Sample records for sex combs asx

  1. Drosophila Sex Combs as a Model of Evolutionary Innovations

    PubMed Central

    Kopp, Artyom

    2011-01-01

    The diversity of animal and plant forms is shaped by nested evolutionary innovations. Understanding the genetic and molecular changes responsible for these innovations is therefore one of the key goals of evolutionary biology. From the genetic point of view, the origin of novel traits implies the origin of new regulatory pathways to control their development. To understand how these new pathways are assembled in the course of evolution, we need model systems that combine relatively recent innovations with a powerful set of genetic and molecular tools. One such model is provided by the Drosophila sex comb – a male-specific morphological structure that evolved in a relatively small lineage related to the model species D. melanogaster. Our extensive knowledge of sex comb development in D. melanogaster provides the basis for investigating the genetic changes responsible for sex comb origin and diversification. At the same time, sex combs can change on microevolutionary timescales and differ spectacularly among closely related species, providing opportunities for direct genetic analysis and for integrating developmental and population-genetic approaches. Sex comb evolution is associated with the origin of novel interactions between HOX and sex determination genes. Activity of the sex determination pathway was brought under the control of the HOX code to become segment-specific, while HOX gene expression became sexually dimorphic. At the same time, both HOX and sex determination genes were integrated into the intrasegmental spatial patterning network, and acquired new joint downstream targets. Phylogenetic analysis shows that similar sex comb morphologies evolved independently in different lineages. Convergent evolution at the phenotypic level reflects convergent changes in the expression of HOX and sex determination genes, involving both independent gains and losses of regulatory interactions. However, the downstream cell differentiation programs have diverged between species, and in some lineages similar adult morphologies are produced by different morphogenetic mechanisms. These features make the sex comb an excellent model for examining not only the genetic changes responsible for its evolution, but also the cellular processes that translate DNA sequence changes into morphological diversity. The origin and diversification of sex combs provides insights into the roles of modularity, cooption, and regulatory changes in evolutionary innovations, and can serve as a model for understanding the origin of the more drastic novelties that define higher-order taxa. PMID:23016935

  2. Evolution of Drosophila sex comb length illustrates the inextricable interplay between selection and variation

    PubMed Central

    Malagón, Juan N.; Ahuja, Abha; Sivapatham, Gabilan; Hung, Julian; Lee, Jiwon; Muñoz-Gómez, Sergio A.; Atallah, Joel; Singh, Rama S.; Larsen, Ellen

    2014-01-01

    In spite of the diversity of possible biological forms observed in nature, a limited range of morphospace is frequently occupied for a given trait. Several mechanisms have been proposed to explain this bias in the distribution of phenotypes including selection, drift, and developmental constraints. Despite extensive work on phenotypic bias, the underlying developmental mechanisms explaining why particular regions of morphological space remain unoccupied are poorly understood. To address this issue, we studied the sex comb, a group of modified bristles used in courtship that shows marked morphological diversity among Drosophila species. In many Drosophila species including Drosophila melanogaster, the sex comb rotates 90° to a vertical position during development. Here we analyze the effect of changing D. melanogaster sex comb length on the process of rotation. We find that artificial selection changes the number of bristles per comb without a proportional change in the space available for rotation. As a result, when increasing sex comb length, rather than displaying a similar straight vertical shape observed in other Drosophila species, long sex combs bend because rotation is blocked by a neighboring row of bristles. Our results show ways in which morphologies that would be favored by natural selection are apparently impossible to achieve developmentally. These findings highlight the potential role of development in modifying selectable variation in the evolution of Drosophila sex comb length. PMID:25197080

  3. Evolutionary Conservation and Predicted Structure of the Drosophila extra sex combs Repressor Protein

    Microsoft Academic Search

    JOYCE NG; RENHAO LI; KELLY MORGAN; JEFFREY SIMON

    1997-01-01

    The Drosophila extra sex combs (esc) protein, a member of the Polycomb group (PcG), is a transcriptional repressor of homeotic genes. Genetic studies have shown that esc protein is required in early embryos at about the time that other PcG proteins become engaged in homeotic gene repression. The esc protein consists pri- marily of multiple copies of the WD repeat,

  4. Expression and Properties of Wild-Type and Mutant Forms of the Drosophila Sex Comb on Midleg (SCM) Repressor Protein

    Microsoft Academic Search

    Douglas Bornemann; Ellen Miller; Jeffrey Simon

    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 \\

  5. A Functional and Structural Analysis of the Sex Combs Reduced Locus of Drosophila Melanogaster

    PubMed Central

    Pattatucci, A. M.; Otteson, D. C.; Kaufman, T. C.

    1991-01-01

    We have undertaken a developmental genetic analysis of the homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster by examining embryonic and adult phenotypes of mutations affecting Scr gene function. Molecular mapping of Scr breakpoint lesions has defined a segment of >70 kb of DNA necessary for proper Scr gene function. This region is split by the fushi tarazu (ftz) gene, with lesions affecting embryonic Scr function molecularly mapping to the region proximal (5') to ftz and those exhibiting polyphasic semilethality predominantly mapping distal (3') to ftz. Gain-of-function mutations are associated with genomic rearrangements and map throughout the Scr locus. Our analysis has revealed that the Scr locus encompasses genetic elements that are responsible for functions in both the embryonic and larval to adult periods of development. From these studies, we conclude that Scr is a complex genetic locus with an extensive regulatory region that directs functions required for normal head and thoracic development in both the embryo and the adult and that the regulation of Scr during these two periods is distinct. PMID:1743486

  6. Evolutionary conservation and predicted structure of the Drosophila extra sex combs repressor protein.

    PubMed

    Ng, J; Li, R; Morgan, K; Simon, J

    1997-11-01

    The Drosophila extra sex combs (esc) protein, a member of the Polycomb group (PcG), is a transcriptional repressor of homeotic genes. Genetic studies have shown that esc protein is required in early embryos at about the time that other PcG proteins become engaged in homeotic gene repression. The esc protein consists primarily of multiple copies of the WD repeat, a motif that has been implicated in protein-protein interaction. To further investigate the domain organization of esc protein, we have isolated and characterized esc homologs from divergent insect species. We report that esc protein is highly conserved in housefly (72% identical to Drosophila esc), butterfly (55% identical), and grasshopper (56% identical). We show that the butterfly homolog provides esc function in Drosophila, indicating that the sequence similarities reflect functional conservation. Homology modeling using the crystal structure of another WD repeat protein, the G-protein beta-subunit, predicts that esc protein adopts a beta-propeller structure. The sequence comparisons and modeling suggest that there are seven WD repeats in esc protein which together form a seven-bladed beta-propeller. We locate the conserved regions in esc protein with respect to this predicted structure. Site-directed mutagenesis of specific loops, predicted to extend from the propeller surface, identifies conserved parts of esc protein required for function in vivo. We suggest that these regions might mediate physical interaction with esc partner proteins. PMID:9343430

  7. Setting limits on homeotic gene function: restraint of Sex combs reduced activity by teashirt and other homeotic genes.

    PubMed Central

    Andrew, D J; Horner, M A; Petitt, M G; Smolik, S M; Scott, M P

    1994-01-01

    Each of the homeotic genes of the HOM or HOX complexes is expressed in a limited domain along the anterior-posterior axis. Each homeotic protein directs the formation of characteristic structures, such as wings or ribs. In flies, when a heat shock-inducible homeotic gene is used to produce a homeotic protein in all cells of the embryo, only some cells respond by altering their fates. We have identified genes that limit where the homeotic gene Sex combs reduced (Scr) can affect cell fates in the Drosophila embryo. In the abdominal cuticle Scr is prevented from inducing prothoracic structures by the three bithorax complex (BX-C) homeotic genes. However, two of the BX-C homeotic genes, Ultrabithorax (Ubx) and abdominal-A (abd-A), have no effect on the ability of Scr to direct the formation of salivary glands. Instead, salivary gland induction by Scr is limited in the trunk by the homeotic gene teashirt (tsh) and in the last abdominal segment by the third BX-C gene, Abdominal-B (AbdB). Therefore, spatial restrictions on homeotic gene activity differ between tissues and result both from the regulation of homeotic gene transcription and from restraints on where homeotic proteins can function. Images PMID:7907545

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

    PubMed

    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 ? 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. PMID:26063573

  9. Identification of Polycomb and Trithorax Group Responsive Elements in the Regulatory Region of the Drosophila Homeotic Gene Sex Combs Reduced

    PubMed Central

    Gindhart-Jr., J. G.; Kaufman, T. C.

    1995-01-01

    The Drosophila homeotic gene Sex combs reduced (Scr) is necessary for the establishment and maintenance of the morphological identity of the labial and prothoracic segments. In the early embryo, its expression pattern is established through the activity of several gap and segmentation gene products, as well as other transcription factors. Once established, the Polycomb group (Pc-G) and trithorax group (trx-G) gene products maintain the spatial pattern of Scr expression for the remainder of development. We report the identification of DNA fragments in the Scr regulatory region that may be important for its regulation by Polycomb and trithorax group gene products. When DNA fragments containing these regulatory sequences are subcloned into P-element vectors containing a white minigene, transformants containing these constructs exhibit mosaic patterns of pigmentation in the adult eye, indicating that white minigene expression is repressed in a clonally heritable manner. The size of pigmented and nonpigmented clones in the adult eye suggests that the event determining whether a cell in the eye anlagen will express white occurs at least as early as the first larval instar. The amount of white minigene repression is reduced in some Polycomb group mutants, whereas repression is enhanced in flies mutant for a subset of trithorax group loci. The repressor activity of one fragment, normally located in Scr Intron 2, is increased when it is able to homologously pair, a property consistent with genetic data suggesting that Scr exhibits transvection. Another Scr regulatory fragment, normally located 40 kb upstream of the Scr promoter, silences ectopic expression of an Scr-lacZ fusion gene in the embryo and does so in a Polycomb-dependent manner. We propose that the regulatory sequences located within these DNA fragments may normally mediate the regulation of Scr by proteins encoded by members of the Polycomb and trithorax group loci. PMID:7713433

  10. Acquisition of a Leucine Zipper Motif as a Mechanism of Antimorphy for an Allele of the Drosophila Hox Gene Sex Combs Reduced

    PubMed Central

    Sivanantharajah, Lovesha; Percival-Smith, Anthony

    2014-01-01

    In 1932, Müller first used the term "antimorphic" to describe mutant alleles that have an effect that is antagonistic to that of the wild-type allele from which they were derived. In a previous characterization of mutant alleles of the Drosophila melanogaster Hox gene, Sex combs reduced (Scr), we identified the missense, antimorphic allele Scr14, which is a Ser10-to-Leu change in the N-terminally located, bilateran-specific octapeptide motif. Here we propose that the cause of Scr14 antimorphy is the acquisition of a leucine zipper oligomerization motif spanning the octapeptide motif and adjacently located protostome-specific LASCY motif. Analysis of the primary and predicted secondary structures of the SCR N-terminus suggests that while the SCR+ encodes a short, ?-helical region containing one putative heptad repeat, the same region in SCR14 encodes a longer, ?-helical region containing two putative heptad repeats. In addition, in vitro cross-linking assays demonstrated strong oligomerization of SCR14 but not SCR+. For in vivo sex comb formation, we observed reciprocal inhibition of endogenous SCR+ and SCR14 activity by ectopic expression of truncated SCR14 and SCR+ peptides, respectively. The acquisition of an oligomerization domain in SCR14 presents a novel mechanism of antimorphy relative to the dominant negative mechanism, which maintains oligomerization between the wild-type and mutant protein subunits. PMID:24622333

  11. Acquisition of a leucine zipper motif as a mechanism of antimorphy for an allele of the Drosophila Hox gene Sex combs reduced.

    PubMed

    Sivanantharajah, Lovesha; Percival-Smith, Anthony

    2014-05-01

    In 1932, Müller first used the term "antimorphic" to describe mutant alleles that have an effect that is antagonistic to that of the wild-type allele from which they were derived. In a previous characterization of mutant alleles of the Drosophila melanogaster Hox gene, Sex combs reduced (Scr), we identified the missense, antimorphic allele Scr(14), which is a Ser10-to-Leu change in the N-terminally located, bilateran-specific octapeptide motif. Here we propose that the cause of Scr(14) antimorphy is the acquisition of a leucine zipper oligomerization motif spanning the octapeptide motif and adjacently located protostome-specific LASCY motif. Analysis of the primary and predicted secondary structures of the SCR N-terminus suggests that while the SCR(+) encodes a short, ?-helical region containing one putative heptad repeat, the same region in SCR(14) encodes a longer, ?-helical region containing two putative heptad repeats. In addition, in vitro cross-linking assays demonstrated strong oligomerization of SCR(14) but not SCR(+). For in vivo sex comb formation, we observed reciprocal inhibition of endogenous SCR(+) and SCR(14) activity by ectopic expression of truncated SCR(14) and SCR(+) peptides, respectively. The acquisition of an oligomerization domain in SCR(14) presents a novel mechanism of antimorphy relative to the dominant negative mechanism, which maintains oligomerization between the wild-type and mutant protein subunits. PMID:24622333

  12. The gap gene Krüppel of Rhodnius prolixus is required for segmentation and for repression of the homeotic gene sex comb-reduced.

    PubMed

    Lavore, Andrés; Esponda-Behrens, Natalia; Pagola, Lucía; Rivera-Pomar, Rolando

    2014-03-01

    The establishment of the anterior-posterior segmentation in insects requires the concerted action of a hierarchical gene network. Here, we study the orthologue of Krüppel gap gene in the hemipteran Rhodnius prolixus (Rp-Kr). We characterized its structure, expression pattern and function. The genomic sequence upstream of the Rp-Kr transcriptional unit shows a putative regulatory region conserved in the orthologue genes from Drosophila melanogaster and Tribolium castaneum. Rp-Kr expression is zygotic and it is expressed in the anterior half of the embryo (the posterior half of the egg) during the blastoderm stage and germ band formation; later, during germ band extension, it is expressed in a central domain, from T2 to A3. The Rp-Kr loss of function phenotypes shows disrupted thoracic and abdominal segmentation. Embryos with weak segmentation phenotypes show homeotic transformations, in which an ectopic tibial comb, typical of T1 leg, appears in T2, which correlates with the ectopic expression of Rp-sex-comb reduced in this leg. PMID:24406318

  13. Drosophila O-GlcNAc transferase (OGT) is encoded by the Polycomb group (PcG) gene, super sex combs (sxc)

    PubMed Central

    Sinclair, Donald A. R.; Syrzycka, Monika; Macauley, Matthew S.; Rastgardani, Tara; Komljenovic, Ivana; Vocadlo, David J.; Brock, Hugh W.; Honda, Barry M.

    2009-01-01

    O-linked N-acetylglucosamine transferase (OGT) reversibly modifies serine and threonine residues of many intracellular proteins with a single ?-O-linked N-acetylglucosamine residue (O-GlcNAc), and has been implicated in insulin signaling, neurodegenerative disease, cellular stress response, and other important processes in mammals. OGT also glycosylates RNA polymerase II and various transcription factors, which suggests that it might be directly involved in transcriptional regulation. We report here that the Drosophila OGT is encoded by the Polycomb group (PcG) gene, super sex combs (sxc). Furthermore, major sites of O-GlcNAc modification on polytene chromosomes correspond to PcG protein binding sites. Our results thus suggest a direct role for O-linked glycosylation by OGT in PcG-mediated epigenetic gene silencing, which is important in developmental regulation, stem cell maintenance, genomic imprinting, and cancer. In addition, we observe rescue of sxc lethality by a human Ogt cDNA transgene; thus Drosophila may provide an ideal model to study important functional roles of OGT in mammals. PMID:19666537

  14. Decentralized control of drone comb construction in honey bee colonies

    Microsoft Academic Search

    Stephen C. Pratt

    1998-01-01

    Honey bee colonies furnish their nests with two types of comb distinguished by cell size: large cells for rearing males (drone\\u000a comb) and small cells for rearing workers (worker comb). The bees actively regulate the relative quantity of each type, a\\u000a behavior likely to be important in setting a colony's sex ratio. Experimental analysis of the information pathways and control

  15. Frequency comb swept lasers

    E-print Network

    Tsai, Tsung-Han

    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 ...

  16. Evidence for Quasi Tetrahedral S=As(S1/2)3 local structures in AsxS1-x glasses

    NASA Astrophysics Data System (ADS)

    Chen, Ping; Boolchand, P.; Holbrook, C.; Jackson, K.; Georgiev, D.; Micoulaut, M.

    2008-03-01

    Raman scattering and modulated DSC on bulk AsxS1-x glasses in the 0.08 < x < 0.41 range is studied^1. Vibrational spectroscopy results supported by first principles cluster calculations reveal that modes near 335, 380 and 490 cm-1 represent respectively symmetric stretch, asymmetric stretch and As=S stretch of Quasi- Tetrahedral (QT) S=As(S1/2)3 local structures. Mode at 365 cm-1 is attributed to both symmetric and asymmetric stretch of pyramidal (PYR) As(S1/2)3 units. In addition, modes of Sn chains near 460 cm-1 and those of S8 rings near 475, 430, 217,and 150 cm-1 are observed at x < 0.25. Scattering strengths of modes of QT units are found to display a broad global maximum in the 0.20 < x < 0.30 composition range, while modes of PYR units increase monotonically with x, and modes of Sn and S8 rings monotonically decrease with x in the range examined. These findings are in harmony with the existence of a reversibility window (RW) in the 0.20 < x < 0.30 range. ^1 D.G. Georgiev Ph.D. Thesis, Univ. of Cincinnati (unpublished) 2003. ^2 D.G.Georgiev and P.Boolchand Phil. Mag.83, 2941(2003). * Supported by NSF grant DMR 04-56472

  17. Smooth Combs Inside Hedgehogs

    E-print Network

    Biswas, Kingshook

    2009-01-01

    We use techniques of tube-log Riemann surfaces due to R.Perez-Marco to construct a hedgehog containing smooth $C^{\\infty}$ combs. The hedgehog is a common hedgehog for a family of commuting non-linearisable holomorphic maps with a common indifferent fixed point. The comb is made up of smooth curves, and is transversally bi-H\\"older regular.

  18. Femtosecond Optical Frequency Combs

    NASA Astrophysics Data System (ADS)

    Udem, Thomas; Holzwarth, Ronald; Hänsch, Theodor

    A laser frequency comb allows the conversion of the very rapid oscillations of visible light down to frequencies that can be handled with conventional electronics. This has enabled the most precise laser spectroscopy experiments yet, to determine fundamental constants and to limit their possible slow drift. Using an optical frequency reference in combination with a laser frequency comb has made it possible to construct all optical atomic clocks. Frequency combs are also used to calibrate astronomical spectrographs and might reach an accuracy that is sufficient to observe the change of the expansion rate of the universe in real time.

  19. Femtosecond optical frequency combs

    NASA Astrophysics Data System (ADS)

    Udem, Th.; Holzwarth, R.; Hänsch, Th.

    2009-06-01

    A laser frequency comb allows the conversion of the very rapid oscillations of visible light of some 100’s of THz down to frequencies that can be handled with conventional electronics. This capability has enabled the most precise laser spectroscopy experiments yet that allowed to test quantum electrodynamics, to determine fundamental constants and to search for possible slow changes of these constants. Using an optical frequency reference in combination with a laser frequency comb has made it possible to construct all optical atomic clocks, that are now outperforming even the best cesium atomic clocks. In future direct frequency comb spectroscopy might enable high resolution laser spectroscopy in the extreme ultraviolet for the first time. Frequency combs are also used to calibrate astronomical spectrographs and might reach an accuracy that is sufficient to observe the expansion of the universe in real time.

  20. Comb and brush acne.

    PubMed

    Petrozzi, J W

    1980-12-01

    Frequent combing or brushing of the hair may result in an exacerbation of existing acne or be the cause of localized acne. Because of today's hair styling habits and methods, this type of acne is commonly encountered but poorly appreciated by physicians. Patient education is the most important factor in the management of this condition. Comb and brush acne is another external factor to be added to the list of causes of "acne mechanica." PMID:6449356

  1. Frequency comb swept lasers

    PubMed Central

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

    2010-01-01

    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 ~?1.2dB sensitivity roll off over ~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. PMID:19997365

  2. Long Term Aging of AsxSe1-x glasses and the Intermediate Phase

    NASA Astrophysics Data System (ADS)

    Chen, Ping; Wachtman, Jacob; Boolchand, P.

    2009-03-01

    The reversibility window in AsxSe1-x glasses was reportedootnotetextD.G. Georgiev et al. Phys. Rev. B 62, R9228(2000). 8 years ago to reside in the 28% < x < 37% range. We have re-examined those samples in m-DSC and Raman scattering. Both the 8 year old hermetically sealed samples in Al holders (set A) and samples from the same batch preparation but stored in plastic vials (set B) at laboratory ambient environment were studied. The reversibility window in samples of set A, after 8 years of aging, is found to be intact. In set B, analysis of the Tg endotherm becomes difficult because of a precursor exotherm that appears in the 32% < x < 60% range, and steadily increases with x. In addition, in both set of samples, one observes a sub Tg endotherm upon aging in the 90 ^oC < T < 120 ^oC range. These m-DSC results supported by Raman scattering suggest that the exotherm is due to light induced nanocrystallization (nc) of As4Se4 fragments (an extrinsic effect), while the sub-Tg feature is due to nc fragments of trigonal Se formed upon long term aging(an intrinsic effect). These findings will be compared to a recent report.ootnotetextR. Golovchak et al. Phys. Rev. B 78, 014202(2008).

  3. Dual-comb MIXSEL

    NASA Astrophysics Data System (ADS)

    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.

  4. Hair breakage during combing. IV. Brushing and combing hair.

    PubMed

    Robbins, Clarence; Kamath, Yash

    2007-01-01

    During combing of hair, longer fiber breaks (>2.5 cm) occur principally by impact loading of looped crossover hairs, while short segment breaks (<2.5 cm) occur primarily by end wrapping. Brushing provides breakage similarly but with a higher ratio of long-to-short segment breaks, and the ratio of long-to-short segment breaks (L/S) is a good way to follow these two pathways of breakage under different conditions. For example, bleaching hair, a longer comb stroke, increasing fiber curvature, wet combing versus dry combing, and brushing versus combing all provide for an increase in long segment breaks and this ratio, with the largest effect produced by brushing. PMID:18305876

  5. Dielectric functions and electronic structure of InAsxP1-x films on InP

    NASA Astrophysics Data System (ADS)

    Choi, S. G.; Palmstrøm, C. J.; Kim, Y. D.; Aspnes, D. E.; Kim, H. J.; Chang, Yia-Chung

    2007-07-01

    The authors present room-temperature pseudodielectric function spectra ??? of InAsxP1-x films grown on (001) InP by chemical beam epitaxy. A wet-chemical etching procedure was used to remove overlayers and obtain the best approximation to the bulk dielectric responses ? of the films. By line shape fitting, we determine the compositional dependences of the E1, E1+?1, E0', E2, and E2' critical-point energies. The results are in good agreement with calculations of the electronic structure done by the linear augmented Slater-type orbital method.

  6. Squeezing frequency combs

    E-print Network

    German J. De Valcarcel; Giuseppe Patera; Nicolas Treps; Claude Fabre

    2006-05-15

    We have developed the full theory of a synchronously pumped type I optical parametric oscillator (SPOPO). We derive expressions for the oscillation threshold and the characteristics of the generated mode-locked signal beam. We calculate the output quantum fluctuations of the device, and find that, in the degenerate case (coincident signal and idler set of frequencies), perfect squeezing is obtained when one approaches threshold from below for a well defined "super-mode', or frequency comb, consisting of a coherent linear superposition of signal modes of different frequencies which are resonant in the cavity.

  7. Tensile-strained GaAs quantum wells and quantum dots in a GaAsxSb1-x matrix

    NASA Astrophysics Data System (ADS)

    Toropov, A. A.; Lyublinskaya, O. G.; Meltser, B. Ya.; Solov'Ev, V. A.; Sitnikova, A. A.; Nestoklon, M. O.; Rykhova, O. V.; Ivanov, S. V.; Thonke, K.; Sauer, R.

    2004-11-01

    We report on the fabrication and analysis of tensily strained thin GaAs layers (“insertion layers”) in a GaAsxSb1-x matrix (x<0.05) . The GaAs insertion layers vary in nominal thickness in the range of 0.6-2 monolayers. They were grown by molecular beam epitaxy on GaSb substrates. Transmission electron microscopy studies indicated either growth of ultra-thin quantum wells (QWs) or self-organized formation of quantum dots (QDs), depending on the nominal thickness of the insertion layers. Two photoluminescence (PL) peaks are observed at photon energies below the GaAsxSb1-x band edge. One of them, detected near 0.7eV for any insertion layer thickness, is attributed to the emission of a type II QW. The second peak shifted toward smaller energies in the thicker insertion layers is assigned to the PL of type II QDs. This assignment is supported by microscopic tight-binding calculations of the QW electron states.

  8. Mid-infrared frequency combs

    E-print Network

    Schliesser, Albert; Hänsch, Theodor W

    2012-01-01

    Laser frequency combs are coherent light sources that emit a broad spectrum consisting of discrete, evenly spaced narrow lines, each having an absolute frequency measurable within the accuracy of an atomic clock. Their development, a decade ago, in the near-infrared and visible domains has revolutionized frequency metrology with numerous windfalls into other fields such as astronomy or attosecond science. Extension of frequency comb techniques to the mid-infrared spectral region is now under exploration. Versatile mid-infrared frequency comb generators, based on novel laser gain media, nonlinear frequency conversion or microresonators, promise to significantly expand the tree of applications of frequency combs. In particular, novel approaches to molecular spectroscopy in the fingerprint region, with dramatically improved precision, sensitivity, recording time and/or spectral bandwidth may spark off new discoveries in the various fields relevant to molecular sciences.

  9. Be-implantation doping of GaAsxP1 - x/GaP strained-layer superlattices

    NASA Astrophysics Data System (ADS)

    Myers, D. R.; Biefeld, R. M.; Fritz, I. J.; Picraux, S. T.; Zipperian, T. E.

    1984-06-01

    We present Hall-effect measurements of the first localized p-type doping in GaAsxP1-x /GaP strained-layer superlattices achieved by implantation of 1×1015 cm-2, 75 kV 9Be+ followed by controlled-atmosphere annealing at 825 °C for 10 min. The acceptor activation (˜15% at 300 K) and the mobilities in the p regions (˜20 cm2/Vs at 300 K) are consistent with the values expected for type-converted GaP-based alloys. Depth-dependent structural characterization by ion channeling demonstrates that the superlattice structure survived the implantation and annealing without loss of layer strain. These results demonstrate that Be implantation can be applied to produce localized doping in a strained-layer superlattice system and reflect favorably on the stability of strained-layer superlattices under particle bombardment and thermal cycling.

  10. Scaling of confined and interacting comb polymers

    NASA Astrophysics Data System (ADS)

    Yeh, Catherine; Pincus, Philip

    2011-03-01

    We study the scaling of polymer chains grafted to a line, i.e. a 1-D brush or comb polymer, on a repulsive plane in good solvent using classical molecular dynamics. The grafting density is large enough to cause chain stretching. The confined comb geometry is motivated by intermediate filaments where the unstructured monomer c-termini form annular rings that can be modeled as a confined comb bent into a ring. We find that the scaling of brush size as a function of the number of monomers per chain is the same for a comb with and without confinement by a repulsive plane. We also consider the transition of a line of parallel interacting combs to the planar brush geometry as they are compressed from isolated combs; we present results for the dependence of brush height on the distance between combs.

  11. Rosetta Scoring Function Steven Combs

    E-print Network

    Meiler, Jens

    Rosetta Scoring Function Steven Combs #12;Rosetta Software Suite is a Premier Software Suite Distance (Å) van der Waals Energy Animation by: Kristian Kaufmann #12;High Resolution ­ Solvation · fa Animation by: Kristian Kaufmann #12;Lovell SC et al. (2003) Proteins 50 (3): 437­450. High Resolution

  12. Red, Green, and Blue Astro-combs

    NASA Astrophysics Data System (ADS)

    Phillips, David; Glenday, Alex; Li, Chih-Hao; Korzennik, Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner, Franz; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald

    2011-06-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. Astro-combs, a combination of an octave spanning femtosecond laser and a mode-filtering cavity provide a likely route to increased calibration precision and accuracy. We present results from three astro-combs operating in the red/near-IR, green and blue spectral ranges. Light from a 1-GHz, octave-spanning Ti:Sapphire laser is filtered by a Fabry-Perot Cavity (FPC) constructed from Doubly-Chirped Mirrors to produce a red astro-comb with 100 nm of optical bandwidth. This astro-comb has calibrated an astrophysical spectrograph at the 1 m/s level. In the blue astro-comb, Ti:Sapphire comb light, doubled in a BBO crystal is filtered to 50 GHz mode spacing with an FPC. The blue astro-comb has performed 50 cm/s calibrations. In the ``green'' astro-comb, light from the 1 GHz Ti:Sapphire comb laser is broadened in a photonic crystal fiber optimized to produce light in the green. This 1-GHz spaced green light is then filtered to roughly 40 GHz via an FPC with zero group delay dispersion mirrors, providing approximately 50 nm of astro-comb light centered near 550 nm.

  13. Broadband midinfrared frequency comb with tooth scanning

    NASA Astrophysics Data System (ADS)

    Lee, Kevin F.; Mas?owski, 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 ?m. We verify comb scanning by resolving the 200 MHz wide absorption lines of the entire fundamental CO vibrational manifold at 11 Torr pressure.

  14. Old honey bee brood combs are more infested by the mite Varroa destructor than are new brood combs

    Microsoft Academic Search

    David De

    Varroa destructor preferentially invades larger honey bee brood cells. Consequently, it was expected that brood in old combs with reduced-size cells would be less infested than the brood in new comb cells. An old brood comb was placed in each of eight Africanized honey bee colonies, along with a new, naturally constructed comb (without comb foundation). The mean percentage of

  15. Femtosecond laser comb based subterahertz synthesizer

    NASA Astrophysics Data System (ADS)

    Makarov, D. S.; Tretyakov, M. Yu.; Shkaev, A. P.; Kiselev, A. M.; Stepanov, A. N.; Parshin, V. V.

    2014-08-01

    Functioning layout of a frequency comb-based subterahertz synthesizer is demonstrated. A primary subterahertz oscillator was phase-locked against the Ti:Sapphire femtosecond laser frequency comb down-converted to the subterahertz range by the semiconductor mixer. Synthesizer operation is demonstrated through Fabri-Perot resonator response curve recording experiment. Spectral purity of the synthesizer was estimated. The advantage of the comb-based synthesizer over the synthesizer based on the Agilent E8257D device was shown.

  16. Atomic quantum memory for multimode frequency combs

    E-print Network

    Z. Zheng; O. Mishina; N. Treps; C. Fabre

    2015-04-06

    We propose a Raman quantum memory scheme that uses several atomic ensembles to store and retrieve the multimode highly entangled state of an optical quantum frequency comb, such as the one produced by parametric down-conversion of a pump frequency comb. We analyse the efficiency and the fidelity of such a quantum memory. Results show that our proposal may be helpful to multimode information processing using the different frequency bands of an optical frequency comb.

  17. Visible wavelength astro-comb.

    PubMed

    Benedick, Andrew J; Chang, Guoqing; Birge, Jonathan R; Chen, Li-Jin; Glenday, Alexander G; Li, Chih-Hao; Phillips, David F; Szentgyorgyi, Andrew; Korzennik, Sylvain; Furesz, Gabor; Walsworth, Ronald L; Kärtner, Franz X

    2010-08-30

    We demonstrate a tunable laser frequency comb operating near 420 nm with mode spacing of 20-50 GHz, usable bandwidth of 15 nm and output power per line of ~20 nW. Using the TRES spectrograph at the Fred Lawrence Whipple Observatory, we characterize this system to an accuracy below 1m/s, suitable for calibrating high-resolution astrophysical spectrographs used, e.g., in exoplanet studies. PMID:20940813

  18. A Josephson radiation comb generator

    E-print Network

    P. Solinas; S. Gasparinetti; D. Golubev; F. Giazotto

    2015-01-27

    We propose the implementation of a Josephson radiation comb generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of $\\pi$ and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate from several hundreds to a thousand of harmonics of the driving frequency. For example, a chain of $10^3$ identical high-critical-temperature SQUIDs driven at 1 GHz can deliver up to a few hundreds nW at 200 GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, will pave the way to a number of technological applications, from metrology to sub-millimeter wave generation.

  19. A Josephson radiation comb generator

    PubMed Central

    Solinas, P.; Gasparinetti, S.; Golubev, D.; Giazotto, F.

    2015-01-01

    We propose the implementation of a Josephson Radiation Comb Generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. When the magnetic flux crosses a diffraction node of the critical current interference pattern, the superconducting phase undergoes a jump of ? and a voltage pulse is generated at the extremes of the SQUID. Under periodic drive this allows one to generate a sequence of sharp, evenly spaced voltage pulses. In the frequency domain, this corresponds to a comb-like structure similar to the one exploited in optics and metrology. With this device it is possible to generate up to several hundreds of harmonics of the driving frequency. For example, a chain of 50 identical high-critical-temperature SQUIDs driven at 1?GHz can deliver up to a 0.5?nW at 200?GHz. The availability of a fully solid-state radiation comb generator such as the JRCG, easily integrable on chip, may pave the way to a number of technological applications, from metrology to sub-millimeter wave generation. PMID:26193628

  20. Arthur Wright Combs: A Humanistic Pioneer

    ERIC Educational Resources Information Center

    Magnuson, Sandy

    2012-01-01

    Arthur Wright Combs (1912-1999) championed humanistic counseling and education. He proposed a theory that incorporated humanistic values and cognitive factors. This article features a review of his contributions, an overview of his theory, a synthesis of stories about Combs that were acquired during research interviews, and my commentary on his…

  1. Analysis of comb transducers with sliding teeth

    Microsoft Academic Search

    Eugene J. Danicki

    2011-01-01

    Ultrasonic comb transducer generates surface acoustic waves on an elastic substrate by periodic traction exerted by its vibrating periodic teeth on the substrate surface. In this paper, the comb teeth are actually sliding elastic spacers between an acoustic buffer and the substrate. The incident wave in acoustic buffer scatters on periodic spacers producing interface waves in the system which transform

  2. A frequency comb in the extreme ultraviolet

    Microsoft Academic Search

    Christoph Gohle; Thomas Udem; Maximilian Herrmann; Jens Rauschenberger; Ronald Holzwarth; Hans A. Schuessler; Ferenc Krausz; Theodor W. Hänsch

    2005-01-01

    Since 1998, the interaction of precision spectroscopy and ultrafast laser science has led to several notable accomplishments. Femtosecond laser optical frequency `combs' (evenly spaced spectral lines) have revolutionized the measurement of optical frequencies and enabled optical atomic clocks. The same comb techniques have been used to control the waveform of ultrafast laser pulses, which permitted the generation of single attosecond

  3. Bichromatically pumped microresonator frequency combs

    NASA Astrophysics Data System (ADS)

    Hansson, T.; Wabnitz, S.

    2014-07-01

    A study is made of the nonlinear dynamics of bichromatically pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schrödinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four-wave model is derived for the pump modes and the dominant sideband pair, which is found to be able to describe much of the essential dynamical behavior of the full equation. The stability of stationary states within the four-wave model is investigated, and numerical simulations are made to demonstrate that a large range of solutions, including cavity solitons, are possible beyond previously considered low-intensity patterns.

  4. Long term comparison of two fiber based frequency comb systems

    Microsoft Academic Search

    Philipp Kubina; Peter Adel; Florian Adler; Gesine Grosche; Theodor W. Hänsch; Ronald Holzwarth; Alfred Leitenstorfer; Burghard Lipphardt; Harald Schnatz

    2005-01-01

    Mode-locked erbium-doped fiber lasers are ideal comb generators for optical frequency metrology. We compare two fiber frequency combs by measuring an optical frequency independently with both combs and comparing their results. The two frequency measurements agree within 6×10-16. This is to our knowledge the first direct comparison between two fiber based frequency combs.

  5. Dual-comb modelocked laser.

    PubMed

    Link, Sandro M; Klenner, Alexander; Mangold, Mario; Zaugg, Christian A; Golling, Matthias; Tilma, Bauke W; Keller, Ursula

    2015-03-01

    In this paper we present the first semiconductor disk laser (SDL) emitting simultaneously two collinearly overlapping cross-polarized gigahertz modelocked pulse trains with different pulse repetition rates. Using only a simple photo detector and a microwave spectrum analyzer directly down-converts the frequency comb difference from the optical to the microwave frequency domain. With this setup, the relative carrier-envelope-offset (CEO) frequency can be accessed directly without an f-to2f interferometer. A very compact design is obtained using the modelocked integrated external-cavity surface emitting laser (MIXSEL) which is part of the family of optically pumped SDLs and similar to a vertical external cavity surface emitting laser (VECSEL) but with both gain and saturable absorber integrated into the same semiconductor wafer (i.e. MIXSEL chip). We then simply added an additional intracavity birefringent crystal inside the linear straight cavity between the output coupler and the MIXSEL chip which splits the cavity beam into two collinear but spatially separated cross-polarized beams on the MIXSEL chip. This results in two modelocked collinear and fully overlapping cross-polarized output beams with adjustable pulse repetition frequencies with excellent noise performance. We stabilized both pulse repetition rates of the dual comb MIXSEL. PMID:25836785

  6. Optically controlled Sagnac loop comb filter.

    PubMed

    Lee, K; Fok, M; Wan, S; Shu, C

    2004-12-13

    We propose a new type of dynamically tunable birefringence comb filter based on a semiconductor optical amplifier Sagnac loop interferometer. By optically modulating the birefringence of the amplifier, we demonstrate a tuning of the output wavelengths. The shift of wavelength increases monotonically with the power of the control light until saturation occurs. The tuning relation is independent of the comb spacing governed by the length and birefringence of the polarization maintaining fiber inside the loop. A tuning range up to 59% of the comb spacing has been achieved at 18.5 dBm input power. PMID:19488280

  7. Fractional diffusion on a fractal grid comb.

    PubMed

    Sandev, Trifce; Iomin, Alexander; Kantz, Holger

    2015-03-01

    A grid comb model is a generalization of the well known comb model, and it consists of N backbones. For N=1 the system reduces to the comb model where subdiffusion takes place with the transport exponent 1/2. We present an exact analytical evaluation of the transport exponent of anomalous diffusion for finite and infinite number of backbones. We show that for an arbitrarily large but finite number of backbones the transport exponent does not change. Contrary to that, for an infinite number of backbones, the transport exponent depends on the fractal dimension of the backbone structure. PMID:25871055

  8. Fractional diffusion on a fractal grid comb

    NASA Astrophysics Data System (ADS)

    Sandev, Trifce; Iomin, Alexander; Kantz, Holger

    2015-03-01

    A grid comb model is a generalization of the well known comb model, and it consists of N backbones. For N =1 the system reduces to the comb model where subdiffusion takes place with the transport exponent 1 /2 . We present an exact analytical evaluation of the transport exponent of anomalous diffusion for finite and infinite number of backbones. We show that for an arbitrarily large but finite number of backbones the transport exponent does not change. Contrary to that, for an infinite number of backbones, the transport exponent depends on the fractal dimension of the backbone structure.

  9. Light beam frequency comb generator

    DOEpatents

    Priatko, G.J.; Kaskey, J.A.

    1992-11-24

    A light beam frequency comb generator uses an acousto-optic modulator to generate a plurality of light beams with frequencies which are uniformly separated and possess common noise and drift characteristics. A well collimated monochromatic input light beam is passed through this modulator to produce a set of both frequency shifted and unshifted optical beams. An optical system directs one or more frequency shifted beams along a path which is parallel to the path of the input light beam such that the frequency shifted beams are made incident on the modulator proximate to but separated from the point of incidence of the input light beam. After the beam is thus returned to and passed through the modulator repeatedly, a plurality of mutually parallel beams are generated which are frequency-shifted different numbers of times and possess common noise and drift characteristics. 2 figs.

  10. Frequency Comb Generation in Superconducting Resonators

    NASA Astrophysics Data System (ADS)

    Pappas, David; Erickson, Robert; Vissers, Michael; Ku, Hsiang-Sheng

    2015-03-01

    We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ? = 2 resonators at T =3 K. Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 108 The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves. Generation of combs in this frequency range allows for unprecedented analysis of this non-linear phenomena in the time domain. We acknowledge DARPA and the NIST Quantum Information program.

  11. Computing partial DFT for comb spectrum evaluation

    Microsoft Academic Search

    Shousheng He; M. Torkelson

    1996-01-01

    A comb spectrum evaluation problem arises in the (de)modulation for orthogonal frequency division multiplexing-based (OFDM-based) multichannel communication system. Efficient algorithms for this special type of partial discrete Fourier transform (DFT) computation are studied. For an M-component comb spectrum evaluation with transform length N, it is shown that only O(N+MlogM) multiplications are needed, compared with O(NlogM) multiplications necessary for a narrowband

  12. OLD BROOD COMBS ARE MORE INFESTED BY THE MITE VARROA JACOBSONI THAN NEW BROOD COMBS

    Microsoft Academic Search

    G. A. PICCIRILLO; D. DE JONG

    Usually, drone cells and worker brood cells with larger diameters are preferred by the mite Varroa jacobsoni. We studied the infestation rate in different types of worker cells in eight africanized honey bee colonies. New brood combs (NC) built naturally by the africanized honey bees and old brood combs (OC) with relatively smaller cells were placed in the same colony,

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

    NASA Technical Reports Server (NTRS)

    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.

  14. Frequency comb swept lasers for optical coherence tomography

    E-print Network

    Tsai, Tsung-Han

    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 ...

  15. Broadband degenerate OPO for mid-infrared frequency comb generation

    E-print Network

    Byer, Robert L.

    Broadband degenerate OPO for mid-infrared frequency comb generation Nick Leindecker,* Alireza for generating broadband phase- and frequency-locked frequency combs in the mid-infrared. Our source is based, C. Gohle, and R. Holzwarth, "Time-domain mid-infrared frequency-comb spectrometer," Opt. Lett. 29

  16. Microresonator-based optical frequency combs.

    PubMed

    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. PMID:21527707

  17. Comb models for transport along spiny dendrites

    E-print Network

    Méndez, V

    2015-01-01

    This chapter is a contribution in the "Handbook of Applications of Chaos Theory" ed. by Prof. Christos H Skiadas. The chapter is organized as follows. First we study the statistical properties of combs and explain how to reduce the effect of teeth on the movement along the backbone as a waiting time distribution between consecutive jumps. Second, we justify an employment of a comb-like structure as a paradigm for further exploration of a spiny dendrite. In particular, we show how a comb-like structure can sustain the phenomenon of the anomalous diffusion, reaction-diffusion and L\\'evy walks. Finally, we illustrate how the same models can be also useful to deal with the mechanism of ta translocation wave / translocation waves of CaMKII and its propagation failure. We also present a brief introduction to the fractional integro-differentiation in appendix at the end of the chapter.

  18. Frequency-agile dual-comb spectroscopy

    E-print Network

    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.

  19. Safe sex

    MedlinePLUS

    Safe sex means taking steps before and during sex that can prevent you from getting an infection, or from ... the skin around the genital area. Before having sex: Get to know your partner and discuss your ...

  20. Dual-comb spectroscopy based on quantum-cascade-laser frequency combs.

    PubMed

    Villares, Gustavo; Hugi, Andreas; Blaser, Stéphane; Faist, Jérôme

    2014-01-01

    Dual-comb spectroscopy performed in the mid-infrared-where molecules have their strongest rotovibrational absorption lines-offers the promise of high spectral resolution broadband spectroscopy with very short acquisition times (?s) and no moving parts. Recently, we demonstrated frequency comb operation of a quantum-cascade-laser. We now use that device in a compact, dual-comb spectrometer. The noise properties of the heterodyne beat are close to the shot noise limit. Broadband (15?cm(-1)) high-resolution (80?MHz) absorption spectroscopy of both a GaAs etalon and water vapour is demonstrated, showing the potential of quantum-cascade-laser frequency combs as the basis for a compact, all solid-state, broadband chemical sensor. PMID:25307936

  1. Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs

    PubMed Central

    Hsieh, Yi-Da; Iyonaga, Yuki; Sakaguchi, Yoshiyuki; Yokoyama, Shuko; Inaba, Hajime; Minoshima, Kaoru; Hindle, Francis; Araki, Tsutomu; Yasui, Takeshi

    2014-01-01

    Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5?MHz and enhanced spectral accuracy of 8.39 × 10?7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy. PMID:24448604

  2. The microrheology of polystyrene sulfonate combs in aqueous solution

    NASA Astrophysics Data System (ADS)

    Papagiannopoulos, A.; Fernyhough, C. M.; Waigh, T. A.

    2005-12-01

    Video particle tracking (VPT) and diffusing wave spectroscopy were used to characterize the microrheology of polystyrene sulfonate combs in aqueous solutions. At low frequencies VPT demonstrated predominantly viscous behavior. The manner in which the viscosity scaled as a function of monomer concentration was a sensitive function of the comb architecture. Densely branched combs or combs with long side chains demonstrated entangled polyelectrolyte scaling above the overlap concentration, whereas sparsely branched combs had unentangled polyelectrolyte scaling. A dynamic scaling model was developed for the viscosity of unentangled semidilute solutions of comb polyelectrolytes. Diffusing wave spectroscopy demonstrated Rouse modes (G'˜G?˜?1/2) for the high-frequency dynamics of the semidilute comb solutions. The form of the high-frequency viscoelasticity was independent of the chain architecture and the modulus scaled as expected for linear flexible polyelectrolytes.

  3. Combe d'Arc Cave Paintings

    NSDL National Science Digital Library

    France's Ministry of Culture has placed four high-resolution pictures of last month's newly-discovered Combe d'Arc cave paintings on-line. They are truly exquisite and this may be the only place where you can catch a peek at them.

  4. Combing Euclidean buildings Gennady A. Noskov

    E-print Network

    Bielefeld, University of

    Combing Euclidean buildings Gennady A. Noskov Abstract For an arbitrary Euclidean building we automorphisms on a Euclidean building of one of the types A n ; B n ; C n admits a biautomatic structure. 1 #12; Contents 1 Introduction 3 2 Euclidean Coxeter complexes 4 3 Ordering Euclidean buildings 10 4 Definition

  5. Quantum cascade laser Kerr frequency comb

    E-print Network

    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...

  6. A Quantitative Characterization of Combing Force

    Microsoft Academic Search

    WALTER NEWMAN; GEORGE L. COHEN; CLETUS HAYES

    Synopsis-A quantitative method for measuring and comparing the effect of various cos- metic treatments and products on the amount of FORCE needed to COMB a tress of HAIR is described. Photographs of the apparatus and a detailed description of the experi- mental procedure are provided. The results of several experiments evaluating the effects of several commercial hair conditioners, bleaching, and

  7. Common File Formats in Rosetta Steven Combs

    E-print Network

    Meiler, Jens

    ://www.rosettacommons.org/manuals/archive/rosetta3.2 _user_guide/resfiles.html header> start #12;Params Files · Definition for residuesCommon File Formats in Rosetta Steven Combs #12;The Files · Flags/Option files · Resfiles · Params in 3 different ways space / tab indented Fixbb.release @options.txt ­database -in -file -s 1

  8. Time sequence photography of Roosters Comb

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  9. Cavity-enhanced dual-comb spectroscopy

    Microsoft Academic Search

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

    2010-01-01

    The sensitivity of molecular fingerprinting is dramatically improved when the absorbing sample is placed in a high-finesse optical cavity, because the effective path length is increased. 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. However, efficient analysis of

  10. Stephen C. Pratt Decentralized control of drone comb construction in honey bee colonies

    E-print Network

    Pratt, Stephen

    Stephen C. Pratt Decentralized control of drone comb construction in honey bee colonies Received with two types of comb distinguished by cell size: large cells for rearing males (drone comb) and small of drone comb in a nest is governed by negative feedback from drone comb already constructed. This feedback

  11. The Rose-comb Mutation in Chickens Constitutes a Structural Rearrangement Causing Both Altered Comb Morphology and Defective Sperm Motility

    PubMed Central

    Boije, Henrik; Bed'hom, Bertrand; Fillon, Valérie; Dorshorst, Ben; Rubin, Carl-Johan; Liu, Ranran; Gao, Yu; Gu, Xiaorong; Wang, Yanqiang; Gourichon, David; Zody, Michael C.; Zecchin, William; Vieaud, Agathe; Tixier-Boichard, Michèle; Hu, Xiaoxiang; Hallböök, Finn; Li, Ning; Andersson, Leif

    2012-01-01

    Rose-comb, a classical monogenic trait of chickens, is characterized by a drastically altered comb morphology compared to the single-combed wild-type. Here we show that Rose-comb is caused by a 7.4 Mb inversion on chromosome 7 and that a second Rose-comb allele arose by unequal crossing over between a Rose-comb and wild-type chromosome. The comb phenotype is caused by the relocalization of the MNR2 homeodomain protein gene leading to transient ectopic expression of MNR2 during comb development. We also provide a molecular explanation for the first example of epistatic interaction reported by Bateson and Punnett 104 years ago, namely that walnut-comb is caused by the combined effects of the Rose-comb and Pea-comb alleles. Transient ectopic expression of MNR2 and SOX5 (causing the Pea-comb phenotype) occurs in the same population of mesenchymal cells and with at least partially overlapping expression in individual cells in the comb primordium. Rose-comb has pleiotropic effects, as homozygosity in males has been associated with poor sperm motility. We postulate that this is caused by the disruption of the CCDC108 gene located at one of the inversion breakpoints. CCDC108 is a poorly characterized protein, but it contains a MSP (major sperm protein) domain and is expressed in testis. The study illustrates several characteristic features of the genetic diversity present in domestic animals, including the evolution of alleles by two or more consecutive mutations and the fact that structural changes have contributed to fast phenotypic evolution. PMID:22761584

  12. High-Temperature Thermoelectric Properties of the Solid–Solution Zintl Phase Eu11Cd6Sb12–xAsx (x < 3)

    SciTech Connect

    Kazem, Nasrin; Xie, Weiwei; Ohno, Saneyuki; Zevalkink, Alexandra; Miller, Gordon J; Snyder, G Jeffrey; Kauzlarich, Susan M

    2014-02-11

    Zintl phases are compounds that have shown promise for thermoelectric applications. The title solid–solution Zintl compounds were prepared from the elements as single crystals using a tin flux for compositions x = 0, 1, 2, and 3. Eu11Cd6Sb12–xAsx (x < 3) crystallize isostructurally in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12 structure type (Pearson symbol mC58). Efforts to make the As compositions for x exceeding ?3 resulted in structures other than the Sr11Cd6Sb12 structure type. Single-crystal X-ray diffraction indicates that As does not randomly substitute for Sb in the structure but is site specific for each composition. The amount of As determined by structural refinement was verified by electron microprobe analysis. Electronic structures and energies calculated for various model structures of Eu11Cd6Sb10As2 (x = 2) indicated that the preferred As substitution pattern involves a mixture of three of the six pnicogen sites in the asymmetric unit. In addition, As substitution at the Pn4 site opens an energy gap at the Fermi level, whereas substitution at the other five pnicogen sites remains semimetallic with a pseudo gap. Thermoelectric properties of these compounds were measured on hot-pressed, fully densified pellets. Samples show exceptionally low lattice thermal conductivities from room temperature to 775 K: 0.78–0.49 W/mK for x = 0; 0.72–0.53 W/mK for x = 1; and 0.70–0.56 W/mK for x = 2. Eu11Cd6Sb12 shows a high p-type Seebeck coefficient (from +118 to 153 ? V/K) but also high electrical resistivity (6.8 to 12.8 m?·cm). The value of zT reaches 0.23 at 774 K. The properties of Eu11Cd6Sb12–xAsx are interpreted in discussion with the As site substitution.

  13. Coherent data transmission with microresonator Kerr frequency combs

    E-print Network

    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 (...

  14. Broadband 2.5-6?m frequency comb source for dual-comb molecular spectroscopy

    NASA Astrophysics Data System (ADS)

    Smolski, V. O.; Vodopyanov, K. L.

    2015-02-01

    Absorption spectroscopy with frequency combs in the molecular fingerprint portion of the spectrum (2-10 ?m) has great potential for trace molecular detection and in particular for such applications as monitoring of the atmosphere and medical breath analysis. Especially attractive is dual-comb Fourier transform spectroscopy where full advantage is taken of temporal and spatial coherence of frequency combs as well as of their broadband nature. The promise is high speed, broad spectral coverage, superior sensitivity, high spectral resolution, and the possibility of absolute frequency calibration of molecular resonances. Here we report a system suitable for performing dual-comb spectroscopy in the range of 2.5-6 ?m and beyond. Broadband mid-IR frequency combs are obtained via a doubly-resonant near-degenerate synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned GaAs (OP-GaAs) pumped by a femtosecond Tm-fiber laser at 2-?m wavelength. Low pump threshold (7 mW), high coherence, and broad instantaneous spectral coverage make this system extremely promising for spectroscopic studies.

  15. Recent advances in ultrafast optical parametric oscillator frequency combs

    NASA Astrophysics Data System (ADS)

    McCracken, Richard A.; Zhang, Zhaowei; Reid, Derryck T.

    2014-12-01

    We discuss recent advances in the stabilization and application of femtosecond frequency combs based on optical parametric oscillators (OPOs) pumped by femtosecond lasers at 800 and 1060 nm. A method for locking to zero the carrier-envelope-offset of a Ti:sapphire-pumped OPO comb is described. The application of Yb:KYW-laser-pumped dual-combs for mid-infrared spectroscopy is detailed, specifically methane spectroscopy at approximately a 0.7% concentration at 1 atm.

  16. Comb-Actuated Resonant Torsional Microscanner With Mechanical Amplification

    Microsoft Academic Search

    Aslihan Arslan; Dean Brown; Wyatt O. Davis; Sven Holmstrom; Sertan Kutal Gokce; Hakan Urey

    2010-01-01

    A comb-actuated torsional microscanner is developed for high-resolution laser-scanning display systems. Typical torsional comb-drive scanners have fingers placed around the perimeter of the scanning mirror. In contrast, the structure in this paper uses cascaded frames, where the comb fingers are placed on an outer drive frame, and the motion is transferred to the inner mirror frame with a mechanical gain.

  17. Laser frequency combs for astronomical observations

    E-print Network

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

    2008-09-09

    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 about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate 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 about 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.

  18. Laser frequency combs for astronomical observations

    E-print Network

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

    2008-01-01

    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 about 1 centimeter per second per year, and astronomical spectrographs have not yet been calibrated to this tolerance. We demonstrate 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 about 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 acceler...

  19. Optimization of an electromagnetic comb drive actuator

    Microsoft Academic Search

    S. Schonhardt; J. G. Korvink; J. Mohr; U. Hollenbach; U. Wallrabe

    2009-01-01

    We present the first electromagnetic comb drive actuator which allows for over 100?m of linear actuator motion at large air gap widths of 25?m at 300 coil windings, a structural height of 400?m and for an applied current of 8mA. Previously reported designs require very narrow air gaps of 3?m at structural heights of up to 1mm [K. Fischer, H.

  20. Integrated Photonic Comb Generation: Applications in Coherent Communication and Sensing

    NASA Astrophysics Data System (ADS)

    Parker, John S.

    Integrated photonics combines many optical components including lasers, modulators, waveguides, and detectors in close proximity via homogeneous (monolithic) or heterogeneous (using multiple materials) integration. This improves stability for interferometers and lasers, reduces the occurrence of unwanted reflections, and it avoids coupling losses between different components as they are on the same chip. Thus, less power is needed to compensate for these added losses, and less heat needs to be removed due to these power savings. In addition, integration allows the many components that comprise a system to be fabricated together, thereby reducing the cost per system and allowing rapid scaling in production throughput. Integrated optical combs have many applications including: metrology, THz frequency generation, arbitrary waveform generation, optical clocks, photonic analog-to-digital converters, sensing (imaging), spectroscopy, and data communication. A comb is a set of optical sources evenly spaced in frequency. Several methods of comb generation including mode-locking and optical parametric oscillation produce phase-matched optical outputs with a fixed phase relationship between the frequency lines. When the absolute frequency of a single comb line is stabilized along with the frequency spacing between comb lines, absolute phase and frequency precision can be achieved over the entire comb bandwidth. This functionality provides tremendous benefits to many applications such as coherent communication and optical sensing. The goals for this work were achieving a broad comb bandwidth and noise reduction, i.e., frequency and phase stability. Integrated mode-locked lasers on the InGaAsP/InP material platform were chosen, as they could be monolithically integrated with the wide range of highly functional and versatile photonic integrated circuits (PICs) previously demonstrated on this platform at UCSB. Gain flattening filters were implemented to increase the comb bandwidths to 2.5 THz. Active mode-locking with an RF source was used to precisely set the frequency spacing between comb lines with better than 10 Hz accuracy. An integrated optical phase-locked loop (OPLL) for the comb was designed, built, and tested. The OPLL fixed a single comb line to a stable single linewidth laser, demonstrating a ˜430 Hz FWHM optical linewidth on the locked comb line and 20º RMS phase deviation between the comb and optical reference. The free-running linewidth is 50--100 MHz, demonstrating over 50 dB improvement in optical linewidth via locking. An integrated tunable laser (SG-DBR) with an OPLL was phase-locked to a comb source with a fixed offset frequency, thus showing the potential for using a comb with SG-DBRs as a compact frequency synthesizer.

  1. Optical study of narrow band gap InAsxSb1 -x (x =0 , 0.25, 0.5, 0.75, 1) alloys

    NASA Astrophysics Data System (ADS)

    Namjoo, Shirin; Rozatian, Amir S. H.; Jabbari, Iraj; Puschnig, Peter

    2015-05-01

    The structural, electronic, and optical properties of InAs, InSb, and their ternary alloys InAsxSb1 -x (x =0.25 , 0.5, 0.75) are investigated within density functional theory utilizing the wien2k package. We find that the lattice constants and bulk moduli as a function of x are in best agreement with Vegard's linear rule. When computing the electronic band structures with the modified Becke-Johnson exchange-correlation functional (mBJLDA), our results for the band gaps of InAs, InSb, and their ternary alloys are in good agreement with the available experimental results while the conventional Wu-Cohen generalized gradient approximation (GGA) functional leads to zero or close to zero band gaps. In particular, our mBJLDA results confirm experimental evidence that the minimum band gap occurs for As concentrations around x ?0.3 . Furthermore, we investigate the dielectric function of these compounds within the random phase approximation using both the Wu-Cohen GGA and the mBJLDA functionals. While the mBJLDA results of our fully first-principles calculations show good agreement of the peak positions in ?2(? ) with experiments, the peaks in the optical spectra based on the Wu-Cohen GGA band structure appear redshifted compared to experiment. We further identify the interband transitions responsible for the structures in the spectra. Looking at the optical matrix element, we note that the major peaks are dominated by transition from the Sb 5 p (As 4 p ) states to In s states for InSb and InAs0.25Sb0.75 (InAs, InAs0.75Sb0.25 , and InAs0.5Sb0.5 ).

  2. Microresonator frequency comb optical clock SCOTT B. PAPP,1,

    E-print Network

    Microresonator frequency comb optical clock SCOTT B. PAPP,1, * KATJA BEHA,1 PASCAL DEL'HAYE,1 FRANKLYN QUINLAN,1 HANSUEK LEE,2 KERRY J. VAHALA,2 AND SCOTT A. DIDDAMS 1 1 Time and Frequency Division 688); published 22 July 2014 Optical frequency combs serve as the clockwork of optical clocks, which are now

  3. Original article Drone production and drone comb utilization

    E-print Network

    Paris-Sud XI, Université de

    Original article Drone production and drone comb utilization in colonies of the African honey bee June 1994) Summary — Drone production and drone comb utilization were investigated in naturally, Botswana. Drone production occurred primarily in larger, thriving and swarming colonies that contained

  4. Geotropism of hornet comb construction under persistent acceleration

    Microsoft Academic Search

    Jacob Ishay; Dror Sadeh

    1977-01-01

    1.The effect of persistent acceleration on comb construction by Oriental hornet (Vespa orientalis) workers was assessed experimentally within breeding boxes of various sizes, and shapes. Groups of hornets in the building phase were subjected to a centrifugal and gravitational force whose resultant ranged between 26° and 45°. The comb construction within such boxes was compared to that within control boxes

  5. A Note on Rotor-Router Aggregation on the Comb

    E-print Network

    Huss, Wilfried

    2011-01-01

    We prove a shape theorem for rotor-router aggregation on the comb, for a specific initial rotor configuration and clockwise rotor sequence for all vertices. Furthermore, as an application of rotor-router walks, we describe the harmonic measure for the limiting shape of rotor-router aggregation, which is useful in the study of other growth models on the comb.

  6. Visible wavelength astro-comb Andrew J. Benedick1,*

    E-print Network

    Walsworth, Ronald L.

    -Jin Chen1 , Alexander G. Glenday2,3 , Chih-Hao Li2 , David F. Phillips2 , Andrew Szentgyorgyi2 , SylvainVisible wavelength astro-comb Andrew J. Benedick1,* , Guoqing Chang1, , Jonathan R. Birge1 , Li, Cambridge Ma 02138 USA *andrew_b@mit.edu Abstract: We demonstrate a tunable laser frequency comb operating

  7. Distribution of an Ultrastable Frequency Reference Using Optical Frequency Combs

    E-print Network

    Jin, Deborah

    that will be provided by optical clocks, and even the stability they currently offer, has applications in several fields scheme. To minimize loss during transmission, it is necessary to transmit a 1550-nm comb instead of the 800-nm Ti:sapphire comb. Therefore, the stabilization of a 1550-nm mode-locked laser diode to the Ti

  8. Continuous comparison of two fiber based fs-frequency combs

    Microsoft Academic Search

    P. Kubina; P. Adel; T. W. Hansch; R. Holzwarth; H. Schnatz; B. Lipphardt; G. Grosche

    2005-01-01

    Erbium-doped femtosecond fiber lasers are ideal comb generators for optical frequency metrology. We compare two such systems and find agreement within 2×10-16. This is to our knowledge the first thorough test of fiber-based frequency combs.

  9. Theory and applications of sampled analog recursive CTD comb filters

    NASA Technical Reports Server (NTRS)

    Tao, T. F.; Holmes, S. V.; Ejaz, A.; Piazza, F.; Saetre, L. T.; Freund, B.

    1976-01-01

    Sampled analog comb filter using a recursive filter implementation was studied. Charge transfer device delay lines were used as the delay elements. The similarities and differences between sampled analog recursive filter and digital recursive filter were pointed out. Both canceller type and integrator type comb filter using the first order or the second order canonical circuits were studied. Experimental results of frequency response are presented to show their difference from that of digital filters. A theoretical analysis was presented based essentially on the digital filter theory but modified to take into account the differences described above. The usefulness of this theory in analyzing the comb filter characteristics was discussed. Several applications of both the canceller type comb filter and the integrator type comb filter were demonstrated.

  10. Laboratory Demonstration of a Green Astro-comb

    NASA Astrophysics Data System (ADS)

    Li, Chih-Hao; Glenday, Alex; Phillips, David F.; Korzennik, Sylvain; Noah Chang, Guoqing; Benedick, Andrew; Chen, Li-Jin; Kaertner, Franz X.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald

    2010-03-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. Astro-combs, a combination of an octave spanning femtosecond laser and a mode-filtering cavity provide a likely route to increased calibration precision and accuracy. Initial astro-comb demonstrations have been performed in the near infrared where broadband lasers are available. Here we present initial laboratory results on a ``green'' astro-comb providing approximately 50 nm of stable astro-comb light centered near 550 nm. Light from a 1 GHz, octave-spanning Ti:Sapphire laser is broadened in a photonic crystal fiber optimized to produce light in the green. This 1 GHz spaced green light is then filtered to roughly 30 GHz mode spacing via a Fabry-Perot cavity with ultra-low dispersion mirrors. Current progress on the characterization of this green astro-comb will be presented.

  11. Microresonator-Based Comb Generation without an External Laser Source

    E-print Network

    Johnson, Adrea R; Lamont, Michael R E; Levy, Jacob S; Lipson, Michal; Gaeta, Alexander L

    2013-01-01

    Recent developments demonstrate that parametric four-wave mixing (FWM) in high-Q microresonators is a highly promising and effective approach for optical frequency comb generation, with applications including spectroscopy, optical clocks, arbitrary waveform generation, frequency metrology, and astronomical spectrograph calibration. Each of these microresonator platforms utilizes a scheme in which the system is pumped by a single-frequency laser at a cavity resonance. This scheme requires tuning of the pump wavelength into resonance and the generated comb is susceptible to fluctuations in pump power or frequency which can disrupt the soft thermal lock and comb generation. We demonstrate a novel fiber-microresonator dual-cavity architecture that preferentially oscillates at modes of the microresonator due to its high density of states and generates robust and broadband combs (> 900 nm) without an external pump laser. Such a scheme could greatly simplify the comb generation process and allow for a fully-integrat...

  12. Adaptive real-time dual-comb spectroscopy

    E-print Network

    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...

  13. Optical frequency comb generation from a monolithic microresonator.

    PubMed

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

    2007-12-20

    Optical frequency combs provide equidistant frequency markers in the infrared, visible and ultraviolet, and can be used to link an unknown optical frequency to a radio or microwave frequency reference. Since their inception, frequency combs have triggered substantial advances in optical frequency metrology and precision measurements and in applications such as broadband laser-based gas sensing and molecular fingerprinting. Early work generated frequency combs by intra-cavity phase modulation; subsequently, frequency combs have been generated using the comb-like mode structure of mode-locked lasers, whose repetition rate and carrier envelope phase can be stabilized. Here we report a substantially different approach to comb generation, in which equally spaced frequency markers are produced by the interaction between a continuous-wave pump laser of a known frequency with the modes of a monolithic ultra-high-Q microresonator via the Kerr nonlinearity. The intrinsically broadband nature of parametric gain makes it possible to generate discrete comb modes over a 500-nm-wide span (approximately 70 THz) around 1,550 nm without relying on any external spectral broadening. Optical-heterodyne-based measurements reveal that cascaded parametric interactions give rise to an optical frequency comb, overcoming passive cavity dispersion. The uniformity of the mode spacing has been verified to within a relative experimental precision of 7.3 x 10(-18). In contrast to femtosecond mode-locked lasers, this work represents a step towards a monolithic optical frequency comb generator, allowing considerable reduction in size, complexity and power consumption. Moreover, the approach can operate at previously unattainable repetition rates, exceeding 100 GHz, which are useful in applications where access to individual comb modes is required, such as optical waveform synthesis, high capacity telecommunications or astrophysical spectrometer calibration. PMID:18097405

  14. Efficiency optimization for Atomic Frequency Comb storage

    E-print Network

    M. Bonarota; J. Ruggiero; J. -L. Le Gouët; T. Chanelière

    2009-11-23

    We study the efficiency of the Atomic Frequency Comb storage protocol. We show that for a given optical depth, the preparation procedure can be optimize to significantly improve the retrieval. Our prediction is well supported by the experimental implementation of the protocol in a \\TMYAG crystal. We observe a net gain in efficiency from 10% to 17% by applying the optimized preparation procedure. In the perspective of high bandwidth storage, we investigate the protocol under different magnetic fields. We analyze the effect of the Zeeman and superhyperfine interaction.

  15. Efficiency optimization for atomic frequency comb storage

    SciTech Connect

    Bonarota, M.; Ruggiero, J.; Le Goueet, J.-L.; Chaneliere, T. [Laboratoire Aime Cotton, CNRS-UPR 3321, Univ. Paris-Sud, Bat. 505, F-91405 Orsay Cedex (France)

    2010-03-15

    We study the efficiency of the atomic frequency comb storage protocol. We show that for a given optical depth, the preparation procedure can be optimize to significantly improve the retrieval. Our prediction is well supported by the experimental implementation of the protocol in a Tm{sup 3+}:YAG crystal. We observe a net gain in efficiency from 10 to 17% by applying the optimized preparation procedure. In the perspective of high bandwidth storage, we investigate the protocol under different magnetic fields. We analyze the effect of the Zeeman and superhyperfine interaction.

  16. Superdiffusion of cancer on a comb structure

    NASA Astrophysics Data System (ADS)

    Iomin, Alexander

    2005-01-01

    The influence of cell fission on transport properties of the vessel network is studied. A simple mathematical model is proposed by virtue of heuristic arguments on tumor development. The constructed model is a modification of a so-called comb structure. In the framework of this model we are able to show that the tumor development corresponds to fractional transport of cells. A possible answer to the question how the malignant neoplasm cells appear at an arbitrary distance from the primary tumor is proposed. The model could also be a possible mechanism for diffusive cancers.

  17. Cavity-enhanced dual-comb spectroscopy

    E-print Network

    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 ...

  18. Coherent terabit communications with microresonator Kerr frequency combs

    PubMed Central

    Pfeifle, Joerg; Brasch, Victor; Lauermann, Matthias; Yu, Yimin; Wegner, Daniel; Herr, Tobias; Hartinger, Klaus; Schindler, Philipp; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Weimann, Claudius; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J.; Koos, Christian

    2014-01-01

    Optical frequency combs have the potential to revolutionize terabit communications1. Generation of Kerr combs in nonlinear microresonators2 represents a particularly promising option3 enabling line spacings of tens of GHz. However, such combs may exhibit strong phase noise4-6, which has made high-speed data transmission impossible up to now. Here we demonstrate that systematic adjustment of pump conditions for low phase noise4,7-9 enables coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the comb. In a first experiment, we encode a data stream of 392 Gbit/s on a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment demonstrates feedback-stabilization of the comb and transmission of a 1.44 Tbit/s data stream over up to 300 km. The results show that Kerr combs meet the highly demanding requirements of coherent communications and thus offer an attractive solution towards chip-scale terabit/s transceivers. PMID:24860615

  19. Silicon-chip mid-infrared frequency comb generation.

    PubMed

    Griffith, Austin G; Lau, Ryan K W; Cardenas, Jaime; Okawachi, Yoshitomo; Mohanty, Aseema; Fain, Romy; Lee, Yoon Ho Daniel; Yu, Mengjie; Phare, Christopher T; Poitras, Carl B; Gaeta, Alexander L; Lipson, Michal

    2015-01-01

    Optical frequency combs are a revolutionary light source for high-precision spectroscopy because of their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared spectral region (2-20??m) is important for molecular gas detection owing to the presence of a large number of absorption lines in this wavelength regime. Microresonator-based frequency comb sources can provide a compact and robust platform for comb generation that can operate with relatively low optical powers. However, material and dispersion engineering limitations have prevented the realization of an on-chip integrated mid-infrared microresonator comb source. Here we demonstrate a complementary metal-oxide-semiconductor compatible platform for on-chip comb generation using silicon microresonators, and realize a broadband frequency comb spanning from 2.1 to 3.5??m. This platform is compact and robust and offers the potential to be versatile for use outside the laboratory environment for applications such as real-time monitoring of atmospheric gas conditions. PMID:25708922

  20. Silicon-chip mid-infrared frequency comb generation

    NASA Astrophysics Data System (ADS)

    Griffith, Austin G.; Lau, Ryan K. W.; Cardenas, Jaime; Okawachi, Yoshitomo; Mohanty, Aseema; Fain, Romy; Lee, Yoon Ho Daniel; Yu, Mengjie; Phare, Christopher T.; Poitras, Carl B.; Gaeta, Alexander L.; Lipson, Michal

    2015-02-01

    Optical frequency combs are a revolutionary light source for high-precision spectroscopy because of their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared spectral region (2–20??m) is important for molecular gas detection owing to the presence of a large number of absorption lines in this wavelength regime. Microresonator-based frequency comb sources can provide a compact and robust platform for comb generation that can operate with relatively low optical powers. However, material and dispersion engineering limitations have prevented the realization of an on-chip integrated mid-infrared microresonator comb source. Here we demonstrate a complementary metal–oxide–semiconductor compatible platform for on-chip comb generation using silicon microresonators, and realize a broadband frequency comb spanning from 2.1 to 3.5??m. This platform is compact and robust and offers the potential to be versatile for use outside the laboratory environment for applications such as real-time monitoring of atmospheric gas conditions.

  1. A phase-stabilized carbon nanotube fiber laser frequency comb.

    PubMed

    Lim, Jinkang; Knabe, Kevin; Tillman, Karl A; Neely, William; Wang, Yishan; Amezcua-Correa, Rodrigo; Couny, François; Light, Philip S; Benabid, Fetah; Knight, Jonathan C; Corwin, Kristan L; Nicholson, Jeffrey W; Washburn, Brian R

    2009-08-01

    A frequency comb generated by a 167 MHz repetition frequency erbium-doped fiber ring laser using a carbon nanotube saturable absorber is phase-stabilized for the first time. Measurements of the in-loop phase noise show an integrated phase error on the carrier envelope offset frequency of 0.35 radians. The carbon nanotube fiber laser comb is compared with a CW laser near 1533 nm stabilized to the nu(1) + nu(3) overtone transition in an acetylene-filled kagome photonic crystal fiber reference, while the CW laser is simultaneously compared to another frequency comb based on a Cr:Forsterite laser. These measurements demonstrate that the stability of a GPS-disciplined Rb clock is transferred to the comb, resulting in an upper limit on the locked comb's frequency instability of 1.2 x 10(-11) in 1 s, and a relative instability of <3 x 10(-12) in 1 s. The carbon nanotube laser frequency comb offers much promise as a robust and inexpensive all-fiber frequency comb with potential for scaling to higher repetition frequencies. PMID:19654821

  2. Coherent terabit communications with microresonator Kerr frequency combs.

    PubMed

    Pfeifle, Joerg; Brasch, Victor; Lauermann, Matthias; Yu, Yimin; Wegner, Daniel; Herr, Tobias; Hartinger, Klaus; Schindler, Philipp; Li, Jingshi; Hillerkuss, David; Schmogrow, Rene; Weimann, Claudius; Holzwarth, Ronald; Freude, Wolfgang; Leuthold, Juerg; Kippenberg, Tobias J; Koos, Christian

    2014-05-01

    Optical frequency combs have the potential to revolutionize terabit communications(1). Generation of Kerr combs in nonlinear microresonators(2) represents a particularly promising option(3) enabling line spacings of tens of GHz. However, such combs may exhibit strong phase noise(4-6), which has made high-speed data transmission impossible up to now. Here we demonstrate that systematic adjustment of pump conditions for low phase noise(4,7-9) enables coherent data transmission with advanced modulation formats that pose stringent requirements on the spectral purity of the comb. In a first experiment, we encode a data stream of 392 Gbit/s on a Kerr comb using quadrature phase shift keying (QPSK) and 16-state quadrature amplitude modulation (16QAM). A second experiment demonstrates feedback-stabilization of the comb and transmission of a 1.44 Tbit/s data stream over up to 300 km. The results show that Kerr combs meet the highly demanding requirements of coherent communications and thus offer an attractive solution towards chip-scale terabit/s transceivers. PMID:24860615

  3. Versatile and Sensitive Dual Comb Fourier Transform Spectroscopy

    NASA Astrophysics Data System (ADS)

    Jacquey, M.; Jacquet, P.; Mandon, J.; Thon, R.; Guelachvili, G.; Hänsch, T. W.; Picqué, N.

    2010-06-01

    Fourier transform spectroscopy based on time-domain interferences between two slightly detuned frequency comb sources holds much promise for the real-time diagnostic of gaseous, liquid or solid-state samples. In one very recent example, cavity-enhanced absorption spectroscopy with two infrared frequency combs has demonstrated a dramatically enhanced sensitivity, compared to conventional Fourier spectroscopy, with intriguing implications for instantaneous trace gas analysis. It however remains challenging to match continuously the comb and cavity modes across a broad spectral bandwidth during the time of a measurement. An obvious alternative for reaching a long interaction path is a conventional multipass cell. Additionally, differential detection schemes may be devised to increase the dynamic range of the interferometric measurements, thus providing enhanced signal to noise ratio. Experimental demonstrations will be given in the 1.5 ?m region with a dual comb set-up based on two Er-doped fiber femtosecond lasers. The versatility and performances of these solutions will be compared to the cavity-enhanced dual comb technique and other state-of-the-art alternatives. P. Jacquet, J. Mandon, B. Bernhardt, R. Holzwarth, G. Guelachvili, T. W. Hänsch, N. Picqué, Frequency Comb Fourier Transform Spectroscopy with kHz Optical Resolution, The Optical Society of America, Washington, DC 2009, paper FMB2 (2009). B. Bernhardt, A. Ozawa, P. Jacquet, M. Jacquey, Y. Kobayashi, T. Udem, R. Holzwarth, G. Guelachvili, T.W. Hänsch, N. Picqué, Cavity-enhanced dual-comb spectroscopy, Nature Photonics 4, 55-57 (2010),

  4. Precision spectroscopy using a partially stabilized frequency comb.

    PubMed

    Lyon, M; Bergeson, S D

    2014-08-10

    We present a simple method for precision spectroscopy using an optical frequency comb. One mode of a 1 GHz repetition rate mode-locked Ti:sapphire laser is offset-locked to an Rb-stabilized diode laser. This partially stabilized frequency comb stays locked, unattended, for hours at a time. Using the measured offset frequency and repetition rate, we calculate the frequency of each comb mode with absolute uncertainty of about 10 kHz in a 10 s measurement window. We demonstrate the capabilities and limitations of this approach with measurements in Rb, Cs, and Ca. PMID:25320925

  5. High-coherence mid-infrared frequency comb.

    PubMed

    Galli, I; Cappelli, F; Cancio, P; Giusfredi, G; Mazzotti, D; Bartalini, S; De Natale, P

    2013-11-18

    We report on the generation of a frequency comb around 4330 nm with an unprecedented coherence of the single teeth. Generating the comb within a Ti:sapphire laser cavity by a difference-frequency process and using a phase-lock scheme based on direct digital synthesis, we achieve a tooth linewidth of 2.0 kHz in a 1-s timescale (750 Hz in 20 ms). The generated per-tooth power of 1 ?W ranks this comb among the best ever realized in the mid-infrared in terms of power spectral density. PMID:24514401

  6. Nonlinear conversion efficiency in Kerr frequency comb generation.

    PubMed

    Bao, Changjing; Zhang, Lin; Matsko, Andrey; Yan, Yan; Zhao, Zhe; Xie, Guodong; Agarwal, Anuradha M; Kimerling, Lionel C; Michel, Jurgen; Maleki, Lute; Willner, Alan E

    2014-11-01

    We analytically and numerically investigate the nonlinear conversion efficiency in ring microresonator-based mode-locked frequency combs under different dispersion conditions. Efficiency is defined as the ratio of the average round trip energy values for the generated pulse(s) to the input pump light. We find that the efficiency degrades with growth of the comb spectral width and is inversely proportional to the number of comb lines. It depends on the cold-cavity properties of a microresonator only and can be improved by increasing the coupling coefficient. Also, it can be increased in the multi-soliton state. PMID:25361295

  7. Measurement of Length and Position with Frequency Combs

    NASA Astrophysics Data System (ADS)

    Weimann, C.; Hoeller, F.; Schleitzer, Y.; Diez, C. A.; Spruck, B.; Freude, W.; Boeck, Y.; Koos, C.

    2015-04-01

    We show two different absolute distance measurement methods with micrometer accuracy based on frequency combs, and we discuss possible applications. Using a mode- locked laser and MEMS-based tracking optics, we measure the 3D position of a retroreflector within 10 ms and with a 24 ?m volumetric accuracy. We also investigate modulator-based combs and show that they enable highly sensitive surface topography measurements with microsecond acquisition times and micrometer precision. Moreover, the potential for photonic integration of frequency comb sources is explored.

  8. Towards an eficient atomic frequency comb quantum memory

    E-print Network

    A. Amari; A. Walther; M. Sabooni; M. Huang; S. Kröll; M. Afzelius; I. Usmani; B. Lauritzen; N. Sangouard; H. de Riedmatten; N. Gisin

    2009-11-11

    We present an efficient photon-echo experiment based on atomic frequency combs [Phys. Rev. A 79, 052329 (2009)]. Echoes containing an energy of up to 35% of that of the input pulse are observed in a Pr3+-doped Y2SiO5 crystal. This material allows for the precise spectral holeburning needed to make a sharp and highly absorbing comb structure. We compare our results with a simple theoretical model with satisfactory agreement. Our results show that atomic frequency combs has the potential for high-efficiency storage of single photons as required in future long-distance communication based on quantum repeaters.

  9. Towards an efficient atomic frequency comb quantum memory

    NASA Astrophysics Data System (ADS)

    Amari, A.; Walther, A.; Sabooni, M.; Huang, M.; Kröll, S.; Afzelius, M.; Usmani, I.; Lauritzen, B.; Sangouard, N.; de Riedmatten, H.

    2010-09-01

    We present an efficient photon-echo experiment based on atomic frequency combs [Phys. Rev. A 79, 052329 (2009)]. Echoes containing an energy of up to 35% of that of the input pulse are observed in a Pr3+-doped Y2SiO5 crystal. This material allows for the precise spectral holeburning needed to make a sharp and highly absorbing comb structure. We compare our results with a simple theoretical model with satisfactory agreement. Our results show that atomic frequency combs has the potential for high-efficiency storage of single photons as required in future long-distance communication based on quantum repeaters.

  10. Dual frequency comb spectroscopy with a single laser.

    PubMed

    Znakovskaya, I; Fill, E; Forget, N; Tournois, P; Seidel, M; Pronin, O; Krausz, F; Apolonski, A

    2014-10-01

    We demonstrate a simple scheme for dual frequency comb spectroscopy in which the second frequency comb is generated by propagating the primary pulse train through a dazzler. The two frequency combs are combined behind a Mach-Zehnder interferometer, and the optical spectrum is read out by an rf-spectrum analyzer. The method is applied to record the overtone absorption spectrum of C2H2 (acetylene) in the wavelength region around 1.03 ?m. A spectrum with a resolution of 4??cm(-1) is obtained, which compares well with that from the HITRAN database. A simple method for improving the spectral resolution is demonstrated. PMID:25360905

  11. A Genomic Duplication is Associated with Ectopic Eomesodermin Expression in the Embryonic Chicken Comb and Two Duplex-comb Phenotypes

    PubMed Central

    Dorshorst, Ben; Rubin, Carl-Johan; Ashwell, Chris; Gourichon, David; Tixier-Boichard, Michèle; Hallböök, Finn; Andersson, Leif

    2015-01-01

    Duplex-comb (D) is one of three major loci affecting comb morphology in the domestic chicken. Here we show that the two Duplex-comb alleles, V-shaped (D*V) and Buttercup (D*C), are both associated with a 20 Kb tandem duplication containing several conserved putative regulatory elements located 200 Kb upstream of the eomesodermin gene (EOMES). EOMES is a T-box transcription factor that is involved in mesoderm specification during gastrulation. In D*V and D*C chicken embryos we find that EOMES is ectopically expressed in the ectoderm of the comb-developing region as compared to wild-type embryos. The confinement of the ectopic expression of EOMES to the ectoderm is in stark contrast to the causal mechanisms underlying the two other major comb loci in the chicken (Rose-comb and Pea-comb) in which the transcription factors MNR2 and SOX5 are ectopically expressed strictly in the mesenchyme. Interestingly, the causal mutations of all three major comb loci in the chicken are now known to be composed of large-scale structural genomic variants that each result in ectopic expression of transcription factors. The Duplex-comb locus also illustrates the evolution of alleles in domestic animals, which means that alleles evolve by the accumulation of two or more consecutive mutations affecting the phenotype. We do not yet know whether the V-shaped or Buttercup allele correspond to the second mutation that occurred on the haplotype of the original duplication event. PMID:25789773

  12. Parentage and relatedness in polyandrous comb-crested jacanas using ISSRs

    USGS Publications Warehouse

    Haig, Susan M.; Mace, Terrence R.; Mullins, Thomas D.

    2003-01-01

    In this article we present the first analysis of parentage and relatedness in a natural vertebrate population, using Intersimple Sequence Repeat (ISSR) markers. Thus, 28 ISSR markers were used in a study of a sex-role reversed, simultaneously polyandrous shorebird from northeastern Australia, the comb-crested jacana (Irediparra gallinacea). Assessment of parentage was based on comparison of field observations, novel bands, individual-specific bands found in 7/9 males and 4/6 females, and a 99% CI exclusion criteria. Integrating results from these approaches resulted in confirmation of paternity in all 36 chicks. In only one case (2.8% of chicks) was a co-mate assigned paternity. Thus, comb-crested jacanas appear to be genetically monogamous. These results showed resemblance to sequentially polyandrous birds but differed from the simultaneously polyandrous wattled jacana ( Jacana jacana; Emlen et al. 1998). A significant relationship between relatedness and ISSR similarity resulted in recognition that 14/15 adults sampled may be related to at least one other adult by 0.25 or more. Lack of dispersal may be explained by physical limitations and adequate regional habitat. ISSRs proved to be simple and helpful in resolving these issues.

  13. Sex Offender Registration Information Sex Offender Registration

    E-print Network

    Escher, Christine

    Sex Offender Registration Information Sex Offender Registration In accordance to the "Campus Sex Police Sex Offender Registry. This act requires institutions of higher education to issue a statement sex offenders may be obtained. It also requires sex offenders already required to register in a State

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

    PubMed

    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. PMID:25968529

  15. Stabilized Ultrafast Pulse Generation and Optical Frequency Combs Techniques

    E-print Network

    Van Stryland, Eric

    Stabilized Ultrafast Pulse Generation and Optical Frequency Combs ­ Techniques and Applications Length, Intracavity Power, PDH · Applications ­ Optical Sampling (ADC's), Waveform Generation (DAC Gold wire Ceramic stand Gold coated copper stud Copper block Thermoelectric cooler + I 4mm Mounted

  16. Femtosecond laser frequency comb for precision astrophysical spectroscopy

    E-print Network

    Kartner, Franz X.

    High-resolution spectroscopy is a crucial tool for cosmology and the search for extrasolar planets. We present a laser comb with up to 40-GHz line spacing for use as a new spectrographic calibration source.

  17. Raman-induced Kerr-effect dual-comb spectroscopy

    E-print Network

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

    2012-01-01

    We report on the first demonstration of nonlinear dual-frequency-comb spectroscopy. In multi-heterodyne femtosecond Raman-induced Kerr-effect spectroscopy, the Raman gain resulting from the coherent excitation of molecular vibrations by a spectrally-narrow pump is imprinted onto the femtosecond laser frequency comb probe spectrum. The birefringence signal induced by the nonlinear interaction of these beams and the sample is heterodyned against a frequency comb local oscillator with a repetition frequency slightly different from that of the comb probe. Such time-domain interference provides multiplex access to the phase and amplitude Raman spectra over a broad spectral bandwidth within a short measurement time. Experimental demonstration, at a spectral resolution of 200 GHz, a measurement time of 293 {\\mu}s and a sensitivity of 10^-6, is given on liquid samples exhibiting a C-H stretch Raman shift.

  18. Safe sex

    NSDL National Science Digital Library

    Olivia Worland (Purdue University; Biological Sciences)

    2008-07-09

    There are many diseases that humans can contract through sexual contact with each other. Humans can lower their risk of contracting these diseases by practicing safe sex techniques if they choose to participate in those kinds of actions.

  19. Study of colour discrimination with comb-filtered spectra

    Microsoft Academic Search

    Valérie Bonnardel; Eva M. Valero

    2001-01-01

    Techniques that involve the use of comb-filtered spectra to study human colour vision have been developed in previous work (Bonnardel, V., Bellemare, H., Mollon, J.D., 1996. Measurements of human sensitivity to comb-filtered spectra, Vision Research 36, 2713–2720; Bonnardel, V., Ruderman D.L., Barlow, H.B., 1997. A fast determination of the Spectral Modulation Sensitivity Function: a comparison between trichromats and deuteranopes. In:

  20. Effect of empty comb on defensive behavior of honeybees

    Microsoft Academic Search

    Anita M. Collins; Thomas E. Rinderer

    1985-01-01

    Honeybees in colonies with 6.36-m2 surface area of empty comb responded faster to moving targets and stung the targets more often than bees from colonies with 3.18-m2 surface area of empty honeycomb. The two groups did not differ significantly in speed of response to alarm pheromone or in number of bees defending the colony. Volatiles from the comb are suggested

  1. Specific-heat measurements and critical exponents of the ferroelastic phase transition in Pb3(PO4)2 and Pb3(P1-xAsxO4)2

    Microsoft Academic Search

    E. Salje; B. Wruck

    1983-01-01

    The ferroelastic phase transitions in Pb3(PO4)2 and Pb3(P1-xAsxO4)2 are accompanied by large excess specific heats in a wide temperature range above Tc and critical crossover above and below Tc. Critical exponents of the specific heat alpha'=0.363(4), 0.360(5), and 0.36(1) for Pb3(PO4)2, Pb3(P0.97As0.03O4)2, and Pb3(P0.2As0.8O4)2, respectively, agree with theoretical predictions of a q=3, d=2, Potts model. Along with other experimental results

  2. Phase-stabilized 167 MHz repetition frequency carbon nanotube fiber laser frequency comb

    Microsoft Academic Search

    Jinkang Lim; Kevin Knabe; Yishan Wang; Rodrigo Amezcua-Correa; François Couny; Philip S. Light; Fetah Benabid; Jonathan C. Knight; Kristan L. Corwin; Jeffrey W. Nicholson; Brian R. Washburn

    2009-01-01

    The frequency comb generated by a high repetition frequency erbium-doped fiber ring laser using carbon nanotube saturable absorber is phase-stabilized for the first time. The comb's stability is compared a photonic crystal fiber acetylene reference.

  3. Nonlinear Dual-Comb Spectroscopy with Two-Photon Excitation

    NASA Astrophysics Data System (ADS)

    Meek, S. A.; Hipke, A.; Hansch, T. W.; Picque, N.

    2013-06-01

    Dual frequency comb spectroscopy has proven to be a powerful method for acquiring broadband, high resolution spectra with measurement times that are much shorter than in traditional moving-mirror Fourier transform spectroscopy. Because the measurements are carried out with femtosecond lasers, this technique has great potential for decreasing the measurement times and improving the signal-to-noise ratio of nonlinear spectroscopic measurements, such as two-photon excitation or Raman processes. In the case of two-photon excitation, an entire spectrum can be obtained at a given signal level using dual-comb spectroscopy in the same time that a measurement of a single transition frequency would be obtained with a continuous laser of the same average power. In this presentation, I will show the latest results in extending the dual-comb technique to two-photon excitation spectroscopy, with measurements on gas-phase rubidium and liquid-phase dye samples. In our realization of dual-comb spectroscopy, two frequency combs with slightly different repetition rates are combined on a beam splitter and directed into a sample, and we measure the intensity of the resulting fluorescence as a function of time. Because of the different repetition rates, the time delay between a pulse from the first comb and the next pulse from the second comb changes linearly with time, simulating the action of the moving mirror in a traditional Michelson interferometer. The Fourier transform of the measured time-domain interferogram produces a radio-frequency spectrum that can be directly converted to a broadband optical spectrum through a linear scaling of the frequency. To achieve the highest possible resolution, it is necessary to compensate the residual relative fluctuations of the repetition rate and the carrier-envelope offset frequency of the frequency combs. Measuring RF beatnotes of each comb with two CW lasers provides two error signals that can be used to correct the recorded interferograms. This correction is applied differently for one-photon and two-photon spectra, providing a method of distinguishing the two.

  4. Sex Education.

    ERIC Educational Resources Information Center

    Williams, Sue

    1991-01-01

    This discussion of sex education for individuals with intellectual disabilities outlines Delys Sergeant's "coat hanger theory," which involves three coats or phases of sexuality: a physiological stimulus response coat; a reproductive coat; and a coat of attitudes, values, and self-esteem. Influences acting on individuals' sexuality include family,…

  5. Influence of comb parameters on picking properties for chamomile flowers ( Matricaria recutita)

    Microsoft Academic Search

    Detlef Ehlert; Rolf Adamek; Antje Giebel; Hans-Juergen Horn

    2011-01-01

    Tools in the form of a comb are generally used to harvest chamomile flowers. The combs can be hand-operated or machine-based. To achieve good picking quality and low losses, the comb parameters have to be optimized. In this paper, the influence of comb thickness (0.5mm, 1.0mm and 2mm) and the shape of the gap between the tines (3 variants) on

  6. A novel strain sensor based on a pair of fiber Bragg grating comb filters

    Microsoft Academic Search

    Feifei Yin; Ye Zhang; Shizhong Xie

    2008-01-01

    A pair of fiber Bragg grating (FBG) comb filters with different channel-spacings are designed and fabricated to measure strain. The reflection peaks of one comb filter shift when the strain changes. And the other comb filter is used as calibration standard. The two comb filters have different channel-spacings, 1.00 nm and 0.95 nm, which can be regard as the structure

  7. 1-GHz harmonically pumped femtosecond optical parametric oscillator frequency comb.

    PubMed

    Balskus, K; Leitch, S M; Zhang, Z; McCracken, R A; Reid, D T

    2015-01-26

    We present the first example of a femtosecond optical parametric oscillator frequency comb harmonically-pumped by a 333-MHz Ti:sapphire laser to achieve a stabilized signal comb at 1-GHz mode spacing in the 1.1-1.6-µm wavelength band. Simultaneous locking of the comb carrier-envelope-offset and repetition frequencies is achieved with uncertainties over 1 s of 0.27 Hz and 5 mHz respectively, which are comparable with those of 0.27 Hz and 1.5 mHz achieved for 333-MHz fundamental pumping. The phase-noise power-spectral density of the CEO frequency integrated from 1 Hz-64 kHz was 2.8 rad for the harmonic comb, 1.0 rad greater than for fundamental pumping. The results show that harmonic operation does not substantially compromise the frequency-stability of the comb, which is shown to be limited only by the Rb atomic frequency reference used. PMID:25835887

  8. A quantitative mode-resolved frequency comb spectrometer.

    PubMed

    Hébert, Nicolas Bourbeau; Scholten, Sarah K; White, Richard T; Genest, Jérôme; Luiten, Andre N; Anstie, James D

    2015-06-01

    We have developed a frequency-comb spectrometer that records 35-nm (4 THz) spectra with 2-pm (250 MHz) spectral sampling and an absolute frequency accuracy of 2 kHz. We achieve a signal-to-noise ratio of ~400 in a measurement time of 8.2 s. The spectrometer is based on a commercial frequency comb decimated by a variable-length, low-finesse Fabry Pérot filter cavity to fully resolve the comb modes as imaged by a virtually imaged phased array (VIPA), diffraction grating and near-IR camera. By tuning the cavity length, spectra derived from all unique decimated combs are acquired and then interleaved to achieve frequency sampling at the comb repetition rate of 250 MHz. We have validated the performance of the spectrometer by comparison with a previous high-precision absorption measurement of H13C14N near 1543 nm. We find excellent agreement, with deviations from the expected line centers and widths of, at most, 1 pm (125 MHz) and 3 pm (360 MHz), respectively. PMID:26072768

  9. Brood comb as a humidity buffer in honeybee nests

    NASA Astrophysics Data System (ADS)

    Ellis, Michael B.; Nicolson, Sue W.; Crewe, Robin M.; Dietemann, Vincent

    2010-04-01

    Adverse environmental conditions can be evaded, tolerated or modified in order for an organism to survive. During their development, some insect larvae spin cocoons which, in addition to protecting their occupants against predators, modify microclimatic conditions, thus facilitating thermoregulation or reducing evaporative water loss. Silk cocoons are spun by honeybee ( Apis mellifera) larvae and subsequently incorporated into the cell walls of the wax combs in which they develop. The accumulation of this hygroscopic silk in the thousands of cells used for brood rearing may significantly affect nest homeostasis by buffering humidity fluctuations. This study investigates the extent to which the comb may influence homeostasis by quantifying the hygroscopic capacity of the cocoons spun by honeybee larvae. When comb containing cocoons was placed at high humidity, it absorbed 11% of its own mass in water within 4 days. Newly drawn comb composed of hydrophobic wax and devoid of cocoons absorbed only 3% of its own mass. Therefore, the accumulation of cocoons in the comb may increase brood survivorship by maintaining a high and stable humidity in the cells.

  10. The Structure and Dynamics of Flexible Polyelectrolyte Combs

    E-print Network

    A. Papagiannopoulos; T. A. Waigh; C. Fernyhough; T. Hardingham; M. Heinrich

    2005-08-27

    The structure and dynamics of a range of polystyrene sulphonate comb polyelectrolytes with well defined chain architectures were examined with static light scattering, dynamic light scattering, small angle neutron/X-ray scattering, particle tracking microrheology and diffusing wave spectroscopy. The chains adopted extended cylindrical conformations in dilute solutions. In semi-dilute solutions a universal behaviour was found for the correlation length (X) on the monomer concentration (c), X=(3.0/b)c^-0.47, independent of the comb architecture (b is the monomer size). The high frequency viscoelasticity (104-106Hz) is found to be in agreement with a model for the Rouse dynamics of the chains and is again independent of the architecture of the combs. However the architecture had a significant impact on the low frequency viscosity of the solutions and the particle tracking data was in good agreement with a dynamic scaling theory for the unentangled dynamics of the combs. Analogous results are found with the biological comb polyelectrolyte aggrecan.

  11. Process for High Speed Micro Electro Mechanical Systems (MEMS) Scanning Mirrors with Vertical Comb Drives

    Microsoft Academic Search

    Hiroyuki Wada; Daesung Lee; Uma Krishnamoorthy; Stefan Zappe; Olav Solgaard

    2002-01-01

    We present a three-level fabrication process for fast scanning micromirrors actuated by vertical comb drives. The process uses only front side lithography to create combdrives with selfaligned comb teeth. Selfalignment of the movable and stationary comb teeth allows the use of high voltages that are necessary for fast scanning. The fabrication process is based on two wafer-bonding steps to create

  12. Bandwidth scaling and spectral flatness enhancement of optical frequency combs from phase-modulated

    E-print Network

    Purdue University

    Bandwidth scaling and spectral flatness enhancement of optical frequency combs from phase-modulated-wave mixing technique that scales up the bandwidth of frequency combs gen- erated by phase modulation a 10 GHz frequency comb with over 100 lines in a 10 dB bandwidth in which a record 75 lines are within

  13. The effect of drone comb on a honey bee colony'sproduction of honey

    Microsoft Academic Search

    Thomas D. Seeley

    2002-01-01

    This study examined the impact on a colony's honey production of providing it with a nat- ural amount (20%) of drone comb. Over 3 summers, for the period mid May to late August, I mea- sured the weight gains of 10 colonies, 5 with drone comb and 5 without it. Colonies with drone comb gained only 25.2 ± 16.0 kg

  14. Original article The effect of drone comb on a honey bee colony's

    E-print Network

    Paris-Sud XI, Université de

    Original article The effect of drone comb on a honey bee colony's production of honey* Thomas D on a colony's honey production of providing it with a nat- ural amount (20%) of drone comb. Over 3 summers, for the period mid May to late August, I mea- sured the weight gains of 10 colonies, 5 with drone comb and 5

  15. Calibration of an astrophysical spectrograph below 1 m/s using a laser frequency comb

    E-print Network

    Phillips, David F.

    We deployed two wavelength calibrators based on laser frequency combs (“astro-combs”) at an astronomical telescope. One astro-comb operated over a 100 nm band in the deep red (~ 800 nm) and a second operated over a 20 nm ...

  16. Reciprocal interactions between honeybees and combs in the integration of some colony

    E-print Network

    Paris-Sud XI, Université de

    Review Reciprocal interactions between honeybees and combs in the integration of some colony in studies of the reciprocal interactions between honeybees and their combs are reviewed. Wax secretion in the waggle dance and recruitment of new foragers. © Inra/ DIB/AGIB/Elsevier, Paris honeybee / combs

  17. Elimination of pump-induced frequency jitter on fiber-laser frequency combs

    E-print Network

    Washburn, Brian

    Elimination of pump-induced frequency jitter on fiber-laser frequency combs J. J. McFerran, W. C. ID 68330) Optical frequency combs generated by femtosecond fiber lasers typically exhibit significant frequency noise that causes broad optical linewidths, particularly in the comb wings and in the carrier

  18. Sex during Pregnancy

    MedlinePLUS

    ... satisfying and safe sexual relationship during pregnancy. Is Sex During Pregnancy Safe? Sex is considered safe during ... frequently asked questions about sex during pregnancy. Can sex harm my baby? No. Your baby is fully ...

  19. Decade-spanning high-precision terahertz frequency comb.

    PubMed

    Finneran, Ian A; Good, Jacob T; Holland, Daniel B; Carroll, P Brandon; Allodi, Marco A; Blake, Geoffrey A

    2015-04-24

    The generation and detection of a decade-spanning terahertz (THz) frequency comb is reported using two Ti:sapphire femtosecond laser oscillators and asynchronous optical sampling THz time-domain spectroscopy. The comb extends from 0.15 to 2.4 THz, with a tooth spacing of 80 MHz, a linewidth of 3.7 kHz, and a fractional precision of 1.8×10^{-9}. With time-domain detection of the comb, we measure three transitions of water vapor at 10 mTorr between 1-2 THz with an average Doppler-limited fractional accuracy of 6.1×10^{-8}. Significant improvements in bandwidth, resolution, and sensitivity are possible with existing technologies. PMID:25955051

  20. Quantum cascade laser combs: effects of modulation and dispersion.

    PubMed

    Villares, Gustavo; Faist, Jérôme

    2015-01-26

    Frequency comb formation in quantum cascade lasers is studied theoretically using a Maxwell-Bloch formalism based on a modal decomposition, where dispersion is considered. In the mid-infrared, comb formation persists in the presence of weak cavity dispersion (500 fs2 mm-1) but disappears when much larger values are used (30'000 fs2 mm-1). Active modulation at the round-trip frequency is found to induce mode-locking in THz devices, where the upper state lifetime is in the tens of picoseconds. Our results show that mode-locking based on four-wave mixing in broadband gain, low dispersion cavities is the most promising way of achieving broadband quantum cascade laser frequency combs. PMID:25835922

  1. Study of colour discrimination with comb-filtered spectra.

    PubMed

    Bonnardel, V; Valero, E M

    2001-03-01

    Techniques that involve the use of comb-filtered spectra to study human colour vision have been developed in previous work (Bonnardel, V., Bellemare, H., Mollon, J.D., 1996. Measurements of human sensitivity to comb-filtered spectra, Vision Research 36, 2713-2720; Bonnardel, V., Ruderman D.L., Barlow, H.B., 1997. A fast determination of the Spectral Modulation Sensitivity Function: a comparison between trichromats and deuteranopes. In: C.R. Cavonius (ed.), Color vision deficiencies XIII. Dordrecht: Kluver 415-424). These techniques are applied in the present study to measure colour discrimination among deuteranomalous observers and normal trichromats, with the aim of determining the spectral position of the anomalous cone fundamentals. Results show that comb-filtered spectra are useful in determining the extent to which variability in colour discrimination among anomalous and normal trichromatic colour observers is accounted for by the spectral properties of photoreceptors. PMID:11226500

  2. Hair breakage during combing. III. The effects of bleaching and conditioning on short and long segment breakage by wet and dry combing of tresses.

    PubMed

    Robbins, Clarence; Kamath, Yash

    2007-01-01

    A recent publication (1), provided evidence for two types of hair breakage during combing, short segment breakage (approximately less than 1.27 cm) and longer segment breakage. We have confirmed these results and refined the separation distance between short and long segment breakage at about 2.54 cm. Furthermore, chemical bleaching increased both short and long segment breakage while a commercial hair conditioner decreased both types of breakage. Whether the hair is chemically bleached or conditioned, for dry combing, short segment breakage increases with increasing comb strokes, that is, short segment breakage increases as combing damages the ends of the hair, however, long segment breakage does not increase with increasing comb strokes. Wet combing provided a decrease in short segment breakage and an increase in long segment breaks, but no increase in breakage with increasing comb strokes. Mechanical combing of tresses shows similar results qualitatively, however the variance was too large and adjustments need to be made to provide for a larger number of broken hairs to bring the mechanical and hand combing results in line. For dry combing, as the comb descends through the hair, hairs above it are made parallel and those beneath are either made parallel or knot by, hairs looping around other hairs or hairs looping around comb teeth and other hairs several cm between the comb and the hair tips. As the comb advances through the looped/knotted hairs long breaks occur or as the comb descends near the tips wrapped ends can result. End wrapping by inertia & possibly static charge produces short segment breaks which are more severe if the hair is cut at 90 degrees versus a tapered cut. For wet combing, clumping of hairs by a capillary action produces fewer short segment breaks, by reducing end wrapping: however, crossed hair interactions occur & because of higher friction more severe snags arise higher up in the tress, and lower hair breaking load due to plasticization by water, producing a larger number of long segment breaks. The very best practical way to evaluate hair strength is by counting the actual number of short and long segment breaks and by considering both wet and dry combing. PMID:17728947

  3. Phone Sex

    E-print Network

    Flamingo

    1995-01-01

    Phone Se by Flamingo art by KOZ PrmtedinUSA $SJ fS wv) p?l iSI PHCNE %t\\ By flamingo Illustrated by KOZ Editors: Tosya Stohn La Gavia Text & Titles: Jazz Printer: Kinko's ofGrand Rapids, MI Authorized Distributor TbGavia Flamingo Layout & Binding: Tosya Stohn Publisher: Bodacious Press PHONE SEX by Flamingo Copyright? May 1995. All rights reserved. No part of this publication may be reproduced without...

  4. Power optimization of XUV frequency combs for spectroscopy applications [Invited].

    PubMed

    Yost, D C; Cingöz, A; Allison, T K; Ruehl, A; Fermann, M E; Hartl, I; Ye, J

    2011-11-01

    We address technical impediments to the generation of high-photon flux XUV frequency combs through cavity-enhanced high harmonic generation. These difficulties arise from mirror damage, cavity nonlinearity, the intracavity plasma generated during the HHG process, and imperfect phase-matching. By eliminating or minimizing each of these effects we have developed a system capable of generating > 200 ?W and delivering ~20 ?W of average power for each spectrally separated harmonic (wavelengths ranging from 50 nm - 120 nm), to actual comb-based spectroscopy experiments. PMID:22109226

  5. Study of colour discrimination with comb-filtered spectra

    Microsoft Academic Search

    Vale Rie Bonnardel; Eva M. Valero

    Abstract Techniques,that involve the use of comb-filtered spectra to study human,colour vision have,been developed,in previous,work (Bonnardel, V., Bellemare, H., Mollon, J.D., 1996. Measurements of human sensitivity to comb-filtered spectra, Vision Research 36, 2713?2720; Bonnardel, V., Ruderman D.L., Barlow, H.B., 1997. A fast determination of the Spectral Modulation Sensitivity Function: a comparison between trichromats and deuteranopes. In: C.R. Cavonius (ed.), Color

  6. Honeybee combs: how the circular cells transform into rounded hexagons

    PubMed Central

    Karihaloo, B. L.; Zhang, K.; Wang, J.

    2013-01-01

    We report that the cells in a natural honeybee comb have a circular shape at ‘birth’ but quickly transform into the familiar rounded hexagonal shape, while the comb is being built. The mechanism for this transformation is the flow of molten visco-elastic wax near the triple junction between the neighbouring circular cells. The flow may be unconstrained or constrained by the unmolten wax away from the junction. The heat for melting the wax is provided by the ‘hot’ worker bees. PMID:23864500

  7. The generation of continuous-variable entanglement frequency comb.

    PubMed

    Yu, Youbin; Cheng, Xiaomin; Wang, Huaijun; Shi, Zhongtao; Zhao, Junwei; Ji, Fengmin; Yin, Zhi; Wang, Yajuan

    2015-01-01

    Continuous-variable (CV) entanglement frequency comb can be produced by enhanced Raman scattering in an above-threshold optical oscillator cavity in which a hexagonally-poled LiTaO3 crystal resides as a Raman gain medium. The Stokes and anti-Stokes Raman signals are enhanced by a coupled quasi-phase-matching optical parametric process and the entanglement natures among these Raman signals and pump are demonstrated by applying a sufficient inseparability criterion for CV entanglement. Such entanglement frequency comb source with different frequencies and continuously tunable frequency interval may be very significant for the applications in quantum communication and networks. PMID:25600617

  8. Frequency-Comb-Assisted Terahertz Quantum Cascade Laser Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bartalini, S.; Consolino, L.; Cancio, P.; De Natale, P.; Bartolini, P.; Taschin, A.; De Pas, M.; Beere, H.; Ritchie, D.; Vitiello, M. S.; Torre, R.

    2014-04-01

    We report a metrological-grade THz spectroscopy based on the combination of a THz frequency-comb synthesizer (FCS) and a THz quantum cascade laser (QCL). The QCL, emitting at 2.5 THz, is phase locked to the free-space THz FCS, and its frequency is swept across a methanol transition by tuning the comb-repetition rate, which is ultimately disciplined by the Cs primary frequency standard. The absolute frequency scale provides an uncertainty of a few parts in 10-11 on the laser frequency and 10-9 on the line-center determination, ranking this technique among the most precise ever developed in the THz range.

  9. Mid-infrared frequency comb for broadband high precision and sensitivity molecular spectroscopy.

    PubMed

    Galli, I; Bartalini, S; Cancio, P; Cappelli, F; Giusfredi, G; Mazzotti, D; Akikusa, N; Yamanishi, M; De Natale, P

    2014-09-01

    We report on the experimental demonstration of the metrological and spectroscopic performances of a mid-infrared comb generated by a nonlinear downconversion process from a Ti:sapphire-based near-infrared comb. A quantum cascade laser at 4330 nm was phase-locked to a single tooth of this mid-infrared comb and its frequency-noise power spectral density was measured. The mid-infrared comb itself was also used as a multifrequency highly coherent source to perform ambient air direct comb spectroscopy with the Vernier technique, by demultiplexing it with a high-finesse Fabry-Perot cavity. PMID:25166071

  10. A stable frequency comb directly referenced to rubidium electromagnetically induced transparency and two-photon transitions

    SciTech Connect

    Hou, Dong; Wu, Jiutao; Zhang, Shuangyou; Ren, Quansheng; Zhang, Zhigang; Zhao, Jianye, E-mail: zhaojianye@pku.edu.cn [Department of Electronics, Peking University, Beijing, 100871 (China)

    2014-03-17

    We demonstrate an approach to create a stable erbium-fiber-based frequency comb at communication band by directly locking the combs to two rubidium atomic transitions resonances (electromagnetically induced transparency absorption and two-photon absorption), respectively. This approach directly transfers the precision and stability of the atomic transitions to the comb. With its distinguishing feature of compactness by removing the conventional octave-spanning spectrum and f-to-2f beating facilities and the ability to directly control the comb's frequency at the atomic transition frequency, this stable optical comb can be widely used in optical communication, frequency standard, and optical spectroscopy and microscopy.

  11. Target micro-displacement measurement by a "comb" structure of intensity distribution in laser plasma propulsion

    NASA Astrophysics Data System (ADS)

    Zheng, Z. Y.; Zhang, S. Q.; Gao, L.; Gao, H.

    2015-05-01

    A "comb" structure of beam intensity distribution is designed and achieved to measure a target displacement of micrometer level in laser plasma propulsion. Base on the "comb" structure, the target displacement generated by nanosecond laser ablation solid target is measured and discussed. It is found that the "comb" structure is more suitable for a thin film target with a velocity lower than tens of millimeters per second. Combing with a light-electric monitor, the `comb' structure can be used to measure a large range velocity.

  12. Comparative efficacy of commercial combs in removing head lice (Pediculus humanus capitis) (Phthiraptera: Pediculidae).

    PubMed

    Gallardo, Anabella; Toloza, Ariel; Vassena, Claudia; Picollo, María Inés; Mougabure-Cueto, Gastón

    2013-03-01

    The use of a fine comb for removing lice from the head of the human host is a relevant tool both in the diagnosis of infestations and as part of an integrated control strategy of head lice. The effectiveness of a fine comb depends, in part, on the design and material they are built. The aim of this study was to compare in vivo the efficacy of metal and plastic combs that are currently used in the removal of head lice and eggs worldwide. The space between comb teeth and the length was 0.23 and 13 mm in KSL® plastic, 0.3 and 10.7 mm in NOPUCID® plastic, 0.15 and 31 mm in KSL® metal and 0.09 and 37 mm in ASSY® metal. The assays were performed comparing the combs in pairs: (a) KSL® vs. NOPUCID® plastic combs, (b) KSL® vs. ASSY® metal combs and (c) KSL® plastic comb vs. ASSY® metal comb. The most effective plastic comb was KSL®, removing a higher number of individuals of all stages. The most effective metal comb was ASSY®, removing more insects of all stages (except adults). The comparative test between KSL® plastic and ASSY® metal showed that ASSY® was the most effective in removing head lice and their eggs. PMID:23212391

  13. Genomics of sex determination.

    PubMed

    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. PMID:24682067

  14. Computer-aided design of synchronous generators with comb rotors

    Microsoft Academic Search

    Vaagn L Zakarian; Mark J Kaiser

    1999-01-01

    A mathematical model of a synchronous generator with comb rotor is implemented in a computer-aided design (CAD) package. The model integrates the differential equations characteristic of an electric machine; tabled data and empirical coefficients; and geometric, electromagnetic, and economic parameters of machine design. The complexity of the model requires that the solution procedure adopt a naive random search methodology, and

  15. Performance predictions and topology improvements for optical serrodyne comb generators

    Microsoft Academic Search

    Arthur Lowery

    2005-01-01

    Detailed simulations identify which optical components affect the performance of a radio frequency (RF) and optical comb generator based on an optical loop with a phase modulator. The simulations suggest that the topology of the loop can be modified to give a flatter RF spectrum and a greater resilience to fluctuations in the optical phase length of the loop. Furthermore,

  16. Astronomical spectrograph calibration with broad-spectrum frequency combs

    E-print Network

    D. A. Braje; M. S. Kirchner; S. Osterman; T. Fortier; S. A. Diddams

    2008-03-04

    Broadband femtosecond-laser frequency combs are filtered to spectrographically resolvable frequency-mode spacing, and the limitations of using cavities for spectral filtering are considered. Data and theory are used to show implications to spectrographic calibration of high-resolution, astronomical spectrometers.

  17. TOWARDS A LINEAR RESPONSE OF VERTICAL COMB-DRIVE ACTUATORS

    E-print Network

    Rimon, Elon

    the use of electrostatic Vertical Comb-Drive (VCD) actuators in micromirror devices. However, in this work it is shown that current VCD actuators have a nonlinear response due to the motion induced in secondary degrees of freedom. In this work, a novel design of a VCD actuator is presented in which the motion

  18. A phase-stabilized carbon nanotube fiber laser frequency comb

    E-print Network

    Washburn, Brian

    -filled kagome photonic crystal fiber reference, while the CW laser is simultaneously compared to anotherA phase-stabilized carbon nanotube fiber laser frequency comb Jinkang Lim1 , Kevin Knabe1 , Karl A by a 167 MHz repetition frequency erbium-doped fiber ring laser using a carbon nanotube saturable absorber

  19. Femtosecond Frequency Combs for Optical Clocks and Timing Transfer

    E-print Network

    Jin, Deborah

    Mudd College, 2001 A thesis submitted to the Faculty of the Graduate School of the University-free clockwork for an optical clock based on the 3.39-µm transition in methane. The clockwork's simplicity leads as the robustly-running phase-coherent clockwork for an 87Sr optical lattice clock. The optical comb distributes

  20. Precision spectroscopy of hydrogen and femtosecond laser frequency combs

    E-print Network

    Hänsch, Theodor W.

    Precision spectroscopy of hydrogen and femtosecond laser frequency combs BY T. W. HA¨ NSCH 1,2 , J physics, and it has inspired many advances in high resolution laser spectroscopy and optical frequency metrology. Techniques such as laser-cooling of atomic gases, Doppler-free two-photon spectroscopy, or more

  1. Adaptive dual-comb spectroscopy in the green region

    E-print Network

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

    2012-01-01

    Dual-comb spectroscopy is extended to the visible spectral range with a set-up based on two frequency-doubled femtosecond ytterbium-doped fiber lasers. The dense rovibronic spectrum of iodine around 19240 cm-1 is recorded within 12 ms at Doppler-limited resolution with a simple scheme that only uses free-running femtosecond lasers.

  2. Prostitution & Sex Trafficking

    E-print Network

    New Hampshire, University of

    Prostitution & Sex Trafficking in Spain BY: Brittany Rittenberry Political Science & International purchased sex There are 1.5 Million sex transactions everyday #12;Argument: Sex trafficking in Spain would/3 #12;What was concluded... Terminology Demand Supply Sex Trafficking Prostitution #12;#12;For more

  3. Sex, dependency, and helping

    Microsoft Academic Search

    Charles L. Gruder; Thomas D. Cook

    1971-01-01

    Examined whether the difference in the helping behavior of males and females is due to the sex of the person giving help or the sex of the person receiving it. In an experiment with 52 male and 52 female undergraduates, dependency, sex of potential helper, and sex of dependent person were all varied factorially. An interaction of dependency and sex

  4. [Sex hormones].

    PubMed

    van der Kuy, A; van den Bemd, A A; Beysens, A J

    1977-03-15

    An overview of the sex hormones is presented. Testosterone is a natural androgen produced in the testes, adrenal glands, and ovaries. It has anabolic as well as androgenic effects. Testosterone is used to treat inoperable breast cancer and osteoporosis, and to stimulate erythropoesis. Androgens are absolutely counterindicated in cases of prostate cancer. Estrone, estradiol, and estriol are natural estrogens produced in the ovaries, placenta, testes, and adrenal glands. These hormones also influence the production of gonadotropins by the pituitary gland. Estrogens are used to treat menopausal disorders, ovarial insufficiency, estrogen-independent breast cancer, prostate cancer, and in some cases pregnancy disorders. Estrogens and progestagens are 2 components used in oral contraceptives. Progesterone, a natural progestagen, is produced by the corpus luteum. It promotes the proliferation phase of the endometrium, fertilization, and nidation, and it works to maintain pregnancy. Progesterone is used to treat spontaneous abortion, corpus luteum insufficiency, and endometrial cancer. PMID:242426

  5. Sex and Arthritis

    MedlinePLUS

    ... Pain Pregnancy and Rheumatic Disease Sex and Arthritis Sex and Arthritis PRINT Download PDF Description Sexuality is ... sensation Erectile dysfunction or impotence Begin overcoming barriers Sex is not simply about reaching rapid orgasm with ...

  6. Sex-linked dominant

    MedlinePLUS

    Inheritance - sex-linked dominant; Genetics - sex-linked dominant; X-linked dominant; Y-linked dominant ... type of chromosome that is affected (autosomal or sex chromosome). It also depends on whether the trait ...

  7. Progress Report on a Portable TI:SAPPHIRE Comb Laser with Frequencies Referring to Cesium Atom Two-Photon Transitions

    NASA Astrophysics Data System (ADS)

    Cheng, Wang-Yau; Wu, Chien-Ming; Liu, Tz-Wei; Chen, Yo-Huan

    2010-06-01

    A portable Ti:sapphire comb laser would contribute significantly to generalize comb-laser applications, such as the astro-comb missions or other interdisciplinary collaborations. To develop a portable comb laser, three barriers lie ahead: one is to miniaturize and robotize the frequency reference system of the comb laser; the second is to ensure the long-term frequency accuracy without satellite connection, and the third is to miniaturize the pumping laser system. We developed two hand-size cesium-stabilized diode lasers at 822 nm and 884 nm to serve as frequency references for a comb laser and we carried out a comb-laser-based CPT experiment with one single cesium cell that might offer a locking procedure for long-term comb laser accuracy. We will also report our plans and progress on a fiber laser pumped Ti:sapphire comb laser.

  8. Multiplexed Detection of CO2 Using a Novel Dual Comb Spectrometer

    NASA Astrophysics Data System (ADS)

    Fleisher, Adam J.; Long, David A.; Hodges, Joseph; Plusquellic, David F.

    2014-06-01

    We report multiheterodyne-detected cavity-enhanced absorption spectroscopy (MH-CEAS) of CO2 in the near-infrared using a novel frequency comb light source generated from the electro-optical modulation of a single continuous-wave laser. Using a pair of dual-drive Mach Zehnder modulators we create two frequency combs of slightly different comb mode spacing. The probe comb is coupled to a high-finesse optical cavity containing CO2 and then combined with the local oscillator comb on a photodetector. This results in down-conversion of the optical comb to radio frequencies, therefore facilitating fast, multiplexed analysis of the CO2 direct absorption signal. The noise-equivalent absorption coefficient for MH-CEAS as initially demonstrated here is 3×10-10 cm-1 Hz-1/2 per spectral element for ˜50 simultaneously resolved channels of unique optical frequency.

  9. Mode-resolved 10-GHz frequency comb from a femtosecond optical parametric oscillator.

    PubMed

    Zhang, Zhaowei; Balskus, Karolis; McCracken, Richard A; Reid, Derryck T

    2015-06-15

    We report a 10-GHz frequency comb generated by filtering a 333.3-MHz OPO frequency comb with a Fabry-Perot (FP) cavity, which was directly stabilized to the incident fundamental comb. This result is supported by a detailed analysis of the Vernier-effect-induced multiple peaks in the transmitted comb power as the FP cavity spacing is detuned. Modes of the generated 10-GHz comb were clearly resolved by a Fourier transform spectrometer with a spectral resolution of 830 MHz, considerably better than the Nyquist sampling limit. The potentially broad tuning range of this mode-resolved OPO frequency comb opens unique opportunities for precise frequency metrology and high-precision spectroscopy. PMID:26076238

  10. Direct fiber comb stabilization to a gas-filled hollow-core photonic crystal fiber.

    PubMed

    Wu, Shun; Wang, Chenchen; Fourcade-Dutin, Coralie; Washburn, Brian R; Benabid, Fetah; Corwin, Kristan L

    2014-09-22

    We have isolated a single tooth from a fiber laser-based optical frequency comb for nonlinear spectroscopy and thereby directly referenced the comb. An 89 MHz erbium fiber laser frequency comb is directly stabilized to the P(23) (1539.43 nm) overtone transition of (12)C(2)H(2) inside a hollow-core photonic crystal fiber. To do this, a single comb tooth is isolated and amplified from 20 nW to 40 mW with sufficient fidelity to perform saturated absorption spectroscopy. The fractional stability of the comb, ~7 nm away from the stabilized tooth, is shown to be 6 × 10(-12) at 100 ms gate time, which is over an order of magnitude better than that of a comb referenced to a GPS-disciplined Rb oscillator. PMID:25321837

  11. Calibration of an Astrophysical Spectrograph with an Astro-comb

    NASA Astrophysics Data System (ADS)

    Phillips, David F.; Glenday, Alex; Li, Chih-Hao; Cramer, Claire; Korzennik, Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner, Franz X.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.

    2010-03-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. To find a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude improvement in state-of-the-art radial velocity spectroscopy is necessary. An astro-comb, the combination of an ocatve-spanning laser frequency comb with a Fabry-Perot cavity, producing evenly spaced frequency markers with the potential for large wavelength coverage is a promising avenue towards improved wavelength calibration. Here we demonstrate the calibration of a high-resolution astrophysical spectrograph below the 1 m/s level in the 800-900 nm spectral band using an octave-spanning Ti:Sapphire laser and an ultra-low dispersion Fabry-Perot filter cavity adjusted for a mode spacing of approximately 31 GHz. Modeling of spectrograph response function and overall system stability and reproducibility will be described.

  12. Frequency comb injection locking of mode locked lasers

    NASA Astrophysics Data System (ADS)

    Gat, Omri; Kielpinski, David

    2013-03-01

    The two-frequency problem of synchronization of the pulse train of a passively mode locked soliton laser to an externally injected pulse train is solved in the weak injection regime. The source and target frequency combs are distinguished by the spacing and offset frequency mismatches. Locking diagrams map the domain in the mismatch parameter space where stable locking of the combs is possible. We analyze the dependence of the locking behavior on the relative frequency and chirp of the source and target pulses, and the conditions where the relative offset frequency has to be actively stabilized. Locked steady states are characterized by a fixed source-target time and phase shifts that map the locking domain.

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

    E-print Network

    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...

  14. Intraspecific comb usurpation in the social wasp Polistes fuscatus

    Microsoft Academic Search

    J. Klahn

    1988-01-01

    Incidents of usurpation were observed in colonies of Polistes fuscatus nesting on farm buildings (1977–79) and in nestboxes (1980–84) in Johnson County, Iowa, USA. Most usurpations (84.8%) occurred in the latter half of the preworker phase of the colony cycle, which coincided with periods of high predation of combs by vertebrates. Usurpers were probably displaced single foundresses which did not

  15. Generation of a frequency comb and applications thereof

    DOEpatents

    Hagmann, Mark J; Yarotski, Dmitry A

    2013-12-03

    Apparatus for generating a microwave frequency comb (MFC) in the DC tunneling current of a scanning tunneling microscope (STM) by fast optical rectification, cause by nonlinearity of the DC current vs. voltage curve for the tunneling junction, of regularly-spaced, short pulses of optical radiation from a focused mode-locked, ultrafast laser, directed onto the tunneling junction, is described. Application of the MFC to high resolution dopant profiling in semiconductors is simulated. Application of the MFC to other measurements is described.

  16. Kilohertz-Resolution Spectroscopy of Cold Atoms with an Optical Frequency Comb

    SciTech Connect

    Fortier, T. M. [Los Alamos National Laboratory, P-23 Physics Division MS H803, Los Alamos, New Mexico 87545 (United States); Le Coq, Y.; Stalnaker, J. E.; Diddams, S. A.; Oates, C. W.; Hollberg, L. [National Institute of Standards and Technology, Time and Frequency Division, MS 847 Boulder, Colorado 80305 (United States); Ortega, D. [Gleb Wataghin Physics Institute, State University of Campinas (UNICAMP), C.P. 6165, Campinas, SP 13083-970 (Brazil)

    2006-10-20

    We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.

  17. Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb

    E-print Network

    Fortier, T M; Stalnaker, J E; Ortega, D; Diddams, S A; Oates, C W; Hollberg, L

    2006-01-01

    We have performed sub-Doppler spectroscopy on the narrow intercombination line of cold calcium atoms using the amplified output of a femtosecond laser frequency comb. Injection locking of a 657-nm diode laser with a femtosecond comb allows for two regimes of amplification, one in which many lines of the comb are amplified, and one where a single line is predominantly amplified. The output of the laser in both regimes was used to perform kilohertz-level spectroscopy. This experiment demonstrates the potential for high-resolution absolute-frequency spectroscopy over the entire spectrum of the frequency comb output using a single high-finesse optical reference cavity.

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

    PubMed

    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. PMID:23038314

  19. Full phase stabilization of a Yb:fiber femtosecond frequency comb

    E-print Network

    , National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309 generation [5]. Fiber frequency combs used for optical clockwork are actively stabilized using an optical

  20. Comb-locked cavity ring-down spectrometer.

    PubMed

    Gatti, Davide; Sala, Tommaso; Gotti, Riccardo; Cocola, Lorenzo; Poletto, Luca; Prevedelli, Marco; Laporta, Paolo; Marangoni, Marco

    2015-02-21

    Extreme frequency accuracy and high sensitivity are obtained with a novel comb-locked cavity-ring-down spectrometer operating in the near-infrared from 1.5 to 1.63 ?m. A key feature of our approach is the tight frequency locking of the probe laser to the comb, ensuring very high reproducibility and accuracy to the frequency axis upon scanning the comb repetition rate, as well as an efficient light injection into a length-swept high-finesse passive cavity containing the gas sample. Spectroscopic tests on the (30012) ? (00001) P14e line of CO2 at ?1.57 ?m demonstrate an accuracy of ?17 kHz on the line center frequency in a Doppler broadening regime over the time scale of about 5 min, corresponding to four consecutive spectral scans of the absorption line. Over a single scan, which consists of 1500 spectral points over 75 s, the limit of detection is as low as 5.7 × 10(-11) cm(-1). PMID:25702008

  1. Comb-locked cavity ring-down spectrometer

    NASA Astrophysics Data System (ADS)

    Gatti, Davide; Sala, Tommaso; Gotti, Riccardo; Cocola, Lorenzo; Poletto, Luca; Prevedelli, Marco; Laporta, Paolo; Marangoni, Marco

    2015-02-01

    Extreme frequency accuracy and high sensitivity are obtained with a novel comb-locked cavity-ring-down spectrometer operating in the near-infrared from 1.5 to 1.63 ?m. A key feature of our approach is the tight frequency locking of the probe laser to the comb, ensuring very high reproducibility and accuracy to the frequency axis upon scanning the comb repetition rate, as well as an efficient light injection into a length-swept high-finesse passive cavity containing the gas sample. Spectroscopic tests on the (30012) ? (00001) P14e line of CO2 at ˜1.57 ?m demonstrate an accuracy of ˜17 kHz on the line center frequency in a Doppler broadening regime over the time scale of about 5 min, corresponding to four consecutive spectral scans of the absorption line. Over a single scan, which consists of 1500 spectral points over 75 s, the limit of detection is as low as 5.7 × 10-11 cm-1.

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

    NASA Astrophysics Data System (ADS)

    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 ?m. 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 ?m. 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, massively parallel line shape parameters retrieval combined with analysis reaching beyond the VP and with absolute frequency calibration delivered by frequency combs. R. Wehr et al. J. Mol. Spec. 235 54-68 (2003) A. Cygan, et al. Eur. Phys. J. Special Topics 222 2119-2142 (2013)

  3. Sex Education for Patients

    PubMed Central

    Zitner, David

    1985-01-01

    Sex education evokes a wide variety of responses in the community and from teachers. Consequently, physicians have a responsibility to present sex education material in a factual, objective way. Many people are misinformed about sexual behavior. Physicians can help patients and the community by being aware of appropriate sex education for each age group. A curriculum for sex education, and opportunities to provide sex information for patients of different ages and stages in the lifecycle, are described. PMID:21274069

  4. Many-mode Floquet theoretical approach for coherent control of multiphoton dynamics driven by intense frequency-comb laser fields

    E-print Network

    Son, Sang-Kil; Chu, Shih-I

    2008-06-05

    We extend the many-mode Floquet theorem (MMFT) for the investigation of multiphoton resonance dynamics driven by intense frequency-comb laser fields. The frequency comb structure generated by a train of short laser pulses ...

  5. Physicochemical characterization of PEG-based comb-like amphiphilic copolymer structures for possible imaging and therapeutic applications

    E-print Network

    Dawson, Jin Zhou

    2008-01-01

    Comb-like copolymer structures, also known as graft/comb copolymers, have obtained a significant amount of attention in biomedical and industrial applications because of their unique compositional flexibility, which can ...

  6. 75 FR 11559 - Certain Combed Cotton Yarns: Effect of Modification of U.S.-Bahrain FTA Rules of Origin

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ...Bahrain-FTA-103-025] Certain Combed Cotton Yarns: Effect of Modification of U...Bahrain FTA-103-025, Certain Combed Cotton Yarns: Effect of Modification of U...of origin to the FTA for certain combed cotton yarns used in the production of...

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Wavelength-Routed Optical Networks-on-Chip Built with Comb Switches1 Xianfang Tan1

    E-print Network

    Yang, Mei

    , University of Nevada, Las Vegas, NV 2 Department of Engineering and Aviation Sciences, University of Maryland University, Hangzhou, China Emails: tanx@unlv.nevada.edu, Mei.Yang@unlv.edu, lzhang@umes.edu Abstract Comb]. Drop i = r r Input i Through i r Drop i Through i Ï Input i (a) General switch (b) Comb switch Fig. 1

  9. Astronomical optical frequency comb generation and test in a fiber-fed MUSE spectrograph

    NASA Astrophysics Data System (ADS)

    Chavez Boggio, J. M.; Fremberg, T.; Moralejo, B.; Rutowska, M.; Hernandez, E.; Zajnulina, M.; Kelz, A.; Bodenmüller, D.; Sandin, C.; Wysmolek, M.; Sayinc, H.; Neumann, J.; Haynes, R.; Roth, M. M.

    2014-07-01

    We here report on recent progress on astronomical optical frequency comb generation at innoFSPEC-Potsdam and present preliminary test results using the fiber-fed Multi Unit Spectroscopic Explorer (MUSE) spectrograph. The frequency comb is generated by propagating two free-running lasers at 1554.3 and 1558.9 nm through two dispersionoptimized nonlinear fibers. The generated comb is centered at 1590 nm and comprises more than one hundred lines with an optical-signal-to-noise ratio larger than 30 dB. A nonlinear crystal is used to frequency double the whole comb spectrum, which is efficiently converted into the 800 nm spectral band. We evaluate first the wavelength stability using an optical spectrum analyzer with 0.02 nm resolution and wavelength grid of 0.01 nm. After confirming the stability within 0.01 nm, we compare the spectra of the astro-comb and the Ne and Hg calibration lamps: the astro-comb exhibits a much larger number of lines than lamp calibration sources. A series of preliminary tests using a fiber-fed MUSE spectrograph are subsequently carried out with the main goal of assessing the equidistancy of the comb lines. Using a P3d data reduction software we determine the centroid and the width of each comb line (for each of the 400 fibers feeding the spectrograph): equidistancy is confirmed with an absolute accuracy of 0.4 pm.

  10. Thermal energy conduction in a honey bee comb due to cell-heating bees

    Microsoft Academic Search

    J. A. C. Humphreya; E. S. Dykes

    2008-01-01

    Theoretical analysis and numerical calculations are performed to characterize the unsteady two-dimensional conduction of thermal energy in an idealized honey bee comb. The situation explored corresponds to a comb containing a number of brood cells occupied by pupae. These cells are surrounded by other cells containing pollen which, in turn, are surrounded (above) by cells containing honey and (below) by

  11. Interview with a quality leader: Dr. John Combes on boards and governance.

    PubMed

    White, Susan V

    2014-01-01

    Dr. Combes is senior vice president at the American Hospital Association (AHA) and president and COO of the Center for Healthcare Governance. The Interview with Dr. John Combes on Boards and Governance provides a perspective on key changes, issues, competencies, and metrics that hospital boards must address. The role of quality professionals to be effective with boards is also described. PMID:23980796

  12. RELATIONSHIP BETWEEN GENES AT THE PEA AND SINGLE COMB LOCUS AND ECONOMIC TRAITS IN BROILER CHICKEN

    E-print Network

    Paris-Sud XI, Université de

    RELATIONSHIP BETWEEN GENES AT THE PEA AND SINGLE COMB LOCUS AND ECONOMIC TRAITS IN BROILER CHICKEN hatches of pedigreed broilers, comprising a total of7593 offsprings from 223 Cornish- type sires, m2 Sci,. 40, 824-826) there was no evidence of an association between comb type and broiler growth

  13. Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration

    E-print Network

    Purdue University

    Comb-based radio-frequency photonic filtering with 20 ns bandwidth reconfiguration Rui Wu,* Minhyup We present a scheme to generate a 10 GHz optical frequency comb that is bandwidth reconfigurable to demonstrate, for the first time to our knowledge, bandwidth-reconfigurable RF filtering with transition times

  14. Stabilized frequency comb with a self-referenced femtosecond Cr:forsterite laser

    E-print Network

    Washburn, Brian

    Stabilized frequency comb with a self-referenced femtosecond Cr:forsterite laser K. Kim, B. R is generated with a Cr:forsterite femtosecond laser, spectrally broadened through a highly nonlinear optical of the stabilized frequency combs from this Cr:forsterite system and a Ti:sapphire laser agree at the 10-13 level

  15. Phase-stabilized 167 MHz Repetition Frequency Carbon Nanotube Fiber Laser Frequency Comb

    E-print Network

    Washburn, Brian

    a 1532 nm CW laser stabilized to an acetylene-filled kagome photonic crystal fiber infrared reference [5Phase-stabilized 167 MHz Repetition Frequency Carbon Nanotube Fiber Laser Frequency Comb Jinkang@phys.ksu.edu Abstract: The frequency comb generated by a high repetition frequency erbium-doped fiber ring laser using

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

    Microsoft Academic Search

    Kristan Corwin

    2009-01-01

    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

  17. THE COMBS OF HONEYBEES AS COMPOSITE MATERIALS H.R. HEPBURN S.P. KURSTJENS

    E-print Network

    Paris-Sud XI, Université de

    THE COMBS OF HONEYBEES AS COMPOSITE MATERIALS H.R. HEPBURN S.P. KURSTJENS Department of Physiology of the African honeybee, A. m. scutellata, in relation to maturation and temperature were measured. Combs ranged a structure with new properties that differ from its individual constituents. INTRODUCTION The honeybee nest

  18. On the numerical simulation of Kerr frequency combs using coupled mode equations

    NASA Astrophysics Data System (ADS)

    Hansson, T.; Modotto, D.; Wabnitz, S.

    2014-02-01

    It is demonstrated that Kerr frequency comb generation described by coupled mode equations can be numerically simulated using Fast Fourier Transform methods. This allows broadband frequency combs spanning a full octave to be efficiently simulated using standard algorithms, resulting in orders of magnitude improvements in the computation time.

  19. A CMOS-MEMS mirror with curled-hinge comb drives

    Microsoft Academic Search

    Huikai Xie; Yingtian Pan; Gary K. Fedder

    2003-01-01

    A micromirror achieves up to ±4.7° angular displacement with 18 Vdc by a comb-drive design that uses vertical angled offset of the comb fingers. Structures are made from a combination of CMOS interconnect layers and a thick underlying silicon layer. Electrical isolation of the silicon fingers is realized with a slight silicon undercut etch, which disconnects sufficiently narrow pieces of

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

    E-print Network

    Mid-infrared dual-comb spectroscopy with an optical parametric oscillator Zhaowei Zhang,1,2, * Tom July 26, 2013 (Doc. ID 189369); published August 14, 2013 We present the first implementation of mid-infrared at 2900­3050 cm-1 . The average power from each individual mid-infrared comb line was 1 W, representing

  1. Optical antenna of comb-shaped split ring architecture for increased field localization in

    E-print Network

    Demir, Hilmi Volkan

    Optical antenna of comb-shaped split ring architecture for increased field localization in NIR designs of optical antennas based on comb-shaped split ring architecture that display multi resonance. With these optical antennas, localizing near infrared (NIR) and mid infrared (MIR) lights within a region of tens

  2. White-light frequency comb generation with a diode-pumped Cr:LiSAF laser.

    PubMed

    Holzwarth, R; Zimmermann, M; Udem, T; Hánsch, T W; Russbüldt, P; Gäbel, K; Poprawe, R; Knight, J C; Wadsworth, W J; Russell, P S

    2001-09-01

    We have created a broad spectrum spanning more than an optical octave by launching femtosecond pulses from a battery operated Cr:LiSAF laser into a photonic crystal fiber. Despite the massive broadening in the fiber, the comb structure of the spectrum is preserved, and this frequency comb is perfectly suited for applications in optical frequency metrology. PMID:18049614

  3. Complete characterization of a broadband high-finesse cavity using an optical frequency comb

    Microsoft Academic Search

    Albert Schliesser; Christoph Gohle; Thomas Udem; Theodor W. Hänsch

    2006-01-01

    We demonstrate a new method to simultaneously measure spectrally resolved dispersion and losses (finesse) of a passive optical cavity over the entire bandwidth of an optical frequency comb. To this end, we record and analyze the spectral Moiré pattern between the perfectly equidistant frequency comb emitted from a Ti:Sapphire laser and the longitudinal modes of the passive cavity as a

  4. White-light frequency comb generation with a diode-pumped CrLiSAF laser

    Microsoft Academic Search

    R. Holzwarth; M. Zimmermann; Th. Udem; T. W. Hänsch; P. Russbüldt; K. Gäbel; R. Poprawe; J. C. Knight; W. J. Wadsworth; P. St. J. Russell

    2001-01-01

    Received January 3, 2001 We have created a broad spectrum spanning more than an optical octave by launching femtosecond pulses from a battery operated Cr:LiSAF laser into a photonic crystal fiber. Despite the massive broadening in the fiber, the comb structure of the spectrum is preserved, and this frequency comb is perfectly suited for applications in optical frequency metrology. ?

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

    E-print Network

    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.

  6. Tunable silicon Fabry-Perot comb filters formed by Sagnac loop mirrors.

    PubMed

    Sun, Xiaomeng; Zhou, Linjie; Xie, Jingya; Zou, Zhi; Lu, Liangjun; Zhu, Haike; Li, Xinwan; Chen, Jianping

    2013-02-15

    We experimentally demonstrate tunable silicon comb filters based on Fabry-Perot (FP) resonators composed of two Sagnac loop mirrors. The comb filter resolves up to 54 comb lines with a 115 GHz channel spacing over a spectral range from 1510 to 1560 nm. The comb line extinction ratio is ~26.3 dB and the quality factor is ~57,000 around 1550 nm wavelength. Electrical tuning is enabled via periodically interleaved PN junctions embedded inside the FP resonator. The comb lines are blue shifted by ~0.92 nm (one channel spacing) with a 5 mA forward-bias current and red-shifted by ~0.05 nm with a -10 V reverse-bias voltage. PMID:23455138

  7. Precision measurements and applications of femtosecond frequency combs

    NASA Astrophysics Data System (ADS)

    Jones, R. Jason

    2002-05-01

    The merging of femtosecond (fs) laser physics with the field of optical f requency metrology over recent years has had a profound impact on both di sciplines. Precision control of the broad frequency bandwidth from fs la sers has enabled new areas of exploration in ultrafast physics and revolu tionized optical frequency measurement and precision spectroscopy. Most recently, the transition frequency of the length standard at 514.7 nm,^ 127I2 P(13) 43-0 a3 has been measured in our lab with an improvement of more than 100 times in precision. Interesting molecular dynamics and s tructure are being explored using absolute frequency map of molecular tra nsitions over a large wavelength range. The iodine transition at 532 nm h as been used to establish an optical atomic clock with a fs comb providin g both an RF standard with stability comparable to the best atomic clocks and millions of optical frequencies across the visible and near IR spect rum, each stable to the Hz level. Work is presently underway to directly compare the iodine optical clocks at JILA with the Hg and Ca optical cloc ks currently being refined at NIST via a direct optical fiber link. A wi dely tunable single frequency laser in combination with a fs comb has bee n employed to realize an optical frequency synthesizer. Frequency combs of two independent ultrafast lasers have been coherently locked, enablin g several different avenues of application such as synthesis of arbitrary waveforms, coherent control of quantum systems, and coherent anti-Stokes Raman scattering microscopy. This talk will review these recent accompl ishments from our lab and discuss plans for further improving the control and precision of fs laser based measurements. te

  8. Frequency Combs with Weakly Lasing Exciton-Polariton Condensates

    NASA Astrophysics Data System (ADS)

    Rayanov, K.; Altshuler, B. L.; Rubo, Y. G.; Flach, S.

    2015-05-01

    We predict the spontaneous modulated emission from a pair of exciton-polariton condensates due to coherent (Josephson) and dissipative coupling. We show that strong polariton-polariton interaction generates complex dynamics in the weak-lasing domain way beyond Hopf bifurcations. As a result, the exciton-polariton condensates exhibit self-induced oscillations and emit an equidistant frequency comb light spectrum. A plethora of possible emission spectra with asymmetric peak distributions appears due to spontaneously broken time-reversal symmetry. The lasing dynamics is affected by the shot noise arising from the influx of polaritons. That results in a complex inhomogeneous line broadening.

  9. Flow-through comb electroporation device for delivery of macromolecules.

    PubMed

    Adamo, Andrea; Arione, Alessandro; Sharei, Armon; Jensen, Klavs F

    2013-02-01

    We present a microfluidic electroporation device with a comb electrode layout fabricated in polydimethylsiloxane (PMDS) and glass. Characterization experiments with HeLa cells and fluorescent dextran show efficient delivery (?95%) with low toxicity (cell viability ?85%) as well as rapid pore closure after electroporation. The activity of delivered molecules is also verified by silencing RNA (siRNA) studies that demonstrate gene knockdown in GFP expressing cells. This simple, scalable approach to microfluidic, flow-through electroporation could facilitate the integration of electroporation modules within cell analysis devices that perform multiple operations. PMID:23259401

  10. Measurements of human sensitivity to comb-filtered spectra.

    PubMed

    Bonnardel, V; Bellemare, H; Mollon, J D

    1996-09-01

    Using a novel stimulator that incorporates a liquid crystal display, the spectral modulation sensitivity function of the colour vision system was derived by measuring discrimination thresholds for comb-filtered spectra. This function shows a peak of sensitivity at 0.97 c/300 nm with a plateau that extends to 1.67 c/300 nm. Extrapolation of the curve gives an estimated high-frequency cut-off at 5 c/300 nm. The thresholds are also transformed to the CIE (1931) diagram and the elliptical isosensitivity contours thus obtained are compared with the classical discrimination ellipse of MacAdam for the corresponding region of colour space. PMID:8917758

  11. Frequency combs with weakly lasing exciton-polariton condensates.

    PubMed

    Rayanov, K; Altshuler, B L; Rubo, Y G; Flach, S

    2015-05-15

    We predict the spontaneous modulated emission from a pair of exciton-polariton condensates due to coherent (Josephson) and dissipative coupling. We show that strong polariton-polariton interaction generates complex dynamics in the weak-lasing domain way beyond Hopf bifurcations. As a result, the exciton-polariton condensates exhibit self-induced oscillations and emit an equidistant frequency comb light spectrum. A plethora of possible emission spectra with asymmetric peak distributions appears due to spontaneously broken time-reversal symmetry. The lasing dynamics is affected by the shot noise arising from the influx of polaritons. That results in a complex inhomogeneous line broadening. PMID:26024173

  12. Noninvasive fetal ECG estimation using adaptive comb filter.

    PubMed

    Wei, Zheng; Xueyun, Wei; Jian jian, Zhong; Hongxing, Liu

    2013-10-01

    This paper describes a robust and simple algorithm for fetal electrocardiogram (FECG) estimation from abdominal signal using adaptive comb filter (ACF). The ACF can adjust itself to the temporal variations in fundamental frequency, which makes it qualified for the estimation of quasi-periodic component from physiologic signal, such as ECG. The validity and performance of the described method are confirmed through experiments on real fetal ECG data. A comparison with the well-known independent component analysis (ICA) method has also been presented. PMID:23942332

  13. Curcumin reduces injury progression in a rat comb burn model.

    PubMed

    Singer, Adam J; Taira, Breena R; Lin, Fubao; Lim, Taeho; Anderson, Ryon; McClain, Steve A; Clark, Richard A F

    2011-01-01

    The oriental spice curcumin has anti-inflammatory and antioxidant effects. When given orally before injury, curcumin reduces burn progression in a rat comb burn model. The authors hypothesized that intravenous administration of curcumin after injury would reduce burn progression and that its effects are mediated through iron chelation. Two comb burns were created on the dorsum of Sprague-Dawley rats (weight, 300 g) using a brass comb with four rectangular prongs preheated in boiling water and applied for 30 seconds resulting in four rectangular 10 × 20 mm full-thickness burns separated by three 5 × 20 mm unburned interspaces (zone of ischemia). Animals were randomized to receive one of four doses of crude curcumin or one of six doses of purified curcumin intravenously 1 and 24 hours after injury. Another set of animals were randomized to deferoxamine or control vehicle. Wounds were observed at 7 days after injury for visual evidence of necrosis in the unburned interspaces. Full-thickness biopsies from the interspaces were evaluated with Hematoxylin and Eosin staining 7 days after injury for evidence of necrosis. The percentage of unburned interspaces undergoing necrosis at 1 week by purified curcumin doses was 0 ?g/kg, 74%; 0.3 ?g/kg, 58%; 1 ?g/kg, 53%; 3 ?g/kg, 37%; 10 ?g/kg, 63%; 30 ?g/kg, 53%; and 100 ?g/kg, 26%. The differences among the groups were significant (P = .03). When compared with controls, the 1 and 3 ?g/kg curcumin treatment groups had significantly less progression of interspaces to necrosis (P = .04 and .002) as did the 30 and 100 ?g/kg treatment groups (P = .03 and <.001). Deferoxamine did not reduce burn progression. When administered intravenously 1 and 24 hours after injury, both crude and purified curcumin reduce the percentage of unburned interspaces that undergo necrosis in a rat hot comb burn model. The effects of purified curcumin appear to be bimodal, suggesting more than one mechanism of action. The effects of curcumin do not appear to be mediated by iron chelation. PMID:21088615

  14. Sex-Offender Tracking

    MedlinePLUS

    ... Safety & Prevention Law Enforcement Training Victim & Family Support Sex Offender Tracking The primary goal of the National Center for Missing & Exploited Children's Sex Offender Tracking Team ® is to provide assistance to ...

  15. Practice Safer Sex

    MedlinePLUS

    ... This information in Spanish ( en español ) Practice safer sex Related information Men's health Screening tests and vaccines ... Return to top More information on Practice safer sex Explore other publications and websites Addressing HIV, Other ...

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

    PubMed Central

    Gallagher, Else; Moussa, Walied

    2014-01-01

    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. PMID:25350504

  17. Fair Trade Sex: Reflections on God, Sex, and Economics

    Microsoft Academic Search

    Thia Cooper

    2011-01-01

    God, sex, and economics are all intertwined. The trafficking of people for sex intensifies each year. The sex trade crosses a spectrum from ‘high class’ escorts to sex slaves. The sex industry includes toys, pornography, and the exchange of sex between buyers, sellers, and managers. In this market exists sexual poverty caused by injustice, the imbalance of sexual power between

  18. When Sex Is Painful

    MedlinePLUS

    How common is painful sex? Pain during intercourse is very common—nearly 3 out of 4 women have pain during intercourse at some time during ... a long-term problem. What causes pain during sex? Pain during sex may be a sign of ...

  19. Single-Sex Classrooms

    ERIC Educational Resources Information Center

    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

  20. The psychology of sex

    Microsoft Academic Search

    Helen Thompson Woolley

    1914-01-01

    Reviews 88 publications of studies on psychology of sex (1910-1914). Sex differences have been investigated for the following: heredity; physical development; motor ability; sensation and perception; memory; the effect of drill; association; attention; judgment and reasoning; general intelligence; affective processes, tastes and ideals; creative ability in art and letters; suggestibility; and variability. According to some, sex differences are most marked

  1. Sex Equality Bibliographies.

    ERIC Educational Resources Information Center

    Hohenshil, Thomas H.; Linkous, Carolyn Maddy

    This partially annotated bibliography is one of a series designed to help educational personnel increase sex equality in vocational guidance and counseling programs. Its purpose is to help counselors and other educators to identify and eliminate sex bias and sex stereotyping, both factors which constrict career options and consequently the choice…

  2. Rethinking University Sex Education

    Microsoft Academic Search

    Margaret Brooks

    2011-01-01

    In recent years, some universities have allowed student organizations to hire sex workers, pornography producers and performers, and sex toy sales representatives to provide sex education on their campuses. Yet these individuals are not medical professionals, and the sexual health information they provide to students, if any, can sometimes be wrong. In addition, students attending these workshops can face additional

  3. Sex Differences in Stroke

    Microsoft Academic Search

    L. Christine Turtzo; Louise D. McCullough

    2008-01-01

    Increasing evidence suggests that sex differences exist in the etiology, presentation, treatment, and outcome from stroke. The reasons for these sex disparities are becoming increasingly explored, but large gaps still exist in our knowledge. Experimental studies over the past several years have demonstrated intrinsic sex differences both in vivo and in animal models which may have relevance to our understanding

  4. Comb polymers prepared by ATRP from hydroxypropyl cellulose.

    PubMed

    Ostmark, Emma; Harrisson, Simon; Wooley, Karen L; Malmström, Eva E

    2007-04-01

    Hydroxypropyl cellulose (HPC) was used as a core molecule for controlled grafting of monomers by ATRP, the aim being to produce densely grafted comb polymers. HPC was either allowed to react with an ATRP initiator or the first generation initiator-functionalized 2,2-bis(methylol)propionic acid dendron to create macroinitiators having high degrees of functionality. The macroinitiators were then "grafted from" using ATRP of methyl methacrylate (MMA) or hexadecyl methacrylate. Block copolymers were obtained by chain extending PMMA-grafted HPCs via the ATRP of tert-butyl acrylate. Subsequent selective acidolysis of the tert-butyl ester moieties was performed to form a block of poly(acrylic acid) resulting in amphiphilic block copolymer grafts. The graft copolymers were characterized by 1H NMR and FT-IR spectroscopies, DSC, TGA, rheological measurements, DLS, and tapping mode AFM on samples spin coated upon mica. It was found that the comb (co)polymers were in the nanometer size range and that the dendronization had an interesting effect on the rheological properties. PMID:17367185

  5. Geotropism of hornet comb construction under persistent acceleration.

    PubMed

    Ishay, J; Sadeh, D

    1978-01-01

    Social wasps (Vespinae) are insects which build in a precise geotactical orientation. The effect of persistent acceleration on comb construction by Oriental hornet (Vespa orientalis) workers was assessed experimentally within breeding boxes of various size and shape. Groups of hornets at the building phase were subjected to a centrifugal and gravitational force with a resultant ranging between 26 degrees and 45 degrees. The comb construction within such boxes was compared to that within control boxes under ordinary gravitational pull. It was found that: a) juvenile hornets (1-2 days of age) placed in quasi-rectangular boxes built in the direction of the resultant force; b) juvenile and adult hornets (3-7 days of age) placed in spherical shaped containers also built in the direction of the resultant force; c) adult hornets who had spent their first days of life in a stationary rectangular box, apparently learned the direction of the gravitational force and "tried" to build in this direction when exposed to a centrifugal force; d) adult hornets made to spin in quasi-rectangular boxes tilted in the direction of the calculated resultant force built in the direction of the resultant. These results suggest that hornets learn the direction of the gravitational force during the first days of life and that geometrical cues within the breeding box enable them to build in the direction of the force to which they have become habituated. From the standpoint of geometric cues, only the roof of the breeding box is of critical importance. PMID:11965666

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

    E-print Network

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

    2015-06-13

    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 2.76. Our biphoton frequency comb provides a platform in photon-efficient quantum communications towards the ultimate channel capacity through energy-time-polarization high-dimensional encoding.

  7. Comb construction in mixed-species colonies of honeybees, Apis cerana and Apis mellifera.

    PubMed

    Yang, Ming-Xian; Tan, Ken; Radloff, Sarah E; Phiancharoen, Mananya; Hepburn, H Randall

    2010-05-01

    Comb building in mixed-species colonies of Apis cerana and Apis mellifera was studied. Two types of cell-size foundation were made from the waxes of these species and inserted into mixed colonies headed either by an A. cerana or an A. mellifera queen. The colonies did not discriminate between the waxes but the A. cerana cell-size foundation was modified during comb building by the workers of both species. In pure A. cerana colonies workers did not accept any foundation but secreted wax and built on foundation in mixed colonies. Comb building is performed by small groups of workers through a mechanism of self-organisation. The two species cooperate in comb building and construct nearly normal combs but they contain many irregular cells. In pure A. mellifera colonies, the A. cerana cell size was modified and the queens were reluctant to lay eggs on such combs. In pure A. cerana colonies, the A. mellifera cell size was built without any modification but these cells were used either for drone brood rearing or for food storing. The principal elements of comb-building behaviour are common to both species, which indicates that they evolved prior to and were conserved after speciation. PMID:20435816

  8. Terabit/s communications using chip-scale frequency comb sources

    NASA Astrophysics Data System (ADS)

    Koos, Christian; Kippenberg, Tobias J.; Barry, Liam P.; Dalton, Larry; Freude, Wolfgang; Leuthold, Juerg; Pfeifle, Joerg; Weimann, Claudius; Lauermann, Matthias; Kemal, Juned N.; Palmer, Robert; Koeber, Sebastian; Schindler, Philipp C.; Herr, Tobias; Brasch, Victor; Watts, Regan T.; Elder, Delwin

    2015-03-01

    High-speed optical interconnects rely on advanced wavelength-division multiplexing (WDM) schemes. However, while photonic-electronic interfaces can be efficiently realized on silicon-on-insulator chips, dense integration of the necessary light sources still represents a major challenge. Chip-scale frequency comb sources present an attractive alternative for providing a multitude of optical carriers for WDM transmission. In this paper, we give an overview of our recent progress towards terabit communications with chip-scale frequency comb sources. In a first set of experiments, we demonstrate frequency comb generation based on silicon-organic hybrid (SOH) electro-optic modulators, enabling line rates up to 1.152 Tbit/s. In a second set of experiments, we use injection locking of a gain-switched laser diode to enerate frequency combs. This approach leads to line rates of more than 2 Tbit/s. A third set of experiments is finally dedicated to using Kerr nonlinearities in integrated nonlinear microcavities for frequency comb generation. We demonstrate coherent communication using Kerr frequency comb sources, thereby achieving line rates up to 1.44 Tbit/s. Our experiments show that frequency comb generation in chip-scale devices represents a viable approach to terabit communications.

  9. Sexing young snowy owls

    USGS Publications Warehouse

    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.

  10. Towards efficient octave-spanning comb with micro-structured crystalline resonator

    NASA Astrophysics Data System (ADS)

    Grudinin, Ivan S.; Yu, Nan

    2015-03-01

    Optical frequency combs, typically produced by mode locked lasers, have revolutionized many applications in science and technology. Frequency combs were recently generated by micro resonators through nonlinear Kerr processes. However, the comb span from micro resonators was found to be limited by resonator dispersion and mode spectrum. While dispersion engineering has been reported in on-chip devices, monolithic crystalline resonators offer an advantage of high optical quality factor. Moreover, most resonators used for comb generation support many mode families, leading to unavoidable crossings in resonator spectrum. Such crossings strongly influence comb dynamics and may prevent stable coherent mode-locking and soliton states. We report a new crystalline resonator approach supporting dispersion control and single mode spectrum while maintaining high quality factor. Dispersion engineering by waveguide micro-structuring is used to flatten the dispersion in our MgF2 resonator. Both absolute magnitude of dispersion and its slopes can be altered over a wavelength span exceeding an octave. Dispersion flattening leads to generation of an octave-spanning frequency comb with repetition rate of 46 GHz and coupled pump power below 100 mW. We also demonstrate that the micro- structuring dispersion engineering approach can be used to achieve flattened and anomalous dispersion in a CaF2 resonator near 1550 nm wavelength. In addition, we describe observation of discrete steps between the modulation instability states of the primary comb and on the three-stage comb unfolding dynamics. The micro-structured resonators may enable efficient low repetition rate coherent octave spanning frequency combs without external broadening, ideal for applications in optical frequency synthesis, metrology, spectroscopy, and communications.

  11. Sex Determination and Sex Chromosomes Differentiation Between Different Sexes Occurs Even in ________________________.

    E-print Network

    Cutler, Chris

    Sex Determination and Sex Chromosomes Differentiation Between Different Sexes Occurs Even Determination Some of these Genes are on the Sex Chromosomes but Others are ____________ . In Multi Chromosome) = Male Sex Chromosomes The role of in Sex Determination was Initially Discovered Early in the 20

  12. Quantum-fluctuation-initiated coherence in multioctave Raman optical frequency combs.

    PubMed

    Wang, Y Y; Wu, Chunbai; Couny, F; Raymer, M G; Benabid, F

    2010-09-17

    We show experimentally and theoretically that the spectral components of a multioctave frequency comb spontaneously created by stimulated Raman scattering in a hydrogen-filled hollow-core photonic crystal fiber exhibit strong self-coherence and mutual coherence within each 12 ns driving laser pulse. This coherence arises in spite of the field's initiation being from quantum zero-point fluctuations, which causes each spectral component to show large phase and energy fluctuations. This points to the possibility of an optical frequency comb with nonclassical correlations between all comb lines. PMID:20867639

  13. Characterization of frequency noise on a broadband infrared frequency comb using optical heterodyne techniques.

    PubMed

    Kim, K; Nicholson, J W; Yan, M; Knight, J C; Newbury, N R; Diddams, S A

    2007-12-24

    We measure the frequency noise across a Cr:forsterite infrared frequency comb through the optical heterodyne beat of different comb teeth against stable continuous wave (CW) lasers. This sensitive measurement shows strong correlations of the frequency noise between spectral components of the comb, relative to a fixed optical frequency near the 1.3 micron carrier of the Cr:forsterite laser. The correlated frequency fluctuations are shown to arise from amplitude noise on the pump laser. We also report a preliminary comparison of excess noise that occurs during supercontinuum generation in both highly nonlinear fiber and an extruded glass microstructured fiber. PMID:19551068

  14. High contrast, low noise selection and amplification of an individual optical frequency comb line.

    PubMed

    Rohde, Felix; Benkler, Erik; Telle, Harald R

    2013-01-15

    We present a frequency-selective amplifier for optical frequency combs based on stimulated Brillouin scattering and the effect of a Brillouin dynamic grating. A user defined individual frequency comb line is amplified while the other comb lines are efficiently suppressed, rendering a frequency-stable clean-up oscillator unnecessary. A measured signal to noise ratio of 89 dBc/Hz proves the suitability of the method for phase coherent measurements. The overall noise figure is 6 dB. PMID:23454929

  15. Sex differences in same-sex friendship

    Microsoft Academic Search

    Mayta A. Caldwell; Letitia Anne Peplau

    1982-01-01

    Two studies examined sex differences in the same-sex friendships of college men and women. In a questionnaire study, self-reports were obtained of number of friends and frequency of interaction, typical and preferred kinds of interactions with friends, and emotional intimacy. A role-play study provided more direct information about conversations between friends. Men and women did not differ in quantitative aspects

  16. Charge-optimized many-body (COMB) potential for zirconium

    NASA Astrophysics Data System (ADS)

    Noordhoek, Mark J.; Liang, Tao; Lu, Zizhe; Shan, Tzu-Ray; Sinnott, Susan B.; Phillpot, Simon R.

    2013-10-01

    An interatomic potential for zirconium is developed within the charge-optimized many-body (COMB) formalism. The potential correctly predicts the hexagonal close-packed (HCP) structure as the ground state with cohesive energy, lattice parameters, and elastic constants matching experiment well. The most stable interstitial position is the basal octahedral followed by basal split, in agreement with recent first principles calculations. Stacking fault energies within the prism and basal planes satisfactorily match first principles calculations. A tensile test using nanocrystalline zirconium exhibits both prismatic {1 0 1bar 0}<1 1 2bar 0> slip and pyramidal {1 1 2bar 2}<1 1 2bar 3bar> slip, showing the model is capable of reproducing the mechanical deformation modes observed in experiments.

  17. Time-Delay Interferometry with optical frequency comb

    E-print Network

    Massimo Tinto; Nan Yu

    2015-02-23

    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.

  18. Time-Delay Interferometry with optical frequency comb

    E-print Network

    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.

  19. Dual-etalon frequency-comb cavity ringdown spectrometer

    NASA Astrophysics Data System (ADS)

    Chandler, David W.; Strecker, Kevin E.

    2012-04-01

    We have demonstrated a spectroscopic technique for simultaneously obtaining broad spectral bandwidth and high frequency resolution absorption measurements, with 5 ?s temporal resolution, continuously for tens of microseconds in an apparatus with no active stabilization. The technique utilizes two passive air-gap etalons to imprint two frequency comb patterns onto a single pulsed light source. The air-gap etalons also serve as cavity ringdown cells increasing the sensitivity of the absorption spectroscopy by increasing the interrogation path length. Here, we demonstrate the operation of the spectrometer utilizing a ˜0.15 cm-1 bandwidth pulsed dye laser and two nearly identical 300 MHz free-spectral range confocal air-gap etalons each with a finesse of ˜1 × 105, to investigate the (1,1,3) overtone of water and the R(7) transition of the O2 b^1 ? _g ^+ leftarrow X^3 ? _g^- (2,0) band with high spectral resolution.

  20. Coherent Raman spectro-imaging with laser frequency combs

    E-print Network

    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...

  1. Temperature Sex Reversal Implies Sex Gene Dosage in a Reptile

    E-print Network

    Canberra, University of

    Temperature Sex Reversal Implies Sex Gene Dosage in a Reptile Alexander E. Quinn,1 * Arthur Georges by genes on sex chromo- somes in many vertebrates [genotypic sex determination (GSD)], but may also be determined by temperature during embryonic development [temperature-dependent sex de- termination (TSD)] (1

  2. SEX-RATIO EVOLUTION IN SEX CHANGING ANIMALS

    Microsoft Academic Search

    David J. Allsop; Stuart A. West

    2004-01-01

    Sex allocation theory is often able to make clear predictions about when individuals should facultatively adjust their offspring sex ratio (proportion male) in response to local conditions, but not the consequences for the overall population sex ratio. A notable exception to this is in sex changing organisms, where theory predicts that: (1) organisms should have a sex ratio biased toward

  3. Electromagnetically induced transparency in rubidium vapor prepared by a comb of short optical pulses 

    E-print Network

    Sautenkov, V. A.; Rostovtsev, Y. V.; Ye, C. Y.; Welch, George R.; Kocharovskaya, O.; Scully, Marlan O.

    2005-01-01

    It was shown by Kocharovskaya and Khanin [Sov. Phys. JETP 63, 945 (1986)] that a comb of optical pulses can induce a ground-state atomic coherence and change the optical response of an atomic medium. In our experiment, we ...

  4. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide.

    PubMed

    Kuyken, Bart; Ideguchi, Takuro; Holzner, Simon; Yan, Ming; Hänsch, Theodor W; Van Campenhout, Joris; Verheyen, Peter; Coen, Stéphane; Leo, Francois; Baets, Roel; Roelkens, Gunther; Picqué, Nathalie

    2015-01-01

    Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500-3,300 nm) spectra with a coupled input pulse energy as low as 16 pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip. PMID:25697764

  5. Composite frequency comb spanning 0.42.4 m from a phase-controlled femtosecond

    E-print Network

    optical frequency combs that can be locked to microwave frequency standards, vastly simplifying optical supercontinuum gener- ated from the photonic crystal fiber (PCF) in the nonlinear interferometer as a common

  6. Phase-locked, erbium-fiber-laser-based frequency comb in the near infrared.

    PubMed

    Washburn, Brian R; Diddams, Scott A; Newbury, Nathan R; Nicholson, Jeffrey W; Yan, Man F; Jørgensen, Carsten G

    2004-02-01

    A phase-locked frequency comb in the near infrared is demonstrated with a mode-locked, erbium-doped, fiber laser whose output is amplified and spectrally broadened in dispersion-flattened, highly nonlinear optical fiber to span from 1100 to >2200 nm. The supercontinuum output comprises a frequency comb with a spacing set by the laser repetition rate and an offset by the carrier-envelope offset frequency, which is detected with the standard f-to-2f heterodyne technique. The comb spacing and offset frequency are phase locked to a stable rf signal with a fiber stretcher in the laser cavity and by control of the pump laser power, respectively. This infrared comb permits frequency metrology experiments in the near infrared in a compact, fiber-laser-based system. PMID:14759041

  7. Characteristics of distributed-type inorganic electroluminescence panels with comb-shaped electrodes

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin-Ichi; Uraoka, Yukiharu; Taguchi, Nobuyoshi; Nonaka, Toshihiro

    2013-09-01

    We deposited comb electrodes with narrow gaps between the teeth on a glass substrate, thus realizing a high electric field intensity that cannot be achieved with conventional structures. Au electrodes are deposited to form a comb shape and then spin-coated with a phosphor layer obtained by mixing ZnS phosphor particles with resins in a certain ratio. An AC voltage was applied to the gaps between the teeth of the comb electrode to emit light, from which the luminance was measured for different electric field intensities. The luminance was not affected by the transmittance of the electrodes themselves when measured from the phosphor layer side. Therefore, it may be possible to produce a display that does not require transparent electrodes by using the phosphor layer side of a device with comb electrodes made of metals, such as Au, for the display.

  8. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide

    NASA Astrophysics Data System (ADS)

    Kuyken, Bart; Ideguchi, Takuro; Holzner, Simon; Yan, Ming; Hänsch, Theodor W.; van Campenhout, Joris; Verheyen, Peter; Coen, Stéphane; Leo, Francois; Baets, Roel; Roelkens, Gunther; Picqué, Nathalie

    2015-02-01

    Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500–3,300?nm) spectra with a coupled input pulse energy as low as 16?pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip.

  9. Electromagnetically induced transparency in rubidium vapor prepared by a comb of short optical pulses

    E-print Network

    Sautenkov, V. A.; Rostovtsev, Y. V.; Ye, C. Y.; Welch, George R.; Kocharovskaya, O.; Scully, Marlan O.

    2005-01-01

    of a comb of optical pulses produced by a mode-locked diode laser in rubidium atomic vapor. Electromagnetically induced transparency (EIT) was observed when the pulse repetition rate is a subharmonic of the hyperfine splitting of the ground state...

  10. Morphology and molecular bridging in comb- and star-shaped diblock copolymers.

    PubMed

    Hart, Kyle E; Abbott, Lauren J; Lísal, Martin; Colina, Coray M

    2014-11-28

    Block copolymers spontaneously self-assemble into nanostructured morphologies with industrially attractive properties; however, the relationships between polymer architecture and self-assembled morphology are difficult to tailor for copolymers with increased conformational restrictions. Using Dissipative Particle Dynamics, the self-assembled morphology of comb- and star-shaped diblock copolymers was simulated as a function of the number of arms, arm length, weight fraction, and A-B incompatibility. As the number of arms on the star, or grafting points for the comb, was increased from three to four to six, the ability to self-assemble into ordered morphologies was restricted. The molecular bridging between adjacent ordered domains was observed for both comb- and star-shaped copolymers, which was found to be enhanced with increasing number of arms. This study illustrates that comb- and star-shaped copolymers are viable alternatives for applications that would benefit from highly bridged nanostructural domains. PMID:25429957

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

    E-print Network

    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.

  12. An octave-spanning mid-infrared frequency comb generated in a silicon nanophotonic wire waveguide

    PubMed Central

    Kuyken, Bart; Ideguchi, Takuro; Holzner, Simon; Yan, Ming; Hänsch, Theodor W.; Van Campenhout, Joris; Verheyen, Peter; Coen, Stéphane; Leo, Francois; Baets, Roel; Roelkens, Gunther; Picqué, Nathalie

    2015-01-01

    Laser frequency combs, sources with a spectrum consisting of hundred thousands evenly spaced narrow lines, have an exhilarating potential for new approaches to molecular spectroscopy and sensing in the mid-infrared region. The generation of such broadband coherent sources is presently under active exploration. Technical challenges have slowed down such developments. Identifying a versatile highly nonlinear medium for significantly broadening a mid-infrared comb spectrum remains challenging. Here we take a different approach to spectral broadening of mid-infrared frequency combs and investigate CMOS-compatible highly nonlinear dispersion-engineered silicon nanophotonic waveguides on a silicon-on-insulator chip. We record octave-spanning (1,500–3,300?nm) spectra with a coupled input pulse energy as low as 16?pJ. We demonstrate phase-coherent comb spectra broadened on a room-temperature-operating CMOS-compatible chip. PMID:25697764

  13. Applications and noise properties of high repetition rate : TiSapphire frequency combs

    E-print Network

    Benedick, Andrew John

    2011-01-01

    Femtosecond mode-locked lasers are a unique laser technology due to their broad optical bandwidth and potential for linking the optical and radio frequency domains when these lasers are configured as frequency combs. ...

  14. Design, fabrication and vacuum operation characteristics of two-dimensional comb-drive micro-scanner

    Microsoft Academic Search

    Hoang Manh Chu; Kazuhiro Hane

    2011-01-01

    We present design, fabrication, and characteristics of two-dimensional micro-machined comb-drive scanner to operate in vacuum. The scanner can be actuated in two orthogonal axes using the slanted electrostatic comb-drive and silicon conductive V-shaped torsion hinges fabricated from a silicon-on-insulator wafer. The resonant frequencies of the inner mirror and the gimbal frame are 40kHz and 162Hz, respectively. The resonant frequency ratio

  15. Synthesis and characterization of novel comb-type amphiphilic graft copolymers containing polypropylene and polyethylene glycol

    Microsoft Academic Search

    Murat Balc?; Abdulkadir All?; Baki Hazer; Olgun Güven; Kevin Cavicchi; Mukerrem Cakmak

    2010-01-01

    Amphiphilic comb-type graft copolymers containing polypropylene (PP) and polyethylene glycol (PEG) have been prepared. Polypropylene-g-polyethylene glycol comb-type thermoplastic amphiphilic copolymers were synthesized by the reaction between chlorinated polypropylene\\u000a and polyethylene glycol in the presence of a base via a “grafting to” technique. A series of graft copolymers containing PEGs\\u000a with molecular weights of 600 and 2,000 Da in the range of

  16. Rapid communication Study of colour discrimination with comb-filtered spectra

    Microsoft Academic Search

    Valerie Bonnardel; Eva M. Valero

    Techniques that involve the use of comb-filtered spectra to study human colour vision have been developed in previous work (Bonnardel, V., Bellemare, H., Mollon, J.D., 1996. Measurements of human sensitivity to comb-filtered spectra, Vision Research 36, 2713-2720; Bonnardel, V., Ruderman D.L., Barlow, H.B., 1997. A fast determination of the Spectral Modulation Sensitivity Function: a comparison between trichromats and deuteranopes. In:

  17. Electrochemical properties of amorphous comb-shaped composite PEO polymer electrolyte

    Microsoft Academic Search

    J.-S Chung; H.-J Sohn

    2002-01-01

    The electrochemical behaviour of a polyethylene oxide (PEO)-based composite polymer electrolyte are studied. The crystallinity of the PEO is suppressed by using a comb-shaped polymer to improve polymer chain mobility. An amorphous comb-shaped polymer, ‘TEC-24’, with a side-chain content of 24mol%, is designed and fine silica powder is dispersed within it to enhance the mechanical properties above the melting point.

  18. Optimization of Comb-Driven Devices for Mechanical Testing of Polymeric Nanofibers Subjected to Large Deformations

    Microsoft Academic Search

    Mohammad Naraghi; Ioannis Chasiotis

    2009-01-01

    Comb-driven electrostatic actuators applied to mechanical testing of nanostructures are usually designed by a ldquobrute-forcerdquo approach for maximum electrostatic-force output, which results in limited actuation range. This issue is more prevalent when testing soft nanofibers with large ductility. In this paper, the design considerations for a comb-driven platform for nanoscale mechanical testing of ductile nanofibers subjected to 50%, or larger,

  19. Frequency comb generation and carrier-envelope phase control in femtosecond optical parametric oscillators

    Microsoft Academic Search

    D. T. Reid; B. J. S. Gale; J. Sun

    2008-01-01

    We describe progress in the measurement and control of the carrier-envelope phase-slip frequencies of pulses generated by\\u000a a femtosecond optical parametric oscillator. Example applications of such control are presented and include the generation\\u000a of a frequency comb spanning nearly three optical octaves, and the creation of a train of 30-fs pulses via coherent pulse\\u000a synthesis. Future prospects for frequency combs

  20. Optimally coherent Kerr combs generated with crystalline whispering gallery mode resonators for ultrahigh capacity fiber communications.

    PubMed

    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?10^{9} 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. PMID:25793816

  1. Broadband high-resolution two-photon spectroscopy with laser frequency combs

    E-print Network

    Hipke, Arthur; Ideguchi, Takuro; Hänsch, Theodor W; Picqué, Nathalie

    2013-01-01

    Two-photon excitation spectroscopy with broad spectral span is demonstrated at Doppler-limited resolution. We describe first Fourier transform two-photon spectroscopy of an atomic sample with two mode-locked laser oscillators in a dual-comb technique. Each transition is uniquely identified by the modulation imparted by the interfering comb excitations. The temporal modulation of the spontaneous two-photon fluorescence is monitored with a single photodetector, and the spectrum is revealed by a Fourier transform.

  2. Modeling of a high force density fishbone shaped electrostatic comb drive microactuator.

    PubMed

    Megat Hasnan, Megat Muhammad Ikhsan; Mohd Sabri, Mohd Faizul; Mohd Said, Suhana; Nik Ghazali, Nik Nazri

    2014-01-01

    This paper presents the design and evaluation of a high force density fishbone shaped electrostatic comb drive actuator. This comb drive actuator has a branched structure similar to a fishbone, which is intended to increase the capacitance of the electrodes and hence increase the electrostatic actuation force. Two-dimensional finite element analysis was used to simulate the motion of the fishbone shaped electrostatic comb drive actuator and compared against the performance of a straight sided electrostatic comb drive actuator. Performances of both designs are evaluated by comparison of displacement and electrostatic force. For both cases, the active area and the minimum gap distance between the two electrodes were constant. An active area of 800 × 300 ?m, which contained 16 fingers of fishbone shaped actuators and 40 fingers of straight sided actuators, respectively, was used. Through simulation, improvement of drive force of the fishbone shaped electrostatic comb driver is approximately 485% higher than conventional electrostatic comb driver. These results indicate that the fishbone actuator design provides good potential for applications as high force density electrostatic microactuator in MEMS systems. PMID:25165751

  3. Analysis of microwave frequency combs generated by semiconductor lasers under hybrid optical injections

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Ting; Wu, Yi-Hua; Juan, Yu-Shan

    2015-03-01

    Microwave frequency combs utilizing hybrid optical injections schemes by varying the operational parameters, injection strength, repetition frequency, and detuning frequency are demonstrated and characterized. The dynamical hybrid optical injections are realized by both optical pulse injection and optical cw injection to the slave laser simultaneously under the condition of zero detuning frequency between two injecting source lasers. For pure pulse injection case, the amplitude variation of ±27.3 dB in a 30 GHz range is obtained. By further applying the injection strength of the cw injection to the pulses injected semiconductor laser, the amplitude variation of ±3.3 dB in a 30 GHz range in microwave frequency combs are observed when operating the cw injection system in a stable locking state. In order to examine the microwave frequency comb precisely, each operational parameters of the hybrid optical injections schemes are analyzed. The amplitude variation of microwave frequency combs is also strongly influenced by operating the cw injection system in different states. Comparing to the cw injection system operated in period-one states, the amplitude variation is reduced when operated in the stable locking states. Moreover, the bandwidth broadening in microwave frequency comb is expected when the cw injection system operating in a stable locking state. In this paper, strongly improve the amplitude variation of the microwave frequency combs generated utilizing hybrid injections scheme compared to single injection case are obtained and compared.

  4. Modeling of a High Force Density Fishbone Shaped Electrostatic Comb Drive Microactuator

    PubMed Central

    Megat Hasnan, Megat Muhammad Ikhsan; Mohd Sabri, Mohd Faizul; Mohd Said, Suhana; Nik Ghazali, Nik Nazri

    2014-01-01

    This paper presents the design and evaluation of a high force density fishbone shaped electrostatic comb drive actuator. This comb drive actuator has a branched structure similar to a fishbone, which is intended to increase the capacitance of the electrodes and hence increase the electrostatic actuation force. Two-dimensional finite element analysis was used to simulate the motion of the fishbone shaped electrostatic comb drive actuator and compared against the performance of a straight sided electrostatic comb drive actuator. Performances of both designs are evaluated by comparison of displacement and electrostatic force. For both cases, the active area and the minimum gap distance between the two electrodes were constant. An active area of 800 × 300??m, which contained 16 fingers of fishbone shaped actuators and 40 fingers of straight sided actuators, respectively, was used. Through simulation, improvement of drive force of the fishbone shaped electrostatic comb driver is approximately 485% higher than conventional electrostatic comb driver. These results indicate that the fishbone actuator design provides good potential for applications as high force density electrostatic microactuator in MEMS systems. PMID:25165751

  5. Toward a broadband astro-comb: effects of nonlinear spectral broadening in optical fibers.

    PubMed

    Chang, Guoqing; Li, Chih-Hao; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X

    2010-06-01

    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 approximately 100,000; 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. Spanning more than 300 nm with 16 GHz line spacing, the resulting astro-comb is predicted to provide 1 cm/s (approximately 10 kHz) radial velocity calibration accuracy for an astrophysical spectrograph. Such extreme performance will be necessary for the search for and characterization of Earth-like extra-solar planets, and in direct measurements of the change of the rate of cosmological expansion. PMID:20588402

  6. Sex: Making the Right Decision

    MedlinePLUS

    MENU Return to Web version Sex: Making the Right Decision Sex: Making the Right Decision What is sex? The word sex is used in several ways. It can refer ... by the penis. It also can mean what sex you were born (male or female) or physical ...

  7. Nonvolitional Sex and Sexual Health

    Microsoft Academic Search

    Debra Kalmuss

    2004-01-01

    Nonvolitional sex is sexual behavior that violates a person's right to choose when and with whom to have sex and what sexual behaviors to engage in. The more extreme forms of this behavior include rape, forced sex, childhood sexual abuse, sex trafficking, and violence against people with nonconventional sexual identities. More nuanced forms of nonvolitional sex include engaging in sexual

  8. Sex, sexuality, safer sex, and HIV.

    PubMed

    Dustow, C

    1995-07-01

    Recommendations for health care providers on how to openly and constructively discuss HIV and sexuality with their clients, and suggestions about approaches for self-protection when engaging in sexual activities are provided. The author focuses on the provider/client relationship, stressing the importance of gathering pertinent information about the client's sex life in order to better help create changes in their attitudes and behaviors. Specific areas covered include using the same vernacular regarding sex that the client uses to avoid alienating the client due to language barriers; determining the client's sexual preference; and asking HIV assessment questions to determine risk level. Suggested counseling methods are provided for advising clients to adopt safer sex practices. PMID:11362551

  9. Sex tourism in Thailand.

    PubMed

    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. PMID:12286018

  10. Sex chromosomes and sex determination in Lepidoptera.

    PubMed

    Traut, W; Sahara, K; Marec, F

    2007-01-01

    The speciose insect order Lepidoptera (moths and butterflies) and their closest relatives, Trichoptera (caddis flies), share a female-heterogametic sex chromosome system. Originally a Z/ZZ (female/male) system, it evolved by chromosome rearrangement to a WZ/ZZ (female/male) system in the most species-rich branch of Lepidoptera, a monophyletic group consisting of Ditrysia and Tischeriina, which together comprise more than 98% of all species. Further sporadic rearrangements created multi-sex chromosome systems; sporadic losses of the W changed the system formally back to Z/ZZ in some species. Primary sex determination depends on a Z-counting mechanism in Z/ZZ species, but on a female-determining gene, Fem, in the W chromosome of the silkworm. The molecular mechanism is unknown in both cases. The silkworm shares the last step, dsx, of the hierarchical sex-determining pathway with Drosophila and other insects investigated, but probably not the intermediate steps between the primary signal and dsx. The W chromosome is heterochromatic in most species. It contains few genes and is flooded with interspersed repetitive elements. In interphase nuclei of females it is readily discernible as a heterochromatic body which grows with increasing degree of polyploidy in somatic cells. It is used as a marker for the genetic sex in studies of intersexes and Wolbachia infections. The sex chromosome system is being exploited in economically important species. Special strains have been devised for mass rearing of male-only broods in the silkworm for higher silk production and in pest species for the release of sterile males in pest management programs. PMID:18391545

  11. Colony development and establishment of the fungus comb in Microtermes sp. nr. Usambaricus (Sjöstedt) (Isoptera: Macrotermitinae) from Nigeria

    Microsoft Academic Search

    R. A. Johnson

    1981-01-01

    Summary Incipient colonies of the fungus-growing termiteMicrotermes sp. nr.usambaricus (Macrotermitinæ) have been successfully cultured in the laboratory up to the stage where a viable fungus comb was established. The primordial fungus comb is inoculated with fungusTermitomyces by the female reproductive which ingests asexual spores (conidia) from the comb before leaving the parental nest. These conidia survive in the digestive tube

  12. Functional and Topological Characterization of Novel Components of the comB DNA Transformation Competence System in Helicobacter pylori

    PubMed Central

    Karnholz, Arno; Hoefler, Claudia; Odenbreit, Stefan; Fischer, Wolfgang; Hofreuter, Dirk; Haas, Rainer

    2006-01-01

    Helicobacter pylori is one of the most diverse bacterial species known. A rational basis for this genetic variation may be provided by its natural competence for genetic transformation and high-frequency recombination. Many bacterial competence systems have homology with proteins that are involved in the assembly of type IV pili and type II secretion systems. In H. pylori, DNA uptake relies on a transport system related to type IV secretion systems (T4SS) designated the comB system. The prototype of a T4SS in Agrobacterium tumefaciens consists of 11 VirB proteins and VirD4, which form the core unit necessary for the delivery of single proteins or large nucleoprotein complexes into target cells. In the past we identified proteins ComB4 and ComB7 through ComB10 as being involved in the process of DNA uptake in H. pylori. In this study we identified and functionally characterized further (T4SS-homologous) components of the comB transformation competence system. By combining computer prediction modeling, experimental topology determination, generation of knockout strains, and genetic complementation studies we identified ComB2, ComB3, and ComB6 as essential components of the transformation apparatus, structurally and functionally homologous to VirB2, VirB3, and VirB6, respectively. comB2, comB3, and comB4 are organized as a separate operon. Thus, for the H. pylori comB system, all T4SS core components have been identified except for homologues to VirB1, VirD4, VirB5, and VirB11. PMID:16428391

  13. Attitudes Towards Premarital Sex

    NSDL National Science Digital Library

    Tracy Dietz

    This activity is used in a General Sociology class for undergraduate students. This activity looks attitudes towards prematiral sex in the U.S. by race, sex, age, political party and education. This activity uses General Social Survey data provided on the Wadsworth Publishing Company website. See instructions in the exercise documents under teaching materials to open the data analyzer.

  14. The sex killer

    Microsoft Academic Search

    R. Langevin; M. H. Ben-Aron; P. Wright; V. Marchese; L. Handy

    1988-01-01

    Thirteen sex killers were compared to 13 nonsex killers and 13 nonhomicidal sexually aggressive men on sexual history, substance abuse, history of violence, mental illness and personality, brain pathology and endocrine abnormalities. There were more similarities among the three groups than differences. Among the findings, the presence of transvestism and the early appearance of sadism differentiated the sex killers from

  15. Sex Differences in Revascularization

    Microsoft Academic Search

    Peter W. Groeneveld; William A. Ghali

    TO THE EDITOR: The excellent study of sex and coronary revascu- larization by Ghali and colleagues (1) highlights an important ques- tion facing those who use observational data to investigate ethnic and gender disparities: Are administrative databases sufficiently detailed to control for potential confounders in the relationship of ethnicity and sex to health outcomes? Ghali and colleagues found that the

  16. Sex Away from Home

    ERIC Educational Resources Information Center

    Greenwald, Harold

    1971-01-01

    The reasons why people who are normally truthful to their spouses engage in sex away from home are discussed. These reasons can include loneliness, ego building or the opportunity to have homosexual relations. Sex away from home is likely to increase since the number of people traveling is increasing. (Author/CG)

  17. Mid-infrared frequency comb based on a quantum cascade laser.

    PubMed

    Hugi, Andreas; Villares, Gustavo; Blaser, Stéphane; Liu, H C; Faist, Jérôme

    2012-12-13

    Optical frequency combs act as rulers in the frequency domain and have opened new avenues in many fields such as fundamental time metrology, spectroscopy and frequency synthesis. In particular, spectroscopy by means of optical frequency combs has surpassed the precision and speed of Fourier spectrometers. Such a spectroscopy technique is especially relevant for the mid-infrared range, where the fundamental rotational-vibrational bands of most light molecules are found. Most mid-infrared comb sources are based on down-conversion of near-infrared, mode-locked, ultrafast lasers using nonlinear crystals. Their use in frequency comb spectroscopy applications has resulted in an unequalled combination of spectral coverage, resolution and sensitivity. Another means of comb generation is pumping an ultrahigh-quality factor microresonator with a continuous-wave laser. However, these combs depend on a chain of optical components, which limits their use. Therefore, to widen the spectroscopic applications of such mid-infrared combs, a more direct and compact generation scheme, using electrical injection, is preferable. Here we present a compact, broadband, semiconductor frequency comb generator that operates in the mid-infrared. We demonstrate that the modes of a continuous-wave, free-running, broadband quantum cascade laser are phase-locked. Combining mode proliferation based on four-wave mixing with gain provided by the quantum cascade laser leads to a phase relation similar to that of a frequency-modulated laser. The comb centre carrier wavelength is 7?micrometres. We identify a narrow drive current range with intermode beat linewidths narrower than 10?hertz. We find comb bandwidths of 4.4 per cent with an intermode stability of less than or equal to 200?hertz. The intermode beat can be varied over a frequency range of 65?kilohertz by radio-frequency injection. The large gain bandwidth and independent control over the carrier frequency offset and the mode spacing open the way to broadband, compact, all-solid-state mid-infrared spectrometers. PMID:23235876

  18. Comparison of Germline Mosaics of Genes in the Polycomb Group of Drosophila Melanogaster

    PubMed Central

    Soto, M. C.; Chou, T. B.; Bender, W.

    1995-01-01

    The genes of the Polycomb group (PcG) repress the genes of the bithorax and Antennapedia complexes, among others. To observe a null phenotype for a PcG gene, one must remove its maternal as well as zygotic contribution to the embryo. Five members of the PcG group are compared here: Enhancer of Polycomb [E(Pc)], Additional sex combs (Asx), Posterior sex combs (Psc), Suppressor of zeste 2 [Su(z)2] and Polycomblike (Pcl). The yeast recombinase (FLP) system was used to induce mitotic recombination in the maternal germline. Mutant embryos were analyzed by staining with antibodies against six target genes of the PcG. The loss of the maternal component leads to enhanced homeotic phenotypes and to unique patterns of misexpression. E(Pc) and Su(z)2 mutations had only subtle effects on the target genes, even when the maternal contributions were removed. Asx and Pcl mutants show derepression of the targets only in specific cell types. Psc shows unusual effects on two of the targets, Ultrabithorax and abdominal-A. These results show that the PcG genes do not act only in a common complex or pathway; they must have some independent functions. PMID:7635288

  19. [Negotiating safer sex].

    PubMed

    Gordon, G; Charnock, D

    1991-01-01

    Women have generally assumed responsibility for contraception since the appearance of oral contraceptives and IUDs. But AIDS prevention programs are now asking women to assume responsibility for safer sex through use of condoms, a male method. Women are being asked to carry condoms, to negotiate their use each time they have sex, and to insist if the partner resists. The problem with this strategy is that frequently it is the male partner who makes sexual decisions, and women have less negotiating power. Women are considered feminine if they assume a passive role in sexual activity. This work suggests strategies to improve the negotiating power of women. Options and problems of speaking about safer sex vary in accordance with the nature of the relationship. A woman with a new partner can try to ascertain his sexual history, but may gain no information on his probable health even if he tells her the truth. It may be easier to convince him to use a condom at least in the beginning of the romance. Women working in the sex industry often have greater trouble convincing their friends and lovers to use a condom than their clients. Some family planning workers have begun to speak of safer sex with all their clients. Role playing and workshops or discussions with small groups of women having similar problems may help women overcome their reticence about discussing sexual topics. Some general suggestions to help women negotiate safer sex include choosing an opportune moment and planning in advance what to say; daring to speak directly without beating around the bush (the partner may also be gathering courage to speak); practicing placing condoms on objects and if necessary placing one on the partner without speaking; being honest with the partner about sex, love, and fidelity; and remembering that protection from condoms is mutual given that it is not possible to know who is infected. Until now, programs to help women practice safer sex have concentrated on sex industry workers or family planning clients. Adolescents are a particularly vulnerable group because of their usual lack of knowledge when the initiate their sex lives. Some sex education classes are beginning to include materials instructing young girls in how to negotiate with boys seeking sexual favors. Printed materials such as simple pamphlets made available by family planning programs to young people can help to raise the topics of HIV infection and safer sex. Greater societal awareness of the problem and improvements in the opportunities for women to exercise their basic rights will be needed to ensure all women the power to protect their own health. PMID:12285215

  20. Optical frequency measurement by a one-octave optical frequency comb generated by an ultra-fast mode-locked laser and a photonic-crystal fiber

    Microsoft Academic Search

    K. Sugiyama; A. Onae; Feng-Lei Hong; S. N. Slyusarev; T. Ikegami; J. Ishikawa; K. Minoshima; H. Matsumoto; J. C. Knight; W. J. Wadsworth; S. J. Russell

    2001-01-01

    We have developed a direct comparison between microwave and optical frequencies by an ultra-fast mode-locked laser comb broadened with a photonic-crystal fiber. Control of the comb frequency to improve the measurement precision is presented

  1. The Assembly of Nanorods in Comb Polymer Supramolecules

    NASA Astrophysics Data System (ADS)

    Mastroianni, Alexander; Thorkelsson, Kari; Luther, Joseph; Alivisatos, Paul; Xu, Ting

    2010-03-01

    Inorganic nanoparticles exhibit a wide range of size-dependent properties and present great promise in technological applications. Fully harnessing this potential requires developing bottom-up strategies to assemble nanoparticles over multiple length scales simultaneously. Nanoparticles have been co-assembled with block copolymers (BCPs). Often this approach requires delicate balance between particle-polymer interactions and entropic penalty associated with polymer chain deformation upon particle incorporation. Recently, we showed that a coil-comb supramolecule formed by non- covalent attachment of small molecule amphiphiles to one block of a BCP can be used to direct nanoparticle assemblies with high precision. The alkyl tail of the small molecules chosen interacts favorably with the native alkyl ligands of a wide variety of inorganic nanoparticles and eliminates the need for particle surface modification. Upon attaching small molecule to one BCP block, the polymer chain stiffens, providing entropic driving force to further direct nanoparticle organization within BCP microdomains. Here, the co-assembly of these supramolecules with nanorods was systematically investigated as a function of small molecule loading, supramolecular morphology, nanorod diameter, and aspect ratio. The presented fundamental studies pave a path toward nanorod-based device fabrication.

  2. Cationic comb-type copolymers for DNA analysis

    NASA Astrophysics Data System (ADS)

    Kim, Won Jong; Sato, Yuichi; Akaike, Toshihiro; Maruyama, Atsushi

    2003-12-01

    Genetic diagnoses, such as single nucleotide polymorphism (SNP) typing, allow elucidation of gene-based physiological differences, such as susceptibility to diseases and response to drugs, among individuals. Many detection technologies, including allele-specific hybridization, allele-specific primer extension and oligonucleotide ligation, are being used to discriminate SNP alleles. These methods still have many unsolved practical issues. In general they require adequate and specific hybridizations of primer or probe DNAs with target DNAs. This frequently needs optimization of the probe/primer structures and operating conditions. In nature, highly homology-sensitive hybridization is assisted by a nucleic acid chaperone that reduces the energy barrier associated with breakage and reassociation of nucleic base pairs. Here we report a simple, quick, precise but enzyme-free method for SNP analysis. The method uses cationic comb-type copolymers (CCCs) producing high nucleic acid chaperone activities. A single-base mismatch in 20-mer DNA can be detected within a few minutes at ambient temperatures (25-37 °C). Even without careful optimization processes, the method has the sensitivity to detect the mismatches causing subtle changes (?Tm ~ 1 °C) in duplex thermal stability. CCCs may have various bioanalytical applications where precise hybridization of nucleic acids is needed.

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

    NASA Astrophysics Data System (ADS)

    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 ?m 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.

  4. Parasitic effects in SQUID-based radiation comb generators

    E-print Network

    Riccardo Bosisio; Francesco Giazotto; Paolo Solinas

    2015-05-23

    We study several parasitic effects on the implementation of a Josephson radiation comb generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how assuming a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of this device. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is in general negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited up to a large extent with a suitable choice of fabrication parameters.

  5. The comb jelly opsins and the origins of animal phototransduction.

    PubMed

    Feuda, Roberto; Rota-Stabelli, Omar; Oakley, Todd H; Pisani, Davide

    2014-08-01

    Opsins mediate light detection in most animals, and understanding their evolution is key to clarify the origin of vision. Despite the public availability of a substantial collection of well-characterized opsins, early opsin evolution has yet to be fully understood, in large part because of the high level of divergence observed among opsins belonging to different subfamilies. As a result, different studies have investigated deep opsin evolution using alternative data sets and reached contradictory results. Here, we integrated the data and methods of three, key, recent studies to further clarify opsin evolution. We show that the opsin relationships are sensitive to outgroup choice; we generate new support for the existence of Rhabdomeric opsins in Cnidaria (e.g., corals and jellyfishes) and show that all comb jelly opsins belong to well-recognized opsin groups (the Go-coupled opsins or the Ciliary opsins), which are also known in Bilateria (e.g., humans, fruit flies, snails, and their allies) and Cnidaria. Our results are most parsimoniously interpreted assuming a traditional animal phylogeny where Ctenophora are not the sister group of all the other animals. PMID:25062921

  6. The Comb Jelly Opsins and the Origins of Animal Phototransduction

    PubMed Central

    Feuda, Roberto; Rota-Stabelli, Omar; Oakley, Todd H.; Pisani, Davide

    2014-01-01

    Opsins mediate light detection in most animals, and understanding their evolution is key to clarify the origin of vision. Despite the public availability of a substantial collection of well-characterized opsins, early opsin evolution has yet to be fully understood, in large part because of the high level of divergence observed among opsins belonging to different subfamilies. As a result, different studies have investigated deep opsin evolution using alternative data sets and reached contradictory results. Here, we integrated the data and methods of three, key, recent studies to further clarify opsin evolution. We show that the opsin relationships are sensitive to outgroup choice; we generate new support for the existence of Rhabdomeric opsins in Cnidaria (e.g., corals and jellyfishes) and show that all comb jelly opsins belong to well-recognized opsin groups (the Go-coupled opsins or the Ciliary opsins), which are also known in Bilateria (e.g., humans, fruit flies, snails, and their allies) and Cnidaria. Our results are most parsimoniously interpreted assuming a traditional animal phylogeny where Ctenophora are not the sister group of all the other animals. PMID:25062921

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

    SciTech Connect

    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.

  8. Qcl Spectroscopy at 9 ?M Calibrated with a High-Power Thulium-Based Frequency Comb

    NASA Astrophysics Data System (ADS)

    Mills, Andrew A.; Jiang, Jie; Hartl, Ingmar; Fermann, Martin; Gatti, Davide; Marangoni, Marco

    2012-06-01

    Optical frequency comb synthesizers (OFCS) comprised of mode-locked femtosecond lasers can be stabilized with Hertz-level accuracy and used in combination with cw lasers for high resolution spectroscopy. As currently established OFCS technologies are confined to the near-IR, mid-IR spectroscopy requires either down-conversion of near-IR combs or up-conversion of the probing laser. Due to the near-IR absorption edge of the nonlinear crystals with extended mid-IR transparency, the conversion efficiency of nonlinear processes increases with the wavelength of the interacting fields. A more straightforward and efficient link between comb and probing laser is thus expected to be obtained by increasing the wavelength of the comb synthesizer. In this work, the use of a novel, powerful Thulium-based OFCS with emission wavelengths near 2 ?m is shown to be an excellent candidate to obtain absolute frequency calibration of quantum cascade lasers (QCL) operating at wavelengths as long as 9 ?m. Specifically, by combining the frequencies of a 9 ?m QCL with the high power 2 ?m comb in a AgGaSe_2 crystal, SFG light is created near 1.6 ?m. A portion of the 2 ?m comb is non-linearly shifted to 1.6 ?m. As the carrier envelope offset frequency (fceo) is the same for the SFG radiation and the shifted comb at 1.6 ?m, heterodyning the two signals produces a beat signal independent of fceo, eliminating the need for an octave spanning comb and f-2f interferometer. We report on the development of this instrument, and the absolute line transitions of NH_3 at 9 ?m, enabled by rapid scanning of the repetition rate of the comb enabled to increase the signal-to-noise ratio. J. Jiang, C. Mohr, J. Bethge, M. Fermann, and I. Hartl, in CLEO/Europe and EQEC 2011 Conference Digest, OSA Technical Digest (CD) PDB_1, 2001 D. Gatti, A. Gambetta, A. Castrillo, G. Galzerano, P. Laporta, L. Gainfrani and M. Marangoni Op. Exp. 19, 17520 2011

  9. Reclassification of Brevibacterium imperiale (Steinhaus) and "Corynebacterium laevaniformans" (Dias and Bhat) in a Redefined Genus Microbacterium (Orla-Jensen), as Microbacterium imperiale comb. nov. and Microbacterium laevaniformans nom. rev.; comb. nov.

    PubMed

    Collins, M D; Jones, D; Kroppenstedt, R M

    1983-01-01

    Chemical, morphological and physiological data indicate a close relationship between Brevibacterium imperiale (Steinhaus), "Corynebacterium laevaniforms" (Dias and Bhat) and the species Microbacterium lacticum (Orla-Jensen). It is suggested that B. imperiale and "C. laevaniformans" be reclassified in a redefined genus Microbacterium, as Microbacterium imperiale (Steinhaus) comb. nov. and Microbacterium laevaniformans (Dias and Bhat) nom. rev.; comb, nov., respectively. PMID:23196300

  10. Bandwidth scaling of a phase-modulated continuous-wave comb through four-wave mixing in a silicon nano-waveguide.

    PubMed

    Liu, Yang; Metcalf, Andrew J; Company, Victor Torres; Wu, Rui; Fan, Li; Varghese, Leo T; Qi, Minghao; Weiner, Andrew M

    2014-11-15

    We demonstrate an on-chip four-wave mixing (FWM) scheme in a silicon nanowaveguide to scale the bandwidth of a frequency comb generated by phase modulation of continuous-wave (CW) lasers. The FWM process doubles the bandwidth of the initial comb generated by the modulation of a CW laser. For example, a wavelength-tunable frequency comb with >100 comb lines spaced by 10 GHz within a bandwidth of 5 dB is generated. PMID:25490498

  11. Sex Chromosomes and Sex Determination in Lepidoptera

    Microsoft Academic Search

    W. Traut; K. Sahara; F. Marec

    2007-01-01

    The speciose insect order Lepidoptera (moths and butterflies) and their closest relatives, Trichoptera (caddis flies), share a female-heterogametic sex chromosome system. Originally a Z\\/ZZ (female\\/male) system, it evolved by chromosome rearrangement to a WZ\\/ZZ (female\\/male) system in the most species-rich branch of Lepidoptera, a monophyletic group consisting of Ditrysia and Tischeriina, which together comprise more than 98% of all species.

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

    E-print Network

    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...

  13. Effect of structure of cationic comb copolymers on their adsorption and stabilization of titania nanoparticles.

    PubMed

    Klimkevicius, Vaidas; Graule, Thomas; Makuska, Ricardas

    2015-02-24

    Cationic linear polymer poly([2-(methacryloyloxy)ethyl] trimethylammonium chloride) p(METAC), neutral brush polymer poly(poly(ethylene glycol) methyl ether methacrylate) p(PEO22MEMA), and cationic comb copolymers p(METAC-PEO(x)MEMA) were used for the stabilization of titania dispersions under neutral and alkaline conditions. Random comb copolymers p(METAC-PEO(x)MEMA) differing in charge density and length of PEO side chains were synthesized by RAFT. The adsorption of cationic polymers on titania nanoparticles was evaluated by thermogravimetric analysis; changes in surface potential, by measuring the zeta potential; and the stability of the treated TiO2 dispersions, by laser diffraction and DLS. Cationic linear and comb copolymers containing relatively short PEO side chains promoted the inversion of nanoparticle surface potential from strongly negative (-60 mV) to moderately positive (10-35 mV). Cationic comb copolymers containing longer PEO side chains increased the zeta potential of the treated nanoparticles but did not invert it to positive. Aqueous dispersions of titania nanoparticles stabilized by cationic comb copolymers under alkaline conditions (pH 10) were dispersed by high-energy planetary ball milling up to a primary particle size of 20 nm and were stable for at least 2 days. PMID:25625601

  14. High Accuracy Characterization of an Astro-comb with an FTS

    NASA Astrophysics Data System (ADS)

    Glenday, Alex; Li, Chih-Hao; Phillips, David; Korzennik, Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner, Franz; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald

    2011-06-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. To find a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude improvement in state-of-the-art radial velocity spectroscopy is necessary. An astro-comb, the combination of an ocatve-spanning laser frequency comb with a Fabry-Perot cavity, producing evenly spaced frequency markers with the potential for large wavelength coverage is a promising avenue towards improved wavelength calibration. Key to achieving high accuracy and long-term stability of the astro-comb is high-quality suppression of undesired comb laser lines by the Fabry-Perot filter cavity. Here we present a characterization of a green astro-comb produced by broadening a Ti:Sapphire laser using photonic crystal fiber (PCF) and filtered through zero group delay dispersion mirror sets optimized for the green. The characterization is performed using a high-resolution FTS constructed in our laboratory.

  15. Exposing Sex Stereotypes in Recent Same-Sex Marriage Jurisprudence

    Microsoft Academic Search

    Deborah A. Widiss; Elizabeth Rosenblatt; Douglas NeJaime

    2007-01-01

    This article examines sex discrimination arguments in recent same-sex marriage cases. Since 1993, when the Hawaii Supreme Court held in Baehr v. Lewin that denying same-sex couples the right to marry could state a claim of sex discrimination, every state high court to consider the issue has rejected the claim. But many recent decisions have in fact relied upon sex-based

  16. Single Sex Education. WEEA Digest.

    ERIC Educational Resources Information Center

    Pollard, Diane S.

    Title IX of the Educational Amendments of 1972 prohibits discrimination on the basis of sex in educational institutions that receive federal financial assistance. This digest focuses on the theme of single-sex education. Articles featured in this issue include: (1) "Single-Sex Education" (Diane S. Pollard); (2) "A Legal Framework for Single-Sex

  17. "Sex Health" Deaf Health Talks,

    E-print Network

    Goldman, Steven A.

    relationship Sex is enjoyable Sex is safe It is never forced It is never abused or violent Picture: newsinfo prostate cancer risk Strengthens pelvis Better sleep http://www.webmd.com/sex-relationships/features/10"Sex Health" Deaf Health Talks, March 17, 2011 #12;Supporters Deaf Health Community Committee

  18. [Rheumatic diseases and sex differences].

    PubMed

    Ochiai, Moeko; Yamanaka, Hisashi

    2015-04-01

    Recently a concept of "sex differences" in medicine has been spreading. It is well known that autoimmune diseases, especially rheumatoid arthritis or systemic lupus erythematosus mostly affect women, and it is clear that there is a strong sex differences in many rheumatic diseases. Sex difference influences to progression or prognosis of the disease. Although the mechanisms of sex difference are not clear, the influence of sex hormones or sex chromosomes which gives immune system is partially elucidated. In addition, sex hormones may become the future new treatment target, and progress in the study regarding this event is expected in the future. PMID:25936155

  19. Absolute frequency measurement of the iodine-stabilized Ar+ at 514.6 nm using a femtosecond optical frequency comb.

    E-print Network

    Boyer, Edmond

    Absolute frequency measurement of the iodine-stabilized Ar+ laser at 514.6 nm using a femtosecond laser frequency comb generator. The measured frequency at an iodine pressure of 0.12 Pa is 67.3(0.75) k frequency comb transfer oscillator. Secondary laser frequency references based on iodine absorption lines

  20. Absolute frequency measurement of an SF6 two-photon line using a femtosecond optical comb and sum-frequency

    E-print Network

    Paris-Sud XI, Université de

    Absolute frequency measurement of an SF6 two-photon line using a femtosecond optical comb and sum-frequency to measure IR frequencies near 30 THz using a femtosecond (fs) laser optical comb and sum-frequency generation. The optical frequency is directly compared to the distance between two modes of the fs laser

  1. Numerical investigation into the injection-locking phenomena of gain switched lasers for optical frequency comb generation

    E-print Network

    Duill, Sean P O; Zhou, Rui; Barry, Liam P

    2015-01-01

    We present detailed numerical simulations of the laser dynamics that describe optical frequency comb formation by injection-locking a gain-switched laser. The typical rate equations for semiconductor lasers including stochastic carrier recombination and spontaneous emission suffice to show the injection-locking behavior of gain switched lasers, and we show how the optical frequency comb evolves starting from the free-running state, right through the final injection- locked state. Unlike the locking of continuous wave lasers, we show that the locking range for gain switched lasers is considerably greater because injection locking can be achieved by injecting at frequencies close to one of the comb lines. The quality of the comb lines are formally assessed by calculating the FM-noise spectral density and we show that under injection-locking conditions the FM-noise spectral density of the comb lines tend to that of the maser laser.

  2. Velocity-selective direct frequency-comb spectroscopy of atomic vapors

    E-print Network

    Stalnaker, J E; Rowan, M E; Nguyen, K; Pradhananga, T; Palm, C A; Kimball, D F Jackson

    2015-01-01

    We present an experimental and theoretical investigation of two-photon direct frequency-comb spectroscopy performed through velocity-selective excitation. In particular, we explore the effect of repetition rate on the $\\textrm{5S}_{1/2}\\rightarrow \\textrm{5D}_{3/2, 5/2}$ two-photon transitions excited in a rubidium atomic vapor cell. The transitions occur via step-wise excitation through the $\\textrm{5P}_{1/2, 3/2}$ states by use of the direct output of an optical frequency comb. Experiments were performed with two different frequency combs, one with a repetition rate of $\\approx 925$ MHz and one with a repetition rate of $\\approx 250$ MHz. The experimental spectra are compared to each other and to a theoretical model.

  3. Phase-stabilized, 1.5 W frequency comb at 2.8-4.8 microm.

    PubMed

    Adler, Florian; Cossel, Kevin C; Thorpe, Michael J; Hartl, Ingmar; Fermann, Martin E; Ye, Jun

    2009-05-01

    We present a high-power optical-parametric-oscillator (OPO) based frequency comb in the mid-IR wavelength region. The system employs periodically poled lithium niobate and is singly resonant for the signal. It is synchronously pumped by a 10 W femtosecond Yb:fiber laser centered at 1.07 microm. The idler (signal) wavelength can be continuously tuned from 2.8 to 4.8 microm (1.76 to 1.37 microm) with a simultaneous bandwidth as high as 0.3 microm and a maximum average idler output power of 1.50 W. We also demonstrate the performance of the stabilized comb by recording the heterodyne beat with a narrow-linewidth diode laser. This OPO is an ideal source for frequency comb spectroscopy in the mid-IR. PMID:19412262

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

    E-print Network

    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.

  5. A Novel Comb Architecture for Enhancing the Sensitivity of Bulk Mode Gyroscopes

    PubMed Central

    Elsayed, Mohannad Y.; Nabki, Frederic; El-Gamal, Mourad N.

    2013-01-01

    This work introduces a novel architecture for increasing the sensitivity of bulk mode gyroscopes. It is based on adding parallel plate comb drives to the points of maximum vibration amplitude, and tuning the stiffness of the combs. This increases the drive strength and results in a significant sensitivity improvement. The architecture is targeted for technologies with ?100 nm transducer gaps in order to achieve very high performance devices. In this work, this sensitivity enhancement concept was implemented in SOIMUMPs, a commercial relatively large gap technology. Prototypes were measured to operate at frequencies of ?1.5 MHz, with quality factors of ?33,000, at a 10 mTorr vacuum level. Measurements using discrete electronics show a rate sensitivity of 0.31 ?V/°/s, corresponding to a capacitance sensitivity of 0.43 aF/°/s/electrode, two orders of magnitude higher than a similar design without combs, fabricated in the same technology.

  6. AIDS and sex tourism.

    PubMed

    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. PMID:12286016

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

    PubMed

    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. PMID:24977809

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

    NASA Astrophysics Data System (ADS)

    Balling, Petr; Mašika, Pavel; K?en, 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. Comb-like oligoaminoethane carriers: change in topology improves pDNA delivery.

    PubMed

    Scholz, Claudia; Kos, Petra; Wagner, Ernst

    2014-02-19

    Establishing precise structure-activity relationships is important for the optimization of synthetic carriers for gene delivery. Sequence-defined oligomers with branched or linear shapes were synthesized to investigate the influence of topology on their biophysical properties and biological performance. Comb-like structures were synthesized consisting of an oligolysine peptide backbone modified at the ?-amino groups with four different artificial oligoamino acids, succinyl-diethylene triamine (Sdt), succinyl-triethylene tetramine (Stt), succinyl-tetraethylene pentamine (Stp), and succinyl-pentaethylene hexamine (Sph). Optionally the amino acids histidine and alanine were inserted into the oligolysine backbone to assess a possible buffer or spacer effect. After the evaluation of biophysical properties, the best performing oligomers, containing the Stp or Sph building blocks, were compared to corresponding linear oligomers where Stp or Sph are directly integrated into the linear oligolysine row. Clear differences between the comb and linear carriers were observed in the comparison of properties such as DNA complexation ability, buffer capacity, cellular association and internalization, and gene transfer. For the Stp containing structures, the comb topology mediated an increased buffer capacity at endosomal pH. For the Sph containing structures, in sharp contrast, the linear topology displayed advantageous endosomal buffering. Interestingly, for both Stp and Sph carriers, the comb in comparison to the linear topologies mediated a higher overall cellular uptake despite a lower cell association. For Stp combs, the combined advantage in both buffering and cellular uptake resulted in a strong (10- to >100-fold) increase in DNA transfection efficiency. In the case of Sph carriers, comb topology mediated only moderately (maximum 4-fold) enhanced gene transfer over the linear topology. PMID:24359105

  10. Electromagnetically induced transparency in rubidium vapor prepared by a comb of short optical pulses

    SciTech Connect

    Sautenkov, Vladimir A. [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Lebedev Physical Institute, RAS, Moscow 119991 (Russian Federation); Rostovtsev, Yuri V.; Ye, C.Y.; Welch, George R. [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Kocharovskaya, Olga [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Institute of Applied Physics, RAS, Nizhny Novgorod 603120 (Russian Federation); Scully, Marlan O. [Department of Physics and Institute for Quantum Studies, Texas A and M University, College Station, Texas 77843 (United States); Department of Chemistry, Princeton University, Princeton, New Jersey 08544 (United States)

    2005-06-15

    It was shown by Kocharovskaya and Khanin [Sov. Phys. JETP 63, 945 (1986)] that a comb of optical pulses can induce a ground-state atomic coherence and change the optical response of an atomic medium. In our experiment, we studied the propagation of a comb of optical pulses produced by a mode-locked diode laser in rubidium atomic vapor. Electromagnetically induced transparency (EIT) was observed when the pulse repetition rate is a subharmonic of the hyperfine splitting of the ground state. The width of the EIT resonance is determined by the relaxation rate of the ground-state coherence. Possible applications to magnetometery, atomic clocks, and frequency chains are discussed.

  11. Design of flat-top comb filter based on photonic crystal fiber Sagnac loop

    NASA Astrophysics Data System (ADS)

    Wang, Xude; Li, Suwen

    2011-12-01

    A novel all-fiber flat-top comb filter is proposed based on Sagnac loop interferometer of photonic crystal fiber (PCF). The transmission function of the proposed Sagnac loop filter is expressed theoretically by Jones transmit-matrix. The influences of birefringence of PCF, the lengths of two sections of PCFs and the rotatable angle of polarization controllers on its output spectra are numerically studied. On the basis of theoretical analysis, a wavelength switchable comb filter with flat-top spectral response is realized. This kind of filter can be expected to be used widely in DWDM systems in the future.

  12. Comments on turbulence theory by Qian and by Edwards and McComb

    E-print Network

    Pandya, R V R

    2015-01-01

    We reexamine Liouville equation based turbulence theories proposed by Qian {[}Phys. Fluids \\textbf{26}, 2098 (1983){]} and Edwards and McComb {[}J. Phys. A: Math. Gen. \\textbf{2}, 157 (1969){]}, which are compatible with Kolmogorov spectrum. These theories obtained identical equation for spectral density $q(k)$ and different results for damping coefficient. Qian proposed variational approach and Edwards and McComb proposed maximal entropy principle to obtain equation for the damping coefficient. We show that assumptions used in these theories to obtain damping coefficient correspond to unphysical conditions.

  13. High-bandwidth transfer of phase stability through a fiber frequency comb

    E-print Network

    Scharnhorst, Nils; Hannig, Stephan; Jakobsen, Kornelius; Kramer, Johannes; Leroux, Ian D; Schmidt, Piet O

    2015-01-01

    We demonstrate phase locking of a 729 nm diode laser to a 1542 nm master laser via an erbium-doped-fiber frequency comb. Thanks to a transfer-oscillator feedforward scheme which suppresses the effect of comb noise in an unprecedented 1.8 MHz bandwidth, the phase lock requires no pre-stabilization of the slave diode laser. We illustrate the performance of the system by carrying out coherent manipulations of a trapped calcium ion with a fidelity in excess of 99% even at few-microsecond timescales.

  14. Radiative effects driven by shock waves in cavity-less four-wave mixing combs.

    PubMed

    Conforti, Matteo; Trillo, Stefano

    2014-10-01

    We investigate the frequency comb spectrum produced in an optical fiber via multiple four-wave mixing pumped in the normal group-velocity region close to the zero-dispersion wavelength. We show that the dynamics are strongly affected by shock formation. In this regime, the resonant radiation emitted by the shock waves correctly explains the enhanced spectral peaks in the comb. The resonant frequencies found by means of perturbation theory accurately fit those observed from the numerical simulation based on the generalized nonlinear Schrödinger equation. PMID:25360978

  15. Generation of optical combs in a whispering gallery mode resonator from a bichromatic pump

    NASA Astrophysics Data System (ADS)

    Strekalov, Dmitry V.; Yu, Nan

    2009-04-01

    An optical comb is shown to arise from a whispering gallery mode resonator pumped by two optical frequencies. Two externally excited modes couple due to Kerr nonlinearity to initially empty modes and give rise to new frequency components. This thresholdless process is much more efficient than the previously reported single-pump four-wave mixing. As a result, a few milliwatt pump is sufficient to generate strong secondary fields that efficiently generate higher-order frequency components and so on in a cascade process leading to an optical comb.

  16. Phase conjugation frequency dissemination based on harmonics of optical comb at 10?¹? instability level.

    PubMed

    Li, Dawei; Hou, Dong; Hu, Ermeng; Zhao, Jianye

    2014-09-01

    We demonstrate a phase conjugation frequency dissemination scheme using an optical frequency comb as a coherent source. After the comb's radio frequency is detected by a photodiode, its repetition frequency's first harmonic is used to modulate a laser, which is injected into a 10 km fiber link. The round-trip signal is mixed with the triple harmonic thereby obtaining a signal that is immune to the fluctuation at the remote end. This method results in frequency instability of 1.1×10(-17) at 10(4) s. Our scheme provides a potential approach to deliver coherent frequencies to many places with high stability. PMID:25166073

  17. Analysis of the second harmonic generation of a femtosecond optical frequency comb

    NASA Astrophysics Data System (ADS)

    Wei, Dong; Aketagawa, Masato

    2014-12-01

    The second harmonic generation (SHG) of a femtosecond optical frequency comb (FOFC) has been studied. This work focuses on the SHG frequencies that are generated by the mixing of even-numbered frequency components from the original comb with odd-numbered components. It is observed that the generation of those frequencies is the reason the original FOFC and FOFC-based SHG signal have the same repetition frequency. The theoretical derivation agrees with the result of an optical experiment. Our results may be of use with the high-harmonic-generation process and FOFC-based SHG applications, including high-resolution spectroscopy, attosecond pulse generation, and precision length measurement.

  18. Synthesis, characterization, and antibacterial activity of metal nanoparticles embedded into amphiphilic comb-type graft copolymers

    Microsoft Academic Search

    Özlem A. Kalayc?; Füsun B. Cömert; Baki Hazer; Turgay Atalay; Kevin A. Cavicchi; Mukerrem Cakmak

    2010-01-01

    The synthesis, spectroscopic characterization, and antimicrobial efficiency of gold and silver nanoparticles embedded in novel\\u000a amphiphilic comb-type graft copolymers having good film-forming properties have been described. Amphiphilic comb-type graft\\u000a copolymers were synthesized by the reaction of chlorinated polypropylene (PP) (M\\u000a w = 140,000 Da) with polyethylene glycol (PEG) (M\\u000a \\u000a n\\u000a  = 2,000 Da) at different molar ratios. Metal nanoparticles embedded graft copolymers were prepared by

  19. Direct link of a mid-infrared QCL to a frequency comb by optical injection.

    PubMed

    Borri, S; Galli, I; Cappelli, F; Bismuto, A; Bartalini, S; Cancio, P; Giusfredi, G; Mazzotti, D; Faist, J; De Natale, P

    2012-03-15

    A narrow-linewidth comb-linked nonlinear source is used as master radiation to injection lock a room-temperature mid-infrared quantum cascade laser (QCL). This process leads to a direct lock of the QCL to the optical frequency comb, providing the unique features of narrow linewidth, absolute frequency, higher output power, and wide mode-hop-free tunability. The QCL reproduces the injected radiation within more than 94%, with a reduction of the frequency-noise spectral density by 3 to 4 orders of magnitude up to about 100 kHz, and a linewidth narrowing from a few MHz to 20 kHz. PMID:22446207

  20. Evidence for frequency comb emission from a Fabry-Pérot terahertz quantum-cascade laser.

    PubMed

    Wienold, M; Röben, B; Schrottke, L; Grahn, H T

    2014-12-15

    We report on a broad-band terahertz quantum-cascade laser (QCL) with a long Fabry-Pérot ridge cavity, for which the tuning range of the individual laser modes exceeds the mode spacing. While a spectral range of approximately 60 GHz (2 cm(-1)) is continuously covered by current and temperature tuning, the total emission range spans more than 270 GHz (9 cm(-1)). Within certain operating ranges, we found evidence for stable frequency comb operation of the QCL. An experimental technique is presented to characterize frequency comb operation, which is based on the self-mixing effect. PMID:25606987

  1. Safer sex: Why bother? Sex and sexuality are important components of health. For many, sex is an integral part of life. Sex can be

    E-print Network

    Doedel, Eusebius

    24 Safer sex: Why bother? Sex and sexuality are important components of health. For many, sex is an integral part of life. Sex can be pleasurable, fun and exciting. Unfortunately, sex can also lead to health of these consequences through safer sex practices. What are safer sex practices? We hear this term a lot, but what

  2. How to sell safer sex.

    PubMed

    Overs, C

    1991-09-01

    Social and economic factors determine the extent of the sex industry in societies. Despite AIDS, the sex industry will continue to thrive. Accordingly, health promotion strategies aimed at sex workers and their clients should not stem from the belief that the industry should cease to exist. This paper offers advice in developing and implementing programs to promote safer sex among sex workers. The social context is 1 element to consider in planning successful campaigns. Interventions must be combined with well-planned prevention campaigns aimed at entire populations. The opinions and participation of those involved in the industry should also be sought, while worker discussion and action upon other community issues should not be discouraged. Care should be given to target the numerous and diverse sex worker audiences in addition to other persons related to and involved in the industry. Programs should address the main obstacles to practicing safer sex, and attention should be given to ensure the provision of an adequate and regular supply of cheap or free condoms through varied distribution channels. In the area of service provision, sex workers need easy access to social support and health care services from which they are often excluded. Activities conducted around the world include the marketing of safer sex, distributing printed information on HIV and AIDS to clients, training sex workers to pass designated constructive ideas to others involved in the sex industry, referring sex workers to sex businesses supportive of safer sex practices, and developing street theater and cabaret shows in bars. PMID:12284682

  3. Reclassification of Bacteriovorax marinus as Halobacteriovorax marinus gen. nov., comb. nov. and Bacteriovorax litoralis as Halobacteriovorax litoralis comb. nov.; description of Halobacteriovoraceae fam. nov. in the class Deltaproteobacteria.

    PubMed

    Koval, Susan F; Williams, Henry N; Stine, O Colin

    2015-02-01

    The taxonomic status of saltwater Bdellovibrio-like prokaryotic predators has been revised to assign species to Halobacteriovorax gen. nov. A reclassification of Bacteriovorax marinus as Halobacteriovorax marinus comb. nov. (type strain ATCC BAA-682(T)?= DSM 15412(T)) and Bacteriovorax litoralis as Halobacteriovorax litoralis comb. nov. (type strain ATCC BAA-684(T)?= DSM 15409(T)) is proposed. This revision is necessary because a previous proposal to retain saltwater isolates as species of Bacteriovorax and reclassify Bacteriovorax stolpii as Bacteriolyticum stolpii was not approved. The type species of a genus cannot be reassigned to another genus. Bacteriovorax stolpii is thus retained as the type species of Bacteriovorax and Halobacteriovorax marinus is the type species of Halobacteriovorax and of Halobacteriovoraceae fam. nov. PMID:25406234

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

    SciTech Connect

    Quinlan, F.; Diddams, S. A. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States); Ycas, G. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States); Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Osterman, S. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, Colorado 80309 (United States)

    2010-06-15

    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 {approx}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.

  5. Scalable and reconfigurable generation of flat optical comb for WDM-based next-generation broadband optical access networks

    NASA Astrophysics Data System (ADS)

    Chen, Chen; Zhang, Chongfu; Zhang, Wei; Jin, Wei; Qiu, Kun

    2014-06-01

    A tunable comb generator (TCG) by cascading a single phase modulator (PM) with two identical intensity modulators (IMs) is proposed for the scalable and reconfigurable generation of flat optical comb. Detailed theoretical analysis is performed to find out the optimized condition for flat optical comb generation using the proposed TCG and the scalability of the generated optical comb is also analyzed under the optimized condition. An experiment is conducted to verify the feasibility of the TCG and the experimental results agree well with the theoretical prediction. The reconfigurability and stability of the obtained optical comb are discussed as well in the experiment. After that, the obtained optical comb is utilized as the optical source for a wavelength-division multiplexed radio-over-fiber (WDM-RoF) system and a hybrid WDM orthogonal frequency-division multiple access passive optical network (WDM-OFDMA-PON). Two corresponding experimental demonstrations are presented to verify the feasibility of employing the obtained flat optical comb as the WDM optical source, respectively. In the WDM-RoF system, 17 WDM channels each carrying 16×5 Gb/s non-return-to-zero (NRZ) data have been up-converted to 10 GHz simultaneously. In the hybrid WDM-OFDMA-PON, 17-channel OFDM-WDM double-sideband (DSB) signal achieving 10.85 Gb/s traffic per channel is successfully transmitted for both wired baseband OFDM access and wireless 10 GHz OFDM access.

  6. Solution NMR structure of the DNA-binding domain from Scml2 (sex comb on midleg-like 2).

    PubMed

    Bezsonova, Irina

    2014-05-30

    Scml2 is a member of the Polycomb group of proteins involved in epigenetic gene silencing. Human Scml2 is a part of a multisubunit protein complex, PRC1 (Polycomb repressive complex 1), which is responsible for maintenance of gene repression, prevention of chromatin remodeling, preservation of the "stemness" of the cell, and cell differentiation. Although the majority of PRC1 subunits have been recently characterized, the structure of Scml2 and its role in PRC1-mediated gene silencing remain unknown. In this work a conserved protein domain within human Scml2 has been identified, and its structure was determined by solution NMR spectroscopy. This module was named Scm-like embedded domain, or SLED. Evolutionarily, the SLED domain emerges in the first multicellular organisms, consistent with the role of Scml2 in cell differentiation. Furthermore, it is exclusively found within the Scm-like family of proteins, often accompanied by malignant brain tumor domain (MBT) and sterile ? motif (SAM) domains. The domain adopts a novel ?/? fold with no structural analogues found in the Protein Data Bank (PDB). The ability of the SLED to bind double-stranded DNA was also examined, and the isolated domain was shown to interact with DNA in a sequence-specific manner. Because PRC1 complexes localize to the promoters of a specific subset of developmental genes in vivo, the SLED domain of Scml2 may provide an important link connecting the PRC1 complexes to their target genes. PMID:24727478

  7. Solution NMR Structure of the DNA-binding Domain from Scml2 (Sex Comb on Midleg-like 2)?

    PubMed Central

    Bezsonova, Irina

    2014-01-01

    Scml2 is a member of the Polycomb group of proteins involved in epigenetic gene silencing. Human Scml2 is a part of a multisubunit protein complex, PRC1 (Polycomb repressive complex 1), which is responsible for maintenance of gene repression, prevention of chromatin remodeling, preservation of the “stemness” of the cell, and cell differentiation. Although the majority of PRC1 subunits have been recently characterized, the structure of Scml2 and its role in PRC1-mediated gene silencing remain unknown. In this work a conserved protein domain within human Scml2 has been identified, and its structure was determined by solution NMR spectroscopy. This module was named Scm-like embedded domain, or SLED. Evolutionarily, the SLED domain emerges in the first multicellular organisms, consistent with the role of Scml2 in cell differentiation. Furthermore, it is exclusively found within the Scm-like family of proteins, often accompanied by malignant brain tumor domain (MBT) and sterile ? motif (SAM) domains. The domain adopts a novel ?/? fold with no structural analogues found in the Protein Data Bank (PDB). The ability of the SLED to bind double-stranded DNA was also examined, and the isolated domain was shown to interact with DNA in a sequence-specific manner. Because PRC1 complexes localize to the promoters of a specific subset of developmental genes in vivo, the SLED domain of Scml2 may provide an important link connecting the PRC1 complexes to their target genes. PMID:24727478

  8. Disestablishing Sex: The Case for Released-Time Sex Education

    ERIC Educational Resources Information Center

    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…

  9. Sex Role Attitudes and Sex Role Stereotyping: Recent Literature.

    ERIC Educational Resources Information Center

    New Jersey Research Bulletin, 1996

    1996-01-01

    This annotated bibliography profiles 17 publications examining sex role attitudes/sex role stereotyping from the perspectives of ethnicity, gender, and age. Cited in the section on ethnicity are studies of work satisfaction/family functioning among working-class Mexican-American women and cultural variations in sex typing by students in the United…

  10. Sex in Geneva, sex in Lilongwe, and sex in Balaka.

    PubMed

    Tawfik, Linda; Watkins, Susan Cotts

    2007-03-01

    This paper compares three interpretations of women and the transmission of HIV in rural Malawi. One is disseminated world-wide by institutions with a global reach such as the World Health Organization in Geneva and United States Agency for International Development (USAID); the second is provided by urban Malawians situated in the capital of Lilongwe, the seat of government and the site of the many international and national non-governmental agencies; the third is articulated by rural women and men in Balaka District, Malawi. We focus on women's motivations for extramarital sex, using qualitative interview data. We find that whereas in Geneva and Lilongwe women from rural Malawi are said to engage in sexual relationships outside of marriage because they need money for survival, in Balaka they are said to be motivated not only by money for survival but also for attractive consumer goods as well as by passion and by revenge for a husband's infidelity. We also find that data collection procedures influence explanations for women's affairs, as does the respondent's gender. An implication of this study is that AIDS-prevention policies based on the view from Geneva and Lilongwe need modification for Balaka, and by implication for rural Africa more generally. PMID:17123678

  11. Self-organizing pattern formation on the combs of honey bee colonies

    Microsoft Academic Search

    Scott Camazine

    1991-01-01

    Summary A characteristic pattern of brood, pollen, and honey develops on the combs of a honey bee colony, consisting of three distinct concentric regions — a central brood area, a surrounding rim of pollen, and a large peripheral region of honey. That the pattern is consistent and well-organized suggests its adaptive value for the colony, yet the mechanism of pattern

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Measuring the shift of a femtosecond laser frequency comb by the interference method

    SciTech Connect

    Basnak, Dmitriy V; Bikmukhametov, K A; Dmitriev, Aleksandr K; Dychkov, Aleksandr S; Kuznetsov, Sergei A; Lugovoy, A A; Mitsziti, P

    2012-01-31

    We have demonstrated the possibility of measuring the femtosecond laser frequency comb shift by the position of a Fabry - Perot interferometer's transmission bands with a statistical error of 10{sup -2} and a systematic shift of 10{sup -1}. (control of laser radiation parameters)

  14. Optical zooming interferometer for subnanometer positioning using an optical frequency comb

    SciTech Connect

    Kajima, Mariko; Minoshima, Kaoru

    2010-10-20

    A high-precision positioning stage based on an optical zooming interferometer is proposed. Two external-cavity diode lasers, stabilized to a femtosecond optical frequency comb, are used as optical sources. The zooming principle is demonstrated, and the positioning resolution of 0.2 nm is achieved. The positioning accuracy was partly evaluated.

  15. Laser Graphic Video Display using Silicon Scanning Mirrors with Vertical Comb Fingers

    Microsoft Academic Search

    Jin-Ho Lee; Young-Chul Ko; Yong-Kweun Mun; Byoung-So Choi; Jong-Min Kim; Duk Young Jeon

    2002-01-01

    We acquired a two-dimensional (2D) laser vector graphic video image using 1500 mum× 1200 mum silicon scanning mirrors with vertical comb fingers. Vector image signals from the graphic board were applied to two scanning mirrors, and a SHG green laser was directly modulated to shape independent graphic images. These scanning mirrors were originally designed for laser raster video display as

  16. First record of Colletogloeopsis zuluense comb. nov., causing a stem canker of Eucalyptus in China

    E-print Network

    First record of Colletogloeopsis zuluense comb. nov., causing a stem canker of Eucalyptus in China. WINGFIELDa , Michael J. WINGFIELDa a Department of Genetics, Forestry and Agricultural Biotechnology Province, P.R. China d Centraalbureau voor Schimmelcultures, Uppsalalaan 8, 3584 CT Utrecht

  17. Quantum-Noise-Limited Optical Frequency Comb Spectroscopy Aleksandra Foltynowicz,* Ticijana Ban,

    E-print Network

    efficient coupling of the comb light into the cavity [9,10]. Several detection schemes have been proposed transmitted through the cavity has been detected using a dispersive element and a multide- tector array [11 is limited only by the cavity dispersion, and not by the number of detection elements [17]. However

  18. A high sensitivity SOI electric-field sensor with novel comb-shaped microelectrodes

    Microsoft Academic Search

    Pengfei Yang; Chunrong Peng; Haiyan Zhang; Shiguo Liu; Dongming Fang; Shanhong Xia

    2011-01-01

    We have developed a highly sensitive electric-field sensor with novel comb-shaped microelectrodes. The sensor is based on modulating an incident field with a grounded shutter and measuring the induced charge of sensing electrodes. Owing to the shutter covering the side wall of the sensing electrodes, the fringing fields are no longer a factor that reduces the performance of the sensor.

  19. High-power widely tunable thulium fiber lasers Timothy S. McComb,1,2

    E-print Network

    Richardson, Martin C.

    High-power widely tunable thulium fiber lasers Timothy S. McComb,1,2 R. Andrew Sims,1 Christina C requiring long-range atmospheric propagation are driving the development of high-power thulium fiber lasers. We report on the performance of two different laser configurations for high-power tunable thulium

  20. Osmotic pressure and virial coefficients of star and comb polymer solutions: Dissipative particle dynamics

    NASA Astrophysics Data System (ADS)

    Wang, Tzu-Yu; Fang, Che-Ming; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2009-03-01

    The effects of macromolecular architecture on the osmotic pressure ? and virial coefficients (B2 and B3) of star and comb polymers in good solvents are studied by dissipative particle dynamics simulations for both dilute and semiconcentrated regimes. The dependence of the osmotic pressure on polymer concentration is directly calculated by considering two reservoirs separated by a semipermeable, fictitious membrane. Our simulation results show that the ratios An +1?Bn +1/R?g3n are essentially constant and A2 and A3 are arm number (f) dependent, where R?g is zero-density radius of gyration. The value of dimensionless virial ratio g =A3/A22 increases with arm number of stars whereas it is essentially arm number independent for comb polymers. In semiconcentrated regime the scaling relation between osmotic pressure and volume fraction, ? ???, still holds for both star and comb polymers. For comb polymers, the exponent ? is close to ?? (?2.73 for linear chains) and is independent of the arm number. However, for star polymers, the exponent ? deviates from ?? and actually grows with increasing the arm number. This may be attributed to the significant ternary interactions near the star core in the many-arm systems.

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

    E-print Network

    Walsworth, Ronald L.

    .J. Russell, "Octave-spanning supercontinuum generated in SF6-glass PCF by a 1060 nm mode-locked fibre laser fiber. Spanning more than 300 nm with 16 GHz line spacing, the resulting astro- comb is predicted. Hollberg, and S. A. Diddams, "Generation of 20 GHz, sub-40 fs pulses at 960 nm via repetition

  2. Gravity orientation in social wasp comb cells (Vespinae) and the possible role of embedded minerals

    NASA Astrophysics Data System (ADS)

    Ishay, Jacob S.; Barkay, Zahava; Eliaz, Noam; Plotkin, Marian; Volynchik, Stanislav; Bergman, David J.

    2008-04-01

    Social wasps and hornets maintain their nest in the dark. The building of the combs by all Vespinae is always in the direction of the gravitational force of Earth, and in each cell’s ceiling, at least one ‘keystone’ is embedded and fastened by saliva. The sensory mechanisms that enable both building of sizeable symmetrical combs and nursing of the brood in the darkness merit investigation, and the aim of the present study was to identify and characterize the ‘keystones’ that exist in the ceiling and in the walls of the social wasp comb cells. Bio-ferrography was used to isolate magnetic particles on slides. These slides, as well as original cells, were analyzed in an environmental scanning electron microscope by a variety of analytical tools. It was found that both the roof and the walls of each comb cell bear minerals, like ferrites, as well as Ti and Zr. The latter two elements are less abundant in the soil around the nest. Ti and Zr are known to reflect infrared (IR) light. IR imaging showed a thermoregulatory center in the dorsal thorax of the adult Oriental hornet. It is not known yet whether these insects can sense IR light.

  3. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers.

    PubMed

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  4. Power, Prayers, and Protection: Comb Ridge as a Case Study in Navajo Thought

    ERIC Educational Resources Information Center

    McPherson, Robert S.

    2010-01-01

    Beginning in 2005, a five-year survey of cultural resources began to unfold in southeastern Utah along a prominent sandstone rock formation known as Comb Ridge. This visually dramatic monocline stretches a considerable distance from the southwestern corner of Blue Mountain (Abajos) in Utah to Kayenta, Arizona, approximately one hundred miles to…

  5. A gigahertz multimode-diode-pumped Yb:KGW enables a strong frequency comb offset beat

    E-print Network

    Keller, Ursula

    A gigahertz multimode-diode-pumped Yb:KGW enables a strong frequency comb offset beat signal SESAM modelocked Yb:KGW laser is pumped with a commercial multimode diode laser and enables a strong oscillators: a success story for the last 20 years with no end in sight," Appl. Phys. B 100(1), 15­28 (2010

  6. Transfer of Brevibacterium ammoniagenes (Cooke and Keith) to the Genus Corynebacterium as Corynebacterium ammoniagenes comb. nov

    Microsoft Academic Search

    M. D. COLLINS

    Brevibacterium ammoniagenes (Cooke and Keith) differs so much from the type species of the genus Brevibacterium, Brevibacterium linens, that it should not be retained within this genus. On the basis of biochemical and chemical criteria, it is proposed that Brevibacterium ammoniagenes be reclassified in the genus Corynebacterium as Corynebacterium ammoniagenes comb. nov. The type strain is ATCC 6871 (NCIB 8143).

  7. COMB-LIKE MACROMOLECULE CONFORMATION IN SMECTIC PHASE. INTERPRETATION OF NEUTRON-SCATTERING DATA

    E-print Network

    Paris-Sud XI, Université de

    2015 COMB-LIKE MACROMOLECULE CONFORMATION IN SMECTIC PHASE. INTERPRETATION OF NEUTRON. Abstract : Simple theoretical considera- tions allow us to define the conformation of the macromolecule macromolecule which was measured by small angle neutron scattering. LE JOURNAL DE PHYSIQUE Tome 47 N° 12

  8. Hexagonal comb cells of honeybees are not produced via a liquid equilibrium process

    NASA Astrophysics Data System (ADS)

    Bauer, Daniel; Bienefeld, Kaspar

    2013-01-01

    The nests of European honeybees ( Apis mellifera) are organised into wax combs that contain many cells with a hexagonal structure. Many previous studies on comb-building behaviour have been made in order to understand how bees produce this geometrical structure; however, it still remains a mystery. Direct construction of hexagons by bees was suggested previously, while a recent hypothesis postulated the self-organised construction of hexagonal comb cell arrays; however, infrared and thermographic video observations of comb building in the present study failed to support the self-organisation hypothesis because bees were shown to be engaged in direct construction. Bees used their antennae, mandibles and legs in a regular sequence to manipulate the wax, while some bees supported their work by actively warming the wax. During the construction of hexagonal cells, the wax temperature was between 33.6 and 37.6 °C. This is well below 40 °C, i.e. the temperature at which wax is assumed to exist in the liquid equilibrium that is essential for self-organised building.

  9. Thermooptically tunable side-polished fiber comb filter and its application

    Microsoft Academic Search

    Kyung-Rak Sohn; Jae-Won Song

    2002-01-01

    Tunable side-polished fiber comb filters based on the thermooptic effect of a polymer layer inserted between a side-polished fiber and an overlay waveguide are presented. The thermal electrodes formed on a polymer layer control the refractive index of one and its index variation induces the shift in coupling wavelength by the phase change of an evanescent field at the overlay

  10. ADVANCES IN ATOMIC, MOLECULAR AND OPTICAL PHYSICS, VOL. 55 DIRECT FREQUENCY COMB

    E-print Network

    and SCOTT A. DIDDAMS2 1JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, University of Colorado, Boulder, Colorado 80309-0440, USA 2Time and Frequency Division . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Abstract Besides serving as a frequency counter or clockwork, an optical frequency comb can

  11. A ROOT-KNOT NEMATODE PATHOGENIC TO COCK'S COMB, CELOSIA ARGENTEA L

    Microsoft Academic Search

    S. A. ANWAR; A. ZIA; Q. SHAKEEL

    The presence of root-knot nematode, Meloidogyne incognita was assessed on roots and rhizosphere soil of cock's comb (Celosia argentea L.) planted in 5 lawns located at the campus of University of Agriculture, Faisalabad. The infected plants were stunted with galled and rotted roots. Four fungal pathogens including Fusarium, Pythium, Rhizoctonia and Sclerotia were isolated from nematode-fungal complex infected roots. Plant

  12. The inverted pendulum, interface phonons and optic Tamm states Nicolas Combe

    E-print Network

    The inverted pendulum, interface phonons and optic Tamm states Nicolas Combe Centre d that a parametric pendulum oscillates in the vicinity of its unstable equilibrium positions to the case of waves of an unstable equilibrium position using a parametric excita- tion (in the inverted pendulum experiment

  13. The inverted pendulum, interface phonons and optic Tamm states Nicolas Combe

    E-print Network

    Paris-Sud XI, Université de

    The inverted pendulum, interface phonons and optic Tamm states Nicolas Combe Centre d that a parametric pendulum oscillates in the vicinity of its unstable equilibrium positions to the case of waves of an unstable equilibrium position using a para- metric excitation (in the inverted pendulum experiment

  14. Collective control of the timing and type of comb construction by honey bees ( Apis mellifera )

    Microsoft Academic Search

    Stephen C. Pratt

    2004-01-01

    This review considers how a honey bee colony optimally controls the timing and type of new comb construction. Optimal timing requires bees to balance the energy costs of construction with the opportunity costs of lacking storage space during nectar flows. They do so by conditioning the start of building on (1) the attainment of a fullness threshold, and (2) the

  15. Fiber-laser-based frequency comb with a tunable repetition rate

    E-print Network

    Washburn, Brian

    . Newbury National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305 brianw. R. Telle, "Phase-locked carrier-envelope-offset frequency at 1560 nm," Opt. Express 12, 770-locked femtosecond-laser comb used for absolute optical frequency measurements," IEEE J.. Sel. Top. Quantum Electron

  16. Stresa, Italy, 25-27 April 2007 GAS DAMPING COEFFICIENT RESEARCH FOR THE MEMS COMB

    E-print Network

    Paris-Sud XI, Université de

    Stresa, Italy, 25-27 April 2007 GAS DAMPING COEFFICIENT RESEARCH FOR THE MEMS COMB LINEAR VIBRATION University, Heilongjiang Harbin 150001) ABSTRACT Silicon-MEMS gyroscope is an important part of MEMS ( Micro largely influences the performance of the MEMS gyroscope. Different air pressure causes different gas

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  18. Adaptive sampling dual terahertz comb spectroscopy using dual free-running femtosecond lasers

    PubMed Central

    Yasui, Takeshi; Ichikawa, Ryuji; Hsieh, Yi-Da; Hayashi, Kenta; Cahyadi, Harsono; Hindle, Francis; Sakaguchi, Yoshiyuki; Iwata, Tetsuo; Mizutani, Yasuhiro; Yamamoto, Hirotsugu; Minoshima, Kaoru; Inaba, Hajime

    2015-01-01

    Terahertz (THz) dual comb spectroscopy (DCS) is a promising method for high-accuracy, high-resolution, broadband THz spectroscopy because the mode-resolved THz comb spectrum includes both broadband THz radiation and narrow-line CW-THz radiation characteristics. In addition, all frequency modes of a THz comb can be phase-locked to a microwave frequency standard, providing excellent traceability. However, the need for stabilization of dual femtosecond lasers has often hindered its wide use. To overcome this limitation, here we have demonstrated adaptive-sampling THz-DCS, allowing the use of free-running femtosecond lasers. To correct the fluctuation of the time and frequency scales caused by the laser timing jitter, an adaptive sampling clock is generated by dual THz-comb-referenced spectrum analysers and is used for a timing clock signal in a data acquisition board. The results not only indicated the successful implementation of THz-DCS with free-running lasers but also showed that this configuration outperforms standard THz-DCS with stabilized lasers due to the slight jitter remained in the stabilized lasers. PMID:26035687

  19. Cavity-enhanced optical frequency comb spectroscopy: application to human breath

    E-print Network

    . Machado et al., "Detection of Lung Cancer by Sensor Array Analyses of Exhaled Breath," Am. J. Respir. CritCavity-enhanced optical frequency comb spectroscopy: application to human breath analysis Michael J://www.colorado.edu/YeLabs Abstract: Broad-bandwidth, high-spectral-resolution optical detection of human breath has identified

  20. Evidence for Paralytic Shellfish Poisons in the Freshwater Cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov

    Microsoft Academic Search

    W. W. CARMICHAEL; W. R. EVANS; Q. Q. YIN; P. BELL; E. MOCZYDLOWSKI

    1997-01-01

    Lyngbya wollei (Farlow ex Gomont) comb. nov., a perennial mat-forming filamentous cyanobacterium prev- alent in lakes and reservoirs of the southeastern United States, was found to produce a potent, acutely lethal neurotoxin when tested in the mouse bioassay. Signs of poisoning were similar to those of paralytic shellfish poisoning. As part of the Tennessee Valley Authority master plan for Guntersville

  1. Frequency Comb Vernier Spectroscopy for Broadband, High-Resolution, High-Sensitivity Absorption and Dispersion Spectra

    Microsoft Academic Search

    Christoph Gohle; Björn Stein; Albert Schliesser; Thomas Udem; Theodor W. Hänsch

    2007-01-01

    A femtosecond frequency comb provides a vast number of equidistantly spaced narrow band laser modes that can be simultaneously tuned and frequency calibrated with 15 digit accuracy. Our Vernier spectrometer utilizes all of theses modes in a massively parallel manner to rapidly record both absorption and dispersion spectra with a sensitivity that is provided by a high finesse broadband optical

  2. Low Phase Noise 250 MHz Repetition Rate Fiber fs Laser for Frequency Comb Applications

    Microsoft Academic Search

    T. Wilken; T. W. Hansch; R. Holzwarth; P. Adel; M. Mei

    2007-01-01

    Er3+ -doped fiber-lasers efficiently generate frequency-combs for optical frequency metrology. We have for the first time resolved the two main concerns against fiber lasers vs the well established Ti:Sa technology by increasing the repetition rate to 250 MHz and decreasing the carrier envelope offset phase noise well below 1 rad.

  3. Sex Education and Ideals

    ERIC Educational Resources Information Center

    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…

  4. Sex and Cognition.

    ERIC Educational Resources Information Center

    Kimura, Doreen

    This book describes the major differences between men and women in cognitive or problem-solving abilities and discusses the possible biological contributions to such differences. The book argues that sex differences in cognitive patterns and in motor skills arose out of complementary evolutionary histories of men and women and that evidence for…

  5. Child sex rings

    Microsoft Academic Search

    N J Wild; J M Wynne

    1986-01-01

    Details of 11 child sex rings identified in one working class community were obtained by interviewing investigating police officers and examining health and social services records. The rings contained 14 adult male perpetrators and 175 children aged 6-15 years. Most perpetrators used child ringleaders to recruit victims; others became a \\

  6. Let's talk about sex.

    PubMed

    Warriner, Jason; Power, Lisa

    In a bid to ensure UK adults know the facts when it comes to sexual health, the Department of Health and the Department for Children, Schools and Families, together with the National Chlamydia Screening Programme have launched the 'Sex. Worth Talking About' campaign. Jason Warriner and Lisa Power explore the crucial role that nurses can play in educating and empowering young adults. PMID:20081688

  7. SHBG (Sex Hormone Binding Globulin)

    MedlinePLUS

    ... as: Testosterone-estrogen Binding Globulin; TeBG Formal name: Sex Hormone Binding Globulin Related tests: Testosterone , Free Testosterone, ... know? How is it used? The test for sex hormone binding globulin (SHBG) is primarily ordered in ...

  8. Sex and Fertility After SCI

    MedlinePLUS

    Experts \\ Sex and Fertility After Spinal Cord Injury Topics Adult Injuries Spinal Cord Injury 101 The Basics of Spinal ... from Hospital to Home Spasticity, Physical Therapy-Lokomat Sex and Fertility After Spinal Cord Injury Coping with ...

  9. Making Healthy Decisions About Sex

    MedlinePLUS

    ... Listen Español Text Size Email Print Share For Teens: How to Make Healthy Decisions About Sex Article ... a new condom for every act of vaginal, anal, and oral sex throughout the entire sexual act ( ...

  10. Abnormal human sex chromosome constitutions

    SciTech Connect

    NONE

    1993-12-31

    Chapter 22, discusses abnormal human sex chromosome constitution. Aneuploidy of X chromosomes with a female phenotype, sex chromosome aneuploidy with a male phenotype, and various abnormalities in X chromosome behavior are described. 31 refs., 2 figs.

  11. The ABCs of Sex Ed.

    ERIC Educational Resources Information Center

    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)

  12. Sex education in Cyprus.

    PubMed

    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 Ministry of Education to make sex education a major agenda due to the AIDs threat. This resulted in FPAC's being identified as the primary source for extracurricular sex education and teacher training. FPAC has also set up liaisons with the Educational Council and the Parliamentary Education Committee. PMID:12343181

  13. XUV frequency-comb metrology on the ground state of helium

    SciTech Connect

    Kandula, Dominik Z.; Gohle, Christoph; Pinkert, Tjeerd J.; Ubachs, Wim; Eikema, Kjeld S. E. [LaserLaB Amsterdam, VU University, De Boelelaan 1081, NL-1081HV Amsterdam (Netherlands)

    2011-12-15

    The operation of a frequency comb at extreme ultraviolet (xuv) wavelengths based on pairwise amplification and nonlinear upconversion to the 15th harmonic of pulses from a frequency-comb laser in the near-infrared range is reported. It is experimentally demonstrated that the resulting spectrum at 51 nm is fully phase coherent and can be applied to precision metrology. The pulses are used in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p {sup 1} P{sub 1} states. Laser ionization by auxiliary 1064 nm pulses is used to detect the excited-state population, resulting in a cosine-like signal as a function of the repetition rate of the frequency comb with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium atom as a precision phase ruler, yields an estimated timing jitter between the two upconverted-comb laser pulses of 50 attoseconds, which is equivalent to a phase jitter of 0.38 (6) cycles in the xuv at 51 nm. This sets a quantitative figure of merit for the operation of the xuv comb and indicates that extension to even shorter wavelengths should be feasible. The helium metrology investigation results in transition frequencies of 5 740 806 993 (10) and 5 814 248 672 (6) MHz for excitation of the 1s4p and 1s5p {sup 1} P{sub 1} states, respectively. This constitutes an important frequency measurement in the xuv, attaining high accuracy in this windowless part of the electromagnetic spectrum. From the measured transition frequencies an eight-fold-improved {sup 4}He ionization energy of 5 945 204 212 (6) MHz is derived. Also, a new value for the {sup 4}He ground-state Lamb shift is found of 41 247 (6) MHz. This experimental value is in agreement with recent theoretical calculations up to order m{alpha}{sup 6} and m{sup 2}/M{alpha}{sup 5}, but with a six-times-higher precision, therewith providing a stringent test of quantum electrodynamics in bound two-electron systems.

  14. Selection and amplification of modes of an optical frequency comb using a femtosecond laser injection-locking technique

    SciTech Connect

    Moon, H. S.; Kim, E. B.; Park, S. E.; Park, C. Y. [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Division of Physical Metrology, Korea Research Institute of Standards and Science, Daejeon 305-340 (Korea, Republic of)

    2006-10-30

    The authors have demonstrated the selection and the amplification of the components of an optical frequency comb using a femtosecond laser injectionlocking technique. The author used a mode-locked femtosecond Ti:sapphire laser as the master laser and a single-mode diode laser as the slave laser. The femtosecond laser injection-locking technique was applied to a filter for mode selection of the optical frequency comb and an amplifier for amplification of the selected mode. The authors could obtain the laser source selected only the desired mode of the optical frequency comb and amplified the power of the selected modes several thousand times.

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

    E-print Network

    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$^8$.

  16. Effect of partial comb and wattle trim on pullet behavior and thermoregulation,1.

    PubMed

    Hester, P Y; Al-Ramamneh, D S; Makagon, M M; Cheng, H W

    2015-05-01

    The wattles and comb of chickens are important for thermoregulation allowing for heat exchange during high temperatures. These integumentary tissues are sometimes trimmed to prevent tears if caught on cage equipment and to also improve feed efficiency; however, the procedure itself could be painful to chicks. Our objective was to determine the effect of trimming the comb and wattles on behavior, BW, feed usage, and the surface temperature of pullets. The wattles and comb of Leghorns were partially trimmed at 21?d age (n = 6 cages, 13 chicks each) with another 6 cages serving as controls. Behaviors were recorded 3 times daily for 1?h starting at 0800, 1200, and 1500 using instantaneous scan sampling observations conducted every 5 min prior to, on the d of, and after the trim. Group BW at 21, 28, and 36?d age and the amount of feed used for 7?d beginning at 21 and 29?d age were measured per cage. At 1300?h on d before and after the trim, thermal images of the pullet's beak, comb, eye, wattle, and shank were randomly taken on 3 pullets/cage. Smaller proportions of trimmed chicks were eating and greater proportions were sitting on the d of the trim as compared to the controls with the opposite trend occurring on 4?d post-trim (treatment by age interaction, P = 0.03 and 0.0001, respectively). Standing behavior differed only on the d of the trim where smaller proportions of trimmed pullets stood as compared to intact controls (treatment by age interaction, P = 0.0002). Trimming the comb and wattles did not affect preening, running, BW, feed utilization, and the surface temperature of the pullet. The indices of behavior suggest that on the d of the trim, pullets may have experienced temporary distress, but they returned to normal behavior by 5?h post-trim with no long-term effect on BW, feed usage, or surface body temperature. PMID:25796274

  17. Morphology and phase diagram of comb block copolymer Am+1(BC)m.

    PubMed

    Jiang, Zhibin; Wang, Rong; Xue, Gi

    2009-05-28

    The morphologies and the phase diagram of comb copolymer Am+1(BC)m are investigated by the self-consistent field theory. By changing the volume fractions of the blocks, the interaction parameters between the different blocks, and the side chain number, nine phases are found, including the two-colored lamellar phase, three-colored lamellar phase, hexagonal lattice phase, core shell hexagonal lattice phase, two interpenetrating tetragonal lattice, core shell tetragonal lattice, lamellar phase with beads inside, lamellar phase with alternating beads, and disordered phase. The phase diagrams are constructed for Am+1(BC)m with different side chain numbers of m=1, 2, 3, and 5. Due to the asymmetric topology of comb copolymer Am+1(BC)m, the phases and the diagrams are very different from linear ABC triblock copolymer or star ABC triblock copolymer. When the volume fraction of one of the blocks is the domination, the (core shell) hexagonal phase or two interpenetrating tetragonal lattice can form, depending on which block dominates and the interaction between the blocks. The (core shell) hexagonal phase easily forms at the corner of the block A (fA>or=0.5). The side chain number m affects the phase diagram largely due to the fact that the architecture of a comb copolymer is not invariant under the interchange between the three different monomers. Due to the connectivity of the blocks B and the inner blocks A, Am+1(BC)m comb copolymers with the longer main chain A or longer side chain with short block C, i.e., longer block B, are difficult to phase separate. The results are helpful to design nano- or biomaterials with complex architecture or tailor the phase behavior of comb copolymers. PMID:19422259

  18. Generation of green frequency comb from chirped ?(2) nonlinear photonic crystals

    NASA Astrophysics Data System (ADS)

    Lai, C.-M.; Chang, K.-H.; Yang, Z.-Y.; Fu, S.-H.; Tsai, S.-T.; Hsu, C.-W.; Yu, N. E.; Boudrioua, A.; Kung, A. H.; Peng, L.-H.

    2014-12-01

    Spectrally broad frequency comb generation over 510-555 nm range was reported on chirped quasi-phase-matching (QPM) ?(2) nonlinear photonic crystals of 12 mm length with periodicity stepwise increased from 5.9 ?m to 7.1 ?m. 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.

  19. SEX CHROMOSOMES IN FLOWERING PLANTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sex chromosomes in dioecious and polygamous plants evolved as a mechanism for ensuring outcrossing to increase genetic variation in the offspring. Sex specificity has evolved in 75% of plant families by male sterile or female sterile mutations, but well defined heteromorphic sex chromosomes are know...

  20. Liberating genetic variance through sex

    E-print Network

    Otto, Sarah

    Liberating genetic variance through sex Andrew D. Peters and Sarah P. Otto* Summary Genetic of reproduction. Indeed, it has long been thought that sex enhances fitness variation and that this explains that sex need not always increase genetic variation in fitness. In particular, if fitness interactions

  1. Sex Stereotyping Hurts All Kids.

    ERIC Educational Resources Information Center

    Cutright, Melitta J.

    1991-01-01

    Sex stereotyping (raising boys and girls to be different because of their sex) begins at birth. The article reviews studies detailing sex stereotyping practices and offers suggestions on what parents can do to avoid them. A list of suggestions for raising children in a nonsexist way is included. (SM)

  2. The control of sex chromatin

    Microsoft Academic Search

    O. J. Miller; Dorothy Warburton

    1968-01-01

    Sex chromatin counts for more than 50 individuals with three or more X chromosomes in their complement were analyzed. The observed distribution of cells with 0, 1, 2,...n sex chromatin bodies in polysomic-X individuals was compared with the binomial distribution expected on the assumption of a constant probability that an X chromosome will form a visible sex chromatin body. The

  3. Attitudes about Sex Selection and Sex Preference in Iranian Couples Referred for Sex Selection Technology

    PubMed Central

    Ahmadi, Seyedeh Fatemeh; Shirzad, Mahdi; Kamali, Koorosh; Ranjbar, Fahimeh; Behjati-Ardakani, Zohreh; Akhondi, Mohammad Mehdi

    2015-01-01

    Background Gender preference is prevalent in some communities and using medical techniques to choose the baby's sex may cause the gender discrimination and gender imbalance in communities. Therefore, evaluating the gender preferences and attitudes towards using sex selection technologies seems to be necessary. Methods This cross-sectional study was conducted in Avicenna Fertility Center. Participants were 100 women with one child who were referred for sex selection. Data were collected through self-developed questionnaires. The questions were designed by the researchers at the experts’ panel. To determine the validity of the questionnaire, the viewpoints of professors specialized in these issues were obtained. The statistical analysis of the data was performed using SPSS software (Version 11.5), and p < 0.05 was considered significant. Results Tendency toward the male was more than female sex (55.5% male, 15.5% female and 28.5% no tendency). Majority of participants agreed with sex selection with medical reason and sex selection in order to balance the family. Women's level of education had positive effect on agreements to fetal sex selection with medical and non-medical reasons (p < 0.001). Conclusion Although gender preferences were toward the male sex but this preference was not very strong. Most participants agreed with non-medical sex selection for balancing the sex composition of their children. It doesn't seem that non-medical sex selection for family balancing causes severe sex imbalance in Iran. PMID:25717434

  4. [Sex and love].

    PubMed

    Winaver, D

    2002-04-01

    Sex is established as soon as spermatozoid and ovule have met. Except for rare cases of ambiguity, you clearly see at birth whether the baby is a boy or a girl. This mere factual difference evolves into sexual identity through childhood and fully blossoms in teenagers. Is sexual maturity happily completed then? Not always. Unrational sexual pulsions and survival instincts belong to the whole animal species but for man's child, as soon as he is born and until he dies, feelings will be intimately involved with sexuality in all its various stages. Teenagers' sexuality is both the end stage of childhood sexuality, being as such full of psychological traps, and the beginning of a search for a balance between sex and love, which is perhaps our modern way of trying to achieve self-fulfilment and happiness. PMID:12043506

  5. Frequency-reconfigurable terahertz wireless transmission using an optical frequency comb based on radio-over-fiber technology

    NASA Astrophysics Data System (ADS)

    Zhang, Chan; Ning, Tigang; Li, Jing; Li, Chao; Ma, Shaoshuo

    2014-12-01

    We propose a prototype for frequency-reconfigurable terahertz (THz) wireless transmission using an optical comb based on radio-over-fiber technology. In the proposal, an electro-absorption modulator (EAM) followed by a phase modulator and an intensity modulator are used to generate a flat optical comb with a tunable frequency spacing. Then, a different THz signal can be generated by photo-mixing of optical two-tone signals from the comb lines. In the scheme, we obtain 46 comb lines within a 1-dB power deviation with an interval of about 10 GHz, and a THz up to 440 GHz is obtained. Moreover, a much higher bandwidth can be easily reached by adjusting the driving signal of the EAM. The feasibility and tunability of the proposed scheme are confirmed by the simulations. This method shows a simple cost-efficient configuration and good performance over long-distance delivery.

  6. Femtosecond spectroscopy of acoustic frequency combs in the 100-GHz frequency range in Al/Si membranes

    NASA Astrophysics Data System (ADS)

    Grossmann, Martin; Klingele, Matthias; Scheel, Patricia; Ristow, Oliver; Hettich, Mike; He, Chuan; Waitz, Reimar; Schubert, Martin; Bruchhausen, Axel; Gusev, Vitalyi; Scheer, Elke; Dekorsy, Thomas

    2013-11-01

    Acoustic frequency combs are optically excited and detected in silicon membranes covered with thin aluminum layers by femtosecond pump-probe spectroscopy. The various frequency combs consist of 11 up to 45 modes ranging in frequency from 10 up to 500 GHz. Evaluating the different modes of the combs allows us to quantify the dynamic properties of this two-layer system with great precision. Deviations of the frequencies of higher modes from a linear relation can be quantitatively understood. The time domain traces show clearly defined pulses which are detected in regular time intervals after each roundtrip in the acoustic cavity formed by the membrane and the metal film. By analyzing the individual reflected pulses and their evolution in time, damping times for the whole frequency range are determined. We analytically derive a deviation of the individual comb modes from integer values of the fundamental frequency which is corroborated by the experiments.

  7. The SW Sex enigma

    E-print Network

    Dhillon, V S; Marsh, T R

    2012-01-01

    The SW Sex stars are a class of cataclysmic variables, originally identified because they shared a number of enigmatic properties - most notably, single-peaked emission lines instead of the double-peaked lines one would expect from their high-inclination accretion discs. We present high time-resolution spectrophotometry of the eclipsing nova-like variables SW Sex and DW UMa, two of the founding members of the SW Sex class. Both systems show single-peaked Balmer and HeII 4686A emission lines that appear to originate from a region in the disc that lies close to, but downstream of, the bright spot. The emission-line light curves are consistent with the finding from X-ray and ultraviolet observations that we predominantly see the flared disc rim and the unobscured back portion of the disc in these systems. In DW UMa, the HeII 4686A emission line originates from close to the white dwarf and exhibits flaring. Such flares have been used to argue for magnetically-channelled accretion, as in the intermediate polars, b...

  8. Generation of Optical Combs in a WGM Resonator from a Bichromatic Pump

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry V.; Yu, Nan; Matsko, Andrey B.

    2010-01-01

    Optical combs generated by a monolithic resonator with Kerrmedium can be used in a number of applications, including orbital clocks and frequency standards of extremely high accuracy, such as astronomy, molecular spectroscopy, and the like. The main difficulty of this approach is the relatively high pump power that has to be used in such devices, causing undesired thermorefractive effects, as well as stimulated Raman scattering, and limiting the optical comb quality and utility. In order to overcome this problem, this innovation uses a different approach to excitation of the nonlinear oscillations in a Kerr-nonlinear whispering gallery mode (WGM) resonator and generation of the optical comb. By coupling to the resonator two optical pump frequencies instead of just one, the efficiency of the comb source can be increased considerably. It therefore can operate in a lowerpower regime where the undesirable effects are not present. This process does not have a power threshold; therefore, the new optical component can easily be made strong enough to generate further components, making the optical comb spread in a cascade fashion. Additionally, the comb spacing can be made in an arbitrary number of the resonator free spectral ranges (FSR). The experimental setup for this innovation used a fluorite resonator with OMEGA= 13.56 GHz. This material has very low dispersion at the wavelength of 1.5 microns, so the resonator spectrum around this wavelength is highly equidistant. Light was coupled in and out of the resonator using two optical fibers polished at the optimal coupling angle. The gap between the resonator and the fibers, affecting the light coupling and the resonator loading, was controlled by piezo positioners. The light from the input fiber that did not go into the resonator reflected off of its rim, and was collected by a photodetector. This enabled observation and measurement of the (absorption) spectrum of the resonator. The input fiber combined light from two lasers centered at around 1,560 nanometers. Both laser frequencies were simultaneously scanned around the selected WGMs of the same family. However, they were separated by one, two, three, or ten FSRs. This was achieved by fine-tuning each laser frequency offset until the selected resonances overlap on the oscilloscope screen. The resonator quality factor Q = 7 x 10(exp 7) was relatively low to increase the linewidth and, therefore, the duty cycle of both lasers simultaneously coupled into their WGMs. The optical spectrum analyzer (OSA) connected to the output fiber was continuously acquiring data, asynchronously with the laser scan. The instrument was set to retain the peak power values; therefore, a trace recorded for a sufficiently long period of time reflected the situation with both lasers maximally coupled to the WGMs.

  9. Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy

    NASA Astrophysics Data System (ADS)

    Zajnulina, M.; Boggio, J. M. Chavez; Böhm, M.; Rieznik, A. A.; Fremberg, T.; Haynes, R.; Roth, M. M.

    2015-07-01

    We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrödinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.

  10. Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy

    NASA Astrophysics Data System (ADS)

    Zajnulina, M.; Boggio, J. M. Chavez; Böhm, M.; Rieznik, A. A.; Fremberg, T.; Haynes, R.; Roth, M. M.

    2015-05-01

    We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrödinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.

  11. Sex Typing and the Avoidance of Cross-Sex Behavior

    Microsoft Academic Search

    Sandra L. Bem; Ellen Lenney

    1976-01-01

    This article presents evidence for the hypothesis that cross-sex behavior is motivationally problematic for sex-typed individuals and that they actively avoid it as a result. In particular, when asked to indicate which of a series of paired activities they would prefer to perform for pay while being photographed, sex-typed subjects were more likely than either androgynous or sexreversed subjects to

  12. Hierarchical, multilayered cell walls reinforced by recycled silk cocoons enhance the structural integrity of honeybee combs.

    PubMed

    Zhang, Kai; Duan, Huiling; Karihaloo, Bhushan L; Wang, Jianxiang

    2010-05-25

    We reveal the sophisticated and hierarchical structure of honeybee combs and measure the elastic properties of fresh and old natural honeycombs at different scales by optical microscope, environmental scanning electron microscope, nano/microindentation, and by tension and shear tests. We demonstrate that the comb walls are continuously strengthened and stiffened without becoming fragile by the addition of thin wax layers reinforced by recycled silk cocoons reminiscent of modern fiber-reinforced composite laminates. This is done to increase its margin of safety against collapse due to a temperature increase. Artificial engineering honeycombs mimic only the macroscopic geometry of natural honeycombs, but have yet to achieve the microstructural sophistication of their natural counterparts. The natural honeycombs serve as a prototype of truly biomimetic cellular materials with hitherto unattainable improvement in stiffness, strength, toughness, and thermal stability. PMID:20439765

  13. Implementation of a single femtosecond optical frequency comb for rovibrational cooling

    SciTech Connect

    Shi, W.; Malinovskaya, S. [Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030 (United States)

    2010-07-15

    We show that a single femtosecond optical frequency comb may be used to induce two-photon transitions between molecular vibrational levels to form ultracold molecules (e.g., KRb). The phase across an individual pulse in the pulse train is sinusoidally modulated with a carefully chosen modulation amplitude and frequency. Piecewise adiabatic population transfer is fulfilled to the final state by each pulse in the applied pulse train, providing a controlled population accumulation in the final state. Detuning the pulse train carrier and modulation frequency from one-photon resonances changes the time scale of molecular dynamics but leads to the same complete population transfer to the ultracold state. A standard optical frequency comb with no modulation is shown to induce similar dynamics, leading to rovibrational cooling.

  14. Combs: open source python library for RVE generation. Application to microscale diffusion simulations in cementitious materials

    NASA Astrophysics Data System (ADS)

    Bourcier, C.; Dridi, W.; Chomat, L.; Laucoin, E.; Bary, B.; Adam, E.

    2014-06-01

    The developed tools are used to create a representative volume element (RVE) of cementitious materials and then assess the diffusive properties. The algorithms developed in Combs target a fast placement of the inclusions and a fast generation of the RVE shape and its mesh. Two application cases are considered: the unaltered material diffusivity and the degraded material diffusivity. The first case of application focuses on the description of the capillary porosity. The second application case focuses on the description of the degradation of cementitious material (mineral and porosity) and the diffusive properties associated. The reliability of the analytical effective medium approximations (MT and SC) is confirmed from 3D finite elements (FE) calculations performed on a matrix-inclusions microstructure obtained by RVE generation with Combs. The results also show the need to take into account the percolation behavior.

  15. Resonant light scattering of a laser frequency comb by a quantum dot

    NASA Astrophysics Data System (ADS)

    Konthasinghe, K.; Peiris, M.; Muller, A.

    2014-08-01

    We investigate the spectral and temporal properties of light scattered near resonantly by a single quantum dot when the incident laser field is a frequency comb consisting of a superposition of monochromatic waves equidistant in frequency. Such fields encompass those generated by, e.g., a periodically pulsed laser. A general theoretical treatment for the calculation of first- and second-order correlation functions is given which takes account of spectral diffusion through a slowly varying detuning from resonance, permitting accurate comparison with experiments. We explore the two distinct regimes in which the frequency-comb separation is either larger or smaller than the radiative decay rate. We verify the validity of our calculations by a comparison with experimental data for the case of a bichromatic field and discuss the manifestation of phase coherence between the incoming field and the scattered single-photon wave packet.

  16. Novel active comb-shaped dry electrode for EEG measurement in hairy site.

    PubMed

    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. PMID:25137719

  17. Generation and photonic guidance of multi-octave optical-frequency combs.

    PubMed

    Couny, F; Benabid, F; Roberts, P J; Light, P S; Raymer, M G

    2007-11-16

    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 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) infrared laser, producing 12-nanosecond-duration pulses. This represents a reduction by six orders of magnitude in the required laser powers over previous equivalent techniques and opens up a robust and much simplified route to synthesizing attosecond pulses. PMID:18006741

  18. Frequency-comb-referenced mid-infrared source for high-precision spectroscopy.

    PubMed

    Peltola, Jari; Vainio, Markku; Fordell, Thomas; Hieta, Tuomas; Merimaa, Mikko; Halonen, Lauri

    2014-12-29

    We report on a tunable continuous-wave mid-infrared optical parametric oscillator (OPO), which is locked to a fully stabilized near-infrared optical frequency comb using a frequency doubling scheme. The OPO is used for 40 GHz mode-hop-free, frequency-comb-locked scans in the wavelength region between 2.7 and 3.4 ?m. We demonstrate the applicability of the method to high-precision cavity-ring-down spectroscopy of nitrous oxide (N2O) and water (H2O) at 2.85 µm and of methane (CH4) at 3.2 ?m. PMID:25607205

  19. Evanescent-wave comb spectroscopy of liquids with strongly dispersive optical fiber cavities

    NASA Astrophysics Data System (ADS)

    Avino, S.; Giorgini, A.; Salza, M.; Fabian, M.; Gagliardi, G.; De Natale, P.

    2013-05-01

    We demonstrate evanescent-wave fiber cavity-enhanced spectroscopy in the liquid phase using a near-infrared frequency comb. Exploiting strong fiber-dispersion effects, we show that liquid absorption spectra can be recorded without any external dispersive element. The fiber cavity is used both as sensor and spectrometer. The resonance modes are frequency locked to the comb teeth while the cavity photon lifetime is measured over 155 nm, from 1515 nm to 1670 nm, where absorption bands of liquid polyamines are detected as a proof of concept. Our fiber spectrometer lends itself to in situ, real-time chemical analysis in environmental monitoring, biomedical assays, and micro-opto-fluidic systems.

  20. A Laser Frequency Comb System for Absolute Calibration of the VTT Echelle Spectrograph

    NASA Astrophysics Data System (ADS)

    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.

  1. Performance of a laser frequency comb calibration system with a high-resolution solar echelle spectrograph

    NASA Astrophysics Data System (ADS)

    Doerr, H.-P.; Kentischer, T. J.; Steinmetz, T.; Probst, R. A.; Franz, M.; Holzwarth, R.; Udem, Th.; Hänsch, T. W.; Schmidt, W.

    2012-09-01

    Laser frequency combs (LFC) provide a direct link between the radio frequency (RF) and the optical frequency regime. The comb-like spectrum of an LFC is formed by exact equidistant laser modes, whose absolute optical frequencies are controlled by RF-references such as atomic clocks or GPS receivers. While nowadays LFCs are routinely used in metrological and spectroscopic fields, their application in astronomy was delayed until recently when systems became available with a mode spacing and wavelength coverage suitable for calibration of astronomical spectrographs. We developed a LFC based calibration system for the high-resolution echelle spectrograph at the German Vacuum Tower Telescope (VTT), located at the Teide observatory, Tenerife, Canary Islands. To characterize the calibration performance of the instrument, we use an all-fiber setup where sunlight and calibration light are fed to the spectrograph by the same single-mode fiber, eliminating systematic effects related to variable grating illumination.

  2. Phase-locked widely tunable optical single-frequency generator based on a femtosecond comb.

    PubMed

    Schibli, T R; Minoshima, K; Hong, E L; Inaba, H; Bitou, Y; Onae, A; Matsumoto, H

    2005-09-01

    We present an arbitrary optical single-frequency generator based on a femtosecond optical frequency comb. The functions of this device are comparable to those of a radio-frequency synthesizer. However, this device operates at hundreds of terahertz. The absolute frequency accuracy of this synthesizer is approximately 1 kHz at a 282 THz carrier frequency. The stability is approximately 2 x 10(-14) at 100 s, and the tuning speed exceeds 30 GHz/s. This source demonstrates the integration of a phase-locked optical comb into a versatile and easy-to-use system for the generation of tunable, absolute optical frequencies. By using downconversion, one could generate tunable terahertz frequencies that are phase locked to a microwave reference, such as a Cs atomic clock, and high-precision interferometry could benefit greatly from the stability and accuracy of this widely tunable source. PMID:16190458

  3. Calibration of an Astrophysical Spectrograph with an Astro-comb in the Visible Spectral Range

    NASA Astrophysics Data System (ADS)

    Li, Chih-Hao; Glenday, Alex; Phillips, David; Korzennik, Sylvain; Noah Chang, Guoqing; Chen, Li-Jin; Benedick, Andrew; Kaertner, Franz; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald

    2011-06-01

    Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. To find a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude improvement in state-of-the-art radial velocity spectroscopy is necessary. An astro-comb, the combination of an ocatve-spanning laser frequency comb with a Fabry-Perot cavity, producing evenly spaced frequency markers with the potential for large wavelength coverage is a promising avenue towards improved wavelength calibration. Here we demonstrate the calibration of a high-resolution astrophysical spectrograph below the 50 cm/s level in the visible spectral range around 420 nm using an octave-spanning Ti:Sapphire laser and an ultra-low dispersion Fabry-Perot filter cavity adjusted for a mode spacing of approximately 50 GHz. Modeling of spectrograph response function and overall system stability and reproducibility will be described.

  4. Complete characterization of a broadband high-finesse cavity using an optical frequency comb.

    PubMed

    Schliesser, Albert; Gohle, Christoph; Udem, Thomas; Hänsch, Theodor W

    2006-06-26

    We demonstrate a new method to simultaneously measure spectrally resolved dispersion and losses (finesse) of a passive optical cavity over the entire bandwidth of an optical frequency comb. To this end, we record and analyze the spectral Moiré pattern between the perfectly equidistant frequency comb emitted from a Ti:Sapphire laser and the longitudinal modes of the passive cavity as a function of the laser's carrier-envelope-offset phase slippage (ø)CE. In the group-delay dispersion measurement of additionally introduced optical elements we verify a 2fs(2) accuracy in a 2THz resolution bandwidth and find good agreement of the measured performance and the target design of a high reflectance dielectric mirror. The sensitivity of the method is essentially equivalent to a cavity ring down technique allowing us also to readily observe signatures of atmospheric gas species. PMID:19516768

  5. Self referenced Yb-fiber-laser frequency comb using a dispersion micromanaged tapered holey fiber.

    PubMed

    Pal, Parama; Knox, Wayne H; Hartl, Ingmar; Fermann, Martin E

    2007-09-17

    We demonstrate a fully stabilized frequency comb in the 1mum spectral region based on an Yb-fiber oscillator and a cladding pumped chirped pulse Yb-fiber amplifier whose output is spectrally broadened in a dispersion micromanaged holey fiber. The dispersion micromanaged fiber is used to generate efficient, low noise spectral components at 523nm which are heterodyned with the second harmonic of the amplifier output for standard f-to-2f self-referenced carrier envelope offset frequency detection. For comb stabilization we phase-lock this offset frequency and the oscillator repetition frequency simultaneously to an RF reference by feedback controlling the oscillator pump diode current and the driving voltage of an intracavity piezo-electric fiber stretcher respectively. PMID:19547582

  6. Impact of dispersion on amplitude and frequency noise in a Yb-fiber laser comb.

    PubMed

    Nugent-Glandorf, Lora; Johnson, Todd A; Kobayashi, Yohei; Diddams, Scott A

    2011-05-01

    We describe a Yb-fiber-based laser comb, with a focus on the relationship between the net-cavity dispersion and frequency noise on the comb. While tuning the net-cavity dispersion from anomalous to normal, we measure the relative intensity noise, offset frequency (f(CEO)) linewidth, and the resulting frequency noise spectrum on the f(CEO). We find that the laser operating at zero net-cavity dispersion has many advantages, including an approximately 100× reduction in free-running f(CEO) linewidth and frequency noise power spectral density when compared to the normal-dispersion regime. At the zero-dispersion point, we demonstrate a phase-locked f(CEO) beat with low residual noise. PMID:21540933

  7. Asymptotic Capacity of Wireless Ad Hoc Networks with Realistic Links under a Honey Comb Topology

    E-print Network

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  9. Invasive Species Fact Sheets: Carp, Snail, Aphid, Comb Jelly, Chocolate Vine

    NSDL National Science Digital Library

    This resource from ATEEC provides a number of fact sheets on invasive species which may be printed out or used as presentation material. The species described here are the big head carp, the giant African snail, the balsam wooly aphid, the comb jelly and the chocolate vine. The lesson plan is available for download as a PDF; users must create a free, quick login with ATEEC to access the materials.

  10. Micro robot system with moving micro-car driven by electrostatic comb-drive actuators

    Microsoft Academic Search

    Phuc Hong Pham; Lam Bao Dang; Hung Ngoc Vu

    2010-01-01

    This paper describes a silicon micro robot system (MRS) that is capable of driving micro-cars in different directions based\\u000a on a ratchet mechanism and electrostatic comb-drive actuators. Lateral movement of the ratchet racks makes the micro-car move\\u000a in the perpendicular direction with different velocities. Based on MEMS technology, the MRS described in this article was\\u000a fabricated from a silicon on

  11. Monolithic 2-D scanning mirror using self-aligned angular vertical comb drives

    Microsoft Academic Search

    Jongbaeg Kim; Dane Christensen; Liwei Lin

    2005-01-01

    We have demonstrated microfabricated, monolithic two degrees of freedom (two-dimensional) electrostatic torsional mirrors using a three-mask process on silicon-on-insulator wafer with a single plastic deformation step. The mirror operated independently in two orthogonal directions as controlled by two sets of self-aligned angular vertical combs. The measured dynamic performance showed resonant frequencies of 10.56 and 1.54 kHz with optical scanning angles

  12. Frequency comb generation beyond the Lugiato–Lefever equation: multi-stability and super cavity solitons

    NASA Astrophysics Data System (ADS)

    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.

  13. A Design Method of In-plane MEMS Electret Energy Harvester with Comb Drives

    NASA Astrophysics Data System (ADS)

    Fu, Qianyan; Suzuki, Yuji

    2014-11-01

    In this report, a design method is proposed for in-plane MEMS electrostatic energy harvesters with comb drives. Dependent on the device layer thickness and the achievable aspect ratio of the DRIE process, either the overlapping-area-change or the gap-closing converter has higher output power than the other. Two prototypes of MEMS electret energy harvesters are developed to verify the present design method.

  14. Wavelength Multicasting via Frequency Comb Generation in a Bandwidth-Enhanced Fiber Optical Parametric Mixer

    Microsoft Academic Search

    Bill P.-P. Kuo; Evgeny Myslivets; Nikola Alic; Stojan Radic

    2011-01-01

    We demonstrate a self-seeded multicasting device ca- pable of delivering a large number of signal integrity preserving spectrally-distinct copies. The new multicasting device relies on ef- ficient higher-order mixing in a two-pump parametric mixer. Pre- cise dispersion engineering was deployed to generate a frequency- comb spanning over a 140-nm band, and resulted in the creation of more than 60 spectral

  15. The fractional Fokker-Planck equation on comb-like model

    NASA Astrophysics Data System (ADS)

    Zahran, M. A.; Abulwafa, E. M.; Elwakil, S. A.

    2003-05-01

    The fractional Fokker-Planck equation, were used to describe the anomalous diffusion in external fields, is derived using a comb-like structure as a background model. For the force-free case, the distribution function associated with space dependence diffusion coefficient along the backbone of the structure are obtained in a closed form of H-function. The operator method has been used to solve the fractional Fokker-Planck equation taking the external field into account.

  16. Surface and bulk- micromachined two-dimensional scanner driven by angular vertical comb actuators

    Microsoft Academic Search

    Wibool Piyawattanametha; Pamela R. Patterson; Dooyoung Hah; Hiroshi Toshiyoshi; Ming C. Wu

    2005-01-01

    In this paper, we present the design, fabrication, and measurements of a two-dimensional (2-D) optical scanner with electrostatic angular vertical comb (AVC) actuators. The scanner is realized by combining a foundry-based surface-micromachining process (Multi-User MEMS Processes-MUMPs) with a three-mask deep-reactive ion-etching (DRIE) postfabrication process. The surface-micromachining provides versatile mechanical design and electrical interconnect while the bulk micromachining offers high-aspect ratio

  17. Ciliary reversal without rotation of axonemal structures in ctenophore comb plates

    PubMed Central

    1981-01-01

    We have used a newly discovered reversal response of ctenophore comb plates to investigate the structural mechanisms controlling the direction of ciliary bending. High K+ concentrations cause cydippid larvae of the ctenophore Pleurobrachia to swim backward. High-speed cine films of backward-swimming animals show a 180 degree reversal in beat direction of the comb plates. Ion substitution and blocking experiments with artificial seawaters demonstrate that ciliary reversal is a Ca++-dependent response. Comb plate cilia possess unique morphological markers for numbering specific outer-doublet microtubules and identifying the sidedness of the central pair. Comb plates of forward- and backward-swimming ctenophores were frozen in different stages of the beat cycle by an "instantaneous fixation" method. Analysis of transverse and longitudinal sections of instantaneously fixed cilia showed that the assembly of outer doublets does not twist during ciliary reversal. This directly confirms the existence of radial switching mechanism regulating the sequence of active sliding on opposite sides of the axoneme. We also found that the axis of the central pair always remains perpendicular to the plane of bending; more importantly, the ultrastructural marker showed that the central pair does not rotate during a 180 degree reversal in beat direction. Thus, the orientation of the central pair does not control the direction of ciliary bending (i.e., the pattern of active sliding around the axoneme). We discuss the validity of this finding for three-dimensional as well as two-dimensional ciliary beat cycles and conclude that models of central-pair function based on correlative data alone must now be re- examined in light of these new findings on causal relations. PMID:6114102

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

    NASA Astrophysics Data System (ADS)

    Raith, Philipp; Ott, Christian; Anderson, Christopher P.; Kaldun, Andreas; Meyer, Kristina; Laux, Martin; Zhang, Yizhu; Pfeifer, Thomas

    2013-03-01

    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.

  19. Do Bees and Hornets Use Acoustic Resonance in Order to Monitor and Coordinate Comb Construction?

    Microsoft Academic Search

    David J. Bergman; Jacob S. Ishay

    2007-01-01

    We propose that social hornets and bees, who construct large arrays (known as combs) of cells for hatching and brooding their\\u000a offspring, exploit ultrasonic acoustic resonances in those cells in order to implement the accurate honeycomb structure exhibited\\u000a by those arrays. This idea is supported by a number of theoretical considerations, including a detailed analysis of the spectrum\\u000a of lateral

  20. High-accuracy absolute distance measurement using frequency comb referenced multiwavelength source

    SciTech Connect

    Salvade, Yves; Schuhler, Nicolas; Leve-circumflexque, Samuel; Le Floch, Sebastien

    2008-05-10

    We propose a new approach to multiple-wavelength interferometry, targeted to high bandwidth absolute distance measurement, with nanometer accuracy over long distances. Two cw lasers are stabilized over a wide range of frequency intervals defined by an optical frequency comb, thus offering an unprecedented large choice of synthetic wavelengths. By applying a superheterodyne detection technique, we demonstrated experimentally an accuracy of 8 nm over 800 mm for target velocities up to 50 mm/s.

  1. High-accuracy absolute distance measurement using frequency comb referenced multiwavelength source.

    PubMed

    Salvadé, Yves; Schuhler, Nicolas; Lévêque, Samuel; Le Floch, Sébastien

    2008-05-10

    We propose a new approach to multiple-wavelength interferometry, targeted to high bandwidth absolute distance measurement, with nanometer accuracy over long distances. Two cw lasers are stabilized over a wide range of frequency intervals defined by an optical frequency comb, thus offering an unprecedented large choice of synthetic wavelengths. By applying a superheterodyne detection technique, we demonstrated experimentally an accuracy of 8 nm over 800 mm for target velocities up to 50 mm/s. PMID:18470268

  2. Optical clockworks and the measurement of laser frequencies with a mode-locked frequency comb

    Microsoft Academic Search

    R. Holzwarth; M. Zimmermann; Thomas Udem; T. W. Hansch

    2001-01-01

    Femtosecond laser-frequency comb techniques are vastly simplifying the measurement and synthesis of optical fre- quencies. A single mode-locked femtosecond laser, with its spec- trum broadened by self-phase modulation in a microstructured or tapered nonlinear fiber, can produce millions of sharp laser lines in a precise evenly spaced grid spanning much of the visible and near- infrared spectrum. The absolute frequency

  3. Direct Link between Microwave and Optical Frequencies with a 300 THz Femtosecond Laser Comb

    Microsoft Academic Search

    Scott A. Diddams; David J. Jones; Jun Ye; Steven T. Cundiff; John L. Hall; Jinendra K. Ranka; Robert S. Windeler; Ronald Holzwarth; Thomas Udem; T. W. Hänsch

    2000-01-01

    We demonstrate a great simplification in the long-standing problem of measuring optical frequencies in terms of the cesium primary standard. An air-silica microstructure optical fiber broadens the frequency comb of a femtosecond laser to span the optical octave from 1064 to 532 nm, enabling us to measure the 282 THz frequency of an iodine-stabilized Nd:YAG laser directly in terms of

  4. High-precision wavelength calibration of astronomical spectrographs with laser frequency combs

    Microsoft Academic Search

    M. T. Murphy; Th. Udem; R. Holzwarth; A. Sizmann; L. Pasquini; C. Araujo-Hauck; H. Dekker; S. D'Odorico; M. Fischer; T. W. Hänsch; A. Manescau

    2007-01-01

    We describe a possible new technique for precise wavelength calibration of high-resolution astronomical spectrographs using femtosecond-pulsed mode-locked lasers controlled by stable oscillators such as atomic clocks. Such `frequency combs' provide a series of narrow modes which are uniformly spaced according to the laser's pulse repetition rate and whose absolute frequencies are known a priori with relative precision better than 10-12.

  5. Fabry–Pérot filter cavities for wide-spaced frequency combs with large spectral bandwidth

    Microsoft Academic Search

    T. Steinmetz; T. Wilken; C. Araujo-Hauck; R. Holzwarth; T. W. Hänsch; T. Udem

    2009-01-01

    We use low-finesse Fabry–Pérot cavities in series to generate frequency combs with a large mode spacing in a way that allows\\u000a its application to a large optical bandwidth. The attenuation of laser modes closest to the pass bands of the cavity exceeds\\u000a 70 dB for a filter ratio of m=20 relative to the resonant modes centered within the pass bands. We

  6. Why Sex is Good

    NSDL National Science Digital Library

    Clyde Freeman Herreid

    2005-01-01

    This interrupted case is based on a 2005 article in Nature written by three scientists from the Imperial College London that deals with the issue of sexual vs. asexual reproduction and their relative merits—a question that has bedeviled biologists for over 100 years. The article serves as the final stage of this case focusing on why sex is good (at least in some circumstances). Written for a general biology class where the question of evolution is considered, the case would also be appropriate for use in an evolution or ecology course.

  7. Sex and flagellation.

    PubMed

    Hurst, L; Grafen, A

    1990-12-01

    The centriole is one of the cell's more enigmatic structures. It lives a Jekyll and Hyde existence, changing from the basal body, which seeds the production of cilia and flagellae, into the centriole, in which guise it is of uncertain function. Recent work has indicated the possibility of DNA tightly packed into the structure's core. This finding sheds light on theories of the evolutionary origins of the centriole and of its possible involvement in the evolution of sex. Recent experimental work has been testing this latter possibility. PMID:21232406

  8. Sex differentials in health.

    PubMed Central

    Verbrugge, L M

    1982-01-01

    Health status and health behavior of males and females in the United States are compared; the data employed in the analysis are from community studies and the surveys of the National Center for Health Statistics. Females generally show a higher incidence of acute conditions, higher prevalence of minor chronic conditions, more short-term restricted activity, and more use of health services (especially outpatient services) and medicines. By contrast, males have higher prevalence rates for life-threatening chronic conditions, higher incidence of injuries, more long-term disability, and after about age 50, higher rates of hospitalization. These sex differences appear at all ages, except for early childhood when boys have a worse health profile than girls. The following interpretations are consistent with the data; they are hypotheses rather than demonstrated facts. Women are more frequently ill than men, but with relatively mild problems. By contrast, men feel ill less often, but their illnesses and injuries are more serious. These morbidity differences help to explain sex differentials in health behavior; frequent symptoms lead to more restricted activity, physician and dentist visits, and drug use for women; severe symptoms lead to more permanent limitations and hospitalization for men. But attitudes about symptoms, medical care, drugs, and self-care are also extremely important. Males may be socialized to ignore physical discomforts; thus, they are unaware of symptoms that females feel keenly. Also, men may be less willing and able to seek medical care for perceived symptoms. When diagnosis and treatment are finally obtained, men's conditions are probably more advanced and less amenable to control. Finally, men may be less willing and able to restrict their activities when ill or injured. Four important factors than underlie sex differentials in health are discussed: inherited risks of illness, acquired risks of illness and injury, illness and prevention orientations, and health reporting behavior. Statistics show that women ultimately have lower mortality rates than men--despite women's more frequent morbidity and possibly because of more care for their illnesses and injuries. The apparent contradiction between sex differences in morbidity and mortality (females are sicker but males die sooner) is explored. PMID:6750677

  9. Bayesian Reconstruction of Two-Sex Populations by Age: Estimating Sex Ratios at Birth and Sex Ratios of

    E-print Network

    Raftery, Adrian

    Bayesian Reconstruction of Two-Sex Populations by Age: Estimating Sex Ratios at Birth and Sex past with uncertainty, produced estimates for female-only populations. Here we show how two-sex populations can be similarly reconstructed and probabilistic estimates of various sex ratio quantities

  10. A comb-sampling method for enhanced mass analysis in linear electrostatic ion traps

    SciTech Connect

    Greenwood, J. B.; Kelly, O.; Calvert, C. R.; Duffy, M. J.; King, R. B.; Belshaw, L.; Graham, L.; Alexander, J. D.; Williams, I. D. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Bryan, W. A. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Turcu, I. C. E.; Cacho, C. M.; Springate, E. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom)

    2011-04-15

    In this paper an algorithm for extracting spectral information from signals containing a series of narrow periodic impulses is presented. Such signals can typically be acquired by pickup detectors from the image-charge of ion bunches oscillating in a linear electrostatic ion trap, where frequency analysis provides a scheme for high-resolution mass spectrometry. To provide an improved technique for such frequency analysis, we introduce the CHIMERA algorithm (Comb-sampling for High-resolution IMpulse-train frequency ExtRAaction). This algorithm utilizes a comb function to generate frequency coefficients, rather than using sinusoids via a Fourier transform, since the comb provides a superior match to the data. This new technique is developed theoretically, applied to synthetic data, and then used to perform high resolution mass spectrometry on real data from an ion trap. If the ions are generated at a localized point in time and space, and the data is simultaneously acquired with multiple pickup rings, the method is shown to be a significant improvement on Fourier analysis. The mass spectra generated typically have an order of magnitude higher resolution compared with that obtained from fundamental Fourier frequencies, and are absent of large contributions from harmonic frequency components.

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

    PubMed

    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. PMID:25607050

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

    PubMed

    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. PMID:24332547

  13. Optical frequency comb generation based on chirping of Mach-Zehnder Modulators

    NASA Astrophysics Data System (ADS)

    Hmood, Jassim K.; Emami, Siamak D.; Noordin, Kamarul A.; Ahmad, Harith; Harun, Sulaiman W.; Shalaby, Hossam M. H.

    2015-06-01

    A new approach for the generation of an optical frequency comb, based on chirping of modulators, is proposed and numerically demonstrated. The setup includes two cascaded Mach-Zehnder Modulators (MZMs), a sinusoidal wave oscillator, and an electrical time delay. The first MZM is driven directly by a sinusoidal wave, while the second MZM is driven by a delayed replica of the sinusoidal wave. A mathematical model of the proposed system is formulated and modeled using the Matlab software. It is shown that the number of the frequency lines is directly proportional to the chirp factor. In order to achieve the highest number of frequency comb lines with the best flatness, the time delay between the driving voltages of the two MZMs is optimized. Our results reveal that at least 51 frequency lines can be observed at the output spectrum. In addition, 27 of these lines have power fluctuations of less than 1 dB. The performance of the proposed system is also simulated using a split-step numerical analysis. An optical frequency comb, with tunable frequency spacing ranging from 5 to 40 GHz, is successfully generated.

  14. Radius of Gyration of Polystyrene Combs and Centipedes in a O Solvent

    SciTech Connect

    Terao, Ken [University of Tennessee, Knoxville (UTK) & Gunma University, Kiryu Gunma; Farmer, Brandon S [University of Tennessee, Knoxville (UTK); Nakamura, Yo [University of Tennessee, Knoxville (UTK) & Kyoto University, Nishikyo-ku Kyoto; Iatrou, Hermis [University of Athens, Athens, Greece; Hong, Kunlun [ORNL; Mays, Jimmy [ORNL

    2005-01-01

    The molecular weight dependence of the radii of gyration R{sub g} in a {var_theta} solvent (trans-decalin) of one regular branched comb and three regular centipede polystyrenes was studied using a gel permeation chromatography system equipped with a two-angle light scattering detector and a refractive index detector. R{sub g} in trans-decalin for each sample of particular molecular weight was about 25% smaller than that in a good solvent (tetrahydrofuran, THF). On the other hand, they are 20--40% larger than the theoretical values from the Gaussian chain model. This difference can be explained with the wormlike comb model developed by Nakamura et al. (Macromolecules 2000, 33, 8323-8328). Persistence lengths thus obtained for each sample were about half of that determined in THF solution. However, they are significantly larger than that for linear polystyrene. These results suggest that a main chain stiffening effect exists in comb polystyrenes even in a {var_theta} solvent.

  15. 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.

    PubMed

    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. PMID:24860109

  16. Sex Knowledge, Sex Guilt and Sexual Behavior among University Students.

    ERIC Educational Resources Information Center

    Brown, Idalyn S.; Pollack, Robert H.

    Previous research has suggested a high level of sexual activity among students, often involving unprotected intercourse. To better understand what factors contribute to consistent use of effective contraception, the relationship between sexual knowledge and sexual behavior and the relationship of sex guilt to sex knowledge were investigated in a…

  17. Self-Disclosure: A Function of Sex or Sex Role?

    ERIC Educational Resources Information Center

    Lombardo, John P.; Lavine, Linda O.

    Sex role differences in self disclosure are more clearly defined than are gender differences. Students filled out a Bem Sex Role Inventory (BSRI) as part of an introductory course requirement. Males and females who scored as either androgynous or stereotyped were selected for four targets: mother, father, male best friend, female best friend. Some…

  18. Sex differences in same- and cross-sex supportive relationships

    Microsoft Academic Search

    Robin A. Buhrke; Dale R. Fuqua

    1987-01-01

    The current study focused on sex differences in same- and cross-sex supportive relationships. Subjects, 249 female and 103 male volunteers, completed a questionnaire designed to assess the nature and quality of supportive relationships. Four dimensions of relationships were examined: the relative frequency and patterning of interactions, closeness, diversity of interactions, and interpersonal perception. A 2×2 multivariate analysis of variance (MANOVA)

  19. Sex Role Complementarity in Job Stereotypy.

    ERIC Educational Resources Information Center

    Koenig, Esther J.

    1989-01-01

    Compared effects of gender and sex role on perceived suitability by college students (N=605) of hypothetical job applicants for sex-typed jobs. Found no main effect resulting from job sex-type, sex role of applicants, or gender. Found for specific applicant-job pairings a complementarity of gender and sex role was evident. (Author/ABL)

  20. RESEARCH Open Access Sex chromosome complement regulates

    E-print Network

    Sibille, Etienne

    RESEARCH Open Access Sex chromosome complement regulates expression of mood-related genes Marianne-related factors (sex chromosome complement, developmental gonadal sex, or adult circulating hormones) to frontal is determined by sex chromosome complement, the role of sex chromosomes cannot be investigated individually

  1. Contemporary Sex Roles for Adolescents

    Microsoft Academic Search

    Dianne F. Harrison; R. Clark Pennell

    1989-01-01

    This article reviews various social influences and their effects on adolescent sex role development, including parents, peers, media, schools, race, social class and religion. The authors conclude that teens may experience sex role strain based on pressures to conform to gender expectations. Implications for social work practice are discussed.

  2. Adolescent pregnancy and sex roles

    Microsoft Academic Search

    Carol J. Ireson

    1984-01-01

    Traditional sex roles are related to the occurrence of adolescent pregnancy in this study. Sex-role orientation and related variables were measured by a questionnaire administered to 161 young women aged 13 to 18 years when they sought pregnancy tests or birth control information at one of several clinics. The hypothesis of the study, that adolescents who get pregnant are more

  3. The sex ratio in anencephaly

    Microsoft Academic Search

    W H James

    1979-01-01

    A review of the data supports the suggestion of Knox (1974) that the sex ratio and incidence of anencephalics vary together within populations, as they are known to do between populations. There seems some doubts, though, whether Knox was correct in hypothesising that the sex ratio of anencephalics varies with their incidence in relation to the dizygotic twinning rate. The

  4. Sex Differences in Fetal Habituation

    ERIC Educational Resources Information Center

    Hepper, Peter G.; Dornan, James C.; Lynch, Catherine

    2012-01-01

    There is some evidence for sex differences in habituation in the human fetus, but it is unknown whether this is due to differences in central processing (habituation) or in more peripheral processes, sensory or motor, involved in the response. This study examined whether the sex of the fetus influenced auditory habituation at 33 weeks of…

  5. [Sex-linked juvenile retinoschisis].

    PubMed

    François, P; Turut, P; Soltysik, C; Hache, J C

    1976-02-01

    About 13 observations of sexe linked juvenile retinoschisis, the authors describe the ophthalmoscopic, fluorographic and functional aspects of the disease whose caracteristics are:--its sexe linked recessive heredity; --its clinical characterestics associating: a microcystic macular degeneration, peripheral retinal lesions, vitreous body alterations, --an electroretinogram of the negative type. PMID:132916

  6. The Consequences of Sex Selection

    ERIC Educational Resources Information Center

    Rothman, Barbara Katz

    2006-01-01

    A group of researchers at Baylor College of Medicine in Houston are set to do a long-term study of families that would permit to select the sex of their babies through genetic testing before implanting the embryo in the mother. Technologies such as in vitro fertilization involved in selecting a baby's sex has societal and psychological…

  7. Schizophrenia and Sex Chromosome Anomalies

    Microsoft Academic Search

    Lynn E. DeLisi; Ursula Friedrich; Jan Wahlstrom; Angela Boccio-Smith; Anders Foreman; Kurt Eklund; Timothy J. Crow

    1994-01-01

    An apparent excess of sex chromosome aneuploidies (XXY, XXX, and possibly XYY) has been reported in populations of patients with schizophrenia by a number of authors. These reports have received little attention because transmission of psychosis is regarded as autosomal and not sex linked, and the detection of extra X chromosomes by Barr body estimation alone is not a reliable

  8. Sex Roles and Marriage Adjustment.

    ERIC Educational Resources Information Center

    Murstein, Bernard I.; Williams, Paul D.

    1983-01-01

    Married couples (N=82) completed the Bem Sex Role Inventory (BSRI), the Behavioral Inventory (BI), and the Spanier Dyadic Adjustment Test to examine the relationship of marital adjustment to androgyny. Sex-role behavior of husbands was of primary importance, both for their marital adjustment and their wives. (HLM)

  9. Teaching Sex Education in Thailand

    ERIC Educational Resources Information Center

    Kay, Noy S.; Jones, Megan R.; Jantaraweragul, Sudgasame

    2010-01-01

    The purposes of this study were to examine the current situation pertaining to the teaching of sex education and identify barriers to teaching sex education among Thai health education teachers. A survey questionnaire was administered to 193 health education teachers who participated in this study. The questionnaire was comprised of three parts:…

  10. Sex hormones and brain aging

    Microsoft Academic Search

    Sergio Veiga; Roberto C. Melcangi; Lydia L. DonCarlos; Luis M. Garcia-Segura; Iñigo Azcoitia

    2004-01-01

    Sex steroids exert pleiotropic effects in the nervous system, preserving neural function and promoting neuronal survival. Therefore, the age-related decrease in sex steroids may have a negative impact on neural function. Progesterone, testosterone and estradiol prevent neuronal loss in the central nervous system in different experimental animal models of neurodegeneration. Furthermore, progesterone and its reduced derivatives dihydroprogesterone and tetrahydroprogesterone reduce

  11. Moral Pluralism and Sex Education

    ERIC Educational Resources Information Center

    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…

  12. Sex Hormones and Immune Dimorphism

    PubMed Central

    Bhatia, Aruna; Sekhon, Harmandeep Kaur; Kaur, Gurpreet

    2014-01-01

    The functioning of the immune system of the body is regulated by many factors. The abnormal regulation of the immune system may result in some pathological conditions. Sex hormones of reproductive system are one of the major factors that regulate immune system due to the presence of hormone receptors on immune cells. The interaction of sex hormones and immune cells through the receptors on these cells effect the release of cytokines which determines the proliferation, differentiation, and maturation of different types of immunocytes and as a result the outcome of inflammatory or autoimmune diseases. The different regulations of sex hormones in both sexes result in immune dimorphism. In this review article the mechanism of regulation of immune system in different sexes and its impact are discussed. PMID:25478584

  13. 78 FR 23835 - Sex Offender Registration Amendments

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-23

    ...COLUMBIA 28 CFR Part 811 RIN 3225-AA10 Sex Offender Registration Amendments AGENCY...verification of registration information for sex offenders. Furthermore, the rule permits CSOSA to verify addresses of sex offenders by conducting home visits...

  14. A Framework for Sex Role Counseling.

    ERIC Educational Resources Information Center

    Cook, Ellen Piel

    1985-01-01

    The androgyny model of masculinity and femininity serves as the basis for a framework for sex role counseling applicable to both sexes. Examples of sex role problems, counseling goals, and interventions are described. (Author/BL)

  15. A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s$^{-1}$

    E-print Network

    Chih-Hao Li; Andrew J. Benedick; Peter Fendel; Alexander G. Glenday; Franz X. Kaertner; David F. Phillips; Dimitar Sasselov; Andrew Szentgyorgyi; Ronald L. Walsworth

    2008-04-07

    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 velocity measurements.

  16. Sex ratios in bumble bees

    PubMed Central

    Bourke, A. F. G.

    1997-01-01

    The median proportion of investment in females among 11 populations of seven bumble bee (Bombus) species was 0.32 (range 0.07 to 0.64). By contrast, two species of workerless social parasites in the related genus Psithyrus had female-biased sex allocation, the reasons for which remain unclear. Male-biased sex allocation in Bombus contradicts the predictions of Trivers and Hare's sex ratio model for the social Hymenoptera, which are that the population sex investment ratio should be 0.5 (1:1) under queen control and 0.75 (3:1 females:males) under worker control (assuming single, once-mated, outbred queens and non-reproductive workers). Male bias in Bombus does not appear to be either an artefact, or purely the result of symbiotic sex ratio distorters. According to modifications of the Trivers–Hare model, the level of worker male-production in Bombus is insufficient to account for observed levels of male bias. There is also no evidence that male bias arises from either local resource competition (related females compete for resources) or local mate enhancement (related males cooperate in securing mates). Bulmer presented models predicting sexual selection for protandry (males are produced before females) in annual social Hymenoptera and, as a consequence (given some parameter values), male-biased sex allocation. Bumble bees fit the assumptions of Bulmer's models and are protandrous. These models therefore represent the best current explanation for the bees' male-biased sex investment ratios. This conclusion suggests that the relative timing of the production of the sexes strongly influences sex allocation in the social Hymenoptera.

  17. Theory and experiment of flat-top all-fiber comb filter based on two high birefringence fiber Sagnac loop filters

    NASA Astrophysics Data System (ADS)

    Qiao, Guorong; Cao, Zhigang; Wang, Rui; Ji, Xiaochun; Gao, Bing; Peng, Jun; Xu, Feng; Yu, Benli

    2012-06-01

    A simple flat-top all-fiber comb filter based on two high birefringence fiber (HBF) Sagnac loop filters is presented. The proposed flat-top comb filter consists of two HBF Sagnac loop filters with two polarization controllers (PCs) and a fiber circulator. According to the theoretical analysis, with proper settings of the polarization state of the PCs, the comb filter can realize flat-top passband and the channel spacing also can be switched when the comb filter is convex spectrum. The 0.3 dB bandwidth of the flat-top passband is 0.49 nm with a free spectral range of 1.4 nm. The maximum extinction ratio is nearly 20 dB. The comb filter with switchable channel spacing can be obtained from 0.7 nm to 1.4 nm.

  18. 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.

    PubMed

    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. PMID:11155999

  19. Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism

    SciTech Connect

    Tillman, Karl A.; Thapa, Rajesh; Knabe, Kevin; Wu Shun; Lim, Jinkang; Washburn, Brian R.; Corwin, Kristan L.

    2009-12-20

    The frequency comb from a prism-based Cr:forsterite laser has been frequency stabilized using intracavity prism insertion and pump power modulation. Absolute frequency measurements of a CW fiber laser stabilized to the P(13) transition of acetylene demonstrate a fractional instability of {approx}2x10{sup -11} at a 1 s gate time, limited by a commercial Global Positioning System (GPS)-disciplined rubidium oscillator. Additionally, absolute frequency measurements made simultaneously using a second frequency comb indicate relative instabilities of 3x10{sup -12} for both combs for a 1 s gate time. Estimations of the carrier-envelope offset frequency linewidth based on relative intensity noise and the response dynamics of the carrier-envelope offset to pump power changes confirm the observed linewidths.

  20. All-Optical OC-192 RZ data decision gating in dark optical comb injected semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Liao, Yu-Sheng; Yu, Kun-Chieh; Lin, Gong-Ru

    2006-09-01

    We demonstrate a novel all-optical RZ decision gate by using one dark-optical-comb injected SOA which is controlled by a reshaped optical clock with extremely high cross-gain-modulation (XGM) depth and narrow gain window. Such a decision gate exhibits improved 3R regeneration performances including timing tolerance of 33.5 ps, Q factor of 8.1 and extinction ratio of 13.6 dB. The correlation between backward injected dark-comb and input data wavelength region for optimizing the extinction ratio of the decision gated RZ data is determined. Under a threshold operating dark-optical comb power of 7 dBm, such a decision gate can recover the degraded RZ data with a bit-error-rate of less than 10 -9 at 10 Gbits/s.

  1. Phase-stabilized, 1.5-W frequency comb at 2.8 to 4.8 micron

    E-print Network

    Adler, Florian; Thorpe, Michael J; Hartl, Ingmar; Fermann, Martin E; Ye, Jun

    2009-01-01

    We present a high-power optical parametric oscillator-based frequency comb in the mid-infrared wavelength region using periodically poled lithium niobate. The system is synchronously pumped by a 10-W femtosecond Yb:fiber laser centered at 1.07 um and is singly resonant for the signal. The idler (signal) wavelength can be continuously tuned from 2.8 to 4.8 um (1.76 to 1.37 um) with a simultaneous bandwidth as high as 0.3 um and a maximum average idler output power of 1.50 W. We also demonstrate the performance of the stabilized comb by recording the heterodyne beat with a narrow-linewidth diode laser. This OPO is an ideal source for frequency comb spectroscopy in the mid-IR.

  2. Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism.

    PubMed

    Tillman, Karl A; Thapa, Rajesh; Knabe, Kevin; Wu, Shun; Lim, Jinkang; Washburn, Brian R; Corwin, Kristan L

    2009-12-20

    The frequency comb from a prism-based Cr:forsterite laser has been frequency stabilized using intracavity prism insertion and pump power modulation. Absolute frequency measurements of a CW fiber laser stabilized to the P(13) transition of acetylene demonstrate a fractional instability of approximately 2 x 10(-11) at a 1 s gate time, limited by a commercial Global Positioning System (GPS)-disciplined rubidium oscillator. Additionally, absolute frequency measurements made simultaneously using a second frequency comb indicate relative instabilities of 3 x 10(-12) for both combs for a 1 s gate time. Estimations of the carrier-envelope offset frequency linewidth based on relative intensity noise and the response dynamics of the carrier-envelope offset to pump power changes confirm the observed linewidths. PMID:20029601

  3. High-power, hybrid Er:fiber/Tm:fiber frequency comb source in the 2 {\\mu}m wavelength region

    E-print Network

    Adler, Florian

    2012-01-01

    We present a 2-\\mum frequency comb based on a reliable mode-locked Er:fiber laser with 100 MHz repetition rate. After shifting the spectrum of the amplified Er:fiber comb to longer wavelengths, a single-clad Tm/Ho:fiber is used as a self-pumped pre-amplifier to generate a coherent and broadband spectrum centered at 1.93 \\mum. Subsequently, a cladding-pumped Tm:fiber amplifier boosts the system to a maximum output power of 4.8 W at 1.96 \\mum. After compression in a compact grating compressor, our amplified Er:fiber/Tm:fiber hybrid system delivers as much as 2.9 W with a pulse duration of 141 fs. The system's comb properties are examined via heterodyne measurement.

  4. [Sex role and sports].

    PubMed

    Darlison, E

    2000-11-01

    Gender inequality in all areas of life remains a global problem despite efforts over the past twenty years in particular to address the situation. In physical activity and sport the inequality between women and men is particularly pronounced in almost all countries, although it differs in degree. Two of the main reasons why inequality between women and men physical activity and sport is more extreme than in many other areas of social life are the result of the close association between the attributes required for sport and those associated with traditional concepts of stereotypical, hegemonic masculinity, and a lack of understanding of the difference between sex and gender. In sport and physical activity physical differences between men and women have been confused with socially constructed differences i.e. physical differences have been confused with gender differences, and this confusion has been used to justify women's lesser and limited participation at all levels. To achieve equality between women and men in physical activity and sport it will be essential that gender is identified and understood as a socially constructed and fluid concept which is a product of the relations between women and men. The fact that women bear children or are generally less physically powerful than men is not sufficient to justify why it is not considered appropriate for women to participate in certain forms of physical activity or why their participation is less valued than the participation of men. An understanding of gender and of the construction of gender relations is an important pre-requisite to addressing the inequality between women and men in physical activity and sport and in developing policies and programs which include, and are of equal benefit to both sexes. While more research on the benefits of participation in physical activity is needed, there is currently sufficient information available to identify the health related and social value of participation to both women and men. What is now needed to ensure equality between women and men in physical activity and sport is the adoption of a gender-relations approach to policy and program planning by governments, civil society and specifically by those "experts" in the field who have the power to advocate and to influence decision makers at all levels. PMID:11149281

  5. Dissemination of an optical frequency comb over fiber with 3 × 10(-18) fractional accuracy.

    PubMed

    Marra, Giuseppe; Margolis, Helen S; Richardson, David J

    2012-01-16

    We demonstrate that the structure of an optical frequency comb transferred over several km of fiber can be preserved at a level compatible with the best optical frequency references currently available. Using an optical phase detection technique we measure the noise introduced by the fiber link and suppress it by stabilizing the optical path length. The measured fractional frequency stability of the transferred optical modes is 2 × 10(-18) at a few thousand seconds and the mode spacing stability after optical-microwave conversion is better than 4 × 10(-17) over the same time scale. PMID:22274521

  6. Monolithically cascaded micromirror pair driven by angular vertical combs for two-axis scanning

    Microsoft Academic Search

    Makoto Fujino; Pamela R. Patterson; Hung Nguyen; Wibool Piyawattanametha; Ming C. Wu

    2004-01-01

    In this work, monolithically cascaded one-axis micromirrors driven by angular vertical comb drives are designed and fabricated. Using W-shaped folded-beam optics, we demonstrate two-axis scanning covering ±6.0° two-dimensional area at resonant modes of 7.5 kHz, ±17 V for a fast-scanning mirror and 1.2 kHz, ±7 V for a slow-scanning mirror. The experimental results satisfy the requirements for a surveying instrument.

  7. Solution structure of a modified comb-like polymer from octadecyl methacrylate and acrylic acid

    NASA Astrophysics Data System (ADS)

    Joseph Milton Gaspar, L.; Baskar, Geetha; Baran Mandal, Asit

    2001-11-01

    A water soluble comb-like polymer from the statistical copolymer of acrylic acid and octadecyl methacrylate has been accomplished through transesterification reaction with methoxy poly(ethylene glycol) of molecular weight 5000. The high non-polar characteristics of microdomains as suggested from an higher I3/ I1 emission intensity ratio of pyrene, and a very high aggregation number of 821±4, demonstrate that PEO grafts play a significant role in promoting the hydrophobic association process in aqueous medium. A very low intrinsic viscosity (29 ml/g) and the linear variation of ?sp/ c with c demonstrate formation of aggregated structures in compact coil conformation.

  8. Dual-etalon cavity ring-down frequency-comb spectroscopy with broad band light source

    DOEpatents

    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.

  9. Experimental Realization of Multipartite Entanglement of 60 Modes of a Quantum Optical Frequency Comb

    NASA Astrophysics Data System (ADS)

    Chen, Moran; Menicucci, Nicolas C.; Pfister, Olivier

    2014-03-01

    We report the experimental realization and characterization of one 60-mode copy and of two 30-mode copies of a dual-rail quantum-wire cluster state in the quantum optical frequency comb of a bimodally pumped optical parametric oscillator. This is the largest entangled system ever created whose subsystems are all available simultaneously. The entanglement proceeds from the coherent concatenation of a multitude of Einstein, Podolsky, and Rosen pairs by a single beam splitter, a procedure which is also a building block for the realization of hypercubic-lattice cluster states for universal quantum computing.

  10. Pulse dynamics in a mode-locked fiber laser and its quantum limited comb frequency uncertainty.

    PubMed

    Bao, Chengying; Funk, Andrew C; Yang, Changxi; Cundiff, Steven T

    2014-06-01

    We present an experimental study of pulse dynamics in a mode-locked Er:fiber laser. By injecting a continuous wave laser with sinusoidal intensity modulation into the fiber laser, we are able to modulate the gain. Measuring the response of the pulse energy, central frequency, central pulse time, and phase to the gain modulation allows determination of the parameters that describe their coupling. Based on the experimentally derived parameters, we evaluate the free running comb linewidth and frequency uncertainty with feedback included, assuming quantum noise is the limiting factor. Optimization of fiber lasers is also discussed. PMID:24876029

  11. Microwave synthesis from a continuous-wave terahertz oscillator using a photocarrier terahertz frequency comb.

    PubMed

    Nagano, Shigeo; Ito, Hiroyuki; Kumagai, Motohiro; Kajita, Masatoshi; Hanado, Yuko

    2013-06-15

    We report low-noise microwave synthesis from radiation with a frequency of 0.3 THz using a photocarrier frequency comb in a photoconductive antenna. The synthesized microwave signal at 1 GHz is phase coherent to the 0.3 THz radiation and has a fractional instability of 1×10(-15) within 300 s averaging times and single-sideband phase noise of -105 dB/Hz at a 100 Hz offset from the carrier. This terahertz (THz)-to-microwave synthesizer is capable of being a THz frequency divider, which would be indispensable to not only THz metrology but also future high-speed wireless networks. PMID:23939002

  12. Broadband quasiphasematching for large-scale entanglement in the quantum optical frequency comb

    E-print Network

    Wang, Pei; Pfister, Olivier

    2014-01-01

    We observed a remarkably broad sum frequency generation quasiphasematching bandwidth in periodically poled KTiOPO4, in the 1058-1070 nm wavelength and 15-40oC temperature ranges. The quasiphasematching efficiency was constant over 3.178(2) THz, only limited by laser tuning range. This is consistent with our theoretical prediction of a 4.74 THz quasiphasematching full width at 99% maximum near the 9 {\\mu}m poling period in PPKTP. This broad phasematching bandwidth is key to defining very large (10,000-qumode) quantum computing registers by creating continuous-variable cluster states in the quantum optical frequency comb.

  13. Analysis of polarization-independent tunable optical comb filter by cascading MZI and phase modulating Sagnac loop

    NASA Astrophysics Data System (ADS)

    Guo, Jin-Jin; Yang, Yuanhong; Peng, Gang-Ding

    2011-10-01

    A novel scheme of tunable optical comb filter constructed by cascading a polarization-swapping MZI and a phase modulating Sagnac loop is proposed. The key features of this comb filter design are its polarization-independence and high speed in wavelength tuning. The wavelength tunability can be readily achieved by incorporating an electro-optic phase modulator into the Sagnac loop. In addition, the filter can be made amplitude adjustable as well. The filter will be desirable for multi-wavelength fiber lasers, multi-channel optical signal processing and optical WDM systems.

  14. Effect of surface acoustic waves on the catalytic decomposition of ethanol employing a comb transducer for ultrasonic generation

    SciTech Connect

    S. J. Reese; D. H. Hurley; H.W. Rollins

    2006-04-01

    The effect of surface acoustic waves, generated on a silver catalyst using a comb transducer, on the catalytic decomposition of ethanol is examined. The comb transducer employs purely mechanical means for surface acoustic wave (SAW) transduction. Unlike interdigital SAW transducers on piezoelectric substrates, the complicating effects of heat generation due to electromechanical coupling, high electric fields between adjacent electrodes, and acoustoelectric currents are avoided. The ethanol decomposition reactions are carried out at 473 K. The rates of acetaldehyde and ethylene production are retarded when acoustic waves are applied. The rates recover to varying degrees when acoustic excitation ceases.

  15. Generation of a noiselike soliton molecule induced by a comb filter in a figure-eight fiber laser

    NASA Astrophysics Data System (ADS)

    Luo, Ai-Ping; Zheng, Xu-Wu; Liu, Meng; Liu, Hao; Zhao, Nian; Ning, Qiu-Yi; Luo, Zhi-Chao; Xu, Wen-Cheng

    2015-04-01

    We report on the generation of a noiselike soliton molecule induced by a comb filter in a figure-eight fiber laser. Despite the noiselike mode-locked operation, there were always several peaks riding on a wide shoulder when the mode-locked operation was obtained; this phenomenon was called the noiselike soliton molecule. It was found that the formation of the noiselike soliton molecule is induced by the intracavity comb filter. The observed results would give further insight towards understanding both the fundamental physics of soliton molecules and the noiselike pulses in passively mode-locked fiber lasers.

  16. Coherent phase lock of a 9 ?m quantum cascade laser to a 2 ?m thulium optical frequency comb.

    PubMed

    Mills, Andrew A; Gatti, Davide; Jiang, Jie; Mohr, Christian; Mefford, Will; Gianfrani, Livio; Fermann, Martin; Hartl, Ingmar; Marangoni, Marco

    2012-10-01

    We demonstrate coherent phase locking of a room-temperature continuous-wave quantum cascade laser (QCL) at 9.1 ?m to a Tm-fiber laser frequency comb centered at 2 ?m, with an integrated residual phase error of 0.9 rad (30 mHz to 1.5 MHz). This resulted in a QCL linewidth reduction from 525 to 25 kHz at 1 ms observation time, limited by the linewidth of the free-running frequency comb. PMID:23027286

  17. Generation of three-octave-spanning transient Raman comb in hydrogen-filled hollow-core PCF.

    PubMed

    Tani, F; Belli, F; Abdolvand, A; Travers, J C; Russell, P St J

    2015-03-15

    A noise-seeded transient comb of Raman sidebands spanning three octaves from 180 to 2400 nm, is generated by pumping a hydrogen-filled hollow-core photonic crystal fiber with 26-?J, 300-fs pulses at 800 nm. The pump pulses are spectrally broadened by both Kerr and Raman-related self-phase modulation (SPM), and the broadening is then transferred to the Raman lines. In spite of the high intensity, and in contrast to bulk gas-cell based experiments, neither SPM broadening nor ionization are detrimental to comb formation. PMID:25768173

  18. Generation of a phase-locked Raman frequency comb in gas-filled hollow-core photonic crystal fiber.

    PubMed

    Abdolvand, A; Walser, A M; Ziemienczuk, M; Nguyen, T; Russell, P St J

    2012-11-01

    In a relatively simple setup consisting of a microchip laser as pump source and two hydrogen-filled hollow-core photonic crystal fibers, a broad, phase-locked, purely rotational frequency comb is generated. This is achieved by producing a clean first Stokes seed pulse in a narrowband guiding photonic bandgap fiber via stimulated Raman scattering and then driving the same Raman transition resonantly with a pump and Stokes fields in a second broadband guiding kagomé-style fiber. Using a spectral interferometric technique based on sum frequency generation, we show that the comb components are phase locked. PMID:23114296

  19. Classifying sex biased congenital anomalies

    SciTech Connect

    Lubinsky, M.S. [Medical College of Wisconsin and Children`s Hospital, Milwaukee, WI (United States)] [Medical College of Wisconsin and Children`s Hospital, Milwaukee, WI (United States)

    1997-03-31

    The reasons for sex biases in congenital anomalies that arise before structural or hormonal dimorphisms are established has long been unclear. A review of such disorders shows that patterning and tissue anomalies are female biased, and structural findings are more common in males. This suggests different gender dependent susceptibilities to developmental disturbances, with female vulnerabilities focused on early blastogenesis/determination, while males are more likely to involve later organogenesis/morphogenesis. A dual origin for some anomalies explains paradoxical reductions of sex biases with greater severity (i.e., multiple rather than single malformations), presumably as more severe events increase the involvement of an otherwise minor process with opposite biases to those of the primary mechanism. The cause for these sex differences is unknown, but early dimorphisms, such as differences in growth or presence of H-Y antigen, may be responsible. This model provides a useful rationale for understanding and classifying sex-biased congenital anomalies. 42 refs., 7 tabs.

  20. Sex and Violence in Neuroscience.

    ERIC Educational Resources Information Center

    Barnes, Deborah M.

    1988-01-01

    Describes advances made in the understanding of how sex hormones may modify various cognitive skills, how normal brain signaling mechanisms may cause nerve cell death, and how many cells appear to hold genetic agents which determine their own destruction. (RT)

  1. Differential Freshman Admission by Sex

    ERIC Educational Resources Information Center

    Suddick, David E.; McBee, M. Louise

    1974-01-01

    The authors report on a study whose purpose was to determine if, after adjusting for initial differences in high school averages and SAT scores via separate regression equations, differential admissions criterion by sex is justifiable. No justification is found. (RP)

  2. A Review of The Sex EDcyclopedia

    ERIC Educational Resources Information Center

    Herman, Jeff; Andelloux, Megan

    2012-01-01

    While virtually all sex education books for teenagers focus on sexual health, Jo Langford's "The Sex EDcyclopedia" offers comprehensive and empowering information specifically for teen males about their sexuality and how it may be positively experienced. This review examines the strengths of "The Sex EDcyclopedia" as a sex education resource and…

  3. Sex selection for non-medical purposes

    Microsoft Academic Search

    JM Milliez

    2007-01-01

    Sex selection of the future offspring is usually regarded as acceptable when medically indicated, in order to avoid the transmission of severe sex-linked genetic diseases. The principle of sex selection for personal or social convenience opposes those who support women's rights to reproductive autonomy and those who condemn any gender discrimination. Sex selection can be performed before conception by sperm

  4. Sibship Sex Composition: Effects on Educational Attainment

    Microsoft Academic Search

    Dalton Conley

    2000-01-01

    This study decomposes the detrimental effects of increased sibship on educational attainment by the sex of the respondent and his\\/her siblings. Previous theories regarding the interaction of gender and sibship sex composition are reviewed and a new hypothesis is offered: a revision of the sex minority hypothesis, positing that an increased number of siblings of the opposite sex (regardless of

  5. Commentary on the Status of Sex Research

    Microsoft Academic Search

    Albert Ellis

    1990-01-01

    The sex revolution that started in the United Slates in the 1960s has many advantages for many pcoplc much of the time. Thus, it has led to increased democracy, freedom, flexibility, and pluralism. It has helped enhance both individualism and sociality. It has augmented and improved sex education, sex therapy, love and marital relationships, women's and gay liberation, and sex-love

  6. Sex stereotyping in children's toy advertisements

    Microsoft Academic Search

    Lori A. Schwartz; William T. Markham

    1985-01-01

    Forty-eight categories of toys were rated in terms of sex appropriateness by 48 students. A sample of 392 pictures of children with toys in 12 toy catalogs and 538 pictures of children with toys on toy packages in four retail stores was coded according to toy type and sex(es) of children shown. The rated sex stereotype of the toy category

  7. First,service Relationships,sex and

    E-print Network

    Xuan, Dong

    First,service Relationships,sex and health among lesbian and bisexual women Laurie Henderson Sigma.1 Survey 1: Sexual Health for All 3 2.2 Survey 2:The Lesbian & Bisexual Women's Sex Survey 3 2 partners 9 3.3 Length of time known partner prior to first sex 10 3.4 Length of time since sex with someone

  8. When Street Sex Workers Are Mothers

    Microsoft Academic Search

    Christine M. Sloss; Gary W. Harper

    2004-01-01

    Many women who engage in street sex work experience pregnancies and become mothers. Unfortunately, little research has examined how their pregnancies and parenting impact themselves as street sex workers and their street sex work. In this qualitative research study, 16 mothers who were currently involved in street sex work in a Midwestern city of the United States participated in semistructured

  9. Male Sex Workers in Three Australian Cities

    Microsoft Academic Search

    Victor Minichiello; Rodrigo Marino; Jan Browne; Maggie Jamieson; Kirk Peterson; Brad Reuter; Kenn Robinson

    2002-01-01

    This article describes the socio-demographic and sex work characteristics of sex workers in Sydney, Melbourne, and Brisbane. A total of 185 male sex workers completed the questionnaire component of the study. The results of this study serve to debunk many of the myths surrounding the popular view of the male sex worker (MS W). The respondents in this study were

  10. Sex differences in human gregariousness

    PubMed Central

    Stella, Sandra; Ferranti, Anthony

    2015-01-01

    Research on human sociality rarely includes kinship, social structure, sex, and familiarity, even though these variables influence sociality in non-human primates. However, cross-cultural ethnographic and observational studies with humans indicate that, beginning after age 5 years, males and females form differing social structures with unrelated individuals in a community. Specifically, compared with females, human males exhibit greater tolerance for and form larger, interconnected groups of peers which we term “gregariousness.” To examine sex differences in gregariousness early in life when children first interact with peers without adult supervision, 3- to 6-year-old children were given the choice to enter one of three play areas: an empty one, one with an adult, or one with a familiar, same-sex peer. More males than females initially chose the play area with the same-sex peer, especially after age 5 years. Sex differences in gregariousness with same-sex peers likely constitute one facet of human sociality. PMID:26038729

  11. The Stability of Same-Sex Cohabitation, Different-Sex Cohabitation, and Marriage

    ERIC Educational Resources Information Center

    Lau, Charles Q.

    2012-01-01

    This study contributes to the emerging demographic literature on same-sex couples by comparing the level and correlates of union stability among 4 types of couples: (a) male same-sex cohabitation, (b) female same-sex cohabitation, (c) different-sex cohabitation, and (d) different-sex marriage. The author analyzed data from 2 British birth cohort…

  12. Sex-biased gene expression at homomorphic sex chromosomes in emus and its implication for

    E-print Network

    Nachman, Michael

    Sex-biased gene expression at homomorphic sex chromosomes in emus and its implication for sex York, NY, and approved March 8, 2013 (received for review October 1, 2012) Sex chromosomes originate for a loss of recombination and sets in motion the evolutionary processes generating heteromorphic sex

  13. Do not have any sex (oral, vaginal, anal or using sex

    E-print Network

    Talbot, James P.

    Do not have any sex (oral, vaginal, anal or using sex toys) with a partner until their treatment has also been completed Prevention Preventing Chlamydia · Use condoms every time you have sex sex (oral, vaginal, anal or using sex toys) with a partner until their treatment has also been

  14. Sex Research and the Media --1 Turning Sexual Science into News: Sex Research and the Media

    E-print Network

    assessed include: reporting accuracy; sex researchers' comfort with various topics, media, and journalistsSex Research and the Media -- 1 Turning Sexual Science into News: Sex Research and the Media@indiana.edu Keywords: SEX RESEARCH; SEXUALITY; MEDIA; JOURNALISM; MEDIA TRAINING #12;Sex Research and the Media -- 2

  15. Mechanisms of Disease: transcription factors in sex determination—relevance to human disorders of sex development

    Microsoft Academic Search

    Ganka Nikolova; Eric Vilain

    2006-01-01

    Sex determination is the series of molecular events that direct the undifferentiated bipotential gonad to become either a testis or an ovary. In humans, disruption of this process results in intersexuality, also referred to as disorders of sex development (DSD). Despite the discovery of the sex-determining gene SRY (sex-determining region Y) 15 years ago, the molecular mechanisms of sex determination

  16. Effective heritability of targets of sex-ratio selection under environmental sex determination

    E-print Network

    Janzen, Fredric

    Effective heritability of targets of sex-ratio selection under environmental sex determination S. E, 2008; Robinson et al., 2009). In many organisms, sex of the offspring is determined by environmental-by-environment interaction; nest-site choice; phenotypic plasticity; sex ratio; temperature-dependent sex determination

  17. Does inbreeding distort sex-ratios?

    Microsoft Academic Search

    Richard Frankham; Jonathan Wilcken

    2006-01-01

    Inbreeding is reputed to distort sex-ratios by reducing the proportion of the homogametic sex. However, many data sets do not show such an effect, and there is a known selective publication bias. To resolve the issue, we (a) developed detailed theoretical expectations for the effects of inbreeding on sex-ratios for autosomal and sex-linked loci with sex-limited effects or with equal

  18. Hardware comb filter enhances dynamic range and noise performance of sensors in noisy environments.

    PubMed

    Prance, H; Prance, R J; Stiffell, P B

    2007-07-01

    We present the results of combining a hardware implementation of an analog comb filter with an ultralow noise electromagnetic sensor. The comb filter is designed to attenuate mains related interference, at either 50 or 60 Hz, and related harmonics. The sensor chosen for this work is an induction magnetometer, but the method is applicable to any low noise high dynamic range sensor. The resultant system, in this case, uses only a single coil, not a gradiometric configuration, thus providing a magnetometer capable of sensing field as opposed to field gradient. This combination of filter and sensor allows additional gain to be added and the full sensitivity of the system to be achieved, previously only realized in an electromagnetically screened room. At the same time, the high dynamic range, low noise performance, and original bandwidth of the sensor are maintained. The technique is illustrated by using the system in an urban environment to observe Schumann resonance phenomena. This approach to acquiring small signals in a noisy environment is compared with conventional analog filter and digital signal processing techniques. PMID:17672781

  19. Continuous Variable Cluster State Generation over the Optical Spatial Mode Comb

    E-print Network

    Raphael Pooser; Jietai Jing

    2014-12-30

    One way quantum computing uses single qubit projective measurements performed on a cluster state (a highly entangled state of multiple qubits) in order to enact quantum gates. The model is promising due to its potential scalability; the cluster state may be produced at the beginning of the computation and operated on over time. Continuous variables (CV) offer another potential benefit in the form of deterministic entanglement generation. This determinism can lead to robust cluster states and scalable quantum computation. Recent demonstrations of CV cluster states have made great strides on the path to scalability utilizing either time or frequency multiplexing in optical parametric oscillators (OPO) both above and below threshold. The techniques relied on a combination of entangling operators and beam splitter transformations. Here we show that an analogous transformation exists for amplifiers with Gaussian inputs states operating on multiple spatial modes. By judicious selection of local oscillators (LOs), the spatial mode distribution is analogous to the optical frequency comb consisting of axial modes in an OPO cavity. We outline an experimental system that generates cluster states across the spatial frequency comb which can also scale the amount of quantum noise reduction to potentially larger than in other systems.

  20. Self-referenceable frequency comb from an ultrafast thin disk laser.

    PubMed

    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. PMID:22535056