Note: This page contains sample records for the topic sex combs asx from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Additional Sex Combs-Like 2 Is Required for Polycomb Repressive Complex 2 Binding at Select Targets  

PubMed Central

Polycomb Group (PcG) proteins are epigenetic repressors of gene expression. The Drosophila Additional sex combs (Asx) gene and its mammalian homologs exhibit PcG function in genetic assays; however, the mechanism by which Asx family proteins mediate gene repression is not well understood. ASXL2, one of three mammalian homologs for Asx, is highly expressed in the mammalian heart and is required for the maintenance of cardiac function. We have previously shown that Asxl2 deficiency results in a reduction in the bulk level of histone H3 lysine 27 trimethylation (H3K27me3), a repressive mark generated by the Polycomb Repressive Complex 2 (PRC2). Here we identify several ASXL2 target genes in the heart and investigate the mechanism by which ASXL2 facilitates their repression. We show that the Asxl2-deficient heart is defective in converting H3K27me2 to H3K27me3 and in removing ubiquitin from mono-ubiquitinated histone H2A. ASXL2 and PRC2 interact in the adult heart and co-localize to target promoters. ASXL2 is required for the binding of PRC2 and for the enrichment of H3K27me3 at target promoters. These results add a new perspective to our understanding of the mechanisms that regulate PcG activity and gene repression.

Lai, Hsiao-Lei; Wang, Q. Tian

2013-01-01

2

Drosophila Sex Combs as a Model of Evolutionary Innovations  

PubMed Central

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.

Kopp, Artyom

2011-01-01

3

Sex Combs are Important for Male Mating Success in Drosophila melanogaster  

Microsoft Academic Search

The sex comb is one of the most rapidly evolving male-specific traits in Drosophila, making it an attractive model to study sexual selection and developmental evolution. Drosophila males use their sex combs to grasp the females’ abdomen and genitalia and to spread their wings prior to copulation. To test\\u000a the role of this structure in male mating success in Drosophila

Chen Siang Ng; Artyom Kopp

2008-01-01

4

Sexual selection and the evolution of secondary sexual traits: sex comb evolution in Drosophila.  

PubMed

Sexual selection can drive rapid evolutionary change in reproductive behaviour, morphology and physiology. This often leads to the evolution of sexual dimorphism, and continued exaggerated expression of dimorphic sexual characteristics, although a variety of other alternative selection scenarios exist. Here, we examined the evolutionary significance of a rapidly evolving, sexually dimorphic trait, sex comb tooth number, in two Drosophila species. The presence of the sex comb in both D. melanogaster and D. pseudoobscura is known to be positively related to mating success, although little is yet known about the sexually selected benefits of sex comb structure. In this study, we used experimental evolution to test the idea that enhancing or eliminating sexual selection would lead to variation in sex comb tooth number. However, the results showed no effect of either enforced monogamy or elevated promiscuity on this trait. We discuss several hypotheses to explain the lack of divergence, focussing on sexually antagonistic coevolution, stabilizing selection via species recognition and nonlinear selection. We discuss how these are important, but relatively ignored, alternatives in understanding the evolution of rapidly evolving sexually dimorphic traits. PMID:23496332

Snook, Rhonda R; Gidaszewski, Nelly A; Chapman, Tracey; Simmons, Leigh W

2013-04-01

5

Genetic Basis of a Violation of Dollo's Law: Re-Evolution of Rotating Sex Combs in Drosophila bipectinata  

PubMed Central

Phylogenetic analyses suggest that violations of “Dollo’s law”—that is, re-evolution of lost complex structures—do occur, albeit infrequently. However, the genetic basis of such reversals has not been examined. Here, we address this question using the Drosophila sex comb, a recently evolved, male-specific morphological structure composed of modified bristles. In some species, sex comb development involves only the modification of individual bristles, while other species have more complex “rotated” sex combs that are shaped by coordinated migration of epithelial tissues. Rotated sex combs were lost in the ananassae species subgroup and subsequently re-evolved, ?12 million years later, in Drosophila bipectinata and its sibling species. We examine the genetic basis of the differences in sex comb morphology between D. bipectinata and D. malerkotliana, a closely related species with a much simpler sex comb representing the ancestral condition. QTL mapping reveals that >50% of this difference is controlled by one chromosomal inversion that covers ?5% of the genome. Several other, larger inversions do not contribute appreciably to the phenotype. This genetic architecture suggests that rotating sex combs may have re-evolved through changes in relatively few genes. We discuss potential developmental mechanisms that may allow lost complex structures to be regained.

Seher, Thaddeus D.; Ng, Chen Siang; Signor, Sarah A.; Podlaha, Ondrej; Barmina, Olga; Kopp, Artyom

2012-01-01

6

Condition dependence and the nature of genetic variation for male sex comb bristle number in Drosophila melanogaster  

Microsoft Academic Search

Genetic architecture of variation underlying male sex comb bristle number, a rapidly evolving secondary sexual character of\\u000a Drosophila, was examined. First, in order to test for condition dependence, diet was manipulated in a set of ten Drosophila melanogaster full-sib families. We confirmed heightened condition dependent expression of sex comb bristle number and its female homologue\\u000a (distal transverse row bristles) as

Abha Ahuja; Scott De Vito; Rama S. Singh

2011-01-01

7

The Drosophila Polycomb group gene Sex combs extra encodes the ortholog of mammalian Ring1 proteins  

Microsoft Academic Search

Abstract In Drosophila, the Polycomb group (PcG) of genes is required for the maintenance of homeotic gene repression during development. Here, we have characterized the Drosophila ortholog of the products of the mammalian,Ring1=Ring1A and Rnf 2=Ring1B genes. We show,that Drosophila Ring corresponds to the Sex combs extra (Sce), a previously described PcG gene. We find that Ring=Sce is expressed and

Nicole Gorfinkiel; Laura Fanti; Teresa Melgar; Emiliano Garc?a; Sergio Pimpinelli; Isabel Guerrero; Miguel Vidal

2004-01-01

8

Participation of Polycomb group gene extra sex combs in hedgehog signaling pathway  

Microsoft Academic Search

Polycomb group (PcG) genes are required for stable inheritance of epigenetic states across cell divisions, a phenomenon termed cellular memory. PcG proteins form multimeric nuclear complex which modifies the chromatin structure of target site. Drosophila PcG gene extra sex combs (esc) and its vertebrate orthologs constitute a member of ESC–E(Z) complex, which possesses histone methyltransferase activity. Here we report isolation

Norihisa Shindo; Atsushi Sakai; Kouji Yamada; Toru Higashinakagawa

2004-01-01

9

The Drosophila Polycomb group gene Sex combs extra encodes the ortholog of mammalian Ring1 proteins  

Microsoft Academic Search

In Drosophila, the Polycomb group (PcG) of genes is required for the maintenance of homeotic gene repression during development. Here, we have characterized the Drosophila ortholog of the products of the mammalian Ring1\\/Ring1A and Rnf2\\/Ring1B genes. We show that Drosophila Ring corresponds to the Sex combs extra (Sce), a previously described PcG gene. We find that Ring\\/Sce is expressed and

Nicole Gorfinkiel; Laura Fanti; Teresa Melgar; Emiliano Garc??a; Sergio Pimpinelli; Isabel Guerrero; Miguel Vidal

2004-01-01

10

Requirement for Sex Comb on Midleg Protein Interactions in Drosophila Polycomb Group Repression  

Microsoft Academic Search

The Drosophila Sex Comb on Midleg (SCM) protein is a transcriptional repressor of the Polycomb group (PcG). Although genetic studies establish SCM as a crucial PcG member, its molecular role is not known. To investigate how SCM might link to PcG complexes, we analyzed the in vivo role of a conserved protein interaction module, the SPM domain. This domain is

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

2004-01-01

11

Beetle horns are regulated by the Hox gene, Sex combs reduced, in a species- and sex-specific manner.  

PubMed

Discovering the mechanisms that underlie the origin of novel features represents a major frontier in developmental and evolutionary biology. Here we begin to characterize the role of the Hox gene Sex combs reduced (Scr) during the development and evolution of a morphologically novel trait: beetle horns. Beetle horns develop as epidermal outgrowths from the prothorax and/or head, and size and location vary dramatically across species and between sexes. Using both comparative gene expression and larval RNA interference in two species of the horned beetle genus Onthophagus, we show that Scr functions in patterning adult labial mouthpart identity and suppressing wing development in the prothorax. At the same time, however, our results illustrate that Scr has acquired, within its ancestral domain of expression, additional new functions including the regulation of prepupal growth and pupal remodeling of pronotal horn primordia. Furthermore, comparative analyses of our results across both Onthophagus species, which differ in location of horn development (thoracic horns vs. thoracic and head horns) as well as patterns of sexual dimorphism (traditional vs. reversed sexual dimorphism), reveal surprising differences in exactly when, where, and to what degree Scr regulates horn formation in different sexes. These observations suggest that the interactions between Scr and its targets in the regulation of horn development can diversify quickly over remarkably short phylogenetic distances. More generally, our results suggest that the Hox complex can play an integral role in the development and evolution of novel complex traits while maintaining traditional patterning responsibilities. PMID:20618431

Wasik, Bethany R; Rose, Debra J; Moczek, Armin P

2010-01-01

12

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

PubMed Central

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.

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

1997-01-01

13

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

PubMed Central

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

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

2004-01-01

14

Regulation of larval hematopoiesis in Drosophila melanogaster: a role for the multi sex combs gene.  

PubMed Central

Drosophila larval hematopoietic organs produce circulating hemocytes that ensure the cellular host defense by recognizing and neutralizing non-self or noxious objects through phagocytosis or encapsulation and melanization. Hematopoietic lineage specification as well as blood cell proliferation and differentiation are tightly controlled. Mutations in genes that regulate lymph gland cell proliferation and hemocyte numbers in the body cavity cause hematopoietic organ overgrowth and hemocyte overproliferation. Occasionally, mutant hemocytes invade self-tissues, behaving like neoplastic malignant cells. Two alleles of the Polycomb group (PcG) gene multi sex combs (mxc) were previously isolated as such lethal malignant blood neoplasm mutations. PcG genes regulate Hox gene expression in vertebrates and invertebrates and participate in mammalian hematopoiesis control. Hence we investigated the need for mxc in Drosophila hematopoietic organs and circulating hemocytes. We show that mxc-induced hematopoietic hyperplasia is cell autonomous and that mxc mainly controls plasmatocyte lineage proliferation and differentiation in lymph glands and circulating hemocytes. Loss of the Toll pathway, which plays a similar role in hematopoiesis, counteracted mxc hemocyte proliferation but not mxc hemocyte differentiation. Several PcG genes tested in trans had no effects on mxc hematopoietic phenotypes, whereas the trithorax group gene brahma is important for normal and mutant hematopoiesis control. We propose that mxc provides one of the regulatory inputs in larval hematopoiesis that control normal rates of plasmatocyte and crystal lineage proliferation as well as normal rates and timing of hemocyte differentiation.

Remillieux-Leschelle, Nathalie; Santamaria, Pedro; Randsholt, Neel B

2002-01-01

15

Characterization of the cis-regulatory region of the Drosophila homeotic gene Sex combs reduced  

SciTech Connect

The Drosophilia homeotic gene Sex combs reduced (Scr) controls the segmental identity of the labial and prothoracic segments in the embryo and adult. It encodes a sequence-specific transcription factor that controls, in concert with other gene products, differentiative pathways of tissues in which Scr is expressed. During embryogenesis, Scr accumulation is observed in a discrete spatiotemporal pattern that includes the labial and prothoracic ectoderm, the subesophageal ganglion of the ventral nerve cord and the visceral mesoderm of the anterior and posterior midgut. Previous analyses have demonstrated that breakpoint mutations located in a 75-kb interval, including the Scr transcription unit and 50 kb of upstream DNA, cause Scr misexpression during development, presumably because these mutations remove Scr cis-regulatory sequences from the proximity of the Scr promoter. To gain a better understanding of the regulatory interactions necessary for the control of Scr transcription during embryogenesis, we have begun a molecular analysis of the Scr regulatory interval. DNA fragments from this 75-kb region were subcloned into P-element vectors containing either an Scr-lacZ or hsp70-lacZ fusion gene, and patterns of reporter gene expression were assayed in transgenic embryos. Several fragments appear to contain Scr regulatory sequences, as they direct reporter gene expression in patterns similar to those normally observed for Scr, whereas other DNA fragments direct Scr reporter gene expression in developmentally interesting but non-Scr-like patterns during embryogenesis. Scr expression in some tissues appears to be controlled by multiple regulatory elements that are separated, in some cases, by more than 20 kb of intervening DNA. This analysis provides an entry point for the study of how Scr transcription is regulated at the molecular level. 60 refs., 7 figs., 1 tab.

Gindhart, J.G. Jr.; King, N.A.; Kaufman, T.C. [Indiana Univ., Bloomington, IN (United States)

1995-02-01

16

Characterization of the Cis-Regulatory Region of the Drosophila Homeotic Gene Sex Combs Reduced  

PubMed Central

The Drosophila homeotic gene Sex combs reduced (Scr) controls the segmental identity of the labial and prothoracic segments in the embryo and adult. It encodes a sequence-specific transcription factor that controls, in concert with other gene products, differentiative pathways of tissues in which Scr is expressed. During embryogenesis, Scr accumulation is observed in a discrete spatiotemporal pattern that includes the labial and prothoracic ectoderm, the subesophageal ganglion of the ventral nerve cord and the visceral mesoderm of the anterior and posterior midgut. Previous analyses have demonstrated that breakpoint mutations located in a 75-kb interval, including the Scr transcription unit and 50 kb of upstream DNA, cause Scr misexpression during development, presumably because these mutations remove Scr cis-regulatory sequences from the proximity of the Scr promoter. To gain a better understanding of the regulatory interactions necessary for the control of Scr transcription during embryogenesis, we have begun a molecular analysis of the Scr regulatory interval. DNA fragments from this 75-kb region were subcloned into P-element vectors containing either an Scr-lacZ or hsp70-lacZ fusion gene, and patterns of reporter gene expression were assayed in transgenic embryos. Several fragments appear to contain Scr regulatory sequences, as they direct reporter gene expression in patterns similar to those normally observed for Scr, whereas other DNA fragments direct Scr reporter gene expression in developmentally interesting but non-Scr-like patterns during embryogenesis. Scr expression in some tissues appears to be controlled by multiple regulatory elements that are separated, in some cases, by more than 20 kb of intervening DNA. Interestingly, regulatory sequences that direct reporter gene expression in an Scr-like pattern in the anterior and posterior midgut are imbedded in the regulatory region of the segmentation gene fushi tarazu (ftz), which is normally located between 10 and 20 kb 5' of the Scr transcription start site. This analysis provides an entry point for the study of how Scr transcription is regulated at the molecular level.

Gindhart-Jr., J. G.; King, A. N.; Kaufman, T. C.

1995-01-01

17

Audit committees: voluntary formation by ASX non-top 500  

Microsoft Academic Search

Purpose – This paper aims to examine the relationship between firm characteristics and incentives for the voluntary formation of audit committees by non-top 500 firms listed on the Australian Stock Exchange (ASX). Design\\/methodology\\/approach – Data are obtained from a random sample of 224 non-top 500 firms listed on the ASX for the year 2005. Logistic regression analysis is used to

Alan Kilgore; Renee Radich

2009-01-01

18

A novel member of murine Polycomb-group proteins, Sex comb on midleg homolog protein, is highly conserved, and interacts with RAE28\\/mph1 in vitro  

Microsoft Academic Search

The Polycomb group of (PcG) genes were originally described in Drosophila, but many PcG genes have mammalian homologs. Genetic studies in flies and mice show that mutations in PcG genes cause posterior transformations caused by failure to maintain repression of homeotic loci, suggesting that PcG proteins have conserved functions. The Drosophila gene Sex comb on midleg (Scm) encodes an unusual

Daihachiro Tomotsune; Yoshihiro Takihara; Joel Berger; David Duhl; Sunghae Joo; Michael Kyba; Manabu Shirai; Hideaki Ohta; Yoichi Matsuda; Barry M. Honda; Jeffrey Simon; Kazunori Shimada; Hugh W. Brock; Filippo Randazzo

1999-01-01

19

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

PubMed Central

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

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

1994-01-01

20

Identification of polycomb and trithorax group responsive elements in the regulatory region of the Drosophila homeotic gene Sex combs reduced  

SciTech Connect

The Drosophilia 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 Polycomb and trithorax group loci. 98 refs., 6 figs., 4 tabs.

Gindhart, J.G. Jr.; Kaufman, T.C. [Indiana Univ., Bloomington, IN (United States)

1995-02-01

21

Genetic Analysis of Embryonic Cis-Acting Regulatory Elements of the Drosophila Homeotic Gene Sex Combs Reduced  

PubMed Central

The homeotic gene Sex combs reduced (Scr) of Drosophila melanogaster is expressed in the labial and prothoracic segments of the ectoderm, in parasegments two and three of the CNS, and in the visceral mesoderm of the anterior and posterior midgut. The mutationally defined function of Scr is to specify the identity of the labial and prothoracic segments and to control the development of the gastric caeca. The Scr locus occupies a chromosomal region of ~80 kb within the Antennapedia complex (ANT-C). To understand how Scr's spatiotemporal expression pattern is generated in the embryo, we have mapped its transcriptional regulatory elements using three approaches. First, we examined the expression pattern of Scr in embryos containing chromosomal rearrangements that remove potential Scr regulatory elements. Second, we made and analyzed a set of Scr minigene transformants. Third, we analyzed a set of Scr-lacZ enhancer tester constructs. Using more sensitive anti-SCR antisera, we discovered that Scr is expressed in tissues that were not previously thought to accumulate SCR: a stripe of ectodermal cells in the parasegment 2 region of stage 5 embryos, the embryonic salivary glands, and the dorsal ridge. Four DNA fragments that had previously been shown in an analysis of Scr-lacZ reporter constructs to contain putative Scr enhancer elements were found to have functional enhancers; similarly, another Scr fragment was found to contain a functional repressor. Our results suggest that regulation of Scr in the labial segment and the CNS requires the apparently synergistic action of multiple, widely spaced enhancer elements. Regulation in the prothorax also appears to be controlled by multiple enhancers: one complete pattern element and one subpattern element. In contrast, Scr regulation in the visceral mesoderm is controlled by an enhancer(s) located in only one DNA fragment.

Gorman, M. J.; Kaufman, T. C.

1995-01-01

22

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

PubMed Central

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.

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

1995-01-01

23

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

PubMed Central

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.

Sivanantharajah, Lovesha; Percival-Smith, Anthony

2014-01-01

24

pc1 and psc1, zebrafish homologs of Drosophila Polycomb and Posterior sex combs, encode nuclear proteins capable of complex interactions.  

PubMed

Drosophila Polycomb group proteins are thought to form multimeric nuclear complexes that are responsible for stable transmission of repressed states of gene expression during the proliferation of differentiating embryos. In this study, we cloned, sequenced, and characterized two Polycomb group homologs, designated pc1 and psc1, in zebrafish. Amino acid sequence analyses determined that pc1 is a structural homolog of Drosophila Polycomb and that psc1 is a homolog of Drosophila Posterior sex combs. Northern blots and whole-mount in situ hybridization revealed that pc1 and psc1 had overlapping expression patterns at successive stages of embryogenesis. Immunocytochemistry localized both Pc1 and Psc1 protein in blastomere nuclei. Pull-down assays and two-hybrid system deletion analyses showed that these proteins were capable of homotypic and heterotypic interactions and identified the regions required for these interactions. The evidence supports the idea that zebrafish Polycomb group proteins, like those of other species, form nuclear complexes with compositions that may vary in a spatio-temporal manner during development. PMID:12051733

Kawamura, Akinori; Yokota, Shin'ichiro; Yamada, Kouji; Inoue, Hitoshi; Inohaya, Keiji; Yamazaki, Ken; Yasumasu, Ikuo; Higashinakagawa, Toru

2002-06-01

25

Comparative Analysis of Chromatin Binding by Sex Comb on Midleg (SCM) and Other Polycomb Group Repressors at a Drosophila Hox Gene?  

PubMed Central

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

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

2010-01-01

26

Decentralized control of drone comb construction in honey bee colonies  

Microsoft Academic Search

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

Stephen C. Pratt

1998-01-01

27

Electronic band structure and derived properties of AlAsxSb1-x alloys  

NASA Astrophysics Data System (ADS)

Based on the pseudopotential formalism under the virtual crystal approximation, the composition dependence of electronic and optical properties of zinc-blende AlAsxSb1-x ternary alloys have been investigated. Good agreement is obtained between our results and the available experimental data. The absorption at the optical gaps suggested that AlAsxSb1-x is an indirect (?-X) band gap semiconductor within a whole composition range. Besides, our results support the linear variation of the direct energy gap (?-?) previously assumed by many workers. The nature of the chemical bond is examined and discussed by means of the electron charge densities. The information derived from the present study may be useful for mid-infrared lasers applications.

Al-Assiri, M. S.; Bouarissa, N.

2013-07-01

28

Compact electrostatic comb actuator  

DOEpatents

A compact electrostatic comb actuator is disclosed for microelectromechanical (MEM) applications. The actuator is based upon a plurality of meshed electrostatic combs, some of which are stationary and others of which are moveable. One or more restoring springs are fabricated within an outline of the electrostatic combs (i.e. superposed with the moveable electrostatic combs) to considerably reduce the space required for the actuator. Additionally, a truss structure is provided to support the moveable electrostatic combs and prevent bending or distortion of these combs due to unbalanced electrostatic forces or external loading. The truss structure formed about the moveable electrostatic combs allows the spacing between the interdigitated fingers of the combs to be reduced to about one micron or less, thereby substantially increasing the number of active fingers which can be provided in a given area. Finally, electrostatic shields can be used in the actuator to substantially reduce unwanted electrostatic fields to further improve performance of the device. As a result, the compact electrostatic comb actuator of the present invention occupies only a fraction of the space required for conventional electrostatic comb actuators, while providing a substantial increase in the available drive force (up to one-hundred times).

Rodgers, M. Steven (Albuquerque, NM); Burg, Michael S. (Albuquerque, NM); Jensen, Brian D. (Albuquerque, NM); Miller, Samuel L. (Albuquerque, NM); Barnes, Stephen M. (Albuquerque, NM)

2000-01-01

29

Phase diagram of KH2(P1-xAsx)O4 mixed crystals  

NASA Astrophysics Data System (ADS)

The phase transitions of KH2(P1-xAsx)O4 solid solutions between ferroelectric KH2PO4 and its isomorphous ferroelectric KH2AsO4 have been studied by dielectric measurements over the whole concentration range 0<=x<=1. The transition temperature versus x, Tc(x), showed a large bowing downwards. The ferroelectricity below Tc was confirmed by a D-E hysteresis loop, which became weakened near x=0.68.

Lee, Kwang-Sei; Ju, Su-Mi; Kim, Jeong-Bae

1994-04-01

30

Phase diagram of KH2(P1-xAsx)O4 mixed crystals  

Microsoft Academic Search

The phase transitions of KH2(P1-xAsx)O4 solid solutions between ferroelectric KH2PO4 and its isomorphous ferroelectric KH2AsO4 have been studied by dielectric measurements over the whole concentration range 0<=x<=1. The transition temperature versus x, Tc(x), showed a large bowing downwards. The ferroelectricity below Tc was confirmed by a D-E hysteresis loop, which became weakened near x=0.68.

Kwang-Sei Lee; Su-Mi Ju; Jeong-Bae Kim

1994-01-01

31

Intermediate phase, network demixing, boson and floppy modes, and compositional trends in glass transition temperatures of binary AsxS1-x system  

NASA Astrophysics Data System (ADS)

The structure of binary AsxS1-x glasses is elucidated using modulated differential scanning calorimetry, Raman scattering, IR reflectance, and molar volume experiments over a wide range (8%29.5% . Raman scattering supported by first-principles cluster calculations reveals that the observed vibrational density of states has features of both pyramidal (PYR) [As(S1/2)3] and quasitetrahedral (QT) [S=As(S1/2)3] local structures. The QT unit concentrations show a global maximum in the intermediate phase (IP), while the concentration of PYR units becomes comparable to those of QT units in that phase, suggesting that both these local structures contribute to the width of the IP. The IP centroid in the sulfides is shifted to lower As content x than in corresponding selenides, a feature identified with excess chalcogen partially segregating from the backbone in the sulfides, but forming part of the backbone in selenides. These ideas are corroborated by the proportionately larger free volumes of sulfides than selenides and the absence of chemical bond-strength scaling of Tg ’s between As sulfides and As selenides. Low-frequency Raman modes increase in scattering strength almost linearly as As content x of glasses decreases from x=20% to 8% and glasses become flexible, with a slope that is close to the floppy mode fraction predicted by rigidity theory. These results show that floppy modes contribute to the excess vibrations observed at low frequency. In the intermediate and stressed rigid elastic phases low-frequency Raman modes persist and are identified as boson modes. Some consequences of the present findings on the optoelectronic properties of these glasses are commented upon.

Chen, Ping; Holbrook, Chad; Boolchand, P.; Georgiev, D. G.; Jackson, K. A.; Micoulaut, M.

2008-12-01

32

Frequency comb swept lasers  

PubMed Central

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.

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

2010-01-01

33

Microwave Comb Generator  

NASA Technical Reports Server (NTRS)

Stable reference tones aid testing and calibration of microwave receivers. Signal generator puts out stable tones in frequency range of 2 to 10 GHz at all multiples of reference input frequency, at any frequency up to 1 MHz. Called "comb generator" because spectral plot resembles comb. DC reverse-bias current switched on and off at 1 MHz to generate sharp pulses in step-recovery diode. Microwave components mounted on back of special connector containing built-in attenuator. Used in testing microwave and spread-spectrum wide-band receivers.

Sigman, E. H.

1989-01-01

34

Spectrally resolved frequency comb interferometry  

NASA Astrophysics Data System (ADS)

In this contribution a novel method for interferometric distance measurement is presented, that is based on unraveling the spectrum of a femtosecond frequency comb. The light of a frequency comb is sent into a Michelson interferometer. The output of the interferometer is analyzed by a high-resolution spectrometer, resolving the individual comb modes. The path-length difference between the two arms is determined on the level of tens of nm, by utilizing the wealth of information present in the unraveled spectrum, showing homodyne interference for each individual frequency comb mode. The measurement method allows for high-accuracy measurements in combination with a large range of non-ambiguity.

van den Berg, S.

2014-04-01

35

Dual Comb Fourier Transform Spectroscopy  

NASA Astrophysics Data System (ADS)

The advent of laser frequency combs a decade ago has already revolutionized optical frequency metrology and precision spectroscopy. Extensions of laser combs from the THz region to the extreme ultraviolet and soft x-ray frequencies are now under exploration. Such laser combs have become enabling tools for a growing tree of applications, from optical atomic clocks to attosecond science. Recently, the millions of precisely controlled laser comb lines that can be produced with a train of ultrashort laser pulses have been harnessed for highly multiplexed molecular spectroscopy. Fourier multi-heterodyne spectroscopy, dual comb spectroscopy, or asynchronous optical sampling spectroscopy with frequency combs are emerging as powerful new spectroscopic tools. Even the first proof-of-principle experiments have demonstrated a very exciting potential for ultra-rapid and ultra-sensitive recording of complex molecular spectra. Compared to conventional Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds, with intriguing prospects for spectroscopy of short lived transient species. Longer recording times allow high resolution spectroscopy of molecules with extreme precision, since the absolute frequency of each laser comb line can be known with the accuracy of an atomic clock. The spectral structure of sharp lines of a laser comb can be very useful even in the recording of broadband spectra without sharp features, as they are e.g. encountered for molecular gases or in the liquid phase. A second frequency comb of different line spacing permits the generation of a comb of radio frequency beat notes, which effectively map the optical spectrum into the radio frequency regime, so that it can be recorded with a single fast photodetector, followed by digital signal analysis. In the time domain, a pulse train of a mode-locked femtosecond laser excites some molecular medium at regular time intervals. A second pulse train of different repetition frequency interferometrically samples the transient response or "free induction decay" of the medium, akin to an optical sampling oscilloscope.

Hänsch, T. W.; Picqué, N.

2010-06-01

36

Molecular Comb Development  

SciTech Connect

This CRADA was developed to enable ORNL to assist Protein Discovery, Inc. to develop a novel biomolecular separation system based on an ORNL patent application 'Photoelectrochemical Molecular Comb' by Thundat, Ferrell, and Brown. The Molecular Comb concept is based on creating light-induced charge carriers at a semiconductor-liquid interface, which is kept at a potential control such that a depletion layer is formed in the semiconductor. Focusing light from a low-power illumination source creates electron-hole pairs, which get separated in the depletion layer. The light-induced charge carriers reaching the surface attract oppositely charged biomolecules present in the solution. The solution is a buffer solution with very small concentrations of biomolecules. As the focused light is moved across the surface of the semiconductor-liquid interface, the accumulated biomolecules follow the light beam. A thin layer of gel or other similar material on the surface of the semiconductor can act as a sieving medium for separating the biomolecules according to their sizes.

Ferrell, T.L.; Thundat, G.T.; Witkowski, C.E., III (Protein Discovery, Inc.)

2007-07-17

37

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

NASA Astrophysics Data System (ADS)

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 V 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.

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

2007-07-01

38

Terahertz laser frequency combs  

NASA Astrophysics Data System (ADS)

Terahertz light can be used to identify numerous complex molecules, but has traditionally remained unexploited due to the lack of powerful broadband sources. Pulsed lasers can be used to generate broadband radiation, but such sources are bulky and produce only microwatts of average power. Conversely, although terahertz quantum cascade lasers are compact semiconductor sources of high-power terahertz radiation, their narrowband emission makes them unsuitable for complex spectroscopy. In this work, we demonstrate frequency combs based on terahertz quantum cascade lasers, which combine the high power of lasers with the broadband capabilities of pulsed sources. By fully exploiting the quantum-mechanically broadened gain spectrum available to these lasers, we can generate 5 mW of terahertz power spread across 70 laser lines. This radiation is sufficiently powerful to be detected by Schottky-diode mixers, and will lead to compact terahertz spectrometers.

Burghoff, David; Kao, Tsung-Yu; Han, Ningren; Chan, Chun Wang Ivan; Cai, Xiaowei; Yang, Yang; Hayton, Darren J.; Gao, Jian-Rong; Reno, John L.; Hu, Qing

2014-06-01

39

Mid-infrared frequency combs  

NASA Astrophysics Data System (ADS)

Laser frequency combs are coherent light sources that emit a broad spectrum of discrete, evenly spaced narrow lines whose absolute frequency can be measured to within the accuracy of an atomic clock. Their development in the near-infrared and visible domains has revolutionized frequency metrology while also providing numerous unexpected opportunities in other fields such as astronomy and attosecond science. Researchers are now exploring how to extend frequency comb techniques to the mid-infrared spectral region. Versatile mid-infrared frequency comb generators based on novel laser gain media, nonlinear frequency conversion or microresonators promise to significantly expand the 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 lead to new discoveries in the various fields relevant to molecular science.

Schliesser, Albert; Picqué, Nathalie; Hänsch, Theodor W.

2012-07-01

40

Towards VECSEL frequency combs  

NASA Astrophysics Data System (ADS)

Significant progress has been made over the last year towards generating frequency combs using VECSELs. Here, I will discuss recent progress made generating < 4kW peak power femtosecond pulse VECSELs, where we have achieved 3.3 W average power with 400 fs pulse duration at 1.7 GHz repetition rate. This has been achieved by exploiting the rapid power scaling progress made in the field of CW VECSELs [1]. The gain structure used here is grown and processed by the University of Marburg, and the window layer is etched for anti-resonance to increase the gain bandwidth and reduce the dispersion [2]. We have used this to generate supercontinuum, achieving 45 % throughput in a 2.2 micron core photonic crystal fiber when the VECSEL produced 1 W average output power. A continuum with a width of 175 nm is generated. At higher average powers heating of the fiber tip reduces coupling efficiency which limits the supercontinuum bandwidth and we will discuss measures to avoid this. Finally, I will outline approaches to further reduce the pulse length, whilst maintaining the average power, to a point where generating coherent octave spanning supercontinuum, suitable for F-2F stabilization should become a reality.

Wilcox, Keith G.

2013-02-01

41

Ab initio calculation of the elastic properties and the lattice dynamics of the AlAsxSb1?x alloy under pressure  

Microsoft Academic Search

The lattice dynamics and the elastic properties of the ternary AlAsxSb1?x alloy have been studied using the density-functional perturbation theory within the local density approximation and employing the virtual-crystal approximation. We study the variation of the optical phonon frequencies (?TO and ?LO), the high-frequency (??) and static (?0) dielectric coefficients, the dynamic effective charge (Z*) and the elastic constants (C11,

K. Daoud; Kh. Bouamama; P. Djemia; S. M. Chérif

2011-01-01

42

Efficient optical frequency-comb generator  

NASA Astrophysics Data System (ADS)

We have demonstrated a method that efficiently transfers the power from a single-frequency laser into a wideband frequency comb. The comb was produced by a 2.7-GHz electro-optic modulator in a resonant optical cavity. A coupled cavity technique was used to transfer 8.5% of the laser power into a comb with a span of 400 modes, or more than 1 THz.

Bell, A. S.; McFarlane, G. M.; Riis, E.; Ferguson, A. I.

1995-06-01

43

Correlation between structure and physical properties of chalcogenide glasses in the AsxSe1-x system  

NASA Astrophysics Data System (ADS)

Physical properties of chalcogenide glasses in the AsxSe1-x system have been measured as a function of composition including the Young’s modulus E , shear modulus G , bulk modulus K , Poisson’s ratio ? , the density ? , and the glass transition Tg . All these properties exhibit a relatively sharp extremum at the average coordination number ?r?=2.4 . The structural origin of this trend is investigated by Raman spectroscopy and nuclear magnetic resonance. It is shown that the reticulation of the glass structure increases continuously until x=0.4 following the “chain crossing model” and then undergoes a transition toward a lower dimension pyramidal network containing an increasing number of molecular inclusions at x>0.4 . Simple theoretical estimates of the network bonding energy confirm a mismatch between the values of mechanical properties measured experimentally and the values predicted from a continuously reticulated structure, therefore corroborating the formation of a lower dimension network at high As content. The evolution of a wide range of physical properties is consistent with this sharp structural transition and suggests that there is no intermediate phase in these glasses at room temperature.

Yang, Guang; Bureau, Bruno; Rouxel, Tanguy; Gueguen, Yann; Gulbiten, Ozgur; Roiland, Claire; Soignard, Emmanuel; Yarger, Jeffery L.; Troles, Johann; Sangleboeuf, Jean-Christophe; Lucas, Pierre

2010-11-01

44

Coherence properties of Kerr frequency combs  

NASA Astrophysics Data System (ADS)

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

Erkintalo, Miro; Coen, Stéphane

2014-01-01

45

Coherence properties of Kerr frequency combs.  

PubMed

We use numerical simulations based on an extended Lugiato-Lefever equation (LLE) to investigate the stability properties of Kerr frequency combs generated in microresonators. In particular, we show that an ensemble average calculated over sequences of output fields separated by a fixed number of resonator roundtrips allows the coherence of Kerr combs to be quantified in terms of the complex degree of first-order coherence. We identify different regimes of comb coherence, linked to the solutions of the LLE. Our approach provides a practical and unambiguous way of assessing the stability of Kerr combs that is directly connected to an accessible experimental quantity. PMID:24562127

Erkintalo, Miro; Coen, Stéphane

2014-01-15

46

PROGRAMMABLE MODIFIED FRACTIONAL COMB DECIMATION FILTER  

Microsoft Academic Search

In multistandard radio receivers, the hardware should be configurable or programmable for the reception of different types of signals having different symbol rates. The decimation by a non-integer factor becomes a critical functionality of the multistandard radio. The Cascaded Integrator-Comb (CIC) filters are commonly used for decimation by an integer. By using polynomial interpolation filter between integrator and comb stages

Djordje Babic; Markku Renfors

47

Mapping of the optical frequency comb to the atom-velocity comb  

SciTech Connect

A mode-locked femtosecond laser is used to physically map the laser frequency comb into the velocity comb of the excited Rb atoms at room temperature. Upon resonant excitation by discrete optical frequencies the velocity distribution of the excited Rb atoms shows comblike structure. Simultaneously, velocity-selective population transfer occurs between ground-state hyperfine levels. Both facts are observed by modified direct frequency comb spectroscopy and verified by a detailed density matrix treatment of the multilevel system in resonant field.

Ban, T.; Aumiler, D.; Skenderovic, H.; Pichler, G. [Institute of Physics, Bijenicka 46, Zagreb (Croatia)

2006-04-15

48

Light beam frequency comb generator  

DOEpatents

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.

Priatko, Gordon J. (Cupertino, CA); Kaskey, Jeffrey A. (Livermore, CA)

1992-01-01

49

Light beam frequency comb generator  

DOEpatents

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.

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

1992-11-24

50

Tracking Comb Filter Suppresses Welder Harmonics  

NASA Technical Reports Server (NTRS)

Tracking comb filter includes charge-coupled-device delay line and phase-locked loop. Filter removes harmonics of frequency of repetition of welding-current pulses from acoustic-emission signal. Spurious signals reduced almost to fundamental limit.

Delcher, Ray C.

1992-01-01

51

Structural, Electronic, Thermodynamic and Thermal Properties of Zinc-Blende InP, InAs and Their InAsx P1-x Ternary Alloys via First Principles Calculations  

NASA Astrophysics Data System (ADS)

First-principles calculations are performed to study the structural, electronic, thermodynamic and thermal properties of the InP and InAs bulk materials and InAsxP1-x ternary alloys using the full potential-linearized augmented plane wave method (FP-LAPW) within the density functional theory (DFT). The dependence of the lattice constant, bulk modulus, band gap, Debye temperature, heat capacity and mixing entropy on the composition x was analyzed. The lattice constant for InAsxP1-x alloys exhibits a marginal deviation from the Vegard's law. A large deviation of the bulk modulus from linear concentration dependence (LCD) was observed for our alloys. We found that the composition dependence of the energy band gap is almost linear by using the mBJ and EV-GGA approximations. The microscopic origins of the gap bowing were explained and detailed by using the approach of Zunger and co-workers. Furthermore, the calculated phase diagram shows a miscibility gap for these alloys with a high critical temperature. Thermal effects on some macroscopic properties of InAsxP1-x alloys are predicted using the quasi-harmonic Debye model, in which the phononic effects are considered. This is the first quantitative theoretical prediction of the thermal properties of the InAsxP1-x alloys, and we still expect the confirmation of experimental studies.

Nemiri, O.; Ghemid, S.; Chouahda, Z.; Meradji, H.; El Haj Hassan, F.

2013-10-01

52

Electrostatic Comb Drive Levitation And Control Method  

Microsoft Academic Search

Abstmct-This paper presents the theory, slmulatlon results, and experimental study of the levitating force (normal to the substr8te) assoc&led with interdigitated capacitor (cleetrostatk comb) Inter81 actuators. For compliant suspensions, normal displacements of over 2 pm for 8 comb bias of 30 V are observed. This phenomenon is due to electrostatic attractkm induced on top of the suspended structure. By electrically

William C. Tang; Martin G. Lim; Roger T. Howe

1992-01-01

53

Frequency-Comb Mid-Infrared Spectroscopy  

Microsoft Academic Search

A new class of IR coherent sources and IR frequency combs, that combine optical frequency-comb synthesizers (OFCSs) and optical parametric up\\/down-conversions, is already available and still progressing at a very fast pace. Peculiar features for IR radiation produced by difference-frequency-generation (DFG) set-ups or quantum-cascade lasers (QCLs) can he achieved when they are phase and frequency controlled by the OFCS. Indeed,

P. de Natale; D. Mazzotti; G. Giusfredi; S. Bartalini; P. Cancio; P. Maddaloni; P. Malara; G. Gagliardi; I. Galli; S. Borri

2008-01-01

54

Electrostatic comb drive for vertical actuation  

SciTech Connect

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

Lee, A. P., LLNL

1997-07-10

55

Discretely tunable comb spacing of a frequency comb by multilevel phase modulation of a periodic pulse train.  

PubMed

We experimentally demonstrate tunable comb spacing of an original 10-GHz periodic frequency comb by spectral Talbot effect over an unprecedented range of even and odd comb spacing division factors, from 2 to 9. The implementation has been achieved by periodic electro-optic (EO) temporal phase modulation of the original comb (conventional mode-locked optical pulse train) with multilevel modulation functions, produced by an arbitrary waveform generator (AWG). These comb spacing division processes have been observed through the use of a high-resolution (20-MHz) optical spectrum analyzer. Comb spacing tuning is achieved without essentially affecting the spectral bandwidth and total energy of the original comb signal. Our results also confirm that the spectral Talbot method does not require carrier-envelope phase stabilization in the input frequency comb. Numerical studies on the impact of deviations in the applied phase modulation functions confirm the robustness of the technique, in agreement with the experimental results. PMID:23481947

Malacarne, Antonio; Azaña, José

2013-02-25

56

Self-assembly of (A-comb-C)-b-(B-comb-C) diblock copolymer-based comb copolymers.  

PubMed

The phase behavior of (A-comb-C)-b-(B-comb-C) diblock copolymer melts is investigated using the strong segregation theory approach. Three different regimes are distinguished. In regime 1 both disordered comb blocks are microphase separated from each other, in regime 2 the side chains C are microphase separated from the disordered A-b-B diblock backbones, and, finally, in regime 3 all species A, B, and C are microphase separated. In the first regime the behavior is similar to that of a simple diblock copolymer melt with a renormalized Flory-Huggins interaction parameter. In regime 2 the region of stability of the different phases is significantly changed compared to simple diblocks due to the comb architecture. The fully microphase separated case, regime 3, is characterized by hierarchical structure formation. We restrict the analysis to systems where self-assembly results in the formation of alternating C layers and internally microphase separated AB layers. The latter consist of alternating A and B layers or disks of the minority component. In the former case, the A and B layers are generally perpendicular to the C layers. The parallel orientation is only possible for small grafting densities. PMID:22181165

Markov, V; Subbotin, A; ten Brinke, G

2011-10-01

57

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

PubMed

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

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

2014-01-01

58

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

PubMed Central

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.

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

2014-01-01

59

Video-signal improvement using comb filtering techniques.  

NASA Technical Reports Server (NTRS)

Significant improvement in the signal-to-noise performance of television signals has been obtained through the application of comb filtering techniques. This improvement is achieved by removing the inherent redundancy in the television signal through linear prediction and by utilizing the unique noise-rejection characteristics of the receiver comb filter. Theoretical and experimental results describe the signal-to-noise ratio and picture-quality improvement obtained through the use of baseband comb filters and the implementation of a comb network as the loop filter in a phase-lock-loop demodulator. Attention is given to the fact that noise becomes correlated when processed by the receiver comb filter.

Arndt, G. D.; Stuber, F. M.; Panneton, R. J.

1973-01-01

60

A Quantitative Characterization of Combing Force  

Microsoft Academic Search

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

WALTER NEWMAN; GEORGE L. COHEN; CLETUS HAYES

61

Coherence and Incoherence in an Optical Comb  

NASA Astrophysics Data System (ADS)

We demonstrate a coexistence of coherent and incoherent modes in the optical comb generated by a passively mode-locked quantum dot laser. This is experimentally achieved by means of optical linewidth, radio frequency spectrum, and optical spectrum measurements and confirmed numerically by a delay-differential equation model showing excellent agreement with the experiment. We interpret the state as a chimera state.

Viktorov, Evgeny A.; Habruseva, Tatiana; Hegarty, Stephen P.; Huyet, Guillaume; Kelleher, Bryan

2014-06-01

62

Establishment of fungus comb in Laboratory colonies of Macrotermes michaelseni and Odontotermes montanus (Isoptera, Macrotermitinae)  

Microsoft Academic Search

Summary Wonkers in incipient laboratory colonies ofMacrotermes michaelseni andOdontotermes montanus build fæcal combs but are unable to inoculate these combs with fungus. These combs are eaten up and the colonies die unless fungus comb from a field colony is introduced when the first workers start foraging. This study investigated whether workers of the two species could produce fungus comb when

Robert Sieber

1983-01-01

63

Conformation of adsorbed comb copolymer dispersants.  

PubMed

Comb copolymers with an adsorbing backbone and nonadsorbing side chains can be very effective dispersants, particularly when a high ionic strength strongly penalizes electrostatic stabilization. For this reason, they have become essential components of concrete over the past decade. This article examines the steric hindrance characteristics of such polymers through the use of atomic force microscopy (AFM) on calcium silicate hydrate, the main hydration product of Portland cement. It is found that solution and surface properties (hydrodynamic radius, radius of gyration, surface coverage, steric layer thickness) and force-distance curves obtained during AFM measurements can be well described by a scaling approach derived in this paper. This represents the first real quantitative step in relating these properties directly to the molecular structure of such comb copolymer dispersants. PMID:19086886

Flatt, Robert J; Schober, Irene; Raphael, Elie; Plassard, Cédric; Lesniewska, Eric

2009-01-20

64

Coherence and incoherence in an optical comb.  

PubMed

We demonstrate a coexistence of coherent and incoherent modes in the optical comb generated by a passively mode-locked quantum dot laser. This is experimentally achieved by means of optical linewidth, radio frequency spectrum, and optical spectrum measurements and confirmed numerically by a delay-differential equation model showing excellent agreement with the experiment. We interpret the state as a chimera state. PMID:24949771

Viktorov, Evgeny A; Habruseva, Tatiana; Hegarty, Stephen P; Huyet, Guillaume; Kelleher, Bryan

2014-06-01

65

Generation of Expanded Optical Frequency Combs  

Microsoft Academic Search

We present a method to expand optical frequency combs (OFC) using self-phase modulation in an optical fiber. The initial OFC\\u000a is generated using a resonant electro-optic modulator and exhibits a span of less than 10 THz. The span of a broadened OFC\\u000a can reach up to 50 THz in the 1.5 µm wavelength domain. Second-Harmonic Generation (SHG) of this OFC

Motonobu Kourogi; Kazuhiro Imai; Bambang Widiyatmoko; Motoichi Ohtsu

2001-01-01

66

Mapping of the Optical Frequency Comb to the Atom Velocity Comb  

SciTech Connect

We present the experimental and theoretical study of the resonant excitation of rubidium and cesium atoms with fs pulse train in the conditions when the pulse repetition period is shorter than the atomic relaxation time. Velocity selective optical pumping of the ground state hyperfine levels and velocity comb-like excited state hyperfine level populations is demonstrated. Both effects are a direct consequence of the fs pulse train excitation considered in the frequency domain. A simple experimental apparatus was employed to develop a modified direct frequency comb spectroscopy which uses a fixed frequency comb for the 85,87Rb 5s 2S1/2 {yields} 5s 2P1/2,3/2 and 133Cs 6s 2S1/2 {yields} 6p 2P1/2,3/2 excitation, and a weak cw scanning probe laser at 780 and 852 nm for Rb and Cs ground levels population monitoring.

Pichler, G.; Aumiler, D.; Vujicic, N.; Vdovic, S.; Ban, T.; Skenderovic, H. [Institute of physics, Bijenicka 46, Zagreb (Croatia)

2006-11-15

67

Endless frequency shifting of optical frequency comb lines.  

PubMed

The functional principle of a novel technique for frequency shifting lines of an optical frequency comb is demonstrated. The underlying principle is to shift the carrier frequency by changing the carrier phase within the time span between subsequent pulses of a mode-locked laser used as comb generator. This universal frequency shifter does not require intrusion into the comb generator and provides high agility for arbitrary temporal frequency evolutions. PMID:23482149

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

2013-03-11

68

Wet combing for the eradication of head lice.  

PubMed

Manual removal (using conditioner and comb or a wet comb) can be used in the treatment of head lice. Head lice infestation (Pediculosis humanus capitis) is a common problem. It is diagnosed by visualising the lice. As half of people infested with head lice will not scratch, all people in contact with a person affected with head lice should be manually checked for infestations. Wet combing is easily and safely performed at home, but persistence is needed. This article describes the process of head lice removal using a wet comb. It has NHMRC Level 2 evidence of efficacy and no serious adverse effects have been reported. PMID:23529522

2013-03-01

69

Frequency comb from a microresonator with engineered spectrum.  

PubMed

We demonstrate that by varying the ratio between the linewidth and dispersion of a whispering gallery mode resonator we are able to control the number N of free spectral ranges separating the first generated comb sidebands from the pump. We observed combs with N = 19 and N = 1. For the comb with N = 1 we have achieved a span of over 200 nm using a 0.4 mm MgF? resonator pumped with 50 mW at 1560 nm. This pump power is a factor of 10 lower than previously reported for combs with comparable bandwidth. PMID:22418543

Grudinin, Ivan S; Baumgartel, Lukas; Yu, Nan

2012-03-12

70

Impact of cavity spectrum on span in microresonator frequency combs.  

PubMed

We experimentally study the factors that limit the span in frequency combs derived from the crystalline whispering gallery mode resonators. We observe that cavity dispersion is the key property that governs the parameters of the combs resulting from cascaded four wave mixing process. Two different regimes of comb generation are observed depending on the precise cavity dispersion behavior at the pump wavelength. In addition, the comb generation efficiency is found to be affected by the crossing of modes of different families. The influence of Raman lasing and its dependence on temperature is discussed. PMID:24216915

Grudinin, Ivan S; Baumgartel, Lukas; Yu, Nan

2013-11-01

71

Integrated Photonic Comb Generation: Applications in Coherent Communication and Sensing  

NASA Astrophysics Data System (ADS)

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.

Parker, John S.

72

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

73

An improved Combes-Thomas estimate of magnetic Schrödinger operators  

NASA Astrophysics Data System (ADS)

In the present paper, we prove an improved Combes-Thomas estimate, viz. the Combes-Thomas estimate in trace-class norms, for magnetic Schrödinger operators under general assumptions. In particular, we allow for unbounded potentials. We also show that for any function in the Schwartz space on the reals the operator kernel decays, in trace-class norms, faster than any polynomial.

Shen, Zhongwei

2013-12-01

74

Optical frequency comb generation for terahertz difference-frequency measurements  

Microsoft Academic Search

We describe the operation of an optical frequency comb generator and its utility in measuring optical frequency differences in the terahertz range. The comb generator is a high-frequency resonant electro-optic modulator capable of generating hundreds of sidebands with a sideband spacing of 17 GHz and a span of at ;east 3 THz. The span is currently limited by the dispersion

L. R. Brothers; Ngai C. Wong

1995-01-01

75

VLSI Implementation of Cascaded Integrator Comb Filters for DSP Applications  

Microsoft Academic Search

The recursive comb filters or Cascaded Integrator Comb filter (CIC) are commonly used as decimators for the sigma delta modulators. This paper presents the VLSI implementation, analysis and design of high speed CIC filters which are based on a low-pass filter. These filters are used in the signal decimation which has the effect on reducing the sampling rate. It is

Rozita Teymourzadeh; Masuri Othman

76

On timing jitter of mode locked Kerr frequency combs.  

PubMed

We study fundamental timing jitter in repetition rate of a mode locked Kerr frequency comb generated in an externally pumped nonlinear ring resonator. We show that the increase in the integrated power of the comb harmonics, and the corresponding decrease of the duration of the associated pulse, results in the increase of low frequency noise, and a decrease in high frequency noise. PMID:24514400

Matsko, Andrey B; Maleki, Lute

2013-11-18

77

Comb-shaped optical-fiber strain sensor  

Microsoft Academic Search

In this paper, a new class of comb-shaped optical fiber strain sensor is fabricated and tested. The measurement strain range of the comb-shaped sensor is 1 (mu) E to 4000 (mu) E. The gauge factor is among 30 to 50. Experimental results show that the optical fiber strain sensor has advantage of both linear and singularity.

Kaide Zha; Pingsheng Tang

1994-01-01

78

The basidiomycetous yeast Rhodotorula yarrowii comb. nov.  

PubMed

Sequence analysis of the D1/D2 domains of the large subunit rDNA of Cryptococcus yarrowii (CBS 7417) indicates that this species does not belong to the hymenomycetous fungi, but instead is of urediniomycetous affinity. Therefore, the name change Rhodotorula yarrowii comb. nov. is proposed. The cell wall of the species contains xylose, a character considered by most authors to indicate fungi of hymenomycetous affinity. However, our results show that xylose may occur in minor amounts in the cell walls of urediniomycetous fungi. A high mannose content of the cell walls may be a more reliable character for urediniomycetous yeasts. PMID:10959564

Boekhout, T; Fell, J W; Fonseca, A; Prillinger, H J; Lopandic, K; Roeijmans, H

2000-05-01

79

Processing of optical combs with fiber optic parametric amplifiers.  

PubMed

Low noise optical frequency combs consist of equally spaced narrow-linewidth optical tones. They are useful in many applications including, for example, line-by-line pulse shaping, THz generation, and coherent communications. In such applications the comb spacing, extent of spectral coverage, degree of spectral flatness, optical tone power and tone-to-noise ratio represent key considerations. Simultaneously achieving the level of performance required in each of these parameters is often challenging using existing comb generation technologies. Herein we suggest and demonstrate how fiber optic parametric amplifiers can be used to enhance all of these key comb parameters, allowing frequency span multiplication, low noise amplification with simultaneous comb spectrum flattening, and improvement in optical tone-to-noise ratio through various phase insensitive as well as phase sensitive implementations. PMID:22535096

Slavík, R; Kakande, J; Petropoulos, P; Richardson, D J

2012-04-23

80

Phase and coherence of optical microresonator frequency combs  

NASA Astrophysics Data System (ADS)

We use a combination of theoretical analysis, numerical simulation, and experimental measurement to investigate the near-threshold phase and coherence properties of parametric optical frequency combs generated in low-loss dielectric microresonators. Our analysis reveals that near threshold the phases of the comb lines do not stabilize to a constant value across the spectrum, although well-defined phase relationships relative to the pump laser do exist. Our results are supported by numerical simulations of two different microresonator combs operated under varying conditions of input drive, dispersion, and detuning. These results are also experimentally confirmed through phase measurements of the individual comb lines. We also investigate the processes leading to the breakdown of the equidistant frequency spacing of the modes in a microresonator comb.

Loh, William; Del'Haye, Pascal; Papp, Scott B.; Diddams, Scott A.

2014-05-01

81

Comparative analysis of spectral coherence in microresonator frequency combs.  

PubMed

Microresonator combs exploit parametric oscillation and nonlinear mixing in an ultrahigh-Q cavity. This new comb generator offers unique potential for chip integration and access to high repetition rates. However, time-domain studies reveal an intricate spectral coherence behavior in this type of platform. In particular, coherent, partially coherent or incoherent combs have been observed using the same microresonator under different pumping conditions. In this work, we provide a numerical analysis of the coherence dynamics that supports the above experimental findings and verify particular design rules to achieve spectrally coherent microresonator combs. A particular emphasis is placed in understanding the differences between so-called Type I and Type II combs. PMID:24663786

Torres-Company, Victor; Castelló-Lurbe, David; Silvestre, Enrique

2014-02-24

82

Theory and applications of sampled analog recursive CTD comb filters  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

83

Tunable Surface Properties from Bioinspired Comb Copolymers  

NASA Astrophysics Data System (ADS)

A modular polymer system which incorporates multiple functionalities simultaneously while keeping an identical backbone chemistry is a useful tool in determining necessary functionalities for marine antifouling properties. We have investigated the surface properties and antifouling behavior of polypeptoids, a class of non-natural biomimetic polymers based on an N-substituted glycine backbone, that combine many of the advantageous properties of bulk polymers with those of synthetically produced proteins, including controllable chain shape, sequence, and self-assembled structure. Using thiol-ene click chemistry, thiol functionalized amphiphilic peptoid sequences consisting of hydrophilic methoxyethyl and hydrophobic heptafluorobutyl side chains were attached to polystyrene-block-poly(ethylene oxide-stat-allyl glycidyl ether), creating comb-shaped molecules. Near edge X-ray absorption fine structure spectroscopy (NEXAFS) was used to study the surface characteristics as a function of peptoid length and composition. Only 20% of fluorinated groups in the peptoid were sufficient for promoting surface display of the otherwise hydrophilic PEO/peptoid comb block. Antifouling experiments with spores of the green algae Ulva indicated an influence of sequence.

van Zoelen, Wendy; Buss, Hilda; Ellebracht, Nathan; Zuckermann, Ronald; Segalman, Rachel

2013-03-01

84

Nanoscale clustering of RGD peptides at surfaces using comb polymers. 2. Surface segregation of comb polymers in polylactide.  

PubMed

Part 1 of these studies described poly(methyl methacrylate-r-polyoxyethylene methacrylate) P(MMA-r-POEM) comb polymers that present Arg-Gly-Asp (RGD) peptides at a surface in nanoscale clusters on a protein-resistant background for control of cell adhesion. Here in part 2, we examine surface segregation of these peptide-modified and unmodified comb polymers blended with polylactide (PLA) as a self-assembly approach suitable for surface modification of porous tissue engineering scaffolds. Multiple thermodynamic driving forces for surface enrichment of the comb polymer are exploited by annealing PLA/P(MMA-r-POEM) blends above the glass transition of the blend components but below the melting point of PLA, while in contact with water. Predictions of the interfacial composition profiles of annealed blends were made using a self-consistent field (SCF) lattice model. The calculations predict strong enrichment of the comb in the top approximately 50 A of blends, and organization of comb molecules in quasi-2D conformations at the interface, similar to the apparent structure of pure comb surfaces in contact with water described in part 1. Experimentally, PLA/comb blend surfaces were characterized by contact angle measurements, XPS, quantification of ligand-cluster surface density and stability by AFM and fluorescent nanosphere labeling, and cell attachment assays. These data were consistent with SCF predictions, showing significant enrichment of the comb at water-annealed surfaces and RGD cluster densities consistent with 2D conformations for comb molecules in the surface layer. Bulk miscibility of the blends was verified by dynamic rheometry, small-angle neutron scattering, DSC and X-ray diffraction studies. Surface segregation of combs provided tunable cell adhesion on PLA through surface-localized nanoclusters of RGD atop a cell-resistant background. PMID:11749219

Irvine, D J; Ruzette, A V; Mayes, A M; Griffith, L G

2001-01-01

85

Digital processing of RF signals from optical frequency combs  

NASA Astrophysics Data System (ADS)

The presented work is focused on digital processing of beat note signals from a femtosecond optical frequency comb. The levels of mixing products of single spectral components of the comb with CW laser sources are usually very low compared to products of mixing all the comb components together. RF counters are more likely to measure the frequency of the strongest spectral component rather than a weak beat note. Proposed experimental digital signal processing system solves this problem by analyzing the whole spectrum of the output RF signal and using software defined radio (SDR) algorithms. Our efforts concentrate in two main areas: Firstly, using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. Secondly, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique used for assessing the offset and repetition frequencies of the comb, resulting in digital servo-loop stabilization of the fs comb. Software capable of computing and analyzing the beat-note RF spectrums using FFT and peak detection was developed. A SDR algorithm performing phase demodulation on the f- 2f signal is used as a regulation error signal source for a digital phase-locked loop stabilizing the offset frequency of the fs comb.

Cizek, Martin; Smid, Radek; Buchta, Zden?k.; Mikel, B?etislav; Lazar, Josef; Cip, Ond?ej

2013-01-01

86

A phase-stabilized carbon nanotube fiber laser frequency comb.  

PubMed

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

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

87

Coherent terabit communications with microresonator Kerr frequency combs  

NASA Astrophysics Data System (ADS)

Optical frequency combs have the potential to revolutionize terabit communications. The generation of Kerr combs in nonlinear microresonators is particularly promising, enabling line spacings of tens of gigahertz. However, such combs may exhibit strong phase noise, which has made high-speed data transmission impossible up to now. Here, we demonstrate that systematic adjustment of the pump conditions for low phase noise 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-1 on a Kerr comb using quadrature phase-shift keying and 16-state quadrature amplitude modulation. A second experiment demonstrates feedback stabilization of the comb and transmission of a 1.44 Tbit s-1 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 route towards chip-scale terabit-per-second transceivers.

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

88

Dual-comb spectroscopy using frequency-doubled combs around 775 nm.  

PubMed

Two frequency-doubled combs are generated by nonlinear frequency conversion to realize spectroscopic measurements around 775 nm. Frequency-doubled interferograms are corrected in real-time by monitoring the relative instabilities between the combs at their fundamental frequency. Rubidium absorption lines are used to demonstrate the technique's accuracy and serve as absolute references to calibrate the frequency grid of computed spectra. The method allows frequency-doubled interferograms to be averaged without distortion during long periods of time. The calibrated frequency grid is validated by the measurement of the oxygen A-band. Moreover, the measurement analysis of the acetylene ?(1) + 3?(3) overtone band has revealed some discrepancies with previous publications. PMID:24514646

Potvin, Simon; Genest, Jérôme

2013-12-16

89

Linear and Nonlinear Molecular Spectroscopy with Laser Frequency Combs  

NASA Astrophysics Data System (ADS)

The regular pulse train of a mode-locked femtosecond laser can give rise to a comb spectrum of millions of laser modes with a spacing precisely equal to the pulse repetition frequency. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. They are now becoming enabling tools for an increasing number of applications, including molecular spectroscopy. Recent experiments of multi-heterodyne frequency comb Fourier transform spectroscopy (also called dual-comb spectroscopy) have demonstrated that the precisely spaced spectral lines of a laser frequency comb can be harnessed for new techniques of linear absorption spectroscopy. The first proof-of-principle experiments have demonstrated a very exciting potential of dual-comb spectroscopy without moving parts for ultra-rapid and ultra-sensitive recording of complex broad spectral bandwidth molecular spectra. Compared to conventional Michelson-based Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds, with intriguing prospects for spectroscopy of short lived transient species. The resolution improves proportionally to the measurement time. Therefore longer recordings allow high resolution spectroscopy of molecules with extreme precision, since the absolute frequency of each laser comb line can be known with the accuracy of an atomic clock. Moreover, since laser frequency combs involve intense ultrashort laser pulses, nonlinear interactions can be harnessed. Broad spectral bandwidth ultra-rapid nonlinear molecular spectroscopy and imaging with two laser frequency combs is demonstrated with coherent Raman effects and two-photon excitation. Real-time multiplex accessing of hyperspectral images may dramatically expand the range of applications of nonlinear microscopy. B. Bernhardt et al., Nature Photonics 4, 55-57 (2010); A. Schliesser et al. Nature Photonics 6, 440-449 (2012); T. Ideguchi et al. arXiv:1201.4177 (2012) T. Ideguchi et al., Optics letters 37, 4498-4500 (2012); T. Ideguchi et al. arXiv:1302.2414 (2013)

Picque, Nathalie

2013-06-01

90

Route to stabilized ultrabroadband microresonator-based frequency combs.  

PubMed

We perform the first theoretical modeling of the full spectral-temporal dynamics of octave-spanning parametric microresonator comb generation through use of the Lugiato-Lefever model extended to include higher-order dispersion and self-steepening. We show that three distinct stages are necessary to achieve single-pulse modelocking and discuss the dispersion characteristics required for ultrabroadband, stabilized comb generation. Our simulations agree well with previous experimental demonstrations and predict many of the observed features, including multipulse generation, dispersive wave generation, modelocking, and comb stabilization. PMID:24104792

Lamont, Michael R E; Okawachi, Yoshitomo; Gaeta, Alexander L

2013-09-15

91

Nonlinear dynamics of comb generation in optical microresonators  

NASA Astrophysics Data System (ADS)

Various aspects of the nonlinear dynamics of Kerr frequency comb generation in optical microresonators are considered. It is shown that the comb generation process can, for the case of a single continuous wave pump, be given a simple interpretation in terms of modulational instability and that the essential dynamics can be captured using a three wave mode truncation for the pump mode and the dominant sideband pair. This idea is also extended using a four wave model to analyze an alternative dual pump configuration, for which comb generation may occur without a pump intensity threshold in both the normal and the anomalous dispersion regime.

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

2014-03-01

92

High-coherence mid-infrared frequency comb.  

PubMed

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

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

2013-11-18

93

Comb entanglement in quantum spin chains  

SciTech Connect

Bipartite entanglement in the ground state of a chain of N quantum spins can be quantified either by computing pairwise concurrence or by dividing the chain into two complementary subsystems. In the latter case the smaller subsystem is usually a single spin or a block of adjacent spins and the entanglement differentiates between critical and noncritical regimes. Here we extend this approach by considering a more general setting: our smaller subsystem S{sub A} consists of a comb of L spins, spaced p sites apart. Our results are thus not restricted to a simple area law, but contain nonlocal information, parametrized by the spacing p. For the XX model we calculate the von Neumann entropy analytically when N{yields}{infinity} and investigate its dependence on L and p. We find that an external magnetic field induces an unexpected length scale for entanglement in this case.

Keating, J. P.; Mezzadri, F.; Novaes, M. [School of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom)

2006-07-15

94

Multicolor Detection of Combed DNA Molecules Using Quantum Dots  

NASA Astrophysics Data System (ADS)

DNA combing is a useful strategy for manipulating single DNA molecules and has a wide range of applications in genetics, single molecule studies, and nanobiotechnology. Visualization of combed DNA molecules is usually performed by using DNA binding organic dyes. Such dyes are not suitable in all circumstances, especially because of their photoreactivity. We have developed a method for the detection of combed DNA molecules by fluorescence microscopy that avoids the use of DNA-staining agents and does not perturb the structure of the DNA molecule. Biotin- and/or digoxigenin-modified DNA fragments are covalently linked at both ends of a DNA molecule via sequence-specific hybridization and subsequent ligation. After the modified DNA molecules have been combed on a polystyrene-coated surface, their ends are visualized by multicolor fluorescence microscopy using conjugated quantum dots.

Escudé, Christophe; Géron-Landre, Bénédicte; Crut, Aurélien; Desbiolles, Pierre

95

Probing coherence in microcavity frequency combs via optical pulse shaping.  

PubMed

Recent investigations of microcavity frequency combs based on cascaded four-wave mixing have revealed a link between the evolution of the optical spectrum and the observed temporal coherence. Here we study a silicon nitride microresonator for which the initial four-wave mixing sidebands are spaced by multiple free spectral ranges (FSRs) from the pump. Additional lines then fill in to yield a comb with single FSR spacing, resulting in partial coherence. By using a pulse shaper to select and manipulate the phase of various subsets of spectral lines, we are able to probe the structure of the coherence within the partially coherent comb. Our data demonstrate strong variation in the degree of mutual coherence between different groups of lines and provide support for a simple model of partially coherent comb formation. PMID:23037227

Ferdous, Fahmida; Miao, Houxun; Wang, Pei-Hsun; Leaird, Daniel E; Srinivasan, Kartik; Chen, Lei; Aksyuk, Vladimir; Weiner, Andrew M

2012-09-10

96

Optimal Sharpening of Compensated Comb Decimation Filters: Analysis and Design  

PubMed Central

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

Troncoso Romero, David Ernesto

2014-01-01

97

Quantum memory based on a spatiospectral atomic comb  

NASA Astrophysics Data System (ADS)

An atomic comb structure consisting of both spatial and spectral components is proposed for the implementation of quantum memory using inhomogeneously broadened atomic ensembles, such as rare-earth ions trapped in solids. The spatiospectral comb can be prepared in two-level atoms provided a third energy level is available for atomic population storage. The output photon is retrieved from the memory as a spatially diffracted photon echo. The angle between the input and output directions is controlled by the spatial component of the atomic comb. The memory efficiency is analyzed using coupled wave theory, which results in memory efficiency varying with the retrieval angle: 54.1% in collinear, 81.6% in perpendicular, and 100% in counterpropagating configurations. An experimental method for creating a multidimensional atomic comb is suggested.

Tian, Mingzhen; Vega, Devin; Dilles, Jacob

2013-04-01

98

Radiative properties tailoring of grating by comb-drive microactuator  

NASA Astrophysics Data System (ADS)

Micro-scale grating structures are widely researched in recent years. Although micro-scale fabrication technology is highly advanced today, with grating aspect ratio greater than 25:1 being achievable some fabrication requirements, such as fine groove processing, are still challenging. Comb-drive microactuator is proposed in this paper to be utilized on simple binary grating structures for tailoring or modulating spectral radiation properties by active adjustment. The rigorous coupled-wave analysis (RCWA) is used to calculate the absorptance of proposed structures and to investigate the impacts brought by the geometry and displacement of comb-drive microactuator. The results show that the utilization of comb-drive microactuator on grating improves the absorptance of simple binary grating while avoiding the difficulty fine groove processing. Spectral radiation property tailoring after gratings are fabricated becomes possible with the comb-drive microactuator structure.

Jiao, Y.; Liu, L. H.; Liu, L. J.; Hsu, P.-f.

2014-08-01

99

Entanglement of Atomic Qubits Using an Optical Frequency Comb.  

National Technical Information Service (NTIS)

We demonstrate the use of an optical frequency comb to coherently control and entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used to efficiently and coherently transfer population between electronic and vibrational states of tra...

D. Hayes D. Hucul D. N. Matsukevich P. Maunz Q. Quraishi

2010-01-01

100

CombFunc: predicting protein function using heterogeneous data sources  

PubMed Central

Only a small fraction of known proteins have been functionally characterized, making protein function prediction essential to propose annotations for uncharacterized proteins. In recent years many function prediction methods have been developed using various sources of biological data from protein sequence and structure to gene expression data. Here we present the CombFunc web server, which makes Gene Ontology (GO)-based protein function predictions. CombFunc incorporates ConFunc, our existing function prediction method, with other approaches for function prediction that use protein sequence, gene expression and protein–protein interaction data. In benchmarking on a set of 1686 proteins CombFunc obtains precision and recall of 0.71 and 0.64 respectively for gene ontology molecular function terms. For biological process GO terms precision of 0.74 and recall of 0.41 is obtained. CombFunc is available at http://www.sbg.bio.ic.ac.uk/combfunc.

Wass, Mark N.; Barton, Geraint; Sternberg, Michael J. E.

2012-01-01

101

Direct frequency comb spectroscopy in the extreme ultraviolet.  

PubMed

The development of the optical frequency comb (a spectrum consisting of a series of evenly spaced lines) has revolutionized metrology and precision spectroscopy owing to its ability to provide a precise and direct link between microwave and optical frequencies. A further advance in frequency comb technology is the generation of frequency combs in the extreme-ultraviolet spectral range by means of high-harmonic generation in a femtosecond enhancement cavity. Until now, combs produced by this method have lacked sufficient power for applications, a drawback that has also hampered efforts to observe phase coherence of the high-repetition-rate pulse train produced by high-harmonic generation, which is an extremely nonlinear process. Here we report the generation of extreme-ultraviolet frequency combs, reaching wavelengths of 40?nanometres, by coupling a high-power near-infrared frequency comb to a robust femtosecond enhancement cavity. These combs are powerful enough for us to observe single-photon spectroscopy signals for both an argon transition at 82?nanometres and a neon transition at 63?nanometres, thus confirming the combs' coherence in the extreme ultraviolet. The absolute frequency of the argon transition has been determined by direct frequency comb spectroscopy. The resolved ten-megahertz linewidth of the transition, which is limited by the temperature of the argon atoms, is unprecedented in this spectral region and places a stringent upper limit on the linewidth of individual comb teeth. Owing to the lack of continuous-wave lasers, extreme-ultraviolet frequency combs are at present the only promising route to extending ultrahigh-precision spectroscopy to the spectral region below 100?nanometres. At such wavelengths there is a wide range of applications, including the spectroscopy of electronic transitions in molecules, experimental tests of bound-state and many-body quantum electrodynamics in singly ionized helium and neutral helium, the development of next-generation 'nuclear' clocks and searches for variation of fundamental constants using the enhanced sensitivity of highly charged ions. PMID:22297971

Cingöz, Arman; Yost, Dylan C; Allison, Thomas K; Ruehl, Axel; Fermann, Martin E; Hartl, Ingmar; Ye, Jun

2012-02-01

102

Sex Chromosome  

NSDL National Science Digital Library

A sex chromosome is one of the two chromosomes that specify an organism's genetic sex. Humans have two kinds of sex chromosomes, one called X and the other Y. Normal females possess two X chromosomes and normal males one X and one Y.

BEGIN:VCARD VERSION:2.1 FN:Darryl Leja N:Leja;Darryl ORG:National Human Genome Research Institute REV:2005-04-14 END:VCARD

2005-04-14

103

Dynamics of the modulational instability in microresonator frequency combs  

NASA Astrophysics Data System (ADS)

A study is made of frequency-comb generation described by the driven and damped nonlinear Schrödinger equation on a finite interval. It is shown that frequency-comb generation can be interpreted as a modulational instability of the continuous-wave pump mode, and a linear stability analysis, taking into account the cavity boundary conditions, is performed. Further, a truncated three-wave model is derived, which allows one to gain additional insight into the dynamical behavior of the comb generation. This formalism describes the pump mode and the most unstable sideband and is found to connect the coupled mode theory with the conventional theory of modulational instability. An in-depth analysis is done of the nonlinear three-wave model. It is demonstrated that stable frequency-comb states can be interpreted as attractive fixed points of a dynamical system. The possibility of soft and hard excitation states in both the normal and the anomalous dispersion regime is discussed. Investigations are made of bistable comb states and the dependence of the final state on the way the comb has been generated. The analytical predictions are verified by means of direct comparison with numerical simulations of the full equation and the agreement is discussed.

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

2013-08-01

104

Adaptive real-time dual-comb spectroscopy  

NASA Astrophysics Data System (ADS)

The spectrum of a laser frequency comb consists of several hundred thousand equally spaced lines over a broad spectral bandwidth. Such frequency combs have revolutionized optical frequency metrology and they now hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite an intriguing potential for the measurement of molecular spectra spanning tens of nanometres within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the demanding stability requirements of the laser combs. Here we overcome this difficulty and experimentally demonstrate a concept of real-time dual-comb spectroscopy, which compensates for laser instabilities by electronic signal processing. It only uses free-running mode-locked lasers without any phase-lock electronics. We record spectra spanning the full bandwidth of near-infrared fibre lasers with Doppler-limited line profiles highly suitable for measurements of concentrations or line intensities. Our new technique of adaptive dual-comb spectroscopy offers a powerful transdisciplinary instrument for analytical sciences.

Ideguchi, Takuro; Poisson, Antonin; Guelachvili, Guy; Picqué, Nathalie; Hänsch, Theodor W.

2014-02-01

105

Parentage and relatedness in polyandrous comb-crested jacanas using ISSRs  

USGS Publications Warehouse

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.

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

2003-01-01

106

Self-injection locking and phase-locked states in microresonator-based optical frequency combs.  

PubMed

Microresonator-based optical frequency combs have been a topic of extensive research during the last few years. Several theoretical models for the comb generation have been proposed; however, they do not comprehensively address experimental results that show a variety of independent comb generation mechanisms. Here, we present frequency-domain experiments that illuminate the transition of microcombs into phase-locked states, which show characteristics of injection locking between ensembles of comb modes. In addition, we demonstrate the existence of equidistant optical frequency combs that are phase stable but have nondeterministic phase relationships between individual comb modes. PMID:24580454

Del'Haye, Pascal; Beha, Katja; Papp, Scott B; Diddams, Scott A

2014-01-31

107

Self-Injection Locking and Phase-Locked States in Microresonator-Based Optical Frequency Combs  

NASA Astrophysics Data System (ADS)

Microresonator-based optical frequency combs have been a topic of extensive research during the last few years. Several theoretical models for the comb generation have been proposed; however, they do not comprehensively address experimental results that show a variety of independent comb generation mechanisms. Here, we present frequency-domain experiments that illuminate the transition of microcombs into phase-locked states, which show characteristics of injection locking between ensembles of comb modes. In addition, we demonstrate the existence of equidistant optical frequency combs that are phase stable but have nondeterministic phase relationships between individual comb modes.

Del'Haye, Pascal; Beha, Katja; Papp, Scott B.; Diddams, Scott A.

2014-01-01

108

Comb Polymer Architectures for Versatile Nanoparticle Assembly  

NASA Astrophysics Data System (ADS)

Nanoparticles are a material of interest in photovoltaic research due to their optical absorption properties. However, there have been many challenges for device fabrication. It has been difficult to produce continuous, homogenous films, and successes in this area have been highly dependent on the actual nanoparticles used, and have thus been hard to apply generally to different materials of interest. We show how this challenge can be overcome using a comb polymer architecture. Here, pentadecyl phenol small molecules are hydrogen bonded to polyvinyl pyridine. This alkyl moiety produced is compatible with the ligand shells of many nanomaterials. We incorporated these small molecules and nanoparticles into polystrene-polyvinyl pyridine block copolymers. This strategy was successful for assembling nanoparticles made out of a variety of materials, without special considerations for the actual core material or morphology. Following these successes in bulk samples we extended our studies to thin films of these composites. Here, the morphology is controlled by the interfacial interactions. These materials have the potential to be used for photovoltaic devices, as they are easily solution-processible. This strategy is generally applicable with the choice of small molecule mediating interactions with any desired nanomaterial.

Mastroianni, Alexander; Thorkelsson, Kari; Zhao, Yue; Luther, Joseph; Millstone, Jill; Alivisatos, Paul; Frechet, Jean; Xu, Ting

2009-03-01

109

Brood comb as a humidity buffer in honeybee nests  

NASA Astrophysics Data System (ADS)

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.

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

2010-04-01

110

Microresonator-based comb generation without an external laser source  

NASA Astrophysics Data System (ADS)

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-integrated chip-scale source with an on-chip amplifier.

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

2014-01-01

111

Development of Chip-Based Frequency Combs for Spectral and Timing Applications.  

National Technical Information Service (NTIS)

This report describes research results in developing the technology for the generation of a broadband parametric frequency combs with flexible operating wavelengths and comb spacing. The research showed the flexibility in operating wavelengths with demons...

Y. Okawachi

2011-01-01

112

Production, Detection, and Control of Ultracold Molecules via Optical Frequency Combs.  

National Technical Information Service (NTIS)

Cavity-enhanced direct frequency comb spectroscopy combines broad bandwidth, high spectral resolution, and ultrahigh detection sensitivity in one experimental platform based on an optical frequency comb efficiently coupled to a high-finesse cavity. The ef...

J. Ye

2012-01-01

113

CombNET-III: A Support Vector Machine Based Large Scale Classifier with Probabilistic Framework  

Microsoft Academic Search

Abstract—CombNET-II was one of the first methods proposed for solving classification problems with large number,of categories. This paper proposes an extension to this model, named CombNET-III, which replaces the MLP branch networks with multiclass SVMs and introduces a new probabilistic framework. The experiments show that CombNET-III outperforms both CombNET-II and a single multiclass SVM. Keywords— large scale classification problems,

Mauricio Kugler; Susumu Kuroyanagi; Anto Satriyo Nugroho; Akira Iwata

2006-01-01

114

Honeybee combs: construction through a liquid equilibrium process?  

NASA Astrophysics Data System (ADS)

Geometrical investigations of honeycombs and speculations on how honeybees measure and construct the hexagons and rhombi of their cells are centuries old. Here we show that honeybees neither have to measure nor construct the highly regular structures of a honeycomb, and that the observed pattern of combs can be parsimoniously explained by wax flowing in liquid equilibrium. The structure of the combs of honeybees results from wax as a thermoplastic building medium, which softens and hardens as a result of increasing and decreasing temperatures. It flows among an array of transient, close-packed cylinders which are actually the self-heated honeybees themselves. The three apparent rhomboids forming the base of each cell do not exist but arise as optical artefacts from looking through semi-transparent combs.

Pirk, C. W. W.; Hepburn, H. R.; Radloff, S. E.; Tautz, J.

115

Frequency stability of a femtosecond optical parametric oscillator frequency comb.  

PubMed

Carrier-envelope-offset (CEO) and pulse-repetition frequencies of a Ti:sapphire-pumped femtosecond optical parametric oscillator were locked to uncertainties of 0.09 Hz and 0.16 mHz respectively, with the CEO beat signal linewidth being stabilized to 15 Hz (instrument limited). In-loop phase-noise power spectral density measurements showed a contribution of our servo electronics to the comb-line frequency uncertainty of up to 110 Hz. Complementary time-series data implied an in-loop comb instability of 2 x 10(-11) (1-s gate time), matching the Rb-stabilized reference used and verifying that dual servo-control of the CEO and repetition frequencies was effective in stabilizing the comb to at least this precision. PMID:22109442

Ferreiro, Teresa I; Sun, Jinghua; Reid, Derryck T

2011-11-21

116

Tunable Mid-Ir Frequency Comb for Molecular Spectroscopy  

NASA Astrophysics Data System (ADS)

A mid-infrared frequency comb tunable from 2.7?m to 4.7?m (3700cm-1 to 2100cm-1) has been produced using a fiber laser and difference frequency generation in a periodically poled LiNbO_3 (PPLN) crystal. An amplified Yb-doped femtosecond fiber laser is centered at a wavelength of 1.04?m, with 100MHz repetition frequency and up to 2.5W average output power. Part of this laser power is focused into a photonic crystal fiber to produce a Raman-shifted soliton tunable over a range from 1.3?m to 1.7?m. The remaining 1.04?m light is combined with the wavelength-shifted spectrum and focused into the PPLN to produce a difference frequency comb spanning ˜200nm (180cm-1) in the mid-infrared. By adjusting the Raman-shifted soliton and PPLN, the center wavelength of the MIR comb is tuned over the output range, with a maximum power of up to 35mW near 3.3?m. Sum frequency generation between the MIR comb and a CW 1064nm laser shifts the frequency comb spectrum back into the near-infrared around 800nm. This sum frequency step is taken in order to utilize detectors and techniques that are currently more accessible in the visible and near-infrared ranges. Preliminary results have shown MIR methane absorption lines observable in the upconverted 800nm spectrum on a commercial optical spectrum analyzer. We intend to measure this upconverted spectrum at high resolution using a two-dimensional dispersion and imaging technique to take advantage of the precisely known frequency characteristics of each individual MIR comb line. L. Hollberg, V. Mbele, and S. A. Diddams, Nature 445, 627 (2007).

Johnson, Todd A.; Diddams, Scott A.

2010-06-01

117

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

Microsoft Academic Search

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

Thomas D. Seeley

2002-01-01

118

80 W, 120 fs Yb-fiber frequency comb.  

PubMed

We report on a high-power fiber frequency comb exhibiting linear chirped-pulse amplification up to 80 W and generating 120 fs pulses. By proper matching of the group delay between the fiber stretcher and compressor, a compression ratio of 3100 could be achieved. Carrier envelope offset self-referencing and long-term phase locking to an rf reference is demonstrated, exemplifying the suitability of this system for generating vacuum and extreme-UV frequency combs via enhancement in passive cavities and high harmonic generation. PMID:20847763

Ruehl, Axel; Marcinkevicius, Andrius; Fermann, Martin E; Hartl, Ingmar

2010-09-15

119

Generation and characterization of multimode quantum frequency combs.  

PubMed

Multimode nonclassical states of light are an essential resource in quantum computation with continuous variables, for example, in cluster state computation. We report in this Letter the first experimental evidence of a multimode nonclassical frequency comb in a femtosecond synchronously pumped optical parametric oscillator. In addition to a global reduction of its quantum intensity fluctuations, the system features quantum correlations between different parts of its frequency spectrum. This allows us to show that the frequency comb is composed of several uncorrelated eigenmodes having specific spectral shapes, two of them at least being squeezed, and to characterize their spectral shapes. PMID:22463528

Pinel, Olivier; Jian, Pu; Medeiros de Araújo, Renné; Feng, Jinxia; Chalopin, Benoît; Fabre, Claude; Treps, Nicolas

2012-02-24

120

Occupation times on a comb with ramified teeth  

NASA Astrophysics Data System (ADS)

We investigate occupation time statistics for random walks on a comb with ramified teeth. This is achieved through the relation between the occupation time and the first passage times. Statistics of occupation times in half space follows Lamperti's distribution, i.e., the generalized arcsine law holds. Transitions between different behaviors are observed, which are controlled by the size of the backbone and teeth of the comb, as well as bias. Occupation time on a nonsimply connected domain is analyzed with a mean-field theory and numerical simulations. In that case, the generalized arcsine law is not valid.

Rebenshtok, A.; Barkai, E.

2013-11-01

121

Octave-spanning Raman comb with carrier envelope offset control.  

PubMed

We report that adiabatic manipulation of a Raman process allows us to produce an optical-frequency comb from single-frequency lasers. We realize an octave-spanning Raman comb with carrier-envelope-offset frequency control, by using dual-frequency laser radiation locked on a single laser cavity and simultaneously its second harmonic. It is shown that in both the temporal and spectral domains, locking the dual frequencies on a single laser cavity provides control of the carrier-envelope-offset frequency at integer multiples of the free spectral range of the laser cavity. PMID:19113620

Suzuki, Takayuki; Hirai, Masataka; Katsuragawa, Masayuki

2008-12-12

122

Frequency-Comb-Assisted Terahertz Quantum Cascade Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

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.

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

123

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

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

Robbins, Clarence; Kamath, Yash

2007-01-01

124

Safe sex  

NSDL National Science Digital Library

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.

Olivia Worland (Purdue University;Biological Sciences)

2008-07-09

125

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

NASA Astrophysics Data System (ADS)

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.

Hou, Dong; Wu, Jiutao; Zhang, Shuangyou; Ren, Quansheng; Zhang, Zhigang; Zhao, Jianye

2014-03-01

126

Sex work and sex trafficking.  

PubMed

Preventing HIV infection and other sexually transmitted diseases (STDs), as well as sexual and physical violence, are major occupational health and safety concerns for prostitutes. Considerable evidence shows that anti-prostitution laws facilitate violence and abuse against prostitutes and may increase their risk of contracting HIV/STDs. For example, police often take advantage of existing laws against prostitution to demand money or sex. In general, the strict enforcement of anti-prostitution laws marginalizes prostitutes from services which could help them avoid abuse and promotes an environment in which prostitutes must take risks to avoid detection and arrest. One strategy to improve prostitutes' lives would therefore be to remove laws which prevent them from working safely and from travelling abroad to work legally. Projects in which prostitutes are actively involved have helped break down stereotypes against prostitutes, while police-sex worker liaison projects in Scotland and Australia have led to higher levels of reporting of crimes against prostitutes. The Network of Sex Work Projects (NSWP), an organization which links sex worker health programs around the world, has found that the incidence of HIV/STDs among prostitutes is lowest when they have control over their work conditions; access to condoms, lubricants, and other safe sex materials; and respect of their basic human and legal rights. People need to understand that consensual involvement in sex work is different from forced sex trafficking. PMID:12348692

Ditmore, M; Saunders, P

1998-01-01

127

Reconfigurable optical comb filter based on Opto-ULSI processing  

Microsoft Academic Search

In this paper, we demonstrate a reconfigurable 6-channel 0.5 nm-bandwidth optical comb filter employing an Opto-ULSI processor. Independent control of the pass-band transmission and centre wavelength is demonstrated over more than 10 nm wavelength range.

Chung Kiak Poh; Zhenglin Wang; Kamal Alameh; Rong Zheng

2005-01-01

128

Paleontology: a cock's comb on a duck-billed dinosaur.  

PubMed

A soft tissue structure has been discovered on the head of the duck-billed dinosaur Edmontosaurus. Its similarity to a cock's comb and other sexually dimorphic structures of birds suggests that potential sexual signals existed in these extinct animals. PMID:24456984

Horner, John R

2014-01-20

129

ANALYSIS OF PIANO TONES USING AN INHARMONIC INVERSE COMB FILTER  

Microsoft Academic Search

This paper presents a filter configuration for canceling and separat- ing partials from inharmonic piano tones. The proposed configu- ration is based on inverse comb filtering, in which the delay line is replaced with a high-order filter that has a proper phase response. Two filter design techniques are tested with the method: an FIR fil- ter, which is designed using

Heidi-Maria Lehtonen

2008-01-01

130

Frequency combs and precision spectroscopy in the extreme ultraviolet  

NASA Astrophysics Data System (ADS)

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

Cingöz, Arman

2012-06-01

131

[Technique progress of high-precision gas absorption spectroscopy with femtosecond optical frequency comb].  

PubMed

Femtosecond optical frequency comb, with large spectral range, narrow pulse width, high stability of frequency and many other remarkable properties, has a significant impact on optical frequency metrology, absolute distance measurement and high-precision spectroscopy. The time-domain and frequency-domain properties of femtosecond optical frequency comb is traced back to the microwave frequency standard, making it possible to open up the door to high-precision gas absorption spectrum detection. Femtosecond optical frequency comb spectroscopy has some excellent performances, such as fast measurement, high sensitivity, high resolution, high signal-to-noise ratio and so on. Therefore, more investments on femtosecond optical frequency comb spectroscopy will better make contribution to the environmental protection, industrial production, biological medicine, scientific research and other social fields. High-precision gas absorption spectroscopy with femtosecond optical frequency comb mainly includes frequency comb based cavity ring-down spectroscopy, cavity-enhanced frequency comb spectroscopy and dual-comb multi-heterodyne spectroscopy. Among them, according to the data collection, cavity-enhanced frequency comb spectroscopy can be divided into comb vernier method, virtually imaged phased array method and Fourier transform method. At present, related research has been widely carried out abroad, and domestic research is still in its infancy. This review summarizes main techniques in the high-precision gas absorption spectrum detection based on optical frequency comb, and demonstrates typical experimental schemes for different methods. It also analyzes the advantages and disadvantages of each method, and tracks frontier achievements of main research groups. PMID:24822396

Yang, Hong-Lei; Wei, Hao-Yun; Li, Yan; Ren, Li-Bing; Zhang, Hong-Yuan

2014-02-01

132

Observation of correlation between route to formation, coherence, noise, and communication performance of Kerr combs.  

PubMed

Microresonator optical frequency combs based on cascaded four-wave mixing are potentially attractive as a multi-wavelength source for on-chip optical communications. In this paper we compare time domain coherence, radio-frequency (RF) intensity noise, and individual line optical communications performance for combs generated from two different silicon nitride microresonators. The comb generated by one microresonator forms directly with lines spaced by a single free spectral range (FSR) and exhibits high coherence, low noise, and excellent 10 Gbit/s optical communications results. The comb generated by the second microresonator forms initially with multiple FSR line spacing, with additional lines later filling to reach single FSR spacing. This comb exhibits degraded coherence, increased intensity noise, and severely degraded communications performance. This study is to our knowledge the first to simultaneously investigate and observe a correlation between the route to comb formation, the coherence, noise, and optical communications performance of a Kerr comb. PMID:23388754

Wang, Pei-Hsun; Ferdous, Fahmida; Miao, Houxun; Wang, Jian; Leaird, Daniel E; Srinivasan, Kartik; Chen, Lei; Aksyuk, Vladimir; Weiner, Andrew M

2012-12-31

133

Frequency comb injection locking of mode locked lasers  

NASA Astrophysics Data System (ADS)

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.

Gat, Omri; Kielpinski, David

2013-03-01

134

Intraspecific comb usurpation in the social wasp Polistes fuscatus  

Microsoft Academic Search

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

J. Klahn

1988-01-01

135

Infrared frequency combs and supercontinua for multiplex high sensitivity spectroscopy  

PubMed Central

An infrared high-brightness light source based on supercontinuum generation through a SF6 photonic crystal fiber seeded by a Cr4+:YAG femtosecond oscillator is developed for high resolution multiplex spectroscopy in the 1.5 ?m region. Moreover, a multiplex high resolution approach based on a Cr4+:YAG frequency comb enables to probe large spectral domains, with simultaneous sensitive measurement of the absorption and the dispersion associated with all individual spectral features.

Mandon, J.; Sorokin, E.; Sorokina, I.T; Guelachvili, G.; Picque, N.

2010-01-01

136

Electrostatic-comb drive of lateral polysilicon resonators  

Microsoft Academic Search

This paper mvestlgates the elcctrostatlc dnve and sense of polynhcon resonators parallel to the substrate, using an mterdlgtated capacitor (elec- trostatic comb) Three expenmental methods are used nucroscoplc observation mth contmuous or stroboscopic iummatlon, capacltlve sensing using an amphtude-modulation technique and SEM ob- servation The mtnnslc quality factor of the phosphorus-doped low-pressure chemlcal-vapor- deposited (LPCVD) polyslhcon resonators is 49 000

William C. Tang; Tu-Cuong H. Nguyen; Michael W. Judy; Roger T. Howe

1990-01-01

137

Generation of a frequency comb and applications thereof  

DOEpatents

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.

Hagmann, Mark J; Yarotski, Dmitry A

2013-12-03

138

Reclassification of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov.  

PubMed

This paper describes a phenotypic and genotypic investigation of the taxonomy of [Haemophilus] paragallinarum, Pasteurella gallinarum, Pasteurella avium and Pasteurella volantium, a major subcluster within the avian 16S rRNA cluster 18 of the family Pasteurellaceae. An extended phenotypic characterization was performed of the type strain of [Haemophilus] paragallinarum, which is NAD-dependent, and eight NAD-independent strains of [Haemophilus] paragallinarum. Complete 16S rRNA gene sequences were obtained for one NAD-independent and four NAD-dependent [Haemophilus] paragallinarum strains. These five sequences along with existing 16S rRNA gene sequences for 11 other taxa within avian 16S rRNA cluster 18 as well as seven other taxa from the Pasteurellaceae were subjected to phylogenetic analysis. The analysis demonstrated that [Haemophilus] paragallinarum, Pasteurella gallinarum, Pasteurella avium and Pasteurella volantium formed a monophyletic group with a minimum of 96.8 % sequence similarity. This group can also be separated by phenotypic testing from all other recognized and named taxa within the Pasteurellaceae. As both genotypic and phenotypic testing support the separate and distinct nature of this subcluster, the transfer is proposed of Pasteurella gallinarum, [Haemophilus] paragallinarum, Pasteurella avium and Pasteurella volantium to a new genus Avibacterium as Avibacterium gallinarum gen. nov., comb. nov., Avibacterium paragallinarum comb. nov., Avibacterium avium comb. nov. and Avibacterium volantium comb. nov. The type strains are NCTC 1118T (Avibacterium gallinarum), NCTC 11296T (Avibacterium paragallinarum), NCTC 11297T (Avibacterium avium) and NCTC 3438T (Avibacterium volantium). Key characteristics that separate these four species are catalase activity (absent only in Avibacterium paragallinarum) and production of acid from galactose (negative only in Avibacterium paragallinarum), maltose (negative only in Avibacterium avium) and mannitol (negative in Avibacterium gallinarum and Avibacterium avium). PMID:15653900

Blackall, Patrick J; Christensen, Henrik; Beckenham, Tim; Blackall, Linda L; Bisgaard, Magne

2005-01-01

139

The Efficient Design and Modification of Cascaded Integrator Comb Filter  

Microsoft Academic Search

The traditional Cascaded Integrator Comb (CIC) filter is introduced at first, and its pass-band attenuation and mirror-aliasing can not meet the requirements of the GSM radio remote unit (RRU) system. Then a compensation technique, Interpolated Second Order Polynomial (ISOP) method, is studied to improve the frequency response of the traditional CIC filter, which can enhance the performance in pass-band. However,

Peng Hong; Zhang Yuhua

2010-01-01

140

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

PubMed

The mechanism of the exclusive growth of Termitomyces in fungus combs with fungi-growing termites, O. formosanus was examined using laboratory scale fungus combs. In the combs without the termites, vigorous growth of unidentified fungi was observed although no significant change was found in the case of the combs with termites. In addition, these results were reproducible even when incubated in a separated dish, suggesting that the physicochemical conditions were not the reason for the growth. With the molecular based analysis for the microbial communities in the combs, monoculture of the Termitomyces in the combs with termites was confirmed while the bacterial communities were independent either with or without termites. Possible mechanism of the exclusive growth of Termitomyces, such as the selective grazing of pathogenic fungi or contribution of antifungal activity giving actinomycetes were also discussed. PMID:16141705

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

2005-08-01

141

Optical frequency comb comparison between optical clock mode and optical frequency synthesizer mode  

NASA Astrophysics Data System (ADS)

We report on an accuracy limit test result of the optical frequency comb technique by comparing the frequencies of two optical frequency combs that operate in two different modes. These two modes are distinguished by the reference frequency for the comb frequency stabilization; an optical frequency (in an optical clock mode) or a microwave frequency (in an optical frequency synthesizer mode). The comparison of the two combs was carried out by simultaneously measuring an absolute frequency of an acetylene-stabilized diode laser with both combs. The frequencies of the two combs agreed with each other within the uncertainty of 16 Hz at 194 THz. The uncertainty is reduced by more than an order compared with a previous report.

Kim, Eok Bong; Park, Chang Yong; Yu, Dai-Hyuk; Park, Sang Eon; Lee, Won-Kyu

2011-02-01

142

Penalty-free wavelength conversion with variable channel separation using gain-switched comb source  

NASA Astrophysics Data System (ADS)

We demonstrate penalty-free all-optical wavelength conversion of 10.7 GBaud QPSK data using four-wave mixing and dual-correlated pumps derived from a gain switched comb source having large phase noise characteristics. We perform all-optical wavelength conversion over a 90 GHz bandwidth and show that the non-degenerate scheme is independent of the phase noise of the dual-pumps as long as they have correlated phase noise. The RF linewidth of the beat tone of the comb lines with separations up to 90 GHz is used to show excellent phase correlation between the comb lines. We obtain an error floor when all-optical wavelength conversion is performed using a single comb line from the gain-switched comb source as a pump in a partially degenerate scheme. The wavelength range for conversion is limited only by the spectral bandwidth of the gain-switched comb source.

Anthur, Aravind P.; Watts, Regan T.; Zhou, Rui; Anandarajah, Prince; Venkitesh, Deepa; Barry, Liam P.

143

Coherent Raman spectro-imaging with laser frequency combs  

NASA Astrophysics Data System (ADS)

Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques.

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

2013-10-01

144

Coherent Raman spectro-imaging with laser frequency combs.  

PubMed

Advances in optical spectroscopy and microscopy have had a profound impact throughout the physical, chemical and biological sciences. One example is coherent Raman spectroscopy, a versatile technique interrogating vibrational transitions in molecules. It offers high spatial resolution and three-dimensional sectioning capabilities that make it a label-free tool for the non-destructive and chemically selective probing of complex systems. Indeed, single-colour Raman bands have been imaged in biological tissue at video rates by using ultra-short-pulse lasers. However, identifying multiple, and possibly unknown, molecules requires broad spectral bandwidth and high resolution. Moderate spectral spans combined with high-speed acquisition are now within reach using multichannel detection or frequency-swept laser beams. Laser frequency combs are finding increasing use for broadband molecular linear absorption spectroscopy. Here we show, by exploring their potential for nonlinear spectroscopy, that they can be harnessed for coherent anti-Stokes Raman spectroscopy and spectro-imaging. The method uses two combs and can simultaneously measure, on the microsecond timescale, all spectral elements over a wide bandwidth and with high resolution on a single photodetector. Although the overall measurement time in our proof-of-principle experiments is limited by the waiting times between successive spectral acquisitions, this limitation can be overcome with further system development. We therefore expect that our approach of using laser frequency combs will not only enable new applications for nonlinear microscopy but also benefit other nonlinear spectroscopic techniques. PMID:24132293

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

2013-10-17

145

Reduced complexity comb-filters for decimation and interpolation in mobile communications terminals  

Microsoft Academic Search

In mobile communications systems complexity and efficiency are issues of paramount importance. Therefore when implementing integer factor sample-rate conversion, comb-filters-especially cascaded-integrator-comb (CIC) filters-are a good choice of realizing linear-phase filters with low complexity. However, neither the direct implementation of comb-filters as transversal filters nor their implementation as CIC-filters are minimal realizations. Since both, decimators and interpolators are time-variant systems, the

Tim Hentschel; Gerhard Fettweis

1999-01-01

146

Silicon-organic hybrid (SOH) frequency comb sources for terabit/s data transmission.  

PubMed

We demonstrate frequency comb sources based on silicon-organic hybrid (SOH) electro-optic modulators. Frequency combs with line spacings of 25 GHz and 40 GHz are generated, featuring flat-top spectra with less than 2 dB power variations over up to 7 lines. The combs are used for WDM data transmission at terabit/s data rates and distances of up to 300 km. PMID:24663654

Weimann, C; Schindler, P C; Palmer, R; Wolf, S; Bekele, D; Korn, D; Pfeifle, J; Koeber, S; Schmogrow, R; Alloatti, L; Elder, D; Yu, H; Bogaerts, W; Dalton, L R; Freude, W; Leuthold, J; Koos, C

2014-02-10

147

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 ...

148

Sex and Heart Disease  

MedlinePLUS

Sex and Heart Disease Updated:Mar 2,2012 Is sex safe for heart disease patients? Readjusting to everyday ... disease, also called cardiovascular disease, will affect your sex life — or if it’s safe to have sex ...

149

Heliconema minnanensis n. sp. (Physalopteroidae: Physalopteridae) and Raphidascaris trichiuri (Yin and Zhang) n. comb. (Ascaridoidea: Anisakidae) in marine fishes.  

PubMed

Heliconema minnanensis n. sp. is described from the Chiloscyllium plagiosum south of the Minnan-Taiwan Bank Fishing Ground, Taiwan Strait. It is characterized by having the following combination of features. There are no longitudinal ridges in the posterior part of the body; the male has 4 pairs of precloacal papillae and 6-7 pairs of postcloacal papillae. The right spicule averages 0.2 mm long (1.1% of body length), and the left spicule averages 1.2 mm long (5.6% of body length), making an average spicule ratio of 1:5.2. The female has a vulva located on the left side of a thick membrane and 56-65% of the body length from the anterior end. Raphidascaris trichiuri (Yin and Zhang, 1983) comb. n., known previously from males only, is transferred from Cloeoascaris and redescribed, including material of both sexes from Muraenesox cinereus from the type locality. PMID:11695371

Damin, L; Heqing, H

2001-10-01

150

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

NASA Astrophysics Data System (ADS)

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 band in the blue (? 400 nm). We used these red and blue astro-combs to calibrate a high-resolution astrophysical spectrograph integrated with a 1.5 m telescope, and demonstrated calibration precision and stability suffici ent to enable detection of changes in stellar radial velocity < 1 m/s.

Phillips, David F.; Glenday, Alexander G.; Li, Chih-Hao; Cramer, Claire; Furesz, Gabor; Chang, Guoqing; Benedick, Andrew J.; Chen, Li-Jin; Kärtner, Franz X.; Korzennik, Sylvain; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.

2012-06-01

151

Erbium fiber laser-based direct frequency comb spectroscopy of Rb two-photon transitions.  

PubMed

We demonstrate the direct frequency comb spectroscopy of Rb 5S?5D two-photon transitions directly excited by an optical frequency comb (OFC) in 1.5 ?m fiber communication bands. A chain of comb spectral manipulation and quantum coherence control is implemented to enhance the efficiency of second harmonic OFC generation and eliminate the Doppler-broadening background. The direct frequency comb spectroscopy with clearly resolved transition lines is obtained. Our scheme provides a potential approach to realize the OFC at ~1.5 ?m with high stability and accuracy. PMID:24281501

Wu, Jiutao; Hou, Dong; Qin, Zhengyu; Dai, Xiaoliang; Zhang, Zhigang; Zhao, Jianye

2013-12-01

152

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

PubMed

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

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

2012-07-30

153

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

PubMed

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 band in the blue (? 400 nm). We used these red and blue astro-combs to calibrate a high-resolution astrophysical spectrograph integrated with a 1.5 m telescope, and demonstrated calibration precision and stability sufficient to enable detection of changes in stellar radial velocity < 1 m/s. PMID:22714437

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

2012-06-18

154

Optical generation of a precise microwave frequency comb by harmonic frequency locking  

NASA Astrophysics Data System (ADS)

A semiconductor laser under negative optoelectronic feedback is applied to the generation of a microwave frequency comb through the nonlinear dynamics. The laser system is operated in a harmonic frequency-locked pulsing state, where its power spectrum is a microwave frequency comb that consists of multiples of a locking frequency. Every frequency component of the comb can be simultaneously stabilized by simply injecting an external microwave modulation at any component of the comb. This phenomenon can be viewed as a kind of microwave injection locking of the laser dynamics.

Chan, Sze-Chun; Xia, Guang-Qiong; Liu, Jia-Ming

2007-07-01

155

Electrical tuning and switching of an optical frequency comb generated in aluminum nitride microring resonators.  

PubMed

Aluminum nitride (AlN) has been shown to possess both strong Kerr nonlinearity and electro-optic Pockels effect. By combining these two effects, here we demonstrate on-chip reversible on/off switching of the optical frequency comb generated by an AlN microring resonator. We optimize the design of gating electrodes and the underneath resonator structure to effectively apply an electric field without increasing the optical loss. The switching of the comb is monitored by measuring one of the frequency comb peaks while varying the electric field. The controlled comb electro-optic response is investigated for direct comparison with the transient thermal effect. PMID:24365828

Jung, Hojoong; Fong, King Y; Xiong, Chi; Tang, Hong X

2014-01-01

156

Electrical tuning and switching of an optical frequency comb generated in aluminum nitride microring resonators  

NASA Astrophysics Data System (ADS)

Aluminum nitride has been shown to possess both strong Kerr nonlinearity and electro-optic Pockels effect. By combining these two effects, here we demonstrate on-chip reversible on/off switching of the optical frequency comb generated by an aluminum nitride microring resonator. We optimize the design of gating electrodes and the underneath resonator structure to effectively apply electric field without increasing the optical loss. The switching of the comb is monitored by measuring one of the frequency comb peaks while varying the electric field. The controlled comb electro-optic response is investigated for direct comparison with the transient thermal effect.

Jung, Hojoong; Fong, King Y.; Xiong, Chi; Tang, Hong X.

2014-01-01

157

Low-noise and broadband optical frequency comb generation based on an optoelectronic oscillator.  

PubMed

A novel scheme to generate broadband high-repetition-rate optical frequency combs and low phase noise microwave signals simultaneously is proposed and experimentally demonstrated. By incorporating an optical frequency comb generator in an optoelectronic oscillator loop, more than 200 lines are generated for a 25 GHz optical frequency comb, and the single-sideband phase noise is as low as -122??dBc/Hz at 10 kHz offset for the 25 GHz microwave signal. 10 and 20 GHz optical frequency combs and microwave signals are also generated. Unlike the microwave frequency synthesizer, the phase noise of the microwave signals generated by this new scheme is frequency independent. PMID:24562206

Xie, Xiaopeng; Sun, Tao; Peng, Huanfa; Zhang, Cheng; Guo, Peng; Zhu, Lixin; Hu, Weiwei; Chen, Zhangyuan

2014-02-15

158

Nest-mate recognition template of guard honeybees (Apis mellifera) is modified by wax comb transfer.  

PubMed

In recognition, discriminators use sensory information to make decisions. For example, honeybee (Apis mellifera) entrance guards discriminate between nest-mates and intruders by comparing their odours with a template of the colony odour. Comb wax plays a major role in honeybee recognition. We measured the rejection rates of nest-mate and non-nest-mate worker bees by entrance guards before and after a unidirectional transfer of wax comb from a 'comb donor' hive to a 'comb receiver' hive. Our results showed a significant effect that occurred in one direction. Guards in the comb receiver hive became more accepting of non-nest-mates from the comb donor hive (rejection decreased from 70 to 47%); however, guards in the comb donor hive did not become more accepting of bees from the comb receiver hive. These data strongly support the hypothesis that the transfer of wax comb increases the acceptance of non-nest-mates not by changing the odour of the bees, but by changing the template used by guards. PMID:17493913

Couvillon, Margaret J; Caple, Jamie P; Endsor, Samuel L; Kärcher, Martin; Russell, Trudy E; Storey, Darren E; Ratnieks, Francis L W

2007-06-22

159

Molecular and genetic analysis of the Polycomb group gene Sex combs extra\\/Ring in Drosophila  

Microsoft Academic Search

Polycomb group (PcG) proteins repress homeotic genes and other developmental regulatory genes in cells where these genes must remain inactive during development. In Drosophila and in vertebrates, PcG proteins exist in two distinct multiprotein complexes, the Esc\\/Eed–E(z) complex and PRC1. Drosophila PRC1 contains Polycomb, Posterior sexcombs and Polyhomeotic, the products of three PcG genes that are critically needed for PcG

Cornelia Fritsch; Dirk Beuchle; Jürg Müller

2003-01-01

160

Genomics of sex determination.  

PubMed

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

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

2014-04-01

161

SubLethal Effects of Pesticide Residues in Brood Comb on Worker Honey Bee (Apis mellifera) Development and Longevity  

Microsoft Academic Search

BackgroundNumerous surveys reveal high levels of pesticide residue contamination in honey bee comb. We conducted studies to examine possible direct and indirect effects of pesticide exposure from contaminated brood comb on developing worker bees and adult worker lifespan.Methodology\\/Principal FindingsWorker bees were reared in brood comb containing high levels of known pesticide residues (treatment) or in relatively uncontaminated brood comb (control).

Judy Y. Wu; Carol M. Anelli; Walter S. Sheppard; Frederic Marion-Poll

2011-01-01

162

Low finesse Fabry-Perot cavities for wide spaced frequency combs with large spectral bandwidth  

Microsoft Academic Search

We use low finesse Fabry-Perot cavities in series to generate frequency combs with large mode spacing by simultaneously maintaining high spectral bandwidth. The attenuation of laser modes closest to the pass band exceeds 70 dB relative to the modes centered within the pass band for a 5 GHz Fabry-Perot filtering a 250 MHz frequency comb.

T. Steinmetz; T. Wilken; R. Holzwarth; T. W. Hansch; T. Udem; C. Araujo-Hauck

2009-01-01

163

Dichotic Presentation for Binaural Hearing Aids Using Perceptually Balanced Critical Bandwidth Based Comb Filters  

Microsoft Academic Search

Splitting of speech using comb filters with complementary magnitude response and presenting them to the two ears has helped in improving the perception of speech in sensorineural hearing impaired p ersons. The pair of comb filters with 18 bands based on auditory critical bandwidths over 5 k Hz band, were designed initially with sharp transition between pass and stop bands.

Alice N. Cheeran; Prem C. Pandey

164

Adsorption Mechanism of Comb Polymer Dispersants at the Cement\\/Water Interface  

Microsoft Academic Search

Comb polymers are commonly used as dispersants to stabilize highly concentrated cement suspensions. The effectiveness of such polymeric additives to stabilize these suspensions is determined to a large extent by the amount adsorbed. In this study we investigated the adsorption characteristics of various comb dispersant containing different graft densities on surfaces of cement particle. The effect of inorganic salts on

Qianping Ran; Ponisseril Somasundaran; Changwen Miao; Jiaping Liu; Shishan Wu; Jian Shen

2010-01-01

165

High Resolution Atomic Coherent Control via Spectral Phase Manipulation of an Optical Frequency Comb  

SciTech Connect

We demonstrate high resolution coherent control of cold atomic rubidium utilizing spectral phase manipulation of a femtosecond optical frequency comb. Transient coherent accumulation is directly manifested by the enhancement of signal amplitude and spectral resolution via the pulse number. The combination of frequency comb technology and spectral phase manipulation enables coherent control techniques to enter a new regime with natural linewidth resolution.

Stowe, Matthew C.; Cruz, Flavio C.; Marian, Adela; Ye Jun [JILA, National Institute of Standards and Technology and University of Colorado, Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2006-04-21

166

High channel-count comb filter based on chirped sampled fiber Bragg grating and phase shift  

Microsoft Academic Search

Based on strongly chirped sampled fiber Bragg grating and phase shifts, a novel approach to obtain high channel-count comb filters is proposed in this letter. Various channel spacing can be achieved by a single strongly chirped phase mask where the required phase shifts can be gained by a precise translation stage. Comb filters with channel spacing of 50, 100, and

Yitang Dai; Xiangfei Chen; Ximing Xu; Chongcheng Fan; Shizhong Xie

2005-01-01

167

Multiwavelength generation in an erbium-doped fiber laser using in-fiber comb filters  

Microsoft Academic Search

Simultaneous continuous wave multiwavelength operation of an erbium-doped fiber laser has been demonstrated using two types of recently developed in-fiber grating comb filters. The lasing wavelengths and linewidths were determined by the comb filter, which was inserted in a ring cavity with a single inhomogeneously broadened gain medium.

Jong Chow; Graham Town; Ben Eggleton; Morten Ibsen; Kate Sugden; Ian Bennion

1996-01-01

168

23—STUDIES ON THE NOBLE COMB. PART II: HOLDING POWER AND ITS PRACTICAL APPLICATION  

Microsoft Academic Search

An account is given of a study of the combing performance of the Noble comb in which the slivers emerging from the small and large circles were kept separate. Variations in the temperatures and pin densities of the circles produced changes in the holding power of the large circle of from 50 to 90% and in the ratio A\\/B of

D. W. F. Turpie; P. J. Kruger

1972-01-01

169

Dual port MZM based optical comb generator for all-optical microwave photonic devices  

NASA Astrophysics Data System (ADS)

We demonstrate optical comb generator based on dual drive Mach-Zehnder modulator with tunable output spectrum and its application in ROF filters. Mathematically it has been shown how to obtain comb spectrum with adjusted number of harmonics with desired amplitudes and necessary wavelength separation. The results of numerical simulations are presented.

Aybatov, Dmitriy L.; Morozov, Oleg G.; Sadeev, Tagir S.

2010-12-01

170

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

Microsoft Academic Search

Fungus-growing termites cultivate their mutualistic basidiomycete Termitomyces species on a substrate called a fungal comb. Here, the Suicide Polymerase Endonuclease Restriction (SuPER) method was adapted for the first time to a fungal study to determine the entire fungal community of fungal combs and to test whether fungi other than the symbiotic cultivar interact with termite hosts. Our molecular analyses show

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

2009-01-01

171

Supercontinuum generation in microstructure fiber at the advent of femtosecond combs  

NASA Astrophysics Data System (ADS)

The ability to generate a supercontinuum in microstructure fiber using only the unamplified pulses from a mode-locked oscillator was critical to the development of optical frequency combs. I will briefly introduce the key concepts for stabilizing the comb spectrum of a mode-locked laser and how it relies on continuum generation.

Cundiff, Steven T.

2014-03-01

172

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

173

Laser comb with velocity bunching: Preliminary results at SPARC  

NASA Astrophysics Data System (ADS)

A new technique, named “laser comb”, was tested during the last SPARC run. It is able to produce electron pulse trains with a charge of some hundreds pC, a repetition rate of some terahertz, and a sub-picosecond length. This technique is based on the velocity bunching configuration of the SPARC injector. It can be useful to drive pump and probe free-electron laser experiments, to generate coherent excitation of plasma waves in plasma accelerators, and to produce narrow band terahertz radiation. In this paper, we describe the experimental results achieved so far and provide a comparison with simulations.

Ferrario, M.; Alesini, D.; Bacci, A.; Bellaveglia, M.; Boni, R.; Boscolo, M.; Calvani, P.; Castellano, M.; Chiadroni, E.; Cianchi, A.; Cultrera, L.; di Pirro, G.; Ficcadenti, L.; Filippetto, D.; Gallo, A.; Gatti, G.; Giannessi, L.; Labat, M.; Lupi, S.; Marchetti, B.; Marrelli, C.; Migliorati, M.; Mostacci, A.; Nicoletti, D.; Pace, E.; Palumbo, L.; Petrillo, V.; Quattromini, M.; Ronsivalle, C.; Rossi, A. R.; Rosenzweig, J.; Serafini, L.; Serluca, M.; Spataro, B.; Tomizawa, H.; Vaccarezza, C.; Vicario, C.

2011-05-01

174

Flow-through comb electroporation device for delivery of macromolecules  

PubMed Central

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.

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

2013-01-01

175

Tunable Mid-Ir Frequency Comb for Molecular Spectroscopy  

Microsoft Academic Search

A mid-infrared frequency comb tunable from 2.7mum to 4.7mum (3700cm-1 to 2100cm-1) has been produced using a fiber laser and difference frequency generation in a periodically poled LiNbO_3 (PPLN) crystal. An amplified Yb-doped femtosecond fiber laser is centered at a wavelength of 1.04mum, with 100MHz repetition frequency and up to 2.5W average output power. Part of this laser power is

Todd A. Johnson; Scott A. Diddams

2010-01-01

176

Precise Control of Molecular Dynamics with a Femtosecond Frequency Comb  

NASA Astrophysics Data System (ADS)

We present a general and highly efficient scheme for performing narrow-band Raman transitions between molecular vibrational levels using a coherent train of weak pump-dump pairs of shaped ultrashort pulses. The use of weak pulses permits an analytic description within the framework of coherent control in the perturbative regime, while coherent accumulation of many pulse pairs enables near unity transfer efficiency with a high spectral selectivity, thus forming a powerful combination of pump-dump control schemes and the precision of the frequency comb. Simulations verify the feasibility and robustness of this concept, with the aim to form deeply bound, ultracold molecules.

Pe'Er, Avi; Shapiro, Evgeny A.; Stowe, Matthew C.; Shapiro, Moshe; Ye, Jun

2007-03-01

177

Entanglement of Atomic Qubits Using an Optical Frequency Comb  

SciTech Connect

We demonstrate the use of an optical frequency comb to coherently control and entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used to efficiently and coherently transfer population between electronic and vibrational states of trapped atomic ions and implement an entangling quantum logic gate with high fidelity. This technique can be extended to the high field regime where operations can be performed faster than the trap frequency. This general approach can be applied to more complex quantum systems, such as large collections of interacting atoms or molecules.

Hayes, D.; Matsukevich, D. N.; Maunz, P.; Hucul, D.; Quraishi, Q.; Olmschenk, S.; Campbell, W.; Mizrahi, J.; Senko, C.; Monroe, C. [Joint Quantum Institute, Department of Physics, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742 (United States)

2010-04-09

178

Entanglement of atomic qubits using an optical frequency comb.  

PubMed

We demonstrate the use of an optical frequency comb to coherently control and entangle atomic qubits. A train of off-resonant ultrafast laser pulses is used to efficiently and coherently transfer population between electronic and vibrational states of trapped atomic ions and implement an entangling quantum logic gate with high fidelity. This technique can be extended to the high field regime where operations can be performed faster than the trap frequency. This general approach can be applied to more complex quantum systems, such as large collections of interacting atoms or molecules. PMID:20481925

Hayes, D; Matsukevich, D N; Maunz, P; Hucul, D; Quraishi, Q; Olmschenk, S; Campbell, W; Mizrahi, J; Senko, C; Monroe, C

2010-04-01

179

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

PubMed

We report a fully stabilized 1030-nm Yb-fiber frequency comb operating at a pulse repetition frequency of 375 MHz. The comb spacing was referenced to a Rb-stabilized microwave synthesizer and the comb offset was stabilized by generating a super-continuum containing a coherent component at 780.2 nm which was heterodyned with a 87Rb-stabilized external cavity diode laser to produce a radio-frequency beat used to actuate the carrier-envelope offset frequency of the Yb-fiber laser. The two-sample frequency deviation of the locked comb was 235 kHz for an averaging time of 50 seconds, and the comb remained locked for over 60 minutes with a root mean squared deviation of 236 kHz. PMID:24921751

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

2014-05-01

180

Mid-infrared optical frequency combs at 2.5 ?m based on crystalline microresonators  

PubMed Central

The mid-infrared spectral range (?~2–20??m) is of particular importance as many molecules exhibit strong vibrational fingerprints in this region. Optical frequency combs—broadband optical sources consisting of equally spaced and mutually coherent sharp lines—are creating new opportunities for advanced spectroscopy. Here we demonstrate a novel approach to create mid-infrared optical frequency combs via four-wave mixing in a continuous-wave pumped ultra-high Q crystalline microresonator made of magnesium fluoride. Careful choice of the resonator material and design made it possible to generate a broadband, low-phase noise Kerr comb at ?=2.5??m spanning 200?nm (?10?THz) with a line spacing of 100?GHz. With its distinguishing features of compactness, efficient conversion, large mode spacing and high power per comb line, this novel frequency comb source holds promise for new approaches to molecular spectroscopy and is suitable to be extended further into the mid-infrared.

Wang, C. Y.; Herr, T.; Del'Haye, P.; Schliesser, A.; Hofer, J.; Holzwarth, R.; Hansch, T. W.; Picque, N.; Kippenberg, T. J.

2013-01-01

181

A Variable Pitch Comb Fixture for Rayleigh Wave Generation and Reception  

NASA Astrophysics Data System (ADS)

Several methods are available for the generation and reception of Rayleigh waves on a part surface. The use of the so-called ``comb'' is one method, where the comb elements or ``fingers'' contact the surface with a spacing between adjacent fingers equal to the Rayleigh wavelength of the substrate for a given frequency. Although efficient and simple, a fixed pitch comb is typically useful only at one frequency for a particular substrate. A simple ``parallel link'' fixture has been developed where the pitch of the fingers can be varied over a range of spacings, allowing the operator to set the comb pitch for a particular material/frequency at will. The comb elements may be glued to the wear plate of a longitudinal transducer or simply fluid coupled. Elements of the fixture and tests results of the fixtures used for generating Rayleigh waves on aluminum and steel substrates are shown.

Barnard, Daniel J.

2007-03-01

182

Polarization division multiplexed photonic radio-frequency channelizer using an optical comb  

NASA Astrophysics Data System (ADS)

A polarization division multiplexed photonic radio-frequency (RF) channelizer based on an optical comb is proposed and numerically investigated. A flat optical comb with nine lines is generated using two cascaded Mach-Zehnder modulators. The input broadband signal is simultaneously multicast by the optical comb and its frequency-shifted duplicate. These two combs are polarization multiplexed, spectrally sliced by a Fabry-Pérot etalon (FPE), polarization de multiplexed and then channelized by wavelength division multiplexers (WDMs). The key advantage of the proposed approach is that it releases the trade-off between the measurement range and accuracy of a conventional optical comb based channelizer by a factor of 2. The impact of the polarization misalignment, the capability of monitoring multi-frequency RF signals with different powers and the reconfigurability of the system are also evaluated.

Xian Wang, Li; Hua Zhu, Ning; Li, Wei; Wang, Hui; Yu Zheng, Jian; Guo Liu, Jian

2013-01-01

183

Investigating the resonance spectrum of optical frequency combs in fiber-optic cavities.  

PubMed

We report a detailed theoretical and experimental study of fiber-optic cavities under broadband excitation by mode-locked laser combs. We calculate the effects of fiber dispersion on the cavity transmission. For any integer ratio between the comb repetition rate and cavity free spectral range, the theoretical resonant output spectrum exhibits a narrow group of resonant teeth, surrounded by minor, unevenly spaced resonances. Also, the central resonance can be rapidly and precisely tuned over the entire comb span by only acting on its repetition rate. Experimental observations are provided by a single-mode fiber ring and a telecom-wavelength comb laser. The resulting spectral pattern agrees very well with our theoretical prediction, allowing a thorough characterization of the cavity dispersion and opening new perspectives for comb spectroscopy in dielectric resonators. PMID:23736632

Avino, S; Malara, A Giorgini P; Gagliardi, G; De Natale, P

2013-06-01

184

Sex Bias in Children.  

ERIC Educational Resources Information Center

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

Zalk, Sue Rosenberg; And Others

185

Effects of Aromatase Inhibitor on Sex Differentiation and Levels of P450 17?and P450 aromMessenger Ribonucleic Acid of Gonads in Chicken Embryos  

Microsoft Academic Search

On Day 5 of incubation fertilized eggs of single-comb White Leghorn hens were injected with an aromatase inhibitor (AI) and the sex reversal effect and levels of mRNA of P45017?-hydroxylase(P45017?) and P450aromatase(P450arom) were evaluated by observation of gonadal phenotype and by Northern and slot blot analysis. Individual genetic sex was evaluated by Southern blot analysis of red blood cells using

K Abinawanto; Kiyoshi Shimada; Kumiko Yoshida; Noboru Saito

1996-01-01

186

Quantum Information Processing with Atomic Qubits and Optical Frequency Combs  

NASA Astrophysics Data System (ADS)

Pulsed optical fields from mode-locked lasers have found widespread use as tools for precision quantum control and are well suited for implementation in quantum information processing and quantum simulation. We experimentally demonstrate two distinct regimes of the interaction between hyperfine atomic ion qubits and stimulated Raman transitions driven by picosecond pulses from a far off- resonant mode-locked laser. In the weak pulse regime, the coherent accumulation of successive pulses from an optical frequency comb performs single qubit operations and is used to entangle two trapped atomic ion qubits. In the strong pulse regime, a single pulse is used to implement a fast (<10 ps) Hadamard gate and we show how a few pulses may be used to address the atom's motion by imparting state-dependent momentum kicks. To entangle multiple ions, optical frequency combs operated near the strong pulse regime may be used to implement motion-mediated gates that can be performed much faster than a collective motional period.[4pt] [1] Garc'ia-Ripoll et al., PRL 91, 157901 (2003).[0pt] [2] Duan, PRL 93, 100502 (2004).

Campbell, Wesley

2010-03-01

187

Sex-linked dominant  

MedlinePLUS

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

188

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

PubMed

The taxonomy of Enterobacter has a complicated history, with several species transferred to and from this genus. Classification of strains is difficult owing to its polyphyletic nature, based on 16S rRNA gene sequences. It has been previously acknowledged that Enterobacter contains species which should be transferred to other genera. In an attempt to resolve the taxonomy of Enterobacter, MLSA based on partial sequencing of protein-encoding genes (gyrB, rpoB, infB and atpD) was performed on the type strains and reference strains of Enterobacter, Cronobacter and Serratia species, as well as members of the closely related genera Citrobacter, Klebsiella, Kluyvera, Leclercia, Mangrovibacter, Raoultella and Yokenella. Phylogenetic analyses of the concatenated nucleotide sequences revealed that Enterobacter can be divided into five strongly supported MLSA groups, suggesting that the species should be reclassified into five different genera. Further support for this was provided by a concatenated amino acid tree, phenotypic characteristics and fatty acid profiles, enabling differentiation of the MLSA groups. Three novel genera are proposed: Lelliottia gen. nov., Pluralibacter gen. nov. and Kosakonia gen. nov. and the following new combinations: Lelliottia nimipressuralis comb. nov., Lelliottia amnigena comb. nov., Pluralibacter gergoviae comb. nov., Pluralibacter pyrinus comb. nov., Kosakonia cowanii comb. nov., Kosakonia radicincitans comb. nov., Kosakonia oryzae comb. nov., Kosakonia arachidis comb. nov., Cronobacter helveticus comb. nov. and Cronobacter pulveris comb. nov. Additionally, the novel epithet Cronobacter zurichensis nom. nov. is proposed for the reclassification of Enterobacter turicensis into the genus Cronobacter, as Cronobacter turicensis (Iversen et al., 2008) is already in use. PMID:23632228

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

2013-07-01

189

A Fine-Tooth Comb to Measure the Accelerating Universe  

NASA Astrophysics Data System (ADS)

Astronomical instruments needed to answer crucial questions, such as the search for Earth-like planets or the way the Universe expands, have come a step closer with the first demonstration at the telescope of a new calibration system for precise spectrographs. The method uses a Nobel Prize-winning technology called a 'laser frequency comb', and is published in this week's issue of Science. Uncovering the disc ESO PR Photo 26a/08 A Laser Comb for Astronomy "It looks as if we are on the way to fulfil one of astronomers' dreams," says team member Theodor Hänsch, director at the Max Planck Institute for Quantum Optics (MPQ) in Germany. Hänsch, together with John Hall, was awarded the 2005 Nobel Prize in Physics for work including the frequency comb technique. Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colours, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colours rather than distances, with an extremely accurate and fine grid. New, extremely precise spectrographs will be needed in experiments planned for the future European Extremely Large Telescope (E-ELT), which is being designed by ESO, the European Southern Observatory. These new spectrographs will need to be calibrated with even more accurate 'rulers'. In fact, they must be accurate to about one part in 30 billions - a feat equivalent to measuring the circumference of the Earth to about a millimetre! "We'll need something beyond what current technology can offer, and that's where the laser frequency comb comes in. It is worth recalling that the kind of precision required, 1 cm/s, corresponds, on the focal plane of a typical high-resolution spectrograph, to a shift of a few tenths of a nanometre, that is, the size of some molecules," explains PhD student and team member Constanza Araujo-Hauck from ESO. The new calibration technique comes from the combination of astronomy and quantum optics, in a collaboration between researchers at ESO and the Max Planck Institute for Quantum Optics. It uses ultra-short pulses of laser light to create a 'frequency comb' - light at many frequencies separated by a constant interval - to create just the kind of precise 'ruler' needed to calibrate a spectrograph. After successful tests in the MPQ laboratory in 2007, the team have successfully tested a prototype device using the laser comb at the VTT (Vacuum Tower Telescope) solar telescope in Tenerife, on 8 March 2008, measuring the spectrum of the Sun in infrared light. The results are already impressive, and the technique promises to achieve the accuracy needed to study these big astronomical questions. "In our tests in Tenerife, we have already achieved beyond state-of-the-art accuracy. Now we are going to make the system more versatile, and develop it even further," says team member Tilo Steinmetz, from Menlo Systems GmbH, a spin-off company from the Max Planck Institute, which was founded to commercialise the frequency comb technique. Having tested the technique on a solar telescope, a new version of the system is now being built for the HARPS planet-finder instrument on ESO's 3.6-metre telescope at La Silla in Chile, before being considered for future generations of instruments. One of the ambitious project to be realised with the E-ELT, called CODEX, aims to measure the recently discovered acceleration of the universe directly, by following the velocities of distant galaxies and quasars over a 20-year period. This would let astronomers test Einstein's general relativity and the nature of the recently discovered, and mysterious, dark energy. "We have to measu

2008-09-01

190

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

PubMed

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

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

2010-09-17

191

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

PubMed

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

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

2007-12-24

192

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

PubMed

We present the first implementation of mid-infrared dual-comb spectroscopy with an optical parametric oscillator. Methane absorption spectroscopy was demonstrated with a resolution of 0.2 cm(-1) (5 GHz) at an acquisition time of ~10.4 ms over a spectral coverage at 2900-3050 cm(-1). The average power from each individual mid-infrared comb line was ~1 ?W, representing a power level much greater than typical difference-frequency-generation sources. Mid-infrared dual-comb spectroscopy opens up unique opportunities to perform broadband spectroscopic measurements with high resolution, high requisition rate, and high detection sensitivity. PMID:24104672

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

2013-08-15

193

Spatial and spectral coherent control with frequency combs  

NASA Astrophysics Data System (ADS)

Quantum coherent control is a powerful tool for steering the outcome of quantum processes towards a desired final state by the accurate manipulation of quantum interference between multiple pathways. Although coherent control techniques have found applications in many fields of science, the possibilities for spatial and high-resolution frequency control have remained limited. Here, we show that the use of counter-propagating broadband pulses enables the generation of fully controlled spatial excitation patterns. This spatial control approach also provides decoherence reduction, which allows the use of the high-frequency resolution of an optical frequency comb. We exploit the counter-propagating geometry to perform spatially selective excitation of individual species in a multicomponent gas mixture, as well as frequency determination of hyperfine constants of atomic rubidium with unprecedented accuracy. The combination of spectral and spatial coherent control adds a new dimension to coherent control, with applications in nonlinear spectroscopy, microscopy and high-precision frequency metrology, among others.

Barmes, Itan; Witte, Stefan; Eikema, Kjeld S. E.

2013-01-01

194

A novel, multichannel, comb-frequency Doppler backscatter system  

NASA Astrophysics Data System (ADS)

Doppler backscattering has emerged in recent years as a powerful diagnostic tool in high temperature fusion plasmas. The technique is sensitive to plasma turbulence flow and has been utilized to determine radial electric field and to study geodesic acoustic modes, zonal flows, and intermediate scale density turbulence. The current manuscript describes a novel technique for creating a stable, multichannel system covering the V-band frequency range (50-75 GHz) which enables simultaneous monitoring of turbulent flows and fluctuation levels at eight distinct spatial locations. The system is based on a high-frequency, low phase noise comb-frequency generator combined with a filter bank and quadrature detection system. The system is now in operation on DIII-D and has allowed monitoring of the flow and turbulence levels across the plasma radius during events such as the L-H transition.

Peebles, W. A.; Rhodes, T. L.; Hillesheim, J. C.; Zeng, L.; Wannberg, C.

2010-10-01

195

Fiber optic resonator sensors based on comb synthesizers  

NASA Astrophysics Data System (ADS)

Over the past several years, fiber-optic resonators have been successfully used as mechanical probes by virtue of their intrinsic sensitivity to length changes. In a recent work, we devised a diode-laser system for strain interrogation of a high-finesse fiber Bragg-grating cavity, achieving a 10-13 resolution in the infrasonic and acoustic frequency ranges, thanks to the exceptional stability of an optical frequency comb (OFC). A Pound-Drever-Hall (PDH) frequency locking technique is implemented for low-noise and wide dynamic range readout of the sensor keeping the interrogating laser always linked to the OFC reference. In this way, the low-frequency strain noisefloor is free from laser noise and possibly limited by thermodynamic phase fluctuations or other thermal effects in the fiber.

Gagliardi, G.

2012-02-01

196

Frequency-comb-induced radiative force on cold rubidium atoms  

NASA Astrophysics Data System (ADS)

We experimentally investigate the radiative force and laser-induced fluorescence (LIF) in cold rubidium atoms induced by pulse-train (frequency-comb) excitation. Three configurations are studied: (i) single-pulse-train excitation, (ii) two in-phase counterpropagating pulse trains, and (iii) two out-of-phase counterpropagating pulse trains. In all configurations, measured LIF is in agreement with calculations based on the optical Bloch equations. The observed forces in the first two configurations are in qualitative agreement with the model(s) used for calculating mechanical action of a pulse train on atoms; however, this is not the case for the third configuration. Possible resolution of the discrepancy is discussed.

Kregar, G.; Šanti?, N.; Aumiler, D.; Buljan, H.; Ban, T.

2014-05-01

197

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

NASA Astrophysics Data System (ADS)

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 1¯ 0}<1 1 2¯ 0> slip and pyramidal {1 1 2¯ 2}<1 1 2¯ 3¯> slip, showing the model is capable of reproducing the mechanical deformation modes observed in experiments.

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

2013-10-01

198

Dual-etalon frequency-comb cavity ringdown spectrometer.  

PubMed

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 × 10(5), to investigate the (1,1,3) overtone of water and the R(7) transition of the O(2) b(1)?(g)(+)?X(3)?(g)(-) (2,0) band with high spectral resolution. PMID:22519318

Chandler, David W; Strecker, Kevin E

2012-04-21

199

Sex determination in amphibians  

Microsoft Academic Search

The heterogametic sex is male in all mammals, whereas it is female in almost all birds. By contrast, there are two heterogametic types (XX\\/XY and ZZ\\/ZW) for genetic sex determination in amphibians. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. Indeed, the

Masahisa Nakamura

2009-01-01

200

The Riddle of Sex.  

ERIC Educational Resources Information Center

Discusses the work of evolutionary biologists in determining how sexual reproduction arose. Topics explored include the nature of sex, bacterial sex, meiotic sex, and asexual reproduction. A diagram (which can be used as a duplicating master) illustrating types of bacterial sex is included. (DH)

Sagan, Dorion; Margulis, Lynn

1985-01-01

201

Sex Education for Patients  

PubMed Central

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.

Zitner, David

1985-01-01

202

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

PubMed

A frequency comb is generated with a Cr:forsterite femtosecond laser, spectrally broadened through a highly nonlinear optical fiber to span from 1.0 to 2.2 ,m, and stabilized using the f-to-2f self-referencing technique. The repetition rate and the carrier-envelope offset frequency are stabilized to a hydrogen maser, calibrated by a cesium atomic fountain clock. Simultaneous frequency measurement of a 657-nm cw laser by use of the stabilized frequency combs from this Cr:forsterite system and a Ti:sapphire laser agree at the 10(-13) level. The frequency noise of the comb components is observed at 1064, 1314, and 1550 nm by comparing the measured beat frequencies between cw lasers and the supercontinuum frequency combs. PMID:15865403

Kim, K; Washburn, B R; Wilpers, G; Oates, C W; Hollberg, L; Newbury, N R; Diddams, S A; Nicholson, J W; Yan, M F

2005-04-15

203

Proposal for a 10-THz Precision Optical Frequency Comb Generator. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

A novel scheme for generating a comb of precisely known optical frequency markers with kilohertz accuracy over a 10-THz span is proposed. Based on the use of optical parametric oscillator frequency dividers, the method provides absolute frequency identifi...

N. C. Wong

1992-01-01

204

Design of an Electrostatic Comb Actuator Based on Finite Element Method  

NASA Astrophysics Data System (ADS)

Electrostatic comb actuators were designed using finite element modeling and analysis, so-called finite element method (FEM). Design objective was to generate maximum actuating force within the constraints. 2D and 3D FE models of the comb structures were developed in general-purpose FE code. The element geometries were 4-node plate element for 2D model and 8-node brick element for 3D models. Electrostatic field strength and voltage analysis of the FE models were performed to compute generated voltage and electrostatic force in the structure. Subsequently done was the structural analysis to examine structural response to the electrostatic force. The initial finite element model was verified with the published experimental result. Based on the amount of force generated and lateral deflection of the comb fingers, the best possible design of choice was determined. The finite element computations show that the comb structure having high aspect ratio with smaller gaps can provide higher actuation force.

Mon, Thet Thet; Ghazalli, Zakri; Ahmad, Asnul Hadi; Ismail, Mohd Fazli; Muhamad, Khairul Fikri

2011-05-01

205

Proposal of Ensifer psoraleae sp. nov., Ensifer sesbaniae sp. nov., Ensifer morelense comb. nov. and Ensifer americanum comb. nov.  

PubMed

In a survey of rhizobia associated with the native legumes in Yunnan Province, China, seven and nine strains isolated from the root nodules of Psoralea corylifolia, Sesbania cannabina and Medicago lupulina were respectively classified into the novel genomic species groups I and II in the genus Ensifer (former Sinorhizobium) based on the sequence analyses of the 16S rRNA gene. Analyses of concatenated housekeeping genes (atpD, recA and glnII) further revealed that they were distinct lineages in the genus, and group I was most similar to Ensifer terangae and Ensifer garamanticus (both with 94.2% similarity), while group II was most similar to Ensifer adhaerens (94.0%). These groups could be distinguished from closely related species by DNA-DNA relatedness, MALID-TOF MS, cellular fatty acid profiles and a series of phenotypic characters. Therefore, two novel species were proposed: Ensifer psoraleae sp. nov. (seven strains, type strain CCBAU 65732(T)=LMG 26835(T)=HAMBI 3286(T)) and Ensifer sesbaniae sp. nov. (nine strains, type strain CCBAU 65729(T)=LMG 26833(T)=HAMBI 3287(T)). They had a DNA G+C mol% (Tm) of 58.9 and 60.4, respectively. Both of the type strains formed effective nodules on common bean (Phaseolus vulgaris) and their hosts of origin. In addition, the previously described species Sinorhizobium morelense and Sinorhizobium americanum were renamed as Ensifer morelense comb. nov. and Ensifer americanum comb. nov. according to the accumulated data from different studies. PMID:23759600

Wang, Yuan Chun; Wang, Fang; Hou, Bao Chao; Wang, En Tao; Chen, Wen Feng; Sui, Xin Hua; Chen, Wen Xin; Li, Yan; Zhang, Ya Bo

2013-10-01

206

Dual-comb electric-field cross-correlation technique for optical arbitrary waveform characterization.  

PubMed

We present an electric-field cross-correlation technique that uses a pair of frequency combs to sweep phase and group delays independently without a mechanical stage. We demonstrate this technique for characterization of optical arbitrary waveforms composed of ~30 spectral lines from a 10 GHz frequency comb. Rapid data acquisition (tens of microseconds) enables interferometric spectral phase measurement of pulses subject to propagation over 20 km of optical fiber. PMID:20016643

Ferdous, Fahmida; Leaird, Daniel E; Huang, Chen-Bin; Weiner, A M

2009-12-15

207

Generation of wideband frequency combs by continuous-wave seeding of multistage mixers with synthesized dispersion.  

PubMed

We numerically and experimentally demonstrate efficient generation of an equalized optical comb with 150-nm bandwidth. The comb was generated by low-power, continuous-wave seeds, eliminating the need for pulsed laser sources. The new architecture relies on efficient creation of higher-order mixing tones in phase-matched nonlinear fiber stages separated by a linear compressor. Wideband generation was enabled by precise dispersion engineering of multiple-stage parametric mixers. PMID:22330571

Myslivets, Evgeny; Kuo, Bill P P; Alic, Nikola; Radic, Stojan

2012-01-30

208

The inoculation of newly formed fungus comb with Termitomyces in Macrotermes colonies (Isoptera, Macrotermitinae)  

Microsoft Academic Search

The substrate of newly constructedMacrotermes fungus combs is inoculated from the start with viableTermitomyces conidia (asexual spores) which guarantee fast proliferation of the symbiotic fungus. The substrate is vegetable matter which has passed rapidly through the intestine of the young workers which are comb-builders and nurses. These ingest the vegetable matter which has been collected by the foragers and also

R. H. Leuthold; S. Badertscher; H. Imboden

1989-01-01

209

Molecular structure and order-to-disorder transitions of comb polymers at air and solid interfaces  

Microsoft Academic Search

In this study, we investigate the interfacial structure and transitions of alkyl side chain comb polymers using a non-linear optical technique called infrared-visible sum frequency generation spectroscopy (SFG). The two main comb polymer systems studied are, poly(vinyl octadecyl carbamate-co-vinyl acetate) and the poly(n-alkyl acrylate) series, where side chain length 'n' is varied between 8, 12, 16, 18, and 22 units.

Keshav Srinivasan Gautam

2002-01-01

210

Preparation, structure and properties of comb-branched waterborne polyurethane\\/OMMT nanocomposites  

Microsoft Academic Search

Comb-branched waterborne polyurethane\\/organo-montmorillonite (CWPU\\/OMMT) nanocomposites were prepared by in situ intercalating polymerization process based on the main materials including IPDI, DMPA, polycaprolactone diols, comb-branched polymeric diols and OMMT. The average particle size of emulsion increases and the particle size distribution of emulsion becomes broader with the increase of OMMT content. The results of X-ray diffraction (XRD) and transmission electron microscope

Xianghua Deng; Fang Liu; Yuanfang Luo; Yongjun Chen; Demin Jia

2007-01-01

211

The large mammals of Roc de Combe (Lot, France): The Châtelperronian and Aurignacian assemblages  

Microsoft Academic Search

Roc de Combe is a small cave that has played a large role in debates over the nature of the Middle-to-Upper Paleolithic transition in southwestern Europe. Recent work [Bordes, J.-G., 2002. Les interstratifications Châtelperronien\\/Aurignacien du Roc-de-Combe et du Piage (Lot, France). Thèse présentée à l’Université Bordeaux I, no. 2614.] has shown that securely interleaved Châtelperronian and Aurignacian deposits do not

Donald K. Grayson; Françoise Delpech

2008-01-01

212

Tunable Programmable Microwave Photonic Filters Based on an Optical Frequency Comb  

Microsoft Academic Search

We demonstrate the application of optical combs to implement tunable programmable microwave photonic filters. We design well-known multi-tap microwave photonic filters; however, the utilization of an optical comb with a dispersive medium enables scaling of these filters to a large number of taps. We use optical line-by-line pulse shaping to program tap weights, which allows us to shape the filter's

E. Hamidi; D. E. Leaird; A. M. Weiner

2010-01-01

213

Midinfrared frequency combs from coherent supercontinuum in chalcogenide and optical parametric oscillation.  

PubMed

We observe the coherence of the supercontinuum generated in a nanospike chalcogenide-silica hybrid waveguide pumped at 2 ?m. The supercontinuum is shown to be coherent with the pump by interfering it with a doubly resonant optical parametric oscillator (OPO) that is itself coherent with the shared pump laser. This enables coherent locking of the OPO to the optically referenced pump frequency comb, resulting in a composite frequency comb with wavelengths from 1 to 6 ?m. PMID:24686673

Lee, Kevin F; Granzow, N; Schmidt, M A; Chang, W; Wang, L; Coulombier, Q; Troles, J; Leindecker, Nick; Vodopyanov, Konstantin L; Schunemann, Peter G; Fermann, M E; Russell, P St J; Hartl, I

2014-04-01

214

A new method for determining the plasma electron density using optical frequency comb interferometer.  

PubMed

A new method of plasma electron density measurement using interferometric phases (fractional fringes) of an optical frequency comb interferometer is proposed. Using the characteristics of the optical frequency comb laser, high density measurement can be achieved without fringe counting errors. Simulations show that the short wavelength and wide wavelength range of the laser source and low noise in interferometric phases measurements are effective to reduce ambiguity of measured density. PMID:24784608

Arakawa, Hiroyuki; Tojo, Hiroshi; Sasao, Hajime; Kawano, Yasunori; Itami, Kiyoshi

2014-04-01

215

Frequency comb expansion based on optical feedback, highly nonlinear and erbium-doped fibers  

NASA Astrophysics Data System (ADS)

This works presents an efficient technique for generating multi-wavelength sources, which consist of an expanded optical frequency comb based on the nonlinear process of multiple four-wave mixing. The nonlinear efficiency is significantly enhanced by the use of the proposed scheme based on optical feedback, highly nonlinear and erbium-doped fibers. Numerical and experimental results illustrate its efficiency and applicability by expanding a comb from 20 to over 200 coherent lines spaced by only 12.5 GHz.

Melo, S. A. S.; do Nascimento, A. R.; Cerqueira S., Arismar; Carvalho, L. H. H.; Pataca, D. M.; Oliveira, J. C. R. F.; Fragnito, H. L.

2014-02-01

216

Electrochemical properties of amorphous comb-shaped composite PEO polymer electrolyte  

Microsoft Academic Search

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.

J.-S Chung; H.-J Sohn

2002-01-01

217

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

PubMed

Fungus-growing termites cultivate their mutualistic basidiomycete Termitomyces species on a substrate called a fungal comb. Here, the Suicide Polymerase Endonuclease Restriction (SuPER) method was adapted for the first time to a fungal study to determine the entire fungal community of fungal combs and to test whether fungi other than the symbiotic cultivar interact with termite hosts. Our molecular analyses show that although active combs are dominated by Termitomyces fungi isolated with direct Polymerase Endonuclease Restriction - Denaturing Gradient Gel Electrophoresis (PCR-DGGE), they can also harbor some filamentous fungi and yeasts only revealed by SuPER PCR-DGGE. This is the first molecular evidence of the presence of non-Termitomyces species in active combs. However, because there is no evidence for a species-specific relationship between these fungi and termites, they are mere transient guests with no specialization in the symbiosis. It is however surprising to notice that termite-associated Xylaria strains were not isolated from active combs even though they are frequently retrieved when nests are abandoned by termites. This finding highlights the implication of fungus-growing termites in the regulation of fungi occurring within the combs and also suggests that they might not have any particular evolutionary-based association with Xylaria species. PMID:19576985

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

2009-10-01

218

Thermoresponsive comb-shaped copolymer-Si(100) hybrids for accelerated temperature-dependent cell detachment.  

PubMed

Well-defined comb-shaped copolymer-Si(100) hybrids were prepared, via successive surface-initiated atom transfer radical polymerizations (ATRPs) of glycidyl methacrylate (GMA) and N-isopropylacrylamide (NIPAAm), for accelerated cell detachment at a lower temperature. The Si-C bonded comb copolymer consisted of a well-defined (nearly monodispersed) poly(glycidyl methacrylate) (P(GMA)) main chain, a well-defined NIPAAm polymer (P(NIPAAm) block, and well-defined P(NIPAAm) side chains. The ring opening reaction of epoxy groups of the P(GMA) main chain with 2-chloropropionic acid resulted in the immobilization of the alpha-chloroester groups (the ATRP initiators for the NIPAAm side chains) and the concomitant formation of hydroxyl groups. P(NIPAAm) acted as the thermoresponsive side chains of the comb copolymer for control of cell adhesion and detachment, while the P(GMA) main chain with hydroxyl groups provided a local hydrophilic microenvironment. The unique microstructure of the comb copolymer brushes facilitated cell recovery at 20 degrees C (below the lower critical solution temperature (LCST) of P(NIPAAm)) without restraining cell attachments and growth at 37 degrees C. The accelerated detachment of cells indicated that the underlying hydrophilic environment of the comb copolymer brushes contributed to speedy hydration of the P(NIPAAm) segments below the LCST. The thermoresponsive comb copolymer-Si(100) hybrids are potentially useful as adhesion modifiers for cells in silicon-based biomedical devices. PMID:16182362

Xu, F J; Zhong, S P; Yung, L Y L; Tong, Y W; Kang, En-Tang; Neoh, K G

2006-03-01

219

Coherent dual-comb spectroscopy at high signal-to-noise ratio  

SciTech Connect

Two coherent frequency combs are used to measure the full complex response of a sample in a configuration analogous to a dispersive Fourier transform spectrometer, infrared time domain spectrometer, or a multiheterodyne laser spectrometer. This dual-comb spectrometer retains the frequency accuracy and resolution of the reference underlying the stabilized combs. We discuss the specific design of our coherent dual-comb spectrometer and demonstrate the potential of this technique by measuring the overtone vibration of hydrogen cyanide, centered at 194 THz (1545 nm). We measure the fully normalized, complex response of the gas over a 9 THz bandwidth at 220 MHz frequency resolution yielding 41,000 resolution elements. The average spectral signal-to-noise ratio (SNR) over the 9 THz bandwidth is 2500 for both the magnitude and phase of the measured spectral response and the peak SNR is 4000. This peak SNR corresponds to a fractional absorption sensitivity of 0.05% and a phase sensitivity of 250 microradians. As the spectral coverage of combs expands, coherent dual-comb spectroscopy could provide high-frequency accuracy and resolution measurements of a complex sample response across a range of spectral regions. Work of U. S. government, not subject to copyright.

Coddington, I.; Swann, W. C.; Newbury, N. R. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States)

2010-10-15

220

Simultaneous suppression of time and energy uncertainties in a single-photon frequency-comb state  

NASA Astrophysics Data System (ADS)

A single photon prepared in a time-energy state described by a frequency comb combines the extreme precision of energy defined by a single tooth of the comb with a high sensitivity to small shifts in time defined by the narrowness of a single pulse in the long sequence of pulses that describe the frequency-comb state in the time domain. We show how this simultaneous suppression of time and energy uncertainties can be described by a separation of scales, and we compare this with the suppression of uncertainties in the two-particle correlations of an entangled state. To illustrate the sensitivity of the frequency-comb states to small shifts in time and frequency, we consider the Hong-Ou-Mandel dips observed in two-photon interference when both time and frequency shifts between the input photons are varied. It is shown that the interference of two photons in equivalent frequency-comb states results in a two-dimensional Hong-Ou-Mandel dip that is narrow in both time and frequency, while the corresponding entangled photon pairs are only sensitive to temporal shifts. Frequency-comb states thus represent an alternative approach to quantum operations beyond the uncertainty limit.

Ren, Changliang; Hofmann, Holger F.

2014-05-01

221

An improved divergent synthesis of comb-type branched oligodeoxyribonucleotides (bDNA) containing multiple secondary sequences.  

PubMed Central

The divergent synthesis of branched DNA (bDNA) comb structures is described. This new type of bDNA contains one unique oligonucleotide, the primary sequence, covalently attached through a comb-like branch network to many identical copies of a different oligonucleotide, the secondary sequence. The bDNA comb structures were assembled on a solid support and several synthesis parameters were investigated and optimized. The bDNA comb molecules were characterized by polyacrylamide gel electrophoretic methods and by controlled cleavage at periodate-cleavable moieties incorporated during synthesis. The developed chemistry allows synthesis of bDNA comb molecules containing multiple secondary sequences. In the accompanying article we describe the synthesis and characterization of large bDNA combs containing all four deoxynucleotides for use as signal amplifiers in nucleic acid quantification assays.

Horn, T; Chang, C A; Urdea, M S

1997-01-01

222

Sex, Sex Roles, and Familial Love  

Microsoft Academic Search

Though the effects of sex role socialization on love in romantic heterosexual relationships have been explored, little is known about the influence of sex role socialization on the expression of love among family members. In the present study, 51 male and 90 female undergraduates reported their feelings and behaviors of love toward a family member as assessed by Swenson's Scale

Lawrence H. Ganong; Marilyn Coleman

1987-01-01

223

Sex, Sex Differences, and Social Behavior  

Microsoft Academic Search

Sex differences in social behavior are center stage in recent formu- lations of evolutionary psychology. Evolutionary psychology, with its emphasis on the long-term consequences of early adaptations, offers itself as an alterna- tive meta-theory to mainstream social psychology, which emphasizes the impor- tance of social structures in determining the existence and extent of social and cognitive sex differences. Using a

VITA CARULLI

224

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

PubMed

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

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

2012-12-13

225

Wideband repetition rate tunability of ultrashort pulse generation using MZ-modulator-based flat comb generator and DF-DDF  

Microsoft Academic Search

We have demonstrated wideband frequency-tunable ultrashort pulse generation using a Mach-Zehnder-modulator-based flat comb generator (MZ-FCG) and a dispersion- flattened dispersion-decreasing fiber. Continuous wave lights were converted to ultraflat comb signals by the MZ-FCG. The comb signals were formed into picosecond pulse trains by chirp compensation, and they are compressed into femtosecond ones by a soliton compression technique. Pulse trains of

Isao Morohashi; Takahide Sakamoto; Tetsuya Kawanishi; Iwao Hosako; Masahiro Tsuchiya; Hideyuki Sotobayashi

2008-01-01

226

Vertical-actuated electrostatic comb drive with in situ capacitive position correction for application in phase shifting diffraction interferometry  

Microsoft Academic Search

This research utilizes the levitation effect of electrostatic comb fingers to design vertical-to-the-substrate actuation for optical phase shifting interferometry applications. For typical polysilicon comb drives with 2 ?m gaps between the stationary and moving fingers, as well as between the microstructures and the substrate, the equilibrium position is nominally 1-2 ?m above the stationary comb fingers. This distance is ideal

Abraham P. Lee; Charles F. McConaghy; Gary Sommargren; Peter Krulevitch; Eugene W. Campbell

2003-01-01

227

On the generation of octave-spanning optical frequency combs using monolithic whispering-gallery-mode microresonators.  

PubMed

Octave-spanning optical frequency combs are especially interesting in optical metrology owing to the ability of self-referencing. We report a theoretical study on the generation of octave-spanning combs in the whispering gallery modes of a microresonator. Through a modal expansion model simulation in a calcium fluoride microcavity, we show that a combination of suitable pump power, Kerr nonlinearity, and dispersion profile can lead to stable and robust octave-spanning optical frequency combs. PMID:20717427

Chembo, Yanne K; Yu, Nan

2010-08-15

228

Copy Number Variation in Intron 1 of SOX5 Causes the Pea-comb Phenotype in Chickens  

Microsoft Academic Search

Pea-comb is a dominant mutation in chickens that drastically reduces the size of the comb and wattles. It is an adaptive trait in cold climates as it reduces heat loss and makes the chicken less susceptible to frost lesions. Here we report that Pea-comb is caused by a massive amplification of a duplicated sequence located near evolutionary conserved non-coding sequences

Dominic Wright; Henrik Boije; Jennifer R. S. Meadows; Bertrand Bedhom; David Gourichon; Agathe Vieaud; Michèle Tixier-Boichard; Carl-Johan Rubin; Freyja Imsland; Finn Hallböök; Leif Andersson

2009-01-01

229

[Disorders of sex chromosome].  

PubMed

Disorders of sex chromosome, X and Y, consist of abnormality of the number or structure of the sex chromosome. Because sex chromosomes have a variety of genes related to sexual differentiation, disorders of sex chromosome induce a variety of disorders of sexual differentiation. At first, in this title, the process of normal sexual differentiation is shown. Classical disorders of sex chromosome are Klinefelter syndrome, XX male, XYY male, Turner syndrome, XXX female, and XY female. True hermphroiditism, mixed gonadal dysgenesis, and pure gonadal dysgenesis are also included, because most of these disorders have abnormal sex chromosome. Molecular analysis of sex chromosome is clarifying disorders with a minute abnormality of sex chromosome. They include male infertility, premature ovarian failure, and fragile X syndrome. Explanations of the above disorders are given briefly. PMID:9396296

Namiki, M; Koh, E

1997-11-01

230

Sex-Offender Registration  

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 ® (SOTT) is to provide assistance ...

231

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 ...

232

Sex Differences in Obesity  

MedlinePLUS

... Bones PECC More Campaigns Informational Videos Fact Sheet: Sex Differences in Obesity Part 1: Definitions and Epidemiology ... ethnic divide exists for overall obesity and for sex differences in obesity. Among black people, 54.3% ...

233

Same sex, no sex, and unaware sex in neurotoxicology.  

PubMed

Males and females of virtually all species differ in how they respond to their environment. Because such differences exist in almost all biological realms, including disease patterns and therapeutic outcomes, they have evoked calls by various bodies to incorporate their assessment in research. Neurobehavioral indices pose special questions because, unlike outwardly visible markers, they are described by complex functional outcomes or subtle alterations in brain structure. These divergent responses arise because they are inscribed in the genome itself and then by endocrine mechanisms that govern sexual differentiation of the brain during development and operate throughout life. Other organ systems that exhibit sex differences include the liver, an important consideration for neurotoxicology because it may process many toxic chemicals differentially in males and females. Despite the scope and pervasiveness of sex differences, however, they are disregarded by much of neurotoxicology research. Males predominate in behavioral experiments, few such experiments study both sexes, some investigators fail to even describe the sex of their subjects, and in vitro studies tend to wholly ignore sex, even for model systems aimed at neurological disorders that display marked sex differences. The public is acutely aware of sex differences in behavior, as attested by its appetite for books on the topic. It closely follows debates about the proportion of women in professions that feature science and mathematics. Neurotoxicology, especially in the domain of laboratory research, will be hindered in its ability to translate its findings into human health measures if it assigns sex differences to a minor role. It must also be sensitive to how such debates are framed. Often, the differences evoking the most discussion are subtle in scope. They do not lend themselves to the typical analyses conducted by experimenters; that is, reliance on mean differences and null hypothesis testing. PMID:20875453

Weiss, Bernard

2011-10-01

234

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

SciTech Connect

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.

Strecker, Kevin E.; Chandler, David W.

2010-10-01

235

Polarized spectral combs probe optical fiber surface plasmons.  

PubMed

The high-order cladding modes of conventional single mode fiber come in semi-degenerate pairs corresponding to mostly radially or mostly azimuthally polarized light. Using tilted fiber Bragg gratings to excite these mode families separately, we show how plasmonic coupling to a thin gold coating on the surface of the fiber modifies the effective indices of the modes differently according to polarization and to mode order. In particular, we show the existence of a single "apolarized" grating resonance, with equal effective index for all input polarization states. This special resonance provides direct evidence of the excitation of a surface plasmon on the metal surface but also an absolute wavelength reference that allows for the precise localization of the most sensitive resonances in refractometric and biochemical sensing applications. Two plasmon interrogation methods are proposed, based on wavelength and amplitude measurements. Finally, we use a biotin-streptavidin biomolecular recognition experiment to demonstrate that differential spectral transmission measurements of a fine comb of cladding mode resonances in the vicinity of the apolarized resonance provide the most accurate method to extract information from plasmon-assisted Tilted fiber Bragg gratings, down to pM concentrations and at least 10(-5) refractive index changes. PMID:23481763

Caucheteur, Christophe; Voisin, Valérie; Albert, Jacques

2013-02-11

236

Broadband Spectroscopy with Dual Combs and Cavity Enhancement  

NASA Astrophysics Data System (ADS)

Classical FTIRs handle the task of massively parallel spectroscopic probing by interferometric detection. In contrast a frequency comb Fourier transform spectrometer (FC-FTS) retains the principle of combining two interferometer beams but uses two inputs from two independent sources. Thus we can offset their frequencies to facilitate multifrequency heterodyne signal processing. The advantages of this spectrometer compared with the classical FTIR include ease of operation (no cumbersome moving delay lines), speed of acquisition (18 ?s demonstrated), collimated long-distance propagation, possibly diffraction-limited microscopic probing, and mid infrared as well as THz operation if necessary. In a recent proof of principle experiment we have dramatically improved the sensitivity by the implementation of an enhancement cavity around the probing volume We recorded, within 18 ?s, spectra of the ammonia 1.0 ?m overtone bands comprising 1500 spectral elements and spanning 20 nm with 4.5 GHz resolution and a noise-equivalent-absorption at one-second-averaging of 1 10-10 cm-1Hz-1/2, thus opening a route to time-resolved spectroscopy of rapidly-evolving single-events. Since FC-FTS only needs one detector that is easily available in practically all spectral regions, it can be envisioned that cavity-enhanced FC-FTS will assume a position of dominance for the measurements of real-time ultra-sensitive spectra in the molecular fingerprint region. B. Bernhardt et. al., Nature Photonics, 4 (55), January 2010.

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

2010-06-01

237

Modeling and characterization of comb-actuated resonant microscanners  

NASA Astrophysics Data System (ADS)

The dynamics of the out-of-plane comb-drive actuator used in a torsional resonant mode microscanner is discussed. The microscanner is fabricated using the standard SOI technology by Fraunhofer, IPMS and utilized in various display, barcode scanning, spectroscopy and other imaging applications. The device is a parametrically excited system and exhibits hysteretic frequency response, nonlinear transient response, subharmonic oscillations, multiple parametric resonances, and alternating-oscillation-frequency behavior. Analytical and numerical models are developed to predict the parametric system dynamics. The analytical model is based on the solution of the linear Mathieu equation and valid for small angular displacements. The numerical model is valid for both small and large deflection angles. The analytical and numerical models are validated with the experimental results under various ambient pressures and excitation schemes and successfully predict the dynamics of the parametric nature of the microscanner. As many as four parametric resonances are observed at 30 mTorr. The models developed in this paper can be used to optimize the structure and the actuator.

Ataman, Caglar; Urey, Hakan

2006-01-01

238

Quantum dot mode locked lasers for coherent frequency comb generation  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

239

Localised Acquired Trichorrhexis Nodosa of the Scalp Hair Induced by a Specific Comb and Combing Habit - A Report of Three Cases  

PubMed Central

Trichorrhexis nodosa is a hair shaft disorder often encountered in clinical practice. Acquired trichorrhexis is commoner of the two types and is most often due to weathering from physical or chemical causes. We report three representative cases of localized acquired trichorrhexis encountered in our clinic attributable to a specific comb, used commonly in Kerala, a Southern state of India.

Martin, Abhay Mani; Sugathan, P

2011-01-01

240

Coeducation and Sex Roles.  

ERIC Educational Resources Information Center

A study of the sex role stereotypes held by 538 first-term Australian university students from single-sex and coeducational high schools is presented. Results suggest that coeducational schooling may have some advantages for fostering interactions with the opposite sex. (MSE)

Harris, Mary B.

1986-01-01

241

Sex Differences in Stroke  

Microsoft Academic Search

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

L. Christine Turtzo; Louise D. McCullough

2008-01-01

242

Sex Chromosomes and Speciation  

Microsoft Academic Search

Studies of reproductive isolation between animal species have shown (i) that if one sex of the hybrids between two species is sterile or inviable, it is usually the heterogametic sex (Haldane's rule), and (ii) the genes on the sex chromosomes play a particularly large role in hybrid sterility and inviability. We propose an explanation for these two observations which is

Eva Jablonka; Marion J. Lamb

1991-01-01

243

Sex Equality Bibliographies.  

ERIC Educational Resources Information Center

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…

Hohenshil, Thomas H.; Linkous, Carolyn Maddy

244

Integrated Sex Education  

PubMed Central

If sex education consists of factual information only, a distorted picture results. Children and teenagers can teach us how sex is firmly embedded in the whole person, which should direct us in our approach. The problems of parental embarrassment, of finding opportunities and of the sex education we give unwittingly, are touched on.

Vandermaas, Alan

1974-01-01

245

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 ...

246

Single-Sex Classrooms  

ERIC Educational Resources Information Center

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

Protheroe, Nancy

2009-01-01

247

Students' sex preferences and sex role expectancies for counselors  

Microsoft Academic Search

Examined sex role expectancies for counselors as a function of sex of student, preference for counselor's sex, and sex of counselor being rated. 128 male and 249 female college students were asked what sex of counselor they would prefer if they were seeking help with personal or social concerns, and then they were randomly assigned to rate their sex role

Deborah H. Johnson

1978-01-01

248

Neuroprotection of Sex Steroids  

PubMed Central

Sex steroids are essential for reproduction and development in animals and humans, and sex steroids also play an important role in neuroprotection following brain injury. New data indicate that sex-specific responses to brain injury occur at the cellular and molecular levels. This review summarizes the current understanding of neuroprotection by sex steroids, particularly estrogen, androgen, and progesterone, based on both in vitro and in vivo studies. Better understanding of the role of sex steroids under physiological and pathological conditions will help us to develop novel effective therapeutic strategies for brain injury.

Liu, Mingyue; Kelley, Melissa H.; Herson, Paco S.; Hurn, Patricia D.

2011-01-01

249

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

250

Plastic detection comb better than visual screening for diagnosis of head louse infestation  

PubMed Central

SUMMARY Finding lice can be difficult in head louse infestation. We compared a new louse detection comb with visual inspection. All children in two rural Turkish schools were screened by the two methods. Those with lice were offered treatment and the results monitored by detection combing. Children with nits only were re-screened to identify latent infestations. Using visual inspection we found 214/461 children (46%) with nits but only 30 (6·5%) with live lice. In contrast detection combing found 96 (21%) with live lice, of whom 20 had no nits. Detection combing was 3·84 times more effective than visual inspection for finding live lice. Only 10/138 (7·2%) children with nits and no lice were found to have active infestation by day 16. We found that the detection comb is significantly (P<0·001) more effective than visual screening for diagnosis; that nits are not a good indicator of active infestation; and that treatment with 1% permethrin was 89·6% effective.

BALCIOGLU, C.; BURGESS, I. F.; LIMONCU, M. E.; SAHIN, M. T.; OZBEL, Y.; BILAC, C.; KURT, O.; LARSEN, K. S.

2008-01-01

251

Plastic detection comb better than visual screening for diagnosis of head louse infestation.  

PubMed

Finding lice can be difficult in head louse infestation. We compared a new louse detection comb with visual inspection. All children in two rural Turkish schools were screened by the two methods. Those with lice were offered treatment and the results monitored by detection combing. Children with nits only were re-screened to identify latent infestations. Using visual inspection we found 214/461 children (46%) with nits but only 30 (6.5%) with live lice. In contrast detection combing found 96 (21%) with live lice, of whom 20 had no nits. Detection combing was 3.84 times more effective than visual inspection for finding live lice. Only 10/138 (7.2%) children with nits and no lice were found to have active infestation by day 16. We found that the detection comb is significantly (P<0.001) more effective than visual screening for diagnosis; that nits are not a good indicator of active infestation; and that treatment with 1% permethrin was 89.6% effective. PMID:18177517

Balcioglu, C; Burgess, I F; Limoncu, M E; Sahin, M T; Ozbel, Y; Bilaç, C; Kurt, O; Larsen, K S

2008-10-01

252

Modal expansion approach to optical-frequency-comb generation with monolithic whispering-gallery-mode resonators  

SciTech Connect

We describe a general framework based on modal expansion for the study of optical-frequency combs generated with monolithic whispering-gallery-mode resonators. We obtain a set of time-domain rate equations describing the dynamics of each mode as a function of the main characteristics of the cavity, namely, Kerr nonlinearity, absorption, coupling losses, and cavity dispersion (geometrical and material). A stability analysis of the various side modes is performed, which finds analytically the threshold power needed for comb generation. We show that the various whispering gallery modes are excited in a nontrivial way, strongly dependent on the value of the overall cavity dispersion. We demonstrate that the combs are not simply generated through a direct transfer of energy from the pumped mode to all their neighbors but rather through complex intermediate interactions. Anomalous cavity dispersion is also demonstrated to be critical for these cascading processes, and comb generation is thereby unambiguously linked to modulational instability. This theory accurately describes the emergence of spectral modulation and free spectral-range tunability in the comb. It also enables a clear understanding of the various phenomena responsible for the spectral span limitation. Our theoretical predictions are in excellent agreement with the numerical simulations, and they successfully explain the internal mechanisms responsible for the generation of hundreds of Kerr modes in monolithic whispering-gallery-mode resonators.

Chembo, Yanne K.; Yu, Nan [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

2010-09-15

253

Comb-branched Polymer Electrolytes: Architectural Changes That Promote Increased Li^+ Transport  

NASA Astrophysics Data System (ADS)

The use of solid polymer electrolytes (SPEs) in the batteries of next generation technology applications is promising due to their safety and stability, yet is also hindered by low conductivity and high temperature requirements. Recent simulations of comb-branched poly(epoxide ether)-based SPEs have shown the comb-branched architecture to be able to overcome some of these hindrances. While providing the advantage of preventing crystallinity and allowing the optimization of the backbone to be decoupled from that of the side chain, the comb-branched SPE studied suffers from slow Li^+ cation dynamics due to coordination with the backbone. To improve Li^+ transport, we have modified the architecture of the comb-branched poly(epoxide ether) by attaching the side chains to the backbone with non-coordinating, flexible spacers. Inclusion of these spacers has resulted in a five-fold increase in the diffusion of Li^+ cation effected through 1) an increased side chain flexibility, 2) a decreased interaction of the cation with the dynamically slow backbone, and 3) quick conformational dynamics of the entire side chain. Additionally we report on other desirable architectural changes, such as including carbonate solvating moieties, to comb-branched SPEs allowing enhanced mobility of Li^+.

Demille, Robert; Murthy, Sowmya; Bedrov, Dmitry; Smith, Grant

2012-02-01

254

Highly stable, anion conductive, comb-shaped copolymers for alkaline fuel cells.  

PubMed

To produce an anion-conductive and durable polymer electrolyte for alkaline fuel cell applications, a series of quaternized poly(2,6-dimethyl phenylene oxide)s containing long alkyl side chains pendant to the nitrogen-centered cation were synthesized using a Menshutkin reaction to form comb-shaped structures. The pendant alkyl chains were responsible for the development of highly conductive ionic domains, as confirmed by small-angle X-ray scattering (SAXS). The comb-shaped polymers having one alkyl side chain showed higher hydroxide conductivities than those with benzyltrimethyl ammonium moieties or structures with more than one alkyl side chain per cationic site. The highest conductivity was observed for comb-shaped polymers with benzyldimethylhexadecyl ammonium cations. The chemical stabilities of the comb-shaped membranes were evaluated under severe, accelerated-aging conditions, and degradation was observed by measuring IEC and ion conductivity changes during aging. The comb-shaped membranes retained their high ion conductivity in 1 M NaOH at 80 °C for 2000 h. These cationic polymers were employed as ionomers in catalyst layers for alkaline fuel cells. The results indicated that the C-16 alkyl side chain ionomer had a slightly better initial performance, despite its low IEC value, but very poor durability in the fuel cell. In contrast, 90% of the initial performance was retained for the alkaline fuel cell with electrodes containing the C-6 side chain after 60 h of fuel cell operation. PMID:23721192

Li, Nanwen; Leng, Yongjun; Hickner, Michael A; Wang, Chao-Yang

2013-07-10

255

Uncombed Sunspot Penumbrae Are Combed by Large Flares  

NASA Astrophysics Data System (ADS)

In the past two decades, the complex nature of sunspots is disclosed with high resolution observations. One of the most important findings is the ``uncombed'' penumbral structure, where the bright grains are more vertical while dark fibrils are more horizontal (Solanki and Montavon 1993). The Evershed flows are more closely associated with the horizontal component. On the other hand, it was found that flares may change the topology of the sunspot structure in delta configuration: the central structure at the flaring polarity inversion line becomes darkened while sections of peripheral penumbrae may disappear permanently associated with flares (Liu et al. 2005). The high spatial and temporal resolution observations obtained with Hinode/SOT on December 6, 2006 and June 4, 2007 provide an excellent opportunity to study the evolution of penumbral fine structure associated with major flares. We found that in sections of penumbrae swept by flare ribbons, the dark fibrils completely disappear, while the bright grains evolve into faculae that resemble the structure of vertical magnetic flux tubes. Therefore, the original uncombed penumbral structure seems to be combed toward the vertical direction---the dark and bright components are no longer separated in orientation after the flares. These results provide a new insight into the possible impact by the coronal transients on the photospheric magnetic structure of sunspots, and shed new light on the obscure formation and decay mechanism of penumbrae. Reference Liu, C., Deng, N., Liu, Y., Falconer, D., Goode, P.R., Denker, C. & Wang, H., 2005, Ap.J., 622, 722 Solanki, S.K. & Montavon, C.A.P., 1993, A & A, 275, 283

Wang, Haimin; Liu, C.; Deng, N.

2011-05-01

256

Sex determination in amphibians.  

PubMed

The heterogametic sex is male in all mammals, whereas it is female in almost all birds. By contrast, there are two heterogametic types (XX/XY and ZZ/ZW) for genetic sex determination in amphibians. Though the original heterogametic sex was female in amphibians, the two heterogametic types were probably interchangeable, suggesting that sex chromosomes evolved several times in this lineage. Indeed, the frog Rana rugosa has the XX/XY and ZZ/ZW sex-determining systems within a single species, depending on the local population in Japan. The XY and ZW geographic forms with differentiated sex chromosomes probably have a common origin as undifferentiated sex chromosomes resulted from the hybridization between the primary populations of West Japan and Kanto forms. It is clear that the sex chromosomes are still undergoing evolution in this species group. Regardless of the presence of a sex-determining gene in amphibians, the gonadal sex of some species can be changed by sex steroids. Namely, sex steroids can induce the sex reversal, with estrogens inducing the male-to-female sex reversal, whereas androgens have the opposite effect. In R. rugosa, gonadal activity of CYP19 (P450 aromatase) is correlated with the feminization of gonads. Of particular interest is that high levels of CYP19 expression are observed in indifferent gonads at time before sex determination. Increases in the expression of CYP19 in female gonads and CYP17 (P450 17alpha-hydroxylase/C17-20 lyase) in male gonads suggest that the former plays an important role in phenotypic female determination, whereas the latter is needed for male determination. Thus, steroids could be the key factor for sex determination in R. rugosa. In addition to the role of sex steroids in gonadal sex determination in this species, Foxl2 and Sox3 are capable of promoting CYP19 expression. Since both the genes are autosomal, another factor up-regulating CYP19 expression must be recruited. The factor, which may be located on the X or W chromosome, intervenes directly or indirectly, in the transcriptional regulation of the CYP19 gene for feminization in amphibians. A factor up-regulating CYP17 expression remains to be identified. PMID:18996493

Nakamura, Masahisa

2009-05-01

257

Doppler cooling with coherent trains of laser pulses and a tunable velocity comb  

NASA Astrophysics Data System (ADS)

We explore the possibility of decelerating and Doppler cooling an ensemble of two-level atoms by a coherent train of short, nonoverlapping laser pulses. We derive analytical expressions for mechanical force exerted by the train. In frequency space the force pattern reflects the underlying frequency comb structure. The pattern depends strongly on the ratio of the atomic lifetime to the repetition time between the pulses and pulse area. For example, in the limit of short lifetimes, the frequency-space peaks of the optical force wash out. We propose to tune the carrier-envelope offset frequency to follow the Doppler-shifted detuning as atoms decelerate; this leads to compression of atomic velocity distribution about comb teeth and results in a “velocity comb”—a series of narrow equidistant peaks in the velocity space.

Ilinova, Ekaterina; Ahmad, Mahmoud; Derevianko, Andrei

2011-09-01

258

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

PubMed

On the ceiling of the Oriental hornet comb cell, there are mineral granules of polycrystalline material known to belong to the group of perovskites. In a comb cell intended to house a worker hornet, the roof base usually carries one or several such perovskite granules containing titanium (Ti), whereas in the roof base of a cell housing a developing queen, there are usually several granules containing a high percentage of silicon (Si), aluminum (Al), calcium (Ca), and iron (Fe), but very little if any Ti. In worker comb cells, Ti usually appears as ilmenite (FeTiO3). Besides documenting the above-mentioned facts, this report discusses possible reasons for the appearance of ilmenite crystals in worker cells only and not in queen cells. PMID:15940685

Ishay, J S; Joseph, Z; Galushko, D; Ermakov, N; Bergman, D J; Barkay, Z; Stokroos, I; van der Want, J

2005-04-01

259

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

PubMed

We present a novel scheme of frequency scan and wavelength modulation of a difference-frequency-generation source for comb-referenced sensitive spectroscopy. While the pump and signal frequencies are phase-locked to an optical frequency comb (OFC), the offset frequency between the signal wave and the nearest comb tooth is modulated to apply a wavelength-modulation technique, and the idler wave frequency is repeatedly swept for signal accumulation by changing the repetition frequency of the OFC. The spectrometer is applied to absolute frequency measurement of weak hyperfine-resolved rovibration transitions of the ?(1) band of CH(3)I, and the uncertainty in frequency determination is reduced by one order of magnitude in compared with that of the previous work published in Optics Express 20, 9178-9186 (2012). PMID:23787670

Iwakuni, Kana; Okubo, Sho; Sasada, Hiroyuki

2013-06-17

260

Frequency chirp linearization for ultraflat optical frequency comb generation based on group velocity dispersion.  

PubMed

We propose to insert group velocity dispersion between cascaded phase and amplitude modulation for ultraflat optical frequency comb (OFC) generation. With the dispersion, the sinusoidally varied chirp of the continuous wave light induced by phase modulation becomes linear within a relatively wide time interval. This is useful to improve the flatness of the generated OFC by directly cascaded phase and amplitude modulation. Simulation shows a flat comb of 37 tones within 0.88 dB power variation when the modulation index of the phase modulation reaches 20. An ultraflat comb generator with 10 GHz frequency spacing is also demonstrated. The flatness of the 15 tones around the center wavelength has been improved to 0.98 dB. PMID:23811872

Xing, Yanfei; Wang, Qiang; Huo, Li; Lou, Caiyun

2013-07-01

261

A wavelength-tunable fiber laser based on a twin-core fiber comb filter  

NASA Astrophysics Data System (ADS)

A wavelength-tunable fiber laser based on a twin-core fiber (TCF) comb filter is proposed and demonstrated. The TCF comb filter is fabricated by splicing a 0.85 m long TCF between two standard single mode fibers (SMFs) and with exhibits a good linear strain characteristic with a sensitivity of 1.23 pm/??. The wavelength of the laser can be linearly tuned from 1558.04 nm to 1553.62 nm by applying an axial strain to the TCF comb filter. The optical signal-to-noise ratio (OSNR) of the fiber laser reaches 45 dB. The 3 dB bandwidth is 0.02 nm. The fluctuation of the laser peak in the output power and the wavelength is less than 0.5 dB and within 0.05 nm, respectively. The fiber laser has the advantages of having a simple structure and stable operation under room temperature.

Zou, Hui; Lou, Shuqin; Yin, Guolu

2013-02-01

262

Generation of a flexible optical comb in a periodically poled lithium niobate waveguide.  

PubMed

We propose and demonstrate a technique for the generation of an optical comb with tunable line spacing in a periodically poled lithium niobate (PPLN) waveguide. The technique is implemented with four input continuous waves (CWs), which generate a 19-line comb tuned to the spacing of 25 and 20 GHz. We show that each additional CW switched on out of the quasi phase-matching band at the PPLN waveguide input generates the growth of six new lines. The performance of the comb is tested modulating the lines with a 40 Gb/s differential quadrature phase shift keying data, demonstrating error-free operation. Nonuniform spacing of the input seed CWs improves the efficiency of the line generation process. PMID:24686591

Scaffardi, Mirco; Pinna, Sergio; Lazzeri, Emma; Bogoni, Antonella

2014-04-01

263

Frustrated crystallisation and hierarchical self-assembly behaviour of comb-like polymers.  

PubMed

Comb-like polymers with flexible side chains chemically pended onto a polymeric backbone afford some unusual properties due to their hierarchical structures, such as nanoscale confined crystallisation, phase transition and conformational variations, length scale effects, etc. Considerable attention has been paid to these featured polymers, regarding their importance in understanding the correlation between hierarchical structure and the assembled morphologies. In this review, we reviewed the recent research progress on the structure-property correlations of comb-like polymers. This article brings together and highlights the fabrication, structure determination and morphology characterization for comb-like polymers, especially for nanostructured packing patterns and frustrated mobility of chain segments from the selected examples. PMID:23243663

Shi, Haifeng; Zhao, Ying; Dong, Xia; Zhou, Yong; Wang, Dujin

2013-03-01

264

Comb-calibrated frequency-modulated continuous-wave ladar for absolute distance measurements.  

PubMed

We demonstrate a comb-calibrated frequency-modulated continuous-wave laser detection and ranging (FMCW ladar) system for absolute distance measurements. The FMCW ladar uses a compact external cavity laser that is swept quasi-sinusoidally over 1 THz at a 1 kHz rate. The system simultaneously records the heterodyne FMCW ladar signal and the instantaneous laser frequency at sweep rates up to 3400 THz/s, as measured against a free-running frequency comb (femtosecond fiber laser). Demodulation of the ladar signal against the instantaneous laser frequency yields the range to the target with 1 ms update rates, bandwidth-limited 130 ?m resolution and a ~100 nm accuracy that is directly linked to the counted repetition rate of the comb. The precision is <100 nm at the 1 ms update rate and reaches ~6 nm for a 100 ms average. PMID:23938965

Baumann, Esther; Giorgetta, Fabrizio R; Coddington, Ian; Sinclair, Laura C; Knabe, Kevin; Swann, William C; Newbury, Nathan R

2013-06-15

265

On the robustness of phase locking in Kerr optical frequency combs.  

PubMed

We theoretically investigate the phase locking phenomena between the spectral components of Kerr optical frequency combs in the dynamical regime of Turing patterns. We show that these Turing patterns display a particularly strong and robust phase locking, originating from a cascade of phase locked triplets which asymptotically lead to a global phase locking between the modes. The local and global phase locking relationships defining the shape of the comb are analytically determined. Our analysis also shows that solitons display a much weaker phase locking that can be destroyed more easily than in the Turing pattern regime. Our results indicate that Turing patterns are generally the most suitable for applications requiring the highest stability. Experimental generation of such combs is also discussed in detail, and is in excellent agreement with the numerical simulations. PMID:24690830

Coillet, Aurélien; Chembo, Yanne

2014-03-15

266

A Precision Radial Velocity Pathfinder Instrument in the H Band with a Laser Frequency Comb  

NASA Astrophysics Data System (ADS)

We describe changes to the warm-bench, fiber-fed, Penn State Pathfinder instrument that enabled us to test the ability to recover precision radial velocities in the H-band. The use of thermal blocking filters that cut off at 1.7 microns allows us to observe in the H-band by blocking the overwhelming thermal flux beyond 2 microns. A PK-50 window provides further suppression of this thermal flux. We also describe the observations, reduction, and results from an August 2010 test run of this instrument with a 25 GHz NIST laser frequency comb calibration system. We obtained radial velocities of several bright stars with on-sky observation with the laser comb. Our results demonstrate the potential of our testbed configuration for obtaining precision radial velocities in the NIR, as well as the utility of laser frequency combs as wavelength calibrators in this wavelength regime.

Terrien, Ryan; Mahadevan, S.; Ramsey, L.; Bender, C.; Redman, S.; Osterman, S.; Diddams, S.; Ycas, G.; Quinlan, F.; Botzer, B.

2011-01-01

267

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

PubMed Central

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.

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

2013-01-01

268

Vertical comb drive microscanners for beam steering, linear scanning, and laser projection applications  

NASA Astrophysics Data System (ADS)

This paper describes in detail our concept of quasi-static micro scanning mirrors enabling large static deflections and linearized scanning using vertical out-of-plane comb drives. The vertical comb configuration is realized from a planar scanner substrate by wafer bonding. The device concept is highly flexible by design; different kinds of vertical combs (e.g. staggered and angular) can be realized without changing the technological process flow but by design modifications, only. First demonstrator devices are presented: a) quasi-static 1D-scanners with 4 mm mirror diameter and +/-7.5° mechanical tilt angle for beam steering and b) a quasi-static / resonant 2D-scanner enabling 2D raster scanning with SVGA resolution.

Jung, Denis; Sandner, Thilo; Kallweit, David; Schenk, Harald

2012-02-01

269

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

PubMed

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/Hz2/3 for a signal with a carrier frequency of 35.8 GHz, compared with 94 dB/Hz2/3 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

Sherman, Alexander; Horowitz, Moshe; Zach, Shlomo

2014-06-30

270

Optical clockwork with an offset-free difference-frequency comb: accuracy of sum- and difference-frequency generation.  

PubMed

We demonstrate a simple optical clockwork mechanism based on the broadened frequency comb of a femtosecond laser and on difference-frequency generation (DFG) in a nonlinear crystal. The DFG comb possesses a vanishing carrier envelope offset frequency that permits the construction of a simple and thus potentially more stable optical clockwork. In addition it offers the possibility of extending the frequency comb into the infrared spectral region. The overall accuracy and stability of the DFG comb relative to the initial frequency comb were measured to be 6.6 x 10(-21) and 10(-18) tau(-1), respectively, where tau is the averaging time in seconds. Assuming that sum- and difference-frequency generation are independent processes, our measurements suggest a <10(-20) accuracy for them. PMID:14759061

Zimmermann, Marcus; Gohle, Christoph; Holzwarth, Ronald; Udem, Thomas; Hänsch, Theodor W

2004-02-01

271

Magnetic minerals. Keystone-like crystals in cells of hornet combs.  

PubMed

The hexagonal brood-rearing cells inside the nest combs of the hornet Vespa orientalis are uniform in both their architecture and orientation. We have discovered that each cell contains a minute crystal that projects down from the centre of its domed roof and has a composition typical of the magnetic mineral ilmenite. These tiny crystals form a network that may act like a surveyor's spirit-level, helping the hornets to assess the symmetry and balance of the cells and the direction of gravity while they are building the comb. PMID:11395756

Stokroos, I; Litinetsky, L; van der Want, J J; Ishay, J S

2001-06-01

272

Terahertz optical frequency comb generation and phase locking of an optical parametric oscillator at 665 GHz.  

PubMed

We have achieved efficient electro-optic phase modulation at high frequencies in a resonant modulator cavity. We enhance modulation by matching the phase velocities of the optical and microwave fields in the modulator substrate and by placing the modulator inside an optical cavity that is resonant for the input optical beam and the generated sidebands. An optical frequency comb with a span of 3 THz and at a spacing of 17 GHz is generated with 1 W of microwave power. The terahertz comb is utilized to phase lock an optical parametric oscillator at a signal-idler difference frequency of 665 GHz. PMID:19829605

Brothers, L R; Lee, D; Wong, N C

1994-02-15

273

Preparation and properties of comb-like surfactants containing poly(ethylene oxide) methyl ether grafts  

Microsoft Academic Search

The comb-like surfactants, poly(styrene-co-maleic anhydride)-g-(poly(ethylene glycol) monomethyl ether), poly(St-co-MA)-g-(MPEG), have been prepared using a macromonomer approach to get controlled molecular structures. The macromonomer (MAMPEG) was obtained by esterification of poly(ethylene glycol) monomethyl ether with maleic anhydride. Poly(St-co-MA)-g-(MPEG) with various molar ratios of St to MAMPEG (R) were then constructed by radical copolymerization. The comb-like structures of the surfactants were confirmed

Wei Zhang; Zhiping Du; Chien-Hsiang Chang; Guoyong Wang

2009-01-01

274

Control of Four-Level Quantum Coherence via Discrete Spectral Shaping of an Optical Frequency Comb  

SciTech Connect

We present experiments demonstrating high-resolution and wide-bandwidth coherent control of a four-level atomic system in a diamond configuration. A femtosecond frequency comb is used to excite a specific pair of two-photon transitions in cold {sup 87}Rb. The optical-phase-sensitive response of the closed-loop diamond system is studied by controlling the phase of the comb modes with a pulse shaper. Finally, the pulse shape is optimized resulting in a 256% increase in the two-photon transition rate by forcing constructive interference between the mode pairs detuned from an intermediate resonance.

Stowe, Matthew C.; Peer, Avi; Ye Jun [JILA, National Institute of Standards and Technology and University of Colorado (United States); Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2008-05-23

275

Coherent frequency combs produced by self frequency modulation in quantum cascade lasers  

NASA Astrophysics Data System (ADS)

One salient characteristic of Quantum Cascade Laser (QCL) is its very short ? ˜ 1 ps gain recovery time that so far thwarted the attempts to achieve self-mode locking of the device into a train of single pulses. We show theoretically that four wave mixing, combined with the short gain recovery time causes QCL to operate in the self-frequency-modulated regime characterized by a constant power in time domain and stable coherent comb in the frequency domain. Coherent frequency comb may enable many potential applications of QCL's in sensing and measurement.

Khurgin, J. B.; Dikmelik, Y.; Hugi, A.; Faist, J.

2014-02-01

276

Pair-by-pair pulse shaping for optical arbitrary waveform generation by dual-comb heterodyne.  

PubMed

We present a novel optical arbitrary waveform generation approach based on pair-by-pair pulse shaping. Based on the heterodyne between a pair of optical frequency combs with different repetition rates, the repetition rate of the generated signals can be flexibly tuned from MHz to GHz without changing the setup. The restriction of the spectral resolution of the optical spectrum processor is overcome by the pair-by-pair approach while the spectral resolution of the system can be improved to MHz by dual-comb heterodyne. Hyperfine control of a higher resolution spectrum at MHz is achieved, which benefits the generation of the ultrawideband signals. PMID:24322250

Zhou, Xin; Zheng, Xiaoping; Wen, He; Zhang, Hanyi; Zhou, Bingkun

2013-12-15

277

Multiheterodyne spectroscopy with optical frequency combs generated from a continuous-wave laser.  

PubMed

Dual-drive Mach-Zehnder modulators were utilized to produce power-leveled optical frequency combs (OFCs) from a continuous-wave laser. The resulting OFCs contained up to 50 unique frequency components and spanned more than 200 GHz. Simple changes to the modulation frequency allowed for agile control of the comb spacing. These OFCs were then utilized for broadband, multiheterodyne measurements of CO2 using both a multipass cell and an optical cavity. This technique allows for robust measurements of trace gas species and alleviates much of the cost and complexity associated with the use of femtosecond OFCs produced with mode-locked pulsed lasers. PMID:24784078

Long, D A; Fleisher, A J; Douglass, K O; Maxwell, S E; Bielska, K; Hodges, J T; Plusquellic, D F

2014-05-01

278

Comb transmission filters defined by phase-shifted superstructure Bragg gratings.  

PubMed

We present a design method and numerical results describing the construction of distributed feedback grating filters that support discrete combs of transmission resonances. These filter designs define open superstructure grating resonators with transmission channels that can be placed at predetermined frequencies, such as those defined by the wavelength division multiplexing grid or by a secondary frequency comb source. Focusing on a specific example with 40 GHz channel spacing, we optimize an active structure that defines three low-threshold lasing modes. How our design approach relates to filter synthesis techniques based on cascaded grating resonators is also discussed. PMID:24562284

O'Brien, Stephen

2014-02-15

279

Comb/serpentine/cross-bridge test structure for fabrication process evaluation  

NASA Technical Reports Server (NTRS)

The comb/serpentine/cross-bridge structure was developed to monitor and evaluate same layer shorts and step coverage problems (open and high-resistance wire over steps) for integrated circuit fabrication processes. The cross-bridge provides local measurements of wire sheet resistance and wirewidth. These local parametric measurements are used in the analysis of the serpentine wire, which identifies step coverage problems. The comb/serpentine/cross-bridge structure was fabricated with 3 microns CMOS/bulk p-well process and tested using a computer-controlled parametric test system.

Sayah, Hoshyar R.; Buehler, Martin G.

1988-01-01

280

Surface acoustic wave opto-mechanical oscillator and frequency comb generator  

NASA Astrophysics Data System (ADS)

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

Savchenkov, A. A.; Matsko, A. B.; Ilchenko, V. S.; Seidel, D.; Maleki, L.

2011-09-01

281

Application of Laser Frequency Combs and Nitrogen Vacancy Diamond Magnetometers to Searches for New Physics  

NASA Astrophysics Data System (ADS)

Searches for new physics often benefit from improved technologies. Here we discuss possible applications of two emerging technologies to searches for physics beyond the Standard Model. First, laser frequency combs enable broad spectral coverage and coherent conversion between optical and RF signals. We are investigating tests of the nonminimal Standard-Model Extension using frequency combs coupled to broadband optical cavities. Second, nitrogen vacancy centers in diamond enable precision nanoscale magnetometry with applications from imaging to quantum science. We are investigating their use in searches for short-range spin-spin couplings.

Phillips, D. F.; Walsworth, R. L.

2014-01-01

282

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

PubMed

Fungus-growing termites efficiently decompose plant litter through their symbiotic relationship with basidiomycete fungi of the genus Termitomyces. Here, we investigated phenol-oxidizing enzymes in symbiotic fungi and fungus combs (a substrate used to cultivate symbiotic fungi) from termites belonging to the genera Macrotermes, Odontotermes, and Microtermes in Thailand, because these enzymes are potentially involved in the degradation of phenolic compounds during fungus comb aging. Laccase activity was detected in all the fungus combs examined as well as in the culture supernatants of isolated symbiotic fungi. Conversely, no peroxidase activity was detected in any of the fungus combs or the symbiotic fungal cultures. The laccase cDNA fragments were amplified directly from RNA extracted from fungus combs of five termite species and a fungal isolate using degenerate primers targeting conserved copper binding domains of basidiomycete laccases, resulting in a total of 13 putative laccase cDNA sequences being identified. The full-length sequences of the laccase cDNA and the corresponding gene, lcc1-2, were identified from the fungus comb of Macrotermes gilvus and a Termitomyces strain isolated from the same fungus comb, respectively. Partial purification of laccase from the fungus comb showed that the lcc1-2 gene product was a dominant laccase in the fungus comb. These findings indicate that the symbiotic fungus secretes laccase to the fungus comb. In addition to laccase, we report novel genes that showed a significant similarity with fungal laccases, but the gene product lacked laccase activity. Interestingly, these genes were highly expressed in symbiotic fungi of all the termite hosts examined. PMID:16332742

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

2005-12-01

283

Symbiotic Fungi Produce Laccases Potentially Involved in Phenol Degradation in Fungus Combs of Fungus-Growing Termites in Thailand†  

PubMed Central

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

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

2005-01-01

284

Sex Education and Its Influences on College Sex Practices  

Microsoft Academic Search

This was a relational study to examine the possibly of a correlation between type of high school sex education and types of attitudes and behaviors towards sex within the context of the college social environment. A review of the literature shows that comprehensive sex education has been more effective than no sex education or abstinence only sex education in delaying

Matthew Yetsko

2011-01-01

285

Nonvolitional Sex and Sexual Health  

Microsoft Academic Search

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

Debra Kalmuss

2004-01-01

286

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 ...

287

Age and Sex  

Microsoft Academic Search

Of all the characteristics of human populations, age and sex are arguably the most important and relevant for demographers. So important are they for demographic analysis that they are referred to as ‘‘the demographic variables’’ (Bogue 1969: 147). Their importance lies in the fact that the interaction of the demographic processes produces a population’s age and sex structure (Horiuchi and

Dudley L. Poston

288

Stimulants, Sex, and Gender  

Microsoft Academic Search

This article examines the differential effects of cocaine and methamphetamine (MA) on sexual drive, performance, and pleasure among men and women. Based on a self-report questionnaire, we examine cocaine (n = 56) and MA (n = 52) users' associations between substance use and sex. Overall, the cocaine group endorsed primarily negative associations between drug use and sex, whereas MA users

Alison Hamilton Brown; Catherine P. Domier; Richard A. Rawson

2005-01-01

289

Attitudes Towards Premarital Sex  

NSDL National Science Digital Library

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.

Dietz, Tracy

290

TA and Sex Stereotypes  

ERIC Educational Resources Information Center

Author discusses sex stereotypes and how they relate to transactional analysis. Thus, she claims there are striking similarities between female and male stereotypes and the Child and Adult respectively. Sex stereotypes hinder the attaining of the "I'm O.K. You're O.K." state between males and females. (SE)

Roney, Anne M.

1975-01-01

291

Recidivism of Sex Offenders.  

National Technical Information Service (NTIS)

The purpose of this paper is to examine the critical issues in defining recidivism and provide a synthesis of the current research on the re-offense rates of sex offenders. The following sections summarize and discuss research findings on sex offenders, f...

2001-01-01

292

Sex and School Reform.  

ERIC Educational Resources Information Center

Predicts that reformers will not attack sex education as an inappropriate addition to otherwise rigorous academic programs. Examines (1) some of the political, social, and practical reasons behind this avoidance and (2) the ineffectiveness of existing programs in preventing teenage pregnancies. Suggests that sex education programs may even hinder…

Cuban, Larry

1986-01-01

293

Advocating Elementary Sex Education.  

ERIC Educational Resources Information Center

Sex education is an important asset to personal growth during the elementary years. Though many parents are opposed to sex education during these early years, sexual knowledge acts as an antidote to fear and does not contribute to promiscuity. New programs in sexuality and family life are presently being developed. (JN)

McNab, Warren L.

1981-01-01

294

Sex differences in stroke  

PubMed Central

Sex differences in stroke are observed across epidemiologic studies, pathophysiology, treatments, and outcomes. These sex differences have profound implications for effective prevention and treatment and are the focus of this review. Epidemiologic studies reveal a clear age-by-sex interaction in stroke prevalence, incidence, and mortality. While premenopausal women experience fewer strokes than men of comparable age, stroke rates increase among postmenopausal women compared with age-matched men. This postmenopausal phenomenon, in combination with living longer, are reasons for women being older at stroke onset and suffering more severe strokes. Thus, a primary focus of stroke prevention has been based on sex steroid hormone-dependent mechanisms. Sex hormones affect different (patho)physiologic functions of the cerebral circulation. Clarifying the impact of sex hormones on cerebral vasculature using suitable animal models is essential to elucidate male–female differences in stroke pathophysiology and development of sex-specific treatments. Much remains to be learned about sex differences in stroke as anatomic and genetic factors may also contribute, revealing its multifactorial nature. In addition, the aftermath of stroke appears to be more adverse in women than in men, again based on older age at stroke onset, longer prehospital delays, and potentially, differences in treatment.

Haast, Roy A M; Gustafson, Deborah R; Kiliaan, Amanda J

2012-01-01

295

Muslims and Sex Education  

Microsoft Academic Search

Objections to contemporary practice in sex education are examined in the light of recent calls by Muslim leaders in Britain for Muslim parents to withdraw their children from sex education classes. The dilemma facing liberal policy makers is discussed, as they seek to reconcile the public interest, the wishes of parents with a wide diversity of beliefs and values and

J. Mark Halstead

1997-01-01

296

Asynchronous mid-infrared broadband optical parametric oscillator for dual-comb spectroscopy  

NASA Astrophysics Data System (ADS)

Two asynchronous, broadband 3.3-?m pulse trains with a stabilized repetition-rate difference of up to 5-kHz were generated from a single optical parametric oscillator. With additional carrier-envelope-offset stabilization, it could be applied to coherent dual-frequency-comb spectroscopy.

Zhang, Zhaowei; Gu, Chenglin; Sun, Jinghua; Wang, Chingyue; Gardiner, Tom; Reid, Derryck T.

2013-03-01

297

Molecular combing in the analysis of developmentally regulated amplified segments of Bradysia hygida.  

PubMed

Molecular combing technology is an important new tool for the functional and physical mapping of genome segments. It is designed to identify amplifications, microdeletions, and rearrangements in a DNA sequence and to study the process of DNA replication. This technique has recently been used to identify and analyze the dynamics of replication in amplified domains. In Bradysia hygida, multiple amplification initiation sites are predicted to exist upstream of the BhC4-1 gene. However, it has been impossible to identify them using the available standard techniques. The aim of this study was to optimize molecular combing technology to obtain DNA fibers from the polytene nuclei of the salivary glands of B. hygida to study the dynamics of DNA replication in this organism. Our results suggest that combing this DNA without prior purification of the polytene nuclei is possible. The density, integrity, and linearity of the DNA fibers were analyzed, fibers 50 to 300 kb in length were detected, and a 9-kb fragment within the amplified region was visualized using biotin detected by Alexa Fluor 488-conjugated streptavidin technique. The feasibility of physically mapping these fibers demonstrated in this study suggests that molecular combing may be used to identify the replication origin of the BhC4-1 amplicon. PMID:22911590

Passos, K J R; Togoro, S Y; Carignon, S; Koundrioukoff, S; Lachages, A-M; Debatisse, M; Fernandez, M A

2012-01-01

298

Optical Comb Generation for Streak Camera Calibration for Inertial Confinement Fusion Experiments  

SciTech Connect

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) is coming on-line to support physics experimentation for the U.S. Department of Energy (DOE) programs in Inertial Confinement Fusion (ICF) and Stockpile Stewardship (SS). Optical streak cameras are an integral part of the experimental diagnostics instrumentation at NIF. To accurately reduce streak camera data a highly accurate temporal calibration is required. This article describes a technique for simultaneously generating a precise +/- 2 ps optical marker pulse (fiducial reference) and trains of precisely timed, short-duration optical pulses (so-called “comb” pulse trains) that are suitable for the timing calibrations. These optical pulse generators are used with the LLNL optical streak cameras. They are small, portable light sources that, in the comb mode, produce a series of temporally short, uniformly spaced optical pulses, using a laser diode source. Comb generators have been produced with pulse-train repetition rates up to 10 GHz at 780 nm, and somewhat lower frequencies at 664 nm. Individual pulses can be as short as 25-ps FWHM. Signal output is via a fiber-optic connector on the front panel of the generator box. The optical signal is transported from comb generator to streak camera through multi-mode, graded-index optical fiber.

Ronald Justin, Terence Davies, Frans Janson, Bruce Marshall, Perry Bell, Daniel Kalantar, Joseph Kimbrough, Stephen Vernon, Oliver Sweningsen

2008-09-18

299

Tunable optical correlator using an optical frequency comb and a nonlinear multiplexer.  

PubMed

We experimentally demonstrate a tunable optical correlator to search for multiple patterns among QPSK symbols. We utilize an optical frequency comb to generate the coherent signals and multiplex them coherently in a single PPLN waveguide. Multiple patterns with different lengths are successfully searched within QPSK symbols in a 40-Gb/s signal. PMID:24514968

Ziyadi, Morteza; Chitgarha, Mohammad Reza; Khaleghi, Salman; Mohajerin-Ariaei, Amirhossein; Almaiman, Ahmed; Touch, Joe; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Willner, Alan E

2014-01-13

300

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

Microsoft Academic Search

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

Stephen C. Pratt

2004-01-01

301

Characteristics of microwave frequency combs generated by a semiconductor laser under dynamical dual-beam injection  

NASA Astrophysics Data System (ADS)

We demonstrate and characterize the microwave frequency combs utilizing both the dynamical single-beam and dual-beam injection schemes numerically. The dynamical single-beam injection scheme is realized by optical pulse injection to the slave laser (SL) from a pulsed laser. When the SL subjected to only the optical pulse injection from the pulsed laser, microwave frequency combs are generated by the nonlinear dynamics of the frequency-locked states with different locking ratios. The amplitude variation of +/-18 dB in a 30 GHz range is obtained by precisely varying the operational parameters, injection strength, repetition frequency, and detuning frequency. In this paper, we propose the dynamical dual-beam injection scheme to improve the amplitude variation of the microwave frequency comb generated. The dynamical dual-beam injection is realized by both optical pulse injection and optical cw injection to the semiconducor laser. By utilizing the hybrid scheme consists of double optical injections, the advantages of each individual dynamical system are added and enhanced. As the result, the amplitude variation of the microwave frequency comb of +/-3.0 dB in a 30 GHz range is achieved when operating the cw and pulse injection to the slave laser in stable locking and frequency locked states, respectively. In addition, the bandwidth enhancement of over 25 GHz is also observed.

Lin, Cheng-Ting; Juan, Yu-Shan

2014-03-01

302

Comb-like ionomers from sustainable resources: Copolymers of itaconic anhydride-co-stearyl methacrylate  

Microsoft Academic Search

Comb-like random copolymers of itaconic anhydride (ITA) and stearyl methacrylate (SM) copolymers were synthesized by free-radical polymerization. Both monomers are derived from natural and renewable resources. Ionomers (Na, Ca or Zn carboxylates) were prepared by partial neutralization of the copolymers. The incorporation of the ionic groups decreased the melting point, which was lower than the glass transition temperature (Tg) and

Shurui Shang; Samuel J. Huang; R. A. Weiss

2011-01-01

303

Photoacoustic evaluation of the thermal effusivity in the isotropic phase of certain comb-shaped polymers  

Microsoft Academic Search

The thermal effusivity values in the isotropic phase of certain comb-shaped polymers have been evaluated for the first time using an open photoacoustic cell configuration. The compounds investigated have siloxane and acrylate backbone and they carry mesogenic groups in their side chain. The results indicate that the polymer chain length as well as the side chain length have pronounced influence

Nibu A. George; C. P. G. Vallabhan; V. P. N. Nampoori; A. K. George; P. Radhakrishnan

2001-01-01

304

Differential Stark shift measurement of clock states of Yb+ using an optical frequency comb  

Microsoft Academic Search

Quantum information processing with trapped ions has traditionally involved state preparation, manipulation (eg. quantum gates) and detection using CW lasers. Quantum gates implemented with ions typically involve optical Raman transitions between two atomic levels. An optical frequency comb, emitted by a pulsed laser, is an excellent tool for bridging atomic frequency differences. Previously, we demonstrated quantum gates and separately, ultrafast

Qudsia Quraishi; David Hayes; David Hucul; Dzmitry Matsukevich; Shantanu Debnath; Susan Clark; Chris Monroe

2011-01-01

305

Cost-effective multirate cascaded integrator comb decimator filter design on field programmable gate arrays  

Microsoft Academic Search

Cascaded Integrator Comb (CIC) filters are one of the most economical multirate filters widely used as decimators in digital receivers. Size\\/power improvements in this crucial unit of a digital receiver may essentially improve system performance including battery lifetime of the wireless portable system. Since, the only block in this filter structure that can be improved for better size\\/power performance is

Suhasini R. Rao; Uwe H. Meyer-Baese

2004-01-01

306

An improved architecture and implementation of cascaded integrator-comb decimation filters  

Microsoft Academic Search

In this paper an improved version of the nonrecursive carry-save-adder-based structure for CIC (cascaded-integrator-comb) decimation filters is proposed for high speed applications. By employing parallel processing techniques, the improved structure can further increase the sampling rate of CIC filters. Low-complexity implementation of the parallel stages is also discussed

Yonghong Gao; Lihong Jia; H. Tenhunen

1999-01-01

307

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

NASA Astrophysics Data System (ADS)

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.

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

2008-04-01

308

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

NASA Astrophysics Data System (ADS)

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.

Bauer, Daniel; Bienefeld, Kaspar

2013-01-01

309

Digital approach to stabilizing optical frequency combs and beat notes of CW lasers  

NASA Astrophysics Data System (ADS)

In cases when it is necessary to lock optical frequencies generated by an optical frequency comb to a precise radio frequency (RF) standard (GPS-disciplined oscillator, H-maser, etc.) the usual practice is to implement phase and frequency-locked loops. Such system takes the signal generated by the RF standard (usually 10 MHz or 100 MHz) as a reference and stabilizes the repetition and offset frequencies of the comb contained in the RF output of the f-2f interferometer. These control loops are usually built around analog electronic circuits processing the output signals from photo detectors. This results in transferring the stability of the standard from RF to optical frequency domain. The presented work describes a different approach based on digital signal processing and software-defined radio algorithms used for processing the f-2f and beat-note signals. Several applications of digital phase and frequency locks to a RF standard are demonstrated: the repetition (frep) and offset frequency (fceo) of the comb, and the frequency of the beat note between a CW laser source and a single component of the optical frequency comb spectrum.

?ížek, Martin; ?íp, Ond?ej; Å míd, Radek; Hrabina, Jan; Mikel, B?etislav; Lazar, Josef

2013-10-01

310

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

ERIC Educational Resources Information Center

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…

McPherson, Robert S.

2010-01-01

311

Calibration of an astronomical spectrograph using a 25 GHz laser frequency comb  

Microsoft Academic Search

A 25 GHz frequency comb for calibration of astronomical spectrographs in the 1.4-1.65 ?m region is demonstrated with the R=50,000 ?\\/?? Pathfinder spectrograph at the Hobby-Eberly telescope. OCIS codes: (300.6340) Spectroscopy, infrared; (320.7110) Ultrafast nonlinear optics; (350.1270) Astronomy and astrophysics

G. Ycas; S. Diddams; F Quinlan; S. Osterman; C. Bender; Suvrath Mahadevan; L. Ramsey; S. Redman; R. Terrien

2011-01-01

312

Wideband optical vector network analyzer based on optical single-sideband modulation and optical frequency comb.  

PubMed

A novel approach to increase the measurement range of the optical vector network analyzer (OVNA) based on optical single-sideband (OSSB) modulation is proposed and experimentally demonstrated. In the proposed system, each comb line in an optical frequency comb (OFC) is selected by an optical filter and used as the optical carrier for the OSSB-based OVNA. The frequency responses of an optical device-under-test (ODUT) are thus measured channel by channel. Because the comb lines in the OFC have fixed frequency spacing, by fitting the responses measured in all channels together, the magnitude and phase responses of the ODUT can be accurately achieved in a large range. A proof-of-concept experiment is performed. A measurement range of 105 GHz and a resolution of 1 MHz is achieved when a five-comb-line OFC with a frequency spacing of 20 GHz is applied to measure the magnitude and phase responses of a fiber Bragg grating. PMID:24322161

Xue, Min; Pan, Shilong; He, Chao; Guo, Ronghui; Zhao, Yongjiu

2013-11-15

313

Impact of Optical Comb Stability on Waveforms Generated via Spectral Line-by-Line Pulse Shaping.  

National Technical Information Service (NTIS)

Optical arbitrary waveform generation using the line-by-line pulse shaping technique has been shown to be sensitive to variations in the offset frequency of the input frequency comb due to time-domain waveform interference. Here we present a frequency-dom...

A. M. Weiner C. Huang D. E. Leaird Z. Jiang

2007-01-01

314

Expanding frequency comb by means of enhanced multiple four-wave mixing  

NASA Astrophysics Data System (ADS)

This works presents an efficient scheme for enhancing multiple four-wave mixing by using optical feedback, highly nonlinear and erbium-doped fibers. Numerical results illustrate the efficiency of the proposed method and its applicability is experimentally demonstrated by expanding an original frequency comb from 20 to 100 optical mutually coherent lines.

Melo, S. A. S.; Nascimento, A. R.; Cerqueira S., Arismar; Carvalho, L. H.; Pataca, D. M.; Oliveira, J. C. R. F.

2014-02-01

315

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

Microsoft Academic Search

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

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

1997-01-01

316

Phase-locking to a free-space terahertz comb for metrological-grade terahertz lasers.  

PubMed

Optical frequency comb synthesizers have represented a revolutionary approach to frequency metrology, providing a grid of frequency references for any laser emitting within their spectral coverage. Extending the metrological features of optical frequency comb synthesizers to the terahertz domain would be a major breakthrough, due to the widespread range of accessible strategic applications and the availability of stable, high-power and widely tunable sources such as quantum cascade lasers. Here we demonstrate phase-locking of a 2.5 THz quantum cascade laser to a free-space comb, generated in a LiNbO(3) waveguide and covering the 0.1-6 THz frequency range. We show that even a small fraction (<100 nW) of the radiation emitted from the quantum cascade laser is sufficient to generate a beat note suitable for phase-locking to the comb, paving the way to novel metrological-grade terahertz applications, including high-resolution spectroscopy, manipulation of cold molecules, astronomy and telecommunications. PMID:22948822

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

2012-01-01

317

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

PubMed

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. PMID:23149932

Bauer, Daniel; Bienefeld, Kaspar

2013-01-01

318

Optical Fourier transform based in-plane vibration characterization for MEMS comb structure.  

PubMed

On-line and on-wafer characterizations of mechanical properties of Micro-Electro-Mechanical-System (MEMS) with efficiency are very important to the mass production of MEMS foundry in the near future. However, challenges still remain. In this paper, we present an in-plane vibration characterizing method for MEMS comb using optical Fourier transform (OFT). In the experiment, the intensity distribution at the focal plane was captured to characterize the displacement of the vibrator in the MEMS comb structure. A typical MEMS comb was tested to verify the principle. The shape and the movement of MEMS comb was imitated and tested to calibrate the measurement by using a spatial light modulator (SLM). The relative standard deviations (RSD) of the measured displacements were better than 5%, where the RSD is defined as the ratio of the standard deviation to the mean. It is convinced that the presented method is feasible for on-line and on-wafer characterizations for MEMS with great convenience, high efficiency and low cost. PMID:23482039

Gao, Yongfeng; Cao, Liangcai; You, Zheng; Zhao, Jiahao; Zhang, Zichen; Yang, Jianzhong

2013-02-25

319

SEX DETERMINATION, SEX RATIOS, AND GENETIC CONFLICT  

Microsoft Academic Search

Genetic mechanisms of sex determination are unexpectedly diverse and change rapidly during evolution. We review the role of genetic conflict as the driving force behind this diversity and turnover. Genetic conflict occurs when different components of a genetic system are subject to selection in opposite directions. Conflict may occur between genomes (including paternal-maternal and parental- zygotic conflicts) or within genomes

John H. Werren; Leo W. Beukeboom

1998-01-01

320

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

321

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

SciTech Connect

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.

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

322

Sex role identity and its relationships to sex role attributes and sex role stereotypes  

Microsoft Academic Search

Examines J. Kagan's (1964) and L. A. Kohlberg's (1966) theories of sex role identity. Both premise relationships among an individual's sex role identity, perception of sex role stereotypes, and own masculine and feminine sex role attributes, but the theories specify different patterns of correlations among these variables. Kagan's theory views sex role identity as the product of the mutual influence

Michael D. Storms

1979-01-01

323

Sex Role Identity, Androgyny, and Sex Role Transcendence: A Sex Role Strain Analysis.  

ERIC Educational Resources Information Center

This paper first reviews three different theoretical constructs concerning the psychological significance of sex-role-related characteristics in personality functioning: sex role identity, androgyny, and sex role transcendence. A new conceptual analysis concerning sex-typing, sex role strain analysis, is presented. Implications of this analysis…

Garnets, Linda; Pleck, Joseph H.

1979-01-01

324

The invariant-comb approach and its relation to the balancedness of multipartite entangled states  

NASA Astrophysics Data System (ADS)

The invariant-comb approach is a method to construct entanglement measures for multipartite systems of qubits. The essential step is the construction of an antilinear operator that we call comb in reference to the hairy-ball theorem. An appealing feature of this approach is that, for qubits (or spins 1/2), the combs are automatically invariant under SL(2,{\\rm\\kern.24em \\vrule width.04em height1.46ex depth-.07ex\\kern-.30em C}) , which implies that the obtained invariants are entanglement monotones by construction. By asking which property of a state determines whether or not it is detected by a polynomial SL(2,{\\rm\\kern.24em \\vrule width.04em height1.46ex depth-.07ex \\kern-.30em {C}}) invariant, we find that it is the presence of a balanced part that persists under local unitary transformations. We present a detailed analysis for the maximally entangled states detected by such polynomial invariants, which leads to the concept of irreducibly balanced states. The latter indicates a tight connection with stochastic local operations and classical communication (SLOCC) classifications of qubit entanglement. Combs may also help to define measures for multipartite entanglement of higher-dimensional subsystems. However, for higher spins there are many independent combs, such that it is nontrivial to find an invariant one. By restricting the allowed local operations to rotations of the coordinate system (i.e. again to the SL(2,{\\rm\\kern.24em \\vrule width.04em height1.46ex depth-.07ex \\kern-.30em C}) ), we manage to define a unique extension of the concurrence to general half-integer spin with an analytic convex-roof expression for mixed states.

Osterloh, Andreas; Siewert, Jens

2010-07-01

325

Wide-bandwidth phase lock between a CW laser and a frequency comb based on a feed-forward configuration.  

PubMed

Wide-bandwidth phase lock between the tooth of a frequency comb and a CW extended-cavity diode laser at 1.55 ?m is achieved by the use of an acousto-optical frequency shifter in a feed-forward configuration. The coherence properties of the comb are efficiently transferred to the CW laser, whose linewidth is narrowed down to the ?10 KHz comb level. A maximum control bandwidth of ?0.6 MHz has been experimentally achieved, limited by the transit time of the acoustic wave inside the frequency shifter. PMID:22743465

Sala, T; Gatti, D; Gambetta, A; Coluccelli, N; Galzerano, G; Laporta, P; Marangoni, M

2012-07-01

326

Sex: a sensitive issue.  

PubMed

Health care workers and educators may need to improve their skills in discussing sensitive issues in order to elicit and understand what influences people's attitudes toward sex. While the health worker may be bent upon preventing HIV infection, advising on family planning, or teaching youth about sexual relationships, his or her audience may have other priorities. A good counselor/teacher must learn what people's concerns are and discuss sexual health within that context. It can be difficult talking about sex because sex is a private concern and many people are embarrassed discussing it. Even sex partners often find it difficult to talk to each other about sex. Appropriate communication techniques vary depending upon the situation. It depends upon whether one is addressing people on an individual basis or in groups, which people are being addressed, which organization one is representing, and what one's role is. Good communication is a two-way sharing of information. The different stages of life, common beliefs and myths, culture and religion, relationships between men and women, reasons for having sex, and sex practices are discussed. PMID:12348243

1997-01-01

327

Sex Chromosomes and Sex Determination in Lepidoptera  

Microsoft Academic Search

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.

W. Traut; K. Sahara; F. Marec

2007-01-01

328

Sex and Arthritis  

MedlinePLUS

... or decreased orgasmic sensation Erectile dysfunction or impotence Begin overcoming barriers Sex is not simply about reaching ... of returning pleasure can build excitement and intimacy. Begin overcoming potential barriers by letting your partner know ...

329

Testicular Cancer and Sex  

MedlinePLUS

... remove just one testicle, called an inguinal orchiectomy (IO), does not make a patient impotent and seldom ... everything from having sex the day after their IO (ouch!) all the way through having to go ...

330

Transforming Teen Sex Education  

MedlinePLUS

... note health and sex education is declining in middle and high schools across the U.S. as limited resources are reallocated to support reading, writing, math, and science education. While the authors support the latter investment, ...

331

Teenage Boys and Sex  

MedlinePLUS Videos and Cool Tools

... Site Map FAQs Contact Us Search MedlinePlus Health Topics Drugs & Supplements Videos & Cool Tools To use the ... more important to teenage boys than sex new research suggests. In fact reporting in the American Journal ...

332

High-power mid-infrared frequency comb from a continuous-wave-pumped bulk optical parametric oscillator.  

PubMed

We demonstrate that it is possible to obtain a mid-infrared optical frequency comb (OFC) experimentally by using a continuous-wave-pumped optical parametric oscillator (OPO). The comb is generated without any active modulation. It is based on cascading quadratic nonlinearities that arise from intra-cavity phase mismatched second harmonic generation of the signal wave that resonates in the OPO. The generated OFC is transferred from the signal wavelength (near-infrared) to the idler wavelength (mid-infrared) by intracavity difference frequency generation between the OPO pump wave and the signal comb. We have produced a mid-infrared frequency comb which is tunable from 3.0 to 3.4 µm with an average output power of up to 3.1 W. PMID:24921755

Ulvila, Ville; Phillips, C R; Halonen, Lauri; Vainio, Markku

2014-05-01

333

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

PubMed

We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of ?10 m/s (?6 MHz) was achieved from the comb-calibrated spectra. PMID:22418547

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

2012-03-12

334

High-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator.  

PubMed

We report on a high-power mid-infrared (MIR) frequency comb source based on a femtosecond (fs) Er:fiber oscillator with a stabilized repetition rate of 250 MHz. The MIR frequency comb is produced through difference frequency generation in a periodically poled MgO-doped lithium niobate crystal. The output power is about 120 mW, with a pulse duration of about 80 fs and spectrum coverage from 2.9 to 3.6 ?m, and the single comb mode power is larger than 0.3 ?W over the range of 700 nm. The coherence properties of the produced high-power broadband MIR frequency comb are maintained, which was verified by heterodyne measurements. As the first application, the spectrum of a ~200 ppm methane-air mixture in a short 20 cm glass cell at ambient atmospheric pressure and temperature was measured. PMID:23811928

Zhu, Feng; Hundertmark, Holger; Kolomenskii, Alexandre A; Strohaber, James; Holzwarth, Ronald; Schuessler, Hans A

2013-07-01

335

Generation of two-cycle pulses and octave-spanning frequency combs in a dispersion-flattened micro-resonator.  

PubMed

We show that octave-spanning Kerr frequency combs with improved spectral flatness of comb lines can be generated in dispersion-flattened microring resonators. The resonator is formed by a strip/slot hybrid waveguide, exhibiting a flat and low anomalous dispersion between two zero-dispersion wavelengths that are separated by one octave from near-infrared to mid-infrared. Such flattened dispersion profiles allow for the generation of mode-locked frequency combs, using relatively low pump power to obtain two-cycle cavity solitons on a chip, associated with the octave-spanning comb bandwidth. The wavelength dependence of the optical loss and of the coupling coefficient and thus wavelength dependent Q-factor are also considered. PMID:24281525

Zhang, Lin; Bao, Chengying; Singh, Vivek; Mu, Jianwei; Yang, Changxi; Agarwal, Anuradha M; Kimerling, Lionel C; Michel, Jurgen

2013-12-01

336

Spectral self-imaging of time-periodic coherent frequency combs by parabolic cross-phase modulation.  

PubMed

Integer and fractional spectral self-imaging effects are induced on infinite-duration periodic frequency combs (probe signal) using cross-phase modulation (XPM) with a parabolic pulse train as pump signal. Free-spectral-range tuning (fractional effects) or wavelength-shifting (integer effects) of the frequency comb can be achieved by changing the parabolic pulse peak power or/and repetition rate without affecting the spectral envelope shape and bandwidth of the original comb. For design purposes, we derive the complete family of different pump signals that allow implementing a desired spectral self-imaging process. Numerical simulation results validate our theoretical analysis. We also investigate the detrimental influence of group-delay walk-off and deviations in the nominal temporal shape or power of the pump pulses on the generated output frequency combs. PMID:24514395

Maram, Reza; Azaña, José

2013-11-18

337

FINDSITE(comb): a threading/structure-based, proteomic-scale virtual ligand screening approach.  

PubMed

Virtual ligand screening is an integral part of the modern drug discovery process. Traditional ligand-based, virtual screening approaches are fast but require a set of structurally diverse ligands known to bind to the target. Traditional structure-based approaches require high-resolution target protein structures and are computationally demanding. In contrast, the recently developed threading/structure-based FINDSITE-based approaches have the advantage that they are as fast as traditional ligand-based approaches and yet overcome the limitations of traditional ligand- or structure-based approaches. These new methods can use predicted low-resolution structures and infer the likelihood of a ligand binding to a target by utilizing ligand information excised from the target's remote or close homologous proteins and/or libraries of ligand binding databases. Here, we develop an improved version of FINDSITE, FINDSITE(filt), that filters out false positive ligands in threading identified templates by a better binding site detection procedure that includes information about the binding site amino acid similarity. We then combine FINDSITE(filt) with FINDSITE(X) that uses publicly available binding databases ChEMBL and DrugBank for virtual ligand screening. The combined approach, FINDSITE(comb), is compared to two traditional docking methods, AUTODOCK Vina and DOCK 6, on the DUD benchmark set. It is shown to be significantly better in terms of enrichment factor, dependence on target structure quality, and speed. FINDSITE(comb) is then tested for virtual ligand screening on a large set of 3576 generic targets from the DrugBank database as well as a set of 168 Human GPCRs. Excluding close homologues, FINDSITE(comb) gives an average enrichment factor of 52.1 for generic targets and 22.3 for GPCRs within the top 1% of the screened compound library. Around 65% of the targets have better than random enrichment factors. The performance is insensitive to target structure quality, as long as it has a TM-score ? 0.4 to native. Thus, FINDSITE(comb) makes the screening of millions of compounds across entire proteomes feasible. The FINDSITE(comb) web service is freely available for academic users at http://cssb.biology.gatech.edu/skolnick/webservice/FINDSITE-COMB/index.html. PMID:23240691

Zhou, Hongyi; Skolnick, Jeffrey

2013-01-28

338

Immunocytochemical Localization of Androgen Receptor in the Comb, Uropygial Gland, Testis, and Epididymis in the Domestic Chicken  

Microsoft Academic Search

Nuclear, but not cytoplasmic androgen receptors (AR), were localized immunocytochemically in the comb, uropygial (preen) gland, testis, and epididymis of juvenile and adult cockerels. Androgen receptor immunoreactivity (AR-ir) was seen in the comb, in thestratum germinativumof the epidermis and in fibromucoid cells in the dermis in juvenile and adult cockerels. AR-ir was observed in the glandular epithelial (sebum-producing) cells lining

Bhagyashri A. Shanbhag; Peter J. Sharp

1996-01-01

339

The impact of optical comb stability on waveforms generated via spectral line-by-line pulse shaping  

Microsoft Academic Search

Optical arbitrary waveform generation using the line-by-line pulse shaping technique has been shown to be sensitive to variations in the offset frequency of the input frequency comb due to time-domain waveform interference. Here we present a frequency-domain model that is able to predict waveform changes arising from offset frequency variations. In experiments we controllably shift the frequency of a comb

Chen-Bin Huang; Zhi Jiang; Daniel E. Leaird; Andrew M. Weiner

2006-01-01

340

Generation of Flat Optical Frequency Comb based on Mach-Zehnder Modulator and Recirculating Frequency Shifter Loop  

NASA Astrophysics Data System (ADS)

We propose a novel scheme to generate optical frequency comb by using Mach-Zehnder modulator and recirculating frequency shifter loop based on IQ modulator driven by radio frequency clock signals. A system of 4 flat and stable comb lines generation based on Mach-Zehnder modulator is set as the seed light source of the recirculating loop. Through theorical analysis and simulation it is shown that the proposed theoretical model is proved in good agreement with simulation results.

Wu, Shibao; Li, Yulong; Fei, Yue; Hu, Faze

2014-06-01

341

Measurement of carrier envelope offset frequency for a 10 GHz etalon-stabilized semiconductor optical frequency comb.  

PubMed

We report Carrier Envelope Offset (CEO) frequency measurements of a 10 GHz harmonically mode-locked, Fabry-Perot etalon-stabilized, semiconductor optical frequency comb source. A modified multi-heterodyne mixing technique with a reference frequency comb was utilized for the measurement. Also, preliminary results from an attempt at f-2f self-referencing measurement are presented. The CEO frequency was found to be ~1.47 GHz for the particular etalon that was used. PMID:21935046

Akbulut, M; Davila-Rodriguez, J; Ozdur, I; Quinlan, F; Ozharar, S; Hoghooghi, N; Delfyett, P J

2011-08-29

342

Channel estimation for OFDM systems based on comb-type pilot arrangement in frequency selective fading channels  

Microsoft Academic Search

The channel estimation methods for OFDM systems based on a comb-type pilot sub-carrier arrangement are investigated. The channel estimation algorithm based on comb-type pilots is divided into pilot signal estimation and channel interpolation. The pilot signal estimation based on LS or MMSE criteria, together with channel interpolation based on piecewise-linear interpolation or piecewise second-order polynomial interpolation is studied. Owing to

Meng-Han Hsieh; Che-Ho Wei

1998-01-01

343

Sex chromosomes and brain gender  

Microsoft Academic Search

In birds and mammals, differences in development between the sexes arise from the differential actions of genes that are encoded on the sex chromosomes. These genes are differentially represented in the cells of males and females, and have been selected for sex-specific roles. The brain is a sexually dimorphic organ and is also shaped by sex-specific selection pressures. Genes on

Arthur P. Arnold

2004-01-01

344

Sex Equity: Is It Feasible?  

ERIC Educational Resources Information Center

This guide presents a model and plan to expedite implementation of sex equity in vocational education through the elimination of sex stereotyping and sex bias. Aimed at vocational education administrators, the guide is organized into the four steps of the plan. Step 1 provides a rationale for the decision to implement a model sex equity program,…

Shocklee, Georgia

345

Single Sex Education. WEEA Digest.  

ERIC Educational Resources Information Center

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

Pollard, Diane S.

346

Why sex matters for neuroscience  

Microsoft Academic Search

A rapidly burgeoning literature documents copious sex influences on brain anatomy, chemistry and function. This article highlights some of the more intriguing recent discoveries and their implications. Consideration of the effects of sex can help to explain seemingly contradictory findings. Research into sex influences is mandatory to fully understand a host of brain disorders with sex differences in their incidence

Larry Cahill

2006-01-01

347

Degradable, pH-sensitive, membrane-destabilizing, comb-like polymers for intracellular delivery of nucleic acids.  

PubMed

This report describes the design and synthesis of a new series of degradable, pH-sensitive, membrane-destabilizing, comb-like polymers that can enhance the intracellular delivery of therapeutic nucleic acids. These comb-like polymers are based on a diblock polymer backbone where the first block is a copolymer of pH-sensitive ethyl acrylic acid (EAA) monomers and hydrophobic butyl methacrylate (BMA) or hexyl methacrylate monomers. The second block is a homopolymer of N-acryloxy succinimide (NASI) or ss-benzyl l-aspartate N-carboxy-anhydride (BLA-NCA) monomers, which are functionalized to allow controlled grafting of hydrophobic HMA and cationic trimethyl aminoethyl methacrylate (TMAEMA) copolymers via acid-labile hydrazone linkages. These comb-like polymers displayed high hemolytic activity in acidic solutions, which increased with the increase in polymer concentration. All comb-like polymers degraded into small fragments upon incubation in an acidic solution (pH 5.8) due to hydrolysis of the hydrazone linkages connecting the hydrophobic/cationic grafts to the polymer backbone. Comb-like polymers successfully complexed anti-GAPDH siRNA molecules into serum- and nuclease-stable particles, which successfully silenced GAPDH expression at both the mRNA and protein levels. These results collectively indicate the potential of these new comb-like polymers to serve as vehicles for effective intracellular delivery of therapeutic nucleic acids. PMID:20579726

Lin, Yen-Ling; Jiang, Guohua; Birrell, Lisa K; El-Sayed, Mohamed E H

2010-09-01

348

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

PubMed

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

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

2007-11-16

349

The SRI method based on the optical frequency comb on absolute distance measurement  

NASA Astrophysics Data System (ADS)

A novel absolute distance measurement method based on the optical frequency comb of the Ti:sapphire femtosecond laser was presented. In the spectrally-resolved interferometry (SRI), all modes interference signals of the optical frequency comb was obtained by the femtosecond light pulses traveling along different optical path between the reference and measurement arms. The interference intensity in the frequency domain was inverse Fourier-transformed into the time domain, and the phase peak was isolated by use of an appropriate Hamming window, then the phase difference which was caused by the distance was resolved in the frequency domain. The simulation results indicated that this algorithm could satisfy the demand of the small scale profile measurement with the non-ambiguity range of millimeter level, and the resolution of nanometer level. Furthermore, combined with the conventional phase ranging method, the max measurement distance of our method can be extended to several dozen meters.

Xu, Yan; Zhou, Weihu; Liu, Deming; Ding, Lei

2011-11-01

350

Phase noise analysis of injected gain switched comb source for coherent communications.  

PubMed

We present experimentally and analytically the phase noise characterization of an externally injected gain switched comb source. The results reveal the residual high frequency FM noise in the comb lines, which stays unnoticed in the optical linewidth value but leads to an increased phase-error variance. The potential impact of the residual phase noise is investigated in a 10.7 GBaud optical DQPSK system where a 2 dB power penalty is recorded at BER of 10(-9). In a 10.7 GBaud digital coherent QPSK system no penalty is observed but with 5 GBaud 16-QAM format a 3 dBpenalty exists at the FEC limit of 4.4e-3. PMID:24718188

Zhou, Rui; Huynh, Tam N; Vujicic, Vidak; Anandarajah, Prince M; Barry, Liam P

2014-04-01

351

Frequency-comb-referenced multi-wavelength profilometry for largely stepped surfaces.  

PubMed

3-D profiles of discontinuous surfaces patterned with high step structures are measured using four wavelengths generated by phase-locking to the frequency comb of an Er-doped fiber femtosecond laser stabilized to the Rb atomic clock. This frequency-comb-referenced method of multi-wavelength interferometry permits extending the phase non-ambiguity range by a factor of 64,500 while maintaining the sub-wavelength measurement precision of single-wavelength interferometry. Experimental results show a repeatability of 3.13 nm (one-sigma) in measuring step heights of 1800, 500, and 70 ?m. The proposed method is accurate enough for the standard calibration of gauge blocks and also fast to be suited for the industrial inspection of microelectronics products. PMID:23609685

Hyun, Sangwon; Choi, Minah; Chun, Byung Jae; Kim, Seungman; Kim, Seung-Woo; Kim, Young-Jin

2013-04-22

352

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

NASA Astrophysics Data System (ADS)

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.

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

353

Frequency comb assisted mid-infrared spectroscopy of cold molecular ions  

NASA Astrophysics Data System (ADS)

A mid-infrared spectrometer consisting of a high power optical parametric oscillator, a frequency comb, and a cold ion trap is described and characterized. The idler frequency at 3 ?m is measured accurately by analyzing the pump and signal beat frequencies with the comb. This is done via two spectrum analyzers, allowing for a wide and continuous scanning ideal for spectroscopy of cold molecules with unknown spectra. The potential of this approach is demonstrated by measuring a ro-vibrational line of CH5+ in a 22-pole ion trap via action spectroscopy of only several thousand cold ions. The current setup limits the precision of the line center frequency determination to some 100 kHz with ample room for future improvements. Following this approach, ground state combination differences of molecular ions can be predicted in order to identify them in astronomical objects.

Asvany, Oskar; Krieg, Jürgen; Schlemmer, Stephan

2012-09-01

354

Raman comb lasing in a ring cavity with high-birefringence fiber loop mirror  

NASA Astrophysics Data System (ADS)

We demonstrate a 400-wavelength Raman comb lasing based on the nonlinear polarization rotation (NPR) in a ring cavity with high-birefringence fiber loop mirror (HBFLM). The comb-line intensities are equalized by the NPR mechanism. As the length of polarization-maintaining fiber (PMF) in the HBFLM is changed from 5.4 to 120 m, the line spacing varies from 1.17 to 0.0533 nm and the 10 dB spectral bandwidth is kept at the similar level. In case of a 120 m long PMF, more than 400 wavelengths with the signal-noise ratio higher than 10 dB are obtained in the 10 dB bandwidth of 22.4 nm.

Gao, Weiqing; Liao, Meisong; Deng, Dinghuan; Cheng, Tonglei; Suzuki, Takenobu; Ohishi, Yasutake

2013-07-01

355

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

356

First Stellar Radial Velocities with a Laser Frequency Comb: Observations in the NIR H Band  

NASA Astrophysics Data System (ADS)

Advances in high precision radial velocity spectroscopy have been hindered by the lack of suitable wavelength references. This has been especially the case in the infrared where until recently radial velocity precision has been limited to 50-100m/s, hindering investigations such as the search for extrasolar planets orbiting cooler M stars at these wavelengths. To redress deficiency this we have developed a 25GHz laser frequency comb spanning the H band and suitable for use with spectrographs with spectral resolution in the range of 40,000 - 60,000, with RV precision limited by instrument stability and object S/N rather than by the lack of a suitable wavelength standard. We will present CU/NIST frequency comb performance and results obtained using the Pennsylvania State University's Pathfinder Spectrograph on the Hobby Eberly Telescope and will discuss lessons learned.

Osterman, Steve; Diddams, S.; Quinlan, F.; Ycas, G.; Mahadevan, S.; Ramsey, L.; Bender, C.; Redman, S.; Terrien, R.; Botzer, B.

2011-01-01

357

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

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

358

Evaluation of the clock laser for an Yb lattice clock using an optic fiber comb.  

PubMed

A light source to drive the (1)S0-(3)P0 transition in Yb atoms is generated by 2 solid state lasers: a Nd:YAG laser and an Yb:YAG laser, using a sum-frequency generation (SFG) scheme. With a ridge waveguide (WG) periodically poled lithium niobate (PPLN) device, SFG power of about 150 mW is obtained at the required frequency. The zero-expansion temperature of a Fabry-Pérot etalon was determined by using a home-made fiber-based optical frequency comb running continuously for weeks. Frequency stabilization of the clock laser system was also evaluated by the optical frequency comb. PMID:20211777

Hosaka, Kazumoto; Inaba, Hajime; Nakajima, Yoshiaki; Yasuda, Masami; Kohno, Takuya; Onae, Atsushi; Hong, Feng-Lei

2010-03-01

359

Optical phase-noise dynamics of Titanium:sapphire optical frequency combs  

NASA Astrophysics Data System (ADS)

Stabilized optical frequency combs (OFC) can have remarkable levels of coherence across their broad spectral bandwidth. We study the scaling of the optical noise across hundreds of nanometers of optical spectra. We measure the residual phase noise between two OFC?s (having offset frequencies f0(1) and f0(2)) referenced to a common cavity-stabilized narrow linewidth CW laser. Their relative offset frequency ?f0=f0(2)-f0(1), which appears across their entire spectra, provides a convenient measure of the phase noise. By comparing ?f0 at different spectral regions, we demonstrate that the observed scaling of the residual phase noise is in very good agreement with the noise predicted from the standard frequency comb equation.

Quraishi, Qudsia; Diddams, Scott A.; Hollberg, Leo

2014-06-01

360

Fully referenced single-comb interferometry using optical sampling by laser-cavity tuning.  

PubMed

The correction of setup and laser instabilities in a single-comb interferometric measurement using optical sampling by laser-cavity tuning is investigated. A two-reference solution that allows full correction of the interferogram is presented. The technique is compared to a slightly simpler one-reference correction. For the one-reference case, all the subtleties involved in this partial correction and the dependence between the achievable measurement accuracy and the setup parameters are highlighted. The parameters considered are the comb bandwidth, the laser-frequency noise, the required spectral resolution, the cavity scan speed, and the length of the delay line. For both referencing approaches, experimental results using a fiber delay line of 10 km and a 100 MHz mode-locked laser with its repetition rate swept at 500 Hz are shown. PMID:23314642

Potvin, Simon; Boudreau, Sylvain; Deschênes, Jean-Daniel; Genest, Jérôme

2013-01-10

361

Characterization of growth and arachidonic acid production of Parietochloris incisa comb. nov (Trebouxiophyceae, Chlorophyta)  

Microsoft Academic Search

Arachidonic acid (AA) is a precursor of biologically activeprostaglandines and leukotrienes. The commercial source for AA at present is afungus, but the recently discovered coccoid green alga,Parietochlorisincisa comb. nov., in which over 90% of total AA is deposited intriacylglycerols, makes this species a potential candidate for commercialproduction of AA. We investigated the effect of the light-regime on cell-AAcontent and on

Zhang Cheng-Wu; Zvi Cohen; Inna Khozin-Goldberg; Amos Richmond

2002-01-01

362

Amphiphilic comb-like polymer for harvest of conductive nano-cellulose  

Microsoft Academic Search

In this study, electrically conductive bacterial cellulose (BC) was prepared by culturing Gluconacetobacter xylinus in a carbon nanotube (CNT)-dispersed medium. The CNTs were dispersed by adopting a non-covalent approach in the presence of non-ionic amphiphilic comb-like polymer (CLP). Specifically, the hydrophobic backbone of CLP was chemophysically attached to the surface of the CNTs and the hydrophilic side chains were released

Jaeyoo Choi; Jie Cheng; Jinho Hyun

363

Preparation of protein-adsorption-resistant polyethersulfone ultrafiltration membranes through surface segregation of amphiphilic comb copolymer  

Microsoft Academic Search

An amphiphilic comb copolymer with polystyrene as hydrophobic parts and poly(ethyl glycol) (PEG) as hydrophilic parts was blended with polyethersulfone (PES) to fabricate high protein-adsorption-resistant ultrafiltration membranes through a phase inversion process. The hydrophilic PEG segments were spontaneously segregated to the membrane surface during immersion precipitation, which was confirmed by the water contact angle measurement and X-ray photoelectron spectroscopy (XPS).

Xiaole Ma; Yanlei Su; Qiang Sun; Yanqiang Wang; Zhongyi Jiang

2007-01-01

364

Multitap microwave photonic filters with programmable phase response via optical frequency comb shaping.  

PubMed

We present a programmable multitap microwave photonic filter with an arbitrary phase response operating over a broad bandwidth. Complex coefficient taps are achieved by optical line-by-line pulse shaping on a 10 GHz flat optical frequency comb using a novel interferometric scheme. Through high-speed real-time measurements, we demonstrate programmable chirp control of a waveform via phase filtering. This achievement enables us to compress broadband microwave signals to their corresponding bandwidth-limited pulse duration. PMID:22378413

Song, Minhyup; Torres-Company, Victor; Metcalf, Andrew J; Weiner, Andrew M

2012-03-01

365

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.

2013-06-17

366

A near infrared laser frequency comb for high precision Doppler planet surveys  

NASA Astrophysics Data System (ADS)

Perhaps the most exciting area of astronomical research today is the study of exoplanets and exoplanetary systems, engaging the imagination not just of the astronomical community, but of the general population. Astronomical instrumentation has matured to the level where it is possible to detect terrestrial planets orbiting distant stars via radial velocity (RV) measurements, with the most stable visible light spectrographs reporting RV results the order of 1 m/s. This, however, is an order of magnitude away from the precision needed to detect an Earth analog orbiting a star such as our sun, the Holy Grail of these efforts. By performing these observations in near infrared (NIR) there is the potential to simplify the search for distant terrestrial planets by studying cooler, less massive, much more numerous class M stars, with a tighter habitable zone and correspondingly larger RV signal. This NIR advantage is undone by the lack of a suitable high precision, high stability wavelength standard, limiting NIR RV measurements to tens or hundreds of m/s [1, 2]. With the improved spectroscopic precision provided by a laser frequency comb based wavelength reference producing a set of bright, densely and uniformly spaced lines, it will be possible to achieve up to two orders of magnitude improvement in RV precision, limited only by the precision and sensitivity of existing spectrographs, enabling the observation of Earth analogs through RV measurements. We discuss the laser frequency comb as an astronomical wavelength reference, and describe progress towards a near infrared laser frequency comb at the National Institute of Standards and Technology and at the University of Colorado where we are operating a laser frequency comb suitable for use with a high resolution H band astronomical spectrograph.

Osterman, S.; Diddams, S.; Quinlan, F.; Bally, J.; Ge, J.; Ycas, G.

2011-07-01

367

Anti-fouling ultrafiltration membranes containing polyacrylonitrile- graft-poly(ethylene oxide) comb copolymer additives  

Microsoft Academic Search

Membrane fouling is one of the most important challenges faced in membrane ultrafiltration (UF) operations. In this study, polyacrylonitrile-graft-poly(ethylene oxide) (PAN-g-PEO), an amphiphilic comb copolymer with a water-insoluble polyacrylonitrile (PAN) backbone and hydrophilic poly(ethylene oxide) (PEO) side chains, was used as an additive in the manufacture of novel PAN UF membranes. During casting, the PAN-g-PEO additive segregates to form a

Ayse Asatekin; Seoktae Kang; Menachem Elimelech; Anne M. Mayes

2007-01-01

368

Synthesis of comb-like copolymers from renewable resources: Itaconic anhydride, stearyl methacrylate and lactic acid  

Microsoft Academic Search

The synthesis and properties of comb-like copolymers and ionomers derived from renewable resources: itaconic anhydride (ITA), stearyl methacrylate (SM) and lactic acid (LA) are described. The copolymers based on ITA and SM (ITA-SM) were nearly random with a slight alternating tendency. The copolymers exhibited a nanophase-separated morphology, with the stearate side-chains forming a bilayer, semi-crystalline structure. The crystalline side-chains suppressed

Shurui Shang

2009-01-01

369

Low-cost video decoder with 2D2L comb filter for NTSC digital TVs  

Microsoft Academic Search

A low-cost video decoder for NTSC signals is described in this paper. The proposed NTSC video decoder design employs a 2D2L comb filter, and a DDFS (direct digital frequency synthesizer)-based DCO (digital control oscillator) based on a trigonometric quadruple angle formula in a digital PLL to track and lock the demodulation clocks. The complexity of the digital video decoder is

Chua-Chin Wang; Ching-Li Lee; Ming-Kai Chang

2005-01-01

370

Polyphase Implementation of Non-recursive Comb Decimators for Sigma-Delta A\\/D Converters  

Microsoft Academic Search

In a sigma-delta analog to digital (A\\/D) converter, the most computationally intensive block is the decimation filter and its hardware implementation may require millions of transistors. Since these converters are now targeted for a portable application, a hardware efficient design is an implicit requirement. In this effect, this paper presents a computationally efficient polyphase implementation of non-recursive cascaded integrator comb

T. K. Shahana; R. K. James; B. R. Jose; K. Poulose Jacob; S. Sasi

2007-01-01

371

Non-recursive cascaded integrator-comb decimation filters with integer multiple factors  

Microsoft Academic Search

In this paper, multi-rate non-recursive architecture for Cascaded Integrator-Comb (CIC) decimation filters with an arbitrary factor is proposed. The CIC filters are widely used in high speed wireless communication systems since they have multiplier-less and multi-rate low-power structure. Even conventional non-recursive CIC structure is multi-rate, this architecture can be structured only in case of M-th power-of-two decimation factor. This paper

Youngbeom Jang; Sejung Yang

2001-01-01

372

Application of filter sharpening to cascaded integrator-comb decimation filters  

Microsoft Academic Search

A new architecture for the implementation of high-order decimation filters is described. It combines the cascaded integrator-comb (CIC) multirate filter structure with filter sharpening techniques to improve the filter's passband response. This allows the first-stage CIC decimation filter to be followed by a fixed-coefficient second-stage filter, rather than a programmable filter, thereby achieving a significant hardware reduction over existing approaches.

Alan Y. Kwentus; Zhongnong Jiang

1997-01-01

373

A silicon-on-glass Z-axis accelerometer with vertical sensing comb capacitors  

Microsoft Academic Search

A Z-axis accelerometer with asymmetrical vertical sensing comb capacitors and high aspect ratio single crystal mechanical structures is presented. A 5-mask silicon-on-glass (SOG) process combined with silicon\\/glass anodic bonding and multiple deep ion reactive etching (DRIE) is used to fabricate the accelerometer. With the specially designed out-of-plane springs, the accelerometer shows a cross-axis sensitivity of 0.46%. The scale factor and

Jiankun Wang; Zhenchuan Yang; Guizhen Yan

2012-01-01

374

High-precision wavelength calibration of astronomical spectrographs with laser frequency combs  

Microsoft Academic Search

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.

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

375

Tb\\/s Coherent Optical OFDM Systems Enabled by Optical Frequency Combs  

Microsoft Academic Search

This paper discusses the realization of terabit per second high speed and high spectral-efficiency optical transmissions using much lower speed electronics and optoelectronics through parallel processing of coherent optical frequency combs at both the transmitter and receiver. The coherent and parallel processing enables electrical-to-optical and optical-to-electrical (E\\/O and O\\/E) conversion of wide-bandwidth optical signals which would otherwise exceeds the capability

Xingwen Yi; Nicolas K. Fontaine; Ryan P. Scott; S. J. Ben Yoo

2010-01-01

376

Direct Link between Microwave and Optical Frequencies with a 300 THz Femtosecond Laser Comb  

Microsoft Academic Search

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

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

377

An etalon stabilized 10-GHz comb source using a slab coupled waveguide amplifier  

NASA Astrophysics Data System (ADS)

An optical comb source based on a slab-coupled optical waveguide amplifier (SCOWA) is presented. The laser is harmonically mode-locked at 10.287 GHz repetition rate and stabilized to an intra-cavity Fabry-Pérot etalon via Pound- Drever-Hall locking. The Fabry-Pérot etalon serves as a reference for the optical frequency of the comb-lines and suppresses the fiber cavity modes to allow only a single longitudinal mode-set to oscillate, generating a frequency comb spaced by the repetition rate. The pulse-to-pulse timing jitter and energy fluctuations are < 2 fs and < 0.03%, respectively (integrated from 1Hz to 100 MHz). Fundamental to this result is the incorporation of the SCOW amplifier as the gain medium and the use of an ultra-low noise sapphire-loaded cavity oscillator to mode-lock the laser. The SCOWA has higher saturation power than commercially available gain media, permitting higher intra-cavity power as well as available power at the output, increasing the power of the photodetected RF tones which increases their signal-to-noise ratio. A high visibility optical frequency comb is observed spanning ~3 nm (at -10 dB), with optical SNR > 60 dB for a cavity with no dispersion compensation. Initial results of a dispersion compensated cavity are presented. A spectral width of ~7.6 nm (-10 dB) was obtained for this case and the pulses can be compressed to near the transform limit at ~930 fs.

Davila-Rodriguez, Josue; Ozdur, Ibrahim T.; Mandridis, Dimitrios; Williams, Charles; Delfyett, Peter J.; Plant, Jason J.; Juodawlkis, Paul W.

2011-05-01

378

Bias-dependent distortion in optical comb-based analog optical links.  

PubMed

We provide the first experimental demonstration of the impact of bias-frequency on second-order distortion in sampled analog optical links. We show proper selection of bias frequency yields >48 dB improvement in second-order distortion performance. In addition, we demonstrate that measurement of the average frequency of the optical comb may be used to determine the optimum bias frequency - without the need for involved radio-frequency distortion measurements. PMID:24104282

McKinney, Jason D; Urick, Vincent J; Hastings, Alexander S

2013-10-01

379

Widely time-dispersion-tuned fiber optical oscillator and frequency comb based on multiple nonlinear processes.  

PubMed

An all-fiber optical oscillator based on three nonlinear processes, namely stimulated Raman scattering and broad-band and narrow-band optical parametric amplification, is presented and experimentally characterized. The wavelength tuning is achieved by means of the time-dispersion technique and spans over 160 nm. Through the same technique a fast tunable optical frequency comb has been realized exploiting cascaded four-wave mixing. PMID:24322089

Chiarello, Fabrizio; Palmieri, Luca; Galtarossa, Andrea; Santagiustina, Marco

2013-11-15

380

Sex, immunity and influenza.  

PubMed

Sex-specific endocrine and immune responses are widely recognized to account for differential disease outcomes between females and males. Surprisingly, sex-specific risk assessments for influenza, a viral pathogen that affects human populations worldwide through seasonal epidemics and irregular occurring pandemics, are sparse and-if available-ambiguous. To date, this precludes proposing an unequivocal sex-dependent susceptibility to influenza. However, one undisputable observation recurrently confirmed during influenza seasons of the last decades is the significantly increased risk for pregnant women. This increased risk is likely attributable to the contradictory demands for the maternal immune system to adapt to pregnancy and to simultaneously mount an immune response to clear the influenza virus infection. Here, we review published evidence on the potential association between sex on influenza risk and propose that future epidemiologic studies should carefully dissect surveillance data for sex-specific effects. Moreover, we propose potential mechanisms involved in enhanced risk for severe influenza during pregnancy that could be studied to identify causal pathways. PMID:24966196

Gabriel, Gülsah; Arck, Petra Clara

2014-07-15

381

Straight movement of micro containers based on ratchet mechanisms and electrostatic comb-drive actuators  

NASA Astrophysics Data System (ADS)

This paper describes the design, simulation and fabrication of a micro conveyer system (MCS) with straight displacement of micro containers based on ratchet mechanisms and electrostatic comb-drive actuators. This MCS consists of linear comb actuators, micro containers and ratchet racks. The micro containers can be moved with different velocities by comb-drive actuators through ratchet teeth. In this study, a SOI wafer with a device layer of 30 µm and a buried SiO2 layer of 4 µm is used. Each module of the MCS has dimensions of 6 × 6 mm2, is fabricated by using only one mask, ICP-RIE and vapor HF etching techniques, and can be assembled to create more complex conveyance systems for different applications, such as in bio-chemical analysis or a micro total analysis system (µ-TAS) to transport and classify small samples. In our experiments, the movement of the micro container has been tested with a driving frequency ranging from 5 Hz to 40 Hz. The velocity of the container was proportional to the frequency and matched very well with theoretical calculation.

Pham, Phuc Hong; Viet Dao, Dzung; Amaya, Satoshi; Kitada, Ryoji; Sugiyama, Susumu

2006-12-01

382

Radius of Gyration of Polystyrene Combs and Centipedes in a O Solvent  

SciTech Connect

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.

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

383

Validity of the mean-field approximation for diffusion on a random comb  

NASA Astrophysics Data System (ADS)

We consider unbiased diffusion on a random comb structure (an infinitely long backbone with loopless branches of arbitrary length emanating from it). If w=T0 is the mean time (averaged over all random walks) for first passage from an arbitrary origin 0 on the backbone to either of the sites +j or -j on it in a given realization of the structure, the exact diffusion constant for the problem is defined as K=limj-->?j2<1/T0>c, where < >c stands for the configuration average over the realizations of the random comb. The diffusion constant in the mean-field approximation is given by KMF=limj-->?j2/c. We compute T0 exactly for an arbitrary realization of the comb and then show rigorously that, owing to the suppression of the relative fluctuations in T0 in the ``thermodynamic limit'' j-->?, we have KMF=K whenever the moments of certain random variables ?(L,?,?) are finite; here the site-dependent random variables L, ?, and ? are, respectively, the branch length, stay probability at the tip of a branch, and the backbone-to-branch jump probability. Finally, we discuss different situations in which K will not be equal to KMF, although the transport remains diffusive, as opposed to those in which anomalous diffusion occurs.

Revathi, S.; Balakrishnan, V.; Lakshmibala, S.; Murthy, K. P. N.

1996-09-01

384

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

PubMed

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

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

2014-01-01

385

Frequency response of piezoresistive-based MASA resonators with electrostatic vertical comb-drive actuation.  

SciTech Connect

We report on experimental work that characterizes the frequency response of resonators of Microfabricated Acoustic Spectrum Analyzer (MASA) devices which were fabricated using Sandia's SUMMiT processing technology. A 1.1 micron silicon nitride layer was used in the fabrication to isolate the sense mechanism from the actuation mechanism. The devices are actuated using electrostatic vertical comb-drive actuation in a 30-50 mTorr vacuum and the frequency response is measured using a piezo-resistive readout mechanism. Two MASA devices are tested using comb-drive ac signals (e.g., 200mV) superimposed on a dc bias (e.g., 15V). In addition, dc bias voltages placed on the comb-drive are shown to tune the resonant frequency of the resonator. The frequency response of the piezo-resistive readout mechanism is measured using a 10V dc supply voltage supplied across its Wheatstone bridge. The results show that the piezo-resistive readout mechanism can detect resonant behavior and determine resonant frequency. A laser doppler vibrometer is used as an independent means to characterize the frequency response and verify the results.

Stalford, Harold Lenn (University of Oklahoma, Norman, OK); Epp, David S.

2005-01-01

386

xComb: a cross-linked peptide database approach to protein-protein interaction analysis  

PubMed Central

We developed an informatic method to identify tandem mass spectra composed of chemically cross-linked peptides from those of linear peptides and to assign sequence to each of the two unique peptide sequences. For a given set of proteins the key software tool, xComb, combs through all theoretically feasible cross-linked peptides to create a database consisting of a subset of all combinations represented as peptide FASTA files. The xComb library of select theoretical cross-linked peptides may then be used as a database that is examined by a standard proteomic search engine to match tandem mass spectral datasets to identify cross-linked peptides. The database search may be conducted against as many as 50 proteins with a number of common proteomic search engines, e.g. Phenyx, Sequest, OMSSA, Mascot and X!Tandem. By searching against a peptide library of linearized, cross-linked peptides, rather than a linearized protein library, search times are decreased and the process is decoupled from any specific search engine. A further benefit of decoupling from the search engine is that protein cross-linking studies may be conducted with readily available informatics tools for which scoring routines already exist within the proteomic community.

Panchaud, Alexandre; Singh, Pragya; Shaffer, Scott A.; Goodlett, David R.

2010-01-01

387

Plasma protein adsorption and platelet adhesion onto comb-like PEO gradient surfaces.  

PubMed

Comb-like polyethylene oxide (PEO) surfaces were prepared on low-density polyethylene (PE). The comb-like PEO chain density was changed gradually along the sample lengths by corona discharge treatment with gradually increasing power and the following graft copolymerization of poly(ethylene glycol) monomethacrylate macromers (PEO-MA). The macromers with different PEO repeat unit, 1, 5, and 10, were used. The prepared comb-like PEO gradient surfaces were characterized by water contact angle, Fourier transform infrared spectroscopy in the attenuated total reflectance mode, and electron spectroscopy for chemical analysis. All these measurements indicated that the PEO chains are grafted on the PE surface with gradually increasing density of PEO. Plasma protein adsorption and platelet adhesion on the PEO gradient surfaces decreased with increasing PEO chain length and surface density. As observed by scanning electron microscopy, PEO10-MA-grafted surface with high PEO density was very effective in preventing protein adsorption and platelet adhesion and did not activate the platelets. PMID:8978659

Lee, J H; Jeong, B J; Lee, H B

1997-01-01

388

Sex And People.  

ERIC Educational Resources Information Center

This textbook for the college student emphasizes human sexuality as a part of the whole human life experience and contains a balance of biological, psychological, and sociological material. In 16 chapters the following topics are covered: (1) sex and society; (2) historical and cultural perspectives; (3) glandular control of sexual physiology; (4)…

Jones, Kenneth L.; And Others

389

Hands Off Consensual Sex.  

ERIC Educational Resources Information Center

Exception is taken to language proposed for a university's sexual-harassment policy, arguing that anything vitiating privacy must have strong, readily apparent benefit for the common good; that students cannot be stripped of their ability to make choices; and that teachers' decisions about consensual sex must be made in context of their own…

Alston, Kal

1998-01-01

390

Brain, Sex and Ideology  

Microsoft Academic Search

Since the 19th century, and despite tremendous progress in science, the topic of ‘brain and sex’ remains a matter of misleading interpretations, far beyond the field of science. The media are not solely responsible for this situation. Some scientific circles still actively promote the ideology of biological determinism in their attempt to explain differences in behaviour and cognitive abilities between

Catherine Vidal

2005-01-01

391

Sex Therapy and Mastectomy  

ERIC Educational Resources Information Center

Because the emotional trauma associated with a mastectomy exceeds the physical trauma, the recovery of the woman is greatly affected by the response of her husband or lover. Sex therapy, therefore, involves the couple. The approach described is aimed at assisting the couple to confront and integrate the mastectomy experience. (Author)

Witkin, Mildred Hope

1975-01-01

392

Television's New Sex Education  

ERIC Educational Resources Information Center

Author is concerned with sexual identity as it may be being learned by youngsters (including her youngster) from their TV screens. She is concerned that young people are viewing as natural and normal the presentation of sex on television as a routine, affectless experience in which women are the objects of men's lust. (Editor/RK)

Levinsohn, Florence Hamlish

1977-01-01

393

Sex, Technology and Morality.  

ERIC Educational Resources Information Center

Provides an overview of the course "Sex, Technology, and Morality" which focuses on the human reproductive process and examines the advances in reproductive technology. The course emphasizes the social, political, and ethical implications of actual and possible technologies associated with human reproduction. (ML)

Case, Verna; And Others

1986-01-01

394

How Sex Attitudes Develop  

ERIC Educational Resources Information Center

Excerpt from "The Roots of Love" (Helene S. Arnstein, 1975). Book is concerned with feelings that are part of child's developmental stages. Included in excerpt are: genital self-discovery, masturbation, discovery of sex differences, and birth fantasies. Stresses importance of parent's feelings which are communicated to child.

Arnstein, Helene S.

1976-01-01

395

Evolution, Sex, and Jealousy  

Microsoft Academic Search

When asked to choose which would be most upsetting, a mate’s sexual or emotional infidelity, past research has demonstrated that men are more likely than women to choose sexual infidelity, whereas women are more likely than men to choose emotional infidelity. Explanation of this sex difference has been controversial. In the current study we attempted to replicate previous research by

Michael W. Wiederman; Erica Kendall

1999-01-01

396

Disestablishing Sex: The Case for Released-Time Sex Education  

ERIC Educational Resources Information Center

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…

Glanzer, Perry L.

2011-01-01

397

Women, Middle Age and Sex  

MedlinePLUS Videos and Cool Tools

... important is sex to a woman's health-related quality of life as she ages? And what factors ... were both associated with continued sexual activity but quality of sex was not. And as women aged, ...

398

Hypnotic Psychotherapy with Sex Offenders  

ERIC Educational Resources Information Center

The authors review the literature on the prevalence of sex offenders; multiple treatment modalities; and implications of the use of hypnotic psychotherapy, coupled with cognitive behavioral treatment programs, for treating sex offenders. (Contains 2 tables.)

Moseley, Sullivan; Briggs, Wanda P.; Magnus, Virginia

2005-01-01

399

SHBG (Sex Hormone Binding Globulin)  

MedlinePLUS

... as: Testosterone-estrogen Binding Globulin; TeBG Formal name: Sex Hormone Binding Globulin Related tests: Testosterone , Free Testosterone, ... Get Tested? To evaluate whether the concentration of sex hormone binding globulin (SHBG) is affecting the amount ...

400

Sex and Fertility After SCI  

MedlinePLUS

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

401

Dyspareunia: Painful Sex for Women  

MedlinePLUS

... part of the genitals can cause pain during sex. Some conditions affect the skin around the vagina. ... types of birth control) does not fit correctly, sex may also be painful. Vaginismus (say: "vag-in- ...

402

Same-Sex Relationship Violence  

MedlinePLUS

... of violence against women Violence Against Women Same-sex relationship violence Click the red escape button above ... punishments. Return to top More information on Same-sex relationship violence Explore other publications and websites Dating ...

403

The ABCs of Sex Ed.  

ERIC Educational Resources Information Center

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)

Sroka, Stephen R.

2002-01-01

404

Sex Differences in Academic Prediction  

ERIC Educational Resources Information Center

A study was conducted with seventh grade students to investigate sex differential of scores on the Short Test of Educational Ability in predicting academic performance. No significant sex differences were found. (Author/EK)

Jones, W. Paul

1970-01-01

405

Emotional scripts of sex panics  

Microsoft Academic Search

This article examines the emotional dynamics of local sex panics over sex education. It argues that local sex panics are not\\u000a spontaneous eruptions of community outrage; they are political events with a strikingly scripted quality. Sex panics are fueled\\u000a by emotional scripts—rhetoric strategically crafted to produce volatile emotional responses. In turn, these emotional scripts\\u000a produce heated emotions—anger and disgust—displayed in

Janice M. Irvine

2006-01-01

406

Echelle spectrograph calibration with a frequency comb based on a harmonically mode-locked fiber laser: a proposal.  

PubMed

Details for constructing an astronomical frequency comb suitable as a wavelength reference for échelle spectrographs associated with optical telescopes are outlined. The source laser for the frequency comb is a harmonically mode-locked fiber laser with a central wavelength of 1.56 microm. The means of producing a repetition rate greater than 7 GHz and a peak optical power of approximately 8 kW are discussed. Conversion of the oscillator light into the visible can occur through a two-step process of (i) nonlinear conversion in periodically poled lithium niobate and (ii) spectral broadening in photonic crystal fiber. While not necessarily octave spanning in spectral range to permit the use of an f -to- 2f interferometer for offset frequency control, the frequency comb can be granted accuracy by linking the mode spacing and a comb tooth to separate frequency references. The design avoids the use of a Fabry-Perot cavity to increase the mode spacing of the frequency comb; however, the level of supermode suppression and sideband asymmetry in the fiber oscillator and in the subsequent frequency conversion stages are aspects that need to be experimentally tested. PMID:19424399

McFerran, J J

2009-05-10

407

SMA-g-MPEG comb-like polymer as a dispersant for Al 2O 3 suspensions  

NASA Astrophysics Data System (ADS)

SMA-g-MPEG comb-like polymer is first employed as the dispersant of Al 2O 3 suspensions in this paper. The comb-like polymer has anionic polycarboxylate backbone, which makes the polymer easily absorbed on the cationic surface of Al 2O 3 particles; on the other hand, the comb-like polymer has hydrophilic MPEG side chains, which extend into the solution to provide steric repulsion after the comb-like polymer is absorbed on the surface of Al 2O 3 particles. The adsorption behavior, zeta potential, apparent viscosity, granularity and TEM images of the Al 2O 3 suspensions using SMA-g-MPEG as dispersant are investigated. The addition of SMA-g-MPEG improves the dispersibility and decreases the apparent viscosity of the Al 2O 3 suspension observably. The impacts of the length of side chains on the dispersion of Al 2O 3 suspensions are particularly discussed. The adsorbed molecular number of the dispersant decreased by increasing the length of side chains. The zeta potential of Al 2O 3 suspension is more negative by using comb-like polymer with shorter side chains. Based on the steric repulsion and adsorbed molecular number, SMA-g-MPEG with moderate length of side chain is found to have the best dispersibility for Al 2O 3 suspension.

Ran, Qianping; Qiao, Min; Liu, Jiaping; Miao, Changwen

2012-01-01

408

Echelle spectrograph calibration with a frequency comb based on a harmonically mode-locked fiber laser: a proposal  

SciTech Connect

Details for constructing an astronomical frequency comb suitable as a wavelength reference for echelle spectrographs associated with optical telescopes are outlined. The source laser for the frequency comb is a harmonically mode-locked fiber laser with a central wavelength of 1.56 {mu}m. The means of producing a repetition rate greater than 7 GHz and a peak optical power of {approx}8 kW are discussed. Conversion of the oscillator light into the visible can occur through a two-step process of (i) nonlinear conversion in periodically poled lithium niobate and (ii) spectral broadening in photonic crystal fiber. While not necessarily octave spanning in spectral range to permit the use of an f -to- 2f interferometer for offset frequency control, the frequency comb can be granted accuracy by linking the mode spacing and a comb tooth to separate frequency references. The design avoids the use of a Fabry-Perot cavity to increase the mode spacing of the frequency comb; however, the level of supermode suppression and sideband asymmetry in the fiber oscillator and in the subsequent frequency conversion stages are aspects that need to be experimentally tested.

McFerran, J. J.

2009-05-10

409

Gender Specific Sex Role Development.  

ERIC Educational Resources Information Center

Research has indicated that gender constancy and categorization are achieved in childhood and that autonomous sex-role integration occurs during adulthood, well after a secure sense of gender identity is established. To examine developmental sex-role identification, college students rated themselves on a "current" Bem Sex Role Inventory (BSRI) and…

Urbonas-Bendikas, Irena

410

Counselor Renewal in Sex Equality.  

ERIC Educational Resources Information Center

Discusses sex equality, and documents continuing significance of sex bias issues and their relevance for counseling personnel. This article also presents a rationale for counselor renewal in sex equality, competency areas for renewal efforts, and programs relevant for each area of competency. (Author)

Sundal-Hansen, L. Sunny; Watt, Mary Ann

1979-01-01

411

Sex and Women with Cancer -- Overview  

MedlinePLUS

... and sex Radiation and sex Chemotherapy (chemo) and sex Hormone treatment and sex To learn more about your ... Your Area Cancer Information Cancer Basics Cancer Prevention & Detection Signs & Symptoms of Cancer Treatments & Side Effects Cancer ...

412

46,XX sex reversal.  

PubMed

In humans, sexual differentiation is directed by SRY, a master regulatory gene located at the Y chromosome. This gene initiates the male pathway or represses the female pathway by regulating the transcription of downstream genes; however, the precise mechanisms by which SRY acts are largely unknown. Moreover, several genes have recently been implicated in the development of the bipotential gonad even before SRY is expressed. In some individuals, the normal process of sexual differentiation is altered and a sex reversal disorder is observed. These subjects present the chromosomes of one sex but the physical attributes of the other. Over the past years, considerable progress has been achieved in the molecular characterization of these disorders by using a combination of strategies including cell biology, animal models, and by studying patients with these pathologic entities. PMID:11750731

Zenteno-Ruiz, J C; Kofman-Alfaro, S; Méndez, J P

2001-01-01

413

A quantitative performance measure for a clinical evaluation of comb structure removal algorithms in flexible endoscopy  

NASA Astrophysics Data System (ADS)

Modern techniques for technical inspection as well as medical diagnostics and therapy in keyhole-surgery scenarios make use of flexible endoscopes. Common to both application fields are very small natural or manmade entry points to the observed scene, as well as the complexity of the hollow itself. These make the use of rigid lens-based endoscopes or tip chip videoscopes impossible. Due to the fact that the fiber-optic image guide of a flexible endoscope introduces a comb structure to the acquired images, many research has been devoted to algorithms for an effective removal of such artifacts. Oftentimes, this research has been motivated by the fact, that the comb structure prevents an application of some well-established methods offered by the computer vision and image processing community. Unfortunately, the performance of the presented approaches are commonly visually evaluated or with respect to proprietary, non-standardized metrics. Thus, the performances of individual algorithms are hard to compare with each other. For this reasons, we propose a performance measure for fiber-optic imaging devices that has been motivated by the physics of optics. In this field, an optical system is frequently described by linear systems theory and the system's quality can be expressed by its transfer function. The determination of this transfer function has been standardized by the ISO for lens based imaging systems and represents a widely accepted measure for the quality of such systems. In this contribution, we present methods that account for fiber-optic imaging systems and thus enable a standardized performance evaluation. Finally, we demonstrate its use by comparing two recent state of the art comb structure removal algorithms, each of them being a representative of a spatial and a frequency domain method, respectively.

Rupp, Stephan

2008-04-01

414

Cascaded integrator comb filters with smoothly varying coefficients for reduced delay in synchrotron feedback loops  

NASA Astrophysics Data System (ADS)

The Rapid Cycling Synchrotron (RCS) of the J-PARC complex in Tokai, Japan, is designed to accelerate a high intensity proton beam from 181 MeV, and later 400 MeV to 3 GeV in 20 ms within the 40 ms machine cycle. The beam power up to 1 MW demands a stable beam control to avoid excessive losses and activation of the accelerator chain. The fully digital control system is based on quadrature modulation and demodulation. In the amplitude control loops standard FIR filters separate the harmonics (h=2) and (h=4) after down conversion. For the phase loops at (h=2) and (h=4), intended to damp synchrotron oscillations, the delay in a FIR filter would limit the loop stability. Cascaded integrator comb filters, also called CIC filters, provide a shorter delay because they filter the longitudinal beam signal only where it is necessary. The notches are located at multiples of the revolution frequency of the proton beam. For fixed frequency accelerator applications, digital comb filters with fixed clock frequency are widely used to improve loop stability. For variable frequency accelerator applications, as in a proton synchrotron, where the frequency swing is larger than the notch width, usually the clock frequency of the comb filter is variable and chosen to be an integer multiple of the particle revolution frequency. At J-PARC RCS, the clock frequency has to be fixed. Tracking the frequency would require a variable noninteger number of filter taps. Here we present a filter, based on the weighted output of 2 CIC filters with variable length, and one tap difference. The filter function looks like a CIC with smoothly varying coefficients, where the notches follow the revolution frequency of the proton beam. The delay of this filter is approximately half of the corresponding FIR filter, so that the phase loops have a higher stability margin.

Schnase, A.; Nomura, M.; Tamura, F.; Yamamoto, M.; Anami, S.; Ezura, E.; Hara, K.; Ohmori, C.; Takagi, A.; Yoshii, M.

2005-12-01

415

Why Humans Have Sex  

Microsoft Academic Search

Historically, the reasons people have sex have been assumed to be few in number and simple in nature–to reproduce, to experience\\u000a pleasure, or to relieve sexual tension. Several theoretical perspectives suggest that motives for engaging in sexual intercourse\\u000a may be larger in number and psychologically complex in nature. Study 1 used a nomination procedure that identified 237 expressed\\u000a reasons for

Cindy M. Meston; David M. Buss

2007-01-01

416

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

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

Yamada, Y

2000-11-01

417

High-power, hybrid Er:fiber/Tm:fiber frequency comb source in the 2 ?m wavelength region.  

PubMed

We present a 2 ?m 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 ?m. Subsequently, a cladding-pumped Tm:fiber amplifier boosts the system to a maximum output power of 4.8 W at 1.96 ?m. 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. PMID:22555684

Adler, Florian; Diddams, Scott A

2012-05-01

418

Spectroscopy of 171Yb in an optical lattice based on laser linewidth transfer using a narrow linewidth frequency comb.  

PubMed

We propose a novel, high-performance, and practical laser source system for optical clocks. The laser linewidth of a fiber-based frequency comb is reduced by phase locking a comb mode to an ultrastable master laser at 1064 nm with a broad servo bandwidth. A slave laser at 578 nm is successively phase locked to a comb mode at 578 nm with a broad servo bandwidth without any pre-stabilization. Laser frequency characteristics such as spectral linewidth and frequency stability are transferred to the 578-nm slave laser from the 1064-nm master laser. Using the slave laser, we have succeeded in observing the clock transition of (171)Yb atoms confined in an optical lattice with a 20-Hz spectral linewidth. PMID:23571880

Inaba, Hajime; Hosaka, Kazumoto; Yasuda, Masami; Nakajima, Yoshiaki; Iwakuni, Kana; Akamatsu, Daisuke; Okubo, Sho; Kohno, Takuya; Onae, Atsushi; Hong, Feng-Lei

2013-04-01

419

Optical frequency combs generated by four-wave mixing in optical fibers for astrophysical spectrometer calibration and metrology.  

PubMed

Optical frequency combs generated by multiple four-wave mixing in short and highly nonlinear optical fibers are proposed for use as high precision frequency markers, calibration of astrophysical spectrometers, broadband spectroscopy and metrology. Implementations can involve two optical frequency standards as input lasers, or one standard and a second laser phase-locked to it using a stable microwave reference oscillator. Energy and momentum conservation required by the parametric generation assures phase coherence among comb frequencies, while fibers with short lengths can avoid linewidth broadening and stimulated Brillouin scattering. In contrast to combs from mode-locked lasers or microcavities, the absence of a resonator allows large tuning of the frequency spacing from tens of gigahertz to beyond teraHertz. PMID:18711563

Cruz, Flavio C

2008-08-18

420

Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism  

SciTech Connect

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.

Tillman, Karl A.; Thapa, Rajesh; Knabe, Kevin; Wu Shun; Lim, Jinkang; Washburn, Brian R.; Corwin, Kristan L.

2009-12-20

421

Stabilization of a self-referenced, prism-based, Cr:forsterite laser frequency comb using an intracavity prism.  

PubMed

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

Tillman, Karl A; Thapa, Rajesh; Knabe, Kevin; Wu, Shun; Lim, Jinkang; Washburn, Brian R; Corwin, Kristan L

2009-12-20

422

All-Optical OC-192 RZ data decision gating in dark optical comb injected semiconductor optical amplifier  

NASA Astrophysics Data System (ADS)

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.

Liao, Yu-Sheng; Yu, Kun-Chieh; Lin, Gong-Ru

2006-10-01

423

Design of waveguide-integrated semiconductor laser sources for optical frequency comb generation.  

PubMed

A numerical study of threshold gain and modal dispersion in integrated semiconductor laser optical frequency comb sources is presented. We consider an example device where one of the cleaved facets of the laser is replaced by a short Bragg grating section and show that as many as 16 modes can be selected at the first harmonic of the underlying Fabry-Perot cavity. An intracavity approach to limiting the grating-induced dispersion that can be implemented directly through the grating profile is demonstrated. PMID:21808380

Bitauld, David; Osborne, Simon; O'Brien, Stephen

2011-08-01

424

500??MHz spaced Yb:fiber laser frequency comb without amplifiers.  

PubMed

An optical frequency comb based on Yb:ring fiber laser was demonstrated. This is the first time, to our knowledge, fceo has been generated directly from the oscillator without further amplifications above 500 MHz repetition rate. The signal-to-noise ratio of the offset frequency was above 40 dB at 300 kHz resolution bandwidth, which supports easy stabilization. The offset frequency was stabilized for more than 6 h in an open air environment without temperature control. The stabilized repetition rate has an in-loop tracking stability of 4.46×10-13/?1/2. PMID:24784038

Wang, Guizhong; Meng, Fei; Li, Chen; Jiang, Tongxiao; Wang, Aimin; Fang, Zhanjun; Zhang, Zhigang

2014-05-01

425

Toward an all-optically stabilized frequency comb based on a mode-locked fiber laser.  

PubMed

We present an erbium-doped mode-locked fiber laser comprising two all-optical control mechanisms acting on the carrier envelope offset (CEO)-frequency as well as the repetition frequency. The laser's repetition frequency is stabilized via optically pumping a distinct ytterbium-doped fiber module. By proving that additionally controlling the pump power of the erbium-doped gain fiber acts sufficiently complementary on the laser's CEO-frequency compared with repetition frequency stabilization, we demonstrate the feasibility of this concept for an all-optically controlled frequency comb in an all-fiber setup. PMID:24487856

Hellwig, Tim; Rieger, Steffen; Fallnich, Carsten

2014-02-01

426

Study on the temporal coherence function of a femtosecond optical frequency comb  

NASA Astrophysics Data System (ADS)

The interference measurement using the femtosecond optical frequency comb (FOFC) is in progress at present. We analyzed the temporal coherence function (TCF) of an FOFC since which is the fundamental description of the interference phenomenon. As a result, it has been understood that the same high coherence peak exists during the time which is equal to the repetitions interval in the traveling direction of the FOFC. The theoretical derivation has been used to model the TCF of an FOFC and shows good agreement with experimental measurements which is taken with a combination of an ordinary Michelson interferometer and an unbalanced optical-path Michelson interferometer.

Wei, Dong; Takahashi, Satoru; Takamasu, Kiyoshi; Matsumoto, Hirokazu

2009-06-01

427

Pulse dynamics in a mode-locked fiber laser and its quantum limited comb frequency uncertainty.  

PubMed

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

Bao, Chengying; Funk, Andrew C; Yang, Changxi; Cundiff, Steven T

2014-06-01

428

Kerr parametric oscillations and frequency comb generation from dispersion compensated silica micro-bubble resonators.  

PubMed

Silica micro-bubble resonators (MBRs) with cavity quality factor as high as Q = 5 × 10(7) are fabricated. The total dispersion of MBRs is analyzed. The thin-wall structure opens a new anomalous dispersion window and thus supports the dispersion compensation for hyper-parametric frequency conversion processes. Experimentally, Kerr parametric oscillation is observed in a 136 ?m diameter MBR, frequency comb generation is also realized. Meanwhile the same nonlinear process is not allowed in solid silica spheres with size smaller than 150 ?m. PMID:23938539

Li, Ming; Wu, Xiang; Liu, Liying; Xu, Lei

2013-07-15

429

Frequency-comb-referenced multi-channel fiber laser for DWDM communication.  

PubMed

We propose an all-fiber-based multi-channel optical scheme that enables simultaneous generation of multiple continuous-wave laser wavelengths with stabilization to the frequency comb of a femtosecond laser. The intention is to produce highly stable, accurate wavelength channels with immunity to environmental disturbance so as to enhance the transmission capacity of dense wavelength division multiplexing (DWDM) communications. Generated wavelengths lie over a wide spectral range of 5 THz about 1550 nm, each yielding a narrow linewidth of less than 24 kHz with an absolute position uncertainty of ~2.24 × 10¹² (10 s averaging) traceable directly to the atomic Rb clock. PMID:24514469

Chun, Byung Jae; Hyun, Sangwon; Kim, Seungman; Kim, Seung-Woo; Kim, Young-Jin

2013-12-01

430

Comparison of length measurements provided by a femtosecond optical frequency comb.  

PubMed

This paper presents a comparison of length measurements between the wavelength and the adjacent pulse repetition interval length (APRIL) provided by a femtosecond optical frequency comb. A theoretical estimation of the frequency stability for stabilizing the wavelength and APRIL, the frequency parameters that affect the stability of the APRIL in air, and the ambiguity in the length measurement by the APRIL are investigated. We find that the APRIL can be used as a low-cost measurement for the absolute length over a range of hundreds of meters in laboratory conditions. PMID:24664052

Wei, Dong; Aketagawa, Masato

2014-03-24

431

Description of Noviherbaspirillum malthae gen. nov., sp. nov., isolated from an oil-contaminated soil, and proposal to reclassify Herbaspirillum soli, Herbaspirillum aurantiacum, Herbaspirillum canariense and Herbaspirillum psychrotolerans as Noviherbaspirillum soli comb. nov., Noviherbaspirillum aurantiacum comb. nov., Noviherbaspirillum canariense comb. nov. and Noviherbaspirillum psychrotolerans comb. nov. based on polyphasic analysis.  

PubMed

An aerobic, Gram-negative, rod-shaped bacterium with polar flagella, strain CC-AFH3(T), was isolated from an oil-contaminated site located in Kaohsiung county, Taiwan. Strain CC-AFH3(T) grew at 20-40 °C, pH 5.0-10.0 and <2?% (w/v) NaCl. 16S rRNA gene sequence analysis indicated that strain CC-AFH3(T) showed the greatest degree of similarity to Herbaspirillum soli SUEMI10(T) (96.5?%), H. aurantiacum SUEMI08(T) (96.3?%), H. canariense SUEMI03(T) (96.0?%), H. psychrotolerans PB1(T) (95.4?%) and members of other Herbaspirillum species (94.1-95.2?%), and lower similarity to members of other genera (<94?%). Phylogenetic analyses also positioned the novel strain in the genus Herbaspirillum as an independent lineage. The major fatty acids in strain CC-AFH3(T) were C10?:?0 3-OH, C12?:?0, C14?:?0 2-OH, C16?:?0, iso-C15?:?0 3-OH, C17?:?0 cyclo, C16?:?1?7c/C16?:?1?6c and C18?:?1?7c/C18?:?1?6c. The major polar lipids of strain CC-AFH3(T) were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylcholine. The predominant quinone was ubiquinone 8 (Q-8) and the DNA G+C content was 63.4 mol%. On the basis of 16S rRNA gene sequence analysis in combination with physiological and chemotaxonomic data, strain CC-AFH3(T) represents a novel species in a new genus, for which we propose the name Noviherbaspirillum malthae gen. nov., sp. nov.; the type strain of Noviherbaspirillum malthae is CC-AFH3(T) (?=?BCRC 80516(T)?=?JCM 18414(T)). We also propose the reclassification of Herbaspirillum soli, Herbaspirillum aurantiacum, Herbaspirillum canariense and 'Herbaspirillum psychrotolerans' as Noviherbaspirillum soli comb. nov. (type strain SUEMI10(T)?=?LMG 26149(T)?=?CECT 7840(T)), Noviherbaspirillum aurantiacum comb. nov. (type strain SUEMI08(T)?=?LMG 26150(T)?=?CECT 7839(T)), Noviherbaspirillum canariense comb. nov. (type strain SUEMI03(T)?=?LMG 26151(T)?=?CECT 7838(T)) and Noviherbaspirillum psychrotolerans comb. nov. (type strain PB1(T)?=?DSM 26001(T)?=?LMG 27282(T)), respectively. An emended description of Herbaspirillum seropedicae is also presented. PMID:23749276

Lin, Shih-Yao; Hameed, Asif; Arun, A B; Liu, You-Cheng; Hsu, Yi-Han; Lai, Wei-An; Rekha, P D; Young, Chiu-Chung

2013-11-01

432

Energy transportation in a subwavelength waveguide composed of a pair of comb-shape nanorod chains.  

PubMed

A subwavelength plasmonic waveguide composed of a pair of comb-shape nanorod chains is proposed. The electromagnetic energy can be transported in the waveguide via the interaction strength of magnetoinductive coupling as well as conduction current exchange. Finite Element Method simulation results reveal that for such a waveguide composed of 50 pairs of 400 nm-long-nanorods, a passband ranging from zero to cutoff frequency 156.2 THz, and an effective propagation length of 20.87 ?m can be achieved simultaneously. The proposed mechanism of energy transport in the nanoscale has potential applications in subwavelength transmission lines for a wide range of integrated optical devices. PMID:22968277

Shen, Bing; Huang, Yongqing; Duan, Xiaofeng; Ren, Xiaomin; Zhang, Xia; Wang, Qi; Zhang, Dong

2012-09-10

433

Microwave synthesis from a continuous-wave terahertz oscillator using a photocarrier terahertz frequency comb.  

PubMed

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

Nagano, Shigeo; Ito, Hiroyuki; Kumagai, Motohiro; Kajita, Masatoshi; Hanado, Yuko

2013-06-15

434

Experimental realization of multipartite entanglement of 60 modes of a quantum optical frequency comb.  

PubMed

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. PMID:24724640

Chen, Moran; Menicucci, Nicolas C; Pfister, Olivier

2014-03-28

435

Experimental Realization of Multipartite Entanglement of 60 Modes of a Quantum Optical Frequency Comb  

NASA Astrophysics Data System (ADS)

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.

Chen, Moran; Menicucci, Nicolas C.; Pfister, Olivier

2014-03-01

436

Sex Differences in Constitutive Autophagy  

PubMed Central

Sex bias has been described nowadays in biomedical research on animal models, although sexual dimorphism has been confirmed widely under pathological and physiological conditions. The main objective of our work was to study the sex differences in constitutive autophagy in spinal cord and skeletal muscle tissue from wild type mice. To examine the influence of sex on autophagy, mRNA and proteins were extracted from male and female mice tissues. The expressions of microtubule-associated protein 1 light chain 3 (LC3) and sequestosome 1 (p62), markers to monitor autophagy, were analyzed at 40, 60, 90, and 120 days of age. We found significant sex differences in the expression of LC3 and p62 in both tissues at these ages. The results indicated that sex and tissue specific differences exist in constitutive autophagy. These data underlined the need to include both sexes in the experimental groups to minimize any sex bias.

Olivan, Sara; Calvo, Ana Cristina; Manzano, Raquel; Zaragoza, Pilar

2014-01-01

437

Conflicting Philosophies of School Sex Education  

Microsoft Academic Search

This paper surveys the range of philosophical positions currently found in school sex education materials. Five main positions are identified: school sex education should not occur; school sex education should promote physical health; school sex education should promote personal autonomy; school sex education should promote responsible sexual behaviour; school sex education should take place within a religious framework. The strengths

Michael J. Reiss

1995-01-01

438

"Sex Hormones" in Secondary School Biology Textbooks  

ERIC Educational Resources Information Center

This study explores the extent to which the term "sex hormone" is used in science textbooks, and whether the use of the term "sex hormone" is associated with pre-empirical concepts of sex dualism, in particular the misconceptions that these so-called "sex hormones" are sex specific and restricted to sex-related physiological functioning. We found…

Nehm, Ross H.; Young, Rebecca

2008-01-01

439

Sex-role orientation and attachment styles of sex offenders.  

PubMed

Given the increase of individuals who have a history of sexual offenses, there has been an increase in research on the etiology of sex-offending behavior. The present purpose was to evaluate the relationship between sex-role orientation and attachment styles of males who were sex offenders. Analysis yielded statistically significant differences between comparison (n = 22) and clinical groups (n = 21) in gender roles, with little sign of the androgynous gender type for sex offenders. The offender group showed significantly lower frequency of androgyny scores and significantly higher scores on feminine and undifferentiated orientations, supporting the theoretical view of sex offenders as being "cross-sex-typed." In addition, the sex offender group had a significantly higher mean score on anxious-avoidant relationship attachment. Based on the present findings, there appears to be a need to help sex offenders explore how their gender roles may relate to their sex-offending behavior and assist sex offenders in the development of adaptive relationships with reduced anxiety and ambivalence. PMID:22662415

Schneck, Mary M; Bowers, Thomas G; Turkson, Maria A

2012-04-01

440

The quantum-limited comb lineshape of a mode-locked laser: fundamental limits on frequency uncertainty.  

PubMed

We calculate the quantum-limited shape of the comb lines from a mode-locked Ti:sapphire laser using experimentally-derived parameters for the linear response of the laser to perturbations. The free-running width of the comb lines is found across the laser spectrum. By modeling the effect of a simple feedback loop, we calculate the spectrum of the residual phase noise in terms of the quantum noise and the feedback parameters. Finally, we calculate the frequency uncertainty in an optical frequency measurement if the limiting factor is quantum noise in the detection of the optical heterodyne beat. PMID:19581948

Wahlstrand, J K; Willits, J T; Menyuk, C R; Cundiff, S T

2008-11-10

441

Effect of surface acoustic waves on the catalytic decomposition of ethanol employing a comb transducer for ultrasonic generation  

SciTech Connect

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.

S. J. Reese; D. H. Hurley; H.W. Rollins

2006-04-01

442

Generation of a phase-locked Raman frequency comb in gas-filled hollow-core photonic crystal fiber.  

PubMed

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

Abdolvand, A; Walser, A M; Ziemienczuk, M; Nguyen, T; Russell, P St J

2012-11-01

443

Development of an incoherent optical frequency comb interferometer for long-range and scanless profilometry and tomography  

NASA Astrophysics Data System (ADS)

An optical resonator was installed as an incoherent frequency comb generator into a two-dimensional single-shot profilometry and tomography system to increase the measurement range up to 30 times compared with a conventional white-light interferometer. The dynamic range of the sample set position was experimentally confirmed to be ˜28 mm, equivalent to the coherency of the resonator. Scanless measurement can be achieved through high-order comb interference. In this study, we demonstrated tomography with a resolution of ˜11 ?m and effective high-order interference fringe discrimination.

Banh, Tuan Quoc; Suzuki, Kohei; Shioda, Tatsutoshi

2013-06-01

444

Facies relationships and depositional environments of lower Tuscaloosa Formation reservoir sandstones in McComb and Little Creek field areas, southwest Mississippi  

SciTech Connect

Detailed core and electric log studies reveal that the main producing sandstone in the McComb field area (McComb sand) was deposited as a transgressive barrier-island complex along a coastline influenced by wave action and tides. Isopachs show the McComb sand thickens to the west. This thickening pattern is consistent with regional structural maps in the McComb field area, which indicate that seaward directions lay to the west and southwest during deposition of the lower Tuscaloosa Formation. The producing sandstone in Little Creek field (Denkman Sandstone) differs from those in McComb field with respect to depositional environment and stratigraphic position. The Denkman Sandstone occupies a lower stratigraphic position in the stringer sand section than the McComb sand. The McComb sand is approximately 50-60 ft below the base of the middle marine shale formation, a unit clearly of marine origin on the basis of glauconite occurrence and fossil evidence. The Denkman Sandstone is 70-80 ft below the middle marine Tuscaloosa Formation, closer stratigraphically to the Dantzler Formation (Lower Cretaceous), which is continental in origin. The results of this study show that two major depositional facies characterize producing lower Tuscaloosa Formation sandstone reservoirs in this area: a lower fluvial sequence (Little Creek) topped by nearshore marine deposits (McComb). The study also indicates that the McComb sandstone was deposited as a transgressed barrier-island system at a time when sand supply was diminishing. Thus, the barrier complex marks the shore zone of the Upper Cretaceous marine transgression in the McComb field area.

Hamilton, W.S.; Cameron, C.P.

1986-09-01

445

Sexing sperm of domestic animals.  

PubMed

The ability to preselect or predetermine the sex of offspring prior to conception is a highly desired technological tool for assisted female breeding programs specifically for milk production, and in males, for meat production and increasing livestock numbers. The current technology is based on the well-known differences in X- and Y-sperm in the amount of DNA. The technology uses modified flow cytometric instrumentation for sorting X- and Y-bearing sperm. The method can be validated on the basis of live births, laboratory reanalysis of sorted sperm for DNA content, and embryo biopsy for sex determination. Currently, the sex of animals has been predetermined with 90 % accuracy by sexing spermatozoa. In the bovine breeding industry, flow cytometric sperm sexing has not fulfilled its original promise. Sexed sperm doses are too expensive for widespread application while the fertility of sexed sperm doses is lower than unsexed ones. Essentially all bovine sexed semen is frozen and then applied through artificial insemination (AI) or in vitro fertilization. There is still a need in the animal breeding industry to develop a technique for sperm sexing that provides sufficient spermatozoa for AI doses, does not compromise sperm fertility, and is widely applicable to a range of species. In this review, we will summarize the current state-of-the-art in sex preselection in domestic animals and some wildlife species using flow cytometric sperm-sorting of X from Y sperm based on DNA differences. PMID:22829354

Espinosa-Cervantes, Román; Córdova-Izquierdo, Alejandro

2012-12-01

446

Nonvolitional sex and sexual health.  

PubMed

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 behavior that masks one's nonconventional sexual identity, or that protects one's position with peers, or that represents a quid pro quo for the economic support that one obtains within an intimate relationship. The aim of this essay is to highlight the ways in which nonvolitional sex threatens sexual health and to identify strategies for ameliorating this problem. These strategies will have to be as broad in scope as is the problem that they are designed to address. The essay discusses the following strategies to reduce nonvolitional sex: (1) advocacy for sexual rights, gender equality, and equality for individuals with nonconventional sexual identities; (2) primary prevention programs and interventions that offer comprehensive sexuality education that establishes volitional sex and sexual health as basic human rights; (3) health services that routinely ask clients about their experiences with nonvolitional sex in an open and culturally appropriate manner; and (4) secondary prevention programs to meet the needs of victims of nonvolitional sex identified by the "screening" programs. PMID:15129039

Kalmuss, Debra

2004-06-01

447

Gigahertz self-referenceable frequency comb from a semiconductor disk laser.  

PubMed

We present a 1.75-GHz self-referenceable frequency comb from a vertical external-cavity surface-emitting laser (VECSEL) passively modelocked with a semiconductor saturable absorber mirror (SESAM). The VECSEL delivers 231-fs pulses with an average power of 100 mW and is optimized for stable and reliable operation. The optical spectrum was centered around 1038 nm and nearly transform-limited with a full width half maximum (FWHM) bandwidth of 5.5 nm. The pulses were first amplified to an average power of 5.5 W using a backward-pumped Yb-doped double-clad large mode area (LMA) fiber and then compressed to 85 fs with 2.2 W of average power with a passive LMA fiber and transmission gratings. Subsequently, we launched the pulses into a highly nonlinear photonic crystal fiber (PCF) and generated a coherent octave-spanning supercontinuum (SC). We then detected the carrier-envelope offset (CEO) frequency (fCEO) beat note using a standard f-to-2f-interferometer. The fCEO exhibits a signal-to-noise ratio of 17 dB in a 100-kHz resolution bandwidth and a FWHM of ?10 MHz. To our knowledge, this is the first report on the detection of the fCEO from a semiconductor laser, opening the door to fully stabilized compact frequency combs based on modelocked semiconductor disk lasers. PMID:24977894

Zaugg, Christian A; Klenner, Alexander; Mangold, Mario; Mayer, Aline S; Link, Sandro M; Emaury, Florian; Golling, Matthias; Gini, Emilio; Saraceno, Clara J; Tilma, Bauke W; Keller, Ursula

2014-06-30

448

A charge optimized many-body (comb) potential for titanium and titania.  

PubMed

This work proposes an empirical, variable charge potential for Ti and TiO2 systems based on the charge-optimized many-body (COMB) potential framework. The parameters of the potential function are fit to the structural and mechanical properties of the Ti hcp phase, the TiO2 rutile phase, and the energetics of polymorphs of both Ti and TiO2. The relative stabilities of TiO2 rutile surfaces are predicted and compared to the results of density functional theory (DFT) and empirical potential calculations. The transferability of the developed potential is demonstrated by determining the adsorption energy of Cu clusters of various sizes on the rutile TiO2(1?1?0) surface using molecular dynamics simulations. The results indicate that the adsorption energy is dependent on the number of Cu-Cu bonds and Cu-O bonds formed at the Cu/TiO2 interface. The adsorption energies of Cu clusters on the reduced and oxidized TiO2(1?1?0) surfaces are also investigated, and the COMB potential predicts enhanced bonding between Cu clusters and the oxidized surface, which is consistent with both experimental observations and the results of DFT calculations for other transition metals (Au and Ag) on this oxidized surface. PMID:24943265

Cheng, Yu-Ting; Shan, Tzu-Ray; Liang, Tao; Behera, Rakesh K; Phillpot, Simon R; Sinnott, Susan B

2014-08-01

449

Femtosecond frequency comb measurement of absolute frequencies and hyperfine coupling constants in cesium vapor  

SciTech Connect

We report measurements of absolute transition frequencies and hyperfine coupling constants for the 8S{sub 1/2}, 9S{sub 1/2}, 7D{sub 3/2}, and 7D{sub 5/2} states in {sup 133}Cs vapor. The stepwise excitation through either the 6P{sub 1/2} or 6P{sub 3/2} intermediate state is performed directly with broadband laser light from a stabilized femtosecond laser optical-frequency comb. The laser beam is split, counterpropagated, and focused into a room-temperature Cs vapor cell. The repetition rate of the frequency comb is scanned and we detect the fluorescence on the 7P{sub 1/2,3/2{yields}}6S{sub 1/2} branches of the decay of the excited states. The excitations to the different states are isolated by the introduction of narrow-bandwidth interference filters in the laser beam paths. Using a nonlinear least-squares method we find measurements of transition frequencies and hyperfine coupling constants that are in agreement with other recent measurements for the 8S state and provide improvement by 2 orders of magnitude over previously published results for the 9S and 7D states.

Stalnaker, Jason E. [Department of Physics and Astronomy, Oberlin College, 110 N. Professor St., Oberlin, OH 44074 (United States); Time and Frequency Division, National Institute of Standards and Technology, 325 Broadway MS 847, Boulder, CO 80305 (United States); Mbele, Vela [Time and Frequency Division, National Institute of Standards and Technology, 325 Broadway MS 847, Boulder, CO 80305 (United States) and School of Physics, University of Witwatersrand, Private Bag 3, WITS, 2050, RSA; Gerginov, Vladislav; Fortier, Tara M.; Diddams, Scott A.; Hollberg, Leo [Time and Frequency Division, National Institute of Standards and Technology, 325 Broadway MS 847, Boulder, CO 80305 (United States); Tanner, Carol E. [Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556-5670 (United States)

2010-04-15

450

Optical Comb from a Whispering Gallery Mode Resonator for Spectroscopy and Astronomy Instruments Calibration  

NASA Technical Reports Server (NTRS)

The most accurate astronomical data is available from space-based observations that are not impeded by the Earth's atmosphere. Such measurements may require spectral samples taken as long as decades apart, with the 1 cm/s velocity precision integrated over a broad wavelength range. This raises the requirements specifically for instruments used in astrophysics research missions -- their stringent wavelength resolution and accuracy must be maintained over years and possibly decades. Therefore, a stable and broadband optical calibration technique compatible with spaceflights becomes essential. The space-based spectroscopic instruments need to be calibrated in situ, which puts forth specific requirements to the calibration sources, mainly concerned with their mass, power consumption, and reliability. A high-precision, high-resolution reference wavelength comb source for astronomical and astrophysics spectroscopic observations has been developed that is deployable in space. The optical comb will be used for wavelength calibrations of spectrographs and will enable Doppler measurements to better than 10 cm/s precision, one hundred times better than the current state-of-the- art.

Strekalov, Dmitry V.; Yu, Nam; Thompson, Robert J.

2012-01-01

451

Shaping calcite crystals by means of comb polyelectrolytes having neutral hydrophilic teeth.  

PubMed

Comb polyelectrolytes (CPs) having neutral hydrophilic teeth, similar to double hydrophilic block copolymers, are a powerful tool to modify the chemical-physical properties of inorganic crystalline materials. One of their main applications is in concrete technology, where they work as superplasticizers, particle-dispersing agents. Here, CPs, having the same poly(acrylic acid) (PAA) backbone chain and differing in the grafting with methoxy poly(ethylene glycol) chains (MPEG) of two molecular weights, were used to investigate the influence of tooth chains in polymer aggregation and in control on morphology and aggregation of calcite particles. These polymers aggregate, forming interpolymer hydrogen bonds between carboxylic groups and ether oxygen functionalities. The presence of calcium ions in solution further enhances aggregation. Crystallization experiments of calcite in the presence of CPs show that the specificity of interactions between polymers and crystal planes and control on aggregation and size of particles is a function of the content and chain length of the MPEG in the PAA backbone. These parameters limit and can make specific the electrostatic interactions with ionic crystalline planes. Moreover, the mechanism of crystallization, classical or nonclassical, is addressed by the CP structure and concentration. These findings have implications in the understanding of the complex chemical processes associated to concrete superplasticizers action and in the study of the biomineralization processes, where biological comb polyelectrolytes, the acidic glycoproteins, govern formation of calcitic structures. PMID:23320460

Malferrari, Danilo; Fermani, Simona; Galletti, Paola; Goisis, Marco; Tagliavini, Emilio; Falini, Giuseppe

2013-02-12

452

Extremely high-accuracy correction of air refractive index using two-colour optical frequency combs  

PubMed Central

Optical frequency combs have become an essential tool for distance metrology, showing great advantages compared with traditional laser interferometry. However, there is not yet an appropriate method for air refractive index correction to ensure the high performance of such techniques when they are applied in air. In this study, we developed a novel heterodyne interferometry technique based on two-colour frequency combs for air refractive index correction. In continuous 500-second tests, a stability of 1.0 × 10?11 was achieved in the measurement of the difference in the optical distance between two wavelengths. Furthermore, the measurement results and the calculations are in nearly perfect agreement, with a standard deviation of 3.8 × 10?11 throughout the 10-hour period. The final two-colour correction of the refractive index of air over a path length of 61 m was demonstrated to exhibit an uncertainty better than 1.4 × 10?8, which is the best result ever reported without precise knowledge of environmental parameters.

Wu, Guanhao; Takahashi, Mayumi; Arai, Kaoru; Inaba, Hajime; Minoshima, Kaoru

2013-01-01

453

Finite Element Analysis of the Vertical Levitation Force in an Electrostatic MEMS Comb Drive Actuator  

NASA Astrophysics Data System (ADS)

A vertical levitation electrostatic comb drive actuator was manufactured for the purpose of measuring piezoelectric coefficients in small-scale materials and devices. Previous modelling work on comb drive levitation has focussed on control of the levitation in standard poly-silicon devices in order to minimize effects on lateral modes of operation required for the accelerometer and gyroscope applications. The actuator developed in this study was manufactured using a 20 ?m electroplated Ni process with a 25 ?m trench created beneath the released structure through chemical wet etching. A finite element analysis using ZINC was used to model electrostatic potential around a cross section of one static and one movable electrode, from which the net levitation force per unit electrode was calculated. The model was first verified using the electrode geometry from previously studied systems, and then used to study the variation of force as a function of decreasing substrate-electrode distance. With the top electrode surfaces collinear the calculated force density is 0.00651 epsilon0V2M?m-1, equivalent to a total force for the device of 36.4 ?N at an applied voltage of VM=100 V, just 16% larger than the observed value. The measured increase in force with distance was smaller than predicted with the FEA, due to the geometry of the device in which the electrodes at the anchored ends of the supporting spring structure displace by a smaller amount than those at the centre.

Wooldridge, J.; Blackburn, J.; Muniz-Piniella, A.; Stewart, M.; Shean, T. A. V.; Weaver, P. M.; Cain, M. G.

2013-11-01

454

Rotary MEMS comb-drive actuator with large deflection for photonic applications  

NASA Astrophysics Data System (ADS)

Rotary comb-drive electrostatic actuators with smooth vertical sidewalls were designed and fabricated for photonic applications. Silicon on insulator (SOI) wafers with device layer thicknesses of up to 100 ?m and oxide layers of 1-2 ?m were used. Structures were fabricated through bulk micromachining of the handle layer followed by removal of the buried oxide. Deep reactive ion etching (DRIE) of the device layer defined the comb structure with simultaneous release of the moving arm. Thick photoresist and oxide masking layers were used for the high aspect ratio deep etches. Notching effects or depth variations of device layers were not observed. Etch/ passivation cycles in DRIE were optimized to obtain smooth sidewalls. Traces of etch scallops were confined only to the first few microns of the top and bottom edges of the reflecting sidewall. A movable arm length of 2 mm with a maximum rotation of 2.8 degrees was achieved. The edge deflection was over 100 ?m at 100 volts. The fabricated structure provides a long reflecting sidewall that is accessible for hybrid integration in three dimensional space. The fabricated structures can be reliably operated in the kilohertz range.

Huda, M. Q.; Amin, T. M. F.; Ning, Y.; McKinnon, G.; Tulip, J.; Jäger, W.

2012-02-01

455

Global phase and frequency comb structures in nonlinear Compton and Thomson scattering  

NASA Astrophysics Data System (ADS)

The Compton and Thomson radiation spectra generated in collisions of an electron beam with a powerful laser beam are studied in the framework of quantum and classical electrodynamics, respectively. We show that there are frequency regimes where both radiation spectra are nearly identical, which for Compton scattering relates to the process which preserves the electron spin. Although the radiation spectra are nearly identical, the corresponding probability amplitudes exhibit different global phases. This has pronounced consequences, which we demonstrate by investigating temporal power distributions in both cases. We show that, contrary to Thomson scattering, it is not always possible to synthesize short laser pulses from Compton radiation. This happens when the global phase of the Compton amplitude varies in a nonlinear way with the frequency of emitted photons. We also demonstrate that, while the Compton process driven by a nonchirped laser pulse can generate chirped bursts of radiation, this is not the case for the Thomson process. In principle, both processes can lead to a generation of coherent frequency combs when single or multiple driving laser pulse collide with electrons. Once we synthesize these combs into short bursts of radiation, we can control them, for instance, by changing the time delay between the driving pulses.

Krajewska, K.; Twardy, M.; Kami?ski, J. Z.

2014-05-01

456

Self-referenceable frequency comb from an ultrafast thin disk laser.  

PubMed

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

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

457

Quantum Information Processing with Ytterbium Ions and a Frequency Comb in a Surface Trap  

NASA Astrophysics Data System (ADS)

Microfabricated surface ion traps are one of the key components for building a trapped ion quantum information processor.These multi-segmented traps are fabricated using existing silicon processing technology and can provide the fields to store a chain of ions and shuttle ions within the trap structure. Using a surface trap microfabricated by Sandia National Laboratories [1] we trap individual Yb-171 ions and demonstrate fundamental quantum information processing primitives. Low light scatter from the trap and the use of photon arrival times during fluorescence state detection enables a state detection fidelity of 98%. High fidelity rotations of the hyperfine clock state qubit have been performed using a resonant microwave field. Furthermore, we have realized single qubit rotations using Raman transitions driven by a repetition-rate stabilized frequency comb, a prerequisite for realizing motional gates with frequency combs [2]. Microelectromechanical systems (MEMS) mirrors will be used to focus Raman laser beams on individual ions in a chain to perform single qubit gates. MEMS beam steering systems can easily be scaled to multiple beams to realize two-ion gates between arbitrary ions in the chain.[4pt] [1] D Stick et al., arXiv:1008.0990v2 2010[0pt] [2] D Hayes et al., PRL 104(14)2010

Mount, Emily; Baek, So-Young; Gaultney, Daniel; Crain, Stephen; Noek, Rachel; Maunz, Peter; Kim, Jungsang

2012-06-01

458

Sex Typing and the Avoidance of Cross-Sex Behavior  

Microsoft Academic Search

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

Sandra L. Bem; Ellen Lenney

1976-01-01

459

Schizophrenia: sex differences.  

PubMed

This paper reports epidemiological findings which support the hypothesis that the influence of gender on schizophrenia is a significant, transcultural phenomenon. Male/female differences in the illness are discussed with particular attention to age of onset, chronicity and prodromal personality characteristics. Evidence is presented indicating additional male/female contrasts in the incidence of birth complications, seasonality of birth, and birth order. The author refers to cognitive as well as neurobiological differences between the sexes in the general population which can elucidate differences in the nature and expression of schizophrenia. PMID:3896453

Flor-Henry, P

1985-08-01

460

Sex differentials in health.  

PubMed

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

Verbrugge, L M

1982-01-01

461

Why Sex is Good  

NSDL National Science Digital Library

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.

Herreid, Clyde F.