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1

How Drosophila change their combs: the Hox gene Sex combs reduced and sex comb variation among Sophophora species.  

PubMed

Identification of the events responsible for rapid morphological variation during evolution can help understand how developmental processes are changed by genetic modifications and thus produce diverse body features and shapes. Sex combs, a sexually dimorphic structure, show considerable variation in morphology and numbers among males from related species of Sophophora, a subgenus of Drosophila. To address which evolutionary changes in developmental processes underlie this diversity, we first analyzed the genetic network that controls morphogenesis of a single sex comb in the model D. melanogaster. We show that it depends on positive and negative regulatory inputs from proximo-distal identity specifying genes, including dachshund, bric à brac, and sex combs distal. All contribute to spatial regulation of the Hox gene Sex combs reduced (Scr), which is crucial for comb formation. We next analyzed the expression of these genes in sexually dimorphic species with different comb numbers. Only Scr shows considerable expression plasticity, which is correlated with comb number variation in these species. We suggest that differences in comb numbers reflect changes of Scr expression in tarsus primordia, and discuss how initial comb formation could have occurred in an ancestral Sophophora fly following regulatory modifications of developmental programs both parallel to and downstream of Scr. PMID:18184363

Randsholt, Neel B; Santamaria, Pedro

2

Drosophila Sex Combs as a Model of Evolutionary Innovations  

PubMed Central

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

Kopp, Artyom

2011-01-01

3

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

PubMed

Sexually dimorphic characters have two-fold complexities in pattern formation as they have to get input from both somatic sex determination as well as the positional determining regulators. Sex comb development in Drosophila requires functions of the somatic sex-determining gene doublesex and the homeotic gene Sex combs reduced. Attempts have not been made to decipher the role of dsx in imparting sexually dimorphic expression of SCR and the differential function of sex-specific variants of dsx products in sex comb development. Our results in this study indicate that male-like pattern of SCR expression is independent of dsx function, and dsx F must be responsible for bringing about dimorphism in SCR expression, whereas dsx M function is required with Scr for the morphogenesis of sex comb. PMID:23938378

Devi, Thangjam Ranjita; Shyamala, B V

2013-09-01

4

Wing Defects in Drosophila xenicid Mutant Clones Are Caused by C-Terminal Deletion of Additional Sex Combs (Asx)  

PubMed Central

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

Bischoff, Kara; Ballew, Anna C.; Simon, Michael A.; O'Reilly, Alana M.

2009-01-01

5

Variation and Evolution of Male Sex Combs in Drosophila: Nature of Selection Response and Theories of Genetic Variation for Sexual Traits  

PubMed Central

We investigated the genetic architecture of variation in male sex comb bristle number, a rapidly evolving secondary sexual character of Drosophila. Twenty-four generations of divergent artificial selection for sex comb bristle number in a heterogeneous population of Drosophila melanogaster resulted in a significant response that was more pronounced in the direction of low bristle numbers. We observed a strong positive correlated response to selection in the corresponding female transverse bristle row. The correlated response in male abdominal and sternopleural bristle numbers, on the other hand, did not follow the same pattern as sex comb bristle number differences between selection lines. Relaxation-of-selection experiments along with mate choice and fecundity assays using the selection lines developed demonstrated the action of stabilizing selection on sex comb bristle number. Our results show (1) substantial genetic variation underlying sex comb bristle number variation; (2) a weak relationship between the sex comb and developmentally related, non-sex bristle systems; and (3) that sexual selection may be a driving force in sex comb evolution, indicating the potential of sex combs to diversify rapidly during population differentiation and speciation. We discuss the implications of these results for theories of genetic variation in display and nondisplay male sex traits.

Ahuja, Abha; Singh, Rama S.

2008-01-01

6

Evolution of sex comb from the primitive bristle pattern in Drosophila is associated with modification in the developmental regulatory protein Dachshund.  

PubMed

Sex comb is a recently evolved male specific character confined to the Sophophoran group of Drosophila. Such innovations in phenotypes as Waddington proposed, are, outcome of "canalization" in developmental pathways that occur due to mutations creating "choice points" in genetic regulatory pathways. Our interest in the present study is to understand the shifts in genetic network, which has lead to the origin of sex comb from the basic bristle pattern that is seen in rest of the members of Drosophilidae. Here we have made a comparative analysis of expression of some of the key regulators of sex comb morphogenesis, between D. melanogaster and a group of selected species, which primitively lack sex comb. Sex combs reduced (Scr), dachshund (dac), and bric-a-brac (bab) gene expression were studied. We show that, primitive bristle pattern is marked by a strikingly down regulated expression of Sex combs reduced in the first tarsal segment of the prothoracic leg discs of male flies. Further a remarkable change with respect to Dachshund, an activator of sex combs reduced gene in the sex comb regulatory pathway, is seen. This is attributed to changes in DAC protein that might have taken place between the two groups of species. bric-a-brac does not reveal any significant expression modulation between the sex comb bearing and the primitive patterned species. Earlier works had shown that within the Sophophoran group, dynamic changes in SCR expression is responsible for the diversity seen in sex comb morphology, where as no such variation is witnessed with respect to DAC expression. Our findings have demonstrated that the scenario is different between the group primitively lacking sex comb and D. melanogaster wherein an obvious change in the protein has taken place. genesis 51:97-109, 2013, 2013. © 2012 Wiley Periodicals, Inc. PMID:23197370

Devi, Thangjam Ranjita; Amruthavalli, C; Shyamala, B V

2013-01-25

7

The Tribolium castaneum ortholog of Sex combs reduced controls dorsal ridge development.  

PubMed

In insects, the boundary between the embryonic head and thorax is formed by the dorsal ridge, a fused structure composed of portions of the maxillary and labial segments. However, the mechanisms that promote development of this unusual structure remain a mystery. In Drosophila, mutations in the Hox genes Sex combs reduced and Deformed have been reported to cause abnormal dorsal ridge formation, but the significance of these abnormalities is not clear. We have identified three mutant allele classes of Cephalothorax, the Tribolium castaneum (red flour beetle) ortholog of Sex combs reduced, each of which has a different effect on dorsal ridge development. By using Engrailed expression to monitor dorsal ridge development in these mutants, we demonstrate that Cephalothorax promotes the fusion and subsequent dorsolateral extension of the maxillary and labial Engrailed stripes (posterior compartments) during dorsal ridge formation. Molecular and genetic analysis of these alleles indicates that the N terminus of Cephalothorax is important for the fusion step, but is dispensable for Engrailed stripe extension. Thus, we find that specific regions of Cephalothorax are required for discrete steps in dorsal ridge formation. PMID:16849608

Shippy, Teresa D; Rogers, Carmelle D; Beeman, Richard W; Brown, Susan J; Denell, Robin E

2006-07-18

8

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

PubMed Central

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

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

2002-01-01

9

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

SciTech Connect

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

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

1995-02-01

10

ASX: An Object-Oriented Framework for Developing Distributed Applications  

Microsoft Academic Search

The ADAPTIVE Service eXecutive (ASX) is a highly modular and extensible object-oriented framework that simplifies the development and configuration of distributed applications on shared memory multi-processor platforms. This paper describes the structure and functionality of theASX frame- work's object-oriented architecture. In addition, the paper presents the results of performance experiments conducted using ASX-based implementations of connection-oriented and connectionless protocols from

Douglas C. Schmidt

1994-01-01

11

A Logical OR Redundancy within the Asx-Pro-Asx-Gly Type 1 {Beta}-Turn Motif  

SciTech Connect

Turn secondary structure is essential to the formation of globular protein architecture. Turn structures are, however, much more complex than either {alpha}-helix or {beta}-sheet, and the thermodynamics and folding kinetics are poorly understood. Type I {beta}-turns are the most common type of reverse turn, and they exhibit a statistical consensus sequence of Asx-Pro-Asx-Gly (where Asx is Asp or Asn). A comprehensive series of individual and combined Asx mutations has been constructed within three separate type I 3:5 G1 bulge {beta}-turns in human fibroblast growth factor-1, and their effects on structure, stability, and folding have been determined. The results show a fundamental logical OR relationship between the Asx residues in the motif, involving H-bond interactions with main-chain amides within the turn. These interactions can be modulated by additional interactions with residues adjacent to the turn at positions i + 4 and i + 6. The results show that the Asx residues in the turn motif make a substantial contribution to the overall stability of the protein, and the Asx logical OR relationship defines a redundant system that can compensate for deleterious point mutations. The results also show that the stability of the turn is unlikely to be the prime determinant of formation of turn structure in the folding transition state.

Lee, Jihun; Dubey, Vikash Kumar; Longo, Lian M.; Blaber, Michael (FSU)

2008-04-19

12

A Logical OR Redundancy Within the Asx-Pro-Asx-Gly Type I beta-Turn Motif  

SciTech Connect

Turn secondary structure is essential to the formation of globular protein architecture. Turn structures are, however, much more complex than either ?-helix or ?-sheet, and the thermodynamics and folding kinetics are poorly understood. Type I ?-turns are the most common type of reverse turn, and they exhibit a statistical consensus sequence of Asx-Pro-Asx-Gly (where Asx is Asp or Asn). A comprehensive series of individual and combined Asx mutations has been constructed within three separate type I 3:5 G1 bulge ?-turns in human fibroblast growth factor-1, and their effects on structure, stability, and folding have been determined. The results show a fundamental logical OR relationship between the Asx residues in the motif, involving H-bond interactions with main-chain amides within the turn. These interactions can be modulated by additional interactions with residues adjacent to the turn at positions i + 4 and i + 6. The results show that the Asx residues in the turn motif make a substantial contribution to the overall stability of the protein, and the Asx logical OR relationship defines a redundant system that can compensate for deleterious point mutations. The results also show that the stability of the turn is unlikely to be the prime determinant of formation of turn structure in the folding transition state.

Lee,J.; Dubey, V.; Longo, L.; Blaber, M.

2008-01-01

13

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

SciTech Connect

The Drosophilia homeotic gene Sex combs reduced (Scr) is necessary for the establishment and maintenance of the morphological identity of the labial and prothoracic segments. In the early embryo, its expression pattern is established through the activity of several gap and segmentation gene products, as well as other transcription factors. Once established, the Polycomb group (Pc-G) and trithorax group (trx-G) gene products maintain the spatial pattern of Scr expression for the remainder of development. We report the identification of DNA fragments in the Scr regulatory region that may be important for its regulation by Polycomb and trithorax group gene products. When DNA fragments containing these regulatory sequences are subcloned into P-element vectors containing a white minigene, transformants containing these constructs exhibit mosaic patterns of pigmentation in the adult eye, indicating that white minigene expression is repressed in a clonally heritable manner. The size of pigmented and nonpigmented clones in the adult eye suggests that the event determining whether a cell in the eye anlagen will express white occurs at least as early as the first larval instar. The amount of white minigene repression is reduced in some Polycomb group mutants, whereas repression is enhanced in flies mutant for a subset of trithorax group loci. The repressor activity of one fragment, normally located in Scr Intron 2, is increased when it is able to homologously pair, a property consistent with genetic data suggesting that Scr exhibits transvection. Another Scr regulatory fragment, normally located 40 kb upstream of the Scr promoter, silences ectopic expression of an Scr-lacZ fusion gene in the embryo and does so in a Polycomb-dependent manner. We propose that the regulatory sequences located within these DNA fragments may normally mediate the regulation of Scr by proteins encoded by members of Polycomb and trithorax group loci. 98 refs., 6 figs., 4 tabs.

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

1995-02-01

14

Decentralized control of drone comb construction in honey bee colonies  

Microsoft Academic Search

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

Stephen C. Pratt

1998-01-01

15

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

16

Low gap amorphous GaN1-xAsx alloys grown on glass substrate  

NASA Astrophysics Data System (ADS)

Amorphous GaN1-xAsx layers with As content in the range of x=0.1 to 0.6 were grown by molecular beam epitaxy on Pyrex glass substrate. These alloys exhibit a wide range of band gap values from 2.2 to 1.3 eV. We found that the density of the amorphous films is ~0.8-0.85 of their corresponding crystalline value. These amorphous films have smooth morphology, homogeneous composition, and sharp well defined optical absorption edges. The measured band gap values for the crystalline and amorphous GaN1-xAsx alloys are in excellent agreement with the predictions of the band anticrossing model. The high absorption coefficient of ~105 cm-1 for the amorphous GaN1-xAsx films suggests that relatively thin films (on the order of 1 ?m) are necessary for photovoltaic application.

Yu, K. M.; Novikov, S. V.; Broesler, R.; Liliental-Weber, Z.; Levander, A. X.; Kao, V. M.; Dubon, O. D.; Wu, J.; Walukiewicz, W.; Foxon, C. T.

2010-09-01

17

Differential Action Extractor Comb.  

National Technical Information Service (NTIS)

The invention relates to a unique method of combing stripper harvested seed cotton in order to facilitate the removal of trash components such as large sticks and burrs. Further it relates to a coarse-tooth, reverse pitch, combing saw cylinders, turning w...

L. A. Smith

1978-01-01

18

Femtosecond Optical Frequency Combs  

NASA Astrophysics Data System (ADS)

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

Udem, Thomas; Holzwarth, Ronald; Hänsch, Theodor

19

Low-temperature thermal properties of amorphous AsxSe1-x  

Microsoft Academic Search

We have measured the low-temperature specific heat C and thermal conductivity kappa (1.5 K<=T<=30 K) of amorphous AsxSe1-x in the concentration range of 0<=x<=0.72. The maximum in C\\/T3 and the plateau in kappa display consistent but nonmonotonic concentration dependences, similar to the earlier specific-heat results for the same samples below 1 K. Our results give unambiguous evidence that the behavior

X. Liu; H. V. hneysen

1993-01-01

20

Amorphous GaN1?xAsx alloys for multi-junction solar cells  

Microsoft Academic Search

We propose GaN1-xAsx as a new absorber material for single alloy multi-junction solar cells. Our recent results reported the first controlled growth of the material system across the full composition range and showed that the band gap can be tuned from 0.8eV to 3.4eV. Our low temperature molecular beam epitaxy (MBE) growth method results in amorphous films across much of

R. Broesler; K. M. Yu; S. V. Novikov; Z. Liliental-Weber; E. E. Haller; W. Walukiewicz; C. T. Foxon

2010-01-01

21

Dual Comb Fourier Transform Spectroscopy  

NASA Astrophysics Data System (ADS)

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

Hänsch, T. W.; Picqué, N.

2010-06-01

22

Molecular Comb Development  

SciTech Connect

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

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

2007-07-17

23

Self-catalyzed MBE grown GaAs/GaAsxSb1-x core-shell nanowires in ZB and WZ crystal structures.  

PubMed

We have investigated the growth of self-catalyzed GaAs/GaAsxSb1-x core-shell nanowires directly on Si(111) substrates by molecular beam epitaxy. The compositions of the GaAsxSb1-x shells are tuned in a wide range where the Sb-content is varied from 10 to ?70%, covering the miscibility gap. In addition, the GaAsxSb1-x shells are grown on both zinc blende (ZB) and wurtzite (WZ) crystal structures. Morphological and structural characterizations of the grown nanowires indicate successful transfer of the GaAs core crystal structure to the GaAsxSb1-x shells for both ZB and WZ nanowires, with slower shell growth rate on the WZ segments. PMID:24028926

Ghalamestani, Sepideh Gorji; Mazid Munshi, A; Dheeraj, Dasa L; Fimland, Bjørn-Ove; Weman, Helge; Dick, Kimberly A

2013-09-12

24

Self-catalyzed MBE grown GaAs/GaAsxSb1-x core-shell nanowires in ZB and WZ crystal structures  

NASA Astrophysics Data System (ADS)

We have investigated the growth of self-catalyzed GaAs/GaAsxSb1-x core-shell nanowires directly on Si(111) substrates by molecular beam epitaxy. The compositions of the GaAsxSb1-x shells are tuned in a wide range where the Sb-content is varied from 10 to ˜70%, covering the miscibility gap. In addition, the GaAsxSb1-x shells are grown on both zinc blende (ZB) and wurtzite (WZ) crystal structures. Morphological and structural characterizations of the grown nanowires indicate successful transfer of the GaAs core crystal structure to the GaAsxSb1-x shells for both ZB and WZ nanowires, with slower shell growth rate on the WZ segments.

Gorji Ghalamestani, Sepideh; Mazid Munshi, A.; Dheeraj, Dasa L.; Fimland, Bjørn-Ove; Weman, Helge; Dick, Kimberly A.

2013-10-01

25

Photoluminescence in Glassy AsxSe 1-x at 77 K  

NASA Astrophysics Data System (ADS)

Photoluminescence (PL) has been measured in a series of glassy AsxSe1-x samples with x between 0.3 and 0.6. The experimental apparatus included excitation with a Ti Sapphire laser at approximately 720 nm, a 3/4 m monochromator, a Ge photodetector, and lock-in detection at 19 Hz. Although the relative intensities of the PL signals are not well determined, there is no strong dependence on x. The peak energies of the PL spectra shift to lower energy with increasing x. At x=0.4 the peak energy is 0.9 eV. The widths of the PL spectra increase slightly with increasing x. At x=0.4 the full-width at half-maximum is approximately 0.3 eV. These results will be compared with the compositional dependence of the optical properties of these glasses.

Derbidge, C. M.; Ahn, E.; Taylor, P. C.

2002-10-01

26

Mid-infrared frequency combs  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

27

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

PubMed

Genetic models of sex and caste determination in eusocial 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 conditions, such as food and temperature, could also contribute to non-random spatial configuration. We converted the positions of the hexagonal cells in a brood comb to Cartesian coordinates, labeled by sex or caste of the individuals inside. To detect and locate clustered patterns, the mapped brood combs were evaluated by indexes of dispersion (MMC, mean distance of cells of a given category from their centroid) and eccentricity (DMB, distance between this centroid and the overall brood comb centroid) that we developed. After randomizing the labels and recalculating the indexes, we calculated probabilities that the original values had been generated by chance. We created sets of binary brood combs in which males were aggregated, regularly or randomly distributed among females. These stylized maps were used to describe the power of MMC and DMB, and they were applied to evaluate the male distribution in the sampled Nannotrigona testaceicornis brood combs. MMC was very sensitive to slight deviations from a perfectly rounded clump; DMB detected any asymmetry in the location of these compact to fuzzy clusters. Six of the 82 brood combs of N. testaceicornis that we analyzed had more than nine males, distributed according to variations in spatial patterns, as indicated by the two indexes. PMID:19551646

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

2009-05-19

28

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

29

Side chain: backbone projections in aromatic and ASX residues from NMR cross-correlated relaxation.  

PubMed

The measurements of cross-correlated relaxation rates between H(N)-N and C(beta)-C(gamma) intraresidual and sequential dipolar interactions is demonstrated in ASN, ASP and aromatic residues. The experiment can be used for deuterated samples and no additional knowledge such as Karplus parametrizations is required for the analysis. The data constitutes a new type of information since no other method relates the C(beta)-C(gamma) bond to H(N)-N. Using this method the dominant populations of rotamer states of chi 1 can be readily cross checked provided that phi or psi are known. In addition, dynamics on all timescales can be probed. As opposed to standard dynamics analysis of isolated bonds, the presented observables depend on relative dynamics with an interesting prospect to analyze correlated fluctuations of the two torsion angles phi or psi with chi 1. Experimental rates are compared to single conformer and ensemble representations of GB3 and ubiquitin. In particular, it is found that the recently published ubiquitin ensemble 2k39 improves the agreement obtained for 1UBQ. In general, however, input data restricting ASX and aromatic side chains in structure calculation is sparse highlighting the need for new NMR observables. PMID:19904498

Vögeli, Beat; Riek, Roland

2009-11-11

30

Crossover from pure to random-field critical susceptibility in KH2AsxP1-xO4  

Microsoft Academic Search

Using precise dielectric constant measurements we have determined the critical susceptibility of ferroelectric KH2AsxP1-xO4 samples with x=0.35 and x=0.45 . A clear and essentially complete crossover from pure to random-field critical behavior is observed as a function of reduced temperature t=T\\/Tc-1 . The effective susceptibility exponent varies in a nonmonotonic fashion from ˜1.2 near t=0.1 to ˜1.7 for small t

D. R. Taylor; J. T. Love; G. J. Topping; J. G. A. Dane

2005-01-01

31

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

32

Visible wavelength astro-comb.  

PubMed

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

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

2010-08-30

33

Scaling of Yb-Fiber Frequency Combs  

NASA Astrophysics Data System (ADS)

Immediately after their introduction in 1999, femtosecond laser frequency combs revolutionized the field of precision optical frequency metrology and are key elements in many experiments. Frequency combs based on femtosecond Er-fiber lasers based were demonstrated in 2005, allowing additionally rugged, compact set-ups and reliable unattended long-term operation. The introduction of Yb-fiber technology led to an dramatic improvement in fiber-comb performance in various aspects. Low-noise Yb-fiber femtosecond oscillators enabled a reduction of relative comb tooth linewidth to the sub-Hz level as well as scaling of the fundamental comb spacings up to 1 GHz. This is beneficial for any frequency-domain comb application due to the higher power per comb-mode. Many spectroscopic applications require, however, frequency combs way beyond the wavelength range accessible with broad band laser materials, so nonlinear conversion and hence higher peak intensity is required. We demonstrated power scaling of Yb-fiber frequency combs up to 80 W average power in a strictly linear chirped-pulse amplification schemes compatible with low-noise phase control. These high-power Yb-fiber-frequency combs facilitated not only the extension to the mid-IR spectral region. When coupled to a passive enhancement cavity, the average power can be further scaled to the kW-level opening new capabilities for XUV frequency combs via high-harmonic generation. All these advances of fiber-based frequency combs will trigger many novel applications both in fundamental and applied sciences. Schibli et al., Nature Photonics 2 355 (2008). Hartl et al., MF9 in Advanced Solid-State Photonics. 2009, Optical Society of America. Ruehl et al., AWC7 in Advanced Solid-State Photonics. 2010, Optical Society of America. Adler et al., Optics Letters 34 1330 (2009). Yost et al., Nature Physics 5 815 (2009).

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

2010-06-01

34

Fragile-strong behavior in the AsxSe1-x glass forming system in relation to structural dimensionality  

NASA Astrophysics Data System (ADS)

A series of physical properties have been measured throughout and above the glass transition for the whole AsxSe1-x system, including the activation for viscous flow E?, the activation energy for enthalpy relaxation EH, and the activation energy for structural relaxation Ea obtained by specific heat spectroscopy. All properties show a double minimum at an average coordination number = 2.3 and = 2.5 with a local maximum at = 2.4. This is in stark contrast to the physical properties previously measured on the same samples at room temperature and which instead show a single minimum centered at = 2.4. The observed trend is consistent with the dimensionality of the network derived from structural data obtained by nuclear magnetic resonance. An analysis of the complex heat capacity also reveals a bimodal relaxation process in As-rich glasses, which explains why they are kinetically fragile but appear thermodynamically strong. Finally, these results demonstrate that previous observations of an “intermediate phase” in AsxSe1-x glasses near = 2.3 is associated with the high temperature behavior of the glassy network and should be interpreted in terms of the temperature dependence of structural constraints rather than the number of constraints in the room-temperature glass.

Yang, Guang; Gulbiten, Ozgur; Gueguen, Yann; Bureau, Bruno; Sangleboeuf, Jean-Christophe; Roiland, Claire; King, Ellyn A.; Lucas, Pierre

2012-04-01

35

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.

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

36

PROGRAMMABLE MODIFIED FRACTIONAL COMB DECIMATION FILTER  

Microsoft Academic Search

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

Djordje Babic; Markku Renfors

37

Vertically supported two-directional comb drive  

Microsoft Academic Search

A vertically supported comb drive with the feasibility of actuation in two perpendicular directions utilizing electrostatic force from interdigitated comb-shape electrodes has been demonstrated. The prototype microstructures are made of 2 µm thick polysilicon by a standard surface micromachining process. They are vertically lifted after the final sacrificial layer releasing process and are fixed on the substrate with the assistance

Ki Bang Lee; Liwei Lin

2005-01-01

38

Arthur Wright Combs: A Humanistic Pioneer  

ERIC Educational Resources Information Center

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

Magnuson, Sandy

2012-01-01

39

The role of wax comb in honey bee nestmate recognition  

Microsoft Academic Search

WORKER honey bees,Apis mellifera, are able to discriminate between combs on the basis of genetic similarity to a learned comb. The nestmate recognition cues that they acquire from the comb also have a genetically correlated component. Cues are acquired from comb in very short exposure periods (5min or less) and can be transferred among bees that are in physical contact.

MICHAEL D. BREED; MELISSA F. GARRY; ALISON N. PEARCE; BRUCE E. HIBBARD; LOUIS B. BJOSTAD

1995-01-01

40

Rapid thermal redistribution of copper impurities in GaAsxP1-x at temperatures above 250 °C  

NASA Astrophysics Data System (ADS)

Light emitting GaAsxP1-x diodes with As concentrations below x = 0.6 have been Cu-doped and life-tested. Beside strongly decreased efficiencies, tested diodes exhibit deteriorated, i. e. soft reverse voltage characteristics related to microplasma formation. The sites where microplasmas are formed are dislocations penetrating the p-n junction. Heat treatment for 25 min at temperatures as low as 250 °C strongly improves the reverse voltage characteristic. Full recovery of the original characteristic may be established at 300 °C within about 2 hours. The heat treatment causes the microplasmas to disappear completely, the original optical efficiency, however, is not regained. The cycle: optical testing, heat treatment with the recovery of the electrical characteristic, optical testing, etc. can be repeated many times. During this cycling the microplasmas of diffused diodes change from a distribution evenly spread over the dislocations of the diffused area into a narrow ring close to the edge of the diffusion window.

Schairer, Werner

1984-05-01

41

The Continuing Evolution of Femtosecond Frequency Combs  

NASA Astrophysics Data System (ADS)

Following their development in early 2000, femtosecond frequency combs found immediate application as reference rulers in optical frequency metrology. Stabilization of the frequency comb emitted by an ultrafast laser has also enabled production of carrier-envelope phase-stabilized femtosecond pulses, thereby spurring seminal work in attosecond metrology. As the comb technology itself has matured, new areas of application have emerged such as precise calibration of astronomical spectrographs, arbitrary optical waveform synthesis, and precision spectroscopy. In this talk, I will highlight these new developments and discuss related and current work at UBC on these topics.

Jones, David

2008-05-01

42

Direct Frequency Comb Spectroscopy of Trapped Ions  

NASA Astrophysics Data System (ADS)

Direct frequency comb spectroscopy of trapped ions is demonstrated for the first time. It is shown that the 4sS1/22-4pP3/22 transition in calcium ions can be excited directly with a frequency comb laser that is up-converted to 393 nm. Detection of the transition is performed using a shelving scheme to suppress the background signal from nonresonant comb modes. The measured transition frequency of f=761905012.7(0.5)MHz presents an improvement in accuracy of more than 2 orders of magnitude.

Wolf, A. L.; van den Berg, S. A.; Ubachs, W.; Eikema, K. S. E.

2009-06-01

43

Surface acoustic wave frequency comb  

NASA Astrophysics Data System (ADS)

We investigate opto-mechanical oscillation (OMO) and subsequent generation of acoustic wave frequency combs in monolithic crystalline whispering gallery mode (WGM) resonators. The OMO is observed in resonators made of electro-optic (lithium tantalate), non-electro-optic birefringent (magnesium fluoride), and non-birefringent (calcium fluoride) materials. The phenomenon manifests itself as generation of optical harmonics separated by the eigenfrequency of a surface acoustic wave (SAW) mechanical mode of the same WGM resonator. We show that the light escaping the resonator and demodulated on a fast photodiode produces a spectrally pure radio frequency (RF) signal. For instance, we demonstrate generation of 200 MHz signals with instantaneous linewidth of 0.2 Hz.

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

2012-02-01

44

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

SciTech Connect

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

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

2006-04-15

45

On phase locking phenomena in Kerr combs  

NASA Astrophysics Data System (ADS)

Based on a modal description of the evolution Kerr combs in a whispering-gallery mode resonator, we numerically investigate the phase bhavior of the different spectral lines of the spectrum. We show that a stable phase relation exists between adjacent modes in primary combs. This result is of great interest for metrological applications where one phase noise is an issue. For high input power however, chaotic signals are observed.

Coillet, Aurélien; Balakireva, Irina; Henriet, Rémi; Larger, Laurent; Chembo, Yanne

2013-02-01

46

Digital processing of signals from femtosecond 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, we are experimenting with digital signal processing of the RF beat note spectrum produced by f-2f 1 technique and with fully digital servo-loop stabilization of the fs comb. Secondly, we are using digital servo-loop techniques for locking free running continuous laser sources on single components of the fs comb spectrum. 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 and repetition frequencies of the fs comb.

?ížek, Martin; Šmíd, Radek; Buchta, Zden?k.; Mikel, B?etislav; Lazar, Josef; ?íp, Ondrej

2012-01-01

47

Fiber-laser frequency combs with subhertz relative linewidths  

NASA Astrophysics Data System (ADS)

We investigate the comb linewidths of self-referenced, fiber-laser-based frequency combs by measuring the heterodyne beat signal between two independent frequency combs that are phase locked to a common cw optical reference. We demonstrate that the optical comb lines can exhibit instrument-limited, subhertz relative linewidths across the comb spectra from 1200 to 1720 nm with a residual integrated optical phase jitter of ˜1 rad in a 60 mHz to 500 kHz bandwidth. The projected relative pulse timing jitter is ˜1 fs. This performance approaches that of Ti:sapphire frequency combs.

Swann, W. C.; McFerran, J. J.; Coddington, I.; Newbury, N. R.; Hartl, I.; Fermann, M. E.; Westbrook, P. S.; Nicholson, J. W.; Feder, K. S.; Langrock, C.; Fejer, M. M.

2006-10-01

48

Electrostatic comb drive for vertical actuation  

SciTech Connect

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

Lee, A. P., LLNL

1997-07-10

49

Ultrasonic comb transducer for smart materials  

NASA Astrophysics Data System (ADS)

Installation of a small multi-element comb type ultrasonic transducer is proposed as a component of a smart structure. It can be used in either an active or passive mode in carrying out ultrasonic bulk or guided wave nondestructive evaluation. Theoretical methods are developed and experimental results are presented for guided wave generation and mode control with this very efficient and versatile novel comb type ultrasonic transducer. Excitation and probe design is crucial in mode selection. The comb transducer generates waves that are influenced by such parameters as number of elements, spacing between elements, dimension, pulsing sequence, and pressure distribution. The excited elastic field depends on the excitation frequency, plate thickness, and elastic properties. Techniques are studied to optimize the applied loading and the comb transducer design parameters so that only modes that are most sensitive to particular material characteristics can be generated. Complete understanding of the comb transducer parameters and their impact on the elastic field allows us to efficiently generate higher order modes as well as low phase velocity modes which are valuable in composite material characterization. Sample experiments are presented for various plate and tube like structures.

Rose, J. L.

1998-04-01

50

Sensitivity Scaling of Dual Frequency Comb Spectroscopy  

NASA Astrophysics Data System (ADS)

Coherent dual comb spectroscopy can harness many inherent strengths of frequency combs to provide high-resolution, high-accuracy measurements of a sample response (in both magnitude and phase) on a single detector. We will discuss the noise scaling properties of this technique and show that a useful figure of merit is the product of the signal-to-noise ratio and the number of spectral elements. When normalized by the square root of the observation time, this figure of merit is 106 to 107 Hz1/2 for a single detector and fiber-laser based system. We will discuss the scaling laws, performance, and corresponding strengths and weaknesses of coherent dual comb spectroscopy in the context of our recent results that achieved a figure of merit of 2 × 106 Hz1/2 in a spectral band around 1560 nm.

Coddington, I.; Swann, W. C.; Newbury, N. R.

2010-06-01

51

Evolution of Sex-Specific Traits through Changes in HOX-Dependent doublesex Expression  

PubMed Central

Almost every animal lineage is characterized by unique sex-specific traits, implying that such traits are gained and lost frequently in evolution. However, the genetic mechanisms responsible for these changes are not understood. In Drosophila, the activity of the sex determination pathway is restricted to sexually dimorphic tissues, suggesting that spatial regulation of this pathway may contribute to the evolution of sex-specific traits. We examine the regulation and function of doublesex (dsx), the main transcriptional effector of the sex determination pathway, in the development and evolution of Drosophila sex combs. Sex combs are a recent evolutionary innovation and show dramatic diversity in the relatively few Drosophila species that have them. We show that dsx expression in the presumptive sex comb region is activated by the HOX gene Sex combs reduced (Scr), and that the male isoform of dsx up-regulates Scr so that both genes become expressed at high levels in this region in males but not in females. Precise spatial regulation of dsx is essential for defining sex comb position and morphology. Comparative analysis of Scr and dsx expression reveals a tight correlation between sex comb morphology and the expression patterns of both genes. In species that primitively lack sex combs, no dsx expression is observed in the homologous region, suggesting that the origin and diversification of this structure were linked to the gain of a new dsx expression domain. Two other, distantly related fly lineages that independently evolved novel male-specific structures show evolutionary gains of dsx expression in the corresponding tissues, where dsx may also be controlled by Scr. These findings suggest that changes in the spatial regulation of sex-determining genes are a key mechanism that enables the evolution of new sex-specific traits, contributing to some of the most dramatic examples of phenotypic diversification in nature.

Tanaka, Kohtaro; Barmina, Olga; Sanders, Laura E.; Arbeitman, Michelle N.; Kopp, Artyom

2011-01-01

52

Comb Actuated resonant torsional scanner for microdisplays  

Microsoft Academic Search

A comb-actuated 1D torsional MEMS scanner is developed for high resolution projection display systems using mechanical coupling principle. 64deg TOSA (total optical scan angle) is achieved at 22.1 kHz with 170 V peak-to-peak excitation voltages.

Aslihan Arslan; Sven Holmstrom; S. Kutal Gokce; Hakan Urey

2009-01-01

53

Universal scaling laws of Kerr frequency combs.  

PubMed

Using the known solutions of the Lugiato-Lefever equation, we derive universal trends of Kerr frequency combs. In particular, normalized properties of temporal cavity soliton solutions lead us to a simple analytic estimate of the maximum attainable bandwidth for given pump resonator parameters. The result is validated via comparison with past experiments encompassing a diverse range of resonator configurations and parameters. PMID:23722745

Coen, Stéphane; Erkintalo, Miro

2013-06-01

54

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.

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

2012-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

56

Precision spectroscopy with frequency combs at 3.4 ?m  

NASA Astrophysics Data System (ADS)

We discuss precision spectroscopy with a comb-based spectrometer at 3.4 ?m. Our goal is to explore comb-based spectroscopy as an alternative method for fast, highly resolved, accurate measurements of gas line shapes. The spectrometer uses dual 1.5 ?m frequency combs down converted to 3.4 ?m via difference frequency generation (DFG) with a stabilized 1 ?m fiber laser. One 3.4 ?m comb is transmitted through methane and heterodyned against the second, offset comb to measure the gas absorption and dispersion. Doppler-broadened methane spectral lines are measured to below 1 MHz uncertainty. We also discuss the higher sensitivity alternative of a comb-assisted swept-laser DFG spectrometer.

Baumann, Esther; Giorgetta, Fabrizio R.; Swann, William C.; Zolot, Alex M.; Coddington, Ian; Newbury, Nathan R.

2011-09-01

57

Low-noise fiber-laser frequency combs (Invited)  

NASA Astrophysics Data System (ADS)

We discuss experimental and theoretical aspects of a low-noise fiber-laser frequency comb, including the experimental configuration and the major contributions to the frequency noise and linewidth of the individual comb modes. Intracavity noise sources acting on the mode-locked laser determine the free-running comb linewidth and include environmental changes, pump noise, and amplified spontaneous emission (ASE). Extracavity noise sources acting outside of the laser typically determine the signal-to-noise ratio on the comb lines and include environmental effects, shot noise, and noise generated during supercontinuum generation. Feedback strongly suppresses these intracavity noise contributions, yielding a system that operates with comb linewidths and timing jitter below the quantum limit set by the intracavity ASE. Finally, we discuss correlations in the residual noise across a phase-locked comb.

Newbury, Nathan R.; Swann, William C.

2007-08-01

58

Morphology of the cockerel's comb after androgen administration  

Microsoft Academic Search

1.?Androgen receptor (AR) expression and morphological changes in blood capillaries were investigated in the comb of cockerels, both untreated controls and after the administration of testosterone (T) or the androgen antagonist flutamide (F) for 7 weeks.2.?Twenty-six male Single Comb White Leghorn roosters were divided into T-treated, F-treated and untreated groups. Tissue sections were examined histologically, immunohistochemically, and comb blood vessel

K. Yoshioka; Y. Watahiki; A. Kanie; M. Tsujio; H. Ikadai; T. Kashimoto; K. Mutoh

2010-01-01

59

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

60

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

61

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

62

Superdiffusion of cancer on a comb structure  

NASA Astrophysics Data System (ADS)

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

Iomin, Alexander

2005-01-01

63

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

64

VLSI Implementation of Cascaded Integrator Comb Filters for DSP Applications  

Microsoft Academic Search

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

Rozita Teymourzadeh; Masuri Othman

65

Pressure-induced variation of effective dynamic charge in InP1-xAsx alloys due to charge transfer within cation sublattice  

NASA Astrophysics Data System (ADS)

From the measurements of Raman spectra of ternary InP1-xAsx (x=0.4, 0.6, and 0.8) under high pressure, the pressure-dependence of the ionicity was found to be strongly affected by the As mole fraction x. In particular, for x=0.6 and 0.8 ternary alloys, the effective dynamic charge of InP-like mode strictly increases with pressure, in sharp contrast to the corresponding behavior satisfied by the majority of III-V and II-VI binary compounds including InP. This can be understood by the charge transfer from As to P in the cation sublattice when the ternary alloys are under pressure.

Park, Ta-Ryeong; Byun, Jun Seok; Kim, Tae Jung; Kim, Young Dong

2012-12-01

66

Optical frequency comb generation from a monolithic microresonator.  

PubMed

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

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

2007-12-20

67

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

68

Entanglement of Atomic Qubits Using an Optical Frequency Comb.  

National Technical Information Service (NTIS)

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

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

2010-01-01

69

Optical combing to align photoreceptors in detached retinas  

NASA Astrophysics Data System (ADS)

In this paper, we presented a novel micro-manipulating method, called 'optical combing', that could improve the retina reattachment surgery results. Optical combing adopts the working principle of optical tweezers (i.e., focused Gaussian beam produces a trapping force when it incidents onto a micro-object. The trapping force can pull the micro-object to the central point of focused laser beam. Optical combing is implemented by scanning a focused laser beam on the misaligned micro objects (such as misaligned photoreceptors). In our preliminary experiment, a set of misaligned micro glass rods was re-aligned by applying this optical combing technology, which verified our theory. In the future, this technique will be used to re-align misaligned photoreceptors in real retina.

Yin, Shizhuo; Gardner, Thomas W.; Wu, Fei; Cholker, Milind S.

2004-07-01

70

CombFunc: predicting protein function using heterogeneous data sources  

PubMed Central

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

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

2012-01-01

71

Multicolor Detection of Combed DNA Molecules Using Quantum Dots  

NASA Astrophysics Data System (ADS)

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

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

72

How to Determine the Sex of Living Honeybee Larvas (Rozpoznawanie Plci Zywych Larw Pszczelich).  

National Technical Information Service (NTIS)

The present paper presents a method for the practical determination of the sex of the living specimens without the damage of larvas. The method should enable one to determine the sex of larvas without taking it out from the comb cell or rearing dish. The ...

J. Woyke

1972-01-01

73

Higher Precision In Radial Velocity Measurement By Laser Frequency Combs  

NASA Astrophysics Data System (ADS)

Spectroscopy is a crucial tool of the defining fields of 21st century astrophysics - cosmology and the search for extrasolar planets. Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines resulting from the motion of the host star around the barycenter of an exo-solar system, have recently achieved a precision of 60 cm s-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 5 cm s-1 is necessary. The current precision of the astrophysical spectrograph is limited by the lack of an adequate wavelength calibration source. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to improve the sensitivity. We report the fabrication and tests of a filtered laser comb with up to 40-GHz ( 1 Å ) line spacing, generated from a 1-GHz repetition-rate source, without compromise on long-term stability or reproducibility. This wide-line spacing comb, or "astro-comb", is well matched to the resolving power of high-resolution astrophysical spectrographs. The application of the astro-comb to astrophysics should allow a precision as high as 1 cm s-1 in astronomical radial velocity measurements In 2008, an astro-comb has been deployed at the Whipple Observatory to calibrate the TRES spectrograph, with >1,000 unltra-stable emission lines in the range of 8,000 - 9,000 Å. Preliminary data analysis indicates that the astro-comb is capable of improving the precision of the TRES. By enabling improved Doppler velocity-shift precision with broad wavelength coverage and reproducibility over many years and between telescopes, astro-combs should revolutionize astrophysical spectroscopy.

Li, Chih-Hao; Benedick, A.; Blake, C.; Cramer, C.; Chang, G.; Chen, L.; Fendel, P.; Furesz, G.; Glenday, A.; Irwin, J.; Kärtner, F.; Phillips, D.; Sasselov, D.; Szentgyorgyi, A.; Walsworth, R.

2009-12-01

74

A phase-stabilized carbon nanotube fiber laser frequency comb  

Microsoft Academic Search

A frequency comb generated by a 167 MHz repetition frequency erbium-doped fiber ring laser using a carbon nanotube saturable absorber is phase-stabilized for the first time. Measurements of the in-loop phase noise show an integrated phase error on the carrier envelope offset frequency of 0.35 radians. The carbon nanotube fiber laser comb is compared with a CW laser near 1533

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

2009-01-01

75

Observation by fluorescence microscopy of transcription on single combed DNA  

PubMed Central

Molecular combing is a powerful procedure for aligning a large array of DNA molecules onto a surface. This technique usually leads to an overstretching of about 150% of the molecules' contour length. By changing the magnitude of capillary forces during the combing process, we were able to reduce the relative extension of the DNA molecules. Thus we achieved combing of T7 DNA with an extension close to its molecule contour length. We checked the ability of combed DNA to interact with DNA binding proteins. Using the T7 bacteriophage transcription system, we investigated the transcription activity of RNA polymerase on combed DNA by direct visualization of newly synthesized fluorescent RNAs. Our experiments show that no transcription activity occurs on overstretched DNA molecules, whereas we observe a transcription activity for nonoverstretched molecules. This activity is observed both in multiple initiation experiments and for one immobilized T7 RNA polymerase per promoter. These results open possibilities for the study of single enzyme actions on combed DNA by optical methods.

Gueroui, Z.; Place, C.; Freyssingeas, E.; Berge, B.

2002-01-01

76

Dynamics of the modulational instability in microresonator frequency combs  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

77

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

PubMed

In this article we present the first analysis of parentage and relatedness in a natural vertebrate population, using Intersimple Sequence Repeat (ISSR) markers. Thus, 28 ISSR markers were used in a study of a sex-role reversed, simultaneously polyandrous shorebird from northeastern Australia, the comb-crested jacana (Irediparra gallinacea). Assessment of parentage was based on comparison of field observations, novel bands, individual-specific bands found in 7/9 males and 4/6 females, and a 99% CI exclusion criteria. Integrating results from these approaches resulted in confirmation of paternity in all 36 chicks. In only one case (2.8% of chicks) was a co-mate assigned paternity. Thus, comb-crested jacanas appear to be genetically monogamous. These results showed resemblance to sequentially polyandrous birds but differed from the simultaneously polyandrous wattled jacana ( Jacana jacana; Emlen et al. 1998). A significant relationship between relatedness and ISSR similarity resulted in recognition that 14/15 adults sampled may be related to at least one other adult by 0.25 or more. Lack of dispersal may be explained by physical limitations and adequate regional habitat. ISSRs proved to be simple and helpful in resolving these issues. PMID:12920101

Haig, S M; Mace, T R; Mullins, T D

78

Parentage and relatedness in polyandrous comb-crested jacanas using ISSRs  

USGS Publications Warehouse

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

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

2003-01-01

79

Roughness of organ pipe sound due to frequency comb.  

PubMed

In the sound spectrum of flue organ pipes in addition to the usual harmonic partials, sometimes a series of equidistant but not harmonic lines can be found. This phenomenon has been observed in the recorded sound of pipes from different pipe ranks. The second set of spectral lines is similar to "frequency combs" used in optics for accurate measurement of optical frequencies. Analysis of measured sound spectra with and without frequency comb and simulations are presented and discussed in the paper. The appearance of frequency combs in the sound spectrum is explained by a model that assumes the presence of a mouth tone in addition to the pipe sound. Mouth tone bursts are generated when the oscillating air jet passes the upper lip. The burst repetition frequency is locked to the fundamental frequency of the pipe and the bursts are coherent with a pulse-to-pulse phase shift. The phase shift explains the observed frequency offset of the frequency comb to the harmonic frequencies. The simulations also show that weak and fluctuating mouth tones cannot generate frequency comb due to a lack of coherence. PMID:22280697

Trommer, Thomas; Angster, Judit; Miklós, András

2012-01-01

80

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

Microsoft Academic Search

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

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

2009-01-01

81

Corps of Engineers Operations and Maintenance Budget Decision Support System - (COMB-DSS-D).  

National Technical Information Service (NTIS)

The COMB-DSS-D is an acronym for Corps Operation and Maintenance Budget Decision Support System - Division Version. The COMB-DSS prototype was originally developed as part of the Improvement of Operations and Management Techniques (IOMT) research program....

C. A. Strus R. M. Males

1994-01-01

82

Selective amplification of frequency comb modes via optical injection locking of a semiconductor laser: influence of adjacent unlocked comb modes  

NASA Astrophysics Data System (ADS)

Optical injection locking can be used to isolate and amplify individual comb modes from an optical frequency comb (OFC). However, it has been observed that for narrow spaced OFCs (e.g. 250 MHz), the adjacent comb modes are still present in the output of the locked laser. These residual modes experience some amplification relative to the injected signal, however the gain is significantly less than for the locked mode. We report the measurement of this sidemode amplification for a semiconductor laser injection locked to a 250 MHz spaced OFC. It was found that this amplification can be well suppressed by tuning the frequency difference between the free running laser and the OFC mode it was locked to. The sidemode amplification was then investigated numerically by solving the laser rate equations under optical injection. It was found that the main contribution to the sidemode amplification was due to phase modulation induced by the residual comb modes. The detuning dependent suppression occurs due to destructive interference between pairs of equidistant comb modes.

Wu, David S.; Richardson, David J.; Slavík, Radan

2013-05-01

83

Whispering Gallery Mode Oscillators and Optical Comb Generators  

NASA Astrophysics Data System (ADS)

We discuss an approach for generating optical combs using four-wave mixing process in a nonlinear whispering gallery mode resonator. We show that pumping the resonator with strong enough continuous wave coherent light results in appearance of optical sidebands around the optical carrier. The pumping threshold of the oscillation can be in a few microWatt range for resonators with an ultra-high quality factor. Natural cascading of the the nonlinear process leads to mode locking of the sidebands and emergence of an optical frequency comb. Demodulation of the comb by means of a fast photodiode produces a high frequency spectrally pure RF signal, the frequency of which is given by the resonator morphology.

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

2009-04-01

84

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

85

Quantum dot multiwavelength comb lasers with Si ring resonator  

NASA Astrophysics Data System (ADS)

The gain media of the quantum dot lasers consist of InAs QDs in an InGaAsP matrix on an InP substrate. The quantum dot lasers have different free spacing ranges (FSRs) corresponding to Fabry-Pérot (F-P) cavity lengths. A silicon ring resonator and a QD laser have been combined to form comb laser. The output characteristics of the combined comb laser were investigated. The measured FSR was about 2.8nm and the extinction ratio was about 10(dB) when the FSR of the QD laser was about 0.4nm and the FSR of the ring resonator was about 0.47nm. The experimental results show that the ring resonator had a strong control on the FSR and extinction ratio of the comb laser.

Li, W. Y.; Lu, Z. G.; Xu, D. X.; Liu, J. R.; Poole, P.; Barrios, P.; Poitras, D.; Ma, R.; Lapointe, J.; Vachon, M.; Janz, S.

2010-06-01

86

Honeybee combs: construction through a liquid equilibrium process?  

NASA Astrophysics Data System (ADS)

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

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

87

Broadband degenerate OPO for mid-infrared frequency comb generation.  

PubMed

We present a new technique suitable for generating broadband phase- and frequency-locked frequency combs in the mid-infrared. Our source is based on a degenerate optical parametric oscillator (OPO) which rigorously both down-converts and augments the spectrum of a pump frequency comb provided by a commercial mode-locked near-IR laser. Low intracavity dispersion, combined with extensive cross-mixing of comb components, results in extremely broad instantaneous mid-IR bandwidths. We achieve an output power of 60 mW and 20 dB bandwidth extending from 2500 to 3800 nm. Among other applications, such a source is well-suited for coherent Fourier-transform spectroscopy in the absorption-rich mid-IR 'molecular fingerprint' region. PMID:21451655

Leindecker, Nick; Marandi, Alireza; Byer, Robert L; Vodopyanov, Konstantin L

2011-03-28

88

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

Microsoft Academic Search

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

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

2011-01-01

89

Safe sex  

MedlinePLUS

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

90

Coherent Multiheterodyne Spectroscopy Using Stabilized Optical Frequency Combs  

NASA Astrophysics Data System (ADS)

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

Coddington, Ian; Swann, William C.; Newbury, Nathan R.

2008-01-01

91

80 W, 120 fs Yb-fiber frequency comb.  

PubMed

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

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

2010-09-15

92

10-GHz Self-Referenced Optical Frequency Comb  

NASA Astrophysics Data System (ADS)

The femtosecond laser-based frequency comb has played a key role in high-precision optical frequency metrology for a decade. Although often referred to as a precise optical frequency ruler, its tick marks are in fact too densely spaced for direct observation and individual use, limiting important applications in spectroscopy, astronomy, and ultrafast electromagnetic waveform control. We report on a femtosecond laser frequency comb with a 10-gigahertz repetition rate that creates a stabilized output spectrum with coverage from 470 to 1130 nanometers. The individual modes can be directly resolved with a grating spectrometer and are visible by eye.

Bartels, Albrecht; Heinecke, Dirk; Diddams, Scott A.

2009-10-01

93

Automatic Transcription Method for Polyphonic Music Based on Adaptive Comb Filter and Neural Network  

Microsoft Academic Search

This paper presents a method to transcribe polyphonic music based on adaptive comb filter and neural network. In the method, the input audio is firstly divided into snapshots by a BP neural network, and then comb filters of different notes are used to calculate features. Comb filter can be adjusted to take inharmonicity and note pitch error into consideration. Note

Zheng Guibin; Liu Sheng

2007-01-01

94

Pitch estimation of polyphony based on controlling delays of comb filters for transcription  

Microsoft Academic Search

A new pitch estimation method for polyphony based on controlling the delays of comb filters is presented. This method takes the iterative process that extracts a period candidate from the output signal of cascaded comb filters and controls the delay of the comb filter with the extracted period candidate, until the same repetition of a set of extracted candidates is

Michiru Yamaguchi; Yoshiaki Tadokoro

2004-01-01

95

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

Microsoft Academic Search

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

Thomas D. Seeley

2002-01-01

96

Design and modeling for comb drive actuator with enlarged static displacement  

Microsoft Academic Search

New comb drives using high stiffness ratio springs are designed and modeled to provide capabilities of large static displacement and continuous motion for applications, such as micro XY stage, two dimensional lens scanner, variable optical attenuator, and optical switch, etc. The maximum static displacement of conventional comb drive is constrained by the side sticking effect of comb finger electrodes. Since

Chihchung Chen; Chengkuo Lee

2004-01-01

97

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

98

Spectrum and dynamics of optical frequency combs generated with monolithic whispering gallery mode resonators.  

PubMed

Optical frequency comb generation in whispering gallery mode resonators has been demonstrated in several experiments. The spectra of the combs exhibit a wide variety of complex profiles that are not fully understood. We report a detailed study on frequency comb generation in whispering gallery mode resonators including a complete stability analysis and numerical simulations. We show that the interaction of dispersion and nonlinearity is the key in determining the stability of the comb, the complex characteristics of its spectral profile, and its frequency span. The results will be important for understanding the essential physical processes leading to efficient comb generation. PMID:20366426

Chembo, Yanne K; Strekalov, Dmitry V; Yu, Nan

2010-03-11

99

Spectrum and Dynamics of Optical Frequency Combs Generated with Monolithic Whispering Gallery Mode Resonators  

NASA Astrophysics Data System (ADS)

Optical frequency comb generation in whispering gallery mode resonators has been demonstrated in several experiments. The spectra of the combs exhibit a wide variety of complex profiles that are not fully understood. We report a detailed study on frequency comb generation in whispering gallery mode resonators including a complete stability analysis and numerical simulations. We show that the interaction of dispersion and nonlinearity is the key in determining the stability of the comb, the complex characteristics of its spectral profile, and its frequency span. The results will be important for understanding the essential physical processes leading to efficient comb generation.

Chembo, Yanne K.; Strekalov, Dmitry V.; Yu, Nan

2010-03-01

100

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

101

Femtosecond laser frequency comb for precision astrophysical spectroscopy  

NASA Astrophysics Data System (ADS)

Spectroscopy is a crucial tool for cosmology and the search for extrasolar planets. Broadband frequency combs have revolutionized precision spectroscopy in the laboratory with absolute frequencies determined to better than one part in 10^15. Good long-term stability and reproducibility are also major advantages of the frequency comb. However, their application to any astrophysical spectrograph requires increasing the comb-line spacing by at least 10-fold from today's high repetition rate sources operating at about 1 GHz. We report measurements of a 39-GHz comb generated from a 1-GHz source using the TRES spectrograph at the Fred Lawrence Whipple Observatory. Repeated measurements show that we can reach the expected stability limit of the spectrograph. The application of this novel technique to astrophysics should allow more than a 10-fold improvement in Doppler-shift sensitivity, with significant impact to many fields, including the search for extrasolar Earths, the direct measurement of the universe expansion and the detection of the temporal variation of physical constants.

Glenday, Alex; Cramer, Claire; Benedick, Andrew; Li, Chih-Hao; Kaertner, Franz X.; Phillips, David F.; Szentgyorgi, Andrew; Walsworth, Ronald L.

2009-05-01

102

Tunable Laser Spectroscopy Referenced with Dual Frequency Combs  

NASA Astrophysics Data System (ADS)

Frequency combs provide broadband spectroscopic measurements with high frequency accuracy and precision. However, because the comb power is distributed over a broad spectrum, the sensitivity can be low unless some form of multiplexed detection or cavity enhancement is used. In contrast, tunable laser spectroscopy can achieve much higher sensitivities because the full laser power is within the measured frequency window, but the frequency accuracy and precision of a rapidly tuned laser is challenging to characterize and control. We propose to combine the advantages of these two forms of spectroscopy by performing tunable cw laser spectroscopy in conjunction with a dual frequency comb setup. The cw laser would provide broadband high SNR measurements of a sample's transmission spectrum on a single detector, while dual frequency combs would provide absolute instantaneous frequency measurements of the cw laser. Preliminary measurements characterizing a tunable laser have demonstrated Kilohertz frequency accuracy and resolution with a measurement time of a few milliseconds over a 25 nm band around 1550 nm.

Giorgetta, F. R.; Coddington, I.; Baumann, E.; Swann, W. C.; Newbury, N. R.

2010-06-01

103

Frequency combs and precision spectroscopy in the extreme ultraviolet  

NASA Astrophysics Data System (ADS)

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

Cingöz, Arman

2012-06-01

104

Noise reduction of a carbon nanotube fiber laser frequency comb  

Microsoft Academic Search

We report the reduction of noise in a carbon nanotube fiber laser frequency comb using pump attenuation and phase-lead compensation. The measured f0 linewidth was decreased by a factor of four. ©2011 Optical Society of America OCIS codes: (120.3930) Metrological instrumentation; (140.3510) Lasers, fiber; (320.7090) Ultrafast lasers

Jinkang Lim; Brian R. Washburn

2011-01-01

105

Bonding technologies for silicon scanning mirror having vertical comb fingers  

NASA Astrophysics Data System (ADS)

A 1500 micrometers X 1200 micrometers silicon scanning mirror for laser display has been fabricated. This scanning mirror is mainly composed of two structures having vertical comb fingers. By anodic bonding of the silicon wafer and the Pyrex glass substrate, and followed deep ICPRIE (Inductively Coupled Plasma Reactive Ion Etching), isolated comb electrodes were fabricated at the lower structure. But in this anodic bonding, gold signal lines for electrical connection to the electrodes, which were inserted between silicon and Pyrex glass, were cut off by mechanical pressure or damaged to agglomerate by diffusion. To remove these phenomena, Pyrex glass was trenched about 2000 Angstroms in depth in the shape of signal lines, and Cr/Au signal lines were formed along the etched grooves about 500 Angstroms/3500 Angstroms in depth, and then annealed at 400 degree(s)C, N2 atmosphere, for 1 hour before anodic bonding. As a result, gold signal lines were successfully fabricated and the contact resistance was acquired below several tens ohms. By flip chip bonding, the upper and lower structure having vertical comb fingers were assembled. Vertical comb fingers of two structures were aligned with a microscope and the frames of two structures were bonded at 300 degree(s)C for 20 sec. using the eutectic bonding material, electroplated AuSn. Using these bonding technologies, the scanning mirror was successfully fabricated and it could be used for laser display as a galvanometric vertical scanner.

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

2001-11-01

106

Bonding of silicon scanning mirror having vertical comb fingers  

NASA Astrophysics Data System (ADS)

A 1500 ?m × 1200 ?m silicon scanning mirror has been fabricated by using anodic bonding and flip chip bonding. This scanning mirror is mainly composed of two structures having vertical comb fingers. By anodic bonding between the silicon wafer and the Pyrex glass substrate, and following deep inductively coupled plasma reactive ion etching (ICPRIE), isolated comb electrodes were fabricated at the lower structure. However, gold signal lines for electrical connection to the electrodes, which were inserted between silicon and Pyrex glass, were damaged during anodic bonding. This problem was solved by using the proposed processes and signal lines were successfully fabricated with the contact resistance below several tens of ohms. By flip chip bonding, the upper and lower structures having vertical comb fingers were assembled. Vertical comb fingers of two structures were aligned with a microscope and the frames of two structures were bonded at 300 °C for 20 s using the eutectic bonding material - electroplated AuSn. Finally, the scanning mirror was successfully fabricated and could be used for laser display as a galvanometric vertical scanner.

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

2002-09-01

107

A comb filter on the acoustooptical delay line  

NASA Astrophysics Data System (ADS)

Expressions relating the main parameters of an acoustooptical delay line (ADL) and minimizing its dimensions are obtained. The experimental results are in good agreement with the theoretical ones and corroborate the possibility of comb filters design on the basis of ADL with electronic frequency change. This filters can be used in selection of periodic signals from noise.

Buchenskij, A. F.; Lonskij, A. P.; Morozov, S. V.; Yakovlev, V. I.

1994-03-01

108

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

2012-12-02

109

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

PubMed

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

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

2012-12-31

110

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

111

Precision mid-infrared frequency combs and spectroscopic applications  

NASA Astrophysics Data System (ADS)

The combination of frequency combs and quantum cascade lasers is opening new opportunities in the field of precision spectroscopy in the mid-infrared. Frequency combs allow quantum cascade lasers to be referenced to a highly repeatable, precise and absolute frequency axis. Repeatability is a key feature to obtain high quality measurements of absorption profiles and thus accurate determination of spectroscopic parameters, while absolute frequency calibration makes it possible the comparison of spectroscopic data acquired in different laboratories and at different times, as well as comparison with theoretical predictions or existing databases. This work reviews some of the main results achieved at 4.3 ?m by investigation of a manifold of rovibrational lines of CO2. Spectroscopic parameters such as line-centre frequencies, line intensity factors, pressure shift and pressure broadening coefficients are retrieved with an unprecedented quality from the metrological point of view.

Gatti, D.; Castrillo, A.; Gambetta, A.; Sala, T.; Galzerano, G.; Laporta, P.; Gianfrani, L.; Marangoni, M.

2013-03-01

112

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

113

The Efficient Design and Modification of Cascaded Integrator Comb Filter  

Microsoft Academic Search

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

Peng Hong; Zhang Yuhua

2010-01-01

114

Synthesis of complex architectures of comb block copolymers  

Microsoft Academic Search

The synthesis of comb block copolymers by ring opening metathesis polymerization (ROMP), ring opening polymerization (ROP), and atom transfer radical polymerization (ATRP) is described. Block copolymers were synthesized by the ROMP of oxanorbornene and norbornene monomers followed by hydrogenation of the olefins along the backbone. One block of these diblock copolymers possessed initiators either for the ROP of (3S)-cis-3,6-dimethyl-1,4-dioxane-2,5-dione or

Jun Yoo; M. Brett Runge; Ned B. Bowden

2011-01-01

115

Intraspecific comb usurpation in the social wasp Polistes fuscatus  

Microsoft Academic Search

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

J. Klahn

1988-01-01

116

Coherent Raman spectro-imaging with laser frequency combs.  

PubMed

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

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

2013-10-17

117

Coherent Raman spectro-imaging with laser frequency combs  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

118

Nanodiamond lateral comb array field emission diode for high current applications  

Microsoft Academic Search

Nanodiamond comb-shaped lateral field emitter arrays in diode configuration were fabricated and characterized for high current field emission. Nitrogen-incorporated nanocrystalline diamond with grain size of 5–10 nm was micropatterned using RIE to realize interconnected arrays of comb structures equipped with uniformly spaced high aspect ratio lateral emitter fingers. A 9000-fingered nanodiamond lateral comb array diode with an inter-electrode spacing of 8 ?m

K. Subramanian; W. P. Kang; J. L. Davidson; B. K. Choi; M. Howell

2006-01-01

119

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

Microsoft Academic Search

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

Tim Hentschel; Gerhard Fettweis

1999-01-01

120

Submicrometer Comb-Drive Actuators Fabricated on Thin Single Crystalline Silicon Layer  

Microsoft Academic Search

Electrostatic comb-drive microactuators were fabricated by electron beam lithography on a 260-nm-thick silicon layer of a silicon-on-insulator wafer. The actuators consisted of comb electrodes, springs, and a frame. Two kinds of microactuators with doubly clamped and double-folded springs were designed and fabricated. The comb electrode was as small as 2.5 mum wide and 8 mum long and was composed of

Kazunori Takahashi; Erdal Bulgan; Yoshiaki Kanamori; Kazuhiro Hane

2009-01-01

121

Modeling of optical frequency comb generation in whispering gallery mode resonators and limiting effects  

NASA Astrophysics Data System (ADS)

We report a detailed study about the various physical mechanisms that may limit the spectral span of optical frequency combs generated with whispering gallery mode resonators. We developed a modal expansion model able to track the individual dynamics of the various modes, and identify the key parameters determining the comb spectral features. We show that, although the walk-off between the dispersive WGM eigenfrequency distribution and the ideal equidistant comb is the main limiting factor, other phenomena such as modal confinement, material absorption, and modal overlap may also play an important role in extending the comb span.

Chembo, Yanne K.; Yu, Nan

2010-02-01

122

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

123

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

124

Precision measurements and applications of femtosecond frequency combs  

NASA Astrophysics Data System (ADS)

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

Jones, R. Jason

2002-05-01

125

Entanglement of Atomic Qubits Using an Optical Frequency Comb  

SciTech Connect

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

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

2010-04-09

126

Entanglement of atomic qubits using an optical frequency comb.  

PubMed

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

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

2010-04-05

127

Flow-through comb electroporation device for delivery of macromolecules.  

PubMed

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

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

2013-01-14

128

Sex Stereotyping.  

ERIC Educational Resources Information Center

|This article uses findings from several previous studies to define the kinds of sex stereotyping present in our society. The author considers sex roles as dealt with in children's literature, public schools, advertising, and vocational counseling. He describes, in particular, the situation at an unnamed state university, and cites the woman's…

Rivas, Richard G.

129

Sex Offenders.  

ERIC Educational Resources Information Center

This paper on the problem of sex offending among individuals with intellectual disabilities examines the incidence of this problem, characteristics of intellectually disabled sex offenders, determination of whether the behavior is a paraphilia or functional age-related behavior, and treatment options, with emphasis on the situation in New South…

Hayes, Susan

1991-01-01

130

Sex Therapy  

ERIC Educational Resources Information Center

|Notes that no single theory of psychotherapy dominates the field of sex therapy. On one hand, sex therapy is not subject to the rigid dogmas of many areas of psychotherapy. But on the other hand, many techniques are invented at the whim of clinicians with no basis in theory. (Author/AM)|

Hogan, Douglas

1977-01-01

131

Sex Selection  

Microsoft Academic Search

People have always attempted to influence the sex of their children. Until recently, prenatal screening followed by abortion of the undesired fetus was the only effective method, and most people who used that method did it to avoid the birth of girls. Today, preconception sex selection is becoming available, and people in the West are more likely to want to

Dena S Davis

2003-01-01

132

Temporal dynamics of Kerr frequency combs in whispering-gallery mode resonators  

NASA Astrophysics Data System (ADS)

Based on a modal description of the evolution of the mode's amplitude in a whispering-gallery mode resonator, we numerically study the generation of Kerr combs. We show that a stable primary comb appear for pump power slightly above threshold, enabling potential applications in metrology. For high input power however, chaotic signals are observed.

Coillet, Aurélien; Balakireva, Irina; Henriet, Rémi; Larger, Laurent; Chembo, Yanne

2013-02-01

133

Comb-like supercontinuum generated by dual-pulse filamentation in air  

NASA Astrophysics Data System (ADS)

Comb-like supercontinuum generation is investigated with dual-pulse filamentation in air. The period of spectral fringes varies with the time delay between collinearly propagating pulses. The comb-like supercontinuum may be a potential tool for optical remote sensing.

Zhang, Zong-xin; Li, Yan-yan; Lu, Xiao-ming; Xu, Yi; Liu, Peng; Leng, Yu-xin; Li, Ru-xin

2013-09-01

134

Narrow-band hairpin-comb filters for HTS and other applications  

Microsoft Academic Search

The folded half-wavelength resonators in hairpin-comb filters all have the same orientation whereas the orientations of the resonators in conventional hairpin filters alternates. Hairpin-comb filters have attractive properties for design of compact, narrow-band filters such as are often desired for high-temperature-superconductivity and other applications

G. L. Matthaei; N. O. Fenzi; R. Forse; S. Rohlfing

1996-01-01

135

HAZIR VE ESKPETEKLERN BAKTERYOLOJK VE MKOLOJK YÖNDENNCELENMES ? Isolation of Bacteria and Fungi from Combs and Foundations  

Microsoft Academic Search

The goal of this study was to isolate bacteria and fungi sp. from 24 combs taken from different apiar ies, and 11 commercial foundations and their effects on honeybee and human health in Bursa-Yalova provinces. Washing solutions, taken from suspected comb cells and commercial foundations for AFB, EFB causative agents Paenibacillus alvei and Melissococcus pluton and other agents, were incubated.

Cüneyt ÖZAKIN; Levent AYDIN

136

Damping effects of capacitive comb fingers on biomimetic MEMS directional microphone  

Microsoft Academic Search

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

John Roth; Michael Touse; Jose Sinibaldi; Gamani Karunasiri

2011-01-01

137

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

PubMed

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

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

2001-09-01

138

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

Microsoft Academic Search

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

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

2008-01-01

139

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

Microsoft Academic Search

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

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

2001-01-01

140

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

Microsoft Academic Search

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

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

1996-01-01

141

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

142

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

PubMed Central

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

Wu, Judy Y.; Anelli, Carol M.; Sheppard, Walter S.

2011-01-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

144

A Variable Pitch Comb Fixture for Rayleigh Wave Generation and Reception  

SciTech Connect

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

Barnard, Daniel J. [Materials and Engineering Physics Program, Ames Laboratory, USDOE Ames, IA 50011 (United States)

2007-03-21

145

Fabrication of high-aspect-ratio polymer-based electrostatic comb drives using the hot embossing technique  

Microsoft Academic Search

We report on the formation of a lateral comb drive on poly-methyl-meth-acrylate (PMMA) using the hot embossing technique. A hot embossing mold insert is fabricated on a silicon wafer by means of lithography and inductive coupled plasma dry etching. The comb drive microstructure is hot embossed under a molding force of 35000 N at 130 °C. We demonstrate the comb

Yongjun Zhao; Tianhong Cui

2003-01-01

146

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

Federal Register 2010, 2011, 2012, 2013

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

2010-03-11

147

Comparative reproduction of Varroa destructor in different types of Russian and Italian honey bee combs.  

PubMed

Earlier studies showed that Russian honey bees support slow growth of varroa mite population. We studied whether or not comb type influenced varroa reproduction in both Russian and Italian honey bees, and whether Russian bees produced comb which inhibited varroa reproduction. The major differences found in this study concerned honey bee type. Overall, the Russian honey bees had lower (2.44 +/- 0.18%) levels of varroa infestation than Italian honey bees (7.20 +/- 0.60%). This decreased infestation resulted in part from a reduced number of viable female offspring per foundress in the Russian (0.85 +/- 0.04 female) compared to the Italian (1.23 +/- 0.04 females) honey bee colonies. In addition, there was an effect by the comb built by the Russian honey bee colonies that reduced varroa reproduction. When comparing combs having Russian or Italian colony origins, Russian honey bee colonies had more non-reproducing foundress mites and fewer viable female offspring in Russian honey bee comb. This difference did not occur in Italian colonies. The age of comb in this study had mixed effects. Older comb produced similar responses for six of the seven varroa infestation parameters measured. In colonies of Italian honey bees, the older comb (2001 dark) had fewer (1.13 +/- 0.07 females) viable female offspring per foundress than were found in the 2002 new (1.21 +/- 0.06 females) and 1980s new (1.36 +/- 0.08 females) combs. This difference did not occur with Russian honey bee colonies where the number of viable female offspring was low in all three types of combs. This study suggests that honey bee type largely influences growth of varroa mite population in a colony. PMID:18392942

de Guzman, Lilia I; Rinderer, Thomas E; Frake, Amanda M

2008-04-08

148

Quantum Information Processing with Atomic Qubits and Optical Frequency Combs  

NASA Astrophysics Data System (ADS)

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

Campbell, Wesley

2010-03-01

149

Laser frequency comb for improved exoplanet detection and cosmology  

NASA Astrophysics Data System (ADS)

Searches for extrasolar planets using the periodic Doppler shift of stellar lines are approaching Earth-like planet sensitivity. To find a 1-Earth-mass planet in an Earth-like orbit, an order of magnitude improvement in state-of-the-art radial velocity spectroscopy is necessary. An approach that combines a laser frequency comb with a Fabry-Perot cavity has been suggested as a promising avenue to improved wavelength calibration. Here we report the fabrication of such a laser comb with up to 40 GHz ( 1 å) line-spacing, without compromise of long-term stability, reproducibility or spectral resolution and that is well matched to the resolving power of high-resolution astrophysical spectrographs. The instrument will be deployed on the MMT in May 2008 to calibrate the Hectochelle spectrograph in a demonstration project to search for dark matter in globular clusters and in 2009/10 at the HARPS clone spectrograph on the William Herschel telescope to search for exoplanets.

Li, Chih-Hao; Benedick, Andrew J.; Fendel, Peter; Glenday, Alex; Kaertner, Franz X.; Phillips, David F.; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L.

2008-05-01

150

Geotropism of hornet comb construction under persistent acceleration.  

PubMed

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

Ishay, J; Sadeh, D

1978-01-01

151

Safe sex  

NSDL National Science Digital Library

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

Olivia Worland (Purdue University;Biological Sciences)

2008-07-09

152

A Fine-Tooth Comb to Measure the Accelerating Universe  

NASA Astrophysics Data System (ADS)

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

2008-09-01

153

The Development and Implementation of Chirped-Pulse Frequency Combs at Millimeter Wavelengths  

NASA Astrophysics Data System (ADS)

Technological advances in such areas as active multiplier chains and high-speed digital electronics are enabling the development of sensitive high-throughput spectroscopic instruments in the millimeter and submillimeter ranges. Recently there has been an effort to develop multiplexed direct absorption spectroscopy techniques that use frequency comb sources derived from phase-locked pulse trains (often created using ultrafast lasers). We have used a high-speed arbitrary waveform generator (AWG with 12 GHz sample rate) to create frequency combs at mm-wave wavelengths using a chirped pulse as the repeating waveform. This waveform has important advantages including 100% duty cycle for the light output and compatibility with the use of frequency multiplier chains that extend the bandwidth of the comb proportional to the frequency multiplication factor. A new spectrometer operating in the 260-290 GHz range using active multiplier chains has been constructed to test the capabilities of chirped-pulse frequency comb spectroscopy for molecular rotational spectroscopy. The spectral properties of the mm-wave combs generated following x24 frequency multiplication, methods for compressed bandwidth detection using a dual-comb approach, and frequency comb analogs of FM spectroscopy will be presented.

Steber, Amanda L.; Harris, Brent J.; Neill, Justin L.; Lehmann, Kevin K.; Pate, Brooks H.

2012-06-01

154

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

NASA Astrophysics Data System (ADS)

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

Chembo, Yanne K.; Menyuk, Curtis R.

2013-05-01

155

Manipulation of the generation dynamics of a microresonator-based frequency comb via selective mode filtering  

NASA Astrophysics Data System (ADS)

We suggest a scheme to manipulate the generation dynamics of high-Q microresonator-based frequency combs (microcombs). Our simulation demonstrates that a certain subfamily of comb teeth can be suppressed via selectively filtering out limited modes, from which high-quality mode-locked pulses can be generated. Mode-pulling in microcomb generation is also analyzed quantitatively to explain the results. These results can help us better understand microcomb generation dynamics and will be beneficial in controlling the generated comb line number and spacing.

Bao, Chengying; Xiao, Xiaosheng; Yang, Changxi

2013-05-01

156

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

PubMed

We theoretically and experimentally investigate the chaotic regime of optical frequency combs generated in nonlinear ring microresonators pumped with continuous wave light. We show that the chaotic regime reveals itself by a flat top symmetric envelope of the frequency spectrum, when observed by means of an optical spectrum analyzer. The comb, demodulated on a fast photodiode, produces a noisy radio frequency signal with spectral width significantly exceeding the linear bandwidth of the microresonator mode. We discuss practical ways of excitation of a coherent frequency comb and avoiding the chaotic regime. PMID:23455124

Matsko, A B; Liang, W; Savchenkov, A A; Maleki, L

2013-02-15

157

Multimode quantum memory based on atomic frequency combs  

SciTech Connect

An efficient multimode quantum memory is a crucial resource for long-distance quantum communication based on quantum repeaters. We propose a quantum memory based on spectral shaping of an inhomogeneously broadened optical transition into an atomic frequency comb (AFC). The spectral width of the AFC allows efficient storage of multiple temporal modes without the need to increase the absorption depth of the storage material, in contrast to previously known quantum memories. Efficient readout is possible thanks to rephasing of the atomic dipoles due to the AFC structure. Long-time storage and on-demand readout is achieved by use of spin states in a lambda-type configuration. We show that an AFC quantum memory realized in solids doped with rare-earth-metal ions could store hundreds of modes or more with close to unit efficiency, for material parameters achievable today.

Afzelius, Mikael; Simon, Christoph; Riedmatten, Hugues de; Gisin, Nicolas [Group of Applied Physics, University of Geneva, CH-1211 Geneva 4 (Switzerland)

2009-05-15

158

THz photomixing synthesizer based on a fiber frequency comb.  

PubMed

A frequency doubled erbium doped modelocked fiber frequency comb is used to implement a THz photomixing synthesizer. The useful THz linewidth is in order of 150 kHz and has been assessed along with the frequency accuracy by spectroscopic measurements demonstrating a relative accuracy of 10(-8) at frequencies around 1 THz. The THz synthesizer is used to implement a THz spectrometer to study the rotational absorption spectrum of carbonyl sulfide (OCS). Measurement of the principal transitions between 813 GHz and 1283 GHz allowed the properties of the THz spectrometer to be compared with competing techniques, and demonstrates the potential of the THz photomixing synthesizer as an alternative means to explore the THz domain. PMID:19997448

Mouret, Gaël; Hindle, Francis; Cuisset, Arnaud; Yang, Chun; Bocquet, Robin; Lours, Michel; Rovera, Daniele

2009-11-23

159

A novel, multichannel, comb-frequency Doppler backscatter system  

SciTech Connect

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

Peebles, W. A.; Rhodes, T. L.; Hillesheim, J. C.; Zeng, L.; Wannberg, C. [University of California, Los Angeles, California 90095 (United States)

2010-10-15

160

Dual-etalon frequency-comb cavity ringdown spectrometer  

NASA Astrophysics Data System (ADS)

We have demonstrated a spectroscopic technique for simultaneously obtaining broad spectral bandwidth and high frequency resolution absorption measurements, with 5 ?s temporal resolution, continuously for tens of microseconds in an apparatus with no active stabilization. The technique utilizes two passive air-gap etalons to imprint two frequency comb patterns onto a single pulsed light source. The air-gap etalons also serve as cavity ringdown cells increasing the sensitivity of the absorption spectroscopy by increasing the interrogation path length. Here, we demonstrate the operation of the spectrometer utilizing a ~0.15 cm-1 bandwidth pulsed dye laser and two nearly identical 300 MHz free-spectral range confocal air-gap etalons each with a finesse of ~1 × 105, to investigate the (1,1,3) overtone of water and the R(7) transition of the O2 b1?g+<--X3?g- (2,0) band with high spectral resolution.

Chandler, David W.; Strecker, Kevin E.

2012-04-01

161

Multimode quantum memory based on atomic frequency combs  

NASA Astrophysics Data System (ADS)

An efficient multimode quantum memory is a crucial resource for long-distance quantum communication based on quantum repeaters. We propose a quantum memory based on spectral shaping of an inhomogeneously broadened optical transition into an atomic frequency comb (AFC). The spectral width of the AFC allows efficient storage of multiple temporal modes without the need to increase the absorption depth of the storage material, in contrast to previously known quantum memories. Efficient readout is possible thanks to rephasing of the atomic dipoles due to the AFC structure. Long-time storage and on-demand readout is achieved by use of spin states in a lambda-type configuration. We show that an AFC quantum memory realized in solids doped with rare-earth-metal ions could store hundreds of modes or more with close to unit efficiency, for material parameters achievable today.

Afzelius, Mikael; Simon, Christoph; de Riedmatten, Hugues; Gisin, Nicolas

2009-05-01

162

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

163

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

NASA Astrophysics Data System (ADS)

An interatomic potential for zirconium is developed within the charge-optimized many-body (COMB) formalism. The potential correctly predicts the hexagonal close-packed (HCP) structure as the ground state with cohesive energy, lattice parameters, and elastic constants matching experiment well. The most stable interstitial position is the basal octahedral followed by basal split, in agreement with recent first principles calculations. Stacking fault energies within the prism and basal planes satisfactorily match first principles calculations. A tensile test using nanocrystalline zirconium exhibits both prismatic {101¯0}<112¯0> slip and pyramidal {112¯2}<112¯3¯> slip, showing the model is capable of reproducing the mechanical deformation modes observed in experiments.

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

2013-10-01

164

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

PubMed

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

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

2013-06-04

165

Response dynamics of the frequency comb output from a femtosecond fiber laser  

NASA Astrophysics Data System (ADS)

The frequency comb from a mode-locked fiber laser can be stabilized through feedback to the pump power. An understanding of the mechanisms and bandwidth governing this feedback is of practical importance for frequency comb design and of basic interest since it provides insight into the rich nonlinear laser dynamics. We compare experimental measurements of the response of a fiber-laser frequency comb to theory. The laser response to a pump-power change follows that of a simple low-pass filter with a time constant set by the gain relaxation time and the system-dependent nonlinear loss. Five different effects contribute to the magnitude of the response of the frequency comb spacing and offset frequency but the dominant effects are from the resonant contribution to the group velocity and intensity-dependent spectral shifts. The origins of the intensity-dependent spectral shifts are explained in terms of the laser parameters

Washburn, B. R.; Swann, W. C.; Newbury, N. R.

2005-12-01

166

Spectroscopy with a coherent dual frequency comb interferometer at 3.4 ?m  

NASA Astrophysics Data System (ADS)

A coherent dual fiber-comb spectrometer centered at 1.5 ?m wavelengths is transferred to 3.4 ?m by differencefrequency generation with a 1064 nm cw laser. It is shown that the residual linewidth between the comb teeth at 3.4 ?m is resolution-limited to 200 mHz; such narrow linewidths can enable coherent dual-comb spectroscopy at high-precision and signal-to-noise ratio. We then discuss different interferometric configurations for coherent dual-comb spectroscopy. We find that a two-branch interferometric setup is appropriate to measure both the magnitude and phase spectrum of purely Doppler-broadened absorption lines. An initial measurement of methane lines in the ?3 band P-branch with a resolution of 114 MHz is demonstrated.

Baumann, Esther; Giorgetta, Fabrizio R.; Coddington, Ian; Swann, William C.; Newbury, Nathan R.

2010-08-01

167

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

168

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

Microsoft Academic Search

We have studied the behavior of polyelectrolyte-based comb polymers in dilute solution and on the rheological property evolution of concentrated Portland cement suspensions. These species consisted of charge-neutral, poly(ethylene oxide) (PEO) \\

Glen Harold Kirby

2003-01-01

169

Native Chemical Ligation at Asx-Cys, Glx-Cys: Chemical Synthesis and High-Resolution X-ray Structure of ShK Toxin by Racemic Protein Crystallography.  

PubMed

We have re-examined the utility of native chemical ligation at -Gln/Glu-Cys- [Glx-Cys] and -Asn/Asp-Cys- [Asx-Cys] sites. Using the improved thioaryl catalyst 4-mercaptophenylacetic acid (MPAA), native chemical ligation could be performed at -Gln-Cys- and Asn-Cys- sites without side reactions. After optimization, ligation at a -Glu-Cys- site could also be used as a ligation site, with minimal levels of byproduct formation. However, -Asp-Cys- is not appropriate for use as a site for native chemical ligation because of formation of significant amounts of ?-linked byproduct. The feasibility of native chemical ligation at -Gln-Cys- enabled a convergent total chemical synthesis of the enantiomeric forms of the ShK toxin protein molecule. The d-ShK protein molecule was ?50,000-fold less active in blocking the Kv1.3 channel than the l-ShK protein molecule. Racemic protein crystallography was used to obtain high-resolution X-ray diffraction data for ShK toxin. The structure was solved by direct methods and showed significant differences from the previously reported NMR structures in some regions of the ShK protein molecule. PMID:23919482

Dang, Bobo; Kubota, Tomoya; Mandal, Kalyaneswar; Bezanilla, Francisco; Kent, Stephen B H

2013-08-06

170

Safe sex?  

PubMed

The author has a Master of Arts degree in religion from the International School of Theology and he has lectured to thousands of students and professors at universities on six continents. He argues that condom use does not guarantee 100% protection against the transmission of HIV and that the only truly safe sex occurs in a faithful mutually monogamous relationship between two HIV-seronegative individuals. It is the author's belief that young people should wait until marriage before having sexual intercourse. It is known that condoms can slip, break, and leak during in vivo use. Condoms have a 15% failure rate in protecting against unplanned pregnancy. A sperm cell, however, is much larger than the human immunodeficiency virus. This failure rate therefore indicates that if sperm cells can penetrate/bypass the condom when having sex, the far smaller HIV can most certainly do the same thing. HIV can easily pass through many of the tiny pores in latex condoms. The author further argues that while premarital sex is physically risky, one can also be hurt emotionally and relationally. Sex can breed insecurity and generate performance fears which impede sexual response. Waiting until marriage helps both partners to have the confidence, security, trust, and self-respect which a solid, intimate relationship needs. In closing, the author acknowledges the physical and emotional difficulty of delaying the initiation of sexual intercourse. PMID:7600801

Wright, R

1995-05-01

171

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

Microsoft Academic Search

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

Donald K. Grayson; Françoise Delpech

2008-01-01

172

Possibility of comb-type rf shield structure for high-current accelerators  

Microsoft Academic Search

A novel rf shield structure for bellows chambers or gate valves in high-current accelerators is proposed. The rf shield has no thin fingers, but nested comb teeth instead at the inner surface of the beam duct. The comb-type rf shield has a higher thermal strength structurally than the conventional finger-type one. A simulation also indicates its lower impedance. Especially, the

Y. Suetsugu; M. Shirai; K. Shibata

2003-01-01

173

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

Microsoft Academic Search

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

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

2010-01-01

174

PAA\\/PEO comb polymer effects on rheological properties and interparticle forces in aqueous silica suspensions  

Microsoft Academic Search

The effects of a poly(acrylic acid) (PAA)–poly(ethylene) (PEO) comb polymer dispersant on the rheological properties and interparticle forces in aqueous silica suspensions have been studied under varying pH conditions. The comb polymer was found to adsorb more strongly under acidic than basic conditions, indicating that the PAA backbone of the copolymer preferentially adsorbs onto silica surfaces with the PEO “teeth”

Catherine P. Whitby; Peter J. Scales; Franz Grieser; Thomas W. Healy; Glen Kirby; Jennifer A. Lewis; Charles F. Zukoski

2003-01-01

175

Synthesis and aqueous solution properties of a novel non-ionic, amphiphilic comb-type polyacrylamide  

Microsoft Academic Search

Nowadays comb-type polyacrylamides are deemed to be the most promising oil-displacing agent in the field of enhanced oil recovery (EOR). We describe the synthesis of a non-ionic, amphiphilic macromer (OPAE) with acrylic acid (AA) and t-octylphenoxypolyoxyehylene (OP) by an esterification reaction. The macromer was then copolymerized with acrylamide (AM) under a free radical initiator system and a comb-type modified polyacrylamide

Yuntao Xu; Pin Gao; Mingzhu Yang; Guangsu Huang; Bingjie Wang

2011-01-01

176

Synthesis and Aqueous Solution Properties of a Novel NonIonic, Amphiphilic Comb-Type Polyacrylamide  

Microsoft Academic Search

Nowadays comb-type polyacrylamides are deemed to be the most promising oil-displacing agent in the field of enhanced oil recovery (EOR). We describe the synthesis of a nonionic, amphiphilic macromer (OPAE) with acrylic acid (AA) and t-octylphenoxypolyoxyehylene (OP) by an esterification reaction. The macromer was then copolymerized with acrylamide (AM) under a free radical initiator system and a comb-type modified polyacrylamide

Yuntao Xu; Pin Gao; Mingzhu Yang; Guangsu Huang; Bingjie Wang

2011-01-01

177

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

PubMed

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

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

2012-01-30

178

Methyl-combing: single-molecule analysis of DNA methylation on stretched DNA fibers.  

PubMed

The methyl-combing technique combines the dynamic molecular combing method with the detection of DNA modifications. The assay allows the single-molecule analysis of epigenetic marks on regularly stretched DNA fibers, at the megabase scale with kilobase resolution. The protocol presented in this chapter is based on proof-of-principle experiments where the single-molecule detection of DNA methylation has been performed on unmethylated and in vitro methylated ? phage DNA. PMID:24162992

Németh, Attila

2014-01-01

179

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

NASA Astrophysics Data System (ADS)

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.

2010-10-01

180

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

PubMed

The generation of high-repetition-rate optical frequency combs with an ultra-broad, coherent and smooth spectrum is important for many applications in optical communications, radio-frequency photonics and optical arbitrary waveform generation. Usually, nonlinear broadening techniques of comb-based sources do not provide the required flatness over the whole available bandwidth. Here we present a 10-GHz ultra-broadband flat-topped optical frequency comb (> 3.64-THz or 28 nm bandwidth with ~365 spectral lines within 3.5-dB power variation) covering the entire C-band. The key enabling point is the development of a pre-shaping-free directly generated Gaussian comb-based 10-GHz pulse train to seed a highly nonlinear fiber with normal dispersion profile. The combination of the temporal characteristics of the seed pulses with the nonlinear device allows the pulses to enter into the optical wave-breaking regime, thus achieving a smooth flat-topped comb spectral envelope. To further illustrate the high spectral coherence of the comb, we demonstrate high-quality pedestal-free short pulse compression to the transform-limited duration. PMID:23482172

Wu, Rui; Torres-Company, Victor; Leaird, Daniel E; Weiner, Andrew M

2013-03-11

181

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

182

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

PubMed

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

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

2012-12-13

183

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

184

Optical frequency comb with an absolute linewidth of 0.6 Hz-1.2 Hz over an octave spectrum  

NASA Astrophysics Data System (ADS)

We demonstrate a narrow-linewidth optical frequency comb based on a femtosecond Ti:sapphire laser by precisely phase-locking it to a subhertz-linewidth Nd:YAG laser at 1064 nm. Each comb tooth inherits the phase coherence and frequency stability of the subhertz-linewidth laser. By comparing against other independent narrow-linewidth lasers, we measured the absolute linewidth of the comb teeth to be 0.6 Hz-1.2 Hz over an octave spectrum.

Fang, Su; Chen, Haiqin; Wang, Tianyin; Jiang, Yanyi; Bi, Zhiyi; Ma, Longsheng

2013-06-01

185

Sex during Pregnancy  

MedlinePLUS

... satisfying and safe sexual relationship during pregnancy. Is Sex During Pregnancy Safe? Sex is considered safe during ... frequently asked questions about sex during pregnancy. Can sex harm my baby? No, not directly. Your baby ...

186

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

187

Multifunction double-ring resonant optical comb filter  

NASA Astrophysics Data System (ADS)

As a kind of optical comb fiber, double-ring resonator formed by a 3 X 3 fiber directional coupler can be used in optical communication system. By changing the parameters such as the coupling angle of the directional coupler, physical lengths of the double rings, loss, and gain factors. It behaves like a device with multi-function involving multi-channel band-pass and band-stop filter, laser resonator or amplifier, optical all-pass filter and so on. In this paper, characteristics of double ring resonator formed by an equal triangle 3 X 3 fiber directional coupler is numerically analyzed in detail, for the double- ring resonator with equal lengths, a minor peak appears near every main resonant peak, they change in reverse dynamically with the increase of the gain coefficient for fixed loss. For unequal lengths case, active cavity brings about clear Vernier effect, and free spectral range is increased. At last, applications of this component in the construction of flattop interleaver and dispersion compensator in FDM system are discussed.

Meng, Yichao; Huang, Zhaoming; Wang, Lutang

2002-08-01

188

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

189

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

NASA Astrophysics Data System (ADS)

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

2010-09-01

190

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

PubMed Central

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

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

2008-01-01

191

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

PubMed

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

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

2013-06-27

192

Drop-port study of microresonator frequency combs: power transfer, spectra and time-domain characterization.  

PubMed

We use a drop-port geometry to characterize frequency combs generated from silicon nitride on-chip microresonators in the normal group velocity regime. In sharp contrast with the traditional transmission geometry, we observe smooth output spectra with comparable powers in the pump and adjacent comb lines. The power transfer into the comb may be explained to a large extent by the coupling parameters characterizing the linear operation of the resonances studied. Furthermore, comparison of thru- and drop-port spectra shows that much of the ASE noise is filtered out by transmission to the drop-port. Autocorrelation measurements are performed on the drop-port output, without the need to filter out or suppress the strong pump line as is necessary in thru-port experiments. Passively mode-locked pulses with low background are observed in a normal dispersion microcavity. PMID:24104133

Wang, Pei-Hsun; Xuan, Yi; Fan, Li; Varghese, Leo Tom; Wang, Jian; Liu, Yang; Xue, Xiaoxiao; Leaird, Daniel E; Qi, Minghao; Weiner, Andrew M

2013-09-23

193

Novel fabrication process for a monolithic PMMA torsion mirror and vertical comb actuator  

NASA Astrophysics Data System (ADS)

This paper presents a novel fabrication process for monolithic PMMA (polymethylmethacrylate) vertical comb-drive actuators utilizing hot embossing, surface-activated direct bonding and elliptical vibration cutting. The robustness and capability of the method are demonstrated through the fabrication of sophisticated PMMA freestanding microstructures, such as a rotation mirror device integrated with vertical comb actuators. The fabrication process consists of silicon mold fabrication by deep-RIE, PMMA microstructure formation by hot embossing, PMMA-PMMA direct bonding by surface activation, releasing or removal of a PMMA layer remaining after hot embossing by elliptical vibration cutting, and finally, metallization by sputtering to form electrodes. An efficient technique to protect the PMMA microstructures during the release process using reinforcement material is applied. A monolithic PMMA torsion mirror driven by a vertical comb actuator has been fabricated successfully.

Amaya, Satoshi; Viet Dao, Dzung; Sugiyama, Susumu

2011-06-01

194

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

195

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

NASA Astrophysics Data System (ADS)

Optical frequency combs generated by femtosecond fiber lasers typically exhibit significant frequency noise that causes broad optical linewidths, particularly in the comb wings and in the carrier-envelope offset frequency (fceo) signal. We show these broad linewidths are mainly a result of white amplitude noise on the pump diode laser that leads to a breathing-like motion of the comb about a central fixed frequency. By a combination of passive noise reduction and active feedback using phase-lead compensation, this noise source is eliminated, thereby reducing the fceo linewidth from 250 kHz to <1 Hz. The in-loop carrier-envelope offset phase jitter, integrated to 100 kHz, is 1.3 rad.

McFerran, J. J.; Swann, W. C.; Washburn, B. R.; Newbury, N. R.

2006-07-01

196

Cesium atom ground state coherence created by an optical frequency comb laser  

NASA Astrophysics Data System (ADS)

Quantum interference resolved by the coherent laser modes from a mode-locked laser is significant in demonstrating femtosecond-laser based high resolution spectroscopy. Moreover, the high Q frequency discriminator resulted from quantum interference phenomenon could possibly serve for comb laser repetition rate stabilization. We discovered a 5-Hz width transparent window when the repetition rate of our optical frequency comb laser [1] was adjusted to be on resonance of cesium atom ground state hyperfine transition. We showed that cesium atom ground state coherence might be created by the comb laser modes, based on the observation of Zeeman effects. We performed our experiment with 8700 Pascal Neon buffer gas and 100^oC (1 mK instability) wall temperature. Frequency shift by wall temperature and the other effects will be presented.[3pt] [1] Appl. Phys. B 92, 13-18 (2008).

Cheng, Wang-Yau; Wu, Tsung-Han; Lu, Sheng-Huei

2009-05-01

197

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

PubMed

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

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

2013-08-15

198

Effect of diflubenzuron (Dimilin; TH--6040) on the hyaluronic acid concentration in chicken combs.  

PubMed

The addition of N-[[(4-chlorphenyl)amino]carbonyl]-2,6-difluorobenzamide(diflubenzuron; Dimilin; TH-6040) up to levels of 250 ppm of the total diet of both male broilers and layers for 98 days did not affect the hyaluronic acid (HA) concentration (microgram/g tissue) in the combs. The concentration was measured at 21, 28, 42, 56, and 98 days on feed. The concentration in the combs of the layers were not significantly different at any sampling period regardless of diet. At the end of 56 days on feed, the combs of the broiler controls had a significantly (P less than .025) higher concentration than did any of the groups fed diflubenzuron. There were no differences observed at 21, 28, 42, or 98 days in the broilers. The HA concentration increased as the chickens matured and became larger; however, large variations were observed within the various groups at a given sample period. PMID:353778

Crookshank, H R; Sowa, B A; Kubena, L; Holman, G M; Smalley, H E; Morison, R

1978-05-01

199

Design of High Channel-Count Comb Filter Based on Digital Concatenated Grating With Multiple Phase Shifts (MPS-DCG)  

Microsoft Academic Search

The multiple phase shifts technique is introduced into digital concatenated grating to design fiber grating comb filters. Detailed analysis is given for the first time. We find that by increasing the channel multiplication factor and concatenated grating segment number, reflection spectrum can be broadened and channel density can be increased without increasing the sampling period. Comb filters covering the -band

Jialin Zhao; Yonglin Yu; Yichao Tang

2011-01-01

200

Sex Bias in Children.  

ERIC Educational Resources Information Center

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

Zalk, Sue Rosenberg; And Others

201

Ab Initio Theoretical Investigation of the Frequency Comb Structure in the XUV Regime via High Harmonic Generation  

NASA Astrophysics Data System (ADS)

We present an ab initio quantum investigation of the frequency comb structure formed within each high harmonic generation (HHG) power spectrum driven by a train of equal- spacing short laser pulses. The HHG power spectrum of atomic hydrogen is calculated by solving the time-dependent Schr"o dinger equation accurately and efficiently by means of the time- dependent generalized pseudospectral method. We found that the frequency comb structure is preserved within each harmonic. In addition, the repetition frequency of the comb laser depends upon the pulse separation ? and the spectral width of each individual comb fringe is inversely proportional to the number of pulses (n) used. However, the global HHG power spectrum pattern depends only upon the laser frequency and intensity used and is not sensitive to the ? and n parameters. Finally, the frequency comb structure persists even in the presence of appreciable ionization.

Carrera, Juan J.; Son, Sang-Kil; Chu, Shih-I.

2007-06-01

202

Interactions and dispersion stability of aluminum oxide colloidal particles in electroless nickel solutions in the presence of comb polyelectrolytes.  

PubMed

The effect of comb polyelectrolytes on the dispersion stability of colloidal alumina particles in DI water and commercial electroless nickel (EN) solutions was investigated. Adsorption of polyelectrolytes and major EN components onto colloidal alumina was assessed by TGA, chemical analysis, and zeta potential measurements. Zeta potential measurements were made during titrations of comb-polyelectrolyte-stabilized dispersions with EN solutions to full ionic strength for the first time. The compilation of titration curves made with varying amounts of comb polyelectrolytes provides high resolution and novel insight into the particle/surfactant/EN systems. Continuous decrease in particle/EN components surface interactions with the increase in comb polyelectrolyte coverage is observed. Laser diffraction measurements reveal steric stabilization of nano- and submicronmeter alumina dispersions in both DI water and EN solutions with >7 wt% and >2 wt% comb polyelectrolyte, respectively. PMID:18439613

de Hazan, Yoram; Reuter, Torben; Werner, Dennis; Clasen, Rolf; Graule, Thomas

2008-04-24

203

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

NASA Astrophysics Data System (ADS)

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

Strekalov, Dmitry V.; Yu, Nan

2009-04-01

204

Surface acoustic wave opto-mechanical oscillator and frequency comb generator  

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

205

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

206

Investigation of frictional properties on wire combed PCC (Portland Cement Concrete) pavement surfaces  

NASA Astrophysics Data System (ADS)

This report involves PCC Pavements constructed with surface textures produced by a wide variety of wire combs. A small amount of testing was also performed on PCCP with other textures as a follow up of previous research on frictional properties. A limited amount of noise evaluation by rating panels and sound level (dbA) meters was conducted to assist in selection of an optimum the spacing for wire combs on future PCC Pavement projects. Included in this report is a brief description of each major project with summaries of friction number tests, standpatch texture depth tests, and sound level measurements.

1982-09-01

207

Silicon nitride waveguides and micro ring-resonators for astronomical optical frequency comb generation  

NASA Astrophysics Data System (ADS)

Silicon nitride ring resonators with diameter of 250 and 500 ?m are fabricated and their spectral characteristics investigated with the ultimate goal of optical frequency comb generation for astronomical spectrograph calibration. A continuously tunable laser was used to evaluate the spectral characteristics (propagation losses and transmission properties) of PECVD silicon nitride waveguides and ring-resonators. Losses were measured to be smaller than 0.75 dB/cm over the range between 1500 nm and 1620 nm. The transmission properties of the fabricated ring resonators were assessed for the TE and TM modes, showing promise for the ultimate goal of astronomical optical frequency comb generation.

Fremberg, T.; Chavez Boggio, J. M.; Bodenmüller, D.; Haynes, R.; Roth, M. M.; Eisermann, R.; Zimmermann, L.; Böhm, M.

2013-05-01

208

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

NASA Astrophysics Data System (ADS)

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.

1988-02-01

209

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

PubMed Central

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

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

2005-01-01

210

Sex-linked dominant  

MedlinePLUS

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

211

Safer Sex Guidelines  

MedlinePLUS

... 2012 Select a Language: Fact Sheet 151 Safer Sex Guidelines HOW DOES HIV SPREAD DURING SEX? UNSAFE ... Be sure to use water-based lubricants. Oral sex has some risk of transmitting HIV, especially if ...

212

Sex and Arthritis  

MedlinePLUS

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

213

Plant sex determination and sex chromosomes  

Microsoft Academic Search

Sex determination systems in plants have evolved many times from hermaphroditic ancestors (including monoecious plants with separate male and female flowers on the same individual), and sex chromosome systems have arisen several times in flowering plant evolution. Consistent with theoretical models for the evolutionary transition from hermaphroditism to monoecy, multiple sex determining genes are involved, including male-sterility and female-sterility factors.

D Charlesworth

2002-01-01

214

Genomics of Sex and Sex Chromosomes  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sex chromosomes are distinctive, not only because of their gender determining role, but also for genomic features that reflect their evolutionary history. The genomic sequences in the ancient sex chromosomes of humans and in the incipient sex chromosomes of medaka, stickleback, and papaya exhibit u...

215

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

PubMed

The nests of European honeybees (Apis mellifera) are organised into wax combs that contain many cells with a hexagonal structure. Many previous studies on comb-building behaviour have been made in order to understand how bees produce this geometrical structure; however, it still remains a mystery. Direct construction of hexagons by bees was suggested previously, while a recent hypothesis postulated the self-organised construction of hexagonal comb cell arrays; however, infrared and thermographic video observations of comb building in the present study failed to support the self-organisation hypothesis because bees were shown to be engaged in direct construction. Bees used their antennae, mandibles and legs in a regular sequence to manipulate the wax, while some bees supported their work by actively warming the wax. During the construction of hexagonal cells, the wax temperature was between 33.6 and 37.6 °C. This is well below 40 °C, i.e. the temperature at which wax is assumed to exist in the liquid equilibrium that is essential for self-organised building. PMID:23149932

Bauer, Daniel; Bienefeld, Kaspar

2012-11-14

216

Microassembly process to fabricate a microoptoelectromechanical systems scanning mirror with angular vertical comb electrodes  

NASA Astrophysics Data System (ADS)

We present a simple microassembly technology that easily realizes angular vertical combs for a microoptoelectromechanical systems scanner. The scanner is composed of a device section with comb electrodes and a tilting section with four tapered pillars. During the microassembly process, two tilting pillars push down the levers so that the comb electrodes connected with the micromirror are tilted; the other two alignment pillars fit into the alignment holes of the device section, which is fabricated via a deep reactive ion etching process of a silicon-on-insulator wafer. The tilting section is fabricated through a series of anisotropic wet etching of a (100) silicon wafer and patterning processes of SU-8, which is robust enough to ensure repeatability of the initial tilted angles of the movable comb electrodes. The pull-in investigation function is analyzed through a numerical estimation to obtain a large scan angle with stable behavior. The fabricated microscanner shows an optical scan angle of up to 4.23 deg at 90 V in the static mode and stable actuation of up to 11.3 deg at a resonant frequency of 2.87 kHz. The roughness of the mirror surface is less than 10 nm, which will have a negligible effect on imaging quality. The initial tilted angles in the microassembly process showed high repeatability within 10% error.

Jun, Min-Ho; Moon, Seunghwan; Lee, Jong-Hyun

2013-01-01

217

Possibility of comb-type rf shield structure for high-current accelerators  

NASA Astrophysics Data System (ADS)

A novel rf shield structure for bellows chambers or gate valves in high-current accelerators is proposed. The rf shield has no thin fingers, but nested comb teeth instead at the inner surface of the beam duct. The comb-type rf shield has a higher thermal strength structurally than the conventional finger-type one. A simulation also indicates its lower impedance. Especially, the leak of a TE modelike higher order mode through the axial slits, which causes mainly heating of these components, is almost suppressed due to thick teeth. An abrasion test in a vacuum using a test piece of the comb-type rf shield shows less dust generation compared to the finger type. Another preliminary test transmitting 508MHz microwaves through a prototype rf shield in the atmosphere found no abnormal heating or arcing. A trial model of bellows chambers with the comb-type rf shield will be installed and tested using a real beam in the KEK B-factory positron ring this year.

Suetsugu, Y.; Shirai, M.; Shibata, K.

2003-10-01

218

Machine Vision Assistance for Flex Cable-Actuator Comb Manufacturing in Hard Disk Drives  

Microsoft Academic Search

The work presented in this paper suggests an automated manufacturing method for assembling of flexible printed circuit cable assembly onto actuator comb-like structure in high capacity hard disk drives. Apart from traditional alignment methods, robotic vision guided method and assembling system are developed and discussed in this paper. Its capabilities of reaching micro-scale position and alignment accuracy are demonstrated in

J. Y. Chang; J. Y. Shen

2008-01-01

219

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

Microsoft Academic Search

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

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

1997-01-01

220

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

221

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

Microsoft Academic Search

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

Yonghong Gao; Lihong Jia; H. Tenhunen

1999-01-01

222

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

Microsoft Academic Search

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

Suhasini R. Rao; Uwe H. Meyer-Baese

2004-01-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

224

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

SciTech Connect

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

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

2008-09-18

225

Reclassification of Brevibacterium oxydans (Chatelain and Second 1966) as Microbacterium oxydans comb. nov.  

PubMed

Phylogenetic and chemotaxonomic analyses indicate that Brevibacterium oxydans is closely related to species of the genus Microbacterium, namely Microbacterium liquefaciens, Microbacterium luteolum and Microbacterium saperdae. DNA-DNA reassociation values of less than 60% between Brevibacterium oxydans and these three Microbacterium species support the distinctness of this misclassified Brevibacterium species, which is reclassified as Microbacterium oxydans comb. nov. PMID:10028259

Schumann, P; Rainey, F A; Burghardt, J; Stackebrandt, E; Weiss, N

1999-01-01

226

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

Microsoft Academic Search

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.

Peter Schumann; Norbert Weiss; Erko Stackebrandt

227

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

PubMed

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

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

2013-02-25

228

Comb wax mediates the acquisition of nest-mate recognition cues in honey bees  

PubMed Central

Honey bees, Apis mellifera, acquire nest-mate recognition cues from wax, the predominant material used in nest construction. Exposure of a newly emerged worker bee to wax-comb substrate significantly reduced the acceptability of that worker to sister bees. Cues acquired from the comb provided colony-specific information about the identity of worker bees; moreover, the effect of comb exposure has been previously shown to override individually produced cues. Food odors (anise oil), when dissolved in paraffin wax, affected worker-recognition characteristics but food odors did not affect these characteristics when fed to bees in sugar candy. Paraffin wax alone did not affect the recognition cues of bees, showing that the wax can be a neutral medium for the transmission of cues. The wax comb in the colony and the hydrocarbon outer layer of the bee cuticle may be a continuous medium for any hydrocarbon-soluble substances used by honey bees in nest-mate recognition; if so, a mechanism by which environmental cues are acquired by honey bees is provided.

Breed, Michael D.; Williams, Kristina R.; Fewell, Jennifer H.

1988-01-01

229

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

Microsoft Academic Search

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

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

230

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

Microsoft Academic Search

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

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

2011-01-01

231

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

PubMed

The male Laneella perisi (Mariluis) n. comb. is described based on specimens collected in the Cordillera Oriental (1,370-1,450 m asl), Florencia-Suaza, Caquetá, Colombia. A key to separate the two species of the genus Laneella and illustrations of the male genitalia and female abdomen, terminalia, and spermatheca are also presented. PMID:23949713

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

2012-11-01

232

Direct Force Measurement of Comb Silicone Surfactants in Alcoholic Media by Atomic Force Microscopy  

Microsoft Academic Search

The interaction forces provided by silicone polyether (SPE) surfactants, adsorbed at the interface of octadecyltrichlorosilan monolayer and aqueous surfactant solution, were measured by atomic force microscopy. Changes in the forces in the presence of ethanol were examined for a series of comb-type SPE surfactants. It was found that the steric repulsion provided by the SPE molecules persisted up to an

Anfeng Wang; Liping Jiang; Guangzhao Mao; Yihan Liu

2001-01-01

233

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

234

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

235

Corps of Engineers Operations Maintenance Budget Decision Support System. Division Prototype (COMB-DSS-D).  

National Technical Information Service (NTIS)

This report describes the development and use of a PC-based decision support system to assist with O and M budget analysis. The Corps Operations and Maintenance Budget Decision Support System-Division (COMB DSS-D) is the second product of the work unit en...

1993-01-01

236

DIGITAL SOUND EFFECTS ECHO AND REVERB BASED ON NON EXPONENTIALLY DECAYING COMB FILTER  

Microsoft Academic Search

This paper presents algorithms of two digital sound effects based on the NEDCF (Non-Exponentially Decaying Comb Filter). The first part of the paper deals with the description of a NEDCF structure and with the algorithm of the digital sound effect of Echo type with easily controllable parame- ters. The second part describes an extension of the previous algorithm for obtaining

Vitezslav Kot

2006-01-01

237

Optical zooming interferometer for subnanometer positioning using an optical frequency comb  

SciTech Connect

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

Kajima, Mariko; Minoshima, Kaoru

2010-10-20

238

Atomic and molecular spectroscopy with optical-frequency-comb-referenced IR coherent sources  

NASA Astrophysics Data System (ADS)

We provide a review of progress in the development of metrological-grade measurements in atomic and molecular systems through the extension, in the mid-infrared and far-infrared range, of optical frequency combs (OFCs) and the introduction of new techniques and highly coherent sources.

Cancio, P.; Bartalini, S.; De Rosa, M.; Giusfredi, G.; Mazzotti, D.; Maddaloni, P.; Vitiello, M. S.; De Natale, P.

2013-08-01

239

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

Microsoft Academic Search

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

Stephen C. Pratt

2004-01-01

240

Astronomical optical frequency comb generation in nonlinear fibres and ring resonators: optimization studies  

NASA Astrophysics Data System (ADS)

We here discuss recent progress on astronomical optical frequency comb generation at innoFSPEC-Potsdam. Two different platforms (and approaches) are numerically and experimentally investigated targeting medium and low resolution spectrographs at astronomical facilities in which innoFSPEC is currently involved. In the first approach, a frequency comb is generated by propagating two lasers through three nonlinear stages - the first two stages serve for the generation of low-noise ultra-short pulses, while the final stage is a low-dispersion highly-nonlinear fibre where the pulses undergo strong spectral broadening. In our approach, the wavelength of one of the lasers can be tuned allowing the comb line spacing being continuously varied during the calibration procedure - this tuning capability is expected to improve the calibration accuracy since the CCD detector response can be fully scanned. The input power, the dispersion, the nonlinear coefficient, and fibre lengths in the nonlinear stages are defined and optimized by solving the Generalized Nonlinear Schrodinger Equation. Experimentally, we generate the 250GHz line-spacing frequency comb using two narrow linewidth lasers that are adiabatically compressed in a standard fibre first and then in a double-clad Er/Yb doped fibre. The spectral broadening finally takes place in a highly nonlinear fibre resulting in an astro-comb with 250 calibration lines (covering a bandwidth of 500 nm) with good spectral equalization. In the second approach, we aim to generate optical frequency combs in dispersion-optimized silicon nitride ring resonators. A technique for lowering and flattening the chromatic dispersion in silicon nitride waveguides with silica cladding is proposed and demonstrated. By minimizing the waveguide dispersion in the resonator two goals are targeted: enhancing the phase matching for non-linear interactions and producing equally spaced resonances. For this purpose, instead of one cladding layer our design incorporates two layers with appropriate thicknesses. We demonstrate a nearly zero dispersion (with +/- 4 ps/nm-km variation) over the spectral region from 1.4 to 2.3 microns. The techniques reported here should open new avenues for the generation of compact astronomical frequency comb sources on a chip or in nonlinear fibres.

Chavez Boggio, J. M.; Fremberg, T.; Bodenmüller, D.; Wysmolek, M.; Sanyic, H.; Fernando, H.; Neumann, J.; Kracht, D.; Haynes, R.; Roth, M. M.

2012-09-01

241

XUV frequency-comb metrology on the ground state of helium  

SciTech Connect

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

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

2011-12-15

242

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

243

Synthesis and Properties of Star-Comb Polymers and Their Doxorubicin Conjugates  

PubMed Central

We describe a six step synthesis to water soluble doxorubicin (DOX)-loaded biodegradable PEGylated star-comb polymers with favorable pharmaceutical properties by atom transfer radical polymerization (ATRP) starting with a commercially available tripentaerythritol carrying eight reactive sites. The low polydispersity polymers degrade in a stepwise manner into lower molecular weight (MW) fragments by 15 days at 37 °C at either pH 5.0 or pH 7.4. The half-life of the star-comb polymers in blood is dependent upon the molecular weight; the 44 kDa star-comb has a t1/2, ? of 30.5 ± 2.1 h, which is not significantly changed (28.6 ±2.7 h) when 6.6 wt% of DOX is attached to it via a pH-sensitive hydrazone linker. The star-comb polymers have low accumulation in organs but a high accumulation in C26 flank tumors implanted in Balb/C mice. The hydrodynamic diameter of polymer-DOX conjugates measured by dynamic light scattering increases from 8 to 35 to 41 nm as the loading is increased from 6.6 to 8.4 to 10.2 wt%. Although there is no significant difference in the t1/2, ? or in the accumulation of polymer-DOX in C-26 tumors, the uptake of polymer in the spleen is significantly higher for polymers with DOX loadings greater than 6.6 wt%. Polymer accumulation in other vital organs is independent of the DOX loading. The facile synthesis, biodegradability, long circulation time and high tumor accumulation of the attached drug suggests that the water-soluble star-comb polymers have promise in therapeutic applications.

Chen, Bo; van der Poll, Derek G.; Jerger, Katherine; Floyd, William C.; Frechet, Jean M. J.; Szoka, Francis C.

2011-01-01

244

The Riddle of Sex.  

ERIC Educational Resources Information Center

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

Sagan, Dorion; Margulis, Lynn

1985-01-01

245

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

SciTech Connect

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

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

2006-10-30

246

Self-assembly of pH-responsive and fluorescent comb-like amphiphilic copolymers in aqueous media  

Microsoft Academic Search

Comb-like” graft copolymers, consisting of a poly((N-vinylcarbazole)-co-(4-vinylbenzyl chloride)) (P(NVK-co-VBC)) copolymer backbone from free radical polymerization and poly(((2-dimethylamino)ethyl methacrylate)-co-(tert-butyl acrylate)) (P(DMAEMA-co-tBA)) side chains from atom transfer radical polymerization (ATRP), were hydrolyzed to produce the acrylic acid (AAc)-containing “comb-like” graft copolymers of P(NVK-co-VBC)-comb-P(DMAEMA-co-AAc). The amphiphilic copolymers possess a fluorescent hydrophobic P(NVK-co-VBC) backbone and pH-sensitive hydrophilic P(DMAEMA-co-AAc) side chains. Arising from acid–base interaction

Min Li; Guo Liang Li; Zhiguo Zhang; Jun Li; Koon-Gee Neoh; En-Tang Kang

2010-01-01

247

Oral Sex and HIV Risk  

MedlinePLUS

... Añadir en... Favorites Delicious Digg Google Bookmarks Oral Sex and HIV Risk Oral Sex Is Not Risk Free Like all sexual activity, ... HIV or another STD through oral sex. Oral Sex is a Common Practice Oral sex involves giving ...

248

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

PubMed

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

Zhou, Hongyi; Skolnick, Jeffrey

2012-12-28

249

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

PubMed

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

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

2013-07-01

250

Measurement of the carrier envelope offset frequency of a femtosecond frequency comb using a Fabry-Perot interferometer  

SciTech Connect

A method for measuring the carrier envelope offset (CEO) frequency of the femtosecond frequency comb with a bandwidth of less than one octave by using a Fabry-Perot interferometer is proposed and experimentally demonstrated. (laser components)

Basnak, D V; Bikmukhametov, K A; Dmitrieva, N I [Novosibirsk State Technical University, Novosibirsk (Russian Federation); Dmitriev, Aleksandr K; Lugovoi, A A [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Pokasov, P V; Chepurov, S V [Novosibirsk State University, Novosibirsk (Russian Federation)

2010-10-15

251

High-power ultra-broadband frequency comb from ultraviolet to infrared by high-power fiber amplifiers.  

PubMed

A high-power ultra-broadband frequency comb covering the spectral range from ultraviolet to infrared was generated directly by nonlinear frequency conversion of a multi-stage high-power fiber comb amplifier. The 1030-nm infrared spectral fraction of a broadband Ti:sapphire femtosecond frequency comb was power-scaled up to 100 W average power by using a large-mode-area fiber chirped-pulse amplifier. We obtained a frequency-doubled green comb at 515 nm and frequency-quadrupled ultraviolet pulses at 258 nm with the average power of 12.8 and 1.62 W under the input infrared power of 42.2 W, respectively. The carrier envelope phase stabilization was accomplished with an ultra-narrow line-width of 1.86 mHz and a quite low accumulated phase jitter of 0.41 rad, corresponding to a timing jitter of 143 as. PMID:22714317

Yang, Kangwen; Li, Wenxue; Yan, Ming; Shen, Xuling; Zhao, Jian; Zeng, Heping

2012-06-01

252

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

PubMed

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

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

2012-03-12

253

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

Microsoft Academic Search

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

Meng-Han Hsieh; Che-Ho Wei

1998-01-01

254

Investigating the Reliability of Electrostatic Comb-Drive Actuators Utilized in Microfluidic and Space systems Using Finite Element Analysis  

Microsoft Academic Search

This study focuses on investigating the design parameters of lateral Electrostatic Comb-Drive actuators, where the effect of these parameters on the actuation performance is explored using Finite Element Analysis (FEA). This level of analysis is essential to the design process of system-on-a-chip MEMS applications, where a Comb-Drive can represent the main source of actuation within the chip system. Of particular

Walied A. Moussa; Wael Badawy; Medhat Moussa

255

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

256

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

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

257

A comparative study of seven pediculicides and their packaged nit removal combs.  

PubMed

The incidence of pediculosis infestation is greater than that for all childhood communicable diseases combined. Each year approximately 6 to 12 million persons become infested, resulting in an estimated cost of $367 million to manage the problem. Pediatric health care providers are often confused regarding proper management of head lice because of the multitude of manufacturer claims in the competitive advertising market. This comparative study was designed to evaluate the combined efficacy of seven pediculicidal agents with their supplied nit removal combs in the treatment of head lice. A sample of children (n = 223) was studied from 4271 children screened at various elementary schools throughout Florida. The results of this study can assist school health care providers and pediatric nurse practitioners in identifying the most effective nit removal comb and those children at risk for head lice infestations. PMID:7684080

Clore, E R; Longyear, L A

258

Spectroscopy of the methane ?3 band with an accurate midinfrared coherent dual-comb spectrometer  

NASA Astrophysics Data System (ADS)

We demonstrate a high-accuracy dual-comb spectrometer centered at 3.4 ?m. The amplitude and phase spectra of the P, Q, and partial R branches of the methane ?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 10-3 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.

2011-12-01

259

Laser Frequency Comb Supported Stellar Radial Velocity Determination in the NIR: Initial Results.  

NASA Astrophysics Data System (ADS)

The laser frequency comb presents the potential for a revolutionary increase in radial velocity precision by providing a calibration reference of unprecedented quality in terms of wavelength knowledge, repeatability, number, density and regularity of lines. Promising first steps have been taken leading to the derivation of stellar radial velocities in the NIR H band, a wavelength range well suited to the observation of M dwarfs. These stars, with low mass and low luminosity, are the most prevalent class of stars within 10 parsecs and can be expected to yield a higher reflex velocity for a terrestrial mass planet in the liquid water habitable zone than would be the case with a more massive star such as our own. We present the design and both laboratory and on-sky performance of an H-band laser frequency comb used in conjunction with the Penn State Pathfinder testbed spectrograph and discuss lessons learned and plans for follow on testing.

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

2011-09-01

260

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

NASA Astrophysics Data System (ADS)

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 "fingerprints". Our method will allow identification of hazardous substances with high detection sensitivity and real-time data processing. A two-octave-wide mid-infrared frequency comb output will be produced by a cascaded sub-harmonic optical parametric oscillator (OPO) pumped by a fiber laser. The proposed device will use the principle of coherent Fourier-transform infrared spectrometer and offer an unprecedented precision and speed of acquisition of spectral information.

Vodopyanov, Konstantin L.

2009-05-01

261

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

NASA Astrophysics Data System (ADS)

A wavelength calibration system based on a laser frequency comb (LFC) was developed in a co-operation between the Kiepenheuer-Institut für Sonnenphysik, Freiburg, Germany and the Max-Planck-Institut für Quantenoptik, Garching, Germany for permanent installation at the German Vacuum Tower Telescope (VTT) on Tenerife, Canary Islands. The system was installed successfully in October 2011. By simultaneously recording the spectra from the Sun and the LFC, for each exposure a calibration curve can be derived from the known frequencies of the comb modes that is suitable for absolute calibration at the meters per second level. We briefly summarize some topics in solar physics that benefit from absolute spectroscopy and point out the advantages of LFC compared to traditional calibration techniques. We also sketch the basic setup of the VTT calibration system and its integration with the existing echelle spectrograph.

Doerr, H.-P.; Steinmetz, T.; Holzwarth, R.; Kentischer, T.; Schmidt, W.

2012-10-01

262

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

263

A tunable polarization-independent comb filter based on high-order mode fiber  

NASA Astrophysics Data System (ADS)

This paper presents an all-fiber tunable comb filter based on high-order mode fiber (HOMF). The filter is constructed by splicing a segment of HOMF between two sections of conventional single-mode fibers (SMFs), with an intentionally introduced offset at the first joint between the SMF and HOMF, and without an offset at the second joint between the HOMF and SMF, to optimize the visibility of the transmission spectrum. The optimal transverse offset of the fibers at the first joint and the tunable polarization-independent properties of the filter were studied theoretically and experimentally. An example of using this tunable comb filter in the application of a sensor, based on demodulating the wavelength shift of a fiber Bragg grating, has also been demonstrated. The particular advantages of this all-fiber tunable filter make it valuable in various applications.

Wei, Chunfen; Lin, Ganbin; Dong, Xiaopeng; Tao, Sicong

2013-05-01

264

Measuring the camber deformation of a dragonfly wing using projected comb fringe  

NASA Astrophysics Data System (ADS)

The camber deformations of the flapping insect wing provide important information for lift force analysis. Recent measurements are nearly all based on the hypothesis of the rigid wing, neglecting the camber deformation. In this article, a measurement system based on fringe pattern projection is introduced. Projected comb fringes, whose intensity function is near a comb function, were used instead of conventional sine fringes because of their high intensity and sharpness, allowing us to take the distorted fringes on the transparent dragonfly wing easily. The camber deformation and torsion angle of a flapping dragonfly wing can be measured without hypothesizing that the wing is a rigid plate. The experimental result shows that the camber deformation is different during upstroke and downstroke. It is very important for the explanation of the lift force.

Song, Deqiang; Wang, Hao; Zeng, Lijiang; Yin, Chunyong

2001-05-01

265

Implementation of a single femtosecond optical frequency comb for rovibrational cooling  

SciTech Connect

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

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

2010-07-15

266

Multi-delay, phase coherent pulse pair generation for precision Ramsey-frequency comb spectroscopy.  

PubMed

We demonstrate the generation of phase-stable mJ-pulse pairs at programmable inter-pulse delays up to hundreds of nanoseconds. A detailed investigation of potential sources for phase shifts during the parametric amplification of the selected pulses from a Ti:Sapphire frequency comb is presented, both numerically and experimentally. It is shown that within the statistical error of the phase measurement of 10 mrad, there is no dependence of the differential phase shift over the investigated inter-pulse delay range of more than 300 ns. In combination with nonlinear upconversion of the amplified pulses, the presented system will potentially enable short wavelength (<100 nm), multi-transition Ramsey-frequency comb spectroscopy at the kHz-level. PMID:23482099

Morgenweg, J; Eikema, K S E

2013-03-11

267

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

268

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

269

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

PubMed

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

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

2013-10-01

270

Optical clockworks and the measurement of laser frequencies with a mode-locked frequency comb  

Microsoft Academic Search

Femtosecond laser-frequency comb techniques are vastly simplifying the measurement and synthesis of optical fre- quencies. A single mode-locked femtosecond laser, with its spec- trum broadened by self-phase modulation in a microstructured or tapered nonlinear fiber, can produce millions of sharp laser lines in a precise evenly spaced grid spanning much of the visible and near- infrared spectrum. The absolute frequency

R. Holzwarth; M. Zimmermann; Thomas Udem; T. W. Hansch

2001-01-01

271

ComB: SNP Calling and Mapping Analysis for Color and Nucleotide Space Platforms  

PubMed Central

Abstract The determination of single nucleotide polymorphisms (SNPs) has become faster and more cost effective since the advent of short read data from next generation sequencing platforms such as Roche's 454 Sequencer, Illumina's Solexa platform, and Applied Biosystems SOLiD sequencer. The SOLiD sequencing platform, which is capable of producing more than 6?GB of sequence data in a single run, uses a unique encoding scheme where color reads represent transitions between adjacent nucleotides. The determination of SNPs from color reads usually involves the translation of color alignments to likely nucleotide strings to facilitate the use of tools designed for nucleotide reads. This technique results in the loss of significant information in the color read, producing many incorrect SNP calls, especially if regions exist with dense or adjacent polymorphism. Additionally, color reads align ambiguously and incorrectly more often than nucleotide reads making integrated SNP calling a difficult challenge. We have developed ComB, a SNP calling tool which operates directly in color space, using a Bayesian model to incorporate unique and ambiguous reads to iteratively determine SNP identity. ComB is capable of accurately calling short consecutive nucleotide polymorphisms and densely clustered SNPs; both of which other SNP calling tools fail to identify. ComB, which is capable of using billions of short reads to accurately and efficiently perform whole human genome SNP calling in parallel, is also capable of using sequence data or even integrating sequence and color space data sets. We use real and simulated data to demonstrate that ComB's iterative strategy and recalibration of quality scores allow it to discover more true SNPs while calling fewer false positives than tools which use only color alignments as well as tools which translate color reads to nucleotide strings.

Souaiaia, Tade; Frazier, Zach

2011-01-01

272

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

Microsoft Academic Search

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

Youngbeom Jang; Sejung Yang

2001-01-01

273

Mid-Infrared Frequency Comb Spectroscopy with Two Cr2+:ZnSe Femtosecond Oscillators  

NASA Astrophysics Data System (ADS)

The mid-infrared part of the electromagnetic spectrum is the so-called molecular fingerprint region because gases have tell-tale absorption features associated with molecular rovibrations. It also contains windows (in particular 2.0-2.4 ?m, 3-5 ?m and 8-13 ?m) where the atmosphere is relatively transparent. These regions can be for instance exploited to detect small traces of environmental and toxic vapours down to sensitivities of parts-per-billion in atmospheric and industrial applications. Novel Fourier transform spectroscopy without moving parts, based on time-domain interferences between two comb sources, can in particular benefit optical diagnostics and precision spectroscopy. To date, high-resolution and -sensitivity proof-of-principle experiments have only been reported in the near-infrared region where frequency comb oscillators are conveniently available. However, as most of molecular transitions in this region are due to weak overtone bands, such techniques can hardly be harnessed for sensitive trace gas detection. Developing mid-infrared dual comb Fourier transform spectroscopy is therefore a demanding but highly desirable task. Here we present a proof-of-principle experiment of frequency comb Fourier transform spectroscopy with two Cr2+:ZnSe femtosecond oscillators directly emitting in the 2.4 ?m mid-infrared region. Spectra of acetylene in the region of the ?_1+?_5^1 band extend from 3970 cm-1 to 4200 cm-1. With 0.4 cm-1 resolution, the acquisition time of the corresponding interferograms is 10 ?s, without averaging. This demonstrates the feasibility of our approach.

Jacquet, P.; Thon, R.; Becker, T.; Bernhardt, B.; Sorokin, E.; Sorokina, I. T.; Picqué, N.; Hänsch, T. W.

2010-06-01

274

A new method to generate relativistic comb bunches with tunable subpicosecond spacing  

Microsoft Academic Search

We propose and analyze a scheme to produce comb bunches, i.e. a bunch consisting of micro-bunch trains, with tunable subpicosecond spacing. In the scheme, the electron beam is first deflected by a deflecting cavity which introduces a longitudinal-dependent linear transverse kick to the particles. After passing through a drift space, the transverse beam size is linearly coupled to the longitudinal

Du Ying-Chao; Huang Wen-Hui; Tang Chuan-Xiang

2012-01-01

275

Generation of optical frequency combs with a CaF2 resonator.  

PubMed

We demonstrate optical frequency combs using the fluorite whispering gallery mode resonator as a nonlinear Kerr medium. Two regimes of generation are observed, giving the record low repetition rate of 13 GHz, equal to the cavity's free spectral range (FSR) or high repetition rates of multiples of cavity FSR. An intermediate regime was also observed. Raman lasing spectrum similar to modulation instability in fibers was observed for the first time to the best of our knowledge. PMID:19340157

Grudinin, Ivan S; Yu, Nan; Maleki, Lute

2009-04-01

276

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

Microsoft Academic Search

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

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

2007-01-01

277

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

Microsoft Academic Search

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

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

2007-01-01

278

Application of filter sharpening to cascaded integrator-comb decimation filters  

Microsoft Academic Search

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

Alan Y. Kwentus; Zhongnong Jiang

1997-01-01

279

Triteleia peyerimhoffi comb. n., a remarkably variable circum-Mediterranean scelionid (Hymenoptera, Platygastroidea)  

PubMed Central

Abstract Triteleia peyerimhoffi comb. n. (Kieffer, 1906) is redescribed taking into account its great variability and is considered the senior synonym of Triteleia dubia (Kieffer, 1908), Calliscelio lugens (Kieffer, 1910) and Triteleia striolata Kononova & Petrov, 2000, syn. n. Neotypes are designated for Triteleia dubia and Triteleia peyerimhoffi. Triteleia peyerimhoffi is a new record for Greece, France and Croatia and was reared for the first time from eggs of Orthoptera laid in the dead wood of Quercus sp. and Tilia sp. in Romania.

Popovici, Ovidiu Alin; Bin, Ferdinando; Masner, Lubomir; Popovici, Mariana; Notton, David

2011-01-01

280

Direct Evidence of Molecular Orientation and Packing of Hydrophobic Alkyl Chains at Comb Copolymer Surfaces  

Microsoft Academic Search

Surface sensitive IR-visible sum frequency generation (SFG) has been used to provide a molecular insight into wetting behavior at polymer surfaces. As a model system polymer-air interfaces of comb copolymers with hydrophobic octadecyl side chains are investigated using both SFG and contact angle measurements. These results are compared to octadecyl triethoxy silane self-assembled monolayers (SAM) on mica surfaces. The SFG

Keshav Gautam; Ali Dhinojwala

2000-01-01

281

Molecular combing in studies of the genome organization and DNA replication  

Microsoft Academic Search

Molecular combing (MC) yields preparations where individual DNA molecules are uniformly stretched and are parallel to each\\u000a other. Fluorescence in situ hybridization on such preparations allows an exact mapping of DNA sequences, and pulsed incorporation\\u000a of halogenated deoxyuridine analogs and their detection using fluorochrome-conjugated antibodies makes it possible to visualize\\u000a replication. The MC technique was adapted for studying DNA replication

T. D. Kolesnikova; S. A. Demakov; A. V. Ivankin; I. F. Zhimulev

2010-01-01

282

Micro robot system with moving micro-car driven by electrostatic comb-drive actuators  

Microsoft Academic Search

This paper describes a silicon micro robot system (MRS) that is capable of driving micro-cars in different directions based\\u000a on a ratchet mechanism and electrostatic comb-drive actuators. Lateral movement of the ratchet racks makes the micro-car move\\u000a in the perpendicular direction with different velocities. Based on MEMS technology, the MRS described in this article was\\u000a fabricated from a silicon on

Phuc Hong Pham; Lam Bao Dang; Hung Ngoc Vu

2010-01-01

283

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

284

Direct frequency comb generation from an octave-spanning, prismless Ti:sapphire laser  

Microsoft Academic Search

We describe a self-referenced optical frequency comb generator based on an octave-spanning, prismless Tisapphire laser. Dispersion compensation is provided by novel double-chirped mirror pairs and BaF2 wedges. Current versions operate at 80 and 150 MHz. The compact prismless design allows system scaling to a gigahertz repetition rate. Its carrier-envelope beat note is intrinsically stable with a signal-to-noise ratio of 30

L. Matos; D. Kleppner; O. Kuzucu; T. R. Schibli; J. Kim; E. P. Ippen; F. X. Kaertner

2004-01-01

285

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

PubMed

Theoretical analysis and numerical calculations are performed to characterize the unsteady two-dimensional conduction of thermal energy in an idealized honey bee comb. The situation explored corresponds to a comb containing a number of brood cells occupied by pupae. These cells are surrounded by other cells containing pollen which, in turn, are surrounded (above) by cells containing honey and (below) by vacant cells containing air. Up to five vacant cells in the brood region can be occupied by cell-heating bees which, through the isometrical contraction of their flight muscles, can generate sufficient energy to raise their body temperatures by a few degrees. In this way, the cell-heating bees alter the heat flux and temperature distributions in the brood region so as to maintain conditions that benefit the pupae. The calculations show that the number of cell-heating bees significantly affects the magnitude, time rate of change, and spatial distribution of temperature throughout the comb. They also reveal a vertically aligned asymmetry in the spatial distribution of temperature that is due to the large heat capacity and thermal conductivity of honey relative to air, whereby air-filled cells experience larger temperature increases than honey-filled cells. Analysis shows that convection and radiation represent negligible modes of thermal energy transfer at all levels in the problem considered. Also, because of its small thickness, the wax wall of a comb cell simultaneously presents negligible resistance to conduction heat transfer normal to it and very large resistance along it. As a consequence the walls of a cell play no thermal role, but simply serve as mechanical supports for the materials they contain. PMID:17976654

Humphrey, J A C; Dykes, E S

2007-09-26

286

Designer multi-functional comb-polymers for surface engineering of quantum dots on the nanoscale  

Microsoft Academic Search

Synthesis, characterization and cell-biomarker applications for a novel series of comb-copolymers featuring hydrophobic amide side groups, carboxylates and other functionalities such as polymerizable side chains and PEG oligomers are reported. When used as polymer ligand shell for trioctylphosphine oxide (TOPO) coated quantum dots (QDs) these copolymers effectively solubilise CdSe\\/ZnS QDs in water. A systematic study was carried out to find

Dominik Ja?czewski; Nikodem Tomczak; Yin Win Khin; Ming-Yong Han; G. Julius Vancso

2009-01-01

287

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

PubMed

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

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

2012-03-01

288

Surface-micromachined electrostatic-comb driven scanning micromirrors for barcode scanners  

Microsoft Academic Search

This paper describes the design and fabrication of micromachined resonant scanners that have large scan angles at fast scan speeds. Driven by an electrostatic comb motor, these 200 ?m by 250 ?m scanning-micromirrors can scan about 12° (optical) at the resonance frequency of 3 kHz with a sinusoidal voltage input of 20 V in amplitude. Fabricated with a four-poly-layer silicon-surface-micromachining

Meng-Hsiung Kiang; Olav Solgaard; Richard S. Muller; Kam Y. Lau

1996-01-01

289

Graphene oxide scrolls on hydrophobic substrates fabricated by molecular combing and their application in gas sensing.  

PubMed

Well-aligned graphene oxide (GO) scrolls are prepared through the controlled folding/scrolling of single-layer GO sheets using molecular combing on hydrophobic substrates, such as aged gold substrate, polydimethylsiloxane film, poly(L-lactic acid) film, and octadecyltrimethoxysilane-modified silicon dioxide. As a proof of concept, the gas sensor fabricated with a single reduced GO scroll is used to detect NO(2) gas with a concentration as low as 0.4 ppm. PMID:23065912

Li, Hai; Wu, Jumiati; Qi, Xiaoying; He, Qiyuan; Liusman, Cipto; Lu, Gang; Zhou, Xiaozhu; Zhang, Hua

2012-10-15

290

Reclassification of [Glaciecola] lipolytica and [Aestuariibacter] litoralis in Aliiglaciecola gen. nov., as Aliiglaciecola lipolytica comb. nov. and Aliiglaciecola litoralis comb. nov., respectively.  

PubMed

Following phylogenetic analysis based on 16S rRNA gene sequences, together with DNA G+C contents and differential chemotaxonomic and physiological characteristics, a new genus with the name Aliiglaciecola gen. nov. is proposed to more appropriately accommodate two recognized species of the genera Glaciecola and Aestuariibacter. Accordingly, [Glaciecola] lipolytica and [Aestuariibacter] litoralis should be reassigned to the novel genus as Aliiglaciecola lipolytica comb. nov. (type strain, E3(T) = JCM 15139(T) = CGMCC 1.7001(T)) and Aliiglaciecola litoralis comb. nov. (type strain, KMM 3894(T) = JCM 15896(T) = NRIC 0754(T)), respectively. Aliiglaciecola lipolytica is proposed as the type species of this new genus. Physiologically, the combined characteristics of positive reactions for nitrate reduction and growth at 4 °C and 36 °C distinguish the new genus from the genera Aestuariibacter and Glaciecola by one to three traits. Moreover, the new genus is also distinguished from the genus Glaciecola by the fatty acid profile and distinguished from the genus Aestuariibacter by the differences of major isoprenoid quinone (MK-7 vs Q-8) and DNA G+C content (40.8-43.0 mol% vs 48.0-54.0 mol%). PMID:23315410

Jean, Wen Dar; Hsu, Cheng Yu; Huang, Ssu-Po; Chen, Jwo-Sheng; Lin, Saulwood; Su, Mong-Huai; Shieh, Wung Yang

2013-01-11

291

Practice Safer Sex  

MedlinePLUS

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

292

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

293

From a discrete to a continuous model for interpulse interference with a frequency-comb laser  

SciTech Connect

We have investigated correlation patterns generated by a frequency-comb laser in a dispersive unbalanced Michelson interferometer and apply the developed formalism to the case of distance metrology. Due to group velocity dispersion, the position of the brightest fringe of the correlation pattern, which is used for distance determination, cannot be derived by simply using the definition of group refractive index of the dispersive medium. It is shown that the discrete spectrum of the optical frequency comb gives rise to correlation functions which can be represented by a series, namely a discrete correlation series. We have developed a general formalism, valid for any pulse train, extending the discrete model to a continuous model of cross-correlation functions using the Poisson summation. Our model is relevant for any offset and repetition frequency of the frequency comb. From the continuous cross-correlation model we show that, even for a homogeneous dispersive medium the position of the brightest fringe varies nonlinearly for small delay distances and stabilizes for longer ones. We have compared the theoretical results to measurements of pulse propagation in air for path-lengths up to 200 m.

Zeitouny, M. G.; Cui, M.; Bhattacharya, N.; Urbach, H. P.; Berg, S. A. van den; Janssen, A. J. E. M. [Technische Universiteit Delft, Lorentzweg 1, 2628 CJ Delft (Netherlands); VSL, Thijsseweg 11, 2629 JA Delft (Netherlands); Technical University Eindhoven, Department EE and EURANDOM, LG-1, P. O. Box 513, 5600 MB Eindhoven (Netherlands)

2010-08-15

294

A comb-drive actuator driven by capacitively-coupled-power.  

PubMed

This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced at the rotor due to the capacitive coupling. Then, an electrostatic force would be exerted onto the rotor due to the voltage differences between the stators and the rotor. The actuator's static displacement and resonant frequency were theoretically analyzed. To verify the design, a comb-drive actuator with different initial finger overlaps, i.e., 159.3 ?m and 48.9 ?m on each side, was fabricated and tested. The results show that the actuator worked well using the proposed actuation mechanism. A static displacement of 41.7 ?m and a resonant frequency of 577 Hz were achieved. Using the actuation mechanism, no electrical connection is required between the rotor and the outside power supply. This makes some comb-drive actuators containing heterogeneous structures easy to design and actuate. PMID:23112635

Chang, Chao-Min; Wang, Shao-Yu; Chen, Rongshun; Yeh, J Andrew; Hou, Max T

2012-08-07

295

Stellar radial velocities using a laser frequency comb: Application and observations in the near infrared  

NASA Astrophysics Data System (ADS)

The laser frequency comb presents the potential for a revolutionary increase in radial velocity precision by providing a calibration reference of unprecedented quality in terms of wavelength knowledge, repeatability, number, density, and regularity of lines. However, implementation has proven challenging, particularly in the near infrared. Nevertheless, with the right combination of comb and instrument, promising first steps have been taken, allowing for the derivation of stellar radial velocities in a wavelength range which is well suited to the observation of M dwarfs. These stars, with low mass and low luminosity, are the most prevalent class of stars within 10 parsecs and can be expected to yield a higher reflex velocity for a terrestrial mass planet in the liquid water habitable zone than would be the case with a more massive star such as our own. We present the design and both laboratory and on-sky performance of an H-band laser frequency comb used in conjunction with the Penn State Pathfinder testbed spectrograph and discuss lessons learned and plans for follow on testing with both the Pathfinder and the CSHELL instruments.

Osterman, Steve

2011-04-01

296

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

297

A Comb-Drive Actuator Driven by Capacitively-Coupled-Power  

PubMed Central

This paper presents a new actuation mechanism to drive comb-drive actuators. An asymmetric configuration of the finger overlap was used to generate capacitive coupling for the actuation mechanism. When the driving voltages were applied on the stators, a voltage would be induced at the rotor due to the capacitive coupling. Then, an electrostatic force would be exerted onto the rotor due to the voltage differences between the stators and the rotor. The actuator's static displacement and resonant frequency were theoretically analyzed. To verify the design, a comb-drive actuator with different initial finger overlaps, i.e., 159.3 ?m and 48.9 ?m on each side, was fabricated and tested. The results show that the actuator worked well using the proposed actuation mechanism. A static displacement of 41.7 ?m and a resonant frequency of 577 Hz were achieved. Using the actuation mechanism, no electrical connection is required between the rotor and the outside power supply. This makes some comb-drive actuators containing heterogeneous structures easy to design and actuate.

Chang, Chao-Min; Wang, Shao-Yu; Chen, Rongshun; Yeh, J. Andrew; Hou, Max T.

2012-01-01

298

The Sex Equity Pamphlet.  

ERIC Educational Resources Information Center

|This report on comic books, designed to overcome sex stereotyping in elementary school children by exposing them to new role models, includes: (1) a discussion of sex-role learning, stereotyped sex-role characteristics, and comic books; (2) summaries of the story lines of three comic books developed to depict new role models; (3) a black and…

Chitayat, Deanna

299

When Sex Is Painful  

MedlinePLUS

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

300

Sex in Tantras  

Microsoft Academic Search

A consideration of the content of the Tantras, a series of Sanskrit sacred writings, shows that the sex motive runs throughout. In the account of the deities and their activities, the creation, and resulting human nature sex is of prime importance, and much sex symbolism can be made out. The sexual libido excited in the conjugal embrace of the deities

K. C. Mukherjee

1926-01-01

301

Integrated Sex Education  

PubMed Central

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

Vandermaas, Alan

1974-01-01

302

Changing Sex Roles.  

ERIC Educational Resources Information Center

This article reviews literature on sex role change in children and points to areas which need further research. Competing ideologies which support or reject sex typing of role behaviors are briefly discussed in the introduction. The sources of sex role change are divided into two categories: (1) planned direct intervention programs and (2) natural…

Worell, Judith

303

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

304

Muslims and Sex Education.  

ERIC Educational Resources Information Center

Examines objections to sex education practices and calls by British Muslim leaders to withdraw Muslim children from sex education classes. Discusses policy makers' dilemmas as they try to reconcile the public interest with diverse beliefs. Considers whether an approach to sex education that is acceptable to all groups is possible. (DSK)

Halstead, J. Mark

1997-01-01

305

Sex Chromosomes and Speciation  

Microsoft Academic Search

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

Eva Jablonka; Marion J. Lamb

1991-01-01

306

Neuroprotection of Sex Steroids  

PubMed Central

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

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

2011-01-01

307

Osho - Insights on sex  

PubMed Central

Sex is a mysterious phenomenon, which has puzzled even great sages. Human beings have researched and mastered the biology of sex. But that is not all. Sex needs to be understood from the spiritual perspective too. The vision of Osho is an enlightening experience in this regard. Out of the thousands of lectures, five lectures on sex made Osho most notorious. Born into a Jain family of Madhya Pradesh, Rajneesh, who later wanted himself to be called Osho, is a great master. He has spoken volumes on a wide range of topics ranging from sex to super-consciousness. His contributions in the area of sex are based on the principles of “Tantra” which has its origin from Buddhism. This article focuses on his life and insights on sex, which if understood properly, can be a stepping stone for enlightenment.

Nagaraj, Anil Kumar Mysore

2013-01-01

308

Osho - Insights on sex.  

PubMed

Sex is a mysterious phenomenon, which has puzzled even great sages. Human beings have researched and mastered the biology of sex. But that is not all. Sex needs to be understood from the spiritual perspective too. The vision of Osho is an enlightening experience in this regard. Out of the thousands of lectures, five lectures on sex made Osho most notorious. Born into a Jain family of Madhya Pradesh, Rajneesh, who later wanted himself to be called Osho, is a great master. He has spoken volumes on a wide range of topics ranging from sex to super-consciousness. His contributions in the area of sex are based on the principles of "Tantra" which has its origin from Buddhism. This article focuses on his life and insights on sex, which if understood properly, can be a stepping stone for enlightenment. PMID:23858266

Nagaraj, Anil Kumar Mysore

2013-01-01

309

Sex education and sex-related behavior.  

PubMed

This editorial reviews 2 studies, the William Marsiglio and Frank Mott study, and the Deborah Dawson study. Both studies examine the relationship of sex education to sexual initiation, contraceptive usage and pregnancy among teenagers. Though the studies lack certain data, both suggest that sex education as it is taught now has little if any effect on the decision of young people to begin sex. Half of teenagers who become sexually active do not take a sex education course before starting intercourse. Dawson finds that young women who have had formal instruction about contraception are more likely to have used a method, and those who have had instruction prior to 1st intercourse are more likely to use effective methods than those who have never taken a course. Both researchers find that having taken a course is the only variable that is a significant predictor of effective contraceptive use. Neither study finds a statistically significant impact of sex education on subsequent premarital pregnancy, although the direction of the findings in both studies is negative, i.e., teenagers who have had sex education are less likely to later become premaritally pregnant. Because of the gross underreporting of abortions in both studies, pregnancies are considerably underestimated. The 2 studies differ in significant ways. 1 analysis is cross-sectional; the other is longitudinal. 1 study asks about "formal instruction" on specific topics in various settings and the other about "a course relating to sex education." The sex education topics identified are overlapping but not identical. Other research than that cited here provides some idea about what kinds of programs and policies make a difference as far as teenage pregnancy is concerned. A study of 37 developed countries has found that a greater openness about sex-related matters in the society is correlated with low levels of teenage pregnancy. If 1 goal of sex education is to prevent unplanned adolescent pregnancies, then it is necessary to evaluate schools that offer programs that have such a stated goal (most do not) and compare them with schools that do have such programs. Marsiglio and Mott maintain that nothing the schools do will "substantially alter teenage sexual behavior...until the American public resolves its ambivalence over what sex education in the schools should and should not do." PMID:3792527

310

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

SciTech Connect

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

McFerran, J. J.

2009-05-10

311

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

312

Cascaded integrator comb filters with smoothly varying coefficients for reduced delay in synchrotron feedback loops  

NASA Astrophysics Data System (ADS)

The Rapid Cycling Synchrotron (RCS) of the J-PARC complex in Tokai, Japan, is designed to accelerate a high intensity proton beam from 181 MeV, and later 400 MeV to 3 GeV in 20 ms within the 40 ms machine cycle. The beam power up to 1 MW demands a stable beam control to avoid excessive losses and activation of the accelerator chain. The fully digital control system is based on quadrature modulation and demodulation. In the amplitude control loops standard FIR filters separate the harmonics (h=2) and (h=4) after down conversion. For the phase loops at (h=2) and (h=4), intended to damp synchrotron oscillations, the delay in a FIR filter would limit the loop stability. Cascaded integrator comb filters, also called CIC filters, provide a shorter delay because they filter the longitudinal beam signal only where it is necessary. The notches are located at multiples of the revolution frequency of the proton beam. For fixed frequency accelerator applications, digital comb filters with fixed clock frequency are widely used to improve loop stability. For variable frequency accelerator applications, as in a proton synchrotron, where the frequency swing is larger than the notch width, usually the clock frequency of the comb filter is variable and chosen to be an integer multiple of the particle revolution frequency. At J-PARC RCS, the clock frequency has to be fixed. Tracking the frequency would require a variable noninteger number of filter taps. Here we present a filter, based on the weighted output of 2 CIC filters with variable length, and one tap difference. The filter function looks like a CIC with smoothly varying coefficients, where the notches follow the revolution frequency of the proton beam. The delay of this filter is approximately half of the corresponding FIR filter, so that the phase loops have a higher stability margin.

Schnase, A.; Nomura, M.; Tamura, F.; Yamamoto, M.; Anami, S.; Ezura, E.; Hara, K.; Ohmori, C.; Takagi, A.; Yoshii, M.

2005-12-01

313

Generation of an astronomical optical frequency comb in three fibre-based nonlinear stages  

NASA Astrophysics Data System (ADS)

The generation of a broadband optical frequency comb with 80 GHz spacing by propagation of a sinusoidal wave through three dispersion-optimized nonlinear stages is numerically investigated. The input power, the dispersion, the nonlinear coefficient, and lengths are optimized for the first two stages for the generation of low-noise ultra-short pulses. The final stage is a low-dispersion highly-nonlinear fibre where the ultra-short pulses undergo self-phase modulation for strong spectral broadening. The modeling is performed using a Generalized Nonlinear Schrodinger Equation incorporating Kerr and Raman nonlinearities, self-steepening, high-order dispersion and gain. In the proposed approach the sinusoidal input field is pre-compressed in the first fibre section. This is shown to be necessary to keep the soliton order below ten to minimize the noise build-up during adiabatic pulse compression, when the pulses are subsequently amplified in the next fibre section (rare-earth-doped-fibre with anomalous dispersion). We demonstrate that there is an optimum balance between dispersion, input power and nonlinearities, in order to have adiabatic pulse compression. It is shown that the intensity noise grows exponentially as the pulses start to be compressed in the amplifying fibre. Eventually, the noise decreases and reaches a minimum when the pulses are maximally compressed. A train of 70 fs pulses with up to 3.45 kW peak power and negligible noise is generated in our simulations, which can be spectrally broadened in a highly-nonlinear fibre. The main drawback of this compression technique is the small fibre length tolerance where noise is negligible (smaller than 10 cm for erbium-doped fibre length of 15 m). We finally investigate how the frequency comb characteristics are modified by incorporating an optical feedback. We show that frequency combs appropriate for calibration of astronomical spectrographs can be improved by using this technique.

Chavez Boggio, J. M.; Rieznik, A. A.; Zajnulina, M.; Böhm, M.; Bodenmüller, D.; Wysmolek, M.; Sayinc, H.; Neumann, Jörg; Kracht, Dietmar; Haynes, R.; Roth, M. M.

2012-05-01

314

Searches for extra-solar Earths with astro-combs, why and how  

NASA Astrophysics Data System (ADS)

Searches for Earth-like extra-solar planets using the precision radial velocity (PRV) technique requires <10 cm/s accuracy on stellar RVs, which is ˜10 times smaller than the current sensitivity, over several years. Astro-combs, a combination of an octave spanning femtosecond laser and a mode-filtering cavity, provide a promising route to increased accuracy and long-term stability on the astrophysical spectrograph calibration. Here I present several techniques to achieve the required calibration accuracy and our calibration results on the TRES spectrograph for a 1.5-m telescope at the Whipple Observatory.

Li, Chih-Hao

2011-04-01

315

Laser frequency combs and ultracold neutrons to probe braneworlds through induced matter swapping between branes  

SciTech Connect

This paper investigates a new experimental framework to test the braneworld hypothesis. Recent theoretical results have shown the possibility of matter exchange between branes under the influence of suitable magnetic vector potentials. It is shown that the required conditions might be achieved with present-day technology. The experiment uses a source of pulsed and coherent electromagnetic radiation and relies on the Haensch frequency comb technique well-known in ultrahigh-precision spectroscopy. A good matter candidate for testing the hypothesis is a polarized ultracold neutron gas for which the number of swapped neutrons is measured.

Sarrazin, Michaeel [Department of Physics, University of Namur (FUNDP), 61 rue de Bruxelles, B-5000 Namur (Belgium); Petit, Fabrice [Belgian Ceramic Research Centre, 4 avenue du gouverneur Cornez, B-7000 Mons (Belgium)

2011-02-01

316

Coherent fiber-based frequency combs and CW lasers at 1550 nm  

NASA Astrophysics Data System (ADS)

Coherent optical sources in the 1550 nm region of the spectrum have a number of applications in frequency metrology, stable frequency transfer, precision spectroscopy and remote sensing. A narrow-linewidth (~ 1 Hz) single-frequency source can be generated by phase-locking a cw fiber laser to a stable optical cavity. A comb of such narrow linewidth sources can be generated by phase-locking a mode-locked, femtosecond fiber laser to a single narrow cw source. We will discuss the current development of our narrow linewidth cw and pulsed sources at 1550 nm and some of the applications that can benefit from such coherent sources.

Newbury, N. R.; Swann, W. C.; Coddington, I.; Williams, P. A.

2007-10-01

317

Modelocking and femtosecond pulse generation in chip-based frequency combs.  

PubMed

We investigate simultaneously the temporal and optical and radio-frequency spectral properties of parametric frequency combs generated in silicon-nitride microresonators and observe that the system undergoes a transition to a mode-locked state. We demonstrate the generation of sub-200-fs pulses at a repetition rate of 99 GHz. Our calculations show that pulse generation in this system is consistent with soliton modelocking. Ultimately, such parametric devices offer the potential of producing ultra-short laser pulses from the visible to mid-infrared regime at repetition rates from GHz to THz. PMID:23389027

Saha, Kasturi; Okawachi, Yoshitomo; Shim, Bonggu; Levy, Jacob S; Salem, Reza; Johnson, Adrea R; Foster, Mark A; Lamont, Michael R E; Lipson, Michal; Gaeta, Alexander L

2013-01-14

318

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

319

The development of fracture sets in folded sedimentary rocks at Raplee Ridge and Comb Ridge, UT  

NASA Astrophysics Data System (ADS)

Fractures at Raplee Ridge, a 14 km-long, monoclinal fold of Pennsylvanian sedimentary rock in southeast Utah, have been examined to determine their sequential development and to explain the mechanical relationships among the three primary fracture sets and this fold. Slip on an unexposed thrust fault, during the Laramide orogeny, is suggested as the mechanism for development of this fold on the Monument Upwarp. Fracture orientations were measured and mapped within the Rico Formation, revealing three main stages of fracture formation. Stages 1 and 2 occurred pre-folding and are defined, respectively, by E-W trending fracture Set I and N-S trending fracture Set II. Set I fractures are characterized by a unimodal distribution of measured attitudes, an intermediately-developed map pattern, and continuous, linear traces on bedding surfaces. Set II fractures have a greater dispersion of orientations and are poorly- to intermediately-developed. Abutting relationships confirm that Set I fractures are older than Set II. Stage 3 occurred during folding when NW-SE trending Set III fractures initiated both from isolated flaws and as wing-cracks due to right-lateral shearing along reactivated Set I fractures. Fracture Sets I and II are found throughout the surrounding Monument Upwarp and are attributed to the stresses that formed this uplifted structure, whereas Set III fracture formation is attributed to local stresses induced by monoclinal folding and/or thrusting on the underlying fault. Current research on the three main fracture sets at Raplee Ridge and the main fracture sets within the neighboring Comb Ridge to the east is focused on determining their burial and exhumation history and on investigating the subsurface fluids that used the interconnected fracture networks as conduits. Comb Ridge is a monocline that is ~150 km in length and bounds the eastern edge of the Monument Upwarp. The portion of Comb Ridge adjacent to Raplee Ridge is most significant due to its proximity and the near-parallel orientation of its fold axis to Raplee. Core samples of fractures have been collected from limestone and siltstone rock units along each ridge and from one volcanic dike in Comb Ridge. Thirty-one samples represent several fracture geometries of each systematic fracture set. Fracture geometries include single, linear fractures, fracture tips, abutment relationships, overlapping fractures, shear fractures, local shear zones, splay fractures, splay initiation and termination points, and a minor thrust fault. The data gathered from petrologic analysis of thin sections and geochemical analysis of fracture fill material will be described to elucidate the relative timing and depth of burial of fracturing.

Seyum, S.; Mynatt, I.; Pollard, D. D.

2009-12-01

320

Cationic comb-type copolymers for boosting DNA-fueled nanomachines.  

PubMed

For the better applications and developments of DNA nanomachines, their responding kinetics, output, and sequence-selectivity need to be improved. Furthermore, the DNA nanomachines currently have several limitations in operating conditions. Here we show that a simple addition of a cationic comb-type copolymer, poly(l-lysine)-graft-dextran, produces the robust and quick responses of DNA nanomachines under moderate conditions including physiologically relevant conditions even at very low strand concentrations (nanomoles per liter range) through hybrid stabilization and DNA strand exchange acceleration. PMID:17212459

Choi, Sung Won; Makita, Naoki; Inoue, Satoru; Lesoil, Charles; Yamayoshi, Asako; Kano, Arihiro; Akaike, Toshihiro; Maruyama, Atsushi

2007-01-01

321

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

PubMed

We experimentally demonstrate that a femtosecond frequency comb laser can be applied as a tool for long-distance measurement in air. Our method is based on the measurement of cross correlation between individual pulses in a Michelson interferometer. From the position of the correlation functions, distances of up to 50 m have been measured. We have compared this measurement to a counting laser interferometer, showing an agreement with the measured distance within 2 microm (4x10(-8) at 50 m). PMID:19571973

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

2009-07-01

322

Diffraction of electromagnetic waves by a thick dielectric comb and a grating made of rectangular bars  

NASA Astrophysics Data System (ADS)

Dispersion formulas and formulas analogous to Fresnel formulas are obtained for arbitrary angles of incidence of E- and H-polarized electromagnetic waves on a thick dielectric comb and a rectangular-bar grating. It is shown that wave transmission through such structures has a dual character: resonant and nonresonant (the Maliuzhints effect). Conditions are determined for the existence of these phenomena depending on the geometry of the structures and the incident-wave polarization. A numerical analysis of the reflection coefficients and the angles of total nonresonant transmission was performed.

Borovskii, I. V.; Khizhniak, N. A.

323

Reclassification of Actinomyces humiferus (Gledhill and Casida) as Cellulomonas humilata nom. corrig., comb. nov.  

PubMed

The placement of Actinomyces humiferus within the genus Actinomyces has always been controversial. A humiferus differs from typical members of the genus both phenotypically and in possessing a relatively high DNA G + C content. Comparative 16S rRNA gene sequencing has shown that A. humiferus is related only distantly to other species of the genus Actinomyces and is, in fact, a member of the genus Cellulomonas. On the basis of phylogenetic evidence, it is proposed that A. humiferus be reclassified in the genus Cellulomonas as Cellulomonas humilata nom. corrig., comb. nov. PMID:10758873

Collins, M D; Pascual, C

2000-03-01

324

Quantum Dot Optical Frequency Comb Laser with Mode-Selection Technique for 1-?m Waveband Photonic Transport System  

NASA Astrophysics Data System (ADS)

An optical frequency comb was generated from a single quantum dot laser diode (QD-LD) in the 1-?m waveband using an Sb-irradiated InGaAs/GaAs QD active medium. A single-mode-selection technique and interference injection-seeding technique are proposed for selecting the optical mode of a QD optical frequency comb laser (QD-CML). In the 1-?m waveband, a wavelength-tunable single-mode light source and a multiple-wavelength generator of a comb with 100-GHz spacing and ultrafine teeth are successfully demonstrated by applying the optical-mode-selection techniques to the QD-CML. Additionally, by applying the single-mode-selection technique to the QD-CML, a 10-Gbps clear eye opening for multiple-wavelengths in 1-?m waveband photonic transport over a 1.5-km-long holey fiber is obtained.

Naokatsu Yamamoto,; Kouichi Akahane,; Tetsuya Kawanishi,; Redouane Katouf,; Hideyuki Sotobayashi,

2010-04-01

325

Absolute molecular density determinations by direct referencing of a quantum cascade laser to an optical frequency comb  

NASA Astrophysics Data System (ADS)

We propose a new approach to chemical gas analysis in the gas phase by direct referencing of a quantum cascade laser (QCL) to a near-infrared optical frequency comb. The concept was demonstrated through measurements of CO2 molecular densities, reaching a precision of 0.2 %. Thanks to the robust phase lock of the QCL to the comb, absorption profiles could be recorded with high accuracy and repeatability by tuning the repetition rate of the comb. Such a scheme gave us the opportunity to test a variety of semiclassical line-shape models, accounting for both Dicke narrowing and speed-dependent effects. The success of the speed-dependent Nelkin-Ghatak model, with a hypergeometric dependence of the pressure broadening coefficient on the absorber speed, was demonstrated. Finally, the dependence of molecular density determinations on the choice of the line-shape model was investigated, thus demonstrating the inadequacy of the Voigt profile.

Castrillo, A.; Gambetta, A.; Gatti, D.; Galzerano, G.; Laporta, P.; Marangoni, M.; Gianfrani, L.

2013-02-01

326

Mid-infrared supercontinuum generation in tapered chalcogenide fiber for producing octave-spanning frequency comb around 3 ?m.  

PubMed

We demonstrate mid-infrared (mid-IR) supercontinuum generation (SCG) with instantaneous bandwidth from 2.2 to 5 ?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 As(2)S(3) 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. PMID:23187184

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

2012-10-22

327

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

328

High-power, hybrid Er:fiber/Tm:fiber frequency comb source in the 2 ?m wavelength region.  

PubMed

We present a 2 ?m frequency comb based on a reliable mode-locked Er:fiber laser with 100 MHz repetition rate. After shifting the spectrum of the amplified Er:fiber comb to longer wavelengths, a single-clad Tm/Ho:fiber is used as a self-pumped pre-amplifier to generate a coherent and broadband spectrum centered at 1.93 ?m. Subsequently, a cladding-pumped Tm:fiber amplifier boosts the system to a maximum output power of 4.8 W at 1.96 ?m. After compression in a compact grating compressor, our amplified Er:fiber/Tm:fiber hybrid system delivers as much as 2.9 W with a pulse duration of 141 fs. The system's comb properties are examined via heterodyne measurement. PMID:22555684

Adler, Florian; Diddams, Scott A

2012-05-01

329

SEX-RATIO EVOLUTION IN SEX CHANGING ANIMALS  

Microsoft Academic Search

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

David J. Allsop; Stuart A. West

2004-01-01

330

Sex: Making the Right Decision  

MedlinePLUS

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

331

MECHANISMS FOR BRAIN SEX DIFFERENTIATION  

Microsoft Academic Search

Distinctive sex differences in reproductive behavior and physiology have been attributed not to differences in hormones ~onad secretes in each sex but differences in particuhr brain structures. Interestingly enough. brain sex difference is determined mostly by gonadal hormones during ontogeny independent of genetic sex. In many laboratory mammals. brain sex can be manipulated at a particular stage of omogeny called

Yasuo Sakuma

2007-01-01

332

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

333

Attitudes Towards Premarital Sex  

NSDL National Science Digital Library

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

Dietz, Tracy

334

Sex Discrimination in Education.  

ERIC Educational Resources Information Center

|Presents findings of an examination of the representation of the sexes in an elementary level language textbook used in China. Indicates a lopsided emphasis on males and a tendency to portray women as subordinates. Identifies differences in personal characteristics ascribed to the sexes. Seeks to highlight the issue for the purpose of improving…

Nan, Ning

1992-01-01

335

Cytological Sexing of Cetacea.  

National Technical Information Service (NTIS)

A biopsy dart, that can be shot from a gun or crossbow, was developed to obtain skin samples of whales at sea. Determination of sex was found possible by staining and locating sex chromatin bodies in the nuclei of female skin cells. This procedure will be...

H. E. Winn W. L. Bischoff A. G. Taruski

1973-01-01

336

Sex: Who Cares? Introduction.  

ERIC Educational Resources Information Center

Presents evidence supporting claim that sex and gender are important to the explanatory as well as the descriptive goals of developmental psychology. Maintains that studying psychosocial and biological components of gender and sex helps one to develop hypotheses about causal mechanisms for developmental outcomes more generally. Introduces the…

Liben, Lynn S.

2000-01-01

337

Sex and Heart Disease  

MedlinePLUS

Sex and Heart Disease Updated:Mar 2,2012 Is sex safe for heart disease patients? Readjusting to everyday life can be tough for heart disease patients. You wonder about everything: Should I eat this food? Can I do that activity? ...

338

Age and Sex  

Microsoft Academic Search

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

Dudley L. Poston

339

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

340

SEX DETERMINATION, SEX RATIOS, AND GENETIC CONFLICT  

Microsoft Academic Search

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

John H. Werren; Leo W. Beukeboom

1998-01-01

341

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.

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

2012-01-01

342

Argentophilic structures of the miracidia and cercariae of Philophthalmus distomatosa n. comb. from Israel.  

PubMed

The morphology and patterns of distribution of the argentophilic structures of miracidia and cercariae of Philophthalmus distomatosa n. comb. are described. The epidermal plate arrangement of the vast majority (94.2%) of miracidia studied conformed to the formula 6:8:4:2 = 20. The rest (5.8%) displayed the following patterns of arrangement of epidermal plates: 6:7:4:2 = 19; 6:6:4:2 = 18; and 6:4:4:2 = 16. Twenty papillalike structures were observed on the terebratorium. They were arranged along 1 axis, in 3 groups. Most commonly, 16 papillae were present on the body, located between epidermal plates of the first and second rows. The eye spots were located dorsally, near interepidermal space S1. The numbers, arrangements, and locations of the excretory pores varied. Patterns of distribution of the tegumentary papillae of P. distomatosa n. comb. cercariae are given, including those of the cephalic regions, periacetabular region, and tail. Argentophilic structures of the mentioned larval stages and of other parameters clearly distinguishing between the presently described species and those of P. lucipetus from Israel are summarized. On the basis of comparison of the presently described larval stages and those of other Melanoides tuberculata-associated larval stages of Philophthalmus in Israel and Jordan, the possibility exists that a third species occurs in Israel. PMID:11191898

Dimitrov, V; Kanev, I; Panaiotova, M; Radev, V; Gold, D

2000-12-01

343

Coherent control of neutral atoms on chip traps using optical frequency combs  

NASA Astrophysics Data System (ADS)

Optical frequency combs (OFCs), emitted by ultrafast modelocked pulsed lasers, are excellent tools to perform quantum coherent control. The spectral purity, large bandwidth and high pulse powers makes these sources attractive for precision control of multi-level atoms. Recent experiments have shown that an OFC can be used to coherently control and entangle trapped ion qubits by means of off-resonant Raman transitions [1]. Here, we propose to extend this technique to neutral atoms confined on an atom chip and we also propose to implement an all-optical technique for hyperfine qubit manipulation using OFCs. We envisage using pairs of OFC modes to drive stimulated Raman transitions between the two hyperfine clock states of 87Rb confined on an atom chip. The Raman transitions will be driven using a four photon technique whereby the first photon pair drives off-resonantly to the intermediate state 2S1/2 |F=2, mf=0> and then a second photon pair resonantly drives to 2S1/2 |F=2, mf=+1>. Co-propagating Raman fields impart only a spin flip whereas non-copropagating fields transfer two photon recoil momentum to the atoms, thus entangling the internal spin with the external motion of the atoms. We plan on using the frequency comb to impart state dependent forces to the atomic cloud.

Quraishi, Qudsia; Malinovsky, Vladimir; Alexander, Jason; Prieto, Violeta; Rowlett, Chris; Lee, Patricia

2011-06-01

344

Hardware comb filter enhances dynamic range and noise performance of sensors in noisy environments.  

PubMed

We present the results of combining a hardware implementation of an analog comb filter with an ultralow noise electromagnetic sensor. The comb filter is designed to attenuate mains related interference, at either 50 or 60 Hz, and related harmonics. The sensor chosen for this work is an induction magnetometer, but the method is applicable to any low noise high dynamic range sensor. The resultant system, in this case, uses only a single coil, not a gradiometric configuration, thus providing a magnetometer capable of sensing field as opposed to field gradient. This combination of filter and sensor allows additional gain to be added and the full sensitivity of the system to be achieved, previously only realized in an electromagnetically screened room. At the same time, the high dynamic range, low noise performance, and original bandwidth of the sensor are maintained. The technique is illustrated by using the system in an urban environment to observe Schumann resonance phenomena. This approach to acquiring small signals in a noisy environment is compared with conventional analog filter and digital signal processing techniques. PMID:17672781

Prance, H; Prance, R J; Stiffell, P B

2007-07-01

345

An Electron Cyclotron Resonance Ion Source with Cylindrically Comb-Shaped Magnetic Field Configuration  

SciTech Connect

A new concept on magnetic field of plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. The magnetic field configuration is constructed by a pair of comb-shaped magnet which has opposite polarity each other, and which cylindrically surrounds the plasma chamber. This magnetic configuration suppresses the loss due to ExB drift, and then plasma confinement is enhanced. The resonance zones of the fundamental and the second harmonics for 2.45GHz microwaves detach from the wall of the chamber. The connection length of the magnetic field lines through the resonance zone is elongated, and the confinement is better than that of the simple multipole magnetic field. The 2.45 GHz microwaves are fed from the side wall by the rod antenna. The electron density attained to about four times cutoff density for the 2.45GHz microwave at the low Ar pressure below 0.08Pa and also the low microwave power below 300W. We compare profiles of the electron density and temperature in the comb-shaped magnetic field configuration with those in the simple multipole magnetic field.

Kato, Yushi; Sasaki, Hiroshi; Kubo, Takashi; Sato, Fuminobu; Iida, Toshiyuki [Devision of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka Univ., 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan); Asaji, Toyohisa [Devision of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka Univ., 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan); Tateyama Machine Co., Ltd., 30 Shimonoban, Toyama 930-1305 (Japan)

2006-11-13

346

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

347

Multiheterodyne interference spectroscopy using a probing optical frequency comb and a reference single-frequency laser  

NASA Astrophysics Data System (ADS)

We discuss multiheterodyne interference between the laser beams of optical frequency-comb (FC) and single-frequency (SF) lasers. The beat signal generated by the interference contains a dc component, discrete-frequency elements with the same frequency interval generated by interference between the two elements of the FC laser, and elements generated by the interference between the FC and the SF lasers. The beat-signal elements between them can be used for absorption spectroscopy around the SF-laser frequency, which is called frequency-comb interference spectroscopy (FCIS). In this paper, we compare the beat-signal spectrum predicted through theoretical descriptions of multiheterodyne interference with experimental results to improve understanding of FCIS and similar techniques. Our FCIS experiments use a probing Ti:sapphire mode-locked laser, which is the beam experiencing absorption, and a reference diode laser. We also discuss the potential of this method to measure the small shift in absorption profiles using the measurement results of argon metastable atoms.

Urabe, Keiichiro; Sakai, Osamu

2013-08-01

348

A convenient way to synthesize comb-shaped chitosan-graft-poly (N-isopropylacrylamide) copolymer.  

PubMed

Comb-shaped copolymers comprised of hydrophobic and hydrophilic blocks are self-assembled in aqueous solution, which results that they are suitable for delivery of hydrophobic drug molecules. Chitosan (CS) is an important biomaterial used widely in medical applications. Herein, a comb-shaped cationic copolymer composed of long biocompatible CS main chains and short PNIPAAm side chains was prepared via atom transfer radical polymerization (ATRP) by attaching an ATRP initiating group to N-phthaloyl chitosan. By subsequent removal of the protective groups on N-phthaloyl chitosan-graft-poly(N-isopropylacrylamide) (PHCS-g-PNIPAAm) copolymer with N(2)H(4)·H(2)O lead to the polymer pendant amino groups, this study attempted to synthesize a pH/temperature multi-responsive material. This chitosan-graft-poly(N-isopropylacrylamide) (CS-g-PNIPAAm) copolymer is self-assembled in aqueous solution into stimuli-responsive core-shell micelles with hydrodynamic diameters of about 170 nm. Structural organization and solution behavior were then investigated utilizing (1)H NMR spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). PMID:23218344

Chen, Chen; Liu, Mingzhu; Gao, Chunmei; Lü, Shaoyu; Chen, Jiucun; Yu, Xiyong; Ding, Enyong; Yu, Chuanming; Guo, Jing; Cui, Guijia

2012-09-17

349

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

350

Absolute distance measurement by dual-comb interferometry with adjustable synthetic wavelength  

NASA Astrophysics Data System (ADS)

Absolute distances were measured using two femtosecond lasers of different pulse repetition rates by revisiting the dual-comb interferometric method proposed by Coddington et al (2009 Nature Photon. 3 351-6). The apparatus built for experiments was designed to eliminate the dead zones in the measurement range by separating the measurement pulses from the reference pulses using orthogonal polarization. In addition, the pulse repetition rate of the signal laser was made tunable in order to extend the non-ambiguity range (NAR) by adaptively adjusting the synthetic wavelength in consideration of the de facto measurement stability in the air. Actual tests performed in the open air proved that a target distance of 69.3 m is measured without interruptions at a 200 µs update rate in the presence of a ˜170 µm drift of the optical path length caused by the fluctuation of the refractive index of air. The proposed hardware system design for effective NAR extension will facilitate the use of dual-comb interferometry for various terrestrial applications.

Lee, Joohyung; Han, Seongheum; Lee, Keunwoo; Bae, Eundeok; Kim, Seungman; Lee, Sanghyun; Kim, Seung-Woo; Kim, Young-Jin

2013-04-01

351

Hardware comb filter enhances dynamic range and noise performance of sensors in noisy environments  

NASA Astrophysics Data System (ADS)

We present the results of combining a hardware implementation of an analog comb filter with an ultralow noise electromagnetic sensor. The comb filter is designed to attenuate mains related interference, at either 50 or 60 Hz, and related harmonics. The sensor chosen for this work is an induction magnetometer, but the method is applicable to any low noise high dynamic range sensor. The resultant system, in this case, uses only a single coil, not a gradiometric configuration, thus providing a magnetometer capable of sensing field as opposed to field gradient. This combination of filter and sensor allows additional gain to be added and the full sensitivity of the system to be achieved, previously only realized in an electromagnetically screened room. At the same time, the high dynamic range, low noise performance, and original bandwidth of the sensor are maintained. The technique is illustrated by using the system in an urban environment to observe Schumann resonance phenomena. This approach to acquiring small signals in a noisy environment is compared with conventional analog filter and digital signal processing techniques.

Prance, H.; Prance, R. J.; Stiffell, P. B.

2007-07-01

352

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

353

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

354

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

355

Sex education in Portugal.  

PubMed

The article on sex education in Portugal covers background, the educational system, the clashes of the 1960's over sex education, the Committee for the Study of Sexuality and Education (CSSE), the policies, politics and social movements during the period 1974 - 1984, the discussions in Parliament, the 1988 Reform of the Educational System, the Family Planning Association (FPA) and sex education, and the future role of the FPA. It was not until the institution of the multiparity parliamentary system in 1974 that discussing social and political changes was possible, culminating in 1984 with new legislation on abortion, family planning, and sex education. School reform came in 1987/8 with the Ministry of Education primarily responsible for curricula. The 1960's brought with it the influence of the Catholic Church. Change came in the form of progressivism among Catholics who replaced dogma with dialogue and listening. Sex education was considered as preparation for marriage, but masturbation, contraception, and prostitution were also discussed. In addition, the founder of FPA chaired the CSSE in 1971 and opened up debate on sex issues and drafted a bill to establish co-education in Portuguese schools. The revolution of 1974 brought an end to censorship and brought forth a policy of developing family planning. Changed in the Family Code gave women greater equality. UNFPA supported teacher training in non-sexist education. With human reproduction included in the natural sciences, there was still no school sex education policy and contraception was only sometimes represented in the biology curriculum. The focus of FPA was on contraception and abortion. Finally in the 1980's, the first sex education programs were developed for out-of-school youth. Even though in the 1970's there were leftists groups promoting sex education, it took leftist parliamentary power to get legislation on sex education in the schools adopted. The Ministry of Education however was pressured by the Catholic Church. As in 1973, committees were formed but no action was taken. Sex education activity increased nonetheless - the first FPA document on school education prepared. In 1986 Personal and Social Education was approved by parliament providing an alternative (due to the Catholic Church) to Religious Education, but even with FPA support documents, the implementation did not begin until the end of 1990. In brief the FPA's emphasis was on the body, sexuality, sex and interpersonal relationships, and sexual reproduction. The role of FPA continues at the grass roots level in stimulating discussion; cooperating with schools, students and parents; and acting as a resource center. PMID:12343180

Frade, A; Vilar, D

1991-05-01

356

Short temporal coherence digital holography with a femtosecond frequency comb laser for multi-level optical sectioning.  

PubMed

In this paper, we demonstrate how short temporal coherence digital holography with a femtosecond frequency comb laser source may be used for multi-level optical sectioning. The object shape is obtained by digitally reconstructing and processing a sequence of holograms recorded during stepwise shifting of a mirror in the reference arm. Experimental results are presented. PMID:22453405

Körner, Klaus; Pedrini, Giancarlo; Alexeenko, Igor; Steinmetz, Tilo; Holzwarth, R; Osten, W

2012-03-26

357

Optical frequency comb using polarization maintaining Er-doped ultrashort pulse fiber laser with carbon-nanotube polyimide film  

Microsoft Academic Search

Fiber based optical frequency comb was developed using polarization maintaining Er- doped ultrashort pulse fiber laser using polyimide film dispersed with single wall carbon nanotube. fceo was stable and locked with EO modulator and LD driver. ?2011 Optical Society of America OCIS codes: (060.2320) Fiber optics amplifiers and oscillators, (320.7140) Ultrafast processes in fibers.

Norihiko Nishizawa; Youichi Sakakibara; Emiko Itoga; Hiromichi Kataura

2011-01-01

358

DISINFECTION WITH METHYL BROMIDE OF EXPERIMENTALLY OR NATURALLY INFECTED COMBS WITE THE PATHOGENIC GERMS OF AMERICAN AND EUROPEAN FOULBROOD  

Microsoft Academic Search

Lately, the method of disinfections of combs as well as of other bee equipment and things by means of gases has gained preference, as gases penetrate quickly, evaporate easily and do not change the quality of the material. The disinfections with gases do es not require great expenses and special efforts, as gases spread easily. That is why, among the

S. S. NAZAROV

359

Generation of combs of wavelengths in the infrared and visible using cascaded stimulated Raman scattering in potassium titanyl phosphate  

Microsoft Academic Search

We report the generation of a comb of emission wavelengths in the near-infrared, and wavelength-tunable emission at up to five discrete wavelengths in the visible between 534 nm and 572 nm by making use of cascaded stimulated Raman scattering in potassium titnyl phosphate in combination with Nd:GdVO4 and Nd:YLF laser crystals.

Andrew. J. Lee; Jonas Jakutis-Neto; Helen. M. Pask

2011-01-01

360

ROTORDYNAMIC COEFFICIENTS OF LABSEALS FOR TURBINES - COMPARING CFD RESULTS WITH EXPERIMENTAL DATA ON A COMB-GROOVED LABYRINTH  

Microsoft Academic Search

The main goal of this paper is to improve identification methods for rotordynamic coefficients of labseals for turbines. This aim was achieved in joint effort of the Technische Universität München, working on experimental identification methods for rotordynamic coefficients, the University of Technology, Darmstadt, working on prediction methods, and Siemens AG, realizing the results. The paper focuses on a short comb-grooved

Joachim Schettel; Klaus Kwanka; Bernd Lüneburg; Rainer Nordmann

361

Doing Gender in Sex and Sex Research  

Microsoft Academic Search

Gender is central to sexuality, and vice versa, but there are a number of difficulties with the treatment of gender in sex\\u000a research. Apparently, it is hard to find a balance between two conflicting needs. First, obviously, it is necessary to make\\u000a distinctions between women and men, for political as well as research-technical and theoretical reasons. A second requirement,\\u000a at

Ine Vanwesenbeeck

2009-01-01

362

Non-fisherian sex ratios with sex change and environmental sex determination  

Microsoft Academic Search

FISHER'S theory of sex-ratio evolution1 explains why 1:1 sex ratios are so prevalent2-8. Recent work has therefore emphasized situations in which biased sex ratios tend to evolve (for example, local mate competition7, non-mendelian inheritance of sex-ratio factors7,9,10, haplodiploid social insects11,12 and others6,13). In species where individuals change sex during their adult lifetimes, and in species where sex is determined by

Eric L. Charnov; J. J. Bull

1989-01-01

363

Developing Stabilized Lasers, Measuring their Frequencies, demoting the Metre, inventing the Comb, and further consequences  

NASA Astrophysics Data System (ADS)

Michelson's 1907 proposal to define the SI Metre in terms of an optical wavelength was realized only in 1960, based on a ^86Krypton discharge lamp. The same year saw the cw HeNe laser arrive and a future redefinition based on laser technology assured. Separation in the late 60's of the laser's gain and spectral-reference-gas functions led to unprecedented levels of laser frequency stability and reproducibility. In addition to HeNe:CH4 system at 3392 nm and HeNe:I2 at 633 nm, systems at 514 nm and 10600 nm were studied. Absolute frequency measurement became the holy grail and some NBS team experiences will be shared. We measured both frequency and wavelength in 1972, and so obtained a speed of light value, improved 100-fold in accuracy. During the next decade, the NBS value of c was confirmed by other national labs, and frequency metrology was extended to the 473 THz (633 nm) Iodine-based wavelength standard. This frequency to ˜10 digit accuracy was obtained in 1983, thus setting the stage for redefining the SI Metre. By consensus choice the value 299 792 458 m/s was adopted for the speed of light, effectively reducing the Metre to a derived SI quantity. Knowledge of the frequency of the particular laser being utilized was controlled by International intercomparisons, but the need for a fast and accurate means to make these laser frequency measurements was obvious. Creative proposals by H"ansch and by Chebotayev were to use ultra-fast repetitive pulses to create an ``Optical Comb,'' but it was years before any technical basis existed to implement their Fourier dreams. Finally, in 1999 the last needed capability was demonstrated -- continuum production at 100 MHz rates and non-destructive power levels. By May 2000 phase-locked combs were operational in both Garching and Boulder, substantially accelerated by their collaborative interactions. Within 18 months all the known proposed ``optical frequency standards'' had been accurately measured via Comb techniques. )

Hall, John L.

2010-02-01

364

Cross-Sex Friendship  

ERIC Educational Resources Information Center

|Interview data from 800 middle-aged and elderly urban residents reveal that while only a minority report cross-sex friends, they constitute a significant segment of the interpersonal resources of a number of adults. (Author)|

Booth, Alan; Hess, Elaine

1974-01-01

365

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

366

Sex Allocation and Sex Determination in Squamate Reptiles  

Microsoft Academic Search

Reptiles possess a wide variety of sex determining mechanisms, more so than any other vertebrate group. They offer outstanding opportunities to understand the evolutionary transitions between modes of sex determination. In this review, we argue that sex allocation theory is fundamental for understanding the selective causes of such shifts. Whether selection for biased sex allocation actually results in evolutionary shifts

E. Wapstra; D. A. Warner

2010-01-01

367

Sex, Gender and Vulnerability  

Microsoft Academic Search

ABSTRACT This paper is concerned with how sex chromosomes,and gendered experience differentially contribute to health outcomes, and how gender effects provide an under- explored avenue for health intervention. Research on gender and health is currently undermined,by conflation of sex and gender in much,of the epidemiologic and clinical literature. This precludes any meaningful reflection on the extent to which our genetic

Rachel C. Snow

2007-01-01

368

Sex Preselection in Mammals  

Microsoft Academic Search

Since a long time, sex preselection has been a goal of the dairy and meat industry to increase the rate of response to selection,\\u000a to reduce the cost of progeny testing for elite males and to produce desired specialized and genetically superior offsprings.\\u000a Over the past 10 years, the technology has been further developed and proven effective for sex preselection

R. Renaville; V. Haezebroeck; I. Parmentier; M. Pirard; S. Fontaine; D. Portetelle

369

Frequency-stabilized 1 W optical comb at 2.2-2.6 ?m by Cr2+:ZnSe multipass amplification.  

PubMed

We present a frequency comb source with power level up to 150 ?W per comb mode, tunable in the 2.2-2.6 ?m wavelength region, based on a Cr(2+):ZnSe multipass solid-state amplifier seeded by the output of an actively stabilized optical parametric oscillator, synchronously pumped by a commercial 250 MHz Er:fiber laser. Phase relationship between idler, signal, and pump waves is exploited to perform frequency comb stabilization in the whole 2.2-2.6 ?m mid-infrared spectral region. PMID:23114322

Coluccelli, Nicola; Gambetta, Alessio; Sala, Tommaso; Gatti, Davide; Marangoni, Marco; Laporta, Paolo; Galzerano, Gianluca

2012-11-01

370

A New Matrix Formulation for One-Dimensional Scattering in Dirac Comb (Electromagnetic Waves Approach)  

NASA Astrophysics Data System (ADS)

A formulation of the reflection and transmission of electromagnetic waves by a stratified planer structure is demonstrated. This formula uses the so-called elementary symmetric functions that are extensively used in the mathematical theory of polynomials. The reflection and transmission coefficients of any number of quantum wells or barriers can be written in a similar way. Finally, one-dimensional scattering from a series of delta-function barriers (a system that is called Dirac Comb) is investigated. An excellent agreement has been found with the earlier results based on other approaches. This approach is also shown to be a powerful technique and can be easily used for analyzing various complicated mesoscopic structures and devices.

Shabat, M. M.; Taya, Sofyan A.

371

Direct frequency comb generation from an octave-spanning, prismless Ti:sapphire laser.  

PubMed

We describe a self-referenced optical frequency comb generator based on an octave-spanning, prismless Ti:sapphire laser. Dispersion compensation is provided by novel double-chirped mirror pairs and BaF2 wedges. Current versions operate at 80 and 150 MHz. The compact prismless design allows system scaling to a gigahertz repetition rate. Its carrier-envelope beat note is intrinsically stable with a signal-to-noise ratio of 30 dB in a 100-kHz bandwidth. The octave is reached at 25 dB below the average power level. The in-loop accumulated phase error is 1.4 rad (20 mHz to 1 MHz). The technique has the advantages of simplicity and stability compared with previous designs. PMID:15309859

Matos, L; Kleppner, D; Kuzucu, O; Schibli, T R; Kim, J; Ippen, E P; Kaertner, F X

2004-07-15

372

Coherent storage of temporally multimode light using a spin-wave atomic frequency comb memory  

NASA Astrophysics Data System (ADS)

We report on the coherent and multi-temporal mode storage of light using the full atomic frequency comb memory scheme. The scheme involves the transfer of optical atomic excitations in Pr3+:Y2SiO5 to spin waves in hyperfine levels using strong single-frequency transfer pulses. Using this scheme, a total of five temporal modes are stored and recalled on-demand from the memory. The coherence of the storage and retrieval is characterized using a time-bin interference measurement resulting in visibilities higher than 80%, independent of the storage time. This coherent and multimode spin-wave memory is promising as a quantum memory for light.

Gündo?an, M.; Mazzera, M.; Ledingham, P. M.; Cristiani, M.; de Riedmatten, H.

2013-04-01

373

Microwave synthesis from a continuous-wave terahertz oscillator using a photocarrier terahertz frequency comb.  

PubMed

We report low-noise microwave synthesis from radiation with a frequency of 0.3 THz using a photocarrier frequency comb in a photoconductive antenna. The synthesized microwave signal at 1 GHz is phase coherent to the 0.3 THz radiation and has a fractional instability of 1×10-15 within 300 s averaging times and single-sideband phase noise of -105??dB/Hz at a 100 Hz offset from the carrier. This terahertz (THz)-to-microwave synthesizer is capable of being a THz frequency divider, which would be indispensable to not only THz metrology but also future high-speed wireless networks. PMID:23939002

Nagano, Shigeo; Ito, Hiroyuki; Kumagai, Motohiro; Kajita, Masatoshi; Hanado, Yuko

2013-06-15

374

Optical Frequency Comb Refernced Sub-Doppler Resolution Difference-Frequency Infrared Spectrometer  

NASA Astrophysics Data System (ADS)

We have determined absolute frequencies of 56 transition of the ?_3 band of 12CH_4 and 13CH_4 with at a typical uncertainty level of 2 kHz. While the frequency of the difference-frequency-generation (DFG) source is stabilized to the Lamb dip of the methane transition, the frequencies of the pump and signal source are measured with a 1.5-?m optical frequency comb (OFC). The determined value is consistent with the International Committee for Weight and Measures recommendation within the uncertainty. We have also developed OFC-referenced frequency sweep, which allow us to accumulate spectral data for long time without any frequency drift and to determine the frequency of the transition which are too weak to use the frequency reference for the frequency stabilization.

Iwakuni, K.; Okubo, S.; Nakayama, H.; Sasada, H.; Inaba, H.

2012-06-01

375

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

376

Second-order all-fiber comb filter based on polarization-diversity loop configuration.  

PubMed

By concatenating three birefringence loops in series, a second-order all-fiber comb filter based on a polarization-diversity loop configuration is newly proposed. The proposed filter consists of one polarization beam splitter, polarization-maintaining fibers, and two halfwave plates. The effect of a second-order structure of polarization-maintaining fiber loops on a bandwidth of the filter passband was theoretically analyzed and experimentally demonstrated. Transmission output of the second-order filter (flat-top and narrow-band transmission spectra) could be obtained by adjusting two half-wave plates. 1 and 3 dB bandwidths of the proposed filter in flat-top and narrow-band operations were greater by approximately 102.9 and 44.3 % and smaller by approximately 47.9 and 47.1 % than those of a conventional Sagnac birefringence filter, respectively. PMID:18542484

Lee, Yong Wook; Kim, Hyun-Tak; Lee, Yong Wan

2008-03-17

377

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

378

Coarse-Frequency-Comb Multiple-Beam Interferometry: Phase Assessment Using Common Phase Shifting Procedures  

NASA Astrophysics Data System (ADS)

Real wedge interferometers of the Fizeau-type do not allow for fringes in case of a spectral broad band source -or in short: for white light fringes. Here, the use of a suitable frequency comb source will help to overcome this limitation on the one hand and on the other it offers the capability for enhanced phase sensitivity in high precision measurements of surface deviations. Frequency combs can be produced by passive filtering of the light emitted by a broad band source as a superlum-diode or a fs-laser. The frequency comb produced by a common fs-laser is extremely fine, i.e., the frequency difference of consecutive peaks is very small or the distance of consecutive pulses of the pulse train might be of the order of 1 m. Therefore, the coarse pulse train produced by passive filtering of a broad band source is better adapted to the needs of surface testing interferometers. White light fringes are either applied for the profiling of discontinuous surfaces or can serve as an indication for the correct choice of the subdivision of the inter order distance for multiple beam fringes. During the last decennium it became more and more clear that spatially incoherent sources provide better measuring accuracy in surface measurements due to the reduced influence of dust diffraction patterns. The advantage of laser illumination can nevertheless be maintained if the laser light is made spatially incoherent through moving scatterers in the light path. Here, we will discuss the application of spatially incoherent broad band light frequency filtered through a Fabry-Perot filter. The main applications are in the following fields: (1) surface profiling applications using two-beam Fizeau interferometers, (2) selection of single cavities out of a series of interlaced cavities, and (3) sensitivity enhancement for multi-beam interferometers for planeness or sphericity measurements. The emphasis of the presented work will be on the sensitivity enhancement provided by multiple beam interferometry in combination with frequency comb illumination. Through the use of a set of properly selected wavelengths the resulting interference pattern will become on the one hand more and more cosine-type with increasing enhancement factors and on the other hand it will be shown how the nonlinear relationship of the intensity distribution on the phase in the multiple beam interferometer can be overcome. Typical systematic errors show a periodicity with 4-times the fringe frequency of the interference pattern. By using the averaging of the measuring results of two measurements having a phase offset of ?/4 it is possible to reduce this error by at least one order of magnitude. The impact of the nonlinear intensity profile of multiple beam fringes in transmitted light can in addition be reduced through inverted intensity values in the common phase shifting equations. It will be shown that in this way repeatability values can be obtained of 1.2 A? peak to valley and 0.12 A? rms.

Schwider, J.

2010-04-01

379

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

380

The evolution of sex ratios and sex-determining systems  

Microsoft Academic Search

Sex determination is a fundamental process governed by diverse mechanisms. Sex ratio selection is commonly implicated in the evolution of sex-determining systems, although formal models are rare. Here, we argue that, although sex ratio selection can induce shifts in sex determination, genomic conflicts between parents and offspringcanexplainwhysingle-factorsystems(e.g. XY\\/ XX or ZW\\/ZZ) are common even in species that experi- ence selection

Tobias Uller; Ido Pen; Erik Wapstra; Leo W. Beukeboom; Jan Komdeur

2007-01-01

381

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

382

Parallel-kinematic-mechanism-based monolithic XY micropositioning stage with rotary comb drive actuators  

NASA Astrophysics Data System (ADS)

Micro-positioning stages fabricated using Micro Electro Mechanical Systems (MEMS) based processes have been critical in enabling micro/nano manipulation and probing. These stages have been extensively used in micro-force sensors, scanning probe microscopy and micro optical lens scanners. This paper presents the design, kinematic and dynamic analysis, fabrication and characterization of a novel monolithic micro-positioning XY stage. The design of the proposed micro-positioning stage is based on a Parallel Kinematic Mechanism (PKM). The PKM based design decouples the motion in the XY direction. Additionally, it restricts the parasitic rotation of the end-effector (table) of the micro-positioning stage while providing an increased motion range. The motion of the stage is linear in the operating range thus simplifying its kinematics. The truss like parallel kinematic mechanism design of the stage structure reduces its mass while keeping the stage stiffness high. This leads to a high natural frequency of the micro-positioning stage (1250Hz) and a high Q-factor of 156. The stage mechanism is fabricated on a Silicon-On-Insulator (SOI) substrate and is actuated by integrated electrostatic rotary comb drives. The fabrication process uses multi-layer patterning along with an Inductively Coupled Plasma Deep Reactive Ion Etching (ICP-DRIE). The use of ICP-DRIE enables the high aspect ratio etching that is required for the stage fabrication and its optimal actuation using the integrated electrostatic rotary comb drives. The fabricated stages have a motion range of more than 30 microns of decoupled displacements along the X and Y directions at a driving voltage of 200V.

Mukhopadhyay, Deepkishore; Dong, Jingyan; Ferreira, Placidus M.

2008-03-01

383

Sex Bias in Research Design.  

ERIC Educational Resources Information Center

Presents feminist criticisms of selected aspects of research methods in psychology. Reviews data relevant to sex bias in topic selection, subject selection and single-sex designs, operationalization of variables, testing for sex differences, and interpretation of results. Suggestions for achieving more "sex fair" research methods are discussed.…

Grady, Kathleen E.

1981-01-01

384

When is sex environmentally determined?  

Microsoft Academic Search

THERE are several sex determining mechanisms which produce two sexes in a population (dioecy or gonochorism)1-5. In many of these, the offspring's sex is determined at or before conception, as in male or female heterogamety. In several organisms, however, the offspring's sex is determined later than conception, by some environmental influence upon the offspring. We consider here why these environmental

Eric L. Charnov; James Bull

1977-01-01

385

Sex Equity: Is It Feasible?  

ERIC Educational Resources Information Center

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

Shocklee, Georgia

386

Sex chromosomes and brain gender  

Microsoft Academic Search

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

Arthur P. Arnold

2004-01-01

387

The problem of sex education  

Microsoft Academic Search

Discusses problems associated with sex education. Suggests that children should be instructed in matters of sex. There are different opinions regarding the best method of teaching. The problem of sex education should considered as important as those of an educational nature by the parents. However, no scientific data is available for judgments regarding the opinions on sex education. The teachers

W. A. Cook

1913-01-01

388

AIDS and sex tourism.  

PubMed

Tourists traveling internationally lower their inhibitions and take greater risks than they would typically in their home cultures. Loneliness, boredom, and a sense of freedom contribute to this behavioral change. Some tourists travel internationally in search of sexual gratification. This motivation may be actively conscious or subconscious to the traveler. Billed as romantic with great natural beauty, Thailand, the Philippines, Brazil, the Dominican Republic, and Kenya are popular destinations of tourists seeking sex. The Netherlands and countries in eastern Europe are also popular. With most initial cases of HIV infection in Europe having histories of international travel, mass tourism is a major factor in the international transmission of AIDS. While abroad, tourists have sex with casual partners, sex workers, and/or other tourists. Far from all tourists, however, carry and consistently use condoms with these partners. One study found female and non white travelers to be less likely than Whites and males to carry condoms. The risk of HIV infection increases in circumstances where condoms are not readily available in the host country and/or are of poor quality. Regarding actual condom use, a study found only 34% of sex tourists from Switzerland to consistently use condoms while abroad. 28% of men in an STD clinic in Melbourne, Australia, reported consistent condom use in sexual relations while traveling in Asia; STDs were identified in 73% of men examined. The few studies of tourists suggest that a significant proportion engage in risky behavior while traveling. HIV prevalence is rapidly increasing in countries known as destinations for sex tourism. High infection rates are especially evident among teenage sex workers in Thailand. Simply documenting the prevalence of risky behavior among sex tourists will not suffice. More research is needed on travelers and AIDS with particular attention upon the motivating factors supporting persistent high-risk behavior. PMID:12286016

Herold, E S; Van Kerkwijk, C

389

Genes and brain sex differences  

Microsoft Academic Search

Throughout development, numerous biological events occur that differentially affect males and females. Specifically, sex-determining genes that are triggered by the sex-chromosome complement initiate a series of events that determine an organism’s sex and lead to the differentiation of the body in sex-specific ways. Such events contribute to many unique sex differences, including the susceptibility to different diseases. Although it was

Francisco J. Sánchez; Eric Vilain

2010-01-01

390

Sex differences in schizophrenia.  

PubMed

Evidence suggests sex differences in schizophrenia reflect differences in both neurodevelopmental processes and social effects on disease risk and course. Male:female incidence approximates 1.4:1 but at older onset women predominate. Prevalence differences appear smaller. Men have poorer premorbid adjustment and present with worse negative and less depressive symptoms than women, which may explain their worse medium term outcome according to a range of measures. Substance abuse is a predominantly male activity in this group, as elsewhere. Findings of sex differences in brain morphology are inconsistent but occur in areas that normally show sexual dimorphism, implying that the same factors are important drivers of sex differences in both normal neurodevelopmental processes and those associated with schizophrenia. There are sex differences in antipsychotic responses but sex-specific endocrine effects on illness and response to antipsychotics are potentially complex. Oestrogen's role as an adjunctive medication is not yet clear due to methodological differences between the few randomized controlled trials. Services that are sensitive to differences in gender can better meet their patients' specific needs and potentially improve outcome. PMID:21047156

Abel, Kathryn M; Drake, Richard; Goldstein, Jill M

2010-01-01

391

Application of living ionic polymerizations to the design of AB-type comb-like copolymers of various topologies and organizations  

Microsoft Academic Search

Living anionic and cationic polymerizations have been combined to prepare various types of comb-like copolymers composed of\\u000a polystyrene (PS) and polyisoprene (PI) blocks, with a precisely controlled architecture. According to the relative placement\\u000a of these elementary building blocks, combs with randomly distributed PS and PI or with poly(styrene-b-isoprene) diblock branches (I &II, respectively) can be prepared. The reaction procedure initially

David Lanson; Fumi Ariura; Michel Schappacher; Redouane Borsali; Alain Deffieux

2007-01-01

392

Sex and Gender Similarities and Differences in Communication Values in Same-Sex and Cross-Sex Friendships  

Microsoft Academic Search

This study extends research on sex differences and similarities in communication values by examining (a) the influence of sex of friend on ratings of functional communication skills in same-sex and cross-sex friendships, (b) the moderating role of friend's sex in sex differences in evaluations, and (c) the mediating role of psychological gender in sex differences in communication values. Participants (144

Amanda J. Holmstrom

2009-01-01

393

A frequency-stabilized Yb:KYW femtosecond laser frequency comb and its application to low-phase-noise microwave generation  

NASA Astrophysics Data System (ADS)

We present an optically stabilized Yb:KYW fs-laser frequency comb. We use an f-2f nonlinear interferometer to measure the carrier envelope offset frequency (f 0) and the heterodyne beatnote between the comb and a stable CW laser at 1068 nm to detect fluctuations in the comb repetition rate (f_{rep}). Both of these degrees of freedom of the comb are then controlled using phase-locked loops. As a demonstration of the frequency-stabilized comb, we generate low-phase-noise 10 GHz microwaves through detection of the pulse train on a high bandwidth photodiode. The phase noise of the resulting 10 GHz microwaves was -99 dBc/Hz at 1 Hz and the corresponding Allen deviation was <2.6 × 10-15 at 1 s, measured by comparison to an independently stabilized Ti:sapphire frequency comb. This room-temperature, optically based source of microwaves has close-to-carrier phase noise comparable to the very best cryogenic microwave oscillators.

Meyer, Stephanie A.; Fortier, Tara M.; Lecomte, Steve; Diddams, Scott A.

2013-07-01

394

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

395

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

396

Optical Frequency Comb as a general-purpose and wide-band calibration source for astronomical high resolution infrared spectrographs  

NASA Astrophysics Data System (ADS)

A spectrally filtered Optical Frequency Comb (OFC) laser is proposed as a versatile calibration source for astronomical spectrometers in the 1-2 ?m spectral range. Such a source overcomes the limitations of current calibration lamps providing a uniform spectrum of equally spaced lines with similar intensity and extremely high long-term frequency stability. We present preliminary studies and results of a system which filters the OFC from a 100 MHz comb spacing to 16 GHz one, an adequate spacing for spectrometers with resolving power ??/? >30000. The first approach employs two Fabry-Perot cavities in series, made of dielectric coated mirrors, followed by a non-linear optical broadening system. The limitations of such a filtering process are discussed. These can be overcome by the second approach, based on filtering cavities with metallic coated mirrors.

Schettino, Giulia; Oliva, Ernesto; Inguscio, Massimo; Baffa, Carlo; Giani, Elisabetta; Tozzi, Andrea; Pastor, Pablo Cancio

2011-08-01

397

Experimental study of quasi-one-dimensional comb-like photonic crystals containing left-handed material  

Microsoft Academic Search

Quasi-one-dimensional comb-like photonic crystals with backbone waveguide made of left-handed material are physically fabricated by using transmission lines. The transmission properties are experimentally investigated and it is found that the structures possess a special band gap. The gap does not originate from the conventional Bragg scattering mechanism in that it is invariant with the change of scale length. Moreover, the

Liwei Zhang; Zhiguo Wang; Hong Chen; Hongqiang Li; Yewen Zhang

2008-01-01

398

A Poly-Si-Based Vertical Comb-Drive TwoAxis Gimbaled Scanner for Optical Applications  

Microsoft Academic Search

This work presents a novel two-axis gimbaled mirror for optical scanning applications. This scanner has been implemented using the molded surface-micromachining and bulk etching release (MOSBE II) process. Thus, the vertical comb-drive actuators are employed to realize the large stroke. The thin-film electrical routings are employed to drive the actuators individually. The rib-reinforced structures are exploited to increase the stiffness

Mingching Wu; Hung-Yi Lin; Weileun Fang

2006-01-01

399

Brain, Sex and Ideology  

Microsoft Academic Search

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

Catherine Vidal

2005-01-01

400

Sex and Cognition.  

ERIC Educational Resources Information Center

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

Kimura, Doreen

401

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

402

Sex Discrimination in Athletics  

ERIC Educational Resources Information Center

|Using applicable common law and statutory standards, this comment examines from several perspectives the constitutionality of section 86.41 of the Title IX regulations. It is concluded that the alternative to section 86.41 and the entire separate but equal system is to classify by ability rather than by sex. (LBH)|

Kutner, Joan Ruth

1976-01-01

403

Hands Off Consensual Sex.  

ERIC Educational Resources Information Center

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

Alston, Kal

1998-01-01

404

Divorce and sex  

Microsoft Academic Search

Studies on the sex lives of the divorced are relatively few and somewhat dated. Although they give a rather optimistic view of the subject, this research is flawed by high respondent refusal rates and poor representativeness of samples. Further, a major gap in this literature is that the possible predictors of sexual activity of the divorced remain largely unexplored. The

Steven Stack; James H. Gundlach

1992-01-01

405

Sex and occupational choice  

Microsoft Academic Search

Compared the omnibus personality inventory score patterns of 275 males and 248 females graduating in majors classified into the 5 occupational categories of J. Holland (see pa, vol. 40:12652) in a 5 * 2 multivariate analysis of variance design. Although significant differences were found by sex and occupational category, it was the significant interaction effect which supported the conclusion that

Harriett A. Rose; Charles F. Elton

1971-01-01

406

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

407

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

408

Sex education for parents  

Microsoft Academic Search

Finds research shows that while parents are potentially an important source of information and support to their children on sexual issues, in practice many parents feel that they lack the skills and confidence to play a direct role in these matters. Presents findings from a pilot project undertaken by Health Promotion Wales and FPA Cymru to enhance parents’ sex education

Virginia Blakey; Jane Frankland

1996-01-01

409

Sex education and ideals  

Microsoft Academic Search

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 ideals.

Doret J. de Ruyter; Ben Spiecker

2008-01-01

410

Sociology of Sex Work  

Microsoft Academic Search

This review examines key dimensions of contemporary sex work, particularly prostitution. Most research focuses exclusively on street prostitution and female workers, with much less attention devoted to indoor prostitution, male and transgender workers, customers, and managers. Furthermore, most of the literature examines prostitution where it is illegal, neglecting contexts where it is legal and regulated by the government. The review

Ronald Weitzer

2009-01-01

411

Sex therapy and penectomy  

Microsoft Academic Search

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

Mildred Hope Witkin; Helen S. Kaplan

1982-01-01

412

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

413

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

NASA Astrophysics Data System (ADS)

The synthesis and properties of comb-like copolymers and ionomers derived from renewable resources: itaconic anhydride (ITA), stearyl methacrylate (SM) and lactic acid (LA) are described. The copolymers based on ITA and SM (ITA-SM) were nearly random with a slight alternating tendency. The copolymers exhibited a nanophase-separated morphology, with the stearate side-chains forming a bilayer, semi-crystalline structure. The crystalline side-chains suppressed molecular motion of the main-chain, so that a glass transition temperature (Tg) was not resolved unless the ITA concentration was sufficiently high so that Tg > the melting point (Tm). The softening point and modulus of the copolymers increased with the increasing ITA concentration, but the thermal stability decreased. The ITA moiety along the main chain of the copolymers was neutralized with metal acetates to produce Na-, Ca- and Zn- random ionomers with comb-like architectures. In general, the incorporation of the ionic groups increased the Tg and suppressed the crystallinity of the side-chain packing. Ionomers with high SM side-chain density had two competing driving forces for self-assembled nano-phase separation: ionic aggregation and side-chain crystalline packing. Upon neutralization, a morphological transition from semi-crystalline lamella to spherical ionic aggregation was observed by small angle X-ray scattering (SAXS) analysis and transmission electron microscopy (TEM). Thermomechanical analysis revealed an increasing resistance to penetration deformation with an increasing degree of neutralization and an apparent rubbery plateau was observed above Tg. A controlled transesterification of PLA in glassware was an effective way to prepare a methacrylate functionalized PLA macromonomer with controlled molecular weight, which was used to synthesize a variety of copolymers. The copolymerization of this functionalized PLA macromonomer with ITA totally suppressed the side-chain crystallinity for the PLA chain length range studied. An increase of Tg was observed for sufficiently high neutralization level. The kinetics of ionic aggregation in this ionomer was very slow, but annealing at elevated temperature helped to reach equilibrium of the microstructure.

Shang, Shurui

414

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

2010-09-01

415

Wavelength switchable flat-top all-fiber comb filter based on a double-loop Mach-Zehnder interferometer.  

PubMed

A wavelength switchable all-fiber comb filter with flat-top spectral response based on a double-loop Mach-Zehnder (M-Z) interferometer is proposed and demonstrated. The proposed flat-top filter consists of a rotatable polarizer and a double-loop M-Z interferometer composed of two fiber couplers with a polarization controller (PC) in the first loop. In the theoretical analysis, when the second coupler of the M-Z interferometer is a non-3dB one, with proper settings of the polarization state of the input light and the PC, the wavelength switchable comb filter with flat-top passband can be obtained. Theoretical prediction was verified by experimental demonstration. The measured 1 dB bandwidth was 0.51 nm with a channel spacing of 0.98 nm, indicating that the flat-top passband of 1 dB bandwidth extends to about 50% of the comb spacing. PMID:20389626

Luo, Ai-Ping; Luo, Zhi-Chao; Xu, Wen-Cheng; Cui, Hu

2010-03-15

416

Contribution of the bees and combs to honey volatiles: blank-trial probe for chemical profiling of honey biodiversity.  

PubMed

This research is focused on the immediate contribution of the bees and combs to honey volatiles in order to exclude these compounds as botanical-origin biomarkers for honey authentification. Therefore, the bees were closed in a hive containing empty combs under controlled food-flow conditions (saccharose solution). The obtained 'saccharose honey' probe samples were subjected to ultrasonic solvent extraction (USE), followed by gas chromatography and mass spectrometry analyses (GC and GC/MS). A total of 66 compounds were identified. Higher alcohols made up ca. 50% of the total volatiles, mainly (Z)-octadec-9-en-1-ol, hexadecan-1-ol, and octadecan-1-ol, with minor percentages of undecan-1-ol, dodecan-1-ol, tetradecan-1-ol, pentadecan-1-ol, and heptadecan-1-ol. Other abundant compounds were saturated long-chain linear hydrocarbons, C(10)-C(25), C(27), and C(28), particularly C(23), C(25), and C(27)). Identified chemical structures were related to the composition of combs and cuticular waxes, and less to the bee pheromones. In addition, the impact of two-hour heat treatment at 80 degrees and one-year storage at room temperature on the same probe was investigated in order to identify thermal and storage artefacts. These findings can be considered as blank-trial probe (no plant source) for honey chemical profiling and identification of reliable botanical origin biomarkers. PMID:20491078

Jerkovi?, Igor; Marijanovi?, Zvonimir; Ljubici?, I; Gugi?, M

2010-05-01

417

Broad-band frequency references in the near-infrared: Accurate dual comb spectroscopy of methane and acetylene  

NASA Astrophysics Data System (ADS)

The Doppler-limited spectra of methane between 176 THz and 184 THz (5870-6130 cm-1) and acetylene between 193 THz and 199 THz (6430-6630 cm-1) are acquired via comb-tooth resolved dual comb spectroscopy with frequency accuracy traceable to atomic standards. A least squares analysis of the measured absorbance and phase line shapes provides line center frequencies with absolute accuracy of 0.2 MHz, or less than one thousandth of the room temperature Doppler width. This accuracy is verified through comparison with previous saturated absorption spectroscopy of 37 strong isolated lines of acetylene. For the methane spectrum, the center frequencies of 46 well-isolated strong lines are determined with similar high accuracy, along with the center frequencies for 1107 non-isolated lines at lower accuracy. The measured methane line-center frequencies have an uncertainty comparable to the few available laser heterodyne measurements in this region but span a much larger optical bandwidth, marking the first broad-band measurements of the methane 2?3 region directly referenced to atomic frequency standards. This study demonstrates the promise of dual comb spectroscopy to obtain high resolution broadband spectra that are comparable to state-of-the-art Fourier-transform spectrometer measurements but with much improved frequency accuracy.Work of the US government, not subject to US copyright.

Zolot, A. M.; Giorgetta, F. R.; Baumann, E.; Swann, W. C.; Coddington, I.; Newbury, N. R.

2013-03-01

418

Cavity-enhanced optical frequency comb spectroscopy in the mid-infrared application to trace detection of hydrogen peroxide  

NASA Astrophysics Data System (ADS)

We demonstrate the first cavity-enhanced optical frequency comb spectroscopy in the mid-infrared wavelength region and report the sensitive real-time trace detection of hydrogen peroxide in the presence of a large amount of water. The experimental apparatus is based on a mid-infrared optical parametric oscillator synchronously pumped by a high-power Yb:fiber laser, a high-finesse broadband cavity, and a fast-scanning Fourier transform spectrometer with autobalancing detection. The comb spectrum with a bandwidth of 200 nm centered around 3.76 ?m is simultaneously coupled to the cavity and both degrees of freedom of the comb, i.e. the repetition rate and carrier envelope offset frequency, are locked to the cavity to ensure stable transmission. The autobalancing detection scheme reduces the intensity noise by a factor of 300, and a sensitivity of 5.4×10-9 cm-1 Hz-1/2 with a resolution of 800 MHz is achieved (corresponding to 6.9×10-11 cm-1 Hz-1/2 per spectral element for 6000 resolved elements). This yields a noise equivalent detection limit for hydrogen peroxide of 8 parts-per-billion (ppb); in the presence of 2.8 % of water the detection limit is 130 ppb. Spectra of acetylene, methane, and nitrous oxide at atmospheric pressure are also presented, and a line-shape model is developed to simulate the experimental data.

Foltynowicz, A.; Mas?owski, P.; Fleisher, A. J.; Bjork, B. J.; Ye, J.

2013-02-01

419

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

420

Local behavioral rules sustain the cell allocation pattern in the combs of honey bee colonies (Apis mellifera).  

PubMed

In the beeswax combs of honey bees, the cells of brood, pollen, and honey have a consistent spatial pattern that is sustained throughout the life of a colony. This spatial pattern is believed to emerge from simple behavioral rules that specify how the queen moves, where foragers deposit honey/pollen and how honey/pollen is consumed from cells. Prior work has shown that a set of such rules can explain the formation of the allocation pattern starting from an empty comb. We show that these rules cannot maintain the pattern once the brood start to vacate their cells, and we propose new, biologically realistic rules that better sustain the observed allocation pattern. We analyze the three resulting models by performing hundreds of simulation runs over many gestational periods and a wide range of parameter values. We develop new metrics for pattern assessment and employ them in analyzing pattern retention over each simulation run. Applied to our simulation results, these metrics show alteration of an accepted model for honey/pollen consumption based on local information can stabilize the cell allocation pattern over time. We also show that adding global information, by biasing the queen's movements towards the center of the comb, expands the parameter regime over which pattern retention occurs. PMID:23876764

Montovan, Kathryn J; Karst, Nathaniel; Jones, Laura E; Seeley, Thomas D

2013-07-19

421

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

422

[Sex chromosomes and meiosis].  

PubMed

Sex chromosome behaviour fundamentally differs between male and female meiosis. In oocyte, X chromosomes synapse giving a XX bivalent which is not recognizable in their morphology and behaviour from autosomal bivalents. In human male, X and Y chromosomes differ from one another in their morphology and their genetic content, leading to a limited pairing and preventing genetic recombination, excepted in homologous region PAR1. During pachytene stage of the first meiotic prophase, X and Y chromosomes undergo a progressive condensation and form a transcriptionally silenced peripheral XY body. The condensation of the XY bivalent during pachytene stage led us to describe four pachytene substages and to localize the pachytene checkpoint between substages 2 and 3. We also defined the pachytene index (PI=P1+P2/P1+P2+P3+P4) which is always less than 0.50 in normal meiosis. XY body undergoes decondensation at diplotene stage, but transcriptional inactivation of the two sex chromosomes or Meiotic Sex Chromosome Inactivation (MSCI) persists through to the end of spermatogenesis. Sex chromosome inactivation involves several proteins, some of them were now identified. Two isoforms of the HP1 protein, HP1beta and HP1gamma, are involved in the facultative heterochromatinization of the XY body, but the initiation of this process involves the phosphorylation of the protein H2AX by the kinase ATR whose recruitment depends on BRCA1. Extensive researches on the inactivation of the sex chromosomes during male meiosis will allow to a better understanding of some male infertilities. PMID:19819743

Guichaoua, M-R; Geoffroy-Siraudin, C; Tassistro, V; Ghalamoun-Slaimi, R; Perrin, J; Metzler-Guillemain, C

2009-10-12

423

Origin of Sex Revisited  

NASA Astrophysics Data System (ADS)

Why did sex ever arise in the first place? Why it does not disappear in view of the greater efficiency of asexuals? These are clearly two different questions, and we suggest here that the solution for the origin of sex does not necessarily come from theoretical considerations based on currently existing genetic systems. Thus, while we agree with a number of authors in that the emergence of sex (understood as the exchange of genetic material between genomes) is deeply rooted in the origin of life and happened during the very early stages in the transition from individual genes (`replicators') to bacteria-like cells (`reproducers'), we challenge the idea that recombinational repair was the major selective force for the emergence of sex. Taking the stochastic corrector model as a starting point, we provide arguments that question the putative costs of redundancy in primitive protocells. In addition, if genes that cause intragenomic conflict (i.e., parasites) are taken into account, it is certainly wrong to suggest that cellular fusion would be beneficial at the population level (although this strong claim needs some qualifications). However, when a continuous input of deleterious mutations that impair the fitness of the protocell as a whole is considered in the model (in the realistic range in which stable mutant distributions of quasi-species within compartments are established), there are circumstances when sex could be beneficial as a side effect of the dynamic equilibrium between cellular fusion-mutation-selection. The scenario we have explored numerically is fully consistent with the idea that the universal ancestor was not a discrete entity but an ensemble of proto-organisms that exchanged much genetic information.

Santos, Mauro; Zintzaras, Elias; Szathmáry, Eörs

2003-10-01

424

Disestablishing Sex: The Case for Released-Time Sex Education  

ERIC Educational Resources Information Center

Allowing nonschool organizations to provide sex education in a released-time format would disestablish state-funded sex education and give families a choice in the sex education that would be provided for their children. Released-time programs, as originally conceived and currently practiced, allow students to be released for a period of time…

Glanzer, Perry L.

2011-01-01

425

Cultural Sex Role Expectations and Children's Sex Role Concepts.  

ERIC Educational Resources Information Center

|In research on sex role attitudes, career choices, and considered appropriateness of men and women participating in 14 sex-stereotyped occupations, children demonstrated nonstereotypic attitudes toward the 14 occupations, chose traditional careers (those dominated by the subject's sex) for themselves, and gave stereotypic reasons for preferring…

Zuckerman, Diana M.; Sayre, Donald H.

1982-01-01

426

Sex Role Attitudes and Sex Role Stereotyping: Recent Literature.  

ERIC Educational Resources Information Center

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

New Jersey Research Bulletin, 1996

1996-01-01

427

Sex Role Attitudes and Sex Role Stereotyping: Recent Literature.  

ERIC Educational Resources Information Center

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

New Jersey Research Bulletin, 1996

1996-01-01

428

Sex differences in college major  

Microsoft Academic Search

Analysis of sex differences in choice of college major in the United States in 1955 and 1973, using nationwide data. Data on college major distribution by sex; Analysis of differences; Empirical estimation. (Abstract copyright EBSCO.)

Solomon William Polachek

1978-01-01

429

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

430

Sex Differences and Sex Steroids in Lung Health and Disease  

PubMed Central

Sex differences in the biology of different organ systems and the influence of sex hormones in modulating health and disease are increasingly relevant in clinical and research areas. Although work has focused on sex differences and sex hormones in cardiovascular, musculoskeletal, and neuronal systems, there is now increasing clinical evidence for sex differences in incidence, morbidity, and mortality of lung diseases including allergic diseases (such as asthma), chronic obstructive pulmonary disease, pulmonary fibrosis, lung cancer, as well as pulmonary hypertension. Whether such differences are inherent and/or whether sex steroids play a role in modulating these differences is currently under investigation. The purpose of this review is to define sex differences in lung structure/function under normal and specific disease states, with exploration of whether and how sex hormone signaling mechanisms may explain these clinical observations. Focusing on adult age groups, the review addresses the following: 1) inherent sex differences in lung anatomy and physiology; 2) the importance of certain time points in life such as puberty, pregnancy, menopause, and aging; 3) expression and signaling of sex steroid receptors under normal vs. disease states; 4) potential interplay between different sex steroids; 5) the question of whether sex steroids are beneficial or detrimental to the lung; and 6) the potential use of sex steroid signaling as biomarkers and therapeutic avenues in lung diseases. The importance of focusing on sex differences and sex steroids in the lung lies in the increasing incidence of lung diseases in women and the need to address lung diseases across the life span.

Townsend, Elizabeth A.; Miller, Virginia M.

2012-01-01

431

Gender Specific Sex Role Development.  

ERIC Educational Resources Information Center

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

Urbonas-Bendikas, Irena

432

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

433

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

434

Some problems in sex education  

Microsoft Academic Search

Discusses two general methods of sex education, the old fashioned and the modern type. The former method is not explicit, and is achieved mainly through observation and instruction from older children. The latter method uses explicit instruction. The possible reasons for making sex-related issues mysterious,is traced back to the early days of sex worship. A counter education of an unsentimental

Helen Williston Brown

1919-01-01

435

Sex Stereotyping by Tomorrow's Executives.  

ERIC Educational Resources Information Center

Describes a study in which 512 college seniors were surveyed to see if members of one sex would implicitly stereotype by sex to a greater degree than the other. Questions concerned job/home conflicts and selection and promotion. Results indicated that men and women are equally guilty of sex stereotyping, which works against women in the workplace.…

Kovach, Kenneth A.

1985-01-01

436

High solids loading ceramic colloidal dispersions in UV curable media via comb-polyelectrolyte surfactants.  

PubMed

Ceramic articles and ceramic/polymer composites with complex 3d shapes can be produced by rapid prototyping techniques such as stereolithography of ceramic dispersions in UV curable resins. Nanometer and submicrometer ceramic particles are advantageous for high resolution microstructures, surface quality and reduced sintering temperatures. Frequently, special surfactants are needed to maximize solids loading while maintaining suitable rheological properties for stereolithography applications (viscosity <5 Pa s, 301/s). We present here a general scheme for relatively high loading/low viscosity dispersions of nanometer and submicrometer particles in UV curable resins using comb-polyelectrolyte surfactants. In the present approach, adsorption is favorably carried out in aqueous media and the dry particles with adsorbed surfactant are transferred to the organic media through centrifugation, washing, drying and dry milling. The method is demonstrated for Al(2)O(3), ZnO and mixed Al(2)O(3)/ZnO colloidal dispersions. Dispersions containing >48 vol% particles suitable for stereolithography have been achieved. Dispersions containing 36 vol% particles are predicted to have viscosities in the range suitable for direct inkjet printing applications at 75 degrees C. The particle stabilization and transfer schemes, rheological behavior and UV curing characteristics are presented. PMID:19501831

De Hazan, Yoram; Heinecke, Judit; Weber, Alfred; Graule, Thomas

2009-05-12

437

A new method to generate relativistic comb bunches with tunable subpicosecond spacing  

NASA Astrophysics Data System (ADS)

We propose and analyze a scheme to produce comb bunches, i.e. a bunch consisting of micro-bunch trains, with tunable subpicosecond spacing. In the scheme, the electron beam is first deflected by a deflecting cavity which introduces a longitudinal-dependent linear transverse kick to the particles. After passing through a drift space, the transverse beam size is linearly coupled to the longitudinal position of the particle inside the beam, and a mask is placed there to tailor the beam, then the mask distribution is imprinted on the beam's longitudinal distribution. A quadrupole magnet and another deflecting cavity are used in the beam line to compensate the transverse angle due to the first deflecting cavity. Analysis shows that the number, length, and spacing of the trains can be controlled through the parameters of the deflecting cavity and the mask. Such electron bunch trains can be applied to an infrared free electron laser, a plasma-wakefield accelerator and a supper-radiance THz source.

Du, Ying-Chao; Huang, Wen-Hui; Tang, Chuan-Xiang

2012-02-01

438

Biocleavable comb-shaped gene carriers from dextran backbones with bioreducible ATRP initiation sites.  

PubMed

It is of crucial importance to design reduction-sensitive polysaccharide-based copolymers for intracellular triggered gene and drug delivery. In this work, a simple two-step method involving the reaction of hydroxyl groups of dextran with cystamine was first developed to introduce reduction-sensitive disulfide linked initiation sites of atom transfer radical polymerization (ATRP) onto dextran. Well-defined biocleavable comb-shaped vectors consisting of nonionic dextran backbones and disulfide-linked cationic P(DMAEMA) side chains were subsequently prepared via ATRP for highly efficient gene delivery. The P(DMAEMA) side chains can be readily cleavable from the dextran backbones under reducible conditions. Moreover, the bioreducible P(DMAEMA) side chains can be functionalized by poly(poly(ethylene glycol)ethyl ether methacrylate) (P(PEGEEMA)) end blocks to reduce the cytotoxicity and further enhance the gene transfection efficiency. This present study demonstrated that properly grafting short bioreducible polycation side chains from a nonionic polysaccharide backbone with biocleavable ATRP initiation sites is an effective means to produce a class of polysaccharide-based gene delivery vectors. PMID:22136712

Wang, Zeng-Hui; Zhu, Yun; Chai, Ming-Ying; Yang, Wan-Tai; Xu, Fu-Jian

2011-12-01

439

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

440

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

PubMed

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 (4)He and in the normal and superfluid states of (3)He 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. PMID:23464242

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

2013-02-01

441

Delta-comb potential in modeling three-phase contact line (TPCL) on periodically patterned surfaces.  

PubMed

This work is a study of wetting of small water droplets on smooth glass surfaces with periodic patterns in the form of imprinted net with hydrophilic cells and hydrophobic bars. Microcover slides consisted of soda lime glass were used. The imprinted images of the net were with cell sizes in the range 40-200 ?m, which corresponds to a quite narrow scope of hydrophilic surface fractions f(1)(30-36%) due to the relative increase in the size of the hydrophobic bars. The receding contact angles ?(R) of small water droplets, positioned on the patterned surfaces, were measured. The experiment showed significantly lower receding contact angles as compared to the theoretical expectations by the Cassie formula, which accounts for the contribution to the contact angle of the surface fraction of the imprinted hydrophobic/hydrophilic net. For this reason, we developed new theory accounting for the periodicity of the surface and the contribution of the three-phase contact line on the contact angle. This new theory considered delta-comb potential energy ?(x,y) of the surface, effective line tension ?, and the lattice parameter a. The restriction of theory was discussed as well. It was pointed out that the theory is not valid for very small and very large lattice parameters. PMID:23078081

Tsekov, Roumen; Grozev, Nikolay A; Delcheva, Iliyana V; Ivanov, Ivan T; Balashev, Konstantin; Karakashev, Stoyan I

2012-10-24

442

Motion-compensated MR valve imaging with COMB tag tracking and super-resolution enhancement.  

PubMed

Understanding the morphology and function of heart valves is important to the study of underlying causes of heart failure. Existing techniques such as those based on echocardiography are limited by the relatively low signal-to-noise ratio (SNR), attenuation artefacts, and restricted access. The alternative of cardiovascular MR imaging offers versatility and accuracy in 3D localisation, but is hampered by large movements of the valves throughout the cardiac cycle. This paper presents a motion-compensated adaptive imaging approach for MR valve imaging. To illustrate its clinical potential, 3D motion of the aortic valve plane is first captured through a single breath-hold COMB tag pre-scan and then tracked in real-time with an automatic method based on multi-resolution image registration. Motion-compensated coverage of the aortic valve is then acquired prospectively, thus allowing its clear 3D reconstruction and visualisation. To provide isotropic voxel coverage of the imaging volume, retrospective projection onto convex sets (POCS) super-resolution enhancement is applied to the slice-select direction. In vivo results demonstrate the effectiveness of the proposed motion-compensation and super-resolution schemes for depicting the structure of the valve leaflets throughout the cardiac cycle. The proposed method fundamentally changes the way MR imaging is performed by transforming it from a spatially to materially localised imaging method. This also has important implications for quantifying blood flow and myocardial perfusion, as well as tracking anatomy and function of the heart. PMID:17804277

Dowsey, Andrew W; Keegan, Jennifer; Lerotic, Mirna; Thom, Simon; Firmin, David; Yang, Guang-Zhong

2007-07-24

443

Self-assembly of ultrahigh molecular weight comb block copolymer at the air/water interface  

NASA Astrophysics Data System (ADS)

Self-assembly of a newly synthesized, amphiphilic comb block copolymer (CBCP) at the air/water interface was systematically explored using the Langmuir Blodgett (LB) technique. The CBCP had an ultra high molecular weight (MW = 510 x 10^3 g/mol) with polystyrene arms grafted along one block of long hydrophilic backbone. At the air/water interface, the CBCP molecules spontaneously assembled into ribbon-like structures and cellular patterns at the zero surface pressure when volatile solvent (i.e., chloroform) and less volatile solvent (i.e., toluene) were used, respectively. This spontaneous self-assembly behavior of CBCP was induced by the dewetting process. The mechanism for the morphological change as a function of surface pressure was scrutinized and further confirmed by the compression-expansion cycle and solvent vapor annealing studies. To the best of our knowledge, this is the first study of self-assembly of ultrahigh MW, amphiphilic CBCP at the air/water interface. As such, it provides insight into the design of controllable pattern formation using amphiphilic copolymers.

Zhao, Lei; Goodman, Matthew; Bowden, Ned; Lin, Zhiqun

2010-03-01

444

REVIEW ARTICLE: Optical frequency comb generation in gas-filled hollow core photonic crystal fibres  

NASA Astrophysics Data System (ADS)

The efficiency of gas-based nonlinear processes is often limited by the diffraction of the pump laser as it propagates through the nonlinear medium. As a consequence, phenomena with strong nonlinear response requirements, such as high harmonic generation or Raman sideband generation, lack the required laser-matter interaction to fulfil their potential. Indeed, the conversion efficiency of these techniques is usually low and the experimental set-up cumbersome. The advent of hollow core photonic crystal fibre technology drafts new territories for nonlinear optics, and in particular offers new alternatives for sub-femtosecond pulse generation. The air-guiding fibre combines unprecedented laser confinement over long interaction lengths and, when filled with an adequate nonlinear gas, offers improved conversion efficiency and up to a million-fold reduction of the pump power threshold. This paper presents a review of the types of hollow core PCF available for nonlinear applications and the results obtained for efficient Raman conversion in H2-filled hollow core PCF that led to the observation of a multi-octave frequency comb spanning from ~325 to ~2300 nm using a single pump laser with relatively low power. The generated ultra-broad spectrum creates a simple route towards a compact source of attosecond pulses.

Couny, F.; Benabid, F.

2009-10-01

445

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

PubMed

In this study, electrically conductive bacterial cellulose (BC) was prepared by culturing Gluconacetobacter xylinus in a carbon nanotube (CNT)-dispersed medium. The CNTs were dispersed by adopting a non-covalent approach in the presence of non-ionic amphiphilic comb-like polymer (CLP). Specifically, the hydrophobic backbone of CLP was chemophysically attached to the surface of the CNTs and the hydrophilic side chains were released freely toward the medium in an aqueous environment. CLP-modified CNTs were stable and did not show any noticeable sediment, even after centrifugation at 15,000 rpm for 30 min. Notably, the dispersion solution of CLP-modified CNTs was stable at room temperature for several months because the long-range entropic repulsion among polymer-decorated tubes acted as a barrier to aggregation. The morphology of the BC membrane was studied by field-emission scanning electron microscopy. The presence of CLP bound to the CNT surface was characterized by Fourier transform infrared spectroscopy and the conductivity of the CNT-incorporated BC membrane was measured by four-probe measurements. PMID:21974907

Choi, Jaeyoo; Park, Subeom; Cheng, Jie; Park, Minsung; Hyun, Jinho

2011-09-12

446

Child sex rings.  

PubMed Central

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 "family friend" or obtained a position of authority over children. Secrecy was encouraged and bribery, threats, and peer pressure used to induce participation in sexual activities. Offences reported included fondling, masturbation, pornography, and oral, vaginal, and anal intercourse. Eleven perpetrators were successfully prosecuted; all but one received a sentence of three years or less. Behavioural problems were common among those children who had participated for a long time. Child sex rings are difficult to detect and may be common. Many children are seriously abused as a consequence of them.

Wild, N J; Wynne, J M

1986-01-01

447

Child sex rings.  

PubMed

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 "family friend" or obtained a position of authority over children. Secrecy was encouraged and bribery, threats, and peer pressure used to induce participation in sexual activities. Offences reported included fondling, masturbation, pornography, and oral, vaginal, and anal intercourse. Eleven perpetrators were successfully prosecuted; all but one received a sentence of three years or less. Behavioural problems were common among those children who had participated for a long time. Child sex rings are difficult to detect and may be common. Many children are seriously abused as a consequence of them. PMID:3730803

Wild, N J; Wynne, J M

1986-07-19

448

46,XX sex reversal.  

PubMed

In humans, sexual differentiation is directed by SRY, a master regulatory gene located at the Y chromosome. This gene initiates the male pathway or represses the female pathway by regulating the transcription of downstream genes; however, the precise mechanisms by which SRY acts are largely unknown. Moreover, several genes have recently been implicated in the development of the bipotential gonad even before SRY is expressed. In some individuals, the normal process of sexual differentiation is altered and a sex reversal disorder is observed. These subjects present the chromosomes of one sex but the physical attributes of the other. Over the past years, considerable progress has been achieved in the molecular characterization of these disorders by using a combination of strategies including cell biology, animal models, and by studying patients with these pathologic entities. PMID:11750731

Zenteno-Ruiz, J C; Kofman-Alfaro, S; Méndez, J P

449

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

450

Sex, Songs, and Censorship  

Microsoft Academic Search

This study examines the tendency of popular music critics to focus their censorship attention on recordings containing sex-related imagery or explicitly sensual commentaries. The author explores the changing nature of lyrical interpretation from singularly audio sources through contemporary mixed-media presentations. The positive role of anti-authority statements as potential controls against abuses of political, religious, and economics power in a democratic

B. Lee Cooper

1995-01-01

451

Disorders of sex development  

Microsoft Academic Search

Disorders of sex development (DSD) occur in 1–2\\/10,000 live births, with a specific molecular diagnosis only possible in 20% of cases. Presentation is usually at birth, and gender assignment must be avoided before review by an expert multidisciplinary team. Initial investigations allow a working diagnosis to be made within 48 hours. In 46,XY DSD, surgery may be necessary to correct

Mark Woodward; Nitin Patwardhan

2010-01-01

452

Sex steroids and schizophrenia  

Microsoft Academic Search

The peak in incidence for schizophrenia is during late adolescence for both sexes, but within this time frame the peak is\\u000a both earlier and steeper for males. Additionally, women have a second peak in incidence following menopause. Two meta-analyses\\u000a have reported that men have an overall ?40% greater chance of developing schizophrenia than do women (Aleman et al., 2003;\\u000a McGrath

Julie A. Markham

453

Adolescent Sex Offenders  

Microsoft Academic Search

Sexual assault is one of the fastest growing violent crimes in the United States (Shaw, 1999). Around the country, police,\\u000a prosecutors, mental health professionals, and probation officers continue to struggle to deal with the rise in the number\\u000a of juvenile sex offenders. It is estimated that in the United States, juveniles commit almost half of all child molestations\\u000a and about

Christina M. Camp; Laura F. Salazar; Ralph J. DiClemente; Gina M. Wingood

454

Why humans have sex.  

PubMed

Historically, the reasons people have sex have been assumed to be few in number and simple in nature-to reproduce, to experience pleasure, or to relieve sexual tension. Several theoretical perspectives suggest that motives for engaging in sexual intercourse may be larger in number and psychologically complex in nature. Study 1 used a nomination procedure that identified 237 expressed reasons for having sex, ranging from the mundane (e.g., "I wanted to experience physical pleasure") to the spiritual (e.g., "I wanted to get closer to God"), from altruistic (e.g., "I wanted the person to feel good about himself/herself") to vengeful (e.g., "I wanted to get back at my partner for having cheated on me"). Study 2 asked participants (N = 1,549) to evaluate the degree to which each of the 237 reasons had led them to have sexual intercourse. Factor analyses yielded four large factors and 13 subfactors, producing a hierarchical taxonomy. The Physical reasons subfactors included Stress Reduction, Pleasure, Physical Desirability, and Experience Seeking. The Goal Attainment subfactors included Resources, Social Status, Revenge, and Utilitarian. The Emotional subfactors included Love and Commitment and Expression. The three Insecurity subfactors included Self-Esteem Boost, Duty/Pressure, and Mate Guarding. Significant gender differences supported several previously advanced theories. Individual differences in expressed reasons for having sex were coherently linked with personality traits and with individual differences in sexual strategies. Discussion focused on the complexity of sexual motivation and directions for future research. PMID:17610060

Meston, Cindy M; Buss, David M

2007-07-03

455

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.

Schon, Isabelle; Martens, Koen

2003-01-01

456

Abnormalities of sex differentiation.  

PubMed

Sex differentiation is determined by a cascade of events proceeding from chromosomal sex to the completion of sexual maturation at puberty. Many factors involved in this cascade have been identified. Here we focus on DAX-1, androgen receptor and cytochrome P450c17, and discuss their functions in sex differentiation. We analyzed the DAX-1 genes of two unrelated Japanese patients with congenital adrenal hypoplasia and hypogonadotropic hypogonadism using PCR amplification of genomic DNA and complete exonic sequencing, and established that congenital adrenal hypoplasia and hypogonadotropic hypogonadism result from not only inherited but also de novo mutation in the DAX-1 gene. Androgen insensitivity syndrome (AIS) is a good model to clarify the relationship between the structure and function of androgen receptor, the androgen receptor gene mutation and clinical phenotype. We analyzed 15 cases of AIS and demonstrate the structural and functional relationships of the androgen receptor. We have sequenced the CYP17 (P450c17) gene in DNA from several patients with 17 alpha-hydroxylase deficiency, reconstructed the mutations in a human P450c17 cDNA and expressed the mutant P450c17 in COSl cells to characterize the kinetic properties of 17 alpha-hydroxylase and 17,20-lyase activities. The molecular bases of cases clinically reported as 17 alpha-hydroxylase deficiency have turned out to be complete or partial combined deficiencies of 17 alpha-hydroxylase/17,20-lyase. PMID:8864743

Nawata, H; Takayanagi, R; Yanase, T; Ikuyama, S; Okabe, T

1996-01-01

457

Reinforcement and sex linkage.  

PubMed

We present a general model for the effect of sex linkage on the evolution of reinforcement of mating preferences on an island. We find that the level of reinforcement can vary up to 80% depending on the mode of inheritance of the female preference and male trait. When reinforcement is driven mainly by selection in the male trait and intrinsic hybrid incompatibilities are weak, sex-linked preferences and autosomal male traits are the most conducive to reinforcement, whereas autosomal preferences and X-linked traits are the least. Surprisingly, the effect of mode of inheritance on reinforcement is poorly predicted by its effect on the genetic correlation between the male trait and female preference. Sex-linkage of genetic incompatibility loci increases reinforcement, though this is not due solely to the occurrence of Haldane's rule. We find that reinforcement can lead to complete reproductive isolation in some cases but not others and that the mode of inheritance can determine which outcome occurs. PMID:16817532

Hall, David W; Kirkpatrick, Mark

2006-05-01

458

Do operational sex ratios influence sex allocation in viviparous lizards with temperature-dependent sex determination?  

Microsoft Academic Search

Under certain environmental situations, selection may favour the ability of females to adjust the sex ratio of their offspring. Two recent studies have suggested that viviparous scincid lizards can modify the sex ratio of the offspring they produce in response to the operational sex ratio (OSR). Both of the species in question belong to genera that have also recently been

D. J. ALLSOP; D. A. WARNER; T. LANGKILDE; W. DU; R. SHINE

2006-01-01

459

"Sex Hormones" in Secondary School Biology Textbooks  

ERIC Educational Resources Information Center

This study explores the extent to which the term "sex hormone" is used in science textbooks, and whether the use of the term "sex hormone" is associated with pre-empirical concepts of sex dualism, in particular the misconceptions that these so-called "sex hormones" are sex specific and restricted to sex-related physiological functioning. We found…

Nehm, Ross H.; Young, Rebecca

2008-01-01

460

"Sex Hormones" in Secondary School Biology Textbooks  

ERIC Educational Resources Information Center

|This study explores the extent to which the term "sex hormone" is used in science textbooks, and whether the use of the term "sex hormone" is associated with pre-empirical concepts of sex dualism, in particular the misconceptions that these so-called "sex hormones" are sex specific and restricted to sex-related physiological functioning. We found…

Nehm, Ross H.; Young, Rebecca

2008-01-01

461

Sex workers talk about sex work: six contradictory characteristics of legalised sex work in Melbourne, Australia.  

PubMed

Despite research suggesting that legal sex work is safe and that emotional risks and social stigma are of greater concern than health risks, much research on sex work has focused on health risks. Given the legalisation of sex work in Victoria, Australia, it is timely to look beyond health. Three focus groups were conducted with a total of 14 female sex workers on their experience of legal sex work, both positive and negative, and the social acceptability of their profession. Thematic analysis was used to identify the key ways that sex workers described sex work. Women saw legal sex work as safer than illegal sex work, but still not socially acceptable. However, they also described six contradictory elements of sex work, which was seen as: financially rewarding and entrapping; empowering and demeaning; increasing some opportunities while reducing others; flexible and demanding; offering both intimacy and competition; and leading to a 'double life'. While legalisation has improved the safety of sex work, stigma and discrimination persist. PMID:23173716

Begum, Sufia; Hocking, Jane S; Groves, Jan; Fairley, Christopher K; Keogh, Louise A

2012-11-23

462

Chlamydia trachomatis species specific serology: ImmunoComb Chlamydia bivalent versus microimmunofluorescence (MIF).  

PubMed

The ImmunoComb Chlamydia Bivalent IgG/IgA (Orgenics, Israel) is a new quantitative serologic test that employs LPS extracted Chlamydia trachomatis L2 and LPS extracted Chlamydia pneumoniae elementary bodies on two separate antigenic spots. The Bivalent C. trachomatis specific test results were compared with microimmunofluorescence (MIF), the gold standard of chlamydial species specific serology. For C. trachomatis IgG the Bivalent was highly concordant with the MIF: the rate