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Sample records for additional sex combs

  1. Male- and female-specific variants of doublesex gene products have different roles to play towards regulation of Sex combs reduced expression and sex comb morphogenesis in Drosophila

    Indian Academy of Sciences (India)

    Thangjam Ranjita Devi; B V Shyamala

    2013-09-01

    Sexually dimorphic characters have two-fold complexities in pattern formation as they have to get input fromboth somatic sex determination as well as the positional determining regulators. Sex comb development in Drosophila requires functions of the somatic sex-determining gene doublesex and the homeotic gene Sex combs reduced. Attempts have not been made to decipher the role of dsx in imparting sexually dimorphic expression of SCR and the differential function of sex-specific variants of dsx products in sex comb development. Our results in this study indicate that male-like pattern of SCR expression is independent of dsx function, and dsxF must be responsible for bringing about dimorphism in SCR expression, whereas dsxM function is required with Scr for the morphogenesis of sex comb.

  2. Analysis of the Sequence and Phenotype of Drosophila Sex combs reduced Alleles Reveals Potential Functions of Conserved Protein Motifs of the Sex combs reduced Protein

    OpenAIRE

    Sivanantharajah, Lovesha; Percival-Smith, Anthony

    2009-01-01

    The Drosophila Hox gene, Sex combs reduced (Scr), is required for patterning the larval and adult, labial and prothoracic segments. Fifteen Scr alleles were sequenced and the phenotypes analyzed in detail. Six null alleles were nonsense mutations (Scr2, Scr4, Scr11, Scr13, Scr13A, and Scr16) and one was an intragenic deletion (Scr17). Five hypomorphic alleles were missense mutations (Scr1, Scr3, Scr5, Scr6, and Scr8) and one was a small protein deletion (Scr15). Protein sequence changes were ...

  3. Evolution of the insect body plan as revealed by the Sex combs reduced expression pattern.

    Science.gov (United States)

    Rogers, B T; Peterson, M D; Kaufman, T C

    1997-01-01

    The products of the HOM/Hox homeotic genes form a set of evolutionarily conserved transcription factors that control elaborate developmental processes and specify cell fates in many metazoans. We examined the expression of the ortholog of the homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster in insects of three divergent orders: Hemiptera, Orthoptera and Thysanura. Our data reflect how the conservation and variation of Scr expression has affected the morphological evolution of insects. Whereas the anterior epidermal expression of Scr, in a small part of the posterior maxillary and all of the labial segment, is found to be in common among all four insect orders, the posterior (thoracic) expression domains vary. Unlike what is observed in flies, the Scr orthologs of other insects are not expressed broadly over the first thoracic segment, but are restricted to small patches. We show here that Scr is required for suppression of wings on the prothorax of Drosophila. Moreover, Scr expression at the dorsal base of the prothoracic limb in two other winged insects, crickets (Orthoptera) and milkweed bugs (Hemiptera), is consistent with Scr acting as a suppressor of prothoracic wings in these insects. Scr is also expressed in a small patch of cells near the basitarsal-tibial junction of milkweed bugs, precisely where a leg comb develops, suggesting that Scr promotes comb formation, as it does in Drosophila. Surprisingly, the dorsal prothoracic expression of Scr is also present in the primitively wingless firebrat (Thysanura) and the leg patch is seen in crickets, which have no comb. Mapping both gene expression patterns and morphological characters onto the insect phylogenetic tree demonstrates that in the cases of wing suppression and comb formation the appearance of expression of Scr in the prothorax apparently precedes these specific functions.

  4. Requirement for sex comb on midleg protein interactions in Drosophila polycomb group repression.

    OpenAIRE

    Aidan J Peterson; Mallin, Daniel R.; Francis, Nicole J.; Ketel, Carrie S.; Stamm, Joyce; Voeller, Rochus K.; Kingston, Robert E.; Jeffrey A Simon

    2004-01-01

    The Drosophila Sex Comb on Midleg (SCM) protein is a transcriptional repressor of the Polycomb group (PcG). Although genetic studies establish SCM as a crucial PcG member, its molecular role is not known. To investigate how SCM might link to PcG complexes, we analyzed the in vivo role of a conserved protein interaction module, the SPM domain. This domain is found in SCM and in another PcG protein, Polyhomeotic (PH), which is a core component of Polycomb repressive complex 1 (PRC1). SCM-PH int...

  5. Requirement for sex comb on midleg protein interactions in Drosophila polycomb group repression.

    Science.gov (United States)

    Peterson, Aidan J; Mallin, Daniel R; Francis, Nicole J; Ketel, Carrie S; Stamm, Joyce; Voeller, Rochus K; Kingston, Robert E; Simon, Jeffrey A

    2004-07-01

    The Drosophila Sex Comb on Midleg (SCM) protein is a transcriptional repressor of the Polycomb group (PcG). Although genetic studies establish SCM as a crucial PcG member, its molecular role is not known. To investigate how SCM might link to PcG complexes, we analyzed the in vivo role of a conserved protein interaction module, the SPM domain. This domain is found in SCM and in another PcG protein, Polyhomeotic (PH), which is a core component of Polycomb repressive complex 1 (PRC1). SCM-PH interactions in vitro are mediated by their respective SPM domains. Yeast two-hybrid and in vitro binding assays were used to isolate and characterize >30 missense mutations in the SPM domain of SCM. Genetic rescue assays showed that SCM repressor function in vivo is disrupted by mutations that impair SPM domain interactions in vitro. Furthermore, overexpression of an isolated, wild-type SPM domain produced PcG loss-of-function phenotypes in flies. Coassembly of SCM with a reconstituted PRC1 core complex shows that SCM can partner with PRC1. However, gel filtration chromatography showed that the bulk of SCM is biochemically separable from PH in embryo nuclear extracts. These results suggest that SCM, although not a core component of PRC1, interacts and functions with PRC1 in gene silencing.

  6. Cloning of the homeotic Sex combs reduced gene in Drosophila and in situ localization of its transcripts.

    Science.gov (United States)

    Kuroiwa, A; Kloter, U; Baumgartner, P; Gehring, W J

    1985-12-30

    We have extended our ;chromosomal walk' in the Antennapedia-complex (ANT-C) by isolating overlapping DNA sequences spanning the chromosomal segment between Antennapedia (Antp) and Deformed (Dfd). The transcription units, homeoboxes and M-repeats were mapped within this region. Four transcription units Antp, fushi tarazu (ftz), Sex combs reduced (Scr) and Dfd contain both a homeobox and an M repeat, whereas at least two additional transcription units, x and z, were found to lack these elements. The Scr locus was identified by deletion mapping. It consists of at least two exonic regions separated by a large intron. The homeobox is located in the 3' exon and is 82% homologous to the one in Antp. Scr encodes a major 3.9-kb RNA. A corresponding cDNA clone was used as a probe for in situ hybridization to sections of various embryonic stages. At gastrula stages Scr transcripts accumulate in the posterior head and the anterior thoracic region of the germ band. At later stages a strong accumulation of transcripts is observed in the suboesophageal and the prothoracic ganglion of the ventral nervous system.

  7. Sex comb on midleg (Scm) is a functional link between PcG-repressive complexes in Drosophila.

    Science.gov (United States)

    Kang, Hyuckjoon; McElroy, Kyle A; Jung, Youngsook Lucy; Alekseyenko, Artyom A; Zee, Barry M; Park, Peter J; Kuroda, Mitzi I

    2015-06-01

    The Polycomb group (PcG) proteins are key regulators of development in Drosophila and are strongly implicated in human health and disease. How PcG complexes form repressive chromatin domains remains unclear. Using cross-linked affinity purifications of BioTAP-Polycomb (Pc) or BioTAP-Enhancer of zeste [E(z)], we captured all PcG-repressive complex 1 (PRC1) or PRC2 core components and Sex comb on midleg (Scm) as the only protein strongly enriched with both complexes. Although previously not linked to PRC2, we confirmed direct binding of Scm and PRC2 using recombinant protein expression and colocalization of Scm with PRC1, PRC2, and H3K27me3 in embryos and cultured cells using ChIP-seq (chromatin immunoprecipitation [ChIP] combined with deep sequencing). Furthermore, we found that RNAi knockdown of Scm and overexpression of the dominant-negative Scm-SAM (sterile α motif) domain both affected the binding pattern of E(z) on polytene chromosomes. Aberrant localization of the Scm-SAM domain in long contiguous regions on polytene chromosomes revealed its independent ability to spread on chromatin, consistent with its previously described ability to oligomerize in vitro. Pull-downs of BioTAP-Scm captured PRC1 and PRC2 and additional repressive complexes, including PhoRC, LINT, and CtBP. We propose that Scm is a key mediator connecting PRC1, PRC2, and transcriptional silencing. Combined with previous structural and genetic analyses, our results strongly suggest that Scm coordinates PcG complexes and polymerizes to produce broad domains of PcG silencing.

  8. The large X-effect on secondary sexual characters and the genetics of variation in sex comb tooth number in Drosophila subobscura.

    Science.gov (United States)

    Mittleman, Briana E; Manzano-Winkler, Brenda; Hall, Julianne B; Korunes, Katharine L; Noor, Mohamed A F

    2017-01-01

    Genetic studies of secondary sexual traits provide insights into whether and how selection drove their divergence among populations, and these studies often focus on the fraction of variation attributable to genes on the X-chromosome. However, such studies may sometimes misinterpret the amount of variation attributable to the X-chromosome if using only simple reciprocal F1 crosses, or they may presume sexual selection has affected the observed phenotypic variation. We examined the genetics of a secondary sexual trait, male sex comb size, in Drosophila subobscura. This species bears unusually large sex combs for its species group, and therefore, this trait may be a good candidate for having been affected by natural or sexual selection. We observed significant heritable variation in number of teeth of the distal sex comb across strains. While reciprocal F1 crosses seemed to implicate a disproportionate X-chromosome effect, further examination in the F2 progeny showed that transgressive autosomal effects inflated the estimate of variation associated with the X-chromosome in the F1. Instead, the X-chromosome appears to confer the smallest contribution of all major chromosomes to the observed phenotypic variation. Further, we failed to detect effects on copulation latency or duration associated with the observed phenotypic variation. Overall, this study presents an examination of the genetics underlying segregating phenotypic variation within species and illustrates two common pitfalls associated with some past studies of the genetic basis of secondary sexual traits.

  9. Expression and properties of wild-type and mutant forms of the Drosophila sex comb on midleg (SCM) repressor protein.

    Science.gov (United States)

    Bornemann, D; Miller, E; Simon, J

    1998-10-01

    The Sex comb on midleg (Scm) gene encodes a transcriptional repressor of the Polycomb group (PcG). Here we show that SCM protein is nuclear and that its expression is widespread during fly development. SCM protein contains a C-terminal domain, termed the SPM domain, which mediates protein-protein interactions. The biochemical function of another domain consisting of two 100-amino-acid-long repeats, termed "mbt" repeats, is unknown. We have determined the molecular lesions of nine Scm mutant alleles, which identify functional requirements for specific domains. The Scm alleles were tested for genetic interactions with mutations in other PcG genes. Intriguingly, three hypomorphic Scm mutations, which map within an mbt repeat, interact with PcG mutations more strongly than do Scm null alleles. The strongest interactions produce partial synthetic lethality that affects doubly heterozygous females more severely than males. We show that mbt repeat alleles produce stable SCM proteins that associate with normal sites in polytene chromosomes. We also analyzed progeny from Scm mutant germline clones to compare the effects of an mbt repeat mutation during embryonic vs. pupal development. We suggest that the mbt repeat alleles produce altered SCM proteins that incorporate into and impair function of PcG protein complexes.

  10. RNAi analysis of Deformed, proboscipedia and Sex combs reduced in the milkweed bug Oncopeltus fasciatus: novel roles for Hox genes in the hemipteran head.

    Science.gov (United States)

    Hughes, C L; Kaufman, T C

    2000-09-01

    Insects have evolved a large variety of specialized feeding strategies, with a corresponding variability in mouthpart morphology. We have, however, little understanding of the developmental mechanisms that underlie this diversity. Until recently it was difficult to perform any analysis of gene function outside of the genetic model insects Drosophila melanogaster and Tribolium castaneum. In this paper, we report the use of dsRNA-mediated interference (RNAi) to dissect gene function in the development of the milkweed bug Oncopeltus fasciatus, which has specialized suctorial mouthparts. The Hox genes Deformed (Dfd), proboscipedia (pb) and Sex combs reduced (Scr) have previously been shown to be expressed in the gnathal appendages of this species. Strikingly, the milkweed bug was found to have an unusual expression pattern of pb. Here, by analyzing single and combination RNAi depletions, we find that Dfd, pb and Scr are used in the milkweed bug to specify the identity of the mouthparts. The exact roles of the genes, however, are different from what is known in the two genetic model insects. The maxillary appendages in the bug are determined by the activities of the genes Dfd and Scr, rather than Dfd and pb as in the fly and beetle. The mandibular appendages are specified by Dfd, but their unique morphology in Oncopeltus suggests that Dfd's target genes are different. As in flies and beetles, the labium is specified by the combined activities of pb and Scr, but again, the function of pb appears to be different. Additionally, the regulatory control of pb by the other two genes seems to be different in the bug than in either of the other species. These novelties in Hox function, expression pattern and regulatory relationships may have been important for the evolution of the unique Hemipteran head.

  11. A genetic screen in Drosophila implicates Sex comb on midleg (Scm) in tissue overgrowth and mechanisms of Scm degradation by Wds.

    Science.gov (United States)

    Guo, Jiwei; Jin, Dan

    2015-05-01

    The sex comb on midleg (scm) gene encodes a transcriptional repressor and belongs to the Polycomb group (PcG) of genes, which regulates growth in Drosophila. Scm interacts with Polyhomeotic (a PcG protein) in vitro by recognizing its SPM domain. The homologous human protein, Sex comb on midleg-like 2 (Scml2), has been implicated in malignant brain tumors. Will die slowly (Wds) is another factor that regulates Drosophila development, and its homologous human protein, WD repeat domain 5(Wdr5), is part of the mixed lineage leukemia 1(MLL1) complex that promotes histone H3Lys4 methylation. Like Scml2, Wdr5 has been implicated in certain cancers; this protein plays an important role in leukemogenesis. In this study, we find that loss-of-function mutations in Scm result in non-autonomous tissue overgrowth in Drosophila, and determine that Scm is essential for ommatidium development and important for cell survival in Drosophila. Furthermore, our research suggests a relationship between Wds and Scm; Wds promotes Scm degradation through ubiquitination in vitro in Drosophila.

  12. Frequency comb swept lasers.

    Science.gov (United States)

    Tsai, Tsung-Han; Zhou, Chao; Adler, Desmond C; Fujimoto, James G

    2009-11-09

    We demonstrate a frequency comb (FC) swept laser and a frequency comb Fourier domain mode locked (FC-FDML) laser for applications in optical coherence tomography (OCT). The fiber-based FC swept lasers operate at a sweep rate of 1kHz and 120kHz, respectively over a 135nm tuning range centered at 1310nm with average output powers of 50mW. A 25GHz free spectral range frequency comb filter in the swept lasers causes the lasers to generate a series of well defined frequency steps. The narrow bandwidth (0.015nm) of the frequency comb filter enables a approximately -1.2dB sensitivity roll off over approximately 3mm range, compared to conventional swept source and FDML lasers which have -10dB and -5dB roll offs, respectively. Measurements at very long ranges are possible with minimal sensitivity loss, however reflections from outside the principal measurement range of 0-3mm appear aliased back into the principal range. In addition, the frequency comb output from the lasers are equally spaced in frequency (linear in k-space). The filtered laser output can be used to self-clock the OCT interference signal sampling, enabling direct fast Fourier transformation of the fringe signals, without the need for fringe recalibration procedures. The design and operation principles of FC swept lasers are discussed and designs for short cavity lasers for OCT and interferometric measurement applications are proposed.

  13. Comparative analysis of chromatin binding by Sex Comb on Midleg (SCM) and other polycomb group repressors at a Drosophila Hox gene.

    Science.gov (United States)

    Wang, Liangjun; Jahren, Neal; Miller, Ellen L; Ketel, Carrie S; Mallin, Daniel R; Simon, Jeffrey A

    2010-06-01

    Sex Comb on Midleg (SCM) is a transcriptional repressor in the Polycomb group (PcG), but its molecular role in PcG silencing is not known. Although SCM can interact with Polycomb repressive complex 1 (PRC1) in vitro, biochemical studies have indicated that SCM is not a core constituent of PRC1 or PRC2. Nevertheless, SCM is just as critical for Drosophila Hox gene silencing as canonical subunits of these well-characterized PcG complexes. To address functional relationships between SCM and other PcG components, we have performed chromatin immunoprecipitation studies using cultured Drosophila Schneider line 2 (S2) cells and larval imaginal discs. We find that SCM associates with a Polycomb response element (PRE) upstream of the Ubx gene which also binds PRC1, PRC2, and the DNA-binding PcG protein Pleiohomeotic (PHO). However, SCM is retained at this Ubx PRE despite genetic disruption or knockdown of PHO, PRC1, or PRC2, suggesting that SCM chromatin targeting does not require prior association of these other PcG components. Chromatin immunoprecipitations (IPs) to test the consequences of SCM genetic disruption or knockdown revealed that PHO association is unaffected, but reduced levels of PRE-bound PRC2 and PRC1 were observed. We discuss these results in light of current models for recruitment of PcG complexes to chromatin targets.

  14. Wing defects in Drosophila xenicid mutant clones are caused by C-terminal deletion of additional sex combs (Asx.

    Directory of Open Access Journals (Sweden)

    Kara Bischoff

    Full Text Available BACKGROUND: The coordinated action of genes that control patterning, cell fate determination, cell size, and cell adhesion is required for proper wing formation in Drosophila. Defects in any of these basic processes can lead to wing aberrations, including blisters. The xenicid mutation was originally identified in a screen designed to uncover regulators of adhesion between wing surfaces [1]. PRINCIPAL FINDINGS: Here, we demonstrate that expression of the betaPS integrin or the patterning protein Engrailed are not affected in developing wing imaginal discs in xenicid mutants. Instead, expression of the homeotic protein Ultrabithorax (Ubx is strongly increased in xenicid mutant cells. CONCLUSION: Our results suggest that upregulation of Ubx transforms cells from a wing blade fate to a haltere fate, and that the presence of haltere cells within the wing blade is the primary defect leading to the adult wing phenotypes observed.

  15. Phononic Frequency Comb via Intrinsic Three-Wave Mixing

    Science.gov (United States)

    Ganesan, Adarsh; Do, Cuong; Seshia, Ashwin

    2017-01-01

    Optical frequency combs have resulted in significant advances in optical frequency metrology and found wide applications in precise physical measurements and molecular fingerprinting. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this Letter, we report the first clear experimental evidence for a phononic frequency comb. We show that the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an autoparametrically excited subharmonic mode. The experiments depict the comb generation process evidenced by a spectral response consisting of equally spaced discrete and phase coherent comb lines. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define the attributes to control the features associated with comb formation in such a system. In addition to the demonstration of frequency comb, the interplay between the nonlinear resonances and the well-known Duffing phenomenon is also observed.

  16. Modeling Frequency Comb Sources

    Directory of Open Access Journals (Sweden)

    Li Feng

    2016-06-01

    Full Text Available Frequency comb sources have revolutionized metrology and spectroscopy and found applications in many fields. Stable, low-cost, high-quality frequency comb sources are important to these applications. Modeling of the frequency comb sources will help the understanding of the operation mechanism and optimization of the design of such sources. In this paper,we review the theoretical models used and recent progress of the modeling of frequency comb sources.

  17. Hyperfine phononic frequency comb

    CERN Document Server

    Ganesan, Adarsh; Seshia, Ashwin A

    2016-01-01

    Optical frequency combs [1-8] have resulted in significant advances in optical frequency metrology and found wide application to precise physical measurements [1-4, 9] and molecular fingerprinting [8]. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this letter, we report the first clear experimental evidence for a phononic frequency comb. In contrast to the Kerr nonlinearity [10] in optical frequency comb formation, the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an auto-parametrically excited sub-harmonic mode [16]. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define attributes to control the features [17-18] associated with comb formation in such a system. Further, the interplay between these nonlinear resonances and the well-known Duffing phenomenon [12-14] is also observed. The present...

  18. Universal Optical Frequency Comb

    CERN Document Server

    Savchenkov, A A; Liang, W; Ilchenko, V S; Seidel, D; Maleki, L

    2010-01-01

    We demonstrate that whispering gallery mode resonators can be utilized to generate optical frequency combs based on four wave mixing process at virtually any frequency that lies in the transparency window of the resonator host material. We show theoretically how the morphology of the resonator can be engineered to produce a family of spectrally equidistant modes with anomalous group velocity dispersion appropriate for the comb generation. We present experimental results for a frequency comb centered at 794 nm to support our theoretical findings.

  19. Combing the Globe

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    China’s top comb maker aims to sell its high-end hand-crafted products to overseas customers while improving its brand image For some, woodcarving and small carpentry work are hobbies. But for Tan Chuanhua and his Carpenter Tan comb brand, the woodworking craft has become a deep-rooted moneymaker. The Chongqing-based handcraft wood comb maker raised HK$140 million ($18 mil-

  20. Dynamics of comb-of-comb networks

    Science.gov (United States)

    Liu, Hongxiao; Lin, Yuan; Dolgushev, Maxim; Zhang, Zhongzhi

    2016-03-01

    The dynamics of complex networks, a current hot topic in many scientific fields, is often coded through the corresponding Laplacian matrix. The spectrum of this matrix carries the main features of the networks' dynamics. Here we consider the deterministic networks which can be viewed as "comb-of-comb" iterative structures. For their Laplacian spectra we find analytical equations involving Chebyshev polynomials whose properties allow one to analyze the spectra in deep. Here, in particular, we find that in the infinite size limit the corresponding spectral dimension goes as ds→2 . The ds leaves its fingerprint on many dynamical processes, as we exemplarily show by considering the dynamical properties of polymer networks, including single monomer displacement under a constant force, mechanical relaxation, and fluorescence depolarization.

  1. Dynamics of comb-of-comb-network polymers in random layered flows

    Science.gov (United States)

    Katyal, Divya; Kant, Rama

    2016-12-01

    We analyze the dynamics of comb-of-comb-network polymers in the presence of external random flows. The dynamics of such structures is evaluated through relevant physical quantities, viz., average square displacement (ASD) and the velocity autocorrelation function (VACF). We focus on comparing the dynamics of the comb-of-comb network with the linear polymer. The present work displays an anomalous diffusive behavior of this flexible network in the random layered flows. The effect of the polymer topology on the dynamics is analyzed by varying the number of generations and branch lengths in these networks. In addition, we investigate the influence of external flow on the dynamics by varying flow parameters, like the flow exponent α and flow strength Wα. Our analysis highlights two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The anomalous long-time dynamics is governed by the temporal exponent ν of ASD, viz., ν =2 -α /2 . Compared to a linear polymer, the comb-of-comb network shows a shorter crossover time (from the subdiffusive to superdiffusive regime) but a reduced magnitude of ASD. Our theory displays an anomalous VACF in the random layered flows that scales as t-α /2. We show that the network with greater total mass moves faster.

  2. Dynamics of microresonator frequency comb generation: models and stability

    Science.gov (United States)

    Hansson, Tobias; Wabnitz, Stefan

    2016-06-01

    Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

  3. Dynamics of microresonator frequency comb generation: models and stability

    Directory of Open Access Journals (Sweden)

    Hansson Tobias

    2016-06-01

    Full Text Available Microresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

  4. Dissipative soliton comb

    CERN Document Server

    Podivilov, Evgeniy V; Bednyakova, Anastasia E; Fedoruk, Mikhail P; Babin, Sergey A

    2016-01-01

    Dissipative solitons are stable localized coherent structures with linear frequency chirp generated in normal-dispersion mode-locked lasers. The soliton energy in fiber lasers is limited by the Raman effect, but implementation of intracavity feedback for the Stokes wave enables synchronous generation of a coherent Raman dissipative soliton. Here we demonstrate a new approach for generating chirped pulses at new wavelengths by mixing in a highly-nonlinear fiber of two frequency-shifted dissipative solitons, as well as cascaded generation of their clones forming a "dissipative soliton comb" in the frequency domain. We observed up to eight equidistant components in a 400-nm interval demonstrating compressibility from ~10 ps to ~300 fs. This approach, being different from traditional frequency combs, can inspire new developments in fundamental science and applications.

  5. Dual-comb MIXSEL

    Science.gov (United States)

    Link, S. M.; Zaugg, C. A.; Klenner, A.; Mangold, M.; Golling, M.; Tilma, B. W.; Keller, U.

    2015-03-01

    We present a single semiconductor disk laser simultaneously emitting two different gigahertz modelocked pulse trains. A birefringent crystal inside a modelocked integrated external-cavity surface-emitting laser (MIXSEL) separates the cavity beam into two spatially separated beams with perpendicular polarizations on the MIXSEL chip. This MIXSEL then generates two orthogonally polarized collinear modelocked pulse trains from one simple straight cavity. Superimposing the beams on a photo detector creates a microwave beat signal, representing a strikingly simple setup to down-convert the terahertz optical frequencies into the electronically accessible microwave regime. This makes the dual-comb MIXSEL scheme an ultra-compact and cost-efficient candidate for dual-comb spectroscopy applications.

  6. Biological and Biomimetic Comb Polyelectrolytes

    Directory of Open Access Journals (Sweden)

    Aristeidis Papagiannopoulos

    2010-05-01

    Full Text Available Some new phenomena involved in the physical properties of comb polyelectrolyte solutions are reviewed. Special emphasis is given to synthetic biomimetic materials, and the structures formed by these molecules are compared with those of naturally occurring glycoprotein and proteoglycan solutions. Developments in the determination of the structure and dynamics (viscoelasticity of comb polymers in solution are also covered. Specifically the appearance of multi-globular structures, helical instabilities, liquid crystalline phases, and the self-assembly of the materials to produce hierarchical comb morphologies is examined. Comb polyelectrolytes are surface active and a short review is made of some recent experiments in this area that relate to their morphology when suspended in solution. We hope to emphasize the wide variety of phenomena demonstrated by the vast range of naturally occurring comb polyelectrolytes and the challenges presented to synthetic chemists designing biomimetic materials.

  7. Optimal Sharpening of Compensated Comb Decimation Filters: Analysis and Design

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    David Ernesto Troncoso Romero

    2014-01-01

    Full Text Available Comb filters are a class of low-complexity filters especially useful for multistage decimation processes. However, the magnitude response of comb filters presents a droop in the passband region and low stopband attenuation, which is undesirable in many applications. In this work, it is shown that, for stringent magnitude specifications, sharpening compensated comb filters requires a lower-degree sharpening polynomial compared to sharpening comb filters without compensation, resulting in a solution with lower computational complexity. Using a simple three-addition compensator and an optimization-based derivation of sharpening polynomials, we introduce an effective low-complexity filtering scheme. Design examples are presented in order to show the performance improvement in terms of passband distortion and selectivity compared to other methods based on the traditional Kaiser-Hamming sharpening and the Chebyshev sharpening techniques recently introduced in the literature.

  8. Optical frequency combs generated mechanically

    CERN Document Server

    Sumetsky, M

    2016-01-01

    It is shown that a highly equidistant optical frequency comb can be generated by the parametric excitation of an optical bottle microresonator with nanoscale effective radius variation by its natural mechanical vibrations.

  9. Sub-lethal effects of pesticide residues in brood comb on worker honey bee (Apis mellifera development and longevity.

    Directory of Open Access Journals (Sweden)

    Judy Y Wu

    Full Text Available BACKGROUND: Numerous surveys reveal high levels of pesticide residue contamination in honey bee comb. We conducted studies to examine possible direct and indirect effects of pesticide exposure from contaminated brood comb on developing worker bees and adult worker lifespan. METHODOLOGY/PRINCIPAL FINDINGS: Worker bees were reared in brood comb containing high levels of known pesticide residues (treatment or in relatively uncontaminated brood comb (control. Delayed development was observed in bees reared in treatment combs containing high levels of pesticides particularly in the early stages (day 4 and 8 of worker bee development. Adult longevity was reduced by 4 days in bees exposed to pesticide residues in contaminated brood comb during development. Pesticide residue migration from comb containing high pesticide residues caused contamination of control comb after multiple brood cycles and provided insight on how quickly residues move through wax. Higher brood mortality and delayed adult emergence occurred after multiple brood cycles in contaminated control combs. In contrast, survivability increased in bees reared in treatment comb after multiple brood cycles when pesticide residues had been reduced in treatment combs due to residue migration into uncontaminated control combs, supporting comb replacement efforts. Chemical analysis after the experiment confirmed the migration of pesticide residues from treatment combs into previously uncontaminated control comb. CONCLUSIONS/SIGNIFICANCE: This study is the first to demonstrate sub-lethal effects on worker honey bees from pesticide residue exposure from contaminated brood comb. Sub-lethal effects, including delayed larval development and adult emergence or shortened adult longevity, can have indirect effects on the colony such as premature shifts in hive roles and foraging activity. In addition, longer development time for bees may provide a reproductive advantage for parasitic Varroa destructor

  10. Scientific Opinion on Rooster Combs Extract

    Directory of Open Access Journals (Sweden)

    EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA

    2013-06-01

    Full Text Available Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA was asked to carry out the additional assessment for ‘Rooster Combs Extract’ (RCE as a food ingredient in the context of Regulation (EC No 258/97, taking into account the comments and objections of a scientific nature raised by Member States. Rooster combs extract results from a production process involving enzymatic hydrolysis of rooster combs and subsequent filtration, concentration and precipitation steps. The principle constituents of RCE are the glycosaminoglycans hyaluronic acid, chondroitin sulphate A and dermatan sulphate. The applicant intends to add RCE to a number of dairy products with a recommended maximum intake of 80 mg RCE per portion and per day. The target population is the general population, with the exception of pregnant women, children and people with adverse reactions to sodium hyaluronate and/or avian protein. In the high intake scenario for “consumers only”, the highest daily intake would occur in adults in Belgium (0.788 g. The highest intake scenario for “all subjects” was estimated for adolescents in Denmark (0.427 g/day. The Panel notes that no adverse effects were observed at the highest tested dose of 600 mg/kg bw per day in a 90-day oral toxicity study in rats. Considering the nature, the natural occurrence and previous consumption of RCE constituents, the Panel is of the opinion that the margin between the intended as well as the estimated maximum possible intake of RCE in relation to the highest dose administered to rats without adverse effects in a subchronic oral toxicity study is sufficient. The Panel concludes that the novel food ingredient, Rooster Comb Extract, is safe under the proposed uses and use levels.

  11. [Gender, medicine and consumer culture: the cultural history of comb in the Ming and Qing Dynasties].

    Science.gov (United States)

    Chen, Siyan

    2014-09-01

    In the Ming and Qing Dynasties, in addition to combing the hair, the comb also gradually played a role in people's daily life for disease treatment and keeping people's health. In short, during this period, the characteristic of comb reveal, as a whole, its reinforcing practicability and weakening of its ornamentality. During its application, people's behavioral activities endowed the comb with definite cultural connotation, which, thanks to the presence of gender and personality, became the symbol for expressing love between man and woman. By analogizing people's thought, since the comb could dredge something. Therefore, it can be used to cure diseases. Thus, it could be seen that, based on consumer's cultural description, the comb, tiny as it may be, did reflect the aesthetic ideas and interests and daily life-preservation habit of the literati due to the flourishing of book market in the Ming and Qing Dynasties.

  12. Termite-regulated fungal monoculture in fungus combs of a macrotermitine termite Odontotermes formosanus.

    Science.gov (United States)

    Shinzato, Naoya; Muramatsu, Mizuho; Watanabe, Yoshio; Matsui, Toru

    2005-08-01

    The mechanism of the exclusive growth of Termitomyces in fungus combs with fungi-growing termites, O. formosanus was examined using laboratory scale fungus combs. In the combs without the termites, vigorous growth of unidentified fungi was observed although no significant change was found in the case of the combs with termites. In addition, these results were reproducible even when incubated in a separated dish, suggesting that the physicochemical conditions were not the reason for the growth. With the molecular based analysis for the microbial communities in the combs, monoculture of the Termitomyces in the combs with termites was confirmed while the bacterial communities were independent either with or without termites. Possible mechanism of the exclusive growth of Termitomyces, such as the selective grazing of pathogenic fungi or contribution of antifungal activity giving actinomycetes were also discussed.

  13. Schizocordulia gen. nov. related to Aeschnosom Selys with description of the female and additional data on the male of Schizocordulia rustica (Selys comb. nov. (Odonata, Corduliidae Schizocordulia gen. nov. relacionado a Aeschnosoma Selys com descrição da fêmea e dados adicionais sobre o macho de Schizocordulia rustica (Selys comb. nov. (Odonata, Corduliidae

    Directory of Open Access Journals (Sweden)

    Angelo B.M. Machado

    2005-09-01

    Full Text Available The monotypical genus Schizocordulia is created for Schizocordulia rustica (Selys, 1871 comb. nov. known from a single male from Bahia, Brazil lacking the anal appendages. The female is described and the redescription of the male made by GEIJKES (1970 is completed by the description and illustration of the penis, the anal appendages and the pilose plate. The main characters separating the new genus from the closely related Aeschnosoma Selys, 1870 are the bifid male inferior appendage, the very long internal branch of the hamulus, the presence of a pilose plate on the male 7th abdominal segment, and the large and complex valvula vulvae of the female. The study was based on 33 males and 2 females, which allowed an evaluation of the intraspecific variations in Schizocordulia rustica.Cria-se o gênero monotípico Schizocordulia para Schizocordulia rustica (Selys, 1871 comb. nov. espécie conhecida de um único exemplar macho sem os apêndices anais. Descreve-se a fêmea e a redescrição do macho feita por GEIJKES (1970 é completada pela descrição e ilustração do pênis, da placa pilosa e dos apêndices anais. Os principais caracteres utilizados para separar Schizocordulia do gênero afim Aeschnosoma Selys, 1870 são o apêndice inferior do macho bífido, o ramo interno do hâmulo muito longo, a presença de uma placa pilosa no 7º segmento abdominal e a válvula da vulva da fêmea grande e complexa. Este estudo foi baseado em 33 machos e 2 fêmeas, o que permitiu uma avaliação das variações intraespecíficas em Schizocordulia rustica.

  14. Surface Acoustic Wave Frequency Comb

    CERN Document Server

    Savchenkov, A A; Ilchenko, V S; Seidel, D; Maleki, L

    2011-01-01

    We report on realization of an efficient triply-resonant coupling between two long lived optical modes and a high frequency surface acoustic wave (SAW) mode of the same monolithic crystalline whispering gallery mode resonator. The coupling results in an opto-mechanical oscillation and generation of a monochromatic SAW. A strong nonlinear interaction of this mechanical mode with other equidistant SAW modes leads to mechanical hyper-parametric oscillation and generation of a SAW pulse train and associated frequency comb in the resonator. We visualized the comb observing the modulation of the modulated light escaping the resonator.

  15. Monolithically integrated absolute frequency comb laser system

    Energy Technology Data Exchange (ETDEWEB)

    Wanke, Michael C.

    2016-07-12

    Rather than down-convert optical frequencies, a QCL laser system directly generates a THz frequency comb in a compact monolithically integrated chip that can be locked to an absolute frequency without the need of a frequency-comb synthesizer. The monolithic, absolute frequency comb can provide a THz frequency reference and tool for high-resolution broad band spectroscopy.

  16. On Frequency Combs in Monolithic Resonators

    Science.gov (United States)

    Savchenkov, A. A.; Matsko, A. B.; Maleki, L.

    2016-06-01

    Optical frequency combs have become indispensable in astronomical measurements, biological fingerprinting, optical metrology, and radio frequency photonic signal generation. Recently demonstrated microring resonator-based Kerr frequency combs point the way towards chip scale optical frequency comb generator retaining major properties of the lab scale devices. This technique is promising for integrated miniature radiofrequency and microwave sources, atomic clocks, optical references and femtosecond pulse generators. Here we present Kerr frequency comb development in a historical perspective emphasizing its similarities and differences with other physical phenomena. We elucidate fundamental principles and describe practical implementations of Kerr comb oscillators, highlighting associated solved and unsolved problems.

  17. On Frequency Combs in Monolithic Resonators

    Directory of Open Access Journals (Sweden)

    Savchenkov A. A.

    2016-06-01

    Full Text Available Optical frequency combs have become indispensable in astronomical measurements, biological fingerprinting, optical metrology, and radio frequency photonic signal generation. Recently demonstrated microring resonator-based Kerr frequency combs point the way towards chip scale optical frequency comb generator retaining major properties of the lab scale devices. This technique is promising for integrated miniature radiofrequency and microwave sources, atomic clocks, optical references and femtosecond pulse generators. Here we present Kerr frequency comb development in a historical perspective emphasizing its similarities and differences with other physical phenomena. We elucidate fundamental principles and describe practical implementations of Kerr comb oscillators, highlighting associated solved and unsolved problems.

  18. Chileotrecha romero (Kraus, 1966) comb. nov. and Pseudocleobis patagonicus (Roewer, 1934) comb. nov. transferral from Mummuciidae to Ammotrechidae (Arachnida, Solifugae).

    Science.gov (United States)

    Botero-Trujillo, Ricardo; Iuri, Hernán A

    2015-07-27

    The solifuge species Mummucina romero Kraus, 1966, from Chile, and Mummucia patagonica Roewer, 1934, from Argentina, are here transferred from Mummuciidae Roewer, 1934 to Ammotrechidae Roewer, 1934. Chileotrecha romero (Kraus, 1966) comb. nov. and Pseudocleobis patagonicus (Roewer, 1934) comb. nov. are proposed. Comments on their morphology are made and previous distributional records are discussed. Pseudocleobis patagonicus is proposed as a nomen dubium. In addition, we confirm that female and immature specimens of the family Mummuciidae, just like males, can be reliably recognized based on features that had been suggested by Maury (1984).

  19. Ultrafast electrooptic dual-comb interferometry

    CERN Document Server

    Duran, Vicente; Torres-Company, Victor

    2015-01-01

    The femtosecond laser frequency comb has enabled the 21st century revolution in optical synthesis and metrology. A particularly compelling technique that relies on the broadband coherence of two laser frequency combs is dual-comb interferometry. This method is rapidly advancing the field of optical spectroscopy and empowering new applications, from nonlinear microscopy to laser ranging. Up to now, most dual-comb interferometers were based on modelocked lasers, whose repetition rates have restricted the measurement speed to ~ kHz. Here we demonstrate a novel dual-comb interferometer that is based on electrooptic frequency comb technology and measures consecutive complex spectra at a record-high refresh rate of 25 MHz. These results pave the way for novel scientific and metrology applications of frequency comb generators beyond the realm of molecular spectroscopy, where the measurement of ultrabroadband waveforms is of paramount relevance.

  20. Broadband midinfrared frequency comb with tooth scanning

    Science.gov (United States)

    Lee, Kevin F.; Masłowski, P.; Mills, A.; Mohr, C.; Jiang, Jie; Schunemann, Peter G.; Fermann, M. E.

    2015-03-01

    Frequency combs are a massively parallel source of extremely accurate optical frequencies. Frequency combs generally operate at the visible or near-infrared wavelengths, but fundamental molecular vibrations occur at midinfrared wavelengths. We demonstrate an optically-referenced, broadband midinfrared frequency comb based on a doublyresonant optical parametric oscillator (OPO). By tuning the wavelength of the reference laser, the comb line frequencies are tuned as well. By scanning the reference wavelength, any frequency can be accessed, not just the frequencies of the base comb. Combined with our comb-resolving Fourier transform spectrometer, we can measure 200 wavenumber wide broadband absorption spectra with 200 kHz linewidth comb teeth. Our OPO is pumped by an amplified Tm fiber frequency comb, with phase-locked carrier envelope offset frequency, and repetition rate fixed by phase-locking a frequency comb line to a narrow linewidth diode laser at a telecom channel. The frequency comb is referenced to GPS by long-term stabilization of the repetition rate to a selected value using the temperature of the reference laser as the control. The resulting pump comb is about 3W of 100 fs pulses at 418 MHz repetition rate at 1950 nm. Part of the comb is used for supercontinuum generation for frequency stabilization, and the rest pumps an orientation-patterned gallium arsenide (OP-GaAs) crystal in a doubly-resonant optical parametric oscillator cavity, yielding collinear signal and idler beams from about 3 to 5.5 μm. We verify comb scanning by resolving the 200 MHz wide absorption lines of the entire fundamental CO vibrational manifold at 11 Torr pressure.

  1. Quantum Cascade Laser Frequency Combs

    CERN Document Server

    Faist, Jérôme; Scalari, Giacomo; Rösch, Markus; Bonzon, Christopher; Hugi, Andreas; Beck, Mattias

    2015-01-01

    It was recently demonstrated that broadband quantum cascade lasers can operate as frequency combs. As such, they operate under direct electrical pumping at both mid-infrared and THz frequencies, making them very attractive for dual-comb spectroscopy. Performance levels are continuously improving, with average powers over 100 mW and frequency coverage of 100 cm$^{-1}$ in the mid-infrared. In the THz range, 10 mW of average power and 600 GHz of frequency coverage are reported. As a result of the very short upper state lifetime of the gain medium, the mode proliferation in these sources arises from four wave mixing rather than saturable absorption. As a result, their optical output is characterized by the tendency of small intensity modulation of the output power, and the relative phases of the modes to be similar to the ones of a frequency modulated laser. Recent results include the proof of comb operation down to a metrological level, the observation of a Schawlow-Townes broadened linewidth, as well as the fir...

  2. Autosomal and X-Linked Additive Genetic Variation for Lifespan and Aging: Comparisons Within and Between the Sexes in Drosophila melanogaster.

    Science.gov (United States)

    Griffin, Robert M; Schielzeth, Holger; Friberg, Urban

    2016-12-07

    Theory makes several predictions concerning differences in genetic variation between the X chromosome and the autosomes due to male X hemizygosity. The X chromosome should: (i) typically show relatively less standing genetic variation than the autosomes, (ii) exhibit more variation in males compared to females because of dosage compensation, and (iii) potentially be enriched with sex-specific genetic variation. Here, we address each of these predictions for lifespan and aging in Drosophila melanogaster To achieve unbiased estimates of X and autosomal additive genetic variance, we use 80 chromosome substitution lines; 40 for the X chromosome and 40 combining the two major autosomes, which we assay for sex-specific and cross-sex genetic (co)variation. We find significant X and autosomal additive genetic variance for both traits in both sexes (with reservation for X-linked variation of aging in females), but no conclusive evidence for depletion of X-linked variation (measured through females). Males display more X-linked variation for lifespan than females, but it is unclear if this is due to dosage compensation since also autosomal variation is larger in males. Finally, our results suggest that the X chromosome is enriched for sex-specific genetic variation in lifespan but results were less conclusive for aging overall. Collectively, these results suggest that the X chromosome has reduced capacity to respond to sexually concordant selection on lifespan from standing genetic variation, while its ability to respond to sexually antagonistic selection may be augmented.

  3. Autosomal and X-Linked Additive Genetic Variation for Lifespan and Aging: Comparisons Within and Between the Sexes in Drosophila melanogaster

    Directory of Open Access Journals (Sweden)

    Robert M. Griffin

    2016-12-01

    Full Text Available Theory makes several predictions concerning differences in genetic variation between the X chromosome and the autosomes due to male X hemizygosity. The X chromosome should: (i typically show relatively less standing genetic variation than the autosomes, (ii exhibit more variation in males compared to females because of dosage compensation, and (iii potentially be enriched with sex-specific genetic variation. Here, we address each of these predictions for lifespan and aging in Drosophila melanogaster. To achieve unbiased estimates of X and autosomal additive genetic variance, we use 80 chromosome substitution lines; 40 for the X chromosome and 40 combining the two major autosomes, which we assay for sex-specific and cross-sex genetic (covariation. We find significant X and autosomal additive genetic variance for both traits in both sexes (with reservation for X-linked variation of aging in females, but no conclusive evidence for depletion of X-linked variation (measured through females. Males display more X-linked variation for lifespan than females, but it is unclear if this is due to dosage compensation since also autosomal variation is larger in males. Finally, our results suggest that the X chromosome is enriched for sex-specific genetic variation in lifespan but results were less conclusive for aging overall. Collectively, these results suggest that the X chromosome has reduced capacity to respond to sexually concordant selection on lifespan from standing genetic variation, while its ability to respond to sexually antagonistic selection may be augmented.

  4. Flexible radio-frequency photonics: Optoelectronic frequency combs and integrated pulse shaping

    Science.gov (United States)

    Metcalf, Andrew J.

    Microwave photonics is a discipline which leverages optoelectronics to enhance the generation, transport, and processing of high-frequency electrical signals. At the heart of many emerging techniques is the optical frequency comb. A comb is a lightwave source whose spectrum is made up of discrete equally spaced spectral components that share a fixed phase relationship. These discrete coherent oscillators --known as comb lines-- collectively form a Fourier basis that describe a periodic optical waveform. Within the last two decades frequency-stabilized broadband combs produced from mode-locked lasers have led to revolutionary advancements in precision optical frequency synthesis and metrology. Meanwhile, Fourier-transform optical pulse shaping, which provides a means to control a comb's Fourier basis in both amplitude and phase, has emerged as an integral tool in optical communications, broadband waveform generation, and microwave photonic filtering. However, traditional comb and pulse shaping architectures are often plagued by complex and bulky setups, rendering robust and cost effective implementation outside of the laboratory a challenge. In addition, traditional comb sources based on short-pulse lasers do not possess qualities which are ideally suited for this new application regime. Motivated by the shortcomings in current architectures, and empowered by recent advancements in optoelectronic technology, this dissertation focuses on developing novel and robust schemes in optical frequency comb generation and line-by-line pulse shaping. Our results include: the invention and low-noise characterization of a broadband flat-top comb source; the realization of an optoelectronic-based time cloak; and finally, the development of an integrated pulse shaper, which we use in conjunction with our flat-top comb source to demonstrate a rapidly reconfigurable microwave photonic filter.

  5. On-chip dual-comb based on quantum cascade laser frequency combs

    Energy Technology Data Exchange (ETDEWEB)

    Villares, G., E-mail: gustavo.villares@phys.ethz.ch; Wolf, J.; Kazakov, D.; Süess, M. J.; Beck, M.; Faist, J., E-mail: jfaist@phys.ethz.ch [Institute for Quantum Electronics, ETH Zürich, CH-8093 Zürich (Switzerland); Hugi, A. [IRsweep GmbH, CH-8093 Zürich (Switzerland)

    2015-12-21

    Dual-comb spectroscopy is emerging as an appealing application of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs. Here, we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs. Control of the combs repetition and offset frequencies is obtained by integrating micro-heaters next to each laser. We show that a full control of the dual-comb system is possible, by measuring a multi-heterodyne beating corresponding to an optical bandwidth of 32 cm{sup −1} centered at 1330 cm{sup −1} (7.52 μm), demonstrating that this device represents a critical step towards compact dual-comb systems.

  6. Taxonomic evaluation of the genus Enterobacter based on multilocus sequence analysis (MLSA): proposal to reclassify E. nimipressuralis and E. amnigenus into Lelliottia gen. nov. as Lelliottia nimipressuralis comb. nov. and Lelliottia amnigena comb. nov., respectively, E. gergoviae and E. pyrinus into Pluralibacter gen. nov. as Pluralibacter gergoviae comb. nov. and Pluralibacter pyrinus comb. nov., respectively, E. cowanii, E. radicincitans, E. oryzae and E. arachidis into Kosakonia gen. nov. as Kosakonia cowanii comb. nov., Kosakonia radicincitans comb. nov., Kosakonia oryzae comb. nov. and Kosakonia arachidis comb. nov., respectively, and E. turicensis, E. helveticus and E. pulveris into Cronobacter as Cronobacter zurichensis nom. nov., Cronobacter helveticus comb. nov. and Cronobacter pulveris comb. nov., respectively, and emended description of the genera Enterobacter and Cronobacter.

    Science.gov (United States)

    Brady, Carrie; Cleenwerck, Ilse; Venter, Stephanus; Coutinho, Teresa; De Vos, Paul

    2013-07-01

    The taxonomy of Enterobacter has a complicated history, with several species transferred to and from this genus. Classification of strains is difficult owing to its polyphyletic nature, based on 16S rRNA gene sequences. It has been previously acknowledged that Enterobacter contains species which should be transferred to other genera. In an attempt to resolve the taxonomy of Enterobacter, MLSA based on partial sequencing of protein-encoding genes (gyrB, rpoB, infB and atpD) was performed on the type strains and reference strains of Enterobacter, Cronobacter and Serratia species, as well as members of the closely related genera Citrobacter, Klebsiella, Kluyvera, Leclercia, Mangrovibacter, Raoultella and Yokenella. Phylogenetic analyses of the concatenated nucleotide sequences revealed that Enterobacter can be divided into five strongly supported MLSA groups, suggesting that the species should be reclassified into five different genera. Further support for this was provided by a concatenated amino acid tree, phenotypic characteristics and fatty acid profiles, enabling differentiation of the MLSA groups. Three novel genera are proposed: Lelliottia gen. nov., Pluralibacter gen. nov. and Kosakonia gen. nov. and the following new combinations: Lelliottia nimipressuralis comb. nov., Lelliottia amnigena comb. nov., Pluralibacter gergoviae comb. nov., Pluralibacter pyrinus comb. nov., Kosakonia cowanii comb. nov., Kosakonia radicincitans comb. nov., Kosakonia oryzae comb. nov., Kosakonia arachidis comb. nov., Cronobacter helveticus comb. nov. and Cronobacter pulveris comb. nov. Additionally, the novel epithet Cronobacter zurichensis nom. nov. is proposed for the reclassification of Enterobacter turicensis into the genus Cronobacter, as Cronobacter turicensis (Iversen et al., 2008) is already in use.

  7. Transient Regime of Kerr Frequency Comb Formation

    CERN Document Server

    Savchenkov, Anatoliy A; Liang, Wei; Ilchenko, Vladimir S; Seidel, David; Maleki, Lute

    2011-01-01

    Temporal growth of an optical Kerr frequency comb generated in a microresonator is studied both experimentally and numerically. We find that the comb emerges from vacuum fluctuations of the electromagnetic field on timescales significantly exceeding the ringdown time of the resonator modes. The frequency harmonics of the comb spread starting from the optically pumped mode if the microresonator is characterized with anomalous group velocity dispersion. The harmonics have different growth rates resulting from sequential four-wave mixing process that explains intrinsic modelocking of the comb.

  8. Coherence properties of Kerr frequency combs

    CERN Document Server

    Erkintalo, Miro

    2014-01-01

    We use numerical simulations based on an extended Lugiato-Lefever equation (LLE) to investigate the stability properties of Kerr frequency combs generated in microresonators. In particular, we show that an ensemble average calculated over sequences of output fields separated by a fixed number of resonator roundtrips allows the coherence of Kerr combs to be quantified in terms of the complex-degree of first-order coherence. We identify different regimes of comb coherence, linked to the solutions of the LLE. Our approach provides a practical and unambiguous way of assessing the stability of Kerr combs that is directly connected to an accessible experimental quantity.

  9. Coherence properties of Kerr frequency combs.

    Science.gov (United States)

    Erkintalo, Miro; Coen, Stéphane

    2014-01-15

    We use numerical simulations based on an extended Lugiato-Lefever equation (LLE) to investigate the stability properties of Kerr frequency combs generated in microresonators. In particular, we show that an ensemble average calculated over sequences of output fields separated by a fixed number of resonator roundtrips allows the coherence of Kerr combs to be quantified in terms of the complex degree of first-order coherence. We identify different regimes of comb coherence, linked to the solutions of the LLE. Our approach provides a practical and unambiguous way of assessing the stability of Kerr combs that is directly connected to an accessible experimental quantity.

  10. Accurate frequency referencing for fieldable dual-comb spectroscopy

    CERN Document Server

    Truong, Gar-Wing; Cossel, Kevin C; Baumann, Esther; Klose, Andrew; Giorgetta, Fabrizio R; Swann, William C; Newbury, Nathan R; Coddington, Ian

    2016-01-01

    A fieldable dual-comb spectrometer is described based on a "bootstrapped" frequency referencing scheme in which short-term optical phase coherence between combs is attained by referencing each to a free-running diode laser, whilst high frequency resolution and long-term accuracy is derived from a stable quartz oscillator. This fieldable dual-comb spectrometer was used to measure spectra with full comb-tooth resolution spanning from 140 THz (2.14 um, 4670 cm^-1) to 184 THz (1.63 um, 6140 cm^-1) in the near infrared with a frequency sampling of 200 MHz (0.0067 cm^-1), ~ 120 kHz frequency resolution, and ~ 1 MHz frequency accuracy. High resolution spectra of water and carbon dioxide transitions at 1.77 um, 1.96 um and 2.06 um show that the molecular transmission acquired with this fieldable system did not deviate from those measured with a laboratory-based system (referenced to a maser and cavity-stabilized laser) to within 5.6x10^-4. Additionally, the fieldable system optimized for carbon dioxide quantification...

  11. Microresonator Soliton Dual-Comb Spectroscopy

    CERN Document Server

    Suh, Myoung-Gyun; Yang, Ki Youl; Yi, Xu; Vahala, Kerry

    2016-01-01

    Rapid characterization of optical and vibrational spectra with high resolution can identify species in cluttered environments and is important for assays and early alerts. In this regard, dual-comb spectroscopy has emerged as a powerful approach to acquire nearly instantaneous Raman and optical spectra with unprecedented resolution. Spectra are generated directly in the electrical domain and avoid bulky mechanical spectrometers. Recently, a miniature soliton-based comb has emerged that can potentially transfer the dual-comb method to a chip platform. Unlike earlier microcombs, these new devices achieve high-coherence, pulsed mode locking. They generate broad, reproducible spectral envelopes, which is essential for dual-comb spectroscopy. Here, dual-comb spectroscopy is demonstrated using these devices. This work shows the potential for integrated, high signal-to-noise spectroscopy with fast acquisition rates.

  12. Laser frequency combs for precision astronomical spectroscopy

    Science.gov (United States)

    Ycas, Gabriel George

    Laser frequency comb sources promise to enable precision astronomical spectroscopy at the 10-11 level, enabling observations aimed at locating potentially habitable planets. Frequency combs allow for the simultaneous generation of thousands of individual laser lines, each with optical frequency referenced to the SI second, and are capable of providing a bright, simple, and stable spectrum ideal for the calibration of grating-based astronomical spectrographs. In order for frequency combs and spectrographs to be used in tandem, key technical challenges must be addressed. Most critically, it is necessary to increase the mode-spacing of the frequency comb to more than 20 GHz while simultaneously retaining the stability and broad optical bandwidth of the comb. This thesis also offers an overview of modern astronomical spectroscopy, along with a thorough discussion of the technical details of mode-locked lasers and frequency comb design. This thesis begins by presenting a frequency comb system with mode-spacing of 25 GHz suitable for the near-infrared between 1500 and 1700 nm. Examples are shown from the successful calibration of the Penn State University Pathfinder astronomical spectrograph located at the Hobby-Eberly telescope using the frequency comb system. In the second half of the thesis, the erbium-fiber frequency comb is shown to generate highly coherent, ultrafast, and bright pulses at 1050 nm. The short duration and high peak power of these pulses enable coherent and continuous extension of the comb to visible wavelengths. Next, an accurate model of a nonlinear fiber optic amplifiers is developed and tested, then applied to optimize the selection of fiber lengths in the design of ultrafast nonlinear fiber-optic systems. Finally, a broad-bandwidth optical filter cavity for the generation of a 980--1110 nm suitable for calibration of next-generation spectrographs was designed and tested.

  13. All Optical Stabilization of a Soliton Frequency Comb in a Crystalline Microresonator

    CERN Document Server

    Jost, J D; Herr, T; Lecaplain, C; Brasch, V; Pfeiffer, M H P; Kippenberg, T J

    2015-01-01

    Microresonator based optical frequency combs (MFC) have demonstrated promise in extending the capabilities of optical frequency combs. Here we demonstrate all optical stabilization of a low noise temporal soliton based MFC in a crystalline resonator via a new technique to control the repetition rate. This is accomplished by thermally heating the microresonator with an additional probe laser coupled to an auxiliary optical resonator mode. The offset frequency is controlled by stabilization of the pump laser frequency to a reference optical frequency comb. We analyze the stabilization by performing an out of loop comparison and measure the overlapping Allan deviation. This all optical stabilization technique can prove useful as a low added noise actuator for self-referenced microresonator frequency combs.

  14. A bidirectional dual-comb ring laser for simple and robust dual-comb spectroscopy

    CERN Document Server

    Ideguchi, Takuro; Kobayashi, Yohei; Goda, Keisuke

    2015-01-01

    Fourier-transform spectroscopy is an indispensable tool for analyzing chemical samples in scientific research as well as chemical and pharmaceutical industries. Recently, its measurement speed, sensitivity, and precision have been shown to be significantly enhanced by using dual frequency combs. However, wide acceptance of this technique is hindered by its requirement for two frequency combs and active stabilization of the combs. Here we overcome this predicament with a Kerr-lens mode-locked bidirectional ring laser that generates two frequency combs with slightly different pulse repetition rates and a tunable yet highly stable rate difference. This peculiar lasing principle builds on a slight difference in optical cavity length between two counter-propagating lasing modes due to Kerr lensing. Since these combs are produced by the one and same laser cavity, their relative coherence stays passively stable without the need for active stabilization. To show its utility, we demonstrate broadband dual-comb spectro...

  15. Cantharellus gallaecicus (Blanco-Dios Olariaga, comb. & stat. nov (Cantharellaceae

    Directory of Open Access Journals (Sweden)

    Olariaga, Ibai

    2007-12-01

    Full Text Available Cantharellus gallaecicus comb. & stat. nov. is proposed, after the examination of its holotype and additional material. Based on the characters observed in all the studied material (i.e., thinwalled hyphae of the pileipelis, minute basidiomata with white to grey pileus, and surface that turns yellow when bruised it is considered that C. gallaecicus is more closely related to C. romagnesianus than to C. cibarius.Se propone Cantharellus gallaecicus comb. & stat. nov. tras revisar su holótipo y material adicional disponible. Dado que todo el material examinado posee hifas del pileipelis de pared delgada, basidiomas pequeños con píleo de blanco a gris, y superficie que vira a amarillo al roce, se considera que C. gallaecicus es una especie más estrechamente relacionada con C. romagnesianus que con C. cibarius.

  16. Combing gravitational hair in 2+1 dimensions

    CERN Document Server

    Donnelly, William; Mintun, Eric

    2015-01-01

    The gravitational Gauss law requires any addition of energy to be accompanied by the addition of gravitational flux. The possible configurations of this flux for a given source may be called gravitational hair, and several recent works discuss gravitational observables (`gravitational Wilson lines') which create this hair in highly-collimated `combed' configurations. We construct and analyze time-symmetric classical solutions of 2+1 Einstein-Hilbert gravity such as might be created by smeared versions of such operators. We focus on the AdS$_3$ case, where this hair is characterized by the profile of the boundary stress tensor; the desired solutions are those where the boundary stress tensor at initial time $t=0$ agrees precisely with its vacuum value outside an angular interval $[-\\alpha,\\alpha]$. At linear order in source strength the energy is independent of the combing parameter $\\alpha$, but non-linearities cause the full energy to diverge as $\\alpha \\to 0$. In general, solutions with combed gravitational...

  17. Additions to the family Miroviaceae (Coniferae) from the Lower Cretaceous of West Greenland and Germany: Mirovia groenlandica n. sp., Tritaenia crassa (Seward) comb, nov., and Tritaenia linkii Magdefrau et Rudolph emend.

    OpenAIRE

    N. Bose, Mahendra; Manum, Svein B.

    1991-01-01

    The genus Tritaenia with its type species T. linkii Magdefrau et Rudolph emend, from the Wealden of Germany has been referred to the family Miroviaceae Bose et Manum, comprising Mesozoic and mostly Arctic conifer foliage with ‘Sciadopitys-like’ stomatal distribution. Two other additions to the Miroviaceae, both from the Lower Cretaceous of West Greenland, arc Pityophyllum crassum Seward, now attributed to Tritaenia, and Mirovia groenlandica n. sp., described on leafy stems and detached leaves...

  18. Efficient Two-Comb Fourier Spectroscopy

    CERN Document Server

    Mandon, Julien; Picqué, Nathalie

    2008-01-01

    Molecular fingerprinting through absorption spectroscopy is a powerful analytical method. Wide spectral ranges are explored with Doppler-limited resolution. Fast data acquisition, accurate measurements of frequency, intensity, and line shape; time-resolved, selective spectra are achieved with excellent sensitivities. However, presently spectrometers are unable to provide all these features at once. Here we show that, based on frequency comb lasers, a spectrometer may overcome this difficulty. We have recorded two series of spectra with a 1.5 $\\mu$m Cr:YAG frequency comb. In the first series, we propose to use the comb structure to considerably improve the recording time and signal to noise ratio of Doppler-resolved spectra, (Fourier Transform (FT) of the beating signatures of two combs issued from the same initial laser). The second series demonstrates that under very simple experimental conditions, FT spectroscopists may record much more sensitive spectra than with the usual incoherent white light source. We...

  19. The codevelopment of skill at and preference for use of retrieval-based processes for solving addition problems: individual and sex differences from first to sixth grades.

    Science.gov (United States)

    Bailey, Drew H; Littlefield, Andrew; Geary, David C

    2012-09-01

    The ability to retrieve basic arithmetic facts from long-term memory contributes to individual and perhaps sex differences in mathematics achievement. The current study tracked the codevelopment of preference for using retrieval over other strategies to solve single-digit addition problems, independent of accuracy, and skilled use of retrieval (i.e., accuracy and reaction time [RT]) from first to sixth grades inclusive (N=311). Accurate retrieval in first grade was related to working memory capacity and intelligence, and it predicted a preference for retrieval in second grade. In later grades, the relation between skill and preference changed such that preference in one grade predicted accuracy and RT in the next grade as RT and accuracy continued to predict future gains in preference. In comparison with girls, boys had a consistent preference for retrieval over other strategies and had faster retrieval speeds, but the sex difference in retrieval accuracy varied across grades. Results indicate that ability influences early skilled retrieval, but both practice and skill influence each other in a feedback loop later in development and provide insights into the source of the sex difference in problem-solving approaches.

  20. Silicon-Chip-Based Optical Frequency Combs

    Science.gov (United States)

    2015-10-26

    frequencies . This phenomenon appears in many systems spanning biology, chemistry, neuroscience, and physics [29,30]. Examples include power grid networks... Frequency Combs," Phys. Rev. Lett. 100, 013902 (2008). [91] F. Leo, et al., “Dispersive wave emission and supercontinuum generation in a silicon wire...AFRL-AFOSR-VA-TR-2015-0365 Silicon-Chip-Based Optical Frequency Combs Alexander Gaeta CORNELL UNIVERSITY Final Report 10/26/2015 DISTRIBUTION A

  1. Symbiotic fungi produce laccases potentially involved in phenol degradation in fungus combs of fungus-growing termites in Thailand.

    Science.gov (United States)

    Taprab, Yaovapa; Johjima, Toru; Maeda, Yoshimasa; Moriya, Shigeharu; Trakulnaleamsai, Savitr; Noparatnaraporn, Napavarn; Ohkuma, Moriya; Kudo, Toshiaki

    2005-12-01

    Fungus-growing termites efficiently decompose plant litter through their symbiotic relationship with basidiomycete fungi of the genus Termitomyces. Here, we investigated phenol-oxidizing enzymes in symbiotic fungi and fungus combs (a substrate used to cultivate symbiotic fungi) from termites belonging to the genera Macrotermes, Odontotermes, and Microtermes in Thailand, because these enzymes are potentially involved in the degradation of phenolic compounds during fungus comb aging. Laccase activity was detected in all the fungus combs examined as well as in the culture supernatants of isolated symbiotic fungi. Conversely, no peroxidase activity was detected in any of the fungus combs or the symbiotic fungal cultures. The laccase cDNA fragments were amplified directly from RNA extracted from fungus combs of five termite species and a fungal isolate using degenerate primers targeting conserved copper binding domains of basidiomycete laccases, resulting in a total of 13 putative laccase cDNA sequences being identified. The full-length sequences of the laccase cDNA and the corresponding gene, lcc1-2, were identified from the fungus comb of Macrotermes gilvus and a Termitomyces strain isolated from the same fungus comb, respectively. Partial purification of laccase from the fungus comb showed that the lcc1-2 gene product was a dominant laccase in the fungus comb. These findings indicate that the symbiotic fungus secretes laccase to the fungus comb. In addition to laccase, we report novel genes that showed a significant similarity with fungal laccases, but the gene product lacked laccase activity. Interestingly, these genes were highly expressed in symbiotic fungi of all the termite hosts examined.

  2. George Combe and common sense.

    Science.gov (United States)

    Dyde, Sean

    2015-06-01

    This article examines the history of two fields of enquiry in late eighteenth- and early nineteenth-century Scotland: the rise and fall of the common sense school of philosophy and phrenology as presented in the works of George Combe. Although many previous historians have construed these histories as separate, indeed sometimes incommensurate, I propose that their paths were intertwined to a greater extent than has previously been given credit. The philosophy of common sense was a response to problems raised by Enlightenment thinkers, particularly David Hume, and spurred a theory of the mind and its mode of study. In order to succeed, or even to be considered a rival of these established understandings, phrenologists adapted their arguments for the sake of engaging in philosophical dispute. I argue that this debate contributed to the relative success of these groups: phrenology as a well-known historical subject, common sense now largely forgotten. Moreover, this history seeks to question the place of phrenology within the sciences of mind in nineteenth-century Britain.

  3. Frequency combs for cavity cascades: OPO combs and graphene-coupled cavities

    Science.gov (United States)

    Lee, Kevin F.; Kowzan, Grzegorz; Lee, C.-C.; Mohr, C.; Jiang, Jie; Schunemann, Peter G.; Schibli, T. R.; Maslowski, Piotr; Fermann, M. E.

    2017-01-01

    Frequency combs can be used directly, for example as a highly precise spectroscopic light source. They can also be used indirectly, as a bridge between devices whose high precision requirements would normally make them incompatible. Here, we demonstrate two ways that a frequency comb enables new technologies by matching optical cavities. One cavity is the laser oscillator. A second cavity is a low-threshold doubly-resonant optical parametric oscillator (OPO). Extending optical referencing to the doubly-resonant OPO turns the otherwise unstable device into an extremely precise midinfrared frequency comb. Another cavity is an optical enhancement cavity for amplifying spectral absorption in a gas. With the high speed of a graphene-modulated frequency comb, we can couple a frequency comb directly into a high-finesse cavity for trace gas detection.

  4. Laboratory duplication of comb layering in the Rhum pluton. [igneous rocks with comb layered texture

    Science.gov (United States)

    Donaldson, C. H.

    1977-01-01

    A description is provided of the texture of harrisite comb layers, taking into account the results of crystallization experiments at controlled cooling rates, which have reproduced the textural change from 'cumulate' to comb-layered harrisite. Melted samples of harrisite were used in the dynamic crystallization experiments considered. The differentiation of a cooling rate run with respect to olivine grain size and shape is shown and three possible origins of hopper olivine in differentiated crystallization runs are considered. It is found that olivine nucleation occurred throughout cooling, except for the incubation period during early cooling. The elongate combed olivines in harrisite apparently grew as the magma locally supercooled to at least 30 C. It is suggested that the branching crystals in most comb layers, including comb-layered harrisite, probably grew along thermal gradients.

  5. Sonic Hedgehog-signalling patterns the developing chicken comb as revealed by exploration of the pea-comb mutation.

    Directory of Open Access Journals (Sweden)

    Henrik Boije

    Full Text Available The genetic basis and mechanisms behind the morphological variation observed throughout the animal kingdom is still relatively unknown. In the present work we have focused on the establishment of the chicken comb-morphology by exploring the Pea-comb mutant. The wild-type single-comb is reduced in size and distorted in the Pea-comb mutant. Pea-comb is formed by a lateral expansion of the central comb anlage into three ridges and is caused by a mutation in SOX5, which induces ectopic expression of the SOX5 transcription factor in mesenchyme under the developing comb. Analysis of differential gene expression identified decreased Sonic hedgehog (SHH receptor expression in Pea-comb mesenchyme. By experimentally blocking SHH with cyclopamine, the wild-type single-comb was transformed into a Pea-comb-like phenotype. The results show that the patterning of the chicken comb is under the control of SHH and suggest that ectopic SOX5 expression in the Pea-comb change the response of mesenchyme to SHH signalling with altered comb morphogenesis as a result. A role for the mesenchyme during comb morphogenesis is further supported by the recent finding that another comb-mutant (Rose-comb, is caused by ectopic expression of a transcription factor in comb mesenchyme. The present study does not only give knowledge about how the chicken comb is formed, it also adds to our understanding how mutations or genetic polymorphisms may contribute to inherited variations in the human face.

  6. Electrostatic comb drive for vertical actuation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, A. P., LLNL

    1997-07-10

    The electrostatic comb finger drive has become an integral design for microsensor and microactuator applications. This paper reports on utilizing the levitation effect of comb fingers to design vertical-to-the-substrate actuation for interferometric applications. For typical polysilicon comb drives with 2 {micro}m gaps between the stationary and moving fingers, as well as between the microstructures and the substrate, the equilibrium position is nominally 1-2 {micro}m above the stationary comb fingers. This distance is ideal for many phase shifting interferometric applications. Theoretical calculations of the vertical actuation characteristics are compared with the experimental results, and a general design guideline is derived from these results. The suspension flexure stiffnesses, gravity forces, squeeze film damping, and comb finger thicknesses are parameters investigated which affect the displacement curve of the vertical microactuator. By designing a parallel plate capacitor between the suspended mass and the substrate, in situ position sensing can be used to control the vertical movement, providing a total feedback-controlled system. Fundamentals of various capacitive position sensing techniques are discussed. Experimental verification is carried out by a Zygo distance measurement interferometer.

  7. Broadband Mid-Infrared Comb-Resolved Fourier Transform Spectroscopy

    Science.gov (United States)

    Lee, Kevin; Mills, Andrew; Mohr, Christian; Jiang, Jie; Fermann, Martin; Maslowski, Piotr

    2014-06-01

    We report on a comb-resolved, broadband, direct-comb spectroscopy system in the mid-IR and its application to the detection of trace gases and molecular line shape analysis. By coupling an optical parametric oscillator (OPO), a 100 m multipass cell, and a high-resolution Fourier transform spectrometer (FTS), sensitive, comb-resolved broadband spectroscopy of dilute gases is possible. The OPO has radiation output at 3.1-3.7 and 4.5-5.5 μm. The laser repetition rate is scanned to arbitrary values with 1 Hz accuracy around 417 MHz. The comb-resolved spectrum is produced with an absolute frequency axis depending only on the RF reference (in this case a GPS disciplined oscillator), stable to 1 part in 10^9. The minimum detectable absorption is 1.6x10-6 wn Hz-1/2. The operating range of the experimental setup enables access to strong fundamental transitions of numerous molecular species for applications based on trace gas detection such as environmental monitoring, industrial gas calibration or medical application of human breath analysis. In addition to these capabilities, we show the application for careful line shape analysis of argon-broadened CO band spectra around 4.7 μm. Fits of the obtained spectra clearly illustrate the discrepancy between the measured spectra and the Voigt profile (VP), indicating the need to include effects such as Dicke narrowing and the speed-dependence of the collisional width and shift in the line shape model, as was shown in previous cw-laser studies. In contrast to cw-laser based experiments, in this case the entire spectrum (˜ 250 wn) covering the whole P and R branches can be measured in 16 s with 417 MHz resolution, decreasing the acquisition time by orders of magnitude. The parallel acquisition allows collection of multiple lines simultaneously, removing the correlation of possible temperature and pressure drifts. While cw-systems are capable of measuring spectra with higher precision, this demonstration opens the door for fast

  8. Spatiotemporal evolution of a cosine-modulated stationary field and Kerr frequency comb generation in a microresonator.

    Science.gov (United States)

    Hu, Xiaohong; Liu, Yuanshan; Xu, Xin; Feng, Ye; Zhang, Wenfu; Wang, Weiqiang; Song, Jiazheng; Wang, Yishan; Zhao, Wei

    2015-10-10

    Based on the normalized spatiotemporal Lugiato-Lefever equation, the evolutions of cosine-modulated stationary fields relating to the generation of single-free spectral range (FSR) or multi-FSR Kerr frequency combs in a microresonator with anomalous dispersion are studied numerically. The research results show that a single-FSR comb arises when a dissipative soliton pulse or multiple nonequidistant soliton pulses form in the cavity. Compared with the smooth and regular spectral structure of a single soliton pulse, the comb corresponding to the uneven distribution of multiple soliton pulses exhibits a complex and irregular profile. When the stable intracavity field consists of a "roll" Turing pattern or N(N>1) evenly distributed soliton pulses separated by 2π/N, multi-FSR combs can be generated. In the case of the "roll" Turing pattern solution, it is found that third-order dispersion could modify the comb mode spacing and decrease the intensity of high-order comb modes. For the situation of multiple soliton pulse generation, the simulation results indicate that both the number and locations of the soliton pulses can be actively controlled through the careful selection of modulation frequency. In addition, for the selected cosine-modulated initial field profile, only those modes with the mode numbers being equal to an integer multiple of N can be greatly amplified by the parametric gain during propagation in the microresonator. This process eventually leads to the formation of a N-FSR frequency comb.

  9. Microresonator-based optical frequency combs.

    Science.gov (United States)

    Kippenberg, T J; Holzwarth, R; Diddams, S A

    2011-04-29

    The series of precisely spaced, sharp spectral lines that form an optical frequency comb is enabling unprecedented measurement capabilities and new applications in a wide range of topics that include precision spectroscopy, atomic clocks, ultracold gases, and molecular fingerprinting. A new optical frequency comb generation principle has emerged that uses parametric frequency conversion in high resonance quality factor (Q) microresonators. This approach provides access to high repetition rates in the range of 10 to 1000 gigahertz through compact, chip-scale integration, permitting an increased number of comb applications, such as in astronomy, microwave photonics, or telecommunications. We review this emerging area and discuss opportunities that it presents for novel technologies as well as for fundamental science.

  10. Direct frequency comb laser cooling and trapping

    CERN Document Server

    Jayich, A M; Campbell, W C

    2016-01-01

    Continuous wave (CW) lasers are the enabling technology for producing ultracold atoms and molecules through laser cooling and trapping. The resulting pristine samples of slow moving particles are the de facto starting point for both fundamental and applied science when a highly-controlled quantum system is required. Laser cooled atoms have recently led to major advances in quantum information, the search to understand dark energy, quantum chemistry, and quantum sensors. However, CW laser technology currently limits laser cooling and trapping to special types of elements that do not include highly abundant and chemically relevant atoms such as hydrogen, carbon, oxygen, and nitrogen. Here, we demonstrate that Doppler cooling and trapping by optical frequency combs may provide a route to trapped, ultracold atoms whose spectra are not amenable to CW lasers. We laser cool a gas of atoms by driving a two-photon transition with an optical frequency comb, an efficient process to which every comb tooth coherently cont...

  11. Frequency-agile dual-comb spectroscopy

    CERN Document Server

    Millot, Guy; Yan, Ming; Hovannysyan, Tatevik; Bendahmane, Abdelkrim; Hänsch, Theodor W; Picqué, Nathalie

    2015-01-01

    We propose a new approach to near-infrared molecular spectroscopy, harnessing advanced concepts of optical telecommunications and supercontinuum photonics. We generate, without mode-locked lasers, two frequency combs of slightly different repetition frequencies and moderate, but rapidly tunable, spectral span. The output of a frequency-agile continuous wave laser is split and sent into two electro-optic intensity modulators. Flat-top low-noise frequency combs are produced by wave-breaking in a nonlinear optical fiber of normal dispersion. With a dual-comb spectrometer, we record Doppler-limited spectra spanning 60 GHz within 13 microseconds and 80-kHz refresh rate, at a tuning speed of 10 nm.s^(-1). The sensitivity for weak absorption is enhanced by a long gas-filled hollow-core fiber.

  12. Frequency comb generation in quadratic nonlinear media

    CERN Document Server

    Ricciardi, Iolanda; Parisi, Maria; Maddaloni, Pasquale; Santamaria, Luigi; De Natale, Paolo; De Rosa, Maurizio

    2014-01-01

    Optical frequency combs are nowadays routinely used tools in a wide range of scientific and technological applications. Different techniques have been developed for generating optical frequency combs, like mode-locking in lasers and third-order interactions in microresonators, or to extend their spectral capabilities, using frequency conversion processes in nonlinear materials. Here, we experimentally demonstrate and theoretically explain the onset of optical frequency combs in a simple cavity-enhanced second-harmonic-generation system, exploiting second-order nonlinear interactions. We develop an elemental model which provides a deep physical insight into the observed dynamics. Moreover, despite the different underlying physical mechanism, the proposed model is remarkably similar to the description of third-order effects in microresonators, revealing a potential variety of new effects to be explored. Finally, exploiting a nonlinearity intrinsically stronger than the third-order one, our work lays the groundw...

  13. Full stabilization of a microresonator-based optical frequency comb.

    Science.gov (United States)

    Del'Haye, P; Arcizet, O; Schliesser, A; Holzwarth, R; Kippenberg, T J

    2008-08-01

    We demonstrate control and stabilization of an optical frequency comb generated by four-wave mixing in a monolithic microresonator with a mode spacing in the microwave regime (86 GHz). The comb parameters (mode spacing and offset frequency) are controlled via the power and the frequency of the pump laser, which constitutes one of the comb modes. Furthermore, generation of a microwave beat note at the comb's mode spacing frequency is demonstrated, enabling direct stabilization to a microwave frequency standard.

  14. Frequency comb velocity-modulation spectroscopy.

    Science.gov (United States)

    Sinclair, Laura C; Cossel, Kevin C; Coffey, Tyler; Ye, Jun; Cornell, Eric A

    2011-08-26

    We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity-modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF⁺ and achieved a fractional absorption sensitivity of 3×10⁻⁷ recorded over 1500 simultaneous channels spanning 150  cm⁻¹ around 800 nm with an absolute frequency accuracy of 30 MHz (0.001  cm⁻¹). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 min.

  15. Frequency Comb Velocity-Modulation Spectroscopy

    CERN Document Server

    Sinclair, Laura C; Coffey, Tyler; Ye, Jun; Cornell, Eric A

    2011-01-01

    We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF+ and achieved a fractional absorption sensitivity of 3 x 10-7 recorded over 1500 simultaneous channels spanning 150 cm-1 around 800 nm with an absolute frequency accuracy of 30 MHz (0.001 cm-1). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 minutes.

  16. Microresonator-Based Optical Frequency Combs: A Time Domain Perspective

    Science.gov (United States)

    2016-04-19

    operation deep into the visible spectrum (where normal dispersion dominates), may be compatible with thinner, lower loss films, and may provide...Electrical and Computer Engineering, Purdue University phone: 765-494-5574 email: amw@purdue.edu web : https://engineering.purdue.edu/~amw...mode interactions for more dependable comb initiation. Comb generation from normal dispersion micoresonators offers potential for comb operation deep

  17. Transmission comb of a distributed Bragg reflector induced by two surface dielectric gratings

    CERN Document Server

    Zhao, Xiaobo; Zhang, Yongyou

    2015-01-01

    With transfer matrix theory, we study the transmission of a distributed Bragg reflector (DBR) with two dielectric gratings on top and on the bottom. Owing to the diffraction of the two gratings, the transmission shows a comb-like spectrum which red shifts with increasing the grating period during the forbidden band of the DBR. The number density of the comb peaks increases with increasing the number of the DBR cells, while the ratio of the average full width at half maximum (FWHM) of the transmission peaks in the transmission comb to the corresponding average free spectral range, being about 0.04 and 0.02 for the TE and TM incident waves, is almost invariant. The average FWHM of the TM waves is about half of the TE waves, and both they could be narrower than 0.1 nm. In addition, the transmission comb peaks of the TE and TM waves can be fully separated during certain waveband. We further prove that the transmission comb is robust against the randomness of the heights of the DBR layers, even when a 15\\% randomn...

  18. Non-contact precision profile measurement to rough-surface objects with optical frequency combs

    Science.gov (United States)

    Onoe, Taro; Takahashi, Satoru; Takamasu, Kiyoshi; Matsumoto, Hirokazu

    2016-12-01

    In this research, we developed a new method for the high precision and contactless profile measurement of rough-surfaced objects using optical frequency combs. The uncertainty of the frequency beats of an optical frequency comb is very small (relative uncertainty is 10-10 in our laboratory). In addition, the wavelengths corresponding to these frequency beats are long enough to measure rough-surfaced objects. We can conduct high-precision measurement because several GHz frequency beats can be used if the capability of the detector permits. Moreover, two optical frequency combs with Rb-stabilized repetition frequencies are used for the measurement instead of an RF frequency oscillator; thus, we can avoid the cyclic error caused by the RF frequency oscillator. We measured the profile of a wood cylinder with a rough surface (diameter is approximately 113.2 mm) and compared the result with that of coordinate measuring machine (CMM).

  19. High efficiency quantum cascade laser frequency comb

    Science.gov (United States)

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-01-01

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm−1 at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy. PMID:28262834

  20. Time sequence photography of Roosters Comb

    Science.gov (United States)

    The importance of understanding natural landscape changes is key in properly determining rangeland ecology. Time sequence photography allows a landscape snapshot to be documented and enables the ability to compare natural changes overtime. Photographs of Roosters Comb were taken from the same vantag...

  1. Comb to Pipeline: Fast Software Encryption Revisited

    DEFF Research Database (Denmark)

    Bogdanov, Andrey; Lauridsen, Martin Mehl; Tischhauser, Elmar Wolfgang

    2015-01-01

    (vs. 1.63 cpb and 1.51 cpb, resp.), despite Haswell’s heavily improved binary field multiplication. This suggests CCM as an AE mode of choice as it is NIST-recommended, does not have any weak-key issues like GCM, and is royalty-free as opposed to OCB3. Among the CAESAR contestants, the comb scheduler...

  2. Comb-drive actuators for large displacements

    NARCIS (Netherlands)

    Legtenberg, Rob; Groeneveld, A.W.; Elwenspoek, M.

    1996-01-01

    The design, fabrication and experimental results of lateral-comb-drive actuators for large displacements at low driving voltages is presented. A comparison of several suspension designs is given, and the lateral large deflection behaviour of clamped - clamped beams and a folded flexure design is mod

  3. High efficiency quantum cascade laser frequency comb

    Science.gov (United States)

    Lu, Quanyong; Wu, Donghai; Slivken, Steven; Razeghi, Manijeh

    2017-03-01

    An efficient mid-infrared frequency comb source is of great interest to high speed, high resolution spectroscopy and metrology. Here we demonstrate a mid-IR quantum cascade laser frequency comb with a high power output and narrow beatnote linewidth at room temperature. The active region was designed with a strong-coupling between the injector and the upper lasing level for high internal quantum efficiency and a broadband gain. The group velocity dispersion was engineered for efficient, broadband mode-locking via four wave mixing. The comb device exhibits a narrow intermode beatnote linewidth of 50.5 Hz and a maximum wall-plug efficiency of 6.5% covering a spectral coverage of 110 cm‑1 at λ ~ 8 μm. The efficiency is improved by a factor of 6 compared with previous demonstrations. The high power efficiency and narrow beatnote linewidth will greatly expand the applications of quantum cascade laser frequency combs including high-precision remote sensing and spectroscopy.

  4. Universal scaling laws of Kerr frequency combs.

    Science.gov (United States)

    Coen, Stéphane; Erkintalo, Miro

    2013-06-01

    Using the known solutions of the Lugiato-Lefever equation, we derive universal trends of Kerr frequency combs. In particular, normalized properties of temporal cavity soliton solutions lead us to a simple analytic estimate of the maximum attainable bandwidth for given pump resonator parameters. The result is validated via comparison with past experiments encompassing a diverse range of resonator configurations and parameters.

  5. Universal scaling laws of Kerr frequency combs

    CERN Document Server

    Coen, Stephane

    2013-01-01

    Using the known solutions of the Lugiato-Lefever equation, we derive universal trends of Kerr frequency combs. In particular, normalized properties of temporal cavity soliton solutions lead us to a simple analytic estimate of the maximum attainable bandwidth for given pump-resonator parameters. The result is validated via comparison with past experiments encompassing a diverse range of resonator configurations and parameters.

  6. Quantum cascade laser Kerr frequency comb

    CERN Document Server

    Lecaplain, Caroline; Lucas, Erwan; Jost, John D; Kippenberg, Tobias J

    2015-01-01

    The mid-infrared (mid-IR) regime (typically the wavelength regime of $\\lambda \\sim 2.5-20 \\ \\mathrm{\\mu m}$) is an important spectral range for spectroscopy as many molecules have their fundamental rotational-vibrational absorption in this band. Recently optical frequency combs based on optical microresonators ("Kerr" combs) at the onset of the mid-IR region have been generated using crystalline resonators and integrated planar silicon micro-resonators. Here we extend for the first time Kerr combs deep into the mid-IR i.e. the 'molecular fingerprint' region. This is achieved by combining an ultra high quality (Q) factor mid-IR microresonator based on crystalline $\\mathrm{MgF_{2}}$ with the quantum cascade laser (QCL) technology. Using a tapered chalgogenide (ChG) fiber and a QCL continuous wave pump laser, frequency combs at $\\lambda\\sim 4.4\\ \\mathrm{\\mu m}$ (i.e. 2270cm$^{-1}$) are generated, that span over 600nm (i.e. 300cm$^{-1}$) in bandwidth, with a mode spacing of 14.3GHz (0.5cm$^{-1}$), corresponding t...

  7. Unidirectional, dual-comb lasing under multiple pulse formation mechanisms in a passively mode-locked fiber ring laser

    CERN Document Server

    Liu, Ya; Hu, Guoqing; Li, Cui; Zhao, Bofeng; Zheng, Zheng

    2016-01-01

    Dual-comb lasers from which asynchronous ultrashort pulses can be simultaneously generated have recently become an interesting research subject. They could be an intriguing alternative to the current dual-laser optical-frequency-comb source with highly sophisticated electronic control systems. If generated through a common light path traveled by all pulses, the common-mode noises between the spectral lines of different pulse trains could be significantly reduced. Therefore, coherent dual-comb generation from a completely common-path, unidirectional lasing cavity would be an interesting territory to explore. In this paper, we demonstrate such a dual-comb lasing scheme based on a nanomaterial saturable absorber with additional pulse narrowing and broadening mechanisms concurrently introduced into a mode-locked fiber laser. The interactions between multiple soliton formation mechanisms result in unusual bifurcation into two-pulse states with quite different characteristics. Simultaneous oscillation of pulses wit...

  8. Maximum likelihood molecular clock comb: analytic solutions.

    Science.gov (United States)

    Chor, Benny; Khetan, Amit; Snir, Sagi

    2006-04-01

    Maximum likelihood (ML) is increasingly used as an optimality criterion for selecting evolutionary trees, but finding the global optimum is a hard computational task. Because no general analytic solution is known, numeric techniques such as hill climbing or expectation maximization (EM), are used in order to find optimal parameters for a given tree. So far, analytic solutions were derived only for the simplest model--three taxa, two state characters, under a molecular clock. Four taxa rooted trees have two topologies--the fork (two subtrees with two leaves each) and the comb (one subtree with three leaves, the other with a single leaf). In a previous work, we devised a closed form analytic solution for the ML molecular clock fork. In this work, we extend the state of the art in the area of analytic solutions ML trees to the family of all four taxa trees under the molecular clock assumption. The change from the fork topology to the comb incurs a major increase in the complexity of the underlying algebraic system and requires novel techniques and approaches. We combine the ultrametric properties of molecular clock trees with the Hadamard conjugation to derive a number of topology dependent identities. Employing these identities, we substantially simplify the system of polynomial equations. We finally use tools from algebraic geometry (e.g., Gröbner bases, ideal saturation, resultants) and employ symbolic algebra software to obtain analytic solutions for the comb. We show that in contrast to the fork, the comb has no closed form solutions (expressed by radicals in the input data). In general, four taxa trees can have multiple ML points. In contrast, we can now prove that under the molecular clock assumption, the comb has a unique (local and global) ML point. (Such uniqueness was previously shown for the fork.).

  9. a Portable Dual Frequency Comb Spectrometer for Atmospheric Applications

    Science.gov (United States)

    Cossel, Kevin C.; Waxman, Eleanor; Truong, Gar-Wing; Giorgetta, Fabrizio; Swann, William C.; Coburn, Sean; Wright, Robert; Rieker, Greg B.; Coddington, Ian; Newbury, Nathan R.

    2016-06-01

    Dual frequency comb (DFC) spectroscopy is a new technique that combines broad spectral bandwidth, high spectral resolution, rapid data acquisition, and high sensitivity. In addition, unlike standard Fourier-transform spectroscopy, it has an almost ideal instrument lineshape function, does not require recalibration, and has no moving parts. These features make DFC spectroscopy well suited for accurate measurements of multiple species simultaneously. Because the frequency comb lasers can be well collimated, such a system can be used for long open-path measurements with path lengths ranging from hundreds of meters to several kilometers. This length scale bridges the gap between point measurements and satellite-based measurements and is ideal for providing information about local sources and quantifying emissions. Here we show a fully portable DFC spectrometer operating over a wide spectral region in the near-infrared (about 1.5-2.1 μm or 6670-4750 cm-1 sampled at 0.0067 cm-1) and across several different open-air paths up to a path length of 11.8 km. The current spectrometer fits in about a 500 L volume and has low power consumption. It provides simultaneous measurements of CO_2, CH_4, and water isotopes with a time resolution of seconds to minutes. This system has several potential applications for atmospheric measurements including continuous monitoring city-scale emissions and localizing methane leaks from oil and gas wells. G. B. Rieker, F. R. Giorgetta, W. C. Swann, J. Kofler, A. M. Zolot, L. C. Sinclair, E. Baumann, C. Cromer, G. Petron, C. Sweeney, P. P. Tans, I. Coddington, and N. R. Newbury, Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths, Optica, 1(5), 290-298 (2014).

  10. Modelocked mid-infrared frequency combs in a silicon microresonator

    CERN Document Server

    Yu, Mengjie; Griffith, Austin G; Lipson, Michal; Gaeta, Alexander L

    2016-01-01

    Mid-infrared (mid-IR) frequency combs have broad applications in molecular spectroscopy and chemical/biological sensing. Recently developed microresonator-based combs in this wavelength regime could enable portable and robust devices using a single-frequency pump field. Here, we report the first demonstration of a modelocked microresonator-based frequency comb in the mid-IR spanning 2.4 {\\mu}m to 4.3 {\\mu}m. We observe high pump-to-comb conversion efficiency, in which 40% of the pump power is converted to the output comb power. Utilizing an integrated PIN structure allows for tuning the silicon microresonator and controling modelocking and cavity soliton formation, simplifying the generation, monitoring and stabilization of mid-IR frequency combs via free-carrier detection and control. Our results significantly advance microresonator-based comb technology towards a portable and robust mid-IR spectroscopic device that operates at low pump powers.

  11. Laser frequency combs for astronomical observations.

    Science.gov (United States)

    Steinmetz, Tilo; Wilken, Tobias; Araujo-Hauck, Constanza; Holzwarth, Ronald; Hänsch, Theodor W; Pasquini, Luca; Manescau, Antonio; D'Odorico, Sandro; Murphy, Michael T; Kentischer, Thomas; Schmidt, Wolfgang; Udem, Thomas

    2008-09-05

    A direct measurement of the universe's expansion history could be made by observing in real time the evolution of the cosmological redshift of distant objects. However, this would require measurements of Doppler velocity drifts of approximately 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrated the first use of a laser frequency comb for wavelength calibration of an astronomical telescope. Even with a simple analysis, absolute calibration is achieved with an equivalent Doppler precision of approximately 9 meters per second at approximately 1.5 micrometers-beyond state-of-the-art accuracy. We show that tracking complex, time-varying systematic effects in the spectrograph and detector system is a particular advantage of laser frequency comb calibration. This technique promises an effective means for modeling and removal of such systematic effects to the accuracy required by future experiments to see direct evidence of the universe's putative acceleration.

  12. Interference comb-spectroscopy with increasing sensitivity

    Science.gov (United States)

    Pulkin, Sergey; Borisov, Evgenii; Balabas, Michail; Uvarova, Svetlana; Shevtzov, Vladimir; Kalinichev, Alexei; Shoev, Vladislav; Venediktov, Dmitrii; Venediktov, Vladimir

    2016-10-01

    The paper considers the use of holographic interferometer for hologram recording of the wide spectrum from the comb - generator of the femtosecond laser was applied for illuminating of Michelson interferometer with atomic vapor. The behavior of spectral interference fringes on the exit slit of spectrograph reflects the behavior of nonlinear refractive index. The method of holographic interferometry with increasing sensitivity using phase modulator was applied for digital hologram processing.

  13. A microresonator frequency comb optical clock

    CERN Document Server

    Papp, Scott B; DelHaye, Pascal; Quinlan, Franklyn; Lee, Hansuek; Vahala, Kerry J; Diddams, Scott A

    2013-01-01

    Optical-frequency combs enable measurement precision at the 20th digit, and accuracy entirely commensurate with their reference oscillator. A new direction in experiments is the creation of ultracompact frequency combs by way of nonlinear parametric optics in microresonators. We refer to these as microcombs, and here we report a silicon-chip-based microcomb optical clock that phase-coherently converts an optical-frequency reference to a microwave signal. A low-noise comb spectrum with 25 THz span is generated with a 2 mm diameter silica disk and broadening in nonlinear fiber. This spectrum is stabilized to rubidium frequency references separated by 3.5 THz by controlling two teeth 108 modes apart. The optical clocks output is the electronically countable 33 GHz microcomb line spacing, which features an absolute stability better than the rubidium transitions by the expected factor of 108. Our work demonstrates the comprehensive set of tools needed for interfacing microcombs to state-of-the-art optical clocks.

  14. Time-Delay Interferometry with optical frequency comb

    CERN Document Server

    Tinto, Massimo

    2015-01-01

    Heterodyne laser phase measurements in a space-based gravitational wave interferometer are degraded by the phase fluctuations of the onboard clocks, resulting in unacceptable sensitivity performance levels of the interferometric data. In order to calibrate out the clock phase noises it has been previously suggested that additional inter-spacecraft phase measurements must be performed by modulating the laser beams. This technique, however, considerably increases system complexity and probability of subsystem failure. With the advent of self-referenced optical frequency combs, it is possible to generate the heterodyne microwave signal that is coherently referenced to the onboard laser. We show in this case that the microwave noise can be cancelled directly by applying modified second-generation Time-Delay Interferometric combinations to the heterodyne phase measurements. This approach avoids use of modulated laser beams as well as the need of additional ultra-stable oscillator clocks.

  15. Coherent data transmission with microresonator Kerr frequency combs

    CERN Document Server

    Pfeifle, Joerg; Wegner, Daniel; Brasch, Victor; Herr, Tobias; Hartinger, Klaus; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J; Koos, Christian

    2013-01-01

    Optical frequency combs enable coherent data transmission on hundreds of wavelength channels and have the potential to revolutionize terabit communications. Generation of Kerr combs in nonlinear integrated microcavities represents a particularly promising option enabling line spacings of tens of GHz, compliant with wavelength-division multiplexing (WDM) grids. However, Kerr combs may exhibit strong phase noise and multiplet spectral lines, and this has made high-speed data transmission impossible up to now. Recent work has shown that systematic adjustment of pump conditions allows generating low phase-noise Kerr combs with singlet spectral lines. Here, by employing an integrated Si3N4 microresonator, we demonstrate that Kerr combs are suited for coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the optical source. In our experiment, we encode a data stream of 392 Gbit/s on subsequent lines of a Kerr comb using quadrature phase shift keying (...

  16. Thermally Controlled Comb Generation and Soliton Modelocking in Microresonators

    CERN Document Server

    Joshi, Chaitanya; Luke, Kevin; Ji, Xingchen; Miller, Steven A; Klenner, Alexander; Okawachi, Yoshitomo; Lipson, Michal; Gaeta, Alexander L

    2016-01-01

    We report the first demonstration of thermally controlled soliton modelocked frequency comb generation in microresonators. By controlling the electric current through heaters integrated with silicon nitride microresonators, we demonstrate a systematic and repeatable pathway to single- and multi-soliton modelocked states without adjusting the pump laser wavelength. Such an approach could greatly simplify the generation of modelocked frequency combs and facilitate applications such as chip-based dual-comb spectroscopy.

  17. Single-molecule studies of DNA by molecular combing

    Institute of Scientific and Technical Information of China (English)

    Liu Yuying; Wang Pengye; Dou Shuoxing

    2007-01-01

    Molecular combing is a powerful method for aligning a large array of DNA molecules onto a surface. It is a process whereby DNA molecules are stretched and aligned on a glass surface by the force via fluid flow. The ability to comb up to several hundred DNAs on a single cover slip allows for a statistically significant number of measurements to be made. These features make molecular combing an attractive tool for genomic studies, such as DNA replication, DNA transcription, DNA-protein interaction and so on. In this review article, we discuss the molecular combing principle, method and its applications.

  18. Intrinsic linewidth of quantum cascade laser frequency combs

    CERN Document Server

    Cappelli, Francesco; Riedi, Sabine; Faist, Jerome

    2015-01-01

    The frequency noise power spectral density of a free-running quantum cascade laser frequency comb is investigated. A plateau is observed at high frequencies, attributed to the quantum noise limit set by the Schawlow-Townes formula for the total laser power on all comb lines. In our experiment, a linewidth of 292 Hz is measured for a total power of 25 mW. This result proves that the four-wave mixing process, responsible for the comb operation, effectively correlates the quantum noise of the individual comb lines.

  19. Optical combs with a crystalline whispering gallery mode resonator

    CERN Document Server

    Savchenkov, Anatoliy A; Ilchenko, Vladimir S; Solomatine, Iouri; Seidel, David; Maleki, Lute

    2008-01-01

    We report on the experimental demonstration of a tunable monolithic optical frequency comb generator. The device is based on the four-wave mixing in a crystalline calcium fluoride whispering gallery mode resonator. The frequency spacing of the comb is given by an integer number of the free spectral range of the resonator. We select the desired number by tuning the pumping laser frequency with respect to the corresponding resonator mode. We also observe interacting optical combs and high-frequency hyperparametric oscillation, depending on the experimental conditions. A potential application of the comb for generating narrowband frequency microwave signals is demonstrated.

  20. Combing genomic DNA for structural and functional studies.

    Science.gov (United States)

    Schurra, Catherine; Bensimon, Aaron

    2009-01-01

    Molecular combing is a process whereby single DNA molecules bind by their extremities to a silanised surface and are then uniformly stretched and aligned by a receding air/water interface (1). This method, with a high resolution ranging from a few kilobases to megabases, has many applications in the field of molecular cytogenetics, allowing structural and functional analysis at the genome level. Here we describe protocols for preparing DNA for combing and for the use of fluorescent hybridisation (FH) applied to combed DNA to conduct physical mapping or genomic structural analysis. We also present the methodology for visualising and studying DNA replication using combed DNA.

  1. On-chip dual comb source for spectroscopy

    CERN Document Server

    Dutt, Avik; Ji, Xingchen; Cardenas, Jaime; Okawachi, Yoshitomo; Luke, Kevin; Gaeta, Alexander L; Lipson, Michal

    2016-01-01

    Dual-comb spectroscopy is a powerful technique for real-time, broadband optical sampling of molecular spectra which requires no moving components. Recent developments with microresonator-based platforms have enabled frequency combs at the chip scale. However, the need to precisely match the resonance wavelengths of distinct high-quality-factor microcavities has hindered the development of an on-chip dual comb source. Here, we report the first simultaneous generation of two microresonator combs on the same chip from a single laser. The combs span a broad bandwidth of 51 THz around a wavelength of 1.56 $\\mu$m. We demonstrate low-noise operation of both frequency combs by deterministically tuning into soliton mode-locked states using integrated microheaters, resulting in narrow ($<$ 10 kHz) microwave beatnotes. We further use one mode-locked comb as a reference to probe the formation dynamics of the other comb, thus introducing a technique to investigate comb evolution without auxiliary lasers or microwave os...

  2. Multispectral Kerr frequency comb initiated by Faraday ripples

    CERN Document Server

    Huang, Shu-Wei

    2016-01-01

    In a uniform microresonator, the generation of a broadband Kerr frequency comb is triggered by Turing patterns. Here, we study a distinctly different route to initiate the Kerr frequency comb by Faraday ripples. Momentum conservation is ensured by azimuthal modulation of the cavity dispersion. With a good agreement with the theoretical analysis, we demonstrate a multispectral Kerr frequency comb covering telecommunication O, C, L, and 2 {\\mu}m bands. Comb coherence and absence of a subcomb offset are confirmed by cw heterodyne beat note and amplitude noise spectra measurements. The device can be used for achieving broadband optical frequency synthesizer and high-capacity coherent telecommunication.

  3. Tunable Frequency Comb Generation from a Microring with a Thermal Heater

    CERN Document Server

    Xue, Xiaoxiao; Wang, Pei-Hsun; Wang, Jian; Leaird, Dan E; Qi, Minghao; Weiner, Andrew M

    2014-01-01

    We demonstrate a novel comb tuning method for microresonator-based Kerr comb generators. Continuously tunable, low-noise, and coherent comb generation is achieved in a CMOS-compatible silicon nitride microring resonator.

  4. Frequency domain processing of on-chip biphoton frequency comb

    CERN Document Server

    Jaramillo-Villegas, Jose A; Odele, Ogaga D; Leaird, Daniel E; Ou, Zhe-Yu; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    Quantum information processing (QIP) promises to improve the security of our communications as well as to solve some algorithms with exponential complexity in polynomial time. Biphotons have been demonstrated as one of the most promising platforms for real implementations of QIP systems. In particular, time-bin entangled photons have been used for implementations of quantum gates which require highly stable interferometers. On the other hand, frequency-bin entanglement has been proposed to avoid the use of interferometers and the complexity of their stabilization, which potentially makes the implementation of quantum gates highly scalable. Through Fourier transform pulse shaping and electro-optic modulation, there has been a wide range of experiments that show control of entangled photons in the frequency domain. In addition, biphoton frequency combs (BFC) have also been generated using bulk optics and frequency filtering of broadband continuous biphoton spectra. However, on-chip entangled photon pair generat...

  5. Photonic generation of linearly chirped millimeter wave based on comb-spacing tunable optical frequency comb

    Science.gov (United States)

    Xia, Zongyang; Xie, Weilin; Sun, Dongning; Shi, Hongxiao; Dong, Yi; Hu, Weisheng

    2013-12-01

    We demonstrated a photonic approach to generate a phase-continuous frequency-linear-chirped millimeter-wave (mm-wave) signal with high linearity based on continuous-wave phase modulated optical frequency comb and cascaded interleavers. Through linearly sweeping the frequency of the radio frequency (RF) driving signal, high-order frequency-linear-chirped optical comb lines are generated and then extracted by the cascaded interleavers. By beating the filtered high-order comb lines, center frequency and chirp range multiplied linear-chirp microwave signals are generated. Frequency doubled and quadrupled linear-chirp mm-wave signals of range 48.6 to 52.6 GHz and 97.2 to 105.2 GHz at chirp rates of 133.33 and 266.67 GHz/s are demonstrated with the ±1st and ±2nd optical comb lines, respectively, while the RF driving signal is of chirp range 24.3 to 26.3 GHz and chirp time 30 ms.

  6. Feshbach Resonances in Kerr Frequency Combs

    CERN Document Server

    Matsko, Andrey B

    2014-01-01

    We show that both the power and repetition rate of a frequency comb generated in a nonlinear ring resonator, pumped with continuous wave (cw) coherent light, are modulated. The modulation is brought about by the interaction of the cw background with optical pulses excited in the resonator, and occurs in resonators with nonzero high-order chromatic dispersion and wavelength-dependent quality factor. The modulation frequency corresponds to the detuning of the pump frequency from the eigenfrequency of the pumped mode in the resonator.

  7. An additional field method to sex adult Barn Swallows during the non-breeding season in Zambia: white spot length in the outer tail feather

    NARCIS (Netherlands)

    Duijns, S.; Dijk, van J.G.B.; Kraus, R.H.S.; Kerlen-Matema, A.C.; Brink, van den B.; Hooft, van W.F.

    2011-01-01

    Adult Barn Swallows Hirundo rustica exhibit strong sexual size dimorphism in the length of the outermost tail feathers, which are longer in males compared with females. This trait is traditionally used to sex adult Barn Swallows in the field. However, due to the wear and breakage of the tips of the

  8. Generation of green frequency comb from chirped χ{sup (2)} nonlinear photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lai, C.-M. [Department of Electronic Engineering, Ming Chuan University, Taoyuan, Taiwan (China); Chang, K.-H.; Yang, Z.-Y.; Fu, S.-H.; Tsai, S.-T.; Hsu, C.-W.; Peng, L.-H. [Department of Electrical Engineering and Graduate Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan (China); Yu, N. E. [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Boudrioua, A. [LPL, CNRS - UMR 7538, Université Paris 13, Sorbone Paris Cité (France); Kung, A. H. [Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan (China); Institute of Photonics Technologies, National Tsing Hua University, Hsinchu, Taiwan (China)

    2014-12-01

    Spectrally broad frequency comb generation over 510–555 nm range was reported on chirped quasi-phase-matching (QPM) χ{sup (2)} nonlinear photonic crystals of 12 mm length with periodicity stepwise increased from 5.9 μm to 7.1 μm. When pumped with nanosecond infrared (IR) frequency comb derived from a QPM optical parametric oscillator (OPO) and spanned over 1040 nm to 1090 nm wavelength range, the 520 nm to 545 nm up-converted green spectra were shown to consist of contributions from (a) second-harmonic generation among the signal or the idler modes, and (b) sum-frequency generation (SFG) from the neighboring pairs of the signal or the idler modes. These mechanisms led the up-converted green frequency comb to have the same mode spacing of 450 GHz as that in the IR-OPO pump comb. As the pump was further detuned from the aforementioned near-degeneracy point and moved toward the signal (1020–1040 nm) and the idler (1090–1110 nm) spectral range, the above QPM parametric processes were preserved in the chirped QPM devices to support up-converted green generation in the 510–520 nm and the 545–555 nm spectral regime. Additional 530–535 nm green spectral generation was also observed due to concurrence of multi-wavelength SFG processes between the (signal, idler) mode pairs. These mechanisms facilitate the chirped QPM device to support a single-pass up-conversion efficiency ∼10% when subject to an IR-OPO pump comb with 200 mW average power operated near- or off- the degeneracy point.

  9. Wax combs mediate nestmate recognition by guard honeybees

    DEFF Research Database (Denmark)

    D'Ettorre, Patrizia; Wenseleers, Tom; Dawson, Jenny

    2006-01-01

    Research has shown that the wax combs are important in the acquisition of colony odour in the honeybee, Apis mellifera. However, many of these studies were conducted in the laboratory or under artificial conditions. We investigated the role of the wax combs in nestmate recognition in the natural...

  10. Comb Capacitor Structures for On-Chip Physical Uncloneable Function

    NARCIS (Netherlands)

    Roy, D.; Klootwijk, J.H.; Verhaegh, N.A.M.; Roosen, H.H.A.J.; Wolters, R.A.M.

    2009-01-01

    Planar inter-digitated comb capacitor structures are an excellent tool for on-chip capacitance measurement and evaluation of properties of coating layers with varying composition. These comb structures are easily fabricated in a single step in the last metallization layer of a standard IC process. C

  11. Generation of Kerr Frequency Combs in Resonators with Normal GVD

    CERN Document Server

    Matsko, Andrey B; Maleki, Lute

    2011-01-01

    We show via numerical simulation that Kerr frequency combs can be generated in a nonlinear resonator characterized with normal group velocity dispersion (GVD). We find the spectral shape of the comb and temporal envelope of the corresponding optical pulses formed in the resonator.

  12. Gas Damping Coefficient Research for MEMS Comb Linear Vibration Gyroscope

    CERN Document Server

    Qiufen, G; Feng, S; Fuqiang, L

    2008-01-01

    Silicon-MEMS gyroscope is an important part of MEMS (Micro Electrical Mechanical System). There are some disturb ignored in traditional gyroscope that must be evaluated newly because of its smaller size (reach the level of micron). In these disturb, the air pressure largely influences the performance of MEMS gyroscope. Different air pressure causes different gas damping coefficient for the MEMS comb linear vibration gyroscope and different gas damping coefficient influences the quality factor of the gyroscope directive. The quality factor influences the dynamic working bandwidth of the MEMS comb linear vibration gyroscope, so it is influences the output characteristic of the MEMS comb linear vibration gyroscope. The paper shows the relationship between the air pressure and the output amplified and phase of the detecting axis through analyzing the air pressure influence on the MEMS comb linear vibration gyroscope. It discusses the influence on the frequency distribute and quality factor of the MEMS comb linear...

  13. Miniature Optical Atomic Clock: Stabilization of a Kerr Comb Oscillator

    CERN Document Server

    Savchenkov, A A; Liang, W; Ilchenko, V S; Byrd, J; Matsko, A B; Seidel, D; Maleki, L

    2013-01-01

    Mechanical clocks consist of a pendulum and a clockwork that translates the pendulum period to displayed time. The most advanced clocks utilize optical transitions in atoms in place of the pendulum and an optical frequency comb generated by a femtosecond laser as the clockwork. The comb must be stabilized at two points along its frequency spectrum: one with a laser to lock a comb line to a transition in the atom, and another through self referencing to stabilize the frequency interval between the comb lines. This approach requires advanced techniques, so optical atomic clocks are currently laboratory devices in specialized labs. In this paper we leverage unique properties of Kerr comb oscillators for realization of optical atomic clocks in miniature form factors. In particular, we describe a clock based on D1 transition of 87Rb that fits in the palm of the hand, and can be further miniaturized to chip scale.

  14. Adaptive real-time dual-comb spectroscopy

    CERN Document Server

    Ideguchi, Takuro; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W

    2012-01-01

    With the advent of laser frequency combs, coherent light sources that offer equally-spaced sharp lines over a broad spectral bandwidth have become available. One decade after revolutionizing optical frequency metrology, frequency combs hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite its intriguing potential for the measurement of molecular spectra spanning tens of nanometers within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the extremely demanding high-bandwidth servo-control conditions of the laser combs. Here we overcome this difficulty. We experimentally demonstrate a straightforward concept of real-time dual-comb spectroscopy, which only uses free-running mode-locked lasers without any phase-lock electronics, a posteriori data-processing, or the need for expertise in frequency metrology. The resulting simplicity and versatility of our new technique of adaptive dual-com...

  15. Difference-frequency combs in cold atom physics

    CERN Document Server

    Kliese, Russell; Puppe, Thomas; Rohde, Felix; Sell, Alexander; Zach, Armin; Leisching, Patrick; Kaenders, Wilhelm; Keegan, Niamh C; Bounds, Alistair D; Bridge, Elizabeth M; Leonard, Jack; Adams, Charles S; Cornish, Simon L; Jones, Matthew P A

    2016-01-01

    Optical frequency combs provide the clockwork to relate optical frequencies to radio frequencies. Hence, combs allow to measure optical frequencies with respect to a radio frequency where the accuracy is limited only by the reference signal. In order to provide a stable link between the radio and optical frequencies, the two parameters of the frequency comb must be fixed: the carrier envelope offset frequency $f_{\\rm ceo}$ and the pulse repetition-rate $f_{\\rm rep}$. We have developed the first optical frequency comb based on difference frequency generation (DFG) that eliminates $f_{\\rm ceo}$ by design - specifically tailored for applications in cold atom physics. An $f_{\\rm ceo}$-free spectrum at 1550 nm is generated from a super continuum spanning more than an optical octave. Established amplification and frequency conversion techniques based on reliable telecom fiber technology allow generation of multiple wavelength outputs. In this paper we discuss the frequency comb design, characterization, and optical...

  16. Microresonator Kerr frequency combs with high conversion efficiency

    CERN Document Server

    Xue, Xiaoxiao; Xuan, Yi; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    Microresonator-based Kerr frequency comb (microcomb) generation can potentially revolutionize a variety of applications ranging from telecommunications to optical frequency synthesis. However, phase-locked microcombs have generally had low conversion efficiency limited to a few percent. Here we report experimental results that achieve ~30% conversion efficiency (~200 mW on-chip comb power excluding the pump) in the fiber telecommunication band with broadband mode-locked dark-pulse combs. We present a general analysis on the efficiency which is applicable to any phase-locked microcomb state. The effective coupling condition for the pump as well as the duty cycle of localized time-domain structures play a key role in determining the conversion efficiency. Our observation of high efficiency comb states is relevant for applications such as optical communications which require high power per comb line.

  17. Comb-locked Lamb-dip spectrometer

    Science.gov (United States)

    Gatti, Davide; Gotti, Riccardo; Gambetta, Alessio; Belmonte, Michele; Galzerano, Gianluca; Laporta, Paolo; Marangoni, Marco

    2016-06-01

    Overcoming the Doppler broadening limit is a cornerstone of precision spectroscopy. Nevertheless, the achievement of a Doppler-free regime is severely hampered by the need of high field intensities to saturate absorption transitions and of a high signal-to-noise ratio to detect tiny Lamb-dip features. Here we present a novel comb-assisted spectrometer ensuring over a broad range from 1.5 to 1.63 μm intra-cavity field enhancement up to 1.5 kW/cm2, which is suitable for saturation of transitions with extremely weak electric dipole moments. Referencing to an optical frequency comb allows the spectrometer to operate with kHz-level frequency accuracy, while an extremely tight locking of the probe laser to the enhancement cavity enables a 10-11 cm-1 absorption sensitivity to be reached over 200 s in a purely dc direct-detection-mode at the cavity output. The particularly simple and robust detection and operating scheme, together with the wide tunability available, makes the system suitable to explore thousands of lines of several molecules never observed so far in a Doppler-free regime. As a demonstration, Lamb-dip spectroscopy is performed on the P(15) line of the 01120-00000 band of acetylene, featuring a line-strength below 10-23 cm/mol and an Einstein coefficient of 5 mHz, among the weakest ever observed.

  18. Cavity-enhanced dual-comb spectroscopy

    CERN Document Server

    Bernhardt, Birgitta; Jacquet, Patrick; Jacquey, Marion; Kobayashi, Yohei; Udem, Thomas; Holzwarth, Ronald; Guelachvili, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2009-01-01

    The sensitivity of molecular fingerprinting is dramatically improved when placing the absorbing sample in a high-finesse optical cavity, thanks to the large increase of the effective path-length. As demonstrated recently, when the equidistant lines from a laser frequency comb are simultaneously injected into the cavity over a large spectral range, multiple trace-gases may be identified within a few milliseconds. Analyzing efficiently the light transmitted through the cavity however still remains challenging. Here, a novel approach, cavity-enhanced frequency comb Fourier transform spectroscopy, fully overcomes this difficulty and measures ultrasensitive, broad-bandwidth, high-resolution spectra within a few tens of $\\mu$s. It could be implemented from the Terahertz to the ultraviolet regions without any need for detector arrays. We recorded, within 18 $\\mu$s, spectra of the 1.0 $\\mu$m overtone bands of ammonia spanning 20 nm with 4.5 GHz resolution and a noise-equivalent-absorption at one-second-averaging per ...

  19. Autosomal and X-Linked Additive Genetic Variation for Lifespan and Aging: Comparisons Within and Between the Sexes in Drosophila melanogaster

    OpenAIRE

    Robert M. Griffin; Holger Schielzeth; Urban Friberg

    2016-01-01

    Theory makes several predictions concerning differences in genetic variation between the X chromosome and the autosomes due to male X hemizygosity. The X chromosome should: (i) typically show relatively less standing genetic variation than the autosomes, (ii) exhibit more variation in males compared to females because of dosage compensation, and (iii) potentially be enriched with sex-specific genetic variation. Here, we address each of these predictions for lifespan and aging in Drosophila me...

  20. A tunable comb filter using single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop

    Institute of Scientific and Technical Information of China (English)

    Ruan Juan; Zhang Wei-Gang; Zhang Hao; Geng Peng-Cheng; Bai Zhi-Yong

    2013-01-01

    A novel tunable comb filter composed of a single-mode/multimode/polarization-maintaining-fiber-based Sagnac fiber loop is proposed and experimentally demonstrated.The filter tunability is achieved by rotating the polarization controller.The spectral shift is dependent on rotation direction and the position of the polarization controller.In addition,the adjustable range achieved by rotating the half-wave-plate polarization controller is twice higher than that of the quarter-wave-plate one.

  1. Chipscale optical frequency combs: from soliton physics to coherent communication (Conference Presentation)

    Science.gov (United States)

    Brasch, Victor; Geiselmann, Michael; Herr, Tobias; Lihachev, Grigoriy; Pfeiffer, Martin H. P.; Gorodetsky, Michael L.; Kippenberg, Tobias J.

    2016-04-01

    In our experiment we use silicon nitride waveguides embedded in silicon dioxide on a silicon chip. The cross section of the waveguide is approximately 1.8µm width by 0.8µm height and the ring resonator has a radius of 120µm. This resonator is coupled to a bus waveguide that is used to couple the continuous wave pump light into the resonator and the light from the resonator out again. The pump laser is an amplified diode laser which provides around 2W of pump power in the bus waveguide on the photonic chip. If the pump light is in resonance with one of the resonances of the resonator we can generate a frequency comb from the pump light via the Kerr nonlinearity of the material. The spacing in between the lines of the frequency comb is close to the free spectral range of the resonator, which is 190 GHz for the resonator used. By tuning the pump laser through the resonance and modulating the power of the pump light we can achieve a stable state with a pulsed-shape waveform circulating inside the microresonator. These states are known as dissipative Kerr soliton states and they are solutions to the Lugiato-Lefever equation, which describes the nonlinear physics of the system. So far they had been experimentally demonstrated in fiber-ring cavities as well as crystalline microresonators. The main benefits of these states for Kerr frequency combs is that they allow for low-noise but broadband frequency combs with low modulation in the spectrum. In our case we report a 3-dB bandwidth of 10THz which is equivalent to sub-30fs pulses inside the resonator. Because of the chosen geometry of the waveguide cross section we also observe an effect which is caused by higher-order dispersion. Higher-order dispersion are terms that describe the dispersion beyond the quadratic group velocity dispersion. In order for dissipative Kerr solitons to form, anomalous group velocity dispersion is required. If higher-order terms are present as well, the soliton can still exist but additional

  2. From "Dirac combs" to Fourier-positivity

    CERN Document Server

    Giraud, Bertrand G

    2015-01-01

    Motivated by various problems in physics and applied mathematics, we look for constraints and properties of real Fourier-positive functions, i.e. with positive Fourier transforms. Properties of the "Dirac comb" distribution and of its tensor products in higher dimensions lead to Poisson resummation, allowing for a useful approximation formula of a Fourier transform in terms of a limited number of terms. A connection with the Bochner theorem on positive definiteness of Fourier-positive functions is discussed. As a practical application, we find simple and rapid analytic algorithms for checking Fourier-positivity in 1- and (radial) 2-dimensions among a large variety of real positive functions. This may provide a step towards a classification of positive positive-definite functions.

  3. Frequency comb metrology with an optical parametric oscillator.

    Science.gov (United States)

    Balskus, K; Schilt, S; Wittwer, V J; Brochard, P; Ploetzing, T; Jornod, N; McCracken, R A; Zhang, Z; Bartels, A; Reid, D T; Südmeyer, T

    2016-04-18

    We report on the first demonstration of absolute frequency comb metrology with an optical parametric oscillator (OPO) frequency comb. The synchronously-pumped OPO operated in the 1.5-µm spectral region and was referenced to an H-maser atomic clock. Using different techniques, we thoroughly characterized the frequency noise power spectral density (PSD) of the repetition rate frep, of the carrier-envelope offset frequency fCEO, and of an optical comb line νN. The comb mode optical linewidth at 1557 nm was determined to be ~70 kHz for an observation time of 1 s from the measured frequency noise PSD, and was limited by the stability of the microwave frequency standard available for the stabilization of the comb repetition rate. We achieved a tight lock of the carrier envelope offset frequency with only ~300 mrad residual integrated phase noise, which makes its contribution to the optical linewidth negligible. The OPO comb was used to measure the absolute optical frequency of a near-infrared laser whose second-harmonic component was locked to the F = 2→3 transition of the 87Rb D2 line at 780 nm, leading to a measured transition frequency of νRb = 384,228,115,346 ± 16 kHz. We performed the same measurement with a commercial fiber-laser comb operating in the 1.5-µm region. Both the OPO comb and the commercial fiber comb achieved similar performance. The measurement accuracy was limited by interferometric noise in the fibered setup of the Rb-stabilized laser.

  4. EFSA NDA Panel (EFSA Panel on Dietetic Products, Nutrition and Allergies), 2013 . Scientific Opinion on Rooster Combs Extract

    DEFF Research Database (Denmark)

    Tetens, Inge

    Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to carry out the additional assessment for „Rooster Combs Extract‟ (RCE) as a food ingredient in the context of Regulation (EC) No 258/97, taking into account the comment...

  5. Third-order chromatic dispersion stabilizes Kerr frequency combs

    CERN Document Server

    Parra-Rivas, Pedro; Leo, Francois; Coen, Stephane; Gelens, Lendert

    2014-01-01

    Using numerical simulations of an extended Lugiato-Lefever equation, we analyze the stability and nonlinear dynamics of Kerr frequency combs generated in microresonators and fiber resonators taking into account third-order dispersion effects. We show that cavity solitons underlying Kerr frequency combs, normally sensitive to oscillatory and chaotic instabilities, are stabilized in a wide range of parameter space by third-order dispersion. Moreover, we demonstrate how the snaking structure organizing compound states of multiple cavity solitons is qualitatively changed by third-order dispersion, promoting an increased stability of Kerr combs underlined by a single cavity soliton.

  6. Third-order chromatic dispersion stabilizes Kerr frequency combs.

    Science.gov (United States)

    Parra-Rivas, Pedro; Gomila, Damià; Leo, François; Coen, Stéphane; Gelens, Lendert

    2014-05-15

    Using numerical simulations of an extended Lugiato-Lefever equation we analyze the stability and nonlinear dynamics of Kerr frequency combs generated in microresonators and fiber resonators, taking into account third-order dispersion effects. We show that cavity solitons underlying Kerr frequency combs, normally sensitive to oscillatory and chaotic instabilities, are stabilized in a wide range of parameter space by third-order dispersion. Moreover, we demonstrate how the snaking structure organizing compound states of multiple cavity solitons is qualitatively changed by third-order dispersion, promoting an increased stability of Kerr combs underlined by a single cavity soliton.

  7. A Compact, Waveguide Based Programmable Optical Comb Generator Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This NASA Phase I STTR effort will establish the feasibility of developing a compact broadband near to mid-IR programmable optical comb for use in laser based remote...

  8. Multiplexed sub-Doppler spectroscopy with an optical frequency comb

    CERN Document Server

    Long, David A; Plusquellic, David F; Hodges, Joseph T

    2016-01-01

    An optical frequency comb generated with an electro-optic phase modulator and a chirped radiofrequency waveform is used to perform saturation and pump-probe spectroscopy on the $D_1$ and $D_2$ transitions of atomic potassium. With a comb tooth spacing of 200 kHz and an optical bandwidth of 2 GHz the hyperfine transitions can be simultaneously observed. Interferograms are recorded in as little as 5 $\\mu$s (a timescale corresponding to the inverse of the comb tooth spacing). Importantly, the sub-Doppler features can be measured as long as the laser carrier frequency lies within the Doppler profile, thus removing the need for slow scanning or a priori knowledge of the frequencies of the sub-Doppler features. Sub-Doppler optical frequency comb spectroscopy has the potential to dramatically reduce acquisition times and allow for rapid and accurate assignment of complex molecular and atomic spectra which are presently intractable.

  9. Spectro-temporal dynamics of Kerr combs with parametric seeding.

    Science.gov (United States)

    Lin, Guoping; Martinenghi, Romain; Diallo, Souleymane; Saleh, Khaldoun; Coillet, Aurélien; Chembo, Yanne K

    2015-03-20

    We report a joint theoretical and experimental investigation of the parametric seeding of a primary Kerr optical frequency comb. Electro-optic modulation sidebands matching multiple free-spectral ranges of an ultrahigh-Q millimeter-size magnesium fluoride disk resonator are used as seed signals. These seed signals interact through four-wave mixing with the spectral components of a stable primary comb and give rise to complex spectro-temporal patterns. We show that the new frequency combs feature multiscale frequency spacing, with major frequency gaps in the order of a few hundred gigahertz, and minor frequency spacing in the order of a few tens of gigahertz. The experimental results are in agreement with numerical simulations using the Lugiato-Lefever equation. We expect such versatile and coherent optical frequency combs to have potential applications in optical communications systems where frequency management assigns predefined spectral windows at the emitter stage.

  10. Performance analysis and experimental study on Flat Optical Comb Generation

    Directory of Open Access Journals (Sweden)

    Haining Li

    2013-01-01

    Full Text Available The performance of the optical frequency comb generation based on the re-circulating frequency shifter has been analyzed and demonstrated in this paper. We have theoretically analyzed the condition for flatness of the optical frequency comb and the relative intensity noise influence. We find out the influence to the flatness of optical comb owing to amplifier relative intensity noise and modulator relative factors imperfect, such as input RF signals amplitude and phase deviation and modulator defect owing to manufacture for the first time. Moreover, to verify the theoretical analysis, a 16 comb lines and spacing 12.5 GHz RFS generation system have also been carried out, and the results are in good agreement with the theoretical analysis results.

  11. Ramsey-comb spectroscopy with intense ultrashort laser pulses

    CERN Document Server

    Morgenweg, Jonas; Eikema, Kjeld S E

    2014-01-01

    Optical frequency combs based on mode-locked lasers have revolutionised the field of metrology and precision spectroscopy by providing precisely calibrated optical frequencies and coherent pulse trains. Amplification of the pulsed output from these lasers is very desirable, as nonlinear processes can then be employed to cover a much wider range of transitions and wavelengths for ultra-high precision, direct frequency comb spectroscopy. Therefore full repetition rate laser amplifiers and enhancement resonators have been employed to produce up to microjoule-level pulse energies. Here we show that the full frequency comb accuracy and resolution can be obtained by using only two frequency comb pulses amplified to the millijoule pulse energy level, orders of magnitude more energetic than what has previously been possible. The novel properties of this approach, such as cancellation of optical light-shift effects, is demonstrated on weak two-photon transitions in atomic rubidium and caesium, thereby improving the fr...

  12. Micro--structured crystalline resonators for optical frequency comb generation

    CERN Document Server

    Grudinin, Ivan S

    2014-01-01

    Optical frequency combs have recently been demonstrated in micro--resonators through nonlinear Kerr processes. Investigations in the past few years provided better understanding of micro--combs and showed that spectral span and mode locking are governed by cavity spectrum and dispersion. While various cavities provide unique advantages, dispersion engineering has been reported only for planar waveguides. In this Letter, we report a resonator design that combines dispersion control, mode crossing free spectrum, and ultra--high quality factor. We experimentally show that as the dispersion of a MgF2 resonator is flattened, the comb span increases reaching 700 nm with as low as 60 mW pump power at 1560 nm wavelength, corresponding to nearly 2000 lines separated by 46 GHz. The new resonator design may enable efficient low repetition rate coherent octave spanning frequency combs without the need for external broadening, ideal for applications in optical frequency synthesis, metrology, spectroscopy, and communicatio...

  13. Mid-IR Microresonator-Based Optical Frequency Combs

    Science.gov (United States)

    2015-09-01

    publication of 14 refereed papers in Nature Communications, Optica, Optics Letters , etc. One more paper is currently under consideration in Laser...A. Matsko et al. Optics Letters 38, 525 (2013). Chaotic combs Numerical solutions of Eq. (2) showed that a chaotic comb generation regime...34 Optics Letters 39 (10), 2920-2923 (2014). http://dx.doi.org/10.1364/OL.39.002920 10. Andrey B. Matsko and L. Maleki, “On timing jitter of mode

  14. Kerr optical frequency combs: theory, applications and perspectives

    Science.gov (United States)

    Chembo, Yanne K.

    2016-06-01

    The optical frequency comb technology is one of the most important breakthrough in photonics in recent years. This concept has revolutionized the science of ultra-stable lightwave and microwave signal generation. These combs were originally generated using ultrafast mode-locked lasers, but in the past decade, a simple and elegant alternativewas proposed,which consisted in pumping an ultra-high-Q optical resonator with Kerr nonlinearity using a continuous-wave laser. When optimal conditions are met, the intracavity pump photons are redistributed via four-wave mixing to the neighboring cavity modes, thereby creating the so-called Kerr optical frequency comb. Beyond being energy-efficient, conceptually simple, and structurally robust, Kerr comb generators are very compact devices (millimetric down to micrometric size) which can be integrated on a chip. They are, therefore, considered as very promising candidates to replace femtosecond mode-locked lasers for the generation of broadband and coherent optical frequency combs in the spectral domain, or equivalently, narrow optical pulses in the temporal domain. These combs are, moreover, expected to provide breakthroughs in many technological areas, such as integrated photonics, metrology, optical telecommunications, and aerospace engineering. The purpose of this review article is to present a comprehensive survey of the topic of Kerr optical frequency combs.We provide an overview of the main theoretical and experimental results that have been obtained so far. We also highlight the potential of Kerr combs for current or prospective applications, and discuss as well some of the open challenges that are to be met at the fundamental and applied level.

  15. A mummified duck-billed dinosaur with a soft-tissue cock's comb.

    Science.gov (United States)

    Bell, Phil R; Fanti, Federico; Currie, Philip J; Arbour, Victoria M

    2014-01-01

    Among living vertebrates, soft tissues are responsible for labile appendages (combs, wattles, proboscides) that are critical for activities ranging from locomotion to sexual display [1]. However, soft tissues rarely fossilize, and such soft-tissue appendages are unknown for many extinct taxa, including dinosaurs. Here we report a remarkable "mummified" specimen of the hadrosaurid dinosaur Edmontosaurus regalis from the latest Cretaceous Wapiti Formation, Alberta, Canada, that preserves a three-dimensional cranial crest (or "comb") composed entirely of soft tissue. Previously, crest function has centered on the hypertrophied nasal passages of lambeosaurine hadrosaurids, which acted as resonance chambers during vocalization [2-4]. The fleshy comb in Edmontosaurus necessitates an alternative explanation most likely related to either social signaling or sexual selection [5-7]. This discovery provides the first view of bizarre, soft-tissue signaling structures in a dinosaur and provides additional evidence for social behavior. Crest evolution within Hadrosaurinae apparently culminated in the secondary loss of the bony crest at the terminal Cretaceous; however, the new specimen indicates that cranial ornamentation was in fact not lost but substituted in Edmontosaurus by a fleshy display structure. It also implies that visual display played a key role in the evolution of hadrosaurine crests and raises the possibility of similar soft-tissue structures among other dinosaurs.

  16. Gigahertz frequency comb from a diode-pumped solid-state laser.

    Science.gov (United States)

    Klenner, Alexander; Schilt, Stéphane; Südmeyer, Thomas; Keller, Ursula

    2014-12-15

    We present the first stabilization of the frequency comb offset from a diode-pumped gigahertz solid-state laser oscillator. No additional external amplification and/or compression of the output pulses is required. The laser is reliably modelocked using a SESAM and is based on a diode-pumped Yb:CALGO gain crystal. It generates 1.7-W average output power and pulse durations as short as 64 fs at a pulse repetition rate of 1 GHz. We generate an octave-spanning supercontinuum in a highly nonlinear fiber and use the standard f-to-2f carrier-envelope offset (CEO) frequency fCEO detection method. As a pump source, we use a reliable and cost-efficient commercial diode laser. Its multi-spatial-mode beam profile leads to a relatively broad frequency comb offset beat signal, which nevertheless can be phase-locked by feedback to its current. Using improved electronics, we reached a feedback-loop-bandwidth of up to 300 kHz. A combination of digital and analog electronics is used to achieve a tight phase-lock of fCEO to an external microwave reference with a low in-loop residual integrated phase-noise of 744 mrad in an integration bandwidth of [1 Hz, 5 MHz]. An analysis of the laser noise and response functions is presented which gives detailed insights into the CEO stabilization of this frequency comb.

  17. Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs.

    Science.gov (United States)

    Posada-Roman, Julio E; Garcia-Souto, Jose A; Poiana, Dragos A; Acedo, Pablo

    2016-11-26

    Optical frequency combs (OFC) generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG) sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz). Measurements of ultrasounds (40 kHz and 120 kHz) are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal.

  18. 75 FR 14491 - Listing of Color Additives Exempt From Certification; Bismuth Citrate

    Science.gov (United States)

    2010-03-26

    ... action is in response to a petition filed by Combe, Inc. DATES: This rule is effective April 27, 2010... additive petition (CAP 8C0286) had been filed by Combe, Inc., c/o EAS Consulting Group, LLC, 1940 Duke St... per volume (w/v)) to 2.0 percent (w/v). II. Evaluation of Safety A. Determination of Safety...

  19. Regulation of Raoultella terrigena comb.nov. phytase expression.

    Science.gov (United States)

    Zamudio, Marcela; González, Aracely; Bastarrachea, Fernando

    2002-01-01

    Phytases catalyze the release of phosphate from phytate (myo-inositol hexakisphosphate) to inositol polyphosphates. Raoultella terrigena comb.nov. phytase activity is known to increase markedly after cells reach the stationary phase. In this study, phytase activity measurements made on single batch cultures indicated that specific enzyme activity was subject to catabolite repression. Cyclic AMP (cAMP) showed a positive effect in expression during exponential growth and a negative effect during stationary phase. RpoS exhibited the opposite effect during both growth phases; the induction to stationary phase decreased twofold in the rpoS::Tn10 mutant, but the effect of RpoS was not clearly determined. Two phy::MudI1734 mutants, MW49 and MW52, were isolated. These formed small colonies in comparison with the MW25 parent strain when plated on Luria-Bertani (LB) or LB supplemented with glucose. They did not grow in minimal media or under anaerobiosis, but did grow aerobically on LB and LB glucose at a lower rate than did MW25. The beta-galactosidase activity level in these mutants increased three to four fold during stationary growth in LB glucose and during anaerobiosis. Addition of cAMP during the exponential growth of MW52 on LB glucose provoked a decrease in beta-galactosidase activity during the stationary phase, confirming its negative effect on phytase expression during stationary growth.

  20. Clinically insignificant improvement of prostate cancer prediction by addition of sex steroid hormones and SHBG serum levels to serum PSA, fPSA%, and age in a screening setting.

    Science.gov (United States)

    Heidegger, Isabel; Popovscaia, Marina; Ramoner, Reinhold; Schäfer, Georg; Stenzel, Birgit; Bektic, Jasmin; Horninger, Wolfgang; Klocker, Helmut

    2012-10-01

    Abstract Various findings implicate sex hormones in prostate growth and development and also in prostate carcinogenesis. We investigated if addition of sex steroid hormone and sex hormone binding globulin (SHBG) serum levels to standard risk assessment parameters [prostate-specific antigen (PSA), free PSA percentage (fPSA%), and age] improves prostate cancer prediction in a PSA screening setting. Steroid hormones testosterone (T), free testosterone (fT), and estradiol (E2), and binding protein SHBG levels were measured in 762 men undergoing prostate biopsy due to suspect PSA serum levels. Prostate cancer was diagnosed in 286 (37.5%) of these men. Our data confirmed that PSA (mean BE=5.09; mean CA=6.05; p=1.24×10-5), fPSA% (mean BE=22.08; mean CA=18.67; p=1.97×10-7), and age (mean BE=60.64; mean CA=64.5; p=7.05×10-10) differentiate men with cancer (CA) and men with benign disease (BE), such as benign prostate hyperplasia. In addition, SHBG (mean BE=50.3; mean CA=54.9; p=0.008) also differed statistically significantly between these two groups. All hormones except E2 and tumor markers correlated significantly with age (T: ρ=-0.09; fT: ρ=-0.27; SHBG: ρ=0.21; PSA: ρ=0.32; and fPSA%: ρ=0.22). Furthermore, we found that PSA correlates with E2 (ρ=0.08), and fPSA% with SHBG (ρ=0.1) and fT (ρ=-0.09). Addition of hormones and SHBG to a baseline marker model including PSA, fPSA%, and age improved cancer prediction in three multivariate classification methods; however, the improvement was minimal. The best improvement by 0.8% was obtained in the logistic regression model with the addition of T and SHBG or of E2 and SHBG, or in the support vector machine model with the addition of SHBG and all steroid hormones to the combination of standard markers PSA, fPSA%, and age; however, this additional gain of accuracy is too small to justify the additional efforts and costs.

  1. Interaction Between Waves and A Comb-Type Breakwater

    Institute of Scientific and Technical Information of China (English)

    董国海; 李玉成; 孙昭晨; 孙洋; 牛恩宗; 毛铠

    2003-01-01

    The characteristics of wave transmission, reflection and energy dissipation of comb-type caisson breakwaters are studied through laboratory physical model tests. Regular and irregular waves, with a wide range of wave heights and periods and a constant water depth, are considered. Different dimensions of each portion of the comb-type caisson breakwater are tested. Empirical formulae for calculating the reduction coefficient k, which is the ratio of horizontal wave force on unit length of the comb-type breakwater to that on unit length of the vertical wall breakwater, and for calculating the reflection coefficient of waves kr are obtained from the measurements. The comb-type caisson breakwater has been found to be very efficient in dissipating incident wave energy and in reducing wave reflection, and has already been used for the construction of an island breakwater in the Dayao Bay of Dalian Port, Liaoning Province, China. Compared with the cost of a common caisson breakwater, about 24.5% of the investment has been saved owing to the use of this comb-type breakwater.

  2. Solution and Melt Rheology of Polypropylene Comb and Star Polymers

    Science.gov (United States)

    Ghosh, Arnav; Colby, Ralph H.; Rose, Jeffrey M.; Cherian, Anna E.; Coates, Geoffrey W.

    2006-03-01

    Syndiotactic polypropylene macromonomer arms have been prepared by coordination-insertion polymerization. These arms have been made into polypropylene star polymers by the homopolymerization of the syndiotactic arms with a living alkene polymerization catalyst. The macromonomer arms have also been randomly copolymerized with propylene using rac-dimethylsilyl(2-methyl-4-phenylindenyl) zirconium dichloride catalysts to make polypropylene combs. Consequently we have star polymers and a series of comb polymers with different backbone lengths that are all made from the same macromonomer arms. We compare linear viscoelastic data on star and comb polypropylene melts and solutions in squalane to predictions of the tube dilation model and the tube model without tube dilation. The ratio of comb terminal relaxation time to star terminal relaxation time eliminates the friction coefficient and allows determination of the extent of tube dilation the backbone experiences when it relaxes. The concentration dependence of the comb/star terminal relaxation time ratio can be described by either model, owing to adjustable parameters that are not known apriori, so independent means to evaluate those parameters will be discussed.

  3. Adsorption of comb copolymers on weakly attractive solid surfaces

    Science.gov (United States)

    Striolo, A.; Jayaraman, A.; Genzer, J.; Hall, C. K.

    2005-08-01

    In this work continuum and lattice Monte Carlo simulation methods are used to study the adsorption of linear and comb polymers on flat surfaces. Selected polymer segments, located at the tips of the side chains in comb polymers or equally spaced along the linear polymers, are attracted to each other and to the surface via square-well potentials. The rest of the polymer segments are modeled as tangent hard spheres in the continuum model and as self-avoiding random walks in the lattice model. Results are presented in terms of segment-density profiles, distribution functions, and radii of gyration of the adsorbed polymers. At infinite dilution the presence of short side chains promotes the adsorption of polymers favoring both a decrease in the depletion-layer thickness and a spreading of the polymer molecule on the surface. The presence of long side chains favors the adsorption of polymers on the surface, but does not permit the spreading of the polymers. At finite concentration linear polymers and comb polymers with long side chains readily adsorb on the solid surface, while comb polymers with short side chains are unlikely to adsorb. The simple models of comb copolymers with short side chains used here show properties similar to those of associating polymers and of globular proteins in aqueous solutions, and can be used as a first approximation to investigate the mechanism of adsorption of proteins onto hydrophobic surfaces.

  4. Sex determination in amphibians.

    Science.gov (United States)

    Nakamura, Masahisa

    2009-05-01

    The heterogametic sex is male in all mammals, whereas it is female in almost all birds. By contrast, there are two heterogametic types (XX/XY and ZZ/ZW) for genetic sex determination in amphibians. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. Indeed, the frog Rana rugosa has the XX/XY and ZZ/ZW sex-determining systems within a single species, depending on the local population in Japan. The XY and ZW geographic forms with differentiated sex chromosomes probably have a common origin as undifferentiated sex chromosomes resulted from the hybridization between the primary populations of West Japan and Kanto forms. It is clear that the sex chromosomes are still undergoing evolution in this species group. Regardless of the presence of a sex-determining gene in amphibians, the gonadal sex of some species can be changed by sex steroids. Namely, sex steroids can induce the sex reversal, with estrogens inducing the male-to-female sex reversal, whereas androgens have the opposite effect. In R. rugosa, gonadal activity of CYP19 (P450 aromatase) is correlated with the feminization of gonads. Of particular interest is that high levels of CYP19 expression are observed in indifferent gonads at time before sex determination. Increases in the expression of CYP19 in female gonads and CYP17 (P450 17alpha-hydroxylase/C17-20 lyase) in male gonads suggest that the former plays an important role in phenotypic female determination, whereas the latter is needed for male determination. Thus, steroids could be the key factor for sex determination in R. rugosa. In addition to the role of sex steroids in gonadal sex determination in this species, Foxl2 and Sox3 are capable of promoting CYP19 expression. Since both the genes are autosomal, another factor up-regulating CYP19 expression must be recruited. The factor, which may be located on the X or W

  5. A quadratic-shaped-finger comb parametric resonator

    Science.gov (United States)

    Guo, Congzhong; Fedder, Gary K.

    2013-09-01

    A large-stroke (8 µm) parametric resonator excited by an in-plane ‘shaped-finger’ electrostatic comb drive is fabricated using a 15 µm thick silicon-on-insulator microelectromechanical systems (SOI-MEMS) process. A quadratic capacitance-engagement response is synthesized by engineering a custom-shaped comb finger profile. A folded-flexure suspension allows lateral motion while constraining rotational modes. The excitation of the nonlinear parametric resonance is realized by selecting an appropriate combination of the linear and cubic electrostatic stiffness coefficients through a specific varying-gap comb-finger design. The large-amplitude parametric resonance promotes high signal-to-noise ratio for potential use in sensitive chemical gravimetric sensors, strain gauges, and mode-matched gyroscope applications.

  6. Enabling Arbitrary Wavelength Optical Frequency Combs on Chip

    CERN Document Server

    Soltani, Mohammad; Maleki, Lute

    2015-01-01

    A necessary condition for generation of bright soliton Kerr frequency combs in microresonators is to achieve anomalous group velocity dispersion (GVD) for the resonator modes. This condition is hard to implement in visible as well as ultraviolet since the majority of optical materials are characterized with large normal GVD in these wavelength regions. We overcome this challenge by borrowing ideas from strongly dispersive coupled systems in solid state physics and optics. We show that photonic compound ring resonators can possess large anomalous GVD at any desirable wavelength, even if each individual resonator is characterized with normal GVD. Based on this concept we design a mode locked frequency comb with thin-film silicon nitride compound ring resonators in the vicinity of Rubidium D1 line (794.6nm) and propose to use this optical comb as a flywheel for chip-scale optical clocks.

  7. Continuum Random Combs and Scale Dependent Spectral Dimension

    CERN Document Server

    Atkin, Max R; Wheater, John F

    2011-01-01

    Numerical computations have suggested that in causal dynamical triangulation models of quantum gravity the effective dimension of spacetime in the UV is lower than in the IR. In this paper we develop a simple model based on previous work on random combs, which share some of the properties of CDT, in which this effect can be shown to occur analytically. We construct a definition for short and long distance spectral dimensions and show that the random comb models exhibit scale dependent spectral dimension defined in this way. We also observe that a hierarchy of apparent spectral dimensions may be obtained in the cross-over region between UV and IR regimes for suitable choices of the continuum variables. Our main result is valid for a wide class of tooth length distributions thereby extending previous work on random combs by Durhuus et al.

  8. Femtosecond Optical Frequency Comb Technology Principle, Operation and Application

    CERN Document Server

    Ye, Jun

    2005-01-01

    Over the last few years, there has been a remarkable convergence among the fields of ultrafast optics, optical frequency metrology, and precision laser spectroscopy. This convergence has enabled unprecedented advances in control of the electric field of the pulses produced by femtosecond mode-locked lasers. The resulting spectrum consists of a comb of sharp spectral lines with well-defined frequencies. These new techniques and capabilities are generally known as "femtosecond comb technology." They have had dramatic impact on the diverse fields of precision measurement and extreme nonlinear optical physics. This book provides an introductory description of mode-locked lasers, the connection between time and frequency descriptions of their output and the physical origins of the electric field dynamics, together with an overview of applications of femtosecond comb technology. Individual chapters go into more detail on mode-locked laser development, spectral broadening in microstructure fiber, optical parametric ...

  9. A deep-UV optical frequency comb at 205 nm.

    Science.gov (United States)

    Peters, E; Diddams, S A; Fendel, P; Reinhardt, S; Hänsch, T W; Udem, Th

    2009-05-25

    By frequency quadrupling a picosecond pulse train from a Ti:sapphire laser at 820 nm we generate a frequency comb at 205 nm with nearly bandwidth-limited pulses. The nonlinear frequency conversion is accomplished by two successive frequency doubling stages that take place in resonant cavities that are matched to the pulse repetition rate of 82 MHz. This allows for an overall efficiency of 4.5 % and produces an output power of up to 70 mW for a few minutes and 25 mW with continuous operation for hours. Such a deep UV frequency comb may be employed for direct frequency comb spectroscopy in cases where it is less efficient to convert to these short wavelengths with continuous wave lasers.

  10. Mid-Infrared Frequency Comb Fourier Transform Spectrometer

    CERN Document Server

    Adler, Florian; Foltynowicz, Aleksandra; Cossel, Kevin C; Briles, Travis C; Hartl, Ingmar; Ye, Jun

    2010-01-01

    Optical frequency-comb-based-high-resolution spectrometers offer enormous potential for spectroscopic applications. Although various implementations have been demonstrated, the lack of suitable mid-infrared comb sources has impeded explorations of molecular fingerprinting. Here we present for the first time a frequency-comb Fourier transform spectrometer operating in the 2100-to-3700-cm-1 spectral region that allows fast and simultaneous acquisitions of broadband absorption spectra with up to 0.0056 cm-1 resolution. We demonstrate part-per-billion detection limits in 30 seconds of integration time for various important molecules including methane, ethane, isoprene, and nitrous oxide. Our system enables precise concentration measurements even in gas mixtures that exhibit continuous absorption bands, and it allows detection of molecules at levels below the noise floor via simultaneous analysis of multiple spectral features. This system represents a near real-time, high-resolution, high-bandwidth mid-infrared sp...

  11. Mid-Infrared Optical Frequency Combs based on Crystalline Microresonators

    CERN Document Server

    Wang, C Y; Del'Haye, P; Schliesser, A; Hofer, J; Holzwarth, R; Hänsch, T W; Picqué, N; Kippenberg, T J

    2011-01-01

    The mid-infrared spectral range (\\lambda ~ 2 \\mu m to 20 \\mu m) is known as the "molecular fingerprint" region as many molecules have their highly characteristic, fundamental ro-vibrational bands in this part of the electromagnetic spectrum. Broadband mid-infrared spectroscopy therefore constitutes a powerful and ubiquitous tool for optical analysis of chemical components that is used in biochemistry, astronomy, pharmaceutical monitoring and material science. Optical frequency combs, i.e. broad spectral bandwidth coherent light sources consisting of equally spaced sharp lines, have revolutionized optical frequency metrology one decade ago. They now demonstrate dramatically improved acquisition rates, resolution and sensitivity for molecular spectroscopy mostly in the visible and near-infrared ranges. Mid-infrared frequency combs have therefore become highly desirable and recent progress in generating such combs by nonlinear frequency conversion has opened access to this spectral region. Here we report on a pr...

  12. Self-referencing of an on-chip soliton Kerr frequency comb without external broadening

    CERN Document Server

    Brasch, Victor; Jost, John D; Geiselmann, Michael; Kippenberg, Tobias J

    2016-01-01

    Self-referencing turns pulsed laser systems into self-referenced frequency combs. Such frequency combs allow counting of optical frequencies and have a wide range of applications. The required optical bandwidth to implement self-referencing is typically obtained via nonlinear broadening in optical fibers. Recent advances in the field of Kerr frequency combs have provided a path towards the development of compact frequency comb sources that provide broadband frequency combs, exhibit microwave repetition rates and that are compatible with on-chip photonic integration. These devices have the potential to significantly expand the use of frequency combs. Yet to date self-referencing of such Kerr frequency combs has only been attained by applying conventional, fiber based broadening techniques. Here we demonstrate external broadening-free self-referencing of a Kerr frequency comb. An optical spectrum that spans two-thirds of an octave is directly synthesized from a continuous wave laser-driven silicon nitride micro...

  13. Device Characterization of High Performance Quantum Dot Comb Laser

    KAUST Repository

    Rafi, Kazi

    2012-02-01

    The cost effective comb based laser sources are considered to be one of the prominent emitters used in optical communication (OC) and photonic integrated circuits (PIC). With the rising demand for delivering triple-play services (voice, data and video) in FTTH and FTTP-based WDM-PON networks, metropolitan area network (MAN), and short-reach rack-to-rack optical computer communications, a versatile and cost effective WDM transmitter design is required, where several DFB lasers can be replaced by a cost effective broadband comb laser to support on-chip optical signaling. Therefore, high performance quantum dot (Q.Dot) comb lasers need to satisfy several challenges before real system implementations. These challenges include a high uniform broadband gain spectrum from the active layer, small relative intensity noise with lower bit error rate (BER) and better temperature stability. Thus, such short wavelength comb lasers offering higher bandwidth can be a feasible solution to address these challenges. However, they still require thorough characterization before implementation. In this project, we briefly characterized the novel quantum dot comb laser using duty cycle based electrical injection and temperature variations where we have observed the presence of reduced thermal conductivity in the active layer. This phenomenon is responsible for the degradation of device performance. Hence, different performance trends, such as broadband emission and spectrum stability were studied with pulse and continuous electrical pumping. The tested comb laser is found to be an attractive solution for several applications but requires further experiments in order to be considered for photonic intergraded circuits and to support next generation computer-communications.

  14. Sex Stereotype

    Institute of Scientific and Technical Information of China (English)

    倪媛

    2014-01-01

    This paper analyzes the social phenomenon—sex stereotype.The paper illustrates the characteristics of stereotype and discusses about the factors which influence sex stereotypes and the reasons of its existence.And it also found the positive role that sex stereotype plays in the communication.

  15. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  16. Optical Kerr Frequency Comb Generation in Overmoded Resonators

    CERN Document Server

    Matsko, A B; Liang, W; Ilchenko, V S; Seidel, D; Maleki, L

    2012-01-01

    We show that scattering-based interaction among nearly degenerate optical modes is the key factor in low threshold generation of Kerr frequency combs in nonlinear optical resonators possessing small group velocity dispersion (GVD). The mode interaction is capable of producing drastic change in the local GVD, resulting in either a significant reduction or increase of the oscillation threshold. It is also responsible for the majority of observed combs in resonators characterized with large normal GVD. We present results of our numerical simulations as well as supporting experimental data.

  17. Optical frequency comb interference profilometry using compressive sensing.

    Science.gov (United States)

    Pham, Quang Duc; Hayasaki, Yoshio

    2013-08-12

    We describe a new optical system using an ultra-stable mode-locked frequency comb femtosecond laser and compressive sensing to measure an object's surface profile. The ultra-stable frequency comb laser was used to precisely measure an object with a large depth, over a wide dynamic range. The compressive sensing technique was able to obtain the spatial information of the object with two single-pixel fast photo-receivers, with no mechanical scanning and fewer measurements than the number of sampling points. An optical experiment was performed to verify the advantages of the proposed method.

  18. Noise conversion in Kerr comb RF photonic oscillators

    CERN Document Server

    Matsko, Andrey B

    2014-01-01

    Transfer of amplitude and phase noise from a continuous wave optical pump to the repetition rate of a Kerr frequency comb is studied theoretically, with focus on generation of spectrally pure radio frequency (RF) signals via demodulation of the frequency comb on a fast photodiode. It is shown that both the high order chromatic dispersion of the resonator spectrum and frequency-dependent quality factor of the resonator modes facilitate the optical-to-RF noise conversion that limits spectral purity of the RF signal.

  19. Coherent, multi-heterodyne spectroscopy using stabilized optical frequency combs

    CERN Document Server

    Coddington, Ian; Newbury, Nathan R

    2007-01-01

    The broadband, coherent nature of narrow-linewidth fiber frequency combs is exploited to measure the full complex spectrum of a molecular gas through multi-heterodyne spectroscopy. We measure the absorption and phase shift experienced by each of 155,000 individual frequency comb lines, spaced by 100 MHz and spanning from 1495 nm to 1620 nm, after passing through a hydrogen cyanide gas. The measured phase spectrum agrees with Kramers-Kronig transformation of the absorption spectrum. This technique can provide a full complex spectrum rapidly, over wide bandwidths, and with hertz-level accuracy.

  20. Frequency Comb Assisted Broadband Precision Spectroscopy with Cascaded Diode Lasers

    CERN Document Server

    Liu, Junqiu; Pfeiffer, Martin H P; Kordts, Arne; Kamel, Ayman N; Guo, Hairun; Geiselmann, Michael; Kippenberg, Tobias J

    2016-01-01

    Frequency comb assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this letter we present a novel method using cascaded frequency agile diode lasers, which allows extending the measurement bandwidth to 37.4 THz (1355 to 1630 nm) at MHz resolution with scanning speeds above 1 THz/s. It is demonstrated as a useful tool to characterize a broadband spectrum for molecular spectroscopy and in particular it enables to characterize the dispersion of integrated microresonators up to the fourth order.

  1. Over-five octaves wide Raman combs in high-power picosecond-laser pumped H(2)-filled inhibited coupling Kagome fiber.

    Science.gov (United States)

    Benoît, Aurélien; Beaudou, Benoit; Alharbi, Meshaal; Debord, Benoit; Gérôme, Frédéric; Salin, François; Benabid, Fetah

    2015-06-01

    We report on the generation of over 5 octaves wide Raman combs using inhibited coupling Kagome guiding hollow-core photonic crystal fiber filled with hydrogen and pumped with 22.7 W average power and 27 picosecond pulsed fiber laser. Combs spanning from ~321 nm in the UV to ~12.5 µm in the long-wavelength IR (i.e. from 24 THz to 933 THz) with different spectral content and with an output average power of up to ~10 W were generated. In addition to the clear potential of such a comb as a laser source emitting at spectral ranges, which existing technology poorly addresses like long-wavelength IR and UV, the combination of high Raman net gain and short pump-pulse duration makes these spectra an excellent candidate for intra-pulse waveform synthesis.

  2. Coherent cavity-enhanced dual-comb spectroscopy

    CERN Document Server

    Fleisher, Adam J; Reed, Zachary D; Hodges, Joseph T; Plusquellic, David F

    2016-01-01

    Dual-comb spectroscopy allows for the rapid, multiplexed acquisition of high-resolution spectra without the need for moving parts or low-resolution dispersive optics. This method of broadband spectroscopy is most often accomplished via tight phase locking of two mode-locked lasers, or via sophisticated signal processing algorithms, and therefore long integration times are difficult to achieve. Here we demonstrate an alternative approach to dual-comb spectroscopy using two phase modulator combs originating from a single continuous-wave laser capable of > 2 hours of coherent real-time averaging. The combs of > 250 teeth and 203 MHz spacing were generated by driving the phase modulators with step-recovery diodes, passive devices that provided low-phase-noise harmonics for efficient coupling into an enhancement cavity at picowatt optical powers. With this approach, we demonstrate the sensitivity to simultaneously monitor ambient levels of CO$_2$, CO, HDO, and H$_2$O at a maximum acquisition rate of 150 kHz. Robus...

  3. An Atlas of Medieval Combs from Northern Europe

    Directory of Open Access Journals (Sweden)

    Steven P. Ashby

    2011-07-01

    Full Text Available As an aid to understanding chronology, economics, identity and culture contact, the early medieval bone/antler hair-comb is an under-exploited resource, despite the existence of an extensive literature borne out of a long-standing tradition of empirical research. Such research has been undertaken according to diverse traditions, is scattered amongst site reports and grey literature, regional, national, and international journals, and is published in a number of different languages. The present article provides a general synthesis of this data, together with the author's personal research, situated within a broad view of chronology and geography. It presents the author's classification of early medieval composite combs, and applies this in a review of comb typology in space and time. It makes use of recently excavated material from little-known and unpublished sites, as well as the classic studies of familiar towns and 'emporia'. The atlas is intended for use as a reference piece that may be accessed according to need, and read in a non-linear fashion. Thus, it may act as a first port-of-call for scholars researching the material culture of a particular spatio-temporal context, while simultaneously facilitating rapid characterisation of freshly excavated finds material. It should provide a useful complement to recent and ongoing question-oriented research on combs.

  4. Hard and Soft Excitation Regimes of Kerr Frequency Combs

    CERN Document Server

    Matsko, Andrey B; Ilchenko, Vladimir S; Seidel, David; Maleki, Lute

    2011-01-01

    We theoretically study the stability conditions and excitation regimes of hyper-parametric oscillation and Kerr frequency comb generation in continuously pumped nonlinear optical resonators possessing anomalous group velocity dispersion. We show that both hard and soft excitation regimes are possible in the resonators. Selection between the regimes is achieved via change in the parameters of the pumping light.

  5. Invited Article: A compact optically coherent fiber frequency comb.

    Science.gov (United States)

    Sinclair, L C; Deschênes, J-D; Sonderhouse, L; Swann, W C; Khader, I H; Baumann, E; Newbury, N R; Coddington, I

    2015-08-01

    We describe the design, fabrication, and performance of a self-referenced, optically coherent frequency comb. The system robustness is derived from a combination of an optics package based on polarization-maintaining fiber, saturable absorbers for mode-locking, high signal-to-noise ratio (SNR) detection of the control signals, and digital feedback control for frequency stabilization. The output is phase-coherent over a 1-2 μm octave-spanning spectrum with a pulse repetition rate of ∼200 MHz and a residual pulse-to-pulse timing jitter <3 fs well within the requirements of most frequency-comb applications. Digital control enables phase coherent operation for over 90 h, critical for phase-sensitive applications such as timekeeping. We show that this phase-slip free operation follows the fundamental limit set by the SNR of the control signals. Performance metrics from three nearly identical combs are presented. This laptop-sized comb should enable a wide-range of applications beyond the laboratory.

  6. Frequency combs and precision spectroscopy in the extreme ultraviolet

    Science.gov (United States)

    Cingöz, Arman

    2012-06-01

    Development of the optical frequency comb has revolutionized optical metrology and precision spectroscopy due to its ability to provide a precise link between microwave and optical frequencies. A novel application that aims to extend the precision and accuracy obtained to the extreme ultraviolet (XUV) is the generation of XUV frequency combs via intracavity high harmonic generation (HHG). Recently, we have been able to generate > 200 μW average power per harmonic and demonstrate the comb structure of the high harmonics by resolving atomic argon and neon lines at 82 and 63 nm, respectively [1]. The argon transition linewidth of 10 MHz, limited by residual Doppler broadening, is unprecedented in this spectral region and places a stringent upper limit on the linewidth of individual comb teeth. To overcome this limitation, we have constructed two independent intracavity HHG sources to study the phase coherence directly via the heterodyne beats between them. With these developments, ultrahigh precision spectroscopy in the XUV is within grasp and has a wide range of applications that include tests of bound state quantum electrodynamics, development of nuclear clocks, and searches for variation of fundamental constants using the enhanced sensitivity of highly charged ions.[4pt] [1] Arman Cing"oz et al., Nature 482, 68 (2012).

  7. Optimized comb drive finger shape for shock-resistant actuation

    NARCIS (Netherlands)

    Engelen, Johan B.C.; Abelmann, Leon; Elwenspoek, Miko C.

    2010-01-01

    This work presents the analytical solution, realization and measurement of a comb drive with finger shapes optimized for shock-resistant actuation. The available force for actuating an external load determines how large shock forces can be compensated for. An analytical expression is presented for t

  8. The effect of drone comb on a honey bee colony's production of honey

    OpenAIRE

    Seeley, Thomas

    2002-01-01

    International audience; This study examined the impact on a colony's honey production of providing it with a natural amount (20%) of drone comb. Over 3 summers, for the period mid May to late August, I measured the weight gains of 10 colonies, 5 with drone comb and 5 without it. Colonies with drone comb gained only 25.2 $\\pm$ 16.0 kg whereas those without drone comb gained 48.8 $\\pm$ 14.8 kg. Colonies with drone comb also had a higher mean rate of drone flights and a lower incidence of drone ...

  9. Spectral characterization of a frequency comb based on cascaded quadratic nonlinearities inside an optical parametric oscillator

    CERN Document Server

    Ulvila, Ville; Halonen, Lauri; Vainio, Markku

    2015-01-01

    We present an experimental study of optical frequency comb generation based on cascaded quadratic nonlinearities inside a continuous-wave-pumped optical parametric oscillator. We demonstrate comb states which produce narrow-linewidth intermode beat note signals, and we verify the mode spacing uniformity of the comb at the Hz level. We also show that spectral quality of the comb can be improved by modulating the parametric gain at a frequency that corresponds to the comb mode spacing. We have reached a high average output power of over 4 W in the near-infrared region, at ~2 {\\mu}m.

  10. On-chip, self-detected THz dual-comb spectrometer

    CERN Document Server

    Rösch, Markus; Villares, Gustavo; Bosco, Lorenzo; Beck, Mattias; Faist, Jérôme

    2016-01-01

    We present a directly generated on-chip dual-comb source at THz frequencies. The multi-heterodyne beating signal of two free-running THz quantum cascade laser frequency combs is measured electrically using one of the combs as a detector, fully exploiting the unique characteristics of quantum cascade active regions. Up to 30 modes can be detected corresponding to a spectral bandwidth of 630 GHz, being the available bandwidth of the dual comb configuration. The multi-heterodyne signal is used to investigate the equidistance of the comb modes showing an accuracy of $10^{-12}$ at the carrier frequency of 2.5 THz.

  11. Fast Interrogation of Fiber Bragg Gratings with Electro-Optical Dual Optical Frequency Combs

    Directory of Open Access Journals (Sweden)

    Julio E. Posada-Roman

    2016-11-01

    Full Text Available Optical frequency combs (OFC generated by electro-optic modulation of continuous-wave lasers provide broadband coherent sources with high power per line and independent control of line spacing and the number of lines. In addition to their application in spectroscopy, they offer flexible and optimized sources for the interrogation of other sensors based on wavelength change or wavelength filtering, such as fiber Bragg grating (FBG sensors. In this paper, a dual-OFC FBG interrogation system based on a single laser and two optical-phase modulators is presented. This architecture allows for the configuration of multimode optical source parameters such as the number of modes and their position within the reflected spectrum of the FBG. A direct read-out is obtained by mapping the optical spectrum onto the radio-frequency spectrum output of the dual-comb. This interrogation scheme is proposed for measuring fast phenomena such as vibrations and ultrasounds. Results are presented for dual-comb operation under optimized control. The optical modes are mapped onto detectable tones that are multiples of 0.5 MHz around a center radiofrequency tone (40 MHz. Measurements of ultrasounds (40 kHz and 120 kHz are demonstrated with this sensing system. Ultrasounds induce dynamic strain onto the fiber, which generates changes in the reflected Bragg wavelength and, hence, modulates the amplitude of the OFC modes within the reflected spectrum. The amplitude modulation of two counterphase tones is detected to obtain a differential measurement proportional to the ultrasound signal.

  12. Electro-optic dual-comb interferometry over 40-nm bandwidth

    CERN Document Server

    Duran, Vicente; Torres-Company, Victor

    2016-01-01

    Dual-comb interferometry is a measurement technique that uses two laser frequency combs to retrieve complex spectra in a line-by-line basis. This technique can be implemented with electro-optic frequency combs, offering intrinsic mutual coherence, high acquisition speed and flexible repetition-rate operation. A challenge with the operation of this kind of frequency comb in dual-comb interferometry is its limited optical bandwidth. Here, we use coherent spectral broadening and demonstrate electro-optic dual-comb interferometry over the entire telecommunications C band (200 lines covering ~ 40 nm, measured within 10 microseconds at 100 signal-to-noise ratio per spectral line). These results offer new prospects for electro-optic dual-comb interferometry as a suitable technology for high-speed broadband metrology, for example in optical coherence tomography or coherent Raman microscopy.

  13. Dynamics of dual-polarization VCSEL-based optical frequency combs under optical injection locking.

    Science.gov (United States)

    Prior, E; de Dios, C; Criado, R; Ortsiefer, M; Meissner, P; Acedo, P

    2016-09-01

    The present experimental work studies the dynamics of dual-polarization optical frequency combs (OFCs) based on gain switching (GS) vertical-cavity surface-emitting laser (VCSEL) diodes under optical injection locking (OIL). This study presents two main results. First, we have obtained an overall comb formed by two orthogonally polarized sub-combs with comparable span and power. The overall comb shows enhanced optical span and flatness and high coherence between its modes. The second result is that we have been able to control the polarization state of the overall comb by tuning the polarization state of the injected light by locking the same single teeth of the comb. This produces an overall comb with single polarization that is parallel or orthogonal. These are novel findings that provide for the development of efficient and compact OFCs based on GS VCSEL sources with versatile polarization dynamics.

  14. A stabilized chip-scale Kerr frequency comb via a high-Q reference photonic microresonator

    CERN Document Server

    Lim, Jinkang; Vinod, Abhinav K; Mortazavian, Parastou; Yu, Mingbin; Kwong, Dim-Lee; Savchenkov, Anatoliy A; Matsko, Andrey B; Maleki, Lute; Wong, Chee Wei

    2016-01-01

    We stabilize a chip-scale Si3N4 phase-locked Kerr frequency comb via locking the pump laser to an independent stable high-Q reference microresonator and locking the comb spacing to an external microwave oscillator. In this comb, the pump laser shift induces negligible impact on the comb spacing change. This scheme is a step towards miniaturization of the stabilized Kerr comb system as the microresonator reference can potentially be integrated on-chip. Fractional instability of the optical harmonics of the stabilized comb is limited by the microwave oscillator used for comb spacing lock below 1 s averaging time and coincides with the pump laser drift in the long term.

  15. Methane Detection for Oil and Gas Production Sites Using Portable Dual-Comb Spectrometry

    Science.gov (United States)

    Coburn, Sean; Wright, Robert; Cossel, Kevin C.; Truong, Gar-Wing; Baumann, Esther; Coddington, Ian; Newbury, Nathan R.; Alden, Caroline; Ghosh, Subhomoy; Prasad, Kuldeep; Rieker, Greg B.

    2016-06-01

    Considerable uncertainty exists regarding the contribution of oil and gas operations to anthropogenic emissions of atmospheric methane. Additionally, new proposed EPA regulations on volatile organic compound (VOC) emissions from oil and gas production facilities have been expanded to include methane, making this a topic of growing importance to the oil and gas industry as well as regulators. In order to gain a better understanding of emissions, reliable techniques that enable long-term monitoring of entire production facilities are needed. Recent advances in the development of compact and robust fiber frequency combs are enabling the use of this powerful spectroscopic tool outside of the laboratory. Here we characterize and demonstrate a dual comb spectrometer (DCS) system with the potential to locate and size methane leaks from oil and gas production sites over extended periods of time. The DCS operates over kilometer scale open paths, and the path integrated methane measurements will ultimately be coupled with an atmospheric inversion utilizing local meteorology and a high resolution fluid dynamics simulation to determine leak location and also derive a leak rate. High instrument precision is needed in order to accurately perform the measurement inversion on the highly varying methane background, thus the DCS system has been fully optimized for the detection of atmospheric methane in the methane absorption region around 180-184 THz.

  16. Optical Frequency Comb Spectroscopy of Rare Earth Atoms

    Science.gov (United States)

    Swiatlowski, Jerlyn; Palm, Christopher; Joshi, Trinity; Montcrieffe, Caitlin; Jackson Kimball, Derek

    2013-05-01

    We discuss progress in our experimental program to employ optical-frequency-comb-based spectroscopy to understand the complex spectra of rare-earth atoms. We plan to carry out systematic measurements of atomic transitions in rare-earth atoms to elucidate the energy level structure and term assignment and determine presently unknown atomic state parameters. This spectroscopic information is important in view of the increasing interest in rare-earth atoms for atomic frequency standards, in astrophysical investigations of chemically peculiar stars, and in tests of fundamental physics (tests of parity and time-reversal invariance, searches for time variation of fundamental constants, etc.). We are presently studying the use of hollow cathode lamps as atomic sources for two-photon frequency comb spectroscopy. Supported by the National Science Foundation under grant PHY-0958749.

  17. High-Q Bandpass Comb Filter for Mains Interference Extraction

    Directory of Open Access Journals (Sweden)

    Neycheva T.

    2009-12-01

    Full Text Available This paper presents a simple digital high-Q bandpass comb filter for power-line (PL or other periodical interference extraction. The filter concept relies on a correlated signal average resulting in alternating constructive and destructive spectrum interference i.e. the so-called comb frequency response. The presented filter is evaluated by Matlab simulations with real ECG signal contaminated with low amplitude PL interference. The made simulations show that this filter accurately extract the PL interference. It has high-Q notches only at PL odd harmonics and is appropriate for extraction of any kind of odd harmonic interference including rectangular shape. The filter is suitable for real-time operation with popular low-cost microcontrollers.

  18. Comb-referenced laser distance interferometer for industrial nanotechnology

    Science.gov (United States)

    Jang, Yoon-Soo; Wang, Guochao; Hyun, Sangwon; Kang, Hyun Jay; Chun, Byung Jae; Kim, Young-Jin; Kim, Seung-Woo

    2016-08-01

    A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond laser for mass-production of optoelectronic devices such as flat panel displays and solar cell devices. This comb-referenced interferometer uses four different wavelengths simultaneously to enable absolute distance measurement with the capability of comprehensive evaluation of the measurement stability and uncertainty. The measurement result reveals that the stability reaches 3.4 nm for a 3.8 m distance at 1.0 s averaging, which further reduces to 0.57 nm at 100 s averaging with a fractional stability of 1.5 × 10-10. The uncertainty is estimated to be in a 10-8 level when distance is measured in air due to the inevitable ambiguity in estimating the refractive index, but it can be enhanced to a 10-10 level in vacuum.

  19. Frequency comb vernier spectroscopy in the near infrared

    CERN Document Server

    Zhu, F; Bicer, A; Strohaber, J; Kolomenskii, A A; Gohle, C; Amani, M; Schuessler, H A

    2014-01-01

    We perform femtosecond frequency comb vernier spectroscopy in the near infrared with a femtosecond Er doped fiber laser, a scanning high-finesse cavity and an InGaAs camera. By utilizing the properties of a frequency comb and a scanning high-finesse cavity such spectroscopy provides broad spectral bandwidth, high spectral resolution, and high detection sensitivity on a short time scale. We achieved an absorption sensitivity of ~8E-8 cm-1Hz-1/2 corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency range of ~5 THz. These measurements have broad applications for sensing other greenhouse gases in this fingerprint near IR region with a simple apparatus.

  20. Comb-assisted coherence transfer between laser fields

    CERN Document Server

    Sala, Tommaso; Burkart, Johannes; Marangoni, Marco; Romanini, Daniele

    2014-01-01

    Single mode laser fields oscillate at frequencies well outside the realm of electronics, but their phase/frequency fluctuations fall into the radio frequency domain, where direct manipulation is possible. Electro-optic devices have sufficient bandwidth for controlling and tailoring the dynamics of a laser field down to sub-nanosecond time scales. Thus, a laser field can be arbitrarily reshaped and in particular its phase/frequency fluctuations can be in principle removed. In practice, the time evolution of a reference laser field can be cloned to replace the fluctuations of another laser field, at a close-by frequency. In fact, it is possible to exploit a partially stabilized optical comb to perform the cloning across a large frequency gap. We realize this long-haul phase transfer by using a fibered Mach-Zehnder single-sideband modulator driven by an appropriate mix of the beat notes of the master and the slave laser with the comb.

  1. High density THz frequency comb produced by coherent synchrotron radiation

    CERN Document Server

    Tammaro, S; Roy, P; Lampin, J -F; Ducournau, G; Cuisset, A; Hindle, F; Mouret, G

    2014-01-01

    Frequency combs (FC) have radically changed the landscape of frequency metrology and high-resolution spectroscopy investigations extending tremendously the achievable resolution while increasing signal to noise ratio. Initially developed in the visible and near-IR spectral regions, the use of FC has been expanded to mid-IR, extreme ultra-violet and X-ray. Significant effort is presently dedicated to the generation of FC at THz frequencies. One solution based on converting a stabilized optical frequency comb using a photoconductive terahertz emitter, remains hampered by the low available THz power. Another approach is based on active mode locked THz quantum-cascade-lasers providing intense FC over a relatively limited spectral extension. Alternatively, here we show that dense powerful THz FC is generated over one decade of frequency by coherent synchrotron radiation (CSR). In this mode, the entire ring behaves in a similar fashion to a THz resonator wherein electron bunches emit powerful THz pulses quasi-synch...

  2. Micro-Doppler Frequency Comb Generation by Axially Rotating Scatterers

    CERN Document Server

    Kozlov, Vitali; Yankelevich, Yefim; Ginzburg, Pavel

    2016-01-01

    Electromagnetic scattering in accelerating reference frames inspires a variety of phenomena, requiring employment of general relativity for their description. While the quasi-stationary field analysis could be applied to slowly-accelerating bodies as a first-order approximation, the scattering problem remains fundamentally nonlinear in boundary conditions, giving rise to multiple frequency generation (micro-Doppler shifts). Here a frequency comb, generated by an axially rotating subwavelength (cm-range) wire and split ring resonator (SRR), is analyzed theoretically and observed experimentally by illuminating the system with a 2GHz carrier wave. Highly accurate lock in detection scheme enables factorization of the carrier and observation of more than ten peaks in a comb. The Hallen integral equation is employed for deriving the currents induced on the scatterer at rest and a set of coordinate transformations, connecting laboratory and rotating frames, is applied in order to predict the spectral positions and a...

  3. One-way quantum computing in the optical frequency comb.

    Science.gov (United States)

    Menicucci, Nicolas C; Flammia, Steven T; Pfister, Olivier

    2008-09-26

    One-way quantum computing allows any quantum algorithm to be implemented easily using just measurements. The difficult part is creating the universal resource, a cluster state, on which the measurements are made. We propose a scalable method that uses a single, multimode optical parametric oscillator (OPO). The method is very efficient and generates a continuous-variable cluster state, universal for quantum computation, with quantum information encoded in the quadratures of the optical frequency comb of the OPO.

  4. Computation of Capacitance for MEMS Comb-Drive Structures

    Institute of Scientific and Technical Information of China (English)

    LI Ming-hui; GAO Shi-qiao; LIU Hai-peng; LIANG Xin-jian

    2009-01-01

    According to the characteristics of comb-drive structures,the electrical potential field is analyzed;the model based on corner capacitor is presented and solved with the capacitance characteristic formula of nonlinear capacitor.Compared with the results of finite element method simulation,the model based on corner capacitor is more accurate than the models based on infinite parallel plate capacitor and parallel plate capacitor with edge effects,

  5. A Novel Nit Comb Concept Using Ultrasound Actuation: Preclinical Evaluation.

    Science.gov (United States)

    Burgess, Mark N; Brunton, Elizabeth R; Burgess, Ian F

    2016-01-01

    Nit combing and removal of head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), eggs is a task made more difficult because "nit combs" vary in efficiency. There is currently no evidence that the binding of the eggshell to the hair can be loosened chemically and few hair treatments improve the slip of the louse eggs along the hair. Ultrasound, applied through the teeth of a nit comb, may facilitate the flow of fluids into the gap between the hair shaft and the tube of fixative holding louse eggs in place to improve lubrication. Ultrasound alone had little effect to initiate sliding, requiring a force of 121.5 ± 23.8 millinewtons (mN) compared with 125.8 ± 18.0 mN without ultrasound, but once the egg started to move it made the process easier. In the presence of a conditioner-like creamy lotion, ultrasound reduced the Peak force required to start movement to 24.3 ± 8.8 mN from 50.4 ± 13.0 mN without ultrasound. In contrast, some head louse treatments made removal of eggs more difficult, requiring approximately twice the Peak force to initiate movement compared with dry hair in the absence of ultrasound. However, following application of ultrasound, the forces required to initiate movement increased for an essential oil product, remained the same for isopropyl myristate and cyclomethicone, and halved for 4% dimeticone lotion. Fixing the nit comb at an estimated angle of 16.5° to the direction of pull gave an optimum effect to improve the removal process when a suitable lubricant was used.

  6. Single DNA Condensation Induced by Hexammine Cobalt with Molecular Combing

    Institute of Scientific and Technical Information of China (English)

    Gao-ming Hu; Yu Lin; Shi-yong Ran; Yan-wei Wang; Guang-can Yang

    2012-01-01

    We investigated the interaction between DNA and hexammine cobalt Ⅲ [Co(NH3)6]3+ by a simple molecular combing method and dynamic light scattering.The average extension of λ-DNA-YOYO-1 complex is found to be 20.9 μm,about 30% longer than the contour length of the DNA in TE buffer (10 mmol/L Tris,1 mmol/L EDTA,pH=8.0),due to bis-intercalation of YOYO-1.A multivalent cation,hexammine cobalt,is used for DNA condensation.We find that the length of DNA-[Co(NH3)6]3+ complexes decrease from 20.9 μm to 5.9 μm as the concentration of the [Co(NH3)6]3+ vary from 0 to 3 μmol/L.This observation provides a direct visualization of single DNA condensation induced by hexammine cobalt.The results from the molecular combing studies are supported by dynamic light scattering investigation,where the average hydrodynamic radius of the DNA complex decreases from 203.8 nm to 39.26 nm under the same conditions.It shows that the molecular combing method is feasible for quantitative conformation characterization of single bio-macromolecules.

  7. Bottle microresonator broadband and low repetition rate frequency comb generator

    CERN Document Server

    Dvoyrin, V

    2016-01-01

    We propose a new type of broadband and low repetition rate frequency comb generator which has the shape of an elongated and nanoscale-shallow optical bottle microresonator created at the surface of an optical fiber. The free spectral range (FSR) of the broadband azimuthal eigenfrequency series of this resonator is the exact multiple of the FSR of the dense and narrowband axial series. The effective radius variation of the microresonator is close to a parabola with a nanoscale height which is greater or equal to lambda/2pi*n0 (here lambda is the characteristic radiation wavelength and n0 is the refractive index of the microresonator material). Overall, the microresonator possesses a broadband, small FSR, and accurately equidistant spectrum convenient for the generation of a broadband and low repetition rate optical frequency comb. It is shown that this comb can be generated by pumping with a cw laser, which radiation frequency matches a single axial eigenfrequency of the microresonator, or, alternatively, by p...

  8. Frequency-Comb Spectrum of Periodic-Patterned Signals

    Science.gov (United States)

    Steinmann, Johannes L.; Blomley, Edmund; Brosi, Miriam; Bründermann, Erik; Caselle, Michele; Hesler, Jeffrey L.; Hiller, Nicole; Kehrer, Benjamin; Mathis, Yves-Laurent; Nasse, Michael J.; Raasch, Juliane; Schedler, Manuel; Schönfeldt, Patrik; Schuh, Marcel; Schwarz, Markus; Siegel, Michael; Smale, Nigel; Weber, Marc; Müller, Anke-Susanne

    2016-10-01

    Using arbitrary periodic pulse patterns we show the enhancement of specific frequencies in a frequency comb. The envelope of a regular frequency comb originates from equally spaced, identical pulses and mimics the single pulse spectrum. We investigated spectra originating from the periodic emission of pulse trains with gaps and individual pulse heights, which are commonly observed, for example, at high-repetition-rate free electron lasers, high power lasers, and synchrotrons. The ANKA synchrotron light source was filled with defined patterns of short electron bunches generating coherent synchrotron radiation in the terahertz range. We resolved the intensities of the frequency comb around 0.258 THz using the heterodyne mixing spectroscopy with a resolution of down to 1 Hz and provide a comprehensive theoretical description. Adjusting the electron's revolution frequency, a gapless spectrum can be recorded, improving the resolution by up to 7 and 5 orders of magnitude compared to FTIR and recent heterodyne measurements, respectively. The results imply avenues to optimize and increase the signal-to-noise ratio of specific frequencies in the emitted synchrotron radiation spectrum to enable novel ultrahigh resolution spectroscopy and metrology applications from the terahertz to the x-ray region.

  9. Dual-Colored DNA Comb Polymers for Single Molecule Rheology

    Science.gov (United States)

    Mai, Danielle; Marciel, Amanda; Schroeder, Charles

    2014-03-01

    We report the synthesis and characterization of branched biopolymers for single molecule rheology. In our work, we utilize a hybrid enzymatic-synthetic approach to graft ``short'' DNA branches to ``long'' DNA backbones, thereby producing macromolecular DNA comb polymers. The branches and backbones are synthesized via polymerase chain reaction with chemically modified deoxyribonucleotides (dNTPs): ``short'' branches consist of Cy5-labeled dNTPs and a terminal azide group, and ``long'' backbones contain dibenzylcyclooctyne-modified (DBCO) dNTPs. In this way, we utilize strain-promoted, copper-free cycloaddition ``click'' reactions for facile grafting of azide-terminated branches at DBCO sites along backbones. Copper-free click reactions are bio-orthogonal and nearly quantitative when carried out under mild conditions. Moreover, comb polymers can be labeled with an intercalating dye (e.g., YOYO) for dual-color fluorescence imaging. We characterized these materials using gel electrophoresis, HPLC, and optical microscopy, with atomic force microscopy in progress. Overall, DNA combs are suitable for single molecule dynamics, and in this way, our work holds the potential to improve our understanding of topologically complex polymer melts and solutions.

  10. Coherent combs in ionization by intense and short laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Krajewska, K., E-mail: Katarzyna.Krajewska@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland); Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0299 (United States); Kamiński, J.Z., E-mail: Jerzy.Kaminski@fuw.edu.pl [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa (Poland)

    2016-03-22

    Photoionization of positive ions by a train of intense, short laser pulses is investigated within the relativistic strong field approximation, using the velocity gauge. The formation of broad peak structures in the high-energy domain of photoelectrons is observed and interpreted. The emergence of coherent photoelectron energy combs within these structures is demonstrated, and it is interpreted as the consequence of the Fraunhofer-type interference/diffraction of probability amplitudes of ionization from individual pulses comprising the train. Extensions to the coherent angular combs are also studied, and effects related to the radiation pressure are presented. - Highlights: • We develop relativistic Strong-Field Approximation for ionization by intense and short laser pulses of arbitrary spectral compositions. • We show that the consistent interpretation of results is provided by the Keldysh-type saddle point analysis of probability amplitudes. • We derive a general Fraunhofer-type interference/diffraction formula for finite train of pulses. • We study the coherent combs in photoelectron probability distributions.

  11. "Nail" and "comb" effects of cholesterol modified NIPAm oligomers on cancer targeting liposomes

    KAUST Repository

    Li, Wengang

    2014-01-01

    Thermosensitive liposomes are a promising approach to controlled release and reduced drug cytotoxicity. Low molecular weight N-isopropylacrylamide (NIPAm) oligomers (NOs) with different architectures (main chain NOs (MCNOs) and side chain NOs (SCNOs)) were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and radical polymerization and then separately used to prepare thermosensitive liposomes. A more controlled and enhanced release was observed for both NO liposomes compared to pristine ones. Two release mechanisms depending on the oligomer architecture, namely "nail" for MCNOs and "comb" for SCNOs, are proposed. In addition to thermosensitivity, the cancer targeting property of NO liposomes was achieved by further biotinylation of the delivery system. © The Royal Society of Chemistry.

  12. Sex education in Portugal.

    Science.gov (United States)

    Frade, A; Vilar, D

    1991-05-01

    The article on sex education in Portugal covers background, the educational system, the clashes of the 1960's over sex education, the Committee for the Study of Sexuality and Education (CSSE), the policies, politics and social movements during the period 1974 - 1984, the discussions in Parliament, the 1988 Reform of the Educational System, the Family Planning Association (FPA) and sex education, and the future role of the FPA. It was not until the institution of the multiparity parliamentary system in 1974 that discussing social and political changes was possible, culminating in 1984 with new legislation on abortion, family planning, and sex education. School reform came in 1987/8 with the Ministry of Education primarily responsible for curricula. The 1960's brought with it the influence of the Catholic Church. Change came in the form of progressivism among Catholics who replaced dogma with dialogue and listening. Sex education was considered as preparation for marriage, but masturbation, contraception, and prostitution were also discussed. In addition, the founder of FPA chaired the CSSE in 1971 and opened up debate on sex issues and drafted a bill to establish co-education in Portuguese schools. The revolution of 1974 brought an end to censorship and brought forth a policy of developing family planning. Changed in the Family Code gave women greater equality. UNFPA supported teacher training in non-sexist education. With human reproduction included in the natural sciences, there was still no school sex education policy and contraception was only sometimes represented in the biology curriculum. The focus of FPA was on contraception and abortion. Finally in the 1980's, the first sex education programs were developed for out-of-school youth. Even though in the 1970's there were leftists groups promoting sex education, it took leftist parliamentary power to get legislation on sex education in the schools adopted. The Ministry of Education however was pressured by the

  13. Sex determination

    OpenAIRE

    McCullagh, W. McK. H.

    2013-01-01

    How the sex of offspring is determined has puzzled philosophers and scientists for millennia. Modern science has identified both genetic and environmental factors, but the question is still not yet fully answered.

  14. Why Sex?

    DEFF Research Database (Denmark)

    Nielsen, Rasmus

    2006-01-01

    It is assumed that most organisms have sex because the resulting genetic recombination allows Darwinian selection to work better. It is now shown that in water fleas, recombination does lead to fewer deleterious mutations.......It is assumed that most organisms have sex because the resulting genetic recombination allows Darwinian selection to work better. It is now shown that in water fleas, recombination does lead to fewer deleterious mutations....

  15. Second-harmonic mode coupling in microresonator-based optical frequency comb generation

    CERN Document Server

    Xue, Xiaoxiao; Xuan, Yi; Jaramillo-Villegas, Jose A; Wang, Pei-Hsun; Leaird, Daniel E; Erkintalo, Miro; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    Microresonator-based optical frequency comb (microcomb) generation can potentially achieve ultra-compact volume and low power consumption for portable applications. The comb formation is a consequence of cascaded four-wave-mixing due to the third-order Kerr nonlinearity. Mode coupling can affect the comb self-starting and mode-locking behaviors, resulting in complex dynamics that is far from well understood. Understanding the mechanism of mode coupling in comb generation proves highly important to achieve stable and robust microcomb sources. Here, we report a nonlinear mode coupling mechanism in microresonators with simultaneous second- and third-order nonlinearities. The nonlinear dynamics governed by the third-order nonlinearity is altered by second-harmonic mode coupling. As a demonstration of this effect, second-harmonic assisted coherent comb generation is achieved in the normal dispersion region, where comb creation is prohibited in the absence of mode coupling. Since second-order nonlinearity has been ...

  16. A simple application technique of fibrin-coated collagen fleece (TachoComb) in laparoscopic surgery.

    Science.gov (United States)

    Nakajima, Kiyokazu; Yasumasa, Keigo; Endo, Shunji; Takahashi, Tsuyoshi; Kai, Yasuyuki; Nezu, Riichiro; Nishida, Toshirou

    2007-01-01

    A fibrin-coated collagen fleece (TachoComb, Nycomed, Denmark) is a powerful topical hemostatic agent, which has been aggressively used in conventional open surgery with a favorable clinical outcome. However, the use of TachoComb in laparoscopic surgery has not yet gained wide clinical acceptance, because a simple and well-functioning application system is not available. The authors have newly developed a quick, simple, and effective laparoscopic TachoComb application technique: housing a small strip of TachoComb in a rubber tube, then conveying it into the peritoneal cavity, and applying it using standard laparoscopic forceps. The repeated application of TachoComb strips is feasible and of practical value especially in laparoscopic surgery, since a small TachoComb never compromises either the application procedure or laparoscopic visualization.

  17. Direct generation of optical frequency combs in $\\chi^{(2)}$ nonlinear cavities

    CERN Document Server

    Mosca, S; Parisi, M; Maddaloni, P; Santamaria, L; De Natale, P; De Rosa, M

    2015-01-01

    Quadratic nonlinear processes are currently exploited for frequency comb transfer and extension from the visible and near infrared regions to other spectral ranges where direct comb generation cannot be accomplished. However, frequency comb generation has been directly observed in continuously-pumped quadratic nonlinear crystals placed inside an optical cavity. At the same time, an introductory theoretical description of the phenomenon has been provided, showing a remarkable analogy with the dynamics of third-order Kerr microresonators. Here, we give an overview of our recent work on $\\chi^{(2)}$ frequency comb generation. Furthermore, we generalize the preliminary three-wave spectral model to a many-mode comb and present a stability analysis of different cavity field regimes. Although at a very early stage, our work lays the groundwork for a novel class of highly efficient and versatile frequency comb synthesizers based on second-order nonlinear materials.

  18. Symmetry Breaking of Frequency Comb in Varying Normal Dispersion Fiber Ring Cavity

    CERN Document Server

    Afzal, Muhammad Imran; Lee, Yong Tak

    2016-01-01

    We build on a previously reported frequency comb of mode spacing 0.136 nm in a fiber ring cavity of varying normal dispersion [1], to generate, for the first time, a frequency comb of mode spacing 0.144 nm centered at 978.544 nm to demonstrate the symmetry-breaking. By controlling the birefringence of the optical cavity through fiber stretching and polarization control, the spacing of the comb lines increases from 0.136 nm to 0.144 nm, and this small change in mode spacing generates very different spectral symmetry-breaking in the frequency comb relative to the frequency comb of mode spacing 0.136 nm. Interestingly, non-uniform depletion of primary modes is also observed. The experimental results are an important contribution in the continuing effort of understanding the dynamics of frequency combs involving large number of modes, nontrivial nonlinear waves and deterministic chaos.

  19. Direct generation of optical frequency combs in χ(2 nonlinear cavities

    Directory of Open Access Journals (Sweden)

    Mosca Simona

    2016-06-01

    Full Text Available Quadratic nonlinear processes are currently exploited for frequency comb transfer and extension from the visible and near infrared regions to other spectral ranges where direct comb generation cannot be accomplished. However, frequency comb generation has been directly observed in continuously pumped quadratic nonlinear crystals placed inside an optical cavity. At the same time, an introductory theoretical description of the phenomenon has been provided, showing a remarkable analogy with the dynamics of third-order Kerr microresonators. Here, we give an overview of our recent work on χ(2 frequency comb generation. Furthermore, we generalize the preliminary three-wave spectral model to a many-mode comb and present a stability analysis of different cavity field regimes. Although our work is a very early stage, it lays the groundwork for a novel class of highly efficient and versatile frequency comb synthesizers based on second-order nonlinear materials.

  20. Hydrocarbon Composition of Beeswax (Apis Mellifera) Collected from Light and Dark Coloured Combs

    OpenAIRE

    Waś Ewa; Szczęsna Teresa; Rybak-Chmielewska Helena

    2014-01-01

    The hydrocarbon composition of beeswax secreted by Apis mellifera was characterised. In the studies, analyses were made of virgin beeswax (obtained from light combs, socalled „wild-built combs“) that was collected at different dates, and beeswax obtained from dark combs („brood combs“). A qualitative analysis did not show any differences in the hydrocarbon composition of beeswax originating from light and dark coloured combs. The same hydrocarbons (n-alkanes, alkenes, and dienes) were identif...

  1. Spectral linewidth preservation in parametric frequency combs seeded by dual pumps.

    Science.gov (United States)

    Tong, Zhi; Wiberg, Andreas O J; Myslivets, Evgeny; Kuo, Bill P P; Alic, Nikola; Radic, Stojan

    2012-07-30

    We demonstrate new technique for generation of programmable-pitch, wideband frequency combs with low phase noise. The comb generation was achieved using cavity-less, multistage mixer driven by two tunable continuous-wave pump seeds. The approach relies on phase-correlated continuous-wave pumps in order to cancel spectral linewidth broadening inherent to parametric comb generation. Parametric combs with over 200-nm bandwidth were obtained and characterized with respect to phase noise scaling to demonstrate linewidth preservation over 100 generated tones.

  2. Mid-infrared dual-comb spectroscopy with electro-optic modulators

    CERN Document Server

    Yan, Ming; Iwakuni, Kana; Millot, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2016-01-01

    We demonstrate dual-comb spectroscopy based on difference frequency generation of frequency-agile near-infrared frequency combs, produced with the help of electro-optic modulators. The combs have a remarkably flat intensity distribution and their positions and line spacings can be selected freely by simply dialing a knob. We record, in the 3-micron region, Doppler-limited absorption spectra with resolved comb lines within milliseconds. Precise molecular line parameters are retrieved. Our technique holds promise for fast and sensitive time-resolved studies e.g. of trace gases.

  3. Two-photon frequency comb spectroscopy of the 6s-8s transition in cesium.

    Science.gov (United States)

    Fendel, P; Bergeson, S D; Udem, Th; Hänsch, T W

    2007-03-15

    We report a new absolute frequency measurement of the Cs 6s-8s two-photon transition measured using frequency comb spectroscopy. The fractional frequency uncertainty is 5x10(-11), a factor of 6 better than previous results. The comb is derived from a stabilized picosecond laser and referenced to an octave-spanning femtosecond frequency comb. The relative merits of picosecond-based frequency combs are discussed, and it is shown that the AC Stark shift of the transition is determined by the average rather than the much larger peak intensity.

  4. Extra sex combs, chromatin, and cancer: Exploring epigenetic regulation and tumorigenesis in Drosophila

    Institute of Scientific and Technical Information of China (English)

    Can Zhang; Bo Liu; Guangyao Li; Lei Zhou

    2011-01-01

    Developmental genetic studies in Drosophila unraveled the importance of Polycomb group (PcG) and Trithorax group (TrxG) genes in controlling cellular identity.PcG and TrxG proteins form histone modifying complexes that catalyze repressive or activating histone modifications,respectively,and thus maintaining the expression status of homeotic genes.Human orthologs of PcG and TrxG genes are implicated in tumorigenesis as well as in determining the prognosis of individual cancers.Recent whole genome analyses of cancers also highlighted the importance of histone modifying proteins in controlling tumorigenesis.Comprehensive understanding of the mechanistic relationship between histone regulation and tumorigenesis holds the promise of significantly advancing our understanding and management of cancer.It is anticipated that Drosophila melanogaster,the model organism that contributed significantly to our understanding of the functional role of histone regulation in development,could also provide unique insight for our understanding of how histone dysregulation can lead to cancer.In this review,we will discuss several recent advances in this regard.

  5. Moral Pluralism and Sex Education

    Science.gov (United States)

    Corngold, Josh

    2013-01-01

    How should common schools in a liberal pluralist society approach sex education in the face of deep disagreement about sexual morality? Should they eschew sex education altogether? Should they narrow its focus to facts about biology, reproduction, and disease prevention? Should they, in addition to providing a broad palette of information about…

  6. A new Generation of Spectrometer Calibration Techniques based on Optical Frequency Combs

    CERN Document Server

    Schmidt, Piet O; Kimeswenger, Stefan

    2007-01-01

    Typical astronomical spectrographs have a resolution ranging between a few hundred to 200.000. Deconvolution and correlation techniques are being employed with a significance down to 1/1000 th of a pixel. HeAr and ThAr lamps are usually used for calibration in low and high resolution spectroscopy, respectively. Unfortunately, the emitted lines typically cover only a small fraction of the spectrometer's spectral range. Furthermore, their exact position depends strongly on environmental conditions. A problem is the strong intensity variation between different (intensity ratios {>300). In addition, the brightness of the lamps is insufficient to illuminate a spectrograph via an integrating sphere, which in turn is important to calibrate a long-slit spectrograph, as this is the only way to assure a uniform illumination of the spectrograph pupil. Laboratory precision laser spectroscopy has experienced a major advance with the development of optical frequency combs generated by pulsed femto-second lasers. These lase...

  7. Viscoelasticity and nonlinear simple shear flow behavior of an entangled asymmetric exact comb polymer solution

    KAUST Repository

    Snijkers, F.

    2016-03-31

    We report upon the characterization of the steady-state shear stresses and first normal stress differences as a function of shear rate using mechanical rheometry (both with a standard cone and plate and with a cone partitioned plate) and optical rheometry (with a flow-birefringence setup) of an entangled solution of asymmetric exact combs. The combs are polybutadienes (1,4-addition) consisting of an H-skeleton with an additional off-center branch on the backbone. We chose to investigate a solution in order to obtain reliable nonlinear shear data in overlapping dynamic regions with the two different techniques. The transient measurements obtained by cone partitioned plate indicated the appearance of overshoots in both the shear stress and the first normal stress difference during start-up shear flow. Interestingly, the overshoots in the start-up normal stress difference started to occur only at rates above the inverse stretch time of the backbone, when the stretch time of the backbone was estimated in analogy with linear chains including the effects of dynamic dilution of the branches but neglecting the effects of branch point friction, in excellent agreement with the situation for linear polymers. Flow-birefringence measurements were performed in a Couette geometry, and the extracted steady-state shear and first normal stress differences were found to agree well with the mechanical data, but were limited to relatively low rates below the inverse stretch time of the backbone. Finally, the steady-state properties were found to be in good agreement with model predictions based on a nonlinear multimode tube model developed for linear polymers when the branches are treated as solvent.

  8. Precision spectroscopy of hydrogen and femtosecond laser frequency combs.

    Science.gov (United States)

    Hänsch, T W; Alnis, J; Fendel, P; Fischer, M; Gohle, C; Herrmann, M; Holzwarth, R; Kolachevsky, N; Udem, Th; Zimmermann, M

    2005-09-15

    Precision spectroscopy of the simple hydrogen atom has inspired dramatic advances in optical frequency metrology: femtosecond laser optical frequency comb synthesizers have revolutionized the precise measurement of optical frequencies, and they provide a reliable clock mechanism for optical atomic clocks. Precision spectroscopy of the hydrogen 1S-2S two-photon resonance has reached an accuracy of 1.4 parts in 10(14), and considerable future improvements are envisioned. Such laboratory experiments are setting new limits for possible slow variations of the fine structure constant alpha and the magnetic moment of the caesium nucleus mu(Cs) in units of the Bohr magneton mu(B).

  9. Sex differences in the brain-an interplay of sex steroid hormones and sex chromosomes.

    Science.gov (United States)

    Grgurevic, Neza; Majdic, Gregor

    2016-09-01

    Although considerable progress has been made in our understanding of brain function, many questions remain unanswered. The ultimate goal of studying the brain is to understand the connection between brain structure and function and behavioural outcomes. Since sex differences in brain morphology were first observed, subsequent studies suggest different functional organization of the male and female brains in humans. Sex and gender have been identified as being a significant factor in understanding human physiology, health and disease, and the biological differences between the sexes is not limited to the gonads and secondary sexual characteristics, but also affects the structure and, more crucially, the function of the brain and other organs. Significant variability in brain structures between individuals, in addition to between the sexes, is factor that complicates the study of sex differences in the brain. In this review, we explore the current understanding of sex differences in the brain, mostly focusing on preclinical animal studies.

  10. Somatic sex determination.

    Science.gov (United States)

    Zarkower, David

    2006-02-10

    C. elegans occurs in two natural sexes, the XX hermaphrodite and the XO male, which differ extensively in anatomy, physiology, and behavior. All somatic differences between the sexes result from the differential activity of a "global" sex determination regulatory pathway. This pathway also controls X chromosome dosage compensation, which is coordinated with sex determination by the action of the three SDC proteins. The SDC proteins control somatic and germline sex by transcriptional repression of the her-1 gene. HER-1 is a secreted protein that controls a regulatory module consisting of a transmembrane receptor, TRA-2, three intracellular FEM proteins, and the zinc finger transcription factor TRA-1. The molecular workings of this regulatory module are still being elucidated. Similarity of TRA-2 to patched receptors and of TRA-1 to GLI proteins suggests that parts of the global pathway originally derived from a Hedgehog signaling pathway. TRA-1 controls all aspects of somatic sexual differentiation, presumably by regulating a variety of tissue- and cell-specific downstream targets, including the cell death regulator EGL-1 and the male sexual regulator MAB-3. Sex determination evolves rapidly, and conservation of sexual regulators between phyla has been elusive. An apparent exception involves DM domain proteins, including MAB-3, which control sexual differentiation in nematodes, arthropods, and vertebrates. Important issues needing more study include the detailed molecular mechanisms of the global pathway, the identities of additional sexual regulators acting in the global pathway and downstream of TRA-1, and the evolutionary history of the sex determination pathway. Recently developed genetic and genomic technologies and comparative studies in divergent species have begun to address these issues.

  11. PAA/PEO comb polymer effects on the rheological property evolution in concentrated cement suspensions

    Science.gov (United States)

    Kirby, Glen Harold

    We have studied the behavior of polyelectrolyte-based comb polymers in dilute solution and on the rheological property evolution of concentrated Portland cement suspensions. These species consisted of charge-neutral, poly(ethylene oxide) (PEO) "teeth" grafted onto a poly(acrylic acid) (PAA) "backbone" that contains one ionizable carboxylic acid group (COOH) per monomer unit. As a benchmark, our observations were compared to those obtained for pure cement pastes and systems containing pure polyelectrolyte species, i.e., sulfonated naphthalene formaldehyde (SNF) and poly(acrylic acid) (PAA). The behavior of PAA/PEO comb polymers, SNF, and PAA in dilute solution was studied as a function of pH in the absence and presence of mono-, di-, and trivalent counterions. Light scattering and turbidity measurements were carried out to assess their hydrodynamic radius and stability in aqueous solution, respectively. PAA experienced large conformational changes as a function of solution pH and ionic strength. Moreover, dilute solutions of ionized SNF and PAA species became unstable in the presence of multivalent counterions due to ion-bridging interactions. PAA/PEO solutions exhibited enhanced stability relative to pure polyelectrolytes under analogous conditions. The charge neutral PEO teeth shielded the underlying PAA backbone from ion-bridging interactions. In addition, such species hindered conformational changes in solution due to steric interactions between adjacent teeth. A new oscillatory shear technique was developed to probe the rheological property evolution of concentrated cement systems. The rheological property evolution of ordinary and white Portland cement systems were studied in the absence and presence of pure polyelectrolytes and PAA/PEO comb polymers with a wide range of PAA backbone molecular weight, PEO teeth molecular weight, and acid:imide ratio. Cement-PAA suspensions experienced rapid irreversible stiffening and set at 6 min due to ion

  12. Dual-frequency comb generation with differing GHz repetition rates by parallel Fabry-Perot cavity filtering of a single broadband frequency comb source

    Science.gov (United States)

    Mildner, Jutta; Meiners-Hagen, Karl; Pollinger, Florian

    2016-07-01

    We present a dual-comb-generator based on a coupled Fabry-Perot filtering cavity doublet and a single seed laser source. By filtering a commercial erbium-doped fiber-based optical frequency comb with CEO-stabilisation and 250 MHz repetition rate, two broadband coherent combs of different repetition rates in the GHz range are generated. The filtering doublet consists of two Fabry-Perot cavities with a tunable spacing and Pound-Drever-Hall stabilisation scheme. As a prerequisite for the development of such a filtering unit, we present a method to determine the actual free spectral range and transmission bandwidth of a Fabry-Perot cavity in situ. The transmitted beat signal of two diode lasers is measured as a function of their tunable frequency difference. Finally, the filtering performance and resulting beat signals of the heterodyned combs are discussed as well as the optimisation measures of the whole system.

  13. Fourier transform spectroscopy around 3 microns with a broad difference frequency comb

    CERN Document Server

    Meek, Samuel A; Guelachvili, Guy; Hänsch, Theodor W; Picqué, Nathalie

    2013-01-01

    We characterize a new mid-infrared frequency comb generator based on difference frequency generation around 3.2 microns. High power per comb mode (>10-7 W/mode) is obtained over a broad spectral span (>700 nm). The source is used for direct absorption spectroscopy with a Michelson-based Fourier transform interferometer.

  14. Gaussian-shaped Optical Frequency Comb Generation for Microwave Photonic Filtering

    CERN Document Server

    Wu, Rui; Hamidi, Ehsan; Supradeepa, V R; Song, Min Hyup; Leaird, Daniel E; Weiner, Andrew M

    2011-01-01

    Using only electro-optic modulators, we generate a 41-line 10-GHz Gaussian-shaped optical frequency comb. We use this comb to demonstrate apodized microwave photonic filters with greater than 43-dB sidelobe suppression without the need for a pulse shaper.

  15. MICROBIOLOGICAL COMPARISON BETWEEN HONEY IN JAR AND HONEY IN COMB FOR HUMAN CONSUMPTION

    Directory of Open Access Journals (Sweden)

    G. Formato

    2013-02-01

    Full Text Available The Istituto Zooprofilattico Sperimentale delle Regioni Lazio e Toscana, during August-July 2007 analyzed, for the microbial aspects, 37 samples of jar honey and 53 samples of honey in comb obtained from 37 farms of Latium Region. In the jar honey there weren’t values up to 1*103 colony-forming unit (CFU/g of bacteria mesophiles, while in the honey in comb it was not up to 2*103 CFU/g. Bacillus cereus was found in 22 samples (41,5% of honey in comb and in 18 samples (48,6% of jar honey; Clostridium perfringens was found in 6 (11,3% samples of honey in comb and in 6 samples (16,2% of jar honey; Clostridium baratii was found in 1 (1,9% sample of honey in comb and in 1 sample (2,7% of jar honey; coagulase-positive staphylococci were found in 4 (11,3% samples of honey in comb and in 4 samples (10,8% of jar honey; Clostridium sordelli was found in 2 samples (3,8% of honey in comb and in 1 sample (2,7% of jar honey. Only 2 samples of honey in comb and 1 sample of jar honey had yeasts up to 1000 CFU/g. Finally, 9 samples (24,3% of jar honey and 16 samples (30,2% of honey in jar were positives for moulds.

  16. Efficient frequency comb generation in AlGaAs-on-insulator

    DEFF Research Database (Denmark)

    Pu, Minhao; Ottaviano, Luisa; Semenova, Elizaveta;

    2016-01-01

    The combination of nonlinear and integrated photonics enables Kerr frequency comb generation in stable chip-based microresonators. Such a comb system will revolutionize applications, including multi-wavelength lasers, metrology, and spectroscopy. Aluminum gallium arsenide (AlGaAs) exhibits very h...

  17. Widely-tunable mid-infrared frequency comb source based on difference frequency generation

    NARCIS (Netherlands)

    Ruehl, A.; Gambetta, A.; Hartl, I.; Fermann, M.E.; Eikema, K.S.E.; Marangoni, M.

    2012-01-01

    We report on a mid-IR frequency comb source of unprecedented tunability covering the entire 3-10 mu m molecular fingerprint region. The system is based on difference frequency generation in a GaSe crystal pumped by a 151 MHz Yb:fiber frequency comb. The process was seeded with Raman-shifted solitons

  18. Mode-resolved frequency comb interferometry for high-accuracy long distance measurement

    NARCIS (Netherlands)

    Van den Berg, S.A.; Van Eldik, S.; Bhattacharya, N.

    2015-01-01

    Optical frequency combs have developed into powerful tools for distance metrology. In this paper we demonstrate absolute long distance measurement using a single femtosecond frequency comb laser as a multi-wavelength source. By applying a high-resolution spectrometer based on a virtually imaged phas

  19. Perovskites in the comb roof base of hornets : Their possible function

    NARCIS (Netherlands)

    Ishay, JS; Joseph, Z; Galushko, D; Ermakov, N; Bergman, DJ; Barkay, Z; Stokroos, [No Value; Van der Want, J

    2005-01-01

    On the ceiling of the Oriental hornet comb cell, there are mineral granules of poly-crystalline material known to belong to the group of perovskites. In a comb cell intended to house a worker hornet, the roof base usually carries one or several such perovskite granules containing titanium (Ti), wher

  20. Optimally Coherent Kerr Combs Generated with Crystalline Whispering Gallery Mode Resonators for Ultrahigh Capacity Fiber Communications

    Science.gov (United States)

    Pfeifle, Joerg; Coillet, Aurélien; Henriet, Rémi; Saleh, Khaldoun; Schindler, Philipp; Weimann, Claudius; Freude, Wolfgang; Balakireva, Irina V.; Larger, Laurent; Koos, Christian; Chembo, Yanne K.

    2015-03-01

    Optical Kerr frequency combs are known to be effective coherent multiwavelength sources for ultrahigh capacity fiber communications. These combs are the frequency-domain counterparts of a wide variety of spatiotemporal dissipative structures, such as cavity solitons, chaos, or Turing patterns (rolls). In this Letter, we demonstrate that Turing patterns, which correspond to the so-called primary combs in the spectral domain, are optimally coherent in the sense that for the same pump power they provide the most robust carriers for coherent data transmission in fiber communications using advanced modulation formats. Our model is based on a stochastic Lugiato-Lefever equation which accounts for laser pump frequency jitter and amplified spontaneous emission noise induced by the erbium-doped fiber amplifier. Using crystalline whispering-gallery-mode resonators with quality factor Q ˜109 for the comb generation, we show that when the noise is accounted for, the coherence of a primary comb is significantly higher than the coherence of their solitonic or chaotic counterparts for the same pump power. In order to confirm this theoretical finding, we perform an optical fiber transmission experiment using advanced modulation formats, and we show that the coherence of the primary comb is high enough to enable data transmission of up to 144 Gbit /s per comb line, the highest value achieved with a Kerr comb so far. This performance evidences that compact crystalline photonic systems have the potential to play a key role in a new generation of coherent fiber communication networks, alongside fully integrated systems.

  1. Fully stabilized mid-infrared frequency comb for high-precision molecular spectroscopy.

    Science.gov (United States)

    Vainio, Markku; Karhu, Juho

    2017-02-20

    A fully stabilized mid-infrared optical frequency comb spanning from 2.9 to 3.4 µm is described in this article. The comb is based on half-harmonic generation in a femtosecond optical parametric oscillator, which transfers the high phase coherence of a fully stabilized near-infrared Er-doped fiber laser comb to the mid-infrared region. The method is simple, as no phase-locked loops or reference lasers are needed. Precise locking of optical frequencies of the mid-infrared comb to the pump comb is experimentally verified at sub-20 mHz level, which corresponds to a fractional statistical uncertainty of 2 × 10-16 at the center frequency of the mid-infrared comb. The fully stabilized mid-infrared comb is an ideal tool for high-precision molecular spectroscopy, as well as for optical frequency metrology in the mid-infrared region, which is difficult to access with other stabilized frequency comb techniques.

  2. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    DEFF Research Database (Denmark)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.;

    2016-01-01

    Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers...

  3. Picometer-resolution dual-comb spectroscopy with a free-running fibre laser

    CERN Document Server

    Zhao, Xin; Zhao, Bofeng; Li, Cui; Pan, Yingling; Liu, Ya; Yasui, Takeshi; Zheng, Zheng

    2016-01-01

    Dual-comb spectroscopy utilizes two sets of comb lines with slightly different comb-tooth-spacings, and optical spectral information is acquired by measuring the radio-frequency beat notes between the sets of comb lines. It holds the promise as a real-time, high-resolution analytical spectroscopy tool for a range of important applications. However, the stringent requirement on the coherence between comb lines from two separate lasers and the sophisticated control system to achieve that have confined the technology to the top metrology laboratories. By replacing electronics with the law of physics in lasers, a much simpler, dual-comb spectroscopy scheme is demonstrated here using just one dual-wavelength, passively mode-locked fiber laser. Dual-comb pulses with a repetition-frequency difference determined by the intracavity dispersion are shown to be robust against common-mode cavity drifts and noises. As sufficiently low relative linewidth is maintained between two sets of comb lines, capability to resolve pi...

  4. Modeling of octave-spanning Kerr frequency combs using a generalized mean-field Lugiato-Lefever model

    OpenAIRE

    Coen, Stephane; Randle, Hamish G.; Sylvestre, Thibaut; Erkintalo, Miro

    2012-01-01

    A generalized Lugiato-Lefever equation is numerically solved with a Newton-Raphson method to model Kerr frequency combs. We obtain excellent agreement with past experiments, even for an octave-spanning comb. Simulations are much faster than with any other technique despite including more modes than ever before. Our study reveals that Kerr combs are associated with temporal cavity solitons and dispersive waves, and opens up new avenues for the understanding of Kerr comb formation.

  5. Modeling of octave-spanning Kerr frequency combs using a generalized mean-field Lugiato-Lefever model.

    Science.gov (United States)

    Coen, Stéphane; Randle, Hamish G; Sylvestre, Thibaut; Erkintalo, Miro

    2013-01-01

    A generalized Lugiato-Lefever equation is numerically solved with a Newton-Raphson method to model Kerr frequency combs. We obtain excellent agreement with past experiments, even for an octave-spanning comb. Simulations are much faster than with any other technique despite including more modes than ever before. Our study reveals that Kerr combs are associated with temporal cavity solitons and dispersive waves, and opens up new avenues for the understanding of Kerr-comb formation.

  6. Modeling of octave-spanning Kerr frequency combs using a generalized mean-field Lugiato-Lefever model

    CERN Document Server

    Coen, Stephane; Erkintalo, Miro

    2013-01-01

    We model Kerr frequency combs with a generalized Lugiato-Lefever equation combined with a Newton-Raphson solver. Results in excellent agreement with past experiments are obtained much faster than with any other technique, and we simulate for the first time to our knowledge an octave-spanning Kerr frequency comb. Our study reveals that Kerr combs are associated with temporal cavity solitons and dispersive waves, and opens up new avenues for the understanding of comb formation in ring resonators.

  7. Bathygrillotia n. g. (Cestoda: Trypanorhyncha), with redescriptions of B. rowei (Campbell, 1977) n. comb. and B. kovalevae (Palm, 1995) n. comb.

    Science.gov (United States)

    Beveridge, I; Campbell, R A

    2012-07-01

    Bathygrillotia n. g. (Cestoda: Trypanorhyncha) is erected for B. rowei (Campbell, 1977) n. comb. and B. kovalevae (Palm, 1995) n. comb. The new genus is based on the possession of two bothria, an atypical, heteroacanthous, heteromorphous armature with longitudinal files of hooks on the external surface of the tentacle associated with each principal row, each consisting of a large anterior hook followed by two smaller hooks. Bathygrillotia is allocated to the Lacistorhynchoidea Guiart, 1927 and its relationships with Grillotia Guiart, 1927 are discussed.

  8. Nonlinear Doppler - Free comb-spectroscopy in counter-propagating fields

    CERN Document Server

    Pulkin, S A; Arnautov, V; Uvarova, S V; Savel'eva, S

    2014-01-01

    The method of Doppler - free comb - spectroscopy for dipole transitions was proposed. The calculations for susceptibility spectrum for moving two-level atoms driving by strong counter propagating combs have been done. The used theoretical method based on the Fourier expansion of the components of density matrix on two rows on kv (v-velocity of group of atoms, k-projection of wave vector) and {\\Omega} (frequency between comb components). For testing of validity of this method the direct numerical integration was done. The narrow peaks with homogeneous width arise on the background of Doppler counter. The contrast of these peaks is large for largest amplitudes of comb-components. Power broadening is increasing with increase of field amplitudes. The spectral range of absorption spectrum is determined by the spectral range of comb generator and all homogeneous lines arise simultaneously. The spectral resolution is determined by the width of homogeneously-broadening lines. The physical nature of narrow peaks is in...

  9. Phase stabilization of Kerr frequency comb internally without nonlinear optical interferometry

    CERN Document Server

    Huang, S -W; Yang, J; Yu, M; Kwong, D -L; Wong, C W

    2016-01-01

    Optical frequency comb (OFC) technology has been the cornerstone for scientific breakthroughs such as precision frequency metrology, redefinition of time, extreme light-matter interaction, and attosecond sciences. While the current mode-locked laser-based OFC has had great success in extending the scientific frontier, its use in real-world applications beyond the laboratory setting remains an unsolved challenge. Microresonator-based OFCs, or Kerr frequency comb, have recently emerged as a candidate solution to the challenge because of their preferable size, weight, and power consumption (SWaP). On the other hand, the current phase stabilization technology requires either external optical references or power-demanding nonlinear processes, overturning the SWaP benefit of Kerr frequency combs. Introducing a new concept in phase control, here we report an internally phase stabilized Kerr frequency comb without the need of any optical references or nonlinear processes. We describe the comb generation analytically ...

  10. Operation of an optically coherent frequency comb outside the metrology lab

    CERN Document Server

    Sinclair, Laura C; Swann, William C; Rieker, Greg B; Hati, Archita; Iwakuni, Kana; Newbury, Nathan R

    2013-01-01

    We demonstrate a self-referenced fiber frequency comb that can operate outside the well-controlled optical laboratory. The frequency comb has residual optical linewidths of < 1 Hz, sub-radian residual optical phase noise, and residual pulse-to-pulse timing jitter of 2.4 - 5 fs, when locked to an optical reference. This fully phase-locked frequency comb has been successfully operated in a moving vehicle with 0.5 g peak accelerations and on a shaker table with a sustained 0.5 g rms integrated acceleration, while retaining its optical coherence and 5-fs-level timing jitter. This frequency comb should enable metrological measurements outside the laboratory with the precision and accuracy that are the hallmarks of comb-based systems. Work of the U.S. government, not subject to copyright

  11. Operation of an optically coherent frequency comb outside the metrology lab.

    Science.gov (United States)

    Sinclair, L C; Coddington, I; Swann, W C; Rieker, G B; Hati, A; Iwakuni, K; Newbury, N R

    2014-03-24

    We demonstrate a self-referenced fiber frequency comb that can operate outside the well-controlled optical laboratory. The frequency comb has residual optical linewidths of < 1 Hz, sub-radian residual optical phase noise, and residual pulse-to-pulse timing jitter of 2.4 - 5 fs, when locked to an optical reference. This fully phase-locked frequency comb has been successfully operated in a moving vehicle with 0.5 g peak accelerations and on a shaker table with a sustained 0.5 g rms integrated acceleration, while retaining its optical coherence and 5-fs-level timing jitter. This frequency comb should enable metrological measurements outside the laboratory with the precision and accuracy that are the hallmarks of comb-based systems.

  12. Phase-locking transition in Raman combs generated with whispering gallery mode resonators.

    Science.gov (United States)

    Lin, Guoping; Chembo, Yanne K

    2016-08-15

    We investigate the mechanisms leading to phase locking in Raman optical frequency combs generated with ultrahigh Q crystalline whispering gallery mode disk resonators. We show that several regimes can be triggered depending on the pumping conditions, such as single-frequency Raman lasing, multimode operation involving more than one family of cavity eigenmodes, and Kerr-assisted Raman frequency comb generation. The phase locking and coherence of the combs are experimentally monitored through the measurement of beat signal spectra. These phase-locked combs, which feature high coherence and wide spectral spans, are obtained with pump powers in the range of a few tens of mW. In particular, Raman frequency combs with multiple free-spectral range spacings are reported, and the measured beat signal in the microwave domain features a 3 dB linewidth smaller than 50 Hz, thereby indicating phase locking.

  13. (87)Rb-stabilized 375-MHz Yb:fiber femtosecond frequency comb.

    Science.gov (United States)

    Schratwieser, Thomas C; Balskus, Karolis; McCracken, Richard A; Farrell, Carl; Leburn, Christopher G; Zhang, Zhaowei; Lamour, Tobias P; Ferreiro, Teresa I; Marandi, Alireza; Arnold, Aidan S; Reid, Derryck T

    2014-05-01

    We report a fully stabilized 1030-nm Yb-fiber frequency comb operating at a pulse repetition frequency of 375 MHz. The comb spacing was referenced to a Rb-stabilized microwave synthesizer and the comb offset was stabilized by generating a super-continuum containing a coherent component at 780.2 nm which was heterodyned with a (87)Rb-stabilized external cavity diode laser to produce a radio-frequency beat used to actuate the carrier-envelope offset frequency of the Yb-fiber laser. The two-sample frequency deviation of the locked comb was 235 kHz for an averaging time of 50 seconds, and the comb remained locked for over 60 minutes with a root mean squared deviation of 236 kHz.

  14. A Fine-Tooth Comb to Measure the Accelerating Universe

    Science.gov (United States)

    2008-09-01

    Astronomical instruments needed to answer crucial questions, such as the search for Earth-like planets or the way the Universe expands, have come a step closer with the first demonstration at the telescope of a new calibration system for precise spectrographs. The method uses a Nobel Prize-winning technology called a 'laser frequency comb', and is published in this week's issue of Science. Uncovering the disc ESO PR Photo 26a/08 A Laser Comb for Astronomy "It looks as if we are on the way to fulfil one of astronomers' dreams," says team member Theodor Hänsch, director at the Max Planck Institute for Quantum Optics (MPQ) in Germany. Hänsch, together with John Hall, was awarded the 2005 Nobel Prize in Physics for work including the frequency comb technique. Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colours, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colours rather than distances, with an extremely accurate and fine grid. New, extremely precise spectrographs will be needed in experiments planned for the future European Extremely Large Telescope (E-ELT), which is being designed by ESO, the European Southern Observatory. These new spectrographs will need to be calibrated with even more accurate 'rulers'. In fact, they must be accurate to about one part in 30 billions - a feat equivalent to measuring the circumference of the Earth to about a millimetre! "We'll need something beyond what current technology can offer, and that's where the laser frequency comb comes in. It is

  15. Arbitrary optical frequency synthesis traced to an optical frequency comb

    Science.gov (United States)

    Cai, Zihang; Zhang, Weipeng; Yang, Honglei; Li, Yan; Wei, Haoyun

    2016-11-01

    An arbitrary optical frequency synthesizer with a broad tuning range and high frequency accuracy is presented. The system includes an external cavity diode laser (ECDL) as the output laser, an Erbium-doped optical frequency comb being a frequency reference, and a control module. The optical frequency from the synthesizer can be continuously tuned by the large-scale trans-tooth switch and the fine intra-tooth adjustment. Robust feedback control by regulating the current and PZT voltage enables the ECDL to phase-lock to the Erbium-doped optical frequency comb, therefore to keep stable frequency output. In the meanwhile, the absolute frequency of the synthesizer is determined by the repetition rate, the offset frequency and the beat frequency. All the phase lock loops in the system are traced back to a Rubidium clock. A powerful and friendly software is developed to make the operation convenient by integrating the functions of frequency setting, tuning, tracing, locking and measuring into a LabVIEW interface. The output frequency tuning span and the uncertainty of the system are evaluated as >6 THz and <3 kHz, respectively. The arbitrary optical frequency synthesizer will be a versatile tool in diverse applications, such as synthetic wavelength based absolute distance measurement and frequency-stabilized Cavity Ring-Down Spectroscopy.

  16. Lévy processes on a generalized fractal comb

    Science.gov (United States)

    Sandev, Trifce; Iomin, Alexander; Méndez, Vicenç

    2016-09-01

    Comb geometry, constituted of a backbone and fingers, is one of the most simple paradigm of a two-dimensional structure, where anomalous diffusion can be realized in the framework of Markov processes. However, the intrinsic properties of the structure can destroy this Markovian transport. These effects can be described by the memory and spatial kernels. In particular, the fractal structure of the fingers, which is controlled by the spatial kernel in both the real and the Fourier spaces, leads to the Lévy processes (Lévy flights) and superdiffusion. This generalization of the fractional diffusion is described by the Riesz space fractional derivative. In the framework of this generalized fractal comb model, Lévy processes are considered, and exact solutions for the probability distribution functions are obtained in terms of the Fox H-function for a variety of the memory kernels, and the rate of the superdiffusive spreading is studied by calculating the fractional moments. For a special form of the memory kernels, we also observed a competition between long rests and long jumps. Finally, we considered the fractal structure of the fingers controlled by a Weierstrass function, which leads to the power-law kernel in the Fourier space. This is a special case, when the second moment exists for superdiffusion in this competition between long rests and long jumps.

  17. Comb-referenced laser distance interferometer for industrial nanotechnology

    Science.gov (United States)

    Jang, Yoon-Soo; Wang, Guochao; Hyun, Sangwon; Kang, Hyun Jay; Chun, Byung Jae; Kim, Young-Jin; Kim, Seung-Woo

    2016-01-01

    A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond laser for mass-production of optoelectronic devices such as flat panel displays and solar cell devices. This comb-referenced interferometer uses four different wavelengths simultaneously to enable absolute distance measurement with the capability of comprehensive evaluation of the measurement stability and uncertainty. The measurement result reveals that the stability reaches 3.4 nm for a 3.8 m distance at 1.0 s averaging, which further reduces to 0.57 nm at 100 s averaging with a fractional stability of 1.5 × 10−10. The uncertainty is estimated to be in a 10−8 level when distance is measured in air due to the inevitable ambiguity in estimating the refractive index, but it can be enhanced to a 10−10 level in vacuum. PMID:27558016

  18. Scanning micro-resonator direct-comb absolute spectroscopy

    CERN Document Server

    Gambetta, Alessio; Gatti, Davide; Laporta, Paolo; Galzerano, Gianluca

    2016-01-01

    Direct optical frequency Comb Spectroscopy (DCS) is proving to be a fundamental tool in many areas of science and technology thanks to its unique performance in terms of ultra-broadband, high-speed detection and frequency accuracy, allowing for high-fidelity mapping of atomic and molecular energy structure. Here we present a novel DCS approach based on a scanning Fabry-Perot micro-cavity resonator (SMART) providing a simple, compact and accurate method to resolve the mode structure of an optical frequency comb. The SMART approach, while drastically reducing system complexity, allows for a straightforward absolute calibration of the optical-frequency axis with an ultimate resolution limited by the micro-resonator resonance linewidth and can be used in any spectral region from XUV to THz. An application to high-precision spectroscopy of acetylene at 1.54 um is presented, demonstrating frequency resolution as low as 20 MHz with a single-scan optical bandwidth up to 1 THz in 20-ms measurement time and a noise-equ...

  19. [Lethal sex].

    Science.gov (United States)

    Rabinerson, David; Ben-Shitrit, Gadi; Glezerman, Marek

    2011-03-01

    Asphyxiophilic sex is a form of autoerotic activity, in which the user creates mechanical means (such as hanging or bondage) in order to achieve cerebral hypoxia, which, in turn, enhances sexual, as well as orgasmic, stimulus. Failure of safety mechanisms, created by the user, may lead to instant death as a result of asphyxiation or strangulation. This kind of sexual practice is more prevalent among men than in women. In cases of death, it is difficult to relate it to the sexual practice itself. Suicide and homicide are the main differential diagnoses. Closely related derivatives of asphyxiophilic sex are anesthesiophilia (inhalation of variable volatile substances) and electrophilia (use of electric current during sexual activity)--both also intended to enhance the sexual stimulation. These forms of sexual practice are less prevalent than asphyxiophilia.

  20. Sex during Pregnancy

    Science.gov (United States)

    ... Your 1- to 2-Year-Old Sex During Pregnancy KidsHealth > For Parents > Sex During Pregnancy A A ... safe sexual relationship during pregnancy. Is Sex During Pregnancy Safe? Sex is considered safe during all stages ...

  1. When Sex Is Painful

    Science.gov (United States)

    ... AQ FREQUENTLY ASKED QUESTIONS GYNECOLOGIC PROBLEMS FAQ020 When Sex Is Painful • How common is painful sex? • What causes pain during sex? • Where is pain during sex felt? • When should ...

  2. Sex during Pregnancy

    Science.gov (United States)

    ... Old Feeding Your 1- to 2-Year-Old Sex During Pregnancy KidsHealth > For Parents > Sex During Pregnancy ... satisfying and safe sexual relationship during pregnancy. Is Sex During Pregnancy Safe? Sex is considered safe during ...

  3. Sex work among men who have sex with men and transgender women in Bogotá.

    Science.gov (United States)

    Bianchi, Fernanda T; Reisen, Carol A; Zea, Maria Cecilia; Vidal-Ortiz, Salvador; Gonzales, Felisa A; Betancourt, Fabián; Aguilar, Marcela; Poppen, Paul J

    2014-11-01

    This qualitative study examined sex work among internally displaced male and transgender female sex workers in Bogotá, Colombia. Internal displacement has occurred in Colombia as a result of decades of conflict among armed groups and has created large-scale migration from rural to urban areas. Informed by the polymorphous model of sex work, which posits that contextual conditions shape the experience of sex work, we examined three main research questions. The first dealt with how internal displacement was related to the initiation of sex work; the second concerned the effect of agency on sex worker satisfaction; and the third examined how sex work in this context was related to HIV and other risks. Life history interviews were conducted with 26 displaced individuals who had done sex work: 14 were men who have sex with men and 12 were transgender women (natal males). Findings revealed that many participants began doing sex work in the period immediately after displacement, because of a lack of money, housing, and social support. HIV risk was greater during this time due to limited knowledge of HIV and inexperience negotiating safer sex with clients. Other findings indicated that sex workers who exerted more control and choice in the circumstances of their work reported greater satisfaction. In addition, we found that although many sex workers insisted on condom use with clients, several noted that they would sometimes have unprotected sex for additional money. Specific characteristics affecting the experience of sex work among the transgender women were also discussed.

  4. A Study of the Effect of the Fringe Fields on the Electrostatic Force in Vertical Comb Drives

    Directory of Open Access Journals (Sweden)

    Else Gallagher

    2014-10-01

    Full Text Available The equation that describes the relationship between the applied voltage and the resulting electrostatic force within comb drives is often used to assist in choosing the dimensions for their design. This paper re-examines how some of these dimensions—particularly the cross-sectional dimensions of the comb teeth—affect this relationship in vertical comb drives. The electrostatic forces in several vertical comb drives fabricated for this study were measured and compared to predictions made with four different mathematical models in order to explore the amount of complexity required within a model to accurately predict the electrostatic forces in the comb drives.

  5. Wolbachia and Sex

    OpenAIRE

    Aper, Ian J.; Weglarz, Katie; Dohlen, Carol Von

    2016-01-01

    Insects with complex life cycles provide an ideal system for investigating the relationship between sex-skewing bacterial symbionts and the secondary loss of sexual reproduction. This research utilized the insect family Adelgidae, a group notorious for having peculiar and complex life cycles. In this family, some species have lost their sexual generation entirely, trapping them in asexual reproduction. Additionally, these insects are known to harbor multiple symbionts, both obligate and facul...

  6. Damages to the Black Sea, Caspian Sea and Baltic Sea by the invader comb jelly Mnemiopsis leidyi

    Directory of Open Access Journals (Sweden)

    Elif Eker Develi

    2011-10-01

    Full Text Available In the present study changes in ecosystems of the Black Sea, Caspian Sea and Baltic Sea after the invasion of ctenophore Mnemiopsis leidyi were investigated. Excessive increase in plant plankton as a result of antrophogenic eutrophication leads to a shift in mesozooplankton com¬position, which is the main food item of these comb jellies. For instance, while some mesozoo¬plankton species disappeared from the environment or substantially decreased in number, some others increased in quantity. These changes in food chain may promote the rise of jellyfishes rather than fish in the environment. In addition, decrease in planktivorous fish abundance as a consequence of overfishing also triggers the increase of newly introduced comb jellies, which were possibly introduced via ballast waters of ships, in the ecosystem. Increase in abundance of M. leidyi, which compete with planktivorous fishes (anchovy, Engraulis encrasicolus ponticus in the Black Sea, kilka, Clupeonella spp. in the Caspian Sea for their food, causes to decrease of planktivorous fish stocks which have already been vulnerable due to overfishing. Another reason for successfully adaption of M. leidyi to its new ecosystems could be linked to global warming which provides favourable temperature ranges for reproduction and growth of this ctenophore. Although there are still many debates related to possible negative effects, one of the ways to reduce harmful impacts of invaders might be the transport of natural predators of these invaders to the new ecosystems of invaders. For example, it was reported that the abun¬dance of Mnemiopsis leidyi decreased to very low levels during 1999-2004 in the Black Sea following the introduction of another comb jelly, Beroe ovata, which feed on this ctenophore.

  7. Ptychographic hyperspectral spectromicroscopy with an extreme ultraviolet high harmonic comb

    CERN Document Server

    Zhang, Bosheng; Seaberg, Matthew H; Shanblatt, Elisabeth R; Porter, Christina L; Karl,, Robert; Mancuso, Christopher A; Kapteyn, Henry C; Murnane, Margaret M; Adams, Daniel E

    2016-01-01

    We demonstrate a new scheme of spectromicroscopy in the extreme ultraviolet (EUV) spectral range, where the spectral response of the sample at different wavelengths is imaged simultaneously. It is enabled by applying ptychographical information multiplexing (PIM) to a tabletop EUV source based on high harmonic generation, where four spectrally narrow harmonics near 30 nm form a spectral comb structure. Extending PIM from previously demonstrated visible wavelengths to the EUV/X-ray wavelengths promises much higher spatial resolution and more powerful spectral contrast mechanism, making PIM an attractive spectromicroscopy method in both the microscopy and the spectroscopy aspects. Besides the sample, the multicolor EUV beam is also imaged in situ, making our method a powerful beam characterization technique. No hardware is used to separate or narrow down the wavelengths, leading to efficient use of the EUV radiation.

  8. Direct frequency comb two-photon laser cooling and trapping

    Science.gov (United States)

    Jayich, Andrew; Long, Xueping; Campbell, Wesley C.

    2016-05-01

    Generating and manipulating high energy photons for spectroscopy on electric dipole transitions of atoms and molecules with deeply bound valence electrons is difficult. Further, laser cooling of such species is even more challenging for lack of laser power. A possible solution is to drive two-photon transitions. This may alleviate the photon energy problem and open the door to cold, trapped samples of highly desirable species with tightly bound electrons. We perform a proof of principle experiment with rubidium by driving a two-photon transition with an optical frequency comb. We perform optical cooling and extend this technique to trapping, where we are able to make a magneto-optical trap in one dimension. This work is supported by the National Science Foundation CAREER program.

  9. Steering optical comb frequency by rotating polarization state

    CERN Document Server

    Zhang, Y; Zhang, X F; Zhang, L; Han, W; Guo, W; Jiang, H; Zhang, S

    2016-01-01

    Optical frequency combs, with precise control of repetition rate and carrier-envelope-offset frequency, have revolutionized many fields, such as fine optical spectroscopy, optical frequency standards, ultra-fast science research, ultra-stable microwave generation and precise ranging measurement. However, existing high bandwidth frequency control methods have small dynamic range, requiring complex hybrid control techniques. To overcome this limitation, we develop a new approach, where a home-made intra-cavity electro-optic modulator tunes polarization state of laser signal rather than only optical length of the cavity, to steer frequencies of a nonlinear-polarization-rotation mode-locked laser. By taking advantage of birefringence of the whole cavity, this approach results in not only broadband but also relative large-dynamic frequency control. Experimental results show that frequency control dynamic range increase at least one order in comparison with the traditional intra-cavity electro-optic modulator techn...

  10. High spectral purity Kerr frequency comb radio frequency photonic oscillator.

    Science.gov (United States)

    Liang, W; Eliyahu, D; Ilchenko, V S; Savchenkov, A A; Matsko, A B; Seidel, D; Maleki, L

    2015-08-11

    Femtosecond laser-based generation of radio frequency signals has produced astonishing improvements in achievable spectral purity, one of the basic features characterizing the performance of an radio frequency oscillator. Kerr frequency combs hold promise for transforming these lab-scale oscillators to chip-scale level. In this work we demonstrate a miniature 10 GHz radio frequency photonic oscillator characterized with phase noise better than -60 dBc Hz(-1) at 10 Hz, -90 dBc Hz(-1) at 100 Hz and -170 dBc Hz(-1) at 10 MHz. The frequency stability of this device, as represented by Allan deviation measurements, is at the level of 10(-10) at 1-100 s integration time-orders of magnitude better than existing radio frequency photonic devices of similar size, weight and power consumption.

  11. Coherent Raman spectro-imaging with laser frequency combs

    CERN Document Server

    Ideguchi, Takuro; Bernhardt, Birgitta; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W

    2013-01-01

    Optical spectroscopy and imaging of microscopic samples have opened up a wide range of applications throughout the physical, chemical, and biological sciences. High chemical specificity may be achieved by directly interrogating the fundamental or low-lying vibrational energy levels of the compound molecules. Amongst the available prevailing label-free techniques, coherent Raman scattering has the distinguishing features of high spatial resolution down to 200 nm and three-dimensional sectioning. However, combining fast imaging speed and identification of multiple - and possibly unexpected- compounds remains challenging: existing high spectral resolution schemes require long measurement times to achieve broad spectral spans. Here we overcome this difficulty and introduce a novel concept of coherent anti-Stokes Raman scattering (CARS) spectro-imaging with two laser frequency combs. We illustrate the power of our technique with high resolution (4 cm-1) Raman spectra spanning more than 1200 cm-1 recorded within le...

  12. Direct frequency comb measurement of OD + CO → DOCO kinetics.

    Science.gov (United States)

    Bjork, B J; Bui, T Q; Heckl, O H; Changala, P B; Spaun, B; Heu, P; Follman, D; Deutsch, C; Cole, G D; Aspelmeyer, M; Okumura, M; Ye, J

    2016-10-28

    The kinetics of the hydroxyl radical (OH) + carbon monoxide (CO) reaction, which is fundamental to both atmospheric and combustion chemistry, are complex because of the formation of the hydrocarboxyl radical (HOCO) intermediate. Despite extensive studies of this reaction, HOCO has not been observed under thermal reaction conditions. Exploiting the sensitive, broadband, and high-resolution capabilities of time-resolved cavity-enhanced direct frequency comb spectroscopy, we observed deuteroxyl radical (OD) + CO reaction kinetics and detected stabilized trans-DOCO, the deuterated analog of trans-HOCO. By simultaneously measuring the time-dependent concentrations of the trans-DOCO and OD species, we observed unambiguous low-pressure termolecular dependence of the reaction rate coefficients for N2 and CO bath gases. These results confirm the HOCO formation mechanism and quantify its yield.

  13. Direct Frequency Comb Measurement of OD + CO -> DOCO Kinetics

    CERN Document Server

    Bjork, Bryce J; Heckl, Oliver H; Changala, P Bryan; Spaun, Ben; Heu, Paula; Follman, David; Deutsch, Christoph; Cole, Garrett D; Aspelmeyer, Markus; Okumura, Mitchio; Ye, Jun

    2016-01-01

    The kinetics of the OH + CO reaction, fundamental to both atmospheric and combustion chemistry, are complex due to the formation of the HOCO intermediate. Despite extensive studies on this reaction, HOCO has not been observed at thermal reaction conditions. Exploiting the sensitive, broadband, and high-resolution capabilities of time-resolved cavity-enhanced direct frequency comb spectroscopy, we observe OD + CO reaction kinetics with the detection of stabilized trans-DOCO, the deuterated analogue of trans-HOCO, and its yield. By simultaneously measuring the time-dependent concentrations of both trans-DOCO and OD species, we observe unambiguous low-pressure termolecular dependence on the reaction rate coefficients for both N2 and CO bath gases. These results confirm the HOCO formation mechanism and quantify its yield.

  14. Comb mode filtering silver mirror cavity for spectroscopic distance measurement

    Science.gov (United States)

    Šmíd, R.; Hänsel, A.; Pravdová, L.; Sobota, J.; Číp, O.; Bhattacharya, N.

    2016-09-01

    In this work we present a design of an external optical cavity based on Fabry-Perot etalons applied to a 100 MHz Er-doped fiber optical frequency comb working at 1560 nm to increase its repetition frequency. A Fabry-Perot cavity is constructed based on a transportable cage system with two silver mirrors in plano-concave geometry including the mode-matching lenses, fiber coupled collimation package and detection unit. The system enables full 3D angle mirror tilting and x-y off axis movement as well as distance between the mirrors. We demonstrate the increase of repetition frequency by direct measurement of the beat frequency and spectrally by using the virtually imaged phased array images.

  15. X-ray harmonic comb from relativistic electron spikes

    CERN Document Server

    Pirozhkov, Alexander S; Esirkepov, Timur Zh; Ragozin, Eugene N; Faenov, Anatoly Ya; Pikuz, Tatiana A; Kawachi, Tetsuya; Sagisaka, Akito; Mori, Michiaki; Kawase, Keigo; Koga, James K; Kameshima, Takashi; Fukuda, Yuji; Chen, Liming; Daito, Izuru; Ogura, Koichi; Hayashi, Yukio; Kotaki, Hideyuki; Kiriyama, Hiromitsu; Okada, Hajime; Nishimori, Nobuyuki; Kondo, Kiminori; Kimura, Toyoaki; Tajima, Toshiki; Daido, Hiroyuki; Kato, Yoshiaki; Bulanov, Sergei V

    2010-01-01

    X-ray devices are far superior to optical ones for providing nanometre spatial and attosecond temporal resolutions. Such resolution is indispensable in biology, medicine, physics, material sciences, and their applications. A bright ultrafast coherent X-ray source is highly desirable, for example, for the diffractive imaging of individual large molecules, viruses, or cells. Here we demonstrate experimentally a new compact X-ray source involving high-order harmonics produced by a relativistic-irradiance femtosecond laser in a gas target. In our first implementation using a 9 Terawatt laser, coherent soft X-rays are emitted with a comb-like spectrum reaching the 'water window' range. The generation mechanism is robust being based on phenomena inherent in relativistic laser plasmas: self-focusing, nonlinear wave generation accompanied by electron density singularities, and collective radiation by a compact electric charge. The formation of singularities (electron density spikes) is described by the elegant mathem...

  16. Modeling Kerr frequency combs using the Lugiato-Lefever equation: a characterization of the multistable landscape

    Science.gov (United States)

    Parra-Rivas, P.; Gomila, D.; Matias, M. A.; Leo, F.; Coen, S.; Gelens, L.

    2014-05-01

    Optical frequency combs can be used to measure light frequencies and time intervals more easily and precisely than ever before, opening a large avenue for applications. Traditional frequency combs are usually associated with trains of evenly spaced, very short pulses. More recently, a new generation of comb sources has been demonstrated in compact high-Q optical microresonators with a Kerr nonlinearity pumped by continuous-wave laser light. These combs are now referred to as Kerr frequency combs and have attracted a lot of interest in the last few years. Kerr frequency combs can be modeled in a way that is strongly reminiscent of temporal cavity solitons (CSs) in nonlinear cavities. Temporal CSs have been experimentally studied in fiber resonators and their description is based on a now classical equation, the Lugiato-Lefever equation, that describes pattern formation in optical systems. In this work, we first perform a theoretical study of the correspondence between the CSs and patterns with frequency combs. It is known that the CSs appear in reversible systems that present bistability between a pattern and a homogeneous steady state through what it is called a homoclinic snaking structure. In this snaking region, single and multi-peak CSs coexist with patterns and homogeneous solutions, creating a largely multistable landscape. We study the changes of the homoclinic snaking for different parameter regimes in the Lugiato-Lefever equation and determine the stability and shape of the frequency combs through comparison with the underlying CSs and patterns. Secondly, we include third order dispersion in the system and study its effect on the multistable snaking structure. For high dispersion strengths the CS structures and the corresponding Kerr frequency combs disappear.

  17. Sex reduces genetic variation: a multidisciplinary review.

    Science.gov (United States)

    Gorelick, Root; Heng, Henry H Q

    2011-04-01

    For over a century, the paradigm has been that sex invariably increases genetic variation, despite many renowned biologists asserting that sex decreases most genetic variation. Sex is usually perceived as the source of additive genetic variance that drives eukaryotic evolution vis-à-vis adaptation and Fisher's fundamental theorem. However, evidence for sex decreasing genetic variation appears in ecology, paleontology, population genetics, and cancer biology. The common thread among many of these disciplines is that sex acts like a coarse filter, weeding out major changes, such as chromosomal rearrangements (that are almost always deleterious), but letting minor variation, such as changes at the nucleotide or gene level (that are often neutral), flow through the sexual sieve. Sex acts as a constraint on genomic and epigenetic variation, thereby limiting adaptive evolution. The diverse reasons for sex reducing genetic variation (especially at the genome level) and slowing down evolution may provide a sufficient benefit to offset the famed costs of sex.

  18. A direct frequency comb for two-photon transition spectroscopy in a cesium vapor

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi-Chi; Wu Ji-Zhou; Li Yu-Qing; Jin Li; Ma Jie; Wang Li-Rong; Zhao Yan-Ting; Xiao Lian-Tuan; Jia Suo-Tang

    2012-01-01

    A phase-stabilized femtosecond frequency comb is used to measure high-resolution spectra of two-photon transition 62S1/2-62P1/2,3/2-82S1/2 in a cesium vapor.The broadband laser output from a femtosecond frequency comb is split into counter-propagating parts,shaped in an original way,and focused into a room-temperature cesium vapor.We obtain high-resolution two-photon spectroscopy by scanning the repetition rate of femtosecond frequency comb,and through absolute frequency measurements.

  19. Spatiotemporal Lugiato-Lefever formalism for Kerr-comb generation in whispering-gallery-mode resonators

    Science.gov (United States)

    Chembo, Yanne K.; Menyuk, Curtis R.

    2013-05-01

    We demonstrate that frequency (Kerr) comb generation in whispering-gallery-mode resonators can be modeled by a variant of the Lugiato-Lefever equation that includes higher-order dispersion and nonlinearity. This spatiotemporal model allows us to explore pulse formation in which a large number of modes interact cooperatively. Pulse formation is shown to play a critical role in comb generation, and we find conditions under which single pulses (dissipative solitons) and multiple pulses (rolls) form. We show that a broadband comb is the spectral signature of a dissipative soliton, and we also show that these solitons can be obtained by using a weak anomalous dispersion and subcritical pumping.

  20. Mid-Infrared Optical Frequency Combs based on Difference Frequency Generation for Molecular Spectroscopy

    CERN Document Server

    Cruz, Flavio C; Johnson, Todd; Ycas, Gabriel; Klose, Andrew; Giorgetta, Fabrizio R; Coddington, Ian; Diddams, Scott A

    2015-01-01

    Mid-infrared femtosecond optical frequency combs were produced by difference frequency generation of the spectral components of a near-infrared comb in a 3-mm-long MgO:PPLN crystal. We observe strong pump depletion and 9.3 dB parametric gain in the 1.5 \\mu m signal, which yields powers above 500 mW (3 \\mu W/mode) in the idler with spectra covering 2.8 \\mu m to 3.5 \\mu m. Potential for broadband, high-resolution molecular spectroscopy is demonstrated by absorption spectra and interferograms obtained by heterodyning two combs.

  1. Mid-infrared dual-comb spectroscopy with an optical parametric oscillator.

    Science.gov (United States)

    Zhang, Zhaowei; Gardiner, Tom; Reid, Derryck T

    2013-08-15

    We present the first implementation of mid-infrared dual-comb spectroscopy with an optical parametric oscillator. Methane absorption spectroscopy was demonstrated with a resolution of 0.2 cm(-1) (5 GHz) at an acquisition time of ~10.4 ms over a spectral coverage at 2900-3050 cm(-1). The average power from each individual mid-infrared comb line was ~1 μW, representing a power level much greater than typical difference-frequency-generation sources. Mid-infrared dual-comb spectroscopy opens up unique opportunities to perform broadband spectroscopic measurements with high resolution, high requisition rate, and high detection sensitivity.

  2. Glucose sensor based on redox-cycling between selectively modified and unmodified combs of carbon interdigitated array nanoelectrodes.

    Science.gov (United States)

    Sharma, Deepti; Lim, Yeongjin; Lee, Yunjeong; Shin, Heungjoo

    2015-08-19

    We present a novel electrochemical glucose sensor employing an interdigitated array (IDA) of 1:1 aspect ratio carbon nanoelectrodes for the electrochemical-enzymatic redox cycling of redox species (ferricyanide/ferrocyanide) between glucose oxidase (GOx) and the two comb-shaped nanoelectrodes of the IDA. The carbon nanoelectrodes were fabricated using a simple, cost-effective, reproducible microfabrication technology known as the carbon-microelectromechanical-systems (C-MEMS) process. One comb (comb 1) of the IDA was selectively modified with GOx via the electrochemical reduction of an aryl diazonium salt, while the other comb (comb 2) remained unmodified; this facilitates electrochemically more active surface of comb 2, resulting in sensitive glucose detection. Ferricyanide is reduced to ferrocyanide by the GOx in the presence of glucose, and ferrocyanide diffuses to both combs of the IDA where it is oxidized. The limited electrochemical current collection at the surface-modified comb 1 is counterbalanced by the efficient redox cycling between the enzyme sites at comb 1 and the bare carbon surface of comb 2. Reducing the electrode-to-electrode gap between the two combs (gap = 1.9 μm) increases the diffusion flux of redox species at comb 2 hence, enhanced the sensitivity and limit of detection of the glucose sensor by ∼2.3 and ∼295 times, respectively at comb 2 compared to comb 1. The developed IDA-based glucose sensor demonstrated good amperometric response to glucose, affording two linear ranges from 0.001 to 1 mM and from 1 to 10 mM, with limits of detection of 0.4 and 61 μM and sensitivities of 823.2 and 70.0 μA mM(-1) cm(-2), respectively.

  3. Genomics of sex determination.

    Science.gov (United States)

    Zhang, Jisen; Boualem, Adnane; Bendahmane, Abdelhafid; Ming, Ray

    2014-04-01

    Sex determination is a major switch in the evolutionary history of angiosperm, resulting 11% monoecious and dioecious species. The genomic sequences of papaya sex chromosomes unveiled the molecular basis of recombination suppression in the sex determination region, and candidate genes for sex determination. Identification and analyses of sex determination genes in cucurbits and maize demonstrated conservation of sex determination mechanism in one lineage and divergence between the two systems. Epigenetic control and hormonal influence of sex determination were elucidated in both plants and animals. Intensive investigation of potential sex determination genes in model species will improve our understanding of sex determination gene network. Such network will in turn accelerate the identification of sex determination genes in dioecious species with sex chromosomes, which are burdensome due to no recombination in sex determining regions. The sex determination genes in dioecious species are crucial for understanding the origin of dioecy and sex chromosomes, particularly in their early stage of evolution.

  4. Same sex families and children

    Directory of Open Access Journals (Sweden)

    Mršević Zorica

    2009-01-01

    Full Text Available Introduction comprises the information on two main forms of same sex families, civic partnership (same sex partnership and same sex marriage. Countries and various status modalities of legal regulations are mentioned. The main part of the text is dedicated to presentation of the findings of the most recent research on various aspects regarding children of same sex partnerships. It comprises presentations grouped in four main chapters: acceptance of same sex partnerships, acceptance of legal recognition of the same sex partnerships, family plans of homosexual teenagers, and raising children within and by the same sex partners. Also the real life cases mirroring legal changes through their life destinies are presented, such is e.g. the Irish way to legalization of the same sex partnerships. In addition, a love story of two women crowned by giving birth of their four children is mentioned. Reasons against and negative reactions the author puts under the title Homophobia. In the Concluding remarks, the author presents the most recent examples of legal changes happened in Norway, Ecuador, and in the American states of California and Connecticut. It was also stated that in European countries of low birth rate, the same sex families are inevitably identified as one of demographically valuable source of creating and raising children, which is worthy to be supported, rather than being hindered without reason and discriminated. Although different than a model of heterosexual family, same sex partnerships neither are harrowing to traditional family values, nor reflex of any kind of promiscuous, antisocial behavior, avoidance of parenthood, and negation of family. Quite opposite, these families are an outcome of endeavors of homosexuals not to be deprived of family, parenthood and all of other values of stabile, monogamous, emotional/sexual socially accepted and legally recognized and regulated conventional family. .

  5. SEX EDUCATION

    Directory of Open Access Journals (Sweden)

    R N Srivastava

    1994-06-01

    Full Text Available Sex, though not everything in life, is a profoundly important aspect of human existence. It has evolved to serve more than reproductive functions; relational and recreational functions having taken precedence over procrea­tional. Sex has come to play a much wider socio-psychological function.Human sexuality is complex and multidimensional. It is subject to influence by multitude of factors often grouped as biological (e.g. genes, hormones, psychological (e.g. fear, anxiety, mood and socio-cultural (e.g. sex roles, values- religious/moral/ethical, customs. It is the interaction and interrelationship of these factors from the time of conception, through intrauterine life, infancy, childhood and adolescence, till adulthood (even later in life that determine the sexual development expressed as sexual attitudes and behaviour of the people. Learning, both social and cognitive, plays a significantly important role in such development.Sexual dysfunctions in men and women, result from factors often categorised as physical or organic and psychological; more often a combination may be involved. Experience has shown that in majority of men and women in India having sexual problems, ignorance misconceptions and prevailing myths are invariably responsible in the causation of Ihese problems. Sexual problems in individual man (e.g. erectile failure and woman (e.g. vaginismus cause anxiety, feelings of frustration, lowered self esteem and symptoms of depression. The condition may also affect the spouse; he/she, as a reaction to the problem in the partner, may develop sexual and psychosocial problems including distressed marital relationship. This may also have influence on general couple relationship, effecting adversely the quality of family life.Modern therapeutic endevours have made it possible now to offer effective therapy to most people who seek help for their sexual problems, thus preventing the consequences on couple relationship. However, there is also

  6. Tracing part-per-billion line shifts with direct-frequency-comb Vernier spectroscopy

    Science.gov (United States)

    Siciliani de Cumis, M.; Eramo, R.; Coluccelli, N.; Cassinerio, M.; Galzerano, G.; Laporta, P.; De Natale, P.; Cancio Pastor, P.

    2015-01-01

    Accurate frequency measurements of molecular transitions around 2 μ m are performed by using a direct-frequency-comb spectroscopy approach that combines an Er+ frequency-comb oscillator at 1.5 μ m , a Tm-Ho fiber amplifier, and a Fabry-Perot-filter, high-resolution dispersive spectrometer optical multiplex-detection system. This apparatus has unique performances in terms of a wide dynamic range to integrate the intensity per comb mode, which allows one to measure molecular absorption profiles with high precision. Spectroscopic information about transition frequencies and linewidths is very accurately determined. Relative frequency uncertainties of the order of a few parts in 10-9 are achieved for rovibrational transitions of the CO2 molecule around 5100 cm-1. Moreover, tiny frequency shifts due to molecular collisions and interacting laser power using direct comb spectroscopy are investigated in a systematic way.

  7. A near infrared frequency comb for Y+J band astronomical spectroscopy

    CERN Document Server

    Osterman, Steve; Diddams, Scott A; Quinlan, Franklyn; Mahadevan, Suvrath; Ramsey, Lawrence; Bender, Chad F; Terrien, Ryan; Botzer, Brandon; Sigurddson, Steinn; Redman, Stephen L

    2012-01-01

    Radial velocity (RV) surveys supported by high precision wavelength references (notably ThAr lamps and I2 cells) have successfully identified hundreds of exoplanets; however, as the search for exoplanets moves to cooler, lower mass stars, the optimum wave band for observation for these objects moves into the near infrared (NIR) and new wavelength standards are required. To address this need we are following up our successful deployment of an H band(1.45-1.7{\\mu}m) laser frequency comb based wavelength reference with a comb working in the Y and J bands (0.98-1.3{\\mu}m). This comb will be optimized for use with a 50,000 resolution NIR spectrograph such as the Penn State Habitable Zone Planet Finder. We present design and performance details of the current Y+J band comb.

  8. Photonic chip based optical frequency comb using soliton induced Cherenkov radiation

    CERN Document Server

    Brasch, Victor; Geiselmann, Michael; Lihachev, Grigoriy; Pfeiffer, Martin H P; Gorodetsky, Michael L; Kippenberg, Tobias J

    2014-01-01

    By continuous wave pumping of a dispersion engineered, planar silicon nitride microresonator, continuously circulating, sub-30fs short temporal dissipative solitons are generated, that correspond to pulses of 6 optical cycles and constitute a coherent optical frequency comb in the spectral domain. Emission of soliton induced Cherenkov radiation caused by higher order dispersion broadens the spectral bandwidth to 2/3 of an octave, sufficient for self referencing, in excellent agreement with recent theoretical predictions and the broadest coherent microresonator frequency comb generated to date. The ability to preserve coherence over a broad spectral bandwidth using soliton induced Cherenkov radiation marks a critical milestone in the development of planar optical frequency combs, enabling on one hand application in e.g. coherent communications, broadband dual comb spectroscopy and Raman spectral imaging, while on the other hand significantly relaxing dispersion requirements for broadband microresonator frequen...

  9. Comb-calibrated solar spectroscopy through a multiplexed single-mode fiber channel

    CERN Document Server

    Probst, R A; Doerr, H-P; Steinmetz, T; Kentischer, T J; Zhao, G; Hänsch, T W; Udem, Th; Holzwarth, R; Schmidt, W

    2015-01-01

    We investigate a new scheme for astronomical spectrograph calibration using the laser frequency comb at the Solar Vacuum Tower Telescope on Tenerife. Our concept is based upon a single-mode fiber channel, that simultaneously feeds the spectrograph with comb light and sunlight. This yields nearly perfect spatial mode matching between the two sources. In combination with the absolute calibration provided by the frequency comb, this method enables extremely robust and accurate spectroscopic measurements. The performance of this scheme is compared to a sequence of alternating comb and sunlight, and to absorption lines from Earth's atmosphere. We also show how the method can be used for radial-velocity detection by measuring the well-explored 5-minute oscillations averaged over the full solar disk. Our method is currently restricted to solar spectroscopy, but with further evolving fiber-injection techniques it could become an option even for faint astronomical targets.

  10. Microwave and RF Applications for Micro-resonator based Frequency Combs

    CERN Document Server

    Nguyen, Thach G; Ferrera, Marcello; Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T; Little, Brent E; Morandotti, Roberto; Mitchell, Arnan; Moss, David J

    2015-01-01

    Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is generated using a nonlinear microring resonator based on a CMOS compatible, high-index contr...

  11. TREATMENT OF 50 CASES OF MIGRAINE BY SCALP ACUPUNCTURE COMBINED WITH ELECTRO-COMB STIMULATION

    Institute of Scientific and Technical Information of China (English)

    CAO Renjun; SHI Qing

    2002-01-01

    @@ The authors of the present paper treated 50cases of migraine by scalp acupuncture plus electro-comb stimulation from 1995 to 1999 and achieved satisfactory therapeutic effects. It is reported as follows.

  12. Intracavity characterization of micro-comb generation in the single-soliton regime

    CERN Document Server

    Wang, Pei-Hsun; Xuan, Yi; Xue, Xiaoxiao; Bao, Chengying; Leaird, Daniel E; Qi, Minghao; Weiner, Andrew M

    2016-01-01

    Soliton formation in on-chip micro-comb generation balances cavity dispersion and nonlinearity and allows coherent, low-noise comb operation. We study the intracavity waveform of an on-chip microcavity soliton in a silicon nitride microresonator configured with a drop port. Whereas combs measured at the through port are accompanied by a very strong pump line which accounts for >99% of the output power, our experiments reveal that inside the microcavity, most of the power is in the soliton. Time-domain measurements performed at the drop port provide information that directly reflects the intracavity field. Data confirm a train of bright, close to bandwidth-limited pulses, accompanied by a weak continuous wave (CW) background with a small phase shift relative to the comb.

  13. Spatiotemporal Model for Kerr Comb Generation in Whispering Gallery Mode Resonators

    CERN Document Server

    Chembo, Yanne K

    2012-01-01

    We establish an exact partial differential equation to model Kerr comb generation in whispering-gallery mode resonators. This equation is a variant of the Lugiato-Lefever equation that includes higher-order dispersion and nonlinearity. This spatio-temporal model, whose main variable is the total intracavity field, is significantly more suitable than the modal expansion approach for the theoretical understanding and the numerical simulation of wide-span combs. It allows us to explore pulse formation in which a large number of modes interact cooperatively. This versatile approach can be straightforwardly extended to include higher-order dispersion, as well as other phenomena like Raman, Brillouin and Rayleigh scattering. We demonstrate for the first time that when the dispersion is anomalous, Kerr comb generation can arise as the spectral signature of dissipative cavity solitons, leading to wide-span combs with low pumping.

  14. Generation of high-frequency combs locked to atomic resonances by quantum phase modulation

    CERN Document Server

    Liu, Zuoye; Cavaletto, Stefano M; Harman, Zoltán; Keitel, Christoph H; Pfeifer, Thomas

    2013-01-01

    A general mechanism for the generation of frequency combs referenced to atomic resonances is put forward. The mechanism is based on the periodic phase control of a quantum system's dipole response. We develop an analytic description of the comb spectral structure, depending on both the atomic and the phase-control properties. We further suggest an experimental implementation of our scheme: Generating a frequency comb in the soft-x-ray spectral region, which can be realized with currently available techniques and radiation sources. The universality of this mechanism allows the generalization of frequency-comb technology to arbitrary frequencies, including the hard-x-ray regime by using reference transitions in highly charged ions.

  15. Dynamics of mode-coupling-induced microresonator frequency combs in normal dispersion

    CERN Document Server

    Jang, Jae K; Yu, Mengjie; Luke, Kevin; Ji, Xingchen; Lipson, Michal; Gaeta, Alexander L

    2016-01-01

    We experimentally and theoretically investigate the dynamics of microresonator-based frequency comb generation assisted by mode coupling in the normal group-velocity dispersion (GVD) regime. We show that mode coupling can initiate intracavity modulation instability (MI) by directly perturbing the pump-resonance mode. We also observe the formation of a low-noise comb as the pump frequency is tuned further into resonance from the MI point. We determine the phase-matching conditions that accurately predict all the essential features of the MI and comb spectra, and extend the existing analogy between mode coupling and high-order dispersion to the normal GVD regime. We discuss the applicability of our analysis to the possibility of broadband comb generation in the normal GVD regime.

  16. Ultra-broadband dual-comb spectroscopy across 1.0-1.9 {\\mu}m

    CERN Document Server

    Okubo, Sho; Inaba, Hajime; Hosaka, Kazumoto; Onae, Atsushi; Sasada, Hiroyuki; Hong, Feng-Lei

    2015-01-01

    We have carried out dual-comb spectroscopy and observed in a simultaneous acquisition a 140-THz-wide spectrum from 1.0 to 1.9 {\\mu}m using two fiber-based frequency combs phase-locked to each other. This ultra-broad wavelength bandwidth is realized by setting the difference between the repetition rates of the two combs to 7.6 Hz using the sub-Hz-linewidth fiber combs. The recorded spectrum contains five vibration-rotation bands of C${_2}$H${_2}$, CH${_4}$, and H${_2}$O at different wavelengths across the whole spectrum. The determined transition frequencies of C${_2}$H${_2}$ agree with those from the previous sub-Doppler resolution measurement of individual lines using CW lasers within 2 MHz.

  17. Sex Bias in Children.

    Science.gov (United States)

    Zalk, Sue Rosenberg; And Others

    This study investigated children's sex biased attitudes as a function of the sex, age, and race of the child as well as a geographical-SES factor. Two attitudes were measured on a 55-item questionnaire: Sex Pride (attributing positive characteristics to a child of the same sex) and Sex Prejudice (attributing negative characteristics to a child of…

  18. Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations.

    Science.gov (United States)

    Yu, W H; Kang, E T; Neoh, K G

    2005-01-04

    Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.

  19. DWDM Fiber-Wireless Access System with Centralized Optical Frequency Comb-based RF Carrier Generation

    DEFF Research Database (Denmark)

    Pang, Xiaodan; Beltrán, Marta; Sánchez, José;

    2013-01-01

    We propose and experimentally demonstrate an optical wireless DWDM system at 60 GHz with optical incoherent heterodyne up-conversion using an optical frequency comb. Multiple users with wireline and wireless services are simultaneously supported.......We propose and experimentally demonstrate an optical wireless DWDM system at 60 GHz with optical incoherent heterodyne up-conversion using an optical frequency comb. Multiple users with wireline and wireless services are simultaneously supported....

  20. Broadband Kerr frequency combs and intracavity soliton dynamics influenced by high-order cavity dispersion

    DEFF Research Database (Denmark)

    Wang, Shaofei; Guo, Hairun; Bai, Xuekun

    2014-01-01

    , showing that temporal shifts of steady-state intracavity solitons are induced by high-odd-order dispersion rather than high-even-order dispersion. The role of HOD on comb spectral envelopes is also elucidated through analyzing the intracavity dispersive wave generations. We further demonstrate...... that the spectral envelope of a broadband optical frequency comb can be engineered by using a cavity dispersion profile with multiple zero dispersion wavelengths. © 2014 Optical Society of America....

  1. Chaotic dynamics of frequency combs generated with continuously pumped nonlinear microresonators

    CERN Document Server

    Matsko, Andrey B; Savchenkov, Anatoliy A; Maleki, Lute

    2012-01-01

    We theoretically and experimentally investigate the chaotic regime of optical frequency combs generated in nonlinear ring microresonators pumped with continuous wave light. We show that the chaotic regime reveals itself, in an apparently counter-intuitive way, by a flat top symmetric envelope of the frequency spectrum, when observed by means of an optical spectrum analyzer. The comb demodulated on a fast photodiode produces a noisy radio frequency signal with an spectral width significantly exceeding the linear bandwidth of the microresonator mode.

  2. Occurrence of fungi in combs of fungus-growing termites (Isoptera: Termitidae, Macrotermitinae).

    Science.gov (United States)

    Guedegbe, Herbert J; Miambi, Edouard; Pando, Anne; Roman, Jocelyne; Houngnandan, Pascal; Rouland-Lefevre, Corinne

    2009-10-01

    Fungus-growing termites cultivate their mutualistic basidiomycete Termitomyces species on a substrate called a fungal comb. Here, the Suicide Polymerase Endonuclease Restriction (SuPER) method was adapted for the first time to a fungal study to determine the entire fungal community of fungal combs and to test whether fungi other than the symbiotic cultivar interact with termite hosts. Our molecular analyses show that although active combs are dominated by Termitomyces fungi isolated with direct Polymerase Endonuclease Restriction - Denaturing Gradient Gel Electrophoresis (PCR-DGGE), they can also harbor some filamentous fungi and yeasts only revealed by SuPER PCR-DGGE. This is the first molecular evidence of the presence of non-Termitomyces species in active combs. However, because there is no evidence for a species-specific relationship between these fungi and termites, they are mere transient guests with no specialization in the symbiosis. It is however surprising to notice that termite-associated Xylaria strains were not isolated from active combs even though they are frequently retrieved when nests are abandoned by termites. This finding highlights the implication of fungus-growing termites in the regulation of fungi occurring within the combs and also suggests that they might not have any particular evolutionary-based association with Xylaria species.

  3. Dispersing Zwitterions into Comb Polymers for Nonviral Transfection: Experiments and Molecular Simulation.

    Science.gov (United States)

    Ghobadi, Ahmadreza F; Letteri, Rachel; Parelkar, Sangram S; Zhao, Yue; Chan-Seng, Delphine; Emrick, Todd; Jayaraman, Arthi

    2016-02-08

    Polymer-based gene delivery vehicles benefit from the presence of hydrophilic groups that mitigate the inherent toxicity of polycations and that provide tunable polymer-DNA binding strength and stable complexes (polyplexes). However, hydrophilic groups screen charge, and as such can reduce cell uptake and transfection efficiency. We report the effect of embedding zwitterionic sulfobetaine (SB) groups in cationic comb polymers, using a combination of experiments and molecular simulations. Ring-opening metathesis polymerization (ROMP) produced comb polymers with tetralysine (K4) and SB pendent groups. Dynamic light scattering, zeta potential measurements, and fluorescence-based experiments, together with coarse-grained molecular dynamics simulations, described the effect of SB groups on the size, shape, surface charge, composition, and DNA binding strength of polyplexes formed using these comb polymers. Experiments and simulations showed that increasing SB composition in the comb polymers decreased polymer-DNA binding strength, while simulations indicated that the SB groups distributed throughout the polyplex. This allows polyplexes to maintain a positive surface charge and provide high levels of gene expression in live cells. Notably, comb polymers with nearly 50 mol % SB form polyplexes that exhibit positive surface charge similarly as polyplexes formed from purely cationic comb polymers, indicating the ability to introduce an appreciable amount of SB functionality without screening surface charge. This integrated simulation-experimental study demonstrates the effectiveness of incorporating zwitterions in polyplexes, while guiding the design of new and effective gene delivery vectors.

  4. Hydrocarbon Composition of Beeswax (Apis Mellifera Collected from Light and Dark Coloured Combs

    Directory of Open Access Journals (Sweden)

    Waś Ewa

    2014-12-01

    Full Text Available The hydrocarbon composition of beeswax secreted by Apis mellifera was characterised. In the studies, analyses were made of virgin beeswax (obtained from light combs, socalled „wild-built combs“ that was collected at different dates, and beeswax obtained from dark combs („brood combs“. A qualitative analysis did not show any differences in the hydrocarbon composition of beeswax originating from light and dark coloured combs. The same hydrocarbons (n-alkanes, alkenes, and dienes were identified in virgin beeswax and beeswax collected from brood combs. However, the studies showed differences in the content of n-alkanes in the beeswax obtained from light and dark coloured combs. In comparison to the virgin beeswax, the beeswax obtained from dark combs had higher content of the total n-alkanes, higher total contents of even-numbered alkanes and odd-numbered alkanes, and higher contents of certain alkanes. Furthermore, it has been found that the hydrocarbon composition of beeswax did not depend on the collection period.

  5. Reference-free, high-resolution measurement method of timing jitter spectra of optical frequency combs

    Science.gov (United States)

    Kwon, Dohyeon; Jeon, Chan-Gi; Shin, Junho; Heo, Myoung-Sun; Park, Sang Eon; Song, Youjian; Kim, Jungwon

    2017-01-01

    Timing jitter is one of the most important properties of femtosecond mode-locked lasers and optical frequency combs. Accurate measurement of timing jitter power spectral density (PSD) is a critical prerequisite for optimizing overall noise performance and further advancing comb applications both in the time and frequency domains. Commonly used jitter measurement methods require a reference mode-locked laser with timing jitter similar to or lower than that of the laser-under-test, which is a demanding requirement for many laser laboratories, and/or have limited measurement resolution. Here we show a high-resolution and reference-source-free measurement method of timing jitter spectra of optical frequency combs using an optical fibre delay line and optical carrier interference. The demonstrated method works well for both mode-locked oscillators and supercontinua, with 2 × 10−9 fs2/Hz (equivalent to −174 dBc/Hz at 10-GHz carrier frequency) measurement noise floor. The demonstrated method can serve as a simple and powerful characterization tool for timing jitter PSDs of various comb sources including mode-locked oscillators, supercontinua and recently emerging Kerr-frequency combs; the jitter measurement results enabled by our method will provide new insights for understanding and optimizing timing noise in such comb sources. PMID:28102352

  6. Sex-linked dominant

    Science.gov (United States)

    Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant ... can be either an autosomal chromosome or a sex chromosome. It also depends on whether the trait ...

  7. Influence of Wheat-Milled Products and Their Additive Blends on Pasta Dough Rheological, Microstructure, and Product Quality Characteristics

    Directory of Open Access Journals (Sweden)

    B. Dhiraj

    2013-01-01

    Full Text Available This study is aimed to assess the suitability of T. aestivum wheat milled products and its combinations with T. durum semolina with additives such as ascorbic acid, vital gluten and HPMC (Hydroxypropyl methyl cellulose for pasta processing quality characteristics such as pasta dough rheology, microstructure, cooking quality, and sensory evaluation. Rheological studies showed maximum dough stability in Comb1 (T. aestivum wheat flour and semolina. Colour and cooking quality of Comb2 (T. durum semolina and T. aestivum wheat flour and Comb3 (T. aestivum wheat semolina and T. durum semolina were comparable with control. Pasting results indicated that T. aestivum semolina gave the lowest onset gelatinization temperature (66.9°C but the highest peak viscosity (1.053 BU. Starch release was maximum in Comb1 (53.45% when compared with control (44.9% as also proved by microstructure studies. Firmness was seen to be slightly high in Comb3 (2.430 N when compared with control (2.304 N, and sensory evaluations were also in the acceptable range for the same. The present study concludes that Comb3 comprising 50% T. durum semolina and 50% T. aestivum refined wheat flour with additives would be optimal alternate for 100% T. durum semolina for production of financially viable pasta.

  8. Dual-etalon, cavity-ring-down, frequency comb spectroscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Strecker, Kevin E.; Chandler, David W.

    2010-10-01

    The 'dual etalon frequency comb spectrometer' is a novel low cost spectometer with limited moving parts. A broad band light source (pulsed laser, LED, lamp ...) is split into two beam paths. One travels through an etalon and a sample gas, while the second arm is just an etalon cavity, and the two beams are recombined onto a single detector. If the free spectral ranges (FSR) of the two cavities are not identical, the intensity pattern at the detector with consist of a series of heterodyne frequencies. Each mode out of the sample arm etalon with have a unique frequency in RF (radio-frequency) range, where modern electronics can easily record the signals. By monitoring these RF beat frequencies we can then determine when an optical frequencies is absorbed. The resolution is set by the FSR of the cavity, typically 10 MHz, with a bandwidth up to 100s of cm{sup -1}. In this report, the new spectrometer is described in detail and demonstration experiments on Iodine absorption are carried out. Further we discuss powerful potential next generation steps to developing this into a point sensor for monitoring combustion by-products, environmental pollutants, and warfare agents.

  9. Harnessing high-dimensional hyperentanglement through a biphoton frequency comb

    CERN Document Server

    Xie, Zhenda; Shrestha, Sajan; Xu, XinAn; Liang, Junlin; Gong, Yan-Xiao; Bienfang, Joshua C; Restelli, Alessandro; Shapiro, Jeffrey H; Wong, Franco N C; Wong, Chee Wei

    2015-01-01

    Quantum entanglement is a fundamental resource for secure information processing and communications, where hyperentanglement or high-dimensional entanglement has been separately proposed towards high data capacity and error resilience. The continuous-variable nature of the energy-time entanglement makes it an ideal candidate for efficient high-dimensional coding with minimal limitations. Here we demonstrate the first simultaneous high-dimensional hyperentanglement using a biphoton frequency comb to harness the full potential in both energy and time domain. The long-postulated Hong-Ou-Mandel quantum revival is exhibited, with up to 19 time-bins, 96.5% visibilities. We further witness the high-dimensional energy-time entanglement through Franson revivals, which is observed periodically at integer time-bins, with 97.8% visibility. This qudit state is observed to simultaneously violate the generalized Bell inequality by up to 10.95 deviations while observing recurrent Clauser-Horne-Shimony-Holt S-parameters up to...

  10. Quantum dot mode locked lasers for coherent frequency comb generation

    Science.gov (United States)

    Martinez, A.; Calò, C.; Rosales, R.; Watts, R. T.; Merghem, K.; Accard, A.; Lelarge, F.; Barry, L. P.; Ramdane, A.

    2013-12-01

    Monolithic semiconductor passively mode locked lasers (MLL) are very attractive components for many applications including high bit rate telecommunications, microwave photonics and instrumentation. Owing to the three dimensional confinement of the charge carriers, quantum dot based mode-locked lasers have been the subject of intense investigations because of their improved performance compared to conventional material systems. Indeed, the inhomogeneous gain broadening and the ultrafast absorption recovery dynamics are an asset for short pulse generation. Moreover, the weak coupling of amplified spontaneous emission with the guided modes plus low loss waveguide leads to low timing jitter. Our work concentrates on InAs quantum dash nanostructures grown on InP substrate, intended for applications in the 1.55 μm telecom window. InAs/InP quantum dash based lasers, in particular, have demonstrated efficient mode locking in single section Fabry-Perot configurations. The flat optical spectrum of about 12 nm, combined with the narrow RF beat note linewidth of about 10 kHz make them a promising technology for optical frequency comb generation. Coherence between spectral modes was assessed by means of spectral phase measurements. The parabolic spectral phase profile indicates that short pulses can be obtained provided the intracavity dispersion can be compensated by inserting a single mode fiber.

  11. Food additives

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/002435.htm Food additives To use the sharing features on this page, please enable JavaScript. Food additives are substances that become part of a food ...

  12. Absolute-frequency measurements with a stabilized near-infrared opticalfrequency comb from a Cr:forsterite laser

    OpenAIRE

    Corwin, Kristan L.; Thomann, Isabell; Dennis, Tasshi; Fox, Richard W.; Swann, William; Curtis, Anne; Oates, Chris W.; Wilpers, Guido; Bartels, Albrecht; Gilbert, Sarah L.; Hollberg, Leo; Newbury, Nathan R.; Diddams, Scott A.; Nicholson, Jeffrey W.; Yan, Man F.

    2004-01-01

    A frequency comb is generated with a chromium-doped forsterite femtosecond laser, spectrally broadened in a dispersion-shifted highly nonlinear fiber, and stabilized. The resultant evenly spaced comb of frequencies ranges from 1.1 to beyond 1.8,um. The frequency comb was referenced simultaneously to the National Institute of Standards and Technology's optical frequency standard based on neutral calcium and to a hydrogen maser that is calibrated by a cesium atomic fountain clock. With this com...

  13. SYNTHESIS OF AMPHIPHILIC COMB-SHAPED COPOLYMERS USED FOR SURFACE MODIFICATION OF PVDF MEMBRANES

    Institute of Scientific and Technical Information of China (English)

    Jian-hua Li; You-yi Xu; Jian-hua Wang; Chun-hui Du

    2009-01-01

    The synthesis of a novel amphiphilic comb-shaped copolymer consisting of a main chain of styrene-(N-(4-hydroxyphenyl) maleimide) (SHMI) copolymer and poly(ethylene glycol) methyl ether methacrylate (PEGMA) side groups was achieved by atom transfer radical polymerization (ATRP). The amphiphilic copolymers were characterized by ~1H-NMR, Fourier transform infrared (FTIR) spectroscopy and gel permeation chromatography (GPC). From thermogravimetric analysis (TGA), the decomposition temperature of SHMI-g-PEGMA is lower than that of SHMI, and the graft ratio of PEGMA in the SHMI is 18.6%. The experimental results of solubilities showed that SHMI, SHMI-Br and SHMI-g-PEGMA had excellent solubility in polar solvents, such as DMF, DMSO and NMP. SHMI-g-PEGMA had higher solubilities in H_2O and methanol, while lower solubility in CHCl_3 than SHMI and SHMI-Br. PVDF blend membranes were prepared via the standard immersion precipitation phase inversion process, using amphiphilic SHMI-g-PEGMA copolymer as additives. The morphology and hydrophilicity of the blend membrane surfaces were characterized by SEM and water contact angle. It is demonstrated that the blend membranes display enhanced hydrophilicity compared to unmodified PVDF membranes. Finally, the permeation and anti-fouling properties were investigated. The result shows that amphiphilic SHMI-g-PEGMA copolymer increases the permeatability and anti-fouling property of PVDF membranes greatly.

  14. Generation of a coherent near-infrared Kerr frequency comb in a monolithic microresonator with normal GVD

    CERN Document Server

    Liang, Wei; Ilchenko, Vladimir S; Eliyahu, Danny; Seidel, David; Matsko, Andrey B; Maleki, Lute

    2014-01-01

    We demonstrate experimentally, and explain theoretically, generation of a wide, fundamentally phase locked Kerr frequency comb in a nonlinear resonator with a normal group velocity dispersion. A magnesium fluoride whispering gallery resonator characterized with 10 GHz free spectral range and pumped either at 780 nm or 795 nm is used in the experiment. The envelope of the observed frequency comb differs significantly from the Kerr frequency comb spectra reported previously. We show via numerical simulation that, while the frequency comb does not correspond to generation of short optical pulses, the relative phases of the generated harmonics are fixed.

  15. 梳状波导结构中石墨烯表面等离子体的传播性质∗%Propagation prop erties of the graphene surface plasmon in comb-like waveguide

    Institute of Scientific and Technical Information of China (English)

    乔文涛; 龚健; 张利伟; 王勤; 王国东; 廉书鹏; 陈鹏辉; 孟威威

    2015-01-01

    We investigate theoretically the electromagnetic propagation properties of graphene plasmons in a comb-like dielectric-graphene-dielectric (DGD) waveguide. The effective index of surface plasmon mode supported by the waveg-uide is analysed numerically, and it is found that the effective refractive index increases with the refractive index of the dielectric and decreases with Fermi energy of the graphene sheet. For a comb-like DGD waveguide with a finite branch length, a subwavelength plasmon filter can be formed by Fabry-Perot resonance caused by the reflection of the guided mode at the branch. The central frequencies of the gaps can be changed by varying the length of the branch, Fermi energy, the refractive index of the dielectric and the layer number of graphene sheets. The analytic and simulated result reveals that a novel nanometric plasmonic filter in such a comb-shaped waveguide can be realized with ultracompact size in a length of a few hundred nanometers in the mid-infrared range. We find that the frequencies of the stopband increase with Fermi energy and the layer number of graphene sheets, while will they decrease nonlinearly with the length of the branch and the refractive index of the dielectric. In addition, the width of the gap can be increased with the number of comb branches. Such electromagnetic properties could be utilized to develop ultracompact photonic filters for high integration.

  16. Heteromorphic sex chromosomes: navigating meiosis without a homologous partner.

    Science.gov (United States)

    Checchi, Paula M; Engebrecht, Joanne

    2011-09-01

    Accurate chromosome segregation during meiosis relies on homology between the maternal and paternal chromosomes. Yet by definition, sex chromosomes of the heterogametic sex lack a homologous partner. Recent studies in a number of systems have shed light on the unique meiotic behavior of heteromorphic sex chromosomes, and highlight both the commonalities and differences in divergent species. During meiotic prophase, the homology-dependent processes of pairing, synapsis, and recombination have been modified in many different ways to ensure segregation of heteromorphic sex chromosomes at the first meiotic division. Additionally, an almost universal feature of heteromorphic sex chromosomes during meiosis is transcriptional silencing, or meiotic sex chromosome inactivation, an essential process proposed to prevent expression of genes deleterious to meiosis in the heterogametic sex as well as to shield unpaired sex chromosomes from recognition by meiotic checkpoints. Comparative analyses of the meiotic behavior of sex chromosomes in nematodes, mammals, and birds reveal important conserved features as well as provide insight into sex chromosome evolution.

  17. A novel approach for generating flat optical frequency comb based on externally injected gain-switching distributed feedback semiconductor laser

    Science.gov (United States)

    Zhu, Huatao; Wang, Rong; Pu, Tao; Xiang, Peng; Zheng, Jilin; Fang, Tao

    2017-02-01

    In this paper, a novel approach for generating flat optical frequency comb (OFC) based on externally injected gain-switched distributed feedback (DFB) semiconductor laser is proposed and experimentally demonstrated. In the proposed system, the flatness, the number of OFC spectral lines, and the spectral line to background noise ratio can be tuned to their optimized values by adjusting the current of the modulation signal, the injection ratio and the detuning frequency. Since the frequency of the modulation signal decides the frequency spacing of the output spectral lines, OFC spectral lines of different spacing can be achieved. In the experiment, 10 spectral lines with 1.5 dB power variation are demonstrated to verify the proposed approach. In addition, the expansion of the spectral line is investigated.

  18. Stretching and imaging of single DNA chains on a hydrophobic polymer surface made of amphiphilic alternating comb-copolymer.

    Science.gov (United States)

    Liu, Rongrong; Wong, Sheau Tyug; Lau, Peggy Pei Zhi; Tomczak, Nikodem

    2014-02-26

    Functionalization of amine derivatized glass slides with a poly(maleic anhydride)-based comb-copolymer to facilitate stretching, aligning, and imaging of individual dsDNA chains is presented. The polymer-coated surface is hydrophobic due to the presence of the long alkyl side chains along the polymer backbone. The surface is also characterized by low roughness and a globular morphology. Stretched and aligned bacteriophage λ-DNA chains were obtained using a robust method based on stretching by a receding water meniscus at pH 7.8 without the need for small droplet volumes or precoating the surface with additional layers of (bio)molecules. Although the dye to DNA base pairs ratio did not influence substantially the stretching length distributions, a clear peak at stretching lengths close to the contour length of the dsDNA is visible at larger staining ratios.

  19. Simulation of Electrostatic Actuation in Interdigitated Comb Drive MEMS Resonator for Energy Harvester Applications

    Science.gov (United States)

    Sathya, S.; Pavithra, M.; Muruganand, S.

    2016-09-01

    This paper presents an actuation mechanism based on the interdigitated comb drive MEMS resonator. The important role of that device is to establish MEMS resonators for the second order systems. Comb drive model is one of the basic model which uses the principle of electrostatic and force can be generated for the capacitive sensors. This work is done by overlapping movable and fixed comb fingers which produces an energy. The specific range of the polyimide material properties of young's modulus of 3.1GPa and density of 1300 Kg/m3. Results are shown in the structural domain performance of a lateral motion which corresponds to the applying voltage between the interdigitated comb fingers. It has laterally driven about 40pm with driving voltage. Also the resonance frequency 24Hz and 15Hz with high quality factors are depending on the spring length 260pm and 360pm and structure thickness of 2μm and 5 μm. Here Finite element method (FEM) is used to simulate the various physics scenario and it is designed as two dimensional structure multiphysics domain. The prototype of comb drive MEMS resonator has been suitable for energy harvesting system applications.

  20. Toward a Broadband Astro-comb: Effects of Nonlinear Spectral Broadening in Optical Fibers

    CERN Document Server

    Chang, Guoqing; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X

    2010-01-01

    We propose and analyze a new approach to generate a broadband astro-comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber. Numerical modeling shows that cascaded four-wave-mixing dramatically degrades the input comb's side-mode suppression and causes side-mode amplitude asymmetry. These two detrimental effects can systematically shift the center-of-gravity of astro-comb spectral lines as measured by an astrophysical spectrograph with resolution \\approx100,000; and thus lead to wavelength calibration inaccuracy and instability. Our simulations indicate that this performance penalty, as a result of nonlinear spectral broadening, can be compensated by using a filtering cavity configured for double-pass. As an explicit example, we present a design based on an Yb-fiber source comb (with 1 GHz repetition rate) that is filtered by double-passing through a low finesse cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm, SF6-glass photonic crystal fiber. Spann...

  1. Cascaded half-harmonic generation of femtosecond frequency combs in mid-IR

    CERN Document Server

    Marandi, Alireza; Jankowski, Marc; Byer, Robert L

    2015-01-01

    For the growing demand of frequency combs in mid-infrared (mid-IR), known as the "molecular fingerprint" region of the spectrum [1], down conversion of near-IR frequency combs through half- harmonic generation offers numerous benefits including high conversion efficiency and intrinsic phase and frequency locking to the near-IR pump [2]. Hence cascaded half-harmonic generation promises a simple path towards extending the wavelength coverage of stable frequency combs. Here, we report a two-octave down-conversion of a frequency comb around 1 {\\mu}m through cascaded half-harmonic generation with ~64% efficiency in the first stage, and ~18% in the second stage. We obtain broadband intrinsically-frequency-locked frequency combs with ~50-fs pulses at ~2 {\\mu}m and ~110-fs pulses at ~4 {\\mu}m. These results indicate the effectiveness of half-harmonic generation as a universal tool for efficient phase- and frequency-locked down-conversion, which can be beneficial for numerous applications requiring long-wavelength coh...

  2. Recent developments in fiber-based optical frequency comb and its applications

    Science.gov (United States)

    Xia, Wei; Chen, Xuzong

    2016-04-01

    Fiber-based optical frequency combs, characterized by compact configuration and outstanding optical properties, have been developed into state-of-the-art precision instruments which are no longer used just for optical frequency metrology, but for a number of applications, including optical clocks, attosecond science, exoplanet searches, medical diagnostics, physicochemical processes control and advanced manufacturing. This short perspective presents some of the milestones and highlights in the evolution of fiber-based optical frequency combs and the technical revolution that are brought by them for a wide range of applications. Along the way, both the challenges and opportunities in the future development of the fiber-based optical frequency comb technology have been described as well.

  3. Surpassing the Path-Limited Resolution of a Fourier Transform Spectrometer with Frequency Combs

    CERN Document Server

    Maslowski, Piotr; Johansson, Alexandra C; Khodabakhsh, Amir; Kowzan, Grzegorz; Rutkowski, Lucile; Mills, Andrew A; Mohr, Christian; Jiang, Jie; Fermann, Martin E; Foltynowicz, Aleksandra

    2015-01-01

    Fourier transform spectroscopy based on incoherent light sources is a well-established tool in research fields from molecular spectroscopy and atmospheric monitoring to material science and biophysics. It provides broadband molecular spectra and information about the molecular structure and composition of absorptive media. However, the spectral resolution is fundamentally limited by the maximum delay range ({\\Delta}$_{max}$) of the interferometer, so acquisition of high-resolution spectra implies long measurement times and large instrument size. We overcome this limit by combining the Fourier transform spectrometer with an optical frequency comb and measuring the intensities of individual comb lines by precisely matching the {\\Delta}$_{max}$ to the comb line spacing. This allows measurements of absorption lines narrower than the nominal (optical path-limited) resolution without ringing effects from the instrumental lineshape and reduces the acquisition time and interferometer length by orders of magnitude.

  4. Nearly octave-spanning frequency comb generation in AlN-on-sapphire microresonators

    CERN Document Server

    Liu, Xianwen; Xiong, Bing; Wang, Lai; Wang, Jian; Han, Yanjun; Hao, Zhibiao; Li, Hongtao; Luo, Yi; Yan, Jianchang; Wei, Tongbo; Zhang, Yun; Wang, Junxi

    2016-01-01

    We report a nearly octave-spanning optical frequency comb generation with a coverage of $\\sim$1000 nm in continuous-wave pumped aluminum nitride (AlN)-on-sapphire microring resonators. Thanks to optimized device design and fabrication process, high-quality-factor AlN microrings with high cavity finesse and low insertion loss are demonstrated. By tailoring the cavity dimension, a broadband anomalous dispersion is secured to facilitate the frequency comb generation. Blue-shifted dispersive wave emission as well as stimulated Raman scattering is observed, which helps extend the comb spectrum coverage. Our work suggests that AlN-on-sapphire can be an appealing platform for integrated nonlinear optics.

  5. A novel frequency control scheme for comb-referenced sensitive difference-frequency-generation spectroscopy.

    Science.gov (United States)

    Iwakuni, Kana; Okubo, Sho; Sasada, Hiroyuki

    2013-06-17

    We present a novel scheme of frequency scan and wavelength modulation of a difference-frequency-generation source for comb-referenced sensitive spectroscopy. While the pump and signal frequencies are phase-locked to an optical frequency comb (OFC), the offset frequency between the signal wave and the nearest comb tooth is modulated to apply a wavelength-modulation technique, and the idler wave frequency is repeatedly swept for signal accumulation by changing the repetition frequency of the OFC. The spectrometer is applied to absolute frequency measurement of weak hyperfine-resolved rovibration transitions of the ν(1) band of CH(3)I, and the uncertainty in frequency determination is reduced by one order of magnitude in compared with that of the previous work published in Optics Express 20, 9178-9186 (2012).

  6. Mach-zehnder based optical marker/comb generator for streak camera calibration

    Science.gov (United States)

    Miller, Edward Kirk

    2015-03-03

    This disclosure is directed to a method and apparatus for generating marker and comb indicia in an optical environment using a Mach-Zehnder (M-Z) modulator. High speed recording devices are configured to record image or other data defining a high speed event. To calibrate and establish time reference, the markers or combs are indicia which serve as timing pulses (markers) or a constant-frequency train of optical pulses (comb) to be imaged on a streak camera for accurate time based calibration and time reference. The system includes a camera, an optic signal generator which provides an optic signal to an M-Z modulator and biasing and modulation signal generators configured to provide input to the M-Z modulator. An optical reference signal is provided to the M-Z modulator. The M-Z modulator modulates the reference signal to a higher frequency optical signal which is output through a fiber coupled link to the streak camera.

  7. Optical under-sampling by using a broadband optical comb with a high average power.

    Science.gov (United States)

    Sherman, Alexander; Horowitz, Moshe; Zach, Shlomo

    2014-06-30

    We demonstrate a new method to improve the performance of photonic assisted analog to digital converters (ADCs) that are based on frequency down-conversion obtained by optical under-sampling. The under-sampling is performed by multiplying the radio frequency signal by ultra-low jitter broadband phase-locked optical comb. The comb wave intensity has a smooth periodic function in the time domain rather than a train of short pulses that is currently used in most photonic assisted ADCs. Hence, the signal energy at the photo-detector output can be increased and the signal to noise ratio of the system might be improved without decreasing its bandwidth. We have experimentally demonstrated a system for electro-optical under-sampling with a 6-dB bandwidth of 38.5 GHz and a spur free dynamic range of 99 dB/Hz(2/3) for a signal with a carrier frequency of 35.8 GHz, compared with 94 dB/Hz(2/3) for a signal at 6.2 GHz that was obtained in the same system when a pulsed optical source was used. The optical comb was generated by mixing signals from two dielectric resonator oscillators in a Mach-Zehnder modulator. The comb spacing is equal to 4 GHz and its bandwidth was greater than 48 GHz. The temporal jitter of the comb measured by integrating the phase noise in a frequency region of 10 kHz to 10 MHz around comb frequencies of 16 and 20 GHz was only about 15 and 11 fs, respectively.

  8. Length and refractive index measurement by Fourier transform interferometry and frequency comb spectroscopy

    Science.gov (United States)

    Balling, Petr; Mašika, Pavel; Křen, Petr; Doležal, Miroslav

    2012-09-01

    In this paper we describe the progress we have made in our simultaneous length measurement and the femtosecond comb interferometric spectroscopy in a conventional arrangement with a moving mirror. Scanning and detection over an interval longer than the distance between two consecutive pulses of the frequency comb allow for a spectral resolution of the individual frequency modes of the comb. Precise knowledge of comb mode frequency leads to a precise estimation of the spectral characteristics of inspected phenomena. Using the pulse train of the frequency comb allows for measurement with highly unbalanced lengths of interferometer arms, i.e. an absolute long distance measurement. Further, we present a non-contact (double sided) method of measurement of the length/thickness of plane-parallel objects (gauge blocks, glass samples) by combining the fs comb (white light) with single frequency laser interferometry. The position of a fringe packet is evaluated by estimating the stationary phase position for any wavelength in the spectral band used. The repeatability of this position estimation is a few nanometres regardless of whether dispersion of the arms is compensated (transform limited fringe packet ˜10 fringes FWHM) or highly different (fringe packet stretched to >200 fringes FWHM). The measurement of steel gauge block by this method was compared with the standard method, and deviation (+13 ± 12) nm for gauge blocks (2 to 100) mm was found. The measurement of low reflecting ceramic gauges or clear glass samples was also tested. In the case of glass, it becomes possible to measure simultaneously both the thickness and the refractive index (and dispersion) of flat samples.

  9. A stabilized 18 GHz chip-scale optical frequency comb at 2.8x10-16 relative inaccuracy

    CERN Document Server

    Huang, S -W; Yu, M; McGuyer, B H; Kwong, D -L; Zelevinsky, T; Wong, C W

    2015-01-01

    Optical frequency combs, coherent light sources that connect optical frequencies with microwave oscillations, have become the enabling tool for precision spectroscopy, optical clockwork and attosecond physics over the past decades. Current benchmark systems are self-referenced femtosecond mode-locked lasers, but four-wave-mixing in high-Q resonators have emerged as alternative platforms. Here we report the generation and full stabilization of CMOS-compatible optical frequency combs. The spiral microcomb's two degrees-of-freedom, one of the comb line and the native 18 GHz comb spacing, are first simultaneously phase-locked to known optical and microwave references. Second, with pump power control, active comb spacing stabilization improves the long-term stability by six orders-of-magnitude, reaching an instrument-limited 3.6 mHz/sqrt(t) residual instability. Third, referencing thirty-three of the nitride frequency comb lines against a fiber comb, we demonstrate the comb tooth-to-tooth frequency relative inaccu...

  10. Bacterial communities in termite fungus combs are comprised of consistent gut deposits and contributions from the environment

    DEFF Research Database (Denmark)

    Otani, Saria; Hansen, Lars H.; Sørensen, Søren Johannes;

    2016-01-01

    time. These shifts did not appear to be due to changes in the taxa present, but rather due to differences in the relative abundances of primarily gut-derived bacteria within fungus combs. This indicates that fungus comb microbiotas are largely termite species-specific due to major contributions from...

  11. Additivity dominance

    Directory of Open Access Journals (Sweden)

    Paul Rozin

    2009-10-01

    Full Text Available Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned. In support of this, skim milk (with major subtraction of fat is rated as more natural than whole milk with a small amount of natural vitamin D added. It is also noted that ``additives'' is a common word, with a synonym reported by a native speaker in 17 of 18 languages, whereas ``subtractive'' is lexicalized in only 1 of the 18 languages. We consider reasons for additivity dominance, relating it to omission bias, feature positive bias, and notions of purity.

  12. Experimental observation of coherent cavity soliton frequency combs in silica microspheres

    CERN Document Server

    Webb, Karen E; Coen, Stéphane; Murdoch, Stuart G

    2016-01-01

    We report on the experimental observation of coherent cavity soliton frequency combs in silica microspheres. Specifically, we demonstrate that careful alignment of the microsphere relative to the coupling fiber taper allows for the suppression of higher-order spatial modes, reducing mode interactions and enabling soliton formation. Our measurements show that the temporal cavity solitons have sub-100-fs durations, exhibit considerable Raman self-frequency shift, and generally come in groups of three or four, occasionally with equidistant spacing in the time domain. RF amplitude noise measurements and spectral interferometry confirm the high coherence of the observed soliton frequency combs, and numerical simulations show good agreement with experiments.

  13. Spin-wave storage using chirped control fields in atomic frequency comb-based quantum memory

    OpenAIRE

    2010-01-01

    It has been shown that an inhomogeneously broadened optical transition shaped into an atomic frequency comb can store a large number of temporal modes of the electromagnetic field at the single photon level without the need to increase the optical depth of the storage material. The readout of light modes is made efficient thanks to the rephasing of the optical-wavelength coherence similarly to photon echo-type techniques and the re-emission time is given by the comb structure. For on-demand r...

  14. Demonstration of atomic frequency comb memory for light with spin-wave storage

    OpenAIRE

    2009-01-01

    We present a light-storage experiment in a praseodymium-doped crystal where the light is mapped onto an inhomogeneously broadened optical transition shaped into an atomic frequency comb. After absorption of the light the optical excitation is converted into a spin-wave excitation by a control pulse. A second control pulse reads the memory (on-demand) by reconverting the spin-wave excitation to an optical one, where the comb structure causes a photon-echo type rephasing of the dipole moments a...

  15. Optical Nyquist channel generation using a comb-based tunable optical tapped-delay-line.

    Science.gov (United States)

    Ziyadi, Morteza; Chitgarha, Mohammad Reza; Mohajerin-Ariaei, Amirhossein; Khaleghi, Salman; Almaiman, Ahmed; Cao, Yinwen; Willner, Moshe J; Tur, Moshe; Paraschis, Loukas; Langrock, Carsten; Fejer, Martin M; Touch, Joseph D; Willner, Alan E

    2014-12-01

    We demonstrate optical Nyquist channel generation based on a comb-based optical tapped-delay-line. The frequency lines of an optical frequency comb are used as the taps of the optical tapped-delay-line to perform a finite-impulse response (FIR) filter function. A single optical nonlinear element is utilized to multiplex the taps and form the Nyquist signal. The tunablity of the approach over the baud rate and modulation format is shown. Optical signal-to-noise ratio penalty of 2.8 dB is measured for the 11-tap Nyquist filtering of 32-Gbaud QPSK signal.

  16. Monte Carlo simulation for the micellar behavior of amphiphilic comb-like copolymers

    Institute of Scientific and Technical Information of China (English)

    冯莺; 隋家贤; 赵季若; 陈欣方

    2000-01-01

    Micellar behaviors in 2D and 3D lattice models for amphiphilic comb-like copolymers in water phase and in water/oil mixtures were simulated. A dynamical algorithm together with chain reptation movements was used in the simulation. Three-dimension displaying program was pro-grammed and free energy was estimated by Monte Carlo technigue. The results demonstrate that reduced interaction energy influences morphological structures of micelle and emulsion ??stems greatly; 3D simulation showing can display more direct images of morphological structures; the amphiphilic comb-like polymers with a hydrophobic main chain and hydrophilic side chains have lower energy in water than in oil.

  17. Generation and Photonic Guidance of Multi-Octave Optical-Frequency Combs

    DEFF Research Database (Denmark)

    Couny, F.; Benabid, F.; Roberts, John;

    2007-01-01

    crystal fiber. The waveguidance results not from a photonic band gap but from the inhibited coupling between the core and cladding modes. The spectrum consists of up to 45 high-order Stokes and anti-Stokes lines and is generated by driving the confined gas with a single, moderately powerful (10-kilowatt......Ultrabroad coherent comb-like optical spectra spanning several octaves are a chief ingredient in the emerging field of attoscience. We demonstrate generation and guidance of a three-octave spectral comb, spanning wavelengths from 325 to 2300 nanometers, in a hydrogen-filled hollow-core photonic...

  18. Self-Frequency Shift of Cavity Soliton in Kerr Frequency Comb

    CERN Document Server

    Zhang, Lin; Kimerling, Lionel C; Michel, Jurgen

    2014-01-01

    We show that the ultrashort cavity soliton in octave-spanning Kerr frequency comb generation exhibits striking self-adaptiveness and robustness to external perturbations, resulting in a novel frequency shifting/cancellation mechanism and gigantic dispersive wave generation in response to the strong frequency dependence of Kerr nonlinearity, Raman scattering, chromatic dispersion, and cavity Q. These observations open up a great avenue towards versatile manipulation of nonlinear soliton dynamics, flexible spectrum engineering of mode-locked Kerr frequency combs, and highly efficient frequency translation of optical waves.

  19. Synthesis and characterization of star-comb polybutadiene and poly(ethylene-co-butene)

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel star-comb polybutadiene(SC-PB) was synthesized with n-butyllithium(n-BuLi) as initiator,epoxidized star liquid polybutadiene(ESPB) as coupling agent,cyclohexane as solvent by living anionic polymerization and grafting-onto technology. The SC-PB was subsequently hydrogenated by homogeneous catalysis(catalytic hydrogenation using nickel naphthenate/ triisobutyl aluminum),to transform the SC-PB into the corresponding star-comb poly(ethylene-co-butene)(SC-PEB).The SC-PB was characterized by SEC-TALLS...

  20. Self-organization in Kerr-cavity-soliton formation in parametric frequency combs

    Science.gov (United States)

    Wen, Y. Henry; Lamont, Michael R. E.; Strogatz, Steven H.; Gaeta, Alexander L.

    2016-12-01

    We show that self-organization and synchronization underlie Kerr-cavity-soliton formation in parametric frequency combs. By reducing the Lugiato-Lefever equation to a set of phase equations, we find that self-organization arises from a two-stage process via pump-degenerate and pump-nondegenerate four-wave mixing. The reduced phase equations are akin to the Kuramoto model of coupled oscillators and intuitively explain the origin of the pump phase offset, predict antisymmetrization of the intracavity field before phase synchronization, and clarify the role of chaos in Kerr-cavity-soliton formation in parametric combs.

  1. Coherent combs of anti-matter from nonlinear electron-positron pair creation

    CERN Document Server

    Krajewska, K

    2014-01-01

    Electron-positron pair creation in collisions of a modulated laser pulse with a high-energy photon (nonlinear Breit-Wheeler process) is studied by means of strong-field quantum electrodynamics. It is shown that the driving pulse modulations lead to appearance of comb structures in the energy spectra of produced positrons (electrons). It is demonstrated that these combs result from a coherent enhancement of probability amplitudes of pair creation from different modulations of the laser pulse. Thus, resembling the Young-double slit experiment for anti-matter (matter) waves.

  2. Green, red and IR frequency comb line generation from single IR pump in AlN microring resonator

    CERN Document Server

    Jung, Hojoong; Guo, Xiang; Fischer, Debra; Tang, Hong X

    2014-01-01

    On-chip frequency comb generations enable compact broadband sources for spectroscopic sensing and precision spectroscopy. Recent microcomb studies focus on infrared spectral regime and have difficulty in accessing visible regime. Here, we demonstrate comb-like visible frequency line generation through second, third harmonic, and sum frequency conversion of a Kerr comb within a high Q aluminum nitride microring resonator pumped by a single telecom laser. The strong power enhancement, in conjunction with the unique combination of Pockels and Kerr optical nonlinearity of aluminum nitride, leads to cascaded frequency conversions in the visible spectrum. High-resolution spectroscopic study of the visible frequency lines indicates matched free spectrum range over all the bands. This frequency doubling and tripling effect in a single microcomb structure offers great potential for comb spectroscopy and self-referencing comb.

  3. Bacterial communities in termite fungus combs are comprised of consistent gut deposits and contributions from the environment

    DEFF Research Database (Denmark)

    Otani, Saria; Hansen, Lars Hestbjerg; Sørensen, Søren J

    2016-01-01

    Fungus-growing termites (subfamily Macrotermitinae) mix plant forage with asexual spores of their plant-degrading fungal symbiont Termitomyces in their guts and deposit this blend in fungus comb structures, within which the plant matter is degraded. As Termitomyces grows, it produces nodules...... with asexual spores, which the termites feed on. Since all comb material passes through termite guts, it is inevitable that gut bacteria are also deposited in the comb, but it has remained unknown which bacteria are deposited and whether distinct comb bacterial communities are sustained. Using high......-throughput sequencing of the 16S rRNA gene, we explored the bacterial community compositions of 33 fungus comb samples from four termite species (three genera) collected at four South African geographic locations in 2011 and 2013. We identified 33 bacterial phyla, with Firmicutes, Bacteroidetes, Proteobacteria...

  4. Multifrequency sources of quantum correlated photon pairs on-chip: a path toward integrated Quantum Frequency Combs

    Science.gov (United States)

    Caspani, Lucia; Reimer, Christian; Kues, Michael; Roztocki, Piotr; Clerici, Matteo; Wetzel, Benjamin; Jestin, Yoann; Ferrera, Marcello; Peccianti, Marco; Pasquazi, Alessia; Razzari, Luca; Little, Brent E.; Chu, Sai T.; Moss, David J.; Morandotti, Roberto

    2016-06-01

    Recent developments in quantum photonics have initiated the process of bringing photonic-quantumbased systems out-of-the-lab and into real-world applications. As an example, devices to enable the exchange of a cryptographic key secured by the laws of quantum mechanics are already commercially available. In order to further boost this process, the next step is to transfer the results achieved by means of bulky and expensive setups into miniaturized and affordable devices. Integrated quantum photonics is exactly addressing this issue. In this paper, we briefly review the most recent advancements in the generation of quantum states of light on-chip. In particular, we focus on optical microcavities, as they can offer a solution to the problem of low efficiency that is characteristic of the materials typically used in integrated platforms. In addition, we show that specifically designed microcavities can also offer further advantages, such as compatibility with telecom standards (for exploiting existing fibre networks) and quantum memories (necessary to extend the communication distance), as well as giving a longitudinal multimode character for larger information transfer and processing. This last property (i.e., the increased dimensionality of the photon quantum state) is achieved through the ability to generate multiple photon pairs on a frequency comb, corresponding to the microcavity resonances. Further achievements include the possibility of fully exploiting the polarization degree of freedom, even for integrated devices. These results pave the way for the generation of integrated quantum frequency combs that, in turn, may find important applications toward the realization of a compact quantum-computing platform.

  5. Bacterial communities in termite fungus combs are comprised of consistent gut deposits and contributions from the environment.

    Science.gov (United States)

    Otani, Saria; Hansen, Lars H; Sørensen, Søren J; Poulsen, Michael

    2016-01-01

    Fungus-growing termites (subfamily Macrotermitinae) mix plant forage with asexual spores of their plant-degrading fungal symbiont Termitomyces in their guts and deposit this blend in fungus comb structures, within which the plant matter is degraded. As Termitomyces grows, it produces nodules with asexual spores, which the termites feed on. Since all comb material passes through termite guts, it is inevitable that gut bacteria are also deposited in the comb, but it has remained unknown which bacteria are deposited and whether distinct comb bacterial communities are sustained. Using high-throughput sequencing of the 16S rRNA gene, we explored the bacterial community compositions of 33 fungus comb samples from four termite species (three genera) collected at four South African geographic locations in 2011 and 2013. We identified 33 bacterial phyla, with Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Candidate division TM7 jointly accounting for 92 % of the reads. Analyses of gut microbiotas from 25 of the 33 colonies showed that dominant fungus comb taxa originate from the termite gut. While gut communities were consistent between 2011 and 2013, comb community compositions shifted over time. These shifts did not appear to be due to changes in the taxa present, but rather due to differences in the relative abundances of primarily gut-derived bacteria within fungus combs. This indicates that fungus comb microbiotas are largely termite species-specific due to major contributions from gut deposits and also that environment affects which gut bacteria dominate comb communities at a given point in time.

  6. Why we should consider sex (and study sex differences) in addiction research.

    Science.gov (United States)

    Sanchis-Segura, Carla; Becker, Jill B

    2016-09-01

    Among mammals, every cell has a biological sex, and the sex of an individual pervades its body and brain. In this review, we describe the processes through which mammals become phenotypically male or female by organizational and activational influences of genes and hormones throughout development. We emphasized that the molecular and cellular changes triggered by sex chromosomes and steroid hormones may generate sex differences in overt physiological functions and behavior, but they may alternatively promote end-point convergences between males and females. Clinical and pre-clinical evidences suggest that sex and gender differences modulate drug consumption as well as of the transition towards drug-promoted pathological states such as dependence and addiction. Additionally, sex differences in drug pharmacokinetics and pharmacodynamics will also influence dependence and addiction as well as side effects of drugs. These effects will further interact with socially gendered factors to result in sex differences in the access to, engagement in and efficacy of any therapeutic attempt. Finally, we maintain that 'sex sameness' is as important as 'sex differences' when building a complete understanding of biology for both males and females and provide a framework with which to classify and guide investigation into the mechanisms mediating sex differences and sex sameness.

  7. Potlining Additives

    Energy Technology Data Exchange (ETDEWEB)

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  8. Additivity dominance

    OpenAIRE

    2009-01-01

    Judgments of naturalness of foods tend to be more influenced by the process history of a food, rather than its actual constituents. Two types of processing of a ``natural'' food are to add something or to remove something. We report in this study, based on a large random sample of individuals from six countries (France, Germany, Italy, Switzerland, UK and USA) that additives are considered defining features of what makes a food not natural, whereas ``subtractives'' are almost never mentioned....

  9. Modeling ovarian follicle growth in commercial and heritage Single Comb White Leghorn hens.

    Science.gov (United States)

    McLeod, E S; Jalal, M A; Zuidhof, M J

    2014-11-01

    Approximately 84% of the energy in chicken eggs resides in the yolk. A robust model of ovarian follicle development is therefore valuable for estimating energy requirements of laying hens. The current experiment was designed to model the growth of ovarian follicles in 32-wk-old modern commercial line (CL) and unselected heritage line (HL) Single Comb White Leghorn hens. The volume of yolk deposited daily during the rapid growth phase (RGP) was estimated using a double dye technique. For 21 d, 8 CL and 8 HL hens were fed capsules (no. 1) containing Sudan IV (red) and Sudan Black dyes on alternate days. An additional 8 control CL hens were fed empty capsules. Eggs were collected, and the daily volume of yolk deposited was estimated. Significant differences are reported where P hens, respectively. Duration of the RGP was shorter (7.35 d) in the CL hens compared with the HL hens (7.95 d). A nonlinear Lomolino model described follicular weight, which varied between strains over d 2 to 9 of follicle development; at each day during development, follicle weights were higher where RGP were shorter. The volume of yolk deposited for the 8 d preceding oviposition in CL was 0.17, 0.28, 0.43, 0.99, 1.84, 2.47, 2.82, 2.86, and 2.51 cm(3); and in HL was 0.17, 0.33, 0.72, 1.40, 2.15, 2.46, 2.48, 2.32, and 1.93 cm(3). The HL had a higher rate of yolk deposition 7 to 5 d before oviposition, and CL had a higher rate of yolk deposition 3 to 1 d before oviposition with no significant difference between lines on d 4 before oviposition. Although growth patterns differed, there were no differences among lines in final follicle weights (14.1 g) or retained energy (42.4 kcal).

  10. Insects and sex

    OpenAIRE

    Beukeboom, Leo

    2005-01-01

    Most organisms reproduce sexually, but the evolution of sexual reproduction is not yet well understood. Sexual reproduction leads to new variation and adaptations to the environment, but sex is also costly. Some insects reproduce without sex through parthenogenesis or paedogenesis. Almost all sexual insects have two separate sexes, male and female. There are many mechanisms of sex determination. Most insects have male heterogamety (males XY, females XX). Female heterogamety and haplodiploidy ...

  11. Female Sex Offenders: Public Awareness and Attributions.

    Science.gov (United States)

    Cain, Calli M; Anderson, Amy L

    2016-09-16

    Traditional gender roles, sex scripts, and the way female sex offenders are portrayed in the media may lead to misconceptions about who can commit sexual offenses. Sexual crimes by women may go unnoticed or unreported if there is a general lack of awareness that females commit these crimes. Data from the 2012 Nebraska Annual Social Indicators Survey were used to determine whether the public perceives women as capable sex offenders and the perceived causes of female sex offending. The traditional focus on male sex offenders by researchers, media, and politicians, in addition to gender stereotypes, introduces the possibility of group differences (e.g., between men and women) in perceptions of female sex offenders. Consequently, two secondary analyses were conducted that tested for group differences in both the public's perception of whether females can commit sex offenses and the explanations selected for why females sexually offend. The findings suggest that the public does perceive women as capable sex offenders, although there were group differences in the causal attributions for female sex offending.

  12. Sex Differences in Cognition

    Science.gov (United States)

    Fairweather, Hugh

    1976-01-01

    Sex differences in cognitive skills, grouped into motor, spatial and linguistic areas, are assessed in relation to current theories of cerebral lateralization. Few convincing sex differences exist, either overall, or in interactions with functional localization. Qualifying criteria include age, birth order, culture, sex of experimenter and sex…

  13. Sex differences in the HPA axis.

    Science.gov (United States)

    Goel, Nirupa; Workman, Joanna L; Lee, Tiffany T; Innala, Leyla; Viau, Victor

    2014-07-01

    The hypothalamic-pituitary-adrenal (HPA) axis is a major component of the systems that respond to stress, by coordinating the neuroendocrine and autonomic responses. Tightly controlled regulation of HPA responses is critical for maintaining mental and physical health, as hyper- and hypo-activity have been linked to disease states. A long history of research has revealed sex differences in numerous components of the HPA stress system and its responses, which may partially form the basis for sex disparities in disease development. Despite this, many studies use male subjects exclusively, while fewer reports involve females or provide direct sex comparisons. The purpose of this article is to present sex comparisons in the functional and molecular aspects of the HPA axis, through various phases of activity, including basal, acute stress, and chronic stress conditions. The HPA axis in females initiates more rapidly and produces a greater output of stress hormones. This review focuses on the interactions between the gonadal hormone system and the HPA axis as the key mediators of these sex differences, whereby androgens increase and estrogens decrease HPA activity in adulthood. In addition to the effects of gonadal hormones on the adult response, morphological impacts of hormone exposure during development are also involved in mediating sex differences. Additional systems impinging on the HPA axis that contribute to sex differences include the monoamine neurotransmitters norepinephrine and serotonin. Diverse signals originating from the brain and periphery are integrated to determine the level of HPA axis activity, and these signals are, in many cases, sex-specific.

  14. Look closer: Time sequence photography of Roosters Comb in the Sheep Creek Range, Nevada

    Science.gov (United States)

    The importance of understanding natural landscape changes is key in properly determining rangeland ecology. Time sequence photography allows a snapshot of a landscape to be documented and enables the ability to compare natural changes overtime. Photographs of Roosters Comb were taken from the same v...

  15. Hybrid Optical Comb Filter with Multi-Port Fiber Coupler for DWDM Optical Network

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Optical comb filters based on multi-port fused fiber couplers are proposed and numerically analyzed, 3-arm MZI composed by 1×7 fiber splitter and 3×3 fiber coupler, and 2-stage cascaded FIR type MZI interleave filter.

  16. Full phase stabilization of a Yb:fiber femtosecond frequency comb via high-bandwidth transducers

    NARCIS (Netherlands)

    Benko, C.; Ruehl, A.; Martin, M.J.; Eikema, K.S.E.; Fermann, M.E.; Hartl, I.; Ye, J.

    2012-01-01

    We present full phase stabilization of an amplified Yb:fiber femtosecond frequency comb using an intracavity electro-optic modulator and an acousto-optic modulator. These transducers provide high servo bandwidths of 580 kHz and 250 kHz for f(rep) and f(ceo), producing a robust and low phase noise fi

  17. Controlled deposition and combing of DNA across lithographically defined patterns on silicon

    DEFF Research Database (Denmark)

    Nazari, Zeniab Esmail; Gurevich, Leonid

    2013-01-01

    We have developed a new procedure for efficient combing of DNA on a silicon substrate, which allows reproducible deposition and alignment of DNA molecules across lithographically defined patterns. The technique involves surface modification of Si/SiO2 substrates with a hydrophobic silane by using...

  18. Fibers and combs: weaving a portable frequency reference in the near-IR

    Science.gov (United States)

    Corwin, Kristan

    2009-05-01

    Ten years after the advent of femtosecond optical frequency combs, they are now used for many applications. Here, we use near infrared combs to characterize and develop portable frequency references based on gas-filled hollow optical fibers. We explore the accuracy and stability of saturated absorption features in acetylene gas confined inside both 10 micron core diameter photonic bandgap fibers and ˜60 micron core diameter kagome-structured photonic crystal fibers. A cw fiber laser referenced to these features has resulted in stabilities of ˜10-11 in 1 s, competitive with iodine-stabilized HeNe lasers. Most of these studies have been performed using a femtosecond fiber laser that relies on a carbon nanotube saturable absorber. However, we have also explored Cr:forsterite femtosecond lasers with intracavity prisms, which reveal dramatic narrowing of the carrier-envelope offset beat when a knife edge is inserted in the cavity. Such observations and subsequent noise dynamics studies will lead to a better understanding of noise in these solid state combs, making Cr:forsterite laser combs more competitive for spectroscopy and other applications.

  19. High-accuracy long-distance measurements in air with a frequency comb laser

    NARCIS (Netherlands)

    Cui, M.; Zeitouny, M.G.; Bhattacharya, N.; Van den Berg, S.A.; Urbach, H.P.; Braat, J.J.M.

    2009-01-01

    We experimentally demonstrate that a femtosecond frequency comb laser can be applied as a tool for longdistance measurement in air. Our method is based on the measurement of cross correlation between individual pulses in a Michelson interferometer. From the position of the correlation functions, dis

  20. Improvement of FISH mapping resolution on combed DNA molecules by iterative constrained deconvolution: a quantitative study.

    Science.gov (United States)

    Monier, K; Heliot, L; Rougeulle, C; Heard, E; Robert-Nicoud, M; Vourc'h, C; Bensimon, A; Usson, Y

    2001-01-01

    Image restoration approaches, such as digital deconvolution, are becoming widely used for improving the quality of microscopic images. However, no quantification of the gain in resolution of fluorescence images is available. We show that, after iterative constrained deconvolution, fluorescent cosmid signals appear to be 25% smaller, and 1.2-kb fragment signals on combed molecules faithfully display the expected length.

  1. Silicon-chip-based mid-infrared dual-comb spectroscopy

    CERN Document Server

    Yu, Mengjie; Griffith, Austin G; Picqué, Nathalie; Lipson, Michal; Gaeta, Alexander L

    2016-01-01

    On-chip spectroscopy that could realize real-time fingerprinting with label-free and high-throughput detection of trace molecules is one of the 'holy grails" of sensing. Such miniaturized spectrometers would greatly enable applications in chemistry, bio-medicine, material science or space instrumentation, such as hyperspectral microscopy of live cells or pharmaceutical quality control. Dual-comb spectroscopy (DCS), a recent technique of Fourier transform spectroscopy without moving parts, is particularly promising since it measures high-precision spectra in the gas phase using only a single detector. Here, we present a microresonator-based platform designed for mid-infrared (mid-IR) DCS. A single continuous-wave (CW) low-power pump source generates two mutually coherent mode-locked frequency combs spanning from 2.6 $\\mu$m to 4.1 $\\mu$m in two silicon micro-resonators. Thermal control and free-carrier injection control modelocking of each comb and tune the dual-comb parameters. The large line spacing of the co...

  2. ComB proteins expression levels determine Helicobacter pylori competence capacity

    Science.gov (United States)

    Corbinais, Christopher; Mathieu, Aurélie; Damke, Prashant P.; Kortulewski, Thierry; Busso, Didier; Prado-Acosta, Mariano; Radicella, J. Pablo; Marsin, Stéphanie

    2017-01-01

    Helicobacter pylori chronically colonises half of the world’s human population and is the main cause of ulcers and gastric cancers. Its prevalence and the increase in antibiotic resistance observed recently reflect the high genetic adaptability of this pathogen. Together with high mutation rates and an efficient DNA recombination system, horizontal gene transfer through natural competence makes of H. pylori one of the most genetically diverse bacteria. We show here that transformation capacity is enhanced in strains defective for recN, extending previous work with other homologous recombination genes. However, inactivation of either mutY or polA has no effect on DNA transformation, suggesting that natural competence can be boosted in H. pylori by the persistence of DNA breaks but not by enhanced mutagenesis. The transformation efficiency of the different DNA repair impaired strains correlates with the number of transforming DNA foci formed on the cell surface and with the expression of comB8 and comB10 competence genes. Overexpression of the comB6-B10 operon is sufficient to increase the transformation capacity of a wild type strain, indicating that the ComB complex, present in the bacterial wall and essential for DNA uptake, can be a limiting factor for transformation efficiency. PMID:28128333

  3. Impact of Decoherence on Internal State Cooling using Optical Frequency Combs

    CERN Document Server

    Malinovskaya, S A

    2012-01-01

    We discuss femtosecond Raman type techniques to control molecular vibrations, which can be implemented for internal state cooling from Feshbach states with the use of optical frequency combs with and without modulation. The technique makes use of multiple two-photon resonances induced by optical frequencies present in the comb. It provides us with a useful tool to study the details of molecular dynamics at ultracold temperatures. In our theoretical model we take into account decoherence in the form of spontaneous emission and collisional dephasing in order to ascertain an accurate model of the population transfer in the three-level system. We analyze the effects of odd and even chirps of the optical frequency comb in the form of sine and cosine functions on the population transfer. We compare the effects of these chirps to the results attained with the standard optical frequency comb to see if they increase the population transfer to the final deeply bound state in the presence of decoherence. We also analyze...

  4. Ultra-pure RF tone from a micro-ring resonator based optical frequency comb source

    CERN Document Server

    Pasquazi, Alessia; Little, Brent E; Chu, Sai T; Moss, David J; Morandotti, Roberto

    2014-01-01

    We demonstrate a novel mode locked ultrafast laser, based on an integrated high-Q micr-oring resonator. Our scheme exhibits stable operation of two slightly shifted spectral optical comb replicas. It generates a highly monochromatic radiofrequency modulation of 60MHz on a 200GHz output pulse train, with a linewidth < 10kHz

  5. Description of the male of Laneella perisi (Mariluis) (Diptera: Calliphoridae) n. comb.

    Science.gov (United States)

    Wolff, M; Ramos-Pastrana, Y; Pujol-Luz, J R

    2013-02-01

    The male Laneella perisi (Mariluis) n. comb. is described based on specimens collected in the Cordillera Oriental (1,370-1,450 m asl), Florencia-Suaza, Caquetá, Colombia. A key to separate the two species of the genus Laneella and illustrations of the male genitalia and female abdomen, terminalia, and spermatheca are also presented.

  6. Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy

    CERN Document Server

    Rutkowski, Lucile

    2016-01-01

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique and we present the corresponding formalism for quantitative broadband spectroscopy. We achieve high sensitivity and broadband performance by acquiring spectra covering more than 2000 cm$^{-1}$ around 12600 cm$^{-1}$ (800 nm), resolving the 3$\

  7. To observe the effect of feed additives on the level of sex hormones puppies%观察饲料添加剂二次蓄积对幼犬性激素水平的影响

    Institute of Scientific and Technical Information of China (English)

    李惠; 沈澎; 卢大雷; 徐丹; 王卫杰

    2014-01-01

    This experiment aims to study and analysis the feed additives widely used on the mar-ket, and discuss the effect of feed additives accumulation on growth and reproductive development of the second-feed male pups. 12 one-month-old male pups were select to randomly divided into ex-perimental and control groups. The control group was fed the normal diet and rat meat. The experi-mental group was fed the normal diet and high-dose rat meat. After the dogs mature, to test if high-dose rat meat could effect on male pups growth and reproductive development. Detected indica-tors of dogs serum hormone levels by using ELISA kits method. The results showed that: in experi-mental group the estradiol and follicle-stimulating hormone levels were significantly increased (P<0.01), testosterone levels significantly decreased (P<0.01), serm luteinizing was no signifi-cant change in high-dose group. Feeding rats can lead male pups endocrine hormones levels to be abnormal: 11-month-old male pups, estradiol and follicle stimulating hormone levels increased, testosterone level reduced. There was an impact on the reproductive development of male pups through interfering with the function of testicles in tip experimental groups of male pups fed rat meat.%本试验旨在研究分析市场上正在广泛使用的饲料添加剂,探讨二次饲喂雄性幼犬后饲料添加剂蓄积对其生长、生殖发育的影响研究。选用12只1月龄犬,随机分为试验组和对照组,对照组犬饲喂正常日粮和大鼠鼠肉,试验组犬饲喂正常日粮和高剂量组大鼠鼠肉,喂养幼犬直至成熟,检测食用饲料添加剂高剂量组大鼠鼠肉是否对雄性犬的生长、生殖发育产生影响。采用酶联免疫试剂盒的方法来检测犬血清激素指标水平。结果显示:试验组雌二醇、促卵泡激素含量明显升高(P<0.01),而睾酮含量明显降低,有显著性差异(P<0.01),饲料添加剂高剂量组

  8. Sexing young snowy owls

    Science.gov (United States)

    Seidensticker, M.T.; Holt, D.W.; Detienne, J.; Talbot, S.; Gray, K.

    2011-01-01

    We predicted sex of 140 Snowy Owl (Bubo scandiacus) nestlings out of 34 nests at our Barrow, Alaska, study area to develop a technique for sexing these owls in the field. We primarily sexed young, flightless owls (3844 d old) by quantifying plumage markings on the remiges and tail, predicting sex, and collecting blood samples to test our field predictions using molecular sexing techniques. We categorized and quantified three different plumage markings: two types of bars (defined as markings that touch the rachis) and spots (defined as markings that do not touch the rachis). We predicted sex in the field assuming that males had more spots than bars and females more bars than spots on the remiges and rectrices. Molecular data indicated that we correctly sexed 100% of the nestlings. We modeled the data using random forests and classification trees. Both models indicated that the number and type of markings on the secondary feathers were the most important in classifying nestling sex. The statistical models verified our initial qualitative prediction that males have more spots than bars and females more bars than spots on flight feathers P6P10 for both wings and tail feathers T1 and T2. This study provides researchers with an easily replicable and highly accurate method for sexing young Snowy Owls in the field, which should aid further studies of sex-ratios and sex-related variation in behavior and growth of this circumpolar owl species. ?? 2011 The Raptor Research Foundation, Inc.

  9. A 12.5 GHz-spaced optical frequency comb spanning >400 nm for near-infrared astronomical spectrograph calibration.

    Science.gov (United States)

    Quinlan, F; Ycas, G; Osterman, S; Diddams, S A

    2010-06-01

    A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined oscillator for near-infrared (IR) spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380-1820 nm, providing complete coverage over the H-band transmission window of earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth, and instability of the comb has been examined to estimate potential wavelength biases in spectrograph calibration. Sidemode suppression varies between 20 and 45 dB, and the optical linewidth is approximately 350 kHz at 1550 nm. The comb frequency uncertainty is bounded by +/-30 kHz (corresponding to a radial velocity of +/-5 cm/s), limited by the global positioning system disciplined oscillator reference. These results indicate that this comb can readily support radial velocity measurements below 1 m/s in the near IR.

  10. Surficial geology of the lower Comb Wash, San Juan County, Utah

    Science.gov (United States)

    Longpré, Claire I.

    2001-01-01

    The surficial geologic map of lower Comb Wash was produced as part of a master’s thesis for Northern Arizona University Quaternary Sciences program. The map area includes the portion of the Comb Wash alluvial valley between Highway 163 and Highway 95 on the Colorado Plateau in southeastern Utah. The late Quaternary geology of this part of the Colorado Plateau had not previously been mapped in adequate detail. The geologic information in this report will be useful for biological studies, land management and range management for federal, state and private industries. Comb Wash is a south flowing ephemeral tributary of the San Juan River, flanked to the east by Comb Ridge and to the west by Cedar Mesa (Figure 1). The nearest settlement is Bluff, about 7 km to the east of the area. Elevations range from 1951 m where Highway 95 crosses Comb Wash to 1291 m at the confluence with the San Juan River. Primary vehicle access to lower Comb Wash is provided by a well-maintained dirt road that parallels the active channel of Comb Wash between Highway 163 and Highway 95. For much of the year this road can be traversed without the aid of four-wheel drive. However, during inclement weather such as rain or snow the road becomes treacherous even with four-wheel drive. The Comb Wash watershed is public land managed by the Bureau of Land management (BLM) office in Monticello, Utah. The semi-arid climate of Comb Wash and the surrounding area is typical of the Great Basin Desert. Temperature in Bluff, Utah ranges from a minimum of –8° C in January to a maximum of 35° C in July with a mean annual temperature of 9.8° C (U.S. Department of Commerce, 1999). The difference between day and nighttime temperatures is as great as 20° C. Between 1928 and 1998, annual rainfall in Bluff averaged 178 mm per year (U.S. Department of Commerce, 1999). Annual rainfall in Comb Wash averaged 240 mm per year from 1991 to 1999 while Bluff received an average of 193 mm for the same 8 year period

  11. Generation of a 650 nm - 2000 nm Laser Frequency Comb based on an Erbium-Doped Fiber Laser

    CERN Document Server

    Ycas, Gabriel; Diddams, Scott A

    2012-01-01

    We present a laser frequency comb based upon a 250 MHz mode-locked erbium-doped fiber laser that spans more than 300 terahertz of bandwidth, from 660 nm to 2000 nm. The system generates 1.2 nJ, 70 fs pulses at 1050 nm by amplifying the 1580 nm laser light in Er:fiber, followed by nonlinear broadening to 1050 nm and amplification in Yb:fiber. Extension of the frequency comb into the visible is achieved by supercontinuum generation from the 1050 nm light. Comb coherence is verified with cascaded f-2f interferometry and comparison to a frequency stabilized laser.

  12. Generation of Kerr combs centered at 4.5{\\mu}m in crystalline microresonators pumped by quantum cascade lasers

    CERN Document Server

    Savchenkov, Anatoliy A; Di Teodoro, Fabio; Belden, Paul M; Lotshaw, William T; Matsko, Andrey B; Maleki, Lute

    2015-01-01

    We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF$_2$ and MgF$_2$ whispering-gallery mode resonators pumped with continuous wave room temperature quantum cascade lasers. The combs were centered at 4.5$\\mu$m, the longest wavelength to date. A frequency comb wider than a half of an octave was demonstrated when approximately 20mW of pump power was coupled to an MgF2 resonator characterized with quality factor exceeding 10$^8$.

  13. Generation of a frequency comb spanning more than 3.6 octaves from ultraviolet to mid infrared.

    Science.gov (United States)

    Iwakuni, Kana; Okubo, Sho; Tadanaga, Osamu; Inaba, Hajime; Onae, Atsushi; Hong, Feng-Lei; Sasada, Hiroyuki

    2016-09-01

    We have observed an ultra-broadband frequency comb with a wavelength range of at least 0.35 to 4.4 μm in a ridge-waveguide-type periodically poled lithium niobate device. The PPLN waveguide is pumped by a 1.0-2.4 μm wide frequency comb with an average power of 120 mW generated using an erbium-based mode-locked fiber laser and a following highly nonlinear fiber. The coherence of the extended comb is confirmed in both the visible (around 633 nm) and the mid-infrared regions.

  14. Sex, epilepsy, and epigenetics.

    Science.gov (United States)

    Qureshi, Irfan A; Mehler, Mark F

    2014-12-01

    Epilepsy refers to a heterogeneous group of disorders that are associated with a wide range of pathogenic mechanisms, seizure manifestations, comorbidity profiles, and therapeutic responses. These characteristics are all influenced quite significantly by sex. As with other conditions exhibiting such patterns, sex differences in epilepsy are thought to arise-at the most fundamental level-from the "organizational" and "activational" effects of sex hormones as well as from the direct actions of the sex chromosomes. However, our understanding of the specific molecular, cellular, and network level processes responsible for mediating sex differences in epilepsy remains limited. Because increasing evidence suggests that epigenetic mechanisms are involved both in epilepsy and in brain sexual dimorphism, we make the case here that analyzing epigenetic regulation will provide novel insights into the basis for sex differences in epilepsy.

  15. Sex, epilepsy, and epigenetics

    OpenAIRE

    2014-01-01

    Epilepsy refers to a heterogeneous group of disorders that are associated with a wide range of pathogenic mechanisms, seizure manifestations, comorbidity profiles, and therapeutic responses. These characteristics are all influenced quite significantly by sex. As with other conditions exhibiting such patterns, sex differences in epilepsy are thought to arise—at the most fundamental level—from the “organizational” and “activational” effects of sex hormones as well as from the direct actions of ...

  16. Demonstration of on-sky calibration of astronomical spectra using a 25 GHz near-IR laser frequency comb.

    Science.gov (United States)

    Ycas, Gabriel G; Quinlan, Franklyn; Diddams, Scott A; Osterman, Steve; Mahadevan, Suvrath; Redman, Stephen; Terrien, Ryan; Ramsey, Lawrence; Bender, Chad F; Botzer, Brandon; Sigurdsson, Steinn

    2012-03-12

    We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of ∼10 m/s (∼6 MHz) was achieved from the comb-calibrated spectra.

  17. Four-wave mixing parametric oscillation and frequency comb generation at visible wavelengths in a silica microbubble resonator

    CERN Document Server

    Yang, Yong; Kasumie, Sho; Zhao, Guangming; Xu, Linhua; Ward, Jonathan; Yang, Lan; Chormaic, Síle Nic

    2016-01-01

    Frequency comb generation in microresonators at visible wavelengths has found applications in a variety of areas such as metrology, sensing, and imaging. To achieve Kerr combs based on four-wave mixing in a microresonator, dispersion must be in the anomalous regime. In this work, we demonstrate dispersion engineering in a microbubble resonator (MBR) fabricated by a two-CO$_2$ laser beam technique. By decreasing the wall thickness of the MBR down to 1.4 $\\mu$m, the zero dispersion wavelength shifts to values shorter than 764 nm, making phase matching possible around 765 nm. With the optical \\textit{Q}-factor of the MBR modes being greater than $10^7$, four-wave mixing is observed at 765 nm for a pump power of 3 mW. By increasing the pump power, parametric oscillation is achieved, and a frequency comb with 14 comb lines is generated at visible wavelengths.

  18. Demonstration of On-Sky Calibration of Astronomical Spectra using a 25 GHz near-IR Laser Frequency Comb

    CERN Document Server

    Ycas, Gabriel G; Diddams, Scott A; Osterman, Steve; Mahadevan, Suvrath; Redman, Stephen; Terrien, Ryan; Ramsey, Lawrence; Bender, Chad F; Botzer, Brandon; Sigurdsson, Steinn

    2012-01-01

    We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of ~10 m/s (~6 MHz) was achieved from the comb-calibrated spectra.

  19. Single envelope equation modelling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearity

    CERN Document Server

    Hansson, T; Erkintalo, M; Anthony, J; Coen, S; Ricciardi, I; De Rosa, M; Wabnitz, S

    2016-01-01

    We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator (WGR). We examine both separate and co-existing intra-cavity doubly resonant second-harmonic generation and parametric oscillation processes, and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains, or isolated pulses.

  20. Single-branch Er:fiber frequency comb for optical synthesis at the $10^{-18}$ level

    CERN Document Server

    Leopardi, Holly; Quinlan, Franklyn; Olson, Judith; Diddams, Scott; Fortier, Tara

    2016-01-01

    Laser frequency combs based on erbium-doped fiber mode-locked lasers have shown great potential for compact, robust and efficient optical clock comparisons. However, to simultaneously compare multiple optical clock species, fiber laser frequency combs typically require multiple amplifiers and fiber optic paths that reduce the achievable frequency stability near 1 part in $10^{16}$ at 1s. In this paper we describe an erbium-fiber laser frequency comb that overcomes these conventional challenges and supports optical frequency synthesis at the millihertz level, or fractionally $3 x 10^{-18}$ $tau^{-1/2}$ by ensuring that all critical fiber paths are within the servo-controlled feedback loop. We demonstrate the application of this frequency comb as a synthesizer for optical clocks operating across a wavelength range from 650 nm to 2100 nm.

  1. Spectral self-imaging of time-periodic coherent frequency combs by parabolic cross-phase modulation.

    Science.gov (United States)

    Maram, Reza; Azaña, José

    2013-11-18

    Integer and fractional spectral self-imaging effects are induced on infinite-duration periodic frequency combs (probe signal) using cross-phase modulation (XPM) with a parabolic pulse train as pump signal. Free-spectral-range tuning (fractional effects) or wavelength-shifting (integer effects) of the frequency comb can be achieved by changing the parabolic pulse peak power or/and repetition rate without affecting the spectral envelope shape and bandwidth of the original comb. For design purposes, we derive the complete family of different pump signals that allow implementing a desired spectral self-imaging process. Numerical simulation results validate our theoretical analysis. We also investigate the detrimental influence of group-delay walk-off and deviations in the nominal temporal shape or power of the pump pulses on the generated output frequency combs.

  2. Comb-shaped polyesters of aliphatic dicarboxylic acids and 2-octadecyl-1,3-propanediol: 1. Synthesis and microstructure

    DEFF Research Database (Denmark)

    Andruzzi, F.; Hvilsted, S.

    1991-01-01

    Comb-shaped polyesters are prepared by polytransesterification of 2-octadecyl-1,3-propanediol and diphenyl suberate, sebacate, dodecanedioate, tetradecanedioate and hexadecanedioate in turn. The developed melt polycondensation procedure generally results in polyesters with intrinsic viscosities i...

  3. An Analysis of Near Field and Application of a New Comb-shaped Antenna for Radio Frequency Identification

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new comb-shaped antenna for radio frequency identification is proposed. The kind of antenna can replace some antenna array. So it is very convenient for omnidirectional identification. The test result proves this antenna is viable.

  4. The evolution of sex ratios and sex-determining systems

    NARCIS (Netherlands)

    Uller, Tobias; Pen, Ido; Wapstra, Erik; Beukeboom, Leo W.; Komdeur, Jan

    2007-01-01

    Sex determination is a fundamental process governed by diverse mechanisms. Sex ratio selection is commonly implicated in the evolution of sex-determining systems, although formal models are rare. Here, we argue that, although sex ratio selection can induce shifts in sex determination, genomic confli

  5. Synthesis and characterization of an exact comb polyisoprene with three branches having the middle branch twice the molecular weight of the other two identical external branches

    KAUST Repository

    Ratkanthwar, Kedar

    2013-01-01

    An exact comb polyisoprene (PI) with three branches, with the middle branch having twice the molecular weight of the two other identical external branches, was synthesized by using anionic polymerization high vacuum techniques and appropriate chlorosilane chemistry. The synthetic approach involves (a) the selective replacement of the two chlorines of 4-(dichloromethylsilyl) diphenylethylene (DCMSDPE, key molecule) with identical PI chains by titration with PILi, (b) the addition of sec-BuLi to the double bond of DPE followed by the polymerization of isoprene from the newly created anionic site to form a 3-arm living star PI, (c) the selective replacement of the two chlorines of trichloromethylsilane with 3-arm star PI to form an H-shape intermediate, and (d) the replacement of the remaining chlorine of trichloromethylsilane by linear PI chains with double the molecular weight. All intermediate and final products were characterized via size exclusion chromatography, temperature gradient interaction chromatography and 1H-NMR spectroscopy. As expected, due to the inability to control the exact stoichiometry of the linking reactants, the main product (exact comb PI) is contaminated by a few by-products, despite the fact that anionic polymerization is the most efficient way to produce well-defined polymers. © 2013 The Royal Society of Chemistry.

  6. The evolution of sex chromosomes in organisms with separate haploid sexes.

    Science.gov (United States)

    Immler, Simone; Otto, Sarah Perin

    2015-03-01

    The evolution of dimorphic sex chromosomes is driven largely by the evolution of reduced recombination and the subsequent accumulation of deleterious mutations. Although these processes are increasingly well understood in diploid organisms, the evolution of dimorphic sex chromosomes in haploid organisms (U/V) has been virtually unstudied theoretically. We analyze a model to investigate the evolution of linkage between fitness loci and the sex-determining region in U/V species. In a second step, we test how prone nonrecombining regions are to degeneration due to accumulation of deleterious mutations. Our modeling predicts that the decay of recombination on the sex chromosomes and the addition of strata via fusions will be just as much a part of the evolution of haploid sex chromosomes as in diploid sex chromosome systems. Reduced recombination is broadly favored, as long as there is some fitness difference between haploid males and females. The degeneration of the sex-determining region due to the accumulation of deleterious mutations is expected to be slower in haploid organisms because of the absence of masking. Nevertheless, balancing selection often drives greater differentiation between the U/V sex chromosomes than in X/Y and Z/W systems. We summarize empirical evidence for haploid sex chromosome evolution and discuss our predictions in light of these findings.

  7. Analysis of the Offspring Sex Ratio of Chicken by Using Molecular Sexing

    Institute of Scientific and Technical Information of China (English)

    FENG Yan-ping; GONG Yan-zhang; Nabeel Ahmed Affara; PENG Xiu-li; YUAN Jin-feng; ZHAO Rui-xia; Mohammed Yusuf; Osman Jeffer; ZHANG Shu-jun

    2006-01-01

    The overall sex ratio of offspring (dead embryos and hatch chicks) from all the fertilized eggs of 140 hens collected for30 days was studied using duplex PCR of certain fragments of sex chromosomes. Additional 894 dead embryos over a period of 21 days of incubation were also investigated to verify the sex ratio of the dead embryos. The sex of the early dead embryos was identified using this molecular sexing technique. The sex ratio of the hatch chicks and the total offspring of the hens investigated in this experiment did not differ from the expected sex ratio (i.e., 1:1). However, the number of female dead embryos was significantly more than that of males. The data indicated that the different physiologic function of males and females contributed to female-biased mortality during incubation. It was also found by further analysis that the sex ratios of the offspring of some hens were significantly biased to female or male over the period investigated, which suggested that the sex ratio of offspring might be influenced by the maternal condition to some degrees.

  8. Novel Concept of Frequency-Combs Interferometric Spectroscopy in the Mid-IR for Significantly Enhanced Detection of Explosives

    Science.gov (United States)

    2015-12-01

    submit the attached Interim Report due December 31. 2015 for the above referenced grant titled "Novel concept of frequency- combs interferometric...ucf.edu . Sincerely, v ~~ Vicky Ortiz, M.A. Coordinator of Research Programs UCF College of Optics and Photonics, CREOL & FPCE Phone: 407-823...From - To) 02/29/2016 Interim 5/1/14-9/30/15 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Novel concept of frequency- combs interferometric

  9. Sex tourism in Thailand.

    Science.gov (United States)

    Van Kerkwijk, C

    1992-01-01

    Many foreigners visit Thailand in search of sex. While long-distance tourism was long enjoyed by members of more privileged social classes, even the lower economical classes of Japan, Malaysia, Europe, America, and Australia can now afford to travel over long distances. This relatively new breed of tourist is more likely to be of lower socioeconomic and educational status and less likely to use condoms when having sex. An estimated 30,000 sex workers are active in Bangkok, of whom 7000/10,000 are females who work specifically in the tourism sector. 1/2-1/3 of the 600 commercial sex establishments in the city are visited by foreigners. Phuket, Pattaya, Koh Samui, and Chiangmai are also well-frequented by sex tourists. Overall, a large, diverse, inexpensive, and accessible commercial sex market exists in Thailand. One may meet sex workers quasi-ubiquitously and be assured to find someone capable of meeting one's sexual needs. With these attributes, Thailand strongly attracts tourists in search of sex. A certain degree of recklessness also prevails among those on vacation. Away from the peers and social mores of their native lands, tourists may engage in sexually activities without criticism. Likewise, Thai sex workers who cater to foreigners, especially females, enjoy more freedom and control in sexual relations than their peers who work among nationals. Neither single nor married women in Thailand are allowed much sexual freedom and are traditionally expected to be obliging docile, and submissive. The greater than normal personal latitude enjoyed by both sex worker and foreigner lead to more negotiation on condom use and overall lower use. As such, Thailand's commercial sex market with foreigners' involvement therein threatens to spread HIV to many other countries throughout the world.

  10. Plant Sex Determination.

    Science.gov (United States)

    Pannell, John R

    2017-03-06

    Sex determination is as important for the fitness of plants as it is for animals, but its mechanisms appear to vary much more among plants than among animals, and the expression of gender in plants differs in important respects from that in most animals. In this Minireview, I provide an overview of the broad variety of ways in which plants determine sex. I suggest that several important peculiarities of plant sex determination can be understood by recognising that: plants show an alternation of generations between sporophytic and gametophytic phases (either of which may take control of sex determination); plants are modular in structure and lack a germ line (allowing for a quantitative expression of gender that is not common in animals); and separate sexes in plants have ultimately evolved from hermaphroditic ancestors. Most theorising about sex determination in plants has focused on dioecious species, but we have much to learn from monecious or hermaphroditic species, where sex is determined at the level of modules, tissues or cells. Because of the fundamental modularity of plant development and potentially important evolutionary links between monoecy and dioecy, it may be useful to relax the distinction often made between 'developmental sex determination' (which underpins the development of male versus female flowers in monoecious species) and 'genetic sex determination' (which underpins the separation of males and females in dioecious species, often mediated by a genetic polymorphism and sex chromosomes). I also argue for relaxing the distinction between sex determination involving a genetic polymorphism and that involving responses to environmental or hormonal cues, because non-genetic cues might easily be converted into genetic switches.

  11. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    CERN Document Server

    Doerr, H -P; Holzwarth, R; Schmidt, T Kentischer und W

    2012-01-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut f\\"ur Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut f\\"ur Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

  12. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    Science.gov (United States)

    Doerr, H.-P.; Steinmetz, T.; Holzwarth, R.; Kentischer, T.; Schmidt, W.

    2012-10-01

    A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

  13. Demonstration of atomic frequency comb memory for light with spin-wave storage.

    Science.gov (United States)

    Afzelius, Mikael; Usmani, Imam; Amari, Atia; Lauritzen, Björn; Walther, Andreas; Simon, Christoph; Sangouard, Nicolas; Minár, Jirí; de Riedmatten, Hugues; Gisin, Nicolas; Kröll, Stefan

    2010-01-29

    We present a light-storage experiment in a praseodymium-doped crystal where the light is mapped onto an inhomogeneously broadened optical transition shaped into an atomic frequency comb. After absorption of the light, the optical excitation is converted into a spin-wave excitation by a control pulse. A second control pulse reads the memory (on-demand) by reconverting the spin-wave excitation to an optical one, where the comb structure causes a photon-echo-type rephasing of the dipole moments and directional retrieval of the light. This combination of photon-echo and spin-wave storage allows us to store submicrosecond (450 ns) pulses for up to 20 mus. The scheme has a high potential for storing multiple temporal modes in the single-photon regime, which is an important resource for future long-distance quantum communication based on quantum repeaters.

  14. Evaluation and modelling of integral capacitors produced by interdigitated comb electrodes

    Directory of Open Access Journals (Sweden)

    Leandro Alfredo Ramajo

    2008-12-01

    Full Text Available Integral capacitors (IC of one or two-layer printed wiring board (PWB circuits were produced using comb electrodes fixtures and dielectric composites as the inter-electrode material. ICs were fabricated at laboratory scale, using copper comb electrodes and BaTiO3-epoxy composite materials deposited on a glass-Epoxy FR4 board. They were experimentally tested in order to obtain their electrical response. Furthermore, ICs behaviour was modelled through 2-dimensional models applying finite element method (FEM. Results showed that by this laboratory technique it was possible to obtained integral capacitors with low dielectric losses. Moreover, acceptable agreement was found between numerical and experimental capacitance results for all the different analysed ICs. In conclusion, 2D FEM models are a suitable tool to predict electric response of IC devices.

  15. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering.

    Science.gov (United States)

    Morville, Jérôme; Rutkowski, Lucile; Dobrev, Georgi; Crozet, Patrick

    2015-06-01

    We present a new approach to Cavity Enhanced - Direct Frequency Comb Spectroscopy where the full emission bandwidth of a Titanium:Sapphire laser is exploited at GHz resolution. The technique is based on a low-resolution Vernier filtering obtained with an appreciable -actively stabilized- mismatch between the cavity Free Spectral Range and the laser repetition rate, using a diffraction grating and a split-photodiode. This particular approach provides an immunity to frequency-amplitude noise conversion, reaching an absorption baseline noise in the 10-9 cm-1 range with a cavity finesse of only 3000. Spectra covering 1800 cm-1 (˜ 55 THz) are acquired in recording times of about 1 second, providing an absorption figure of merit of a few 10-11 cm-1/√{Hz}. Initially tested with ambient air, we report progress in using the Vernier frequency comb method with a discharge source of small radicals. Rutkowski et al, Opt. Lett., 39(23)2014

  16. Transmission comb of a distributed Bragg reflector with two surface dielectric gratings

    KAUST Repository

    Zhao, Xiaobo

    2016-02-19

    The transmission behaviour of a distributed Bragg reector (DBR) with surface dielectric gratings on top and bottom is studied. The transmission shows a comb-like spectrum in the DBR band gap, which is explained in the Fano picture. The number density of the transmission peaks increases with increasing number of cells of the DBR, while the ratio of the average full width at half maximum to the corresponding average free spectral range, being only few percent for both transversal electric and magnetic waves, is almost invariant. The transmission peaks can be narrower than 0.1 nm and are fully separated from each other in certain wavebands. We further prove that the transmission combs are robust against randomness in the heights of the DBR layers. Therefore, the proposed structure is a candidate for an ultra-narrow-band multichannel filter or polarizer.

  17. [Molecular combing method in the research of DNA replication parameters in isolated organs of Drosophyla melanogaster].

    Science.gov (United States)

    Ivankin, A V; Kolesnikova, T D; Demakov, S A; Andreenkov, O V; Bil'danova, E R; Andreenkova, N G; Zhimulev, I F

    2011-01-01

    Methods of physical DNA mapping and direct visualization of replication and transcription in specific regions of genome play crucial role in the researches of structural and functional organization of eukaryotic genomes. Since DNA strands in the cells are organized into high-fold structure and present as highly compacted chromosomes, the majority of these methods have lower resolution at chromosomal level. One of the approaches to enhance the resolution and mapping accuracy is the method of molecular combing. The method is based on the process of stretching and alignment of DNA molecules that are covalently attached with one of the ends to the cover glass surface. In this article we describe the major methodological steps of molecular combing and their adaptation for researches of DNA replication parameters in polyploidy and diploid tissues of Drosophyla larvae.

  18. Unified approach to cascaded stimulated Brillouin scattering and frequency-comb generation

    Science.gov (United States)

    Dong, Mark; Winful, Herbert G.

    2016-04-01

    We present a unified approach to cascaded stimulated Brillouin scattering and frequency-comb generation in which the multitude of interacting pump, Stokes, and anti-Stokes optical fields is described by a single forward wave and a single backward wave at a single carrier frequency. The envelopes of these two waves are modulated through coupling to a single acoustic oscillation and through four-wave mixing. Starting from a single pump field, we observe the emergence of a comb of frequencies as the intensity is increased. The set of three differential equations derived here is sufficient to describe the generation of any number of Brillouin sidebands in oscillator systems that would have required hundreds of coupled equations in the standard approach. We test this approach on some published experiments and find excellent agreement with the results.

  19. Gigahertz dual-comb modelocked diode-pumped semiconductor and solid-state lasers

    Science.gov (United States)

    Link, S. M.; Mangold, M.; Golling, M.; Klenner, A.; Keller, U.

    2016-03-01

    We present a simple approach to generate simultaneously two gigahertz mode-locked pulse trains from a single gain element. A bi-refringent crystal in the laser cavity splits the one cavity beam into two cross-polarized and spatially separated beams. This polarization-duplexing is successfully demonstrated for both a semiconductor disk laser (i.e. MIXSEL) and a diode-pumped solid-state Nd:YAG laser. The beat between the two beams results in a microwave frequency comb, which represents a direct link between the terahertz optical frequencies and the electronically accessible microwave regime. This dual-output technique enables compact and cost-efficient dual-comb lasers for spectroscopy applications.

  20. Sensitivity and resolution in frequency comb spectroscopy of buffer gas cooled polyatomic molecules

    Science.gov (United States)

    Changala, P. Bryan; Spaun, Ben; Patterson, David; Doyle, John M.; Ye, Jun

    2016-12-01

    We discuss the use of cavity-enhanced direct frequency comb spectroscopy in the mid-infrared region with buffer gas cooling of polyatomic molecules for high-precision rovibrational absorption spectroscopy. A frequency comb coupled to an optical enhancement cavity allows us to collect high-resolution, broad-bandwidth infrared spectra of translationally and rotationally cold (10-20 K) gas-phase molecules with high absorption sensitivity and fast acquisition times. The design and performance of the combined apparatus are discussed in detail. Recorded rovibrational spectra in the CH stretching region of several organic molecules, including vinyl bromide (CH_2CHBr), adamantane (C_{10}H_{16}), and diamantane (C_{14}H_{20}) demonstrate the resolution and sensitivity of this technique, as well as the intrinsic challenges faced in extending the frontier of high-resolution spectroscopy to large complex molecules.

  1. WDM-CAP-PON integration with VLLC system based on optical frequency comb

    Science.gov (United States)

    He, Jing; Dong, Huan; Deng, Rui; Shi, Jin; Chen, Lin

    2016-09-01

    In this paper, a wavelength division multiplexing carrier-less amplitude phase modulation passive optical network (WDM-CAP-PON) integration with visible laser light communication (VLLC) system is proposed and experimentally demonstrated. To reduce the cost of WDM system, the optical frequency comb scheme using one Mach-Zehnder modulator (MZM) is utilized and five flat optical combs can be generated. Meanwhile, a blue laser diode (LD) as a VLLC optical source can provide high data rate and long transmission distance. Utilizing overlap frequency domain equalization (OFDE) and negative chirp of MZM, the system performance in both Q-factor and receiver sensitivity can be improved. After 20 km standard single mode fiber (SSMF) and 4.5 m free space transmission, the experimental results show that 10 Gb/s CAP signal can be achieved under 7% forward error correction (FEC) limit of 3 . 8 × 10-3.

  2. Bandwidth enhancement of a multilayered polymeric comb array antenna for millimeter-wave applications

    Science.gov (United States)

    Muhamad, Wan Asilah Wan; Ngah, Razali; Jamlos, Mohd Faizal; Soh, Ping Jack; Ali, Mohd Tarmizi; Narbudowicz, Adam

    2017-01-01

    This paper introduces a new multilayered polymeric comb array antenna fabricated on a polydimethylsiloxane (PDMS) dielectric substrate. PDMS is selected due to its excellent electrical and mechanical properties such as low permittivity, water resistance and robustness. The polymeric comb array antenna consists of a zigzag array aligned at -90° with respect to the radiating patch with full ground plane. The radiating patch is embedded inside the PDMS substrate while the coaxial connector is located at the bottom of the transmission line. The proposed antenna functions from 22.649 to 27.792 GHz. Simulated and measured reflection coefficients and radiation patterns agreed well. A maximum gain of 9.856 dB is recorded at 25 GHz, indicating suitability for implementation in millimeter-wave applications.

  3. A distance meter using a terahertz intermode beat in an optical frequency comb.

    Science.gov (United States)

    Yokoyama, Shuko; Yokoyama, Toshiyuki; Hagihara, Yuki; Araki, Tsutomu; Yasui, Takeshi

    2009-09-28

    We propose a distance meter that utilizes an intermode beat of terahertz frequency in an optical frequency comb to perform high resolution and high dynamic range absolute distance measurements. The proposed system is based on a novel method, called multiheterodyne cross-correlation detection, in which intermode beat frequencies are scaled down to radio frequencies by optical mixing of two detuned optical frequency combs with a nonlinear optical crystal. Using this method, we obtained a 1.056 THz intermode beat and achieved a distance resolution of 0.820 microm from its phase measurement. Absolute distance measurement using 1.056 THz and 8.187 GHz intermode beats was also demonstrated in the range of 10 mm, resulting in a precision of 0.688 microm.

  4. ACADEMIC TRAINING: Probing nature with high precision; particle traps, laser spectroscopy and optical combs

    CERN Multimedia

    Françoise Benz

    2002-01-01

    17, 18, 19 June LECTURE SERIES from 11.00 to 12.00 hrs - Auditorium, bldg. 500 Probing nature with high precision; particle traps, laser spectroscopy and optical combs by G. GABRIELSE / Harvard University, USA Experiments with atomic energy scales probe nature and its symmetries with exquisite precision. Particle traps allow the manipulation of single charged particles for months at a time, allow the most accurate comparison of theory and experiment, and promise to allow better measurement of fundamental quantities like the fine structure constant. Ions and atoms can be probed with lasers that are phase locked to microwave frequency standards via optical combs, thus calibrating optical sources in terms of the official cesium second. A series of three lectures will illustrate what can be measured and discuss key techniques.  ACADEMIC TRAINING Françoise Benz Tel. 73127 francoise.benz@cern.ch

  5. Continuous probe of cold complex molecules with infrared frequency comb spectroscopy

    CERN Document Server

    Spaun, Ben; Patterson, David; Bjork, Bryce J; Heckl, Oliver H; Doyle, John M; Ye, Jun

    2016-01-01

    Cavity-enhanced frequency comb spectroscopy for molecule detection in the mid-infrared powerfully combines high resolution, high sensitivity, and broad spectral coverage. However, this technique, and essentially all spectroscopic methods, is limited in application to relatively small, simple molecules. Here we integrate comb spectroscopy with continuous, cold samples of molecules produced via buffer gas cooling, thus enabling the study of significantly more complex molecules. We report simultaneous gains in resolution, sensitivity, and bandwidth and demonstrate this combined capability with the first rotationally resolved direct absorption spectra in the CH stretch region of several complex molecules. These include nitromethane (CH$_3$NO$_2$), a model system that presents challenging questions to the understanding of large amplitude vibrational motion, as well as several large organic molecules with fundamental spectroscopic and astrochemical relevance, including naphthalene (C$_{10}$H$_8$), adamantane (C$_{1...

  6. Optical fiber strain sensor using fiber resonator based on frequency comb Vernier spectroscopy

    DEFF Research Database (Denmark)

    Zhang, Liang; Lu, Ping; Chen, Li;

    2012-01-01

    A novel (to our best knowledge) optical fiber strain sensor using a fiber ring resonator based on frequency comb Vernier spectroscopy is proposed and demonstrated. A passively mode-locked optical fiber laser is employed to generate a phased-locked frequency comb. Strain applied to the optical fiber...... be proportionally improved by increasing the length of the optical fiber ring resonator....... of the fiber ring resonator can be measured with the transmission spectrum. A good linearity is obtained between displacement and the inverse of wavelength spacing with an R2 of 0.9989, and high sensitivities better than 40  pm/με within the range of 0 to 10  με are achieved. The sensitivity can...

  7. Novel active comb-shaped dry electrode for EEG measurement in hairy site.

    Science.gov (United States)

    Huang, Yan-Jun; Wu, Chung-Yu; Wong, Alice May-Kuen; Lin, Bor-Shyh

    2015-01-01

    Electroencephalography (EEG) is an important biopotential, and has been widely applied in clinical applications. The conventional EEG electrode with conductive gels is usually used for measuring EEG. However, the use of conductive gel also encounters with the issue of drying and hardening. Recently, many dry EEG electrodes based on different conductive materials and techniques were proposed to solve the previous issue. However, measuring EEG in the hairy site is still a difficult challenge. In this study, a novel active comb-shaped dry electrode was proposed to measure EEG in hairy site. Different form other comb-shaped or spike-shaped dry electrodes, it can provide more excellent performance of avoiding the signal attenuation, phase distortion, and the reduction of common mode rejection ratio. Even under walking motion, it can effectively acquire EEG in hairy site. Finally, the experiments for alpha rhythm and steady-state visually evoked potential were also tested to validate the proposed electrode.

  8. Comb-shaped single ion conductors based on polyacrylate ethers and lithium alkyl sulfonate

    Energy Technology Data Exchange (ETDEWEB)

    Sun Xiaoguang [Lawrence Berkeley National Laboratory, EETD, MS 62-203, One Cyclotron Road, Berkeley, CA 94720 (United States)]. E-mail: xsun@lbl.gov; Hou Jun [Lawrence Berkeley National Laboratory, EETD, MS 62-203, One Cyclotron Road, Berkeley, CA 94720 (United States); Kerr, John B. [Lawrence Berkeley National Laboratory, EETD, MS 62-203, One Cyclotron Road, Berkeley, CA 94720 (United States)]. E-mail: jbkerr@lbl.gov

    2005-01-15

    Comb-shaped single ion conductors have been synthesized by (1) sulfonation of small molecule chloroethyleneglycols, which, after ion exchange to the Li{sup +} salt were then converted to the acrylate by reaction with acryloyl chloride and copolymerized with polyethylene glycol monomethyl ether acrylate (Mn = 454, n = 8) (PAE{sub 8}-co-E{sub 3}SO{sub 3}Li); (2) sulfonation of chloride end groups grafted on to prepolymers of polyacrylate ethers (PAE{sub 8}-g-E{sub n}SO{sub 3}Li, n = 2, 3). The highest conductivity at 25 deg. C of 2.0 x 10{sup -7} S cm{sup -1} was obtained for the PAE{sub 8}-co-E{sub 3}SO{sub 3}Li with a salt concentration of EO/Li = 40. The conductivity of PAE{sub 8}-g-E{sub 3}SO{sub 3}Li is lower than that of PAE{sub 8}-co-E{sub 3}SO{sub 3}Li at similar salt concentrations, which is related to the incomplete sulfonation of the grafted polymer that leads to a lower concentration of Li{sup +}. The addition of 50 wt.% of plasticizer, PC/EMC (1/1, v/v), to PAE{sub 8}-g-E{sub 2}SO{sub 3}Li increases the ambient conductivity by three orders of magnitude, which is due to the increased ion mobility in a micro-liquid environment and an increase concentration of free ions as a result of the higher dielectric constant of the solvent. A symmetrical Li/Li cell with an electrolyte membrane consisting of 75 wt.% PC/EMC (1/1, v/v) was cycled at a current density of 100 {mu}A cm{sup -2} at 85 deg. C. The cycling profile showed no concentration polarization after a break-in period during the first few cycles, which was apparently due to reaction of the solvent at the lithium metal surface that reacted with lithium metal to form a stable SEI layer.

  9. Comb-shaped single ion conductors based on polyacrylate ethers and lithium alkyl sulfonate

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Guang Sun; Jan Hou; Kerr, J.B. [Lawrence Berkeley National Lab., CA (United States). EETD

    2005-01-15

    Comb-shaped single ion conductors have been synthesized by (1) sulfonation of small molecule chloroethyleneglycols, which, after ion exchange to the Li{sup +} salt were then converted to the acrylate by reaction with acryloyl chloride and copolymerized with polyethylene glycol monomethyl ether acrylate (Mn = 454, n = 8) (PAE{sub 8}-co-E{sub 3}SO{sub 3}Li); (2) sulfonation of chloride end groups grafted on to prepolymers of polyacrylate ethers (PAE{sub 8}-g-E{sub n}SO{sub 3}Li, n = 2, 3). The highest conductivity at 25 {sup o}C of 2.0 x {sup -7} S cm{sup -1} was obtained for the PAE{sub 8}-co-E{sub 3}SO{sub 3}Li with a salt concentration of EO/Li = 40. The conductivity of PAE{sub 8}-g-E{sub 3}SO{sub 3}Li is lower than that of PAE{sub 8}-co-E{sub 3}SO{sub 3}Li at similar salt concentrations, which is related to the incomplete sulfonation of the grafted polymer that leads to a lower concentration of Li{sup +}. The addition of 50 wt.% of plasticizer, PC/EMC (1/1, v/v), to PAE{sub 8}-g-E{sub 2}SO{sub 3}Li increases the ambient conductivity by three orders of magnitude, which is due to the increased ion mobility in a micro-liquid environment and an increase concentration of free ions as a result of the higher dielectric constant of the solvent. A symmetrical Li/Li cell with an electrolyte membrane consisting of 75 wt.% PC/EMC (1/1, v/v) was cycled at a current density of 100 {mu}A cm{sup -2} at 85 {sup o}C. The cycling profile showed no concentration polarization after a break-in period during the first few cycles, which was apparently due to reaction of the solvent at the lithium metal surface that reacted with lithium metal to form a stable SEI layer. (Author)

  10. Phase-Locked Loop using a comb filter with fractional delay

    OpenAIRE

    Griñó Cubero, Robert; Mughal, Umair Najeeb

    2011-01-01

    A Phase Locked Loop is a feedback system combining a Voltage Controlled Oscillator and a Phase Comparator These are connected so that the oscillator maintains a constant phase angle relative to a reference signal. Phase locked loops can be used, for example to generate stable output frequency signals from a fixed frequency signal. A Comb Filter is a kind of Notch Filter (Non Recursive Filter) that is normally used to remove the harmonic terms from a particular signal. In this Design, a ...

  11. Direct Spectroscopy in Hollow Optical with Fiber-Based Optical Frequency Combs

    Science.gov (United States)

    2015-07-09

    stabilization To fully stabilize the comb, there are three servo loops, shown in Fig. 1, that lock the carrier offset frequency f0 to an RF synthesizer ...GPS-Rb oscillator serves as the external reference for all synthesizers and frequency counters. The filtering cavity is stabilized to a particular...filled frequency reference in a 10 m length. Since optimal single-modedness is expected at longer lengths (~10-30 m), a gas such as ammonia , with weaker

  12. Liquid-state acoustically-nonlinear nanoplasmonic source of optical frequency combs

    CERN Document Server

    Maksymov, Ivan S

    2016-01-01

    Nonlinear acoustic interactions in liquids are effectively stronger than nonlinear optical interactions in solids. Thus, harnessing these interactions will offer new possibilities in the design of ultra-compact nonlinear photonic devices. We theoretically demonstrate a hybrid, liquid-state and nanoplasmonic, source of optical frequency combs compatible with fibre-optic technology. This source relies on a nanoantenna to harness the strength of nonlinear acoustic effects and synthesise optical spectra from ultrasound.

  13. Development of Chip-Based Frequency Combs for Spectral and Timing Applications

    Science.gov (United States)

    2011-12-01

    by measuring the RF beat note. A 1-nm section of the comb spectrum is filtered at 1540 nm and amplified with an EDFA . The output is sent to a fast...amplitude Approved for public release; distribution unlimited. 13 noise from the EDFA and the laser. We estimate a frequency shift of approximately 100...oxide-semiconductor EDFA erbium-doped fiber amplifier FSR free spectral range FWM four-wave mixing IR infrared OPO optical parametric

  14. A near infrared laser frequency comb for high precision Doppler planet surveys

    Directory of Open Access Journals (Sweden)

    Bally J.

    2011-07-01

    Full Text Available Perhaps the most exciting area of astronomical research today is the study of exoplanets and exoplanetary systems, engaging the imagination not just of the astronomical community, but of the general population. Astronomical instrumentation has matured to the level where it is possible to detect terrestrial planets orbiting distant stars via radial velocity (RV measurements, with the most stable visible light spectrographs reporting RV results the order of 1 m/s. This, however, is an order of magnitude away from the precision needed to detect an Earth analog orbiting a star such as our sun, the Holy Grail of these efforts. By performing these observations in near infrared (NIR there is the potential to simplify the search for distant terrestrial planets by studying cooler, less massive, much more numerous class M stars, with a tighter habitable zone and correspondingly larger RV signal. This NIR advantage is undone by the lack of a suitable high precision, high stability wavelength standard, limiting NIR RV measurements to tens or hundreds of m/s [1, 2]. With the improved spectroscopic precision provided by a laser frequency comb based wavelength reference producing a set of bright, densely and uniformly spaced lines, it will be possible to achieve up to two orders of magnitude improvement in RV precision, limited only by the precision and sensitivity of existing spectrographs, enabling the observation of Earth analogs through RV measurements. We discuss the laser frequency comb as an astronomical wavelength reference, and describe progress towards a near infrared laser frequency comb at the National Institute of Standards and Technology and at the University of Colorado where we are operating a laser frequency comb suitable for use with a high resolution H band astronomical spectrograph.

  15. Brazilian species of Gadila (Mollusca: Scaphopoda: Gadilidae): rediscovery of Gadila elongata comb. nov. and shell morphometrics

    OpenAIRE

    Caetano,Carlos H. S.; Victor Scarabino; Ricardo S. Absalão

    2010-01-01

    Gadila elongata comb. nov. was described in 1920 from the northern Gulf of Mexico. Until recently, it was only known from the type locality. Herein we present the first record of G. elongata from Brazil (Northeast coast, Ceará state, collected at 177 m) and a morphometrics analysis of the Brazilian species of Gadila. A multivariate Discriminant Function Analysis, based on nine shell morphometric variables (length, maximum diameter, length to maximum diameter ratio, distance of point of maximu...

  16. Reclassification of Brevibacterium incertum (Breed 1953) as Desemzia incerta gen. nov., comb. nov.

    Science.gov (United States)

    Stackebrandt, E; Schumann, P; Swiderski, J; Weiss, N

    1999-01-01

    Phylogenetic analysis of 16S rDNA indicates that Brevibacterium incertum is not a member of the genus Brevibacterium but related to species of the genus Carnobacterium. Hence, Brevibacterium incertum is not a member of the class Actinobacteria but belongs to the phylogenetically defined broad Bacillus-Lactobacillus cluster. Based upon properties that taxonomically clearly distinguishes Brevibacterium incertum from species of the phylogenetic sister genus Carnobacterium, Brevibacterium incertum is reclassified as Desemzia incerta gen. nov., comb. nov.

  17. Frequency comb generation beyond the Lugiato-Lefever equation: multi-stability and super cavity solitons

    OpenAIRE

    Hansson, Tobias; Wabnitz, Stefan

    2015-01-01

    The generation of optical frequency combs in microresonators is considered without resorting to the mean-field approximation. New dynamical regimes are found to appear for high intracavity power that cannot be modeled using the Lugiato-Lefever equation. Using the Ikeda map we show the existence of multi-valued stationary states and analyse their stability. Period doubled patterns are considered and a novel type of super cavity soliton associated with the multi-stable states is predicted.

  18. Frequency comb generation beyond the Lugiato-Lefever equation: multi-stability and super cavity solitons

    Science.gov (United States)

    Hansson, Tobias; Wabnitz, Stefan

    2015-07-01

    The generation of optical frequency combs in microresonators is considered without resorting to the mean-field approximation. New dynamical regimes are found to appear for high intracavity power that cannot be modeled using the Lugiato-Lefever equation. Using the Ikeda map we show the existence of multi-valued stationary states and analyse their stability. Period doubled patterns are considered and a novel type of super cavity soliton associated with the multi-stable states is predicted.

  19. Asymptotic Capacity of Wireless Ad Hoc Networks with Realistic Links under a Honey Comb Topology

    CERN Document Server

    Asnani, Himanshu

    2007-01-01

    We consider the effects of Rayleigh fading and lognormal shadowing in the physical interference model for all the successful transmissions of traffic across the network. New bounds are derived for the capacity of a given random ad hoc wireless network that reflect packet drop or capture probability of the transmission links. These bounds are based on a simplified network topology termed as honey-comb topology under a given routing and scheduling scheme.

  20. Molecular phylogeny of Urosomoida agilis, and new combinations: Hemiurosomoida longa gen. nov., comb. nov., and Heterourosomoida lanceolata gen. nov., comb. nov. (Ciliophora, Hypotricha).

    Science.gov (United States)

    Singh, Jasbir; Kamra, Komal

    2015-02-01

    For years, systematics of three species, Urosomoida agilis (Engelmann, 1862) Hemberger in Foissner, 1982, Urosomoida longa (Gelei and Szabados, 1950) Foissner et al., 1991 and Oxytricha lanceolata Shibuya, 1930, has remained unresolved due to lack of adequate molecular data. Though, it is known since several years that the three species are not very closely related. In the present paper, 18S rRNA gene sequences for two key species, U. agilis and U. longa, and their morphology and morphometry have been analyzed. Molecular phylogeny inferred from maximum likelihood, neighbour joining and maximum parsimony methods has adequately removed ambiguity over their systematics. In phylogenetic trees, U. agilis clustered consistently with non-stylonychine oxytrichids. Both Urosomoida longa and Oxytricha lanceolata clustered consistently away from U. agilis and O. granulifera, the type species of the genera Urosomoida and Oxytricha, respectively. As a result of the current molecular phylogenetic investigation and based on previously inferred morphological and morphogenetic data it is proposed to remove Urosomoida longa and Oxytricha lanceolata from Urosomoida and incertae sedis in Oxytricha, respectively, and establish two new generic combinations, Hemiurosomoida longa gen. nov., comb. nov. and Heterourosomoida lanceolata gen. nov., comb. nov. for them.

  1. Proposal of Effusibacillus lacus gen. nov., sp. nov., and reclassification of Alicyclobacillus pohliae as Effusibacillus pohliae comb. nov. and Alicyclobacillus consociatus as Effusibacillus consociatus comb. nov.

    Science.gov (United States)

    Watanabe, Miho; Kojima, Hisaya; Fukui, Manabu

    2014-08-01

    A novel thermophilic, facultatively anaerobic bacterium, strain skLN1(T), was isolated from the sediment of a freshwater lake in Japan. Cells of strain skLN1(T) were rod-shaped and Gram-stain-variable. A KOH lysis test suggested that the cell wall of the isolate has a Gram-positive structure. For aerobic growth, the optimum pH was pH 7.25-7.50 and the optimum temperature was 50-52 °C. The G+C content of the genomic DNA was 50.8 mol%. Nitrate was reduced to nitrite. Alicyclic fatty acids were not detected, and branched-chain fatty acids were major components in the cellular fatty acid profile. MK-7 was the predominant respiratory quinone. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolated strain was related most closely to Alicyclobacillus consociatus CCUG 53762(T) (95% similarity). This analysis also showed that the monophyly of the genus Alicyclobacillus had been lost. On the basis of phylogenetic and phenotypic characterization, Effusibacillus lacus gen. nov., sp. nov. is proposed. The type strain of Effusibacillus lacus is skLN1(T) ( = NBRC 109614(T) = DSM 27172(T)). It is also proposed that Alicyclobacillus pohliae and Alicyclobacillus consociatus should be reclassified to the genus Effusibacillus as Effusibacillus pohliae comb. nov. and Effusibacillus consociatus comb. nov., respectively.

  2. Sex Discrimination in Coaching.

    Science.gov (United States)

    Dessem, Lawrence

    1980-01-01

    Even in situations in which the underpayment of girls' coaches is due to the sex of the students coached rather than to the sex of the coaches, the coaches and the girls coached are victims of unlawful discrimination. Available from Harvard Women's Law Journal, Harvard Law School, Cambridge, MA 02138. (Author/IRT)

  3. Insects and sex

    NARCIS (Netherlands)

    Beukeboom, Leo

    2005-01-01

    Most organisms reproduce sexually, but the evolution of sexual reproduction is not yet well understood. Sexual reproduction leads to new variation and adaptations to the environment, but sex is also costly. Some insects reproduce without sex through parthenogenesis or paedogenesis. Almost all sexual

  4. Single-Sex Classrooms

    Science.gov (United States)

    Protheroe, Nancy

    2009-01-01

    Although single-sex education was once the norm in the U.S., the practice has largely been confined to private schools for more than a century. However, with the introduction of the final version of the U.S. Department of Education's so-called single-sex regulations in 2006, public schools were allowed greater flexibility to offer single-sex…

  5. Repetition rate multiplication of frequency comb using all-pass fiber resonator

    Science.gov (United States)

    Yang, Lijun; Yang, Honglei; Zhang, Hongyuan; Wei, Haoyun; Li, Yan

    2016-09-01

    We propose a stable method for repetition rate multiplication of a 250-MHz Er-fiber frequency comb by a phase-locked all-pass fiber ring resonator, whose phase-locking configuration is simple. The optical path length of the fiber ring resonator is automatically controlled to be accurately an odd multiple of half of the original cavity length using an electronical phase-locking unit with an optical delay line. As for shorter cavity length of the comb, high-order odd multiple is preferable. Because the power loss depends only on the net-attenuation of the fiber ring resonator, the energetic efficiency of the proposed method is high. The input and output optical spectrums show that the spectral width of the frequency comb is clearly preserved. Besides, experimental results show less pulse intensity fluctuation and 35 dB suppression ratio of side-modes while providing a good long-term and short-term frequency stability. Higher-order repetition rate multiplication to several GHz can be obtained by using several fiber ring resonators in cascade configuration.

  6. Wintering Reserve Queens in Mini-Plus and 3-Comb Nuclei

    Directory of Open Access Journals (Sweden)

    Siuda Maciej

    2014-06-01

    Full Text Available The aim of this study was to develop an effective method of overwintering reserve honey bee queens in two-storey mini-plus mating nuclei and in 3-comb nuclei (frames 36 x 26 cm, Wielkopolski hive. The assay was performed during three wintering seasons (2005 - 2008 parallel at two centers in Poland: the Division of Apiculture at the University of Life Sciences (SGGW in Warsaw, and the Apiculture Division at the University of Warmia and Mazury (UWM in Olsztyn. The results showed that 59% of queens overwintered in mini-plus nuclei and 77% in 3-comb nuclei. Among queens in mini-plus nuclei 63% overwintered in bee yard and only 55% in cellar. Within queens in 3-comb nuclei, 62% overwintered in Olsztyn and 91% in Warsaw. The highest survival rate of 93% was observed in Warsaw during the first season. Due to low survival rate, it is not recommended to overwinter the queens in miniplus nuclei.

  7. A comb filter based signal processing method to effectively reduce motion artifacts from photoplethysmographic signals.

    Science.gov (United States)

    Peng, Fulai; Liu, Hongyun; Wang, Weidong

    2015-10-01

    A photoplethysmographic (PPG) signal can provide very useful information about a subject's cardiovascular status. Motion artifacts (MAs), which usually deteriorate the waveform of a PPG signal, severely obstruct its applications in the clinical diagnosis and healthcare area. To reduce the MAs from a PPG signal, in the present study we present a comb filter based signal processing method. Firstly, wavelet de-noising was implemented to preliminarily suppress a part of the MAs. Then, the PPG signal in the time domain was transformed into the frequency domain by a fast Fourier transform (FFT). Thirdly, the PPG signal period was estimated from the frequency domain by tracking the fundamental frequency peak of the PPG signal. Lastly, the MAs were removed by the comb filter which was designed based on the obtained PPG signal period. Experiments with synthetic and real-world datasets were implemented to validate the performance of the method. Results show that the proposed method can effectively restore the PPG signals from the MA corrupted signals. Also, the accuracy of blood oxygen saturation (SpO2), calculated from red and infrared PPG signals, was significantly improved after the MA reduction by the proposed method. Our study demonstrates that the comb filter can effectively reduce the MAs from a PPG signal provided that the PPG signal period is obtained.

  8. Massively parallel dual-comb molecular detection with subharmonic optical parametric oscillators

    CERN Document Server

    Smolski, Viktor O; Xu, Jia; Vodopyanov, Konstantin L

    2016-01-01

    Mid-infrared (mid-IR) spectroscopy offers unparalleled sensitivity for the detection of trace gases, solids and liquids, which is based on the existence of strong telltale vibrational bands in this part of the spectrum. It was shown more than a decade ago that a dual-comb Fourier spectroscopy could provide superior spectral coverage combined with high resolution and extremely fast data acquisition. Capabilities of this method were limited because of difficulty of producing twins of mutually coherent frequency combs in the mid- IR. Here we report a phase-coherent and broadband dual-comb system that is based on a pair of subharmonic (frequency-divide-by-two) optical parametric oscillators, pumped in turn by two phase-locked thulium fiber lasers at 2-micron wavelength. We demonstrate simultaneous detection of multiple molecular species in the whole band of 3.2-5.3 microns (frequency span 1200 cm^{-1}) augmented by the pump laser band of 1.85-2 microns (span 400 cm^{-1}), with spectral resolution 0.01-0.07 cm^{-1...

  9. Real-time closed-loop control for micro mirrors with quasistatic comb drives

    Science.gov (United States)

    Schroedter, Richard; Sandner, Thilo; Janschek, Klaus; Roth, Matthias; Hruschka, Clemens

    2016-03-01

    This paper presents the application of a real-time closed-loop control for the quasistatic axis of electrostatic micro scanning mirrors. In comparison to resonantly driven mirrors, the quasistatic comb drive allows arbitrary motion profiles with frequencies up to its eigenfrequency. A current mirror setup at Fraunhofer IPMS is manufactured with a staggered vertical comb (SVC) drive and equipped with an integrated piezo-resistive deflection sensor, which can potentially be used as position feedback sensor. The control design is accomplished based on a nonlinear mechatronic system model and the preliminary parameter characterization. In previous papers [1, 2] we have shown that jerk-limited trajectories, calculated offline, provide a suitable method for parametric trajectory design, taking into account physical limitations given by the electrostatic comb and thus decreasing the dynamic requirements. The open-loop control shows in general unfavorable residual eigenfrequency oscillations leading to considerable tracking errors for desired triangle trajectories [3]. With real-time closed-loop control, implemented on a dSPACE system using an optical feedback, we can significantly reduce these errors and stabilize the mirror motion against external disturbances. In this paper we compare linear and different nonlinear closed-loop control strategies as well as two observer variants for state estimation. Finally, we evaluate the simulation and experimental results in terms of steady state accuracy and the concept feasibility for a low-cost realization.

  10. Stably accessing octave-spanning microresonator frequency combs in the soliton regime

    CERN Document Server

    Li, Qing; Westly, Daron A; Drake, Tara E; Stone, Jordan R; Ilic, B Robert; Diddams, Scott A; Papp, Scott B; Srinivasan, Kartik

    2016-01-01

    Microresonator frequency combs can be an enabling technology for optical frequency synthesis and timekeeping in low size, weight, and power architectures. Such systems require comb operation in low-noise, phase-coherent states such as solitons, with broad spectral bandwidths (e.g., octave-spanning) for self-referencing to detect the carrier-envelope offset frequency. However, stably accessing such states is complicated by thermo-optic dispersion. For example, in the Si3N4 platform, precisely dispersion-engineered structures can support broadband operation, but microsecond thermal time constants have necessitated fast pump power or frequency control to stabilize the solitons. In contrast, here we consider how broadband soliton states can be accessed with simple pump laser frequency tuning, at a rate much slower than the thermal dynamics. We demonstrate octave-spanning soliton frequency combs in Si3N4 microresonators, including the generation of a multi-soliton state with a pump power near 40 mW and a single-so...

  11. Sex Determination, Sex Ratios, and Genetic Conflict

    NARCIS (Netherlands)

    Werren, John H.; Beukeboom, Leo W.

    1998-01-01

    Genetic mechanisms of sex determination are unexpectedly diverse and change rapidly during evolution. We review the role of genetic conflict as the driving force behind this diversity and turnover. Genetic conflict occurs when different components of a genetic system are subject to selection in oppo

  12. Hierarchical structure formation in supramolecular comb-shaped block copolymers

    NARCIS (Netherlands)

    Hofman, Anton; ten Brinke, Gerrit; Loos, Katja

    2016-01-01

    Block copolymers are known to spontaneously form ordered structures at the nano-to mesoscale. Although the number of different morphologies is rather limited in diblock copolymer systems, their phase behavior becomes increasingly more complex with each additional building block. Synthesis of such al

  13. A predictive relationship between population and genetic sex ratios in clonal species

    Science.gov (United States)

    McLetchie, D. Nicholas; García-Ramos, Gisela

    2017-04-01

    Sexual reproduction depends on mate availability that is reflected by local sex ratios. In species where both sexes can clonally expand, the population sex ratio describes the proportion of males, including clonally derived individuals (ramets) in addition to sexually produced individuals (genets). In contrast to population sex ratio that accounts for the overall abundance of the sexes, the genetic sex ratio reflects the relative abundance of genetically unique mates, which is critical in predicting effective population size but is difficult to estimate in the field. While an intuitive positive relationship between population (ramet) sex ratio and genetic (genet) sex ratio is expected, an explicit relationship is unknown. In this study, we determined a mathematical expression in the form of a hyperbola that encompasses a linear to a nonlinear positive relationship between ramet and genet sex ratios. As expected when both sexes clonally have equal number of ramets per genet both sex ratios are identical, and thus ramet sex ratio becomes a linear function of genet sex ratio. Conversely, if sex differences in ramet number occur, this mathematical relationship becomes nonlinear and a discrepancy between the sex ratios amplifies from extreme sex ratios values towards intermediate values. We evaluated our predictions with empirical data that simultaneously quantified ramet and genet sex ratios in populations of several species. We found that the data support the predicted positive nonlinear relationship, indicating sex differences in ramet number across populations. However, some data may also fit the null model, which suggests that sex differences in ramet number were not extensive, or the number of populations was too small to capture the curvature of the nonlinear relationship. Data with lack of fit suggest the presence of factors capable of weakening the positive relationship between the sex ratios. Advantages of this model include predicting genet sex ratio using

  14. Coherence properties of a 2.6-7.5  μm frequency comb produced as a subharmonic of a Tm-fiber laser.

    Science.gov (United States)

    Smolski, V O; Yang, H; Gorelov, S D; Schunemann, P G; Vodopyanov, K L

    2016-04-01

    We study the temporal coherence of an ultrabroadband frequency comb produced in a degenerate GaAs optical parametric oscillator (OPO) pumped by a stabilized Tm-fiber comb, by observing multiheterodyne beats in the RF domain. We infer that in such a regime the OPO automatically produces a stable frequency comb that is phase and frequency locked to the pump. By varying intracavity dispersion, we achieve a comb spanning 2.6-7.5 μm at a -20  dB level. Low pump threshold (down to 7 mW), high average power (up to 73 mW), broad spectral coverage, flat spectrum, and high coherence make this comb a source suitable for various applications, foremost dual-comb molecular spectroscopy.

  15. Demonstration of a near-IR line-referenced electro-optical laser frequency comb for precision radial velocity measurements in astronomy.

    Science.gov (United States)

    Yi, X; Vahala, K; Li, J; Diddams, S; Ycas, G; Plavchan, P; Leifer, S; Sandhu, J; Vasisht, G; Chen, P; Gao, P; Gagne, J; Furlan, E; Bottom, M; Martin, E C; Fitzgerald, M P; Doppmann, G; Beichman, C

    2016-01-27

    An important technique for discovering and characterizing planets beyond our solar system relies upon measurement of weak Doppler shifts in the spectra of host stars induced by the influence of orbiting planets. A recent advance has been the introduction of optical frequency combs as frequency references. Frequency combs produce a series of equally spaced reference frequencies and they offer extreme accuracy and spectral grasp that can potentially revolutionize exoplanet detection. Here we demonstrate a laser frequency comb using an alternate comb generation method based on electro-optical modulation, with the comb centre wavelength stabilized to a molecular or atomic reference. In contrast to mode-locked combs, the line spacing is readily resolvable using typical astronomical grating spectrographs. Built using commercial off-the-shelf components, the instrument is relatively simple and reliable. Proof of concept experiments operated at near-infrared wavelengths were carried out at the NASA Infrared Telescope Facility and the Keck-II telescope.

  16. Sex and Fertility After SCI

    Science.gov (United States)

    ... About Blog Facing Disability Jeff Shannon Donate Experts \\ Sex and Fertility After Spinal Cord Injury Topics Adult ... Spasticity, Physical Therapy-Lokomat Spasticity, Physical Therapy-Lokomat Sex and Fertility After Spinal Cord Injury Sex and ...

  17. Hepatitis C: Sex and Sexuality

    Science.gov (United States)

    ... with Hepatitis » Sex and Sexuality: Entire Lesson Viral Hepatitis Menu Menu Viral Hepatitis Viral Hepatitis Home For ... hepatitis C virus through sex. Can you pass hepatitis C to a sex partner? Yes, but it ...

  18. Comb-Type Grafted Hydrogels of PNIPAM and PDMAEMA with Reversed Network-Graft Architectures from Controlled Radical Polymerizations

    Directory of Open Access Journals (Sweden)

    Sheng-Qi Chen

    2016-02-01

    Full Text Available Dual thermo- and pH-responsive comb-type grafted hydrogels of poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA and poly(N-isopropylacrylamide (PNIPAM with reversed network-graft architectures were synthesized by the combination of atom transfer radical polymerization (ATRP, reversible addition-fragmentation chain transfer (RAFT polymerization and click chemistry. Two kinds of macro-cross-linkers with two azido groups at one chain-end and different chain length [PNIPAM–(N32 and PDMAEMA–(N32] were prepared with N,N-di(β-azidoethyl 2-halocarboxylamide as the ATRP initiator. Through RAFT copolymerization of DMAEMA or NIPAM with propargyl acrylate (ProA using dibenzyltrithiocarbonate as a chain transfer agent, two network precursors with different content of alkynyl side-groups [P(DMAEMA-co-ProA and P(NIPAM-co-ProA] were obtained. The subsequent azido-alkynyl click reaction of macro-cross-linkers and network precursors led to the formation of the network-graft hydrogels. These dual stimulus-sensitive hydrogels exhibited rapid response, high swelling ratio and reproducible swelling/de-swelling cycles under different temperatures and pH values. The influences of cross-linkage density and network-graft architecture on the properties of the hydrogels were investigated. The release of ceftriaxone sodium from these hydrogels showed both thermal- and pH-dependence, suggesting the feasibility of these hydrogels as thermo- and pH-dependent drug release devices.

  19. Extensive Frequency Comb Velocity Modulation Spectroscopy of ThF^+ for Use in the Jila Electron Edm Experiment

    Science.gov (United States)

    Gresh, Dan; Cossel, Kevin; Ye, Jun; Cornell, Eric

    2014-06-01

    The metastable ^3Δ_1 state in trapped HfF^+ is being used for an ongoing measurement of the electron electric dipole moment (eEDM) ThF^+, which has a larger effective electric field and a longer-lived ^3Δ_1 state, offers increased sensitivity for an eEDM measurement. Recently, the Heaven group has spectroscopically studied the low-lying states of ThF^+. However, to date there is no detailed information available about technically-accessible laser transitions in the near-infrared region of the spectrum, which are necessary for state preparation and detection in an eEDM experiment. By applying the technique of frequency comb velocity modulation spectroscopy (VMS) to ThF^+ we can acquire 150 cm-1 of continuous, ion-sensitive spectra with 150 MHz resolution in 25 minutes. Here, we report on extensive broadband, high-resolution survey spectroscopy of ThF^+ in the near-IR where we have observed and accurately fit several rovibronic transitions. In addition, we have observed and characterized numerous rovibronic transitions from an unknown thoriated species of molecular ions. H. Loh, K. C. Cossel, M. C. Grau, K.-K. Ni, E. R. Meyer, J. L. Bohn, J. Ye, E. A. Cornell, Science 342, 1220 (2013). B. J. Barker, I. O. Antonov, M. C. Heaven, K. A. Peterson, J. Chem. Phys. 136, 104305 (2012). L. C. Sinclair, K. C. Cossel, T. Coffey, J. Ye, E. A. Cornell, PRL 107, 093002 (2011).

  20. Offset-Free Gigahertz Midinfrared Frequency Comb Based on Optical Parametric Amplification in a Periodically Poled Lithium Niobate Waveguide

    Science.gov (United States)

    Mayer, A. S.; Phillips, C. R.; Langrock, C.; Klenner, A.; Johnson, A. R.; Luke, K.; Okawachi, Y.; Lipson, M.; Gaeta, A. L.; Fejer, M. M.; Keller, U.

    2016-11-01

    We report the generation of an optical-frequency comb in the midinfrared region with 1-GHz comb-line spacing and no offset with respect to absolute-zero frequency. This comb is tunable from 2.5 to 4.2 μ m and covers a critical spectral region for important environmental and industrial applications, such as molecular spectroscopy of trace gases. We obtain such a comb using a highly efficient frequency conversion of a near-infrared frequency comb. The latter is based on a compact diode-pumped semiconductor saturable absorber mirror-mode-locked ytterbium-doped calcium-aluminum gadolynate (Yb:CALGO) laser operating at 1 μ m . The frequency-conversion process is based on optical parametric amplification (OPA) in a periodically poled lithium niobate (PPLN) chip containing buried waveguides fabricated by reverse proton exchange. The laser with a repetition rate of 1 GHz is the only active element of the system. It provides the pump pulses for the OPA process as well as seed photons in the range of 1.4 - 1.8 μ m via supercontinuum generation in a silicon-nitride (Si3 N4 ) waveguide. Both the PPLN and Si3 N4 waveguides represent particularly suitable platforms for low-energy nonlinear interactions; they allow for mid-IR comb powers per comb line at the microwatt level and signal amplification levels up to 35 dB, with 2 orders of magnitude less pulse energy than reported in OPA systems using bulk devices. Based on numerical simulations, we explain how high amplification can be achieved at low energy using the interplay between mode confinement and a favorable group-velocity mismatch configuration where the mid-IR pulse moves at the same velocity as the pump.

  1. Sex investment ratios in eusocial Hymenoptera support inclusive fitness theory.

    Science.gov (United States)

    Bourke, A F G

    2015-11-01

    Inclusive fitness theory predicts that sex investment ratios in eusocial Hymenoptera are a function of the relatedness asymmetry (relative relatedness to females and males) of the individuals controlling sex allocation. In monogynous ants (with one queen per colony), assuming worker control, the theory therefore predicts female-biased sex investment ratios, as found in natural populations. Recently, E.O. Wilson and M.A. Nowak criticized this explanation and presented an alternative hypothesis. The Wilson-Nowak sex ratio hypothesis proposes that, in monogynous ants, there is selection for a 1 : 1 numerical sex ratio to avoid males remaining unmated, which, given queens exceed males in size, results in a female-biased sex investment ratio. The hypothesis also asserts that, contrary to inclusive fitness theory, queens not workers control sex allocation and queen-worker conflict over sex allocation is absent. Here, I argue that the Wilson-Nowak sex ratio hypothesis is flawed because it contradicts Fisher's sex ratio theory, which shows that selection on sex ratio does not maximize the number of mated offspring and that the sex ratio proposed by the hypothesis is not an equilibrium for the queen. In addition, the hypothesis is not supported by empirical evidence, as it fails to explain 'split' (bimodal) sex ratios or data showing queen and worker control and ongoing queen-worker conflict. By contrast, these phenomena match predictions of inclusive fitness theory. Hence, the Wilson-Nowak sex ratio hypothesis fails both as an alternative hypothesis for sex investment ratios in eusocial Hymenoptera and as a critique of inclusive fitness theory.

  2. B chromosomes and sex in animals.

    Science.gov (United States)

    Camacho, J P M; Schmid, M; Cabrero, J

    2011-01-01

    Supernumerary (B) chromosomes are dispensable elements found in many eukaryote genomes in addition to standard (A) chromosomes. In many respects, B chromosomes resemble sex chromosomes, so that a common ancestry for them has frequently been suggested. For instance, B chromosomes in grasshoppers, and other insects, show a pycnotic cycle of condensation-decondensation during meiosis remarkably similar to that of the X chromosome. In some cases, B chromosome size is even very similar to that of the X chromosome. These resemblances have led to suggest the X as the B ancestor in many cases. In addition, sex chromosome origin from B chromosomes has also been suggested. In this article, we review the existing evidence for both evolutionary pathways, as well as sex differences for B frequency at adult and embryo progeny levels, B chromosome effects or B chromosome transmission. In addition, we review cases found in the literature showing sex-ratio distortion associated with B chromosome presence, the most extreme case being the paternal sex ratio (PSR) chromosomes in some Hymenoptera. We finally analyse the possibility of B chromosome regularisation within the host genome and, as a consequence of it, whether B chromosomes can become regular members of the host genome.

  3. Multiple sex-associated regions and a putative sex chromosome in zebrafish revealed by RAD mapping and population genomics.

    Directory of Open Access Journals (Sweden)

    Jennifer L Anderson

    Full Text Available Within vertebrates, major sex determining genes can differ among taxa and even within species. In zebrafish (Danio rerio, neither heteromorphic sex chromosomes nor single sex determination genes of large effect, like Sry in mammals, have yet been identified. Furthermore, environmental factors can influence zebrafish sex determination. Although progress has been made in understanding zebrafish gonad differentiation (e.g. the influence of germ cells on gonad fate, the primary genetic basis of zebrafish sex determination remains poorly understood. To identify genetic loci associated with sex, we analyzed F(2 offspring of reciprocal crosses between Oregon *AB and Nadia (NA wild-type zebrafish stocks. Genome-wide linkage analysis, using more than 5,000 sequence-based polymorphic restriction site associated (RAD-tag markers and population genomic analysis of more than 30,000 single nucleotide polymorphisms in our *ABxNA crosses revealed a sex-associated locus on the end of the long arm of chr-4 for both cross families, and an additional locus in the middle of chr-3 in one cross family. Additional sequencing showed that two SNPs in dmrt1 previously suggested to be functional candidates for sex determination in a cross of ABxIndia wild-type zebrafish, are not associated with sex in our AB fish. Our data show that sex determination in zebrafish is polygenic and that different genes may influence sex determination in different strains or that different genes become more important under different environmental conditions. The association of the end of chr-4 with sex is remarkable because, unique in the karyotype, this chromosome arm shares features with known sex chromosomes: it is highly heterochromatic, repetitive, late replicating, and has reduced recombination. Our results reveal that chr-4 has functional and structural properties expected of a sex chromosome.

  4. Multiple sex-associated regions and a putative sex chromosome in zebrafish revealed by RAD mapping and population genomics.

    Science.gov (United States)

    Anderson, Jennifer L; Rodríguez Marí, Adriana; Braasch, Ingo; Amores, Angel; Hohenlohe, Paul; Batzel, Peter; Postlethwait, John H

    2012-01-01

    Within vertebrates, major sex determining genes can differ among taxa and even within species. In zebrafish (Danio rerio), neither heteromorphic sex chromosomes nor single sex determination genes of large effect, like Sry in mammals, have yet been identified. Furthermore, environmental factors can influence zebrafish sex determination. Although progress has been made in understanding zebrafish gonad differentiation (e.g. the influence of germ cells on gonad fate), the primary genetic basis of zebrafish sex determination remains poorly understood. To identify genetic loci associated with sex, we analyzed F(2) offspring of reciprocal crosses between Oregon *AB and Nadia (NA) wild-type zebrafish stocks. Genome-wide linkage analysis, using more than 5,000 sequence-based polymorphic restriction site associated (RAD-tag) markers and population genomic analysis of more than 30,000 single nucleotide polymorphisms in our *ABxNA crosses revealed a sex-associated locus on the end of the long arm of chr-4 for both cross families, and an additional locus in the middle of chr-3 in one cross family. Additional sequencing showed that two SNPs in dmrt1 previously suggested to be functional candidates for sex determination in a cross of ABxIndia wild-type zebrafish, are not associated with sex in our AB fish. Our data show that sex determination in zebrafish is polygenic and that different genes may influence sex determination in different strains or that different genes become more important under different environmental conditions. The association of the end of chr-4 with sex is remarkable because, unique in the karyotype, this chromosome arm shares features with known sex chromosomes: it is highly heterochromatic, repetitive, late replicating, and has reduced recombination. Our results reveal that chr-4 has functional and structural properties expected of a sex chromosome.

  5. Juvenile Sex Offenders.

    Science.gov (United States)

    Ryan, Eileen P; Otonichar, Joseph M

    2016-07-01

    Sexual offending by juveniles accounts for a sizable percentage of sexual offenses, especially against young children. In this article, recent research on female juvenile sex offenders (JSOs), risk factors for offending in juveniles, treatment, and the ways in which these youth may differ from general delinquents will be reviewed. Most JSOs do not go on to develop paraphilic disorders or to commit sex offenses during adulthood, and as a group, they are more similar to nonsexual offending juvenile delinquents than to adult sex offenders. Recent research has elucidated some differences between youth who commit sex offenses and general delinquents in the areas of atypical sexual interests, the use of pornography, and early sexual victimization during childhood.

  6. Sex, Deportation and Rescue

    DEFF Research Database (Denmark)

    Plambech, Sine

    2017-01-01

    This contribution explores the economies interlinked by the migration of Nigerian women sex workers. The literature and politics of sex work migration and human trafficking economies are commonly relegated to the realm that focuses on profits for criminal networks and pimps, in particular...... recirculating the claim that human trafficking is the “third largest” criminal economy after drugs and weapons. Based on ethnographic fieldwork among Nigerian sex worker migrants conducted in Benin City, Nigeria, in 2011 and 2012, this study brings together four otherwise isolated migration economies...... – facilitation, remittances, deportation, and rescue – and suggests that we have to examine multiple sites and relink these in order to more fully understand the complexity of sex work migration. Drawing upon literature within transnational feminist analysis, critical human trafficking studies, and migration...

  7. New and improved molecular sexing methods for museum bird specimens.

    Science.gov (United States)

    Bantock, Tristan M; Prys-Jones, Robert P; Lee, Patricia L M

    2008-05-01

    We present two new avian molecular sexing techniques for nonpasserine and passerine birds (Neognathae), which are more suitable for use with museum specimens than earlier methods. The technique for nonpasserines is based on a new primer (M5) which, in combination with the existing P8 primer, targets a smaller amplicon in the CHD1 sex-linked gene than previously. Primers targeting ATP5A1, an avian sex-linked gene not previously used for sex identification, were developed for passerines. Comprehensive testing across species demonstrated that both primer pairs sex a range of different species within their respective taxonomic groups. Rigorous evaluation of each method within species showed that these permitted sexing of specimens dating from the 1850s. For corn bunting museum specimens, the ATP5A1 method sexed 98% of 63 samples (1857-1966). The M5/P8 CHD1 method was similarly successful, sexing 90% of 384 moorhen specimens from six different museum collections (1855-2001). In contrast, the original P2/P8 CHD1 sexing method only identified the sex of less than half of 111 museum moorhen samples. In addition to dried skin samples, these methods may be useful for other types of material that yield degraded or damaged DNA, and are hence potential new sexing tools for avian conservation genetics, population management and wildlife forensics.

  8. Transfer of Bacillus mucilaginosus and Bacillus edaphicus to the genus Paenibacillus as Paenibacillus mucilaginosus comb. nov. and Paenibacillus edaphicus comb. nov.

    Science.gov (United States)

    Hu, Xiu-Fang; Li, Shi-Xiao; Wu, Jin-Guang; Wang, Jian-Feng; Fang, Qiong-Lou; Chen, Ji-Shuang

    2010-01-01

    Bacillus mucilaginosus and Bacillus edaphicus were reclassified based on their 16S rRNA and gyrB gene sequences, DNA-DNA hybridization, fatty acid methyl esters and other taxonomic characteristics. Phylogenetic analysis based on 16S rRNA and gyrB gene sequences indicated that strains of B. mucilaginosus and B. edaphicus were members of the genus Paenibacillus, with over 90.4 % and 70.3 % sequence similarity, respectively. Their DNA G+C contents were 54.5-56.8 mol%. The DNA-DNA relatedness values of B. edaphicus VKPM B-7517(T) with B. mucilaginosus KNP414 and B. mucilaginosus CGMCC 1.236 were 89.2 % and 88.7 %, respectively. The major isoprenoid quinone of B. mucilaginosus and B. edaphicus was MK-7 (94.1-95.7 %). The peptidoglycan type was A1gamma (meso-diaminopimelic acid) and the major polar lipids were phosphatidylglycerol and diphosphatidylglycerol. The major fatty acids were anteiso-C(15 : 0), C(16 : 1)omega11c and C(16 : 0). Phenotypic features and fatty acid profiles supported the similarity of B. mucilaginosus and B. edaphicus to Paenibacillus validus CCTCC 95016(T) and confirmed their relationship with members of the genus Paenibacillus. Therefore, it is proposed that Bacillus mucilaginosus and Bacillus edaphicus be transferred to the genus Paenibacillus as Paenibacillus mucilaginosus comb. nov. (type strain HSCC 1605(T)=VKPM B-7519(T)=VKM B-1480D(T)=CIP 105815(T)=KCTC 3870(T)) and Paenibacillus edaphicus comb. nov. (type strain VKPM B-7517(T)=DSM 12974(T)=CIP 105814(T)), respectively.

  9. Anal sex role, circumcision status, and HIV infection among men who have sex with men in Chongqing, China.

    Science.gov (United States)

    Zhou, Chao; Raymond, H Fisher; Ding, Xianbin; Lu, Rongrong; Xu, Jing; Wu, Guohui; Feng, Liangui; Fan, Song; Li, Xuefeng; McFarland, Willi; Xiao, Yan; Ruan, Yuhua; Shao, Yiming

    2013-10-01

    Men who have sex with men (MSM) in China face a rapidly expanding HIV epidemic. Anal sex role plays a significant role in HIV infection. Research has already begun in China investigating the potential for circumcision-based interventions to slow the rise of HIV among Chinese MSM. Using peer referral recruitment, we sampled 491 men who reported anal sex role preference. We analyzed preferred anal sex role, enacted sex role during recent sexual behavior, and circumcision status and HIV infection among MSM in one Chinese city. Men reported on their anal sex role preference and reported on up to three male sexual partners. Men were asked to report on whether they were "top" or "bottom" with each of the partners. Those that preferred being bottom and versatile were significantly younger than those who preferred being top. Men who preferred bottoming and those that preferred the versatile role were significantly more likely to be HIV-infected than those who preferred to be tops. There was no significant association between circumcision and HIV infection among men who maintained their preferred top role. In terms of anal sex role behavior, prevalence was not statistically different across anal sex roles. Circumcision conferred no additional protection to men who preferred and who engaged the top role during anal sex. HIV interventions will need to address anal sex roles in more sophisticated ways than perhaps originally thought. Simplistic assumptions that anal sex role is a fixed behavior undermines interventions such as circumcision among MSM.

  10. A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).

    Science.gov (United States)

    Li, Chih-Hao; Benedick, Andrew J; Fendel, Peter; Glenday, Alexander G; Kärtner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

    2008-04-03

    Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements.

  11. A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s$^{-1}$

    CERN Document Server

    Li, Chih-Hao; Fendel, Peter; Glenday, Alexander G; Kaertner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

    2008-01-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm/s (ref 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earthlike orbit, a precision of 5 cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40- GHz (1-A) line spacing, generated from a 1- GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or `astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm/s in astronomical radial ve...

  12. Sex-Related Differences in GI Disorders.

    Science.gov (United States)

    Prusator, Dawn K; Chang, Lin

    2017-02-24

    Epidemiological studies indicate sex-related differences among functional gastrointestinal disorders (FGIDs) wherein females are more likely to receive a diagnosis than their male counterparts. However, the mechanism by which females exhibit an increased vulnerability for development of these pathophysiologies remains largely unknown, and therapeutic treatments are limited. The current chapter focuses on clinical research outlining our current knowledge of factors that contribute to the female predominance among FGID patients such as the menstrual cycle and sex hormones. In addition, we will discuss progress in preclinical research, including animal models, which serve as valuable tools for the investigation of the development and long term manifestation of symptoms observed within the patient population. Although much progress has been made, additional longitudinal studies in both clinical and preclinical research are necessary to identify more specific mechanisms underlying sex-related differences in FGIDs as well as targets for improved therapeutic approaches.

  13. A quantitative performance measure for a clinical evaluation of comb structure removal algorithms in flexible endoscopy

    Science.gov (United States)

    Rupp, Stephan

    2008-03-01

    Modern techniques for technical inspection as well as medical diagnostics and therapy in keyhole-surgery scenarios make use of flexible endoscopes. Common to both application fields are very small natural or manmade entry points to the observed scene, as well as the complexity of the hollow itself. These make the use of rigid lens-based endoscopes or tip chip videoscopes impossible. Due to the fact that the fiber-optic image guide of a flexible endoscope introduces a comb structure to the acquired images, many research has been devoted to algorithms for an effective removal of such artifacts. Oftentimes, this research has been motivated by the fact, that the comb structure prevents an application of some well-established methods offered by the computer vision and image processing community. Unfortunately, the performance of the presented approaches are commonly visually evaluated or with respect to proprietary, non-standardized metrics. Thus, the performances of individual algorithms are hard to compare with each other. For this reasons, we propose a performance measure for fiber-optic imaging devices that has been motivated by the physics of optics. In this field, an optical system is frequently described by linear systems theory and the system's quality can be expressed by its transfer function. The determination of this transfer function has been standardized by the ISO for lens based imaging systems and represents a widely accepted measure for the quality of such systems. In this contribution, we present methods that account for fiber-optic imaging systems and thus enable a standardized performance evaluation. Finally, we demonstrate its use by comparing two recent state of the art comb structure removal algorithms, each of them being a representative of a spatial and a frequency domain method, respectively.

  14. Sex hormones and adult hippocampal neurogenesis: Regulation, implications, and potential mechanisms.

    Science.gov (United States)

    Mahmoud, Rand; Wainwright, Steven R; Galea, Liisa A M

    2016-04-01

    Neurogenesis within the adult hippocampus is modulated by endogenous and exogenous factors. Here, we review the role of sex hormones in the regulation of adult hippocampal neurogenesis in males and females. The review is framed around the potential functional implications of sex hormone regulation of adult hippocampal neurogenesis, with a focus on cognitive function and mood regulation, which may be related to sex differences in incidence and severity of dementia and depression. We present findings from preclinical studies of endogenous fluctuations in sex hormones relating to reproductive function and ageing, and from studies of exogenous hormone manipulations. In addition, we discuss the modulating roles of sex, age, and reproductive history on the relationship between sex hormones and neurogenesis. Because sex hormones have diverse targets in the central nervous system, we overview potential mechanisms through which sex hormones may influence hippocampal neurogenesis. Lastly, we advocate for a more systematic consideration of sex and sex hormones in studying the functional implications of adult hippocampal neurogenesis.

  15. AIDS and sex tourism.

    Science.gov (United States)

    Herold, E S; Van Kerkwijk, C

    1992-01-01

    Tourists traveling internationally lower their inhibitions and take greater risks than they would typically in their home cultures. Loneliness, boredom, and a sense of freedom contribute to this behavioral change. Some tourists travel internationally in search of sexual gratification. This motivation may be actively conscious or subconscious to the traveler. Billed as romantic with great natural beauty, Thailand, the Philippines, Brazil, the Dominican Republic, and Kenya are popular destinations of tourists seeking sex. The Netherlands and countries in eastern Europe are also popular. With most initial cases of HIV infection in Europe having histories of international travel, mass tourism is a major factor in the international transmission of AIDS. While abroad, tourists have sex with casual partners, sex workers, and/or other tourists. Far from all tourists, however, carry and consistently use condoms with these partners. One study found female and non white travelers to be less likely than Whites and males to carry condoms. The risk of HIV infection increases in circumstances where condoms are not readily available in the host country and/or are of poor quality. Regarding actual condom use, a study found only 34% of sex tourists from Switzerland to consistently use condoms while abroad. 28% of men in an STD clinic in Melbourne, Australia, reported consistent condom use in sexual relations while traveling in Asia; STDs were identified in 73% of men examined. The few studies of tourists suggest that a significant proportion engage in risky behavior while traveling. HIV prevalence is rapidly increasing in countries known as destinations for sex tourism. High infection rates are especially evident among teenage sex workers in Thailand. Simply documenting the prevalence of risky behavior among sex tourists will not suffice. More research is needed on travelers and AIDS with particular attention upon the motivating factors supporting persistent high-risk behavior.

  16. Weaving quantum optical frequency combs into continuous-variable hypercubic cluster states

    Science.gov (United States)

    Wang, Pei; Chen, Moran; Menicucci, Nicolas C.; Pfister, Olivier

    2014-09-01

    Cluster states with higher-dimensional lattices that cannot be physically embedded in three-dimensional space have important theoretical interest in quantum computation and quantum simulation of topologically ordered condensed-matter systems. We present a simple, scalable, top-down method of entangling the quantum optical frequency comb into hypercubic-lattice continuous-variable cluster states of a size of about 104 quantum field modes, using existing technology. A hypercubic lattice of dimension D (linear, square, cubic, hypercubic, etc.) requires but D optical parametric oscillators with bichromatic pumps whose frequency splittings alone determine the lattice dimensionality and the number of copies of the state.

  17. SYNTHESIS AND CHARACTERIZATION OF COMB-LIKE POLYMERS BEARING HETEROCYCLIC AZO GROUP AND MESOGENIC GROUP

    Institute of Scientific and Technical Information of China (English)

    Hui-qi Zhang; Wen-qiang Huang; Chen-xi Li; Bing-lin He

    1999-01-01

    The synthesis and characterization of a series of novel comb-like polymethacrylates bearing heterocyclic azo group and mesogenic group are described. The thermal properties of the polymers such as thermal stability and phase transition behavior were investigated by thermogravimetric analysis, differential thermal analysis and polarizing optical microscopy techniques. The experimental results show that all the synthesized polymers do not exhibit liquid crystallinity except the homopolymer of the mesogenic monomer MAPB2 and the glass transition temperatures of the polymers increase with increasing content of azo moiety in polymers linearly.

  18. IONIC CONDUCTIVITY IN THE COMPLEXES OF COMB-SHAPED POLYETHER WITH LITHIUM AROMATIC SULFONATE

    Institute of Scientific and Technical Information of China (English)

    ZHANG Shengshui; QIU Weihua; XUE Dacui; LIU Qingguo

    1993-01-01

    Complexes of comb-shaped polyether and lithium aromatic sulfonates bearing different negative charge number were prepared by in situ thermal polymerization. Their conductivity depends deeply on salt content, ambient temperature and negative charge number of the added salts. Results show that anions can be partly immobilized by increasing their negative charges at lower temperature.Against discharge time the short circuit current of the battery (Li/complex film/Lix V3O8) is stabilized by increasing the anionic charge number of the complex.

  19. Ultra-broadband Photonic Harmonic Mixer Based on Optical Comb Generation

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei;

    2012-01-01

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... is experimentally demonstrated. Moreover, the error vector magnitude (EVM) performance of a multi-gigabit quadrature phase shift keying (QPSK) signal at 62.5, 82.5 and 102.5GHz carrier frequencies is studied to evaluate the downconversion efficiency. The proposed photonic harmonic mixer can be a candidate...

  20. Erratum to “Ultra-Broadband Photonic Harmonic Mixer Based on Optical Comb Generation”

    DEFF Research Database (Denmark)

    Zhao, Ying; Pang, Xiaodan; Deng, Lei;

    2012-01-01

    We propose a novel photonic harmonic mixer operating at frequencies up to the millimeter-wave (MMW) band. By combining a broadband fiber-wireless signal with highorder harmonics of a fundamental local oscillator in an optical frequency comb generator, frequency down-conversion can be implemented...... is experimentally demonstrated. Moreover, the error vector magnitude (EVM) performance of a multi-gigabit quadrature phase shift keying (QPSK) signal at 62.5, 82.5 and 102.5GHz carrier frequencies is studied to evaluate the downconversion efficiency. The proposed photonic harmonic mixer can be a candidate...

  1. Combing and self-assembly phenomena in dry films of Taxol-stabilized microtubules

    Directory of Open Access Journals (Sweden)

    Rose Franck

    2007-01-01

    Full Text Available AbstractMicrotubules are filamentous proteins that act as a substrate for the translocation of motor proteins. As such, they may be envisioned as a scaffold for the self-assembly of functional materials and devices. Physisorption, self-assembly and combing are here investigated as a potential prelude to microtubule-templated self-assembly. Dense films of self-assembled microtubules were successfully produced, as well as patterns of both dendritic and non-dendritic bundles of microtubules. They are presented in the present paper and the mechanism of their formation is discussed.

  2. A proposal for the generation of optical frequency comb in temperature insensitive microcavity

    Science.gov (United States)

    Lei, Xun; Bian, Dandan; Chen, Shaowu

    2016-11-01

    We numerically simulate the generation of an optical frequency comb (OFC) in a microring based on the traditional Si3N4 strip waveguide and a temperature compensated slot waveguide. The results show that OFCs are susceptible to temperature with strip waveguide while they can keep stable when temperature changes 10 K in either low-Q (105) or high-Q (106) microcavity with the well-designed slot waveguide, which has great superiority in practical applications where the temperature drift of the cavity due to the intense pump or surrounding change is unavoidable. Project supported by the National Natural Science Foundation of China (Grant Nos. 61435002, 61527823, and 61321063).

  3. Dual-etalon cavity ring-down frequency-comb spectroscopy with broad band light source

    Science.gov (United States)

    Chandler, David W; Strecker, Kevin E

    2014-04-01

    In an embodiment, a dual-etalon cavity-ring-down frequency-comb spectrometer system is described. A broad band light source is split into two beams. One beam travels through a first etalon and a sample under test, while the other beam travels through a second etalon, and the two beams are recombined onto a single detector. If the free spectral ranges ("FSR") of the two etalons are not identical, the interference pattern at the detector will consist of a series of beat frequencies. By monitoring these beat frequencies, optical frequencies where light is absorbed may be determined.

  4. Dispersing multi-component and unstable powders in aqueous media using comb-type anionic polymers

    DEFF Research Database (Denmark)

    Laarz, E.; Kauppi, A.; Andersson, K.M.;

    2006-01-01

    We have investigated the effect of polymeric dispersants on the rheological properties and consolidation behavior of concentrated cemented carbide (WC-Co) and magnesia (MgO) suspensions. The relatively novel types of comb-type anionic polymers with grafted non-ionic side chains are effective...... of the grafted ethylene oxide side chains showed that the dispersants adsorb onto a MgO surface and infer a repulsion where the range scales with the length of the poly ethylene oxide side chains. The compressibility and the consolidation behavior of MgO particle networks in response to a centrifugal force field...

  5. Measurement of the Group Velocity Dispersion of air using a femtosecond comb

    Science.gov (United States)

    Al salamah, Reem

    In this thesis, the Group Velocity Dispersion (GVD) of air has been measured by using a femtosecond frequency comb at 1.5 microm. By comparing the spectra from a balanced and unbalanced Mach - Zehnder interferometer, the need for vacuum tube is eliminated. The method employs the Fast Fourier Transform of both auto- and cross correlation to find the spectral and their differences. The GVD of air is then calculated from these spectral phase differences. With twenty-five independent measurements, the GVD of air was found to be 0.0120 fs2/mm, with a standard deviation of 0.0075 fs2/mm.

  6. Transfer of Acetobacter oboediens Sokollek et al 1998 and Acetobacter intermedius Boesch et al. 1998 to the genus Gluconacetobacter as Gluconacetobacter oboediens comb. nov. and Gluconacetobacter intermedius comb. nov.

    Science.gov (United States)

    Yamada, Y

    2000-11-01

    Acetobacter oboediens Sokollek et al. 1998 and Acetobacter intermedius Boesch et al. 1998 are transferred to the genus Gluconacetobacter as Gluconacetobacter oboediens comb. nov. and Gluconacetobacter intermedius comb. nov. because, on the basis of their 16S rRNA gene sequences, the type strains of both species are located in the cluster of the genus Gluconacetobacter along with those of Gluconacetobacter xylinus, Gluconacetobacter europaeus, Gluconacetobacter hansenii, Gluconacetobacter liquefaciens (the type species) and Gluconacetobacter diazotrophicus. The significance of growth on mannitol agar and the presence of a ubiquinone isoprenologue composed of Q-10 is discussed for characterization of the genus Gluconacetobacter.

  7. Frequency Comb Generation in 300 nm Thick SiN Concentric-Racetrack-Resonators: Overcoming the Material Dispersion Limit

    CERN Document Server

    Kim, Sangsik; Wang, Cong; Jaramillo-Villegas, Jose A; Xue, Xiaoxiao; Bao, Chengying; Xuan, Yi; Leaird, Daniel E; Weiner, Andrew M; Qi, Minghao

    2016-01-01

    Kerr nonlinearity based frequency combs and solitons have been generated from on-chip optical microresonators with high quality factors and global or local anomalous dispersion. However, fabrication of such resonators usually requires materials and/or processes that are not standard in semiconductor manufacturing facilities. Moreover, in certain frequency regimes such as visible and ultra-violet, the large normal material dispersion makes it extremely difficult to achieve anomalous dispersion. Here we present a concentric racetrack-shaped resonator that achieves anomalous dispersion in a 300 nm thick silicon nitride film, suitable for semiconductor manufacturing but previously thought to result only in waveguides with high normal dispersion, a high intrinsic Q of 1.5 million, and a novel mode-selective coupling scheme that allows coherent combs to be generated. We also provide evidence suggestive of soliton-like pulse formation in the generated comb. Our method can achieve anomalous dispersion over moderately...

  8. Comb-based radio-frequency photonic filters: rounts to nanosecond tuning speed and extremely high stopband attenuation

    CERN Document Server

    Supradeepa, V R; Wu, Rui; Ferdous, Fahmida; Hamidi, Ehsan; Leaird, Daniel E; Weiner, Andrew M

    2011-01-01

    Photonic technologies have received considerable attention for enhancement of radio-frequency (RF) electrical systems, including high-frequency analog signal transmission, control of phased arrays, analog-to-digital conversion, and signal processing. Although the potential of radio-frequency photonics for implementation of tunable electrical filters over broad RF bandwidths has been much discussed, realization of programmable filters with highly selective filter lineshapes has faced significant challenges. In this paper we show that a new approach based on optical frequency combs enables dramatic progress. A novel comb generation scheme employing tailored electro-optic modulation and cascaded four-wave mixing results in approximately Gaussian RF filter lineshapes with extremely high (>60 dB) out-of-band suppression. A modification of our approach provides RF filter tuning through optical delay variation and decouples filter tuning and lineshape control. By exploiting a dual-comb scheme, the optical delay and ...

  9. Multi-service small-cell cloud wired/wireless access network based on tunable optical frequency comb

    Science.gov (United States)

    Xiang, Yu; Zhou, Kun; Yang, Liu; Pan, Lei; Liao, Zhen-wan; Zhang, Qiang

    2015-11-01

    In this paper, we demonstrate a novel multi-service wired/wireless integrated access architecture of cloud radio access network (C-RAN) based on radio-over-fiber passive optical network (RoF-PON) system, which utilizes scalable multiple- frequency millimeter-wave (MF-MMW) generation based on tunable optical frequency comb (TOFC). In the baseband unit (BBU) pool, the generated optical comb lines are modulated into wired, RoF and WiFi/WiMAX signals, respectively. The multi-frequency RoF signals are generated by beating the optical comb line pairs in the small cell. The WiFi/WiMAX signals are demodulated after passing through the band pass filter (BPF) and band stop filter (BSF), respectively, whereas the wired signal can be received directly. The feasibility and scalability of the proposed multi-service wired/wireless integrated C-RAN are confirmed by the simulations.

  10. High-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator

    CERN Document Server

    Zhu, Feng; Kolomenskii, Alexandre A; Strohaber, James; Holzwarth, Ronald; Schuessler, Hans A

    2013-01-01

    We report on a high-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator with a stabilized repetition rate at 250 MHz. The mid-infrared frequency comb is produced through difference frequency generation in a periodically poled MgO-doped lithium niobate crystal. The output power is about 120 mW with a pulse duration of about 80 fs, and spectrum coverage from 2.9 to 3.6 um. The coherence properties of the produced high-power broadband mid-infrared frequency comb are maintained, which was verified by heterodyne measurements. As the first application, the spectrum of a ~200 ppm methane-air mixture in a short 20 cm glass cell at ambient atmospheric pressure and temperature was measured.

  11. Spectroscopy of 171Yb in an optical lattice based on laser linewidth transfer using a narrow linewidth frequency comb.

    Science.gov (United States)

    Inaba, Hajime; Hosaka, Kazumoto; Yasuda, Masami; Nakajima, Yoshiaki; Iwakuni, Kana; Akamatsu, Daisuke; Okubo, Sho; Kohno, Takuya; Onae, Atsushi; Hong, Feng-Lei

    2013-04-08

    We propose a novel, high-performance, and practical laser source system for optical clocks. The laser linewidth of a fiber-based frequency comb is reduced by phase locking a comb mode to an ultrastable master laser at 1064 nm with a broad servo bandwidth. A slave laser at 578 nm is successively phase locked to a comb mode at 578 nm with a broad servo bandwidth without any pre-stabilization. Laser frequency characteristics such as spectral linewidth and frequency stability are transferred to the 578-nm slave laser from the 1064-nm master laser. Using the slave laser, we have succeeded in observing the clock transition of (171)Yb atoms confined in an optical lattice with a 20-Hz spectral linewidth.

  12. What Asexuality Contributes to the Same-Sex Marriage Discussion.

    Science.gov (United States)

    Scherrer, Kristin S

    2010-01-01

    While same-sex marriage debates have captured public attention, it is but one component of a broader discussion regarding the role of marriage in a changing society. To inform this discussion, I draw on qualitative, Internet survey data from 102 self-identified asexual individuals. I find that asexual relationships are complicated and nuanced in ways that have implications for a GLBTQ political agenda, including same-sex marriage recognition. In addition, findings indicate that assumptions of sex and sexuality in relationships are problematic and that present language for describing relationships is limiting. Findings suggest a social justice agenda for marginalized sexualities should be broader in scope than same-sex marriage.

  13. Nuclear charge radii of light isotopes based on frequency comb measurements

    Energy Technology Data Exchange (ETDEWEB)

    Zakova, Monika

    2010-02-11

    Optical frequency comb technology has been used in this work for the first time to investigate the nuclear structure of light radioactive isotopes. Therefore, three laser systems were stabilized with different techniques to accurately known optical frequencies and used in two specialized experiments. Absolute transition frequency measurements of lithium and beryllium isotopes were performed with accuracy on the order of 10{sup -10}. Such a high accuracy is required for the light elements since the nuclear volume effect has only a 10{sup -9} contribution to the total transition frequency. For beryllium, the isotope shift was determined with an accuracy that is sufficient to extract information about the proton distribution inside the nucleus. A Doppler-free two-photon spectroscopy on the stable lithium isotopes {sup 6,7}Li was performed in order to determine the absolute frequency of the 2S {yields} 3S transition. The achieved relative accuracy of 2 x 10{sup -10} is improved by one order of magnitude compared to previous measurements. The results provide an opportunity to determine the nuclear charge radius of the stable and short-lived isotopes in a pure optical way but this requires an improvement of the theoretical calculations by two orders of magnitude. The second experiment presented here was performed at ISOLDE/CERN, where the absolute transition frequencies of the D{sub 1} and D{sub 2} lines in beryllium ions for the isotopes {sup 7,9,10,11}Be were measured with an accuracy of about 1 MHz. Therefore, an advanced collinear laser spectroscopy technique involving two counter-propagating frequency-stabilized laser beams with a known absolute frequency was developed. The extracted isotope shifts were combined with recent accurate mass shift calculations and the root-mean square nuclear charge radii of {sup 7,10}Be and the one-neutron halo nucleus {sup 11}Be were determined. Obtained charge radii are decreasing from {sup 7}Be to {sup 10}Be and increasing again for

  14. Sex and the single cell. II. There is a time and place for sex.

    Directory of Open Access Journals (Sweden)

    Carmen C Robinett

    2010-05-01

    Full Text Available The Drosophila melanogaster sex hierarchy controls sexual differentiation of somatic cells via the activities of the terminal genes in the hierarchy, doublesex (dsx and fruitless (fru. We have targeted an insertion of GAL4 into the dsx gene, allowing us to visualize dsx-expressing cells in both sexes. Developmentally and as adults, we find that both XX and XY individuals are fine mosaics of cells and tissues that express dsx and/or fruitless (fru(M, and hence have the potential to sexually differentiate, and those that don't. Evolutionary considerations suggest such a mosaic expression of sexuality is likely to be a property of other animal species having two sexes. These results have also led to a major revision of our view of how sex-specific functions are regulated by the sex hierarchy in flies. Rather than there being a single regulatory event that governs the activities of all downstream sex determination regulatory genes-turning on Sex lethal (Sxl RNA splicing activity in females while leaving it turned off in males-there are, in addition, elaborate temporal and spatial transcriptional controls on the expression of the terminal regulatory genes, dsx and fru. Thus tissue-specific aspects of sexual development are jointly specified by post-transcriptional control by Sxl and by the transcriptional controls of dsx and fru expression.

  15. Generation of tunable, high repetition rate frequency combs with equalized spectra using carrier injection based silicon modulators

    Science.gov (United States)

    Nagarjun, K. P.; Selvaraja, Shankar Kumar; Supradeepa, V. R.

    2016-03-01

    High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN - waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

  16. Frequency measurement of THz waves by electro-optic sampling using Mach-Zehnder-modulator-based flat comb generator

    Science.gov (United States)

    Morohashi, Isao; Kirigaya, Mayu; Kaneko, Yuta; Katayama, Ikufumi; Sakamoto, Takahide; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

    2016-02-01

    In the recent progress in terahertz (THz) devices, various kinds of source devices, such as resonant tunneling diodes, quantum cascade lasers and so forth, have been developed. Frequency measurement of THz radiations, which can operate in high speed and at room-temperature, is important for development of high-performance THz source devices. Recently, frequency measurement using optical combs are demonstrated by several groups. In these techniques, modelocked lasers (MLLs) are used for optical comb source, so that phase-locking techniques are required in order to stabilize the repetition frequency of the MLLs. On the other hand, a modulator-based optical comb generator has high accuracy and stability in the comb spacing, which is comparable to that of microwave signal driving the modulator. Thus it is suitable for frequency measurement of THz waves. In this paper, we demonstrated frequency measurement of THz waves using a Mach-Zehnder-modulator-based flat comb generator (MZ-FCG). The frequency measurement was carried out by an electro-optic (EO) sampling method, where an optical two-tone signal extracted from the optical comb generated by the MZ-FCG was used for the probe light. A 100 GHz signal generated by a W-band frequency multiplier and the probe beam collinearly traveled through an EO crystal, and beat signals between them were measured by a combination of a balanced photodetector and a spectrum analyzer. As a result, frequency measurement of the 100 GHz wave was successfully demonstrated, in which the linewidth of the beat signal was less than 1 Hz.

  17. Sex guilt and life satisfaction in Iranian-american women.

    Science.gov (United States)

    Abdolsalehi-Najafi, Emon; Beckman, Linda J

    2013-08-01

    Although the experience of sex guilt has been considered among a variety of ethnic groups, the area has not yet been empirically explored among Iranian American women. The present study investigated the relationship between sexual self-schema (i.e., beliefs about the sexual aspects of oneself), acculturation, and sex guilt, and it further examined the association between sex guilt and life satisfaction in Iranian American women. A total of 65 Iranian American women, with a mean age of 31.3 years (SD = 11.7), completed five self-administered questionnaires. Findings indicated a significant inverse correlation between sexual self-schema and sex guilt. More specifically, women who endorsed negative self-views regarding their sexual self reported higher levels sex guilt. Results revealed that acculturation was unrelated to sex guilt, when the effect of being Muslim or non-Muslim was controlled. Women with high sex guilt reported significantly lower levels of life satisfaction. Moreover, analyses for mediation effects supported sex guilt as a partially mediating variable between sexual self-schema and life satisfaction. Levels of sex guilt were higher among Muslim women when compared to women of other religious affiliations. Additionally, Muslim women appeared to be significantly less acculturated to Western ideals than other religious groups. The present findings suggest that mental health professionals who provide services to Iranian American women need to consider the negative effects of sex guilt, particularly among Muslim women.

  18. Sex Determination and Sexual Organ Differentiation in Flowering Plants

    Institute of Scientific and Technical Information of China (English)

    Hou Yanan; Li Fenglan; Gao Shumin

    2004-01-01

    The research in the genetics of sex determination and the differentiation of reproductive organs in flowering plants has long been a topic in recent years. Understanding the genetic and molecular mechanisms that control sex determination in flowering plants relies on detailed studies of the differentiation of sexual organs. Current theories about sex chromosomes have illuminated the mechanisms of plant sex determination. In addition, recent progress in cloning floral homeotic genes which regulate the identity of the floral organs has generated molecular markers to compare the developmental programs of male, female and hermaphrodite flowers in several species. In this review, the authors focus attention on these recent findings and provide a brief overview of the genetics of plant sex determination and the mechanism of sex determination gene expression and gene programs.

  19. Sex Hormones and Tendon

    DEFF Research Database (Denmark)

    Hansen, Mette; Kjaer, Michael

    2016-01-01

    The risk of overuse and traumatic tendon and ligament injuries differ between women and men. Part of this gender difference in injury risk is probably explained by sex hormonal differences which are specifically distinct during the sexual maturation in the teenage years and during young adulthood....... The effects of the separate sex hormones are not fully elucidated. However, in women, the presence of estrogen in contrast to very low estrogen levels may be beneficial during regular loading of the tissue or during recovering after an injury, as estrogen can enhance tendon collagen synthesis rate. Yet...... has also been linked to a reduced responsiveness to relaxin. The present chapter will focus on sex difference in tendon injury risk, tendon morphology and tendon collagen turnover, but also on the specific effects of estrogen and androgens....

  20. Corruption and sex

    Directory of Open Access Journals (Sweden)

    Milutinović-Bojanić Sanja

    2013-01-01

    Full Text Available Taking into account the difference between the ancient and modern (even postmodern understandings of corruption, I am curious to explore why the bond linking corruption and sex seems so obvious. I have no intention of investigating both phenomena in the context of any moral category. What then did Flaubert have on his mind when he wrote that Rodolphe “treated Emma quite sans façon. He made of her something supple and corrupt.” What underpins the irresistible attraction between corruption and sex? Why is it impossible to eradicate corruption and repress sex and perceive them as solely functional strategies of generation and reproduction? This short outline follows certain philosophical remarks of Luce Irigaray and her thematization of the sexual difference in the demarcation of generation and corruption.

  1. A new type of HTc superconducting film comb-shape resonator for radio frequency superconducting quantum interference devices

    Institute of Scientific and Technical Information of China (English)

    MAO Hai-yan; WANG Fu-ren; MENG Shu-chao; MAO Bo; LI Zhuang-zhi; NIE Rui-juan; LIU Xin-yuan; DAI Yuan-dong

    2006-01-01

    A new type of HTc superconducting film combshape resonator for radio frequency superconducting quantum interference devices (RF SQUID) has been designed.This new type of superconducting film comb-shape resonator is formed by a foursquare microstrip line without a flux concentrator.The range of the center frequency of this type of resonator varies from 800 MHz to 1300 MHz by changing the length of the teeth.In this paper,we report on simulating the relationship of the value of the center frequency and the length of the teeth,and testing the noise of HTc RF SQUID coupling this comb-shape resonator.

  2. A priori bounds and global bifurcation results for frequency combs modeled by the Lugiato-Lefever equation

    OpenAIRE

    Mandel, Rainer; Reichel, Wolfgang

    2016-01-01

    In nonlinear optics $2\\pi$-periodic solutions $a\\in C^2([0,2\\pi];\\mathbb{C})$ of the stationary Lugiato-Lefever equation $-d a"= ({\\rm i} -\\zeta)a +|a|^2a-{\\rm i} f$ serve as a model for frequency combs, which are optical signals consisting of a superposition of modes with equally spaced frequencies. We prove that nontrivial frequency combs can only be observed for special ranges of values of the forcing and detuning parameters $f$ and $\\zeta$, as it has been previously documented in experime...

  3. Finite Element Analysis of the Vertical Levitation Force in an Electrostatic MEMS Comb Drive Actuator

    Science.gov (United States)

    Wooldridge, J.; Blackburn, J.; Muniz-Piniella, A.; Stewart, M.; Shean, T. A. V.; Weaver, P. M.; Cain, M. G.

    2013-11-01

    A vertical levitation electrostatic comb drive actuator was manufactured for the purpose of measuring piezoelectric coefficients in small-scale materials and devices. Previous modelling work on comb drive levitation has focussed on control of the levitation in standard poly-silicon devices in order to minimize effects on lateral modes of operation required for the accelerometer and gyroscope applications. The actuator developed in this study was manufactured using a 20 μm electroplated Ni process with a 25 μm trench created beneath the released structure through chemical wet etching. A finite element analysis using ZINC was used to model electrostatic potential around a cross section of one static and one movable electrode, from which the net levitation force per unit electrode was calculated. The model was first verified using the electrode geometry from previously studied systems, and then used to study the variation of force as a function of decreasing substrate-electrode distance. With the top electrode surfaces collinear the calculated force density is 0.00651 epsilon0V2Mμm-1, equivalent to a total force for the device of 36.4 μN at an applied voltage of VM=100 V, just 16% larger than the observed value. The measured increase in force with distance was smaller than predicted with the FEA, due to the geometry of the device in which the electrodes at the anchored ends of the supporting spring structure displace by a smaller amount than those at the centre.

  4. Channel Estimation Based in Comb-Type Pilots Arrangement for OFDM System over Time Varying Channel

    Directory of Open Access Journals (Sweden)

    Hala M. Mahmoud

    2010-07-01

    Full Text Available Orthogonal Frequency Division Multiplexing (OFDM has been recently applied widely in wireless communication systems, due to its high data rate, transmission capability with high bandwidth, efficiency and its robustness to multipath delay .Channel estimation is an essential problem in OFDM system. Pilot-aided channel estimation has been used; a good choice of the pilot pattern should match the channel behavior both in time and frequency domains. We explored comb pilot arrangements. The advantage for comb type pilots arrangement in channel estimation is the ability to track the variation of the channel caused by doppler frequency, it is observed that the doppler effect can be reduced, and so this will increase the system mobility. Kalman and Least Square (LS estimators have been proposed to estimate the Channel Frequency Response (CFR at the pilots location, then CFR at data sub channels are obtained by mean of interpolation between estimates at pilot locations. Different types of interpolations have been used such as; low pass interpolation; spline cubic interpolation and linear interpolation. Kalman estimation has better performance than LS estimation. The estimators perform about the same for SNR lower than 10 dB. The performances of all schemes have been compared by finding Bit Error Rate (BER, where BPSK modulation scheme was used.

  5. Production and characterization of bacterial cellulose membranes with hyaluronic acid from chicken comb.

    Science.gov (United States)

    de Oliveira, Sabrina Alves; da Silva, Bruno Campos; Riegel-Vidotti, Izabel Cristina; Urbano, Alexandre; de Sousa Faria-Tischer, Paula Cristina; Tischer, Cesar Augusto

    2017-04-01

    The bacterial cellulose (BC), from Gluconacetobacter hansenii, is a biofilm with a high degree of crystallinity that can be used for therapeutic purposes and as a candidate for healing wounds. Hyaluronic acid (HA) is a constitutive polysaccharide found in the extracellular matrix and is a material used in tissue engineering and scaffolding for tissue regeneration. In this study, polymeric composites were produced in presence of hyaluronic acid isolated from chicken comb on different days of fermentation, specifically on the first (BCHA-SABT0) and third day (BCHA-SABT3) of fermentation. The structural characteristics, thermal stability and molar mass of hyaluronic acid from chicken comb were evaluated. Native membrane and polymeric composites were characterized with respect to their morphology and crystallinity. The optimized process of extraction and purification of hyaluronic acid resulted in low molar mass hyaluronic acid with structural characteristics similar to the standard commercial hyaluronic acid. The results demonstrate that the polymeric composites (BC/HA-SAB) can be produced in situ. The membranes produced on the third day presented better incorporation of HA-SAB between cellulose microfiber, resulting in membranes with higher thermal stability, higher roughness and lower crystallinity. The biocompatiblily of bacterial cellulose and the importance of hyaluronic acid as a component of extracellular matrix qualify the polymeric composites as promising biomaterials for tissue engineering.

  6. Integrated wideband optical frequency combs with high stability and their application in microwave photonic filters

    Science.gov (United States)

    Sun, Wenhui; Wang, Sunlong; Zhong, Xin; Liu, Jianguo; Wang, Wenting; Tong, Youwan; Chen, Wei; Yuan, Haiqing; Yu, Lijuan; Zhu, Ninghua

    2016-08-01

    An integrated wideband optical frequency comb (OFC) based on a semiconductor quantum dot laser is realized with high stability. The OFC module is packaged in our lab. A circuit which is designed to provide a low-ripple current and control the temperature regards as a servo system to enhance the stability of the OFC. The frequency stability of the OFC is 2.7×10-9 (Allan Variance). The free spectral range (FSR) of the OFC is 40 GHz and the number of comb lines is up to 55. The flatness of the OFC over span of 4 nm can be limited to 0.5 dB. Negative coefficients microwave photonic filters with multiple taps are generated based on the proposed OFC. For the 10 taps microwave photonic filter, the pass-band at 8.74 GHz has a 3 dB bandwidth of 630 MHz with 16.58 dB side-lobe suppression. Compared with the published microwave photonic filters, the proposed system is more stable, of more compact structures, and of less power consumption.

  7. Self-referenceable frequency comb from an ultrafast thin disk laser.

    Science.gov (United States)

    Saraceno, Clara J; Pekarek, Selina; Heckl, Oliver H; Baer, Cyrill R E; Schriber, Cinia; Golling, Matthias; Beil, Kolja; Kränkel, Christian; Huber, Günter; Keller, Ursula; Südmeyer, Thomas

    2012-04-23

    We present the first measurement of the carrier envelope offset (CEO) frequency of an ultrafast thin disk laser (TDL). The TDL used for this proof-of-principle experiment was based on the gain material Yb:Lu(2)O(3) and delivered 7 W of average power in 142-fs pulses, which is more than two times shorter than previously realized with this material. Using only 65 mW of the output of the laser, we generated a coherent octave-spanning supercontinuum (SC) in a highly nonlinear photonic crystal fiber (PCF). We detected the CEO beat signal using a standard f-to-2f interferometer, achieving a signal-to-noise ratio of >25 dB (3 kHz resolution bandwidth). The CEO frequency was tunable with the pump current with a slope of 33 kHz/mA. This result opens the door towards high-power frequency combs from unamplified oscillators. Furthermore, it confirms the suitability of these sources for future intralaser extreme nonlinear optics experiments such as high harmonic generation and VUV frequency comb generation from compact sources.

  8. Nonlinear dynamics of spring softening and hardening in folded-mems comb drive resonators

    KAUST Repository

    Elshurafa, Amro M.

    2011-08-01

    This paper studies analytically and numerically the spring softening and hardening phenomena that occur in electrostatically actuated microelectromechanical systems comb drive resonators utilizing folded suspension beams. An analytical expression for the electrostatic force generated between the combs of the rotor and the stator is derived and takes into account both the transverse and longitudinal capacitances present. After formulating the problem, the resulting stiff differential equations are solved analytically using the method of multiple scales, and a closed-form solution is obtained. Furthermore, the nonlinear boundary value problem that describes the dynamics of inextensional spring beams is solved using straightforward perturbation to obtain the linear and nonlinear spring constants of the beam. The analytical solution is verified numerically using a Matlab/Simulink environment, and the results from both analyses exhibit excellent agreement. Stability analysis based on phase plane trajectory is also presented and fully explains previously reported empirical results that lacked sufficient theoretical description. Finally, the proposed solutions are, once again, verified with previously published measurement results. The closed-form solutions provided are easy to apply and enable predicting the actual behavior of resonators and gyroscopes with similar structures. © 2011 IEEE.

  9. Nonlinear Cavity and Frequency Comb Radiations Induced by Negative Frequency Field Effects

    Science.gov (United States)

    Lourés, Cristian Redondo; Faccio, Daniele; Biancalana, Fabio

    2015-11-01

    Optical Kerr frequency combs (KFCs) are an increasingly important optical metrology tool with applications ranging from ultraprecise spectroscopy to time keeping. KFCs may be generated in compact resonators with extremely high quality factors. Here, we show that the same features that lead to high quality frequency combs in these resonators also lead to an enhancement of nonlinear emissions that may be identified as originating from the presence of a negative frequency (NF) component in the optical spectrum. While the negative frequency component of the spectrum is naturally always present in the real-valued optical field, it is not included in the principal theoretical model used to model nonlinear cavities, i.e., the Lugiato-Lefever equation. We therefore extend these equations in order to include the contribution of NF components and show that the predicted emissions may be studied analytically, in excellent agreement with full numerical simulations. These results are of importance for a variety of fields, such as Bose-Einstein condensates, mode-locked lasers, nonlinear plasmonics, and polaritonics.

  10. Frequency Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths

    CERN Document Server

    Rieker, Gregory B; Swann, William C; Kofler, Jon; Zolot, Alex M; Sinclair, Laura C; Baumann, Esther; Cromer, Christopher; Petron, Gabrielle; Sweeney, Colm; Tans, Pieter P; Coddington, Ian; Newbury, Nathan R

    2014-01-01

    We demonstrate coherent dual frequency-comb spectroscopy for detecting variations in greenhouse gases. High signal-to-noise spectra are acquired spanning 5990 to 6260 cm^-1 (1600 to 1670 nm) covering ~700 absorption features from CO2, CH4, H2O, HDO, and 13CO2, across a 2-km open-air path. The transmission of each frequency comb tooth is resolved, leading to spectra with <1 kHz frequency accuracy, no instrument lineshape, and a 0.0033-cm^-1 point spacing. The fitted path-averaged concentrations and temperature yield dry-air mole fractions. These are compared with a point sensor under well-mixed conditions to evaluate current absorption models for real atmospheres. In heterogeneous conditions, time-resolved data demonstrate tracking of strong variations in mole fractions. A precision of <1 ppm for CO2 and <3 ppb for CH4 is achieved in 5 minutes in this initial demonstration. Future portable systems could support regional emissions monitoring and validation of the spectral databases critical to global s...

  11. Lithium battery with solid polymer electrolyte based on comb-like copolymers

    Science.gov (United States)

    Daigle, Jean-Christophe; Vijh, Ashok; Hovington, Pierre; Gagnon, Catherine; Hamel-Pâquet, Julie; Verreault, Serge; Turcotte, Nancy; Clément, Daniel; Guerfi, Abdelbast; Zaghib, Karim

    2015-04-01

    In this paper we report on the synthesis of comb-like copolymers as solid polymer electrolytes (SPE). The synthesis involved anionic polymerization of styrene (St) and 4-vinylanisole (VA) as the followed by grafting of poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) by Atom Transfer Radical Polymerization (ATRP). The comb-like copolymer's structure was analyzed by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The membranes were made by solvent casting and the morphologies were analyzed by atomic forces microscopy (AFM) and scanning electron microscopy (SEM). We observed that a nano and micro phase separation occurs which improves ionic conductivity. The ionic conductivities were determined by AC Impedance, which showed that the SPEs have good conductivities (10-5 Scm-1) at room temperature owing to the negligible values (<10 kJ mol-1) of the activation energies for conductivity. The batteries with these polymers exhibit a capacity of 146 mAh g-1 at C/24, and no evidence of degradation after intense cycling was observed. However, poor cycle life was observed at C/6 and C/3, which is a consequence of several factors. We partially explain that behavior by arguing that whereas PEO lightly "solvates" Li+ thus slowing Li-ion mobility, and PEGMA chains "solvate" Li ions too strongly, trapping and inhibiting their mobility.

  12. Smooth and flat phase-locked Kerr frequency comb generation by higher order mode suppression.

    Science.gov (United States)

    Huang, S-W; Liu, H; Yang, J; Yu, M; Kwong, D-L; Wong, C W

    2016-05-16

    High-Q microresonator is perceived as a promising platform for optical frequency comb generation, via dissipative soliton formation. In order to achieve a higher quality factor and obtain the necessary anomalous dispersion, multi-mode waveguides were previously implemented in Si3N4 microresonators. However, coupling between different transverse mode families in multi-mode waveguides results in periodic disruption of dispersion and quality factor, and consequently causes perturbation to dissipative soliton formation and amplitude modulation to the corresponding spectrum. Careful choice of pump wavelength to avoid the mode crossing region is thus critical in conventional Si3N4 microresonators. Here, we report a novel design of Si3N4 microresonator in which single-mode operation, high quality factor, and anomalous dispersion are attained simultaneously. The novel microresonator is consisted of uniform single-mode waveguides in the semi-circle region, to eliminate bending induced mode coupling, and adiabatically tapered waveguides in the straight region, to avoid excitation of higher order modes. The intrinsic quality factor of the microresonator reaches 1.36 × 10(6) while the group velocity dispersion remains to be anomalous at -50 fs(2)/mm. With this novel microresonator, we demonstrate that broadband phase-locked Kerr frequency combs with flat and smooth spectra can be generated by pumping at any resonances in the optical C-band.

  13. Alignment of Gold Nanoparticle-Decorated DNA Origami Nanotubes: Substrate Prepatterning versus Molecular Combing.

    Science.gov (United States)

    Teschome, Bezu; Facsko, Stefan; Gothelf, Kurt V; Keller, Adrian

    2015-11-24

    DNA origami has become an established technique for designing well-defined nanostructures with any desired shape and for the controlled arrangement of functional nanostructures with few nanometer resolution. These unique features make DNA origami nanostructures promising candidates for use as scaffolds in nanoelectronics and nanophotonics device fabrication. Consequently, a number of studies have shown the precise organization of metallic nanoparticles on various DNA origami shapes. In this work, we fabricated large arrays of aligned DNA origami decorated with a high density of gold nanoparticles (AuNPs). To this end, we first demonstrate the high-yield assembly of high-density AuNP arrangements on DNA origami adsorbed to Si surfaces with few unbound background nanoparticles by carefully controlling the concentrations of MgCl2 and AuNPs in the hybridization buffer and the hybridization time. Then, we evaluate two methods, i.e., hybridization to prealigned DNA origami and molecular combing in a receding meniscus, with respect to their potential to yield large arrays of aligned AuNP-decorated DNA origami nanotubes. Because of the comparatively low MgCl2 concentration required for the efficient immobilization of the AuNPs, the prealigned DNA origami become mobile and displaced from their original positions, thereby decreasing the alignment yield. This increased mobility, on the other hand, makes the adsorbed origami susceptible to molecular combing, and a total alignment yield of 86% is obtained in this way.

  14. Genomic data do not support comb jellies as the sister group to all other animals.

    Science.gov (United States)

    Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert

    2015-12-15

    Understanding how complex traits, such as epithelia, nervous systems, muscles, or guts, originated depends on a well-supported hypothesis about the phylogenetic relationships among major animal lineages. Traditionally, sponges (Porifera) have been interpreted as the sister group to the remaining animals, a hypothesis consistent with the conventional view that the last common animal ancestor was relatively simple and more complex body plans arose later in evolution. However, this premise has recently been challenged by analyses of the genomes of comb jellies (Ctenophora), which, instead, found ctenophores as the sister group to the remaining animals (the "Ctenophora-sister" hypothesis). Because ctenophores are morphologically complex predators with true epithelia, nervous systems, muscles, and guts, this scenario implies these traits were either present in the last common ancestor of all animals and were lost secondarily in sponges and placozoans (Trichoplax) or, alternatively, evolved convergently in comb jellies. Here, we analyze representative datasets from recent studies supporting Ctenophora-sister, including genome-scale alignments of concatenated protein sequences, as well as a genomic gene content dataset. We found no support for Ctenophora-sister and conclude it is an artifact resulting from inadequate methodology, especially the use of simplistic evolutionary models and inappropriate choice of species to root the metazoan tree. Our results reinforce a traditional scenario for the evolution of complexity in animals, and indicate that inferences about the evolution of Metazoa based on the Ctenophora-sister hypothesis are not supported by the currently available data.

  15. Optical Comb from a Whispering Gallery Mode Resonator for Spectroscopy and Astronomy Instruments Calibration

    Science.gov (United States)

    Strekalov, Dmitry V.; Yu, Nam; Thompson, Robert J.

    2012-01-01

    The most accurate astronomical data is available from space-based observations that are not impeded by the Earth's atmosphere. Such measurements may require spectral samples taken as long as decades apart, with the 1 cm/s velocity precision integrated over a broad wavelength range. This raises the requirements specifically for instruments used in astrophysics research missions -- their stringent wavelength resolution and accuracy must be maintained over years and possibly decades. Therefore, a stable and broadband optical calibration technique compatible with spaceflights becomes essential. The space-based spectroscopic instruments need to be calibrated in situ, which puts forth specific requirements to the calibration sources, mainly concerned with their mass, power consumption, and reliability. A high-precision, high-resolution reference wavelength comb source for astronomical and astrophysics spectroscopic observations has been developed that is deployable in space. The optical comb will be used for wavelength calibrations of spectrographs and will enable Doppler measurements to better than 10 cm/s precision, one hundred times better than the current state-of-the- art.

  16. Slow light enhanced atomic frequency comb quantum memories in photonic crystal waveguides

    Science.gov (United States)

    Yuan, Chenzhi; Zhang, Wei; Huang, Yidong; Peng, Jiangde

    2016-09-01

    In this paper, we propose a slow light-enhanced quantum memory with high efficiency based on atomic frequency comb (AFC) in ion-doped photonic crystal waveguide (PCW). The performance of the quantum memory is investigated theoretically, considering the impact of the signal bandwidth. Both the forward and backward retrieval schemes are analyzed. In the forward retrieval scheme, the analysis shows that a moderate slow light effect can improve the retrieval efficiency to above 50% with very high fidelity, even when the intrinsic optical depth is very low and the signal bandwidth is comparable with the AFC bandwidth. In the backward retrieval scheme, retrieval efficiency larger than 90% can be obtained and fidelity can remain above 90% for signal with bandwidth much narrower than AFC bandwidth, when moderate slow light is introduced into waveguide with low intrinsic optical depth. Although the phase mismatching effect limits the slow light enhancement on retrieval efficiency and decreases the fidelity for signal with bandwidth approaching AFC bandwidth, we design a modified atomic frequency comb structure (MAFC) based on which a moderate slow light can make the retrieval efficiency larger than 85% and keep the fidelity above 80%. Our calculations show that the proposed scheme provides a promising way to realize high efficiency on-chip quantum memory.

  17. The Predominant Relationship Between Sexual Environment Characteristics and HIV-Serodiscordant Condomless Anal Sex Among HIV-Positive Men Who Have Sex with Men (MSM).

    Science.gov (United States)

    Perry, Nicholas S; Wade Taylor, S; Elsesser, Steven; Safren, Steven A; O'Cleirigh, Conall

    2016-06-01

    In some studies, situational factors have been shown to be stronger predictors of condomless sex than individual risk factors. Cross-sectional relationships between condomless anal sex (CAS) with HIV-serodiscordant partners and risk factors across ecological levels (individual, sexual environment) were examined using a sample (N = 60) of HIV-positive men who have sex with men (MSM) who reported multiple recent episodes of CAS. Negative binomial regressions were used to evaluate the association of contextual risk factors (e.g., substance use during sex, transactional sex, public sex, sex at a sex party) with recent condomless sex, controlling for demographics and mental health. Results demonstrated that sexual environment factors, particularly sex under the influence of drugs or alcohol (B = .019, p sex (B = .035, p sex (B = .039, p sex at a sex party was not related to CAS (p = .39). For each additional sexual environment in which men engaged, their rates of CAS increased (B = .39, p < .01). Secondary prevention interventions that are tailored to the proximal sexual environment could be maximally effective, particularly if they address substance use and other challenging sexual situations.

  18. Sex Education: Talking to Toddlers and Preschoolers about Sex

    Science.gov (United States)

    Healthy Lifestyle Sexual health Sex education often begins with a child's curiosity about his or her body. Here's how to set the stage for sex education — and how to answer your child's questions. ...

  19. When Sex Meets Law

    Institute of Scientific and Technical Information of China (English)

    YIN PUMIN

    2010-01-01

    @@ Ma Yaohai,an associate professor of computer science at Nanjing University of Technology in east China's Jiangsu Province,was sentenced to three and a half years in prison on May 20 for organizing group-sex parties,renewing nationwide debate on sexual freedom in China.

  20. Sex, Courtship, and Marriage.

    Science.gov (United States)

    Seiferth, Berniece

    The author presents an historical perspective on abortion, contraception and marriage as a prelude to an examination of changing attitudes toward sex. The article deals with the negative effects attributed to the increased incidence of early dating and early marriage of teenagers in the United States. The author also assumes positions on such…

  1. Sex and deleterious mutations.

    Science.gov (United States)

    Gordo, Isabel; Campos, Paulo R A

    2008-05-01

    The evolutionary advantage of sexual reproduction has been considered as one of the most pressing questions in evolutionary biology. While a pluralistic view of the evolution of sex and recombination has been suggested by some, here we take a simpler view and try to quantify the conditions under which sex can evolve given a set of minimal assumptions. Since real populations are finite and also subject to recurrent deleterious mutations, this minimal model should apply generally to all populations. We show that the maximum advantage of recombination occurs for an intermediate value of the deleterious effect of mutations. Furthermore we show that the conditions under which the biggest advantage of sex is achieved are those that produce the fastest fitness decline in the corresponding asexual population and are therefore the conditions for which Muller's ratchet has the strongest effect. We also show that the selective advantage of a modifier of the recombination rate depends on its strength. The quantification of the range of selective effects that favors recombination then leads us to suggest that, if in stressful environments the effect of deleterious mutations is enhanced, a connection between sex and stress could be expected, as it is found in several species.

  2. Sex Education and Ideals

    Science.gov (United States)

    de Ruyter, Doret J.; Spiecker, Ben

    2008-01-01

    This article argues that sex education should include sexual ideals. Sexual ideals are divided into sexual ideals in the strict sense and sexual ideals in the broad sense. It is argued that ideals that refer to the context that is deemed to be most ideal for the gratification of sexual ideals in the strict sense are rightfully called sexual…

  3. Sex Therapy and Mastectomy

    Science.gov (United States)

    Witkin, Mildred Hope

    1975-01-01

    Because the emotional trauma associated with a mastectomy exceeds the physical trauma, the recovery of the woman is greatly affected by the response of her husband or lover. Sex therapy, therefore, involves the couple. The approach described is aimed at assisting the couple to confront and integrate the mastectomy experience. (Author)

  4. Sex education in Cyprus.

    Science.gov (United States)

    Patsalides, N

    1991-05-01

    The objective of educating people on family planning and sexuality issues has been carried forth by the Family Planning Association of Cyprus (FPAC) since 1971. The promotion of sex education in schools has generated respect for their expertise. Sex education has reached the agenda of the General Assembly of Parliament only to be postponed due to the April 1991 end of term dismissal. A newly elected Parliament are not expected to act immediately. The Ministry of Education Committee on Health Education has been actively counseled since 1974, and most recently in their examination of the possibilities of school sex education and training of high school teachers. The Ministry of Education has authority over primary and secondary education, which is compulsory up to 3 years of secondary education. The approach of FPAC has been to work with parents first in education lectures at various well publicized locations. The agenda was to inform about FPAC, explain the purpose and meaning of sex education, and show the Merry-Go-Round educational film followed by a question and answer session. Eventually, presentations involved children with parent observation. In 1977, authorization from the Ministry of Education gave official approval to FPAC, but not on school premises. FPAC went directly to headmasters and gained support in primary schools to organize sessions on school premises, which successfully involved many primary schools even in the much needed rural areas. Home Economics and Child Care, offered in the 5th and 6th grades was the only vehicle for gaining permission to enter secondary schools. In Larnaca, secondary school headmasters at the 3rd and 6th grade levels permitted invitations which requested parental permission. Lecture topics on human reproduction, sex roles, and disease and contraception were also provided in a follow-up letter. Higher education levels were involved through youth clubs and evening lectures. In 1988, FPAC urged the Director General of the

  5. Sex and gender differences in clinical medicine.

    Science.gov (United States)

    Regitz-Zagrosek, Vera; Seeland, Ute

    2012-01-01

    Sex and gender differences in frequent diseases are more widespread than one may assume. In addition, they have significant yet frequently underestimated consequences on the daily practice of medicine, on outcomes and effects of therapies. Gender medicine is a novel medical discipline that takes into account the effects of sex and gender on the health of women and men. The major goal is to improve health and health care for both, for women as well as for men. We give in this chapter an overview on sex and gender differences in a number of clinical areas, in cardiovascular diseases, pulmonary diseases, gastroenterology and hepatology, in nephrology, autoimmune diseases, endocrinology, hematology, neurology. We discuss the preferential use of male animals in drug development, the underrepresentation of women in early and cardiovascular clinical trials, sex and gender differences in pharmacology, in pharmacokinetics and pharmacodynamics, in management and drug use. Most guidelines do not include even well-known sex and gender differences. European guidelines for the management of cardiovascular diseases in pregnancy have only recently been published. Personalized medicine cannot replace gender-based medicine. Large databases reveal that gender remains an independent risk factor after ethnicity, age, comorbidities, and scored risk factors have been taken into account. Some genetic variants carry a different risk in women and men. The sociocultural dimension of gender integrating lifestyle, environment, stress, and other variables cannot be replaced by a sum of biological parameters. Because of this prominent role of gender, clinical care algorithms must include gender-based assessment.

  6. [Sex chromosomes and meiosis].

    Science.gov (United States)

    Guichaoua, M-R; Geoffroy-Siraudin, C; Tassistro, V; Ghalamoun-Slaimi, R; Perrin, J; Metzler-Guillemain, C

    2009-01-01

    Sex chromosome behaviour fundamentally differs between male and female meiosis. In oocyte, X chromosomes synapse giving a XX bivalent which is not recognizable in their morphology and behaviour from autosomal bivalents. In human male, X and Y chromosomes differ from one another in their morphology and their genetic content, leading to a limited pairing and preventing genetic recombination, excepted in homologous region PAR1. During pachytene stage of the first meiotic prophase, X and Y chromosomes undergo a progressive condensation and form a transcriptionally silenced peripheral XY body. The condensation of the XY bivalent during pachytene stage led us to describe four pachytene substages and to localize the pachytene checkpoint between substages 2 and 3. We also defined the pachytene index (PI=P1+P2/P1+P2+P3+P4) which is always less than 0.50 in normal meiosis. XY body undergoes decondensation at diplotene stage, but transcriptional inactivation of the two sex chromosomes or Meiotic Sex Chromosome Inactivation (MSCI) persists through to the end of spermatogenesis. Sex chromosome inactivation involves several proteins, some of them were now identified. Two isoforms of the HP1 protein, HP1beta and HP1gamma, are involved in the facultative heterochromatinization of the XY body, but the initiation of this process involves the phosphorylation of the protein H2AX by the kinase ATR whose recruitment depends on BRCA1. Extensive researches on the inactivation of the sex chromosomes during male meiosis will allow to a better understanding of some male infertilities.

  7. Disestablishing Sex: The Case for Released-Time Sex Education

    Science.gov (United States)

    Glanzer, Perry L.

    2011-01-01

    Allowing nonschool organizations to provide sex education in a released-time format would disestablish state-funded sex education and give families a choice in the sex education that would be provided for their children. Released-time programs, as originally conceived and currently practiced, allow students to be released for a period of time…

  8. Evolutionary transitions between sex-determining mechanisms : A review of theory

    NARCIS (Netherlands)

    van Doorn, G. S.

    2014-01-01

    The extraordinary diversity of sex-determining mechanisms found in nature is thought to have arisen by the addition, modification or replacement of regulators at the upstream end of the sex-determining pathway. The spread of a novel regulator of sex determination can manifest itself by an evolutiona

  9. Hypnotic Psychotherapy with Sex Offenders

    Science.gov (United States)

    Moseley, Sullivan; Briggs, Wanda P.; Magnus, Virginia

    2005-01-01

    The authors review the literature on the prevalence of sex offenders; multiple treatment modalities; and implications of the use of hypnotic psychotherapy, coupled with cognitive behavioral treatment programs, for treating sex offenders. (Contains 2 tables.)

  10. SHBG (Sex Hormone Binding Globulin)

    Science.gov (United States)

    ... as: Testosterone-estrogen Binding Globulin; TeBG Formal name: Sex Hormone Binding Globulin Related tests: Testosterone , Free Testosterone, ... I should know? How is it used? The sex hormone binding globulin (SHBG) test may be used ...

  11. Sex and Fertility After SCI

    Medline Plus

    Full Text Available ... having sex after a spinal cord injury? Can men and women still have sex after a spinal ... spinal cord injury? How is sexual function in men affected by a spinal cord injury ? What are ...

  12. The ABCs of Sex Ed.

    Science.gov (United States)

    Sroka, Stephen R.

    2002-01-01

    Cites statistics on extent of sexually transmitted diseases and pregnancies among adolescents; describes ideological dispute over how to teach sex education; advocates teaching the ABCs of sex education: Abstinence, Be Monogamous, and Condoms. (PKP)

  13. Broadband Continuous-Wave Multi-Harmonic Optical Comb Based on a Frequency Division-by-Three Optical Parametric Oscillator

    Directory of Open Access Journals (Sweden)

    Yen-Yin Lin

    2014-11-01

    Full Text Available We report a multi-watt broadband continuous-wave multi-harmonic optical comb based on a frequency division-by-three singly-resonant optical parametric oscillator. This cw optical comb is frequency-stabilized with the help of a beat signal derived from the signal and frequency-doubled idler waves. The measured frequency fluctuation in one standard deviation is ~437 kHz. This is comparable to the linewidth of the pump laser which is a master-oscillator seeded Yb:doped fiber amplifier at ~1064 nm. The measured powers of the fundamental wave and the harmonic waves up to the 6th harmonic wave are 1.64 W, 0.77 W, 3.9 W, 0.78 W, 0.17 W, and 0.11 W, respectively. The total spectral width covered by this multi-harmonic comb is ~470 THz. When properly phased, this multi-harmonic optical comb can be expected to produce by Fourier synthesis a light source consisting of periodic optical field waveforms that have an envelope full-width at half-maximum of 1.59 fs in each period.

  14. MATHEMATICAL MODEL OF RR-TYPE MICROMECHANICAL GYRO CAPACITIVE COMB-TYPE SENSORS WITH ACCOUNT FOR VIBRATIONS

    Directory of Open Access Journals (Sweden)

    M. I. Evstifeev

    2016-05-01

    Full Text Available Subject of Research.The reasons for subharmonic resonances in RR-type micromechanical gyro output under linear vibrations are investigated. In ideal case, this type of gyro should be insensitive to this kind of impact due to primary and secondary angular oscillations. However, experimental results reveal significant increase in output signal under external vibrations in 20 Hz - 2 kHz bandwidth, though the device natural frequencies are above 3 kHz. This effect is caused by characteristicsnonlinearity of plate-type and comb-type capacitive sensors. Method. Mathematical model of the capacitive comb-type sensors is clarified. Electromechanical interactions in the sensors under external vibrations are described. Simulink modeling of specified mathematical model is carried out. External vibration modeling is doneby “oscillating frequency” method with constant accelerationamplitude in 20 Hz - 2 kHz bandwidth. Main Results.We have received good agreement of modeling and experimental results in the form of occurrence of subharmonic resonances under linear vibrations in three orthogonal directions. Obtained effects are explained by proposed mathematical models. The main reason for subharmonic resonances in RR-type micromechanical gyro output is that combs of stator and combs of proof mass jump out of mesh. Practical Relevance. The provided investigation gives the possibility to determine algorithmic and construction compensation methods of studied interactions for enhancing vibration resistance of RR-type micromechanical gyro.

  15. Flexible terabit/s Nyquist-WDM super-channels using a gain-switched comb source.

    Science.gov (United States)

    Pfeifle, Joerg; Vujicic, Vidak; Watts, Regan T; Schindler, Philipp C; Weimann, Claudius; Zhou, Rui; Freude, Wolfgang; Barry, Liam P; Koos, Christian

    2015-01-26

    Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission. This approach stands out due to its extraordinary stability and flexibility in tuning both center wavelength and line spacing. We perform a series of transmission experiments using different comb line spacings and modulation formats. Using 9 comb lines and 16QAM signaling, an aggregate line rate (net data rate) of 1.296 Tbit/s (1.109 Tbit/s) is achieved for transmission over 150 km of standard single mode fiber (SSMF) using a spectral bandwidth of 166.5 GHz, which corresponds to a (net) spectral efficiency of 7.8 bit/s/Hz (6.7 bit/s/Hz). The line rate (net data rate) can be boosted to 2.112 Tbit/s (1.867 Tbit/s) for transmission over 300 km of SSMF by using a bandwidth of 300 GHz and QPSK modulation on the weaker carriers. For the reported net data rates and spectral efficiencies, we assume a variable overhead of either 7% or 20% for forward- error correction depending on the individual sub-channel quality after fiber transmission.

  16. Microbial community analysis in the termite gut and fungus comb of Odontotermes formosanus: the implication of Bacillus as mutualists.

    Science.gov (United States)

    Mathew, Gincy Marina; Ju, Yu-Ming; Lai, Chi-Yung; Mathew, Dony Chacko; Huang, Chieh Chen

    2012-02-01

    The microbial communities harbored in the gut and fungus comb of the fungus-growing termite Odontotermes formosanus were analyzed by both culture-dependent and culture-independent methods to better understand the community structure of their microflora. The microorganisms detected by denaturing gradient gel electrophoresis (DGGE), clonal selection, and culture-dependent methods were hypothesized to contribute to cellulose-hemicellulose hydrolysis, gut fermentation, nutrient production, the breakdown of the fungus comb and the initiation of the growth of the symbiotic fungus Termitomyces. The predominant bacterial cultivars isolated by the cultural approach belonged to the genus Bacillus (Phylum Firmicutes). Apart from their function in lignocellulosic degradation, the Bacillus isolates suppressed the growth of the microfungus Trichoderma harzianum (genus Hypocrea), which grew voraciously on the fungus comb in the absence of termites but grew in harmony with the symbiotic fungus Termitomyces. The in vitro studies suggested that the Bacillus sp. may function as mutualists in the termite-gut-fungus-comb microbial ecosystem.

  17. Polarization dependence of the direct two photon transitions of 87Rb atoms by erbium: Fiber laser frequency comb

    Science.gov (United States)

    Dai, Shaoyang; Xia, Wei; Zhang, Yin; Zhao, Jianye; Zhou, Dawei; Wang, Qing; Yu, Qi; Li, Kunqian; Qi, Xianghui; Chen, Xuzong

    2016-11-01

    The femtosecond fiber-based optical frequency combs have been proved to be powerful tools for investigating the energy levels of atoms and molecules. In this paper, an Er-doped fiber femtosecond optical frequency comb has been implemented for studying the polarization dependence of 5S-5D two-photon transitions in thermal gas of atomic rubidium 87 using an entirely symmetrical optical configuration. By changing the polarization states of the counter-propagating light beams, the polarization dependence of direct two photon transition spectrum is demonstrated, and a dramatic variation (up to 5.5 times) of the two-photon transitions strength has been observed. The theory for the polarization dependence of two photon transition based on the second-order perturbation was established, which is in good agreement with the experimental results. The measurement results indicate that the polarization state manipulation with the existing frequency comb is used for femtosecond optical frequency comb based two photon transition spectroscopic purposes, which will improve the precision measurement of the absolute transition frequency and related applications.

  18. Sex differences in learning processes of classical and operant conditioning.

    Science.gov (United States)

    Dalla, Christina; Shors, Tracey J

    2009-05-25

    Males and females learn and remember differently at different times in their lives. These differences occur in most species, from invertebrates to humans. We review here sex differences as they occur in laboratory rodent species. We focus on classical and operant conditioning paradigms, including classical eyeblink conditioning, fear-conditioning, active avoidance and conditioned taste aversion. Sex differences have been reported during acquisition, retention and extinction in most of these paradigms. In general, females perform better than males in the classical eyeblink conditioning, in fear-potentiated startle and in most operant conditioning tasks, such as the active avoidance test. However, in the classical fear-conditioning paradigm, in certain lever-pressing paradigms and in the conditioned taste aversion, males outperform females or are more resistant to extinction. Most sex differences in conditioning are dependent on organizational effects of gonadal hormones during early development of the brain, in addition to modulation by activational effects during puberty and adulthood. Critically, sex differences in performance account for some of the reported effects on learning and these are discussed throughout the review. Because so many mental disorders are more prevalent in one sex than the other, it is important to consider sex differences in learning when applying animal models of learning for these disorders. Finally, we discuss how sex differences in learning continue to alter the brain throughout the lifespan. Thus, sex differences in learning are not only mediated by sex differences in the brain, but also contribute to them.

  19. Chromium:forsterite laser frequency comb stabilization and development of portable frequency references inside a hollow optical fiber

    Science.gov (United States)

    Thapa, Rajesh

    We have made significant accomplishments in the development of portable frequency standard inside hollow optical fibers. Such standards will improve portable optical frequency references available to the telecommunications industry. Our approach relies on the development of a stabilized Cr:forsterite laser to generate the frequency comb in the near-IR region. This laser is self referenced and locked to a CW laser which in turn is stabilized to a sub-Doppler feature of a molecular transition. The molecular transition is realized using a hollow core fiber filled with acetylene gas. We finally measured the absolute frequency of these molecular transitions to characterize the references. In this thesis, the major ideas, techniques and experimental results for the development and absolute frequency measurement of the portable frequency references are presented. A prism-based Cr:forsterite frequency comb is stabilized. We have effectively used the prism modulation along with power modulation inside the cavity in order to actively stabilize the frequency comb. We have also studied the carrier-envelope-offset frequency (f0) dynamics of the laser and its effect on laser stabilization. A reduction of f0 linewidth from ˜2 MHz to ˜20 kHz has also been observed. Both our in-loop and out-of-loop measurements of the comb stability showed that the comb is stable within a part in 1011 at 1-s gate time and is currently limited by our reference signal. In order to develop this portable frequency standard, saturated absorption spectroscopy is performed on the acetylene v1 + v3 band near 1532 nm inside different kinds of hollow optical fibers. The observed linewidths are a factor 2 narrower in the 20 mum fiber as compared to 10 mum fiber, and vary from 20-40 MHz depending on pressure and power. The 70 mum kagome fiber shows a further reduction in linewidth to less than 10 MHz. In order to seal the gas inside the hollow optical fiber, we have also developed a technique of splicing the

  20. The mechanisms underlying sexual differentiation of behavior and physiology in mammals and birds: relative contributions of sex steroids and sex chromosomes

    Directory of Open Access Journals (Sweden)

    Fumihiko eMaekawa

    2014-08-01

    Full Text Available From a classical viewpoint, sex-specific behavior and physiological functions as well as the brain structures of mammals such as rats and mice, have been thought to be influenced by perinatal sex steroids secreted by the gonads. Sex steroids have also been thought to affect the differentiation of the sex-typical behavior of a few members of the avian order Galliformes, including the Japanese quail and chickens, during their development in ovo. However, recent mammalian studies that focused on the artificial shuffling or knockout of the sex-determining gene, Sry, have revealed that sex chromosomal effects may be associated with particular types of sex-linked differences such as aggression levels, social interaction, and autoimmune diseases, independently of sex steroid-mediated effects. In addition, studies on naturally occurring, rare phenomena such as gynandromorphic birds and experimentally constructed chimeras in which the composition of sex chromosomes in the brain differs from that in the other parts of the body, indicated that sex chromosomes play certain direct roles in the sex-specific differentiation of the gonads and the brain. In this article, we review the relative contributions of sex steroids and sex chromosomes in the determination of brain functions related to sexual behavior and reproductive physiology in mammals and birds.