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Sample records for plant clock system

  1. Network news: prime time for systems biology of the plant circadian clock truncated form of the title: Plant circadian clocks

    PubMed Central

    McClung, C. Robertson; Gutiérrez, Rodrigo A.

    2011-01-01

    Summary Whole-transcriptome analyses have established that the plant circadian clock regulates virtually every plant biological process and most prominently hormonal and stress response pathways. Systems biology efforts have successfully modeled the plant central clock machinery and an iterative process of model refinement and experimental validation has contributed significantly to the current view of the central clock machinery. The challenge now is to connect this central clock to the output pathways for understanding how the plant circadian clock contributes to plant growth and fitness in a changing environment. Undoubtedly, systems approaches will be needed to integrate and model the vastly increased volume of experimental data in order to extract meaningful biological information. Thus, we have entered an era of systems modeling, experimental testing, and refinement. This approach, coupled with advances from the genetic and biochemical analyses of clock function, is accelerating our progress towards a comprehensive understanding of the plant circadian clock network. PMID:20889330

  2. Network news: prime time for systems biology of the plant circadian clock.

    PubMed

    McClung, C Robertson; Gutiérrez, Rodrigo A

    2010-12-01

    Whole-transcriptome analyses have established that the plant circadian clock regulates virtually every plant biological process and most prominently hormonal and stress response pathways. Systems biology efforts have successfully modeled the plant central clock machinery and an iterative process of model refinement and experimental validation has contributed significantly to the current view of the central clock machinery. The challenge now is to connect this central clock to the output pathways for understanding how the plant circadian clock contributes to plant growth and fitness in a changing environment. Undoubtedly, systems approaches will be needed to integrate and model the vastly increased volume of experimental data in order to extract meaningful biological information. Thus, we have entered an era of systems modeling, experimental testing, and refinement. This approach, coupled with advances from the genetic and biochemical analyses of clock function, is accelerating our progress towards a comprehensive understanding of the plant circadian clock network. PMID:20889330

  3. BUGS system clock distributor

    NASA Astrophysics Data System (ADS)

    Dietrich, Thomas M.

    1991-11-01

    A printed circuit board which will provide external clocks and precisely measure the time at which events take place was designed for the Bristol University Gas Spectrometer (BUGS). The board, which was designed to interface both mechanically and electrically to the Computer Automated Measurement and Control (CAMAC) system, has been named the BUGS system clock control. The board's design and use are described.

  4. BUGS system clock distributor

    NASA Technical Reports Server (NTRS)

    Dietrich, Thomas M.

    1991-01-01

    A printed circuit board which will provide external clocks and precisely measure the time at which events take place was designed for the Bristol University Gas Spectrometer (BUGS). The board, which was designed to interface both mechanically and electrically to the Computer Automated Measurement and Control (CAMAC) system, has been named the BUGS system clock control. The board's design and use are described.

  5. Tutorial: Clock and Clock Systems Performance Measures

    NASA Technical Reports Server (NTRS)

    Allan, David W.

    1996-01-01

    This tutorial contains basic material - familiar to many. This will be used as a foundation upon which we will build - bringing forth some new material and equations that have been developed especially for this tutorial. These will provide increased understanding toward parameter estimation of clock and clock system's performance. There is a very important International Telecommunications Union (ITU) handbook being prepared at this time which goes much further than this tutorial has time to do. I highly recommend it as an excellent resource document. The final draft is just now being completed, and it should be ready late in 1996. It is an outstanding handbook; Dr. Sydnor proposed to the ITU-R several years ago, and is the editor with my assistance. We have some of the best contributors in the community from around the world who have written the ten chapters in this handbook. The title of the handbook is 'Selection and use of Precise Frequency and Time Systems'. It will be available from the ITU secretariat in Geneva, Switzerland, but NAVTEC Seminars also plans to be a distributor.

  6. Organ specificity in the plant circadian system is explained by different light inputs to the shoot and root clocks.

    PubMed

    Bordage, Simon; Sullivan, Stuart; Laird, Janet; Millar, Andrew J; Nimmo, Hugh G

    2016-10-01

    Circadian clocks allow the temporal compartmentalization of biological processes. In Arabidopsis, circadian rhythms display organ specificity but the underlying molecular causes have not been identified. We investigated the mechanisms responsible for the similarities and differences between the clocks of mature shoots and roots in constant conditions and in light : dark cycles. We developed an imaging system to monitor clock gene expression in shoots and light- or dark-grown roots, modified a recent mathematical model of the Arabidopsis clock and used this to simulate our new data. We showed that the shoot and root circadian clocks have different rhythmic properties (period and amplitude) and respond differently to light quality. The root clock was entrained by direct exposure to low-intensity light, even in antiphase to the illumination of shoots. Differences between the clocks were more pronounced in conditions where light was present than in constant darkness, and persisted in the presence of sucrose. We simulated the data successfully by modifying those parameters of a clock model that are related to light inputs. We conclude that differences and similarities between the shoot and root clocks can largely be explained by organ-specific light inputs. This provides mechanistic insight into the developing field of organ-specific clocks.

  7. Organ specificity in the plant circadian system is explained by different light inputs to the shoot and root clocks.

    PubMed

    Bordage, Simon; Sullivan, Stuart; Laird, Janet; Millar, Andrew J; Nimmo, Hugh G

    2016-10-01

    Circadian clocks allow the temporal compartmentalization of biological processes. In Arabidopsis, circadian rhythms display organ specificity but the underlying molecular causes have not been identified. We investigated the mechanisms responsible for the similarities and differences between the clocks of mature shoots and roots in constant conditions and in light : dark cycles. We developed an imaging system to monitor clock gene expression in shoots and light- or dark-grown roots, modified a recent mathematical model of the Arabidopsis clock and used this to simulate our new data. We showed that the shoot and root circadian clocks have different rhythmic properties (period and amplitude) and respond differently to light quality. The root clock was entrained by direct exposure to low-intensity light, even in antiphase to the illumination of shoots. Differences between the clocks were more pronounced in conditions where light was present than in constant darkness, and persisted in the presence of sucrose. We simulated the data successfully by modifying those parameters of a clock model that are related to light inputs. We conclude that differences and similarities between the shoot and root clocks can largely be explained by organ-specific light inputs. This provides mechanistic insight into the developing field of organ-specific clocks. PMID:27240972

  8. Thermoplasticity in the plant circadian clock

    PubMed Central

    James, Allan B.; Syed, Naeem Hasan; Brown, John W. S.; Nimmo, Hugh G.

    2012-01-01

    In the March 2012 issue of The Plant Cell we describe extensive alternative splicing (AS) of Arabidopsis circadian clock genes. Notably these distinct post-transcriptional events associate with different steady-state temperatures and also with plants undergoing temperature transitions leading us to propose that temperature-associated AS is an additional mechanism involved in the operation and control of the plant circadian clock. Here we show that temperature associated AS also extends to REVEILLE 8 (RVE8), demonstrating a hitherto unrecognized link between the expression of this clock associated gene and temperature. Finally we discuss our observations of the plastic nature of clock gene expression at the post-transcriptional level in the context of the ongoing fascination of how plants respond to temperature. PMID:22902701

  9. Primary Atomic Clock Reference System

    NASA Technical Reports Server (NTRS)

    2001-01-01

    An artist's concept of the Primary Atomic Clock Reference System (PARCS) plarned to fly on the International Space Station (ISS). PARCS will make even more accurate atomic time available to everyone, from physicists testing Einstein's Theory of Relativity, to hikers using the Global Positioning System to find their way. In ground-based atomic clocks, lasers are used to cool and nearly stop atoms of cesium whose vibrations are used as the time base. The microgravity of space will allow the atoms to be suspended in the clock rather than circulated in an atomic fountain, as required on Earth. PARCS is being developed by the Jet Propulsion Laboratory with principal investigators at the National Institutes of Standards and Technology and the University of Colorado, Boulder. See also No. 0103191

  10. Primary Atomic Clock Reference System

    NASA Technical Reports Server (NTRS)

    2001-01-01

    An artist's concept of the Primary Atomic Clock Reference System (PARCS) plarned to fly on the International Space Station (ISS). PARCS will make even more accurate atomic time available to everyone, from physicists testing Einstein's Theory of Relativity, to hikers using the Global Positioning System to find their way. In ground-based atomic clocks, lasers are used to cool and nearly stop atoms of cesium whose vibrations are used as the time base. The microgravity of space will allow the atoms to be suspended in the clock rather than circulated in an atomic fountain, as required on Earth. PARCS is being developed by the Jet Propulsion Laboratory with principal investigators at the National Institutes of Standards and Technology and the University of Colorado, Boulder. See also No. 0100120.

  11. The plant circadian clock looks like a traditional Japanese clock rather than a modern Western clock

    PubMed Central

    Mizuno, Takeshi; Yamashino, Takafumi

    2015-01-01

    Life cycle adaptation to seasonal changes in photoperiod and ambient temperature is a major determinant of the ecological success behind the widespread domestication of flowering plants. The circadian clock plays a role in the underlying mechanism for adaptation through generating endogenous rhythms that allow plants to adapt and adjust to both the 24 h diurnal rotation and 365 d seasonal revolution. Nevertheless, the mechanism by which the circadian clock tracks seasonal changes in photoperiod and temperature is a longstanding subject in the field. Recently, we have begun to understand the question of how the light and ambient temperature signals feed into the circadian clock transcriptional circuitry in day-night cycles in order to track seasonal changes in photoperiod and ambient temperature.1-4 Our results collectively indicate that the evening complex (EC) nighttime repressor consisting of LUX-ELF3-ELF4 plays a crucial role in this respect. Here, we discuss about these recent studies to add further implications. PMID:26382718

  12. A Compact Model for the Complex Plant Circadian Clock.

    PubMed

    De Caluwé, Joëlle; Xiao, Qiying; Hermans, Christian; Verbruggen, Nathalie; Leloup, Jean-Christophe; Gonze, Didier

    2016-01-01

    The circadian clock is an endogenous timekeeper that allows organisms to anticipate and adapt to the daily variations of their environment. The plant clock is an intricate network of interlocked feedback loops, in which transcription factors regulate each other to generate oscillations with expression peaks at specific times of the day. Over the last decade, mathematical modeling approaches have been used to understand the inner workings of the clock in the model plant Arabidopsis thaliana. Those efforts have produced a number of models of ever increasing complexity. Here, we present an alternative model that combines a low number of equations and parameters, similar to the very earliest models, with the complex network structure found in more recent ones. This simple model describes the temporal evolution of the abundance of eight clock gene mRNA/protein and captures key features of the clock on a qualitative level, namely the entrained and free-running behaviors of the wild type clock, as well as the defects found in knockout mutants (such as altered free-running periods, lack of entrainment, or changes in the expression of other clock genes). Additionally, our model produces complex responses to various light cues, such as extreme photoperiods and non-24 h environmental cycles, and can describe the control of hypocotyl growth by the clock. Our model constitutes a useful tool to probe dynamical properties of the core clock as well as clock-dependent processes. PMID:26904049

  13. A Compact Model for the Complex Plant Circadian Clock

    PubMed Central

    De Caluwé, Joëlle; Xiao, Qiying; Hermans, Christian; Verbruggen, Nathalie; Leloup, Jean-Christophe; Gonze, Didier

    2016-01-01

    The circadian clock is an endogenous timekeeper that allows organisms to anticipate and adapt to the daily variations of their environment. The plant clock is an intricate network of interlocked feedback loops, in which transcription factors regulate each other to generate oscillations with expression peaks at specific times of the day. Over the last decade, mathematical modeling approaches have been used to understand the inner workings of the clock in the model plant Arabidopsis thaliana. Those efforts have produced a number of models of ever increasing complexity. Here, we present an alternative model that combines a low number of equations and parameters, similar to the very earliest models, with the complex network structure found in more recent ones. This simple model describes the temporal evolution of the abundance of eight clock gene mRNA/protein and captures key features of the clock on a qualitative level, namely the entrained and free-running behaviors of the wild type clock, as well as the defects found in knockout mutants (such as altered free-running periods, lack of entrainment, or changes in the expression of other clock genes). Additionally, our model produces complex responses to various light cues, such as extreme photoperiods and non-24 h environmental cycles, and can describe the control of hypocotyl growth by the clock. Our model constitutes a useful tool to probe dynamical properties of the core clock as well as clock-dependent processes. PMID:26904049

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

    PubMed

    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.

  15. Phase measurement system using a dithered clock

    DOEpatents

    Fairley, C.R.; Patterson, S.R.

    1991-05-28

    A phase measurement system is disclosed which measures the phase shift between two signals by dithering a clock signal and averaging a plurality of measurements of the phase differences between the two signals. 8 figures.

  16. The circadian clock and defence signalling in plants.

    PubMed

    Sharma, Mayank; Bhatt, Deepesh

    2015-02-01

    The circadian clock is the internal time-keeping machinery in higher organisms. Cross-talk between the circadian clock and a diverse range of physiological processes in plants, including stress acclimatization, hormone signalling, photomorphogenesis and defence signalling, is currently being explored. Recent studies on circadian clock genes and genes involved in defence signalling have indicated a possible reciprocal interaction between the two. It has been proposed that the circadian clock shapes the outcome of plant-pathogen interactions. In this review, we highlight the studies carried out so far on two model plant pathogens, namely Pseudomonas syringae and Hyaloperonospora arabidopsidis, and the involvement of the circadian clock in gating effector-triggered immunity and pathogen-associated molecular pattern-triggered immunity. We focus on how the circadian clock gates the expression of various stress-related transcripts in a prolific manner to enhance plant fitness. An understanding of this dynamic relationship between clock and stress will open up new avenues in the understanding of endogenous mechanisms of defence signalling in plants.

  17. Method and system for downhole clock synchronization

    DOEpatents

    Hall, David R.; Bartholomew, David B.; Johnson, Monte; Moon, Justin; Koehler, Roger O.

    2006-11-28

    A method and system for use in synchronizing at least two clocks in a downhole network are disclosed. The method comprises determining a total signal latency between a controlling processing element and at least one downhole processing element in a downhole network and sending a synchronizing time over the downhole network to the at least one downhole processing element adjusted for the signal latency. Electronic time stamps may be used to measure latency between processing elements. A system for electrically synchronizing at least two clocks connected to a downhole network comprises a controlling processing element connected to a synchronizing clock in communication over a downhole network with at least one downhole processing element comprising at least one downhole clock. Preferably, the downhole network is integrated into a downhole tool string.

  18. The regulation of plant growth by the circadian clock.

    PubMed

    Farré, E M

    2012-05-01

    Circadian regulated changes in growth rates have been observed in numerous plants as well as in unicellular and multicellular algae. The circadian clock regulates a multitude of factors that affect growth in plants, such as water and carbon availability and light and hormone signalling pathways. The combination of high-resolution growth rate analyses with mutant and biochemical analysis is helping us elucidate the time-dependent interactions between these factors and discover the molecular mechanisms involved. At the molecular level, growth in plants is modulated through a complex regulatory network, in which the circadian clock acts at multiple levels.

  19. Circadian Clocks in the Immune System.

    PubMed

    Labrecque, Nathalie; Cermakian, Nicolas

    2015-08-01

    The immune system is a complex set of physiological mechanisms whose general aim is to defend the organism against non-self-bodies, such as pathogens (bacteria, viruses, parasites), as well as cancer cells. Circadian rhythms are endogenous 24-h variations found in virtually all physiological processes. These circadian rhythms are generated by circadian clocks, located in most cell types, including cells of the immune system. This review presents an overview of the clocks in the immune system and of the circadian regulation of the function of immune cells. Most immune cells express circadian clock genes and present a wide array of genes expressed with a 24-h rhythm. This has profound impacts on cellular functions, including a daily rhythm in the synthesis and release of cytokines, chemokines and cytolytic factors, the daily gating of the response occurring through pattern recognition receptors, circadian rhythms of cellular functions such as phagocytosis, migration to inflamed or infected tissue, cytolytic activity, and proliferative response to antigens. Consequently, alterations of circadian rhythms (e.g., clock gene mutation in mice or environmental disruption similar to shift work) lead to disturbed immune responses. We discuss the implications of these data for human health and the areas that future research should aim to address.

  20. Navstar Global Positioning System (GPS) clock program: Present and future

    NASA Technical Reports Server (NTRS)

    Tennant, D. M.

    1981-01-01

    Global Positioning System (GPS) program status are discussed and plans for ensuring the long term continuation of the program are presented. Performance of GPS clocks is presented in terms of on orbit data as portrayed by GPS master control station kalman filter processing. The GPS Clock reliability program is reviewed in depth and future plans fo the overall clock program are published.

  1. Field operations with cesium clocks in HF navigation systems

    NASA Technical Reports Server (NTRS)

    Christy, E. H.; Clayton, D. A.

    1982-01-01

    Networks of HF phase comparison marine navigation stations employing cesium clocks are discussed. The largest permanent network is in the Gulf of Mexico where some fourteen base stations are continuously active and others are activated as needed. These HF phase comparison systems, which operate on a single transmission path, require a clock on the mobile unit as well. Inventory consists of upwards of 70 clocks from two different manufacturers. The maintenance of this network as an operating system requires a coordinated effort involving clock preparation, clock environment control, station performance monitoring and field service.

  2. Clock distribution system for digital computers

    DOEpatents

    Wyman, Robert H.; Loomis, Jr., Herschel H.

    1981-01-01

    Apparatus for eliminating, in each clock distribution amplifier of a clock distribution system, sequential pulse catch-up error due to one pulse "overtaking" a prior clock pulse. The apparatus includes timing means to produce a periodic electromagnetic signal with a fundamental frequency having a fundamental frequency component V'.sub.01 (t); an array of N signal characteristic detector means, with detector means No. 1 receiving the timing means signal and producing a change-of-state signal V.sub.1 (t) in response to receipt of a signal above a predetermined threshold; N substantially identical filter means, one filter means being operatively associated with each detector means, for receiving the change-of-state signal V.sub.n (t) and producing a modified change-of-state signal V'.sub.n (t) (n=1, . . . , N) having a fundamental frequency component that is substantially proportional to V'.sub.01 (t-.theta..sub.n (t) with a cumulative phase shift .theta..sub.n (t) having a time derivative that may be made uniformly and arbitrarily small; and with the detector means n+1 (1.ltoreq.n

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

    DOEpatents

    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.

  4. Clocking and synchronization circuits in multiprocessor systems

    SciTech Connect

    Jeong, Deog-Kyoon.

    1989-01-01

    Microprocessors based on RISC (Reduced Instruction Set Computer) concepts have demonstrated an ability to provide more computing power at a given level of integration than conventional microprocessors. The next step is multiprocessors composed of RISC processing elements. Communication bandwidth among such microprocessors is critical in achieving efficient hardware utilization. This thesis focuses on the communication capability of VLSI circuits and presents new circuit techniques as a guide to build an interconnection network of VLSI microprocessors. Two of the most prominent problems in a synchronous system, which most of the current computer systems are based on, have been clock skew and synchronization failure. A new concept called self-timed systems solves such problems but has not been accepted in microprocessor implementations yet because of its complex design procedure and increased overhead. With this in mind, this thesis concentrates on a system in which individual synchronous subsystems are connected asynchronously. Synchronous subsystems operate with a better control over clock skew using a phase locked loop (PLL) technique. Communication among subsystems is done asynchronously with a controlled synchronization failure rate. One advantage is that conventional VLSI design methodologies which are more efficient can still be applied. Circuit techniques for PLL-based clock generation are described along with stability criteria. The main objective of the circuit is to realize a zero delay buffer. Experimental results show the feasibility of such circuits in VLSI. Synchronizer circuit configurations in both bipolar and MOS technology that best utilize each device, or overcome the technology limit using a bandwidth doubling technique are shown. Interface techniques including handshake mechanisms in such a system are also described.

  5. Heterogeneity of cellular circadian clocks in intact plants and its correction under light-dark cycles

    PubMed Central

    Muranaka, Tomoaki; Oyama, Tokitaka

    2016-01-01

    Recent advances in single-cell analysis have revealed the stochasticity and nongenetic heterogeneity inherent to cellular processes. However, our knowledge of the actual cellular behaviors in a living multicellular organism is still limited. By using a single-cell bioluminescence imaging technique on duckweed, Lemna gibba, we demonstrate that, under constant conditions, cells in the intact plant work as individual circadian clocks that oscillate with their own frequencies and respond independently to external stimuli. Quantitative analysis uncovered the heterogeneity and instability of cellular clocks and partial synchronization between neighboring cells. Furthermore, we found that cellular clocks in the plant body under light-dark cycles showed a centrifugal phase pattern in which the effect of cell-to-cell heterogeneity in period lengths was almost masked. The inherent heterogeneity in the properties of cellular clocks observed under constant conditions is corrected under light-dark cycles to coordinate the daily rhythms of the plant body. These findings provide a novel perspective of spatiotemporal architectures in the plant circadian system. PMID:27453946

  6. Heterogeneity of cellular circadian clocks in intact plants and its correction under light-dark cycles.

    PubMed

    Muranaka, Tomoaki; Oyama, Tokitaka

    2016-07-01

    Recent advances in single-cell analysis have revealed the stochasticity and nongenetic heterogeneity inherent to cellular processes. However, our knowledge of the actual cellular behaviors in a living multicellular organism is still limited. By using a single-cell bioluminescence imaging technique on duckweed, Lemna gibba, we demonstrate that, under constant conditions, cells in the intact plant work as individual circadian clocks that oscillate with their own frequencies and respond independently to external stimuli. Quantitative analysis uncovered the heterogeneity and instability of cellular clocks and partial synchronization between neighboring cells. Furthermore, we found that cellular clocks in the plant body under light-dark cycles showed a centrifugal phase pattern in which the effect of cell-to-cell heterogeneity in period lengths was almost masked. The inherent heterogeneity in the properties of cellular clocks observed under constant conditions is corrected under light-dark cycles to coordinate the daily rhythms of the plant body. These findings provide a novel perspective of spatiotemporal architectures in the plant circadian system. PMID:27453946

  7. Clocked Schroedinger equation in the meaning of the measurement system

    SciTech Connect

    Boonchui, Sutee; Sa-yakanit, Virulh; Sritrakool, W.

    2006-01-15

    The clocked Schroedinger equation was proposed by Sokolovski using the Feynman path integral with constraint (Phys. Rev. A 52, R2, 1995). Sokolovski pointed out that the clocked Schroedinger equation cannot be derived directly from the Schroedinger equation. In this paper, we show that the clocked Schroedinger equation can be derived by starting from the normal Schroedinger equation for a composite system, composed of the observed system and the measuring device, as defined by von Neumann. Details of the derivation and the physical meaning of the clocked Schroedinger equation are given.

  8. Clocking and synchronization circuits in multiprocessor systems

    SciTech Connect

    Jeong, D.K.

    1989-01-01

    Microprocessors based on RISC (Reduced Instruction Set Computer) concepts have demonstrated an ability to provide more computing power at a given level of integration than conventional microprocessors. The next step is multiprocessors composed of RISC processing elements. Communication bandwidth among such microprocessors is critical in achieving efficient hardware utilization. This thesis focuses on the communication capability of VLSI circuits and presents new circuit techniques as a guide to build an interconnection network of VLSI microprocessors. Circuit techniques for PLL-based clock generation are described along with stability criteria. The main objective of the circuit is to realize a zero delay buffer. Experimental results show the feasibility of such circuits in VLSI. Synchronizer circuit configurations in both bipolar and MOS technology that best utilize each device, or overcome the technology limit using a bandwidth doubling technique are shown. Interface techniques including handshake mechanisms in such a system are also described.

  9. A Novel Method of Clock Synchronization in Distributed System

    NASA Astrophysics Data System (ADS)

    Li, G.; Niu, M. J.; Cai, Y. S.; Chen, X.; Ren, Y. Q.

    2016-03-01

    Time synchronization plays an important role in application of aircraft flying formation and constellation autonomous navigation, etc. In application of clock synchronization in the network system, it is not always true that each observed node may be interconnected, therefore, it is difficult to achieve time synchronization of network system with high precision in the condition that a certain node can only obtain the measurement information of clock from one of its corresponding neighbors, and cannot obtain from other nodes. According to this special problem, a novel method of high precision time synchronization of network system has been proposed. In this paper, we regard each clock as a node in the network system, and based on different distributed topology definition, the following three control algorithms of time synchronization under three circumstances have been designed: without a master clock (reference clock), with a master clock (reference clock), and with a fixed communication delay in the network system. The validity of the designed clock synchronization protocol has been proved both theoretically and through numerical simulation.

  10. Optical system design for femtosecond-level synchronization of clocks

    NASA Astrophysics Data System (ADS)

    Sinclair, Laura C.; Swann, William C.; Deschênes, Jean-Daniel; Bergeron, Hugo; Giorgetta, Fabrizio R.; Baumann, Esther; Cermak, Michael; Coddington, Ian; Newbury, Nathan R.

    2016-03-01

    Synchronization of optical clocks via optical two-way time-frequency transfer across free-space links can result in time offsets between the two clocks below tens of femtoseconds over many hours. The complex optical system necessary to support such synchronization is described in detail here.

  11. Beyond Arabidopsis: the circadian clock in non-model plant species.

    PubMed

    McClung, C Robertson

    2013-05-01

    Circadian clocks allow plants to temporally coordinate many aspects of their biology with the diurnal cycle derived from the rotation of Earth on its axis. Although there is a rich history of the study of clocks in many plant species, in recent years much progress in elucidating the architecture and function of the plant clock has emerged from studies of the model plant, Arabidopsis thaliana. There is considerable interest in extending this knowledge of the circadian clock into diverse plant species in order to address its role in topics as varied as agricultural productivity and the responses of individual species and plant communities to global climate change and environmental degradation. The analysis of circadian clocks in the green lineage provides insight into evolutionary processes in plants and throughout the eukaryotes.

  12. Circadian clock system in the pineal gland.

    PubMed

    Fukada, Yoshitaka; Okano, Toshiyuki

    2002-02-01

    The pineal gland is a neuroendocrine organ that functions as a central circadian oscillator in a variety of nonmammalian vertebrates. In many cases, the pineal gland retains photic input and endocrinal-output pathways both linked tightly to the oscillator. This contrasts well with the mammalian pineal gland equipped only with the output of melatonin production that is subject to neuronal regulation by central circadian oscillator located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Molecular studies on animal clock genes were performed first in Drosophila and later developed in rodents. More recently, clock genes such as Per, Cry, Clock, and Bmal have been found in a variety of vertebrate clock structures including the avian pineal gland. The profiles of the temporal change of the clock gene expression in the avian pineal gland are more similar to those in the mammalian SCN rather than to those in the mammalian pineal gland. Avian pineal gland and mammalian SCN seem to share a fundamental molecular framework of the clock oscillator composed of a transcription/translation-based autoregulatory feedback loop. The circadian time-keeping mechanism also requires several post-translational events, such as protein translocation and degradation processes, in which protein phosphorylation plays a very important role for the stable 24-h cycling of the oscillator and/or the photic-input pathway for entrainment of the clock. PMID:11890455

  13. Master Clock and Time-Signal-Distribution System

    NASA Technical Reports Server (NTRS)

    Tjoelker, Robert; Calhoun, Malcolm; Kuhnle, Paul; Sydnor, Richard; Lauf, John

    2007-01-01

    A timing system comprising an electronic master clock and a subsystem for distributing time signals from the master clock to end users is undergoing development to satisfy anticipated timing requirements of NASA s Deep Space Network (DSN) for the next 20 to 30 years. This system has a modular, flexible, expandable architecture that is easier to operate and maintain than the present frequency and timing subsystem (FTS).

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

    NASA Technical Reports Server (NTRS)

    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. Chlamydomonas reinhardtii as a new model system for studying the molecular basis of the circadian clock.

    PubMed

    Matsuo, Takuya; Ishiura, Masahiro

    2011-05-20

    The genome of the unicellular green alga Chlamydomonas reinhardtii has both plant-like and animal-like genes. It is of interest to know which types of clock genes this alga has. Recent forward and reverse genetic studies have revealed that its clock has both plant-like and algal clock components. In addition, since C. reinhardtii is a useful model organism also called "green yeast", the identification of clock genes will make C. reinhardtii a powerful model for studying the molecular basis of the eukaryotic circadian clock. In this review, we describe our forward genetic approach in C. reinhardtii and discuss some recent findings about its circadian clock.

  16. Reference clock parameters for digital communications systems applications

    NASA Technical Reports Server (NTRS)

    Kartaschoff, P.

    1981-01-01

    The basic parameters relevant to the design of network timing systems describe the random and systematic time departures of the system elements, i.e., master (or reference) clocks, transmission links, and other clocks controlled over the links. The quantitative relations between these parameters were established and illustrated by means of numerical examples based on available measured data. The examples were limited to a simple PLL control system but the analysis can eventually be applied to more sophisticated systems at the cost of increased computational effort.

  17. Functional conservation of clock-related genes in flowering plants: overexpression and RNA interference analyses of the circadian rhythm in the monocotyledon Lemna gibba.

    PubMed

    Serikawa, Masayuki; Miwa, Kumiko; Kondo, Takao; Oyama, Tokitaka

    2008-04-01

    Circadian rhythms are found in organisms from cyanobacteria to plants and animals. In flowering plants, the circadian clock is involved in the regulation of various physiological phenomena, including growth, leaf movement, stomata opening, and floral transitions. Molecular mechanisms underlying the circadian clock have been identified using Arabidopsis (Arabidopsis thaliana); the functions and genetic networks of a number of clock-related genes, including CIRCADIAN CLOCK ASSOCIATED1, LATE ELONGATED HYPOCOTYL (LHY), TIMING OF CAB EXPRESSION1, GIGANTEA (GI), and EARLY FLOWERING3 (ELF3), have been analyzed. The degree to which clock systems are conserved among flowering plants, however, is still unclear. We previously isolated homologs for Arabidopsis clock-related genes from monocotyledon Lemna plants. Here, we report the physiological roles of these Lemna gibba genes (LgLHYH1, LgLHYH2, LgGIH1, and LgELF3H1) in the circadian system. We studied the effects of overexpression and RNA interference (RNAi) of these genes on the rhythmic expression of morning- and evening-specific reporters. Overexpression of each gene disrupted the rhythmicity of either or both reporters, suggesting that these four homologs can be involved in the circadian system. RNAi of each of the genes except LgLHYH2 affected the bioluminescence rhythms of both reporters. These results indicated that these homologs are involved in the circadian system of Lemna plants and that the structure of the circadian clock is likely to be conserved between monocotyledons and dicotyledons. Interestingly, RNAi of LgGIH1 almost completely abolished the circadian rhythm; because this effect appeared to be much stronger than the phenotype observed in an Arabidopsis gi loss-of-function mutant, the precise role of each clock gene may have diverged in the clock systems of Lemna and Arabidopsis. PMID:18281417

  18. General flat four-dimensional world pictures and clock systems

    NASA Technical Reports Server (NTRS)

    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.

  19. A two-clock model of circadian timing in the immune system of mammals.

    PubMed

    Berger, J

    2008-07-01

    It has been confirmed that clock genes, as well as the pineal hormone, have a role in the hypothalamic suprachiasmatic nucleus, the circadian endogenous pacemaker. It seems that the peripheral clock genes in the cells of the immune system subtly control biorhythms; their seeming lack of impact only showing that they work well. Some biorhythms even seem to be independent of a light/dark circadian regime. This apparent conflict in the mammalian time structure can be resolved by a two-clocks control model involving: (a) the endogenous gene clock, which is dominant in the neural system and (b) the exogenous clock of the immune system. Interactions between these two clocks can explain both the frequently observed individual differences in circadian rhythms and the subtle role of the peripheral clock genes. The endogenous clock facilitates an alternation in the immune system which counters external attacks in daytime and induces repair and advancement by night.

  20. Validation of a fault-tolerant clock synchronization system

    NASA Technical Reports Server (NTRS)

    Butler, R. W.; Johnson, S. C.

    1984-01-01

    A validation method for the synchronization subsystem of a fault tolerant computer system is investigated. The method combines formal design verification with experimental testing. The design proof reduces the correctness of the clock synchronization system to the correctness of a set of axioms which are experimentally validated. Since the reliability requirements are often extreme, requiring the estimation of extremely large quantiles, an asymptotic approach to estimation in the tail of a distribution is employed.

  1. Digital clocks: simple Boolean models can quantitatively describe circadian systems

    PubMed Central

    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

  2. System and method for clock synchronization and position determination using entangled photon pairs

    NASA Technical Reports Server (NTRS)

    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.

  3. Ultra-stable clock laser system development towards space applications

    NASA Astrophysics Data System (ADS)

    Świerad, Dariusz; Häfner, Sebastian; Vogt, Stefan; Venon, Bertrand; Holleville, David; Bize, Sébastien; Kulosa, André; Bode, Sebastian; Singh, Yeshpal; Bongs, Kai; Rasel, Ernst Maria; Lodewyck, Jérôme; Le Targat, Rodolphe; Lisdat, Christian; Sterr, Uwe

    2016-09-01

    The increasing performance of optical lattice clocks has made them attractive for scientific applications in space and thus has pushed the development of their components including the interrogation lasers of the clock transitions towards being suitable for space, which amongst others requires making them more power efficient, radiation hardened, smaller, lighter as well as more mechanically stable. Here we present the development towards a space-compatible interrogation laser system for a strontium lattice clock constructed within the Space Optical Clock (SOC2) project where we have concentrated on mechanical rigidity and size. The laser reaches a fractional frequency instability of 7.9 × 10‑16 at 300 ms averaging time. The laser system uses a single extended cavity diode laser that gives enough power for interrogating the atoms, frequency comparison by a frequency comb and diagnostics. It includes fibre link stabilisation to the atomic package and to the comb. The optics module containing the laser has dimensions 60 × 45 × 8 cm3 and the ultra-stable reference cavity used for frequency stabilisation with its vacuum system takes 30 × 30 × 30 cm3. The acceleration sensitivities in three orthogonal directions of the cavity are 3.6 × 10‑10/g, 5.8 × 10‑10/g and 3.1 × 10‑10/g, where g ≈ 9.8 m/s2 is the standard gravitational acceleration.

  4. Ultra-stable clock laser system development towards space applications

    PubMed Central

    Świerad, Dariusz; Häfner, Sebastian; Vogt, Stefan; Venon, Bertrand; Holleville, David; Bize, Sébastien; Kulosa, André; Bode, Sebastian; Singh, Yeshpal; Bongs, Kai; Rasel, Ernst Maria; Lodewyck, Jérôme; Le Targat, Rodolphe; Lisdat, Christian; Sterr, Uwe

    2016-01-01

    The increasing performance of optical lattice clocks has made them attractive for scientific applications in space and thus has pushed the development of their components including the interrogation lasers of the clock transitions towards being suitable for space, which amongst others requires making them more power efficient, radiation hardened, smaller, lighter as well as more mechanically stable. Here we present the development towards a space-compatible interrogation laser system for a strontium lattice clock constructed within the Space Optical Clock (SOC2) project where we have concentrated on mechanical rigidity and size. The laser reaches a fractional frequency instability of 7.9 × 10−16 at 300 ms averaging time. The laser system uses a single extended cavity diode laser that gives enough power for interrogating the atoms, frequency comparison by a frequency comb and diagnostics. It includes fibre link stabilisation to the atomic package and to the comb. The optics module containing the laser has dimensions 60 × 45 × 8 cm3; and the ultra-stable reference cavity used for frequency stabilisation with its vacuum system takes 30 × 30 × 30 cm3. The acceleration sensitivities in three orthogonal directions of the cavity are 3.6 × 10−10/g, 5.8 × 10−10/g and 3.1 × 10−10/g, where g ≈ 9.8 m/s2 is the standard gravitational acceleration. PMID:27667640

  5. Clocks for airborne systems. [performance of rubidium oscillators

    NASA Technical Reports Server (NTRS)

    Houlding, N.

    1982-01-01

    The potential performance of compact oscillators, needed for the development of accurate clocks for future airborne systems (such as Identification Friend or Foe schemes), is addressed. In particular, extensive testing of rubidium oscillators manufactured by Efratom is discussed. The results indicate that an accuracy of better than 10 microseconds should be achievable in tactical aircraft provided that appropriate measures are adopted to counter the many environmental factors. In a favorable environment a stability of better than 5 x 10 to the -13th power for one day is achievable with present commercial units, but improvements are required to suit operation in an aircraft. With further development of rubidium controlled clocks the ultimate limitation on time accuracy in aircraft will probably be associated with time dissemination, maintenance difficulties and doctrinal hurdles.

  6. Byzantine-fault tolerant self-stabilizing protocol for distributed clock synchronization systems

    NASA Technical Reports Server (NTRS)

    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.

  7. The climate system as a ticking clock

    SciTech Connect

    Kerr, R.A.

    1990-09-14

    Climate researchers are picking up a more or less regular 2-year beat to the global climate system - one that seems to be heard from every quarter. The most recently discovered example of this climatic ticking - and perhaps the most intriguing - comes from the very core of El Nino. Researchers have found that some aspects of this cycle of alternating warm and relatively cold waters along the equatorial Pacific have a tendency to repeat every 2 years. The overlying winds pulsate at the same pace, as do the globe-girdling effects of the El Nino cycle, from winter warmth in Alaska to heavy rains in Peru and drought in Australia. The climatic ticking in the tropical Pacific is hardly as reliable as the changing of the seasons. Sometimes it is muted, and occasionally it skips a beat. But some researchers nevertheless see hope of using it in the prediction of El Nino and its global effects. In any case, climate researchers are eager to determine what makes El Nino tick. The answer could be an underlying pacemaker of this crucial atmospheric cycle.

  8. Hardware-assisted software clock synchronization for homogeneous distributed systems

    NASA Technical Reports Server (NTRS)

    Ramanathan, P.; Kandlur, Dilip D.; Shin, Kang G.

    1990-01-01

    A clock synchronization scheme that strikes a balance between hardware and software solutions is proposed. The proposed is a software algorithm that uses minimal additional hardware to achieve reasonably tight synchronization. Unlike other software solutions, the guaranteed worst-case skews can be made insensitive to the maximum variation of message transit delay in the system. The scheme is particularly suitable for large partially connected distributed systems with topologies that support simple point-to-point broadcast algorithms. Examples of such topologies include the hypercube and the mesh interconnection structures.

  9. An Adaptive Method for Reducing Clock Skew in an Accumulative Z-Axis Interconnect System

    NASA Technical Reports Server (NTRS)

    Bolotin, Gary; Boyce, Lee

    1997-01-01

    This paper will present several methods for adjusting clock skew variations that occur in a n accumulative z-axis interconnect system. In such a system, delay between modules in a function of their distance from one another. Clock distribution in a high-speed system, where clock skew must be kept to a minimum, becomes more challenging when module order is variable before design.

  10. Clock Controller For Ac Self-Timing Analysis Of Logic System

    DOEpatents

    Lo, Tinchee; Flanagan, John D.

    2004-05-18

    A clock controller and clock generating method are provided for AC self-test timing analysis of a logic system. The controller includes latch circuitry which receives a DC input signal at a data input, and a pair of continuous out-of-phase clock signals at capture and launch clock inputs thereof. The latch circuitry outputs two overlapping pulses responsive to the DC input signal going high. The two overlapping pulses are provided to waveform shaper circuitry which produces therefrom two non-overlapping pulses at clock speed of the logic system to be tested. The two non-overlapping pulses are a single pair of clock pulses which facilitate AC self-test timing analysis of the logic system.

  11. Time maintenance of user clocks via the tracking and data relay satellite system

    NASA Technical Reports Server (NTRS)

    Whitworth, G.; Mcintyre, J. W.; Downs, R. E.

    1983-01-01

    A system is described which uses the Tracking and Data Relay Satellite System (TDRSS) itself to compare the user satellite clock with a clock at the White Sands station that is referenced to Universal Time Coordinated (UTC). No command of the spacecraft by the system is required, and actual on-board clock corrections are made by the spacecraft control center at its discretion. Computer models were constructed using basic orbital parameters for user and TDRS satellites. With only first-order corrections and simple averaging techniques for constant clock rates, error measurement precision of better than one microsecond was obtained. More sophisticated computations should allow considerable improvement over this.

  12. Rhythms of Life: The Plant Circadian Clock - (By Katherine Hubbard and Antony Dodd).

    PubMed

    2016-04-01

    Summaryplantcell;28/4/tpc.116.tt0416/FIG1F1fig1This teaching tool explores circadian rhythms in plants. The topic is presented as a series of concepts illustrated by examples, including the architecture of circadian clocks and the connections between the oscillator and circadian-regulated processes such as metabolism and flowering. The Teaching Tool introduces some of the techniques used to investigate circadian biology and explores how understanding circadian rhythms could lead to crop improvement. PMID:27169989

  13. System and method for adaptively deskewing parallel data signals relative to a clock

    DOEpatents

    Jenkins, Philip Nord; Cornett, Frank N.

    2008-10-07

    A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in detected skew.

  14. System and method for adaptively deskewing parallel data signals relative to a clock

    DOEpatents

    Jenkins, Philip Nord; Cornett, Frank N.

    2011-10-04

    A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in detected skew.

  15. [The circadian system in man: From the internal clock to melatonin secretion].

    PubMed

    Touitou, Y

    2016-09-01

    The internal or biological clock which is located in the suprachiasmatic nuclei of the anterior hypothalamus is controlled by clock genes and environmental factors which are able to synchronize the clock to 24h. Rhythm desynchronization (shiftwork and nightwork, transmeridian flights, aging, some psychiatric diseases, blindness, intake of some drugs…) occurs when the internal clock does no longer work in harmony with the astronomical time i.e. our watch. The circadian system consists of three major elements, which are the clock, the retinohypothalamic tract and melatonin which is secreted by the pineal gland and considered as the arrow of the clock. Both light and melatonin present a phase response curve useful for the treatment of sleep circadian disorders.

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

    ERIC Educational Resources Information Center

    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…

  17. Test of an orbiting hydrogen maser clock system using laser time transfer

    NASA Technical Reports Server (NTRS)

    Vessot, Robert F. C.; Mattison, Edward M.; Nystrom, G. U.; Decher, Rudolph

    1992-01-01

    We describe a joint Smithsonian Astrophysical Laboratory/National Aeronautics and Space Administration (SAO/NASA) program for flight testing a atomic hydrogen maser clock system designed for long-term operation in space. The clock system will be carried by a shuttle-launched EURECA spacecraft. Comparisons with earth clocks to measure the clock's long-term frequency stability (tau = 10(exp 4) seconds) will be made using laser time transfer from existing NASA laser tracking stations. We describe the design of the maser clock and its control systems, and the laser timing technique. We describe the precision of station time synchronization and the limitations in the comparison between the earth and space time scales owing to gravitational and relativistic effects. We will explore the implications of determining the spacecraft's location by an on-board Global Position System (GPS) receiver, and of using microwave techniques for time and frequency transfer.

  18. Synchronization of the mammalian circadian timing system: Light can control peripheral clocks independently of the SCN clock

    PubMed Central

    Husse, Jana; Eichele, Gregor

    2015-01-01

    A vast network of cellular circadian clocks regulates 24‐hour rhythms of behavior and physiology in mammals. Complex environments are characterized by multiple, and often conflicting time signals demanding flexible mechanisms of adaptation of endogenous rhythms to external time. Traditionally this process of circadian entrainment has been conceptualized in a hierarchical scheme with a light‐reset master pacemaker residing in the hypothalamus that subsequently aligns subordinate peripheral clocks with each other and with external time. Here we review new experiments using conditional mouse genetics suggesting that resetting of the circadian system occurs in a more “federated” and tissue‐specific fashion, which allows for increased noise resistance and plasticity of circadian timekeeping under natural conditions. PMID:26252253

  19. Clock signal requirement for high-frequency, high dynamic range acquisition systems

    SciTech Connect

    Viscor, Ivo; Halamek, Josef; Villa, Marco

    2005-11-15

    Analog-to-digital converters (ADC's) are increasingly replacing mixers in frequency conversion schemes. To achieve superior performances, in terms of bandwidth and dynamic range, a nearly ideal ADC clock is needed, with a spectral purity higher than the reference signal of the classical mixing scheme. These requirements of spectral purity for the ADC clock are discussed by analyzing in detail the nonuniform sampling process and by characterizing an actual acquisition system. The effect of clock phase imperfections on the output is proportional to the input frequency over sampling frequency ratio. Moreover, at the output we may have a multiple folding of the phase jitter spectrum. These effects are illustrated by three sets of measurements performed using our system: transfer of spurious clock components, aliasing of these components, and transfer of clock phase noise.

  20. When the circadian clock meets the melanin pigmentary system.

    PubMed

    Slominski, Andrzej T; Hardeland, Rüdiger; Reiter, Russel J

    2015-04-01

    Silencing of BMAL1 and PER1 stimulates melanogenic activity of follicular and epidermal melanocytes, indicating a novel role for peripheral circadian clock processes in the regulation of melanin pigmentation. Linking the expression levels of BMAL1/PER1 with changes in melanogenesis opens exciting opportunities to study the role of the local molecular clock in modulation of melanocyte functions in the hair follicle and the epidermis with attendant effects on epidermal barrier functions in general. PMID:25785947

  1. Systems Biology of the Clock in Neurospora crassa

    PubMed Central

    Dong, Wubei; Tang, Xiaojia; Yu, Yihai; Nilsen, Roger; Kim, Rosemary; Griffith, James; Arnold, Jonathan; Schüttler, H.-Bernd

    2008-01-01

    A model-driven discovery process, Computing Life, is used to identify an ensemble of genetic networks that describe the biological clock. A clock mechanism involving the genes white-collar-1 and white-collar-2 (wc-1 and wc-2) that encode a transcriptional activator (as well as a blue-light receptor) and an oscillator frequency (frq) that encodes a cyclin that deactivates the activator is used to guide this discovery process through three cycles of microarray experiments. Central to this discovery process is a new methodology for the rational design of a Maximally Informative Next Experiment (MINE), based on the genetic network ensemble. In each experimentation cycle, the MINE approach is used to select the most informative new experiment in order to mine for clock-controlled genes, the outputs of the clock. As much as 25% of the N. crassa transcriptome appears to be under clock-control. Clock outputs include genes with products in DNA metabolism, ribosome biogenesis in RNA metabolism, cell cycle, protein metabolism, transport, carbon metabolism, isoprenoid (including carotenoid) biosynthesis, development, and varied signaling processes. Genes under the transcription factor complex WCC ( = WC-1/WC-2) control were resolved into four classes, circadian only (612 genes), light-responsive only (396), both circadian and light-responsive (328), and neither circadian nor light-responsive (987). In each of three cycles of microarray experiments data support that wc-1 and wc-2 are auto-regulated by WCC. Among 11,000 N. crassa genes a total of 295 genes, including a large fraction of phosphatases/kinases, appear to be under the immediate control of the FRQ oscillator as validated by 4 independent microarray experiments. Ribosomal RNA processing and assembly rather than its transcription appears to be under clock control, suggesting a new mechanism for the post-transcriptional control of clock-controlled genes. PMID:18769678

  2. Circadian clock adjustment to plant iron status depends on chloroplast and phytochrome function

    PubMed Central

    Salomé, Patrice A; Oliva, Michele; Weigel, Detlef; Krämer, Ute

    2013-01-01

    Plant chloroplasts are not only the main cellular location for storage of elemental iron (Fe), but also the main site for Fe, which is incorporated into chlorophyll, haem and the photosynthetic machinery. How plants measure internal Fe levels is unknown. We describe here a new Fe-dependent response, a change in the period of the circadian clock. In Arabidopsis, the period lengthens when Fe becomes limiting, and gradually shortens as external Fe levels increase. Etiolated seedlings or light-grown plants treated with plastid translation inhibitors do not respond to changes in Fe supply, pointing to developed chloroplasts as central hubs for circadian Fe sensing. Phytochrome-deficient mutants maintain a short period even under Fe deficiency, stressing the role of early light signalling in coupling the clock to Fe responses. Further mutant and pharmacological analyses suggest that known players in plastid-to-nucleus signalling do not directly participate in Fe sensing. We propose that the sensor governing circadian Fe responses defines a new retrograde pathway that involves a plastid-encoded protein that depends on phytochromes and the functional state of chloroplasts. PMID:23241948

  3. Circadian clock adjustment to plant iron status depends on chloroplast and phytochrome function.

    PubMed

    Salomé, Patrice A; Oliva, Michele; Weigel, Detlef; Krämer, Ute

    2013-02-20

    Plant chloroplasts are not only the main cellular location for storage of elemental iron (Fe), but also the main site for Fe, which is incorporated into chlorophyll, haem and the photosynthetic machinery. How plants measure internal Fe levels is unknown. We describe here a new Fe-dependent response, a change in the period of the circadian clock. In Arabidopsis, the period lengthens when Fe becomes limiting, and gradually shortens as external Fe levels increase. Etiolated seedlings or light-grown plants treated with plastid translation inhibitors do not respond to changes in Fe supply, pointing to developed chloroplasts as central hubs for circadian Fe sensing. Phytochrome-deficient mutants maintain a short period even under Fe deficiency, stressing the role of early light signalling in coupling the clock to Fe responses. Further mutant and pharmacological analyses suggest that known players in plastid-to-nucleus signalling do not directly participate in Fe sensing. We propose that the sensor governing circadian Fe responses defines a new retrograde pathway that involves a plastid-encoded protein that depends on phytochromes and the functional state of chloroplasts. PMID:23241948

  4. Synchronization of motor controller and PC system clocks

    NASA Astrophysics Data System (ADS)

    Kittmann, Frank; Bertram, Thomas; Briegel, Florian; Mohr, Lars; Berwein, Jürgen

    2010-07-01

    The power of the Large Binocular Telescope (LBT) with its two 8.4m primary mirrors sharing a common mount will unfold its full potential with the LINC-NIRVANA (LN) instrument. LINC-NIRVANA is a German-Italian beam combiner for the LBT and will interfere the light from the two 8.4m mirrors of the LBT in Fizeau mode. More than 140 motors have to be handled by custom developed Motor Controllers (MoCons). One important feature of the MoCon is the support of externally computed trajectories. Motion profiles provide information on the movement of the motor along a defined path over a certain period of time. Such profiles can be uploaded to the MoCon over Ethernet and can be started at a specific time. For field derotation it is critical that the derotation trajectories are executed with a very precise relative and absolute timing. This raises the problem of the synchronization of the MoCon internal clock with the system time of the servers that are hosting LINCNIRVANA's Instrument Control Software. The MoCon time should be known by the servers with an uncertainty of few milliseconds in order to match the start time of the motion profile and the field rotation trajectory. In this paper we will discuss how to synchronize the MoCon internal time and the PC system time.

  5. Self-stabilizing byzantine-fault-tolerant clock synchronization system and method

    NASA Technical Reports Server (NTRS)

    Malekpour, Mahyar R. (Inventor)

    2012-01-01

    Systems and methods for rapid Byzantine-fault-tolerant self-stabilizing clock synchronization are provided. The systems and methods are based on a protocol comprising a state machine and a set of monitors that execute once every local oscillator tick. The protocol is independent of specific application specific requirements. The faults are assumed to be arbitrary and/or malicious. All timing measures of variables are based on the node's local clock and thus no central clock or externally generated pulse is used. Instances of the protocol are shown to tolerate bursts of transient failures and deterministically converge with a linear convergence time with respect to the synchronization period as predicted.

  6. Spaceborne clock system: Some alternatives for a proposed NASA experiment

    NASA Technical Reports Server (NTRS)

    Beehler, R. E.

    1971-01-01

    A spaceborne clock experiment is proposed with the objectives of improving international time and frequency comparisons, studying precise one-way Doppler tracking and one-way ranging techniques, performing relativistic studies, and developing new atomic frequency standards technology. Various alternatives are considered for accomplishing these goals, including the use of existing satellite and earth-based time dissemination systems as well as the development of a new frequency standard for this specific application. One conclusion is that several attractive alternatives already exist for meeting the goal of improved time and frequency dissemination. However, to achieve all the other 4 goals at the NASA-stated levels of accuracy, a spaceborne atomic frequency standard may be required. An analysis of achievements to date with quartz oscillators, rubidium standards, cesium beam standards, hydrogen masers, and several other possibilities leads to the conclusion that cesium and rubidium standards offer the best choices for the experiment as proposed by NASA. The greatest obstacle to a spaceborne atomic standard appears to be its electrical power requirements.

  7. Stochastic models of cellular circadian rhythms in plants help to understand the impact of noise on robustness and clock structure

    PubMed Central

    Guerriero, Maria L.; Akman, Ozgur E.; van Ooijen, Gerben

    2014-01-01

    Rhythmic behavior is essential for plants; for example, daily (circadian) rhythms control photosynthesis and seasonal rhythms regulate their life cycle. The core of the circadian clock is a genetic network that coordinates the expression of specific clock genes in a circadian rhythm reflecting the 24-h day/night cycle. Circadian clocks exhibit stochastic noise due to the low copy numbers of clock genes and the consequent cell-to-cell variation: this intrinsic noise plays a major role in circadian clocks by inducing more robust oscillatory behavior. Another source of noise is the environment, which causes variation in temperature and light intensity: this extrinsic noise is part of the requirement for the structural complexity of clock networks. Advances in experimental techniques now permit single-cell measurements and the development of single-cell models. Here we present some modeling studies showing the importance of considering both types of noise in understanding how plants adapt to regular and irregular light variations. Stochastic models have proven useful for understanding the effect of regular variations. By contrast, the impact of irregular variations and the interaction of different noise sources are less well studied. PMID:25374576

  8. Circadian rhythmicity and photoperiodism in the pitcher-plant mosquito: can the seasonal timer evolve independently of the circadian clock?

    PubMed

    Bradshaw, W E; Holzapfel, C M; Mathias, D

    2006-04-01

    The two major rhythms of the biosphere are daily and seasonal; the two major adaptations to these rhythms are the circadian clock, mediating daily activities, and the photoperiodic timer, mediating seasonal activities. The mechanistic connection between the circadian clock and the photoperiodic timer remains unresolved. Herein, we show that the rhythmic developmental response to exotic light:dark cycles, usually used to infer a causal connection between the circadian clock and the photoperiodic timer, has evolved independently of the photoperiodic timer in the pitcher-plant mosquito Wyeomyia smithii across the climatic gradient of eastern North America from Florida to Canada and from the coastal plain to the mountains. We conclude that the photoperiodic timing of seasonal events can evolve independently of the daily circadian clock.

  9. Automatic Clock and Time Signal System of the Astronomical Agency in East Asia Area

    NASA Astrophysics Data System (ADS)

    Lee, Yong Sam

    2009-09-01

    We analysed the old automatic clock and time signal system that was used by the national astronomical agency in East Asian Area. Jagyeongnu is a kind of water clock that was operated by the flowing water in Joseon Dynasty. Seowoongwan managed the water clock so as to keep the standard time system in the dynasty from the 16th year (1434) of King Sejong's reign. In 1438 the Okru that was invented in the period. Such kind of clock system already was used in China, which was Shui yun i hsiang t'ai (?) in 1092. During the period Joseon Dynasty, China and Japan had been kept the time system that one day is divided into 12 shin (?2?) or 100 gak (?). However detailed part of the system had a little difference among the three countries. Though the whole system of water clock in Joseon had manufactured on the basis of Chinese, it had been gradually developed by own method and idea. In this study we show the historical records of the standard time keeping system in East Asian history. And then we can inform materials on the structure and functional devises for the purpose of new restoration models about the automatic clock and time system.

  10. System and method for adaptively deskewing parallel data signals relative to a clock

    DOEpatents

    Jenkins, Philip Nord; Cornett, Frank N.

    2006-04-18

    A system and method of reducing skew between a plurality of signals transmitted with a transmit clock is described. Skew is detected between the received transmit clock and each of received data signals. Delay is added to the clock or to one or more of the plurality of data signals to compensate for the detected skew. Each of the plurality of delayed signals is compared to a reference signal to detect changes in the skew. The delay added to each of the plurality of delayed signals is updated to adapt to changes in the detected skew.

  11. Green Web or megabiased clock? Plant fossils from Gondwanan Patagonia speak on evolutionary radiations.

    PubMed

    Wilf, Peter; Escapa, Ignacio H

    2015-07-01

    Evolutionary divergence-age estimates derived from molecular 'clocks' are frequently correlated with paleogeographic, paleoclimatic and extinction events. One prominent hypothesis based on molecular data states that the dominant pattern of Southern Hemisphere biogeography is post-Gondwanan clade origins and subsequent dispersal across the oceans in a metaphoric 'Green Web'. We tested this idea against well-dated Patagonian fossils of 19 plant lineages, representing organisms that actually lived on Gondwana. Most of these occurrences are substantially older than their respective, often post-Gondwanan molecular dates. The Green Web interpretation probably results from directional bias in molecular results. Gondwanan history remains fundamental to understanding Southern Hemisphere plant radiations, and we urge significantly greater caution when using molecular dating to interpret the biological impacts of geological events.

  12. Running on time: the role of circadian clocks in the musculoskeletal system.

    PubMed

    Dudek, Michal; Meng, Qing-Jun

    2014-10-01

    The night and day cycle governs the circadian (24 hourly) rhythm of activity and rest in animals and humans. This is reflected in daily changes of the global gene expression pattern and metabolism, but also in the local physiology of various tissues. A central clock in the brain co-ordinates the rhythmic locomotion behaviour, as well as synchronizing various local oscillators, such as those found in the musculoskeletal system. It has become increasingly recognized that the internal molecular clocks in cells allow a tissue to anticipate the rhythmic changes in their local environment and the specific demands of that tissue. Consequently, the majority of the rhythmic clock controlled genes and pathways are tissue specific. The concept of the tissue-specific function of circadian clocks is further supported by the diverse musculoskeletal phenotypes in mice with deletions or mutations of various core clock components, ranging from increased bone mass, dwarfism, arthropathy, reduced muscle strength and tendon calcification. The present review summarizes the current understanding of the circadian clocks in muscle, bone, cartilage and tendon tissues, with particular focus on the evidence of circadian rhythms in tissue physiology, their entrainment mechanisms and disease links, and the tissue-specific clock target genes/pathways. Research in this area holds strong potential to advance our understanding of how circadian rhythms control the health and disease of the musculoskeletal tissues, which has major implications in diseases associated with advancing age. It could also have potential implications in sports performance and sports medicine. PMID:25195734

  13. Carbon partitioning in Arabidopsis thaliana is a dynamic process controlled by the plants metabolic status and its circadian clock

    PubMed Central

    Kölling, Katharina; Thalmann, Matthias; Müller, Antonia; Jenny, Camilla; Zeeman, Samuel C

    2015-01-01

    Abstract Plant growth involves the coordinated distribution of carbon resources both towards structural components and towards storage compounds that assure a steady carbon supply over the complete diurnal cycle. We used 14CO2 labelling to track assimilated carbon in both source and sink tissues. Source tissues exhibit large variations in carbon allocation throughout the light period. The most prominent change was detected in partitioning towards starch, being low in the morning and more than double later in the day. Export into sink tissues showed reciprocal changes. Fewer and smaller changes in carbon allocation occurred in sink tissues where, in most respects, carbon was partitioned similarly, whether the sink leaf assimilated it through photosynthesis or imported it from source leaves. Mutants deficient in the production or remobilization of leaf starch exhibited major alterations in carbon allocation. Low-starch mutants that suffer from carbon starvation at night allocated much more carbon into neutral sugars and had higher rates of export than the wild type, partly because of the reduced allocation into starch, but also because of reduced allocation into structural components. Moreover, mutants deficient in the plant’s circadian system showed considerable changes in their carbon partitioning pattern suggesting control by the circadian clock. This work focusses on the temporal changes in the allocation and transport of photoassimilates within Arabidopsis rosettes, helping to fill a gap in our understanding of plant growth. Using short pulses of 14C-labelled carbon dioxide, we quantified how much carbon is used for growth and how much is stored as starch for use at night. In source leaves, partitioning is surprisingly dynamic during the day, even though photosynthesis is relatively constant, while in sink leaves, utilisation is more constant. Furthermore, by analysing metabolic mutants and clock mutants, and by manipulating the growth conditions, we show that

  14. Mammalian circadian clock system: Molecular mechanisms for pharmaceutical and medical sciences.

    PubMed

    Okamura, Hitoshi; Doi, Masao; Fustin, Jean-Michel; Yamaguchi, Yoshiaki; Matsuo, Masahiro

    2010-07-31

    An internal circadian (from the Latin "circa" meaning "about" and "dien" meaning "day") clock has been found across kingdoms of life, a testimony that circadian rhythms are a basic feature of life on earth. Physiologically relevant circadian time is generated at the level of transcription-(post)translation feedback loop of clock genes, which machinery can be found in most cells throughout the body. Lesions of the hypothalamic suprachiasmatic nucleus (SCN) abolish clock oscillations in the body, indicating thereby that rhythm generation is a hierarchial system with the SCN at the top. Disrupting this exquisitely harmonious system causes abnormal expression of cell-type specific clock-controlled genes, as revealed by the etiology of life-style related diseases such as hypertension. PMID:20620185

  15. A Byzantine-Fault Tolerant Self-Stabilizing Protocol for Distributed Clock Synchronization Systems

    NASA Technical Reports Server (NTRS)

    Malekpour, Mahyar R.

    2006-01-01

    Embedded distributed systems have become an integral part of safety-critical computing applications, necessitating system designs that incorporate fault tolerant clock synchronization in order to achieve ultra-reliable assurance levels. Many efficient clock synchronization protocols do not, however, address Byzantine failures, and most protocols that do tolerate Byzantine failures do not self-stabilize. Of the Byzantine self-stabilizing clock synchronization algorithms that exist in the literature, they are based on either unjustifiably strong assumptions about initial synchrony of the nodes or on the existence of a common pulse at the nodes. The Byzantine self-stabilizing clock synchronization protocol presented here 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 proposed 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. Proofs of the correctness of the protocol as well as the results of formal verification efforts are reported.

  16. Design and analysis of intelligent temperature control and temperature compensating system of CAT for hydrogen clock

    NASA Astrophysics Data System (ADS)

    Lu, Hua-Yu

    2006-03-01

    This paper presents a new design of temperature control system of hydrogen clock. By integrating three temperature control units into one system, the design can reduce size of circuit and simplify temperature control. This design includes two parts: hardware and software. In the hardware design, we select 32 bits ARM (Advanced Risc Machine) processor LPC2132, which is powerful and helpful to reduce the complexity of circuit board. In the software design, we introduce real time operation system UCOS-II (Micro Controller Operation System). By using it, we can enhance real time performance of the temperature control system. In addition, voltage of varactor which controls CAT (cavity auto tuning) in hydrogen clock may drift out of normal range, and the voltage drift will influence frequency stability and drift rate of hydrogen clock directly. Therefore, we bring forward an idea of temperature compensating for CAT, which based on the new temperature control system.

  17. Defining the robust behaviour of the plant clock gene circuit with absolute RNA timeseries and open infrastructure.

    PubMed

    Flis, Anna; Fernández, Aurora Piñas; Zielinski, Tomasz; Mengin, Virginie; Sulpice, Ronan; Stratford, Kevin; Hume, Alastair; Pokhilko, Alexandra; Southern, Megan M; Seaton, Daniel D; McWatters, Harriet G; Stitt, Mark; Halliday, Karen J; Millar, Andrew J

    2015-10-01

    Our understanding of the complex, transcriptional feedback loops in the circadian clock mechanism has depended upon quantitative, timeseries data from disparate sources. We measure clock gene RNA profiles in Arabidopsis thaliana seedlings, grown with or without exogenous sucrose, or in soil-grown plants and in wild-type and mutant backgrounds. The RNA profiles were strikingly robust across the experimental conditions, so current mathematical models are likely to be broadly applicable in leaf tissue. In addition to providing reference data, unexpected behaviours included co-expression of PRR9 and ELF4, and regulation of PRR5 by GI. Absolute RNA quantification revealed low levels of PRR9 transcripts (peak approx. 50 copies cell(-1)) compared with other clock genes, and threefold higher levels of LHY RNA (more than 1500 copies cell(-1)) than of its close relative CCA1. The data are disseminated from BioDare, an online repository for focused timeseries data, which is expected to benefit mechanistic modelling. One data subset successfully constrained clock gene expression in a complex model, using publicly available software on parallel computers, without expert tuning or programming. We outline the empirical and mathematical justification for data aggregation in understanding highly interconnected, dynamic networks such as the clock, and the observed design constraints on the resources required to make this approach widely accessible. PMID:26468131

  18. Defining the robust behaviour of the plant clock gene circuit with absolute RNA timeseries and open infrastructure.

    PubMed

    Flis, Anna; Fernández, Aurora Piñas; Zielinski, Tomasz; Mengin, Virginie; Sulpice, Ronan; Stratford, Kevin; Hume, Alastair; Pokhilko, Alexandra; Southern, Megan M; Seaton, Daniel D; McWatters, Harriet G; Stitt, Mark; Halliday, Karen J; Millar, Andrew J

    2015-10-01

    Our understanding of the complex, transcriptional feedback loops in the circadian clock mechanism has depended upon quantitative, timeseries data from disparate sources. We measure clock gene RNA profiles in Arabidopsis thaliana seedlings, grown with or without exogenous sucrose, or in soil-grown plants and in wild-type and mutant backgrounds. The RNA profiles were strikingly robust across the experimental conditions, so current mathematical models are likely to be broadly applicable in leaf tissue. In addition to providing reference data, unexpected behaviours included co-expression of PRR9 and ELF4, and regulation of PRR5 by GI. Absolute RNA quantification revealed low levels of PRR9 transcripts (peak approx. 50 copies cell(-1)) compared with other clock genes, and threefold higher levels of LHY RNA (more than 1500 copies cell(-1)) than of its close relative CCA1. The data are disseminated from BioDare, an online repository for focused timeseries data, which is expected to benefit mechanistic modelling. One data subset successfully constrained clock gene expression in a complex model, using publicly available software on parallel computers, without expert tuning or programming. We outline the empirical and mathematical justification for data aggregation in understanding highly interconnected, dynamic networks such as the clock, and the observed design constraints on the resources required to make this approach widely accessible.

  19. Defining the robust behaviour of the plant clock gene circuit with absolute RNA timeseries and open infrastructure

    PubMed Central

    Flis, Anna; Fernández, Aurora Piñas; Zielinski, Tomasz; Mengin, Virginie; Sulpice, Ronan; Stratford, Kevin; Hume, Alastair; Pokhilko, Alexandra; Southern, Megan M.; Seaton, Daniel D.; McWatters, Harriet G.; Stitt, Mark; Halliday, Karen J.; Millar, Andrew J.

    2015-01-01

    Our understanding of the complex, transcriptional feedback loops in the circadian clock mechanism has depended upon quantitative, timeseries data from disparate sources. We measure clock gene RNA profiles in Arabidopsis thaliana seedlings, grown with or without exogenous sucrose, or in soil-grown plants and in wild-type and mutant backgrounds. The RNA profiles were strikingly robust across the experimental conditions, so current mathematical models are likely to be broadly applicable in leaf tissue. In addition to providing reference data, unexpected behaviours included co-expression of PRR9 and ELF4, and regulation of PRR5 by GI. Absolute RNA quantification revealed low levels of PRR9 transcripts (peak approx. 50 copies cell−1) compared with other clock genes, and threefold higher levels of LHY RNA (more than 1500 copies cell−1) than of its close relative CCA1. The data are disseminated from BioDare, an online repository for focused timeseries data, which is expected to benefit mechanistic modelling. One data subset successfully constrained clock gene expression in a complex model, using publicly available software on parallel computers, without expert tuning or programming. We outline the empirical and mathematical justification for data aggregation in understanding highly interconnected, dynamic networks such as the clock, and the observed design constraints on the resources required to make this approach widely accessible. PMID:26468131

  20. RighTime: A real time clock correcting program for MS-DOS-based computer systems

    NASA Technical Reports Server (NTRS)

    Becker, G. Thomas

    1993-01-01

    A computer program is described which effectively eliminates the misgivings of the DOS system clock in PC/AT-class computers. RighTime is a small, sophisticated memory-resident program that automatically corrects both the DOS system clock and the hardware 'CMOS' real time clock (RTC) in real time. RighTime learns what corrections are required without operator interaction beyond the occasional accurate time set. Both warm (power on) and cool (power off) errors are corrected, usually yielding better than one part per million accuracy in the typical desktop computer with no additional hardware, and RighTime increases the system clock resolution from approximately 0.0549 second to 0.01 second. Program tools are also available which allow visualization of RighTime's actions, verification of its performance, display of its history log, and which provide data for graphing of the system clock behavior. The program has found application in a wide variety of industries, including astronomy, satellite tracking, communications, broadcasting, transportation, public utilities, manufacturing, medicine, and the military.

  1. Carbon partitioning in Arabidopsis thaliana is a dynamic process controlled by the plants metabolic status and its circadian clock.

    PubMed

    Kölling, Katharina; Thalmann, Matthias; Müller, Antonia; Jenny, Camilla; Zeeman, Samuel C

    2015-10-01

    Plant growth involves the coordinated distribution of carbon resources both towards structural components and towards storage compounds that assure a steady carbon supply over the complete diurnal cycle. We used (14) CO2 labelling to track assimilated carbon in both source and sink tissues. Source tissues exhibit large variations in carbon allocation throughout the light period. The most prominent change was detected in partitioning towards starch, being low in the morning and more than double later in the day. Export into sink tissues showed reciprocal changes. Fewer and smaller changes in carbon allocation occurred in sink tissues where, in most respects, carbon was partitioned similarly, whether the sink leaf assimilated it through photosynthesis or imported it from source leaves. Mutants deficient in the production or remobilization of leaf starch exhibited major alterations in carbon allocation. Low-starch mutants that suffer from carbon starvation at night allocated much more carbon into neutral sugars and had higher rates of export than the wild type, partly because of the reduced allocation into starch, but also because of reduced allocation into structural components. Moreover, mutants deficient in the plant's circadian system showed considerable changes in their carbon partitioning pattern suggesting control by the circadian clock.

  2. Simultaneous single epoch satellite clock modelling in Global Navigation Satellite Systems

    NASA Astrophysics Data System (ADS)

    Thongtan, Thayathip

    In order to obtain high quality positions from navigation satellites, range errors have to be identified and either modelled or estimated. This thesis focuses on satellite clock errors, which are needed to be known because satellite clocks are not perfectly synchronised with navigation system time. A new approach, invented at UCL, for the simultaneous estimation, in a single epoch, of all satellite clock offsets within a Global Navigation Satellite System (GNSS) from range data collected at a large number of globally distributed ground stations is presented. The method was originally tested using only data from a limited number of GPS satellites and ground stations. In this work a total of 50 globally distributed stations and the whole GPS constellation are used in order to investigate more fully the capabilities of the method, in terms of both accuracy and reliability. A number of different estimation models have been tested. These include those with different weighting schemes, those with and without tropospheric bias parameters and those that include assumptions regarding prior knowledge of satellite orbits. In all cases conclusions have been drawn based on formal error propagation theory. Accuracy has been assessed largely through the sizes of the predicted satellite clock standard deviations and, in the case of simultaneously estimating satellite positions, their error ellipsoids. Both internal and external reliability have been assessed as these are important contributors to integrity, something that is essential for many practical applications. It has been found that the accuracy and reliability of satellite clock offsets are functions of the number of known ground station clocks and distance from them, quality of orbits and quality of range measurement. Also the introduction of tropospheric zenith delay parameters into the model reduces both accuracy and reliability by amounts depending on satellite elevation angles. (Abstract shortened by UMI.)

  3. Circadian clock- and PIF4-controlled plant growth: a coincidence mechanism directly integrates a hormone signaling network into the photoperiodic control of plant architectures in Arabidopsis thaliana.

    PubMed

    Nomoto, Yuji; Nomoto, Yuichi; Kubozono, Saori; Yamashino, Takafumi; Nakamichi, Norihito; Mizuno, Takeshi

    2012-11-01

    The plant circadian clock generates rhythms with a period close to 24 h, and it controls a wide variety of physiological and developmental events, enabling plants to adapt to ever-changing environmental light conditions. In Arabidopsis thaliana, the clock regulates the diurnal and photoperiodic plant growth including the elongation of hypocotyls and petioles in a time-of-day-specific and short-day (SD)-specific manner. In this mechanism, the clock-regulated PHYTOCHROME-INTERACTING FACTOR 4 gene encoding a basic helix-loop-helix transcription factor, together with phytochromes (mainly phyB), plays crucial roles. This diurnal and photoperiodic control of plant growth is best explained by the accumulation of the PIF4 protein at the end of the night-time specifically under SDs, due to coincidence between the internal (circadian rhythm) and external (photoperiod) cues. In this model, however, the PIF4-controlled downstream factors are not fully identified, although it has been generally proposed that the auxin-mediated signal transduction is crucially implicated. Here, we identified a set of hormone-associated genes as the specific PIF4 targets implicated in the photoperiodic control of plant growth. They include not only auxin-associated genes (GH3.5, IAA19 and IAA29), but also genes associated with other growth-regulating hormones such as brassinosteroids (BR6ox2), gibberellic acids (GAI), ethylene (ACS8) and cytokinin (CKX5). The dawn- and SD-specific expression profiles of these genes are modified in a set of phyB and clock mutants, both of which compromise the coincidence mechanism. The results of this study suggest that the circadian clock orchestrates a variety of hormone signaling pathways to regulate the photoperiod-dependent morphogenesis in A. thaliana.

  4. Real-time simulation clock

    NASA Technical Reports Server (NTRS)

    Bennington, Donald R. (Inventor); Crawford, Daniel J. (Inventor)

    1990-01-01

    The invention is a clock for synchronizing operations within a high-speed, distributed data processing network. The clock is actually a distributed system comprising a central clock and multiple site clock interface units (SCIUs) which are connected by means of a fiber optic star network and which operate under control of separate clock software. The presently preferred embodiment is a part of the flight simulation system now in current use at the NASA Langley Research Center.

  5. Real-time simulation clock

    NASA Astrophysics Data System (ADS)

    Bennington, Donald R.; Crawford, Daniel J.

    1990-04-01

    The invention is a clock for synchronizing operations within a high-speed, distributed data processing network. The clock is actually a distributed system comprising a central clock and multiple site clock interface units (SCIUs) which are connected by means of a fiber optic star network and which operate under control of separate clock software. The presently preferred embodiment is a part of the flight simulation system now in current use at the NASA Langley Research Center.

  6. Interaction of Arabidopsis DET1 with CCA1 and LHY in mediating transcriptional repression in the plant circadian clock

    PubMed Central

    Lau, On Sun; Huang, Xi; Charron, Jean-Benoit; Lee, Jae-Hoon; Li, Gang; Deng, Xing Wang

    2011-01-01

    SUMMARY The COP10-DET1-DDB1 (CDD) complex is an evolutionarily conserved protein complex discovered for its role in the repression of photomorphogenesis in Arabidopsis, and is important in many cellular and developmental processes in both plants and animals. However, its molecular mode of action remains poorly understood. Here, we show that the CDD component, DET1, possesses transcriptional repression activity and physically interacts with two closely related MYB transcription factors, CCA1 and LHY, which are core components of the plant circadian clock. DET1 associates with the promoter of CCA1/LHY target genes, such as TOC1, in a CCA1/LHY-dependent manner and is required for their repression, suggesting a recruitment of DET1 by the central oscillator components to regulate the clock. Our results reveal DET1 as a core transcriptional repression factor important for clock progression. Overall, the CDD complex may function as a transcriptional co-repressor in diverse processes through direct interaction with distinct transcription factors. PMID:21884973

  7. Evaluating the Effect of Global Positioning System (GPS) Satellite Clock Error via GPS Simulation

    NASA Astrophysics Data System (ADS)

    Sathyamoorthy, Dinesh; Shafii, Shalini; Amin, Zainal Fitry M.; Jusoh, Asmariah; Zainun Ali, Siti

    2016-06-01

    This study is aimed at evaluating the effect of Global Positioning System (GPS) satellite clock error using GPS simulation. Two conditions of tests are used; Case 1: All the GPS satellites have clock errors within the normal range of 0 to 7 ns, corresponding to pseudorange error range of 0 to 2.1 m; Case 2: One GPS satellite suffers from critical failure, resulting in clock error in the pseudorange of up to 1 km. It is found that increase of GPS satellite clock error causes increase of average positional error due to increase of pseudorange error in the GPS satellite signals, which results in increasing error in the coordinates computed by the GPS receiver. Varying average positional error patterns are observed for the each of the readings. This is due to the GPS satellite constellation being dynamic, causing varying GPS satellite geometry over location and time, resulting in GPS accuracy being location / time dependent. For Case 1, in general, the highest average positional error values are observed for readings with the highest PDOP values, while the lowest average positional error values are observed for readings with the lowest PDOP values. For Case 2, no correlation is observed between the average positional error values and PDOP, indicating that the error generated is random.

  8. Measurement and simulation of clock errors from resource-constrained embedded systems

    NASA Astrophysics Data System (ADS)

    Collett, M. A.; Matthews, C. E.; Esward, T. J.; Whibberley, P. B.

    2010-07-01

    Resource-constrained embedded systems such as wireless sensor networks are becoming increasingly sought-after in a range of critical sensing applications. Hardware for such systems is typically developed as a general tool, intended for research and flexibility. These systems often have unexpected limitations and sources of error when being implemented for specific applications. We investigate via measurement and simulation the output of the onboard clock of a Crossbow MICAz testbed, comprising a quartz oscillator accessed via a combination of hardware and software. We show that the clock output available to the user suffers a number of instabilities and errors. Using a simple software simulation of the system based on a series of nested loops, we identify the source of each component of the error, finding that there is a 7.5 × 10-6 probability that a given oscillation from the governing crystal will be miscounted, resulting in frequency jitter over a 60 µHz range.

  9. Slot clock recovery in optical PPM communication systems with avalanche photodiode photodetectors

    NASA Technical Reports Server (NTRS)

    Davidson, Frederic M.; Sun, Xiaoli

    1989-01-01

    Slot timing recovery in a direct-detection optical PPM communication system can be achieved by processing the photodetector output waveform with a nonlinear device whose output forms the input to a phase-locked loop. The choice of a simple transition detector as the nonlinearity is shown to give satisfactory synchronization performance. The rms phase error of the recovered slot clock and the effect of slot timing jitter on the bit error probability were directly measured. The experimental system consisted of an AlGaAs laser diode (wavelength = 834 nm) and a silicon avalanche photodiode photodetector. The system used Q = 4 PPM signaling and operated at a source data rate of 25 Mbits/s. The mathematical model developed to compute the rms phase error of the recovered clock is shown to be in good agreement with results of actual measurements of phase errors. The use of the recovered slot clock in the receiver resulted in no significant degradation in receiver sensitivity compared to a system with perfect slot timing. The system achieved a bit error probability of 10 to the -6th at a received optical signal energy of 55 detected photons per information bit.

  10. A compact ultranarrow high-power laser system for experiments with 578 nm ytterbium clock transition

    SciTech Connect

    Cappellini, G.; Lombardi, P.; Mancini, M.; Pagano, G.; Pizzocaro, M.; Fallani, L.; Catani, J.

    2015-07-15

    In this paper, we present the realization of a compact, high-power laser system able to excite the ytterbium clock transition at 578 nm. Starting from an external-cavity laser based on a quantum dot chip at 1156 nm with an intra-cavity electro-optic modulator, we were able to obtain up to 60 mW of visible light at 578 nm via frequency doubling. The laser is locked with a 500 kHz bandwidth to an ultra-low-expansion glass cavity stabilized at its zero coefficient of thermal expansion temperature through an original thermal insulation and correction system. This laser allowed the observation of the clock transition in fermionic {sup 173}Y b with a <50 Hz linewidth over 5 min, limited only by a residual frequency drift of some 0.1 Hz/s.

  11. A space system for high-accuracy global time and frequency comparison of clocks

    NASA Technical Reports Server (NTRS)

    Decher, R.; Allan, D. W.; Alley, C. O.; Vessot, R. F. C.; Winkler, G. M. R.

    1981-01-01

    A Space Shuttle experiment in which a hydrogen maser clock on board the Space Shuttle will be compared with clocks on the ground using two-way microwave and short pulse laser signals is described. The accuracy goal for the experiment is 1 nsec or better for the time transfer and 10 to the minus 14th power for the frequency comparison. A direct frequency comparison of primary standards at the 10 to the minus 14th power accuracy level is a unique feature of the proposed system. Both time and frequency transfer will be accomplished by microwave transmission, while the laser signals provide calibration of the system as well as subnanosecond time transfer.

  12. A compact ultranarrow high-power laser system for experiments with 578 nm ytterbium clock transition

    NASA Astrophysics Data System (ADS)

    Cappellini, G.; Lombardi, P.; Mancini, M.; Pagano, G.; Pizzocaro, M.; Fallani, L.; Catani, J.

    2015-07-01

    In this paper, we present the realization of a compact, high-power laser system able to excite the ytterbium clock transition at 578 nm. Starting from an external-cavity laser based on a quantum dot chip at 1156 nm with an intra-cavity electro-optic modulator, we were able to obtain up to 60 mW of visible light at 578 nm via frequency doubling. The laser is locked with a 500 kHz bandwidth to an ultra-low-expansion glass cavity stabilized at its zero coefficient of thermal expansion temperature through an original thermal insulation and correction system. This laser allowed the observation of the clock transition in fermionic 173Y b with a <50 Hz linewidth over 5 min, limited only by a residual frequency drift of some 0.1 Hz/s.

  13. A quantum many-body spin system in an optical lattice clock.

    PubMed

    Martin, M J; Bishof, M; Swallows, M D; Zhang, X; Benko, C; von-Stecher, J; Gorshkov, A V; Rey, A M; Ye, Jun

    2013-08-01

    Strongly interacting quantum many-body systems arise in many areas of physics, but their complexity generally precludes exact solutions to their dynamics. We explored a strongly interacting two-level system formed by the clock states in (87)Sr as a laboratory for the study of quantum many-body effects. Our collective spin measurements reveal signatures of the development of many-body correlations during the dynamical evolution. We derived a many-body Hamiltonian that describes the experimental observation of atomic spin coherence decay, density-dependent frequency shifts, severely distorted lineshapes, and correlated spin noise. These investigations open the door to further explorations of quantum many-body effects and entanglement through use of highly coherent and precisely controlled optical lattice clocks. PMID:23929976

  14. Resetting Biological Clocks

    ERIC Educational Resources Information Center

    Winfree, Arthur T.

    1975-01-01

    Reports on experiments conducted on two biological clocks, in organisms in the plant and animal kingdoms, which indicate that biological oscillation can be arrested by a single stimulus of a definite strength delivered at the proper time. (GS)

  15. Variable frequency microprocessor clock generator

    SciTech Connect

    Branson, C.N.

    1989-04-04

    A microprocessor-based system is described comprising: a digital central microprocessor provided with a clock input and having a rate of operation determined by the frequency of a clock signal input thereto; memory means operably coupled to the central microprocessor for storing programs respectively including a plurality of instructions and addressable by the central microprocessor; peripheral device operably connected to the central microprocessor, the first peripheral device being addressable by the central microprocessor for control thereby; a system clock generator for generating a digital reference clock signal having a reference frequency rate; and frequency rate reduction circuit means connected between the clock generator and the clock input of the central microprocessor for selectively dividing the reference clock signal to generate a microprocessor clock signal as an input to the central microprocessor for clocking the central microprocessor.

  16. THE mPER2 CLOCK GENE MODULATES COCAINE ACTIONS IN THE MOUSE CIRCADIAN SYSTEM

    PubMed Central

    Brager, Allison J.; Stowie, Adam C.; Prosser, Rebecca A.; Glass, J. David

    2014-01-01

    Cocaine is a potent disruptor of photic and non-photic pathways for circadian entrainment of the master circadian clock of the suprachiasmatic nucleus (SCN). These actions of cocaine likely involve its modulation of molecular (clock gene) components for SCN clock timekeeping. At present, however, the physiological basis of such an interaction is unclear. To address this question, we compared photic and non-photic phase-resetting responses between wild-type (WT) and Per2 mutant mice expressing nonfunctional PER2 protein to systemic and intra-SCN cocaine administrations. In the systemic trials, cocaine was administered i.p. (20 mg/kg) either at midday or prior to a light pulse in the early night to assess its non-photic and photic behavioral phase-resetting actions, respectively. In the intra-SCN trial, cocaine was administered by reverse microdialysis at midday to determine if the SCN is a direct target for its non-photic phase-resetting action. Non-photic phase-advancing responses to i.p. cocaine at midday were significantly (~3.5-fold) greater in Per2 mutants than WTs. However, the phase-advancing action of intra-SCN cocaine perfusion at midday did not differ between genotypes. In the light pulse trial, Per2 mutants exhibited larger photic phase-delays than did WTs, and the attenuating action of cocaine on this response was proportionately larger than in WTs. These data indicate that the Per2 clock gene is a potent modulator of cocaine’s actions in the circadian system. With regard to non-photic phase-resetting, the SCN is confirmed as a direct target of cocaine action; however, Per2 modulation of this effect likely occurs outside of the SCN. PMID:23333842

  17. Molecular clocks and the early evolution of metazoan nervous systems.

    PubMed

    Wray, Gregory A

    2015-12-19

    The timing of early animal evolution remains poorly resolved, yet remains critical for understanding nervous system evolution. Methods for estimating divergence times from sequence data have improved considerably, providing a more refined understanding of key divergences. The best molecular estimates point to the origin of metazoans and bilaterians tens to hundreds of millions of years earlier than their first appearances in the fossil record. Both the molecular and fossil records are compatible, however, with the possibility of tiny, unskeletonized, low energy budget animals during the Proterozoic that had planktonic, benthic, or meiofaunal lifestyles. Such animals would likely have had relatively simple nervous systems equipped primarily to detect food, avoid inhospitable environments and locate mates. The appearance of the first macropredators during the Cambrian would have changed the selective landscape dramatically, likely driving the evolution of complex sense organs, sophisticated sensory processing systems, and diverse effector systems involved in capturing prey and avoiding predation. PMID:26554040

  18. Molecular clocks and the early evolution of metazoan nervous systems.

    PubMed

    Wray, Gregory A

    2015-12-19

    The timing of early animal evolution remains poorly resolved, yet remains critical for understanding nervous system evolution. Methods for estimating divergence times from sequence data have improved considerably, providing a more refined understanding of key divergences. The best molecular estimates point to the origin of metazoans and bilaterians tens to hundreds of millions of years earlier than their first appearances in the fossil record. Both the molecular and fossil records are compatible, however, with the possibility of tiny, unskeletonized, low energy budget animals during the Proterozoic that had planktonic, benthic, or meiofaunal lifestyles. Such animals would likely have had relatively simple nervous systems equipped primarily to detect food, avoid inhospitable environments and locate mates. The appearance of the first macropredators during the Cambrian would have changed the selective landscape dramatically, likely driving the evolution of complex sense organs, sophisticated sensory processing systems, and diverse effector systems involved in capturing prey and avoiding predation.

  19. Verification of fault-tolerant clock synchronization systems. M.S. Thesis - College of William and Mary, 1992

    NASA Technical Reports Server (NTRS)

    Miner, Paul S.

    1993-01-01

    A critical function in a fault-tolerant computer architecture is the synchronization of the redundant computing elements. The synchronization algorithm must include safeguards to ensure that failed components do not corrupt the behavior of good clocks. Reasoning about fault-tolerant clock synchronization is difficult because of the possibility of subtle interactions involving failed components. Therefore, mechanical proof systems are used to ensure that the verification of the synchronization system is correct. In 1987, Schneider presented a general proof of correctness for several fault-tolerant clock synchronization algorithms. Subsequently, Shankar verified Schneider's proof by using the mechanical proof system EHDM. This proof ensures that any system satisfying its underlying assumptions will provide Byzantine fault-tolerant clock synchronization. The utility of Shankar's mechanization of Schneider's theory for the verification of clock synchronization systems is explored. Some limitations of Shankar's mechanically verified theory were encountered. With minor modifications to the theory, a mechanically checked proof is provided that removes these limitations. The revised theory also allows for proven recovery from transient faults. Use of the revised theory is illustrated with the verification of an abstract design of a clock synchronization system.

  20. Synchronization of the mammalian circadian timing system: Light can control peripheral clocks independently of the SCN clock: alternate routes of entrainment optimize the alignment of the body's circadian clock network with external time.

    PubMed

    Husse, Jana; Eichele, Gregor; Oster, Henrik

    2015-10-01

    A vast network of cellular circadian clocks regulates 24-hour rhythms of behavior and physiology in mammals. Complex environments are characterized by multiple, and often conflicting time signals demanding flexible mechanisms of adaptation of endogenous rhythms to external time. Traditionally this process of circadian entrainment has been conceptualized in a hierarchical scheme with a light-reset master pacemaker residing in the hypothalamus that subsequently aligns subordinate peripheral clocks with each other and with external time. Here we review new experiments using conditional mouse genetics suggesting that resetting of the circadian system occurs in a more "federated" and tissue-specific fashion, which allows for increased noise resistance and plasticity of circadian timekeeping under natural conditions.

  1. Circadian Stress Regimes Affect the Circadian Clock and Cause Jasmonic Acid-Dependent Cell Death in Cytokinin-Deficient Arabidopsis Plants.

    PubMed

    Nitschke, Silvia; Cortleven, Anne; Iven, Tim; Feussner, Ivo; Havaux, Michel; Riefler, Michael; Schmülling, Thomas

    2016-07-01

    The circadian clock helps plants measure daylength and adapt to changes in the day-night rhythm. We found that changes in the light-dark regime triggered stress responses, eventually leading to cell death, in leaves of Arabidopsis thaliana plants with reduced cytokinin levels or defective cytokinin signaling. Prolonged light treatment followed by a dark period induced stress and cell death marker genes while reducing photosynthetic efficiency. This response, called circadian stress, is also characterized by altered expression of clock and clock output genes. In particular, this treatment strongly reduced the expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). Intriguingly, similar changes in gene expression and cell death were observed in clock mutants lacking proper CCA1 and LHY function. Circadian stress caused strong changes in reactive oxygen species- and jasmonic acid (JA)-related gene expression. The activation of the JA pathway, involving the accumulation of JA metabolites, was crucial for the induction of cell death, since the cell death phenotype was strongly reduced in the jasmonate resistant1 mutant background. We propose that adaptation to circadian stress regimes requires a normal cytokinin status which, acting primarily through the AHK3 receptor, supports circadian clock function to guard against the detrimental effects of circadian stress.

  2. Circadian Stress Regimes Affect the Circadian Clock and Cause Jasmonic Acid-Dependent Cell Death in Cytokinin-Deficient Arabidopsis Plants.

    PubMed

    Nitschke, Silvia; Cortleven, Anne; Iven, Tim; Feussner, Ivo; Havaux, Michel; Riefler, Michael; Schmülling, Thomas

    2016-07-01

    The circadian clock helps plants measure daylength and adapt to changes in the day-night rhythm. We found that changes in the light-dark regime triggered stress responses, eventually leading to cell death, in leaves of Arabidopsis thaliana plants with reduced cytokinin levels or defective cytokinin signaling. Prolonged light treatment followed by a dark period induced stress and cell death marker genes while reducing photosynthetic efficiency. This response, called circadian stress, is also characterized by altered expression of clock and clock output genes. In particular, this treatment strongly reduced the expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). Intriguingly, similar changes in gene expression and cell death were observed in clock mutants lacking proper CCA1 and LHY function. Circadian stress caused strong changes in reactive oxygen species- and jasmonic acid (JA)-related gene expression. The activation of the JA pathway, involving the accumulation of JA metabolites, was crucial for the induction of cell death, since the cell death phenotype was strongly reduced in the jasmonate resistant1 mutant background. We propose that adaptation to circadian stress regimes requires a normal cytokinin status which, acting primarily through the AHK3 receptor, supports circadian clock function to guard against the detrimental effects of circadian stress. PMID:27354555

  3. Circadian Stress Regimes Affect the Circadian Clock and Cause Jasmonic Acid-Dependent Cell Death in Cytokinin-Deficient Arabidopsis Plants[OPEN

    PubMed Central

    Nitschke, Silvia; Cortleven, Anne; Iven, Tim; Havaux, Michel; Schmülling, Thomas

    2016-01-01

    The circadian clock helps plants measure daylength and adapt to changes in the day-night rhythm. We found that changes in the light-dark regime triggered stress responses, eventually leading to cell death, in leaves of Arabidopsis thaliana plants with reduced cytokinin levels or defective cytokinin signaling. Prolonged light treatment followed by a dark period induced stress and cell death marker genes while reducing photosynthetic efficiency. This response, called circadian stress, is also characterized by altered expression of clock and clock output genes. In particular, this treatment strongly reduced the expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). Intriguingly, similar changes in gene expression and cell death were observed in clock mutants lacking proper CCA1 and LHY function. Circadian stress caused strong changes in reactive oxygen species- and jasmonic acid (JA)-related gene expression. The activation of the JA pathway, involving the accumulation of JA metabolites, was crucial for the induction of cell death, since the cell death phenotype was strongly reduced in the jasmonate resistant1 mutant background. We propose that adaptation to circadian stress regimes requires a normal cytokinin status which, acting primarily through the AHK3 receptor, supports circadian clock function to guard against the detrimental effects of circadian stress. PMID:27354555

  4. The development of the hardware for studying biological clock systems under microgravity conditions, using scorpions as animal models

    NASA Astrophysics Data System (ADS)

    Serafini, L.; Viganò, W.; Donati, A.; Porciani, M.; Zolesi, V.; Schulze-Varnholt, D.; Manieri, P.; El-Din Sallam, A.; Schmäh, M.; Horn, E. R.

    2007-02-01

    The study of internal clock systems of scorpions in weightless conditions is the goal of the SCORPI experiment. SCORPI was selected for flight on the International Space Station (ISS) and will be mounted in the European facility BIOLAB, the European Space Agency (ESA) laboratory designed to support biological experiments on micro-organisms, cells, tissue, cultures, small plants and small invertebrates. This paper outlines the main features of a breadboard designed and developed in order to allow the analysis of critical aspects of the experiment. It is a complete tool to simulate the experiment mission on ground and it can be customised, adapted and tuned to the scientific requirements. The paper introduces the SCORPI-T experiment which represents an important precursor for the success of the SCORPI on BIOLAB. The capabilities of the hardware developed show its potential use for future similar experiments in space.

  5. Performance analysis of a complete adiabatic logic system driven by the proposed power clock generator

    NASA Astrophysics Data System (ADS)

    Kanungo, Jitendra; Dasgupta, S.

    2014-09-01

    We analyze the energy performance of a complete adiabatic circuit/system including the Power Clock Generator (PCG) at the 90 nm CMOS technology node. The energy performance in terms of the conversion efficiency of the PCG is extensively carried out under the variations of supply voltage, process corner and the driver transistor's width. We propose an energy-efficient singe cycle control circuit based on the two-stage comparator for the synchronous charge recovery sinusoidal power clock generator (PCG). The proposed PCG is used to drive the 4-bit adiabatic Ripple Carry Adder (RCA) and their simulation results are compared with the adiabatic RCA driven by the reported PCG. We have also simulated the logically equivalent static CMOS RCA circuit to compare the energy saving of adiabatic and non-adiabatic logic circuits. In the clock frequency range from 25 MHz to 1GHz, the proposed PCG gives a maximum conversion efficiency of 56.48%. This research work shows how the design of an efficient PCG increases the energy saving of adiabatic logic.

  6. Plant uptake-assisted round-the-clock photocatalysis for complete purification of aquaculture wastewater using sunlight.

    PubMed

    Bian, Zhenfeng; Cao, Fenglei; Zhu, Jian; Li, Hexing

    2015-02-17

    A novel reactor equipped with solar batteries, Bi2O3/TiO2 film photocatalyst, and celery plant was designed and used for purification of aquaculture wastewater. The Bi2O3/TiO2 film photocatalyst started photocatalytic degradation of organonitrogen compounds under irradiation of sunlight. Meanwhile, the solar batteries absorbed and converted excess sunlight into electric energy and then started UV lamps at night, leading to round-the-clock photocatalysis. Subsequently, the inorganic nitrogen species including NH4(+), NO2(-), and NO3(-) resulting from photocatalytic degradation of the organonitrogen compounds could subsequently be uptaken by the celery plant as the fertilizer to reduce the secondary pollution. It was found that, after 24 h circulation, both organonitrogen compounds and NO2(-) species were completely removed, while NH4(+) and NO3(-) contents also decreased by 30% and 50%, respectively. The reactor could be used repetitively, showing a good potential in practical application. PMID:25625860

  7. Plant uptake-assisted round-the-clock photocatalysis for complete purification of aquaculture wastewater using sunlight.

    PubMed

    Bian, Zhenfeng; Cao, Fenglei; Zhu, Jian; Li, Hexing

    2015-02-17

    A novel reactor equipped with solar batteries, Bi2O3/TiO2 film photocatalyst, and celery plant was designed and used for purification of aquaculture wastewater. The Bi2O3/TiO2 film photocatalyst started photocatalytic degradation of organonitrogen compounds under irradiation of sunlight. Meanwhile, the solar batteries absorbed and converted excess sunlight into electric energy and then started UV lamps at night, leading to round-the-clock photocatalysis. Subsequently, the inorganic nitrogen species including NH4(+), NO2(-), and NO3(-) resulting from photocatalytic degradation of the organonitrogen compounds could subsequently be uptaken by the celery plant as the fertilizer to reduce the secondary pollution. It was found that, after 24 h circulation, both organonitrogen compounds and NO2(-) species were completely removed, while NH4(+) and NO3(-) contents also decreased by 30% and 50%, respectively. The reactor could be used repetitively, showing a good potential in practical application.

  8. Plant Phenotype Characterization System

    SciTech Connect

    Daniel W McDonald; Ronald B Michaels

    2005-09-09

    This report is the final scientific report for the DOE Inventions and Innovations Project: Plant Phenotype Characterization System, DE-FG36-04GO14334. The period of performance was September 30, 2004 through July 15, 2005. The project objective is to demonstrate the viability of a new scientific instrument concept for the study of plant root systems. The root systems of plants are thought to be important in plant yield and thus important to DOE goals in renewable energy sources. The scientific study and understanding of plant root systems is hampered by the difficulty in observing root activity and the inadequacy of existing root study instrumentation options. We have demonstrated a high throughput, non-invasive, high resolution technique for visualizing plant root systems in-situ. Our approach is based upon low-energy x-ray radiography and the use of containers and substrates (artificial soil) which are virtually transparent to x-rays. The system allows us to germinate and grow plant specimens in our containers and substrates and to generate x-ray images of the developing root system over time. The same plant can be imaged at different times in its development. The system can be used for root studies in plant physiology, plant morphology, plant breeding, plant functional genomics and plant genotype screening.

  9. Oscillating perceptions: the ups and downs of the CLOCK protein in the mouse circadian system.

    PubMed

    Debruyne, Jason P

    2008-12-01

    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 view. In this review, I discuss how this recent work impacts and alters the previous view of the role of CLOCK in the mouse circadian clockwork.

  10. Spatiotemporal variation of metabolism in a plant circadian rhythm: the biological clock as an assembly of coupled individual oscillators.

    PubMed

    Rascher, U; Hütt, M T; Siebke, K; Osmond, B; Beck, F; Lüttge, U

    2001-09-25

    The complex dynamic properties of biological timing in organisms remain a central enigma in biology despite the increasingly precise genetic characterization of oscillating units and their components. Although attempts to obtain the time constants from oscillations of gene activity and biochemical units have led to substantial progress, we are still far from a full molecular understanding of endogenous rhythmicity and the physiological manifestations of biological clocks. Applications of nonlinear dynamics have revolutionized thinking in physics and in biomedical and life sciences research, and spatiotemporal considerations are now advancing our understanding of development and rhythmicity. Here we show that the well known circadian rhythm of a metabolic cycle in a higher plant, namely the crassulacean acid metabolism mode of photosynthesis, is expressed as dynamic patterns of independently initiated variations in photosynthetic efficiency (phi(PSII)) over a single leaf. Noninvasive highly sensitive chlorophyll fluorescence imaging reveals randomly initiated patches of varying phi(PSII) that are propagated within minutes to hours in wave fronts, forming dynamically expanding and contracting clusters and clearly dephased regions of phi(PSII). Thus, this biological clock is a spatiotemporal product of many weakly coupled individual oscillators, defined by the metabolic constraints of crassulacean acid metabolism. The oscillators operate independently in space and time as a consequence of the dynamics of metabolic pools and limitations of CO(2) diffusion between tightly packed cells.

  11. Early results from a prototype VLBI clock monitoring system. [Deep Space Network

    NASA Technical Reports Server (NTRS)

    Yunck, T. P.; Madrid, G. A.

    1979-01-01

    Four sets of experiments were conducted to measure the relative epoch offsets between atomic clocks in California, Australia, and Spain by means of very long baseline interferometry (VLBI). The experiments were conducted using an incomplete R & D VLBI system with a number of inherent limitations. The results indicate that the measurement objective of epoch offset to 10 nanoseconds will be met. Tables show the measured offset, the residual to fit, and the square root Allan variance. Graphs show the rate change and the rate reset.

  12. Power Plant Systems Analysis

    NASA Technical Reports Server (NTRS)

    Williams, J. R.; Yang, Y. Y.

    1973-01-01

    Three basic thermodynamic cycles of advanced nuclear MHD power plant systems are studied. The effect of reactor exit temperature and space radiator temperature on the overall thermal efficiency of a regenerative turbine compressor power plant system is shown. The effect of MHD pressure ratio on plant efficiency is also described, along with the dependence of MHD power output, compressor power requirement, turbine power output, mass flow rate of H2, and overall plant efficiency on the reactor exit temperature for a specific configuration.

  13. Feeding and circadian clocks.

    PubMed

    Pardini, Lissia; Kaeffer, Bertrand

    2006-01-01

    The mammalian genome encodes at least a dozen of genes directly involved in the regulation of the feedback loops constituting the circadian clock. The circadian system is built up on a multitude of oscillators organized according to a hierarchical model in which neurons of the suprachiasmatic nuclei of the hypothalamus may drive the central circadian clock and all the other somatic cells may possess the molecular components allowing tissues and organs to constitute peripheral clocks. Suprachiasmatic neurons are driving the central circadian clock which is reset by lighting cues captured and integrated by the melanopsin cells of the retina and define the daily rhythms of locomotor activity and associated physiological regulatory pathways like feeding and metabolism. This central clock entrains peripheral clocks which can be synchronized by non-photic environmental cues and uncoupled from the central one depending on the nature and the strength of the circadian signal. The human circadian clock and its functioning in central or peripheral tissues are currently being explored to increase the therapeutic efficacy of timed administration of drugs or radiation, and to offer better advice on lighting and meal timing useful for frequent travelers suffering from jet lag and for night workers' comfort. However, the molecular mechanism driving and coordinating the central and peripheral clocks through a wide range of synchronizers (lighting, feeding, physical or social activities) remains a mystery.

  14. Plant Systems Biology (editorial)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In June 2003, Plant Physiology published an Arabidopsis special issue devoted to plant systems biology. The intention of Natasha Raikhel and Gloria Coruzzi, the two editors of this first-of-its-kind issue, was ‘‘to help nucleate this new effort within the plant community’’ as they considered that ‘‘...

  15. Highly reliable optical system for a rubidium space cold atom clock.

    PubMed

    Ren, Wei; Sun, Yanguang; Wang, Bin; Xia, Wenbing; Qu, Qiuzhi; Xiang, Jingfeng; Dong, Zuoren; Lü, Desheng; Liu, Liang

    2016-05-01

    We describe a highly reliable optical system designed for a rubidium space cold atom clock (SCAC), presenting its design, key technologies, and optical components. All of the optical and electronic components are integrated onto an optimized two-sided 300  mm×290  mm×30  mm optical bench. The compact optical structure and special thermal design ensure that the optical system can pass all of the space environmental qualification tests including both thermal vacuum and mechanical tests. To verify its performance, the optical system is carefully checked before and after each test. The results indicate that this optical system is suitably robust for the space applications for which the rubidium SCAC was built. PMID:27140378

  16. Circadian Clocks and Metabolism

    PubMed Central

    Marcheva, Biliana; Ramsey, Kathryn M.; Peek, Clara B.; Affinati, Alison; Maury, Eleonore; Bass, Joseph

    2014-01-01

    Circadian clocks maintain periodicity in internal cycles of behavior, physiology, and metabolism, enabling organisms to anticipate the 24-h rotation of the Earth. In mammals, circadian integration of metabolic systems optimizes energy harvesting and utilization across the light/dark cycle. Disruption of clock genes has recently been linked to sleep disorders and to the development of cardiometabolic disease. Conversely, aberrant nutrient signaling affects circadian rhythms of behavior. This chapter reviews the emerging relationship between the molecular clock and metabolic systems and examines evidence that circadian disruption exerts deleterious consequences on human health. PMID:23604478

  17. The JPL near-real-time VLBI system and its application to clock synchronization and earth orientation measurements

    NASA Technical Reports Server (NTRS)

    Callahan, P. S.; Eubanks, T. M.; Roth, M. G.; Steppe, J. A.; Esposito, P. B.

    1983-01-01

    The JPL near-real-time VLBI system called Block I is discussed. The hardware and software of the system are described, and the Time and Earth Motion Precision Observations (TEMPO) which utilize Block I are discussed. These observations are designed to provide interstation clock synchronization to 10 nsec and to determine earth orientation (UT1 and polar motion - UTPM) to 30 cm or better in each component. TEMPO results for clock synchronization and UTPM are presented with data from the July 1980-August 1981 analyzed using the most recent JPL solution software and source catalog. Future plans for TEMPO and Block I are discussed.

  18. Clock recovery PLL with gated PFD for NRZ ON-OFF Modulated Signals in a retinal implant system.

    PubMed

    Brendler, Christian; Aryan, Naser Pour; Rieger, Viola; Rothermel, Albrecht

    2013-01-01

    A Clock Recovery Phase Locked Loop with Gated Phase Frequency Detector (GPLL) for NRZ ON-OFF Modulated Signals with low data transmission rates for an inductively powered subretinal implant system is presented. Low data transmission rate leads to a long absence of inductive powering in the system when zeros are transmitted. Consequently there is no possibility to extract any clock in these pauses, thus the digital circuitry can not work any more. Compared to a commonly used PLL for clock extraction, no certain amount of data transitions is needed. This is achieved by having two operating modes. In one mode the GPLL tracks the HF input signal. In the other, the GPLL is an adjustable oscillator oscillating at the last used frequency. The proposed GPLL is fabricated and measured using a 350 nm High Voltage CMOS technology.

  19. Osmotic stress at the barley root affects expression of circadian clock genes in the shoot.

    PubMed

    Habte, Ermias; Müller, Lukas M; Shtaya, Munqez; Davis, Seth J; von Korff, Maria

    2014-06-01

    The circadian clock is an important timing system that controls physiological responses to abiotic stresses in plants. However, there is little information on the effects of the clock on stress adaptation in important crops, like barley. In addition, we do not know how osmotic stress perceived at the roots affect the shoot circadian clock. Barley genotypes, carrying natural variation at the photoperiod response and clock genes Ppd-H1 and HvELF3, were grown under control and osmotic stress conditions to record changes in the diurnal expression of clock and stress-response genes and in physiological traits. Variation at HvELF3 affected the expression phase and shape of clock and stress-response genes, while variation at Ppd-H1 only affected the expression levels of stress genes. Osmotic stress up-regulated expression of clock and stress-response genes and advanced their expression peaks. Clock genes controlled the expression of stress-response genes, but had minor effects on gas exchange and leaf transpiration. This study demonstrated that osmotic stress at the barley root altered clock gene expression in the shoot and acted as a spatial input signal into the clock. Unlike in Arabidopsis, barley primary assimilation was less controlled by the clock and more responsive to environmental perturbations, such as osmotic stress. PMID:24895755

  20. Circadian clocks in fuel harvesting and energy homeostasis.

    PubMed

    Ramsey, K M; Bass, J

    2011-01-01

    Circadian systems have evolved in plants, eubacteria, neurospora, and the metazoa as a mechanism to optimize energy acquisition and storage in synchrony with the rotation of the Earth on its axis. In plants, circadian clocks drive the expression of genes involved in oxygenic photosynthesis during the light and nitrogen fixation during the dark, repeating this cycle each day. In mammals, the core clock in the suprachiasmatic nucleus (SCN) functions to entrain extra-SCN and peripheral clocks to the light cycle, including regions central to energy homeostasis and sleep, as well as peripheral tissues involved in glucose and lipid metabolism. Tissue-specific gene targeting has shown a primary role of clock genes in endocrine pancreas insulin secretion, indicating that local clocks play a cell-autonomous role in organismal homeostasis. A present focus is to dissect the consequences of clock disruption on modulation of nuclear hormone receptor signaling and on posttranscriptional regulation of intermediary metabolism. Experimental genetic studies have pointed toward extensive interplay between circadian and metabolic systems and offer a means to dissect the impact of local tissue molecular clocks on fuel utilization across the sleep-wake cycle.

  1. Autonomous Rubidium Clock Weak Frequency Jump Detector for Onboard Navigation Satellite System.

    PubMed

    Khare, Akshay; Arora, Rajat; Banik, Alak; Mehta, Sanjay D

    2016-02-01

    Frequency jumps are common in rubidium frequency sources. They affect the estimation of user position in navigational satellite systems. These jumps must be detected and corrected immediately as they have direct impact on the navigation system integrity. A novel weak frequency jump detector is proposed based on a Kalman filter with a multi-interval approach. This detector can be applied for both "sudden" and "slow" frequency transitions. In this detection method, noises of clock data are reduced by Kalman filtering, for accurate estimation of jump size with less latency. Analysis on in-orbit rubidium atomic frequency standard (RAFS) phase telemetry data shows that the detector can be used for fast detection and correction of weak frequency jumps. Furthermore, performance comparison of different existing frequency jump detection techniques with the proposed detector is discussed. A multialgorithm-based strategy is proposed depending on the jump size and latency for onboard navigation satellites having RAFS as the primary frequency source.

  2. Autonomous Rubidium Clock Weak Frequency Jump Detector for Onboard Navigation Satellite System.

    PubMed

    Khare, Akshay; Arora, Rajat; Banik, Alak; Mehta, Sanjay D

    2016-02-01

    Frequency jumps are common in rubidium frequency sources. They affect the estimation of user position in navigational satellite systems. These jumps must be detected and corrected immediately as they have direct impact on the navigation system integrity. A novel weak frequency jump detector is proposed based on a Kalman filter with a multi-interval approach. This detector can be applied for both "sudden" and "slow" frequency transitions. In this detection method, noises of clock data are reduced by Kalman filtering, for accurate estimation of jump size with less latency. Analysis on in-orbit rubidium atomic frequency standard (RAFS) phase telemetry data shows that the detector can be used for fast detection and correction of weak frequency jumps. Furthermore, performance comparison of different existing frequency jump detection techniques with the proposed detector is discussed. A multialgorithm-based strategy is proposed depending on the jump size and latency for onboard navigation satellites having RAFS as the primary frequency source. PMID:26685233

  3. Interdependence of nutrient metabolism and the circadian clock system: Importance for metabolic health

    PubMed Central

    Ribas-Latre, Aleix; Eckel-Mahan, Kristin

    2016-01-01

    Background While additional research is needed, a number of large epidemiological studies show an association between circadian disruption and metabolic disorders. Specifically, obesity, insulin resistance, cardiovascular disease, and other signs of metabolic syndrome all have been linked to circadian disruption in humans. Studies in other species support this association and generally reveal that feeding that is not in phase with the external light/dark cycle, as often occurs with night or rotating shift workers, is disadvantageous in terms of energy balance. As food is a strong driver of circadian rhythms in the periphery, understanding how nutrient metabolism drives clocks across the body is important for dissecting out why circadian misalignment may produce such metabolic effects. A number of circadian clock proteins as well as their accessory proteins (such as nuclear receptors) are highly sensitive to nutrient metabolism. Macronutrients and micronutrients can function as zeitgebers for the clock in a tissue-specific way and can thus impair synchrony between clocks across the body, or potentially restore synchrony in the case of circadian misalignment. Circadian nuclear receptors are particularly sensitive to nutrient metabolism and can alter tissue-specific rhythms in response to changes in the diet. Finally, SNPs in human clock genes appear to be correlated with diet-specific responses and along with chronotype eventually may provide valuable information from a clinical perspective on how to use diet and nutrition to treat metabolic disorders. Scope of review This article presents a background of the circadian clock components and their interrelated metabolic and transcriptional feedback loops, followed by a review of some recent studies in humans and rodents that address the effects of nutrient metabolism on the circadian clock and vice versa. We focus on studies in which results suggest that nutrients provide an opportunity to restore or, alternatively

  4. Pseudonoise (PN) synchronization of data system with derivation of clock frequency from received signal for clocking receiver PN generator

    NASA Technical Reports Server (NTRS)

    Couvillon, L. A., Jr. (Inventor)

    1968-01-01

    A digital communicating system for automatically synchronizing signals for data detection is described. The systems consists of biphase modulating a subcarrier frequency by the binary data and transmitting a carrier phase modulated by this signal to a receiver, where coherent phase detection is employed to recover the subcarrier. Data detection is achieved by providing, in the receiver, a demodulated reference which is in synchronism with the unmodulated subcarrier in transmitting system. The output of the detector is passed through a matched filter where the signal is integrated over a bit period. As a result, random noise components are averaged out, so that the probability of detecting the correct data transmitted is maximized.

  5. Atomic and gravitational clocks

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Goldman, I.

    1982-01-01

    Atomic and gravitational clocks are governed by the laws of electrodynamics and gravity, respectively. While the strong equivalence principle (SEP) assumes that the two clocks have been synchronous at all times, recent planetary data seem to suggest a possible violation of the SEP. Past analysis of the implications of an SEP violation on different physical phenomena revealed no disagreement. However, these studies assumed that the two different clocks can be consistently constructed within the framework. The concept of scale invariance, and the physical meaning of different systems of units, are now reviewed and the construction of two clocks that do not remain synchronous - whose rates are related by a non-constant function beta sub a - is demonstrated. The cosmological character of beta sub a is also discussed.

  6. Clock Works.

    ERIC Educational Resources Information Center

    Markle, Sandra

    1988-01-01

    A science unit on clocks demonstrates the need to control variables to obtain reliable results from an experiment. Two activities, one for beginners and one for advanced students, are included. Directions for making a sundial are offered. (MT)

  7. Circadian Clock, Cancer, and Chemotherapy

    PubMed Central

    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

  8. Model Checking a Byzantine-Fault-Tolerant Self-Stabilizing Protocol for Distributed Clock Synchronization Systems

    NASA Technical Reports Server (NTRS)

    Malekpour, Mahyar R.

    2007-01-01

    This report presents the mechanical verification of a simplified model of a rapid Byzantine-fault-tolerant self-stabilizing protocol for distributed clock synchronization systems. This protocol does not rely on any assumptions about the initial state of the system. This protocol tolerates bursts of transient failures, and deterministically converges within a time bound that is a linear function of the self-stabilization period. A simplified model of the protocol is verified using the Symbolic Model Verifier (SMV) [SMV]. The system under study consists of 4 nodes, where at most one of the nodes is assumed to be Byzantine faulty. The model checking effort is focused on verifying correctness of the simplified model of the protocol in the presence of a permanent Byzantine fault as well as confirmation of claims of determinism and linear convergence with respect to the self-stabilization period. Although model checking results of the simplified model of the protocol confirm the theoretical predictions, these results do not necessarily confirm that the protocol solves the general case of this problem. Modeling challenges of the protocol and the system are addressed. A number of abstractions are utilized in order to reduce the state space. Also, additional innovative state space reduction techniques are introduced that can be used in future verification efforts applied to this and other protocols.

  9. Time-related dynamics of variation in core clock gene expression levels in tissues relevant to the immune system.

    PubMed

    Mazzoccoli, G; Sothern, R B; Greco, A; Pazienza, V; Vinciguerra, M; Liu, S; Cai, Y

    2011-01-01

    Immune parameters show rhythmic changes with a 24-h periodicity driven by an internal circadian timing system that relies on clock genes (CGs). CGs form interlocked transcription-translation feedback loops to generate and maintain 24-h mRNA and protein oscillations. In this study we evaluate and compare the profiles and the dynamics of variation of CG expression in peripheral blood, and two lymphoid tissues of mice. Expression levels of seven recognized key CGs (mBmal1, mClock, mPer1, mPer2, mCry1, mCry2, and Rev-erbalpha) were evaluated by quantitative RT- PCR in spleen, thymus and peripheral blood of C57BL/6 male mice housed on a 12-h light (L)-dark (D) cycle and sacrificed every 4 h for 24 h (3-4 mice/time point). We found a statistically significant time-effect in spleen (S), thymus (T) and blood (B) for the original values of expression level of mBmal1 (S), mClock (T, B), mPer1 (S, B), mPer2 (S), mCry1 (S), mCry2 (B) and mRev-Erbalpha (S, T, B) and for the fractional variation calculated between single time-point expression value of mBmal1 (B), mPer2 (T), mCry2 (B) and mRev-Erbalpha (S). A significant 24-h rhythm was validated for five CGs in blood (mClock, mPer1, mPer2, mCry2, mRev-Erbalpha), for four CGs in the spleen (mBmal1, mPer1, mPer2, mRev-Erbalpha), and for three CGs in the thymus (mClock, mPer2, mRev-Erbalpha). The original values of acrophases for mBmal1, mClock, mPer1, mPer2, mCry1 and mCry2 were very similar for spleen and thymus and advanced by several hours for peripheral blood compared to the lymphoid tissues, whereas the phases of mRev-Erbalpha were coincident for all three tissues. In conclusion, central and peripheral lymphoid tissues in the mouse show different sequences of activation of clock gene expression compared to peripheral blood. These differences may underlie the compartmental pattern of web functioning in the immune system.

  10. Time-related dynamics of variation in core clock gene expression levels in tissues relevant to the immune system.

    PubMed

    Mazzoccoli, G; Sothern, R B; Greco, A; Pazienza, V; Vinciguerra, M; Liu, S; Cai, Y

    2011-01-01

    Immune parameters show rhythmic changes with a 24-h periodicity driven by an internal circadian timing system that relies on clock genes (CGs). CGs form interlocked transcription-translation feedback loops to generate and maintain 24-h mRNA and protein oscillations. In this study we evaluate and compare the profiles and the dynamics of variation of CG expression in peripheral blood, and two lymphoid tissues of mice. Expression levels of seven recognized key CGs (mBmal1, mClock, mPer1, mPer2, mCry1, mCry2, and Rev-erbalpha) were evaluated by quantitative RT- PCR in spleen, thymus and peripheral blood of C57BL/6 male mice housed on a 12-h light (L)-dark (D) cycle and sacrificed every 4 h for 24 h (3-4 mice/time point). We found a statistically significant time-effect in spleen (S), thymus (T) and blood (B) for the original values of expression level of mBmal1 (S), mClock (T, B), mPer1 (S, B), mPer2 (S), mCry1 (S), mCry2 (B) and mRev-Erbalpha (S, T, B) and for the fractional variation calculated between single time-point expression value of mBmal1 (B), mPer2 (T), mCry2 (B) and mRev-Erbalpha (S). A significant 24-h rhythm was validated for five CGs in blood (mClock, mPer1, mPer2, mCry2, mRev-Erbalpha), for four CGs in the spleen (mBmal1, mPer1, mPer2, mRev-Erbalpha), and for three CGs in the thymus (mClock, mPer2, mRev-Erbalpha). The original values of acrophases for mBmal1, mClock, mPer1, mPer2, mCry1 and mCry2 were very similar for spleen and thymus and advanced by several hours for peripheral blood compared to the lymphoid tissues, whereas the phases of mRev-Erbalpha were coincident for all three tissues. In conclusion, central and peripheral lymphoid tissues in the mouse show different sequences of activation of clock gene expression compared to peripheral blood. These differences may underlie the compartmental pattern of web functioning in the immune system. PMID:22230394

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

    PubMed

    Teschke, Mathias; Wendt, Sabrina; Kawaguchi, So; Kramer, Achim; Meyer, Bettina

    2011-01-01

    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.

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

    PubMed

    Teschke, Mathias; Wendt, Sabrina; Kawaguchi, So; Kramer, Achim; Meyer, Bettina

    2011-01-01

    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. PMID:22022521

  13. Endogenous circannual clock and HP complex in a hibernation control system.

    PubMed

    Kondo, N

    2007-01-01

    Hibernation in mammals is a mysterious biological phenomenon that appears on a seasonal basis for surviving a potentially lethal low body temperature (Tb) near 0 degrees C and protecting organisms from various diseases and harmful events during hibernation. The exact mechanism by which such a unique ability is seasonally developed is still unknown. On the basis of our previous finding that the source of calcium ions for excitation-contraction coupling in myocardium of chipmunks, a rodent hibernator, is seasonally modulated for hibernation, the liver-derived hibernation-specific protein (HP) complex was discovered. Recently, the HP complex was identified as a promising candidate hormone that carries a hibernation signal to the brain independently of Tb and environmental changes for developing a capacity for tolerating low Tb. This finding will promote new approaches to understanding biological hibernation systems, including a circannual clock and its signaling pathway between the brain and the periphery. A new definition of hibernation and a possible model of a hibernation control system are proposed. PMID:18419320

  14. A gallium-arsenide digital phase shifter for clock and control signal distribution in high-speed digital systems

    NASA Technical Reports Server (NTRS)

    Fouts, Douglas J.

    1992-01-01

    The design, implementation, testing, and applications of a gallium-arsenide digital phase shifter and fan-out buffer are described. The integrated circuit provides a method for adjusting the phase of high-speed clock and control signals in digital systems, without the need for pruning cables, multiplexing between cables of different lengths, delay lines, or similar techniques. The phase of signals distributed with the described chip can be dynamically adjusted in eight different steps of approximately 60 ps per step. The IC also serves as a fan-out buffer and provides 12 in-phase outputs. The chip is useful for distributing high-speed clock and control signals in synchronous digital systems, especially if components are distributed over a large physical area or if there is a large number of components.

  15. Biochemical Frequency Control by Synchronisation of Coupled Repressilators: An In Silico Study of Modules for Circadian Clock Systems

    PubMed Central

    Hinze, Thomas; Schumann, Mathias; Bodenstein, Christian; Heiland, Ines; Schuster, Stefan

    2011-01-01

    Exploration of chronobiological systems emerges as a growing research field within bioinformatics focusing on various applications in medicine, agriculture, and material sciences. From a systems biological perspective, the question arises whether biological control systems for regulation of oscillatory signals and their technical counterparts utilise similar mechanisms. If so, modelling approaches and parameterisation adopted from building blocks can help to identify general components for frequency control in circadian clocks along with gaining insight into mechanisms of clock synchronisation to external stimuli like the daily rhythm of sunlight and darkness. Phase-locked loops could be an interesting candidate in this context. Both, biology and engineering, can benefit from a unified view resulting from systems modularisation. In a first experimental study, we analyse a model of coupled repressilators. We demonstrate its ability to synchronise clock signals in a monofrequential manner. Several oscillators initially deviate in phase difference and frequency with respect to explicit reaction and diffusion rates. Accordingly, the duration of the synchronisation process depends on dedicated reaction and diffusion parameters whose settings still lack to be sufficiently captured analytically. PMID:22046179

  16. Design and implementation of fast bipolar clock drivers for CCD imaging systems in space applications

    NASA Astrophysics Data System (ADS)

    Jayarajan, Jayesh; Kumar, Nishant; Verma, Amarnath; Thaker, Ramkrishna

    2016-05-01

    Drive electronics for generating fast, bipolar clocks, which can drive capacitive loads of the order of 5-10nF are indispensable for present day Charge Coupled Devices (CCDs). Design of these high speed bipolar clocks is challenging because of the capacitive loads that have to be driven and a strict constraint on the rise and fall times. Designing drive electronics circuits for space applications becomes even more challenging due to limited number of available discrete devices, which can survive in the harsh radiation prone space environment. This paper presents the design, simulations and test results of a set of such high speed, bipolar clock drivers. The design has been tested under a thermal cycle of -15 deg C to +55 deg C under vacuum conditions and has been designed using radiation hardened components. The test results show that the design meets the stringent rise/fall time requirements of 50+/-10ns for Multiple Vertical CCD (VCCD) clocks and 20+/-5ns for Horizontal CCD (HCCD) clocks with sufficient design margins across full temperature range, with a pixel readout rate of 6.6MHz. The full design has been realized in flexi-rigid PCB with package volume of 140x160x50 mm3.

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

    DOEpatents

    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.

  18. Formulation of geopotential difference determination using optical-atomic clocks onboard satellites and on ground based on Doppler cancellation system

    NASA Astrophysics Data System (ADS)

    Shen, Ziyu; Shen, Wen-Bin; Zhang, Shuangxi

    2016-06-01

    In this study we propose an approach for determining the geopotential difference using high-frequency-stability microwave links between satellite and ground station based on Doppler cancelation system. Suppose a satellite and a ground station are equipped with precise optical-atomic clocks and oscillators. The ground oscillator emits a signal with frequency fa towards the satellite and the satellite receiver (connected with the satellite oscillator) receives this signal with frequency fb which contains the gravitational frequency shift effect and other signals and noises. After receiving this signal, the satellite oscillator transmits and emits respectively two signals with frequencies fb and fc towards the ground station. Via Doppler cancellation technique, the geopotential difference between the satellite and the ground station can be determined based on gravitational frequency shift equation by a combination of these three frequencies. For arbitrary two stations on ground, based on similar procedures as described above, we may determine the geopotential difference between these two stations via a satellite. Our analysis shows that the accuracy can reach 1 {m^2/s^2} based on the clocks' inaccuracy of about 10-17 (s/s) level. Since optical-atomic clocks with instability around 10-18 in several hours and inaccuracy around 10-18 level have been generated in laboratory, the proposed approach may have prospective applications in geoscience, and especially, based on this approach a unified world height system could be realized with one-centimeter level accuracy in the near future.

  19. Rethinking transcriptional activation in the Arabidopsis circadian clock.

    PubMed

    Fogelmark, Karl; Troein, Carl

    2014-07-01

    Circadian clocks are biological timekeepers that allow living cells to time their activity in anticipation of predictable daily changes in light and other environmental factors. The complexity of the circadian clock in higher plants makes it difficult to understand the role of individual genes or molecular interactions, and mathematical modelling has been useful in guiding clock research in model organisms such as Arabidopsis thaliana. We present a model of the circadian clock in Arabidopsis, based on a large corpus of published time course data. It appears from experimental evidence in the literature that most interactions in the clock are repressive. Hence, we remove all transcriptional activation found in previous models of this system, and instead extend the system by including two new components, the morning-expressed activator RVE8 and the nightly repressor/activator NOX. Our modelling results demonstrate that the clock does not need a large number of activators in order to reproduce the observed gene expression patterns. For example, the sequential expression of the PRR genes does not require the genes to be connected as a series of activators. In the presented model, transcriptional activation is exclusively the task of RVE8. Predictions of how strongly RVE8 affects its targets are found to agree with earlier interpretations of the experimental data, but generally we find that the many negative feedbacks in the system should discourage intuitive interpretations of mutant phenotypes. The dynamics of the clock are difficult to predict without mathematical modelling, and the clock is better viewed as a tangled web than as a series of loops.

  20. Quasars as very-accurate clock synchronizers

    NASA Technical Reports Server (NTRS)

    Hurd, W. J.; Goldstein, R. M.

    1975-01-01

    Quasars can be employed to synchronize global data communications, geophysical measurements, and atomic clocks. It is potentially two to three orders of magnitude better than presently-used Moon-bounce system. Comparisons between quasar and clock pulses are used to develop correction or synchronization factors for station clocks.

  1. Initial results of precise orbit and clock determination for COMPASS navigation satellite system

    NASA Astrophysics Data System (ADS)

    Zhao, Qile; Guo, Jing; Li, Min; Qu, Lizhong; Hu, Zhigang; Shi, Chuang; Liu, Jingnan

    2013-05-01

    The development of the COMPASS satellite system is introduced, and the regional tracking network and data availability are described. The precise orbit determination strategy of COMPASS satellites is presented. Data of June 2012 are processed. The obtained orbits are evaluated by analysis of post-fit residuals, orbit overlap comparison and SLR (satellite laser ranging) validation. The RMS (root mean square) values of post-fit residuals for one month's data are smaller than 2.0 cm for ionosphere-free phase measurements and 2.6 m for ionosphere-free code observations. The 48-h orbit overlap comparison shows that the RMS values of differences in the radial component are much smaller than 10 cm and those of the cross-track component are smaller than 20 cm. The SLR validation shows that the overall RMS of observed minus computed residuals is 68.5 cm for G01 and 10.8 cm for I03. The static and kinematic PPP solutions are produced to further evaluate the accuracy of COMPASS orbit and clock products. The static daily COMPASS PPP solutions achieve an accuracy of better than 1 cm in horizontal and 3 cm in vertical. The accuracy of the COMPASS kinematic PPP solutions is within 1-2 cm in the horizontal and 4-7 cm in the vertical. In addition, we find that the COMPASS kinematic solutions are generally better than the GPS ones for the selected location. Furthermore, the COMPASS/GPS combinations significantly improve the accuracy of GPS only PPP solutions. The RMS values are basically smaller than 1 cm in the horizontal components and 3-4 cm in the vertical component.

  2. Circadian clocks: lessons from fish.

    PubMed

    Idda, M Laura; Bertolucci, Cristiano; Vallone, Daniela; Gothilf, Yoav; Sánchez-Vázquez, Francisco Javier; Foulkes, Nicholas S

    2012-01-01

    Our understanding of the molecular and cellular organization of the circadian timing system in vertebrates has increased enormously over the past decade. In large part, progress has been based on genetic studies in the mouse as well as on fundamental similarities between vertebrate and Drosophila clocks. The zebrafish was initially considered as a potentially attractive genetic model for identifying vertebrate clock genes. However, instead, fish have ultimately proven to be valuable complementary models for studying various aspects of clock biology. For example, many fish can shift from diurnal to nocturnal activity implying specific flexibility in their clock function. We have learned much about the function of light input pathways, and the ontogeny and function of the pineal organ, the fish central pacemaker. Finally, blind cavefish have also provided new insight into the evolution of the circadian clock under extreme environmental conditions. PMID:22877658

  3. A Bioluminescence Resonance Energy Transfer (BRET) System: Application to Interacting Circadian Clock Proteins

    NASA Astrophysics Data System (ADS)

    Xu, Yao; Piston, David W.; Hirschie Johnson, Carl

    1999-01-01

    We describe a method for assaying protein interactions that offers some attractive advantages over previous assays. This method, called bioluminescence resonance energy transfer (BRET), uses a bioluminescent luciferase that is genetically fused to one candidate protein, and a green fluorescent protein mutant fused to another protein of interest. Interactions between the two fusion proteins can bring the luciferase and green fluorescent protein close enough for resonance energy transfer to occur, thus changing the color of the bioluminescent emission. By using proteins encoded by circadian (daily) clock genes from cyanobacteria, we use the BRET technique to demonstrate that the clock protein KaiB interacts to form homodimers. BRET should be particularly useful for testing protein interactions within native cells, especially with integral membrane proteins or proteins targeted to specific organelles.

  4. Chlamydomonas reinhardtii strain CC-124 is highly sensitive to blue light in addition to green and red light in resetting its circadian clock, with the blue-light photoreceptor plant cryptochrome likely acting as negative modulator.

    PubMed

    Forbes-Stovall, Jennifer; Howton, Jonathan; Young, Matthew; Davis, Gavin; Chandler, Todd; Kessler, Bruce; Rinehart, Claire A; Jacobshagen, Sigrid

    2014-02-01

    The unicellular green alga Chlamydomonas reinhardtii has long served as model organism for studies on the circadian clock. This clock is present in all eukaryotes and some prokaryotes allowing them to anticipate and take advantage of the daily oscillations in the environment. Although much is known about the circadian clock in C. reinhardtii, the photoreceptors mediating entrainment of the clock to the daily changes of light remain obscure. Based on its circadian rhythm of phototaxis as a reporter of the clock's phase, we show here that C. reinhardtii strain CC-124 is highly sensitive to blue light of 440 nm when resetting its circadian clock upon light pulses. Thus, CC-124 differs in this respect from what was previously reported for a cell wall-deficient strain. An action spectrum analysis revealed that CC-124 also responds with high sensitivity to green (540 nm), red (640-660 nm), and possibly UV-A (≤400 nm) light, and therefore shows similarities as well to what has been reported for the cell wall-deficient strain. We also investigated two RNA interference strains with reductions in the level of the blue light photoreceptor plant cryptochrome (CPH1). One of them, the strain with the greater reduction, surprisingly showed an increased sensitivity in clock resetting upon blue light pulses of 440 nm. This increase in sensitivity reverted to wild-type levels when the RNA interference strain reverted to wild-type protein levels. It suggests that plant cryptochrome in C. reinhardtii could function as negative rather than positive modulator of circadian clock resetting.

  5. Molecular clocks.

    PubMed

    Lee, Michael S Y; Ho, Simon Y W

    2016-05-23

    In the 1960s, several groups of scientists, including Emile Zuckerkandl and Linus Pauling, had noted that proteins experience amino acid replacements at a surprisingly consistent rate across very different species. This presumed single, uniform rate of genetic evolution was subsequently described using the term 'molecular clock'. Biologists quickly realised that such a universal pacemaker could be used as a yardstick for measuring the timescale of evolutionary divergences: estimating the rate of amino acid exchanges per unit of time and applying it to protein differences across a range of organisms would allow deduction of the divergence times of their respective lineages (Figure 1). PMID:27218841

  6. All-optical clock recovery, photonic balancing, and saturated asymmetric filtering for fiber optic communication systems

    NASA Astrophysics Data System (ADS)

    Parsons, Earl Ryan

    In this dissertation I investigated a multi-channel and multi-bit rate all-optical clock recovery device. This device, a birefringent Fabry-Perot resonator, had previously been demonstrated to simultaneously recover the clock signal from 10 wavelength channels operating at 10 Gb/s and one channel at 40 Gb/s. Similar to clock signals recovered from a conventional Fabry-Perot resonator, the clock signal from the birefringent resonator suffers from a bit pattern effect. I investigated this bit pattern effect for birefringent resonators numerically and experimentally and found that the bit pattern effect is less prominent than for clock signals from a conventional Fabry-Perot resonator. I also demonstrated photonic balancing which is an all-optical alternative to electrical balanced detection for phase shift keyed signals. An RZ-DPSK data signal was demodulated using a delay interferometer. The two logically opposite outputs from the delay interferometer then counter-propagated in a saturated SOA. This process created a differential signal which used all the signal power present in two consecutive symbols. I showed that this scheme could provide an optical alternative to electrical balanced detection by reducing the required OSNR by 3 dB. I also show how this method can provide amplitude regeneration to a signal after modulation format conversion. In this case an RZ-DPSK signal was converted to an amplitude modulation signal by the delay interferometer. The resulting amplitude modulated signal is degraded by both the amplitude noise and the phase noise of the original signal. The two logically opposite outputs from the delay interferometer again counter-propagated in a saturated SOA. Through limiting amplification and noise modulation this scheme provided amplitude regeneration and improved the Q-factor of the demodulated signal by 3.5 dB. Finally I investigated how SPM provided by the SOA can provide a method to reduce the in-band noise of a communication signal. The

  7. RNA around the clock – regulation at the RNA level in biological timing

    PubMed Central

    Nolte, Christine; Staiger, Dorothee

    2015-01-01

    The circadian timing system in plants synchronizes their physiological functions with the environment. This is achieved by a global control of gene expression programs with a considerable part of the transcriptome undergoing 24-h oscillations in steady-state abundance. These circadian oscillations are driven by a set of core clock proteins that generate their own 24-h rhythm through periodic feedback on their own transcription. Additionally, post-transcriptional events are instrumental for oscillations of core clock genes and genes in clock output. Here we provide an update on molecular events at the RNA level that contribute to the 24-h rhythm of the core clock proteins and shape the circadian transcriptome. We focus on the circadian system of the model plant Arabidopsis thaliana but also discuss selected regulatory principles in other organisms. PMID:25999975

  8. OCT system for plant measurement

    NASA Astrophysics Data System (ADS)

    Shiina, Tatsuo; Kishiwaki, Daisuke; Ito, Masafumi; Honda, Toshio; Okamura, Yasuyuki

    2005-09-01

    An Optical coherence tomography system (OCT system) was developed to measure physiological response inside plant. This system has a unique optical scanner of wide scanning range of 40mm to adapt the OCT measurement to irregular features and many breeds of plant samples. To use in the outdoor field, which plants volunteers, the system should be compact, stable, and have high repetition frequency of measurement. We designed the OCT system with the original optical scanner and optical fiber optics for the purpose. The transmittance and reflectance characteristics of the plant leaves were examined to check the water absorption. The SLD-light of the wavelength of 830nm was selected for the measurement light source. Various kinds of plant samples were measured to evaluate the system performance and its adaptive flexibility. Cell structure of plant surface, its change due to the water content, and growth monitoring of plant tissue were measured. The concrete application was also demonstrated.

  9. Circadian Clocks, Stress, and Immunity

    PubMed Central

    Dumbell, Rebecca; Matveeva, Olga; Oster, Henrik

    2016-01-01

    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. PMID:27199894

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

    NASA Technical Reports Server (NTRS)

    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.

  11. Metamorphosis of a clock: remodeling of the circadian timing system in the brain of Rhodnius prolixus (Hemiptera) during larval-adult development.

    PubMed

    Vafopoulou, Xanthe; Steel, Colin G H

    2012-04-15

    The rhythmic phenomena expressed by organisms change over their lifetimes, but little is known of accompanying reorganization of the central circadian timing system in the brain. Especially dramatic changes in overt rhythms and morphology occur during transformation of larval insects into the adult form (metamorphosis). In Rhodnius prolixus, both the physiology of metamorphosis and its hormonal control are known in detail. Here we report changes in the brain timing system as revealed by pigment dispersing factor immunohistochemistry and confocal microscopy. Most of the features of the larval system are retained, but new clock cells differentiate and the arborizations of their axons increase in complexity, as do pathways connecting the lateral (LNs) and dorsal (DNs) groups of clock neurons. Early in metamorphosis, the LNs increase from 8 to 11 in number, becoming five small and six large LNs. Two large LNs then migrate to new positions in the protocerebrum. Another clock cell differentiates in the posterior protocerebrum. Each change occurs at a characteristic concentration of the ecdysteroid molting hormones that regulate metamorphosis. Clock cell axons invade the mushroom body and corpus allatum and travel down the ventral nerve cord. New overt rhythms develop during metamorphosis, in which these structures participate. The neuroendocrine cells of the brain receive more extensive branches of clock cell axons than in larvae. These increases in size and complexity of the circadian system during metamorphosis imply a greater complexity and diversity of outputs from it to both behavioral and hormonal rhythms in the adult.

  12. Unraveling the circadian clock in Arabidopsis

    PubMed Central

    Wang, Xiaoxue; Ma, Ligeng

    2013-01-01

    The circadian clock is an endogenous timing system responsible for coordinating an organism’s biological processes with its environment. Interlocked transcriptional feedback loops constitute the fundamental architecture of the circadian clock. In Arabidopsis, three feedback loops, the core loop, morning loop and evening loop, comprise a network that is the basis of the circadian clock. The components of these three loops are regulated in distinct ways, including transcriptional, post-transcriptional and posttranslational mechanisms. The discovery of the DNA-binding and repressive activities of TOC1 has overturned our initial concept of its function in the circadian clock. The alternative splicing of circadian clock-related genes plays an essential role in normal functioning of the clock and enables organisms to sense environmental changes. In this review, we describe the regulatory mechanisms of the circadian clock that have been identified in Arabidopsis. PMID:23221775

  13. Formulation of geopotential difference determination using optical-atomic clocks onboard satellites and on ground based on Doppler cancellation system

    NASA Astrophysics Data System (ADS)

    Shen, Ziyu; Shen, Wen-Bin; Zhang, Shuangxi

    2016-08-01

    In this study, we propose an approach for determining the geopotential difference using high-frequency-stability microwave links between satellite and ground station based on Doppler cancellation system. Suppose a satellite and a ground station are equipped with precise optical-atomic clocks (OACs) and oscillators. The ground oscillator emits a signal with frequency fa towards the satellite and the satellite receiver (connected with the satellite oscillator) receives this signal with frequency fb which contains the gravitational frequency shift effect and other signals and noises. After receiving this signal, the satellite oscillator transmits and emits, respectively, two signals with frequencies fb and fc towards the ground station. Via Doppler cancellation technique, the geopotential difference between the satellite and the ground station can be determined based on gravitational frequency shift equation by a combination of these three frequencies. For arbitrary two stations on ground, based on similar procedures as described above, we may determine the geopotential difference between these two stations via a satellite. Our analysis shows that the accuracy can reach 1 m2 s- 2 based on the clocks' inaccuracy of about 10-17 (s s-1) level. Since OACs with instability around 10-18 in several hours and inaccuracy around 10-18 level have been generated in laboratory, the proposed approach may have prospective applications in geoscience, and especially, based on this approach a unified world height system could be realized with one-centimetre level accuracy in the near future.

  14. 25 MHz clock continuous-variable quantum key distribution system over 50 km fiber channel

    PubMed Central

    Wang, Chao; Huang, Duan; Huang, Peng; Lin, Dakai; Peng, Jinye; Zeng, Guihua

    2015-01-01

    In this paper, a practical continuous-variable quantum key distribution system is developed and it runs in the real-world conditions with 25 MHz clock rate. To reach high-rate, we have employed a homodyne detector with maximal bandwidth to 300 MHz and an optimal high-efficiency error reconciliation algorithm with processing speed up to 25 Mbps. To optimize the stability of the system, several key techniques are developed, which include a novel phase compensation algorithm, a polarization feedback algorithm, and related stability method on the modulators. Practically, our system is tested for more than 12 hours with a final secret key rate of 52 kbps over 50 km transmission distance, which is the highest rate so far in such distance. Our system may pave the road for practical broadband secure quantum communication with continuous variables in the commercial conditions. PMID:26419413

  15. 25 MHz clock continuous-variable quantum key distribution system over 50 km fiber channel.

    PubMed

    Wang, Chao; Huang, Duan; Huang, Peng; Lin, Dakai; Peng, Jinye; Zeng, Guihua

    2015-01-01

    In this paper, a practical continuous-variable quantum key distribution system is developed and it runs in the real-world conditions with 25 MHz clock rate. To reach high-rate, we have employed a homodyne detector with maximal bandwidth to 300 MHz and an optimal high-efficiency error reconciliation algorithm with processing speed up to 25 Mbps. To optimize the stability of the system, several key techniques are developed, which include a novel phase compensation algorithm, a polarization feedback algorithm, and related stability method on the modulators. Practically, our system is tested for more than 12 hours with a final secret key rate of 52 kbps over 50 km transmission distance, which is the highest rate so far in such distance. Our system may pave the road for practical broadband secure quantum communication with continuous variables in the commercial conditions.

  16. 25 MHz clock continuous-variable quantum key distribution system over 50 km fiber channel

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Huang, Duan; Huang, Peng; Lin, Dakai; Peng, Jinye; Zeng, Guihua

    2015-09-01

    In this paper, a practical continuous-variable quantum key distribution system is developed and it runs in the real-world conditions with 25 MHz clock rate. To reach high-rate, we have employed a homodyne detector with maximal bandwidth to 300 MHz and an optimal high-efficiency error reconciliation algorithm with processing speed up to 25 Mbps. To optimize the stability of the system, several key techniques are developed, which include a novel phase compensation algorithm, a polarization feedback algorithm, and related stability method on the modulators. Practically, our system is tested for more than 12 hours with a final secret key rate of 52 kbps over 50 km transmission distance, which is the highest rate so far in such distance. Our system may pave the road for practical broadband secure quantum communication with continuous variables in the commercial conditions.

  17. A transportable optical lattice clock

    NASA Astrophysics Data System (ADS)

    Vogt, Stefan; Häfner, Sebastian; Grotti, Jacopo; Koller, Silvio; Al-Masoudi, Ali; Sterr, Uwe; Lisdat, Christian

    2016-06-01

    We present the experimental setup and first results of PTB's transportable 87Sr clock. It consists of a physics package, several compact laser breadboards, and a transportable high finesse cavity for the clock laser. A comparison of the transportable system with our stationary optical lattice clock yields an instability of 2.2 x 10-15 √s/τ for the transportable clock. The current fractional uncertainty of 1 × 10-15 is still limited by the not yet fully evaluated light shift from the free running optical lattice laser operated near the magic wavelength. We are currently improving our transportable system to reach an uncertainty at or below the 10-17 level, which will finaly be limited by the uncertainty in blackbody radiation shift correction.

  18. Impact of round-the-clock CSF Gram stain on empirical therapy for suspected central nervous system infections.

    PubMed

    Tissot, F; Prod'hom, G; Manuel, O; Greub, G

    2015-09-01

    The impact of round-the-clock cerebrospinal fluid (CSF) Gram stain on overnight empirical therapy for suspected central nervous system (CNS) infections was investigated. All consecutive overnight CSF Gram stains between 2006 and 2011 were included. The impact of a positive or a negative test on empirical therapy was evaluated and compared to other clinical and biological indications based on institutional guidelines. Bacterial CNS infection was documented in 51/241 suspected cases. Overnight CSF Gram stain was positive in 24/51. Upon validation, there were two false-positive and one false-negative results. The sensitivity and specificity were 41 and 99 %, respectively. All patients but one had other indications for empirical therapy than Gram stain alone. Upon obtaining the Gram result, empirical therapy was modified in 7/24, including the addition of an appropriate agent (1), addition of unnecessary agents (3) and simplification of unnecessary combination therapy (3/11). Among 74 cases with a negative CSF Gram stain and without formal indication for empirical therapy, antibiotics were withheld in only 29. Round-the-clock CSF Gram stain had a low impact on overnight empirical therapy for suspected CNS infections and was associated with several misinterpretation errors. Clinicians showed little confidence in CSF direct examination for simplifying or withholding therapy before definite microbiological results.

  19. Expression of clock genes period and timeless in the central nervous system of the Mediterranean flour moth, Ephestia kuehniella.

    PubMed

    Kobelková, Alena; Závodská, Radka; Sauman, Ivo; Bazalová, Olga; Dolezel, David

    2015-04-01

    Homologous circadian genes are found in all insect clocks, but their contribution to species-specific circadian timing systems differs. The aim of this study was to extend research within Lepidoptera to gain a better understanding of the molecular mechanism underlying circadian clock plasticity and evolution. The Mediterranean flour moth, Ephestia kuehniella (Pyralidae), represents a phylogenetically ancestral lepidopteran species. We have identified circadian rhythms in egg hatching, adult emergence, and adult locomotor activity. Cloning full-length complementary DNAs and further characterization confirmed one copy of period and timeless genes in both sexes. Both per and tim transcripts oscillate in their abundance in E. kuehniella heads under light-dark conditions. PER-like immunoreactivity (PER-lir) was observed in nuclei and cytoplasm of most neurons in the central brain, the ventral part of subesophageal complex, the neurohemal organs, the optic lobes, and eyes. PER-lir in photoreceptor nuclei oscillated during the day with maximal intensity in the light phase of the photoperiodic regime and lack of a signal in the middle of the dark phase. Expression patterns of per and tim messenger RNAs (mRNAs) were revealed in the identical location as the PER-lir was detected. In the photoreceptors, a daily rhythm in the intensity of expression of both per mRNA and tim mRNA was found. These findings suggest E. kuehniella as a potential lepidopteran model for circadian studies. PMID:25637625

  20. The cyanobacterial clock and metabolism.

    PubMed

    Pattanayak, Gopal; Rust, Michael J

    2014-04-01

    Cyanobacteria possess the simplest known circadian clock, which presents a unique opportunity to study how rhythms are generated and how input signals from the environment reset the clock time. The kaiABC locus forms the core of the oscillator, and the remarkable ability to reconstitute oscillations using purified KaiABC proteins has allowed researchers to study mechanism using the tools of quantitative biochemistry. Autotrophic cyanobacteria experience major shifts in metabolism following a light-dark transition, and recent work suggests that input mechanisms that couple the day-night cycle to the clock involve energy and redox metabolites acting directly on clock proteins. We offer a summary of the current state of knowledge in this system and present a perspective for future lines of investigation.

  1. Precise time dissemination via portable atomic clocks

    NASA Technical Reports Server (NTRS)

    Putkovich, K.

    1982-01-01

    The most precise operational method of time dissemination over long distances presently available to the Precise Time and Time Interval (PTTI) community of users is by means of portable atomic clocks. The Global Positioning System (GPS), the latest system showing promise of replacing portable clocks for global PTTI dissemination, was evaluated. Although GPS has the technical capability of providing superior world-wide dissemination, the question of present cost and future accessibility may require a continued reliance on portable clocks for a number of years. For these reasons a study of portable clock operations as they are carried out today was made. The portable clock system that was utilized by the U.S. Naval Observatory (NAVOBSY) in the global synchronization of clocks over the past 17 years is described and the concepts on which it is based are explained. Some of its capabilities and limitations are also discussed.

  2. Clocks in algae.

    PubMed

    Noordally, Zeenat B; Millar, Andrew J

    2015-01-20

    As major contributors to global oxygen levels and producers of fatty acids, carotenoids, sterols, and phycocolloids, algae have significant ecological and commercial roles. Early algal models have contributed much to our understanding of circadian clocks at physiological and biochemical levels. The genetic and molecular approaches that identified clock components in other taxa have not been as widely applied to algae. We review results from seven species: the chlorophytes Chlamydomonas reinhardtii, Ostreococcus tauri, and Acetabularia spp.; the dinoflagellates Lingulodinium polyedrum and Symbiodinium spp.; the euglenozoa Euglena gracilis; and the red alga Cyanidioschyzon merolae. The relative simplicity, experimental tractability, and ecological and evolutionary diversity of algal systems may now make them particularly useful in integrating quantitative data from "omic" technologies (e.g., genomics, transcriptomics, metabolomics, and proteomics) with computational and mathematical methods.

  3. Precise clock synchronization protocol

    NASA Astrophysics Data System (ADS)

    Luit, E. J.; Martin, J. M. M.

    1993-12-01

    A distributed clock synchronization protocol is presented which achieves a very high precision without the need for very frequent resynchronizations. The protocol tolerates failures of the clocks: clocks may be too slow or too fast, exhibit omission failures and report inconsistent values. Synchronization takes place in synchronization rounds as in many other synchronization protocols. At the end of each round, clock times are exchanged between the clocks. Each clock applies a convergence function (CF) to the values obtained. This function estimates the difference between its clock and an average clock and corrects its clock accordingly. Clocks are corrected for drift relative to this average clock during the next synchronization round. The protocol is based on the assumption that clock reading errors are small with respect to the required precision of synchronization. It is shown that the CF resynchronizes the clocks with high precision even when relatively large clock drifts are possible. It is also shown that the drift-corrected clocks remain synchronized until the end of the next synchronization round. The stability of the protocol is proven.

  4. Synchronization of clocks

    NASA Astrophysics Data System (ADS)

    Kapitaniak, Marcin; Czolczynski, Krzysztof; Perlikowski, Przemysław; Stefanski, Andrzej; Kapitaniak, Tomasz

    2012-08-01

    In this report we recall the famous Huygens’ experiment which gave the first evidence of the synchronization phenomenon. We consider the synchronization of two clocks which are accurate (show the same time) but have pendula with different masses. It has been shown that such clocks hanging on the same beam can show the almost complete (in-phase) and almost antiphase synchronizations. By almost complete and almost antiphase synchronization we defined the periodic motion of the pendula in which the phase shift between the displacements of the pendula is respectively close (but not equal) to 0 or π. We give evidence that almost antiphase synchronization was the phenomenon observed by Huygens in XVII century. We support our numerical studies by considering the energy balance in the system and showing how the energy is transferred between the pendula via oscillating beam allowing the pendula’s synchronization. Additionally we discuss the synchronization of a number of different pendulum clocks hanging from a horizontal beam which can roll on the parallel surface. It has been shown that after a transient, different types of synchronization between pendula can be observed; (i) the complete synchronization in which all pendula behave identically, (ii) pendula create three or five clusters of synchronized pendula. We derive the equations for the estimation of the phase differences between phase synchronized clusters. The evidence, why other configurations with a different number of clusters are not observed, is given.

  5. Foucault pendulum ``wall clock''

    NASA Astrophysics Data System (ADS)

    Crane, H. Richard

    1995-01-01

    Details are given for the construction of a 70-cm-long Foucault pendulum to be mounted on the wall, and for a simple modification that will make it display local clock time. The possibility of having a Foucault pendulum of such short length is the result of finding new or improved ways of reducing four perturbing effects that become more severe as the length is decreased. They relate to: precession due to ellipticity in the motion, the drive system for maintaining the amplitude, the means of limiting the growth of ellipticity, and the method of gripping the suspending wire at the top. With those improvements, successful Foucault operation was attained in pendulums as short as 15 cm, support to center of bob. Following that severe test, the length for the ``wall clock'' was set at a conservative 70 cm. At that length it is highly reliable, and accurate to within 2% when timed for the full revolution. Uniformity in rate when comparing different intervals of azimuth is of course less. A simple method of making the pendulum read local time is described. Two clocks, one in the author's office and one at home, have been in continuous operation for more than ten years.

  6. Circadian clock and PIF4-mediated external coincidence mechanism coordinately integrates both of the cues from seasonal changes in photoperiod and temperature to regulate plant growth in Arabidopsis thaliana.

    PubMed

    Nomoto, Yuji; Kubozono, Saori; Miyachi, Miki; Yamashino, Takafumi; Nakamichi, Norihito; Mizuno, Takeshi

    2013-02-01

    In Arabidopsis thaliana, the circadian clock regulates the photoperiodic plant growth including the elongation of hypocotyls in a short-days (SDs)-specific manner. The clock-controlled PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) gene encoding a basic helix-loop-helix (bHLH) transcription factor plays crucial roles in this regulation. The SDs-specific elongation of hypocotyls is best explained by accumulation of the active PIF4 proteins at the end of night specifically in SDs due to coincidence between internal (circadian clock) and external (photoperiod) cues. However, this external coincidence model was challenged with the recent finding that the elongation of hypocotyls is markedly promoted at high growth temperature (28˚C) even in long-days (LDs), implying that the model to explain the photoperiodic response of plant architecture appears to be conditional on ambient temperature. With regard to this problem, the results of this and previous studies showed that the model holds under a wide range of ambient temperature conditions (16˚C to 28˚C). We propose that the circadian clock and PIF4-mediated external coincidence mechanism coordinately integrates both of the cues from seasonal changes in photoperiod and temperature to regulate plant growth in natural habitats.

  7. Orexin as an input of circadian system in goldfish: Effects on clock gene expression and locomotor activity rhythms.

    PubMed

    Nisembaum, Laura G; de Pedro, Nuria; Delgado, María J; Sánchez-Bretaño, Aída; Isorna, Esther

    2014-02-01

    Orexins are neuropeptides mainly known for regulating feeding behavior and sleep-wakefulness cycle in vertebrates. Daily variations of orexin-A expression have been reported in fish, with the highest levels preceding feeding time. However, it is unknown if such variations could be related with daily rhythms of clock genes, which form the molecular core of circadian oscillators. The aim of the present study was to identify the possible role of orexin as an input element of the goldfish circadian system. It was investigated the effects of orexin-A (10ng/gbw) intracerebroventricular injections on the expression of clock genes, NPY and ghrelin, as well as on daily locomotor activity rhythms. Goldfish held under 12L:12D photoperiod and injected at midday with orexin or saline, were sacrificed at 1 and 3h post-injection. The analysis of genes expression by qReal Time PCR showed an increment of Per genes in hypothalamus and foregut at 3h post-injection, but not in hindgut and liver. The gBmal1a expression remained unaltered in all the studied tissues. Orexin induced NPY in the hypothalamus and ghrelin in the foregut. Locomotor activity was studied in fish daily injected with orexin for several consecutive days under different experimental conditions. Orexin synchronized locomotor activity in goldfish maintained in 24L and fasting conditions. Present results support a cross-talking between orexin-A and other feeding regulators at central and peripheral level, and suggest, for the first time, a role of this peptide as an input of the circadian system in fish.

  8. Synchronization of Biological Clock Neurons by Light and Peripheral Feedback Systems Promotes Circadian Rhythms and Health

    PubMed Central

    Ramkisoensing, Ashna; Meijer, Johanna H.

    2015-01-01

    In mammals, the suprachiasmatic nucleus (SCN) functions as a circadian clock that drives 24-h rhythms in both physiology and behavior. The SCN is a multicellular oscillator in which individual neurons function as cell-autonomous oscillators. The production of a coherent output rhythm is dependent upon mutual synchronization among single cells and requires both synaptic communication and gap junctions. Changes in phase-synchronization between individual cells have consequences on the amplitude of the SCN’s electrical activity rhythm, and these changes play a major role in the ability to adapt to seasonal changes. Both aging and sleep deprivation negatively affect the circadian amplitude of the SCN, whereas behavioral activity (i.e., exercise) has a positive effect on amplitude. Given that the amplitude of the SCN’s electrical activity rhythm is essential for achieving robust rhythmicity in physiology and behavior, the mechanisms that underlie neuronal synchronization warrant further study. A growing body of evidence suggests that the functional integrity of the SCN contributes to health, well-being, cognitive performance, and alertness; in contrast, deterioration of the 24-h rhythm is a risk factor for neurodegenerative disease, cancer, depression, and sleep disorders. PMID:26097465

  9. Synchronization of Biological Clock Neurons by Light and Peripheral Feedback Systems Promotes Circadian Rhythms and Health.

    PubMed

    Ramkisoensing, Ashna; Meijer, Johanna H

    2015-01-01

    In mammals, the suprachiasmatic nucleus (SCN) functions as a circadian clock that drives 24-h rhythms in both physiology and behavior. The SCN is a multicellular oscillator in which individual neurons function as cell-autonomous oscillators. The production of a coherent output rhythm is dependent upon mutual synchronization among single cells and requires both synaptic communication and gap junctions. Changes in phase-synchronization between individual cells have consequences on the amplitude of the SCN's electrical activity rhythm, and these changes play a major role in the ability to adapt to seasonal changes. Both aging and sleep deprivation negatively affect the circadian amplitude of the SCN, whereas behavioral activity (i.e., exercise) has a positive effect on amplitude. Given that the amplitude of the SCN's electrical activity rhythm is essential for achieving robust rhythmicity in physiology and behavior, the mechanisms that underlie neuronal synchronization warrant further study. A growing body of evidence suggests that the functional integrity of the SCN contributes to health, well-being, cognitive performance, and alertness; in contrast, deterioration of the 24-h rhythm is a risk factor for neurodegenerative disease, cancer, depression, and sleep disorders. PMID:26097465

  10. Priming in Systemic Plant Immunity

    SciTech Connect

    Jung, Ho Won; Tschaplinski, Timothy J; Wang, Lin; Glazebrook, Jane; Greenberg, Jean T.

    2009-01-01

    Upon local infection, plants possess inducible systemic defense responses against their natural enemies. Bacterial infection results in the accumulation to high levels of the mobile metabolite C9-dicarboxylic acid azelaic acid in the vascular sap of Arabidopsis. Azelaic acid confers local and systemic resistance against Pseudomonas syringae. The compound primes plants to strongly accumulate salicylic acid (SA), a known defense signal, upon infection. Mutation of a gene induced by azelaic acid (AZI1) results in the specific loss in plants of systemic immunity triggered by pathogen or azelaic acid and of the priming of SA induction. AZI1, a predicted secreted protein, is also important for generating vascular sap that confers disease resistance. Thus, azelaic acid and AZI1 comprise novel components of plant systemic immunity involved in priming defenses.

  11. COKEMASTER: Coke plant management system

    SciTech Connect

    Johanning, J.; Reinke, M.

    1996-12-31

    To keep coke utilization in ironmaking as competitive as possible, the potential to improve the economics of coke production has to be utilized. As one measure to meet this need of its customers, Krupp Koppers has expanded its existing ECOTROL computer system for battery heating control to a comprehensive Coke Plant Management System. Increased capacity utilization, lower energy consumption, stabilization of plant operation and ease of operation are the main targets.

  12. Fossil power plant systems description

    SciTech Connect

    Not Available

    1984-01-01

    This single-volume, looseleaf text presents the functions and relationships between each major component and its auxiliaries within a system. The text also describes the relationships between systems. All major components are addressed, and system boundaries are defined for a generic fossil power plant.

  13. The Pendulum Clock.

    ERIC Educational Resources Information Center

    Carlson, John E.

    1991-01-01

    The development and function of the pendulum clock is discussed from a historical perspective. Computations for the period of and forces acting on a pendulum are presented. The remarkable workmanship of early clock makers is described. (CW)

  14. A high-speed photonic clock and carrier regenerator

    NASA Technical Reports Server (NTRS)

    Yao, X. S.; Lutes, G.

    1995-01-01

    As data communications rates climb toward 10 Gbits/s, clock recovery and synchronization become more difficult, if not impossible, using conventional electronic circuits. The high-speed photonic clock regenerator described in this article may be more suitable for such use. This photonic regenerator is based on a previously reported photonic oscillator capable of fast acquisition and synchronization. With both electrical and optical clock inputs and outputs, the device is easily interfaced with fiber-optic systems. The recovered electrical clock can be used locally and the optical clock can be used anywhere within a several kilometer radius of the clock/carrier regenerator.

  15. VLBI clock synchronization. [for atomic clock rate

    NASA Technical Reports Server (NTRS)

    Counselman, C. C., III; Shapiro, I. I.; Rogers, A. E. E.; Hinteregger, H. F.; Knight, C. A.; Whitney, A. R.; Clark, T. A.

    1977-01-01

    The potential accuracy of VLBI (very long baseline interferometry) for clock epoch and rate comparisons was demonstrated by results from long- and short-baseline experiments. It was found that atomic clocks at widely separated sites (several thousand kilometers apart) can be synchronized to within several nanoseconds from a few minutes of VLBI observations and to within one nanosecond from several hours of observations.

  16. The countdown continues. Hospitals and healthcare systems are racing the clock to determine the severity of the year-2000 bug infestation.

    PubMed

    Morrissey, J; Hensley, S

    1998-08-10

    As the clock continues to tick toward the new millennium, healthcare systems are racing to determine the severity of the year-2000 bug infestation. One system putting its computers and medical devices to the test so far has found a 20% failure rate. The system also has found that some devices just can't be tested. As one expert said: "This is not a technology problem; it's a management challenge."

  17. Design and performance of clock-recovery GaAs ICs for high-speed optical communication systems

    NASA Astrophysics Data System (ADS)

    Imai, Yuhki; Sano, Eiichi; Nakamura, Makoto; Ishihara, Noboru; Kikuchi, Hiroyuki; Ono, Takashi

    1993-05-01

    Design and performance of clock-recovery GaAs ICs are presented. Four kinds of ICs were developed: a limiting amplifier, a tuning amplifier, a rectifier, and a differentiator. The cascaded limiting amplifier together with a tuning amplifier achieved a 58-dB gain and a 10-degree phase deviation with 20-dB input dynamic range at 10 GHz. A clock-recovery circuit successfully extracts a low-jitter 10-GHz clock signal of 1-dBm constant power from 10-Gb/s NRZ pseudorandom bit streams using a pulse pattern generator.

  18. Circadian clock proteins and immunity.

    PubMed

    Curtis, Anne M; Bellet, Marina M; Sassone-Corsi, Paolo; O'Neill, Luke A J

    2014-02-20

    Immune parameters change with time of day and disruption of circadian rhythms has been linked to inflammatory pathologies. A circadian-clock-controlled immune system might allow an organism to anticipate daily changes in activity and feeding and the associated risk of infection or tissue damage to the host. Responses to bacteria have been shown to vary depending on time of infection, with mice being more at risk of sepsis when challenged ahead of their activity phase. Studies highlight the extent to which the molecular clock, most notably the core clock proteins BMAL1, CLOCK, and REV-ERBα, control fundamental aspects of the immune response. Examples include the BMAL1:CLOCK heterodimer regulating toll-like receptor 9 (TLR9) expression and repressing expression of the inflammatory monocyte chemokine ligand (CCL2) as well as REV-ERBα suppressing the induction of interleukin-6. Understanding the daily rhythm of the immune system could have implications for vaccinations and how we manage infectious and inflammatory diseases.

  19. Experimental validation of clock synchronization algorithms

    NASA Technical Reports Server (NTRS)

    Palumbo, Daniel L.; Graham, R. Lynn

    1992-01-01

    The objective of this work is to validate mathematically derived clock synchronization theories and their associated algorithms through experiment. Two theories are considered, the Interactive Convergence Clock Synchronization Algorithm and the Midpoint Algorithm. Special clock circuitry was designed and built so that several operating conditions and failure modes (including malicious failures) could be tested. Both theories are shown to predict conservative upper bounds (i.e., measured values of clock skew were always less than the theory prediction). Insight gained during experimentation led to alternative derivations of the theories. These new theories accurately predict the behavior of the clock system. It is found that a 100 percent penalty is paid to tolerate worst-case failures. It is also shown that under optimal conditions (with minimum error and no failures) the clock skew can be as much as three clock ticks. Clock skew grows to six clock ticks when failures are present. Finally, it is concluded that one cannot rely solely on test procedures or theoretical analysis to predict worst-case conditions.

  20. Song I-Yeong's Armillary Clock

    NASA Astrophysics Data System (ADS)

    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.

  1. Network Quantitative Trait Loci Mapping of Circadian Clock Outputs Identifies Metabolic Pathway-to-Clock Linkages in Arabidopsis[C][W

    PubMed Central

    Kerwin, Rachel E.; Jimenez-Gomez, Jose M.; Fulop, Daniel; Harmer, Stacey L.; Maloof, Julin N.; Kliebenstein, Daniel J.

    2011-01-01

    Modern systems biology permits the study of complex networks, such as circadian clocks, and the use of complex methodologies, such as quantitative genetics. However, it is difficult to combine these approaches due to factorial expansion in experiments when networks are examined using complex methods. We developed a genomic quantitative genetic approach to overcome this problem, allowing us to examine the function(s) of the plant circadian clock in different populations derived from natural accessions. Using existing microarray data, we defined 24 circadian time phase groups (i.e., groups of genes with peak phases of expression at particular times of day). These groups were used to examine natural variation in circadian clock function using existing single time point microarray experiments from a recombinant inbred line population. We identified naturally variable loci that altered circadian clock outputs and linked these circadian quantitative trait loci to preexisting metabolomics quantitative trait loci, thereby identifying possible links between clock function and metabolism. Using single-gene isogenic lines, we found that circadian clock output was altered by natural variation in Arabidopsis thaliana secondary metabolism. Specifically, genetic manipulation of a secondary metabolic enzyme led to altered free-running rhythms. This represents a unique and valuable approach to the study of complex networks using quantitative genetics. PMID:21343415

  2. Circadian clocks and cell division

    PubMed Central

    2010-01-01

    Evolution has selected a system of two intertwined cell cycles: the cell division cycle (CDC) and the daily (circadian) biological clock. The circadian clock keeps track of solar time and programs biological processes to occur at environmentally appropriate times. One of these processes is the CDC, which is often gated by the circadian clock. The intermeshing of these two cell cycles is probably responsible for the observation that disruption of the circadian system enhances susceptibility to some kinds of cancer. The core mechanism underlying the circadian clockwork has been thought to be a transcription and translation feedback loop (TTFL), but recent evidence from studies with cyanobacteria, synthetic oscillators and immortalized cell lines suggests that the core circadian pacemaking mechanism that gates cell division in mammalian cells could be a post-translational oscillator (PTO). PMID:20890114

  3. Gigabit Ethernet Asynchronous Clock Compensation FIFO

    NASA Technical Reports Server (NTRS)

    Duhachek, Jeff

    2012-01-01

    Clock compensation for Gigabit Ethernet is necessary because the clock recovered from the 1.25 Gb/s serial data stream has the potential to be 200 ppm slower or faster than the system clock. The serial data is converted to 10-bit parallel data at a 125 MHz rate on a clock recovered from the serial data stream. This recovered data needs to be processed by a system clock that is also running at a nominal rate of 125 MHz, but not synchronous to the recovered clock. To cross clock domains, an asynchronous FIFO (first-in-first-out) is used, with the write pointer (wprt) in the recovered clock domain and the read pointer (rptr) in the system clock domain. Because the clocks are generated from separate sources, there is potential for FIFO overflow or underflow. Clock compensation in Gigabit Ethernet is possible by taking advantage of the protocol data stream features. There are two distinct data streams that occur in Gigabit Ethernet where identical data is transmitted for a period of time. The first is configuration, which happens during auto-negotiation. The second is idle, which occurs at the end of auto-negotiation and between every packet. The identical data in the FIFO can be repeated by decrementing the read pointer, thus compensating for a FIFO that is draining too fast. The identical data in the FIFO can also be skipped by incrementing the read pointer, which compensates for a FIFO draining too slowly. The unique and novel features of this FIFO are that it works in both the idle stream and the configuration streams. The increment or decrement of the read pointer is different in the idle and compensation streams to preserve disparity. Another unique feature is that the read pointer to write pointer difference range changes between compensation and idle to minimize FIFO latency during packet transmission.

  4. Measurement of time by quantum clocks

    NASA Astrophysics Data System (ADS)

    Peres, Asher

    1980-07-01

    A clock is a dynamical system which passes through a succession of states at constant time intervals. If coupled to another system, it can measure the duration of a physical process and even keep a permanent record of it, such as in a time-of-flight experiment or in observing the lifetime of an unstable atom. A clock can also be used to control the duration of a process, e.g., the precession of a spin in a magnetic field which is turned on and off at prescribed times. This article shows how to construct time-independent Hamiltonians describing these possible uses of a quantum clock. As expected, a good time resolution entails a large energy exchange between the clock and the other system, thereby modifying the evolution of the latter. This evolution may even be halted by using a clock which is too precise (this is the quantum analog of Zeno's paradox).

  5. Rigorously modeling self-stabilizing fault-tolerant circuits: An ultra-robust clocking scheme for systems-on-chip☆

    PubMed Central

    Dolev, Danny; Függer, Matthias; Posch, Markus; Schmid, Ulrich; Steininger, Andreas; Lenzen, Christoph

    2014-01-01

    We present the first implementation of a distributed clock generation scheme for Systems-on-Chip that recovers from an unbounded number of arbitrary transient faults despite a large number of arbitrary permanent faults. We devise self-stabilizing hardware building blocks and a hybrid synchronous/asynchronous state machine enabling metastability-free transitions of the algorithm's states. We provide a comprehensive modeling approach that permits to prove, given correctness of the constructed low-level building blocks, the high-level properties of the synchronization algorithm (which have been established in a more abstract model). We believe this approach to be of interest in its own right, since this is the first technique permitting to mathematically verify, at manageable complexity, high-level properties of a fault-prone system in terms of its very basic components. We evaluate a prototype implementation, which has been designed in VHDL, using the Petrify tool in conjunction with some extensions, and synthesized for an Altera Cyclone FPGA. PMID:26516290

  6. MCFC power plant system verification

    SciTech Connect

    Farooque, M.; Bernard, R.; Doyon, J.; Paetsch, L.; Patel, P.; Skok, A.; Yuh, C.

    1993-11-01

    In pursuit of commercialization, efforts are underway to: (1) advance the technology base by enhancing performance and demonstrating endurance, (2) scale up stack to the full area and height, (3) acquire stack manufacturing capability and experience, (4) establish capability as well as gain experience for power plant system testing of the full-height carbonate fuel cell stack, (5) and define power plant design and develop critical subsystem components. All the major project objectives have already been attained. Over the last year, significant progress has been achieved in establishing the full-height stack design, gaining stack manufacturing and system integrated testing experience, and verifying the major equipment design in power plant system tests. In this paper, recent progresses on stack scaleup, demonstration testing, BOP verification, and stack endurance are presented.

  7. The Ozone-Iodine-Chlorate Clock Reaction

    PubMed Central

    Sant'Anna, Rafaela T. P.; Monteiro, Emily V.; Pereira, Juliano R. T.; Faria, Roberto B.

    2013-01-01

    This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions. PMID:24386257

  8. The ozone-iodine-chlorate clock reaction.

    PubMed

    Sant'Anna, Rafaela T P; Monteiro, Emily V; Pereira, Juliano R T; Faria, Roberto B

    2013-01-01

    This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions. PMID:24386257

  9. The ozone-iodine-chlorate clock reaction.

    PubMed

    Sant'Anna, Rafaela T P; Monteiro, Emily V; Pereira, Juliano R T; Faria, Roberto B

    2013-01-01

    This work presents a new clock reaction based on ozone, iodine, and chlorate that differs from the known chlorate-iodine clock reaction because it does not require UV light. The induction period for this new clock reaction depends inversely on the initial concentrations of ozone, chlorate, and perchloric acid but is independent of the initial iodine concentration. The proposed mechanism considers the reaction of ozone and iodide to form HOI, which is a key species for producing non-linear autocatalytic behavior. The novelty of this system lies in the presence of ozone, whose participation has never been observed in complex systems such as clock or oscillating reactions. Thus, the autocatalysis demonstrated in this new clock reaction should open the possibility for a new family of oscillating reactions.

  10. Circadian clock genes universally control key agricultural traits

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  11. Deciphering the Duality of Clock and Growth Metabolism in a Cell Autonomous System Using NMR Profiling of the Secretome.

    PubMed

    Sengupta, Arjun; Krishnaiah, Saikumari Y; Rhoades, Seth; Growe, Jacqueline; Slaff, Barry; Venkataraman, Anand; Olarerin-George, Anthony O; Van Dang, Chi; Hogenesch, John B; Weljie, Aalim M

    2016-01-01

    Oscillations in circadian metabolism are crucial to the well being of organism. Our understanding of metabolic rhythms has been greatly enhanced by recent advances in high-throughput systems biology experimental techniques and data analysis. In an in vitro setting, metabolite rhythms can be measured by time-dependent sampling over an experimental period spanning one or more days at sufficent resolution to elucidate rhythms. We hypothesized that cellular metabolic effects over such a time course would be influenced by both oscillatory and circadian-independent cell metabolic effects. Here we use nuclear magnetic resonance (NMR) spectroscopy-based metabolic profiling of mammalian cell culture media of synchronized U2 OS cells containing an intact transcriptional clock. The experiment was conducted over 48 h, typical for circadian biology studies, and samples collected at 2 h resolution to unravel such non-oscillatory effects. Our data suggest specific metabolic activities exist that change continuously over time in this settting and we demonstrate that the non-oscillatory effects are generally monotonic and possible to model with multivariate regression. Deconvolution of such non-circadian persistent changes are of paramount importance to consider while studying circadian metabolic oscillations. PMID:27472375

  12. Deciphering the Duality of Clock and Growth Metabolism in a Cell Autonomous System Using NMR Profiling of the Secretome

    PubMed Central

    Sengupta, Arjun; Krishnaiah, Saikumari Y.; Rhoades, Seth; Growe, Jacqueline; Slaff, Barry; Venkataraman, Anand; Olarerin-George, Anthony O.; Van Dang, Chi; Hogenesch, John B.; Weljie, Aalim M.

    2016-01-01

    Oscillations in circadian metabolism are crucial to the well being of organism. Our understanding of metabolic rhythms has been greatly enhanced by recent advances in high-throughput systems biology experimental techniques and data analysis. In an in vitro setting, metabolite rhythms can be measured by time-dependent sampling over an experimental period spanning one or more days at sufficent resolution to elucidate rhythms. We hypothesized that cellular metabolic effects over such a time course would be influenced by both oscillatory and circadian-independent cell metabolic effects. Here we use nuclear magnetic resonance (NMR) spectroscopy-based metabolic profiling of mammalian cell culture media of synchronized U2 OS cells containing an intact transcriptional clock. The experiment was conducted over 48 h, typical for circadian biology studies, and samples collected at 2 h resolution to unravel such non-oscillatory effects. Our data suggest specific metabolic activities exist that change continuously over time in this settting and we demonstrate that the non-oscillatory effects are generally monotonic and possible to model with multivariate regression. Deconvolution of such non-circadian persistent changes are of paramount importance to consider while studying circadian metabolic oscillations. PMID:27472375

  13. Design and Evaluation of a Clock Multiplexing Circuit for the SSRL Booster Accelerator Timing System - Oral Presentation

    SciTech Connect

    Araya, Million

    2015-08-25

    SPEAR3 is a 234 m circular storage ring at SLAC’s synchrotron radiation facility (SSRL) in which a 3 GeV electron beam is stored for user access. Typically the electron beam decays with a time constant of approximately 10hr due to electron lose. In order to replenish the lost electrons, a booster synchrotron is used to accelerate fresh electrons up to 3GeV for injection into SPEAR3. In order to maintain a constant electron beam current of 500mA, the injection process occurs at 5 minute intervals. At these times the booster synchrotron accelerates electrons for injection at a 10Hz rate. A 10Hz 'injection ready' clock pulse train is generated when the booster synchrotron is operating. Between injection intervalswhere the booster is not running and hence the 10 Hz ‘injection ready’ signal is not present-a 10Hz clock is derived from the power line supplied by Pacific Gas and Electric (PG&E) to keep track of the injection timing. For this project I constructed a multiplexing circuit to 'switch' between the booster synchrotron 'injection ready' clock signal and PG&E based clock signal. The circuit uses digital IC components and is capable of making glitch-free transitions between the two clocks. This report details construction of a prototype multiplexing circuit including test results and suggests improvement opportunities for the final design.

  14. Design and Evaluation of a Clock Multiplexing Circuit for the SSRL Booster Accelerator Timing System - Final Paper

    SciTech Connect

    Araya, Million

    2015-08-21

    SPEAR3 is a 234 m circular storage ring at SLAC’s synchrotron radiation facility (SSRL) in which a 3 GeV electron beam is stored for user access. Typically the electron beam decays with a time constant of approximately 10hr due to electron lose. In order to replenish the lost electrons, a booster synchrotron is used to accelerate fresh electrons up to 3GeV for injection into SPEAR3. In order to maintain a constant electron beam current of 500mA, the injection process occurs at 5 minute intervals. At these times the booster synchrotron accelerates electrons for injection at a 10Hz rate. A 10Hz 'injection ready' clock pulse train is generated when the booster synchrotron is operating. Between injection intervals-where the booster is not running and hence the 10 Hz ‘injection ready’ signal is not present-a 10Hz clock is derived from the power line supplied by Pacific Gas and Electric (PG&E) to keep track of the injection timing. For this project I constructed a multiplexing circuit to 'switch' between the booster synchrotron 'injection ready' clock signal and PG&E based clock signal. The circuit uses digital IC components and is capable of making glitch-free transitions between the two clocks. This report details construction of a prototype multiplexing circuit including test results and suggests improvement opportunities for the final design.

  15. Sweet immunity in the plant circadian regulatory network.

    PubMed

    Bolouri Moghaddam, Mohammad Reza; Van den Ende, Wim

    2013-04-01

    All organisms have an internal timing mechanism, termed the circadian clock, to anticipate the light/dark cycle. The clock, with an oscillating rhythm that approximates 24h, is a rather robust system persisting to a great extent in continuous light and dark. It is widely accepted that plant growth and development are regulated by the clock, hormones, and sugar signals. On the one hand, sugar signalling can affect circadian rhythms by altering the expression pattern of clock-regulated genes. More in particular, the clock seems to be particularly sensitive to sucrose-mediated signalling which is also associated with immunity and abiotic stress responses. Also, hormonal interaction with the clock can contribute to appropriate plant immune responses. Recent data show a prominent role for the clock in growth and stress responses. On the other hand, the clock seems to be essential in controlling the gene expression and activity of an array of carbohydrate-metabolizing enzymes, suggesting a complex reciprocal relationship between the clock and metabolic signalling processes. Therefore, the clock fulfils a crucial role at the heart of cellular networks. The players involved in the complex plant circadian network and their possible contribution to the novel 'sweet immunity' concept are discussed.

  16. Double-modulation CPT cesium compact clock

    NASA Astrophysics Data System (ADS)

    Yun, Peter; Mejri, Sinda; Tricot, Francois; Abdel Hafiz, Moustafa; Boudot, Rodolphe; de Clercq, Emeric; Guérandel, Stéphane

    2016-06-01

    Double-modulation coherent population trapping (CPT) is based on a synchronous modulation of Raman phase and laser polarization, which allows the atomic population to accumulate in a common dark state. The high contrast signal obtained on the clock transition with a relative compact and robust laser system is interesting as basis of a high performance microwave clock. Here we study the parameters of a double-modulation CPT Cs clock working in cw mode. The optimal polarization modulation frequency and cell temperature for maximum contrast of clock transition are investigated. The parameters of the detection are also studied. With the optimal parameters, we observe a CPT signal with contrast of 10% and linewidth of 492 Hz, which is well suited for implementing a cw atomic clock.

  17. The performance of primary Cs beam clocks using quadrupole and hexapole deflection systems. Consequences for time keeping

    NASA Technical Reports Server (NTRS)

    Becker, G.

    1979-01-01

    Since 1978 the time-and-frequency standard CS1 of the Physikalisch-Technische Bundesanstalt (PTB) has operated continuously as a 'primary clock'. Its uncertainty (7.1 to the negative 15th power) is considerably smaller than that of the other existing primary standards. The CS1 is equipped with a combination of quadrupole and hexapole magnets and uses a longitudinal C-field. Consequences of utilizing primary clocks of this quality for the generation of the International Atomic Time Scale TAI are discussed.

  18. [Molecular mechanisms of circadian clock functioning].

    PubMed

    Karbovskyĭ, L L; Minchenko, D O; Garmash, Ia A; Minchenko, O G

    2011-01-01

    Most physiological processes of all organisms are rhythmic with a period of about 24 h and are generated by an endogenous biological CLOCK present in all cells. However, there is also a central CLOCK--the primary circadian pacemaker which is localized in the suprachiasmatic nuclei of the mammalian hypothalamus. Factors of groups Period (PER1, PER2 and PER3), BMAL (BMAL1 and BMAL2), CRYptochromes (CRY1 and CRY2) as well as some other factors are the components of this circadian CLOCK system. Some of these genes contain E-box sequences and their expression is regulated by a transcription factor complex CLOCK-BMAL1. The enzymes responsible for the post-translational modification of circadian gene products are also the components of circadian CLOCK system. These enzymes define CLOCK's work and determine the duration of circadian biorhythm and functional state of the whole organism. The most important of these enzymes are casein kinase-1epsilon and -1delta. We have analysed data about the interconnection between the circadian CLOCK system, cell cycle, and cancerogenesis as well as about the sensitivity of circadian gene expression to the action of toxic agents and nanomaterials.

  19. Clock genes and cancer.

    PubMed

    Wood, Patricia A; Yang, Xiaoming; Hrushesky, William J M

    2009-12-01

    Period genes ( Per2, Per1) are essential circadian clock genes. They also function as negative growth regulators. Per2 mutant mice show de novo and radiation-induced epithelial hyperplasia, tumors, and an abnormal DNA damage response. Human tumors show Period gene mutations or decreased expression. Other murine clock gene mutations are not associated with a tumor prone phenotype. Shift work and nocturnal light exposure are associated with circadian clock disruption and with increased cancer risk. The mechanisms responsible for the connection between the circadian clock and cancer are not well defined. We propose that circadian disruption per se is not uniformly tumor promoting and the mechanisms for tumor promotion by specific circadian clock disturbances will differ dependent upon the genes and pathways involved. We propose that Period clock gene mutations promote tumorigenesis by unique molecular pathways. Per2 and Per1 modulate beta-catenin and cell proliferation in colon and non-colon cancer cells. Per2 mutation increases intestinal beta-catenin levels and colon polyp formation. Per2 mutation also increases Apc(Min/+)-mediated intestinal and colonic polyp formation. Intestinal tumorigenesis per se may also alter clock function as a result of increased beta-catenin destabilizing PER2 protein. Levels and circadian rhythm of PER2 in Apc(Min/+) mouse intestine are markedly decreased, and selective abnormalities in intestinal clock gene and clock-controlled gene expression are seen. We propose that tumor promotion by loss of PERIOD clock proteins is unique to these clock genes as a result of altered beta-catenin signaling and DNA damage response. PERIOD proteins may offer new targets for cancer prevention and control.

  20. Timing is everything: a collection on how clocks affect resilience in biological systems

    PubMed Central

    Karatsoreos, Ilia N.; McEwen, Bruce S.

    2014-01-01

    Why do some people get sick, and others do not? This basic question, of vulnerability and resilience, is of crucial importance in physical and mental health research. Determining factors that impart resilience, or contribute to vulnerability, could be a turning point in our fundamental understanding of disease. This collection explores current data on the role of two systems that seem indispensible for health: Circadian rhythms, and Sleep. While we have learned a great deal about the mechanisms that control these two biological processes, we are only at the beginning of our understanding of how these systems impact mood, cognition, immune function, and metabolism. The concepts of resilience and vulnerability may be useful in understanding the myriad effects of circadian rhythm and sleep disruption on mental and physical health, and perhaps provide new insights to how we can predict – and protect against – negative outcomes while amplifying positive health effects. PMID:25580235

  1. Intermediate term frequency measurements with the HP computing counter in the USNO clock time system

    NASA Technical Reports Server (NTRS)

    Winkler, G. M. R.

    1972-01-01

    High precision frequency measurements with various integration times can be made with conventional counters by using variable gate times. The Hewlett-Packard (HP) computing counter allows such measurements over a wide range of frequencies and measurement times. This instrument can also convert period measurements into frequency by means of its arithmetic capabilities: The program library contains programs to facilitate frequency stability measurements in the most direct and convenient way. This method was used as the basis for all time scale computations, until requirements for highest resolution justified the development of an automatic data acquisition system. The phase measurements are now being made with the HP computing counter (with time interval plug-in unit) under program control from the HP System Programmer.

  2. A microbial clock provides an accurate estimate of the postmortem interval in a mouse model system

    PubMed Central

    Metcalf, Jessica L; Wegener Parfrey, Laura; Gonzalez, Antonio; Lauber, Christian L; Knights, Dan; Ackermann, Gail; Humphrey, Gregory C; Gebert, Matthew J; Van Treuren, Will; Berg-Lyons, Donna; Keepers, Kyle; Guo, Yan; Bullard, James; Fierer, Noah; Carter, David O; Knight, Rob

    2013-01-01

    Establishing the time since death is critical in every death investigation, yet existing techniques are susceptible to a range of errors and biases. For example, forensic entomology is widely used to assess the postmortem interval (PMI), but errors can range from days to months. Microbes may provide a novel method for estimating PMI that avoids many of these limitations. Here we show that postmortem microbial community changes are dramatic, measurable, and repeatable in a mouse model system, allowing PMI to be estimated within approximately 3 days over 48 days. Our results provide a detailed understanding of bacterial and microbial eukaryotic ecology within a decomposing corpse system and suggest that microbial community data can be developed into a forensic tool for estimating PMI. DOI: http://dx.doi.org/10.7554/eLife.01104.001 PMID:24137541

  3. LED Systems Target Plant Growth

    NASA Technical Reports Server (NTRS)

    2010-01-01

    To help develop technologies for growing edible biomass (food crops) in space, Kennedy Space Center partnered with Orbital Technologies Corporation (ORBITEC), of Madison, Wisconsin, through the Small Business Innovation Research (SBIR) program. One result of this research was the High Efficiency Lighting with Integrated Adaptive Control (HELIAC) system, components of which have been incorporated into a variety of agricultural greenhouse and consumer aquarium lighting features. The new lighting systems can be adapted to a specific plant species during a specific growth stage, allowing maximum efficiency in light absorption by all available photosynthetic tissues.

  4. Biological Clocks & Circadian Rhythms

    ERIC Educational Resources Information Center

    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…

  5. Egyptian "Star Clocks"

    NASA Astrophysics Data System (ADS)

    Symons, Sarah

    Diagonal, transit, and Ramesside star clocks are tables of astronomical information occasionally found in ancient Egyptian temples, tombs, and papyri. The tables represent the motions of selected stars (decans and hour stars) throughout the Egyptian civil year. Analysis of star clocks leads to greater understanding of ancient Egyptian constellations, ritual astronomical activities, observational practices, and pharaonic chronology.

  6. Cesium clocks keep the world on time

    SciTech Connect

    Hellwig, H.

    1985-09-01

    The development of timekeeping systems based on the natural resonance of cesium atoms is reviewed. The design of a typical cesium clock using a frequency lock servo is described. Some common applications of cesium beam frequency and time reference systems are discussed, including Navstar GPS navigation referencing; military satellite communications; and measurements of relative gravitational effects. The possibility of increasing timekeeping accuracies using improved cesium clock designs is evaluated.

  7. Chitosan Effects on Plant Systems.

    PubMed

    Malerba, Massimo; Cerana, Raffaella

    2016-06-23

    Chitosan (CHT) is a natural, safe, and cheap product of chitin deacetylation, widely used by several industries because of its interesting features. The availability of industrial quantities of CHT in the late 1980s enabled it to be tested in agriculture. CHT has been proven to stimulate plant growth, to protect the safety of edible products, and to induce abiotic and biotic stress tolerance in various horticultural commodities. The stimulating effect of different enzyme activities to detoxify reactive oxygen species suggests the involvement of hydrogen peroxide and nitric oxide in CHT signaling. CHT could also interact with chromatin and directly affect gene expression. Recent innovative uses of CHT include synthesis of CHT nanoparticles as a valuable delivery system for fertilizers, herbicides, pesticides, and micronutrients for crop growth promotion by a balanced and sustained nutrition. In addition, CHT nanoparticles can safely deliver genetic material for plant transformation. This review presents an overview on the status of the use of CHT in plant systems. Attention was given to the research that suggested the use of CHT for sustainable crop productivity.

  8. Chitosan Effects on Plant Systems

    PubMed Central

    Malerba, Massimo; Cerana, Raffaella

    2016-01-01

    Chitosan (CHT) is a natural, safe, and cheap product of chitin deacetylation, widely used by several industries because of its interesting features. The availability of industrial quantities of CHT in the late 1980s enabled it to be tested in agriculture. CHT has been proven to stimulate plant growth, to protect the safety of edible products, and to induce abiotic and biotic stress tolerance in various horticultural commodities. The stimulating effect of different enzyme activities to detoxify reactive oxygen species suggests the involvement of hydrogen peroxide and nitric oxide in CHT signaling. CHT could also interact with chromatin and directly affect gene expression. Recent innovative uses of CHT include synthesis of CHT nanoparticles as a valuable delivery system for fertilizers, herbicides, pesticides, and micronutrients for crop growth promotion by a balanced and sustained nutrition. In addition, CHT nanoparticles can safely deliver genetic material for plant transformation. This review presents an overview on the status of the use of CHT in plant systems. Attention was given to the research that suggested the use of CHT for sustainable crop productivity. PMID:27347928

  9. Chitosan Effects on Plant Systems.

    PubMed

    Malerba, Massimo; Cerana, Raffaella

    2016-01-01

    Chitosan (CHT) is a natural, safe, and cheap product of chitin deacetylation, widely used by several industries because of its interesting features. The availability of industrial quantities of CHT in the late 1980s enabled it to be tested in agriculture. CHT has been proven to stimulate plant growth, to protect the safety of edible products, and to induce abiotic and biotic stress tolerance in various horticultural commodities. The stimulating effect of different enzyme activities to detoxify reactive oxygen species suggests the involvement of hydrogen peroxide and nitric oxide in CHT signaling. CHT could also interact with chromatin and directly affect gene expression. Recent innovative uses of CHT include synthesis of CHT nanoparticles as a valuable delivery system for fertilizers, herbicides, pesticides, and micronutrients for crop growth promotion by a balanced and sustained nutrition. In addition, CHT nanoparticles can safely deliver genetic material for plant transformation. This review presents an overview on the status of the use of CHT in plant systems. Attention was given to the research that suggested the use of CHT for sustainable crop productivity. PMID:27347928

  10. The LASSO experiment. [clock synchronization

    NASA Technical Reports Server (NTRS)

    Serene, B.

    1979-01-01

    An international coordinated experimental assessment of a system which promises to provide a synchronization of clocks bound to time and frequency standard laboratories, with an accuracy of one nanosecond using existing or near ground-based laser stations via a geostationary satellite (SIRIO-2) is detailed. The system performance and the technical details concerning the on-board equiment, the ground segment, and the operational configuration are discussed. Finally, the future prospects of the LASSO experiment and possible implementations are examined together.

  11. A low cost concept for data acquisition systems applied to decentralized renewable energy plants.

    PubMed

    Jucá, Sandro C S; Carvalho, Paulo C M; Brito, Fábio T

    2011-01-01

    The present paper describes experiences of the use of monitoring and data acquisition systems (DAS) and proposes a new concept of a low cost DAS applied to decentralized renewable energy (RE) plants with an USB interface. The use of such systems contributes to disseminate these plants, recognizing in real time local energy resources, monitoring energy conversion efficiency and sending information concerning failures. These aspects are important, mainly for developing countries, where decentralized power plants based on renewable sources are in some cases the best option for supplying electricity to rural areas. Nevertheless, the cost of commercial DAS is still a barrier for a greater dissemination of such systems in developing countries. The proposed USB based DAS presents a new dual clock operation philosophy, in which the acquisition system contains two clock sources for parallel information processing from different communication protocols. To ensure the low cost of the DAS and to promote the dissemination of this technology in developing countries, the proposed data acquisition firmware and the software for USB microcontrollers programming is a free and open source software, executable in the Linux and Windows® operating systems.

  12. A Low Cost Concept for Data Acquisition Systems Applied to Decentralized Renewable Energy Plants

    PubMed Central

    Jucá, Sandro C. S.; Carvalho, Paulo C. M.; Brito, Fábio T.

    2011-01-01

    The present paper describes experiences of the use of monitoring and data acquisition systems (DAS) and proposes a new concept of a low cost DAS applied to decentralized renewable energy (RE) plants with an USB interface. The use of such systems contributes to disseminate these plants, recognizing in real time local energy resources, monitoring energy conversion efficiency and sending information concerning failures. These aspects are important, mainly for developing countries, where decentralized power plants based on renewable sources are in some cases the best option for supplying electricity to rural areas. Nevertheless, the cost of commercial DAS is still a barrier for a greater dissemination of such systems in developing countries. The proposed USB based DAS presents a new dual clock operation philosophy, in which the acquisition system contains two clock sources for parallel information processing from different communication protocols. To ensure the low cost of the DAS and to promote the dissemination of this technology in developing countries, the proposed data acquisition firmware and the software for USB microcontrollers programming is a free and open source software, executable in the Linux and Windows® operating systems. PMID:22346600

  13. A low cost concept for data acquisition systems applied to decentralized renewable energy plants.

    PubMed

    Jucá, Sandro C S; Carvalho, Paulo C M; Brito, Fábio T

    2011-01-01

    The present paper describes experiences of the use of monitoring and data acquisition systems (DAS) and proposes a new concept of a low cost DAS applied to decentralized renewable energy (RE) plants with an USB interface. The use of such systems contributes to disseminate these plants, recognizing in real time local energy resources, monitoring energy conversion efficiency and sending information concerning failures. These aspects are important, mainly for developing countries, where decentralized power plants based on renewable sources are in some cases the best option for supplying electricity to rural areas. Nevertheless, the cost of commercial DAS is still a barrier for a greater dissemination of such systems in developing countries. The proposed USB based DAS presents a new dual clock operation philosophy, in which the acquisition system contains two clock sources for parallel information processing from different communication protocols. To ensure the low cost of the DAS and to promote the dissemination of this technology in developing countries, the proposed data acquisition firmware and the software for USB microcontrollers programming is a free and open source software, executable in the Linux and Windows® operating systems. PMID:22346600

  14. GIGANTEA acts in blue light signaling and has biochemically separable roles in circadian clock and flowering time regulation.

    PubMed

    Martin-Tryon, Ellen L; Kreps, Joel A; Harmer, Stacey L

    2007-01-01

    Circadian clocks are widespread in nature. In higher plants, they confer a selective advantage, providing information regarding not only time of day but also time of year. Forward genetic screens in Arabidopsis (Arabidopsis thaliana) have led to the identification of many clock components, but the functions of most of these genes remain obscure. To identify both new constituents of the circadian clock and new alleles of known clock-associated genes, we performed a mutant screen. Using a clock-regulated luciferase reporter, we isolated new alleles of ZEITLUPE, LATE ELONGATED HYPOCOTYL, and GIGANTEA (GI). GI has previously been reported to function in red light signaling, central clock function, and flowering time regulation. Characterization of this and other GI alleles has helped us to further define GI function in the circadian system. We found that GI acts in photomorphogenic and circadian blue light signaling pathways and is differentially required for clock function in constant red versus blue light. Gene expression and epistasis analyses show that TIMING OF CHLOROPHYLL A/B BINDING PROTEIN1 (TOC1) expression is not solely dependent upon GI and that GI expression is only indirectly affected by TOC1, suggesting that GI acts both in series with and in parallel to TOC1 within the central circadian oscillator. Finally, we found that the GI-dependent promotion of CONSTANS expression and flowering is intact in a gi mutant with altered circadian regulation. Thus GI function in the regulation of a clock output can be biochemically separated from its role within the circadian clock.

  15. Controlling the Cyanobacterial Clock by Synthetically Rewiring Metabolism

    PubMed Central

    Pattanayak, Gopal K.; Lambert, Guillaume; Bernat, Kevin; Rust, Michael J.

    2015-01-01

    Summary Circadian clocks are oscillatory systems and allow organisms to anticipate rhythmic changes in the environment. Several studies have shown that circadian clocks are connected to metabolism, but it is not generally clear whether metabolic signaling is one voice among many that influence the clock, or whether metabolic cycling is the major clock synchronizer. To address this question in cyanobacteria, we used a synthetic biology approach to make normally autotrophic cells capable of growth on exogenous sugar. This allowed us to manipulate metabolism independently from the light and dark. We found that feeding sugar to cultures blocked the clock-resetting effect of a dark pulse. Further, in the absence of light, the clock efficiently synchronizes to metabolic cycles driven by rhythmic feeding. We conclude that metabolic activity, independent of its source, is the primary clock driver in cyanobacteria. PMID:26686627

  16. Biological clocks and the practice of psychiatry

    PubMed Central

    Schulz, Pierre

    2007-01-01

    Endogenous biological clocks enable living species to acquire some independence in relation to time. They improve the efficiency of biological systems, by allowing them to anticipate future constraints on major physyological systems and cell energy metabolism. The temporal organization of a giwen biological function can be impaired in its coordination with astronomical time or with other biological function. There are also external conditions that influence biological clocks. This temporal organization is complex, and it is possible that a series of psychiatric disorders and syndromes involve primary or secondary changes in biological clocks: seasonal and other mood disorders, premenstrual syndromes, social jet lag, free-running rhythms, and several sleep disorders are among them. In this review, we describe the main concepts relevant to chronobiology and explore the relevance of knowledge about biological clocks to the clinical practice of psychiatry PMID:17969862

  17. Clock jitter generator with picoseconds resolution

    NASA Astrophysics Data System (ADS)

    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.

  18. The Neurospora circadian clock: simple or complex?

    PubMed Central

    Bell-Pedersen, D; Crosthwaite, S K; Lakin-Thomas, P L; Merrow, M; Økland, M

    2001-01-01

    The fungus Neurospora crassa is being used by a number of research groups as a model organism to investigate circadian (daily) rhythmicity. In this review we concentrate on recent work relating to the complexity of the circadian system in this organism. We discuss: the advantages of Neurospora as a model system for clock studies; the frequency (frq), white collar-1 and white collar-2 genes and their roles in rhythmicity; the phenomenon of rhythmicity in null frq mutants and its implications for clock mechanisms; the study of output pathways using clock-controlled genes; other rhythms in fungi; mathematical modelling of the Neurospora circadian system; and the application of new technologies to the study of Neurospora rhythmicity. We conclude that there may be many gene products involved in the clock mechanism, there may be multiple interacting oscillators comprising the clock mechanism, there may be feedback from output pathways onto the oscillator(s) and from the oscillator(s) onto input pathways, and there may be several independent clocks coexisting in one organism. Thus even a relatively simple lower eukaryote can be used to address questions about a complex, networked circadian system. PMID:11710976

  19. Optical clocks and relativity.

    PubMed

    Chou, C W; Hume, D B; Rosenband, T; Wineland, D J

    2010-09-24

    Observers in relative motion or at different gravitational potentials measure disparate clock rates. These predictions of relativity have previously been observed with atomic clocks at high velocities and with large changes in elevation. We observed time dilation from relative speeds of less than 10 meters per second by comparing two optical atomic clocks connected by a 75-meter length of optical fiber. We can now also detect time dilation due to a change in height near Earth's surface of less than 1 meter. This technique may be extended to the field of geodesy, with applications in geophysics and hydrology as well as in space-based tests of fundamental physics.

  20. Crosstalking between the "gut-brain" hormone ghrelin and the circadian system in the goldfish. Effects on clock gene expression and food anticipatory activity.

    PubMed

    Nisembaum, Laura G; de Pedro, Nuria; Delgado, María J; Isorna, Esther

    2014-09-01

    Ghrelin is a potent orexigenic signal mainly synthesized in the stomach and foregut of vertebrates. Recent studies in rodents point out that ghrelin could also act as an input for the circadian system and/or as an output of peripheral food-entrainable oscillators, being involved in the food anticipatory activity (FAA). In this study we pursue the possible interaction of ghrelin with the circadian system in a teleost, the goldfish (Carassius auratus). First, we analyzed if ghrelin is able to modulate the core clock functioning by regulating clock gene expression in fish under a light/dark cycle 12L:12D and fed at 10 am. As expected the acute intraperitoneal (IP) injection of goldfish ghrelin (gGRL[1-19], 44 pmol/g bw) induced the expression of hypothalamic orexin. Moreover, ghrelin also induced (∼ 2-fold) some Per clock genes in hypothalamus and liver. This effect was partially counteracted in liver by the ghrelin antagonist ([D-Lys(3)]-GHRP-6, 100 pmol/g bw). Second, we investigated if ghrelin is involved in daily FAA rhythms. With this aim locomotor activity was studied in response to IP injections (5-10 days) of gGRL[1-19] and [D-Lys(3)]-GHRP-6 at the doses above indicated. Ghrelin and saline injected fish showed similar 24h activity patterns. However, ghrelin antagonist treatment abolished the FAA in schedule fed fish under 24h light, suggesting the involvement of the endogenous ghrelin system in this pre-feeding activity. Altogether these results suggest that ghrelin could be acting as an input for the entrainment of the food-entrainable oscillators in the circadian organization of goldfish.

  1. A tunable artificial circadian clock in clock-defective mice

    PubMed Central

    D'Alessandro, Matthew; Beesley, Stephen; Kim, Jae Kyoung; Chen, Rongmin; Abich, Estela; Cheng, Wayne; Yi, Paul; Takahashi, Joseph S.; Lee, Choogon

    2015-01-01

    Self-sustaining oscillations are essential for diverse physiological functions such as the cell cycle, insulin secretion and circadian rhythms. Synthetic oscillators using biochemical feedback circuits have been generated in cell culture. These synthetic systems provide important insight into design principles for biological oscillators, but have limited similarity to physiological pathways. Here we report the generation of an artificial, mammalian circadian clock in vivo, capable of generating robust, tunable circadian rhythms. In mice deficient in Per1 and Per2 genes (thus lacking circadian rhythms), we artificially generate PER2 rhythms and restore circadian sleep/wake cycles with an inducible Per2 transgene. Our artificial clock is tunable as the period and phase of the rhythms can be modulated predictably. This feature, and other design principles of our work, might enhance the study and treatment of circadian dysfunction and broader aspects of physiology involving biological oscillators. PMID:26617050

  2. A tunable artificial circadian clock in clock-defective mice.

    PubMed

    D'Alessandro, Matthew; Beesley, Stephen; Kim, Jae Kyoung; Chen, Rongmin; Abich, Estela; Cheng, Wayne; Yi, Paul; Takahashi, Joseph S; Lee, Choogon

    2015-11-30

    Self-sustaining oscillations are essential for diverse physiological functions such as the cell cycle, insulin secretion and circadian rhythms. Synthetic oscillators using biochemical feedback circuits have been generated in cell culture. These synthetic systems provide important insight into design principles for biological oscillators, but have limited similarity to physiological pathways. Here we report the generation of an artificial, mammalian circadian clock in vivo, capable of generating robust, tunable circadian rhythms. In mice deficient in Per1 and Per2 genes (thus lacking circadian rhythms), we artificially generate PER2 rhythms and restore circadian sleep/wake cycles with an inducible Per2 transgene. Our artificial clock is tunable as the period and phase of the rhythms can be modulated predictably. This feature, and other design principles of our work, might enhance the study and treatment of circadian dysfunction and broader aspects of physiology involving biological oscillators.

  3. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

    Describes a combination of solutions that can be used in the study of kinetics using the iodine clock reaction. The combination slows down degradation of the prepared solutions and can be used successfully for several weeks. (JRH)

  4. Atomic clocks for astrophysical measurements

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.; Mattison, E. M.

    1982-01-01

    It is noted that recently developed atomic hydrogen masers have achieved stability well into the 10 to the -16th domain for averaging time intervals beyond 1000 sec and that further improvements are in prospect. These devices are highly adaptable for space use in very high precision measurements of angle through Very Long Baseline Interferometry (VLBI) and of range and range-rate through Doppler techniques. Space missions that will use these clocks for measuring the sun's gravity field distribution and for testing gravitation and relativity (a project that will include a search for pulsed low-frequency gravitational waves) are discussed. Estimates are made of system performance capability, and the accuracy capability of relativistic measurements is evaluated in terms of the results from the 1976 NASA/SAO spaceborne clock test of the Einstein Equivalence Principle.

  5. Coupling governs entrainment range of circadian clocks

    PubMed Central

    Abraham, Ute; Granada, Adrián E; Westermark, Pål O; Heine, Markus; Kramer, Achim; Herzel, Hanspeter

    2010-01-01

    Circadian clocks are endogenous oscillators driving daily rhythms in physiology and behavior. Synchronization of these timers to environmental light–dark cycles (‘entrainment') is crucial for an organism's fitness. Little is known about which oscillator qualities determine entrainment, i.e., entrainment range, phase and amplitude. In a systematic theoretical and experimental study, we uncovered these qualities for circadian oscillators in the suprachiasmatic nucleus (SCN—the master clock in mammals) and the lung (a peripheral clock): (i) the ratio between stimulus (zeitgeber) strength and oscillator amplitude and (ii) the rigidity of the oscillatory system (relaxation rate upon perturbation) determine entrainment properties. Coupling among oscillators affects both qualities resulting in increased amplitude and rigidity. These principles explain our experimental findings that lung clocks entrain to extreme zeitgeber cycles, whereas SCN clocks do not. We confirmed our theoretical predictions by showing that pharmacological inhibition of coupling in the SCN leads to larger ranges of entrainment. These differences between master and the peripheral clocks suggest that coupling-induced rigidity in the SCN filters environmental noise to create a robust circadian system. PMID:21119632

  6. DIE NEUTRALIS and LATE BLOOMER 1 Contribute to Regulation of the Pea Circadian Clock[W

    PubMed Central

    Liew, Lim Chee; Hecht, Valérie; Laurie, Rebecca E.; Knowles, Claire L.; Vander Schoor, Jacqueline K.; Macknight, Richard C.; Weller, James L.

    2009-01-01

    The DIE NEUTRALIS (DNE) locus in garden pea (Pisum sativum) was previously shown to inhibit flowering under noninductive short-day conditions and to affect a graft-transmissible flowering signal. In this study, we establish that DNE has a role in diurnal and/or circadian regulation of several clock genes, including the pea GIGANTEA (GI) ortholog LATE BLOOMER 1 (LATE1) and orthologs of the Arabidopsis thaliana genes LATE ELONGATED HYPOCOTYL and TIMING OF CHLOROPHYLL A/B BINDING PROTEIN EXPRESSION 1. We also confirm that LATE1 participates in the clock and provide evidence that DNE is the ortholog of Arabidopsis EARLY FLOWERING4 (ELF4). Circadian rhythms of clock gene expression in wild-type plants under constant light were weaker in pea than in Arabidopsis, and a number of differences were also seen in the effects of both DNE/ELF4 and LATE1/GI on clock gene expression. Grafting studies suggest that DNE controls flowering at least in part through a LATE1-dependent mobile stimulus, and dne mutants show elevated expression of a FLOWERING LOCUS T homolog under short-day conditions. However, the early flowering of the dne mutant is not associated with altered expression of a previously described CONSTANS-like gene. Collectively, our results characterize the clock system and reveal its importance for photoperiod responsiveness in a model legume. PMID:19843842

  7. Network balance via CRY signalling controls the Arabidopsis circadian clock over ambient temperatures

    PubMed Central

    Gould, Peter D; Ugarte, Nicolas; Domijan, Mirela; Costa, Maria; Foreman, Julia; MacGregor, Dana; Rose, Ken; Griffiths, Jayne; Millar, Andrew J; Finkenstädt, Bärbel; Penfield, Steven; Rand, David A; Halliday, Karen J; Hall, Anthony J W

    2013-01-01

    Circadian clocks exhibit ‘temperature compensation', meaning that they show only small changes in period over a broad temperature range. Several clock genes have been implicated in the temperature-dependent control of period in Arabidopsis. We show that blue light is essential for this, suggesting that the effects of light and temperature interact or converge upon common targets in the circadian clock. Our data demonstrate that two cryptochrome photoreceptors differentially control circadian period and sustain rhythmicity across the physiological temperature range. In order to test the hypothesis that the targets of light regulation are sufficient to mediate temperature compensation, we constructed a temperature-compensated clock model by adding passive temperature effects into only the light-sensitive processes in the model. Remarkably, this model was not only capable of full temperature compensation and consistent with mRNA profiles across a temperature range, but also predicted the temperature-dependent change in the level of LATE ELONGATED HYPOCOTYL, a key clock protein. Our analysis provides a systems-level understanding of period control in the plant circadian oscillator. PMID:23511208

  8. Control of Daily Transcript Oscillations in Drosophila by Light and the Circadian Clock

    PubMed Central

    Boothroyd, Catharine; Claridge-Chang, Adam; Young, Michael W

    2006-01-01

    The transcriptional circuits of circadian clocks control physiological and behavioral rhythms. Light may affect such overt rhythms in two ways: (1) by entraining the clock circuits and (2) via clock-independent molecular pathways. In this study we examine the relationship between autonomous transcript oscillations and light-driven transcript responses. Transcript profiles of wild-type and arrhythmic mutant Drosophila were recorded both in the presence of an environmental photocycle and in constant darkness. Systematic autonomous oscillations in the 12- to 48-h period range were detectable only in wild-type flies and occurred preferentially at the circadian period length. However, an extensive program of light-driven expression was confirmed in arrhythmic mutant flies. Many light-responsive transcripts are preferentially expressed in the compound eyes and the phospholipase C component of phototransduction, NORPA (no receptor potential), is required for their light-dependent regulation. Although there is evidence for the existence of multiple molecular clock circuits in cyanobacteria, protists, plants, and fungi, Drosophila appears to possess only one such system. The sustained photic expression responses identified here are partially coupled to the circadian clock and may reflect a mechanism for flies to modulate functions such as visual sensitivity and synaptic transmission in response to seasonal changes in photoperiod. PMID:16565745

  9. Control of daily transcript oscillations in Drosophila by light and the circadian clock.

    PubMed

    Wijnen, Herman; Naef, Felix; Boothroyd, Catharine; Claridge-Chang, Adam; Young, Michael W

    2006-03-01

    The transcriptional circuits of circadian clocks control physiological and behavioral rhythms. Light may affect such overt rhythms in two ways: (1) by entraining the clock circuits and (2) via clock-independent molecular pathways. In this study we examine the relationship between autonomous transcript oscillations and light-driven transcript responses. Transcript profiles of wild-type and arrhythmic mutant Drosophila were recorded both in the presence of an environmental photocycle and in constant darkness. Systematic autonomous oscillations in the 12- to 48-h period range were detectable only in wild-type flies and occurred preferentially at the circadian period length. However, an extensive program of light-driven expression was confirmed in arrhythmic mutant flies. Many light-responsive transcripts are preferentially expressed in the compound eyes and the phospholipase C component of phototransduction, NORPA (no receptor potential), is required for their light-dependent regulation. Although there is evidence for the existence of multiple molecular clock circuits in cyanobacteria, protists, plants, and fungi, Drosophila appears to possess only one such system. The sustained photic expression responses identified here are partially coupled to the circadian clock and may reflect a mechanism for flies to modulate functions such as visual sensitivity and synaptic transmission in response to seasonal changes in photoperiod.

  10. Conserved expression profiles of circadian clock-related genes in two Lemna species showing long-day and short-day photoperiodic flowering responses.

    PubMed

    Miwa, Kumiko; Serikawa, Masayuki; Suzuki, Sayaka; Kondo, Takao; Oyama, Tokitaka

    2006-05-01

    The Lemna genus is a group of monocotyledonous plants with tiny, floating bodies. Lemna gibba G3 and L. paucicostata 6746 were once intensively analyzed for physiological timing systems of photoperiodic flowering and circadian rhythms since they showed obligatory and sensitive photoperiodic responses of a long-day and a short-day plant, respectively. We attempted to approach the divergence of biological timing systems at the molecular level using these plants. We first employed molecular techniques to study their circadian clock systems. We developed a convenient bioluminescent reporter system to monitor the circadian rhythms of Lemna plants. As in Arabidopsis, the Arabidopsis CCA1 promoter produced circadian expression in Lemna plants, though the phases and the sustainability of bioluminescence rhythms were somewhat diverged between them. Lemna homologs of the Arabidopsis clock-related genes LHY/CCA1, GI, ELF3 and PRRs were then isolated as candidates for clock-related genes in these plants. These genes showed rhythmic expression profiles that were basically similar to those of Arabidopsis under light-dark conditions. Results from co-transfection assays using the bioluminescence reporter and overexpression effectors suggested that the LHY and GI homologs of Lemna can function in the circadian clock system like the counterparts of Arabidopsis. All these results suggested that the frame of the circadian clock appeared to be conserved not only between the two Lemna plants but also between monocotyledons and dicotyledons. However, divergence of gene numbers and expression profiles for LHY/CCA1 homologs were found between Lemna, rice and Arabidopsis, suggesting that some modification of clock-related components occurred through their evolution.

  11. Conserved expression profiles of circadian clock-related genes in two Lemna species showing long-day and short-day photoperiodic flowering responses.

    PubMed

    Miwa, Kumiko; Serikawa, Masayuki; Suzuki, Sayaka; Kondo, Takao; Oyama, Tokitaka

    2006-05-01

    The Lemna genus is a group of monocotyledonous plants with tiny, floating bodies. Lemna gibba G3 and L. paucicostata 6746 were once intensively analyzed for physiological timing systems of photoperiodic flowering and circadian rhythms since they showed obligatory and sensitive photoperiodic responses of a long-day and a short-day plant, respectively. We attempted to approach the divergence of biological timing systems at the molecular level using these plants. We first employed molecular techniques to study their circadian clock systems. We developed a convenient bioluminescent reporter system to monitor the circadian rhythms of Lemna plants. As in Arabidopsis, the Arabidopsis CCA1 promoter produced circadian expression in Lemna plants, though the phases and the sustainability of bioluminescence rhythms were somewhat diverged between them. Lemna homologs of the Arabidopsis clock-related genes LHY/CCA1, GI, ELF3 and PRRs were then isolated as candidates for clock-related genes in these plants. These genes showed rhythmic expression profiles that were basically similar to those of Arabidopsis under light-dark conditions. Results from co-transfection assays using the bioluminescence reporter and overexpression effectors suggested that the LHY and GI homologs of Lemna can function in the circadian clock system like the counterparts of Arabidopsis. All these results suggested that the frame of the circadian clock appeared to be conserved not only between the two Lemna plants but also between monocotyledons and dicotyledons. However, divergence of gene numbers and expression profiles for LHY/CCA1 homologs were found between Lemna, rice and Arabidopsis, suggesting that some modification of clock-related components occurred through their evolution. PMID:16524874

  12. Geopotential measurements with synchronously linked optical lattice clocks

    NASA Astrophysics Data System (ADS)

    Takano, Tetsushi; Takamoto, Masao; Ushijima, Ichiro; Ohmae, Noriaki; Akatsuka, Tomoya; Yamaguchi, Atsushi; Kuroishi, Yuki; Munekane, Hiroshi; Miyahara, Basara; Katori, Hidetoshi

    2016-10-01

    According to Einstein's theory of relativity, the passage of time changes in a gravitational field. On Earth, raising a clock by 1 cm increases its apparent tick rate by 1.1 parts in 1018, allowing chronometric levelling through comparison of optical clocks. Here, we demonstrate such geopotential measurements by determining the height difference of master and slave clocks separated by 15 km with an uncertainty of 5 cm. A subharmonic of the master clock laser is delivered through a telecom fibre to synchronously operate the distant clocks. Clocks operated under such phase coherence reject clock laser noise and facilitate proposals for linking clocks and interferometers. Taken over half a year, 11 measurements determine the fractional frequency difference between the two clocks to be 1,652.9(5.9) × 10-18, consistent with an independent measurement by levelling and gravimetry. Our system demonstrates a building block for an internet of clocks, which may constitute ‘quantum benchmarks’, serving as height references with dynamic responses.

  13. Circadian clock mutation disrupts estrous cyclicity and maintenance of pregnancy.

    PubMed

    Miller, Brooke H; Olson, Susan Losee; Turek, Fred W; Levine, Jon E; Horton, Teresa H; Takahashi, Joseph S

    2004-08-10

    Classic experiments have shown that ovulation and estrous cyclicity are under circadian control and that surgical ablation of the suprachiasmatic nuclei (SCN) results in estrous acyclicity in rats. Here, we characterized reproductive function in the circadian Clock mutant mouse and found that the circadian Clock mutation both disrupts estrous cyclicity and interferes with the maintenance of pregnancy. Clock mutant females have extended, irregular estrous cycles, lack a coordinated luteinizing hormone (LH) surge on the day of proestrus, exhibit increased fetal reabsorption during pregnancy, and have a high rate of full-term pregnancy failure. Clock mutants also show an unexpected decline in progesterone levels at midpregnancy and a shortened duration of pseudopregnancy, suggesting that maternal prolactin release may be abnormal. In a second set of experiments, we interrogated the function of each level of the hypothalamic-pituitary-gonadal (HPG) axis in order to determine how the Clock mutation disrupts estrous cyclicity. We report that Clock mutants fail to show an LH surge following estradiol priming in spite of the fact that hypothalamic levels of gonadotropin-releasing hormone (GnRH), pituitary release of LH, and serum levels of estradiol and progesterone are all normal in Clock/Clock females. These data suggest that Clock mutants lack an appropriate circadian daily-timing signal required to coordinate hypothalamic hormone secretion. Defining the mechanisms by which the Clock mutation disrupts reproductive function offers a model for understanding how circadian genes affect complex physiological systems.

  14. The regulation of central and peripheral circadian clocks in humans.

    PubMed

    Cermakian, N; Boivin, D B

    2009-11-01

    Many circadian rhythms are controlled by the central clock of the suprachiasmatic nucleus of the hypothalamus, as well as clocks located in other brain regions and most peripheral tissues. These central and peripheral clocks are based on clock genes and their protein products. In recent years, the expression of clock genes has started to be investigated in human samples, primarily white blood cells, but also skin, oral mucosa, colon cells, adipose tissue as well as post-mortem brain tissue. The expression of clock genes in those peripheral tissues offers a way to monitor human peripheral clocks and to compare their function and regulation with those of the central clock, which is followed by markers such as melatonin, cortisol and core body temperature. We have recently used such an approach to compare central and peripheral rhythms in subjects under different lighting conditions. In particular, we have monitored the entrainment of the clock of blood cells in subjects undergoing a simulated night shift protocol with bright light treatment, known to efficiently reset the central clock. This line of research will be helpful for learning more about the human circadian system and to find ways to alleviate health problems of shift workers, and other populations experiencing altered circadian rhythms. PMID:19849799

  15. Do Caucasian and Asian clocks tick differently?

    PubMed

    Barbosa, A A; Pedrazzoli, M; Koike, B D V; Tufik, S

    2010-01-01

    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.

  16. Towards Self-Clocked Gated OCDMA Receiver

    NASA Astrophysics Data System (ADS)

    Idris, S.; Osadola, T.; Glesk, I.

    2013-02-01

    A novel incoherent OCDMA receiver with incorporated all-optical clock recovery for self-synchronization of a time gate for the multi access interferences (MAI) suppression and minimizing the effect of data time jitter in incoherent OCDMA system was successfully developed and demonstrated. The solution was implemented and tested in a multiuser environment in an out of the laboratory OCDMA testbed with two-dimensional wavelength-hopping time-spreading coding scheme and OC-48 (2.5 Gbp/s) data rate. The self-clocked all-optical time gate uses SOA-based fibre ring laser optical clock, recovered all-optically from the received OCDMA traffic to control its switching window for cleaning the autocorrelation peak from the surrounding MAI. A wider eye opening was achieved when the all-optically recovered clock from received data was used for synchronization if compared to a static approach with the RF clock being generated by a RF synthesizer. Clean eye diagram was also achieved when recovered clock is used to drive time gating.

  17. Adipose Clocks: Burning the Midnight Oil.

    PubMed

    Henriksson, Emma; Lamia, Katja A

    2015-10-01

    Circadian clocks optimize the timing of physiological processes in synchrony with daily recurring and therefore predictable changes in the environment. Until the late 1990s, circadian clocks were thought to exist only in the central nervous systems of animals; elegant studies in cultured fibroblasts and using genetically encoded reporters in Drosophila melanogaster and in mice showed that clocks are ubiquitous and cell autonomous. These findings inspired investigations of the advantages construed by enabling each organ to independently adjust its function to the time of day. Studies of rhythmic gene expression in several organs suggested that peripheral organ clocks might play an important role in optimizing metabolic physiology by synchronizing tissue-intrinsic metabolic processes to cycles of nutrient availability and energy requirements. The effects of clock disruption in liver, pancreas, muscle, and adipose tissues support that hypothesis. Adipose tissues coordinate energy storage and utilization and modulate behavior and the physiology of other organs by secreting hormones known as "adipokines." Due to behavior- and environment-driven diurnal variations in supply and demand for chemical and thermal energy, adipose tissues might represent an important peripheral location for coordinating circadian energy balance (intake, storage, and utilization) over the whole organism. Given the complexity of adipose cell types and depots, the sensitivity of adipose tissue biology to age and diet composition, and the plethora of known and yet-to-be-discovered adipokines and lipokines, we have just begun to scratch the surface of understanding the role of circadian clocks in adipose tissues.

  18. Body weight, metabolism and clock genes

    PubMed Central

    2010-01-01

    Biological rhythms are present in the lives of almost all organisms ranging from plants to more evolved creatures. These oscillations allow the anticipation of many physiological and behavioral mechanisms thus enabling coordination of rhythms in a timely manner, adaption to environmental changes and more efficient organization of the cellular processes responsible for survival of both the individual and the species. Many components of energy homeostasis exhibit circadian rhythms, which are regulated by central (suprachiasmatic nucleus) and peripheral (located in other tissues) circadian clocks. Adipocyte plays an important role in the regulation of energy homeostasis, the signaling of satiety and cellular differentiation and proliferation. Also, the adipocyte circadian clock is probably involved in the control of many of these functions. Thus, circadian clocks are implicated in the control of energy balance, feeding behavior and consequently in the regulation of body weight. In this regard, alterations in clock genes and rhythms can interfere with the complex mechanism of metabolic and hormonal anticipation, contributing to multifactorial diseases such as obesity and diabetes. The aim of this review was to define circadian clocks by describing their functioning and role in the whole body and in adipocyte metabolism, as well as their influence on body weight control and the development of obesity. PMID:20712885

  19. Body weight, metabolism and clock genes.

    PubMed

    Zanquetta, Melissa M; Corrêa-Giannella, Maria Lúcia; Monteiro, Maria Beatriz; Villares, Sandra Mf

    2010-08-16

    Biological rhythms are present in the lives of almost all organisms ranging from plants to more evolved creatures. These oscillations allow the anticipation of many physiological and behavioral mechanisms thus enabling coordination of rhythms in a timely manner, adaption to environmental changes and more efficient organization of the cellular processes responsible for survival of both the individual and the species. Many components of energy homeostasis exhibit circadian rhythms, which are regulated by central (suprachiasmatic nucleus) and peripheral (located in other tissues) circadian clocks. Adipocyte plays an important role in the regulation of energy homeostasis, the signaling of satiety and cellular differentiation and proliferation. Also, the adipocyte circadian clock is probably involved in the control of many of these functions. Thus, circadian clocks are implicated in the control of energy balance, feeding behavior and consequently in the regulation of body weight. In this regard, alterations in clock genes and rhythms can interfere with the complex mechanism of metabolic and hormonal anticipation, contributing to multifactorial diseases such as obesity and diabetes. The aim of this review was to define circadian clocks by describing their functioning and role in the whole body and in adipocyte metabolism, as well as their influence on body weight control and the development of obesity.

  20. Quantum primordial standard clocks

    NASA Astrophysics Data System (ADS)

    Chen, Xingang; Namjoo, Mohammad Hossein; Wang, Yi

    2016-02-01

    In this paper, we point out and study a generic type of signals existing in the primordial universe models, which can be used to model-independently distinguish the inflation scenario from alternatives. These signals are generated by massive fields that function as standard clocks. The role of massive fields as standard clocks has been realized in previous works. Although the existence of such massive fields is generic, the previous realizations require sharp features to classically excite the oscillations of the massive clock fields. Here, we point out that the quantum fluctuations of massive fields can actually serve the same purpose as the standard clocks. We show that they are also able to directly record the defining property of the scenario type, namely, the scale factor of the primordial universe as a function of time a(t), but through shape-dependent oscillatory features in non-Gaussianities. Since quantum fluctuating massive fields exist in any realistic primordial universe models, these quantum primordial standard clock signals are present in any inflation models, and should exist quite generally in alternative-to-inflation scenarios as well. However, the amplitude of such signals is very model-dependent.

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

    PubMed

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

    2016-01-22

    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. PMID:26849600

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Room 103, transom woodwork and original clock. All clocks are ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Room 103, transom woodwork and original clock. All clocks are driven by a common signal. - San Bernardino Valley College, Life Science Building, 701 South Mount Vernon Avenue, San Bernardino, San Bernardino County, CA

  4. Optical atomic clocks

    NASA Astrophysics Data System (ADS)

    Poli, N.; Oates, C. W.; Gill, P.; Tino, G. M.

    2013-12-01

    In the last ten years extraordinary results in time and frequency metrology have been demonstrated. Frequency-stabilization techniques for continuous-wave lasers and femtosecond optical frequency combs have enabled a rapid development of frequency standards based on optical transitions in ultra-cold neutral atoms and trapped ions. As a result, today's best performing atomic clocks tick at an optical rate and allow scientists to perform high-resolution measurements with a precision approaching a few parts in 1018. This paper reviews the history and the state of the art in optical-clock research and addresses the implementation of optical clocks in a possible future redefinition of the SI second as well as in tests of fundamental physics.

  5. Orbit and clock determination of BDS regional navigation satellite system based on IGS M-GEX and WHU BETS tracking network

    NASA Astrophysics Data System (ADS)

    GENG, T.; Zhao, Q.; Shi, C.; Shum, C.; Guo, J.; Su, X.

    2013-12-01

    BeiDou Navigation Satellite System (BDS) began to provide the regional open service on December 27th 2012 and will provide the global open service by the end of 2020. Compared to GPS, the space segment of BDS Regional System consists of 5 Geostationary Earth Orbit satellites (GEO), 5 Inclined Geosynchronous Orbit satellites (IGSO) and 4 Medium Earth orbit (MEO) satellites. Since 2011, IGS Multiple-GNSS Experiment (M-GEX) focuses on tracking the newly available GNSS signals. This includes all signals from the modernized satellites of the GPS and GLONASS systems, as well as signals of the BDS, Galileo and QZSS systems. Up to now, BDS satellites are tracked by around 25 stations with a variety of different antennas and receivers from different GNSS manufacture communities in M-GEX network. Meanwhile, there are 17 stations with Unicore Communications Incorporation's GPS/BDS receivers in BeiDou Experimental Tracking Stations (BETS) network by Wuhan University. In addition, 5 BDS satellites have been tracking by the International Laser Ranging Service (ILRS). BDS performance is expected to be further studied by the GNSS communities. Following an introduction of the BDS system and above different tracking network, this paper discusses the achieved BDS characterization and performance assessment. Firstly, the BDS signal and measurement quality are analyzed with different antennas and receivers in detail compared to GPS. This includes depth of coverage for satellite observation, carrier-to-noise-density ratios, code noise and multipath, carrier phase errors. Secondly, BDS Precise Orbit Determination (POD) is processed. Different arc lengths and sets of orbit parameters are tested using Position And Navigation Data Analysis software (PANDA) which is developed at the Wuhan University. GEO, IGSO and MEO satellites orbit quality will be assessed using overlap comparison, 2-day orbit fit and external validations with Satellite Laser Range (SLR). Then BDS satellites are equipped

  6. Central and peripheral circadian clocks in mammals.

    PubMed

    Mohawk, Jennifer A; Green, Carla B; Takahashi, Joseph S

    2012-01-01

    The circadian system of mammals is composed of a hierarchy of oscillators that function at the cellular, tissue, and systems levels. A common molecular mechanism underlies the cell-autonomous circadian oscillator throughout the body, yet this clock system is adapted to different functional contexts. In the central suprachiasmatic nucleus (SCN) of the hypothalamus, a coupled population of neuronal circadian oscillators acts as a master pacemaker for the organism to drive rhythms in activity and rest, feeding, body temperature, and hormones. Coupling within the SCN network confers robustness to the SCN pacemaker, which in turn provides stability to the overall temporal architecture of the organism. Throughout the majority of the cells in the body, cell-autonomous circadian clocks are intimately enmeshed within metabolic pathways. Thus, an emerging view for the adaptive significance of circadian clocks is their fundamental role in orchestrating metabolism.

  7. Partners in time: EARLY BIRD associates with ZEITLUPE and regulates the speed of the Arabidopsis clock.

    PubMed

    Johansson, Mikael; McWatters, Harriet G; Bakó, László; Takata, Naoki; Gyula, Péter; Hall, Anthony; Somers, David E; Millar, Andrew J; Eriksson, Maria E

    2011-04-01

    The circadian clock of the model plant Arabidopsis (Arabidopsis thaliana) is made up of a complex series of interacting feedback loops whereby proteins regulate their own expression across day and night. early bird (ebi) is a circadian mutation that causes the clock to speed up: ebi plants have short circadian periods, early phase of clock gene expression, and are early flowering. We show that EBI associates with ZEITLUPE (ZTL), known to act in the plant clock as a posttranslational mediator of protein degradation. However, EBI is not degraded by its interaction with ZTL. Instead, ZTL counteracts the effect of EBI during the day and increases it at night, modulating the expression of key circadian components. The partnership of EBI with ZTL reveals a novel mechanism involved in controlling the complex transcription-translation feedback loops of the clock. This work highlights the importance of cross talk between the ubiquitination pathway and transcriptional control for regulation of the plant clock.

  8. Inducible gene expression systems for plants.

    PubMed

    Borghi, Lorenzo

    2010-01-01

    Several systems for induction of transgene expression in plants have been described recently. Inducible systems were used mainly in tobacco, rice, Arabidopsis, tomato, and maize. Inducible systems offer researchers the possibility to deregulate gene expression levels at particular stages of plant development and in particular tissues of interest. The more precise temporal and spatial control, obtained by providing the transgenic plant with the appropriate chemical compound or treatment, permits to analyze also the function of those genes required for plant viability. In addition, inducible systems allow promoting local changes in gene expression levels without causing gross alterations to the whole plant development. Here, protocols will be presented to work with five different inducible systems: AlcR/AlcA (ethanol inducible); GR fusions, GVG, and pOp/LhGR (dexamethasone inducible); XVE/OlexA (beta-estradiol inducible); and heat shock induction. PMID:20734254

  9. A Novel Photonic Clock and Carrier Recovery Device

    NASA Technical Reports Server (NTRS)

    Yao, X. Steve; Lutes, George; Maleki, Lute

    1996-01-01

    As data communication rates climb toward ten Gb/s, clock recovery and synchronization become more difficult, if not impossible, using conventional electronic circuits. We present in this article experimental results of a high speed clock and carrier recovery using a novel device called a photonic oscillator that we recently developed in our laboratory. This device is capable of recovering clock signals up to 70 GHz. To recover the clock, the incoming data is injected into the photonic oscillator either through the optical injection port or the electrical injection port. The free running photonic oscillator is tuned to oscillate at a nominal frequency equal to the clock frequency of the incoming data. With the injection of the data, the photonic oscillator will be quickly locked to clock frequency of the data stream while rejecting other frequency components associated with the data. Consequently, the output of the locked photonic oscillator is a continuous periodical wave synchronized with the incoming data or simply the recovered clock. We have demonstrated a clock to spur ratio of more than 60 dB of the recovered clock using this technique. Similar to the clock recovery, the photonic oscillator can be used to recover a high frequency carrier degraded by noise and an improvement of about 50 dB in signal-to-noise ratio was demonstrated. The photonic oscillator has both electrical and optical inputs and outputs and can be directly interfaced with a photonic system without signal conversion. In addition to clock and carrier recovery, the photonic oscillator can also be used for (1) stable high frequency clock signal generation, (2) frequency multiplication, (3) square wave and comb frequency generation, and (4) photonic phase locked loop.

  10. Molecular mechanisms of circadian rhythm in Lotus japonicus and Arabidopsis thaliana are sufficiently compatible to regulate heterologous core clock genes robustly.

    PubMed

    Ueoka-Nakanishi, Hanayo; Yamashino, Takafumi; Ishida, Kai; Kamioka, Mari; Nakamichi, Norihito; Mizuno, Takeshi

    2012-01-01

    Recent intensive studies of the model plant Arabidopsis thaliana have revealed the molecular mechanisms underlying circadian rhythms in detail. Results of phylogenetic analyses indicated that some of core clock genes are widely conserved throughout the plant kingdom. For another model plant the legume Lotus japonicus, we have reported that it has a set of putative clock genes highly homologous to A. thaliana. Taking advantage of the L. japonicus hairy root transformation system, in this study we characterized the promoter activity of A. thaliana core clock genes CCA1 and PRR5 in heterologous L. japonicus cells and found that the molecular mechanism of circadian rhythm in L. japonicus is compatible with that of A. thaliana. PMID:23221703

  11. Derivation and experimental verification of clock synchronization theory

    NASA Astrophysics Data System (ADS)

    Palumbo, Daniel L.

    1994-06-01

    The objective of this work is to validate mathematically derived clock synchronization theories and their associated algorithms through experiment. Two theories are considered, the Interactive Convergence Clock Synchronization Algorithm and the Mid-Point Algorithm. Special clock circuitry was designed and built so that several operating conditions and failure modes (including malicious failures) could be tested. Both theories are shown to predict conservative upper bounds (i.e., measured values of clock skew were always less than the theory prediction). Insight gained during experimentation led to alternative derivations of the theories. These new theories accurately predict the clock system's behavior. It is found that a 100% penalty is paid to tolerate worst case failures. It is also shown that under optimal conditions (with minimum error and no failures) the clock skew can be as much as 3 clock ticks. Clock skew grows to 6 clock ticks when failures are present. Finally, it is concluded that one cannot rely solely on test procedures or theoretical analysis to predict worst case conditions. conditions.

  12. Derivation and experimental verification of clock synchronization theory

    NASA Technical Reports Server (NTRS)

    Palumbo, Daniel L.

    1994-01-01

    The objective of this work is to validate mathematically derived clock synchronization theories and their associated algorithms through experiment. Two theories are considered, the Interactive Convergence Clock Synchronization Algorithm and the Mid-Point Algorithm. Special clock circuitry was designed and built so that several operating conditions and failure modes (including malicious failures) could be tested. Both theories are shown to predict conservative upper bounds (i.e., measured values of clock skew were always less than the theory prediction). Insight gained during experimentation led to alternative derivations of the theories. These new theories accurately predict the clock system's behavior. It is found that a 100% penalty is paid to tolerate worst case failures. It is also shown that under optimal conditions (with minimum error and no failures) the clock skew can be as much as 3 clock ticks. Clock skew grows to 6 clock ticks when failures are present. Finally, it is concluded that one cannot rely solely on test procedures or theoretical analysis to predict worst case conditions. conditions.

  13. Glucocorticoids entrain molecular clock components in human peripheral cells.

    PubMed

    Cuesta, Marc; Cermakian, Nicolas; Boivin, Diane B

    2015-04-01

    In humans, shift work induces a desynchronization between the circadian system and the outside world, which contributes to shift work-associated medical disorders. Using a simulated night shift experiment, we previously showed that 3 d of bright light at night fully synchronize the central clock to the inverted sleep schedule, whereas the peripheral clocks located in peripheral blood mononuclear cells (PBMCs) took longer to reset. This underlines the need for testing the effects of synchronizers on both the central and peripheral clocks. Glucocorticoids display circadian rhythms controlled by the central clock and are thought to act as synchronizers of rodent peripheral clocks. In the present study, we tested whether the human central and peripheral clocks were sensitive to exogenous glucocorticoids (Cortef) administered in the late afternoon. We showed that 20 mg Cortef taken orally acutely increased PER1 expression in PBMC peripheral clocks. After 6 d of Cortef administration, the phases of central markers were not affected, whereas those of PER2-3 and BMAL1 expression in PBMCs were shifted by ∼ 9.5-11.5 h. These results demonstrate, for the first time, that human peripheral clocks are entrained by glucocorticoids. Importantly, they suggest innovative interventions for shift workers and jet-lag travelers, combining synchronizing agents for the central and peripheral clocks.

  14. Dynamics of statistical distance: Quantum limits for two-level clocks

    SciTech Connect

    Braunstein, S.L. ); Milburn, G.J. )

    1995-03-01

    We study the evolution of statistical distance on the Bloch sphere under unitary and nonunitary dynamics. This corresponds to studying the limits to clock precision for a clock constructed from a two-state system. We find that the initial motion away from pure states under nonunitary dynamics yields the greatest accuracy for a one-tick'' clock; in this case the clock's precision is not limited by the largest frequency of the system.

  15. Quantum Clock Synchronization with a Single Qudit

    PubMed Central

    Tavakoli, Armin; Cabello, Adán; Żukowski, Marek; Bourennane, Mohamed

    2015-01-01

    Clock synchronization for nonfaulty processes in multiprocess networks is indispensable for a variety of technologies. A reliable system must be able to resynchronize the nonfaulty processes upon some components failing causing the distribution of incorrect or conflicting information in the network. The task of synchronizing such networks is related to Byzantine agreement (BA), which can classically be solved using recursive algorithms if and only if less than one-third of the processes are faulty. Here we introduce a nonrecursive quantum algorithm, based on a quantum solution of the detectable BA, which achieves clock synchronization in the presence of arbitrary many faulty processes by using only a single quantum system. PMID:25613754

  16. Quantum clock synchronization with a single qudit.

    PubMed

    Tavakoli, Armin; Cabello, Adán; Żukowski, Marek; Bourennane, Mohamed

    2015-01-23

    Clock synchronization for nonfaulty processes in multiprocess networks is indispensable for a variety of technologies. A reliable system must be able to resynchronize the nonfaulty processes upon some components failing causing the distribution of incorrect or conflicting information in the network. The task of synchronizing such networks is related to Byzantine agreement (BA), which can classically be solved using recursive algorithms if and only if less than one-third of the processes are faulty. Here we introduce a nonrecursive quantum algorithm, based on a quantum solution of the detectable BA, which achieves clock synchronization in the presence of arbitrary many faulty processes by using only a single quantum system.

  17. Quantum Clock Synchronization with a Single Qudit

    NASA Astrophysics Data System (ADS)

    Tavakoli, Armin; Cabello, Adán; Żukowski, Marek; Bourennane, Mohamed

    2015-01-01

    Clock synchronization for nonfaulty processes in multiprocess networks is indispensable for a variety of technologies. A reliable system must be able to resynchronize the nonfaulty processes upon some components failing causing the distribution of incorrect or conflicting information in the network. The task of synchronizing such networks is related to Byzantine agreement (BA), which can classically be solved using recursive algorithms if and only if less than one-third of the processes are faulty. Here we introduce a nonrecursive quantum algorithm, based on a quantum solution of the detectable BA, which achieves clock synchronization in the presence of arbitrary many faulty processes by using only a single quantum system.

  18. Clock Reaction: Outreach Attraction

    ERIC Educational Resources Information Center

    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. Clock shifts in the Unitary Bose Gas

    NASA Astrophysics Data System (ADS)

    Fletcher, Richard; Man, Jay; Lopes, Raphael; Navon, Nir; Smith, Robert; Hadzibabic, Zoran

    2016-05-01

    Clock shifts are interaction-induced changes in the transition frequency between atomic spin states. So-called because of their importance as systematic errors in atomic clocks, they reveal details of both the interaction energy within a gas and the particle correlations. In this work, we employ a RF-injection technique to rapidly project a thermal Bose gas into the unitary regime on a timescale much shorter than three-body losses. Working with a two-state system, one of which exhibits strong intrastate interactions, we carry out Ramsey spectroscopy to extract the variation in the clock shift across a Feshbach resonance. Thanks to the relationship between these shifts and particle correlations, we use our measurements to infer the contact as a function of both interaction strength and degeneracy. This quantity plays a central role in the many-body physics of strongly correlated systems, offering a link between few-body and thermodynamic behaviour.

  20. Redox rhythm reinforces the circadian clock to gate immune response.

    PubMed

    Zhou, Mian; Wang, Wei; Karapetyan, Sargis; Mwimba, Musoki; Marqués, Jorge; Buchler, Nicolas E; Dong, Xinnian

    2015-07-23

    Recent studies have shown that in addition to the transcriptional circadian clock, many organisms, including Arabidopsis, have a circadian redox rhythm driven by the organism's metabolic activities. It has been hypothesized that the redox rhythm is linked to the circadian clock, but the mechanism and the biological significance of this link have only begun to be investigated. Here we report that the master immune regulator NPR1 (non-expressor of pathogenesis-related gene 1) of Arabidopsis is a sensor of the plant's redox state and regulates transcription of core circadian clock genes even in the absence of pathogen challenge. Surprisingly, acute perturbation in the redox status triggered by the immune signal salicylic acid does not compromise the circadian clock but rather leads to its reinforcement. Mathematical modelling and subsequent experiments show that NPR1 reinforces the circadian clock without changing the period by regulating both the morning and the evening clock genes. This balanced network architecture helps plants gate their immune responses towards the morning and minimize costs on growth at night. Our study demonstrates how a sensitive redox rhythm interacts with a robust circadian clock to ensure proper responsiveness to environmental stimuli without compromising fitness of the organism.

  1. Seismic monitoring system replacement at Temelin plant

    SciTech Connect

    Baltus, R.; Palusamy, S.S.

    1996-12-01

    The VVER-1000 plants under construction at Temelin (Czech Republic) were designed with an automatic reactor trip system triggered on seismic peak accelerations. Within the plant I and C upgrade, Westinghouse designed a digital Seismic Monitoring System to be integrated in an Artificial Intelligence based Diagnostic and Monitoring System. The system meets the requirements of the emerging standards prepared by the US NRC on the basis of EPRI studies, which recommend a detailed data evaluation and a pre-shutdown plant inspection before orderly shutdown, if required, rather than immediate emergency shutdown. The paper presents the arguments about automatic trip, as discussed in an IAEA meeting attended by expert consultants from Japan, Russia, US and Eastern and Western Europe. It describes the system installed at Temelin, including the plant specific criteria for OBE exceedance. Finally it presents the capabilities and limitations of the integration into an overall Diagnostic and Monitoring System.

  2. Pulsed Optically Pumped Rb clock

    NASA Astrophysics Data System (ADS)

    Micalizio, S.; Levi, F.; Godone, A.; Calosso, C. E.; François, B.; Boudot, R.; Affolderbach, C.; Kang, S.; Gharavipour, M.; Gruet, F.; Mileti, G.

    2016-06-01

    INRIM demonstrated a Rb vapour cell clock based on pulsed optical pumping (POP) with unprecedented frequency stability performances, both in the short and in the medium-long term period. In the frame of a EMRP project, we are developing a new clock based on the same POP principle but adopting solutions aimed at reducing the noise sources affecting the INRIM clock. At the same time, concerning possible technological applications, particular care are devoted in the project to reduce the size and the weight of the clock, still keeping the excellent stability of the INRIM clock. The paper resumes the main results of this activity.

  3. Circadian Clock Control of Liver Metabolic Functions.

    PubMed

    Reinke, Hans; Asher, Gad

    2016-03-01

    The circadian clock is an endogenous biological timekeeping system that synchronizes physiology and behavior to day/night cycles. A wide variety of processes throughout the entire gastrointestinal tract and notably the liver appear to be under circadian control. These include various metabolic functions such as nutrient uptake, processing, and detoxification, which align organ function to cycle with nutrient supply and demand. Remarkably, genetic or environmental disruption of the circadian clock can cause metabolic diseases or exacerbate pathological states. In addition, modern lifestyles force more and more people worldwide into asynchrony between the external time and their circadian clock, resulting in a constant state of social jetlag. Recent evidence indicates that interactions between altered energy metabolism and disruptions in the circadian clock create a downward spiral that can lead to diabetes and other metabolic diseases. In this review, we provide an overview of rhythmic processes in the liver and highlight the functions of circadian clock genes under physiological and pathological conditions; we focus on their roles in regulation of hepatic glucose as well as lipid and bile acid metabolism and detoxification and their potential effects on the development of fatty liver and nonalcoholic steatohepatitis.

  4. A precise clock distribution network for MRPC-based experiments

    NASA Astrophysics Data System (ADS)

    Wang, S.; Cao, P.; Shang, L.; An, Q.

    2016-06-01

    In high energy physics experiments, the MRPC (Multi-Gap Resistive Plate Chamber) detectors are widely used recently which can provide higher-resolution measurement for particle identification. However, the application of MRPC detectors leads to a series of challenges in electronics design with large number of front-end electronic channels, especially for distributing clock precisely. To deal with these challenges, this paper presents a universal scheme of clock transmission network for MRPC-based experiments with advantages of both precise clock distribution and global command synchronization. For precise clock distributing, the clock network is designed into a tree architecture with two stages: the first one has a point-to-multipoint long range bidirectional distribution with optical channels and the second one has a fan-out structure with copper link inside readout crates. To guarantee the precision of clock frequency or phase, the r-PTP (reduced Precision Time Protocol) and the DDMTD (digital Dual Mixer Time Difference) methods are used for frequency synthesis, phase measurement and adjustment, which is implemented by FPGA (Field Programmable Gate Array) in real-time. In addition, to synchronize global command execution, based upon this clock distribution network, synchronous signals are coded with clock for transmission. With technique of encoding/decoding and clock data recovery, signals such as global triggers or system control commands, can be distributed to all front-end channels synchronously, which greatly simplifies the system design. The experimental results show that both the clock jitter (RMS) and the clock skew can be less than 100 ps.

  5. Single electron relativistic clock interferometer

    NASA Astrophysics Data System (ADS)

    Bushev, P. A.; Cole, J. H.; Sholokhov, D.; Kukharchyk, N.; Zych, M.

    2016-09-01

    Although time is one of the fundamental notions in physics, it does not have a unique description. In quantum theory time is a parameter ordering the succession of the probability amplitudes of a quantum system, while according to relativity theory each system experiences in general a different proper time, depending on the system's world line, due to time dilation. It is therefore of fundamental interest to test the notion of time in the regime where both quantum and relativistic effects play a role, for example, when different amplitudes of a single quantum clock experience different magnitudes of time dilation. Here we propose a realization of such an experiment with a single electron in a Penning trap. The clock can be implemented in the electronic spin precession and its time dilation then depends on the radial (cyclotron) state of the electron. We show that coherent manipulation and detection of the electron can be achieved already with present day technology. A single electron in a Penning trap is a technologically ready platform where the notion of time can be probed in a hitherto untested regime, where it requires a relativistic as well as quantum description.

  6. The circadian clock-associated gene gigantea1 affects maize developmental transitions.

    PubMed

    Bendix, Claire; Mendoza, Juan M; Stanley, Desiree N; Meeley, Robert; Harmon, Frank G

    2013-07-01

    The circadian clock is an internal timing mechanism that allows plants to make developmental decisions in accordance with environmental conditions. In model plants, circadian clock-associated gigantea (gi) genes are directly involved in control of growth and developmental transitions. The maize gigantea1 (gi1) gene is the more highly expressed of the two gi homeologs, and its function is uncharacterized. To understand the role of gi1 in the regulatory networks of the maize circadian clock system, gi1 mutants were evaluated for changes in flowering time, phase change and growth control. When grown in long-day (LD) photoperiods, gi1 mutants flowered earlier than non-mutant plants, but this difference was not apparent in short-day (SD) photoperiods. Therefore, gi1 participates in a pathway that suppresses flowering in LD photoperiods, but not in SD. Part of the underlying cause of early flowering was up-regulated expression of the FT-like floral activator gene zea mays centroradialis8 (zcn8) and the CONSTANS-like flowering regulatory gene constans of zea mays1 (conz1). gi1 mutants also underwent vegetative phase change earlier and grew taller than non-mutant plants. These findings indicate gi1 has a repressive function in multiple regulatory pathways that govern maize growth and development. PMID:23336247

  7. Synergism of coupled subsarcolemmal Ca2+ clocks and sarcolemmal voltage clocks confers robust and flexible pacemaker function in a novel pacemaker cell model

    PubMed Central

    Maltsev, Victor A.; Lakatta, Edward G.

    2009-01-01

    Recent experimental studies have demonstrated that sinoatrial node cells (SANC) generate spontaneous, rhythmic, local subsarcolemmal Ca2+ releases (Ca2+ clock), which occur during late diastolic depolarization (DD) and interact with the classic sarcolemmal voltage oscillator (membrane clock) by activating Na+-Ca2+ exchanger current (INCX). This and other interactions between clocks, however, are not captured by existing essentially membrane-delimited cardiac pacemaker cell numerical models. Using wide-scale parametric analysis of classic formulations of membrane clock and Ca2+ cycling, we have constructed and initially explored a prototype rabbit SANC model featuring both clocks. Our coupled oscillator system exhibits greater robustness and flexibility than membrane clock operating alone. Rhythmic spontaneous Ca2+ releases of sarcoplasmic reticulum (SR)-based Ca2+ clock ignite rhythmic action potentials via late DD INCX over much broader ranges of membrane clock parameters [e.g., L-type Ca2+ current (ICaL) and/or hyperpolarization-activated (“funny”) current (If) conductances]. The system Ca2+ clock includes SR and sarcolemmal Ca2+ fluxes, which optimize cell Ca2+ balance to increase amplitudes of both SR Ca2+ release and late DD INCX as SR Ca2+ pumping rate increases, resulting in a broad pacemaker rate modulation (1.8–4.6 Hz). In contrast, the rate modulation range via membrane clock parameters is substantially smaller when Ca2+ clock is unchanged or lacking. When Ca2+ clock is disabled, the system parametric space for fail-safe SANC operation considerably shrinks: without rhythmic late DD INCX ignition signals membrane clock substantially slows, becomes dysrhythmic, or halts. In conclusion, the Ca2+ clock is a new critical dimension in SANC function. A synergism of the coupled function of Ca2+ and membrane clocks confers fail-safe SANC operation at greatly varying rates. PMID:19136600

  8. Calcium messenger system in plants

    NASA Technical Reports Server (NTRS)

    Poovaiah, B. W.; Reddy, A. S.

    1987-01-01

    The purpose of this review is to delineate the ubiquitous and pivotal role of Ca2+ in diverse physiological processes. Emphasis will be given to the role of Ca2+ in stimulus-response coupling. In addition to reviewing the present status of research, our intention is to critically evaluate the existing data and describe the newly developing areas of Ca2+ research in plants.

  9. Real clocks and the Zeno effect

    SciTech Connect

    Egusquiza, Inigo L.; Garay, Luis J.

    2003-08-01

    Real clocks are not perfect. This must have an effect in our predictions for the behavior of a quantum system, an effect for which we present a unified description, encompassing several previous proposals. We study the relevance of clock errors in the Zeno effect and find that generically no Zeno effect can be present (in such a way that there is no contradiction with currently available experimental data). We further observe that, within the class of stochasticities in time addressed here, there is no modification in emission line shapes.

  10. A relativistic analysis of clock synchronization

    NASA Technical Reports Server (NTRS)

    Thomas, J. B.

    1974-01-01

    The relativistic conversion between coordinate time and atomic time is reformulated to allow simpler time calculations relating analysis in solar-system barycentric coordinates (using coordinate time) with earth-fixed observations (measuring earth-bound proper time or atomic time.) After an interpretation of terms, this simplified formulation, which has a rate accuracy of about 10 to the minus 15th power, is used to explain the conventions required in the synchronization of a world wide clock network and to analyze two synchronization techniques-portable clocks and radio interferometry. Finally, pertinent experiment tests of relativity are briefly discussed in terms of the reformulated time conversion.

  11. Desynchronization of Noisy Multi-cellular Clocks Underlies the Population-level Singularity Behavior of Mammalian Circadian Clock

    NASA Astrophysics Data System (ADS)

    Kobayashi, Tetsuya J.; Ukai, Hideki; Ueda, Hiroki R.

    2007-07-01

    The singularity behavior of circadian clocks defined as the suppression of circadian oscillation by critical perturbation is one of the intriguing dynamical properties of circadian rhythms. Although the singularity behaviors have been observed in various organisms, its mechanism has not yet been elucidated, because the hierarchical structure of multi-cell-level circadian clocks exists behind the organism-level circadian rhythm. In vitro light-responsible circadian system is indispensable for extracting the underlying mechanism of the singularity behavior behind the hierarchical structure of multi-cell organisms. To obtain such in vitro system, we synthetically constructed light-responsible mammalian clock cells by exogenously introducing a photo-responsible receptor. By using this synthetic system and population-level high-throughput promoter activity assay, we found that a light pulse with critical timing and strength can induce population-level singularity behavior of the light-responsible mammalian clock cells. Subsequent single-cell measurement revealed that desynchronization of multi-cellular clocks underlies the population-level singularity. A mathematical model consistently explains our population-level and single-cell-level experimental data, and also demonstrates that the synchronization and desynchronization of cellular clocks is the underlying mechanism of population-level response of circadian clocks to external perturbation. In addition, our model suggests that fluctuation in single-cell-level behavior of the clock cells is the key determinant of the observable singularity behavior.

  12. Biochemical basis for the biological clock

    NASA Technical Reports Server (NTRS)

    Morre, D. James; Chueh, Pin-Ju; Pletcher, Jake; Tang, Xiaoyu; Wu, Lian-Ying; Morre, Dorothy M.

    2002-01-01

    NADH oxidases at the external surface of plant and animal cells (ECTO-NOX proteins) exhibit stable and recurring patterns of oscillations with potentially clock-related, entrainable, and temperature-compensated period lengths of 24 min. To determine if ECTO-NOX proteins might represent the ultradian time keepers (pacemakers) of the biological clock, COS cells were transfected with cDNAs encoding tNOX proteins having a period length of 22 min or with C575A or C558A cysteine to alanine replacements having period lengths of 36 or 42 min. Here we demonstrate that such transfectants exhibited 22, 36, or 40 to 42 h circadian patterns in the activity of glyceraldehyde-3-phosphate dehydrogenase, a common clock-regulated protein, in addition to the endogenous 24 h circadian period length. The fact that the expression of a single oscillatory ECTO-NOX protein determines the period length of a circadian biochemical marker (60 X the ECTO-NOX period length) provides compelling evidence that ECTO-NOX proteins are the biochemical ultradian drivers of the cellular biological clock.

  13. Sample-Clock Phase-Control Feedback

    NASA Technical Reports Server (NTRS)

    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.

  14. Synthetic gene networks in plant systems.

    PubMed

    Junker, Astrid; Junker, Björn H

    2012-01-01

    Synthetic biology methods are routinely applied in the plant field as in other eukaryotic model systems. Several synthetic components have been developed in plants and an increasing number of studies report on the assembly into functional synthetic genetic circuits. This chapter gives an overview of the existing plant genetic networks and describes in detail the application of two systems for inducible gene expression. The ethanol-inducible system relies on the ethanol-responsive interaction of the AlcA transcriptional activator and the AlcR receptor resulting in the transcription of the gene of interest (GOI). In comparison, the translational fusion of GOI and the glucocorticoid receptor (GR) domain leads to the dexamethasone-dependent nuclear translocation of the GOI::GR protein. This chapter contains detailed protocols for the application of both systems in the model plants potato and Arabidopsis, respectively.

  15. Air ion exposure system for plants

    NASA Technical Reports Server (NTRS)

    Morrow, R. C.; Tibbitts, T. W.

    1987-01-01

    A system was developed for subjecting plants to elevated air ion levels. This system consisted of a rectangular Plexiglas chamber lined with a Faraday cage. Air ions were generated by corona discharge from frayed stainless steel fibers placed at one end of the chamber. This source was capable of producing varying levels of either positive or negative air ions. During plant exposures, environmental conditions were controlled by operating the unit in a growth chamber.

  16. Generating clock signals for a cycle accurate, cycle reproducible FPGA based hardware accelerator

    DOEpatents

    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.

  17. Ontogeny of the circadian system during embryogenesis in rainbow trout (Oncorhynchus mykyss) and the effect of prolonged exposure to continuous illumination on daily rhythms of per1, clock, and aanat2 expression.

    PubMed

    Davie, Andrew; Sanchez, Jose A; Vera, Luisa M; Sanchez-Vazquez, J; Migaud, H

    2011-04-01

    It is widely held that the development of the circadian system during embryogenesis is important for future survival of an organism. Work in teleosts has been, to date, limited to zebrafish, which provides little insight into the diversity of this system within such a large vertebrate class. In this study, the authors analyzed the diel expression of per1, clock, and aanat2 in unfertilized rainbow trout oocytes and embryos maintained under either a 12:12-h light:dark (LD) cycle or continuous illumination (LL) from fertilization. 24-h profiles in expression were measured at fertilization as well as 8, 21 42, and 57 days postfertilization (dpf). Both per1 and clock were expressed in unfertilized oocytes and all embryonic stages, whereas aanat2 expression was only measureable from 8 dpf. A reduction in both per1 and clock mean expression levels between unfertilized oocytes/0-1 dpf embryos and 8-9 dpf embryos was suggestive of a transition from maternal RNA to endogenous mRNA expression. Although aanat2 expression was not clearly associated with photic conditions, photoperiod treatment did alter the expression of per1 and clock expression/rhythmicity from as early as 8 dpf (per1), which could suggest the presence and functionality of an as yet unidentified "photoreceptor." As a whole, this work demonstrates that clock systems are present and functional during embryonic development in rainbow trout. Further studies of their expression and regulation will help understand how the environment interacts with embryonic development in the species.

  18. FLOWERING LOCUS C -dependent and -independent regulation of the circadian clock by the autonomous and vernalization pathways

    PubMed Central

    Salathia, Neeraj; Davis, Seth J; Lynn, James R; Michaels, Scott D; Amasino, Richard M; Millar, Andrew J

    2006-01-01

    Background The circadian system drives pervasive biological rhythms in plants. Circadian clocks integrate endogenous timing information with environmental signals, in order to match rhythmic outputs to the local day/night cycle. Multiple signaling pathways affect the circadian system, in ways that are likely to be adaptively significant. Our previous studies of natural genetic variation in Arabidopsis thaliana accessions implicated FLOWERING LOCUS C (FLC) as a circadian-clock regulator. The MADS-box transcription factor FLC is best known as a regulator of flowering time. Its activity is regulated by many regulatory genes in the "autonomous" and vernalization-dependent flowering pathways. We tested whether these same pathways affect the circadian system. Results Genes in the autonomous flowering pathway, including FLC, were found to regulate circadian period in Arabidopsis. The mechanisms involved are similar, but not identical, to the control of flowering time. By mutant analyses, we demonstrate a graded effect of FLC expression upon circadian period. Related MADS-box genes had less effect on clock function. We also reveal an unexpected vernalization-dependent alteration of periodicity. Conclusion This study has aided in the understanding of FLC's role in the clock, as it reveals that the network affecting circadian timing is partially overlapping with the floral-regulatory network. We also show a link between vernalization and circadian period. This finding may be of ecological relevance for developmental programing in other plant species. PMID:16737527

  19. Clock Synchronization for Multihop Wireless Sensor Networks

    ERIC Educational Resources Information Center

    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…

  20. A Bayesian approach for parameter estimation in the extended clock gene circuit of Arabidopsis thaliana.

    PubMed

    Higham, Catherine F; Husmeier, Dirk

    2013-01-01

    The circadian clock is an important molecular mechanism that enables many organisms to anticipate and adapt to environmental change. Pokhilko et al. recently built a deterministic ODE mathematical model of the plant circadian clock in order to understand the behaviour, mechanisms and properties of the system. The model comprises 30 molecular species (genes, mRNAs and proteins) and over 100 parameters. The parameters have been fitted heuristically to available gene expression time series data and the calibrated model has been shown to reproduce the behaviour of the clock components. Ongoing work is extending the clock model to cover downstream effects, in particular metabolism, necessitating further parameter estimation and model selection. This work investigates the challenges facing a full Bayesian treatment of parameter estimation. Using an efficient adaptive MCMC proposed by Haario et al. and working in a high performance computing setting, we quantify the posterior distribution around the proposed parameter values and explore the basin of attraction. We investigate if Bayesian inference is feasible in this high dimensional setting and thoroughly assess convergence and mixing with different statistical diagnostics, to prevent apparent convergence in some domains masking poor mixing in others.

  1. Clock Synchronization in Wireless Sensor Networks: An Overview

    PubMed Central

    Rhee, Ill-Keun; Lee, Jaehan; Kim, Jangsub; Serpedin, Erchin; Wu, Yik-Chung

    2009-01-01

    The development of tiny, low-cost, low-power and multifunctional sensor nodes equipped with sensing, data processing, and communicating components, have been made possible by the recent advances in micro-electro-mechanical systems (MEMS) technology. Wireless sensor networks (WSNs) assume a collection of such tiny sensing devices connected wirelessly and which are used to observe and monitor a variety of phenomena in the real physical world. Many applications based on these WSNs assume local clocks at each sensor node that need to be synchronized to a common notion of time. This paper reviews the existing clock synchronization protocols for WSNs and the methods of estimating clock offset and clock skew in the most representative clock synchronization protocols for WSNs. PMID:22389588

  2. Lattice-induced nonadiabatic frequency shifts in optical lattice clocks

    SciTech Connect

    Beloy, K.

    2010-09-15

    We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.

  3. The molecular clock mediates leptin-regulated bone formation.

    PubMed

    Fu, Loning; Patel, Millan S; Bradley, Allan; Wagner, Erwin F; Karsenty, Gerard

    2005-09-01

    The hormone leptin is a regulator of bone remodeling, a homeostatic function maintaining bone mass constant. Mice lacking molecular-clock components (Per and Cry), or lacking Per genes in osteoblasts, display high bone mass, suggesting that bone remodeling may also be subject to circadian regulation. Moreover, Per-deficient mice experience a paradoxical increase in bone mass following leptin intracerebroventricular infusion. Thus, clock genes may mediate the leptin-dependent sympathetic regulation of bone formation. We show that expression of clock genes in osteoblasts is regulated by the sympathetic nervous system and leptin. Clock genes mediate the antiproliferative function of sympathetic signaling by inhibiting G1 cyclin expression. Partially antagonizing this inhibitory loop, leptin also upregulates AP-1 gene expression, which promotes cyclin D1 expression, osteoblast proliferation, and bone formation. Thus, leptin determines the extent of bone formation by modulating, via sympathetic signaling, osteoblast proliferation through two antagonistic pathways, one of which involves the molecular clock.

  4. Clocking in the face of unpredictability beyond quantum uncertainty

    NASA Astrophysics Data System (ADS)

    Madjid, F. Hadi; Myers, John M.

    2015-05-01

    In earlier papers we showed unpredictability beyond quantum uncertainty in atomic clocks, ensuing from a proven gap between given evidence and explanations of that evidence. Here we reconceive a clock, not as an isolated entity, but as enmeshed in a self-adjusting communications network adapted to one or another particular investigation, in contact with an unpredictable environment. From the practical uses of clocks, we abstract a clock enlivened with the computational capacity of a Turing machine, modified to transmit and to receive numerical communications. Such "live clocks" phase the steps of their computations to mesh with the arrival of transmitted numbers. We lift this phasing, known in digital communications, to a principle of logical synchronization, distinct from the synchronization defined by Einstein in special relativity. Logical synchronization elevates digital communication to a topic in physics, including applications to biology. One explores how feedback loops in clocking affect numerical signaling among entities functioning in the face of unpredictable influences, making the influences themselves into subjects of investigation. The formulation of communications networks in terms of live clocks extends information theory by expressing the need to actively maintain communications channels, and potentially, to create or drop them. We show how networks of live clocks are presupposed by the concept of coordinates in a spacetime. A network serves as an organizing principle, even when the concept of the rigid body that anchors a special-relativistic coordinate system is inapplicable, as is the case, for example, in a generic curved spacetime.

  5. Velocity response curves demonstrate the complexity of modeling entrainable clocks.

    PubMed

    Taylor, Stephanie R; Cheever, Allyson; Harmon, Sarah M

    2014-12-21

    Circadian clocks are biological oscillators that regulate daily behaviors in organisms across the kingdoms of life. Their rhythms are generated by complex systems, generally involving interlocked regulatory feedback loops. These rhythms are entrained by the daily light/dark cycle, ensuring that the internal clock time is coordinated with the environment. Mathematical models play an important role in understanding how the components work together to function as a clock which can be entrained by light. For a clock to entrain, it must be possible for it to be sped up or slowed down at appropriate times. To understand how biophysical processes affect the speed of the clock, one can compute velocity response curves (VRCs). Here, in a case study involving the fruit fly clock, we demonstrate that VRC analysis provides insight into a clock׳s response to light. We also show that biochemical mechanisms and parameters together determine a model׳s ability to respond realistically to light. The implication is that, if one is developing a model and its current form has an unrealistic response to light, then one must reexamine one׳s model structure, because searching for better parameter values is unlikely to lead to a realistic response to light. PMID:25193284

  6. Circadian Clocks as Modulators of Metabolic Comorbidity in Psychiatric Disorders.

    PubMed

    Barandas, Rita; Landgraf, Dominic; McCarthy, Michael J; Welsh, David K

    2015-12-01

    Psychiatric disorders such as schizophrenia, bipolar disorder, and major depressive disorder are often accompanied by metabolic dysfunction symptoms, including obesity and diabetes. Since the circadian system controls important brain systems that regulate affective, cognitive, and metabolic functions, and neuropsychiatric and metabolic diseases are often correlated with disturbances of circadian rhythms, we hypothesize that dysregulation of circadian clocks plays a central role in metabolic comorbidity in psychiatric disorders. In this review paper, we highlight the role of circadian clocks in glucocorticoid, dopamine, and orexin/melanin-concentrating hormone systems and describe how a dysfunction of these clocks may contribute to the simultaneous development of psychiatric and metabolic symptoms. PMID:26483181

  7. Operational development of small plant growth systems

    NASA Technical Reports Server (NTRS)

    Scheld, H. W.; Magnuson, J. W.; Sauer, R. L.

    1986-01-01

    The results of a study undertaken on the first phase of an empricial effort in the development of small plant growth chambers for production of salad type vegetables on space shuttle or space station are discussed. The overall effort is visualized as providing the underpinning of practical experience in handling of plant systems in space which will provide major support for future efforts in planning, design, and construction of plant-based (phytomechanical) systems for support of human habitation in space. The assumptions underlying the effort hold that large scale phytomechanical habitability support systems for future space stations must evolve from the simple to the complex. The highly complex final systems will be developed from the accumulated experience and data gathered from repetitive tests and trials of fragments or subsystems of the whole in an operational mode. These developing system components will, meanwhile, serve a useful operational function in providing psychological support and diversion for the crews.

  8. Circadian clocks in the ovary.

    PubMed

    Sellix, Michael T; Menaker, Michael

    2010-10-01

    Clock gene expression has been observed in tissues of the hypothalamic-pituitary-gonadal (HPG) axis. Whereas the contribution of hypothalamic oscillators to the timing of reproductive biology is well known, the role of peripheral oscillators like those in the ovary is less clear. Circadian clocks in the ovary might play a role in the timing of ovulation. Disruption of the clock in ovarian cells or desynchrony between ovarian clocks and circadian oscillators elsewhere in the body may contribute to the onset and progression of various reproductive pathologies. In this paper, we review evidence for clock function in the ovary across a number of species and offer a novel perspective into the role of this clock in normal ovarian physiology and in diseases that negatively affect fertility.

  9. Disruption of the circadian clock due to the Clock mutation has discrete effects on aging and carcinogenesis

    PubMed Central

    Antoch, Marina P.; Gorbacheva, Victoria Y.; Vykhovanets, Olena; Toshkov, Illia A.; Kondratov, Roman V.; Kondratova, Anna A.; Lee, Choogon; Nikitin, Alexander Yu.

    2009-01-01

    The mammalian circadian system has been implicated in the regulation of various biological processes including those involved in genotoxic stress responses and tumor suppression. Here we report that mice with the functional deficiency in circadian transcription factor CLOCK (Clock/Clock mutant mice) do not display predisposition to tumor formation both during their normal lifespan or when challenged by γ-radiation. This phenotype is consistent with high apoptotic and low proliferation rate in lymphoid tissues of Clock mutant mice and is supported by the gene expression profiling of a number of apoptosis and cell cycle-related genes, as well as by growth inhibition of cells with CLOCK downregulation. At the same time, Clock mutant mice respond to low-dose irradiation by accelerating their aging program, and develop phenotypes that are reminiscent of those in Bmal1-deficient mice. Taken together, our results demonstrate the dichotomy in biological consequences of the disruption of the circadian clock with respect to ageing and cancer. They also highlight the existence of a complex interconnection between ageing, carcinogenesis and individual components of the circadian clock machinery. PMID:18418054

  10. A mixed relaxed clock model.

    PubMed

    Lartillot, Nicolas; Phillips, Matthew J; Ronquist, Fredrik

    2016-07-19

    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'.

  11. Incentive theory III: Adaptive clocks.

    PubMed

    Killeen, P R

    1984-01-01

    Incentive theory is extended to address the phenomenon of autoshaping. To do so, it is necessary to permit the speed of the animal's internal clock to vary with rates of reinforcement; clock speed is the basis for the animal's calculations of reinforcement densities. This notion of an "adaptive clock" is consistent with other effects, such as the partial-reinforcement extinction effect, and permits us to deal with the various experimental manipulations that are found in autoshaping experiments from a unified perspective.

  12. The Vitamin C Clock Reaction

    NASA Astrophysics Data System (ADS)

    Wright, Stephen W.

    2002-01-01

    An iodine clock reaction that gives a colorless to black result similar to that of the familiar Landolt iodate-bisulfite clock reaction is described. The vitamin C clock reaction uses chemicals that are readily available on the retail market: vitamin C, tincture of iodine, 3% hydrogen peroxide, and laundry starch. Orange juice may be used as the vitamin C source to give an orange to black reaction.

  13. Plants and the central nervous system.

    PubMed

    Carlini, E A

    2003-06-01

    This review article draws the attention to the many species of plants possessing activity on the central nervous system (CNS). In fact, they cover the whole spectrum of central activity such as psychoanaleptic, psycholeptic and psychodysleptic effects, and several of these plants are currently used in therapeutics to treat human ailments. Among the psychoanaleptic (stimulant) plants, those utilized by human beings to reduce body weight [Ephedra spp. (Ma Huang), Paullinia spp. (guaraná), Catha edulis Forssk. (khat)] and plants used to improve general health conditions (plant adaptogens) were scrutinized. Many species of hallucinogenic (psychodysleptic) plants are used by humans throughout the world to achieve states of mind distortions; among those, a few have been used for therapeutic purposes, such as Cannabis sativa L., Tabernanthe iboga Baill. and the mixture of Psychotria viridis Ruiz and Pav. and Banisteriopsis caapi (Spruce ex Griseb.) C.V. Morton. Plants showing central psycholeptic activities, such as analgesic or anxiolytic actions (Passiflora incarnata L., Valeriana spp. and Piper methysticum G. Forst.), were also analysed.Finally, the use of crude or semipurified extracts of such plants instead of the active substances seemingly responsible for their therapeutic effect is discussed.

  14. Metabolism control by the circadian clock and vice versa

    PubMed Central

    Eckel-Mahan, Kristin; Sassone-Corsi, Paolo

    2014-01-01

    Circadian rhythms govern a wide variety of physiological and metabolic functions in most organisms. At the heart of these regulatory pathways in mammals is the clock machinery, a remarkably coordinated transcription-translation system that relies on dynamic changes in chromatin states. Recent findings indicate that regulation also goes the other way, as specific elements of the clock can sense changes in the cellular metabolism. Understanding in full detail the intimate links between cellular metabolism and the circadian clock machinery will provide not only crucial insights into system physiology but also new avenues toward pharmacological intervention of metabolic disorders. PMID:19421159

  15. EGR1 regulates hepatic clock gene amplitude by activating Per1 transcription

    PubMed Central

    Tao, Weiwei; Wu, Jing; Zhang, Qian; Lai, Shan-Shan; Jiang, Shan; Jiang, Chen; Xu, Ying; Xue, Bin; Du, Jie; Li, Chao-Jun

    2015-01-01

    The mammalian clock system is composed of a master clock and peripheral clocks. At the molecular level, the rhythm-generating mechanism is controlled by a molecular clock composed of positive and negative feedback loops. However, the underlying mechanisms for molecular clock regulation that affect circadian clock function remain unclear. Here, we show that Egr1 (early growth response 1), an early growth response gene, is expressed in mouse liver in a circadian manner. Consistently, Egr1 is transactivated by the CLOCK/BMAL1 heterodimer through a conserved E-box response element. In hepatocytes, EGR1 regulates the transcription of several core clock genes, including Bmal1, Per1, Per2, Rev-erbα and Rev-erbβ, and the rhythm amplitude of their expression is dependent on EGR1’s transcriptional function. Further mechanistic studies indicated that EGR1 binds to the proximal region of the Per1 promoter to activate its transcription directly. When the peripheral clock is altered by light or feeding behavior transposition in Egr1-deficient mice, the expression phase of hepatic clock genes shifts normally, but the amplitude is also altered. Our data reveal a critical role for EGR1 in the regulation of hepatic clock circuitry, which may contribute to the rhythm stability of peripheral clock oscillators. PMID:26471974

  16. Insect photoperiodic calendar and circadian clock: independence, cooperation, or unity?

    PubMed

    Koštál, Vladimír

    2011-05-01

    The photoperiodic calendar is a seasonal time measurement system which allows insects to cope with annual cycles of environmental conditions. Seasonal timing of entry into diapause is the most often studied photoperiodic response of insects. Research on insect photoperiodism has an approximately 80-year-old tradition. Despite that long history, the physiological mechanisms underlying functionality of the photoperiodic calendar remain poorly understood. Thus far, a consensus has not been reached on the role of another time measurement system, the biological circadian clock, in the photoperiodic calendar. Are the two systems physically separated and functionally independent, or do they cooperate, or is it a single system with dual output? The relationship between calendar and clock functions are the focus of this review, with particular emphasis on the potential roles of circadian clock genes, and the circadian clock system as a whole, in the transduction pathway for photoperiodic token stimulus to the overt expression of facultative diapause.

  17. The Retina and Other Light-sensitive Ocular Clocks.

    PubMed

    Besharse, Joseph C; McMahon, Douglas G

    2016-06-01

    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 nonmammalian 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 nonmammalian 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 nonmammalian 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 nonmammalian 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 affect diseases such as glaucoma or retinal degeneration syndromes. PMID:27095816

  18. Transcriptional Control of Antioxidant Defense by the Circadian Clock

    PubMed Central

    Patel, Sonal A.; Velingkaar, Nikkhil S.

    2014-01-01

    Abstract Significance: The circadian clock, an internal timekeeping system, is implicated in the regulation of metabolism and physiology, and circadian dysfunctions are associated with pathological changes in model organisms and increased risk of some diseases in humans. Recent Advances: Data obtained in different organisms, including humans, have established a tight connection between the clock and cellular redox signaling making it among the major candidates for a link between the circadian system and physiological processes. Critical Issues: In spite of the recent progress in understanding the importance of the circadian clock in the regulation of reactive oxygen species homeostasis, molecular mechanisms and key regulators are mostly unknown. Future Directions: Here we review, with an emphasis on transcriptional control, the circadian-clock-dependent control of oxidative stress response system as a potential mechanism in age-associated diseases. We will discuss the roles of the core clock components such as brain and muscle ARNT-like 1, Circadian Locomotor Output Cycles Kaput, the circadian-clock-controlled transcriptional factors such as nuclear factor erythroid-2-related factor, and peroxisome proliferator-activated receptor and circadian clock control chromatin modifying enzymes from sirtuin family in the regulation of cellular and organism antioxidant defense. Antioxid. Redox Signal. 20, 2997–3006. PMID:24111970

  19. Phylogenetics and molecular clocks reveal the repeated evolution of ant-plants after the late Miocene in Africa and the early Miocene in Australasia and the Neotropics.

    PubMed

    Chomicki, Guillaume; Renner, Susanne S

    2015-07-01

    Ant-plant symbioses involve over 110 ant species in five subfamilies that are facultative or obligate occupants of stem, leaf or root domatia formed by hundreds of ant-plant species. The phylogenetic distribution and geological ages of these associations, and the frequency of gains or losses of domatium, are largely unknown. We compiled an up-to-date list of ant domatium-bearing plants, estimated their probable true number from model-based statistical inference, generated dated phylogenies that include c. 50% of ant-plant lineages, and traced the occurrence of domatia and extrafloral nectaries on a 1181-species tree, using likelihood and Bayesian methods. We found 681 vascular plants with domatia (159 genera in 50 families) resulting from minimally 158 inferred domatium origins and 43 secondary losses over the last 19 Myr. The oldest African ant-plant symbioses are younger than those in Australasia and the Neotropics. The best statistical model suggests that the true number of myrmecophytes may approach 1140 species. The phylogenetic distribution of ant-plants shows that domatia evolved from a range of pre-adapted morphological structures and have been lost frequently, suggesting that domatia have no generalizable effect on diversification. The Miocene origin of ant-plant symbioses is consistent with inferred changes in diet and behaviour during ant evolution.

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

    ERIC Educational Resources Information Center

    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…

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

    NASA Technical Reports Server (NTRS)

    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.

  2. Digital processing clock

    NASA Technical Reports Server (NTRS)

    Phillips, D. H.

    1982-01-01

    Tthe digital processing clock SG 1157/U is described. It is compatible with the PTTI world where it can be driven by an external cesium source. Built-in test equipment shows synchronization with cesium through 1 pulse per second. It is built to be expandable to accommodate future time-keeping needs of the Navy as well as any other time ordered functions. Examples of this expandibility are the inclusion of an unmodulated XR3 time code and the 2137 modulate time code (XR3 with 1 kHz carrier).

  3. Biological switches and clocks

    PubMed Central

    Tyson, John J.; Albert, Reka; Goldbeter, Albert; Ruoff, Peter; Sible, Jill

    2008-01-01

    To introduce this special issue on biological switches and clocks, we review the historical development of mathematical models of bistability and oscillations in chemical reaction networks. In the 1960s and 1970s, these models were limited to well-studied biochemical examples, such as glycolytic oscillations and cyclic AMP signalling. After the molecular genetics revolution of the 1980s, the field of molecular cell biology was thrown wide open to mathematical modellers. We review recent advances in modelling the gene–protein interaction networks that control circadian rhythms, cell cycle progression, signal processing and the design of synthetic gene networks. PMID:18522926

  4. Einstein’s Clocks

    SciTech Connect

    Lincoln, Don

    2015-09-09

    One of the most non-intuitive physics theories ever devised is Einstein’s Theory of Special Relativity, which claim such crazy-sounding things as two people disagreeing on such familiar concepts as length and time. In this video, Fermilab’s Dr. Don Lincoln shows that every single day particle physicists prove that moving clocks tick more slowly than stationary ones. He uses an easy to understand example of particles that move for far longer distances than you would expect from combining their velocity and stationary lifetime.

  5. Clocks and cardiovascular function

    PubMed Central

    McLoughlin, Sarah C.; Haines, Philip; FitzGerald, Garret A.

    2016-01-01

    Circadian clocks in central and peripheral tissues enable the temporal synchronization and organization of molecular and physiological processes of rhythmic animals, allowing optimum functioning of cells and organisms at the most appropriate time of day. Disruption of circadian rhythms, from external or internal forces, leads to widespread biological disruption and is postulated to underlie many human conditions, such as the incidence and timing of cardiovascular disease. Here, we describe in vivo and in vitro methodology relevant to studying the role of circadian rhythms in cardiovascular function and dysfunction PMID:25707279

  6. A mixed relaxed clock model

    PubMed Central

    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

  7. The Mouse Clock Mutation Behaves as an Antimorph and Maps within the W(19h) Deletion, Distal of Kit

    PubMed Central

    King, D. P.; Vitaterna, M. H.; Chang, A. M.; Dove, W. F.; Pinto, L. H.; Turek, F. W.; Takahashi, J. S.

    1997-01-01

    Clock is a semidominant mutation identified from an N-ethyl-N-nitrosourea mutagenesis screen in mice. Mice carrying the Clock mutation exhibit abnormalities of circadian behavior, including lengthening of endogenous period and loss of rhythmicity. To identify the gene affected by this mutation, we have generated a high-resolution genetic map (>1800 meioses) of the Clock locus. We report that Clock is 0.7 cM distal of Kit on mouse chromosome 5. Mapping shows that Clock lies within the W(19H) deletion. Complementation analysis of different Clock and W(19H) compound genotypes indicates that the Clock mutation behaves as an antimorph. This antimorphic behavior of Clock strongly argues that Clock defines a gene centrally involved in the mammalian circadian system. PMID:9215907

  8. Relativistic effects of the rotation of the earth on remote clock synchronization

    NASA Technical Reports Server (NTRS)

    Reinhardt, V.

    1974-01-01

    A treatment is given of relativistic clock synchronization effects due to the rotation of the earth. Unlike other approaches, the point of view of an earth fixed coordinate system is used which offers insight to many problems. An attempt is made to give the reader an intuitive grasp of the subject as well as to provide formulae for his use. Specific applications to global timekeeping, navigation, VLBI, relativistic clock experiments, and satellite clock synchronization are discussed. The question of whether atomic clocks are ideal clocks is also treated.

  9. Wheels within wheels: new transcriptional feedback loops in the Arabidopsis circadian clock.

    PubMed

    McClung, C Robertson

    2014-01-01

    The circadian clock allows organisms to temporally coordinate their biology with the diurnal oscillation of the environment, which enhances plant performance. Accordingly, a fuller understanding of the circadian clock mechanism may contribute to efforts to optimize plant performance. One recurring theme in clock mechanism is coupled transcription-translation feedback loops. To date, the majority of plant transcription factors constituting these loops, including the central oscillator components CIRCADIAN CLOCK ASSOCIATED 1 (CCA1), LATE ELONGATED HYPOCOTYL (LHY), and TIMING OF CAB2 EXPRESSION 1 (TOC1), and the related PSEUDO-RESPONSE REGULATORS (PRRs), are transcriptional repressors, leading to a model of the clock emphasizing repressive interactions. Recent work, however, has revealed that a subset of the REVEILLE (RVE) family of Myb transcription factors closely related to CCA1 and LHY are transcriptional activators in novel feedback transcription-translation feedback loops. Other recently identified transcriptional activators that contribute to clock function include LIGHT-REGULATED WD 1 (LWD1) and LWD2 and night light-inducible and clock-regulated transcription factors NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED1 (LNK1) and LNK2. Collectively, these advances permit a substantial reconfiguration of the clock model.

  10. Diffuse-Illumination Systems for Growing Plants

    NASA Technical Reports Server (NTRS)

    May, George; Ryan, Robert

    2010-01-01

    Agriculture in both terrestrial and space-controlled environments relies heavily on artificial illumination for efficient photosynthesis. Plant-growth illumination systems require high photon flux in the spectral range corresponding with plant photosynthetic active radiation (PAR) (400 700 nm), high spatial uniformity to promote uniform growth, and high energy efficiency to minimize electricity usage. The proposed plant-growth system takes advantage of the highly diffuse reflective surfaces on the interior of a sphere, hemisphere, or other nearly enclosed structure that is coated with highly reflective materials. This type of surface and structure uniformly mixes discrete light sources to produce highly uniform illumination. Multiple reflections from within the domelike structures are exploited to obtain diffuse illumination, which promotes the efficient reuse of photons that have not yet been absorbed by plants. The highly reflective surfaces encourage only the plant tissue (placed inside the sphere or enclosure) to absorb the light. Discrete light sources, such as light emitting diodes (LEDs), are typically used because of their high efficiency, wavelength selection, and electronically dimmable properties. The light sources are arranged to minimize shadowing and to improve uniformity. Different wavelengths of LEDs (typically blue, green, and red) are used for photosynthesis. Wavelengths outside the PAR range can be added for plant diagnostics or for growth regulation

  11. European plans for new clocks in space

    NASA Technical Reports Server (NTRS)

    Leschiutta, Sigfrido M.; Tavella, Patrizia

    1995-01-01

    An outline of the future European space research program where precise clocks are necessary is presented, pointing out how space applications are posing impressive requirements as regards clock mass, power, ruggedness, long life, accuracy and, in some cases, spectral purity. The material presented was gathered in some laboratories; useful information was obtained from the Space Agencies of France (CNES), Germany (DARA) and Italy (ASI), but the bulk is coming from a recent exercise promoted inside ESA (the European Space Agency) and aimed to prefigure space research activities at the beginning of the next millennium. This exercise was called Horizon 2000 plus; the outcomings were summarized in two reports, presented by ESA in may 1994. Precise clocks and time measurements are needed not only for deep-space or out-ward space missions, but are essential tools also for Earth oriented activities. In this latter field, the European views and needs were discussed in October 1994, in a meeting organized by ESA and devoted to Earth Observation problems. By a scrutiny of these reports, an analysis was performed on the missions requiring a precise clock on board and the driving requirements were pointed out, leading to a survey of the necessary PTTI developments that, to some extent, are in the realm of possibility but that pose serious challenges. In this report the use of frequency standards in the satellite navigation systems is not considered.

  12. ^87Sr Clock Comparisons at JILA

    NASA Astrophysics Data System (ADS)

    Williams, Jason; Nicholson, Travis; Bloom, Benjamin; Campbell, Sara; Martin, Michael; Swallows, Matthew; Bishof, Michael; Ye, Jun

    2012-06-01

    Great advances are being realized with optical lattice clocks, where spectroscopy at optical frequencies and large ensembles of neutral atoms combine to offer extremely high frequency precision and stability. Recent results from the Strontium 87 optical atomic clock at JILA have demonstrated that strong interactions among fermions confined in a two-dimensional (2D) optical lattice suppress the collisional frequency shift and its uncertainty to the level of 10-17 [1]. We report on the progress of a second optical lattice clock at JILA, in which fermionic ^87Sr atoms are confined in a lattice potential derived from optical buildup cavities to provide strong confinement over a very large volume in one, two, and three dimensional lattices. Intercomparisons of the two clocks at JILA will be used to explore in greater detail the physics governing the transition shifts and uncertainties in our two ^87Sr optical lattice systems and will provide a significant improvement of our systematic errors.[4pt] [1] M D. Swallows et al. Science, 331, 1043 (2011)

  13. Use of Very Stable Clocks in Satellite Geodesy

    NASA Astrophysics Data System (ADS)

    Hugentobler, Urs; Romanyuk, Tetyana

    2016-07-01

    Time and frequency play an essential role in satellite geodesy and navigation. Global Navigation Satellite Systems (GNSS) rely on precise measurements of signal travel times. The satellite and receiver clocks involved in measuring this time interval need to be synchronized at the picosecond level. The concept of GNSS allows for an epoch-wise synchronization of space and ground clocks, a feature which is consequently used in satellite geodesy by estimating epoch-wise clock corrections for all clocks in the system, either explicitly or implicitly by forming double differences. Ultra-stable clocks allow to estimate only few parameters for each clock, e.g., offset and drift. The much reduced number of parameters should stabilize GNSS solutions, e.g., tracking network station coordinates. On the other hand systematic errors, e.g., from troposphere or orbit modeling deficiencies or temperature induced hardware delay variations may systematically affect the solutions. The presentation shows trade-offs of modelling higly stable clocks and negative impact of error sources based on simulations.

  14. Maximum likelihood molecular clock comb: analytic solutions.

    PubMed

    Chor, Benny; Khetan, Amit; Snir, Sagi

    2006-04-01

    Maximum likelihood (ML) is increasingly used as an optimality criterion for selecting evolutionary trees, but finding the global optimum is a hard computational task. Because no general analytic solution is known, numeric techniques such as hill climbing or expectation maximization (EM), are used in order to find optimal parameters for a given tree. So far, analytic solutions were derived only for the simplest model--three taxa, two state characters, under a molecular clock. Four taxa rooted trees have two topologies--the fork (two subtrees with two leaves each) and the comb (one subtree with three leaves, the other with a single leaf). In a previous work, we devised a closed form analytic solution for the ML molecular clock fork. In this work, we extend the state of the art in the area of analytic solutions ML trees to the family of all four taxa trees under the molecular clock assumption. The change from the fork topology to the comb incurs a major increase in the complexity of the underlying algebraic system and requires novel techniques and approaches. We combine the ultrametric properties of molecular clock trees with the Hadamard conjugation to derive a number of topology dependent identities. Employing these identities, we substantially simplify the system of polynomial equations. We finally use tools from algebraic geometry (e.g., Gröbner bases, ideal saturation, resultants) and employ symbolic algebra software to obtain analytic solutions for the comb. We show that in contrast to the fork, the comb has no closed form solutions (expressed by radicals in the input data). In general, four taxa trees can have multiple ML points. In contrast, we can now prove that under the molecular clock assumption, the comb has a unique (local and global) ML point. (Such uniqueness was previously shown for the fork.).

  15. Using a transportable optical clock for chronometric levelling

    NASA Astrophysics Data System (ADS)

    Lisdat, Christian; Sterr, Uwe; Koller, Silvio; Grotti, Jacopo; Vogt, Stefan; Häfner, Sebastian; Herbers, Sofia; Al-Masoudi, Ali

    2016-07-01

    With their supreme accuracy and precision, optical clocks in combination with new methods of long-distance frequency transfer can be used to determine height differences by measuring the gravitational red shift between two clocks without accumulation of measurement errors, as in classical levelling. We are developing transportable optical clocks for this purpose that will also serve for the technology development regarding optical clocks in Space and for international comparisons between optical clocks that cannot be linked with sufficient accuracy otherwise. In this talk we will focus on the transportable strontium lattice clock that we are developing and its first evaluation. Presently, we achieve a fractional frequency instability of 3 × 10^{-17} after 1000 s averaging time, which is equivalent to a height resolution of 30 cm. The first uncertainty evaluation of the system yielded 7 × 10^{-17}. We expect rapid improvements to an uncertainty of a few parts in 10^{17}. The clock is now located within a car trailer, which requires compact and rugged lasers systems and physics package. Special care has been taken in the design of the ultra-frequency stable interrogation laser that has to achieve fractional frequency instabilities of considerably below 10^{-15}. Typical laboratory constructions of the reference resonator system used to pre-stabilize the laser frequency are not compatible with the requirement of transportability. In an actual levelling campaign, this clock will be connected via a stabilized optical fibre link with another, stationary frequency standard. The measured gravitational red shift will be compared with the ones calculated from potential differences derived with state of the art geodetic data and models. We will discuss the status of measurements of geodetic relevance with optical clocks and give an outlook on our next steps. This work is supported by QUEST, DFG (RTG 1729, CRC 1128), EU-FP7 (FACT) and EMRP (ITOC). The EMRP is jointly funded

  16. The Vitamin C Clock Reaction.

    ERIC Educational Resources Information Center

    Wright, Stephen W.

    2002-01-01

    Describes an iodine clock reaction that produces an effect similar to the Landolt clock reaction. This reaction uses supermarket chemicals and avoids iodate, bisulfite, and mercury compounds. Ascorbic acid and tincture of iodine are the main reactants with alternate procedures provided for vitamin C tablets and orange juice. (DDR)

  17. Nuclear plants gain integrated information systems

    SciTech Connect

    Villavicencio-Ramirez, A.; Rodriquez-Alvarez, J.M.

    1994-10-01

    With the objective of simplifying the complex mesh of computing devices employed within nuclear power plants, modern technology and integration techniques are being used to form centralized (but backed up) databases and distributed processing and display networks. Benefits are immediate as a result of the integration and the use of standards. The use of a unique data acquisition and database subsystem optimizes the high costs of engineering, as this task is done only once for the life span of the system. This also contributes towards a uniform user interface and allows for graceful expansion and maintenance. This article features an integrated information system, Sistema Integral de Informacion de Proceso (SIIP). The development of this system enabled the Laguna Verde Nuclear Power plant to fully use the already existing universe of signals and its related engineering during all plant conditions, namely, start up, normal operation, transient analysis, and emergency operation. Integrated systems offer many advantages over segregated systems, and this experience should benefit similar development efforts in other electric power utilities, not only for nuclear but also for other types of generating plants.

  18. Integration of computer systems for California aqueduct power plant systems

    SciTech Connect

    Delfin, E.L. ); Gaushell, D.J. )

    1993-06-01

    The California State Water Project is one of the largest water and power systems in the world and includes over 130 hydroelectric units. This paper provides an overview of the planning and implementation of the control and communication systems replacement for the entire Project. New control system features include a multi-agency control center, off-site backup control center, four area control systems, ten major pumping/generating plant control systems, and a 400 mile fiber optic communication system.

  19. Partners in Time: EARLY BIRD Associates with ZEITLUPE and Regulates the Speed of the Arabidopsis Clock1[W][OA

    PubMed Central

    Johansson, Mikael; McWatters, Harriet G.; Bakó, László; Takata, Naoki; Gyula, Péter; Hall, Anthony; Somers, David E.; Millar, Andrew J.; Eriksson, Maria E.

    2011-01-01

    The circadian clock of the model plant Arabidopsis (Arabidopsis thaliana) is made up of a complex series of interacting feedback loops whereby proteins regulate their own expression across day and night. early bird (ebi) is a circadian mutation that causes the clock to speed up: ebi plants have short circadian periods, early phase of clock gene expression, and are early flowering. We show that EBI associates with ZEITLUPE (ZTL), known to act in the plant clock as a posttranslational mediator of protein degradation. However, EBI is not degraded by its interaction with ZTL. Instead, ZTL counteracts the effect of EBI during the day and increases it at night, modulating the expression of key circadian components. The partnership of EBI with ZTL reveals a novel mechanism involved in controlling the complex transcription-translation feedback loops of the clock. This work highlights the importance of cross talk between the ubiquitination pathway and transcriptional control for regulation of the plant clock. PMID:21300918

  20. An atomic clock with 10(-18) instability.

    PubMed

    Hinkley, N; Sherman, J A; Phillips, N B; Schioppo, M; Lemke, N D; Beloy, K; Pizzocaro, M; Oates, C W; Ludlow, A D

    2013-09-13

    Atomic clocks have been instrumental in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Timekeeping precision at 1 part in 10(18) enables new timing applications in relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests of physics beyond the standard model. Here, we describe the development and operation of two optical lattice clocks, both using spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of 1.6 × 10(-18) after only 7 hours of averaging.

  1. Detection of weak frequency jumps for GNSS onboard clocks.

    PubMed

    Huang, Xinming; Gong, Hang; Ou, Gang

    2014-05-01

    In this paper, a weak frequency jump detection method is developed for onboard clocks in global navigation satellite systems (GNSS). A Kalman filter is employed to facilitate the onboard real-time processing of atomic clock measurements, whose N-step prediction residuals are used to construct the weak frequency jump detector. Numerical simulations show that the method can successfully detect weak frequency jumps. The detection method proposed in this paper is helpful for autonomous integrity monitoring of GNSS satellite clocks, and can also be applied to other frequency anomalies with an appropriately modified detector.

  2. An atomic clock with 10(-18) instability.

    PubMed

    Hinkley, N; Sherman, J A; Phillips, N B; Schioppo, M; Lemke, N D; Beloy, K; Pizzocaro, M; Oates, C W; Ludlow, A D

    2013-09-13

    Atomic clocks have been instrumental in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Timekeeping precision at 1 part in 10(18) enables new timing applications in relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests of physics beyond the standard model. Here, we describe the development and operation of two optical lattice clocks, both using spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of 1.6 × 10(-18) after only 7 hours of averaging. PMID:23970562

  3. Detection of weak frequency jumps for GNSS onboard clocks.

    PubMed

    Huang, Xinming; Gong, Hang; Ou, Gang

    2014-05-01

    In this paper, a weak frequency jump detection method is developed for onboard clocks in global navigation satellite systems (GNSS). A Kalman filter is employed to facilitate the onboard real-time processing of atomic clock measurements, whose N-step prediction residuals are used to construct the weak frequency jump detector. Numerical simulations show that the method can successfully detect weak frequency jumps. The detection method proposed in this paper is helpful for autonomous integrity monitoring of GNSS satellite clocks, and can also be applied to other frequency anomalies with an appropriately modified detector. PMID:24802723

  4. The problem of clock synchronization - A relativistic approach

    NASA Astrophysics Data System (ADS)

    Klioner, Sergei A.

    1992-03-01

    The problem of synchronization of the earth-based clocks has been discussed in the framework of General Relativity Theory. The synchronization is considered as the transformation of the observers' proper time scales to the coordinate time scale of local inertial geocentric reference system, which is single for all the observers. The formulas for the relativistic corrections occurring in some methods of earth-based clock synchronization (transported clock, duplex communication via geostationary satellite and meteor-burst link, LASSO experiments) have been derived enabling one to attain the accuracy of 0.1 ns.

  5. The bird of time: cognition and the avian biological clock

    PubMed Central

    Cassone, Vincent M.; Westneat, David F.

    2012-01-01

    Avian behavior and physiology are embedded in time at many levels of biological organization. Biological clock function in birds is critical for sleep/wake cycles, but may also regulate the acquisition of place memory, learning of song from tutors, social integration, and time-compensated navigation. This relationship has two major implications. First, mechanisms of the circadian clock should be linked in some way to the mechanisms of all these behaviors. How is not yet clear, and evidence that the central clock has effects is piecemeal. Second, selection acting on characters that are linked to the circadian clock should influence aspects of the clock mechanism itself. Little evidence exists for this in birds, but there have been few attempts to assess this idea. At its core, the avian circadian clock is a multi-oscillator system comprising the pineal gland, the retinae, and the avian homologs of the suprachiasmatic nuclei, whose mutual interactions ensure coordinated physiological functions, which are in turn synchronized to ambient light cycles (LD) via encephalic, pineal, and retinal photoreceptors. At the molecular level, avian biological clocks comprise a genetic network of “positive elements” clock and bmal1 whose interactions with the “negative elements” period 2 (per2), period 3 (per3), and the cryptochromes form an oscillatory feedback loop that circumnavigates the 24 h of the day. We assess the possibilities for dual integration of the clock with time-dependent cognitive processes. Closer examination of the molecular, physiological, and behavioral elements of the circadian system would place birds at a very interesting fulcrum in the neurobiology of time in learning, memory, and navigation. PMID:22461765

  6. An Automated and Continuous Plant Weight Measurement System for Plant Factory.

    PubMed

    Chen, Wei-Tai; Yeh, Yu-Hui F; Liu, Ting-Yu; Lin, Ta-Te

    2016-01-01

    In plant factories, plants are usually cultivated in nutrient solution under a controllable environment. Plant quality and growth are closely monitored and precisely controlled. For plant growth evaluation, plant weight is an important and commonly used indicator. Traditional plant weight measurements are destructive and laborious. In order to measure and record the plant weight during plant growth, an automated measurement system was designed and developed herein. The weight measurement system comprises a weight measurement device and an imaging system. The weight measurement device consists of a top disk, a bottom disk, a plant holder and a load cell. The load cell with a resolution of 0.1 g converts the plant weight on the plant holder disk to an analog electrical signal for a precise measurement. The top disk and bottom disk are designed to be durable for different plant sizes, so plant weight can be measured continuously throughout the whole growth period, without hindering plant growth. The results show that plant weights measured by the weight measurement device are highly correlated with the weights estimated by the stereo-vision imaging system; hence, plant weight can be measured by either method. The weight growth of selected vegetables growing in the National Taiwan University plant factory were monitored and measured using our automated plant growth weight measurement system. The experimental results demonstrate the functionality, stability and durability of this system. The information gathered by this weight system can be valuable and beneficial for hydroponic plants monitoring research and agricultural research applications.

  7. An Automated and Continuous Plant Weight Measurement System for Plant Factory

    PubMed Central

    Chen, Wei-Tai; Yeh, Yu-Hui F.; Liu, Ting-Yu; Lin, Ta-Te

    2016-01-01

    In plant factories, plants are usually cultivated in nutrient solution under a controllable environment. Plant quality and growth are closely monitored and precisely controlled. For plant growth evaluation, plant weight is an important and commonly used indicator. Traditional plant weight measurements are destructive and laborious. In order to measure and record the plant weight during plant growth, an automated measurement system was designed and developed herein. The weight measurement system comprises a weight measurement device and an imaging system. The weight measurement device consists of a top disk, a bottom disk, a plant holder and a load cell. The load cell with a resolution of 0.1 g converts the plant weight on the plant holder disk to an analog electrical signal for a precise measurement. The top disk and bottom disk are designed to be durable for different plant sizes, so plant weight can be measured continuously throughout the whole growth period, without hindering plant growth. The results show that plant weights measured by the weight measurement device are highly correlated with the weights estimated by the stereo-vision imaging system; hence, plant weight can be measured by either method. The weight growth of selected vegetables growing in the National Taiwan University plant factory were monitored and measured using our automated plant growth weight measurement system. The experimental results demonstrate the functionality, stability and durability of this system. The information gathered by this weight system can be valuable and beneficial for hydroponic plants monitoring research and agricultural research applications. PMID:27066040

  8. An Automated and Continuous Plant Weight Measurement System for Plant Factory.

    PubMed

    Chen, Wei-Tai; Yeh, Yu-Hui F; Liu, Ting-Yu; Lin, Ta-Te

    2016-01-01

    In plant factories, plants are usually cultivated in nutrient solution under a controllable environment. Plant quality and growth are closely monitored and precisely controlled. For plant growth evaluation, plant weight is an important and commonly used indicator. Traditional plant weight measurements are destructive and laborious. In order to measure and record the plant weight during plant growth, an automated measurement system was designed and developed herein. The weight measurement system comprises a weight measurement device and an imaging system. The weight measurement device consists of a top disk, a bottom disk, a plant holder and a load cell. The load cell with a resolution of 0.1 g converts the plant weight on the plant holder disk to an analog electrical signal for a precise measurement. The top disk and bottom disk are designed to be durable for different plant sizes, so plant weight can be measured continuously throughout the whole growth period, without hindering plant growth. The results show that plant weights measured by the weight measurement device are highly correlated with the weights estimated by the stereo-vision imaging system; hence, plant weight can be measured by either method. The weight growth of selected vegetables growing in the National Taiwan University plant factory were monitored and measured using our automated plant growth weight measurement system. The experimental results demonstrate the functionality, stability and durability of this system. The information gathered by this weight system can be valuable and beneficial for hydroponic plants monitoring research and agricultural research applications. PMID:27066040

  9. Gas Centrifuge Enrichment Plant Safeguards System Modeling

    SciTech Connect

    Elayat, H A; O'Connell, W J; Boyer, B D

    2006-06-05

    The U.S. Department of Energy (DOE) is interested in developing tools and methods for potential U.S. use in designing and evaluating safeguards systems used in enrichment facilities. This research focuses on analyzing the effectiveness of the safeguards in protecting against the range of safeguards concerns for enrichment plants, including diversion of attractive material and unauthorized modes of use. We developed an Extend simulation model for a generic medium-sized centrifuge enrichment plant. We modeled the material flow in normal operation, plant operational upset modes, and selected diversion scenarios, for selected safeguards systems. Simulation modeling is used to analyze both authorized and unauthorized use of a plant and the flow of safeguards information. Simulation tracks the movement of materials and isotopes, identifies the signatures of unauthorized use, tracks the flow and compilation of safeguards data, and evaluates the effectiveness of the safeguards system in detecting misuse signatures. The simulation model developed could be of use to the International Atomic Energy Agency IAEA, enabling the IAEA to observe and draw conclusions that uranium enrichment facilities are being used only within authorized limits for peaceful uses of nuclear energy. It will evaluate improved approaches to nonproliferation concerns, facilitating deployment of enhanced and cost-effective safeguards systems for an important part of the nuclear power fuel cycle.

  10. Automatic minimisation of micromotion in a 88Sr+ optical clock

    NASA Astrophysics Data System (ADS)

    Barwood, G. P.; Huang, G.; Klein, H. A.; Gill, P.

    2015-07-01

    Optical clocks based on narrow linewidth transitions in single cold ions confined in RF traps are being developed at a number of laboratories worldwide. For these ion clock systems, excess micromotion can cause both Stark and Doppler frequency shifts and also a degradation of frequency stability as a result of a reduced excitation rate to the clock transition. At NPL, we detect micromotion in our 88Sr+ optical clocks by observing the correlation between photon arrival times and the zero crossing of the RF trap drive signal. Recently, two nominally identical 88Sr+ optical clocks have been operated over several days and their frequencies compared against one another. During this time the dc voltages on the endcap and compensation voltage electrodes required to minimise the micromotion can change significantly, particularly following the loading of an ion. This paper describes an automatic method to monitor and minimise micromotion applicable to single ion clocks and which we demonstrate using our two NPL 88Sr+ ion clocks.

  11. Using a transportable optical clock for chronometric levelling

    NASA Astrophysics Data System (ADS)

    Vogt, Stefan; Grotti, Jacopo; Koller, Silvio; Häfner, Sebastian; Herbers, Sofia; Al-Masoudi, Ali; Grosche, Gesine; Denker, Heiner; Sterr, Uwe; Lisdat, Christian

    2016-04-01

    With their supreme accuracy and precision, optical clocks and new methods of long distance frequency transfer can be used to determine height differences by measuring the gravitational red shift between two clocks. We are developing transportable optical clocks and optical fibre-based means for clock comparisons that can bridge distances of hundredths of kilometres without accumulation of measurement errors. In this talk, we will focus on the transportable strontium lattice clock we are developing and its first evaluation. Presently, we achieve a fractional frequency instability of 3 × 10-17 after 1000 s averaging time, which is equivalent to a height resolution of 30 cm. The first uncertainty evaluation of the system yielded 9 × 10-17. We expect rapid improvements to an uncertainty of few parts in 10-17. This clock will be connected via stabilized optical fibre links with other, stationary frequency standards. The measured red shifts will be compared with the ones calculated from potential differences derived with state of the art geodetic data and models. We will discuss the status of measurements of geodetic relevance with optical clocks and give an outlook on our next steps. This work is supported by QUEST, DFG (RTG 1729, CRC 1128), EU-FP7 (FACT) and EMRP (ITOC). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.

  12. Control system for electric power plant

    SciTech Connect

    McManus, K.L.; McManus, P.J.

    1988-11-29

    This patent describes a control system for a power plant. The power plant consists of a generator including means for producing a generator filed, a turbine for converting the flow of a fluid into mechanical power to drive the generator, a control means for regulating the flow of the fluid, a voltage regulator for controlling the generator field to thereby control the voltage produced by the generator, a bus, and a main circuit breaker for selectively connecting the generator to the bus, the control system comprising: nonvolatile memory means for storing configuration data comprising a plurality of configuration parameters for the power plants; input means for producing input data including data indicating a speed of the turbine, a position of the control means, a current and a voltage produced by the generator, a current and a voltage produced by the generator, a current and a voltage on the bus, and a position of the main circuit breaker; multitasking processing means for processing the input data in accordance with the configuration data, to thereby produce control signals including breaker signals for tripping and closing the main circuit breaker, voltage level signals for establishing a voltage setpoint for the voltage regulator, and a control signal for controlling the position of the control means and, edit means for enabling an operator to edit the configuration data, to thereby configure the control system for a particular power plant.

  13. Clock controls angiogenesis

    PubMed Central

    Jensen, Lasse Dahl; Cao, Yihai

    2013-01-01

    Circadian rhythms control multiple physiological and pathological processes, including embryonic development in mammals and development of various human diseases. We have recently, in a developing zebrafish embryonic model, discovered that the circadian oscillation controls developmental angiogenesis. Disruption of crucial circadian regulatory genes, including Bmal1 and Period2, results in marked impairment or enhancement of vascular development in zebrafish. At the molecular level, we show that the circadian regulator Bmal1 directly targets the promoter region of the vegf gene in zebrafish, leading to an elevated expression of VEGF. These findings can reasonably be extended to developmental angiogenesis in mammals and even pathological angiogenesis in humans. Thus, our findings, for the first time, shed new light on mechanisms that underlie circadian clock-regulated angiogenesis. PMID:23324349

  14. A Superfluid Clock

    NASA Technical Reports Server (NTRS)

    Penanen, Konstantin

    2004-01-01

    The performance of clocks is limited by the characteristics of the underlying oscillator. Both the quality factor of the oscillator and the signal-to-noise ratio for the resonator state measurement are important. A superfluid helium Helmholtz resonator operating at approx.100mK temperatures has the potential of maintaining frequency stability of 5x10(exp -15)/t(exp 1/2) on the time scale of a few months. The high dynamic range of lossless SQUID position displacement measurement, and low losses associated with the superfluid flow, combined with high mechanical stability of cryogenic assemblies, contribute to the projected stability. Low overall mass of the assembly allows for multiple stages of vibration isolation.

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

    PubMed

    Dubrovsky, Yulia V; Samsa, William E; Kondratov, Roman V

    2010-12-01

    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 mice, while maximum lifespan is reduced by more than 20%. CLOCK deficiency also results in the development of two age-specific pathologies in these mice, cataracts and dermatitis, at a much higher rate than in wild type mice. In contrast to BMAL1 deficient animals, Clock-/- mice do not develop a premature aging phenotype and do not develop the multiple age-associated pathologies characteristic of BMAL1 deficiency. Thus, although CLOCK and BMAL1 form a transcriptional complex, the physiological result of their deficiency is different. Our results suggest that CLOCK plays an important role in aging, specifically; CLOCK activity is critical for the regulation of normal physiology and aging of the lens and skin.

  16. Synthesis of Genetic Clock with Combinational Biologic Circuits.

    PubMed

    Chen, Po-Kuei; Lin, Chun-Liang

    2015-01-01

    The potential of genetic clock lies in its role to triggering logic reaction for sequential biological circuits. In general, biochemical reaction of the biological system is extremely slow. However, a square wave generator used as a genetic clock the transient response should be fast enough to catch the reaction change between two logic levels. Therefore, the requirement for instantaneous changes in logic status is not likely to exist in biological systems. This paper presents a method of synthesizing a genetic clock generator based on the combination of a toggle switch with two biological logic gates. A dual repressor is used to connect the two fundamental biologic circuits. Analysis of the characteristic responses of this genetic clock with its relation to the key parameters is provided. PMID:26451832

  17. Improving OFDR spatial resolution by reducing external clock sampling error

    NASA Astrophysics Data System (ADS)

    Feng, Bowen; Liu, Kun; Liu, Tiegen; Jiang, Junfeng; Du, Yang

    2016-03-01

    Utilizing an auxiliary interferometer to produce external clock signals as the data acquirement clock is widely used to compensate the nonlinearity of the tunable laser source (TLS) in optical frequency domain reflectometry (OFDR). However, this method is not always accurate because of the large optical length difference of both arms in the auxiliary interferometer. To investigate the deviation, we study the source and influence of the external clock sampling error in OFDR system. Based on the model, we find that the sampling error declines with the increase of the TLS's optical frequency tuning rate. The spatial resolution can be as high as 4.8 cm and the strain sensing location accuracy can be up to 0.15 m at the measurement length of 310 m under the minimum sampling error with the optical frequency tuning rate of 2500 GHz/s. Hence, the spatial resolution can be improved by reducing external clock sampling error in OFDR system.

  18. Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

    PubMed Central

    Lefta, Mellani; Wolff, Gretchen; Esser, Karyn A.

    2015-01-01

    Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At this time, very little is known about circadian aspects of skeletal muscle function/metabolism but some progress has been made on understanding the molecular clock in skeletal muscle. The goal of this chapter is to provide the basic terminology and concepts of circadian rhythms with a more detailed review of the current state of knowledge of the molecular clock, with reference to what is known in skeletal muscle. Research has demonstrated that the molecular clock is active in skeletal muscles and that the muscle-specific transcription factor, MyoD, is a direct target of the molecular clock. Skeletal muscle of clock-compromised mice, Bmal1−/− and ClockΔ19 mice, are weak and exhibit significant disruptions in expression of many genes required for adult muscle structure and metabolism. We suggest that the interaction between the molecular clock, MyoD, and metabolic factors, such as PGC-1, provide a potential system of feedback loops that may be critical for both maintenance and adaptation of skeletal muscle. PMID:21621073

  19. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

    Lefta, Mellani; Wolff, Gretchen; Esser, Karyn A

    2011-01-01

    Almost all organisms ranging from single cell bacteria to humans exhibit a variety of behavioral, physiological, and biochemical rhythms. In mammals, circadian rhythms control the timing of many physiological processes over a 24-h period, including sleep-wake cycles, body temperature, feeding, and hormone production. This body of research has led to defined characteristics of circadian rhythms based on period length, phase, and amplitude. Underlying circadian behaviors is a molecular clock mechanism found in most, if not all, cell types including skeletal muscle. The mammalian molecular clock is a complex of multiple oscillating networks that are regulated through transcriptional mechanisms, timed protein turnover, and input from small molecules. At this time, very little is known about circadian aspects of skeletal muscle function/metabolism but some progress has been made on understanding the molecular clock in skeletal muscle. The goal of this chapter is to provide the basic terminology and concepts of circadian rhythms with a more detailed review of the current state of knowledge of the molecular clock, with reference to what is known in skeletal muscle. Research has demonstrated that the molecular clock is active in skeletal muscles and that the muscle-specific transcription factor, MyoD, is a direct target of the molecular clock. Skeletal muscle of clock-compromised mice, Bmal1(-/-) and Clock(Δ19) mice, are weak and exhibit significant disruptions in expression of many genes required for adult muscle structure and metabolism. We suggest that the interaction between the molecular clock, MyoD, and metabolic factors, such as PGC-1, provide a potential system of feedback loops that may be critical for both maintenance and adaptation of skeletal muscle.

  20. Design and simulation of a plant control system for a GCFR demonstration plant

    SciTech Connect

    Estrine, E.A.; Greiner, H.G.

    1980-02-01

    A plant control system is being designed for a 300 MW(e) Gas Cooled Fast Breeder Reactor (GCFR) demonstration plant. Control analysis is being performed as an integral part of the plant design process to ensure that control requirements are satisfied as the plant design evolves. Plant models and simulations are being developed to generate information necessary to further define control system requirements for subsequent plant design iterations.

  1. A single-cell bioluminescence imaging system for monitoring cellular gene expression in a plant body.

    PubMed

    Muranaka, Tomoaki; Kubota, Saya; Oyama, Tokitaka

    2013-12-01

    Gene expression is a fundamental cellular process and expression dynamics are of great interest in life science. We succeeded in monitoring cellular gene expression in a duckweed plant, Lemna gibba, using bioluminescent reporters. Using particle bombardment, epidermal and mesophyll cells were transfected with the luciferase gene (luc+) under the control of a constitutive [Cauliflower mosaic virus 35S (CaMV35S)] and a rhythmic [Arabidopsis thaliana CIRCADIAN CLOCK ASSOCIATED 1 (AtCCA1)] promoter. Bioluminescence images were captured using an EM-CCD (electron multiply charged couple device) camera. Luminescent spots of the transfected cells in the plant body were quantitatively measured at the single-cell level. Luminescence intensities varied over a 1,000-fold range among CaMV35S::luc+-transfected cells in the same plant body and showed a log-normal-like frequency distribution. We monitored cellular gene expression under light-dark conditions by capturing bioluminescence images every hour. Luminescence traces of ≥50 individual cells in a frond were successfully obtained in each monitoring procedure. Rhythmic and constitutive luminescence behaviors were observed in cells transfected with AtCCA1::luc+ and CaMV35S::luc+, respectively. Diurnal rhythms were observed in every AtCCA1::luc+-introduced cell with traceable luminescence, and slight differences were detected in their rhythmic waveforms. Thus the single-cell bioluminescence monitoring system was useful for the characterization of cellular gene expression in a plant body. PMID:24058151

  2. A single-cell bioluminescence imaging system for monitoring cellular gene expression in a plant body.

    PubMed

    Muranaka, Tomoaki; Kubota, Saya; Oyama, Tokitaka

    2013-12-01

    Gene expression is a fundamental cellular process and expression dynamics are of great interest in life science. We succeeded in monitoring cellular gene expression in a duckweed plant, Lemna gibba, using bioluminescent reporters. Using particle bombardment, epidermal and mesophyll cells were transfected with the luciferase gene (luc+) under the control of a constitutive [Cauliflower mosaic virus 35S (CaMV35S)] and a rhythmic [Arabidopsis thaliana CIRCADIAN CLOCK ASSOCIATED 1 (AtCCA1)] promoter. Bioluminescence images were captured using an EM-CCD (electron multiply charged couple device) camera. Luminescent spots of the transfected cells in the plant body were quantitatively measured at the single-cell level. Luminescence intensities varied over a 1,000-fold range among CaMV35S::luc+-transfected cells in the same plant body and showed a log-normal-like frequency distribution. We monitored cellular gene expression under light-dark conditions by capturing bioluminescence images every hour. Luminescence traces of ≥50 individual cells in a frond were successfully obtained in each monitoring procedure. Rhythmic and constitutive luminescence behaviors were observed in cells transfected with AtCCA1::luc+ and CaMV35S::luc+, respectively. Diurnal rhythms were observed in every AtCCA1::luc+-introduced cell with traceable luminescence, and slight differences were detected in their rhythmic waveforms. Thus the single-cell bioluminescence monitoring system was useful for the characterization of cellular gene expression in a plant body.

  3. Catabolic cytokines disrupt the circadian clock and the expression of clock-controlled genes in cartilage via an NFкB-dependent pathway

    PubMed Central

    Guo, B.; Yang, N.; Borysiewicz, E.; Dudek, M.; Williams, J.L.; Li, J.; Maywood, E.S.; Adamson, A.; Hastings, M.H.; Bateman, J.F.; White, M.R.H.; Boot-Handford, R.P.; Meng, Q.J.

    2015-01-01

    Summary Objective To define how the catabolic cytokines (Interleukin 1 (IL-1) and tumor necrosis factor alpha (TNFα)) affect the circadian clock mechanism and the expression of clock-controlled catabolic genes within cartilage, and to identify the downstream pathways linking the cytokines to the molecular clock within chondrocytes. Methods Ex vivo cartilage explants were isolated from the Cry1-luc or PER2::LUC clock reporter mice. Clock gene dynamics were monitored in real-time by bioluminescence photon counting. Gene expression changes were studied by qRT-PCR. Functional luc assays were used to study the function of the core Clock/BMAL1 complex in SW-1353 cells. NFкB pathway inhibitor and fluorescence live-imaging of cartilage were performed to study the underlying mechanisms. Results Exposure to IL-1β severely disrupted circadian gene expression rhythms in cartilage. This effect was reversed by an anti-inflammatory drug dexamethasone, but not by other clock synchronizing agents. Circadian disruption mediated by IL-1β was accompanied by disregulated expression of endogenous clock genes and clock-controlled catabolic pathways. Mechanistically, NFкB signalling was involved in the effect of IL-1β on the cartilage clock in part through functional interference with the core Clock/BMAL1 complex. In contrast, TNFα had little impact on the circadian rhythm and clock gene expression in cartilage. Conclusion In our experimental system (young healthy mouse cartilage), we demonstrate that IL-1β (but not TNFα) abolishes circadian rhythms in Cry1-luc and PER2::LUC gene expression. These data implicate disruption of the chondrocyte clock as a novel aspect of the catabolic responses of cartilage to pro-inflammatory cytokines, and provide an additional mechanism for how chronic joint inflammation may contribute to osteoarthritis (OA). PMID:26521744

  4. Clock Genes in Glia Cells

    PubMed Central

    Chi-Castañeda, Donají

    2016-01-01

    Circadian rhythms are periodic patterns in biological processes that allow the organisms to anticipate changes in the environment. These rhythms are driven by the suprachiasmatic nucleus (SCN), the master circadian clock in vertebrates. At a molecular level, circadian rhythms are regulated by the so-called clock genes, which oscillate in a periodic manner. The protein products of clock genes are transcription factors that control their own and other genes’ transcription, collectively known as “clock-controlled genes.” Several brain regions other than the SCN express circadian rhythms of clock genes, including the amygdala, the olfactory bulb, the retina, and the cerebellum. Glia cells in these structures are expected to participate in rhythmicity. However, only certain types of glia cells may be called “glial clocks,” since they express PER-based circadian oscillators, which depend of the SCN for their synchronization. This contribution summarizes the current information about clock genes in glia cells, their plausible role as oscillators and their medical implications. PMID:27666286

  5. On-orbit frequency stability analysis of the GPS NAVSTAR 8 rubidium clock and NAVSTARS 9 and 10 cesium clocks. Memorandum report, January-December 1985

    SciTech Connect

    Buisson, J.A.; Largay, M.M.

    1987-09-17

    This report describes the on-orbit frequency stability performance analysis of the Global Positioning System (GPS) NAVSTAR 8 rubidium clock and the NAVSTARs 9 and 10 cesium clocks. Time-domain measurements, taken from three GPS monitor sites and from the United States Naval Observatory (USNO), were analyzed to determine the short and long-term frequency-stability performance of the NAVSTAR clocks. The data presented include measurements from 1985.

  6. Beyond Cannabis: Plants and the Endocannabinoid System.

    PubMed

    Russo, Ethan B

    2016-07-01

    Plants have been the predominant source of medicines throughout the vast majority of human history, and remain so today outside of industrialized societies. One of the most versatile in terms of its phytochemistry is cannabis, whose investigation has led directly to the discovery of a unique and widespread homeostatic physiological regulator, the endocannabinoid system. While it had been the conventional wisdom until recently that only cannabis harbored active agents affecting the endocannabinoid system, in recent decades the search has widened and identified numerous additional plants whose components stimulate, antagonize, or modulate different aspects of this system. These include common foodstuffs, herbs, spices, and more exotic ingredients: kava, chocolate, black pepper, and many others that are examined in this review. PMID:27179600

  7. Diagnostic system monitors gearboxes at hydro plant

    SciTech Connect

    1995-06-01

    This article describes how, by applying real-time, tooth-by-tooth vibration ``imaging,`` this system detects gear-tooth defects -- such as pitting and cracking. To keep Swan Falls hydroelectric generating station in service, Idaho Power Co constructed a new two-unit, open-pit-turbine powerhouse. Swan Falls, Kuna, Idaho, the oldest on the Snake River, services southern Idaho and parts of Oregon -- one of 17 hydroelectric plants maintained by the utility. The hydro units use speed increasers (gearboxes) so higher-speed generators are possible. To monitor these gearboxes, engineers at Swan Falls required a continuous on-line predictive maintenance system. The system monitors the planetary step-up gearboxes in the two main 12.5-MW pit turbine/generators. In some Idaho Power plants with a similar hydro turbine/generator design, the gearboxes have experienced major failures, leading to hundreds of thousands of dollars in collateral damage.

  8. A mercury optical lattice clock at LNE-SYRTE

    NASA Astrophysics Data System (ADS)

    De Sarlo, L.; Favier, M.; Tyumenev, R.; Bize, S.

    2016-06-01

    We describe the development of an optical lattice clock based on mercury and the results obtained since the 7 th SFSM. We briefly present a new solution for the cooling laser system and an improved lattice trap that allows us to interrogate a few thousand atoms in parallel. This translates into a fractional short term stability of 1.2 x 10-15 at the clock frequency of 1.129 PHz.

  9. Circadian clocks and breast cancer.

    PubMed

    Blakeman, Victoria; Williams, Jack L; Meng, Qing-Jun; Streuli, Charles H

    2016-01-01

    Circadian clocks respond to environmental time cues to coordinate 24-hour oscillations in almost every tissue of the body. In the breast, circadian clocks regulate the rhythmic expression of numerous genes. Disrupted expression of circadian genes can alter breast biology and may promote cancer. Here we overview circadian mechanisms, and the connection between the molecular clock and breast biology. We describe how disruption of circadian genes contributes to cancer via multiple mechanisms, and link this to increased tumour risk in women who work irregular shift patterns. Understanding the influence of circadian rhythms on breast cancer could lead to more efficacious therapies, reformed public health policy and improved patient outcome. PMID:27590298

  10. A model for plant lighting system selection

    NASA Technical Reports Server (NTRS)

    Ciolkosz, D. E.; Albright, L. D.; Sager, J. C.; Langhans, R. W.

    2002-01-01

    A decision model is presented that compares lighting systems for a plant growth scenario and chooses the most appropriate system from a given set of possible choices. The model utilizes a Multiple Attribute Utility Theory approach, and incorporates expert input and performance simulations to calculate a utility value for each lighting system being considered. The system with the highest utility is deemed the most appropriate system. The model was applied to a greenhouse scenario, and analyses were conducted to test the model's output for validity. Parameter variation indicates that the model performed as expected. Analysis of model output indicates that differences in utility among the candidate lighting systems were sufficiently large to give confidence that the model's order of selection was valid.

  11. Laser Ranging Experiment on Lunar Reconnaissance Orbiter: Clocks and Ranges

    NASA Astrophysics Data System (ADS)

    Mao, D.; Rowlands, D. D.; McGarry, J.; Zuber, M. T.; Smith, D. E.; Torrence, M. H.; Neumann, G. A.; Mazarico, E.; Sun, X.; Zagwodzki, T. W.; Cavanaugh, J. F.; Ramos-Izquierdo, L.

    2010-12-01

    Accurate ranges from Earth to the Lunar Reconnaissance Orbiter (LRO) spacecraft Laser Ranging (LR) system supplement the precision orbit determination (POD) of LRO. LRO is tracked by ten LR stations from the International Laser Ranging Service (ILRS), using H-maser, GPS steered Rb, and Cs standard oscillators as reference clocks. The LR system routinely makes one-way range measurements via laser time-of-flight from Earth to LRO. Uplink photons are received by a telescope mounted on the high-gain antenna on LRO , transferred through a fiber optic cable to the Lunar Orbiter Laser Altimeter (LOLA), and timed-tagged by the spacecraft clock. The range from the LR Earth station to LRO is derived from paired outgoing and received times. Accurate ranges can only be obtained after solving for both the spacecraft and ground station clock errors. The drift rate and aging rate of the LRO clock are calculated from data provided by the primary LR station, NASA's Next Generation Satellite Laser Ranging System (NGSLR) in Greenbelt, Maryland. The results confirm the LRO clock oscillator mid to long term stability measured during ground testing. These rates also agree well with those determined through POD. Simultaneous and near-simultaneous ranging to LRO from multiple LR stations in America, Europe, and Australia has been successfully achieved within a 10 hour window. Data analysis of these ranging experiments allows for precision modeling of the clock behaviors of each LR ground station and characterization of the station ground fire times.

  12. Applications of Clocks to Space Navigation & "Planetary GPS"

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.

    2004-01-01

    The ability to fly atomic clocks on GPS satellites has profoundly defined the capabilities and limitations of GPS in near-Earth applications. It is likely that future infrastructure for Lunar and Mars applications will be constrained by financial factors. The development of a low cost, small, high performance space clock -- or ultrahigh performance space clocks -- could revolutionize and drive the entire approach to GPS-like systems at the Moon (or Mars), and possibly even change the future of GPS at Earth. Many system trade studies are required. The performance of future GPS-like tracking systems at the Moon or Mars will depend critically on clock performance, availability of inertial sensors, and constellation coverage. Example: present-day GPS carry 10(exp -13) clocks and require several updates per day. With 10(exp -15) clocks, a constellation at Mars could operate autonomously with updates just once per month. Use of GPS tracking at the Moon should be evaluated in a technical study.

  13. Clock auto-synchronization method for BESIII ETOF upgrade

    NASA Astrophysics Data System (ADS)

    Wang, Si-Yu; Cao, Ping; Liu, Shu-Bin; An, Qi

    2015-12-01

    An automatic clock synchronization method implemented in a field programmable gate array (FPGA) is proposed in this paper. It is developed for the clock system which will be applied in the end-cap time of flight (ETOF) upgrade of the Beijing Spectrometer (BESIII). In this design, an FPGA is used to automatically monitor the synchronization circuit and deal with signals coming from the external clock synchronization circuit. By testing different delay time of the detection signal and analyzing the signal state returned, the synchronization windows can be found automatically by the FPGA. The new clock system not only retains low clock jitter which is less than 20ps root mean square (RMS), but also demonstrates automatic synchronization to the beam bunches. So far, the clock auto-synchronizing function has been working successfully under a series of tests. It will greatly simplify the system initialization and maintenance in the future. Supported by National Natural Science Foundation of China (10979003, 11005107), CAS Center for Excellence in Particle Physics (CCEPP)

  14. Energy requirements for tillage-planting systems

    SciTech Connect

    Griffith, D.R.; Parsons, s.D.

    1981-01-01

    Fuel saved by omitting field operations or changing to operations with lower power requirements is easily understood and can be measured directly or estimated from research data. However, several other energy consuming inputs may be altered by changing tillage practices: the type and amount of pesticides required, the form and amount of fertilizer applied; and the particular equipment used. these other energy components are frequently overlooked because they are not easily defined and not highly visible at the arm level. They may, however, tip the energy balance in favor of one tillage-planting system over another when comparing the total energy burden on society. this paper attempts to put these various energy components into perspective as they relate to the selection of a tillage-planting system for corn and soybean production. 15 refs.

  15. Waste receiving and processing plant control system; system design description

    SciTech Connect

    LANE, M.P.

    1999-02-24

    The Plant Control System (PCS) is a heterogeneous computer system composed of numerous sub-systems. The PCS represents every major computer system that is used to support operation of the Waste Receiving and Processing (WRAP) facility. This document, the System Design Description (PCS SDD), includes several chapters and appendices. Each chapter is devoted to a separate PCS sub-system. Typically, each chapter includes an overview description of the system, a list of associated documents related to operation of that system, and a detailed description of relevant system features. Each appendice provides configuration information for selected PCS sub-systems. The appendices are designed as separate sections to assist in maintaining this document due to frequent changes in system configurations. This document is intended to serve as the primary reference for configuration of PCS computer systems. The use of this document is further described in the WRAP System Configuration Management Plan, WMH-350, Section 4.1.

  16. Synthesising gene clock with toggle switch and oscillator.

    PubMed

    Lin, Chun-Liang; Chen, Po-Kuei; Cheng, Young-Yi

    2015-06-01

    The usefulness of a genetic clock lies in its role to stimulate a sequence of logic reactions for sequential biological circuits. A clock signal is a periodic square wave, its amplitude alternates at a steady frequency between fixed minimal and maximal levels. Transition between the minimum and the maximum is instantaneous for an ideal square wave; however, the function is unrealisable in physical bio-systems. This research develops a new genetic clock generator based on a genetic oscillator, in which, a sine wave generator is adopted as a signal oscillator. It is shown that combination of a genetic oscillator with a toggle switch is able to generate clock signals forming an efficient way to generate a near square wave. In silico study confirms the proposed idea. PMID:26021329

  17. NAVEX: A space shuttle experiment with atomic clocks

    NASA Technical Reports Server (NTRS)

    Starker, S.; Nau, H.; Hamesfahr, J.; Tschiesche, H.

    1983-01-01

    A navigation and time transfer experiment (NAVEX) to be flown within the payload of the first German Spacelab mission D-1 is discussed. The objectives of the experiment are to synchronize distant ground stations with an accuracy of better than 10 nsec and to demonstrate one way ranging with an accuracy of better than 30 m. Spread spectrum signals are used and the related technique is tested. On board a Cs and a Rb clock is used. The relativistic effect of these clocks is about -25 microsec per day. On the ground at least two receiving stations and one transmitting-receiving station will be installed. The synchronization of the ground clocks by shuttle signals is compared to those achieved with clock transportations and with GPS measurements. A system description of this experiment is given containing details on the technical concept, the hardware and the planned data evaluation. The present state of the preparatory work is briefly reviewed.

  18. Recent progress of neutral mercury lattice clock in SIOM

    NASA Astrophysics Data System (ADS)

    Zhao, R. C.; Fu, X. H.; Liu, K. K.; Gou, W.; Sun, J. F.; Xu, Z.; Wang, Y. Z.

    2016-06-01

    Neutral mercury atom is one of good candidates of optical lattice clock. Due to its large atomic number, mercury atom is insensitive to black body radiation, which is the severe limitation for the development of optical clocks. However, the challenge of neutral mercury lattice clock is the requirement of high power deep-UV lasers, especially for both the cooling laser and the lattice laser. Here, we report the recent progress of neutral mercury lattice clock in SIOM, including the development for laser cooling of mercury atom and the cooling laser system with fiber laser amplifier. We have realized the magneto-optical trap of mercury atoms and measured the parameters of cold mercury atoms. A home-made external cavity diode laser works as a seed laser for a room temperature 1014.8 nm fiber laser amplifier. A new efficient frequency-doubling cavity from 1015 nm to 507 nm has been developed.

  19. Synthesising gene clock with toggle switch and oscillator.

    PubMed

    Lin, Chun-Liang; Chen, Po-Kuei; Cheng, Young-Yi

    2015-06-01

    The usefulness of a genetic clock lies in its role to stimulate a sequence of logic reactions for sequential biological circuits. A clock signal is a periodic square wave, its amplitude alternates at a steady frequency between fixed minimal and maximal levels. Transition between the minimum and the maximum is instantaneous for an ideal square wave; however, the function is unrealisable in physical bio-systems. This research develops a new genetic clock generator based on a genetic oscillator, in which, a sine wave generator is adopted as a signal oscillator. It is shown that combination of a genetic oscillator with a toggle switch is able to generate clock signals forming an efficient way to generate a near square wave. In silico study confirms the proposed idea.

  20. Diurnal expression of functional and clock-related genes throughout the rat HPA axis: system-wide shifts in response to a restricted feeding schedule.

    PubMed

    Girotti, Milena; Weinberg, Marc S; Spencer, Robert L

    2009-04-01

    The diurnal rhythm of glucocorticoid secretion depends on the suprachiasmatic (SCN) and dorsomedial (putative food-entrainable oscillator; FEO) nuclei of the hypothalamus, two brain regions critical for coordination of physiological responses to photoperiod and feeding cues, respectively. In both cases, time keeping relies upon diurnal oscillations in clock gene (per1, per2, and bmal) expression. Glucocorticoids may play a key role in synchronization of the rest of the body to photoperiod and food availability. Thus glucocorticoid secretion may be both a target and an important effector of SCN and FEO output. Remarkably little, however, is known about the functional diurnal rhythms of the individual components of the hypothalamic-pituitary-adrenal (HPA) axis. We examined the 24-h pattern of hormonal secretion (ACTH and corticosterone), functional gene expression (c-fos, crh, pomc, star), and clock gene expression (per1, per2 and bmal) in each compartment of the HPA axis under a 12:12-h light-dark cycle and compared with relevant SCN gene expression. We found that each anatomic component of the HPA axis has a unique circadian signature of functional and clock gene expression. We then tested the susceptibility of these measures to nonphotic entrainment cues by restricting food availability to only a portion of the light phase of a 12:12-h light-dark cycle. Restricted feeding is a strong zeitgeber that can dramatically alter functional and clock gene expression at all levels of the HPA axis, despite ongoing photoperiod cues and only minor changes in SCN clock gene expression. Thus the HPA axis may be an important mediator of the body entrainment to the FEO.

  1. Physical Time and Thermal Clocks

    NASA Astrophysics Data System (ADS)

    Borghi, Claudio

    2016-10-01

    In this paper I discuss the concept of time in physics. I consider the thermal time hypothesis and I claim that thermal clocks and atomic clocks measure different physical times, whereby thermal time and relativistic time are not compatible with each other. This hypothesis opens the possibility of a new foundation of the theory of physical time, and new perspectives in theoretical and philosophical researches.

  2. Stochastic models for atomic clocks

    NASA Technical Reports Server (NTRS)

    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.

  3. Physical Time and Thermal Clocks

    NASA Astrophysics Data System (ADS)

    Borghi, Claudio

    2016-07-01

    In this paper I discuss the concept of time in physics. I consider the thermal time hypothesis and I claim that thermal clocks and atomic clocks measure different physical times, whereby thermal time and relativistic time are not compatible with each other. This hypothesis opens the possibility of a new foundation of the theory of physical time, and new perspectives in theoretical and philosophical researches.

  4. Molecular Clocks and the Human Condition

    PubMed Central

    FitzGerald, G.A.; Yang, G; Paschos, G.K.; Liang, X.; Skarke, C.

    2015-01-01

    Molecular clockworks knit together diverse biological networks and compelling evidence from model systems infers their importance in metabolism, immunological and cardiovascular function. Despite this and the diurnal variation in many aspects of human physiology and the phenotypic expression of disease, our understanding of the role and importance of clock function and dysfunction in humans is modest. There are tantalizing hints of connection across the translational divide and some correlative evidence of gene variation and human disease but most of what we know derives from forced desynchrony protocols in controlled environments. We now have the ability to monitor quantitatively ex vivo or in vivo the genome, metabolome, proteome and microbiome of humans in the wild. Combining this capability, with the power of mobile telephony and the evolution of remote sensing affords a new opportunity for deep phenotyping, including the characterization of diurnal behavior and the assessment of the impact of the clock on approved drug function. PMID:26332979

  5. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

    Harfmann, Brianna D; Schroder, Elizabeth A; Esser, Karyn A

    2015-04-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle. PMID:25512305

  6. Circadian Rhythms, the Molecular Clock, and Skeletal Muscle

    PubMed Central

    Harfmann, Brianna D.; Schroder, Elizabeth A.; Esser, Karyn A.

    2015-01-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle. PMID:25512305

  7. Circadian rhythms, the molecular clock, and skeletal muscle.

    PubMed

    Harfmann, Brianna D; Schroder, Elizabeth A; Esser, Karyn A

    2015-04-01

    Circadian rhythms are the approximate 24-h biological cycles that function to prepare an organism for daily environmental changes. They are driven by the molecular clock, a transcriptional:translational feedback mechanism that in mammals involves the core clock genes Bmal1, Clock, Per1/2, and Cry1/2. The molecular clock is present in virtually all cells of an organism. The central clock in the suprachiasmatic nucleus (SCN) has been well studied, but the clocks in the peripheral tissues, such as heart and skeletal muscle, have just begun to be investigated. Skeletal muscle is one of the largest organs in the body, comprising approximately 45% of total body mass. More than 2300 genes in skeletal muscle are expressed in a circadian pattern, and these genes participate in a wide range of functions, including myogenesis, transcription, and metabolism. The circadian rhythms of skeletal muscle can be entrained both indirectly through light input to the SCN and directly through time of feeding and activity. It is critical for the skeletal muscle molecular clock not only to be entrained to the environment but also to be in synchrony with rhythms of other tissues. When circadian rhythms are disrupted, the observed effects on skeletal muscle include fiber-type shifts, altered sarcomeric structure, reduced mitochondrial respiration, and impaired muscle function. Furthermore, there are detrimental effects on metabolic health, including impaired glucose tolerance and insulin sensitivity, which skeletal muscle likely contributes to considering it is a key metabolic tissue. These data indicate a critical role for skeletal muscle circadian rhythms for both muscle and systems health. Future research is needed to determine the mechanisms of molecular clock function in skeletal muscle, identify the means by which skeletal muscle entrainment occurs, and provide a stringent comparison of circadian gene expression across the diverse tissue system of skeletal muscle.

  8. Entrainment of circadian clocks in mammals by arousal and food.

    PubMed

    Mistlberger, Ralph E; Antle, Michael C

    2011-06-30

    Circadian rhythms in mammals are regulated by a system of endogenous circadian oscillators (clock cells) in the brain and in most peripheral organs and tissues. One group of clock cells in the hypothalamic SCN (suprachiasmatic nuclei) functions as a pacemaker for co-ordinating the timing of oscillators elsewhere in the brain and body. This master clock can be reset and entrained by daily LD (light-dark) cycles and thereby also serves to interface internal with external time, ensuring an appropriate alignment of behavioural and physiological rhythms with the solar day. Two features of the mammalian circadian system provide flexibility in circadian programming to exploit temporal regularities of social stimuli or food availability. One feature is the sensitivity of the SCN pacemaker to behavioural arousal stimulated during the usual sleep period, which can reset its phase and modulate its response to LD stimuli. Neural pathways from the brainstem and thalamus mediate these effects by releasing neurochemicals that inhibit retinal inputs to the SCN clock or that alter clock-gene expression in SCN clock cells. A second feature is the sensitivity of circadian oscillators outside of the SCN to stimuli associated with food intake, which enables animals to uncouple rhythms of behaviour and physiology from LD cycles and align these with predictable daily mealtimes. The location of oscillators necessary for food-entrained behavioural rhythms is not yet certain. Persistence of these rhythms in mice with clock-gene mutations that disable the SCN pacemaker suggests diversity in the molecular basis of light- and food-entrainable clocks. PMID:21819388

  9. 22. TIME CLOCK AREA, WITH LUNCH ROOM IN DISTANCE. RAIL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. TIME CLOCK AREA, WITH LUNCH ROOM IN DISTANCE. RAIL SPUR FOLDING DOORS ARE HIDDEN BEHIND OFFICE AT PHOTO CENTER. VIEW TO EAST-NORTHEAST. - Ford Motor Company Long Beach Assembly Plant, Assembly Building, 700 Henry Ford Avenue, Long Beach, Los Angeles County, CA

  10. System identification of the Arabidopsis plant circadian system

    NASA Astrophysics Data System (ADS)

    Foo, Mathias; Somers, David E.; Kim, Pan-Jun

    2015-02-01

    The circadian system generates an endogenous oscillatory rhythm that governs the daily activities of organisms in nature. It offers adaptive advantages to organisms through a coordination of their biological functions with the optimal time of day. In this paper, a model of the circadian system in the plant Arabidopsis (species thaliana) is built by using system identification techniques. Prior knowledge about the physical interactions of the genes and the proteins in the plant circadian system is incorporated in the model building exercise. The model is built by using primarily experimentally-verified direct interactions between the genes and the proteins with the available data on mRNA and protein abundances from the circadian system. Our analysis reveals a great performance of the model in predicting the dynamics of the plant circadian system through the effect of diverse internal and external perturbations (gene knockouts and day-length changes). Furthermore, we found that the circadian oscillatory rhythm is robust and does not vary much with the biochemical parameters except those of a light-sensitive protein P and a transcription factor TOC1. In other words, the circadian rhythmic profile is largely a consequence of the network's architecture rather than its particular parameters. Our work suggests that the current experimental knowledge of the gene-to-protein interactions in the plant Arabidopsis, without considering any additional hypothetical interactions, seems to suffice for system-level modeling of the circadian system of this plant and to present an exemplary platform for the control of network dynamics in complex living organisms.

  11. A hydroponic system for microgravity plant experiments

    NASA Technical Reports Server (NTRS)

    Wright, B. D.; Bausch, W. C.; Knott, W. M.

    1988-01-01

    The construction of a permanently manned space station will provide the opportunity to grow plants for weeks or months in orbit for experiments or food production. With this opportunity comes the need for a method to provide plants with a continuous supply of water and nutrients in microgravity. The Capillary Effect Root Environment System (CERES) uses capillary forces to maintain control of circulating plant nutrient solution in the weightless environment of an orbiting spacecraft. The nutrient solution is maintained at a pressure slightly less than the ambient air pressure while it flows on one side of a porous membrane. The root, on the other side of the membrane, is surrounded by a thin film of nutrient solution where it contacts the moist surface of the membrane. The root is provided with water, nutrients and air simultaneously. Air bubbles in the nutrient solution are removed using a hydrophobic/hydrophilic membrane system. A model scaled to the size necessary for flight hardware to test CERES in the space shuttle was constructed.

  12. Tissue-intrinsic dysfunction of circadian clock confers transplant arteriosclerosis.

    PubMed

    Cheng, Bo; Anea, Ciprian B; Yao, Lin; Chen, Feng; Patel, Vijay; Merloiu, Ana; Pati, Paramita; Caldwell, R William; Fulton, David J; Rudic, R Daniel

    2011-10-11

    The suprachiasmatic nucleus of the brain is the circadian center, relaying rhythmic environmental and behavioral information to peripheral tissues to control circadian physiology. As such, central clock dysfunction can alter systemic homeostasis to consequently impair peripheral physiology in a manner that is secondary to circadian malfunction. To determine the impact of circadian clock function in organ transplantation and dissect the influence of intrinsic tissue clocks versus extrinsic clocks, we implemented a blood vessel grafting approach to surgically assemble a chimeric mouse that was part wild-type (WT) and part circadian clock mutant. Arterial isografts from donor WT mice that had been anastamosed to common carotid arteries of recipient WT mice (WT:WT) exhibited no pathology in this syngeneic transplant strategy. Similarly, when WT grafts were anastamosed to mice with disrupted circadian clocks, the structural features of the WT grafts immersed in the milieu of circadian malfunction were normal and absent of lesions, comparable to WT:WT grafts. In contrast, aortic grafts from Bmal1 knockout (KO) or Period-2,3 double-KO mice transplanted into littermate control WT mice developed robust arteriosclerotic disease. These lesions observed in donor grafts of Bmal1-KO were associated with up-regulation in T-cell receptors, macrophages, and infiltrating cells in the vascular grafts, but were independent of hemodynamics and B and T cell-mediated immunity. These data demonstrate the significance of intrinsic tissue clocks as an autonomous influence in experimental models of arteriosclerotic disease, which may have implications with regard to the influence of circadian clock function in organ transplantation.

  13. Plant Metabolomics: An Indispensable System Biology Tool for Plant Science.

    PubMed

    Hong, Jun; Yang, Litao; Zhang, Dabing; Shi, Jianxin

    2016-01-01

    As genomes of many plant species have been sequenced, demand for functional genomics has dramatically accelerated the improvement of other omics including metabolomics. Despite a large amount of metabolites still remaining to be identified, metabolomics has contributed significantly not only to the understanding of plant physiology and biology from the view of small chemical molecules that reflect the end point of biological activities, but also in past decades to the attempts to improve plant behavior under both normal and stressed conditions. Hereby, we summarize the current knowledge on the genetic and biochemical mechanisms underlying plant growth, development, and stress responses, focusing further on the contributions of metabolomics to practical applications in crop quality improvement and food safety assessment, as well as plant metabolic engineering. We also highlight the current challenges and future perspectives in this inspiring area, with the aim to stimulate further studies leading to better crop improvement of yield and quality. PMID:27258266

  14. Plant Metabolomics: An Indispensable System Biology Tool for Plant Science

    PubMed Central

    Hong, Jun; Yang, Litao; Zhang, Dabing; Shi, Jianxin

    2016-01-01

    As genomes of many plant species have been sequenced, demand for functional genomics has dramatically accelerated the improvement of other omics including metabolomics. Despite a large amount of metabolites still remaining to be identified, metabolomics has contributed significantly not only to the understanding of plant physiology and biology from the view of small chemical molecules that reflect the end point of biological activities, but also in past decades to the attempts to improve plant behavior under both normal and stressed conditions. Hereby, we summarize the current knowledge on the genetic and biochemical mechanisms underlying plant growth, development, and stress responses, focusing further on the contributions of metabolomics to practical applications in crop quality improvement and food safety assessment, as well as plant metabolic engineering. We also highlight the current challenges and future perspectives in this inspiring area, with the aim to stimulate further studies leading to better crop improvement of yield and quality. PMID:27258266

  15. Plant Metabolomics: An Indispensable System Biology Tool for Plant Science.

    PubMed

    Hong, Jun; Yang, Litao; Zhang, Dabing; Shi, Jianxin

    2016-01-01

    As genomes of many plant species have been sequenced, demand for functional genomics has dramatically accelerated the improvement of other omics including metabolomics. Despite a large amount of metabolites still remaining to be identified, metabolomics has contributed significantly not only to the understanding of plant physiology and biology from the view of small chemical molecules that reflect the end point of biological activities, but also in past decades to the attempts to improve plant behavior under both normal and stressed conditions. Hereby, we summarize the current knowledge on the genetic and biochemical mechanisms underlying plant growth, development, and stress responses, focusing further on the contributions of metabolomics to practical applications in crop quality improvement and food safety assessment, as well as plant metabolic engineering. We also highlight the current challenges and future perspectives in this inspiring area, with the aim to stimulate further studies leading to better crop improvement of yield and quality.

  16. Human skeletal myotubes display a cell-autonomous circadian clock implicated in basal myokine secretion

    PubMed Central

    Perrin, Laurent; Loizides-Mangold, Ursula; Skarupelova, Svetlana; Pulimeno, Pamela; Chanon, Stephanie; Robert, Maud; Bouzakri, Karim; Modoux, Christine; Roux-Lombard, Pascale; Vidal, Hubert; Lefai, Etienne; Dibner, Charna

    2015-01-01

    Objective Circadian clocks are functional in all light-sensitive organisms, allowing an adaptation to the external world in anticipation of daily environmental changes. In view of the potential role of the skeletal muscle clock in the regulation of glucose metabolism, we aimed to characterize circadian rhythms in primary human skeletal myotubes and investigate their roles in myokine secretion. Methods We established a system for long-term bioluminescence recording in differentiated human myotubes, employing lentivector gene delivery of the Bmal1-luciferase and Per2-luciferase core clock reporters. Furthermore, we disrupted the circadian clock in skeletal muscle cells by transfecting siRNA targeting CLOCK. Next, we assessed the basal secretion of a large panel of myokines in a circadian manner in the presence or absence of a functional clock. Results Bioluminescence reporter assays revealed that human skeletal myotubes, synchronized in vitro, exhibit a self-sustained circadian rhythm, which was further confirmed by endogenous core clock transcript expression. Moreover, we demonstrate that the basal secretion of IL-6, IL-8 and MCP-1 by synchronized skeletal myotubes has a circadian profile. Importantly, the secretion of IL-6 and several additional myokines was strongly downregulated upon siClock-mediated clock disruption. Conclusions Our study provides for the first time evidence that primary human skeletal myotubes possess a high-amplitude cell-autonomous circadian clock, which could be attenuated. Furthermore, this oscillator plays an important role in the regulation of basal myokine secretion by skeletal myotubes. PMID:26629407

  17. Quantum arrival and dwell times via idealized clocks

    SciTech Connect

    Yearsley, J. M.; Downs, D. A.; Halliwell, J. J.; Hashagen, A. K.

    2011-08-15

    A number of approaches to the problem of defining arrival- and dwell-time probabilities in quantum theory makes use of idealized models of clocks. An interesting question is the extent to which the probabilities obtained in this way are related to standard semiclassical results. In this paper, we explore this question using a reasonably general clock model, solved using path-integral methods. We find that, in the weak-coupling regime, where the energy of the clock is much less than the energy of the particle it is measuring, the probability for the clock pointer can be expressed in terms of the probability current in the case of arrival times, and the dwell-time operator in the case of dwell times, the expected semiclassical results. In the regime of strong system-clock coupling, we find that the arrival-time probability is proportional to the kinetic-energy density, consistent with an earlier model involving a complex potential. We argue that, properly normalized, this may be the generically expected result in this regime. We show that these conclusions are largely independent of the form of the clock Hamiltonian.

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

    PubMed Central

    Udoh, Uduak S.; Valcin, Jennifer A.; Gamble, Karen L.; Bailey, Shannon M.

    2015-01-01

    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. PMID:26473939

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

    PubMed

    Udoh, Uduak S; Valcin, Jennifer A; Gamble, Karen L; Bailey, Shannon M

    2015-10-14

    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.

  20. Orthometric height determination using optical clocks

    NASA Astrophysics Data System (ADS)

    Shen, WenBin

    2013-04-01

    General relativity theory predicts that there exists a gravity frequency shift (gravitational red shift) if an electromagnetic signal propagates from one point to another point, and the frequency shift depends on the geopotential difference between these two points. Inversely, by measuring the gravity frequency shift between arbitrary two points we may determine the geopotential and consequently the orthometric height difference between these two points. To improve our previous investigations (Shen and Peng 2012), the present study provides further foundation of the optical-fiber frequency transfer approach (OFTA; Shen and Peng 2012) and describes in details how to determine the orthometric height between two points using optical clocks via optical fiber. Optical clocks have achieved a stability of 10E-17 to 10E-18. In another aspect, remote optical fiber communication (e.g. Predehl et al. 2012) demonstrates a frequency comparison accuracy at the level of 10E-18 (or better), which is equivalent to a height variation of 1cm. The quick development of time-frequency science, including the high-precise optical clocks, provides potential of determining the orthometric height between arbitrary two points which are connected by optical fiber. This study suggests that determining the orthometric height difference between two points using optical clocks via optical fiber frequency transfer communication technique is prospective and potential. The realization of the OFTA may greatly contribute to the unification of the world height system (WHS). This work was supported partly by the NSFC (grant No. 41174011), National 973 Project China (grant No. 2013CB733305), NSFC (grant No. 41210006, 41128003, 41021061, 40974015).

  1. Atomic clocks with suppressed blackbody radiation shift.

    PubMed

    Yudin, V I; Taichenachev, A V; Okhapkin, M V; Bagayev, S N; Tamm, Chr; Peik, E; Huntemann, N; Mehlstäubler, T E; Riehle, F

    2011-07-15

    We develop a concept of atomic clocks where the blackbody radiation shift and its fluctuations can be suppressed by 1-3 orders of magnitude independent of the environmental temperature. The suppression is based on the fact that in a system with two accessible clock transitions (with frequencies ν1 and ν2) which are exposed to the same thermal environment, there exists a "synthetic" frequency ν(syn) ∝ (ν1 - ε12ν2) largely immune to the blackbody radiation shift. For example, in the case of 171Yb+ it is possible to create a synthetic-frequency-based clock in which the fractional blackbody radiation shift can be suppressed to the level of 10(-18) in a broad interval near room temperature (300±15  K). We also propose a realization of our method with the use of an optical frequency comb generator stabilized to both frequencies ν1 and ν2, where the frequency ν(syn) is generated as one of the components of the comb spectrum.

  2. Into the Evening: Complex Interactions in the Arabidopsis Circadian Clock.

    PubMed

    Huang, He; Nusinow, Dmitri A

    2016-10-01

    In Arabidopsis thaliana an assembly of proteins named the evening complex (EC) has been established as an essential component of the circadian clock with conserved functions in regulating plant growth and development. Recent studies identifying EC-regulated genes and EC-interacting proteins have expanded our understanding of EC function. In this review we focus on new progress uncovering how the EC contributes to the circadian network through the integration of environmental inputs and the direct regulation of key clock genes. We also summarize new findings of how the EC directly regulates clock outputs, such as photoperiodic and thermoresponsive growth, and provide new perspectives on future experiments to address unsolved questions related to the EC. PMID:27594171

  3. Hydrogen Maser Clock (HMC) Experiment

    NASA Technical Reports Server (NTRS)

    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.

  4. Melatonin: both master clock output and internal time-giver in the circadian clocks network.

    PubMed

    Pevet, Paul; Challet, Etienne

    2011-12-01

    Daily rhythms in physiological and behavioral processes are controlled by a network of circadian clocks, reset by inputs and delivering circadian signals to the brain and peripheral organs. In mammals, at the top of the network is a master clock located in the suprachiasmatic nuclei (SCN) of the hypothalamus, mainly reset by ambient light. The nocturnal synthesis and release of melatonin by the pineal gland are tightly controlled by the SCN clock and inhibited by light exposure. Several roles of melatonin in the circadian system have been identified. As a major hormonal output, melatonin distributes temporal cues generated by the SCN to the multitude of tissue targets expressing melatonin receptors. In some target structures, like the Pars tuberalis of the adenohypophysis, these melatonin signals can drive daily rhythmicity that would otherwise be lacking. In other target structures, melatonin signals are used for the synchronization (i.e., adjustment of the timing of existing oscillations) of peripheral oscillators, such as the fetal adrenal gland. Due to the expression of melatonin receptors in the SCN, endogenous melatonin is also able to feedback onto the master clock, although its physiological significance needs further characterization. Of note, pharmacological treatment with exogenous melatonin can synchronize the SCN clock. From a clinical point of view, provided that the subject is not exposed to light at night, the daily profile of circulating melatonin provides a reliable estimate of the timing of the human SCN. During the past decade, a number of melatonin agonists have been developed for treating circadian, psychiatric and sleep disorders. These drugs may target the SCN for improving circadian timing or act indirectly at some downstream level of the circadian network to restore proper internal synchronization.

  5. Biomass Production System (BPS) Plant Growth Unit

    NASA Astrophysics Data System (ADS)

    Morrow, R. C.; Crabb, T. M.

    The Biomass Production System (BPS) was developed under the Small Business Innovative Research (SBIR) program to meet science, biotechnology and commercial plant growth needs in the Space Station era. The BPS is equivalent in size to a double middeck locker, but uses it's own custom enclosure with a slide out structure to which internal components mount. The BPS contains four internal growth chambers, each with a growing volume of more than 4 liters. Each of the growth chambers has active nutrient delivery, and independent control of temperature, humidity, lighting, and CO2 set-points. Temperature control is achieved using a thermoelectric heat exchanger system. Humidity control is achieved using a heat exchanger with a porous interface which can both humidify and dehumidify. The control software utilizes fuzzy logic for nonlinear, coupled temperature and humidity control. The fluorescent lighting system can be dimmed to provide a range of light levels. CO2 levels are controlled by injecting pure CO2 to the system based on input from an infrared gas analyzer. The unit currently does not scrub CO2, but has been designed to accept scrubber cartridges. In addition to providing environmental control, a number of features are included to facilitate science. The BPS chambers are sealed to allow CO2 and water vapor exchange measurements. The plant chambers can be removed to allow manipulation or sampling of specimens, and each chamber has gas/fluid sample ports. A video camera is provided for each chamber, and frame-grabs and complete environmental data for all science and hardware system sensors are stored on an internal hard drive. Data files can also be transferred to 3.5-inch disks using the front panel disk drive

  6. Biomass Production System (BPS) plant growth unit.

    PubMed

    Morrow, R C; Crabb, T M

    2000-01-01

    The Biomass Production System (BPS) was developed under the Small Business Innovative Research (SBIR) program to meet science, biotechnology and commercial plant growth needs in the Space Station era. The BPS is equivalent in size to a double middeck locker, but uses its own custom enclosure with a slide out structure to which internal components mount. The BPS contains four internal growth chambers, each with a growing volume of more than 4 liters. Each of the growth chambers has active nutrient delivery, and independent control of temperature, humidity, lighting, and CO2 set-points. Temperature control is achieved using a thermoelectric heat exchanger system. Humidity control is achieved using a heat exchanger with a porous interface which can both humidify and dehumidify. The control software utilizes fuzzy logic for nonlinear, coupled temperature and humidity control. The fluorescent lighting system can be dimmed to provide a range of light levels. CO2 levels are controlled by injecting pure CO2 to the system based on input from an infrared gas analyzer. The unit currently does not scrub CO2, but has been designed to accept scrubber cartridges. In addition to providing environmental control, a number of features are included to facilitate science. The BPS chambers are sealed to allow CO2 and water vapor exchange measurements. The plant chambers can be removed to allow manipulation or sampling of specimens, and each chamber has gas/fluid sample ports. A video camera is provided for each chamber, and frame-grabs and complete environmental data for all science and hardware system sensors are stored on an internal hard drive. Data files can also be transferred to 3.5-inch disks using the front panel disk drive. PMID:11543164

  7. Biological clocks: mechanisms and developments.

    PubMed

    Nongkynrih, P; Sharma, V K

    1992-05-15

    Almost all organisms ranging from unicellular protists to mammals were found to show biological rhythms. Many workers have performed various kinds of experiment to understand the mechanism as well as to find the origin of the clock responsible for these rhythms. However, there is no doubt about the existence of a biologically controlled clock in almost all organisms; yet its origin and mechanism still remain a mystery. Many theories have been put forward to explain the mechanism of these biological clocks and it seems that the cell membrane may play a key role. The existence of a very high electric field of the order of 10(5) V cm-1 across the cell membrane may have some role in the mechanism of the biological clock. Of all the factors which have the effects on biological rhythms, light and temperature are found to be the most common. Also, the study of these biological clocks can help to solve the sleeping problems of international travellers and shift workers as well as to improve diagnosis, cure and prevention from diseases.

  8. A tale of a clock

    NASA Astrophysics Data System (ADS)

    Crook, A. W.

    2001-09-01

    A computer model has been constructed of a long case clock standing on a resilient surface, or within a case of impaired shear stiffness, whereby the head of the clock rocks in response to the swinging of its pendulum. The equations of motion are written in matrix form, and are solved by matrix inversion. The model accounts for the tendency of such a clock to stop when its driving weight has descended to about the level of the bob of the pendulum. The model predicts that the lengthening of the suspension of the weight by insertion of a link would permit the clock to run on until the weight becomes grounded. It also predicts that use of the chiming weight as a resonant absorber, by hanging it from a tuned suspension of fixed length, not only allows such a clock to run for the full term of a wind, but improves the constancy of its rate. The effects of a link, and of the resonant absorber, have been verified experimentally.

  9. Closing the circadian loop: CLOCK-induced transcription of its own inhibitors per and tim.

    PubMed

    Darlington, T K; Wager-Smith, K; Ceriani, M F; Staknis, D; Gekakis, N; Steeves, T D; Weitz, C J; Takahashi, J S; Kay, S A

    1998-06-01

    The circadian oscillator generates a rhythmic output with a period of about 24 hours. Despite extensive studies in several model systems, the biochemical mode of action has not yet been demonstrated for any of its components. Here, the Drosophila CLOCK protein was shown to induce transcription of the circadian rhythm genes period and timeless. dCLOCK functioned as a heterodimer with a Drosophila homolog of BMAL1. These proteins acted through an E-box sequence in the period promoter. The timeless promoter contains an 18-base pair element encompassing an E-box, which was sufficient to confer dCLOCK responsiveness to a reporter gene. PERIOD and TIMELESS proteins blocked dCLOCK's ability to transactivate their promoters via the E-box. Thus, dCLOCK drives expression of period and timeless, which in turn inhibit dCLOCK's activity and close the circadian loop.

  10. Entrainment of the mouse circadian clock by sub-acute physical and psychological stress.

    PubMed

    Tahara, Yu; Shiraishi, Takuya; Kikuchi, Yosuke; Haraguchi, Atsushi; Kuriki, Daisuke; Sasaki, Hiroyuki; Motohashi, Hiroaki; Sakai, Tomoko; Shibata, Shigenobu

    2015-01-01

    The effects of acute stress on the peripheral circadian system are not well understood in vivo. Here, we show that sub-acute stress caused by restraint or social defeat potently altered clock gene expression in the peripheral tissues of mice. In these peripheral tissues, as well as the hippocampus and cortex, stressful stimuli induced time-of-day-dependent phase-advances or -delays in rhythmic clock gene expression patterns; however, such changes were not observed in the suprachiasmatic nucleus, i.e. the central circadian clock. Moreover, several days of stress exposure at the beginning of the light period abolished circadian oscillations and caused internal desynchronisation of peripheral clocks. Stress-induced changes in circadian rhythmicity showed habituation and disappeared with long-term exposure to repeated stress. These findings suggest that sub-acute physical/psychological stress potently entrains peripheral clocks and causes transient dysregulation of circadian clocks in vivo.

  11. A novel hybrid seed system for plants.

    PubMed

    Gils, Mario; Marillonnet, Sylvestre; Werner, Stefan; Grützner, Ramona; Giritch, Anatoli; Engler, Carola; Schachschneider, Ralf; Klimyuk, Victor; Gleba, Yuri

    2008-04-01

    A two-component hybrid seed system has been developed that is broadly applicable and provides for effective generation and maintenance of the male-sterile parent, hybrid seed production and full restoration of fertility in the hybrid seed. The technology is based on the functional interaction of two loci that are inserted in the same position on two homologous chromosomes, and thus are 'linked in repulsion', and that jointly code for male sterility and herbicide resistance, both traits being expressed in heterozygous plants only. The localization to the same locus on a chromosome is achieved by the genetic transformation of plants with a construct containing both genetic elements (loci), and subsequent derivatization from the primary pro-locus of the two precursor lines using site-specific deletions. The functional interaction of the two loci is achieved through intein-based trans-splicing of two pairs of complementary protein fragments that provide for male sterility and herbicide resistance. Unlike the hybrid seed systems that are currently in use, the technology relies on the genetic modification of just one parent, and is therefore much simpler to develop and use. Arabidopsis has been used for the proof of principle presented here, but the essential elements of the technology are generic and have been shown to work in many crop species. PMID:18086236

  12. Comparison of tree and straight-line clocking for long systolic arrays

    SciTech Connect

    Dikaiakos, M.D.; Steiglitz, K.

    1990-01-01

    This report presents the critical problem in building long systolic arrays that lies in efficient and reliable synchronization. The authors address this problem in the context of synchronous systems by introducing probabilistic models for two alternative clock distribution schemes: tree and straight-line clocking. They present analytic bounds for the probability of failure and the mean time to failure, and examine the trade-offs between reliability and throughput in both schemes. Their basic conclusion is that as the one-dimensional systolic array gets very long, tree clocking becomes more advantageous over straight-line clocking.

  13. Low-power, miniature {sup 171}Yb ion clock using an ultra-small vacuum package

    SciTech Connect

    Jau, Y.-Y.; Schwindt, P. D. D.; Partner, H.; Prestage, J. D.; Kellogg, J. R.; Yu, N.

    2012-12-17

    We report a demonstration of a very small microwave atomic clock using the 12.6 GHz hyperfine transition of the trapped {sup 171}Yb ions inside a miniature, completely sealed-off 3 cm{sup 3} ion-trap vacuum package. In the ion clock system, all of the components are highly miniaturized with low power consumption except the 369 nm optical pumping laser still under development for miniaturization. The entire clock, including the control electronics, consumes <300 mW. The fractional frequency instability of the miniature Yb{sup +} clock reaches the 10{sup -14} range after a few days of integration.

  14. Potential Conservation of Circadian Clock Proteins in the phylum Nematoda as Revealed by Bioinformatic Searches

    PubMed Central

    Romanowski, Andrés; Garavaglia, Matías Javier; Goya, María Eugenia; Ghiringhelli, Pablo Daniel; Golombek, Diego Andrés

    2014-01-01

    Although several circadian rhythms have been described in C. elegans, its molecular clock remains elusive. In this work we employed a novel bioinformatic approach, applying probabilistic methodologies, to search for circadian clock proteins of several of the best studied circadian model organisms of different taxa (Mus musculus, Drosophila melanogaster, Neurospora crassa, Arabidopsis thaliana and Synechoccocus elongatus) in the proteomes of C. elegans and other members of the phylum Nematoda. With this approach we found that the Nematoda contain proteins most related to the core and accessory proteins of the insect and mammalian clocks, which provide new insights into the nematode clock and the evolution of the circadian system. PMID:25396739

  15. Potential conservation of circadian clock proteins in the phylum Nematoda as revealed by bioinformatic searches.

    PubMed

    Romanowski, Andrés; Garavaglia, Matías Javier; Goya, María Eugenia; Ghiringhelli, Pablo Daniel; Golombek, Diego Andrés

    2014-01-01

    Although several circadian rhythms have been described in C. elegans, its molecular clock remains elusive. In this work we employed a novel bioinformatic approach, applying probabilistic methodologies, to search for circadian clock proteins of several of the best studied circadian model organisms of different taxa (Mus musculus, Drosophila melanogaster, Neurospora crassa, Arabidopsis thaliana and Synechoccocus elongatus) in the proteomes of C. elegans and other members of the phylum Nematoda. With this approach we found that the Nematoda contain proteins most related to the core and accessory proteins of the insect and mammalian clocks, which provide new insights into the nematode clock and the evolution of the circadian system.

  16. Sr+ single-ion clock

    NASA Astrophysics Data System (ADS)

    Dubé, P.; Madej, A. A.; Jian, B.

    2016-06-01

    The evaluated uncertainty of the 88Sr+ ion optical clock has decreased by several orders of magnitude during the last 15 years, currently reaching a level of 1.2 x 10-17. In this paper, we review the methods developed to control very effectively the largest frequency shifts that once were the main sources of uncertainty for the 88Sr+ single-ion clock. These shifts are the micromotion shifts, the electric quadrupole shift and the blackbody radiation shift. With further improvements to the evaluation of the systematic shifts, especially the blackbody radiation shift, it is expected that the total uncertainty of the single-ion clock transition frequency will reach the low 10-18 level in the near future.

  17. Synchronous clock stopper for microprocessor

    NASA Technical Reports Server (NTRS)

    Kitchin, David A. (Inventor)

    1985-01-01

    A synchronous clock stopper circuit for inhibiting clock pulses to a microprocessor in response to a stop request signal, and for reinstating the clock pulses in response to a start request signal thereby to conserve power consumption of the microprocessor when used in an environment of limited power. The stopping and starting of the microprocessor is synchronized, by a phase tracker, with the occurrences of a predetermined phase in the instruction cycle of the microprocessor in which the I/O data and address lines of the microprocessor are of high impedance so that a shared memory connected to the I/O lines may be accessed by other peripheral devices. The starting and stopping occur when the microprocessor initiates and completes, respectively, an instruction, as well as before and after transferring data with a memory. Also, the phase tracker transmits phase information signals over a bus to other peripheral devices which signals identify the current operational phase of the microprocessor.

  18. Clocks, Metabolism, and the Epigenome

    PubMed Central

    Feng, Dan; Lazar, Mitchell A.

    2012-01-01

    Many behaviors and physiological activities in living organisms display circadian rhythms, allowing them to anticipate and prepare for the diurnal changes in the living environment. In this way, metabolic processes are aligned with the periodic environmental changes and behavioral cycles, such as the sleep/wake and fasting/feeding cycles. Disturbances of this alignment significantly increase the risk of metabolic diseases. Meanwhile, the circadian clock receives signals from the environment and feedback from metabolic pathways, and adjusts its activity and function. Growing evidence connects the circadian clock with epigenomic regulators. Here we review the recent advances in understanding the crosstalk between the circadian clock and energy metabolism through epigenomic programming and transcriptional regulation. PMID:22841001

  19. Water-Conserving Plant-Growth System

    NASA Technical Reports Server (NTRS)

    Dreschel, Thomas W.; Brown, Christopher S.

    1993-01-01

    Report presents further information about plant-growth apparatus described in "Tubular Membrane Plant-Growth Unit" (KSC-11375). Apparatus provides nutrient solution to roots of seedlings without flooding. Conserves water by helping to prevent evaporation from plant bed. Solution supplied only as utilized by seedlings. Device developed for supporting plant growth in space, also has applications for growing plants with minimum of water, such as in arid environments.

  20. How does the body know how old it is? Introducing the epigenetic clock hypothesis.

    PubMed

    Mitteldorf, J J

    2013-09-01

    Animals and plants have biological clocks that help to regulate circadian cycles, seasonal rhythms, growth, development, and sexual maturity. It is reasonable to suspect that the timing of senescence is also influenced by one or more biological clocks. Evolutionary reasoning first articulated by G. Williams suggests that multiple, redundant clocks might influence organismal aging. Some aging clocks that have been proposed include the suprachiasmatic nucleus, the hypothalamus, involution of the thymus, and cellular senescence. Cellular senescence, mediated by telomere attrition, is in a class by itself, having recently been validated as a primary regulator of aging. Gene expression is known to change in characteristic ways with age, and in particular DNA methylation changes in age-related ways. Herein, I propose a new candidate for an aging clock, based on epigenetics and the state of chromosome methylation, particularly in stem cells. If validated, this mechanism would present a challenging target for medical intervention. PMID:24228927

  1. Relativistic theory for syntonization of clocks in the vicinity of the Earth

    NASA Technical Reports Server (NTRS)

    Wolf, Peter; Petit, G.

    1995-01-01

    A well known prediction of Einstein's general theory of relativity states that two ideal clocks that move with a relative velocity, and are submitted to different gravitational fields will, in general, be observed to run at different rates. Similarly the rate of a clock with respect to the coordinate time of some spacetime reference system is dependent on the velocity of the clock in that reference system and on the gravitational fields it is submitted to. For the syntonization of clocks and the realization of coordinate times (like TAI) this rate shift has to be taken into account at an accuracy level which should be below the frequency stability of the clocks in question, i.e. all terms that are larger than the instability of the clocks should be corrected for. We present a theory for the calculation of the relativistic rate shift for clocks in the vicinity of the Earth, including all terms larger than one part in 10(exp 18). This, together with previous work on clock synchronization (Petit & Wolf 1993, 1994), amounts to a complete relativistic theory for the realization of coordinate time scales at picosecond synchronization and 10(exp -18) syntonization accuracy, which should be sufficient to accommodate future developments in time transfer and clock technology.

  2. Circadian molecular clocks and cancer.

    PubMed

    Kelleher, Fergal C; Rao, Aparna; Maguire, Anne

    2014-01-01

    Physiological processes such as the sleep-wake cycle, metabolism and hormone secretion are controlled by a circadian rhythm adapted to 24h day-night periodicity. This circadian synchronisation is in part controlled by ambient light decreasing melatonin secretion by the pineal gland and co-ordinated by the suprachiasmatic nucleus of the hypothalamus. Peripheral cell autonomous circadian clocks controlled by the suprachiasmatic nucleus, the master regulator, exist within every cell of the body and are comprised of at least twelve genes. These include the basic helix-loop-helix/PAS domain containing transcription factors; Clock, BMal1 and Npas2 which activate transcription of the periodic genes (Per1 and Per2) and cryptochrome genes (Cry1 and Cry2). Points of coupling exist between the cellular clock and the cell cycle. Cell cycle genes which are affected by the molecular circadian clock include c-Myc, Wee1, cyclin D and p21. Therefore the rhythm of the circadian clock and cancer are interlinked. Molecular examples exist including activation of Per2 leads to c-myc overexpression and an increased tumor incidence. Mice with mutations in Cryptochrome 1 and 2 are arrhythmic (lack a circadian rhythm) and arrhythmic mice have a faster rate of growth of implanted tumors. Epidemiological finding of relevance include 'The Nurses' Health Study' where it was established that women working rotational night shifts have an increased incidence of breast cancer. Compounds that affect circadian rhythm exist with attendant future therapeutic possibilities. These include casein kinase I inhibitors and a candidate small molecule KL001 that affects the degradation of cryptochrome. Theoretically the cell cycle and malignant disease may be targeted vicariously by selective alteration of the cellular molecular clock. PMID:24099911

  3. The Airspace Concepts Evaluation System Architecture and System Plant

    NASA Technical Reports Server (NTRS)

    Windhorst, Robert; Meyn, Larry; Manikonda, Vikram; Carlos, Patrick; Capozzi, Brian

    2006-01-01

    The Airspace Concepts Evaluation System is a simulation of the National Airspace System. It includes models of flights, airports, airspaces, air traffic controls, traffic flow managements, and airline operation centers operating throughout the United States. It is used to predict system delays in response to future capacity and demand scenarios and perform benefits assessments of current and future airspace technologies and operational concepts. Facilitation of these studies requires that the simulation architecture supports plug and play of different air traffic control, traffic flow management, and airline operation center models and multi-fidelity modeling of flights, airports, and airspaces. The simulation is divided into two parts that are named, borrowing from classical control theory terminology, control and plant. The control consists of air traffic control, traffic flow management, and airline operation center models, and the plant consists of flight, airport, and airspace models. The plant can run open loop, in the absence of the control. However, undesired affects, such as conflicts and over congestions in the airspaces and airports, can occur. Different controls are applied, "plug and played", to the plant. A particular control is evaluated by analyzing how well it managed conflicts and congestions. Furthermore, the terminal area plants consist of models of airports and terminal airspaces. Each model consists of a set of nodes and links which are connected by the user to form a network. Nodes model runways, fixes, taxi intersections, gates, and/or other points of interest, and links model taxiways, departure paths, and arrival paths. Metering, flow distribution, and sequencing functions can be applied at nodes. Different fidelity model of how a flight transits are can be used by links. The fidelity of the model can be adjusted by the user by either changing the complexity of the node/link network-or the way that the link models how the flights transit

  4. Optimized multiparty quantum clock synchronization

    SciTech Connect

    Ben-Av, Radel; Exman, Iaakov

    2011-07-15

    A multiparty protocol for distributed quantum clock synchronization has been claimed to provide universal limits on the clock accuracy, viz., that accuracy monotonically decreases with the number n of party members. But this is only true for synchronization when one limits oneself to W states. This work shows that the usage of Z (Symmetric Dicke) states, a generalization of W states, results in improved accuracy, having a maximum when Left-Floor n/2 Right-Floor of its members have their qubits with a |1> eigenstate.

  5. Colloquium: Physics of optical lattice clocks

    SciTech Connect

    Derevianko, Andrei; Katori, Hidetoshi

    2011-04-01

    Recently invented and demonstrated optical lattice clocks hold great promise for improving the precision of modern time keeping. These clocks aim at the 10{sup -18} fractional accuracy, which translates into a clock that would neither lose nor gain a fraction of a second over an estimated age of the Universe. In these clocks, millions of atoms are trapped and interrogated simultaneously, dramatically improving clock stability. Here the principles of operation of these clocks are discussed and, in particular, a novel concept of magic trapping of atoms in optical lattices. Recently proposed microwave lattice clocks are also highlights and several applications that employ the optical lattice clocks as a platform for precision measurements and quantum information processing.

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

    ERIC Educational Resources Information Center

    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…

  7. Phase response of the Arabidopsis thaliana circadian clock to light pulses of different wavelengths.

    PubMed

    Ohara, Takayuki; Fukuda, Hirokazu; Tokuda, Isao T

    2015-04-01

    Light is known as one of the most powerful environmental time cues for the circadian system. The quality of light is characterized by its intensity and wavelength. We examined how the phase response of Arabidopsis thaliana depends on the wavelength of the stimulus light and the type of light perturbation. Using transgenic A. thaliana expressing a luciferase gene, we monitored the rhythm of the bioluminescence signal. We stimulated the plants under constant red light using 3 light perturbation treatments: (1) increasing the red light intensity, (2) turning on a blue light while turning off the red light, and (3) turning on a blue light while keeping the red light on. To examine the phase response properties, we generated a phase transition curve (PTC), which plots the phase after the perturbation as a function of the phase before the perturbation. To evaluate the effect of the 3 light perturbation treatments, we simulated PTCs using a mathematical model of the plant circadian clock and fitted the simulated PTCs to the experimentally measured PTCs. Among the 3 treatments, perturbation (3) provided the strongest stimulus. The results indicate that the color of the stimulus light and the type of pulse administration affect the phase response in a complex manner. Moreover, the results suggest the involvement of interaction between red and blue light signaling pathways in resetting of the plant circadian clock.

  8. Single-transistor-clocked flip-flop

    DOEpatents

    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.

  9. MEDICINAL PLANTS OF RAJASTHAN IN INDIAN SYSTEM OF MEDICINE

    PubMed Central

    Tripathi, Y.C.; Prabhu, V.V.; Pal, R.S.; Mishra, R.N.

    1996-01-01

    Medicinal plants used in Indian system of medicine from Rajasthan state have been surveyed and catagorised systematically. The paper deals with 205 medicinal plants, thoroughly indexed along with their important traditional application for the cure of various ailments. PMID:22556743

  10. Multiple light inputs to a simple clock circuit allow complex biological rhythms.

    PubMed

    Troein, Carl; Corellou, Florence; Dixon, Laura E; van Ooijen, Gerben; O'Neill, John S; Bouget, François-Yves; Millar, Andrew J

    2011-04-01

    Circadian clocks are biological timekeepers that allow living cells to time their activity in anticipation of predictable environmental changes. Detailed understanding of the circadian network of higher plants, such as Arabidopsis thaliana, is hampered by the high number of partially redundant genes. However, the picoeukaryotic alga Ostreococcus tauri, which was recently shown to possess a small number of non-redundant clock genes, presents an attractive alternative target for detailed modelling of circadian clocks in the green lineage. Based on extensive time-series data from in vivo reporter gene assays, we developed a model of the Ostreococcus clock as a feedback loop between the genes TOC1 and CCA1. The model reproduces the dynamics of the transcriptional and translational reporters over a range of photoperiods. Surprisingly, the model is also able to predict the transient behaviour of the clock when the light conditions are altered. Despite the apparent simplicity of the clock circuit, it displays considerable complexity in its response to changing light conditions. Systematic screening of the effects of altered day length revealed a complex relationship between phase and photoperiod, which is also captured by the model. The complex light response is shown to stem from circadian gating of light-dependent mechanisms. This study provides insights into the contributions of light inputs to the Ostreococcus clock. The model suggests that a high number of light-dependent reactions are important for flexible timing in a circadian clock with only one feedback loop.

  11. Preparation of plant and system design description documents

    SciTech Connect

    Not Available

    1989-01-01

    This standard prescribes the purpose, scope, organization, and content of plant design requirements (PDR) documents and system design descriptions (SDDs), to provide a unified approach to their preparation and use by a project as the principal means to establish the plant design requirements and to establish, describe, and control the individual system designs from conception and throughout the lifetime of the plant. The Electric Power Research Institute's Advanced Light Water Reactor (LWR) Requirements Document should be considered for LWR plants.

  12. Preparation of plant and system design description documents

    SciTech Connect

    Not Available

    1989-01-01

    This standard prescribes the purpose, scope, organization, and content of plant design requirements (PDR) documents and system design descriptions (SDDs), to provide a unified approach to their preparation and use by a project as the principal means to establish the plant design requirements and to establish, describe, and control the individual system designs from conception and throughout the lifetime of the plant. The Electric Power Research Institute`s Advanced Light Water Reactor (LWR) Requirements Document should be considered for LWR plants.

  13. Compressed Air System Redesign Results in Increased Production at a Fuel System Plant (Caterpillar Fuel Systems Pontiac Plant)

    SciTech Connect

    2001-06-01

    This case study is one in a series on industrial firms who are implementing energy efficient technologies and system improvements into their manufacturing processes. This case study documents the activities, savings, and lessons learned on the Caterpillar's Pontiac Plant project.

  14. Spin squeezing in a Rydberg lattice clock.

    PubMed

    Gil, L I R; Mukherjee, R; Bridge, E M; Jones, M P A; Pohl, T

    2014-03-14

    We theoretically demonstrate a viable approach to spin squeezing in optical lattice clocks via optical dressing of one clock state to a highly excited Rydberg state, generating switchable atomic interactions. For realistic experimental parameters, these interactions are shown to generate over 10 dB of squeezing in large ensembles within a few microseconds and without degrading the subsequent clock interrogation. PMID:24679291

  15. Microwave Cavity Clocks On Space Station

    NASA Technical Reports Server (NTRS)

    Lipa, J. a.; Nissen, J. A.; Wang, S.; Stricker, D. A.; Avaloff, D.

    2003-01-01

    We describe the status of a microwave cavity clock experiment to perform improved tests of Local Position Invariance and Lorentz Invariance on the International Space Station in conjunction with atomic clocks. Significant improvements over present bounds are expected in both cases. The oscillators can also be used to enhance the performance of atomic clocks at short time scales for other experiments.

  16. Chemical inducers of systemic immunity in plants.

    PubMed

    Gao, Qing-Ming; Kachroo, Aardra; Kachroo, Pradeep

    2014-04-01

    Systemic acquired resistance (SAR) is a highly desirable form of resistance that protects against a broad-spectrum of related or unrelated pathogens. SAR involves the generation of multiple signals at the site of primary infection, which arms distal portions against subsequent secondary infections. The last decade has witnessed considerable progress, and a number of chemical signals contributing to SAR have been isolated and characterized. The diverse chemical nature of these chemicals had led to the growing belief that SAR might involve interplay of multiple diverse and independent signals. However, recent results suggest that coordinated signalling from diverse signalling components facilitates SAR in plants. This review mainly discusses organized signalling by two such chemicals, glycerol-3-phoshphate and azelaic acid, and the role of basal salicylic acid levels in G3P-conferred SAR.

  17. Buffer Gas Experiments in Mercury (Hg+) Ion Clock

    NASA Technical Reports Server (NTRS)

    Chung, Sang K.; Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    2004-01-01

    We describe the results of the frequency shifts measured from various buffer gases that might be used as a buffer gas to increase the loading efficiency and cooling of ions trapped in a small mercury ion clock. The small mass, volume and power requirement of space clock precludes the use of turbo pumps. Hence, a hermetically sealed vacuum system, incorporating a suitable getter material with a fixed amount of inert buffer gas may be a practical alternative to the groundbased system. The collision shifts of 40,507,347.996xx Hz clock transition for helium, neon and argon buffer gases were measured in the ambient earth magnetic field. In addition to the above non-getterable inert gases we also measured the frequency shifts due to getterable, molecular hydrogen and nitrogen gases which may be used as buffer gases when incorporated with a miniature ion pump. We also examined the frequency shift due to the low methane gas partial pressure in a fixed higher pressure neon buffer gas environment. Methane gas interacted with mercury ions in a peculiar way as to preserve the ion number but to relax the population difference in the two hyperfine clock states and thereby reducing the clock resonance signal. The same population relaxation was also observed for other molecular buffer gases (N H,) but at much reduced rate.

  18. MYC/MIZ1-dependent gene repression inversely coordinates the circadian clock with cell cycle and proliferation

    PubMed Central

    Shostak, Anton; Ruppert, Bianca; Ha, Nati; Bruns, Philipp; Toprak, Umut H.; Lawerenz, Chris; Lichter, Peter; Radlwimmer, Bernhard; Eils, Jürgen; Brors, Benedikt; Radomski, Sylwester; Scholz, Ingrid; Richter, Gesine; Siebert, Reiner; Wagner, Susanne; Haake, Andrea; Richter, Julia; Aukema, Sietse; Ammerpohl, Ole; Lopez, Christina; Nagel, Inga; Vater, Inga; Wagner, Rabea; Borst, Christoph; Haas, Siegfried; Rohde, Marius; Burkhardt, Birgit; Lisfeld, Jasmin; Claviez, Alexander; Dreyling, Martin; Eberth, Sonja; Trümper, Lorenz; Kube, Dieter; Stadler, Christina; Einsele, Hermann; Frickhofen, Norbert; Hansmann, Martin-Leo; Karsch, Dennis; Kneba, Michael; Mantovani-Löffler, Luisa; Staib, Peter; Stilgenbauer, Stephan; Ott, German; Küppers, Ralf; Weniger, Marc; Hummel, Michael; Lenze, Dido; Szczepanowski, Monika; Klapper, Wolfram; Kostezka, Ulrike; Möller, Peter; Rosenwald, Andreas; Leich, Ellen; Pischimariov, Jordan; Binder, Vera; Borkhardt, Arndt; Hezaveh, Kebria; Hoell, Jessica; Rosenstiel, Philip; Schilhabel, Markus; Schreiber, Stefan; Bernhart, Stephan H.; Doose, Gero; Hoffmann, Steve; Kretzmer, Helene; Langenberger, David; Binder, Hans; Hopp, Lydia; Kreuz, Markus; Loeffler, Markus; Rosolowski, Maciej; Korbel, Jan; Sungalee, Stefanie; Stadler, Peter F.; Zenz, Thorsten; Eils, Roland; Schlesner, Matthias; Diernfellner, Axel; Brunner, Michael

    2016-01-01

    The circadian clock and the cell cycle are major cellular systems that organize global physiology in temporal fashion. It seems conceivable that the potentially conflicting programs are coordinated. We show here that overexpression of MYC in U2OS cells attenuates the clock and conversely promotes cell proliferation while downregulation of MYC strengthens the clock and reduces proliferation. Inhibition of the circadian clock is crucially dependent on the formation of repressive complexes of MYC with MIZ1 and subsequent downregulation of the core clock genes BMAL1 (ARNTL), CLOCK and NPAS2. We show furthermore that BMAL1 expression levels correlate inversely with MYC levels in 102 human lymphomas. Our data suggest that MYC acts as a master coordinator that inversely modulates the impact of cell cycle and circadian clock on gene expression. PMID:27339797

  19. Biological clocks: riding the tides.

    PubMed

    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.

  20. Cannabinoids excite circadian clock neurons.

    PubMed

    Acuna-Goycolea, Claudio; Obrietan, Karl; van den Pol, Anthony N

    2010-07-28

    Cannabinoids, the primary active agent in drugs of abuse such as marijuana and hashish, tend to generate a distorted sense of time. Here we study the effect of cannabinoids on the brain's circadian clock, the suprachiasmatic nucleus (SCN), using patch clamp and cell-attached electrophysiological recordings, RT-PCR, immunocytochemistry, and behavioral analysis. The SCN showed strong expression of the cannabinoid receptor CB1R, as detected with RT-PCR. SCN neurons, including those using GABA as a transmitter, and axons within the SCN, expressed CB1R immunoreactivity. Behaviorally, cannabinoids did not alter the endogenous free-running circadian rhythm in the mouse brain, but did attenuate the ability of the circadian clock to entrain to light zeitgebers. In the absence of light, infusion of the CB1R antagonist AM251 caused a modest phase shift, suggesting endocannabinoid modulation of clock timing. Interestingly, cannabinoids had no effect on glutamate release from the retinohypothalamic projection, suggesting a direct action of cannabinoids on the retinohypothalamic tract was unlikely to explain the inhibition of the phase shift. Within the SCN, cannabinoids were excitatory by a mechanism based on presynaptic CB1R attenuation of axonal GABA release. These data raise the possibility that the time dissociation described by cannabinoid users may result in part from altered circadian clock function and/or entrainment to environmental time cues. PMID:20668190

  1. Biological Clocks: Riding the Tides

    PubMed Central

    de la Iglesia, Horacio O.; Johnson, Carl Hirschie

    2015-01-01

    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. PMID:24156810

  2. Time and clock synchronization with AFCK for CBM

    NASA Astrophysics Data System (ADS)

    Gumiński, M.; Zabołotny, W.; Kasprowicz, G.; Poźniak, K.; Romaniuk, R.

    2015-09-01

    The AMC FMC Carrier Kintex (AFCK) board is a prototype of Data Processing Board (DPB) for CBM experiment. AFCK is open hardware and was designed to be a versatile solution, applicable in multiple systems. In CBM experiment AFCK will serve as a data hub and communication interconnection. One of DPB's functions is synchronization of Front End Electronics (FEE). To provide this functionality, it is necessary to receive the reference clock and timing signals from the Timing and Flow Control system. The received clock after the jitter cleaning will be used as a reference clock for GBT-FPGA based 4.8 Gbps links used for communication with front end electronics. This article will briefly describe AFCK board function in CBM experiment. Afterwards it will focus on jitter cleaning technique based on White Rabbit solution that can be used on AFCK board.

  3. Multi-GNSS Orbit and Clock Combination: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Fritsche, Mathias

    2016-04-01

    In the framework of the Multi-GNSS Experiment (MGEX) a number of Analysis Centers (ACs) extended their software capabilities to process signals from the BeiDou, Galileo, and QZSS systems in addition to the well established systems GPS and GLONASS. Currently, the MGEX product portfolio covers precise satellite orbits and clocks, receiver clocks, signal biases, and Earth rotation parameters generated by the individual ACs. This presentation will provide an overview on the available AC-specific MGEX products. In addition, an introduction to a multi-GNSS orbit and clock combination procedure will be given. Finally, preliminary results from that multi-GNSS combination including a comparison with corresponding operational IGS products will be reported along with a discussion of the results.

  4. Rapid attenuation of circadian clock gene oscillations in the rat heart following ischemia-reperfusion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The intracellular circadian clock consists of a series of transcriptional modulators that together allow the cell to perceive the time of day. Circadian clocks have been identified within various components of the cardiovascular system (e.g., cardiomyocytes, vascular smooth muscle cells) and possess...

  5. Phase 1 Navstar/GPS ephemeris and space vehicle clock performance summary

    NASA Technical Reports Server (NTRS)

    Bierman, A. B.

    1980-01-01

    The Navstar/Global Positioning System (GPS) is considered. The issue of control segment accuracy in predicting space vehicle (SV) clock and ephemeris states for broadcast to the user community is addressed. Both the highly precise ephemeris and clock prediction data blocks and the less precise (but longer period of utility) almanac data block are evaluated.

  6. On the Stable Limit Cycle of a Weight-Driven Pendulum Clock

    ERIC Educational Resources Information Center

    Llibre, J; Teixeira, M. A.

    2010-01-01

    In a recent paper (Denny 2002 Eur. J. Phys. 23 449-58), entitled "The pendulum clock: a venerable dynamical system", Denny showed that in a first approximation the steady-state motion of a weight-driven pendulum clock is shown to be a stable limit cycle. He placed the problem in a historical context and obtained an approximate solution using the…

  7. Equivalencing the Collector System of a Large Wind Power Plant

    SciTech Connect

    Muljadi, E.; Butterfield, C. P.; Ellis, A.; Mechenbier, J.; Hocheimer, J.; Young, R.; Miller, N.; Delmerico, R.; Zavadil, R.; Smith, J. C.

    2006-01-01

    As the size and number of wind power plants (also called wind farms) increases, power system planners will need to study their impact on the power system in more detail. As the level of wind power penetration into the grid increases, the transmission system integration requirements will become more critical [1-2]. A very large wind power plant may contain hundreds of megawatt-size wind turbines. These turbines are interconnected by an intricate collector system. While the impact of individual turbines on the larger power system network is minimal, collectively, wind turbines can have a significant impact on the power systems during a severe disturbance such as a nearby fault. Since it is not practical to represent all individual wind turbines to conduct simulations, a simplified equivalent representation is required. This paper focuses on our effort to develop an equivalent representation of a wind power plant collector system for power system planning studies. The layout of the wind power plant, the size and type of conductors used, and the method of delivery (overhead or buried cables) all influence the performance of the collector system inside the wind power plant. Our effort to develop an equivalent representation of the collector system for wind power plants is an attempt to simplify power system modeling for future developments or planned expansions of wind power plants. Although we use a specific large wind power plant as a case study, the concept is applicable for any type of wind power plant.

  8. Fuel cell power plant integrated systems evaluation

    NASA Astrophysics Data System (ADS)

    Bonds, T. L.; Dawes, M. H.; Schnacke, A. W.; Spradlin, L. W.

    1981-01-01

    Power plant configurations for a central station (675 MW) fueled by coal and small dispersed plan generation plants fueled by oil were defined. Capital costs and costs for electricity were evaluated for both plants. Parametric variations and the impact on plants and components are discussed. Alternate oil fueled oil fired cycles as well as several alternate coal gasifiers were examined to show effects on plant performance. The economic attractiveness of the coal fired plant was confirmed and a scenario is established for an oil fired plant with reject heat recovery. Performance for the coal fired plant exceeds the study goal of 6800 Btu/kWh. The oil fired plant performance of 7627 Btu/kWh is very close to the study goal of 7500 Btu/kWh. The development of a finite slice computer model of the carbonate fuel cell is reported and an initial parametric cell and plant performance study was performed using the model. Preliminary subsystem description sheets and plant layout arrangements are presented.

  9. Punctual Transcriptional Regulation by the Rice Circadian Clock under Fluctuating Field Conditions[OPEN

    PubMed Central

    Matsuzaki, Jun; Kawahara, Yoshihiro; Izawa, Takeshi

    2015-01-01

    Plant circadian clocks that oscillate autonomously with a roughly 24-h period are entrained by fluctuating light and temperature and globally regulate downstream genes in the field. However, it remains unknown how punctual internal time produced by the circadian clock in the field is and how it is affected by environmental fluctuations due to weather or daylength. Using hundreds of samples of field-grown rice (Oryza sativa) leaves, we developed a statistical model for the expression of circadian clock-related genes integrating diurnally entrained circadian clock with phase setting by light, both responses to light and temperature gated by the circadian clock. We show that expression of individual genes was strongly affected by temperature. However, internal time estimated from expression of multiple genes, which may reflect transcriptional regulation of downstream genes, is punctual to 22 min and not affected by weather, daylength, or plant developmental age in the field. We also revealed perturbed progression of internal time under controlled environment or in a mutant of the circadian clock gene GIGANTEA. Thus, we demonstrated that the circadian clock is a regulatory network of multiple genes that retains accurate physical time of day by integrating the perturbations on individual genes under fluctuating environments in the field. PMID:25757473

  10. Analysis of a magnetically trapped atom clock

    SciTech Connect

    Kadio, D.; Band, Y. B.

    2006-11-15

    We consider optimization of a rubidium atom clock that uses magnetically trapped Bose condensed atoms in a highly elongated trap, and determine the optimal conditions for minimum Allan variance of the clock using microwave Ramsey fringe spectroscopy. Elimination of magnetic field shifts and collisional shifts are considered. The effects of spin-dipolar relaxation are addressed in the optimization of the clock. We find that for the interstate interaction strength equal to or larger than the intrastate interaction strengths, a modulational instability results in phase separation and symmetry breaking of the two-component condensate composed of the ground and excited hyperfine clock levels, and this mechanism limits the clock accuracy.

  11. A thin film hydroponic system for plant studies

    NASA Technical Reports Server (NTRS)

    Hines, Robert; Prince, Ralph; Muller, Eldon; Schuerger, Andrew

    1990-01-01

    The Land Pavillion, EPCOT Center, houses a hydroponic, thin film growing system identical to that residing in NASA's Biomass Production Chamber at Kennedy Space Center. The system is targeted for plant disease and nutrition studies. The system is described.

  12. The regulation of UV-B responses by the circadian clock.

    PubMed

    Horak, Elyse; Farré, Eva M

    2015-01-01

    The circadian clock modulates plant responses to environmental stimuli. In a recent study we showed that light and the circadian clock regulate daily changes in sensitivity to short treatments of high UV-B. Here we demonstrate that these time dependent changes in UV-B stress sensitivity are not mediated by the UV-B receptor UV resistantce locus 8. We also discuss the potential mechanisms involved in this process and the role of the circadian clock in the acclimation to UV-B.

  13. The regulation of UV-B responses by the circadian clock

    PubMed Central

    Horak, Elyse; Farré, Eva M.

    2015-01-01

    The circadian clock modulates plant responses to environmental stimuli. In a recent study we showed that light and the circadian clock regulate daily changes in sensitivity to short treatments of high UV-B. Here we demonstrate that these time dependent changes in UV-B stress sensitivity are not mediated by the UV-B receptor UV RESISTANTCE LOCUS 8. We also discuss the potential mechanisms involved in this process and the role of the circadian clock in the acclimation to UV-B. PMID:26039469

  14. Daily Rhythmicity of Clock Gene Transcripts in Atlantic Cod Fast Skeletal Muscle

    PubMed Central

    Lazado, Carlo C.; Kumaratunga, Hiruni P. S.; Nagasawa, Kazue; Babiak, Igor; Giannetto, Alessia; Fernandes, Jorge M. O.

    2014-01-01

    The classical notion of a centralized clock that governs circadian rhythmicity has been challenged with the discovery of peripheral oscillators that enable organisms to cope with daily changes in their environment. The present study aimed to identify the molecular clock components in Atlantic cod (Gadus morhua) and to investigate their daily gene expression in fast skeletal muscle. Atlantic cod clock genes were closely related to their orthologs in teleosts and tetrapods. Synteny was conserved to varying degrees in the majority of the 18 clock genes examined. In particular, aryl hydrocarbon receptor nuclear translocator-like 2 (arntl2), RAR-related orphan receptor A (rora) and timeless (tim) displayed high degrees of conservation. Expression profiling during the early ontogenesis revealed that some transcripts were maternally transferred, namely arntl2, cryptochrome 1b and 2 (cry1b and cry2), and period 2a and 2b (per2a and per2b). Most clock genes were ubiquitously expressed in various tissues, suggesting the possible existence of multiple peripheral clock systems in Atlantic cod. In particular, they were all detected in fast skeletal muscle, with the exception of neuronal PAS (Per-Arnt-Single-minded) domain-containing protein (npas1) and rora. Rhythmicity analysis revealed 8 clock genes with daily rhythmic expression, namely arntl2, circadian locomotor output cycles kaput (clock), npas2, cry2, cry3 per2a, nuclear receptor subfamily 1, group D, member 1 (nr1d1), and nr1d2a. Transcript levels of the myogenic genes myogenic factor 5 (myf5) and muscleblind-like 1 (mbnl1) strongly correlated with clock gene expression. This is the first study to unravel the molecular components of peripheral clocks in Atlantic cod. Taken together, our data suggest that the putative clock system in fast skeletal muscle of Atlantic cod has regulatory implications on muscle physiology, particularly in the expression of genes related to myogenesis. PMID:24921252

  15. National Plant Germplasm System: Critical Role of Customer Service

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The National Plant Germplasm System (NPGS) conserves plant genetic resources, not only for use by future generations, but for immediate use by scientists and educators around the world. With a great deal of interaction between genebank curators and users of plant genetic resources, customer service...

  16. Automatic control of clock duty cycle

    NASA Technical Reports Server (NTRS)

    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.

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

    PubMed

    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

  18. Ras-Mediated Deregulation of the Circadian Clock in Cancer

    PubMed Central

    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. Developing Higher Plant Systems in Space

    NASA Technical Reports Server (NTRS)

    Krikorian, A. D.

    1983-01-01

    The effects of hypogravity and microgravity environments on plant cells are discussed. Experiments on embryos of carrots are discussed. Simulation and spacecraft environments were used in experiments.

  20. Representing plant hydraulics in a global Earth system model.

    NASA Astrophysics Data System (ADS)

    Kennedy, D.; Gentine, P.

    2015-12-01

    Earth system models need improvement to reproduce observed seasonal and diurnal cycles of photosynthesis and respiration. Model water stress parameterizations lag behind the plant physiology literature. A plant hydraulics model is developed and deployed in a global Earth system model (NCAR CESM 1.2.2 with CLM 4.5). Assimilation and transpiration are attenuated according to literature cavitation curves. Water stress is evaluated based on plant functional type hydraulic parameters forced by soil moisture and atmospheric conditions. Resolving the plant water status allows for modelling divergent strategies for water stress. The case of isohydric versus anisohydric species is presented, showing that including plant hydraulic traits alter modelled photosynthesis and transpiration.

  1. [Functional polymorphisms in clock genes and circadian rhythm sleep disorders].

    PubMed

    Ebisawa, Takashi

    2007-06-01

    Polymorphisms in clock genes induce circadian rhythm sleep disorders. Mutations in Per2 gene (S662G) or Casein Kinasel delta (CK16) gene (T44A) cause Familial advanced sleep phase syndrome. Missense polymorphisms in Per3 (V647G) and CK1e (S408N) genes increase or decrease the risk of developing delayed sleep phase syndrome. All of these polymorphisms seem to affect the phosphorylation of the clock proteins. Some of the polymorphisms in CK1, which shows reduced enzyme activity in vitro, induced increased phosphorylation of PER proteins in in vivo assays. Careful attention should be paid to analyze the complex system composed of feedback loops, such as the biological clock. PMID:17633519

  2. Spin-orbit coupling in a strontium optical lattice clock

    NASA Astrophysics Data System (ADS)

    Bothwell, Tobias; Bromley, Sarah; Kolkowitz, Shimon; Zhang, Xibo; Wall, Michael; Rey, Ana Maria; Ye, Jun

    2016-05-01

    Synthetic gauge fields are a promising tool for creating complex Hamiltonians with ultracold neutral atoms that may mimic the fractional Quantum Hall effect and other topological states. A promising approach is to use spin-orbit coupling to treat an internal degree of freedom as an effective `synthetic' spatial dimension. Here, this synthetic dimension is comprised by the internal ground and excited states used for high-precision clock spectroscopy in a fermionic strontium optical lattice clock. We report on our progress towards this goal in a system where atoms tunnel through a 1D optical lattice during clock interrogation. We present measurements of the lattice band structure under varying Lamb-Dicke parameters and in a regime where s-wave collisions are expected to contribute density dependent frequency shifts.

  3. Redox rhythmicity: clocks at the core of temporal coherence.

    PubMed

    Lloyd, David; Murray, Douglas B

    2007-05-01

    Ultradian rhythms are those that cycle many times in a day and are therefore measured in hours, minutes, seconds or even fractions of a second. In yeasts and protists, a temperature-compensated clock with a period of about an hour (30-90 minutes) provides the time base upon which all central processes are synchronized. A 40-minute clock in yeast times metabolic, respiratory and transcriptional processes, and controls cell division cycle progression. This system has at its core a redox cycle involving NAD(P)H and dithiol-disulfide interconversions. It provides an archetype for biological time keeping on longer time scales (e.g. the daily cycles driven by circadian clocks) and underpins these rhythms, which cannot be understood in isolation. Ultradian rhythms are the foundation upon which the coherent functioning of the organism depends.

  4. Controlled Ecological Life Support System: Use of Higher Plants

    NASA Technical Reports Server (NTRS)

    Tibbits, T. W.; Alford, D. K.

    1982-01-01

    Results of two workshops concerning the use of higher plants in Controlled Ecological Life Support Systems (CELSS) are summarized. Criteria for plant selection were identified from these categories: food production, nutrition, oxygen production and carbon dioxide utilization, water recycling, waste recycling, and other morphological and physiological considerations. Types of plant species suitable for use in CELSS, growing procedures, and research priorities were recommended. Also included are productivity values for selected plant species.

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

    PubMed

    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. PMID:26941090

  6. A remark on the GNSS single difference model with common clock scheme for attitude determination

    NASA Astrophysics Data System (ADS)

    Chen, Wantong

    2016-09-01

    GNSS-based attitude determination technique is an important field of study, in which two schemes can be used to construct the actual system: the common clock scheme and the non-common clock scheme. Compared with the non-common clock scheme, the common clock scheme can strongly improve both the reliability and the accuracy. However, in order to gain these advantages, specific care must be taken in the implementation. The cares are thus discussed, based on the generating technique of carrier phase measurement in GNSS receivers. A qualitative assessment of potential phase bias contributes is also carried out. Possible technical difficulties are pointed out for the development of single-board multi-antenna GNSS attitude systems with a common clock.

  7. Atomic clock based on transient coherent population trapping

    SciTech Connect

    Guo Tao; Deng Ke; Chen Xuzong; Wang Zhong

    2009-04-13

    We proposed a scheme to implement coherent population trapping (CPT) atomic clock based on the transient CPT phenomenon. We proved that the transient transmitted laser power in a typical {lambda} system near CPT resonance features as a damping oscillation. Also, the oscillating frequency is exactly equal to the frequency detuning from the atomic hyperfine splitting. Therefore, we can directly measure the frequency detuning and then compensated to the output frequency of microwave oscillator to get the standard frequency. By this method, we can further simplify the structure of CPT atomic clock, and make it easier to be digitized and miniaturized.

  8. Assignment of circadian function for the Neurospora clock gene frequency.

    PubMed

    Merrow, M; Brunner, M; Roenneberg, T

    1999-06-10

    Circadian clocks consist of three elements: entrainment pathways (inputs), the mechanism generating the rhythmicity (oscillator), and the output pathways that control the circadian rhythms. It is difficult to assign molecular clock components to any one of these elements. Experiments show that inputs can be circadianly regulated and outputs can feed back on the oscillator. Mathematical simulations indicate that under- or overexpression of a gene product can result in arrhythmicity, whether the protein is part of the oscillator or substantially part of a rhythmically expressed input pathway. To distinguish between these two possibilities, we used traditional circadian entrainment protocols on a genetic model system, Neurospora crassa.

  9. Plant-uptake of uranium: Hydroponic and soil system studies

    USGS Publications Warehouse

    Ramaswami, A.; Carr, P.; Burkhardt, M.

    2001-01-01

    Limited information is available on screening and selection of terrestrial plants for uptake and translocation of uranium from soil. This article evaluates the removal of uranium from water and soil by selected plants, comparing plant performance in hydroponic systems with that in two soil systems (a sandy-loam soil and an organic-rich soil). Plants selected for this study were Sunflower (Helianthus giganteus), Spring Vetch (Vicia sativa), Hairy Vetch (Vicia villosa), Juniper (Juniperus monosperma), Indian Mustard (Brassica juncea), and Bush Bean (Phaseolus nanus). Plant performance was evaluated both in terms of the percent uranium extracted from the three systems, as well as the biological absorption coefficient (BAC) that normalized uranium uptake to plant biomass. Study results indicate that uranium extraction efficiency decreased sharply across hydroponic, sandy and organic soil systems, indicating that soil organic matter sequestered uranium, rendering it largely unavailable for plant uptake. These results indicate that site-specific soils must be used to screen plants for uranium extraction capability; plant behavior in hydroponic systems does not correlate well with that in soil systems. One plant species, Juniper, exhibited consistent uranium extraction efficiencies and BACs in both sandy and organic soils, suggesting unique uranium extraction capabilities.

  10. Green pathways: Metabolic network analysis of plant systems.

    PubMed

    Dersch, Lisa Maria; Beckers, Veronique; Wittmann, Christoph

    2016-03-01

    Metabolic engineering of plants with enhanced crop yield and value-added compositional traits is particularly challenging as they probably exhibit the highest metabolic network complexity of all living organisms. Therefore, approaches of plant metabolic network analysis, which can provide systems-level understanding of plant physiology, appear valuable as guidance for plant metabolic engineers. Strongly supported by the sequencing of plant genomes, a number of different experimental and computational methods have emerged in recent years to study plant systems at various levels: from heterotrophic cell cultures to autotrophic entire plants. The present review presents a state-of-the-art toolbox for plant metabolic network analysis. Among the described approaches are different in silico modeling techniques, including flux balance analysis, elementary flux mode analysis and kinetic flux profiling, as well as different variants of experiments with plant systems which use radioactive and stable isotopes to determine in vivo plant metabolic fluxes. The fundamental principles of these techniques, the required data input and the obtained flux information are enriched by technical advices, specific to plants. In addition, pioneering and high-impacting findings of plant metabolic network analysis highlight the potential of the field.

  11. Green pathways: Metabolic network analysis of plant systems.

    PubMed

    Dersch, Lisa Maria; Beckers, Veronique; Wittmann, Christoph

    2016-03-01

    Metabolic engineering of plants with enhanced crop yield and value-added compositional traits is particularly challenging as they probably exhibit the highest metabolic network complexity of all living organisms. Therefore, approaches of plant metabolic network analysis, which can provide systems-level understanding of plant physiology, appear valuable as guidance for plant metabolic engineers. Strongly supported by the sequencing of plant genomes, a number of different experimental and computational methods have emerged in recent years to study plant systems at various levels: from heterotrophic cell cultures to autotrophic entire plants. The present review presents a state-of-the-art toolbox for plant metabolic network analysis. Among the described approaches are different in silico modeling techniques, including flux balance analysis, elementary flux mode analysis and kinetic flux profiling, as well as different variants of experiments with plant systems which use radioactive and stable isotopes to determine in vivo plant metabolic fluxes. The fundamental principles of these techniques, the required data input and the obtained flux information are enriched by technical advices, specific to plants. In addition, pioneering and high-impacting findings of plant metabolic network analysis highlight the potential of the field. PMID:26704307

  12. Nuclear thiol redox systems in plants.

    PubMed

    Delorme-Hinoux, Valérie; Bangash, Sajid A K; Meyer, Andreas J; Reichheld, Jean-Philippe

    2016-02-01

    Thiol-disulfide redox regulation is essential for many cellular functions in plants. It has major roles in defense mechanisms, maintains the redox status of the cell and plays structural, with regulatory roles for many proteins. Although thiol-based redox regulation has been extensively studied in subcellular organelles such as chloroplasts, it has been much less studied in the nucleus. Thiol-disulfide redox regulation is dependent on the conserved redox proteins, glutathione/glutaredoxin (GRX) and thioredoxin (TRX) systems. We first focus on the functions of glutathione in the nucleus and discuss recent data concerning accumulation of glutathione in the nucleus. We also provide evidence that glutathione reduction is potentially active in the nucleus. Recent data suggests that the nucleus is enriched in specific GRX and TRX isoforms. We discuss the biochemical and molecular characteristics of these isoforms and focus on genetic evidences for their potential nuclear functions. Finally, we make an overview of the different thiol-based redox regulated proteins in the nucleus. These proteins are involved in various pathways including transcriptional regulation, metabolism and signaling. PMID:26795153

  13. How to fix a broken clock

    PubMed Central

    Schroeder, Analyne M.; Colwell, Christopher S.

    2013-01-01

    Fortunate are those who rise out of bed to greet the morning light well rested with the energy and enthusiasm to drive a productive day. Others however, depend on hypnotics for sleep and require stimulants to awaken lethargic bodies. Sleep/wake disruption is a common occurrence in healthy individuals throughout their lifespan and is also a comorbid condition to many diseases (neurodegenerative) and psychiatric disorders (depression and bipolar). There is growing concern that chronic disruption of the sleep/wake cycle contributes to more serious conditions including diabetes (type 2), cardiovascular disease and cancer. A poorly functioning circadian system resulting in misalignments in the timing of clocks throughout the body may be at the root of the problem for many people. In this article, we discuss environmental (light therapy) and lifestyle changes (scheduled meals, exercise and sleep) as interventions to help fix a broken clock. We also discuss the challenges and potential for future development of pharmacological treatments to manipulate this key biological system. PMID:24120229

  14. The Circadian Clock and Human Health.

    PubMed

    Roenneberg, Till; Merrow, Martha

    2016-05-23

    Epidemiological studies provided the first evidence suggesting a connection between the circadian clock and human health. Mutant mice convincingly demonstrate the principle that dysregulation of the circadian system leads to a multitude of pathologies. Chrono-medicine is one of the most important upcoming themes in the field of circadian biology. Although treatments counteracting circadian dysregulation are already being applied (e.g., prescribing strong and regular zeitgebers), we need to comprehend entrainment throughout the body's entire circadian network before understanding the mechanisms that tie circadian dysregulation to pathology. Here, we attempt to provide a systematic approach to understanding the connection between the circadian clock and health. This taxonomy of (mis)alignments on one hand exposes how little we know about entrainment within any organism and which 'eigen-zeitgeber' signals are used for entrainment by the different cells and tissues. On the other hand, it provides focus for experimental approaches and tools that will logically map out how circadian systems contribute to disease as well as how we can treat and prevent them. PMID:27218855

  15. Shift work: coping with the biological clock.

    PubMed

    Arendt, Josephine

    2010-01-01

    The internal circadian clock adapts slowly, if at all, to rapid transitions between different shift schedules. This leads to misalignment (desynchrony) of rhythmic physiological systems, such as sleep, alertness, performance, metabolism and the hormones melatonin and cortisol, with the imposed work-rest schedule. Consequences include sleep deprivation and poor performance. Clock gene variants may influence tolerance of sleep deprivation. Shift work is associated with an increased risk of major disease (heart disease and cancer) and this may also, at least in part, be attributed to frequent circadian desynchrony. Abnormal metabolism has been invoked as a contributory factor to the increased risk of heart disease. There is recent evidence for an increased risk of certain cancers, with hypothesized causal roles of light at night, melatonin suppression and circadian desynchrony. Various strategies exist for coping with circadian desynchrony and for hastening circadian realignment (if desired). The most important factor in manipulating the circadian system is exposure to and/or avoidance of bright light at specific times of the 'biological night'.

  16. MicroRNAs: a potential interface between the circadian clock and human health.

    PubMed

    Hansen, Katelin F; Sakamoto, Kensuke; Obrietan, Karl

    2011-02-17

    The biochemical activity of a stunning diversity of cell types and organ systems is shaped by a 24-hour (circadian) clock. This rhythmic drive to a good deal of the transcriptome (up to 15% of all coding genes) imparts circadian modulation over a wide range of physiological and behavioral processes (from cell division to cognition). Further, dysregulation of the clock has been implicated in the pathogenesis of a large and diverse array of disorders, such as hypertension, cancer and depression. Indeed, the possibility of utilizing therapeutic approaches that target clock physiology (that is, chronotherapy) has gained broad interest. However, a deeper understanding of the underlying molecular mechanisms that modulate the clock, and give rise to organ-specific clock transcriptomes, will be required to fully realize the power of chronotherapies. Recently, microRNAs have emerged as significant players in circadian clock timing, thus raising the possibility that clock-controlled microRNAs could contribute to disorders of the human circadian timing system. Here, we highlight recent work revealing a key role for microRNAs in clock physiology, and discuss potential approaches to unlocking their utility as effectors of circadian physiology and pathophysiology.

  17. Plant Risk Status Information Management System.

    1990-12-12

    Version 00 PRISIM allows inspectors to quickly access probabilistic risk assessment (PRA) information and use it to update risk analysis results, reflecting a nuclear plant's status at any time. PRISIM also allows regulators to access PRA information and modify the information to assess the impact the changes may have on plant safety.

  18. Genomic clocks and evolutionary timescales

    NASA Technical Reports Server (NTRS)

    Blair Hedges, S.; Kumar, Sudhir

    2003-01-01

    For decades, molecular clocks have helped to illuminate the evolutionary timescale of life, but now genomic data pose a challenge for time estimation methods. It is unclear how to integrate data from many genes, each potentially evolving under a different model of substitution and at a different rate. Current methods can be grouped by the way the data are handled (genes considered separately or combined into a 'supergene') and the way gene-specific rate models are applied (global versus local clock). There are advantages and disadvantages to each of these approaches, and the optimal method has not yet emerged. Fortunately, time estimates inferred using many genes or proteins have greater precision and appear to be robust to different approaches.

  19. Conveyor-belt clock synchronization

    SciTech Connect

    Giovannetti, Vittorio; Maccone, Lorenzo; Shapiro, Jeffrey H.; Wong, Franco N.C.; Lloyd, Seth

    2004-10-01

    A protocol for synchronizing distant clocks is proposed that does not rely on the arrival times of the signals which are exchanged, and an optical implementation based on coherent-state pulses is described. This protocol is not limited by any dispersion that may be present in the propagation medium through which the light signals are exchanged. Possible improvements deriving from the use of quantum-mechanical effects are also addressed.

  20. An epigenetic clock controls aging.

    PubMed

    Mitteldorf, Josh

    2016-02-01

    We are accustomed to treating aging as a set of things that go wrong with the body. But for more than twenty years, there has been accumulating evidence that much of the process takes place under genetic control. We have seen that signaling chemistry can make dramatic differences in life span, and that single molecules can significantly affect longevity. We are frequently confronted with puzzling choices the body makes which benefit neither present health nor fertility nor long-term survival. If we permit ourselves a shift of reference frame and regard aging as a programmed biological function like growth and development, then these observations fall into place and make sense. This perspective suggests that aging proceeds under control of a master clock, or several redundant clocks. If this is so, we may learn to reset the clocks with biochemical interventions and make an old body behave like a young body, including repair of many of the modes of damage that we are accustomed to regard as independent symptoms of the senescent phenotype, and for which we have assumed that the body has no remedy.

  1. What starts an internal clock?

    PubMed

    Roberts, S; Holder, M D

    1984-07-01

    Five experiments with rats investigated under what conditions a stimulus is timed by the internal clock used in time-discrimination procedures. In Experiments 1-4, we trained rats to time one stimulus (e.g., light) and then asked whether they timed a stimulus from another modality (e.g., sound). The second stimulus was treated in three ways: exposed (presented alone), paired with food, and extinguished. Experiments 1 and 2 used the peak procedure, similar to a discrete-trial fixed-interval schedule, and paired the treated stimulus with food using instrumental training; Experiments 3 and 4 used a psychophysical choice procedure and paired the treated stimulus with food using classical conditioning. All four experiments found that there was cross-modal transfer of the time discrimination after pairing, but not after exposure or extinction. This suggests that the rat's internal clock timed the treated stimulus after pairing, but not after exposure or extinction. Experiment 5 tested a theory of extinction based on the results of Experiments 1-4; the results suggested that the decline of responding observed in extinction is not due to changes in timing. The main conclusion is that the internal clock apparently times stimuli with signal value (associative strength) and does not time stimuli without signal value.

  2. Hanle detection for optical clocks.

    PubMed

    Zhang, Xiaogang; Zhang, Shengnan; Pan, Duo; Chen, Peipei; Xue, Xiaobo; Zhuang, Wei; Chen, Jingbiao

    2015-01-01

    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.

  3. Hanle detection for optical clocks.

    PubMed

    Zhang, Xiaogang; Zhang, Shengnan; Pan, Duo; Chen, Peipei; Xue, Xiaobo; Zhuang, Wei; Chen, Jingbiao

    2015-01-01

    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. PMID:25734183

  4. An epigenetic clock controls aging.

    PubMed

    Mitteldorf, Josh

    2016-02-01

    We are accustomed to treating aging as a set of things that go wrong with the body. But for more than twenty years, there has been accumulating evidence that much of the process takes place under genetic control. We have seen that signaling chemistry can make dramatic differences in life span, and that single molecules can significantly affect longevity. We are frequently confronted with puzzling choices the body makes which benefit neither present health nor fertility nor long-term survival. If we permit ourselves a shift of reference frame and regard aging as a programmed biological function like growth and development, then these observations fall into place and make sense. This perspective suggests that aging proceeds under control of a master clock, or several redundant clocks. If this is so, we may learn to reset the clocks with biochemical interventions and make an old body behave like a young body, including repair of many of the modes of damage that we are accustomed to regard as independent symptoms of the senescent phenotype, and for which we have assumed that the body has no remedy. PMID:26608516

  5. Design principles underlying circadian clocks.

    PubMed Central

    Rand, D. A.; Shulgin, B. V.; Salazar, D.; Millar, A. J.

    2004-01-01

    A fundamental problem for regulatory networks is to understand the relation between form and function: to uncover the underlying design principles of the network. Circadian clocks present a particularly interesting instance, as recent work has shown that they have complex structures involving multiple interconnected feedback loops with both positive and negative feedback. While several authors have speculated on the reasons for this, a convincing explanation is still lacking.We analyse both the flexibility of clock networks and the relationships between various desirable properties such as robust entrainment, temperature compensation, and stability to environmental variations and parameter fluctuations. We use this to argue that the complexity provides the flexibility necessary to simultaneously attain multiple key properties of circadian clocks. As part of our analysis we show how to quantify the key evolutionary aims using infinitesimal response curves, a tool that we believe will be of general utility in the analysis of regulatory networks. Our results suggest that regulatory and signalling networks might be much less flexible and of lower dimension than their apparent complexity would suggest. PMID:16849158

  6. PIFs: Systems Integrators in Plant Development[W

    PubMed Central

    Leivar, Pablo; Monte, Elena

    2014-01-01

    Phytochrome-interacting factors (PIFs) are members of the Arabidopsis thaliana basic helix-loop-helix family of transcriptional regulators that interact specifically with the active Pfr conformer of phytochrome (phy) photoreceptors. PIFs are central regulators of photomorphogenic development that act to promote stem growth, and this activity is reversed upon interaction with phy in response to light. Recently, significant progress has been made in defining the transcriptional networks directly regulated by PIFs, as well as the convergence of other signaling pathways on the PIFs to modulate growth. Here, we summarize and highlight these findings in the context of PIFs acting as integrators of light and other signals. We discuss progress in our understanding of the transcriptional and posttranslational regulation of PIFs that illustrates the integration of light with hormonal pathways and the circadian clock, and we review seedling hypocotyl growth as a paradigm of PIFs acting at the interface of these signals. Based on these advances, PIFs are emerging as required factors for growth, acting as central components of a regulatory node that integrates multiple internal and external signals to optimize plant development. PMID:24481072

  7. Photons, clocks, and consciousness

    NASA Technical Reports Server (NTRS)

    Brainard, George C.; Hanifin, John P.

    2005-01-01

    Light profoundly impacts human consciousness through the stimulation of the visual system and powerfully regulates the human circadian system, which, in turn, has a broad regulatory impact on virtually all tissues in the body. For more than 25 years, the techniques of action spectroscopy have yielded insights into the wavelength sensitivity of circadian input in humans and other mammalian species. The seminal discovery of melanopsin, the photopigment in intrinsically photosensitive retinal ganglion cells, has provided a significant turning point for understanding human circadian phototransduction. Action spectra in humans show that the peak wavelength sensitivity for this newly discovered sensory system is within the blue portion of the spectrum. This is fundamentally different from the three-cone photopic visual system, as well as the individual rod and cone photoreceptor peaks. Studies on rodents, nonhuman primates, and humans indicate that despite having a different wavelength fingerprint, these classic visual photoreceptors still provide an element of input to the circadian system. These findings open the door to innovations in light therapy for circadian and affective disorders, as well as possible architectural light applications.

  8. Intercellular and systemic spread of RNA and RNAi in plants.

    PubMed

    Nazim Uddin, Mohammad; Kim, Jae-Yean

    2013-01-01

    Plants possess dynamic networks of intercellular communication that are crucial for plant development and physiology. In plants, intercellular communication involves a combination of ligand-receptor-based apoplasmic signaling, and plasmodesmata and phloem-mediated symplasmic signaling. The intercellular trafficking of macromolecules, including RNAs and proteins, has emerged as a novel mechanism of intercellular communication in plants. Various forms of regulatory RNAs move over distinct cellular boundaries through plasmodesmata and phloem. This plant-specific, non-cell-autonomous RNA trafficking network is also involved in development, nutrient homeostasis, gene silencing, pathogen defense, and many other physiological processes. However, the mechanism underlying macromolecular trafficking in plants remains poorly understood. Current progress made in RNA trafficking research and its biological relevance to plant development will be summarized. Diverse plant regulatory mechanisms of cell-to-cell and systemic long-distance transport of RNAs, including mRNAs, viral RNAs, and small RNAs, will also be discussed.

  9. Educational Technology Classics: The Computer versus the Clock

    ERIC Educational Resources Information Center

    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…

  10. Systemic spread of an RNA insect virus in plants expressing plant viral movement protein genes

    PubMed Central

    Dasgupta, Ranjit; Garcia, Bradley H.; Goodman, Robert M.

    2001-01-01

    Flock house virus (FHV), a single-stranded RNA insect virus, has previously been reported to cross the kingdom barrier and replicate in barley protoplasts and in inoculated leaves of several plant species [Selling, B. H., Allison, R. F. & Kaesberg, P. (1990) Proc. Natl. Acad. Sci. USA 87, 434–438]. There was no systemic movement of FHV in plants. We tested the ability of movement proteins (MPs) of plant viruses to provide movement functions and cause systemic spread of FHV in plants. We compared the growth of FHV in leaves of nontransgenic and transgenic plants expressing the MP of tobacco mosaic virus or red clover necrotic mosaic virus (RCNMV). Both MPs mobilized cell-to-cell and systemic movement of FHV in Nicotiana benthamiana plants. The yield of FHV was more than 100-fold higher in the inoculated leaves of transgenic plants than in the inoculated leaves of nontransgenic plants. In addition, FHV accumulated in the noninoculated upper leaves of both MP-transgenic plants. RCNMV MP was more efficient in mobilizing FHV to noninoculated upper leaves. We also report here that FHV replicates in inoculated leaves of six additional plant species: alfalfa, Arabidopsis, Brassica, cucumber, maize, and rice. Our results demonstrate that plant viral MPs cause cell-to-cell and long-distance movement of an animal virus in plants and offer approaches to the study of the evolution of viruses and mechanisms governing mRNA trafficking in plants as well as to the development of promising vectors for transient expression of foreign genes in plants. PMID:11296259

  11. Methods and systems for seed planting management and control

    DOEpatents

    Svoboda, John M.; Hess, J. Richard; Hoskinson, Reed L.; Harker, David J.

    2002-01-01

    A seed planting system providing optimal seed spacing in an agricultural field. The seed planting system includes a mobile seed planter having one or more planting shoes, or members being adapted for towing by a farm vehicle or being self-propelled. Sensors, disposed proximate to respective planting shoes, detect seed planting events and send corresponding signals to a computer. Contemporaneously, a geospatial locator acquires, and transmits to the computer, the geospatial location of each planted seed. The computer correlates the geospatial location data with the seed deposition data and generates a seed distribution profile indicating the location of each seed planted in a zone of interest to enable the control of speed spacing.

  12. PACKAGE PLANTS FOR SMALL SYSTEMS: A FIELD STUDY

    EPA Science Inventory

    A joint field study was conducted by AWWA and the Drinking Water Research Division of USEPA to evaluate existing small community systems that use package plant technology. Forty-eight package plant systems representing a geographic and technological cross section were evaluated t...

  13. RNAi delivery-whole plant systems reducing psyllids and leafhoppers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We developed a system for delivery of dsRNA constructs in whole-plant systems (herbaceous plants, woody grapevine and citrus seedlings and trees) which is currently being evaluated. Successful feeding of dsRNA in sucrose solutions to psyllids was followed by using flush shoots excised from trees. ...

  14. The Sr optical lattice clock at JILA: A new record in atomic clock performance

    NASA Astrophysics Data System (ADS)

    Nicholson, Travis; Bloom, Benjamin; Williams, Jason; Campbell, Sara; Bishof, Michael; Zhang, Xibo; Zhang, Wei; Bromley, Sarah; Hutson, Ross; McNally, Rees; Ye, Jun

    2014-05-01

    The exquisite control exhibited over quantum states of individual particles has revolutionized the field of precision measurement, as exemplified by highly accurate atomic clocks. Optical clocks have been the most accurate frequency standards for the better part of a decade, surpassing even the cesium microwave fountains upon which the SI second is based. Two classes of optical clocks have outperformed cesium: single-ion clocks and optical lattice clocks. Historically ion clocks have always been more accurate, and the precision of ion clocks and lattice clocks has been comparable. For years it has been unclear if lattice clocks can overcome key systematics and become more accurate than ion clocks. In this presentation I report the first lattice clock that has surpassed ion clocks in both precision and accuracy. These measurements represent a tenfold improvement in precision and a factor of 20 improvement in accuracy over the previous best lattice clock results. This work paves the way for a better realization of SI units, the development of more sophisticated quantum sensors, and precision tests of the fundamental laws of nature.

  15. The plant as a biomechatronic system.

    PubMed

    Mazzolai, Barbara; Laschi, Cecilia; Dario, Paolo; Mugnai, Sergio; Mancuso, Stefano

    2010-02-01

    Our vision of plants is changing dramatically: from insensitive and static objects to complex living beings able to sense the environment and to use the information collected to adapt their behaviour. At all times humans imitate ideas and concepts from nature to resolve technological problems. Solutions coming from plants have the potential to face challenges and difficulties of modern engineering design. Characteristic concepts of the plant world such as reiteration, modularity and swarm behaviour could be of great help resolving technological problems. On the other hand a biorobotic approach would facilitate the resolution of many biological problems. In this paper, the concept of a plant-inspired robot is proposed for the investigation of both biological and technological issues. PMID:20023403

  16. Epidemiology of the human circadian clock.

    PubMed

    Roenneberg, Till; Kuehnle, Tim; Juda, Myriam; Kantermann, Thomas; Allebrandt, Karla; Gordijn, Marijke; Merrow, Martha

    2007-12-01

    Humans show large inter-individual differences in organising their behaviour within the 24-h day-this is most obvious in their preferred timing of sleep and wakefulness. Sleep and wake times show a near-Gaussian distribution in a given population, with extreme early types waking up when extreme late types fall asleep. This distribution is predominantly based on differences in an individuals' circadian clock. The relationship between the circadian system and different "chronotypes" is formally and genetically well established in experimental studies in organisms ranging from unicells to mammals. To investigate the epidemiology of the human circadian clock, we developed a simple questionnaire (Munich ChronoType Questionnaire, MCTQ) to assess chronotype. So far, more than 55,000 people have completed the MCTQ, which has been validated with respect to the Horne-Østberg morningness-eveningness questionnaire (MEQ), objective measures of activity and rest (sleep-logs and actimetry), and physiological parameters. As a result of this large survey, we established an algorithm which optimises chronotype assessment by incorporating the information on timing of sleep and wakefulness for both work and free days. The timing and duration of sleep are generally independent. However, when the two are analysed separately for work and free days, sleep duration strongly depends on chronotype. In addition, chronotype is both age- and sex-dependent. PMID:17936039

  17. The melatonin-sensitive circadian clock of the enteric bacterium Enterobacter aerogenes.

    PubMed

    Paulose, Jiffin K; Cassone, Vincent M

    2016-09-01

    Circadian clocks are fundamental properties of all eukaryotic organisms and at least some prokaryotic organisms. Recent studies in our laboratory have shown that the gastrointestinal system contains a circadian clock that controls many, if not all, aspects of gastrointestinal function. We now report that at least one species of intestinal bacteria, Enterobacter aerogenes, responds to the pineal and gastrointestinal hormone melatonin by an increase in swarming activity. This swarming behavior is expressed rhythmically, with a period of approximately 24 hrs. Transformation of E. aerogenes to express luciferase with a MotA promoter reveals circadian patterns of bioluminescence that are synchronized by melatonin and whose periods are temperature compensated from 26°C to 40°C. Bioinformatics suggest similarities between the E. aerogenes and cyanobacterial clocks, suggesting the circadian clock may have evolved very early in the evolution of life. They also point to a coordination of host circadian clocks with those residing in the microbiota themselves. PMID:27387841

  18. CLOCK modulates survival and acute lung injury in mice with polymicrobial sepsis.

    PubMed

    Wang, Chao-Yung; Hsieh, Ming-Jer; Hsieh, I-Chang; Shie, Shian-Sen; Ho, Ming-Yun; Yeh, Jih-Kai; Tsai, Ming-Lung; Yang, Chia-Hung; Hung, Kuo-Chun; Wang, Chun-Chieh; Wen, Ming-Shien

    2016-09-16

    Polymicrobial sepsis is a potentially fatal condition and a significant burden on health care systems. Acute lung injury is the most common complication of sepsis and results in high mortality. However, there has been no recent significant progress in the treatment of sepsis or acute lung injury induced by sepsis. Here we show that mice deficient in the circadian protein CLOCK had better survival than wild-type mice after induction of polymicrobial sepsis by cecal ligation and puncture. Inflammatory cytokine production was attenuated and bacterial clearance was improved in CLOCK-deficient mice. Moreover, acute lung injury after induction of sepsis was significantly decreased in CLOCK-deficient mice. Genome-wide profiling analysis showed that inhibin signaling was reduced in CLOCK-deficient mice. These data establish the importance of circadian CLOCK-inhibin signaling in sepsis, which may have potential therapeutic implications. PMID:27520377

  19. The melatonin-sensitive circadian clock of the enteric bacterium Enterobacter aerogenes.

    PubMed

    Paulose, Jiffin K; Cassone, Vincent M

    2016-09-01

    Circadian clocks are fundamental properties of all eukaryotic organisms and at least some prokaryotic organisms. Recent studies in our laboratory have shown that the gastrointestinal system contains a circadian clock that controls many, if not all, aspects of gastrointestinal function. We now report that at least one species of intestinal bacteria, Enterobacter aerogenes, responds to the pineal and gastrointestinal hormone melatonin by an increase in swarming activity. This swarming behavior is expressed rhythmically, with a period of approximately 24 hrs. Transformation of E. aerogenes to express luciferase with a MotA promoter reveals circadian patterns of bioluminescence that are synchronized by melatonin and whose periods are temperature compensated from 26°C to 40°C. Bioinformatics suggest similarities between the E. aerogenes and cyanobacterial clocks, suggesting the circadian clock may have evolved very early in the evolution of life. They also point to a coordination of host circadian clocks with those residing in the microbiota themselves.

  20. Functional interaction of the circadian clock and UV RESISTANCE LOCUS 8-controlled UV-B signaling pathways in Arabidopsis thaliana.

    PubMed

    Fehér, Balázs; Kozma-Bognár, László; Kevei, Eva; Hajdu, Anita; Binkert, Melanie; Davis, Seth Jon; Schäfer, Eberhard; Ulm, Roman; Nagy, Ferenc

    2011-07-01

    Circadian clocks regulate many molecular and physiological processes in Arabidopsis (Arabidopsis thaliana), allowing the timing of these processes to occur at the most appropriate time of the day in a 24-h period. The accuracy of timing relies on the synchrony of the clock and the environmental day/night cycle. Visible light is the most potent signal for such synchronization, but light-induced responses are also rhythmically attenuated (gated) by the clock. Here, we report a similar mutual interaction of the circadian clock and non-damaging photomorphogenic UV-B light. We show that low-intensity UV-B radiation acts as entraining signal for the clock. UV RESISTANCE LOCUS 8 (UVR8) and CONSTITUTIVELY PHOTOMORPHOGENIC 1 (COP1) are required, but ELONGATED HYPOCOTYL 5 (HY5) and HY5 HOMOLOG (HYH) are dispensable for this process. UV-B responsiveness of clock gene expression suggests that photomorphogenic UV-B entrains the plant clock through transcriptional activation. We also demonstrate that UV-B induction of gene expression under these conditions is gated by the clock in a HY5/HYH-independent manner. The arrhythmic early flowering 3-4 mutant showed non-gated, high-level gene induction by UV-B, yet displayed no increased tolerance to UV-B stress. Thus, the temporal restriction of UV-B responsiveness by the circadian clock can be considered as saving resources during acclimation without losing fitness.

  1. The Arabidopsis Circadian System

    PubMed Central

    McClung, C. Robertson; Salomé, Patrice A.; Michael, Todd P.

    2002-01-01

    Rhythms with periods of approximately 24 hr are widespread in nature. Those that persist in constant conditions are termed circadian rhythms and reflect the activity of an endogenous biological clock. Plants, including Arabidopsis, are richly rhythmic. Expression analysis, most recently on a genomic scale, indicates that the Arabidopsis circadian clock regulates a number of key metabolic pathways and stress responses. A number of sensitive and high-throughput assays have been developed to monitor the Arabidopsis clock. These assays have facilitated the identification of components of plant circadian systems through genetic and molecular biological studies. Although much remains to be learned, the framework of the Arabidopsis circadian system is coming into focus. Dedication This review is dedicated to the memory of DeLill Nasser, a wonderful mentor and an unwavering advocate of both Arabidopsis and circadian rhythms research. PMID:22303209

  2. The Arabidopsis sickle mutant exhibits altered circadian clock responses to cool tempatures and tempature-dependent alternative splicing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The circadian clock allows plants to anticipate and respond to daily changes in ambient temperature. Mechanisms establishing the timing of circadian rhythms in Arabidopsis thaliana through temperature entrainment remain unclear. Also incompletely understood is the temperature compensation mechanism ...

  3. Circadian Clock Dysfunction and Psychiatric Disease: Could Fruit Flies have a Say?

    PubMed Central

    Zordan, Mauro Agostino; Sandrelli, Federica

    2015-01-01

    There is evidence of a link between the circadian system and psychiatric diseases. Studies in humans and mammals suggest that environmental and/or genetic disruption of the circadian system leads to an increased liability to psychiatric disease. Disruption of clock genes and/or the clock network might be related to the etiology of these pathologies; also, some genes, known for their circadian clock functions, might be associated to mental illnesses through clock-independent pleiotropy. Here, we examine the features which we believe make Drosophila melanogaster a model apt to study the role of the circadian clock in psychiatric disease. Despite differences in the organization of the clock system, the molecular architecture of the Drosophila and mammalian circadian oscillators are comparable and many components are evolutionarily related. In addition, Drosophila has a rather complex nervous system, which shares much at the cell and neurobiological level with humans, i.e., a tripartite brain, the main neurotransmitter systems, and behavioral traits: circadian behavior, learning and memory, motivation, addiction, social behavior. There is evidence that the Drosophila brain shares some homologies with the vertebrate cerebellum, basal ganglia, and hypothalamus-pituitary-adrenal axis, the dysfunctions of which have been tied to mental illness. We discuss Drosophila in comparison to mammals with reference to the: organization of the brain and neurotransmitter systems; architecture of the circadian clock; clock-controlled behaviors. We sum up current knowledge on behavioral endophenotypes, which are amenable to modeling in flies, such as defects involving sleep, cognition, or social interactions, and discuss the relationship of the circadian system to these traits. Finally, we consider if Drosophila could be a valuable asset to understand the relationship between circadian clock malfunction and psychiatric disease. PMID:25941512

  4. Generating a fault-tolerant global clock using high-speed control signals for the MetaNet architecture

    SciTech Connect

    Ofek, Y. )

    1994-05-01

    This work describes a new technique, based on exchanging control signals between neighboring nodes, for constructing a stable and fault-tolerant global clock in a distributed system with an arbitrary topology. It is shown that it is possible to construct a global clock reference with time step that is much smaller than the propagation delay over the network's links. The synchronization algorithm ensures that the global clock tick' has a stable periodicity, and therefore, it is possible to tolerate failures of links and clocks that operate faster and/or slower than nominally specified, as well as hard failures. The approach taken in this work is to generate a global clock from the ensemble of the local transmission clocks and not to directly synchronize these high-speed clocks. The steady-state algorithm, which generates the global clock, is executed in hardware by the network interface of each node. At the network interface, it is possible to measure accurately the propagation delay between neighboring nodes with a small error or uncertainty and thereby to achieve global synchronization that is proportional to these error measurements. It is shown that the local clock drift (or rate uncertainty) has only a secondary effect on the maximum global clock rate. The synchronization algorithm can tolerate any physical failure. 18 refs.

  5. The NIM Sr Optical Lattice Clock

    NASA Astrophysics Data System (ADS)

    Lin, Y.; Wang, Q.; Li, Y.; Meng, F.; Lin, B.; Zang, E.; Sun, Z.; Fang, F.; Li, T.; Fang, Z.

    2016-06-01

    A 87Sr optical lattice clock is built at the National Institute of Metrology (NIM) of China. The atoms undergo two stages of laser cooling before being loaded into a horizontal optical lattice at the magic wavelength of 813 nm. After being interrogated by a narrow linewidth 698 nm clock laser pulse, the normalized excitation rate is measured to get the frequency error, which is then used to lock the clock laser to the ultra-narrow 1S0-3P0 clock transition. The total systematic uncertainty of the clock is evaluated to be 2.3 × 10-16, and the absolute frequency of the clock is measured to be 429 228 004 229 873.7(1.4) Hz with reference to the NIM5 cesium fountain.

  6. Diversity of Human Clock Genotypes and Consequences

    PubMed Central

    Zhang, Luoying; Ptáček, Louis J.; Fu, Ying-Hui

    2014-01-01

    The molecular clock consists of a number of genes that form transcriptional and post-transcriptional feedback loops, which function together to generate circadian oscillations that give rise to circadian rhythms of our behavioral and physiological processes. Genetic variations in these clock genes have been shown to be associated with phenotypic effects in a repertoire of biological processes, such as diurnal preference, sleep, metabolism, mood regulation, addiction, and fertility. Consistently, rodent models carrying mutations in clock genes also demonstrate similar phenotypes. Taken together, these studies suggest that human clock-gene variants contribute to the phenotypic differences observed in various behavioral and physiological processes, although to validate this requires further characterization of the molecular consequences of these polymorphisms. Investigating the diversity of human genotypes and the phenotypic effects of these genetic variations shall advance our understanding of the function of the circadian clock and how we can employ the clock to improve our overall health. PMID:23899594

  7. Future Laser-Cooled Microwave Clock Performance

    NASA Technical Reports Server (NTRS)

    Gibble, Kurt

    1997-01-01

    Limitations to the performance of laser-cooled earth and space-based Cs clocks will be critically discussed. The most significant limitation to the stability and accuracy of laser-cooled atomic clocks is the frequency shift due to cold collisions. Because of it, laser-cooled Cs clocks must be operated at low density and this implies that space based Cs clock performance will not be significantly better than earth based. To regain some of the high accuracy and stability lost to the low density, clocks can be designed to multiply launch (or juggle) atoms. Clocks based on other atoms, in particular Rb-87 or possibly Rb-85, may have much smaller cold collision frequency shifts and therefore be capable of higher stability and accuracy, especially in a space environment.

  8. 29 CFR 785.48 - Use of time clocks.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ..., that they do not engage in any work. Their early or late clock punching may be disregarded. Minor... 29 Labor 3 2014-07-01 2014-07-01 false Use of time clocks. 785.48 Section 785.48 Labor Regulations... clocks. (a) Differences between clock records and actual hours worked. Time clocks are not required....

  9. 29 CFR 785.48 - Use of time clocks.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ..., that they do not engage in any work. Their early or late clock punching may be disregarded. Minor... 29 Labor 3 2010-07-01 2010-07-01 false Use of time clocks. 785.48 Section 785.48 Labor Regulations... clocks. (a) Differences between clock records and actual hours worked. Time clocks are not required....

  10. 29 CFR 785.48 - Use of time clocks.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ..., that they do not engage in any work. Their early or late clock punching may be disregarded. Minor... 29 Labor 3 2011-07-01 2011-07-01 false Use of time clocks. 785.48 Section 785.48 Labor Regulations... clocks. (a) Differences between clock records and actual hours worked. Time clocks are not required....

  11. 29 CFR 785.48 - Use of time clocks.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ..., that they do not engage in any work. Their early or late clock punching may be disregarded. Minor... 29 Labor 3 2013-07-01 2013-07-01 false Use of time clocks. 785.48 Section 785.48 Labor Regulations... clocks. (a) Differences between clock records and actual hours worked. Time clocks are not required....

  12. 29 CFR 785.48 - Use of time clocks.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ..., that they do not engage in any work. Their early or late clock punching may be disregarded. Minor... 29 Labor 3 2012-07-01 2012-07-01 false Use of time clocks. 785.48 Section 785.48 Labor Regulations... clocks. (a) Differences between clock records and actual hours worked. Time clocks are not required....

  13. Optical to microwave clock frequency ratios with a nearly continuous strontium optical lattice clock

    NASA Astrophysics Data System (ADS)

    Lodewyck, Jérôme; Bilicki, Sławomir; Bookjans, Eva; Robyr, Jean-Luc; Shi, Chunyan; Vallet, Grégoire; Le Targat, Rodolphe; Nicolodi, Daniele; Le Coq, Yann; Guéna, Jocelyne; Abgrall, Michel; Rosenbusch, Peter; Bize, Sébastien

    2016-08-01

    Optical lattice clocks are at the forefront of frequency metrology. Both the instability and systematic uncertainty of these clocks have been reported to be two orders of magnitude smaller than the best microwave clocks. For this reason, a redefinition of the SI second based on optical clocks seems possible in the near future. However, the operation of optical lattice clocks has not yet reached the reliability that microwave clocks have achieved so far. In this paper, we report on the operation of a strontium optical lattice clock that spans several weeks, with more than 80% uptime. We make use of this long integration time to demonstrate a reproducible measurement of frequency ratios between the strontium clock transition and microwave Cs primary and Rb secondary frequency standards.

  14. The chlorate-iodine clock reaction.

    PubMed

    Oliveira, André P; Faria, Roberto B

    2005-12-28

    A clock reaction produced by mixing chlorate and iodine solutions in perchloric acid media is reported. This is the first example of a clock reaction using chlorate as a reagent. Increasing chlorate and acid concentration reduces the induction period. Changing the initial iodine concentration does not affect the length of the induction period. The discovery of this clock reaction opens the possibility that a new family of oscillation reactions can be built using chlorate as reagent. PMID:16366551

  15. The Square Light Clock and Special Relativity

    ERIC Educational Resources Information Center

    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…

  16. Collisionally induced atomic clock shifts and correlations

    SciTech Connect

    Band, Y. B.; Osherov, I.

    2011-07-15

    We develop a formalism to incorporate exchange symmetry considerations into the calculation of collisional frequency shifts for atomic clocks using a density-matrix formalism. The formalism is developed for both fermionic and bosonic atomic clocks. Numerical results for a finite-temperature {sup 87}Sr {sup 1}S{sub 0} (F=9/2) atomic clock in a magic wavelength optical lattice are presented.

  17. Recognition of bacterial plant pathogens: local, systemic and transgenerational immunity.

    PubMed

    Henry, Elizabeth; Yadeta, Koste A; Coaker, Gitta

    2013-09-01

    Bacterial pathogens can cause multiple plant diseases and plants rely on their innate immune system to recognize and actively respond to these microbes. The plant innate immune system comprises extracellular pattern recognition receptors that recognize conserved microbial patterns and intracellular nucleotide binding leucine-rich repeat (NLR) proteins that recognize specific bacterial effectors delivered into host cells. Plants lack the adaptive immune branch present in animals, but still afford flexibility to pathogen attack through systemic and transgenerational resistance. Here, we focus on current research in plant immune responses against bacterial pathogens. Recent studies shed light onto the activation and inactivation of pattern recognition receptors and systemic acquired resistance. New research has also uncovered additional layers of complexity surrounding NLR immune receptor activation, cooperation and sub-cellular localizations. Taken together, these recent advances bring us closer to understanding the web of molecular interactions responsible for coordinating defense responses and ultimately resistance.

  18. Some features of secretory systems in plants.

    PubMed

    Juniper, B E; Gilchrist, A J; Robins, R J

    1977-09-01

    Recent work on secretion in plants is reviewed, with emphasis on the anatomy and physiology of root cap cells in higher plants, the stalked glands of Drosera capensis, and the secretory mechanism of Dionaea muscipula. Cells of the root cap of higher plants switch from a geo-perceptive role to one of mucilage secretion at maturation. Features of this process, the role of the Golgi and the pathway for mucilage distribution are reviewed. In contrast, the stalked glands of the leaves of Drosera capensis are much longer lived and have a complex anatomy. The mechanisms for mucilage secretion, protein absorption and the role of the cell membranes in the internal secretion of the protein are described, using data from X-ray microscopv. The secretion of fluid and protein by Dionaea is stimulated by various nitrogen-containing compounds. Uric acid, often excreted by captured insects, is particularly effective in this respect.

  19. Carbon and fullerene nanomaterials in plant system

    PubMed Central

    2014-01-01

    Both the functionalized and non functionalized carbon nanomaterials influence fruit and crop production in edible plants and vegetables. The fullerene, C60 and carbon nanotubes have been shown to increase the water retaining capacity, biomass and fruit yield in plants up to ~118% which is a remarkable achievement of nanotechnology in recent years. The fullerene treated bitter melon seeds also increase the phytomedicine contents such as cucurbitacin-B (74%), lycopene (82%), charantin (20%) and insulin (91%). Since as little as 50 μg mL−1 of carbon nanotubes increase the tomato production by about 200%, they may be exploited to enhance the agriculture production in future. It has been observed that, in certain cases, non functionalized multi-wall carbon nanotubes are toxic to both plants and animals but the toxicity can be drastically reduced if they are functionalized. PMID:24766786

  20. Mass Loading Characteristics of Crystal Clock Oscillators

    NASA Technical Reports Server (NTRS)

    Cobb, Janel; Morris, V. R.; Thorpe, A. N.

    1997-01-01

    The 10-MHz piezoelectric quartz-crystal microbalance (QCM) has been used extensively for stratospheric aerosol sampling. We have undertaken laboratory studies of the QCM response to mass loading by trace gases. However, this device requires dual oscillator circuitry and the mass sensitivity can often be affected by the electronics. The coatings on the quartz crystals are sometimes difficult to remove after they have reacted with a particular gas and a disposable crystal system would be desirable. The cost of the dual oscillator-based QCM makes this a prohibitive option. Since our goal is to develop a cost-effective microbalance system with stable electronics we have begun testing of crystal clock oscillators, which are assembled with their own circuitry. We have been using chemically specific coatings for ozone to determine if the sensitivity and mass-frequency ratios are comparable to that of the 10-MHz QCM.