These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Drosophila sex combs as a model of evolutionary innovations.  

PubMed

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

Kopp, Artyom

2011-01-01

2

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

PubMed

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

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

2014-09-30

3

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

PubMed Central

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

Malagon, Juan N.; Ahuja, Abha; Sivapatham, Gabilan; Hung, Julian; Lee, Jiwon; Munoz-Gomez, Sergio A.; Atallah, Joel; Singh, Rama S.; Larsen, Ellen

2014-01-01

4

Genetic basis of a violation of Dollo's Law: re-evolution of rotating sex combs in Drosophila bipectinata.  

PubMed

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. PMID:23086218

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

2012-12-01

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. PMID:23086218

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  

E-print Network

in Drosophila melanogaster Abha Ahuja · Scott De Vito · Rama S. Singh Received: 5 August 2010 / Accepted: 23 was manipulated in a set of ten Drosophila melanogaster full- sib families. We confirmed heightened condition. Keywords Condition dependence Á Drosophila melanogaster Á Sex comb Á Condition Á Genetic variation

Alwes, Frederike

7

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. PMID:15280237

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

8

The Homeotic Gene Sex Combs Reduced of Drosophila Melanogaster Is Differentially Regulated in the Embryonic and Imaginal Stages of Development  

PubMed Central

The Sex combs reduced (Scr) locus is unique among the genes contained within the Antennapedia complex (ANT-C) of Drosophila melanogaster in that it directs functions that are required for both cephalic and thoracic development in the embryo and the adult. Antibodies raised against protein encoded by Scr were used to follow the distribution of this gene product in embryos and imaginal discs of third instar larvae. Analysis of Scr protein accumulation in embryos hemizygous for breakpoint lesions mapping throughout the locus has allowed us to determine that sequences required for establishment of the Scr embryonic pattern are contained within a region of DNA that overlaps with the identified upstream regulatory region of the segmentation gene fushi tarazu (ftz). Gain-of-function mutations in Scr result in the presence of ectopic sex comb teeth on the first tarsal segment of mesothoracic and metathoracic legs of adult males. Heterozygous combinations of gain-of-function alleles with a wild-type Scr gene exhibit no evidence of ectopic protein localization in the second and third thoracic segments of embryos. However, mesothoracic and metathoracic leg imaginal discs can be shown to accumulate ectopically expressed Scr protein, implying a differential regulation of the Scr gene during these two periods of development. Additionally, we have found that the spatial pattern of Scr gene expression in imaginal tissues involved in the development of the adult thorax is governed in part by synapsis of homologous chromosomes in this region of the ANT-C. However, those imaginal discs that arise anteriorly to the prothorax do not appear to be sensitive to this form of gene regulation. Finally, we have demonstrated that the extent of Scr expression is influenced by mutations at the Polycomb (Pc) locus but not by mutant alleles of the zeste (z) gene. Taken together, our data suggests that Scr gene expression is differentially regulated both temporally and spatially in a manner that is sensitive to the structure of the locus. PMID:1683847

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

1991-01-01

9

Additional Sex Comb-like (ASXL) Proteins 1 and 2 Play Opposite Roles in Adipogenesis via Reciprocal Regulation of Peroxisome Proliferator-activated Receptor ?*  

PubMed Central

Our previous studies have suggested that the mammalian additional sex comb-like 1 protein functions as a coactivator or repressor of retinoic acid receptors in a cell-specific manner. Here, we investigated the roles of additional sex comb-like 1 proteins in regulating peroxisome proliferator-activated receptors (PPARs). In pulldown assays in vitro and in immunoprecipitation assays in vivo, ASXL1 and its paralog, ASXL2, interacted with PPAR? and PPAR?. In 3T3-L1 preadipocyte cells, overexpression of ASXL1 inhibited the induction of PPAR? activity by rosiglitazone, as shown by transcription assays, and completely suppressed adipogenesis, as shown by Oil Red O staining. In contrast, overexpression of ASXL2 greatly enhanced rosiglitazone-induced PPAR? activity and enhanced adipogenesis. Deletion of the heterochromatin protein 1 (HP1)-binding domain from ASXL1 caused the mutant protein to enhance adipogenesis similarly to ASXL2, indicating that HP1 binding is required for the adipogenesis-suppressing activity of ASXL1. Adipocyte differentiation was associated with a gradual decrease in ASXL1 expression but did not affect ASXL2 expression. Knockdown of ASXL1 and ASXL2 had reciprocal effects on adipogenesis. In chromatin immunoprecipitation assays in 3T3-L1 cells, ASXL1 occupied the promoter of the PPAR? target gene aP2 together with HP1? and Lys-9-methylated histone H3, whereas ASXL2 occupied the aP2 promoter together with histone-lysine N-methyltransferase MLL1 and Lys-9-acetylated and Lys-4-methylated H3 histones. Finally, microarray analysis demonstrated that ASXL1 represses, whereas ASXL2 increases, the expression of adipogenic genes, most of which are PPAR? targets. These results suggest that members of the additional sex comb-like family provide complex regulation of adipogenesis via differential modulation of PPAR? activity. PMID:21047783

Park, Ui-Hyun; Yoon, Seung Kew; Park, Taesun; Kim, Eun-Joo; Um, Soo-Jong

2011-01-01

10

Cantor's Comb  

NSDL National Science Digital Library

In this activity, students enter in a fraction to be removed from the center of line segments creating what is called Cantorâs Comb. This activity allows students to explore sequences and the idea of limit. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2010-01-01

11

Frequency comb swept lasers  

E-print Network

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 ...

Tsai, Tsung-Han

12

Brownian excursions on combs  

SciTech Connect

In this paper the authors use techniques from Ito excursion theory to analyze Brownian motion on generalized combs. Ito excursion theory is a little-known area of probability theory and we therefore present a brief introduction for the uninitiated. A general method for analyzing transport along the backbone of the comb is demonstrated and the specific case of a comb whose teeth are scalling branching trees is examined. We then present a recursive method for evaluating the distribution of the first passage times on hierarchical combs.

Dean, D.S. (Cambridge Univ. (United Kingdom)); Jansons, K.M. (Univ. College London (United Kingdom))

1993-03-01

13

STATIC ELECTRICITY Plastic combs  

E-print Network

. You may use a variety of materials to try to "charge" the comb or balloon--paper towels, paper, blueSTATIC ELECTRICITY Materials · Plastic combs · Balloons · Thread · Scissors · Cheerios · Paper of Cheerios on a paper plate. 2. Take the plastic lid and rub it against whatever is available (hair, fleece

Benitez-Nelson, Claudia

14

Mössbauer spectral study of the magnetocaloric FeMnP1-xAsx compounds  

Microsoft Academic Search

The magnetic phase transitions in the FeMnP1-xAsx compounds with x= 0.25, 0.35, 0.45, 0.50, and 0.55, have been studied by iron-57 Mössbauer spectroscopy. The ferromagnetic and antiferromagnetic spectra have been analyzed with a model that takes into account the random distribution of the P and As near-neighbor anions of a given iron site. This distribution is a binomial distribution of

Raphaël P. Hermann; O. Tegus; E. H. Brück; K. H. J. Buschow; F. R. de Boer; Gary J. Long; Fernande Grandjean

2004-01-01

15

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

16

Alcuin's “comb” riddle  

Microsoft Academic Search

The presentation of a de luxe comb of elephant ivory by Archbishop Riculf of Mainz to his friend Alcuin of York in c. 794 provided the occasion for two replies, one in a prose letter and the other in a verse epistle, in which Riculf's gift is playfully transformed into the subject of a descriptive riddle. This pair of short

Paul Sorrell

1996-01-01

17

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

18

Squeezing frequency combs  

E-print Network

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

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

2006-05-15

19

Butelase 1 is an Asx-specific ligase enabling peptide macrocyclization and synthesis.  

PubMed

Proteases are ubiquitous in nature, whereas naturally occurring peptide ligases, enzymes catalyzing the reverse reactions of proteases, are rare occurrences. Here we describe the discovery of butelase 1, to our knowledge the first asparagine/aspartate (Asx) peptide ligase to be reported. This highly efficient enzyme was isolated from Clitoria ternatea, a cyclic peptide-producing medicinal plant. Butelase 1 shares 71% sequence identity and the same catalytic triad with legumain proteases but does not hydrolyze the protease substrate of legumain. Instead, butelase 1 cyclizes various peptides of plant and animal origin with yields greater than 95%. With Kcat values of up to 17 s(-1) and catalytic efficiencies as high as 542,000 M(-1) s(-1), butelase 1 is the fastest peptide ligase known. Notably, butelase 1 also displays broad specificity for the N-terminal amino acids of the peptide substrate, thus providing a new tool for C terminus-specific intermolecular peptide ligations. PMID:25038786

Nguyen, Giang K T; Wang, Shujing; Qiu, Yibo; Hemu, Xinya; Lian, Yilong; Tam, James P

2014-09-01

20

Coherent frequency combs and spectroscopy  

Microsoft Academic Search

Optical frequency combs possessing precise phase coherence across the entire visible spectrum have profoundly changed optical frequency metrology and ultrafast science, with breakthrough developments in optical atomic clocks, optical frequency synthesis, direct frequency comb spectroscopy (DFCS), high-resolution quantum control, coherent pulse synthesis and amplification, and control of sub-femtosecond electron dynamics in atoms and molecules. DFCS [1] is a new spectroscopic

Jun Ye

2010-01-01

21

Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 9×1020 cm-3. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 3×1019 cm-3 and mobilities of ~1 cm2/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

Novikov, S. V.; Ting, M.; Yu, K. M.; Sarney, W. L.; Martin, R. W.; Svensson, S. P.; Walukiewicz, W.; Foxon, C. T.

2014-10-01

22

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

23

Monolayer abruptness in highly strained InAsxP1?x\\/InP quantum well interfaces  

Microsoft Academic Search

InAsxP1?x\\/InP strained quantum well structures have been prepared by atmospheric-pressure organometallic vapor phase epitaxy (OMVPE). Structures with compositions of x=0.40–0.67 and quantum well thicknesses of 0.8–16 nm were evaluated using photoluminescence spectroscopy. Strain in the pseudomorphic wells ranged from 1.3 to 2.1%. Doublets and multiplets are observed in the photoluminescence spectra and are attributed to luminescence from regions in the

R. P. Schneider; B. W. Wessels

1989-01-01

24

Band-Selective Infrared Photodetectors with Complete-Composition-Range InAsx P1-x Alloy Nanowires.  

PubMed

Band-selective infrared photodetectors (PDs) are constructed with InAsx P1-x alloy nanowires from the complete composition range (0 ? x ? 1) achieved by a new growth route combining the vapor-liquid-solid mechanism with an additional ion-exchange process. Increasing the composition x value from 0 to 1 in the PDs allows the peak response wavelength to be gradually tuned from ca. 900 to ca. 2900 nm. PMID:25257177

Ren, Pinyun; Hu, Wei; Zhang, Qinglin; Zhu, Xiaoli; Zhuang, Xiujuan; Ma, Liang; Fan, Xiaopeng; Zhou, Hong; Liao, Lei; Duan, Xiangfeng; Pan, Anlian

2014-11-01

25

Scaling combs into the XUV  

NASA Astrophysics Data System (ADS)

Scientists have transferred coherence from a near-infrared frequency comb laser to the extreme-ultraviolet region with no detectable noise. Jun Ye and co-workers explain that this might impact fields from fundamental physics to nuclear clocks.

2014-07-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

27

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

28

[The skull of Combe Capelle].  

PubMed

Since the end of World War II two of the most important anthropological artefacts of the Museum für Vor- und Frühgeschichte in Berlin, the skulls and skeletons of Le Moustier and Combe Capelle, were believed to be missing or destroyed, respectively. The postcrania were severely damaged during a fire after the museum was bombed in February 1945, while the skulls were brought to the Soviet Union in 1945. In 1965, the skull of the Neanderthal man from Le Moustier and the chain of the grave of Combe Capelle were found amongst the art objects returned by the Soviet Union into the German Democratic Republic in 1958. However, the Combe Capelle skull was still missing. In the end of 2001 this skull could be found and identified in a store-house of the museum. Now, one the oldest known representatives of Homo sapiens sapiens is again available for scientific research and public exhibitions. PMID:12529957

Hoffmann, Almut; Wegner, Dietrich

2002-12-01

29

An Interview with Arthur W. Combs.  

ERIC Educational Resources Information Center

Presents biographical summary of Arthur Combs, well known for his perceptual point of view to earlier generation of humanistic educators, counselors, and psychologists. Discusses Combs's background, placing emphasis on academic career. Interview focuses on Combs's entry into humanistic education, his implementation of teacher education program…

Dolliver, Robert H.; Patterson, David C.

1994-01-01

30

Optical properties of thin, strained layers of GaAsxP1-x grown on (111)-oriented GaP  

NASA Astrophysics Data System (ADS)

Thin, perfectly strained quantum wells of indirect band gap GaAsxP1-x between GaP on (111)B-oriented substrates have been grown by metal-organic vapor phase epitaxy. The layers were characterized by low-temperature photoluminescence and by electroreflectance. The evolution of the transition energies of the X and ? conduction-band minima to the valence-band maxima was investigated, as a function of arsenic concentration up to 36% arsenic and compared to a model that treats strain as well as quantum confinement effects. Since the samples are grown in the [111] direction, strain-induced piezoelectric fields are expected to be present. The influence of this field on the experimental transition energies is discussed. Evidence of the ionization of neutral donors by the piezoelectric field is presented. The layers are concluded to be type I. The photoluminescence emission is very similar to bulk GaAsxP1-x and includes the Mx0 emission.

Gerling, M.; Paulsson, G.; Pistol, M.-E.; Samuelson, L.

1993-03-01

31

Material properties and modeling characteristics for MnFeP1-xAsx materials for application in magnetic refrigeration  

NASA Astrophysics Data System (ADS)

Compounds of MnFeP1-xAsx have received attention recently for their use in active magnetic regenerators (AMR) because of their relatively high isothermal entropy change and adiabatic temperature change with magnetization. However, the materials also generally exhibit a significant magnetic and thermal hysteresis, and it is not well understood how the hysteresis will affect performance in a practical AMR device. The amount of hysteresis shown by a material can be controlled to an extent by tuning the processing conditions used during material synthesis; therefore, knowledge of the practical impact of hysteresis is a key element to guide successful material development and synthesis. The properties of a magnetocaloric MnFeP1-xAsx compound are characterized as a function of temperature and applied magnetic field, and the results are used to assess the effects of hysteresis on magnetocaloric properties. Different methods of building property functions from the measured specific heat, magnetization, and adiabatic temperature change are presented. It is shown that model predictions can be highly dependent on how the properties that are used by the AMR model are calculated.

Engelbrecht, K.; Nielsen, K. K.; Bahl, C. R. H.; Carroll, C. P.; van Asten, D.

2013-05-01

32

Structural and electronic properties of Bi-adsorbate-stabilized reconstructions on the InP(100) and GaAsxN1-x(100) surfaces  

NASA Astrophysics Data System (ADS)

Bismuth (Bi) adsorbate-stabilized reconstructions on the InP(100) and GaAsxN1-x(100) surfaces have been studied by scanning tunneling microscopy (STM) and spectroscopy (STS), x-ray photoelectron spectroscopy, and low-energy electron diffraction. With decreasing coverage, Bi is found to stabilize the (2×1) , (2×8) , and (2×4) reconstructions on the InP(100) surface and the (2×1) and (2×4) reconstructions on the GaAsxN1-x(100) . STM results show that both the Bi/InP(100)(2×4) and Bi/GaAsxN1-x(100)(2×4) reconstructions can be described with the ?2 -like structural model. The current-voltage curves measured by STS show the Bi/InP(100)(2×1) and Bi/GaAsxN1-x(100)(2×1) structures, which do not obey the electron counting model, to be semiconducting and metallic, respectively. Combining our experimental findings, we propose atomic models for the (2×1) reconstructions. An issue why Bi stabilizes unusual (2×1) structures is discussed.

Laukkanen, P.; Pakarinen, J.; Ahola-Tuomi, M.; Kuzmin, M.; Perälä, R. E.; Väyrynen, I. J.; Tukiainen, A.; Konttinen, J.; Tuomisto, P.; Pessa, M.

2006-10-01

33

Red, Green, and Blue Astro-combs  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

34

Combs and sexual selection in black grouse (Tetrao tetrix)  

Microsoft Academic Search

We studied supra-orbital combs in lekking black grouse (Tetrao tetrix) in relation to sexual selection at five leks in Finland 1991- 1998 and four leks in Sweden 1992-1995. Comb size was estimated in two ways: by observing its natural size in the field at different behaviors (''observed comb size''), and by measuring the comb size from captured birds (''measured comb

Pekka T. Rintamaki; Rauno V. Alatalo; Osmo Ratti

2000-01-01

35

Coherent frequency combs and spectroscopy  

NASA Astrophysics Data System (ADS)

Optical frequency combs maintain precise phase coherence across the entire visible spectrum and they have profoundly changed optical frequency metrology and ultrafast science, with breakthrough developments in optical atomic clocks, optical frequency synthesis, direct frequency comb spectroscopy (DFCS), high-resolution quantum control, coherent pulse synthesis and amplification, and control of sub-femtosecond electron dynamics in atoms and molecules. DFCS [1] is a new spectroscopic approach that realizes simultaneously broad spectral coverage, high spectral resolution, many parallel detection channels, ultrahigh sensitivity, and real-time analysis [2]. These powerful capabilities have been demonstrated in a series of experiments where identification and quantification of many different molecular states or species are achieved in a massively parallel fashion [3].[4pt] [1] A. Marian et al., Science 306, 2063 (2004). [0pt] [2] M. J. Thorpe et al., Science 311, 1595 (2006). [0pt] [3] M. J. Thorpe & J. Ye, Appl. Phys. B 91, 397 (2008).

Ye, Jun

2010-03-01

36

Coherent frequency combs and spectroscopy  

NASA Astrophysics Data System (ADS)

Optical frequency combs possessing precise phase coherence across the entire visible spectrum have profoundly changed optical frequency metrology and ultrafast science, with breakthrough developments in optical atomic clocks, optical frequency synthesis, direct frequency comb spectroscopy (DFCS), high-resolution quantum control, coherent pulse synthesis and amplification, and control of sub-femtosecond electron dynamics in atoms and molecules. DFCS [1] is a new spectroscopic approach that embraces simultaneously broad spectral coverage, fine spectral resolution, numerous detection channels, ultrahigh sensitivity, and real-time analysis [2]. These powerful capabilities have been demonstrated in a series of experiments where identification and quantification of many different molecular states or species are achieved in a massively parallel fashion [3]. A range of interesting scientific applications will be discussed. [4pt] [1] A. Marian et al., Science 306, 2063 (2004). [0pt] [2] M. J. Thorpe et al., Science 311, 1595 (2006). [0pt] [3] M. J. Thorpe & J. Ye, Appl. Phys. B 91, 397 (2008).

Ye, Jun

2010-03-01

37

Extreme ultraviolet frequency comb metrology.  

PubMed

The remarkable precision of frequency-comb (FC) lasers is transferred to the extreme ultraviolet (XUV, wavelengths shorter than 100 nm), a frequency region previously not accessible to these devices. A frequency comb at XUV wavelengths near 51 nm is generated by amplification and coherent up-conversion of a pair of pulses originating from a near-infrared femtosecond FC laser. The phase coherence of the source in the XUV is demonstrated using helium atoms as a ruler and phase detector. Signals in the form of stable Ramsey-like fringes with high contrast are observed when the FC laser is scanned over P states of helium, from which the absolute transition frequency in the XUV can be extracted. This procedure yields a (4)He ionization energy at h×5?945?204?212(6)??MHz, improved by nearly an order of magnitude in accuracy, thus challenging QED calculations of this two-electron system. PMID:20867977

Kandula, Dominik Z; Gohle, Christoph; Pinkert, Tjeerd J; Ubachs, Wim; Eikema, Kjeld S E

2010-08-01

38

Spatial patterns in the brood combs of Nannotrigona testaceicornis (Hymenoptera: Meliponinae): male clusters  

Microsoft Academic Search

Genetic models of sex and caste determination in euso- cial stingless bees suggest specific patterns of male, worker and gyne cell distribution in the brood comb. Conflict between queen and laying workers over male parentage and center-periphery gradients of condi- tions, such as food and temperature, could also contribute to non-ran- dom spatial configuration. We converted the positions of the

A. Eterovic; G. C. P. Cabral; A. A. Oliveira; V. L. Imperatriz-Fonseca; P. S. Santos-Filho

2009-01-01

39

Femtosecond laser comb based subterahertz synthesizer  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

40

Bichromatically pumped microresonator frequency combs  

NASA Astrophysics Data System (ADS)

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

Hansson, T.; Wabnitz, S.

2014-07-01

41

Sonic Hedgehog-Signalling Patterns the Developing Chicken Comb as Revealed by Exploration of the Pea-comb Mutation  

PubMed Central

The genetic basis and mechanisms behind the morphological variation observed throughout the animal kingdom is still relatively unknown. In the present work we have focused on the establishment of the chicken comb-morphology by exploring the Pea-comb mutant. The wild-type single-comb is reduced in size and distorted in the Pea-comb mutant. Pea-comb is formed by a lateral expansion of the central comb anlage into three ridges and is caused by a mutation in SOX5, which induces ectopic expression of the SOX5 transcription factor in mesenchyme under the developing comb. Analysis of differential gene expression identified decreased Sonic hedgehog (SHH) receptor expression in Pea-comb mesenchyme. By experimentally blocking SHH with cyclopamine, the wild-type single-comb was transformed into a Pea-comb-like phenotype. The results show that the patterning of the chicken comb is under the control of SHH and suggest that ectopic SOX5 expression in the Pea-comb change the response of mesenchyme to SHH signalling with altered comb morphogenesis as a result. A role for the mesenchyme during comb morphogenesis is further supported by the recent finding that another comb-mutant (Rose-comb), is caused by ectopic expression of a transcription factor in comb mesenchyme. The present study does not only give knowledge about how the chicken comb is formed, it also adds to our understanding how mutations or genetic polymorphisms may contribute to inherited variations in the human face. PMID:23227218

Boije, Henrik; Harun-Or-Rashid, Mohammad; Lee, Yu-Jen; Imsland, Freyja; Bruneau, Nicolas; Vieaud, Agathe; Gourichon, David; Tixier-Boichard, Michele; Bed'hom, Bertrand; Andersson, Leif; Hallbook, Finn

2012-01-01

42

Cavity-enhanced direct frequency comb spectroscopy  

E-print Network

Cavity-enhanced direct frequency comb spectroscopy combines broad spectral bandwidth, high spectral resolution, precise frequency calibration, and ultrahigh detection sensitivity, all in one experimental platform based on an optical frequency comb interacting with a high-finesse optical cavity. Precise control of the optical frequency comb allows highly efficient, coherent coupling of individual comb components with corresponding resonant modes of the high-finesse cavity. The long cavity lifetime dramatically enhances the effective interaction between the light field and intracavity matter, increasing the sensitivity for measurement of optical losses by a factor that is on the order of the cavity finesse. The use of low-dispersion mirrors permits almost the entire spectral bandwidth of the frequency comb to be employed for detection, covering a range of ~10% of the actual optical frequency. The light transmitted from the cavity is spectrally resolved to provide a multitude of detection channels with spectral ...

Thorpe, Michael J

2008-01-01

43

Evolution Of The Band Gaps And Band Edges Of Quaternary Ga1-yInyAsxSb1-x\\/InAs Alloys As A Function of Composition  

Microsoft Academic Search

Using atomistic pseudopotential calculations we study the evolution of: (i) the conduction band edge Ec; (ii) the valence band edge Ev , and (iii) the fundamental band gap of the quaternary Ga1-yInyAsxSb1-x alloy lattice-matched to InAs as a function of the composition (x, y). We find a negative bowing parameter for Ec of the quaternary alloy with respect to the

Rita Magri; Alex Zunger; H. Kroemer

2005-01-01

44

High-power asynchronous midinfrared optical parametric oscillator frequency combs  

E-print Network

, with sufficient powers for dual-comb stand-off spectroscopy. The layout of the system for generating rates of combs. To date, most dual-comb spectroscopy has been conducted in the near-infrared [1 frequencies up to 5 kHz apart. This unique source is fully compatible with midinfrared dual-comb spectroscopy

45

Frequency Comb Generation in Superconducting Resonators  

NASA Astrophysics Data System (ADS)

We have generated frequency combs spanning 0.5 to 20 GHz in superconducting ? /2 resonators at T =3 K . Thin films of niobium-titanium nitride enabled this development due to their low loss, high nonlinearity, low frequency dispersion, and high critical temperature. The combs nucleate as sidebands around multiples of the pump frequency. Selection rules for the allowed frequency emission are calculated using perturbation theory, and the measured spectrum is shown to agree with the theory. Sideband spacing is measured to be accurate to 1 part in 1 08. The sidebands coalesce into a continuous comb structure observed to cover at least several frequency octaves.

Erickson, R. P.; Vissers, M. R.; Sandberg, M.; Jefferts, S. R.; Pappas, D. P.

2014-10-01

46

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

47

Far infrared reflection spectra of InAsxSb1-x (x = 0-0.4) thin films  

NASA Astrophysics Data System (ADS)

A series of InAsxSb1-x ternary thin films (x = 0-0.4) has been studied in a far-infrared reflection experiment over the range of 50-4000 cm-1 at room temperature. The obtained spectra are fitted using a multi-oscillator model. Two types of lattice vibration modes, InSb-like and InAs-like, plus one plasmon mode have been identified in x > 0 samples. The lattice vibration in these ternary alloy films shows a typical two-mode behavior. Within the studied fraction range, the InSb transverse-optical (TO) phonon frequency decreases with x, while the InAs TO frequency increases. A random-element-isodisplacement model has been employed to describe the phonon frequency changes. The fitted plasmon parameters have been used to extract the carrier concentrations and mobility. The carrier concentration increases monotonously with the increase of As fraction and is attributed to the bandgap narrowing effect. The mobility decreases with x, indicating an increased scattering.

Huang, L.; Li, Z. F.; Chen, P. P.; Zhang, Y. H.; Lu, W.

2013-06-01

48

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

NASA Technical Reports Server (NTRS)

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

Donaldson, C. H.

1977-01-01

49

Direct Frequency Comb Spectroscopy of Alkali Atoms  

NASA Astrophysics Data System (ADS)

We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Pradhananga, Trinity; Palm, Christopher; Nguyen, Khoa; Guttikonda, Srikanth; Kimball, Derek Jackson

2011-11-01

50

Gapless dual-comb spectroscopy in terahertz region  

E-print Network

We demonstrated combination of gapless terahertz (THz) comb with dual-comb spectroscopy, namely gapless dual-THz-comb spectroscopy, to achieve the spectral resolution equal to width of the THz comb tooth. The gapless THz comb was realized by interpolating frequency gaps between the comb teeth with sweeping of a laser mode-locked frequency. The demonstration of low-pressure gas spectroscopy with gapless dual-THz-comb spectroscopy clearly indicated that the spectral resolution was decreased down to 2.5-MHz width of the comb tooth and the spectral accuracy was enhanced to 10-6 within the spectral range of 1THz. The proposed method will be a powerful tool to simultaneously achieve high resolution, high accuracy, and broad spectral coverage in THz spectroscopy.

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

2014-01-01

51

Frequency comb swept lasers for optical coherence tomography  

E-print Network

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 ...

Tsai, Tsung-Han

52

Engineered slot-comb photonic crystal waveguides  

NASA Astrophysics Data System (ADS)

We report experimental measurements of slow light in Comb Photonic Crystal Waveguides (CPCW). The tailoring of the slot into a comb allows performing dispersion engineering in order to achieve slow light regime, and efficient tapers allow a high coupling efficiency. We also investigate the losses with cut-back measurements and show that losses are comparable with those of a standard W1 Photonic Crystal Waveguide, whereas the nonlinear effective area is strongly reduced. This type of waveguide offers opportunities to realize compact devices with an ultra-high light confinement for achieving optical nonlinearities with a low index material.

Caer, Charles; Le Roux, Xavier; Cassan, Eric

2012-11-01

53

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

54

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. PMID:24448604

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

2014-01-01

55

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

56

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

NASA Astrophysics Data System (ADS)

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

57

Kinetics of phase transitions in vitreous chalcogenide semiconductors AsxSe100m-x-yBiy as studied by the differential thermal analysis and exoelectron emission methods  

NASA Astrophysics Data System (ADS)

Kinetics of glass transition (retrification) in chalcogenide semiconductors AsxSe100-x-yBy (x = 20 or 30, and y = 0 and 1) has been investigated by parallel differential thermal analysis (DTA) and exoelectron emission (EEE) measurements. EEE is a surface effect accompanying the structural transformations in the surface layer, whereas the DTA technique gives information about the transformations occurring in the volume of the sample. Temperature dependencies of the DTA signal and of the EEE intensity have been determined and the values of the activation energy for both the volume and the surface retrification have been determined by the Ozawa method for each of the four investigated materials. It has been found that addition of Bi into the vitreous AsxSe100-x glass changes distinctly the kinetics of both the surface and volume retrification. Addition of Bi causes a distinct decrease in the value of the activation energy for retrification process in both the surface layer and in the volume, i.e. reduces the thermal stability of investigated materials.

Górecki, Cz; Górecki, T.

2011-04-01

58

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

59

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

60

Microresonator-Based Optical Frequency Combs  

E-print Network

the performance of their microwave counterparts by more than an order of magnitude (4). This development involves from the radio frequency (RF) to optical domain on a chip. Principles of Frequency Combs with respect to the car- rier phase from pulse to pulse (Fig. 1A inset), lead- ing to a global offset

61

Combe d'Arc Cave Paintings  

NSDL National Science Digital Library

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

62

[The effect of the husbandry system on comb size and comb color in hens].  

PubMed

The comb size and comb colour of 84 hens (white and brown Hisex), living in battery cages or at free range were investigated. The main question was: does the comb size and colour correlate with the keeping systems i.e. with the quality and intensity of light and the ambient temperature? The results confirm these hypotheses and also show the genetic influence. The crest size of Hisex white hens is larger and paler compared with those of Hisex brown hens. This tendency is more distinct under the conditions of artificial light, less light and higher temperature of the environment in battery cage systems. Comb size and colour are used as a criterium for health and egg production of the hens. The combs are very important for the hen's health for the regulation of the body temperature and for absorbing light and also for the social structure of the flock; the comb form is an essential characteristic to identify the individual animal. PMID:8165660

Fölsch, D W; Sulzer, B; Meier, T; Huber, H U

1994-02-01

63

Broadband high-resolution x-ray frequency combs  

E-print Network

Optical frequency combs have had a remarkable impact on precision spectroscopy. Enabling this technology in the x-ray domain is expected to result in wide-ranging applications, such as stringent tests of astrophysical models and quantum electrodynamics, a more sensitive search for the variability of fundamental constants, and precision studies of nuclear structure. Ultraprecise x-ray atomic clocks may also be envisaged. In this work, an x-ray pulse-shaping method is put forward to generate a comb in the absorption spectrum of an ultrashort high-frequency pulse. The method employs an optical-frequency-comb laser, manipulating the system's dipole response to imprint a comb on an excited transition with a high photon energy. The described scheme provides higher comb frequencies and requires lower optical-comb peak intensities than currently explored methods, preserves the overall width of the optical comb, and may be implemented by presently available x-ray technology.

Cavaletto, Stefano M; Ott, Christian; Buth, Christian; Pfeifer, Thomas; Keitel, Christoph H

2014-01-01

64

Injection locking of Yb-fiber based optical frequency comb.  

PubMed

We demonstrated the synchronization of offset and repetition frequency between two independent Yb-doped fiber mode-locked lasers by injection locking. By injecting master-laser pulse-train into slave laser cavity, stability and accuracy of master frequency comb are transferred to slave comb. Passive stabilization of frequency comb offers robust and convenient way to duplicate frequency comb that can be applied to long-distance comb transfer. Injecting master pulse would also help to initiate and stabilize mode-locking of high repetition rate or ultrabroadband frequency combs. Additionally, we also demonstrated even more robust synchronization of combs can be achieved with the help of active stabilization of relative offset frequency difference. PMID:22565676

Kuse, Naoya; Ozawa, Akira; Nomura, Yutaka; Ito, Isao; Kobayashi, Yohei

2012-05-01

65

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

PubMed Central

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

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

2012-01-01

66

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

E-print Network

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

Pratt, Stephen

67

Laser frequency combs for astronomical observations  

E-print Network

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

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

2008-09-09

68

Terahertz Frequency Combs. Theoretical Aspects and Applications  

NASA Astrophysics Data System (ADS)

We review recent work on THz frequency combs generated by femtosecond lasers. An overview about the underlying theory and application examples for the analysis of THz signals are given. Using different optoelectronic detection methods, spatially resolved measurements of frequency, phase, and amplitude of GHz and THz emitters are presented. The measurement setup allows for high-precision measurements of the frequency (accuracy of 9 · 10- 14within a 10 s measurement interval), relative amplitude (standard deviation of the mean 0.1 %) and phase (standard deviation of the mean 0.2°). Moreover, the accuracy and invasiveness of different optoelectronic techniques are compared. The large spectral coverage provided by THz frequency combs is demonstrated by simultaneously measuring signals at 16 GHz and 28 THz.

Füser, Heiko; Bieler, Mark

2014-08-01

69

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

70

Silicon-Chip Mid-Infrared Frequency Comb Generation  

E-print Network

Optical frequency combs represent a revolutionary technology for high precision spectroscopy due to their narrow linewidths and precise frequency spacing. Generation of such combs in the mid-infrared (IR) spectral region (2-20 um) is of great interest due to the presence of a large number of gas absorption lines in this wavelength regime. Recently, frequency combs have been demonstrated in the MIR in several platforms, including fiber combs, mode-locked lasers, optical parametric oscillators, and quantum cascade lasers. However, these platforms are either relatively bulky or challenging to integrate on-chip. An alternative approach using parametric mixing in microresonators is highly promising since the platform is extremely compact and can operate with relatively low powers. However, material and dispersion engineering limitations have prevented the realization of a microresonator comb source past 2.55 um. Although silicon could in principle provide a CMOS compatible platform for on-chip comb generation deep...

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

2014-01-01

71

Optimization of filtering schemes for broadband astro-combs.  

PubMed

To realize a broadband, large-line-spacing astro-comb, suitable for wavelength calibration of astrophysical spectrographs, from a narrowband, femtosecond laser frequency comb ("source-comb"), one must integrate the source-comb with three additional components: (1) one or more filter cavities to multiply the source-comb's repetition rate and thus line spacing; (2) power amplifiers to boost the power of pulses from the filtered comb; and (3) highly nonlinear optical fiber to spectrally broaden the filtered and amplified narrowband frequency comb. In this paper we analyze the interplay of Fabry-Perot (FP) filter cavities with power amplifiers and nonlinear broadening fiber in the design of astro-combs optimized for radial-velocity (RV) calibration accuracy. We present analytic and numeric models and use them to evaluate a variety of FP filtering schemes (labeled as identical, co-prime, fraction-prime, and conjugate cavities), coupled to chirped-pulse amplification (CPA). We find that even a small nonlinear phase can reduce suppression of filtered comb lines, and increase RV error for spectrograph calibration. In general, filtering with two cavities prior to the CPA fiber amplifier outperforms an amplifier placed between the two cavities. In particular, filtering with conjugate cavities is able to provide <1 cm/s RV calibration error with >300 nm wavelength coverage. Such superior performance will facilitate the search for and characterization of Earth-like exoplanets, which requires <10 cm/s RV calibration error. PMID:23187265

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

2012-10-22

72

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

73

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

74

Efficiency optimization for atomic frequency comb storage  

NASA Astrophysics Data System (ADS)

We study the efficiency of the atomic frequency comb storage protocol. We show that for a given optical depth, the preparation procedure can be optimize to significantly improve the retrieval. Our prediction is well supported by the experimental implementation of the protocol in a Tm3+:YAG crystal. We observe a net gain in efficiency from 10 to 17% by applying the optimized preparation procedure. In the perspective of high bandwidth storage, we investigate the protocol under different magnetic fields. We analyze the effect of the Zeeman and superhyperfine interaction.

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

2010-03-01

75

Efficiency optimization for atomic frequency comb storage  

SciTech Connect

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

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

2010-03-15

76

Feshbach Resonances in Kerr Frequency Combs  

E-print Network

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

Matsko, Andrey B

2014-01-01

77

Original article Drone production and drone comb utilization  

E-print Network

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

Paris-Sud XI, Université de

78

A Note on Rotor-Router Aggregation on the Comb  

E-print Network

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

Huss, Wilfried

2011-01-01

79

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

80

Cavity-Enhanced Optical Frequency Comb Spectroscopy  

NASA Astrophysics Data System (ADS)

Cavity-enhanced optical frequency comb spectroscopy is a new technique that realizes simultaneously broad spectral coverage and high spectral resolution provided by an optical frequency comb as well as ultrahigh detection sensitivities enabled with a high-finesse optical cavity [1]. These powerful capabilities have been demonstrated in a series of experiments where real-time detection and identification of many different molecular states or species are achieved in a massively parallel fashion [2,3]. We will discuss the principle, technical requirements, and various implementations for this spectroscopic approach, as well as applications that include trace gas detections, human breath analysis, and characterization of cold and ultracold molecules [4,5,6]. References: [1] M. J. Thorpe, K. D. Moll, B. Safdi, and J. Ye, Science 311, 1595 (2006). [2] M. J. Thorpe, D. D. Hudson, K. D. Moll, J. Lasri, and J. Ye, Opt. Lett. 32, 307 (2007). [3] C. Gohle, B. Stein, A. Schliesser, T. Udem, and T. W. Hänsch, Phys. Rev. Lett. 99, 263902 (2007). [4] M. J. Thorpe, D. Balslev-Clausen, M. Kirchner, and J. Ye, Opt. Express. 16, 2387 (2008). [5] M. J. Thorpe and J. Ye, Appl. Phys. B 91, 397 (2008). [6] M. J. Thorpe, F. Adler, K. C. Cossel, M. H. G. de Miranda, and J. Ye, Chem. Phys. Lett. 468, 1 (2009).

Ye, Jun; Thorpe, Michael J.; Adler, Florian; Cossel, Kevin C.

2009-06-01

81

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

82

Coherent terabit communications with microresonator Kerr frequency combs  

PubMed Central

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

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

2014-01-01

83

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

84

Third-order chromatic dispersion stabilizes Kerr frequency combs.  

PubMed

Using numerical simulations of an extended Lugiato-Lefever equation we analyze the stability and nonlinear dynamics of Kerr frequency combs generated in microresonators and fiber resonators, taking into account third-order dispersion effects. We show that cavity solitons underlying Kerr frequency combs, normally sensitive to oscillatory and chaotic instabilities, are stabilized in a wide range of parameter space by third-order dispersion. Moreover, we demonstrate how the snaking structure organizing compound states of multiple cavity solitons is qualitatively changed by third-order dispersion, promoting an increased stability of Kerr combs underlined by a single cavity soliton. PMID:24978250

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

2014-05-15

85

Wavelength-multiplexed quantum networks with ultrafast frequency combs  

NASA Astrophysics Data System (ADS)

Highly entangled quantum networks (cluster states) lie at the heart of recent approaches to quantum computing. Yet the current approach for constructing optical quantum networks does so one node at a time, which lacks scalability. Here, we demonstrate the single-step fabrication of a multimode quantum resource from the parametric downconversion of femtosecond-frequency combs. Ultrafast pulse shaping is employed to characterize the comb's spectral entanglement. Each of the 511 possible bipartitions among ten spectral regions is shown to be entangled; furthermore, an eigenmode decomposition reveals that eight independent quantum channels (qumodes) are subsumed within the comb. This multicolour entanglement imports the classical concept of wavelength-division multiplexing to the quantum domain by playing upon frequency entanglement to enhance the capacity of quantum-information processing. The quantum frequency comb is easily addressable, robust with respect to decoherence and scalable, which renders it a unique tool for quantum information.

Roslund, Jonathan; de Araújo, Renné Medeiros; Jiang, Shifeng; Fabre, Claude; Treps, Nicolas

2014-02-01

86

Mechanical control of a microrod-resonator optical frequency comb  

E-print Network

Robust control and stabilization of optical frequency combs enables an extraordinary range of scientific and technological applications, including frequency metrology at extreme levels of precision, novel spectroscopy of quantum gases and of molecules from visible wavelengths to the far infrared, searches for exoplanets, and photonic waveform synthesis. Here we report on the stabilization of a microresonator-based optical comb (microcomb) by way of mechanical actuation. This represents an important step in the development of microcomb technology, which offers a pathway toward fully-integrated comb systems. Residual fluctuations of our 32.6 GHz microcomb line spacing reach a record stability level of $5\\times10^{-15}$ for 1 s averaging, thereby highlighting the potential of microcombs to support modern optical frequency standards. Furthermore, measurements of the line spacing with respect to an independent frequency reference reveal the effective stabilization of different spectral slices of the comb with a $&...

Papp, Scott B; Diddams, Scott A

2012-01-01

87

Well-Defined Comb Polymer for Surface Segregation Study  

NASA Astrophysics Data System (ADS)

Blending polymers with different chain architectures may prove useful in controlling interfacial properties by controlling interfacial segregation. A linear response theory by Wu et al. predicts that a long-chain branched polymer blended with its linear analog will be preferentially segregated to the surface and interface of the blend film. The comb architecture is promising for achieving substantial surface segregation. Its high degree of branching, which makes it more prone to separate from linear analogs in the bulk, also provides a substantial driving force for surface segregation when chain ends prefer the surface. In this study comb polystyrenes with well-defined architectural details were prepared by living anionic polymerization. DSC indicates that phase separation occurs for some blends of the linear and comb analogs, and this is also seen by SANS study of these blends. Surface segregation of comb polystyrene when blended with its linear analog has been quantified using the complementary techniques of neutron reflectivity and SIMS.

Liu, Boxi; Quirk, Roderic; Foster, Mark; Wu, David

2011-04-01

88

Ramsey-comb spectroscopy with intense ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

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

Morgenweg, Jonas; Barmes, Itan; Eikema, Kjeld S. E.

2014-01-01

89

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

90

Curved branching crystals and differentiation in comb-layered rocks  

NASA Technical Reports Server (NTRS)

An investigation is conducted concerning two common features of comb layered rocks. Attention is given to the curvature of oriented, elongate, branching crystals and the tendency to form highly differentiated layers. Crystallization studies of plagioclase show that some degree of supercooling is necessary to produce the skeletal, curved, and branching plagioclase crystal morphologies found in comb-layered rocks and that curved crystals can be grown without the presence of a directed stress.

Lofgren, G. E.; Donaldson, C. H.

1975-01-01

91

Adaptive real-time dual-comb spectroscopy  

PubMed Central

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. PMID:24572636

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

2014-01-01

92

Application of Brillouin scattering to optical frequency combs  

NASA Astrophysics Data System (ADS)

Optical frequency combs are a useful tool for measuring reference laser frequency whose uncertainty depends on the stability and accuracy of the reference clock. The relative uncertainty of the laser frequency measurements in the optical telecommunication band with the frequency comb technique is estimated around 10-12. In this paper, we present the development and implementation of a filtering technique on an optical frequency comb based on an Erbium optical fiber oscillator using Brillouin scattering amplification. This filtering technique allows us to isolate and transmit frequencies generated by a stabilized optical frequency comb. This method has been developed for the remote comparison of frequency combs. Finally, we present the characterization of the optical frequency comb and its application to the calibration of high wavelength resolution meters in the optical telecommunications window. Measurements with uncertainties under the resolution of the own instrument were achieved using stabilized lasers at molecular absorptions. The result is a significant improvement of the measurement capability given by the current equipment.

Galindo-Santos, Juan; Alcon-Camas, Mercedes; Martin-Lopez, Sonia; Carrasco-Sanz, Ana; Corredera, Pedro

2012-06-01

93

Nonlinear Dual-Comb Spectroscopy with Two-Photon Excitation  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

94

Mechanical control of a microrod-resonator optical frequency comb  

E-print Network

Robust control and stabilization of optical frequency combs enables an extraordinary range of scientific and technological applications, including frequency metrology at extreme levels of precision, novel spectroscopy of quantum gases and of molecules from visible wavelengths to the far infrared, searches for exoplanets, and photonic waveform synthesis. Here we report on the stabilization of a microresonator-based optical comb (microcomb) by way of mechanical actuation. This represents an important step in the development of microcomb technology, which offers a pathway toward fully-integrated comb systems. Residual fluctuations of our 32.6 GHz microcomb line spacing reach a record stability level of $5\\times10^{-15}$ for 1 s averaging, thereby highlighting the potential of microcombs to support modern optical frequency standards. Furthermore, measurements of the line spacing with respect to an independent frequency reference reveal the effective stabilization of different spectral slices of the comb with a $<$0.5 mHz variation among 140 comb lines spanning 4.5 THz. These experiments were performed with newly-developed microrod resonators, which were fabricated using a CO$_2$-laser-machining technique.

Scott B. Papp; Pascal Del'Haye; Scott A. Diddams

2012-05-18

95

Two-photon Direct Frequency Comb Spectroscopy of Alkali Atoms  

NASA Astrophysics Data System (ADS)

We are using direct frequency comb spectroscopy to study transition frequencies and excited state hyperfine structure in potassium and rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the atomic vapor of interest. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. The thermal motion of the atoms in the vapor cell actually eliminates the need to fine-tune the offset frequency and repetition rate, alleviating a somewhat challenging requirement for spectroscopy of cold atoms. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Nguyen, Khoa; Pradhananga, Trinity; Palm, Christopher; Stalnaker, Jason; Kimball, Derek Jackson

2012-06-01

96

Self-referenced 1.5 [mu]m fiber frequency combs at GHz repetition rates  

E-print Network

Tremendous advances in recent years to the optical frequency comb, particularly frequency combs deriving from solid-state and fiber architectures, have enabled a host of important new applications to emerge - applications ...

Chao, David, Ph. D. Massachusetts Institute of Technology

2012-01-01

97

Operation of an optically coherent frequency comb outside the metrology lab  

E-print Network

We demonstrate a self-referenced fiber frequency comb that can operate outside the well-controlled optical laboratory. The frequency comb has residual optical linewidths of U.S. government, not subject to copyright

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

2013-01-01

98

Green astro-comb for HARPS-N  

NASA Astrophysics Data System (ADS)

We report the design, installation and testing of a broadband green astro-comb on the HARPS-N spectrograph at the TNG telescope. The astro-comb consists of over 7000 narrow lines (<10-6 nm width) spaced by 16 GHz (0.02 nm at 550 nm) with wavelengths stabilized to the Global Positioning System (GPS) and with flat power from 500 to 620 nm. The narrow lines are used to calibrate the spectrograph and measure its line profile. The short term sensitivity of HARPS-N is measured to be less than 2 cm/s and the long-term drift of the spectrograph is approximately 10 cm/s/day. The astrocomb has been partially automated with future work planned to turn the astro-comb into a fully automated, push button instrument.

Langellier, Nicholas; Li, Chih-Hao; Glenday, Alexander G.; Chang, Guoqing; Chen, Hung-Wen; Lim, Jinkang; Furesz, Gabor; Kärtner, Franz; Phillips, David F.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald

2014-08-01

99

Noise-immune cavity-enhanced optical frequency comb spectroscopy.  

PubMed

We present a new method of optical frequency comb spectroscopy that combines cavity enhancement with frequency modulation to obtain immunity to laser frequency-to-amplitude noise conversion by the cavity modes and, thus, high absorption sensitivity over a broad spectral range. A frequency comb is locked to a cavity with a free spectral range (FSR) equal to 4/3 times the repetition rate of the laser, and phase-modulated at a frequency equal to the cavity FSR. The transmitted light is analyzed by a Fourier transform spectrometer with a high bandwidth detector. Phase-sensitive detection of the interferogram yields a noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) signal. In the first demonstration, we record NICE-OFCS signals from the overtone CO2 band at 1575 nm with absorption sensitivity of 4.3×10(-10) cm(-1) Hz(-1/2) per spectral element, close to the shot noise limit. PMID:25166067

Khodabakhsh, Amir; Abd Alrahman, Chadi; Foltynowicz, Aleksandra

2014-09-01

100

Astro-comb calibration of an Echelle Spectrograph  

NASA Astrophysics Data System (ADS)

We describe recent work calibrating a cross-dispersed spectrograph with an "astro-comb" i.e., a high repetition rate, octave spanning femtosecond laser frequency comb; and a filter cavity suppressing laser modes to match the resolution of the spectrograph. Our astro-comb provides ~1500 evenly spaced (~0.6 A) calibration lines of roughly 100 nW per line between 7800 and 8800 Angstroms. The calibration lines of the laser are stabilized to atomic clocks which can be referenced to GPS providing intrinsic stability of the source laser below 1 cm/s in stellar radial velocity sensitivity, as well as long term stability and reproducibility over years. We present calibration of the TRES spectrograph at the 1.5 m telescope at the Fred L Whipple Observatory below 1 m/s radial velocity sensitivity in six orders from 7800-8800 A.

Li, C.-H.; Phillips, D. F.; Glenday, A. G.; Benedick, A. J.; Chang, G.; Chen, L.-J.; Cramer, C.; Furesz, G.; Kärtner, F. X.; Sasselov, D.; Szentgyorgyi, A.; Walsworth, R. L.

2010-07-01

101

Dislocations in mismatched layers of GaAsxP1 - x in between GaP as observed by low-temperature cathodoluminescence: Part I. Grown on (001) oriented substrates.  

NASA Astrophysics Data System (ADS)

The possibility of growing lattice-mismatched layers and quantum wells becomes more and more interesting for the fabrication of devices. For device performance it is necessary to control the formation of misfit dislocations within the mismatched layers. It is therefore essential to study the onset of misfit dislocations versus amount of mismatch and layer thickness. A preliminary cathodoluminescence (CL) investigation, performed on layers of GaAsxP1-x mismatched to GaP barriers, was presented [A. Gustafsson, J. Jönsson, M. Gerling, M. R. Leys, M.-E. Pistol, L. Samuelson, and H. Titze, Inst. Phys. Conf. Ser. No 100, 771 (1989)]. In this paper the critical thickness with respect to the composition, x, in GaAsxP1-x, is studied from a determination of the onset of the formation of dislocations as observed in the monochromatic CL images. The experimental values of the critical thickness are compared to theoretical predictions for the critical thickness, according to different theories. The best agreement is found with the mechanical equilibrium theory, which assumes that the barrier for the formation of dislocations is negligible.

Gustafsson, A.; Pistol, M.-E.; Gerling, M.; Samuelson, L.; Leys, M. R.; Titze, H.

1991-08-01

102

Frequency comb laser spectroscopy in the vacuum-ultraviolet region  

SciTech Connect

We demonstrate that the output of a frequency comb laser can be amplified and upconverted to the vacuum ultraviolet (vuv) in a gaseous medium while its phase coherence is maintained to a high degree (<(1/30) of a vuv cycle). The produced vuv pulses are well suited to perform frequency comb spectroscopy with sub-MHz accuracy, which is experimentally verified using a Ramsey-type quantum interference scheme to excite a transition in xenon at 125 nm. The achieved resolution constitutes an improvement of six orders of magnitude compared to previous demonstrations of frequency domain quantum interference in this wavelength range.

Zinkstok, Roel Th.; Witte, Stefan; Ubachs, Wim; Hogervorst, Wim; Eikema, Kjeld S.E. [Atomic, Molecular and Laser Physics Group, Laser Centre Vrije Universiteit De Boelelaan 1081, 1081 HV Amsterdam (Netherlands)

2006-06-15

103

Routes to spatiotemporal chaos in Kerr optical frequency combs.  

PubMed

We investigate the various routes to spatiotemporal chaos in Kerr optical frequency combs, obtained through pumping an ultra-high Q-factor whispering-gallery mode resonator with a continuous-wave laser. The Lugiato-Lefever model is used to build bifurcation diagrams with regards to the parameters that are externally controllable, namely, the frequency and the power of the pumping laser. We show that the spatiotemporal chaos emerging from Turing patterns and solitons display distinctive dynamical features. Experimental spectra of chaotic Kerr combs are also presented for both cases, in excellent agreement with theoretical spectra. PMID:24697375

Coillet, Aurélien; Chembo, Yanne K

2014-03-01

104

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

E-print Network

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

Paris-Sud XI, Université de

105

Polaribacter atrinae sp. nov., isolated from the intestine of a comb pen shell, Atrina pectinata  

E-print Network

Polaribacter atrinae sp. nov., isolated from the intestine of a comb pen shell, Atrina pectinata strain WP25T , was isolated from the intestine of a comb pen shell, Atrina pectinata, which was collected as mesophilic. The comb pen shell Atrina pectinata, which belongs to the family Pinnidae, is a large, wedge

Bae, Jin-Woo

106

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

E-print Network

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 ...

Phillips, David F.

107

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

108

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

PubMed

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

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

2014-09-01

109

Spectral and temporal characterization of a fused-quartz-microresonator optical frequency comb  

SciTech Connect

We report on the fabrication of high-Q, fused-quartz microresonators and the parametric generation of a frequency comb with 36-GHz line spacing using them. We have characterized the intrinsic stability of the comb in both the time and frequency domains to assess its suitability for future precision metrology applications. Intensity autocorrelation measurements and line-by-line comb control reveal near-transform-limited picosecond pulse trains that are associated with good relative phase and amplitude stability of the comb lines. The comb's 36-GHz line spacing can be readily photodetected, which enables measurements of its intrinsic and absolute phase fluctuations.

Papp, Scott B.; Diddams, Scott A. [National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

2011-11-15

110

A "comb" structure measurement of a micrometer displacement in laser plasma propulsion  

NASA Astrophysics Data System (ADS)

A "comb" structure of beam intensity distribution is achieved to measure target displacements at the micrometer level in laser plasma propulsion experiments. Compared with single-beam and double-beam detection, the "comb" structure is more suitable for a thin film targets with a velocity lower than 10-2 m/s. Combined with a light-electric monitor, the "comb" structure can be used to measure a velocity range from 10-3 to 1 m/s. Using this "comb" structure, the coupling coefficient of aluminum ablated by nanosecond pulse laser in air is determined and compared. The results indicate that this "comb" structure is an effective experimental approach.

Zheng, Z. Y.; Gao, L.; Gao, H.; Xing, J.; Wu, X. W.

2014-08-01

111

Two-photon direct frequency comb spectroscopy of alkali atoms  

NASA Astrophysics Data System (ADS)

We have studied transition frequencies and excited state hyperfine structure in rubidium using 2-photon transitions excited directly with the frequency-doubled output of a erbium fiber optical frequency comb. The frequency comb output is directed in two counterpropagating directions through a vapor cell containing the rubidium vapor. A pair of optical filters is used to select teeth of the comb in order to identify the transition wavelengths. A photomultiplier tube (PMT) measures fluorescence from a decay channel wavelength selected with another optical filter. Using different combinations of filters enables a wide range of transitions to be investigated. By scanning the repetition rate, a Doppler-free spectrum can be obtained enabling kHz-resolution spectral measurements. An interesting dependence of the 2-photon spectrum on the energy of the intermediate state of the 2-photon transition is discussed. Our investigations are laying the groundwork for a long-term research program to use direct frequency comb spectroscopy to understand the complex spectra of rare-earth atoms.

Palm, Christopher; Pradhananga, Trinity; Nguyen, Khoa; Montcrieffe, Caitlin; Kimball, Derek

2012-11-01

112

TOWARDS A LINEAR RESPONSE OF VERTICAL COMB-DRIVE ACTUATORS  

E-print Network

....................................................................................................... 29 B. Case study - The electromechanical response of an angular parallel-plate type actuatorTOWARDS A LINEAR RESPONSE OF VERTICAL COMB-DRIVE ACTUATORS by Matan Naftali and David Elata-DRIVE ACTUATORS by Matan Naftali and David Elata Faculty of Mechanical Engineering Technion ­ Israel Institute

Rimon, Elon

113

Laser mode hyper-combs Alon Schwartz and Baruch Fischer*  

E-print Network

, and G. Angelow, "Toward single-cycle laser systems," IEEE J. Select. Topics in Quantum. Electron. 9, 990. Fischer, "Melting and freezing of light pulses and modes in mode-locked lasers," Opt. Express 11(25), 3418Laser mode hyper-combs Alon Schwartz and Baruch Fischer* Department of Electrical Engineering

Fischer, Baruch

114

Laser Frequency Combs for Precision Radial Velocity Measurements in Astrophysics  

E-print Network

& high-resolution corrector collimator slit 2D CCD array From telescope cross disperser (low-dispersion slit 2D CCD array From telescope cross disperser (low-dispersion) echelle grating (high dispersion;"Astro-Comb" ·!Precision spectroscopy essential for advances in astrophysics ·!Currently limited

115

Stabilized Ultrafast Pulse Generation and Optical Frequency Combs Techniques  

E-print Network

& Photonics Center for Research & Education in Optics & Lasers (CREOL) University of Central Florida #12;2 Outline · Introduction to Diode Lasers, Modelocking, & Motivation · How to Make Short Pulses from Laser-Field Spectrum Modelocked Spectrum Modulator #12;8 Motivation · What are optical frequency combs? ­ Coherent, cw

Van Stryland, Eric

116

Ramsey-comb spectroscopy: Theory and signal analysis  

NASA Astrophysics Data System (ADS)

We recently demonstrated that the spectroscopic accuracy and resolution of optical frequency combs can be obtained from a series of Ramsey-like measurements using only two amplified frequency comb pulses at variable delays. In this work we present a comprehensive analytical framework of this Ramsey-comb method in both time and frequency domains. It is shown that as opposed to traditional forms of spectroscopy, the signal analysis can be performed purely in the time domain, based on the temporal phases of the individual Ramsey signals. We give a detailed description of the robust fitting algorithm relying solely on this phase information and discuss special features such as an insensitivity to (transition-independent) spectral line-broadening mechanisms and constant phase shifts, e.g., due to the ac Stark effect from the excitation pulses themselves. The precision and resolution of the Ramsey-comb fitting method is assessed via numerical simulations, including cases of transition-dependent broadening mechanisms and phase shifts.

Morgenweg, Jonas; Eikema, Kjeld S. E.

2014-05-01

117

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.

Darryl Leja (National Human Genome Research Institute REV)

2005-04-14

118

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

PubMed

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

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

2013-03-01

119

Dual Comb Fourier Transform Spectroscopy in the Green Region  

NASA Astrophysics Data System (ADS)

Laser combs in combination with other advancing tools of laser science, nonlinear optics, photonics, and electronic signal processing have the potential to vastly enhance the range and capabilities of molecular laser spectroscopy. The high versatility of frequency comb sources can indeed harness new techniques for ultra-rapid and ultra-sensitive recording of complex molecular spectra. The recent proof-of-principle demonstrations of dual comb Fourier transform spectroscopy have mostly been carried out in the near-infrared region, around 1.0 and 1.5 ?m. The mode-locked ytterbium- or erbium-doped fiber femtosecond laser systems emitting in this range indeed require few adjustment thanks to their guided light and permit reliable unattended operation. With expanded wavelength coverage and continued improvements in speed and sensitivity, dual comb spectroscopy should find use as a novel, time-domain spectroscopic analytical tool. As far as molecular spectroscopy is concerned, the mid-infrared and visible-ultraviolet wavelength regions show both the potential for specificity and sensitivity for tracing molecules. In particular, the visible-ultraviolet region complements the mid-infrared molecular fingerprint range, as it provides access to many electronic transitions, in particular belonging to reactive species. In this contribution, we report on our progress in the implementation of dual comb spectroscopy in the 520 nm green region. We present preliminary results on a powerful new sensitive ultra-rapid tool for linear rovibronic absorption spectroscopy, based on frequency-doubled ytterbium-doped fiber lasers and we discuss its intriguing prospects for spectroscopy of short lived transient species.

Knize, R. J.; Bernhardt, B.; Picqué, N.; Hänsch, T. W.

2010-06-01

120

Interferometric homogeneity test using adaptive frequency comb illumination.  

PubMed

The homogeneity test of glass plates in a Fizeau interferometer requires the measurement of the glass sample in reflected as well as in transmitted light. For the measurement in transmitted light, the sample has to be inserted into the ray path of a Fizeau or Twyman-Green interferometer, which leads to a nested cavity setup. To separate the interference signals from the different cavities, we illuminate a Fizeau interferometer with an adaptive frequency comb. In this way, rigid glass plates can be measured, and linear variations in the homogeneity can also be detected. The adaptive frequency comb is provided by a variable Fabry-Perot filter under broadband illumination from a superluminescence diode. Compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher. PMID:23518735

Mantel, Klaus; Schwider, Johannes

2013-03-20

121

Frequency comb vernier spectroscopy in the near infrared  

E-print Network

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

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

2014-01-01

122

Integrated frequency comb source of heralded single photons.  

PubMed

We report an integrated photon pair source based on a CMOS-compatible microring resonator that generates multiple, simultaneous, and independent photon pairs at different wavelengths in a frequency comb compatible with fiber communication wavelength division multiplexing channels (200 GHz channel separation) and with a linewidth that is compatible with quantum memories (110 MHz). It operates in a self-locked pump configuration, avoiding the need for active stabilization, making it extremely robust even at very low power levels. PMID:24664002

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

2014-03-24

123

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

124

Quantum interference in two-photon frequency-comb spectroscopy  

NASA Astrophysics Data System (ADS)

Quantum interference arising from spontaneous emission, or cross-damping, is an important yet frequently overlooked systematic in precision spectroscopy experiments which aim to determine a transition frequency with an uncertainty smaller than the natural linewidth. Here, we calculate the effects of such interference in two-photon frequency-comb spectroscopy using a perturbative approach and by integration of the density matrix equations. We then apply these techniques to the two-photon spectroscopy of the hydrogen 1S-3S transition currently being performed in our group. Depending on the detection geometry, we find distortions of the line shapes which can lead to systematic errors of ˜1 kHz if such interference effects are ignored in the data analysis. This result is independent of whether a cw laser or frequency comb is used for the excitation. Finally, we propose a time-dependent detection scheme which, when used in conjunction with frequency-comb excitation, can mitigate the line distortions arising from such interference.

Yost, D. C.; Matveev, A.; Peters, E.; Beyer, A.; Hänsch, T. W.; Udem, Th.

2014-07-01

125

Frequency comb generation by CW laser injection into a quantum-dot mode-locked laser.  

PubMed

We report on frequency comb generation at 1.5 ?m by injection of a CW laser in a hybridly mode-locked InAs/InP two-section quantum-dot laser (HMLQDL). The generated comb has > 60 modes spaced by ? 4.5 GHz and a -20 dBc width of > 100 GHz (23 modes) at > 30 dB signal to background ratio. Comb generation was observed with the CW laser (red) detuned more than 20 nm outside the HMLQDL spectrum, spanning a large part of the gain spectrum of the quantum dot material. It is shown that the generated comb is fully coherent with the injected CW laser and RF frequency used to drive the hybrid mode-locking. This method of comb generation is of interest for the creation of small and robust frequency combs for use in optical frequency metrology, high-frequency (> 100 GHz) RF generation and telecommunication applications. PMID:23037259

Pinkert, T J; Salumbides, E J; Tahvili, M S; Ubachs, W; Bente, E A J M; Eikema, K S E

2012-09-10

126

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

PubMed

We have isolated a single tooth from a fiber laser-based optical frequency comb for nonlinear spectroscopy and thereby directly referenced the comb. An 89 MHz erbium fiber laser frequency comb is directly stabilized to the P(23) (1539.43 nm) overtone transition of 12C2H2 inside a hollow-core photonic crystal fiber. To do this, a single comb tooth is isolated and amplified from 20 nW to 40 mW with sufficient fidelity to perform saturated absorption spectroscopy. The fractional stability of the comb, ~7 nm away from the stabilized tooth, is shown to be 6 × 10-12 at 100 ms gate time, which is over an order of magnitude better than that of a comb referenced to a GPS-disciplined Rb oscillator. PMID:25321837

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

2014-09-22

127

Mid-Infrared Soliton and Raman Frequency Comb Generation in Silicon Microrings  

E-print Network

We numerically study the mechanisms of frequency comb generation in the mid-infrared spectral region from cw pumped silicon microring resonators. Coherent soliton comb generation may be obtained even for a pump with zero linear cavity detuning, through suitable control of the effective lifetime of free-carriers from multiphoton absorption, which introduces a nonlinear cavity detuning via free-carrier dispersion. Conditions for optimal octave spanning Raman comb generation are also described.

Hansson, Tobias; Wabnitz, Stefan

2014-01-01

128

SiO2 Electret Generated by Potassium Ions on a Comb-Drive Actuator  

NASA Astrophysics Data System (ADS)

Silicon dioxide electret generated by doping potassium ions will be demonstrated by forming it on a comb-drive actuator. The comb-drive actuator made of silicon on an insulator substrate is oxidized with bubbling a stream of KOH solution to form silicon oxide film including potassium ions uniformly on the etched side walls of comb electrodes. After a bias-temperature procedure at about 900-1000 K and 100 V was applied to the device, we confirmed a 40 V built-in potential difference between the opposing comb electrodes. The gradual decay of the potential was observed, but 35 V was maintained even after 1 month.

Sugiyama, Tatsuhiko; Aoyama, Mitsuru; Shibata, Yasushi; Suzuki, Masato; Konno, Takashi; Ataka, Manabu; Fujita, Hiroyuki; Hashiguchi, Gen

2011-11-01

129

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

130

Static FBG strain sensor with high resolution and large dynamic range by dual-comb spectroscopy.  

PubMed

We demonstrate a fiber Bragg grating (FBG) strain sensor with optical frequency combs. To precisely characterize the optical response of the FBG when strain is applied, dual-comb spectroscopy is used. Highly sensitive dual-comb spectroscopy of the FBG enabled strain measurements with a resolution of 34 n?. The optical spectral bandwidth of the measurement exceeds 1 THz. Compared with conventional FBG strain sensor using a continuous-wave laser that requires rather slow frequency scanning with a limited range, the dynamic range and multiplexing capability are significantly improved by using broadband dual-comb spectroscopy. PMID:23669971

Kuse, Naoya; Ozawa, Akira; Kobayashi, Yohei

2013-05-01

131

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

E-print Network

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; Xiong, Chi; Tang, Hong X

2013-01-01

132

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

133

A preliminary investigation of the potential mechanical sensitivity of vertical comb drives  

NASA Astrophysics Data System (ADS)

This article describes a preliminary step taken in investigating the potential of vertical comb drives to be used as force-compensation mechanisms in interfacial force microscopes, by exploring the lower limit of the stiffness of the springs the comb drives can be fabricated with. The stiffness of their springs will affect the sensitivity of the microscope. Six vertical comb drives were fabricated for this study; the dimensions of their spring beams were chosen with the intention of giving them stiffnesses of three different orders of magnitude. During fabrication it was found that etching the tops of some of the teeth down to create the vertical offset between the combs can be done using only photoresist to mask the rest of the teeth. The stiffnesses of the fabricated springs were estimated by applying loads to them and measuring their resulting deflections. Weights were applied to the two comb drives with the stiffest springs. Voltages were also applied to them so as to determine the force-voltage relationship for their comb design. Since the other four comb drives had the same comb design, the stiffnesses of their springs could be estimated from the displacements of their movable combs when voltages were applied to them.

Gallagher, E.; Moussa, W.

2014-10-01

134

[Sex education, sex behavior, contraception].  

PubMed

Sexual behavior has changed during the last decades. Teenage fertility rate, and the number of gonococcal infections are both extremely high; the incidence of HIV-infections is increasing. Preventive measures include sex education. Sex education may help the adolescents to identify their own goals for sexual behavior, to avoid unintended and unwanted pregnancy, and to avoid sexually transmitted diseases. PMID:1945474

Borkenstein, M; Schwingshandl, J; Kuttnig, M; Limbert, C

1991-01-01

135

Sex tourism  

Microsoft Academic Search

\\u000a The following chapter addresses the sex market as an economic sector of tourism. It does not reflect the author's personal\\u000a opinion on religious, health, criminal or moral issues. This chapter is divided into two parts, examining the demand and the\\u000a supply side issues respectively. More specifically, it addresses questions regarding the sex tourism segment's estimated market\\u000a size, consumption patterns, geographical

Daniel Bunn

136

Additional sex combs-like family genes are required for normal cardiovascular development.  

PubMed

Congenital heart disease (CHD) is the most common birth defect. However, the majority of CHD cases have unknown etiology. Here we report the identification of ASXL2 and ASXL1, two homologous chromatin factors, as novel regulators of heart development. Asxl2(-/-) fetuses have reduced body weight and display congenital heart malformations including thickened compact myocardium in the left ventricle, membranous ventricular septal defect, and atrioventricular valval stenosis. Although most Asxl2(-/-) animals survive to term, the neonates have patent ductus arteriosus and consequent lung hemorrhage and die soon after birth. Asxl1(-/-) fetuses have reduced body weight and display cleft palate, anophthalmia as well as ventricular septal defects and a failure in lung maturation. From these results, we conclude that normal heart development requires both ASXL proteins. In particular, ASXL2 plays an important role in heart morphogenesis and the transition from fetal to postnatal circulation. PMID:24860998

McGinley, Andrea L; Li, Yanyang; Deliu, Zane; Wang, Q Tian

2014-07-01

137

Sex Offender Registration Information Sex Offender Registration  

E-print Network

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

Escher, Christine

138

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

E-print Network

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

Dawson, Jin Zhou

2008-01-01

139

Adaptive dual-comb spectroscopy in the green region.  

PubMed

Dual-comb spectroscopy is extended to the visible spectral range with two short-pulse frequency-doubled free-running ytterbium-doped fiber lasers. When the spectrum is shifted to other domains by nonlinear frequency conversion, tracking the relative fluctuations of the femtosecond oscillators at their fundamental wavelength automatically produces the correction signal needed for the recording of distortion-free spectra. The dense rovibronic spectrum of iodine around 19,240 cm(-1) is recorded within 12 ms at Doppler-limited resolution. PMID:23202066

Ideguchi, T; Poisson, A; Guelachvili, G; Hänsch, T W; Picqué, N

2012-12-01

140

Entanglement of Atomic Qubits using an Optical Frequency Comb  

E-print Network

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.

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

2010-01-13

141

Entanglement of Atomic Qubits using an Optical Frequency Comb  

E-print Network

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

2010-01-01

142

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

143

Dynamic time warping comb filter for the enhancement of speech degraded by white Gaussian noise  

Microsoft Academic Search

An attempt is made to enhance speech degraded by added noise by exploiting the periodic nature of voiced speech. A modification of the adaptive comb filter is employed for this purpose. Problems which may arise when using the periodicity of the speech for enhancement include significant distortion caused by comb filtering a time-varying waveform (called temporal smearing) as well as

Joseph T. Graf; Nancy Hubing

1993-01-01

144

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.

2011-04-01

145

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

146

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

E-print Network

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

Paris-Sud XI, Université de

147

Frequency comb assisted diode laser spectroscopy for measurement of microcavity dispersion  

Microsoft Academic Search

Although invented for precision measurements of single atomic transitions, frequency combs have also become a versatile tool for broadband spectroscopy in recent years. Here, we present a novel and simple approach for broadband spectroscopy, combining the accuracy of an optical fibre-laser-based frequency comb with the ease of use of a tunable external cavity diode laser. The scheme enables broadband and

P. Del'Haye; O. Arcizet; M. L. Gorodetsky; R. Holzwarth; T. J. Kippenberg

2009-01-01

148

Silicon-Chip Mid-Infrared Frequency Comb Generation Austin G. Griffith1  

E-print Network

bulky and cannot be integrated. Supercontinuum generation represents another means for generating broadSilicon-Chip Mid-Infrared Frequency Comb Generation Austin G. Griffith1 , Ryan K. W. Lau2 , Jaime spacing. Generation of such combs in the mid-infrared (IR) spectral region (2-20 m) is of great interest

Lipson, Michal

149

Supercontinuum-based 10-GHz flat-topped optical frequency comb generation  

E-print Network

Supercontinuum-based 10-GHz flat-topped optical frequency comb generation Rui Wu,1,* Victor Torres generation from single laser source using supercontinuum in optical fibers," Electron. Lett. 29(10), 862: The generation of high-repetition-rate optical frequency combs with an ultra-broad, coherent and smooth spectrum

Purdue University

150

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

151

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

PubMed

A generalized Lugiato-Lefever equation is numerically solved with a Newton-Raphson method to model Kerr frequency combs. We obtain excellent agreement with past experiments, even for an octave-spanning comb. Simulations are much faster than with any other technique despite including more modes than ever before. Our study reveals that Kerr combs are associated with temporal cavity solitons and dispersive waves, and opens up new avenues for the understanding of Kerr-comb formation. PMID:23282830

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

2013-01-01

152

Fabrication of comb interdigitated electrodes array (IDA) for a microbead-based electrochemical assay system.  

PubMed

This research is directed towards developing a more sensitive and rapid electrochemical sensor for enzyme labeled immunoassays by coupling redox cycling at interdigitated electrode arrays (IDA) with the enzyme label beta-galactosidase. Coplanar and comb IDA electrodes with a 2.4 microm gap were fabricated and their redox cycling currents were measured. ANSYS was used to model steady state currents for electrodes with different geometries. Comb IDA electrodes enhanced the signal about three times more than the coplanar IDAs, which agreed with the results of the simulation. Magnetic microbead-based enzyme assay, as a typical example of biochemical detection, was done using the comb and coplanar IDAs. The enzymes could be placed close to the sensing electrodes (approximately 10 microm for the comb IDAs) and detection took less than 1 min with a limit of detection of 70 amol of beta-galactosidase. We conclude that faster and more sensitive assays can be achieved with the comb IDA. PMID:15522606

Kim, Sang Kyung; Hesketh, Peter J; Li, Changming; Thomas, Jennifer H; Halsall, H Brian; Heineman, William R

2004-11-01

153

A flat and broadband optical frequency comb with tunable bandwidth and frequency spacing  

NASA Astrophysics Data System (ADS)

A flat and broadband optical frequency comb generator based on two cascaded intensity modulators is proposed and experimentally demonstrated. In this scheme, we first use even or odd harmonic sidebands to generate optical frequency comb, so the bandwidth can be improved. By adjusting the power of the microwave signals and the direct current bias applied to the modulators, a flat and broadband optical frequency comb can be achieved. The scheme is relatively simple and adjustable, where the frequencies spacing vary with microwave frequency applied on modulators. 15 and 20 comb lines with the comb flatness within 1 dB can be generated. The generated spectrums can meet the requirement of OFDM modulation, and can be used for high capacity optical transmission systems in the future.

Shang, Lei; Wen, Aijun; Lin, Guibin; Gao, Yongsheng

2014-11-01

154

Frequency-comb-referenced tunable diode laser spectroscopy and laser stabilization applied to laser cooling.  

PubMed

Laser cooling of trapped atoms and ions in optical clocks demands stable light sources with precisely known absolute frequencies. Since a frequency comb is a vital part of any optical clock, the comb lines can be used for stabilizing tunable, user-friendly diode lasers. Here, a light source for laser cooling of trapped strontium ions is described. The megahertz-level stability and absolute frequency required are realized by stabilizing a distributed-feedback semiconductor laser to a frequency comb. Simple electronics is used to lock and scan the laser across the comb lines, and comb mode number ambiguities are resolved by using a separate, saturated absorption cell that exhibits easily distinguishable hyperfine absorption lines with known frequencies. Due to the simplicity, speed, and wide tuning range it offers, the employed technique could find wider use in precision spectroscopy. PMID:25402914

Fordell, Thomas; Wallin, Anders E; Lindvall, Thomas; Vainio, Markku; Merimaa, Mikko

2014-11-01

155

Using sets of combs to control pitch estimation errors J.-S. Lienard, C. Barras and F. Signol  

E-print Network

either by augmenting the comb with intermediary negative teeth, or by setting to zero some of its teeth of the secondary peaks. To do so we define some particular combs, with missing or negative teeth, which produce of unitary teeth regularly spaced in frequency. We call comb frequency Fc the frequency of its first tooth

156

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

157

Dislocations in mismatched layers of GaAsxP1 - x in between GaP as observed by low-temperature cathodoluminescence: Part II. Grown on (111) oriented substrates  

NASA Astrophysics Data System (ADS)

Spectrally resolved low-temperature cathodoluminescence (CL) imaging has been performed on thin, 250 Å, mismatched layers of GaAsxP1-x in between bulk GaP. The layers were grown on (111) oriented substrates by metalorganic vapor phase epitaxy, with layers ranging from perfectly strained to totally relaxed. CL imaging has proven to be a very sensitive technique for the study of the onset of the formation of misfit dislocations and is therefore useful for determination of the critical thickness [A. Gustafsson, M.-E. Pistol, M. Gerling, L. Samuelson, M. R. Leys and H. Titze, J. Appl. Phys. 70, 1660 (1991)]. For the use of perfectly strained layers, growth on (111) oriented substrates can be of interest since the critical thickness predicted by the mechanical equilibrium theory [J. W. Matthews and A. E. Blakeslee, J. Cryst. Growth 27, 118 (1974)] is about twice that for growth on (001) oriented substrates. In this work we show that the dislocations involved in the strain relief for the growth of mismatched layers on (111) oriented substrates are of the perfect 60° type and that the experimental critical thickness agrees well with the value expected from the mechanical equilibrium theory.

Gustafsson, A.; Pistol, M.-E.; Gerling, M.; Samuelson, L.; Titze, H.

1991-08-01

158

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

PubMed

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

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

2010-05-01

159

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

160

Combing non-epitaxially grown nanowires for large-area electronic devices  

NASA Astrophysics Data System (ADS)

A facile route for aligning randomly oriented nanowires synthesized by a vapor-liquid-solid method for the fabrication of nanoelectronic devices was achieved using a polymer combing technique. By controlling the Young’s modulus of the polymer combs, van der Waals interactions and shearing forces between the combs and nanowires can be manipulated and thus the nanowire density and alignment can be controlled. Using the proposed method, field-effect transistors were directly fabricated on as-grown substrates after aligning the nanowires, thereby demonstrating the feasibility of the scheme for the production of nanoelectronic devices.

Song, Hyunwook; Lee, Min Hyung

2013-07-01

161

Combing non-epitaxially grown nanowires for large-area electronic devices.  

PubMed

A facile route for aligning randomly oriented nanowires synthesized by a vapor-liquid-solid method for the fabrication of nanoelectronic devices was achieved using a polymer combing technique. By controlling the Young's modulus of the polymer combs, van der Waals interactions and shearing forces between the combs and nanowires can be manipulated and thus the nanowire density and alignment can be controlled. Using the proposed method, field-effect transistors were directly fabricated on as-grown substrates after aligning the nanowires, thereby demonstrating the feasibility of the scheme for the production of nanoelectronic devices. PMID:23787876

Song, Hyunwook; Lee, Min Hyung

2013-07-19

162

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

PubMed

We numerically investigate the influence of high-order dispersion (HOD) on temporal and spectral characteristics of microresonator-based optical frequency combs. Theoretical analysis based on the moment method associated with numerical simulations are utilized to study the comb evolution dynamics, showing that temporal shifts of steady-state intracavity solitons are induced by high-odd-order dispersion rather than high-even-order dispersion. The role of HOD on comb spectral envelopes is also elucidated through analyzing the intracavity dispersive wave generations. We further demonstrate that the spectral envelope of a broadband optical frequency comb can be engineered by using a cavity dispersion profile with multiple zero dispersion wavelengths. PMID:24978227

Wang, Shaofei; Guo, Hairun; Bai, Xuekun; Zeng, Xianglong

2014-05-15

163

Quest for MeV frequency combs -- proposal for ELI experiments  

E-print Network

The optical frequency comb has become an indispensable tool for high precision spectroscopy. Also experiments in the field of ultrafast physics rely on the frequency comb technique to generate precisely controlled attosecond optical pulses by means of the high-order harmonic generation. However, in order to generate even shorter laser pulses or to apply this technique in investigations of nuclear structure, combs of frequencies of the order of MeV are necessary. It seems that it may not be possible to achieve such photon energies by high-order harmonic generation. In this context the possibility of the generation of Thomson and Compton-based frequency combs is presented. Diffraction of generated radiation by a sequence of laser pulses and its analogy to the diffraction grating is elucidated. Theoretical investigations presented in this report can be considered as the proposal for future ELI experiments [www.eli-laser.eu

Krajewska, Katarzyna

2014-01-01

164

The applications of comb polymer to the study of liver cell adhesion and signaling  

E-print Network

Comb polymer, which consists of a hydrophobic poly(methyl methacrylate) (PMMA) backbone with hydrophilic hydroxy-poly(ethylene oxide) (HPOEM) side chains, is a tool that has many possible applications for the study of liver ...

Yin, David, 1973-

2004-01-01

165

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

E-print Network

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

Benedick, Andrew John

2011-01-01

166

Damping effects of capacitive comb fingers on biomimetic MEMS directional microphone  

NASA Astrophysics Data System (ADS)

MEMS directional sound sensors that use two coupled wings moving in air are subjected to viscous damping. The amplitude of oscillation of the sensors is read out by measuring the capacitance of interdigitated comb fingers along the edges of the wings. In this presentation, effects of damping on MEMS sensors with and without comb fingers will be described. It was found that the sensors with comb fingers have a significantly larger damping indicating that the longer perimeter due to combs is responsible for the observed increase [1]. However, the increase in damping reduces the quality factor which improves the response time of the device. [4pt] [1] W. Zhang and K. Turner, Sensors & Actuators: A. 134 p.594 (2007).

Roth, John; Touse, Michael; Sinibaldi, Jose; Karunasiri, Gamani

2011-03-01

167

Photonic chip based optical frequency comb using soliton induced Cherenkov radiation  

E-print Network

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

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

2014-01-01

168

Properties of a nanocomposite polymer electrolyte from an amorphous comb-branch polymer and nanoparticles  

Microsoft Academic Search

Three fully amorphous comb-branch polymers based on poly(styrene- co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether of different molecular weights as side chains were synthesized. SiO 2 nanoparticles of various contents and the salt LiCF 3SO 3 were added to these comb-branch polymers to obtain nanocomposite polymer electrolytes. The thermal and transport properties of the samples have been

Feng Zhao; Mingkui Wang; Li Qi; Shaojun Dong

2004-01-01

169

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

Microsoft Academic Search

Social wasps and hornets maintain their nest in the dark. The building of the combs by all Vespinae is always in the direction\\u000a of the gravitational force of Earth, and in each cell’s ceiling, at least one ‘keystone’ is embedded and fastened by saliva.\\u000a The sensory mechanisms that enable both building of sizeable symmetrical combs and nursing of the brood

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

2008-01-01

170

Preparation and properties of a new type of comb-shaped, amphiphilic cellulose derivative  

Microsoft Academic Search

Comb-shaped, amphiphilic O-(2- hydroxy-3-butoxypropyl) cellulose (HBPC) was prepared by a homogeneous reaction of cellulose with butyl glycidyl ether (BGE) in a 10% (w\\/w) LiCl--DMAc solution. It was found that: (a) the molar substitution (MS) of water-soluble HBPC ranges from 0.4 to 1.0, and is nearly equal to its degree of substitution (DS), indicating that the HBPC derivatives obtained are comb-shaped

H. Nishimura; N. Donkai; T. Miyamoto

1997-01-01

171

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

172

Superdiffusive comb: application to experimental observation of anomalous diffusion in one dimension.  

PubMed

A possible mechanism of superdiffusion of ultracold atoms in a one-dimensional polarization optical lattice, observed experimentally in Phys. Rev. Lett. 108, 093002 (2012), is suggested. The analysis is based on a consideration of anomalous diffusion in a fractal comb [Phys. Rev. E 83, 052106 (2011)]. It is shown that the transport exponent is determined by the fractal geometry of the comb due to recoil distributions resulting in Lévy flights of atoms. PMID:23030962

Iomin, Alexander

2012-09-01

173

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

174

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

E-print Network

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 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 a unique and different approach towards quantum operations beyond the uncertainty limit.

Changliang Ren; Holger F. Hofmann

2014-03-13

175

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

NASA Astrophysics Data System (ADS)

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. Simulations of frequency comb spectra show that the photon-limited wavelength calibration precision achievable with existing echelle spectrographs should be ~1cms-1 when integrated over a 4000 Å range. Moreover, comb spectra may be used to accurately characterize distortions of the wavelength scale introduced by the spectrograph and detector system. The simulations show that frequency combs with pulse repetition rates of 5-30GHz are required, given the typical resolving power of existing and possible future echelle spectrographs. Achieving such high repetition rates, together with the desire to produce all comb modes with uniform intensity over the entire optical range, represents the only significant challenges in the design of a practical system. Frequency comb systems may remove wavelength calibration uncertainties from all practical spectroscopic experiments, even those combining data from different telescopes over many decades.

Murphy, M. T.; Udem, Th.; Holzwarth, R.; Sizmann, A.; Pasquini, L.; Araujo-Hauck, C.; Dekker, H.; D'Odorico, S.; Fischer, M.; Hänsch, T. W.; Manescau, A.

2007-09-01

176

PHYSICAL REVIEW A 84, 062512 (2011) XUV frequency-comb metrology on the ground state of helium  

E-print Network

PHYSICAL REVIEW A 84, 062512 (2011) XUV frequency-comb metrology on the ground state of helium in a scheme of direct-frequency-comb excitation of helium atoms from the ground state to the 1s4p and 1s5p 1 P with a modulation contrast of up to 55%. Analysis of the visibility of this comb structure, thereby using the helium

177

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

178

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

179

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

180

Prostitution & Sex Trafficking  

E-print Network

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

New Hampshire, University of

181

Sex, dependency, and helping  

Microsoft Academic Search

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

Charles L. Gruder; Thomas D. Cook

1971-01-01

182

Sex ratio, sex change, and natural selection.  

PubMed Central

We describe the analogy between the theory of natural selection on sex ratio in newborn gonochores (which will not change sex), and on the age of sex change in sequential hermaphrodites (which are all born into one sex and change to the other later on). We also discuss the conditions under which natural selection favors sequential hermaphrodites over gonochores and vice versa. We show that, in a nearly stable population of nearly constant age composition, selection favors a rare mutant if it increases the prospective reproduction of its newborn bearers that are (or while they are) members of one sex by a percentage exceeding the percentage loss to the other sex. PMID:1068478

Leigh, E G; Charnov, E L; Warner, R R

1976-01-01

183

Safer Sex Guidelines  

MedlinePLUS

... barriers. Be sure to use water-based lubricants. Oral sex has low risk of transmitting HIV, but it ... the penis, can be used as barriers during oral sex. Condoms without lubricants are best for oral sex. ...

184

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

185

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

E-print Network

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 {\\em comb} in reference to the {\\em hairy-ball theorem}. An appealing feature of this approach is that for qubits (or spins 1/2) the combs are automatically invariant under $SL(2,\\CC)$, 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 $SL(2,\\CC)$ invariant we find that it is the presence of a {\\em 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 {\\em irreducibly balanced} states. The latter indicates a tight connection with 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 non-trivial to find an invariant one. By restricting the allowed local operations to rotations of the coordinate system (i.e. again to the $SL(2,\\CC)$) we manage to define a unique extension of the concurrence to general half-integer spin with an analytic convex-roof expression for mixed states.

A. Osterloh; J. Siewert

2009-08-26

186

A novel vertical comb-drive electrostatic actuator using a one layer process  

NASA Astrophysics Data System (ADS)

This paper presents the design, fabrication and testing of a new residual stress gradient based vertical comb-drive actuator. Conventional vertical comb-drive actuators need two structural layers, i.e. one for the moving fingers and a second for the fixed fingers. A vertical comb-drive actuator based on a single structural layer micromachining process, using the residual stress gradient along the thickness of the nickel of the MetalMUMPs (Metal Multi-User MEMS process) fabrication process, is developed. The MetalMUMPs provides a 20??m thick nickel film and is subject to residual stress gradients along its thickness. Two curve-up beams are devised to curve out of plane after release. The curve-up beams raise a plate with comb fingers above the substrate to form the moving fingers. The fixed comb fingers are connected to the substrate via anchors. When a voltage is applied across the moving and the fixed fingers, the moving fingers move down towards the fixed fingers. Experimental measurements on prototypes have verified the design principle. A vertical displacement of 4.81?µm at 150?V was measured.

Hailu, Zewdu; He, Siyuan; Ben Mrad, Ridha

2014-11-01

187

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. PMID:18177517

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

2008-01-01

188

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

189

Phylogenetic analyses of the genus Glaciecola: emended description of the genus Glaciecola, transfer of Glaciecola mesophila, G. agarilytica, G. aquimarina, G. arctica, G. chathamensis, G. polaris and G. psychrophila to the genus Paraglaciecola gen. nov. as Paraglaciecola mesophila comb. nov., P. agarilytica comb. nov., P. aquimarina comb. nov., P. arctica comb. nov., P. chathamensis comb. nov., P. polaris comb. nov. and P. psychrophila comb. nov., and description of Paraglaciecola oceanifecundans sp. nov., isolated from the Southern Ocean.  

PubMed

Phylogenetic analyses of the genus Glaciecola were performed using the sequences of the 16S rRNA gene and the GyrB protein to establish its taxonomic status. The results indicated a consistent clustering of the genus Glaciecola into two clades, with significant bootstrap values, with all the phylogenetic methods employed. Clade 1 was represented by seven species, Glaciecola agarilytica, G. aquimarina, G. arctica, G. chathamensis, G. mesophila, G. polaris and G. psychrophila, while clade 2 consisted of only three species, Glaciecola nitratireducens, G. pallidula and G. punicea. Evolutionary distances between species of clades 1 and 2, based on 16S rRNA gene and GyrB protein sequences, ranged from 93.0 to 95.0?% and 69.0 to 73.0?%, respectively. In addition, clades 1 and 2 possessed 18 unique signature nucleotides, at positions 132, 184?:?193, 185?:?192, 230, 616?:?624, 631, 632, 633, 738, 829, 1257, 1265, 1281, 1356 and 1366, in the 16S rRNA gene sequence and can be differentiated by the occurrence of a 15 nt signature motif 5'-CAAATCAGAATGTTG at positions 1354-1368 in members of clade 2. Robust clustering of the genus Glaciecola into two clades based on analysis of 16S rRNA gene and GyrB protein sequences, 16S rRNA gene sequence similarity of ?95.0?% and the occurrence of signature nucleotides and signature motifs in the 16S rRNA gene suggested that the genus should be split into two genera. The genus Paraglaciecola gen. nov. is therefore created to accommodate the seven species of clade 1, while the name Glaciecola sensu stricto is retained to represent species of clade 2. The species of clade 1 are transferred to the genus Paraglaciecola as Paraglaciecola mesophila comb. nov. (type strain DSM 15026(T)?=?KMM 241(T)), P. agarilytica comb. nov. (type strain NO2(T)?=?KCTC 12755(T)?=?LMG 23762(T)), P. aquimarina comb. nov. (type strain GGW-M5(T)?=?KCTC 32108(T)?=?CCUG 62918(T)), P. arctica comb. nov. (type strain BSs20135(T)?=?CCTCC AB 209161(T)?=?KACC 14537(T)), P. chathamensis comb. nov. (type strain E3(T)?=?CGMCC 1.7001(T)?=?JCM 15139(T)), P. polaris comb. nov. (type strain ARK 150(T)?=?CIP 108324(T)?=?LMG 21857(T)) and P. psychrophila comb. nov. (type strain 170(T)?=?CGMCC1.6130(T)?=?JCM 13954(T)). The type species of the genus Paraglaciecola is Paraglaciecola mesophila. An emended description of the genus Glaciecola is provided. In addition, a novel strain, 162Z-12(T), was isolated from seawater collected as part of an iron fertilization experiment (LOHAFEX) conducted in the Southern Ocean in 2009 and was subjected to polyphasic taxonomic characterization. Cells of 162Z-12(T) were Gram-negative, aerobic, motile, ovoid to short rod-shaped, obligatorily halophilic and possessed all the characteristics of the genus Paraglaciecola. Strain 162Z-12(T) shared the highest 16S rRNA gene sequence similarity with the type strains of P. agarilytica (99.7?%), P. chathamensis (99.7?%), P. mesophila (98.5?%) and P. polaris (98.3?%). However, it exhibited DNA-DNA relatedness of less than 70.0?% with its nearest phylogenetic relatives, well below the threshold value for species delineation. Further, strain 162Z-12(T) differed from the nearest species in several phenotypic characteristics, in addition to the occurrence of unique nucleotides G, T, T and T at positions 1194, 1269, 1270 and 1271 of the 16S rRNA gene. Based on the cumulative differences it exhibited from its nearest phylogenetic neighbours, strain 162Z-12(T) was identified as a novel member of the genus Paraglaciecola and assigned to the novel species Paraglaciecola oceanifecundans sp. nov. The type strain of Paraglaciecola oceanifecundans is 162Z-12(T) (?=?KCTC 32337(T)?=?LMG 27453(T)). PMID:24981324

Shivaji, Sisinthy; Reddy, Gundlapally Sathyanarayana

2014-09-01

190

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

SciTech Connect

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 [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States)

2011-09-15

191

Optical frequency comb technology for ultra-broadband radio-frequency photonics  

E-print Network

The outstanding phase-noise performance of optical frequency combs has led to a revolution in optical synthesis and metrology, covering a myriad of applications, from molecular spectroscopy to laser ranging and optical communications. However, the ideal characteristics of an optical frequency comb are application dependent. In this review, the different techniques for the generation and processing of high-repetition-rate (>10 GHz) optical frequency combs with technologies compatible with optical communication equipment are covered. Particular emphasis is put on the benefits and prospects of this technology in the general field of radio-frequency photonics, including applications in high-performance microwave photonic filtering, ultra-broadband coherent communications, and radio-frequency arbitrary waveform generation.

Torres-Company, Victor

2014-01-01

192

Quantum teleportation in space and frequency using entangled pairs of photons from a frequency comb  

NASA Astrophysics Data System (ADS)

Using entangled pairs of photons from a frequency comb and wide-band frequency-resolved homodyne detection, we propose a sequential quantum teleportation protocol for continuous variables that teleports an unknown state in space and frequency. A subthreshold optical parametric oscillator (OPO) produces a comb of entangled pairs of photons separated by the free spectral range of the OPO cavity. Wide-band frequency-resolved homodyne detection enables direct access to the sum and difference of quadratures between different teeth in the comb. Such measurements are Einstein-Podolsky-Rosen nullifiers, and can be used as the basis for teleportation protocols. Our protocol for space-and-frequency teleportation effectively links arbitrary frequency channels for frequency-division multiplexing, which has applications in universal quantum computation and large-capacity quantum communication.

Song, Hongbin; Yonezawa, Hidehiro; Kuntz, Katanya B.; Heurs, Michele; Huntington, Elanor H.

2014-10-01

193

An Equivalent Circuit Model for Vertical Comb Drive MEMS Optical Scanner Controlled by Pulse Width Modulation  

NASA Astrophysics Data System (ADS)

An equivalent circuit model for the resonant-type vertical comb-driven optical MEMS (micro electro mechanical system) scanner has been developed based on the simple extension of the parallel-plate model. Both the electrostatic torque and the induction charge models are interpreted by using the equation-defined nonlinear dependent current source on the electrical circuit simulator platform. A systematic procedure has been investigated to fit the analytical model with the experimental results by using fitting parameters including the damping coefficient, the suspension width, and the comb gap. The developed simulation model has been used to verify a new control scheme to tune the scanner's oscillation amplitude in resonance by means of the pulse-width modulation of voltage at a given pulse height; the result indicates the effective use of digital electronics for the comb-driven optical scanner.

Maruyama, Satoshi; Nakada, Muneki; Mita, Makoto; Takahashi, Takuya; Fujita, Hiroyuki; Toshiyoshi, Hiroshi

194

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

195

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

196

Mid-infrared frequency comb generation in coupled silicon microring resonators  

NASA Astrophysics Data System (ADS)

We propose and simulate an on-chip mid-IR frequency comb generator based on the four-wave mixing (FWM) effect in a coupled silicon microring resonator. The resonator is formed by suspended ridge waveguides that are designed to have low group-velocity dispersion. A continuous-wave pump laser coupled into the resonator excites other longitudinal modes of the resonator through FWM-based parametric oscillations. In comparison with the device based on a single-ring resonator, we numerically demonstrate that the pump threshold can be dramatically reduced by introducing an auxiliary ring resonator to compensate the phase mismatch between the pump and the generated comb components. The proposed frequency comb generator has a low pump threshold of ~40 mW and a high efficiency of ~25% at the pump power of 100 mW.

Zhang, Xuezhi; Liu, Tiegen; Jiang, Junfeng; Feng, Ming; Liu, Kun

2014-12-01

197

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

E-print Network

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

Boyer, Edmond

198

Brillouin-enhanced hyperparametric generation of an optical frequency comb in a monolithic highly nonlinear fiber cavity pumped by a cw laser.  

PubMed

We demonstrate self-seeded generation of a broadband comb in a highly nonlinear fiber resonator. When pumped with a cw laser, the fiber cavity generates a comb with two characteristic spacings. Hyperparametric modes spaced by approximately 2 THz create the base structure of the comb, while commensurate Brillouin modes spaced by approximately 10 GHz populate the intermediate frequency gaps. The frequency modes are coherent, and the repetition rate of the comb has been locked to a microwave standard. PMID:19518952

Braje, Danielle; Hollberg, Leo; Diddams, Scott

2009-05-15

199

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/Hz(2/3) for a signal with a carrier frequency of 35.8 GHz, compared with 94 dB/Hz(2/3) for a signal at 6.2 GHz that was obtained in the same system when a pulsed optical source was used. The optical comb was generated by mixing signals from two dielectric resonator oscillators in a Mach-Zehnder modulator. The comb spacing is equal to 4 GHz and its bandwidth was greater than 48 GHz. The temporal jitter of the comb measured by integrating the phase noise in a frequency region of 10 kHz to 10 MHz around comb frequencies of 16 and 20 GHz was only about 15 and 11 fs, respectively. PMID:24977809

Sherman, Alexander; Horowitz, Moshe; Zach, Shlomo

2014-06-30

200

Experimental optimization of the repetition rate difference in dual-comb ranging system  

NASA Astrophysics Data System (ADS)

We investigate the influence of repetition rate difference on the ranging accuracy of a dual-comb system and suggest a two-step guideline for the optimization of the repetition rate difference. The first step is to select the optimal region roughly according to the uncertainty of repetition rate and Nyquist sampling limit. The second is to select specific values in the optimal range according to the pattern and spectrum of the cross-correlation interferogram. With the aid of two-step optimization, the dual-comb ranging system can realize high-accuracy distance measurement.

Wu, Guanhao; Zhou, Qian; Shen, Luofeng; Ni, Kai; Zeng, Xianghui; Li, Yang

2014-10-01

201

Optical frequency comb generation from aluminum nitride micro-ring resonator  

E-print Network

Aluminum nitride is an appealing nonlinear optical material for on-chip wavelength conversion. Here we report optical frequency comb generation from high quality factor aluminum nitride micro-ring resonators integrated on silicon substrates. By engineering the waveguide structure to achieve near-zero dispersion at telecommunication wavelengths and optimizing the phase matching for four-wave mixing, frequency combs are generated with a single wavelength continuous-wave pump laser. The Kerr coefficient (n2) of aluminum nitride is further extracted from our experimental results.

Jung, Hojoong; Fong, King Y; Zhang, Xufeng; Tang, Hong X

2013-01-01

202

Frequency Comb-Based Remote Sensing of Greenhouse Gases over Kilometer Air Paths  

E-print Network

We demonstrate coherent dual frequency-comb spectroscopy for detecting variations in greenhouse gases. High signal-to-noise spectra are acquired spanning 5990 to 6260 cm^-1 (1600 to 1670 nm) covering ~700 absorption features from CO2, CH4, H2O, HDO, and 13CO2, across a 2-km open-air path. The transmission of each frequency comb tooth is resolved, leading to spectra with data demonstrate tracking of strong variations in mole fractions. A precision of initial demonstration. Future portable systems could support regional emissions monitoring and validation of the spectral databases critical to global s...

Rieker, Gregory B; Swann, William C; Kofler, Jon; Zolot, Alex M; Sinclair, Laura C; Baumann, Esther; Cromer, Christopher; Petron, Gabrielle; Sweeney, Colm; Tans, Pieter P; Coddington, Ian; Newbury, Nathan R

2014-01-01

203

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

Microsoft Academic Search

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

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

2010-01-01

204

Dynamic spectral line-by-line pulse shaping by frequency comb shifting.  

PubMed

Traditionally, reconfigurable optical pulse shaping is performed by using programmable spatial light modulators or tunable optical attenuators and phase shifters. We propose a technique to achieve tunability in the line-by-line pulse-shaping regime by controlling the offset frequency of an optical frequency comb. The method requires a high-spectral-resolution line-by-line shaper with channel spacing equal to a submultiple of the comb spacing. As a particular example, we numerically analyze tunable pulse-repetition-rate multiplication by grating-based line-by-line pulse shaping using a fixed phase-only mask. PMID:19572007

Caraquitena, José; Martí, Javier

2009-07-01

205

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

206

Surface acoustic wave opto-mechanical oscillator and frequency comb generator.  

PubMed

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. PMID:21886203

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

2011-09-01

207

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

208

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

E-print Network

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

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

2014-01-01

209

Mode interaction aided soft excitation of dark solitons in normal dispersion microresonators and offset-frequency tunable Kerr combs  

E-print Network

Kerr frequency combs from microresonators are now extensively investigated as a potentially portable technology for a variety of applications. Most studies employ anomalous dispersion microresonators that support modulational instability for comb initiation, and mode-locking transitions resulting in coherent bright soliton-like pulse generation have been reported. However, some experiments show comb generation in normal dispersion microresonators; simulations suggest the formation of dark pulse temporal profiles. Soft excitation of dark pulse solutions is difficult and has been demonstrated neither experimentally nor in simulation. Here we report experiments in which dark pulse combs are formed by mode-interaction-aided soft excitation; for the first time, a mode-locking transition is observed in the normal dispersion regime. A micro-heater actuated tuning scheme provides a new degree of freedom for adjusting the laser-resonator detuning; as a result we are able to substantially tune the comb offset frequency...

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

2014-01-01

210

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. PMID:21274069

Zitner, David

1985-01-01

211

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. PMID:16332742

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

2005-01-01

212

Magnetic mineralsKeystone-like crystals in cells of hornet combs  

Microsoft Academic Search

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

Ietse Stokroos; Luba Litinetsky; Johannes J. L. van der Want; Jacob S. Ishay

2001-01-01

213

Phrenology, Education, and the Politics of Human Nature: The Thought and Influence of George Combe.  

ERIC Educational Resources Information Center

Reviews the career and contributions of George Combe, an Edinburgh lawyer who proselytized for the cause of using phrenology in education. Although dismissed today as pseudoscience, phrenology (attributing various character traits to specific locations in the brain) was taken seriously as a science during the early 19th century. (MJP)

Tomlinson, Stephen

1997-01-01

214

Algorithms, Games, and Networks February 19, 2013 Lecturer: Ariel Procaccia Scribe: Chris McComb  

E-print Network

the lecture. · H.P. Young, "Condorcet's Theory of Voting". America Political Science Review, 1988. · H.P. Young, "Optimal Voting Rules". Journal of Economic Perspectives, 1995. · V. Conitzer, T. Sandholm: Chris McComb 1 Overview We discuss several topics related to the concept of voting rules as Maximum

Procaccia, Ariel

215

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

216

A parallel-plate MEMS variable capacitor with vertical thin-film comb actuators  

Microsoft Academic Search

A novel parallel-plate MEMS variable capacitor with a thin-film vertical comb actuator is proposed. The actuator can vertically displace both plates of the capacitor. Making use of the fringing held, this actuator exhibits linear displacement behavior, caused by the induced electrostatic force between the actuator's electrodes. The proposed capacitor has a low parasitic capacitance and linear capacitance response versus bias

Maher Bakri-Kassem; Raafat R. Mansour

2007-01-01

217

A parallel-plate MEMS variable capacitor with vertical thin-film comb actuators  

Microsoft Academic Search

A novel parallel-plate MEMS variable capacitor with a thin-film vertical comb actuator is proposed. The actuator can vertically displace both plates of the capacitor. Making use of the fringing field, this actuator exhibits linear displacement behavior, caused by the induced electrostatic force between the actuator's electrodes. The proposed capacitor has a low parasitic capacitance and linear capacitance response versus bias

Maher Bakri-Kassem; Raafat R. Mansour

2007-01-01

218

Transfer of Methanococcus frisius to the Genus Methanosarcina as Methanosarcina frisia comb. nov  

Microsoft Academic Search

Several methanogenic bacteria that utilize methanol, acetate, or methylamines have been isolated from marine habitats, including Methanococcus frisius. However, the 1984 description by Mah and Kuhn of the genus Methanococcus excludes methylotrophic methanebacteria such as Methanococcus frisius. Therefore, we propose to transfer this species to the genus Methanosarcina, naming it Methanosarcina frisia comb. nov. (type strain, DSM 3318 ( =

KARL-HEINZ BLOTEVOGEL; ULRICH FISCHER

219

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

Microsoft Academic Search

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

Scott Camazine

1991-01-01

220

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

221

Satellite and Next Generation Networks: proposal for QoS architectures Stphane Combes  

E-print Network

, Messaging, simple data transfer services, Real time and Non-Real time, delay sensitive and delay tolerant1 Satellite and Next Generation Networks: proposal for QoS architectures Stéphane Combes Alcatel Colonel Roche 31077 Toulouse cedex 4, France Abstract Broadband satellite systems will need specific

Paris-Sud XI, Université de

222

Sensing with mid-infrared frequency combs: a novel modality for ultrasensitive detection of hazardous materials  

Microsoft Academic Search

We propose a new concept for point and stand-off detection of chemical and biological agents as well as explosives' vapors and residues on solid surfaces based on frequency comb spectroscopy in the region of mid-IR molecular vibrational \\

Konstantin L. Vodopyanov

2009-01-01

223

Quantum theory of phase correlations in optical frequency combs generated by stimulated Raman scattering  

SciTech Connect

We explore theoretically the phase correlation between multiple generated sidebands in a Raman optical frequency comb under conditions of spontaneous initiation from quantum zero-point noise. We show that there is a near-deterministic correlation between sideband phases in each laser shot which may lead to synthesis of attosecond pulse trains.

Wu Chunbai; Raymer, M. G. [Department of Physics, Oregon Center for Optics, University of Oregon, Eugene, Oregon 97403 (United States); Wang, Y. Y.; Benabid, F. [Gas-Phase Photonic Materials Group, Centre for Photonics and Photonic Materials, University of Bath, Claverton Down, Bath, BA2 7AY (United Kingdom)

2010-11-15

224

Characteristics of sensors based on MEMS grating with interdigitated comb structures  

Microsoft Academic Search

Gratings as important spectral components have been employed in various optics applications, such as spectral analysis, filtering, dispersion compensation, sensing and so on. However, the physical structure of gratings produced by conventional technologies can not be alterable, this limits their applications under some specific requirements. Fortunately, MEMS technology breaks through that restriction, an interdigitated comb structure has been demonstrated in

Naike Wei; Weimin Wang; Jun Yao; Kefan Chen; Jianhua Zhu; Fuhua Gao

2010-01-01

225

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

226

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

227

Unisexual cucumber flowers, sex and sex differentiation.  

PubMed

Sex is a universal phenomenon in the world of eukaryotes. Attempts have been made to understand regulatory mechanisms for plant sex determination by investigating unisexual flowers. The cucumber plant is one of the model systems for studying how sex determination is regulated by phytohormones. A systematic investigation of the development of unisexual cucumber flowers is summarized here, and it is suggested that the mechanism of the unisexual flower can help us to understand how the process leading to one type of gametogenesis is prevented. Based on these findings, we concluded that the unisexual cucumber flowers is not an issue of sex differentiation, but instead a mechanism for avoiding self-pollination. Sex differentiation is essentially the divergent point(s) leading to heterogametogenesis. On the basis of analyses of sex differentiation in unicellular organisms and animals as well as the core process of plant life cycle, a concept of "sexual reproduction cycle" is proposed for understanding the essential role of sex and a "progressive model" for future investigations of sex differentiation in plants. PMID:23809434

Bai, Shu-Nong; Xu, Zhi-Hong

2013-01-01

228

Systematic study of the genus Acetobacter with descriptions of Acetobacter indonesiensis sp. nov., Acetobacter tropicalis sp. nov., Acetobacter orleanensis (Henneberg 1906) comb. nov., Acetobacter lovaniensis (Frateur 1950) comb. nov., and Acetobacter estunensis (Carr 1958) comb. nov.  

PubMed

Thirty-one Acetobacter strains obtained from culture collections and 45 Acetobacter strains isolated from Indonesian sources were investigated for their phenotypic characteristics, ubiquinone systems, DNA base compositions, and levels of DNA-DNA relatedness. Of 31 reference strains, six showed the presence of ubiquinone 10 (Q-10). These strains were eliminated from the genus Acetobacter. The other 25 reference strains and 45 Indonesian isolates were subjected to a systematic study and separated into 8 distinct groups on the basis of DNA-DNA relatedness. The known species, Acetobacter aceti, A. pasteurianus, and A. peroxydans are retained for three of these groups. New combinations, A. orleanensis (Henneberg 1906) comb. nov., A. lovaniensis (Frateur 1950) comb. nov., and A. estunensis (Carr 1958) comb. nov. are proposed for three other groups. Two new species, A. indonesiensis sp. nov. and A. tropicalis sp. nov. are proposed for the remaining two. No Indonesian isolates were identified as A. aceti, A. estunensis, and A. peroxydans. Phylogenetic analysis on the basis of 16S rDNA sequences was carried out for representative strains from each of the groups. This supported that the eight species belonged to the genus Acetobacter. Several strains previously assigned to the species of A. aceti and A. pasteurianus were scattered over the different species. It is evident that the value of DNA-DNA relatedness between strains comprising a new species should be determined for the establishment of the species. Thus current bacterial species without data of DNA-DNA relatedness should be reexamined for the stability of bacterial nomenclature. PMID:12483588

Lisdiyanti, Puspita; Kawasaki, Hiroko; Seki, Tatsuji; Yamada, Yuzo; Uchimura, Tai; Komagata, Kazuo

2000-06-01

229

Perceived Personnel Suitability: A Function of Job Sex Type, Sex Role, and Sex.  

ERIC Educational Resources Information Center

Descriptions varying sex and sex role of job applicants were rated by 605 respondents for suitability for four sex-typed jobs. Results show sex role by job type interaction. A pattern in which sex roles and sex complement each other is noted and interpreted in the context of the positive perception of androgynous applicants in sex role literature.…

Koenig, Esther J.; Juni, Samuel

1985-01-01

230

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

231

Sex Education: Another View  

ERIC Educational Resources Information Center

The mother of a 14-year-old mentally retarded boy comments on the viewpoints of Dr. Sol Gordon (a sex education columnist) regarding masturbation, questions on sex, marriage, and the parents' role. (SBH)

Hamilton, Jennifer

1977-01-01

232

All-fiber frequency comb employing a single walled carbon nanotube saturable absorber for optical frequency metrology in near infrared  

NASA Astrophysics Data System (ADS)

Optical frequency combs produced by mode-locked fiber lasers are us eful tools for high precision frequency metrology and molecular spectroscopy in a robust and portable format. We have specifically investigated erbium doped fiber mode-locked lasers that use single-walled carbon nanotubes as a saturable absorber. We have, for the first time, developed and phase- stabilized a carbon nanotube fiber laser (CNFL) frequency comb. The carbon nanotube saturable absorber, which was fabricated using an optically driven deposition method, permits a high repetition frequency (>150 MHz) since an optical nonlinearity of fibers is not used for mode-locking. The CNFL comb combined with a parabolic pulse erbium doped fiber amplifier (EDFA) has shown a compact, robust, and cost-effective supercontinuum source. The amplified pulse from the parabolic pulse EDFA was compressed with a hollow-core photonic bandgap fiber, which produced a wave-breaking-free pulse with an all-fiber set-up. The stabilized comb has demonstrated a fractional instability of 1.2 x10-11 at 1 sec averaging time, the reference-limited instability. We have performed optical frequency metrology with the CNFL comb and have measured an optical frequency, P(13) which is a molecular overtone transition of C2H2. The measured frequency has shown a good agreement with the known value within an uncertainty of 10 kHz. In order to extend the application of the CNFL comb such as multi-heterodyne dual comb spectroscopy, we have investigated the noise of the CNFL comb and particularly, the broad carrier envelope offset frequency (f0) linewidth of the CNFL comb. The primary noise source is shown to be white amplitude noise on the oscillator pump laser combined with the sensitivity of the mode-locked laser to pump power fluctuations. The control bandwidth of f0 was limited by the response dynamics of the CNFL comb. The significant reduction of comb noise has been observed by implementing a phase-lead compensation to extend control bandwidth of the comb and by reducing the pump relative intensity noise simultaneously. Therefore the f0 linewidth has been narrower from 850 kHz to 220 kHz. The integrated phase noise for the f0 lock is 1.6 radians from 100 Hz to 102 kHz.

Lim, Jinkang

233

Sex Differences in Politicization  

Microsoft Academic Search

The finding of significant preadult sex differences in politicization earlier by Owen and Dennis (1988) is explored further. Here, we examine the relationship between sex roles, mass media use, and preadult politicization. Using data from a study of 10-17 year olds in Wisconsin in the early 1980s, we discover significant sex differences in patterns of mass media use that favor

Diana Owen; Jack Dennis

1993-01-01

234

Sex Education. Chapter Seventeen.  

ERIC Educational Resources Information Center

Information and a framework that permits teachers to plan and initiate a successful sex education program for students with mental disabilities is provided. A major aspect of sex education should be its focus on social relationships, emotions, choice-making, and responsibilities to self and others. Sex education should not be viewed as a…

Caster, Jerry A.

235

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 ... better protection against pregnancy, but may not be right for everyone. For example, spermicides that contain nonoxynol- ...

236

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

PubMed

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

Bezsonova, Irina

2014-05-30

237

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

238

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

239

Reclassification of Rhodospirillum photometricum Molisch 1907, Rhodospirillum sulfurexigens Anil Kumar et al. 2008 and Rhodospirillum oryzae Lakshmi et al. 2013 in a new genus, Pararhodospirillum gen. nov., as Pararhodospirillum photometricum comb. nov., Pararhodospirillum sulfurexigens comb. nov. and Pararhodospirillum oryzae comb. nov., respectively, and emended description of the genus Rhodospirillum.  

PubMed

The genus Rhodospirillum is represented by four species, with three of them showing phylogenetic divergence compared to the type species, Rhodospirillum rubrum. Differences in the major diagnostic properties such as internal photosynthetic membranes, quinones, fatty acids, carotenoid composition and a few other phenotypic properties warrant the reclassification of members of this genus. Resultantly, a new genus, Pararhodospirillum gen. nov., is proposed based on the analysis of nine strains to accommodate Rhodospirillum photometricum, Rhodospirillum sulfurexigens and Rhodospirillum oryzae as Pararhodospirillum photometricum comb. nov., Pararhodospirillum sulfurexigens comb. nov. and Pararhodospirillum oryzae comb. nov., respectively. The type species of the genus is Pararhodospirillum photometricum comb. nov. An emended description of the genus Rhodospirillum is also proposed. PMID:24368693

Lakshmi, K V N S; Divyasree, B; Ramprasad, E V V; Sasikala, Ch; Ramana, Ch V

2014-04-01

240

Optical-frequency-comb generation and entanglement with low-power optical input in a photonic molecule  

NASA Astrophysics Data System (ADS)

Optical-frequency combs consisting of equally spaced sharp lines in frequency space have triggered substantial advances in optical-frequency metrology and precision measurements and in applications such as laser-based gas sensing and molecular fingerprinting. Here, we propose a scheme to generate a type of optical-frequency combs and convert them from one cavity to the other in a hybrid optical system composed of a pair of coupled photonic crystal cavities called a photonic molecule (PM) and a single semiconductor quantum dot (QD) embedded in one cavity of the molecule. Optical-frequency combs are formed by the interaction between a cavity mode and a continuous-wave (CW) two-tone driving laser consisting of a pump field and a seed field via QD-induced strong nonlinearity. In this situation, the initial input pump and seed CW lasers can interact among each other and produce optical higher-order sidebands with equal spacing via parametric frequency conversion provided by QD-induced nonlinear optical effects. Using numerical simulations, it is clearly shown that the beat frequency of the two-tone components plays an important role in determining the comb spacing and matched frequency combs can be formed in the PM. We also demonstrate that the present interacting QD-PM system can serve as a platform to generate large-scale quantum entanglement between two comb modes. The results obtained here may be useful for real experiments in a photonic crystal platform.

Li, Jiahua; Yu, Rong; Ding, Chunling; Wang, Wei; Wu, Ying

2014-09-01

241

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

242

Adaptive frequency comb illumination for interferometry in the case of nested two-beam cavities  

SciTech Connect

The homogeneity test of glass plates in a Fizeau interferometer is hampered by the superposition of multiple interference signals coming from the surfaces of the glass plate as well as the empty Fizeau cavity. To evaluate interferograms resulting from such nested cavities, various approaches such as the use of broadband light sources have been applied. In this paper, we propose an adaptive frequency comb interferometer to accomplish the cavity selection. An adjustable Fabry-Perot resonator is used to generate a variable frequency comb that can be matched to the length of the desired cavity. Owing to its flexibility, the number of measurements needed for the homogeneity test can be reduced to four. Furthermore, compared to approaches using a two-beam interferometer as a filter for the broadband light source, the visibility of the fringe system is considerably higher if a Fabry-Perot filter is applied.

Harder, Irina; Leuchs, Gerd; Mantel, Klaus; Schwider, Johannes

2011-09-01

243

Near infrared frequency comb vernier spectrometer for broadband trace gas detection.  

PubMed

We present a femtosecond frequency comb vernier spectrometer in the near infrared with a femtosecond Er doped fiber laser, a scanning high-finesse cavity and an InGaAs camera. By utilizing the properties of a frequency comb and a scanning high-finesse cavity such a spectrometer provides broad spectral bandwidth, high spectral resolution, and high detection sensitivity on a short time scale. We achieved an absorption sensitivity of ~8 × 10-8 cm-1Hz-1/2, corresponding to a detection limit of ~70 ppbv for acetylene, with a resolution of ~1.1 GHz in single images taken in 0.5 seconds and covering a frequency range of ~5 THz. Such measurements have broad applications for sensing greenhouse gases in this fingerprint near infrared region with a simple apparatus. PMID:25321773

Zhu, Feng; Bounds, James; Bicer, Aysenur; Strohaber, James; Kolomenskii, Alexandre A; Gohle, Christoph; Amani, Mahmood; Schuessler, Hans A

2014-09-22

244

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

245

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

E-print Network

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 $f^{(1)}_0 $ and $f^{(2)}_0$) referenced to a common cavity-stabilized narrow linewidth CW laser. Their relative offset frequency $ \\Delta f_0 = f^{(2)}_0 - f^{(1)}_0 $, which appears across their entire spectra, provides a convenient measure of the phase noise. By comparing $\\Delta f_0$ 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; Hollberg, Leo

2014-01-01

246

Do Bees and Hornets Use Acoustic Resonance in Order to Monitor and Coordinate Comb Construction?  

Microsoft Academic Search

We propose that social hornets and bees, who construct large arrays (known as combs) of cells for hatching and brooding their\\u000a offspring, exploit ultrasonic acoustic resonances in those cells in order to implement the accurate honeycomb structure exhibited\\u000a by those arrays. This idea is supported by a number of theoretical considerations, including a detailed analysis of the spectrum\\u000a of lateral

David J. Bergman; Jacob S. Ishay

2007-01-01

247

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

248

Bulk-Quantity Synthesis and Conductive Properties of Comb-Like Dendritic ZnO Nanostructures  

Microsoft Academic Search

Adopting a simple low-temperature (~500 degrees C) vapour process, we have synthesized bulk quantity comb-like dendritic ZnO nanostructures in large area. An atomic force microscope equipped with Au-coated probes was employed to elucidate the current-voltage characteristic of the individual ZnO nanocomb. The connection electrodes were defined by depositing Pt wires using focused ion beam (FIB). A rectification effect was observed,

Zhi-Min Liao; Hong-Zhou Zhang; Jun Xu; Da-Peng Yu

2005-01-01

249

CMOS-compatible, multiplexed source of heralded photon pairs: towards integrated quantum combs  

E-print Network

We report an integrated photon pair source based on a CMOS-compatible microring resonator that generates multiple, simultaneous, and independent photon pairs at different wavelengths in a frequency comb compatible with fiber communication wavelength division multiplexing channels (200 GHz channel separation) and with a linewidth that is compatible with quantum memories (110 MHz). It operates in a self-locked pump configuration, avoiding the need for active stabilization, making it extremely robust even at very low power levels.

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

2014-03-24

250

Reclassification of Cellulomonas cellulans (Stackebrandt and Keddie 1986) as Cellulosimicrobium cellulans gen. nov., comb. nov.  

PubMed

Phylogenetic analysis of 16S rDNA provides evidence that Cellulomonas cellulans branches outside the phylogenetic confines of the genus Cellulomonas. The distinct phylogenetic and chemotaxonomic status of Cellulomonas cellulans as a phylogenetic neighbour of the genus Promicromonospora, justifies the description of a new genus for which the name Cellulosimicrobium gen. nov. with the type species Cellulosimicrobium cellulans comb. nov. is proposed. PMID:11411667

Schumann, P; Weiss, N; Stackebrandt, E

2001-05-01

251

Music Visualization by Means of Comb Filter and Relaxation Time According to Human Perception  

Microsoft Academic Search

\\u000a The visualization of an audio signal’s time structure is the primary step for every rhythm synchronizer system. To achieve\\u000a this, principle components of the musical signal beats as strength, tempo and onset time must be detected. A filter bank of\\u000a 180 different comb filters (from 60 bpm to 240 bpm) is convolved with different styles of musical signal to visualize

Mahdieh Poostchi; Iman Kamkar; Javad Mohebbi

252

The fractional Fokker–Planck equation on comb-like model  

Microsoft Academic Search

The fractional Fokker–Planck equation, were used to describe the anomalous diffusion in external fields, is derived using a comb-like structure as a background model. For the force-free case, the distribution function associated with space dependence diffusion coefficient along the backbone of the structure are obtained in a closed form of H-function. The operator method has been used to solve the

M. A. Zahran; E. M. Abulwafa; S. A. Elwakil

2003-01-01

253

Design of Planer type Comb-Line Bandpass Filter And Design Parameter Extraction Using FE Analysis  

Microsoft Academic Search

In this paper, we present a design procedure of comb-line bandpass filter with asymmetrical coupled-lines, which has small size in comparison with other planar type filters to take full advantage of reducing the size of RF and microwave components. Based on a parallel coupled-line theory, we develop admittance inverter model for each asymmetric coupled-line pair. By combining equivalent circuits of

Jae-Ho Youn; Hyeong-Seok Kim; Byeong-Gwon Kang; Jun-Seok Park; Sun-Hyung Kim; Jae-Bong Lim

2002-01-01

254

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

255

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

E-print Network

We demonstrate an octave-spanning frequency comb with a spectrum covering wavelengths from 1,540 nm up to 3,200 nm. The supercontinuum is generated by pumping a 1-cm long dispersion engineered silicon wire waveguide by 70 fs pulses with an energy of merely 15 pJ. We confirm the phase coherence of the output spectrum by beating the supercontinuum with narrow bandwidth CW lasers. We show that the experimental results are in agreement with numerical simulations.

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

2014-01-01

256

Proposal of Effusibacillus lacus gen. nov., sp. nov., and reclassification of Alicyclobacillus pohliae as Effusibacillus pohliae comb. nov. and Alicyclobacillus consociatus as Effusibacillus consociatus comb. nov.  

PubMed

A novel thermophilic, facultatively anaerobic bacterium, strain skLN1(T), was isolated from the sediment of a freshwater lake in Japan. Cells of strain skLN1(T) were rod-shaped and Gram-stain-variable. A KOH lysis test suggested that the cell wall of the isolate has a Gram-positive structure. For aerobic growth, the optimum pH was pH 7.25-7.50 and the optimum temperature was 50-52 °C. The G+C content of the genomic DNA was 50.8 mol%. Nitrate was reduced to nitrite. Alicyclic fatty acids were not detected, and branched-chain fatty acids were major components in the cellular fatty acid profile. MK-7 was the predominant respiratory quinone. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolated strain was related most closely to Alicyclobacillus consociatus CCUG 53762(T) (95% similarity). This analysis also showed that the monophyly of the genus Alicyclobacillus had been lost. On the basis of phylogenetic and phenotypic characterization, Effusibacillus lacus gen. nov., sp. nov. is proposed. The type strain of Effusibacillus lacus is skLN1(T) (?=?NBRC 109614(T)?=?DSM 27172(T)). It is also proposed that Alicyclobacillus pohliae and Alicyclobacillus consociatus should be reclassified to the genus Effusibacillus as Effusibacillus pohliae comb. nov. and Effusibacillus consociatus comb. nov., respectively. PMID:24860109

Watanabe, Miho; Kojima, Hisaya; Fukui, Manabu

2014-08-01

257

Reclassification of Methanogenium tationis and Methanogenium liminatans as Methanofollis tationis gen. nov., comb. nov. and Methanofollis liminatans comb. nov. and description of a new strain of Methanofollis liminatans  

NASA Technical Reports Server (NTRS)

Sequencing of 16S rRNA genes and phylogenetic analysis of Methanogenium tationis DSM 2702T (OCM 43T) (T = type strain) and Methanogenium liminatans GKZPZT (= DSM 4140T) as well as other members of the family Methanomicrobiaceae revealed that both species belong to a separate line of descent within this family. In addition, a new strain of Methanogenium liminatans, strain BM1 (= DSM 10196), was isolated from a butyrate-degrading, fluidized bed reactor and characterized. Cells of both species are mesophilic, highly irregular cocci that use H2/CO2 and formate for growth and methanogenesis. In addition, Methanogenium liminatans strains GKZPZT and BM1 used 2-propanol/CO2, 2-butanol/CO2 and cyclopentanol/CO2. Both species contained diether and tetraether lipids. The polar lipids comprised amino-phosphopentanetetrol derivatives, which appear to be characteristic lipids within the family Methanomicrobiaceae. The pattern of glycolipids, phosphoglycolipids and amino-phosphoglycolipids was consistent with the assignment of these two species to a taxon within the family Methanomicrobiaceae, but also permitted them to be distinguished from other higher taxa within this family. The G+C contents of the DNA of Methanogenium tationis and Methanogenium liminatans were 54 and 60 mol% (Tm and HPLC), respectively. On the basis of the data presented, the transfer of Methanogenium tationis and Methanogenium liminatans to the genus Methanofollis gen. nov. as Methanofollis tationis comb. nov. and Methanofollis liminatans comb. nov., respectively, is proposed, with Methanofollis tationis as the type species.

Zellner, G.; Boone, D. R.; Keswani, J.; Whitman, W. B.; Woese, C. R.; Hagelstein, A.; Tindall, B. J.; Stackebrandt, E.

1999-01-01

258

A Y+J Band Laser Frequency Comb for the Habitable Zone Planet Finder  

NASA Astrophysics Data System (ADS)

The Habitable Zone Planet Finder (HPF) scheduled for deployment to the Hobby-Eberly Telescope in late 2015 will extend the radial velocity search for exoplanets into the near infrared by providing a high precision, stabilized near infrared spectrograph spanning the Y+J bands (0.98-1.3?m) with 50,000 resolution. Working in the near infrared will allow the HPF to study cooler, lower mass stars than is possible with the current generation of optical spectrographs. In order to extend the precision of the HPF to lower minimum RV signatures we are proposing to develop a deployable, fully autonomous version of the Y+J band laser frequency comb currently in operation at the NIST Time and Frequency Division in Boulder, Colorado. The Y+J comb is derived from the H band (1.45-1.7?m) comb which was successfully demonstrated at the Hobby-Eberly Telescope in 2010. The deployed version will leverage off of existing hardware and demonstrated technology. We present instrument architecture and current performance as well as results of long term stability tests, filter modeling, modal noise reduction results and predicted end-to-end performance.

Osterman, Steve; Ycas, G. G.; Diddams, S. A.; Bender, C. F.; Donaldson, C. L.; Mahadevan, S.; Quinlan, F.; Ramsey, L. W.

2013-01-01

259

Design of optical frequency comb for sky survey astronomical spectrograph calibration  

NASA Astrophysics Data System (ADS)

Sky survey telescope is an important approach to ground-based observation of external galaxies, and further research on large-scale structure of the universe, galaxy formation and evolution. Sky survey spectrograph (SSS) with low resolution is included in such kind of telescope system. The spectral measurement accuracy of SSS will determine the accuracy and scientific value of mass spectral data. Currently iodine absorption cell or Thorium-Argon lamp is adopted as the calibration source for SSS. However, the spectral lines are sparse, with non-uniform spectral interval and intensity, and even instable over long time. The novel astro-comb cannot be applied to SSS directly because the spectral intervals are still too dense to be used in SSS with relatively lower resolution. In this paper, spectral mode filtering method with acceptable energy reduction and accurate spectral line frequency is studied to improve current astro-comb to properly distributed spectral lines and solve the above critical problem. Aiming at calibration for the measuring of the spectral lines in 3700-5900 Å region, we design an improved astro-comb system based on Erbium-doped fiber laser and Fabry-Perot filter series. Feasible systematical parameters are given. It will help develop a novel calibration approach with systematic error reduction to less than 1/10000 of that of the current calibration methods.

Hu, Yao; Wang, Xiang

2013-12-01

260

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

261

A comb-sampling method for enhanced mass analysis in linear electrostatic ion traps  

SciTech Connect

In this paper an algorithm for extracting spectral information from signals containing a series of narrow periodic impulses is presented. Such signals can typically be acquired by pickup detectors from the image-charge of ion bunches oscillating in a linear electrostatic ion trap, where frequency analysis provides a scheme for high-resolution mass spectrometry. To provide an improved technique for such frequency analysis, we introduce the CHIMERA algorithm (Comb-sampling for High-resolution IMpulse-train frequency ExtRAaction). This algorithm utilizes a comb function to generate frequency coefficients, rather than using sinusoids via a Fourier transform, since the comb provides a superior match to the data. This new technique is developed theoretically, applied to synthetic data, and then used to perform high resolution mass spectrometry on real data from an ion trap. If the ions are generated at a localized point in time and space, and the data is simultaneously acquired with multiple pickup rings, the method is shown to be a significant improvement on Fourier analysis. The mass spectra generated typically have an order of magnitude higher resolution compared with that obtained from fundamental Fourier frequencies, and are absent of large contributions from harmonic frequency components.

Greenwood, J. B.; Kelly, O.; Calvert, C. R.; Duffy, M. J.; King, R. B.; Belshaw, L.; Graham, L.; Alexander, J. D.; Williams, I. D. [Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Bryan, W. A. [Department of Physics, Swansea University, Swansea SA2 8PP (United Kingdom); Turcu, I. C. E.; Cacho, C. M.; Springate, E. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0QX (United Kingdom)

2011-04-15

262

Flat optical frequency comb generation and its application for optical waveform generation  

NASA Astrophysics Data System (ADS)

We demonstrate the generation of a flat optical frequency comb (OFC) using an electro absorption modulator (EAM) and two cascaded phase modulators (PM). Compared with previous flat OFC generation schemes using a Mach-Zehnder modulator (MZM) for amplitude gating of the phase modulated light, an EAM creates much shorter time window for amplitude gating, and more flattened OFC spectrum is obtained using EAM as an amplitude gate. In our experiment, a very flat OFC having 11 lines within 3-dB bandwidth (3.8 nm), and 40 GHz comb line spacing is generated. Besides the excellent spectral flatness, the strong time-domain linear-chirp of the generated OFC can be simply compensated by a dispersion compensation fiber (DCF) link, which is preferred for optical waveform generation based on spectral manipulation. In this paper, we also demonstrate the OFC application for generation of several optical waveforms by manipulating the amplitude and phase of the comb lines. High repetition-rate optical cosine pulse, optical pulse burst, optical square and triangle pulses are successfully generated.

Zhang, Fangzheng; Wu, Jian; Li, Yan; Lin, Jintong

2013-03-01

263

Pleasure and Prevention: When Good Sex Is Safer Sex  

Microsoft Academic Search

Most sexual health education programmes use fear and risk of disease to try to motivate people to practise safer sex. This gives the impression that safer sex and pleasurable sex are mutually exclusive. Yet there is growing evidence that promoting pleasure alongside safer sex messaging can increase the consistent use of condoms and other forms of safer sex. To this

Anne Philpott; Wendy Knerr; Vicky Boydellc

264

Temperature Sex Reversal Implies Sex Gene Dosage in a Reptile  

E-print Network

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

Canberra, University of

265

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

266

Sex education leads to safer sex.  

PubMed

This article reports on a range of topics about sex education and the effectiveness in reducing the initiation of sexual activity and in increasing contraceptive use. A teenager's perspective is given on what the primary barriers are to contraceptive use. These barriers are identified as guilt and embarrassment, lack of knowledge, peer pressure, communication difficulties, inexperience, lack of access, official and cultural barriers, physiological considerations, coercion, and philosophical issues. Program effectiveness is influenced by the nature and extent of community involvement. Community norms must be respected and incorporated into the sex education program. The risk of program opposition is thought to increase when teachers, parents, and community leaders are not consulted. Program success may depend on parental permission and accessibility. Effective programs must offer accurate information and creative learning activities, such as role plays and peer counseling. Adolescents must be consulted about their views on social norms on sexual activity and contraceptive use and given the opportunity to make their own decisions. Information must be given in a nonjudgmental way. The Director of the International Center on Adolescent Fertility recommends among other things, the involvement of males and linking pregnancy prevention with AIDS prevention. The Director of the San Jose School Health Centers in the US recommends jobs for youths or other youth opportunities as the best contraceptive. The Guyana Responsible Parenthood Association trains out of school youth in sex education and vocational skills. Studies of school based clinics in the US reveal access to contraception does not increase or hasten sexual activity. Evaluations of adolescent sex education programs are difficult, costly, and not comparable between programs. A World Health Organization review of nineteen sex education programs in schools finds that sexual activity is delayed or decreased. The timing of sex education before the onset of sexual activity is considered important. PMID:12287158

Blaney, C L

1993-10-01

267

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

268

Sex, Sexuality, and Sensuality  

Microsoft Academic Search

There are few words that pique our interest more than sex, and few words of passion that are filled with more innate sensation and emotion than sensuality. Yet, amazingly, relatively little is known about the inherent benefits of sexuality and sensuality on our physical, emotional and mental well-being. Some scientists have, however, begun exploring the relationship of sex on longevity

Chad L. Cross

269

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

270

CyberSex  

Microsoft Academic Search

While percentages of extramarital sex (EMS) vary from study to study, it can be estimated that 50-60% of married men and 45-55% of married women engage in extramarital sex at some time or another during their marriage and almost half come to therapy because of it. EMS appears in several different forms, only some of which are sexual in nature.

Joan D. Atwood; Limor Schwartz

2002-01-01

271

WOMEN AND CHILDREN LAST: SEX TRAFFICKING AND SEX OFFENSES: PROSECUTION OF SEX TRAFFICKERS AS SEX OFFENDERS: THE NEED FOR A SEX TRAFFICKER REGISTRY  

Microsoft Academic Search

The purpose of this article is to explore the application of U.S. sex offender laws to the sex traffickers. Sex offender laws seek to dramatically decrease recidivism of sex offenders. Applying sex offender laws to sex traffickers could have the same deterrent effect. This article is divided into seven sections. Part one defines human trafficking. Part two analyzes three different

Geneva O Brown

2011-01-01

272

WOMEN AND CHILDREN LAST: SEX TRAFFICKING AND SEX OFFENSES: PROSECUTION OF SEX TRAFFICKERS AS SEX OFFENDERS: THE NEED FOR A SEX TRAFFICKER REGISTRY  

Microsoft Academic Search

The purpose of this article is to explore the application of U.S. sex offender laws to the sex traffickers. Sex offender laws seek to dramatically decrease recidivism of sex offenders. Applying sex offender laws to sex traffickers could have the same deterrent effect. This article is divided into seven sections. Part one defines human trafficking. Part two analyzes three different

Geneva O Brown

2010-01-01

273

Sex in Fungi  

PubMed Central

Sexual reproduction enables genetic exchange in eukaryotic organisms as diverse as fungi, animals, plants, and ciliates. Given its ubiquity, sex is thought to have evolved once, possibly concomitant with or shortly after the origin of eukaryotic organisms themselves. The basic principles of sex are conserved, including ploidy changes, the formation of gametes via meiosis, mate recognition, and cell-cell fusion leading to the production of a zygote. Although the basic tenants are shared, sex determination and sexual reproduction occur in myriad forms throughout nature, including outbreeding systems with more than two mating types or sexes, unisexual selfing, and even examples in which organisms switch mating type. As robust and diverse genetic models, fungi provide insights into the molecular nature of sex, sexual specification, and evolution to advance our understanding of sexual reproduction and its impact throughout the eukaryotic tree of life. PMID:21942368

Ni, Min; Feretzaki, Marianna; Sun, Sheng; Wang, Xuying; Heitman, Joseph

2012-01-01

274

A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).  

PubMed

Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements. PMID:18385734

Li, Chih-Hao; Benedick, Andrew J; Fendel, Peter; Glenday, Alexander G; Kärtner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

2008-04-01

275

Sex education drive opposed.  

PubMed

The Catholic Bishop's Conference of the Philippines (CBCP) recently expressed its opposition to sex education modules being taught in elementary and secondary schools under the government's population education program. In a press statement, CBCP president, Archbishop Oscar Cruz stressed that parents are responsible for teaching their children about sex and that they should closely monitor initiatives to provide their children with sex education outside of the home. The CBCP supports parents' right to reject and withdraw their children from any form of sex education which is not subsidiary and subordinate to their parents' guidance and control. That position is consistent with the doctrine affirmed in Pope John Paul II's Encyclical Familiaris Consortio. Meanwhile, in Davao City, nongovernmental organizations have appealed to educators to provide sex education correctly and accurately, without fear and religious admonition. World Health Organization research has found that teaching youth about sex correctly and accurately delays the initiation of their sexual activity. Otherwise, media influences and the earlier onset of puberty are making adolescents sexually active at earlier ages. Many teachers are afraid to discuss sex, partly due to prevailing religious conservatism. PMID:12294580

1998-11-01

276

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

2008-03-01

277

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

278

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

279

A signal processing system of remote sensing infrared camera based on oversample and comb filter  

NASA Astrophysics Data System (ADS)

Remote sensing infrared camera is two-dimensional thermal imaging equipment. In this paper, a new data acquiring and processing system of TDI infrared detector is given. This system is consisted of FPGA, ADC, SRAM memory, and so on. Low-pass filtering, pixel response non-uniformity correction, data synthesis and conversion of data output is implemented by a single FPGA. The SNR is improved by denoising algorithm based on oversample and comb filter. This system is easy to implement and can be applied in imaging device widely. The performance of imaging system is improved.

Lei, Ning; Wei, Zhiyong; Wang, Hua; Li, Tao

2012-12-01

280

A laser frequency comb featuring sub-cm/s precision for routine operation on HARPS  

NASA Astrophysics Data System (ADS)

We present a re-engineered version of the laser frequency comb that has proven a few-cm/s calibration repeatability on the HARPS spectrograph during past campaigns. The new design features even better performance characteristics. The newly arranged oscillator, filter cavities and fiber injection for spectral broadening allow robust long term operation, controlled from a remote site. Its automation features enable easy operation for non-experts. The system is being prepared for installation on the HARPS spectrograph in fall of 2014, and will subsequently become available to the astronomical community.

Probst, Rafael A.; Lo Curto, Gaspare; Avila, Gerardo; Canto Martins, Bruno L.; de Medeiros, José R.; Esposito, Massimiliano; González Hernández, Jonay I.; Hänsch, Theodor W.; Holzwarth, Ronald; Kerber, Florian; Leão, Izan C.; Manescau, Antonio; Pasquini, Luca; Rebolo-López, Rafael; Steinmetz, Tilo; Udem, Thomas; Wu, Yuanjie

2014-07-01

281

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

E-print Network

Electromagnetically induced transparency in rubidium vapor prepared by a comb of short optical pulses Vladimir A. Sautenkov,1,3 Yuri V. Rostovtsev,1 C. Y. Ye,1 George R. Welch,1 Olga Kocharovskaya,1,4 and Marlan O. Scully1,2 1Department... and Information Task Force sTITFd Initia- tive, and the Welch Foundation sGrant No. A1261d. f1g O. A. Kocharovskaya and Y. I. Khanin, Zh. Eksp. Teor. Fiz. 90, 1610 s1986d fSov. Phys. JETP 63, 945 s1986dg. f2g E. Arimondo, in Progress in Optics, edited by E...

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

2005-01-01

282

Amphiphilic comb-like polymers based on poly(oxyethylene)s as drug-delivery carriers.  

PubMed

Comb-like polymers with biocompatible oxyethylene backbones and amphiphilic side groups were synthesized via polymer-analogous reactions. Using these polymers, indomethacin-loaded polymeric micelles were fabricated with various drug-to-polymer weight ratios using the oil-in-water emulsion technique. In addition, the size, size distribution, CMC, drug-loading content, and entrapment efficiency of the polymeric micelles were analyzed. The volume-weighted diameters of polymeric micelles ranged from 10 to 140 nm and were narrowly distributed for passive targeting drug delivery. The CMCs were lower (approximately 10(-8) M) than for conventional surfactants and block copolymers. PMID:18098266

Kim, Ki-Hyun; Lee, Jong-Chan; Lee, Jonghwi

2008-04-01

283

Weaving quantum optical frequency combs into continuous-variable hypercubic cluster states  

NASA Astrophysics Data System (ADS)

Cluster states with higher-dimensional lattices that cannot be physically embedded in three-dimensional space have important theoretical interest in quantum computation and quantum simulation of topologically ordered condensed-matter systems. We present a simple, scalable, top-down method of entangling the quantum optical frequency comb into hypercubic-lattice continuous-variable cluster states of a size of about 104 quantum field modes, using existing technology. A hypercubic lattice of dimension D (linear, square, cubic, hypercubic, etc.) requires but D optical parametric oscillators with bichromatic pumps whose frequency splittings alone determine the lattice dimensionality and the number of copies of the state.

Wang, Pei; Chen, Moran; Menicucci, Nicolas C.; Pfister, Olivier

2014-09-01

284

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

285

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

286

Reclassification of species of the spiral-shaped phototrophic purple non-sulfur bacteria of the alpha-Proteobacteria: description of the new genera Phaeospirillum gen. nov., Rhodovibrio gen. nov., Rhodothalassium gen. nov. and Roseospira gen. nov. as well as transfer of Rhodospirillum fulvum to Phaeospirillum fulvum comb. nov., of Rhodospirillum molischianum to Phaeospirillum molischianum comb. nov., of Rhodospirillum salinarum to Rhodovibrio salexigens.  

PubMed

The 165 rDNA sequence of Rhodospirillum mediosalinum was determined and compared with corresponding sequences from other spiral-shaped purple non-sulfur bacteria classified as or related to the genus Rhodospirillum in the alpha subclass of the Proteobacteria. Sequence similarities separate the currently recognized Rhodospirillum species into five different groups with no more than 91% sequence similarity, clearly indicating the necessity to recognize these groups as different genera. Major diagnostic properties of these bacteria are compared and new genera Phaeospirillum gen. nov., Roseospira gen. nov., Rhodothalassium gen. nov. and Rhodovibrio gen. nov. are described with the species Phaeospirillum fulvum comb. nov., Phaeospirillum molischianum comb. nov., Rhodovibrio salinarum comb. nov., Rhodovibrio sodomensis comb. nov., Rhodothalassium salexigens comb. nov. and Roseospira mediosalina comb. nov. The genus Rhodospirillum is represented by Rhodospirillum rubrum and Rhodospirillum photometricum and an emended description of this genus is also given. PMID:9734033

Imhoff, J F; Petri, R; Süling, J

1998-07-01

287

Sex Differences in Obesity  

MedlinePLUS

... Campaigns Informational Videos Fact Sheet: Sex Differences in Obesity Part 1: Definitions and Epidemiology Part 2: Effects ... Part 3: Effects of Fat Distribution Part 4: Obesity’s Impact on Co-morbidities Part 5: Neural Mechanisms ...

288

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 ...

289

Testicular Cancer and Sex  

MedlinePLUS

Testicular Cancer and Sex When the topic of TC comes about, undoubtedly one of the main concerns raised ... and its effects, men who receive chemotherapy for testicular cancer continue to function sexually, although some anticancer drugs ...

290

Practice Safer Sex  

MedlinePLUS

... your body. Get screened for STIs . Having an STI, particularly genital herpes, increases your chances of becoming ... HIV during sex. If your partner has an STI in addition to HIV, that also increases your ...

291

Sex Sells, But Risky Sex Sell for More  

Microsoft Academic Search

Each day close to 20,000 people become infected with the HIV virus worldwide; a large portion of which are infected through unprotected sex with commercial sex workers. While condoms are an effective defense against the transmission of HIV and other sexually transmitted infections, large numbers of sex workers are not using them with their clients. We argue that sex workers

Paul Gertler; Manisha Shah; Stefano Bertozzi

292

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

293

An optical comb filter for the stochastic cooling system at the Nuclotron accelerator (Joint Institute for Nuclear Research, Russia)  

NASA Astrophysics Data System (ADS)

To carry out longitudinal stochastic cooling of charge particle beams at the Nuclotron of the Joint Institute for Nuclear Research (Dubna), a unique optical comb filter was designed and developed. The designed filter has space-saving size, low insertion losses, and small dispersion. The comb filter tuning was automated using a specially designed software, which made it possible to reduce the tuning time and increase tuning accuracy up to several hertz. The designed filter with automatic tuning was successfully tested in an experiment on deuteron beam cooling. In this work, characteristics of the designed filter are presented and an algorithm of its automatic tuning is considered.

Kadenko, I.; Bezshyyko, O.; Hohov, D.; Sidorin, A.; Trubnikov, G.; Shurkhno, N.; Stassen, R.

2014-09-01

294

Mid-IR frequency measurement using an optical frequency comb and a long-distance remote frequency reference  

E-print Network

We have built a frequency chain which enables to measure the absolute frequency of a laser emitting in the 28-31 THz frequency range and stabilized onto a molecular absorption line. The set-up uses an optical frequency comb and an ultrastable 1.55 $\\mu$m frequency reference signal, transferred from LNE-SYRTE to LPL through an optical link. We are now progressing towards the stabilization of the mid-IR laser via the frequency comb and the extension of this technique to quantum cascade lasers. Such a development is very challenging for ultrahigh resolution molecular spectroscopy and fundamental tests of physics with molecules.

Bruno Chanteau; Olivier Lopez; Wei Zhang; Giorgio Santarelli; Yann Le Coq; Frédéric Auguste; Benoît Darquié; Christian Chardonnet; Anne Amy-Klein

2012-10-13

295

Television, Sex-Role Attitudes, and Sex-Role Behavior  

Microsoft Academic Search

Amount of television viewing, sex-role attitudes, and sex-role behavior were measured at two points in time in a sample of 287 adolescents. The sex-role measures concern respondents' attitudes about the sex-specific appropriateness of various household chores and their own self-reported tendency to perform those chores. The data show that television viewing makes an independent contribution to adolescents' sex-role attitudes over

Michael Morgan

1987-01-01

296

Exposing Sex Stereotypes in Recent Same-Sex Marriage Jurisprudence  

Microsoft Academic Search

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

Deborah A. Widiss; Elizabeth Rosenblatt; Douglas NeJaime

2007-01-01

297

Continuous Variable Cluster State Generation over the Optical Spatial Mode Comb  

SciTech Connect

One way quantum computing uses single qubit projective measurements performed on a cluster state (a highly entangled state of multiple qubits) in order to enact quantum gates. The model is promising due to its potential scalability; the cluster state may be produced at the beginning of the computation and operated on over time. Continuous variables (CV) offer another potential benefit in the form of deterministic entanglement generation. This determinism can lead to robust cluster states and scalable quantum computation. Recent demonstrations of CV cluster states have made great strides on the path to scalability utilizing either time or frequency multiplexing in optical parametric oscillators (OPO) both above and below threshold. The techniques relied on a combination of entangling operators and beam splitter transformations. Here we show that an analogous transformation exists for amplifiers with Gaussian inputs states operating on multiple spatial modes. By judicious selection of local oscillators (LOs), the spatial mode distribution is analogous to the optical frequency comb consisting of axial modes in an OPO cavity. We outline an experimental system that generates cluster states across the spatial frequency comb which can also scale the amount of quantum noise reduction to potentially larger than in other systems.

Pooser, Raphael C [ORNL; Jing, Jietai [East China Normal University (ECNU)

2014-01-01

298

A keystone-like grain in hornet comb cells: its nature and physical properties.  

PubMed

In the roof of cells built by the Oriental hornet, Vespa orientalis (Vespinae, Hymenoptera), there is one or more grains differing in their composition and shape from the surrounding structures. These grains have a diameter of 100-200 microm and protrude slightly from the roof inward. They contain primarily a large percentage of Ti but also Fe and occasionally Si. The mineral makeup in the grains is still uncertain, but it seems that the minerals belong to the group called perovskite. These grains in the hornet's comb may originate from the soil around the nest, that is, comprised of ceramic matter, but it is also possible that they are secreted from a gland within the frons plate of the hornet because the fungus-like secretion in this gland contains elements similar to those in the roof of the comb cells. We conjecture that the grain in question serves as a reference point for the hornets that build the cell walls in the direction of gravity. The cement whereby the building hornets conjoin the various building materials, whether organic (cellulose and the like) or inorganic (sand grains or tiny stones), is a saliva that is secreted from their oral gland, which upon release hardens into a polymeric glue. The ceramic grain embedded within this polymeric matrix is endowed with different physical properties and can therefore respond differently to the tension or pressure of the surrounding walls. PMID:12741781

Ishay, Jacob S; Riabinin, Ksenia; Kozhevnikov, Maria; van der Want, Hans; Stokroos, Ietse

2003-01-01

299

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

NASA Astrophysics Data System (ADS)

It has been shown that an inhomogeneously broadened optical transition shaped into an atomic frequency comb can store a large number of temporal modes of the electromagnetic field at the single-photon level without the need to increase the optical depth of the storage material. The readout of light modes is made efficient thanks to the rephasing of the optical-wavelength coherence similar to photon-echo-type techniques, and the reemission time is given by the comb structure. For on-demand readout and long storage times, two control fields are used to transfer the optical coherence back and forth into a spin wave. Here, we present a detailed analysis of the spin-wave storage based on chirped adiabatic control fields. In particular, we verify that chirped fields require significantly weaker intensities than ? pulses. The price to pay is a reduction of the multimode storage capacity that we quantify for realistic material parameters associated with solids doped with rare-earth-metal ions.

Miná?, Ji?í; Sangouard, Nicolas; Afzelius, Mikael; de Riedmatten, Hugues; Gisin, Nicolas

2010-10-01

300

Continuous-variable cluster-state generation over the optical spatial mode comb  

NASA Astrophysics Data System (ADS)

One-way quantum computing uses single-qubit projective measurements performed on a cluster state (a highly entangled state of multiple qubits) in order to enact quantum gates. The model is promising due to its potential scalability; the cluster state may be produced at the beginning of the computation and operated on over time. Continuous variables (CV) offer another potential benefit in the form of deterministic entanglement generation. This determinism can lead to robust cluster states and scalable quantum computation. Recent demonstrations of CV cluster states have made great strides on the path to scalability, utilizing either time or frequency multiplexing in optical parametric oscillators (OPO), both above and below threshold. The techniques relied on a combination of entangling operators and beam-splitter transformations. Here we show that an analogous transformation exists for amplifiers with Gaussian inputs states operating on multiple spatial modes. By judicious selection of local oscillators, the spatial mode distribution is analogous to the optical frequency comb consisting of axial modes in an OPO cavity. We outline an experimental system that generates cluster states across the spatial frequency comb, which can also scale the amount of quantum noise reduction to potentially larger than in other systems.

Pooser, Raphael; Jing, Jietai

2014-10-01

301

Large range dual-axis micro-stage driven by electrostatic comb-drive actuators  

NASA Astrophysics Data System (ADS)

This paper presents a micro XY stage that employs electrostatic comb-drive actuators and achieves a bi-directional displacement range greater than 225 µm per motion axis. The proposed XY stage design comprises four rigid stages (ground, motion stage, and two intermediate stages) interconnected via flexure modules. The motion stage, which has two translational degrees of freedom, is connected to two independent single degree of freedom intermediate stages via respective parallelogram (P) transmission flexures. The intermediate stages are connected to the ground via respective clamped paired double parallelogram (C-DP-DP) guidance flexures. The C-DP-DP flexure, unlike conventional flexures such as the paired double parallelogram flexure (DP-DP), provides high bearing direction stiffness (Kb) while maintaining low motion direction stiffness (Km) over a large range of motion direction displacement. This helps delay the onset of sideways instability in the comb-drive actuators that are integrated with the intermediate stages, thereby offering a significantly greater actuation stroke compared to existing designs. The presented work includes closed-form stiffness analysis of the proposed micro-stage, finite elements simulation, and experimental measurements of its static and dynamic behavior.

Olfatnia, Mohammad; Cui, Leqing; Chopra, Pankaj; Awtar, Shorya

2013-10-01

302

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

303

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. PMID:23719387

Wu, Guanhao; Takahashi, Mayumi; Arai, Kaoru; Inaba, Hajime; Minoshima, Kaoru

2013-01-01

304

A charge optimized many-body (COMB) potential for titanium and titania.  

PubMed

This work proposes an empirical, variable charge potential for Ti and TiO(2) 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 TiO(2) rutile phase, and the energetics of polymorphs of both Ti and TiO(2). The relative stabilities of TiO(2) 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 TiO(2)(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/TiO(2) interface. The adsorption energies of Cu clusters on the reduced and oxidized TiO(2)(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

305

DNA combing on low-pressure oxygen plasma modified polysilsesquioxane substrates for single-molecule studies.  

PubMed

Molecular combing and flow-induced stretching are the most commonly used methods to immobilize and stretch DNA molecules. While both approaches require functionalization steps for the substrate surface and the molecules, conventionally the former does not take advantage of, as the latter, the versatility of microfluidics regarding robustness, buffer exchange capability, and molecule manipulation using external forces for single molecule studies. Here, we demonstrate a simple one-step combing process involving only low-pressure oxygen (O2) plasma modified polysilsesquioxane (PSQ) polymer layer to facilitate both room temperature microfluidic device bonding and immobilization of stretched single DNA molecules without molecular functionalization step. Atomic force microscopy and Kelvin probe force microscopy experiments revealed a significant increase in surface roughness and surface potential on low-pressure O2 plasma treated PSQ, in contrast to that with high-pressure O2 plasma treatment, which are proposed to be responsible for enabling effective DNA immobilization. We further demonstrate the use of our platform to observe DNA-RNA polymerase complexes and cancer drug cisplatin induced DNA condensation using wide-field fluorescence imaging. PMID:25332730

Sriram, K K; Chang, Chun-Ling; Rajesh Kumar, U; Chou, Chia-Fu

2014-09-01

306

Gigahertz self-referenceable frequency comb from a semiconductor disk laser  

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

307

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

E-print Network

Typical astronomical spectrographs have a resolution ranging between a few hundred to 200.000. Deconvolution and correlation techniques are being employed with a significance down to 1/1000 th of a pixel. HeAr and ThAr lamps are usually used for calibration in low and high resolution spectroscopy, respectively. Unfortunately, the emitted lines typically cover only a small fraction of the spectrometer's spectral range. Furthermore, their exact position depends strongly on environmental conditions. A problem is the strong intensity variation between different (intensity ratios {>300). In addition, the brightness of the lamps is insufficient to illuminate a spectrograph via an integrating sphere, which in turn is important to calibrate a long-slit spectrograph, as this is the only way to assure a uniform illumination of the spectrograph pupil. Laboratory precision laser spectroscopy has experienced a major advance with the development of optical frequency combs generated by pulsed femto-second lasers. These lasers emit a broad spectrum (several hundred nanometers in the visible and near infra-red) of equally-spaced "comb" lines with almost uniform intensity (intensity ratios typically GPS) time signal as the reference. The exploration of the merits of this new technology holds the promise for broad-band, highly accurate and reproducible calibration required for reliable operation of current and next generation astronomic spectrometers.

Piet O. Schmidt; Stefan Kimeswenger; Hans Ulrich Kaeufl

2007-05-05

308

Evolution of monogenean parasites across vertebrate hosts illuminated by the phylogenetic position of Euzetrema Combes, 1965 within the Monopisthocotylea  

Microsoft Academic Search

The Monogenea, which is divided into two clades, namely the Monopisthocotylea and Polyopisthocotylea, is a highly diversified group of platyhelminth parasites that infest mainly actinopterygian and chondrichthyan fishes but also, to a lesser extent, freshwater sarcopterygian hosts. Euzetrema knoepffleri Combes, 1965 (Monogenea: Iagotrema- tidae), which is specific to the salamander Euproctus montanus Savi, 1838 is among the rare monopisthocotylean parasites

SOPHIE BENTZ; CLAUDE COMBES; LOUIS EUZET; JEAN-JACQUES RIUTORD; OLIVIER VERNEAU

2003-01-01

309

Off-pump suture repair of left ventricular rupture utilizing TachoComb® sheet: a case report and literature review  

PubMed Central

A 70-year-old woman was admitted to our institution with acute myocardial infarction. Coronary angiography demonstrated total occlusion of the left anterior descending artery, which was successfully revascularized. Four days later, the patient suddenly went into shock. The subsequent emergency operation revealed a blowout rupture of the left ventricular free wall. Several TachoComb® (CSL Behring, Tokyo, Japan) sheets were applied to control bleeding and avoid the need for a cardiopulmonary bypass. Horizontal mattress sutures were used in combination with a pair of Teflon felt strips for reinforcement. The combination of TachoComb® sheets and sutures is a novel hybrid method and an effective life-saving procedure for the treatment of left ventricular blowout ruptures. This approach avoids the need for a cardiopulmonary bypass. Sutureless repairs with TachoComb® sheet achieve rapid hemostasis without the need for cardiopulmonary bypass. This stabilizes patient hemodynamics immediately and preserves the fragile myocardium. This allows emergency room physicians to open the chest and apply the TachoComb® sheet to stabilize the patient before the cardiac surgeons arrive at the operating room. This technique will be very useful in emergency situations. PMID:23890151

2013-01-01

310

Advanced noise reduction techniques for ultra-low phase noise optical-to-microwave division with femtosecond fiber combs.  

PubMed

We report what we believe to be the lowest phase noise optical-to-microwave frequency division using fiber-based femtosecond optical frequency combs: a residual phase noise of -120 dBc/Hz at 1 Hz offset from an 11.55 GHz carrier frequency. Furthermore, we report a detailed investigation into the fundamental noise sources which affect the division process itself. Two frequency combs with quasi-identical configurations are referenced to a common ultrastable cavity laser source. To identify each of the limiting effects, we implement an ultra-low noise carrier-suppression measurement system, which avoids the detection and amplification noise of more conventional techniques. This technique suppresses these unwanted sources of noise to very low levels. In the Fourier frequency range of ?200 Hz to 100 kHz, a feed-forward technique based on a voltage-controlled phase shifter delivers a further noise reduction of 10 dB. For lower Fourier frequencies, optical power stabilization is implemented to reduce the relative intensity noise which causes unwanted phase noise through power-to-phase conversion in the detector. We implement and compare two possible control schemes based on an acousto-optical modulator and comb pump current. We also present wideband measurements of the relative intensity noise of the fiber comb. PMID:21622045

Zhang, Wei; Xu, Zhenyu; Lours, Michel; Boudot, Rodolphe; Kersalé, Yann; Luiten, Andre N; Le Coq, Yann; Santarelli, Giorgio

2011-05-01

311

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

E-print Network

June 2010 A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined is bounded by 30 kHz corresponding to a radial velocity of 5 cm/s , limited by the global positioning system

312

NOISE-ROBUST F0 ESTIMATION USING SNR-WEIGHTED SUMMARY CORRELOGRAMS FROM MULTI-BAND COMB FILTERS  

E-print Network

(F0) or pitch information of voiced speech is required for many speech applications. Although F0 and spectral comb function with teeth of decreasing amplitude, and variable teeth inter- vals, gives more of the sources, be- fore performing F0 estimation on individual signals [15]. Motivated by the information

Alwan, Abeer

313

A new analysis of reciprocated beam bending in electrostatic comb drives using a semi-analytical approach  

NASA Astrophysics Data System (ADS)

This paper investigates a new modeling and analysis of the voltage induced reciprocated beam bending effects in the unit cell of a planar, variable gap type, capacitive comb drive structures. A semi-analytical approach has been efficiently formulated to solve this coupled electromechanical problem under a steady state condition. The effect of fringe field is also incorporated to improvise on the accuracy of the solution. Additionally, an energy-based method as well as a finite element (FE) based model has been constructed to simulate and validate the semi-analytical approach. The results show that the reciprocated bending of the beams has significant effects on the performance parameters like displacement, capacitance and pull-in characteristics in the comb drive systems. This effect is also seen to vary with applied voltage and stiffness of the combs and springs. Further, a comparison with conventional lumped model shows considerable difference in the estimated values for different parameters indicating a more practical prediction through the proposed approach. Finally, a set of design guidelines is discussed to reduce this bending, so that its effects on the performance of comb drive systems can be minimized.

Mukherjee, Banibrata; Swamy, K. B. M.; Sen, Siddhartha

2014-06-01

314

The Snygg-Combs Phenomenological Theory of Perception and Its Implications for Adult Education Theory and Practice.  

ERIC Educational Resources Information Center

The Snygg-Combs theory of perception was examined as to its utility in subsuming and explaining the interaction of common elements found among variables in adult teaching and learning situations. Answers were sought to 15 questions regarding the origins, essential characteristics, criticisms, and methodologies of the theory; its philosophical…

Russell, John Tennyson

315

A NEW SPECIES OF NEOCYPHOLAELAPS(ACARI : AMEROSEIIDAE) FROM BROOD COMBS OF THE INDIAN HONEY BEE (1)  

E-print Network

A NEW SPECIES OF NEOCYPHOLAELAPS(ACARI : AMEROSEIIDAE) FROM BROOD COMBS OF THE INDIAN HONEY BEE (1 of the Indian honey bee, Apis cerana indica Fabr., from Pakistan. A list of known species of Neocypholaelaps Indian honey bees (Apis cerana indica Fabr.) were received recently from Mr. Rafiq Ahmad of the Pakistan

Paris-Sud XI, Université de

316

CombNET-III with Nonlinear Gating Network and Its Application in Large-Scale Classification Problems  

NASA Astrophysics Data System (ADS)

Modern applications of pattern recognition generate very large amounts of data, which require large computational effort to process. However, the majority of the methods intended for large-scale problems aim to merely adapt standard classification methods without considering if those algorithms are appropriated for large-scale problems. CombNETII was one of the first methods specifically proposed for such kind of a task. Recently, an extension of this model, named CombNET-III, was proposed. The main modifications over the previous model was the substitution of the expert networks by Support Vectors Machines (SVM) and the development of a general probabilistic framework. Although the previous model's performance and flexibility were improved, the low accuracy of the gating network was still compromising CombNET-III's classification results. In addition, due to the use of SVM based experts, the computational complexity is higher than CombNET-II. This paper proposes a new two-layered gating network structure that reduces the compromise between number of clusters and accuracy, increasing the model's performance with only a small complexity increase. This high-accuracy gating network also enables the removal the low confidence expert networks from the decoding procedure. This, in addition to a new faster strategy for calculating multiclass SVM outputs significantly reduced the computational complexity. Experimental results of problems with large number of categories show that the proposed model outperforms the original CombNET-III, while presenting a computational complexity more than one order of magnitude smaller. Moreover, when applied to a database with a large number of samples, it outperformed all compared methods, confirming the proposed model's flexibility.

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

317

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

E-print Network

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

Doedel, Eusebius

318

High-speed, rate-scalable photonic-assisted digitizer equalization by frequency comb referencing.  

PubMed

A scalable analog-to-digital converter based on polychromatic sampling and optical-domain frequency referencing is described. The new architecture relies on low-distortion replication of an optical signal to spectrally distinct copies and subsequent polychromatic parametric sampling. Frequency comb referencing of parametric replication and sampling was used to convert processor distortions into quasi-stationary impairments and enable a practical equalization implementation. The operation of the new digitizer was demonstrated at 30 GS/s, achieving 6.5 effective number of bits in the first Nyquist zone. In contrast to conventional analog-to-digital converters, the new preprocessor sampling bandwidth is not restricted to the first Nyquist zone, and can operate in the second and third Nyquist zones beyond 40 GHz. PMID:25321503

Wiberg, A O J; Esman, D J; Temprana, E; Myslivets, E; Kuo, B P-P; Alic, N; Radic, S

2014-09-01

319

Large-Stroke Self-Aligned Vertical Comb Drive Actuators for Adaptive Optics Applications  

SciTech Connect

A high-stroke micro-actuator array was designed, modeled, fabricated and tested. Each pixel in the 4x4 array consists of a self-aligned vertical comb drive actuator. This micro-actuator array was designed to become the foundation of a micro-mirror array that will be used as a deformable mirror for adaptive optics applications. Analytical models combined with CoventorWare{reg_sign} simulations were used to design actuators that would move up to 10{micro}m in piston motion with 100V applied. Devices were fabricated according to this design and testing of these devices demonstrated an actuator displacement of 1.4{micro}m with 200V applied. Further investigation revealed that fabrication process inaccuracy led to significantly stiffer mechanical springs in the fabricated devices. The increased stiffness of the springs was shown to account for the reduced displacement of the actuators relative to the design.

Carr, E J; Olivier, S S; Solgaard, O

2005-10-27

320

Generation of three-primary-color Raman comb in the continuous-wave regime  

NASA Astrophysics Data System (ADS)

We demonstrate the generation of continuous-wave Stokes and anti-Stokes Raman sidebands including the three-primary-color (683, 532, and 436 nm) components. The Raman sidebands are generated through both stimulated and coherent anti-Stokes Raman scattering in a broadband high-finesse optical cavity filled with gas-phase hydrogen as a Raman-active medium and covering the entire visible spectral range (420-680 nm). The blue emission is considerably enhanced by matching the frequency with one of the longitudinal modes of the optical cavity, and high conversion efficiencies are observed when the coherent length corresponds to an integral multiple of the round-trip length of the optical cavity. This indicates that phase-matching plays a critical role in determining the efficiency of the Raman comb generation.

Takabayashi, Jumpei; Zaitsu, Shin-ichi; Imasaka, Totaro

2014-10-01

321

Wavelength stabilization using a frequency comb for differential absorption lidar measurements of atmospheric greenhouse gases  

NASA Astrophysics Data System (ADS)

Many studies recently have investigated the active remote sensing of atmospheric greenhouse gases, such as CO2 and CH4, by means of differential absorption lidar systems. According to them, the accuracy of the laser wavelengths used is one of the most important issues of this technique in terms of conformance to the high measurement sensitivity requirements defined. The most common method to stabilize the wavelength of the lidar transmitter is the use of an absorption cell, filled with the respective trace gas or another gas with appropriate absorption lines. However, the performance of this method is limited. Here, we present the application of a frequency comb. It is a powerful tool for high precision wavelength stabilization purposes providing the knowledge of the absolute wavelength. By this means the online and offline radiations of a DIAL system can be stabilized to any wavelengths needed with highest accuracy and precision.

Amediek, A.; Ehret, G.; Quatrevalet, M.; Fix, A.; Wirth, M.

2009-12-01

322

Comb-assisted subkilohertz linewidth quantum cascade laser for high-precision mid-infrared spectroscopy  

SciTech Connect

We report on the linewidth narrowing of a room-temperature mid-infrared quantum cascade laser by phase-locking to a difference-frequency-generated radiation referenced to an optical frequency comb synthesizer. A locking bandwidth of 250 kHz, with a residual rms phase-noise of 0.56 rad, has been achieved. The laser linewidth is narrowed by more than 2 orders of magnitude below 1 kHz, and its frequency is stabilized with an absolute traceability of 2 Multiplication-Sign 10{sup -12}. This source has allowed the measurement of the absolute frequency of a CO{sub 2} molecular transition with an uncertainty of about 1 kHz.

Galli, I.; Cappelli, F.; Bartalini, S.; Mazzotti, D.; Giusfredi, G.; Cancio, P.; De Natale, P. [CNR-INO-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, FI (Italy) [CNR-INO-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, FI (Italy); LENS-European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino, FI (Italy); Siciliani de Cumis, M. [CNR-INO-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, FI (Italy)] [CNR-INO-Istituto Nazionale di Ottica, Largo E. Fermi 6, 50125 Firenze, FI (Italy); Borri, S. [CNR-IFN-Istituto di Fotonica e Nanotecnologie, Via Amendola 173, 70126 Bari, BA (Italy)] [CNR-IFN-Istituto di Fotonica e Nanotecnologie, Via Amendola 173, 70126 Bari, BA (Italy); Montori, A. [LENS-European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino, FI (Italy)] [LENS-European Laboratory for Non-Linear Spectroscopy, Via Carrara 1, 50019 Sesto Fiorentino, FI (Italy); Akikusa, N. [Development Bureau Laser Device R and D Group, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)] [Development Bureau Laser Device R and D Group, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan); Yamanishi, M. [Central Research Laboratories, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)] [Central Research Laboratories, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)

2013-03-25

323

Properties of ultrasonic acoustic resonances for exploitation in comb construction by social hornets and honeybees  

NASA Astrophysics Data System (ADS)

Physical and mathematical considerations are presented in support of the suggestion that social hornets and bees, which construct brood combs with large arrays of cells in a honeycomb structure, exploit ultrasonic acoustic resonances in those cells in order to achieve the great accuracy of the hexagonal symmetry exhibited by these honeycomb-structured arrays. We present a numerical calculation of those resonances for the case of a perfect-hexagon duct utilizing a Bloch-Floquet-type theorem. We calculate the rate of energy dissipation in those resonances and use that, along with other considerations, to identify the resonance that is best suited for the suggested use by bees and hornets. Previously recorded ultrasonic data on social hornets and honeybees are cited which agree with some of our predictions and thus provide support for the above-mentioned suggestion.

Kadmon, Jonathan; Ishay, Jacob S.; Bergman, David J.

2009-06-01

324

Highly Stable Wideband Microwave Extraction by Synchronizing Widely Tunable Optoelectronic Oscillator with Optical Frequency Comb  

NASA Astrophysics Data System (ADS)

Optical frequency combs (OFCs), based on mode-locked lasers (MLLs), have attracted considerable attention in many fields over recent years. Among the applications of OFCs, one of the most challenging works is the extraction of a highly stable microwave with low phase noise. Many synchronisation schemes have been exploited to synchronise an electronic oscillator with the pulse train from a MLL, helping to extract an ultra-stable microwave. Here, we demonstrate novel wideband microwave extraction from a stable OFC by synchronising a single widely tunable optoelectronic oscillator (OEO) with an OFC at different harmonic frequencies, using an optical phase detection technique. The tunable range of the proposed microwave extraction extends from 2 GHz to 4 GHz, and in a long-term synchronisation experiment over 12 hours, the proposed synchronisation scheme provided a rms timing drift of 18 fs and frequency instabilities at 1.2 × 10-15/1 s and 2.2 × 10-18/10000 s.

Hou, D.; Xie, X. P.; Zhang, Y. L.; Wu, J. T.; Chen, Z. Y.; Zhao, J. Y.

2013-12-01

325

Transmission characteristics of Mach-Zehnder interferometer comb filter based on thermal operation  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate switchable and tunable transmission characteristics of a Mach-Zehnder interferometer comb filter based on thermal operation. Its temperature characteristics are investigated to reveal a shift in the peak wavelength position from 0.003 to 0.004 nm/°C and a tunable range of wavelength spacing of 0.76-0.90 nm for maximum and minimum effective lengths, respectively. This configuration provides the unique advantages of an all-fiber structure, tunable wavelength spacing, switchable spectral peaks, independent tuning of the center wavelength and wavelength spacing of the spectral peaks, and low polarization sensitivity. It is relatively simple to fabricate and expected to have applications in temperature fiber optic sensors and multiwavelength fiber laser sources.

Islam, M. S.; Mohammad, A. B.

2014-10-01

326

Generation of a 50-tone optical frequency comb with a tone-to-noise ratio larger than 37 dB  

NASA Astrophysics Data System (ADS)

By inserting an asymmetric Mach-Zehnder interferometer (AMZI) into the re-circulating frequency shift loop, we experimentally obtained a 50-tone optical frequency comb with a tone-to-noise ratio larger than 37 dB. The simulation and experimental results show that the amplified spontaneous emission (ASE) noise of the optical frequency comb can be suppressed by 3 dB after the first loop, and the tone-to-noise ratio of the 50-tone optical frequency comb is enhanced by 23.5 dB compared to that without the AMZI.

Zhang, Xia; Lin, Jiachuan; Xi, Lixia; Zhang, Xiaoguang; Bai, Chenglin

2014-03-01

327

Sex Role Concepts.  

ERIC Educational Resources Information Center

Sex-role concepts in 120 children aged three to seven were assessed by means of an instrument that allowed children to categorize attributes as being characteristic of males only, females only, both males and females or nobody. The children sorted attributes once for adult peer stimulus figures and once for peer stimulus figures. The relationship…

Urberg, Kathryn

328

Empathy in sex offenders  

Microsoft Academic Search

Sex offenders are thought to suffer from deficits in their capacity to experience empathy, and this is considered to be important in the development, and particularly the maintenance, of their deviant behaviour. The concept of empathy, however, is confused. A multicomponent staged model of empathy is outlined, and it is suggested that empathy deficits may be more person-specific than has

Yolanda Maria Fernandez

1995-01-01

329

Adolescent Sex Offenders  

Microsoft Academic Search

In this article, we review the research literature on sexual offenses committed by adolescents. Given the large number of adolescent sex offenders and the even larger number of their victims, most of whom are younger children, this is a subject matter in need of much more empirical study than it has so far received. Topics covered are incidence statistics, offense

Glen E. Davis; Harold Leitenberg

1987-01-01

330

Teens, Sex and Sexting  

MedlinePLUS Videos and Cool Tools

... HealthDay October 6, 2014 Related MedlinePlus Pages Internet Safety Teen Sexual Health Transcript Which comes first teen sexting or teen sex? The answer, researchers say, may help health care providers talk to and treat adolescents. In a new study published in the journal ...

331

Sexing Geography, Teaching Sexualities.  

ERIC Educational Resources Information Center

Draws on experiences as a straight feminist geographer to address questions regarding teaching sexualities in geography. Looks at "sexing" and "queering" geography curricula at the college level; discusses strategies to make universities and classrooms less heterosexist and lesbo/homophobic; and discusses dilemmas of disclosing sexuality in the…

England, Kim

1999-01-01

332

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

333

Sexe et sentiments  

Microsoft Academic Search

Sex is established as soon as spermatozoid and ovule have met. Except for rare cases of ambiguity, you clearly see at birth whether the baby is a boy or a girl. This mere factual difference evolves into sexual identity through childhood and fully blossoms in teenagers. Is sexual maturity happily completed then ? Not always.Unrational sexual pulsions and survival instincts belong

D. Winaver

2002-01-01

334

Sex, Courtship, and Marriage.  

ERIC Educational Resources Information Center

The author presents an historical perspective on abortion, contraception and marriage as a prelude to an examination of changing attitudes toward sex. The article deals with the negative effects attributed to the increased incidence of early dating and early marriage of teenagers in the United States. The author also assumes positions on such…

Seiferth, Berniece

335

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

336

Child sex rings  

Microsoft Academic Search

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

N J Wild; J M Wynne

1986-01-01

337

Teenage sex talk.  

PubMed

Although an international study recently revealed that 87% of the UK's teenage mothers are unmarried, the highest figure in the world according to Alan Guttmacher Institute data of 1998, the teen conception rate in the country has declined considerably over the past 25 years and the number of teen mothers has been almost halved. Teens, as well as couples in other age groups, are increasingly cohabiting outside of marriage rather than getting married; more than two-thirds of babies born to teenagers are jointly registered by both parents. However, despite the decline in teenage conceptions since 1970, the UK still has one of the highest rates in Europe. The UK's real scandal is its failure to give young people the information they need to manage their sexual health. International research has proven that sexual health can be improved if societies are open about sex, accept teenage sexuality, and permit discussion about sex without embarrassment. Moreover, sex and relationships education should start at an early age, and young people should have easy access to free and confidential sex advice. Individuals under age 16 years have the right to the same degree of confidentiality as that afforded to adults. Vast potential exists for nurses to increase teenagers' use of services by removing the key obstacles which deter them from seeking advice: fears about confidentiality, lack of service publicity, and inappropriate opening times. PMID:9749022

Hadley, A

338

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

339

Sex Education and Ideals  

ERIC Educational Resources Information Center

This article argues that sex education should include sexual ideals. Sexual ideals are divided into sexual ideals in the strict sense and sexual ideals in the broad sense. It is argued that ideals that refer to the context that is deemed to be most ideal for the gratification of sexual ideals in the strict sense are rightfully called sexual…

de Ruyter, Doret J.; Spiecker, Ben

2008-01-01

340

Combinations of Earth Orientation Measurements: SPACE94, COMB94, and POLE94  

NASA Technical Reports Server (NTRS)

A Kalman filter has been used to combine independent measurements of the Earth's orientation taken by the space-geodetic observing techniques of lunar laser ranging, satellite laser ranging, very long baseline interferometry, and the Global Positioning System. Prior to their combination, the data series were adjusted to have the same bias and rate, the stated uncertainties of the measurements were adjusted, and data points considered to be outliers were deleted. The resulting combination, SPACE94, consists of smoothed, interpolated polar motion and UT1-UTC values spanning October 6, 1976, to January 27, 1995, at 1-day intervals. The Kalman filter was then used to combine the space-geodetic series comprising SPACE94 with two different, independent series of Earth orientation measurements taken by the technique of optical astrometry. Prior to their combination with SPACE94, the bias, rate and annual term of the optical astrometric series were corrected, the stated uncertainties of the measurements were adjusted, and data points considered to be outliers were deleted. The adjusted optical astrometric series were then combined with SPACE94 in two steps: (1) the Bureau International de l'Heure (BIH) optical astrometric series was combined with SPACE94 to form COMB94, a combined series of smoothed, interpolated polar motion and UT1-UTC values spanning January 20, 1962, to January 27, 1995, at 5-day intervals, and (2) the International Latitude Service (ILS) optical astrometric series was combined with COMB94 to form POLE94, a combined series of smoothed, interpolated polar motion values spanning January 20, 1900, to January 21, 1995, at 30.4375-day intervals.

Gross, Richard S.

1996-01-01

341

Sex education in France.  

PubMed

The French Family Planning Movement (MFPF) has actively been involved in sex education within schools. In 1989, more than 1500 presentations were made to 23,000 pupils. Another activity is monitoring the application of statutes and regulations, for abortion, contraception, and sex education, and fighting to save and advance the rights of sexuality experts. Because of MFPF prominence in serious risks such as AIDs, sexual abuse, and rape, credibility has been enhanced. MFPF serves as a vehicle to change attitudes on male/female relationships. The government has permitted involvement in the preparation of a teaching program dealing with sexual abuse. The dominant influence of the Catholic Church on education has been evident since 1807. Up to WWI, religious morality was dominant. With Freud's contributions to the importance of sexuality in individual life, there were questions raised and a call for change in values and customs. In 1967, the statute was passed which authorized contraception, and sex education became an important issue. In 1973, Fontanet as Minister of Education outlined the recommendation for sex information and education in schools, including reproduction. Further official supportive recommendations were not made until 1985 when life education was entered into the primary syllabus. There was no provision even for teacher training; hence a wide variability in skills, commitment, and attitudes prevailed. MFPF reflects a position on tolerance in listening to others, expression and analysis of differences and critical thinking, identifying difficulties in talking about sex with respect to cultural and religious diversity, and help for the young in learning about their bodies, expressing feelings, and taking charge of emotions. PMID:12343168

Gallard, C

1991-05-01

342

Sex and stripping  

PubMed Central

Wolbachia pipientis is known to infect only arthropods and nematodes (mainly filarial worms). A unique feature shared by the two Phyla is the ability to replace the exoskeleton, a process known as ecdysis. This shared characteristic is thought to reflect a common ancestry. Arthropod moulting is induced by the steroid hormone 20-hydroxyecdysone (20E) and a role for ecdysteroids in nematode ecdysis has also been suggested. Removing Wolbachia from filarial worms impairs the host’s development. From analyses of the genome of Wolbachia harbored by the filarial nematode Brugia malayi and that of its host, the bacterium may provide a source of heme, an essential component of cytochrome P450’s that are necessary for steroid hormone biosynthetic pathways. In arthropods, Wolbachia is a reproductive manipulator, inducing various phenotypic effects that may be due to differences in host physiology, in particular, endocrine-related processes governing development and reproduction. Insect steroids have well-defined roles in the coordination of multiple developmental processes, and in adults they control important aspects of reproduction, including ovarian development, oogenesis, sexual behavior, and in some taxa vitellogenin biosynthesis. According to some authors ecdysteroids may also act as sex hormones. In insects sex differentiation is generally thought to be a strictly genetic process, in which each cell decides its own sexual fate based on its sex chromosome constitution, but, surprisingly, recent data demonstrate that in Drosophila sex determination is not cell-autonomous, as it happens in mammals. Thus the presence of signals coordinating the development of a gender-specific phenotype cannot be excluded. This could explain why Wolbachia interferes with insect reproduction; and also could explain why Wolbachia interferes with insect development. Thus, is “sex (=reproduction) and stripping (=ecdysis)” the key to the intimate relationship between Wolbachia and its host? PMID:20585501

Pellecchia, Marco; Greve, Pierre; Daffonchio, Daniele; Bandi, Claudio; Alma, Alberto

2010-01-01

343

Genetics of Sex part 1 I. Sex Determina.on  

E-print Network

.on) · X:A · XX/XY · ZW/ZZ · ESD (environmental sex determina.on) In Zebra fish- both. #12;8/29/12 2 · Some fish - gene.cally programmed sex change during development first, protandrous = male first Sparus aratus protandrous hermaphrodite Sex Determination

Dever, Jennifer A.

344

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

345

Sex, Violence and Movie Viewing  

MedlinePLUS

... lower right-hand corner of the player. Sex, Violence and Movie Viewing HealthDay October 20, 2014 Related ... Health Parenting Transcript Are parents becoming desensitized to violence and sex in movies targeting kids? Researchers recruited ...

346

Sex and Sexuality and HIV  

MedlinePLUS

... to transmit HIV, whether the infected partner is performing or receiving oral sex. But the risk is ... practice, you may want to use protection when performing oral sex on someone who has HIV. Dental ...

347

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

348

Liberating genetic variance through sex  

E-print Network

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

Otto, Sarah

349

Juvenile Sex Offenders in Diversion  

Microsoft Academic Search

This study was designed to address the treatment of juvenile sex offenders within diversion programs. Using data from 32 diversion programs in Colorado during the 1998–1999 fiscal year, the study observed the demographic and legal characteristics of 112 juvenile (Mean age = 14.64) sex offenders referred to diversion programs for seven types of sex assault, incest, and indecent exposure charges.

Justin S. Campbell; Cherise Lerew

2002-01-01

350

Sex Education with Young Children.  

ERIC Educational Resources Information Center

Discusses guidelines (developed by the Oregon State University Early Childhood Sex Education Project) for developing teacher-parent cooperation in providing sex education to young children. The guidelines concern how to talk about body differences and body functions; how to deal with masturbation, sex play and obscene language; and how to involve…

Koblinsky, Sally; And Others

1980-01-01

351

Promoting single sex acute units.  

PubMed

This article discusses an audit to explore patients' experiences of being nursed in mixed sex accommodation on an acute medicine unit. It outlines achievements resulting from the audit, which include staff awareness of the effect of mixed sex areas on patients and changing the culture in the unit to embrace single sex bays. PMID:21366027

Lees, Liz; Buggy, Grainne

352

Honey bees (Apis mellifera) reared in brood combs containing high levels of pesticide residues exhibit increased susceptibility to Nosema (Microsporidia) infection.  

PubMed

Nosema ceranae and pesticide exposure can contribute to honey bee health decline. Bees reared from brood comb containing high or low levels of pesticide residues were placed in two common colony environments. One colony was inoculated weekly with N. ceranae spores in sugar syrup and the other colony received sugar syrup only. Worker honey bees were sampled weekly from the treatment and control colonies and analyzed for Nosema spore levels. Regardless of the colony environment (spores+syrup added or syrup only added), a higher proportion of bees reared from the high pesticide residue brood comb became infected with N. ceranae, and at a younger age, compared to those reared in low residue brood combs. These data suggest that developmental exposure to pesticides in brood comb increases the susceptibility of bees to N. ceranae infection. PMID:22285445

Wu, Judy Y; Smart, Matthew D; Anelli, Carol M; Sheppard, Walter S

2012-03-01

353

[Sex and love].  

PubMed

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

Winaver, D

2002-04-01

354

Sex, mixability, and modularity  

PubMed Central

The assumption that different genetic elements can make separate contributions to the same quantitative trait was originally made in order to reconcile biometry and Mendelism and ever since has been used in population genetics, specifically for the trait of fitness. Here we show that sex is responsible for the existence of separate genetic effects on fitness and, more generally, for the existence of a hierarchy of genetic evolutionary modules. Using the tools developed in the process, we also demonstrate that in terms of their fitness effects, separation and fusion of genes are associated with the increase and decrease of the recombination rate between them, respectively. Implications for sex and evolution theory are discussed. PMID:20080594

Livnat, Adi; Papadimitriou, Christos; Pippenger, Nicholas; Feldman, Marcus W.

2010-01-01

355

Sex therapy and penectomy.  

PubMed

A 65-year-old man, having undergone a penectomy operation that spared the ejaculatory apparatus and some erotically responsive areas, experienced a spontaneous orgasm, with ejaculation, upon being touched in the perineal area during a massage. Unable to duplicate the experience, he (and later his wife) entered sex therapy, which resulted in his being able to have orgasms during lovemaking. The course of the therapy is described, as are certain issues arising from the therapy. Regaining of the man's orgasmic ability was accompanied by a striking improvement in the intrapsychic and interpersonal functioning of the couple, and this is taken to be an example of the "ripple effect" of successful sex therapy. The implications for this therapeutic approach for the rehabilitation of other penectomy patients and their spouses are discussed. Finally the question of surgical penile reconstruction in such cases is explored. PMID:7143459

Witkin, M H; Kaplan, H S

1982-01-01

356

Phylogenetic analysis of the genus Actinomyces based on 16S rRNA gene sequences: description of Arcanobacterium phocae sp. nov., Arcanobacterium bernardiae comb. nov., and Arcanobacterium pyogenes comb. nov.  

PubMed

A systematic phylogenetic analysis of the genus Actinomyces was performed. The 16S rRNA gene sequences of 13 Actinomyces species, an unnamed Actinomyces strain (ATCC 49338), and an Actinomyces-like isolate from sea mammals were determined. Comparative sequence analysis with closely related taxa revealed phylogenetic diversity and internal structure within the genus Actinomyces. In addition, some members of other genera (viz., the genera Arcanobacterium, Mobiluncus, and Rothia) were shown to be phylogenetically intermixed with the Actinomyces species. It was evident from both distance and tree topology considerations that the genus Actinomyces is in urgent need of taxonomic revision and requires subdivision into several genera. Based on the results of the present study it is proposed that Actinomyces bernardiae and Actinomyces pyogenes be assigned to the genus Arcanobacterium as Arcanobacterium bernardiae comb. nov. and Arcanobacterium pyogenes comb. nov., respectively. In addition, a new species, Arcanobacterium phocae, is proposed for Actinomyces-like bacteria isolated from seals. PMID:8995800

Ramos, C P; Foster, G; Collins, M D

1997-01-01

357

Acceptable sex selection.  

PubMed

John Robertson presents a persuasive argument against government prohibition of preconception sex selection (PSS) as long as there is no actual evidence of significant social harm from allowing the technology to be freely available. I am convinced by what he says about PSS and have argued along similar lines in my own work (Rhodes 1995). In these comments, I will press Robertson's conclusion in several directions to show what more he might have said in its defense. PMID:11808590

Rhodes, R

2001-01-01

358

The SW Sex enigma  

NASA Astrophysics Data System (ADS)

The SW Sex stars are a class of cataclysmic variables, originally identified because they shared a number of enigmatic properties - most notably, single-peaked emission lines instead of the double-peaked lines one would expect from their high-inclination accretion discs. We present high-time-resolution spectrophotometry of the eclipsing nova-like variables SW Sex and DW UMa, two of the founding members of the SW Sex class. Both systems show single-peaked Balmer and He ii ?4686 Å emission lines that appear to originate from a region in the disc that lies close to, but downstream of, the bright spot. The emission-line light curves are consistent with the finding from X-ray and ultraviolet observations that we predominantly see the flared disc rim and the unobscured back portion of the disc in these systems. In DW UMa, the He ii ?4686 Å emission line originates from close to the white dwarf and exhibits flaring. Such flares have been used to argue for magnetically channelled accretion, as in the intermediate polars, but the lack of a clear periodicity in the flares argues for a simpler model in which we are viewing the central regions of the disc through the non-uniform upper edge of a flared disc rim. We also observe narrow, blueshifted, transient absorption features in the Balmer lines of DW UMa, which we attribute to blobs of material ejected from the system, possibly by a magnetic propeller, that happen to be passing between us and the binary. Our results suggest that the solution to the SW Sex enigma is a combination of dominant bright-spot emission and a self-occulting disc. We also propose a simplified classification scheme for nova-like variables.

Dhillon, V. S.; Smith, D. A.; Marsh, T. R.

2013-02-01

359

No slave to sex.  

PubMed Central

Fully asexual lineages cannot purge accumulating mutations from their genome through recombination. In ancient asexuals that have persisted without sex for millions of years, this should lead to high allelic divergences (the 'Meselson effect') as has been shown for bdelloid rotifers. Homogenizing mechanisms can counter this effect, resulting in low genetic diversity within and between individuals. Here, we show that the ancient asexual ostracod species Darwinula stevensoni has very low nucleotide sequence divergence in three nuclear regions. Differences in genetic diversity between embryos and adults furthermore indicate that up to half of the observed genetic changes in adults can be caused by somatic mutations. Likelihood permutation tests confirm the presence of gene conversion in the multi-copy internal transcribed spacer sequence, but reject rare or cryptic forms of sex as a general explanation for the low genetic diversity in D. stevensoni. Other special mechanisms (such as highly efficient DNA repair) might have been selected for in this ancient asexual to overcome the mutational load and Muller's ratchet. In this case, our data support these hypotheses on the prevalence of sex, even if the two extant ancient asexual groups (bdelloids and darwinulids) seem to follow opposite evolutionary strategies. PMID:12737661

Schon, Isabelle; Martens, Koen

2003-01-01

360

The SW Sex enigma  

E-print Network

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

Dhillon, V S; Marsh, T R

2012-01-01

361

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. PMID:24719882

Olivan, Sara; Calvo, Ana Cristina; Manzano, Raquel; Zaragoza, Pilar

2014-01-01

362

Cavity-enhanced optical frequency comb spectroscopy of high-temperature H2O in a flame.  

PubMed

We demonstrate near-infrared cavity-enhanced optical frequency comb spectroscopy of water in a premixed methane/air flat flame. The detection system is based on an Er:fiber femtosecond laser, a high finesse optical cavity containing the flame, and a fast-scanning Fourier transform spectrometer (FTS). High absorption sensitivity is obtained by the combination of a high-bandwidth two-point comb-cavity lock and auto-balanced detection in the FTS. The system allows recording high-temperature water absorption spectra with a resolution of 1 GHz and a bandwidth of 50 nm in an acquisition time of 0.4 s, with absorption sensitivity of 4.2 × 10(-9) cm(-1) Hz(-1/2) per spectral element. PMID:24921580

Abd Alrahman, Chadi; Khodabakhsh, Amir; Schmidt, Florian M; Qu, Zhechao; Foltynowicz, Aleksandra

2014-06-01

363

Experimental Measurement of the Absolute Frequencies and Hyperfine Coupling Constants of 133Cs Using a Femtosecond Optical Frequency Comb  

NASA Astrophysics Data System (ADS)

High resolution two-photon spectrum of the transitions 6S1/2 ? 6P3/2 ? 8S1/2, 9S1/2 and 6S1/2 ? 6P1/2 ? 7D3/2 in neutral 133Cs are presented in a room-temperature vapor cell using a femtosecond optical frequency comb. Spectra are obtained by scanning the repetition frequency of the femtosecond optical frequency comb over the two-photon hyperfine structure. The centroid frequency of the 6S1/2 ? 8S1/2, 9S1/2, 7D3/2 transitions are 729009798.80(17) MHz, 806761363.96(11) MHz, and 780894762.595(23) MHz, respectively. The hyperfine coupling constants of the corresponding states are also obtained. The results are consistent with the previous measurements.

Jin, Li; Zhang, Yi-Chi; Xiang, Shao-Shan; Wang, Li-Rong; Ma, Jie; Zhao, Yan-Ting; Xiao, Lian-Tuan; Jia, Suo-Tang

2013-10-01

364

Flattened comb generation using only phase modulators driven by fundamental frequency sinusoidal sources with small frequency offset.  

PubMed

We propose and experimentally demonstrate a simple scheme to generate flattened optical subcarriers at low insertion loss using only phase modulators driven by fundamental frequency sinusoidal sources. A small frequency offset is introduced in the second stage to obtain phase-insensitive, stable, and flattened subcarriers. Theoretical and numerical analysis with experimental results are carried out on this scheme. Twenty-one stable comb tones with 25 GHz frequency spacing are obtained with power difference less than 3 dB. The good bit-error-ratio performance of 160.8 Gb/s polarization-division-multiplexing quadrature-phase-shift-keying signal carried by one selected subcarrier clearly demonstrates the feasibility of this comb generation scheme. PMID:23455133

Zhang, Junwen; Yu, Jianjun; Chi, Nan; Dong, Ze; Li, Xinying; Shao, Yufeng; Yu, Jianguo; Tao, Li

2013-02-15

365

Two-crystal mid-infrared optical parametric oscillator for absorption and dispersion dual-comb spectroscopy.  

PubMed

We present a femtosecond optical parametric oscillator (OPO) containing two magnesium-doped periodically poled lithium niobate crystals in a singly resonant ring cavity, pumped by two mode-locked Yb-fiber lasers. As such, the OPO generates two idler combs (up to 220 mW), covering a wavelength range from 2.7 to 4.2 ?m, from which a mid-infrared dual-comb Fourier transform spectrometer is constructed. By detecting the heterodyning signal between the two idler beams a full broadband spectrum of a molecular gas can be observed over 250??cm(-1) within 70 ?s with a spectral resolution of 15 GHz. The absorption and dispersion spectra of acetylene and methane have been measured around 3000??cm(-1), indicating that this OPO represents an ideal broadband mid-infrared source for fast chemical sensing. PMID:24876030

Jin, Yuwei; Cristescu, Simona M; Harren, Frans J M; Mandon, Julien

2014-06-01

366

Spectroscopy of the methane {nu}{sub 3} band with an accurate midinfrared coherent dual-comb spectrometer  

SciTech Connect

We demonstrate a high-accuracy dual-comb spectrometer centered at 3.4 {mu}m. The amplitude and phase spectra of the P, Q, and partial R branches of the methane {nu}{sub 3} band are measured at 25 to 100 MHz point spacing with resolution under 10 kHz and a signal-to-noise ratio of up to 3500. A fit of the absorbance and phase spectra yields the center frequency of 132 rovibrational lines. The systematic uncertainty is estimated to be 300 kHz, which is 10{sup -3} of the Doppler width and a 10-fold improvement over Fourier transform spectroscopy. These data quantify the accuracy and resolution achievable with direct comb spectroscopy in the midinfrared.

Baumann, E.; Giorgetta, F. R.; Swann, W. C.; Zolot, A. M.; Coddington, I.; Newbury, N. R. [National Institute of Standards and Technology, 325 Broadway, Boulder, Colorado 80305 (United States)

2011-12-15

367

Frequency comb generation by a continuous-wave-pumped optical parametric oscillator based on cascading quadratic nonlinearities.  

PubMed

We report optical frequency comb generation by a continuous-wave pumped optical parametric oscillator (OPO) without any active modulation. The OPO is configured as singly resonant with an additional nonlinear crystal (periodically poled MgO:LiNbO3) placed inside the OPO for phase mismatched second harmonic generation (SHG) of the resonating signal beam. The phase mismatched SHG causes cascading ?(2) nonlinearities, which can substantially increase the effective ?(3) nonlinearity in MgO:LiNbO3, leading to spectral broadening of the OPO signal beam via self-phase modulation. The OPO generates a stable 4 THz wide (-30 dB) frequency comb centered at 1.56 ?m. PMID:24177073

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

2013-11-01

368

Full characterization of a highly multimode entangled state embedded in an optical frequency comb using pulse shaping  

E-print Network

We present a detailed analysis of the multimode quantum state embedded in an optical frequency comb generated by a Synchronously Pumped Optical Parametric Oscillator (SPOPO). The full covariance matrix of the state is obtained with homodyne detection where the local oscillator is spectrally controlled with pulse shaping techniques. The resulting matrix reveals genuine multipartite entanglement. Additionally, the beam is comprised of several independent eigenmodes that correspond to specific pulse shapes. The experimental data is confirmed with numerical simulations. Finally, the potential to create continuous-variable cluster states from the quantum comb is analyzed. Multiple cluster states are shown to be simultaneously embedded in the SPOPO state, and these states can be revealed by a suitable basis change applied to the measured covariance matrix.

Renné Medeiros de Araújo; Jonathan Roslund; Yin Cai; Giulia Ferrini; Claude Fabre; Nicolas Treps

2014-01-20

369

Sex ratio dependent dispersal when sex ratios vary between patches.  

PubMed

Female biased sex ratios reduce competition between brothers when mating takes place within local patches. Male dispersal prior to mating is another strategy that reduces competition between brothers. One may thus expect these two traits to co-evolve and this is partially met in that sex ratios becomes less female biased as dispersal increases. However, the evolutionary stable degree of dispersal is unaffected by the sex ratio. The analytical models developed to reach these conclusions ignored variance in sex ratios, since this increases the structural complexity of models. For similar reasons finite clutch sizes are also routinely ignored. To overcome these shortfalls, we developed individual based simulations that allowed us to incorporate realistic clutch sizes and binomial variance in sex ratios between patches. We show that under variable sex ratios, males evolve to more readily disperse away from patches with higher sex ratios than lower sex ratios. We show that, while the dispersal rate is insensitive to the sex ratio when sex ratios are precise, it is affected by the number of males with dispersal decreasing as the number of males decreases. PMID:21893071

Nelson, Ronald M; Greeff, Jaco M

2011-12-01

370

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

371

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

372

Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers  

NASA Astrophysics Data System (ADS)

We propose a robust and reliable method of active mode locking of mid-infrared quantum cascade lasers and develop its theoretical description. Its key element is the use of an external ring cavity, which circumvents fundamental issues undermining the stability of mode locking in quantum cascade lasers. We show that active mode locking can give rise to the generation of picosecond pulses and phase-locked frequency combs containing thousands of the ring cavity modes.

Wójcik, Aleksander K.; Malara, Pietro; Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico; Belyanin, Alexey

2013-12-01

373

Precise frequency measurement and characterization of a continuous scanning single-mode laser with an optical frequency comb.  

PubMed

We developed a high-precision frequency-measurement system for continuously scanning single-mode cw lasers. The high precision for wide frequency range is realized by employing an optical frequency comb. The developed system operates as a strong tool for analyzing the spectral profile and scan characteristics of lasers, which is suitable for high-resolution molecular spectroscopy. We demonstrated the ability of our system with Doppler-free spectroscopy of molecular iodine. PMID:25121909

Nishiyama, Akiko; Matsuba, Ayumi; Misono, Masatoshi

2014-08-15

374

Frequency Comb-Referenced Measurements of - and Nitrogen-Perturbed Line Shapes in the ?_1 + ?_3 Band of Acetylene  

NASA Astrophysics Data System (ADS)

Frequency comb technology has the potential to dramatically improve precision and accuracy in measured spectra, but few applications have yet been reported. One application that can benefit from the high stability of spectrometers referenced to frequency combs is the measurement of spectral line shapes. We have built an absorption spectrometer based on an extended cavity diode laser locked to an Er-fiber-based frequency comb operating near 1550 nm. Here we report the first measurements of line shapes using a frequency comb as a reference. We studied the P(11) line in the ?_1 + ?_3 combination band of acetylene at 195 739.649 513(8) GHz at several temperatures from 296K down to 175K. This talk focuses on the data taken at 296K. We used a hard collision model (Rautian-Sobel'man) fit to the measurements to determine self- and nitrogen- pressure broadening, pressure shift and Dicke narrowing parameters that are at least 2 orders of magnitude more precise than those reported in previous measurements. We compare these hard collision model results with those of two other widely-used models: the Galatry (soft collision) and the Voigt function. The temperature- and rotational level- dependence of these parameters have been measured and some of the results will be discussed in a separate talk. Acknowledgements:Acknowledgement is made to the Donors of the American Chemical Society Petroleum Research Fund for partial support of this research. CPM gratefully acknowledges support by DOE EPSCoR grant DOE-07ER46361 for work conducted at the University of Oklahoma. The measurements and analyses were performed under grants NNX09AJ93G and NNX08AO78G from the NASA Planetary and Atmospheres program.

Cich, Matthew J.; Lopez, Gary V.; Sears, Trevor J.; McRaven, C. P.; Mantz, A. W.; Hurtmans, Daniel

2011-06-01

375

Transfer of Halobacterium denitrificans (Tomlinson, Jahnke, and Hochstein) to the genus Haloferax as Haloferax denitrificans comb. nov  

NASA Technical Reports Server (NTRS)

Halobacterium denitrificans (Tomlinson, Jahnke, and Hochstein) was described at a time when the taxonomic subdivision of the family Halobacteriaceae was in a state of flux. On the basis of both biochemical and chemotaxonomic data, this organism exhibits features which indicate that it is more closely related to members of the genus Haloferax. On the basis of such criteria, we propose that Halobacterium denitrificans be reclassified as Haloferax denitrificans comb. nov. The type strain is strain ATCC 35960 (= DSM 4425).

Tindall, B. J.; Tomlinson, G. A.; Hochstein, L. I.

1989-01-01

376

Precision absolute frequency laser spectroscopy of argon II in parallel and antiparallel geometry using a frequency comb for calibration  

E-print Network

PRECISION ABSOLUTE FREQUENCY LASER SPECTROSCOPY OF ARGON II IN PARALLEL AND ANTIPARALLEL GEOMETRY USING A FREQUENCY COMB FOR CALIBRATION A Dissertation by VLADIMIR LIOUBIMOV Submitted to the Office of Graduate Studies of Texas A&M University... Dissertation by VLADIMIR LIOUBIMOV Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Hans A.Schuessler Committee Members, Teruki...

Lioubimov, Vladimir

2010-01-14

377

A silicon Mach Zehnder comb switch for low power operation in on-chip optical data communications  

NASA Astrophysics Data System (ADS)

A novel method to significantly decrease power consumption in a silicon switch based on an asymmetric Mach-Zehnder interferometer (MZI) structure is proposed and experimentally demonstrated. A radical power consumption reduction up to 50% is achieved for switching digital data at bit rates from 10 to 30Gbps with respect to a conventional switch based on a symmetric MZI. Furthermore, the broadband performance of the proposed silicon MZI comb switch is also demonstrated by transmitting a 120 Gbps DWDM data stream.

Sánchez, L.; Brimont, A.; Lechago, S.; Griol, A.; Sanchis, P.

2014-05-01

378

Frequency comb stabilization with bandwidth beyond the limit of gain lifetime by an intracavity graphene electro-optic modulator.  

PubMed

Intracavity loss modulation enables offset-frequency control with bandwidths beyond what is possible by pump power modulation. To demonstrate this new method, we use a subwavelength thick graphene electro-optic modulator to stabilize the offset frequency in a Tm:fiber frequency comb at 1.95 ?m wavelength. Record-low residual phase noise of 144 mrads was achieved with this new locking scheme. PMID:22859093

Lee, C-C; Mohr, C; Bethge, J; Suzuki, S; Fermann, M E; Hartl, I; Schibli, T R

2012-08-01

379

Generation of picosecond pulses and frequency combs in actively mode locked external ring cavity quantum cascade lasers  

SciTech Connect

We propose a robust and reliable method of active mode locking of mid-infrared quantum cascade lasers and develop its theoretical description. Its key element is the use of an external ring cavity, which circumvents fundamental issues undermining the stability of mode locking in quantum cascade lasers. We show that active mode locking can give rise to the generation of picosecond pulses and phase-locked frequency combs containing thousands of the ring cavity modes.

Wójcik, Aleksander K.; Belyanin, Alexey, E-mail: belyanin@tamu.edu [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843-4242 (United States)] [Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843-4242 (United States); Malara, Pietro [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States) [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States); Consiglio Nazionale delle Ricerche—Istituto Nazionale di Ottica, and European Laboratory for Nonlinear Spectroscopy (LENS), 80078 Pozzuoli (Italy); Blanchard, Romain; Mansuripur, Tobias S.; Capasso, Federico [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)] [School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138 (United States)

2013-12-02

380

Frequency Stabilization of High-Power 3.3 ?m CW Laser with a Frequency Comb System  

NASA Astrophysics Data System (ADS)

%TEXT OF YOUR ABSTRACT The development of optical frequency combs has enabled a broad range of lasers to be stabilized. In this study, we have developed a system to stabilize high-power CW mid-infrared (MIR) radiation at 3.3 ?m using a NIR-VIS frequency comb. The mid-infrared radiation at 3.3 ?m were generated as an idler of a CW OPO laser pumped by a 1.064 ?m fibre laser. To stabilize the MIR radiation with a frequency comb system in 450 nm to 1.25 ?m range, the pump frequency at 1.064 ?m and the sum frequency of the MIR radiation and the pump radiation were locked simultaneously to the comb laser. The sum frequency of the MIR and pump radiations was generated in a PPLN crystal. With this technique, we have successfully obtained a width of better than 50 kHz at 3.3 ?m with a power of more than 1 W. The stability is currently limited by the response of the PZT in an OPO cavity. Further improvement is underway. The stabilized MIR radiation at 3.3 ?m can be used as a source for ultra-high-resolution spectroscopy of vibration-rotation transitions of molecules. Especially, it may be used to decrease the frequency uncertainty of the ?_3 F_2(2) component of the P(7) transition of CH_4, which is one of the optical frequency standards recommended by CIPM. Another application of frequency stabilized MIR radiation is to build-up MIR radiation in a cavity for optical manipulation and trapping of cold molecules we have proposed in New. J. Phys. 11. 055023 (2009).

Kuma, Susumu; Momose, Takamasa

2010-06-01

381

In-situ determination of astro-comb calibrator lines to better than 10 cm s(-1).  

PubMed

Improved wavelength calibrators for high-resolution astrophysical spectrographs will be essential for precision radial velocity (RV) detection of Earth-like exoplanets and direct observation of cosmological deceleration. The astro-comb is a combination of an octave-spanning femtosecond laser frequency comb and a Fabry-Pérot cavity used to achieve calibrator line spacings that can be resolved by an astrophysical spectrograph. Systematic spectral shifts associated with the cavity can be 0.1-1 MHz, corresponding to RV errors of 10-100 cm/s, due to the dispersive properties of the cavity mirrors over broad spectral widths. Although these systematic shifts are very stable, their correction is crucial to high accuracy astrophysical spectroscopy. Here, we demonstrate an in-situ technique to determine the systematic shifts of astro-comb lines due to finite Fabry-Pérot cavity dispersion. The technique is practical for implementation at a telescope-based spectrograph to enable wavelength calibration accuracy better than 10 cm/s. PMID:20588453

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

2010-06-01

382

Monitor of mirror distance of Fabry-Perot cavity by the use of stabilized femtosecond laser comb  

NASA Astrophysics Data System (ADS)

The use of an ultra low expansion cavity plays a crucial role in laser stabilization, and in atomic or ion clocks. We propose an easy method of precise monitoring of optical path distance in Fabry-Perot interferometer. The spacing of mirrors of the Fabry-Perot interferometer in ambient air represents the optical path distance referenced to stable optical frequency of the femtosecond mode-locked laser. With the help of highly selective optical filter it is possible to get only a few of separate spectral components of laser comb. Optical path distance is transfered to optical frequency of the comb component and through the repetition frequency of the laser to the radio-frequency domain. Repetition frequency of the laser can be monitored with the uncertainty referenced to the any local oscillator or through the GPS to the atomic clock standard. By using this mehod we are able to measure and lock the Fabry-Perot cavity to a selected single component of optical frequency comb an to measure the optical path distance directly in rf domain.

Šmíd, Radek; Ježek, Jan; Buchta, Zden?k; ?ížek, Martin; Mikel, B?etislav; Lazar, Josef; ?íp, Ond?ej

2010-12-01

383

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

384

Sex and justice.  

PubMed

On the 25th anniversary of Pope Paul VI's signing of the Humanae Vitae "On the Regulation of Birth" and his reaffirming of the ban on birth control, this most controversial encyclical's anniversary will pass unnoticed at east in most US churches. Silence prevails as the utmost expression of dissent that priests and bishops can safely risk. Under the papacy of John Paul II, fidelity to the contraceptive ban is a loyalty test; public dissent by theologians and clerics invites reproach and punishment. Yet a church-sanctioned survey of priests found that more than 80% of Catholic clergy did not insist on the acceptance of the teaching in the confessional. The typical American Catholic uses birth control in the same numbers as everyone else. The Humanae Vitae's claims about sexuality are even more damaging than its position on banning contraception. It exalts sex as sacred, yet implies that sex is an animal impulse that must be suppressed, thus glorifying abstinence. According to Humanae Vitae, "each and every marriage act must remain open to the transmission of life." By insisting on the primacy of procreation in sexual behavior, the church loses its ability to sensibly address an array of societal problems, including AIDS, teen pregnancy, and population pressures. Many Catholics, far ahead of the institution, have crafted their own sexual ethic using the perspective the church uses in every other issue that comes before it: justice. With justice regulating sexual behavior, the concerns become one of respect and equality, the good of one's partner, the welfare of one's children, and the values of determining the number and spacing of births. With this viewpoint, Catholics and others would listen when the church talks about sex; now there is only silence. PMID:12178861

Kissling, F

1994-01-01

385

Sex differentials in health.  

PubMed Central

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

386

Re-examination of the taxonomic status of Enterobacter helveticus, Enterobacter pulveris and Enterobacter turicensis as members of the genus Cronobacter and their reclassification in the genera Franconibacter gen. nov. and Siccibacter gen. nov. as Franconibacter helveticus comb. nov., Franconibacter pulveris comb. nov. and Siccibacter turicensis comb. nov., respectively  

PubMed Central

Recently, a taxonomical re-evaluation of the genus Enterobacter, based on multi-locus sequence typing (MLST) analysis, has led to the proposal that the species Enterobacter pulveris, Enterobacter helveticus and Enterobacter turicensis should be reclassified as novel species of the genus Cronobacter. In the present work, new genome-scale analyses, including average nucleotide identity, genome-scale phylogeny and k-mer analysis, coupled with previously reported DNA–DNA hybridization values and biochemical characterization strongly indicate that these three species of the genus Enterobacter are not members of the genus Cronobacter, nor do they belong to the re-evaluated genus Enterobacter. Furthermore, data from this polyphasic study indicated that all three species constitute two new genera. We propose reclassifying Enterobacter pulveris and Enterobacter helveticus in the genus Franconibacter gen. nov. as Franconibacter pulveris comb. nov. (type strain 601/05T?=?LMG 24057T?=?DSM 19144T) and Franconibacter helveticus comb. nov. (type strain 513/05T?=?LMG 23732T?=?DSM 18396T), respectively, and Enterobacter turicensis in the genus Siccibacter gen. nov. as Siccibacter turicensis comb. nov. (type strain 508/05T?=?LMG 23730T?=?DSM 18397T). PMID:25028159

Grim, Christopher J.; Gopinath, Gopal R.; Mammel, Mark K.; Sathyamoorthy, Venugopal; Trach, Larisa H.; Chase, Hannah R.; Fanning, Seamus; Tall, Ben D.

2014-01-01

387

Re-examination of the taxonomic status of Enterobacter helveticus, Enterobacter pulveris and Enterobacter turicensis as members of the genus Cronobacter and their reclassification in the genera Franconibacter gen. nov. and Siccibacter gen. nov. as Franconibacter helveticus comb. nov., Franconibacter pulveris comb. nov. and Siccibacter turicensis comb. nov., respectively.  

PubMed

Recently, a taxonomical re-evaluation of the genus Enterobacter, based on multi-locus sequence typing (MLST) analysis, has led to the proposal that the species Enterobacter pulveris, Enterobacter helveticus and Enterobacter turicensis should be reclassified as novel species of the genus Cronobacter. In the present work, new genome-scale analyses, including average nucleotide identity, genome-scale phylogeny and k-mer analysis, coupled with previously reported DNA-DNA hybridization values and biochemical characterization strongly indicate that these three species of the genus Enterobacter are not members of the genus Cronobacter, nor do they belong to the re-evaluated genus Enterobacter. Furthermore, data from this polyphasic study indicated that all three species constitute two new genera. We propose reclassifying Enterobacter pulveris and Enterobacter helveticus in the genus Franconibacter gen. nov. as Franconibacter pulveris comb. nov. (type strain 601/05(T) = LMG 24057(T) = DSM 19144(T)) and Franconibacter helveticus comb. nov. (type strain 513/05(T) = LMG 23732(T) = DSM 18396(T)), respectively, and Enterobacter turicensis in the genus Siccibacter gen. nov. as Siccibacter turicensis comb. nov. (type strain 508/05(T) = LMG 23730(T) = DSM 18397(T)). PMID:25028159

Stephan, Roger; Grim, Christopher J; Gopinath, Gopal R; Mammel, Mark K; Sathyamoorthy, Venugopal; Trach, Larisa H; Chase, Hannah R; Fanning, Séamus; Tall, Ben D

2014-10-01

388

Transfer of Nosema locustae (Microsporidia) to Antonospora locustae n. comb. based on molecular and ultrastructural data.  

PubMed

Nosema locustae is a microsporidian parasite of grasshopper pests that is used as a biological control agent, and is one of the emerging model systems for microsporidia. Due largely to its diplokaryotic nuclei, N. locustae has been classified in the genus Nosema, a large genus with members that infect a wide variety of insects. However, some molecular studies have cast doubt on the validity of certain Nosema species, and on the taxonomic position of N. locustae. To clarify the affinities of this important insect parasite we sequenced part of the rRNA operon of N. locustae and conducted a phylogenetic analysis using the complete small subunit rRNA gene. Nosema locustae is only distantly related to the nominotypic N. bombycis, and is instead closely related to Antonospora scoticae, a recently described parasite of bees. We examined the ultrastructure of mature N. locustae spores, and found the spore wall to differ from true Nosema species in having a multi-layered exospore resembling that of Antonospora (one of the distinguishing features of that genus). Based on both molecular and morphological evidence, therefore, we propose transferring N. locustae to the genus Antonospora, as Antonospora locustae n. comb. PMID:15134257

Slamovits, Claudio H; Williams, Bryony A P; Keeling, Patrick J

2004-01-01

389

Combinations of Earth Orientation Measurements: SPACE2005, COMB2005, and POLE2005  

NASA Technical Reports Server (NTRS)

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, by very long baseline interferometry, and by the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2005, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to January 7, 2006, at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2005 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2005, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to January 7, 2006, at daily intervals and which is also available in versions whose epochs are given at either midnight or noon; and (2) POLE2005, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to December 21, 2005, at 30.4375-day intervals.

Gross, Richard S.

2006-01-01

390

Combinations of Earth Orientation Measurements: SPACE2011, COMB2011, and POLE2011  

NASA Technical Reports Server (NTRS)

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2011, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to July 13, 2012, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2011 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2011, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to July 13, 2012, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2011, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 21, 2012, at 30.4375-day intervals.

Ratcliff, J. T.; Gross, R. S.

2013-01-01

391

Combinations of Earth Orientation Measurements: SPACE2004, COMB2004, and POLE2004  

NASA Technical Reports Server (NTRS)

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the global positioning system have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2004, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to January 22, 2005, at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2004 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2004, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to January 22, 2005, at daily intervals and which is also available in versions whose epochs are given at either midnight or noon, and (2) POLE2004, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to January 20, 2005, at 30.4375-day intervals.

Gross, Richard R.

2005-01-01

392

Combinations of Earth Orientation Measurements: SPACE2001, COMB2001, and POLE2001  

NASA Technical Reports Server (NTRS)

Independent Earth-orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the global positioning system have been combined using a Kalman filter. The resulting combined Earth-orientation series, SPACE2001, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28.0, 1976 to January 19.0, 2002 at daily intervals. The space-geodetic measurements used to generate SPACE2001 have been combined with optical astrometric measurements to form two additional combined Earth-orientation series: (1) COMB2001, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20.0, 1962 to January 15.0, 2002 at five-day intervals, and (2) POLE2001, consisting of values and uncertainties for polar motion and its rates that span from January 20, 1900 to December 21, 2001 at 30.4375-day intervals.

Gross, Richard S.

2002-01-01

393

Comb-drive micro-electro-mechanical systems oscillators for low temperature experiments  

NASA Astrophysics Data System (ADS)

We have designed and characterized micro-electro-mechanical systems (MEMS) for applications at low temperatures. The mechanical resonators were fabricated using a surface micromachining process. The devices consist of a pair of parallel plates with a well defined gap. The top plate can be actuated for shear motion relative to the bottom fixed plate through a set of comb-drive electrodes. Details on the operation and fabrication of the devices are discussed. The geometry was chosen to study the transport properties of the fluid entrained in the gap. An atomic force microscopy study was performed in order to characterize the surface. A full characterization of their resonance properties in air and at room temperature was conducted as a function of pressure, from 10 mTorr to 760 Torr, ranging from a highly rarefied gas to a hydrodynamic regime. We demonstrate the operation of our resonator at low temperatures immersed in superfluid 4He and in the normal and superfluid states of 3He down to 0.3 mK. These MEMS oscillators show potential for use in a wide range of low temperature experiments, in particular, to probe novel phenomena in quantum fluids.

González, M.; Zheng, P.; Garcell, E.; Lee, Y.; Chan, H. B.

2013-02-01

394

Development of compact and ultra-high-resolution spectrograph with multi-GHz optical frequency comb  

NASA Astrophysics Data System (ADS)

In recent years, a calibration method for an astronomical spectrograph using an optical frequency comb (OFC) with a repetition rate of more than ten GHz has been developed successfully [1-5]. But controlling filtering cavities that are used for thinning out longitudinal modes precludes long term stability. The super-mode noise coming from the fundamental repetition rate is an additional problem. We developed a laser-diode pumped Yb:Y2O3 ceramic oscillator, which enabled the generation of 4-GHz (maximum repetition rate of 6.7 GHz) pulse trains directly with a spectrum width of 7 nm (full-width half-maximum, FWHM), and controlled its optical frequency within a MHz level of accuracy using a beat note between the 4-GHz laser and a 246-MHz Yb-fiber OFC. The optical frequency of the Yb-fiber OFC was phase locked to a Rb clock frequency standard. Furthermore we also built a table-top multi-pass spectrograph with a maximum frequency resolution of 600 MHz and a bandwidth of 1 nm using a large-size high-efficiency transmission grating. The resolution could be changed by selecting the number of passes through the grating. This spectrograph could resolve each longitudinal mode of our 4-GHz OFC clearly, and more than 10% throughput was obtained when the resolution was set to 600 MHz. We believe that small and middle scale astronomical observatories could easily implement such an OFC-calibrated spectrograph.

Endo, Mamoru; Sukegawa, Takashi; Silva, Alissa; Kobayashi, Yohei

2014-08-01

395

Reclassification of Promicromonospora pachnodae Cazemier et al. 2004 as Xylanimicrobium pachnodae gen. nov., comb. nov.  

PubMed

The recently described facultatively anaerobic Promicromonospora pachnodae is phylogenetically only moderately related to authentic members of Promicromonospora. P. pachnodae is closely related to Xylanibacterium ulmi and slightly less closely related to Xylanimonas cellulosilytica and Isoptericola variabilis (basonym Cellulosimicrobium variabile). Members of the different genera of Promicromonosporaceae have similar chemotaxonomic properties; they share the same peptidoglycan type (A4alpha) and have similar profiles of polar lipids, menaquinones, fatty acids and whole cell sugars. However, they differ from each other in the detailed amino acid composition of peptidoglycan, a taxonomically significant character that has previously been used in the delineation of actinobacterial genera. Recognized Promicromonospora species and Xylanibacterium ulmi exhibit the L-Lys-L-Ala-D-Glu type, Xylanimonas cellulosilytica and I. variabilis show the L-Lys-D-Asp type, whereas P. pachnodae has the L-Lys-L-Ser-D-Glu type. This property, together with the distinct phylogenetic position of Promicromonospora pachnodae, suggests a novel genus for the xylanolytic organism Xylanimicrobium pachnodae (Cazemier et al. 2004) gen. nov., comb. nov. PMID:15280318

Stackebrandt, Erko; Schumann, Peter

2004-07-01

396

ERIC-PCR genotyping of paenibacillus larvae in southern Italian honey and brood combs.  

PubMed

Given the considerable economic loss to beekeepers worldwide and the possible public health implications related to the presence of antibiotics in honey, an American Foulbrood (AFB) monitoring/prevention program for Paenibacillus larvae is regarded as essential. This study investigates the occurrence and distribution of P. larvae genotypes in honey and brood combs from Apulia (Italy). Genotyping of P. larvae isolates using ERIC-PCR generated a total of four different ERIC banding patterns (ERIC-A, ERIC-B, ERIC-C, ERIC-D), including fragments ranging from 200 to 3000 bp. Considering that the genotype has an influence on P. larvae infections and multi-genotype infections of colonies or apiaries may increase the complexity of P. larvae infections by influencing the type and speed of the development of clinical symptoms, the findings of the present study could be helpful for training veterinarians, bee inspector's extension staff, and beekeepers, thus improving the detection of AFB infections in the field. PMID:21853316

Di Pinto, Angela; Novello, Lucia; Terio, Valentina; Tantillo, Giuseppina

2011-11-01

397

Highly Stable Wideband Microwave Extraction by Synchronizing Widely Tunable Optoelectronic Oscillator with Optical Frequency Comb  

PubMed Central

Optical frequency combs (OFCs), based on mode-locked lasers (MLLs), have attracted considerable attention in many fields over recent years. Among the applications of OFCs, one of the most challenging works is the extraction of a highly stable microwave with low phase noise. Many synchronisation schemes have been exploited to synchronise an electronic oscillator with the pulse train from a MLL, helping to extract an ultra-stable microwave. Here, we demonstrate novel wideband microwave extraction from a stable OFC by synchronising a single widely tunable optoelectronic oscillator (OEO) with an OFC at different harmonic frequencies, using an optical phase detection technique. The tunable range of the proposed microwave extraction extends from 2?GHz to 4?GHz, and in a long-term synchronisation experiment over 12 hours, the proposed synchronisation scheme provided a rms timing drift of 18?fs and frequency instabilities at 1.2 × 10?15/1?s and 2.2 × 10?18/10000 s. PMID:24336459

Hou, D.; Xie, X. P.; Zhang, Y. L.; Wu, J. T.; Chen, Z. Y.; Zhao, J. Y.

2013-01-01

398

Reclassification of Cellulosimicrobium variabile Bakalidou et al. 2002 as Isoptericola variabilis gen. nov., comb. nov.  

PubMed

As already depicted in the original publication, the type strain of the species Cellulosimicrobium variabile Bakalidou et al. 2002, DSM 10177(T), does not cluster unambiguously with the type species, Cellulosimicrobium cellulans DSM 43879(T), in phylogenetic analysis. Strain DSM 10177(T) is moderately related to the recently described species Xylanimonas cellulosilytica, Promicromonospora pachnodae and Xylanibacterium ulmi, forming a lineage that branches between C. cellulans and members of the genus Promicromonospora in most dendrograms generated on the basis of different algorithms and reference strains. The type strains of the two Cellulosimicrobium species resemble each other in morphology, composition of fatty acids, DNA G+C content, phospholipids and the presence of lysine in position 3 of the peptide subunit of peptidoglycan. However, the two strains differ from each other in cell-wall sugars and in the amino acid composition of the A4alpha-type peptidoglycan, which contains serine and aspartic acid in C. cellulans, whereas only aspartic acid is present in the interpeptide bridge of C. variabile. This type is also present in Xylanimonas cellulosilytica XIL07(T), but not in the neighbouring species P. pachnodae DSM 12657(T), which exhibits the L-lys-L-ser-D-Glu type. On the basis of distinct phylogenetic position and the amino acid composition of peptidoglycan, a novel genus and combination for C. variabile, Isoptericola variabilis gen. nov., comb. nov., is proposed. PMID:15143008

Stackebrandt, Erko; Schumann, Peter; Cui, Xiao-Long

2004-05-01

399

Plasmonic nano-comb structures for efficient large-area second harmonic generation.  

PubMed

We propose and demonstrate plasmonic nano-comb (PNC) structures for efficient large-area second-harmonic generation (SHG). The PNCs are made of 250 nm-thick gold film and have equally-spaced 30 nm-slits filled with ployvinylidene fluoride-co-trifluoroethylene (P(VDF-TrFE)). The PNC with 1.0 ?m-spacing couples resonantly with 1.56 ?m 100-fs laser beams. For the 1.0 ?m-spacing PNCs under the fixed-pump-power condition, the nonlinear SHG power remains almost independent of the pump diameter ranging from 2 ?m to 6 ?m. The SHG power from the resonant PNC is measured to be 8 times larger than that of the single-nano-gap metallic structure, when the pump beam is tightly-focused to 2 ?m in diameter in both cases. This relative enhancement of the total nonlinear SHG signal power reaches up to >200 when the pump beam diameter is increased to 6 ?m. We attribute this unusual phenomenon to the resonant coupling of the finite-size pump wave with the finite-size one-dimensional plasmonic mode. PMID:25090526

Sim, Hongchul; Lim, Hee-Jin; Song, Jung-Hwan; Kim, Myung-Ki; Lee, Yong-Hee

2014-07-14

400

Gigahertz Self-referenceable Frequency Comb from a Semiconductor Disk Laser  

E-print Network

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 10...

Zaugg, Christian A; Mangold, Mario; Mayer, Aline S; Link, Sandro M; Emaury, Florian; Golling, Matthias; Gini, Emilio; Saraceno, Clara J; Tilma, Bauke W; Keller, Ursula

2014-01-01

401

Disorders of Sex Development  

PubMed Central

The birth of a new baby is one of the most dramatic events in a family, and the first question is usually "is it a boy or a girl?" The newborn infant with ambiguous external genitalia often comes as a surprise for the doctors as well as the parents and is sometimes described as an endocrine emergency situation presenting a problem of sex assignment. The nomenclature such as 'intersex', 'hermaphrodite', and 'pseudohermaphrodite' is out of date as well as confusing, and many urologists are concerned that these confusing terms could be perceived to be pejorative by some affected families. In response to concerns regarding outdated and controversial terms, the Chicago Consensus held in 2005 recommended new terminology based on the umbrella term disorders of sex differentiation (DSDs). The term DSD has a comprehensive definition including any problem noted at birth in which the genitalia are atypical in relation to the chromosomes or gonads. The karyotype is used as a prefix defining the classification of DSD. DSDs are rare and complex. The optimal management of patients with DSD must be individualized and multidisciplinary, considering all aspects, including psychological care and full disclosure of alternatives relating to surgery type and timing. Although further studies are necessary to confirm guidelines and recommendations fitting for the individual patients with DSD, this article is an attempt to provide a balanced perspective for new taxonomy, clinical evaluation, and medical, surgical, and psychological management of DSD. PMID:22323966

Kim, Jongwon

2012-01-01

402

Sex and today's youth.  

PubMed

Changes in sexual activities and attitudes of today's (1974) youth are reviewed. It is concluded that adolescent sexual behavior is not much different from what it was in the last decade, although young people tend to have their 1st sexual experience earlier than in the past and tend to talk about sex more openly. The percent of women who are not virgins at marriage is not markedly higher than it was in the 1920s, nor has the incidence of school-age unwed mothers increased in the last few years. It has become increasingly popular for young, unmarried men and women to live together in recent years and coed dorms have become more widespread, although little sexual activity occurs among the inhabitants of these dorms. The incidence of premarital sex among engaged couples has increased. Young and middle-aged couples today are more ready to experiment with variations in foreplay and coitus. Homosexuals live more comfortably with their sexual behavior and the rate of transexualism has risen. Drug users are more likely to have coitus earler in life, more regularly, and with a greater number of partners. PMID:4471709

Godenne, G D

1974-01-01

403

Sex Education In Our Schools  

Microsoft Academic Search

This research project involved interviewing 42 parents with children between the ages of 12 to 18-years-old regarding their views and opinions on sex education for today’s youth. All 42 parents agreed they wanted a more informative sex education for their children than what they were exposed to as children. This included those with formal sex education as well as those

Kelley Conti

2012-01-01

404

Mixed-Sex or Single-Sex Education: How Would Young People Like Their Sex Education and Why?  

ERIC Educational Resources Information Center

Examined adolescents views about sex education, specifically their views about interaction in single- and mixed-sex groups. Surveys of English secondary school students indicated that most girls, and one-third of boys, want some or all of their sex education to be delivered in single-sex groups. Girls' experiences of sex education with boys…

Strange, Vicki; Forrest, Simon; Oakley, Ann

2003-01-01

405

Bayesian Reconstruction of Two-Sex Populations by Age: Estimating Sex Ratios at Birth and Sex Ratios of  

E-print Network

Bayesian Reconstruction of Two-Sex Populations by Age: Estimating Sex Ratios at Birth and Sex past with uncertainty, produced estimates for female-only populations. Here we show how two-sex populations can be similarly reconstructed and probabilistic estimates of various sex ratio quantities

Raftery, Adrian

406

Sex determination and sex reversal: genotype, phenotype, dogma and semantics  

Microsoft Academic Search

The genetic terminology of sex determination and sex differentiation is examined in relation to its underlying biological basis. On the assumption that the function of the testis is to produce hormones and spermatozoa, the hypothesis of a single Y-chromosomal testis-determining gene with a dominant effect is shown to run counter to the following observed facts: a lowering in testosterone levels

Ursula Mittwoch

1992-01-01

407

Elusive sex acts: pleasure and politics in Norwegian sex education  

Microsoft Academic Search

While there is little political opposition towards sex education as such in Norway, recent attempts at reforming the subject reveal underlying heteronormative presumptions that seem resistant to reform. While a focus on homosexuality is included in the national curriculum at all levels of compulsory education, the sexual practices involved in same-sex relations remain conspicuously absent from the education provided. This

Stine H. Bang Svendsen

2012-01-01

408

THE INDIVIDUAL, SOCIETY AND SEX. BACKGROUND READINGS FOR SEX EDUCATORS.  

ERIC Educational Resources Information Center

THIS BOOK IS DESIGNED AS A TEXT PRIMARILY FOR COLLEGE STUDENTS PREPARING TO TEACH SEX EDUCATION OR "EDUCATION IN THE NATURE OF HUMAN SEXUALITY AND THE RELATIONS BETWEEN THE SEXES" IN ELEMENTARY AND SECONDARY SCHOOLS. AN ATTEMPT IS MADE BY THE 13 WRITERS, MOST OF THEM SOCIOLOGISTS OR PSYCHOLOGISTS, TO DISTINGUISH BETWEEN THE KNOWLEDGE WHICH THE…

BRODERICK, CARLFRED B.; AND OTHERS

409

Attitudes Toward Sex Education and Values in Sex Education.  

ERIC Educational Resources Information Center

Results of a survey of 130 mothers of school children in grades 6, 9 and 12 in Ontario, Canada, found most supported the teaching of sex education but were divided about which values should be taught. The strongest variable related both to attitudes and values in sex education was premarital sexual attitudes. (Author/BL)

Marsman, Joan C.; Herold, Edward S.

1986-01-01

410

Measurements of CO2, CH4, H2O, and HDO over a 2-km Outdoor Path with Dual-Comb Spectroscopy  

NASA Astrophysics Data System (ADS)

We demonstrate simultaneous sensing of CO2, CH4, H2O, and HDO over a 2-km outdoor open air path using dual-frequency-comb absorption spectroscopy (DCS). Our implementation of the DCS technique simultaneously offers broad spectral coverage (>8 THz, 267 cm-1) and fine spectral point spacing (100 MHz, 0.0033 cm-1) with a coherent eye-safe beam. The spectrometer, which is adapted from [Zolot et al., 2012], consists of two mutually coherent Erbium-doped fiber frequency-comb lasers which create a broad spectrum of perfectly spaced narrow linewidth frequency elements (';comb teeth') near 1.6 ?m. The comb light is transmitted by a telescope and active steering mirrors from the roof of the NIST Boulder laboratory to a 50-cm flat mirror located 1 km away. The return light is received by a second telescope and carried via multimode fiber to a detector. The greenhouse gas absorption attenuates the teeth from the two combs that are coincident with the relevant molecular resonant frequencies. We purposefully offset the frequencies between the two frequency combs in a Vernier-like fashion so that each pair of comb teeth from the two combs results in a unique rf heterodyne beat frequency on the photodiode. The spectral spacing between subsequent comb teeth pairs is 100 MHz, far lower than the ~4 GHz linewidths of small molecule absorption features in the atmosphere. Because of the narrow comb linewidth, there is an essentially negligible instrument lineshape. The measured absorption spectrum can thus resolve neighboring absorption features of different species, and can be compared directly with HITRAN and recent greenhouse gas absorption models developed for satellite- and ground-based carbon observatories to determine the path-integrated concentrations of the absorbing species. Measurements covering the complete 30013?00001 absorption band of CO2 and absorption features of CH4, H2O and HDO between 1.6-1.67 ?m were performed under a variety of atmospheric conditions. During windy conditions when the atmosphere is well-mixed and species concentrations are stable, long-time-average data (240 min) are used to achieve high signal-to-noise ratio for careful comparisons of different spectral absorption models to the measured spectrum. Shorter five minute time resolution spectra are used to track fluctuations in atmospheric greenhouse gas concentrations over diurnal cycles and different weather conditions, and compared with simultaneous point-sampled measurements using a commercial cavity ringdown-based gas sensor. A. M. Zolot, F. R. Giorgetta, E. Baumann, J. W. Nicholson, W. C. Swann, I. Coddington, and N. R. Newbury (2012), Direct-Comb Molecular Spectroscopy with Accurate, Resolved Comb Teeth over 43 THz, Opt. Lett., 37(4), 638-640. a) Transmitted intensity spectrum over the 2-km outdoor path showing the spectral intensity variations of the combs and fine structure from gas absorption. b) Background-corrected absorbance of CO2 (blue) fitted with a Hitran model (red). The CO2 concentration measured from the fit is 408 ppm.

Rieker, G. B.; Giorgetta, F. R.; Coddington, I.; Swann, W. C.; Sinclair, L. C.; Cromer, C.; Baumann, E.; Newbury, N. R.; Kofler, J.; Petron, G.; Sweeney, C.; Tans, P. P.

2013-12-01

411

Abnormalities of human sex determination  

Microsoft Academic Search

Summary Cytogenetic and molecular studies in patients with abnormalities of sex determination have been the key to the isolation and investigation of candidates for the primary testis determining factor (TDF). A gene, SRY, isolated from the sex determining region of the Y chromosome within 5 kilobases of the pairing segment boundary, has been characterized recently which fulfils the expectations of

M. A. Ferguson-Smith

1992-01-01

412

Erroneous theories of sex determination  

Microsoft Academic Search

Throughout the major part of history, theories of sex determination had to be formulated in the absence of knowledge of ova and spermatozoa. The most persistent theory postulated that males are associated with the right parental side and females with the left side. At the end of the 19th century, sex was thought to be determined by nutrition. Recent findings

U Mittwoch

1985-01-01

413

Sex Chromosomes in Land Plants  

E-print Network

Sex Chromosomes in Land Plants Ray Ming,1 Abdelhafid Bendahmane,2,3 and Susanne S. Renner4 1 chromosomes, suppression of recombination Abstract Sex chromosomes in land plants can evolve as a consequence chromosomes in hepatics, mosses, and gymnosperms are morphologically heteromor- phic. In angiosperms

Renner, Susanne

414

Sex Differences in Statistical Reasoning  

Microsoft Academic Search

Despite considerable research having been done in the area of sex differences in mathematical ability, statistical ability has rarely been the subject of a major research effort. This study focuses on the question of whether there are sex differences in statistical reasoning for college students. Participants included 245 college students in Taiwan and 267 American college students. The Statistical Reasoning

HUI-JU C. LIU; JOAN B. GARFIELD

2002-01-01

415

Acknowledging mixed-sex people  

Microsoft Academic Search

This article calls attention to the importance of more carefully defining femaleness and maleness and more fully acknowledging the existence of mixed-sex people. Mixed-sex people are defined as people with at least one female and one male characteristic, where female or male characteristics are defined as characteristics that are possessed by no more than roughly half the population (the distribution

Thomas L. McKain

1996-01-01

416

Sex Differences in College Major.  

ERIC Educational Resources Information Center

This study uses new nationwide data to analyze sex differences in choice of college majors in 1955 and 1973. The implied link between sex differences in the labor market and the human capital market is important, the author suggests, for both research and policymaking. (MF)

Polachek, Solomon William

1978-01-01

417

"Sex Health" Deaf Health Talks,  

E-print Network

;Sexual Dysfunction- Males Types of Erectile Dysfunction (unable to get erect or stay "up" for sex dysfunction? What are common types of sexually transmitted diseases (STDs)? How can we protect our sexual-surprising-health-benefits-of-sex?page=3 #12;Sexual Health Issues Sexual dysfunction Male and female Common

Goldman, Steven A.

418

Sex research and social change  

Microsoft Academic Search

The history of scientific sex research which emerged at the turn of the century with the exemplary work of Sigmund Freud and Havelock Ellis has been complexly interactive with changing general social conditions, specific trends in sexual conduct, the content of sexual ideologies, and the developing techniques of scientific inquiry. The earliest sex researchers, although serving to bring sexuality out

John H. Gagnon

1975-01-01

419

Teenage relationships and sex education  

Microsoft Academic Search

Most of the consequences of early intercourse affect the woman and much research has focused upon her. As part of a study on teenage pregnancy, where 137 women were interviewed, 46 men were also interviewed. They were less likely to have had teaching about sex from parents and were subject to less parental supervision than the women. Both sexes had

H A Curtis; J H Tripp; C Lawrence; W L Clarke

1988-01-01

420

Sex Role and Depressive Mood.  

ERIC Educational Resources Information Center

Research has suggested that an association exists between sex role identity and typing and affective states. The relationship of sex role type and depressive mood was explored through the direct manipulation of affect in a mood induction procedure. Female (N=208) and male (N=131) subjects, classified as either androgynous, masculine, feminine, or…

Small, Arnold; And Others

421

Sex Differences in Dichotic Listening  

ERIC Educational Resources Information Center

The present study quantified the magnitude of sex differences in perceptual asymmetries as measured with dichotic listening. This was achieved by means of a meta-analysis of the literature dating back from the initial use of dichotic listening as a measure of laterality. The meta-analysis included 249 effect sizes pertaining to sex differences and…

Voyer, Daniel

2011-01-01

422

Contemporary Sex Roles for Adolescents  

Microsoft Academic Search

This article reviews various social influences and their effects on adolescent sex role development, including parents, peers, media, schools, race, social class and religion. The authors conclude that teens may experience sex role strain based on pressures to conform to gender expectations. Implications for social work practice are discussed.

Dianne F. Harrison; R. Clark Pennell

1989-01-01

423

Brain Dysfunction in Sex Offenders.  

ERIC Educational Resources Information Center

Attempted to establish the connection between disordered sexuality and brain impairment by using newly developed techniques of neuropsychological investigation with sex offenders (n=35). Results indicated a major portion of the sex offenders showed impaired brain functioning on Luria-Nebraska Neuropsychological Battery. (Author/ABL)

Galski, Thomas; And Others

1990-01-01

424

Types of Juvenile Sex Offenders  

ERIC Educational Resources Information Center

Although juvenile sex offenders (JSOs) account for a significant percentage of sex crimes committed in this country, researchers have only recently begun to study this population. One line of inquiry has been to investigate sub-types of offenders, in order to determine whether different types of offenders have different personality profiles and…

Bauman, Sheri

2002-01-01

425

Moral Pluralism and Sex Education  

ERIC Educational Resources Information Center

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

Corngold, Josh

2013-01-01

426

Teaching Sex Education in Thailand  

ERIC Educational Resources Information Center

The purposes of this study were to examine the current situation pertaining to the teaching of sex education and identify barriers to teaching sex education among Thai health education teachers. A survey questionnaire was administered to 193 health education teachers who participated in this study. The questionnaire was comprised of three parts:…

Kay, Noy S.; Jones, Megan R.; Jantaraweragul, Sudgasame

2010-01-01

427

Sex guilt in abortion patients  

Microsoft Academic Search

Mosher's Forced-Choice Sex Guilt Inventory was administered to 45 clients of a university problem pregnancy counseling service who were planning to have abortions and to 47 sexually active nonpregnant university coeds. Sex guilt was found to be significantly higher for abortion Ss than for nonpregnant Ss. It was also found that for each type of contraceptive, abortion Ss had higher

Meg Gerrard

1977-01-01

428

Heterosexuality and Sex-Typing.  

ERIC Educational Resources Information Center

Previous research (Bem, 1976) has shown that sex-typed and androgynous persons differ in their behavior in a variety of situations. The present paper describes four studies of the relationship of sex-typing to sexual socialization and to heterosexual attitudes and behavior. This program of research indicates that persons do differ in their sexual…

Allgeier, Elizabeth R.

429

The joy of sex pheromones  

PubMed Central

Sex pheromones provide an important means of communication to unite individuals for successful reproduction. Although sex pheromones are highly diverse across animals, these signals fulfil common fundamental roles in enabling identification of a mating partner of the opposite sex, the appropriate species and of optimal fecundity. In this review, we synthesize both classic and recent investigations on sex pheromones in a range of species, spanning nematode worms, insects and mammals. These studies reveal comparable strategies in how these chemical signals are produced, detected and processed in the brain to regulate sexual behaviours. Elucidation of sex pheromone communication mechanisms both defines outstanding models to understand the molecular and neuronal basis of chemosensory behaviours, and reveals how similar evolutionary selection pressures yield convergent solutions in distinct animal nervous systems. EMBO reports advance online publication 13 September 2013; doi:10.1038/embor.2013.140 PMID:24030282

Gomez-Diaz, Carolina; Benton, Richard

2013-01-01

430

Sex differences in primary hypertension  

PubMed Central

Men have higher blood pressure than women through much of life regardless of race and ethnicity. This is a robust and highly conserved sex difference that it is also observed across species including dogs, rats, mice and chickens and it is found in induced, genetic and transgenic animal models of hypertension. Not only do the differences between the ovarian and testicular hormonal milieu contribute to this sexual dimorphism in blood pressure, the sex chromosomes also play a role in and of themselves. This review primarily focuses on epidemiological studies of blood pressure in men and women and experimental models of hypertension in both sexes. Gaps in current knowledge regarding what underlie male-female differences in blood pressure control are discussed. Elucidating the mechanisms underlying sex differences in hypertension may lead to the development of anti-hypertensives tailored to one's sex and ultimately to improved therapeutic strategies for treating this disease and preventing its devastating consequences. PMID:22417477

2012-01-01

431

The joy of sex pheromones.  

PubMed

Sex pheromones provide an important means of communication to unite individuals for successful reproduction. Although sex pheromones are highly diverse across animals, these signals fulfil common fundamental roles in enabling identification of a mating partner of the opposite sex, the appropriate species and of optimal fecundity. In this review, we synthesize both classic and recent investigations on sex pheromones in a range of species, spanning nematode worms, insects and mammals. These studies reveal comparable strategies in how these chemical signals are produced, detected and processed in the brain to regulate sexual behaviours. Elucidation of sex pheromone communication mechanisms both defines outstanding models to understand the molecular and neuronal basis of chemosensory behaviours, and reveals how similar evolutionary selection pressures yield convergent solutions in distinct animal nervous systems. PMID:24030282

Gomez-Diaz, Carolina; Benton, Richard

2013-10-01

432

Generation of optical frequency combs in fibres: an optical pulse analysis  

NASA Astrophysics Data System (ADS)

The innovation of optical frequency combs (OFCs) generated in passive mode-locked lasers has provided astronomy with unprecedented accuracy for wavelength calibration in high-resolution spectroscopy in research areas such as the discovery of exoplanets or the measurement of fundamental constants. The unique properties of OCFs, namely a highly dense spectrum of uniformly spaced emission lines of nearly equal intensity over the nominal wavelength range, is not only beneficial for high-resolution spectroscopy. Also in the low- to medium-resolution domain, the OFCs hold the promise to revolutionise the calibration techniques. Here, we present a novel method for generation of OFCs. As opposed to the mode-locked laser-based approach that can be complex, costly, and difficult to stabilise, we propose an all optical fibre-based system that is simple, compact, stable, and low-cost. Our system consists of three optical fibres where the first one is a conventional single-mode fibre, the second one is an erbium-doped fibre and the third one is a highly nonlinear low-dispersion fibre. The system is pumped by two equally intense continuous-wave (CW) lasers. To be able to control the quality and the bandwidth of the OFCs, it is crucial to understand how optical solitons arise out of the initial modulated CW field in the first fibre. Here, we numerically investigate the pulse evolution in the first fibre using the technique of the solitons radiation beat analysis. Having applied this technique, we realised that formation of higherorder solitons is supported in the low-energy region, whereas, in the high-energy region, Kuznetsov-Ma solitons appear.

Zajnulina, Marina; Böhm, Michael; Blow, Keith; Chavez Boggio, José M.; Rieznik, Andres A.; Haynes, Roger; Roth, Martin M.

2014-07-01

433

Reconstructing the Evolution of Vertebrate Sex Chromosomes  

E-print Network

Sex chromosomes and their evolution have captivated researchers since their discovery. For more than 100 years, the dominant model of sex chromosome evolution has held that differentiated sex chromosomes, such as the X and ...

Bellott, Daniel W.

434

Wider-frequency combs generation, noise reduction, and repetition rate tuning in quantum-dot mode-locked lasers  

NASA Astrophysics Data System (ADS)

We describe the technique allowing for generation of low-noise wider frequency combs and pulses of shorter duration in quantum-dot mode-locked lasers. We compare experimentally noise stabilization techniques in semiconductor mode-locked lasers. We discuss the benefits of electrical modulation of the laser absorber voltage (hybrid mode-locking), combination of hybrid mode-locking with optical injection seeding from the narrow linewidth continues wave master source and optical injection seeding of two coherent sidebands separated by the laser repetition rate.

Habruseva, T.; Arsenijevi?, D.; Bimberg, D.; Huyet, Guillaume; Hegarty, S. P.

2014-05-01

435

Efficient spectral hole-burning and atomic frequency comb storage in Nd3+:YLiF4  

PubMed Central

We present spectral hole-burning measurements of the 4I9/2 ? 4F3/2 transition in Nd3+:YLiF4. The isotope shifts of Nd3+ can be directly resolved in the optical absorption spectrum. We report atomic frequency comb storage with an echo efficiency of up to 35% and a memory bandwidth of 60?MHz in this material. The interesting properties show the potential of this material for use in both quantum and classical information processing. PMID:24067549

Zhou, Zong-Quan; Wang, Jian; Li, Chuan-Feng; Guo, Guang-Can

2013-01-01

436

A Wide Spaced Femtosecond Ti:Sapphire Frequency Comb at 15 GHz by a Fabry—Pérot Filter Cavity  

NASA Astrophysics Data System (ADS)

We realize a wide spaced frequency comb by using an external low-fineness Fabry—Pérot (F-P) cavity to filter few-cycle laser pulses from a Kerr-lens mode-locked Ti:sapphire laser at the fundamental repetition rate of 350MHz. Mode spacing as wide as 15 GHz with spectrum covered from 690 nm to 710 nm is demonstrated, corresponding to a filter multiple of about 43. The scanning transmission peaks after the F-P cavity with cavity lengths are also simulated numerically, and the results are in agreement with the experiment.

Hou, Lei; Han, Hai-Nian; Zhang, Jin-Wei; Li, De-Hua; Wei, Zhi-Yi

2013-10-01

437

Ultralow noise microwave generation with fiber-based optical frequency comb and application to atomic fountain clock  

NASA Astrophysics Data System (ADS)

We demonstrate the use of a fiber-based femtosecond laser locked onto an ultrastable optical cavity to generate a low-noise microwave reference signal. Comparison with both a cryogenic sapphire oscillator (CSO) and a titanium-sapphire-based optical frequency comb system exhibit a stability of about 3×10-15 between 1 and 10 s. The microwave signal from the fiber system is used to perform Ramsey spectroscopy in a state-of-the-art cesium fountain clock. The resulting clock is compared to the CSO and exhibits a stability of 3.5×10-14?-1/2.

Millo, J.; Abgrall, M.; Lours, M.; English, E. M. L.; Jiang, H.; Guéna, J.; Clairon, A.; Tobar, M. E.; Bize, S.; Le Coq, Y.; Santarelli, G.

2009-04-01

438

Tunable comb-filter using thermally expanded core fiber and ytterbium doped fiber and its application to multi-wavelength fiber laser  

NASA Astrophysics Data System (ADS)

We constructed a novel tunable comb-filter by splicing a commercial Yb 3+ doped fiber (YDF) between 2 thermally expanded core (TEC) fibers at their core-expanded ends. This structure forms an all-fiber Mach-Zehnder interferometer due to the interference between the core mode and the cladding modes of the YDF. The interference fringes shifts to the longer wavelength region as the YDF is pumped by a 980 nm laser diode (LD). We then demonstrated application of this newly proposed tunable comb-filter to a SOA-based ring laser and obtained multi-wavelength lasing. The lasing wavelengths can be also tuned by pumping the YDF in the proposed comb-filter.

Nguyen, Linh Viet; Hwang, Du-sun; Moon, Dae Seung; Chung, Youngjoo

2008-12-01

439

Dynamics of localized and patterned structures in the Lugiato-Lefever equation determine the stability and shape of optical frequency combs  

E-print Network

It has been recently uncovered that coherent structures in microresonators such as cavity solitons and patterns are intimately related to Kerr frequency combs. In this work, we present a general analysis of the regions of existence and stability of cavity solitons and patterns in the Lugiato-Lefever equation, a mean-field model that finds applications in many different nonlinear optical cavities. We demonstrate that the rich dynamics and coexistence of multiple solutions in the Lugiato-Lefever equation are of key importance to understanding frequency comb generation. A detailed map of how and where to target stable Kerr frequency combs in the parameter space defined by the frequency detuning and the pump power is provided. Moreover, the work presented also includes the organization of various dynamical regimes in terms of bifurcation points of higher co-dimension in regions of parameter space that were previously unexplored in the Lugiato-Lefever equation. We discuss different dynamical instabilities such as ...

Parra-Rivas, P; Matias, M A; Coen, S; Gelens, L

2014-01-01

440

Mid-infrared supercontinuum generation in tapered chalcogenide fiber for producing octave-spanning frequency comb around 3 {\\mu}m  

E-print Network

We demonstrate mid-infrared (mid-IR) supercontinuum generation (SCG) with instantaneous bandwidth from 2.2 to 5 {\\mu}m at 40 dB below the peak, covering the wavelength range desirable for molecular spectroscopy and numerous other applications. The SCG occurs in a tapered As2S3 fiber prepared by in-situ tapering and is pumped by femtosecond pulses from the subharmonic of a mode-locked Er-doped fiber laser. Interference with a narrow linewidth c.w. laser verifies that the coherence properties of the near-IR frequency comb have been preserved through these cascaded nonlinear processes. With this approach stable broad mid-IR frequency combs can be derived from commercially available near-IR frequency combs without an extra stabilization mechanism.

Marandi, Alireza; Plotnichenko, Victor G; Dianov, Evgeny M; Vodopyanov, Konstantin L; Byer, Robert L

2012-01-01

441

Sex offender recidivism: a review.  

PubMed

The increasing recognition of the large number of people victimized by sexual assault has focused considerable attention on methods for deterring its perpetrators. In particular, law enforcement and mental health professions alike seek ways to prevent sex offenders from repeating their criminal behavior. Some evidence suggests sex offenders often continue offending even after incarceration or clinical treatment. However, recidivism rates for sex offenders are unusually hard to establish, owing to gross underreporting of sex crimes. This article presents a comprehensive review of empirical studies of sex offender recidivism. It brings together data from a wide variety of studies on both treated and untreated sex offenders of all types. Because of the variety and gravity of methodological problems in these studies, guidelines are discussed for sample selection and description, study design, criterion assessment, and data analysis. With these methodological principles in mind, the results of some 42 studies are examined for what they can tell us about sex offender recidivism and efforts to reduce it. PMID:2648438

Furby, L; Weinrott, M R; Blackshaw, L

1989-01-01

442

[Teens and sex education].  

PubMed

It is widely debated among mental health professionals, among whom I include myself; the fact that not only teenagers who come to our clinics need good sex education, but that parents and/or legal guardians, often also it would be beneficial. I do not mean much to the sexual practice itself; the mechanics or completion of the act, as well as the training that is not received, when dealing with certain issues with young adolescents. Why can cost both accept that, well before age 17, have already fully developed sexuality? The answer could be as simple as saying that, it's not on focusing on the "do" but, from the "feel" and the latter field seems to be much more muddy and complex than the first. The management process of sexual development of our children and teens, begins when we are ready to grow ourselves in this respect, to overcome conflicts, needs, fears and insecurities of their own. Only then, when we will be able to become true and effective sexual educators and counselors of the young. PMID:23654187

Buj Pereda, M José

2013-03-01

443

Large range dual-axis micro-stage driven by electrostatic comb-drive actuators This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Large range dual-axis micro-stage driven by electrostatic comb-drive actuators This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2013 J. Micromech-stage driven by electrostatic comb-drive actuators Mohammad Olfatnia, Leqing Cui, Pankaj Chopra and Shorya

Awtar, Shorya

444

Adolescents, sex, and the media.  

PubMed

In the absence of effective sex education in the United States, the media have arguably become the leading sex educator for children and teenagers. Considerable research now exists that attests to the ability of the media to influence adolescents' attitudes and beliefs about sex and sexuality. In addition, new research has found a significant link between exposure to sexual content in the media and earlier onset of sexual intercourse. Although there is little research on the behavioral effects of "new" media, they are discussed as well. Suggestions for clinicians, parents, the federal government, and the entertainment industry are provided. PMID:22764553

Strasburger, Victor C

2012-04-01

445

Mammalian sex hormones in plants.  

PubMed

The occurrence of mammalian sex hormones and their physiological role in plants is reviewed. These hormones, such as 17beta-estradiol, androsterone, testosterone or progesterone, were present in 60-80% of the plant species investigated. Enzymes responsible for their biosynthesis and conversion were also found in plants. Treatment of the plants with sex hormones or their precursors influenced plant development: cell divisions, root and shoot growth, embryo growth, flowering, pollen tube growth and callus proliferation. The regulatory abilities of mammalian sex hormones in plants makes possible their use in practice, especially in plant in vitro culture. PMID:16044944

Janeczko, Anna; Skoczowski, Andrzej

2005-01-01

446

Virtual Sex Ed: Youth, Race, Sex, and New Media  

Microsoft Academic Search

This article is an introduction to the special issue of Sexuality Research and Social Policy, in which we give an overview and highlight the important themes covered by the featured articles. Each paper is based on\\u000a a presentation given at an interdisciplinary conference, Virtual Sex Ed: Youth, Race, Sex, and New Media, hosted by the Section\\u000a of Family Planning and

Melissa Gilliam; Claire Brindis

2011-01-01

447

Studies on the Sex-Specific Lethals of DROSOPHILA MELANOGASTER. V. Sex Transformation Caused by Interactions between a Female-Specific Lethal, Sxlf#1, and the Male-Specific Lethals mle(3)132, msl-227, and mle  

PubMed Central

Interactions between a female-specific lethal mutant, Sxlf#1, and each of three male-specific lethal mutants, mle(3)132, msl-227 and mle, of Drosophila melanogaster were observed to produce morphological changes in various sexually dimorphic external characters. Chromosomal females heterozygous for Sxlf#1 and homozygous for any one of the male-specific lethals (and to a lesser degree heterozygous for male-specific lethals) sometimes had sex combs, male-type tergites, male-type sternites, male-type anal plates or male-type external genitalia. Penetrance was not high and expression was often incomplete; single individuals never had all the sexually dimorphic structures transformed. When mothers were homozygous for male-specific lethals, higher proportions of female progeny were affected than when mothers were heterozygous, suggesting a maternal effect. PMID:6818105

Uenoyama, T.; Fukunaga, A.; Ioshi, K.

1982-01-01

448

Evidence for paralytic shellfish poisons in the freshwater cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov.  

PubMed Central

Lyngbya wollei (Farlow ex Gomont) comb. nov., a perennial mat-forming filamentous cyanobacterium prevalent 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 Reservoir, the mat-forming filamentous cyanobacterium L. wollei, a species that had recently invaded from other areas of the southern United States, was studied to determine if it could produce any of the known cyanotoxins. Of the 91 field samples collected at 10 locations at Guntersville Reservoir, Ala., on the Tennessee River, over a 3-year period, 72.5% were toxic. The minimum 100% lethal doses of the toxic samples ranged from 150 to 1,500 mg kg of lyophilized L. wollei cells-1, with the majority of samples being toxic at 500 mg kg-1. Samples bioassayed for paralytic shellfish toxins by the Association of Official Analytical Chemists method exhibited saxitoxin equivalents ranging from 0 to 58 micrograms g (dry weight)-1. Characteristics of the neurotoxic compound(s), such as the lack of adsorption by C18 solid-phase extraction columns, the short retention times on C18 high-performance liquid chromatography (HPLC) columns, the interaction of the neurotoxins with saxiphilin (a soluble saxitoxin-binding protein), and external blockage of voltage-sensitive sodium channels, led to our discovery that this neurotoxin(s) is related to the saxitoxins, the compounds responsible for paralytic shellfish poisonings. The major saxitoxin compounds thus far identified by comparison of HPLC fluorescence retention times are decarbamoyl gonyautoxins 2 and 3. There was no evidence of paralytic shellfish poison C toxins being produced by L. wollei. Fifty field samples were placed in unialgal culture and grown under defined culture conditions. Toxicity and signs of poisoning for these laboratory-grown strains of L. wollei were similar to those of the field collection samples. PMID:9251196

Carmichael, W W; Evans, W R; Yin, Q Q; Bell, P; Moczydlowski, E

1997-01-01

449

Evidence for paralytic shellfish poisons in the freshwater cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov.  

PubMed

Lyngbya wollei (Farlow ex Gomont) comb. nov., a perennial mat-forming filamentous cyanobacterium prevalent 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 Reservoir, the mat-forming filamentous cyanobacterium L. wollei, a species that had recently invaded from other areas of the southern United States, was studied to determine if it could produce any of the known cyanotoxins. Of the 91 field samples collected at 10 locations at Guntersville Reservoir, Ala., on the Tennessee River, over a 3-year period, 72.5% were toxic. The minimum 100% lethal doses of the toxic samples ranged from 150 to 1,500 mg kg of lyophilized L. wollei cells-1, with the majority of samples being toxic at 500 mg kg-1. Samples bioassayed for paralytic shellfish toxins by the Association of Official Analytical Chemists method exhibited saxitoxin equivalents ranging from 0 to 58 micrograms g (dry weight)-1. Characteristics of the neurotoxic compound(s), such as the lack of adsorption by C18 solid-phase extraction columns, the short retention times on C18 high-performance liquid chromatography (HPLC) columns, the interaction of the neurotoxins with saxiphilin (a soluble saxitoxin-binding protein), and external blockage of voltage-sensitive sodium channels, led to our discovery that this neurotoxin(s) is related to the saxitoxins, the compounds responsible for paralytic shellfish poisonings. The major saxitoxin compounds thus far identified by comparison of HPLC fluorescence retention times are decarbamoyl gonyautoxins 2 and 3. There was no evidence of paralytic shellfish poison C toxins being produced by L. wollei. Fifty field samples were placed in unialgal culture and grown under defined culture conditions. Toxicity and signs of poisoning for these laboratory-grown strains of L. wollei were similar to those of the field collection samples. PMID:9251196

Carmichael, W W; Evans, W R; Yin, Q Q; Bell, P; Moczydlowski, E

1997-08-01

450

Frequency Comb-Referenced Spectroscopy in the ?1 + ?3 Region of Acetylene  

NASA Astrophysics Data System (ADS)

class="MsoNormal">By using saturation dip absorption spectroscopy with an extended cavity diode laser locked to a frequency comb, we have measured the rest frequencies of transitions in the ?4 = 1 and ?5 = 1 hot bands in the ?1 + ?3 combination band of acetylene. The measured line frequencies are accurate to approximately 20 kHz i.e. approximately one part in 1011. Positions of the hot-band lines quoted in the HITRAN database, which are derived from the analysis of high-resolution FTIR spectra, are of the order of 10's of MHz in error. These measurements were undertaken because pressure broadened lineshape measurements of rotational lines in the combination band indicated that weak underlying hot band features were not correctly accounted for on the basis of their previously reported positions. As a result, measured line profiles in the band could not be accurately fit leading to errors of up to 1% in acetylene concentrations derived from the measurements. In addition, the pressure broadened P(11) line in the ?1 + ?3 combination band has been studied as a function of varying concentration of the absorber in nitrogen. Mixture concentrations of 1, 5 and 10% at 296 K and pressures between a few Torr and one atmosphere were made and the measurements analyzed using two different speeddependent broadening models. These experiments are designed to test the additivity of contributions to pressure broadening and shift in speed-dependent line-shape modeling, i.e. whether the lineshape parameters follow partial pressure weighting in the binary mixtures. P(11) is relatively isolated with respect to underlying hot band transitions and neighboring transitions of the same band, but it was found that the accurate positions of underlying hot-band transitions were crucial to the successful modeling of the observed line shapes, even though these lines are typically 100-1000 times weaker than P(11) itself and are many Doppler line widths removed from the line center. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy and supported by its Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences.

Cich, Matthew J.; Forthomme, Damien; Hall, Gregory E.; Mcraven, Christopher P.; Sears, Trevor J.; Twagirayezu, Sylvestre

2014-06-01

451

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

PubMed

Approximately 84% of the energy in chicken eggs resides in the yolk. A robust model of ovarian follicle development is therefore valuable for estimating energy requirements of laying hens. The current experiment was designed to model the growth of ovarian follicles in 32-wk-old modern commercial line (CL) and unselected heritage line (HL) Single Comb White Leghorn hens. The volume of yolk deposited daily during the rapid growth phase (RGP) was estimated using a double dye technique. For 21 d, 8 CL and 8 HL hens were fed capsules (no. 1) containing Sudan IV (red) and Sudan Black dyes on alternate days. An additional 8 control CL hens were fed empty capsules. Eggs were collected, and the daily volume of yolk deposited was estimated. Significant differences are reported where P < 0.05. Dye had no significant effect on BW, ME intake, or egg weight. Maintenance ME requirements were 192 and 177 kcal/kg(0.67) for CL and HL hens, respectively. Duration of the RGP was shorter (7.35 d) in the CL hens compared with the HL hens (7.95 d). A nonlinear Lomolino model described follicular weight, which varied between strains over d 2 to 9 of follicle development; at each day during development, follicle weights were higher where RGP were shorter. The volume of yolk deposited for the 8 d preceding oviposition in CL was 0.17, 0.28, 0.43, 0.99, 1.84, 2.47, 2.82, 2.86, and 2.51 cm(3); and in HL was 0.17, 0.33, 0.72, 1.40, 2.15, 2.46, 2.48, 2.32, and 1.93 cm(3). The HL had a higher rate of yolk deposition 7 to 5 d before oviposition, and CL had a higher rate of yolk deposition 3 to 1 d before oviposition with no significant difference between lines on d 4 before oviposition. Although growth patterns differed, there were no differences among lines in final follicle weights (14.1 g) or retained energy (42.4 kcal). PMID:25214554

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

2014-11-01

452

Making Healthy Decisions About Sex  

MedlinePLUS

... To protect against getting a disease from having oral sex, use a condom, dental dam, or non-microwavable ... Date Rape Sexting is Connected with Other Risky Sexual Behaviors in Teens Study Finds 2.5 Percent of ...

453

From psychotherapy to sex therapy  

Microsoft Academic Search

Much has been made, in the last two decades, of the American sexual revolution. Frequently cited components of this revolution include greater openness about sex in media and conversation, greater public acceptance of \\

Joseph LoPiccolo

1977-01-01

454

Safe Sex Tips for Seniors  

MedlinePLUS

... Safe Sex Tips for Seniors Tools and Tips Printer-friendly PDF Click here to see our other ... common sexual problems such as vaginal dryness and erectile dysfunction (ED). There are effective treatments for vaginal dryness, ...

455

Teaching Retarded Children about Sex.  

ERIC Educational Resources Information Center

Mentally retarded children need sex education, not only about biological factors involved in sexuality, but also in terms of emotional and social development as well. Ways that parents can prepare retarded youngsters to cope with emerging sexuality are discussed. (PP)

Kempton, Winifred

1983-01-01

456

Sex differences in Parkinson's disease.  

PubMed

Parkinson's disease (PD) displays a greater prevalence and earlier age at onset in men. This review addresses the concept that sex differences in PD are determined, largely, by biological sex differences in the NSDA system which, in turn, arise from hormonal, genetic and environmental influences. Current therapies for PD rely on dopamine replacement strategies to treat symptoms, and there is an urgent, unmet need for disease modifying agents. As a significant degree of neuroprotection against the early stages of clinical or experimental PD is seen, respectively, in human and rodent females compared with males, a better understanding of brain sex dimorphisms in the intact and injured NSDA system will shed light on mechanisms which have the potential to delay, or even halt, the progression of PD. Available evidence suggests that sex-specific, hormone-based therapeutic agents hold particular promise for developing treatments with optimal efficacy in men and women. PMID:24607323

Gillies, Glenda E; Pienaar, Ilse S; Vohra, Shiv; Qamhawi, Zahi

2014-08-01

457

High-rate pulse-train generation by phase-only filtering of an electrooptic frequency comb: Analysis and optimization  

NASA Astrophysics Data System (ADS)

We investigate the generation of high-rate optical pulse trains by spectral phase-only filtering of a frequency comb derived from an electrooptically phase-modulated continuous-wave laser. The technique is initially analyzed as a two-step filtering process. First, a fundamental pulse-train with repetition-rate equal to the modulation frequency is obtained by line-by-line phase-cancellation of the electrooptic frequency comb. Second, the temporal Talbot-effect is considered so that the output pulse repetition-rate is an integer multiple of the electrooptic modulation frequency. Nonidealities found in the fundamental train lead, in general, to multiplied trains with important degradations. We numerically analyze optimum modulation conditions for generation of output pulse trains with minimum peak-to-peak variations and/or maximum extinction level. On the other hand, a genetic algorithm is considered to numerically find optimum line-by-line phase-only filters that generate output multiplied trains with minimized degradations. Numerical simulations show that, in general, this second approach allows for improvement in the quality of the resultant multiplied trains, in terms of the uniformity degree and/or noise-level, compared with the pulse trains resulting from the Talbot-effect-based approach.

Caraquitena, José; Martí, Javier

2009-09-01

458

Noise-immune cavity-enhanced optical frequency comb spectroscopy: A sensitive technique for high-resolution broadband molecular detection  

E-print Network

Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS), and validate the model by comparing it to experimental CO2 spectra around 1575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long term stability of the system, a...

Khodabakhsh, Amir; Foltynowicz, Aleksandra

2014-01-01

459

Investigating the interplay between mechanisms of anomalous diffusion via fractional Brownian walks on a comb-like structure  

E-print Network

The comb model is a simplified description for anomalous diffusion under geometric constraints. It represents particles spreading out in a two-dimensional space where the motions in the x-direction are allowed only when the y coordinate of the particle is zero. Here, we propose an extension for the comb model via Langevin-like equations driven by fractional Gaussian noises (long-range correlated). By carrying out computer simulations, we show that the correlations in the y-direction affect the diffusive behavior in the x-direction in a non-trivial fashion, resulting in a quite rich diffusive scenario characterized by usual, superdiffusive or subdiffusive scaling of second moment in the x-direction. We further show that the long-range correlations affect the probability distribution of the particle positions in the x-direction, making their tails longer when noise in the y-direction is persistent and shorter for anti-persistent noise. Our model thus combines and allows the study/analysis of the interplay betwe...

Ribeiro, H V; Alves, L G A; Zola, R S; Lenzi, E L

2014-01-01

460

Investigating the interplay between mechanisms of anomalous diffusion via fractional Brownian walks on a comb-like structure  

NASA Astrophysics Data System (ADS)

The comb model is a simplified description for anomalous diffusion under geometric constraints. It represents particles spreading out in a two-dimensional space where the motions in the x-direction are allowed only when the y coordinate of the particle is zero. Here, we propose an extension for the comb model via Langevin-like equations driven by fractional Gaussian noises (long-range correlated). By carrying out computer simulations, we show that the correlations in the y-direction affect the diffusive behavior in the x-direction in a non-trivial fashion, resulting in a quite rich diffusive scenario characterized by usual, superdiffusive or subdiffusive scaling of second moment in the x-direction. We further show that the long-range correlations affect the probability distribution of the particle positions in the x-direction, making their tails longer when noise in the y-direction is persistent and shorter for anti-persistent noise. Our model thus combines and allows the study/analysis of the interplay between different mechanisms of anomalous diffusion (geometric constraints and long-range correlations) and may find direct applications for describing diffusion in complex systems such as living cells.

Ribeiro, Haroldo V.; Tateishi, Angel A.; Alves, Luiz G. A.; Zola, Rafael S.; Lenzi, Ervin K.

2014-09-01