ICESpy009, a Conjugative Genetic Element Carrying mef(E) in Streptococcus pyogenes.

PubMed

Del Grosso, Maria; Camilli, Romina; Rizzi, Ermanno; Pietrelli, Alessandro; De Bellis, Gianluca; Pantosti, Annalisa

2016-07-01

Efflux-mediated macrolide resistance due to mef(E) and mel, carried by the mega element, is common in Streptococcus pneumoniae, for which it was originally characterized, but it is rare in Streptococcus pyogenes In S. pyogenes, mega was previously found to be enclosed in Tn2009, a composite genetic element of the Tn916 family containing tet(M) and conferring erythromycin and tetracycline resistance. In this study, S. pyogenes isolates containing mef(E), apparently not associated with other resistance determinants, were examined to characterize the genetic context of mega. By whole-genome sequencing of one isolate, MB56Spyo009, we identified a novel composite integrative and conjugative element (ICE) carrying mega, designated ICESpy009, belonging to the ICESa2603 family. ICESpy009 was 55 kb long, contained 61 putative open reading frames (ORFs), and was found to be integrated into hylA, a novel integration site for the ICESa2603 family. The modular organization of the ICE was similar to that of members of the ICESa2603 family carried by different streptococcal species. In addition, a novel cluster of accessory resistance genes was found inside a region that encloses mega. PCR mapping targeting ICESpy009 revealed the presence of a similar ICE in five other isolates under study. While in three isolates the integration site was the same as that of ICESpy009, in two isolates the ICE was integrated into rplL, the typical integration site of the ICESa2603 family. ICESpy009 was able to transfer macrolide resistance by conjugation to both S. pyogenes and S. pneumoniae, showing the first evidence of the transferability of mega from S. pyogenes. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

ICESpy009, a Conjugative Genetic Element Carrying mef(E) in Streptococcus pyogenes

PubMed Central

Camilli, Romina; Rizzi, Ermanno; Pietrelli, Alessandro; De Bellis, Gianluca; Pantosti, Annalisa

2016-01-01

Efflux-mediated macrolide resistance due to mef(E) and mel, carried by the mega element, is common in Streptococcus pneumoniae, for which it was originally characterized, but it is rare in Streptococcus pyogenes. In S. pyogenes, mega was previously found to be enclosed in Tn2009, a composite genetic element of the Tn916 family containing tet(M) and conferring erythromycin and tetracycline resistance. In this study, S. pyogenes isolates containing mef(E), apparently not associated with other resistance determinants, were examined to characterize the genetic context of mega. By whole-genome sequencing of one isolate, MB56Spyo009, we identified a novel composite integrative and conjugative element (ICE) carrying mega, designated ICESpy009, belonging to the ICESa2603 family. ICESpy009 was 55 kb long, contained 61 putative open reading frames (ORFs), and was found to be integrated into hylA, a novel integration site for the ICESa2603 family. The modular organization of the ICE was similar to that of members of the ICESa2603 family carried by different streptococcal species. In addition, a novel cluster of accessory resistance genes was found inside a region that encloses mega. PCR mapping targeting ICESpy009 revealed the presence of a similar ICE in five other isolates under study. While in three isolates the integration site was the same as that of ICESpy009, in two isolates the ICE was integrated into rplL, the typical integration site of the ICESa2603 family. ICESpy009 was able to transfer macrolide resistance by conjugation to both S. pyogenes and S. pneumoniae, showing the first evidence of the transferability of mega from S. pyogenes. PMID:27067338

Characterization of Three Novel SXT/R391 Integrating Conjugative Elements ICE MfuInd1a and ICE MfuInd1b, and ICE MprChn1 Identified in the Genomes of Marinomonas fungiae JCM 18476 T and Marinomonas profundimaris Strain D104

DOE Office of Scientific and Technical Information (OSTI.GOV)

Badhai, Jhasketan; Das, Subrata K.

The genus Marinomonas comprises Gram negative bacteria which are widespread in the marine environment and there is no report on the genomic analysis of SXT/R391 ICEs derived from this group of bacteria. This study describes the genomic features of three new SXT/R391 integrating conjugating elements (ICEs) identified in the genome of Marinomonas fungiae JCM 18476 T (ICE MfuInd1a and ICE MfuInd1b) and in Marinomonas profundimaris strain D104 (ICE MprChn1). Structural organizations of the three ICEs were similar to the typical SXT/R391 family of ICEs and showed high degree of conservation in the core genes. Sequence analysis revealed ICE MfuInd1b andmore » ICE MprChn1 were inserted into the genome at 5'-end of an typical host prfC gene, while ICE MfuInd1a was inserted at 5'-end of an atypical hipA-like gene. Despite their coexistence, the ICE MfuInd1a and ICE MfuInd1b were not present in a tandem fashion in the genome of M. fungiae. Phylogenetic analyses revealed the three ICEs either evolved independently or high degrees of recombination events had masked their evolution from a common SXT ancestor. Further, we found that the typical entry exclusion mechanism mediated by the TraG/EeX protein pair was likely defective in preventing the conjugative transfer of a second copy of the same S (SXT) group ICE into the M. fungiae genome due to mutations. Our analysis showed the presence of 16, 25, and 27 variable genes in the hotspots of ICE MfuInd1a, ICE MfuInd1b, and ICE MprChn1, respectively, many of which were not reported earlier for SXT/R391 ICEs. Sequence analysis predicted these hot spot regions were shaped by acquisition of genes through homologous recombination between the SXT and R391 related ICEs or mobile genetic elements present in disparate marine bacteria. Multidrug resistance genes which are hallmark feature of SXT/R391 ICEs were not present in either of the two ICEs from M. fungiae but were present within a transposon cassette in the HS-1 of the ICE MprChn1 from M. profundimaris. Lastly, our data provided information on the genetic diversity and predicted functions encoded by variable genes present in the hotspot regions of these new ICEs.« less

Characterization of Three Novel SXT/R391 Integrating Conjugative Elements ICE MfuInd1a and ICE MfuInd1b, and ICE MprChn1 Identified in the Genomes of Marinomonas fungiae JCM 18476 T and Marinomonas profundimaris Strain D104

DOE PAGES

Badhai, Jhasketan; Das, Subrata K.

2016-11-25

The genus Marinomonas comprises Gram negative bacteria which are widespread in the marine environment and there is no report on the genomic analysis of SXT/R391 ICEs derived from this group of bacteria. This study describes the genomic features of three new SXT/R391 integrating conjugating elements (ICEs) identified in the genome of Marinomonas fungiae JCM 18476 T (ICE MfuInd1a and ICE MfuInd1b) and in Marinomonas profundimaris strain D104 (ICE MprChn1). Structural organizations of the three ICEs were similar to the typical SXT/R391 family of ICEs and showed high degree of conservation in the core genes. Sequence analysis revealed ICE MfuInd1b andmore » ICE MprChn1 were inserted into the genome at 5'-end of an typical host prfC gene, while ICE MfuInd1a was inserted at 5'-end of an atypical hipA-like gene. Despite their coexistence, the ICE MfuInd1a and ICE MfuInd1b were not present in a tandem fashion in the genome of M. fungiae. Phylogenetic analyses revealed the three ICEs either evolved independently or high degrees of recombination events had masked their evolution from a common SXT ancestor. Further, we found that the typical entry exclusion mechanism mediated by the TraG/EeX protein pair was likely defective in preventing the conjugative transfer of a second copy of the same S (SXT) group ICE into the M. fungiae genome due to mutations. Our analysis showed the presence of 16, 25, and 27 variable genes in the hotspots of ICE MfuInd1a, ICE MfuInd1b, and ICE MprChn1, respectively, many of which were not reported earlier for SXT/R391 ICEs. Sequence analysis predicted these hot spot regions were shaped by acquisition of genes through homologous recombination between the SXT and R391 related ICEs or mobile genetic elements present in disparate marine bacteria. Multidrug resistance genes which are hallmark feature of SXT/R391 ICEs were not present in either of the two ICEs from M. fungiae but were present within a transposon cassette in the HS-1 of the ICE MprChn1 from M. profundimaris. Lastly, our data provided information on the genetic diversity and predicted functions encoded by variable genes present in the hotspot regions of these new ICEs.« less

Recombination between Streptococcus suis ICESsu32457 and Streptococcus agalactiae ICESa2603 yields a hybrid ICE transferable to Streptococcus pyogenes.

PubMed

Marini, Emanuela; Palmieri, Claudio; Magi, Gloria; Facinelli, Bruna

2015-07-09

Integrative conjugative elements (ICEs) are mobile genetic elements that reside in the chromosome but retain the ability to undergo excision and to transfer by conjugation. Genes involved in drug resistance, virulence, or niche adaptation are often found among backbone genes as cargo DNA. We recently characterized in Streptococcus suis an ICE (ICESsu32457) carrying resistance genes [tet(O/W/32/O), tet(40), erm(B), aphA, and aadE] in the 15K unstable genetic element, which is flanked by two ∼1.3kb direct repeats. Remarkably, ∼1.3-kb sequences are conserved in ICESa2603 of Streptococcus agalactiae 2603V/R, which carry heavy metal resistance genes cadC/cadA and mer. In matings between S. suis 32457 (donor) and S. agalactiae 2603V/R (recipient), transconjugants were obtained. PCR experiments, PFGE, and sequence analysis of transconjugants demonstrated a tandem array between ICESsu32457 and ICESa2603. Matings between tandem array-containing S. agalactiae 2603V/R (donor) and Streptococcus pyogenes RF12 (recipient) yielded a single transconjugant containing a hybrid ICE, here named ICESa2603/ICESsu32457. The hybrid formed by recombination of the left ∼1.3-kb sequence of ICESsu32457 and the ∼1.3-kb sequence of ICESa2603. Interestingly, the hybrid ICE was transferable between S. pyogenes strains, thus demonstrating that it behaves as a conventional ICE. These findings suggest that both tandem arrays and hybrid ICEs may contribute to the evolution of antibiotic resistance in streptococci, creating novel mobile elements capable of disseminating new combinations of antibiotic resistance genes. Copyright © 2015 Elsevier B.V. All rights reserved.

ICEPmu1, an integrative conjugative element (ICE) of Pasteurella multocida: structure and transfer.

PubMed

Michael, Geovana Brenner; Kadlec, Kristina; Sweeney, Michael T; Brzuszkiewicz, Elzbieta; Liesegang, Heiko; Daniel, Rolf; Murray, Robert W; Watts, Jeffrey L; Schwarz, Stefan

2012-01-01

Integrative and conjugative elements (ICEs) have not been detected in Pasteurella multocida. In this study the multiresistance ICEPmu1 from bovine P. multocida was analysed for its core genes and its ability to conjugatively transfer into strains of the same and different genera. ICEPmu1 was identified during whole genome sequencing. Coding sequences were predicted by bioinformatic tools and manually curated using the annotation software ERGO. Conjugation into P. multocida, Mannheimia haemolytica and Escherichia coli recipients was performed by mating assays. The presence of ICEPmu1 and its circular intermediate in the recipient strains was confirmed by PCR and sequence analysis. Integration sites were sequenced. Susceptibility testing of the ICEPmu1-carrying recipients was conducted by broth microdilution. The 82 214 bp ICEPmu1 harbours 88 genes. The core genes of ICEPmu1, which are involved in excision/integration and conjugative transfer, resemble those found in a 66 641 bp ICE from Histophilus somni. ICEPmu1 integrates into a tRNA(Leu) and is flanked by 13 bp direct repeats. It is able to conjugatively transfer to P. multocida, M. haemolytica and E. coli, where it also uses a tRNA(Leu) for integration and produces closely related 13 bp direct repeats. PCR assays and susceptibility testing confirmed the presence and the functional activity of the ICEPmu1-associated resistance genes in the recipient strains. The observation that the multiresistance ICEPmu1 is present in a bovine P. multocida and can easily spread across strain and genus boundaries underlines the risk of a rapid dissemination of multiple resistance genes, which will distinctly decrease the therapeutic options.

Acquisition and evolution of SXT-R391 integrative conjugative elements in the seventh-pandemic Vibrio cholerae lineage.

PubMed

Spagnoletti, Matteo; Ceccarelli, Daniela; Rieux, Adrien; Fondi, Marco; Taviani, Elisa; Fani, Renato; Colombo, Mauro M; Colwell, Rita R; Balloux, François

2014-08-19

SXT-R391 Integrative conjugative elements (ICEs) are self-transmissible mobile genetic elements able to confer multidrug resistance and other adaptive features to bacterial hosts, including Vibrio cholerae, the causative agent of cholera. ICEs are arranged in a mosaic genetic structure composed of a conserved backbone interspersed with variable DNA clusters located in conserved hot spots. In this study, we investigated ICE acquisition and subsequent microevolution in pandemic V. cholerae. Ninety-six ICEs were retrieved from publicly available sequence databases from V. cholerae clinical strains and were compared to a set of reference ICEs. Comparative genomics highlighted the existence of five main ICE groups with a distinct genetic makeup, exemplified by ICEVchInd5, ICEVchMoz10, SXT, ICEVchInd6, and ICEVchBan11. ICEVchInd5 (the most frequent element, represented by 70 of 96 elements analyzed) displayed no sequence rearrangements and was characterized by 46 single nucleotide polymorphisms (SNPs). SNP analysis revealed that recent inter-ICE homologous recombination between ICEVchInd5 and other ICEs circulating in gammaproteobacteria generated ICEVchMoz10, ICEVchInd6, and ICEVchBan11. Bayesian phylogenetic analyses indicated that ICEVchInd5 and SXT were independently acquired by the current pandemic V. cholerae O1 and O139 lineages, respectively, within a period of only a few years. SXT-R391 ICEs have been recognized as key vectors of antibiotic resistance in the seventh-pandemic lineage of V. cholerae, which remains a major cause of mortality and morbidity on a global scale. ICEs were acquired only recently in this clade and are acknowledged to be major contributors to horizontal gene transfer and the acquisition of new traits in bacterial species. We have reconstructed the temporal dynamics of SXT-R391 ICE acquisition and spread and have identified subsequent recombination events generating significant diversity in ICEs currently circulating among V. cholerae clinical strains. Our results showed that acquisition of SXT-R391 ICEs provided the V. cholerae seventh-pandemic lineage not only with a multidrug resistance phenotype but also with a powerful molecular tool for rapidly accessing the pan-genome of a large number of gammaproteobacteria. Copyright © 2014 Spagnoletti et al.

Phylogeographic diversity and mosaicism of the Helicobacter pylori tfs integrative and conjugative elements.

PubMed

Delahay, Robin M; Croxall, Nicola J; Stephens, Amberley D

2018-01-01

The genome of the gastric pathogen Helicobacter pylori is characterised by considerable variation of both gene sequence and content, much of which is contained within three large genomic islands comprising the cag pathogenicity island ( cag PAI) and two mobile integrative and conjugative elements (ICEs) termed tfs3 and tfs4 . All three islands are implicated as virulence factors, although whereas the cag PAI is well characterised, understanding of how the tfs elements influence H. pylori interactions with different human hosts is significantly confounded by limited definition of their distribution, diversity and structural representation in the global H. pylori population. To gain a global perspective of tfs ICE population dynamics we established a bioinformatics workflow to extract and precisely define the full tfs pan-gene content contained within a global collection of 221 draft and complete H. pylori genome sequences. Complete (ca. 35-55kbp) and remnant tfs ICE clusters were reconstructed from a dataset comprising > 12,000 genes, from which orthologous gene complements and distinct alleles descriptive of different tfs ICE types were defined and classified in comparative analyses. The genetic variation within defined ICE modular segments was subsequently used to provide a complete description of tfs ICE diversity and a comprehensive assessment of their phylogeographic context. Our further examination of the apparent ICE modular types identified an ancient and complex history of ICE residence, mobility and interaction within particular H. pylori phylogeographic lineages and further, provided evidence of both contemporary inter-lineage and inter-species ICE transfer and displacement. Our collective results establish a clear view of tfs ICE diversity and phylogeographic representation in the global H. pylori population, and provide a robust contextual framework for elucidating the functional role of the tfs ICEs particularly as it relates to the risk of gastric disease associated with different tfs ICE genotypes.

Interactions between inner membrane proteins in donor and recipient cells limit conjugal DNA transfer.

PubMed

Marrero, Joeli; Waldor, Matthew K

2005-06-01

Conjugation enables horizontal transmission of DNA among bacteria, thereby facilitating the rapid spread of genes such as those conferring resistance to antibiotics. Cell-cell contact is required for conjugative DNA transfer but does not ensure its success. The presence of certain plasmids in potential recipient cells inhibits redundant transfer of these plasmids from competent donors despite contact between donor and recipient cells. Here, we used two closely related integrating conjugative elements (ICEs), SXT and R391, to identify genes that inhibit redundant conjugative transfer. Cells containing SXT exclude transfer of a second copy of SXT but not R391 and vice versa. The specific exclusion of SXT and R391 is dependent upon variants of TraG and Eex, ICE-encoded inner membrane proteins in donor and recipient cells, respectively. We identified short sequences within each variant that determine the exquisite specificity of self-recognition; these data suggest that direct interactions between TraG and Eex mediate exclusion.

ICESag37, a Novel Integrative and Conjugative Element Carrying Antimicrobial Resistance Genes and Potential Virulence Factors in Streptococcus agalactiae.

PubMed

Zhou, Kaixin; Xie, Lianyan; Han, Lizhong; Guo, Xiaokui; Wang, Yong; Sun, Jingyong

2017-01-01

ICE Sag37 , a novel integrative and conjugative element carrying multidrug resistance and potential virulence factors, was characterized in a clinical isolate of Streptococcus agalactiae . Two clinical strains of S. agalactiae , Sag37 and Sag158, were isolated from blood samples of new-borns with bacteremia. Sag37 was highly resistant to erythromycin and tetracycline, and susceptible to levofloxacin and penicillin, while Sag158 was resistant to tetracycline and levofloxacin, and susceptible to erythromycin. Transfer experiments were performed and selection was carried out with suitable antibiotic concentrations. Through mating experiments, the erythromycin resistance gene was found to be transferable from Sag37 to Sag158. Sma I-PFGE revealed a new Sma I fragment, confirming the transfer of the fragment containing the erythromycin resistance gene. Whole genome sequencing and sequence analysis revealed a mobile element, ICE Sag37 , which was characterized using several molecular methods and in silico analyses. ICE Sag37 was excised to generate a covalent circular intermediate, which was transferable to S. agalactiae . Inverse PCR was performed to detect the circular form. A serine family integrase mediated its chromosomal integration into rumA , which is a known hotspot for the integration of streptococcal ICEs. The integration site was confirmed using PCR. ICE Sag37 carried genes for resistance to multiple antibiotics, including erythromycin [ erm(B) ], tetracycline [ tet(O) ], and aminoglycosides [ aadE, aphA , and ant(6) ]. Potential virulence factors, including a two-component signal transduction system ( nisK/nisR ), were also observed in ICE Sag37 . S1-PFGE analysis ruled out the existence of plasmids. ICE Sag37 is the first ICE Sa2603 family-like element identified in S. agalactiae carrying both resistance and potential virulence determinants. It might act as a vehicle for the dissemination of multidrug resistance and pathogenicity among S. agalactiae .

Horizontal Gene Transfers in Mycoplasmas (Mollicutes).

PubMed

Citti, C; Dordet-Frisoni, E; Nouvel, L X; Kuo, C H; Baranowski, E

2018-04-12

The class Mollicutes (trivial name "mycoplasma") is composed of wall-less bacteria with reduced genomes whose evolution was long thought to be only driven by gene losses. Recent evidences of massive horizontal gene transfer (HGT) within and across species provided a new frame to understand the successful adaptation of these minimal bacteria to a broad range of hosts. Mobile genetic elements are being identified in a growing number of mycoplasma species, but integrative and conjugative elements (ICEs) are emerging as pivotal in HGT. While sharing common traits with other bacterial ICEs, such as their chromosomal integration and the use of a type IV secretion system to mediate horizontal dissemination, mycoplasma ICEs (MICEs) revealed unique features: their chromosomal integration is totally random and driven by a DDE recombinase related to the Mutator-like superfamily. Mycoplasma conjugation is not restricted to ICE transmission, but also involves the transfer of large chromosomal fragments that generates progenies with mosaic genomes, nearly every position of chromosome being mobile. Mycoplasmas have thus developed efficient ways to gain access to a considerable reservoir of genetic resources distributed among a vast number of species expanding the concept of minimal cell to the broader context of flowing information.

Evolution and Diversity of the Antimicrobial Resistance Associated Mobilome in Streptococcus suis: A Probable Mobile Genetic Elements Reservoir for Other Streptococci.

PubMed

Huang, Jinhu; Ma, Jiale; Shang, Kexin; Hu, Xiao; Liang, Yuan; Li, Daiwei; Wu, Zuowei; Dai, Lei; Chen, Li; Wang, Liping

2016-01-01

Streptococcus suis is a previously neglected, newly emerging multidrug-resistant zoonotic pathogen. Mobile genetic elements (MGEs) play a key role in intra- and interspecies horizontal transfer of antimicrobial resistance (AMR) determinants. Although, previous studies showed the presence of several MGEs, a comprehensive analysis of AMR-associated mobilome as well as their interaction and evolution has not been performed. In this study, we presented the AMR-associated mobilome and their insertion hotspots in S. suis . Integrative conjugative elements (ICEs), prophages and tandem MGEs were located at different insertion sites, while 86% of the AMR-associated MGEs were inserted at rplL and rum loci. Comprehensive analysis of insertions at rplL and rum loci among four pathogenic Streptococcus species ( Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes , and S. suis ) revealed the existence of different groups of MGEs, including Tn5252, ICE Sp 1108, and TnGBS2 groups ICEs, Φm46.1 group prophage, ICE_ICE and ICE_prophage tandem MGEs. Comparative ICE genomics of ICE Sa 2603 family revealed that module exchange and acquisition/deletion were the main mechanisms in MGEs' expansion and evolution. Furthermore, the observation of tandem MGEs reflected a novel mechanism for MGE diversity. Moreover, an in vitro competition assay showed no visible fitness cost was observed between different MGE-carrying isolates and a conjugation assay revealed the transferability of ICE Sa 2603 family of ICEs. Our statistics further indicated that the prevalence and diversity of MGEs in S. suis is much greater than in other three species which prompted our hypothesis that S. suis is probably a MGEs reservoir for other streptococci. In conclusion, our results showed that acquisition of MGEs confers S. suis not only its capability as a multidrug resistance pathogen, but also represents a paradigm to study the modular evolution and matryoshkas of MGEs.

Macrolide resistance gene erm(TR) and erm(TR)-carrying genetic elements in Streptococcus agalactiae: characterization of ICESagTR7, a new composite element containing IMESp2907.

PubMed

Mingoia, Marina; Morici, Eleonora; Marini, Emanuela; Brenciani, Andrea; Giovanetti, Eleonora; Varaldo, Pietro E

2016-03-01

The objective of this study was to investigate macrolide-resistant Streptococcus agalactiae isolates harbouring erm(TR), an erm(A) gene subclass, with emphasis on their erm(TR)-carrying genetic elements. Four erm(TR)-carrying elements have been described to date: three closely related (ICE10750-RD.2, Tn1806 and ICESp1108) in Streptococcus pyogenes, Streptococcus pneumoniae and S. pyogenes, respectively; and one completely different (IMESp2907, embedded in ICESp2906 to form ICESp2905) in S. pyogenes. Seventeen macrolide-resistant erm(TR)-positive S. agalactiae isolates were phenotypically and genotypically characterized. Their erm(TR)-carrying elements were explored by analysing the distinctive recombination genes of known erm(TR)-carrying integrative and conjugative elements (ICEs) and by PCR mapping. The new genetic context and organization of IMESp2907 in S. agalactiae were explored using several experimental procedures and in silico analyses. Five isolates harboured ICE10750-RD.2/Tn1806, five isolates harboured ICESp1108 and five isolates bore unknown erm(TR)-carrying elements. The remaining two isolates, exhibiting identical serotypes and pulsotypes, harboured IMESp2907 in a new genetic environment, which was further investigated in one of the two isolates, SagTR7. IMESp2907 was circularizable in S. agalactiae, as described in S. pyogenes. The new IMESp2907 junctions were identified based on its site-specific integration; the att sites were almost identical to those in S. pyogenes. In strain SagTR7, erm(TR)-carrying IMESp2907 was embedded in an erm(TR)-less internal element related to ICE10750-RD.2/Tn1806, which, in turn, was embedded in an ICESde3396-like element. The resulting whole ICE, ICESagTR7 (∼129 kb), was integrated into the chromosome downstream of the rplL gene, and was excisable in circular form and transferable by conjugation. This is the first study exploring erm(TR)-carrying genetic elements in S. agalactiae. © The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Evolution and Diversity of the Antimicrobial Resistance Associated Mobilome in Streptococcus suis: A Probable Mobile Genetic Elements Reservoir for Other Streptococci

PubMed Central

Huang, Jinhu; Ma, Jiale; Shang, Kexin; Hu, Xiao; Liang, Yuan; Li, Daiwei; Wu, Zuowei; Dai, Lei; Chen, Li; Wang, Liping

2016-01-01

Streptococcus suis is a previously neglected, newly emerging multidrug-resistant zoonotic pathogen. Mobile genetic elements (MGEs) play a key role in intra- and interspecies horizontal transfer of antimicrobial resistance (AMR) determinants. Although, previous studies showed the presence of several MGEs, a comprehensive analysis of AMR-associated mobilome as well as their interaction and evolution has not been performed. In this study, we presented the AMR-associated mobilome and their insertion hotspots in S. suis. Integrative conjugative elements (ICEs), prophages and tandem MGEs were located at different insertion sites, while 86% of the AMR-associated MGEs were inserted at rplL and rum loci. Comprehensive analysis of insertions at rplL and rum loci among four pathogenic Streptococcus species (Streptococcus agalactiae, Streptococcus pneumoniae, Streptococcus pyogenes, and S. suis) revealed the existence of different groups of MGEs, including Tn5252, ICESp1108, and TnGBS2 groups ICEs, Φm46.1 group prophage, ICE_ICE and ICE_prophage tandem MGEs. Comparative ICE genomics of ICESa2603 family revealed that module exchange and acquisition/deletion were the main mechanisms in MGEs' expansion and evolution. Furthermore, the observation of tandem MGEs reflected a novel mechanism for MGE diversity. Moreover, an in vitro competition assay showed no visible fitness cost was observed between different MGE-carrying isolates and a conjugation assay revealed the transferability of ICESa2603 family of ICEs. Our statistics further indicated that the prevalence and diversity of MGEs in S. suis is much greater than in other three species which prompted our hypothesis that S. suis is probably a MGEs reservoir for other streptococci. In conclusion, our results showed that acquisition of MGEs confers S. suis not only its capability as a multidrug resistance pathogen, but also represents a paradigm to study the modular evolution and matryoshkas of MGEs. PMID:27774436

Comparative analysis of the Hrp pathogenicity island of Rubus- and Spiraeoideae-infecting Erwinia amylovora strains identifies the IT region as a remnant of an integrative conjugative element.

PubMed

Mann, Rachel A; Blom, Jochen; Bühlmann, Andreas; Plummer, Kim M; Beer, Steven V; Luck, Joanne E; Goesmann, Alexander; Frey, Jürg E; Rodoni, Brendan C; Duffy, Brion; Smits, Theo H M

2012-08-01

The Hrp pathogenicity island (hrpPAI) of Erwinia amylovora not only encodes a type III secretion system (T3SS) and other genes required for pathogenesis on host plants, but also includes the so-called island transfer (IT) region, a region that originates from an integrative conjugative element (ICE). Comparative genomic analysis of the IT regions of two Spiraeoideae- and three Rubus-infecting strains revealed that the regions in Spiraeoideae-infecting strains were syntenic and highly conserved in length and genetic information, but that the IT regions of the Rubus-infecting strains varied in gene content and length, showing a mosaic structure. None of the ICEs in E. amylovora strains were complete, as conserved ICE genes and the left border were missing, probably due to reductive genome evolution. Comparison of the hrpPAI region of E. amylovora strains to syntenic regions from other Erwinia spp. indicates that the hrpPAI and the IT regions are the result of several insertion and deletion events that have occurred within the ICE. It also suggests that the T3SS was present in a common ancestor of the pathoadapted Erwinia spp. and that insertion and deletion events in the IT region occurred during speciation. Copyright © 2012 Elsevier B.V. All rights reserved.

Pathogens of Bovine Respiratory Disease in North American Feedlots Conferring Multidrug Resistance via Integrative Conjugative Elements

PubMed Central

Klima, Cassidy L.; Zaheer, Rahat; Cook, Shaun R.; Booker, Calvin W.; Hendrick, Steve

2014-01-01

In this study, we determined the prevalence of bovine respiratory disease (BRD)-associated viral and bacterial pathogens in cattle and characterized the genetic profiles, antimicrobial susceptibilities, and nature of antimicrobial resistance determinants in collected bacteria. Nasopharyngeal swab and lung tissue samples from 68 BRD mortalities in Alberta, Canada (n = 42), Texas (n = 6), and Nebraska (n = 20) were screened using PCR for bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus, bovine herpesvirus 1, parainfluenza type 3 virus, Mycoplasma bovis, Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. Excepting bovine herpesvirus 1, all agents were detected. M. haemolytica (91%) and BVDV (69%) were the most prevalent, with cooccurrence in 63% of the cattle. Isolates of M. haemolytica (n = 55), P. multocida (n = 8), and H. somni (n = 10) from lungs were also collected. Among M. haemolytica isolates, a clonal subpopulation (n = 8) was obtained from a Nebraskan feedlot. All three bacterial pathogens exhibited a high rate of antimicrobial resistance, with 45% exhibiting resistance to three or more antimicrobials. M. haemolytica (n = 18), P. multocida (n = 3), and H. somni (n = 3) from Texas and Nebraska possessed integrative conjugative elements (ICE) that conferred resistance for up to seven different antimicrobial classes. ICE were shown to be transferred via conjugation from P. multocida to Escherichia coli and from M. haemolytica and H. somni to P. multocida. ICE-mediated multidrug-resistant profiles of bacterial BRD pathogens could be a major detriment to many of the therapeutic antimicrobial strategies currently used to control BRD. PMID:24478472

Pathogens of bovine respiratory disease in North American feedlots conferring multidrug resistance via integrative conjugative elements.

PubMed

Klima, Cassidy L; Zaheer, Rahat; Cook, Shaun R; Booker, Calvin W; Hendrick, Steve; Alexander, Trevor W; McAllister, Tim A

2014-02-01

In this study, we determined the prevalence of bovine respiratory disease (BRD)-associated viral and bacterial pathogens in cattle and characterized the genetic profiles, antimicrobial susceptibilities, and nature of antimicrobial resistance determinants in collected bacteria. Nasopharyngeal swab and lung tissue samples from 68 BRD mortalities in Alberta, Canada (n = 42), Texas (n = 6), and Nebraska (n = 20) were screened using PCR for bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus, bovine herpesvirus 1, parainfluenza type 3 virus, Mycoplasma bovis, Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. Excepting bovine herpesvirus 1, all agents were detected. M. haemolytica (91%) and BVDV (69%) were the most prevalent, with cooccurrence in 63% of the cattle. Isolates of M. haemolytica (n = 55), P. multocida (n = 8), and H. somni (n = 10) from lungs were also collected. Among M. haemolytica isolates, a clonal subpopulation (n = 8) was obtained from a Nebraskan feedlot. All three bacterial pathogens exhibited a high rate of antimicrobial resistance, with 45% exhibiting resistance to three or more antimicrobials. M. haemolytica (n = 18), P. multocida (n = 3), and H. somni (n = 3) from Texas and Nebraska possessed integrative conjugative elements (ICE) that conferred resistance for up to seven different antimicrobial classes. ICE were shown to be transferred via conjugation from P. multocida to Escherichia coli and from M. haemolytica and H. somni to P. multocida. ICE-mediated multidrug-resistant profiles of bacterial BRD pathogens could be a major detriment to many of the therapeutic antimicrobial strategies currently used to control BRD.

Unveiling the pan-genome of the SXT/R391 family of ICEs: molecular characterisation of new variable regions of SXT/R391-like ICEs detected in Pseudoalteromonas sp. and Vibrio scophthalmi.

PubMed

Rodríguez-Blanco, Arturo; Lemos, Manuel L; Osorio, Carlos R

2016-08-01

Integrating conjugative elements (ICEs) of the SXT/R391 family have been identified in fish-isolated bacterial strains collected from marine aquaculture environments of the northwestern Iberian Peninsula. Here we analysed the variable regions of two ICEs, one preliminarily characterised in a previous study (ICEVscSpa3) and one newly identified (ICEPspSpa1). Bacterial strains harboring these ICEs were phylogenetically assigned to Vibrio scophthalmi and Pseudoalteromonas sp., thus constituting the first evidence of SXT/R391-like ICEs in the genus Pseudoalteromonas to date. Variable DNA regions, which confer element-specific properties to ICEs of this family, were characterised. Interestingly, the two ICEs contained 29 genes not found in variable DNA insertions of previously described ICEs. Most notably, variable gene content for ICEVscSpa3 showed similarity to genes potentially involved in housekeeping functions of replication, nucleotide metabolism and transcription. For these genes, closest homologues were found clustered in the genome of Pseudomonas psychrotolerans L19, suggesting a transfer as a block to ICEVscSpa3. Genes encoding antibiotic resistance, restriction modification systems and toxin/antitoxin systems were absent from hotspots of ICEVscSpa3. In contrast, the variable gene content of ICEPspSpa1 included genes involved in restriction/modification functions in two different hotspots and genes related to ICE maintenance. The present study unveils a relatively large number of novel genes in SXT/R391-ICEs, and demonstrates the major role of ICE elements as contributors to horizontal gene transfer.

Comparative genomic analysis of six new-found integrative conjugative elements (ICEs) in Vibrio alginolyticus.

PubMed

Luo, Peng; He, Xiangyan; Wang, Yanhong; Liu, Qiuting; Hu, Chaoqun

2016-05-04

Vibrio alginolyticus is ubiquitous in marine and estuarine environments. In 2012-2013, SXT/R391-like integrative conjugative elements (ICEs) in environmental V. alginolyticus strains were discovered and found to occur in 8.9 % of 192 V. alginolyticus strains, which suggests that V. alginolyticus may be a natural pool possessing resourceful ICEs. However, complete ICE sequences originating from this bacterium have not been reported, which represents a significant barrier to characterizing the ICEs of this bacterium and exploring their relationships with other ICEs. In the present study, we acquired six ICE sequences from five V. alginolyticus strains and performed a comparative analysis of these ICE genomes. A sequence analysis showed that there were only 14 variable bases dispersed between ICEValE0601 and ICEValHN492. ICEValE0601 and ICEValHN492 were treated as the same ICE. ICEValA056-1, ICEValE0601 and ICEValHN492 integrate into the 5' end of the host's prfC gene, and their Int and Xis share at least 97 % identity with their counterparts from SXT. ICEValE0601 or ICEValHN492 contain 50 of 52 conserved core genes in the SXT/R391 ICEs (not s025 or s026). ICEValA056-2, ICEValHN396 and ICEValHN437 have a different tRNA-ser integration site and a distinct int/xis module; however, the remaining backbone genes are highly similar to their counterparts in SXT/R391 ICEs. DNA sequences inserted into hotspot and variable regions of the ICEs are of various sizes. The variable genes of six ICEs encode a large array of functions to bestow various adaptive abilities upon their hosts, and only ICEValA056-1 contains drug-resistant genes. Many variable genes have orthologous and functionally related genes to those found in SXT/R391 ICEs, such as genes coding for a toxin-antitoxin system, a restriction-modification system, helicases and endonucleases. Six ICEs also contain a large number of unique genes or gene clusters that were not found in other ICEs. Six ICEs harbor more abundant transposase genes compared with other parts of their host genomes. A phylogenetic analysis indicated that transposase genes in these ICEs are highly diverse. ICEValA056-1, ICEValE0601 and ICEValHN492 are typical members of the SXT/R391 family. ICEValA056-2, ICEValHN396 and ICEValHN437 form a new atypical group belonging to the SXT/R391 family. In addition to the many genes found to be present in other ICEs, six ICEs contain a large number of unique genes or gene clusters that were not found in other ICEs. ICEs may serve as a carrier for transposable genetic elements (TEs) and largely facilitate the dissemination of TEs.

A new mosaic integrative and conjugative element from Streptococcus agalactiae carrying resistance genes for chloramphenicol (catQ) and macrolides [mef(I) and erm(TR)].

PubMed

Morici, Eleonora; Simoni, Serena; Brenciani, Andrea; Giovanetti, Eleonora; Varaldo, Pietro E; Mingoia, Marina

2017-01-01

To investigate the genetic basis of catQ-mediated chloramphenicol resistance in Streptococcus agalactiae. Two clinical strains of catQ-positive chloramphenicol-resistant S. agalactiae (Sag236 and Sag403) were recently isolated, typed (MLST, PFGE pulsotypes, capsular types) and their antibiotic resistances investigated by phenotypic and genotypic approaches. Several molecular methods (PCR mapping, restriction assays, Southern blotting, sequencing and sequence analysis, conjugal transfer assays) were used to determine the genetic context of catQ and characterize a genetic element detected in the isolates. Sag236 and Sag403 shared the same ST (ST19), but exhibited a different capsular type (III and V, respectively) and pulsotype. Both harboured the macrolide resistance genes mef(I) and erm(TR) and the tetracycline resistance gene tet(M). Accordingly, they were resistant to chloramphenicol, erythromycin and tetracycline. catQ and mef(I) were associated in an IQ module that was indistinguishable in Sag236 and Sag403. In mating assays, chloramphenicol and erythromycin resistance proved transferable, at low frequency, only from Sag236. Transconjugants carried not only catQ and mef(I), but also erm(TR), suggesting a linkage of the three resistance genes in a mobile element, which, though seemingly non-mobile, was also detected in Sag403. The new element (designated ICESag236, ∼110 kb) results from recombination of two integrative and conjugative elements (ICEs) originally described in different streptococcal species: S. agalactiae ICESagTR7, carrying erm(TR); and Streptococcus pneumoniae ICESpn529IQ, carrying the prototype IQ module. These findings strengthen the notion that widespread streptococcal ICEs may form mosaics that enhance their diversity and spread, broaden their host range and carry new cargo genes. © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Plant nodulation inducers enhance horizontal gene transfer of Azorhizobium caulinodans symbiosis island.

PubMed

Ling, Jun; Wang, Hui; Wu, Ping; Li, Tao; Tang, Yu; Naseer, Nawar; Zheng, Huiming; Masson-Boivin, Catherine; Zhong, Zengtao; Zhu, Jun

2016-11-29

Horizontal gene transfer (HGT) of genomic islands is a driving force of bacterial evolution. Many pathogens and symbionts use this mechanism to spread mobile genetic elements that carry genes important for interaction with their eukaryotic hosts. However, the role of the host in this process remains unclear. Here, we show that plant compounds inducing the nodulation process in the rhizobium-legume mutualistic symbiosis also enhance the transfer of symbiosis islands. We demonstrate that the symbiosis island of the Sesbania rostrata symbiont, Azorhizobium caulinodans, is an 87.6-kb integrative and conjugative element (ICE Ac ) that is able to excise, form a circular DNA, and conjugatively transfer to a specific site of gly-tRNA gene of other rhizobial genera, expanding their host range. The HGT frequency was significantly increased in the rhizosphere. An ICE Ac -located LysR-family transcriptional regulatory protein AhaR triggered the HGT process in response to plant flavonoids that induce the expression of nodulation genes through another LysR-type protein, NodD. Our study suggests that rhizobia may sense rhizosphere environments and transfer their symbiosis gene contents to other genera of rhizobia, thereby broadening rhizobial host-range specificity.

Biology of Three ICE Families: SXT/R391, ICEBs1, and ICESt1/ICESt3.

PubMed

Carraro, Nicolas; Burrus, Vincent

2014-12-01

Integrative and Conjugative Elements (ICEs) are bacterial mobile genetic elements that play a key role in bacterial genomes dynamics and evolution. ICEs are widely distributed among virtually all bacterial genera. Recent extensive studies have unraveled their high diversity and complexity. The present review depicts the general conserved features of ICEs and describes more precisely three major families of ICEs that have been extensively studied in the past decade for their biology, their evolution and their impact on genomes dynamics. First, the large SXT/R391 family of ICEs disseminates antibiotic resistance genes and drives the exchange of mobilizable genomic islands (MGIs) between many enteric pathogens such as Vibrio cholerae. Second, ICEBs1 of Bacillus subtilis is the most well understood ICE of Gram-positive bacteria, notably regarding the regulation of its dissemination and its initially unforeseen extrachromosomal replication, which could be a common feature of ICEs of both Gram-positive and Gram-negative bacteria. Finally, ICESt1 and ICESt3 of Streptococcus thermophilus are the prototypes of a large family of ICEs widely distributed among various streptococci. These ICEs carry an original regulation module that associates regulators related to those of both SXT/R391 and ICEBs1. Study of ICESt1 and ICESt3 uncovered the cis-mobilization of related genomic islands (CIMEs) by a mechanism called accretion-mobilization, which likely represents a paradigm for the evolution of many ICEs and genomic islands. These three major families of ICEs give a glimpse about ICEs dynamics and their high impact on bacterial adaptation.

Genome Sequence of Vibrio cholerae Strain O1 Ogawa El Tor, Isolated in Mexico, 2013

PubMed Central

Hernández-Monroy, Irma; López-Martínez, Irma; Ortiz-Alcántara, Joanna; González-Durán, Elizabeth; Ruiz-Matus, Cuitláhuac; Kuri-Morales, Pablo; Ramírez-González, José Ernesto

2014-01-01

We present the draft genome sequence of Vibrio cholerae InDRE 3140 recovered in 2013 during a cholera outbreak in Mexico. The genome showed the Vibrio 7th pandemic islands VSP1 and VSP2, the pathogenic islands VPI-1 and VPI-2, the integrative and conjugative element SXT/R391 (ICE-SXT), and both prophages CTXφ and RS1φ. PMID:25359919

The Diversity of Prokaryotic DDE Transposases of the Mutator Superfamily, Insertion Specificity, and Association with Conjugation Machineries

PubMed Central

Guérillot, Romain; Siguier, Patricia; Gourbeyre, Edith; Chandler, Michael; Glaser, Philippe

2014-01-01

Transposable elements (TEs) are major components of both prokaryotic and eukaryotic genomes and play a significant role in their evolution. In this study, we have identified new prokaryotic DDE transposase families related to the eukaryotic Mutator-like transposases. These genes were retrieved by cascade PSI-Blast using as initial query the transposase of the streptococcal integrative and conjugative element (ICE) TnGBS2. By combining secondary structure predictions and protein sequence alignments, we predicted the DDE catalytic triad and the DNA-binding domain recognizing the terminal inverted repeats. Furthermore, we systematically characterized the organization and the insertion specificity of the TEs relying on these prokaryotic Mutator-like transposases (p-MULT) for their mobility. Strikingly, two distant TE families target their integration upstream σA dependent promoters. This allowed us to identify a transposase sequence signature associated with this unique insertion specificity and to show that the dissymmetry between the two inverted repeats is responsible for the orientation of the insertion. Surprisingly, while DDE transposases are generally associated with small and simple transposons such as insertion sequences (ISs), p-MULT encoding TEs show an unprecedented diversity with several families of IS, transposons, and ICEs ranging in size from 1.1 to 52 kb. PMID:24418649

A globally distributed mobile genetic element inhibits natural transformation of Vibrio cholerae

PubMed Central

Dalia, Ankur B.; Seed, Kimberley D.; Calderwood, Stephen B.; Camilli, Andrew

2015-01-01

Natural transformation is one mechanism of horizontal gene transfer (HGT) in Vibrio cholerae, the causative agent of cholera. Recently, it was found that V. cholerae isolates from the Haiti outbreak were poorly transformed by this mechanism. Here, we show that an integrating conjugative element (ICE)-encoded DNase, which we name IdeA, is necessary and sufficient for inhibiting natural transformation of Haiti outbreak strains. We demonstrate that IdeA inhibits this mechanism of HGT in cis via DNA endonuclease activity that is localized to the periplasm. Furthermore, we show that natural transformation between cholera strains in a relevant environmental context is inhibited by IdeA. The ICE encoding IdeA is globally distributed. Therefore, we analyzed the prevalence and role for this ICE in limiting natural transformation of isolates from Bangladesh collected between 2001 and 2011. We found that IdeA+ ICEs were nearly ubiquitous in isolates from 2001 to 2005; however, their prevalence decreased to ∼40% from 2006 to 2011. Thus, IdeA+ ICEs may have limited the role of natural transformation in V. cholerae. However, the rise in prevalence of strains lacking IdeA may now increase the role of this conserved mechanism of HGT in the evolution of this pathogen. PMID:26240317

Combinatorial events of insertion sequences and ICE in Gram-negative bacteria.

PubMed

Toleman, Mark A; Walsh, Timothy R

2011-09-01

The emergence of antibiotic and antimicrobial resistance in Gram-negative bacteria is incremental and linked to genetic elements that function in a so-called 'one-ended transposition' manner, including ISEcp1, ISCR elements and Tn3-like transposons. The power of these elements lies in their inability to consistently recognize one of their own terminal sequences, while recognizing more genetically distant surrogate sequences. This has the effect of mobilizing the DNA sequence found adjacent to their initial location. In general, resistance in Gram-negatives is closely linked to a few one-off events. These include the capture of the class 1 integron by a Tn5090-like transposon; the formation of the 3' conserved segment (3'-CS); and the fusion of the ISCR1 element to the 3'-CS. The structures formed by these rare events have been massively amplified and disseminated in Gram-negative bacteria, but hitherto, are rarely found in Gram-positives. Such events dominate current resistance gene acquisition and are instrumental in the construction of large resistance gene islands on chromosomes and plasmids. Similar combinatorial events appear to have occurred between conjugative plasmids and phages constructing hybrid elements called integrative and conjugative elements or conjugative transposons. These elements are beginning to be closely linked to some of the more powerful resistance mechanisms such as the extended spectrum β-lactamases, metallo- and AmpC type β-lactamases. Antibiotic resistance in Gram-negative bacteria is dominated by unusual combinatorial mistakes of Insertion sequences and gene fusions which have been selected and amplified by antibiotic pressure enabling the formation of extended resistance islands. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer

PubMed Central

Lorenzo-Diaz, Fabian; Fernández-Lopez, Cris; Douarre, Pierre-Emmanuel; Baez-Ortega, Adrian; Flores, Carlos; Glaser, Philippe

2016-01-01

Streptococcus agalactiae or Group B Streptococcus (GBS) are opportunistic bacteria that can cause lethal sepsis in children and immuno-compromised patients. Their genome is a reservoir of mobile genetic elements that can be horizontally transferred. Among them, integrative and conjugative elements (ICEs) and the smaller integrative and mobilizable elements (IMEs) primarily reside in the bacterial chromosome, yet have the ability to be transferred between cells by conjugation. ICEs and IMEs are therefore a source of genetic variability that participates in the spread of antibiotic resistance. Although IMEs seem to be the most prevalent class of elements transferable by conjugation, they are poorly known. Here, we have studied a GBS-IME, termed IMESag-rpsI, which is widely distributed in GBS despite not carrying any apparent virulence trait. Analyses of 240 whole genomes showed that IMESag-rpsI is present in approximately 47% of the genomes, has a roughly constant size (approx. 9 kb) and is always integrated at a single location, the 3′-end of the gene encoding the ribosomal protein S9 (rpsI). Based on their genetic variation, several IMESag-rpsI types were defined (A–J) and classified in clonal complexes (CCs). CC1 was the most populated by IMESag-rpsI (more than 95%), mostly of type-A (71%). One CC1 strain (S. agalactiae HRC) was deep-sequenced to understand the rationale underlying type-A IMESag-rpsI enrichment in GBS. Thirteen open reading frames were identified, one of them encoding a protein (MobSag) belonging to the broadly distributed family of relaxases MOBV1. Protein MobSag was purified and, by a newly developed method, shown to cleave DNA at a specific dinucleotide. The S. agalactiae HRC-IMESag-rpsI is able to excise from the chromosome, as shown by the presence of circular intermediates, and it harbours a fully functional mobilization module. Further, the mobSag gene encoded by this mobile element is able to promote plasmid transfer among pneumococcal strains, suggesting that MobSag facilitates the spread of IMESag-rpsI and that this spread would explain the presence of the same IMESag-rpsI type in GBS strains belonging to different CCs. PMID:27707895

Streptococcal group B integrative and mobilizable element IMESag-rpsI encodes a functional relaxase involved in its transfer.

PubMed

Lorenzo-Diaz, Fabian; Fernández-Lopez, Cris; Douarre, Pierre-Emmanuel; Baez-Ortega, Adrian; Flores, Carlos; Glaser, Philippe; Espinosa, Manuel

2016-10-01

Streptococcus agalactiae or Group B Streptococcus (GBS) are opportunistic bacteria that can cause lethal sepsis in children and immuno-compromised patients. Their genome is a reservoir of mobile genetic elements that can be horizontally transferred. Among them, integrative and conjugative elements (ICEs) and the smaller integrative and mobilizable elements (IMEs) primarily reside in the bacterial chromosome, yet have the ability to be transferred between cells by conjugation. ICEs and IMEs are therefore a source of genetic variability that participates in the spread of antibiotic resistance. Although IMEs seem to be the most prevalent class of elements transferable by conjugation, they are poorly known. Here, we have studied a GBS-IME, termed IMESag-rpsI, which is widely distributed in GBS despite not carrying any apparent virulence trait. Analyses of 240 whole genomes showed that IMESag-rpsI is present in approximately 47% of the genomes, has a roughly constant size (approx. 9 kb) and is always integrated at a single location, the 3'-end of the gene encoding the ribosomal protein S9 (rpsI). Based on their genetic variation, several IMESag-rpsI types were defined (A-J) and classified in clonal complexes (CCs). CC1 was the most populated by IMESag-rpsI (more than 95%), mostly of type-A (71%). One CC1 strain (S. agalactiae HRC) was deep-sequenced to understand the rationale underlying type-A IMESag-rpsI enrichment in GBS. Thirteen open reading frames were identified, one of them encoding a protein (MobSag) belonging to the broadly distributed family of relaxases MOB V1 Protein MobSag was purified and, by a newly developed method, shown to cleave DNA at a specific dinucleotide. The S. agalactiae HRC-IMESag-rpsI is able to excise from the chromosome, as shown by the presence of circular intermediates, and it harbours a fully functional mobilization module. Further, the mobSag gene encoded by this mobile element is able to promote plasmid transfer among pneumococcal strains, suggesting that MobSag facilitates the spread of IMESag-rpsI and that this spread would explain the presence of the same IMESag-rpsI type in GBS strains belonging to different CCs. © 2016 The Authors.

Genome Sequence of Vibrio cholerae Strain O1 Ogawa El Tor, Isolated in Mexico, 2013.

PubMed

Díaz-Quiñonez, José Alberto; Hernández-Monroy, Irma; López-Martínez, Irma; Ortiz-Alcántara, Joanna; González-Durán, Elizabeth; Ruiz-Matus, Cuitláhuac; Kuri-Morales, Pablo; Ramírez-González, José Ernesto

2014-10-30

We present the draft genome sequence of Vibrio cholerae InDRE 3140 recovered in 2013 during a cholera outbreak in Mexico. The genome showed the Vibrio 7th pandemic islands VSP1 and VSP2, the pathogenic islands VPI-1 and VPI-2, the integrative and conjugative element SXT/R391 (ICE-SXT), and both prophages CTXφ and RS1φ. Copyright © 2014 Díaz-Quiñonez et al.

Genome analysis of a clinical isolate of Shewanella sp. uncovered an active hybrid integrative and conjugative element carrying an integron platform inserted in a novel genomic locus.

PubMed

Parmeciano Di Noto, Gisela; Jara, Eugenio; Iriarte, Andrés; Centrón, Daniela; Quiroga, Cecilia

2016-08-01

Shewanella spp. are currently considered to be emerging pathogens that can code for a blaOXA carbapenemase in their chromosome. Complete genome analysis of the clinical isolate Shewanella sp. Sh95 revealed that this strain is a novel species, which shares a lineage with marine isolates. Characterization of its resistome showed that it codes for genes drfA15, qacH and blaOXA-48. We propose that Shewanella sp. Sh95 acts as reservoir of blaOXA-48. Moreover, analysis of mobilome showed that it contains a novel integrative and conjugative element (ICE), named ICESh95. Comparative analysis between the close relatives ICESpuPO1 from Shewanella sp. W3-18-1 and ICE SXTMO10 from Vibrio cholerae showed that ICESh95 encompassed two new regions, a type III restriction modification system and a multidrug resistance integron. The integron platform contained a novel arrangement formed by gene cassettes drfA15 and qacH, and a class C-attC group II intron. Furthermore, insertion of ICESh95 occurred at a unique target site, which correlated with the presence of a different xis/int module. Mobility of ICESh95 was assessed and demonstrated its ability to self-transfer with high efficiency to different species of bacteria. Our results show that ICESh95 is a self-transmissible, mobile element, which can contribute to the dissemination of antimicrobial resistance; this is clearly a threat when natural bacteria from water ecosystems, such as Shewanella, act as vectors in its propagation.

Emergence of scarlet fever Streptococcus pyogenes emm12 clones in Hong Kong is associated with toxin acquisition and multidrug resistance.

PubMed

Davies, Mark R; Holden, Matthew T; Coupland, Paul; Chen, Jonathan H K; Venturini, Carola; Barnett, Timothy C; Zakour, Nouri L Ben; Tse, Herman; Dougan, Gordon; Yuen, Kwok-Yung; Walker, Mark J

2015-01-01

A scarlet fever outbreak began in mainland China and Hong Kong in 2011 (refs. 1-6). Macrolide- and tetracycline-resistant Streptococcus pyogenes emm12 isolates represent the majority of clinical cases. Recently, we identified two mobile genetic elements that were closely associated with emm12 outbreak isolates: the integrative and conjugative element ICE-emm12, encoding genes for tetracycline and macrolide resistance, and prophage ΦHKU.vir, encoding the superantigens SSA and SpeC, as well as the DNase Spd1 (ref. 4). Here we sequenced the genomes of 141 emm12 isolates, including 132 isolated in Hong Kong between 2005 and 2011. We found that the introduction of several ICE-emm12 variants, ΦHKU.vir and a new prophage, ΦHKU.ssa, occurred in three distinct emm12 lineages late in the twentieth century. Acquisition of ssa and transposable elements encoding multidrug resistance genes triggered the expansion of scarlet fever-associated emm12 lineages in Hong Kong. The occurrence of multidrug-resistant ssa-harboring scarlet fever strains should prompt heightened surveillance within China and abroad for the dissemination of these mobile genetic elements.

Networking in microbes: conjugative elements and plasmids in the genus Alteromonas.

PubMed

López-Pérez, Mario; Ramon-Marco, Nieves; Rodriguez-Valera, Francisco

2017-01-05

To develop evolutionary models for the free living bacterium Alteromonas the genome sequences of isolates of the genus have been extensively analyzed. However, the main genetic exchange drivers in these microbes, conjugative elements (CEs), have not been considered in detail thus far. In this work, CEs have been searched in several complete Alteromonas genomes and their sequence studied to understand their role in the evolution of this genus. Six genomes are reported here for the first time. We have found nine different plasmids of sizes ranging from 85 to 600 Kb, most of them were found in a single strain. Networks of gene similarity could be established among six of the plasmids that were also connected with another cluster of plasmids found in Shewanella strains. The cargo genes found in these plasmids included cassettes found before in chromosome flexible genomic islands of Alteromonas strains. We describe also the plasmids pAMCP48-600 and pAMCP49-600, the largest found in Alteromonas thus far (ca. 600 Kb) and containing all the hallmarks to be classified as chromids. We found in them some housekeeping genes and a cluster that code for an exocellular polysaccharide. They could represent the transport vectors for the previously described replacement flexible genomic islands. Integrative and conjugative elements (ICEs) were more common than plasmids and showed similar patterns of variation with cargo genes coding for components of additive flexible genomic islands. A nearly identical ICE was found in A. mediterranea MED64 and Vibrio cholera AHV1003 isolated from a human pathogen, indicating the potential exchange of these genes across phylogenetic distances exceeding the family threshold. We have seen evidence of how CEs can be vectors to transfer gene cassettes acquired in the chromosomal flexible genomic islands, both of the additive and replacement kind. These CEs showed evidence of how genetic material is exchanged among members of the same species but also (albeit less frequently) across genus and family barriers. These gradients of exchange frequency are probably one of the main drivers of species origin and maintenance in prokaryotes and also provide these taxa with large genetic diversity.

The Obscure World of Integrative and Mobilizable Elements, Highly Widespread Elements that Pirate Bacterial Conjugative Systems

PubMed Central

Guédon, Gérard; Libante, Virginie; Coluzzi, Charles; Payot, Sophie

2017-01-01

Conjugation is a key mechanism of bacterial evolution that involves mobile genetic elements. Recent findings indicated that the main actors of conjugative transfer are not the well-known conjugative or mobilizable plasmids but are the integrated elements. This paper reviews current knowledge on “integrative and mobilizable elements” (IMEs) that have recently been shown to be highly diverse and highly widespread but are still rarely described. IMEs encode their own excision and integration and use the conjugation machinery of unrelated co-resident conjugative element for their own transfer. Recent studies revealed a much more complex and much more diverse lifecycle than initially thought. Besides their main transmission as integrated elements, IMEs probably use plasmid-like strategies to ensure their maintenance after excision. Their interaction with conjugative elements reveals not only harmless hitchhikers but also hunters that use conjugative elements as target for their integration or harmful parasites that subvert the conjugative apparatus of incoming elements to invade cells that harbor them. IMEs carry genes conferring various functions, such as resistance to antibiotics, that can enhance the fitness of their hosts and that contribute to their maintenance in bacterial populations. Taken as a whole, IMEs are probably major contributors to bacterial evolution. PMID:29165361

A Novel aadA Aminoglycoside Resistance Gene in Bovine and Porcine Pathogens.

PubMed

Cameron, Andrew; Klima, Cassidy L; Ha, Reuben; Gruninger, Robert J; Zaheer, Rahat; McAllister, Tim A

2018-01-01

A novel variant of the AAD(3″) class of aminoglycoside-modifying enzymes was discovered in fatal bovine respiratory disease-associated pathogens Pasteurella multocida and Histophilus somni . The aadA31 gene encodes a spectinomycin/streptomycin adenylyltransferase and was located in a variant of the integrative and conjugative element ICE Mh1 , a mobile genetic element transmissible among members of the family Pasteurellaceae . The gene was also detected in Mannheimia haemolytica from a case of porcine pneumonia and in Moraxella bovoculi from a case of keratoconjunctivitis. IMPORTANCE Aminoglycosides are important antimicrobials used worldwide for prophylaxis and/or therapy in multiple production animal species. The emergence of new resistance genes jeopardizes current pathogen detection and treatment methods. The risk of resistance gene transfer to other animal and human pathogens is elevated when resistance genes are carried by mobile genetic elements. This study identified a new variant of a spectinomycin/streptomycin resistance gene harbored in a self-transmissible mobile element. The gene was also present in four different bovine pathogen species.

Characterization of a Streptococcus suis tet(O/W/32/O)-carrying element transferable to major streptococcal pathogens.

PubMed

Palmieri, Claudio; Magi, Gloria; Mingoia, Marina; Bagnarelli, Patrizia; Ripa, Sandro; Varaldo, Pietro E; Facinelli, Bruna

2012-09-01

Mosaic tetracycline resistance determinants are a recently discovered class of hybrids of ribosomal protection tet genes. They may show different patterns of mosaicism, but their final size has remained unaltered. Initially thought to be confined to a small group of anaerobic bacteria, mosaic tet genes were then found to be widespread. In the genus Streptococcus, a mosaic tet gene [tet(O/W/32/O)] was first discovered in Streptococcus suis, an emerging drug-resistant pig and human pathogen. In this study, we report the molecular characterization of a tet(O/W/32/O) gene-carrying mobile element from an S. suis isolate. tet(O/W/32/O) was detected, in tandem with tet(40), in a circular 14,741-bp genetic element (39.1% G+C; 17 open reading frames [ORFs] identified). The novel element, which we designated 15K, also carried the macrolide resistance determinant erm(B) and an aminoglycoside resistance four-gene cluster including aadE (streptomycin) and aphA (kanamycin). 15K appeared to be an unstable genetic element that, in the absence of recombinases, is capable of undergoing spontaneous excision under standard growth conditions. In the integrated form, 15K was found inside a 54,879-bp integrative and conjugative element (ICE) (50.5% G+C; 55 ORFs), which we designated ICESsu32457. An ∼1.3-kb segment that apparently served as the att site for excision of the unstable 15K element was identified. The novel ICE was transferable at high frequency to recipients from pathogenic Streptococcus species (S. suis, Streptococcus pyogenes, Streptococcus pneumoniae, and Streptococcus agalactiae), suggesting that the multiresistance 15K element can successfully spread within streptococcal populations.

Multivalent Display of Antifreeze Proteins by Fusion to Self-Assembling Protein Cages Enhances Ice-Binding Activities.

PubMed

Phippen, Sean W; Stevens, Corey A; Vance, Tyler D R; King, Neil P; Baker, David; Davies, Peter L

2016-12-13

Antifreeze proteins (AFPs) are small monomeric proteins that adsorb to the surface of ice to inhibit ice crystal growth and impart freeze resistance to the organisms producing them. Previously, monomeric AFPs have been conjugated to the termini of branched polymers to increase their activity through the simultaneous binding of more than one AFP to ice. Here, we describe a superior approach to increasing AFP activity through oligomerization that eliminates the need for conjugation reactions with varying levels of efficiency. A moderately active AFP from a fish and a hyperactive AFP from an Antarctic bacterium were genetically fused to the C-termini of one component of the 24-subunit protein cage T33-21, resulting in protein nanoparticles that multivalently display exactly 12 AFPs. The resulting nanoparticles exhibited freezing point depression >50-fold greater than that seen with the same concentration of monomeric AFP and a similar increase in the level of ice-recrystallization inhibition. These results support the anchored clathrate mechanism of binding of AFP to ice. The enhanced freezing point depression could be due to the difficulty of overgrowing a larger AFP on the ice surface and the improved ice-recrystallization inhibition to the ability of the nanoparticle to simultaneously bind multiple ice grains. Oligomerization of these proteins using self-assembling protein cages will be useful in a variety of biotechnology and cryobiology applications.

A comprehensive analysis of Helicobacter pylori plasticity zones reveals that they are integrating conjugative elements with intermediate integration specificity.

PubMed

Fischer, Wolfgang; Breithaupt, Ute; Kern, Beate; Smith, Stella I; Spicher, Carolin; Haas, Rainer

2014-04-27

The human gastric pathogen Helicobacter pylori is a paradigm for chronic bacterial infections. Its persistence in the stomach mucosa is facilitated by several mechanisms of immune evasion and immune modulation, but also by an unusual genetic variability which might account for the capability to adapt to changing environmental conditions during long-term colonization. This variability is reflected by the fact that almost each infected individual is colonized by a genetically unique strain. Strain-specific genes are dispersed throughout the genome, but clusters of genes organized as genomic islands may also collectively be present or absent. We have comparatively analysed such clusters, which are commonly termed plasticity zones, in a high number of H. pylori strains of varying geographical origin. We show that these regions contain fixed gene sets, rather than being true regions of genome plasticity, but two different types and several subtypes with partly diverging gene content can be distinguished. Their genetic diversity is incongruent with variations in the rest of the genome, suggesting that they are subject to horizontal gene transfer within H. pylori populations. We identified 40 distinct integration sites in 45 genome sequences, with a conserved heptanucleotide motif that seems to be the minimal requirement for integration. The significant number of possible integration sites, together with the requirement for a short conserved integration motif and the high level of gene conservation, indicates that these elements are best described as integrating conjugative elements (ICEs) with an intermediate integration site specificity.

Characterisation of a novel integrative and conjugative element ICESsD9 carrying erm(B) and tet(O) resistance determinants in Streptococcus suis, and the distribution of ICESsD9-like elements in clinical isolates.

PubMed

Huang, Kaisong; Song, Yajing; Zhang, Qiang; Zhang, Anding; Jin, Meilin

2016-12-01

This study identified a novel integrative and conjugative element (ICESsD9) carrying erm(B) and tet(O) resistance determinants in Streptococcus suis D9 and determined its prevalence in clinical isolates. Comparative genome analysis was performed using Mauve and Artemis Comparison Tool visualisation programs. Inverse PCR was utilised to detect its circular intermediate. The transfer capacity of ICESsD9 was evaluated by mating assays using S. suis A7 and Enterococcus faecalis JH2-2 as recipients. A genome walking approach was employed to analyse the characteristics of integration sites in transconjugants. A total of 118 clinical S. suis isolates were tested by PCR mapping assays to detect ICESsD9-like elements. MLST was performed on isolates containing ICESsD9 variants to determine their clonal relatedness. This 55 683-bp element can actively excise from the chromosome. Additionally, it was capable of transferring both into S. suis and E. faecalis with frequencies of 1.2×10 -4 and 5.8×10 -6 per donor, respectively. When investigating integration site features, it was found that ICESsD9 can enter S. suis and E. faecalis chromosomes by different sites, generating 15-bp and 3-bp direct repeat sequences, respectively. Twelve isolates mainly belonging to sequence types ST1, ST7 and ST28 were confirmed to harbour ICESsD9-like elements. In conclusion, this study provides the first description of an ICE in S. suis that is capable of transferring both into S. suis and E. faecalis. The presence of different ICESsD9 variants in clinical isolates suggests already wide dissemination of this family element in S. suis in China. Copyright © 2016 International Society for Chemotherapy of Infection and Cancer. Published by Elsevier Ltd. All rights reserved.

Efficient conjugate gradient algorithms for computation of the manipulator forward dynamics

NASA Technical Reports Server (NTRS)

Fijany, Amir; Scheid, Robert E.

1989-01-01

The applicability of conjugate gradient algorithms for computation of the manipulator forward dynamics is investigated. The redundancies in the previously proposed conjugate gradient algorithm are analyzed. A new version is developed which, by avoiding these redundancies, achieves a significantly greater efficiency. A preconditioned conjugate gradient algorithm is also presented. A diagonal matrix whose elements are the diagonal elements of the inertia matrix is proposed as the preconditioner. In order to increase the computational efficiency, an algorithm is developed which exploits the synergism between the computation of the diagonal elements of the inertia matrix and that required by the conjugate gradient algorithm.

Enrichment of functional properties of ice cream with pomegranate by-products.

PubMed

Çam, Mustafa; Erdoğan, Fatma; Aslan, Duygu; Dinç, Merve

2013-10-01

Pomegranate peel rich in phenolics, and pomegranate seed which contain a conjugated fatty acid namely punicic acid in lipid fraction remain as by-products after processing the fruit into juice. Ice cream is poor in polyunsaturated fatty acids and phenolics, therefore, this study was conducted to improve the functional properties of ice cream by incorporating pomegranate peel phenolics and pomegranate seed oil. Incorporation of the peel phenolics into ice cream at the levels of 0.1% and 0.4% (w/w) resulted in significant changes in the pH, total acidity, and color of the samples. The most prominent outcomes of phenolic incorporation were sharp improvements in antioxidant and antidiabetic activities as well as the phenolic content of ice creams. Replacement of pomegranate seed oil by milk fat at the levels of 2.0% and 4.0% (w/w) increased the conjugated fatty acid content. However, perception of oxidized flavor increased with the additional seed oil. When one considers the functional and nutritional improvements in the enrichment of the ice cream together with overall acceptability results of the sensory analysis, then it follows from this study that ice creams enriched with pomegranate peel phenolics up to 0.4% (w/w) and pomegranate seed oil up to 2.0% (w/w) could be introduced to markets as functional ice cream. Enrichment of ice creams with pomegranate by-products might provide consumers health benefits with striking functional properties of punicalagins in pomegranate peel, and punicic acid in pomegranate seed oil. © 2013 Institute of Food Technologists®

Conjugated Gammadion Chiral Metamaterial with Uniaxial Optical Activity and Negative Refractive Index

DTIC Science & Technology

2011-01-10

in Fig. 4, we discuss a procedure of transmutation from the simple -particle chiral element to the conjugated gammadion chiral metamaterial. The...the transmutation from the simple -particle chiral element to the conjugated gammadion chiral metamaterial. The procedure shows how the magnetic or

SmaggIce 2.0: Additional Capabilities for Interactive Grid Generation of Iced Airfoils

NASA Technical Reports Server (NTRS)

Kreeger, Richard E.; Baez, Marivell; Braun, Donald C.; Schilling, Herbert W.; Vickerman, Mary B.

2008-01-01

The Surface Modeling and Grid Generation for Iced Airfoils (SmaggIce) software toolkit has been extended to allow interactive grid generation for multi-element iced airfoils. The essential phases of an icing effects study include geometry preparation, block creation and grid generation. SmaggIce Version 2.0 now includes these main capabilities for both single and multi-element airfoils, plus an improved flow solver interface and a variety of additional tools to enhance the efficiency and accuracy of icing effects studies. An overview of these features is given, especially the new multi-element blocking strategy using the multiple wakes method. Examples are given which illustrate the capabilities of SmaggIce for conducting an icing effects study for both single and multi-element airfoils.

Iterative methods for elliptic finite element equations on general meshes

NASA Technical Reports Server (NTRS)

Nicolaides, R. A.; Choudhury, Shenaz

1986-01-01

Iterative methods for arbitrary mesh discretizations of elliptic partial differential equations are surveyed. The methods discussed are preconditioned conjugate gradients, algebraic multigrid, deflated conjugate gradients, an element-by-element techniques, and domain decomposition. Computational results are included.

Identification of genetic and environmental factors stimulating excision from Streptomyces scabiei chromosome of the toxicogenic region responsible for pathogenicity.

PubMed

Chapleau, Mélanie; Guertin, Julien F; Farrokhi, Ali; Lerat, Sylvain; Burrus, Vincent; Beaulieu, Carole

2016-05-01

The genes conferring pathogenicity in Streptomyces turgidiscabies, a pathogen causing common scab of potato, are grouped together on a pathogenicity island (PAI), which has been found to be mobile and appears to transfer and disseminate like an integrative and conjugative element (ICE). However, in Streptomyces scabiei, another common scab-inducing species, the pathogenicity genes are clustered in two regions: the toxicogenic region (TR) and the colonization region. The S. scabiei 87.22 genome was analysed to investigate the potential mobility of the TR. Attachment sites (att), short homologous sequences that delineate ICEs, were identified at both extremities of the TR. An internal att site was also found, suggesting that the TR has a composite structure (TR1 and TR2). Thaxtomin biosynthetic genes, essential for pathogenicity, were found in TR1, whereas candidate genes with known functions in recombination, replication and conjugal transfer were found in TR2. Excision of the TR1 or TR2 subregions alone, or of the entire TR region, was observed, although the excision frequency of TR was low. However, the excision frequency was considerably increased in the presence of either mitomycin C or Streptomyces coelicolor cells. A composite TR structure was not observed in all S. scabiei and Streptomyces acidiscabies strains tested. Of the ten strains analysed, seven lacked TR2 and no TR excision event could be detected in these strains, thus suggesting the implication of TR2 in the mobilization of S. scabiei TR. © 2015 BSPP AND JOHN WILEY & SONS LTD.

Homology among tet determinants in conjugative elements of streptococci.

PubMed Central

Smith, M D; Hazum, S; Guild, W R

1981-01-01

A mutation to tetracycline sensitivity in a resistant strain of Streptococcus pneumoniae was shown by several criteria to be due to a point mutation in the conjugative omega (cat-tet) element found in the chromosomes of strains derived from BM6001, a clinical strain resistant to tetracycline and chloramphenicol. Strains carrying the mutation were transformed back to tetracycline resistance with the high efficiency of a point marker by donor deoxyribonucleic acids from its ancestral strain and from nine other clinical isolates of pneumococcus and by deoxyribonucleic acids from group D Streptococcus faecalis and group B Streptococcus agalactiae strains that also carry conjugative tet elements in their chromosomes. It was not transformed to resistance by tet plasmid deoxyribonucleic acids from either gram-negative or gram-positive species, except for one that carried transposon Tn916, the conjugative tet element present in the chromosomes of some S. faecalis strains. The results showed that the tet determinants in conjugative elements of several streptococcal species share a high degree of deoxyribonucleic acid sequence homology and suggested that they differ from other tet genes. PMID:6270063

Ice Detection and Mitigation Device

NASA Technical Reports Server (NTRS)

Gambino, Richard J. (Inventor); Gouldstone, Christopher (Inventor); Gutleber, Jonathan (Inventor); Hubble, David (Inventor); Trelewicz, Jason (Inventor)

2016-01-01

A method for deicing an aerostructure includes driving a sensing current through a heater element coated to an aerostructure, the heater element having a resistance that is temperature dependent. A resistance of the heater element is monitored. It is determined whether there is icing at the heater element using the monitored resistance of the heater element. A melting current is driven through the heater element when it is determined that there is icing at the heater element.

NASA Engine Icing Research Overview: Aeronautics Evaluation and Test Capabilities (AETC) Project

NASA Technical Reports Server (NTRS)

Veres, Joseph P.

2015-01-01

The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported by airlines under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion by the engine. The ice crystals can result in degraded engine performance, loss of thrust control, compressor surge or stall, and flameout of the combustor. The Aviation Safety Program at NASA has taken on the technical challenge of a turbofan engine icing caused by ice crystals which can exist in high altitude convective clouds. The NASA engine icing project consists of an integrated approach with four concurrent and ongoing research elements, each of which feeds critical information to the next element. The project objective is to gain understanding of high altitude ice crystals by developing knowledge bases and test facilities for testing full engines and engine components. The first element is to utilize a highly instrumented aircraft to characterize the high altitude convective cloud environment. The second element is the enhancement of the Propulsion Systems Laboratory altitude test facility for gas turbine engines to include the addition of an ice crystal cloud. The third element is basic research of the fundamental physics associated with ice crystal ice accretion. The fourth and final element is the development of computational tools with the goal of simulating the effects of ice crystal ingestion on compressor and gas turbine engine performance. The NASA goal is to provide knowledge to the engine and aircraft manufacturing communities to help mitigate, or eliminate turbofan engine interruptions, engine damage, and failures due to ice crystal ingestion.

Trace and Ultra-trace Elements in the Deepest Part of the Vostok Ice Core, Antarctica: Geochemical Characterization of the Sub-glacial Lake Environment

NASA Astrophysics Data System (ADS)

Turetta, C.; Planchon, F.; Gabrielli, P.; Cozzi, G.; Cairns, W.; Barbaro, E.; Petit, J. R.; Bulat, S.; Boutron, C.; Barbante, C.

2016-12-01

We present in this study comprehensive data on the occurrence of 25 trace and ultra-trace elements in the deepest part of the Vostok ice core. The determination of Li, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Ba, Pb, Bi and U has been performed in the different types of ice encountered from 3271 m to 3609 m of depth, corresponding to atmospheric ice, glacial flour and to accreted ice originating from the freezing of Lake Vostok waters. From atmospheric ice and glacial flour, the relative contributions of primary aerosols were evaluated for each element using a chemical mass balance approach in order to provide a first order evaluation of their partition between soluble (sea-salt) and insoluble (wind-blown dust) fractions in the ice. Sea-salt spray aerosols are the main source of impurities to the ice for certain elements (Na, Mg and K levels, and in a lesser extent to Ca, Sr, Rb, Li and U) while for other elements (Al, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, Sb, Ba and Pb as well as the non sea salt fractions of Mg, K, Ca, Sr, Rb, Li and U) dust inputs appear to primarily control their depositional variability. For the glacial flour, the comparable levels of elements with the overlying atmospheric ice suggest that incorporation of abrasion debris at the glacier is quite limited in the sections considered. For the accreted ice originating from the subglacial waters of Lake Vostok, we observed a major chemical shift in the composition of the ice showing two distinct trends that we assumed to be derived from the chemical speciation of elements. The study of the glacier ice and the glacial flour has allowed us to perform a detailed characterisation of elemental abundances related to the aerosol sources variability and also to illustrate the interaction between the ice-sheet and the bedrock.

Icing Test Results on an Advanced Two-Dimensional High-Lift Multi-Element Airfoil

NASA Technical Reports Server (NTRS)

Shin, Jaiwon; Wilcox, Peter; Chin, Vincent; Sheldon, David

1994-01-01

An experimental study has been conducted to investigate ice accretions on a high-lift, multi-element airfoil in the Icing Research Tunnel at the NASA Lewis Research Center. The airfoil is representative of an advanced transport wing design. The experimental work was conducted as part of a cooperative program between McDonnell Douglas Aerospace and the NASA Lewis Research Center to improve current understanding of ice accretion characteristics on the multi-element airfoil. The experimental effort also provided ice shapes for future aerodynamic tests at flight Reynolds numbers to ascertain high-lift performance effects. Ice shapes documented for a landing configuration over a variety of icing conditions are presented along with analyses.

A New Integrative Conjugative Element Occurs in Mycoplasma agalactiae as Chromosomal and Free Circular Forms

PubMed Central

Marenda, Marc; Barbe, Valérie; Gourgues, Géraldine; Mangenot, Sophie; Sagne, Evelyne; Citti, Christine

2006-01-01

An integrative conjugative element, ICEA, was characterized in Mycoplasma agalactiae strain 5632, in which it occurs as multiple chromosomal copies and as a free circular form. The distribution of ICEA sequences in M. agalactiae strains and their occurrence in Mycoplasma bovis suggest the spreading of the element within or between species. PMID:16707706

An Assessment of the Icing Blade and the SEA Multi-Element Sensor for Liquid Water Content Calibration of the NASA GRC Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Ide, Robert F.; Van Zante, Judith Foss

2017-01-01

The Icing Research Tunnel at NASA Glenn has recently switched to from using the Icing Blade to using the SEA Multi-Element Sensor (also known as the multi-wire) for its calibration of cloud liquid water content. In order to perform this transition, tests were completed to compare the Multi-Element Sensor to the Icing Blade, particularly with respect to liquid water content, airspeed, and drop size. The two instruments were found to compare well for the majority of Appendix C conditions. However, it was discovered that the Icing Blade under-measures when the conditions approach the Ludlam Limit. This paper also describes data processing procedures for the Multi-Element Sensor in the IRT, including collection efficiency corrections, mounting underneath a splitter plate, and correcting for a jump in the compensation wire power. Further data is presented to describe the repeatability of the IRT with the Multi-Element sensor, health-monitoring checks for the instrument, and a sensing-element configuration comparison.

A distinct and divergent lineage of genomic island-associated Type IV Secretion Systems in Legionella.

PubMed

Wee, Bryan A; Woolfit, Megan; Beatson, Scott A; Petty, Nicola K

2013-01-01

Legionella encodes multiple classes of Type IV Secretion Systems (T4SSs), including the Dot/Icm protein secretion system that is essential for intracellular multiplication in amoebal and human hosts. Other T4SSs not essential for virulence are thought to facilitate the acquisition of niche-specific adaptation genes including the numerous effector genes that are a hallmark of this genus. Previously, we identified two novel gene clusters in the draft genome of Legionella pneumophila strain 130b that encode homologues of a subtype of T4SS, the genomic island-associated T4SS (GI-T4SS), usually associated with integrative and conjugative elements (ICE). In this study, we performed genomic analyses of 14 homologous GI-T4SS clusters found in eight publicly available Legionella genomes and show that this cluster is unusually well conserved in a region of high plasticity. Phylogenetic analyses show that Legionella GI-T4SSs are substantially divergent from other members of this subtype of T4SS and represent a novel clade of GI-T4SSs only found in this genus. The GI-T4SS was found to be under purifying selection, suggesting it is functional and may play an important role in the evolution and adaptation of Legionella. Like other GI-T4SSs, the Legionella clusters are also associated with ICEs, but lack the typical integration and replication modules of related ICEs. The absence of complete replication and DNA pre-processing modules, together with the presence of Legionella-specific regulatory elements, suggest the Legionella GI-T4SS-associated ICE is unique and may employ novel mechanisms of regulation, maintenance and excision. The Legionella GI-T4SS cluster was found to be associated with several cargo genes, including numerous antibiotic resistance and virulence factors, which may confer a fitness benefit to the organism. The in-silico characterisation of this new T4SS furthers our understanding of the diversity of secretion systems involved in the frequent horizontal gene transfers that allow Legionella to adapt to and exploit diverse environmental niches.

A Distinct and Divergent Lineage of Genomic Island-Associated Type IV Secretion Systems in Legionella

PubMed Central

Wee, Bryan A.; Woolfit, Megan; Beatson, Scott A.; Petty, Nicola K.

2013-01-01

Legionella encodes multiple classes of Type IV Secretion Systems (T4SSs), including the Dot/Icm protein secretion system that is essential for intracellular multiplication in amoebal and human hosts. Other T4SSs not essential for virulence are thought to facilitate the acquisition of niche-specific adaptation genes including the numerous effector genes that are a hallmark of this genus. Previously, we identified two novel gene clusters in the draft genome of Legionella pneumophila strain 130b that encode homologues of a subtype of T4SS, the genomic island-associated T4SS (GI-T4SS), usually associated with integrative and conjugative elements (ICE). In this study, we performed genomic analyses of 14 homologous GI-T4SS clusters found in eight publicly available Legionella genomes and show that this cluster is unusually well conserved in a region of high plasticity. Phylogenetic analyses show that Legionella GI-T4SSs are substantially divergent from other members of this subtype of T4SS and represent a novel clade of GI-T4SSs only found in this genus. The GI-T4SS was found to be under purifying selection, suggesting it is functional and may play an important role in the evolution and adaptation of Legionella. Like other GI-T4SSs, the Legionella clusters are also associated with ICEs, but lack the typical integration and replication modules of related ICEs. The absence of complete replication and DNA pre-processing modules, together with the presence of Legionella-specific regulatory elements, suggest the Legionella GI-T4SS-associated ICE is unique and may employ novel mechanisms of regulation, maintenance and excision. The Legionella GI-T4SS cluster was found to be associated with several cargo genes, including numerous antibiotic resistance and virulence factors, which may confer a fitness benefit to the organism. The in-silico characterisation of this new T4SS furthers our understanding of the diversity of secretion systems involved in the frequent horizontal gene transfers that allow Legionella to adapt to and exploit diverse environmental niches. PMID:24358157

The novel conjugative transposon tn1207.3 carries the macrolide efflux gene mef(A) in Streptococcus pyogenes.

PubMed

Santagati, Maria; Iannelli, Francesco; Cascone, Carmela; Campanile, Floriana; Oggioni, Marco R; Stefani, Stefania; Pozzi, Gianni

2003-01-01

The macrolide efflux gene mef(A) of the Streptococcus pyogenes clinical strain 2812A was found to be carried by a 52-kb chromosomal genetic element that could be transferred by conjugation to the chromosome of other streptococcal species. The characteristics of this genetic element are typical of conjugative transposons and was named Tn1207.3. The size of Tn1207.3 was established by pulsed-field gel electrophoresis (PFGE), and DNA sequencing analysis showed that the 7,244 bp at the left end of Tn1207.3 were identical to those of the pneumococcal Tn1207.1 element. Tn1207.3-like genetic elements were found to be inserted at a single specific chromosomal site in 12 different clinical isolates S. pyogenes exhibiting the M phenotype of resistance to macrolides and carrying the mef(A) gene. Tn1207.3 was transferred from S. pyogenes 2812A to Streptococcus pneumoniae, and sequence analysis carried out on six independent transconjugants showed that insertion of Tn1207.3 in the pneumococcal genome always occurred at a single specific site as in Tn1207.1. Using MF2, a representative S. pneumoniae transconjugant, as a donor, Tn1207.3 was transferred again by conjugation to S. pyogenes and Streptococcus gordonii. The previously described nonconjugative element Tn1207.1 of S. pneumoniae appears to be a defective element, part of a longer conjugative transposon that carries mef(A) and is found in clinical isolates of S. pyogenes.

Convection from Hemispherical and Conical Model Ice Roughness Elements in Stagnation Region Flows

NASA Technical Reports Server (NTRS)

Hughes, Michael T.; Shannon, Timothy A.; McClain, Stephen T.; Vargas, Mario; Broeren, Andy

2016-01-01

To improve ice accretion prediction codes, more data regarding ice roughness and its effects on convective heat transfer are required. The Vertical Icing Studies Tunnel (VIST) at NASA Glenn Research was used to model realistic ice roughness in the stagnation region of a NACA 0012 airfoil. In the VIST, a test plate representing the leading 2% chord of the airfoil was subjected to flows of 7.62 m/s (25 ft/s), 12.19 m/s (40 ft/s), and 16.76 m/s (55 ft/s). The test plate was fitted with multiple surfaces or sets of roughness panels, each with a different representation of ice roughness. The sets of roughness panels were constructed using two element distribution patterns that were created based on a laser scan of an iced airfoil acquired in the Icing Research Tunnel at NASA Glenn. For both roughness patterns, surfaces were constructed using plastic hemispherical elements, plastic conical elements, and aluminum conical elements. Infrared surface thermometry data from tests run in the VIST were used to calculate area averaged heat transfer coefficient values. The values from the roughness surfaces were compared to the smooth control surface, showing convective enhancement as high as 400% in some cases. The data gathered during this study will ultimately be used to improve the physical modeling in LEWICE or other ice accretion codes and produce predictions of in-flight ice accretion on aircraft surfaces with greater confidence.

Modeling and Grid Generation of Iced Airfoils

NASA Technical Reports Server (NTRS)

Vickerman, Mary B.; Baez, Marivell; Braun, Donald C.; Hackenberg, Anthony W.; Pennline, James A.; Schilling, Herbert W.

2007-01-01

SmaggIce Version 2.0 is a software toolkit for geometric modeling and grid generation for two-dimensional, singleand multi-element, clean and iced airfoils. A previous version of SmaggIce was described in Preparing and Analyzing Iced Airfoils, NASA Tech Briefs, Vol. 28, No. 8 (August 2004), page 32. To recapitulate: Ice shapes make it difficult to generate quality grids around airfoils, yet these grids are essential for predicting ice-induced complex flow. This software efficiently creates high-quality structured grids with tools that are uniquely tailored for various ice shapes. SmaggIce Version 2.0 significantly enhances the previous version primarily by adding the capability to generate grids for multi-element airfoils. This version of the software is an important step in streamlining the aeronautical analysis of ice airfoils using computational fluid dynamics (CFD) tools. The user may prepare the ice shape, define the flow domain, decompose it into blocks, generate grids, modify/divide/merge blocks, and control grid density and smoothness. All these steps may be performed efficiently even for the difficult glaze and rime ice shapes. Providing the means to generate highly controlled grids near rough ice, the software includes the creation of a wrap-around block (called the "viscous sublayer block"), which is a thin, C-type block around the wake line and iced airfoil. For multi-element airfoils, the software makes use of grids that wrap around and fill in the areas between the viscous sub-layer blocks for all elements that make up the airfoil. A scripting feature records the history of interactive steps, which can be edited and replayed later to produce other grids. Using this version of SmaggIce, ice shape handling and grid generation can become a practical engineering process, rather than a laborious research effort.

An Assessment of the Icing Blade and the SEA Multi-Element Sensor for Liquid Water Content Calibration of the NASA GRC Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Ide, Robert F.; Van Zante, Judith F.

2016-01-01

The Icing Research Tunnel at NASA Glenn has recently switched from using the Icing Blade to using the SEA Multi-Element Sensor (also known as the multi-wire) for its calibration of cloud liquid water content. In order to peform this transition, tests were completed to compare the Multi-Element Sensor to the Icing Blade, particularly with respect to liquid water content, airspeed, and drop size. The two instruments were found to compare well for the majority of Appendix C conditions. However, it was discovered that the Icing Blade under-measures when the conditions approach the Ludlam Limit. This paper also describes data processing procedures for the Multi-Element Sensor in the IRT, including collision efficiency corrections, mounting underneath a splitter plate, and correcting for a jump in the compensation wire power. Further data is presented to describe the repeatability of the IRT with the Multi-Element Sensor, health-monitoring checks for the instrument, and a sensing-element configuration comparison. Ultimately these tests showed that in the IRT, the multi-wire is a better instrument for measuring cloud liquid water content than the blade.

Mechanisms of basal ice formation in polar glaciers: An evaluation of the apron entrainment model

NASA Astrophysics Data System (ADS)

Fitzsimons, Sean; Webb, Nicola; Mager, Sarah; MacDonell, Shelley; Lorrain, Regi; Samyn, Denis

2008-06-01

Previous studies of polar glaciers have argued that basal ice can form when these glaciers override and entrain ice marginal aprons that accumulate adjacent to steep ice cliffs. To test this idea, we have studied the morphology, structure, composition, and deformation of the apron and basal ice at the terminus of Victoria Upper Glacier in the McMurdo dry valleys, which are located on the western coast of the Ross Sea at 77°S in southern Victoria Land, Antarctica. Our results show that the apron has two structural elements: an inner element that consists of strongly foliated ice that has a steep up-glacier dip, and an outer element that lacks a consistent foliation and has a down-glacier, slope-parallel dip. Although strain measurements show that the entire apron is deforming, the inner element is characterized by high strain rates, whereas relatively low rates of strain characterize the outer part of the apron. Co-isotopic analyses of the ice, together with analysis of solute chemistry and sedimentary characteristics, show that the apron is compositionally different from the basal ice. Our observations show that aprons may become deformed and partially entrained by advancing glaciers. However, such an ice marginal process does not provide a satisfactory explanation for the origin of basal ice observed at the ice margin. Our interpretation of the origin of basal ice is that it is formed by subglacial processes, which are likely to include deformation and entrainment of subglacial permafrost.

The effect of acidified sample storage time on the determination of trace element concentration in ice cores by ICP-SFMS

NASA Astrophysics Data System (ADS)

Uglietti, C.; Gabrielli, P.; Lutton, A.; Olesik, J.; Thompson, L. G.

2012-12-01

Trace elements in micro-particles entrapped in ice cores are a valuable proxy of past climate and environmental variations. Inductively coupled plasma sector field mass spectrometry (ICP-SFMS) is generally recognized as a sensitive and accurate technique for the quantification of ultra-trace element concentrations in ice cores. Usually, ICP-SFMS analyses of ice core samples are performed by melting and acidifying aliquots. Acidification is important to transfer trace elements from particles into solution by partial and/or complete dissolution. Only elements in solution and in sufficiently small particles will be vaporized and converted to elemental ions in the plasma for detection by ICP-SFMS. However, experimental results indicate that differences in acidified sample storage time at room temperature may lead to the recovery of different trace element fractions. Moreover, different lithologies of the relatively abundant crustal material entrapped in the ice matrix could also influence the fraction of trace elements that are converted into elemental ions in the plasma. These factors might affect the determination of trace elements concentrations in ice core samples and hamper the comparison of results obtained from ice cores from different locations and/or epochs. In order to monitor the transfer of elements from particles into solution in acidified melted ice core samples during storage, a test was performed on sections from nine ice cores retrieved from low latitude drilling sites around the world. When compared to ice cores from polar regions, these samples are characterized by a relative high content of micro-particles that may leach trace elements into solution differently. Of the nine ice cores, five are from the Tibetan Plateau (Dasuopu, Guliya, Naimonanyi, Puruogangri and Dunde), two from the Andes (Quelccaya and Huascaran), one from Africa (Kilimanjaro) and one from the Eastern Alps (Ortles). These samples were decontaminated by triple rinsing, melted and stored in pre-cleaned low-density polyethylene bottles, and kept frozen until acidification (2% v/v ultra-pure HNO3). Determination of twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V, and Zn) was repeated at different times after acidification using the same aliquot. Analyses show a mean increase of 40-50% in trace element concentration in all the samples during the first 15 days of storage after acidification, except Al, Fe, V and Cr, which show a larger increase (90-100%). After 15 days the trace element concentrations reach generally stable values (with small increases within measurement uncertainty), except for the Naimonanyi and Kilimanjaro samples which continue to increase. In contrast, Ag concentration decreases after one week, likely due to its low stability in the acidified solution that may depend on the Cl- concentration. We froze the samples 43 days after the acidification. After two weeks the samples were melted and re-analyzed by ICP-SFMS in two different laboratories as an inter-calibration exercise. The results show a good correspondence between the measured concentrations determined by the two instruments and a consistent additional increase of 20-30% of measured trace element concentrations in almost all samples.

Ice Particle Impact on Cloud Water Content Instrumentation

NASA Technical Reports Server (NTRS)

Emery, Edward F.; Miller, Dean R.; Plaskon, Stephen R.; Strapp, Walter; Lillie, Lyle

2004-01-01

Determining the total amount of water contained in an icing cloud necessitates the measurement of both the liquid droplets and ice particles. One commonly accepted method for measuring cloud water content utilizes a hot wire sensing element, which is maintained at a constant temperature. In this approach, the cloud water content is equated with the power required to keep the sense element at a constant temperature. This method inherently assumes that impinging cloud particles remain on the sensing element surface long enough to be evaporated. In the case of ice particles, this assumption requires that the particles do not bounce off the surface after impact. Recent tests aimed at characterizing ice particle impact on a thermally heated wing section, have raised questions about the validity of this assumption. Ice particles were observed to bounce off the heated wing section a very high percentage of the time. This result could have implications for Total Water Content sensors which are designed to capture ice particles, and thus do not account for bouncing or breakup of ice particles. Based on these results, a test was conducted to investigate ice particle impact on the sensing elements of the following hot-wire cloud water content probes: (1) Nevzorov Total Water Content (TWC)/Liquid Water Content (LWC) probe, (2) Science Engineering Associates TWC probe, and (3) Particle Measuring Systems King probe. Close-up video imaging was used to study ice particle impact on the sensing element of each probe. The measured water content from each probe was also determined for each cloud condition. This paper will present results from this investigation and attempt to evaluate the significance of ice particle impact on hot-wire cloud water content measurements.

An Assessment of the SEA Multi-Element Sensor for Liquid Water Content Calibration of the NASA GRC Icing Research Tunnel

NASA Technical Reports Server (NTRS)

Steen, Laura E.; Ide, Robert F.; Van Zante, Judith F.

2015-01-01

The NASA Glenn Icing Research tunnel has been using an Icing Blade technique to measure cloud liquid water content (LWC) since 1980. The IRT conducted tests with SEA Multi-Element sensors from 2009 to 2011 to assess their performance in measuring LWC. These tests revealed that the Multi-Element sensors showed some significant advantages over the Icing Blade, particularly at higher water contents, higher impingement rates, and large drop sizes. Results of these and other tests are presented here.

High-Quality draft genome sequence of the Lotus spp. microsymbiont Mesorhizobium loti strain CJ3Sym

DOE PAGES

Reeve, Wayne; Sullivan, John; Ronson, Clive; ...

2015-08-14

Mesorhizobium loti strain CJ3Sym was isolated in 1998 following transfer of the integrative and conjugative element ICE Ml Sym R7A , also known as the R7A symbiosis island, in a laboratory mating from the donor M. loti strain R7A to a nonsymbiotic recipient Mesorhizobium strain CJ3. Strain CJ3 was originally isolated from a field site in the Rocklands range in New Zealand in 1994. CJ3Sym is an aerobic, Gram-negative, non-spore-forming rod. This report reveals the genome of M. loti strain CJ3Sym currently comprises 70 scaffolds totaling 7,563,725 bp. In conclusion, the high-quality draft genome is arranged in 70 scaffolds ofmore » 71 contigs, contains 7,331 protein-coding genes and 70 RNA-only encoding genes, and is part of the GEBA-RNB project proposal.« less

High-Quality draft genome sequence of the Lotus spp. microsymbiont Mesorhizobium loti strain CJ3Sym

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reeve, Wayne; Sullivan, John; Ronson, Clive

Mesorhizobium loti strain CJ3Sym was isolated in 1998 following transfer of the integrative and conjugative element ICE Ml Sym R7A , also known as the R7A symbiosis island, in a laboratory mating from the donor M. loti strain R7A to a nonsymbiotic recipient Mesorhizobium strain CJ3. Strain CJ3 was originally isolated from a field site in the Rocklands range in New Zealand in 1994. CJ3Sym is an aerobic, Gram-negative, non-spore-forming rod. This report reveals the genome of M. loti strain CJ3Sym currently comprises 70 scaffolds totaling 7,563,725 bp. In conclusion, the high-quality draft genome is arranged in 70 scaffolds ofmore » 71 contigs, contains 7,331 protein-coding genes and 70 RNA-only encoding genes, and is part of the GEBA-RNB project proposal.« less

Oxidative Processing Lowers the Ice Nucleation Activity of Birch and Alder Pollen

NASA Astrophysics Data System (ADS)

Gute, Ellen; Abbatt, Jonathan P. D.

2018-02-01

Pollen carry water extractable compounds with ice nucleating (IN) activity. This study investigates whether the hydroxyl radical, as the major atmospheric oxidant, can affect the IN activity of silver birch and grey alder subpollen particles under in-cloud conditions for deposition freezing mode conditions at 234 K. It is found that oxidation increases the supersaturation ratio with respect to ice necessary for the onset of ice nucleation and decreases the fraction of particles which initiate ice nucleation. This reduction of IN activity under equivalent oxidation conditions does not occur with a mineral dust sample (Arizona Test Dust). Chemical analysis of fresh and oxidized pollen material indicates a change of molecular structure with a loss of conjugation and an increase in oxidized functional groups, such as carbonyls. This is the first demonstration that in-cloud oxidation may lower the IN abilities of biological particles such as pollen.

Functional conjugated pyridines via main-group element tuning.

PubMed

Stolar, Monika; Baumgartner, Thomas

2018-03-29

Pyridine-based materials have seen widespread attention for the development of n-type organic materials. In recent years, the incorporation of main-group elements has also explored significant advantages for the development and tunability of organic conjugated materials. The unique chemical and electronic structure of main-group elements has led to several enhancements in conventional organic materials. This Feature article highlights recent main-group based pyridine materials by discussing property enhancements and application in organic electronics.

NASA/FAA Tailplane Icing Program Overview

NASA Technical Reports Server (NTRS)

Ratvasky, Thomas P.; VanZante, Judith Foss; Riley, James T.

1999-01-01

The effects of tailplane icing were investigated in a four-year NASA/FAA Tailplane Icing, Program (TIP). This research program was developed to improve the understanding, of iced tailplane aeroperformance and aircraft aerodynamics, and to develop design and training aides to help reduce the number of incidents and accidents caused by tailplane icing. To do this, the TIP was constructed with elements that included icing, wind tunnel testing, dry-air aerodynamic wind tunnel testing, flight tests, and analytical code development. This paper provides an overview of the entire program demonstrating the interconnectivity of the program elements and reports on current accomplishments.

Observations on the Growth of Roughness Elements Into Icing Feathers

NASA Technical Reports Server (NTRS)

Vargas, Mario; Tsao, Jen, Ching

2007-01-01

This work presents the results of an experiment conducted in the Icing Research Tunnel at NASA Glenn Research Center to understand the process by which icing feathers are formed in the initial stages of ice accretion formation on swept wings. Close-up photographic data were taken on an aluminum NACA 0012 swept wing tip airfoil. Two types of photographic data were obtained: time sequence close-up photographic data during the run and close-up photographic data of the ice accretion at the end of each run. Icing runs were conducted for short ice accretion times from 10 to 180 sec. The time sequence close-up photographic data was used to study the process frame by frame and to create movies of how the process developed. The movies confirmed that at glaze icing conditions in the attachment line area icing feathers develop from roughness elements. The close-up photographic data at the end of each run showed that roughness elements change into a pointed shape with an upstream facet and join on the side with other elements having the same change to form ridges with pointed shape and upstream facet. The ridges develop into feathers when the upstream facet grows away to form the stem of the feather. The ridges and their growth into feathers were observed to form the initial scallop tips present in complete scallops.

The Influence of Viscous Effects on Ice Accretion Prediction and Airfoil Performance Predictions

NASA Technical Reports Server (NTRS)

Kreeger, Richard E.; Wright, William B.

2005-01-01

A computational study was conducted to evaluate the effectiveness of using a viscous flow solution in an ice accretion code and the resulting accuracy of aerodynamic performance prediction. Ice shapes were obtained for one single-element and one multi-element airfoil using both potential flow and Navier-Stokes flowfields in the LEWICE ice accretion code. Aerodynamics were then calculated using a Navier-Stokes flow solver.

Ice cream structural elements that affect melting rate and hardness.

PubMed

Muse, M R; Hartel, R W

2004-01-01

Statistical models were developed to reveal which structural elements of ice cream affect melting rate and hardness. Ice creams were frozen in a batch freezer with three types of sweetener, three levels of the emulsifier polysorbate 80, and two different draw temperatures to produce ice creams with a range of microstructures. Ice cream mixes were analyzed for viscosity, and finished ice creams were analyzed for air cell and ice crystal size, overrun, and fat destabilization. The ice phase volume of each ice cream were calculated based on the freezing point of the mix. Melting rate and hardness of each hardened ice cream was measured and correlated with the structural attributes by using analysis of variance and multiple linear regression. Fat destabilization, ice crystal size, and the consistency coefficient of the mix were found to affect the melting rate of ice cream, whereas hardness was influenced by ice phase volume, ice crystal size, overrun, fat destabilization, and the rheological properties of the mix.

Investigating the Microscopic Location of Trace Elements in High-Alpine Glacier Ice

NASA Astrophysics Data System (ADS)

Avak, Sven Erik; Birrer, Mario; Laurent, Oscar; Guillong, Marcel; Wälle, Markus; Jenk, Theo Manuel; Bartels-Rausch, Thorsten; Schwikowski, Margit; Eichler, Anja

2017-04-01

Past changes in atmospheric pollution can be reconstructed from high-alpine ice core trace element records (Schwikowski et al., 2004). Percolation of meltwater alters the information originally stored in these environmental archives. Eichler et al. (2001) suggested that the preservation of major ions with respect to meltwater percolation depends on their location in the crystal ice lattice, i.e. grain boundaries versus grain interiors. Other studies have also focused on the effect of meltwater on organic pollutant concentrations as well as on stable isotope profiles in ice cores, whereas no information exists about trace elements. Here, we investigate for the first time the effect of the microscopic location of anthropogenic, dust and volcanic related trace elements on the behavior during meltwater percolation by using two different approaches. On the one hand we assess the microscopic location of trace elements indirectly by analyzing trace element concentrations in a high-alpine ice core, which has been shown to be affected by an inflow of meltwater, using discrete inductively coupled plasma mass spectrometry (ICP-MS). Impurities located at grain boundaries are prone to be removed by meltwater and tend to be depleted in the affected section of the record whereas those incorporated into the ice interior are preserved and not disturbed in the record. In the second approach we work towards a direct quantification of differences in concentrations of trace elements between ice grain boundaries and grain interiors in samples both from unaffected and affected sections of this ice core. Therefore we use cryocell laser ablation (LA) ICP-MS, which is the method of choice for the direct in situ chemical analysis of trace elements at a sub-millimeter resolution in glacier ice (Reinhardt et al., 2001, Della Lunga et al., 2014, Sneed et al., 2015). We will present first results of both approaches with regard to the evaluation of the potential of trace elements as environmental proxies in glaciers partially affected by melting. References Della Lunga, D., Müller, W., Rasmussen, S. O. & Svensson, A. 2014: Location of cation impurities in NGRIP deep ice revealed by cryo-cell UV-laser-ablation ICPMS, Journal of Glaciology, 60, 970-988. Eichler, A., Schwikowski, M., Gäggeler, H. W. 2001: Meltwater-induced relocation of chemical species in Alpine firn, Tellus B, 53, 192-203. Reinhardt, H., Kriews, M., Miller, H., Schrems, O., Lüdke, C., Hoffmann, E. & Skole, J. 2001: Laser ablation inductively coupled plasma mass spectrometry: a new tool for trace element analysis in ice cores, Fresenius' Journal of Analytical Chemistry, 370, 629-636. Schwikowski, M., Barbante, C., Doering, T., Gäggeler, H. W., Boutron, C., Schotterer, U., Tobler, L., van de Velde, K., Ferrari, C., Cozzi, G., Rosman, K., Cescon, P. 2004: Post-17th-Century Changes of European Lead Emissions Recorded in High-Altitude Alpine Snow and Ice, Environmental Science & Technology, 38, 957-964. Sneed, S. B., Mayewski, P. A., Sayre, W. G., Handley, M. J., Kurbatov, A. V., Taylor, K. C., Bohleber, P., Wagenbach, D., Erhardt, T. & Spaulding, N. E. 2015: New LA-ICP-MS cryocell and calibration technique for sub-millimeter analysis of ice cores, Journal of Glaciology, 61, 233-242.

A new method for geochemical characterization of atmospheric mineral dust from polar ice cores: preliminary results from Talos Dome ice core (East Antarctica, Pacific-Ross Sea sector)

NASA Astrophysics Data System (ADS)

Baccolo, Giovanni; Delmonte, Barbara; Clemenza, Massimiliano; Previtali, Ezio; Maggi, Valter

2015-04-01

Assessing the elemental composition of atmospheric dust entrapped in polar ice cores is important for the identification of the potential dust sources and thus for the reconstruction of past atmospheric circulation, at local, regional and global scale. Accurate determination of major and trace elements in the insoluble fraction of dust extracted from ice cores is also useful to better understand some geochemical and biogeochemical mechanisms which are linked with the climate system. The extremely reduced concentration of dust in polar ice (typical Antarctic concentrations during interglacials are in the range of 10 ppb), the limited availability of such samples and the high risk of contamination make these analyses a challenge. A new method based on low background Instrumental Neutron Activation Analysis (INAA) was specifically developed for this kind of samples. The method allows the determination of the concentration of up to 35 elements in extremely reduced dust samples (20-30 μg). These elements span from major to trace and ultra-trace elements. Preliminary results from TALDICE (TALos Dome Ice CorE, East Antarctica, Pacific-Ross Sea Sector) ice core are presented along with results from potential source areas in Victoria Land. A set of 5 samples from Talos Dome, corresponding to the last termination, MIS3, MIS4 and MIS6 were prepared and analyzed by INAA.

Microfluidic Cold-Finger Device for the Investigation of Ice-Binding Proteins.

PubMed

Haleva, Lotem; Celik, Yeliz; Bar-Dolev, Maya; Pertaya-Braun, Natalya; Kaner, Avigail; Davies, Peter L; Braslavsky, Ido

2016-09-20

Ice-binding proteins (IBPs) bind to ice crystals and control their structure, enlargement, and melting, thereby helping their host organisms to avoid injuries associated with ice growth. IBPs are useful in applications where ice growth control is necessary, such as cryopreservation, food storage, and anti-icing. The study of an IBP's mechanism of action is limited by the technological difficulties of in situ observations of molecules at the dynamic interface between ice and water. We describe herein a new, to our knowledge, apparatus designed to generate a controlled temperature gradient in a microfluidic chip, called a microfluidic cold finger (MCF). This device allows growth of a stable ice crystal that can be easily manipulated with or without IBPs in solution. Using the MCF, we show that the fluorescence signal of IBPs conjugated to green fluorescent protein is reduced upon freezing and recovers at melting. This finding strengthens the evidence for irreversible binding of IBPs to their ligand, ice. We also used the MCF to demonstrate the basal-plane affinity of several IBPs, including a recently described IBP from Rhagium inquisitor. Use of the MCF device, along with a temperature-controlled setup, provides a relatively simple and robust technique that can be widely used for further analysis of materials at the ice/water interface. Copyright © 2016. Published by Elsevier Inc.

Vibrio cholerae O1 epidemic variants in Angola: a retrospective study between 1992 and 2006.

PubMed

Valia, Romy; Taviani, Elisa; Spagnoletti, Matteo; Ceccarelli, Daniela; Cappuccinelli, Piero; Colombo, Mauro M

2013-01-01

Cholera is still a major public health concern in many African countries. In Angola, after a decade of absence, cholera reemerged in 1987, spreading throughout the country until 1996, with outbreaks recurring in a seasonal pattern. In 2006 Angola was hit by one of the most severe outbreaks of the last decade, with ca. 240,000 cases reported. We analyzed 21 clinical strains isolated between 1992 and 2006 from several provinces throughout the country: Benguela, Bengo, Luanda, Cuando Cubango, and Cabinda. We used two multiplex PCR assays to investigate discriminatory mobile genetic elements (MGE) [Integrative Conjugative Elements (ICEs), VSP-II, GI12, GI14, GI15, K, and TLC phages] and we compared the profiles obtained with those of different reference V. cholerae O1 variants (prototypical, altered, and hybrid), responsible for the ongoing 7th pandemic. We also tested the strains for the presence of specific VSP-II variants and for the presence of a genomic island (GI) (WASA-1), correlated with the transmission of seventh pandemic cholera from Africa to South America. Based on the presence/absence of the analyzed genetic elements, five novel profiles were detected in the epidemic strains circulating in the 1990s. The most frequent profiles, F and G, were characterized by the absence of ICEs and the three GIs tested, and the presence of GI WASA-1 and the WASA variant of the VSP-II island. Our results identified unexpected variability within the 1990s epidemic, showing different rearrangements in a dynamic part of the genome not present in the prototypical V. cholerae O1 N16961. Moreover the 2006 strains differed from the current pandemic V. cholerae O1 strain. Taken together, our results highlight the role of horizontal gene transfer (HGT) in diversifying the genetic background of V. cholerae within a single epidemic.

High Performance Computing Technologies for Modeling the Dynamics and Dispersion of Ice Chunks in the Arctic Ocean

DTIC Science & Technology

2016-08-23

SECURITY CLASSIFICATION OF: Hybrid finite element / finite volume based CaMEL shallow water flow solvers have been successfully extended to study wave...effects on ice floes in a simplified 10 sq-km ocean domain. Our solver combines the merits of both the finite element and finite volume methods and...ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 sea ice dynamics, shallow water, finite element , finite volume

Interplay of a non-conjugative integrative element and a conjugative plasmid in the spread of antibiotic resistance via suicidal plasmid transfer from an aquaculture Vibrio isolate.

PubMed

Nonaka, Lisa; Yamamoto, Tatsuya; Maruyama, Fumito; Hirose, Yuu; Onishi, Yuki; Kobayashi, Takeshi; Suzuki, Satoru; Nomura, Nobuhiko; Masuda, Michiaki; Yano, Hirokazu

2018-01-01

The capture of antimicrobial resistance genes (ARGs) by mobile genetic elements (MGEs) plays a critical role in resistance acquisition for human-associated bacteria. Although aquaculture environments are recognized as important reservoirs of ARGs, intra- and intercellular mobility of MGEs discovered in marine organisms is poorly characterized. Here, we show a new pattern of interspecies ARGs transfer involving a 'non-conjugative' integrative element. To identify active MGEs in a Vibrio ponticus isolate, we conducted whole-genome sequencing of a transconjugant obtained by mating between Escherichia coli and Vibrio ponticus. This revealed integration of a plasmid (designated pSEA1) into the chromosome, consisting of a self-transmissible plasmid backbone of the MOBH group, ARGs, and a 13.8-kb integrative element Tn6283. Molecular genetics analysis suggested a two-step gene transfer model. First, Tn6283 integrates into the recipient chromosome during suicidal plasmid transfer, followed by homologous recombination between the Tn6283 copy in the chromosome and that in the newly transferred pSEA1. Tn6283 is unusual among integrative elements in that it apparently does not encode transfer function and its excision barely generates unoccupied donor sites. Thus, its movement is analogous to the transposition of insertion sequences rather than to that of canonical integrative and conjugative elements. Overall, this study reveals the presence of a previously unrecognized type of MGE in a marine organism, highlighting diversity in the mode of interspecies gene transfer.

Characterization of Ice Roughness From Simulated Icing Encounters

NASA Technical Reports Server (NTRS)

Anderson, David N.; Shin, Jaiwon

1997-01-01

Detailed measurements of the size of roughness elements on ice accreted on models in the NASA Lewis Icing Research Tunnel (IRT) were made in a previous study. Only limited data from that study have been published, but included were the roughness element height, diameter and spacing. In the present study, the height and spacing data were found to correlate with the element diameter, and the diameter was found to be a function primarily of the non-dimensional parameters freezing fraction and accumulation parameter. The width of the smooth zone which forms at the leading edge of the model was found to decrease with increasing accumulation parameter. Although preliminary, the success of these correlations suggests that it may be possible to develop simple relationships between ice roughness and icing conditions for use in ice-accretion-prediction codes. These codes now require an ice-roughness estimate to determine convective heat transfer. Studies using a 7.6-cm-diameter cylinder and a 53.3-cm-chord NACA 0012 airfoil were also performed in which a 1/2-min icing spray at an initial set of conditions was followed by a 9-1/2-min spray at a second set of conditions. The resulting ice shape was compared with that from a full 10-min spray at the second set of conditions. The initial ice accumulation appeared to have no effect on the final ice shape. From this result, it would appear the accreting ice is affected very little by the initial roughness or shape features.

Comparative genomics of Enterococcus spp. isolated from bovine feces.

PubMed

Beukers, Alicia G; Zaheer, Rahat; Goji, Noriko; Amoako, Kingsley K; Chaves, Alexandre V; Ward, Michael P; McAllister, Tim A

2017-03-08

Enterococcus is ubiquitous in nature and is a commensal of both the bovine and human gastrointestinal (GI) tract. It is also associated with clinical infections in humans. Subtherapeutic administration of antibiotics to cattle selects for antibiotic resistant enterococci in the bovine GI tract. Antibiotic resistance genes (ARGs) may be present in enterococci following antibiotic use in cattle. If located on mobile genetic elements (MGEs) their dissemination between Enterococcus species and to pathogenic bacteria may be promoted, reducing the efficacy of antibiotics. We present a comparative genomic analysis of twenty-one Enterococcus spp. isolated from bovine feces including Enterococcus hirae (n = 10), Enterococcus faecium (n = 3), Enterococcus villorum (n = 2), Enterococcus casseliflavus (n = 2), Enterococcus faecalis (n = 1), Enterococcus durans (n = 1), Enterococcus gallinarum (n = 1) and Enterococcus thailandicus (n = 1). The analysis revealed E. faecium and E. faecalis from bovine feces share features with human clinical isolates, including virulence factors. The Tn917 transposon conferring macrolide-lincosamide-streptogramin B resistance was identified in both E. faecium and E. hirae, suggesting dissemination of ARGs on MGEs may occur in the bovine GI tract. An E. faecium isolate was also identified with two integrative conjugative elements (ICEs) belonging to the Tn916 family of ICE, Tn916 and Tn5801, both conferring tetracycline resistance. This study confirms the presence of enterococci in the bovine GI tract possessing ARGs on MGEs, but the predominant species in cattle, E. hirae is not commonly associated with infections in humans. Analysis using additional complete genomes of E. faecium from the NCBI database demonstrated differential clustering of commensal and clinical isolates, suggesting that these strains may be specifically adapted to their respective environments.

An Integrated Approach to Swept Wing Icing Simulation

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.; Broeren, Andy P.

2017-01-01

This paper describes the various elements of a simulation approach used to develop a database of ice shape geometries and the resulting aerodynamic performance data for a representative commercial transport wing model exposed to a variety of icing conditions. This effort included testing in the NASA Icing Research Tunnel, the Wichita State University Walter H. Beech Wind Tunnel, and the ONERA F1 Subsonic Wind Tunnel as well as the use of ice accretion codes, an inviscid design code, and computational fluid dynamics codes. Additionally, methods for capturing full three-dimensional ice shape geometries, geometry interpolation along the span of the wing, and creation of artificial ice shapes based upon that geometric data were developed for this effort. The icing conditions used for this effort were representative of actual ice shape encounter scenarios and run the gamut from ice roughness to full three-dimensional scalloped ice shapes. The effort is still underway so this paper is a status report of work accomplished to date and a description of the remaining elements of the effort.

Ice Accretion and Performance Degradation Calculations with LEWICE/NS

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.; Al-Khalil, Kamel M.; Velazquez, Matthew T.

1993-01-01

The LEWICE ice accretion computer code has been extended to include the solution of the two-dimensional Navier-Stokes equations. The code is modular and contains separate stand-alone program elements that create a grid, calculate the flow field parameters, calculate the droplet trajectory paths, determine the amount of ice growth, calculate aeroperformance changes, and plot results. The new elements of the code are described. Calculated results are compared to experiment for several cases, including both ice shape and drag rise.

Finite elements and the method of conjugate gradients on a concurrent processor

NASA Technical Reports Server (NTRS)

Lyzenga, G. A.; Raefsky, A.; Hager, G. H.

1985-01-01

An algorithm for the iterative solution of finite element problems on a concurrent processor is presented. The method of conjugate gradients is used to solve the system of matrix equations, which is distributed among the processors of a MIMD computer according to an element-based spatial decomposition. This algorithm is implemented in a two-dimensional elastostatics program on the Caltech Hypercube concurrent processor. The results of tests on up to 32 processors show nearly linear concurrent speedup, with efficiencies over 90 percent for sufficiently large problems.

Finite elements and the method of conjugate gradients on a concurrent processor

NASA Technical Reports Server (NTRS)

Lyzenga, G. A.; Raefsky, A.; Hager, B. H.

1984-01-01

An algorithm for the iterative solution of finite element problems on a concurrent processor is presented. The method of conjugate gradients is used to solve the system of matrix equations, which is distributed among the processors of a MIMD computer according to an element-based spatial decomposition. This algorithm is implemented in a two-dimensional elastostatics program on the Caltech Hypercube concurrent processor. The results of tests on up to 32 processors show nearly linear concurrent speedup, with efficiencies over 90% for sufficiently large problems.

International Workshop on Antarctic Meteorites

NASA Technical Reports Server (NTRS)

Annexstad, J. O.; Schultz, L.; Waenke, H.

1986-01-01

Topics addressed include: meteorite concentration mechanisms; meteorites and the Antarctic ice sheet; iron meteorites; iodine overabundance in meteorites; entrainment, transport, and concentration of meteorites in polar ice sheets; weathering of stony meteorites; cosmic ray records; radiocarbon dating; element distribution and noble gas isotopic abundances in lunar meteorites; thermoanalytical characterization; trace elements; thermoluminescence; parent sources; and meteorite ablation and fusion spherules in Antarctic ice.

A finite element conjugate gradient FFT method for scattering

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Ross, Dan; Jin, J.-M.; Chatterjee, A.; Volakis, John L.

1991-01-01

Validated results are presented for the new 3D body of revolution finite element boundary integral code. A Fourier series expansion of the vector electric and mangnetic fields is employed to reduce the dimensionality of the system, and the exact boundary condition is employed to terminate the finite element mesh. The mesh termination boundary is chosen such that is leads to convolutional boundary operatores of low O(n) memory demand. Improvements of this code are discussed along with the proposed formulation for a full 3D implementation of the finite element boundary integral method in conjunction with a conjugate gradiant fast Fourier transformation (CGFFT) solution.

Seasonal Study of Mercury Species in the Antarctic Sea Ice Environment.

PubMed

Nerentorp Mastromonaco, Michelle G; Gårdfeldt, Katarina; Langer, Sarka; Dommergue, Aurélien

2016-12-06

Limited studies have been conducted on mercury concentrations in the polar cryosphere and the factors affecting the distribution of mercury within sea ice and snow are poorly understood. Here we present the first comprehensive seasonal study of elemental and total mercury concentrations in the Antarctic sea ice environment covering data from measurements in air, sea ice, seawater, snow, frost flowers, and brine. The average concentration of total mercury in sea ice decreased from winter (9.7 ng L -1 ) to spring (4.7 ng L -1 ) while the average elemental mercury concentration increased from winter (0.07 ng L -1 ) to summer (0.105 ng L -1 ). The opposite trends suggest potential photo- or dark oxidation/reduction processes within the ice and an eventual loss of mercury via brine drainage or gas evasion of elemental mercury. Our results indicate a seasonal variation of mercury species in the polar sea ice environment probably due to varying factors such as solar radiation, temperature, brine volume, and atmospheric deposition. This study shows that the sea ice environment is a significant interphase between the polar ocean and the atmosphere and should be accounted for when studying how climate change may affect the mercury cycle in polar regions.

Horizontal transfer of chromosomal markers mediated by the large conjugative plasmid pXO16 from Bacillus thuringiensis serovar israelensis.

PubMed

Makart, Lionel; Commans, Florian; Gillis, Annika; Mahillon, Jacques

2017-05-01

pXO16, a large plasmid originating from Bacillus thuringiensis serovar israelensis, displays unique conjugation capacities: besides efficient self-transfer, it is able to mobilize and retro-mobilize non-conjugative plasmids, including those missing an oriT and/or a mob gene, also known as "non-mobilizable" plasmids. In this paper, another peculiar transfer property of pXO16 is described. This element is indeed able to transfer chromosomal loci at frequencies of ca. 10 -5 -10 -6 transconjugants/donor cell. Whereas most other chromosomal transfer systems occur via the integration of the conjugative elements into the chromosome prior to its transfer, pXO16 appears to transfer the chromosomal markers in the absence of physical integration, but rather through a "donation-type" mobilization. Copyright © 2017 Elsevier Inc. All rights reserved.

Analysis of water ice and water ice/soil mixtures using laser-induced breakdown spectroscopy: application to Mars polar exploration.

PubMed

Arp, Zane A; Cremers, David A; Wiens, Roger C; Wayne, David M; Sallé, Béatrice; Maurice, Sylvestre

2004-08-01

Recently, laser-induced breakdown spectroscopy (LIBS) has been developed for the elemental analysis of geological samples for application to space exploration. There is also interest in using the technique for the analysis of water ice and ice/dust mixtures located at the Mars polar regions. The application is a compact instrument for a lander or rover to the Martian poles to interrogate stratified layers of ice and dusts that contain a record of past geologic history, believed to date back several million years. Here we present results of a study of the use of LIBS for the analysis of water ice and ice/dust mixtures in situ and at short stand-off distances (< 6.5 m) using experimental parameters appropriate for a compact instrument. Characteristics of LIBS spectra of water ice, ice/soil mixtures, element detection limits, and the ability to ablate through ice samples to monitor subsurface dust deposits are discussed.

Open-water and under-ice seasonal variations in trace element content and physicochemical associations in fluvial bed sediment.

PubMed

Doig, Lorne E; Carr, Meghan K; Meissner, Anna G N; Jardine, Tim D; Jones, Paul D; Bharadwaj, Lalita; Lindenschmidt, Karl-Erich

2017-11-01

Across the circumpolar world, intensive anthropogenic activities in the southern reaches of many large, northward-flowing rivers can cause sediment contamination in the downstream depositional environment. The influence of ice cover on concentrations of inorganic contaminants in bed sediment (i.e., sediment quality) is unknown in these rivers, where winter is the dominant season. A geomorphic response unit approach was used to select hydraulically diverse sampling sites across a northern test-case system, the Slave River and delta (Northwest Territories, Canada). Surface sediment samples (top 1 cm) were collected from 6 predefined geomorphic response units (12 sites) to assess the relationships between bed sediment physicochemistry (particle size distribution and total organic carbon content) and trace element content (mercury and 18 other trace elements) during open-water conditions. A subset of sites was resampled under-ice to assess the influence of season on these relationships and on total trace element content. Concentrations of the majority of trace elements were strongly correlated with percent fines and proxies for grain size (aluminum and iron), with similar trace element grain size/grain size proxy relationships between seasons. However, finer materials were deposited under ice with associated increases in sediment total organic carbon content and the concentrations of most trace elements investigated. The geomorphic response unit approach was effective at identifying diverse hydrological environments for sampling prior to field operations. Our data demonstrate the need for under-ice sampling to confirm year-round consistency in trace element-geochemical relationships in fluvial systems and to define the upper extremes of these relationships. Whether contaminated or not, under-ice bed sediment can represent a "worst-case" scenario in terms of trace element concentrations and exposure for sediment-associated organisms in northern fluvial systems. Environ Toxicol Chem 2017;36:2916-2924. © 2017 SETAC. © 2017 SETAC.

Pseudomonas syringae pv. actinidiae from Recent Outbreaks of Kiwifruit Bacterial Canker Belong to Different Clones That Originated in China

PubMed Central

Butler, Margi I.; Stockwell, Peter A.; Black, Michael A.; Day, Robert C.; Lamont, Iain L.; Poulter, Russell T. M.

2013-01-01

A recently emerged plant disease, bacterial canker of kiwifruit (Actinidia deliciosa and A. chinensis), is caused by Pseudomonas syringae pv. actinidiae (PSA). The disease was first reported in China and Japan in the 1980s. A severe outbreak of PSA began in Italy in 2008 and has spread to other European countries. PSA was found in both New Zealand and Chile in 2010. To study the evolution of the pathogen and analyse the transmission of PSA between countries, genomes of strains from China and Japan (where the genus Actinidia is endemic), Italy, New Zealand and Chile were sequenced. The genomes of PSA strains are very similar. However, all strains from New Zealand share several single nucleotide polymorphisms (SNPs) that distinguish them from all other PSA strains. Similarly, all the PSA strains from the 2008 Italian outbreak form a distinct clonal group and those from Chile form a third group. In addition to the rare SNPs present in the core genomes, there is abundant genetic diversity in a genomic island that is part of the accessory genome. The island from several Chinese strains is almost identical to the island present in the New Zealand strains. The island from a different Chinese strain is identical to the island present in the strains from the recent Italian outbreak. The Chilean strains of PSA carry a third variant of this island. These genomic islands are integrative conjugative elements (ICEs). Sequencing of these ICEs provides evidence of three recent horizontal transmissions of ICE from other strains of Pseudomonas syringae to PSA. The analyses of the core genome SNPs and the ICEs, combined with disease history, all support the hypothesis of an independent Chinese origin for both the Italian and the New Zealand outbreaks and suggest the Chilean strains also originate from China. PMID:23555547

Surface conforming thermal/pressure seal. [tail assemblies of space shuttle orbiters

NASA Technical Reports Server (NTRS)

Stevens, M. L. (Inventor)

1981-01-01

An assembly is disclosed for sealing a variable gap between the surface of element and a second element in movable relation to it. A seal housing is attached to the second element for movement therewith and has a sealing surface. At least one elongated seal member carried by the housing has first and second conjugate sealing surfaces. The first sealing surface is for rubbing and sealing engagement with the first element surface and the second sealing surface is for sliding and sealing engagement with the housing sealing surface. A biasing assembly may be carried by the housing for biasing the first and second conjugate sealing surfaces of the sealing member toward sealing engagement with the first element surface and housing sealing surface, respectively.

A finite element study of the EIDI system. [Electro-Impulse De-Icing System

NASA Technical Reports Server (NTRS)

Khatkhate, A. A.; Scavuzzo, R. J.; Chu, M. L.

1988-01-01

This paper presents a method for modeling the structural dynamics of an Electro-Impulse De-Icing System, using finite element analyses procedures. A guideline for building a representative finite element model is discussed. Modeling was done initially using four noded cubic elements, four noded isoparametric plate elements and eight noded isoparametric shell elements. Due to the size of the problem and due to the underestimation of shear stress results when compared to previous analytical work an approximate model was created to predict possible areas of shedding of ice. There appears to be good agreement with the test data provided by The Boeing Commercial Airplane Company. Thus these initial results of this method were found to be encouraging. Additional analytical work and comparison with experiment is needed in order to completely evaluate this approach.

Full Stokes finite-element modeling of ice sheets using a graphics processing unit

NASA Astrophysics Data System (ADS)

Seddik, H.; Greve, R.

2016-12-01

Thermo-mechanical simulation of ice sheets is an important approach to understand and predict their evolution in a changing climate. For that purpose, higher order (e.g., ISSM, BISICLES) and full Stokes (e.g., Elmer/Ice, http://elmerice.elmerfem.org) models are increasingly used to more accurately model the flow of entire ice sheets. In parallel to this development, the rapidly improving performance and capabilities of Graphics Processing Units (GPUs) allows to efficiently offload more calculations of complex and computationally demanding problems on those devices. Thus, in order to continue the trend of using full Stokes models with greater resolutions, using GPUs should be considered for the implementation of ice sheet models. We developed the GPU-accelerated ice-sheet model Sainō. Sainō is an Elmer (http://www.csc.fi/english/pages/elmer) derivative implemented in Objective-C which solves the full Stokes equations with the finite element method. It uses the standard OpenCL language (http://www.khronos.org/opencl/) to offload the assembly of the finite element matrix on the GPU. A mesh-coloring scheme is used so that elements with the same color (non-sharing nodes) are assembled in parallel on the GPU without the need for synchronization primitives. The current implementation shows that, for the ISMIP-HOM experiment A, during the matrix assembly in double precision with 8000, 87,500 and 252,000 brick elements, Sainō is respectively 2x, 10x and 14x faster than Elmer/Ice (when both models are run on a single processing unit). In single precision, Sainō is even 3x, 20x and 25x faster than Elmer/Ice. A detailed description of the comparative results between Sainō and Elmer/Ice will be presented, and further perspectives in optimization and the limitations of the current implementation.

Structural properties of impact ices accreted on aircraft structures

NASA Technical Reports Server (NTRS)

Scavuzzo, R. J.; Chu, M. L.

1987-01-01

The structural properties of ice accretions formed on aircraft surfaces are studied. The overall objectives are to measure basic structural properties of impact ices and to develop finite element analytical procedures for use in the design of all deicing systems. The Icing Research Tunnel (IRT) was used to produce simulated natural ice accretion over a wide range of icing conditions. Two different test apparatus were used to measure each of the three basic mechanical properties: tensile, shear, and peeling. Data was obtained on both adhesive shear strength of impact ices and peeling forces for various icing conditions. The influences of various icing parameters such as tunnel air temperature and velocity, icing cloud drop size, material substrate, surface temperature at ice/material interface, and ice thickness were studied. A finite element analysis of the shear test apparatus was developed in order to gain more insight in the evaluation of the test data. A comparison with other investigators was made. The result shows that the adhesive shear strength of impact ice typically varies between 40 and 50 psi, with peak strength reaching 120 psi and is not dependent on the kind of substrate used, the thickness of accreted ice, and tunnel temperature below 4 C.

Study of energy parameters of machine parts of water-ice jet cleaning applications

NASA Astrophysics Data System (ADS)

Prezhbilov, A. N.; Burnashov, M. A.

2018-03-01

The reader will achieve a benchmark understanding of the essence of cleaning for the removal of contaminants from machine elements by means of cryo jet/water-ice jet with particles prepared beforehand. This paper represents the classification of the most common contaminants appearing on the surfaces of machine elements after a long-term service. The conceptual contribution of the paper is to represent a thermo-physical model of contaminant removal by means of a water ice jet. In conclusion, it is evident that this study has shown the dependencies between the friction force of an ice particle with an obstacle (contamination), a dimensional change of an ice particle in the cleaning process and the quantity of heat transmitted to an ice particle.

Ice Shape Characterization Using Self-Organizing Maps

NASA Technical Reports Server (NTRS)

McClain, Stephen T.; Tino, Peter; Kreeger, Richard E.

2011-01-01

A method for characterizing ice shapes using a self-organizing map (SOM) technique is presented. Self-organizing maps are neural-network techniques for representing noisy, multi-dimensional data aligned along a lower-dimensional and possibly nonlinear manifold. For a large set of noisy data, each element of a finite set of codebook vectors is iteratively moved in the direction of the data closest to the winner codebook vector. Through successive iterations, the codebook vectors begin to align with the trends of the higher-dimensional data. In information processing, the intent of SOM methods is to transmit the codebook vectors, which contains far fewer elements and requires much less memory or bandwidth, than the original noisy data set. When applied to airfoil ice accretion shapes, the properties of the codebook vectors and the statistical nature of the SOM methods allows for a quantitative comparison of experimentally measured mean or average ice shapes to ice shapes predicted using computer codes such as LEWICE. The nature of the codebook vectors also enables grid generation and surface roughness descriptions for use with the discrete-element roughness approach. In the present study, SOM characterizations are applied to a rime ice shape, a glaze ice shape at an angle of attack, a bi-modal glaze ice shape, and a multi-horn glaze ice shape. Improvements and future explorations will be discussed.

Tipping elements in the Arctic marine ecosystem.

PubMed

Duarte, Carlos M; Agustí, Susana; Wassmann, Paul; Arrieta, Jesús M; Alcaraz, Miquel; Coello, Alexandra; Marbà, Núria; Hendriks, Iris E; Holding, Johnna; García-Zarandona, Iñigo; Kritzberg, Emma; Vaqué, Dolors

2012-02-01

The Arctic marine ecosystem contains multiple elements that present alternative states. The most obvious of which is an Arctic Ocean largely covered by an ice sheet in summer versus one largely devoid of such cover. Ecosystems under pressure typically shift between such alternative states in an abrupt, rather than smooth manner, with the level of forcing required for shifting this status termed threshold or tipping point. Loss of Arctic ice due to anthropogenic climate change is accelerating, with the extent of Arctic sea ice displaying increased variance at present, a leading indicator of the proximity of a possible tipping point. Reduced ice extent is expected, in turn, to trigger a number of additional tipping elements, physical, chemical, and biological, in motion, with potentially large impacts on the Arctic marine ecosystem.

Test and Analysis Correlation of High Speed Impacts of Ice Cylinders

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Boitnott, Richard L.; Kellas, Sotiris

2006-01-01

During the space shuttle return-to-flight preparations following the Columbia accident, finite element models were needed that could predict the threshold of critical damage to the orbiter s wing leading edge from ice debris impacts. Hence, an experimental program was initiated to provide crushing data from impacted ice for use in dynamic finite element material models. A high-speed drop tower was configured to capture force time-histories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, the force-time history depended heavily on the internal crystalline structure of the ice. However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a fluid, and the subsequent force-time history curves were much less dependent on the internal crystalline structure.

Dynamic Crush Characterization of Ice

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Boitnott, Richard L.; Kellas, Sotiris

2006-01-01

During the space shuttle return-to-flight preparations following the Columbia accident, finite element models were needed that could predict the threshold of critical damage to the orbiter's wing leading edge from ice debris impacts. Hence, an experimental program was initiated to provide crushing data from impacted ice for use in dynamic finite element material models. A high-speed drop tower was configured to capture force time histories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, the force-time history depended heavily on the internal crystalline structure of the ice. However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a fluid, and the subsequent force-time history curves were much less dependent on the internal crystalline structure.

Quelccaya Ice Core Evidence of Widespread Atmospheric Pollution from Colonial Metallurgy after the Spanish Conquest of South America (1532 AD)

NASA Astrophysics Data System (ADS)

Gabrielli, P.; Uglietti, C.; Cooke, C. A.; Thompson, L. G.

2014-12-01

A few ice core records recovered from remote arctic regions suggest a widespread impact of toxic trace elements (Pb, Cu, Sb, As and Bi) to the North Hemisphere atmosphere prior to the onset of the Industrial Revolution (1780s-1830s). In the Southern Hemisphere, evidence for preindustrial trace element emissions are, to date, limited to sediment cores recovered from lakes located within the immediate airshed of major metallurgical centers of South America. Thus it remains unresolved whether they could have had a larger scale impact. Here, we present an annually resolved ice core record of anthropogenic trace element deposition from the remote drilling site of the Quelccaya Ice Cap (Peru) that spans 793-1989 AD. During the pre-Inca period (i.e., prior to ~1450 AD) the deposition of trace elements was dominated by the fallout of aeolian dust from the deglaciated margins of the ice cap and of ash from occasional volcanic eruptions. In contrast, the ice core record indicates a clear anthropogenic signal emerging after the onset of large scale colonial mining and metallurgy (1532-1820 AD), ~300 years prior to the Industrial Revolution during the last part of the Little Ice Age. This shift was coincidental with a major technological transition for silver extraction (1572 AD), from lead-based smelting to mercury amalgamation, that initiated a major increase in ore mining and milling that likely resulted in an increase of metallic dust emissions. While atmospheric trace element deposition resulting from colonial metallurgy was certainly much larger than during the pre-Colonial period, trace element fallout during the Colonial era was still several factors lower than during the 20th century, when the construction of the trans-Andean railway and highways promoted a widespread societal and industrial development of South America.

Instrument for Aircraft-Icing and Cloud-Physics Measurements

NASA Technical Reports Server (NTRS)

Lilie, Lyle; Bouley, Dan; Sivo, Chris

2006-01-01

The figure shows a compact, rugged, simple sensor head that is part of an instrumentation system for making measurements to characterize the severity of aircraft-icing conditions and/or to perform research on cloud physics. The quantities that are calculated from measurement data acquired by this system and that are used to quantify the severity of icing conditions include sizes of cloud water drops, cloud liquid water content (LWC), cloud ice water content (IWC), and cloud total water content (TWC). The sensor head is mounted on the outside of an aircraft, positioned and oriented to intercept the ambient airflow. The sensor head consists of an open housing that is heated in a controlled manner to keep it free of ice and that contains four hot-wire elements. The hot-wire sensing elements have different shapes and sizes and, therefore, exhibit different measurement efficiencies with respect to droplet size and water phase (liquid, frozen, or mixed). Three of the hot-wire sensing elements are oriented across the airflow so as to intercept incoming cloud water. For each of these elements, the LWC or TWC affects the power required to maintain a constant temperature in the presence of cloud water.

Synchrotron X-ray fluorescence spectroscopy of salts in natural sea ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Obbard, Rachel W.; Lieb-Lappen, Ross M.; Nordick, Katherine V.

We describe the use of synchrotron-based X-ray fluorescence spectroscopy to examine the microstructural location of specific elements, primarily salts, in sea ice. This work was part of an investigation of the location of bromine in the sea ice-snowpack-blowing snow system, where it plays a part in the heterogeneous chemistry that contributes to tropospheric ozone depletion episodes. We analyzed samples at beamline 13-ID-E of the Advanced Photon Source at Argonne National Laboratory. Using an 18 keV incident energy beam, we produced elemental maps of salts for sea ice samples from the Ross Sea, Antarctica. The distribution of salts in sea icemore » depends on ice type. In our columnar ice samples, Br was located in parallel lines spaced roughly 0.5 mm apart, corresponding to the spacing of lamellae in the skeletal region during initial ice growth. The maps revealed concentrations of Br in linear features in samples from all but the topmost and bottommost depths. For those samples, the maps revealed rounded features. Calibration of the Br elemental maps showed bulk concentrations to be 5–10 g/m 3, with concentrations ten times larger in the linear features. Through comparison with horizontal thin sections, we could verify that these linear features were brine sheets or layers.« less

Synchrotron X-ray fluorescence spectroscopy of salts in natural sea ice

DOE PAGES

Obbard, Rachel W.; Lieb-Lappen, Ross M.; Nordick, Katherine V.; ...

2016-10-23

We describe the use of synchrotron-based X-ray fluorescence spectroscopy to examine the microstructural location of specific elements, primarily salts, in sea ice. This work was part of an investigation of the location of bromine in the sea ice-snowpack-blowing snow system, where it plays a part in the heterogeneous chemistry that contributes to tropospheric ozone depletion episodes. We analyzed samples at beamline 13-ID-E of the Advanced Photon Source at Argonne National Laboratory. Using an 18 keV incident energy beam, we produced elemental maps of salts for sea ice samples from the Ross Sea, Antarctica. The distribution of salts in sea icemore » depends on ice type. In our columnar ice samples, Br was located in parallel lines spaced roughly 0.5 mm apart, corresponding to the spacing of lamellae in the skeletal region during initial ice growth. The maps revealed concentrations of Br in linear features in samples from all but the topmost and bottommost depths. For those samples, the maps revealed rounded features. Calibration of the Br elemental maps showed bulk concentrations to be 5–10 g/m 3, with concentrations ten times larger in the linear features. Through comparison with horizontal thin sections, we could verify that these linear features were brine sheets or layers.« less

Pilots' Information Needs and Strategies for Operating in Icing Conditions

NASA Technical Reports Server (NTRS)

Vigeant-Langlois, Laurence N.; Hansman, R. John

2003-01-01

Pilot current use of icing information, pilot encounters and strategies for dealing with in-flight aircraft structural icing situations, and desired attributes of new icing information systems were investigated through a survey of pilots of several operational categories. The survey identified important information elements and fiequently used information paths for obtaining icing-related information. Free- response questions solicited descriptions of significant , icing encounters, and probed key icing-related decision and information criteria. Results indicated the information needs for the horizontal and vertical location of icing conditions and the identification of icing-free zones.

A discrete-element model for viscoelastic deformation and fracture of glacial ice

NASA Astrophysics Data System (ADS)

Riikilä, T. I.; Tallinen, T.; Åström, J.; Timonen, J.

2015-10-01

A discrete-element model was developed to study the behavior of viscoelastic materials that are allowed to fracture. Applicable to many materials, the main objective of this analysis was to develop a model specifically for ice dynamics. A realistic model of glacial ice must include elasticity, brittle fracture and slow viscous deformations. Here the model is described in detail and tested with several benchmark simulations. The model was used to simulate various ice-specific applications with resulting flow rates that were compatible with Glen's law, and produced under fragmentation fragment-size distributions that agreed with the known analytical and experimental results.

Ice-shelf Dynamics Near the Front of Filchner-Ronne Ice Shelf, Antarctica, Revealed by SAR Interferometry: Model/Interferogram Comparison

NASA Technical Reports Server (NTRS)

MacAyeal, D. R.; Rignot, E.; Hulbe, C. L.

1998-01-01

We compare Earth Remote Sensing (ERS) satellite synthetic-aperture radar (SAR) interferograms with artificial interferograms constructed using output of a finite-element ice-shelf flow model to study the dynamics of Filchner-Ronne Ice Shelf (FRIS) near Hemmen Ice Rise (HIR) where the iceberg-calving front itersects Berkener Island (BI).

Reconfigurable wave band structure of an artificial square ice

DOE PAGES

lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; ...

2016-04-18

Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less

Reconfigurable wave band structure of an artificial square ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.

Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less

The Tcp conjugation system of Clostridium perfringens.

PubMed

Wisniewski, Jessica A; Rood, Julian I

2017-05-01

The Gram-positive pathogen Clostridium perfringens possesses a family of large conjugative plasmids that is typified by the tetracycline resistance plasmid pCW3. Since these plasmids may carry antibiotic resistance genes or genes encoding extracellular or sporulation-associated toxins, the conjugative transfer of these plasmids appears to be important for the epidemiology of C. perfringens-mediated diseases. Sequence analysis of members of this plasmid family identified a highly conserved 35kb region that encodes proteins with various functions, including plasmid replication and partitioning. The tcp conjugation locus also was identified in this region, initially based on low-level amino acid sequence identity to conjugation proteins from the integrative conjugative element Tn916. Genetic studies confirmed that the tcp locus is required for conjugative transfer and combined with biochemical and structural analyses have led to the development of a functional model of the Tcp conjugation apparatus. This review summarises our current understanding of the Tcp conjugation system, which is now one of the best-characterized conjugation systems in Gram-positive bacteria. Copyright © 2017 Elsevier Inc. All rights reserved.

Blasim: A computational tool to assess ice impact damage on engine blades

NASA Astrophysics Data System (ADS)

Reddy, E. S.; Abumeri, G. H.; Chamis, C. C.

1993-04-01

A portable computer called BLASIM was developed at NASA LeRC to assess ice impact damage on aircraft engine blades. In addition to ice impact analyses, the code also contains static, dynamic, resonance margin, and supersonic flutter analysis capabilities. Solid, hollow, superhybrid, and composite blades are supported. An optional preprocessor (input generator) was also developed to interactively generate input for BLASIM. The blade geometry can be defined using a series of airfoils at discrete input stations or by a finite element grid. The code employs a coarse, fixed finite element mesh containing triangular plate finite elements to minimize program execution time. Ice piece is modeled using an equivalent spherical objective that has a high velocity opposite that of the aircraft and parallel to the engine axis. For local impact damage assessment, the impact load is considered as a distributed force acting over a region around the impact point. The average radial strain of the finite elements along the leading edge is used as a measure of the local damage. To estimate damage at the blade root, the impact is treated as an impulse and a combined stress failure criteria is employed. Parametric studies of local and root ice impact damage, and post-impact dynamics are discussed for solid and composite blades.

Convective Enhancement of Icing Roughness Elements in Stagnation Region Flows

NASA Technical Reports Server (NTRS)

Hughes, Michael T.; McClain, Stephen T.; Vargas, Mario; Broeren, Andy

2015-01-01

To improve existing ice accretion simulation codes, more data regarding ice roughness and its effects on convective heat transfer are required. To build on existing research on this topic, this study used the Vertical Icing Studies Tunnel (VIST) at NASA Glenn Research to model realistic ice roughness in the stagnation region of a NACA 0012 airfoil. Using the VIST, a test plate representing the leading 2% chord of the airfoil was subjected to flows of 7.62 m/s (25 ft/s), 12.19 m/s (40 ft/s), and 16.76 m/s (55 ft/s). The test plate was fitted with 3 surfaces, each with a different representation of ice roughness: 1) a control surface with no ice roughness, 2) a surface with ice roughness with element height scaled by 10x and streamwise rough zone width from the stagnation point scaled by 10x, and 3) a surface with ice roughness with element height scaled by 10x and streamwise rough zone width from the stagnation point scaled by 25x. Temperature data from the tests were recorded using an infrared camera and thermocouples imbedded in the test plate. From the temperature data, a convective heat transfer coefficient map was created for each case. Additional testing was also performed to validate the VIST's flow quality. These tests included five-hole probe and hot-wire probe velocity traces to provide flow visualization and to study boundary layer formation on the various test surfaces. The knowledge gained during the experiments will help improve ice accretion codes by providing heat transfer coefficient validation data and by providing flow visualization data helping understand current and future experiments performed in the VIST.

Ice Engineering - study of Related Properties of Floating Sea-Ice Sheets and Summary of Elastic and Viscoelastic Analyses

DTIC Science & Technology

1977-12-01

Ice Plate Example. To demonstrate the capability of the visco- elastic finite-element computer code (5), the structural response of an infinite ... sea -ice plate on a fluid foundation is investigated for a simulated aircraft loading condition and, using relaxation functions, is determined

Population Structure and Antimicrobial Resistance Profiles of Streptococcus suis Serotype 2 Sequence Type 25 Strains.

PubMed

Athey, Taryn B T; Teatero, Sarah; Takamatsu, Daisuke; Wasserscheid, Jessica; Dewar, Ken; Gottschalk, Marcelo; Fittipaldi, Nahuel

2016-01-01

Strains of serotype 2 Streptococcus suis are responsible for swine and human infections. Different serotype 2 genetic backgrounds have been defined using multilocus sequence typing (MLST). However, little is known about the genetic diversity within each MLST sequence type (ST). Here, we used whole-genome sequencing to test the hypothesis that S. suis serotype 2 strains of the ST25 lineage are genetically heterogeneous. We evaluated 51 serotype 2 ST25 S. suis strains isolated from diseased pigs and humans in Canada, the United States of America, and Thailand. Whole-genome sequencing revealed numerous large-scale rearrangements in the ST25 genome, compared to the genomes of ST1 and ST28 S. suis strains, which result, among other changes, in disruption of a pilus island locus. We report that recombination and lateral gene transfer contribute to ST25 genetic diversity. Phylogenetic analysis identified two main and distinct Thai and North American clades grouping most strains investigated. These clades also possessed distinct patterns of antimicrobial resistance genes, which correlated with acquisition of different integrative and conjugative elements (ICEs). Some of these ICEs were found to be integrated at a recombination hot spot, previously identified as the site of integration of the 89K pathogenicity island in serotype 2 ST7 S. suis strains. Our results highlight the limitations of MLST for phylogenetic analysis of S. suis, and the importance of lateral gene transfer and recombination as drivers of diversity in this swine pathogen and zoonotic agent.

Population Structure and Antimicrobial Resistance Profiles of Streptococcus suis Serotype 2 Sequence Type 25 Strains

PubMed Central

Athey, Taryn B. T.; Teatero, Sarah; Takamatsu, Daisuke; Wasserscheid, Jessica; Dewar, Ken; Gottschalk, Marcelo; Fittipaldi, Nahuel

2016-01-01

Strains of serotype 2 Streptococcus suis are responsible for swine and human infections. Different serotype 2 genetic backgrounds have been defined using multilocus sequence typing (MLST). However, little is known about the genetic diversity within each MLST sequence type (ST). Here, we used whole-genome sequencing to test the hypothesis that S. suis serotype 2 strains of the ST25 lineage are genetically heterogeneous. We evaluated 51 serotype 2 ST25 S. suis strains isolated from diseased pigs and humans in Canada, the United States of America, and Thailand. Whole-genome sequencing revealed numerous large-scale rearrangements in the ST25 genome, compared to the genomes of ST1 and ST28 S. suis strains, which result, among other changes, in disruption of a pilus island locus. We report that recombination and lateral gene transfer contribute to ST25 genetic diversity. Phylogenetic analysis identified two main and distinct Thai and North American clades grouping most strains investigated. These clades also possessed distinct patterns of antimicrobial resistance genes, which correlated with acquisition of different integrative and conjugative elements (ICEs). Some of these ICEs were found to be integrated at a recombination hot spot, previously identified as the site of integration of the 89K pathogenicity island in serotype 2 ST7 S. suis strains. Our results highlight the limitations of MLST for phylogenetic analysis of S. suis, and the importance of lateral gene transfer and recombination as drivers of diversity in this swine pathogen and zoonotic agent. PMID:26954687

Basal friction evolution and crevasse distribution during the surge of Basin 3, Austfonna ice-cap - offline coupling between a continuum ice dynamic model and a discrete element model

NASA Astrophysics Data System (ADS)

Gong, Yongmei; Zwinger, Thomas; Åström, Jan; Gladstone, Rupert; Schellenberger, Thomas; Altena, Bas; Moore, John

2017-04-01

The outlet glacier at Basin 3, Austfonna ice-cap entered its active surge phase in autumn 2012. We assess the evolution of the basal friction during the surge through inverse modelling of basal friction coefficients using recent velocity observation from 2012 to 2014 in a continuum ice dynamic model Elmer/ice. The obtained basal friction coefficient distributions at different time instances are further used as a boundary condition in a discrete element model (HiDEM) that is capable of computing fracturing of ice. The inverted basal friction coefficient evolution shows a gradual 'unplugging' of the stagnant frontal area and northwards and inland expansion of the fast flowing region in the southern basin. The validation between the modeled crevasses distribution and the satellite observation in August 2013 shows a good agreement in shear zones inland and at the frontal area. Crevasse distributions of the summer before and after the glacier reached its maximum velocity in January 2013 (August 2012 and August 2014, respectively) are also evaluated. Previous studies suggest the triggering and development of the surge are linked to surface melt water penetrating through ice to form an efficient basal hydrology system thereby triggering a hydro- thermodynamic feedback. This preliminary offline coupling between a continuum ice dynamic model and a discrete element model will give a hint on future model development of linking supra-glacial to sub-glacial hydrology system.

Investigating the crustal elements of the central Antarctic Plate (ICECAP): How long-range aerogeophysics is critical to understanding the evolution of the East Antarctic ice sheet

NASA Astrophysics Data System (ADS)

Blankenship, D. D.; Brozena, J. M.; Siegert, M. J.; Morse, D. L.; Dalziel, I. W.; Lawver, L. A.; Holt, J. W.; Childers, V. A.; Bamber, J. L.; Payne, A. J.

2004-12-01

The highlands of the central Antarctic Plate have been the nursery for East Antarctic ice sheets since at least the early Oligocene separation of Antarctica and Australia. Significant strides have been made in deciphering the marine geological, geophysical, and geochemical record of the deposits left by these sheets and the Pleistocene paleoclimate record from ice cores taken from the central reaches of the contemporary ice sheet. Most recently, the scientific community has realized the importance of the isolated biome represented by the subglacial lakes that characterize the domes of the central East Antarctic ice sheet and evolve in concert with them. Understanding the evolution of the East Antarctic ice sheet and its sub-glacial environment would be a major contribution to the IPY 2007-2008 international effort. Critical to understanding offshore and ice core records of paleoclimate, as well as the distribution/isolation of any subglacial lake systems, is developing a comprehensive understanding of the crustal elements of the central Antarctic Plate. A complete understanding of the evolution of East Antarctic ice sheets throughout the Cenozoic requires knowledge of the boundaries, elevation and paleolatitude of these crustal elements through time as well as evidence of their morphological, sedimentological and tectono-thermal history. The basic impediments to gaining this understanding are the subcontinental scale of the central Antarctic Plate and the one to four kilometers of ice cover that inhibits direct access. It is possible however to provide a substantial framework for understanding these crustal elements through a comprehensive program of long-range airborne geophysical observations. We have proposed a plan to measure gravity, magnetics, ice-penetrating radar, and laser/radar altimetry over the Gamburtsev, Vostok and Belgica subglacial highlands beneath Domes A - C of the contemporary East Antarctic ice sheet using a Navy P-3 aircraft based in McMurdo. Such measurements would help characterize crustal boundaries, establish absolute bedrock elevation and contemporary basal melt distribution (for boundary conditions of ice sheet and lake evolution), and reveal detailed subglacial geomorphology. A P-3 aircraft based in McMurdo would provide access to more than half of the continent without the difficult logistic support of remote field camps and fuel caches.

A feasibility study of a 3-D finite element solution scheme for aeroengine duct acoustics

NASA Technical Reports Server (NTRS)

Abrahamson, A. L.

1980-01-01

The advantage from development of a 3-D model of aeroengine duct acoustics is the ability to analyze axial and circumferential liner segmentation simultaneously. The feasibility of a 3-D duct acoustics model was investigated using Galerkin or least squares element formulations combined with Gaussian elimination, successive over-relaxation, or conjugate gradient solution algorithms on conventional scalar computers and on a vector machine. A least squares element formulation combined with a conjugate gradient solver on a CDC Star vector computer initially appeared to have great promise, but severe difficulties were encountered with matrix ill-conditioning. These difficulties in conditioning rendered this technique impractical for realistic problems.

An Integrated Approach to Swept Wing Icing Simulation

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.; Broeren, Andy P.

2017-01-01

This presentation describes the various elements of a simulation approach used to develop a database of ice shape geometries and the resulting aerodynamic performance data for a representative commercial transport wing model exposed to a variety of icing conditions. Methods for capturing full three-dimensional ice shape geometries, geometry interpolation along the span of the wing, and creation of artificial ice shapes based upon that geometric data were developed for this effort. The icing conditions used for this effort were representative of actual ice shape encounter scenarios and run the gamut from ice roughness to full three-dimensional scalloped ice shapes.

The marriage of metallacycle transfer chemistry with Suzuki-Miyaura cross-coupling to give main group element-containing conjugated polymers.

PubMed

He, Gang; Kang, Le; Torres Delgado, William; Shynkaruk, Olena; Ferguson, Michael J; McDonald, Robert; Rivard, Eric

2013-04-10

A versatile and general synthetic route for the synthesis of conjugated main group element-based polymers, previously inaccessible by conventional means, is reported. These polymers contain five-membered chalcogenophene rings based on S, Se, and Te, and we demonstrate that optoelectronic properties can be readily tuned via controlled atom substitution chemistry. In addition, regioregular hybrid thiophene-selenophene-tellurophene and selenophene-fluorene copolymers were synthesized to provide a further illustration of the scope of the presented metallacycle transfer/cross-coupling polymerization method.

An experimental investigation of multi-element airfoil ice accretion and resulting performance degradation

NASA Technical Reports Server (NTRS)

Potapczuk, Mark G.; Berkowitz, Brian M.

1989-01-01

An investigation of the ice accretion pattern and performance characteristics of a multi-element airfoil was undertaken in the NASA Lewis 6- by 9-Foot Icing Research Tunnel. Several configurations of main airfoil, slat, and flaps were employed to examine the effects of ice accretion and provide further experimental information for code validation purposes. The text matrix consisted of glaze, rime, and mixed icing conditions. Airflow and icing cloud conditions were set to correspond to those typical of the operating environment anticipated tor a commercial transport vehicle. Results obtained included ice profile tracings, photographs of the ice accretions, and force balance measurements obtained both during the accretion process and in a post-accretion evaluation over a range of angles of attack. The tracings and photographs indicated significant accretions on the slat leading edge, in gaps between slat or flaps and the main wing, on the flap leading-edge surfaces, and on flap lower surfaces. Force measurments indicate the possibility of severe performance degradation, especially near C sub Lmax, for both light and heavy ice accretion and performance analysis codes presently in use. The LEWICE code was used to evaluate the ice accretion shape developed during one of the rime ice tests. The actual ice shape was then evaluated, using a Navier-Strokes code, for changes in performance characteristics. These predicted results were compared to the measured results and indicate very good agreement.

Wave-induced stress and breaking of sea ice in a coupled hydrodynamic discrete-element wave-ice model

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2017-11-01

In this paper, a coupled sea ice-wave model is developed and used to analyze wave-induced stress and breaking in sea ice for a range of wave and ice conditions. The sea ice module is a discrete-element bonded-particle model, in which ice is represented as cuboid grains floating on the water surface that can be connected to their neighbors by elastic joints. The joints may break if instantaneous stresses acting on them exceed their strength. The wave module is based on an open-source version of the Non-Hydrostatic WAVE model (NHWAVE). The two modules are coupled with proper boundary conditions for pressure and velocity, exchanged at every wave model time step. In the present version, the model operates in two dimensions (one vertical and one horizontal) and is suitable for simulating compact ice in which heave and pitch motion dominates over surge. In a series of simulations with varying sea ice properties and incoming wavelength it is shown that wave-induced stress reaches maximum values at a certain distance from the ice edge. The value of maximum stress depends on both ice properties and characteristics of incoming waves, but, crucially for ice breaking, the location at which the maximum occurs does not change with the incoming wavelength. Consequently, both regular and random (Jonswap spectrum) waves break the ice into floes with almost identical sizes. The width of the zone of broken ice depends on ice strength and wave attenuation rates in the ice.

Investigating the Greenland ice sheet evolution under changing climate using a three-dimensional full-Stokes model

NASA Astrophysics Data System (ADS)

Seddik, H.; Greve, R.; Zwinger, T.; Gillet-Chaulet, F.; Gagliardini, O.

2010-12-01

A three-dimensional, thermo-mechanically coupled model is applied to the Greenland ice sheet. The model implements the full-Stokes equations for the ice dynamics, and the system is solved with the finite-element method (FEM) using the open source multi-physics package Elmer (http://www.csc.fi/elmer/). The finite-element mesh for the computational domain has been created using the Greenland surface and bedrock DEM data with a spatial resolution of 5 km (SeaRise community effort, based on Bamber and others, 2001). The study is particularly aimed at better understanding the ice dynamics near the major Greenland ice streams. The meshing procedure starts with the bedrock footprint where a mesh with triangle elements and a resolution of 5 km is constructed. Since the resulting mesh is unnecessarily dense in areas with slow ice dynamics, an anisotropic mesh adaptation procedure has been introduced. Using the measured surface velocities to evaluate the Hessian matrix of the velocities, a metric tensor is computed at the mesh vertices in order to define the adaptation scheme. The resulting meshed footprint obtained with the automatic tool YAMS shows a high density of elements in the vicinities of the North-East Greenland Ice Stream (NEGIS), the Jakobshavn ice stream (JIS) and the Kangerdlugssuaq (KL) and Helheim (HH) glaciers. On the other hand, elements with a coarser resolution are generated away from the ice streams and domain margins. The final three-dimensional mesh is obtained by extruding the 2D footprint with 21 vertical layers, so that the resulting mesh contains 400860 wedge elements and 233583 nodes. The numerical solution of the Stokes and the heat transfer equations involves direct and iterative solvers depending on the simulation case, and both methods are coupled with stabilization procedures. The boundary conditions are such that the temperature at the surface uses the present-day mean annual air temperature given by a parameterization or directly from the available data, the geothermal heat flux at the bedrock is prescribed as spatially constant and the lateral sides are open boundaries. A non-linear Weertman law is used for the basal sliding. The project goal is to better assess the effects of dynamical changes of the Greenland ice sheet on sea level rise under global-warming conditions. Hence, the simulations have been conducted in order to investigate the ice sheet evolution using the climate forcing experiments defined in the SeaRISE project. For that purpose, four different experiments have been conducted, (i) constant climate control run beginning at present (epoch 2004-1-1 0:0:0) and running up to 500 years holding the climate constant to its present state, (ii) constant climate forcing with increased basal lubrication, (iii) AR4 climate run forced by anomalies derived from results given in the IPCC 4th Assessment Report (AR4) for the A1B emission scenario, (iv) AR4 climate run with increased basal lubrication.

Improvements in the chronology, geochemistry and correlation techniques of tephra in Antarctic ice

NASA Astrophysics Data System (ADS)

Iverson, N. A.; Dunbar, N. W.; McIntosh, W. C.; Pearce, N. J.; Kyle, P. R.

2013-12-01

Visible and crypto tephra layers found in West Antarctic ice provide an excellent record of Antarctic volcanism over the past 100ka. Tephra layers are deposited almost instantaneously across wide areas creating horizons that, if found in several locations, provide 'pinning points' to adjust ice time scales that may otherwise be lacking detailed chronology. Individual tephra layers can have distinct chemical fingerprints allowing them to correlate over great distances. Advances in sample preparation, geochemical analyses (major and trace elements) of fine grained tephra and higher precision 40Ar/39Ar dating of young (<100ka) proximal volcanic deposits are improving an already established tephra record in West Antarctica. Forty three of the potential hundreds of silicate layers found in a recently drilled deep West Antarctic Ice Sheet Divide core (WDC06A) have been analyzed for major elements and a subset for trace elements. Of these layers, at least 16 are homogenous tephra that could be correlated to other ice cores (e.g. Siple Dome, SDMA) and/or to source volcanoes found throughout Antarctica and even extra-continental eruptions (e.g. Sub-Antarctic islands and South America). Combining ice core tephra with those exposed in blue ice areas provide more locations to correlate widespread eruptions. For example, a period of heightened eruptive activity at Mt. Berlin, West Antarctica between 24 and 28ka produced a set of tephra layers that are found in WDC06A and SDMA ice cores, as well as at a nearby blue ice area at Mt. Moulton (BIT-151 and BIT-152). Possible correlative tephra layers are found at ice ages of 26.4, 26.9 and 28.8ka in WDC06A and 26.5, 27.0, and 28.7ka in SDMA cores. The geochemical similarities of major elements in these layers mean that ongoing trace element analyses will be vital to decipher the sequence of events during this phase of activity at Mt. Berlin. Sample WDC06A-2767.117 (ice age of 28.6×1.0ka) appears to correlate to blue ice tephra BIT-152 and to tephra layer SDMA-5683 (ice age of 28.5ka). This tephra layer also appears to be present in blue ice at Mt. Terra Nova on Ross Island, 1400km away, suggesting that it may be a possible to link ice cores in East Antarctica (e.g. Talos Dome and Law Dome). The amount of feldspar in ice core tephra is typically too small to be directly dated by 40Ar/39Ar method, making it very important to geochemically correlate these layers to proximal deposits where more and larger feldspar can be sampled. The correlation of WDC06A-2767.117 to the coarse, proximal BIT-152 provides one such link. The New Mexico Geochronology Research Lab (NMGRL) has two new multi-collector ARGUS VI mass spectrometers that can provide single crystal laser fusion ages that are approximately an order of magnitude more precise than the previous determinations. With these advancements in analytical technology, we hope to improve precision on 'pinning points' in the deep ice cores where annual layer counting becomes less precise.

Toward High Performance Photovoltaic Cells based on Conjugated Polymers

DTIC Science & Technology

2016-12-26

AFRL-AFOSR-JP-TR-2016-0103 Toward High Performance Photovoltaic Cells based on Conjugated Polymers Kung-Hwa Wei National Chiao Tung University Final...Conjugated Polymers 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-15-1-4113 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) Kung-Hwa Wei 5d.  PROJECT...gap polymer with good packing order as the active layer for a single-junction photovoltaic device. The light absorptions for the small molecule and the

Adaptation of an unstructured-mesh, finite-element ocean model to the simulation of ocean circulation beneath ice shelves

NASA Astrophysics Data System (ADS)

Kimura, Satoshi; Candy, Adam S.; Holland, Paul R.; Piggott, Matthew D.; Jenkins, Adrian

2013-07-01

Several different classes of ocean model are capable of representing floating glacial ice shelves. We describe the incorporation of ice shelves into Fluidity-ICOM, a nonhydrostatic finite-element ocean model with the capacity to utilize meshes that are unstructured and adaptive in three dimensions. This geometric flexibility offers several advantages over previous approaches. The model represents melting and freezing on all ice-shelf surfaces including vertical faces, treats the ice shelf topography as continuous rather than stepped, and does not require any smoothing of the ice topography or any of the additional parameterisations of the ocean mixed layer used in isopycnal or z-coordinate models. The model can also represent a water column that decreases to zero thickness at the 'grounding line', where the floating ice shelf is joined to its tributary ice streams. The model is applied to idealised ice-shelf geometries in order to demonstrate these capabilities. In these simple experiments, arbitrarily coarsening the mesh outside the ice-shelf cavity has little effect on the ice-shelf melt rate, while the mesh resolution within the cavity is found to be highly influential. Smoothing the vertical ice front results in faster flow along the smoothed ice front, allowing greater exchange with the ocean than in simulations with a realistic ice front. A vanishing water-column thickness at the grounding line has little effect in the simulations studied. We also investigate the response of ice shelf basal melting to variations in deep water temperature in the presence of salt stratification.

Trace Element Determination from the Guliya Ice Core to Characterize Aerosol Deposition over the Western Tibetan Plateau during the Last 500 Years

NASA Astrophysics Data System (ADS)

Sierra Hernandez, R.; Gabrielli, P.; Beaudon, E.; Wegner, A.; Thompson, L. G.

2014-12-01

The Tibetan Plateau or Third Pole covers over 5 million km2, and has ~46,000 glaciers that collectively contain one of the Earth's largest stores of fresh water. The Guliya ice cap located in the western Kunlun Shan on the Qinghai-Tibetan Plateau, China, is the largest (> 200 km2) ice cap in the subtropical zone. In 1992, a 308.6 m ice core to bedrock was recovered from the Guliya ice cap. The deepest 20 meters yielded the first record extending back through the last glacial cycle found outside of the Polar Regions. Because of its continental location on the northwestern side of the Tibetan Plateau, the atmospheric circulation over the Guliya ice cap is dominated by westerly air flow from the Eurasian region. Therefore the site is expected to be unaffected by the fallout of anthropogenic trace metals originating from the inner Asian continent and rather may serve to characterize trace metal emissions from the western countries. Here we present preliminary results of the determination of 29 trace elements, Rb, Sr, Nb, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Ta, Tl, Pb, Bi, U, Li, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, and As, from Guliya ice core samples spanning the period 1500 - 1992 AD at seasonal (1750-1992 AD) and annual (1500-1750 AD) resolution. This Guliya trace element record will complement the developing records from the Dasuopu glacier, central Himalaya, and from the Puruogangri ice cap in the western Tanggula Shan in central Tibetan Plateau, which in contrast to Guliya are influenced by the monsoon. We investigate the possible sources both natural and anthropogenic of atmospheric trace elements and their fluxes over the Tibetan Plateau during the last 500 years.

Hydroelastic analysis of ice shelves under long wave excitation

NASA Astrophysics Data System (ADS)

Papathanasiou, T. K.; Karperaki, A. E.; Theotokoglou, E. E.; Belibassakis, K. A.

2015-05-01

The transient hydroelastic response of an ice shelf under long wave excitation is analysed by means of the finite element method. The simple model, presented in this work, is used for the simulation of the generated kinematic and stress fields in an ice shelf, when the latter interacts with a tsunami wave. The ice shelf, being of large length compared to its thickness, is modelled as an elastic Euler-Bernoulli beam, constrained at the grounding line. The hydrodynamic field is represented by the linearised shallow water equations. The numerical solution is based on the development of a special hydroelastic finite element for the system of governing of equations. Motivated by the 2011 Sulzberger Ice Shelf (SIS) calving event and its correlation with the Honshu Tsunami, the SIS stable configuration is studied. The extreme values of the bending moment distribution in both space and time are examined. Finally, the location of these extrema is investigated for different values of ice shelf thickness and tsunami wave length.

Hydroelastic analysis of ice shelves under long wave excitation

NASA Astrophysics Data System (ADS)

Papathanasiou, T. K.; Karperaki, A. E.; Theotokoglou, E. E.; Belibassakis, K. A.

2015-08-01

The transient hydroelastic response of an ice shelf under long wave excitation is analysed by means of the finite element method. The simple model, presented in this work, is used for the simulation of the generated kinematic and stress fields in an ice shelf, when the latter interacts with a tsunami wave. The ice shelf, being of large length compared to its thickness, is modelled as an elastic Euler-Bernoulli beam, constrained at the grounding line. The hydrodynamic field is represented by the linearised shallow water equations. The numerical solution is based on the development of a special hydroelastic finite element for the system of governing of equations. Motivated by the 2011 Sulzberger Ice Shelf (SIS) calving event and its correlation with the Honshu Tsunami, the SIS stable configuration is studied. The extreme values of the bending moment distribution in both space and time are examined. Finally, the location of these extrema is investigated for different values of ice shelf thickness and tsunami wave length.

pTC Plasmids from Sulfolobus Species in the Geothermal Area of Tengchong, China: Genomic Conservation and Naturally-Occurring Variations as a Result of Transposition by Mobile Genetic Elements

PubMed Central

Xiang, Xiaoyu; Huang, Xiaoxing; Wang, Haina; Huang, Li

2015-01-01

Plasmids occur frequently in Archaea. A novel plasmid (denoted pTC1) containing typical conjugation functions has been isolated from Sulfolobus tengchongensis RT8-4, a strain obtained from a hot spring in Tengchong, China, and characterized. The plasmid is a circular double-stranded DNA molecule of 20,417 bp. Among a total of 26 predicted pTC1 ORFs, 23 have homologues in other known Sulfolobus conjugative plasmids (CPs). pTC1 resembles other Sulfolobus CPs in genome architecture, and is most highly conserved in the genomic region encoding conjugation functions. However, attempts to demonstrate experimentally the capacity of the plasmid for conjugational transfer were unsuccessful. A survey revealed that pTC1 and its closely related plasmid variants were widespread in the geothermal area of Tengchong. Variations of the plasmids at the target sites for transposition by an insertion sequence (IS) and a miniature inverted-repeat transposable element (MITE) were readily detected. The IS was efficiently inserted into the pTC1 genome, and the inserted sequence was inactivated and degraded more frequently in an imprecise manner than in a precise manner. These results suggest that the host organism has evolved a strategy to maintain a balance between the insertion and elimination of mobile genetic elements to permit genomic plasticity while inhibiting their fast spreading. PMID:25686154

pTC Plasmids from Sulfolobus Species in the Geothermal Area of Tengchong, China: Genomic Conservation and Naturally-Occurring Variations as a Result of Transposition by Mobile Genetic Elements.

PubMed

Xiang, Xiaoyu; Huang, Xiaoxing; Wang, Haina; Huang, Li

2015-02-12

Plasmids occur frequently in Archaea. A novel plasmid (denoted pTC1) containing typical conjugation functions has been isolated from Sulfolobus tengchongensis RT8-4, a strain obtained from a hot spring in Tengchong, China, and characterized. The plasmid is a circular double-stranded DNA molecule of 20,417 bp. Among a total of 26 predicted pTC1 ORFs, 23 have homologues in other known Sulfolobus conjugative plasmids (CPs). pTC1 resembles other Sulfolobus CPs in genome architecture, and is most highly conserved in the genomic region encoding conjugation functions. However, attempts to demonstrate experimentally the capacity of the plasmid for conjugational transfer were unsuccessful. A survey revealed that pTC1 and its closely related plasmid variants were widespread in the geothermal area of Tengchong. Variations of the plasmids at the target sites for transposition by an insertion sequence (IS) and a miniature inverted-repeat transposable element (MITE) were readily detected. The IS was efficiently inserted into the pTC1 genome, and the inserted sequence was inactivated and degraded more frequently in an imprecise manner than in a precise manner. These results suggest that the host organism has evolved a strategy to maintain a balance between the insertion and elimination of mobile genetic elements to permit genomic plasticity while inhibiting their fast spreading.

Numerical Simulations of Single Flow Element in a Nuclear Thermal Thrust Chamber

NASA Technical Reports Server (NTRS)

Cheng, Gary; Ito, Yasushi; Ross, Doug; Chen, Yen-Sen; Wang, Ten-See

2007-01-01

The objective of this effort is to develop an efficient and accurate computational methodology to predict both detailed and global thermo-fluid environments of a single now element in a hypothetical solid-core nuclear thermal thrust chamber assembly, Several numerical and multi-physics thermo-fluid models, such as chemical reactions, turbulence, conjugate heat transfer, porosity, and power generation, were incorporated into an unstructured-grid, pressure-based computational fluid dynamics solver. The numerical simulations of a single now element provide a detailed thermo-fluid environment for thermal stress estimation and insight for possible occurrence of mid-section corrosion. In addition, detailed conjugate heat transfer simulations were employed to develop the porosity models for efficient pressure drop and thermal load calculations.

Data assimilation and prognostic whole ice sheet modelling with the variationally derived, higher order, open source, and fully parallel ice sheet model VarGlaS

NASA Astrophysics Data System (ADS)

Brinkerhoff, D. J.; Johnson, J. V.

2013-07-01

We introduce a novel, higher order, finite element ice sheet model called VarGlaS (Variational Glacier Simulator), which is built on the finite element framework FEniCS. Contrary to standard procedure in ice sheet modelling, VarGlaS formulates ice sheet motion as the minimization of an energy functional, conferring advantages such as a consistent platform for making numerical approximations, a coherent relationship between motion and heat generation, and implicit boundary treatment. VarGlaS also solves the equations of enthalpy rather than temperature, avoiding the solution of a contact problem. Rather than include a lengthy model spin-up procedure, VarGlaS possesses an automated framework for model inversion. These capabilities are brought to bear on several benchmark problems in ice sheet modelling, as well as a 500 yr simulation of the Greenland ice sheet at high resolution. VarGlaS performs well in benchmarking experiments and, given a constant climate and a 100 yr relaxation period, predicts a mass evolution of the Greenland ice sheet that matches present-day observations of mass loss. VarGlaS predicts a thinning in the interior and thickening of the margins of the ice sheet.

An object-oriented, coprocessor-accelerated model for ice sheet simulations

NASA Astrophysics Data System (ADS)

Seddik, H.; Greve, R.

2013-12-01

Recently, numerous models capable of modeling the thermo-dynamics of ice sheets have been developed within the ice sheet modeling community. Their capabilities have been characterized by a wide range of features with different numerical methods (finite difference or finite element), different implementations of the ice flow mechanics (shallow-ice, higher-order, full Stokes) and different treatments for the basal and coastal areas (basal hydrology, basal sliding, ice shelves). Shallow-ice models (SICOPOLIS, IcIES, PISM, etc) have been widely used for modeling whole ice sheets (Greenland and Antarctica) due to the relatively low computational cost of the shallow-ice approximation but higher order (ISSM, AIF) and full Stokes (Elmer/Ice) models have been recently used to model the Greenland ice sheet. The advance in processor speed and the decrease in cost for accessing large amount of memory and storage have undoubtedly been the driving force in the commoditization of models with higher capabilities, and the popularity of Elmer/Ice (http://elmerice.elmerfem.com) with an active user base is a notable representation of this trend. Elmer/Ice is a full Stokes model built on top of the multi-physics package Elmer (http://www.csc.fi/english/pages/elmer) which provides the full machinery for the complex finite element procedure and is fully parallel (mesh partitioning with OpenMPI communication). Elmer is mainly written in Fortran 90 and targets essentially traditional processors as the code base was not initially written to run on modern coprocessors (yet adding support for the recently introduced x86 based coprocessors is possible). Furthermore, a truly modular and object-oriented implementation is required for quick adaptation to fast evolving capabilities in hardware (Fortran 2003 provides an object-oriented programming model while not being clean and requiring a tricky refactoring of Elmer code). In this work, the object-oriented, coprocessor-accelerated finite element code Sainou is introduced. Sainou is an Elmer fork which is reimplemented in Objective C and used for experimenting with ice sheet models running on coprocessors, essentially GPU devices. GPUs are highly parallel processors that provide opportunities for fine-grained parallelization of the full Stokes problem using the standard OpenCL language (http://www.khronos.org/opencl/) to access the device. Sainou is built upon a collection of Objective C base classes that service a modular kernel (itself a base class) which provides the core methods to solve the finite element problem. An early implementation of Sainou will be presented with emphasis on the object architecture and the strategies of parallelizations. The computation of a simple heat conduction problem is used to test the implementation which also provides experimental support for running the global matrix assembly on GPU.

Preliminary result of the solar multi-conjugate adaptive optics for 1m new vacuum solar telescope

NASA Astrophysics Data System (ADS)

Zhang, Lanqiang; Kong, Lin; Bao, Hua; Zhu, Lei; Rao, Xuejun; Rao, Changhui

2016-07-01

Solar observation with high resolution in large field of view (FoV) is required for some solar active regions with the typical sizes of 1' to 3'. Conventional adaptive optics (AO) could not satisfy this demand because of the atmospheric anisoplanatism. Through compensating the turbulence in different heights, multi-conjugate adaptive optics (MCAO) has been proved to obtain a larger corrected FoV. A MCAO experimental system including a conventional 151-element AO system and a 37-element MCAO part is being developed. The MCAO part contains a 37-element deformable mirror conjugated into the 2km to 5km height and a multi-direction Shack-Hartmann wavefront sensor (MD-SHWFS) with 7×7 subaperture array and 60 arcsec FoV, the frame rate of the MD-SHWFS is up to 840Hz. Three-dimensional (3-D) wavefront sensing utilizing atmospheric tomography had been validated by solar observation. Based on these results, a ground layer adaptive optics (GLAO) experimental system including a 151-element deformable mirror and the MD-SHWFS has been built at the 1m New Vacuum Solar Telescope (NVST). In this paper, the MCAO experimental system will be introduced. The preliminary experimental results of three-dimensional wavefront sensing and GLAO on the NVST of Full-shine Lake Solar Observatory are presented.

Detailed history of atmospheric trace elements from the Quelccaya ice core (Southern Peru) during the last 1200 years

NASA Astrophysics Data System (ADS)

Uglietti, C.; Gabrielli, P.; Thompson, L. G.

2013-12-01

The recent increase in trace element concentrations, for example Cr, Cu, Zn, Ag, Pb, Bi, and U, in polar snow and ice has provided compelling evidence of a hemispheric change in atmospheric composition since the nineteenth century. This change has been concomitant with the expansion of the Industrial Revolution and points towards an anthropogenic source of trace elements in the atmosphere. There are very few low latitude trace element ice core records and these are believed to be sensitive to perturbations of regional significance. To date, these records have not been used to document a preindustrial anthropogenic impact on atmospheric composition at low latitudes. Ice cores retrieved from the tropical Andes are particularly interesting because they have the potential to reveal detailed information about the evolution and environmental consequences of mineral exploitation related to the Pre Inca Civilizations, the Inca Empire (1438-1533 AD) and the subsequent Spanish invasion and dominance (1532-1833 AD). The chemical record preserved in the ice of the Quelccaya ice cap (southern Peruvian Andes) offers the exceptional opportunity to geochemically constrain the composition of the tropical atmosphere at high resolution over the last ~1200 years. Quantification of twenty trace elements (Ag, Al, As, Bi, Cd, Co, Cr, Cu, Fe, Mn, Mo, Pb, Rb, Sb, Sn, Ti, Tl, U, V, and Zn) was performed by ICP-SFMS over 105 m of the Quelccaya North Dome core (5600 m asl, 128.57 m) by analyzing 2450 samples. This provides the first atmospheric trace element record in South America spanning continuously and at high resolution for the time period between 1990 and 790 AD. Ag, As, Bi, Cd, Cr, Co, Cu, Mn, Mo, Sb, Sn, Pb and Zn show increases in concentration and crustal enrichment factor starting at different times between 1450 and 1550 AD, in concomitance with the expansions of the Inca Empire and, subsequently, the Spanish Empire well before the inception of the Industrial Revolution. This indicates that there have been additional anthropogenic sources that have impacted the South American atmosphere during the past ~550 years. Furthermore, As, Bi and Pb record shows, the two most significant increases have occurred in the 20th century, one beginning in ~1905 AD and peaking in the 1920s and the second beginning in ~1955 AD and peaking in the 1970s. Comparison with other trace element records from Greenland and Antarctica reveals concomitant peaks of different amplitude in Pb concentration and crustal enrichment factor, possibly pointing to an unexpected larger than regional scale significance for the Quelccaya ice core record during the last century. In conclusion, the Quelccaya ice core indicates that societal and industrial development influenced the atmospheric composition in South America, from different large scale sources, during the last ~550 years. This is the first time that a low latitude ice core record has been used to reconstruct pre-industrial anthropogenic forcing on the atmosphere.

ISSM: Ice Sheet System Model

NASA Technical Reports Server (NTRS)

Larour, Eric; Schiermeier, John E.; Seroussi, Helene; Morlinghem, Mathieu

2013-01-01

In order to have the capability to use satellite data from its own missions to inform future sea-level rise projections, JPL needed a full-fledged ice-sheet/iceshelf flow model, capable of modeling the mass balance of Antarctica and Greenland into the near future. ISSM was developed with such a goal in mind, as a massively parallelized, multi-purpose finite-element framework dedicated to ice-sheet modeling. ISSM features unstructured meshes (Tria in 2D, and Penta in 3D) along with corresponding finite elements for both types of meshes. Each finite element can carry out diagnostic, prognostic, transient, thermal 3D, surface, and bed slope simulations. Anisotropic meshing enables adaptation of meshes to a certain metric, and the 2D Shelfy-Stream, 3D Blatter/Pattyn, and 3D Full-Stokes formulations capture the bulk of the ice-flow physics. These elements can be coupled together, based on the Arlequin method, so that on a large scale model such as Antarctica, each type of finite element is used in the most efficient manner. For each finite element referenced above, ISSM implements an adjoint. This adjoint can be used to carry out model inversions of unknown model parameters, typically ice rheology and basal drag at the ice/bedrock interface, using a metric such as the observed InSAR surface velocity. This data assimilation capability is crucial to allow spinning up of ice flow models using available satellite data. ISSM relies on the PETSc library for its vectors, matrices, and solvers. This allows ISSM to run efficiently on any parallel platform, whether shared or distrib- ISSM: Ice Sheet System Model NASA's Jet Propulsion Laboratory, Pasadena, California uted. It can run on the largest clusters, and is fully scalable. This allows ISSM to tackle models the size of continents. ISSM is embedded into MATLAB and Python, both open scientific platforms. This improves its outreach within the science community. It is entirely written in C/C++, which gives it flexibility in its design, and the power/speed that C/C++ allows. ISSM is svn (subversion) hosted, on a JPL repository, to facilitate its development and maintenance. ISSM can also model propagation of rifts using contact mechanics and mesh splitting, and can interface to the Dakota software. To carry out sensitivity analysis, mesh partitioning algorithms are available, based on the Scotch, Chaco, and Metis partitioners that ensure equal area mesh partitions can be done, which are then usable for sampling and local reliability methods.

Ice particles trapped by temperature gradients at mbar pressure

NASA Astrophysics Data System (ADS)

Kelling, Thorben; Wurm, Gerhard; Dürmann, Christoph

2011-11-01

In laboratory experiments we observe that ice particles (⩽100 μm) entrained in a low pressure atmosphere (˜1 mbar) get trapped by temperature gradients between three reservoirs at different temperature. Confining elements are a peltier element at 250 K (bottom), a liquid nitrogen reservoir at 77 K (top), and the surrounding vacuum chamber at 293 K. Particle levitation and trapping is modeled by an interplay of thermophoresis, photophoresis, and gravity. A number of ice particles are trapped simultaneously in close spatial distance to each other at least up to minutes and are accessible for further experiments.

An investigation of the astronomical theory of the ice ages using a simple climate-ice sheet model

NASA Technical Reports Server (NTRS)

Pollard, D.

1978-01-01

The astronomical theory of the Quaternary ice ages is incorporated into a simple climate model for global weather; important features of the model include the albedo feedback, topography and dynamics of the ice sheets. For various parameterizations of the orbital elements, the model yields realistic assessments of the northern ice sheet. Lack of a land-sea heat capacity contrast represents one of the chief difficulties of the model.

Discovery of a conjugative megaplasmid in Bifidobacterium breve.

PubMed

Bottacini, Francesca; O'Connell Motherway, Mary; Casey, Eoghan; McDonnell, Brian; Mahony, Jennifer; Ventura, Marco; van Sinderen, Douwe

2015-01-01

Bifidobacterium breve is a common and sometimes very abundant inhabitant of the human gut. Genome sequencing of B. breve JCM 7017 revealed the presence of an extrachromosomal element, designated pMP7017 consisting of >190 kb, thus representing the first reported bifidobacterial megaplasmid. In silico characterization of this element revealed several genomic features supporting a stable establishment of the megaplasmid in its host, illustrated by predicted CRISPR-Cas functions that are known to protect the host against intrusion of foreign DNA. Interestingly, pMP7017 is also predicted to encode a conjugative DNA transfer apparatus and, consistent with this notion, we demonstrate here the conjugal transfer of pMP7017 to representative strains of B. breve and B. longum subsp. longum. We also demonstrate the presence of a megaplasmid with homology to pMP7017 in three B. longum subsp. longum strains. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Discovery of a Conjugative Megaplasmid in Bifidobacterium breve

PubMed Central

Bottacini, Francesca; O'Connell Motherway, Mary; Casey, Eoghan; McDonnell, Brian; Mahony, Jennifer; Ventura, Marco

2014-01-01

Bifidobacterium breve is a common and sometimes very abundant inhabitant of the human gut. Genome sequencing of B. breve JCM 7017 revealed the presence of an extrachromosomal element, designated pMP7017 consisting of >190 kb, thus representing the first reported bifidobacterial megaplasmid. In silico characterization of this element revealed several genomic features supporting a stable establishment of the megaplasmid in its host, illustrated by predicted CRISPR-Cas functions that are known to protect the host against intrusion of foreign DNA. Interestingly, pMP7017 is also predicted to encode a conjugative DNA transfer apparatus and, consistent with this notion, we demonstrate here the conjugal transfer of pMP7017 to representative strains of B. breve and B. longum subsp. longum. We also demonstrate the presence of a megaplasmid with homology to pMP7017 in three B. longum subsp. longum strains. PMID:25326305

On a concurrent element-by-element preconditioned conjugate gradient algorithm for multiple load cases

NASA Technical Reports Server (NTRS)

Watson, Brian; Kamat, M. P.

1990-01-01

Element-by-element preconditioned conjugate gradient (EBE-PCG) algorithms have been advocated for use in parallel/vector processing environments as being superior to the conventional LDL(exp T) decomposition algorithm for single load cases. Although there may be some advantages in using such algorithms for a single load case, when it comes to situations involving multiple load cases, the LDL(exp T) decomposition algorithm would appear to be decidedly more cost-effective. The authors have outlined an EBE-PCG algorithm suitable for multiple load cases and compared its effectiveness to the highly efficient LDL(exp T) decomposition scheme. The proposed algorithm offers almost no advantages over the LDL(exp T) algorithm for the linear problems investigated on the Alliant FX/8. However, there may be some merit in the algorithm in solving nonlinear problems with load incrementation, but that remains to be investigated.

A combined finite element-boundary element formulation for solution of two-dimensional problems via CGFFT

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Jin, Jian-Ming; Volakis, John L.

1990-01-01

A method for the computation of electromagnetic scattering from arbitrary two-dimensional bodies is presented. The method combines the finite element and boundary element methods leading to a system for solution via the conjugate gradient Fast Fourier Transform (FFT) algorithm. Two forms of boundaries aimed at reducing the storage requirement of the boundary integral are investigated. It is shown that the boundary integral becomes convolutional when a circular enclosure is chosen, resulting in reduced storage requirement when the system is solved via the conjugate gradient FFT method. The same holds for the ogival enclosure, except that some of the boundary integrals are not convolutional and must be carefully treated to maintain O(N) memory requirement. Results for several circular and ogival structures are presented and shown to be in excellent agreement with those obtained by traditional methods.

Anti-icing and de-icing superhydrophobic concrete to improve the safety on critical elements on roadway pavements.

DOT National Transportation Integrated Search

2013-09-01

Icy roads lead to treacherous driving conditions in regions of the U.S. resulting in over 450 fatalities per year. Deicing chemicals, such as rock salt help to reduce ice formation on roadways to an extent, however also result in detrimental effects ...

An M-step preconditioned conjugate gradient method for parallel computation

NASA Technical Reports Server (NTRS)

Adams, L.

1983-01-01

This paper describes a preconditioned conjugate gradient method that can be effectively implemented on both vector machines and parallel arrays to solve sparse symmetric and positive definite systems of linear equations. The implementation on the CYBER 203/205 and on the Finite Element Machine is discussed and results obtained using the method on these machines are given.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Haixia; Zhang, Jing

We propose a scheme for continuous-variable quantum cloning of coherent states with phase-conjugate input modes using linear optics. The quantum cloning machine yields M identical optimal clones from N replicas of a coherent state and N replicas of its phase conjugate. This scheme can be straightforwardly implemented with the setups accessible at present since its optical implementation only employs simple linear optical elements and homodyne detection. Compared with the original scheme for continuous-variable quantum cloning with phase-conjugate input modes proposed by Cerf and Iblisdir [Phys. Rev. Lett. 87, 247903 (2001)], which utilized a nondegenerate optical parametric amplifier, our scheme losesmore » the output of phase-conjugate clones and is regarded as irreversible quantum cloning.« less

Exploiting the co-reliance of tumours upon transport of amino acids and lactate: Gln and Tyr conjugates of MCT1 inhibitors.

PubMed

Nair, Reji N; Mishra, Jitendra K; Li, Fangzheng; Tortosa, Mariola; Yang, Chunying; Doherty, Joanne R; Cameron, Michael; Cleveland, John L; Roush, William R; Bannister, Thomas D

2016-05-01

Glutamine and tyrosine-based amino acid conjugates of monocarboxylate transporter types 1 and 2 inhibitors (MCT1/2) were designed, synthesized and evaluated for their potency in blocking the proliferation of a human B lymphoma cell line that expresses the transporters Asct2, LAT1 and MCT1. Appropriate placement of an amino acid transporter recognition element was shown to augment anti-tumour efficacy vs. Raji cells. Amino acid conjugation also improves the pharmacodynamic properties of experimental MCT1/2 inhibitors.

Cross Flow Effects on Glaze Ice Roughness Formation

NASA Technical Reports Server (NTRS)

Tsao, Jen-Ching

2004-01-01

The present study examines the impact of large-scale cross flow on the creation of ice roughness elements on the leading edge of a swept wing under glaze icing conditions. A three-dimensional triple-deck structure is developed to describe the local interaction of a 3 D air boundary layer with ice sheets and liquid films. A linear stability analysis is presented here. It is found that, as the sweep angle increases, the local icing instabilities enhance and the most linearly unstable modes are strictly three dimensional.

Tuning the properties of conjugated polyelectrolytes and application in a biosensor platform

DOEpatents

Chen, Liaohai

2004-05-18

The present invention provides a method of detecting a biological agent including contacting a sample with a sensor including a polymer system capable of having an alterable measurable property from the group of luminescence, anisotropy, redox potential and uv/vis absorption, the polymer system including an ionic conjugated polymer and an electronically inert polyelectrolyte having a biological agent recognition element bound thereto, the electronically inert polyelectrolyte adapted for undergoing a conformational structural change upon exposure to a biological agent having affinity for binding to the recognition element bound to the electronically inert polyelectrolyte, and, detecting the detectable change in the alterable measurable property. A chemical moiety being the reaction product of (i) a polyelectrolyte monomer and (ii) a biological agent recognition element-substituted polyelectrolyte monomer is also provided.

Studies on transposable elements in yeast. I. ROAM mutations causing increased expression of yeast genes: their activation by signals directed toward conjugation functions and their formation by insertion of Tyl repetitive elements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Errede, B.; Cardillo, T.S.; Wever, G.

1981-01-01

Mechanisms available to eukaryotic organisms for the coordinate regulation of gene expression are being examined by genetic and biochemical characterization of an unusual mutation, CYC7-H2, which causes over-production of iso-2-cytochrome c in the yeast Saccharomyces cerevisiae. The CYC7-H2 mutation causes overproduction in haploid strains but only a 1- to 40-fold overproduction in MATa/MAT..cap alpha.. diploid strains. This regulation of overproduction has been characterized as a response to signals controlling conjugation in yeast. Furthermore, the abnormal controlling region has been identified as an insertion of a transposable and reiterated Ty1 element adjacent to the structural gene. Therefore, we suggest that Ty1more » elements or portions of Ty1 elements occur adjacent to some of the genes required for conjugation and that they normally function to control expression of this process. The suggested role of reiterated sequences may represent a general mechanism of coordinate regulation in eukaryotes. The CYC7-H2 mutation is closely related to other regulatory mutations occurring at the cargA, cargB and DUR1,2 loci. Similar to the CYC7-H2 mutation, the mutations designated cargA/sup +/O/sup h/, cargB/sup +/O/sup h/, and durO/sup h/ cause constitutive production of their respective gene products at much lower levels of MATa/MAT..cap alpha.. diploid strains than in the corresponding haploid strains. A consistent relationship between conjugation competence and the level of overproduction in all four mutants has been established. Observations characterizing the regulation of overproduction in the CYC7-H2 mutant are presented with the additional and parallel observations for the O/sup h/ mutants. Together these results provide a demonstration of the specificity and equivalence of regulatory control exhibited by ROAM mutants.« less

Detecting Near-Surface Ice Formation Over Time Using the Kennaugh Elements Approach From TerraSAR-X

NASA Astrophysics Data System (ADS)

Fernandes, L.

2016-12-01

The summer melting has increased substantially at higher elevations on the Canadian Arctic ice caps. The resulting meltwater percolates into the upper layers of snow and firn and then refreeze, building massive ice bodies. It seems likely that these within-firn ice bodies now limit meltwater penetration into the firn and may be creating a feedback whereby the fraction of melt that runs off to the ocean is increasing. Although changes in firn structure as presence of ice layers and ice bodies are well documented over the Devon ice cap, the firm has shown that it exerts a crucial role to predict more accurately the contribution of small ice caps to the sea level rise. However it is still challenging to assess the extent of these features within the shallow subsurface using ice cores and GPR (Ground Penetrating Radar) data collected along a limited number of linear transects. Studying changes in the distribution of ice bodies' formation over time has the potential to provide information about how the growth of ice bodies in the firn is affecting the pattern of water flow in the firn layer. The objective is investigate the potential of Kennaugh Elements (KE) derived from x-band SAR (Synthetic Aperture Radar) for mapping the distribution and growth of large ice bodies within the firn and the evolution of their distribution over time. The evaluation of this method could reveal a new approach suitable for other glacierized regions that would reduce the costs and amount of field work for studying such properties.

Direct detection of the multidrug resistance genome of Haemophilus influenzae in cerebrospinal fluid of children: implications for treatment of meningitis.

PubMed

Saha, Samir K; Darmstadt, Gary L; Baqui, Abdullah H; Islam, Nurul; Qazi, Shamim; Islam, Maksuda; El Arifeen, Shams; Santosham, Mathuram; Black, Robert E; Crook, Derrick W

2008-01-01

Multidrug resistance (MDR), specifically to ampicillin and chloramphenicol, has complicated the treatment of Haemophilus influenzae type b (Hib) meningitis. This is worsened by use of prior antibiotics, which limits identification of the causative agent by culture and increases reliance on antigen detection. We aimed to develop a PCR assay for detecting the family of Haemophilus integrating and conjugative elements (ICEs) represented by ICEHin1056 among antibiotic resistant Hib, and then apply this directly to CSF to diagnose Hib meningitis and predict organism susceptibility, irrespective of culture results. Primers specific for orf 51 of ICEHin1056 were designed and multiplexed with Bex primers, specific for H. influenzae, and tested on culture positive and negative cases. Of 73 Hib isolates, orf 51 PCR amplicons, predicting the presence of ICEs, were found in all 33 MDR isolates while only in 1 of 33 sensitive strains. The remaining 7 ampicillin susceptible, chloramphenicol and tetracycline resistant strains did not produce a PCR product to orf 51. PCR amplification from CSF specimens of these culture positive cases produced identical results with 100% and 97% positive and negative predictive values, respectively. Multiplex PCR to detect Bex and orf 51 identified another 16 MDR Hib cases among 81 culture-negative CSF samples. Direct PCR for orf 51 in CSF identified resistance pattern of 51% more Hib strains than culture alone (110 versus 73). The ability to detect MDR, in culture negative Hib meningitis cases has significant implications for better directing antibiotic treatment of meningitis cases and thus for preventing disability and death.

Targeting FR-expressing cells in ovarian cancer with Fab-functionalized nanoparticles: a full study to provide the proof of principle from in vitro to in vivo

NASA Astrophysics Data System (ADS)

Quarta, Alessandra; Bernareggi, Davide; Benigni, Fabio; Luison, Elena; Nano, Giuseppe; Nitti, Simone; Cesta, Maria Candida; di Ciccio, Luciano; Canevari, Silvana; Pellegrino, Teresa; Figini, Mariangela

2015-01-01

Efficient targeting in tumor therapies is still an open issue: systemic biodistribution and poor specific accumulation of drugs weaken efficacy of treatments. Engineered nanoparticles are expected to bring benefits by allowing specific delivery of drug to the tumor or acting themselves as localized therapeutic agents. In this study we have targeted epithelial ovarian cancer with inorganic nanoparticles conjugated to a human antibody fragment against the folate receptor over-expressed on cancer cells. The conjugation approach is generally applicable. Indeed several types of nanoparticles (either magnetic or fluorescent) were engineered with the fragment, and their biological activity was preserved as demonstrated by biochemical methods in vitro. In vivo studies with mice bearing orthotopic and subcutaneous tumors were performed. Elemental and histological analyses showed that the conjugated magnetic nanoparticles accumulated specifically and were retained at tumor sites longer than the non-conjugated nanoparticles.Efficient targeting in tumor therapies is still an open issue: systemic biodistribution and poor specific accumulation of drugs weaken efficacy of treatments. Engineered nanoparticles are expected to bring benefits by allowing specific delivery of drug to the tumor or acting themselves as localized therapeutic agents. In this study we have targeted epithelial ovarian cancer with inorganic nanoparticles conjugated to a human antibody fragment against the folate receptor over-expressed on cancer cells. The conjugation approach is generally applicable. Indeed several types of nanoparticles (either magnetic or fluorescent) were engineered with the fragment, and their biological activity was preserved as demonstrated by biochemical methods in vitro. In vivo studies with mice bearing orthotopic and subcutaneous tumors were performed. Elemental and histological analyses showed that the conjugated magnetic nanoparticles accumulated specifically and were retained at tumor sites longer than the non-conjugated nanoparticles. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04426f

Evaluating the Discrete Element Method as a Tool for Predicting the Seasonal Evolution of the MIZ

DTIC Science & Technology

2014-09-30

distribution (Hopkins & Thorndike 2006). The DEM treats sea ice as a collection of discrete pieces of ice, thus affording the method certain...Annals of Glaciology, 33(1), 355-360. Hopkins, M. A., & Thorndike , A. S. (2006) Floe formation in Arctic sea ice. Journal of Geophysical Research

Single domain antibody-quantum dot conjugates for ricin detection by both fluoroimmunoassay and surface plasmon resonance.

PubMed

Anderson, George P; Glaven, Richard H; Algar, W Russ; Susumu, Kimihiro; Stewart, Michael H; Medintz, Igor L; Goldman, Ellen R

2013-07-05

The combination of stable biorecognition elements and robust quantum dots (QDs) has the potential to yield highly effective reporters for bioanalyses. Llama-derived single domain antibodies (sdAb) provide small thermostable recognition elements that can be easily manipulated using standard DNA methods. The sdAb was self-assembled on dihydrolipoic acid (DHLA) ligand-capped CdSe-ZnS core-shell QDs made in our laboratory through the polyhistidine tail of the protein, which coordinated to zinc ions on the QD surface. The sdAb-QD bioconjugates were then applied in both fluorometric and surface plasmon resonance (SPR) immunoassays for the detection of ricin, a potential biothreat agent. The sdAb-QD conjugates functioned in fluoroimmunoassays for the detection of ricin, providing equivalent limits of detection when compared to the same anti-ricin sdAb labeled with a conventional fluorophore. In addition, the DHLA-QD-sdAb conjugates were very effective reporter elements in SPR sandwich assays, providing more sensitive detection with a signal enhancement of ~10-fold over sdAb reporters and 2-4 fold over full sized antibody reporters. Commercially prepared streptavidin-modified polymer-coated QDs also amplified the SPR signal for the detection of ricin when applied to locations where biotinylated anti-ricin sdAb was bound to target; however, we observed a 4-fold greater amplification when using the DHLA-QD-sdAb conjugates in this format. Copyright © 2013. Published by Elsevier B.V.

Ice particles trapped by temperature gradients at mbar pressure.

PubMed

Kelling, Thorben; Wurm, Gerhard; Dürmann, Christoph

2011-11-01

In laboratory experiments we observe that ice particles (≤100 μm) entrained in a low pressure atmosphere (~1 mbar) get trapped by temperature gradients between three reservoirs at different temperature. Confining elements are a peltier element at 250 K (bottom), a liquid nitrogen reservoir at 77 K (top), and the surrounding vacuum chamber at 293 K. Particle levitation and trapping is modeled by an interplay of thermophoresis, photophoresis, and gravity. A number of ice particles are trapped simultaneously in close spatial distance to each other at least up to minutes and are accessible for further experiments. © 2011 American Institute of Physics

Synthesis of galabiose-chitosan conjugate as potent inhibitor of Streptococcus suis adhesion.

PubMed

Xu, Yaozu; Fan, Hongjie; Lu, Chengping; Gao, George F; Li, Xuebing

2010-07-12

The aim of this work is to construct a safe and effective drug candidate against Streptococcus suis infection. A panel of chitosan-based polymer conjugates with branched galabiose (Galalpha1-4Gal) side chains was synthesized as inhibitors of S. suis adhesion. The synthesis was achieved by using an aldehyde-functionalized galabiose derivative to graft it onto chitosan amino groups. Structural compositions of the conjugates were verified by 1H NMR spectroscopy and CHN elemental analyses. Potent inhibitory activities of the conjugates against S. suis adhesion to human erythrocytes were determined at low nanomolar concentration by HAI assay. An SPR study revealed a high affinity binding (Kd=39.6 nM) of the conjugate with BSI-B4 lectin. By using biocompatible chitosan as the scaffold for presenting S. suis -specific galabiose units, as well as the concise route tailored for the conjugate syntheses, the present study provides a practical way for explorations of new anti- S. suis therapies.

9,10-Azaboraphenanthrene-containing small molecules and conjugated polymers: synthesis and their application in chemodosimeters for the ratiometric detection of fluoride ions.

PubMed

Zhang, Weidong; Li, Guoping; Xu, Letian; Zhuo, Yue; Wan, Wenming; Yan, Ni; He, Gang

2018-05-21

The introduction of main group elements into conjugated scaffolds is emerging as a key route to novel optoelectronic materials. Herein, an efficient and versatile way to synthesize polymerizable 9,10-azaboraphenanthrene ( BNP )-containing monomers by aromaticity-driven ring expansion reactions between highly antiaromatic borafluorene and azides is reported, and the corresponding conjugated small molecules and polymers are developed as well. The BNP -containing small molecules and conjugated polymers showed good air/moisture stability and notable fluorescence properties. Addition of fluoride ions to the BNP -based small molecules and polymers induced a rapid change in the emission color from blue to green/yellow, respectively, accompanied by strong intensity changes. The conjugated polymers showed better ratiometric sensing performance than small molecules due to the exciton migration along the conjugated chains. Further experiments showed that the sensing process is fully reversible. The films prepared by solution-deposition of BNP -based compounds in the presence of polycaprolactone also showed good ratiometric sensing for fluoride ions.

Splicing of a group II intron involved in the conjugative transfer of pRS01 in lactococci.

PubMed

Mills, D A; McKay, L L; Dunny, G M

1996-06-01

Analysis of a region involved in the conjugative transfer of the lactococcal conjugative element pRS01 has revealed a bacteria] group II intron. Splicing of this lactococcal intron (designated Ll.ltrB) in vivo resulted in the ligation of two exon messages (ltrBE1 and ltrBE2) which encoded a putative conjugative relaxase essential for the transfer of pRS01. Like many group II introns, the Ll.ltrB intron possessed an open reading frame (ltrA) with homology to reverse transcriptases. Remarkably, sequence analysis of ltrA suggested a greater similarity to open reading frames encoded by eukaryotic mitochondrial group II introns than to those identified to date from other bacteria. Several insertional mutations within ltrA resulted in plasmids exhibiting a conjugative transfer-deficient phenotype. These results provide the first direct evidence for splicing of a prokaryotic group II intron in vivo and suggest that conjugative transfer is a mechanism for group II intron dissemination in bacteria.

Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

NASA Astrophysics Data System (ADS)

Gabrielli, Paolo; Planchon, Frederic; Barbante, Carlo; Boutron, Claude F.; Petit, Jean Robert; Bulat, Sergey; Hong, Sungmin; Cozzi, Giulio; Cescon, Paolo

2009-10-01

This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g -1 for Ce and 0.0035-0.24 pg g -1 for Lu in glacier ice, and between <0.1-24 pg g -1 for Ce and <0.0004-0.02 pg g -1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC 1; characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC 2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC 1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC 1 formation. Interestingly, if the LREE enrichment found in AC 1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica

NASA Astrophysics Data System (ADS)

Barbante, C.; Gabrielli, P.; Turetta, C.; Planchon, F.; Boutron, C.; Petit, J. R.; Bulat, S.; Hong, S.; Cozzi, G.; Cescon, P.

2009-12-01

We report the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g-1 for Ce and 0.0035- 0.24 pg g-1 for Lu in glacier ice, and between <0.1-24 pg g-1 for Ce and <0.0004-0.02 pg g-1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC1;characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC1 formation. Interestingly, if the LREE enrichment found in AC1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.

Constraining the parameters of the EAP sea ice rheology from satellite observations and discrete element model

NASA Astrophysics Data System (ADS)

Tsamados, Michel; Heorton, Harry; Feltham, Daniel; Muir, Alan; Baker, Steven

2016-04-01

The new elastic-plastic anisotropic (EAP) rheology that explicitly accounts for the sub-continuum anisotropy of the sea ice cover has been implemented into the latest version of the Los Alamos sea ice model CICE. The EAP rheology is widely used in the climate modeling scientific community (i.e. CPOM stand alone, RASM high resolution regional ice-ocean model, MetOffice fully coupled model). Early results from sensitivity studies (Tsamados et al, 2013) have shown the potential for an improved representation of the observed main sea ice characteristics with a substantial change of the spatial distribution of ice thickness and ice drift relative to model runs with the reference visco-plastic (VP) rheology. The model contains one new prognostic variable, the local structure tensor, which quantifies the degree of anisotropy of the sea ice, and two parameters that set the time scale of the evolution of this tensor. Observations from high resolution satellite SAR imagery as well as numerical simulation results from a discrete element model (DEM, see Wilchinsky, 2010) have shown that these individual floes can organize under external wind and thermal forcing to form an emergent isotropic sea ice state (via thermodynamic healing, thermal cracking) or an anisotropic sea ice state (via Coulombic failure lines due to shear rupture). In this work we use for the first time in the context of sea ice research a mathematical metric, the Tensorial Minkowski functionals (Schroeder-Turk, 2010), to measure quantitatively the degree of anisotropy and alignment of the sea ice at different scales. We apply the methodology on the GlobICE Envisat satellite deformation product (www.globice.info), on a prototype modified version of GlobICE applied on Sentinel-1 Synthetic Aperture Radar (SAR) imagery and on the DEM ice floe aggregates. By comparing these independent measurements of the sea ice anisotropy as well as its temporal evolution against the EAP model we are able to constrain the uncertain model parameters and functions in the EAP model.

oriTfinder: a web-based tool for the identification of origin of transfers in DNA sequences of bacterial mobile genetic elements.

PubMed

Li, Xiaobin; Xie, Yingzhou; Liu, Meng; Tai, Cui; Sun, Jingyong; Deng, Zixin; Ou, Hong-Yu

2018-05-04

oriTfinder is a web server that facilitates the rapid identification of the origin of transfer site (oriT) of a conjugative plasmid or chromosome-borne integrative and conjugative element. The utilized back-end database oriTDB was built upon more than one thousand known oriT regions of bacterial mobile genetic elements (MGEs) as well as the known MGE-encoding relaxases and type IV coupling proteins (T4CP). With a combination of similarity searches for the oriTDB-archived oriT nucleotide sequences and the co-localization of the flanking relaxase homologous genes, the oriTfinder can predict the oriT region with high accuracy in the DNA sequence of a bacterial plasmid or chromosome in minutes. The server also detects the other transfer-related modules, including the potential relaxase gene, T4CP gene and the type IV secretion system gene cluster, and the putative genes coding for virulence factors and acquired antibiotic resistance determinants. oriTfinder may contribute to meeting the increasing demands of re-annotations for bacterial conjugative, mobilizable or non-transferable elements and aid in the rapid risk accession of disease-relevant trait dissemination in pathogenic bacteria of interest. oriTfinder is freely available to all users without any login requirement at http://bioinfo-mml.sjtu.edu.cn/oriTfinder.

A New Multielement Method for LA-ICP-MS Data Acquisition from Glacier Ice Cores.

PubMed

Spaulding, Nicole E; Sneed, Sharon B; Handley, Michael J; Bohleber, Pascal; Kurbatov, Andrei V; Pearce, Nicholas J; Erhardt, Tobias; Mayewski, Paul A

2017-11-21

To answer pressing new research questions about the rate and timing of abrupt climate transitions, a robust system for ultrahigh-resolution sampling of glacier ice is needed. Here, we present a multielement method of LA-ICP-MS analysis wherein an array of chemical elements is simultaneously measured from the same ablation area. Although multielement techniques are commonplace for high-concentration materials, prior to the development of this method, all LA-ICP-MS analyses of glacier ice involved a single element per ablation pass or spot. This new method, developed using the LA-ICP-MS system at the W. M. Keck Laser Ice Facility at the University of Maine Climate Change Institute, has already been used to shed light on our flawed understanding of natural levels of Pb in Earth's atmosphere.

NASA's program on icing research and technology

NASA Technical Reports Server (NTRS)

Reinmann, John J.; Shaw, Robert J.; Ranaudo, Richard J.

1989-01-01

NASA's program in aircraft icing research and technology is reviewed. The program relies heavily on computer codes and modern applied physics technology in seeking icing solutions on a finer scale than those offered in earlier programs. Three major goals of this program are to offer new approaches to ice protection, to improve our ability to model the response of an aircraft to an icing encounter, and to provide improved techniques and facilities for ground and flight testing. This paper reviews the following program elements: (1) new approaches to ice protection; (2) numerical codes for deicer analysis; (3) measurement and prediction of ice accretion and its effect on aircraft and aircraft components; (4) special wind tunnel test techniques for rotorcraft icing; (5) improvements of icing wind tunnels and research aircraft; (6) ground de-icing fluids used in winter operation; (7) fundamental studies in icing; and (8) droplet sizing instruments for icing clouds.

Freezing Directed Construction of Bio/Nano Interfaces: Reagentless Conjugation, Denser Spherical Nucleic Acids, and Better Nanoflares.

PubMed

Liu, Biwu; Liu, Juewen

2017-07-19

While nanoparticle solutions cannot freeze in general, they may remain stable in the presence of polymer stabilizers. We herein communicate that gold nanoparticles (AuNPs) are stable in the presence of thiolated DNA after a freeze-thaw cycle. The DNA is conjugated to AuNPs during freezing without additional reagents and the conjugation can be completed in a few minutes. More importantly, the DNA density is 20-30% higher than that prepared by the typical salt-aging method. By lowering temperature, DNA hybridization is also promoted, allowing the construction of better nanoflares with doubled probe density and signaling sensitivity. This freezing method works for AuNPs from 5 to 100 nm and all tested DNA sequences. The mechanism was studied by separating the effect of temperature, freezing and thawing, where the exclusion of salt and AuNPs by the growing ice crystals is deemed critical. In addition to developing a simple method, this study articulates unique physical processes during freezing with important fundamental surface science implications, and it could be extended to other systems.

A Cool Sport Full of Physics

ERIC Educational Resources Information Center

Hache, Alain

2008-01-01

Of all sports, ice hockey is possibly the one with the widest array of physics elements in it. The game provides many examples that can bring physics to life in the classroom. Ice hockey (or just "hockey" as many Canadians would say) sees athletes sliding on ice at high speeds and in various ways, shooting and slapping pucks, and…

Ultra-Wideband Radars for Measurements over Land and Sea Ice

NASA Astrophysics Data System (ADS)

Gogineni, S.; Hale, R.; Miller, H. G.; Yan, S.; Rodriguez-Morales, F.; Leuschen, C.; Wang, Z.; Gomez-Garcia, D.; Binder, T.; Steinhage, D.; Gehrmann, M.; Braaten, D. A.

2015-12-01

We developed two ultra-wideband (UWB) radars for measurements over the ice sheets in Greenland and Antarctica and sea ice. One of the UWB radars operates over a 150-600 MHz frequency range with a large, cross-track 24-element array. It is designed to sound ice, image the ice-bed interface, and map internal layers with fine resolution. The 24-element array consists of three 8-element sub-arrays. One of these sub-arrays is mounted under the fuselage of a BT-67 aircraft; the other two are mounted under the wings. The polarization of each antenna element can be individually reconfigured depending on the target of interest. The measured inflight VSWR is less than 2 over the operating range. The fuselage sub-array is used both for transmission and reception, and the wing-mounted sub-arrays are used for reception. The transmitter consists of an 8-channel digital waveform generator to synthesize chirped pulses of selectable pulse width, duration, and bandwidth. It also consists of drivers and power amplifiers to increase the power level of each individual channel to about 1 kW and a fast high-power transmit/receive switch. Each receiver consists of a limiter, switches, low-noise and driver amplifiers, and filters to shape and amplify received signals to the level required for digitization. The digital sub-section consists of timing and control sub-systems and 24 14-bit A/D converters to digitize received signals at a rate of 1.6 GSPS. The radar performance is evaluated using an optical delay line to simulate returns from about 2 km thick ice, and the measured radar loop sensitivity is about 215 dB. The other UWB microwave radar operates over a 2-18 GHz frequency range in Frequency-Modulated Continuous Wave (FM-CW) mode. It is designed to sound more than 1 m of snow over sea ice and map internal layers to a depth about 25-40 m in polar firn and ice. We operated the microwave radar over snow-covered sea ice and mapped snow as thin as 5 cm and as thick as 60 cm. We mapped internal layers with an early version of the radar to a depth of 45 m with fine resolution in West Antarctica. In this presentation, we will discuss design considerations and present laboratory results to document radar performance, including the impulse response functions. We will also show the results from a field campaign over the Greenland ice sheet.

Uncertainty of tipping elements on risk analysis in hydrology under climate change

NASA Astrophysics Data System (ADS)

Kiguchi, M.; Iseri, Y.; Tawatari, R.; Kanae, S.; Oki, T.

2015-12-01

Risk analysis in this study characterizes the events that could be caused by climate change and estimates their effects on society. In order to characterize climate change risks, events that might be caused by climate change will be investigated focusing on critical geophysical phenomena such as changes in thermohaline circulation (THC) in oceans and the large-scale melting of the Greenland and other ice sheets. The results of numerical experiments with climate models and paleoclimate studies will be referenced in listing up these phenomena. The trigger mechanisms, tendency to occur and relationship of these phenomena to global climate will be clarified. To clarify that relationship between the RCP scenarios and tipping elements, we identified which year tipping elements in case of "Arctic summer sea ice" and "Greenland ice sheet" are appeared using the increase of global average temperature in 5 GCMs under RCP (2.6, 4.5, 6.0, and 8.5) from Zickfeld et al. (2013) and IPCC (2013), and tipping point of each tipping elements from IPCC (2013). In case of "Greenland ice sheet" (Tipping point takes a value within the range of 1.0oC and 4.0oC), we found that "Greenland ice sheet" may melt down when the tipping point is 1.0oC as lowest value. On the other hand, when tipping point sets as 4.0oC, it may not melt down except for RCP 8.5. As above, we show the uncertainty of tipping point itself. In future, it is necessary how to reflect such uncertainty in risk analysis in hydrology.

The Role of Snow and Ice in the Climate System

ScienceCinema

Barry, Roger G.

2017-12-09

Global snow and ice cover (the 'cryosphere') plays a major role in global climate and hydrology through a range of complex interactions and feedbacks, the best known of which is the ice - albedo feedback. Snow and ice cover undergo marked seasonal and long term changes in extent and thickness. The perennial elements - the major ice sheets and permafrost - play a role in present-day regional and local climate and hydrology, but the large seasonal variations in snow cover and sea ice are of importance on continental to hemispheric scales. The characteristics of these variations, especially in the Northern Hemisphere, and evidence for recent trends in snow and ice extent are discussed.

M-step preconditioned conjugate gradient methods

NASA Technical Reports Server (NTRS)

Adams, L.

1983-01-01

Preconditioned conjugate gradient methods for solving sparse symmetric and positive finite systems of linear equations are described. Necessary and sufficient conditions are given for when these preconditioners can be used and an analysis of their effectiveness is given. Efficient computer implementations of these methods are discussed and results on the CYBER 203 and the Finite Element Machine under construction at NASA Langley Research Center are included.

Movement of Trace Elements During Residence in the Antarctic Ice: a Laboratory Simulation

NASA Technical Reports Server (NTRS)

Strait, Melissa M.

1991-01-01

Recent work has determined that differences in the trace element distribution between Antarctic eucrites and non-Antarctic eucrites may be due to weathering during residence in the ice, and samples that demonstrate trace element disturbances do not necessarily correspond to eucrites that appear badly weathered to the naked eye. This study constitutes a preliminary test of the idea that long-term residence in the ice is the cause of the trace element disturbances observed in the eucrites. Samples of a non-Antarctic eucrite were leached in water at room temperature conditions. Liquid samples were analyzed for rare earth element abundances using ion chromatography. The results for the short-term study showed little or no evidence that leaching had occurred. However, there were tantalizing hints that something may be happening. The residual solid samples are currently being analyzed for the unleached trace metals using instrumental neutron activation analysis and should show evidence of disturbance if the chromatography clues were real. In addition, another set of samples continues to be intermittently sampled for later analysis. The results should give us information about the movement of trace elements under our conditions and allow us to make some tentative extrapolations to what we observe in actual Antarctic eucrite samples.

Group II intron inhibits conjugative relaxase expression in bacteria by mRNA targeting

PubMed Central

Piazza, Carol Lyn; Smith, Dorie

2018-01-01

Group II introns are mobile ribozymes that are rare in bacterial genomes, often cohabiting with various mobile elements, and seldom interrupting housekeeping genes. What accounts for this distribution has not been well understood. Here, we demonstrate that Ll.LtrB, the group II intron residing in a relaxase gene on a conjugative plasmid from Lactococcus lactis, inhibits its host gene expression and restrains the naturally cohabiting mobile element from conjugative horizontal transfer. We show that reduction in gene expression is mainly at the mRNA level, and results from the interaction between exon-binding sequences (EBSs) in the intron and intron-binding sequences (IBSs) in the mRNA. The spliced intron targets the relaxase mRNA and reopens ligated exons, causing major mRNA loss. Taken together, this study provides an explanation for the distribution and paucity of group II introns in bacteria, and suggests a potential force for those introns to evolve into spliceosomal introns. PMID:29905149

Group II intron inhibits conjugative relaxase expression in bacteria by mRNA targeting.

PubMed

Qu, Guosheng; Piazza, Carol Lyn; Smith, Dorie; Belfort, Marlene

2018-06-15

Group II introns are mobile ribozymes that are rare in bacterial genomes, often cohabiting with various mobile elements, and seldom interrupting housekeeping genes. What accounts for this distribution has not been well understood. Here, we demonstrate that Ll.LtrB, the group II intron residing in a relaxase gene on a conjugative plasmid from Lactococcus lactis , inhibits its host gene expression and restrains the naturally cohabiting mobile element from conjugative horizontal transfer. We show that reduction in gene expression is mainly at the mRNA level, and results from the interaction between exon-binding sequences (EBSs) in the intron and intron-binding sequences (IBSs) in the mRNA. The spliced intron targets the relaxase mRNA and reopens ligated exons, causing major mRNA loss. Taken together, this study provides an explanation for the distribution and paucity of group II introns in bacteria, and suggests a potential force for those introns to evolve into spliceosomal introns. © 2018, Qu et al.

An Ice Core Melter System for Continuous Major and Trace Chemical Analyses of a New Mt. Logan Summit Ice Core

NASA Astrophysics Data System (ADS)

Osterberg, E. C.; Handley, M. J.; Sneed, S. D.; Mayewski, P. A.; Kreutz, K. J.; Fisher, D. A.

2004-12-01

The ice core melter system at the University of Maine Climate Change Institute has been recently modified and updated to allow high-resolution (<1-2 cm ice/sample), continuous and coregistered sampling of ice cores, most notably the 2001 Mt. Logan summit ice core (187 m to bedrock), for analyses of 34 trace elements (Sr, Cd, Sb, Cs, Ba, Pb, Bi, U, As, Al, S, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, REE suite) by inductively coupled plasma mass spectrometry (ICP-MS), 8 major ions (Na+, Ca2+, Mg2+, K+, Cl-, SO42-, NO3-, MSA) by ion chromatography (IC), stable water isotopes (δ 18O, δ D, d) and volcanic tephra. The UMaine continuous melter (UMCoM) system is housed in a dedicated clean room with HEPA filtered air. Standard clean room procedures are employed during melting. A Wagenbach-style continuous melter system has been modified to include a pure Nickel melthead that can be easily dismantled for thorough cleaning. The system allows melting of both ice and firn without wicking of the meltwater into unmelted core. Contrary to ice core melter systems in which the meltwater is directly channeled to online instruments for continuous flow analyses, the UMCoM system collects discrete samples for each chemical analysis under ultraclean conditions. Meltwater from the pristine innermost section of the ice core is split between one fraction collector that accumulates ICP-MS samples in acid pre-cleaned polypropylene vials under a class-100 HEPA clean bench, and a second fraction collector that accumulates IC samples. A third fraction collector accumulates isotope and tephra samples from the potentially contaminated outer portion of the core. This method is advantageous because an archive of each sample remains for subsequent analyses (including trace element isotope ratios), and ICP-MS analytes are scanned for longer intervals and in replicate. Method detection limits, calculated from de-ionized water blanks passed through the entire UMCoM system, are below 10% of average Mt. Logan values. A strong correlation (R2>0.9) between Ca and S concentrations measured on different fractions of the same sample by IC and ICP-MS validates sample coregistration. Preliminary analyses of data from the 2001 Mt. Logan summit ice core confirm subannual resolution sampling and annual scale variability of major and trace elements. Accumulation rate models and isotope data suggest that annual resolution will be possible to 1000-2000 y.b.p., with multi-annual to centennial resolution for the remainder of the Holocene and possibly including the last deglaciation. Dust proxy elements, including REEs, strongly co-vary in time-series and reveal concentration ratio fluctuations interpreted as source region changes. Volcanic eruptions are characterized by elevated concentrations of S, SO42-, Cu, Sb, Zn and other trace elements. Concentrations of potential anthropogenic contaminants are also discussed.

Discrete-element simulation of sea-ice mechanics: Contact mechanics and granular jamming

NASA Astrophysics Data System (ADS)

Damsgaard, A.; Adcroft, A.; Sergienko, O. V.; Stern, A. A.

2017-12-01

Lagrangian models of sea-ice dynamics offer several advantages to Eulerian continuum methods. Spatial discretization on the ice-floe scale is natural for Lagrangian models, which additionally offer the convenience of being able to handle arbitrary sea-ice concentrations. This is likely to improve model performance in ice-marginal zones with strong advection. Furthermore, phase transitions in granular rheology around the jamming limit, such as observed when sea ice moves through geometric confinements, includes sharp thresholds in effective viscosity which are typically ignored in Eulerian models. Granular jamming is a stochastic process dependent on having the right grains in the right place at the right time, and the jamming likelihood over time can be described by a probabilistic model. Difficult to parameterize in continuum formulations, jamming occurs naturally in dense granular systems simulated in a Lagrangian framework, and is a very relevant process controlling sea-ice transport through narrow straits. We construct a flexible discrete-element framework for simulating Lagrangian sea-ice dynamics at the ice-floe scale, forced by ocean and atmosphere velocity fields. Using this framework, we demonstrate that frictionless contact models based on compressive stiffness alone are unlikely to jam, and describe two different approaches based on friction and tensile strength which both result in increased bulk shear strength of the granular assemblage. The frictionless but cohesive contact model, with certain tensile strength values, can display jamming behavior which on the large scale is very similar to a more complex and realistic model with contact friction and ice-floe rotation.

Lagrangian Assimilation of Satellite Data for Climate Studies in the Arctic

NASA Technical Reports Server (NTRS)

Lindsay, Ronald W.; Zhang, Jin-Lun; Stern, Harry

2004-01-01

Under this grant we have developed and tested a new Lagrangian model of sea ice. A Lagrangian model keeps track of material parcels as they drift in the model domain. Besides providing a natural framework for the assimilation of Lagrangian data, it has other advantages: 1) a model that follows material elements is well suited for a medium such as sea ice in which an element retains its identity for a long period of time; 2) model cells can be added or dropped as needed, allowing the spatial resolution to be increased in areas of high variability or dense observations; 3) ice from particular regions, such as the marginal seas, can be marked and traced for a long time; and 4) slip lines in the ice motion are accommodated more naturally because there is no internal grid. Our work makes use of these strengths of the Lagrangian formulation.

Microwave phase conjugation using artificial nonlinear microwave surfaces

NASA Astrophysics Data System (ADS)

Chang, Yian

1997-09-01

A new technique is developed and demonstrated to simulate nonlinear materials in the microwave and millimeter wave regime. Such materials are required to extend nonlinear optical techniques into longer wavelength areas. Using an array of antenna coupled mixers as an artificial nonlinear surface, we have demonstrated two-dimensional free space microwave phase conjugation at 10 GHz. The basic concept is to replace the weak nonlinearity of electron distribution in a crystal with the strong nonlinear V-I response of a P-N junction. This demnstration uses a three-wave mixing method with the effective nonlinear susceptibility χ(2) provided by an artificial nonlinear surface. The pump signal at 2ω (20 GHz) can be injected to the mixing elements electrically or optically. Electrical injection was first used to prove the concept of artificial nonlinear surfaces. However, due to the loss and size of microwave components, electrical injection is not practical for an array of artificial nonlinear surfaces, as would be needed in a three-dimensional free space phase conjugation setup. Therefore optical injection was implemented to carry the 2ω microwave pump signal in phase to all mixing elements. In both cases, two-dimensional free space phase conjugation was observed by directly measuring the electric field amplitude and phase distribution. The electric field wavefronts exhibited retro-directivity and auto- correction characteristics of phase conjugation. This demonstration surface also shows a power gain of 10 dB, which is desired for potential communication applications.

Miniature Neutron-Alpha Activation Spectrometer

NASA Astrophysics Data System (ADS)

Rhodes, E.; Goldsten, J.

2001-01-01

We are developing a miniature neutron-alpha activation spectrometer for in situ analysis of samples including rocks, fines, ices, and drill cores, suitable for a lander or Rover platform, that would meet the severe mass, power, and environmental constraints of missions to the outer planets. In the neutron-activation mode, a gamma-ray spectrometer will first perform a penetrating scan of soil, ice, and loose material underfoot (depths to 10 cm or more) to identify appropriate samples. Chosen samples will be analyzed in bulk in neutron-activation mode, and then the sample surfaces will be analyzed in alpha-activation mode using Rutherford backscatter and x-ray spectrometers. The instrument will provide sample composition over a wide range of elements, including rock-forming elements (such as Na, Mg, Si, Fe, and Ca), rare earths (Sm and Eu for example), radioactive elements (K, Th, and U), and light elements present in water, ices, and biological materials (mainly H, C, O, and N). The instrument is expected to have a mass of about l kg and to require less than 1 W power. Additional information is contained in the original extended abstract.

Numerical Analysis on the Rheology of Martian Lobate Debris Aprons

NASA Astrophysics Data System (ADS)

Li, H.; Jing, H.; Zhang, H.; Shi, Y.

2011-10-01

Occurrence of ice in Martian subsurface is indicated by landforms such as lobate debris aprons (LDAs), concentric crater fills, and softened terrains. We used a three dimensional non-Newtonian viscous finite element model to investigate the behavior of ice-rock mixtures numerically. Our preliminary simulation results show that when the volume of rock is less than 40%, the rheology of the mixture is dominated by ice, and there exists a brittle-ductile transition when ice fraction reaches a certain value.

Review of Thermal Properties of Snow, Ice and Sea Ice,

DTIC Science & Technology

1981-06-01

AD-AL03 734 COLD RE61ONS RESEARCH AND ENGINEERING LAS HANOVER NH F/G 8/12AI3 3REVIEW OF THERMAL PROPERTIES OF SNOW. ICE AND SEA ICE,(U)UNCLASSIFIlED...Distribution/ Availability Codes Avail and/or D~ Dis~t Special D 1 7 C- T > L) UNITED STATES ARMY CORPS OF ENGINEERS COLD REGIONS RESEARCH AND ENGINEERING...PROGRAM ELEMENT, PROJECT. TASK AREA A WORK UNIT NUMBERS U.S. Army Cold Regions Research and Engineering Laboratory Hanover, New Hampshire 03755 DA Pr

Discovery of a new family of relaxases in Firmicutes bacteria.

PubMed

Ramachandran, Gayetri; Miguel-Arribas, Andrés; Abia, David; Singh, Praveen K; Crespo, Isidro; Gago-Córdoba, César; Hao, Jian An; Luque-Ortega, Juan Roman; Alfonso, Carlos; Wu, Ling J; Boer, D Roeland; Meijer, Wilfried J J

2017-02-01

Antibiotic resistance is a serious global problem. Antibiotic resistance genes (ARG), which are widespread in environmental bacteria, can be transferred to pathogenic bacteria via horizontal gene transfer (HGT). Gut microbiomes are especially apt for the emergence and dissemination of ARG. Conjugation is the HGT route that is predominantly responsible for the spread of ARG. Little is known about conjugative elements of Gram-positive bacteria, including those of the phylum Firmicutes, which are abundantly present in gut microbiomes. A critical step in the conjugation process is the relaxase-mediated site- and strand-specific nick in the oriT region of the conjugative element. This generates a single-stranded DNA molecule that is transferred from the donor to the recipient cell via a connecting channel. Here we identified and characterized the relaxosome components oriT and the relaxase of the conjugative plasmid pLS20 of the Firmicute Bacillus subtilis. We show that the relaxase gene, named relLS20, is essential for conjugation, that it can function in trans and provide evidence that Tyr26 constitutes the active site residue. In vivo and in vitro analyses revealed that the oriT is located far upstream of the relaxase gene and that the nick site within oriT is located on the template strand of the conjugation genes. Surprisingly, the RelLS20 shows very limited similarity to known relaxases. However, more than 800 genes to which no function had been attributed so far are predicted to encode proteins showing significant similarity to RelLS20. Interestingly, these putative relaxases are encoded almost exclusively in Firmicutes bacteria. Thus, RelLS20 constitutes the prototype of a new family of relaxases. The identification of this novel relaxase family will have an important impact in different aspects of future research in the field of HGT in Gram-positive bacteria in general, and specifically in the phylum of Firmicutes, and in gut microbiome research.

Discovery of a new family of relaxases in Firmicutes bacteria

PubMed Central

Singh, Praveen K.; Hao, Jian An; Luque-Ortega, Juan Roman; Wu, Ling J.; Boer, D. Roeland

2017-01-01

Antibiotic resistance is a serious global problem. Antibiotic resistance genes (ARG), which are widespread in environmental bacteria, can be transferred to pathogenic bacteria via horizontal gene transfer (HGT). Gut microbiomes are especially apt for the emergence and dissemination of ARG. Conjugation is the HGT route that is predominantly responsible for the spread of ARG. Little is known about conjugative elements of Gram-positive bacteria, including those of the phylum Firmicutes, which are abundantly present in gut microbiomes. A critical step in the conjugation process is the relaxase-mediated site- and strand-specific nick in the oriT region of the conjugative element. This generates a single-stranded DNA molecule that is transferred from the donor to the recipient cell via a connecting channel. Here we identified and characterized the relaxosome components oriT and the relaxase of the conjugative plasmid pLS20 of the Firmicute Bacillus subtilis. We show that the relaxase gene, named relLS20, is essential for conjugation, that it can function in trans and provide evidence that Tyr26 constitutes the active site residue. In vivo and in vitro analyses revealed that the oriT is located far upstream of the relaxase gene and that the nick site within oriT is located on the template strand of the conjugation genes. Surprisingly, the RelLS20 shows very limited similarity to known relaxases. However, more than 800 genes to which no function had been attributed so far are predicted to encode proteins showing significant similarity to RelLS20. Interestingly, these putative relaxases are encoded almost exclusively in Firmicutes bacteria. Thus, RelLS20 constitutes the prototype of a new family of relaxases. The identification of this novel relaxase family will have an important impact in different aspects of future research in the field of HGT in Gram-positive bacteria in general, and specifically in the phylum of Firmicutes, and in gut microbiome research. PMID:28207825

Molecular Approach to Conjugated Polymers with Biomimetic Properties.

PubMed

Baek, Paul; Voorhaar, Lenny; Barker, David; Travas-Sejdic, Jadranka

2018-06-13

The field of bioelectronics involves the fascinating interplay between biology and human-made electronics. Applications such as tissue engineering, biosensing, drug delivery, and wearable electronics require biomimetic materials that can translate the physiological and chemical processes of biological systems, such as organs, tissues. and cells, into electrical signals and vice versa. However, the difference in the physical nature of soft biological elements and rigid electronic materials calls for new conductive or electroactive materials with added biomimetic properties that can bridge the gap. Soft electronics that utilize organic materials, such as conjugated polymers, can bring many important features to bioelectronics. Among the many advantages of conjugated polymers, the ability to modulate the biocompatibility, solubility, functionality, and mechanical properties through side chain engineering can alleviate the issues of mechanical mismatch and provide better interface between the electronics and biological elements. Additionally, conjugated polymers, being both ionically and electrically conductive through reversible doping processes provide means for direct sensing and stimulation of biological processes in cells, tissues, and organs. In this Account, we focus on our recent progress in molecular engineering of conjugated polymers with tunable biomimetic properties, such as biocompatibility, responsiveness, stretchability, self-healing, and adhesion. Our approach is general and versatile, which is based on functionalization of conjugated polymers with long side chains, commonly polymeric or biomolecules. Applications for such materials are wide-ranging, where we have demonstrated conductive, stimuli-responsive antifouling, and cell adhesive biointerfaces that can respond to external stimuli such as temperature, salt concentration, and redox reactions, the processes that in turn modify and reversibly switch the surface properties. Furthermore, utilizing the advantageous chemical, physical, mechanical and functional properties of the grafts, we progressed into grafting of the long side chains onto conjugated polymers in solution, with the vision of synthesizing solution-processable conjugated graft copolymers with biomimetic functionalities. Examples of the developed materials to date include rubbery and adhesive photoluminescent plastics, biomolecule-functionalized electrospun biosensors, thermally and dually responsive photoluminescent conjugated polymers, and tunable self-healing, adhesive, and stretchable strain sensors, advanced functional biocidal polymers, and filtration membranes. As outlined in these examples, the applications of these biomimetic, conjugated polymers are still in the development stage toward truly printable, organic bioelectronic devices. However, in this Account, we advocate that molecular engineering of conjugated polymers is an attractive approach to a versatile class of organic electronics with both ionic and electrical conductivity as well as mechanical properties required for next-generation bioelectronics.

KSC ice/frost/debris assessment for space shuttle mission STS-29R

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

An ice/frost/debris assessment was conducted for Space Shuttle Mission STS-29R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the external tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage. The ice/frost/debris conditions of Mission STS-29R and their effect on the Space Shuttle Program are documented.

Ice/frost/debris assessment for space shuttle Mission STS-32 (61-C)

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Speece, Robert F.

1986-01-01

An Ice/Frost/Debris assessment was conducted for Space Shuttle Mission STS-32 (61-C). This assessment begins with debris inspections of the flight elements and launch facilities before and after launch. Ice/Frost formations are calculated during cryogenic loading of the external tank followed by an on-pad assessment of the Shuttle vehicle and pad at T-3 hours in the countdown. High speed films are reviewed after launch to identify Ice/Frost/Debris sources and investigate potential vehicle damage. The Ice/Frost/Debris conditions and their effects on the Space Shuttle are documented.

Ice/frost/debris assessment for space shuttle mission STS-26R

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1988-01-01

An Ice/Frost/Debris Assessment was conducted for Space Shuttle Mission STS-26R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/Frost conditions are assessed by use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is viewed after launch to identify ice/debris sources and evaluate potential vehicle damage. The Ice/Frost/Debris conditions of Mission 26R and their effect on the Space Shuttle Program is documented.

Ice/frost/debris assessment for space shuttle mission STS-27R, December 2, 1988

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

An Ice/Frost/Debris assessment was conducted for Space Shuttle Mission STS-27R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is viewed after launch to identify ice/debris sources and evaluate potential vehicle damage. The Ice/Frost/Debris conditions of Mission STS-27R and their effect on the Space Shuttle Program are documented.

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Reversal of the contrast of optical radiation in round-trip amplifiers with a phase conjugation mirror

NASA Astrophysics Data System (ADS)

Afanas'ev, Anatolii A.; Samson, B. A.

1989-02-01

A description is given of a method for inversion of the contrast of optical radiation in a round-trip amplifier with a phase conjugation mirror and a phase nonreciprocal element. The system can be used to achieve high powers of contrast-reversed radiation because of compensation of phase distortions introduced by amplification.

Nanowire-nanoparticle conjugate photolytic devices for renewable hydrogen production

NASA Astrophysics Data System (ADS)

Maclaskey, Sean Kelly

A clean energy driven economy requires renewable production of zero--emission fuels, such as hydrogen (H2). Photocatalytic generation of H2 is one such method to fulfill this demand. Photocatalytic water splitting is an electrochemical process driven by solar energy to produce H2. Although there have been many investigations on photocatalytic water splitting, the number of concepts utilizing visible light is limited. In the present study, H2 evolution from water splitting is demonstrated using the novel concept of nanowire--nanoparticle (NW--NP) conjugate devices irradiated by visible light. Photolytic nanodevice suspensions are fabricated via sol--gel synthesis of vanadium oxyhydrate (V3O 7·H2O) NWs, followed by solution chemistry with HAuCl 4 for reduction of gold (Au) NPs on the NW surfaces. Characterization of nanodevices was performed via TEM, SEM, and optical spectroscopy. Products of photolysis were quantified and analyzed by Gas Chromatography (GC). The performance of the nanowire--nanoparticle conjugate devices was compared with previous photolytic device designs by the use of quantum and internal conversion efficiencies (QE and ICE, respectively). The present thesis demonstrates photocatalytic production of H2 using V3O7·H 2O NW -- Au NP conjugate devices under 470 nm excitation. The "photolytic nanodevice suspension in water" concept poses the potential for scalable H2 production, in addition to the provision for a low--cost technique due to fabrication by sol--gel synthesis and solution chemistry. The V3O7·H2O aerogel, a recently discovered semiconductor material, is found to be a suitable photoanode due to its narrow band gap energy of 2.18 eV, and its stability during photolysis. The diameters of the V3O7·H2O NWs are found to be 12 nm (+/- 2.4 nm) from SEM images. The decoration of NWs with Au NPs is verified by TEM imaging and Au NPs are estimated to be 7.5 nm (+/- 2.2 nm) in size. After decoration of NWs by Au NPs, a near--field enhancement effect on optical absorption by NWs was observed by UV--visible spectroscopy. Further, the emergence of new optical absorbance peaks indicates possible coupling of incident light into waveguide modes of the NWs. QE and ICE values for the NW--NP conjugate devices are found to be 19.28% and 8.98%, respectively, for the first hour of photolysis.

Bedrock structure and the interpretation of palaeo ice stream footprints: examples from the Pleistocene British Ice Sheet

NASA Astrophysics Data System (ADS)

Krabbendam, M.; Bradwell, T.

2009-04-01

To model past and future behaviour of ice sheets, a good understanding of both modern and ancient ice streams is required. The study of present-day ice streams provides detailed data of short-term dynamic changes, whilst the study of Pleistocene palaeo-ice streams can provide crucial constraints on the longer-term evolution of ice sheets. To date, palaeo-ice streams, such as the classical Dubawnt Lake palaeo-ice stream of the former Laurentide Ice Sheet, have been recognised largely on the basis of extremely elongate drumlins and megascale glacial lineations; all soft-sediment features. Whilst it appears that topographically unconstrained ice streams (eg. within the West Antarctic Ice Sheet) are generally underlain by deformable till, topographically constrained ice streams such as Jakobshavn Isbrae do not require deformable sediment and may occur on a bedrock-dominated bed. Analysis of DEM data and geomorphology and structural geology fieldwork in Northern Scotland and Northern England has shown the occurrence of highly streamlined bedforms in bedrock of the former base of topographically controlled palaeo-ice streams, which drained parts of the British Ice Sheet. The bedforms are predominantly bedrock megagrooves with asymmetric cross-profiles. In the Ullapool tributary of the Minch palaeo ice stream, bedrock megagrooves form the dominant evidence for ice streaming. The megagrooves are typically 5-15 m deep, 10-30 m wide and 500 - 3000 m long. Spacing of megagrooves is typically 100 - 200 m. In both study areas, the bedrock is strongly anisotropic, either consisting of thin-bedded strata or strongly foliated metasedimentary rocks, with the strata or foliation having a gentle dip. Megagrooves are best developed where the strike of the anisotropy is sub-parallel (within 10 - 20°) with palaeo ice flow. The bedrock in both areas has a well-developed, relatively densely spaced (< 1m), conjugate joint system. We suggest that asymmetric megagrooves are formed by "lateral plucking", facilitated by the combination of strong bedding/foliation and the joint pattern. Glacial erosion was laterally more effective than vertically; so that stepped faces subparallel to palaeo ice flow are enhanced rather that destroyed. We propose that: a) Lateral plucking is an effective mechanism to produce streamlined bedrock bedforms by fast ice flow, providing the bedrock and bedrock structure are suitable; b) some topographically controlled palaeo-ice stream beds are dominated by bedrock rather than soft-sediment; c) the recognition of palaeo-ice streams may be dependent on the type of bedrock and the orientation of bedrock structure with respect to palaeo ice flow; d) palaeo-ice stream footprints may have been underestimated in formerly glaciated areas.

Preparation and in vitro characterization of pluronic-attached polyamidoamine dendrimers for drug delivery.

PubMed

Gu, Zhuojun; Wang, Meng; Fang, Qiongyan; Zheng, Huaiyu; Wu, Feiyue; Lin, Dai; Xu, Ying; Jin, Yi

2015-05-01

Polyamidoamine (PAMAM) dendrimers have attracted lots of interest as drug carriers. And little study about whether pluronic-attached PAMAM dendrimers could be potential drug delivery systems has been carried on. Pluronic F127 (PF127) attached PAMAM dendrimers were designed as novel drug carriers. Two conjugation ratios of PF127-attached PAMAM dendrimers were synthesized. (1)H nuclear magnetic resonance ((1)H-NMR), Fourier transform infrared spectrum (FTIR), element analysis and ninhydrin assay were used to characterize the conjugates. Size, zeta potential and critical micelle concentrations (CMC) were also detected. And DOX was incorporated into the hydrophobic interior of the conjugates. Studies on their drug loading and drug release were carried on. Furthermore, hemolysis and cytotoxicity assay were used to evaluate the toxicity of the conjugates. PF127 was successfully conjugated to the fifth generation PAMAM dendrimer at two molar ratios of 19% and 57% (PF127 to surface amine per PAMAM dendrimer molecular). The conjugates showed an increased size and a reduced zeta potential. And higher CMC values were obtained than pure PF127. Compared with unconjugated PAMAM dendrimer, PF127 conjugation significantly reduced the hemolytic toxicity and cytotoxicity of PAMAM dendrimer in vitro. The encapsulation results showed that the ability to encapsulate DOX by the conjugate of 19% conjugation ratio was better than that of 57% conjugation ratio. And the maximum is ∼12.87 DOX molecules per conjugate molecule. Moreover, the complexes showed a sustained release behavior compared to pure DOX. Findings from the in vitro study show that the PF127-attached PAMAM dendrimers may be potential carriers for drug delivery.

Versatile Cas9-Driven Subpopulation Selection Toolbox for Lactococcus lactis.

PubMed

van der Els, Simon; James, Jennelle K; Kleerebezem, Michiel; Bron, Peter A

2018-04-15

CRISPR-Cas9 technology has been exploited for the removal or replacement of genetic elements in a wide range of prokaryotes and eukaryotes. Here, we describe the extension of the Cas9 application toolbox to the industrially important dairy species Lactococcus lactis The Cas9 expression vector pLABTarget, encoding the Streptocccus pyogenes Cas9 under the control of a constitutive promoter, was constructed, allowing plug and play introduction of short guide RNA (sgRNA) sequences to target specific genetic loci. Introduction of a pepN -targeting derivative of pLABTarget into L. lactis strain MG1363 led to a strong reduction in the number of transformants obtained, which did not occur in a pepN deletion derivative of the same strain, demonstrating the specificity and lethality of the Cas9-mediated double-strand breaks in the lactococcal chromosome. Moreover, the same pLABTarget derivative allowed the selection of a pepN deletion subpopulation from its corresponding single-crossover plasmid integrant precursor, accelerating the construction and selection of gene-specific deletion derivatives in L. lactis Finally, pLABTarget, which contained sgRNAs designed to target mobile genetic elements, allowed the effective curing of plasmids, prophages, and integrative conjugative elements (ICEs). These results establish that pLABTarget enables the effective exploitation of Cas9 targeting in L. lactis , while the broad-host-range vector used suggests that this toolbox could readily be expanded to other Gram-positive bacteria. IMPORTANCE Mobile genetic elements in Lactococcus lactis and other lactic acid bacteria (LAB) play an important role in dairy fermentation, having both positive and detrimental effects during the production of fermented dairy products. The pLABTarget vector offers an efficient cloning platform for Cas9 application in lactic acid bacteria. Targeting Cas9 toward mobile genetic elements enabled their effective curing, which is of particular interest in the context of potentially problematic prophages present in a strain. Moreover, Cas9 targeting of other mobile genetic elements enables the deciphering of their contribution to dairy fermentation processes and further establishment of their importance for product characteristics. Copyright © 2018 American Society for Microbiology.

SAR data for river ice monitoring. How to meet requirements?

NASA Astrophysics Data System (ADS)

Łoś, Helena; Osińska-Skotak, Katarzyna; Pluto-Kossakowska, Joanna

2017-04-01

Although river ice is a natural element of rivers regime it can lead to severe problems such as winter floods or damages of bridges and bank revetments. Services that monitor river ice condition are still often based on field observation. For several year, however, Earth observation data have become of a great interest, especially SAR images, which allows to observe ice and river condition independently of clouds and sunlight. One of requirements of an effective monitoring system is frequent and regular data acquisition. To help to meet this requirement we assessed an impact of selected SAR data parameters into automatic ice types identification. Presented work consists of two parts. The first one focuses on comparison of C-band and X-band data in terms of the main ice type detection. The second part contains an analysis of polarisation reduction from quad-pol to dual-pol data. As the main element of data processing we chose the supervised classification with maximum likelihood algorithm adapted to Wishart distribution. The classification was preceded by statistical analysis of radar signal obtained for selected ice types including separability measures. Two river were selected as areas of interest - the Peace River in Canada and the Vistula in Poland. The results shows that using data registered in both bands similar accuracy of classification into main ice types can be obtain. Differences appear with details e.g. thin initial ice. Classification results obtained from quad-pol and dual-pol data were similar while four classes were selected. With six classes, however, differences between polarisation types have been noticed.

Transient sensitivities of sea ice export through the Canadian Arctic Archipelago inferred from a coupled ocean/sea-ice adjoint model

NASA Astrophysics Data System (ADS)

Heimbach, P.; Losch, M.; Menemenlis, D.; Campin, J.; Hill, C.

2008-12-01

The sensitivity of sea-ice export through the Canadian Arctic Archipelago (CAA), measured in terms of its solid freshwater export through Lancaster Sound, to changes in various elements of the ocean and sea-ice state, and to elements of the atmospheric forcing fields through time and space is assessed by means of a coupled ocean/sea-ice adjoint model. The adjoint model furnishes full spatial sensitivity maps (also known as Lagrange multipliers) of the export metric to a variety of model variables at any chosen point in time, providing the unique capability to quantify major drivers of sea-ice export variability. The underlying model is the MIT ocean general circulation model (MITgcm), which is coupled to a Hibler-type dynamic/thermodynamic sea-ice model. The configuration is based on the Arctic face of the ECCO3 high-resolution cubed-sphere model, but coarsened to 36-km horizontal grid spacing. The adjoint of the coupled system has been derived by means of automatic differentiation using the software tool TAF. Finite perturbation simulations are performed to check the information provided by the adjoint. The sea-ice model's performance in the presence of narrow straits is assessed with different sea-ice lateral boundary conditions. The adjoint sensitivity clearly exposes the role of the model trajectory and the transient nature of the problem. The complex interplay between forcing, dynamics, and boundary condition is demonstrated in the comparison between the different calculations. The study is a step towards fully coupled adjoint-based ocean/sea-ice state estimation at basin to global scales as part of the ECCO efforts.

Trace metal concentrations of surface snow from Ingrid Christensen Coast, East Antarctica--spatial variability and possible anthropogenic contributions.

PubMed

Thamban, Meloth; Thakur, Roseline C

2013-04-01

To investigate the distribution and source pathways of environmentally critical trace metals in coastal Antarctica, trace elemental concentrations were analyzed in 36 surface snow samples along a coast to inland transect in the Ingrid Christensen Coast of East Antarctica. The samples were collected and analyzed using the clean protocols and an inductively coupled plasma mass spectrometer. Within the coastal ice-free and ice-covered region, marine elements (Na, Ca, Mg, K, Li, and Sr) revealed enhanced concentrations as compared with inland sites. Along with the sea-salt elements, the coastal ice-free sites were also characterized by enhanced concentrations of Al, Fe, Mn, V, Cr, and Zn. The crustal enrichment factors (Efc) confirm a dominant crustal source for Fe and Al and a significant source for Cr, V, Co, and Ba, which clearly reflects the influence of petrological characteristics of the Larsemann Hills on the trace elemental composition of surface snow. The Efc of elements revealed that Zn, Cu, Mo, Cd, As, Se, Sb, and Pb are highly enriched compared with the known natural sources, suggesting an anthropogenic origin for these elements. Evaluation of the contributions to surface snow from the different sources suggests that while contribution from natural sources is relatively significant, local contamination from the increasing research station and logistic activities within the proximity of study area cannot be ignored.

Volcanic ash layers in blue ice fields (Beardmore Glacier Area, Antarctica): Iridium enrichments

NASA Technical Reports Server (NTRS)

Koeberl, Christian

1988-01-01

Dust bands on blue ice fields in Antarctica have been studied and have been identified to originate from two main sources: bedrock debris scraped up from the ground by the glacial movement (these bands are found predominantly at fractures and shear zones in the ice near moraines), and volcanic debris deposited on and incorporated in the ice by large-scale eruptions of Antarctic (or sub-Antractic) volcanoes. Ice core studies have revealed that most of the dust layers in the ice cores are volcanic (tephra) deposits which may be related to some specific volcanic eruptions. These eruptions have to be related to some specific volcanic eruptions. These eruptions have to be relatively recent (a few thousand years old) since ice cores usually incorporate younger ice. In contrast, dust bands on bare blue ice fields are much older, up to a few hundred thousand years, which may be inferred from the rather high terrestrial age of meteorites found on the ice and from dating the ice using the uranium series method. Also for the volcanic ash layers found on blue ice fields correlations between some specific volcanoes (late Cenozoic) and the volcanic debris have been inferred, mainly using chemical arguments. During a recent field expedition samples of several dust bands found on blue ice fields at the Lewis Cliff Ice Tongue were taken. These dust band samples were divided for age determination using the uranium series method, and chemical investigations to determine the source and origin of the dust bands. The investigations have shown that most of the dust bands found at the Ice Tongue are of volcanic origin and, for chemical and petrological reasons, may be correlated with Cenozoic volcanoes in the Melbourne volcanic province, Northern Victoria Land, which is at least 1500 km away. Major and trace element data have been obtained and have been used for identification and correlation purposes. Recently, some additional trace elements were determined in some of the dust band samples, including Ir. Iridium determinations were made using INAA, with synthetical and natural (meteorite) standards. These findings are discussed.

Computational Simulation of the Formation and Material Behavior of Ice

NASA Technical Reports Server (NTRS)

Tong, Michael T.; Singhal, Surendra N.; Chamis, Christos C.

1994-01-01

Computational methods are described for simulating the formation and the material behavior of ice in prevailing transient environments. The methodology developed at the NASA Lewis Research Center was adopted. A three dimensional finite-element heat transfer analyzer was used to predict the thickness of ice formed under prevailing environmental conditions. A multi-factor interaction model for simulating the material behavior of time-variant ice layers is presented. The model, used in conjunction with laminated composite mechanics, updates the material properties of an ice block as its thickness increases with time. A sample case of ice formation in a body of water was used to demonstrate the methodology. The results showed that the formation and the material behavior of ice can be computationally simulated using the available composites technology.

Small Scale Polygons and the History of Ground Ice on Mars

NASA Technical Reports Server (NTRS)

Mellon, Michael T.

2003-01-01

Recent progress on polygon modeling has focused on the diameter and surface relief that we expect of thermal-contraction polygons in martian permafrost. With this in mind, we developed a finite-element model of thermal-contraction-crack behavior in permafrost in a martian climate. This model was generated from a finite element code by Jay Melosh (called TECTON) originally developed for terrestrial and planetary crustal-deformation studies. We adapted this model to martian permafrost by including time (and temperature) dependent rheologies, boundary conditions, and isotropic thermal-contraction, as well as several small adaptations to a martian environment. We tested our model extensively, including comparison to an analytic solution of pre-fracture stress. We recently published an analysis of two potential sources of water for forming the recent gullies. In this work we first evaluated the potential for near-surface ground ice (in the top meter or so of soil) to melt under conditions of solar heating on sloped surfaces at high obliquity, utilizing both thermal and diffusion-based ground-ice-stability models; our results suggested that the ground ice will sublimate, and the ice table will recede to greater depths before the melting temperature can be reached. An exception can occur only for extremely salt-rich ice, depressing the freezing point.

KSC ice/frost/debris assessment for Space Shuttle Mission STS-30R

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

An ice/frost/debris assessment was conducted for Space Shuttle Mission STS-30R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the external tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by an on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage. The ice/frost/debris conditions of Mission STS-30R and their overall effect on the Space Shuttle Program is documented.

Debris/Ice/TPS Assessment and Photographic Analysis for Shuttle Mission STS-39

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1991-01-01

A Debris/Ice/TPS (thermal protection system) assessment and photographic analysis was conducted for Space Shuttle Mission STS-39. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of launch was analyzed to identify ice/debris anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-39, and their overall effect on the Space Shuttle Program are documented.

Debris/ice/TPS assessment and photographic analysis for Shuttle Mission STS-43

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, James Bradley

1991-01-01

A debris/ice Thermal Protection System (TPS) assessment and photographic analysis was conducted for Space Station Mission STS-43. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank (ET) were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and to evaluate potential vehicle damage and/or in-flight anomalies.

Debris/Ice/TPS Assessment and Photographic Analysis for Shuttle Mission STS-40

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1991-01-01

A debris, ice, Thermal Protection System (TPS) assessment and photographic analysis for Space Shuttle Mission STS-40 was conducted. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice and frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice and debris sources and to evaluate potential vehicle damage and/or in-flight anomalies.

HybridICE® filter: ice separation in freeze desalination of mine waste waters.

PubMed

Adeniyi, A; Maree, J P; Mbaya, R K K; Popoola, A P I; Mtombeni, T; Zvinowanda, C M

2014-01-01

Freeze desalination is an alternative method for the treatment of mine waste waters. HybridICE(®) technology is a freeze desalination process which generates ice slurry in surface scraper heat exchangers that use R404a as the primary refrigerant. Ice separation from the slurry takes place in the HybridICE filter, a cylindrical unit with a centrally mounted filter element. Principally, the filter module achieves separation of the ice through buoyancy force in a continuous process. The HybridICE filter is a new and economical means of separating ice from the slurry and requires no washing of ice with water. The performance of the filter at a flow-rate of 25 L/min was evaluated over time and with varied evaporating temperature of the refrigerant. Behaviours of the ice fraction and residence time were also investigated. The objective was to find ways to improve the performance of the filter. Results showed that filter performance can be improved by controlling the refrigerant evaporating temperature and eliminating overflow.

Sensitivity calculations for iteratively solved problems

NASA Technical Reports Server (NTRS)

Haftka, R. T.

1985-01-01

The calculation of sensitivity derivatives of solutions of iteratively solved systems of algebraic equations is investigated. A modified finite difference procedure is presented which improves the accuracy of the calculated derivatives. The procedure is demonstrated for a simple algebraic example as well as an element-by-element preconditioned conjugate gradient iterative solution technique applied to truss examples.

Records of anthropogenic antimony in the glacial snow from the southeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhang, Yulan; Kang, Shichang; Chen, Pengfei; Li, Xiaofei; Liu, Yajun; Gao, Tanguang; Guo, Junming; Sillanpää, Mika

2016-12-01

Antimony (Sb) is a ubiquitous element in the environment that is potentially toxic at very low concentrations. In this study, surface snow/ice and snowpit samples were collected from four glaciers in the southeastern Tibetan Plateau in June 2015. The concentrations of Sb and other elements were measured in these samples. The results showed that the average concentration of Sb was approximately 2.58 pg g-1 with a range of 1.64-9.20 pg g-1. The average Sb concentration in the study area was comparable to that recorded in a Mt. Everest ice core and higher than that in Arctic and Antarctic snow/ice but much lower than that in Tien Shan and Alps ice cores. Sb presented different variations with other toxic elements (Pb and Cr) and a crustal element (Al) in the three snowpits, which indicated the impact of a different source or post-deposition processes. The enrichment factor of Sb was larger than 10, suggesting that anthropogenic sources provided important contributions to Sb deposition in the glaciers. The Sb in the glacial snow was mainly loaded in the fourth component in principal component analysis, exhibiting discrepancies with crustal elements (Fe and Ca) and other toxic metals (Pb). Backward trajectories revealed that the air mass arriving at the southeastern Tibetan Plateau mostly originated from the Bay of Bengal and the South Asia in June. Thus, pollutants from the South Asia could play an important role in Sb deposition in the studied region. The released Sb from glacier meltwater in the Tibetan Plateau and surrounding areas might pose a risk to the livelihoods and well-being of those in downstream regions.

Heat Transfer Measurements on Surfaces with Natural Ice Castings and Modeled Roughness

NASA Technical Reports Server (NTRS)

Breuer, Kenneth S.; Torres, Benjamin E.; Orr, D. J.; Hansman, R. John

1997-01-01

An experimental method is described to measure and compare the convective heat transfer coefficient of natural and simulated ice accretion roughness and to provide a rational means for determining accretion-related enhanced heat transfer coefficients. The natural ice accretion roughness was a sample casting made from accretions at the NASA Lewis Icing Research Tunnel (IRT). One of these castings was modeled using a Spectral Estimation Technique (SET) to produce three roughness elements patterns that simulate the actual accretion. All four samples were tested in a flat-plate boundary layer at angle of attack in a "dry" wind tunnel test. The convective heat transfer coefficient was measured using infrared thermography. It is shown that, dispite some problems in the current data set, the method does show considerable promise in determining roughness-induced heat transfer coefficients, and that, in addition to the roughness height and spacing in the flow direction, the concentration and spacing of elements in the spanwise direction are important parameters.

Capabilities and performance of Elmer/Ice, a new generation ice-sheet model

NASA Astrophysics Data System (ADS)

Gagliardini, O.; Zwinger, T.; Gillet-Chaulet, F.; Durand, G.; Favier, L.; de Fleurian, B.; Greve, R.; Malinen, M.; Martín, C.; Råback, P.; Ruokolainen, J.; Sacchettini, M.; Schäfer, M.; Seddik, H.; Thies, J.

2013-03-01

The Fourth IPCC Assessment Report concluded that ice-sheet flow models are unable to forecast the current increase of polar ice sheet discharge and the associated contribution to sea-level rise. Since then, the glaciological community has undertaken a huge effort to develop and improve a new generation of ice-flow models, and as a result, a significant number of new ice-sheet models have emerged. Among them is the parallel finite-element model Elmer/Ice, based on the open-source multi-physics code Elmer. It was one of the first full-Stokes models used to make projections for the evolution of the whole Greenland ice sheet for the coming two centuries. Originally developed to solve local ice flow problems of high mechanical and physical complexity, Elmer/Ice has today reached the maturity to solve larger scale problems, earning the status of an ice-sheet model. Here, we summarise almost 10 yr of development performed by different groups. We present the components already included in Elmer/Ice, its numerical performance, selected applications, as well as developments planned for the future.

High sensitive FBG load cell for icing of overhead transmission lines

NASA Astrophysics Data System (ADS)

Mao, Naiqiang; Ma, Guoming; Li, Chengrong; Li, Yabo; Shi, Cheng; Du, Yue

2017-04-01

Heavy ice coating of overhead transmission lines created the serious threat on the safe operation of power grid. The measurement of conductor icing had been an effective and reliable methods to prevent potential risks, such as conductor breakage, insulator flashover and tower collapse. Because of the advantages of immunity to electromagnetic interference and no demand for power supply in site, the optical load cell has been widely applied in monitoring the ice coating of overhead transmission lines. In this paper, we have adopted the shearing structure with additional grooves as elastic element of load cell to detect the eccentric load. Then, two welding package fiber Bragg gratings (FBGs) were mounted onto the grooves of elastic element with a direction deviation of 90° to eliminate temperature effects on strain measurement without extra FBG. After that, to avoid the occurrence of load cell breakage in heavy load measurement, the protection part has been proposed and added to the elastic element. The results of tension experiments indicate that the resolution of the load cell is 7.78 N in the conventional measuring range (0-10 kN). And in addition, the load cell proposed in this paper also has a good performance in actual experiment in which the load and temperature change simultaneously.

Deicing and Anti-Icing Unite

NASA Technical Reports Server (NTRS)

2002-01-01

With funding from Glenn's Small Business Innovation Research (SBIR) program, Cox & Company, Inc., built an ice protection system that combines thermal anti-icing and mechanical deicing to keep airfoils (wings and other lifting surfaces) clear of ice. Cox's concept was to combine an anti-icing system with NASA's Electro-Mechanical Expulsion Deicing System, a mechanical deicer. The anti-icing element of this hybrid would reduce the aerodynamic losses associated with deicing systems. The Cox Low Power Ice Protection System is the first new aircraft ice protection system that has been approved by the Federal Aviation Administration for use on a business jet in 40 years. While the system is currently sized for Premier class aircraft, there are no apparent constraints prohibiting its use on aircraft of any size. The company is investigating further applications, such as adapting the system for unmanned aerial vehicles and other military aircraft.

Coherent perfect absorber and laser modes in purely imaginary metamaterials

NASA Astrophysics Data System (ADS)

Fu, Yangyang; Cao, Yanyan; Cummer, Steven A.; Xu, Yadong; Chen, Huanyang

2017-10-01

Conjugate metamaterials, in which the permittivity and the permeability are complex conjugates of each other, possess the elements of loss and gain simultaneously. By employing a conjugate metamaterial with a purely imaginary form, we propose a mechanism for realizing both coherent perfect absorber (CPA) and laser modes. Moreover, the general conditions for obtaining CPA and laser modes, including obtaining them simultaneously, are revealed by analyzing the wave scattering properties of a slab made of purely imaginary metamaterials (PIMs). Specifically, in a PIM slab with a subunity effective refractive index, the CPA mode can be simplified as a perfect absorption mode and the incident wave from one side could be perfectly absorbed.

Psychosocial Characteristics of Optimum Performance in Isolated and Confined Environments (ICE)

NASA Technical Reports Server (NTRS)

Palinkas, Lawrence A.; Keeton, Kathryn E.; Shea, Camille; Leveton, Lauren B.

2010-01-01

The Behavioral Health and Performance (BHP) Element addresses human health risks in the NASA Human Research Program (HRP), including the Risk of Adverse Behavioral Conditions and the Risk of Psychiatric Disorders. BHP supports and conducts research to help characteristics and mitigate the Behavioral Medicine risk for exploration missions, and in some instances, current Flight Medical Operations. The Behavioral Health and Performance (BHP) Element identified research gaps within the Behavioral Medicine Risk, including Gap BMed6: What psychosocial characteristics predict success in an isolated, confined environment (ICE)? To address this gap, we conducted an extensive and exhaustive literature review to identify the following: 1) psychosocial characteristics that predict success in ICE environments; 2) characteristics that are most malleable; and 3) specific countermeasures that could enhance malleable characteristics.

Energy Transfer between Conjugated Colloidal Ga2O3 and CdSe/CdS Core/Shell Nanocrystals for White Light Emitting Applications

PubMed Central

Stanish, Paul C.; Radovanovic, Pavle V.

2016-01-01

Developing solid state materials capable of generating homogeneous white light in an energy efficient and resource-sustainable way is central to the design of new and improved devices for various lighting applications. Most currently-used phosphors depend on strategically important rare earth elements, and rely on a multicomponent approach, which produces sub-optimal quality white light. Here, we report the design and preparation of a colloidal white-light emitting nanocrystal conjugate. This conjugate is obtained by linking colloidal Ga2O3 and II–VI nanocrystals in the solution phase with a short bifunctional organic molecule (thioglycolic acid). The two types of nanocrystals are electronically coupled by Förster resonance energy transfer owing to the short separation between Ga2O3 (energy donor) and core/shell CdSe/CdS (energy acceptor) nanocrystals, and the spectral overlap between the photoluminescence of the donor and the absorption of the acceptor. Using steady state and time-resolved photoluminescence spectroscopies, we quantified the contribution of the energy transfer to the photoluminescence spectral power distribution and the corresponding chromaticity of this nanocrystal conjugate. Quantitative understanding of this new system allows for tuning of the emission color and the design of quasi-single white light emitting inorganic phosphors without the use of rare-earth elements. PMID:28344289

Using two MEMS deformable mirrors in an adaptive optics test bed for multiconjugate correction

NASA Astrophysics Data System (ADS)

Andrews, Jonathan R.; Martinez, Ty; Teare, Scott W.; Restaino, Sergio R.; Wilcox, Christopher C.; Santiago, Freddie; Payne, Don M.

2010-02-01

Adaptive optics systems have advanced considerably over the past decade and have become common tools for optical engineers. The most recent advances in adaptive optics technology have lead to significant reductions in the cost of most of the key components. Most significantly, the cost of deformable elements and wavefront sensor components have dropped to the point where multiple deformable mirrors and Shack- Hartmann array based wavefront sensor cameras can be included in a single system. Matched with the appropriate hardware and software, formidable systems can be operating in nearly any sized research laboratory. The significant advancement of MEMS deformable mirrors has made them very popular for use as the active corrective element in multi-conjugate adaptive optics systems so that, in particular for astronomical applications, this allows correction in more than one plane. The NRL compact AO system and atmospheric simulation systems has now been expanded to support Multi Conjugate Adaptive Optics (MCAO), taking advantage of using the liquid crystal spatial light modulator (SLM) driven aberration generators in two conjugate planes that are well separated spatially. Thus, by using two SLM based aberration generators and two separate wavefront sensors, the system can measure and apply wavefront correction with two MEMS deformable mirrors. This paper describes the multi-conjugate adaptive optics system and the testing and calibration of the system and demonstrates preliminary results with this system.

Ice sheets play important role in climate change

NASA Astrophysics Data System (ADS)

Clark, Peter U.; MacAyeal, Douglas R.; Andrews, John T.; Bartlein, Patrick J.

Ice sheets once were viewed as passive elements in the climate system enslaved to orbitally generated variations in solar radiation. Today, modeling results and new geologic records suggest that ice sheets actively participated in late-Pleistocene climate change, amplifying or driving significant variability at millennial as well as orbital timescales. Although large changes in global ice volume were ultimately caused by orbital variations (the Milankovitch hypothesis), once in existence, the former ice sheets behaved dynamically and strongly influenced regional and perhaps even global climate by altering atmospheric and oceanic circulation and temperature.Experiments with General Circulation Models (GCMs) yielded the first inklings of ice sheets' climatic significance. Manabe and Broccoli [1985], for example, found that the topographic and albedo effects of ice sheets alone explain much of the Northern Hemisphere cooling identified in paleoclimatic records of the last glacial maximum (˜21 ka).

Nonlinear geometric scaling of coercivity in a three-dimensional nanoscale analog of spin ice

NASA Astrophysics Data System (ADS)

Shishkin, I. S.; Mistonov, A. A.; Dubitskiy, I. S.; Grigoryeva, N. A.; Menzel, D.; Grigoriev, S. V.

2016-08-01

Magnetization hysteresis loops of a three-dimensional nanoscale analog of spin ice based on the nickel inverse opal-like structure (IOLS) have been studied at room temperature. The samples are produced by filling nickel into the voids of artificial opal-like films. The spin ice behavior is induced by tetrahedral elements within the IOLS, which have the same arrangement of magnetic moments as a spin ice. The thickness of the films vary from a two-dimensional, i.e., single-layered, antidot array to a three-dimensional, i.e., multilayered, structure. The coercive force, the saturation, and the irreversibility field have been measured in dependence of the thickness of the IOLS for in-plane and out-of-plane applied fields. The irreversibility and saturation fields change abruptly from the antidot array to the three-dimensional IOLS and remain constant upon further increase of the number of layers n . The coercive force Hc seems to increase logarithmically with increasing n as Hc=Hc 0+α ln(n +1 ) . The logarithmic law implies the avalanchelike remagnetization of anisotropic structural elements connecting tetrahedral and cubic nodes in the IOLS. We conclude that the "ice rule" is the base of mechanism regulating this process.

Aptamer-conjugated nanoparticles for cancer cell detection.

PubMed

Medley, Colin D; Bamrungsap, Suwussa; Tan, Weihong; Smith, Joshua E

2011-02-01

Aptamer-conjugated nanoparticles (ACNPs) have been used for a variety of applications, particularly dual nanoparticles for magnetic extraction and fluorescent labeling. In this type of assay, silica-coated magnetic and fluorophore-doped silica nanoparticles are conjugated to highly selective aptamers to detect and extract targeted cells in a variety of matrixes. However, considerable improvements are required in order to increase the selectivity and sensitivity of this two-particle assay to be useful in a clinical setting. To accomplish this, several parameters were investigated, including nanoparticle size, conjugation chemistry, use of multiple aptamer sequences on the nanoparticles, and use of multiple nanoparticles with different aptamer sequences. After identifying the best-performing elements, the improvements made to this assay's conditional parameters were combined to illustrate the overall enhanced sensitivity and selectivity of the two-particle assay using an innovative multiple aptamer approach, signifying a critical feature in the advancement of this technique.

Ice under cover: Using bulk spatial and physical properties of probable ground ice driven mass wasting features on Ceres to better understand its surface

NASA Astrophysics Data System (ADS)

Hughson, K.; Russell, C.; Schmidt, B. E.; Chilton, H.; Scully, J. E. C.; Castillo, J. C.; Combe, J. P.; Ammannito, E.; Sizemore, H.; Platz, T.; Byrne, S.; Nathues, A.; Raymond, C. A.

2016-12-01

NASA's Dawn spacecraft arrived at Ceres on March 6, 2015, and has been studying the dwarf planet through a series of successively lower orbits, obtaining morphological and topographical image, mineralogical, elemental composition, and gravity data (Russell et al., 2016). Images taken by Dawn's Framing Camera show a multitude of flow features that were broadly interpreted as ground ice related structures either similar to ice cored/ice cemented flows (as seen on Earth and Mars), long run-out landslides, or fluidized ejecta (as seen on Mars) by Schmidt et al. (2016a and 2016b) and Buczkowski et al. (2016). The aforementioned ice cored/ice cemented-like flows are present only at high latitudes. Results from Dawn's Gamma Ray and Neutron Detector (GRaND) indicate a shallow ice table on Ceres above 45-50°N/S, which supports the interpretation that these flows are ice-rich (Prettyman et al., 2016). A near coincident spectral detection of H2O ice with one of these ice cored/ice cemented-like flows in Oxo crater by Dawn's Visual and Infrared spectrometer (VIR) further bolsters this claim (Combe et al., 2016). We use aggregate spatial and physical properties of these ice attributed cerean flows, such as flow orientation, inclination, preference for north or south facing slopes, drop height to run-out length ratio, geographical location, and areal number density to better understand the rheology and distribution of ground ice in Ceres' uppermost layer. By combining these data with local spectroscopic, global elemental abundance, experimentally derived physical properties of cerean analogue material, and other morphological information (such as the morphologies of flow hosting craters) we intend to further test the ground ice hypothesis for the formation of these flows and constrain the global distribution of near surface ground ice on Ceres to a higher fidelity than what would be possible using GRaND and VIR observations alone. References: Buczkowski et al., (2016) Science, AcceptedCombe, J-P., et al. (2016) Science, AcceptedPrettyman, T. H., et al. (2016) LPSC XVII, Abstract #2228 Russell, et al. (2016) Science, AcceptedSchmidt, B. E., et al. (2016a) LPSC XVII, Abstract #2677 Schmidt, B. E., et al. (2016b), Nature Geoscience, In Review

Stereochemical analysis of the functional significance of the conserved inverted CCAAT and TATA elements in the rat bone sialoprotein gene promoter.

PubMed

Su, Ming; Lee, Daniel; Ganss, Bernhard; Sodek, Jaro

2006-04-14

Basal transcription of the bone sialoprotein gene is mediated by highly conserved inverted CCAAT (ICE; ATTGG) and TATA elements (TTTATA) separated by precisely 21 nucleotides. Here we studied the importance of the relative position and orientation of the CCAAT and TATA elements in the proximal promoter by measuring the transcriptional activity of a series of mutated reporter constructs in transient transfection assays. Whereas inverting the TTTATA (wild type) to a TATAAA (consensus TATA) sequence increased transcription slightly, transcription was reduced when the flanking dinucleotides were also inverted. In contrast, reversing the ATTGG (wild type; ICE) to a CCAAT (RICE) sequence caused a marked reduction in transcription, whereas both transcription and NF-Y binding were progressively increased with the simultaneous inversion of flanking nucleotides (f-RICE-f). Reducing the distance between the ICE and TATA elements produced cyclical changes in transcriptional activity that correlated with progressive alterations in the relative positions of the CCAAT and TATA elements on the face of the DNA helix. Minimal transcription was observed after 5 nucleotides were deleted (equivalent to approximately one half turn of the helix), whereas transcription was fully restored after deleting 10 nucleotides (approximately one full turn of the DNA helix), transcriptional activity being progressively lost with deletions beyond 10 nucleotides. In comparison, when deletions were made with the ICE in the reversed (f-RICE-f) orientation transcriptional activity was progressively lost with no recovery. These results show that, although transcription can still occur when the CCAAT box is reversed and/or displaced relative to the TATA box, the activity is dependent upon the flexibility of the intervening DNA helix needed to align the NF-Y complex on the CCAAT box with preinitiation complex proteins that bind to the TATA box. Thus, the precise location and orientation of the CCAAT element is necessary for optimizing basal transcription of the bone sialoprotein gene.

Disk Evolution, Element Abundances and Cloud Properties of Young Gas Giant Planets

PubMed Central

Helling, Christiane; Woitke, Peter; Rimmer, Paul B.; Kamp, Inga; Thi, Wing-Fai; Meijerink, Rowin

2014-01-01

We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. This gas will contain only traces of elements like C, N and O, because those elements have frozen out as ices. ProDiMo protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly. Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionization rate assumed. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The Drift cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying premordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, premordial element abundances are considered as suggested by disk models. PMID:25370190

Disk evolution, element abundances and cloud properties of young gas giant planets.

PubMed

Helling, Christiane; Woitke, Peter; Rimmer, Paul B; Kamp, Inga; Thi, Wing-Fai; Meijerink, Rowin

2014-04-14

We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the atmosphere when young gas giant planets form, in particular discussing the effects of unusual, non-solar carbon and oxygen abundances. Large deviations between the abundances of the host star and its gas giants seem likely to occur if the planet formation follows the core-accretion scenario. These deviations stem from the separate evolution of gas and dust in the disk, where the dust forms the planet cores, followed by the final run-away accretion of the left-over gas. This gas will contain only traces of elements like C, N and O, because those elements have frozen out as ices. PRODIMO protoplanetary disk models are used to predict the chemical evolution of gas and ice in the midplane. We find that cosmic rays play a crucial role in slowly un-blocking the CO, where the liberated oxygen forms water, which then freezes out quickly. Therefore, the C/O ratio in the gas phase is found to gradually increase with time, in a region bracketed by the water and CO ice-lines. In this regions, C/O is found to approach unity after about 5 Myrs, scaling with the cosmic ray ionization rate assumed. We then explore how the atmospheric chemistry and cloud properties in young gas giants are affected when the non-solar C/O ratios predicted by the disk models are assumed. The DRIFT cloud formation model is applied to study the formation of atmospheric clouds under the influence of varying premordial element abundances and its feedback onto the local gas. We demonstrate that element depletion by cloud formation plays a crucial role in converting an oxygen-rich atmosphere gas into carbon-rich gas when non-solar, premordial element abundances are considered as suggested by disk models.

Capabilities and performance of the new generation ice-sheet model Elmer/Ice

NASA Astrophysics Data System (ADS)

Gagliardini, O.; Zwinger, T.; Durand, G.; Favier, L.; de Fleurian, B.; Gillet-chaulet, F.; Seddik, H.; Greve, R.; Mallinen, M.; Martin, C.; Raback, P.; Ruokolainen, J.; Schäfer, M.; Thies, J.

2012-12-01

Since the Fourth IPCC Assessment Report, and its conclusion about the inability of ice-sheet flow models to forecast the current increase of polar ice sheet discharge and associated contribution to sea-level rise, a huge development effort has been undertaken by the glaciological community. All around the world, models have been improved and, interestingly, a significant number of new ice-sheet models have emerged. Among them, the parallel finite-element model Elmer/Ice (based on the open-source multi-physics code Elmer) was one of the first full-Stokes models used to make projections of the future of the whole Greenland ice sheet for the coming two centuries. Originally developed to solve dedicated local ice flow problems of high mechanical and physical complexity, Elmer/Ice has today reached the maturity to solve larger scale problems, earning the status of an ice-sheet model. In this presentation, we summarise the almost 10 years of development performed by different groups. We present the components already included in Elmer/Ice, its numerical performance, selected applications, as well as developments planed for the future.

Debris/ice/TPS assessment and photographic analysis for Shuttle Mission STS-33R

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

A debris/ice/Thermal Protection System (TPS) assessment and photographic analysis was conducted for Space Shuttle Mission STS-33R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the external tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and photographic analysis of Mission STS-33R, and their overall effect on the Space Shuttle Program.

Debris/ice/TPS assessment and photographic analysis for shuttle mission STS-31R

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1990-01-01

A Debris/Ice/Thermal Protection System (TPS) assessment and photographic analysis was conducted for Space Shuttle Mission STS-31R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the External Tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-31R, is presented along with their overall effect on the Space Shuttle Program.

Debris/ice/tps Assessment and Integrated Photographic Analysis of Shuttle Mission STS-81

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Lin, Jill D.

1997-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-81. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-81 and the resulting effect on the Space Shuttle Program.

Debris/ice/tps Assessment and Integrated Photographic Analysis of Shuttle Mission STS-83

NASA Technical Reports Server (NTRS)

Lin, Jill D.; Katnik, Gregory N.

1997-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-83. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-83 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle Mission STS-71

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1995-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-71. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanner data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-71 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-102

NASA Technical Reports Server (NTRS)

Rivera, Jorge E.; Kelly, J. David (Technical Monitor)

2001-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-102. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch were analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or inflight anomalies. This report documents the debris/ice /thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-102 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-94

NASA Technical Reports Server (NTRS)

Bowen, Barry C.; Lin, Jill D.

1997-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-94. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-94 and the resulting effect on the Space Shuttle Program.

Debris/ice/tps Assessment and Integrated Photographic Analysis of Shuttle Mission STS-79

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Lin, Jill D.

1996-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-79. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-79 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle mission STS-73

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Lin, Jill D.

1995-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-73. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanner data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle Mission STS-73 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Photographic Analysis for Shuttle Mission STS-38

NASA Technical Reports Server (NTRS)

Higginbotham, Scott A.; Davis, J. Bradley

1991-01-01

A debris/ice/TPS assessment and photographic analysis was conducted for the Space Shuttle Mission STS-38. Debris inspection of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-38, and their overall effect on the Space Shuttle Program are documented.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis for Shuttle Mission STS-49

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1992-01-01

A debris/ice/Thermal Protection System (TPS) assessment and integrated photographic analysis was conducted for Shuttle Mission STS-49. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. Debris/ice/TPS conditions and integrated photographic analysis of Shuttle Mission STS-49, and the resulting effect on the Space Shuttle Program are discussed.

Debris/ice/TPS assessment and photographic analysis of shuttle mission STS-48

NASA Technical Reports Server (NTRS)

Higginbotham, Scott A.; Davis, J. Bradley

1991-01-01

A Debris/Ice/TPS assessment and photographic analysis was conducted for Space Shuttle Mission STS-48. Debris inspection of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-48 are documented, along with their overall effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Photographic Analysis for Shuttle Mission STS-37

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1991-01-01

A Debris/Ice/TPS assessment and photographic analysis was conducted for Space Shuttle Mission STS-37. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or inflight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-37 are documented, along with their overall effect on the Space Shuttle Program.

Debris/Ice/TPS assessment and integrated photographic analysis of Shuttle Mission STS-77

NASA Technical Reports Server (NTRS)

Katnik, GregoryN.; Lin, Jill D. (Compiler)

1996-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-77. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-77 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle Mission STS-70

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1995-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-70. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanner data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-70 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle Mission STS-51

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1993-01-01

A debris/ice/thermal protection system (TPS) assessment and integrated photographic analysis was conducted for shuttle mission STS-51. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and integrated photographic analysis of Shuttle mission STS-51 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle Mission STS-55

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1993-01-01

A Debris/Ice/TPS assessment and integrated photographic analysis was conducted for Shuttle mission STS-55. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/Frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and integrated photographic analysis of Shuttle mission STS-55, and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and photographic analysis for Shuttle Mission STS-36

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1990-01-01

A Debris/Ice/TPS (Thermal Protection System) assessment and photographic analysis was conducted for Space Shuttle Mission STS-36. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the External Tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-36, and their overall effect on the Space Shuttle Program are documented.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle mission STS-69

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1995-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-69. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanner data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in flight anomalies. This report documents the ice/debris/thermal protection system condition and integrated photographic analysis of Shuttle Mission STS-69 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and photographic analysis for Shuttle Mission STS-42

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1992-01-01

A Debris/Ice/TPS (Thermal Protection System) assessment and photographic analysis was conducted for Shuttle Mission STS-42. Debris inspection of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flighr anomalies. The debris/ice/TPS conditions are documented along with photographic analysis of Mission STS-42, and their overall effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle Mission STS-52

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1992-01-01

A debris/ice/Thermal Protection System (TPS) assessment and integrated photographic analysis was conducted for Shuttle Mission STS-47. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and integrated photographic analysis of Shuttle Mission STS-52, and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-106

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Kelley, J. David (Technical Monitor)

2000-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-106. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-106 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and photographic analysis for Shuttle Mission STS-34

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

A Debris/Ice/Thermal Protection System (TPS) assessment and photographic analysis was conducted for Space Shuttle Mission STS-34. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/frost conditions on the External Tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-34, and their overall effect on the Space Shuttle Program are documented.

Debris/Ice/TPS Assessment and Photographic Analysis for Shuttle Mission STS-41

NASA Technical Reports Server (NTRS)

Higginbotham, Scott A.; Davis, J. Bradley

1990-01-01

A Debris/Ice/Thermal Protection System (TPS) assessment and photographic analysis was conducted for Space Shuttle Mission STS-41. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. Documented here are the debris/ice/TPS conditions and photographic analysis of Mission STS-41, and their overall effect on the Space Shuttle Program.

Debris/Ice/TPS assessment and integrated photographic analysis of shuttle mission STS-76

NASA Technical Reports Server (NTRS)

Lin, Jill D.

1996-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-76. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-76 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle Mission STS-53

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1993-01-01

A Debris/Ice/TPS assessment and integrated photographic analysis was conducted for Shuttle Mission STS-53. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/Frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and integrated photographic analysis of Shuttle Mission STS-53, and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle Mission STS-54

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1993-01-01

A Debris/Ice/TPS assessment and integrated photographic analysis was conducted for Shuttle Mission STS-54. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and integrated photographic analysis of Shuttle Mission STS-54, and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS assessment and integrated photographic analysis for Shuttle Mission STS-61

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1994-01-01

A debris/ice/thermal protection system (TPS) assessment and integrated photographic analysis was conducted for shuttle mission STS-61. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/TPS conditions and integrated photographic analysis of shuttle mission STS-61, and the resulting effect on the space shuttle program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-72

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Lin, Jill D.

1996-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-72. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-72 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle mission STS-58

NASA Technical Reports Server (NTRS)

Davis, J. Bradley; Rivera, Jorge E.; Katnik, Gregory N.; Bowen, Barry C.; Speece, Robert F.; Rosado, Pedro J.

1994-01-01

A debris/ice/thermal protection system (TPS) assessment and integrated photographic analysis was conducted for Shuttle mission STS-58. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The ice/debris/TPS conditions and integrated photographic analysis of Shuttle mission STS-58, and the resulting effect on the Space Shuttle Program are documented.

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle mission STS-47

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, J. Bradley

1992-01-01

A debris/ice/TPS assessment and integrated photographic analysis was conducted for Shuttle Mission STS-47. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/TPS conditions and integrated photographic analysis of Shuttle Mission STS-47, and the resulting effect on the Space Shuttle Program.

Cosmic ray spectrum and composition from three years of IceTop and IceCube

NASA Astrophysics Data System (ADS)

Rawlins, K.; IceCube Collaboration

2016-05-01

IceTop is the surface component of the IceCube Observatory, composed of frozen water tanks at the top of IceCube’s strings. Data from this detector can be analyzed in different ways with the goal of measuring cosmic ray spectrum and composition. The shower size S125 from IceTop alone can be used as a proxy for primary energy, and unfolded into an all-particle spectrum. In addition, S125 from the surface can be combined with high-energy muon energy loss information from the deep IceCube detector for those air showers which pass through both. Using these coincident events in a complementary analysis, both the spectrum and mass composition of primary cosmic rays can be extracted in parallel using a neural network. Both of these analyses have been performed on three years of IceTop and IceCube data. Both all-particle spectra as well as individual spectra for elemental groups are presented.

Numerical simulation of formation and preservation of Ningwu ice cave, Shanxi, China

NASA Astrophysics Data System (ADS)

Yang, S.; Shi, Y.

2015-10-01

Ice caves exist in locations where annual average air temperature is higher than 0 °C. An example is Ningwu ice cave, Shanxi Province, the largest ice cave in China. In order to quantitatively investigate the mechanism of formation and preservation of the ice cave, we use the finite-element method to simulate the heat transfer process at this ice cave. There are two major control factors. First, there is the seasonal asymmetric heat transfer. Heat is transferred into the ice cave from outside very inefficiently by conduction in spring, summer and fall. In winter, thermal convection occurs that transfers heat very efficiently out of the ice cave, thus cooling it down. Secondly, ice-water phase change provides a heat barrier for heat transfer into the cave in summer. The calculation also helps to evaluate effects of global warming, tourists, colored lights, climatic conditions, etc. for sustainable development of the ice cave as a tourism resource. In some other ice caves in China, managers have installed airtight doors at these ice caves' entrances with the intention of "protecting" these caves, but this in fact prevents cooling in winter and these cave ices will entirely melt within tens of years.

Numerical simulation of formation and preservation of Ningwu ice cave, Shanxi, China

NASA Astrophysics Data System (ADS)

Yang, S.; Shi, Y.

2015-04-01

Ice caves exist in locations where annual average temperature in higher than 0 °C. An example is Ningwu ice cave, Shanxi Province, the largest ice cave in China. In order to quantitatively explain the mechanism of formation and preservation of the ice cave, we use Finite Element Method to simulate the heat transfer process at this ice cave. There are two major control factors. First, there is the seasonal asymmetric heat transfer. Heat is transferred into the ice cave from outside, very inefficiently by conduction in spring, summer and fall. In winter, thermal convection occurs that transfers heat very efficiently out of the ice cave, thus cooling it down. Secondly, ice-water phase change provides a heat barrier for heat transfer into the cave in summer. The calculation also helps to evaluate effects of global warming, tourists, etc. for sustainable development of ice cave as tourism resource. In some other ice caves in China, managers installed air-tight doors at these ice caves entrance intending to "protect" these caves, but this prevent cooling down these caves in winters and these cave ices will entirely melt within tens of years.

Strain characterization of embedded aerospace smart materials using shearography

NASA Astrophysics Data System (ADS)

Anisimov, Andrei G.; Müller, Bernhard; Sinke, Jos; Groves, Roger M.

2015-04-01

The development of smart materials for embedding in aerospace composites provides enhanced functionality for future aircraft structures. Critical flight conditions like icing of the leading edges can affect the aircraft functionality and controllability. Hence, anti-icing and de-icing capabilities are used. In case of leading edges made of fibre metal laminates heater elements can be embedded between composite layers. However this local heating causes strains and stresses in the structure due to the different thermal expansion coefficients of the different laminated materials. In order to characterize the structural behaviour during thermal loading full-field strain and shape measurement can be used. In this research, a shearography instrument with three spatially-distributed shearing cameras is used to measure surface displacement gradients which give a quantitative estimation of the in- and out-of-plane surface strain components. For the experimental part, two GLARE (Glass Laminate Aluminum Reinforced Epoxy) specimens with six different embedded copper heater elements were manufactured: two copper mesh shapes (straight and S-shape), three connection techniques (soldered, spot welded and overlapped) and one straight heater element with delaminations. The surface strain behaviour of the specimens due to thermal loading was measured and analysed. The comparison of the connection techniques of heater element parts showed that the overlapped connection has the smallest effect on the surface strain distribution. Furthermore, the possibility of defect detection and defect depth characterisation close to the heater elements was also investigated.

Highly Conductive Carbon Fiber Reinforced Concrete for Icing Prevention and Curing.

PubMed

Galao, Oscar; Bañón, Luis; Baeza, Francisco Javier; Carmona, Jesús; Garcés, Pedro

2016-04-12

This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at -15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e. , -15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention) and deicing (curing), which could turn into an environmentally friendly and cost-effective deicing method.

InSAR Observations and Finite Element Modeling of Crustal Deformation Around a Surging Glacier, Iceland

NASA Astrophysics Data System (ADS)

Spaans, K.; Auriac, A.; Sigmundsson, F.; Hooper, A. J.; Bjornsson, H.; Pálsson, F.; Pinel, V.; Feigl, K. L.

2014-12-01

Icelandic ice caps, covering ~11% of the country, are known to be surging glaciers. Such process implies an important local crustal subsidence due to the large ice mass being transported to the ice edge during the surge in a few months only. In 1993-1995, a glacial surge occurred at four neighboring outlet glaciers in the southwestern part of Vatnajökull ice cap, the largest ice cap in Iceland. We estimated that ~16±1 km3 of ice have been moved during this event while the fronts of some of the outlet glaciers advanced by ~1 km.Surface deformation associated with this surge has been surveyed using Interferometric Synthetic Aperture Radar (InSAR) acquisitions from 1992-2002, providing high resolution ground observations of the study area. The data show about 75 mm subsidence at the ice edge of the outlet glaciers following the transport of the large volume of ice during the surge (Fig. 1). The long time span covered by the InSAR images enabled us to remove ~12 mm/yr of uplift occurring in this area due to glacial isostatic adjustment from the retreat of Vatnajökull ice cap since the end of the Little Ice Age in Iceland. We then used finite element modeling to investigate the elastic Earth response to the surge, as well as confirm that no significant viscoelastic deformation occurred as a consequence of the surge. A statistical approach based on Bayes' rule was used to compare the models to the observations and obtain an estimate of the Young's modulus (E) and Poisson's ratio (v) in Iceland. The best-fitting models are those using a one-kilometer thick top layer with v=0.17 and E between 12.9-15.3 GPa underlain by a layer with v=0.25 and E from 67.3 to 81.9 GPa. Results demonstrate that InSAR data and finite element models can be used successfully to reproduce crustal deformation induced by ice mass variations at Icelandic ice caps.Fig. 1: Interferograms spanning 1993 July 31 to 1995 June 19, showing the surge at Tungnaárjökull (Tu.), Skaftárjökull (Sk.) and Síðujökull (Sí.) outlet glaciers. The black and grey arrows show the azimuth of the satellite and the look direction, respectively. (a) Wrapped interferogram showing the surge deformation (2π = 28.3 mm deformation). (b) Unwrapped interferogram with the black star as the reference area and negative values indicating line of sight lengthening (Auriac et al., 2014, doi:10.1093/gji/ggu205).

Ice & Exercise for Injury Management.

ERIC Educational Resources Information Center

Suspenski, Thomas J.

Utilization of ice and exercise conjunctively decreases recovery time of muscle tendon injury considerably. In the healing process, collagen (a major element of scar formation) is laid down. If heat and rest are used as treatment, healing takes place; however, collagen is laid down in a haphazard arrangement increasing the likelihood of reinjury.…

New insights into trace element wet deposition in the Himalayas: amounts, seasonal patterns, and implications.

PubMed

Cong, Zhiyuan; Kang, Shichang; Zhang, Yulan; Gao, Shaopeng; Wang, Zhongyan; Liu, Bin; Wan, Xin

2015-02-01

Our research provides the first complete year-long dataset of wet deposition of trace elements in the high Himalayas based on a total of 42 wet deposition events on the northern slope of Mt. Qomolangma (Everest). Except for typical crustal elements (Al, Fe, and Mn), the concentration level of most trace elements (Sc, V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Sn, Cs, Pb, Bi, and U) are generally comparable to those preserved in snow pits and ice cores from the nearby East Rongbuk Glacier. Cadmium was the element most affected by anthropogenic emissions. No pronounced seasonal variations are observed for most trace elements despite different transport pathways. In our study, the composition of wet precipitation reflects a regional background condition and is not clearly related to specific source regions. For the trace element record from ice cores and snow pits in the Himalayas, it could be deduced that the pronounced seasonal patterns were caused by the dry deposition of trace elements (aerosols) during their long exposure to the atmosphere after precipitation events. Our findings are of value for the understanding of the trace element deposition mechanisms in the Himalayas.

The clc Element of Pseudomonas sp. Strain B13, a Genomic Island with Various Catabolic Properties

PubMed Central

Gaillard, Muriel; Vallaeys, Tatiana; Vorhölter, Frank Jörg; Minoia, Marco; Werlen, Christoph; Sentchilo, Vladimir; Pühler, Alfred; van der Meer, Jan Roelof

2006-01-01

Pseudomonas sp. strain B13 is a bacterium known to degrade chloroaromatic compounds. The properties to use 3- and 4-chlorocatechol are determined by a self-transferable DNA element, the clc element, which normally resides at two locations in the cell's chromosome. Here we report the complete nucleotide sequence of the clc element, demonstrating the unique catabolic properties while showing its relatedness to genomic islands and integrative and conjugative elements rather than to other known catabolic plasmids. As far as catabolic functions, the clc element harbored, in addition to the genes for chlorocatechol degradation, a complete functional operon for 2-aminophenol degradation and genes for a putative aromatic compound transport protein and for a multicomponent aromatic ring dioxygenase similar to anthranilate hydroxylase. The genes for catabolic functions were inducible under various conditions, suggesting a network of catabolic pathway induction. For about half of the open reading frames (ORFs) on the clc element, no clear functional prediction could be given, although some indications were found for functions that were similar to plasmid conjugation. The region in which these ORFs were situated displayed a high overall conservation of nucleotide sequence and gene order to genomic regions in other recently completed bacterial genomes or to other genomic islands. Most notably, except for two discrete regions, the clc element was almost 100% identical over the whole length to a chromosomal region in Burkholderia xenovorans LB400. This indicates the dynamic evolution of this type of element and the continued transition between elements with a more pathogenic character and those with catabolic properties. PMID:16484212

The 2.5 Å Structure of the Enterococcus Conjugation Protein TraM resembles VirB8 Type IV Secretion Proteins*

PubMed Central

Goessweiner-Mohr, Nikolaus; Grumet, Lukas; Arends, Karsten; Pavkov-Keller, Tea; Gruber, Christian C.; Gruber, Karl; Birner-Gruenberger, Ruth; Kropec-Huebner, Andrea; Huebner, Johannes; Grohmann, Elisabeth; Keller, Walter

2013-01-01

Conjugative plasmid transfer is the most important means of spreading antibiotic resistance and virulence genes among bacteria and therefore presents a serious threat to human health. The process requires direct cell-cell contact made possible by a multiprotein complex that spans cellular membranes and serves as a channel for macromolecular secretion. Thus far, well studied conjugative type IV secretion systems (T4SS) are of Gram-negative (G−) origin. Although many medically relevant pathogens (e.g., enterococci, staphylococci, and streptococci) are Gram-positive (G+), their conjugation systems have received little attention. This study provides structural information for the transfer protein TraM of the G+ broad host range Enterococcus conjugative plasmid pIP501. Immunolocalization demonstrated that the protein localizes to the cell wall. We then used opsonophagocytosis as a novel tool to verify that TraM was exposed on the cell surface. In these assays, antibodies generated to TraM recruited macrophages and enabled killing of pIP501 harboring Enteroccocus faecalis cells. The crystal structure of the C-terminal, surface-exposed domain of TraM was determined to 2.5 Å resolution. The structure, molecular dynamics, and cross-linking studies indicated that a TraM trimer acts as the biological unit. Despite the absence of sequence-based similarity, TraM unexpectedly displayed a fold similar to the T4SS VirB8 proteins from Agrobacterium tumefaciens and Brucella suis (G−) and to the transfer protein TcpC from Clostridium perfringens plasmid pCW3 (G+). Based on the alignments of secondary structure elements of VirB8-like proteins from mobile genetic elements and chromosomally encoded T4SS from G+ and G− bacteria, we propose a new classification scheme of VirB8-like proteins. PMID:23188825

Map of Martian Polar Hydrogen

NASA Image and Video Library

2003-03-13

This gamma ray spectrometer map centered on the north pole of Mars is based on gamma-rays from the element hydrogen. In this region, hydrogen is mainly in the form of water ice. Regions of high ice content are shown in red and those low in ice content are shown in blue. The very ice-rich region at the north pole is due to a permanent polar cap of water ice on the surface. Elsewhere in this region, the ice is buried under several to a few tens of centimeters of dry soil. The sub-surface ice is not uniformly distributed in the north, but varies with both latitude and longitude. In the north, the soil is well over 50 percent ice, which is more than can be accommodated by just filling the pore space in pre-existing soil. This high ice content implies that the ice may have been slowly co-deposited with dust in the past when conditions were wetter. Deposition of ice by this process means it is more likely that the ice deposits are very thick and may even be deep enough to have liquid water at their base. http://photojournal.jpl.nasa.gov/catalog/PIA04254

Modeling CO, CO2, and H2O Ice Abundances in the Envelopes of Young Stellar Objects in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Pauly, Tyler; Garrod, Robin T.

2018-02-01

Massive young stellar objects (MYSOs) in the Magellanic Clouds show infrared absorption features corresponding to significant abundances of CO, CO2, and H2O ice along the line of sight, with the relative abundances of these ices differing between the Magellanic Clouds and the Milky Way. CO ice is not detected toward sources in the Small Magellanic Cloud, and upper limits put its relative abundance well below sources in the Large Magellanic Cloud and the Milky Way. We use our gas-grain chemical code MAGICKAL, with multiple grain sizes and grain temperatures, and further expand it with a treatment for increased interstellar radiation field intensity to model the elevated dust temperatures observed in the MCs. We also adjust the elemental abundances used in the chemical models, guided by observations of H II regions in these metal-poor satellite galaxies. With a grid of models, we are able to reproduce the relative ice fractions observed in MC MYSOs, indicating that metal depletion and elevated grain temperature are important drivers of the MYSO envelope ice composition. Magellanic Cloud elemental abundances have a subgalactic C/O ratio, increasing H2O ice abundances relative to the other ices; elevated grain temperatures favor CO2 production over H2O and CO. The observed shortfall in CO in the Small Magellanic Cloud can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH3OH abundance is found to be enhanced in low-metallicity models, providing seed material for complex organic molecule formation in the Magellanic Clouds.

Modeling dynamics of large tabular icebergs submerged in the ocean

NASA Astrophysics Data System (ADS)

Adcroft, A.; Stern, A. A.; Sergienko, O. V.

2017-12-01

Large tabular icebergs account for a major fraction of the ice calved from the Antarctic ice shelves, and have long lifetimes due to their size. They drift for long distances, interacting with the local ocean circulation, impacting bottom-water formation, sea-ice formation, and biological productivity in the vicinity of the icebergs. However, due to their large horizontal extent and mass, it is challenging to consistently represent large tabular icebergs in global ocean circulation models and so large tabular icebergs are not currently represented in climate models. In this study we develop a novel framework to model large tabular icebergs submerged in the ocean. In this framework, a tabular iceberg is represented by a collection of Lagrangian elements that are linked through rigid bonds. The Lagrangian elements are finite-area modifications of the point-particles used in previous studies to represent small icebergs. These elements interact with the ocean by exerting pressure on the ocean surface, and through melt water and momentum exchange. A breaking of the rigid bonds allows the model to emulate calving events (i.e. detachment of a tabular iceberg from an ice shelf), and to emulate the breaking up of tabular icebergs into smaller pieces. Idealized simulations of the calving of a tabular iceberg, subsequent drift and breakup, demonstrate the capabilities of the new framework with a promise that climate models may soon be able to represent large tabular icebergs.

Design, fabrication, and testing of an ultrasonic de-icing system for helicopter rotor blades

NASA Astrophysics Data System (ADS)

Palacios, Jose Luis

A low-power, non-thermal ultrasonic de-icing system is introduced as a possible substitute for current electro-thermal systems. The system generates delaminating ultrasonic transverse shear stresses at the interface of accreted ice. A PZT-4 disk driven at 28.5 KHz (radial resonance of the disk) instantaneously de-bonds 2 mm thick freezer ice layers. The ice layers are accreted to a 0.7 mm thick, 30.4 cm x 30.4 cm steel plate at an environment temperature of -20°C. A power input of 50 Watts is applied to the actuator (50 V, 19.6 KV/m), which translates to a de-icing power of 0.07 W/cm2. A finite element model of the actuator bonded to the isotropic plate is used to guide the design of the system, and predicts the transverse shear stresses at the ice interface. Wind tunnel icing tests were conducted to demonstrate the potential use of the proposed system under impact icing conditions. Both glaze ice and rime ice were generated on steel and composite plates by changing the cloud conditions of the wind tunnel. Continuous ultrasonic vibration prevented impact ice formation around the actuator location at an input power not exceeding 0.18 W/cm 2 (1.2 W/in2). As ice thickness reached a critical thickness of approximately 1.2 mm, shedding occurred on those locations where ultrasonic transverse shear stresses exceeded the shear adhesion strength of the ice. Finite element transverse shear stress predictions correlate with observed experimental impact ice de-bonding behavior. To increase the traveling distance of propagating ultrasonic waves, ultrasonic shear horizontal wave modes are studied. Wave modes providing large modal interface transverse shear stress concentration coefficients (ISCC) between the host structure (0.7 mm thick steel plate) and accreted ice (2.5 mm thick ice layer) are identified and investigated for a potential increase in the wave propagation distance. Ultrasonic actuators able to trigger these optimum wave modes are designed and fabricated. Despite exciting wave modes with high ISCC values, instantaneous ice de-bonding is not observed at input powers under 100 Watts. The two triggered ultrasonic wave modes of the structure occur at high excitation frequencies, 202 KHz and 500 KHz respectively. At these frequencies, the ultrasonic actuators do not provide large enough transverse shear stresses to exceed the shear adhesion strength of the ice layer. Neither the actuator exciting the SH1 mode (202 KHz), nor the actuator triggering the SH2 mode (500 KHz) instantaneously de-bonds ice layers with an input power under 100 Watts.

Debris/ice/TPS assessment and photographic analysis for shuttle mission STS-35

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Higginbotham, Scott A.; Davis, James Bradley

1991-01-01

A debris/ice/Thermal Protection System (TPS) assessment and photographic analysis was conducted for Space Shuttle Mission STS-35. Debris inspections of the flight elements and launch pad were performed before and after the launch. Ice/frost conditions on the External Tank were assessed by the use of computer programs, monographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. Documented here are the debris/ice/TPS conditions and photographic analysis of Mission STS-35, and the overall effect of these conditions on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-103

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

2000-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-103. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-103 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-91

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1998-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-91. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-91 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-93

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1999-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-93. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis findings of Space Shuttle mission STS-93 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-95

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1999-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-95. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-95 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-90

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1998-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-90. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system-conditions and integrated photographic analysis of Space Shuttle mission STS-90 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-80

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Lin, Jill D.

1997-01-01

A debris/ice/thermal protection system (TPS) assessment and integrated photographic analysis was conducted for Shuttle mission STS-80. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission Space Transportation System (STS-80) and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-89

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1998-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-89. Debris inspections of the flight element and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection systems conditions and integrated photographic analysis of Space Shuttle mission STS-89 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-112

NASA Technical Reports Server (NTRS)

Oliu, Armando

2002-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-112. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The report documents the debris/ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-112 and the resulting effect of the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-74

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Lin, Jill D.

1996-01-01

A debris/ice/thermal protection system (TPS) assessment and integrated photographic analysis was conducted for shuttle mission STS-74. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanner data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of shuttle mission STS-74 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-87

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1998-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-87. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the-use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-87 and the resulting effect on the Space Shuttle Program.

Debris/ice/tps Assessment and Integrated Photographic Analysis of Shuttle Mission STS-96

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1999-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-96. Debris inspections of the flight elements and launch pad were performed before and after launch. icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-96 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-101

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

2000-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle Mission STS-101. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-101 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-88

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

1999-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-88. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-88 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and photographic analysis for Shuttle Mission STS-28R

NASA Technical Reports Server (NTRS)

Stevenson, Charles G.; Katnik, Gregory N.; Higginbotham, Scott A.

1989-01-01

A Debris/Ice/TPS assessment and photographic analysis was conducted for Space Shuttle Mission STS-28R. Debris inspections of the flight elements and launch pad are performed before and after launch. Ice/Frost conditions on the External Tank are assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography is analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and photographic analysis of Mission STS-28R is documented along with their overall effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle Mission STS-64 on 9 August 1994

NASA Technical Reports Server (NTRS)

Davis, J. Bradley; Bowen, Barry C.; Rivera, Jorge E.; Speece, Robert F.; Katnik, Gregory N.

1994-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-64. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-64, and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle mission STS-68

NASA Technical Reports Server (NTRS)

Rivera, Jorge E.; Bowen, Barry C.; Davis, J. Bradley; Speece, Robert F.

1994-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-68. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report-documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-68, and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-111

NASA Technical Reports Server (NTRS)

Oliu, Armando

2005-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-111. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The report documents the debris/ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-111 and the resulting effect of the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-99

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

2000-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-99. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-99 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-98

NASA Technical Reports Server (NTRS)

Speece, Robert F.

2004-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle Mission STS-98. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-98 and the resulting effect on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of shuttle mission STS-63

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1995-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for shuttle mission STS-63. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the external tank were assessed by the use of computer programs, monographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of shuttle mission STS-63, and the resulting effect on the space shuttle program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle mission STS-66

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1995-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-66. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer program nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Shuttle mission STS-66, and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-97

NASA Technical Reports Server (NTRS)

Rivera, Jorge E.; Kelly, J. David (Technical Monitor)

2001-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-97. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch were analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris /ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-97 and the resulting effect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-86

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Lin, Jill D.

1997-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-86. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-86 and the resulting affect on the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-100

NASA Technical Reports Server (NTRS)

Oliu, Armando

2004-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-100. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The report documents the debris/ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-100 and the resulting effect of the Space Shuttle Program.

Debris/Ice/TPS Assessment and Integrated Photographic Analysis of Shuttle Mission STS-92

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.

2000-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for Shuttle mission STS-92. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the External Tank were assessed by the use of computer programs and infrared scanned data during cryogenic loading of the vehicle, followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the debris/ice/thermal protection system conditions and integrated photographic analysis of Space Shuttle mission STS-92 and the resulting effect, if any, on the Space Shuttle Program.

Debris/ice/TPS assessment and integrated photographic analysis of Shuttle Mission STS-65

NASA Technical Reports Server (NTRS)

Katnik, Gregory N.; Bowen, Barry C.; Davis, J. Bradley

1994-01-01

A debris/ice/thermal protection system assessment and integrated photographic analysis was conducted for shuttle mission STS-65. Debris inspections of the flight elements and launch pad were performed before and after launch. Icing conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography of the launch was analyzed to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. This report documents the ice/debris/thermal protection system conditions and integrated photographic analysis of shuttle mission STS-65, and the resulting effect on the Space Shuttle Program.

The Little Ice Age and Solar Activity

NASA Astrophysics Data System (ADS)

Velasco Herrera, Victor Manuel; Leal Silva, C. M. Carmen; Velasco Herrera, Graciela

We analyze the ice winter severity index on the Baltic region since 1501-1995. We found that the variability of this index is modulated among other factors by the secular solar activity. The little ice ages that have appeared in the North Hemisphere occurred during periods of low solar activity. Seemingly our star is experiencing a new quiet stage compared with Maunder or Dalton minimum, this is important because it is estimated that even small changes in weather can represent a great impact in ice index. These results are relevant since ice is a very important element in the climate system of the Baltic region and it can affect directly or indirectly many of the oceanographic, climatic, eco-logical, economical and cultural patterns.

Evaluating the Discrete Element Method as a Tool for Predicting the Seasonal Evolution of the MIZ

DTIC Science & Technology

2015-09-30

wave-ice interaction (Hopkins & Shen 2001), and the mesoscale evolution of the floe size distribution (Hopkins & Thorndike 2006). This modeling effort...33(1), 355-360. Hopkins, M. A., & Thorndike , A. S. (2006) Floe formation in Arctic sea ice. Journal of Geophysical Research: Oceans (1978–2012), 111

Physical Mechanisms of Glaze Ice Scallop Formations on Swept Wings

NASA Technical Reports Server (NTRS)

Vargas, Mario; Reshotko, Eli

1998-01-01

An experiment was conducted to understand the physical mechanisms that lead to the formation of scallops on swept wings. Icing runs were performed on a NACA 0012 swept wing tip at 45 deg, 30 deg, and 15 deg sweep angles. A baseline case was chosen and direct measurements of scallop height and spacing, castings, video data and close-up photographic data were obtained. The results showed the scallops are made of glaze ice feathers that grow from roughness elements that have reached a minimum height and are located beyond a given distance from the attachment line. This distance depends on tunnel conditions and sweep angle, and is the critical parameter in the formation of scallops. It determines if complete scallops, incomplete scallops or no scallops are going to be formed. The mechanisms of growth for complete and incomplete scallops were identified. The effect of velocity, temperature and LWC on scallop formation was studied. The possibility that cross flow instability may be the physical mechanism that triggers the growth of roughness elements into glaze ice feathers is examined.

ICEG2D: An Integrated Software Package for Automated Prediction of Flow Fields for Single-Element Airfoils with Ice Accretion

NASA Technical Reports Server (NTRS)

Thompson, David S.; Soni, Bharat K.

2000-01-01

An integrated software package, ICEG2D, was developed to automate computational fluid dynamics (CFD) simulations for single-element airfoils with ice accretion. ICEG2D is designed to automatically perform three primary functions: (1) generating a grid-ready, surface definition based on the geometrical characteristics of the iced airfoil surface, (2) generating a high-quality grid using the generated surface point distribution, and (3) generating the input and restart files needed to run the general purpose CFD solver NPARC. ICEG2D can be executed in batch mode using a script file or in an interactive mode by entering directives from a command line. This report summarizes activities completed in the first year of a three-year research and development program to address issues related to CFD simulations for aircraft components with ice accretion. Specifically, this document describes the technology employed in the software, the installation procedure, and a description of the operation of the software package. Validation of the geometry and grid generation modules of ICEG2D is also discussed.

Thallium as a tracer for preindustrial volcanic eruptions in an ice core record from Illimani, Bolivia.

PubMed

Kellerhals, Thomas; Tobler, Leonhard; Brütsch, Sabina; Sigl, Michael; Wacker, Lukas; Gäggeler, Heinz W; Schwikowski, Margit

2010-02-01

Trace element records from glacier and ice sheet archives provide insights into biogeochemical cycles, atmospheric circulation changes, and anthropogenic pollution history. We present the first continuous high-resolution thallium (Tl) record, derived from an accurately dated ice core from tropical South America, and discuss Tl as a tracer for volcanic eruptions. We identify four prominent Tl peaks and propose that they represent signals from the massive explosive eruptions of the "unknown 1258" A.D. volcano, of Kuwae ( approximately 1450 A.D.), Tambora (1815 A.D.), and Krakatoa (1883 A.D.). The highly resolved record was obtained with an improved setup for the continuous analysis of trace elements in ice with inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The new setup allowed for a stronger initial acidification of the meltwater and shorter tubing length, thereby reducing the risk of memory effects and losses of analytes to the capillary walls. With a comparison of the continuous method to the established conventional decontamination and analysis procedure for discrete samples, we demonstrate the accuracy of the continuous method for Tl analyses.

The RepA_N replicons of Gram-positive bacteria: a family of broadly distributed but narrow host range plasmids.

PubMed

Weaver, Keith E; Kwong, Stephen M; Firth, Neville; Francia, Maria Victoria

2009-03-01

The pheromone-responsive conjugative plasmids of Enterococcus faecalis and the multiresistance plasmids pSK1 and pSK41 of Staphylococcus aureus are among the best studied plasmids native to Gram-positive bacteria. Although these plasmids seem largely restricted to their native hosts, protein sequence comparison of their replication initiator proteins indicates that they are clearly related. Homology searches indicate that these replicons are representatives of a large family of plasmids and a few phage that are widespread among the low G+C Gram-positive bacteria. We propose to name this family the RepA_N family of replicons after the annotated conserved domain that the initiator protein contains. Detailed sequence comparisons indicate that the initiator protein phylogeny is largely congruent with that of the host, suggesting that the replicons have evolved along with their current hosts and that intergeneric transfer has been rare. However, related proteins were identified on chromosomal regions bearing characteristics indicative of ICE elements, and the phylogeny of these proteins displayed evidence of more frequent intergeneric transfer. Comparison of stability determinants associated with the RepA_N replicons suggests that they have a modular evolution as has been observed in other plasmid families.

The RepA_N replicons of Gram-positive bacteria: a family of broadly distributed but narrow host range plasmids

PubMed Central

Weaver, Keith E.; Kwong, Stephen M.; Firth, Neville; Francia, Maria Victoria

2009-01-01

The pheromone-responsive conjugative plasmids of Enterococcus faecalis and the multi-resistance plasmids pSK1 and pSK41 of Staphylococcus aureus are among the best studied plasmids native to Gram-positive bacteria. Although these plasmids seem largely restricted to their native hosts, protein sequence comparison of their replication initiator proteins indicates that they are clearly related. Homology searches indicate that these replicons are representatives of a large family of plasmids and a few phage that are widespread among the low G+C Gram-positive bacteria. We propose to name this family the RepA_N family of replicons after the annotated conserved domain that the initiator protein contains. Detailed sequence comparisons indicate that the initiator protein phylogeny is largely congruent with that of the host, suggesting that the replicons have evolved along with their current hosts and that intergeneric transfer has been rare. However, related proteins were identified on chromosomal regions bearing characteristics indicative of ICE elements, and the phylogeny of these proteins displayed evidence of more frequent intergeneric transfer. Comparison of stability determinants associated with the RepA_N replicons suggests that they have a modular evolution as has been observed in other plasmid families. PMID:19100285

A Contaminant Ice Visualization Experiment in a Glass Pulse Tube

NASA Technical Reports Server (NTRS)

Hall, J. L.; Ross, R. G., Jr.; Le, A. K.

2000-01-01

Results are presented from pulse tube experiments designed to investigate the effect of 400 parts per million water vapor contamination of the helium working gas. The experiments were conducted in a glass pulse tube to enable visualization of ice formation on internal surfaces. Photographs of this ice formation were taken along with simultaneous coldtip temperature and compressor power measurements. Four types of regenerator elements were tested in various combinations: 200- and 400-mesh stainless steel screens, 1.6 mm diameter glass beads, and 1.6 mm thick perforated plastic plates. Internal spacers were also used to provide clear fields of view into the regenerator stack. Substantial water-ice formation was observed at the cold end of the regenerator and on the inside wall of pulse tube; it appeared to be highly porous, like snow, and was seen to accumulate only in a very localized region at the coldest end, despite changing the cold tip temperature across a range of 150 to 235 K. Ice formation degraded pulse tube thermal performance only in cases where screen regenerators were used at the regenerator cold end. It was concluded that flow blockage was the mechanism by which contaminants affected performance; coarse regenerator elements were largely immune over the tested time scale of a few days. Substantially reduced ice formation and minimal performance loss were also observed in repeated tests where the contaminated gas was reused after warming up and melting of the accumulated internal ice. Significant adsorption of the liquid water onto the regenerator was inferred, a process that depleted the gas phase concentration of water.

Discrete-Element bonded-particle Sea Ice model DESIgn, version 1.3a - model description and implementation

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2016-04-01

This paper presents theoretical foundations, numerical implementation and examples of application of the two-dimensional Discrete-Element bonded-particle Sea Ice model - DESIgn. In the model, sea ice is represented as an assemblage of objects of two types: disk-shaped "grains" and semi-elastic bonds connecting them. Grains move on the sea surface under the influence of forces from the atmosphere and the ocean, as well as interactions with surrounding grains through direct contact (Hertzian contact mechanics) and/or through bonds. The model has an experimental option of taking into account quasi-three-dimensional effects related to the space- and time-varying curvature of the sea surface, thus enabling simulation of ice breaking due to stresses resulting from bending moments associated with surface waves. Examples of the model's application to simple sea ice deformation and breaking problems are presented, with an analysis of the influence of the basic model parameters ("microscopic" properties of grains and bonds) on the large-scale response of the modeled material. The model is written as a toolbox suitable for usage with the open-source numerical library LIGGGHTS. The code, together with full technical documentation and example input files, is freely available with this paper and on the Internet.

Multiplexed protein detection using antibody-conjugated microbead arrays in a microfabricated electrophoretic device

PubMed Central

Barbee, Kristopher D.; Hsiao, Alexander P.; Roller, Eric E.; Huang, Xiaohua

2011-01-01

We report the development of a microfabricated electrophoretic device for assembling high-density arrays of antibody-conjugated microbeads for chip-based protein detection. The device consists of a flow cell formed between a gold-coated silicon chip with an array of microwells etched in a silicon dioxide film and a glass coverslip with a series of thin gold counter electrode lines. We have demonstrated that 0.4 and 1 μm beads conjugated with antibodies can be rapidly assembled into the microwells by applying a pulsed electric field across the chamber. By assembling step-wise a mixture of fluorescently labeled antibody-conjugated microbeads, we incorporated both spatial and fluorescence encoding strategies to demonstrate significant multiplexing capabilities. We have shown that these antibody-conjugated microbead arrays can be used to perform on-chip sandwich immunoassays to detect test antigens at concentrations as low as 40 pM (6 ng/mL). A finite element model was also developed to examine the electric field distribution within the device for different counter electrode configurations over a range of line pitches and chamber heights. This device will be useful for assembling high-density, encoded antibody arrays for multiplexed detection of proteins and other types of protein-conjugated microbeads for applications such as the analysis of protein-protein interactions. PMID:20820631

Ice Roughness in Short Duration SLD Icing Events

NASA Technical Reports Server (NTRS)

McClain, Stephen T.; Reed, Dana; Vargas, Mario; Kreeger, Richard E.; Tsao, Jen-Ching

2014-01-01

Ice accretion codes depend on models of roughness parameters to account for the enhanced heat transfer during the ice accretion process. While mitigating supercooled large droplet (SLD or Appendix O) icing is a significant concern for manufacturers seeking future vehicle certification due to the pending regulation, historical ice roughness studies have been performed using Appendix C icing clouds which exhibit mean volumetric diameters (MVD) much smaller than SLD clouds. Further, the historical studies of roughness focused on extracting parametric representations of ice roughness using multiple images of roughness elements. In this study, the ice roughness developed on a 21-in. NACA 0012 at 0deg angle of attack exposed to short duration SLD icing events was measured in the Icing Research Tunnel at the NASA Glenn Research Center. The MVD's used in the study ranged from 100 micrometer to 200 micrometers, in a 67 m/s flow, with liquid water contents of either 0.6 gm/cubic meters or 0.75 gm/cubic meters. The ice surfaces were measured using a Romer Absolute Arm laser scanning system. The roughness associated with each surface point cloud was measured using the two-dimensional self-organizing map approach developed by McClain and Kreeger (2013) resulting in statistical descriptions of the ice roughness.

Texture analysis of radiometric signatures of new sea ice forming in Arctic leads

NASA Technical Reports Server (NTRS)

Eppler, Duane T.; Farmer, L. Dennis

1991-01-01

Analysis of 33.6-GHz, high-resolution, passive microwave images suggests that new sea ice accumulating in open leads is characterized by a unique textural signature which can be used to discriminate new ice forming in this environment from adjacent surfaces of similar radiometric temperature. Ten training areas were selected from the data set, three of which consisted entirely of first-year ice, four entirely of multilayer ice, and three of new ice in open leads in the process of freezing. A simple gradient operator was used to characterize the radiometric texture in each training region in terms of the degree to which radiometric gradients are oriented. New ice in leads has a sufficiently high proportion of well-oriented features to distinguish it uniquely from first-year ice and multiyear ice. The predominance of well-oriented features probably reflects physical processes by which new ice accumulates in open leads. Banded structures, which are evident in aerial photographs of new ice, apparently give rise to the radiometric signature observed, in which the trend of brightness temperature gradients is aligned parallel to lead trends. First-year ice and multiyear ice, which have been subjected to a more random growth and process history, lack this banded structure and therefore are characterized by signatures in which well-aligned elements are less dominant.

Implications of Contingency Planning Support for Weather and Icing Information

NASA Technical Reports Server (NTRS)

Vigeant-Langlois, Laurence; Hansman, R. John, Jr.

2003-01-01

A human-centered systems analysis was applied to the adverse aircraft weather encounter problem in order to identify desirable functions of weather and icing information. The importance of contingency planning was identified as emerging from a system safety design methodology as well as from results of other aviation decision-making studies. The relationship between contingency planning support and information on regions clear of adverse weather was investigated in a scenario- based analysis. A rapid prototype example of the key elements in the depiction of icing conditions was developed in a case study, and the implications for the components of the icing information system were articulated.

Iterative and multigrid methods in the finite element solution of incompressible and turbulent fluid flow

NASA Astrophysics Data System (ADS)

Lavery, N.; Taylor, C.

1999-07-01

Multigrid and iterative methods are used to reduce the solution time of the matrix equations which arise from the finite element (FE) discretisation of the time-independent equations of motion of the incompressible fluid in turbulent motion. Incompressible flow is solved by using the method of reduce interpolation for the pressure to satisfy the Brezzi-Babuska condition. The k-l model is used to complete the turbulence closure problem. The non-symmetric iterative matrix methods examined are the methods of least squares conjugate gradient (LSCG), biconjugate gradient (BCG), conjugate gradient squared (CGS), and the biconjugate gradient squared stabilised (BCGSTAB). The multigrid algorithm applied is based on the FAS algorithm of Brandt, and uses two and three levels of grids with a V-cycling schedule. These methods are all compared to the non-symmetric frontal solver. Copyright

A Multi-Variate Fit to the Chemical Composition of the Cosmic-Ray Spectrum

NASA Astrophysics Data System (ADS)

Eisch, Jonathan

Since the discovery of cosmic rays over a century ago, evidence of their origins has remained elusive. Deflected by galactic magnetic fields, the only direct evidence of their origin and propagation remain encoded in their energy distribution and chemical composition. Current models of galactic cosmic rays predict variations of the energy distribution of individual elements in an energy region around 3x1015 eV known as the knee. This work presents a method to measure the energy distribution of individual elemental groups in the knee region and its application to a year of data from the IceCube detector. The method uses cosmic rays detected by both IceTop, the surface-array component, and the deep-ice component of IceCube during the 2009-2010 operation of the IC-59 detector. IceTop is used to measure the energy and the relative likelihood of the mass composition using the signal from the cosmic-ray induced extensive air shower reaching the surface. IceCube, 1.5 km below the surface, measures the energy of the high-energy bundle of muons created in the very first interactions after the cosmic ray enters the atmosphere. These event distributions are fit by a constrained model derived from detailed simulations of cosmic rays representing five chemical elements. The results of this analysis are evaluated in terms of the theoretical uncertainties in cosmic-ray interactions and seasonal variations in the atmosphere. The improvements in high-energy cosmic ray hadronic-interaction models informed by this analysis, combined with increased data from subsequent operation of the IceCube detector, could provide crucial limits on the origin of cosmic rays and their propagation through the galaxy. In the course of developing this method, a number of analysis and statistical techniques were developed to deal with the difficulties inherent in this type of measurement. These include a composition-sensitive air shower reconstruction technique, a method to model simulated event distributions with limited statistics, and a method to optimize and estimate the error on a regularized fit.

CUDA GPU based full-Stokes finite difference modelling of glaciers

NASA Astrophysics Data System (ADS)

Brædstrup, C. F.; Egholm, D. L.

2012-04-01

Many have stressed the limitations of using the shallow shelf and shallow ice approximations when modelling ice streams or surging glaciers. Using a full-stokes approach requires either large amounts of computer power or time and is therefore seldom an option for most glaciologists. Recent advances in graphics card (GPU) technology for high performance computing have proven extremely efficient in accelerating many large scale scientific computations. The general purpose GPU (GPGPU) technology is cheap, has a low power consumption and fits into a normal desktop computer. It could therefore provide a powerful tool for many glaciologists. Our full-stokes ice sheet model implements a Red-Black Gauss-Seidel iterative linear solver to solve the full stokes equations. This technique has proven very effective when applied to the stokes equation in geodynamics problems, and should therefore also preform well in glaciological flow probems. The Gauss-Seidel iterator is known to be robust but several other linear solvers have a much faster convergence. To aid convergence, the solver uses a multigrid approach where values are interpolated and extrapolated between different grid resolutions to minimize the short wavelength errors efficiently. This reduces the iteration count by several orders of magnitude. The run-time is further reduced by using the GPGPU technology where each card has up to 448 cores. Researchers utilizing the GPGPU technique in other areas have reported between 2 - 11 times speedup compared to multicore CPU implementations on similar problems. The goal of these initial investigations into the possible usage of GPGPU technology in glacial modelling is to apply the enhanced resolution of a full-stokes solver to ice streams and surging glaciers. This is a area of growing interest because ice streams are the main drainage conjugates for large ice sheets. It is therefore crucial to understand this streaming behavior and it's impact up-ice.

Modeling tabular icebergs submerged in the ocean

NASA Astrophysics Data System (ADS)

Stern, A. A.; Adcroft, A.; Sergienko, O.; Marques, G.

2017-08-01

Large tabular icebergs calved from Antarctic ice shelves have long lifetimes (due to their large size), during which they drift across large distances, altering ambient ocean circulation, bottom-water formation, sea-ice formation, and biological primary productivity in the icebergs' vicinity. However, despite their importance, the current generation of ocean circulation models usually do not represent large tabular icebergs. In this study, we develop a novel framework to model large tabular icebergs submerged in the ocean. In this framework, tabular icebergs are represented by pressure-exerting Lagrangian elements that drift in the ocean. The elements are held together and interact with each other via bonds. A breaking of these bonds allows the model to emulate calving events (i.e., detachment of a tabular iceberg from an ice shelf) and tabular icebergs breaking up into smaller pieces. Idealized simulations of a calving tabular iceberg, its drift, and its breakup demonstrate capabilities of the developed framework.

Ultra high resolution cation analysis of NGRIP deep ice via cryo-cell UV-laser-ablation ICPMS

NASA Astrophysics Data System (ADS)

Della Lunga, Damiano; Muller, Wolfgang; Olander Rasmussen, Sune; Svensson, Anders

2014-05-01

During glacial periods, Earth experienced abrupt climate change events that led to rapid natural warming/ cooling over a few years only (Steffensen et al., 2008). In order to investigate these rapid climate events especially in old thinned ice, highest spatial/time resolution analysis of climate proxies is required. A recently developed methodology at Royal Holloway University of London (Müller et al., 2011), which permits in situ chemical analysis of frozen ice with spatial (and thus time) resolution up to 0.1 mm (100 ?m) using cryo-cell UV-laser ablation inductively-coupled-plasma mass spectrometry (UV-LA-ICPMS), has been optimized and utilized for analysis of (major) elements indicative of dust and/or sea salt (e.g. Fe, Al, Ca, Mg, Na), while maintaining detection limits in the low(est) ppb-range. NGRIP samples of Greenland Stadial GS22 (~86 ka, depth of ~2690 m), representing a minor δ18O shift (of about ± 4) within the stadial phase of D-O event 22, have been selected and analysed. With a single storm-event resolution capability, seasonal, annual and multiannual periodicity of elements have been identified and will be presented with particular focus on the phasing of the climate proxies. Corresponding results include also an optimized UV-LA-ICPMS methodology, particularly with reference to depth-profiling, assessing contamination of the sample surface and standardization. Finally, the location and distribution of soluble and insoluble micro-inclusions in deep ice have also been assessed concerning the partitioning of elements between grain boundaries and grain interiors. Results show that impurities tend to be concentrated along boundaries in clear (winter) ice, whereas in cloudy bands ('dirtier' ice) they distribute equally between boundaries and interiors. References Müller, W., Shelley, J.M.G., Rasmussen, S.O., 2011. Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS. J. Anal. At. Spectrom. 26, 2391-2395. Steffensen, J.P., Andersen, K.K., Bigler, M., Clausen, H.B., Dahl-Jensen, D., Fischer, H., Goto-Azuma, K., Hansson, M., Johnsen, S.J., Jouzel, J., Masson-Delmotte, V., Popp, T., Rasmussen, S.O., Rothlisberger, R., Ruth, U., Stauffer, B., Siggaard-Andersen, M.L., Sveinbjornsdottir, A.E., Svensson, A., White, J.W.C., 2008. High-resolution Greenland Ice Core data show abrupt climate change happens in few years. Science 321, 680-684.

LWC and Temperature Effects on Ice Accretion Formation on Swept Wings at Glaze Ice Conditions

NASA Technical Reports Server (NTRS)

Vargas, Mario; Reshotko, Eli

2000-01-01

An experiment was conducted to study the effect of liquid water content and temperature on the critical distance in ice accretion formation on swept wings at glaze ice conditions. The critical distance is defined as the distance from the attachment line to tile beginning of the zone where roughness elements develop into glaze ice feathers. A baseline case of 150 mph, 25 F, 0.75 g/cu m. Cloud Liquid Water Content (LWC) and 20 micrometers in Water Droplet Median Volume Diameter (MVD) was chosen. Icing runs were performed on a NACA 0012 swept wing tip at 150 mph and MVD of 20 micrometers for liquid water contents of 0.5 g/cu m, 0.75 g/cu m, and 1.0 g/cu m, and for total temperatures of 20 F, 25 F and 30 F. At each tunnel condition, the sweep angle was changed from 0 deg to 45 deg in 5 deg increments. Casting data, ice shape tracings, and close-up photographic data were obtained. The results showed that decreasing the LWC to 0.5 g/cu m decreases the value of the critical distance at a given sweep angle compared to the baseline case, and starts the formation of complete scallops at 30 sweep angle. Increasing the LWC to 1.0 g/cu m increases the value of the critical distance compared to the baseline case, the critical distance remains always above 0 millimeters and complete scallops are not formed. Decreasing the total temperature to 20 F decreases the critical distance with respect to the baseline case and formation of complete scallops begins at 25 deg sweep angle. When the total temperature is increased to 30 F, bumps covered with roughness elements appear on the ice accretion at 25 deg and 30 deg sweep angles, large ice structures appear at 35 deg and 40 deg sweep angles, and complete scallops are formed at 45 deg sweep angle.

Using Continuum Damage Mechanics to Simulate Iceberg Calving from Tidewater Outlet Glaciers

NASA Astrophysics Data System (ADS)

Mercenier, R.; Lüthi, M.; Vieli, A.

2017-12-01

Many ocean terminating glaciers in the Arctic are currently undergoingrapid retreat, thinning and strong accelerations in flow. The processof iceberg calving plays a crucial role for the related dynamical masslosses and occurs when the stresses at the calving front exceed thefracture strength of ice, driving the propagation of cracks andeventually leading to the detachment of ice blocks from the glacierfront. However, the understanding of the processes involved in icebergcalving as well as the capability of flow models to represent thecalving mechanism remain limited.Here, we use a time-dependent two-dimensional finite-element flowmodel coupled to a damage model to simulate the break-off of ice atthe front of idealized tidewater outlet glaciers. The flow modelcomputes flow velocities and the resulting stresses, which are in turnused to calculate the evolution of the glacier geometry anddamage. Damage is defined as a change of rheological properties, e.g.viscosity, due to increasing material degradation. Elements of ice areremoved when the damage variable reaches a critical threshold. Theeffects of material properties and of geometrical parameters such aswater depth, ice thickness and submarine frontal melting on thesimulated calving rates are explored through systematic sensitivityanalyses.The coupled ice flow/damage model allows for successful reproductionof calving front geometries typically observed for different waterdepths. We further use detailed observations from real glaciergeometries to better constrain the model parameters. Theproposed model approach should be applicable to simulate icebergcalving on arbitrary glaciers, and thus be used to analyse theevolution of tidewater glacier variations from the past to the future.

Tidal Modulation of Ice-shelf Flow: a Viscous Model of the Ross Ice Shelf

NASA Technical Reports Server (NTRS)

Brunt, Kelly M.; MacAyeal, Douglas R.

2014-01-01

Three stations near the calving front of the Ross Ice Shelf, Antarctica, recorded GPS data through a full spring-neap tidal cycle in November 2005. The data revealed a diurnal horizontal motion that varied both along and transverse to the long-term average velocity direction, similar to tidal signals observed in other ice shelves and ice streams. Based on its periodicity, it was hypothesized that the signal represents a flow response of the Ross Ice Shelf to the diurnal tides of the Ross Sea. To assess the influence of the tide on the ice-shelf motion, two hypotheses were developed. The first addressed the direct response of the ice shelf to tidal forcing, such as forces due to sea-surface slopes or forces due to sub-ice-shelf currents. The second involved the indirect response of ice-shelf flow to the tidal signals observed in the ice streams that source the ice shelf. A finite-element model, based on viscous creep flow, was developed to test these hypotheses, but succeeded only in falsifying both hypotheses, i.e. showing that direct tidal effects produce too small a response, and indirect tidal effects produce a response that is not smooth in time. This nullification suggests that a combination of viscous and elastic deformation is required to explain the observations.

The far reach of ice-shelf thinning in Antarctica

NASA Astrophysics Data System (ADS)

Reese, R.; Gudmundsson, G. H.; Levermann, A.; Winkelmann, R.

2018-01-01

Floating ice shelves, which fringe most of Antarctica's coastline, regulate ice flow into the Southern Ocean1-3. Their thinning4-7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this `tele-buttressing' enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner-Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10-12, stressing Antarctica's vulnerability to changes in its surrounding ocean.

Measurement of Temperature and Soil Properties for Finite Element Model Verification

DOT National Transportation Integrated Search

2012-08-01

In recent years, ADOT&PF personnel have used TEMP/W, a commercially available two-dimensional finite element program, to conduct thermal modeling of various : embankment configurations in an effort to reduce the thawing of ice-rich permafrost through...

Detection of reactive metabolites using isotope-labeled glutathione trapping and simultaneous neutral loss and precursor ion scanning with ultra-high-pressure liquid chromatography triple quadruple mass spectrometry.

PubMed

Huang, Ke; Huang, Lingyi; van Breemen, Richard B

2015-04-07

Metabolic activation of drugs to electrophilic species is responsible for over 60% of black box warnings and drug withdrawals from the market place in the United States. Reactive metabolite trapping using glutathione (GSH) and analysis using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) or HPLC with high resolution mass spectrometry (mass defect filtering) have enabled screening for metabolic activation to become routine during drug development. However, current MS-based approaches cannot detect all GSH conjugates present in complex mixtures, especially those present in extracts of botanical dietary supplements. To overcome these limitations, a fast triple quadrupole mass spectrometer-based approach was developed that can detect positively and negatively charged GSH conjugates in a single analysis without the need for advanced knowledge of the elemental compositions of potential conjugates and while avoiding false positives. This approach utilized UHPLC instead of HPLC to shorten separation time and enhance sensitivity, incorporated stable-isotope labeled GSH to avoid false positives, and used fast polarity switching electrospray MS/MS to detect GSH conjugates that form positive and/or negative ions. The general new method was then used to test the licorice dietary supplement Glycyrrhiza glabra, which was found to form multiple GSH conjugates upon metabolic activation. Among the GSH conjugates found in the licorice assay were conjugates with isoliquiritigenin and glabridin, which is an irreversible inhibitor of cytochrome P450 enzymes.

Block copolymer modified surfaces for conjugation of biomacromolecules with control of quantity and activity.

PubMed

Li, Xin; Wang, Mengmeng; Wang, Lei; Shi, Xiujuan; Xu, Yajun; Song, Bo; Chen, Hong

2013-01-29

Polymer brush layers based on block copolymers of poly(oligo(ethylene glycol) methacrylate) (POEGMA) and poly(glycidyl methacrylate) (PGMA) were formed on silicon wafers by activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). Different types of biomolecule can be conjugated to these brush layers by reaction of PGMA epoxide groups with amino groups in the biomolecule, while POEGMA, which resists nonspecific protein adsorption, provides an antifouling environment. Surfaces were characterized by water contact angle, ellipsometry, and Fourier transform infrared spectroscopy (FTIR) to confirm the modification reactions. Phase segregation of the copolymer blocks in the layers was observed by AFM. The effect of surface properties on protein conjugation was investigated using radiolabeling methods. It was shown that surfaces with POEGMA layers were protein resistant, while the quantity of protein conjugated to the diblock copolymer modified surfaces increased with increasing PGMA layer thickness. The activity of lysozyme conjugated on the surface could also be controlled by varying the thickness of the copolymer layer. When biotin was conjugated to the block copolymer grafts, the surface remained resistant to nonspecific protein adsorption but showed specific binding of avidin. These properties, that is, well-controlled quantity and activity of conjugated biomolecules and specificity of interaction with target biomolecules may be exploited for the improvement of signal-to-noise ratio in sensor applications. More generally, such surfaces may be useful as biological recognition elements of high specificity for functional biomaterials.

Parallel conjugate gradient algorithms for manipulator dynamic simulation

NASA Technical Reports Server (NTRS)

Fijany, Amir; Scheld, Robert E.

1989-01-01

Parallel conjugate gradient algorithms for the computation of multibody dynamics are developed for the specialized case of a robot manipulator. For an n-dimensional positive-definite linear system, the Classical Conjugate Gradient (CCG) algorithms are guaranteed to converge in n iterations, each with a computation cost of O(n); this leads to a total computational cost of O(n sq) on a serial processor. A conjugate gradient algorithms is presented that provide greater efficiency using a preconditioner, which reduces the number of iterations required, and by exploiting parallelism, which reduces the cost of each iteration. Two Preconditioned Conjugate Gradient (PCG) algorithms are proposed which respectively use a diagonal and a tridiagonal matrix, composed of the diagonal and tridiagonal elements of the mass matrix, as preconditioners. Parallel algorithms are developed to compute the preconditioners and their inversions in O(log sub 2 n) steps using n processors. A parallel algorithm is also presented which, on the same architecture, achieves the computational time of O(log sub 2 n) for each iteration. Simulation results for a seven degree-of-freedom manipulator are presented. Variants of the proposed algorithms are also developed which can be efficiently implemented on the Robot Mathematics Processor (RMP).

Controlling of free radical copolymerization of styrene and maleic anhydride via RAFT process for the preparation of acetaminophen drug conjugates

NASA Astrophysics Data System (ADS)

Sütekin, S. Duygu; Atıcı, Ayşe Bakar; Güven, Olgun; Hoffman, Allan S.

2018-07-01

The presence of maleic anhydride moiety in styrene-maleic anhydride (SMA) copolymer makes it a versatile substrate for conjugation of drugs. In this study biocompatible styrene-maleic anhydride (SMA) copolymer with alternating structure was synthesized by gamma irradiation at room temperature in the presence of 2-phenyl-2-propyl benzodithioate (PPB). The poly(styrene-alt-maleic anhydride) (poly(St-alt-MA)) with narrow molecular weight distribution (Đ: 1.1-1.3) was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization. The synthesized poly(St-alt-MA) structure was characterized by ATR-FTIR spectroscopy, elemental analysis and 1H NMR spectroscopy and molecular weight and dispersity were determined by size exclusion chromatography (SEC). SMA copolymers were further conjugated with acetaminophen via ester linkage and FT-IR, 1H NMR investigation indicated that the acetaminophen was attached to poly(St-alt-MA). Drug release profile of the polymer-drug conjugate was followed by high performance liquid chromatography (HPLC). The drug-conjugate system was found to follow first order release kinetics with Hixson-Crowell model while drug release mechanism was found as non-Fickian diffusion after testing various kinetic models.

Numerical Simulations of Non-Newtonian Convection in Ice: Application to Europa

NASA Technical Reports Server (NTRS)

Barr, A. C.; Pappalardo, R. T.

2003-01-01

Numerical simulations of solid state convection in Europa's ice shell have so far been limited to consideration of Newtonian flow laws, where the viscosity of ice is strongly dependent upon temperature, predicting that a stagnant lid should form at the top (10-40%) of a convecting ice shell. Such large thicknesses seem to contradict estimates of the effective elastic thickness of Europa s ice shell during its geologically active period. Recent laboratory experiments characterize the rheology of ice as the sum of contributions from several temperature and strain rate-dependent creep mechanisms. We present the results of numerical simulations of convection within Europa s ice shell using the finite-element model Citcom, applying the non-Newtonian rheology of grain boundry sliding. Our calculations suggest a shallower brittle/ductile transition and larger interior convective velocities compared to Newtonian rheology. The flow field is time-dependent, with small, localized upwellings and downwellings at the thermal boundary layers that have minimal topographic expression at the surface.

Mapping the resistance-associated mobilome of a carbapenem-resistant Klebsiella pneumoniae strain reveals insights into factors shaping these regions and facilitates generation of a 'resistance-disarmed' model organism.

PubMed

Bi, Dexi; Jiang, Xiaofei; Sheng, Zi-Ke; Ngmenterebo, David; Tai, Cui; Wang, Minggui; Deng, Zixin; Rajakumar, Kumar; Ou, Hong-Yu

2015-10-01

This study aims to investigate the landscape of the mobile genome, with a focus on antibiotic resistance-associated factors in carbapenem-resistant Klebsiella pneumoniae. The mobile genome of the completely sequenced K. pneumoniae HS11286 strain (an ST11, carbapenem-resistant, near-pan-resistant, clinical isolate) was annotated in fine detail. The identified mobile genetic elements were mapped to the genetic contexts of resistance genes. The blaKPC-2 gene and a 26 kb region containing 12 clustered antibiotic resistance genes and one biocide resistance gene were deleted, and the MICs were determined again to ensure that antibiotic resistance had been lost. HS11286 contains six plasmids, 49 ISs, nine transposons, two separate In2-related integron remnants, two integrative and conjugative elements (ICEs) and seven prophages. Sixteen plasmid-borne resistance genes were identified, 14 of which were found to be directly associated with Tn1721-, Tn3-, Tn5393-, In2-, ISCR2- and ISCR3-derived elements. IS26 appears to have actively moulded several of these genetic regions. The deletion of blaKPC-2, followed by the deletion of a 26 kb region containing 12 clustered antibiotic resistance genes, progressively decreased the spectrum and level of resistance exhibited by the resultant mutant strains. This study has reiterated the role of plasmids as bearers of the vast majority of resistance genes in this species and has provided valuable insights into the vital role played by ISs, transposons and integrons in shaping the resistance-coding regions in this important strain. The 'resistance-disarmed' K. pneumoniae ST11 strain generated in this study will offer a more benign and readily genetically modifiable model organism for future extensive functional studies. © The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Method of determining operation parameters of stand tests of vehicle suspension elements under conditions of ultra-low temperatures

NASA Astrophysics Data System (ADS)

Fedyanov, E. A.; Sokolov-Dobrev, N. S.; Ljashenko, M. V.; Shekhovtsov, V. V.; Potapov, P. V.; Dolotov, A. A.; Klementiev, E. V.

2018-05-01

This article presents the description of the method for estimation of heat flows characteristic during research of operability of suspension elements under the conditions of ultralow temperature. The mentioned research is performed at the test bench created in VSTU. Solid carbon dioxide (also known as artificial ice) is used as the coolant. The method provides evaluation of required quantity of artificial ice and cooling dynamics of the test unit in the insulated low-temperature chamber with structurally specified parameters of heat insulation. Also the method allows computation of heat intake into the chamber volume.

Current Experimental Basis for Modeling Ice Accretions on Swept Wings

NASA Technical Reports Server (NTRS)

Vargas, Mario

2005-01-01

This work presents a review of the experimental basis for modeling ice accretions on swept wings. Experimental work related to ice accretion physics on swept wings conducted between 1954 and 2004 is reviewed. Proposed models or explanations of scallop formations are singled out and discussed. Special emphasis is placed on reviewing the work done to determine the basic macroscopic mechanisms of scallop formation. The role of feather growth and its connection to scallop growth is discussed. Conceptual steps in modeling scallop formations are presented. Research elements needed for modeling are discussed.

Cumulative and Synergistic Effects of Physical, Biological, and Acoustic Signals on Marine Mammal Habitat Use Physical Oceanography Component: Soundscapes Under Sea Ice: Can We Listen for Open Water?

DTIC Science & Technology

2013-09-30

Physical, Biological, and Acoustic Signals on Marine Mammal Habitat Use Physical Oceanography Component: Soundscapes Under Sea Ice: Can we listen for... Soundscapes Under Sea Ice: Can we listen for open water? 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...the source. These different sounds can be described as “ soundscapes ”, and graphically represented by comparing two or more features of the sound

Debris/ice/TPS assessment and integrated photographic analysis for Shuttle Mission STS-50

NASA Technical Reports Server (NTRS)

Higginbotham, Scott A.; Davis, J. Bradley; Katnik, Gregory N.

1992-01-01

Thermal Protection System (TPS) assessment and integrated photographic analysis was conducted for Shuttle Mission STS-50. Debris inspections of the flight elements and launch pad were performed before and after launch. Ice/frost conditions on the external tank were assessed by the use of computer programs, nomographs, and infrared scanner data during cryogenic loading of the vehicle followed by on-pad visual inspection. High speed photography was analyzed after launch to identify ice/debris sources and evaluate potential vehicle damage and/or in-flight anomalies. The debris/ice/TPS conditions and integrated photographic analysis of Shuttle Mission STS-50, and the resulting effect on the Space Shuttle Program are documented.

Effects Of Crystallographic Properties On The Ice Nucleation Properties Of Volcanic Ash Particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulkarni, Gourihar R.; Nandasiri, Manjula I.; Zelenyuk, Alla

2015-04-28

Specific chemical and physical properties of volcanic ash particles that could affect their ability to induce ice formation are poorly understood. In this study, the ice nucleating properties of size-selected volcanic ash and mineral dust particles in relation to their surface chemistry and crystalline structure at temperatures ranging from –30 to –38 °C were investigated in deposition mode. Ice nucleation efficiency of dust particles was higher compared to ash particles at all temperature and relative humidity conditions. Particle characterization analysis shows that surface elemental composition of ash and dust particles was similar; however, the structural properties of ash samples weremore » different.« less

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle

NASA Astrophysics Data System (ADS)

Tschauner, O.; Huang, S.; Greenberg, E.; Prakapenka, V. B.; Ma, C.; Rossman, G. R.; Shen, A. H.; Zhang, D.; Newville, M.; Lanzirotti, A.; Tait, K.

2018-03-01

Water-rich regions in Earth’s deeper mantle are suspected to play a key role in the global water budget and the mobility of heat-generating elements. We show that ice-VII occurs as inclusions in natural diamond and serves as an indicator for such water-rich regions. Ice-VII, the residue of aqueous fluid present during growth of diamond, crystallizes upon ascent of the host diamonds but remains at pressures as high as 24 gigapascals; it is now recognized as a mineral by the International Mineralogical Association. In particular, ice-VII in diamonds points toward fluid-rich locations in the upper transition zone and around the 660-kilometer boundary.

Rocket effluent: Its ice nucleation activity and related properties

NASA Technical Reports Server (NTRS)

Parungo, F. P.; Allee, P. A.

1978-01-01

To investigate the possibility of inadvertent weather modification from rocket effluent, aerosol samples were collected from an instrumented aircraft subsequent to the Voyager 1 and 2 launches. The aerosol's morphology, concentration, and size distribution were examined with an electron microscope. The elemental compositions of individual particles were analyzed with an X-ray energy spectrometer. Ice nucleus concentration was measured with a thermal diffusion chamber. The particles' physical and chemical properties were related to their ice nucleation activity. A laboratory experiment on rocket propellant exhaust was conducted under controlled conditions. Both laboratory and field experimental results indicated that rocket propellant exhaust can produce active ice nuclei and modify local weather in suitable meteorological conditions.

Micromechanics of ice friction

NASA Astrophysics Data System (ADS)

Sammonds, P. R.; Bailey, E.; Lishman, B.; Scourfield, S.

2015-12-01

Frictional mechanics are controlled by the ice micro-structure - surface asperities and flaws - but also the ice fabric and permeability network structure of the contacting blocks. Ice properties are dependent upon the temperature of the bulk ice, on the normal stress and on the sliding velocity and acceleration. This means the shear stress required for sliding is likewise dependent on sliding velocity, acceleration, and temperature. We aim to describe the micro-physics of the contacting surface. We review micro-mechanical models of friction: the elastic and ductile deformation of asperities under normal loads and their shear failure by ductile flow, brittle fracture, or melting and hydrodynamic lubrication. Combinations of these give a total of six rheological models of friction. We present experimental results in ice mechanics and physics from laboratory experiments to understand the mechanical models. We then examine the scaling relations of the slip of ice, to examine how the micro-mechanics of ice friction can be captured simple reduced-parameter models, describing the mechanical state and slip rate of the floes. We aim to capture key elements that they may be incorporated into mid and ocean-basin scale modelling.

Characteristics of surface roughness associated with leading edge ice accretion

NASA Technical Reports Server (NTRS)

Shin, Jaiwon

1994-01-01

Detailed size measurements of surface roughness associated with leading edge ice accretions are presented to provide information on characteristics of roughness and trends of roughness development with various icing parameters. Data was obtained from icing tests conducted in the Icing Research Tunnel (IRT) at NASA Lewis Research Center (LeRC) using a NACA 0012 airfoil. Measurements include diameters, heights, and spacing of roughness elements along with chordwise icing limits. Results confirm the existence of smooth and rough ice zones and that the boundary between the two zones (surface roughness transition region) moves upstream towards stagnation region with time. The height of roughness grows as the air temperature and the liquid water content increase, however, the airspeed has little effect on the roughness height. Results also show that the roughness in the surface roughness transition region grows during a very early stage of accretion but reaches a critical height and then remains fairly constant. Results also indicate that a uniformly distributed roughness model is only valid at a very initial stage of the ice accretion process.

Recent progress in the analysis of iced airfoils and wings

NASA Technical Reports Server (NTRS)

Cebeci, Tuncer; Chen, Hsun H.; Kaups, Kalle; Schimke, Sue

1992-01-01

Recent work on the analysis of iced airfoils and wings is described. Ice shapes for multielement airfoils and wings are computed using an extension of the LEWICE code that was developed for single airfoils. The aerodynamic properties of the iced wing are determined with an interactive scheme in which the solutions of the inviscid flow equations are obtained from a panel method and the solutions of the viscous flow equations are obtained from an inverse three-dimensional finite-difference boundary-layer method. A new interaction law is used to couple the inviscid and viscous flow solutions. The newly developed LEWICE multielement code is amplified to a high-lift configuration to calculate the ice shapes on the slat and on the main airfoil and on a four-element airfoil. The application of the LEWICE wing code to the calculation of ice shapes on a MS-317 swept wing shows good agreement with measurements. The interactive boundary-layer method is applied to a tapered iced wing in order to study the effect of icing on the aerodynamic properties of the wing at several angles of attack.

Microreactor and method for preparing a radiolabeled complex or a biomolecule conjugate

DOEpatents

Reichert, David E; Kenis, Paul J. A.; Wheeler, Tobias D; Desai, Amit V; Zeng, Dexing; Onal, Birce C

2015-03-17

A microreactor for preparing a radiolabeled complex or a biomolecule conjugate comprises a microchannel for fluid flow, where the microchannel comprises a mixing portion comprising one or more passive mixing elements, and a reservoir for incubating a mixed fluid. The reservoir is in fluid communication with the microchannel and is disposed downstream of the mixing portion. A method of preparing a radiolabeled complex includes flowing a radiometal solution comprising a metallic radionuclide through a downstream mixing portion of a microchannel, where the downstream mixing portion includes one or more passive mixing elements, and flowing a ligand solution comprising a bifunctional chelator through the downstream mixing portion. The ligand solution and the radiometal solution are passively mixed while in the downstream mixing portion to initiate a chelation reaction between the metallic radionuclide and the bifunctional chelator. The chelation reaction is completed to form a radiolabeled complex.

Parallel processors and nonlinear structural dynamics algorithms and software

NASA Technical Reports Server (NTRS)

Belytschko, Ted

1990-01-01

Techniques are discussed for the implementation and improvement of vectorization and concurrency in nonlinear explicit structural finite element codes. In explicit integration methods, the computation of the element internal force vector consumes the bulk of the computer time. The program can be efficiently vectorized by subdividing the elements into blocks and executing all computations in vector mode. The structuring of elements into blocks also provides a convenient way to implement concurrency by creating tasks which can be assigned to available processors for evaluation. The techniques were implemented in a 3-D nonlinear program with one-point quadrature shell elements. Concurrency and vectorization were first implemented in a single time step version of the program. Techniques were developed to minimize processor idle time and to select the optimal vector length. A comparison of run times between the program executed in scalar, serial mode and the fully vectorized code executed concurrently using eight processors shows speed-ups of over 25. Conjugate gradient methods for solving nonlinear algebraic equations are also readily adapted to a parallel environment. A new technique for improving convergence properties of conjugate gradients in nonlinear problems is developed in conjunction with other techniques such as diagonal scaling. A significant reduction in the number of iterations required for convergence is shown for a statically loaded rigid bar suspended by three equally spaced springs.

Study on galloping behavior of iced eight bundle conductor transmission lines

NASA Astrophysics Data System (ADS)

Zhou, Linshu; Yan, Bo; Zhang, Liang; Zhou, Song

2016-02-01

Wind tunnel test was carried out to obtain the aerodynamic coefficients of an eight bundle conductor accreted with crescent-shaped ice. A user-defined cable element with torsional degree of freedom is developed in ABAQUS software to capture the torsional deformation of the iced conductors during galloping. By means of the user-defined cable element, different damping ratios in in-plane, out-of-plane and torsional directions of the conductors can be defined and the aerodynamic forces varying with their motion status can be exerted on the conductors conveniently when ABAQUS is used to simulate galloping of transmission lines. A wind tunnel test to model galloping of an iced eight bundle conductor segment was carried out, and the validity of the numerical simulation method is demonstrated by the agreement of the galloping orbit of the bundle conductor segment model recorded in the test and that by the numerical simulation. Furthermore, galloping behavior, including dynamic responses, galloping orbits, frequencies, vibration modes and amplitudes, of typical iced eight bundle conductor transmission lines in the cases of different span lengths, initial tensions in sub-conductors, wind velocities, angles of wind attack and damping ratios is studied, and the galloping behavior of the lines with internal resonance conditions is discussed. The obtained results may provide a fundamental tool for the development of anti-galloping techniques of eight bundle conductor transmission lines.

Evolution and comparative genomics of pAQU-like conjugative plasmids in Vibrio species.

PubMed

Li, Ruichao; Ye, Lianwei; Wong, Marcus Ho Yin; Zheng, Zhiwei; Chan, Edward Wai Chi; Chen, Sheng

2017-09-01

To investigate a set of MDR conjugative plasmids found in Vibrio species and characterize the underlying evolution process. pAQU-type plasmids from Vibrio species were sequenced using both Illumina and PacBio platforms. Bioinformatics tools were utilized to analyse the typical MDR regions and core genes in the plasmids. The nine pAQU-type plasmids ranged from ∼160 to 206 kb in size and were found to harbour as many as 111 core genes encoding conjugative, replication and maintenance functions. Eight plasmids were found to carry a typical MDR region, which contained various accessory and resistance genes, including ISCR1-blaPER-1-bearing complex class 1 integrons, ISCR2-floR, ISCR2-tet(D)-tetR-ISCR2, qnrVC6, a Tn10-like structure and others associated with mobile elements. Comparison between a plasmid without resistance genes and different MDR plasmids showed that integration of different mobile elements, such as IS26, ISCR1, ISCR2, IS10 and IS6100, into the plasmid backbone was the key mechanism by which foreign resistance genes were acquired during the evolution process. This study identified pAQU-type plasmids as emerging MDR conjugative plasmids among important pathogens from different origins in Asia. These findings suggest that aquatic bacteria constitute a major reservoir of resistance genes, which may be transmissible to other human pathogens during food production and processing. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Changes in Arctic and Antarctic Sea Ice as a Microcosm of Global Climate Change

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.

2014-01-01

Polar sea ice is a key element of the climate system and has now been monitored through satellite observations for over three and a half decades. The satellite observations reveal considerable information about polar ice and its changes since the late 1970s, including a prominent downward trend in Arctic sea ice coverage and a much lesser upward trend in Antarctic sea ice coverage, illustrative of the important fact that climate change entails spatial contrasts. The decreasing ice coverage in the Arctic corresponds well with contemporaneous Arctic warming and exhibits particularly large decreases in the summers of 2007 and 2012, influenced by both preconditioning and atmospheric conditions. The increasing ice coverage in the Antarctic is not as readily explained, but spatial differences in the Antarctic trends suggest a possible connection with atmospheric circulation changes that have perhaps been influenced by the Antarctic ozone hole. The changes in the polar ice covers and the issues surrounding those changes have many commonalities with broader climate changes and their surrounding issues, allowing the sea ice changes to be viewed in some important ways as a microcosm of global climate change.

Clinical Isolates of Vibrio cholerae O1 El Tor Ogawa of 2009 from Kolkata, India: Preponderance of SXT Element and Presence of Haitian ctxB Variant

PubMed Central

Kutar, Braj M. R. N. S.; Rajpara, Neha; Upadhyay, Hardik; Ramamurthy, Thandavarayan; Bhardwaj, Ashima K.

2013-01-01

Background Increase in the number of multidrug resistant pathogens and the accompanied rise in case fatality rates has hampered the treatment of many infectious diseases including cholera. Unraveling the mechanisms responsible for multidrug resistance in the clinical isolates of Vibrio cholerae would help in understanding evolution of these pathogenic bacteria and their epidemic potential. This study was carried out to identify genetic factors responsible for multiple drug resistance in clinical isolates of Vibrio cholerae O1, serotype Ogawa, biotype El Tor isolated from the patients admitted to the Infectious Diseases Hospital, Kolkata, India, in 2009. Methodology/Principal Findings One hundred and nineteen clinical isolates of V. cholerae were analysed for their antibiotic resistance phenotypes. Antibiogram analysis revealed that majority of the isolates showed resistance to co-trimoxazole, nalidixic acid, polymixin B and streptomycin. In PCR, SXT integrase was detected in 117 isolates and its sequence showed 99% identity notably to ICEVchInd5 from Sevagram, India, ICEVchBan5 from Bangladesh and VC1786ICE sequence from Haiti outbreak among others. Antibiotic resistance traits corresponding to SXT element were transferred from the parent Vibrio isolate to the recipient E. coli XL-1 Blue cells during conjugation. Double-mismatch-amplification mutation assay (DMAMA) revealed the presence of Haitian type ctxB allele of genotype 7 in 55 isolates and the classical ctxB allele of genotype 1 in 59 isolates. Analysis of topoisomerase sequences revealed the presence of mutation Ser83 → Ile in gyrA and Ser85→ Leu in parC. This clearly showed the circulation of SXT-containing V. cholerae as causative agent for cholera in Kolkata. Conclusions There was predominance of SXT element in these clinical isolates from Kolkata region which also accounted for their antibiotic resistance phenotype typical of this element. DMAMA PCR showed them to be a mixture of isolates with different ctxB alleles like classical, El Tor and Haitian variants. PMID:23431378

Antimicrobials & cholera: are we stranded?

PubMed Central

Ghosh, Amit; Ramamurthy, T.

2011-01-01

Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though significant progress in the management of diarrhoeal diseases has been achieved by improved hygiene, development of new antimicrobials and vaccines, the burden remains the same, especially in children below 5 yr of age. In the case of cholera, though oral rehydration treatment is the mainstay, antimicrobial therapy is mandatory at times to reduce the volume of stool and shorten the duration of the disease. Though for many pathogens, antimicrobial resistance emerged soon after the introduction of antibiotics, Vibrio cholerae remained sensitive to most of the antibiotics for quite a long period. However, the scenario changed over the years and today, V. cholerae strains isolated world over are resistant to multiple antibiotics. A myriad number of mechanisms underlie this phenomenon. These include production of extended-spectrum beta-lactamases, enhanced multi-drug efflux pump activity, plasmid-mediated quinolone and fluoroquinolone resistance, and chromosomal mutations. Horizontal transfer of resistance determinants with mobile genetic elements like integrons and the integrating conjugative elements (ICEs), SXTs help in the dissemination of drug resistance. Though all strains isolated are not resistant to all antibiotics and we are not as yet “stranded”, expanding spectrum of drug resistance is a definite cause for concern. Pipelines of discovery of new antibiotics are drying up as major pharmaceutical companies are losing interest in investing money in this endeavour, mainly due to the short shelf-life of the antibiotics and also due to the fast emergence of drug resistance. To address this issue, attempts are now being made to discover drugs which are pathogen specific and target their “virulence mechanisms”. It is expected that development of resistance against such antibiotics would take much longer. This review briefly focuses on all these issues. PMID:21415499

Antimicrobials & cholera: are we stranded?

PubMed

Ghosh, Amit; Ramamurthy, T

2011-02-01

Antimicrobial resistance poses a major threat in the treatment of infectious diseases. Though significant progress in the management of diarrhoeal diseases has been achieved by improved hygiene, development of new antimicrobials and vaccines, the burden remains the same, especially in children below 5 yr of age. In the case of cholera, though oral rehydration treatment is the mainstay, antimicrobial therapy is mandatory at times to reduce the volume of stool and shorten the duration of the disease. Though for many pathogens, antimicrobial resistance emerged soon after the introduction of antibiotics, Vibrio cholerae remained sensitive to most of the antibiotics for quite a long period. However, the scenario changed over the years and today, V. cholerae strains isolated world over are resistant to multiple antibiotics. A myriad number of mechanisms underlie this phenomenon. These include production of extended-spectrum beta-lactamases, enhanced multi-drug efflux pump activity, plasmid-mediated quinolone and fluoroquinolone resistance, and chromosomal mutations. Horizontal transfer of resistance determinants with mobile genetic elements like integrons and the integrating conjugative elements (ICEs), SXTs help in the dissemination of drug resistance. Though all strains isolated are not resistant to all antibiotics and we are not as yet "stranded", expanding spectrum of drug resistance is a definite cause for concern. Pipelines of discovery of new antibiotics are drying up as major pharmaceutical companies are losing interest in investing money in this endeavour, mainly due to the short shelf-life of the antibiotics and also due to the fast emergence of drug resistance. To address this issue, attempts are now being made to discover drugs which are pathogen specific and target their "virulence mechanisms". It is expected that development of resistance against such antibiotics would take much longer. This review briefly focuses on all these issues.

Occurrence and Forms of Water and Ice on the Earth and Beyond, and the Origin(s) of Life

NASA Technical Reports Server (NTRS)

Blake, David F.; DeVincenzi, Donald L. (Technical Monitor)

1998-01-01

The natural history of the biogenic elements (H,C,O,N) from their first association within cold molecular clouds to their delivery to the Earth during the late bombardment of the inner solar system, is intimately linked to water ice. The earliest organic compounds are formed in cold interstellar molecular clouds as a result of UV and thermal processing of sub-micrometer ice grains which contain trapped carbon and nitrogen molecules. Structural changes in the water ice host underlie and fundamentally control important macroscopic phenomena such as the outgassing of volatiles, the rates of chemical reactions, and processing and retention of organic compounds. Prebiotic organic material was in all likelihood delivered the early Earth in a pristine state as a consequence of its sequestration within a protective water ice host.

Presence of faecal coliforms and selected heavy metals in ice cubes from food outlets in Taman Universiti, Johor Bahru, Malaysia.

PubMed

Mahat, N A; Meor Ahmad, Z; Abdul Wahab, R

2015-09-01

Consumption of iced beverages is common in Malaysia although specific research focusing on its safety parameters such as presence of faecal coliforms and heavy metal elements remains scarce. A study conducted in Kelantan indicated that faecal coliforms were detected in the majority of the ice cube samples analyzed, largely attributable to improper handling. Hence, it was found pertinent to conduct similar study in other parts of the country such as Johor Bahru if the similar pattern prevailed. Therefore, this present cross sectional study which randomly sampled ice cubes from 30 permanent food outlets in Taman Universiti, Johor Bahru for detecting contamination by faecal coliforms and selected heavy metal elements (lead, copper, manganese and zinc) acquires significance. Faecal coliforms were detected in 11 (36.67%) of the samples, ranging between 1 CFU/100 mL to > 50 CFU/100 mL; two of the samples were grossly contaminated (>50 CFU/100 mL). Interestingly, while positive detection of lead was observed in 29 of the 30 ice cube samples (mean: 0.511±0.105 ppm; range: 0.489-0.674 ppm), copper, manganese and zinc were not detected. In addition, analysis on commercially bottled mineral water as well as in tap water samples did not detect such contaminations. Therefore, it appears that (1) contamination of faecal coliforms in ice cubes in food outlets in Malaysia may not be sporadic in pattern but rather prevalent and (2) the source of water used for manufacturing the ice cubes that contained significant amount of lead would suggest that (3) it was neither originated from the treated tap water supply nor bottled mineral water or (4) perhaps contaminated during manufacturing process. Further studies exploring the source of water used for manufacturing these ice cubes as well as the handling process among food operators deserve consideration.

Contrasts in Sea Ice Formation and Production in the Arctic Seasonal and Perennial Ice Zones

NASA Technical Reports Server (NTRS)

Kwok, R.

2006-01-01

Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. 3-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the mid-winter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m) - this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by: local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and, the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice.

Application of Conjugate Gradient methods to tidal simulation

USGS Publications Warehouse

Barragy, E.; Carey, G.F.; Walters, R.A.

1993-01-01

A harmonic decomposition technique is applied to the shallow water equations to yield a complex, nonsymmetric, nonlinear, Helmholtz type problem for the sea surface and an accompanying complex, nonlinear diagonal problem for the velocities. The equation for the sea surface is linearized using successive approximation and then discretized with linear, triangular finite elements. The study focuses on applying iterative methods to solve the resulting complex linear systems. The comparative evaluation includes both standard iterative methods for the real subsystems and complex versions of the well known Bi-Conjugate Gradient and Bi-Conjugate Gradient Squared methods. Several Incomplete LU type preconditioners are discussed, and the effects of node ordering, rejection strategy, domain geometry and Coriolis parameter (affecting asymmetry) are investigated. Implementation details for the complex case are discussed. Performance studies are presented and comparisons made with a frontal solver. ?? 1993.

Aerosol deposition (trace elements and black carbon) over the highest glacier of the Eastern European Alps during the last centuries

NASA Astrophysics Data System (ADS)

Bertò, Michele; Barbante, Carlo; Gabrieli, Jacopo; Gabrielli, Paolo; Spolaor, Andrea; Dreossi, Giuliano; Laj, Paolo; Zanatta, Marco; Ginot, Patrick; Fain, Xavier

2016-04-01

Ice cores are an archive of a wide variety of climatic and environmental information from the past, retaining them for hundreds of thousands of years. Anthropogenic pollutants, trace elements, heavy metals and major ions, are preserved as well providing insights on the past atmospheric circulations and allowing evaluating the human impact on the environment. Several ice cores were drilled in glaciers at mid and low latitudes, as in the European Alps. The first ice cores drilled to bedrock in the Eastern Alps were retrieved during autumn 2011 on the "Alto dell`Ortles glacier", the uppermost glacier of the Ortles massif (3905m, South Tirol, Italy), in the frame of the "Ortles Project". A preliminary dating of the core suggests that it should cover at least 300-400 years. Despite the summer temperature increase of the last decades this glacier still contain cold ice. Indeed, O and H isotopes profiles well describe the atmospheric warming as well as the low temperatures recorded during the Little Ice Age (LIA). Moreover, this glacier is located close to densely populated and industrialized areas and can be used for reconstructing for the first time past and recent air pollution and the human impact in the Eastern European Alps. The innermost part of the core is under analysis by means of a "Continuous Flow Analysis" system. This kind of analysis offers a high resolution in data profiles. The separation between the internal and the external parts of the core avoid any kind of contamination. An aluminum melting head melts the core at about 2.5 cm min-1. Simultaneous analyses of conductivity, dust concentration and size distribution (from 0.8 to 80 μm), trace elements with Inductive Coupled Plasma Mass Spectrometer (ICP-MS, Agilent 7500) and refractory black carbon (rBC) with the Single Particle Soot Photometer (SP2, Droplet Measurement Technologies) are performed. A fraction of the melt water is collected by an auto-sampler for further analysis. The analyzed elements are Li, Na, Mg, Al, K, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Rb, Ag, Cd, Sb, I, Ba, Pt, Tl, Pb and U. Trace elements concentrations in the Ortles snow are related to the emissions from the Po Valley, one of the most polluted region of Europe. The results show an increase in the concentration of many heavy metals due to anthropogenic emissions, mainly from the onset of the Industrial Revolution. rBC is one of the most important aerosol species affecting the climate system, particularly the glaciers, by modifying the radiative energy balance. A significant increase of rBC was found in the ice identifying this kind of aerosol as a responsible in forcing the end of the LIA.

Regular patterns of Cs-137 distribution in natural conjugated elementary landscapes as a result of a balanced surface and depth water migration

NASA Astrophysics Data System (ADS)

Korobova, Elena; Romanov, Sergey

2016-04-01

Distribution of artificial radionuclides in the environment has long been used successfully for revealing migration pathways of their stable analogues. Migration of water in natural conjugated elementary landscapes characterizing the system of top-slope-resulting depression, has a specific structure and the radionuclide tracer is inevitably reflecting it by specific sorption and exchange processes. Other important issues are the concentration levels and the difference in characteristic time of chemical element dispersion. Modern biosphere has acquired its sustainable structure within a long period of time and is formed by basic macroelements allowing the water soluble portion of elements functioning as activators of chemical exchange. Water migration is controlled by gravitation, climate and relief while fixation depends upon the parameters of surfaces and chemical composition. The resulting structure depends on specificity and duration of the process. The long-term redistribution of chemical elements in terrestrial environment has led to a distinct geochemical structure of conjugated landscapes with a specific geometry of redistribution and accumulation of chemical elements. Migration of the newly born anthropogenic radionuclides followed natural pathways in biosphere. The initial deposition of the Chernobyl's radionuclides within the elementary landscape-geochemical system was even by condition of aerial deposition. But further exchange process is controlled by the strength of fixation and migration ability of the carriers. Therefore patterns of spatial distribution of artificial radionuclides in natural landscapes are considerably different as compared to those of the long-term forming the basic structure of chemical fields in biosphere. Our monitoring of Cs-137 radial and lateral distribution in the test plots characterizing natural undisturbed conjugated elementary landscapes performed in the period from 2005 until now has revealed a stable and specifically polycentric structure of radiocesium distribution believed to reflect the character of radial and lateral water body migration and a high sensitivity of water distribution to surface parameters. This leads to an unusual wavy type of Cs-137 distribution down, along and across all the slopes examined for surface Cs-137 activity at every measured point. The finding is believed to have an important practical outcome allowing much more detailed evaluation of micronutrients distribution and optimization of their application.

Implementation of higher-order vertical finite elements in ISSM v4.13 for improved ice sheet flow modeling over paleoclimate timescales

NASA Astrophysics Data System (ADS)

Cuzzone, Joshua K.; Morlighem, Mathieu; Larour, Eric; Schlegel, Nicole; Seroussi, Helene

2018-05-01

Paleoclimate proxies are being used in conjunction with ice sheet modeling experiments to determine how the Greenland ice sheet responded to past changes, particularly during the last deglaciation. Although these comparisons have been a critical component in our understanding of the Greenland ice sheet sensitivity to past warming, they often rely on modeling experiments that favor minimizing computational expense over increased model physics. Over Paleoclimate timescales, simulating the thermal structure of the ice sheet has large implications on the modeled ice viscosity, which can feedback onto the basal sliding and ice flow. To accurately capture the thermal field, models often require a high number of vertical layers. This is not the case for the stress balance computation, however, where a high vertical resolution is not necessary. Consequently, since stress balance and thermal equations are generally performed on the same mesh, more time is spent on the stress balance computation than is otherwise necessary. For these reasons, running a higher-order ice sheet model (e.g., Blatter-Pattyn) over timescales equivalent to the paleoclimate record has not been possible without incurring a large computational expense. To mitigate this issue, we propose a method that can be implemented within ice sheet models, whereby the vertical interpolation along the z axis relies on higher-order polynomials, rather than the traditional linear interpolation. This method is tested within the Ice Sheet System Model (ISSM) using quadratic and cubic finite elements for the vertical interpolation on an idealized case and a realistic Greenland configuration. A transient experiment for the ice thickness evolution of a single-dome ice sheet demonstrates improved accuracy using the higher-order vertical interpolation compared to models using the linear vertical interpolation, despite having fewer degrees of freedom. This method is also shown to improve a model's ability to capture sharp thermal gradients in an ice sheet particularly close to the bed, when compared to models using a linear vertical interpolation. This is corroborated in a thermal steady-state simulation of the Greenland ice sheet using a higher-order model. In general, we find that using a higher-order vertical interpolation decreases the need for a high number of vertical layers, while dramatically reducing model runtime for transient simulations. Results indicate that when using a higher-order vertical interpolation, runtimes for a transient ice sheet relaxation are upwards of 5 to 7 times faster than using a model which has a linear vertical interpolation, and this thus requires a higher number of vertical layers to achieve a similar result in simulated ice volume, basal temperature, and ice divide thickness. The findings suggest that this method will allow higher-order models to be used in studies investigating ice sheet behavior over paleoclimate timescales at a fraction of the computational cost than would otherwise be needed for a model using a linear vertical interpolation.

Non-Target Analyses of organic compounds in ice cores using HPLC-ESI-UHRMS

NASA Astrophysics Data System (ADS)

Zuth, Christoph; Müller-Tautges, Christina; Eichler, Anja; Schwikowski, Margit; Hoffmann, Thorsten

2015-04-01

To study the global climatic and environmental changes it is necessary to know the environmental and especially atmospheric conditions of the past. By analysing climate archives, such as for example ice cores, unique environmental information can be obtained. In contrast to the well-established analysis of inorganic species in ice cores, organic compounds have been analysed in ice cores to a much smaller extent. Because of current analytical limitations it has become commonplace to focus on 'total organic carbon' measurements or specific classes of organic molecules, as no analytical methods exist that can provide a broad characterization of the organic material present[1]. On the one hand, it is important to focus on already known atmospheric markers in ice cores and to quantify, where possible, in order to compare them to current conditions. On the other hand, unfortunately a wealth of information is lost when only a small fraction of the organic material is examined. However, recent developments in mass spectrometry in respect to higher mass resolution and mass accuracy enable a new approach to the analysis of complex environmental samples. The qualitative characterization of the complex mixture of water soluble organic carbon (WSOC) in the ice using high-resolution mass spectrometry allows for novel insights concerning the composition and possible sources of aerosol derived WSOC deposited at glacier sites. By performing a non-target analysis of an ice core from the Swiss Alps using previous enrichment by solid-phase extraction (SPE) and high performance liquid chromatography coupled to electrospray ionization and ultra-high resolution mass spectrometry (HPLC-ESI-UHRMS) 475 elemental formulas distributed onto 659 different peaks were detected. The elemental formulas were classified according to their elemental composition into CHO-, CHON-, CHOS-, CHONS-containing compounds and 'others'. Several methods for the analysis of complex data sets of high resolution mass spectrometry were applied to the results of the non-target analysis. By various classifications in Van Krevelen plots[2], amino acids and degradation products of proteins as well as degradation products of lignins have been determined as the main components of the ice core. Furthermore, the majority of WSOC molecular formulas identified in this non-target analysis had molar H/C and O/C ratios similar to mono- and di-carboxylic acids and SOAs[3]. Studies of the carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol showed that a majority of the elemental formulas can be associated with the combustion of biomass as a major source of the WSOC[4]. References: [1] Grannas et al., J. Geophys Res.,2006, 111 [2] Sleighter, RL, Hatcher, PG, J. Mass Spectrom., 2007, 42, 559-574 [3] Wozniak et al., Atmos. Chem. Phys., 2008, 8, 5099-5111 [4] Kroll et al., Nature Chemistry, 2011, 3, 133-139

A novel integrase-containing element may interact with Laem-Singh virus (LSNV) to cause slow growth in giant tiger shrimp

PubMed Central

2011-01-01

Background From 2001-2003 monodon slow growth syndrome (MSGS) caused severe economic losses for Thai shrimp farmers who cultivated the native, giant tiger shrimp, and this led them to adopt exotic stocks of the domesticated whiteleg shrimp as the species of cultivation choice, despite the higher value of giant tiger shrimp. In 2008, newly discovered Laem-Singh virus (LSNV) was proposed as a necessary but insufficient cause of MSGS, and this stimulated the search for the additional component cause(s) of MSGS in the hope that discovery would lead to preventative measures that could revive cultivation of the higher value native shrimp species. Results Using a universal shotgun cloning protocol, a novel RNA, integrase-containing element (ICE) was found in giant tiger shrimp from MSGS ponds (GenBank accession number FJ498866). In situ hybridization probes and RT-PCR tests revealed that ICE and Laem-Singh virus (LSNV) occurred together in lymphoid organs (LO) of shrimp from MSGS ponds but not in shrimp from normal ponds. Tissue homogenates of shrimp from MSGS ponds yielded a fraction that gave positive RT-PCR reactions for both ICE and LSNV and showed viral-like particles by transmission electron microscopy (TEM). Bioassays of this fraction with juvenile giant tiger shrimp resulted in retarded growth with gross signs of MSGS, and in situ hybridization assays revealed ICE and LSNV together in LO, eyes and gills. Viral-like particles similar to those seen in tissue extracts from natural infections were also seen by TEM. Conclusions ICE and LSNV were found together only in shrimp from MSGS ponds and only in shrimp showing gross signs of MSGS after injection with a preparation containing ICE and LSNV. ICE was never found in the absence of LSNV although LSNV was sometimes found in normal shrimp in the absence of ICE. The results suggest that ICE and LSNV may act together as component causes of MSGS, but this cannot be proven conclusively without single and combined bioassays using purified preparations of both ICE and LSNV. Despite this ambiguity, it is recommended in the interim that ICE be added to the agents such as LSNV already listed for exclusion from domesticated stocks of the black tiger shrimp. PMID:21569542

Coupling of a continuum ice sheet model and a discrete element calving model using a scientific workflow system

NASA Astrophysics Data System (ADS)

Memon, Shahbaz; Vallot, Dorothée; Zwinger, Thomas; Neukirchen, Helmut

2017-04-01

Scientific communities generate complex simulations through orchestration of semi-structured analysis pipelines which involves execution of large workflows on multiple, distributed and heterogeneous computing and data resources. Modeling ice dynamics of glaciers requires workflows consisting of many non-trivial, computationally expensive processing tasks which are coupled to each other. From this domain, we present an e-Science use case, a workflow, which requires the execution of a continuum ice flow model and a discrete element based calving model in an iterative manner. Apart from the execution, this workflow also contains data format conversion tasks that support the execution of ice flow and calving by means of transition through sequential, nested and iterative steps. Thus, the management and monitoring of all the processing tasks including data management and transfer of the workflow model becomes more complex. From the implementation perspective, this workflow model was initially developed on a set of scripts using static data input and output references. In the course of application usage when more scripts or modifications introduced as per user requirements, the debugging and validation of results were more cumbersome to achieve. To address these problems, we identified a need to have a high-level scientific workflow tool through which all the above mentioned processes can be achieved in an efficient and usable manner. We decided to make use of the e-Science middleware UNICORE (Uniform Interface to Computing Resources) that allows seamless and automated access to different heterogenous and distributed resources which is supported by a scientific workflow engine. Based on this, we developed a high-level scientific workflow model for coupling of massively parallel High-Performance Computing (HPC) jobs: a continuum ice sheet model (Elmer/Ice) and a discrete element calving and crevassing model (HiDEM). In our talk we present how the use of a high-level scientific workflow middleware enables reproducibility of results more convenient and also provides a reusable and portable workflow template that can be deployed across different computing infrastructures. Acknowledgements This work was kindly supported by NordForsk as part of the Nordic Center of Excellence (NCoE) eSTICC (eScience Tools for Investigating Climate Change at High Northern Latitudes) and the Top-level Research Initiative NCoE SVALI (Stability and Variation of Arctic Land Ice).

Probing Individual Ice Nucleation Events with Environmental Scanning Electron Microscopy

NASA Astrophysics Data System (ADS)

Wang, Bingbing; China, Swarup; Knopf, Daniel; Gilles, Mary; Laskin, Alexander

2016-04-01

Heterogeneous ice nucleation is one of the processes of critical relevance to a range of topics in the fundamental and the applied science and technologies. Heterogeneous ice nucleation initiated by particles proceeds where microscopic properties of particle surfaces essentially control nucleation mechanisms. Ice nucleation in the atmosphere on particles governs the formation of ice and mixed phase clouds, which in turn influence the Earth's radiative budget and climate. Heterogeneous ice nucleation is still insufficiently understood and poses significant challenges in predictive understanding of climate change. We present a novel microscopy platform allowing observation of individual ice nucleation events at temperature range of 193-273 K and relative humidity relevant for ice formation in the atmospheric clouds. The approach utilizes a home built novel ice nucleation cell interfaced with Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system is applied for direct observation of individual ice formation events, determining ice nucleation mechanisms, freezing temperatures, and relative humidity onsets. Reported microanalysis of the ice nucleating particles (INP) include elemental composition detected by the energy dispersed analysis of X-rays (EDX), and advanced speciation of the organic content in particles using scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The performance of the IN-ESEM system is validated through a set of experiments with kaolinite particles with known ice nucleation propensity. We demonstrate an application of the IN-ESEM system to identify and characterize individual INP within a complex mixture of ambient particles.

Relative influences of the metocean forcings on the drifting ice pack and estimation of internal ice stress gradients in the Labrador Sea

NASA Astrophysics Data System (ADS)

Turnbull, I. D.; Torbati, R. Z.; Taylor, R. S.

2017-07-01

Understanding the relative influences of the metocean forcings on the drift of sea ice floes is a crucial component to the overall characterization of an ice environment and to developing an understanding of the factors controlling the ice dynamics. In addition, estimating the magnitude of the internal stress gradients on drifting sea ice floes generated by surrounding ice cover is important for modeling operations, informing the design of offshore structures and vessels in ice environments, and for the proper calibration of Discrete Element Models (DEM) of fields of drifting ice floes. In the spring of 2015 and 2016, four sea ice floes offshore Makkovik, Labrador were tagged with satellite-linked ice tracking buoys along with one satellite-linked weather station on each floe to transmit wind speed and direction. Twenty satellite-linked Lagrangian surface ocean current tracking buoys were also deployed in the open water adjacent to the targeted ice floes. In this paper, the dynamics of the four ice floes are explored in terms of the relative proportions which were forced by the wind, current, sea surface topography, Coriolis, and internal stress gradients. The internal ice stress gradients are calculated as residuals between the observed accelerations of the floes as measured by the tracking buoys and the sums of the other metocean forcings. Results show that internal ice stress gradients accounted for up to 50% of the observed forcing on the floes, and may have reached up to around 0.19 kPa.

Spatial-temporal light modulation by a liquid crystal-polymer photoconductor structure with conjugate bonds

NASA Astrophysics Data System (ADS)

Sliusar', A. V.; Myl'Nikov, V. S.

1991-11-01

A method is proposed for the spatial-temporal modulation of light by a polymer photoconductor-liquid crystal structure using conjugate-bond organic polymers as photosensitive elements. The preparation of such structures and their modulation characteristics are described. It is shown that the spectral absorption and photosensitivity characteristics of the structures are largely determined by the heat treament of the polymer film. Sensitivity limits of a modulator using a polyacrylonitrile film are 5 x 10 exp -6 J/sq cm and 5 x 10 exp -4 W/sq cm for the write and read light, respectively.

Facile rhenium-peptide conjugate synthesis using a one-pot derived Re(CO)3 reagent.

PubMed

Chanawanno, Kullapa; Kondeti, Vinay; Caporoso, Joel; Paruchuri, Sailaja; Leeper, Thomas C; Herrick, Richard S; Ziegler, Christopher J

2016-03-21

We have synthesized two Re(CO)3-modified lysine complexes (1 and 2), where the metal is attached to the amino acid at the Nε position, via a one-pot Schiff base formation reaction. These compounds can be used in the solid phase synthesis of peptides, and to date we have produced four conjugate systems incorporating neurotensin, bombesin, leutenizing hormone releasing hormone, and a nuclear localization sequence. We observed uptake into human umbilical vascular endothelial cells as well as differential uptake depending on peptide sequence identity, as characterized by fluorescence and rhenium elemental analysis.

Real-space observation of magnetic excitations and avalanche behavior in artificial quasicrystal lattices

DOE PAGES

Brajuskovic, V.; Barrows, F.; Phatak, C.; ...

2016-10-03

Artificial spin ice lattices have emerged as model systems for studying magnetic frustration in recent years. Most work to date has looked at periodic artificial spin ice lattices. In this paper, we observe frustration effects in quasicrystal artificial spin ice lattices that lack translational symmetry and contain vertices with different numbers of interacting elements. We find that as the lattice state changes following demagnetizing and annealing, specific vertex motifs retain low-energy configurations, which excites other motifs into higher energy configurations. In addition, we find that unlike the magnetization reversal process for periodic artificial spin ice lattices, which occurs through 1Dmore » avalanches, quasicrystal lattices undergo reversal through a dendritic 2D avalanche mechanism.« less

Real-space observation of magnetic excitations and avalanche behavior in artificial quasicrystal lattices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brajuskovic, V.; Barrows, F.; Phatak, C.

Artificial spin ice lattices have emerged as model systems for studying magnetic frustration in recent years. Most work to date has looked at periodic artificial spin ice lattices. In this paper, we observe frustration effects in quasicrystal artificial spin ice lattices that lack translational symmetry and contain vertices with different numbers of interacting elements. We find that as the lattice state changes following demagnetizing and annealing, specific vertex motifs retain low-energy configurations, which excites other motifs into higher energy configurations. In addition, we find that unlike the magnetization reversal process for periodic artificial spin ice lattices, which occurs through 1Dmore » avalanches, quasicrystal lattices undergo reversal through a dendritic 2D avalanche mechanism.« less

Contrasts in Sea Ice Deformation and Production in the Arctic Seasonal and Perennial Ice Zones

NASA Technical Reports Server (NTRS)

Kwok, K.

2006-01-01

Four years (1997-2000) of RADARSAT Geophysical Processor System (RGPS) data are used to contrast the sea ice deformation and production regionally, and in the seasonal (SIZ) and perennial (PIZ) ice zones. Ice production is of seasonal ice in openings during the winter. Three-day estimates of these quantities are provided within Lagrangian elements initially 10 km on a side. A distinct seasonal cycle is seen in both zones with these estimates highest in the late fall and with seasonal minimums in the midwinter. Regional divergence over the winter could be up to 30%. Spatially, the highest deformation is seen in the SIZ north of coastal Alaska. Both ice deformation and production are higher in the SIZ: deformation-related ice production in the SIZ (approx.0.5 m) is 1.5-2.3 times that of the PIZ (approx.0.3 m): this is connected to ice strength and thickness. Atmospheric forcing and boundary layer structure contribute to only the seasonal and interannual variability. Seasonal ice growth in ice fractures accounts for approx.25-40% of the total ice production of the Arctic Ocean. Uncertainties in these estimates are discussed. By itself, this deformation-ice production relationship could be considered a negative feedback when thickness is perturbed. However, the overall effect on ice production in the face of increasing seasonal and thinner/weaker ice coverage could be modified by local destabilization of the water column promoting overturning of warmer water due to increased brine rejection; and the upwelling of the pynocline associated with increased occurrence of large shear motion in sea ice. Divergence is shown to be negligibly correlated to cyclonic motion in summer and winter in both ice zones.

Towards a Highly Efficient Meshfree Simulation of Non-Newtonian Free Surface Ice Flow: Application to the Haut Glacier d'Arolla

NASA Astrophysics Data System (ADS)

Shcherbakov, V.; Ahlkrona, J.

2016-12-01

In this work we develop a highly efficient meshfree approach to ice sheet modeling. Traditionally mesh based methods such as finite element methods are employed to simulate glacier and ice sheet dynamics. These methods are mature and well developed. However, despite of numerous advantages these methods suffer from some drawbacks such as necessity to remesh the computational domain every time it changes its shape, which significantly complicates the implementation on moving domains, or a costly assembly procedure for nonlinear problems. We introduce a novel meshfree approach that frees us from all these issues. The approach is built upon a radial basis function (RBF) method that, thanks to its meshfree nature, allows for an efficient handling of moving margins and free ice surface. RBF methods are also accurate and easy to implement. Since the formulation is stated in strong form it allows for a substantial reduction of the computational cost associated with the linear system assembly inside the nonlinear solver. We implement a global RBF method that defines an approximation on the entire computational domain. This method exhibits high accuracy properties. However, it suffers from a disadvantage that the coefficient matrix is dense, and therefore the computational efficiency decreases. In order to overcome this issue we also implement a localized RBF method that rests upon a partition of unity approach to subdivide the domain into several smaller subdomains. The radial basis function partition of unity method (RBF-PUM) inherits high approximation characteristics form the global RBF method while resulting in a sparse system of equations, which essentially increases the computational efficiency. To demonstrate the usefulness of the RBF methods we model the velocity field of ice flow in the Haut Glacier d'Arolla. We assume that the flow is governed by the nonlinear Blatter-Pattyn equations. We test the methods for different basal conditions and for a free moving surface. Both RBF methods are compared with a classical finite element method in terms of accuracy and efficiency. We find that the RBF methods are more efficient than the finite element method and well suited for ice dynamics modeling, especially the partition of unity approach.

The Icebreaker Life Mission to Mars: A Search for Biomolecular Evidence for Life

NASA Technical Reports Server (NTRS)

Mckay, Christopher P.; Stoker, Carol R.; Glass, Brian J.; Dave, Arwen I.; Davila, Alfonso F.; Heldmann, Jennifer L.; Marinova, Margarita M.; Fairen, Alberto G; Quinn, Richard C; Zacny, Kris A.;

The Icebreaker Life Mission to Mars: a search for biomolecular evidence for life.

PubMed

McKay, Christopher P; Stoker, Carol R; Glass, Brian J; Davé, Arwen I; Davila, Alfonso F; Heldmann, Jennifer L; Marinova, Margarita M; Fairen, Alberto G; Quinn, Richard C; Zacny, Kris A; Paulsen, Gale; Smith, Peter H; Parro, Victor; Andersen, Dale T; Hecht, Michael H; Lacelle, Denis; Pollard, Wayne H

2013-04-01

The search for evidence of life on Mars is the primary motivation for the exploration of that planet. The results from previous missions, and the Phoenix mission in particular, indicate that the ice-cemented ground in the north polar plains is likely to be the most recently habitable place that is currently known on Mars. The near-surface ice likely provided adequate water activity during periods of high obliquity, ≈ 5 Myr ago. Carbon dioxide and nitrogen are present in the atmosphere, and nitrates may be present in the soil. Perchlorate in the soil together with iron in basaltic rock provides a possible energy source for life. Furthermore, the presence of organics must once again be considered, as the results of the Viking GCMS are now suspect given the discovery of the thermally reactive perchlorate. Ground ice may provide a way to preserve organic molecules for extended periods of time, especially organic biomarkers. The Mars Icebreaker Life mission focuses on the following science goals: (1) Search for specific biomolecules that would be conclusive evidence of life. (2) Perform a general search for organic molecules in the ground ice. (3) Determine the processes of ground ice formation and the role of liquid water. (4) Understand the mechanical properties of the martian polar ice-cemented soil. (5) Assess the recent habitability of the environment with respect to required elements to support life, energy sources, and possible toxic elements. (6) Compare the elemental composition of the northern plains with midlatitude sites. The Icebreaker Life payload has been designed around the Phoenix spacecraft and is targeted to a site near the Phoenix landing site. However, the Icebreaker payload could be supported on other Mars landing systems. Preliminary studies of the SpaceX Dragon lander show that it could support the Icebreaker payload for a landing either at the Phoenix site or at midlatitudes. Duplicate samples could be cached as a target for possible return by a Mars Sample Return mission. If the samples were shown to contain organic biomarkers, interest in returning them to Earth would be high.

Ice-Release and Erosion Resistant Materials for Wind Turbines

NASA Astrophysics Data System (ADS)

Zhang, Wei; Brinn, Cameron; Cook, Alex; Pascual-Marquez, Fernando

2017-11-01

Icing conditions may cause wind turbine generators to partially lose productivity or to be completely shut down to avoid structural damage. At present, commercially available technologies to mitigate this problem consist of expensive, energy hungry heating elements, which costs roughly 70,000 euro per medium size turbine. Conventional passive ice protection coating systems heavily rely on delicate surface structures and expensive materials to create water repellent superhydrophobic / low surface energy surfaces, which have been proven to be ineffective against ice accumulation. The lack of performance among conventional ice protection materials stems from a flaw in the approach to the problem: failure to recognize that water in its liquid form (WATER) and water in its solid form (ICE) are two different things. Something that works for WATER does not automatically work for ICE. Another reason is that many superhydrophobic materials are often reliant upon often fragile micro-structured surfaces to achieve their intended effects. This paper discusses a fundamentally different approach to the creation of a robust, low cost, durable, and multifunctional materials for ice release and erosion resistance. This National Science Foundation sponsored ice-release coating technology holds promise for protecting wind turbine blades and towers, thus potentially increasing reliability for power generation under icing conditions. Because of the vulnerability of wind turbine blades to ice buildup and erosion damages, wind farm facilities stand to reap considerable benefits.

Numerical modeling of runback water on ice protected aircraft surfaces

NASA Technical Reports Server (NTRS)

Al-Khalil, Kamel M.; Keith, Theo G., Jr.; Dewitt, Kenneth J.

1992-01-01

A numerical simulation for 'running wet' aircraft anti-icing systems is developed. The model includes breakup of the water film, which exists in regions of direct impingement, into individual rivulets. The wetness factor distribution resulting from the film breakup and the rivulet configuration on the surface are predicted in the numerical solution procedure. The solid wall is modeled as a multilayer structure and the anti-icing system used is of the thermal type utilizing hot air and/or electrical heating elements embedded with the layers. Details of the calculation procedure and the methods used are presented.

The Population Biology of Bacterial Plasmids: A PRIORI Conditions for the Existence of Conjugationally Transmitted Factors

PubMed Central

Stewart, Frank M.; Levin, Bruce R.

1977-01-01

A mathematical model for the population dynamics of conjugationally transmitted plasmids in bacterial populations is presented and its properties analyzed. Consideration is given to nonbacteriocinogenic factors that are incapable of incorporation into the chromosome of their host cells, and to bacterial populations maintained in either continuous (chemostat) or discrete (serial transfer) culture. The conditions for the establishment and maintenance of these infectious extrachromosomal elements and equilibrium frequencies of cells carrying them are presented for different values of the biological parameters: population growth functions, conjugational transfer and segregation rate constants. With these parameters in a biologically realistic range, the theory predicts a broad set of physical conditions, resource concentrations and dilution rates, where conjugationally transmitted plasmids can become established and where cells carrying them will maintain high frequencies in bacterial populations. This can occur even when plasmid-bearing cells are much less fit (i.e., have substantially lower growth rates) than cells free of these factors. The implications of these results and the reality and limitations of the model are discussed and the values of its parameters in natural populations speculated upon. PMID:17248761

Improving the in vivo therapeutic index of siRNA polymer conjugates through increasing pH responsiveness.

PubMed

Guidry, Erin N; Farand, Julie; Soheili, Arash; Parish, Craig A; Kevin, Nancy J; Pipik, Brenda; Calati, Kathleen B; Ikemoto, Nori; Waldman, Jacob H; Latham, Andrew H; Howell, Bonnie J; Leone, Anthony; Garbaccio, Robert M; Barrett, Stephanie E; Parmar, Rubina Giare; Truong, Quang T; Mao, Bing; Davies, Ian W; Colletti, Steven L; Sepp-Lorenzino, Laura

2014-02-19

Polymer based carriers that aid in endosomal escape have proven to be efficacious siRNA delivery agents in vitro and in vivo; however, most suffer from cytotoxicity due in part to a lack of selectivity for endosomal versus cell membrane lysis. For polymer based carriers to move beyond the laboratory and into the clinic, it is critical to find carriers that are not only efficacious, but also have margins that are clinically relevant. In this paper we report three distinct categories of polymer conjugates that improve the selectivity of endosomal membrane lysis by relying on the change in pH associated with endosomal trafficking, including incorporation of low pKa heterocycles, acid cleavable amino side chains, or carboxylic acid pH sensitive charge switches. Additionally, we determine the therapeutic index of our polymer conjugates in vivo and demonstrate that the incorporation of pH responsive elements dramatically expands the therapeutic index to 10-15, beyond that of the therapeutic index (less than 3), for polymer conjugates previously reported.

Incorporating fluorinated moieties in fully conjugated donor-acceptor block copolymers

NASA Astrophysics Data System (ADS)

Lee, Youngmin; Wang, Qing; Gomez, Enrique D.

Fully conjugated donor-acceptor block copolymers are promising candidates for photovoltaics due to their ability to microphase separate at length scales commensurate with exciton diffusion lengths. These materials can also serve as model systems to study the relationship between molecular structure, microstructure, and optoelectronic properties of conjugated polymers. The development of new donor-acceptor block copolymers relies on the manipulation of the chemical structure to fine tune properties and improve overall performance when employed in photovoltaic devices. To this end, we have demonstrated the incorporation of fluorinated moieties in conjugated block copolymers. The introduction of fluorine, a strong electron withdrawing element, is known to influence phase separation and the bandgap, and as a result, optoelectronic properties. Fluorine was introduced to the acceptor block of poly(3-hexylthiophene-2,5-diyl)-block-poly((9,9-bis(2-octyl)fluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5 ',5?-diyl) (P3HT- b-PFTBT). PFTBTs were prepared with di-fluorinated and mono-fluorinated TBT. We find that fluorination impacts the bandgap, morphology and performance in devices.

A multi-conjugate adaptive optics testbed using two MEMS deformable mirrors

NASA Astrophysics Data System (ADS)

Andrews, Jonathan R.; Martinez, Ty; Teare, Scott W.; Restaino, Sergio R.; Wilcox, Christopher C.; Santiago, Freddie; Payne, Don M.

2011-03-01

Adaptive optics (AO) systems are well demonstrated in the literature with both laboratory and real-world systems being developed. Some of these systems have employed MEMS deformable mirrors as their active corrective element. More recent work in AO for astronomical applications has focused on providing correction in more than one conjugate plane. Additionally, horizontal path AO systems are exploring correction in multiple conjugate planes. This provides challenges for a laboratory system as the aberrations need to be generated and corrected in more than one plane in the optical system. Our work with compact AO systems employing MEMS technology in addition to liquid crystal spatial light modulator (SLM) driven aberration generators has been scaled up to a two conjugate plane testbed. Using two SLM based aberration generators and two separate wavefront sensors, the system can apply correction with two MEMS deformable mirrors. The challenges in such a system are to properly match non-identical components and weight the correction algorithm for correcting in two planes. This paper demonstrates preliminary results and analysis with this system with wavefront data and residual error measurements.

Design, Synthesis, and Pharmacokinetics of a Bone-Targeting Dual-Action Prodrug for the Treatment of Osteoporosis.

PubMed

Xie, Haibo; Chen, Gang; Young, Robert N

2017-08-24

A dual-action bone-targeting prodrug has been designed, synthesized, and evaluated for in vitro and in vivo metabolic stability, in vivo tissue distribution, and rates of release of the active constituents after binding to bones through the use of differentially double-labeled derivatives. The conjugate (general structure 7) embodies the merger of a very potent and proven anabolic selective agonist of the prostaglandin EP4 receptor, compound 5, and alendronic acid, a potent inhibitor of bone resorption, optimally linked through a differentially hydrolyzable linker unit, N-4-carboxymethylphenyl-methyloxycarbonyl-leucinyl-argininyl-para-aminophenylmethylalcohol (Leu-Arg-PABA). Optimized conjugate 16 was designed so that esterase activity will liberate 5 and cathepsin K cleavage of the Leu-Arg-PABA element will liberate alendronic acid. Studies with doubly radiolabeled 16 provide a proof-of-concept for the use of a cathepsin K cleavable peptide-linked conjugate for targeting of bisphosphonate prodrugs to bone and slow release liberation of the active constituents in vivo. Such conjugates are potential therapies for the treatment of bone disorders such as osteoporosis.

Analyses and tests for design of an electro-impulse de-icing system

NASA Technical Reports Server (NTRS)

Zumwalt, G. W.; Schrag, R. L.; Bernhart, W. D.; Friedberg, R. A.

1985-01-01

De-icing of aircraft by using the electro-magnetic impulse phenomenon was proposed and demonstrated in several European countries. However, it is not available as a developed system due to lack of research on the basic physical mechanisms and necessary design parameters. The de-icing is accomplished by rapidly discharging high voltage capacitors into a wire coil rigidly supported just inside the aircraft skin. Induced eddy currents in the skin create a repulsive force resulting in a hammer-like force which cracks, de-bonds, and expels ice on the skin surface. The promised advantages are very low energy, high reliability of de-icing, and low maintenance. Three years of Electo-Impulse De-icing (EIDI) research is summarized and the analytical studies and results of testing done in the laboratory, in the NASA Icing Research Tunnel, and in flight are presented. If properly designed, EIDI was demonstrated to be an effective and practical ice protection system for small aircraft, turbojet engine inlets, elements of transport aircraft, and shows promise for use on helicopter rotor blades. Included are practical techniques of fabrication of impulse coils and their mountings. The use of EIDI with nonmetallic surface materials is also described.

Grounding line dynamics inferred from a 3D full-Stokes model solving the contact problem

NASA Astrophysics Data System (ADS)

Favier, Lionel; Gagliardini, Olivier; Durand, Gael; Zwinger, Thomas

2010-05-01

The mass balance of marine ice-sheets, such as the West Antarctic Ice Sheet, is mostly controlled by their grounding line dynamics. Most numerical models simulating marine ice-sheets involve simplifications and do not include all the stress gradients. First results obtained with a 3D full-Stokes model for the grounded ice-sheet / floating ice-shelf transition, using the finite-element code Elmer/Ice, are presented. The initial geometry, which takes into account a dome and a calving front, has been laterally extruded from a previously investigated 2D flowline geometry. The grounding line migration is computed by solving the contact problem between the ice and the rigid downward sloping bedrock, where a non linear friction law is applied in the two horizontal directions. The evolutions of the sea-air and sea-ice interfaces are determined by the solution of a local transport equation. The consistency between the 3D model and the analogous results of the flowline model is shown by comparing the results in the basic extruded case, with no normal flux through lateral boundaries. Thereafter, spatially non uniform perturbations are introduced, to simulate the grounding line dynamics under fully three-dimensional perturbations.

Effect of Ice-Shell Thickness Variations on the Tidal Deformation of Enceladus

NASA Astrophysics Data System (ADS)

Choblet, G.; Cadek, O.; Behounkova, M.; Tobie, G.; Kozubek, T.

2015-12-01

Recent analysis of Enceladus's gravity and topography has suggested that the thickness of the ice shell significantly varies laterally - from 30-40 km in the south polar region to 60 km elsewhere. These variations may influence the activity of the geysers and increase the tidal heat production in regions where the ice shell is thinned. Using a model including a regional or global subsurface ocean and Maxwell viscoelasticity, we investigate the impact of these variations on the tidal deformation of the moon and its heat production. For that purpose, we use different numerical approaches - finite elements, local application of 1d spectral method, and a generalized spectral method. Results obtained with these three approaches for various models of ice-shell thickness variations are presented and compared. Implications of a reduced ice shell thickness for the south polar terrain activity are discussed.

Measurement of the Critical Distance Parameter Against Icing Conditions on a NACA 0012 Swept Wing Tip

NASA Technical Reports Server (NTRS)

Vargas, Mario; Kreeger, Richard E.

2011-01-01

This work presents the results of three experiments, one conducted in the Icing Research Tunnel (IRT) at NASA Glenn Research Center and two in the Goodrich Icing Wind Tunnel (IWT). The experiments were designed to measure the critical distance parameter on a NACA 0012 Swept Wing Tip at sweep angles of 45deg, 30deg, and 15deg. A time sequence imaging technique (TSIT) was used to obtain real time close-up imaging data during the first 2 min of the ice accretion formation. The time sequence photographic data was used to measure the critical distance at each icing condition and to study how it develops in real time. The effect on the critical distance of liquid water content, drop size, total temperature, and velocity was studied. The results were interpreted using a simple energy balance on a roughness element

Modelling water flow under glaciers and ice sheets.

PubMed

Flowers, Gwenn E

2015-04-08

Recent observations of dynamic water systems beneath the Greenland and Antarctic ice sheets have sparked renewed interest in modelling subglacial drainage. The foundations of today's models were laid decades ago, inspired by measurements from mountain glaciers, discovery of the modern ice streams and the study of landscapes evacuated by former ice sheets. Models have progressed from strict adherence to the principles of groundwater flow, to the incorporation of flow 'elements' specific to the subglacial environment, to sophisticated two-dimensional representations of interacting distributed and channelized drainage. Although presently in a state of rapid development, subglacial drainage models, when coupled to models of ice flow, are now able to reproduce many of the canonical phenomena that characterize this coupled system. Model calibration remains generally out of reach, whereas widespread application of these models to large problems and real geometries awaits the next level of development.

On Spaces of Commuting Elements in Lie Groups

DTIC Science & Technology

2014-02-25

G given by θ(g, t) = gtg −1 = tg, with more details given in Section 2. Definition 1.6. Define Θ : G×NT Assoc(T )→ Comm(G) by the formula Θ(g, (t1...conjugation θn : G× Tn → Hom(Zn, G)1G g × (t1, . . . , tn) 7→ (tg1, . . . , tgn), ON SPACES OF COMMUTING ELEMENTS IN LIE GROUPS 11 where tg = gtg −1. An n

New methods for measuring atmospheric heavy noble gas isotope and elemental ratios in ice core samples.

PubMed

Bereiter, Bernhard; Kawamura, Kenji; Severinghaus, Jeffrey P

2018-05-30

The global ocean constitutes the largest heat buffer in the global climate system, but little is known about its past changes. The isotopic and elemental ratios of heavy noble gases (krypton and xenon), together with argon and nitrogen in trapped air from ice cores, can be used to reconstruct past mean ocean temperatures (MOTs). Here we introduce two successively developed methods to measure these parameters with a sufficient precision to provide new constraints on past changes in MOT. The air from an 800-g ice sample - containing roughly 80 mL STP air - is extracted and processed to be analyzed on two independent dual-inlet isotope ratio mass spectrometers. The primary isotope ratios (δ 15 N, δ 40 Ar and δ 86 Kr values) are obtained with precisions in the range of 1 per meg (0.001‰) per mass unit. The three elemental ratio values δKr/N 2 , δXe/N 2 and δXe/Kr are obtained using sequential (non-simultaneous) peak-jumping, reaching precisions in the range of 0.1-0.3‰. The latest version of the method achieves a 30% to 50% better precision on the elemental ratios and a twofold better sample throughput than the previous one. The method development uncovered an unexpected source of artefactual gas fractionation in a closed system that is caused by adiabatic cooling and warming of gases (termed adiabatic fractionation) - a potential source of measurement artifacts in other methods. The precisions of the three elemental ratios δKr/N 2 , δXe/N 2 and δXe/Kr - which all contain the same MOT information - suggest smaller uncertainties for reconstructed MOTs (±0.3-0.1°C) than previous studies have attained. Due to different sensitivities of the noble gases to changes in MOT, δXe/N 2 provides the best constraints on the MOT under the given precisions followed by δXe/Kr, and δKr/N 2 ; however, using all of them helps to detect methodological artifacts and issues with ice quality. Copyright © 2018 John Wiley & Sons, Ltd.

WARP3D-Release 10.8: Dynamic Nonlinear Analysis of Solids using a Preconditioned Conjugate Gradient Software Architecture

NASA Technical Reports Server (NTRS)

Koppenhoefer, Kyle C.; Gullerud, Arne S.; Ruggieri, Claudio; Dodds, Robert H., Jr.; Healy, Brian E.

1998-01-01

This report describes theoretical background material and commands necessary to use the WARP3D finite element code. WARP3D is under continuing development as a research code for the solution of very large-scale, 3-D solid models subjected to static and dynamic loads. Specific features in the code oriented toward the investigation of ductile fracture in metals include a robust finite strain formulation, a general J-integral computation facility (with inertia, face loading), an element extinction facility to model crack growth, nonlinear material models including viscoplastic effects, and the Gurson-Tver-gaard dilatant plasticity model for void growth. The nonlinear, dynamic equilibrium equations are solved using an incremental-iterative, implicit formulation with full Newton iterations to eliminate residual nodal forces. The history integration of the nonlinear equations of motion is accomplished with Newmarks Beta method. A central feature of WARP3D involves the use of a linear-preconditioned conjugate gradient (LPCG) solver implemented in an element-by-element format to replace a conventional direct linear equation solver. This software architecture dramatically reduces both the memory requirements and CPU time for very large, nonlinear solid models since formation of the assembled (dynamic) stiffness matrix is avoided. Analyses thus exhibit the numerical stability for large time (load) steps provided by the implicit formulation coupled with the low memory requirements characteristic of an explicit code. In addition to the much lower memory requirements of the LPCG solver, the CPU time required for solution of the linear equations during each Newton iteration is generally one-half or less of the CPU time required for a traditional direct solver. All other computational aspects of the code (element stiffnesses, element strains, stress updating, element internal forces) are implemented in the element-by- element, blocked architecture. This greatly improves vectorization of the code on uni-processor hardware and enables straightforward parallel-vector processing of element blocks on multi-processor hardware.

Examination of Surface Roughness on Light Scattering by Long Ice Columns by Use of a Two-Dimensional Finite-Difference Time-Domain Algorithm

NASA Technical Reports Server (NTRS)

Sun, W.; Loeb, N. G.; Videen, G.; Fu, Q.

2004-01-01

Natural particles such as ice crystals in cirrus clouds generally are not pristine but have additional micro-roughness on their surfaces. A two-dimensional finite-difference time-domain (FDTD) program with a perfectly matched layer absorbing boundary condition is developed to calculate the effect of surface roughness on light scattering by long ice columns. When we use a spatial cell size of 1/120 incident wavelength for ice circular cylinders with size parameters of 6 and 24 at wavelengths of 0.55 and 10.8 mum, respectively, the errors in the FDTD results in the extinction, scattering, and absorption efficiencies are smaller than similar to 0.5%. The errors in the FDTD results in the asymmetry factor are smaller than similar to 0.05%. The errors in the FDTD results in the phase-matrix elements are smaller than similar to 5%. By adding a pseudorandom change as great as 10% of the radius of a cylinder, we calculate the scattering properties of randomly oriented rough-surfaced ice columns. We conclude that, although the effect of small surface roughness on light scattering is negligible, the scattering phase-matrix elements change significantly for particles with large surface roughness. The roughness on the particle surface can make the conventional phase function smooth. The most significant effect of the surface roughness is the decay of polarization of the scattered light.

Fiber bundle phase conjugate mirror

DOEpatents

Ward, Benjamin G.

2012-05-01

An improved method and apparatus for passively conjugating the phases of a distorted wavefronts resulting from optical phase mismatch between elements of a fiber laser array are disclosed. A method for passively conjugating a distorted wavefront comprises the steps of: multiplexing a plurality of probe fibers and a bundle pump fiber in a fiber bundle array; passing the multiplexed output from the fiber bundle array through a collimating lens and into one portion of a non-linear medium; passing the output from a pump collection fiber through a focusing lens and into another portion of the non-linear medium so that the output from the pump collection fiber mixes with the multiplexed output from the fiber bundle; adjusting one or more degrees of freedom of one or more of the fiber bundle array, the collimating lens, the focusing lens, the non-linear medium, or the pump collection fiber to produce a standing wave in the non-linear medium.

Development of the Next Generation of Seismological Instrumentation for Polar Environments

NASA Astrophysics Data System (ADS)

Winberry, J. P.; Anderson, K. R.; Huerta, A. D.; Bernsen, S. P.; Parker, T.; Carpenter, P.; Woodward, R.; Beaudoin, B. C.; Bilek, S. L.

2014-12-01

Ice covered regions comprise >10% of Earth's continental area; and include regions with poorly understood ice dynamics, ice shelf stability, hydrology, tectonic histories and basic geologic structure both deep and shallow. Scientific investigations of these regions are challenged by extreme weather, limited and expensive logistics, and the physical conditions of the ice environment. We report on the next development of a new NSF MRI-supported community seismic capability for studying ice-covered regions- the Geophysical Earth Observatory for Ice Covered Environments (GEOICE). This project is fundamentally motivated by the need to densify and optimize the collection of high-quality data relevant to key solid Earth and cryosphere science questions. The instrument capability will include a hybrid seismograph pool of broadband and intermediate elements, for observation of both long-period (e.g., long-period surface waves and slow sources) and intermediate-to-short-period (e.g., teleseismic body waves local seismicity, impulsive or extended glaciogenic signals). The GEOICE instrument, and its power and other ancillary systems, will be specifically designed to both withstand conditions associated with icy environments, including cold/wet conditions and high-latitude solar limitations, and to require minimal installation time and logistical load (i.e., size and weight), while maximizing ease-of-use in the field, in data handling, and in telemetry compatibility. Key features will include a design that integrates the seismometer and data logger into a single environmentally and mechanically robust housing, very low power requirements (<~1 watt) for the intermediate-band systems, and advanced power/battery systems that optimize battery capacity and operational limits. The envisioned ~125 element GEOICE instruments will nearly double the current polar inventory of stations and will be maintained and supported at the IRIS PASSCAL Instrument Center to ensure full and flexible peer-reviewed community use.

Evaluating Ice Nucleating Particle Concentrations From Prognostic Dust Minerals in an Earth System Model

NASA Astrophysics Data System (ADS)

Perlwitz, J. P.; Knopf, D. A.; Fridlind, A. M.; Miller, R. L.; Pérez García-Pando, C.; DeMott, P. J.

2016-12-01

The effect of aerosol particles on the radiative properties of clouds, the so-called, indirect effect of aerosols, is recognized as one of the largest sources of uncertainty in climate prediction. The distribution of water vapor, precipitation, and ice cloud formation are influenced by the atmospheric ice formation, thereby modulating cloud albedo and thus climate. It is well known that different particle types possess different ice formation propensities with mineral dust being a superior ice nucleating particle (INP) compared to soot particles. Furthermore, some dust mineral types are more proficient INP than others, depending on temperature and relative humidity.In recent work, we have presented an improved dust aerosol module in the NASA GISS Earth System ModelE2 with prognostic mineral composition of the dust aerosols. Thus, there are regional variations in dust composition. We evaluated the predicted mineral fractions of dust aerosols by comparing them to measurements from a compilation of about 60 published literature references. Additionally, the capability of the model to reproduce the elemental composition of the simulated dusthas been tested at Izana Observatory at Tenerife, Canary Islands, which is located off-shore of Africa and where frequent dust events are observed. We have been able to show that the new approach delivers a robust improvement of the predicted mineral fractions and elemental composition of dust.In the current study, we use three-dimensional dust mineral fields and thermodynamic conditions, which are simulated using GISS ModelE, to calculate offline the INP concentrations derived using different ice nucleation parameterizations that are currently discussed. We evaluate the calculated INP concentrations from the different parameterizations by comparing them to INP concentrations from field measurements.

ICEG2D (v2.0) - An Integrated Software Package for Automated Prediction of Flow Fields for Single-Element Airfoils With Ice Accretion

NASA Technical Reports Server (NTRS)

Thompson David S.; Soni, Bharat K.

2001-01-01

An integrated geometry/grid/simulation software package, ICEG2D, is being developed to automate computational fluid dynamics (CFD) simulations for single- and multi-element airfoils with ice accretions. The current version, ICEG213 (v2.0), was designed to automatically perform four primary functions: (1) generate a grid-ready surface definition based on the geometrical characteristics of the iced airfoil surface, (2) generate high-quality structured and generalized grids starting from a defined surface definition, (3) generate the input and restart files needed to run the structured grid CFD solver NPARC or the generalized grid CFD solver HYBFL2D, and (4) using the flow solutions, generate solution-adaptive grids. ICEG2D (v2.0) can be operated in either a batch mode using a script file or in an interactive mode by entering directives from a command line within a Unix shell. This report summarizes activities completed in the first two years of a three-year research and development program to address automation issues related to CFD simulations for airfoils with ice accretions. As well as describing the technology employed in the software, this document serves as a users manual providing installation and operating instructions. An evaluation of the software is also presented.

Fram Strait: Atmospheric Forcing of The Sea Ice Flux

NASA Astrophysics Data System (ADS)

Widell, K.; Østerhus, S.; Gammelsrød, T.

Measuring the magnitude and variability of the ice and freshwater flux through Fram Strait is an important element in understanding climate variability in the Arctic. Since the major part of the ice and freshwater that leaves the Arctic passes through Fram Strait, this passage can be considered a key area for estimating the net ice production in the Arctic Ocean. In 1990, the Norwegian Polar Institute (NPI) started a monitoring program in the strait, most years by means of two moorings with Upward Looking Sonars (ULS) measuring ice draft. From 1995 and on, these moorings were also equipped with Doppler Current Meters (DCM) to measure the ice velocity. These measurements give an opportunity to investigate the different forces affecting ice motion in the strait. Maximum correlation coefficient between atmospheric sea level pressure (from NCEP/NCAR reanalysed data) and southward ice velocity is found when using the cross strait pressure difference along 80N between 10W and 5E (R = 0.72) consider- ing monthly means. Subtracting current velocity at 50 m depth (also measured by the DCM) from ice velocity improves the correlation to R = 0.84. This gives insight in the relative importance of current and wind on the ice motion, and indicates that pressure data can be used to make fairly good estimates of the ice velocity in the strait. In combination with data on ice thickness and ice stream width, this result is used to calculate the ice volume transport. By making assumptions on the parameters in- volved, the time series is extended back to 1948, the start of the pressure record. This time series will be presented and compared to literature, and annual and seasonal vari- ation of the ice flux will be discussed.

Capabilities and performance of Elmer/Ice, a new-generation ice sheet model

NASA Astrophysics Data System (ADS)

Gagliardini, O.; Zwinger, T.; Gillet-Chaulet, F.; Durand, G.; Favier, L.; de Fleurian, B.; Greve, R.; Malinen, M.; Martín, C.; Råback, P.; Ruokolainen, J.; Sacchettini, M.; Schäfer, M.; Seddik, H.; Thies, J.

2013-08-01

The Fourth IPCC Assessment Report concluded that ice sheet flow models, in their current state, were unable to provide accurate forecast for the increase of polar ice sheet discharge and the associated contribution to sea level rise. Since then, the glaciological community has undertaken a huge effort to develop and improve a new generation of ice flow models, and as a result a significant number of new ice sheet models have emerged. Among them is the parallel finite-element model Elmer/Ice, based on the open-source multi-physics code Elmer. It was one of the first full-Stokes models used to make projections for the evolution of the whole Greenland ice sheet for the coming two centuries. Originally developed to solve local ice flow problems of high mechanical and physical complexity, Elmer/Ice has today reached the maturity to solve larger-scale problems, earning the status of an ice sheet model. Here, we summarise almost 10 yr of development performed by different groups. Elmer/Ice solves the full-Stokes equations, for isotropic but also anisotropic ice rheology, resolves the grounding line dynamics as a contact problem, and contains various basal friction laws. Derived fields, like the age of the ice, the strain rate or stress, can also be computed. Elmer/Ice includes two recently proposed inverse methods to infer badly known parameters. Elmer is a highly parallelised code thanks to recent developments and the implementation of a block preconditioned solver for the Stokes system. In this paper, all these components are presented in detail, as well as the numerical performance of the Stokes solver and developments planned for the future.

Modeling of surface roughness effects on glaze ice accretion

NASA Technical Reports Server (NTRS)

Hansman, R. John, Jr.; Yamaguchi, Keiko; Berkowitz, Brian M.; Potapczuk, Mark

1990-01-01

A series of experimental investigations focused on studying the cause and effect of roughness on accreting glaze ice surfaces were conducted. Detailed microvideo observations were made of glaze ice accretions on 1 to 4 inch diameter cylinders in three icing wind tunnels (the Data Products of New England six inch test facility, the NASA Lewis Icing Research Tunnel, and the B. F. Goodrich Ice Protection Research Facility). Infrared thermal video recordings were made of accreting ice surfaces in the Goodrich facility. Distinct zones of surface water behavior were observed; a smooth wet zone in the stagnation region with a uniform water film; a rough zone where surface tension effects caused coalescence of surface water into stationary beads; a horn zone where roughness elements grow into horn shapes; a runback zone where surface water ran back as rivulets; and a dry zone where rime feathers formed. The location of the transition from the smooth to the rough zone was found to migrate with time towards the stagnation point. The behavior of the transition appeared to be controlled by boundary layer transition and bead formation mechanisms at the interface between the smooth and rough zones. Regions of wet ice growth and enhanced heat transfer were clearly visible in the infrared video recordings of glaze ice surfaces. A simple multi-zone modification to the current glaze ice accretion model was proposed to include spatial variability in surface roughness.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Bingbing; Knopf, Daniel A.; China, Swarup

Heterogeneous ice nucleation is a physical chemistry process of critical relevance to a range of topics in the fundamental and the applied sciences and technologies. Heterogeneous ice nucleation remains insufficiently understood. This is in part due to the lack of experimental methods capable of in situ visualization of ice formation over nucleating substrates with microscopically characterized morphology and composition. We present development, validation and first applications of a novel electron microscopy platform allowing observation of individual ice nucleation events at temperature and relative humidity (RH) relevant for ice formation in a broad range of environmental and applied technology processes. Themore » approach utilizes a custom-built ice nucleation cell, interfaced with an Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system allows dynamic observations of individual ice formation events over particles of atmospheric relevance and determination of the ice nucleation mechanisms. Additional IN-ESEM experiments allow examination of the location of ice formation on the surface of individual particles and micro-spectroscopy analysis of the ice nucleating particles (INPs). This includes elemental composition detected by the energy dispersed analysis of X-rays (EDX), speciation of the organic content in particles using scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and Helium ion microscopy (HeIM). The capabilities of the IN-ESEM experimental platform are demonstrated first on laboratory standards and then by chemical imaging of INPs using a complex sample of ambient particles.« less

Modeling the fracture of ice sheets on parallel computers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waisman, Haim; Bell, Robin; Keyes, David

2010-03-01

The objective of this project is to investigate the complex fracture of ice and understand its role within larger ice sheet simulations and global climate change. At the present time, ice fracture is not explicitly considered within ice sheet models due in part to large computational costs associated with the accurate modeling of this complex phenomena. However, fracture not only plays an extremely important role in regional behavior but also influences ice dynamics over much larger zones in ways that are currently not well understood. Dramatic illustrations of fracture-induced phenomena most notably include the recent collapse of ice shelves inmore » Antarctica (e.g. partial collapse of the Wilkins shelf in March of 2008 and the diminishing extent of the Larsen B shelf from 1998 to 2002). Other fracture examples include ice calving (fracture of icebergs) which is presently approximated in simplistic ways within ice sheet models, and the draining of supraglacial lakes through a complex network of cracks, a so called ice sheet plumbing system, that is believed to cause accelerated ice sheet flows due essentially to lubrication of the contact surface with the ground. These dramatic changes are emblematic of the ongoing change in the Earth's polar regions and highlight the important role of fracturing ice. To model ice fracture, a simulation capability will be designed centered around extended finite elements and solved by specialized multigrid methods on parallel computers. In addition, appropriate dynamic load balancing techniques will be employed to ensure an approximate equal amount of work for each processor.« less

Worldwide Emerging Environmental Issues Affecting the U.S. Military. December 2009 Report

DTIC Science & Technology

2009-12-01

serious loss of ice sheets and associated sea-level rise • Amazon rainforest ––increased weather-altering deforestation after passing a critical...scientists agree on some tipping elements that are extremely sensitive to climate shifts and therefore might have an important impact on the planetary...trigger radical changes Scientists point out that an additional important unknown element is the interaction of these and other known elements

Spin-ice behavior of three-dimensional inverse opal-like magnetic structures: Micromagnetic simulations

NASA Astrophysics Data System (ADS)

Dubitskiy, I. S.; Syromyatnikov, A. V.; Grigoryeva, N. A.; Mistonov, A. A.; Sapoletova, N. A.; Grigoriev, S. V.

2017-11-01

We perform micromagnetic simulations of the magnetization distribution in inverse opal-like structures (IOLS) made from ferromagnetic materials (nickel and cobalt). It is shown that the unit cell of these complex structures, whose characteristic length is approximately 700 nm, can be divided into a set of structural elements some of which behave like Ising-like objects. A spin-ice behavior of IOLS is observed in a broad range of external magnetic fields. Numerical results describe successfully the experimental hysteresis curves of the magnetization in Ni- and Co-based IOLS. We conclude that ferromagnetic IOLS can be considered as the first realization of three-dimensional artificial spin ice. The problem is discussed of optimal geometrical properties and material characteristics of IOLS for the spin-ice rule fulfillment.

Glaciers and ice sheets as a biome.

PubMed

Anesio, Alexandre M; Laybourn-Parry, Johanna

2012-04-01

The tundra is the coldest biome described in typical geography and biology textbooks. Within the cryosphere, there are large expanses of ice in the Antarctic, Arctic and alpine regions that are not regarded as being part of any biome. During the summer, there is significant melt on the surface of glaciers, ice caps and ice shelves, at which point microbial communities become active and play an important role in the cycling of carbon and other elements within the cryosphere. In this review, we suggest that it is time to recognise the cryosphere as one of the biomes of Earth. The cryospheric biome encompasses extreme environments and is typified by truncated food webs dominated by viruses, bacteria, protozoa and algae with distinct biogeographical structures. Copyright © 2011 Elsevier Ltd. All rights reserved.

Antibiotic Resistance-Susceptibility Profiles of Streptococcus thermophilus Isolated from Raw Milk and Genome Analysis of the Genetic Basis of Acquired Resistances

PubMed Central

Flórez, Ana B.; Mayo, Baltasar

2017-01-01

The food chain is thought to play an important role in the transmission of antibiotic resistances from commensal and beneficial bacteria to pathogens. Streptococcus thermophilus is a lactic acid bacterium of major importance as a starter for the dairy industry. This study reports the minimum inhibitory concentration (MIC) of 16 representative antimicrobial agents to 41 isolates of S. thermophilus derived from raw milk. Strains showing resistance to tetracycline (seven), erythromycin and clindamycin (two), and streptomycin and neomycin (one) were found. PCR amplification identified tet(S) in all the tetracycline-resistant strains, and ermB in the two erythromycin/clindamycin-resistant strains. Hybridisation experiments suggested each resistance gene to be located in the chromosome with a similar genetic organization. Five antibiotic-resistant strains -two resistant to tetracycline (St-2 and St-9), two resistant to erythromycin/clindamycin (St-5 and St-6), and one resistant to streptomycin/neomycin (St-10)- were subjected to genome sequencing and analysis. The tet(S) gene was identified in small contigs of 3.2 and 3.7 kbp in St-2 and St-9, respectively, flanked by truncated copies of insertion sequence (IS) elements. Similarly, ermB in St-6 and St-5 was found in contigs of 1.6 and 28.1 kbp, respectively. Sequence analysis and comparison of the largest contig showed it to contain three segments (21.9, 3.7, and 1.4 kbp long) highly homologous to non-collinear sequences of pRE25 from Enterococcus faecalis. These segments contained the ermB gene, a transference module with an origin of transfer (oriT) plus 15 open reading frames encoding proteins involved in conjugation, and modules for plasmid replication and segregation. Homologous stretches were separated by short, IS-related sequences, resembling the genetic organization of the integrative and conjugative elements (ICEs) found in Streptococcus species. No gene known to provide aminoglycoside resistance was seen in St-10. Four strain-specific amino acid substitutions in the RsmG methyltransferase were scored in this strain; these might be associated to its streptomycin/neomycin resistance. Under yogurt manufacturing and storage conditions, no transfer of either tet(S) or ermB from S. thermophilus to L. delbrueckii was detected. The present results contribute toward characterisation of the antibiotic resistance profiles in S. thermophilus, provide evidence for the genetic basis of acquired resistances and deepen on their transference capability. PMID:29312272

Dansgaard-Oeschger cycles observed in the Greenland ReCAP ice core project

NASA Astrophysics Data System (ADS)

Kjær, Helle Astrid; Vallelonga, Paul; Vinther, Bo; Simonsen, Marius; Maffezzoli, Niccoló; Gkinis, Vasileios; Svensson, Anders; Jensen, Camilla Marie; Dallmayr, Remi; Spolaor, Andrea; Edwards, Ross

2017-04-01

The new REnland ice CAP (RECAP) ice core was drilled in summer 2015 in Greenland and measured by means of Continuous flow analysis (CFA) during the last 3 months of 2015. The Renland ice core was obtained as part of the ReCAP project, extending 584.11 meters to the bottom of the Renland ice cap located in east Greenland. The unique position on a mountain saddle above 2000 meters altitude, but close to the coast, ensures that the Renland ice core offers high accumulation, but also reaches far back in time. Results show that despite the short length the RECAP ice core holds ice all the way back to the past warm interglacial period, the Eemian. The glacial section is strongly thinned and covers on 20 meters of the ReCAP core, but nonetheless due to the high resolution of the measurements all 25 expected DO events could be identified. The record was analyzed for multiple elements including the water isotopes, forest fire tracers NH4+ and black carbon, insoluble dust particles by means of Abakus laser particle counter and the dust ion Ca2+, sea salt Na+, and sea ice proxies as well as acidity useful for finding volcanic layers to date the core. Below the glacial section another 20 meters of warm Eemian ice have been analysed. Here we present the chemistry results as obtained by continuous flow analysis (CFA) and compare the glacial section with the chemistry profile from other Greenland ice cores.

Scattering Properties of Needle-Like and plate-like Ice Spheroids with Moderate Size Parameters

NASA Technical Reports Server (NTRS)

Zakharova, Nadia T.; Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

2000-01-01

We use the current advanced version of the T-matrix method to compute the optical cross sections, the asymmetry parameter of the phase function, and the scattering matrix elements of ice spheroids with aspect ratios up to 20 and surface-equivalent-sphere size parameters up to 12. We demonstrate that plate-like and needle-like particles with moderate size parameters possess unique scattering properties: their asymmetry parameters and phase functions are similar to those of surface-equivalent spheres, whereas all other elements of the scattering matrix are typical of particles much smaller than the wavelength (Rayleigh scatterers). This result may have important implications for optical particle sizing and remote sensing of the terrestrial and planetary atmospheres.

A finite element: Boundary integral method for electromagnetic scattering. Ph.D. Thesis Technical Report, Feb. - Sep. 1992

NASA Technical Reports Server (NTRS)

Collins, J. D.; Volakis, John L.

1992-01-01

A method that combines the finite element and boundary integral techniques for the numerical solution of electromagnetic scattering problems is presented. The finite element method is well known for requiring a low order storage and for its capability to model inhomogeneous structures. Of particular emphasis in this work is the reduction of the storage requirement by terminating the finite element mesh on a boundary in a fashion which renders the boundary integrals in convolutional form. The fast Fourier transform is then used to evaluate these integrals in a conjugate gradient solver, without a need to generate the actual matrix. This method has a marked advantage over traditional integral equation approaches with respect to the storage requirement of highly inhomogeneous structures. Rectangular, circular, and ogival mesh termination boundaries are examined for two-dimensional scattering. In the case of axially symmetric structures, the boundary integral matrix storage is reduced by exploiting matrix symmetries and solving the resulting system via the conjugate gradient method. In each case several results are presented for various scatterers aimed at validating the method and providing an assessment of its capabilities. Important in methods incorporating boundary integral equations is the issue of internal resonance. A method is implemented for their removal, and is shown to be effective in the two-dimensional and three-dimensional applications.

Simulations of the Greenland ice sheet 100 years into the future with the full Stokes model Elmer/Ice

NASA Astrophysics Data System (ADS)

Seddik, H.; Greve, R.; Zwinger, T.; Gillet-Chaulet, F.; Gagliardini, O.

2011-12-01

The full Stokes thermo-mechanically coupled model Elmer/Ice is applied to the Greenland ice sheet. Elmer/Ice employs the finite element method to solve the full Stokes equations, the temperature evolution equation and the evolution equation of the free surface. The general framework of this modeling effort is a contribution to the Sea-level Response to Ice Sheet Evolution (SeaRISE) assessment project, a community-organized effort to estimate the likely range of ice sheet contributions to sea level rise over the next few hundred years (http://tinyurl.com/srise-lanl, http://tinyurl.com/srise-umt). The present geometry (surface and basal topographies) is derived from data where the basal topography was created with the preservation of the troughs at the Jakobshavn Ice Stream, Helheim, Kangerdlussuaq and Petermann glaciers. A mesh of the computational domain is created using an initial footprint which contains elements of 5 km horizontal resolution and to limit the number elements on the footprint while maximizing the spatial resolution, an anisotropic mesh adaptation scheme is employed based on the Hessian matrix of the observed surface velocities. The adaptation is carried out with the tool YAMS and the final footprint is vertically extruded to form a 3D mesh of 320880 elements with 17 equidistant, terrain-following layers. The numerical solution of the Stokes and the heat transfer equations employs direct solvers with stabilization procedures. The boundary conditions are such that the temperature at the surface uses the present-day mean annual air temperature given by a parameterization or directly from the available data, the geothermal heat flux at the bedrock is given by data and the lateral sides are open boundaries. A non-linear Weertman law is used for the basal sliding. Results for the SeaRISE 2011 sensitivity experiments are presented so that six different experiments have been conducted, grouped in two sets. The Set C (three experiments) applies a change to the surface precipitation and temperature and the set S (three experiments) applies an amplification factor to change the basal sliding velocity. The experiments are compared to a constant climate control run beginning at present (epoch 2004-1-1 0:0:0) and running up to 100 years holding the climate constant to its present state. The experiments with the amplification factor (Set S) show high sensitivities. Relative to the control run, the scenario with an amplification factor of 3x applied to the sliding velocity produces a Greenland contribution to sea level rise of ~25 cm. An amplification factor of 2.5x produces a contribution of ~16 cm and an amplification factor 2x produces a contribution of ~9 cm. The experiments with the changes to the surface precipitation and temperature (set C) show a contribution to sea level rise of ~4 cm when a factor 1x is applied to the temperature and precipitation anomalies. A factor 1.5x produces a sea level rise of ~8 cm and a factor 2x produces a sea level rise of ~12 cm.

Type 3 Fimbriae Encoded on Plasmids Are Expressed from a Unique Promoter without Affecting Host Motility, Facilitating an Exceptional Phenotype That Enhances Conjugal Plasmid Transfer

PubMed Central

Madsen, Jonas Stenløkke; Riber, Leise; Kot, Witold; Basfeld, Alrun; Burmølle, Mette; Hansen, Lars Hestbjerg; Sørensen, Søren Johannes

2016-01-01

Horizontal gene transfer (HGT), the transmission of genetic material to a recipient that is not the progeny of the donor, is fundamental in bacterial evolution. HGT is often mediated by mobile genetic elements such as conjugative plasmids, which may be in conflict with the chromosomal elements of the genome because they are independent replicons that may petition their own evolutionary strategy. Here we study differences between type 3 fimbriae encoded on wild type plasmids and in chromosomes. Using known and newly characterized plasmids we show that the expression of type 3 fimbriae encoded on plasmids is systematically different, as MrkH, a c-di-GMP dependent transcriptional activator is not needed for strong expression of the fimbriae. MrkH is required for expression of type 3 fimbriae of the Klebsiella pneumoniae chromosome, wherefrom the fimbriae operon (mrkABCDF) of plasmids is believed to have originated. We find that mrkABCDFs of plasmids are highly expressed via a unique promoter that differs from the original Klebsiella promoter resulting in fundamental behavioral consequences. Plasmid associated mrkABCDFs did not influence the swimming behavior of the host, that hereby acquired an exceptional phenotype being able to both actively swim (planktonic behavior) and express biofilm associated fimbriae (sessile behavior). We show that this exceptional phenotype enhances the conjugal transfer of the plasmid. PMID:27627107

Inversion of Robin coefficient by a spectral stochastic finite element approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin Bangti; Zou Jun

2008-03-01

This paper investigates a variational approach to the nonlinear stochastic inverse problem of probabilistically calibrating the Robin coefficient from boundary measurements for the steady-state heat conduction. The problem is formulated into an optimization problem, and mathematical properties relevant to its numerical computations are investigated. The spectral stochastic finite element method using polynomial chaos is utilized for the discretization of the optimization problem, and its convergence is analyzed. The nonlinear conjugate gradient method is derived for the optimization system. Numerical results for several two-dimensional problems are presented to illustrate the accuracy and efficiency of the stochastic finite element method.

Genetic information transfer promotes cooperation in bacteria

PubMed Central

Dimitriu, Tatiana; Lotton, Chantal; Bénard-Capelle, Julien; Misevic, Dusan; Brown, Sam P.; Lindner, Ariel B.; Taddei, François

2014-01-01

Many bacterial species are social, producing costly secreted “public good” molecules that enhance the growth of neighboring cells. The genes coding for these cooperative traits are often propagated via mobile genetic elements and can be virulence factors from a biomedical perspective. Here, we present an experimental framework that links genetic information exchange and the selection of cooperative traits. Using simulations and experiments based on a synthetic bacterial system to control public good secretion and plasmid conjugation, we demonstrate that horizontal gene transfer can favor cooperation. In a well-mixed environment, horizontal transfer brings a direct infectious advantage to any gene, regardless of its cooperation properties. However, in a structured population transfer selects specifically for cooperation by increasing the assortment among cooperative alleles. Conjugation allows cooperative alleles to overcome rarity thresholds and invade bacterial populations structured purely by stochastic dilution effects. Our results provide an explanation for the prevalence of cooperative genes on mobile elements, and suggest a previously unidentified benefit of horizontal gene transfer for bacteria. PMID:25024219

A combined finite element-boundary integral formulation for solution of two-dimensional scattering problems via CGFFT. [Conjugate Gradient Fast Fourier Transformation

NASA Technical Reports Server (NTRS)

Collins, Jeffery D.; Volakis, John L.; Jin, Jian-Ming

1990-01-01

A new technique is presented for computing the scattering by 2-D structures of arbitrary composition. The proposed solution approach combines the usual finite element method with the boundary-integral equation to formulate a discrete system. This is subsequently solved via the conjugate gradient (CG) algorithm. A particular characteristic of the method is the use of rectangular boundaries to enclose the scatterer. Several of the resulting boundary integrals are therefore convolutions and may be evaluated via the fast Fourier transform (FFT) in the implementation of the CG algorithm. The solution approach offers the principal advantage of having O(N) memory demand and employs a 1-D FFT versus a 2-D FFT as required with a traditional implementation of the CGFFT algorithm. The speed of the proposed solution method is compared with that of the traditional CGFFT algorithm, and results for rectangular bodies are given and shown to be in excellent agreement with the moment method.

Fun at Antarctic grounding lines: Ice-shelf channels and sediment transport

NASA Astrophysics Data System (ADS)

Drews, Reinhard; Mayer, Christoph; Eisen, Olaf; Helm, Veit; Ehlers, Todd A.; Pattyn, Frank; Berger, Sophie; Favier, Lionel; Hewitt, Ian H.; Ng, Felix; Fürst, Johannes J.; Gillet-Chaulet, Fabien; Bergeot, Nicolas; Matsuoka, Kenichi

2017-04-01

Meltwater beneath the polar ice sheets drains, in part, through subglacial conduits. Landforms created by such drainages are abundant in areas formerly covered by ice sheets during the last glacial maximum. However, observations of subglacial conduit dynamics under a contemporary ice sheet are lacking. We present results from ice-penetrating radar to infer the existence of subglacial conduits upstream of the grounding line of Roi Baudouin Ice Shelf, Antarctica. The conduits are aligned with ice-shelf channels, and underlain by esker ridges formed from sediment deposition due to reduced water outflow speed near the grounding line. In turn, the eskers modify local ice flow to initiate the bottom topography of the ice-shelf channels, and create small surface ridges extending onto the shelf. Relict features on the shelf are interpreted to indicate a history of these interactions and variability of past subglacial drainages. Because ice-shelf channels are loci where intense melting occurs to thin an ice shelf, these findings expose a novel link between subglacial drainage, sedimentation, and ice-shelf stability. To investigate the role of sediment transport beneath ice sheets further, we model the sheet-shelf system of the Ekstömisen catchment, Antarctica. A 3D finite element model (Elmer/ICE) is used to solve the transients full Stokes equation for isotropic, isothermal ice with a dynamic grounding line. We initialize the model with surface topography from the TanDEM-X satellites and by inverting simultaneously for ice viscosity and basal drag using present-day surface velocities. Results produce a flow field which is consitent with sattelite and on-site observations. Solving the age-depth relationship allows comparison with radar isochrones from airborne data, and gives information about the atmospheric/dynamic history of this sector. The flow field will eventually be used to identify potential sediment sources and sinks which we compare with more than 400 km of seismic profiles collected over the floating ice shelves and the grounded ice sheet.

Arctic melt ponds and energy balance in the climate system

NASA Astrophysics Data System (ADS)

Sudakov, Ivan

2017-02-01

Elements of Earth's cryosphere, such as the summer Arctic sea ice pack, are melting at precipitous rates that have far outpaced the projections of large scale climate models. Understanding key processes, such as the evolution of melt ponds that form atop Arctic sea ice and control its optical properties, is crucial to improving climate projections. These types of critical phenomena in the cryosphere are of increasing interest as the climate system warms, and are crucial for predicting its stability. In this paper, we consider how geometrical properties of melt ponds can influence ice-albedo feedback and how it can influence the equilibria in the energy balance of the planet.

Preparation of radioactive iodinated cholylhistamine for use in the radioimmunoassay of cholic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinberg, P.B.; Kinkade, J.M. Jr.; Collins, D.C.

1977-11-01

A major handicap in the development of simple and accurate radioimmunoassay procedures for bile acids has been the lack of a radioactive standard of high specific activity. To provide such a compound, we first synthesized cholylhistamine using the carbodiimide reaction. The hypothesized structure was confirmed by elemental analysis, thin-layer chromatography, infrared and mass spectral analysis. The cholylhistamine was then iodinated with /sup 125/I, using the choloramine-T method. The /sup 125/I-cholylhistamine was bound by antisera raised against a cholic acid-bovine serum albumin conjugate. This procedure should prove useful in preparing radioactive conjugates for all of the bile acids.

Enhancement of high-resolution photoacoustic imaging with indocyanine green-conjugated carbon nanotubes

NASA Astrophysics Data System (ADS)

Phuc Nguyen, Van; Oh, Yunok; Ha, Kanglyeol; Oh, Junghwan; Kang, Hyun Wook

2015-07-01

The current study indicates the feasibility of photoacoustic imaging (PAI) enhanced with contrast agents. A single-element ultrasound transducer (20 MHz) was used to detect PA signals for image reconstruction. To improve PA sensitivity, single-walled carbon nanotubes (SWNTs) conjugated with indocyanine green (ICG) were injected into samples at various concentrations. PA signal amplitudes linearly increased with SWNT-ICG concentration owing to strong light absorption. Compared with SWNTs, SWNT-ICG augmented the signal intensity by approximately 2-fold (concentration: 300 nM). The enhanced optical absorption can allow the application of SWNT-ICG to enable PAI for specifically identifying tumors with high sensitivity.

Nature of non-nuclear (3, -3) π-attractor and π-bonding: Theoretical analysis on π-electron density

NASA Astrophysics Data System (ADS)

Lv, Jiao; Yang, Lihua; Sun, Zheng; Meng, Lingpeng; Li, Xiaoyan

2018-01-01

Understanding the nature of π-electron density is important to characterize the conjugate π molecular systems. In this work, the π-electron densities of some typical conjugated π molecular systems were separated from their total electron densities; the positions and natures of non-nuclear (3, -3) π-attractors and the π-bond critical points (π-BCPs) are investigated. The calculated results show that for the same element, the position of the π-attractor is constant, regardless of the chemical surroundings. The position of the π-BCP is closer to the atom with the larger electronegativity.

Use of a three-layer distributed RC network to produce two pairs of complex conjugate zeros

NASA Technical Reports Server (NTRS)

Huelsman, L. P.

1972-01-01

The properties of a three layer distributed RC network consisting of two layers of resistive material separated by a dielectric are described. When the three layer network is used as a three terminal element by connecting conducting terminal strips across the ends of one of the resistive layers and the center of the other resistive layer, the network may be used to produce pairs of complex conjugate transmission zeros. The location of these zeros are determined by the parameters of the network. Design charts for determining the zero positions are included as part of the report.

Aerodynamics and thermal physics of helicopter ice accretion

NASA Astrophysics Data System (ADS)

Han, Yiqiang

Ice accretion on aircraft introduces significant loss in airfoil performance. Reduced lift-to- drag ratio reduces the vehicle capability to maintain altitude and also limits its maneuverability. Current ice accretion performance degradation modeling approaches are calibrated only to a limited envelope of liquid water content, impact velocity, temperature, and water droplet size; consequently inaccurate aerodynamic performance degradations are estimated. The reduced ice accretion prediction capabilities in the glaze ice regime are primarily due to a lack of knowledge of surface roughness induced by ice accretion. A comprehensive understanding of the ice roughness effects on airfoil heat transfer, ice accretion shapes, and ultimately aerodynamics performance is critical for the design of ice protection systems. Surface roughness effects on both heat transfer and aerodynamic performance degradation on airfoils have been experimentally evaluated. Novel techniques, such as ice molding and casting methods and transient heat transfer measurement using non-intrusive thermal imaging methods, were developed at the Adverse Environment Rotor Test Stand (AERTS) facility at Penn State. A novel heat transfer scaling method specifically for turbulent flow regime was also conceived. A heat transfer scaling parameter, labeled as Coefficient of Stanton and Reynolds Number (CSR = Stx/Rex --0.2), has been validated against reference data found in the literature for rough flat plates with Reynolds number (Re) up to 1x107, for rough cylinders with Re ranging from 3x104 to 4x106, and for turbine blades with Re from 7.5x105 to 7x106. This is the first time that the effect of Reynolds number is shown to be successfully eliminated on heat transfer magnitudes measured on rough surfaces. Analytical models for ice roughness distribution, heat transfer prediction, and aerodynamics performance degradation due to ice accretion have also been developed. The ice roughness prediction model was developed based on a set of 82 experimental measurements and also compared to existing predictions tools. Two reference predictions found in the literature yielded 76% and 54% discrepancy with respect to experimental testing, whereas the proposed ice roughness prediction model resulted in a 31% minimum accuracy in prediction. It must be noted that the accuracy of the proposed model is within the ice shape reproduction uncertainty of icing facilities. Based on the new ice roughness prediction model and the CSR heat transfer scaling method, an icing heat transfer model was developed. The approach achieved high accuracy in heat transfer prediction compared to experiments conducted at the AERTS facility. The discrepancy between predictions and experimental results was within +/-15%, which was within the measurement uncertainty range of the facility. By combining both the ice roughness and heat transfer predictions, and incorporating the modules into an existing ice prediction tool (LEWICE), improved prediction capability was obtained, especially for the glaze regime. With the available ice shapes accreted at the AERTS facility and additional experiments found in the literature, 490 sets of experimental ice shapes and corresponding aerodynamics testing data were available. A physics-based performance degradation empirical tool was developed and achieved a mean absolute deviation of 33% when compared to the entire experimental dataset, whereas 60% to 243% discrepancies were observed using legacy drag penalty prediction tools. Rotor torque predictions coupling Blade Element Momentum Theory and the proposed drag performance degradation tool was conducted on a total of 17 validation cases. The coupled prediction tool achieved a 10% predicting error for clean rotor conditions, and 16% error for iced rotor conditions. It was shown that additional roughness element could affect the measured drag by up to 25% during experimental testing, emphasizing the need of realistic ice structures during aerodynamics modeling and testing for ice accretion.

On the origin of alkali metals in Europa exosphere

NASA Astrophysics Data System (ADS)

Ozgurel, Ozge; Pauzat, Françoise; Ellinger, Yves; Markovits, Alexis; Mousis, Olivier; LCT, LAM

2016-10-01

At a time when Europa is considered as a plausible habitat for the development of an early form of life, of particular concern is the origin of neutral sodium and potassium atoms already detected in its exosphere (together with magnesium though in smaller abundance), since these atoms are known to be crucial for building the necessary bricks of prebiotic species. However their origin and history are still poorly understood. The most likely sources could be exogenous and result from the contamination produced by Io's intense volcanism and/or by meteoritic bombardment. These sources could also be endogenous if these volatile elements originate directly from Europa's icy mantle. Here we explore the possibility that neutral sodium and potassium atoms were delivered to the satellite's surface via the upwelling of ices formed in contact with the hidden ocean. These metallic elements would have been transferred as ions to the ocean at early epochs after Europa's formation, by direct contact of water with the rocky core. During Europa's subsequent cooling, the icy layers formed at the top of the ocean would have kept trapped the sodium and potassium, allowing their future progression to the surface and final identification in the exosphere of the satellite. To support this scenario, we have used chemistry numerical models based on first principle periodic density functional theory (DFT). These models are shown to be well adapted to the description of compact ice and are capable to describe the trapping and neutralization of the initial ions in the ice matrix. The process is found relevant for all the elements considered, alkali metals like Na and K, as well as for Mg and probably for Ca, their respective abundances depending essentially of their solubility and chemical capabilities to blend with water ices.

A New Discrete Element Sea-Ice Model for Earth System Modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Adrian Keith

Sea ice forms a frozen crust of sea water oating in high-latitude oceans. It is a critical component of the Earth system because its formation helps to drive the global thermohaline circulation, and its seasonal waxing and waning in the high north and Southern Ocean signi cantly affects planetary albedo. Usually 4{6% of Earth's marine surface is covered by sea ice at any one time, which limits the exchange of heat, momentum, and mass between the atmosphere and ocean in the polar realms. Snow accumulates on sea ice and inhibits its vertical growth, increases its albedo, and contributes to pooledmore » water in melt ponds that darken the Arctic ice surface in the spring. Ice extent and volume are subject to strong seasonal, inter-annual and hemispheric variations, and climatic trends, which Earth System Models (ESMs) are challenged to simulate accurately (Stroeve et al., 2012; Stocker et al., 2013). This is because there are strong coupled feedbacks across the atmosphere-ice-ocean boundary layers, including the ice-albedo feedback, whereby a reduced ice cover leads to increased upper ocean heating, further enhancing sea-ice melt and reducing incident solar radiation re ected back into the atmosphere (Perovich et al., 2008). A reduction in perennial Arctic sea-ice during the satellite era has been implicated in mid-latitude weather changes, including over North America (Overland et al., 2015). Meanwhile, most ESMs have been unable to simulate observed inter-annual variability and trends in Antarctic sea-ice extent during the same period (Gagne et al., 2014).« less

The direct mechanical influence of sea ice state on ice sheet mass loss via iceberg mélange

NASA Astrophysics Data System (ADS)

Robel, A.

2017-12-01

The interaction between sea ice and land ice has typically been considered as a large-scale exchange of moisture, heat and salinity through the ocean and atmosphere. However, recent observations from marine-terminating glaciers in Greenland indicate that the long-term decline of local sea ice cover has been accompanied by an increase in nearby iceberg calving and associated ice sheet mass loss. Near glacier calving fronts, sea ice binds icebergs together into an aggregate granular material known as iceberg mélange. Studies have hypothesized that mélange may suppress calving by exerting a mechanical buttressing force directly on the glacier terminus. Here, we show explicitly how sea ice thickness and concentration play a critical role in setting the material strength of mélange. To do so, we adapt a discrete element model to simulate mélange as a cohesive granular material. In these simulations, mélange laden with thick, dense, landfast sea ice can produce enough resistance to shut down calving at the terminus. When sea ice thins, mélange weakens, reducing the mechanical force of mélange on the glacier terminus, and increasing the likelihood of calving. We discuss whether longer periods of sea-ice-free conditions in winter may lead to a transition from currently slow calving, predominantly occurring in the summer, to rapid calving, occurring throughout the year. We also discuss the potential role of freshwater discharge in promoting sea ice formation in fjords, potentially strengthening mélange.

Map of Martian Polar Hydrogen

NASA Technical Reports Server (NTRS)

2003-01-01

This gamma ray spectrometer map centered on the north pole of Mars is based on gamma-rays from the element hydrogen. In this region, hydrogen is mainly in the form of water ice. Regions of high ice content are shown in red and those low in ice content are shown in blue. The very ice-rich region at the north pole is due to a permanent polar cap of water ice on the surface. Elsewhere in this region, the ice is buried under several to a few tens of centimeters of dry soil. The sub-surface ice is not uniformly distributed in the north, but varies with both latitude and longitude. In the north, the soil is well over 50 percent ice, which is more than can be accommodated by just filling the pore space in pre-existing soil. This high ice content implies that the ice may have been slowly co-deposited with dust in the past when conditions were wetter. Deposition of ice by this process means it is more likely that the ice deposits are very thick and may even be deep enough to have liquid water at their base.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The gamma ray spectrometer was provided by the University of Arizona, Tucson. Lockheed Martin Astronautics, Denver, Colo., is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

Corona from Ice, Thunderstorm Electrification and Lightning Suppression.

DTIC Science & Technology

1980-11-01

rates of droplets highly charged by interaction with corona streamers. Laboratory and theoretical studies have been performed in an effort to explore in...CORONA FROM ICE, THUNDERSTORM ELECTRIFICATION Final AND LIGHTNING SUPPRESSION 1 Sep 77 to 31 Aug 80 6. Performing Org. Report Number 7. Author(s) 8...Contract or Grant Number J. Latham AFOSR-77-3429 O"o 9. Performing Organization Name and Address 10. Program Element, Project, Task Physics Department

Self-assembly of conjugated oligomers and polymers at the interface: structure and properties.

PubMed

Xu, Lirong; Yang, Liu; Lei, Shengbin

2012-08-07

In this review, we give a brief account on the recent scanning tunneling microscopy investigation of interfacial structures and properties of π-conjugated semiconducting oligomers and polymers, either at the solid-air (including solid-vacuum) or at the solid-liquid interface. The structural aspects of the self-assembly of both oligomers and polymers are highlighted. Conjugated oligomers can form well ordered supramolecular assemblies either at the air-solid or liquid-solid interface, thanks to the relatively high mobility and structural uniformity in comparison with polymers. The backbone structure, substitution of side chains and functional groups can affect the assembling behavior significantly, which offers the opportunity to tune the supramolecular structure of these conjugated oligomers at the interface. For conjugated polymers, the large molecular weight limits the mobility on the surface and the distribution in size also prevents the formation of long range ordered supramolecular assembly. The submolecular resolution obtained on the assembling monolayers enables a detailed investigation of the chain folding at the interface, both the structural details and the effect on electronic properties. Besides the ability in studying the assembling structures at the interfaces, STM also provides a reasonable way to evaluate the distribution of the molecular weight of conjugated polymers by statistic of the contour length of the adsorbed polymer chains. Both conjugated oligomers and polymers can form composite assemblies with other materials. The ordered assembly of oligomers can act as a template to controllably disperse other molecules such as coronene or fullerene. These investigations open a new avenue to fine tune the assembling structure at the interface and in turn the properties of the composite materials. To summarize scanning tunneling microscopy has demonstrated its surprising ability in the investigation of the assembling structures and properties of conjugated oligomers and polymers. The information obtained could benefit the understanding of the elements affecting the film morphology and helps the optimization of device performance.

Arctic sea-ice syntheses: Charting across scope, scale, and knowledge systems

NASA Astrophysics Data System (ADS)

Druckenmiller, M. L.; Perovich, D. K.; Francis, J. A.

2017-12-01

Arctic sea ice supports and intersects a multitude of societal benefit areas, including regulating regional and global climates, structuring marine food webs, providing for traditional food provisioning by indigenous peoples, and constraining marine shipping and access. At the same time, sea ice is one of the most rapidly changing elements of the Arctic environment and serves as a source of key physical indicators for monitoring Arctic change. Before the present scientific interest in Arctic sea ice for climate research, it has long been, and remains, a focus of applied research for industry and national security. For generations, the icy coastal seas of the North have also provided a basis for the sharing of local and indigenous knowledge between Arctic residents and researchers, including anthropologists, biologists, and geoscientists. This presentation will summarize an ongoing review of existing synthesis studies of Arctic sea ice. We will chart efforts to achieve system-level understanding across geography, temporal scales, and the ecosystem services that Arctic sea ice supports. In doing so, we aim to illuminate the role of interdisciplinary science, together with local and indigenous experts, in advancing knowledge of the roles of sea ice in the Arctic system and beyond, reveal the historical and scientific evolution of sea-ice research, and assess current gaps in system-scale understanding.

Design, implementation and practice of JBEI-ICE: an open source biological part registry platform and tools.

PubMed

Ham, Timothy S; Dmytriv, Zinovii; Plahar, Hector; Chen, Joanna; Hillson, Nathan J; Keasling, Jay D

2012-10-01

The Joint BioEnergy Institute Inventory of Composable Elements (JBEI-ICEs) is an open source registry platform for managing information about biological parts. It is capable of recording information about 'legacy' parts, such as plasmids, microbial host strains and Arabidopsis seeds, as well as DNA parts in various assembly standards. ICE is built on the idea of a web of registries and thus provides strong support for distributed interconnected use. The information deposited in an ICE installation instance is accessible both via a web browser and through the web application programming interfaces, which allows automated access to parts via third-party programs. JBEI-ICE includes several useful web browser-based graphical applications for sequence annotation, manipulation and analysis that are also open source. As with open source software, users are encouraged to install, use and customize JBEI-ICE and its components for their particular purposes. As a web application programming interface, ICE provides well-developed parts storage functionality for other synthetic biology software projects. A public instance is available at public-registry.jbei.org, where users can try out features, upload parts or simply use it for their projects. The ICE software suite is available via Google Code, a hosting site for community-driven open source projects.

Intercomparison of Antarctic ice-shelf, ocean, and sea-ice interactions simulated by MetROMS-iceshelf and FESOM 1.4

NASA Astrophysics Data System (ADS)

Naughten, Kaitlin A.; Meissner, Katrin J.; Galton-Fenzi, Benjamin K.; England, Matthew H.; Timmermann, Ralph; Hellmer, Hartmut H.; Hattermann, Tore; Debernard, Jens B.

2018-04-01

An increasing number of Southern Ocean models now include Antarctic ice-shelf cavities, and simulate thermodynamics at the ice-shelf/ocean interface. This adds another level of complexity to Southern Ocean simulations, as ice shelves interact directly with the ocean and indirectly with sea ice. Here, we present the first model intercomparison and evaluation of present-day ocean/sea-ice/ice-shelf interactions, as simulated by two models: a circumpolar Antarctic configuration of MetROMS (ROMS: Regional Ocean Modelling System coupled to CICE: Community Ice CodE) and the global model FESOM (Finite Element Sea-ice Ocean Model), where the latter is run at two different levels of horizontal resolution. From a circumpolar Antarctic perspective, we compare and evaluate simulated ice-shelf basal melting and sub-ice-shelf circulation, as well as sea-ice properties and Southern Ocean water mass characteristics as they influence the sub-ice-shelf processes. Despite their differing numerical methods, the two models produce broadly similar results and share similar biases in many cases. Both models reproduce many key features of observations but struggle to reproduce others, such as the high melt rates observed in the small warm-cavity ice shelves of the Amundsen and Bellingshausen seas. Several differences in model design show a particular influence on the simulations. For example, FESOM's greater topographic smoothing can alter the geometry of some ice-shelf cavities enough to affect their melt rates; this improves at higher resolution, since less smoothing is required. In the interior Southern Ocean, the vertical coordinate system affects the degree of water mass erosion due to spurious diapycnal mixing, with MetROMS' terrain-following coordinate leading to more erosion than FESOM's z coordinate. Finally, increased horizontal resolution in FESOM leads to higher basal melt rates for small ice shelves, through a combination of stronger circulation and small-scale intrusions of warm water from offshore.

Microfluidic bioassay system based on microarrays of hydrogel sensing elements entrapping quantum dot-enzyme conjugates.

PubMed

Jang, Eunji; Kim, Sinyoung; Koh, Won-Gun

2012-01-15

This paper presents a simple method to fabricate a microfluidic biosensor that is able to detect substrates for H(2)O(2)-generating oxidase. The biosensor consists of three components (quantum dot-enzyme conjugates, hydrogel microstructures, and a set of microchannels) that were hierarchically integrated into a microfluidic device. The quantum dot (QD)-enzyme conjugates were entrapped within the poly(ethylene glycol) (PEG)-based hydrogel microstructures that were fabricated within the microchannels by a photopatterning process. Glucose oxidase (GOX) and alcohol oxidase (AOX) were chosen as the model oxidase enzymes, conjugated to carboxyl-terminated CdSe/ZnS QDs, and entrapped within the hydrogel microstructures, which resulted in a fluorescent hydrogel microarray that was responsive to glucose or alcohol. The hydrogel-entrapped GOX and AOX were able to perform enzyme-catalyzed oxidation of glucose and alcohol, respectively, to produce H(2)O(2), which subsequently quenched the fluorescence of the conjugated QDs. The fluorescence intensity of the hydrogel microstructures decreased as the glucose and alcohol concentrations increased, and the detection limits of this system were found to be 50 μM of glucose and 70 μM of alcohol. Because each microchannel was able to carry out different assays independently, the simultaneous detection of glucose and alcohol was possible using our novel microfluidic device composed of multiple microchannels. Copyright © 2011 Elsevier B.V. All rights reserved.

A System of Conservative Regridding for Ice-Atmosphere Coupling in a General Circulation Model (GCM)

NASA Technical Reports Server (NTRS)

Fischer, R.; Nowicki, S.; Kelley, M.; Schmidt, G. A.

2014-01-01

The method of elevation classes, in which the ice surface model is run at multiple elevations within each grid cell, has proven to be a useful way for a low-resolution atmosphere inside a general circulation model (GCM) to produce high-resolution downscaled surface mass balance fields for use in one-way studies coupling atmospheres and ice flow models. Past uses of elevation classes have failed to conserve mass and energy because the transformation used to regrid to the atmosphere was inconsistent with the transformation used to downscale to the ice model. This would cause problems for two-way coupling. A strategy that resolves this conservation issue has been designed and is presented here. The approach identifies three grids between which data must be regridded and five transformations between those grids required by a typical coupled atmosphere-ice flow model. This paper develops a theoretical framework for the problem and shows how each of these transformations may be achieved in a consistent, conservative manner. These transformations are implemented in Glint2, a library used to couple atmosphere models with ice models. Source code and documentation are available for download. Confounding real-world issues are discussed, including the use of projections for ice modeling, how to handle dynamically changing ice geometry, and modifications required for finite element ice models.

Mobile, stationary and mixed phase tracers: consequences to sea ice biogeochemistry

NASA Astrophysics Data System (ADS)

Jeffery, N.; Elliott, S.; Hunke, E. C.; Deal, C.; Jin, M.

2016-02-01

Models of brine motion in sea ice have offered mechanisms for transporting biogeochemical compounds vertically within the ice and between the ice-ocean interface. In these models, sea ice microstructure and/or gross physical properties determine the resupply of nitrate, for example, to sympagic algae and that resupply, in large part, constrains sea ice primary production. The assumption of brine transport models is that the transported matter exists in a purely mobile phase within the ice brine channels. As a result, non-reacting, mobile phase tracers evolve like salinity in dynamic sea ice. Field and laboratory observations indicate that this is a good approximation for the primary algal macronutrients - nitrate, silicate and phosphate, but clear deviations are evident for ammonium, micronutrients such as iron, humic substances, algal bi-products such as gels and extracellular polysaccharides, and the algae themselves. This wide range of biogeochemical matter resists brine motion and is present in both the mobile and stationary phases, i.e. these tracers are "mixed" with respect to their transport phases. Although the precise mechanism for this resistance may be due to attachment by frustules, "stickiness" of the material surface, adsorption, or, in the case of microorganisms, active motility, a key common element in all cases is the presence of the ice matrix. In this presentation we investigate the consequences of mixed phase tracers in sea ice on algal concentrations, vertical distributions, and the potential accumulation of biogeochemical matter within the ice. We assume that sea ice growth promotes retention to the stationary phase, while melt and the disintegration of the ice matrix promotes release into the mobile phase. By varying the retention and release timescales of this formulation, we retrieve the purely mobile and maximal accumulation limits.

E2~Ub conjugates regulate the kinase activity of Shigella effector OspG during pathogenesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pruneda, Jonathan N.; Smith, F. Donelson; Daurie, Angela

Pathogenic bacteria introduce effector proteins directly into the cytosol of eukaryotic cells to promote invasion and colonization. OspG, a Shigella spp. effector kinase, plays a role in this process by helping to suppress the host inflammatory response. OspG has been reported to bind host E2 ubiquitin-conjugating enzymes activated with ubiquitin (E2~Ub), a key enzyme complex in ubiquitin transfer pathways. A cocrystal structure of the OspG/UbcH5c~Ub complex reveals that complex formation has important ramifications for the activity of both OspG and the UbcH5c~Ub conjugate. OspG is a minimal kinase domain containing only essential elements required for catalysis. UbcH5c~Ub binding stabilizes anmore » active conformation of the kinase, greatly enhancing OspG kinase activity. In contrast, interaction with OspG stabilizes an extended, less reactive form of UbcH5c~Ub. Recognizing conserved E2 features, OspG can interact with at least ten distinct human E2s~Ub. Mouse oral infection studies indicate that E2~Ub conjugates act as novel regulators of OspG effector kinase function in eukaryotic host cells.« less

Multivalent interaction based carbohydrate biosensors for signal amplification

PubMed Central

Wang, Yanyan; Chalagalla, Srinivas; Li, Tiehai; Sun, Xue-long; Zhao, Wei; Wang, Peng; Zeng, Xiangqun

2010-01-01

Multivalent interaction between boronic acids immobilized on Quartz Crystal Microbalance (QCM) sensor surface and the carbohydrates modified Au - nanoparticle (AuNP) has been demonstrated for the development of a sensitive carbohydrate biosensor. Briefly, a boronic acid - containing polymer (boropolymer) as multivalent carbohydrate receptor was oriented immobilized on the cysteamine coated electrode through isourea bond formation. Carbohydrates were conjugated to AuNPs to generate a multivalent carbohydrates moiety to amplify the response signal. Thus, the binding of the carbohydrate conjugated AuNPs to the boropolymer surface are multivalent which could simultaneously increase the binding affinity and specificity. We systematically studied the binding between five carbohydrate conjugated AuNPs and the boropolymer. Our studies show that the associate constant (Ka) was in the order of fucose < glucose < mannose < galactose < maltose. A linear response in the range from 23 µM to 3.83 mM was observed for mannose conjugated AuNPs and the boropolymer recognition elements, with the lower detection limit of 1.5 µM for the carbohydrate analytes. Furthermore, the multivalent binding between carbohydrates and boronic acids are reversible and allow the regeneration of boropolymer surface by using 1M acetic acid so as to sequentially capture and release the carbohydrate analytes. PMID:20863680

Identification & Characterization of Fungal Ice Nucleation Proteins

NASA Astrophysics Data System (ADS)

Scheel, Jan Frederik; Kunert, Anna Theresa; Kampf, Christopher Johannes; Mauri, Sergio; Weidner, Tobias; Pöschl, Ulrich; Fröhlich-Nowoisky, Janine

2016-04-01

Freezing of water at relatively warm subfreezing temperatures is dependent on ice nucleation catalysis facilitated by ice nuclei (IN). These IN can be of various origins and although extensive research was done and progress was achieved, the nature and mechanisms leading to an effective IN are to date still poorly understood. Some of the most important processes of our geosphere like the water cycle are highly dependent on effective ice nucleation at temperatures between -2°C - -8°C, a temperature range which is almost exclusively covered by biological IN (BioIN). BioIN are usually macromolecular structures of biological polymers. Sugars as well as proteins have been reported to serve as IN and the best characterized BioIN are ice nucleation proteins (IN-P) from gram negative bacteria. Fungal strains from Fusarium spp. were described to be effective IN at subfreezing temperatures up to -2°C already 25 years ago and more and more fungal species are described to serve as efficient IN. Fungal IN are also thought to be proteins or at least contain a proteinaceous compound, but to date the fungal IN-P primary structure as well as their coding genetic elements of all IN active fungi are unknown. The aim of this study is a.) to identify the proteins and their coding genetic elements from IN active fungi (F. acuminatum, F. avenaceum, M. alpina) and b.) to characterize the mechanisms by which fungal IN serve as effective IN. We designed an interdisciplinary approach using biological, analytical and physical methods to identify fungal IN-P and describe their biological, chemical, and physical properties.

Albany/FELIX: A parallel, scalable and robust, finite element, first-order Stokes approximation ice sheet solver built for advanced analysis

DOE PAGES

Tezaur, I. K.; Perego, M.; Salinger, A. G.; ...

2015-04-27

This paper describes a new parallel, scalable and robust finite element based solver for the first-order Stokes momentum balance equations for ice flow. The solver, known as Albany/FELIX, is constructed using the component-based approach to building application codes, in which mature, modular libraries developed as a part of the Trilinos project are combined using abstract interfaces and template-based generic programming, resulting in a final code with access to dozens of algorithmic and advanced analysis capabilities. Following an overview of the relevant partial differential equations and boundary conditions, the numerical methods chosen to discretize the ice flow equations are described, alongmore » with their implementation. The results of several verification studies of the model accuracy are presented using (1) new test cases for simplified two-dimensional (2-D) versions of the governing equations derived using the method of manufactured solutions, and (2) canonical ice sheet modeling benchmarks. Model accuracy and convergence with respect to mesh resolution are then studied on problems involving a realistic Greenland ice sheet geometry discretized using hexahedral and tetrahedral meshes. Also explored as a part of this study is the effect of vertical mesh resolution on the solution accuracy and solver performance. The robustness and scalability of our solver on these problems is demonstrated. Lastly, we show that good scalability can be achieved by preconditioning the iterative linear solver using a new algebraic multilevel preconditioner, constructed based on the idea of semi-coarsening.« less

Hybrid mesh finite volume CFD code for studying heat transfer in a forward-facing step

NASA Astrophysics Data System (ADS)

Jayakumar, J. S.; Kumar, Inder; Eswaran, V.

2010-12-01

Computational fluid dynamics (CFD) methods employ two types of grid: structured and unstructured. Developing the solver and data structures for a finite-volume solver is easier than for unstructured grids. But real-life problems are too complicated to be fitted flexibly by structured grids. Therefore, unstructured grids are widely used for solving real-life problems. However, using only one type of unstructured element consumes a lot of computational time because the number of elements cannot be controlled. Hence, a hybrid grid that contains mixed elements, such as the use of hexahedral elements along with tetrahedral and pyramidal elements, gives the user control over the number of elements in the domain, and thus only the domain that requires a finer grid is meshed finer and not the entire domain. This work aims to develop such a finite-volume hybrid grid solver capable of handling turbulence flows and conjugate heat transfer. It has been extended to solving flow involving separation and subsequent reattachment occurring due to sudden expansion or contraction. A significant effect of mixing high- and low-enthalpy fluid occurs in the reattached regions of these devices. This makes the study of the backward-facing and forward-facing step with heat transfer an important field of research. The problem of the forward-facing step with conjugate heat transfer was taken up and solved for turbulence flow using a two-equation model of k-ω. The variation in the flow profile and heat transfer behavior has been studied with the variation in Re and solid to fluid thermal conductivity ratios. The results for the variation in local Nusselt number, interface temperature and skin friction factor are presented.

Assessment of Ice Shape Roughness Using a Self-Orgainizing Map Approach

NASA Technical Reports Server (NTRS)

Mcclain, Stephen T.; Kreeger, Richard E.

2013-01-01

Self-organizing maps are neural-network techniques for representing noisy, multidimensional data aligned along a lower-dimensional and nonlinear manifold. For a large set of noisy data, each element of a finite set of codebook vectors is iteratively moved in the direction of the data closest to the winner codebook vector. Through successive iterations, the codebook vectors begin to align with the trends of the higher-dimensional data. Prior investigations of ice shapes have focused on using self-organizing maps to characterize mean ice forms. The Icing Research Branch has recently acquired a high resolution three dimensional scanner system capable of resolving ice shape surface roughness. A method is presented for the evaluation of surface roughness variations using high-resolution surface scans based on a self-organizing map representation of the mean ice shape. The new method is demonstrated for 1) an 18-in. NACA 23012 airfoil 2 AOA just after the initial ice coverage of the leading 5 of the suction surface of the airfoil, 2) a 21-in. NACA 0012 at 0AOA following coverage of the leading 10 of the airfoil surface, and 3) a cold-soaked 21-in.NACA 0012 airfoil without ice. The SOM method resulted in descriptions of the statistical coverage limits and a quantitative representation of early stages of ice roughness formation on the airfoils. Limitations of the SOM method are explored, and the uncertainty limits of the method are investigated using the non-iced NACA 0012 airfoil measurements.

Implementation of Combined Feather and Surface-Normal Ice Growth Models in LEWICE/X

NASA Technical Reports Server (NTRS)

Velazquez, M. T.; Hansman, R. J., Jr.

1995-01-01

Experimental observations have shown that discrete rime ice growths called feathers, which grow in approximately the direction of water droplet impingement, play an important role in the growth of ice on accreting surfaces for some thermodynamic conditions. An improved physical model of ice accretion has been implemented in the LEWICE 2D panel-based ice accretion code maintained by the NASA Lewis Research Center. The LEWICE/X model of ice accretion explicitly simulates regions of feather growth within the framework of the LEWICE model. Water droplets impinging on an accreting surface are withheld from the normal LEWICE mass/energy balance and handled in a separate routine; ice growth resulting from these droplets is performed with enhanced convective heat transfer approximately along droplet impingement directions. An independent underlying ice shape is grown along surface normals using the unmodified LEWICE method. The resulting dual-surface ice shape models roughness-induced feather growth observed in icing wind tunnel tests. Experiments indicate that the exact direction of feather growth is dependent on external conditions. Data is presented to support a linear variation of growth direction with temperature and cloud water content. Test runs of LEWICE/X indicate that the sizes of surface regions containing feathers are influenced by initial roughness element height. This suggests that a previous argument that feather region size is determined by boundary layer transition may be incorrect. Simulation results for two typical test cases give improved shape agreement over unmodified LEWICE.

Surfacing behavior and gas release of the physostome sprat (Sprattus sprattus) in ice-free and ice-covered waters.

PubMed

Solberg, Ingrid; Kaartvedt, Stein

2014-01-01

Upward-facing echosounders that provided continuous, long-term measurements were applied to address the surfacing behavior and gas release of the physostome sprat ( Sprattus sprattus ) throughout an entire winter in a 150-m-deep Norwegian fjord. During ice-free conditions, the sprat surfaced and released gas bubbles at night with an estimated surfacing rate of 3.5 times per fish day -1 . The vertical swimming speeds during surfacing were considerably higher (~10 times) than during diel vertical migrations, especially when returning from the surface, and particularly when the fjord was not ice covered. The sprat released gas a few hours after surfacing, suggesting that the sprat gulped atmospheric air during its excursions to the surface. While the surface activity increased after the fjord became ice covered, the records of gas release decreased sharply. The under-ice fish then displayed a behavior interpreted as "searching for the surface" by repeatedly ascending toward the ice, apparently with limited success of filling the swim bladder. This interpretation was supported by lower acoustic target strength in ice-covered waters. The frequent surfacing behavior demonstrated in this study indicates that gulping of atmospheric air is an important element in the life of sprat. While at least part of the population endured overwintering in the ice-covered habitat, ice covering may constrain those physostome fishes that lack a gas-generating gland in ways that remain to be established.

Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth's deep mantle.

PubMed

Tschauner, O; Huang, S; Greenberg, E; Prakapenka, V B; Ma, C; Rossman, G R; Shen, A H; Zhang, D; Newville, M; Lanzirotti, A; Tait, K

2018-03-09

Water-rich regions in Earth's deeper mantle are suspected to play a key role in the global water budget and the mobility of heat-generating elements. We show that ice-VII occurs as inclusions in natural diamond and serves as an indicator for such water-rich regions. Ice-VII, the residue of aqueous fluid present during growth of diamond, crystallizes upon ascent of the host diamonds but remains at pressures as high as 24 gigapascals; it is now recognized as a mineral by the International Mineralogical Association. In particular, ice-VII in diamonds points toward fluid-rich locations in the upper transition zone and around the 660-kilometer boundary. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Fully-Implicit Navier-Stokes (FIN-S)

NASA Technical Reports Server (NTRS)

Kirk, Benjamin S.

2010-01-01

FIN-S is a SUPG finite element code for flow problems under active development at NASA Lyndon B. Johnson Space Center and within PECOS: a) The code is built on top of the libMesh parallel, adaptive finite element library. b) The initial implementation of the code targeted supersonic/hypersonic laminar calorically perfect gas flows & conjugate heat transfer. c) Initial extension to thermochemical nonequilibrium about 9 months ago. d) The technologies in FIN-S have been enhanced through a strongly collaborative research effort with Sandia National Labs.

The Trial Software version for DEMETER power spectrum files visualization and mapping

NASA Astrophysics Data System (ADS)

Lozbin, Anatoliy; Inchin, Alexander; Shpadi, Maxim

2010-05-01

In the frame of Kazakhstan's Scientific Space System creation for earthquakes precursors research, the hardware and software of DEMETER satellite was investigated. The data processing Software of DEMETER is based on package SWAN under IDL Virtual machine and realizes many features, but we can't find an important tool for the spectrograms analysis - space-time visualization of power spectrum files from electromagnetic devices as ICE and IMSC. For elimination of this problem we have developed Software which is offered to use. The DeSS (DEMETER Spectrogram Software) - it is Software for visualization, analysis and a mapping of power spectrum data from electromagnetic devices ICE and IMSC. The Software primary goal is to give the researcher friendly tool for the analysis of electromagnetic data from DEMETER Satellite for earthquake precursors and other ionosphere events researches. The Input data for DeSS Software is a power spectrum files: - Power spectrum of 1 component of the electric field in the VLF range (APID 1132); - Power spectrum of 1 component of the electric field in the HF range (APID 1134); - Power spectrum of 1 component of the magnetic field in the VLF range (APID 1137). The main features and operations of the software is possible: - various time and frequency filtration; - visualization of time dependence of signal intensity on fixed frequency; - spectral density visualization for fixed frequency range; - spectrogram autosize and smooth spectrogram; - the information in each point of the spectrogram: time, frequency and intensity; - the spectrum information in the separate window, consisting of 4 blocks; - data mapping with 6 range scale. On the map we can browse next information: - satellite orbit; - conjugate point at the satellite altitude; - north conjugate point at the altitude 110 km; - south conjugate point at the altitude 110 km. This is only trial software version to help the researchers and we always ready collaborate with scientists for software improvement. References: 1. D.Lagoutte, J.Y. Brochot, D. de Carvalho, L.Madrias and M. Parrot. DEMETER Microsatellite. Scientific Mission Center. Data product description. DMT-SP-9-CM-6054-LPC. 2. D.Lagoutte, J.Y. Brochot, P.Latremoliere. SWAN - Software for Waveform Analysis. LPCE/NI/003.E - Part 1 (User's guide), Part 2 (Analysis tools), Part 3 (User's project interface).

A Cool Sport Full of Physics

NASA Astrophysics Data System (ADS)

Haché, Alain

2008-10-01

Of all sports, ice hockey is possibly the one with the widest array of physics elements in it. The game provides many examples that can bring physics to life in the classroom. Ice hockey (or just "hockey" as many Canadians would say) sees athletes sliding on ice at high speeds and in various ways, shooting and slapping pucks, and colliding against each other. The interaction between the skate blade and the ice is a problem of great physical complexity. The question "Why is ice so slippery?" has puzzled generations of scientists and, surprisingly, clear answers have come relatively recently. There is even some optics involved in hockey: how many sports are watched behind tempered glass (or Plexiglas) windows? The optical and mechanical properties of these materials are worth a physics classroom discussion. In this paper, I will review a few topics discussed at length in my book The Physics of Hockey.1,2 Interested readers may also find additional articles on our website.3

Immersion Freezing of Total Ambient Aerosols and Ice Residuals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kulkarni, Gourihar

This laboratory study reports pre-activation measurements of the size-selected un-activated ambient or total aerosols at the temperature range from -26 to -34°C using two continuous-flow diffusion chamber style ice nucleation chambers. Two different experiments (A and B) were performed in immersion freezing mode. In experiment A, frozen fraction of total aerosol was measured, whereas in experiment B frozen fraction of ice residuals (IR) obtained through sublimation of nucleated ice crystals was measured. Frozen fractions at respective temperatures from experiment B were observed to be higher than A, and therefore it was concluded that ambient particles show pre-activation phenomenon. Furthermore, single-particlemore » elemental composition analyses of the total aerosols showed that majority of the particles are dust particles coated by organic matter. In general, this study suggests that such internally mixed complex total aerosols are efficient ice nucleating particles (INPs) and motivates further research to examine the physio-chemical properties of IR particles to explain the phenomenon of pre-activation.« less

Temporal and diurnal analysis of trace elements in the Cryospheric water at remote Laohugou basin in northeast Tibetan Plateau.

PubMed

Dong, Zhiwen; Kang, Shichang; Qin, Dahe; Qin, Xiang; Yan, Fangping; Du, Wentao; Wei, Ting

2017-03-01

An evaluation of glacial meltwater chemistry is needed under recent dramatic glacier melting when water resources might be significantly impacted. This study investigated trace elements variation in the meltwater stream, and its related aquatic environmental information, at the Laohugou (LHG) glacier basin (4260 m a.s.l.) at a remote location in northeast Tibetan Plateau. We focused on the spatial, temporal and diurnal change of trace elements during the glacier ablation period. Results showed evident elements spatial difference on the glacier surface meltwater, as most of the elements showed increased concentration at the terminus compared to higher elevations sites. Dominant elements in the meltwater were Ba, Sr and Cr, whereas elements with high enrichment factors (EFs) were Sb, Ni, Mo and Zn. Temporal change of some trace elements concentration (e.g. Sc, Cu, and Rb) indicated increasing trend with accelerated snow-ice melting, whereas others (e.g. Ni, Zn, and Pb) showed decreasing trend. We find that, trace elements showed evident diurnal change and a peak value of concentration was observed each day at about 15:00-17:00, and the diurnal change was influenced by runoff level and pH. Moreover, EFs calculations revealed that heavy metals were partially originated from regional anthropogenic sources. Overall, the accelerated diurnal and temporal snow-ice melting (with high runoff level) were correlated to increased elemental concentration, pH, EC and elemental change mode, and thus this work is of great importance for evaluating the impacts of accelerated glacier melting to meltwater chemistry and downstream ecosystem in the northeast Tibetan Plateau. Copyright © 2016 Elsevier Ltd. All rights reserved.

Chemical and physical characterization of fertile soil-derived ice residuals from the Fifth International Ice Nucleation workshop in November 2014 (FIN-1)

NASA Astrophysics Data System (ADS)

Hiranuma, Naruki; Möhler, Ottmar; Kulkarni, Gourihar; Laskin, Alexander; Zelenyuk, Alla

2017-04-01

The climate impact of ice-nucleating particles (INPs) derived from fertile soils on global scale has been recently accented by their diversity and efficient freezing ability. However, their representation in atmospheric models is limited in part due to our incomplete knowledge of fertile soil composition, abundance and associated sensitivity to heterogeneous ice nucleation. To fill given knowledge gap, we have investigated a unique/rich set of ice crystal residual samples derived from a variety of fertile soil samples obtained through our participation in the Fifth International Ice Nucleation workshop (FIN-1). FIN-1 was held at the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) facility at Karlsruhe Institute of Technology (KIT), which is the world's foremost facility for studying ice clouds in a controlled setting, in November 2014 to comprehensively study the heterogeneous ice formation in the atmosphere with collaboration among 10 international groups that were funded through European consortium, NSF and USDOE agencies. Here, we will present the nanoscale surface morphology and elemental/molecular composition of ice crystal residuals as well as that of total aerosol samples from the FIN-1 activity to identify and classify any specific mineral and organic inclusions that may have promoted nucleation of ice. Comparing total aerosols to residuals will shed light on the composition and abundance of certain particle types in INPs. Acknowledgements: The valuable contributions of the INUIT (Ice Nuclei Research Unit) collaborators, the FIN organizers, their institutions and the FIN-1 Workshop science team are gratefully acknowledged.

Ambient temperature enhanced freezing tolerance of Chrysanthemum dichrum CdICE1 Arabidopsis via miR398.

PubMed

Chen, Yu; Jiang, Jiafu; Song, Aiping; Chen, Sumei; Shan, Hong; Luo, Huolin; Gu, Chunsun; Sun, Jing; Zhu, Lu; Fang, Weimin; Chen, Fadi

2013-12-19

ICE (Inducer of CBF Expression) family genes play an important role in the regulation of cold tolerance pathways. In an earlier study, we isolated the gene CdICE1 from Chrysanthemum dichrum and demonstrated that freezing tolerance was enhanced by CdICE1 overexpression. Therefore, we sought to determine the mechanism by which ICE1 family genes participate in freezing tolerance. Using EMSA (Electrophoretic Mobility Shift Assay) and yeast one-hybrid assays, we confirmed that CdICE1 binds specifically to the MYC element in the CdDREBa promoter and activates transcription. In addition, overexpression of CdICE1 enhanced Arabidopsis freezing tolerance after transition from 23°C to 4°C or 16°C. We found that after acclimation to 4°C, CdICE1, like Arabidopsis AtICE1, promoted expression of CBFs (CRT/DRE Binding Factor) and their genes downstream involved in freezing tolerance, including COR15a (Cold-Regulated 15a), COR6.6, and RD29a (Responsive to Dessication 29a). Interestingly, we observed that CdICE1-overexpressing plants experienced significant reduction in miR398. In addition, its target genes CSD1 (Copper/zinc Superoxide Dismutase 1) and CSD2 showed inducible expression under acclimation at 16°C, indicating that the miR398-CSD pathway was involved in the induction of freezing tolerance. Our data indicate that CdICE1-mediated freezing tolerance occurs via different pathways, involving either CBF or miR398, under acclimation at two different temperatures.

Ambient temperature enhanced freezing tolerance of Chrysanthemum dichrum CdICE1 Arabidopsis via miR398

PubMed Central

2013-01-01

Background ICE (Inducer of CBF Expression) family genes play an important role in the regulation of cold tolerance pathways. In an earlier study, we isolated the gene CdICE1 from Chrysanthemum dichrum and demonstrated that freezing tolerance was enhanced by CdICE1 overexpression. Therefore, we sought to determine the mechanism by which ICE1 family genes participate in freezing tolerance. Results Using EMSA (Electrophoretic Mobility Shift Assay) and yeast one-hybrid assays, we confirmed that CdICE1 binds specifically to the MYC element in the CdDREBa promoter and activates transcription. In addition, overexpression of CdICE1 enhanced Arabidopsis freezing tolerance after transition from 23°C to 4°C or 16°C. We found that after acclimation to 4°C, CdICE1, like Arabidopsis AtICE1, promoted expression of CBFs (CRT/DRE Binding Factor) and their genes downstream involved in freezing tolerance, including COR15a (Cold-Regulated 15a), COR6.6, and RD29a (Responsive to Dessication 29a). Interestingly, we observed that CdICE1-overexpressing plants experienced significant reduction in miR398. In addition, its target genes CSD1 (Copper/zinc Superoxide Dismutase 1) and CSD2 showed inducible expression under acclimation at 16°C, indicating that the miR398-CSD pathway was involved in the induction of freezing tolerance. Conclusions Our data indicate that CdICE1-mediated freezing tolerance occurs via different pathways, involving either CBF or miR398, under acclimation at two different temperatures. PMID:24350981

Wind Tunnel Tests Conducted to Develop an Icing Flight Simulator

NASA Technical Reports Server (NTRS)

Ratvasky, Thomas P.

2001-01-01

As part of NASA's Aviation Safety Program goals to reduce aviation accidents due to icing, NASA Glenn Research Center is leading a flight simulator development activity to improve pilot training for the adverse flying characteristics due to icing. Developing flight simulators that incorporate the aerodynamic effects of icing will provide a critical element in pilot training programs by giving pilots a pre-exposure of icing-related hazards, such as ice-contaminated roll upset or tailplane stall. Integrating these effects into training flight simulators will provide an accurate representation of scenarios to develop pilot skills in unusual attitudes and loss-of-control events that may result from airframe icing. In order to achieve a high level of fidelity in the flight simulation, a series of wind tunnel tests have been conducted on a 6.5-percent-scale Twin Otter aircraft model. These wind tunnel tests were conducted at the Wichita State University 7- by 10-ft wind tunnel and Bihrle Applied Research's Large Amplitude Multiple Purpose Facility in Neuburg, Germany. The Twin Otter model was tested without ice (baseline), and with two ice configurations: 1) Ice on the horizontal tail only; 2) Ice on the wing, horizontal tail, and vertical tail. These wind tunnel tests resulted in data bases of aerodynamic forces and moments as functions of angle of attack; sideslip; control surface deflections; forced oscillations in the pitch, roll, and yaw axes; and various rotational speeds. A limited amount of wing and tail surface pressure data were also measured for comparison with data taken at Wichita State and with flight data. The data bases from these tests will be the foundation for a PC-based Icing Flight Simulator to be delivered to Glenn in fiscal year 2001.

Change and Variability in East Antarctic Sea Ice Seasonality, 1979/80–2009/10

PubMed Central

Massom, Robert; Reid, Philip; Stammerjohn, Sharon; Raymond, Ben; Fraser, Alexander; Ushio, Shuki

2013-01-01

Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine “icescape”, including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95–110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160–170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40–100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors. PMID:23705008

Change and variability in East antarctic sea ice seasonality, 1979/80-2009/10.

PubMed

Massom, Robert; Reid, Philip; Stammerjohn, Sharon; Raymond, Ben; Fraser, Alexander; Ushio, Shuki

2013-01-01

Recent analyses have shown that significant changes have occurred in patterns of sea ice seasonality in West Antarctica since 1979, with wide-ranging climatic, biological and biogeochemical consequences. Here, we provide the first detailed report on long-term change and variability in annual timings of sea ice advance, retreat and resultant ice season duration in East Antarctica. These were calculated from satellite-derived ice concentration data for the period 1979/80 to 2009/10. The pattern of change in sea ice seasonality off East Antarctica comprises mixed signals on regional to local scales, with pockets of strongly positive and negative trends occurring in near juxtaposition in certain regions e.g., Prydz Bay. This pattern strongly reflects change and variability in different elements of the marine "icescape", including fast ice, polynyas and the marginal ice zone. A trend towards shorter sea-ice duration (of 1 to 3 days per annum) occurs in fairly isolated pockets in the outer pack from∼95-110°E, and in various near-coastal areas that include an area of particularly strong and persistent change near Australia's Davis Station and between the Amery and West Ice Shelves. These areas are largely associated with coastal polynyas that are important as sites of enhanced sea ice production/melt. Areas of positive trend in ice season duration are more extensive, and include an extensive zone from 160-170°E (i.e., the western Ross Sea sector) and the near-coastal zone between 40-100°E. The East Antarctic pattern is considerably more complex than the well-documented trends in West Antarctica e.g., in the Antarctic Peninsula-Bellingshausen Sea and western Ross Sea sectors.

Biogeochemical Coupling between Ocean and Sea Ice

NASA Astrophysics Data System (ADS)

Wang, S.; Jeffery, N.; Maltrud, M. E.; Elliott, S.; Wolfe, J.

2016-12-01

Biogeochemical processes in ocean and sea ice are tightly coupled at high latitudes. Ongoing changes in Arctic and Antarctic sea ice domain likely influence the coupled system, not only through physical fields but also biogeochemical properties. Investigating the system and its changes requires representation of ocean and sea ice biogeochemical cycles, as well as their coupling in Earth System Models. Our work is based on ACME-HiLAT, a new offshoot of the Community Earth System Model (CESM), including a comprehensive representation of marine ecosystems in the form of the Biogeochemical Elemental Cycling Module (BEC). A full vertical column sea ice biogeochemical module has recently been incorporated into the sea ice component. We have further introduced code modifications to couple key growth-limiting nutrients (N, Si, Fe), dissolved and particulate organic matter, and phytoplankton classes that are important in polar regions between ocean and sea ice. The coupling of ocean and sea ice biology-chemistry will enable representation of key processes such as the release of important climate active constituents or seeding algae from melting sea ice into surface waters. Sensitivity tests suggest sea ice and ocean biogeochemical coupling influences phytoplankton competition, biological production, and the CO2 flux. Sea ice algal seeding plays an important role in determining phytoplankton composition of Arctic early spring blooms, since different groups show various responses to the seeding biomass. Iron coupling leads to increased phytoplankton biomass in the Southern Ocean, which also affects carbon uptake via the biological pump. The coupling of macronutrients and organic matter may have weaker influences on the marine ecosystem. Our developments will allow climate scientists to investigate the fully coupled responses of the sea ice-ocean BGC system to physical changes in polar climate.

Additional Improvements to the NASA Lewis Ice Accretion Code LEWICE

NASA Technical Reports Server (NTRS)

Wright, William B.; Bidwell, Colin S.

1995-01-01

Due to the feedback of the user community, three major features have been added to the NASA Lewis ice accretion code LEWICE. These features include: first, further improvements to the numerics of the code so that more time steps can be run and so that the code is more stable; second, inclusion and refinement of the roughness prediction model described in an earlier paper; third, inclusion of multi-element trajectory and ice accretion capabilities to LEWICE. This paper will describe each of these advancements in full and make comparisons with the experimental data available. Further refinement of these features and inclusion of additional features will be performed as more feedback is received.

The Lunar IceCube Mission Challenge: Attaining Science Orbit Parameters from a Constrained Approach Trajectory

NASA Technical Reports Server (NTRS)

Folta, David C.; Bosanac, Natasha; Cox, Andrew; Howell, Kathleen C.

2017-01-01

The challenges of targeting specific lunar science orbit parameters from a concomitant Sun-EarthMoon system trajectory are examined. While the concept of ballistic lunar capture is well-studied, achieving and controlling the time evolution of the orbital elements to satisfy mission constraints is especially problematic when the spacecraft is equipped with a low-thrust propulsion system. Satisfying these requirements on the lunar approach and capture segments is critical to the success of the Lunar IceCube mission, a 6U CubeSat that will prospect for water in solid (ice), liquid, and vapor forms and other lunar volatiles from a low-periapsis, highly inclined elliptical lunar orbit.

The Lunar IceCube Mission Challenge: Attaining Science Orbit Parameters from a Constrained Approach Trajectory

NASA Technical Reports Server (NTRS)

Folta, David C.; Bosanac, Natasha; Cox, Andrew; Howell, Kathleen C.

2017-01-01

The challenges of targeting specific lunar science orbit parameters from a concomitant Sun-Earth/Moon system trajectory are examined. While the concept of ballistic lunar capture is well-studied, achieving and controlling the time evolution of the orbital elements to satisfy mission constraints is especially problematic when the spacecraft is equipped with a low-thrust propulsion system. Satisfying these requirements on the lunar approach and capture segments is critical to the success of the Lunar IceCube mission, a 6U CubeSat that will prospect for water in solid (ice), liquid, and vapor forms and other lunar volatiles from a low-periapsis, highly inclined elliptical lunar orbit.

Unravelling source regions of ice rafted debris within three NE Atlantic marine sediment cores during the deglacial interval: a multi-proxy approach

NASA Astrophysics Data System (ADS)

Small, David; Hibbert, Fiona; Austin, Bill

2010-05-01

Ice-rafted debris (IRD) within marine sediments of the North Atlantic provide an important archive of glacial activity on adjacent landmasses and attest to the activity of multiple calving ice margins during the last glacial cycle. IRD records therefore provide a means to reconstruct ice sheet dynamics and their interaction with the climate system, providing evidence of both the source of the ice and the location of melting (e.g. Ruddiman, 1977; Bond and Lotti, 1995). The complex interaction of the circum-Atlantic ice sheets and limitations of individual techniques often hinders firm source designations (i.e. IRD may be derived from multiple sources which cannot be differentiated by, for example, visual characterisation). Initial work identified diagnostic grain types that could be attributed to source areas of palaeo ice-sheets (eg: Bond & Lotti 1995) however, for the BIS, "diagnostic" basalt may be derived from sources to the east and west of the cores (Hibbert et al 2009, Scourse et al 2009). We therefore, utilise a multi-proxy approach to investigate the deglacial dynamics of the last British Ice Sheet (BIS) using inter alia lithic characterisation, fluxes of IRD to the core sites, magnetic susceptibility and a magnetic un-mixing model. A novel application of major element geochemistry of garnets contained within ice-rafted debris of the three high resolution marine sediment cores is presented. Garnets can be used to infer provenance (e.g. Oliver 2001) as major element composition may be assigned to specific metamorphic terranes. The IRD present within these cores is believed to be predominantly sourced from the BIS (cf: Knutz et al 2001, Hibbert et al 2009). This assertion is tested through multiple analytical techniques used and replication of records across the Hebridean shelf into the deep ocean. References • Bond, G.C. & Lotti, R., 1995. Iceberg discharges into the North Atlantic on millennial timescales during the last glaciation. Science 267. pp. 1005-1010. • Hibbert, F.D., Austin, W.E.N., Leng, M.J. and Gatliff, R.W., 2009. British Ice Sheet Dynamics inferred from North Atlantice ice-rafted debris records spanning the last 175,000 years. Journal of Quaternary Science. ISSN 0267-8179. • Knutz, P.C., Austin, W.E.N. and Jones, E.J.W., 2001. Millenial-scale depositional cycles related to British Ice Sheet variability and North Atlantic paleocirculation since 45kyr B.P., Barra Fan, U.K. margin. Paleoceanography 16. pp.53-64. • Oliver, G.J.H., 2001. Reconstruction of the Grampian episode in Scotland: it's place in the Caledonian Orogeny. Tectonphysics 332. pp.23-49. • Ruddiman, W.F., 1977. Late Quaternary deposition of ice-rafted sand in the sub-polar North Atlantic (lat 40° to 65°). Geological Society of America Bulletin 88. pp.1813-1821. • Scourse, J.D., Haapaniemi, A.I., Colmenero-Hidalgo, E., Peck, V.L., Hall, I.R., Austin, W.E.N., Knutz, P.C. and Zahn, R., 2009. Growth, dynamics and deglaciation of the last British-Irish Ice Sheet: the deep-sea ice-rafted detritus record. Quaternary Science Reviews 28. pp.3066-3084.

Conjugate Heat Transfer Analyses on the Manifold for Ramjet Fuel Injectors

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen J.

2006-01-01

Three-dimensional conjugate heat transfer analyses on the manifold located upstream of the ramjet fuel injector are performed using CFdesign, a finite-element computational fluid dynamics (CFD) software. The flow field of the hot fuel (JP-7) flowing through the manifold is simulated and the wall temperature of the manifold is computed. The three-dimensional numerical results of the fuel temperature are compared with those obtained using a one-dimensional analysis based on empirical equations, and they showed a good agreement. The numerical results revealed that it takes around 30 to 40 sec to reach the equilibrium where the fuel temperature has dropped about 3 F from the inlet to the exit of the manifold.

Double diffusive conjugate heat transfer: Part II

NASA Astrophysics Data System (ADS)

Azeem, Soudagar, Manzoor Elahi M.

2018-05-01

Conjugate heat transfer in porous medium is an important study involved in many practical applications. The current study is aimed to investigate the double diffusive flow in a square porous cavity subjected to left vertical surface heating and right vertical surface cooling respectively along with left and right surfaces maintained at high and low concentration. The three governing equations are converted into algebraic form of equations by applying finite element method and solved in iterative manner. The study is focused to investigate the effect of presence of solid inside the cavity with respect to varying buoyancy ratio. It is found that the local heat and mass transfer rate decreases along the height of cavity.

New Convex and Spherical Structures of Bare Boron Clusters

NASA Astrophysics Data System (ADS)

Boustani, Ihsan

1997-10-01

New stable structures of bare boron clusters can easily be obtained and constructed with the help of an "Aufbau Principle" suggested by a systematicab initioHF-SCF and direct CI study. It is concluded that boron cluster formation can be established by elemental units of pentagonal and hexagonal pyramids. New convex and small spherical clusters different from the classical known forms of boron crystal structures are obtained by a combination of both basic units. Convex structures simulate boron surfaces which can be considered as segments of open or closed spheres. Both convex clusters B16and B46have energies close to those of their conjugate quasi-planar clusters, which are relatively stable and can be considered to act as a calibration mark. The closed spherical clusters B12, B22, B32, and B42are less stable than the corresponding conjugated quasi-planar structures. As a consequence, highly stable spherical boron clusters can systematically be predicted when their conjugate quasi-planar clusters are determined and energies are compared.

Phased laser array for generating a powerful laser beam

DOEpatents

Holzrichter, John F.; Ruggiero, Anthony J.

2004-02-17

A first injection laser signal and a first part of a reference laser beam are injected into a first laser element. At least one additional injection laser signal and at least one additional part of a reference laser beam are injected into at least one additional laser element. The first part of a reference laser beam and the at least one additional part of a reference laser beam are amplified and phase conjugated producing a first amplified output laser beam emanating from the first laser element and an additional amplified output laser beam emanating from the at least one additional laser element. The first amplified output laser beam and the additional amplified output laser beam are combined into a powerful laser beam.

On the scalability of the Albany/FELIX first-order Stokes approximation ice sheet solver for large-scale simulations of the Greenland and Antarctic ice sheets

DOE PAGES

Tezaur, Irina K.; Tuminaro, Raymond S.; Perego, Mauro; ...

2015-01-01

We examine the scalability of the recently developed Albany/FELIX finite-element based code for the first-order Stokes momentum balance equations for ice flow. We focus our analysis on the performance of two possible preconditioners for the iterative solution of the sparse linear systems that arise from the discretization of the governing equations: (1) a preconditioner based on the incomplete LU (ILU) factorization, and (2) a recently-developed algebraic multigrid (AMG) preconditioner, constructed using the idea of semi-coarsening. A strong scalability study on a realistic, high resolution Greenland ice sheet problem reveals that, for a given number of processor cores, the AMG preconditionermore » results in faster linear solve times but the ILU preconditioner exhibits better scalability. In addition, a weak scalability study is performed on a realistic, moderate resolution Antarctic ice sheet problem, a substantial fraction of which contains floating ice shelves, making it fundamentally different from the Greenland ice sheet problem. We show that as the problem size increases, the performance of the ILU preconditioner deteriorates whereas the AMG preconditioner maintains scalability. This is because the linear systems are extremely ill-conditioned in the presence of floating ice shelves, and the ill-conditioning has a greater negative effect on the ILU preconditioner than on the AMG preconditioner.« less

Characterization of the mechanical behavior of sea ice as a frictional material

NASA Astrophysics Data System (ADS)

Lade, Poul V.

2002-12-01

The mechanical properties of sea ice are determined by the formation process, and the consequent material behavior at the element scale exhibits viscoelastic behavior at the early loading stages, followed by brittle fracture or ductile, irrecoverable deformation that may be captured by hardening/softening plasticity models with nonassociated flow. Failure of sea ice under different loading conditions follows a pattern that demonstrates its highly cross-anisotropic nature as well as its behavior as a frictional material. The interactions between the floes in the pack ice resemble those observed in granular materials. These materials are frictional in nature, they exhibit both contractive and dilative volume changes, the plastic flow is nonassociated, and their stiffnesses and strengths increase with confining pressure, but they do not have any strength when unconfined. The overall behavior of the pack ice may be close to isotropic. Constitutive modeling of this behavior may be achieved by models used in geotechnical engineering. Formation of leads and subsequent freezing of the water results in cementation between the ice floes, and the pack ice becomes stronger. The behavior of the pack ice may now be compared with that observed in cemented soils or concrete. For these materials, increasing amounts of cementation result in increasing rates of dilation when sheared, and this accounts for the largest contribution to the increase in shear strength.

Genomic islands 1 and 2 play key roles in the evolution of extensively drug-resistant ST235 isolates of Pseudomonas aeruginosa

PubMed Central

Scott, Martin; Worden, Paul; Huntington, Peter; Hudson, Bernard; Karagiannis, Thomas; Charles, Ian G.; Djordjevic, Steven P.

2016-01-01

Pseudomonas aeruginosa are noscomially acquired, opportunistic pathogens that pose a major threat to the health of burns patients and the immunocompromised. We sequenced the genomes of P. aeruginosa isolates RNS_PA1, RNS_PA46 and RNS_PAE05, which displayed resistance to almost all frontline antibiotics, including gentamicin, piperacillin, timentin, meropenem, ceftazidime and colistin. We provide evidence that the isolates are representatives of P. aeruginosa sequence type (ST) 235 and carry Tn6162 and Tn6163 in genomic islands 1 (GI1) and 2 (GI2), respectively. GI1 disrupts the endA gene at precisely the same chromosomal location as in P. aeruginosa strain VR-143/97, of unknown ST, creating an identical CA direct repeat. The class 1 integron associated with Tn6163 in GI2 carries a blaGES-5–aacA4–gcuE15–aphA15 cassette array conferring resistance to carbapenems and aminoglycosides. GI2 is flanked by a 12 nt direct repeat motif, abuts a tRNA-gly gene, and encodes proteins with putative roles in integration, conjugative transfer as well as integrative conjugative element-specific proteins. This suggests that GI2 may have evolved from a novel integrative conjugative element. Our data provide further support to the hypothesis that genomic islands play an important role in de novo evolution of multiple antibiotic resistance phenotypes in P. aeruginosa. PMID:26962050

ICE1 of Pyrus ussuriensis functions in cold tolerance by enhancing PuDREBa transcriptional levels through interacting with PuHHP1

NASA Astrophysics Data System (ADS)

Huang, Xiaosan; Li, Kongqing; Jin, Cong; Zhang, Shaoling

2015-12-01

ICE1 transcription factor plays an important role in plant cold stress via regulating the expression of stress-responsive genes. In this study, a PuICE1 gene isolated from Pyrus ussuriensis was characterized for its function in cold tolerance. The expression levels of the PuICE1 were induced by cold, dehydration and salt, with the greatest induction under cold conditions. PuICE1 was localized in the nucleus and could bind specifically to the MYC element in the PuDREBa promoter. The PuICE1 fused to the GAL4 DNA-binding domain to have transcriptional activation activity. Ectopic expression of the PuICE1 in tomato conferred enhanced tolerance to cold stress at cold temperatures, less electrolyte leakage, less MDA content, higher chlorophyll content, higher survival rate, higher proline content, higher activities of enzymes. In additon, steady-state mRNA levels of six stress-responsive genes coding for either functional or regulatory genes were induced to higher levels in the transgenic lines by cold stress. Yeast two-hybrid, transient assay, split luciferase complementation and BiFC assays all revealed that PuHHP1 protein can physically interact with PuICE1. Taken together, these results demonstrated that PuICE1 plays a positive role in cold tolerance, which may be due to enhancement of PuDREBa transcriptional levels through interacting with the PuHHP1.

A Method for Continuous (239)Pu Determinations in Arctic and Antarctic Ice Cores.

PubMed

Arienzo, M M; McConnell, J R; Chellman, N; Criscitiello, A S; Curran, M; Fritzsche, D; Kipfstuhl, S; Mulvaney, R; Nolan, M; Opel, T; Sigl, M; Steffensen, J P

2016-07-05

Atmospheric nuclear weapons testing (NWT) resulted in the injection of plutonium (Pu) into the atmosphere and subsequent global deposition. We present a new method for continuous semiquantitative measurement of (239)Pu in ice cores, which was used to develop annual records of fallout from NWT in ten ice cores from Greenland and Antarctica. The (239)Pu was measured directly using an inductively coupled plasma-sector field mass spectrometer, thereby reducing analysis time and increasing depth-resolution with respect to previous methods. To validate this method, we compared our one year averaged results to published (239)Pu records and other records of NWT. The (239)Pu profiles from the Arctic ice cores reflected global trends in NWT and were in agreement with discrete Pu profiles from lower latitude ice cores. The (239)Pu measurements in the Antarctic ice cores tracked low latitude NWT, consistent with previously published discrete records from Antarctica. Advantages of the continuous (239)Pu measurement method are (1) reduced sample preparation and analysis time; (2) no requirement for additional ice samples for NWT fallout determinations; (3) measurements are exactly coregistered with all other chemical, elemental, isotopic, and gas measurements from the continuous analytical system; and (4) the long half-life means the (239)Pu record is stable through time.

High export of dissolved silica from the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D. W.; Arendt, K. E.; Yde, J. C.; Juul Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F. J. R.

2016-09-01

Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr-1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups.

Simple energy balance model resolving the seasons and the continents - Application to the astronomical theory of the ice ages

NASA Technical Reports Server (NTRS)

North, G. R.; Short, D. A.; Mengel, J. G.

1983-01-01

An analysis is undertaken of the properties of a one-level seasonal energy balance climate model having explicit, two-dimensional land-sea geography, where land and sea surfaces are strictly distinguished by the local thermal inertia employed and transport is governed by a smooth, latitude-dependent diffusion mechanism. Solutions of the seasonal cycle for the cases of both ice feedback exclusion and inclusion yield good agreements with real data, using minimal turning of the adjustable parameters. Discontinuous icecap growth is noted for both a solar constant that is lower by a few percent and a change of orbital elements to favor cool Northern Hemisphere summers. This discontinuous sensitivity is discussed in the context of the Milankovitch theory of the ice ages, and the associated branch structure is shown to be analogous to the 'small ice cap' instability of simpler models.

Magnetoresistance in Permalloy Connected Brickwork Artificial Spin Ice

NASA Astrophysics Data System (ADS)

Park, Jungsik; Le, Brian; Chern, Gia-Wei; Watts, Justin; Leighton, Chris; Schiffer, Peter

Artificial spin ice refers to a two-dimensional array of elongated ferromagnetic elements in which frustrated lattice geometry induces novel magnetic behavior. Here we examine room-temperature magnetoresistance properties of connected permalloy (Ni81Fe19) brickwork artificial spin ice. Both the longitudinal and transverse magnetoresistance of the nanostructure demonstrate an angular sensitivity that has not been previously observed. The observed magnetoresistance behavior can be explained from micromagnetic modelling using an anisotropic magnetoresistance model (AMR). As part of this study, we find that the ground state of the connected brickwork artificial spin ice can be reproducibly created by a simple field sweep in a narrow range of angles, and manifests in the magnetotransport with a distinct signal. Supported by the US Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Grant Number DE-SC0010778. Work at the University of Minnesota was supported by the NSF MRSEC under award DMR-1420013, and DMR-1507048.

Sea ice proxies, marine environmental change, and human societies in Northwest Greenland over the past ca. 4500 years

NASA Astrophysics Data System (ADS)

Ribeiro, Sofia; Weckström, Kaarina; Tallberg, Petra; Risager Kjøller, Marianne; Limoges, Audrey; Massé, Guillaume; Nissen, Martin; Toudal Pedersen, Leif; Mikkelsen, Naja

2016-04-01

Greenland has been inhabited for only ca. 4500 years, but several human colonization events and cultural transitions occurred during this period. This work is part of the ICE-ARC project - Ice, Climate and Economics in the Arctic (EU FP7), aimed at understanding and quantifying the multiple stresses involved in the change in the Arctic marine environment, with particular focus on the rapid retreat and collapse of the Arctic sea ice cover. The overall goal of the project is to assess the climatic (ice, ocean, atmosphere and ecosystem), economic and social impacts of these stresses on regional and global scales. Marine sediment cores were retrieved from the Inglefield Bredning fjord system in the Qaanaaq region, Northwest Greenland, and are being analysed for various climate and environmental proxies, including biological indicators (e.g. dinoflagellate cysts, diatoms), biogeochemical elements (biogenic silica, XRF scanning), and sea-ice specific biomarkers (IP25). We will present the first data from this core material, consisting of a spatial study of sea ice and productivity proxies in 13 surface sediment samples (IP25, biogenic silica, diatoms, and dinoflagellate cysts) which will be compared with satellite-derived sea ice cover data for the Qaanaaq region/ northern Baffin Bay. This spatial study will serve as basis to reconstruct sea ice variability in the area over the past ca. 4500 years, and will be combined with historical and archaeological data in order to identify possible links between past changes in climate and sea ice conditions, and events of human migration and cultural transition in Greenland.

Abrupt Climate Change in the Atlantic Ocean During the Last 20,000 Years: Insights from Multi-Element Analyses of Benthic and Planktic Foraminifera and a Coupled OA-GCM

DTIC Science & Technology

2005-09-01

paleoceanographic and terrestrial climate proxies . Greenland ice cores, in particular, provide evidence of large amplitude, very rapid climate change during...received the most attention because it is the largest Holocene excursion in the GISP2 810 record [Alley et al., 1997]. Multiple proxies in Greenland ice...latitude North Atlantic foraminiferal-based proxies such as modem analogue technique [Marchal et al., 2002; Risebrobakken et al., 2003], but

Linking ice accretion and crown structure: towards a model of the effect of freezing rain on tree canopies

PubMed Central

Nock, Charles A.; Lecigne, Bastien; Taugourdeau, Olivier; Greene, David F.; Dauzat, Jean; Delagrange, Sylvain; Messier, Christian

2016-01-01

Background and Aims Despite a longstanding interest in variation in tree species vulnerability to ice storm damage, quantitative analyses of the influence of crown structure on within-crown variation in ice accretion are rare. In particular, the effect of prior interception by higher branches on lower branch accumulation remains unstudied. The aim of this study was to test the hypothesis that intra-crown ice accretion can be predicted by a measure of the degree of sheltering by neighbouring branches. Methods Freezing rain was artificially applied to Acer platanoides L., and in situ branch-ice thickness was measured directly and from LiDAR point clouds. Two models of freezing rain interception were developed: ‘IceCube’, which uses point clouds to relate ice accretion to a voxel-based index (sheltering factor; SF) of the sheltering effect of branch elements above a measurement point; and ‘IceTree’, a simulation model for in silico evaluation of the interception pattern of freezing rain in virtual tree crowns. Key Results Intra-crown radial ice accretion varied strongly, declining from the tips to the bases of branches and from the top to the base of the crown. SF for branches varied strongly within the crown, and differences among branches were consistent for a range of model parameters. Intra-crown variation in ice accretion on branches was related to SF (R2 = 0·46), with in silico results from IceTree supporting empirical relationships from IceCube. Conclusions Empirical results and simulations confirmed a key role for crown architecture in determining intra-crown patterns of ice accretion. As suspected, the concentration of freezing rain droplets is attenuated by passage through the upper crown, and thus higher branches accumulate more ice than lower branches. This is the first step in developing a model that can provide a quantitative basis for investigating intra-crown and inter-specific variation in freezing rain damage. PMID:27107412

Recent Glaciers on Mars: Description and Solar System Perspective

NASA Astrophysics Data System (ADS)

Kargel, J. S.

2001-11-01

Active or recently active ice deposits occur on Mars at middle and high latitudes in fretted terrain, around massifs in highlands east of Hellas and in southern Argyre, on crater walls in the highlands, and in the south polar cap. Most mid-latitude icy flows are debris covered, apparently stagnant, and eroded by partial sublimation. Others are scarred by fresh crevasses and gullies, thus suggesting recent deformation and surface melting. Erosional features include a variety of small-scale relief elements due mainly to sublimation, but sublimation has not obliterated evidence of flow. Similar to terrestrial glaciers in many respects, there are also notable differences, especially in the nature of accumulation. Deformation of the south polar cap is indicated by folding, boudinage, strike-slip or normal faulting, forebulge tectonics near scarps, and thrust faulting. The north polar cap locally also exhibits flow indicators. The south cap's glacial features suggest interbedding of two or more types of ice of differing volatility and rheology, plus a locally deforming surficial dry-ice cap overlying the other materials. Major ice types may include two (or more) of the following, in order of highest to lowest mechanical strength: CO2 clathrate hydrate, water ice, water ice containing traces of liquid-soluble salts, water ice containing traces of solid-soluble acids, and CO2 ice; dust is another variable. Within our Solar System, the closest geomorphic analog to icy Martian flows are Earth's alpine glaciers, rock glaciers, and continental ice sheets, though key differences are apparent. If made dominantly of water ice, important and recent climatic shifts seem to be implicated. Ice-flow landforms also occur on some outer planet satellites; among them are Io, Europa, Enceladus, Ariel, and Triton. Volatile flows on these bodies may involve diverse materials, such as sulfur, water ice, hydrated salts, ammonia-water ices, and nitrogen ice. Most of these would not be suitable materials on Mars. This work was funded by grants from the NASA Mars Data Analysis Program.

The Behavior of Regular Satellites during the Nice Model's Planetary Close Encounters

NASA Astrophysics Data System (ADS)

Nogueira, E. C.; Gomes, R. S.; Brasser, R.

2014-10-01

In order to explain the behavior of the regular satellites of the ice planets during the instability phase of the Nice model, we used numerical simulations to investigate the evolution of the satellite systems when these two planets experienced encounters with the gas giants. For the initial conditions we placed an ice planet in between Jupiter and Saturn, according to the evolution of Nice model simulations in a jumping Jupiter scenario (Brasser et al. 2009). We used the MERCURY integrator (Chambers 1999) and we obtained 101 successful runs which kept all planets, of which 24 were jumping Jupiter cases. Subsequently we performed additional numerical integrations in which the ice giant that encountered a gas giant was started on the same orbit but with its regular satellites included. This is done as follows: For each of the 101 basic runs, we save the orbital elements of all objects in the integration at all close encounter events. Then we performed a backward integration to start the system 100 years before the encounter and re-enacted the forward integration with the regular satellites around the ice giant. The final orbital elements of the satellites with respect to the ice planet were used to restart the integration for the next planetary encounter. If we assume that Uranus is the ice planet that had encounters with a gas giant, we considered the satellites Miranda, Ariel, Umbriel, Titania and Oberon with their present orbits. For Neptune we introduced Triton with an orbit with a 15% larger than the actual semi-major axis to account for the tidal decay from the LHB to present time. We also assume that Triton was captured through binary disruption (Agnor and Hamilton 2006, Nogueira et al. 2011) and its orbit was circularized by tides during the 500 million years before the LHB.

Anisotropic mesh adaptation for marine ice-sheet modelling

NASA Astrophysics Data System (ADS)

Gillet-Chaulet, Fabien; Tavard, Laure; Merino, Nacho; Peyaud, Vincent; Brondex, Julien; Durand, Gael; Gagliardini, Olivier

2017-04-01

Improving forecasts of ice-sheets contribution to sea-level rise requires, amongst others, to correctly model the dynamics of the grounding line (GL), i.e. the line where the ice detaches from its underlying bed and goes afloat on the ocean. Many numerical studies, including the intercomparison exercises MISMIP and MISMIP3D, have shown that grid refinement in the GL vicinity is a key component to obtain reliable results. Improving model accuracy while maintaining the computational cost affordable has then been an important target for the development of marine icesheet models. Adaptive mesh refinement (AMR) is a method where the accuracy of the solution is controlled by spatially adapting the mesh size. It has become popular in models using the finite element method as they naturally deal with unstructured meshes, but block-structured AMR has also been successfully applied to model GL dynamics. The main difficulty with AMR is to find efficient and reliable estimators of the numerical error to control the mesh size. Here, we use the estimator proposed by Frey and Alauzet (2015). Based on the interpolation error, it has been found effective in practice to control the numerical error, and has some flexibility, such as its ability to combine metrics for different variables, that makes it attractive. Routines to compute the anisotropic metric defining the mesh size have been implemented in the finite element ice flow model Elmer/Ice (Gagliardini et al., 2013). The mesh adaptation is performed using the freely available library MMG (Dapogny et al., 2014) called from Elmer/Ice. Using a setup based on the inter-comparison exercise MISMIP+ (Asay-Davis et al., 2016), we study the accuracy of the solution when the mesh is adapted using various variables (ice thickness, velocity, basal drag, …). We show that combining these variables allows to reduce the number of mesh nodes by more than one order of magnitude, for the same numerical accuracy, when compared to uniform mesh refinement. For transient solutions where the GL is moving, we have implemented an algorithm where the computation is reiterated allowing to anticipate the GL displacement and to adapt the mesh to the transient solution. We discuss the performance and robustness of this algorithm.

Research Applications of Data from Arctic Ocean Drifting Platforms: The Arctic Buoy Program and the Environmental Working Group CD's.

NASA Astrophysics Data System (ADS)

Moritz, R. E.; Rigor, I.

2006-12-01

ABSTRACT: The Arctic Buoy Program was initiated in 1978 to measure surface air pressure, surface temperature and sea-ice motion in the Arctic Ocean, on the space and time scales of synoptic weather systems, and to make the data available for research, forecasting and operations. The program, subsequently renamed the International Arctic Buoy Programme (IABP), has endured and expanded over the past 28 years. A hallmark of the IABP is the production, dissemination and archival of research-quality datasets and analyses. These datasets have been used by the authors of over 500 papers on meteorolgy, sea-ice physics, oceanography, air-sea interactions, climate, remote sensing and other topics. Elements of the IABP are described briefly, including measurements, analysis, data dissemination and data archival. Selected highlights of the research applications are reviewed, including ice dynamics, ocean-ice modeling, low-frequency variability of Arctic air-sea-ice circulation, and recent changes in the age, thickness and extent of Arctic Sea-ice. The extended temporal coverage of the data disseminated on the Environmental Working Group CD's is important for interpreting results in the context of climate.

New Constraints on Post-LGM WAIS Retreat from the Whales Deep Paleo-ice-stream Trough in Eastern Ross Sea

NASA Astrophysics Data System (ADS)

DeCesare, M.; Bart, P. J.; Rosenheim, B. E.

2016-02-01

New multibeam and seismic data acquired during NBP1502 show that a back-stepping cluster containing at least four grounding zone wedges (GZWs) define a bathymetric saddle on the middle shelf of the Whales Deep paleo-ice-stream trough in eastern Ross Sea. Our synthesis of geophysical data with jumbo piston/kasten cores show that we penetrated diamict, sub-ice shelf and open marine sediments associated with four temporally distinct grounding events. A high number of well-preserved benthic and planktonic foraminifera were found in sediments we interpret to have been deposited in sub-ice shelf and open marine environments. A low number of similarly well-preserved benthic foraminifera were recovered from the underlying ice proximal diamict that was deposited on the GZW foreset. We tentatively propose that the pristine foraminifera are in situ and that these specimens provide a unique opportunity to constrain the retreat of grounded and floating ice from the eastern Ross Sea outer continental shelf. Our ongoing synthesis of new radiocarbon dates, stable isotope (δ18O and δ13C) and element/calcium ratios (e.g., Mg/Ca, B/Ca) will be presented.

A microbial ecosystem beneath the West Antarctic ice sheet.

PubMed

Christner, Brent C; Priscu, John C; Achberger, Amanda M; Barbante, Carlo; Carter, Sasha P; Christianson, Knut; Michaud, Alexander B; Mikucki, Jill A; Mitchell, Andrew C; Skidmore, Mark L; Vick-Majors, Trista J

2014-08-21

Liquid water has been known to occur beneath the Antarctic ice sheet for more than 40 years, but only recently have these subglacial aqueous environments been recognized as microbial ecosystems that may influence biogeochemical transformations on a global scale. Here we present the first geomicrobiological description of water and surficial sediments obtained from direct sampling of a subglacial Antarctic lake. Subglacial Lake Whillans (SLW) lies beneath approximately 800 m of ice on the lower portion of the Whillans Ice Stream (WIS) in West Antarctica and is part of an extensive and evolving subglacial drainage network. The water column of SLW contained metabolically active microorganisms and was derived primarily from glacial ice melt with solute sources from lithogenic weathering and a minor seawater component. Heterotrophic and autotrophic production data together with small subunit ribosomal RNA gene sequencing and biogeochemical data indicate that SLW is a chemosynthetically driven ecosystem inhabited by a diverse assemblage of bacteria and archaea. Our results confirm that aquatic environments beneath the Antarctic ice sheet support viable microbial ecosystems, corroborating previous reports suggesting that they contain globally relevant pools of carbon and microbes that can mobilize elements from the lithosphere and influence Southern Ocean geochemical and biological systems.

Production and evaluation of mineral and nutrient contents, chemical composition, and sensory properties of ice creams fortified with laboratory-prepared peach fibre

PubMed Central

Yangılar, Filiz

2016-01-01

Background In the coming years, a nutraceutical food may provide both physical and mental benefits that are commonly attributed to the active components of the food. Objective In this study, we determined the nutrient and mineral contents, sensory properties, and physical and chemical characteristics of ice creams manufactured using peach fibre at different concentrations (1 and 2%). Method A total of five experimental groups were formed: two types (from peach peel and pulp) of flour, two fibre concentrations (1 and 2%), and a control group without fibres. Results Flour obtained from peach pulp and peel was found to have a significant (p<0.05) effect on the chemical composition and elemental composition of ice cream samples, especially the rates of Ca, K, Mg, and P, which increased in the samples depending on the content of peach fibre. Sensory ratings and acceptability of ice creams decreased significantly with increasing peach peel fibre, whereas ice creams made with C (control) and B1 (ice creams made from 1% peach pulp fibre) was the highest scored by the panellists. Conclusions Peach fibre concentrates might be used as a good source of nutraceutical ingredients. PMID:27814781

Close-up analysis of aircraft ice accretion

NASA Technical Reports Server (NTRS)

Hansman, R. John; Breuer, Kenneth S.; Hazan, Didier; Reehorst, Andrew; Vargas, Mario

1993-01-01

Various types of ice formation have been studied by analysis of high magnification video observations. All testing was conducted in the NASA Lewis Icing Research Tunnel (IRT). A faired 8.9 cm (3.5 in.) diameter metal-clad cylinder and a 5.1 (2 in.) aluminum cylinder were observed by close-up and overview video cameras for several wind tunnel conditions. These included close-up grazing angle, close-up side view, as well as overhead and side overview cameras. Still photographs were taken at the end of each spray along with tracings of the subsequent ice shape. While in earlier tests only the stagnation region was observed, the entire area from the stagnation line to the horn region of glaze ice shapes was observed in this test. The modes or horn formation have been identified within the range of conditions observed. In the horn region, Horn Type A ice is formed by 'dry' feather growth into the flow direction and Horn Type B is formed by a 'wet' growth normal to the surface. The feather growth occurs when the freezing fraction is near unity and roughness elements exist to provide an initial growth site.

Assessing the efficiency of carbide drill bits and factors influencing their application to debris-rich subglacial ice

NASA Astrophysics Data System (ADS)

Yang, Cheng; Jiang, Jianliang; Cao, Pinlu; Wang, Jinsong; Fan, Xiaopeng; Shang, Yuequan; Talalay, Pavel

2017-09-01

When drilling into subglacial bedrock, drill operators commonly encounter basal ice containing high concentrations of rock debris and melt water. As such conditions can easily damage conventional ice drills, researchers have experimented with carbide, diamond, and polycrystalline diamond compact drill bits, with varying degrees of success. In this study, we analyzed the relationship between drilling speed and power consumption for a carbide drill bit penetrating debris-rich ice. We also assessed drill load, rotation speed, and various performance parameters for the cutting element, as well as the physical and mechanical properties of rock and ice, to construct mathematical models. We show that our modeled results are in close agreement with the experimental data, and that both penetration speed and power consumption are positively correlated with drill speed and load. When used in ice with 30% rock content, the maximum penetration speed of the carbide bit is 3.4 mm/s with a power consumption of ≤0.5 kW, making the bit suitable for use with existing electromechanical drills. Our study also provides a guide for further research into cutting heat and equipment design.

pA506, a Conjugative Plasmid of the Plant Epiphyte Pseudomonas fluorescens A506

PubMed Central

Stockwell, Virginia O.; Davis, Edward W.; Carey, Alyssa; Shaffer, Brenda T.; Mavrodi, Dmitri V.; Hassan, Karl A.; Hockett, Kevin; Thomashow, Linda S.; Paulsen, Ian T.

2013-01-01

Conjugative plasmids are known to facilitate the acquisition and dispersal of genes contributing to the fitness of Pseudomonas spp. Here, we report the characterization of pA506, the 57-kb conjugative plasmid of Pseudomonas fluorescens A506, a plant epiphyte used in the United States for the biological control of fire blight disease of pear and apple. Twenty-nine of the 67 open reading frames (ORFs) of pA506 have putative functions in conjugation, including a type IV secretion system related to that of MOBP6 family plasmids and a gene cluster for type IV pili. We demonstrate that pA506 is self-transmissible via conjugation between A506 and strains of Pseudomonas spp. or the Enterobacteriaceae. The origin of vegetative replication (oriV) of pA506 is typical of those in pPT23A family plasmids, which are present in many pathovars of Pseudomonas syringae, but pA506 lacks repA, a defining locus for pPT23A plasmids, and has a novel partitioning region. We selected a plasmid-cured derivative of A506 and compared it to the wild type to identify plasmid-encoded phenotypes. pA506 conferred UV resistance, presumably due to the plasmid-borne rulAB genes, but did not influence epiphytic fitness of A506 on pear or apple blossoms in the field. pA506 does not appear to confer resistance to antibiotics or other toxic elements. Based on the conjugative nature of pA506 and the large number of its genes that are shared with plasmids from diverse groups of environmental bacteria, the plasmid is likely to serve as a vehicle for genetic exchange between A506 and its coinhabitants on plant surfaces. PMID:23811504

In-situ fabrication of diketopyrrolopyrrole-carbazole-based conjugated polymer/TiO2 heterojunction for enhanced visible light photocatalysis

NASA Astrophysics Data System (ADS)

Yang, Long; Yu, Yuyan; Zhang, Jianling; Chen, Fu; Meng, Xiao; Qiu, Yong; Dan, Yi; Jiang, Long

2018-03-01

Aiming at developing highly efficient photocatalysts by broadening the light-harvesting region and suppressing photo-generated electron-hole recombination simultaneously, this work reports rational design and fabrication of donor-acceptor (D-A) conjugated polymer/TiO2 heterojunction catalyst with strong interfacial interactions by a facile in-situ thermal treatment. To expand the light-harvesting window, soluable conjugated copolymers with D-A architecture are prepared by Pd-mediated polycondensation of diketopyrrolopyrrole (DPP) and t-butoxycarbonyl (t-Boc) modified carbazole (Car), and used as visible-light-harvesting antenna to couple with TiO2 nanocrystals. The DPP-Car/TiO2 composites show wide range absorption in 300-1000 nm. To improve the interfacial binding at the interface, a facile in-situ thermal treatment is carried out to cleave the pendant t-Boc groups in carbazole units and liberate the polar amino groups (-NH-) which strongly bind to the surface of TiO2 through dipole-dipole interactions, forming a heterojunction interface. This in-situ thermal treatment changes the surface elemental distribution of TiO2, reinforces the interface bonding at the boundary of conjugated polymers/TiO2 and finally improves the photocatalytic efficiency of DPP-Car/TiO2 under visible-light irradiation. The interface changes are characterized and verified through Fourier-transform infrared spectroscopy (FT-IR), photo images, UV/Vis (solution state and powder diffuse reflection spectroscopy), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), fluorescence, scanning electron microscopy(SEM) and transmission electron microscopy (TEM) techniques. This study provides a new strategy to avoid the low solubility of D-A conjugated polymers and construct highly-efficient conjugated polymer/TiO2 heterojunction by enforcing the interface contact and facilitating charge or energy transfer for the applications in photocatalysis.

Plasmid Capture by the Bacillus thuringiensis Conjugative Plasmid pXO16▿

PubMed Central

Timmery, Sophie; Modrie, Pauline; Minet, Olivier; Mahillon, Jacques

2009-01-01

Conjugation, mobilization, and retromobilization are three related mechanisms of horizontal gene transfer in bacteria. They have been extensively studied in gram-negative species, where retromobilization, the capture of DNA from a recipient by a donor cell, was shown to result from two successive steps: the transfer of the conjugative plasmid from the donor to the recipient followed by the retrotransfer of the mobilizable plasmid to the donor. This successive model was established for gram-negative bacteria but was lacking experimental data from the gram-positive counterparts. In the present work, the mobilization and retromobilization abilities of the conjugative plasmid pXO16 from Bacillus thuringiensis subsp. israelensis were studied using the mobilizable plasmids pUB110 and pE194 and the “nonmobilizable” element pC194 lacking the mob and oriT features (all from Staphylococcus aureus). Experimental data suggested a successive model, since different retromobilization frequencies were observed between the small plasmids. More importantly, retromobilization was shown to be delayed by 50 and 150 min for pUB110 and pE194, respectively, compared to pXO16 conjugation. Natural liquid foods (cow milk, soy milk, and rice milk) were used to evaluate the putative ecological impact of these transfers. In cow and soy milk, conjugation, mobilization, and retromobilization were shown to occur at frequencies of 8.0 × 10−1, 1.0 × 10−2, and 1.2 × 10−4 transconjugants per recipient, respectively. These data are comparable to those obtained with LB medium and about 10-fold lower than in the case of rice milk. Taken together, these results emphasize the potential role of plasmid capture played by B. thuringiensis in natural environments. PMID:19181805

Distribution of Cd, Pb and Cu between dissolved fraction, inorganic particulate and phytoplankton in seawater of Terra Nova Bay (Ross Sea, Antarctica) during austral summer 2011-12.

PubMed

Illuminati, S; Annibaldi, A; Romagnoli, T; Libani, G; Antonucci, M; Scarponi, G; Totti, C; Truzzi, C

2017-10-01

During the austral summer 2011-2012, the metal quotas of Cd, Pb and Cu in the phytoplankton of Terra Nova Bay (TNB, Antarctica) were measured for the first time. Evolution of all the three metal distributions between dissolved and particulate fractions during the season was also evaluated. Metal concentrations were mainly affected by the dynamic of the pack ice melting and phytoplankton activity. In mid-December when TNB area was covered by a thick pack ice layer and phytoplankton activity was very low, all the three metals were present mainly in their dissolved species. When the pack ice started to melt and the water column characteristics became ideal (i.e. moderate stratification, ice free area), the phytoplankton bloom occurred. Cd showed a nutrient-type behaviour with dissolved and particulate fractions mainly influenced by phytoplankton activity. Cd quota showed a mean value of 0.12 ± 0.07 nmol L -1 (30-100% of the total particulate). Also Cu showed a nutrient-type behaviour, with its quota in phytoplankton varying between 0.08 and 2.1 nmol L -1 (20-100% of the total particulate). Pb features the typical distribution of a scavenged element with very low algal content (0.03 ± 0.02 nmol L -1 , representing 20-50% of the total particulate). The vertical distribution of this element was influenced by several factors (e.g. pack ice melting, atmospheric inputs), the phytoplankton activity affecting Pb behaviour only partially. Metal:C ratios provide valuable information on the biological requirements for Cd, Pb and Cu, leading us to better understand their biogeochemical cycles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Innovative Approaches to Remote Sensing in NASA's Earth System Science Pathfinder (ESSP) Program

NASA Technical Reports Server (NTRS)

Peri, Frank; Volz, Stephen

2013-01-01

NASA's Earth Venture class (EV) of mission are competitively selected, Principal Investigator (PI) led, relatively low cost and narrowly focused in scientific scope. Investigations address a full spectrum of earth science objectives, including studies of the atmosphere, oceans, land surface, polar ice regions, and solid Earth. EV has three program elements: EV-Suborbital (EVS) are suborbital/airborne investigations; EV-Mission (EVM) element comprises small complete spaceborne missions; and EV-Instrument (EVI) element develops spaceborne instruments for flight as missions-of-opportunity (MoO). To ensure the success of EV, the management approach of each element is tailored according to the specific needs of the element.

Atmospheric depositions of black carbon, inorganic pollutants and mineral dust from the Ortles, Eastern European Alps ice cores during the last 3000 years

NASA Astrophysics Data System (ADS)

Bertò, Michele; Barbante, Carlo; Gabrielli, Paolo; Gabrieli, Jacopo; Spolaor, Andrea; Dreossi, Giuliano; Laj, Paolo; Zanatta, Marco; Stenni, Barbara

2017-04-01

Reconstructions of the atmospheric content of black carbon, heavy metals and mineral dust covering millennial time scales are rare, particularly in the European region. Evaluating the human impact on the environment through mining and industrial activities, road traffic, biomass and coal burning, and the naturally emitted aerosols atmospheric load, is important to know the degree of contaminations and the quality of melting water, the radiative effect on the glacier's radiative balance, the atmospheric aerosols' climatic impacts and the recent decades pollutions emissions policies' efficiencies. Four ice cores were drilled in 2011 from the "Alto dell'Ortles" (3859 m), the highest glacier of the Mt. Ortles massif (South Tirol, Italy). Three 74 m long ice cores were dated by mean of 210Pb, tritium, beta emissions and 14C analyses following also the new dating technique based on filtering the ice for extracting the carbonaceous component of the deposited aerosols. The depth-age curve was obtained by using a Monte Carlo based empirical fitting model (COPRA). The basal ice of core#2 and #3 was dated back to about 7000 years b.p., whereas that of core#1, about one meter shorter, to 3000 years before present. Below the firn-ice transition, at a depth of about 24 m, the borehole temperature revealed the presence of well-preserved cold ice (Gabrielli et al, 2012). The O and H stable isotopes profiles describe well the atmospheric warming as well as the low temperatures recorded during the Little Ice Age (LIA). The proximity of the "Alto dell'Ortles" to densely industrialized areas (Po Valley) makes these ice cores specifically suited for reconstructing the anthropogenic impacts in the Eastern European Alpine region over the last 3 millennia. The ice core#1 was analyzed with a "Continuous Flow Analysis" system (CFA). The separation between internal and external parts of the core prevents any kind of contamination. The core was melted at about 2.5 cm min-1 and simultaneous analyses of conductivity, dust concentration and size distribution (from 0.8 to 80 μm), trace elements with Inductive Coupled Plasma Mass Spectrometer (ICP-MS, Agilent 7500) and refractory black carbon (rBC) with the Single Particle Soot Photometer (SP2, Droplet Measurement Technologies) were performed. A fraction of the melt water was collected by an auto-sampler. More than 1000 samples were analyzed discreetly with a CRC-ICP-MS (with the highest resolution of about 3 cm). The rBC shows significant variability over the last century peaking in concentrations of about 10 ng g-1 from the 1920s to the 1970s, whereas very low values characterized the period from 1000 BC to 1850 AD. The seasonality appears to be preserved even in the firn temperate part of the core as argued from the comparison with the water stable isotopes ratios (δO18). The overall determined trace elements are Li, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Cu, Zn, As, Se, Sr, Ag, Cd, Sb, Te, I, Cs, Ba, Hg, Tl, Pb, Bi, U. The Enrichment Factors (EF) for the crustal elements didn't show any particular trend. While mining and smelting activities appeared to be the most significant heavy metals sources before the 19th century, other anthropogenic heavy metals strongly increased from the onset of the Industrial Revolutions.

The Bacillus subtilis Conjugative Plasmid pLS20 Encodes Two Ribbon-Helix-Helix Type Auxiliary Relaxosome Proteins That Are Essential for Conjugation.

PubMed

Miguel-Arribas, Andrés; Hao, Jian-An; Luque-Ortega, Juan R; Ramachandran, Gayetri; Val-Calvo, Jorge; Gago-Córdoba, César; González-Álvarez, Daniel; Abia, David; Alfonso, Carlos; Wu, Ling J; Meijer, Wilfried J J

2017-01-01

Bacterial conjugation is the process by which a conjugative element (CE) is transferred horizontally from a donor to a recipient cell via a connecting pore. One of the first steps in the conjugation process is the formation of a nucleoprotein complex at the origin of transfer ( oriT ), where one of the components of the nucleoprotein complex, the relaxase, introduces a site- and strand specific nick to initiate the transfer of a single DNA strand into the recipient cell. In most cases, the nucleoprotein complex involves, besides the relaxase, one or more additional proteins, named auxiliary proteins, which are encoded by the CE and/or the host. The conjugative plasmid pLS20 replicates in the Gram-positive Firmicute bacterium Bacillus subtilis . We have recently identified the relaxase gene and the oriT of pLS20, which are separated by a region of almost 1 kb. Here we show that this region contains two auxiliary genes that we name aux1 LS20 and aux2 LS20 , and which we show are essential for conjugation. Both Aux1 LS20 and Aux2 LS20 are predicted to contain a Ribbon-Helix-Helix DNA binding motif near their N-terminus. Analyses of the purified proteins show that Aux1 LS20 and Aux2 LS20 form tetramers and hexamers in solution, respectively, and that they both bind preferentially to oriT LS20 , although with different characteristics and specificities. In silico analyses revealed that genes encoding homologs of Aux1 LS20 and/or Aux2 LS20 are located upstream of almost 400 relaxase genes of the Rel LS20 family (MOB L ) of relaxases. Thus, Aux1 LS20 and Aux2 LS20 of pLS20 constitute the founding member of the first two families of auxiliary proteins described for CEs of Gram-positive origin.

Amphotericin B-conjugated biogenic silver nanoparticles as an innovative strategy for fungal infections.

PubMed

Ahmad, Aftab; Wei, Yun; Syed, Fatima; Tahir, Kamran; Taj, Raheela; Khan, Arif Ullah; Hameed, Muhammad Usman; Yuan, Qipeng

2016-10-01

New strategies are required to improve the efficacy of drugs and to treat the emerging microbial resistance. An effective strategy is to combine drugs with metal nanoparticles for the control of microbial infections and resistance. Keeping in view this fact, we developed a facile and eco-friendly protocol for the synthesis of amphotericin B-conjugated silver nanoparticles and their assessment as an antifungal agent. Phytochemicals from the aqueous extract of Maytenus royleanus and amphotericin B were used as capping agents to prepare two types of silver nanoparticles i.e. (i) biogenic silver nanoparticles (b-AgNPs) and (ii) amphotericin B-conjugated biogenic silver nanoparticles (Amp-bAgNPs). UV-Vis spectroscopy was used to detect the characteristic surface Plasmon resonance peaks (SPR) for the prepared nanoparticles (424-433 nm). High-resolution transmission electron microscopy (HRTEM) study revealed the formation of well dispersed and spherical silver nanoparticles and Amp-bAgNPs with an average particles size of 10 and 15 nm. EDX and FTIR studies confirmed the elemental composition and surface adhered biomolecules in the prepared nanoparticles respectively. Biogenic silver nanoparticles revealed low to moderate antifungal activity (4-8 mm ± 0.2), however, the amphotericin B conjugated silver nanoparticles exhibited significant activity against Candida albicans (16 mm ± 1.4) and Candida tropicalis (18 mm ± 1.5). In conclusion, the enhanced antifungal activity of the Amp-AgNPs conjugate system is due to the synergy between the antifungal activity of amphotericin B and the antimicrobial property of silver. The findings of this study suggest that the conjugated nanoparticles could be used as efficient antifungal agents and drug delivery vehicles. Furthermore, this is the first report describing the synthesis of silver nanoparticles using the aqueous extract of Maytenus royleanus and the conjugation of amphotericin B, an antifungal drug, to the phytosynthesized silver nanoparticles. Copyright © 2016 Elsevier Ltd. All rights reserved.

Deformation of conjugate compliant fault zones induced by the 2013 Mw7.7 Baluchistan (Pakistan) earthquake

NASA Astrophysics Data System (ADS)

Dutta, Rishabh; Wang, Teng; Feng, Guangcai; Harrington, Jonathan; Vasyura-Bathke, Hannes; Jónsson, Sigurjón

2017-04-01

Strain localizations in compliant fault zones (with elastic moduli lower than the surrounding rocks) induced by nearby earthquakes have been detected using geodetic observations in a few cases in the past. Here we observe small-scale changes in interferometric Synthetic Aperture Radar (InSAR) measurements along multiple conjugate faults near the rupture of the 2013 Mw7.7 Baluchistan (Pakistan) earthquake. After removing the main coseismic deformation signal in the interferograms and correcting them for topography-related phase, we observe 2-3 cm signal along several conjugate faults that are 15-30 km from the mainshock fault rupture. These conjugate compliant faults have strikes of N30°E and N45°W. The sense of motion indicates left-lateral deformation across the N30°E faults and right-lateral deformation across the N45°W faults, which suggests the conjugate faults were subjected to extensional coseismic stresses along the WSW-ENE direction. The spacing between the different sets of faults is around 5 to 8 km. We explain the observed strain localizations as an elastic response of the compliant conjugate faults induced by the Baluchistan earthquake. Using 3D Finite Element models (FEM), we impose coseismic static displacements due to the earthquake along the boundaries of the FEM domain to reproduce the coseismic stress changes acting across the compliant faults. The InSAR measurements are used to constrain the geometry and rigidity variations of the compliant faults with respect to the surrounding rocks. The best fitting models show the compliant fault zones to have a width of 0.5 km to 2 km and a reduction of the shear modulus by a factor of 3 to 4. Our study yields similar values as were found for compliant fault zones near the 1992 Landers and the 1999 Hector Mine earthquakes in California, although here the strain localization is occurring on more complex conjugate sets of faults.

Sparse matrix methods based on orthogonality and conjugacy

NASA Technical Reports Server (NTRS)

Lawson, C. L.

1973-01-01

A matrix having a high percentage of zero elements is called spares. In the solution of systems of linear equations or linear least squares problems involving large sparse matrices, significant saving of computer cost can be achieved by taking advantage of the sparsity. The conjugate gradient algorithm and a set of related algorithms are described.

Numerical investigation of roughness effects in aircraft icing calculations

NASA Astrophysics Data System (ADS)

Matheis, Brian Daniel

2008-10-01

Icing codes are playing a role of increasing significance in the design and certification of ice protected aircraft surfaces. However, in the interest of computational efficiency certain small scale physics of the icing problem are grossly approximated by the codes. One such small scale phenomena is the effect of ice roughness on the development of the surface water film and on the convective heat transfer. This study uses computational methods to study the potential effect of ice roughness on both of these small scale phenomena. First, a two-dimensional condensed layer code is used to examine the effect of roughness on surface water development. It is found that the Couette approximation within the film breaks down as the wall shear goes to zero, depending on the film thickness. Roughness elements with initial flow separation in the air induce flow separation in the water layer at steady state, causing a trapping of the film. The amount of trapping for different roughness configurations is examined. Second, a three-dimensional incompressible Navier-Stokes code is developed to examine large scale ice roughness on the leading edge. The effect on the convective heat transfer and potential effect on the surface water dynamics is examined for a number of distributed roughness parameters including Reynolds number, roughness height, streamwise extent, roughness spacing and roughness shape. In most cases the roughness field increases the net average convective heat transfer on the leading edge while narrowing surface shear lines, indicating a choking of the surface water flow. Both effects show significant variation on the scale of the ice roughness. Both the change in heat transfer as well as the potential change in surface water dynamics are presented in terms of the development of singularities in the surface shear pattern. Of particular interest is the effect of the smooth zone upstream of the roughness which shows both a relatively large increase in convective heat transfer as well as excessive choking of the surface shear lines at the upstream end of the roughness field. A summary of the heat transfer results is presented for both the averaged heat transfer as well as the maximum heat transfer over each roughness element, indicating that the roughness Reynolds number is the primary parameter which characterizes the behavior of the roughness for the problem of interest.

Measuring In-Plane Displacements with Variable Sensitivity Using Diffractive Optic Interferometry

NASA Technical Reports Server (NTRS)

Shepherd, Robert L.; Gilbert, John A.; Cole, Helen J.; Ashley, Paul R.

1998-01-01

This paper introduces a method called diffractive optic interferometry (DOI) which allows in-plane displacement components to be measured with variable sensitivity. DOI relies on binary optical elements fabricated as phase-type Dammann gratings which produce multiple diffraction orders of nearly equal intensity. Sensitivity is varied by combining the different wavefronts produced by a conjugate pair of these binary optical elements; a transmission element is used to produce several illumination beams while a reflective element, replicated on the surface of a specimen, provides the reference for the undeformed state. The steps taken to design and fabricate these binary optical elements are described. The specimen grating is characterized, and tested on a disk subjected to diametrical compression. Overall, the results are excellent, with experimental data agreeing to within a few percent of the theoretical predictions.

Integrating Observations and Models to Better Understand a Changing Arctic Sea Ice Cover

NASA Astrophysics Data System (ADS)

Stroeve, J. C.

2017-12-01

TThe loss of the Arctic sea ice cover has captured the world's attention. While much attention has been paid to the summer ice loss, changes are not limited to summer. The last few winters have seen record low sea ice extents, with 2017 marking the 3rdyear in a row with a new record low for the winter maximum extent. More surprising is the number of consecutive months between January 2016 through April 2017 with ice extent anomalies more than 2 standard deviations below the 1981-2010 mean. Additionally, October 2016 through April 2017 saw 7 consecutive months with record low extents, something that had not happened before in the last 4 decades of satellite observations. As larger parts of the Arctic Ocean become ice-free in summer, regional seas gradually transition from a perennial to a seasonal ice cover. The Barents Sea is already only seasonally ice covered, whereas the Kara Sea has recently lost most of its summer ice and is thereby starting to become a seasonally ice covered region. These changes serve as harbinger for what's to come for other Arctic seas. Given the rapid pace of change, there is an urgent need to improve our understanding of the drivers behind Arctic sea ice loss, the implications of this ice loss and to predict future changes to better inform policy makers. Climate models play a fundamental role in helping us synthesize the complex elements of the Arctic sea ice system yet generally fail to simulate key features of the sea ice system and the pace of sea ice loss. Nevertheless, modeling advances continue to provide better means of diagnosing sea ice change, and new insights are likely to be gained with model output from the 6th phase of the Coupled Model Intercomparison Project (CMIP6). The CMIP6 Sea-Ice Model Intercomparison Project (SIMIP) aim is to better understand biases and errors in sea ice simulations so that we can improve our understanding of the likely future evolution of the sea ice cover and its impacts on global climate. To reach this goal, a community-defined set of model output has been recommended that will allow scientists to better characterize the heat, momentum and mass budget of Arctic sea ice. This will allow for better quantification of the role of internal variability, external forcing and model deficiencies.

Clarifying the dominant sources and mechanisms of cirrus cloud formation.

PubMed

Cziczo, Daniel J; Froyd, Karl D; Hoose, Corinna; Jensen, Eric J; Diao, Minghui; Zondlo, Mark A; Smith, Jessica B; Twohy, Cynthia H; Murphy, Daniel M

2013-06-14

Formation of cirrus clouds depends on the availability of ice nuclei to begin condensation of atmospheric water vapor. Although it is known that only a small fraction of atmospheric aerosols are efficient ice nuclei, the critical ingredients that make those aerosols so effective have not been established. We have determined in situ the composition of the residual particles within cirrus crystals after the ice was sublimated. Our results demonstrate that mineral dust and metallic particles are the dominant source of residual particles, whereas sulfate and organic particles are underrepresented, and elemental carbon and biological materials are essentially absent. Further, composition analysis combined with relative humidity measurements suggests that heterogeneous freezing was the dominant formation mechanism of these clouds.

The rhizome of the multidrug-resistant Enterobacter aerogenes genome reveals how new "killer bugs" are created because of a sympatric lifestyle.

PubMed

Diene, Seydina M; Merhej, Vicky; Henry, Mireille; El Filali, Adil; Roux, Véronique; Robert, Catherine; Azza, Saïd; Gavory, Frederick; Barbe, Valérie; La Scola, Bernard; Raoult, Didier; Rolain, Jean-Marc

2013-02-01

Here, we sequenced the 5,419,609 bp circular genome of an Enterobacter aerogenes clinical isolate that killed a patient and was resistant to almost all current antibiotics (except gentamicin) commonly used to treat Enterobacterial infections, including colistin. Genomic and phylogenetic analyses explain the discrepancies of this bacterium and show that its core genome originates from another genus, Klebsiella. Atypical characteristics of this bacterium (i.e., motility, presence of ornithine decarboxylase, and lack of urease activity) are attributed to genomic mosaicism, by acquisition of additional genes, such as the complete 60,582 bp flagellar assembly operon acquired "en bloc" from the genus Serratia. The genealogic tree of the 162,202 bp multidrug-resistant conjugative plasmid shows that it is a chimera of transposons and integrative conjugative elements from various bacterial origins, resembling a rhizome. Moreover, we demonstrate biologically that a G53S mutation in the pmrA gene results in colistin resistance. E. aerogenes has a large RNA population comprising 8 rRNA operons and 87 cognate tRNAs that have the ability to translate transferred genes that use different codons, as exemplified by the significantly different codon usage between genes from the core genome and the "mobilome." On the basis of our findings, the evolution of this bacterium to become a "killer bug" with new genomic repertoires was from three criteria that are "opportunity, power, and usage" to indicate a sympatric lifestyle: "opportunity" to meet other bacteria and exchange foreign sequences since this bacteria was similar to sympatric bacteria; "power" to integrate these foreign sequences such as the acquisition of several mobile genetic elements (plasmids, integrative conjugative element, prophages, transposons, flagellar assembly system, etc.) found in his genome; and "usage" to have the ability to translate these sequences including those from rare codons to serve as a translator of foreign languages.

Determination of lead, cadmium, indium, thallium and silver in ancient ices from Antarctica by isotope dilution-thermal ionization mass spectrometry

USGS Publications Warehouse

Matsumoto, A.; Hinkley, T.K.

1997-01-01

The concentrations of five chalcophile elements (Pb, Cd, In, Tl and Ag) and the lead isotope rarios in ancient ices from the Taylor Dome near coastal Antarctica, have been determined by the isotope dilutionthermal ionization mass spectrometry (ID-TIMS), with ultra-clean laboratory techniques. The samples were selected from segments of cores, one of which included a visible ash layer. Electric conductivity measurement (ECM) or dielectric properties (DEP) gave distinctive sharp peaks for some of the samples c hosen. Exterior portions of the sample segments were trimmed away by methods described here. Samples w ere evaporated to dryness and later separated into fractions for the five elements using an HBr-HNO3 a nion exchange column method. The concentrations are in the range 2.62-36.7 pg Pb/g of ice, 0.413-2.83 pg Cd/g, 0.081-0.34 pg In/g, 0.096-2.8 pg Tl/g and 0.15-0.84 pg Ag/g. respectively. The dispersions in duplicate analyses are about ??1% for lead and cadmium, ??2% for indium. ??4% for thallium and ??6% for silver, respectively. The concentrations of lead obtained are commonly higher than those in the present-day Antarctic surface snows, but the isotope ratios are distinctively higher than those of the present-day snows and close to those of the other ancient ice collected from a different Antarctic area.

Gaseous elemental mercury in the marine boundary layer and air-sea flux in the Southern Ocean in austral summer.

PubMed

Wang, Jiancheng; Xie, Zhouqing; Wang, Feiyue; Kang, Hui

2017-12-15

Gaseous elemental mercury (GEM) in the marine boundary layer (MBL), and dissolved gaseous mercury (DGM) in surface seawater of the Southern Ocean were measured in the austral summer from December 13, 2014 to February 1, 2015. GEM concentrations in the MBL ranged from 0.4 to 1.9ngm -3 (mean±standard deviation: 0.9±0.2ngm -3 ), whereas DGM concentrations in surface seawater ranged from 7.0 to 75.9pgL -1 (mean±standard deviation: 23.7±13.2pgL -1 ). The occasionally observed low GEM in the MBL suggested either the occurrence of atmospheric mercury depletion in summer, or the transport of GEM-depleted air from the Antarctic Plateau. Elevated GEM concentrations in the MBL and DGM concentrations in surface seawater were consistently observed in the ice-covered region of the Ross Sea implying the influence of the sea ice environment. Diminishing sea ice could cause more mercury evasion from the ocean to the air. Using the thin film gas exchange model, the air-sea fluxes of gaseous mercury in non-ice-covered area during the study period were estimated to range from 0.0 to 6.5ngm -2 h -1 with a mean value of 1.5±1.8ngm -2 h -1 , revealing GEM (re-)emission from the East Southern Ocean in summer. Copyright © 2017 Elsevier B.V. All rights reserved.