WorldWideScience

Sample records for strict clock analyses

  1. RelTime Rates Collapse to a Strict Clock When Estimating the Timeline of Animal Diversification.

    Science.gov (United States)

    Lozano-Fernandez, Jesus; Dos Reis, Mario; Donoghue, Philip C J; Pisani, Davide

    2017-05-01

    Establishing an accurate timescale for the history of life is crucial to understand evolutionary processes. For this purpose, relaxed molecular clock models implemented in a Bayesian MCMC framework are generally used. However, these methods are time consuming. RelTime, a non-Bayesian method implementing a fast, ad hoc, algorithm for relative dating, was developed to overcome the computational inefficiencies of Bayesian software. RelTime was recently used to investigate the timing of origin of animals, yielding results consistent with early strict clock studies from the 1980s and 1990s, estimating metazoans to have a Mesoproterozoic origin-over a billion years ago. RelTime results are unexpected and disagree with the largest majority of modern, relaxed, Bayesian molecular clock analyses, which suggest animals originated in the Tonian-Cryogenian (less that 850 million years ago). Here, we demonstrate that RelTime-inferred divergence times for the origin of animals are spurious, a consequence of the inability of RelTime to relax the clock along the internal branches of the animal phylogeny. RelTime-inferred divergence times are comparable to strict-clock estimates because they are essentially inferred under a strict clock. Our results warn us of the danger of using ad hoc algorithms making implicit assumptions about rate changes along a tree. Our study roundly rejects a Mesoproterozoic origin of animals; metazoans emerged in the Tonian-Cryogenian, and diversified in the Ediacaran, in the immediate prelude to the routine fossilization of animals in the Cambrian associated with the emergence of readily preserved skeletons. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  2. Analyses des discours non strictement mathematiques accompagnant des cours de mathematiques (Analysis of Not Strictly Mathematical Discourse in Mathematics Classes).

    Science.gov (United States)

    Robert, Aline

    1995-01-01

    Examines discourse, not strictly mathematical, that teachers might adopt in a mathematics class and presents three major functions of such discourse: communication; structuring and labeling; and reflection. Develops lines for further inquiry, notably on the third function, the most likely focus for specific preparation by the teacher. (13…

  3. [Quantitative and qualitative analyses for characteristics of the clock drawing in Alzheimer's disease].

    Science.gov (United States)

    Konagaya, Yoko; Konagaya, Masaaki; Watanabe, Tomoyuki; Washimi, Yukihiko

    2014-01-01

    We analyzed the results of the clock drawing test (CDT) in patients with Alzheimer's disease (AD) by quantitative and qualitative methods to evaluate its significance for cognitive function screening. We administered the CDT and mini-mental state examination (MMSE) to a total of 156 AD patients, and CDT performance was scored quantitatively in accordance with the method by Freedman, while the CDT error types were qualitatively classified by Rouleau's method. We divided AD patients into three groups by their MMSE total score (A: 23 ≤, B: 18~22, C: ≤ 17). The mean total scores of CDT and MMSE in AD were 11.5 ± 3.4 and 19.8 ± 4.7, respectively, and the total CDT scores showed significant positive correlation with the total MMSE scores (r = 0.450). Fewer than 80% of subjects drew the clock correctly for 8 out of 15 sub-items, and fewer were able to correctly draw clock hands than could correctly draw numbers, contour or a center. In analysis of CDT qualitative error types, the most common error types were spatial and/or planning deficit (SPD) (28.2%), and conceptual deficit (CD) (23.7%), which suggested visuospatial impairments and semantic impairments play essential roles in AD patients' poor clock drawings. The frequency of CD and SPD error types significantly increased as severity of cognitive function worsened (p < 0.001, p < 0.05, respectively), and those of stimulus-bound response and perseveration had tendency to increase as severity of cognitive function. The present study suggests that CDT is a useful screening method not only for the impairment of cognitive function and the severity of cognitive dysfunction, but also for identification of specific cognitive function impairments in AD patients.

  4. Efficient Strictness Analysis of Haskell

    DEFF Research Database (Denmark)

    Jensen, Kristian Damm; Hjæresen, Peter; Rosendahl, Mads

    1994-01-01

    Strictness analysis has been a living field of investigation since Mycroft's original work in 1980, and is getting increasingly significant with the still wider use of lazy functional programming languages. This paper focuses on an actual implementation of a strictness analyser for Haskell...

  5. Analyse und Entwurf von hochbitratigen Clock-and-Data-Recovery Schaltungen in CMOS-Technologie

    Directory of Open Access Journals (Sweden)

    J.-K. Bremer

    2007-06-01

    Full Text Available In dieser Arbeit wird ein neuartiges Schaltungskonzept für die Realisierung eines Phasendetektors einer Clock-and-Data-Recovery Schaltung vorgestellt. Es handelt sich hierbei um eine nichtlineare Phasendetektorarchitektur, die nach dem Verfahren von Alexander arbeitet. Um die Funktionalität des Phasendetektors im Hochfrequenzbereich zu gewährleisten, wurden in dem Design sehr schnell schaltende HLO-Flip-Flops (high-speed latching operation flip-flop verwendet. Ein wesentliches Entwurfsziel war die Begrenzung des selbstgenerierten Jitters des Phasendetektors. Der Schaltungsentwurf wurde mit der Simulationsumgebung Cadence Spectre durchgeführt und die Funktionalität der Schaltung im GHz-Bereich anhand von ausgewählten Simulationen verifiziert.

    This paper presents a novel realization concept for Clock-and-Data-Recovery circuits. Our Design uses a nonlinear phase detector architecture, which is based on the Alexander phase detection method. In order to ensure circuit functionality in the RF region, we use very fast switching HLO-Flip-Flops (high-speed latching operation flip-flop in our design. The primal goal in our design was the minimization of self induced jitter of the phase detector. The accuracy of our circuit design and the functionality in the GHz regime is confirmed by various circuit simulations executed with the SPECTRE Simulator.

  6. The relative ages of ectomycorrhizal mushrooms and their plant hosts estimated using Bayesian relaxed molecular clock analyses

    Science.gov (United States)

    Hibbett, David S; Matheny, P Brandon

    2009-01-01

    Background Ectomycorrhizae (ECM) are symbioses formed by polyphyletic assemblages of fungi (mostly Agaricomycetes) and plants (mostly Pinaceae and angiosperms in the rosid clade). Efforts to reconstruct the evolution of the ECM habit in Agaricomycetes have yielded vastly different results, ranging from scenarios with many relatively recent origins of the symbiosis and no reversals to the free-living condition; a single ancient origin of ECM and many subsequent transitions to the free-living condition; or multiple gains and losses of the association. To test the plausibility of these scenarios, we performed Bayesian relaxed molecular clock analyses including fungi, plants, and other eukaryotes, based on the principle that a symbiosis cannot evolve prior to the origin of both partners. As we were primarily interested in the relative ages of the plants and fungi, we did not attempt to calibrate the molecular clock using the very limited fossil record of Agaricomycetes. Results Topologically constrained and unconstrained analyses suggest that the root node of the Agaricomycetes is much older than either the rosids or Pinaceae. The Agaricomycetidae, a large clade containing the Agaricales and Boletales (collectively representing 70% of Agaricomycetes), is also significantly older than the rosids. The relative age of Agaricomycetidae and Pinaceae, however, is sensitive to tree topology, and the inclusion or exclusion of the gnetophyte Welwitschia mirabilis. Conclusion The ancestor of the Agaricomycetes could not have been an ECM species because it existed long before any of its potential hosts. Within more derived clades of Agaricomycetes, there have been at least eight independent origins of ECM associations involving angiosperms, and at least six to eight origins of associations with gymnosperms. The first ECM symbioses may have involved Pinaceae, which are older than rosids, but several major clades of Agaricomycetes, such as the Boletales and Russulales, are young

  7. Strict confluent drawing

    Directory of Open Access Journals (Sweden)

    David Eppstein

    2016-01-01

    Full Text Available We define strict confluent drawing, a form of confluent drawing in which the existence of an edge is indicated by the presence of a smooth path through a system of arcs and junctions (without crossings, and in which such a path, if it exists, must be unique. We prove that it is NP-complete to determine whether a given graph has a strict confluent drawing but polynomial to determine whether it has an outerplanar strict confluent drawing with a fixed vertex ordering (a drawing within a disk, with the vertices placed in a given order on the boundary.

  8. Analyses of the cellular clock gene expression in peripheral tissue, caudal fin, in the Japanese flounder, Paralichthys olivaceus.

    Science.gov (United States)

    Mogi, Makoto; Yokoi, Hayato; Suzuki, Tohru

    2017-07-01

    Understanding the systems for maintaining the circadian rhythms that give organisms the flexibility to adapt to environmental changes is important in both aquaculture and fish chronobiology, because nursery lighting conditions can affect the survival and growth rates of larvae. We previously demonstrated that in flounder, the suprachiasmatic nucleus (SCN) exhibits daily rhythm in per2 expression, in sharp contrast to zebrafish, in which the SCN does not exhibit clear per2 expression rhythm. To examine whether a hierarchy exists in systems that maintain the expression rhythm of peripheral clock genes in flounder, in the present study we analyzed the in vivo and in vitro expression of three clock genes, per2, per1, and cry1, in the caudal fin and the effects of cortisol and melatonin administration on the expression of each clock gene. In vivo, the fin maintained a daily expression rhythm of all three genes, even in 24-h darkness (DD) when shifted from 12-h light:12-h dark (LD) conditions, but fin explants lost the expression rhythm after a short time of tissue culture, even under LD conditions. Cortisol, but not melatonin, significantly upregulated the expression of the three clock genes in fin both in vitro and in vivo. Therefore, we hypothesize that the SCN-pituitary-adrenal cortex pathway plays a role in the oscillation of the peripheral clock in flounder. However, in vivo, peak expression of per2 and cry1 was shifted 2-4h earlier under DD conditions, and their expression was upregulated in response to short exposures to light when larvae were kept under DD conditions. Therefore, we also hypothesize that in addition to the SCN, a light-responsive coordinating factor also functions in photo-entrainment of the peripheral clock in flounder. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Strictly convex renormings

    Czech Academy of Sciences Publication Activity Database

    Moltó, A.; Orihuela, J.; Troyanski, S.; Zizler, Václav

    2007-01-01

    Roč. 75, č. 3 (2007), s. 647-658 ISSN 0024-6107 R&D Projects: GA AV ČR IAA100190502 Institutional research plan: CEZ:AV0Z10190503 Keywords : strictly convex norms * lattice norm * quasi-diagonal sets Subject RIV: BA - General Mathematics Impact factor: 0.733, year: 2007

  10. Quine's "Strictly Vegetarian" Analyticity

    NARCIS (Netherlands)

    Decock, L.B.

    2017-01-01

    I analyze Quine’s later writings on analyticity from a linguistic point of view. In Word and Object Quine made room for a “strictly vegetarian” notion of analyticity. In later years, he developed this notion into two more precise notions, which I have coined “stimulus analyticity” and “behaviorist

  11. Species Protection in the European Union : How Strict is Strict?

    NARCIS (Netherlands)

    Schoukens, Hendrik; Bastmeijer, Kees; Born et al., Charles-Hubert

    2015-01-01

    European Union law to protect wild species of plants and animals is generally considered as ‘strict’. Opponents of nature conservation law often pick the species protection components of the EU Bird Directive and Habitat Directive as a prime example of an unnecessary strict regulatory scheme that

  12. Strictness Analysis for Attribute Grammars

    DEFF Research Database (Denmark)

    Rosendahl, Mads

    1992-01-01

    interpretation of attribute grammars. The framework is used to construct a strictness analysis for attribute grammars. Results of the analysis enable us to transform an attribute grammar such that attributes are evaluated during parsing, if possible. The analysis is proved correct by relating it to a fixpoint...... semantics for attribute grammars. An implementation of the analysis is discussed and some extensions to the analysis are mentioned....

  13. Strictness Analysis and Denotational Abstract Interpretation

    DEFF Research Database (Denmark)

    Nielson, Flemming

    1988-01-01

    there and this sufices to make the framework applicable to strictness analysis for the lambda-calculus. This shows the possibility of a general theory for the analysis of functional programs and it gives more insight into the relative precision of the various analyses. In particular it is shown that a collecting (static......A theory of abstract interpretation () is developed for a typed lambda-calculus. The typed lambda-calculus may be viewed as the ''static'' part of a two-level denotational metalanguage for which abstract interpretation was developed by ). The present development relaxes a condition imposed...

  14. Flexible or Strict Taxonomic Organization?

    DEFF Research Database (Denmark)

    Glückstad, Fumiko Kano; Mørup, Morten

    2012-01-01

    This work compares methods for constructing feature-based ontologies that are supposed to be used for culturally-specific knowledge transfer. The methods to be compared are the Terminological Ontology (TO) [1], a method of constructing ontology based on strict principles and rules, and the Infinite...... Relational Model (IRM) [2], a novel unsupervised machine learning method that learns multi-dimensional relations among concepts and features from loosely structured datasets. These methods are combined with a novel cognitive model, the Bayesian Model of Generalization (BMG) [3] that maps culturally...

  15. Deep Space Atomic Clock

    Data.gov (United States)

    National Aeronautics and Space Administration — The Deep Space Atomic Clock (DSAC) project will develop a small, low mass atomic clock based on mercury-ion trap technology and demonstrate it in space providing the...

  16. Clocks and their discovery

    OpenAIRE

    Dugan, David

    2004-01-01

    Does technology, or the need for technology in the culture come first? Simon Schaffer in St Alban’s Abbey reflects on the connection between Christianity and clocks. God as the omniscient clock-maker.

  17. Crime clocks and target performance maps

    CSIR Research Space (South Africa)

    Cooper, Antony K

    1999-12-01

    Full Text Available for the prevention and management of crime. This paper describes two innovative techniques that were developed by CSIR for analysing crime: "crime clocks" and "target performance maps"....

  18. Clock Tree Power Analysis

    OpenAIRE

    Austbø, Knut

    2016-01-01

    The buffered clock tree structure is commonly used to distribute the clock signal to the memory elements in digital circuits. Since the clock signal is used as a temporal reference, it has to be distributed to the registers with decent timing characteristics and low skew. In order to achieve this, buffers and inverters are inserted in the clock tree, typically by a synthesis tool. The clock tree is a major contributor to the power consumption. This is a result of a combination of high swit...

  19. Extremely strict ideals in Banach spaces

    Indian Academy of Sciences (India)

    Motivated by the notion of an ideal introduced by Godefroy {\\it et al.} ({\\it Studia Math.} {\\bf 104} (1993) 13–59), in this article, we introduce and study the notion of an extremely strict ideal. For a Poulsen simplex K , we show that the space of affine continuous functions on K is an extremely strict ideal in the space of continuous ...

  20. Hyperbolic spaces are of strictly negative type

    DEFF Research Database (Denmark)

    Hjorth, Poul G.; Kokkendorff, Simon L.; Markvorsen, Steen

    2002-01-01

    We study finite metric spaces with elements picked from, and distances consistent with, ambient Riemannian manifolds. The concepts of negative type and strictly negative type are reviewed, and the conjecture that hyperbolic spaces are of strictly negative type is settled, in the affirmative...

  1. Extremely strict ideals in Banach spaces

    Indian Academy of Sciences (India)

    Abstract. Motivated by the notion of an ideal introduced by Godefroy et al. (Stu- dia Math. 104 (1993) 13–59), in this article, we introduce and study the notion of an extremely strict ideal. For a Poulsen simplex K, we show that the space of affine contin- uous functions on K is an extremely strict ideal in the space of continuous ...

  2. Clock Drawing in Spatial Neglect: A Comprehensive Analysis of Clock Perimeter, Placement, and Accuracy

    Science.gov (United States)

    Chen, Peii; Goedert, Kelly M.

    2012-01-01

    Clock drawings produced by right-brain-damaged (RBD) individuals with spatial neglect often contain an abundance of empty space on the left while numbers and hands are placed on the right. However, the clock perimeter is rarely compromised in neglect patients’ drawings. By analyzing clock drawings produced by 71 RBD and 40 healthy adults, this study investigated whether the geometric characteristics of the clock perimeter reveal novel insights to understanding spatial neglect. Neglect participants drew smaller clocks than either healthy or non-neglect RBD participants. While healthy participants’ clock perimeter was close to circular, RBD participants drew radially extended ellipses. The mechanisms for these phenomena were investigated by examining the relation between clock-drawing characteristics and performance on six subtests of the Behavioral Inattention Test (BIT). The findings indicated that the clock shape was independent of any BIT subtest or the drawing placement on the test sheet and that the clock size was significantly predicted by one BIT subtest: the poorer the figure and shape copying, the smaller the clock perimeter. Further analyses revealed that in all participants, clocks decreased in size as they were placed farther from the center of the paper. However, even when neglect participants placed their clocks towards the center of the page, they were smaller than those produced by healthy or non-neglect RBD participants. These results suggest a neglect-specific reduction in the subjectively available workspace for graphic production from memory, consistent with the hypothesis that neglect patients are impaired in the ability to enlarge the attentional aperture. PMID:22390278

  3. GPS Composite Clock Analysis

    OpenAIRE

    Wright, James R.

    2008-01-01

    The GPS composite clock defines GPS time, the timescale used today in GPS operations. GPS time is illuminated by examination of its role in the complete estimation and control problem relative to UTC/TAI. The phase of each GPS clock is unobservable from GPS pseudorange measurements, and the mean phase of the GPS clock ensemble (GPS time) is unobservable. A new and useful observability definition is presented, together with new observability theorems, to demonstrate explicitly that GPS time is...

  4. Finite Metric Spaces of Strictly negative Type

    DEFF Research Database (Denmark)

    Hjorth, Poul G.

    If a finite metric space is of strictly negative type then its transfinite diameter is uniquely realized by an infinite extent (“load vector''). Finite metric spaces that have this property include all trees, and all finite subspaces of Euclidean and Hyperbolic spaces. We prove that if the distance...... matrix of a finite metric space is both hypermetric and regular, then it is of strictly negative type. We show that the strictly negative type finite subspaces of spheres are precisely those which do not contain two pairs of antipodal points....

  5. Precision Clock Evaluation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Tests and evaluates high-precision atomic clocks for spacecraft, ground, and mobile applications. Supports performance evaluation, environmental testing,...

  6. Mammalian evolution may not be strictly bifurcating.

    Science.gov (United States)

    Hallström, Björn M; Janke, Axel

    2010-12-01

    The massive amount of genomic sequence data that is now available for analyzing evolutionary relationships among 31 placental mammals reduces the stochastic error in phylogenetic analyses to virtually zero. One would expect that this would make it possible to finally resolve controversial branches in the placental mammalian tree. We analyzed a 2,863,797 nucleotide-long alignment (3,364 genes) from 31 placental mammals for reconstructing their evolution. Most placental mammalian relationships were resolved, and a consensus of their evolution is emerging. However, certain branches remain difficult or virtually impossible to resolve. These branches are characterized by short divergence times in the order of 1-4 million years. Computer simulations based on parameters from the real data show that as little as about 12,500 amino acid sites could be sufficient to confidently resolve short branches as old as about 90 million years ago (Ma). Thus, the amount of sequence data should no longer be a limiting factor in resolving the relationships among placental mammals. The timing of the early radiation of placental mammals coincides with a period of climate warming some 100-80 Ma and with continental fragmentation. These global processes may have triggered the rapid diversification of placental mammals. However, the rapid radiations of certain mammalian groups complicate phylogenetic analyses, possibly due to incomplete lineage sorting and introgression. These speciation-related processes led to a mosaic genome and conflicting phylogenetic signals. Split network methods are ideal for visualizing these problematic branches and can therefore depict data conflict and possibly the true evolutionary history better than strictly bifurcating trees. Given the timing of tectonics, of placental mammalian divergences, and the fossil record, a Laurasian rather than Gondwanan origin of placental mammals seems the most parsimonious explanation.

  7. Educational Technology Classics: The Computer versus the Clock

    Science.gov (United States)

    Slack, Charles W.

    2010-01-01

    It is no accident that the first use of computers in school systems was to arrange schedules for students and teachers. The proper use of the computer in the classroom is as a replacement for the clock and its strict temporal schedule. By conveying information through self-instructional content, the computer can schedule work for pupils in…

  8. Hyperbolic spaces are of strictly negative type

    DEFF Research Database (Denmark)

    Hjorth, Poul G.; Kokkendorff, Simon L.; Markvorsen, Steen

    2002-01-01

    We study finite metric spaces with elements picked from, and distances consistent with, ambient Riemannian manifolds. The concepts of negative type and strictly negative type are reviewed, and the conjecture that hyperbolic spaces are of strictly negative type is settled, in the affirmative....... The technique of the proof is subsequently applied to show that every compact manifold of negative type must have trivial fundamental group, and to obtain a necessary criterion for product manifolds to be of negative type....

  9. Biological Clocks & Circadian Rhythms

    Science.gov (United States)

    Robertson, Laura; Jones, M. Gail

    2009-01-01

    The study of biological clocks and circadian rhythms is an excellent way to address the inquiry strand in the National Science Education Standards (NSES) (NRC 1996). Students can study these everyday phenomena by designing experiments, gathering and analyzing data, and generating new experiments. As students explore biological clocks and circadian…

  10. Strictly convex functions on complete Finsler manifolds

    Indian Academy of Sciences (India)

    ... Refresher Courses · Symposia · Live Streaming. Home; Journals; Proceedings – Mathematical Sciences; Volume 126; Issue 4. Strictly convex functions on complete Finsler manifolds. YOE ITOKAWA KATSUHIRO SHIOHAMA BANKTESHWAR TIWARI. Research Article Volume 126 Issue 4 October 2016 pp 623-627 ...

  11. Finite Metric Spaces of Strictly Negative Type

    DEFF Research Database (Denmark)

    Hjorth, Poul; Lisonek, P.; Markvorsen, Steen

    1998-01-01

    We prove that, if a finite metric space is of strictly negative type, then its transfinite diameter is uniquely realized by the infinite extender (load vector). Finite metric spaces that have this property include all spaces on two, three, or four points, all trees, and all finite subspaces of Eu...

  12. Extremely strict ideals in Banach spaces

    Indian Academy of Sciences (India)

    the space of regular Borel measures, it is easy to see that with respect to the projection μ → μ|(0, 1), M is an extremely strict ideal in C([0, 1]) but as the Lebesgue measure is non-atomic, M. ∗. 1 is not the norm closed ..... (Grenoble) 28 (1978) 35–65. [10] Rao T S S R K, On ideals in Banach spaces, Rocky Mountain J. Math.

  13. Pittendrigh: The Darwinian Clock-Watcher

    Indian Academy of Sciences (India)

    cyanobacteria. The abysmal numbers of plant and protists in particular is a reminder that current chronobiology research is very animal-centered, primarily due to the pressure to use models that can be functionally linked to the analyses of human disease. Back in the 1960s when nothing was known about clock genes and ...

  14. Crime clocks and target performance maps

    CSIR Research Space (South Africa)

    Cooper, Anthony K

    1999-12-01

    Full Text Available View), spreadsheets (eg: Excel) and data bases (eg: Access). 2. Crime clocks A map of crime clocks displays the distribution of crime in time and space using scaled pie charts to show the relative crime rates for the selected period being analysed. Each... pie chart shows the total aggregated crime for an area (eg: CAS Block or precinct) and is positioned on the centroid of the relevant area. Hence, the size of each pie chart is proportional to the amount of crime that occurred in that area over...

  15. SRC: Smart Reminder Clock

    Science.gov (United States)

    Kasim, Shahreen; Hafit, Hanayanti; Leong, Tan Hua; Hashim, Rathiah; Ruslai, Husni; Jahidin, Kamaruzzaman; Syafwan Arshad, Mohammad

    2016-11-01

    Nowadays, some people facing the problem to wake up in the morning. This was result to absence of the classes, meetings, and even exams. The aim of this project is to develop an android application that can force the user to wake up. The method used in this application are pedometer and Short Message Service (SMS) function. This application need the user to take their smartphone and walk about 10 steps to disable it, when the alarm clock is activated. After that, when the alarm clock was rang, this alarm application has automatically send a message to the users’ friends or parents phone to wake them up.

  16. 7 CFR 28.441 - Strict Middling Yellow Stained Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Yellow Stained Color. 28.441 Section... Strict Middling Yellow Stained Color. Strict Middling Yellow Stained Color is color which is deeper than that of Strict Middling Tinged Color. [57 FR 34498, Aug. 5, 1992] ...

  17. 7 CFR 28.412 - Strict Middling Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Light Spotted Color. 28.412 Section 28... Light Spotted Color. Strict Middling Light Spotted Color is color which in spot or color, or both, is between Strict Middling Color and Strict Middling Spotted Color. ...

  18. Clock Reaction: Outreach Attraction

    Science.gov (United States)

    Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

    2010-01-01

    Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

  19. Cryptochromes and Biological Clocks

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 9. Cryptochromes and Biological Clocks. V R Bhagwat. General Article Volume 7 Issue 9 September 2002 pp 36-48. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/007/09/0036-0048. Keywords.

  20. Decamp Clock Board Firmware

    International Nuclear Information System (INIS)

    Vicente, J. de; Castilla, J.; Martinez, G.

    2007-01-01

    Decamp (Dark Energy Survey Camera) is a new instrument designed to explore the universe aiming to reveal the nature of Dark Energy. The camera consists of 72 CCDs and 520 Mpixels. The readout electronics of DECam is based on the Monsoon system. Monsoon is a new image acquisition system developed by the NOAO (National Optical Astronomical Observatory) for the new generation of astronomical cameras. The Monsoon system uses three types of boards inserted in a Eurocard format based crate: master control board, acquisition board and clock board. The direct use of the Monsoon system for DECam readout electronics requires nine crates mainly due to the high number of clock boards needed. Unfortunately, the available space for DECam electronics is constrained to four crates at maximum. The major drawback to achieve such desired compaction degree resides in the clock board signal density. This document describes the changes performed at CIEMAT on the programmable logic of the Monsoon clock board aiming to meet such restricted space constraints. (Author) 5 refs

  1. Decamp Clock Board Firmware

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Castilla, J.; Martinez, G.

    2007-09-27

    Decamp (Dark Energy Survey Camera) is a new instrument designed to explore the universe aiming to reveal the nature of Dark Energy. The camera consists of 72 CCDs and 520 Mpixels. The readout electronics of DECam is based on the Monsoon system. Monsoon is a new image acquisition system developed by the NOAO (National Optical Astronomical Observatory) for the new generation of astronomical cameras. The Monsoon system uses three types of boards inserted in a Eurocard format based crate: master control board, acquisition board and clock board. The direct use of the Monsoon system for DECam readout electronics requires nine crates mainly due to the high number of clock boards needed. Unfortunately, the available space for DECam electronics is constrained to four crates at maximum. The major drawback to achieve such desired compaction degree resides in the clock board signal density. This document describes the changes performed at CIEMAT on the programmable logic of the Monsoon clock board aiming to meet such restricted space constraints. (Author) 5 refs.

  2. Geometrical optimization for strictly localized structures

    Science.gov (United States)

    Mo, Yirong

    2003-07-01

    Recently we proposed the block localized wavefunction (BLW) approach which takes the advantages of valence bond theory and molecular orbital theory and defines the wavefunctions for resonance structures based on the assumption that all electrons and orbitals are partitioned into a few subgroups. In this work, we implement the geometrical optimization of the BLW method based on the algorithm proposed by Gianinetti and coworkers. Thus, we can study the conjugation effect on not only the molecular stability, but also the molecular geometry. With this capability, the π conjugation effect in trans-polyenes C2nH2n+2 (n=2-5) as well as in formamide and its analogs are studied by optimizing their delocalized and strictly localized forms with the 6-31G(d) and 6-311+G(d,p) basis sets. Although it has been well presumed that the π resonance shortens the single bonds and lengthens the double bonds with the delocalization of π electrons across the whole line in polyenes, our optimization of the strictly localized structures quantitatively shows that when the conjugation effect is "turned off," the double bond lengths will be identical to the CC bond length in ethylene and the single Csp2-Csp2 bond length will be about 1.513-1.517 Å. In agreement with the classical Hückel theory, the resonance energies in polyenes are approximately in proportion to the number of double bonds. Similarly, resonance is responsible not only for the planarity of formamide, thioformamide, and selenoformamide, but also for the lengthening of the CX (X=O,S,Se) double bond and the shortening of the CN bonds. Although it is assumed that the CX bond polarization decreases in the order of O>S>Se, the π electronic delocalization increases in the opposite order, i.e., formamide

  3. From Regular to Strictly Locally Testable Languages

    Directory of Open Access Journals (Sweden)

    Stefano Crespi Reghizzi

    2011-08-01

    Full Text Available A classical result (often credited to Y. Medvedev states that every language recognized by a finite automaton is the homomorphic image of a local language, over a much larger so-called local alphabet, namely the alphabet of the edges of the transition graph. Local languages are characterized by the value k=2 of the sliding window width in the McNaughton and Papert's infinite hierarchy of strictly locally testable languages (k-slt. We generalize Medvedev's result in a new direction, studying the relationship between the width and the alphabetic ratio telling how much larger the local alphabet is. We prove that every regular language is the image of a k-slt language on an alphabet of doubled size, where the width logarithmically depends on the automaton size, and we exhibit regular languages for which any smaller alphabetic ratio is insufficient. More generally, we express the trade-off between alphabetic ratio and width as a mathematical relation derived from a careful encoding of the states. At last we mention some directions for theoretical development and application.

  4. CLOCK stabilizes CYCLE to initiate clock function inDrosophila.

    Science.gov (United States)

    Liu, Tianxin; Mahesh, Guruswamy; Yu, Wangjie; Hardin, Paul E

    2017-10-10

    The Drosophila circadian clock keeps time via transcriptional feedback loops. These feedback loops are initiated by CLOCK-CYCLE (CLK-CYC) heterodimers, which activate transcription of genes encoding the feedback repressors PERIOD and TIMELESS. Circadian clocks normally operate in ∼150 brain pacemaker neurons and in many peripheral tissues in the head and body, but can also be induced by expressing CLK in nonclock cells. These ectopic clocks also require cyc , yet CYC expression is restricted to canonical clock cells despite evidence that cyc mRNA is widely expressed. Here we show that CLK binds to and stabilizes CYC in cell culture and in nonclock cells in vivo. Ectopic clocks also require the blue light photoreceptor CRYPTOCHROME (CRY), which is required for both light entrainment and clock function in peripheral tissues. These experiments define the genetic architecture required to initiate circadian clock function in Drosophila , reveal mechanisms governing circadian activator stability that are conserved in perhaps all eukaryotes, and suggest that Clk , cyc , and cry expression is sufficient to drive clock expression in naive cells.

  5. 7 CFR 28.404 - Strict Low Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Low Middling Color. 28.404 Section 28.404... for the Color Grade of American Upland Cotton § 28.404 Strict Low Middling Color. Strict Low Middling Color is color which is within the range represented by a set of samples in the custody of the United...

  6. 7 CFR 28.406 - Strict Good Ordinary Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Good Ordinary Color. 28.406 Section 28.406... for the Color Grade of American Upland Cotton § 28.406 Strict Good Ordinary Color. Strict Good Ordinary Color is color which is within the range represented by a set of samples in the custody of the...

  7. 7 CFR 28.402 - Strict Middling Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Color. 28.402 Section 28.402... for the Color Grade of American Upland Cotton § 28.402 Strict Middling Color. Strict Middling Color is color which is within the range represented by a set of samples in the custody of the United States...

  8. Circadian Clock, Cancer, and Chemotherapy

    Science.gov (United States)

    2015-01-01

    The circadian clock is a global regulatory system that interfaces with most other regulatory systems and pathways in mammalian organisms. Investigations of the circadian clock–DNA damage response connections have revealed that nucleotide excision repair, DNA damage checkpoints, and apoptosis are appreciably influenced by the clock. Although several epidemiological studies in humans and a limited number of genetic studies in mouse model systems have indicated that clock disruption may predispose mammals to cancer, well-controlled genetic studies in mice have not supported the commonly held view that circadian clock disruption is a cancer risk factor. In fact, in the appropriate genetic background, clock disruption may instead aid in cancer regression by promoting intrinsic and extrinsic apoptosis. Finally, the clock may affect the efficacy of cancer treatment (chronochemotherapy) by modulating the pharmacokinetics and pharmacodynamics of chemotherapeutic drugs as well as the activity of the DNA repair enzymes that repair the DNA damage caused by anticancer drugs. PMID:25302769

  9. Circadian clock and oral cancer.

    Science.gov (United States)

    Nirvani, Minou; Khuu, Cuong; Utheim, Tor Paaske; Sand, Lars Peter; Sehic, Amer

    2018-02-01

    The circadian clock is comprised of a master component situated in the hypothalamic suprachiasmatic nucleus and subordinate clock genes in almost every cell of the body. The circadian clock genes and their encoded proteins govern the organism to follow the natural signals of time, and adapt to external changes in the environment. The majority of physiological processes in mammals exhibit variable circadian rhythms, which are generated and coordinated by an oscillation in the expression of the clock genes. A number of studies have reported that alteration in the expression level of clock genes is correlated with several pathological conditions, including cancer. However, little is known about the role of clock genes in homeostasis of the oral epithelium and their disturbances in oral carcinogenesis. The present review summarizes the current state of knowledge of the implications of clock genes in oral cancer. It has been demonstrated that the development of oral squamous cell carcinoma undergoes circadian oscillation in relation to tumor volume and proliferation rate. The circadian clock gene period ( PER)1 has been associated with oral cancer pathogenesis and it is suggested that changes in the expression of PER1 may exhibit an important role in the development, invasion, and metastasis of oral squamous cell carcinoma. However, its role remains elusive and there is a need for further research in order to understand the underlying mechanisms of the clock genes in oral cancer pathogenesis.

  10. Clocks and special relativity

    International Nuclear Information System (INIS)

    MacRoberts, D.T.

    1980-01-01

    A kinematic theory without precise definitions of the 'space' and 'time' used is an uninterpreted calculus. The definition of 'time' in special relativity is based on light propagation and the 'constant velocity of light' is a tautological consequence of the definition. When this definition is reified in a 'clock' the phenomenon of 'time dilation' occurs, in terms of the defined time, but is not reciprocal between moving systems; the postulate of relativity is not observed. The new definition of time is compatible with an ether theory without the relativity principle. The derivation of the Lorentz transformations, which requires both postulates, is purely formalistic and is not ontologically sound. (Auth.)

  11. Methodologies for steering clocks

    Science.gov (United States)

    Chadsey, Harold

    1995-01-01

    One of the concerns of the PTTI community is the coordination of one time scale with another. This is accomplished through steering one clock system to another, with a goal of a zero or constant offset in time and frequency. In order to attain this goal, rate differences are calculated and allowed for by the steering algorithm. This paper will present several of these different methods of determining rate differences. Ideally, any change in rate should not cause the offset to change sign (overshoot) by any amount, but certainly not by as much as its previous absolute value. The advantages and disadvantages of each depend on the user's situation.

  12. A Light Clock Satisfying the Clock Hypothesis of Special Relativity

    Science.gov (United States)

    West, Joseph

    2007-01-01

    The design of the FMEL, a floor-mirrored Einstein-Langevin "light clock", is introduced. The clock provides a physically intuitive manner to calculate and visualize the time dilation effects for a spatially extended set of observers (an accelerated "frame") undergoing unidirectional acceleration or observers on a rotating cylinder of constant…

  13. Master/slave clock arrangement for providing reliable clock signal

    Science.gov (United States)

    Abbey, Duane L. (Inventor)

    1977-01-01

    The outputs of two like frequency oscillators are combined to form a single reliable clock signal, with one oscillator functioning as a slave under the control of the other to achieve phase coincidence when the master is operative and in a free-running mode when the master is inoperative so that failure of either oscillator produces no effect on the clock signal.

  14. A mixed relaxed clock model

    Science.gov (United States)

    2016-01-01

    Over recent years, several alternative relaxed clock models have been proposed in the context of Bayesian dating. These models fall in two distinct categories: uncorrelated and autocorrelated across branches. The choice between these two classes of relaxed clocks is still an open question. More fundamentally, the true process of rate variation may have both long-term trends and short-term fluctuations, suggesting that more sophisticated clock models unfolding over multiple time scales should ultimately be developed. Here, a mixed relaxed clock model is introduced, which can be mechanistically interpreted as a rate variation process undergoing short-term fluctuations on the top of Brownian long-term trends. Statistically, this mixed clock represents an alternative solution to the problem of choosing between autocorrelated and uncorrelated relaxed clocks, by proposing instead to combine their respective merits. Fitting this model on a dataset of 105 placental mammals, using both node-dating and tip-dating approaches, suggests that the two pure clocks, Brownian and white noise, are rejected in favour of a mixed model with approximately equal contributions for its uncorrelated and autocorrelated components. The tip-dating analysis is particularly sensitive to the choice of the relaxed clock model. In this context, the classical pure Brownian relaxed clock appears to be overly rigid, leading to biases in divergence time estimation. By contrast, the use of a mixed clock leads to more recent and more reasonable estimates for the crown ages of placental orders and superorders. Altogether, the mixed clock introduced here represents a first step towards empirically more adequate models of the patterns of rate variation across phylogenetic trees. This article is part of the themed issue ‘Dating species divergences using rocks and clocks’. PMID:27325829

  15. Synchronizing clocks in distributed networks

    NARCIS (Netherlands)

    Xia, Weiguo; Cao, Ming

    2011-01-01

    Very recently it has been shown that clocks in distributed networks cannot be synchronized precisely even in idealized situations when asymmetric delays are present [1]. In this paper by determining the clock synchronization errors in the similar settings of the impossibility result just mentioned,

  16. Synchronizing clocks in distributed networks

    NARCIS (Netherlands)

    Xia, Weiguo; Cao, Ming

    2011-01-01

    While various time synchronization protocols for clocks in wired and/or wireless networks are under development, recently it has been shown by Freris, Graham and Kumar that clocks in distributed networks cannot be synchronized precisely even in idealized situations. In this paper by determining the

  17. The circadian clock and asthma.

    Science.gov (United States)

    Durrington, Hannah J; Farrow, Stuart N; Loudon, Andrew S; Ray, David W

    2014-01-01

    It is characteristic of asthma that symptoms worsen overnight, particularly in the early hours of the morning. Nocturnal symptoms in asthma are common and are an important indicator for escalation of treatment. An extensive body of research has demonstrated that nocturnal symptoms of cough and dyspnea are accompanied by circadian variations in airway inflammation and physiologic variables, including airflow limitation and airways hyper-responsiveness. The molecular apparatus that underpins circadian variations, controlled by so called 'clock' genes, has recently been characterised. Clock genes control circadian rhythms both centrally, in the suprachiasmatic nucleus of the brain and peripherally, within every organ of the body. Here, we will discuss how clock genes regulate circadian rhythms. We will focus particularly on the peripheral lung clock and the peripheral immune clock and discuss how these might relate to both the pathogenesis and treatment of asthma.

  18. CLOCK interacts with RANBP9 and is involved in alternative splicing in spermatogenesis.

    Science.gov (United States)

    Yang, Junbao; Zhang, Zhiwei; Zhang, Yingying; Zheng, Xulei; Lu, Yilu; Tao, Dachang; Liu, Yunqiang; Ma, Yongxin

    2018-02-05

    The core circadian gene CLOCK plays an important role in regulating male reproduction. However, the underlying mechanism still remains unclear. In the present study, we executed yeast two-hybrid screening using cDNA fragment of CLOCK PAS A domain as bait, and identified RANBP9 as a novel protein interacting with CLOCK. The interaction between CLOCK and RANBP9 was further validated by in vivo and in vitro assays. Previous studies have confirmed that SF3B3 was a RANBP9 interacting protein. Subsequently, our study also found that CLOCK and SF3B3 can interact with each other by co-immunoprecipitation in mouse testis. In order to dissect the underlying mechanism of CLOCK in spermatogenesis, we also performed RNA-immunoprecipitation followed by high-throughput sequencing (RIP-Seq) in mouse testis. The result of sequence analyses and Gene Ontology enrichment analyses (biological processes) demonstrated that CLOCK can directly bind 186 key mRNA transcripts in mouse spermatogenesis. Taken together, our results firstly showed that CLOCK can interact with RANBP9 and bind with mRNAs, demonstrating that CLOCK is involved in alternative splicing in spermatogenesis. These results reveal a novel mechanism for CLOCK in spermatogenesis. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Plant use in the medicinal practices known as "strict diets" in Chazuta valley (Peruvian Amazon).

    Science.gov (United States)

    Sanz-Biset, Jaume; Cañigueral, Salvador

    2011-09-01

    Strict diets are traditional medicinal practices where plant remedies are consumed with nearly fasting and with some sort of social seclusion. The aim of this work was to describe these practices of Chazuta and the use of plants within, as well as to analyse the possible functions of the last. The information was obtained through interviews to the 6.3% of the district rural adult population (140 individuals, 75% of which was considered Quechua). In total, 122 strict diets were recorded and 106 different plant species were reported to be used. Strict diets present a characteristic structure and plant use. The main effects reported in strict diets were antinflammatory, antiinfective, brain function alteration and depuration. Strict diets are well structured traditional medicinal practices, also with a symbolic significance in the life cycle of chazutian men. Plants used in strict diets can contribute to the main effects through antinflammation, antiinfective actions, psychoactivity and depurative related activities. The correlation between literature evidence of activity of most used plants and effects reported for the correspondent diet (i.e. in which the plant was used) are 36% for antinflammatory activity, 29% for antimicrobial activity, 18% for psychoactivity and 5% for depurative related activities. The percentages go to 77%, 64%, 73% and 32%, respectively, when literature evidences on related taxa are also considered. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

  20. High Precision Clock Bias Prediction Model in Clock Synchronization System

    Directory of Open Access Journals (Sweden)

    Zan Liu

    2016-01-01

    Full Text Available Time synchronization is a fundamental requirement for many services provided by a distributed system. Clock calibration through the time signal is the usual way to realize the synchronization among the clocks used in the distributed system. The interference to time signal transmission or equipment failures may bring about failure to synchronize the time. To solve this problem, a clock bias prediction module is paralleled in the clock calibration system. And for improving the precision of clock bias prediction, the first-order grey model with one variable (GM(1,1 model is proposed. In the traditional GM(1,1 model, the combination of parameters determined by least squares criterion is not optimal; therefore, the particle swarm optimization (PSO is used to optimize GM(1,1 model. At the same time, in order to avoid PSO getting stuck at local optimization and improve its efficiency, the mechanisms that double subgroups and nonlinear decreasing inertia weight are proposed. In order to test the precision of the improved model, we design clock calibration experiments, where time signal is transferred via radio and wired channel, respectively. The improved model is built on the basis of clock bias acquired in the experiments. The results show that the improved model is superior to other models both in precision and in stability. The precision of improved model increased by 66.4%~76.7%.

  1. Simulating Future GPS Clock Scenarios with Two Composite Clock Algorithms

    Science.gov (United States)

    Suess, Matthias; Matsakis, Demetrios; Greenhall, Charles A.

    2010-01-01

    Using the GPS Toolkit, the GPS constellation is simulated using 31 satellites (SV) and a ground network of 17 monitor stations (MS). At every 15-minutes measurement epoch, the monitor stations measure the time signals of all satellites above a parameterized elevation angle. Once a day, the satellite clock estimates the station and satellite clocks. The first composite clock (B) is based on the Brown algorithm, and is now used by GPS. The second one (G) is based on the Greenhall algorithm. The composite clock of G and B performance are investigated using three ground-clock models. Model C simulates the current GPS configuration, in which all stations are equipped with cesium clocks, except for masers at USNO and Alternate Master Clock (AMC) sites. Model M is an improved situation in which every station is equipped with active hydrogen masers. Finally, Models F and O are future scenarios in which the USNO and AMC stations are equipped with fountain clocks instead of masers. Model F is a rubidium fountain, while Model O is more precise but futuristic Optical Fountain. Each model is evaluated using three performance metrics. The timing-related user range error having all satellites available is the first performance index (PI1). The second performance index (PI2) relates to the stability of the broadcast GPS system time itself. The third performance index (PI3) evaluates the stability of the time scales computed by the two composite clocks. A distinction is made between the "Signal-in-Space" accuracy and that available through a GNSS receiver.

  2. Clock genes, ADHD and aggression.

    Science.gov (United States)

    Mogavero, Floriana; Jager, Amanda; Glennon, Jeffrey C

    2016-11-09

    Attention deficit/hyperactivity disorder (ADHD) is frequently associated with comorbid aggression and sleep disturbances. The sleep/wake cycle is under the control of the circadian system which is moderated by clock genes. Clock genes can regulate the transcription of monoamine oxidase A, which is involved in the degradation of monoamines. Disturbances in monoamine interaction with clock genes in those with monoamine gene polymorphisms may regulate susceptibility of ADHD and comorbid aggression/sleep disturbances. While monoamines influence circadian rhythm and clock gene expression, circadian rhythm components modulate aggressive behavior, and altered clock genes expression have been associated with ADHD. We propose a mechanism by which circadian rhythm and clock gene expression may influence ADHD and comorbid aggression through the modulation of neurotransmitters. The role of clock genes in ADHD patients with comorbid aggression awaits further research; therefore we also indicate directions for future studies to help increase understanding of the underlying mechanisms in ADHD with comorbid aggression and sleep disturbances. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Low Power Clock Network Design

    Directory of Open Access Journals (Sweden)

    Inna Vaisband

    2011-05-01

    Full Text Available Power is a primary concern in modern circuits. Clock distribution networks, in particular, are an essential element of a synchronous digital circuit and a significant power consumer. Clock distribution networks are subject to clock skew due to process, voltage, and temperature (PVT variations and load imbalances. A target skew between sequentially-adjacent registers can be obtained in a balanced low power clock tree using techniques such as buffer and wire sizing. Existing skew mitigation techniques in tree-based clock distribution networks, however, are not efficient in coping with post design variations; whereas the latest non-tree mesh-based solutions reliably handle skew variations, albeit with a significant increase in dissipated power. Alternatively, crosslink-based methods provide low power and variation-efficient skew solutions. Existing crosslink-based methods, however, only address skew at the network topology level and do not target low power consumption. Different methods to manage skew and skew variations within tree and non-tree clock distribution networks are reviewed and compared in this paper. Guidelines for inserting crosslinks within a buffered low power clock tree are provided. Metrics to determine the most power efficient technique for a given circuit are discussed and verified with simulation.

  4. Physiological links of circadian clock and biological clock of aging.

    Science.gov (United States)

    Liu, Fang; Chang, Hung-Chun

    2017-07-01

    Circadian rhythms orchestrate biochemical and physiological processes in living organisms to respond the day/night cycle. In mammals, nearly all cells hold self-sustained circadian clocks meanwhile couple the intrinsic rhythms to systemic changes in a hierarchical manner. The suprachiasmatic nucleus (SCN) of the hypothalamus functions as the master pacemaker to initiate daily synchronization according to the photoperiod, in turn determines the phase of peripheral cellular clocks through a variety of signaling relays, including endocrine rhythms and metabolic cycles. With aging, circadian desynchrony occurs at the expense of peripheral metabolic pathologies and central neurodegenerative disorders with sleep symptoms, and genetic ablation of circadian genes in model organisms resembled the aging-related features. Notably, a number of studies have linked longevity nutrient sensing pathways in modulating circadian clocks. Therapeutic strategies that bridge the nutrient sensing pathways and circadian clock might be rational designs to defy aging.

  5. Minimal tool set for a prokaryotic circadian clock.

    Science.gov (United States)

    Schmelling, Nicolas M; Lehmann, Robert; Chaudhury, Paushali; Beck, Christian; Albers, Sonja-Verena; Axmann, Ilka M; Wiegard, Anika

    2017-07-21

    Circadian clocks are found in organisms of almost all domains including photosynthetic Cyanobacteria, whereby large diversity exists within the protein components involved. In the model cyanobacterium Synechococcus elongatus PCC 7942 circadian rhythms are driven by a unique KaiABC protein clock, which is embedded in a network of input and output factors. Homologous proteins to the KaiABC clock have been observed in Bacteria and Archaea, where evidence for circadian behavior in these domains is accumulating. However, interaction and function of non-cyanobacterial Kai-proteins as well as homologous input and output components remain mainly unclear. Using a universal BLAST analyses, we identified putative KaiC-based timing systems in organisms outside as well as variations within Cyanobacteria. A systematic analyses of publicly available microarray data elucidated interesting variations in circadian gene expression between different cyanobacterial strains, which might be correlated to the diversity of genome encoded clock components. Based on statistical analyses of co-occurrences of the clock components homologous to Synechococcus elongatus PCC 7942, we propose putative networks of reduced and fully functional clock systems. Further, we studied KaiC sequence conservation to determine functionally important regions of diverged KaiC homologs. Biochemical characterization of exemplary cyanobacterial KaiC proteins as well as homologs from two thermophilic Archaea demonstrated that kinase activity is always present. However, a KaiA-mediated phosphorylation is only detectable in KaiC1 orthologs. Our analysis of 11,264 genomes clearly demonstrates that components of the Synechococcus elongatus PCC 7942 circadian clock are present in Bacteria and Archaea. However, all components are less abundant in other organisms than Cyanobacteria and KaiA, Pex, LdpA, and CdpA are only present in the latter. Thus, only reduced KaiBC-based or even simpler, solely KaiC-based timing systems

  6. Modal Inclusion Logic: Being Lax is Simpler than Being Strict

    DEFF Research Database (Denmark)

    Hella, Lauri; Kuusisto, Antti Johannes; Meier, Arne

    2015-01-01

    We investigate the computational complexity of the satisfiability problem of modal inclusion logic. We distinguish two variants of the problem: one for strict and another one for lax semantics. The complexity of the lax version turns out to be complete for EXPTIME, whereas with strict semantics...

  7. 7 CFR 28.431 - Strict Middling Tinged Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Tinged Color. 28.431 Section 28.431 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Color. Strict Middling Tinged Color is color which is better than Middling Tinged Color. ...

  8. 7 CFR 28.433 - Strict Low Middling Tinged Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Low Middling Tinged Color. 28.433 Section 28.433 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Tinged Color. Strict Low Middling Tinged Color is color which is within the range represented by a set of...

  9. 7 CFR 28.424 - Strict Low Middling Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Low Middling Spotted Color. 28.424 Section 28.424 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Spotted Color. Strict Low Middling Spotted Color is color which is within the range represented by a set...

  10. 7 CFR 28.426 - Strict Good Ordinary Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Good Ordinary Spotted Color. 28.426 Section 28.426 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Spotted Color. Strict Good Ordinary Spotted Color is color which is within the range represented by a set...

  11. 7 CFR 28.422 - Strict Middling Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Strict Middling Spotted Color. 28.422 Section 28.422 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards... Color. Strict Middling Spotted Color is color which is within the range represented by a set of samples...

  12. Strictly-regular number system and data structures

    DEFF Research Database (Denmark)

    Elmasry, Amr Ahmed Abd Elmoneim; Jensen, Claus; Katajainen, Jyrki

    2010-01-01

    We introduce a new number system that we call the strictly-regular system, which efficiently supports the operations: digit-increment, digit-decrement, cut, concatenate, and add. Compared to other number systems, the strictly-regular system has distinguishable properties. It is superior to the re...

  13. CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance

    Directory of Open Access Journals (Sweden)

    Enric Fernández

    2017-02-01

    Full Text Available Chip Scale Atomic Clocks (CSAC are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility. Current GNSS receivers include a Temperature Compensated Cristal Oscillator (TCXO clock characterized by a short-term stability (τ = 1 s of 10−9 s that leads to an error of 0.3 m in pseudorange measurements. The CSAC can achieve a short-term stability of 2.5 × 10−12 s, which implies a range error of 0.075 m, making for an 87.5% improvement over TCXO. Replacing the internal TCXO clock of GNSS receivers with a higher frequency stability clock such as a CSAC oscillator improves the navigation solution in terms of low satellite visibility positioning accuracy, solution availability, signal recovery (holdover, multipath and jamming mitigation and spoofing attack detection. However, CSAC suffers from internal systematic instabilities and errors that should be minimized if optimal performance is desired. Hence, for operating CSAC at its best, the deterministic errors from the CSAC need to be properly modelled. Currently, this modelling is done by determining and predicting the clock frequency stability (i.e., clock bias and bias rate within the positioning estimation process. The research presented in this paper aims to go a step further, analysing the correlation between temperature and clock stability noise and the impact of its proper modelling in the holdover recovery time and in the positioning performance. Moreover, it shows the potential of fine clock coasting modelling. With the proposed model, an improvement in vertical positioning precision of around 50% with only three satellites can be achieved. Moreover, an increase in the navigation solution availability is also observed, a reduction of holdover recovery time from dozens of seconds to only a few can be achieved.

  14. CSAC Characterization and Its Impact on GNSS Clock Augmentation Performance.

    Science.gov (United States)

    Fernández, Enric; Calero, David; Parés, M Eulàlia

    2017-02-14

    Chip Scale Atomic Clocks (CSAC) are recently-developed electronic instruments that, when used together with a Global Navigation Satellite Systems (GNSS) receiver, help improve the performance of GNSS navigation solutions in certain conditions (i.e., low satellite visibility). Current GNSS receivers include a Temperature Compensated Cristal Oscillator (TCXO) clock characterized by a short-term stability ( τ = 1 s) of 10 -9 s that leads to an error of 0.3 m in pseudorange measurements. The CSAC can achieve a short-term stability of 2.5 × 10 -12 s, which implies a range error of 0.075 m, making for an 87.5% improvement over TCXO. Replacing the internal TCXO clock of GNSS receivers with a higher frequency stability clock such as a CSAC oscillator improves the navigation solution in terms of low satellite visibility positioning accuracy, solution availability, signal recovery (holdover), multipath and jamming mitigation and spoofing attack detection. However, CSAC suffers from internal systematic instabilities and errors that should be minimized if optimal performance is desired. Hence, for operating CSAC at its best, the deterministic errors from the CSAC need to be properly modelled. Currently, this modelling is done by determining and predicting the clock frequency stability (i.e., clock bias and bias rate) within the positioning estimation process. The research presented in this paper aims to go a step further, analysing the correlation between temperature and clock stability noise and the impact of its proper modelling in the holdover recovery time and in the positioning performance. Moreover, it shows the potential of fine clock coasting modelling. With the proposed model, an improvement in vertical positioning precision of around 50% with only three satellites can be achieved. Moreover, an increase in the navigation solution availability is also observed, a reduction of holdover recovery time from dozens of seconds to only a few can be achieved.

  15. Micro Mercury Ion Clock (MMIC)

    Data.gov (United States)

    National Aeronautics and Space Administration — Demonstrate micro clock based on trapped Hg ions with more than 10x size reduction and power; Fractional frequency stability at parts per 1014 level, adequate for...

  16. Stochastic models for atomic clocks

    Science.gov (United States)

    Barnes, J. A.; Jones, R. H.; Tryon, P. V.; Allan, D. W.

    1983-01-01

    For the atomic clocks used in the National Bureau of Standards Time Scales, an adequate model is the superposition of white FM, random walk FM, and linear frequency drift for times longer than about one minute. The model was tested on several clocks using maximum likelihood techniques for parameter estimation and the residuals were acceptably random. Conventional diagnostics indicate that additional model elements contribute no significant improvement to the model even at the expense of the added model complexity.

  17. Circadian clock and vascular disease.

    OpenAIRE

    Takeda, Norihiko; Maemura, Koji

    2010-01-01

    Cardiovascular functions, including blood pressure and vascular functions, show diurnal oscillation. Circadian variations have been clearly shown in the occurrence of cardiovascular events such as acute myocardial infarction. Circadian rhythm strongly influences human biology and pathology. The identification and characterization of mammalian clock genes revealed that they are expressed almost everywhere throughout the body in a circadian manner. In contrast to the central clock in the suprac...

  18. Time without clocks - an attempt

    International Nuclear Information System (INIS)

    Karpman, G.

    1978-01-01

    A definition of time intervals separating two states of systems of elementary particles and observers is attempted. The definition is founded on the notion of instant state of the system and uses no information connected with the use of a clock. Applying the definition to a classical clock and to a sample of unstable particles, results are obtained in agreement with experiment. However, if the system contains 'few' elementary particles, the properties of the time interval present some different features. (author)

  19. Strategy and Aspects of Monitoring / Control Strictly in Coordinated Subsystems

    Directory of Open Access Journals (Sweden)

    William José Borges

    2012-06-01

    Full Text Available This paper aims to discuss the approach structures of the strictly coordinated theoretical framework developed by Zylbersztajn and Farina (1999 as an expanded perspective of the firm, taking into account the food supply chains as an extension of the nexus of contracts proposed by Coase (1937 and taken up by Williamson (1985. The structures stand out as strictly coordinated. Zylbersztajn and Farina (1999 turn to identifying points of common interests that encourage firms to promote contracts between themselves in a strictly coordinated way, considering the degree of asset specificity involved in the transaction and the competitive forces that determine the search for strategic positioning organizations to achieve sustainable superior results.

  20. Strict finitism and the logic of mathematical applications

    CERN Document Server

    Ye, Feng

    2011-01-01

    Exploring the logic behind applied mathematics to the physical world, this volume illustrates how radical naturalism, nominalism and strict finitism can account for the applications of classical mathematics in current theories about natural phenomena.

  1. Strict monotonicity and unique continuation of the biharmonic operator

    Directory of Open Access Journals (Sweden)

    Najib Tsouli

    2012-01-01

    Full Text Available In this paper, we will show that the strict monotonicity of the eigenvalues of the biharmonic operator holds if and only if some unique continuation property is satisfied by the corresponding eigenfunctions.

  2. Two examples of non strictly convex large deviations

    OpenAIRE

    De Marco, Stefano; Jacquier, Antoine; Roome, Patrick

    2016-01-01

    We present two examples of a large deviations principle where the rate function is not strictly convex. This is motivated by a model used in mathematical finance (the Heston model), and adds a new item to the zoology of non strictly convex large deviations. For one of these examples, we show that the rate function of the Cramer-type of large deviations coincides with that of the Freidlin-Wentzell when contraction principles are applied.

  3. Strictly contractive quantum channels and physically realizable quantum computers

    International Nuclear Information System (INIS)

    Raginsky, Maxim

    2002-01-01

    We study the robustness of quantum computers under the influence of errors modeled by strictly contractive channels. A channel T is defined to be strictly contractive if, for any pair of density operators ρ, σ in its domain, parallel Tρ-Tσ parallel 1 ≤k parallel ρ-σ parallel 1 for some 0≤k 1 denotes the trace norm). In other words, strictly contractive channels render the states of the computer less distinguishable in the sense of quantum detection theory. Starting from the premise that all experimental procedures can be carried out with finite precision, we argue that there exists a physically meaningful connection between strictly contractive channels and errors in physically realizable quantum computers. We show that, in the absence of error correction, sensitivity of quantum memories and computers to strictly contractive errors grows exponentially with storage time and computation time, respectively, and depends only on the constant k and the measurement precision. We prove that strict contractivity rules out the possibility of perfect error correction, and give an argument that approximate error correction, which covers previous work on fault-tolerant quantum computation as a special case, is possible

  4. Circadian clocks, epigenetics, and cancer

    KAUST Repository

    Masri, Selma

    2015-01-01

    The interplay between circadian rhythm and cancer has been suggested for more than a decade based on the observations that shift work and cancer incidence are linked. Accumulating evidence implicates the circadian clock in cancer survival and proliferation pathways. At the molecular level, multiple control mechanisms have been proposed to link circadian transcription and cell-cycle control to tumorigenesis.The circadian gating of the cell cycle and subsequent control of cell proliferation is an area of active investigation. Moreover, the circadian clock is a transcriptional system that is intricately regulated at the epigenetic level. Interestingly, the epigenetic landscape at the level of histone modifications, DNA methylation, and small regulatory RNAs are differentially controlled in cancer cells. This concept raises the possibility that epigenetic control is a common thread linking the clock with cancer, though little scientific evidence is known to date.This review focuses on the link between circadian clock and cancer, and speculates on the possible connections at the epigenetic level that could further link the circadian clock to tumor initiation or progression.

  5. Sound Clocks and Sonic Relativity

    Science.gov (United States)

    Todd, Scott L.; Menicucci, Nicolas C.

    2017-10-01

    Sound propagation within certain non-relativistic condensed matter models obeys a relativistic wave equation despite such systems admitting entirely non-relativistic descriptions. A natural question that arises upon consideration of this is, "do devices exist that will experience the relativity in these systems?" We describe a thought experiment in which `acoustic observers' possess devices called sound clocks that can be connected to form chains. Careful investigation shows that appropriately constructed chains of stationary and moving sound clocks are perceived by observers on the other chain as undergoing the relativistic phenomena of length contraction and time dilation by the Lorentz factor, γ , with c the speed of sound. Sound clocks within moving chains actually tick less frequently than stationary ones and must be separated by a shorter distance than when stationary to satisfy simultaneity conditions. Stationary sound clocks appear to be length contracted and time dilated to moving observers due to their misunderstanding of their own state of motion with respect to the laboratory. Observers restricted to using sound clocks describe a universe kinematically consistent with the theory of special relativity, despite the preferred frame of their universe in the laboratory. Such devices show promise in further probing analogue relativity models, for example in investigating phenomena that require careful consideration of the proper time elapsed for observers.

  6. Analysis of the performance of hydrogen maser clocks at the ...

    African Journals Online (AJOL)

    Cilence

    The telescopes function within the framework of the International VLBI Service for .... The 24-hour offset data sets were analysed by using a second quadratic trend model given by Levine et al., (1999) as. 2. 1. 2 .... parameters, enabling the management of maser clocks at HartRAO to function within predefined limits for VLBI ...

  7. Acting with the Clock: Clocking Practices in Early Childhood

    Science.gov (United States)

    Pacini-Ketchabaw, Veronica

    2012-01-01

    In this article, the author addresses intra-actions that take place among humans and non-human others--the physical world, the materials--in early childhood education's everyday practices. Her object of study is the clock. Specifically, she provides an example of what it might mean to account for the intra-activity of the material-discursive…

  8. Naming analog clocks conceptually facilitates naming digital clocks

    NARCIS (Netherlands)

    Meeuwissen, M.H.W.; Roelofs, A.P.A.; Levelt, W.J.M.

    2004-01-01

    Naming digital clocks (e.g., 2:45, say "quarter to three") requires conceptual operations on the minute and hour information displayed in the input for producing the correct relative time expression. The interplay of these conceptual operations was investigated using a repetition priming paradigm.

  9. Direct Repression of Evening Genes by CIRCADIAN CLOCK-ASSOCIATED1 in the Arabidopsis Circadian Clock.

    Science.gov (United States)

    Kamioka, Mari; Takao, Saori; Suzuki, Takamasa; Taki, Kyomi; Higashiyama, Tetsuya; Kinoshita, Toshinori; Nakamichi, Norihito

    2016-03-01

    The circadian clock is a biological timekeeping system that provides organisms with the ability to adapt to day-night cycles. Timing of the expression of four members of the Arabidopsis thaliana PSEUDO-RESPONSE REGULATOR(PRR) family is crucial for proper clock function, and transcriptional control of PRRs remains incompletely defined. Here, we demonstrate that direct regulation of PRR5 by CIRCADIAN CLOCK-ASSOCIATED1 (CCA1) determines the repression state of PRR5 in the morning. Chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) analyses indicated that CCA1 associates with three separate regions upstream of PRR5 CCA1 and its homolog LATE ELONGATED HYPOCOTYL (LHY) suppressed PRR5 promoter activity in a transient assay. The regions bound by CCA1 in the PRR5 promoter gave rhythmic patterns with troughs in the morning, when CCA1 and LHY are at high levels. Furthermore,ChIP-seq revealed that CCA1 associates with at least 449 loci with 863 adjacent genes. Importantly, this gene set contains genes that are repressed but upregulated incca1 lhy double mutants in the morning. This study shows that direct binding by CCA1 in the morning provides strong repression of PRR5, and repression by CCA1 also temporally regulates an evening-expressed gene set that includes PRR5. © 2016 American Society of Plant Biologists. All rights reserved.

  10. Clock and trigger distribution for ALICE using the CRU FPGA card

    CERN Document Server

    Imrek, Jozsef

    2017-01-01

    ALICE is preparing a major upgrade for 2021. Subdetectors upgrading their DAQ electronics will use a common hardware to receive physics data: the Common Readout Unit (CRU). The same CRU will also distribute the LHC clock and trigger to many of the upgrading subdetectors (to 7800 front end cards). Requirements are strict: for the clock the allowed jitter (RMS) is typically <300ps, and <20ps for timing critical subdetectors; the allowed variation of skew is typically <1ns, and <100ps for timing critical subdetectors. A constant latency for distributing the trigger is essential. A novel approach to implement clock forwarding – using only the internal PLLs of the CRU’s onboard FPGA, without using an external jitter cleaner PLL – is presented.

  11. Single-transistor-clocked flip-flop

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Peiyi; Darwish, Tarek; Bayoumi, Magdy

    2005-08-30

    The invention provides a low power, high performance flip-flop. The flip-flop uses only one clocked transistor. The single clocked transistor is shared by the first and second branches of the device. A pulse generator produces a clock pulse to trigger the flip-flop. In one preferred embodiment the device can be made as a static explicit pulsed flip-flop which employs only two clocked transistors.

  12. Convergence theorems for strictly hemi-contractive maps

    International Nuclear Information System (INIS)

    Chidume, C.E.; Osilike, M.O.

    1992-04-01

    It is proved that each of two well-known fixed point iteration methods (the Mann and the Ishikawa iteration methods) converges strongly to the fixed point of strictly hemi-contractive map in real Banach spaces with property (U, λ, m+1,m), λ is an element of R, m is an element of IN. The class of strictly hemi-contractive maps includes all strictly pseudo-contractive maps with nonempty fixed point sets; and Banach spaces with property (U, λ, m+1, m), λ is an element of R, m is an element of IN include the L p (or l p ) spaces, p≥2. Our theorems generalize important known results. (author). 22 refs

  13. 47 CFR 80.935 - Station clock.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Station clock. 80.935 Section 80.935... MARITIME SERVICES Compulsory Radiotelephone Installations for Small Passenger Boats § 80.935 Station clock. Each station subject to this subpart must have a working clock or timepiece readily available to the...

  14. A network of (autonomic) clock outputs

    NARCIS (Netherlands)

    Kalsbeek, A.; Perreau-Lenz, S.; Buijs, R. M.

    2006-01-01

    The circadian clock in the suprachiasmatic nuclei (SCN) is composed of thousands of oscillator neurons, each of which is dependent on the cell-autonomous action of a defined set of circadian clock genes. A major question is still how these individual oscillators are organized into a biological clock

  15. A network of (autonomic) clock outputs

    NARCIS (Netherlands)

    Kalsbeek, A.; Perreau-Lenz, S.; Buijs, R. M.

    2006-01-01

    The circadian clock in the suprachiasmatic nuclei (SCN) is composed of thousands of oscillator neurons, each dependent on the cell-autonomous action of a defined set of circadian clock genes. A major question is still how these individual oscillators are organized into a biological clock that

  16. Gaming in Combinatorial Clock Auctions

    NARCIS (Netherlands)

    M.C.W. Janssen (Maarten); V.A. Karamychev (Vladimir)

    2013-01-01

    textabstractIn recent years, Combinatorial Clock Auctions (CCAs) have been used around the world to allocate frequency spectrum for mobile telecom licenses. CCAs are claimed to significantly reduce the scope for gaming or strategic bidding. In this paper, we show, however, that CCAs significantly

  17. Circadian Clocks : Running on Redox

    NARCIS (Netherlands)

    Merrow, Martha; Roenneberg, Till

    2001-01-01

    The circadian clock in all organisms is so intimately linked to light reception that it appears as if evolution has simply wired a timer into the mechanism that processes photic information. Several recent studies have provided new insights into the role of light input pathways in the circadian

  18. Sundials: Ancestors of Our Clocks

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 16; Issue 1. Sundials: Ancestors of Our Clocks. P D Anoop. General Article Volume 16 Issue 1 January 2011 pp 29-37. Fulltext. Click here to view fulltext PDF. Permanent link: http://www.ias.ac.in/article/fulltext/reso/016/01/0029-0037. Keywords. Sundial ...

  19. Teaching by the Body's Clock.

    Science.gov (United States)

    Loviglio, Lorraine

    1981-01-01

    Discusses studies by Donald LaSalle showing that students' performance can vary widely over the day according to the workings of their individual biological clocks. Presents exercises to help children identify their own "body rhythm prime time" and suggests rescheduling instruction to accommodate these differences. Condensed from…

  20. Biological clocks: riding the tides.

    Science.gov (United States)

    de la Iglesia, Horacio O; Johnson, Carl Hirschie

    2013-10-21

    Animals with habitats in the intertidal zone often display biological rhythms that coordinate with both the tidal and the daily environmental cycles. Two recent studies show that the molecular components of the biological clocks mediating tidal rhythms are likely different from the phylogenetically conserved components that mediate circadian (daily) rhythms. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. <=ryptochromes and Biological Clocks -36 ...

    Indian Academy of Sciences (India)

    form layer; GL - Gangli- onic layer; OF- Optic nerve fibres). The photorecep- tors for vision are present in rod and cone cells in the outer pig1)Jented epithelial layer, whereas the photo- receptors for the biologi- cal clock are located in the inner nuclear layer of the retina. Pigmented epithelial cell. Vitreous humor. Optic nerve.

  2. Clocks do not tick in unison: isolation of Clock and vrille shed new light on the clockwork model of the sand fly Lutzomyia longipalpis.

    Science.gov (United States)

    Gesto, João Silveira Moledo; Rivas, Gustavo Bueno da Silva; Pavan, Marcio Galvão; Meireles-Filho, Antonio Carlos Alves; Amoretty, Paulo Roberto de; Souza, Nataly Araújo de; Bruno, Rafaela Vieira; Peixoto, Alexandre Afranio

    2015-10-06

    Behavior rhythms of insect vectors directly interfere with the dynamics of pathogen transmission to humans. The sand fly Lutzomyia longipalpis is the main vector of visceral leishmaniasis in America and concentrates its activity around dusk. Despite the accumulation of behavioral data, very little is known about the molecular bases of the clock mechanism in this species. This study aims to characterize, within an evolutionary perspective, two important circadian clock genes, Clock and vrille. We have cloned and isolated the coding sequence of L. longipalpis' genes Clock and vrille. The former is structured in eight exons and encodes a protein of 696 amino acids, and the latter comprises three exons and translates to a protein of 469 amino acids. When compared to other insects' orthologues, L. longipalpis CLOCK shows a high degree of conservation in the functional domains bHLH and PAS, but a much shorter glutamine-rich (poly-Q) C-terminal region. As for L. longipalpis VRILLE, a high degree of conservation was found in the bZIP domain. To support these observations and provide an elegant view of the evolution of both genes in insects, phylogenetic analyses based on maximum-likelihood and Bayesian inferences were performed, corroborating the previously known insect systematics. The isolation and phylogenetic analyses of Clock and vrille orthologues in L. longipalpis bring novel and important data to characterize this species' circadian clock. Interestingly, the poly-Q shortening observed in CLOCK suggests that its transcription activity might be impaired and we speculate if this effect could be compensated by other clock factors such as CYCLE.

  3. Expression of core clock genes in colorectal tumour cells compared with normal mucosa

    DEFF Research Database (Denmark)

    Fonnes, S; Donatsky, A M; Gögenur, I

    2015-01-01

    AIM: Experimental studies have shown that some circadian core clock genes may act as tumour suppressors and have an important role in the response to oncological treatment. This study investigated the evidence regarding modified expression of core clock genes in colorectal cancer and its...... expression of colorectal cancer cells compared with healthy mucosa cells from specimens analysed by real-time or quantitative real-time polymer chain reaction. The expression of the core clock genes Period, Cryptochrome, Bmal1 and Clock in colorectal tumours were compared with healthy mucosa and correlated...... with clinicopathological features and survival. RESULTS: Seventy-four articles were identified and 11 studies were included. Overall, gene expression of Period was significantly decreased in colorectal cancer cells compared with healthy mucosa cells. This tendency was also seen in the gene expression of Clock. Other core...

  4. Mann iteration with errors for strictly pseudo-contractive mappings ...

    African Journals Online (AJOL)

    It is well known that any fixed point of a Lipschitzian strictly pseudo-contractive self mapping of a nonempty closed convex and bounded subset K of a Banach space X is unique [6] and may be norm approximated by an iterative procedure. In this paper, we show that Mann iteration with errors can be used to approximate the ...

  5. Dominated operators, absolutely summing operators and the strict ...

    African Journals Online (AJOL)

    b(X;E) be the space of all E-valued bounded continuous functions on X, equipped with the strict topology β. We study dominated and absolutely summing operators T : Cb(X;E) → F. We derive that if X is a locally compact Hausdorff space and E ...

  6. Convergence of GAOR Iterative Method with Strictly Diagonally Dominant Matrices

    Directory of Open Access Journals (Sweden)

    Guangbin Wang

    2011-01-01

    Full Text Available We discuss the convergence of GAOR method for linear systems with strictly diagonally dominant matrices. Moreover, we show that our results are better than ones of Darvishi and Hessari (2006, Tian et al. (2008 by using three numerical examples.

  7. Runaway selection for cooperation and strict-and-severe punishment.

    Science.gov (United States)

    Nakamaru, Mayuko; Dieckmann, Ulf

    2009-03-07

    Punishing defectors is an important means of stabilizing cooperation. When levels of cooperation and punishment are continuous, individuals must employ suitable social standards for defining defectors and for determining punishment levels. Here we investigate the evolution of a social reaction norm, or psychological response function, for determining the punishment level meted out by individuals in dependence on the cooperation level exhibited by their neighbors in a lattice-structured population. We find that (1) cooperation and punishment can undergo runaway selection, with evolution towards enhanced cooperation and an ever more demanding punishment reaction norm mutually reinforcing each other; (2) this mechanism works best when punishment is strict, so that ambiguities in defining defectors are small; (3) when the strictness of punishment can adapt jointly with the threshold and severity of punishment, evolution favors the strict-and-severe punishment of individuals who offer slightly less than average cooperation levels; (4) strict-and-severe punishment naturally evolves and leads to much enhanced cooperation when cooperation without punishment would be weak and neither cooperation nor punishment are too costly; and (5) such evolutionary dynamics enable the bootstrapping of cooperation and punishment, through which defectors who never punish gradually and steadily evolve into cooperators who punish those they define as defectors.

  8. Dominance on Strict Triangular Norms and Mulholland Inequality

    Czech Academy of Sciences Publication Activity Database

    Petrík, Milan

    2018-01-01

    Roč. 335, 15 March (2018), s. 3-17 ISSN 0165-0114 R&D Projects: GA ČR GJ15-07724Y Institutional support: RVO:67985807 Keywords : dominance relation * Mulholland inequality * strict triangular norm * transitivity Subject RIV: BA - General Mathematics Impact factor: 2.718, year: 2016

  9. Automatic control of clock duty cycle

    Science.gov (United States)

    Feng, Xiaoxin (Inventor); Roper, Weston (Inventor); Seefeldt, James D. (Inventor)

    2010-01-01

    In general, this disclosure is directed to a duty cycle correction (DCC) circuit that adjusts a falling edge of a clock signal to achieve a desired duty cycle. In some examples, the DCC circuit may generate a pulse in response to a falling edge of an input clock signal, delay the pulse based on a control voltage, adjust the falling edge of the input clock signal based on the delayed pulse to produce an output clock signal, and adjust the control voltage based on the difference between a duty cycle of the output clock signal and a desired duty cycle. Since the DCC circuit adjusts the falling edge of the clock cycle to achieve a desired duty cycle, the DCC may be incorporated into existing PLL control loops that adjust the rising edge of a clock signal without interfering with the operation of such PLL control loops.

  10. Circadian clock, cell cycle and cancer

    Directory of Open Access Journals (Sweden)

    Cansu Özbayer

    2011-12-01

    Full Text Available There are a few rhythms of our daily lives that we are under the influence. One of them is characterized by predictable changes over a 24-hour timescale called circadian clock. This cellular clock is coordinated by the suprachiasmatic nucleus in the anterior hypothalamus. The clock consist of an autoregulatory transcription-translation feedback loop compose of four genes/proteins; BMAL1, Clock, Cyrptochrome, and Period. BMAL 1 and Clock are transcriptional factors and Period and Cyrptochrome are their targets. Period and Cyrptochrome dimerize in the cytoplasm to enter the nucleus where they inhibit Clock/BMAL activity.It has been demonstrate that circadian clock plays an important role cellular proliferation, DNA damage and repair mechanisms, checkpoints, apoptosis and cancer.

  11. A strict anaerobic extreme thermophilic hydrogen-producing culture enriched from digested household waste

    DEFF Research Database (Denmark)

    Karakashev, Dimitar Borisov; Kotay, Shireen Meher; Trably, Eric

    2009-01-01

    sources. Growth on glucose produced acetate, H-2 and carbon dioxide. Maximal H-2 production rate on glucose was 1.1 mmol l(-1) h(-1) with a maximum H-2 yield of 1.9 mole H-2 per mole glucose. 16S ribosomal DNA clone library analyses showed that the culture members were phylogenetically affiliated......The aim of this study was to enrich, characterize and identify strict anaerobic extreme thermophilic hydrogen (H-2) producers from digested household solid wastes. A strict anaerobic extreme thermophilic H-2 producing bacterial culture was enriched from a lab-scale digester treating household...... wastes at 70 degrees C. The enriched mixed culture consisted of two rod-shaped bacterial members growing at an optimal temperature of 80 degrees C and an optimal pH 8.1. The culture was able to utilize glucose, galactose, mannose, xylose, arabinose, maltose, sucrose, pyruvate and glycerol as carbon...

  12. Clock drawing as a screen for impaired driving in aging and dementia: is it worth the time?

    Science.gov (United States)

    Manning, Kevin J; Davis, Jennifer D; Papandonatos, George D; Ott, Brian R

    2014-02-01

    Clock drawing is recommended by medical and transportation authorities as a screening test for unsafe drivers. The objective of the present study was to assess the usefulness of different clock drawing systems as screening measures of driving performance in 122 healthy and cognitively impaired older drivers. Clock drawing was measured using four different scoring systems. Driving outcomes included global ratings of safety and the error rate on a standardized on-road test. Findings revealed that clock drawing was significantly correlated with the driving score on the road test for each of the scoring systems. However, receiver operator curve analyses showed limited clinical utility for clock drawing as a screening instrument for impaired on-road driving performance with the area under the curve ranging from 0.53 to 0.61. Results from this study indicate that clock drawing has limited utility as a solitary screening measure of on-road driving, even when considering a variety of scoring approaches.

  13. Clocks for quaternary environments in Australia

    International Nuclear Information System (INIS)

    Tuniz, C.

    2002-01-01

    The Australian continent offers a variety of natural systems where records of the Earth's past environment have been stored, including sediment cores, tree rings, rock surfaces and corals. Rock varnish, mud-wasp nests and pack-rat middens provide alternative archives for vegetation and environmental change in arid areas, where continuous sedimentary sequences or trees are not available. Each of these media contain specific information on past climatic conditions but we must determine their chronology and decipher the relevant environmental parameters. Cosmogenic radionuclides, such as 14 C, 10 Be, 26 Al and 36 Cl, analysed by accelerator mass spectrometry, provide valuable radiometric clocks to establish an absolute time scale for the environmental events of the Quaternary. U-series, potassium-argon, argonargon and optically stimulated luminescence are other dating methods used in palaeoenvironmental studies. ANSTO supports the Quaternary science community in Australia providing the analysis of long-lived radionuclides: some significant projects from this program will be illustrated. (author)

  14. Hanle Detection for Optical Clocks

    Directory of Open Access Journals (Sweden)

    Xiaogang Zhang

    2015-01-01

    Full Text Available Considering the strong inhomogeneous spatial polarization and intensity distribution of spontaneous decay fluorescence due to the Hanle effect, we propose and demonstrate a universe Hanle detection configuration of electron-shelving method for optical clocks. Experimental results from Ca atomic beam optical frequency standard with electron-shelving method show that a designed Hanle detection geometry with optimized magnetic field direction, detection laser beam propagation and polarization direction, and detector position can improve the fluorescence collection rate by more than one order of magnitude comparing with that of inefficient geometry. With the fixed 423 nm fluorescence, the improved 657 nm optical frequency standard signal intensity is presented. The potential application of the Hanle detection geometry designed for facilitating the fluorescence collection for optical lattice clock with a limited solid angle of the fluorescence collection has been discussed. The Hanle detection geometry is also effective for ion detection in ion optical clock and quantum information experiments. Besides, a cylinder fluorescence collection structure is designed to increase the solid angle of the fluorescence collection in Ca atomic beam optical frequency standard.

  15. Clock represses preadipocytes adipogenesis via GILZ.

    Science.gov (United States)

    Zhu, Zhu; Xu, Lirong; Cai, Tingting; Yuan, Gongsheng; Sun, Ning; Lu, Chao; Qian, Ruizhe

    2017-12-26

    Adiposity is a worldwide health threat that needs to be prevented. Circadian gene Clock (circadian locomotor output cycles kaput) is closely correlated to adiposity; for example, weight gain, adipocytes size expansion, and serum lipid level rise in Clock Δ19 mice compared to C57BL/6J mice. However, the precise role of Clock during adipogenic differentiation is unknown. Herein, the circadian gene Clock is shown to regulate adipogenesis mediated by GILZ. Clock-mediated attenuation and upregulation influenced lipid synthesis and affected the levels of adipogenic transcriptional factors, C/EBP-β, C/EBP-α, PPAR-γ, and FABP4, both in vivo and in vitro (primary adipose-derived stromal cells and 3T3-L1 cells). Chromatin immunoprecipitation (ChIP) assay, reporter gene assay, and serum shock assay found that Clock transcriptionally regulated the glucocorticoid-induced leucine zipper (GILZ). Furthermore, GILZ attenuation could relieve the inhibitory effect of Clock on lipid synthesis and GILZ overexpression also reduced the promotion role of Clock attenuation in adipogenesis suggesting that Clock inhibits adipogenic differentiation of preadipocytes via GILZ. The current results demonstrate how circadian genes are likely to regulate adiposity, affecting the adipogenic differentiation process, as well as, increasing the fat cells number. Therefore, this study may provide novel insights into the underlying mechanism explaining the correlation between Clock mutation and adiposity. © 2017 Wiley Periodicals, Inc.

  16. Entanglement of quantum clocks through gravity

    Science.gov (United States)

    Castro Ruiz, Esteban; Giacomini, Flaminia; Brukner, Časlav

    2017-03-01

    In general relativity, the picture of space-time assigns an ideal clock to each world line. Being ideal, gravitational effects due to these clocks are ignored and the flow of time according to one clock is not affected by the presence of clocks along nearby world lines. However, if time is defined operationally, as a pointer position of a physical clock that obeys the principles of general relativity and quantum mechanics, such a picture is, at most, a convenient fiction. Specifically, we show that the general relativistic mass-energy equivalence implies gravitational interaction between the clocks, whereas the quantum mechanical superposition of energy eigenstates leads to a nonfixed metric background. Based only on the assumption that both principles hold in this situation, we show that the clocks necessarily get entangled through time dilation effect, which eventually leads to a loss of coherence of a single clock. Hence, the time as measured by a single clock is not well defined. However, the general relativistic notion of time is recovered in the classical limit of clocks.

  17. User-Defined Clocks in the Real-Time Specification for Java

    DEFF Research Database (Denmark)

    Wellings, Andy; Schoeberl, Martin

    2011-01-01

    This paper analyses the new user-defined clock model that is to be supported in Version 1.1 of the Real-Time Specification for Java (RTSJ). The model is a compromise between the current position, where there is no support for user-defined clocks, and a fully integrated model. The paper investigates...... the implications of supporting a fully generalized model from both the specification’s and an implementation’s viewpoint. It concludes that for RTSJ the scope of changes required to fully integrate user-defined clocks into the specification would have a major impact on current implementations....

  18. Dynamics of the slowing segmentation clock reveal alternating two-segment periodicity.

    Science.gov (United States)

    Shih, Nathan P; François, Paul; Delaune, Emilie A; Amacher, Sharon L

    2015-05-15

    The formation of reiterated somites along the vertebrate body axis is controlled by the segmentation clock, a molecular oscillator expressed within presomitic mesoderm (PSM) cells. Although PSM cells oscillate autonomously, they coordinate with neighboring cells to generate a sweeping wave of cyclic gene expression through the PSM that has a periodicity equal to that of somite formation. The velocity of each wave slows as it moves anteriorly through the PSM, although the dynamics of clock slowing have not been well characterized. Here, we investigate segmentation clock dynamics in the anterior PSM in developing zebrafish embryos using an in vivo clock reporter, her1:her1-venus. The her1:her1-venus reporter has single-cell resolution, allowing us to follow segmentation clock oscillations in individual cells in real-time. By retrospectively tracking oscillations of future somite boundary cells, we find that clock reporter signal increases in anterior PSM cells and that the periodicity of reporter oscillations slows to about ∼1.5 times the periodicity in posterior PSM cells. This gradual slowing of the clock in the anterior PSM creates peaks of clock expression that are separated at a two-segment periodicity both spatially and temporally, a phenomenon we observe in single cells and in tissue-wide analyses. These results differ from previous predictions that clock oscillations stop or are stabilized in the anterior PSM. Instead, PSM cells oscillate until they incorporate into somites. Our findings suggest that the segmentation clock may signal somite formation using a phase gradient with a two-somite periodicity. © 2015. Published by The Company of Biologists Ltd.

  19. Mechanism of the circadian clock in physiology

    Science.gov (United States)

    Richards, Jacob

    2013-01-01

    It has been well established that the circadian clock plays a crucial role in the regulation of almost every physiological process. It also plays a critical role in pathophysiological states including those of obesity and diabetes. Recent evidence has highlighted the potential for targeting the circadian clock as a potential drug target. New studies have also demonstrated the existence of “clock-independent effects” of the circadian proteins, leading to exciting new avenues of research in the circadian clock field in physiology. The goal of this review is to provide an introduction to and overview of the circadian clock in physiology, including mechanisms, targets, and role in disease states. The role of the circadian clocks in the regulation of the cardiovascular system, renal function, metabolism, the endocrine system, immune, and reproductive systems will be discussed. PMID:23576606

  20. The Implementation of E1 Clock Recovery

    Directory of Open Access Journals (Sweden)

    Wang Ziyu

    2016-01-01

    Full Text Available Clock transform and recovery is of significant importance in microwave TDM service, and it is always extracted from the E1 line data stream in most cases. However, intrinsically uncertain delay and jitter caused by packet transmission of E1 data information, may lead to the indexes of the data recovery clock exceed the clock performance template. Through analysis of the E1 clock indexes and measuring methods, this paper proposes a new clock recovery method. The method employs two buffers, the first RAM is used as a buffer to deduct excess information, and the second FIFO is used as a buffer to recovery the clock and data. The first buffer has a feedback from the second one, and is able to actively respond to changes in the data link and requests from the second one. The test results validate the effectiveness of the method, and the corresponding scheme is also valuable for the other communication systems.

  1. Melatonin, clock genes and mitochondria in sepsis.

    Science.gov (United States)

    Acuña-Castroviejo, Darío; Rahim, Ibtissem; Acuña-Fernández, Carlos; Fernández-Ortiz, Marisol; Solera-Marín, Jorge; Sayed, Ramy K A; Díaz-Casado, María E; Rusanova, Iryna; López, Luis C; Escames, Germaine

    2017-11-01

    After the characterization of the central pacemaker in the suprachiasmatic nucleus, the expression of clock genes was identified in several peripheral tissues including the immune system. The hierarchical control from the central clock to peripheral clocks extends to other functions including endocrine, metabolic, immune, and mitochondrial responses. Increasing evidence links the disruption of the clock genes expression with multiple diseases and aging. Chronodisruption is associated with alterations of the immune system, immunosenescence, impairment of energy metabolism, and reduction of pineal and extrapineal melatonin production. Regarding sepsis, a condition coursing with an exaggerated response of innate immunity, experimental and clinical data showed an alteration of circadian rhythms that reflects the loss of the normal oscillation of the clock. Moreover, recent data point to that some mediators of the immune system affects the normal function of the clock. Under specific conditions, this control disappears reactivating the immune response. So, it seems that clock gene disruption favors the innate immune response, which in turn induces the expression of proinflammatory mediators, causing a further alteration of the clock. Here, the clock control of the mitochondrial function turns off, leading to a bioenergetic decay and formation of reactive oxygen species that, in turn, activate the inflammasome. This arm of the innate immunity is responsible for the huge increase of interleukin-1β and entrance into a vicious cycle that could lead to the death of the patient. The broken clock is recovered by melatonin administration, that is accompanied by the normalization of the innate immunity and mitochondrial homeostasis. Thus, this review emphasizes the connection between clock genes, innate immunity and mitochondria in health and sepsis, and the role of melatonin to maintain clock homeostasis.

  2. The Square Light Clock and Special Relativity

    Science.gov (United States)

    Galli, J. Ronald; Amiri, Farhang

    2012-01-01

    A thought experiment that includes a square light clock is similar to the traditional vertical light beam and mirror clock, except it is made up of four mirrors placed at a 45[degree] angle at each corner of a square of length L[subscript 0], shown in Fig. 1. Here we have shown the events as measured in the rest frame of the square light clock. By…

  3. Local area network distributed realtime clock synchronization

    Science.gov (United States)

    Wilcox, D. R.

    1991-11-01

    This report applies the strobe realtime clock synchronization technique to serial busses and local area networks in general, and to the IEEE 802.5 and the Fiber Distributed Data Interface token ring local area network standards in particular. Section 2 examines miscellaneous material relating to adjustable-rate realtime clocks. Section 3 presents adjustable rate realtime clock hardware implementation methods considered superior to those in an earlier report. Section 4 presents a hardware implementation of an IEEE 802.5 strobe detector.

  4. Distinction between Clock and Time, and a Suggested Experiment with Different Types of Clocks in GPS

    Science.gov (United States)

    Smarandache, Florentin

    2013-03-01

    The clock is an instrument for measuring the time, instrument that may not run perfectly (accurately) under certain conditions (like, say, in strong electromagnetic field, in strong gravitational field, in extremely high or low temperature, pressure, etc.), but this does not mean that time itself runs slower or faster as Einstein's Theory of Relativity asserts. We are referring to an absolute time, i.e. time measured not with respect to ether or non-ether, but with respect to an absolute mathematical reference frame. Several types of clocks could run at a more slowly rate in a moving frame of reference than other types of clocks; it depends on the construction material and functioning principle of each type of clock. Relativists say that ``gravity slows time''. This is incorrect, since actually gravity slows today's types of clocks. And one type of clock is slowed more or less than another type of clock. Not only gravity but other (electric, magnetic, etc.) fields or various medium composition elements or structures may slow or accelerate clocks that are in that medium. The clocks used today in the satellites for the GPS necessitate a correction with respect to the Earth clocks. But in the future, when new types of clocks will be built based on different construction material and functioning principle, the correction of the GPS clocks would be different. In order to make the distinction between ``clock'' and ``time'', we suggest a Experiment # 1 with different types of clocks for the GPS clocks, in order to prove that the resulted dilation and contraction factors are different from those obtained with today's cesium atomic clock.

  5. Song I-Yeong's Armillary Clock

    Science.gov (United States)

    Kim, Sang Hyuk; Lee, Yong Sam

    In 1669 (the 10th year of the reign of King Hyeonjong), Song I-Yeong (宋以穎, 1619-1692), who was a professor of astronomy at Gwansanggam (Bureau of Astronomy), developed the armillary clock which uses the weight power system of an alarm clock. The armillary clock is a unique astronomical clock that combines the traditional armillary sphere of Joseon and the principle of a Western alarm clock. Song I-Yeong's armillary clock was repaired in 1687-1688 according to the records, and since then not much is known about the history of the armillary clock. After many years, in the early 1930s which was the Japanese colonial era, Inchon (仁村) Kim Seong-Su (金性洙, 1891-1955) purchased the armillary clock at the Insa-dong antique street and donated to the Korea University Museum of the present time (designated as National Treasure No. 230 in 1985). Currently, the armillary clock is not in operation because some of the parts are damaged or lost.

  6. Association between circadian clock genes and diapause incidence in Drosophila triauraria.

    Directory of Open Access Journals (Sweden)

    Hirokazu Yamada

    Full Text Available Diapause is an adaptive response triggered by seasonal photoperiodicity to overcome unfavorable seasons. The photoperiodic clock is a system that controls seasonal physiological processes, but our knowledge about its physiological mechanisms and genetic architecture remains incomplete. The circadian clock is another system that controls daily rhythmic physiological phenomena. It has been argued that there is a connection between the two clocks. To examine the genetic connection between them, we analyzed the associations of five circadian clock genes (period, timeless, Clock, cycle and cryptochrome with the occurrence of diapause in Drosophila triauraria, which shows a robust reproductive diapause with clear photoperiodicity. Non-diapause strains found in low latitudes were compared in genetic crosses with the diapause strain, in which the diapause trait is clearly dominant. Single nucleotide polymorphism and deletion analyses of the five circadian clock genes in backcross progeny revealed that allelic differences in timeless and cryptochrome between the strains were additively associated with the differences in the incidence of diapause. This suggests that there is a molecular link between certain circadian clock genes and the occurrence of diapause.

  7. Multiscale Clock Ensembling Using Wavelets

    Science.gov (United States)

    2010-11-01

    allows an energy decomposition of the signal as well, referred to as the wavelet variance. This variance is defined by ) var ()( 2 llX Wv  (11...and it can be shown that for a very wide class of signals and for an appropriately chosen wavelet that ) var ()( 1 2 Xv l lX     . One such...42 nd Annual Precise Time and Time Interval (PTTI) Meeting 527 MULTISCALE CLOCK ENSEMBLING USING WAVELETS Ken Senior Naval Center

  8. Relaxation Methods for Strictly Convex Regularizations of Piecewise Linear Programs

    International Nuclear Information System (INIS)

    Kiwiel, K. C.

    1998-01-01

    We give an algorithm for minimizing the sum of a strictly convex function and a convex piecewise linear function. It extends several dual coordinate ascent methods for large-scale linearly constrained problems that occur in entropy maximization, quadratic programming, and network flows. In particular, it may solve exact penalty versions of such (possibly inconsistent) problems, and subproblems of bundle methods for nondifferentiable optimization. It is simple, can exploit sparsity, and in certain cases is highly parallelizable. Its global convergence is established in the recent framework of B -functions (generalized Bregman functions)

  9. High Performance Clocks and Gravity Field Determination

    Science.gov (United States)

    Müller, J.; Dirkx, D.; Kopeikin, S. M.; Lion, G.; Panet, I.; Petit, G.; Visser, P. N. A. M.

    2018-02-01

    Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in manufacturing high-precision atomic clocks have rapidly improved their accuracy and stability over the last decade that approached the level of 10^{-18}. This notable achievement along with the direct sensitivity of clocks to the strength of the gravitational field make them practically important for various geodetic applications that are addressed in the present paper. Based on a fully relativistic description of the background gravitational physics, we discuss the impact of those highly-precise clocks on the realization of reference frames and time scales used in geodesy. We discuss the current definitions of basic geodetic concepts and come to the conclusion that the advances in clocks and other metrological technologies will soon require the re-definition of time scales or, at least, clarification to ensure their continuity and consistent use in practice. The relative frequency shift between two clocks is directly related to the difference in the values of the gravity potential at the points of clock's localization. According to general relativity the relative accuracy of clocks in 10^{-18} is equivalent to measuring the gravitational red shift effect between two clocks with the height difference amounting to 1 cm. This makes the clocks an indispensable tool in high-precision geodesy in addition to laser ranging and space geodetic techniques. We show how clock measurements can provide geopotential numbers for the realization of gravity-field-related height systems and can resolve discrepancies in classically-determined height systems as well as between national height systems. Another application of clocks is the direct use of observed potential differences for the improved recovery of regional gravity field solutions. Finally, clock measurements for space-borne gravimetry are analyzed along with

  10. Circadian molecular clock in lung pathophysiology

    Science.gov (United States)

    Sundar, Isaac K.; Yao, Hongwei; Sellix, Michael T.

    2015-01-01

    Disrupted daily or circadian rhythms of lung function and inflammatory responses are common features of chronic airway diseases. At the molecular level these circadian rhythms depend on the activity of an autoregulatory feedback loop oscillator of clock gene transcription factors, including the BMAL1:CLOCK activator complex and the repressors PERIOD and CRYPTOCHROME. The key nuclear receptors and transcription factors REV-ERBα and RORα regulate Bmal1 expression and provide stability to the oscillator. Circadian clock dysfunction is implicated in both immune and inflammatory responses to environmental, inflammatory, and infectious agents. Molecular clock function is altered by exposomes, tobacco smoke, lipopolysaccharide, hyperoxia, allergens, bleomycin, as well as bacterial and viral infections. The deacetylase Sirtuin 1 (SIRT1) regulates the timing of the clock through acetylation of BMAL1 and PER2 and controls the clock-dependent functions, which can also be affected by environmental stressors. Environmental agents and redox modulation may alter the levels of REV-ERBα and RORα in lung tissue in association with a heightened DNA damage response, cellular senescence, and inflammation. A reciprocal relationship exists between the molecular clock and immune/inflammatory responses in the lungs. Molecular clock function in lung cells may be used as a biomarker of disease severity and exacerbations or for assessing the efficacy of chronotherapy for disease management. Here, we provide a comprehensive overview of clock-controlled cellular and molecular functions in the lungs and highlight the repercussions of clock disruption on the pathophysiology of chronic airway diseases and their exacerbations. Furthermore, we highlight the potential for the molecular clock as a novel chronopharmacological target for the management of lung pathophysiology. PMID:26361874

  11. Circadian clocks - the fall and rise of physiology

    NARCIS (Netherlands)

    Roenneberg, Till; Merrow, Martha

    2005-01-01

    Circadian clocks control the daily life of most light-sensitive organisms- from cyanobacteria to humans. Molecular processes generate cellular rhythmicity, and cellular clocks in animals coordinate rhythms through interaction ( known as coupling). This hierarchy of clocks generates a complex,

  12. Phylogenetic footprint of the plant clock system in angiosperms: evolutionary processes of Pseudo-Response Regulators

    Directory of Open Access Journals (Sweden)

    Saito Shigeru

    2010-05-01

    Full Text Available Abstract Background Plant circadian clocks regulate many photoperiodic and diurnal responses that are conserved among plant species. The plant circadian clock system has been uncovered in the model plant, Arabidopsis thaliana, using genetics and systems biology approaches. However, it is still not clear how the clock system had been organized in the evolutionary history of plants. We recently revealed the molecular phylogeny of LHY/CCA1 genes, one of the essential components of the clock system. The aims of this study are to reconstruct the phylogenetic relationships of angiosperm clock-associated PRR genes, the partner of the LHY/CCA1 genes, and to clarify the evolutionary history of the plant clock system in angiosperm lineages. Results In the present study, to investigate the molecular phylogeny of PRR genes, we performed two approaches: reconstruction of phylogenetic trees and examination of syntenic relationships. Phylogenetic analyses revealed that PRR genes had diverged into three clades prior to the speciation of monocots and eudicots. Furthermore, copy numbers of PRR genes have been independently increased in monocots and eudicots as a result of ancient chromosomal duplication events. Conclusions Based on the molecular phylogenies of both PRR genes and LHY/CCA1 genes, we inferred the evolutionary process of the plant clock system in angiosperms. This scenario provides evolutionary information that a common ancestor of monocots and eudicots had retained the basic components required for reconstructing a clock system and that the plant circadian clock may have become a more elaborate mechanism after the speciation of monocots and eudicots because of the gene expansion that resulted from polyploidy events.

  13. Non-strictly black body spectrum from the tunnelling mechanism

    International Nuclear Information System (INIS)

    Corda, Christian

    2013-01-01

    The tunnelling mechanism is widely used to explain Hawking radiation. However, in many cases the analysis used to obtain the Hawking temperature only involves comparing the emission probability for an outgoing particle with the Boltzmann factor. Banerjee and Majhi improved this approach by explicitly finding a black body spectrum associated with black holes. Their result, obtained using a reformulation of the tunnelling mechanism, is in contrast to that of Parikh and Wilczek, who found an emission probability that is compatible with a non-strictly thermal spectrum. Using the recently identified effective state for a black hole, we solve this contradiction via a slight modification of the analysis by Banerjee and Majhi. The final result is a non-strictly black body spectrum from the tunnelling mechanism. We also show that for an effective temperature, we can express the corresponding effective metric using Hawking’s periodicity arguments. Potential important implications for the black hole information puzzle are discussed. -- Highlights: •We review an important result by Banerjee and Majhi on the tunnelling mechanism in the framework of Hawking radiation. •This result is in contrast to another result reported by Parikh and Wilczek. •We introduce the effective state of a black hole. •We explain the contrast via a slight modification of the analysis by Banerjee and Majhi. •We discuss potential important implications for the black hole information puzzle

  14. A clock synchronization skeleton based on RTAI

    NARCIS (Netherlands)

    Huang, Y.; Visser, P.M.; Broenink, Johannes F.

    2006-01-01

    This paper presents a clock synchronization skeleton based on RTAI (Real Time Application Interface). The skeleton is a thin layer that provides unified but extendible interfaces to the underlying operating system, the synchronization algorithms and the upper level applications in need of clock

  15. Systematic Effects in Atomic Fountain Clocks

    Science.gov (United States)

    Gibble, Kurt

    2016-06-01

    We describe recent advances in the accuracies of atomic fountain clocks. New rigorous treatments of the previously large systematic uncertainties, distributed cavity phase, microwave lensing, and background gas collisions, enabled these advances. We also discuss background gas collisions of optical lattice and ion clocks and derive the smooth transition of the microwave lensing frequency shift to photon recoil shifts for large atomic wave packets.

  16. Internal Clock Drift Estimation in Computer Clusters

    Directory of Open Access Journals (Sweden)

    Hicham Marouani

    2008-01-01

    Full Text Available Most computers have several high-resolution timing sources, from the programmable interrupt timer to the cycle counter. Yet, even at a precision of one cycle in ten millions, clocks may drift significantly in a single second at a clock frequency of several GHz. When tracing the low-level system events in computer clusters, such as packet sending or reception, each computer system records its own events using an internal clock. In order to properly understand the global system behavior and performance, as reported by the events recorded on each computer, it is important to estimate precisely the clock differences and drift between the different computers in the system. This article studies the clock precision and stability of several computer systems, with different architectures. It also studies the typical network delay characteristics, since time synchronization algorithms rely on the exchange of network packets and are dependent on the symmetry of the delays. A very precise clock, based on the atomic time provided by the GPS satellite network, was used as a reference to measure clock drifts and network delays. The results obtained are of immediate use to all applications which depend on computer clocks or network time synchronization accuracy.

  17. Circadian clock components in the rat neocortex

    DEFF Research Database (Denmark)

    Rath, Martin Fredensborg; Rohde, Kristian; Fahrenkrug, Jan

    2013-01-01

    in the rat neocortex. Among these, Per1, Per2, Per3, Cry1, Bmal1, Nr1d1 and Dbp were found to exhibit daily rhythms. The amplitude of circadian oscillation in neocortical clock gene expression was damped and the peak delayed as compared with the SCN. Lesions of the SCN revealed that rhythmic clock gene...

  18. Could Atomic clocks be affected by neutrinos?

    CERN Document Server

    Hanafi, Hanaa

    2016-01-01

    An atomic clock is a clock device that uses an electronic transition frequency of the electromagnetic spectrum of atoms as a frequency standard in order to derive a time standard since time is the reciprocal of frequency. If the electronic transition frequencies are in an "optical region", we are talking in this case about optical atomic clocks. If they are in an "microwave region" these atomic clocks are made of the metallic element cesium so they are called Cesium atomic clocks. Atomic clocks are the most accurate time and frequency standards known despite the different perturbations that can affect them, a lot of researches were made in this domain to show how the transitions can be different for different type of perturbations..Since atomic clocks are very sensitive devices, based on coherent states (A coherent state tends to loose coherence after interacting). One question can arise (from a lot of questions) which is why cosmic neutrinos are not affecting these clocks? The answer to this question requir...

  19. "Molecular Clock" Analogs: A Relative Rates Exercise

    Science.gov (United States)

    Wares, John P.

    2008-01-01

    Although molecular clock theory is a commonly discussed facet of evolutionary biology, undergraduates are rarely presented with the underlying information of how this theory is examined relative to empirical data. Here a simple contextual exercise is presented that not only provides insight into molecular clocks, but is also a useful exercise for…

  20. Global synchronization of parallel processors using clock pulse width modulation

    Science.gov (United States)

    Chen, Dong; Ellavsky, Matthew R.; Franke, Ross L.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Jeanson, Mark J.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Littrell, Daniel; Ohmacht, Martin; Reed, Don D.; Schenck, Brandon E.; Swetz, Richard A.

    2013-04-02

    A circuit generates a global clock signal with a pulse width modification to synchronize processors in a parallel computing system. The circuit may include a hardware module and a clock splitter. The hardware module may generate a clock signal and performs a pulse width modification on the clock signal. The pulse width modification changes a pulse width within a clock period in the clock signal. The clock splitter may distribute the pulse width modified clock signal to a plurality of processors in the parallel computing system.

  1. A clock reaction based on molybdenum blue.

    Science.gov (United States)

    Neuenschwander, Ulrich; Negron, Arnaldo; Jensen, Klavs F

    2013-05-30

    Clock reactions are rare kinetic phenomena, so far limited mostly to systems with ionic oxoacids and oxoanions in water. We report a new clock reaction in cyclohexanol that forms molybdenum blue from a noncharged, yellow molybdenum complex as precursor, in the presence of hydrogen peroxide. Interestingly, the concomitant color change is reversible, enabling multiple clock cycles to be executed consecutively. The kinetics of the clock reaction were experimentally characterized, and by adding insights from quantum chemical calculations, a plausible reaction mechanism was postulated. Key elementary reaction steps comprise sigmatropic rearrangements with five-membered or bicyclo[3.1.0] transition states. Importantly, numerical kinetic modeling demonstrated the mechanism's ability to reproduce the experimental findings. It also revealed that clock behavior is intimately connected to the sudden exhaustion of hydrogen peroxide. Due to the stoichiometric coproduction of ketone, the reaction bears potential for application in alcohol oxidation catalysis.

  2. Limitations for near-real-time orbit and clock products and first results of a normal equation stacking approach for orbit and clock determination

    Science.gov (United States)

    Schoenemann, E.; Alfaro, P.; Springer, T.; Becker, M.; Dow, J.; Zandbergen, R.

    2009-04-01

    The Navigation Support Office at the European Space Operations Centre (ESA/ESOC) in Darmstadt, as one of the IGS-AC's, performs routinely precise orbit and clock estimation. We contribute to the common IGS-products, as ultra-rapid, rapid and final orbits and clocks, with latencies of 3 hours, 17 hours and 13 days. Furthermore, we are deeply involved in the IGS Real Time Pilot Project, to which we contribute with an experimental solution. Monitoring tasks, as for hazard mitigation and earth observation desire highly accurate orbits and clocks in near-real-time. Evaluating the products currently available in near-real-time, shows that the predicted orbits (ultra-rapid) provide an adequate accuracy whereas clocks are the weak point. The quality of the prediction of clocks is decreasing rapidly and techniques to keep the prediction time short and to use adequate models are essential. There are different methods for near-real-time clock estimation, delivering more or less middling results. Common for all methods are issues like time delays and data gaps, degrading the already weak network configuration. We analysed these issues and their influences on the near-real-time products, based on recorded real-time and other observation data modified to include gaps, jumps and other potential pitfalls. The poster will present an extract of our analyses, showing the impact of data gaps on selected sites, as well as the impact of different network configurations. One of our current research areas is the definition an implementation of a new method to derive the clocks and orbits by stacking normal equations in quasi-real-time (5 minute batches solutions). These method, and some preliminary results, will be presented. We expect this approach to offer accuracies comparable to the IGS non real-time products (in an ideal scenario with a good and reliable real-time network) but with a delay of minutes.

  3. Comparing Behavior and Clock Gene Expression between Caterpillars, Butterflies, and Moths.

    Science.gov (United States)

    Niepoth, Natalie; Ke, Gao; de Roode, Jacobus C; Groot, Astrid T

    2018-02-01

    Circadian behavior is widely observed in insects; however, the mechanisms that drive its evolution remain a black box. While circadian activity rhythms are well characterized in adults within the order Lepidoptera (i.e., most butterfly species are day active, while most moths are night active), much less is known about daily activity and clock gene expression in the larval stage. Additionally, direct comparison of clock gene expression between day-active and night-active species reared together has not been quantified. Our study characterized the daily rhythms of caterpillar feeding and activity in addition to the gene expression of 2 central circadian clock genes, period ( per) and timeless ( tim), in larvae and adults of the day-active butterfly Danaus plexippus and the night-active moth Heliothis virescens. We found that neither Danaus nor Heliothis caterpillars are strictly diurnal or nocturnal like their adult counterparts; however, we found that slight rhythms in feeding and activity can arise in response to external forces, such as temperature and host plant. Expression levels differed between genes, between butterfly larvae and adults, and between butterfly and moth species, even though expression levels of both per and tim oscillated with a similar phase over 24 hours across all treatments. Our study, the first of its kind to investigate circadian timekeeper gene expression in 2 life stages and 2 species, highlights interesting differences in core clock gene expression patterns that could have potential downstream effects on circadian rhythms.

  4. Rhythmic expression of circadian clock genes in the preovulatory ovarian follicles of the laying hen.

    Directory of Open Access Journals (Sweden)

    Zhichao Zhang

    Full Text Available The circadian clock is reported to play a role in the ovaries in a variety of vertebrate species, including the domestic hen. However, the ovary is an organ that changes daily, and the laying hen maintains a strict follicular hierarchy. The aim of this study was to examine the spatial-temporal expression of several known canonical clock genes in the granulosa and theca layers of six hierarchy follicles. We demonstrated that the granulosa cells (GCs of the F1-F3 follicles harbored intrinsic oscillatory mechanisms in vivo. In addition, cultured granulosa cells (GCs from F1 follicles exposed to luteinizing hormone (LH synchronization displayed Per2 mRNA oscillations, whereas, the less mature GCs (F5 plus F6 displayed no circadian change in Per2 mRNA levels. Cultures containing follicle-stimulating hormone (FSH combined with LH expressed levels of Per2 mRNA that were 2.5-fold higher than those in cultures with LH or FSH alone. These results show that there is spatial specificity in the localization of clock cells in hen preovulatory follicles. In addition, our results support the hypothesis that gonadotropins provide a cue for the development of the functional cellular clock in immature GCs.

  5. An expander system of high stable laser beam for cesium atomic fountain clocks

    Science.gov (United States)

    Chen, Jiang; Lin, Rui; Liu, Dandan; Zhang, Hui; Ruan, Jun; Shi, Junru; Yu, Fengxiang; Zhang, Shougang

    2017-10-01

    The quality of the cold atoms sample plays an important role to improve the performance of cesium atomic fountain clocks. The preparation of cold atoms sample has a strict requirement for cooling lasers characteristics such as power stability, polarization, collimation, uniformity and verticality. This work implements a design of an expander system of high stable laser beam for the cold atom preparation. The cooling laser characteristics can be adjusted by the design, and the use of non-magnetic materials to avoid the magnetic field on the impact of cold atom. The cold atom sample with the number of 2×108 and temperature of 5μk was obtained by expander system. The result meets the requirements of the preparation of cold atoms for cesium atomic fountain clocks.

  6. Effects of a strict cutoff on Quantum Field Theory

    International Nuclear Information System (INIS)

    Sturnfield, J.F.

    1987-01-01

    Standard Quantum Field Theory has a number of integrals which are infinite. Although these are eliminated for some cases by renormalization, this aspect of the theory is not fully satisfactory. A number of theories with fundamental lengths have been introduced as alternatives and it would be useful to be able to distinguish between them. In particular, the effects that a strict cutoff would have on Quantum Field Theory is studied. It is noted that care must be taken in the method used to apply a strict cutoff. This lead to considering a theory where the cutoffs are defined by restricting each internal line. This theory is only piece-wise analytic. The resulting scattering matrix is frame dependent, yet the theory still satisfies the special relativity view that all frames are subjectively identical. The renormalization of this theory is finite. The change in mass from the electron self-energy will be a spinor operator. The main distinctions of this theory from standard theory will occur at super high energies. New poles and resonances which arise from new endpoint singularities will be found. The locations of these singularities will be frame dependent. Some of these singularities will correspond to creations or interactions of the normal particles with tachyons. It will be shown that for the one loop diagram, the form of the cutoff singularities are closely related to the standard singularities. When there is more than one loop, there can appear some new type of behavior. In particular, a cube root type of behavior in the two loop self-energy diagram will be found. Also the asymptotic behavior of the ladder diagram is studied

  7. SCA1+ Cells from the Heart Possess a Molecular Circadian Clock and Display Circadian Oscillations in Cellular Functions

    Directory of Open Access Journals (Sweden)

    Bastiaan C. Du Pré

    2017-09-01

    Full Text Available Stem cell antigen 1-positive (SCA1+ cells (SPCs have been investigated in cell-based cardiac repair and pharmacological research, although improved cardiac function after injection has been variable and the mode of action remains unclear. Circadian (24-hr rhythms are biorhythms regulated by molecular clocks that play an important role in (pathophysiology. Here, we describe (1 the presence of a molecular circadian clock in SPCs and (2 circadian rhythmicity in SPC function. We isolated SPCs from human fetal heart and found that these cells possess a molecular clock based on typical oscillations in core clock components BMAL1 and CRY1. Functional analyses revealed that circadian rhythmicity also governs SPC proliferation, stress tolerance, and growth factor release, with large differences between peaks and troughs. We conclude that SPCs contain a circadian molecular clock that controls crucial cellular functions. Taking circadian rhythms into account may improve reproducibility and outcome of research and therapies using SPCs.

  8. Clock genes alterations and endocrine disorders.

    Science.gov (United States)

    Angelousi, Anna; Kassi, Eva; Nasiri-Ansari, Narjes; Weickert, Martin O; Randeva, Harpal; Kaltsas, Gregory

    2018-03-25

    Various endocrine signals oscillate over the 24-hour period and so does the responsiveness of target tissues. These daily oscillations do not occur solely in response to external stimuli but are also under the control of an intrinsic circadian clock. We searched the PubMed database to identify studies describing the associations of clock genes with endocrine diseases. Various human single nucleotide polymorphisms of BMAL1 and CLOCK genes exhibited significant associations with type 2 diabetes mellitus. ARNTL2 gene expression and upregulation of BMAL1 and PER1 were associated with the development of type 1 diabetes mellitus. Thyroid hormones modulated PER2 expression in a tissue specific way whereas BMAL1 regulated the expression of type 2 iodothyronine deiodinase in specific tissues. Adrenal gland and adrenal adenoma expressed PER1, PER2, CRY2, CLOCK, and BMAL1 genes. Adrenal sensitivity to adrenocorticotrophin was also affected by circadian oscilliations. A significant correlation between the expression of propio-melanocorticotrophin and PER 2 as well as between prolactin and CLOCK was found in corticotroph and lactosomatotroph cells, respectively, in the pituitary. Clock genes and especially BMAL1 showed an important role in fertility whereas estradiol and androgens exhibited tissue-specific effects on clock gene expression. Metabolic disorders were also associated with circadian dysregulation according to studies in shift workers. Clock genes are associated with various endocrine disorders through complex mechanisms. However data on humans are scarce. Moreover, clock genes exhibit a tissue-specific expression representing an additional level of regulation. Their specific role in endocrine disorders and their potential implications remain to be further clarified. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

  9. Circadian rhythms of fetal liver transcription persist in the absence of canonical circadian clock gene expression rhythms in vivo.

    Directory of Open Access Journals (Sweden)

    Chengwei Li

    Full Text Available The cellular circadian clock and systemic cues drive rhythmicity in the transcriptome of adult peripheral tissues. However, the oscillating status of the circadian clocks in fetal tissues, and their response to maternal cues, are less clear. Most clock genes do not cycle in fetal livers from mice and rats, although tissue level rhythms rapidly emerge when fetal mouse liver explants are cultured in vitro. Thus, in the fetal mouse liver, the circadian clock does not oscillate at the cellular level (but is induced to oscillate in culture. To gain a comprehensive overview of the clock status in the fetal liver during late gestation, we performed microarray analyses on fetal liver tissues. In the fetal liver we did not observe circadian rhythms of clock gene expression or many other transcripts known to be rhythmically expressed in the adult liver. Nevertheless, JTK_CYCLE analysis identified some transcripts in the fetal liver that were rhythmically expressed, albeit at low amplitudes. Upon data filtering by coefficient of variation, the expression levels for transcripts related to pancreatic exocrine enzymes and zymogen secretion were found to undergo synchronized daily fluctuations at high amplitudes. These results suggest that maternal cues influence the fetal liver, despite the fact that we did not detect circadian rhythms of canonical clock gene expression in the fetal liver. These results raise important questions on the role of the circadian clock, or lack thereof, during ontogeny.

  10. The Trade-Off Mechanism in Mammalian Circadian Clock Model with Two Time Delays

    Science.gov (United States)

    Yan, Jie; Kang, Xiaxia; Yang, Ling

    Circadian clock is an autonomous oscillator which orchestrates the daily rhythms of physiology and behaviors. This study is devoted to explore how a positive feedback loop affects the dynamics of mammalian circadian clock. We simplify an experimentally validated mathematical model in our previous work, to a nonlinear differential equation with two time delays. This simplified mathematical model incorporates the pacemaker of mammalian circadian clock, a negative primary feedback loop, and a critical positive auxiliary feedback loop, Rev-erbα/Cry1 loop. We perform analytical studies of the system. Delay-dependent conditions for the asymptotic stability of the nontrivial positive steady state of the model are investigated. We also prove the existence of Hopf bifurcation, which leads to self-sustained oscillation of mammalian circadian clock. Our theoretical analyses show that the oscillatory regime is reduced upon the participation of the delayed positive auxiliary loop. However, further simulations reveal that the auxiliary loop can enable the circadian clock gain widely adjustable amplitudes and robust period. Thus, the positive auxiliary feedback loop may provide a trade-off mechanism, to use the small loss in the robustness of oscillation in exchange for adaptable flexibility in mammalian circadian clock. The results obtained from the model may gain new insights into the dynamics of biological oscillators with interlocked feedback loops.

  11. Transcripts from the Circadian Clock: Telling Time and Season

    NARCIS (Netherlands)

    K. Brand (Karl)

    2011-01-01

    textabstractWe all know it when we wake mere moments before an alarm clock is scheduled to wake us: our body clock made the alarm clock redundant. This phenomenon is driven by an endogenous timer known as the biological, or circadian clock. Each revolution of the Earth about its own axis produces

  12. The circadian clock in cancer development and therapy

    Science.gov (United States)

    Most aspects of mammalian function display circadian rhythms driven by an endogenous clock. The circadian clock is operated by genes and comprises a central clock in the brain that responds to environmental cues and controls subordinate clocks in peripheral tissues via circadian output pathways. The...

  13. Regulation of circadian clock transcriptional output by CLOCK:BMAL1.

    Science.gov (United States)

    Trott, Alexandra J; Menet, Jerome S

    2018-01-01

    The mammalian circadian clock relies on the transcription factor CLOCK:BMAL1 to coordinate the rhythmic expression of 15% of the transcriptome and control the daily regulation of biological functions. The recent characterization of CLOCK:BMAL1 cistrome revealed that although CLOCK:BMAL1 binds synchronously to all of its target genes, its transcriptional output is highly heterogeneous. By performing a meta-analysis of several independent genome-wide datasets, we found that the binding of other transcription factors at CLOCK:BMAL1 enhancers likely contribute to the heterogeneity of CLOCK:BMAL1 transcriptional output. While CLOCK:BMAL1 rhythmic DNA binding promotes rhythmic nucleosome removal, it is not sufficient to generate transcriptionally active enhancers as assessed by H3K27ac signal, RNA Polymerase II recruitment, and eRNA expression. Instead, the transcriptional activity of CLOCK:BMAL1 enhancers appears to rely on the activity of ubiquitously expressed transcription factors, and not tissue-specific transcription factors, recruited at nearby binding sites. The contribution of other transcription factors is exemplified by how fasting, which effects several transcription factors but not CLOCK:BMAL1, either decreases or increases the amplitude of many rhythmically expressed CLOCK:BMAL1 target genes. Together, our analysis suggests that CLOCK:BMAL1 promotes a transcriptionally permissive chromatin landscape that primes its target genes for transcription activation rather than directly activating transcription, and provides a new framework to explain how environmental or pathological conditions can reprogram the rhythmic expression of clock-controlled genes.

  14. 7 CFR 28.414 - Strict Low Middling Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Light Spotted Cotton § 28.414 Strict Low Middling Light Spotted Color. Strict Low Middling Light Spotted Color is color which in spot or...

  15. Circadian and Circalunar Clock Interactions in a Marine Annelid

    Directory of Open Access Journals (Sweden)

    Juliane Zantke

    2013-10-01

    Full Text Available Life is controlled by multiple rhythms. Although the interaction of the daily (circadian clock with environmental stimuli, such as light, is well documented, its relationship to endogenous clocks with other periods is little understood. We establish that the marine worm Platynereis dumerilii possesses endogenous circadian and circalunar (monthly clocks and characterize their interactions. The RNAs of likely core circadian oscillator genes localize to a distinct nucleus of the worm’s forebrain. The worm’s forebrain also harbors a circalunar clock entrained by nocturnal light. This monthly clock regulates maturation and persists even when circadian clock oscillations are disrupted by the inhibition of casein kinase 1δ/ε. Both circadian and circalunar clocks converge on the regulation of transcript levels. Furthermore, the circalunar clock changes the period and power of circadian behavior, although the period length of the daily transcriptional oscillations remains unaltered. We conclude that a second endogenous noncircadian clock can influence circadian clock function.

  16. A GPS Satellite Clock Offset Prediction Method Based on Fitting Clock Offset Rates Data

    Directory of Open Access Journals (Sweden)

    WANG Fuhong

    2016-12-01

    Full Text Available It is proposed that a satellite atomic clock offset prediction method based on fitting and modeling clock offset rates data. This method builds quadratic model or linear model combined with periodic terms to fit the time series of clock offset rates, and computes the model coefficients of trend with the best estimation. The clock offset precisely estimated at the initial prediction epoch is directly adopted to calculate the model coefficient of constant. The clock offsets in the rapid ephemeris (IGR provided by IGS are used as modeling data sets to perform certain experiments for different types of GPS satellite clocks. The results show that the clock prediction accuracies of the proposed method for 3, 6, 12 and 24 h achieve 0.43, 0.58, 0.90 and 1.47 ns respectively, which outperform the traditional prediction method based on fitting original clock offsets by 69.3%, 61.8%, 50.5% and 37.2%. Compared with the IGU real-time clock products provided by IGS, the prediction accuracies of the new method have improved about 15.7%, 23.7%, 27.4% and 34.4% respectively.

  17. On N. Chomsky’s strict subcategorization of verbs

    Directory of Open Access Journals (Sweden)

    Janez Orešnik

    1966-12-01

    Full Text Available This paper studies the so-called strict subcategorization rules, and the theory associated with them, in the transformational grammar of. Erigl·ish as proposed by Noarn Chomsky in his Aspects. The syntactic component of English transformational grammar consists of two mutually ordered parts, viz., the base and the transformational subcomponents. The initial part of the base are the so-called categorial rules, which are of almost exclusive interest to us here. Their primary task is to generate what are usually called basic sentence patterns, and will here, with Chomsky (Aspects, p.ll3, be designated with the expression, frames of category symbols.- The rules of the transformational subcomponent modify, in various ways, the frames generated by the base. For several reasons - one of them being that the correct work of the transformational subcomponent quite often depends on the kind of lexical items with which the syntactic positions in the frames of category symbols have been filled, the lexical items must be introduced from the lexicon into the empty positions in the frames before the rules of the transformational subcomponent can be allowed to modify the frames.

  18. Managing Hanford Site solid waste through strict acceptance criteria

    International Nuclear Information System (INIS)

    Jasen, W.G.; Pierce, R.D.; Willis, N.P.

    1993-02-01

    Various types of waste have been generated during the 50-year history of the Hanford Site. Regulatory changes in the last 20 years have provided the emphasis for better management of these wastes. Interpretations of the Atomic Energy Act of 1954 (AEA) and the Resource Conservation and Recovery Act of 1976 (RCRA) have led to the definition of a group of wastes called radioactive mixed wastes (RMW). As a result of the radioactive and hazardous properties of these wastes, strict management programs have been implemented for the management of these wastes. Solid waste management is accomplished through a systems performance approach to waste management that used best-demonstrated available technology (BDAT) and best management practices. The solid waste program at the Hanford Site strives to integrate all aspects of management relative to the treatment, storage and disposal (TSD) of solid waste. Often there are many competing and important needs. It is a difficult task to balance these needs in a manner that is both equitable and productive. Management science is used to help the process of making decisions. Tools used to support the decision making process include five-year planning, cost estimating, resource allocation, performance assessment, waste volume forecasts, input/output models, and waste acceptance criteria. The purpose of this document is to describe how one of these tools, waste acceptance criteria, has helped the Hanford Site manage solid wastes

  19. Effects of strict prolonged bed rest on cardiorespiratory fitness

    DEFF Research Database (Denmark)

    Ried-Larsen, Mathias; Aarts, Hugo M; Joyner, Michael J

    2017-01-01

    with larger declines in V̇o2max). Furthermore, the systematic review revealed a gap in the knowledge about the cardiovascular response to extreme physical inactivity, particularly in older subjects and women of any age group. In addition to its relevance to spaceflight, this lack of data has significant....... Since 1949, 80 studies with a total of 949 participants (>90% men) have been published with data on strict bed rest and V̇o2max The studies were conducted mainly in young participants [median age (interquartile range) 24.5 (22.4-34.0) yr]. The duration of bed rest ranged from 1 to 90 days. V̇o2max...... declined linearly across bed rest duration. No statistical difference in the decline among studies reporting V̇o2max as l/min (-0.3% per day) compared with studies reporting V̇o2max normalized to body weight (ml·kg-1·min-1; -0.43% per day) was observed. Although both total body weight and lean body mass...

  20. Fixed point iterations for strictly hemi-contractive maps in uniformly smooth Banach spaces

    International Nuclear Information System (INIS)

    Chidume, C.E.; Osilike, M.O.

    1993-05-01

    It is proved that the Mann iteration process converges strongly to the fixed point of a strictly hemi-contractive map in real uniformly smooth Banach spaces. The class of strictly hemi-contractive maps includes all strictly pseudo-contractive maps with nonempty fixed point sets. A related result deals with the Ishikawa iteration scheme when the mapping is Lipschitzian and strictly hemi-contractive. Our theorems generalize important known results. (author). 29 refs

  1. Cellular Reprogramming–Turning the Clock Back

    Indian Academy of Sciences (India)

    Cellular Reprogramming - Turning the Clock Back - Nobel Prize in Physiology or Medicine, 2012. Deepa Subramanyam ... Keywords. Embryonic stem cells; pluripotency; reprogramming; differentiation; Nobel Prize 2012. ... National Centre for Cell Science University of Pune Campus Ganeshkhind Pune 411 007, India.

  2. Entrainment of the Neurospora circadian clock

    NARCIS (Netherlands)

    Merrow, M; Boesl, C; Ricken, J; Messerschmitt, M; Goedel, M; Roenneberg, T

    2006-01-01

    Neurospora crassa has been systematically investigated for circadian entrainment behavior. Many aspects of synchronization can be investigated in this simple, cellular system, ranging from systematic entrainment and drivenness to masking. Clock gene expression during entrainment and entrainment

  3. CDDIS_GNSS_products_clocks_rapid

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellite and receiver clock products derived from analysis of Global Navigation Satellite System (GNSS) data. These products are the generated by analysis centers...

  4. Targeting the Circadian Clock to Treat Cancer

    Science.gov (United States)

    Two compounds that target components of the circadian clock killed several types of cancer cells in the lab and slowed the growth of brain cancer in mice without harming healthy cells, as this Cancer Currents post reports.

  5. CDDIS_GNSS_products_clocks_final

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellite and receiver clock products derived from analysis of Global Navigation Satellite System (GNSS) data. These products are the generated by analysis centers...

  6. Clock jitter generator with picoseconds resolution

    Science.gov (United States)

    Jovanović, Goran; Stojčev, Mile; Nikolić, Tatjana

    2013-06-01

    The clock is one of the most critical signals in any synchronous system. As CMOS technology has scaled, supply voltages have dropped chip power consumption has increased and the effects of jitter due to clock frequency increase have become critical and jitter budget has become tighter. This article describes design and development of low-cost mixed-signal programmable jitter generator with high resolution. The digital technique is used for coarse-grain and an analogue technique for fine-grain clock phase shifting. Its structure allows injection of various random and deterministic jitter components in a controllable and programmable fashion. Each jitter component can be switched on or off. The jitter generator can be used in jitter tolerance test and jitter transfer function measurement of high-speed synchronous digital circuits. At operating system clock frequency of 220 MHz, a jitter with 4 ps resolution can be injected.

  7. Draper Clock-Synchronization Protocol in SAL

    Data.gov (United States)

    National Aeronautics and Space Administration — In 1973, Daly, Hpokins, and McKenna (from Draper Lab.) presented a fault-tolerant digital clocking system at the FTCS conference. This is probably one of the first...

  8. Avian Circadian Organization: A Chorus of Clocks

    Science.gov (United States)

    Cassone, Vincent M

    2013-01-01

    In birds, biological clock function pervades all aspects of biology, controlling daily changes in sleep: wake, visual function, song, migratory patterns and orientation, as well as seasonal patterns of reproduction, song and migration. The molecular bases for circadian clocks are highly conserved, and it is likely the avian molecular mechanisms are similar to those expressed in mammals, including humans. The central pacemakers in the avian pineal gland, retinae and SCN dynamically interact to maintain stable phase relationships and then influence downstream rhythms through entrainment of peripheral oscillators in the brain controlling behavior and peripheral tissues. Birds represent an excellent model for the role played by biological clocks in human neurobiology; unlike most rodent models, they are diurnal, they exhibit cognitively complex social interactions, and their circadian clocks are more sensitive to the hormone melatonin than are those of nocturnal rodents. PMID:24157655

  9. Programmable Clock Waveform Generation for CCD Readout

    Energy Technology Data Exchange (ETDEWEB)

    Vicente, J. de; Castilla, J.; Martinez, G.; Marin, J.

    2006-07-01

    Charge transfer efficiency in CCDs is closely related to the clock waveform. In this paper, an experimental framework to explore different FPGA based clock waveform generator designs is described. Two alternative design approaches for controlling the rise/fall edge times and pulse width of the CCD clock signal have been implemented: level-control and time-control. Both approaches provide similar characteristics regarding the edge linearity and noise. Nevertheless, dissimilarities have been found with respect to the area and frequency range of application. Thus, while the time-control approach consumes less area, the level control approach provides a wider range of clock frequencies since it does not suffer capacitor discharge effect. (Author) 8 refs.

  10. The Mechanics of Mechanical Watches and Clocks

    CERN Document Server

    Du, Ruxu

    2013-01-01

    "The Mechanics of Mechanical Watches and Clocks" presents historical views and mathematical models of mechanical watches and clocks. Although now over six hundred years old, mechanical watches and clocks are still popular luxury items that fascinate many people around the world. However few have examined the theory of how they work as presented in this book. The illustrations and computer animations are unique and have never been published before. It will be of significant interest to researchers in mechanical engineering, watchmakers and clockmakers, as well as people who have an engineering background and are interested in mechanical watches and clocks. It will also inspire people in other fields of science and technology, such as mechanical engineering and electronics engineering, to advance their designs. Professor Ruxu Du works at the Chinese University of Hong Kong, China. Assistant Professor Longhan Xie works at the South China University of Technology, China.

  11. Cell-permeable Circadian Clock Proteins

    National Research Council Canada - National Science Library

    Johnson, Carl

    2002-01-01

    .... These 'biological clocks' are important to human physiology. For example, psychiatric and medical studies have shown that circadian rhythmicity is involved in some forms of depressive illness, 'jet lag', drug tolerance/efficacy, memory, and insomnia...

  12. Mini Review: Circadian Clocks, Stress and Immunity

    Directory of Open Access Journals (Sweden)

    Rebecca eDumbell

    2016-05-01

    Full Text Available In mammals, molecular circadian clocks are present in most cells of the body, and this circadian network plays an important role in synchronizing physiological processes and behaviors to the appropriate time of day. The hypothalamic-pituitary-adrenal endocrine axis regulates the response to acute and chronic stress, acting through its final effectors – glucocorticoids – released from the adrenal cortex. Glucocorticoid secretion, characterized by its circadian rhythm, has an important role in synchronizing peripheral clocks and rhythms downstream of the master circadian pacemaker in the suprachiasmatic nucleus. Finally, glucocorticoids are powerfully anti-inflammatory, and recent work has implicated the circadian clock in various aspects and cells of the immune system, suggesting a tight interplay of stress and circadian systems in the regulation of immunity. This mini-review summarizes our current understanding of the role of the circadian clock network in both, the HPA axis and the immune system, and discusses their interactions.

  13. Cellular Reprogramming–Turning the Clock Back

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 18; Issue 6. Cellular Reprogramming - Turning the Clock Back - Nobel Prize in Physiology or Medicine, 2012. Deepa Subramanyam. General Article Volume 18 Issue 6 June 2013 pp 514-521 ...

  14. CDDIS_GNSS_products_clocks_realtime

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellite and receiver clock products derived from analysis of Global Navigation Satellite System (GNSS) data. These products are the generated by analysis centers...

  15. Reduced Kalman Filters for Clock Ensembles

    Science.gov (United States)

    Greenhall, Charles A.

    2011-01-01

    This paper summarizes the author's work ontimescales based on Kalman filters that act upon the clock comparisons. The natural Kalman timescale algorithm tends to optimize long-term timescale stability at the expense of short-term stability. By subjecting each post-measurement error covariance matrix to a non-transparent reduction operation, one obtains corrected clocks with improved short-term stability and little sacrifice of long-term stability.

  16. Molecular components of the mammalian circadian clock

    OpenAIRE

    Buhr, Ethan D.; Takahashi, Joseph S.

    2013-01-01

    Mammals synchronize their circadian activity primarily to the cycles of light and darkness in the environment. This is achieved by ocular photoreception relaying signals to the suprachiasmatic nucleus (SCN) in the hypothalamus. Signals from the SCN cause the synchronization of independent circadian clocks throughout the body to appropriate phases. Signals that can entrain these peripheral clocks include humoral signals, metabolic factors, and body temperature. At the level of individual tissu...

  17. Direct Laser Cooling Al{}^{+} Ion Optical Clocks

    Science.gov (United States)

    Zhang, Jie; Deng, Ke; Luo, Jun; Lu, Ze-Huang

    2017-05-01

    The Al{}+ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of Al{}+ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al{}+ traps are utilized. The first trap is used to trap a large number of Al{}+ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al{}+ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167 nm laser. The expected clock laser stability can reach 9.0× {10}-17/\\sqrt{τ }. For the second trap, in addition to 167 nm laser Doppler cooling, a second stage pulsed 234 nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1× {10}-18. The proposed Al{}+ ion optical clock has the potential to become the most accurate and stable optical clock. Supported by the National Basic Research Program of China under Grant No 2012CB821300, the National Natural Science Foundation of China under Grant Nos 91336213, 11304109, 91536116 and 11174095, and the Program for New Century Excellent Talents by the Ministry of Education under Grant No NCET-11-0176.

  18. Dynamic Power Reduction of Digital Circuits by ClockGating

    OpenAIRE

    Varsha Dewre; Rakesh Mandliya

    2017-01-01

    In this paper we have presented clock gating process for low power VLSI (very large scale integration) circuit design. Clock gating is one of the most quite often used systems in RTL to shrink dynamic power consumption without affecting the performance of the design. One process involves inserting gating requisites in the RTL, which the synthesis tool translates to clock gating cells in the clock-path of a register bank. This helps to diminish the switching activity on the clock network, ther...

  19. The hepatic circadian clock modulates xenobiotic metabolism in mice

    OpenAIRE

    DeBruyne, Jason P; Weaver, David R; Dallmann, Robert

    2014-01-01

    The circadian clock generates daily cycles of gene expression that regulate physiological processes. The liver plays an important role in xenobiotic metabolism, and also has been shown to possess its own cell-based clock. The liver clock is synchronized by the master clock in the brain, and a portion of rhythmic gene expression can be driven by behavior of the organism as a whole even when the hepatic clock is suppressed. So far, however, there is relatively little evidence indicating whether...

  20. Optical atomic clocks with suppressed black body radiation shift

    OpenAIRE

    Kozlov, Alexander; Dzuba, Vladimir; Flambaum, Victor

    2014-01-01

    We study a wide range of neutral atoms and ions suitable for ultra-precise atomic optical clocks with naturally suppressed black body radiation shift of clock transition frequency. Calculations show that scalar polarizabilities of clock states cancel each other for at least one order of magnitude for considered systems. Results for calculations of frequencies, quadrupole moments of the states, clock transition amplitudes and natural widths of upper clock states are presented.

  1. Do Caucasian and Asian clocks tick differently?

    Directory of Open Access Journals (Sweden)

    A.A. Barbosa

    Full Text Available The Period 3 and Clock genes are important components of the mammalian molecular circadian system. Studies have shown association between polymorphisms in these clock genes and circadian phenotypes in different populations. Nevertheless, differences in the pattern of allele frequency and genotyping distribution are systematically observed in studies with different ethnic groups. To investigate and compare the pattern of distribution in a sample of Asian and Caucasian populations living in Brazil, we evaluated two well-studied polymorphisms in the clock genes: a variable number of tandem repeats (VNTR in PER3 and a single nucleotide polymorphism (SNP in CLOCK. The aim of this investigation was to search for clues about human evolutionary processes related to circadian rhythms. We selected 109 Asian and 135 Caucasian descendants. The frequencies of the shorter allele (4 repeats in the PER3 gene and the T allele in the CLOCK gene among Asians (0.86 and 0.84, respectively were significantly higher than among Caucasians (0.69 and 0.71, respectively. Our results directly confirmed the different distribution of these polymorphisms between the Asian and Caucasian ethnic groups. Given the genetic differences found between groups, two points became evident: first, ethnic variations may have implications for the interpretation of results in circadian rhythm association studies, and second, the question may be raised about which evolutionary conditions shaped these genetic clock variations.

  2. Hydrogen Maser Clock (HMC) Experiment

    Science.gov (United States)

    Vessot, Robert F. C.; Mattison, Edward M.

    1997-01-01

    The Hydrogen Maser Clock (HMC) project was originally conceived to fly on a reflight of the European Space Agency (ESA) free flying platform, the European Recoverable Carrier (EURECA) that had been launched into space and recovered by NASA's Space Transportation System (STS). A Phase B study for operation of HMC as one of the twelve EURECA payload components was begun in July 1991, and completed a year later. Phase C/D of HMC began in August 1992 and continued into early 1995. At that time ESA decided not to refly EURECA, leaving HMC without access to space. Approximately 80% of the flight support electronics are presently operating the HMC's physics package in a vacuum tank at the Smithsonian Astrophysical Observatory, and are now considered to be well-tested flight electronics. The package will continue to be operated until the end of 1997 or until a flight opportunity becomes avaiable. Appendices: letters and trip report; proceedings of the symposium on frequency standards and metrology; milli-celsius-stability thermal control for an orbiting frequency standard.

  3. Screening for cognitive dysfunction in Huntington's disease with the clock drawing test.

    Science.gov (United States)

    Terwindt, Paul W; Hubers, Anna A M; Giltay, Erik J; van der Mast, Rose C; van Duijn, Erik

    2016-09-01

    The aim of the study is to investigate the performance of the clock drawing test as a screening tool for cognitive impairment in Huntington's disease (HD) mutation carriers. The performance of the clock drawing test was assessed in 65 mutation carriers using the Shulman and the Freund scoring systems. The mini-mental state examination, the Symbol Digit Modalities Test, the Verbal Fluency Test, and the Stroop tests were used as comparisons for the evaluation of cognitive functioning. Correlations of the clock drawing test with various cognitive tests (convergent validity), neuropsychiatric characteristics (divergent validity) and clinical characteristics were analysed using the Spearman's rank correlation coefficient. Receiver-operator characteristic analyses were performed for the clock drawing test against both the mini-mental state examination and against a composite variable for executive cognitive functioning to assess optimal cut-off scores. Inter-rater reliability was high for both the Shulman and Freund scoring systems (ICC = 0.95 and ICC = 0.90 respectively). The clock drawing tests showed moderate to high correlations with the composite variable for executive cognitive functioning (mean ρ = 0.75) and weaker correlations with the mini-mental state examination (mean ρ = 0.62). Mean sensitivity of the clock drawing tests was 0.82 and mean specificity was 0.79, whereas the mean positive predictive value was 0.66 and the mean negative predictive value was 0.87. The clock drawing test is a suitable screening instrument for cognitive dysfunction in HD, because it was shown to be accurate, particularly so with respect to executive cognitive functioning, and is easy and quick to use. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  4. Strict or graduated punishment? Effect of punishment strictness on the evolution of cooperation in continuous public goods games.

    Directory of Open Access Journals (Sweden)

    Hajime Shimao

    Full Text Available Whether costly punishment encourages cooperation is one of the principal questions in studies on the evolution of cooperation and social sciences. In society, punishment helps deter people from flouting rules in institutions. Specifically, graduated punishment is a design principle for long-enduring common-pool resource institutions. In this study, we investigate whether graduated punishment can promote a higher cooperation level when each individual plays the public goods game and has the opportunity to punish others whose cooperation levels fall below the punisher's threshold. We then examine how spatial structure affects evolutionary dynamics when each individual dies inversely proportional to the game score resulting from the social interaction and another player is randomly chosen from the population to produce offspring to fill the empty site created after a player's death. Our evolutionary simulation outcomes demonstrate that stricter punishment promotes increased cooperation more than graduated punishment in a spatially structured population, whereas graduated punishment increases cooperation more than strict punishment when players interact with randomly chosen opponents from the population. The mathematical analysis also supports the results.

  5. Strict or Graduated Punishment? Effect of Punishment Strictness on the Evolution of Cooperation in Continuous Public Goods Games

    Science.gov (United States)

    Shimao, Hajime; Nakamaru, Mayuko

    2013-01-01

    Whether costly punishment encourages cooperation is one of the principal questions in studies on the evolution of cooperation and social sciences. In society, punishment helps deter people from flouting rules in institutions. Specifically, graduated punishment is a design principle for long-enduring common-pool resource institutions. In this study, we investigate whether graduated punishment can promote a higher cooperation level when each individual plays the public goods game and has the opportunity to punish others whose cooperation levels fall below the punisher’s threshold. We then examine how spatial structure affects evolutionary dynamics when each individual dies inversely proportional to the game score resulting from the social interaction and another player is randomly chosen from the population to produce offspring to fill the empty site created after a player’s death. Our evolutionary simulation outcomes demonstrate that stricter punishment promotes increased cooperation more than graduated punishment in a spatially structured population, whereas graduated punishment increases cooperation more than strict punishment when players interact with randomly chosen opponents from the population. The mathematical analysis also supports the results. PMID:23555826

  6. The clock in the cell : Entrainment of the circadian clock in Neurospora crassa

    NARCIS (Netherlands)

    Madeti Jyothi-Boesl, Cornelia

    2008-01-01

    Since reports of daily leaf movements 2000 years ago, a so-called circadian clock (‘circa diem’ meaning ‘about a day’) has been described in organisms from almost all phyla. The work presented in this thesis gives special emphasis on the circadian clock in the fungus Neurospora crassa, a rather

  7. Sumoylation controls CLOCK-BMAL1-mediated clock resetting via CBP recruitment in nuclear transcriptional foci.

    Science.gov (United States)

    Lee, Yool; Chun, Sung Kook; Kim, Kyungjin

    2015-10-01

    CLOCK-BMAL1 is a key transcription factor complex of the molecular clock system that generates circadian gene expression and physiology in mammals. Here, we demonstrate that sumoylation of BMAL1 mediates the rapid activation of CLOCK-BMAL1 by CREB-binding protein (CBP) in nuclear foci and also the resetting of the circadian clock. Under physiological conditions, a bimolecular fluorescence complementation-based fluorescence resonance energy transfer (BiFC-FRET) assay revealed that CLOCK-BMAL1 rapidly dimerized and formed a ternary complex with CBP in discrete nuclear foci in response to serum stimuli. We found that the formation of this ternary complex requires sumoylation of BMAL1 by SUMO3. These processes were abolished by both the ectopic expression of the SUMP2/3-specific protease, SUSP1, and mutation of the major sumoylation site (Lys259) of BMAL1. Moreover, molecular inhibition of BMAL1 sumoylation abrogated acute Per1 transcription and severely dampened the circadian gene oscillation triggered by clock synchronization stimuli. Taken together, these findings suggest that sumoylation plays a critical role in the spatiotemporal co-activation of CLOCK-BMAL1 by CBP for immediate-early Per induction and the resetting of the circadian clock. Copyright © 2015. Published by Elsevier B.V.

  8. Regulation of clock-controlled genes in mammals.

    Directory of Open Access Journals (Sweden)

    Katarzyna Bozek

    Full Text Available The complexity of tissue- and day time-specific regulation of thousands of clock-controlled genes (CCGs suggests that many regulatory mechanisms contribute to the transcriptional output of the circadian clock. We aim to predict these mechanisms using a large scale promoter analysis of CCGs.Our study is based on a meta-analysis of DNA-array data from rodent tissues. We searched in the promoter regions of 2065 CCGs for highly overrepresented transcription factor binding sites. In order to compensate the relatively high GC-content of CCG promoters, a novel background model to avoid a bias towards GC-rich motifs was employed. We found that many of the transcription factors with overrepresented binding sites in CCG promoters exhibit themselves circadian rhythms. Among the predicted factors are known regulators such as CLOCKratioBMAL1, DBP, HLF, E4BP4, CREB, RORalpha and the recently described regulators HSF1, STAT3, SP1 and HNF-4alpha. As additional promising candidates of circadian transcriptional regulators PAX-4, C/EBP, EVI-1, IRF, E2F, AP-1, HIF-1 and NF-Y were identified. Moreover, GC-rich motifs (SP1, EGR, ZF5, AP-2, WT1, NRF-1 and AT-rich motifs (MEF-2, HMGIY, HNF-1, OCT-1 are significantly overrepresented in promoter regions of CCGs. Putative tissue-specific binding sites such as HNF-3 for liver, NKX2.5 for heart or Myogenin for skeletal muscle were found. The regulation of the erythropoietin (Epo gene was analysed, which exhibits many binding sites for circadian regulators. We provide experimental evidence for its circadian regulated expression in the adult murine kidney. Basing on a comprehensive literature search we integrate our predictions into a regulatory network of core clock and clock-controlled genes. Our large scale analysis of the CCG promoters reveals the complexity and extensiveness of the circadian regulation in mammals. Results of this study point to connections of the circadian clock to other functional systems including

  9. A model of guarded recursion with clock synchronisation

    DEFF Research Database (Denmark)

    Bizjak, Aleš; Møgelberg, Rasmus Ejlers

    2015-01-01

    productivity to be captured in types. The calculus uses clocks representing time streams and clock quantifiers which allow limited and controlled elimination of modalities. The calculus has since been extended to dependent types by Møgelberg. Both works give denotational semantics but no rewrite semantics....... In previous versions of this calculus, different clocks represented separate time streams and clock synchronisation was prohibited. In this paper we show that allowing clock synchronisation is safe by constructing a new model of guarded recursion and clocks. This result will greatly simplify the type theory...

  10. Superconducting single flux quantum 20 Gb/s clock recovery circuit

    Energy Technology Data Exchange (ETDEWEB)

    Kaplunenko, V.; Borzenets, V.; Dubash, N. [Conductus, 969 West Sunnyvale, California 94086 (United States); Van Duzer, T. [University of California, Berkeley, California 94720 (United States)

    1997-07-01

    A clock recovery circuit has been successfully tested at frequencies up to 20 GHz. This cell is designed for a rapid-single-flux-quantum (RSFQ) telecommunication data switch. It serves to set the receiver clock in phase with the incoming digital signal. The circuit consists of a dc-to-SFQ converter, ring oscillator [(RO) is a closed-loop RSFQ Josephson transmission line], confluence buffer, and an 8-bit binary counter. The input signal transforms to SFQ pulses, and each pulse resets the phase of the ring oscillator, giving a locking time of 1 bit. Thus, the pull-in (capture) range and hold-in (tracking) range are the same, and strictly depend on the encoding of the input signal. This range is estimated to be about 1 GHz at frequency 20 GHz, if the sequence of consecutive ONEs or ZEROs does not exceed 20 bits. The quality factor Q{sub RO} of ring oscillator is about 2000, which gives a jitter of 50 fs for a 35-junction RO. A sampling technique was used to demonstrate phase recovery (phase locking) with only one incoming pulse per 512 clock periods. {copyright} {ital 1997 American Institute of Physics.}

  11. Clock-frequency and temperature margins of a high-temperature superconductor delay-line memory

    International Nuclear Information System (INIS)

    Hattori, W.; Tahara, S.

    1999-01-01

    We have developed a 10 GHz 32-bit delay-line memory, using a semiconductor crossbar switch and a YBa 2 Cu 3 O 7-δ coplanar delay line. For use in the high-speed (≥10 GHz) cell-buffer storage of large-throughput (≥1 Tbit/s) asynchronous transfer mode (ATM) switching systems, this memory must be fairly reliable. To evaluate the reliability of the operation, therefore, we measured the clock-frequency and temperature margins and the temperature dependence of the bit-error rate. At 64 K, this memory has a capacity of 32 bits with a clock frequency of 9.89±0.11 GHz. In general, clock frequencies of communication systems are strictly managed so that the margins are less than 10 -6 . Therefore, the frequency margin of this memory (∼2x10 -2 )) is wide enough for use in communication systems. The temperature margin was 71.5±4.3 K at 10 GHz and 33 bits. This memory offered error-free operation (BER -13 ) at 71.5 ±3.5 K. These temperature margins are wide enough to be controlled by a cryocooler. These results show that the memory offers reliability and that it can be applied to high-speed ATM cell-buffer storage. (author)

  12. DNA remodelling by Strict Partial Endoreplication in orchids, an original process in the plant kingdom.

    Science.gov (United States)

    Brown, Spencer C; Bourge, Mickaël; Maunoury, Nicolas; Wong, Maurice; Bianchi, Michele Wolfe; Lepers-Andrzejewski, Sandra; Besse, Pascale; Siljak-Yakovlev, Sonja; Dron, Michel; Satiat-Jeunemaître, Béatrice

    2017-04-13

    DNA remodelling during endoreplication appears to be a strong developmental characteristic in orchids. In this study, we analysed DNA content and nuclei in 41 species of orchids to further map the genome evolution in this plant family. We demonstrate that the DNA remodelling observed in 36 out of 41 orchids studied corresponds to strict partial endoreplication. Such process is developmentally regulated in each wild species studied. Cytometry data analyses allowed us to propose a model where nuclear states 2C, 4E, 8E, etc. form a series comprising a fixed proportion, the euploid genome 2C, plus 2 to 32 additional copies of a complementary part of the genome. The fixed proportion ranged from 89% of the genome in Vanilla mexicana down to 19% in V. pompona, the lowest value for all 148 orchids reported. Insterspecific hybridisation did not suppress this phenomenon. Interestingly, this process was not observed in mass-produced epiphytes. Nucleolar volumes grow with the number of endocopies present, coherent with high transcription activity in endoreplicated nuclei. Our analyses suggest species-specific chromatin rearrangement. Towards understanding endoreplication, V. planifolia constitutes a tractable system for isolating the genomic sequences that confer an advantage via endoreplication from those that apparently suffice at diploid level. © The Author(s) 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  13. Strict liability as a legal mechanism protecting the aggrieved parties' interests within the nuclear liability regime

    International Nuclear Information System (INIS)

    Novotna, Marianna

    2016-01-01

    The no-fault liability principle of nuclear liability regime, its compensation schemes, sociological and legal grounds of its construction as well as liberation grounds are analysed. The simple existence of causation of damage and nuclear accident without necessity of proving negligence or any other type of fault on the part of the operator as an adequate basis for the operator’s strict liability is highlighted thus simplifying the litigation process eliminating potential obstacles, especially such as might exist with the burden of proof. The question of weighing the interests of society in the development of nuclear industry, the necessary extent of protection of victims of nuclear accidents and the interests of operators of nuclear facilities as main determinants of the strict nature of nuclear liability is also described. (orig.)

  14. The Deep Space Atomic Clock Mission

    Science.gov (United States)

    Ely, Todd A.; Koch, Timothy; Kuang, Da; Lee, Karen; Murphy, David; Prestage, John; Tjoelker, Robert; Seubert, Jill

    2012-01-01

    The Deep Space Atomic Clock (DSAC) mission will demonstrate the space flight performance of a small, low-mass, high-stability mercury-ion atomic clock with long term stability and accuracy on par with that of the Deep Space Network. The timing stability introduced by DSAC allows for a 1-Way radiometric tracking paradigm for deep space navigation, with benefits including increased tracking via utilization of the DSN's Multiple Spacecraft Per Aperture (MSPA) capability and full ground station-spacecraft view periods, more accurate radio occultation signals, decreased single-frequency measurement noise, and the possibility for fully autonomous on-board navigation. Specific examples of navigation and radio science benefits to deep space missions are highlighted through simulations of Mars orbiter and Europa flyby missions. Additionally, this paper provides an overview of the mercury-ion trap technology behind DSAC, details of and options for the upcoming 2015/2016 space demonstration, and expected on-orbit clock performance.

  15. Sugars, the clock and transition to flowering

    Directory of Open Access Journals (Sweden)

    Mohammad Reza eBolouri Moghaddam

    2013-02-01

    Full Text Available Sugars do not only act as source of energy, but they also act as signals in plants. This mini review summarizes the emerging links between sucrose-mediated signaling and the cellular networks involved in flowering time control and defense. Cross-talks with gibberellin (GA and jasmonate (JA signaling pathways are highlighted. The circadian clock fulfills a crucial role at the heart of cellular networks and the bilateral relation between sugar signaling and the clock is discussed. It is proposed that important factors controlling plant growth (DELLAs, PIFs, invertases and trehalose- 6-phosphate or T6P might fulfill central roles in the transition to flowering as well. The emerging concept of ‘sweet immunity’, modulated by the clock, might at least partly rely on a sucrose-specific signaling pathway that needs further exploration.

  16. Sample-Clock Phase-Control Feedback

    Science.gov (United States)

    Quirk, Kevin J.; Gin, Jonathan W.; Nguyen, Danh H.; Nguyen, Huy

    2012-01-01

    To demodulate a communication signal, a receiver must recover and synchronize to the symbol timing of a received waveform. In a system that utilizes digital sampling, the fidelity of synchronization is limited by the time between the symbol boundary and closest sample time location. To reduce this error, one typically uses a sample clock in excess of the symbol rate in order to provide multiple samples per symbol, thereby lowering the error limit to a fraction of a symbol time. For systems with a large modulation bandwidth, the required sample clock rate is prohibitive due to current technological barriers and processing complexity. With precise control of the phase of the sample clock, one can sample the received signal at times arbitrarily close to the symbol boundary, thus obviating the need, from a synchronization perspective, for multiple samples per symbol. Sample-clock phase-control feedback was developed for use in the demodulation of an optical communication signal, where multi-GHz modulation bandwidths would require prohibitively large sample clock frequencies for rates in excess of the symbol rate. A custom mixedsignal (RF/digital) offset phase-locked loop circuit was developed to control the phase of the 6.4-GHz clock that samples the photon-counting detector output. The offset phase-locked loop is driven by a feedback mechanism that continuously corrects for variation in the symbol time due to motion between the transmitter and receiver as well as oscillator instability. This innovation will allow significant improvements in receiver throughput; for example, the throughput of a pulse-position modulation (PPM) with 16 slots can increase from 188 Mb/s to 1.5 Gb/s.

  17. Environmental regulation impacts on international trade: aggregate and sectoral analyses with a bilateral trade flow model

    NARCIS (Netherlands)

    van Beers, C.; van den Bergh, J.C.J.M.

    2003-01-01

    An important barrier to the implementation of strict environmental regulations is that they are perceived to negatively affect a country's competitiveness, visible through changes in international trade. Whereas theoretical analyses of trade and the environment indicate that relatively strict

  18. Association of circadian rhythm genes ARNTL/BMAL1 and CLOCK with multiple sclerosis.

    Science.gov (United States)

    Lavtar, Polona; Rudolf, Gorazd; Maver, Aleš; Hodžić, Alenka; Starčević Čizmarević, Nada; Živković, Maja; Šega Jazbec, Saša; Klemenc Ketiš, Zalika; Kapović, Miljenko; Dinčić, Evica; Raičević, Ranko; Sepčić, Juraj; Lovrečić, Luca; Stanković, Aleksandra; Ristić, Smiljana; Peterlin, Borut

    2018-01-01

    Prevalence of multiple sclerosis varies with geographic latitude. We hypothesized that this fact might be partially associated with the influence of latitude on circadian rhythm and consequently that genetic variability of key circadian rhythm regulators, ARNTL and CLOCK genes, might contribute to the risk for multiple sclerosis. Our aim was to analyse selected polymorphisms of ARNTL and CLOCK, and their association with multiple sclerosis. A total of 900 Caucasian patients and 1024 healthy controls were compared for genetic signature at 8 SNPs, 4 for each of both genes. We found a statistically significant difference in genotype (ARNTL rs3789327, P = 7.5·10-5; CLOCK rs6811520 P = 0.02) distributions in patients and controls. The ARNTL rs3789327 CC genotype was associated with higher risk for multiple sclerosis at an OR of 1.67 (95% CI 1.35-2.07, P = 0.0001) and the CLOCK rs6811520 genotype CC at an OR of 1.40 (95% CI 1.13-1.73, P = 0.002). The results of this study suggest that genetic variability in the ARNTL and CLOCK genes might be associated with risk for multiple sclerosis.

  19. Precise Receiver Clock Offset Estimations According to Each Global Navigation Satellite Systems (GNSS) Timescales

    Science.gov (United States)

    Thongtan, Thayathip; Tirawanichakul, Pawit; Satirapod, Chalermchon

    2017-12-01

    Each GNSS constellation operates its own system times; namely, GPS system time (GPST), GLONASS system time (GLONASST), BeiDou system time (BDT) and Galileo system time (GST). They could be traced back to Coordinated Universal Time (UTC) scale and are aligned to GPST. This paper estimates the receiver clock offsets to three timescales: GPST, GLONASST and BDT. The two measurement scenarios use two identical multi-GNSS geodetic receivers connected to the same geodetic antenna through a splitter. One receiver is driven by its internal oscillators and another receiver is connected to the external frequency oscillators, caesium frequency standard, kept as the Thailand standard time scale at the National Institute of Metrology (Thailand) called UTC(NIMT). The three weeks data are observed at 30 seconds sample rate. The receiver clock offsets with respected to the three system time are estimated and analysed through the geodetic technique of static Precise Point Positioning (PPP) using a data processing software developed by Wuhan University - Positioning And Navigation Data Analyst (PANDA) software. The estimated receiver clock offsets are around 32, 33 and 18 nanoseconds from GPST, GLONASST and BDT respectively. This experiment is initially stated that each timescale is inter-operated with GPST and further measurements on receiver internal delay has to be determined for clock comparisons especially the high accuracy clock at timing laboratories.

  20. The Success Rate of Initial {sup 131I} Ablation in Differentiated Thyroid Cancer: Comparison Between Less strict and Very Strict Low Iodine Diets

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Ik Dong; Kim, Sung Hoon; Seo, Ye Young; Oh, Jin Kyoung; O, Joo Hyun; Chung, Soo Kyo [The Catholic Univ. of Korea, Seoul (Korea, Republic of)

    2012-03-15

    To decrease the risk of recurrence or metastasis in differentiated thyroid cancer (DTC), selected patients receive radioactive iodine ablation of remnant thyroid tissue or tumor. A low iodine diet can enhance uptake of radioactive iodine. We compared the success rates of radioactive iodine ablation therapy in patients who followed two different low iodine diets (LIDs). The success rates of postsurgical radioactive iodine ablation in DTC patients receiving empiric doses of 150 mCi were retrospectively reviewed. First-time radioactive iodine ablation therapy was done in 71 patients following less strict LID. Less strict LID restricted seafood, iodized salt, egg yolk, dairy products, processed meat, instant prepared meals, and multivitamins. Very strict LID additionally restricted rice, freshwater fish, spinach, and soybean products. Radioactive iodine ablation therapy was considered successful when follow up {sup 123I} whole body scan was negative and stimulated serum thyroglobulin level was less than 2.0 ng/mL. The success rate of patients following less strict LID was 80.3% and for very strict LID 75.6%. There was no statistically significant difference in the success rates between the two LID groups (P=0.48). Very strict LID may not contribute to improving the success rate of initial radioactive iodine ablation therapy at the cost of great inconvenience to the patient.

  1. Clock frequency estimation under spontaneous emission

    Science.gov (United States)

    Qin, Xi-Zhou; Huang, Jia-Hao; Zhong, Hong-Hua; Lee, Chaohong

    2018-02-01

    We investigate the quantum dynamics of a driven two-level system under spontaneous emission and its application in clock frequency estimation. By using the Lindblad equation to describe the system, we analytically obtain its exact solutions, which show three different regimes: Rabi oscillation, damped oscillation, and overdamped decay. From the analytical solutions, we explore how the spontaneous emission affects the clock frequency estimation. We find that under a moderate spontaneous emission rate, the transition frequency can still be inferred from the Rabi oscillation. Our results enable potential practical applications in frequency measurement and quantum control under decoherence.

  2. Hourly Updated GNSS Orbit and Clock

    Science.gov (United States)

    Song, S.; Xue, J.

    2016-12-01

    With the development of the performance of GNSS, the hourly updated orbit and clock of GNSS are paid much more attention and used by more and more users because of the timeliness and high accuracy. The hourly GNSS orbit and clock are produced routinely in Shanghai Analysis Center(AC) of the International GNSS Monitoring and Assessment Service (iGMAS).In this article, the accuracy of hourly and 6-hourly updated ultra-rapid GPS,GLONASS,GALILEO,BDS orbit and clock (SHU1 and SHU6) are analyzed relative to the final production in detail. The analysis show that, in calculation session, there's no much difference between the mean SHU1 and SHU6 RMS and STD for GNSS orbit and clock. However, for BDS clock in prediction session, the RMS and STD of BDS SHU1 are 2.6ns and 0.5ns respectively, the RMS of BDS SHU6 increase from 2.7ns to 4.5ns from the 1st to the 6th hour prediction session, but there's no much changes of STD. For GPS clock in prediction session, the RMS and STD of GPS SHU1 is quite stable with 0.5ns and 0.2ns.The RMS of GPS SHU6 clock increase from 0.6ns to 1.0ns from the 1st to the 6th hour, but STD is stable at about 0.2ns.For the orbit in calculate session, the RMS of BDS SHU1 is a little less than that of SHU6,the RMS of GPS SHU1 and SHU6 orbit are approximately at the same level. In prediction session, the RMS of IGSO/MEO for BDS SHU1 is relative stable, but the RMS of SHU6 1st-6th hour prediction session increase from about 26.5cm to 32.7cm. The RMS of GPS SHU1 orbit's prediction session is about 3.4cm,but which increase from 3.3cm to 4.3cm for GPS SHU6 1st-6th hour prediction session.The comparison of GLONASS and GALILEO orbit and clock also will be described.The results show that the hourly update is more important for BDS at this stage.Moreover,some problems appearing in satellites and stations can be found earlier by 1 hourly updated frequency.

  3. Clocking Scheme for Switched-Capacitor Circuits

    DEFF Research Database (Denmark)

    Steensgaard-Madsen, Jesper

    1998-01-01

    A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed.......A novel clocking scheme for switched-capacitor (SC) circuits is presented. It can enhance the understanding of SC circuits and the errors caused by MOSFET (MOS) switches. Charge errors, and techniques to make SC circuits less sensitive to them are discussed....

  4. Susceptibility of Redundant Versus Singular Clock Domains Implemented in SRAM-Based FPGA TMR Designs

    Science.gov (United States)

    Berg, Melanie D.; LaBel, Kenneth A.; Pellish, Jonathan

    2016-01-01

    We present the challenges that arise when using redundant clock domains due to their clock-skew. Radiation data show that a singular clock domain (DTMR) provides an improved TMR methodology for SRAM-based FPGAs over redundant clocks.

  5. The clock in the cell: Entrainment of the circadian clock in Neurospora crassa

    OpenAIRE

    Madeti Jyothi-Boesl, Cornelia

    2008-01-01

    Since reports of daily leaf movements 2000 years ago, a so-called circadian clock (‘circa diem’ meaning ‘about a day’) has been described in organisms from almost all phyla. The work presented in this thesis gives special emphasis on the circadian clock in the fungus Neurospora crassa, a rather simple cellular system. Neurospora was used to elucidate basic clock mechanisms are that are comparable to those in more complex organisms. To that end, we investigated chronoecological questions as we...

  6. Pulsed optically pumped atomic clock with zero-dead-time

    Science.gov (United States)

    Lin, Haixiao; Lin, Jinda; Deng, Jianliao; Zhang, Song; Wang, Yuzhu

    2017-12-01

    By alternatively operating two pulsed optically pumped (POP) atomic clocks, the dead time in a single clock can be eliminated, and the local oscillator can be discriminated continuously. A POP atomic clock with a zero-dead-time (ZDT) method is then insensitive to the microwave phase noise. From τ = 0.01 to 1 s, the Allan deviation of the ZDT-POP clock is reduced as nearly τ-1, which is significantly faster than τ-1/2 of a conventional clock. During 1-40 s, the Allan deviation returns to τ-1/2. Moreover, the frequency stability of the ZDT-POP clock is improved by one order of magnitude compared with that of the conventional POP clock. We also analyze the main factors that limit the short-term frequency stability of the POP atomic clock.

  7. Novel transcriptional networks regulated by CLOCK in human neurons.

    Science.gov (United States)

    Fontenot, Miles R; Berto, Stefano; Liu, Yuxiang; Werthmann, Gordon; Douglas, Connor; Usui, Noriyoshi; Gleason, Kelly; Tamminga, Carol A; Takahashi, Joseph S; Konopka, Genevieve

    2017-11-01

    The molecular mechanisms underlying human brain evolution are not fully understood; however, previous work suggested that expression of the transcription factor CLOCK in the human cortex might be relevant to human cognition and disease. In this study, we investigated this novel transcriptional role for CLOCK in human neurons by performing chromatin immunoprecipitation sequencing for endogenous CLOCK in adult neocortices and RNA sequencing following CLOCK knockdown in differentiated human neurons in vitro. These data suggested that CLOCK regulates the expression of genes involved in neuronal migration, and a functional assay showed that CLOCK knockdown increased neuronal migratory distance. Furthermore, dysregulation of CLOCK disrupts coexpressed networks of genes implicated in neuropsychiatric disorders, and the expression of these networks is driven by hub genes with human-specific patterns of expression. These data support a role for CLOCK-regulated transcriptional cascades involved in human brain evolution and function. © 2017 Fontenot et al.; Published by Cold Spring Harbor Laboratory Press.

  8. Clock Synchronization for Multi-hop Ad hoc Networks

    OpenAIRE

    O'Connor, Neil

    2003-01-01

    Clock syncronization is one of the basic requirements of a distributed real-time systems. The greater the precision achievable by the clock synchronization algorithm used, the harder the real-time guarantees that can be given by the system. Numerous clock synchronization algoritms for wired networks have been proposed, which provide varying degrees of precision. Wireless networks provide a number of challenges which clock synchronization algorithms for wired networks do not address satisf...

  9. 47 CFR 80.865 - Radiotelephone station clock.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Radiotelephone station clock. 80.865 Section 80.865 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES... W § 80.865 Radiotelephone station clock. A clock having a face of at least 12.7 cm (5 in.) in...

  10. A practical clock synchronization algorithm for UWB positioning systems

    NARCIS (Netherlands)

    Xie, Y.; Janssen, G.J.M.; van der Veen, A.J.; Dong, Min; Zheng, Thomas Fang

    2016-01-01

    A clock synchronization scheme is crucial for obtaining accuracy in time-based positioning systems. Existing clock synchronization schemes are mostly based on a simplified linear clock model, which unfortunately have a poor long-term synchronization accuracy. Assuming a two-way time transfer

  11. On synchronization of clocks in general space-times

    Directory of Open Access Journals (Sweden)

    M. R. H Khajehpour

    2005-09-01

    Full Text Available   Einstein and transport synchronizations of infinitesimally spaced and distant clocks are considered in a general Riemannian space-time. It is shown that infinitesimally spaced clocks can always be synchronized. In general one can not find observers for whom distant clock are Einstein synchronized but transport synchronized observers do always exit. Whenever both procedures are possible, they are equivalent.

  12. Tick Tock, a Vitamin C Clock.

    Science.gov (United States)

    Wright, Stephen W.

    2002-01-01

    Presents an activity that uses supermarket chemicals to perform a clock reaction in which the endpoint is signaled by an abrupt change in the appearance from colorless to blue-black. This activity can be used to explore reaction kinetics and the effect of reactant concentrations on the apparent rate of reaction. (DDR)

  13. Central and peripheral clocks in ontogeny

    Czech Academy of Sciences Publication Activity Database

    Sumová, Alena; Bendová, Zdeňka; Sládek, Martin; El-Hennamy, Rehab; Laurinová, Kristýna; Jindráková, Zuzana; Illnerová, Helena

    2006-01-01

    Roč. 273, č. S1 (2006), s. 6-6 ISSN 1742-464X. [FEBS Congress /31./. 24.06.2006-29.06.2006, Istanbul] Institutional research plan: CEZ:AV0Z50110509 Keywords : circadian clock * peripheral tissue * ontogeny Subject RIV: FH - Neurology

  14. The Clocks Are Ticking: No More Delays!

    DEFF Research Database (Denmark)

    Bahr, Patrick; Grathwohl, Hans Bugge; Møgelberg, Rasmus Ejlers

    2017-01-01

    these applications can be carried out and machine-checked. In this paper, we take a step towards this goal by devising a suitable reduction semantics. We present Clocked Type Theory, a new type theory for guarded recursion that is more suitable for reduction semantics than the existing ones. We prove confluence...

  15. Food at work around the clock

    DEFF Research Database (Denmark)

    Dahl Lassen, Anne; Beck, Anne Marie; Thorsen, Anne Vibeke

    This report brings together 12 invited presentations and outcomes of a workshop on food and meals for employees working irregular hours “around the clock”. The workshop, “Food at work around the clock – The Nordic Model”, was hosted by the National Food Institute at the Technical University...

  16. The mammalian retina as a clock

    Science.gov (United States)

    Tosini, Gianluca; Fukuhara, Chiaki

    2002-01-01

    Many physiological, cellular, and biochemical parameters in the retina of vertebrates show daily rhythms that, in many cases, also persist under constant conditions. This demonstrates that they are driven by a circadian pacemaker. The presence of an autonomous circadian clock in the retina of vertebrates was first demonstrated in Xenopus laevis and then, several years later, in mammals. In X. laevis and in chicken, the retinal circadian pacemaker has been localized in the photoreceptor layer, whereas in mammals, such information is not yet available. Recent advances in molecular techniques have led to the identification of a group of genes that are believed to constitute the molecular core of the circadian clock. These genes are expressed in the retina, although with a slightly different 24-h profile from that observed in the central circadian pacemaker. This result suggests that some difference (at the molecular level) may exist between the retinal clock and the clock located in the suprachiasmatic nuclei of hypothalamus. The present review will focus on the current knowledge of the retinal rhythmicity and the mechanisms responsible for its control.

  17. Brain clocks for morning and evening behaviour

    Indian Academy of Sciences (India)

    Unknown

    Different subgroups of cells that regu- late the morning and evening components of activity are ... tion of time from circadian pacemaker to target organs? At least two decades ago, a model of circadian clocks .... type behaviour (with robust morning and evening bouts of activity) by expressing UAS-per in the CRY+ cells.

  18. Clock Synchronization for Multihop Wireless Sensor Networks

    Science.gov (United States)

    Solis Robles, Roberto

    2009-01-01

    In wireless sensor networks, more so generally than in other types of distributed systems, clock synchronization is crucial since by having this service available, several applications such as media access protocols, object tracking, or data fusion, would improve their performance. In this dissertation, we propose a set of algorithms to achieve…

  19. The skeletal muscle circadian clock: current insights

    Directory of Open Access Journals (Sweden)

    Nakao R

    2017-11-01

    Full Text Available Reiko Nakao,1 Takeshi Nikawa,2 Katsutaka Oishi1,3,4 1Biological Clock Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST, Tsukuba, 2Department of Nutritional Physiology, Institute of Biomedical Sciences, Tokushima University Graduate School, Tokushima, 3Department of Applied Biological Science, Graduate School of Science and Technology, Tokyo University of Science, Noda, 4Department of Computational and Medical Sciences, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa, Japan Abstract: Skeletal muscle functions in locomotion, postural support, and energy metabolism. The loss of skeletal muscle mass and function leads to diseases such as sarcopenia and metabolic disorders. Inactivity (lack of exercise and an imbalanced diet (increased fat or decreased protein intake are thought to be involved in the prevalence of such pathologies. On the other hand, recent epidemiological studies of humans have suggested that circadian disruption caused by shift work, jet lag, and sleep disorders is associated with obesity and metabolic syndrome. Experimental studies of mice deficient in clock genes have also identified skeletal muscle defects, suggesting a molecular link between circadian clock machinery and skeletal muscle physiology. Furthermore, accumulating evidence about chronotherapy, including chronopharmacology, chrononutrition, and chronoexercise, has indicated that timing is important to optimize medical intervention for various diseases. The present review addresses current understanding of the functional roles of the molecular clock with respect to skeletal muscle and the potential of chronotherapy for diseases associated with skeletal muscle. Keywords: biological rhythm, metabolic syndrome, physical activity, neural signal, chronotherapy

  20. Analytic clock frequency selection for global DVFS

    NARCIS (Netherlands)

    Gerards, Marco Egbertus Theodorus; Hurink, Johann L.; Holzenspies, P.K.F.; Kuper, Jan; Smit, Gerardus Johannes Maria

    2014-01-01

    Computers can reduce their power consumption by decreasing their speed using Dynamic Voltage and Frequency Scaling (DVFS). A form of DVFS for multicore processors is global DVFS, where the voltage and clock frequency is shared among all processor cores. Because global DVFS is efficient and cheap to

  1. Strict versus liberal target range for perioperative glucose in patients undergoing coronary artery bypass grafting: a prospective randomized controlled trial.

    Science.gov (United States)

    Desai, Shalin P; Henry, Linda L; Holmes, Sari D; Hunt, Sharon L; Martin, Chidima T; Hebsur, Shrinivas; Ad, Niv

    2012-02-01

    The purpose of this study was to test the hypothesis that a liberal blood glucose strategy (121-180 mg/dL) is not inferior to a strict blood glucose strategy (90-120 mg/dL) for outcomes in patients after first-time isolated coronary artery bypass grafting and is superior for glucose control and target blood glucose management. A total of 189 patients undergoing coronary artery bypass grafting were investigated in this prospective randomized study to compare 2 glucose control strategies on patient perioperative outcomes. Three methods of analyses (intention to treat, completer, and per protocol) were conducted. Observed power was robust (>80%) for significant results. The groups were similar on preoperative hemoglobin A(1c) and number of diabetic patients. The liberal group was found to be noninferior to the strict group for perioperative complications and superior on glucose control and target range management. The liberal group had significantly fewer patients with hypoglycemic events (liberal range after coronary artery bypass grafting led to similar outcomes compared with a strict target range and was superior in glucose control and target range management. On the basis of the results of this study, a target blood glucose range of 121 to 180 mg/dL is recommended for patients after coronary artery bypass grafting as advocated by the Society of Thoracic Surgeons. Copyright © 2012 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

  2. Clock measurements to improve the geopotential determination

    Science.gov (United States)

    Lion, Guillaume; Panet, Isabelle; Delva, Pacôme; Wolf, Peter; Bize, Sébastien; Guerlin, Christine

    2017-04-01

    Comparisons between optical clocks with an accuracy and stability approaching the 10-18 in term of relative frequency shift are opening new perspectives for the direct determination of geopotential at a centimeter-level accuracy in geoid height. However, so far detailed quantitative estimates of the possible improvement in geoid determination when adding such clock measurements to existing data are lacking. In this context, the present work aims at evaluating the contribution of this new kind of direct measurements in determining the geopotential at high spatial resolution (10 km). We consider the Massif Central area, marked by smooth, moderate altitude mountains and volcanic plateaus leading to variations of the gravitational field over a range of spatial scales. In such type of region, the scarcity of gravity data is an important limitation in deriving accurate high resolution geopotential models. We summarize our methodology to assess the contribution of clock data in the geopotential recovery, in combination with ground gravity measurements. We sample synthetic gravity and disturbing potential data from a spherical harmonics geopotential model, and a topography model, up to 10 km resolution; we also build a potential control grid. From the synthetic data, we estimate the disturbing potential by least-squares collocation. Finally, we assess the quality of the reconstructed potential by comparing it to that of the control grid. We show that adding only a few clock data reduces the reconstruction bias significantly and improves the standard deviation by a factor 3. We discuss the role of different parameters, such as the effect of the data coverage and data quality on these results, the trade-off between the measurement noise level and the number of data, and the optimization of the clock data network.

  3. Pineal clock gene oscillation is disturbed in Alzheimer's disease, due to functional disconnection from the "master clock".

    NARCIS (Netherlands)

    Wu, Y.-H.; Fischer, D.F.; Kalsbeek, A.; Garidou-Boof, M.-L.; Vliet, J. van der; Heijningen, C. van; Liu, R.-Y.; Zhou, J.-N.; Swaab, D.F.

    2006-01-01

    The suprachiasmatic nucleus (SCN) is the "master clock" of the mammalian brain. It coordinates the peripheral clocks in the body, including the pineal clock that receives SCN input via a multisynaptic noradrenergic pathway. Rhythmic pineal melatonin production is disrupted in Alzheimer's disease

  4. Pineal clock gene oscillation is disturbed in Alzheimer's disease, due to functional disconnection from the "master clock"

    NARCIS (Netherlands)

    Wu, Ying-Hui; Fischer, David F.; Kalsbeek, Andries; Garidou-Boof, Marie-Laure; van der Vliet, Jan; van Heijningen, Caroline; Liu, Rong-Yu; Zhou, Jiang-Ning; Swaab, Dick F.

    2006-01-01

    The suprachiasmatic nucleus (SCN) is the "master clock" of the mammalian brain. It coordinates the peripheral clocks in the body, including the pineal clock that receives SCN input via a multisynaptic noradrenergic pathway. Rhythmic pineal melatonin production is disrupted in Alzheimer's disease

  5. Validation of an automatic diagnosis of strict left bundle branch block criteria using 12-lead electrocardiograms

    DEFF Research Database (Denmark)

    Xia, Xiaojuan; Ruwald, Anne-Christine; Ruwald, Martin H

    2017-01-01

    AIMS: Strict left bundle branch block (LBBB) criteria were recently proposed to identify LBBB patients to benefit most from cardiac resynchronization therapy (CRT). The aim of our study was to automate identification of strict LBBB in order to facilitate its broader application. METHODS: We devel...

  6. 7 CFR 28.416 - Strict Good Ordinary Light Spotted Color.

    Science.gov (United States)

    2010-01-01

    ... CONTAINER REGULATIONS COTTON CLASSING, TESTING, AND STANDARDS Standards Light Spotted Cotton § 28.416 Strict Good Ordinary Light Spotted Color. Strict Good Ordinary Light Spotted Color is color which in spot or... Cotton Source: 57 FR 34498, Aug. 5, 1992, unless otherwise noted. ...

  7. Expression of circadian clock genes and proteins in urothelial cancer is related to cancer-associated genes

    International Nuclear Information System (INIS)

    Litlekalsoy, Jorunn; Rostad, Kari; Kalland, Karl-Henning; Hostmark, Jens G.; Laerum, Ole Didrik

    2016-01-01

    The purpose of this study was to evaluate invasive and metastatic potential of urothelial cancer by investigating differential expression of various clock genes/proteins participating in the 24 h circadian rhythms and to compare these gene expressions with transcription of other cancer-associated genes. Twenty seven paired samples of tumour and benign tissue collected from patients who underwent cystectomy were analysed and compared to 15 samples of normal bladder tissue taken from patients who underwent cystoscopy for benign prostate hyperplasia (unrelated donors). Immunohistochemical analyses were made for clock and clock-related proteins. In addition, the gene-expression levels of 22 genes (clock genes, casein kinases, oncogenes, tumour suppressor genes and cytokeratins) were analysed by real-time quantitative PCR (qPCR). Considerable up- or down-regulation and altered cellular distribution of different clock proteins, a reduction of casein kinase1A1 (CSNK1A1) and increase of casein kinase alpha 1 E (CSNK1E) were found. The pattern was significantly correlated with simultaneous up-regulation of stimulatory tumour markers, and a down-regulation of several suppressor genes. The pattern was mainly seen in aneuploid high-grade cancers. Considerable alterations were also found in the neighbouring bladder mucosa. The close correlation between altered expression of various clock genes and common tumour markers in urothelial cancer indicates that disturbed function in the cellular clock work may be an important additional mechanism contributing to cancer progression and malignant behaviour. The online version of this article (doi:10.1186/s12885-016-2580-y) contains supplementary material, which is available to authorized users

  8. Circadian CLOCK gene polymorphisms in relation to sleep patterns and obesity in African Americans: findings from the Jackson heart study.

    Science.gov (United States)

    Riestra, Pia; Gebreab, Samson Y; Xu, Ruihua; Khan, Rumana J; Gaye, Amadou; Correa, Adolfo; Min, Nancy; Sims, Mario; Davis, Sharon K

    2017-06-23

    Circadian rhythms regulate key biological processes and the dysregulation of the intrinsic clock mechanism affects sleep patterns and obesity onset. The CLOCK (circadian locomotor output cycles protein kaput) gene encodes a core transcription factor of the molecular circadian clock influencing diverse metabolic pathways, including glucose and lipid homeostasis. The primary objective of this study was to evaluate the associations between CLOCK single nucleotide polymorphisms (SNPs) and body mass index (BMI). We also evaluated the association of SNPs with BMI related factors such as sleep duration and quality, adiponectin and leptin, in 2962 participants (1116 men and 1810 women) from the Jackson Heart Study. Genotype data for the selected 23 CLOCK gene SNPS was obtained by imputation with IMPUTE2 software and reference phase data from the 1000 genome project. Genetic analyses were conducted with PLINK RESULTS: We found a significant association between the CLOCK SNP rs2070062 and sleep duration, participants carriers of the T allele showed significantly shorter sleep duration compared to non-carriers after the adjustment for individual proportions of European ancestry (PEA), socio economic status (SES), body mass index (BMI), alcohol consumption and smoking status that reach the significance threshold after multiple testing correction. In addition, we found nominal associations of the CLOCK SNP rs6853192 with longer sleep duration and the rs6820823, rs3792603 and rs11726609 with BMI. However, these associations did not reach the significance threshold after correction for multiple testing. In this work, CLOCK gene variants were associated with sleep duration and BMI suggesting that the effects of these polymorphisms on circadian rhythmicity may affect sleep duration and body weight regulation in Africans Americans.

  9. Does exercise training impact clock genes in patients with coronary artery disease and type 2 diabetes mellitus?

    Science.gov (United States)

    Steidle-Kloc, Eva; Schönfelder, Martin; Müller, Edith; Sixt, Sebastian; Schuler, Gerhard; Patsch, Wolfgang; Niebauer, Josef

    2016-09-01

    Recent findings revealed negative effects of deregulated molecular circadian rhythm in coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM). Physical exercise training (ET) has been shown to promote anti-diabetic and anti-atherogenic responses in skeletal muscle of these patients, but the role of the circadian clock-machinery remains unknown. This study investigated whether mRNA expression of clock genes in skeletal muscle of CAD and T2DM patients is influenced by physical ET intervention. Nineteen patients with CAD and T2DM (age 64 ± 5 years) were randomised to either six months of ET (four weeks of in-hospital ET followed by a five-month ambulatory programme) or usual care. At the beginning of the study, after four weeks and after six months parameters of metabolic and cardiovascular risk factors, and physical exercise capacity were assessed. Gene expression was measured in skeletal muscle biopsies by quantitative real-time polymerase chain reaction (PCR). A selection of clock genes and associated components (circadian locomoter output cycle kaput protein (CLOCK), period (PER) 1, cryptochrome (CRY) 2 and aminolevulinate-deltA-synthase-1 (ALAS1)) was reliably measured and used for further analysis. A time-dependent effect in gene expression was observed in CLOCK (p = 0.013) and a significant interaction between time and intervention was observed for ALAS1 (p = 0.032; p = 0.014) as a result of ET. This is the first study to analyse clock gene expression in skeletal muscles of patients with CAD and T2DM participating in a long-lasting exercise intervention. ET, as one of the cornerstones in prevention and rehabilitation of CAD and T2DM, exerts no effects on CLOCK genes but meaningful effects on the clock-associated gene ALAS1. © The European Society of Cardiology 2016.

  10. Metabolism and the Circadian Clock Converge

    Science.gov (United States)

    Eckel-Mahan, Kristin

    2013-01-01

    Circadian rhythms occur in almost all species and control vital aspects of our physiology, from sleeping and waking to neurotransmitter secretion and cellular metabolism. Epidemiological studies from recent decades have supported a unique role for circadian rhythm in metabolism. As evidenced by individuals working night or rotating shifts, but also by rodent models of circadian arrhythmia, disruption of the circadian cycle is strongly associated with metabolic imbalance. Some genetically engineered mouse models of circadian rhythmicity are obese and show hallmark signs of the metabolic syndrome. Whether these phenotypes are due to the loss of distinct circadian clock genes within a specific tissue versus the disruption of rhythmic physiological activities (such as eating and sleeping) remains a cynosure within the fields of chronobiology and metabolism. Becoming more apparent is that from metabolites to transcription factors, the circadian clock interfaces with metabolism in numerous ways that are essential for maintaining metabolic homeostasis. PMID:23303907

  11. Supporting Family Awareness with the Whereabouts Clock

    Science.gov (United States)

    Sellen, Abigail; Taylor, Alex S.; Kaye, Joseph ‘Jofish'; Brown, Barry; Izadi, Shahram

    We report the results of a field trial of a situated awareness device for families called the “Whereabouts Clock”. The Clock displays the location of family members using cellphone data as one of four privacy-preserving, deliberately coarse-grained categories ( HOME, WORK, SCHOOL or ELSEWHERE). The results show that awareness of others through the Clock supports not only family communication and coordination but also more emotive aspects of family life such as reassurance, connectedness, identity and social touch. We discuss how the term “awareness” means many things in practice and highlight the importance of designing not just for family activities, but in order to support the emotional, social and even moral aspects of family life.

  12. The Large Built Water Clock Of Amphiaraeion.

    Science.gov (United States)

    Theodossiou, E.; Katsiotis, M.; Manimanis, V. N.; Mantarakis, P.

    A very well preserved ancient water clock was discovered during excavations at the Amphiaraeion, in Oropos, Greece. The Amphiaraeion, a famous religious and oracle center of the deified healer Amphiaraus, was active from the pre-classic period until the replacement of the ancient religion by Christianity in the 5th Century A.D.. The foretelling was supposedly done through dreams sent by the god to the believers sleeping in a special gallery. In these dreams the god suggesting to them the therapy for their illness or the solution to their problems. The patients, then threw coins into a spring of the sanctuary. In such a place, the measurement of time was a necessity. Therefore, time was kept with both a conical sundial and a water clock in the form of a fountain. According to archeologists, the large built structure that measured the time for the sanctuary dates from the 4th Century B.C.

  13. Synchronization control of cross-strict feedback hyperchaotic system based on cross active backstepping design

    International Nuclear Information System (INIS)

    Wang Jing; Gao Jinfeng; Ma Xikui

    2007-01-01

    This Letter presents a novel cross active backstepping design method for synchronization control of cross-strict feedback hyperchaotic system, in which the ordinary backstepping design is unavailable. The proposed control method, combining backstepping design and active control approach, extends the application of backstepping technique in chaos control. Based on this method, different combinations of controllers can be designed to meet the needs of different applications. The proposed method is applied to achieve chaos synchronization of two identical cross-strict feedback hyperchaotic systems. Also it is used to implement synchronization between cross-strict feedback hyperchaotic system and Roessler hyperchaotic system. Numerical examples illustrate the validity of the control method

  14. Circadian molecular clocks tick along ontogenesis

    Czech Academy of Sciences Publication Activity Database

    Sumová, Alena; Bendová, Zdeňka; Sládek, Martin; El-Hennamy, Rehab; Matějů, Kristýna; Polidarová, Lenka; Sosniyenko, Serhiy; Illnerová, Helena

    2008-01-01

    Roč. 57, Suppl.3 (2008), S139-S148 ISSN 0862-8408 R&D Projects: GA ČR GA309/08/0503; GA AV ČR(CZ) IAA500110605; GA MŠk(CZ) LC554 Grant - others:EC(XE) LSH-2004-115-4-018741 Institutional research plan: CEZ:AV0Z50110509 Keywords : circadian clock * ontogenesis * suprachiasmatic nucleus Subject RIV: FH - Neurology Impact factor: 1.653, year: 2008

  15. Effects of mass defect in atomic clocks

    Science.gov (United States)

    Taichenachev, A. V.; Yudin, V. I.

    2018-01-01

    We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (such as gravitational and quadratic Doppler shifts) can be interpreted as consequences of the mass defect, i.e., without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions..

  16. The circadian clock, reward and memory

    Directory of Open Access Journals (Sweden)

    Urs eAlbrecht

    2011-11-01

    Full Text Available During our daily activities, we experience variations in our cognitive performance, which is often accompanied by cravings for small rewards, such as consuming coffee or chocolate. This indicates that the time of day, cognitive performance and reward may be related to one another. This review will summarize data that describes the influence of the circadian clock on addiction and mood-related behavior and put the data into perspective in relation to memory processes.

  17. Molecular clock in neutral protein evolution

    Directory of Open Access Journals (Sweden)

    Wilke Claus O

    2004-08-01

    Full Text Available Abstract Background A frequent observation in molecular evolution is that amino-acid substitution rates show an index of dispersion (that is, ratio of variance to mean substantially larger than one. This observation has been termed the overdispersed molecular clock. On the basis of in silico protein-evolution experiments, Bastolla and coworkers recently proposed an explanation for this observation: Proteins drift in neutral space, and can temporarily get trapped in regions of substantially reduced neutrality. In these regions, substitution rates are suppressed, which results in an overall substitution process that is not Poissonian. However, the simulation method of Bastolla et al. is representative only for cases in which the product of mutation rate μ and population size Ne is small. How the substitution process behaves when μNe is large is not known. Results Here, I study the behavior of the molecular clock in in silico protein evolution as a function of mutation rate and population size. I find that the index of dispersion decays with increasing μNe, and approaches 1 for large μNe . This observation can be explained with the selective pressure for mutational robustness, which is effective when μNe is large. This pressure keeps the population out of low-neutrality traps, and thus steadies the ticking of the molecular clock. Conclusions The molecular clock in neutral protein evolution can fall into two distinct regimes, a strongly overdispersed one for small μNe, and a mostly Poissonian one for large μNe. The former is relevant for the majority of organisms in the plant and animal kingdom, and the latter may be relevant for RNA viruses.

  18. Early evolution of the land plant circadian clock.

    Science.gov (United States)

    Linde, Anna-Malin; Eklund, D Magnus; Kubota, Akane; Pederson, Eric R A; Holm, Karl; Gyllenstrand, Niclas; Nishihama, Ryuichi; Cronberg, Nils; Muranaka, Tomoaki; Oyama, Tokitaka; Kohchi, Takayuki; Lagercrantz, Ulf

    2017-10-01

    While angiosperm clocks can be described as an intricate network of interlocked transcriptional feedback loops, clocks of green algae have been modelled as a loop of only two genes. To investigate the transition from a simple clock in algae to a complex one in angiosperms, we performed an inventory of circadian clock genes in bryophytes and charophytes. Additionally, we performed functional characterization of putative core clock genes in the liverwort Marchantia polymorpha and the hornwort Anthoceros agrestis. Phylogenetic construction was combined with studies of spatiotemporal expression patterns and analysis of M. polymorpha clock gene mutants. Homologues to core clock genes identified in Arabidopsis were found not only in bryophytes but also in charophytes, albeit in fewer copies. Circadian rhythms were detected for most identified genes in M. polymorpha and A. agrestis, and mutant analysis supports a role for putative clock genes in M. polymorpha. Our data are in line with a recent hypothesis that adaptation to terrestrial life occurred earlier than previously expected in the evolutionary history of charophyte algae. Both gene duplication and acquisition of new genes was important in the evolution of the plant circadian clock, but gene loss has also contributed to shaping the clock of bryophytes. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

  19. The hepatic circadian clock modulates xenobiotic metabolism in mice.

    Science.gov (United States)

    DeBruyne, Jason P; Weaver, David R; Dallmann, Robert

    2014-08-01

    The circadian clock generates daily cycles of gene expression that regulate physiological processes. The liver plays an important role in xenobiotic metabolism and also has been shown to possess its own cell-based clock. The liver clock is synchronized by the master clock in the brain, and a portion of rhythmic gene expression can be driven by behavior of the organism as a whole even when the hepatic clock is suppressed. So far, however, there is relatively little evidence indicating whether the liver clock is functionally important in modulating xenobiotic metabolism. Thus, mice lacking circadian clock function in the whole body or specifically in liver were challenged with pentobarbital and acetaminophen, and pentobarbital sleep time (PBST) and acetaminophen toxicity, respectively, was assessed at different times of day in mutant and control mice. The results suggest that the liver clock is essential for rhythmic changes in xenobiotic detoxification. Surprisingly, it seems that the way in which the clock is disrupted determines the rate of xenobiotic metabolism in the liver. CLOCK-deficient mice are remarkably resistant to acetaminophen and exhibit a longer PBST, while PERIOD-deficient mice have a short PBST. These results indicate an essential role of the tissue-intrinsic peripheral circadian oscillator in the liver in regulating xenobiotic metabolism. © 2014 The Author(s).

  20. Photoperiodic plasticity in circadian clock neurons in insects

    Directory of Open Access Journals (Sweden)

    Sakiko eShiga

    2013-08-01

    Full Text Available Since Bünning’s observation of circadian rhythms and photoperiodism in the runner bean Phaseolus multiflorus in 1936, many studies have shown that photoperiodism is based on the circadian clock system. In insects, involvement of circadian clock genes or neurons has been recently shown in the photoperiodic control of developmental arrests, diapause. Based on molecular and neuronal studies in Drosophila melanogaster, photoperiodic changes have been reported for expression patterns of the circadian clock genes, subcellular distribution of clock proteins, fiber distribution, or the number of plausible clock neurons in different species. Photoperiod sets peaks of per or tim mRNA abundance at lights-off in Sarcophaga crassipalpis, Chymomyza costata and Protophormia terraenovae. Abundance of per and Clock mRNA changes by photoperiod in Pyrrhocoris apterus. Subcellular Per distribution in circadian clock neurons changes with photoperiod in P. terraenovae. Although photoperiodism is not known in Leucophaea maderae, under longer day length, more stomata and longer commissural fibers of circadian clock neurons have been found. These plastic changes in the circadian clock neurons could be an important constituent for photoperiodic clock mechanisms to integrate repetitive photoperiodic information and produce different outputs based on day length.

  1. The Effect of Strict Segregation on Pseudomonas aeruginosa in Cystic Fibrosis Patients

    NARCIS (Netherlands)

    van Mansfeld, Rosa; de Vrankrijker, Angelica; Brimicombe, Roland; Heijerman, Harry; Teding van Berkhout, Ferdinand; Spitoni, Cristian|info:eu-repo/dai/nl/304625957; Grave, Sanne; van der Ent, Cornelis; Wolfs, Tom; Willems, Rob; Bonten, Marc

    2016-01-01

    INTRODUCTION: Segregation of patients with cystic fibrosis (CF) was implemented to prevent chronic infection with epidemic Pseudomonas aeruginosa strains with presumed detrimental clinical effects, but its effectiveness has not been carefully evaluated. METHODS: The effect of strict segregation on

  2. Strict deformation quantization for actions of a class of symplectic lie groups

    International Nuclear Information System (INIS)

    Bieliavsky, Pierre; Massar, Marc

    2002-01-01

    We present explicit universal strict deformation quantization formulae for actions of Iwasawa subgroups AN of SN(1, n). This answers a question raised by Rieffel in [Contemp. Math. 228 (1998), 315]. (author)

  3. Histone lysine demethylase JARID1a activates CLOCK-BMAL1 and influences the circadian clock.

    Science.gov (United States)

    DiTacchio, Luciano; Le, Hiep D; Vollmers, Christopher; Hatori, Megumi; Witcher, Michael; Secombe, Julie; Panda, Satchidananda

    2011-09-30

    In animals, circadian oscillators are based on a transcription-translation circuit that revolves around the transcription factors CLOCK and BMAL1. We found that the JumonjiC (JmjC) and ARID domain-containing histone lysine demethylase 1a (JARID1a) formed a complex with CLOCK-BMAL1, which was recruited to the Per2 promoter. JARID1a increased histone acetylation by inhibiting histone deacetylase 1 function and enhanced transcription by CLOCK-BMAL1 in a demethylase-independent manner. Depletion of JARID1a in mammalian cells reduced Per promoter histone acetylation, dampened expression of canonical circadian genes, and shortened the period of circadian rhythms. Drosophila lines with reduced expression of the Jarid1a homolog, lid, had lowered Per expression and similarly altered circadian rhythms. JARID1a thus has a nonredundant role in circadian oscillator function.

  4. Testing the molecular clock using mechanistic models of fossil preservation and molecular evolution.

    Science.gov (United States)

    Warnock, Rachel C M; Yang, Ziheng; Donoghue, Philip C J

    2017-06-28

    Molecular sequence data provide information about relative times only, and fossil-based age constraints are the ultimate source of information about absolute times in molecular clock dating analyses. Thus, fossil calibrations are critical to molecular clock dating, but competing methods are difficult to evaluate empirically because the true evolutionary time scale is never known. Here, we combine mechanistic models of fossil preservation and sequence evolution in simulations to evaluate different approaches to constructing fossil calibrations and their impact on Bayesian molecular clock dating, and the relative impact of fossil versus molecular sampling. We show that divergence time estimation is impacted by the model of fossil preservation, sampling intensity and tree shape. The addition of sequence data may improve molecular clock estimates, but accuracy and precision is dominated by the quality of the fossil calibrations. Posterior means and medians are poor representatives of true divergence times; posterior intervals provide a much more accurate estimate of divergence times, though they may be wide and often do not have high coverage probability. Our results highlight the importance of increased fossil sampling and improved statistical approaches to generating calibrations, which should incorporate the non-uniform nature of ecological and temporal fossil species distributions. © 2017 The Authors.

  5. Strict optical orthogonal codes for purely asynchronous code-division multiple-access applications

    Science.gov (United States)

    Zhang, Jian-Guo

    1996-12-01

    Strict optical orthogonal codes are presented for purely asynchronous optical code-division multiple-access (CDMA) applications. The proposed code can strictly guarantee the peaks of its cross-correlation functions and the sidelobes of any of its autocorrelation functions to have a value of 1 in purely asynchronous data communications. The basic theory of the proposed codes is given. An experiment on optical CDMA systems is also demonstrated to verify the characteristics of the proposed code.

  6. Synthetic Spin-Orbit Coupling in an Optical Lattice Clock

    Science.gov (United States)

    Wall, Michael L.; Koller, Andrew P.; Li, Shuming; Zhang, Xibo; Cooper, Nigel R.; Ye, Jun; Rey, Ana Maria

    2016-01-01

    We propose the use of optical lattice clocks operated with fermionic alkaline-earth atoms to study spin-orbit coupling (SOC) in interacting many-body systems. The SOC emerges naturally during the clock interrogation, when atoms are allowed to tunnel and accumulate a phase set by the ratio of the "magic" lattice wavelength to the clock transition wavelength. We demonstrate how standard protocols such as Rabi and Ramsey spectroscopy that take advantage of the sub-Hertz resolution of state-of-the-art clock lasers can perform momentum-resolved band tomography and determine SOC-induced s -wave collisions in nuclear-spin-polarized fermions. With the use of a second counterpropagating clock beam, we propose a method for engineering controlled atomic transport and study how it is modified by p - and s -wave interactions. The proposed spectroscopic probes provide clean and well-resolved signatures at current clock operating temperatures.

  7. The Effects of Clock Drift on the Mars Exploration Rovers

    Science.gov (United States)

    Ali, Khaled S.; Vanelli, C. Anthony

    2012-01-01

    All clocks drift by some amount, and the mission clock on the Mars Exploration Rovers (MER) is no exception. The mission clock on both MER rovers drifted significantly since the rovers were launched, and it is still drifting on the Opportunity rover. The drift rate is temperature dependent. Clock drift causes problems for onboard behaviors and spacecraft operations, such as attitude estimation, driving, operation of the robotic arm, pointing for imaging, power analysis, and telecom analysis. The MER operations team has techniques to deal with some of these problems. There are a few techniques for reducing and eliminating the clock drift, but each has drawbacks. This paper presents an explanation of what is meant by clock drift on the rovers, its relationship to temperature, how we measure it, what problems it causes, how we deal with those problems, and techniques for reducing the drift.

  8. FAD regulates CRYPTOCHROME protein stability and circadian clock in mice

    OpenAIRE

    Hirano, Arisa; Braas, Daniel; Fu, Ying-Hui; Ptáček, Louis J.

    2017-01-01

    The circadian clock generates biological rhythms of metabolic and physiological processes, including the sleep-wake cycle. We previously identified a missense mutation in the flavin adenine dinucleotide (FAD) binding pocket of CRYPTOCHROME2 (CRY2), a clock protein that causes human advanced sleep phase. This prompted us to examine the role of FAD as a mediator of the clock and metabolism. FAD stabilized CRY proteins, leading to increased protein levels. In contrast, knockdown of Riboflavin ki...

  9. Relativity theory and time perception: single or multiple clocks?

    Science.gov (United States)

    Buhusi, Catalin V; Meck, Warren H

    2009-07-22

    Current theories of interval timing assume that humans and other animals time as if using a single, absolute stopwatch that can be stopped or reset on command. Here we evaluate the alternative view that psychological time is represented by multiple clocks, and that these clocks create separate temporal contexts by which duration is judged in a relative manner. Two predictions of the multiple-clock hypothesis were tested. First, that the multiple clocks can be manipulated (stopped and/or reset) independently. Second, that an event of a given physical duration would be perceived as having different durations in different temporal contexts, i.e., would be judged differently by each clock. Rats were trained to time three durations (e.g., 10, 30, and 90 s). When timing was interrupted by an unexpected gap in the signal, rats reset the clock used to time the "short" duration, stopped the "medium" duration clock, and continued to run the "long" duration clock. When the duration of the gap was manipulated, the rats reset these clocks in a hierarchical order, first the "short", then the "medium", and finally the "long" clock. Quantitative modeling assuming re-allocation of cognitive resources in proportion to the relative duration of the gap to the multiple, simultaneously timed event durations was used to account for the results. These results indicate that the three event durations were effectively timed by separate clocks operated independently, and that the same gap duration was judged relative to these three temporal contexts. Results suggest that the brain processes the duration of an event in a manner similar to Einstein's special relativity theory: A given time interval is registered differently by independent clocks dependent upon the context.

  10. Relativity theory and time perception: single or multiple clocks?

    Directory of Open Access Journals (Sweden)

    Catalin V Buhusi

    2009-07-01

    Full Text Available Current theories of interval timing assume that humans and other animals time as if using a single, absolute stopwatch that can be stopped or reset on command. Here we evaluate the alternative view that psychological time is represented by multiple clocks, and that these clocks create separate temporal contexts by which duration is judged in a relative manner. Two predictions of the multiple-clock hypothesis were tested. First, that the multiple clocks can be manipulated (stopped and/or reset independently. Second, that an event of a given physical duration would be perceived as having different durations in different temporal contexts, i.e., would be judged differently by each clock.Rats were trained to time three durations (e.g., 10, 30, and 90 s. When timing was interrupted by an unexpected gap in the signal, rats reset the clock used to time the "short" duration, stopped the "medium" duration clock, and continued to run the "long" duration clock. When the duration of the gap was manipulated, the rats reset these clocks in a hierarchical order, first the "short", then the "medium", and finally the "long" clock. Quantitative modeling assuming re-allocation of cognitive resources in proportion to the relative duration of the gap to the multiple, simultaneously timed event durations was used to account for the results.These results indicate that the three event durations were effectively timed by separate clocks operated independently, and that the same gap duration was judged relative to these three temporal contexts. Results suggest that the brain processes the duration of an event in a manner similar to Einstein's special relativity theory: A given time interval is registered differently by independent clocks dependent upon the context.

  11. System-wide power management control via clock distribution network

    Science.gov (United States)

    Coteus, Paul W.; Gara, Alan; Gooding, Thomas M.; Haring, Rudolf A.; Kopcsay, Gerard V.; Liebsch, Thomas A.; Reed, Don D.

    2015-05-19

    An apparatus, method and computer program product for automatically controlling power dissipation of a parallel computing system that includes a plurality of processors. A computing device issues a command to the parallel computing system. A clock pulse-width modulator encodes the command in a system clock signal to be distributed to the plurality of processors. The plurality of processors in the parallel computing system receive the system clock signal including the encoded command, and adjusts power dissipation according to the encoded command.

  12. Synthesizing genetic sequential logic circuit with clock pulse generator

    OpenAIRE

    Chuang, Chia-Hua; Lin, Chun-Liang

    2014-01-01

    Background Rhythmic clock widely occurs in biological systems which controls several aspects of cell physiology. For the different cell types, it is supplied with various rhythmic frequencies. How to synthesize a specific clock signal is a preliminary but a necessary step to further development of a biological computer in the future. Results This paper presents a genetic sequential logic circuit with a clock pulse generator based on a synthesized genetic oscillator, which generates a consecut...

  13. Molecular clock integration of brown adipose tissue formation and function

    OpenAIRE

    Nam, Deokhwa; Yechoor, Vijay K.; Ma, Ke

    2015-01-01

    Abstract The circadian clock is an essential time-keeping mechanism that entrains internal physiology to environmental cues. Despite the well-established link between the molecular clock and metabolic homeostasis, an intimate interplay between the clock machinery and the metabolically active brown adipose tissue (BAT) is only emerging. Recently, we came to appreciate that the formation and metabolic functions of BAT, a key organ for body temperature maintenance, are under an orchestrated circ...

  14. A Sizing Algorithm for Non-Overlapping Clock Signal Generators

    OpenAIRE

    Kavak, Fatih

    2004-01-01

    The non-overlapping clock signal generator circuits are key elements in switched capacitor circuits since non-overlapping clock signals are generally required. Non-overlapping clock signals means signals running at the same frequency and there is a time between the pulses that none of them is high. This time (when both pulses are logic 0) takes place when the pulses are switching from logic 1 to logic 0 or from logic 0 to logic 1. In this thesis this type of clock signal generators are analyz...

  15. Synthesizing genetic sequential logic circuit with clock pulse generator.

    Science.gov (United States)

    Chuang, Chia-Hua; Lin, Chun-Liang

    2014-05-28

    Rhythmic clock widely occurs in biological systems which controls several aspects of cell physiology. For the different cell types, it is supplied with various rhythmic frequencies. How to synthesize a specific clock signal is a preliminary but a necessary step to further development of a biological computer in the future. This paper presents a genetic sequential logic circuit with a clock pulse generator based on a synthesized genetic oscillator, which generates a consecutive clock signal whose frequency is an inverse integer multiple to that of the genetic oscillator. An analogous electronic waveform-shaping circuit is constructed by a series of genetic buffers to shape logic high/low levels of an oscillation input in a basic sinusoidal cycle and generate a pulse-width-modulated (PWM) output with various duty cycles. By controlling the threshold level of the genetic buffer, a genetic clock pulse signal with its frequency consistent to the genetic oscillator is synthesized. A synchronous genetic counter circuit based on the topology of the digital sequential logic circuit is triggered by the clock pulse to synthesize the clock signal with an inverse multiple frequency to the genetic oscillator. The function acts like a frequency divider in electronic circuits which plays a key role in the sequential logic circuit with specific operational frequency. A cascaded genetic logic circuit generating clock pulse signals is proposed. Based on analogous implement of digital sequential logic circuits, genetic sequential logic circuits can be constructed by the proposed approach to generate various clock signals from an oscillation signal.

  16. Diamond Electron-Spin Clocks For Space Navigation and Communication

    Data.gov (United States)

    National Aeronautics and Space Administration — Precision clocks are needed in a broad range of applications, including satellite communication, high-bandwidth wireless communication, computing systems, and...

  17. Crosstalk between the circadian clock and innate immunity in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Chong Zhang

    Full Text Available The circadian clock integrates temporal information with environmental cues in regulating plant development and physiology. Recently, the circadian clock has been shown to affect plant responses to biotic cues. To further examine this role of the circadian clock, we tested disease resistance in mutants disrupted in CCA1 and LHY, which act synergistically to regulate clock activity. We found that cca1 and lhy mutants also synergistically affect basal and resistance gene-mediated defense against Pseudomonas syringae and Hyaloperonospora arabidopsidis. Disrupting the circadian clock caused by overexpression of CCA1 or LHY also resulted in severe susceptibility to P. syringae. We identified a downstream target of CCA1 and LHY, GRP7, a key constituent of a slave oscillator regulated by the circadian clock and previously shown to influence plant defense and stomatal activity. We show that the defense role of CCA1 and LHY against P. syringae is at least partially through circadian control of stomatal aperture but is independent of defense mediated by salicylic acid. Furthermore, we found defense activation by P. syringae infection and treatment with the elicitor flg22 can feedback-regulate clock activity. Together this data strongly supports a direct role of the circadian clock in defense control and reveal for the first time crosstalk between the circadian clock and plant innate immunity.

  18. Improvement of an Atomic Clock using Squeezed Vacuum

    DEFF Research Database (Denmark)

    Kruse, I.; Lange, K; Peise, Jan

    2016-01-01

    , the vacuum noise restricts the precision of the interferometer to the standard quantum limit (SQL). Here, we propose and experimentally demonstrate a novel clock configuration that surpasses the SQL by squeezing the vacuum in the empty input state. We create a squeezed vacuum state containing an average of 0.......75 atoms to improve the clock sensitivity of 10000 atoms by 2.05+0.34−0.37  dB. The SQL poses a significant limitation for today’s microwave fountain clocks, which serve as the main time reference. We evaluate the major technical limitations and challenges for devising a next generation of fountain clocks...

  19. Clock Genes: Critical Modulators of Breast Cancer Risk

    National Research Council Canada - National Science Library

    Kennaway, David J; Butler, Lisa M; Tilley, Wayne D

    2005-01-01

    .... Circadian rhythms are regulated by a panel of specific transcription factors, called clock genes, and our current understanding of endogenous cellular rhythmicity is that both positive and negative...

  20. Strict Host-Symbiont Cospeciation and Reductive Genome Evolution in Insect Gut Bacteria

    Science.gov (United States)

    Hosokawa, Takahiro; Kikuchi, Yoshitomo; Nikoh, Naruo; Shimada, Masakazu; Fukatsu, Takema

    2006-01-01

    Host-symbiont cospeciation and reductive genome evolution have been identified in obligate endocellular insect symbionts, but no such example has been identified from extracellular ones. Here we first report such a case in stinkbugs of the family Plataspidae, wherein a specific gut bacterium is vertically transmitted via “symbiont capsule.” In all of the plataspid species, females produced symbiont capsules upon oviposition and their gut exhibited specialized traits for capsule production. Phylogenetic analysis showed that the plataspid symbionts constituted a distinct group in the γ-Proteobacteria, whose sister group was the aphid obligate endocellular symbionts Buchnera. Removal of the symbionts resulted in retarded growth, mortality, and sterility of the insects. The host phylogeny perfectly agreed with the symbiont phylogeny, indicating strict host-symbiont cospeciation despite the extracellular association. The symbionts exhibited AT-biased nucleotide composition, accelerated molecular evolution, and reduced genome size, as has been observed in obligate endocellular insect symbionts. These findings suggest that not the endocellular conditions themselves but the population genetic attributes of the vertically transmitted symbionts are probably responsible for the peculiar genetic traits of these insect symbionts. We proposed the designation “Candidatus Ishikawaella capsulata” for the plataspid symbionts. The plataspid stinkbugs, wherein the host-symbiont associations can be easily manipulated, provide a novel system that enables experimental approaches to previously untouched aspects of the insect-microbe mutualism. Furthermore, comparative analyses of the sister groups, the endocellular Buchnera and the extracellular Ishikawaella, would lead to insights into how the different symbiotic lifestyles have affected their genomic evolution. PMID:17032065

  1. Polymorphism at the Clock gene predicts phenology of long-distance migration in birds.

    Science.gov (United States)

    Saino, Nicola; Bazzi, Gaia; Gatti, Emanuele; Caprioli, Manuela; Cecere, Jacopo G; Possenti, Cristina D; Galimberti, Andrea; Orioli, Valerio; Bani, Luciano; Rubolini, Diego; Gianfranceschi, Luca; Spina, Fernando

    2015-04-01

    Dissecting phenotypic variance in life history traits into its genetic and environmental components is at the focus of evolutionary studies and of pivotal importance to identify the mechanisms and predict the consequences of human-driven environmental change. The timing of recurrent life history events (phenology) is under strong selection, but the study of the genes that control potential environmental canalization in phenological traits is at its infancy. Candidate genes for circadian behaviour entrained by photoperiod have been screened as potential controllers of phenological variation of breeding and moult in birds, with inconsistent results. Despite photoperiodic control of migration is well established, no study has reported on migration phenology in relation to polymorphism at candidate genes in birds. We analysed variation in spring migration dates within four trans-Saharan migratory species (Luscinia megarhynchos; Ficedula hypoleuca; Anthus trivialis; Saxicola rubetra) at a Mediterranean island in relation to Clock and Adcyap1 polymorphism. Individuals with larger number of glutamine residues in the poly-Q region of Clock gene migrated significantly later in one or, respectively, two species depending on sex and whether the within-individual mean length or the length of the longer Clock allele was considered. The results hinted at dominance of the longer Clock allele. No significant evidence for migration date to covary with Adcyap1 polymorphism emerged. This is the first evidence that migration phenology is associated with Clock in birds. This finding is important for evolutionary studies of migration and sheds light on the mechanisms that drive bird phenological changes and population trends in response to climate change. © 2015 John Wiley & Sons Ltd.

  2. Characterisation, analysis of expression and localisation of circadian clock genes from the perspective of photoperiodism in the aphid Acyrthosiphon pisum.

    Science.gov (United States)

    Barberà, Miquel; Collantes-Alegre, Jorge Mariano; Martínez-Torres, David

    2017-04-01

    Aphids are typical photoperiodic insects that switch from viviparous parthenogenetic reproduction typical of long day seasons to oviparous sexual reproduction triggered by the shortening of photoperiod in autumn yielding an overwintering egg in which an embryonic diapause takes place. While the involvement of the circadian clock genes in photoperiodism in mammals is well established, there is still some controversy on their participation in insects. The availability of the genome of the pea aphid Acyrthosiphon pisum places this species as an excellent model to investigate the involvement of the circadian system in the aphid seasonal response. In the present report, we have advanced in the characterisation of the circadian clock genes and showed that these genes display extensive alternative splicing. Moreover, the expression of circadian clock genes, analysed at different moments of the day, showed a robust cycling of central clock genes period and timeless. Furthermore, the rhythmic expression of these genes was shown to be rapidly dampened under DD (continuous darkness conditions), thus supporting the model of a seasonal response based on a heavily dampened circadian oscillator. Additionally, increased expression of some of the circadian clock genes under short-day conditions suggest their involvement in the induction of the aphid seasonal response. Finally, in situ localisation of transcripts of genes period and timeless in the aphid brain revealed the site of clock neurons for the first time in aphids. Two groups of clock cells were identified: the Dorsal Neurons (DN) and the Lateral Neurons (LN), both in the protocerebrum. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. An association between clock genes and clock-controlled cell cycle genes in murine colorectal tumors

    Czech Academy of Sciences Publication Activity Database

    Soták, Matúš; Polidarová, Lenka; Ergang, Peter; Sumová, Alena; Pácha, Jiří

    2013-01-01

    Roč. 132, č. 5 (2013), s. 1032-1041 ISSN 0020-7136 R&D Projects: GA MZd(CZ) NS9982 Institutional research plan: CEZ:AV0Z50110509 Keywords : cancer * circadian rhythm * peripheral circadian clock Subject RIV: FE - Other Internal Medicine Disciplines Impact factor: 5.007, year: 2013

  4. Code-Phase Clock Bias and Frequency Offset in PPP Clock Solutions.

    Science.gov (United States)

    Defraigne, Pascale; Sleewaegen, Jean-Marie

    2016-07-01

    Precise point positioning (PPP) is a zero-difference single-station technique that has proved to be very effective for time and frequency transfer, enabling the comparison of atomic clocks with a precision of a hundred picoseconds and a one-day stability below the 1e-15 level. It was, however, noted that for some receivers, a frequency difference is observed between the clock solution based on the code measurements and the clock solution based on the carrier-phase measurements. These observations reveal some inconsistency either between the code and carrier phases measured by the receiver or between the data analysis strategy of codes and carrier phases. One explanation for this discrepancy is the time offset that can exist for some receivers between the code and the carrier-phase latching. This paper explains how a code-phase bias in the receiver hardware can induce a frequency difference between the code and the carrier-phase clock solutions. The impact on PPP is then quantified. Finally, the possibility to determine this code-phase bias in the PPP modeling is investigated, and the first results are shown to be inappropriate due to the high level of code noise.

  5. Circadian expression of clock genes and clock-controlled genes in the rat retina

    NARCIS (Netherlands)

    Kamphuis, Willem; Cailotto, Cathy; Dijk, Frederike; Bergen, Arthur; Buijs, Ruud M.

    2005-01-01

    The circadian expression patterns of genes encoding for proteins that make up the core of the circadian clock were measured in rat retina using real-time quantitative PCR (qPCR). Transcript levels of several genes previously used for normalization of qPCR assays were determined and the effect of

  6. Comparisons of Synchronous-Clocking SFQ Adders

    Science.gov (United States)

    Takagi, Naofumi; Tanaka, Masamitsu

    Recent advances of superconducting single-flux-quantum (SFQ) circuit technology make it attractive to investigate computing systems using SFQ circuits, where arithmetic circuits play important roles. In order to develop excellent SFQ arithmetic circuits, we have to design or select their underlying algorithms, called hardware algorithms, from different point of view than CMOS circuits, because SFQ circuits work by pulse logic while CMOS circuits work by level logic. In this paper, we compare implementations of hardware algorithms for addition by synchronous-clocking SFQ circuits. We show that a set of individual bit-serial adders and Kogge-Stone adder are superior to others.

  7. Mass defect effects in atomic clocks

    Science.gov (United States)

    Yudin, Valeriy; Taichenachev, Alexey

    2018-03-01

    We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (the gravitational shift and motion-induced shifts such as quadratic Doppler and micromotion shifts) can be interpreted as consequences of the mass defect in quantum atomic physics, i.e. without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions.

  8. Laser Cooled Atomic Clocks in Space

    Science.gov (United States)

    Thompson, R. J.; Kohel, J.; Klipstein, W. M.; Seidel, D. J.; Maleki, L.

    2000-01-01

    The goals of the Glovebox Laser-cooled Atomic Clock Experiment (GLACE) are: (1) first utilization of tunable, frequency-stabilized lasers in space, (2) demonstrate laser cooling and trapping in microgravity, (3) demonstrate longest 'perturbation-free' interaction time for a precision measurement on neutral atoms, (4) Resolve Ramsey fringes 2-10 times narrower than achievable on Earth. The approach taken is: the use of COTS components, and the utilization of prototype hardware from LCAP flight definition experiments. The launch date is scheduled for Oct. 2002. The Microgravity Science Glovebox (MSG) specifications are reviewed, and a picture of the MSG is shown.

  9. Ultradian feeding in mice not only affects the peripheral clock in the liver, but also the master clock in the brain

    NARCIS (Netherlands)

    Sen, Satish; Raingard, Hélène; Dumont, Stéphanie; Kalsbeek, A.; Vuillez, Patrick; Challet, Etienne

    2017-01-01

    Restricted feeding during the resting period causes pronounced shifts in a number of peripheral clocks, but not the central clock in the suprachiasmatic nucleus (SCN). By contrast, daily caloric restriction impacts also the light-entrained SCN clock, as indicated by shifted oscillations of clock

  10. The Renaissance or the cuckoo clock.

    Science.gov (United States)

    Pines, Jonathon; Hagan, Iain

    2011-12-27

    '…in Italy, for thirty years under the Borgias, they had warfare, terror, murder and bloodshed, but they produced Michelangelo, Leonardo da Vinci and the Renaissance. In Switzerland, they had brotherly love, they had five hundred years of democracy and peace-and what did that produce? The cuckoo clock'. Orson Welles as Harry Lime: The Third Man. Orson Welles might have been a little unfair on the Swiss, after all cuckoo clocks were developed in the Schwartzwald, but, more importantly, Swiss democracy gives remarkably stable government with considerable decision-making at the local level. The alternative is the battling city-states of Renaissance Italy: culturally rich but chaotic at a higher level of organization. As our understanding of the cell cycle improves, it appears that the cell is organized more along the lines of Switzerland than Renaissance Italy, and one major challenge is to determine how local decisions are made and coordinated to produce the robust cell cycle mechanisms that we observe in the cell as a whole.

  11. Synthetic clock transitions via continuous dynamical decoupling

    Science.gov (United States)

    Trypogeorgos, D.; Valdés-Curiel, A.; Lundblad, N.; Spielman, I. B.

    2018-01-01

    Decoherence of quantum systems due to uncontrolled fluctuations of the environment presents fundamental obstacles in quantum science. Clock transitions which are insensitive to such fluctuations are used to improve coherence, however, they are not present in all systems or for arbitrary system parameters. Here we create a trio of synthetic clock transitions using continuous dynamical decoupling in a spin-1 Bose-Einstein condensate in which we observe a reduction of sensitivity to magnetic-field noise of up to four orders of magnitude; this work complements the parallel work by Anderson et al. [R. P. Anderson et al., following paper, Phys. Rev. A 97, 013408 (2018), 10.1103/PhysRevA.97.013408]. In addition, using a concatenated scheme, we demonstrate suppression of sensitivity to fluctuations in our control fields. These field-insensitive states represent an ideal foundation for the next generation of cold-atom experiments focused on fragile many-body phases relevant to quantum magnetism, artificial gauge fields, and topological matter.

  12. Temperature-Compensated Clock Skew Adjustment

    Directory of Open Access Journals (Sweden)

    Joaquín Olivares

    2013-08-01

    Full Text Available This work analyzes several drift compensation mechanisms in wireless sensor networks (WSN. Temperature is an environmental factor that greatly affects oscillators shipped in every WSN mote. This behavior creates the need of improving drift compensation mechanisms in synchronization protocols. Using the Flooding Time Synchronization Protocol (FTSP, this work demonstrates that crystal oscillators are affected by temperature variations. Thus, the influence of temperature provokes a low performance of FTSP in changing conditions of temperature. This article proposes an innovative correction factor that minimizes the impact of temperature in the clock skew. By means of this factor, two new mechanisms are proposed in this paper: the Adjusted Temperature (AT and the Advanced Adjusted Temperature (A2T. These mechanisms have been combined with FTSP to produce AT-FTSP and A2T-FTSP. Both have been tested in a network of TelosB motes running TinyOS. Results show that both AT-FTSP and A2T-FTSP improve the average synchronization errors compared to FTSP and other temperature-compensated protocols (Environment-Aware Clock Skew Estimation and Synchronization for WSN (EACS and Temperature Compensated Time Synchronization (TCTS.

  13. Actions of a separately strict cpo-monoid on pointed directed complete posets

    Directory of Open Access Journals (Sweden)

    Halimeh Moghbeli Damaneh

    2015-07-01

    Full Text Available ‎ In the present article‎, ‎we study some categorical properties of the category {$bf‎ Cpo_{Sep}$-$S$} of all {separately strict $S$-cpo's}; cpo's equipped with‎ a compatible right action of a separately strict cpo-monoid $S$ which is‎ strict continuous in each component‎. ‎In particular‎, we show that this category is reflective and coreflective in the‎ category of $S$-cpo's‎, ‎find the free and cofree functors‎, characterize products and coproducts‎. ‎Furthermore‎, ‎epimorphisms and‎  monomorphisms in {$bf Cpo_{Sep}$-$S$} are studied‎, ‎and show that‎ {$bf Cpo_{Sep}$-$S$} is not cartesian closed‎.

  14. Circadian clock genes universally control key agricultural traits

    Science.gov (United States)

    Circadian clocks are endogenous timers that enable plants to synchronize biological processes with daily and seasonal environmental conditions in order to allocate resources during the most beneficial times of day and year. The circadian clock regulates a number of central plant activities, includin...

  15. Verge and Foliot Clock Escapement: A Simple Dynamical System

    Science.gov (United States)

    Denny, Mark

    2010-01-01

    The earliest mechanical clocks appeared in Europe in the 13th century. From about 1250 CE to 1670 CE, these simple clocks consisted of a weight suspended from a rope or chain that was wrapped around a horizontal axle. To tell time, the weight must fall with a slow uniform speed, but, under the action of gravity alone, such a suspended weight would…

  16. A CONSTANT-FREQUENCY POWER SUPPLY FOR SHIPBOARD ELECTRIC CLOCKS,

    Science.gov (United States)

    static inverter-type power supply , capable of powering up to six internally illuminated clocks per MIL-C-23339, with timekeeping accuracy better than...of a development model of this power supply are described. It is recommended that units of this type be procured for installation in control spaces of ships equipped with electric clocks. (Author)

  17. Self-clocked sequential circuits: - a design example | Aghdasi ...

    African Journals Online (AJOL)

    A number of new design methodologies which involve locally generating a clock and using it to self synchronize the machine have been proposed. Such clock signals are generated whenever an input changes, or by controlled excitation whenever a change of inputs necessitates a change of state. All such designs, where ...

  18. Optimal Infinite Runs in One-Clock Priced Timed Automata

    DEFF Research Database (Denmark)

    David, Alexandre; Ejsing-Duun, Daniel; Fontani, Lisa

    We address the problem of finding an infinite run with the optimal cost-time ratio in a one-clock priced timed automaton and pro- vide an algorithmic solution. Through refinements of the quotient graph obtained by strong time-abstracting bisimulation partitioning, we con- struct a graph with time...... of the one-clock priced timed automaton....

  19. Determination of clock synchronization errors in distributed networks

    NARCIS (Netherlands)

    Xia, Weiguo; Cao, Ming

    2018-01-01

    It has been shown by Freris, Graham and Kumar that clocks in distributed networks cannot be synchronized precisely in the presence of asymmetric time delays even in idealized situations. Motivated by that impossibility result, we test under similar settings the performance of some existing clock

  20. A Novel Method of Clock Synchronization in Distributed Systems

    Science.gov (United States)

    Li, Gun; Niu, Meng-jie; Chai, Yang-shun; Chen, Xin; Ren, Yan-qiu

    2017-04-01

    Time synchronization plays an important role in the spacecraft formation flight and constellation autonomous navigation, etc. For the application of clock synchronization in a network system, it is not always true that all the observed nodes in the network are interconnected, therefore, it is difficult to achieve the high-precision time synchronization of a network system in the condition that a certain node can only obtain the measurement information of clock from a single neighboring node, but cannot obtain it from other nodes. Aiming at this problem, a novel method of high-precision time synchronization in a network system is proposed. In this paper, each clock is regarded as a node in the network system, and based on the definition of different topological structures of a distributed system, the three control algorithms of time synchronization under the following three cases are designed: without a master clock (reference clock), with a master clock (reference clock), and with a fixed communication delay in the network system. And the validity of the designed clock synchronization protocol is proved by both stability analysis and numerical simulation.

  1. The circadian clock regulates auxin signaling and responses in Arabidopsis.

    Directory of Open Access Journals (Sweden)

    Michael F Covington

    2007-08-01

    Full Text Available The circadian clock plays a pervasive role in the temporal regulation of plant physiology, environmental responsiveness, and development. In contrast, the phytohormone auxin plays a similarly far-reaching role in the spatial regulation of plant growth and development. Went and Thimann noted 70 years ago that plant sensitivity to auxin varied according to the time of day, an observation that they could not explain. Here we present work that explains this puzzle, demonstrating that the circadian clock regulates auxin signal transduction. Using genome-wide transcriptional profiling, we found many auxin-induced genes are under clock regulation. We verified that endogenous auxin signaling is clock regulated with a luciferase-based assay. Exogenous auxin has only modest effects on the plant clock, but the clock controls plant sensitivity to applied auxin. Notably, we found both transcriptional and growth responses to exogenous auxin are gated by the clock. Thus the circadian clock regulates some, and perhaps all, auxin responses. Consequently, many aspects of plant physiology not previously thought to be under circadian control may show time-of-day-specific sensitivity, with likely important consequences for plant growth and environmental responses.

  2. The role of biological clock in glucose homeostasis 

    Directory of Open Access Journals (Sweden)

    Piotr Chrościcki

    2013-06-01

    Full Text Available The mechanism of the biological clock is based on a rhythmic expression of clock genes and clock-controlled genes. As a result of their transcripto-translational associations, endogenous rhythms in the synthesis of key proteins of various physiological and metabolic processes are created. The major timekeeping mechanism for these rhythms exists in the central nervous system. The master circadian clock, localized in suprachiasmatic nucleus (SCN, regulates multiple metabolic pathways, while feeding behavior and metabolite availability can in turn regulate the circadian clock. It is also suggested that in the brain there is a food entrainable oscillator (FEO or oscillators, resulting in activation of both food anticipatory activity and hormone secretion that control digestion processes. Moreover, most cells and tissues express autonomous clocks. Maintenance of the glucose homeostasis is particularly important for the proper function of the body, as this sugar is the main source of energy for the brain, retina, erythrocytes and skeletal muscles. Thus, glucose production and utilization are synchronized in time. The hypothalamic excited orexin neurons control energy balance of organism and modulate the glucose production and utilization. Deficiency of orexin action results in narcolepsy and weight gain, whereas glucose and amino acids can affect activity of the orexin cells. Large-scale genetic studies in rodents and humans provide evidence for the involvement of disrupted clock gene expression rhythms in the pathogenesis of obesity and type 2 diabetes. In general, the current lifestyle of the developed modern societies disturbs the action of biological clock

  3. Circadian clocks : from stem cells to tissue homeostasis and regeneration

    NARCIS (Netherlands)

    Dierickx, Pieterjan; Van Laake, Linda W; Geijsen, Niels

    2017-01-01

    The circadian clock is an evolutionarily conserved timekeeper that adapts body physiology to diurnal cycles of around 24 h by influencing a wide variety of processes such as sleep-to-wake transitions, feeding and fasting patterns, body temperature, and hormone regulation. The molecular clock

  4. Molecular clock integration of brown adipose tissue formation and function.

    Science.gov (United States)

    Nam, Deokhwa; Yechoor, Vijay K; Ma, Ke

    2016-01-01

    The circadian clock is an essential time-keeping mechanism that entrains internal physiology to environmental cues. Despite the well-established link between the molecular clock and metabolic homeostasis, an intimate interplay between the clock machinery and the metabolically active brown adipose tissue (BAT) is only emerging. Recently, we came to appreciate that the formation and metabolic functions of BAT, a key organ for body temperature maintenance, are under an orchestrated circadian clock regulation. Two complementary studies from our group uncover that the cell-intrinsic clock machinery exerts concerted control of brown adipogenesis with consequent impacts on adaptive thermogenesis, which adds a previously unappreciated temporal dimension to the regulatory mechanisms governing BAT development and function. The essential clock transcriptional activator, Bmal1, suppresses adipocyte lineage commitment and differentiation, whereas the clock repressor, Rev-erbα, promotes these processes. This newly discovered temporal mechanism in fine-tuning BAT thermogenic capacity may enable energy utilization and body temperature regulation in accordance with external timing signals during development and functional recruitment. Given the important role of BAT in whole-body metabolic homeostasis, pharmacological interventions targeting the BAT-modulatory activities of the clock circuit may offer new avenues for the prevention and treatment of metabolic disorders, particularly those associated with circadian dysregulation.

  5. Frequency comparison of optical lattice clocks beyond the Dick limit

    Science.gov (United States)

    Takamoto, Masao; Takano, Tetsushi; Katori, Hidetoshi

    2011-05-01

    The supreme accuracy of atomic clocks relies on the universality of atomic transition frequencies. The stability of a clock, meanwhile, measures how quickly the clock's statistical uncertainties are reduced. The ultimate measure of stability is provided by the quantum projection noise, which improves as 1/√N by measuring N uncorrelated atoms. Quantum projection noise limited stabilities have been demonstrated in caesium clocks and in single-ion optical clocks, where the quantum noise overwhelms the Dick effect attributed to local oscillator noise. Here, we demonstrate a synchronous frequency comparison of two optical lattice clocks using 87Sr and 88Sr atoms, respectively, for which the Allan standard deviation reached 1 × 10-17 in an averaging time of 1,600 s by cancelling out the Dick effect to approach the quantum projection noise limit. The scheme demonstrates the advantage of using a large number (N ~ 1,000) of atoms in optical clocks and paves the way to investigating the inherent uncertainties of clocks and relativistic geodesy on a timescale of tens of minutes.

  6. Development and entrainment of the colonic circadian clock during ontogenesis

    Czech Academy of Sciences Publication Activity Database

    Polidarová, Lenka; Olejníková, Lucie; Paušlyová, Lucia; Sládek, Martin; Soták, Matúš; Pácha, Jiří; Sumová, Alena

    2014-01-01

    Roč. 306, č. 4 (2014), G346-G356 ISSN 0193-1857 R&D Projects: GA ČR(CZ) GAP303/12/1108 Institutional support: RVO:67985823 Keywords : circadian clock * clock gene * ontogenesis * circadian entrainment Subject RIV: ED - Physiology Impact factor: 3.798, year: 2014

  7. LC-oscillator as a clock for data conversion

    NARCIS (Netherlands)

    Philips, K.J.P.; Verlinden, J.J.A.M.

    2006-01-01

    Following the ever-improving performance of data converters, the accuracy of the clock that is sampling the converter, needs to improveat the same pace. The clock accuracy is especially a problem for high-resolution, wide bandwidth converters.The aim of this project isto provide for a

  8. Clock synchronisation experiment in India using symphonie satellite

    Science.gov (United States)

    Somayajulu, Y. V.; Mathur, B. S.; Banerjee, P.; Garg, S. C.; Singh, L.; Sood, P. C.; Tyagi, T. R.; Jain, C. L.; Kumar, K.

    1979-01-01

    A recent clock synchronization experiment between the National Physical Laboratory (NPL), New Delhi and Space Applications Center (SAC), Ahemedabad, in India via geostationary satellite symphonie 2, stationed at 49 E longitude, is reported. A two-way transmission using a microwave transponder considered to provide the greatest precision in synchronization of two remote clocks is described.

  9. The photon is no strict particle and nonlocality is far from being proven

    Energy Technology Data Exchange (ETDEWEB)

    Greulich, Karl Otto [Fritz Lipmann Institut, Jena (Germany)

    2010-07-01

    Two aspects of philosophical discussions on physics are the wave particle dualism and non locality including entanglement. However the strict particle aspect of the photon, in the common sense view, has never been proven. The accumulation time argument, the only experimental verification of a strictly particle like photon, has so far not yet been satisfied. Also, experiments thought to prove nonlocality have loophole which have so far not yet been safely closed, and now an even more serious loophole emerges. Thus, also nonlocality cannot be seen as proven. This demands some fine tuning of philosophical discussions on critical experiments in physics.

  10. The quantum beat principles and applications of atomic clocks

    CERN Document Server

    Major, F

    2007-01-01

    This work attempts to convey a broad understanding of the physical principles underlying the workings of these quantum-based atomic clocks, with introductory chapters placing them in context with the early development of mechanical clocks and the introduction of electronic time-keeping as embodied in the quartz-controlled clocks. While the book makes no pretense at being a history of atomic clocks, it nevertheless takes a historical perspective in its treatment of the subject. Intended for nonspecialists with some knowledge of physics or engineering, The Quantum Beat covers a wide range of salient topics relevant to atomic clocks, treated in a broad intuitive manner with a minimum of mathematical formalism. Detailed descriptions are given of the design principles of the rubidium, cesium, hydrogen maser, and mercury ion standards; the revolutionary changes that the advent of the laser has made possible, such as laser cooling, optical pumping, the formation of "optical molasses," and the cesium "fountain" stand...

  11. A self-interfering clock as a "which path" witness.

    Science.gov (United States)

    Margalit, Yair; Zhou, Zhifan; Machluf, Shimon; Rohrlich, Daniel; Japha, Yonathan; Folman, Ron

    2015-09-11

    In Einstein's general theory of relativity, time depends locally on gravity; in standard quantum theory, time is global-all clocks "tick" uniformly. We demonstrate a new tool for investigating time in the overlap of these two theories: a self-interfering clock, comprising two atomic spin states. We prepare the clock in a spatial superposition of quantum wave packets, which evolve coherently along two paths into a stable interference pattern. If we make the clock wave packets "tick" at different rates, to simulate a gravitational time lag, the clock time along each path yields "which path" information, degrading the pattern's visibility. In contrast, in standard interferometry, time cannot yield "which path" information. This proof-of-principle experiment may have implications for the study of time and general relativity and their impact on fundamental effects such as decoherence and the emergence of a classical world. Copyright © 2015, American Association for the Advancement of Science.

  12. Standard Clock in primordial density perturbations and cosmic microwave background

    International Nuclear Information System (INIS)

    Chen, Xingang; Namjoo, Mohammad Hossein

    2014-01-01

    Standard Clocks in the primordial epoch leave a special type of features in the primordial perturbations, which can be used to directly measure the scale factor of the primordial universe as a function of time a(t), thus discriminating between inflation and alternatives. We have started to search for such signals in the Planck 2013 data using the key predictions of the Standard Clock. In this Letter, we summarize the key predictions of the Standard Clock and present an interesting candidate example in Planck 2013 data. Motivated by this candidate, we construct and compute full Standard Clock models and use the more complete prediction to make more extensive comparison with data. Although this candidate is not yet statistically significant, we use it to illustrate how Standard Clocks appear in Cosmic Microwave Background (CMB) and how they can be further tested by future data. We also use it to motivate more detailed theoretical model building

  13. The absolute frequency of the 87Sr optical clock transition

    DEFF Research Database (Denmark)

    Campbell, Gretchen K.; Ludlow, Andrew D.; Blatt, Sebastian

    2008-01-01

    The absolute frequency of the 1S0–3P0 clock transition of 87Sr has been measured to be 429 228 004 229 873.65 (37) Hz using lattice-confined atoms, where the fractional uncertainty of 8.6 × 10-16 represents one of the most accurate measurements of an atomic transition frequency to date. After...... a detailed study of systematic effects, which reduced the total systematic uncertainty of the Sr lattice clock to 1.5 × 10-16, the clock frequency is measured against a hydrogen maser which is simultaneously calibrated to the US primary frequency standard, the NIST Cs fountain clock, NIST-F1. The comparison...... is made possible using a femtosecond laser based optical frequency comb to phase coherently connect the optical and microwave spectral regions and by a 3.5 km fibre transfer scheme to compare the remotely located clock signals....

  14. Hyperpolarizability and Operational Magic Wavelength in an Optical Lattice Clock

    Science.gov (United States)

    Brown, R. C.; Phillips, N. B.; Beloy, K.; McGrew, W. F.; Schioppo, M.; Fasano, R. J.; Milani, G.; Zhang, X.; Hinkley, N.; Leopardi, H.; Yoon, T. H.; Nicolodi, D.; Fortier, T. M.; Ludlow, A. D.

    2017-12-01

    Optical clocks benefit from tight atomic confinement enabling extended interrogation times as well as Doppler- and recoil-free operation. However, these benefits come at the cost of frequency shifts that, if not properly controlled, may degrade clock accuracy. Numerous theoretical studies have predicted optical lattice clock frequency shifts that scale nonlinearly with trap depth. To experimentally observe and constrain these shifts in an 171Yb optical lattice clock, we construct a lattice enhancement cavity that exaggerates the light shifts. We observe an atomic temperature that is proportional to the optical trap depth, fundamentally altering the scaling of trap-induced light shifts and simplifying their parametrization. We identify an "operational" magic wavelength where frequency shifts are insensitive to changes in trap depth. These measurements and scaling analysis constitute an essential systematic characterization for clock operation at the 10-18 level and beyond.

  15. Molecular Mechanisms Regulating Temperature Compensation of the Circadian Clock

    Directory of Open Access Journals (Sweden)

    David M. Virshup

    2017-04-01

    Full Text Available An approximately 24-h biological timekeeping mechanism called the circadian clock is present in virtually all light-sensitive organisms from cyanobacteria to humans. The clock system regulates our sleep–wake cycle, feeding–fasting, hormonal secretion, body temperature, and many other physiological functions. Signals from the master circadian oscillator entrain peripheral clocks using a variety of neural and hormonal signals. Even centrally controlled internal temperature fluctuations can entrain the peripheral circadian clocks. But, unlike other chemical reactions, the output of the clock system remains nearly constant with fluctuations in ambient temperature, a phenomenon known as temperature compensation. In this brief review, we focus on recent advances in our understanding of the posttranslational modifications, especially a phosphoswitch mechanism controlling the stability of PER2 and its implications for the regulation of temperature compensation.

  16. Calcium and SOL Protease Mediate Temperature Resetting of Circadian Clocks

    Science.gov (United States)

    Tataroglu, Ozgur; Zhao, Xiaohu; Busza, Ania; Ling, Jinli; O’Neill, John S.; Emery, Patrick

    2015-01-01

    Summary Circadian clocks integrate light and temperature input to remain synchronized with the day/night cycle. Although light input to the clock is well studied, the molecular mechanisms by which circadian clocks respond to temperature remain poorly understood. We found that temperature phase shifts Drosophila circadian clocks through degradation of the pacemaker protein TIM. This degradation is mechanistically distinct from photic CRY-dependent TIM degradation. Thermal TIM degradation is triggered by cytosolic calcium increase and CALMODULIN binding to TIM and is mediated by the atypical calpain protease SOL. This thermal input pathway and CRY-dependent light input thus converge on TIM, providing a molecular mechanism for the integration of circadian light and temperature inputs. Mammals use body temperature cycles to keep peripheral clocks synchronized with their brain pacemaker. Interestingly, downregulating the mammalian SOL homolog SOLH blocks thermal mPER2 degradation and phase shifts. Thus, we propose that circadian thermosensation in insects and mammals share common principles. PMID:26590423

  17. Optical clocks and their contribution to gravity modeling

    Science.gov (United States)

    Naeimi, Mohammad; Mohamadhosseini, Babak; Hatami, Mohsen

    2016-04-01

    Optical clocks, as one of the latest achievements in atomic and molecular physics, have applications more than timing, due to their accuracy and stability. In general relativity, gravitational potential differences in space and time, cause frequency difference in optical clocks. Hence, ultra precise optical clocks can be used as a tool to observe potential differences and consequently as a new gravimetry technique. In this contribution, we investigate the latest optical clocks based on atomic transition in Al+ and derive a simple equation for frequency change related to geo-potential differences. Moreover, we consider the capability of optical clocks for gravity modeling in combination with other gravity observations. Finally, the possibility to detect potential changes in geo-dynamically active zones, such as East-Asia and the requirements for such studies are discussed.

  18. Standard Clock in primordial density perturbations and cosmic microwave background

    Directory of Open Access Journals (Sweden)

    Xingang Chen

    2014-12-01

    Full Text Available Standard Clocks in the primordial epoch leave a special type of features in the primordial perturbations, which can be used to directly measure the scale factor of the primordial universe as a function of time a(t, thus discriminating between inflation and alternatives. We have started to search for such signals in the Planck 2013 data using the key predictions of the Standard Clock. In this Letter, we summarize the key predictions of the Standard Clock and present an interesting candidate example in Planck 2013 data. Motivated by this candidate, we construct and compute full Standard Clock models and use the more complete prediction to make more extensive comparison with data. Although this candidate is not yet statistically significant, we use it to illustrate how Standard Clocks appear in Cosmic Microwave Background (CMB and how they can be further tested by future data. We also use it to motivate more detailed theoretical model building.

  19. A New Trapped Ion Clock Based on Hg-201(+)

    Science.gov (United States)

    Taghavi-Larigani, S.; Burt, E. A.; Lea, S. N.; Prestage, J. D.; Tjoelker, R. L.

    2009-01-01

    There are two stable odd isotopes of mercury with singly ionized hyperfine structure suitable for a microwave clock: Hg-199(+) and Hg-201(+). Virtually all trapped mercury ion clocks to date have used the 199 isotope. We have begun to investigate the viability of a trapped ion clock based on Hg-201(+). We have measured the unperturbed frequency of the (S-2)(sub 1/2) F = 1, m(sub F) = 0 to (S-2)(sub 1/2) F = 2, m(sub F) = 0 clock transition to be 29.9543658211(2) GHz. In this paper we describe initial measurements with Hg-201(+) and new applications to clocks and fundamental physics.

  20. Measurement methods and algorithms for comparison of local and remote clocks

    Science.gov (United States)

    Levine, Judah

    1993-01-01

    Several methods for characterizing the performance of clocks with special emphasis on using calibration information that is acquired via an unreliable or noisy channel is discussed. Time-domain variance estimators and frequency-domain techniques such as cross-spectral analysis are discussed. Each of these methods has advantages and limitations that will be illustrated using data obtained via GPS, ACTS, and other methods. No one technique will be optimum for all of these analyses, and some of these problems cannot be completely characterized by any of the techniques discussed. The inverse problem of communicating frequency and time corrections to a real-time steered clock are also discussed. Methods were developed to mitigate the disastrous problems of data corruption and loss of computer control.

  1. The Retina and other Light Sensitive Ocular Clocks

    Science.gov (United States)

    Besharse, Joseph C.; McMahon, Douglas G.

    2017-01-01

    Ocular clocks, first identified in the retina, are also found in the retinal pigment epithelium (RPE), cornea and ciliary body. The retina is a complex tissue of many cell types and considerable effort has gone into determining which cell types exhibit clock properties. Current data suggest that photoreceptors as well as inner retinal neurons exhibit clock properties with photoreceptors dominating in non-mammalian vertebrates and inner retinal neurons dominating in mice. However, these differences may in part reflect the choice of circadian output, and it is likely that clock properties are widely dispersed among many retinal cell types. The phase of the retinal clock can be set directly by light. In non-mammalian vertebrates direct light sensitivity is commonplace among body clocks, but in mice only the retina and cornea retain direct light-dependent phase regulation. This distinguishes the retina and possibly other ocular clocks from peripheral oscillators whose phase depends on the pace-making properties of the hypothalamic central brain clock, the suprachiasmatic nuclei (SCN). However, in mice retinal circadian oscillations dampen quickly in isolation due to weak coupling of its individual cell autonomous oscillators and there is no evidence that retinal clocks are directly controlled through input from other oscillators. Retinal circadian regulation in both mammals and non-mammalian vertebrates uses melatonin and dopamine as dark- and light-adaptive neuromodulators respectively, and light can regulate circadian phase indirectly through dopamine signaling. The melatonin/dopamine system appears to have evolved among non-mammalian vertebrates and retained with modification in mammals. Circadian clocks in the eye are critical for optimum visual function where they play a role fine tuning visual sensitivity, and their disruption can impact diseases such as glaucoma or retinal degeneration syndromes. PMID:27095816

  2. Circadian Clock Involvement in Zooplankton Diel Vertical Migration.

    Science.gov (United States)

    Häfker, N Sören; Meyer, Bettina; Last, Kim S; Pond, David W; Hüppe, Lukas; Teschke, Mathias

    2017-07-24

    Biological clocks are a ubiquitous ancient and adaptive mechanism enabling organisms to anticipate environmental cycles and to regulate behavioral and physiological processes accordingly [1]. Although terrestrial circadian clocks are well understood, knowledge of clocks in marine organisms is still very limited [2-5]. This is particularly true for abundant species displaying large-scale rhythms like diel vertical migration (DVM) that contribute significantly to shaping their respective ecosystems [6]. Here we describe exogenous cycles and endogenous rhythms associated with DVM of the ecologically important and highly abundant planktic copepod Calanus finmarchicus. In the laboratory, C. finmarchicus shows circadian rhythms of DVM, metabolism, and most core circadian clock genes (clock, period1, period2, timeless, cryptochrome2, and clockwork orange). Most of these genes also cycle in animals assessed in the wild, though expression is less rhythmic at depth (50-140 m) relative to shallow-caught animals (0-50 m). Further, peak expressions of clock genes generally occurred at either sunset or sunrise, coinciding with peak migration times. Including one of the first field investigations of clock genes in a marine species [5, 7], this study couples clock gene measurements with laboratory and field data on DVM. While the mechanistic connection remains elusive, our results imply a high degree of causality between clock gene expression and one of the planet's largest daily migrations of biomass. We thus suggest that circadian clocks increase zooplankton fitness by optimizing the temporal trade-off between feeding and predator avoidance, especially when environmental drivers are weak or absent [8]. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  3. Math Clock: Perangkat Penunjuk Waktu Kreatif untuk Olahraga Otak

    Directory of Open Access Journals (Sweden)

    Galuh Boy Hertantyo

    2014-11-01

    Full Text Available Brain is one of the most vital parts for humans, with the number of brain function that is needed for the body, the brain becomes a very important part of the human body. If there is damage to the brain will certainly cause the performance of the human body will not run properly. Because of that, it’s very important to maintain brain health. There is a way to maintain brain health, for example is by doing brain exercise. Examples of brain exercise is to do simple math calculations or doing brain games like sudoku. Because of that, created a tool that can help the brain to maintain brain exercise. The tool is called math clock. Making math clock tool consists of hardware and software. The hardware consists of RTC as real time data input, ATmega328 as microcontroller and dot matrix 32x16 as a tool to display the output that has been processed by the microcontroller. The software is built using C with Arduino IDE. Math clock will process the data from RTC then processed it, in microcontroller so when output displayed on dot matrix, output will be simple mathematical operation with real time clock data on it. Test results show that, math clock is capable of displaying a simple mathematical calculation operations such as addition, subtraction, multiplication and division. The mathematical operation that display on math clock, appears to be random, so it’s not triggered by same mathematical operation. In math clock the display will change every 20 second, so in 1 minute there are 3 different kinds of mathematical operations. The results of questionnaires of 10 different students, showed 9 out of 10 students said math clock is a tool that easy to use as a clock. Math clock will be alternative for doing brain exercise every day.

  4. More strictly protected areas are not necessarily more protective: evidence from Bolivia, Costa Rica, Indonesia, and Thailand

    International Nuclear Information System (INIS)

    Ferraro, Paul J; Hanauer, Merlin M; Miteva, Daniela A; Pattanayak, Subhrendu K; Canavire-Bacarreza, Gustavo Javier; Sims, Katharine R E

    2013-01-01

    National parks and other protected areas are at the forefront of global efforts to protect biodiversity and ecosystem services. However, not all protection is equal. Some areas are assigned strict legal protection that permits few extractive human uses. Other protected area designations permit a wider range of uses. Whether strictly protected areas are more effective in achieving environmental objectives is an empirical question: although strictly protected areas legally permit less anthropogenic disturbance, the social conflicts associated with assigning strict protection may lead politicians to assign strict protection to less-threatened areas and may lead citizens or enforcement agents to ignore the strict legal restrictions. We contrast the impacts of strictly and less strictly protected areas in four countries using IUCN designations to measure de jure strictness, data on deforestation to measure outcomes, and a quasi-experimental design to estimate impacts. On average, stricter protection reduced deforestation rates more than less strict protection, but the additional impact was not always large and sometimes arose because of where stricter protection was assigned rather than regulatory strictness per se. We also show that, in protected area studies contrasting y management regimes, there are y 2 policy-relevant impacts, rather than only y, as earlier studies have implied. (letter)

  5. On the age of eukaryotes: evaluating evidence from fossils and molecular clocks.

    Science.gov (United States)

    Eme, Laura; Sharpe, Susan C; Brown, Matthew W; Roger, Andrew J

    2014-08-01

    Our understanding of the phylogenetic relationships among eukaryotic lineages has improved dramatically over the few past decades thanks to the development of sophisticated phylogenetic methods and models of evolution, in combination with the increasing availability of sequence data for a variety of eukaryotic lineages. Concurrently, efforts have been made to infer the age of major evolutionary events along the tree of eukaryotes using fossil-calibrated molecular clock-based methods. Here, we review the progress and pitfalls in estimating the age of the last eukaryotic common ancestor (LECA) and major lineages. After reviewing previous attempts to date deep eukaryote divergences, we present the results of a Bayesian relaxed-molecular clock analysis of a large dataset (159 proteins, 85 taxa) using 19 fossil calibrations. We show that for major eukaryote groups estimated dates of divergence, as well as their credible intervals, are heavily influenced by the relaxed molecular clock models and methods used, and by the nature and treatment of fossil calibrations. Whereas the estimated age of LECA varied widely, ranging from 1007 (943-1102) Ma to 1898 (1655-2094) Ma, all analyses suggested that the eukaryotic supergroups subsequently diverged rapidly (i.e., within 300 Ma of LECA). The extreme variability of these and previously published analyses preclude definitive conclusions regarding the age of major eukaryote clades at this time. As more reliable fossil data on eukaryotes from the Proterozoic become available and improvements are made in relaxed molecular clock modeling, we may be able to date the age of extant eukaryotes more precisely. Copyright © 2014 Cold Spring Harbor Laboratory Press; all rights reserved.

  6. An Overview of Monthly Rhythms and Clocks

    Directory of Open Access Journals (Sweden)

    Florian Raible

    2017-05-01

    Full Text Available Organisms have evolved to cope with geophysical cycles of different period lengths. In this review, we focus on the adaptations of animals to the lunar cycle, specifically, on the occurrence of biological rhythms with monthly (circalunar or semi-monthly (circasemilunar period lengths. Systematic experimental investigation, starting in the early twentieth century, has allowed scientists to distinguish between mythological belief and scientific facts concerning the influence of the lunar cycle on animals. These studies revealed that marine animals of various taxa exhibit circalunar or circasemilunar reproductive rhythms. Some of these rely on endogenous oscillators (circalunar or circasemilunar clocks, whereas others are directly driven by external cues, such as the changes in nocturnal illuminance. We review current insight in the molecular and cellular mechanisms involved in circalunar rhythms, focusing on recent work in corals, annelid worms, midges, and fishes. In several of these model systems, the transcript levels of some core circadian clock genes are affected by both light and endogenous circalunar oscillations. How these and other molecular changes relate to the changes in physiology or behavior over the lunar cycle remains to be determined. We further review the possible relevance of circalunar rhythms for terrestrial species, with a particular focus on mammalian reproduction. Studies on circalunar rhythms of conception or birth rates extend to humans, where the lunar cycle was suggested to also affect sleep and mental health. While these reports remain controversial, factors like the increase in “light pollution” by artificial light might contribute to discrepancies between studies. We finally discuss the existence of circalunar oscillations in mammalian physiology. We speculate that these oscillations could be the remnant of ancient circalunar oscillators that were secondarily uncoupled from a natural entrainment mechanism, but

  7. Strict Monotonicity and Unique Continuation for the Third-Order Spectrum of Biharmonic Operator

    Directory of Open Access Journals (Sweden)

    Khalil Ben Haddouch

    2012-01-01

    Full Text Available We will study the spectrum for the biharmonic operator involving the laplacian and the gradient of the laplacian with weight, which we call third-order spectrum. We will show that the strict monotonicity of the eigenvalues of the operator , where , holds if some unique continuation property is satisfied by the corresponding eigenfunctions.

  8. "Let the Master Respond": Should Schools Be Strictly Liable When Employees Sexually Abuse Children?

    Science.gov (United States)

    Fossey, Richard; DeMitchell, Todd

    Although sexual abuse against children is a problem in the public schools, school officials have generally not acted aggressively to stop it. This paper argues for a strict liability standard--the assessment of liability without fault--against a school district in cases of student sexual abuse by a school employee. Part 1 explores the principle of…

  9. Detection of low numbers of microplastics in North Sea fish using strict quality assurance criteria

    NARCIS (Netherlands)

    Hermsen, E.; Pompe, R.; Besseling, E.; Koelmans, A.A.

    2017-01-01

    We investigated 400 individual fish of four North Sea species: Atlantic Herring, Sprat, Common Dab, and Whiting on ingestion of > 20 μm microplastic. Strict quality assurance criteria were followed in order to control contamination during the study. Two plastic particles were found in only 1 (a

  10. History, administration, goals, values, and long-term data of Russia's strictly protected scientific nature reserves

    Science.gov (United States)

    Martin A. Spetich; Anna E. Kvashnina; Y.D. Nukhimovskya; Olin E. Jr. Rhodes

    2009-01-01

    One of the most comprehensive attempts at biodiversity conservation in Russia and the former Soviet Union has been the establishment of an extensive network of protected natural areas. Among all types of protected areas in Russia, zapovedniks (strictly protected scientific preserve) have been the most effective in protecting biodiversity at the ecosystem scale. Russia...

  11. The Preventive Effect of Strict Gun Control Laws on Suicide and Homicide.

    Science.gov (United States)

    Lester, David; Murrell, Mary E.

    1982-01-01

    Examined state gun control laws and used a multidimensional scaling technique to study the relationship of strictness and death rates. Results showed states with stricter laws had lower suicide rates by firearms but higher rates by other means. No effect on homicide was found. (JAC)

  12. Cryptochrome mediates light-dependent magnetosensitivity of Drosophila's circadian clock.

    Directory of Open Access Journals (Sweden)

    Taishi Yoshii

    2009-04-01

    Full Text Available Since 1960, magnetic fields have been discussed as Zeitgebers for circadian clocks, but the mechanism by which clocks perceive and process magnetic information has remained unknown. Recently, the radical-pair model involving light-activated photoreceptors as magnetic field sensors has gained considerable support, and the blue-light photoreceptor cryptochrome (CRY has been proposed as a suitable molecule to mediate such magnetosensitivity. Since CRY is expressed in the circadian clock neurons and acts as a critical photoreceptor of Drosophila's clock, we aimed to test the role of CRY in magnetosensitivity of the circadian clock. In response to light, CRY causes slowing of the clock, ultimately leading to arrhythmic behavior. We expected that in the presence of applied magnetic fields, the impact of CRY on clock rhythmicity should be altered. Furthermore, according to the radical-pair hypothesis this response should be dependent on wavelength and on the field strength applied. We tested the effect of applied static magnetic fields on the circadian clock and found that flies exposed to these fields indeed showed enhanced slowing of clock rhythms. This effect was maximal at 300 muT, and reduced at both higher and lower field strengths. Clock response to magnetic fields was present in blue light, but absent under red-light illumination, which does not activate CRY. Furthermore, cry(b and cry(OUT mutants did not show any response, and flies overexpressing CRY in the clock neurons exhibited an enhanced response to the field. We conclude that Drosophila's circadian clock is sensitive to magnetic fields and that this sensitivity depends on light activation of CRY and on the applied field strength, consistent with the radical pair mechanism. CRY is widespread throughout biological systems and has been suggested as receptor for magnetic compass orientation in migratory birds. The present data establish the circadian clock of Drosophila as a model system

  13. GPS satellite clock determination in case of inter-frequency clock biases for triple-frequency precise point positioning

    Science.gov (United States)

    Guo, Jiang; Geng, Jianghui

    2017-12-01

    Significant time-varying inter-frequency clock biases (IFCBs) within GPS observations prevent the application of the legacy L1/L2 ionosphere-free clock products on L5 signals. Conventional approaches overcoming this problem are to estimate L1/L5 ionosphere-free clocks in addition to their L1/L2 counterparts or to compute IFCBs between the L1/L2 and L1/L5 clocks which are later modeled through a harmonic analysis. In contrast, we start from the undifferenced uncombined GNSS model and propose an alternative approach where a second satellite clock parameter dedicated to the L5 signals is estimated along with the legacy L1/L2 clock. In this manner, we do not need to rely on the correlated L1/L2 and L1/L5 ionosphere-free observables which complicates triple-frequency GPS stochastic models, or account for the unfavorable time-varying hardware biases in undifferenced GPS functional models since they can be absorbed by the L5 clocks. An extra advantage over the ionosphere-free model is that external ionosphere constraints can potentially be introduced to improve PPP. With 27 days of triple-frequency GPS data from globally distributed stations, we find that the RMS of the positioning differences between our GPS model and all conventional models is below 1 mm for all east, north and up components, demonstrating the effectiveness of our model in addressing triple-frequency observations and time-varying IFCBs. Moreover, we can combine the L1/L2 and L5 clocks derived from our model to calculate precisely the L1/L5 clocks which in practice only depart from their legacy counterparts by less than 0.006 ns in RMS. Our triple-frequency GPS model proves convenient and efficient in combating time-varying IFCBs and can be generalized to more than three frequency signals for satellite clock determination.

  14. Integration of biological clocks and rhythms.

    Science.gov (United States)

    Refinetti, Roberto

    2012-04-01

    Animals, plants, and microorganisms exhibit numerous biological rhythms that are generated by numerous biological clocks. This article summarizes experimental data pertinent to the often-ignored issue of integration of multiple rhythms. Five contexts of integration are discussed: (i) integration of circadian rhythms of multiple processes within an individual organism, (ii) integration of biological rhythms operating in different time scales (such as tidal, daily, and seasonal), (iii) integration of rhythms across multiple species, (iv) integration of rhythms of different members of a species, and (v) integration of rhythmicity and physiological homeostasis. Understanding of these multiple rhythmic interactions is an important first step in the eventual thorough understanding of how organisms arrange their vital functions temporally within and without their bodies. © 2012 American Physiological Society. Compr Physiol 2:1213-1239, 2012.

  15. Polarizabilities of the beryllium clock transition

    International Nuclear Information System (INIS)

    Mitroy, J.

    2010-01-01

    The polarizabilities of the three lowest states of the beryllium atom are determined from a large basis configuration interaction calculation. The polarizabilities of the 2s 2 1 S e ground state (37.73a 0 3 ) and the 2s2p 3 P 0 o metastable state (39.04a 0 3 ) are found to be very similar in size and magnitude. This leads to an anomalously small blackbody radiation shift at 300 K of -0.018(4) Hz for the 2s 2 1 S e -2s2p 3 P 0 o clock transition. Magic wavelengths for simultaneous trapping of the ground and metastable states are also computed.

  16. Cosmic time dilation: The clock paradox revisited

    International Nuclear Information System (INIS)

    Tomaschitz, Roman

    2004-01-01

    The relativistic time dilation is reviewed in a cosmological context. We show that a clock or twin paradox does not arise if cosmic time is properly taken into account. The receding galaxy background provides a unique frame of reference, and the proper times of geodesic as well as accelerated observers can be linked to the universal cosmic time parameter. This suggests to compare the proper time differentials of the respective observers by determining their state of motion in the galaxy grid. In this way, each observer can figure out whether his proper time is dilated or contracted relative to any other. In particular one can come to unambiguous conclusions on the aging of uniformly moving observers, without reference to asymmetries in measurement procedures or accelerations they may have undergone

  17. Somitogenesis clock-wave initiation requires differential decay and multiple binding sites for clock protein.

    Directory of Open Access Journals (Sweden)

    Mark Campanelli

    2010-04-01

    Full Text Available Somitogenesis is a process common to all vertebrate embryos in which repeated blocks of cells arise from the presomitic mesoderm (PSM to lay a foundational pattern for trunk and tail development. Somites form in the wake of passing waves of periodic gene expression that originate in the tailbud and sweep posteriorly across the PSM. Previous work has suggested that the waves result from a spatiotemporally graded control protein that affects the oscillation rate of clock-gene expression. With a minimally constructed mathematical model, we study the contribution of two control mechanisms to the initial formation of this gene-expression wave. We test four biologically motivated model scenarios with either one or two clock protein transcription binding sites, and with or without differential decay rates for clock protein monomers and dimers. We examine the sensitivity of wave formation with respect to multiple model parameters and robustness to heterogeneity in cell population. We find that only a model with both multiple binding sites and differential decay rates is able to reproduce experimentally observed waveforms. Our results show that the experimentally observed characteristics of somitogenesis wave initiation constrain the underlying genetic control mechanisms.

  18. Optical lattice clock with strontium atoms: a second generation of cold atom clocks

    International Nuclear Information System (INIS)

    Le Targat, R.

    2007-07-01

    Atomic fountains, based on a microwave transition of Cesium or Rubidium, constitute the state of the art atomic clocks, with a relative accuracy close to 10 -16 . It nevertheless appears today that it will be difficult to go significantly beyond this level with this kind of device. The use of an optical transition, the other parameters being unchanged, gives hope for a 4 or 5 orders of magnitude improvement of the stability and of the relative uncertainty on most systematic effects. As for motional effects on the atoms, they can be controlled on a very different manner if they are trapped in an optical lattice instead of experiencing a free ballistic flight stage, characteristic of fountains. The key point of this approach lies in the fact that the trap can be operated in such a way that a well chosen, weakly allowed, J=0 → J=0 clock transition can be free from light shift effects. In this respect, the strontium atom is one of the most promising candidate, the 1S 0 → 3P 0 transition has a natural width of 1 mHz, and several other easily accessible transitions can be used to efficiently laser cool atoms down to 10 μK. This thesis demonstrates the experimental feasibility of an optical lattice clock based on the strontium atom, and reports on a preliminary evaluation of the relative accuracy with the fermionic isotope 87 Sr, at a level of a few 10 -15 . (author)

  19. A strontium lattice clock with reduced blackbody radiation shift

    Energy Technology Data Exchange (ETDEWEB)

    Al-Masoudi, Ali Khalas Anfoos

    2016-09-30

    Optical clocks have been quickly moving to the forefront of the frequency standards field due to their high spectral resolution, and therefore the potential high stability and accuracy. The accuracy and stability of the optical clocks are nowadays two orders of magnitude better than microwave Cs clocks, which realize the SI second. Envisioned applications of highly accurate optical clocks are to perform tests of fundamental physics, for example, searching for temporal drifts of the fine structure constant α, violations of the Local Position Invariance (LPI), dark matter and dark energy, or to performance relativistic geodesy. In this work, the uncertainty of a strontium lattice clock, based on the {sup 1}S{sub 0}-{sup 3}P{sub 0} transition in {sup 87}Sr, due to the blackbody radiation (BBR) shift has been reduced to less than 1 x 10{sup -18} by more than one order of magnitude compared to the previous evaluation of the BBR shift uncertainty in this clock. The BBR shift has been reduced by interrogating the atoms in a cryogenic environment. The systematic uncertainty of the cryogenic lattice clock is evaluated to be 1.3 x 10{sup -17} which is dominated by the uncertainty of the AC Stark shift of the lattice laser and the uncertainty contribution of the BBR shift is negligible. Concerning the instability of the clock, the detection noise of the clock has been measured, and a model linking noise and clock instability has been developed. This noise model shows that, in our lattice clock, quantum projection noise is reached if more than 130 atoms are interrogated. By combining the noise model with the degradation due to the Dick effect reflecting the frequency noise of the interrogation laser, the instability of the clock is estimated to be 1.6 x 10{sup -16}/√(τ/s) in regular operation. During this work, several high-accuracy comparisons to other atomic clocks have been performed, including several absolute frequency measurements. The Sr clock transition frequency

  20. CLOCK Acetylates ASS1 to Drive Circadian Rhythm of Ureagenesis.

    Science.gov (United States)

    Lin, Ran; Mo, Yan; Zha, Haihong; Qu, Zhipeng; Xie, Pancheng; Zhu, Zheng-Jiang; Xu, Ying; Xiong, Yue; Guan, Kun-Liang

    2017-10-05

    In addition to responding to environmental entrainment with diurnal variation, metabolism is also tightly controlled by cell-autonomous circadian clock. Extensive studies have revealed key roles of transcription in circadian control. Post-transcriptional regulation for the rhythmic gating of metabolic enzymes remains elusive. Here, we show that arginine biosynthesis and subsequent ureagenesis are collectively regulated by CLOCK (circadian locomotor output cycles kaput) in circadian rhythms. Facilitated by BMAL1 (brain and muscle Arnt-like protein), CLOCK directly acetylates K165 and K176 of argininosuccinate synthase (ASS1) to inactivate ASS1, which catalyzes the rate-limiting step of arginine biosynthesis. ASS1 acetylation by CLOCK exhibits circadian oscillation in human cells and mouse liver, possibly caused by rhythmic interaction between CLOCK and ASS1, leading to the circadian regulation of ASS1 and ureagenesis. Furthermore, we also identified NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 9 (NDUFA9) and inosine-5'-monophosphate dehydrogenase 2 (IMPDH2) as acetylation substrates of CLOCK. Taken together, CLOCK modulates metabolic rhythmicity by acting as a rhythmic acetyl-transferase for metabolic enzymes. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. How does general anaesthesia affect the circadian clock?

    Science.gov (United States)

    Poulsen, Raewyn C; Warman, Guy R; Sleigh, Jamie; Ludin, Nicola M; Cheeseman, James F

    2018-02-01

    Post-operative patients experience sleep disturbances. Animal studies demonstrate that general anaesthesia (GA) can disrupt circadian rhythms and cause changes in the molecular clock, indicating that anaesthesia contributes to post-operative circadian disruption. Here we review the effect of anaesthesia on the circadian clock and its rhythms in order to summarise current findings outline commonalities between studies and propose mechanisms by which effects may be mediated. 1) GA has strong effects on the main neurotransmitter systems linked with circadian control (Gamma aminobutyric acid/N-methyl-D-aspartate (GABA/NMDA)) and may act by interfering with light-entrainment of the clock. 2) Expression of the core clock gene per2 is inhibited by GA (possibly via a NMDA/glycogen synthase kinase 3β (GSK3β) pathway). 3) GA's effect on circadian rhythms appears greatest when administered during animals' active phases 4) GA may have different effects when administered under free-running and entrained conditions. 5) Anaesthesia may mimic the mechanism involved in adaptation of the clock to changes in daylength. There is agreement that GA can strongly affect the circadian clock. How anaesthesia-induced changes in the molecular clock lead to changes in behaviour remains unclear. The answer, and what it may mean for patients post-operatively, will rely on systematic studies at molecular, behavioural, and clinical levels using standardised protocols. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Diurnal Oscillations of Soybean Circadian Clock and Drought Responsive Genes

    Science.gov (United States)

    Marcolino-Gomes, Juliana; Rodrigues, Fabiana Aparecida; Fuganti-Pagliarini, Renata; Bendix, Claire; Nakayama, Thiago Jonas; Celaya, Brandon; Molinari, Hugo Bruno Correa; de Oliveira, Maria Cristina Neves; Harmon, Frank G.; Nepomuceno, Alexandre

    2014-01-01

    Rhythms produced by the endogenous circadian clock play a critical role in allowing plants to respond and adapt to the environment. While there is a well-established regulatory link between the circadian clock and responses to abiotic stress in model plants, little is known of the circadian system in crop species like soybean. This study examines how drought impacts diurnal oscillation of both drought responsive and circadian clock genes in soybean. Drought stress induced marked changes in gene expression of several circadian clock-like components, such as LCL1-, GmELF4- and PRR-like genes, which had reduced expression in stressed plants. The same conditions produced a phase advance of expression for the GmTOC1-like, GmLUX-like and GmPRR7-like genes. Similarly, the rhythmic expression pattern of the soybean drought-responsive genes DREB-, bZIP-, GOLS-, RAB18- and Remorin-like changed significantly after plant exposure to drought. In silico analysis of promoter regions of these genes revealed the presence of cis-elements associated both with stress and circadian clock regulation. Furthermore, some soybean genes with upstream ABRE elements were responsive to abscisic acid treatment. Our results indicate that some connection between the drought response and the circadian clock may exist in soybean since (i) drought stress affects gene expression of circadian clock components and (ii) several stress responsive genes display diurnal oscillation in soybeans. PMID:24475115

  3. GNSS Clock Error Impacts on Radio Occultation Retrievals

    Science.gov (United States)

    Weiss, Jan; Sokolovskiy, Sergey; Schreiner, Bill; Yoon, Yoke

    2017-04-01

    We assess the impacts of GPS and GLONASS clock errors on radio occultation retrieval of bending angle, refractivity, and temperature from low Earth orbit. The major contributing factor is the interpretation of GNSS clock offsets sampled at 30 sec or longer intervals. Using 1 Hz GNSS clock estimates as truth we apply several interpolation and fitting schemes to evaluate how they affect the accuracy of atmospheric retrieval products. The results are organized by GPS and GLONASS space vehicle and the GNSS clock interpolation/fitting scheme. We find that bending angle error is roughly similar for all current GPS transmitters (about 0.7 mcrad) but note some differences related to the type of atomic oscillator onboard the transmitter satellite. GLONASS bending angle errors show more variation over the constellation and are approximately two times larger than GPS. An investigation of the transmitter clock spectra reveals this is due to more power in periods between 2-10 sec. Retrieved refractivity and temperature products show clear differences between GNSS satellite generations, and indicate that GNSS clocks sampled at intervals smaller than 5 sec significantly improve accuracy, particularly for GLONASS. We conclude by summarizing the tested GNSS clock estimation and application strategies in the context of current and future radio occultation missions.

  4. Circadian clock-mediated regulation of blood pressure.

    Science.gov (United States)

    Douma, Lauren G; Gumz, Michelle L

    2017-12-02

    Most bodily functions vary over the course of a 24h day. Circadian rhythms in body temperature, sleep-wake cycles, metabolism, and blood pressure (BP) are just a few examples. These circadian rhythms are controlled by the central clock in the suprachiasmatic nucleus (SCN) of the hypothalamus and peripheral clocks located throughout the body. Light and food cues entrain these clocks to the time of day and this synchronicity contributes to the regulation of a variety of physiological processes with effects on overall health. The kidney, brain, nervous system, vasculature, and heart have been identified through the use of mouse models and clinical trials as peripheral clock regulators of BP. The dysregulation of this circadian pattern of BP, with or without hypertension, is associated with increased risk for cardiovascular disease. The mechanism of this dysregulation is unknown and is a growing area of research. In this review, we highlight research of human and mouse circadian models that has provided insight into the roles of these molecular clocks and their effects on physiological functions. Additional tissue-specific studies of the molecular clock mechanism are needed, as well as clinical studies including more diverse populations (different races, female patients, etc.), which will be critical to fully understand the mechanism of circadian regulation of BP. Understanding how these molecular clocks regulate the circadian rhythm of BP is critical in the treatment of circadian BP dysregulation and hypertension. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. Diurnal oscillations of soybean circadian clock and drought responsive genes.

    Directory of Open Access Journals (Sweden)

    Juliana Marcolino-Gomes

    Full Text Available Rhythms produced by the endogenous circadian clock play a critical role in allowing plants to respond and adapt to the environment. While there is a well-established regulatory link between the circadian clock and responses to abiotic stress in model plants, little is known of the circadian system in crop species like soybean. This study examines how drought impacts diurnal oscillation of both drought responsive and circadian clock genes in soybean. Drought stress induced marked changes in gene expression of several circadian clock-like components, such as LCL1-, GmELF4- and PRR-like genes, which had reduced expression in stressed plants. The same conditions produced a phase advance of expression for the GmTOC1-like, GmLUX-like and GmPRR7-like genes. Similarly, the rhythmic expression pattern of the soybean drought-responsive genes DREB-, bZIP-, GOLS-, RAB18- and Remorin-like changed significantly after plant exposure to drought. In silico analysis of promoter regions of these genes revealed the presence of cis-elements associated both with stress and circadian clock regulation. Furthermore, some soybean genes with upstream ABRE elements were responsive to abscisic acid treatment. Our results indicate that some connection between the drought response and the circadian clock may exist in soybean since (i drought stress affects gene expression of circadian clock components and (ii several stress responsive genes display diurnal oscillation in soybeans.

  6. Machine Learning Helps Identify CHRONO as a Circadian Clock Component

    Science.gov (United States)

    Venkataraman, Anand; Ramanathan, Chidambaram; Kavakli, Ibrahim H.; Hughes, Michael E.; Baggs, Julie E.; Growe, Jacqueline; Liu, Andrew C.; Kim, Junhyong; Hogenesch, John B.

    2014-01-01

    Over the last decades, researchers have characterized a set of “clock genes” that drive daily rhythms in physiology and behavior. This arduous work has yielded results with far-reaching consequences in metabolic, psychiatric, and neoplastic disorders. Recent attempts to expand our understanding of circadian regulation have moved beyond the mutagenesis screens that identified the first clock components, employing higher throughput genomic and proteomic techniques. In order to further accelerate clock gene discovery, we utilized a computer-assisted approach to identify and prioritize candidate clock components. We used a simple form of probabilistic machine learning to integrate biologically relevant, genome-scale data and ranked genes on their similarity to known clock components. We then used a secondary experimental screen to characterize the top candidates. We found that several physically interact with known clock components in a mammalian two-hybrid screen and modulate in vitro cellular rhythms in an immortalized mouse fibroblast line (NIH 3T3). One candidate, Gene Model 129, interacts with BMAL1 and functionally represses the key driver of molecular rhythms, the BMAL1/CLOCK transcriptional complex. Given these results, we have renamed the gene CHRONO (computationally highlighted repressor of the network oscillator). Bi-molecular fluorescence complementation and co-immunoprecipitation demonstrate that CHRONO represses by abrogating the binding of BMAL1 to its transcriptional co-activator CBP. Most importantly, CHRONO knockout mice display a prolonged free-running circadian period similar to, or more drastic than, six other clock components. We conclude that CHRONO is a functional clock component providing a new layer of control on circadian molecular dynamics. PMID:24737000

  7. High-precision multi-node clock network distribution

    Science.gov (United States)

    Chen, Xing; Cui, Yifan; Lu, Xing; Ci, Cheng; Zhang, Xuesong; Liu, Bo; Wu, Hong; Tang, Tingsong; Shi, Kebin; Zhang, Zhigang

    2017-10-01

    A high precision multi-node clock network for multiple users was built following the precise frequency transmission and time synchronization of 120 km fiber. The network topology adopts a simple star-shaped network structure. The clock signal of a hydrogen maser (synchronized with UTC) was recovered from a 120 km telecommunication fiber link and then was distributed to 4 sub-stations. The fractional frequency instability of all substations is in the level of 10-15 in a second and the clock offset instability is in sub-ps in root-mean-square average.

  8. Using optical clock to probe quantum many-body physics

    Science.gov (United States)

    Ye, Jun

    2016-05-01

    The progress of optical lattice clock has benefited greatly from the understanding of atomic interactions. At the same time, the precision of clock spectroscopy has been applied to explore many-body spin interactions including SU(N) symmetry. Our recent work on this combined front of quantum metrology and many-body physics includes the probe of spin-orbital physics in the lattice clock and the investigation of a Fermi degenerate gas of 105 87Sr atoms in a three-dimensional magic-wavelength optical lattice.

  9. Plant circadian clocks increase photosynthesis, growth, survival, and competitive advantage.

    Science.gov (United States)

    Dodd, Antony N; Salathia, Neeraj; Hall, Anthony; Kévei, Eva; Tóth, Réka; Nagy, Ferenc; Hibberd, Julian M; Millar, Andrew J; Webb, Alex A R

    2005-07-22

    Circadian clocks are believed to confer an advantage to plants, but the nature of that advantage has been unknown. We show that a substantial photosynthetic advantage is conferred by correct matching of the circadian clock period with that of the external light-dark cycle. In wild type and in long- and short-circadian period mutants of Arabidopsis thaliana, plants with a clock period matched to the environment contain more chlorophyll, fix more carbon, grow faster, and survive better than plants with circadian periods differing from their environment. This explains why plants gain advantage from circadian control.

  10. Open Core Protocol (OCP) Clock Domain Crossing Interfaces

    DEFF Research Database (Denmark)

    Herlev, Mathias; Poulsen, Christian Keis; Sparsø, Jens

    2014-01-01

    The open core protocol (OCP) is an openly licensed configurable and scalable interface protocol for on-chip subsystem communications. The protocol defines read and write transactions from a master towards a slave across a point-to-point connection and the protocol assumes a single common clock....... This paper presents the design of two OCP clock domain crossing interface modules that can be used to construct systems with multiple clock domains. An OCP interface typically has control signals related to both the master issuing a read or write request and the slave producing a response. If all...

  11. High-precision multi-node clock network distribution.

    Science.gov (United States)

    Chen, Xing; Cui, Yifan; Lu, Xing; Ci, Cheng; Zhang, Xuesong; Liu, Bo; Wu, Hong; Tang, Tingsong; Shi, Kebin; Zhang, Zhigang

    2017-10-01

    A high precision multi-node clock network for multiple users was built following the precise frequency transmission and time synchronization of 120 km fiber. The network topology adopts a simple star-shaped network structure. The clock signal of a hydrogen maser (synchronized with UTC) was recovered from a 120 km telecommunication fiber link and then was distributed to 4 sub-stations. The fractional frequency instability of all substations is in the level of 10 -15 in a second and the clock offset instability is in sub-ps in root-mean-square average.

  12. Light and circadian regulation of clock components aids flexible responses to environmental signals

    Science.gov (United States)

    Dixon, Laura E; Hodge, Sarah K; van Ooijen, Gerben; Troein, Carl; Akman, Ozgur E; Millar, Andrew J

    2014-01-01

    The circadian clock measures time across a 24 h period, increasing fitness by phasing biological processes to the most appropriate time of day. The interlocking feedback loop mechanism of the clock is conserved across species; however, the number of loops varies. Mathematical and computational analyses have suggested that loop complexity affects the overall flexibility of the oscillator, including its responses to entrainment signals. We used a discriminating experimental assay, at the transition between different photoperiods, in order to test this proposal in a minimal circadian network (in Ostreococcus tauri) and a more complex network (in Arabidopsis thaliana). Transcriptional and translational reporters in O. tauri primarily tracked dawn or dusk, whereas in A. thaliana, a wider range of responses were observed, consistent with its more flexible clock. Model analysis supported the requirement for this diversity of responses among the components of the more complex network. However, these and earlier data showed that the O. tauri network retains surprising flexibility, despite its simple circuit. We found that models constructed from experimental data can show flexibility either from multiple loops and/or from multiple light inputs. Our results suggest that O. tauri has adopted the latter strategy, possibly as a consequence of genomic reduction. PMID:24842166

  13. The origin of animals: Can molecular clocks and the fossil record be reconciled?

    Science.gov (United States)

    Cunningham, John A; Liu, Alexander G; Bengtson, Stefan; Donoghue, Philip C J

    2017-01-01

    The evolutionary emergence of animals is one of the most significant episodes in the history of life, but its timing remains poorly constrained. Molecular clocks estimate that animals originated and began diversifying over 100 million years before the first definitive metazoan fossil evidence in the Cambrian. However, closer inspection reveals that clock estimates and the fossil record are less divergent than is often claimed. Modern clock analyses do not predict the presence of the crown-representatives of most animal phyla in the Neoproterozoic. Furthermore, despite challenges provided by incomplete preservation, a paucity of phylogenetically informative characters, and uncertain expectations of the anatomy of early animals, a number of Neoproterozoic fossils can reasonably be interpreted as metazoans. A considerable discrepancy remains, but much of this can be explained by the limited preservation potential of early metazoans and the difficulties associated with their identification in the fossil record. Critical assessment of both records may permit better resolution of the tempo and mode of early animal evolution. © 2016 The Authors BioEssays Published by WILEY Periodicals, Inc.

  14. A Low-jitter 2.5-to-10 GHz Clock Multiplier Unit in CMOS

    NARCIS (Netherlands)

    van de Beek, R.C.H.; Vaucher, C.S.; Leenaerts, D.M.W.; Klumperink, Eric A.M.; Nauta, Bram

    2003-01-01

    Abstract— This paper demonstrates a low-jitter clock multiplier unit [1] that generates a 10 GHz output clock from a 2.5 GHz reference clock. An integrated 10 GHz LCoscillator is locked to the input clock, using a simple and fast phase detector circuit. This phase detector overcomes the speed

  15. Regulation of behavioral circadian rhythms and clock protein PER1 by the deubiquitinating enzyme USP2

    DEFF Research Database (Denmark)

    Yang, Yaoming; Duguay, David; Bédard, Nathalie

    2012-01-01

    Endogenous 24-hour rhythms are generated by circadian clocks located in most tissues. The molecular clock mechanism is based on feedback loops involving clock genes and their protein products. Post-translational modifications, including ubiquitination, are important for regulating the clock...

  16. Toward A Neutral Mercury Optical Lattice Clock: Determination of the Magic Wavelength for the Ultraviolet clock Transition

    International Nuclear Information System (INIS)

    Mejri, Sinda

    2012-01-01

    A lattice clock combines the advantages of ion and neutral atom based clocks, namely the recoil and first order Doppler free spectroscopy allowed by the Lamb-Dicke regime. This lattice light field shifts the energy levels of the clock transition. However a wavelength can be found where the light-shift of the clock states cancelled to first order. In this thesis, we present the latest advances in optical lattice clock with mercury atoms developed at LNE-SYRTE. After a review of the current performances of different optical clock are currently under development, we focus on the concept of optical lattice clock and the features of the mercury that make him an excellent candidate for the realization of an optical lattice clock achievement the uncertainty of the level of 10 -17 . The second part is devoted to the characterization of the mercury MOT, using a sensitive detection system, which allowed us to evaluate the temperature of different isotopes present in the MOT and have a good evidence of sub-Doppler cooling for the fermionic isotopes. The third part of this these, present the experimental aspects of the implementation and the development of the laser source required for trapping mercury atoms operating near the predicted magic wavelength. Finally, we report on the Lamb-Dicke spectroscopy of the 1S0 →3 P0 clock transition in the 199 Hg atoms confined in lattice trap. With use of the ultra-stable laser system, linked to LNE-SYRTE primary frequency reference, we have determined the center frequency of the transition for a range of lattice wavelengths and different lattice depths. Analyzing these measurement, we have carried out the first experimental determination of the magic wavelength, which is the crucial step towards achieving a highly accurate frequency standard using mercury. (author)

  17. A Criterium for the Strict Positivity of the Density of the Law of a Poisson Process

    Directory of Open Access Journals (Sweden)

    Léandre Rémi

    2011-01-01

    Full Text Available We translate in semigroup theory our result (Léandre, 1990 giving a necessary condition so that the law of a Markov process with jumps could have a strictly positive density. This result express, that we have to jump in a finite number of jumps in a "submersive" way from the starting point to the end point if the density of the jump process is strictly positive in . We use the Malliavin Calculus of Bismut type of (Léandre, (2008;2010 translated in semi-group theory as a tool, and the interpretation in semi-group theory of some classical results of the stochastic analysis for Poisson process as, for instance, the formula giving the law of a compound Poisson process.

  18. The effect of 8 days of strict bed rest on the incretin effect in healthy volunteers

    DEFF Research Database (Denmark)

    Nielsen, Signe Tellerup; Harder-Lauridsen, Nina Majlund; Benatti, Fabiana Braga

    2016-01-01

    in the levels of GLP-1 and Glucagon. Bed rest led to a mean loss of 2.4 kg of fat-free mass, and induced insulin resistance evaluated by the Matsuda index, but did not affect the incretin effect (P = 0.6). In conclusion, 8 days of bed rest induces insulin resistance, but we did not see evidence of an associated......Bed rest and physical inactivity are the consequences of hospital admission for many patients. Physical inactivity induces changes in glucose metabolism, but its effect on the incretin effect, which is reduced in, e.g., Type 2 diabetes, is unknown. To investigate how 8 days of strict bed rest...... affects the incretin effect, 10 healthy nonobese male volunteers underwent 8 days of strict bed rest. Before and after the intervention, all volunteers underwent an oral glucose tolerance test (OGTT) followed by an intravenous glucose infusion (IVGI) on the following day to mimic the blood glucose profile...

  19. Detection of low numbers of microplastics in North Sea fish using strict quality assurance criteria.

    Science.gov (United States)

    Hermsen, Enya; Pompe, Renske; Besseling, Ellen; Koelmans, Albert A

    2017-09-15

    We investigated 400 individual fish of four North Sea species: Atlantic Herring, Sprat, Common Dab, and Whiting on ingestion of >20μm microplastic. Strict quality assurance criteria were followed in order to control contamination during the study. Two plastic particles were found in only 1 (a Sprat) out of 400 individuals (0.25%, with a 95% confidence interval of 0.09-1.1%). The particles were identified to consist of polymethylmethacrylate (PMMA) through FTIR spectroscopy. No contamination occurred during the study, showing the method applied to be suitable for microplastic ingestion studies in biota. We discuss the low particle count for North Sea fish with those in other studies and suggest a relation between reported particle count and degree of quality assurance applied. Microplastic ingestion by fish may be less common than thought initially, with low incidence shown in this study, and other studies adhering to strict quality assurance criteria. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. A Hybrid P2P Overlay Network for Non-strictly Hierarchically Categorized Content

    Science.gov (United States)

    Wan, Yi; Asaka, Takuya; Takahashi, Tatsuro

    In P2P content distribution systems, there are many cases in which the content can be classified into hierarchically organized categories. In this paper, we propose a hybrid overlay network design suitable for such content called Pastry/NSHCC (Pastry for Non-Strictly Hierarchically Categorized Content). The semantic information of classification hierarchies of the content can be utilized regardless of whether they are in a strict tree structure or not. By doing so, the search scope can be restrained to any granularity, and the number of query messages also decreases while maintaining keyword searching availability. Through simulation, we showed that the proposed method provides better performance and lower overhead than unstructured overlays exploiting the same semantic information.

  1. Superradiance on the millihertz linewidth strontium clock transition

    Science.gov (United States)

    Norcia, Matthew A.; Winchester, Matthew N.; Cline, Julia R. K.; Thompson, James K.

    2016-01-01

    Laser frequency noise contributes a significant limitation to today’s best atomic clocks. A proposed solution to this problem is to create a superradiant laser using an optical clock transition as its gain medium. This laser would act as an active atomic clock and would be highly immune to the fluctuations in reference cavity length that limit today’s best lasers. We demonstrate and characterize superradiant emission from the millihertz linewidth clock transition in an ensemble of laser-cooled 87Sr atoms trapped within a high-finesse optical cavity. We measure a collective enhancement of the emission rate into the cavity mode by a factor of more than 10,000 compared to independently radiating atoms. We also demonstrate a method for seeding superradiant emission and observe interference between two independent transitions lasing simultaneously. We use this interference to characterize the relative spectral properties of the two lasing subensembles. PMID:27757423

  2. Multipolar Polarizabilities and Hyperpolarizabilities in the Sr Optical Lattice Clock

    Science.gov (United States)

    Porsev, S. G.; Safronova, M. S.; Safronova, U. I.; Kozlov, M. G.

    2018-02-01

    We address the problem of the lattice Stark shifts in the Sr clock caused by the multipolar M 1 and E 2 atom-field interactions and by the term nonlinear in lattice intensity and determined by the hyperpolarizability. We develop an approach to calculate hyperpolarizabilities for atoms and ions based on a solution of the inhomogeneous equation which allows us to effectively and accurately carry out complete summations over intermediate states. We apply our method to the calculation of the hyperpolarizabilities for the clock states in Sr. We also carry out an accurate calculation of the multipolar polarizabilities for these states at the magic frequency. Understanding these Stark shifts in optical lattice clocks is crucial for further improvement of the clock accuracy.

  3. The New PTB Caesium Fountain Clock CSF2

    National Research Council Canada - National Science Library

    Wynands, R; Bauch, A; Griebsch, D; Schroeder, R; Weyers, S

    2005-01-01

    At PTB a second caesium fountain clock, CSF2, is in the process of being set up. It differs from the first PTB caesium fountain standard CSF1 in a number of details, which are consecutively specified...

  4. A Summary of the GPS Constellation Clock Performance

    National Research Council Canada - National Science Library

    Oaks, Jay; Buisson, James A; Largay, Marie M

    2007-01-01

    ... (MCS) in Colorado Springs, Colorado. The analysis is based on clock estimates that NRL computes from GPS monitor station carrier-derived pseudo-range measurements and National Geospatial-Intelligence Agency (NGA...

  5. Cellular Clocks : Coupled Circadian Dispatch and Cell Division Cycles

    NARCIS (Netherlands)

    Merrow, Martha; Roenneberg, Till

    2004-01-01

    Gating of cell division by the circadian clock is well known, yet its mechanism is little understood. Genetically tractable model systems have led to new hypotheses and questions concerning the coupling of these two cellular cycles.

  6. CLOCK Genes and Circadian Rhythmicity in Alzheimer Disease

    Directory of Open Access Journals (Sweden)

    J. Thome

    2011-01-01

    Full Text Available Disturbed circadian rhythms with sleep problems and disrupted diurnal activity are often seen in patients suffering from Alzheimer disease (AD. Both endogenous CLOCK genes and external Zeitgeber are responsible for the maintenance of circadian rhythmicity in humans. Therefore, modifications of the internal CLOCK system and its interactions with exogenous factors might constitute the neurobiological basis for clinically observed disruptions in rhythmicity, which often have grave consequences for the quality of life of patients and their caregivers. Presently, more and more data are emerging demonstrating how alterations of the CLOCK gene system might contribute to the pathophysiology of AD and other forms of dementia. At the same time, the impact of neuropsychiatric medication on CLOCK gene expression is under investigation.

  7. Measurement of Magic Wavelengths for the ^{40}Ca^{+} Clock Transition.

    Science.gov (United States)

    Liu, Pei-Liang; Huang, Yao; Bian, Wu; Shao, Hu; Guan, Hua; Tang, Yong-Bo; Li, Cheng-Bin; Mitroy, J; Gao, Ke-Lin

    2015-06-05

    We demonstrate experimentally the existence of magic wavelengths and determine the ratio of oscillator strengths for a single trapped ion. For the first time, two magic wavelengths near 396 nm for the ^{40}Ca^{+} clock transition are measured simultaneously with high precision. By tuning the applied laser to an intermediate wavelength between transitions 4s_{1/2}→4p_{1/2} and 4s_{1/2}→4p_{3/2}, the sensitivity of the clock transition Stark shift to the oscillator strengths is greatly enhanced. Furthermore, with the measured magic wavelengths, we determine the ratio of the oscillator strengths with a deviation of less than 0.5%. Our experimental method may be applied to measure magic wavelengths for other ion clock transitions. Promisingly, the measurement of these magic wavelengths paves the way to building all-optical trapped ion clocks.

  8. Government and industry interactions in the development of clock technology

    Science.gov (United States)

    Hellwig, H.

    1981-01-01

    It appears likely that everyone in the time and frequency community can agree on goals to be realized through the expenditure of resources. These goals are the same as found in most fields of technology: lower cost, better performance, increased reliability, small size and lower power. Related aspects are examined in the process of clock and frequency standard development. Government and industry are reviewed in a highly interactive role. These interactions include judgements on clock performance, what kind of clock, expenditure of resources, transfer of ideas or hardware concepts from government to industry, and control of production. Successful clock development and production requires a government/industry relationship which is characterized by long-term continuity, multidisciplinary team work, focused funding and a separation of reliability and production oriented tasks from performance improvement/research type efforts.

  9. PHARAO space atomic clock: new developments on the laser source

    Science.gov (United States)

    Saccoccio, Muriel; Loesel, Jacques; Coatantiec, Claude; Simon, Eric; Laurent, Philippe; Lemonde, Pierre; Maksimovic, I.; Abgrall, M.

    2017-11-01

    The PHARAO project purpose is to open the way for a new atomic clock generation in space, where laser cooling techniques and microgravity allow high frequency stability and accuracy. The French space agency, CNES is funding and managing the clock construction. The French SYRTE and LKB laboratories are scientific and technical advisers for the clock requirements and the follow-up of subsystem development in industrial companies. EADS SODERN is developing two main subsystems of the PHARAO clock: the Laser Source and the Cesium Tube where atoms are cooled, launched, selected and detected by laser beams. The Laser Source includes an optical bench and electronic devices to generate the laser beams required. This paper describes PHARAO and the role laser beams play in its principle of operation. Then we present the Laser Source design, the technologies involved, and the status of development. Lastly, we focus of a key equipment to reach the performances expected, which is the Extended Cavity Laser Diode.

  10. Liter Sized Ion Clock with 10 (exp -15) Stability

    National Research Council Canada - National Science Library

    Prestage, J. D; Chang, S; Le, T; Lim, L; Maleki, L

    2005-01-01

    .... This development shows that Hmaser quality stabilities can be produced in a small clock package, comparable in size to an ultra-stable quartz oscillator required for holding 1-2x10-13 at 1 second...

  11. Weak asymptotic solution for a non-strictly hyperbolic system of conservation laws-II

    Directory of Open Access Journals (Sweden)

    Manas Ranjan Sahoo

    2016-04-01

    Full Text Available In this article we introduce a concept of entropy weak asymptotic solution for a system of conservation laws and construct the same for a prolonged system of conservation laws which is highly non-strictly hyperbolic. This is first done for Riemann type initial data by introducing $\\delta,\\delta',\\delta''$ waves along a discontinuity curve and then for general initial data by piecing together the Riemann solutions.

  12. Multiple-Set Split Feasibility Problems for κ-Strictly Pseudononspreading Mapping in Hilbert Spaces

    Directory of Open Access Journals (Sweden)

    Jing Quan

    2013-01-01

    Full Text Available The purpose of this paper is to prove some weak and strong convergence theorems for solving the multiple-set split feasibility problems for κ-strictly pseudononspreading mapping in infinite-dimensional Hilbert spaces by using the proposed iterative method. The main results presented in this paper extend and improve the corresponding results of Xu et al. (2006, of Osilike et al. (2011, and of many other authors.

  13. Multiobjective Optimization for the Forecasting Models on the Base of the Strictly Binary Trees

    OpenAIRE

    Nadezhda Astakhova; Liliya Demidova; Evgeny Nikulchev

    2016-01-01

    The optimization problem dealing with the development of the forecasting models on the base of strictly binary trees has been considered. The aim of paper is the comparative analysis of two optimization variants which are applied for the development of the forecasting models. Herewith the first optimization variant assumes the application of one quality indicator of the forecasting model named as the affinity indicator and the second variant realizes the application of two quality indicators ...

  14. Cannabis legalization with strict regulation, the overall superior policy option for public health.

    Science.gov (United States)

    Rehm, J; Fischer, B

    2015-06-01

    Cannabis is the most prevalently used drug globally, with many jurisdictions considering varying reform options to current policies to deal with this substance and associated harm. Three policy options are available: prohibition, decriminalization, and legalization, with prohibition currently the dominant model globally. This contribution gives reasons why legalization with strict regulation should be considered superior to other options with respect to public health in high income countries in North America. © 2015 ASCPT.

  15. Examination of the PCICE method in the nearly incompressible, as well as strictly incompressible, limits

    International Nuclear Information System (INIS)

    Berry, Ray A.; Martineau, Richard C.

    2007-01-01

    The conservative-form, pressure-based PCICE numerical method (Martineau and Berry, 2004) (Berry, 2006), recently developed for computing transient fluid flows of all speeds from very low to very high (with strong shocks), is simplified and generalized. Though the method automatically treats a continuous transition of compressibility, three distinct, limiting compressibility regimes are formally defined for purposes of discussion and comparison with traditional methods - the strictly incompressible limit, the nearly incompressible limit, and the fully compressible limit. The PCICE method's behavior is examined in each limiting regime. In the strictly incompressible limit the PCICE algorithm reduces to the traditional MAC-type method with velocity divergence driving the pressure Poisson equation. In the nearly incompressible limit the PCICE algorithm is found to reduce to a generalization of traditional incompressible methods, i.e. to one in which not only the velocity divergence effect, but also the density gradient effect is included as a driving function in the pressure Poisson equation. This nearly incompressible regime has received little attention, and it appears that in the past, strictly incompressible methods may have been conveniently applied to flows in this regime at the expense of ignoring a potentially important coupling mechanism. This could be significant in many important flows; for example, in natural convection flows resulting from high heat flux. In the fully compressible limit or regime, the algorithm is found to reduce to an expression equivalent to density-based methods for high-speed flow. (author)

  16. Frequency effect on p-nitrophenol degradation under conditions of strict acoustic and electric control

    Directory of Open Access Journals (Sweden)

    Chang-ping Zhu

    2011-03-01

    Full Text Available The process of decomposing p-nitrophenol (PNP with power ultrasound requires strict control of acoustic and electric conditions. In this study, the conditions, including acoustic power and acoustic intensity, but not ultrasonic frequency, were controlled strictly at constant levels. The absorbency and the COD concentrations of the samples were measured in order to show the variation of the sample concentration. The results show significant differences in the trend of the solution degradation rate as acoustic power increases after the PNP solution (with a concentration of 114 mg/L and a pH value of 5.4 is irradiated for 60 min with ultrasonic frequencies of 530.8 kHz, 610.6 kHz, 855.0 kHz, and 1 130.0 kHz. The degradation rate of the solution increases with time and acoustic power (acoustic intensity. On the other hand, the degradation rate of the solution is distinctly dependent on frequency when the acoustic power and intensity are strictly controlled and maintained at constant levels. The degradation rate of the PNP solution declines with ultrasonic frequencies of 530.8 kHz, 610.6 kHz, 855.0 kHz, and 1 130.0 kHz; the COD concentration, on the contrary, increase.

  17. TESTING STRICT HYDROSTATIC EQUILIBRIUM IN SIMULATED CLUSTERS OF GALAXIES: IMPLICATIONS FOR A1689

    International Nuclear Information System (INIS)

    Molnar, S. M.; Umetsu, K.; Chiu, I.-N.; Chen, P.; Hearn, N.; Broadhurst, T.; Bryan, G.; Shang, C.

    2010-01-01

    Accurate mass determination of clusters of galaxies is crucial if they are to be used as cosmological probes. However, there are some discrepancies between cluster masses determined based on gravitational lensing and X-ray observations assuming strict hydrostatic equilibrium (i.e., the equilibrium gas pressure is provided entirely by thermal pressure). Cosmological simulations suggest that turbulent gas motions remaining from hierarchical structure formation may provide a significant contribution to the equilibrium pressure in clusters. We analyze a sample of massive clusters of galaxies drawn from high-resolution cosmological simulations and find a significant contribution (20%-45%) from non-thermal pressure near the center of relaxed clusters, and, in accord with previous studies, a minimum contribution at about 0.1 R vir , growing to about 30%-45% at the virial radius, R vir . Our results strongly suggest that relaxed clusters should have significant non-thermal support in their core region. As an example, we test the validity of strict hydrostatic equilibrium in the well-studied massive galaxy cluster A1689 using the latest high-resolution gravitational lensing and X-ray observations. We find a contribution of about 40% from non-thermal pressure within the core region of A1689, suggesting an alternate explanation for the mass discrepancy: the strict hydrostatic equilibrium is not valid in this region.

  18. Temporary Strict Maternal Avoidance of Cow’s Milk and Infantile Colic

    Directory of Open Access Journals (Sweden)

    Firoozeh Sajedi

    2009-12-01

    Full Text Available Infant colic is a common problem characterized by excessive crying and fussing. We examined whether colic symptoms of exclusively breast-milk-fed infants would be improved by temporary strict maternal avoidance of cows milk. This study is analytic and experimental. Sixty-six subjects were recruited during winter of 2006 from a clinic in Isfahan, Iran. Breast-milk-fed in-fants with "colic", age 3-6 months and to be in otherwise good health were referred by pediatri-cians. The intervention was 1 week period of strict maternal avoidance of cows milk while they continued exclusive breast-milk-feeding. All infants showed improvement in distressed behavior (crying and fussing during intervention. The total recorded crying and fussing time was reduced by an average of 31%. A significant difference was found in cry and fuss time between first and last 2 days of intervention (P = 0.000. Cows milk proteins may play an etiologic role in colic. We propose that a brief intervention with strict maternal avoidance of cows milk may be an effective treatment for colic in some breast-milk-fed infants.

  19. Regulation of Clock Genes by Adrenergic Receptor Signaling in Osteoblasts.

    Science.gov (United States)

    Hirai, Takao

    2018-01-01

    The clock system has been identified as one of the major mechanisms controlling cellular functions. Circadian clock gene oscillations also actively participate in the functions of various cell types including bone-related cells. Previous studies demonstrated that clock genes were expressed in bone tissue and also that their expression exhibited circadian rhythmicity. Recent findings have shown that sympathetic tone plays a central role in biological oscillations in bone. Adrenergic receptor (AR) signaling regulates the expression of clock genes in cancellous bone. Furthermore, α 1 -AR signaling in osteoblasts is known to negatively regulate the expression of bone morphogenetic protein-4 (Bmp4) by up-regulating nuclear factor IL-3 (Nfil3)/e4 promoter-binding protein 4 (E4BP4). The ablation of α 1B -AR signaling also increases the expression of the Bmp4 gene in bone. The findings of transient overexpression and siRNA experiments have supported the involvement of the transcription factor CCAAT/enhancer-binding protein delta (C/EBPδ, Cebpd) in Nfil3 and Bmp4 expression in MC3T3-E1 cells. These findings suggest that the effects of Cebpd are due to the circadian regulation of Bmp4 expression, at least in part, by the up-regulated expression of the clock gene Nfil3 in response to α 1B -AR signaling in osteoblasts. Therefore, AR signaling appears to modulate cellular functionality through the expression of clock genes that are circadian rhythm regulators in osteoblasts. The expression of clock genes regulated by the sympathetic nervous system and clock-controlled genes that affect bone metabolism are described herein.

  20. Interpretable Machine Learning Models for the Digital Clock Drawing Test

    OpenAIRE

    Souillard-Mandar, William; Davis, Randall; Rudin, Cynthia; Au, Rhoda; Penney, Dana

    2016-01-01

    The Clock Drawing Test (CDT) is a rapid, inexpensive, and popular neuropsychological screening tool for cognitive conditions. The Digital Clock Drawing Test (dCDT) uses novel software to analyze data from a digitizing ballpoint pen that reports its position with considerable spatial and temporal precision, making possible the analysis of both the drawing process and final product. We developed methodology to analyze pen stroke data from these drawings, and computed a large collection of featu...

  1. Verification and Synthesis of Clock-Gated Circuits

    OpenAIRE

    Dai, Yu-Yun

    2017-01-01

    As system complexity and transistor density increase, the power consumed by digital integrated circuits has become a critical constraint for VLSI design and manufacturing.To reduce dynamic power dissipation, clock-gating synthesis techniques are applied to circuits to prune register updates by modifying the next-state functions of the registers. Hence to verify this kind of synthesis, sequential equivalence checking (SEC) of clock-gated circuits is required.In this thesis, we examine the appl...

  2. Clock Face Drawing Test Performance in Children with ADHD

    Directory of Open Access Journals (Sweden)

    Ahmad Ghanizadeh

    2013-01-01

    Full Text Available  Introduction: The utility and discriminatory pattern of the clock face drawing test in ADHD is unclear. This study therefore compared Clock Face Drawing test performance in children with ADHD and controls.   Material & methods: 95 children with ADHD and 191 school children were matched for gender ratio and age. ADHD symptoms severities were assessed using DSM-IV ADHD checklist and their intellectual functioning was assessed. The participants completed three clock-drawing tasks, and the following four functions were assessed: Contour score, Numbers score, Hands setting score, and Center score    Results: All the subscales scores of the three clock drawing tests of the ADHD group were lower than that of the control group. In ADHD children, inattention and hyperactivity/impulsivity scores were not related with free drawn clock test scores. When pre-drawn contour test was performed, inattentiveness score was statistically associated with Number score. None of the other variables of age, gender, intellectual functioning, and hand use preference were associated with Numbers score. In pre-drawn clock, no association of ADHD symptoms with any CDT subscales was significant. In addition, more errors are observed with free drawn clock and Pre-drawn contour than pre-drawn clock.    Conclusion: Putting Numbers and Hands setting are more sensitive measures to screen ADHD than Contour and Center drawing. Test performance, except Hands setting, may have already reached a developmental plateau. It is probable that Hand setting deficit in children with ADHD may not decrease from age 8 to 14 years. Performance of children with ADHD is associated with the complexity of CDT.

  3. Clock Synchronization Through Time-Variant Underwater Acoustic Channels

    Science.gov (United States)

    2012-09-01

    Pulse Interval SPI Synchronizing Pulse Interval LFM Linear Frequency - Modulated PDF Probability Density Function... frequency - modulated (LFM) chirp trains and pseudorandom (PRN) binary sequences as the most suitable types of probe signals. A key attribute of LFM and PRN...Reference Clock (B) Synchroni zing Clock (A) x x x x b Reference Pulse Interval (RPI) Synchroni zation Pul se Interval (SPI) 1 2 i n...... A y y y

  4. Protecting Clock Synchronization: Adversary Detection through Network Monitoring

    OpenAIRE

    Elena Lisova; Marina Gutiérrez; Wilfried Steiner; Elisabeth Uhlemann; Johan Åkerberg; Radu Dobrin; Mats Björkman

    2016-01-01

    Nowadays, industrial networks are often used for safety-critical applications with real-time requirements. Such applications usually have a time-triggered nature with message scheduling as a core property. Scheduling requires nodes to share the same notion of time, that is, to be synchronized. Therefore, clock synchronization is a fundamental asset in real-time networks. However, since typical standards for clock synchronization, for example, IEEE 1588, do not provide the required level of se...

  5. Clocking In Turbines: Remarks On Physical Nature And Geometric Requirements

    Directory of Open Access Journals (Sweden)

    Swirydczuk Jerzy

    2015-04-01

    Full Text Available The article discusses two issues relating to the clocking phenomenon in turbines, which are the physical course of stator wake deformation in rotor passages and its further interaction with downstream stator blades, and turbine geometry parameters which are believed to be most favourable for clocking. In both cases, the results presented in the article have made it possible to verify and reformulate the previously accepted opinions.

  6. Deficiency of circadian protein CLOCK reduces lifespan and increases age-related cataract development in mice

    OpenAIRE

    Dubrovsky, Yuliya V.; Samsa, William E.; Kondratov, Roman V.

    2010-01-01

    Circadian clock is implicated in the regulation of aging. The transcription factor CLOCK, a core component of the circadian system, operates in complex with another circadian clock protein BMAL1. Recently it was demonstrated that BMAL1 deficiency results in premature aging in mice. Here we investigate the aging of mice deficient for CLOCK protein. Deficiency of the CLOCK protein significantly affects longevity: the average lifespan of Clock−/− mice is reduced by 15% compared with wild type mi...

  7. Clock Technology Development in the Laser Cooling and Atomic Physics (LCAP) Program

    Science.gov (United States)

    Seidel, Dave; Thompson, R. J.; Klipstein, W. M.; Kohel, J.; Maleki, L.

    2000-01-01

    This paper presents the Laser Cooling and Atomic Physics (LCAP) program. It focuses on clock technology development. The topics include: 1) Overview of LCAP Flight Projects; 2) Space Clock 101; 3) Physics with Clocks in microgravity; 4) Space Clock Challenges; 5) LCAP Timeline; 6) International Space Station (ISS) Science Platforms; 7) ISS Express Rack; 8) Space Qualification of Components; 9) Laser Configuration; 10) Clock Rate Comparisons: GPS Carrier Phase Frequency Transfer; and 11) ISS Model Views. This paper is presented in viewgraph form.

  8. The central clock neurons regulate lipid storage in Drosophila.

    Directory of Open Access Journals (Sweden)

    Justin R DiAngelo

    Full Text Available A proper balance of lipid breakdown and synthesis is essential for achieving energy homeostasis as alterations in either of these processes can lead to pathological states such as obesity. The regulation of lipid metabolism is quite complex with multiple signals integrated to control overall triglyceride levels in metabolic tissues. Based upon studies demonstrating effects of the circadian clock on metabolism, we sought to determine if the central clock cells in the Drosophila brain contribute to lipid levels in the fat body, the main nutrient storage organ of the fly. Here, we show that altering the function of the Drosophila central clock neurons leads to an increase in fat body triglycerides. We also show that although triglyceride levels are not affected by age, they are increased by expression of the amyloid-beta protein in central clock neurons. The effect on lipid storage seems to be independent of circadian clock output as changes in triglycerides are not always observed in genetic manipulations that result in altered locomotor rhythms. These data demonstrate that the activity of the central clock neurons is necessary for proper lipid storage.

  9. The quantum beat the physical principles of atomic clocks

    CERN Document Server

    Major, F G

    1998-01-01

    One of the indicators of the level of technological development of a society has been, throughout history, the precision of clocks it was able to build. This book examines the physical principles underlying the workings of clocks--from the earliest mechanical clocks to the present-day sophisticated clocks based on the properties of individual atoms. Intended for non-specialists with some knowledge of physics or engineering,the book treats the material in a broad intuitive manner, with a minimum of mathematical formalism. The presentation covers a broad range of salient topics relevant to the measurement of frequency and time intervals. The main focus is on electronic time-keeping: clocks based on quartz crystal oscillators and, at greater length, atomic clocks based on quantum resonance in rubidium, cesium, and hydrogen atoms, and, more recently, mercury ions. The book treats the revolutionary changes that the optical laser has wrought on atomic standards through laser cooling and optical pumping, and it disc...

  10. Redox regulation of circadian molecular clock in chronic airway diseases.

    Science.gov (United States)

    Sundar, Isaac K; Sellix, Michael T; Rahman, Irfan

    2017-10-31

    At the cellular level, circadian timing is maintained by the molecular clock, a family of interacting clock gene transcription factors, nuclear receptors and kinases called clock genes. Daily rhythms in pulmonary function are dictated by the circadian timing system, including rhythmic susceptibility to the harmful effects of airborne pollutants, exacerbations in patients with chronic airway disease and the immune-inflammatory response to infection. Further, evidence strongly suggests that the circadian molecular clock has a robust reciprocal interaction with redox signaling and plays a considerable role in the response to oxidative/carbonyl stress. Disruption of the circadian timing system, particularly in airway cells, impairs pulmonary rhythms and lung function, enhances oxidative stress due to airway inhaled pollutants like cigarette smoke and airborne particulate matter and leads to enhanced inflammosenescence, inflammasome activation, DNA damage and fibrosis. Herein, we briefly review recent evidence supporting the role of the lung molecular clock and redox signaling in regulating inflammation, oxidative stress, and DNA damage responses in lung diseases and their exacerbations. We further describe the potential for clock genes as novel biomarkers and therapeutic targets for the treatment of chronic lung diseases. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. A clock network for geodesy and fundamental science.

    Science.gov (United States)

    Lisdat, C; Grosche, G; Quintin, N; Shi, C; Raupach, S M F; Grebing, C; Nicolodi, D; Stefani, F; Al-Masoudi, A; Dörscher, S; Häfner, S; Robyr, J-L; Chiodo, N; Bilicki, S; Bookjans, E; Koczwara, A; Koke, S; Kuhl, A; Wiotte, F; Meynadier, F; Camisard, E; Abgrall, M; Lours, M; Legero, T; Schnatz, H; Sterr, U; Denker, H; Chardonnet, C; Le Coq, Y; Santarelli, G; Amy-Klein, A; Le Targat, R; Lodewyck, J; Lopez, O; Pottie, P-E

    2016-08-09

    Leveraging the unrivalled performance of optical clocks as key tools for geo-science, for astronomy and for fundamental physics beyond the standard model requires comparing the frequency of distant optical clocks faithfully. Here, we report on the comparison and agreement of two strontium optical clocks at an uncertainty of 5 × 10(-17) via a newly established phase-coherent frequency link connecting Paris and Braunschweig using 1,415 km of telecom fibre. The remote comparison is limited only by the instability and uncertainty of the strontium lattice clocks themselves, with negligible contributions from the optical frequency transfer. A fractional precision of 3 × 10(-17) is reached after only 1,000 s averaging time, which is already 10 times better and more than four orders of magnitude faster than any previous long-distance clock comparison. The capability of performing high resolution international clock comparisons paves the way for a redefinition of the unit of time and an all-optical dissemination of the SI-second.

  12. The Molecular Circadian Clock and Alcohol-Induced Liver Injury

    Directory of Open Access Journals (Sweden)

    Uduak S. Udoh

    2015-10-01

    Full Text Available Emerging evidence from both experimental animal studies and clinical human investigations demonstrates strong connections among circadian processes, alcohol use, and alcohol-induced tissue injury. Components of the circadian clock have been shown to influence the pathophysiological effects of alcohol. Conversely, alcohol may alter the expression of circadian clock genes and the rhythmic behavioral and metabolic processes they regulate. Therefore, we propose that alcohol-mediated disruption in circadian rhythms likely underpins many adverse health effects of alcohol that cut across multiple organ systems. In this review, we provide an overview of the circadian clock mechanism and showcase results from new studies in the alcohol field implicating the circadian clock as a key target of alcohol action and toxicity in the liver. We discuss various molecular events through which alcohol may work to negatively impact circadian clock-mediated processes in the liver, and contribute to tissue pathology. Illuminating the mechanistic connections between the circadian clock and alcohol will be critical to the development of new preventative and pharmacological treatments for alcohol use disorders and alcohol-mediated organ diseases.

  13. Extracting dark matter signatures from atomic clock stability measurements

    Science.gov (United States)

    Kalaydzhyan, Tigran; Yu, Nan

    2017-10-01

    We analyze possible effects of the dark matter environment on the atomic clock stability measurements. The dark matter is assumed to exist in the form of waves of ultralight scalar fields or in the form of topological defects (monopoles and strings). We identify dark matter signal signatures in clock Allan deviation plots that can be used to constrain the dark matter coupling to the Standard Model fields. The existing data on the Al+/Hg+ clock comparison are used to put new limits on the dilaton dark matter in the region of masses mϕ>10-15 eV . We also estimate the sensitivities of future atomic clock experiments in space, including the cesium microwave and strontium optical clocks aboard the International Space Station, as well as a potential nuclear clock. These experiments are expected to put new limits on the topological dark matter in the range of masses 10-10 eV

  14. Atomic clocks and the continuous-time random-walk

    Science.gov (United States)

    Formichella, Valerio; Camparo, James; Tavella, Patrizia

    2017-11-01

    Atomic clocks play a fundamental role in many fields, most notably they generate Universal Coordinated Time and are at the heart of all global navigation satellite systems. Notwithstanding their excellent timekeeping performance, their output frequency does vary: it can display deterministic frequency drift; diverse continuous noise processes result in nonstationary clock noise (e.g., random-walk frequency noise, modelled as a Wiener process), and the clock frequency may display sudden changes (i.e., "jumps"). Typically, the clock's frequency instability is evaluated by the Allan or Hadamard variances, whose functional forms can identify the different operative noise processes. Here, we show that the Allan and Hadamard variances of a particular continuous-time random-walk, the compound Poisson process, have the same functional form as for a Wiener process with drift. The compound Poisson process, introduced as a model for observed frequency jumps, is an alternative to the Wiener process for modelling random walk frequency noise. This alternate model fits well the behavior of the rubidium clocks flying on GPS Block-IIR satellites. Further, starting from jump statistics, the model can be improved by considering a more general form of continuous-time random-walk, and this could bring new insights into the physics of atomic clocks.

  15. Influence of relativistic effects on satellite-based clock synchronization

    Science.gov (United States)

    Wang, Jieci; Tian, Zehua; Jing, Jiliang; Fan, Heng

    2016-03-01

    Clock synchronization between the ground and satellites is a fundamental issue in future quantum telecommunication, navigation, and global positioning systems. Here, we propose a scheme of near-Earth orbit satellite-based quantum clock synchronization with atmospheric dispersion cancellation by taking into account the spacetime background of the Earth. Two frequency entangled pulses are employed to synchronize two clocks, one at a ground station and the other at a satellite. The time discrepancy of the two clocks is introduced into the pulses by moving mirrors and is extracted by measuring the coincidence rate of the pulses in the interferometer. We find that the pulses are distorted due to effects of gravity when they propagate between the Earth and the satellite, resulting in remarkably affected coincidence rates. We also find that the precision of the clock synchronization is sensitive to the source parameters and the altitude of the satellite. The scheme provides a solution for satellite-based quantum clock synchronization with high precision, which can be realized, in principle, with current technology.

  16. Clock genes and their genomic distributions in three species of salmonid fishes: Associations with genes regulating sexual maturation and cell cycling

    Directory of Open Access Journals (Sweden)

    Ferguson Moira M

    2010-07-01

    Full Text Available Abstract Background Clock family genes encode transcription factors that regulate clock-controlled genes and thus regulate many physiological mechanisms/processes in a circadian fashion. Clock1 duplicates and copies of Clock3 and NPAS2-like genes were partially characterized (genomic sequencing and mapped using family-based indels/SNPs in rainbow trout (RT(Oncorhynchus mykiss, Arctic charr (AC(Salvelinus alpinus, and Atlantic salmon (AS(Salmo salar mapping panels. Results Clock1 duplicates mapped to linkage groups RT-8/-24, AC-16/-13 and AS-2/-18. Clock3/NPAS2-like genes mapped to RT-9/-20, AC-20/-43, and AS-5. Most of these linkage group regions containing the Clock gene duplicates were derived from the most recent 4R whole genome duplication event specific to the salmonids. These linkage groups contain quantitative trait loci (QTL for life history and growth traits (i.e., reproduction and cell cycling. Comparative synteny analyses with other model teleost species reveal a high degree of conservation for genes in these chromosomal regions suggesting that functionally related or co-regulated genes are clustered in syntenic blocks. For example, anti-müllerian hormone (amh, regulating sexual maturation, and ornithine decarboxylase antizymes (oaz1 and oaz2, regulating cell cycling, are contained within these syntenic blocks. Conclusions Synteny analyses indicate that regions homologous to major life-history QTL regions in salmonids contain many candidate genes that are likely to influence reproduction and cell cycling. The order of these genes is highly conserved across the vertebrate species examined, and as such, these genes may make up a functional cluster of genes that are likely co-regulated. CLOCK, as a transcription factor, is found within this block and therefore has the potential to cis-regulate the processes influenced by these genes. Additionally, clock-controlled genes (CCGs are located in other life-history QTL regions within

  17. Biological clocks and rhythms in intertidal crustaceans.

    Science.gov (United States)

    de la Iglesia, Horacio O; Hsu, Yun-Wei A

    2010-06-01

    Animals with habitats within the intertidal zone are exposed to environmental cycles that include the ebb and flow of tidal waters, changes in tidal levels associated with the lunar month, the light-dark cycle and the alternation of seasons. This intricate temporal environment results in the selection of biological timing systems with endogenous clocks that can oscillate with this wide range of periodicities. Whereas great progress has been made in our understanding of the molecular and neural bases of circadian rhythms, that is, endogenous rhythms synchronized to the solar day, there is little understanding on how circatidal rhythms, namely endogenous rhythms synchronized to tides, are generated. Intertidal crustaceans have been a pivotal group for the demonstration of the endogenous nature of circatidal rhythms and their mechanisms of entrainment. We review here some of the classic work using intertidal crustaceans to unmask basic properties of circatidal systems, as well as work from our laboratory that aims to identify putative chemical signals that could be involved in the circatidal systems of decapod crustaceans.

  18. Maternal feeding controls fetal biological clock.

    Directory of Open Access Journals (Sweden)

    Hidenobu Ohta

    Full Text Available BACKGROUND: It is widely accepted that circadian physiological rhythms of the fetus are affected by oscillators in the maternal brain that are coupled to the environmental light-dark (LD cycle. METHODOLOGY/PRINCIPAL FINDINGS: To study the link between fetal and maternal biological clocks, we investigated the effects of cycles of maternal food availability on the rhythms of Per1 gene expression in the fetal suprachiasmatic nucleus (SCN and liver using a transgenic rat model whose tissues express luciferase in vitro. Although the maternal SCN remained phase-locked to the LD cycle, maternal restricted feeding phase-advanced the fetal SCN and liver by 5 and 7 hours respectively within the 22-day pregnancy. CONCLUSIONS/SIGNIFICANCE: Our results demonstrate that maternal feeding entrains the fetal SCN and liver independently of both the maternal SCN and the LD cycle. This indicates that maternal-feeding signals can be more influential for the fetal SCN and particular organ oscillators than hormonal signals controlled by the maternal SCN, suggesting the importance of a regular maternal feeding schedule for appropriate fetal molecular clockwork during pregnancy.

  19. Reduced Voltage Scaling in Clock Distribution Networks

    Directory of Open Access Journals (Sweden)

    Khader Mohammad

    2009-01-01

    Full Text Available We propose a novel circuit technique to generate a reduced voltage swing (RVS signals for active power reduction on main buses and clocks. This is achieved without performance degradation, without extra power supply requirement, and with minimum area overhead. The technique stops the discharge path on the net that is swinging low at a certain voltage value. It reduces active power on the target net by as much as 33% compared to traditional full swing signaling. The logic 0 voltage value is programmable through control bits. If desired, the reduced-swing mode can also be disabled. The approach assumes that the logic 0 voltage value is always less than the threshold voltage of the nMOS receivers, which eliminate the need of the low to high voltage translation. The reduced noise margin and the increased leakage on the receiver transistors using this approach have been addressed through the selective usage of multithreshold voltage (MTV devices and the programmability of the low voltage value.

  20. Design principles of a genetic alarm clock.

    Directory of Open Access Journals (Sweden)

    Jaroslav Albert

    Full Text Available Turning genes on and off is a mechanism by which cells and tissues make phenotypic decisions. Gene network motifs capable of supporting two or more steady states and thereby providing cells with a plurality of possible phenotypes are referred to as genetic switches. Modeled on the bases of naturally occurring genetic networks, synthetic biologists have successfully constructed artificial switches, thus opening a door to new possibilities for improvement of the known, but also the design of new synthetic genetic circuits. One of many obstacles to overcome in such efforts is to understand and hence control intrinsic noise which is inherent in all biological systems. For some motifs the noise is negligible; for others, fluctuations in the particle number can be comparable to its average. Due to their slowed dynamics, motifs with positive autoregulation tend to be highly sensitive to fluctuations of their chemical environment and are in general very noisy, especially during transition (switching. In this article we use stochastic simulations (Gillespie algorithm to model such a system, in particular a simple bistable motif consisting of a single gene with positive autoregulation. Due to cooperativety, the dynamical behavior of this kind of motif is reminiscent of an alarm clock - the gene is (nearly silent for some time after it is turned on and becomes active very suddenly. We investigate how these sudden transitions are affected by noise and show that under certain conditions accurate timing can be achieved. We also examine how promoter complexity influences the accuracy of this timing mechanism.

  1. Design principles of a genetic alarm clock.

    Science.gov (United States)

    Albert, Jaroslav; Rooman, Marianne

    2012-01-01

    Turning genes on and off is a mechanism by which cells and tissues make phenotypic decisions. Gene network motifs capable of supporting two or more steady states and thereby providing cells with a plurality of possible phenotypes are referred to as genetic switches. Modeled on the bases of naturally occurring genetic networks, synthetic biologists have successfully constructed artificial switches, thus opening a door to new possibilities for improvement of the known, but also the design of new synthetic genetic circuits. One of many obstacles to overcome in such efforts is to understand and hence control intrinsic noise which is inherent in all biological systems. For some motifs the noise is negligible; for others, fluctuations in the particle number can be comparable to its average. Due to their slowed dynamics, motifs with positive autoregulation tend to be highly sensitive to fluctuations of their chemical environment and are in general very noisy, especially during transition (switching). In this article we use stochastic simulations (Gillespie algorithm) to model such a system, in particular a simple bistable motif consisting of a single gene with positive autoregulation. Due to cooperativety, the dynamical behavior of this kind of motif is reminiscent of an alarm clock - the gene is (nearly) silent for some time after it is turned on and becomes active very suddenly. We investigate how these sudden transitions are affected by noise and show that under certain conditions accurate timing can be achieved. We also examine how promoter complexity influences the accuracy of this timing mechanism.

  2. Cascaded clocks measurement and simulation findings

    Science.gov (United States)

    Chislow, Don; Zampetti, George

    1994-05-01

    This paper will examine aspects related to network synchronization distribution and the cascading of timing elements. Methods of timing distribution have become a much debated topic in standards forums and among network service providers (both domestically and internationally). Essentially these concerns focus on the need to migrate their existing network synchronization plans (and capabilities) to those required for the next generation of transport technologies (namely, the Synchronous Digital Hierarchy (SDH), Synchronous Optical Networks (SONET), and Asynchronous Transfer Mode (ATM). The particular choices for synchronization distribution network architectures are now being evaluated and are demonstrating that they can indeed have a profound effect on the overall service performance levels that will be delivered to the customer. The salient aspects of these concerns reduce to the following: (1) identifying that the devil is in the details of the timing element specifications and the distribution of timing information (i.e., small design choices can have a large performance impact); (2) developing a standardized method of performance verification that will yield unambiguous results; and (3) presentation of those results. Specifically, this will be done for two general cases: an ideal input, and a noisy input to a cascaded chain of slave clocks.

  3. The retinal clock in mammals: role in health and disease

    Directory of Open Access Journals (Sweden)

    Felder-Schmittbuhl MP

    2017-05-01

    Full Text Available Marie-Paule Felder-Schmittbuhl,1,* Hugo Calligaro,2 Ouria Dkhissi-Benyahya2,* 1Institute of Cellular and Integratives Neurosciences, UPR3212, CNRS, Université de Strasbourg, Strasbourg, 2University of Lyon, Stem Cell and Brain Research Institute, INSERM U1208, Bron, France *These authors contributed equally to this work Abstract: The mammalian retina contains an extraordinary diversity of cell types that are highly organized into precise circuits to perceive and process visual information in a dynamic manner and transmit it to the brain. Above this builds up another level of complex dynamic, orchestrated by a circadian clock located within the retina, which allows retinal physiology, and hence visual function, to adapt to daily changes in light intensity. The mammalian retina is a remarkable model of circadian clock because it harbors photoreception, self-sustained oscillator function, and physiological outputs within the same tissue. However, the location of the retinal clock in mammals has been a matter of long debate. Current data have shown that clock properties are widely distributed among retinal cells and that the retina is composed of a network of circadian clocks located within distinct cellular layers. Nevertheless, the identity of the major pacemaker, if any, still warrants identification. In addition, the retina coordinates rhythmic behavior by providing visual input to the master hypothalamic circadian clock in the suprachiasmatic nuclei (SCN. This light entrainment of the SCN to the light/dark cycle involves a network of retinal photoreceptor cells: rods, cones, and intrinsically photosensitive retinal ganglion cells (ipRGCs. Although it was considered that these photoreceptors synchronized both retinal and SCN clocks, new data challenge this view, suggesting that none of these photoreceptors is involved in photic entrainment of the retinal clock. Because circadian organization is a ubiquitous feature of the retina and controls

  4. Prediction of Navigation Satellite Clock Bias Considering Clock's Stochastic Variation Behavior with Robust Least Square Collocation

    Directory of Open Access Journals (Sweden)

    WANG Yupu

    2016-06-01

    Full Text Available In order to better express the characteristic of satellite clock bias (SCB and further improve its prediction precision, a new SCB prediction model is proposed, which can take the physical feature, cyclic variation and stochastic variation behaviors of the space-borne atomic clock into consideration by using a robust least square collocation (LSC method. The proposed model firstly uses a quadratic polynomial model with periodic terms to fit and abstract the trend term and cyclic terms of SCB. Then for the residual stochastic variation part and possible gross errors hidden in SCB data, the model employs a robust LSC method to process them. The covariance function of the LSC is determined by selecting an empirical function and combining SCB prediction tests. Using the final precise IGS SCB products to conduct prediction tests, the results show that the proposed model can get better prediction performance. Specifically, the results' prediction accuracy can enhance 0.457 ns and 0.948 ns respectively, and the corresponding prediction stability can improve 0.445 ns and 1.233 ns, compared with the results of quadratic polynomial model and grey model. In addition, the results also show that the proposed covariance function corresponding to the new model is reasonable.

  5. Rate Control Efficacy in Permanent Atrial Fibrillation : Successful and Failed Strict Rate Control Against a Background of Lenient Rate Control

    NARCIS (Netherlands)

    Groenveld, Hessel F.; Tijssen, Jan G. P.; Crijns, Harry J. G. M.; Van den Berg, Maarten P.; Hillege, Hans L.; Alings, Marco; Van Veldhuisen, Dirk J.; Van Gelder, Isabelle C.

    2013-01-01

    Objectives This study sought to investigate differences in outcome between patients treated with successful strict, failed strict, and lenient rate control. Background The RACE II (Rate Control Efficacy in Permanent Atrial Fibrillation) study showed no difference in outcome between lenient and

  6. Strict versus liberal insulin therapy in the cardiac surgery patient: An evidence-based practice development, implementation and evaluation project.

    Science.gov (United States)

    Gordon, Jacqueline M; Lauver, Lori S; Buck, Harleah G

    2018-02-01

    Hyperglycemia post-cardiac surgery is associated with poor clinical outcomes. Recent studies suggest maintaining liberal glycemic control (liberal CII protocol. Retrospective review of 144 strict CII patient records and 147 liberal CII patient records. Mean blood glucose was 159.8mg/dL (liberal CII) compared to 143.3mg/dL (strict CII) (p≤0.001). No surgical site infections occurred in either group. Mean ICU length of stay was 4.5days (liberal) versus 4.4days (strict) (p=0.74). Two 30-day mortalities occurred for the liberal cohort compared to no deaths in the strict group (p=0.49). Hypoglycemia incidence within 24h after surgery was 0.1% (liberal) compared to 0.3% (strict) compared to (p=0.16). Use of a nurse managed liberal CII resulted in similar outcomes with fewer incidents of hypoglycemia. Copyright © 2017. Published by Elsevier Inc.

  7. Strontium Optical Lattice Clock: In Quest of the Ultimate Performance

    International Nuclear Information System (INIS)

    Westergaard, Ph.G.

    2010-10-01

    This thesis presents the latest achievements regarding the Sr optical lattice clock experiment at LNESYRTE, Observatoire de Paris. After having described the general principles for optical lattice clocks and the operation of the clock in question, the emphasis is put on the features that have been added to the experiment since 2007. The most important new elements are an ultra-stable reference cavity for the clock laser, the development of a non-destructive detection technique, and the construction of a second Sr lattice clock. The ultra-stable cavity is constructed from a ULE spacer and fused silica mirrors and has shown a thermal noise floor at 6.5 * 10 -16 , placing it among the best in the world. The non-destructive detection is effectuated by a phase measurement of a weak probe beam that traverses the atoms placed in one arm of a Mach-Zender interferometer. The non-destructive aspect enables a recycling of the atoms from cycle to cycle which consequently increases the duty cycle, allowing for an increase of the stability of the clock. With these new tools the frequency stability is expected to be 2.2 * 10 -16 /√τ for an optimized sequence. The most recent comparisons between the two Sr clocks reach an accuracy level of 10 -16 after about 1000 s, and this way we have been able to characterize lattice related frequency shifts with an unprecedented accuracy. The measurements ensure a control of lattice related effects at the 10 -18 level even for trap depths as large as 50E r . (authors)

  8. British domestic synchronous clocks 1930-1980 the rise and fall of a technology

    CERN Document Server

    Pook, Leslie Philip

    2015-01-01

    This book complements available one-make books on domestic synchronous clocks. It is also a history of science book that sets British domestic synchronous clocks, their manufacturers and technology in their social context. Part I covers the historical background, British domestic synchronous clock manufacturers and brands, how synchronous clocks work, domestic synchronous clock cases, practical advice on the servicing of domestic synchronous clocks, and analysis of the marketing and reliability of British domestic synchronous clocks. This analysis provides an explanation of the rise and eventual fall of their technology. Part II contains galleries of a selection of British domestic synchronous clocks, and of the movements with which they are fitted. There is a front and back view of each clock, together with a brief description. Views of each movement include views with the movement partly dismantled, together with a brief technical description of the movement. This profusely illustrated book is primarily fo...

  9. Deleting the Arntl clock gene in the granular layer of the mouse cerebellum

    DEFF Research Database (Denmark)

    Bering, Tenna; Carstensen, Mikkel Bloss; Rath, Martin Fredensborg

    2017-01-01

    The suprachiasmatic nucleus houses the central circadian clock and is characterized by the timely regulated expression of clock genes. However, neurons of the cerebellar cortex also contain a circadian oscillator with circadian expression of clock genes being controlled by the suprachiasmatic...... is involved in circadian physiology and food anticipation, we therefore by use of Cre-LoxP technology generated a conditional knockout mouse with the core clock gene Arntl deleted specifically in granule cells of the cerebellum, since expression of clock genes in the cerebellar cortex is mainly located...... in this cell type. We here report that deletion of Arntl heavily influences the molecular clock of the cerebellar cortex with significantly altered and arrhythmic expression of other central clock and clock-controlled genes. On the other hand, daily expression of clock genes in the suprachiasmatic nucleus...

  10. Effects of growth temperature and strictly anaerobic recovery on the survival of Listeria monocytogenes during pasteurization.

    Science.gov (United States)

    Knabel, S J; Walker, H W; Hartman, P A; Mendonca, A F

    1990-02-01

    Listeria monocytogenes F5069 was suspended in either Trypticase soy broth-0.6% yeast extract (TSBYE) or sterile, whole milk and heated at 62.8 degrees C in sealed thermal death time tubes. Severely heat-injured cells were recovered in TSBYE within sealed thermal death time tubes because of the formation of reduced conditions in the depths of the TSBYE. Also, the use of strictly anaerobic Hungate techniques significantly increased recovery in TSBYE containing 1.5% agar compared with aerobically incubated controls. The exogenous addition of catalase, but not superoxide dismutase, slightly increased the recovery of heat-injured cells in TSBYE containing 1.5% agar incubated aerobically. Growth of cells at 43 degrees C caused a greater increase in heat resistance as compared with cells heat shocked at 43 degrees C or cells grown at lower temperatures. Growth of L. monocytogenes at 43 degrees C and enumeration by the use of strictly anaerobic Hungate techniques resulted in D62.8 degrees C values that were at least sixfold greater than those previously obtained by using cells grown at 37 degrees C and aerobic plating. Results indicate that, under the conditions of the present study, high levels of L. monocytogenes would survive the minimum low-temperature, long-time treatment required by the U.S. Food and Drug Administration for pasteurizing milk. The possible survival of low levels of L. monocytogenes during high-temperature, short-time pasteurization and enumeration of injured cells by recovery on selective media under strictly anaerobic conditions are discussed.

  11. Effect of cryopreservation and lyophilization on viability and growth of strict anaerobic human gut microbes.

    Science.gov (United States)

    Bircher, Lea; Geirnaert, Annelies; Hammes, Frederik; Lacroix, Christophe; Schwab, Clarissa

    2018-04-17

    Strict anaerobic gut microbes have been suggested as 'next-generation probiotics' for treating several intestinal disorders. The development of preservation techniques is of major importance for therapeutic application. This study investigated cryopreservation (-80°C) and lyophilization survival and storage stability (4°C for 3 months) of the strict anaerobic gut microbes Bacteroides thetaiotaomicron, Faecalibacterium prausnitzii, Roseburia intestinalis, Anaerostipes caccae, Eubacterium hallii and Blautia obeum. To improve preservation survival, protectants sucrose and inulin (both 5% w/v) were added for lyophilization and were also combined with glycerol (15% v/v) for cryopreservation. Bacterial fitness, evaluated by maximum growth rate and lag phase, viability and membrane integrity were determined using a standardized growth assay and by flow cytometry as markers for preservation resistance. Lyophilization was more detrimental to viability and fitness than cryopreservation, but led to better storage stability. Adding sucrose and inulin enhanced viability and the proportion of intact cells during lyophilization of all strains. Viability of protectant-free B. thetaiotaomicron, A. caccae and F. prausnitzii was above 50% after cryopreservation and storage and increased to above 80% if protectants were present. The addition of glycerol, sucrose and inulin strongly enhanced the viability of B. obeum, E. hallii and R. intestinalis from 0.03-2% in protectant-free cultures to 11-37%. This is the first study that quantitatively compared the effect of cryopreservation and lyophilization and the addition of selected protectants on viability and fitness of six strict anaerobic gut microbes. Our results suggest that efficiency of protectants is process- and species-specific. © 2018 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

  12. The Hands of the Pleiades: The Celestial Clock in the Classical Arabic Poetry of Dhū al-Rumma

    Science.gov (United States)

    Adams, W. B.

    2011-06-01

    In the desert poetry of Dhū al-Rumma (d. 117 AH/735 CE), astronomical phenomena sometimes function as familiar celestial timepieces that indicate the poetic timeframe literally and accurately. The literary, lexical, floral and astronomical analyses of a selection from this poetry illustrate the role of the Pleiades star cluster as a celestial clock and illuminate the utility of naked-eye astronomy in interpreting Arabic poetry of the early Islamic period.

  13. Effects of growth temperature and strictly anaerobic recovery on the survival of Listeria monocytogenes during pasteurization.

    OpenAIRE

    Knabel, S J; Walker, H W; Hartman, P A; Mendonca, A F

    1990-01-01

    Listeria monocytogenes F5069 was suspended in either Trypticase soy broth-0.6% yeast extract (TSBYE) or sterile, whole milk and heated at 62.8 degrees C in sealed thermal death time tubes. Severely heat-injured cells were recovered in TSBYE within sealed thermal death time tubes because of the formation of reduced conditions in the depths of the TSBYE. Also, the use of strictly anaerobic Hungate techniques significantly increased recovery in TSBYE containing 1.5% agar compared with aerobicall...

  14. The Dirichlet problem for the Monge-Ampere equation in convex (but not strictly convex domains

    Directory of Open Access Journals (Sweden)

    David Hartenstine

    2006-10-01

    Full Text Available It is well-known that the Dirichlet problem for the Monge-Amp`ere equation $det D^2 u = mu$ in a bounded strictly convex domain $Omega$ in $mathbb{R}^n$ has a weak solution (in the sense of Aleksandrov for any finite Borel measure $mu$ on $Omega$ and for any continuous boundary data. We consider the Dirichlet problem when $Omega$ is only assumed to be convex, and give a necessary and sufficient condition on the boundary data for solvability.

  15. Selections of the metric projection operator and strict solarity of sets with continuous metric projection

    Science.gov (United States)

    Alimov, A. R.

    2017-07-01

    In a broad class of finite-dimensional Banach spaces, we show that a closed set with lower semicontinuous metric projection is a strict sun, admits a continuous selection of the metric projection operator onto it, has contractible intersections with balls, and its (nonempty) intersection with any closed ball is a retract of this ball. For sets with continuous metric projection, a number of new results relating the solarity of such sets to the stability of the operator of best approximation are obtained. Bibliography 25 titles.

  16. Transplanting Diseases from Organ Donors in Western Europe: Fault Liability or Strict Liability?

    Science.gov (United States)

    Broeckx, Nils; Verhoeven, Dimitri

    2015-06-01

    This article will examine the problem of disease transmission through organ transplantation from a civil liability perspective. Both fault liability and strict product liability might be possible. These two types of liability will be compared, while applying them to the actions of the central parties involved in organ donation and transplantation, namely the physician/hospital, the donor and the organ exchange organisation. While product liability is generally an easier way to obtain compensation than fault liability, it might nevertheless place too heavy a burden on the transplant professionals.

  17. Single molecule experiments challenge the strict wave-particle dualism of light.

    Science.gov (United States)

    Greulich, Karl Otto

    2010-01-21

    Single molecule techniques improve our understanding of the photon and light. If the single photon double slit experiment is performed at the "single photon limit" of a multi-atom light source, faint light pulses with more than one photon hamper the interpretation. Single molecules, quantum dots or defect centres in crystals should be used as light source. "Single photon detectors" do not meet their promise-only "photon number resolving single photon detectors" do so. Particularly, the accumulation time argument, the only safe basis for the postulate of a strictly particle like photon, has so far not yet been verified.

  18. Single Molecule Experiments Challenge the Strict Wave-Particle Dualism of Light

    Directory of Open Access Journals (Sweden)

    Karl Otto Greulich

    2010-01-01

    Full Text Available Single molecule techniques improve our understanding of the photon and light. If the single photon double slit experiment is performed at the “single photon limit” of a multi-atom light source, faint light pulses with more than one photon hamper the interpretation. Single molecules, quantum dots or defect centres in crystals should be used as light source. “Single photon detectors” do not meet their promise―only “photon number resolving single photon detectors” do so. Particularly, the accumulation time argument, the only safe basis for the postulate of a strictly particle like photon, has so far not yet been verified.

  19. Beyond fossil calibrations: Realities of molecular clock practices in evolutionary biology

    Directory of Open Access Journals (Sweden)

    Christy Anna Hipsley

    2014-05-01

    Full Text Available Molecular-based divergence dating methods, or molecular clocks, are the primary neontological tool for estimating the temporal origins of clades. While the appropriate use of vertebrate fossils as external clock calibrations has stimulated heated discussions in the paleontological community, less attention has been given to the quality and implementation of other calibration types. In lieu of appropriate fossils, many studies rely on alternative sources of age constraints based on geological events, substitution rates and heterochronous sampling, as well as dates secondarily derived from previous analyses. To illustrate the breadth and frequency of calibration types currently employed, we conducted a literature survey of over 600 articles published from 2007 to 2013. Over half of all analyses implemented one or more fossil dates as constraints, followed by geological events and secondary calibrations (15% each. Vertebrate taxa were subjects of nearly half of all studies, while invertebrates and plants together accounted for 43%, followed by viruses, protists and fungi (3% each. Current patterns in calibration practices were disproportionate to the number of discussions on their proper use, particularly regarding plants and secondarily derived dates, which are both relatively neglected. Based on our survey, we provide a comprehensive overview of the latest approaches in clock calibration, and outline strengths and weaknesses associated with each. This critique should serve as a call to action for researchers across multiple communities, particularly those working on clades for which fossil records are poor, to develop their own guidelines regarding selection and implementation of alternative calibration types. This issue is particularly relevant now, as time-calibrated phylogenies are used for more than dating evolutionary origins, but often serve as the backbone of investigations into biogeography, diversity dynamics and rates of phenotypic

  20. Beyond fossil calibrations: realities of molecular clock practices in evolutionary biology.

    Science.gov (United States)

    Hipsley, Christy A; Müller, Johannes

    2014-01-01

    Molecular-based divergence dating methods, or molecular clocks, are the primary neontological tool for estimating the temporal origins of clades. While the appropriate use of vertebrate fossils as external clock calibrations has stimulated heated discussions in the paleontological community, less attention has been given to the quality and implementation of other calibration types. In lieu of appropriate fossils, many studies rely on alternative sources of age constraints based on geological events, substitution rates and heterochronous sampling, as well as dates secondarily derived from previous analyses. To illustrate the breadth and frequency of calibration types currently employed, we conducted a literature survey of over 600 articles published from 2007 to 2013. Over half of all analyses implemented one or more fossil dates as constraints, followed by geological events and secondary calibrations (15% each). Vertebrate taxa were subjects in nearly half of all studies, while invertebrates and plants together accounted for 43%, followed by viruses, protists and fungi (3% each). Current patterns in calibration practices were disproportionate to the number of discussions on their proper use, particularly regarding plants and secondarily derived dates, which are both relatively neglected in methodological evaluations. Based on our survey, we provide a comprehensive overview of the latest approaches in clock calibration, and outline strengths and weaknesses associated with each. This critique should serve as a call to action for researchers across multiple communities, particularly those working on clades for which fossil records are poor, to develop their own guidelines regarding selection and implementation of alternative calibration types. This issue is particularly relevant now, as time-calibrated phylogenies are used for more than dating evolutionary origins, but often serve as the backbone of investigations into biogeography, diversity dynamics and rates of

  1. Pacemaker-neuron–dependent disturbance of the molecular clockwork by a Drosophila CLOCK mutant homologous to the mouse Clock mutation

    Science.gov (United States)

    Lee, Euna; Cho, Eunjoo; Kang, Doo Hyun; Jeong, Eun Hee; Chen, Zheng; Yoo, Seung-Hee; Kim, Eun Young

    2016-01-01

    Circadian clocks are composed of transcriptional/translational feedback loops (TTFLs) at the cellular level. In Drosophila TTFLs, the transcription factor dCLOCK (dCLK)/CYCLE (CYC) activates clock target gene expression, which is repressed by the physical interaction with PERIOD (PER). Here, we show that amino acids (AA) 657–707 of dCLK, a region that is homologous to the mouse Clock exon 19-encoded region, is crucial for PER binding and E-box–dependent transactivation in S2 cells. Consistently, in transgenic flies expressing dCLK with an AA657–707 deletion in the Clock (Clkout) genetic background (p{dClk-Δ};Clkout), oscillation of core clock genes’ mRNAs displayed diminished amplitude compared with control flies, and the highly abundant dCLKΔ657–707 showed significantly decreased binding to PER. Behaviorally, the p{dClk-Δ};Clkout flies exhibited arrhythmic locomotor behavior in the photic entrainment condition but showed anticipatory activities of temperature transition and improved free-running rhythms in the temperature entrainment condition. Surprisingly, p{dClk-Δ};Clkout flies showed pacemaker-neuron–dependent alterations in molecular rhythms; the abundance of dCLK target clock proteins was reduced in ventral lateral neurons (LNvs) but not in dorsal neurons (DNs) in both entrainment conditions. In p{dClk-Δ};Clkout flies, however, strong but delayed molecular oscillations in temperature cycle-sensitive pacemaker neurons, such as DN1s and DN2s, were correlated with delayed anticipatory activities of temperature transition. Taken together, our study reveals that the LNv molecular clockwork is more sensitive than the clockwork of DNs to dysregulation of dCLK by AA657–707 deletion. Therefore, we propose that the dCLK/CYC-controlled TTFL operates differently in subsets of pacemaker neurons, which may contribute to their specific functions. PMID:27489346

  2. FAD Regulates CRYPTOCHROME Protein Stability and Circadian Clock in Mice.

    Science.gov (United States)

    Hirano, Arisa; Braas, Daniel; Fu, Ying-Hui; Ptáček, Louis J

    2017-04-11

    The circadian clock generates biological rhythms of metabolic and physiological processes, including the sleep-wake cycle. We previously identified a missense mutation in the flavin adenine dinucleotide (FAD) binding pocket of CRYPTOCHROME2 (CRY2), a clock protein that causes human advanced sleep phase. This prompted us to examine the role of FAD as a mediator of the clock and metabolism. FAD stabilized CRY proteins, leading to increased protein levels. In contrast, knockdown of Riboflavin kinase (Rfk), an FAD biosynthetic enzyme, enhanced CRY degradation. RFK protein levels and FAD concentrations oscillate in the nucleus, suggesting that they are subject to circadian control. Knockdown of Rfk combined with a riboflavin-deficient diet altered the CRY levels in mouse liver and the expression profiles of clock and clock-controlled genes (especially those related to metabolism including glucose homeostasis). We conclude that light-independent mechanisms of FAD regulate CRY and contribute to proper circadian oscillation of metabolic genes in mammals. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

  3. FAD Regulates CRYPTOCHROME Protein Stability and Circadian Clock in Mice

    Directory of Open Access Journals (Sweden)

    Arisa Hirano

    2017-04-01

    Full Text Available The circadian clock generates biological rhythms of metabolic and physiological processes, including the sleep-wake cycle. We previously identified a missense mutation in the flavin adenine dinucleotide (FAD binding pocket of CRYPTOCHROME2 (CRY2, a clock protein that causes human advanced sleep phase. This prompted us to examine the role of FAD as a mediator of the clock and metabolism. FAD stabilized CRY proteins, leading to increased protein levels. In contrast, knockdown of Riboflavin kinase (Rfk, an FAD biosynthetic enzyme, enhanced CRY degradation. RFK protein levels and FAD concentrations oscillate in the nucleus, suggesting that they are subject to circadian control. Knockdown of Rfk combined with a riboflavin-deficient diet altered the CRY levels in mouse liver and the expression profiles of clock and clock-controlled genes (especially those related to metabolism including glucose homeostasis. We conclude that light-independent mechanisms of FAD regulate CRY and contribute to proper circadian oscillation of metabolic genes in mammals.

  4. Progress Toward a Compact, Highly Stable Ion Clock

    Science.gov (United States)

    Prestage, John; Chung, Sang

    2009-01-01

    There was an update on the subject of two previous NASA Tech Briefs articles: Compact, Highly Stable Ion Clock (NPO-43075), Vol. 32, No. 5 (May 2008), page 63; and Neon as a Buffer Gas for a Mercury-Ion Clock (NPO-42919), Vol. 32, No. 7 (July 2008), page 62. To recapitulate: A developmental miniature mercury-ion clock has stability comparable to that of a hydrogen-maser clock. The ion-handling components are housed in a sealed vacuum tube, wherein a getter pump maintains the partial vacuum, and the evacuated tube is backfilled with mercury vapor in a neon buffer gas. There was progress in the development of the clock, with emphasis on the design, fabrication, pump-down, and bake-out of the vacuum tube (based on established practice in the travelingwave- tube-amplifier industry) and the ability of the tube to retain a vacuum after a year of operation. Other developments include some aspects of the operation of mercury-vapor source (a small appendage oven containing HgO) so as to maintain the optimum low concentration of mercury vapor, and further efforts to miniaturize the vacuum and optical subsystems to fit within a volume of 2 L.

  5. Bone Resorption Is Regulated by Circadian Clock in Osteoblasts.

    Science.gov (United States)

    Takarada, Takeshi; Xu, Cheng; Ochi, Hiroki; Nakazato, Ryota; Yamada, Daisuke; Nakamura, Saki; Kodama, Ayumi; Shimba, Shigeki; Mieda, Michihiro; Fukasawa, Kazuya; Ozaki, Kakeru; Iezaki, Takashi; Fujikawa, Koichi; Yoneda, Yukio; Numano, Rika; Hida, Akiko; Tei, Hajime; Takeda, Shu; Hinoi, Eiichi

    2017-04-01

    We have previously shown that endochondral ossification is finely regulated by the Clock system expressed in chondrocytes during postnatal skeletogenesis. Here we show a sophisticated modulation of bone resorption and bone mass by the Clock system through its expression in bone-forming osteoblasts. Brain and muscle aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1) and Period1 (Per1) were expressed with oscillatory rhythmicity in the bone in vivo, and circadian rhythm was also observed in cultured osteoblasts of Per1::luciferase transgenic mice. Global deletion of murine Bmal1, a core component of the Clock system, led to a low bone mass, associated with increased bone resorption. This phenotype was recapitulated by the deletion of Bmal1 in osteoblasts alone. Co-culture experiments revealed that Bmal1-deficient osteoblasts have a higher ability to support osteoclastogenesis. Moreover, 1α,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ]-induced receptor activator of nuclear factor κB ligand (Rankl) expression was more strongly enhanced in both Bmal1-deficient bone and cultured osteoblasts, whereas overexpression of Bmal1/Clock conversely inhibited it in osteoblasts. These results suggest that bone resorption and bone mass are regulated at a sophisticated level by osteoblastic Clock system through a mechanism relevant to the modulation of 1,25(OH) 2 D 3 -induced Rankl expression in osteoblasts. © 2017 American Society for Bone and Mineral Research. © 2017 American Society for Bone and Mineral Research.

  6. Neurogenetics of Drosophila circadian clock: expect the unexpected.

    Science.gov (United States)

    Jarabo, Patricia; Martin, Francisco A

    2017-12-01

    Daily biological rhythms (i.e. circadian) are a fundamental part of animal behavior. Numerous reports have shown disruptions of the biological clock in neurodegenerative disorders and cancer. In the latter case, only recently we have gained insight into the molecular mechanisms. After 45 years of intense study of the circadian rhtythms, we find surprising similarities among species on the molecular clock that governs biological rhythms. Indeed, Drosophila is one of the most widely used models in the study of chronobiology. Recent studies in the fruit fly have revealed unpredicted roles for the clock machinery in different aspects of behavior and physiology. Not only the central pacemaker cells do have non-classical circadian functions but also circadian genes work in other cells and tissues different from central clock neurons. In this review, we summarize these new evidences. We also recapitulate the most basic features of Drosophila circadian clock, including recent data about the inputs and outputs that connect the central pacemaker with other regions of the brain. Finally, we discuss the advantages and drawbacks of using natural versus laboratory conditions.

  7. The Circadian Clock-controlled Transcriptome of Developing Soybean Seeds

    Directory of Open Access Journals (Sweden)

    Karen A. Hudson

    2010-07-01

    Full Text Available A number of metabolic and physiological processes in plants are controlled by the circadian clock, which enables a plant to anticipate daily changes in the environment. Relatively little is known about circadian rhythms in developing seeds, which may be important for determining the extent and timing of nutrient storage in grain. Microarray expression profiling was used to identify genes expressed in developing soybean ( seeds that are controlled by the circadian clock. Genes with predicted functions in protein synthesis, fatty acid metabolism, and photosynthesis totaling 1.8% of the mRNAs detected in seed were found to be expressed in a circadian rhythm. Known circadian and light-controlled promoter elements were identified as over-represented in the promoters of clock-controlled seed genes, with the over-represented elements varying according to the phase of circadian expression. A subset of circadian-regulated genes were found to be expressed in different phases in developing seeds with respect to leaves from the same plants, many of which have roles in photosynthesis and carbon metabolism. These results help to characterize the genes and processes in seeds that may be regulated by the circadian clock, and provide some insight into organ-specific phasing of clock controlled gene expression.

  8. Protecting Clock Synchronization: Adversary Detection through Network Monitoring

    Directory of Open Access Journals (Sweden)

    Elena Lisova

    2016-01-01

    Full Text Available Nowadays, industrial networks are often used for safety-critical applications with real-time requirements. Such applications usually have a time-triggered nature with message scheduling as a core property. Scheduling requires nodes to share the same notion of time, that is, to be synchronized. Therefore, clock synchronization is a fundamental asset in real-time networks. However, since typical standards for clock synchronization, for example, IEEE 1588, do not provide the required level of security, it raises the question of clock synchronization protection. In this paper, we identify a way to break synchronization based on the IEEE 1588 standard, by conducting a man-in-the-middle (MIM attack followed by a delay attack. A MIM attack can be accomplished through, for example, Address Resolution Protocol (ARP poisoning. Using the AVISPA tool, we evaluate the potential to perform a delay attack using ARP poisoning and analyze its consequences showing both that the attack can, indeed, break clock synchronization and that some design choices, such as a relaxed synchronization condition mode, delay bounding, and using knowledge of environmental conditions, can make the network more robust/resilient against these kinds of attacks. Lastly, a Configuration Agent is proposed to monitor and detect anomalies introduced by an adversary performing attacks targeting clock synchronization.

  9. A circadian clock in Antarctic krill: an endogenous timing system governs metabolic output rhythms in the euphausid species Euphausia superba.

    Directory of Open Access Journals (Sweden)

    Mathias Teschke

    Full Text Available Antarctic krill, Euphausia superba, shapes the structure of the Southern Ocean ecosystem. Its central position in the food web, the ongoing environmental changes due to climatic warming, and increasing commercial interest on this species emphasize the urgency of understanding the adaptability of krill to its environment. Krill has evolved rhythmic physiological and behavioral functions which are synchronized with the daily and seasonal cycles of the complex Southern Ocean ecosystem. The mechanisms, however, leading to these rhythms are essentially unknown. Here, we show that krill possesses an endogenous circadian clock that governs metabolic and physiological output rhythms. We found that expression of the canonical clock gene cry2 was highly rhythmic both in a light-dark cycle and in constant darkness. We detected a remarkable short circadian period, which we interpret as a special feature of the krill's circadian clock that helps to entrain the circadian system to the extreme range of photoperiods krill is exposed to throughout the year. Furthermore, we found that important key metabolic enzymes of krill showed bimodal circadian oscillations (∼9-12 h period in transcript abundance and enzymatic activity. Oxygen consumption of krill showed ∼9-12 h oscillations that correlated with the temporal activity profile of key enzymes of aerobic energy metabolism. Our results demonstrate the first report of an endogenous circadian timing system in Antarctic krill and its likely link to metabolic key processes. Krill's circadian clock may not only be critical for synchronization to the solar day but also for the control of seasonal events. This study provides a powerful basis for the investigation into the mechanisms of temporal synchronization in this marine key species and will also lead to the first comprehensive analyses of the circadian clock of a polar marine organism through the entire photoperiodic cycle.

  10. Fuzzy Adaptive Decentralized Optimal Control for Strict Feedback Nonlinear Large-Scale Systems.

    Science.gov (United States)

    Sun, Kangkang; Sui, Shuai; Tong, Shaocheng

    2018-04-01

    This paper considers the optimal decentralized fuzzy adaptive control design problem for a class of interconnected large-scale nonlinear systems in strict feedback form and with unknown nonlinear functions. The fuzzy logic systems are introduced to learn the unknown dynamics and cost functions, respectively, and a state estimator is developed. By applying the state estimator and the backstepping recursive design algorithm, a decentralized feedforward controller is established. By using the backstepping decentralized feedforward control scheme, the considered interconnected large-scale nonlinear system in strict feedback form is changed into an equivalent affine large-scale nonlinear system. Subsequently, an optimal decentralized fuzzy adaptive control scheme is constructed. The whole optimal decentralized fuzzy adaptive controller is composed of a decentralized feedforward control and an optimal decentralized control. It is proved that the developed optimal decentralized controller can ensure that all the variables of the control system are uniformly ultimately bounded, and the cost functions are the smallest. Two simulation examples are provided to illustrate the validity of the developed optimal decentralized fuzzy adaptive control scheme.

  11. Molecular clock evidence for survival of Antarctic cyanobacteria (Oscillatoriales, Phormidium autumnale) from Paleozoic times.

    Science.gov (United States)

    Strunecký, Otakar; Elster, Josef; Komárek, Jiří

    2012-11-01

    Cyanobacteria are well adapted to freezing and desiccation; they have been proposed as possible survivors of comprehensive Antarctic glaciations. Filamentous types from the order Oscillatoriales, especially the species Phormidium autumnale Kützing ex Gomont 1892, have widely diverse morphotypes that dominate in Antarctic aquatic microbial mats, seepages, and wet soils. Currently little is known about the dispersion of cyanobacteria in Antarctica and of their population history. We tested the hypothesis that cyanobacteria survived Antarctic glaciations directly on site after the Gondwana breakup by using the relaxed and strict molecular clock in the analysis of the 16S rRNA gene. We estimated that the biogeographic history of Antarctic cyanobacteria belonging to P. autumnale lineages has ancient origins. The oldest go further back in time than the breakup of Gondwana and originated somewhere on the supercontinent between 442 and 297 Ma. Enhanced speciation rate was found around the time of the opening of the Drake Passage (c. 31-45 Ma) with beginning of glaciations (c. 43 Ma). Our results, based primarily on the strains collected in maritime Antarctica, mostly around James Ross Island, support the hypothesis that long-term survival took place in glacial refuges. The high morphological diversification of P. autumnale suggested the coevolution of lineages and formation of complex associations with different morphologies, resulting in a specific endemic Antarctic cyanobacterial flora. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

  12. The Effects of Race Conditions When Implementing Single-Source Redundant Clock Trees in Triple Modular Redundant Synchronous Architectures

    Science.gov (United States)

    Berg, Melanie D.; Kim, Hak S.; Phan, Anthony M.; Seidleck, Christina M.; Label, Kenneth A.; Pellish, Jonathan A.; Campola, Michael J.

    2016-01-01

    We present the challenges that arise when using redundant clock domains due to their time-skew. Radiation data show that a singular clock domain provides an improved triple modular redundant (TMR) scheme over redundant clocks.

  13. CIRCADIAN CLOCK-ASSOCIATED 1 Inhibits Leaf Senescence in Arabidopsis

    Directory of Open Access Journals (Sweden)

    Yi Song

    2018-03-01

    Full Text Available Leaf senescence is an integral part of plant development, and the timing and progressing rate of senescence could substantially affect the yield and quality of crops. It has been known that a circadian rhythm synchronized with external environmental cues is critical for the optimal coordination of various physiological and metabolic processes. However, the reciprocal interactions between the circadian clock and leaf senescence in plants remain unknown. Here, through measuring the physiological and molecular senescence related markers of several circadian components mutants, we found that CIRCADIAN CLOCK-ASSOCIATED 1 inhibits leaf senescence. Further molecular and genetic studies revealed that CCA1 directly activates GLK2 and suppresses ORE1 expression to counteract leaf senescence. As plants age, the expression and periodic amplitude of CCA1 declines and thus weakens the inhibition of senescence. Our findings reveal an age-dependent circadian clock component of the process of leaf senescence.

  14. Fault-tolerant clock synchronization validation methodology. [in computer systems

    Science.gov (United States)

    Butler, Ricky W.; Palumbo, Daniel L.; Johnson, Sally C.

    1987-01-01

    A validation method for the synchronization subsystem of a fault-tolerant computer system is presented. The high reliability requirement of flight-crucial systems precludes the use of most traditional validation methods. The method presented utilizes formal design proof to uncover design and coding errors and experimentation to validate the assumptions of the design proof. The experimental method is described and illustrated by validating the clock synchronization system of the Software Implemented Fault Tolerance computer. The design proof of the algorithm includes a theorem that defines the maximum skew between any two nonfaulty clocks in the system in terms of specific system parameters. Most of these parameters are deterministic. One crucial parameter is the upper bound on the clock read error, which is stochastic. The probability that this upper bound is exceeded is calculated from data obtained by the measurement of system parameters. This probability is then included in a detailed reliability analysis of the system.

  15. Shell neurons of the master circadian clock coordinate the phase of tissue clocks throughout the brain and body.

    Science.gov (United States)

    Evans, Jennifer A; Suen, Ting-Chung; Callif, Ben L; Mitchell, Andrew S; Castanon-Cervantes, Oscar; Baker, Kimberly M; Kloehn, Ian; Baba, Kenkichi; Teubner, Brett J W; Ehlen, J Christopher; Paul, Ketema N; Bartness, Timothy J; Tosini, Gianluca; Leise, Tanya; Davidson, Alec J

    2015-06-23

    Daily rhythms in mammals are programmed by a master clock in the suprachiasmatic nucleus (SCN). The SCN contains two main compartments (shell and core), but the role of each region in system-level coordination remains ill defined. Herein, we use a functional assay to investigate how downstream tissues interpret region-specific outputs by using in vivo exposure to long day photoperiods to temporally dissociate the SCN. We then analyze resulting changes in the rhythms of clocks located throughout the brain and body to examine whether they maintain phase synchrony with the SCN shell or core. Nearly all of the 17 tissues examined in the brain and body maintain phase synchrony with the SCN shell, but not the SCN core, which indicates that downstream oscillators are set by cues controlled specifically by the SCN shell. Interestingly, we also found that SCN dissociation diminished the amplitude of rhythms in core clock gene and protein expression in brain tissues by 50-75 %, which suggests that light-driven changes in the functional organization of the SCN markedly influence the strength of rhythms in downstream tissues. Overall, our results reveal that body clocks receive time-of-day cues specifically from the SCN shell, which may be an adaptive design principle that serves to maintain system-level phase relationships in a changing environment. Further, we demonstrate that lighting conditions alter the amplitude of the molecular clock in downstream tissues, which uncovers a new form of plasticity that may contribute to seasonal changes in physiology and behavior.

  16. Conservation of Arabidopsis thaliana circadian clock genes in Chrysanthemum lavandulifolium.

    Science.gov (United States)

    Fu, Jianxin; Yang, Liwen; Dai, Silan

    2014-07-01

    In Arabidopsis, circadian clock genes play important roles in photoperiod pathway by regulating the daytime expression of CONSTANS (CO), but related reports for chrysanthemum are notably limited. In this study, we isolated eleven circadian clock genes, which lie in the three interconnected negative and positive feedback loops in a wild diploid chrysanthemum, Chrysanthemum lavandulifolium. With the exception of ClELF3, ClPRR1 and ClPRR73, most of the circadian clock genes are expressed more highly in leaves than in other tested tissues. The diurnal rhythms of these circadian clock genes are similar to those of their homologs in Arabidopsis. ClELF3 and ClZTL are constitutively expressed at all time points in both assessed photoperiods. The expression succession from morning to night of the PSEUDO RESPONSE REGULATOR (PRR) gene family occurs in the order ClPRR73/ClPRR37, ClPRR5, and then ClPRR1. ClLHY is expressed during the dawn period, and ClGIs is expressed during the dusk period. The peak expression levels of ClFKF1 and ClGIs are synchronous in the inductive photoperiod. However, in the non-inductive night break (NB) condition or non-24 h photoperiod, the peak expression level of ClFKF1 is significantly changed, indicating that ClFKF1 itself or the synchronous expression of ClFKF1 and ClGIs might be essential to initiate the flowering of C. lavandulifolium. This study provides the first extensive evaluation of circadian clock genes, and it presents a useful foundation for dissecting the functions of circadian clock genes in C. lavandulifolium. Copyright © 2014. Published by Elsevier Masson SAS.

  17. Ras-mediated deregulation of the circadian clock in cancer.

    Directory of Open Access Journals (Sweden)

    Angela Relógio

    Full Text Available Circadian rhythms are essential to the temporal regulation of molecular processes in living systems and as such to life itself. Deregulation of these rhythms leads to failures in biological processes and eventually to the manifestation of pathological phenotypes including cancer. To address the questions as to what are the elicitors of a disrupted clock in cancer, we applied a systems biology approach to correlate experimental, bioinformatics and modelling data from several cell line models for colorectal and skin cancer. We found strong and weak circadian oscillators within the same type of cancer and identified a set of genes, which allows the discrimination between the two oscillator-types. Among those genes are IFNGR2, PITX2, RFWD2, PPARγ, LOXL2, Rab6 and SPARC, all involved in cancer-related pathways. Using a bioinformatics approach, we extended the core-clock network and present its interconnection to the discriminative set of genes. Interestingly, such gene signatures link the clock to oncogenic pathways like the RAS/MAPK pathway. To investigate the potential impact of the RAS/MAPK pathway - a major driver of colorectal carcinogenesis - on the circadian clock, we used a computational model which predicted that perturbation of BMAL1-mediated transcription can generate the circadian phenotypes similar to those observed in metastatic cell lines. Using an inducible RAS expression system, we show that overexpression of RAS disrupts the circadian clock and leads to an increase of the circadian period while RAS inhibition causes a shortening of period length, as predicted by our mathematical simulations. Together, our data demonstrate that perturbations induced by a single oncogene are sufficient to deregulate the mammalian circadian clock.

  18. Ras-Mediated Deregulation of the Circadian Clock in Cancer

    Science.gov (United States)

    Relógio, Angela; Thomas, Philippe; Medina-Pérez, Paula; Reischl, Silke; Bervoets, Sander; Gloc, Ewa; Riemer, Pamela; Mang-Fatehi, Shila; Maier, Bert; Schäfer, Reinhold; Leser, Ulf; Herzel, Hanspeter; Kramer, Achim; Sers, Christine

    2014-01-01

    Circadian rhythms are essential to the temporal regulation of molecular processes in living systems and as such to life itself. Deregulation of these rhythms leads to failures in biological processes and eventually to the manifestation of pathological phenotypes including cancer. To address the questions as to what are the elicitors of a disrupted clock in cancer, we applied a systems biology approach to correlate experimental, bioinformatics and modelling data from several cell line models for colorectal and skin cancer. We found strong and weak circadian oscillators within the same type of cancer and identified a set of genes, which allows the discrimination between the two oscillator-types. Among those genes are IFNGR2, PITX2, RFWD2, PPARγ, LOXL2, Rab6 and SPARC, all involved in cancer-related pathways. Using a bioinformatics approach, we extended the core-clock network and present its interconnection to the discriminative set of genes. Interestingly, such gene signatures link the clock to oncogenic pathways like the RAS/MAPK pathway. To investigate the potential impact of the RAS/MAPK pathway - a major driver of colorectal carcinogenesis - on the circadian clock, we used a computational model which predicted that perturbation of BMAL1-mediated transcription can generate the circadian phenotypes similar to those observed in metastatic cell lines. Using an inducible RAS expression system, we show that overexpression of RAS disrupts the circadian clock and leads to an increase of the circadian period while RAS inhibition causes a shortening of period length, as predicted by our mathematical simulations. Together, our data demonstrate that perturbations induced by a single oncogene are sufficient to deregulate the mammalian circadian clock. PMID:24875049

  19. Atomic clock ensemble in space (ACES) data analysis

    Science.gov (United States)

    Meynadier, F.; Delva, P.; le Poncin-Lafitte, C.; Guerlin, C.; Wolf, P.

    2018-02-01

    The Atomic Clocks Ensemble in Space (ACES/PHARAO mission, ESA & CNES) will be installed on board the International Space Station (ISS) next year. A crucial part of this experiment is its two-way microwave link (MWL), which will compare the timescale generated on board with those provided by several ground stations disseminated on the Earth. A dedicated data analysis center is being implemented at SYRTE—Observatoire de Paris, where our team currently develops theoretical modelling, numerical simulations and the data analysis software itself. In this paper, we present some key aspects of the MWL measurement method and the associated algorithms for simulations and data analysis. We show the results of tests using simulated data with fully realistic effects such as fundamental measurement noise, Doppler, atmospheric delays, or cycle ambiguities. We demonstrate satisfactory performance of the software with respect to the specifications of the ACES mission. The main scientific product of our analysis is the clock desynchronisation between ground and space clocks, i.e. the difference of proper times between the space clocks and ground clocks at participating institutes. While in flight, this measurement will allow for tests of general relativity and Lorentz invariance at unprecedented levels, e.g. measurement of the gravitational redshift at the 3×10-6 level. As a specific example, we use real ISS orbit data with estimated errors at the 10 m level to study the effect of such errors on the clock desynchronisation obtained from MWL data. We demonstrate that the resulting effects are totally negligible.

  20. Study on Environment Performance Evaluation and Regional Differences of Strictly-Environmental-Monitored Cities in China

    Directory of Open Access Journals (Sweden)

    Ji Guo

    2017-12-01

    Full Text Available With the rapid economic growth and development, the problem of environmental pollution in China’s cities is becoming increasingly serious, and environmental pollution takes on a regional difference. There is, however, little comprehensive evaluation on the environmental performance and the regional difference of strictly-environmental-monitored cities in China. In this paper, the environmental performance of 109 strictly-environmental-monitored cities in China is evaluated in terms of natural performance, management performance, and scale performance by Data Envelopment Analysis (DEA, incorporating PM2.5 and PM10 as undesirable outputs. The empirical results show that: (1 At present, the natural performance is quite high, while the management performance is noticeably low for most cities. (2 The gap between the level of economic development and environmental protection among cities in China is large, and the scale efficiency of big cities is better than that of smaller cities. The efficiency value of large-scale cities such as Beijing, Shanghai, Guangzhou, Shenzhen, etc. is high, equaling 1; the value of smaller cities such as Sanmenxia, Baoding, Mudanjiang, and Pingdingshan is low, close to 0, indicating that big cities are characterized by high environmental efficiency. (3 From the perspective of region, the level of environmental performance in China is very uneven. For example, the environmental efficiency level of the Pan-Pearl River Delta region is superior to that of the Pan-Yangtze River region and the Bahia Rim region, whose values of environmental efficiency are 0.858, 0.658, and 0.622 respectively. The average efficiency of the Southern Coastal Economic Zone, Eastern Coastal Comprehensive Economic Zone, and the Comprehensive Economic Zone in the middle reaches of the Yangtze River is higher than that of other regions. Finally, corresponding countermeasures and suggestions are put forward. The method used in this paper is applicable

  1. Disordered strictly jammed binary sphere packings attain an anomalously large range of densities

    Science.gov (United States)

    Hopkins, Adam B.; Stillinger, Frank H.; Torquato, Salvatore

    2013-08-01

    Previous attempts to simulate disordered binary sphere packings have been limited in producing mechanically stable, isostatic packings across a broad spectrum of packing fractions. Here we report that disordered strictly jammed binary packings (packings that remain mechanically stable under general shear deformations and compressions) can be produced with an anomalously large range of average packing fractions 0.634≤ϕ≤0.829 for small to large sphere radius ratios α restricted to α≥0.100. Surprisingly, this range of average packing fractions is obtained for packings containing a subset of spheres (called the backbone) that are exactly strictly jammed, exactly isostatic, and also generated from random initial conditions. Additionally, the average packing fractions of these packings at certain α and small sphere relative number concentrations x approach those of the corresponding densest known ordered packings. These findings suggest for entropic reasons that these high-density disordered packings should be good glass formers and that they may be easy to prepare experimentally. We also identify an unusual feature of the packing fraction of jammed backbones (packings with rattlers excluded). The backbone packing fraction is about 0.624 over the majority of the α-x plane, even when large numbers of small spheres are present in the backbone. Over the (relatively small) area of the α-x plane where the backbone is not roughly constant, we find that backbone packing fractions range from about 0.606 to 0.829, with the volume of rattler spheres comprising between 1.6% and 26.9% of total sphere volume. To generate isostatic strictly jammed packings, we use an implementation of the Torquato-Jiao sequential linear programming algorithm [Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.82.061302 82, 061302 (2010)], which is an efficient producer of inherent structures (mechanically stable configurations at the local maxima in the density landscape). The identification and

  2. Disordered strictly jammed binary sphere packings attain an anomalously large range of densities.

    Science.gov (United States)

    Hopkins, Adam B; Stillinger, Frank H; Torquato, Salvatore

    2013-08-01

    Previous attempts to simulate disordered binary sphere packings have been limited in producing mechanically stable, isostatic packings across a broad spectrum of packing fractions. Here we report that disordered strictly jammed binary packings (packings that remain mechanically stable under general shear deformations and compressions) can be produced with an anomalously large range of average packing fractions 0.634≤φ≤0.829 for small to large sphere radius ratios α restricted to α≥0.100. Surprisingly, this range of average packing fractions is obtained for packings containing a subset of spheres (called the backbone) that are exactly strictly jammed, exactly isostatic, and also generated from random initial conditions. Additionally, the average packing fractions of these packings at certain α and small sphere relative number concentrations x approach those of the corresponding densest known ordered packings. These findings suggest for entropic reasons that these high-density disordered packings should be good glass formers and that they may be easy to prepare experimentally. We also identify an unusual feature of the packing fraction of jammed backbones (packings with rattlers excluded). The backbone packing fraction is about 0.624 over the majority of the α-x plane, even when large numbers of small spheres are present in the backbone. Over the (relatively small) area of the α-x plane where the backbone is not roughly constant, we find that backbone packing fractions range from about 0.606 to 0.829, with the volume of rattler spheres comprising between 1.6% and 26.9% of total sphere volume. To generate isostatic strictly jammed packings, we use an implementation of the Torquato-Jiao sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010)], which is an efficient producer of inherent structures (mechanically stable configurations at the local maxima in the density landscape). The identification and explicit construction of binary packings

  3. Fault-tolerant clock synchronization in distributed systems

    Science.gov (United States)

    Ramanathan, Parameswaran; Shin, Kang G.; Butler, Ricky W.

    1990-01-01

    Existing fault-tolerant clock synchronization algorithms are compared and contrasted. These include the following: software synchronization algorithms, such as convergence-averaging, convergence-nonaveraging, and consistency algorithms, as well as probabilistic synchronization; hardware synchronization algorithms; and hybrid synchronization. The worst-case clock skews guaranteed by representative algorithms are compared, along with other important aspects such as time, message, and cost overhead imposed by the algorithms. More recent developments such as hardware-assisted software synchronization and algorithms for synchronizing large, partially connected distributed systems are especially emphasized.

  4. Aether Theory Clock Retardation vs. Special Relativity Time Dilation

    OpenAIRE

    Levy, Joseph

    2006-01-01

    Assuming a model of aether non-entrained by the motion of celestial bodies, one can provide a rational explanation of the experimental processes affecting the measurement of time when clocks are in motion. Contrary to special relativity, aether theory does not assume that the time itself is affected by motion; the reading displayed by the moving clocks results from two facts: 1/ Due to their movement through the aether, they tick at a slower rate than in the aether frame. 2/ The usual synchro...

  5. General flat four-dimensional world pictures and clock systems

    Science.gov (United States)

    Hsu, J. P.; Underwood, J. A.

    1978-01-01

    We explore the mathematical structure and the physical implications of a general four-dimensional symmetry framework which is consistent with the Poincare-Einstein principle of relativity for physical laws and with experiments. In particular, we discuss a four-dimensional framework in which all observers in different frames use one and the same grid of clocks. The general framework includes special relativity and a recently proposed new four-dimensional symmetry with a nonuniversal light speed as two special simple cases. The connection between the properties of light propagation and the convention concerning clock systems is also discussed, and is seen to be nonunique within the four-dimensional framework.

  6. Blackbody radiation shift of the Ga+ clock transition

    International Nuclear Information System (INIS)

    Cheng, Yongjun; Mitroy, J

    2013-01-01

    The blackbody radiation shift of the Ga + clock transition is computed to be −0.0140 ± 0.0062 Hz at 300 K. The small shift is consistent with the blackbody radiation shifts of the clock transitions of other group III ions which are of a similar size. The polarizabilities of the Ga + states were computed using the configuration interaction method with an underlying semi-empirical core potential. Quadrupole and non-adiabatic dipole polarizabilities were also computed. A byproduct of the analysis involved calculations of the low-lying spectrum and oscillator strengths, including polarizabilities, of the Ga 2+ ion. (paper)

  7. Recent results of the pulsed optically pumped rubidium clock

    Science.gov (United States)

    Levi, F.; Micalizio, S.; Godone, A.; Calosso, C.; Bertacco, E.

    2017-11-01

    A laboratory prototype of a pulsed optically pumped (POP) clock based on a rubidium cell with buffer gas is described. This clock has shown very interesting physical and metrological features, such as negligible light-shift, strongly reduced cavity-pulling and very good frequency stability. In this regard, an Allan deviation of σy(τ) = 1.2 τ-1/2 for measurement times up to τ = 105 s has been measured. These results confirm the interesting perspectives of such a frequency standard and make it very attractive for several technological applications, such as radionavigation.

  8. Clocked quantum-dot cellular automata shift register

    Science.gov (United States)

    Orlov, Alexei O.; Kummamuru, Ravi; Ramasubramaniam, R.; Lent, Craig S.; Bernstein, Gary H.; Snider, Gregory L.

    2003-06-01

    The quantum-dot cellular automata (QCA) computational paradigm provides a means to achieve ultimately low limits of power dissipation by replacing binary coding in currents and voltages with single-electron switching within arrays of quantum dots ("cells"). Clocked control over the cells allows the realization of power gain, memory and pipelining in QCA circuits. We present an experimental demonstration of a clocked QCA two-stage shift register (SR) and use it to mimic the operation of a multi-stage SR. Error-bit rates for binary switching operations in a metal tunnel junction device are experimentally investigated, and discussed for future molecular QCAs.

  9. Timing Jitter Analysis for Clock recovery Circuits Based on an Optoelectronic Phase-Locked Loop (OPLL)

    DEFF Research Database (Denmark)

    Zibar, Darko; Mørk, Jesper; Oxenløwe, Leif Katsuo

    2005-01-01

    Timing jitter of an OPLL based clock recovery is investigated. We demonstrate how loop gain, input and VCO signal jitter, loop filter bandwidth and a loop time delay influence jitter of the extracted clock signal...

  10. Generating clock signals for a cycle accurate, cycle reproducible FPGA based hardware accelerator

    Science.gov (United States)

    Asaad, Sameth W.; Kapur, Mohit

    2016-01-05

    A method, system and computer program product are disclosed for generating clock signals for a cycle accurate FPGA based hardware accelerator used to simulate operations of a device-under-test (DUT). In one embodiment, the DUT includes multiple device clocks generating multiple device clock signals at multiple frequencies and at a defined frequency ratio; and the FPG hardware accelerator includes multiple accelerator clocks generating multiple accelerator clock signals to operate the FPGA hardware accelerator to simulate the operations of the DUT. In one embodiment, operations of the DUT are mapped to the FPGA hardware accelerator, and the accelerator clock signals are generated at multiple frequencies and at the defined frequency ratio of the frequencies of the multiple device clocks, to maintain cycle accuracy between the DUT and the FPGA hardware accelerator. In an embodiment, the FPGA hardware accelerator may be used to control the frequencies of the multiple device clocks.

  11. Lyme Neuroborreliosis: Preliminary Results from an Urban Referral Center Employing Strict CDC Criteria for Case Selection

    Directory of Open Access Journals (Sweden)

    David S. Younger

    2010-01-01

    Full Text Available Lyme neuroborreliosis or “neurological Lyme disease” was evidenced in 2 of 23 patients submitted to strict criteria for case selection of the Centers for Disease Control and Prevention employing a two-tier test to detect antibodies to Borrelia burgdorferi at a single institution. One patient had symptomatic polyradiculoneuritis, dysautonomia, and serological evidence of early infection; and another had symptomatic small fiber sensory neuropathy, distal polyneuropathy, dysautonomia, and serological evidence of late infection. In the remaining patients symptoms initially ascribed to Lyme disease were probably unrelated to B. burgdorferi infection. Our findings suggest early susceptibility and protracted involvement of the nervous system most likely due to the immunological effects of B. burgdorferi infection, although the exact mechanisms remain uncertain.

  12. On The Integral Representation of Strictly Continuous Set-Valued Maps

    Directory of Open Access Journals (Sweden)

    Anaté K. Lakmon

    2015-11-01

    Full Text Available Let T be a completely regular topological space and C(T be the space of bounded, continuous real-valued functions on T. C(T is endowed with the strict topology (the topology generated by seminorms determined by continuous functions vanishing at in_nity. R. Giles ([13], p. 472, Theorem 4.6 proved in 1971 that the dual of C(T can be identi_ed with the space of regular Borel measures on T. We prove this result for positive, additive set-valued maps with values in the space of convex weakly compact non-empty subsets of a Banach space and we deduce from this result the theorem of R. Giles ([13], theorem 4.6, p.473.

  13. A Total Variation Model Based on the Strictly Convex Modification for Image Denoising

    Directory of Open Access Journals (Sweden)

    Boying Wu

    2014-01-01

    Full Text Available We propose a strictly convex functional in which the regular term consists of the total variation term and an adaptive logarithm based convex modification term. We prove the existence and uniqueness of the minimizer for the proposed variational problem. The existence, uniqueness, and long-time behavior of the solution of the associated evolution system is also established. Finally, we present experimental results to illustrate the effectiveness of the model in noise reduction, and a comparison is made in relation to the more classical methods of the traditional total variation (TV, the Perona-Malik (PM, and the more recent D-α-PM method. Additional distinction from the other methods is that the parameters, for manual manipulation, in the proposed algorithm are reduced to basically only one.

  14. Residual diffeomorphisms and symplectic soft hairs: The need to refine strict statement of equivalence principle

    Science.gov (United States)

    Sheikh-Jabbari, M. M.

    2016-09-01

    General covariance is the cornerstone of Einstein’s general relativity (GR) and implies that any two metrics related by diffeomorphisms are physically equivalent. There are, however, many examples pointing to the fact that this strict statement of general covariance needs refinement. There are a very special (measure-zero) subset of diffeomorphisms, the residual diffeomorphisms, to which one can associate well-defined conserved charges. This would hence render these diffeomorphic geometries physically distinct. We discuss that these symmetries may be appropriately called “symplectic symmetries”. Existence of residual diffeomorphisms and symplectic symmetries can be a quite general feature and not limited to the examples discussed so far in the literature. We propose that, in the context of black holes, these diffeomorphic, but distinct, geometries may be viewed as “symplectic soft hair” on black holes. We comment on how this may remedy black hole microstate problem, which in this context are dubbed as “horizon fluffs”.

  15. Reactions to terror attacks in ultra-orthodox jews: the cost of maintaining strict identity.

    Science.gov (United States)

    Ankri, Yael L E; Bachar, Eytan; Shalev, Arieh Y

    2010-01-01

    Traumatic events can shatter faith and beliefs. The responses of Ultra-Orthodox survivors of deadly terrorist attacks illustrate an effort to reconcile dreadful experiences with deeply embedded beliefs. Qualified clinicians prospectively evaluated self-reported and interviewer-generated posttraumatic stress disorder (PTSD) symptoms and cognitive appraisal in Ultra-Orthodox (n = 20) and non-Ultra-Orthodox (n = 33) survivors of suicide bus-bombing incidents in Jerusalem. Ultra-Orthodox survivors reported higher levels of PTSD symptoms and more personal guilt. Their narratives reflected an unshaken belief in Just Providence, within which being a victim of terror was perceived as a Just retribution for known or unknown wrongdoing. Survivors' reactions to trauma often reflect an effort to reconcile incongruous experiences with previously held beliefs. When treating strict believers, helpers should be sensitive to the identity-preserving function of posttraumatic cognitions.

  16. On a class of adjustable rate mortgage loans subject to a strict balance principle

    DEFF Research Database (Denmark)

    Astrup Jensen, Bjarne

    We describe the background and the basic funding mechanisms for the type of adjustable rate mortgageloans that were introduced in the Danish market in 1996. Each loan is funded separately by tap issuingpass-through mortgage bonds (`strict balance principle'). The novelty is a funding mechanism...... that usesa roll-over strategy, where long term loans are funded by sequentially issuing short term pass-throughbonds, and the first issuer of these loans obtained a patent on the funding principles in 1999. Publiclyavailable descriptions of the principles leave an impression of very complicated numerical...... algorithms.The algorithms described here show that the essentials can be reduced to a `back of an envelope' complexity.Keywords: Adjustable rate mortgages, balance principle, patent, yield curve riding...

  17. Strict Liability Versus Policy and Regulation for Environmental Protection and Agricultural Waste Management in Malaysia

    Directory of Open Access Journals (Sweden)

    Mohd Bakri Ishak

    2010-01-01

    Full Text Available Basically, strict liability is part of the mechanism for expressing judgment or sentence by using direct evidence. This principle is very useful in order to obtain remedies from any damage either directly or indirectly. The principle in Rylands v Fletcher is responsible on imposing strict liability where if something brought onto land or collected there escapes liability under this rule can include not only the owner of land but also those who control or occupation on it. However, as a matter of fact, policy and regulation are also important in taking any action against any party who are responsible for environmental pollution or damage, which may include mismanagement of waste or industrial waste or agricultural waste. There are certain policies and regulations on environmental protection such as the National Environmental Policy, certain Acts and several regulations under the Environmental Quality Act 1974 (Act 127, which are very useful for agricultural waste management inter alia: Waters Act 1920 (Act 418, Environmental Quality (Prescribed Premises (Crude Palm Oil Regulations 1977, Environmental Quality (Prescribed Premises (Raw Natural Rubber Regulations 1978, Environmental Quality (Sewage and Industrial Effluents Regulations 1979, and Environmental Quality (Compounding of Offences Rules 1978. As a matter of fact, we should realize that time is of an essence for any parties which are involved in court cases and especially in avoiding the element of externality, which is commonly suffered by the government. In making this paper, therefore, some element of comparison with certain developed jurisdiction such as in the United Kingdom and Japan could not be avoided in order to obtain better outcome and to be more practical for the purpose of environmental protection and agricultural waste management.

  18. The Effect of Strict Segregation on Pseudomonas aeruginosa in Cystic Fibrosis Patients.

    Directory of Open Access Journals (Sweden)

    Rosa van Mansfeld

    Full Text Available Segregation of patients with cystic fibrosis (CF was implemented to prevent chronic infection with epidemic Pseudomonas aeruginosa strains with presumed detrimental clinical effects, but its effectiveness has not been carefully evaluated.The effect of strict segregation on the incidence of P. aeruginosa infection in CF patients was investigated through longitudinal protocolized follow-up of respiratory tract infection before and after segregation. In two nested cross-sectional studies in 2007 and 2011 the P. aeruginosa population structure was investigated and clinical parameters were determined in patients with and without infection with the Dutch epidemic P. aeruginosa clone (ST406.Of 784 included patients 315 and 382 were at risk for acquiring chronic P. aeruginosa infection before and after segregation. Acquisition rates were, respectively, 0.14 and 0.05 per 1,000 days at risk (HR: 0.66, 95% CI [0.2548-1.541]; p = 0.28. An exploratory subgroup analysis indicated lower acquisition after segregation in children < 15 years of age (HR: 0.43, 95% CI[0.21-0.95]; p = 0.04. P. aeruginosa population structure did not change after segregation and ST406 was not associated with lung function decline, death or lung transplantation.Strict segregation was not associated with a statistically significant lower acquisition of chronic P. aeruginosa infection and ST406 was not associated with adverse clinical outcome. After segregation there were no new acquisitions of ST406. In an unplanned exploratory analysis chronic acquisition of P. aeruginosa was lower after implementation of segregation in patients under 15 years of age.

  19. Weight of fitness deviation governs strict physical chaos in replicator dynamics

    Science.gov (United States)

    Pandit, Varun; Mukhopadhyay, Archan; Chakraborty, Sagar

    2018-03-01

    Replicator equation—a paradigm equation in evolutionary game dynamics—mathematizes the frequency dependent selection of competing strategies vying to enhance their fitness (quantified by the average payoffs) with respect to the average fitnesses of the evolving population under consideration. In this paper, we deal with two discrete versions of the replicator equation employed to study evolution in a population where any two players' interaction is modelled by a two-strategy symmetric normal-form game. There are twelve distinct classes of such games, each typified by a particular ordinal relationship among the elements of the corresponding payoff matrix. Here, we find the sufficient conditions for the existence of asymptotic solutions of the replicator equations such that the solutions—fixed points, periodic orbits, and chaotic trajectories—are all strictly physical, meaning that the frequency of any strategy lies inside the closed interval zero to one at all times. Thus, we elaborate on which of the twelve types of games are capable of showing meaningful physical solutions and for which of the two types of replicator equation. Subsequently, we introduce the concept of the weight of fitness deviation that is the scaling factor in a positive affine transformation connecting two payoff matrices such that the corresponding one-shot games have exactly same Nash equilibria and evolutionary stable states. The weight also quantifies how much the excess of fitness of a strategy over the average fitness of the population affects the per capita change in the frequency of the strategy. Intriguingly, the weight's variation is capable of making the Nash equilibria and the evolutionary stable states, useless by introducing strict physical chaos in the replicator dynamics based on the normal-form game.

  20. Selvester scoring in patients with strict LBBB using the QUARESS software.

    Science.gov (United States)

    Xia, Xiaojuan; Chaudhry, Uzma; Wieslander, Björn; Borgquist, Rasmus; Wagner, Galen S; Strauss, David G; Platonov, Pyotr; Ugander, Martin; Couderc, Jean-Philippe

    2015-01-01

    Estimation of the infarct size from body-surface ECGs in post-myocardial infarction patients has become possible using the Selvester scoring method. Automation of this scoring has been proposed in order to speed-up the measurement of the score and improving the inter-observer variability in computing a score that requires strong expertise in electrocardiography. In this work, we evaluated the quality of the QuAReSS software for delivering correct Selvester scoring in a set of standard 12-lead ECGs. Standard 12-lead ECGs were recorded in 105 post-MI patients prescribed implantation of an implantable cardiodefibrillator (ICD). Amongst the 105 patients with standard clinical left bundle branch block (LBBB) patterns, 67 had a LBBB pattern meeting the strict criteria. The QuAReSS software was applied to these 67 tracings by two independent groups of cardiologists (from a clinical group and an ECG core laboratory) to measure the Selvester score semi-automatically. Using various level of agreement metrics, we compared the scores between groups and when automatically measured by the software. The average of the absolute difference in Selvester scores measured by the two independent groups was 1.4±1.5 score points, whereas the difference between automatic method and the two manual adjudications were 1.2±1.2 and 1.3±1.2 points. Eighty-two percent score agreement was observed between the two independent measurements when the difference of score was within two point ranges, while 90% and 84% score agreements were reached using the automatic method compared to the two manual adjudications. The study confirms that the QuAReSS software provides valid measurements of the Selvester score in patients with strict LBBB with minimal correction from cardiologists. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Strict stoichiometric homeostasis of Cryptomonas pyrenoidifera (Cryptophyceae in relation to N:P supply ratios

    Directory of Open Access Journals (Sweden)

    Eloísa Ramos Rodríguez

    2016-11-01

    Full Text Available A common freshwater cryptophyte, Cryptomonas pyrenoidifera, was cultivated in batch-cultures to analyze intraspecific variation in elemental stoichiometry along a broad gradient of pulsed phosphorus (P enrichment during the early acclimation period and to determine the immediate homeostatic capacity of the nitrogen-to-phosphorus (N:P ratio of this alga when nutrients are at saturating levels. Experimental results revealed that nitrogen (N and P cell quotas significantly increased with increasing P concentration. However, despite the wide range of N:P ratios in the medium, Cryptomonas N:P ratios were highly stable at higher P-level treatments, indicating a highly conservative behavior and suggesting strict elemental homeostasis when nutrients are at saturating levels. The strictly homeostatic N:P ratio appears to be attributable to their high potential for a fast luxury consumption of both N and P after a brief and intense episode of increased resource availability and to physiological limits on their nutrient storage capacity. Most importantly, the N:P biomass ratio at nutrient saturating levels converged around 11:1, which was the observed ratio of maximum internal cell quotas for N and P (i.e. Qmax,N:Qmax,P under the prevailing experimental conditions. This value is particularly informative for C. pyrenoidifera because it represents cell storage quotients and may be a taxon-specific evolutionary optimum, providing a reference point to infer the grade of nutrient-limitation. The experimental data give ranges of variation in C. pyrenoidifera elemental composition permitting, among others, proper parameterization of cryptophyte stoichiometry models.

  2. Circadian Clock genes Per2 and clock regulate steroid production, cell proliferation, and luteinizing hormone receptor transcription in ovarian granulosa cells

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu, Takashi, E-mail: shimizut@obihiro.ac.jp [Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555 (Japan); Hirai, Yuko; Murayama, Chiaki; Miyamoto, Akio [Graduate School of Animal and Food Hygiene, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555 (Japan); Miyazaki, Hitoshi [Gene Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8572 (Japan); Miyazaki, Koyomi [Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) Central 6, 1-1-1, Higashi, Tsukuba, Ibaraki 305-8566 (Japan)

    2011-08-19

    Highlights: {yields} Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression. {yields}Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom. {yields} Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. {yields}Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. {yields} The expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. -- Abstract: Circadian Clock genes are associated with the estrous cycle in female animals. Treatment with Per2 and Clock siRNAs decreased the number of granulosa cells and LHr expression in follicle-stimulating hormone FSH-treated granulosa cells. Per2 siRNA treatment did not stimulate the production of estradiol and expression of P450arom, whereas Clock siRNA treatment inhibited the production of estradiol and expression of P450arom mRNA. Per2 and Clock siRNA treatment increased and unchanged, respectively, progesterone production in FSH-treated granulosa cells. Similarly, expression of StAR mRNA was increased by Per2 siRNA and unchanged by Clock siRNA. Our data provide a new insight that Per2 and Clock have different action on ovarian granulosa cell functions.

  3. Strict follow-up programme including CT and (18) F-FDG-PET after curative surgery for colorectal cancer

    DEFF Research Database (Denmark)

    Sørensen, N F; Jensen, A B; Wille-Jørgensen, P

    2010-01-01

    Aim  The risk of local recurrence following curative surgery for colorectal cancer (CRC) is up to 50%. A rigorous follow-up program may increase survival. Guidelines on suitable methods for scheduled follow up examinations are needed. This study evaluates a strict follow-up program including...... supported a strict follow-up program following curative surgery for colorectal cancer. FDG-PET combined with CT should be included in control programs....

  4. Performance Evaluation of Clock Recovery for Coherent Mode Division Multiplexed Systems

    DEFF Research Database (Denmark)

    Medeiros Diniz, Júlio César; Piels, Molly; Zibar, Darko

    2017-01-01

    The impact of mode mixing and group delay spread on clock tone quality of a 6-mode 32 GBd NRZ-QPSK MDM system is investigated. Even for low group delay spread, strong coupling causes clock tone disappearance.......The impact of mode mixing and group delay spread on clock tone quality of a 6-mode 32 GBd NRZ-QPSK MDM system is investigated. Even for low group delay spread, strong coupling causes clock tone disappearance....

  5. System and method for clock synchronization and position determination using entangled photon pairs

    Science.gov (United States)

    Shih, Yanhua (Inventor)

    2010-01-01

    A system and method for clock synchronization and position determination using entangled photon pairs is provided. The present invention relies on the measurement of the second order correlation function of entangled states. Photons from an entangled photon source travel one-way to the clocks to be synchronized. By analyzing photon registration time histories generated at each clock location, the entangled states allow for high accuracy clock synchronization as well as high accuracy position determination.

  6. All-optical clock recovery of NRZ-DPSK signals using optical resonator-type filters

    DEFF Research Database (Denmark)

    Peucheret, Christophe; Seoane, Jorge; Ji, Hua

    2009-01-01

    It is shown how introducing a limited rise time to the driving signal enables all-optical clock recovery of NRZ-DPSK signals generated using a phase modulator. A Fabry-Perot filter is used to generate the optical clock.......It is shown how introducing a limited rise time to the driving signal enables all-optical clock recovery of NRZ-DPSK signals generated using a phase modulator. A Fabry-Perot filter is used to generate the optical clock....

  7. CLOCK phosphorylation by AKT regulates its nuclear accumulation and circadian gene expression in peripheral tissues.

    Science.gov (United States)

    Luciano, Amelia K; Zhou, Wenping; Santana, Jeans M; Kyriakides, Cleo; Velazquez, Heino; Sessa, William C

    2018-03-27

    Circadian locomotor output cycles kaput (CLOCK) is a transcription factor which activates transcription of clock-controlled genes (CCG) by heterodimerizing with BMAL1 and binding to E-box elements on DNA. While several phosphorylation sites on CLOCK have already been identified, this study characterizes a novel phosphorylation site at Serine 845 (S836 in humans). Here we show that CLOCK is a novel AKT substrate in vitro and in cells, and this phosphorylation site is a negative regulator of CLOCK nuclear localization by acting as a binding site for 14-3-3 proteins. To examine the role of CLOCK phosphorylation in vivo, Clock S845A knock-in mice were generated using CRISPR/Cas9 technology. Clock S845A mice are essentially normal with normal central circadian rhythms and hemodynamics. However, examination of core circadian gene expression from peripheral tissues demonstrated that Clock S845A mice have diminished expression of Per2, Reverba, Dbp and Npas2 in skeletal muscle and Per2, Reverba, Dbp, Per1, Rora and Npas2 in the liver during the circadian cycle. The reduction in Dbp levels is associated with reduced H3K9ac at E-boxes where CLOCK binds despite no change in total CLOCK levels. Thus, CLOCK phosphorylation by AKT on S845 regulates its nuclear translocation and the expression levels of certain core circadian genes in insulin sensitive tissues. Published under license by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Telling time from analog and digital clocks: A multiple-route account

    NARCIS (Netherlands)

    Korvorst, M.H.W.; Roelofs, A.P.A.; Levelt, W.J.M.

    2007-01-01

    Does the naming of clocks always require conceptual preparation? To examine this question, speakers were presented with analog and digital clocks that had to be named in Dutch using either a relative (e.g., "quarter to four") or an absolute (e.g., "three forty-five") clock time expression format.

  9. Using Integer Clocks to Verify the Timing-Sync Sensor Network Protocol

    Science.gov (United States)

    Huang, Xiaowan; Singh, Anu; Smolka, Scott A.

    2010-01-01

    We use the UPPAAL model checker for Timed Automata to verify the Timing-Sync time-synchronization protocol for sensor networks (TPSN). The TPSN protocol seeks to provide network-wide synchronization of the distributed clocks in a sensor network. Clock-synchronization algorithms for sensor networks such as TPSN must be able to perform arithmetic on clock values to calculate clock drift and network propagation delays. They must be able to read the value of a local clock and assign it to another local clock. Such operations are not directly supported by the theory of Timed Automata. To overcome this formal-modeling obstacle, we augment the UPPAAL specification language with the integer clock derived type. Integer clocks, which are essentially integer variables that are periodically incremented by a global pulse generator, greatly facilitate the encoding of the operations required to synchronize clocks as in the TPSN protocol. With this integer-clock-based model of TPSN in hand, we use UPPAAL to verify that the protocol achieves network-wide time synchronization and is devoid of deadlock. We also use the UPPAAL Tracer tool to illustrate how integer clocks can be used to capture clock drift and resynchronization during protocol execution

  10. Oscillating perceptions: the ups and downs of the CLOCK protein in ...

    Indian Academy of Sciences (India)

    A functional mouse CLOCK protein has long been thought to be essential for mammalian circadian clockwork function, based mainly on studies of mice bearing a dominant negative, antimorphic mutation in the Clock gene. However, new discoveries using recently developed Clock-null mutant mice have shaken up this ...

  11. A grazing clock for measurement of time spent grazing by cattle ...

    African Journals Online (AJOL)

    To date, time spent grazing has been measured most successfully using an electronic grazing clock. Difficulties experienced with this clock however, were that temperature and stage in the life of the batteries affected the readings. Further, periods of grazing shorter than the units of time registered by the clock could not be ...

  12. The rhythm of feeding : Effect of nutrients on metabolism and the molecular clock

    NARCIS (Netherlands)

    Oosterman, J.E.

    2017-01-01

    This thesis describes studies we performed to assess the relationship between nutrients and the circadian clock. We assessed the effects of sugar and fatty acids on the daily rhythmicity of hepatic clock genes and whole-body metabolism in vivo, and on circadian rhythmicity of clock genes in vitro.

  13. A new stochastic model considering satellite clock interpolation errors in precise point positioning

    Science.gov (United States)

    Wang, Shengli; Yang, Fanlin; Gao, Wang; Yan, Lizi; Ge, Yulong

    2018-03-01

    Precise clock products are typically interpolated based on the sampling interval of the observational data when they are used for in precise point positioning. However, due to the occurrence of white noise in atomic clocks, a residual component of such noise will inevitable reside within the observations when clock errors are interpolated, and such noise will affect the resolution of the positioning results. In this paper, which is based on a twenty-one-week analysis of the atomic clock noise characteristics of numerous satellites, a new stochastic observation model that considers satellite clock interpolation errors is proposed. First, the systematic error of each satellite in the IGR clock product was extracted using a wavelet de-noising method to obtain the empirical characteristics of atomic clock noise within each clock product. Then, based on those empirical characteristics, a stochastic observation model was structured that considered the satellite clock interpolation errors. Subsequently, the IGR and IGS clock products at different time intervals were used for experimental validation. A verification using 179 stations worldwide from the IGS showed that, compared with the conventional model, the convergence times using the stochastic model proposed in this study were respectively shortened by 4.8% and 4.0% when the IGR and IGS 300-s-interval clock products were used and by 19.1% and 19.4% when the 900-s-interval clock products were used. Furthermore, the disturbances during the initial phase of the calculation were also effectively improved.

  14. Oscillating perceptions: the ups and downs of the CLOCK protein in ...

    Indian Academy of Sciences (India)

    2008-12-31

    Dec 31, 2008 ... impacts and alters the previous view of the role of CLOCK in the mouse circadian clockwork. [DeBruyne J. P. 2008 Oscillating perceptions: the ups and downs of the CLOCK protein in the mouse circadian system. J. Genet. 87,. 437–446]. Introduction. Endogenous circadian clocks drive daily rhythms of ...

  15. Regulation of behavioral circadian rhythms and clock protein PER1 by the deubiquitinating enzyme USP2

    Directory of Open Access Journals (Sweden)

    Yaoming Yang

    2012-06-01

    Endogenous 24-hour rhythms are generated by circadian clocks located in most tissues. The molecular clock mechanism is based on feedback loops involving clock genes and their protein products. Post-translational modifications, including ubiquitination, are important for regulating the clock feedback mechanism. Previous work has focused on the role of ubiquitin ligases in the clock mechanism. Here we show a role for the rhythmically-expressed deubiquitinating enzyme ubiquitin specific peptidase 2 (USP2 in clock function. Mice with a deletion of the Usp2 gene (Usp2 KO display a longer free-running period of locomotor activity rhythms and altered responses of the clock to light. This was associated with altered expression of clock genes in synchronized Usp2 KO mouse embryonic fibroblasts and increased levels of clock protein PERIOD1 (PER1. USP2 can be coimmunoprecipitated with several clock proteins but directly interacts specifically with PER1 and deubiquitinates it. Interestingly, this deubiquitination does not alter PER1 stability. Taken together, our results identify USP2 as a new core component of the clock machinery and demonstrate a role for deubiquitination in the regulation of the circadian clock, both at the level of the core pacemaker and its response to external cues.

  16. Resistor Extends Life Of Battery In Clocked CMOS Circuit

    Science.gov (United States)

    Wells, George H., Jr.

    1991-01-01

    Addition of fixed resistor between battery and clocked complementary metal oxide/semiconductor (CMOS) circuit reduces current drawn from battery. Basic idea to minimize current drawn from battery by operating CMOS circuit at lowest possible current consistent with use of simple, fixed off-the-shelf components. Prolongs lives of batteries in such low-power CMOS circuits as watches and calculators.

  17. New methods to assess circadian clocks in humans

    Czech Academy of Sciences Publication Activity Database

    Nováková, Marta; Sumová, Alena

    2014-01-01

    Roč. 52, č. 5 (2014), s. 404-412 ISSN 0019-5189 R&D Projects: GA MZd(CZ) NT11474 Grant - others:Univerzita Karlova(CZ) 22810 Institutional research plan: CEZ:AV0Z50110509 Institutional support: RVO:67985823 Keywords : circadian * clock gene * melatonin * human Subject RIV: ED - Physiology Impact factor: 0.835, year: 2014

  18. Glutamatergic clock output stimulates melatonin synthesis at night

    NARCIS (Netherlands)

    Perreau-Lenz, Stéphanie; Kalsbeek, Andries; Pévet, Paul; Buijs, Ruud M.

    2004-01-01

    The rhythm of melatonin synthesis in the rat pineal gland is under the control of the biological clock, which is located in the suprachiasmatic nucleus of the hypothalamus (SCN). Previous studies demonstrated a daytime inhibitory influence of the SCN on melatonin synthesis, by using

  19. Clock Reading: An Underestimated Topic in Children with Mathematics Difficulties

    Science.gov (United States)

    Burny, Elise; Valcke, Martin; Desoete, Annemie

    2012-01-01

    Recent studies have shown that children with mathematics difficulties (MD) have weaknesses in multiple areas of mathematics. Andersson, for example, recently found that children with MD perform significantly worse than other children on clock reading tasks. The present study builds on this recent finding and aims at a more profound understanding…

  20. Charge domain filter operating up to 20 MHz clock frequency

    NARCIS (Netherlands)

    Gal, R.A.J.; Wallinga, Hans

    1983-01-01

    An analog sampled data low pass third order Butterworth filter has been realised in a buried channel CCD technology. This Charge Domain Filter, composed of transversal and recursive CCD filter sections, has been tested at clock frequencies up to 20 MHz.

  1. Sexual dimorphism in clock genes expression in human adipose tissue

    Science.gov (United States)

    This study was carried out to investigate whether sex-related differences exist in the adipocyte expression of clock genes from subcutaneous abdominal and visceral fat depots in severely obese patients. METHODS: We investigated 16 morbidly obese patients, eight men and eight women (mean age 45 +/- 2...

  2. Analysis of the performance of hydrogen maser clocks at the ...

    African Journals Online (AJOL)

    Hydrogen maser frequency standards are commonly utilised in various space geodetic techniques such as Very Long Baseline Interferometry (VLBI) as local reference clocks. The Hartebeesthoek Radio Astronomy Observatory in South Africa is currently operating two maser frequency standards i.e., an EFOS28 and an ...

  3. Why Do Clocks Move Clockwise? The Dynamics of Collective ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 3; Issue 1. Why Do Clocks Move Clockwise? The Dynamics of Collective Learning. Vivek S Borkar. General Article Volume 3 Issue 1 January 1998 pp 27-35. Fulltext. Click here to view fulltext PDF. Permanent link:

  4. Why Do Clocks Move Clockwise? The Dynamics of Collective ...

    Indian Academy of Sciences (India)

    is always the best possible. The two possible conventions for clocks or for driving are completely equivalent, but this need not be the case in social conventions or technological standards. Examples abound, my own favourite being the old British system of measurements my generation had to. Vivek S Borkar is with the.

  5. Divergence time estimates of mammals from molecular clocks and ...

    Indian Academy of Sciences (India)

    2009-10-30

    Oct 30, 2009 ... This paper presents a brief review of recent advances in the classification of mammals at higher levels using fossils and molecular clocks. It also discusses latest fossil discoveries from the Cretaceous – Eocene (66–55 m.y.) rocks of India and their relevance to our current understanding of placental ...

  6. Special Relativity in Week One: 2) All Clocks Run Slow

    Science.gov (United States)

    Huggins, Elisha

    2011-01-01

    In our initial article on teaching special relativity in the first week of an introductory physics course, we used the principle of relativity and Maxwell's theory of light to derive Einstein's second postulate (that the speed of light is the same to all observers). In this paper we study thought experiments involving a light pulse clock moving…

  7. The Chemical and Educational Appeal of the Orange Juice Clock.

    Science.gov (United States)

    Kelter, Paul B.; And Others

    1996-01-01

    Describes the recent history, chemistry, and educational uses of the Orange Juice Clock demonstration in which a galvanic cell is made from the combination of a magnesium strip, a copper strip, and juice in a beaker. Discusses the chemistry basics, extensions for more advanced students, questions for student/teacher workshop participants, and…

  8. Characterization of Periodic Variations in the GPS Satellite Clocks

    National Research Council Canada - National Science Library

    Senior, Ken L; Beard, Ronald L; Ray, Jim R

    2008-01-01

    ... more stable and show a flicker phase noise component over intervals shorter than about 100 s. Due to the onboard Time Keeping System in the newer Block IIR and IIR-M satellites, their Rb clocks behave in a more complex way...

  9. An epithelial circadian clock controls pulmonary inflammation and glucocorticoid action.

    Science.gov (United States)

    Gibbs, Julie; Ince, Louise; Matthews, Laura; Mei, Junjie; Bell, Thomas; Yang, Nan; Saer, Ben; Begley, Nicola; Poolman, Toryn; Pariollaud, Marie; Farrow, Stuart; DeMayo, Francesco; Hussell, Tracy; Worthen, G Scott; Ray, David; Loudon, Andrew

    2014-08-01

    The circadian system is an important regulator of immune function. Human inflammatory lung diseases frequently show time-of-day variation in symptom severity and lung function, but the mechanisms and cell types underlying these effects remain unclear. We show that pulmonary antibacterial responses are modulated by a circadian clock within epithelial club (Clara) cells. These drive circadian neutrophil recruitment to the lung via the chemokine CXCL5. Genetic ablation of the clock gene Bmal1 (also called Arntl or MOP3) in bronchiolar cells disrupts rhythmic Cxcl5 expression, resulting in exaggerated inflammatory responses to lipopolysaccharide and an impaired host response to Streptococcus pneumoniae infection. Adrenalectomy blocks rhythmic inflammatory responses and the circadian regulation of CXCL5, suggesting a key role for the adrenal axis in driving CXCL5 expression and pulmonary neutrophil recruitment. Glucocorticoid receptor occupancy at the Cxcl5 locus shows circadian oscillations, but this is disrupted in mice with bronchiole-specific ablation of Bmal1, leading to enhanced CXCL5 expression despite normal corticosteroid secretion. The therapeutic effects of the synthetic glucocorticoid dexamethasone depend on intact clock function in the airway. We now define a regulatory mechanism that links the circadian clock and glucocorticoid hormones to control both time-of-day variation and the magnitude of pulmonary inflammation and responses to bacterial infection.

  10. Adaptive Significance of Circadian Rhythms-Biological Clocks and ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 4; Issue 1. Adaptive Significance of Circadian Rhythms - Biological Clocks and Darwinian Fitness in Cyanobacteria. V Sheeba Vijay Kumar Sharma Amitabh Joshi. Research News Volume 4 Issue 1 January 1999 pp 73-75 ...

  11. Ytterbium optical lattice clock with 10-18 level characterization

    Science.gov (United States)

    Phillips, Nathaniel; Sherman, Jeff; Beloy, Kyle; Hinkley, Nathan; Schioppo, Marco; Oates, Chris; Ludlow, Andrew

    2014-05-01

    A recent comparison of two ytterbium-based optical lattice clocks at NIST demonstrated record stability of 1 . 6 parts in 1018 after 25,000s averaging. We report on measurements of the two primary systematic effects that shift the ultra-narrow clock transition, towards a reduction of the clock uncertainty to the 10-18 level. Uncertainty stemming from the blackbody radiation (BBR) shift is largely due to imprecise knowledge of the thermal environment surrounding the atoms. We detail the construction and operation of an in-vacuum, thermally-regulated radiation shield, which permits laser cooling and trapping while enabling an absolute temperature measurement with mK precision. Additionally, while operation of the optical lattice at the magic wavelength (λm) cancels the scalar Stark shift (since both clock states shift equally), higher-order vector and two-photon hyperpolarizability shifts remain. To evaluate these effects, as well as the polarizability away from λm, we implement a lattice buildup cavity around the atoms. The resulting twenty-fold enhancement of the lattice intensity provides a significant lever arm for precise measurement of these effects.

  12. Chaotic map based key agreement with/out clock synchronization

    International Nuclear Information System (INIS)

    Han, S.; Chang, E.

    2009-01-01

    In order to address Bergamo et al.'s attack, Xiao et al. proposed a key agreement protocol using chaotic maps. Han then presented three attacks on Xiao et al.'s protocol. To enhance the security of key agreement based on chaotic maps, Chang et al. proposed a new key agreement using passphrase, which works in clock synchronization environment. However, their protocol still has some issues: one is its passphrase is not easy to remember and much longer than password; the second one is it cannot resist guessing attack if the constructed passphrase is easy to remember and also has already existed in some rational dictionaries; the third one is it cannot work without clock synchronization. In this paper, we will present two different key agreement protocols, which can resist guessing attack. The first one works in clock synchronization environment. The second one can work without clock synchronization. They both use authenticated password for secure communications. The protocols are secure against replaying attacks and a shared session key can be established.

  13. Sampling phase lock loop (PLL) with low power clock buffer

    NARCIS (Netherlands)

    Gao, X.; Bahai, A.; Bohsali, M.; Djabbari, A.; Klumperink, Eric A.M.; Nauta, Bram; Socci, G.

    2013-01-01

    A sampling phase locked loop (PLL) circuit includes a pull-up/down buffer configured to convert an oscillator reference clock into a square wave sampling control signal input to a sampling phase detector. The buffer circuit is configured to reduce power by controlling the switching of the pull-up

  14. Topology and dynamics of the zebrafish segmentation clock core circuit.

    Directory of Open Access Journals (Sweden)

    Christian Schröter

    Full Text Available During vertebrate embryogenesis, the rhythmic and sequential segmentation of the body axis is regulated by an oscillating genetic network termed the segmentation clock. We describe a new dynamic model for the core pace-making circuit of the zebrafish segmentation clock based on a systematic biochemical investigation of the network's topology and precise measurements of somitogenesis dynamics in novel genetic mutants. We show that the core pace-making circuit consists of two distinct negative feedback loops, one with Her1 homodimers and the other with Her7:Hes6 heterodimers, operating in parallel. To explain the observed single and double mutant phenotypes of her1, her7, and hes6 mutant embryos in our dynamic model, we postulate that the availability and effective stability of the dimers with DNA binding activity is controlled in a "dimer cloud" that contains all possible dimeric combinations between the three factors. This feature of our model predicts that Hes6 protein levels should oscillate despite constant hes6 mRNA production, which we confirm experimentally using novel Hes6 antibodies. The control of the circuit's dynamics by a population of dimers with and without DNA binding activity is a new principle for the segmentation clock and may be relevant to other biological clocks and transcriptional regulatory networks.

  15. Living by the clock: the circadian pacemaker in older people.

    NARCIS (Netherlands)

    Hofman, M.A.; Swaab, D.F.

    2006-01-01

    The suprachiasmatic nucleus (SCN) of the hypothalamus is considered to be a critical component of a neural oscillator system implicated in the timing of a wide variety of biological processes. The circadian cycles established by this biological clock occur throughout nature and have a period of

  16. Back to the future: Epigenetic clock plasticity towards healthy aging.

    Science.gov (United States)

    Declerck, Ken; Vanden Berghe, Wim

    2018-01-11

    Aging is the most important risk factor for major human lifestyle diseases, including cancer, neurological and cardiometabolic disorders. Due to the complex interplay between genetics, lifestyle and environmental factors, some individuals seem to age faster than others, whereas centenarians seem to have a slower aging process. Therefore, a biochemical biomarker reflecting the relative biological age would be helpful to predict an individual's health status and aging disease risk. Although it is already known for years that cumulative epigenetic changes occur upon aging, DNA methylation patterns were only recently used to construct an epigenetic clock predictor for biological age, which is a measure of how well your body functions compared to your chronological age. Moreover, the epigenetic DNA methylation clock signature is increasingly applied as a biomarker to estimate aging disease susceptibility and mortality risk. Finally, the epigenetic clock signature could be used as a lifestyle management tool to monitor healthy aging, to evaluate preventive interventions against chronic aging disorders and to extend healthy lifespan. Dissecting the mechanism of the epigenetic aging clock will yield valuable insights into the aging process and how it can be manipulated to improve health span. Copyright © 2018 Elsevier B.V. All rights reserved.

  17. Living by the clock: the circadian pacemaker in older people

    NARCIS (Netherlands)

    Hofman, Michel A.; Swaab, Dick F.

    2006-01-01

    The suprachiasmatic nucleus (SCN) of the hypothalamus is considered to be a critical component of a neural oscillator system implicated in the timing of a wide variety of biological processes. The circadian cycles established by this biological clock occur throughout nature and have a period of

  18. The biological clock: the bodyguard of temporal homeostasis

    NARCIS (Netherlands)

    Perreau-Lenz, Stéphanie; Pévet, Paul; Buijs, Ruud M.; Kalsbeek, Andries

    2004-01-01

    In order for any organism to function properly, it is crucial that it be table to control the timing of its biological functions. An internal biological clock, located, in mammals, in the suprachiasmatic nucleus of the hypothalamus (SCN), therefore carefully guards this temporal homeostasis by

  19. The AGS Ggamma Meter and Calibrating the Gauss Clock

    Energy Technology Data Exchange (ETDEWEB)

    Ahrens, Leif [Brookhaven National Laboratory (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2014-03-31

    During AGS Polarized Proton acceleration periods, one output from the AGS Ggamma Meter, namely the energy (or Ggamma) calculated from the magnetic field in the AGS main magnets and the beam radius- both measured in particular instant, is used to figure out the times in the AGS magnet acceleration cycle when the beam passes through a particular set of depolarizing resonances. The resonance set occur whenever a particle’s Ggamma (energy*(G/m) becomes nearly equal to n*Qx (i.e. any integer multiplied by the horizontal betatron tune). This deliverable is why the machinery is referred to as the ''Ggamma Meter'' rather than the AGS energy meter. The Ggamma Meter takes as inputs a set of measurements of frequency (F(t)), radius (r(t)), and gauss clock counts (GCC(t)). The other energy (GgammaBr) assumes the field when the gauss clock starts counting is known. The change in field to time t is given by the measured accumulated gauss clock counts multiplied by the gauss clock calibration (gauss/GCC). In order to deal with experimental data, this calibration factor gets an added ad hoc complication, namely a correction dependent on the rate of change the counting rate. The Ggamma meter takes GCC(t) and together with the past history for this cycle calculates B(t).

  20. Peripheral circadian clocks are diversely affected by adrenalectomy

    Czech Academy of Sciences Publication Activity Database

    Soták, Matúš; Bryndová, Jana; Ergang, Peter; Vagnerová, Karla; Kvapilová, Pavlína; Vodička, Martin; Pácha, Jiří; Sumová, Alena

    2016-01-01

    Roč. 33, č. 5 (2016), s. 520-529 ISSN 0742-0528 R&D Projects: GA ČR(CZ) GA13-08304S Institutional support: RVO:67985823 Keywords : adrenalectomy * circadian rhythms * corticosterone * peripheral clock Subject RIV: ED - Physiology Impact factor: 2.562, year: 2016

  1. Ultradian rhythm unmasked in the Pdf clock mutant of Drosophila

    Indian Academy of Sciences (India)

    2014-07-20

    Jul 20, 2014 ... temperature compensated. Our results suggest that Drosophila has an endogenous ultradian oscillator that is masked by circadian rhythmic behaviours. [Seki Y and Tanimura T 2014 Ultradian rhythm unmasked in the Pdf clock mutant of Drosophila. J. Biosci. 39 585-594]. DOI 10.1007/s12038-014-9450-z.

  2. Coordination between Differentially Regulated Circadian Clocks Generates Rhythmic Behavior.

    Science.gov (United States)

    Top, Deniz; Young, Michael W

    2017-09-11

    Specialized groups of neurons in the brain are key mediators of circadian rhythms, receiving daily environmental cues and communicating those signals to other tissues in the organism for entrainment and to organize circadian physiology. In Drosophila , the "circadian clock" is housed in seven neuronal clusters, which are defined by their expression of the main circadian proteins, Period, Timeless, Clock, and Cycle. These clusters are distributed across the fly brain and are thereby subject to the respective environments associated with their anatomical locations. While these core components are universally expressed in all neurons of the circadian network, additional regulatory proteins that act on these components are differentially expressed, giving rise to "local clocks" within the network that nonetheless converge to regulate coherent behavioral rhythms. In this review, we describe the communication between the neurons of the circadian network and the molecular differences within neurons of this network. We focus on differences in protein-expression patterns and discuss how such variation can impart functional differences in each local clock. Finally, we summarize our current understanding of how communication within the circadian network intersects with intracellular biochemical mechanisms to ultimately specify behavioral rhythms. We propose that additional efforts are required to identify regulatory mechanisms within each neuronal cluster to understand the molecular basis of circadian behavior. Copyright © 2017 Cold Spring Harbor Laboratory Press; all rights reserved.

  3. Self-clocked sequential circuits: - a design example | Aghdasi ...

    African Journals Online (AJOL)

    This paper uses a design methodology for the State variable toggling through data driven clocks to implement a Direct Memory Access Controller (DMAC) as a design example. The design is simulated on software and also implemented using discrete hardware components. The methodology can be extended to parallel ...

  4. Neutron clock as a friction-meter

    NARCIS (Netherlands)

    Wilczynski, J; SiwekWilczynska, K; Siemssen, RH

    1996-01-01

    Fast-fission reactions in collisions of four heavy systems (well below the fusion extra-push energy threshold), for which Hinde and coworkers had measured the prescission neutron multiplicities, have been analysed in terms of the deterministic dynamic model of Feldmeier coupled to a time-dependent

  5. Suppressing Loss of Ions in an Atomic Clock

    Science.gov (United States)

    Prestage, John; Chung, Sang

    2010-01-01

    An improvement has been made in the design of a compact, highly stable mercury- ion clock to suppress a loss of ions as they are transferred between the quadrupole and higher multipole ion traps. Such clocks are being developed for use aboard spacecraft for navigation and planetary radio science. The modification is also applicable to ion clocks operating on Earth: indeed, the success of the modification has been demonstrated in construction and operation of a terrestrial breadboard prototype of the compact, highly stable mercury-ion clock. Selected aspects of the breadboard prototype at different stages of development were described in previous NASA Tech Briefs articles. The following background information is reviewed from previous articles: In this clock as in some prior ion clocks, mercury ions are shuttled between two ion traps, one a 16- pole linear radio-frequency trap, while the other is a quadrupole radio-frequency trap. In the quadrupole trap, ions are tightly confined and optical state selection from a 202Hg lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions are interrogated by use of a microwave beam at approximately 40.507 GHz. The trapping of ions effectively eliminates the frequency pulling that would otherwise be caused by collisions between clock atoms and the wall of a gas cell. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave-resonance process, so that each of these processes can be optimized independently of the other. This is similar to the operation of an atomic beam clock, except that with ions the beam can be halted and reversed as ions are shuttled back and forth between the two traps. When the two traps are driven at the same radio frequency, the strength of confinement can be reduced near the junction between the two traps, depending upon the relative phase of the RF voltage used to operate each of the two traps, and

  6. Selective entrainment of the Drosophila circadian clock to daily gradients in environmental temperature

    Directory of Open Access Journals (Sweden)

    Goda Tadahiro

    2009-08-01

    Full Text Available Abstract Background Circadian clocks are internal daily time keeping mechanisms that allow organisms to anticipate daily changes in their environment and to organize their behavior and physiology in a coherent schedule. Although circadian clocks use temperature compensation mechanisms to maintain the same pace over a range of temperatures, they are also capable of synchronizing to daily temperature cycles. This study identifies key properties of this process. Results Gradually ramping daily temperature cycles are shown here to synchronize behavioral and molecular daily rhythms in Drosophila with a remarkable efficiency. Entrainment to daily temperature gradients of amplitudes as low as 4°C persisted even in the context of environmental profiles that also included continuous gradual increases or decreases in absolute temperature. To determine which elements of daily temperature gradients acted as the key determinants of circadian activity phase, comparative analyses of daily temperature gradients with different wave forms were performed. The phases of ascending and descending temperature acted together as key determinants of entrained circadian phase. In addition, circadian phase was found to be modulated by the relative temperature of release into free running conditions. Release at or close to the trough temperature of entrainment consistently resulted in phase advances. Re-entrainment to daily temperature gradients after large phase shifts occurred relatively slowly and required several cycles, allowing flies to selectively respond to periodic rather than anecdotal signals. The temperature-entrained phase relationship between clock gene expression rhythms and locomotor activity rhythms strongly resembled that previously observed for light entrainment. Moreover, daily temperature gradient and light/dark entrainment reinforced each other if the phases of ascending and descending temperature were in their natural alignment with the light and

  7. Digital clocks: simple Boolean models can quantitatively describe circadian systems.

    Science.gov (United States)

    Akman, Ozgur E; Watterson, Steven; Parton, Andrew; Binns, Nigel; Millar, Andrew J; Ghazal, Peter

    2012-09-07

    The gene networks that comprise the circadian clock modulate biological function across a range of scales, from gene expression to performance and adaptive behaviour. The clock functions by generating endogenous rhythms that can be entrained to the external 24-h day-night cycle, enabling organisms to optimally time biochemical processes relative to dawn and dusk. In recent years, computational models based on differential equations have become useful tools for dissecting and quantifying the complex regulatory relationships underlying the clock's oscillatory dynamics. However, optimizing the large parameter sets characteristic of these models places intense demands on both computational and experimental resources, limiting the scope of in silico studies. Here, we develop an approach based on Boolean logic that dramatically reduces the parametrization, making the state and parameter spaces finite and tractable. We introduce efficient methods for fitting Boolean models to molecular data, successfully demonstrating their application to synthetic time courses generated by a number of established clock models, as well as experimental expression levels measured using luciferase imaging. Our results indicate that despite their relative simplicity, logic models can (i) simulate circadian oscillations with the correct, experimentally observed phase relationships among genes and (ii) flexibly entrain to light stimuli, reproducing the complex responses to variations in daylength generated by more detailed differential equation formulations. Our work also demonstrates that logic models have sufficient predictive power to identify optimal regulatory structures from experimental data. By presenting the first Boolean models of circadian circuits together with general techniques for their optimization, we hope to establish a new framework for the systematic modelling of more complex clocks, as well as other circuits with different qualitative dynamics. In particular, we anticipate

  8. CULLIN-3 controls TIMELESS oscillations in the Drosophila circadian clock.

    Directory of Open Access Journals (Sweden)

    Brigitte Grima

    Full Text Available Eukaryotic circadian clocks rely on transcriptional feedback loops. In Drosophila, the PERIOD (PER and TIMELESS (TIM proteins accumulate during the night, inhibit the activity of the CLOCK (CLK/CYCLE (CYC transcriptional complex, and are degraded in the early morning. The control of PER and TIM oscillations largely depends on post-translational mechanisms. They involve both light-dependent and light-independent pathways that rely on the phosphorylation, ubiquitination, and proteasomal degradation of the clock proteins. SLMB, which is part of a CULLIN-1-based E3 ubiquitin ligase complex, is required for the circadian degradation of phosphorylated PER. We show here that CULLIN-3 (CUL-3 is required for the circadian control of PER and TIM oscillations. Expression of either Cul-3 RNAi or dominant negative forms of CUL-3 in the clock neurons alters locomotor behavior and dampens PER and TIM oscillations in light-dark cycles. In constant conditions, CUL-3 deregulation induces behavioral arrhythmicity and rapidly abolishes TIM cycling, with slower effects on PER. CUL-3 affects TIM accumulation more strongly in the absence of PER and forms protein complexes with hypo-phosphorylated TIM. In contrast, SLMB affects TIM more strongly in the presence of PER and preferentially associates with phosphorylated TIM. CUL-3 and SLMB show additive effects on TIM and PER, suggesting different roles for the two ubiquitination complexes on PER and TIM cycling. This work thus shows that CUL-3 is a new component of the Drosophila clock, which plays an important role in the control of TIM oscillations.

  9. Digital clocks: simple Boolean models can quantitatively describe circadian systems

    Science.gov (United States)

    Akman, Ozgur E.; Watterson, Steven; Parton, Andrew; Binns, Nigel; Millar, Andrew J.; Ghazal, Peter

    2012-01-01

    The gene networks that comprise the circadian clock modulate biological function across a range of scales, from gene expression to performance and adaptive behaviour. The clock functions by generating endogenous rhythms that can be entrained to the external 24-h day–night cycle, enabling organisms to optimally time biochemical processes relative to dawn and dusk. In recent years, computational models based on differential equations have become useful tools for dissecting and quantifying the complex regulatory relationships underlying the clock's oscillatory dynamics. However, optimizing the large parameter sets characteristic of these models places intense demands on both computational and experimental resources, limiting the scope of in silico studies. Here, we develop an approach based on Boolean logic that dramatically reduces the parametrization, making the state and parameter spaces finite and tractable. We introduce efficient methods for fitting Boolean models to molecular data, successfully demonstrating their application to synthetic time courses generated by a number of established clock models, as well as experimental expression levels measured using luciferase imaging. Our results indicate that despite their relative simplicity, logic models can (i) simulate circadian oscillations with the correct, experimentally observed phase relationships among genes and (ii) flexibly entrain to light stimuli, reproducing the complex responses to variations in daylength generated by more detailed differential equation formulations. Our work also demonstrates that logic models have sufficient predictive power to identify optimal regulatory structures from experimental data. By presenting the first Boolean models of circadian circuits together with general techniques for their optimization, we hope to establish a new framework for the systematic modelling of more complex clocks, as well as other circuits with different qualitative dynamics. In particular, we

  10. Sexual Differentiation of Circadian Clock Function in the Adrenal Gland.

    Science.gov (United States)

    Kloehn, Ian; Pillai, Savin B; Officer, Laurel; Klement, Claire; Gasser, Paul J; Evans, Jennifer A

    2016-05-01

    Sex differences in glucocorticoid production are associated with increased responsiveness of the adrenal gland in females. However, the adrenal-intrinsic mechanisms that establish sexual dimorphic function remain ill defined. Glucocorticoid production is gated at the molecular level by the circadian clock, which may contribute to sexual dimorphic adrenal function. Here we examine sex differences in the adrenal gland using an optical reporter of circadian clock function. Adrenal glands were cultured from male and female Period2::Luciferase (PER2::LUC) mice to assess clock function in vitro in real time. We confirm that there is a pronounced sex difference in the intrinsic capacity to sustain PER2::LUC rhythms in vitro, with higher amplitude rhythms in adrenal glands collected from males than from females. Changes in adrenal PER2::LUC rhythms over the reproductive life span implicate T as an important factor in driving sex differences in adrenal clock function. By directly manipulating hormone levels in adult mice in vivo, we demonstrate that T increases the amplitude of PER2::LUC rhythms in adrenal glands of both male and female mice. In contrast, we find little evidence that ovarian hormones modify adrenal clock function. Lastly, we find that T in vitro can increase the amplitude of PER2::LUC rhythms in male adrenals but not female adrenals, which suggests the existence of sex differences in the mechanisms of T action in vivo. Collectively these results reveal that activational effects of T alter circadian timekeeping in the adrenal gland, which may have implications for sex differences in stress reactivity and stress-related disorders.

  11. Evidence for widespread dysregulation of circadian clock progression in human cancer.

    Science.gov (United States)

    Shilts, Jarrod; Chen, Guanhua; Hughey, Jacob J

    2018-01-01

    The ubiquitous daily rhythms in mammalian physiology are guided by progression of the circadian clock. In mice, systemic disruption of the clock can promote tumor growth. In vitro , multiple oncogenes can disrupt the clock. However, due to the difficulties of studying circadian rhythms in solid tissues in humans, whether the clock is disrupted within human tumors has remained unknown. We sought to determine the state of the circadian clock in human cancer using publicly available transcriptome data. We developed a method, called the clock correlation distance (CCD), to infer circadian clock progression in a group of samples based on the co-expression of 12 clock genes. Our method can be applied to modestly sized datasets in which samples are not labeled with time of day and coverage of the circadian cycle is incomplete. We used the method to define a signature of clock gene co-expression in healthy mouse organs, then validated the signature in healthy human tissues. By then comparing human tumor and non-tumor samples from twenty datasets of a range of cancer types, we discovered that clock gene co-expression in tumors is consistently perturbed. Subsequent analysis of data from clock gene knockouts in mice suggested that perturbed clock gene co-expression in human cancer is not caused solely by the inactivation of clock genes. Furthermore, focusing on lung cancer, we found that human lung tumors showed systematic changes in expression in a large set of genes previously inferred to be rhythmic in healthy lung. Our findings suggest that clock progression is dysregulated in many solid human cancers and that this dysregulation could have broad effects on circadian physiology within tumors. In addition, our approach opens the door to using publicly available data to infer circadian clock progression in a multitude of human phenotypes.

  12. The Clock mutant mouse is a novel experimental model for nocturia and nocturnal polyuria.

    Science.gov (United States)

    Ihara, Tatsuya; Mitsui, Takahiko; Nakamura, Yuki; Kira, Satoru; Miyamoto, Tatsuya; Nakagomi, Hiroshi; Sawada, Norifumi; Hirayama, Yuri; Shibata, Keisuke; Shigetomi, Eiji; Shinozaki, Yoichi; Yoshiyama, Mitsuharu; Andersson, Karl-Erik; Nakao, Atsuhito; Takeda, Masayuki; Koizumi, Schuichi

    2017-04-01

    The pathophysiologies of nocturia (NOC) and nocturnal polyuria (NP) are multifactorial and their etiologies remain unclear in a large number of patients. Clock genes exist in most cells and organs, and the products of Clock regulate circadian rhythms as representative clock genes. Clock genes regulate lower urinary tract function, and a newly suggested concept is that abnormalities in clock genes cause lower urinary tract symptoms. In the present study, we investigated the voiding behavior of Clock mutant (Clock Δ19/Δ19 ) mice in order to determine the effects of clock genes on NOC/NP. Male C57BL/6 mice aged 8-12 weeks (WT) and male C57BL/6 Clock Δ19/Δ19 mice aged 8 weeks were used. They were bred under 12 hr light/dark conditions for 2 weeks and voiding behavior was investigated by measuring water intake volume, urine volume, urine volume/void, and voiding frequency in metabolic cages in the dark and light periods. No significant differences were observed in behavior patterns between Clock Δ19/Δ19 and WT mice. Clock Δ19/Δ19 mice showed greater voiding frequencies and urine volumes during the sleep phase than WT mice. The diurnal change in urine volume/void between the dark and light periods in WT mice was absent in Clock Δ19/Δ19 mice. Additionally, functional bladder capacity was significantly lower in Clock Δ19/Δ19 mice than in WT mice. We demonstrated that Clock Δ19/Δ19 mice showed the phenotype of NOC/NP. The Clock Δ19/Δ19 mouse may be used as an animal model of NOC and NP. Neurourol. Urodynam. 36:1034-1038, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  13. Byzantine-fault tolerant self-stabilizing protocol for distributed clock synchronization systems

    Science.gov (United States)

    Malekpour, Mahyar R. (Inventor)

    2010-01-01

    A rapid Byzantine self-stabilizing clock synchronization protocol that self-stabilizes from any state, tolerates bursts of transient failures, and deterministically converges within a linear convergence time with respect to the self-stabilization period. Upon self-stabilization, all good clocks proceed synchronously. The Byzantine self-stabilizing clock synchronization protocol does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period.

  14. Spin Resonance Clock Transition of the Endohedral Fullerene ^{15}N@C_{60}.

    Science.gov (United States)

    Harding, R T; Zhou, S; Zhou, J; Lindvall, T; Myers, W K; Ardavan, A; Briggs, G A D; Porfyrakis, K; Laird, E A

    2017-10-06

    The endohedral fullerene ^{15}N@C_{60} has narrow electron paramagnetic resonance lines which have been proposed as the basis for a condensed-matter portable atomic clock. We measure the low-frequency spectrum of this molecule, identifying and characterizing a clock transition at which the frequency becomes insensitive to magnetic field. We infer a linewidth at the clock field of 100 kHz. Using experimental data, we are able to place a bound on the clock's projected frequency stability. We discuss ways to improve the frequency stability to be competitive with existing miniature clocks.

  15. The clock gene cycle plays an important role in the circadian clock of the cricket Gryllus bimaculatus.

    Science.gov (United States)

    Uryu, Outa; Karpova, Svetlana G; Tomioka, Kenji

    2013-07-01

    To dissect the molecular oscillatory mechanism of the circadian clock in the cricket Gryllus bimaculatus, we have cloned a cDNA of the clock gene cycle (Gb'cyc) and analyzed its structure and function. Gb'cyc contains four functional domains, i.e. bHLH, PAS-A, PAS-B and BCTR domains, and is expressed rhythmically in light dark cycles, peaking at mid night. The RNA interference (RNAi) of Clock (Gb'Clk) and period (Gb'per) reduced the Gb'cyc mRNA levels and abolished the rhythmic expression, suggesting that the rhythmic expression of Gb'cyc is regulated by a mechanism including Gb'Clk and Gb'per. These features are more similar to those of mammalian orthologue of cyc (Bmal1) than those of Drosophila cyc. A single treatment with double-stranded RNA (dsRNA) of Gb'cyc effectively knocked down the Gb'cyc mRNA level and abolished its rhythmic expression. The cyc RNAi failed to disrupt the locomotor rhythm, but lengthened its free-running period in constant darkness (DD). It is thus likely that Gb'cyc is involved in the circadian clock machinery of the cricket. The cyc RNAi crickets showed a rhythmic expression of Gb'per and timeless (Gb'tim) in the optic lobe in DD, explaining the persistence of the locomotor rhythm. Surprisingly, cyc RNAi revealed a rhythmic expression of Gb'Clk in DD which is otherwise rather constitutively expressed in the optic lobe. These facts suggest that the cricket might have a unique clock oscillatory mechanism in which both Gb'cyc and Gb'Clk are rhythmically controlled and that under abundant expression of Gb'cyc the rhythmic expression of Gb'Clk may be concealed. Copyright © 2013 Elsevier Ltd. All rights reserved.

  16. Immediate effect of instrumentation on the subgingival microflora in deep inflamed pockets under strict plaque control.

    Science.gov (United States)

    Rhemrev, G E; Timmerman, M F; Veldkamp, I; Van Winkelhoff, A J; Van der Velden, U

    2006-01-01

    To investigate (1) reduction in the number of microorganisms obtained directly after subgingival instrumentation, (2) rate of bacterial re-colonization during 2 weeks, under supragingival plaque-free conditions. Effects of subgingival instrumentation were measured at one deep pocket in 22 patients (11 smokers and 11 non-smokers). Immediately after initial therapy, experimental sites, under strict plaque control, were instrumented subgingivally. Microbiological evaluation was performed at pre-instrumentation, immediate post-instrumentation and 1 and 2 weeks post-instrumentation. Mean total anaerobic colony forming units (CFUs) dropped from 3.9 x 10(6) before to 0.09 x 10(6) immediately following instrumentation. Significant reductions were found for Tannerella forsythia, Micromonas micros, Fusobacterium nucleatum and spirochetes. Significant reductions were not observed for Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia and Campylobacter rectus. Except for spirochetes, no reduction in prevalence of specific periodontal bacteria was found immediately after instrumentation. During follow-up, mean total CFU tended to increase. Prevalence of periodontal bacteria further reduced. No effect of smoking was found. Results indicate that subgingival mechanical cleaning in itself, has a limited effect, in actually removing bacteria. The subsequent reduction in prevalence of specific periodontal bacteria shows that it is apparently difficult for these species to survive in treated pockets.

  17. Magnetic resonance imaging quantitation of changes in muscle volume during 7 days of strict bed rest.

    Science.gov (United States)

    Ferrando, A A; Stuart, C A; Brunder, D G; Hillman, G R

    1995-10-01

    Prolonged bed rest results in a loss of leg lean body mass. Previous studies using bed rest as a model for microgravity have shown decreases in leg mass after 12 and 14 d, 5 and 17 wk. As magnetic resonance imaging (MRI) can provide a precise and non-invasive means of determining muscle volume, we sought to determine if changes in leg muscle volume could be detected in bed rest periods as short as 7 d. Five young, healthy, male volunteers were subjected to 7 d of absolute bed rest. Each subject underwent MRI quantitation of segmental muscle volumes of the calves and thighs before and after bed rest. Eleven (calf) and nine (thigh) contiguous 1-cm thick transaxial images were generated over prescribed regions using a Technicare MRI imager with a 0.6T superconducting magnet and body coil. Image processing was performed using a generalized 8-bit medical image analysis package developed at University of Texas Medical Branch. Images were analyzed for muscle and non-muscle volumes (including fat, blood vessel, and bone marrow volumes). The MRI quantitation demonstrated bed rest-induced significant decreases in segmental thigh muscle (approximately 3.0%, p image analysis of MRI images provides a sensitive tool capable of detecting leg volume changes of as little as 3.0% over a 7-d period of strict bed rest.

  18. Managing curriculum transformation within strict university governance structures: an example from Damascus University Medical School.

    Science.gov (United States)

    Kayyal, Mohammad; Gibbs, Trevor

    2012-01-01

    As the world of medical education moves forward, it becomes increasingly clear that the transformative process is not as easy a process for all. Across the globe, there appears to be many barriers that obstruct or threaten innovation and change, most of which cause almost insurmountable problems to many schools. If transformative education is to result in an equitable raising of standards across such an unlevel playing field, schools have to find ways in overcoming these barriers. One seemingly common barrier to development occurs when medical schools are trapped within strict University governance structures; rules and regulations which are frequently inappropriate and obstructive to the transformation that must occur in today's medical educational paradigm. The Faculty of Medicine at Damascus University, one of the oldest and foremost medical schools in the Middle East, is one such school where rigid rules and regulations and traditional values are obstructing transformative change. This paper describes the problems, which the authors believe to be common to many, and explores how attempts have been made to overcome them and move the school into the twenty-first century. It is the ultimate purpose of this paper to raise awareness of the issue, share the lessons learned in order to assist others who are experiencing similar problems and possibly create opportunities for dialogue between schools.

  19. On a holomorphic Lefschetz formula in strictly pseudoconvex subdomains of complex manifolds

    International Nuclear Information System (INIS)

    Kytmanov, A M; Myslivets, S G; Tarkhanov, N N

    2004-01-01

    The classical Lefschetz formula expresses the number of fixed points of a continuous map f:M→M in terms of the transformation induced by f on the cohomology of M. In 1966, Atiyah and Bott extended this formula to elliptic complexes over a compact closed manifold. In particular, they obtained a holomorphic Lefschetz formula on compact complex manifolds without boundary. Brenner and Shubin (1981, 1991) extended the Atiyah-Bott theory to compact manifolds with boundary. On compact complex manifolds with boundary the Dolbeault complex is not elliptic, therefore the Atiyah-Bott theory is not applicable. Bypassing difficulties related to the boundary behaviour of Dolbeault cohomology, Donnelly and Fefferman (1986) obtained a formula for the number of fixed points in terms of the Bergman metric. The aim of this paper is to obtain a Lefschetz formula on relatively compact strictly pseudoconvex subdomains of complex manifolds X with smooth boundary, that is, to find the total Lefschetz number for a holomorphic endomorphism f * of the Dolbeault complex and to express it in terms of local invariants of the fixed points of f.

  20. Divergent changes in serum sterols during a strict uncooked vegan diet in patients with rheumatoid arthritis.

    Science.gov (United States)

    Agren, J J; Tvrzicka, E; Nenonen, M T; Helve, T; Hänninen, O

    2001-02-01

    The effects of a strict uncooked vegan diet on serum lipid and sterol concentrations were studied in patients with rheumatoid arthritis. The subjects were randomized into a vegan diet group (n 16), who consumed a vegan diet for 2-3 months, or into a control group (n 13), who continued their usual omnivorous diets. Serum total and LDL-cholesterol and -phospholipid concentrations were significantly decreased by the vegan diet. The levels of serum cholestanol and lathosterol also decreased, but serum cholestanol:total cholesterol and lathosterol:total cholesterol did not change. The effect of a vegan diet on serum plant sterols was divergent as the concentration of campesterol decreased while that of sitosterol increased. This effect resulted in a significantly greater sitosterol:campesterol value in the vegan diet group than in the control group (1.48 (SD 0.39) v. 0.72 (SD 0.14); P vegan diet changes the relative absorption rates of these sterols and/or their biliary clearance.