG

    2008-01-01

    This paper investigates the stability of (switched) polynomial systems. Using semi-tensor product of matrices, the paper develops two tools for testing the stability of a (switched) polynomial system. One is to convert a product of multi-variable polynomials into a canonical form, and the other is an easily verifiable sufficient condition to justify whether a multi-variable polynomial is positive definite. Using these two tools, the authors construct a polynomial function as a candidate Lyapunov function and via testing its derivative the authors provide some sufficient conditions for the global stability of polynomial systems.

  10. CMOS integrated switching power converters

    CERN Document Server

    Villar-Pique, Gerard

    2011-01-01

    This book describes the structured design and optimization of efficient, energy processing integrated circuits. The approach is multidisciplinary, covering the monolithic integration of IC design techniques, power electronics and control theory. In particular, this book enables readers to conceive, synthesize, design and implement integrated circuits with high-density high-efficiency on-chip switching power regulators. Topics covered encompass the structured design of the on-chip power supply, efficiency optimization, IC-compatible power inductors and capacitors, power MOSFET switches and effi

  11. Switching in electrical transmission and distribution systems

    CERN Document Server

    Smeets, René; Kapetanovic, Mirsad; Peelo, David F; Janssen, Anton

    2014-01-01

    Switching in Electrical Transmission and Distribution Systems presents the issues and technological solutions associated with switching in power systems, from medium to ultra-high voltage. The book systematically discusses the electrical aspects of switching, details the way load and fault currents are interrupted, the impact of fault currents, and compares switching equipment in particular circuit-breakers. The authors also explain all examples of practical switching phenomena by examining real measurements from switching tests. Other highlights include: up to date commentary on new develo

  12. One-cycle control of switching converters

    OpenAIRE

    Smedley, Keyue M.; Ćuk, Slobodan

    1995-01-01

    A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-cycle control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects swit...

  13. Efficient Modeling of PIN Diode Switches Employing Time-Domain Electromagnetic-Physics-Based Simulators

    Energy Technology Data Exchange (ETDEWEB)

    Hussein, Y.A.; Spencer, J.E.; /SLAC; El-Ghazaly, S.M.; /Tennessee U.; Goodnick, S.M.; /Arizona State U.

    2005-09-20

    This paper presents an efficient full-wave time-domain simulator for accurate modeling of PIN diode switches. An equivalent circuit of the PIN diode is extracted under different bias conditions using a drift-diffusion physical model. Net recombination is modeled using a Shockley-Read-Hall process, while generation is assumed to be dominated by impact ionization. The device physics is coupled to Maxwell's equations using extended-FDTD formulism. A complete set of results is presented for the on and off states of the PIN switch. The results are validated through comparison with independent measurements, where good agreement is observed. Using this modeling approach, it is demonstrated that one can efficiently optimize PIN switches for better performance.

  14. CRMAGE: CRISPR Optimized MAGE Recombineering

    Science.gov (United States)

    Ronda, Carlotta; Pedersen, Lasse Ebdrup; Sommer, Morten O. A.; Nielsen, Alex Toftgaard

    2016-01-01

    A bottleneck in metabolic engineering and systems biology approaches is the lack of efficient genome engineering technologies. Here, we combine CRISPR/Cas9 and λ Red recombineering based MAGE technology (CRMAGE) to create a highly efficient and fast method for genome engineering of Escherichia coli. Using CRMAGE, the recombineering efficiency was between 96.5% and 99.7% for gene recoding of three genomic targets, compared to between 0.68% and 5.4% using traditional recombineering. For modulation of protein synthesis (small insertion/RBS substitution) the efficiency was increased from 6% to 70%. CRMAGE can be multiplexed and enables introduction of at least two mutations in a single round of recombineering with similar efficiencies. PAM-independent loci were targeted using degenerate codons, thereby making it possible to modify any site in the genome. CRMAGE is based on two plasmids that are assembled by a USER-cloning approach enabling quick and cost efficient gRNA replacement. CRMAGE furthermore utilizes CRISPR/Cas9 for efficient plasmid curing, thereby enabling multiple engineering rounds per day. To facilitate the design process, a web-based tool was developed to predict both the λ Red oligos and the gRNAs. The CRMAGE platform enables highly efficient and fast genome editing and may open up promising prospective for automation of genome-scale engineering. PMID:26797514

  15. Controlled Release from Recombinant Polymers

    OpenAIRE

    Price, Robert; Poursaid, Azadeh; Ghandehari, Hamidreza

    2014-01-01

    Recombinant polymers provide a high degree of molecular definition for correlating structure with function in controlled release. The wide array of amino acids available as building blocks for these materials lend many advantages including biorecognition, biodegradability, potential biocompatibility, and control over mechanical properties among other attributes. Genetic engineering and DNA manipulation techniques enable the optimization of structure for precise control over spatial and tempor...

  16. Preparing Recombinant Gonad Organ Cultures

    OpenAIRE

    sprotocols

    2014-01-01

    Authors: Blanche Capel and Jordan Batchvarov Corresponding author ([]()) ### INTRODUCTION It can be useful to assay migration between any two adjacent tissues during development. This protocol assays cell migration between the gonad and mesonephros using tissue recombination between genetically marked and unmarked tissue, combined with an organ culture technique. First, agar blocks are prepared in a custom-built mold. The size and sh...

  17. Vaccine escape recombinants emerge after pneumococcal vaccination in the United States.

    Directory of Open Access Journals (Sweden)

    Angela B Brueggemann

    2007-11-01

    Full Text Available The heptavalent pneumococcal conjugate vaccine (PCV7 was introduced in the United States (US in 2000 and has significantly reduced invasive pneumococcal disease; however, the incidence of nonvaccine serotype invasive disease, particularly due to serotype 19A, has increased. The serotype 19A increase can be explained in part by expansion of a genotype that has been circulating in the US prior to vaccine implementation (and other countries since at least 1990, but also by the emergence of a novel "vaccine escape recombinant" pneumococcal strain. This strain has a genotype that previously was only associated with vaccine serotype 4, but now expresses a nonvaccine serotype 19A capsule. Based on prior evidence for capsular switching by recombination at the capsular locus, the genetic event that resulted in this novel serotype/genotype combination might be identifiable from the DNA sequence of individual pneumococcal strains. Therefore, the aim of this study was to characterise the putative recombinational event(s at the capsular locus that resulted in the change from a vaccine to a nonvaccine capsular type. Sequencing the capsular locus flanking regions of 51 vaccine escape (progeny, recipient, and putative donor pneumococci revealed a 39 kb recombinational fragment, which included the capsular locus, flanking regions, and two adjacent penicillin-binding proteins, and thus resulted in a capsular switch and penicillin nonsusceptibility in a single genetic event. Since 2003, 37 such vaccine escape strains have been detected, some of which had evolved further. Furthermore, two new types of serotype 19A vaccine escape strains emerged in 2005. To our knowledge, this is the first time a single recombinational event has been documented in vivo that resulted in both a change of serotype and penicillin nonsusceptibility. Vaccine escape by genetic recombination at the capsular locus has the potential to reduce PCV7 effectiveness in the longer term.

  18. Intragenic recombination in the CSR1 locus of Arabidopsis.

    Science.gov (United States)

    Mourad, G; Haughn, G; King, J

    1994-04-01

    Four classes of herbicides are known to inhibit plant acetolactate synthase (ALS). In Arabidopsis, ALS is encoded by a single gene, CSR1. The dominant csr1-1 allele encodes an ALS resistant to chlorsulfuron and triazolopyrimidine sulfonamide while the dominant csr1-2 allele encodes an ALS resistant to imazapyr and pyrimidyl-oxy-benzoate. The molecular distance between the point mutations in csr1-1 and csr1-2 is 1369 bp. Here we used multiherbicide resistance as a stringent selection to measure the intragenic recombination frequency between these two point mutations. We found this frequency to be 0.008 +/- 0.0028. The recombinant multiherbicide-resistant allele, csr1-4, provides an ideal marker for plant genetic transformation. PMID:8177214

  19. Recombination hotspots flank the Cryptococcus mating-type locus: implications for the evolution of a fungal sex chromosome.

    Directory of Open Access Journals (Sweden)

    Yen-Ping Hsueh

    2006-11-01

    Full Text Available Recombination increases dramatically during meiosis to promote genetic exchange and generate recombinant progeny. Interestingly, meiotic recombination is unevenly distributed throughout genomes, and, as a consequence, genetic and physical map distances do not have a simple linear relationship. Recombination hotspots and coldspots have been described in many organisms and often reflect global features of chromosome structure. In particular, recombination frequencies are often distorted within or outside sex-determining regions of the genome. Here, we report that recombination is elevated adjacent to the mating-type locus (MAT in the pathogenic basidiomycete Cryptococcus neoformans. Among fungi, C. neoformans has an unusually large MAT locus, and recombination is suppressed between the two >100-kilobase mating-type specific alleles. When genetic markers were introduced at defined physical distances from MAT, we found the meiotic recombination frequency to be approximately 20% between MAT and a flanking marker at 5, 10, 50, or 100 kilobases from the right border. As a result, the physical/genetic map ratio in the regions adjacent to MAT is distorted approximately 10- to 50-fold compared to the genome-wide average. Moreover, recombination frequently occurred on both sides of MAT and negative interference between crossovers was observed. MAT heterozygosity was not required for enhanced recombination, implying that this process is not due to a physical distortion from the two non-paired alleles and could also occur during same-sex mating. Sequence analysis revealed a correlation between high G + C content and these hotspot regions. We hypothesize that the presence of recombinational activators may have driven several key events during the assembly and reshaping of the MAT locus and may have played similar roles in the origins of both metabolic and biosynthetic gene clusters. Our findings suggest that during meiosis the MAT locus may be exchanged onto

  20. Multiserver switch scheduling for high speed optical switches

    Science.gov (United States)

    Golla, Prasad; Blanton, John; Damm, Gerard

    2003-10-01

    A switch matrix implemented as an optical crossbar using semiconductor optical amplifiers is able to accommodate extreme concentrations of data traffic. Due to the need to reduce optical guard band overhead it is beneficial to switch fixed size bursts of data cells on a time slot basis. The high capacity of the optical matrix supports multiple optical ports per burst card, and the implementation of multiple queue servers per burst card helps make better use of the multiplicity of ports. Problems associated with arbitrating multiple ports and multiple servers per burst card have been resolved by extending the operation of existing iterative, single server scheduling algorithms. The multiserver arbitration time will be in proportion to the number of servers -- corresponding to the channels of DWDM link -- unless a reconciliation stage is used after each iteration when an arbiter per server is used. The reconciliation stage sets the problem of broken data dependencies between server arbitrations in this case. Further, to address the time limitations for computing the scheduling solution, parallel arbiter implementations have been developed and tested against single arbiter designs. Again, the broken dependencies between iterations of an arbitration are addressed through the use of a grant reconciliation stage. The use of multiple queue servers per burst card also resolves some of the data loss problems related to polarized traffic. Simulations of the multiple server and parallel arbiter implementations have demonstrated their efficiency compared to previous implementations. Compounded to this problem is maintaining high throughput of the switch matrix while observing data transit time limits. This involves balancing two contradictory requirements; switch or line card efficiency and data transit times. To improve efficiency it is desirable to transmit only full packets. However, to prevent loss of data due to timeout it will be necessary to transmit some incomplete

  1. Stability and kinetic studies on recombinant pyroglutamyl peptidase I and two mutant forms

    OpenAIRE

    Mtawae, Karima

    2005-01-01

    This thesis investigates the kinetic and stability characteristics of recombinant human brain pyroglutamyl peptidase PAPI, an omega exopeptidase which cleaves pyroglutamic acid from the N-terminus of peptides and proteins. Three classes of pyroglutamyl peptidase have been found in a variety of bacteria, plant, animal, and human tissues; the first class includes the bacterial and animal type 1, pyroglutamyl peptidase I. The genes encoding bacterial PAPI have been cloned and characterized previ...

  2. STOCHASTIC ADAPTIVE SWITCHING CONTROL BASED ON MULTIPLE MODELS

    Institute of Scientific and Technical Information of China (English)

    ZHANGYanxia; GUOLei

    2002-01-01

    It is well known that the transient behaviors of the traditional adaptive control may be very poor in general,and that the adaptive control designed based in switching between multiple models is an intuitively appealing and practically feasible approach to improve the transient performances.In this paper,we shall prove that for a typical class of linear systems disturbed by random noises,the multiple model based least-equares(LS)adaptive switching control is statble and convergent and has the same convergence rate as that established for the standard least-squares-based self-tunning regulators.Moreover,the mixed case combining adative models with fixed models is also considered.

  3. Thermally induced magnetization switching in Gd/Fe multilayers

    Science.gov (United States)

    Xu, C.; Ostler, T. A.; Chantrell, R. W.

    2016-02-01

    A theoretical model of Gd/Fe multilayers is constructed using the atomistic spin dynamics formalism. By varying the thicknesses and number of layers we have shown that a strong dependence of the energy required for thermally induced magnetization switching (TIMS) is present; with a larger number of interfaces, lower energy is required. The results of the layer resolved dynamics show that the reversal process of the multilayered structures, similar to that of a GdFeCo alloy, is driven by the antiferromagnetic interaction between the transition-metal and rare-earth components. Finally, while the presence of the interface drives the reversal process, we show here that the switching process does not initiate at the surface but from the layers furthest from it, a departure from the alloy behavior which expands the classes of material types exhibiting TIMS.

  4. Optimal foraging in marine ecosystem models: selectivity, profitability and switching

    DEFF Research Database (Denmark)

    Visser, Andre W.; Fiksen, Ø.

    2013-01-01

    to the preference functions commonly used in models today. Indeed, depending on prey class resolution, optimal foraging can yield feeding rates that are considerably different from the ‘switching functions’ often applied in marine ecosystem models. Dietary inclusion is dictated by two optimality choices: 1......) the diet breadth and 2) the actual feeding mode. The optimality model does not generate ‘safety in low densities’, as the ‘switching function’ does in ecosystem models, unless predators are shifting feeding mode adaptively. The actual diet, feeding rate and energy flux in ecosystem models can be determined...... by letting predators maximize energy intake or more properly, some measure of fitness where predation risk and cost are also included. An optimal foraging or fitness maximizing approach will give marine ecosystem models a sound principle to determine trophic interactions...

  5. On-Chip Network Design Automation with Source Routing Switches

    Institute of Scientific and Technical Information of China (English)

    MA Liwei; SUN Yihe

    2007-01-01

    Network-on-chip (NoC) is a new design paradigm for system-on-chip intraconnections in the billion-transistor era. Application specific on-chip network design is essential for NoC success in this new era.This paper presents a class of source routing switch that can be used to efficiently form arbitrary network topologies and that can be optimized for various applications. Hardware description language versions of the networks can be generated automatically for simulations and for syntheses. A series of switches and networks has been configured with their performances including latency, delay, area, and power, and analyzed theoretically and experimentally. The results show that this NoC architecture provides a large design space for application specific on-chip network designs.

  6. Contraction analysis of switched systems: the case of Caratheodory Systems and Networks

    OpenAIRE

    Di Bernardo, Mario; Liuzza, Davide; Russo, Giovanni

    2011-01-01

    In this paper we extend to a generic class of piecewise smooth dynamical systems a fundamental tool for the analysis of convergence of smooth dynamical systems: contraction theory. We focus on switched systems satisfying Caratheodory conditions for the existence and unicity of a solution. After generalizing the classical definition of contraction to this class of dynamical systems, we give sufficient conditions for global exponential convergence of their trajectories. The theoretical results ...

  7. Recombinant DNA: History of the Controversy.

    Science.gov (United States)

    Vigue, Charles L.; Stanziale, William G.

    1979-01-01

    The hazards associated with recombinant DNA research are presented along with some social implications and the development of recombinant DNA research guidelines by the National Institutes of Health. (SA)

  8. Recombinant innovation and endogenous technological transitions

    NARCIS (Netherlands)

    K. Frenken; L.R. Izquierdo; P. Zeppini

    2012-01-01

    We propose a model of technological transitions based on two different types of innovations. Branching innovations refer to technological improvements along a particular path, while recombinant innovations represent fusions of multiple paths. Recombinant innovations create "short-cuts" which reduce

  9. Live recombinant BHV/BRSV vaccine

    NARCIS (Netherlands)

    Keil, G.M.; Rijsewijk, F.A.M.

    1998-01-01

    The present invention refers to synthetic Bovine Respiratory Syncytium virus genes. Also the invention relates to live attenuated Bovine Herpesvirus recombinants carrying such synthetic genes. Furthermore, the invention relates to vaccines based on these live attenuated recombinants, for the protect

  10. Leptospirosis serodiagnosis by ELISA based on recombinant outer membrane protein.

    Science.gov (United States)

    Chalayon, Piyanart; Chanket, Phanita; Boonchawalit, Toungporn; Chattanadee, Siriporn; Srimanote, Potjanee; Kalambaheti, Thareerat

    2011-05-01

    The outer membrane protein LipL21, LipL32, LipL41 and Loa22 of Leptospira interrogans serovar Copenhageni were previously revealed by immunoproteomic analysis, using sera from acute phase infection in a guinea pig. The full-length DNA of each protein was then cloned from the same serovar and expressed in pRSET vector. The obtained molecular weight (MW) of recombinant proteins rLipL21, rLipL32 and rLoa22 were slightly higher than the MW predicted from nucleotide sequences of each inserted gene, while only the N-terminal half of rLipL41 was obtained. Mice antiserum raised against each purified recombinant protein could react with the whole cell lysate of leptospiral serovars, implying that leptospiral native proteins shared a common epitope with recombinant protein. Serodiagnosis using recombinant protein antigen based on indirect ELISA procedure was developed in this study. The optimization of the ELISA components lead to determination of optical density (OD) from a single serum-dilution of 1:1000 in the leptospirosis patients group and normal healthy control group. The cut off OD values for both IgG and IgM class were investigated, and based on this fixed dilution only the IgG class could be used for differential diagnosis of patients and normal individuals. Compared with the MAT assay, ELISA assay utilizing both rLipL32 and rLoa22 as antigen, gave high accuracy and could thus be useful as a confirmative serology test. PMID:21353274

  11. Theoretical and experimental study of fundamental differences in the noise suppression of high-speed SOA-based all-optical switches

    DEFF Research Database (Denmark)

    Nielsen, Mads Lønstrup; Mørk, Jesper; Suzuki, R.;

    2005-01-01

    We identify a fundamental difference between the ASE noise filtering properties of different all-optical SOA-based switch configurations, and divide the switches into two classes. An in-band ASE suppression ratio quantifying the difference is derived theoretically and the impact of the ASE...

  12. A Virtual Class Calculus

    DEFF Research Database (Denmark)

    Ernst, Erik; Ostermann, Klaus; Cook, William Randall

    2006-01-01

    , statically typed model for virtual classes has been a long-standing open question. This paper presents a virtual class calculus, vc, that captures the essence of virtual classes in these full-fledged programming languages. The key contributions of the paper are a formalization of the dynamic and static...

  13. Effect of gamma radiation on retroviral recombination.

    OpenAIRE

    Hu, W S; Temin, H M

    1992-01-01

    To elucidate the mechanism(s) of retroviral recombination, we exposed virions to gamma radiation prior to infecting target cells. By using previously described spleen necrosis virus-based vectors containing multiple markers, recombinant proviruses were studied after a single round of retrovirus replication. The current models of retroviral recombination predict that breaking virion RNA should promote minus-strand recombination (forced copy-choice model), decrease or not affect plus-strand rec...

  14. Semiconductor Switching Devices. .Future Trends

    Directory of Open Access Journals (Sweden)

    S. Ahmad

    1998-01-01

    Full Text Available A variety of semiconductor devices and circuits have been successfully developed usingconduction properties of electrons and holes in a number of elemental and compound semiconductors.Carriers confinement in a potential well, formed out of a thin layer of lower band gap materialsandwitched between two layers of a higher band gap material, has been extended from one to two andthree dimensions. Resultant of two-dimensional carrier sheet, quantum wire and quantum dot havingdiscrete energy levels arising out of quantisation are being presently explored for possible device applications. A number of devices have been fabricated using resonant tunneling across a thin potentialbarrier. This has opened up several newer possibilities of using such structures for various electronicand optoelectronic devices and circuits applications as tunneling is relatively faster than conductionprocess. While looking into the interband tunneling between two quantum dots, possibility of a singleelectron switching has also been examined carefully. The idea of a single electron switching isconceptually being extended from quantl,lm dots to molecules and atoms ultimately. Simulations basedon transmission of electrons through a chain of molecules and atoms have shown that tens of THz speed and functional device density 1012 devices/mm2 are possible with such schemes. Devices basedon atom relay transistor (ART will be ultimate in its performance of switching speed. A brief onpresent-day situation followed by future proposals of fast switching devices for informationelectronics has been discussed.

  15. Intrinsic nanofilamentation in resistive switching

    KAUST Repository

    Wu, Xing

    2013-03-15

    Resistive switching materials are promising candidates for nonvolatile data storage and reconfiguration of electronic applications. Intensive studies have been carried out on sandwiched metal-insulator-metal structures to achieve high density on-chip circuitry and non-volatile memory storage. Here, we provide insight into the mechanisms that govern highly reproducible controlled resistive switching via a nanofilament by using an asymmetric metal-insulator-semiconductor structure. In-situ transmission electron microscopy is used to study in real-time the physical structure and analyze the chemical composition of the nanofilament dynamically during resistive switching. Electrical stressing using an external voltage was applied by a tungsten tip to the nanosized devices having hafnium oxide (HfO2) as the insulator layer. The formation and rupture of the nanofilaments result in up to three orders of magnitude change in the current flowing through the dielectric during the switching event. Oxygen vacancies and metal atoms from the anode constitute the chemistry of the nanofilament.

  16. Robust Stability of Switched Systems

    DEFF Research Database (Denmark)

    Sloth, Christoffer; Wisniewski, Rafael

    This paper presents a linear programming-based method for finding Lyapunov functions of switched systems with polynomial vector fields and parametric uncertainties. We propose to utilize a certificate of positivity in the Bernstein basis to find a Lyapunov function. A certificate of positivity in...

  17. Wide Bandgap Extrinsic Photoconductive Switches

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, James S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-07-03

    Semi-insulating Gallium Nitride, 4H and 6H Silicon Carbide are attractive materials for compact, high voltage, extrinsic, photoconductive switches due to their wide bandgap, high dark resistance, high critical electric field strength and high electron saturation velocity. These wide bandgap semiconductors are made semi-insulating by the addition of vanadium (4H and 6HSiC) and iron (2H-GaN) impurities that form deep acceptors. These deep acceptors trap electrons donated from shallow donor impurities. The electrons can be optically excited from these deep acceptor levels into the conduction band to transition the wide bandgap semiconductor materials from a semi-insulating to a conducting state. Extrinsic photoconductive switches with opposing electrodes have been constructed using vanadium compensated 6H-SiC and iron compensated 2H-GaN. These extrinsic photoconductive switches were tested at high voltage and high power to determine if they could be successfully used as the closing switch in compact medical accelerators.

  18. Switching Costs in Accounting Services

    Directory of Open Access Journals (Sweden)

    Fatih Koç

    2015-06-01

    Full Text Available Switching cost is defined as possible costs that customers may encounter when they want to change the firm they buy service, and an important subject in terms of accounting services. Particularly, small business entrepreneurs’ not having knowledge about accounting procedures, and sharing private information with accounting firms make switching costs more important for accounting services. Thus, the aim of this study is to investigate the concept of switching costs (relational cost, procedural cost and financial cost, its determinants (perceived service quality, service importance, and service failures, and consequences (re-purchasing, and recommen ding to others. Theresearch was conducted on small business entrepreneurs in down-town of Balıkesir in Turkey. Total 405 small business entrepreneur owners were interviewed. According to results of the study, perceived service quality positively affects all dimensions of switching costs, significance of service positively affects procedural and relational costs, and service failures negatively affect procedural and relational costs. The results showed that while procedural and relational costs positively affect re-purchasing and recommending to others variables, financial cost did not have any effect on these variables.

  19. Industry Switching in Developing Countries

    DEFF Research Database (Denmark)

    Newman, Carol; Rand, John; Tarp, Finn

    as compared to entry and exit firms. They tend, inter alia, to be labour-intensive and seek out competitive opportunities in labour-intensive sectors in response to changes in the market environment. We also show that resource reallocations resulting from switching form an important component of...

  20. Multiuser switched diversity scheduling schemes

    KAUST Repository

    Shaqfeh, Mohammad

    2012-09-01

    Multiuser switched-diversity scheduling schemes were recently proposed in order to overcome the heavy feedback requirements of conventional opportunistic scheduling schemes by applying a threshold-based, distributed, and ordered scheduling mechanism. The main idea behind these schemes is that slight reduction in the prospected multiuser diversity gains is an acceptable trade-off for great savings in terms of required channel-state-information feedback messages. In this work, we characterize the achievable rate region of multiuser switched diversity systems and compare it with the rate region of full feedback multiuser diversity systems. We propose also a novel proportional fair multiuser switched-based scheduling scheme and we demonstrate that it can be optimized using a practical and distributed method to obtain the feedback thresholds. We finally demonstrate by numerical examples that switched-diversity scheduling schemes operate within 0.3 bits/sec/Hz from the ultimate network capacity of full feedback systems in Rayleigh fading conditions. © 2012 IEEE.

  1. Optimal switching using coherent control

    DEFF Research Database (Denmark)

    Kristensen, Philip Trøst; Heuck, Mikkel; Mørk, Jesper

    2013-01-01

    We introduce a general framework for the analysis of coherent control in coupled optical cavity-waveguide systems. Within this framework, we use an analytically solvable model, which is validated by independent numerical calculations, to investigate switching in a micro cavity and demonstrate that...

  2. Coherent switching of semiconductor resonator solitons

    OpenAIRE

    Taranenko, V. B.; Ahlers, F. -J.; Pierz, K.

    2002-01-01

    We demonstrate switching on and off of spatial solitons in a semiconductor microresonator by injection of light coherent with the background illumination. Evidence results that the formation of the solitons and their switching does not involve thermal processes.

  3. Ultrafast Beam Switching Using Coupled VCSELs

    Science.gov (United States)

    Ning, Cun-Zheng; Goorjian, Peter

    2001-01-01

    We propose a new approach to performing ultrafast beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The strategy is demonstrated by numerical simulation, showing a beam switching of 10 deg at 42 GHz.

  4. A Demonstration of Automatically Switched Optical Network

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    We build an automatically switched optical network (ASON) testbed with four optical cross-connect nodes. Many fundamental ASON features are demonstrated, which is implemented by control protocols based on generalized multi-protocol label switching (GMPLS) framework.

  5. Digital Switching in the Quantum Domain

    CERN Document Server

    Tsai, I M

    2002-01-01

    In this paper, we present an architecture and implementation algorithm such that digital data can be switched in the quantum domain. First we define the connection digraph which can be used to describe the behavior of a switch at a given time, then we show how a connection digraph can be implemented using elementary quantum gates. The proposed mechanism supports unicasting as well as multicasting, and is strict-sense non-blocking. It can be applied to perform either circuit switching or packet switching. Compared with a traditional space or time domain switch, the proposed switching mechanism is more scalable. Assuming an n-by-n quantum switch, the space consumption grows linearly, i.e. O(n), while the time complexity is O(1) for unicasting, and O(log n) for multicasting. Based on these advantages, a high throughput switching device can be built simply by increasing the number of I/O ports.

  6. The Cosmology Large Angular Scale Surveyor (CLASS)

    Science.gov (United States)

    Harrington, Kathleen; Marriange, Tobias; Aamir, Ali; Appel, John W.; Bennett, Charles L.; Boone, Fletcher; Brewer, Michael; Chan, Manwei; Chuss, David T.; Colazo, Felipe; Denis, Kevin; Moseley, Samuel H.; Rostem, Karwan; Wollack, Edward

    2016-01-01

    The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from in ation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, r, down to a level of 0.01 (95% C.L.).

  7. [Recombination in Drosophila in space flight].

    Science.gov (United States)

    Filatova, L P; Vaulina, E N; Lapteva, N Sh; Grozdova, T Ia

    1988-04-01

    An experiment with Drosophila melanogaster males was performed aboard the Artificial Satellite "Kosmos-1667". Mutagenic effects of a 7-day space flight on intergene recombination in chromosome 2 were studied. The space flight factors decreased the frequency of recombination. A model experiment on a laboratory centrifuge demonstrated insignificant increase in recombination frequency caused by acceleration. PMID:3135244

  8. Direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp

    DEFF Research Database (Denmark)

    Ljusev, Petar; Andersen, Michael Andreas E.

    2005-01-01

    This paper discusses the advantages and problems when implementing direct energy conversion switching-mode audio power amplifiers. It is shown that the total integration of the power supply and Class D audio power amplifier into one compact direct converter can simplify the design, increase effic...... efficiency, reduce the product volume and lower its cost. As an example, the principle of operation and the measurements made on a direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp are presented.......This paper discusses the advantages and problems when implementing direct energy conversion switching-mode audio power amplifiers. It is shown that the total integration of the power supply and Class D audio power amplifier into one compact direct converter can simplify the design, increase...

  9. Adaptive Output-Feedback Neural Control of Switched Uncertain Nonlinear Systems With Average Dwell Time.

    Science.gov (United States)

    Long, Lijun; Zhao, Jun

    2015-07-01

    This paper investigates the problem of adaptive neural tracking control via output-feedback for a class of switched uncertain nonlinear systems without the measurements of the system states. The unknown control signals are approximated directly by neural networks. A novel adaptive neural control technique for the problem studied is set up by exploiting the average dwell time method and backstepping. A switched filter and different update laws are designed to reduce the conservativeness caused by adoption of a common observer and a common update law for all subsystems. The proposed controllers of subsystems guarantee that all closed-loop signals remain bounded under a class of switching signals with average dwell time, while the output tracking error converges to a small neighborhood of the origin. As an application of the proposed design method, adaptive output feedback neural tracking controllers for a mass-spring-damper system are constructed. PMID:25122844

  10. AN EFFECTIVE MODEL TO EVALUATE BLOCKING PROBABILITY OF TIME-SLOTTED OPTICAL BURST SWITCHED NETWORKS

    Institute of Scientific and Technical Information of China (English)

    Yang Zongkai; Ou Liang; Tan Xiansi

    2006-01-01

    Time-slotted optical burst switched network is a potential technique to support IP over Wavelength Division Multiplexing (WDM) by introduce Time Division Multiplexing (TDM) channel to Optical Burst Switching (OBS) technology. This paper presents a framework to evaluate blocking performance of time-slotted OBS networks with multi-fiber wavelength channels. The proposed model is efficient for not only single class traffic such as individual circuit switch traffics or best-effort traffics but also mixed multi-class traffics.The effectiveness of the proposed model is validated by simulation results. The study shows that blocking performance of multi-fiber TS-OBS network is acceptable for future Internet services.

  11. Extended ℋ∞ Estimation for Two-Dimensional Markov Jump Systems under Asynchronous Switching

    Directory of Open Access Journals (Sweden)

    Rui Zhang

    2013-01-01

    Full Text Available This paper is concerned with the problem of designing ℋ∞ filters for a class of two-dimensional (2D Markov jump systems under asynchronous switching. The problem under consideration is primarily motivated by a realistic situation that the switching of candidate filters may have a lag to the switching of system modes. Different from conventional techniques, by a suitable augmentation, the jumping process of the error system is represented by a two-component Markov chain. Then, the extended transition probabilities are provided for the error system. A stochastic Lyapunov function approach is proposed for the design of desired filters that ensure a prescribed ℋ∞ performance for admissible asynchronous switching. Finally, a numerical example is given to illustrate the effectiveness of the developed method.

  12. Spark gap switch with spiral gas flow

    Science.gov (United States)

    Brucker, John P.

    1989-01-01

    A spark gap switch having a contaminate removal system using an injected gas. An annular plate concentric with an electrode of the switch defines flow paths for the injected gas which form a strong spiral flow of the gas in the housing which is effective to remove contaminates from the switch surfaces. The gas along with the contaminates is exhausted from the housing through one of the ends of the switch.

  13. Pinning Synchronization of Switched Complex Dynamical Networks

    OpenAIRE

    Liming Du; Feng Qiao; Fengying Wang

    2015-01-01

    Network topology and node dynamics play a key role in forming synchronization of complex networks. Unfortunately there is no effective synchronization criterion for pinning synchronization of complex dynamical networks with switching topology. In this paper, pinning synchronization of complex dynamical networks with switching topology is studied. Two basic problems are considered: one is pinning synchronization of switched complex networks under arbitrary switching; the other is pinning synch...

  14. Analysis of chickens for recombination within the MHC (B-complex)

    DEFF Research Database (Denmark)

    Skjødt, K; Koch, C; Crone, M

    1985-01-01

    -haplotypes (B21r and B15r) were found by analysing 2,656 F2 chickens representing 5,312 informative typings. In either case, the B-G (class IV) allele was recombined with both the B-F and B-L alleles of the opposite haplotype. MLC typings, tests for direct compatibility by GVH reactions, and absorption analyses...

  15. Robust Hinf control of uncertain switched systems defined on polyhedral sets with Filippov solutions

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal

    2012-01-01

    This paper considers the control problem of a class of uncertain switched systems defined on polyhedral sets known as piecewise linear systems where, instead of the conventional Carathe ́odory solutions, Filippov solutions are studied. In other words, in contrast to the previous studies, solutions...

  16. Soft-switching Grid-connected PV Inverter With Interleaved Flyback Topology

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The flyback topology has advantages of robustness and low cost and is proposed for 200-300 W class grid-connected photovoltaic inverter. However, the flyback converter is known for its low efficiency and low resolution control. Therefore, digitalized soft switching technique and algorithm are to be developed.

  17. Investigation of the genes involved in antigenic switching at the vlsE locus in Borrelia burgdorferi: an essential role for the RuvAB branch migrase.

    Directory of Open Access Journals (Sweden)

    Ashley R Dresser

    2009-12-01

    Full Text Available Persistent infection by pathogenic organisms requires effective strategies for the defense of these organisms against the host immune response. A common strategy employed by many pathogens to escape immune recognition and clearance is to continually vary surface epitopes through recombinational shuffling of genetic information. Borrelia burgdorferi, a causative agent of Lyme borreliosis, encodes a surface-bound lipoprotein, VlsE. This protein is encoded by the vlsE locus carried at the right end of the linear plasmid lp28-1. Adjacent to the expression locus are 15 silent cassettes carrying information that is moved into the vlsE locus through segmental gene conversion events. The protein players and molecular mechanism of recombinational switching at vlsE have not been characterized. In this study, we analyzed the effect of the independent disruption of 17 genes that encode factors involved in DNA recombination, repair or replication on recombinational switching at the vlsE locus during murine infection. In Neisseria gonorrhoeae, 10 such genes have been implicated in recombinational switching at the pilE locus. Eight of these genes, including recA, are either absent from B. burgdorferi, or do not show an obvious requirement for switching at vlsE. The only genes that are required in both organisms are ruvA and ruvB, which encode subunits of a Holliday junction branch migrase. Disruption of these genes results in a dramatic decrease in vlsE recombination with a phenotype similar to that observed for lp28-1 or vls-minus spirochetes: productive infection at week 1 with clearance by day 21. In SCID mice, the persistence defect observed with ruvA and ruvB mutants was fully rescued as previously observed for vlsE-deficient B. burgdorferi. We report the requirement of the RuvAB branch migrase in recombinational switching at vlsE, the first essential factor to be identified in this process. These findings are supported by the independent work of Lin et

  18. Degree of Conversational Code-Switching Enhances Verbal Task Switching in Cantonese-English Bilinguals

    Science.gov (United States)

    Yim, Odilia; Bialystok, Ellen

    2012-01-01

    The study examined individual differences in code-switching to determine the relationship between code-switching frequency and performance in verbal and non-verbal task switching. Seventy-eight Cantonese-English bilinguals completed a semi-structured conversation to quantify natural code-switching, a verbal fluency task requiring language…

  19. A gain-coefficient switched Alexandrite laser

    OpenAIRE

    Lee, Chris J.; van der Slot, Peter J. M.; Boller, Klaus-J.

    2012-01-01

    We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ at a repetition rate of 5 Hz.

  20. A gain-coefficient switched Alexandrite laser

    NARCIS (Netherlands)

    Lee, C. J.; van der Slot, P. J. M.; Boller, K. J.

    2013-01-01

    We report on a gain-coefficient switched Alexandrite laser. An electro-optic modulator is used to switch between high and low gain states by making use of the polarization dependent gain of Alexandrite. In gain-coefficient switched mode, the laser produces 85 ns pulses with a pulse energy of 240 mJ

  1. The increased importance of sector switching

    DEFF Research Database (Denmark)

    Frederiksen, Anders; Hansen, Jesper Rosenberg

    2014-01-01

    Sector switching is an important phenomenon that casts light on public–private differences. Yet our knowledge about its prevalence and trends is limited. We study sector switching using unique Danish register-based employer–employee data covering more than 25 years. We find that sector switching...

  2. A Bilingual Advantage in Task Switching

    Science.gov (United States)

    Prior, Anat; MacWhinney, Brian

    2010-01-01

    This study investigated the possibility that lifelong bilingualism may lead to enhanced efficiency in the ability to shift between mental sets. We compared the performance of monolingual and fluent bilingual college students in a task-switching paradigm. Bilinguals incurred reduced switching costs in the task-switching paradigm when compared with…

  3. Switch for serial or parallel communication networks

    Science.gov (United States)

    Crosette, D.B.

    1994-07-19

    A communication switch apparatus and a method for use in a geographically extensive serial, parallel or hybrid communication network linking a multi-processor or parallel processing system has a very low software processing overhead in order to accommodate random burst of high density data. Associated with each processor is a communication switch. A data source and a data destination, a sensor suite or robot for example, may also be associated with a switch. The configuration of the switches in the network are coordinated through a master processor node and depends on the operational phase of the multi-processor network: data acquisition, data processing, and data exchange. The master processor node passes information on the state to be assumed by each switch to the processor node associated with the switch. The processor node then operates a series of multi-state switches internal to each communication switch. The communication switch does not parse and interpret communication protocol and message routing information. During a data acquisition phase, the communication switch couples sensors producing data to the processor node associated with the switch, to a downlink destination on the communications network, or to both. It also may couple an uplink data source to its processor node. During the data exchange phase, the switch couples its processor node or an uplink data source to a downlink destination (which may include a processor node or a robot), or couples an uplink source to its processor node and its processor node to a downlink destination. 9 figs.

  4. Mechanism of single atom switch on silicon

    DEFF Research Database (Denmark)

    Quaade, Ulrich; Stokbro, Kurt; Thirstrup, C.;

    1998-01-01

    We demonstrate single atom switch on silicon which operates by displacement of a hydrogen atom on the silicon (100) surface at room temperature. We find two principal effects by which the switch is controlled: a pronounced maximum of the switching probability as function of sample bias and a...

  5. Bootstrapped Low-Voltage Analog Switches

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1999-01-01

    Novel low-voltage constant-impedance analog switch circuits are proposed. The switch element is a single MOSFET, and constant-impedance operation is obtained using simple circuits to adjust the gate and bulk voltages relative to the switched signal. Low-voltage (1-volt) operation is made feasible...

  6. Inclusive particle spectra in the quark recombination model

    International Nuclear Information System (INIS)

    The present status of the simple and valon versions of the quark recombination model is reviewed. The model has previously been applied primarily to hadron-hadron collisions in which the fragmenting and produced particles share a single common valence quark. The application of the model is extended to two additional classes of hadron-hadron collisions. (1) Collisions in which no valence quarks are common to the fragmenting and produced particles. (2) Collisions in which all valence quarks of the fragmenting particle are also valence quarks of the produced particle

  7. Selection of Recombinant Human Antibodies.

    Science.gov (United States)

    Tomszak, Florian; Weber, Susanne; Zantow, Jonas; Schirrmann, Thomas; Hust, Michael; Frenzel, André

    2016-01-01

    Since the development of therapeutic antibodies the demand of recombinant human antibodies is steadily increasing. Traditionally, therapeutic antibodies were generated by immunization of rat or mice, the generation of hybridoma clones, cloning of the antibody genes and subsequent humanization and engineering of the lead candidates. In the last few years, techniques were developed that use transgenic animals with a human antibody gene repertoire. Here, modern recombinant DNA technologies can be combined with well established immunization and hybridoma technologies to generate already affinity maturated human antibodies. An alternative are in vitro technologies which enabled the generation of fully human antibodies from antibody gene libraries that even exceed the human antibody repertoire. Specific antibodies can be isolated from these libraries in a very short time and therefore reduce the development time of an antibody drug at a very early stage.In this review, we describe different technologies that are currently used for the in vitro and in vivo generation of human antibodies. PMID:27236551

  8. Mechanisms of sister chromatid recombination

    International Nuclear Information System (INIS)

    Studies using T948 as a model system have been carried out aimed at elucidating the mechanism of sister chromatid recombination (SCR). Characterization of U.V. light- and x-ray-induced SCR, the relationiship between SCR induction and DNA repair using rad mutations, and the relationship between SCR induction and the time of cell division using cdc mutations are presented. It has been supposed that SCR is induced at the phase of S-G2 following DNA replication, that postreplication break of DNA strands is strongly involved in the induction of SCR, and that induction type of SCR, i.e., conversion type or recombination type, is dependent upon the type of molecular damage of DNA. (Namekawa, K.)

  9. Competitive Buffer Management with Class Segregation

    CERN Document Server

    Al-Bawani, Kamal

    2011-01-01

    We introduce a new model for buffer management of network switches with Quality of Service (QoS) requirements and give a tight analysis. Specifically, each network packet is associated with a numerical value, called Class of Service (CoS), which represents its priority. We are furthermore given a network switch with $m$ queues that have individual capacities. Each queue stores packets of a certain CoS, only. A stream of packets arrives over time at the switch and an online algorithm has to decide on the admission and transmission of packets. The objective is to maximize the total CoS-value of the transmitted packets. Our main contribution is a natural online $\\GREEDY$ algorithm, which accepts any arriving packet, if the corresponding CoS-queue is not full. It always sends a buffered packet with highest value. We show that this algorithm is 2-competitive. This result is essentially best-possible since we also show a lower bound of $2 - v_m / (\\sum_{i=1}^m v_i)$ on the competitiveness of any deterministic onlin...

  10. Recombinations of Busy Beaver Machines

    OpenAIRE

    Bátfai, Norbert

    2009-01-01

    Many programmers belive that Turing-based machines cannot think. We also believe in this, however it is interesting to note that the most sophisticated machines are not programmed by human beings. We have only discovered them. In this paper, using well-known Busy Beaver and Placid Platypus machines, we generate further very similar, but not exactly the same machines. We have found a recombinated BB_5 machine which can make 70.740.809 steps before halting.

  11. Recombinant erythropoietin in clinical practice

    OpenAIRE

    Ng, T; Marx, G.; Littlewood, T; Macdougall, I

    2003-01-01

    The introduction of recombinant human erythropoietin (RHuEPO) has revolutionised the treatment of patients with anaemia of chronic renal disease. Clinical studies have demonstrated that RHuEPO is also useful in various non-uraemic conditions including haematological and oncological disorders, prematurity, HIV infection, and perioperative therapies. Besides highlighting both the historical and functional aspects of RHuEPO, this review discusses the applications of RHuEPO in clinical practice a...

  12. Recombinant antibodies and tumor targeting

    OpenAIRE

    Sheikholvaezin, Ali

    2006-01-01

    Different antibody derived constructs are rapidly advancing as putative tools for treatment of malignant diseases. Antibody engineering has added significant new technologies to modify size, affinities, solubility, stability and biodistribution properties for immunoconjugates. In the present thesis, the aim was to increase our knowledge on how new recombinant antibodies could be tailored to optimize localization to experimental tumors in mice. One hybridoma, producing the monoclonal antibody ...

  13. Workshop on Radio Recombination Lines

    CERN Document Server

    1980-01-01

    Since their first detection 15 years ago, radio recombination lines from several elements have been observed in a wide variety of objects including HII regions, planetary nebulae, molecular clouds, the diffuse interstellar medium, and recently, other galaxies. The observations span almost the entire range from 0.1 to 100 GHz, and employ both single­ djsh and aperture synthesis techniques. The theory of radio recombination lines has also advanced strongly, to the point where it is perhaps one of the best-understood in astro­ physics. In a parallel development, it has become possible over the last decade to study these same highly-excited atoms in the laboratory; this work provides further confirmation of the theoretical framework. However there has been continuing controversy over the astrophysical interpre­ tation of radio recombination line observations, especially regarding the role of stimulated emission. A workshop was held in Ottawa on 24-25 August, 1979, bringing together many of the active scientist...

  14. Qualitative aspects on closed loop power switching systems control

    Directory of Open Access Journals (Sweden)

    Dan Olaru

    2009-10-01

    Full Text Available The switching circuit control problem contains various aspects concerning the closed loop operation, the harmonically perturbation generation, the transient regime duration, the dynamic or stationary regime stability, the filtering devices costs, etc. The presented paper presents a class of control methods, based on some mathematical concepts that revel certain important advantages. In this approach there are analyzed only the aspects concerning the theoretical principles that are used and the behavior of certain types of model implementations. The numerical simulations certify the validity of the methods and enable the analysis of the functional operation. These are very useful for the future developments having a concrete and practical character.

  15. Homologous recombination deficiency and ovarian cancer.

    Science.gov (United States)

    Ledermann, Jonathan A; Drew, Yvette; Kristeleit, Rebecca S

    2016-06-01

    The discovery that PARP inhibitors block an essential pathway of DNA repair in cells harbouring a BRCA mutation has opened up a new therapeutic avenue for high-grade ovarian cancers. BRCA1 and BRCA2 proteins are essential for high-fidelity repair of double-strand breaks of DNA through the homologous recombination repair (HRR) pathway. Deficiency in HRR (HRD) is a target for PARP inhibitors. The first PARP inhibitor, olaparib, has now been licensed for BRCA-mutated ovarian cancers. While mutated BRCA genes are individually most commonly associated with HRD other essential HRR proteins may be mutated or functionally deficient potentially widening the therapeutic opportunities for PARP inhibitors. HRD is the first phenotypically defined predictive marker for therapy with PARP inhibitors in ovarian cancer. Several different PARP inhibitors are being trialled in ovarian cancer and this class of drugs has been shown to be a new selective therapy for high-grade ovarian cancer. Around 20% of high-grade serous ovarian cancers harbour germline or somatic BRCA mutations and testing for BRCA mutations should be incorporated into routine clinical practice. The expanded use of PARP inhibitors in HRD deficient (non-BRCA mutant) tumours using a signature of HRD in clinical practice requires validation. PMID:27065456

  16. On the stabilization of switched linear stochastic systems with unobservable switching laws

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    This paper is concerned with the stabilization problem of switched linear stochastic systems with unobservable switching laws. In this paper the system switches among a finite family of linear stochastic systems. Since there are noise perturbations, the switching laws can not be identified in any finite time horizon. We prove that if each individual subsystem is controllable and the switching duration uniformly has a strict positive lower bound, then the system can be stabilized by using a controller that uses online state estimation.

  17. Uricase production by a recombinant Hansenula polymorpha strain harboring Candida utilis uricase gene.

    Science.gov (United States)

    Chen, Zhiyu; Wang, Zhaoyue; He, Xiuping; Guo, Xuena; Li, Weiwei; Zhang, Borun

    2008-06-01

    Uricase is an important medical enzyme which can be used to determine urate in clinical analysis, to therapy gout, hyperuricemia, and tumor lysis syndrome. Uricase of Candida utilis was successfully expressed in Hansenula polymorpha under the control of methanol oxidase promoter using Saccharomyces cerevisiae alpha-factor signal peptide as the secretory sequence. Recombinant H. polymorpha MU200 with the highest extracellular uricase production was characterized with three copies of expression cassette and selected for process optimization for the production of recombinant enzyme. Among the parameters investigated in shaking flask cultures, the pH value of medium and inoculum size had great influence on the recombinant uricase production. The maximum extracellular uricase yield of 2.6 U/ml was obtained in shaking flask culture. The yield of recombinant uricase was significantly improved by the combined use of a high cell-density cultivation technique and a pH control strategy of switching culture pH from 5.5 to 6.5 in the induction phase. After induction for 58 h, the production of recombinant uricase reached 52.3 U/ml (about 2.1 g/l of protein) extracellularly and 60.3 U/ml (about 2.4 g/l) intracellularly in fed-batch fermentation, which are much higher than those expressed in other expression systems. To our knowledge, this is the first report about the heterologous expression of uricase in H. polymorpha. PMID:18437374

  18. Ultrafast all-optical switching in bacteriorhodopsin

    Science.gov (United States)

    Roy, Sukhdev; Singh, C. P.; Reddy, K. P. J.

    2001-04-01

    All-optical switching has been demonstrated in bacteriorhodopsin based on excited-state nonlinear absorption. A probe laser beam at 640 nm corresponding to the O-state absorption maximum is switched due to a strong pulsed pump laser beam at 570 nm, that corresponds to the maximum ground state absorption. We have studied the effect of variation in pulse width and in small signal absorption coefficient on the switching characteristics. The switching time decreases as the pulse width of the pump beam decreases and the small signal absorption coefficient increases. The switching contrast depends mainly on the peak pumping intensity.

  19. Secure videoconferencing equipment switching system and method

    Science.gov (United States)

    Hansen, Michael E.

    2009-01-13

    A switching system and method are provided to facilitate use of videoconference facilities over a plurality of security levels. The system includes a switch coupled to a plurality of codecs and communication networks. Audio/Visual peripheral components are connected to the switch. The switch couples control and data signals between the Audio/Visual peripheral components and one but nor both of the plurality of codecs. The switch additionally couples communication networks of the appropriate security level to each of the codecs. In this manner, a videoconferencing facility is provided for use on both secure and non-secure networks.

  20. Switched control of a nonholonomic mobile robot

    Science.gov (United States)

    Sankaranarayanan, V.; Mahindrakar, Arun D.

    2009-05-01

    We present a switched control algorithm to stabilize a car-like mobile robot which possesses velocity level nonholonomic constraint. The control approach rests on splitting the system into several second-order subsystems and then stabilizing the system sequentially using finite-time controllers, finally resulting in the mobile robot being moved from one point to another point. State dependent switching control is employed in which the controllers switches on a thin surface in the state-space. Robustness analysis is presented by redefining the switching signal using relaxed switching surface. Both, non-robust and robust controllers are validated through numerical simulation.

  1. Semantic Analysis of Virtual Classes and Nested Classes

    DEFF Research Database (Denmark)

    Madsen, Ole Lehrmann

    1999-01-01

    Virtual classes and nested classes are distinguishing features of BETA. Nested classes originated from Simula, but until recently they have not been part of main stream object- oriented languages. C++ has a restricted form of nested classes and they were included in Java 1.1. Virtual classes is the...... classes and parameterized classes have been made. Although virtual classes and nested classes have been used in BETA for more than a decade, their implementation has not been published. The purpose of this paper is to contribute to the understanding of virtual classes and nested classes by presenting the...

  2. Class network routing

    Science.gov (United States)

    Bhanot, Gyan; Blumrich, Matthias A.; Chen, Dong; Coteus, Paul W.; Gara, Alan G.; Giampapa, Mark E.; Heidelberger, Philip; Steinmacher-Burow, Burkhard D.; Takken, Todd E.; Vranas, Pavlos M.

    2009-09-08

    Class network routing is implemented in a network such as a computer network comprising a plurality of parallel compute processors at nodes thereof. Class network routing allows a compute processor to broadcast a message to a range (one or more) of other compute processors in the computer network, such as processors in a column or a row. Normally this type of operation requires a separate message to be sent to each processor. With class network routing pursuant to the invention, a single message is sufficient, which generally reduces the total number of messages in the network as well as the latency to do a broadcast. Class network routing is also applied to dense matrix inversion algorithms on distributed memory parallel supercomputers with hardware class function (multicast) capability. This is achieved by exploiting the fact that the communication patterns of dense matrix inversion can be served by hardware class functions, which results in faster execution times.

  3. Negation switching invariant signed graphs

    Directory of Open Access Journals (Sweden)

    Deepa Sinha

    2014-04-01

    Full Text Available A signed graph (or, $sigraph$ in short is a graph G in which each edge x carries a value $\\sigma(x \\in \\{-, +\\}$ called its sign. Given a sigraph S, the negation $\\eta(S$ of the sigraph S is a sigraph obtained from S by reversing the sign of every edge of S. Two sigraphs $S_{1}$ and $S_{2}$ on the same underlying graph are switching equivalent if it is possible to assign signs `+' (`plus' or `-' (`minus' to vertices of $S_{1}$ such that by reversing the sign of each of its edges that has received opposite signs at its ends, one obtains $S_{2}$. In this paper, we characterize sigraphs which are negation switching invariant and also see for what sigraphs, S and $\\eta (S$ are signed isomorphic.

  4. Frascati Tokamak transformer switching system

    International Nuclear Information System (INIS)

    Plasma ionization and heating, in the Frascati Tokamak, is obtained generating an emf along the plasma column, by switching the dc current flowing in the Tokamak transformer. 30 kA flowing in the 60 mH transformer inductance must be commutated into a resistance to generate 40 kV across the transformer itself. Studies and tests to solve this problem have been conducted, on different types of breakers, in cooperation between Tecnomasio Italiano Brown Boveri, Milan and Laboratori Gas Ionizzati, Frascati. Satisfactory results have finally been obtained using a DLF commercial air blast breaker in a chopper type circuit. A capacitor bank in parallel to the breaker is discharged immediately after the contacts separation and the arc in the switching element is extinguished at the first current zero. A saturable reactance in series with the breaker reduces the current decay rate to allow sufficient deionization time

  5. Shape memory thermal conduction switch

    Science.gov (United States)

    Vaidyanathan, Rajan (Inventor); Krishnan, Vinu (Inventor); Notardonato, William U. (Inventor)

    2010-01-01

    A thermal conduction switch includes a thermally-conductive first member having a first thermal contacting structure for securing the first member as a stationary member to a thermally regulated body or a body requiring thermal regulation. A movable thermally-conductive second member has a second thermal contacting surface. A thermally conductive coupler is interposed between the first member and the second member for thermally coupling the first member to the second member. At least one control spring is coupled between the first member and the second member. The control spring includes a NiTiFe comprising shape memory (SM) material that provides a phase change temperature <273 K, a transformation range <40 K, and a hysteresis of <10 K. A bias spring is between the first member and the second member. At the phase change the switch provides a distance change (displacement) between first and second member by at least 1 mm, such as 2 to 4 mm.

  6. Feline coronavirus type II strains 79-1683 and 79-1146 originate from a double recombination between feline coronavirus type I and canine coronavirus

    NARCIS (Netherlands)

    Horzinek, M.C.; Herrewegh, A.A.; Rottier, P.J.M.; Groot, R.J. de

    1998-01-01

    Recent evidence suggests that the type II feline coronavirus (FCoV) strains 79-1146 and 79-1683 have arisen from a homologous RNA recombination event between FCoV type I and canine coronavirus (CCV). In both cases, the template switch apparently took place between the S and M genes, giving rise to r

  7. Pinning Synchronization of Switched Complex Dynamical Networks

    Directory of Open Access Journals (Sweden)

    Liming Du

    2015-01-01

    Full Text Available Network topology and node dynamics play a key role in forming synchronization of complex networks. Unfortunately there is no effective synchronization criterion for pinning synchronization of complex dynamical networks with switching topology. In this paper, pinning synchronization of complex dynamical networks with switching topology is studied. Two basic problems are considered: one is pinning synchronization of switched complex networks under arbitrary switching; the other is pinning synchronization of switched complex networks by design of switching when synchronization cannot achieved by using any individual connection topology alone. For the two problems, common Lyapunov function method and single Lyapunov function method are used respectively, some global synchronization criteria are proposed and the designed switching law is given. Finally, simulation results verify the validity of the results.

  8. Energy storage, compression, and switching. Vol. 2

    International Nuclear Information System (INIS)

    This book is a compilation of papers presented at the Second International Conference on Energy Storage, Compression, and Switching, which was held in order to assemble active researchers with a major interest in plasma physics, electron beams, electric and magnetic energy storage systems, high voltage and high current switches, free-electron lasers, and pellet implosion plasma focus. Topics covered include: Slow systems: 50-60 Hz machinery, homopolar generators, slow capacitors, inductors, and solid state switches; Intermediate systems: fast capacitor banks; superconducting storage and switching; gas, vacuum, and dielectric switching; nonlinear (magnetic) switching; imploding liners capacitors; explosive generators; and fuses; and Fast systems: Marx, Blumlein, oil, water, and pressurized water dielectrics; switches; magnetic insulation; electron beams; and plasmas

  9. Synchronization in complex networks with switching topology

    International Nuclear Information System (INIS)

    This Letter investigates synchronization issues of complex dynamical networks with switching topology. By constructing a common Lyapunov function, we show that local and global synchronization for a linearly coupled network with switching topology can be evaluated by the time average of second smallest eigenvalues corresponding to the Laplacians of switching topology. This result is quite powerful and can be further used to explore various switching cases for complex dynamical networks. Numerical simulations illustrate the effectiveness of the obtained results in the end. -- Highlights: → Synchronization of complex networks with switching topology is investigated. → A common Lyapunov function is established for synchronization of switching network. → The common Lyapunov function is not necessary to monotonically decrease with time. → Synchronization is determined by the second smallest eigenvalue of its Laplacian. → Synchronization criterion can be used to investigate various switching cases.

  10. Polychromatic polariton laser selector switch

    OpenAIRE

    Grosso, G; Trebaol, S.; Wouters, M.; Morier-Genoud, F; Portella-Oberli, M. T.; Deveaud, B.

    2013-01-01

    Integration of optical elements into scalable chips has been at the center of a large effort in recent years. Concurrently, the separation between the diverse functions, namely switches, detectors or emitters increases significantly the final number of components on chip. Such technical limitations may be overcome by introducing agile devices able, for example, to simultaneously detect, process and emit a coherent signal. Such a pathway has been explored with different approaches that bear ad...

  11. Switch for Good Community Program

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Tabitha; Amran, Martha

    2013-11-19

    Switch4Good is an energy-savings program that helps residents reduce consumption from behavior changes; it was co-developed by Balfour Beatty Military Housing Management (BB) and WattzOn in Phase I of this grant. The program was offered at 11 Navy bases. Three customer engagement strategies were evaluated, and it was found that Digital Nudges (a combination of monthly consumption statements with frequent messaging via text or email) was most cost-effective.

  12. Correlated randomness and switching phenomena

    Science.gov (United States)

    Stanley, H. E.; Buldyrev, S. V.; Franzese, G.; Havlin, S.; Mallamace, F.; Kumar, P.; Plerou, V.; Preis, T.

    2010-08-01

    One challenge of biology, medicine, and economics is that the systems treated by these serious scientific disciplines have no perfect metronome in time and no perfect spatial architecture-crystalline or otherwise. Nonetheless, as if by magic, out of nothing but randomness one finds remarkably fine-tuned processes in time and remarkably fine-tuned structures in space. Further, many of these processes and structures have the remarkable feature of “switching” from one behavior to another as if by magic. The past century has, philosophically, been concerned with placing aside the human tendency to see the universe as a fine-tuned machine. Here we will address the challenge of uncovering how, through randomness (albeit, as we shall see, strongly correlated randomness), one can arrive at some of the many spatial and temporal patterns in biology, medicine, and economics and even begin to characterize the switching phenomena that enables a system to pass from one state to another. Inspired by principles developed by A. Nihat Berker and scores of other statistical physicists in recent years, we discuss some applications of correlated randomness to understand switching phenomena in various fields. Specifically, we present evidence from experiments and from computer simulations supporting the hypothesis that water’s anomalies are related to a switching point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell), and that the bubbles in economic phenomena that occur on all scales are not “outliers” (another Gladwell immortalization). Though more speculative, we support the idea of disease as arising from some kind of yet-to-be-understood complex switching phenomenon, by discussing data on selected examples, including heart disease and Alzheimer disease.

  13. Electrical switching of an antiferromagnet

    Czech Academy of Sciences Publication Activity Database

    Wadley, P.; Howells, B.; Železný, J.; Andrews, C.; Hills, V.; Campion, R. P.; Novák, Vít; Olejník, Kamil; Maccherozzi, F.; Dhesi, S.S.; Martin, S.Y.; Wagner, T.; Wunderlich, Joerg; Freimuth, F.; Mokrousov, Y.; Kuneš, Jan; Chauhan, J.S.; Grzybowski, M.J.; Rushforth, A.W.; Edmonds, K. W.; Gallagher, B. L.; Jungwirth, Tomáš

    2016-01-01

    Roč. 351, č. 6273 (2016), 587-590. ISSN 0036-8075 R&D Projects: GA MŠk(CZ) LM2011026; GA ČR GB14-37427G EU Projects: European Commission(XE) 268066 - 0MSPIN Institutional support: RVO:68378271 Keywords : spintronics * antiferromagnets * current induced switching Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 33.611, year: 2014

  14. Switching strategies to optimize search

    Science.gov (United States)

    Shlesinger, Michael F.

    2016-03-01

    Search strategies are explored when the search time is fixed, success is probabilistic and the estimate for success can diminish with time if there is not a successful result. Under the time constraint the problem is to find the optimal time to switch a search strategy or search location. Several variables are taken into account, including cost, gain, rate of success if a target is present and the probability that a target is present.

  15. Ultrafast photonic crystal optical switching

    Institute of Scientific and Technical Information of China (English)

    GONG Qi-huang; HU Xiao-yong

    2006-01-01

    Photonic crystal,a novel and artificial photonic material with periodic dielectric distribution,possesses photonic bandgap and can control the propagation states of photons.Photonic crystal has been considered to be a promising candidate for the future integrated photonic devices.The properties and the fabrication method of photonic crystal are expounded.The progresses of the study of ultrafast photonic crystal optical switching are discussed in detail.

  16. EMI Prediction of Switching Converters

    OpenAIRE

    Trinchero, Riccardo; Stievano, Igor Simone; Canavero, Flavio

    2015-01-01

    This paper addresses the simulation of the conducted electromagnetic interference produced by circuits with periodically switching elements. The proposed method allows for the computation of their steady-state responses by means of augmented linear time-invariant equivalents built from circuit inspection only, and standard tools for circuit analysis. The approach is demonstrated on a real dc-dc boost converter by comparing simulation results with real measurements

  17. Static Switching Dynamic Buffer Circuit

    OpenAIRE

    Pandey, A. K.; R. A. Mishra; R. K. Nagaria

    2013-01-01

    We proposed footless domino logic buffer circuit. It minimizes redundant switching at the dynamic and the output nodes. The proposed circuit avoids propagation of precharge pulse to the output node and allows the dynamic node which saves power consumption. Simulation is done using 0.18 µm CMOS technology. We have calculated the power consumption, delay, and power delay product of the proposed circuit and compared the results with the existing circuits for different logic function, loading co...

  18. Fostering a Middle Class

    Institute of Scientific and Technical Information of China (English)

    YAO BIN

    2011-01-01

    Though there is no official definition of "middle class" in China,the tag has become one few Chinese people believe they deserve anyway.In early August,the Chinese Academy of Social Sciences released a report on China's urban development,saying China had a middle-class population of 230 million in 2009,or 37 percent of its urban residents.It also forecast half of city dwellers in China would be part of the middle class by 2023.

  19. Coating possibilities for magnetic switches

    International Nuclear Information System (INIS)

    High average power magnetic pulse compression systems are now being considered for use in several applications such as the High Power Radiation Source (HiPoRS) project. Such systems will require high reliability magnetic switches (saturable inductors) that are very efficient and have long lifetimes. One of the weakest components in magnetic switches is their interlaminar insulation. Considerations related to dielectric breakdown, thermal management of compact designs, and economical approaches for achieving these needs must be addressed. Various dielectric insulation and coating materials have been applied to Metglas foil in an attempt to solve the complex technical and practical problems associated with large magnetic switch structures. This work reports various needs, studies, results, and proposals in selecting and evaluating continuous coating approaches for magnetic foil. Techniques such as electrophoretic polymer deposition and surface chemical oxidation are discussed. We also propose continuous photofabrication processes for applying dielectric ribs or spacers to the foil which permit circulation of dielectric liquids for cooling during repetitive operation. 10 refs., 8 figs., 11 tabs

  20. New laser classes

    International Nuclear Information System (INIS)

    By an up-dated international standard (IEC 60825-1 + Amendment 2) on laser safety some new laser classes are introduced. The new set of laser classes consists of 1, 1M, 2, 2M, 3R, 3B, and 4. This is a result of intense discussions in the committee and was laid down in 2000, slightly adjusted 2001. The previous classes 1, 2, 3A, 3B, and 4, established since more than 25 years, are partly abandoned. This paper compares the new classes to the old ones. (orig.)

  1. Class, Culture and Politics

    DEFF Research Database (Denmark)

    Harrits, Gitte Sommer

    2013-01-01

    , discussions within political sociology have not yet utilized the merits of a multidimensional conception of class. In light of this, the article suggests a comprehensive Bourdieusian framework for class analysis, integrating culture as both a structural phenomenon co-constitutive of class and as symbolic...... practice. Further, the article explores this theoretical framework in a multiple correspondence analysis of a Danish survey, demonstrating how class and political practices are indeed homologous. However, the analysis also points at several elements of field autonomy, and the concluding discussion...

  2. Telomerase-null survivor screening identifies novel telomere recombination regulators.

    Directory of Open Access Journals (Sweden)

    Yan Hu

    Full Text Available Telomeres are protein-DNA structures found at the ends of linear chromosomes and are crucial for genome integrity. Telomeric DNA length is primarily maintained by the enzyme telomerase. Cells lacking telomerase will undergo senescence when telomeres become critically short. In Saccharomyces cerevisiae, a very small percentage of cells lacking telomerase can remain viable by lengthening telomeres via two distinct homologous recombination pathways. These "survivor" cells are classified as either Type I or Type II, with each class of survivor possessing distinct telomeric DNA structures and genetic requirements. To elucidate the regulatory pathways contributing to survivor generation, we knocked out the telomerase RNA gene TLC1 in 280 telomere-length-maintenance (TLM gene mutants and examined telomere structures in post-senescent survivors. We uncovered new functional roles for 10 genes that affect the emerging ratio of Type I versus Type II survivors and 22 genes that are required for Type II survivor generation. We further verified that Pif1 helicase was required for Type I recombination and that the INO80 chromatin remodeling complex greatly affected the emerging frequency of Type I survivors. Finally, we found the Rad6-mediated ubiquitination pathway and the KEOPS complex were required for Type II recombination. Our data provide an independent line of evidence supporting the idea that these genes play important roles in telomere dynamics.

  3. Insulating oil, electrical for transformers and switches : a national standard of Canada

    International Nuclear Information System (INIS)

    Standard specifications for insulating oil used in power transformers, instrument transformers, bushings, bulk oil circuit breakers, oil circuit reclosers, and switches were provided. The specifications are divided into Class A and Class B depending on the requirement for kinematic viscosity at -40 degrees C. A Class S oil is also introduced for oil circuit breakers. The standards were prepared by the Technical Committee on Transformer and Switch Oils under the jurisdiction of the Steering Committee on Electrical Engineering, and has been formally approved by these committees. It has been also approved as a National Standard of Canada by the Standards Council of Canada. The document provides a list of reference publications, describes the samples and test procedures, properties and delivery requirements. 1 tab

  4. Current trends of HIV recombination worldwide

    Directory of Open Access Journals (Sweden)

    Katherine A. Lau

    2013-06-01

    Full Text Available One of the major characteristics of HIV-1 is its high genetic variability and extensive heterogeneity. This characteristic is due to its molecular traits, which in turn allows it to vary, recombine, and diversify at a high frequency. As such, it generates complex molecular forms, termed recombinants, which evade the human immune system and so survive. There is no sequence constraint to the recombination pattern as it appears to occur at inter-group (between groups M and O, as well as inter- and intra-subtype within group M. Rapid emergence and active global transmission of HIV-1 recombinants, known as circulating recombinant forms (CRFs and unique recombinant forms (URFs, requires urgent attention. To date, 55 CRFs have been reported around the world. The first CRF01_AE originated from Central Africa but spread widely in Asia. The most recent CRF; CRF55_01B is a recombinant form of CRF01_AE and subtype B, although its origin is yet to be publicly disclosed. HIV-1 recombination is an ongoing event and plays an indispensable role in HIV epidemics in different regions. Africa, Asia and South America are identified as recombination hot-spots. They are affected by continual emergence and co-circulation of newly emerging CRFs and URFs, which are now responsible for almost 20% of HIV-1 infections worldwide. Better understanding of recombinants is necessary to determine their biological and molecular attributes.

  5. Bacteriophage recombination systems and biotechnical applications.

    Science.gov (United States)

    Nafissi, Nafiseh; Slavcev, Roderick

    2014-04-01

    Bacteriophage recombination systems have been widely used in biotechnology for modifying prokaryotic species, for creating transgenic animals and plants, and more recently, for human cell gene manipulation. In contrast to homologous recombination, which benefits from the endogenous recombination machinery of the cell, site-specific recombination requires an exogenous source of recombinase in mammalian cells. The mechanism of bacteriophage evolution and their coexistence with bacterial cells has become a point of interest ever since bacterial viruses' life cycles were first explored. Phage recombinases have already been exploited as valuable genetic tools and new phage enzymes, and their potential application to genetic engineering and genome manipulation, vectorology, and generation of new transgene delivery vectors, and cell therapy are attractive areas of research that continue to be investigated. The significance and role of phage recombination systems in biotechnology is reviewed in this paper, with specific focus on homologous and site-specific recombination conferred by the coli phages, λ, and N15, the integrase from the Streptomyces phage, ΦC31, the recombination system of phage P1, and the recently characterized recombination functions of Yersinia phage, PY54. Key steps of the molecular mechanisms involving phage recombination functions and their application to molecular engineering, our novel exploitations of the PY54-derived recombination system, and its application to the development of new DNA vectors are discussed. PMID:24442504

  6. Switch recombination in fetal porcine thymus is uncoupled from somatic mutation

    Czech Academy of Sciences Publication Activity Database

    Butler, J. E.; Sun, J.; Weber, P.; Ford, S. P.; Řeháková, Zuzana; Šinkora, Jiří; Lager, K.

    Uppsala: International Union of Immunological Societies, 2001. s. 42. [International Veterinary Immunology Symposium /6./. 15.07.2001-20.07.2001, Uppsala] Institutional research plan: CEZ:AV0Z5020903 Subject RIV: EC - Immunology

  7. Switch recombination in fetal porcine thymus is uncoupled from somatic mutation

    Czech Academy of Sciences Publication Activity Database

    Butler, J. E.; Sun, J.; Weber, P.; Ford, S. P.; Řeháková, Zuzana; Šinkora, Jiří; Francis, D.; Lager, K.

    2002-01-01

    Roč. 87, - (2002), s. 307-319. ISSN 0165-2427 Institutional research plan: CEZ:AV0Z5020903 Keywords : fetal * immunoglobulins * transcription Subject RIV: EE - Microbiology, Virology Impact factor: 1.659, year: 2002

  8. CRMAGE: CRISPR Optimized MAGE Recombineering

    DEFF Research Database (Denmark)

    Ronda, Carlotta; Pedersen, Lasse Ebdrup; Sommer, Morten Otto Alexander;

    2016-01-01

    A bottleneck in metabolic engineering and systems biology approaches is the lack of efficient genome engineering technologies. Here, we combine CRISPR/Cas9 and λ Red recombineering based MAGE technology (CRMAGE) to create a highly efficient and fast method for genome engineering of Escherichia coli...... assembled by a USER-cloning approach enabling quick and cost efficient gRNA replacement. CRMAGE furthermore utilizes CRISPR/Cas9 for efficient plasmid curing, thereby enabling multiple engineering rounds per day. To facilitate the design process, a web-based tool was developed to predict both the λ Red...

  9. Teaching Large Evening Classes

    Science.gov (United States)

    Wambuguh, Oscar

    2008-01-01

    High enrollments, conflicting student work schedules, and the sheer convenience of once-a-week classes are pushing many colleges to schedule evening courses. Held from 6 to 9 pm or 7 to 10 pm, these classes are typically packed, sometimes with more than 150 students in a large lecture theater. How can faculty effectively teach, control, or even…

  10. Class in disguise

    DEFF Research Database (Denmark)

    Faber, Stine Thidemann; Prieur, Annick

    This paper asks how class can have importance in one of the worlds’ most equal societies: Denmark. The answer is that class here appears in disguised forms. The field under study is a city, Aalborg, in the midst of transition from a stronghold of industrialism to a post industrial economy...

  11. Teaching Social Class

    Science.gov (United States)

    Tablante, Courtney B.; Fiske, Susan T.

    2015-01-01

    Discussing socioeconomic status in college classes can be challenging. Both teachers and students feel uncomfortable, yet social class matters more than ever. This is especially true, given increased income inequality in the United States and indications that higher education does not reduce this inequality as much as many people hope. Resources…

  12. DEFINING THE MIDDLE CLASS

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Classifying the middle class remains controversial despite its alleged growth China’s cities housed more than 230 million middle-class residents in 2009 or 37 percent of the urban population,according to the 2011 Blue Book of Cities in China released on August 3.

  13. Design and Simulation of Routing-switching Protocol Based on Optical Switch Array

    Institute of Scientific and Technical Information of China (English)

    HE Wei; MAO You-ju; LIU Jiang

    2004-01-01

    An optical routing- switching technology based on optical switch array is proposed. The characteristics of the blocking and nonblocking networks are analyzed and compared, odd- even sorting network is used to realize optical routing- switching, relative routing- switching protocol is designed.Simulation test under load shows that it can reduce a blocking effectively and enhance an efficiency of switching. Further, it can transfer the processing and switching within parallel computer from electric domain to optical domain. It can make parallel computer coordinating computing and processing at much more higher speed, storing and transmitting even more efficiently.

  14. To Switch or Not to Switch: Examine the Code-switching Practices of Teachers of Non-English Majors

    OpenAIRE

    Xu, Qing

    2010-01-01

    The paper analyzes the factors of teachers’ English/Chinese code-switching in EFL teaching for non-English majors. It also interprets the collected data so as to raise EFL teachers’ awareness of their actual use of code-switching in classroom and help them develop an appropriate attitude towards its role in EFL teaching.
    Key words: code-switching; function; classroom discourse; EFL teachers

  15. Kinetics of Xylanase Fermentation by Recombinant Escherichia coli DH5α in Shake Flask Culture

    OpenAIRE

    Farliahati Mohd Rusli; Mohd Shamzi Mohamed; Rosfarizan Mohamad; Ni N. Tri Puspaningsih; Arbakariya A. Ariff

    2009-01-01

    Problem statement: Interest in xylanase enzyme application has markedly increased in pulp and paper processing industries. The switch to xylanase-producing recombinant Escherichia coli DH5α pTP510 is seen here as an economic alternative towards higher productivity and easier downstream purification. Modeling of E. coli DH5α growth and enzyme secretion is thus desired for future optimization in fermentation process. Approach: Kinetics of intracellular xylanase fermentation by a recom...

  16. Adaptive Exponential Stabilization for a Class of Stochastic Nonholonomic Systems

    OpenAIRE

    Xiaoyan Qin

    2013-01-01

    This paper investigates the adaptive stabilization problem for a class of stochastic nonholonomic systems with strong drifts. By using input-state-scaling technique, backstepping recursive approach, and a parameter separation technique, we design an adaptive state feedback controller. Based on the switching strategy to eliminate the phenomenon of uncontrollability, the proposed controller can guarantee that the states of closed-loop system are global bounded in probability.

  17. Comparison of 2 synthetically generated recombinant prions

    OpenAIRE

    Zhang, Yi; Wang, Fei; Wang, Xinhe; Zhang, Zhihong; Xu, Yuanyuan; Yu, Guohua; Yuan, Chonggang; Ma, Jiyan

    2014-01-01

    Prion is a protein-conformation-based infectious agent causing fatal neurodegenerative diseases in humans and animals. Our previous studies revealed that in the presence of cofactors, infectious prions can be synthetically generated in vitro with bacterially expressed recombinant prion protein (PrP). Once initiated, the recombinant prion is able to propagate indefinitely via serial protein misfolding cyclic amplification (sPMCA). In this study, we compared 2 separately initiated recombinant p...

  18. Impact of recombination on bacterial evolution

    OpenAIRE

    Didelot, Xavier; Maiden, Martin C. J.

    2010-01-01

    Genetic exchange plays a defining role in the evolution of many bacteria. The recent accumulation of nucleotide sequence data from multiple members of diverse bacterial genera has facilitated comparative studies that have revealed many features of this process. Here we focus on genetic exchange that has involved homologous recombination and illustrate how nucleotide sequence data have furthered our understanding of: (i) the frequency of recombination; (ii) the impact of recombination in diffe...

  19. Recombination rate variation in closely related species

    OpenAIRE

    Smukowski, C S; Noor, M A F

    2011-01-01

    Despite their importance to successful meiosis and various evolutionary processes, meiotic recombination rates sometimes vary within species or between closely related species. For example, humans and chimpanzees share virtually no recombination hotspot locations in the surveyed portion of the genomes. However, conservation of recombination rates between closely related species has also been documented, raising an apparent contradiction. Here, we evaluate how and why conflicting patterns of r...

  20. Role of ubiquitination in meiotic recombination repair

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Programmed and unprogrammed double-strand breaks (DSBs) often arise from such physiological requirements as meiotic recombination, and exogenous insults, such as ionizing radiation (IR). Due to deleterious impacts on genome stability, DSBs must be appropriately processed and repaired in a regulatory manner. Recent investigations have indicated that ubiquitination is a critical factor in DNA damage response and meiotic recombination repair. This review summarizes the effects of proteins and complexes associated with ubiquitination with regard to homologous recombination (HR)-dependent DSB repair.

  1. Consequences of recombination on traditional phylogenetic analysis

    DEFF Research Database (Denmark)

    Schierup, M H; Hein, J

    2000-01-01

    We investigate the shape of a phylogenetic tree reconstructed from sequences evolving under the coalescent with recombination. The motivation is that evolutionary inferences are often made from phylogenetic trees reconstructed from population data even though recombination may well occur (mtDNA or...... recombination leads to a large overestimation of the substitution rate heterogeneity and the loss of the molecular clock. These results are discussed in relation to viral and mtDNA data sets. Udgivelsesdato: 2000-Oct...

  2. RNA recombination in animal and plant viruses.

    OpenAIRE

    Lai, M M

    1992-01-01

    An increasing number of animal and plant viruses have been shown to undergo RNA-RNA recombination, which is defined as the exchange of genetic information between nonsegmented RNAs. Only some of these viruses have been shown to undergo recombination in experimental infection of tissue culture, animals, and plants. However, a survey of viral RNA structure and sequences suggests that many RNA viruses were derived form homologous or nonhomologous recombination between viruses or between viruses ...

  3. Components of attentional set-switching.

    Science.gov (United States)

    Rushworth, M F S; Passingham, R E; Nobre, A C

    2005-01-01

    A series of distinct event-related potentials (ERPs) have been recorded from the scalp of human subjects as they switch from one task to another. It is possible that task switching may depend on different mechanisms depending on whether the switch requires a change in attentional set, in other words the redirecting of attention to different aspects of a sensory stimulus, or whether it requires a change in intentional set, in others words a change in the way that responses are selected. To address this issue, the current study recorded ERPs while subjects switched between attentional sets and the results were compared with those of a previous investigation in which subjects switched between intentional sets. Subjects selected stimuli according to two conflicting attentional sets, each emphasizing one visual stimulus dimension (colour, shape). Pairs of stimuli, only one of which was to be attended, were presented for between eight and seventeen trials then either a switch or a stay cue was shown. The switch cue instructed subjects to switch from the current attentional set to the other set, while the stay cue instructed subjects to maintain the current set. Comparing ERPs time-locked to the switch and stay cues revealed neural correlates of the initiation of a task switch. Comparing the ERPs time locked to the first stimuli after either stay or switch cues identified neural correlates of the implementation of a task switch. A similar modulation over parietal electrodes was seen when subjects were switching between either attentional or intentional sets. While an intentional set switch began with a medial frontal modulation, attentional set switching began with a lateral frontal modulation. Implementing a new attentional set was associated with modulation of relatively early visual potentials, while implementing a new intentional set was associated with modulation of later response-related potentials. The results confirm that task switching consists of a number of

  4. Class-D audio amplifiers with negative feedback

    OpenAIRE

    Cox, Stephen M.; Candy, B. H.

    2006-01-01

    There are many different designs for audio amplifiers. Class-D, or switching, amplifiers generate their output signal in the form of a high-frequency square wave of variable duty cycle (ratio of on time to off time). The square-wave nature of the output allows a particularly efficient output stage, with minimal losses. The output is ultimately filtered to remove components of the spectrum above the audio range. Mathematical models are derived here for a variety of related class-D amplifier d...

  5. Robust network topologies for generating switch-like cellular responses.

    Directory of Open Access Journals (Sweden)

    Najaf A Shah

    2011-06-01

    Full Text Available Signaling networks that convert graded stimuli into binary, all-or-none cellular responses are critical in processes ranging from cell-cycle control to lineage commitment. To exhaustively enumerate topologies that exhibit this switch-like behavior, we simulated all possible two- and three-component networks on random parameter sets, and assessed the resulting response profiles for both steepness (ultrasensitivity and extent of memory (bistability. Simulations were used to study purely enzymatic networks, purely transcriptional networks, and hybrid enzymatic/transcriptional networks, and the topologies in each class were rank ordered by parametric robustness (i.e., the percentage of applied parameter sets exhibiting ultrasensitivity or bistability. Results reveal that the distribution of network robustness is highly skewed, with the most robust topologies clustering into a small number of motifs. Hybrid networks are the most robust in generating ultrasensitivity (up to 28% and bistability (up to 18%; strikingly, a purely transcriptional framework is the most fragile in generating either ultrasensitive (up to 3% or bistable (up to 1% responses. The disparity in robustness among the network classes is due in part to zero-order ultrasensitivity, an enzyme-specific phenomenon, which repeatedly emerges as a particularly robust mechanism for generating nonlinearity and can act as a building block for switch-like responses. We also highlight experimentally studied examples of topologies enabling switching behavior, in both native and synthetic systems, that rank highly in our simulations. This unbiased approach for identifying topologies capable of a given response may be useful in discovering new natural motifs and in designing robust synthetic gene networks.

  6. Fis is required for illegitimate recombination during formation of lambda bio transducing phage.

    OpenAIRE

    Shanado, Y; Kato, J; Ikeda, H

    1997-01-01

    Specialized transducing particles of phage lambda are formed by illegitimate recombination during prophage induction. We examined the effects of an Esherichia coli int, xis, himA, himD, or fis mutation on illegitimate recombination during formation of lambda Spi- phage, a class of lambda bio transducing phage. This type of phage is distinguishable from the docL and docR particles, which contain one cohesive end and are formed by cutting of the cos site, by plaque formation of lambda bio on Es...

  7. Direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.; Andersen, Michael A.E.

    2005-07-01

    This paper discusses the advantages and problems when implementing direct energy conversion switching-mode audio power amplifiers. It is shown that the total integration of the power supply and Class D audio power amplifier into one compact direct converter can simplify design, increase efficiency and integration level, reduce product volume and lower its cost. As an example, the principle of operation and the measurements made on a direct-conversion switching-mode audio power amplifier with active capacitive voltage clamp are presented. (au)

  8. Finite-time boundedness and stabilization of uncertain switched neural networks with time-varying delay.

    Science.gov (United States)

    Wu, Yuanyuan; Cao, Jinde; Alofi, Abdulaziz; Al-Mazrooei, Abdullah; Elaiw, Ahmed

    2015-09-01

    This paper deals with the finite-time boundedness and stabilization problem for a class of switched neural networks with time-varying delay and parametric uncertainties. Based on Lyapunov-like function method and average dwell time technique, some sufficient conditions are derived to guarantee the finite-time boundedness of considered uncertain switched neural networks. Furthermore, the state feedback controller is designed to solve the finite-time stabilization problem. Moreover, the proposed sufficient conditions can be simplified into the form of linear matrix equalities for conveniently using Matlab LMI toolbox. Finally, two numerical examples are given to show the effectiveness of the main results. PMID:26103615

  9. Attractor and Boundedness of Switched Stochastic Cohen-Grossberg Neural Networks

    Directory of Open Access Journals (Sweden)

    Chuangxia Huang

    2016-01-01

    Full Text Available We address the problem of stochastic attractor and boundedness of a class of switched Cohen-Grossberg neural networks (CGNN with discrete and infinitely distributed delays. With the help of stochastic analysis technology, the Lyapunov-Krasovskii functional method, linear matrix inequalities technique (LMI, and the average dwell time approach (ADT, some novel sufficient conditions regarding the issues of mean-square uniformly ultimate boundedness, the existence of a stochastic attractor, and the mean-square exponential stability for the switched Cohen-Grossberg neural networks are established. Finally, illustrative examples and their simulations are provided to illustrate the effectiveness of the proposed results.

  10. The role of inhibitory control in task switching

    OpenAIRE

    Yang, Violet Hye-Won

    2010-01-01

    Previous research on task switching has been confounded by inhibitory control mechanism and there has been debate on the source of switch costs and how and when the inhibitory control occurs during task switching. In order to circumvent this problem, the thesis aimed to investigate the role of inhibition in task switching by examining switch costs, alternating switch costs and congruency effect in three tasks when two preparation intervals (short and long) are given. Task switching experiment...

  11. Ultra High-Speed Radio Frequency Switch Based on Photonics

    OpenAIRE

    Jia Ge; Fok, Mable P.

    2015-01-01

    Microwave switches, or Radio Frequency (RF) switches have been intensively used in microwave systems for signal routing. Compared with the fast development of microwave and wireless systems, RF switches have been underdeveloped particularly in terms of switching speed and operating bandwidth. In this paper, we propose a photonics based RF switch that is capable of switching at tens of picoseconds speed, which is hundreds of times faster than any existing RF switch technologies. The high-speed...

  12. Know-How on design of switching regulator

    International Nuclear Information System (INIS)

    This book introduces switching regulator from base to application, which deals with fundamentals of switching regulator such as the reason of boom about switching regulator, understanding simple circuit without electric transformer and decision of circuit type with input voltage and output voltage, configuration and characteristic of switching regulator, a concrete design of switching regulator, pulse width control circuit and protection circuit, concrete circuit examples of switching power and the point of switching regulator.

  13. Switching control of an R/C hovercraft: stabilization and smooth switching.

    Science.gov (United States)

    Tanaka, K; Iwasaki, M; Wang, H O

    2001-01-01

    This paper presents stable switching control of an radio-controlled (R/C) hovercraft that is a nonholonomic (nonlinear) system. To exactly represent its nonlinear dynamics, more importantly, to maintain controllability of the system, we newly propose a switching fuzzy model that has locally Takagi-Sugeno (T-S) fuzzy models and switches them according to states, external variables, and/or time. A switching fuzzy controller is constructed by mirroring the rule structure of the switching fuzzy model of an R/C hovercraft. We derive linear matrix inequality (LMI) conditions for ensuring the stability of the closed-loop system consisting of a switching fuzzy model and controller. Furthermore, to guarantee smooth switching of control input at switching boundaries, we also derive a smooth switching condition represented in terms of LMIs. A stable switching fuzzy controller satisfying the smooth switching condition is designed by simultaneously solving both of the LMIs. The simulation and experimental results for the trajectory control of an R/C hovercraft show the validity of the switching fuzzy model and controller design, particularly, the smooth switching condition. PMID:18244851

  14. Human Insulin from Recombinant DNA Technology

    Science.gov (United States)

    Johnson, Irving S.

    1983-02-01

    Human insulin produced by recombinant DNA technology is the first commercial health care product derived from this technology. Work on this product was initiated before there were federal guidelines for large-scale recombinant DNA work or commercial development of recombinant DNA products. The steps taken to facilitate acceptance of large-scale work and proof of the identity and safety of such a product are described. While basic studies in recombinant DNA technology will continue to have a profound impact on research in the life sciences, commercial applications may well be controlled by economic conditions and the availability of investment capital.

  15. Experimental recombination rates for highly charged ions

    International Nuclear Information System (INIS)

    Recent studies of recombination between free electrons and highly charged ions using electron coolers of heavy-ion storage rings have produced accurate rate coefficients of interest for plasma modeling and diagnostics. Some surprises were discovered which can lead to revisions of recombination models. With bare ions one finds at low energy a strong and puzzling deviation from radiative recombination theory. Dielectronic recombination with C3+, N4+) show that jj coupling gives essential contributions to the cross section also for light ions. (author)

  16. MEMS switches having non-metallic crossbeams

    Science.gov (United States)

    Scardelletti, Maximillian C (Inventor)

    2009-01-01

    A RF MEMS switch comprising a crossbeam of SiC, supported by at least one leg above a substrate and above a plurality of transmission lines forming a CPW. Bias is provided by at least one layer of metal disposed on a top surface of the SiC crossbeam, such as a layer of chromium followed by a layer of gold, and extending beyond the switch to a biasing pad on the substrate. The switch utilizes stress and conductivity-controlled non-metallic thin cantilevers or bridges, thereby improving the RF characteristics and operational reliability of the switch. The switch can be fabricated with conventional silicon integrated circuit (IC) processing techniques. The design of the switch is very versatile and can be implemented in many transmission line mediums.

  17. Pulse switching for high energy lasers

    Science.gov (United States)

    Laudenslager, J. B.; Pacala, T. J. (Inventor)

    1981-01-01

    A saturable inductor switch for compressing the width and sharpening the rise time of high voltage pulses from a relatively slow rise time, high voltage generator to an electric discharge gas laser (EDGL) also provides a capability for efficient energy transfer from a high impedance primary source to an intermediate low impedance laser discharge network. The switch is positioned with respect to a capacitive storage device, such as a coaxial cable, so that when a charge build-up in the storage device reaches a predetermined level, saturation of the switch inductor releases or switches energy stored in the capactive storage device to the EDGL. Cascaded saturable inductor switches for providing output pulses having rise times of less than ten nanoseconds and a technique for magnetically biasing the saturable inductor switch are disclosed.

  18. High voltage, magnetically switched pulsed power systems

    International Nuclear Information System (INIS)

    The principles of magnetic switching are briefly described. Then the results of experiments on the following substantive topics for magnetic switching are presented: material properties and how they relate to switch performance, risetime limitations, and core insulation. Magnetic switching is then evaluated from a system perspective. An idealized pulse power system with 200 kJ or stored energy and a 40 ns output pulse is examined. The multi-megavolt electrical insulation requirements impose limitations on the switches. The cost of the magnetically switched system exceeds the cost of the conventional superpower generator system by up to 75%. The potential for reliability, reproducibility, and repetitive pulse capability must be evaluated for each application to offset the increased cost

  19. Exponential stabilization of switched stochastic dynamical networks

    International Nuclear Information System (INIS)

    A switched stochastic dynamical network (SSDN) model will firstly be formulated in this paper, which considers two mutually independent switching signals including individual node switching and network topology switching. In the proposed SSDN model, the stochastic perturbation is described by multi-dimensional Brownian motion, and the switching signals are arbitrary under the constraint of the average dwell time. A multiple Lyapunov function is utilized to cope with the switching problem. A single controller is then designed for the exponential mean square stabilization for SSDNs. The coupling matrix of the SSDN can be assumed to be irreducible symmetric or irreducible asymmetric. The obtained criteria are given in terms of linear matrix inequalities, which can be solved efficiently by standard software packages. Numerical examples, including small-world and scale-free networks, are exploited to illustrate the effectiveness of the theoretical results. It can be observed from the examples that our results are also applicable to large-scale dynamical networks

  20. Multiprocessor switch with selective pairing

    Energy Technology Data Exchange (ETDEWEB)

    Gara, Alan; Gschwind, Michael K; Salapura, Valentina

    2014-03-11

    System, method and computer program product for a multiprocessing system to offer selective pairing of processor cores for increased processing reliability. A selective pairing facility is provided that selectively connects, i.e., pairs, multiple microprocessor or processor cores to provide one highly reliable thread (or thread group). Each paired microprocessor or processor cores that provide one highly reliable thread for high-reliability connect with a system components such as a memory "nest" (or memory hierarchy), an optional system controller, and optional interrupt controller, optional I/O or peripheral devices, etc. The memory nest is attached to a selective pairing facility via a switch or a bus